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Publications (10 of 98) Show all publications
Yang, L., Lu, K., Forsman, M., Lindecrantz, K., Seoane, F., Ekblom, Ö. & Eklund, J. (2019). Evaluation of physiological workload assessment methods using heart rate and accelerometry for a smart wearable system. Ergonomics, 62(5), 694-705
Open this publication in new window or tab >>Evaluation of physiological workload assessment methods using heart rate and accelerometry for a smart wearable system
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2019 (English)In: Ergonomics, ISSN 0014-0139, E-ISSN 1366-5847, Vol. 62, no 5, p. 694-705Article in journal (Refereed) Published
Abstract [en]

Work metabolism (WM) can be accurately estimated by oxygen consumption (VO2), which is commonly assessed by heart rate (HR) in field studies. However, the VO2–HR relationship is influenced by individual capacity and activity characteristics. The purpose of this study was to evaluate three models for estimating WM compared with indirect calorimetry, during simulated work activities. The techniques were: the HR-Flex model; HR branched model, combining HR with hip-worn accelerometers (ACC); and HR + arm-leg ACC model, combining HR with wrist- and thigh-worn ACC. Twelve participants performed five simulated work activities and three submaximal tests. The HR + arm-leg ACC model had the overall best performance with limits of agreement (LoA) of −3.94 and 2.00 mL/min/kg, while the HR-Flex model had −5.01 and 5.36 mL/min/kg and the branched model, −6.71 and 1.52 mL/min/kg. In conclusion, the HR + arm-leg ACC model should, when feasible, be preferred in wearable systems for WM estimation.

Keywords
Heart rate, work metabolism, motion sensing, wearable sensors, risk assessment, estimation models
National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-239148 (URN)10.1080/00140139.2019.1566579 (DOI)000468779800007 ()30806164 (PubMedID)2-s2.0-85062366366 (Scopus ID)
Funder
AFA Insurance, 150039
Note

QC 20190218

Available from: 2018-11-16 Created: 2018-11-16 Last updated: 2019-11-12Bibliographically approved
Vega-Barbas, M., Diaz-Olivares, J. A., Lu, K., Forsman, M., Seoane, F. & Abtahi, F. (2019). P-Ergonomics Platform: Toward Precise, Pervasive, and Personalized Ergonomics using Wearable Sensors and Edge Computing. Sensors, 19(5), Article ID 1225.
Open this publication in new window or tab >>P-Ergonomics Platform: Toward Precise, Pervasive, and Personalized Ergonomics using Wearable Sensors and Edge Computing
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2019 (English)In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 19, no 5, article id 1225Article in journal (Refereed) Published
Abstract [en]

