Search

Wearable device‐based gait data analysis is being used in medical research to prevent and treat serious diseases such as dementia beyond modern health management strategies. For gait‐related data collection and analysis, it is advantageous to place the sensor on the sole of the foot as a foot‐pressure, it is advantageous to use a piezoelectric generator‐based electronic textile (E‐textile) that can supply its own power by converting mechanical energy from the foot into electrical energy. In order to apply E‐textile materials to the sole of the foot, excellent durability, flexibility, and high signal accuracy through noise minimization are required. In this study, a piezoelectric polymer was used to coat the surface of a conductive fiber using the reverse dip coating technique. This method is easily scalable, feasible for large‐scale processing with a continuous process. The electrodes of this process are placed inside a piezoelectric fiber to minimize noise from the electrodes. The inner‐electrode piezoelectric yarn (IEPY) used during the process has excellent tensile strength (maximum stress and strain value: 54.2 MPa, 54%) and strong durability, maintaining its performance over 105 cycles under pushing force of 60 kg and generating excellent piezoelectric output (292 mVmax, 16.2 µW). The IEPY can drive the sensor for gait data, with the sensors being capable of continuous and large‐scale operation and feasible for the manufacturing of custom sensors. [ABSTRACT FROM AUTHOR]

A pulse generator of a one-stage magnetic pulse compression (MPC) modulator, which has an average power of 7.5 kW, was developed. The modulator consists of a constant-current capacitor charger (max. 21.7 kV, 300 Hz), an initial charge capacitor (0.2 [micro]F, 40 kV), a thyratron switch, a pulse transformer with a turn ratio of 1 to 8, ceramic capacitors (2.7 nF, 160 kV), and a magnetic switch. The output voltage, current and the pulsewidth of the modulator were measured to be 85.6 kV, 1.88 kA, and 200 ns (full width half maximum) respectively, with the initial charging voltage of 20 kV. This modulator system can be operated at the maximum repetition rate of 300 Hz and the energy delivery efficiency from the initial charge capacitor to the dummy load is estimated as 55%. The pulse generator is applied to a reactor of pin-to-hole type to investigate the impedance matching between the pulse generator and the reactor, and the experimental results are presented. Index Terms--Impedance matching, N[O.sub.x], pulse generator, reactor.

Introduction. This study aimed to evaluate the effects of resorbable blasting media (RBM) treatment on early stability of orthodontic mini-implants by mechanical, histomorphometric, and histological analyses. Methods. Ninety-six (64 for mechanical study and 32 for histological study and histomorphometric analysis) titanium orthodontic mini-implants (OMIs) with machined (machined group) or RBM-treated (CaP) surface (RBM group) were implanted in the tibiae of 24 rabbits. Maximum initial torque (MIT) was measured during insertion, and maximum removal torque (MRT) and removal angular momentum (RAM) were measured at 2 and 4 weeks after implantation. Bone-to-implant contact (BIC) and bone area (BA) were analyzed at 4 weeks after implantation. Results. RBM group exhibited significantly lower MIT and significantly higher MRT and RAM at 2 weeks than machined group. No significant difference in MRT, RAM, and BIC between the two groups was noted at 4 weeks, although BA was significantly higher in RBM group than in machined group. RBM group showed little bone resorption, whereas machined group showed new bone formation after bone resorption. Conclusions. RBM surface treatment can provide early stability of OMIs around 2 weeks after insertion, whereas stability of machined surface OMIs may decrease in early stages because of bone resorption, although it can subsequently recover by new bone apposition. [ABSTRACT FROM AUTHOR]

This study covers a self-powered wireless communication system that is powered using a piezoelectric energy harvester (PEH) in a shoe. The lead-zirconate-titanate (PZT) ceramic of the PEH was coated with UV resin, which (after curing under UV light) allowed it to withstand periodic pressure. The PEH was designed with a simple structure and placed under the sole of a shoe. The durability of the PEH was tested using a pushing tester and its applicability in shoes was examined. With periodic compression of 60 kg, the PEH produced 52 μW of energy at 280 kΩ. The energy generated by the PEH was used to power a wireless transmitter. A step-down converter with an under-voltage lockout function was used to gather enough energy to operate the wireless transmitter. The transmitter can be operated initially after walking 24 steps. After the transmitter has been activated, it can be operated again after 8 steps. Because a control center receives signals from the transmitter, it is possible to check the status of workers who work outside at night or mostly alone, to detect emergencies. [ABSTRACT FROM AUTHOR]

The purpose of this study is to conduct an economic evaluation of a photovoltaic-energy storage system (PV–ESS system) based on the power generation performance data of photovoltaic operations in Korea, and to calculate the optimal capacity of the energy storage system. In this study, PV systems in Jeju-do and Gyeongsangnam-do were targeted, PV systems in this area were assumed to be installed on a general site, and the research was conducted by applying weights based on the facility's capacity. All the analyses were conducted using the actual amount of Korea power exchange (KPX) transactions of PV systems in 2019. In order to calculate the optimal capacity of the power conditioning system (PCS) and the battery energy storage system (BESS) according to global horizontal irradiation (GHI), PV systems with a minimum/maximum/central value were selected by comparing the solar radiation before the horizontal plane for three years (2017–2019) in the location where the PV systems was installed. As a result of the analysis, in Jeju-do, if the renewable energy certificate(REC) weight decreased to 3.4 when there was no change in the cost of installing a BESS and a PCS, it was more economical to link to the BESS than the operation of the PV system alone. In Gyeongsangnam-do, it was revealed that if the REC weight was reduced to 3.4, it was more likely to link to the BESS than the operation of the PV system alone. [ABSTRACT FROM AUTHOR]

High voltage electric power equipment requires rigorous regulation testing to specific standards which ensure proper and safe operation in the grid. Manufacturers conduct these tests in order to prove standard compliance and product liability. Variable linear or nonlinear loads are necessary for testing medium voltage (MV) high power AC power converters. Generally, those AC power converters or power supplies require performance validation, burn-in and/or lifetime testing under different load conditions, defined by the end-user or standards for the given applications. For flexible and efficient MV verification testing, this paper presents a five-level multilevel converter-based MV regenerative AC electronic load with one-cycle control (OCC), which is based on five-level diode-clamped multilevel converters with back-to-back structure and can emulate any impedance load. In this paper, especially the dc-link capacitor voltage balance of the proposed multilevel MV regenerative AC load is deeply analyzed. Simulation and experimental results are presented to verify the dc-link voltage balance performance of the proposed multilevel MV regenerative AC electronic load. [ABSTRACT FROM AUTHOR]

This paper presents a new multilevel one-cycle control (OCC) technique for a five-level diode-clamped multilevel converter (DCMC)-based static VAR compensator (STATCOM). The OCC algorithm in combination with multi-carrier level-shifted PWM control is used in the proposed five-level DCMC-based STATCOM. The automatic dc link voltage balance is simply realized by four voltage compensators presented as the part of the OCC controller. In this paper the OCC principle of a two-level converter-based STATCOM is reviewed and extended to the five-level DCMC-based STATCOM. The proposed multilevel OCC control method of the five-level DCMC-based STATCOM in steady-state and dynamic operation modes is verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]