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  • 123801. Yuesheng, Ning
    et al.
    Jun, Jiang
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Ziliang, Shi
    Qiang, Fu
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Jianzhao, Liu
    Yi, Luo
    Ben Zhong, Tang
    Nian, Lin
    Single molecule's conductance depending on its orientation2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 1, p. 26-30Article in journal (Refereed)
    Abstract [en]

    Single molecules of 1,1,2,3,4,5-hexaphenylsilole adsorbed on Cu(111) have been investigated using low-temperature scanning tunneling microscopy, scanning tunneling spectroscopy, and quantum chemistry calculations. Two adsorption states have been identified, showing distinctive tunneling conductance. The molecules can switch their states under tip influence. Theoretical calculations indicate that the two states are associated with molecules adsorbed at two 90°-rotated orientations, and the tunneling conductance is attributed to molecular orbitals that spatially bridge tip-to-substrate gap. Our findings demonstrate a decisive dependence of single-molecule conductance on the molecular orientation with respect to electrodes.

  • 123802. Yuheng, Li
    et al.
    Zhenghe, Zhang
    Westlund, Hans
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Urban and Regional Studies.
    Yansui, Liu
    Rural Household Income in Transitional China: Spatio-Temporal Disparity and Its Interpretation2015In: China: An International Journal, ISSN 0219-7472, E-ISSN 0219-8614, Vol. 13, no 2, p. 151-168Article in journal (Refereed)
    Abstract [en]

    This article aims to investigate the evidence of spatio-temporal disparity in rural household income at the provincial level in China during the 1978-2007 period. A research framework is developed to study the transitional processes of decentralisation, marketisation, urbanisation and globalisation. By computing the Moran's I index and using the spatial regression model, the findings indicate a highly clustered, spatio-temporal disparity in rural household income across the eastern, central and western regions in China during the post-reform era. Rural household income tends to be higher in the eastern provinces in comparison to inland provinces. This disparity is attributed to the impacts from the institutional, economic, social and external transitions that become increasingly significant in the recent decades in China.

  • 123803. Yui, A.
    et al.
    Kitajima, T.
    Krajnik, Peter
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Harano, K.
    Sumiya, H.
    Ono, H.
    Effect of cutting fluid on diamond tool life under micro V-groove turning of cobalt-free tungsten carbide2014In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 1017, p. 181-187Article in journal (Refereed)
    Abstract [en]

    Micro-machining of hard dies and molds for optical parts or precision instruments is required to extend die and mold life. This paper investigates the effect of cutting fluid on diamond tool life under micro V-groove turning of cobalt-free tungsten carbide. Zinc dialkyldithiophosphate fluid (ZnDTP) displayed excellent diamond tool wear resistance in previous experiments. The performance of this cutting fluid is compared to newly developed vegetable oil based cutting fluid with dispersed MoS2nanotubes. This paper investigates nano-polycrystalline diamond (NPD) tool life with a rake angle of 0° and -30° under continuous micro V-groove turning (i.e. face turning), of cobalt-free tungsten carbide using the developed cutting fluids. Superior diamond tool edge wear resistance is observed when using the dispersed MoS2nanotubes in vegetable oil and using a NPD tool with a -30° rake angle.

  • 123804. Yukl, Gary
    et al.
    Kaulio, Matti
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Industrial Work Science (closed 20130101).
    Ledarskap i Organisationer2011Book (Other academic)
  • 123805. Yun, D.
    et al.
    Ahn, S.
    Proutiere, Alexandre
    KTH.
    Shin, J.
    Yi, Y.
    Multi-armed bandit with additional observations2018In: SIGMETRICS 2018 - Abstracts of the 2018 ACM International Conference on Measurement and Modeling of Computer Systems, Association for Computing Machinery (ACM), 2018, p. 53-55Conference paper (Refereed)
    Abstract [en]

    We study multi-armed bandit (MAB) problems with additional observations, where in each round, the decision maker selects an arm to play and can also observe rewards of additional arms (within a given budget) by paying certain costs. We propose algorithms that are asymptotic-optimal and order-optimal in their regrets under the settings of stochastic and adversarial rewards, respectively.

  • 123806. Yun, Louis C.
    et al.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Channel assignment and call admission control for spatial division multiple access communication systems1996Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    The methods for channel assignment and channel reassignment are suitable for SDMA systems that accommodate the dynamically adaptive spatial channel conditions and allow for more frequent reuse of conventional channels. Three methods for uplink channel assignment are described: a cost function method, a predictive method, and a hierarchical method. The cost function method computes a cost function for each conventional channel based on a weighted correlation matrix of spatial signatures (vectors) of active subscribers. A spatial channel is created for the selected conventional channel if it is in use. The predictive channel assignment method predicts the uplink received power and interference-plus-noise for each conventional channel. Either the conventional channel with the minimum interference-plus-noise level or the channel with the maximal SINR is selected and a spatial channel is also assigned if the selected channel is in use. The hierarchical method combines the cost function method and the cost function method. The downlink channel assignment method, when not constrained by the uplink channel assignment, assigns a conventional channel to a new connection by estimating the downlink interference-plus-noise level from a subscriber report, spatial signature and weight vector, and computing a predicted downlink received signal level. Three methods for call admission control include: a cost function method, a predictive method, and a load based channel assignment method.

  • 123807.
    Yun, Ruida
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Qin, Yajie
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Signell, Svante
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    LMS-based calibration of pipelined ADCs including linear and nonlinear errors2007In: 2007 European Conference On Circuit Theory And Design: Vols 1-3, 2007, p. 348-351Conference paper (Refereed)
    Abstract [en]

    A least mean square (LMS) based calibration algorithm is proposed to calibrate most known error sources in 1.5 bit/stage pipelined ADCs, known to be immune to moderate comparator offsets. The error sources include linear gain errors, reference voltage errors, systematic offset errors and amplifier non-linear errors of each pipeline stage. LMS is used to estimate the error parameters in the digital domain. After estimation the proposed algorithm calibrate the pipelined ADC using the estimated parameter errors. Simulation results show that the proposed algorithm can improve the ENOB from 6.6 bits to 13.9 bits for a 14 bit 1.5 bits/stage pipelined ADC.

  • 123808. Yun, S H
    et al.
    Karlsson, Ulf O
    KTH, School of Information and Communication Technology (ICT).
    Jonsson, B J
    Rao, K V
    Madsen, L D
    Growth of a-axis-oriented HgBa2CaCu2Ox thin films by rapid quenching1999In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 14, no 8, p. 3181-3184Article in journal (Refereed)
    Abstract [en]

    High-quality a-axis-oriented HgBa2CaCu2Ox superconducting thin films have been grown on (100) LaAlO3 substrates using a modified conventional method that contains a short annealing time of 5 min, rapid-quenching process, and an alternative encapsulated approach. We found that the preferred orientations of HgBa2CaCu2Ox thin films can be controlled by rapid quenching at specific temperatures: 800, 700, 600, and 500 degrees C. The films rapidly quenched in water from 700 degrees C during a cooling cycle showed predominantly a-axis orientation perpendicular to the film surface. Phase was confirmed by x-ray diffraction pole figures. The a-axis films exhibited a zero-resistance transition temperature >120 K, which is comparable to epitaxial c-axis-oriented films.