Preventive healthcare has attracted much attention recently. Improving people's lifestyles and promoting a healthy diet and wellbeing are important, but the importance of work-related diseases should not be undermined. Musculoskeletal disorders (MSDs) are among the most common work-related health problems. Ergonomists already assess MSD risk factors and suggest changes in workplaces. However, existing methods are mainly based on visual observations, which have a relatively low reliability and cover only part of the workday. These suggestions concern the overall workplace and the organization of work, but rarely includes individuals' work techniques. In this work, we propose a precise and pervasive ergonomic platform for continuous risk assessment. The system collects data from wearable sensors, which are synchronized and processed by a mobile computing layer, from which exposure statistics and risk assessments may be drawn, and finally, are stored at the server layer for further analyses at both individual and group levels. The platform also enables continuous feedback to the worker to support behavioral changes. The deployed cloud platform in Amazon Web Services instances showed sufficient system flexibility to affordably fulfill requirements of small to medium enterprises, while it is expandable for larger corporations. The system usability scale of 76.6 indicates an acceptable grade of usability.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
disease prevention, occupational healthcare, P-Ergonomics, precision ergonomics, musculoskeletal disorders, smart textiles, wearable sensors, wellbeing at work
National Category
Occupational Health and Environmental Health
Identifiers
urn:nbn:se:kth:diva-249891 (URN)10.3390/s19051225 (DOI)000462540400244 ()30862019 (PubMedID)2-s2.0-85062856566 (Scopus ID)
Available from: 2019-04-26 Created: 2019-04-26 Last updated: 2019-04-26Bibliographically approved
Yang, K., Yuan, S., Zhan, Y., Zheng, L. & Seoane, F. (2018). A flexible artificial synapse for neuromorphic system. In: 2018 IEEE International Conference on Electron Devices and Solid State Circuits (EDSSC): . Paper presented at Conference on Electron Devices and Solid-State Circuits (EDSSC), Shenzhen, China, June 6-8, 2018.. IEEE conference proceedings
Open this publication in new window or tab >>A flexible artificial synapse for neuromorphic system
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2018 (English)In: 2018 IEEE International Conference on Electron Devices and Solid State Circuits (EDSSC), IEEE conference proceedings, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Neuromorphic computing, as a new paradigm, highlighted for its highly parallel, energy efficient features, has attracted a lot of attention. The hardware implementation for a neuromorphic system proposes the strong desire for suitable building blocks. The synaptic device is a very promising solution because of its stimulation-history-related response, which fits the nature of a neural network. In this work, an artificial synapse based on a memristive transistor fabricated by a simple process is realized. The device not only shows multi-level states which is the main feature of a memristor and is essential to hardware implementation neuromorphic system, but also exhibits physical flexibility, a feature that supports wearable and portable electronics. On this basis, a proof-of-feasibility simulation using the experimental data is performed to realize the pattern classification.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2018
Keywords
Flexible, Memristive, Neuromorphic, Synapse
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-235722 (URN)10.1109/EDSSC.2018.8487170 (DOI)2-s2.0-85056316042 (Scopus ID)
Conference
Conference on Electron Devices and Solid-State Circuits (EDSSC), Shenzhen, China, June 6-8, 2018.
Note

QC 20181008

Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2019-10-28Bibliographically approved
Yang, K., Yuan, S., Zhan, Y., Zheng, L. & Seoane, F. (2018). A photoelectrical artificial synapse for novel neuromorphic network. In: 2018 IEEE 18th International Conference on Nanotechnology (IEEE-NANO): . Paper presented at 2018 IEEE 18th International Conference on Nanotechnology (IEEE-NANO), Cork, Ireland,July 23-36, 2018. Institute of Electrical and Electronics Engineers (IEEE), Article ID 8626411.
Open this publication in new window or tab >>A photoelectrical artificial synapse for novel neuromorphic network
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2018 (English)In: 2018 IEEE 18th International Conference on Nanotechnology (IEEE-NANO), Institute of Electrical and Electronics Engineers (IEEE), 2018, article id 8626411Conference paper, Published paper (Refereed)
Abstract [en]

The requirement of information acquisition and processing is growing rapidly. However, existing systems either suffering from inadequate processing ability or from architecture limitations being restricted by the data sensing and transmission process. In this work, a novel photoelectrical artificial synapse is developed to settle down these issues by proposing a new possibility of having a photoelectrical neuromorphic network. The photoelectrical artificial synapse has both light sensing and non-volatile multilevel states making it a suitable candidate as building block in a sensing-processing merged and photoelectrical- enabled neuromorphic system. The device also has physical flexibility to adapt to flexible and wearable systems. This work initiates a new area of novel artificial synapses and neuromorphic networks.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2018
Series
IEEE International Conference on Nanotechnology, ISSN 1944-9399
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-235726 (URN)10.1109/NANO.2018.8626411 (DOI)000458785600189 ()2-s2.0-85062273885 (Scopus ID)9781538653364 (ISBN)
Conference
2018 IEEE 18th International Conference on Nanotechnology (IEEE-NANO), Cork, Ireland,July 23-36, 2018
Note

