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Frequency modulation control-based wireless power supply (WPS) system adopted for the operating signals of a precharging circuit in solid-state-transformer (SST) is proposed in this article. To guarantee high voltage insulation capability between trolley line and railway vehicle and to decrease the voltage level of railway feeder, a large and heavy main transformer (MTr) operating at 50/60 Hz is conventionally used in railway vehicles. The SST, operating at high frequency for compact size and active control of bidirectional power flow, is an emerging technology in order to substitute a conventional MTr. At initial start of the SST, it is important to slowly charge the capacitor voltages by a precharging circuit connected in series with the trolley line. To operate a precharging circuit in the SST, the proposed WPS system can be utilized for high voltage insulation capability in this article. To transfer operating signals wirelessly through the air, long slim dipole coils for transmitter (Tx) and receiver (Rx) are adopted to fabricate a small size of the whole WPS system. The proposed WPS can be operated at a maximum power efficiency point w.r.t. the wide ranges of the coil distance and load conditions by the proposed frequency modulation control method in the primary side. A 3–30 W prototype of the Tx and Rx coils for the proposed WPS were fabricated and verified by simulation and experiments, showing that 84.0% and 80.2% of high dc–dc efficiencies for PL = 30 and 12 W at dc = 30 mm, respectively. As a result, the proposed control method without communication circuits between Tx and Rx sides has been successfully verified when coil distance and load resistance are widely varied.

This paper proposes a neutral section passing strategy for preventing the inrush current of an electric railway vehicle (ERV) with a solid-state transformer (SST). This inrush current is not generated when the ERV passes the neutral section by maintaining a dc-link voltage at a constant level that is higher than the peak voltage of an electric railway feeder using regenerative energy from the ERV. Depending on the position of the ERV, the control strategies and modes are changed. When the ERV passes the neutral section, the regenerative energy from the ERV charges the dc-link voltage. A dc–ac converter that operates a traction motor takes charge of the dc-link voltage control in the regeneration operation. Simulation results show that the proposed strategy can protect the SST from inrush current when the ERV passes the neutral section. Experiments have been carried out with a scaled-down prototype. Experimental results verify the performance of the proposed neutral section passing strategy.

This article proposes a harmonic voltage injection pulsewidth modulation (PWM) method for a Vienna rectifier with an LCL filter. Existing PWM methods for Vienna rectifiers with full power factor can lead to resonance problems. It generates current oscillation at the resonant frequency. It is analyzed that why the resonance problem occurs in Vienna rectifier with the existing PWM methods. To solve these resonance problems, the proposed method injects a sinusoidal harmonic voltage into the sinusoidal reference voltage. The magnitude and phase of the injection voltage are determined by the power factor of the rectifier-side. Compared to other PWM methods, the proposed PWM method eliminates the possibility of resonant problems. Considering the operation characteristics of the proposed PWM method, this article suggests a design process for an LCL filter. The effectiveness and performance of the proposed PWM method and the design process for an LCL filter are verified by simulation and experiment.

This paper proposes a simple current control method without a grid voltage sensor for a rectifier of traction solid-state transformer. The proposed control scheme estimates the phase angle of grid voltage from the fundamental frequency current of the grid. The extracted phase signal is normalized to generate a sinusoidal current reference by adopting a scaling factor to achieve a unity gain. Since the proposed control method operates without the grid voltage sensor for power factor correction (PFC), it offers a cost-effective solution with a simple implementation structure. However, this method cannot guarantee its control performance under weak grid conditions, where the frequency of grid voltage often varies. Thus, the control parameters of the proposed method are discussed and analyzed to minimize performance degradation. To verify the feasibility of the proposed control method, simulations and experiments are carried out on a 2 kW single-phase PFC converter. The proposed method provides as much control performance as the conventional method, which uses the grid voltage sensor.