  • 123809. Yun, S. -Y
    et al.
    Lelarge, M.
    Proutiere, Alexandre
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fast and memory optimal low-rank matrix approximation2015In: Advances in Neural Information Processing Systems, Neural information processing systems foundation , 2015, p. 3177-3185Conference paper (Refereed)
    Abstract [en]

    In this paper, we revisit the problem of constructing a near-optimal rank k approximation of a matrix M ∈ [0,1]m×n under the streaming data model where the columns of M are revealed sequentially. We present SLA (Streaming Low-rank Approximation), an algorithm that is asymptotically accurate, when ksk+1(M) =o(√mn) where sk+1(M) is the (k + 1)-th largest singular value of M. This means that its average mean-square error converges to 0 as m and n grow large (i.e., || M(k)-M(k)||2 F = o(mn) with high probability, where M(k) and M(k) denote the output of SLA and the optimal rank k approximation of M, respectively). Our algorithm makes one pass on the data if the columns of M are revealed in a random order, and two passes if the columns of M arrive in an arbitrary order. To reduce its memory footprint and complexity, SLA uses random sparsification, and samples each entry of M with a small probability δ. In turn, SLA is memory optimal as its required memory space scales as k(m+n), the dimension of its output. Furthermore, SLA is computationally efficient as it runs in O(δkmn) time (a constant number of operations is made for each observed entry of M), which can be as small as O(k log(m)4n) for an appropriate choice of δ and if n ≥ m.

  • 123810. Yun, S. -Y
    et al.
    Proutiere, Alexandre
    KTH, School of Electrical Engineering (EES), Automatic Control. INRIA, France.
    Community detection via random and adaptive sampling2014In: Journal of machine learning research, ISSN 1532-4435, E-ISSN 1533-7928, Vol. 35, p. 138-175Article in journal (Refereed)
    Abstract [en]

    In this paper, we consider networks consisting of a finite number of non-overlapping communities. To extract these communities, the interaction between pairs of nodes may be sampled from a large available data set, which allows a given node pair to be sampled several times. When a node pair is sampled, the observed outcome is a binary random variable, equal to 1 if nodes interact and to 0 otherwise. The outcome is more likely to be positive if nodes belong to the same communities. For a given budget of node pair samples or observations, we wish to jointly design a sampling strategy (the sequence of sampled node pairs) and a clustering algorithm that recover the hidden communities with the highest possible accuracy. We consider both non-adaptive and adaptive sampling strategies, and for both classes of strategies, we derive fundamental performance limits satisfied by any sampling and clustering algorithm. In particular, we provide necessary conditions for the existence of algorithms recovering the communities accurately as the network size grows large. We also devise simple algorithms that accurately reconstruct the communities when this is at all possible, hence proving that the proposed necessary conditions for accurate community detection are also sufficient. The classical problem of community detection in the stochastic block model can be seen as a particular instance of the problems consider here. But our framework covers more general scenarios where the sequence of sampled node pairs can be designed in an adaptive manner. The paper provides new results for the stochastic block model, and extends the analysis to the case of adaptive sampling.

  • 123811. Yun, S. -Y
    et al.
    Proutiere, Alexandre
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Distributed proportional fair load balancing in heterogenous systems2015In: Performance Evaluation Review, ACM Press, 2015, Vol. 43, no 1, p. 17-30Conference paper (Refereed)
    Abstract [en]

    We consider the problem of distributed load balancing in heterogenous parallel server systems, where the service rate achieved by a user at a server depends on both the user and the server. Such heterogeneity typically arises in wireless networks (e.g., servers may represent frequency bands, and the service rate of a user varies across bands). We assume that each server equally shares in time its capacity among users allocated to it. Users initially attach to an arbitrary server, but at random instants of time, they probe the load at a new server and migrate there if this improves their service rate. The dynamics under this distributed load balancing scheme, referred to as Random Local Search (RLS), may be interpreted as those generated by strategic players updating their strategy in a load balancing game. In closed systems, where the user population is fixed, we show that this game has pure Nash Equilibriums (NEs), and that these equilibriums get close to a Proportionally Fair (PF) allocation of users to servers when the user population grows large. We provide an anytime upper bound of the gap between the allocation under RLS and the PF allocation. In open systems, where users randomly enter the system and leave upon service completion, we establish that the RLS algorithm stabilizes the system whenever this it at all possible under centralized load balancing schemes, i.e., it is throughput-optimal. The proof of this result relies on a novel Lyapounov analysis that captures the dynamics due to both users’ migration and their arrivals and departures. To our knowledge, the RLS algorithm constitutes the first fully distributed and throughputoptimal load balancing scheme in heterogenous parallel server systems. We extend our analysis to various scenarios, e.g. to cases where users can be simultaneously served by several servers. Finally we illustrate through numerical experiments the efficiency of the RLS algorithm.

  • 123812. Yun, S. -Y
    et al.
    Proutiere, Alexandre
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Optimal cluster recovery in the labeled stochastic block model2016In: Advances in Neural Information Processing Systems, Neural information processing systems foundation , 2016, p. 973-981Conference paper (Refereed)
    Abstract [en]

    We consider the problem of community detection or clustering in the labeled Stochastic Block Model (LSBM) with a finite number K of clusters of sizes linearly growing with the global population of items n. Every pair of items is labeled independently at random, and label ℓ appears with probability p(i, j, ℓ) between two items in clusters indexed by i and j, respectively. The objective is to reconstruct the clusters from the observation of these random labels. Clustering under the SBM and their extensions has attracted much attention recently. Most existing work aimed at characterizing the set of parameters such that it is possible to infer clusters either positively correlated with the true clusters, or with a vanishing proportion of misclassified items, or exactly matching the true clusters. We find the set of parameters such that there exists a clustering algorithm with at most s misclassified items in average under the general LSBM and for any s = o(n), which solves one open problem raised in [2]. We further develop an algorithm, based on simple spectral methods, that achieves this fundamental performance limit within O(npolylog(n)) computations and without the a-priori knowledge of the model parameters.

  • 123813.
    Yun, Sang Ho
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Dibos, A.
    Lee, Hyung-Seok
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wu, J. Z.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
    Growth of boron nano-junctions2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 15, p. 5587-5589Article in journal (Refereed)
    Abstract [en]

    In this work, we demonstrate the synthesis of various types of boron nanowire junctions in a self-assembled manner by simple closed-tube thermal vapor transfer method. The Y-type boron nano-junctions and lateral boron-silicon alloy nano-junctions were grown on Si substrates, based on the oxide assisted VLS growth mode at a relatively low processing temperature regime and the VLS growth mode at the high processing temperature regime, respectively.

  • 123814.
    Yun, Sang Ho
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Dibos, A
    Wu, J Z
    Kim, Do-Kyung
    KTH, Superseded Departments, Materials Science and Engineering.
    Effect of quench on crystallinity and alignment of boron nanowires2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, no 15, p. 2892-2894Article in journal (Refereed)
    Abstract [en]

    Fabrication of aligned single-crystalline boron nanowire (BNW) arrays has been a challenge so far. This motivated us to investigate the effect of quench on the crystallinity and alignment of BNW films made in a thermal vapor transfer process on Au-coated Si substrates. A remarkable improvement in both crystallinity and alignment has been observed in BNW films quenched from processing temperatures greater than or equal to1100 degreesC. Without quench, the BNWs formed in the temperature range of 900-1100 degreesC are heavily tangled with either an amorphous or polycrystalline structure. If higher-temperature (greater than or equal to1100 degreesC) processing is followed by a quench, predominantly single-crystalline BNWs of a rhombohedral structure (a=10.94 A and c=23.83 A) and (031) orientation aligned along the normal of the substrates can be obtained. We speculate that the strain induced along the BNW at large temperature gradient is responsible for the observed quench effect.