QC 20181008

Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2019-03-13Bibliographically approved
Yang, K., Yuan, S., Huan, Y., Wang, J., Tu, L., Xu, J., . . . Seoane, F. (2018). Tunable flexible artificial synapses: a new path toward a wearable electronic system. npj Flexible Electronics, 2(20)
Open this publication in new window or tab >>Tunable flexible artificial synapses: a new path toward a wearable electronic system
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2018 (English)In: npj Flexible Electronics, ISSN 2397-4621, Vol. 2, no 20Article in journal, Editorial material (Refereed) Published
Abstract [en]

The flexible electronics has been deemed to be a promising approach to the wearable electronic systems. However, the mismatching between the existing flexible devices and the conventional computing paradigm results an impasse in this field. In this work, a new way to access to this goal is proposed by combining flexible devices and the neuromorphic architecture together. To achieve that, a high-performance flexible artificial synapse is created based on a carefully designed and optimized memristive transistor. The device exhibits high-performance which has near-linear non-volatile resistance change under 10,000 identical pulse signals within the 515% dynamic range, and has the energy consumption as low as 45 fJ per pulse. It also displays multiple synaptic plasticity features, which demonstrates its potential for real-time online learning. Besides, the adaptability by virtue of its three-terminal structure specifically contributes its improved uniformity, repeatability, and reduced power consumption. This work offers a very viable solution for the future wearable computing.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-235721 (URN)10.1038/s41528-018-0033-1 (DOI)
Note

QC 20181129

Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2018-11-29Bibliographically approved
Yang, K., Huan, Y., Xu, J., Zou, Z., Zhan, Y., Zheng, L.-r. & Seoane, F. (2018). Universal and Convenient Optimization Strategies for Three-Terminal Memristors. IEEE Access, 6, 48815-48826, Article ID 8454450.
Open this publication in new window or tab >>Universal and Convenient Optimization Strategies for Three-Terminal Memristors
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2018 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 6, p. 48815-48826, article id 8454450Article in journal (Refereed) Published
Abstract [en]

Neuromorphic computing, i.e., brainlike computing, has attracted a great deal of attention because of its exceptional performance. For the hardware implementation of neuromorphic systems, the desired key building blocks, artificial synapses, have been intensively investigated recently. However, many issues, such as the small state number, low reliability, and high energy consumption, have complicated the path to real applications. Therefore, methods that can improve the performance of the artificial synapses are highly desired. Although different artificial synapses have diverse working mechanisms, universal opti- mization strategies that can be applied to most three-terminal field-effect-transistor-type artificial synapses are proposed in this paper. Instead ofwasting the third terminal in the device structure, the working condition can be effectively tuned by this third terminal. The key parameters, such as the gate electric field intensity and distribution, can be adjusted, and the performance is thereby tuned. In this manner, multiple performance metrics are optimized, such as the current change per pulse (ΔI), the linearity, the uniformity, and the power consumption. The mechanisms behind these strategies are also investigated to strengthen the effectiveness. This paper will push the performance of the current artificial synapses to a new level.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2018
Keywords
Memristors, optimization methods, neuromorphics
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-235715 (URN)10.1109/ACCESS.2018.2866930 (DOI)000445491300001 ()2-s2.0-85052888437 (Scopus ID)
Note

QC 20181129

Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2018-11-29Bibliographically approved
Yang, L., Lu, K., Abtahi, F., Lindecrantz, K., Seoane, F., Forsman, M. & Eklund, J. (2017). A pilot study of using smart clothes for physicalworkload assessment. In: JOY AT WORK: . Paper presented at Conference Proceedings of Nordic Ergonomics Society 49th Annual Conference (pp. 169-170). Lund, Sweden
Open this publication in new window or tab >>A pilot study of using smart clothes for physicalworkload assessment
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2017 (English)In: JOY AT WORK, Lund, Sweden, 2017, p. 169-170Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Lund, Sweden: , 2017
Keywords
Energy expenditure estimation, pulmonary ventilation, heart rate.
National Category
Production Engineering, Human Work Science and Ergonomics
Identifiers
urn:nbn:se:kth:diva-227864 (URN)978-91-7753-152-4 (ISBN)
Conference
Conference Proceedings of Nordic Ergonomics Society 49th Annual Conference
Note

