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| 2. |
- Bergdahl, Lars, 1943, et al.
(författare)
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Förankringen till en vågenergiboj i Kattegatt
- 1981
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Ingår i: Efaringer fra dagens forankringssystemer og krav til morgendagens. Noges sivilingenjörers forening. ; , s. 18-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Sommaren 1979 genomfördes i sjön Lygnern
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| 3. |
- WINGES, JOHAN, 1987, et al.
(författare)
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System Identification and Tuning of Wireless Power Transfer Systems with Multiple Magnetically Coupled Resonators
- 2018
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Ingår i: Transactions on Environment and Electrical Engineering. - : EEEIC International Publishing. - 2450-5730. ; 2:2, s. 86-92
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Tidskriftsartikel (refereegranskat)abstract
- We present a procedure for system identification and tuning of a wireless power transfer (WPT) system with four magnetically coupled resonators, where each resonator consists of a coil and a capacitor bank. The system-identification procedure involves three main steps: 1) individual measurement of the capacitor banks in the system; 2) measurement of the frequency-dependent two-port impedance matrix of the magnetically coupled resonators; and 3) determining the inductance of all coils and their corresponding coupling coefficients using a Bayesian approach. The Bayesian approach involves solving an optimization problem where we minimize the mismatch between the measured and simulated impedance matrix together with a penalization term that incorporates information from a direct measurement procedure of the inductance and losses of the coils. This identification procedure yields an accurate system model which we use to tune the four capacitance values to recover high system-performance and account for, e.g., manufacturing tolerances and coil displacement. For a prototype WPT system, we achieve 3.3 kW power transfer with 91 % system efficiency over an air-gap distance of approximately 20 cm.
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| 4. |
- Winges, Johan, 1987, et al.
(författare)
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Multi-objective optimization of wireless power transfer systems with magnetically coupled resonators and nonlinear loads
- 2019
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Ingår i: Progress in Electromagnetics Research B. - 1937-6472. ; 83:2019, s. 25-42
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Progress In Electromagnetics Research B. We present an optimization procedure for wireless power transfer (WPT) applications and test it numerically for a WPT system design with four resonant circuits that are magnetically coupled by coaxial coils in air, where the magnetic field problem is represented by a fully populated inductance matrix that includes all magnetic interactions that occur between the coils. The magnetically coupled resonators are fed by a square-wave voltage generator and loaded by a rectifier followed by a smoothing filter and a battery. We compute Pareto fronts associated with a multi-objective optimization problem that contrasts: 1) the system efficiency; and 2) the power delivered to the battery. The optimization problem is constrained in terms of: 1) the physical construction of the system and its components; 2) the root-mean-square values of the currents and voltages in the circuit; and 3) bounds on the overtones of the currents in the coils in order assure that the WPT system mainly generates magnetic fields at the operating frequency. We present optimized results for transfer distances from 0.8 to 1.6 times the largest coil radius with a maximum power transfer from 4 kW to 9 kW at 85 kHz, which is achieved at an efficiency larger than 90%.
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| 5. |
- WINGES, JOHAN, 1987, et al.
(författare)
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System Identification and Tuning of WPT Systems
- 2017
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Ingår i: 2017 IEEE 17th International Conference on Environment and Electrical Engineering (EEEIC).
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Konferensbidrag (refereegranskat)abstract
- We present a procedure for system identificationand tuning of a wireless power transfer (WPT) system withfour magnetically coupled resonators, where each resonator consists of a coil and a capacitor bank. The system-identification procedure involves three main steps: 1) individual measurement of the capacitor banks in the system; 2) measurement of the frequency-dependent two-port impedance matrix of the magnetically coupled resonators; and 3) determining the inductance of all coils and their corresponding coupling coefficients using a Bayesian approach. The Bayesian approach involves solving an optimization problem where we minimize the mismatch between the measured and simulated impedance matrix together with a penalization term that incorporates information from a direct measurement procedure of the inductances and losses of the coils.This identification procedure yields an accurate system model which we use to tune the four capacitance values to recover high system-performance and account for, e.g., manufacturing tolerances and coil displacement. For a prototype WPT system, we achieve 3.3 kW power transfer with 91% system efficiency over an air-gap distance of approximately 20 cm.
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| 7. |
- Nordander, Catarina, et al.
(författare)
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Muscular rest and gap frequency as EMG measures of physical exposure: the impact of work tasks and individual related factors
- 2000
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Ingår i: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 43:11, s. 1904-1919
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Tidskriftsartikel (refereegranskat)abstract
- Owing to an orderly recruitment of motor units, low threshold type I fibres are presumed to be vulnerable in contractions of long duration. To study load on these fibres muscular rest was registered as the time fraction of electromyographic (EMG) activity below a threshold. Moreover, the frequency of periods with muscular rest, EMG gaps, was derived, since a low gap frequency has been shown to be a risk factor for musculoskeletal disorders. Trapezius EMG was registered in 24 female hospital cleaners, 21 female office workers and 13 male office workers during one working day. Cleaners have a high risk of neck/shoulder pain and had much less muscular rest than office workers measured as a percentage of total registered time (median value = 1.5%, range = 0.2-13% vs. median value = 12%, range = 0.0-32%, respectively). Gap frequency showed no difference between the two occupational groups. Both measures displayed a wide inter-individual variation. For the cleaners, some of the variance was explained by body mass index (BMI) and age, with lower values of muscular rest for older subjects with a high BMI. Among the office workers, low values of muscular rest and a high gap frequency were registered in subjects with a low subjective muscular tension tendency. Gender, strength, smoking, job strain, employment time and musculoskeletal symptoms had no impact on either EMG measure.
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| 8. |
- Unge, Jeannette, et al.
(författare)
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Physical workload on neck and upper limb using two CAD applications.
- 2002
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Ingår i: Applied Ergonomics. - 1872-9126. ; 33:1, s. 63-74
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to evaluate (1) the physical workload on neck and upper limb in computer-aided design (CAD) work; (2) the impact of two applications (PROFESSIONAL-CADAM and PRO/Engineering) and (3) two input devices (computer mouse and keyboard), as well as (4) sitting and standing work positions. Fifteen CAD operators were interviewed and examined physically. For nine subjects, the physical workload was measured: electromyography (EMG) of trapezius and forearm extensor muscles, inclinometry of the head, the upper back and upper arms, as well as wrist goniometry. The muscular load was low in CAD work, but the inter-individual variation was considerable. Neither the positions were extreme, nor the movements. The applications, per se, did not have a large impact on the workload, but because of the need for different input devices the effect was strong. Using a keyboard meant higher angular velocities than using a mouse. Hence, when choosing a new software, which requires mainly a mouse as input device, this has to be balanced against the risk of disorders.
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