  • 123815.
    Yun, Sang Ho
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Lee, Hyung-Seok
    Kwon, Young Ha
    Göthelid, Mats
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Koo, Sang Mo
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Multifunctional silicon inspired by a wing of male Papilio ulysse2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 3, p. 033109-Article in journal (Refereed)
    Abstract [en]

    Effective entrapment of air and light is a key element for maintaining stable superhydrophobicity and enhancing anti-reflection or absorption. Inspired by a wing of male Papilio ulysse having a unique structure for enabling effective trapping of air and light, we demonstrate that the structure consisting of well-defined multilayer decorated by nanostructures can be obtained on a silicon wafer by a simple microelectromechanical process, consequently resulted in stable superhydrophobocity under static and dynamic conditions, and strong wideband optical absorption.

  • 123816.
    Yun, Sang Ho
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wu, J. I.
    Dibos, A.
    Zou, X. D.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Self-assembled boron nanowire Y-junctions2006In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 6, no 3, p. 385-389Article in journal (Refereed)
    Abstract [en]

    In this work, we demonstrate that boron nanowire Y-junctions can be synthesized in a self-assembled manner by fusing two individual boron nanowires grown inclined toward each other. We show that the presence of a second liquid, in addition to the liquid Au catalyst, is critical to the inclination of the boron nanowire. The structure of the BNYJ arrays that we report here may allow construction of three- or multiple-terminal nanowire devices directly on Si-based readout circuits through controlled nanowire growth.

  • 123817.
    Yun, Sang Ho
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Wu, J. Z.
    Dibos, A.
    Gao, X.
    Karlsson, Ulf O.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Growth of inclined boron nanowire bundle arrays in an oxide-assisted vapor-liquid-solid process2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 11, p. 113109-Article in journal (Refereed)
    Abstract [en]

    In the vapor-liquid-solid process typically employed for semiconductor nanowire growth, nucleation and anisotropic crystal growth of single nanowires are achieved with generation of a solid/liquid alloy interface using metal catalysts. The nucleation and growth mechanism of nanowires may be greatly altered when a second liquid is introduced into the solid/liquid alloy interface. In this work, we demonstrate bundled boron nanowire (BNW) array growth on Au coated Si substrates by introducing a second liquid of B2O3 onto the solid (B)/liquid alloy (Au-B) interface. The BNWs in each bundle are straight but highly inclined with respect to the normal of the substrate. A study of BNW morphology and chemical elemental distribution using electron microscopy and energy dispersive x-ray spectroscopy suggested that the catalyst Au provided the nucleation site for BNW bundles while the liquid B2O3 modified the initiation of BNWs from each nucleation site, resulting in multiple initiation of the BNWs from each site.

  • 123818.
    Yun, Se-Young
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Proutiere, Alexandre
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Distributed Load Balancing in Heterogenous Systems2014In: 2014 48TH ANNUAL CONFERENCE ON INFORMATION SCIENCES AND SYSTEMS (CISS), 2014, p. 6814133-Conference paper (Refereed)
    Abstract [en]

    We consider the problem of distributed load balancing in heterogenous parallel server systems, where the service rate achieved by a user at a server depends on both the user and the server. Such heterogeneity typically arises in wireless networks (e.g., servers may represent frequency bands, and the service rate of a user varies across bands). Users select servers in a distributed manner. They initially attach to an arbitrary server. However, at random instants of time, they may probe the load at a new server and migrate there to improve their service rate. We analyze the system dynamics under the natural Random Local Search (RLS) migration scheme, introduced in [5]. Under this scheme, when a user has the opportunity to switch servers, she does it only if this improves her service rate. The dynamics under RLS may be interpreted as those generated by strategic players updating their strategy in a load balancing game. We show that this game has pure Nash Equilibriums (NEs), and we analyze their efficiency. We further prove that when the user population grows large, pure NEs get closer to a Proportionally Fair (PF) allocation of users to servers, and we characterize the gap between equilibriums and this ideal allocation depending on user population. Under the RLS algorithm, the system converges to pure NEs: we study the time it takes for the system to reach the PF allocation within a certain margin.

  • 123819.
    Yun, Seyoung
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Shin, J.
    Yi, Y.
    CSMA over time-varying channels: Optimality, uniqueness and limited backoff rate2013In: MobiHoc '13 Proceedings of the fourteenth ACM international symposium on Mobile ad hoc networking and computing, ACM Press, 2013, p. 137-146Conference paper (Refereed)
    Abstract [en]

    Recent studies on MAC scheduling have shown that carrier sense multiple access (CSMA) algorithms can be throughput optimal for arbitrary wireless network topology. However, these results are highly sensitive to the underlying assumption on 'static' or 'fixed' system conditions. For example, if channel conditions are time-varying, it is unclear how each node can adjust its CSMA parameters, so-called backoff and channel holding times, using its local channel information for the desired high performance. In this paper, we study 'channel-aware' CSMA (A-CSMA) algorithms in time-varying channels, where they adjust their parameters as some function of the current channel capacity. First, we show that the achievable rate region of A-CSMA equals to the maximum rate region if and only if the function is exponential. Furthermore, given an exponential function in ACSMA, we design updating rules for their parameters, which achieve throughput optimality for an arbitrary wireless network topology. They are the first CSMA algorithms in the literature which are proved to be throughput optimal under time-varying channels. Moreover, we also consider the case when back-off rates of A-CSMA are highly restricted compared to the speed of channel variations, and characterize the throughput performance of A-CSMA in terms of the underlying wireless network topology. Our results not only guide a high-performance design on MAC scheduling under highly time-varying scenarios, but also provide new insights on the performance of CSMA algorithms in relation to their backoff rates and underlying network topologies.

  • 123820.
    Yun, Seyoung
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Shin, J.
    Yi, Y.
    CSMA using the Bethe approximation for utility maximization2013In: IEEE International Symposium on Information Theory: Proceedings, IEEE conference proceedings, 2013, p. 206-210Conference paper (Refereed)
    Abstract [en]

    CSMA (Carrier Sense Multiple Access), which resolves contentions over wireless networks in a fully distributed fashion, has recently gained a lot of attentions since it has been proved that appropriate control of CSMA parameters guarantees optimality in terms of system-wide utility. Most algorithms rely on the popular MCMC (Markov Chain Monte Carlo) technique, which enables one to find optimal CSMA parameters through iterative loops of simulation-and-update. However, such a simulation-based approach often becomes a major cause of exponentially slow convergence, being poorly adaptive to flow/topology changes. In this paper, we develop a distributed iterative algorithm which produces approximate solutions with convergence in polynomial time. Our approach is motivated by a scheme in statistical physics, referred to as the Bethe approximation, allowing us to express approximate solutions via a certain non-linear system with polynomial size. We provide numerical results to show that the algorithm produces highly accurate solutions and converges much faster than prior ones.

  • 123821. Yun, S.-Y.
    et al.
    Lelarge, M.
    Proutiere, Alexandre
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Streaming, memory limited algorithms for community detection2014In: Advances in Neural Information Processing Systems, ISSN 1049-5258, Vol. 4, no January, p. 3167-3175Article in journal (Refereed)
    Abstract [en]

    In this paper, we consider sparse networks consisting of a finite number of non-overlapping communities, i.e. disjoint clusters, so that there is higher density within clusters than across clusters. Both the intra- and inter-cluster edge densities vanish when the size of the graph grows large, making the cluster reconstruction problem nosier and hence difficult to solve. We are interested in scenarios where the network size is very large, so that the adjacency matrix of the graph is hard to manipulate and store. The data stream model in which columns of the adjacency matrix are revealed sequentially constitutes a natural framework in this setting. For this model, we develop two novel clustering algorithms that extract the clusters asymptotically accurately. The first algorithm is offline, as it needs to store and keep the assignments of nodes to clusters, and requires a memory that scales linearly with the network size. The second algorithm is online, as it may classify a node when the corresponding column is revealed and then discard this information. This algorithm requires a memory growing sub-linearly with the network size. To construct these efficient streaming memory-limited clustering algorithms, we first address the problem of clustering with partial information, where only a small proportion of the columns of the adjacency matrix is observed and develop, for this setting, a new spectral algorithm which is of independent interest.