This study proposes a second harmonic reduction method for the zero-voltage switching (ZVS) operation of a DC/DC converter in a fuel cell system. In this system, a boost-type DC/DC converter and single-phase inverter are interconnected. Second harmonic oscillations are generated in the DC link that interconnects the DC/DC converter and inverter. The ripple component reduces the input current generated during the ZVS operation. Consequently, the total efficiency of the system is decreased. Stress-induced effects are also experienced by the fuel cell owing to this ripple component, thereby decreasing the life span of the fuel cell. To ameliorate the effects of the second harmonic ripples, a type-II current controller is used in the DC/DC converter to generate an adequate controller gained at the target frequency. The validity of the proposed control method is verified using PSIM simulations and experiments with the use of a fuel cell system rated at 1 kW.

Organic semiconductor materials for fabricating organic light emitting diodes (OLEDs) have attracted significant attention in the field of novel optical and optoelectronic devices. Particulation of OLEDs’ emitting materials in small-scale has been limited only to tris(8-hydroxyquinoline) aluminum (Alq3) that emits green-light. In this study, we attempted to fabricate, for the first time, red-light emitting nanoparticles of phosphorescent organic semiconductor of bis(1-phenylisoquinoline) (acetylacetonate) iridium (Ir(piq)2(acac)). Rectangular particles with length and thickness of ∼2 μm and ∼50 nm were fabricated with guidance of cetyltrimethylammonium bromide (CTAB) and micro-plates with length and thickness of ∼5 μm and ∼100 nm were fabricated by sodium dodecyl sulfate (SDS). By contrast, single-stranded DNA (ssDNA) induced nano-rods with dimension of ∼400 nm in length and 100 nm in thickness. Hence, the choice of guiding agents resulted in distinctive crystal characteristic so that the nanorods by ssDNAs showed UV absorption with a red-shift in metal-ligand charge transfer (MLCT) by 54 nm whereas the particles by surfactants did 35 nm compared to the dissolved precursor. Higher was the ssDNA-guided nanorods in relative phosphorescence of the intensity at 610 nm over that at 695 nm than the surfactant-guided particles.

This article suggests a cascade output voltage regulation algorithm for an N-phase interleaved DC/DC boost converter based on reference dynamics. The proposed algorithm has two advantages. The first is to guarantee the performance recovery property using the reference dynamics in the presence of a model-plant mismatch, and the second is to present a systematic procedure determining the stabilising control gains by solving an optimisation problem. The closed-loop performance of the proposed method is evaluated through simulations and experiments using a 3-kW four-phase interleaved DC/DC boost converter where the proposed method is compared with the feedback linearising method.

Hydrogel-based sensory structures were developed by embedding polydiacetylene supramolecules into poly-(ethylene glycol)-diacrylate (PEG-DA) to detect chemical gases and cyclodextrin and to determine pH values on the basis of a fluorescence change. We found the optimal condition for patterning-fabrication by controlling the volumetric mixture ratio of the water-soluble PEG-DA and aqueous polydiacetylene vesicle solution. Then, we determined that this hydrogel-based polydiacetylene structure optically responded selectively against vapor-phase targets: ammonia, ethanol, and aldehyde; aqueous solutions with various pH values; and cyclodextrin derivatives. These results could be extended to various label-free sensing applications of hydrogel-based chemo-biosensors.

This paper proposes a model-based optimal control algorithm for the clamp switch of a zero-voltage switching (ZVS) bidirectional DC–DC converter. The bidirectional DC–DC converter (BDC) can accomplish the ZVS operation using the clamp switch. The minimum current for the ZVS operation is maintained, and the inductor current is separated from the input and output voltages by the clamp switch in this topology. The clamp switch can decrease the inductor current ripple, switching loss, and conduction loss of the system. Therefore, the optimal control of the clamp switch is significant to improve the efficiency of the system. This paper proposes a model-based optimal control algorithm using phase shift in a micro-controller unit. The proposed control algorithm is demonstrated by the results of PSIM simulations and an experiment conducted in a 1-kW ZVS BDC system.

A new polydiacetylene lipid/human olfactory receptor nano-assembly was fabricated for the visual detection of an odorant for the first time. The assembly consisted of phospholipid-mixed polydiacetylenes (PDAs) and human olfactory receptors (hORs) in detergent micelles. To overcome the limitations of bioelectronic noses, hOR-embedded chromatic complexes (PDA/hORs) were developed, introducing PDAs that showed color and fluorescence transitions against various stimuli. The chromatic nanocomplexes reacted with target molecules, showing a fluorescence intensity increase in a dose-dependent manner and target selectivity among various odorants. As a result, a color transition of the assembly from blue to purple occurred, allowing the visual detection of the odorant geraniol. Through circular dichroism (CD) spectroscopy and a tryptophan fluorescence quenching method, the structural and functional properties of the hORs embedded in the complexes were confirmed. Based on this first work, future array devices, integrating multiple nano-assemblies, can be substantiated and utilized in environmental assessment and analysis of food quality.

