kth.sePublications
Change search
Refine search result
6789101112 401 - 450 of 1446
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 401. Gu, B.
    et al.
    Yin, M. J.
    Zhang, A. P.
    Qian, J. W.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Low-cost high-performance fiber-optic pH sensor based on thin-core fiber modal interferometer2009In: Optics Express, E-ISSN 1094-4087, Vol. 17, no 25, p. 22296-22302Article in journal (Refereed)
    Abstract [en]

    A new fiber-optic pH sensor based on a thin-core fiber modal interferometer with electrostatic self-assembled nanocoating is presented. After inserting a segment of thin-core fiber into a standard single-mode fiber, high-order cladding modes are excited and interfere with the core mode to form an in-fiber modal interferometer. The side surface of the sensor is then deposited with poly(allylamine hydrochloride) and poly(acrylic acid) nanocoating by electrostatic self-assembly technique. A fast and linear response is obtained in either acid or alkali solution (in the pH range 2.5 to 10) with resolution of 0.013 pH unit.

  • 402. Gu, Bobo
    et al.
    Yin, Ming-Jie
    Zhang, A. Ping
    Qian, Jin-Wen
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Fiber-optic metal ion sensor based on thin-core fiber modal interferometer with nanocoating self-assembled via hydrogen bonding2011In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 160, no 1, p. 1174-1179Article in journal (Refereed)
    Abstract [en]

    A new fiber-optic metal ion sensor based on a thin-core fiber modal interferometer (TCFMI) is presented. Poly(4-vinylpyridine) (P4VP) and poly(acrylic acid) (PAA) are layer-by-layer deposited on the side surface of the TCFMI via hydrogen bonding for the detection of metal ion in aqueous solutions. Ultraviolet-visible (UV-vis) absorption spectroscopy is employed to monitor the self-assembly process, and the thickness and morphology of the nanocoating are characterized by scanning electron microscopy (SEM). When the sensor is immersed into the aqueous solutions containing metal ions, the refractive index (RI) of the nanocoating is changed because of the association of metal ions with the nanocoating, which was verified by energy dispersive X-ray (EDX). Based on the RI sensing capability of TCFMI, one can detect the concentration of metal ions through the measurement of the dip wavelength of the sensor's transmission spectrum. The experiment results exhibit that the sensor is reusable and with a fast response in a wide metal ion concentration range (10 nM-0.1 M). The limit of detection (LOD) of the sensor is around 9.6 nM experimentally.

  • 403. Guan, Z. G.
    et al.
    Zhang, A. P.
    Jiang, M.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Low-coherence interrogation scheme for multiplexed sensors based on long-period-grating Mach-Zehnder interferometers2006In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 18, no 05-8, p. 832-834Article in journal (Refereed)
  • 404. Guan, Zu-Guang
    et al.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Coherence multiplexing system based on asymmetric mach-zehnder interferometers for Faraday sensors2007In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 21-24, p. 1907-1909Article in journal (Refereed)
  • 405.
    Guan, Zu-Guang
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Zhou, Bin
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Liu, Guorong
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Coherence multiplexing of absorption sensors2007In: IEEE SENSOR, 2007, p. 566-569Conference paper (Refereed)
    Abstract [en]

    The coherence multiplexing of absorption sensors is realized based on a path-scanning Michelson interferometer (MI). The sensing units are designed with different optical path lengths, and the signals from the inline sensing array can be demultiplexed by a path-scanning MI. Intra-cavity absorbance in each unit can be deduced from the corresponding signal and the signals of the previous sensing units.

  • 406. Guan, Zu-Guang
    et al.
    Zhou, Bin
    Liu, Guorong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Quasi-distributed absorption sensing system based on a coherent multiplexing technique2007In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 09-12, p. 792-794Article in journal (Refereed)
  • 407.
    Gunhardson, Johanna
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Investigating the benefit of conditionmeasurements for critical componentsin power transmission systems2013Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis project has been conducted as a collaboration between Svenska Kraftnät and the Royal Institute of Technology.

     

    High demands are being put on all components in a transmission system to be available for operation, making the allowed component down-time the limiting factor in the maintenance budget for Svenska Kraftnät and other transmission system operators. By conducting condition measurements that can be performed on-line, excessive down-times could be avoided in a step towards an as efficient maintenance strategy as possible. The approach of this thesis work has been to perform a case study for a population of transmission grid circuit breakers, creating a model of the CBs’ lifetime which has then been simulated with the aim of studying the benefit of periodic on-line condition measurements for power system components. The main potential benefit examined is the decrease in total downtime for the component population, in relation to the respective components’ criticality. The conclusions of this thesis project are summarized below.

    -Replacing the periodic off-line preventive maintenance with on-line condition measurements for the most critical circuit breakers in a power transmission system, significantly diminishes the weighted overall down-time for all circuit breakers in the system.

    - It is most preferable to use frequent intervals for condition measurements for a large part of the circuit breaker population.

    - A maintenance strategy based on condition measurements is best motivated in cases where the randomness of circuit breaker condition deterioration is high, the failure rate is high, or condition measurements have low uncertainty, and least motivated in cases where the conditions are the opposite.

    - Severe transient effects in average age of the component population may appear in response to any changes in maintenance strategy (or the lack of it), having a harsh impact for power system owners.