  • 123822.
    Yunda Lozano, Daniel
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Improving vertical handover performance for RTP streams containing voice: Using network parameters to predict future network conditions in order to make a vertical handover decision2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wireless local area networks WLAN and Voice over IP technologies enable local low cost wireless telephony, while cellular networks offer wide-area coverage. The use of dual mode WLAN-cellular terminals should allow cost savings by automatically switching from GSM to WLAN networks whenever it is feasible. However, in order to allow user mobility during a call, a handover procedure for transferring a call between the WLAN interface and the cellular network should be defined. The decision algorithm that triggers such a handover is critical to maintain voice quality and uninterrupted communication. Information or measurements collected from the network may be used to anticipate when the connection will degrade to such a point that a handover is desirable in order to allow a sufficient time span for the handover’s successful execution. It is the delay in detecting when to make a handover and the time to execute it that motivates the need for a prediction.

    The goal of this thesis is therefore to present a method to predict when a handover should be made based upon network conditions. We selected a number of WLAN and VoIP software tools and adapted them to perform the measurements. These tools allowed us to measure parameters of the WLAN’s physical and link layers. Packet losses and jitter measurements were used as well. We have assumed that there is ubiquitous cellular coverage so that we only have to be concerned with upward handovers (i.e, from the WLAN to the cellular network and not the reverse). Finally we have designed and evaluated a mechanism that triggers the handover based in these measurements.

  • 123823. Yunhua, L.
    et al.
    Eriksson, A.
    An alternative assumed strain method1999In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 178, no 1-2, p. 23-37Article in journal (Refereed)
    Abstract [en]

    In this paper, an Alternative Assumed Strain (AAS) method is put forward, on the basis of a previous work. The method has two main features: the stresses are eliminated from the finite element formulation by satisfying the stress-strain equations with the assumed strains, which is much more convenient than the L2-orthogonal condition in Enhanced Assumed Strain (EAS) method for developing finite elements; the stresses, obtained from the assumed strains with the stress-strain relations, are forced to satisfy the equilibrium equations identically to reduce the number of assumed strain parameters and to improve finite element efficiency. The method is applied to develop several variations of 3-node triangular and 4-node quadrilateral Mindlin plate elements. Numerical examples show that efficient elements could be obtained from the suggested method. © 1999 Elsevier Science S.A.

  • 123824. Yunhua, L.
    et al.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    An alternative assumed strain method1999In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 178, no 1-2, p. 23-37Article in journal (Refereed)
    Abstract [en]

    In this paper, an Alternative Assumed Strain (AAS) method is put forward, on the basis of a previous work. The method has two main features: the stresses are eliminated from the finite element formulation by satisfying the stress-strain equations with the assumed strains, which is much more convenient than the L2-orthogonal condition in Enhanced Assumed Strain (EAS) method for developing finite elements; the stresses, obtained from the assumed strains with the stress-strain relations, are forced to satisfy the equilibrium equations identically to reduce the number of assumed strain parameters and to improve finite element efficiency. The method is applied to develop several variations of 3-node triangular and 4-node quadrilateral Mindlin plate elements. Numerical examples show that efficient elements could be obtained from the suggested method.

  • 123825. Yunhua, L.
    et al.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Extension of field consistence approach into developing plane stress elements1999In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 173, no 1-2, p. 111-134Article in journal (Refereed)
    Abstract [en]

    In this research paper, the possibilities for extending the field consistence approach [L. Yunhua, On shear locking in finite elements, Licentiate Thesis, Stockholm, 1997; L. Yunhua, Explanation and elimination of shear locking and membrane locking with field consistence approach, Comput. Methods Appl. Mech. Engrg., in press], starting from different variational principles, to plane stress elements are investigated. In the extension, two main difficulties are: explicitly solving a set of coupled partial differential equations and satisfying inter-element compatibility. The first one is alleviated by constructing element interpolations from a set of quasi-general solutions, rather than the real general solutions, to the Euler-Lagrangian equations. The second one is solved by combining the field consistence approach with the iso-parametric interpolation technique. The traditional assumed stress method is improved and an efficient plane stress element is obtained. It seems that the relations between the three commonly used variational principles can be more reasonably established in the framework of the field consistence approach.

  • 123826.
    Yunhua, Luo
    KTH, Superseded Departments, Structural Engineering.
    On shear locking in finite elements1997Licentiate thesis, monograph (Other scientific)
  • 123827.
    Yuning, Jiang
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    LCA of Microgrid System: a Case Study at ‘North-five Islands’ of Changshan Archipelago, China2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Microgrid can provide stable, clean, and sustainable electricity supply for remote places since it can operate on renewable energy sources and work isolated from the utility grid. This thesis evaluates the life cycle greenhouse gas (GHG) emissions of the microgrid system which is located at the ‘North-five Islands’ of Changshan archipelago in China. The existing electricity generation technologies of the microgrid system are wind turbine, PV system and diesel generators with the capacity of 2 MW, 300 kW and 2046 kW, respectively. The total demand of electricity (362.2 GWh) will be supplied by the wind turbine, PV system and diesel generators with 32.03%, 2.36% and 65.62%, respectively, if the microgrid system is required to supply the electricity demand for the ‘North-five Islands’ area alone under the islanded mode during 20 years lifespan. The thesis uses the Life Cycle Assessment (LCA) to evaluate the life cycle GHG emissions of the microgrid system. The life cycle stages of this study include: raw material extraction, manufacturing, transportation and operation. In order to assess the environmental benefits of the microgrid system, three electricity supply options – ‘microgrid electricity supply option’, ‘grid extension electricity supply option’, and ‘conventional fossil diesel generators electricity supply option’ are designed to evaluate the life cycle GHG emissions for supplying 20 years electricity demand (362.2 GWh) of the ‘Northfive Islands’. The results show that the life cycle GHG emissions of the ‘microgrid electricity supply option’ are 223.19 million kgCO2eq. Compared to the ‘grid extension electricity supply option’ and ‘conventional fossil diesel generators electricity supply option’, the net savings of the GHG emissions are 70.56 and 112.18 million kgCO2eq, respectively. It mainly results from the differences of the electricity supply methods of the three electricity supply options. For the ‘microgrid electricity supply option’ itself, the operation stage takes the most responsibility of the life cycle GHG emissions with 97.6%. The raw material extraction, manufacturing and transportation stages account for 1.93%, 0.44% and 0.026%, respectively. For the system components of the microgrid system, the wind turbine, PV system, diesel generators, energy storage system, and cables account for 0.34%, 0.18%, 97.75%, 0.60%, and 1.12%, respectively, of the microgrid system’s life cycle GHG emissions. The thesis conducts the sensitivity analysis of diesel burn rate efficiency (L/kWh) of the microgrid system’s diesel generators due to a large quantity (60.84 million L) of diesel consumption by the diesel generators during 20 years operation time. According to the results of the sensitivity analysis, the diesel burn rate efficiency can directly impact the diesel consumption of the diesel generators, and consequently has a significant impact on the life cycle GHG emissions of the ‘North-five Islands’ microgrid system. Since the diesel burn rate efficiency represents the amount of diesel consumption, this results highlight the significance of any factors that affect the diesel consumption (e.g. quantity of diesel, temperature, altitude, etc.), in affecting the life cycle GHG emissions of the ‘North-five Islands’ microgrid system. In addition, the thesis performers the sensitivity analysis of iii renewable energy (wind and solar energy in specific) fraction of the studied microgrid system because of the huge potential of available renewable energy (63.65 MW of wind turbines) nearby the microgrid system. The results of the sensitivity analysis show that the life cycle GHG emissions of the microgrid system decrease linearly with the increase of wind and solar energy fraction. Particularly, the life cycle GHG emissions of the microgrid system decrease 1.46% (3.26 million kgCO2eq) and 1.37% (3.05 million kgCO2eq) with an increase of 1% in wind and solar energy, respectively.