Polydiacetylenic complex films were prepared using 10,12-pentacosadiynoic acid (PCDA) and para-xylenediamine (pXDA) upon acid-base interactions. The thermochromatic reversibility of the complex films was modulated by changing the mixed molar ratio (3 : 1, 2 : 1, and 1 : 1) of the two molecules. The corresponding conformational changes of the complex films were studied by ex situ FTIR analysis upon thermal stimulation for the first time. In addition, the binding specificities of α-, β-, and γ-cyclodextrins (CDs) with the films were studied, where the α-CDs can induce stronger red fluorescent emission of the films. These fundamental results may be useful for platforms that use these polydiacetylenic complex films as optoelectronic devices or chemical/biological sensors.

This paper proposes a predictive control algorithm that includes conduction-mode detection for power factor correction (PFC) converter. In PFC converters, the line current is usually distorted because of the characteristics of the proportional-integral (PI) current controller. To improve the quality of the current, the PI current controller requires additional circuits or algorithms. However, because of the optimal duty cycle determined by estimating the next-state current in both the continuous-conduction mode and the discontinuous-conduction mode, the proposed predictive control method has a fast dynamic response and accuracy compared to the PI current-control method. Moreover, the proposed algorithm can detect the conduction mode without any additional circuitry or mode-detection algorithm using the characteristic of the optimal duty cycle calculated by the predictive control. These advantages of the proposed algorithm improve the quality of the line current for PFC converters. We verify the proposed method by performing experiment using a 1.5-kW PFC converter.

DNA strands have been recently found to play a role in crystallizing organic semiconductors as a substitute for conventional surfactants. Such DNA-guided organic semiconductor particles possessed the recognition ability to complementary target DNAs, resulting in “enhanced luminescence” due to the lesser degree of non-radiative dissipation. Apart from this, in this study we developed selective recognition of mercury ions by utilizing DNA probes having ion-specific thymine-rich motifs. Strikingly, the specific ion–DNA interaction triggered rather distinctive “depressed luminescence” emitting from the particles. The mercury ions were found to be present both at the surface and the inner regions, which were discovered to relate to the drastic morphological distortion of the particles as evidenced by elemental, electron microscopy, and confocal fluorescence microscopy analyses. This novel phenomenon discovered would expand the technological values of organic semiconductors conjugated with oligonucleotides toward a wider range of target-specific applications.

This paper proposes current ripple reduction algorithm for zero voltage switching (ZVS) operation of boost-type DC/DC converter. Fuel-cell system in this paper, DC-DC converter and single-phase inverter are connected. The DC-link voltage contains the second harmonics when the converter interconnected to the single-phase inverter. This AC ripple component makes some defects to the system. The inductor current leaves the ZVS operation region, thus the hard switching of the converter reduces the efficiency of the system. Moreover, this ripple component also makes the stress to the fuel-cell, thus a life time of the fuel-cell is decreased. This paper proposes a current ripple reduction control for ZVS operation of a fuel-cell system. In this paper, the higher type controller with a fast dynamic response is applied to the boost converter. The validity of the proposed control algorithm and the improvement of efficiency of the converter are verified by PSIM simulations with a 1-kW DC-DC converter system.

This paper proposes a model predictive control (MPC) using subdivided voltage vectors for current ripple reduction in an indirect matrix converter (IMC). In the proposed MPC, the number of candidate voltage vectors is increased by the subdivided voltage vectors. It is possible to reduce the input–output current ripple of the IMC. In addition, the proposed MPC reduces computation load, which is caused by the subdivided voltage vectors, by estimating the position of reference voltage vector. Therefore, the input–output current ripple of the IMC is reduced by the proposed MPC without computational burden. The effectiveness of the proposed MPC is verified by simulation results.