    Download full text (pdf)
    fulltext
  • 408. Guo, Changjian
    et al.
    Huang, Lingchen
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Demonstration of 1 Gb/s x 15-User CDM Over WDM-PON Using Electrical Spatial Coding and Subcarrier Multiplexing2011In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 23, no 14, p. 953-955Article in journal (Refereed)
    Abstract [en]

    The downlink transmission of a 1 Gb/s x 15-user code-division multiplexing (CDM) over wavelength-division-multiplexing passive optical network (WDM-PON) based on electrical spatial coding and subcarrier multiplexing is experimentally demonstrated. Two wavelengths with 100-GHz spacing are used to carry the 15 spatial encoded subcarriers generated by an arbitrary waveform generator. Our results show that error-free operation can be achieved after 20-km standard single-mode fiber (SSMF) transmission when 15 simultaneous users are present assuming that forward-error correction coding is used.

  • 409. Guo, Changjian
    et al.
    Nix, Michael
    Yam, Scott S. -H.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Picosecond and Sub-Picosecond Flat-Top Pulse Shaping Using Abrupt Taper Interferometers2010In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 28, no 6, p. 876-881Article in journal (Refereed)
    Abstract [en]

    A picosecond flat-top pulse shaper using an abrupt taper interferometer is proposed and experimentally demonstrated. A theoretical model based on coupled mode equations is also derived to simulate the propagation of picosecond pulses through the abrupt taper interferometer. Through properly designing the abrupt taper interferometer, a 3.8-ps flat-top pulse with less than 4% ripple is successfully generated from a 2.2-ps Gaussian pulse. The proposed technique can also be used in the sub-picosecond regime.

  • 410.
    Guo, Shuwei
    et al.
    JORCEP, Ctr Opt & Electromagnet Res, Zhejiang Prov Key Lab Sensing Technol.
    Sun, Fei
    JORCEP, Ctr Opt & Electromagnet Res, Zhejiang Prov Key Lab Sensing Technol.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. JORCEP, Ctr Opt & Electromagnet Res, Zhejiang Prov Key Lab Sensing Technol.
    Optical surface transformation for reshaping the field intensity distribution2016In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 33, no 9, p. 1847-1851Article in journal (Refereed)
    Abstract [en]

    In this study, we focus on how to reshape the field intensity distribution on the wavefront of an incident beam and produce special optical beams (e.g., asymmetric Gaussian beams, hollow beams, and zeroth-order Bessel beams) using optical surface transformation (OST). The key design method of this paper is based on OST, which is the extension of transformation optics. Numerical simulations are given to verify the performance of the proposed devices.

  • 411.
    Guo, Xinran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Smart grid’s application to projects of Tractebel Engineering France2014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays, we hear much about smart grids as a promising idea that will have a direct

    impact on our life of tomorrow. Research, articles and standards are also numerous on this

    subject. Among them, IEC 61850 is an important standard about communication which could

    have a big influence on electrical substations or even power plants in the future. However, the

    feasibility of this standard has been little investigated.

    This study has been done with Tractebel Engineering France, which is a branch of

    GDF Suez. They have good expertise on hydro power plant, but their projects can also cover

    electrical substations and electrical transmission lines. Smart grid’s development can have

    direct impacts on their activities.

    The study presents firstly the different aspects of smart grid, in order to know the logic

    of motivations and the interesting points for the company. A certain emphasis has been put on

    the electrical gird functioning aspect as well as renewable energies, because they seem to be

    especially important for Tractebel.

    Secondly, the study is focused on the main aim of this article, the feasibility of IEC

    61850 to a substation of Tractebel’s Kaléta project. A presentation and analysis of essential

    notions of the standard 61850 has been done in chapter VII. In the following chapters, the

    study tries to make a judgment of the feasibility by analyzing the aspects of software,

    modeling and practical functioning of the substation.

    The study concludes that despite the fact that IEC 61850 seems to be the standard of

    the future, it is still premature today for Tractebel to use it in the case of Kaléta. Due to the

    independent software tools’ complexity and the lack of interoperability between different

    components, the modeling process remains complicated if we don’t want to choose a software

    program provided by a specific equipment supplier. Moreover, the functioning of an IEC

    61850 substation requires new skills for the staff, which could be another practical problem

    for Kaléta.

    Download full text (pdf)
    fulltext
  • 412. Guo, Zefei
    et al.
    Cai, Fuhong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Optimization For Brain Activity Monitoring With Near Infrared Light In A Four-Layered Model Of The Human Head2013In: Progress In Electromagnetics Research, ISSN 1070-4698, E-ISSN 1559-8985, Vol. 140, p. 277-295Article in journal (Refereed)
    Abstract [en]

    We describe a four-layered model for near infrared light propagation in a human head based on the Monte Carlo method. With the use of three-dimensional voxel-based media discretization, photon migration in the brain is analyzed by both the time-of-flight measurement and the spatial sensitivity profile. In the measurement of brain activity, the selection of light wavelength and the distance between the source and the detector have a great influence on the detected signal. In this study, we compare the detected signals from the detectors with different source-detector spacing at wavelengths of 690 nm, 800 nm and 1300 nm, and find that in our model, the wavelength of 1300 nm is more appropriate for the measurement of brain activity because the signals at 1300 nm get better detection sensitivity and spatial resolution. Source-detector spacing is also optimized.