  • 123828.
    Yuning, Jiang
    KTH, School of Industrial Engineering and Management (ITM).
    LCA of Microgrid System: a Case Study at ‘North-five Islands’ of Changshan Archipelago, China2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Microgrid can provide stable, clean, and sustainable electricity supply for remote places since it can operate on renewable energy sources and work isolated from the utility grid. This thesis evaluates the life cycle greenhouse gas (GHG) emissions of the microgrid system which is located at the ‘North-five Islands’ of Changshan archipelago in China. The existing electricity generation technologies of the microgrid system are wind turbine, PV system and diesel generators with the capacity of 2 MW, 300 kW and 2046 kW, respectively. The total demand of electricity (362.2 GWh) will be supplied by the wind turbine, PV system and diesel generators with 32.03%, 2.36% and 65.62%, respectively, if the microgrid system is required to supply the electricity demand for the ‘North-five Islands’ area alone under the islanded mode during 20 years lifespan. The thesis uses the Life Cycle Assessment (LCA) to evaluate the life cycle GHG emissions of the microgrid system. The life cycle stages of this study include: raw material extraction, manufacturing, transportation and operation. In order to assess the environmental benefits of the microgrid system, three electricity supply options – ‘microgrid electricity supply option’, ‘grid extension electricity supply option’, and ‘conventional fossil diesel generators electricity supply option’ are designed to evaluate the life cycle GHG emissions for supplying 20 years electricity demand (362.2 GWh) of the ‘Northfive Islands’.

    The results show that the life cycle GHG emissions of the ‘microgrid electricity supply option’ are 223.19 million kgCO2eq. Compared to the ‘grid extension electricity supply option’ and ‘conventional fossil diesel generators electricity supply option’, the net savings of the GHG emissions are 70.56 and 112.18 million kgCO2eq, respectively. It mainly results from the differences of the electricity supply methods of the three electricity supply options. For the ‘microgrid electricity supply option’ itself, the operation stage takes the most responsibility of the life cycle GHG emissions with 97.6%. The raw material extraction, manufacturing and transportation stages account for 1.93%, 0.44% and 0.026%, respectively. For the system components of the microgrid system, the wind turbine, PV system, diesel generators, energy storage system, and cables account for 0.34%, 0.18%, 97.75%, 0.60%, and 1.12%, respectively, of the microgrid system’s life cycle GHG emissions.

    The thesis conducts the sensitivity analysis of diesel burn rate efficiency (L/kWh) of the microgrid system’s diesel generators due to a large quantity (60.84 million L) of diesel consumption by the diesel generators during 20 years operation time. According to the results of the sensitivity analysis, the diesel burn rate efficiency can directly impact the diesel consumption of the diesel generators, and consequently has a significant impact on the life cycle GHG emissions of the ‘North-five Islands’ microgrid system. Since the diesel burn rate efficiency represents the amount of diesel consumption, this results highlight the significance of any factors that affect the diesel consumption (e.g. quantity of diesel, temperature, altitude, etc.), in affecting the life cycle GHG emissions of the ‘North-five Islands’ microgrid system. In addition, the thesis performers the sensitivity analysis of renewable energy (wind and solar energy in specific) fraction of the studied microgrid system because of the huge potential of available renewable energy (63.65 MW of wind turbines) nearby the microgrid system. The results of the sensitivity analysis show that the life cycle GHG emissions of the microgrid system decrease linearly with the increase of wind and solar energy fraction. Particularly, the life cycle GHG emissions of the microgrid system decrease 1.46% (3.26 million kgCO2eq) and 1.37% (3.05 million kgCO2eq) with an increase of 1% in wind and solar energy, respectively.

  • 123829.
    Yunkai, Yang
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Services Engineering.
    Numerical study on flow and pollutant dispersion inside street canyons2013Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This thesis analyzes the characteristics of flow pattern and vehicle-emitted pollutant dispersion in roughness surface layer. In an urban environment, wind flow and transported-pollutant source interfere strongly with buildings and other roughness elements on the surface ground, which results in complex characteristics of flow pattern and pollutant dispersion in 3D circumstances. The present study intends to simplify the research domain and investigate the fundamental modeling problems that exist in the field. The current physical research topic is restricted to 2D street canyon in equilibrium conditions. The study is motivated by the fact that characteristics of flow pattern and pollutant distribution inside street canyons are important for public health. The research has applied the computational fluid dynamics (CFD) methodology. To date, insights have typically focused on idealized street canyons without strictly limited boundary conditions and turbulence models. Those approaches face challenges related to their applicability to real urban scenarios or the reliability of prediction results.

    The thesis examines the influence of grid density, turbulence models and turbulent Schmidt number on pollutant distribution at windward and leeward surfaces of street canyon. Since numerical results usually are validated with wind-tunnel measurement data, the results between full-size model and wind-tunnel model are compared in order to test the Reynolds number effect. The lack of measurement data means that the morphometric method is used to generate upcoming wind profile, including the mean vertical velocity and turbulence parameters. The thesis also analyzes the potential errors brought by the method (Scenario A).

    Based on the evaluated numerical model, the thesis continues to study the impacts of surrounding buildings and geometry of street canyon on flow and pollutant distribution inside street canyons. The effect of wind on pollutant distribution inside street canyons was also investigated (Scenario A). Furthermore, the influence of roof shape and configuration of street canyon on characteristics of flow and pollutant distribution is also systematically studied, with the results shown in scenario B.

    The main conclusions of the thesis are that the uncertainty of numerical results derives from different aspects. Wind profile in the inlet profile generated by morphometric method brings major error to the simulation results. Current turbulence models cannot compromise the simulation results between flow field and pollutant distribution field. Ignored small-scale obstacles also need to be handled carefully. Numerical results revealed that flow and pollutant distribution inside street canyons are mainly dominated by the geometry of the street canyon itself. Medium-spaced surrounding buildings are also better able to transport pollutant out of the street canyon. Through systematic analysis, roof shape is proven to have a significant effect on flow and pollutant distribution inside a street canyon. The major impact is altered turbulence intensity depth and strength of shear layer inside the street canyon, which is important for pollutant removal process out of the street canyon.

    In the future, advanced turbulence models accompanied by small-obstacle effect models need to be developed in order to reliably simulate flow and pollutant dispersion simultaneously. Based on the advanced turbulence model, simulation of flow and pollutant dispersion in a complex 3D environment is essential in the next steps for the purpose of engineering application. Accurate vertical wind profile provided for inlet profile is another interesting direction for further development.