This paper presents a cascade output voltage control strategy for an uncertain DC/DC boost converter adopting an adaptive current controller in its inner loop. Considering the non-linearity, load uncertainties and parameter uncertainties of the converter, the proposed controller is designed following the conventional cascade voltage controller design method. The proposed method makes the following three contributions. First, a coordinate transformation is introduced for the inner loop, enabling avoidance of the singularity problem caused by the estimates of uncertain parameters. Second, a slight modification to the adaptation law is performed to guarantee closed-loop stability in the presence of the time-varying component of the load current. Third, the outer-loop controller is devised such that its performance can be adjusted without any parameter information. The closed-loop performance is demonstrated through simulations and experiments using the DSP28335 with a 3 kW DC/DC boost converter.

This paper presents a scheme to improve the line current distortion of power factor corrector (PFC) topology at the zero crossing point using a predictive control algorithm in both the continuous conduction mode (CCM) and discontinuous conduction mode (DCM). The line current in single-phase PFC topology is distorted at the zero crossing point of the input AC voltage because of the characteristic of the general proportional integral (PI) current controller. This distortion degrades the line current quality, such as the total harmonic distortion (THD) and the power factor (PF). Given the optimal duty cycle calculated by estimating the next state current in both the CCM and DCM, the proposed predictive control algorithm has a fast dynamic response and accuracy unlike the conventional PI current control method. These advantages of the proposed algorithm lower the line current distortion of PFC topology. The proposed method is verified through PSIM simulations and experimental results with 1.5 kW bridgeless PFC (BLPFC) topology.

This paper proposes the DC offset compensation algorithm with fast response to the sensed grid voltage in the single-phase grid connected inverter. If the sensor of the grid voltage has problems, the DC offset of the grid voltage can be generated. This error must be resolved because the DC offset can generate the estimated grid frequency error of the phase-locked loop (PLL). In conventional algorithm to compensate the DC offset, the DC offset is estimated by integrating the synchronous reference frame d-axis voltage during one period of the grid voltage. The conventional algorithm has a drawback that is a slow dynamic response because monitoring the one period of the grid voltage is required. the proposed algorithm has fast dynamic response because the DC offset is consecutively estimated by transforming the d-axis voltage to synchronous reference frame without monitoring one cycle time of the grid voltage. The proposed algorithm is verified from PSIM simulation and the experiment.

Previous robot-mediated gait training has been proven several limitations such as pointless repeated motion training, decreased presence, etc. In this research, adult stroke patients were participated in robot-mediated gait training accompanied with virtual reality program. The results indicated virtual reality system could contribute to muscle strength and balance ability.

This paper proposes a two-stage bidirectional DC/DC converter for vehicle-to-grid (V2G). The two-stage converter is composed of the isolated CLLC bidirectional resonant converter and the non-isolated bidirectional converter. The CLLC converter has the symmetric resonant tank and is operated in the high-frequency which can reduce the volume of the transformer. The purpose of this converter is high-frequency isolation without control. The converter is operated in the resonant frequency and the gain is maintained to unity. The non-isolated converter performs the charging and discharging control. This converter has half-bridge structure which has problem in regard of the serious voltage stress of the switches by the hard-switching. To reduce the power loss and achieve the high efficiency, SiC-MOSFET is used in both converters. The proposed two-stage bidirectional converter is verified from PSIM simulation with 15-kW bidirectional DC/DC converter.

Gore Bio-A has been reported to be an ideal synthetic bioabsorbable scaffold material for hernia repair. The purpose of this study was to determine the effectiveness of Gore Bio-A in soft tissue augmentation. Six New Zealand white rabbits were used in the study. Five subcutaneous pockets were created on the back of the rabbit, and20×20 mm sized square shaped Gore Bio-A sheets, each 1.5 mm, 3 mm, 4.5 mm, 6 mm, and 7.5 mm in thickness, were implanted into each pocket (1 layer to 5 layers). To analyze the morphologic and histologic changes, the implants were harvested 1, 3, and 6 months after implantation. Following the gross analysis, absorption rate was accelerated with increased implant duration and decreased thickness. Histological analysis of the implants demonstrated progressive neovascularization, fibroblast infiltration, and neocollagenation over time. Six months after implantation, Gore Bio-A was almost absorbed and degenerated, not maintaining its volume. Based on this study, Gore Bio-A was revealed as a biocompatible material; however, it is not suitable for soft tissue augmentation because it is absorbed in the process of changing into soft tissue without maintaining its own volume. Therefore, this material is incomplete and needs more study to overcome this limitation.