  • 413. Gustafsson, M.
    et al.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    An overview of stored electromagnetic energy2014In: Proceedings - 2014 International Conference on Electromagnetics in Advanced Applications, ICEAA 2014, 2014, p. 793-795Conference paper (Refereed)
    Abstract [en]

    Although, the stored electromagnetic energy of an antenna is used to determine the antenna Q, it is difficult to define the stored energy. The stored energy can be estimated from the input impedance of the antenna, the electromagnetic fields around the antenna, and the current densities in the antenna structure. These estimates are similar but not equal for all antennas. Here, the different approaches to determine the stored energy are discussed.

  • 414. Gustafsson, M.
    et al.
    Kristensson, G.
    Bernland, A.
    Sjöberg, D.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Physical bounds on the partial realized gain2010Conference paper (Refereed)
    Abstract [en]

    An antenna identity, derived from the forward scattering sum rule, shows that the partial realized gain of an antenna is related to the polarizability of the antenna structure. The partial realized gain contains the mismatch, directivity, efficiency, and polarization properties of the antenna. The antenna identity expresses how the performance depends on the electrical size and shape of the antenna structure. It is also the starting point for several antenna bounds. In this paper, the identity, its associated physical bounds, and computational aspects of the polarizability dyadics are discussed.

  • 415. Gustafsson, Mats
    et al.
    Cismasu, Marius
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Physical Bounds and Optimal Currents on Antennas2012In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 60, no 6, p. 2672-2681Article in journal (Refereed)
    Abstract [en]

    Physical bounds on the directivity Q-factor quotient and optimal current distributions are determined for antennas of arbitrary shape and size using an optimization formulation. A variational approach offers closed form solutions for small antennas expressed in the polarizability of the antenna structure. Finite sized antennas are solved using Lagrangian parameters in a method of moments formulation. It is also shown that the optimal charge density for a small antenna can be generated by several current densities. Numerical examples for small and large antennas are used to illustrate the results.

  • 416. Gustafsson, Mats
    et al.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Antenna Q and Stored Energy Expressed in the Fields, Currents, and Input Impedance2015In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 63, no 1, p. 240-249Article in journal (Refereed)
    Abstract [en]

    Although the stored energy of an antenna is instrumental in the evaluation of antenna Q and the associated physical bounds, it is difficult to strictly define stored energy. Classically, the stored energy is either determined from the input impedance of the antenna or the electromagnetic fields around the antenna. The new energy expressions proposed by Vandenbosch express the stored energy in the current densities in the antenna structure. These expressions are equal to the stored energy defined from the difference between the energy density and the far field energy for many but not all cases. Here, the different approaches to determine the stored energy are compared for dipole, loop, inverted L-antennas, and bow-tie antennas. We use Brune synthesized circuit models to determine the stored energy from the input impedance. We also compare the results with differentiation of the input impedance and the obtained bandwidth. The results indicate that the stored energy in the fields, currents, and circuit models agree well for small antennas. For higher frequencies, the stored energy expressed in the currents agrees with the stored energy determined from Brune synthesized circuit models whereas the stored energy approximated by differentiation of input impedance gives a lower value for some cases. The corresponding results for the bandwidth suggest that the inverse proportionality between the fractional bandwidth and Q-factor depends on the threshold level of the reflection coefficient.

  • 417.
    Gustafsson, Mats
    et al.
    Electrical and information technology, Lund University.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Stored electromagnetic energy and antenna Q2015In: Progress In Electromagnetics Research, ISSN 1070-4698, E-ISSN 1559-8985, Vol. 150, p. 13-27Article in journal (Refereed)
    Abstract [en]

    Decomposition of the electromagnetic energy into its stored and radiated parts is instrumental in the evaluation of antenna Q and the corresponding fundamental limitations on antennas. This decomposition is not unique and there are several proposals in the literature. Here, it is shown that stored energy defined from the difference between the energy density and the far field energy equals the energy expressions proposed by Vandenbosch for many but not all cases. This also explains the observed cases with negative stored energy and suggests a possible remedy to them. The results are compared with the classical explicit expressions for spherical regions where the results only differ by the electrical size ka that is interpreted as the far-field energy in the interior of the sphere.

    Download full text (pdf)
    fulltext
  • 418.
    Haji Miragha, Amirhossein
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Generation Control in Small IsolatedPower Systems2005Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis is concerned with the generation control in small isolated power systems consisting of inverter interfaced generation systems. First the components of an individual distributed generation system (DGS) as well as the corresponding control schemes for active and reactive power flow are discussed and implemented. Then the contribution of multiple DGS to meet the requirement of the loads in both gridconnected and island operations are discussed. Having evaluated the performance of each developed model such as voltage source inverter, PQ and PV controlled as well as reference DGS, the impact of voltage degradation on power load control in isolated systems is analyzed. Finally a new method for generation control in a small power system based on power sharing between multiple DGS with voltage degradation consideration as the last alternative for sustaining the system is proposed and implemented.-11D