    Keywords: Flow; Pollutant dispersion; CFD; Street canyon; Reliability

  • 123830.
    Yunqing, Liang
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management.
    Green Facility Management in a Shanghai Office Building: A Case Study of the "Asia Building"2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This paper aims to explore how well green facility management has performed in Shanghai office building and finds the possible way to improve the situation. Together with two interviews, questionnaire based on benchmarking approach is conducted in a case study of the Asia Building, which lead to the conclusion that green facility management has done a fair work in Asia Building, and suggestions that laws and regulations related to green facility management should be established; governmental organization, the Trade Association of Shanghai Property Management, should take responsibility to improve the situation concerning to the issue; property management company should develop a healthy relationship with property owner and occupiers.

  • 123831.
    Yunsi, Hua
    KTH, School of Architecture and the Built Environment (ABE), Architecture.
    Abisko Vistors Observation Center2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    My master thesis aim to propose a vistors observation center in abisko natural park in the north of sweden.As a center the program this building aim to provide a interesting place between to learn and exprience nordic arctic climate and astronomy for public.At same time.This building also want to exihibit the local sami culture.The building perspective considers how to integrate with the relation to landscape in a new norrland understanding of place and identity.The architectural objective is try to find balance between Big structure intervention and original nature. to create a place connect mountain and lake.while providing a space for interesting and engaging learing-envrionment.

  • 123832.
    Yuntian, Chen
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Björk, Gunnar
    KTH, School of Information and Communication Technology (ICT).
    Generation and detection of photonic qutrits2007In: 2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, CLEO, 2007, p. 4386921-Conference paper (Refereed)
  • 123833.
    Yunus, Ender
    KTH, School of Computer Science and Communication (CSC).
    THE ROLE OF SOCIAL MEDIA IN CREATING POLITICAL AWARENESS AND MOBILIZING POLITICAL PROTESTS: A Focus on Turkey2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the recent years, the internet penetration, social media production and consumption have increased dramatically all over the world. This increase has affected the politics in most parts of the world in many ways. Social media became a tool for politicians to carry out their political campaigns and for activists to create awareness on political issues and mobilize protests. Today almost in all social movements in the countries with high rate of internet access, the role of social media is being discussed. Social media has become a costless and extremely effective tool in reaching mass audiences with political purposes.

    This thesis research focuses on the strength of social media in creating political awareness and mobilizing political protests in Turkey. In this study the recent social movements in Turkey are examined as case studies, to understand the role of social media in political movements, to be able to make predictions for the future. The prob-lem was approached with combining qualitative and quantitative research methods. Literature review regarding the subjects related to the social media and politics and information flow in social networks was conducted. After that, two interviews, a sur-vey and a social network analysis to comprehend the role of social media in the two recent major social movements in Turkey, Gezi Parki Protests and Internet Censor-ship Protests, were carried out.

    Depending on the results from research methods conducted, it was found that social media has already become a fundamental part of social movements in Turkey. The young generation in Turkey is extremely interested in joining online social networks. These social networks establish connections between people that are related with weak ties. These connections enable political information to flow on these networks virally, costless and rapidly. Information can be on political news or thoughts to cre-ate political awareness and also to mobilize political protests. These advantages of social media combined with biased and ignorant attitude of mainstream media on po-litical events; social media created an alternative source of information in the eyes of the society. Considering the increasing internet penetration, smart phone and social media use for political purposes, the strength of social media in creating political awareness and mobilizing political protests is expected to rise in the future as well.

  • 123834. Yurindatama, D.
    et al.
    Barsoum, Imad
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures. The Petroleum Institute, United Arab Emirates.
    Constitutive model and failure locus of a polypropylene grade used in offshore intake pipes2017In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 57, p. 245-259Article in journal (Refereed)
    Abstract [en]

    BorECO®™ BA212E is a polypropylene block co-polymer which has become a common material in the manufacturing of large diameter non-pressurized gravity offshore intake pipelines. These lines are used for transportation of sea water for cooling of petrochemical process plants. The pipe sections are joined by butt heat fusion welding to create the pipeline. Recently a few premature failures of such pipelines have been reported in the field. Hence, there is a need to characterize the constitutive behavior of the pipe and weld material in order to properly design these pipes. The aim of this work is to determine the material constitutive behaviors of the pipe material and the welded joint material. Uniaxial tensile tests of both the pipe and weld joint material are conducted at various strain rates. Both the pipe and weld material show a rather high strain rate dependency, with the weld material having about half the yield strength than that of the pipe material. An analytical constitutive material model is developed for both the pipe and weld material, incorporating the effect of strain rate. The failure locus, expressed in terms of the equivalent plastic strain at failure vs. the stress triaxiality, for both materials is also determined as part of the constitutive model using notched dumbbell specimens. The constitutive model and failure loci for the pipe and weld material are implemented in a finite element model (FEM) and are validated by conducting a series of independent four-point bend experiments on both material types. The validation is carried out by comparing the FEM results of the four-point bend model with the experimental results, which show a rather good agreement.

  • 123835. Yurkin, Yu.T.
    et al.
    Carlson, Per
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Gillard, William
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Wu, Yueshi
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Zverev, V. G.
    et al.,
    Trapped antiprotons in the Earth inner radiation belt in PAMELA experiment2011In: Bulletin of the Russian Academy of Sciences: Physics, ISSN 1062-8738, Vol. 75, no 6, p. 854-856Article in journal (Refereed)
    Abstract [en]

    The existence of trapped antiprotons in the Earth's inner radiation belt has been theoretically predicted, but not observed. We present a procedure for antiproton selection and the observation results from the PAMELA space experiment measurements. The PAMELA magnetic spectrometer ensures reliable identification of particles and charge signs, value determination, and energy measurement, thus enabling us to experimentally establish the existence of antiprotons trapped in the Earth's inner radiation belt.

  • 123836.
    Yus, Diego
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Long-term vehicle movement prediction using Machine Learning methods2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The problem of location or movement prediction can be described as the task of predicting the future location of an item using the past locations of that item. It is a problem of increasing interest with the arrival of location-based services and autonomous vehicles. Even if short term prediction is more commonly studied, especially in the case of vehicles, long-term prediction can be useful in many applications like scheduling, resource managing or traffic prediction.

    In this master thesis project, I present a feature representation of movement that can be used for learning of long-term movement patterns and for long-term movement prediction both in space and time. The representation relies on periodicity in data and is based on weighted n-grams of windowed trajectories.

    The algorithm is evaluated on heavy transport vehicles movement data to assess its ability to from a search index retrieve vehicles that with high probability will move along a route that matches a desired transport mission. Experimental results show the algorithm is able to achieve a consistent low prediction distance error rate across different transport lengths in a limited geographical area under business operation conditions. The results also indicate that the total population of vehicles in the index is a critical factor in the algorithm performance and therefore in its real-world applicability.

  • 123837.
    Yushmanov, Pavel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furo, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    A temperature-jump design for conventional NMR probes2006In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 181, no 1, p. 148-153Article in journal (Refereed)
    Abstract [en]

     The design and performance of a simple probe insert for temperature-jump experiments in conventional NMR probes is described. The insert uses the output from conventional NMR amplifiers for heating conductive aqueous samples with a rate of 30-80 K/s for 200 W radiofrequency power. The observed dependence of the heating rate on sample conductivity is explained by the dominance of dielectric heating. Factors governing the temperature gradient within the sample are discussed.