This paper proposes an output current ripple reduction algorithm using a proportional-integral (PI) controller for an energy storage system (ESS). In single-phase systems, the DC/AC inverter has a second-order harmonic at twice the grid frequency of a DC-link voltage caused by pulsation of the DC-link voltage. The output current of a DC/DC converter has a ripple component because of the ripple of the DC-link voltage. The second-order harmonic adversely affects the battery lifetime. The proposed algorithm has an advantage of reducing the second-order harmonic of the output current in the variable frequency system. The proposed algorithm is verified from the PSIM simulation and experiment with the 3 kW ESS model.

This paper proposes a carrier-based pulse width modulation (CB-PWM) method with synchronous switching technique for a Vienna rectifier. In this paper, a Vienna rectifier is one of the 3-level converter topologies. It is similar to a 3-level T-type topology the used back-to-back switches. When CB-PWM switching method is used, a Vienna rectifier is operated with six PWM signals. On the other hand, when the back-to-back switches are synchronized, PWM signals can be reduced to three from six. However, the synchronous switching method has a problem that the current distortion around zero-crossing point is worse than one of the conventional CB-PWM switching method. To improve current distortions, this paper proposes a reactive current injection technique. The performance and effectiveness of the proposed synchronous switching method are verified by simulation with a 5-kW Vienna rectifier.

This paper proposes zero voltage switching (ZVS) bi-directional DC-DC converter with auxiliary circuit. The conventional DC-DC converter has the problem which is switching loss by the hard switching. The proposed ZVS bi-directional DC-DC converter uses the soft switching with an additional circuit to decrease the switching loss. The additional circuit is made up the resonant inductor and back-to-back switch. It is possible to operate ZVS of all switches through the stored energy in resonant inductor of the auxiliary circuit. Therefore, the efficiency of whole system can be improved. The proposed topology is verified from PSIM simulations using 3-kW ZVS bi-directional DC-DC converter.

This paper proposes a control scheme for the wide operation range of an induction generator (IG) with a Vienna rectifier. A Vienna rectifier has the limited operation range because the sign of the current should be the same as that of the voltage in the normal operation. For this reason, the power factor of a Vienna rectifier is also limited. In the IG, the d-axis stator current is necessary for the self-excitation of the IG. Usually, the d-axis stator current is controlled to the rated d-axis current, which means that IG can operate in the low power factor. Therefore, the operation range of the IG with a Vienna rectifier is narrow. The proposed control method adjusts the d-axis current appropriately to extend the operation range and to include the operating power factor in the feasible operation range of a Vienna rectifier. The analysis results of the proposed method are verified from PSIM simulations with a 150-kW IG system using a Vienna rectifier.

This paper proposes an optimal control method of clamp switch for ZVS bi-directional DC-DC converter. The bidirectional DC-DC converter using the clamp switch can achieve zero voltage switching (ZVS) operation. In this topology, the clamp switch separates the inductor current from input and output voltage and maintains minimum current for ZVS operation. The separation of the inductor current can reduce the inductor current ripple and the power loss of the power devices. Therefore, it is important to the optimal control method of clamp switch to improve the system efficiency. This paper proposes the optimal clamp switch control method using micro controller unit (MCU) without the additional circuit. The proposed control is verified from PSIM simulations using 1-kW ZVS bi-directional DC-DC converter system.