    Download full text (pdf)
    fulltext
  • 419. Han, Zhanghua
    et al.
    Forsberg, Erik
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Surface plasmon Bragg gratings formed in metal-insulator-metal waveguides2007In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 02-4, p. 91-93Article in journal (Refereed)
  • 420. Han, Zhanghua
    et al.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Multimode interference effect in plasmonic subwavelength waveguides and an ultra-compact power splitter2007In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 278, no 1, p. 199-203Article in journal (Refereed)
  • 421. Han, Zhanghua
    et al.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Two-dimensional model for three-dimensional index-guided multimode plasmonic waveguides and the design of ultrasmall multimode interference splitters2007In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, no 25, p. 6223-6227Article in journal (Refereed)
  • 422. He, G. S.
    et al.
    Yong, K. T.
    Qin, H. Y.
    Zheng, Q. D.
    Prasad, P. N.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Stimulated Rayleigh-Bragg Scattering From a Two-Photon Absorbing CdSe-CdS-ZnS Quantum-Rods System: Optical Power Limiting and Phase-Conjugation2008In: IEEE Journal of Quantum Electronics, ISSN 0018-9197, E-ISSN 1558-1713, Vol. 44, no 9-10, p. 894-901Article in journal (Refereed)
    Abstract [en]

    This work reports the properties of stimulated Rayleigh-Bragg scattering (SRBS) from a two-photon absorbing CdSe-Cds-ZnS quantum-rods (QRs) solution in chloroform, excited by 1064-nm and similar to 13-ns laser pulses. The two-photon absorbing capability of the scattering medium, as well as the pump threshold, spectral structure, and pulse waveforms of the backward stimulated scattering were measured. Comparing to a pure solvent or an organic dye-solution, the semiconductor QR system has many advantages such as the lower pump threshold, higher energy transfer efficiency, and better photo-physical and photo-chemical stability. The measured output/input characteristic curve shows that the backward SRBS can enhance the optical power limiting performance that is based on two-photon absorption, backward stimulated scattering, and other nonlinear absorption mechanisms. In addition, the backward SRBS beam from our sample medium exhibits a fairly good optical phase-conjugation capability, so that the distortion influence from an inserted aberrator can be automatically removed.

  • 423. He, Guang S.
    et al.
    Qin, Hai-Yan
    Zheng, Qingdong
    Prasad, Paras N.
    Jockusch, Steffen
    Turro, Nicholas J.
    Halim, Marlin
    Sames, Dalibor
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Dynamic properties and optical phase conjugation of two-photon pumped ultrashort blue stimulated emission in a chromophore solution2008In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 77, no 1Article in journal (Refereed)
    Abstract [en]

    The dynamic properties of two-photon pumped blue lasing (similar to 470 nm) in the solution of an organic chromophore [2-acetyl-6-(dimethylamino)naphthalene], excited by similar to 160-fs laser pulses at similar to 775 nm, have been studied. Both the forward and backward stimulated emission are enhanced by feedback from the reflection at the two optical windows of the solution filled cuvette. Under current experimental conditions, the lasing wavelengths in the forward and backward directions were almost the same, but both blueshifted compared to the fluorescence peak wavelength of the sample solution. The temporal behavior of the lasing output was recorded by a high-speed streak camera system. The multipulse structure and spectral properties of the output lasing are semiquantitatively explained. In addition, excellent optical phase-conjugation properties of the backward stimulated emission were observed; the aberration influences from an aberrator on the backward lasing beam were automatically removed.

  • 424. He, J. L.
    et al.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Slow propagation of electromagnetic waves in a dielectric slab waveguide with a left-handed material substrate2006In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 16, no 2, p. 96-98Article in journal (Refereed)
  • 425. He, J. L.
    et al.
    Yi, J.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Giant negative Goos-Hanchen shifts for a photonic crystal with a negative effective index2006In: Optics Express, E-ISSN 1094-4087, Vol. 14, no 7, p. 3024-3029Article in journal (Refereed)
  • 426.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Ao, Xianyu
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Ruan, Zhichao
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Some study of 2D photonic crystals of negative refraction for subwavelength focusing2005In: 2005 IEEE International Workshop on Antenna Technology: Small Antennas Novel MetaMaterials, Proceedings, NEW YORK: IEEE , 2005, p. 29-30Conference paper (Refereed)
  • 427.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Chen, Tuo
    Broadband THz Absorbers With Graphene-Based Anisotropic Metamaterial Films2013In: IEEE Transactions on Terahertz Science and Technology, ISSN 2156-342X, Vol. 3, no 6, p. 757-763Article in journal (Refereed)
    Abstract [en]

    We introduce a broadband THz absorber with an array of graphene-dielectric multilayered frustum pyramids on a metal sheet. The multilayered graphene-dielectric structure can be considered an effectively homogeneous metamaterial with an hyperbolic dispersion and anisotropic permittivity. Surface plasmonic waves are excited on graphene layers and the incident waves of different frequencies are absorbed at different levels of the stacked pyramid, due to the squeezing effect of the slow waves at the tapered waveguide. An absorption dip is observed and explained physically, and finally removed by adding a rectangular portion to the pyramid unit cell. High absorption with an extremely broad bandwidth from 8 THz to over 100 THz is achieved. The absorption spectrum of the present structure can be scaled down to a lower frequency (e.g. 2 THz) by increasing the size of the unit cell.

  • 428.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Cui, Yanxia
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Ye, Yuqian
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Zhang, Pu
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Jin, Yi
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Optical nano-antennas and metamaterials2009In: MATERIALS TODAY, ISSN 1369-7021, Vol. 12, no 12, p. 16-24Article in journal (Refereed)
    Abstract [en]

    We review some recent approaches to transmission enhancement and light harvesting based on optical nano-antennas and metamaterials. Nano-cavity antennas are used to enhance the extraordinary transmission of TM-polarized light through vertical nano-slits in a metal film. The enhanced transmission of TE-polarized waves through an array of subwavelength-slits in a thin metal film at low frequencies (including microwave) is also investigated. Light harvesting with a metamaterial cloaking shell is also demonstrated.