  • 123838.
    Yushmanov, Pavel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Iliopoulos, Ilias
    Kinetics of demixing and remixing transitions in aqueous solutions of poly(N-isopropylacrylamide):  A temperature-jump H-1 NMR study2006In: Macromolecular Chemistry and Physics, ISSN 1022-1352, E-ISSN 1521-3935, Vol. 207, no 21, p. 1972-1979Article in journal (Refereed)
    Abstract [en]

    The time course of the coil-to-globule collapse and intermolecular aggregation of poly(N-isopropylacrylamide) in aqueous solution upon exceeding the lower critical solution temperature (LCST) are investigated by temperature-jump 1H NMR spectroscopy. After the temperature jump, we record the time dependences of (i) the mobile fraction of the polymer chain as revealed by the intensity of the liquid-like NMR signal, (ii) the local mobility of those chains as revealed by the transverse relaxation time T2, and (iii) their self-diffusion coefficient D. The same data are also reported at their temperature-dependent long-time limits. The results suggest a sudden, faster than one second, collapse and intermolecular aggregation into globules and a slower reorganization/redistribution of the individual chains among and within the globular and mobile states. We found that all molecular changes are reversible if the temperature remains less than ca. 6-8 K above the LCST for less than a few minutes; under those conditions, experiments upon sudden temperature quench below the LCST show that the aggregates disintegrate and swell into coils in less than a few seconds.

  • 123839.
    Yushmanov, Pavel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Furó, István
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Industrial NMR Centre.
    Micellar kinetics of a fluorosurfactant through stopped-flow NMR2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 5, p. 2002-2004Article in journal (Refereed)
    Abstract [en]

     F-19 NMR chemical shifts and transverse relaxation times T, were measured as a function of time after quick stopped-flow dilution of aqueous solutions of sodium perfluorooctanoate (NaPFO) with water, Different initial concentrations of micellar solution and different proportions of mixing were tested. Previous stopped-flow studies by time-resolved small-angle X-ray scattering (TR-SAXS) detection indicated a slow (similar to 10 s) micellar relaxation kinetics in NaPFO solutions. In contrast, no evidence of any comparable slow (> 100 ms) relaxation process was found in our NMR studies. Possible artifacts of stopped-flow experiments are discussed as well as differences between NMR and SAXS detection methods. Upper bounds on the relative weight of a slow relaxation process are given within existing kinetic theories of micellar dissolution.

  • 123840.
    Yushmanov, Pavel V.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    NMR Studies of Colloidal Systems in and out of Equilibrium2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The Thesis describes (i) the development of add-on instrumentation extending the capabilities of conventional NMR spectrometers and (ii) the application of the designed equipments and techniques for investigating various colloidal systems. The new equipments are:

    Novel designs of stopped-flow and temperature–jump inserts intended for conventional Bruker wide-bore superconductive magnets. Both inserts are loaded directly from above into the probe space and can be used together with any 10 mm NMR probe with no need for any auxiliary instruments.

    A set of 5 mm and 10 mm 1H – 19F – 2H NMR probes designed for heteronuclear 1H – 19F cross-relaxation experiments in Bruker DMX 200, AMX 300 and DMX 500 spectrometers, respectively.

    A two–stage low-pass filter intended for suppressing RF noise in electrophoretic NMR experiments.

    The kinetics of micellar dissolution and transformation in aqueous solutions of sodium perfluorooctanoate (NaPFO) is investigated using the stopped-flow NMR instrument. The sensitivity of NMR as detection tool for kinetic processes in micellar solutions is clarified and possible artefacts are analysed. In the NaPFO system, the micellar dissolution is found to proceed faster than 100 ms while surfactant precipitation occurs on the time scale of seconds-to-minutes. The kinetics of the coil-to–globule transition and intermolecular aggregation in a poly (Nisopropylacrylamide) solution are investigated by the temperature-jump NMR instrument. As revealed by the time evolution of the 1H spectrum, the T2 relaxation time and the self-diffusion coefficient D, large (>10 nm) and compact aggregates form in less than 1 second upon fast temperature increase and dissolve in less than 3 seconds upon fast temperature decrease.

    The intermolecular 1H – 19F dipole-dipole cross-relaxation between the solvent and solute molecules, whose fast rotational diffusion is in the extreme narrowing limit, is investigated. The solutes are perfluorooctanoate ions either in monomeric or in micellar form and trifluoroacetic acid and the solvent is water. The obtained cross-relaxation rates are frequency-dependent which clearly proves that there is no extreme narrowing regime for intermolecular dipole-dipole relaxation. The data provide strong constraints for the dynamic retardation of solvent by the solute.

  • 123841.
    Yushmanov, Pavel V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    A rapid-mixing design for conventional NMR probes2005In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 175, no 2, p. 264-270Article in journal (Refereed)
    Abstract [en]

    A simple stopped-flow design for rapid mixing of two liquids within the NMR probe is presented. The device uses no switches or relays but exploits instead the torque exerted by the magnetic field on a current-leading-coil to open and close the start and stop valves. Two serially arranged tangential jet mixer blocks provide a homogeneous mixture with, depending on conditions and requirements, a filling time in the 50-100 ms range and a subsequent stabilization time in the range of 10-40 ms as tested by mixing various combinations of liquids and observing their 1H NMR spectrum. Factors influencing the mixing process are analyzed.

  • 123842.
    Yushmanov, Pavel V.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Furó, Istvan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Stilbs, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Stopped-flow F-19 NMR studies of surfactant precipitation2006In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 291, no 1-3, p. 59-62Article in journal (Refereed)
    Abstract [en]

    The kinetics of the phase change in surfactant solutions is studied by F-19 stopped-flow NMR. In the aqueous solution of sodium perfluooctanoate, we observe precipitation and crystal growth induced by the addition of NaCl solution to the system. The time dependences of the NMR signal intensity and chemical shift, evaluated in the framework of a single model, narrow the range of possible scenarios, the most plausible of which is monomer incorporation into the growing crystals. In accordance to existing models of crystallization, both the nucleation rates and the crystal growth rates are strongly dependent on the magnitude of supersaturation.

  • 123843. Yusof, H. H. M.
    et al.
    Harun, S. W.
    Dimyati, K.
    Bora, T.
    Sterckx, K.
    Mohammed, W. S.
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Low-Cost Integrated Zinc Oxide Nanorods Based Humidity Sensors for Arduino Platform2019In: IEEE Sensors Journal, ISSN 1530-437X, Vol. 9, no 7, p. 2442-2449Article in journal (Refereed)
    Abstract [en]

    Realization of a simple integrated and low-cost intensity modulation/direct detection-based humidity and vapor detection system utilizing zinc oxide (ZnO) nanorods as the active material is demonstrated. The sensing device comprises of ZnO nanorods optimally grown on a glass substrate and mounted on 3D printed platform for the alignment with a green light-emitting diode setup for an edge excitation. An Arduino platform was used for the signal processing of the detection of the transmitted light. Both forward and backward scattering are affected due to light leakage while propagating through the glass substrate which are further attenuated in the presence of humidity. In this paper, backward scattering was found to be dominant, and thus, with increasing humidity, a reduction in the transmitted light was monitored. When the sensor was tested in a humidity controlled environment, it was found that the output voltage drops by approximately 750 mV upon changing the relative humidity (RH) level from 35% to 90% in a non-linear fashion. The average sensitivity of the sensor was observed to be-12 mV/% throughout the tested RH levels. Sensitivity was found to be higher at-24.6 mV/% for RH's beyond 70%. An average response time of 3.8 s was obtained for RH levels of 85% with respect to the standard ambient humidity conditions (RH 50%), which showed a quicker recovery time of 2.2 s. The proposed sensor device provides numerous advantages, including low-cost production, simplicity in design, ease of use, and stability during handling.