QC 20180614

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-06-14Bibliographically approved
Atefi, S. R., Seoane, F., Kamalian, S., Rosenthal, E., Lev, M. & Bonmassar, G. (2016). Intracranial haemorrhage alters scalp potential distributions in bioimpedance cerebral monitoring applications: preliminary results from FEM simulation on a realistic head model and human subjects. Medical Physics, 43(2), 675-686
Open this publication in new window or tab >>Intracranial haemorrhage alters scalp potential distributions in bioimpedance cerebral monitoring applications: preliminary results from FEM simulation on a realistic head model and human subjects
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2016 (English)In: Medical Physics, ISSN 2473-4209, Vol. 43, no 2, p. 675-686Article in journal (Refereed) Published
Abstract [en]

Purpose: Current diagnostic neuroimaging for detection of intracranial hemorrhage (ICH) is limited to fixed scanners requiring patient transport and extensive infrastructure support. ICH diagnosis would therefore benefit from a portable diagnostic technology, such as electrical bioimpedance (EBI). Through simulations and patient observation, the authors assessed the influence of unilateral ICH hematomas on quasisymmetric scalp potential distributions in order to establish the feasibility of EBI technology as a potential tool for early diagnosis. Methods: Finite element method (FEM) simulations and experimental leftright hemispheric scalp potential differences of healthy and damaged brains were compared with respect to the asymmetry caused by ICH lesions on quasisymmetric scalp potential distributions. In numerical simulations, this asymmetry was measured at 25 kHz and visualized on the scalp as the normalized potential difference between the healthy and ICH damaged models. Proof-of-concept simulations were extended in a pilot study of experimental scalp potential measurements recorded between 0 and 50 kHz with the authors custom-made bioimpedance spectrometer. Mean leftright scalp potential differences recorded from the frontal, central, and parietal brain regions of ten healthy control and six patients suffering from acute/subacute ICH were compared. The observed differences were measured at the 5% level of significance using the two-sample Welch ttest. Results: The 3D-anatomically accurate FEM simulations showed that the normalized scalp potential difference between the damaged and healthy brain models is zero everywhere on the head surface, except in the vicinity of the lesion, where it can vary up to 5%. The authors preliminary experimental results also confirmed that the leftright scalp potential difference in patients with ICH (e.g., 64 mV) is significantly larger than in healthy subjects (e.g., 20.8 mV; P < 0.05). Conclusions: Realistic, proof-of-concept simulations confirmed that ICH affects quasisymmetric scalp potential distributions. Pilot clinical observations with the authors custom-made bioimpedance spectrometer also showed higher leftright potential differences in the presence of ICH, similar to those of their simulations, that may help to distinguish healthy subjects from ICH patients. Although these pilot clinical observations are in agreement with the computer simulations, the small sample size of this study lacks statistical power to exclude the influence of other possible confounders such as age, ex, and electrode positioning. The agreement with previously published simulation-based and clinical results, however, suggests that EBI technology may be potentially useful for ICH detection. © 2016 American Association of Physicists in Medicine.

Place, publisher, year, edition, pages
American Association of Physicists in Medicine, 2016
Keywords
bioimpedance; FEM simulations; intracranial hemorrhage; prehospital triage; scalp equipotential lines
National Category
Medical Engineering
Research subject
Applied Medical Technology
Identifiers
urn:nbn:se:kth:diva-176635 (URN)10.1118/1.4939256 (DOI)000372030000009 ()2-s2.0-84955480861 (Scopus ID)
Note