  • 429.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Ding, F.
    Mo, L.
    Bao, F.
    Light absorber with an ultra-broad flat band based on multi-sized slow-wave hyperbolic metamaterial thin-films2014In: Progress In Electromagnetics Research, ISSN 1070-4698, E-ISSN 1559-8985, Vol. 147, p. 69-79Article in journal (Refereed)
    Abstract [en]

    Here we realize a broadband absorber by using a hyperbolic metamaterial composed of alternating aluminum-alumina thin films based on superposition of multiple slow-wave modes. Our super absorber ensures broadband and polarization-insensitive light absorption over almost the entire solar spectrum, near-infrared and short-wavelength infrared regime (500-2500 nm) with a simulated absorption of over 90%. The designed structure is fabricated and the measured results are given. This absorber yields an average measured absorption of 85% in the spectrum ranging from 500nm to 2300 nm. The proposed absorbers open an avenue towards realizing thermal emission and energy- harvesting materials.

  • 430.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Yingran
    Jin, Yi
    Revealing the truth about 'trapped rainbow' storage of light in metamaterials2012In: Scientific Reports, ISSN 2045-2322, Vol. 2, p. 583-Article in journal (Refereed)
    Abstract [en]

    It was claimed that the incident light can be gradually slowed down and finally trapped in a tapered metamaterial waveguide. Here we show that the energy incident from the input port of the tapered metamaterial waveguide will be totally reflected (instead of being trapped) due to the strong intermodal coupling between the forward and backward modes. The underlying physical mechanism for this strong intermodal-coupling is given. The occurrence of energy reflection is unambiguously proved using several independent methods, (1) the semi-analytical mode matching technique, (2) the numerical finite element simulation, (3) the requirement of energy and momentum conservation, and (4) an experimental verification at microwave frequency. The dream of 'trapped rainbow' for storage of light might still be possible if this intermodal coupling could be blocked, and our study provides a useful guidance for such an endeavor.

  • 431.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hu, X.
    He, J.
    Li, J.
    Zou, Y.
    Abnormal guiding and filtering properties for some composite structures of right/left-handed metamaterials2005In: Asia-Pacific Microwave Conference Proceedings, APMC, 2005, Vol. 1Conference paper (Refereed)
    Abstract [en]

    We study some abnormal guiding and filtering properties for some multi-layered structures consisting of right/left-handed metamaterials. The extremely slow propagation of guided waves in a slab waveguide with a left-handed material substrate is studied. Resonating and notch filters based on some composite right/left-handed (CRLH) transmission lines are also proposed.

  • 432.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jin, Y.
    Properties and applications of some permeability-near-zero structures2011In: URSI Gen. Assem. Sci. Symp., URSIGASS, 2011, p. 6050638-Conference paper (Refereed)
    Abstract [en]

    Some of our works on some permeability-near-zero structures will be reviewed. It is shown that when a source is surrounded by a dielectric split ring with a gap opened inside a permeability-near-zero shell the electromagnetic energy generated by the source is forced to propagate through the gap. When the gap is narrow, the energy stream density becomes very large and makes the magnetic field enhanced drastically in the gap. It is also shown that the radiation of a line current can be greatly enhanced by choosing appropriately the dimension of a dielectric domain (inside which the source is located) and the dimension of the permeability-near-zero shell.

  • 433.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jin, Y.
    Ruan, Z. C.
    Kuang, J. G.
    On subwavelength and open resonators involving metamaterials of negative refraction index2005In: New Journal of Physics, E-ISSN 1367-2630, Vol. 7Article in journal (Refereed)
  • 434.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Liao, R.
    Romanov, V.
    Explicit formulas for the identification of a small defect in a planar waveguide2005In: Journal of the Optical Society of America a-Optics Image Science and Vision, ISSN 1084-7529, Vol. 22, no 7, p. 1414-1419Article in journal (Refereed)
  • 435.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Liu, Kexin
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    On the possibility of a perfect power combiner2017In: Progress In Electromagnetics Research, ISSN 1070-4698, E-ISSN 1559-8985, Vol. 158, p. 1-6Article in journal (Refereed)
    Abstract [en]

    By reductio ad absurdum, we show that a perfect power combiner of single-mode waveguides is impossible for incoherent input waves of the same frequency and same polarization as it is against the law of conservation of energy. The inevitable 3 dB loss of a three-port power combiner is explained physically. An incoherent power combiner of nearly 100% efficiency can be realized only if the two input fields have different wavelengths, have different polarizations, or are of orthogonal modes.

  • 436.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ruan, Z. -C
    Completely open cavity realized with photonic crystal wedges2005In: JZUS-A - Journal of Zhejiang University. Science, ISSN 1009-3095, Vol. 6 A, no 5, p. 355-357Article in journal (Refereed)
    Abstract [en]

    A completely open cavity, which is formed by three 60-degree wedges of a photonic crystal with negative effective index, is introduced. Such a realizable design for a completely open cavity (i.e., without any reflective wall in the radial direction) is the first of its kind ever been reported. Due to the negative effective refraction index of the photonic crystal and the high transmission at the photonic crystal/air interfaces, a closed path with zero optical path is formed for the resonance. The present open cavity is very suitable for use as a biosensor as it has large air wedges into which a liquid measurand can flow easily.