  • 123844.
    Yusof, Haziezol Helmi Mohd
    et al.
    Univ Malaya, Dept Elect Engn, Fac Engn, Kuala Lumpur 50603, Malaysia.;Univ Tekn Malaysia Melaka, Fac Elect & Comp Engn, Melaka 76100, Malaysia..
    Harun, Sulaiman Wadi
    Univ Malaya, Dept Elect Engn, Fac Engn, Kuala Lumpur 50603, Malaysia..
    Dimyati, Kaharudin
    Univ Malaya, Dept Elect Engn, Fac Engn, Kuala Lumpur 50603, Malaysia..
    Bora, Tanujjal
    Asian Inst Technol, Sch Engn & Technol, Nanotechnol, Klongluang 12120, Pathumthani, Thailand..
    Mohammed, Waleed S.
    BU, Sch Engn, CROCCS, Pathum Thani 12120, Thailand..
    Dutta, Joydeep
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Optical dynamic range maximization for humidity sensing by controlling growth of zinc oxide nanorods2018In: PHOTONICS AND NANOSTRUCTURES-FUNDAMENTALS AND APPLICATIONS, ISSN 1569-4410, Vol. 30, p. 57-64Article in journal (Refereed)
    Abstract [en]

    An experimental study of the dynamic range maximization with Zinc Oxide (ZnO) nanorods coated glass substrates for humidity and vapor sensing is reported. Growth time of the nanorods and the length of the coated segments were controlled to study the differences between a reference environmental condition (normal humidity or dry condition) and water vapor concentrations. In order to achieve long dynamic range of detection with respect to nanorods coverage, several substrates with triangular patterns of ZnO nanostructures were fabricated by selective hydrothermal growth over different durations of time (5 h, 10 h and 15 h). It was found that maximum dynamic range for the humidity sensing occurs for the combination parameters of normalized length (Z) of 0.23 and normalized scattering coefficient (zeta) of 0.3. A reduction in transmittance by 38% at humidity levels of 80% with reference point as 50% humidity was observed. The results could be correlated to a first order approximation model that assumes uniform growth and the optimum operating conditions for humidity sensing device. This study provides an option to correlate ZnO growth conditions for different vapor sensing applications which can set a platform for compact sensors where modulation of light intensity is followed. rights reserved.

  • 123845. Yuste, R.
    et al.
    MacLean, J. N.
    Smith, J.
    Lansner, Anders
    KTH, School of Computer Science and Communication (CSC), Computational Biology, CB.
    The cortex as a central pattern generator2005In: Nature Reviews Neuroscience, ISSN 1471-003X, E-ISSN 1471-0048, Vol. 6, no 6, p. 477-483Article, review/survey (Refereed)
    Abstract [en]

    Vertebrate spinal cord and brainstem central pattern generator (CPG) circuits share profound similarities with neocortical circuits. CPGs can produce meaningful functional output in the absence of sensory inputs. Neocortical circuits could be considered analogous to CPGs as they have rich spontaneous dynamics that, similar to CPGs, are powerfully modulated or engaged by sensory inputs, but can also generate output in their absence. We find compelling evidence for this argument at the anatomical, biophysical, developmental, dynamic and pathological levels of analysis. Although it is possible that cortical circuits are particularly plastic types of CPG ('learning CPGs'), we argue that present knowledge about CPGs is likely to foretell the basic principles of the organization and dynamic function of cortical circuits.

  • 123846.
    Yusuf, Filsan
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Brutar, Desirée
    KTH, School of Industrial Engineering and Management (ITM).
    INDUSTRI 4.0 - Vad kan digitalisering av produktionen itillverkande fordonsföretag ge för potentiella fördelar?2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 123847.
    Yusuf Isse, Jamila
    et al.
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    El Ghouch, Chaimae
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Information Theoretic Similarity Measures for Robust Image Matching: Multimodal Imaging - Infrared and Visible light2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract

    This study aimed to investigate the applicability of three different information theoretic similarity measures in image matching, mutual information (MI), cross-cumulative residual entropy (CCRE) and sum of conditional variances (SCV). An experiment was conducted to assess the impact on the performances of the similarity measures when dealing with multimodality, in this case in the context of infrared and visible light. This was achieved by running simulations of four different scenarios using images taken in infrared and visible light, and additionally with variations in amount of details to create different experimental setups. Namely experimental setup A: unimodal data sets with more and less details and experimental setup B: multimodal datasets with more and less details.

    The result showed that the concept of multimodality gives a statistically significant effect on the performances of all similarity measures. Observations were made that the similarity measures performances also, when trying to match images with different amount of details, differed from each other. This provided a basis for judgement on what measure to use as to give as clear and sound results as possible depending on the variation of detail amount in the data. With this study, it was concluded that the similarity measure CCRE gave the most clear and sound results in the context of multimodality concerning infrared and visible light for both cases of more or less details. Even though the other similarity measures performed well in some cases, CCRE would be to recommend as observed by this study.

    Keywords : Image matching, image registration, information theoretic similarity measures, multimodal imaging, similarity measures, MI, CCRE, SCV, infrared, visible light.

  • 123848.
    Yusuf Isse, Muna
    et al.
    KTH, School of Technology and Health (STH).
    Tahar Aissa, Safia
    KTH, School of Technology and Health (STH).
    Ventilering av koldioxid ur kardiotomi-reservoar2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    During heart surgeries it is necessary to direct the blood away from the heart and connect the patient to an extra corporeal circulation (ECC) with an associated reservoir (cardiotomy-reservoir). In the open wound a continuous flow of carbon dioxide is insufflated. This is to de-air the wound so that no air enters the heart and large vessels during surgery. An exchange of gases occurs between the tissue of the wound and the applied carbon dioxide. Throughout the surgery the wound will bleed and that blood will be evacuated in to the cardiotomy-reservoir. This can increase the total carbon dioxide level of the patient.

    The subject that was studied in this report was how to decrease the carbon dioxide levels in the blood. The method used was to fill the cardiotomy-reservoir with chosen volumes of water and simultaneously insufflate carbon dioxide and air. This was to measure the effectiveness of the evacuation of carbon dioxide. The results were that, despite water levels and carbon dioxide supply, one was able to ventilate the reservoir. The conclusion is that the higher air supply that is used the better ventilation will be achieved.

  • 123849.
    Yuwardi, Yuwardi
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Absorption cooling in district heating network: Temperature difference examination in hot water circuit2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Absorption cooling system driven by district heating network is relized as a smart strategy in Sweden. During summer time when the heating demand is low, the excessive hot water can be directly sold to drive absorption chillers instead of decreasing its production. In addition, this is also one answer to satisfy the cooling demand in more environmentally way since currently only around 26% of cooling demand in Sweden is satisfied by district cooling, the rest is fulfilled by individual air conditioning. Realizing this potential, the purpose of this study is to examine the returning hot water temperature in the district heating network with supply temperature of 70°C and also the effect to the absorption chiller’s COP. Through the simulation result, it is found out that the lowest possible returning water temperature is 55 °C at COP 0,69 with heat rejection (re-cooling) temperature water at 22 °C. This implies that the desired returning hot water temperature of 47 °C cannot be achieved. The lower returning hot water temperature is preferable since it gives the district heating network benefit in term of less distribution pump work, and energy recovery for the condensation process at central heating plant. 

  • 123850.
    Yuyu, Bai
    KTH, School of Engineering Sciences (SCI), Physics.
    Numerical Analysis of Local Flow and Heat Transfer Characteristic in a Regular Arranged Pebble Bed Reactor2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
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