QC 20170111

Available from: 2015-11-09 Created: 2015-11-09 Last updated: 2017-05-11Bibliographically approved
Wollmann, T., Abtahi, F., Eghdam, A., Seoane, F., Lindecrantz, K., Haag, M. & Koch, S. (2016). User-Centred Design and Usability Evaluation of a Heart Rate Variability Biofeedback Game. IEEE Access, 4, 5531-5539
Open this publication in new window or tab >>User-Centred Design and Usability Evaluation of a Heart Rate Variability Biofeedback Game
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2016 (English)In: IEEE Access, E-ISSN 2169-3536, Vol. 4, p. 5531-5539Article in journal (Refereed) Published
Abstract [en]

Background and objective: Reduced heart rate variability (HRV) is an indicatorof a malfunctioning autonomic nervous system. Resonant frequencybreathing is a potential non-invasive means of intervention for improvingthe balance of the autonomic nervous system and increasing HRV. However,such breathing exercises are regarded as boring and monotonous tasks.The use of gaming elements (gamification) or a full gaming experience is awell-recognised method for achieving higher motivation and engagement invarious tasks. However, there is limited documented knowledge on how todesign a game for breathing exercises. In particular, the influence of additionalinteractive elements on the main course of training has not yet beenexplored. In this study, we evaluated the satisfaction levels achieved usingdifferent game elements and how disruptive they were to the main task, i.e.,paced breathing training.

Methods: An Android flight game was developed with three game modes thatdiffer in the degrees of multitasking they require. Design, development and evaluation were conducted using a user-centred approach, including contextanalysis, the design of game principle mock-ups, the selection of game principlesthrough a survey, the design of the game mechanics and GUI mock-up,icon testing and the performance of a summative study through user questionnairesand interviews. A summative evaluation of the developed gamewas performed with 11 healthy participants (ages 40-67) in a controlled setting.Results: The results confirm the potential of video games for motivatingplayers to engage in HRV biofeedback training. The highest training performanceon the first try was achieved through pure visualisation rather thanin a multitasking mode. Players had higher motivation to play the morechallenging game and were more interested in long-term engagement.Conclusion: A framework for gamified HRV biofeedback research is presented.It has been shown that multitasking has considerable influence onHRV biofeedback and should be used with an adaptive challenge level.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2016
Keywords
Autonomic nervous system;Biofeedback;Bioinformatics;Biological control systems;Games;Heart rate variability;Informatics;Multitasking;Patient rehabilitation;Resonant frequency;Consumer Health Informatics (CHI);Exergaming;Gamification for Health;Heart Rate Variability (HRV) Biofeedback;Patient Motivation;Usability
National Category
Human Computer Interaction Other Medical Engineering
Research subject
Medical Technology; Computer Science
Identifiers
urn:nbn:se:kth:diva-191359 (URN)10.1109/ACCESS.2016.2601882 (DOI)000395469000001 ()2-s2.0-85027047802 (Scopus ID)
Note

QC 20160907

Available from: 2016-08-30 Created: 2016-08-30 Last updated: 2018-09-19Bibliographically approved
Abtahi, F., Lu, K., Guangchao, L., Rödby, K. & Seoane, F. (2015). A Knitted Garment using Intarsia Technique for Heart Rate Variability Biofeedback: Evaluation of Initial Prototype.. In: : . Paper presented at Annual I-Pack KTH-VINNOVA Excellence Center Workshop, 2015.
Open this publication in new window or tab >>A Knitted Garment using Intarsia Technique for Heart Rate Variability Biofeedback: Evaluation of Initial Prototype.
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2015 (English)Conference paper, Poster (with or without abstract) (Other academic)
Keywords
Intarsia, textile-electronic integration
National Category
Medical Engineering Textile, Rubber and Polymeric Materials
Research subject
Människan i vården
Identifiers
urn:nbn:se:kth:diva-181871 (URN)
Conference
Annual I-Pack KTH-VINNOVA Excellence Center Workshop, 2015
Note

QC 20160229

Available from: 2016-02-03 Created: 2016-02-05 Last updated: 2017-08-15Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6995-967X

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