  • 437.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Sun, Fei
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Guo, S.
    Zhong, S.
    Lan, L.
    Jiang, W.
    Ma, Y.
    Wu, T.
    Can Maxwell’s fish eye lens really give perfect imaging?: Part III. A careful reconsideration of the “evidence for subwavelength imaging with positive refraction”2015In: Progress In Electromagnetics Research, ISSN 1070-4698, E-ISSN 1559-8985, Vol. 152, p. 1-15Article in journal (Refereed)
    Abstract [en]

    Many scientists do not believe that Maxwell’s fish eye mirror (MFEM) can provide perfect imaging even if there is a drain array around the imaging points. However, one microwave experiment found a case where a 0.2λ resolution could be achieved in an MFEM experiment [1]. In this paper, we show that the MFEM cannot resolve two imaging points at such a subwavelength resolution in most cases even in the presence of a drain array, and an extraordinary case of subwavelength imaging requires a particular phase difference between two coherent sources. Both numerical simulations and experimental results show that the phase difference of two subwavelength-distanced coherent sources greatly influences the field distribution around the drain array. In very few cases (when the phase difference of the two sources is chosen to be a very specific value), we might resolve the image points in the drain array under the assumption that the power absorbed by the scanning cable on the left side of the drain array should be symmetric to that on the right side of the drain array [1]. However, in most cases, we cannot obtain a super-resolution imaging, as other drains around the image points will greatly influence the imaging. We also note that the experiment assumed that the power absorbed by the scanning cable on the left and the right sides of the drain array is symmetric is not correct for the experiment reported in [1], as the drain array itself is not symmetric. The highly non-symmetric distribution of the absorbed power is also verified by our simulation and experimental results. The experimental “result” of resolving two image peaks could potentially be recovered using only a single image peak, which demonstrates the wrong assumption of mirror symmetry. Comparisons and comments on perfect passive drains, “super-resolution” in a spherical geodesic waveguide, and time reverse imaging are also given.

  • 438.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Xiong, Jiang
    Li, Hui
    Jin, Yi
    Patch Antennas Based On a Pair of DPS and SNG Metamaterial2010In: EuCAP 2010 - The 4th European Conference on Antennas and Propagation, 2010Conference paper (Other academic)
    Abstract [en]

    In this talk we show some potential applications of a pair of conventional double positive (DPS) and single negative (SNG) metamaterial blocks for specific patch antennas. We propose two designs. One is a 900- and 1800-MHz dual-band rectangular patch antenna filled with a pair of juxtaposed DPS and mu-negative (MNG) metamaterial blocks. With proper constitutive parameters and filling ratio of the material blocks, the conventional TM(020) mode is modified and broadside radiation pattern can be simultaneously achieved at both bands. The other is a two-layered rectangular patch antenna, with a bilayer of DPS and epsilon-negative (ENG) metamaterial as its substrate. Due to the super-slow TM surface wave mode that the bi-layer structure supports, the size of the patch antenna is substantially reduced as compared to conventional lambda/2 patch antennas.

  • 439.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Ye, Yuqian
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Jin, Yi
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Cui, Yanxia
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Transmission enhancement, perfect absorption and field squeezing with nano-antennas and metamaterials2009In: THEORETICAL AND COMPUTATIONAL NANOPHOTONICS: (TACONA-PHOTONICS 2009) / [ed] Chigrin DN, 2009, Vol. 1176, p. 18-20Conference paper (Refereed)
    Abstract [en]

    We report some of our recent progress in enhancing the extraordinary optical transmission (EOT), perfect absorption and field squeezing. Based on the excitation of surface plasmon waves in optical nano-antennas, the extraordinary transmission of light through a vertical nano-slit in a metal film is realized. Omni-directional, broadband and polarization-insensitive absorption of light is achieved in a thin metamaterial absorber which consists of cross-antennas and a metal ground. A dielectric split ring inside a permeability-near-zero metamaterial is used to squeeze electromagnetic energy and obtain strong magnetic field at the gap without using any resonance mechanism.

  • 440.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Yin, Yuan
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Dai, Daoxin
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Shi, Yaocheng
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wang, Qian
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Some progress in integrated photonics2005In: OPTOELECTRONIC DEVICES AND INTEGRATION, 2005, no PART 1, p. 405-413Conference paper (Refereed)
    Abstract [en]

    A review is presented on some progress we have made recently in planar integrated photonics including arrayed-waveguide gratings (AWGs) and etched diffraction gratings (EDGs), multimode interference (MMI) couplers/splitters, and spot-size converters. Some novel structures and design methods are summarized and presented.

  • 441.
    He, Sailing
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhang, Xizhou
    He, Y.
    Graphene nano-ribbon waveguides of recordsmall mode area and ultra-high effective refractive indices for future VLSI2013In: Optics Express, E-ISSN 1094-4087, Vol. 21, no 25, p. 30664-30673Article in journal (Refereed)
    Abstract [en]

    Electronics circuits keep shrinking in dimensions, as requested by Moore's law. In contrast, photonic waveguides and circuit elements still have lateral dimensions on the order of the wavelength. A key to make photonics have a microelectronics-like development is a drastic reduction of size. To achieve this, we need a low-loss nanoscale waveguide with a drastically reduced mode area and an ultra-high effective refractive index. For this purpose, we propose here several low-loss waveguide structures based on graphene nano-ribbons. An extremely small mode area (∼10-7λ0 2, one order smaller than the smallest mode area of any waveguide that has ever been reported in the literature; here λ0 is the operating wavelength in vacuum) and an extremely large effective refractive index (several hundreds) are achieved. As a device example, a nano-ring cavity of ultrasmall size (with a diameter of ∼10-2λ0) is designed. Our study paves the way for future VLSI (very-large-scale integration) optoelectronics.