Conventional single-phase Vienna rectifiers employ proportional-integral (PI) controllers which are appropriate for controlling DC components, to regulate their line currents. However, in the regions close to the line current’s zero-crossing point, the dynamics of PI controllers are too slow to respond to the reference current, which has an AC component. Hence, the power factor (PF) of the device is degenerated, and total harmonic distortion (THD) increases. A controller with a fast dynamic response is thus required to solve this problem. In this paper, we investigate the use of a model-based predictive controller (MPC), which has a faster dynamic response than a PI controller, to improve the line current quality of a single-phase Vienna rectifier. With this method, the average current in both the continuous current mode (CCM) and the discontinuous current mode (DCM) of operation are controlled using a mode detection method. Moreover, we calculate the optimized duty cycle for the single-phase Vienna rectifier, by predicting the next current state. We verify the operation of the proposed algorithm using a PSIM simulation, and a practical experiment conducted with a 1-kW-rated single-phase Vienna rectifier prototype. With the proposed method, the quality of the line current near the zero-crossing point is improved, and the PF is controlled to unity.

This paper proposes an improved discontinuous PWM (DPWM) method in a grid-connected inverter system. When the conventional 60° DPWM is used in the switching method, the output voltage of the inverter has many harmonics compared to the continuous PWM (CPWM) switching method. In large-scale system, a LCL-filter cannot sufficiency reduce the harmonics of the inverter output voltage. If these harmonics and the resonance frequency band caused by a grid-connected LCL-filter are overlapped, the grid current oscillates. To solve this problem, the proposed method continuously changes the discontinuous modulation signal by injecting triangular wave to modulation signal. The proposed algorithm can reduce the harmonics of inverter output voltage. The proposed DPWM is verified from PSIM simulation with a 600-kW 2-level grid-connected inverter system.

In this study, the effects of Polygala tenuifolia root extract on brain ischemia/reperfusion injury in Mongolian gerbils were investigated. The gerbils were administered ethanol extract of P. tenuifolia and its four sub-fractions orally 2 hours prior to ischemia, and were subjected to a 20-minute no-flow cerebral ischemia in vivo. Thirty minutes and 72 hours after reperfusion, the brain was removed and the ATP, lactate and lipid peroxide levels were determined, and the neurons in the hippocampal CA1 subfield were examined. In the vehicle-treated ischemic gerbils, the brain ATP levels decreased significantly, but this decrease was prevented by pre-treatment with an n-butanol fraction of P. tenuifolia. In contrast, both the lactate content and lipid peroxidation levels were elevated in the vehicle-treated ischemic animals, but this elevation was inhibited by ethanol extract and n-butanol fraction of P. tenuifolia, respectively. Both the ethanol extract and n-butanol fraction of P. tenuifolia attenuated post-ischemic neuronal necrosis in the hippocampal CA1 subfield. Our findings suggest that both ethanol extract and n-butanol fraction of P. tenuifolia root can reduce brain damage during ischemia and reperfusion, and prevent lipid peroxidation and preserve the energy metabolism.

This paper proposes discontinuous pulse width modulation (DPWM) for a grid-connected inverter system using an LCL-filter which consists of two inductors and a capacitor that is connected in parallel per phase. The modulation signal is discontinuously changed, and the harmonic voltages are generated in the wide frequency range at the output terminal of the inverter when the conventional DPWM is used. If these harmonic voltages are present in the resonance frequency band by an LCL-filter, then the resonance problem of the grid current occurs. To suppress the resonance problem, the proposed DPWM injects the sixth harmonic to the modulation signal. Therefore, in the improved DPWM, harmonic voltages at the output terminal of the inverter are sufficiently reduced because the discontinuous change of the modulation signal disappears. The proposed DPWM method is verified by a Powersim (PSIM) simulation (Powersim Inc., Rockville, MD, USA) and experiments with a 3-kW neutral-point clamped (NPC)-type grid-connected inverter system.

This paper proposes an output current ripple reduction algorithm using model-based predictive control (MPC) for an energy storage system (ESS). In single-phase systems, the DC/AC inverter has a second-order harmonic at twice the grid frequency of a DC-link voltage caused by pulsation of the DC-link voltage. The output current of a DC/DC converter has a ripple component because of the ripple of the DC-link voltage. The second-order harmonic adversely affects the battery lifetime. The MPC predicts the output current of next state from a converter model. The optimal duty is determined by minimizing the error between the reference and the predicted current. Due to the calculated optimal duty, the dynamic response is fast. The proposed algorithm has an advantage of reducing the second-order harmonic of the output current in the variable frequency system. The proposed algorithm is verified from the PSIM simulation with the 3 kW ESS model.