  • 442. He, Y.
    et al.
    Shen, J.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    CONSISTENT FORMALISM FOR THE MOMENTUM OF ELECTROMAGNETIC WAVES IN LOSSLESS DISPERSIVE METAMATERIALS AND THE CONSERVATION OF MOMENTUM2011In: PROGRESS IN ELECTROMAGNETICS RESEARCH-PIER, ISSN 1559-8985, Vol. 116, p. 81-106Article in journal (Refereed)
    Abstract [en]

    A new formalism for electromagnetic and mechanical momentum in a metamaterial is developed by means of the technique of wave-packet integrals. The medium has huge mass density and can therefore be regarded as almost stationary upon incident electromagnetic waves. A clear identification of the momentum density and momentum flow, including their electromagnetic and mechanical parts, is obtained by employing this formalism in a lossless dispersive metamaterial (including the cases of impedance matching and mismatching with vacuum). It is found that the ratio of the electromagnetic momentum density to the mechanical momentum density depends on the impedance and group velocity of the electromagnetic wave inside the metamaterial. One of the definite results is that both the electromagnetic momentum and the mechanical momentum in the metamaterial are in the same direction as the energy flow, instead of in the direction of the wave vector. The conservation of total momentum is verified. In addition, the law of energy conservation in the process of normal incidence is also verified by using the wave-packet integral of both the electromagnetic energy density and the mechanical energy density, of which the latter is caused by the interaction between the induced electric/magnetic currents and the electric/magnetic field components of the electromagnetic wave.

  • 443. He, Yingran
    et al.
    Zhou, Hao
    Jin, Yi
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Plasmon induced transparency in a dielectric waveguide2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 4, p. 043113-Article in journal (Refereed)
    Abstract [en]

    A classical effect of electromagnetically induced transparency (EIT) is demonstrated in a dielectric slab waveguide at visible frequencies. Two nano-sized elliptical silver particles are placed inside the waveguide core layer, and their localized plasmonic resonances are utilized to obtain bright and dark states. The destructive interference between the two resonance paths leads to an EIT-like transmission spectrum of the waveguide. The contrast between the transmission peak and dip can be further enhanced by incorporating the Fabry-Perot resonance effect. The influence of Joule loss on the EIT performance is also investigated.

  • 444. He, Z.
    et al.
    Pan, T.
    Liu, H.
    Zhang, Y.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Centre for Optical and Electromagnetic Research, Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China .
    A broadband UHF RFID Tag antenna with a novel T-matching network2014In: Progress in Electromagnetics Research Symposium, ISSN 1559-9450, p. 978-981Article in journal (Refereed)
    Abstract [en]

    In this paper, an-ultra-high frequency (UHF) passive broadband radio frequency identification (RFID) Tag Antenna with a novel T-matching network is presented. By slightly tuned the arm lengths of the T-matching network, the impedance matching between the antenna and the chip and a broad impedance bandwidth is obtained. Thanks to the bent radiating element, the size reduction of the proposed antenna is realized. The bandwidth (S11 < -20 dB) and the corresponding 3 dB PRC bandwidth of the proposed antenna are 133MHz (835-968 MHz) and 88MHz (882-970 MHz) respectively, which means that both bandwidths are wide enough to cover the whole global UHF RFID frequency band. In the simulated results, a smooth and stable gain curve between 0.04 dBi to 1.86 dBi is found throughout the entire operating frequency band, and a gain of 1.38 dBi is obtained at the desired operating frequency point (915 MHz). In conclusion, the designed antenna owns the advantages of low-profile, compact size (56×56mm2), low cost and stable gain. Based on the simple structure, the designed tag antenna can be easily manufacture and widely used in practical applications.

  • 445. Helander, Jakob
    et al.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Sony Mobile Commun AB, Sweden.
    Ying, Zhinong
    Sjöberg, Daniel
    Performance Analysis of Millimeter-Wave Phased Array Antennas in Cellular Handsets2016In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 15, p. 504-507Article in journal (Refereed)
    Abstract [en]

    This letter discusses the usage of high-gain steerable antenna arrays operating at millimeter-wave (mmWave) frequencies for future cellular networks (5G). Based on the probable outline of the 5G networks, a method for characterizing phased array antennas in cellular handsets has been introduced. For analyzing the performance, the total scan pattern of the array configuration together with its respective coverage efficiency are essential to consider in order to compare different antenna designs and topology approaches with each other. Two design approaches and subarray schemes of these have been considered in order to illustrate the relevance of such a characterization method. The results show the importance of evaluating potential array antennas in such manners. The method can be applied to much more complex system models, where polarization diversity, hand and body effect, and statistical modeling of the channel may be included.

  • 446.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Cable Segment Replacement Optimization2014In: Reliability Modeling and Analysis of Smart Power Systems / [ed] Rajesh Karki, Roy Billinton, Ajit Kumar Verma, New Delhi Heidelberg New York Dordrecht London: Springer London, 2014, 1, p. 195-202Chapter in book (Refereed)
  • 447.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Component reliability importance indices for maintenance optimization of electrical networks2005Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Maximum asset performance is one of the major goals for electric power system managers. To reach this goal minimal life cycle cost and maintenance optimization become crucial while meeting demands from customers and regulators. One of the fundamental objectives is therefore to relate maintenance and reliability in an efficiently and effectively way, which is the aim of several maintenance methods such as the Reliability Centered Maintenance method (RCM). Furthermore, this necessitates the determination of the optimal balance between preventive and corrective maintenance to obtain the lowest total cost.

    This thesis proposes methods for defining the importance of individual components in a network with respect to total interruption cost. This is a first step in obtaining an optimal maintenance solution. Since the methods consider several customer nodes simultaneously, they are especially suitable for network structures that serve many purposes/customers e.g. transmission and distribution networks with more than one load point. The major results are three component reliability importance indices, which are applied in two case studies. The first case study is based on a network in the Stockholm area. The second case study is performed for one overhead line system in the rural parts of Kristinehamn. The application studies demonstrate that the indices are possible to implement for existing electrical networks and that they can be used for maintenance prioritization. Consequently these indices constitute a first step in the overall objective of a maintenance optimization method.

    The computations of the indices are performed both with analytical and simulation based techniques. Furthermore, the indices can be used to calculate the component contribution to the total system interruption cost. The approach developed for the importance indices can be utilized in any multi-state network that can be measured with one performance indicator.

    Download full text (pdf)
    FULLTEXT01
  • 448.
    Hilber, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Maintenance optimization for power distribution systems2008Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Maximum asset performance is one of the major goals for electric power distribution system operators (DSOs). To reach this goal minimal life cycle cost and maintenance optimization become crucial while meeting demands from customers and regulators. One of the fundamental objectives is therefore to relate maintenance and reliability in an efficient and effective way. Furthermore, this necessitates the determination of the optimal balance between pre¬ventive and corrective maintenance, which is the main problem addressed in the thesis.

    The balance between preventive and corrective maintenance is approached as a multiobjective optimization problem, with the customer interruption costs on one hand and the maintenance budget of the DSO on the other. Solutions are obtained with meta-heuristics, developed for the specific problem, as well as with an Evolutionary Particle Swarm Optimization algorithm. The methods deliver a Pareto border, a set of several solutions, which the operator can choose between, depending on preferences. The optimization is built on component reliability importance indices, developed specifically for power systems. One vital aspect of the indices is that they work with several supply and load points simultaneously, addressing the multistate-reliability of power systems. For the computation of the indices both analytical and simulation based techniques are used. The indices constitute the connection between component reliability performance and system performance and so enable the maintenance optimization.

    The developed methods have been tested and improved in two case studies, based on real systems and data, proving the methods’ usefulness and showing that they are ready to be applied to power distribution systems. It is in addition noted that the methods could, with some modifications, be applied to other types of infrastructures. However, in order to perform the optimization, a reliability model of the studied power system is required, as well as estimates on effects of maintenance actions (changes in failure rate) and their related costs. Given this, a generally decreased level of total maintenance cost and a better system reliability performance can be given to the DSO and customers respectively. This is achieved by focusing the preventive maintenance to components with a high potential for improvement from system perspective.

    Download full text (pdf)
    FULLTEXT01
  • 449.
    Hilber, Patrik
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bertling, Lina
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Method for Extracting Reliability Importance Indices from Reliability Simulations of Electrical Networks2005In: 15th Power Systems Computation Conference, PSCC 2005, Power Systems Computation Conference ( PSCC ) , 2005Conference paper (Refereed)
    Abstract [en]

    This paper proposes a reliability importance index that is possible to extract from existing reliability simulations at a low additional computational cost. The index utilizes the concept of reliability worth as a measure of system reliability in order to establish the importance of components in systems with several load points. Since the method is based on simulations, it is suitable for large networks with a high level of detail. The index can be used as decision support for asset management, for example where maintenance actions will become most beneficial. The index is evaluated against the background of a number of analytically calculated indices. Furthermore, the index is applied to a network in the Stockholm area. The conclusion of the paper is that the proposed simulation based importance index provides a means of improving analysis of electrical network reliability.

  • 450.
    Hilber, Patrik
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bertling, Lina
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Component Reliability Importance Indices for Electrical Networks2007In: 2007 CONFERENCE PROCEEDINGS IPEC, VOLS 1-3, NEW YORK: IEEE , 2007, p. 257-263Conference paper (Refereed)
    Abstract [en]

    This paper presents three new component reliability importance indices, developed for electrical networks. Component reliability importance indices are useful for prioritization of components as part of a system, especially when considering maintenance activities and/or investment in new equipment. Traditional component reliability importance indices were developed for systems with one input and one output point, which not captures the general function of electrical networks. The proposed indices utilize the concept of reliability worth as a single measure of system reliability in order to establish the importance of the components. This single measure of reliability works over several supply and load points and does for example enable comparisons between components decicated to different load points as well as components from different systems. Furthermore this paper presents data from application studies, which shows on some of the possibilities with the indices. The conclusion of the paper is that the proposed indices provide means of improving analysis of electrical network reliability.

6789101112 401 - 450 of 1446
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf