• Title/Summary/Keyword: Active current density

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Analysis and Design of a New Topology of Soft-Switching Inverters

  • Chen, Rong;Zhang, Jia-Sheng
    • Journal of Power Electronics
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    • v.13 no.1
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    • pp.51-58
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    • 2013
  • This paper proposes the power conversion mechanism of a bailer-charge-transfer zero-current-switching (CT-ZCS) circuit. The operation modes are analyzed and researched using state trajectory equations. The topology of CT-ZCS based on soft-switching inverters offers some merits such as: tracking the input reference signal dynamically, bearing load shock and short circuit, multiplying inverter N+1 redundancy parallel, coordinating power balance for easy control, and soft-switching commutation for high efficiency and large capacity. These advantages are distinctive from conventional inverter topologies and are especially demanded in AC drives: new energy generation and grid, distributed generation systems, switching power amplifier, active power filter, and reactive power compensation and so on. Prototype is manufactured and experiment results show the feasibility and dynamic voltage-tracking characteristics of the topology.

Effect of Moisture on the Current Density for Optimized Cathodic Protection Condition in RC Structures (RC조 구조물의 최적 음극방식 조건 설정을 위한 함수율의 영향에 대한 평가)

  • Park, Dong-Cheon;Cho, Gyu-hwan;Ahn, Jae-Cheol
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2013.05a
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    • pp.29-30
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    • 2013
  • Steel corrosion is the most serious problem in RC structures. Even though patch repair method is normally applied in repair system, the effectiveness is not enough. Cathodic protection in active repair method to deteriorated RC structures. FEM model was developed to simulate the optimized cathodic protection condition. Iro oxidation, hydrogen evolution and oxygen reduction were considered to expect current distribution. Moisture content in concrete which can affect the electrolyte conductivity was used as initial condition.

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Fabrication of High Power Al0.07Ga0.93As Laser Diode Array) (고출력 Al0.07Ga0.93As 레이저 다이오드 어레이 제작)

  • 손노진;박성수;안정작;권오대;계용찬;정지채;최영수;강응철;김재기
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.10
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    • pp.43-50
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    • 1995
  • A laser diode(LD) structure consisting of a single 150\AA Al0.07Ga0.93As quantum well active region operating at λ=809nm, cladded with an AlGaAs graded-index separate confinement heterostructure, has bes been grown by MOCVD. Temperature coefficient of wavelength is approximately 0.2nm C for the diode. The active aperture consists of five emitters separated from each other by means of SiO2 deposition and stripe formation, which creates insulating regions that channel the current to 100-μm-wide stripes placed on 450-μm centers. From a typical uncoated LD, the output power of 0.8W has been obtained at a 1μs, 1kHz pulsed current level of 2.0\AA, which results in about 64% external quantum efficiency. The threshold current density is 736A/cm2 for the case of 500μm cavity length LD's. The measure of an internal quantum efficiency was 75.8% and the internal loss 4.83cm1 . Finally, 3.1W output power has been obtained at a 1μs, 1kHz pulsed current level of 9A from the 500μm-aperture LD array with 460-μm- cavity length.

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Three-Phase Interleaved Isolated High Efficiency Boost Converter (인터리브 방식 삼상 절연형 고효율 부스트 컨버터)

  • Choi, Jung-Wan;Cha, Han-Ju
    • The Transactions of the Korean Institute of Power Electronics
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    • v.14 no.6
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    • pp.496-503
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    • 2009
  • In this paper, a new three-phase interleaved isolated high efficiency boost dc-dc converter with active clamp is proposed. The converter is capable of increased power transfer due to its three-phase power configuration, and it reduces the rms current per phase, thus reducing conduction losses. Further, interleaved operation of three-phase boost converter reduces overall ripple current, which is imposed into fuel cells and realizes smaller sized filter components, increasing effective operating frequency and leading to higher power density. Each output current of three-phase boost converter is combined by the three-phase transformer and flows in the continuous conduction mode by the proposed three-phase PWM strategy. An efficiency of above 96% is mainly achieved by reducing conduction losses and switching losses are reduced by the action of active clamp branches, as well. The proposed converter and three-phase PWM strategy are analyzed, simulated and implemented in hardware. Experimental results are obtained on a 500 W prototype unit, with all of the design verified and analyzed.

Study on the Charging Characteristics of a Sealed Type Ni-Cd Cell (밀폐식 Ni-Cd 전지의 충전특성에 관한 연구)

  • Yung Woo Park;Chai Won Kim;Mu Shik Jhon
    • Journal of the Korean Chemical Society
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    • v.15 no.6
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    • pp.347-352
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    • 1971
  • The variations of the positive and negative electrode potentials, and of internal pressure were measured during the charge of the sealed type Ni-Cd cell. Both polarization characteristics of a paste type Cd-electrode as a gas diffusion electrode in 30% KOH solution and the effects of active carbon electrode as an oxygen consuming auxiliary electrode of the Ni-Cd cell on the charging characteristics of the cell were studied. Peak voltage at the end of charge of the cell is ascribed to the peak at the negative electrode potential, which is due to the concentration polarization by the lack of Cd++ ion and oxygen concentration. And the recovery of the negative electrode potential is resulted from depolarization by the increasing diffusion limiting current density with the increasing oxygen pressure. The active carbon electrode was effective as an oxygen consuming auxiliary electrode. The internal pressure of the cell could be maintained below 200mmHg even at one hour rate charge and overcharge by the use of active carbon electrode as an auxiliary electrode.

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Binder-Free Synthesis of NiCo2S4 Nanowires Grown on Ni Foam as an Efficient Electrocatalyst for Oxygen Evolution Reaction

  • Patil, Komal;Babar, Pravin;Kim, Jin Hyeok
    • Korean Journal of Materials Research
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    • v.30 no.5
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    • pp.217-222
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    • 2020
  • The design and fabrication of catalysts with low-cost and high electrocatalytic activity for the oxygen evolution reaction (OER) have remained challenging because of the sluggish kinetics of this reaction. The key to the pursuit of efficient electrocatalysts is to design them with high surface area and more active sites. In this work, we have successfully synthesized a highly stable and active NiCo2S4 nanowire array on a Ni-foam substrate (NiCo2S4 NW/NF) via a two-step hydrothermal synthesis approach. This NiCo2S4 NW/NF exhibits overpotential as low as 275 mV, delivering a current density of 20 mA cm-2 (versus reversible hydrogen electrode) with a low Tafel slope of 89 mV dec-1 and superior long-term stability for 20 h in 1 M KOH electrolyte. The outstanding performance is ascribed to the inherent activity of the binder-free deposited, vertically aligned nanowire structure, which provides a large number of electrochemically active surface sites, accelerating electron transfer, and simultaneously enhancing the diffusion of electrolyte.

Optical Simulation Study on Indoor Organic Photovoltaics with Textured Electrodes towards Self-powered Photodetector

  • Biswas, Swarup;Kim, Hyeok
    • Journal of Sensor Science and Technology
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    • v.28 no.4
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    • pp.236-239
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    • 2019
  • In this work, we performed an optical simulation study on the performance of a PMDPP3T:PCBM based on an organic photovoltaic (PV) device. The virtual PV device was developed in Lumerical, finite-difference time-domain (FDTD) solutions. Different layers of the PV cell have been defined through the incorporation of complex refractive index value of those layers' constituent materials. During the simulation study, the effect of the variation active layer thickness on an ideal short circuit current density (Jsc,ideal) of the PV cell has been, first, observed. Thereafter, we have investigated the impact of surface roughness of a transparent conducting oxide (TCO) electrode on Jsc,ideal of the PV cells. From this simulation, it has been observed that the Jsc,ideal value of the PV cell is strongly dependent on the thickness of its active layer and the photon absorption of the PV cell has gradually decreased with the increment of the TCO's surface roughness. As a result, the capability of the PV device has been reduced with the increment of the surface roughness of the TCO.

High Efficiency Voltage Balancing Dual Active Bridge Converter for the Bipolar DC Distribution System (양극성 DC 배전 시스템을 위한 고효율 전압 밸런싱 듀얼 액티브 브리지 컨버터)

  • Lee, Minsu;Cheon, Sungmoon;Choi, Dongmin;Moon, Gun-Woo
    • The Transactions of the Korean Institute of Power Electronics
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    • v.27 no.5
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    • pp.391-396
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    • 2022
  • In this study, a new voltage-balancing dual-active bridge converter that integrates a DAB converter with a voltage balancer is proposed for a bipolar DC distribution system. The proposed converter is configured to connect two loads to the transformer secondary center tap of the DAB converter, and no additional components are added. The proposed converter has the same operation as the conventional DAB converter, and it makes both output voltages similar. Moreover, the imbalanced current offset between the two loads is bypassed only on the secondary side of the transformer. Consequently, the proposed converter integrates a voltage balancer without any additional components, and no additional loss occurs in the corresponding components. Thus, high efficiency and high power density can be achieved. The feasibility of the proposed converter is verified using 3 kW prototypes under 380 V input and 190/190 V output conditions.

The Characteristics of Asymmetric Hybrid Supercapacitor Cells and Modules for Power Quality Stabilization (전력품질 안정화용 비대칭 하이브리드 슈퍼커패시터 셀 및 모듈 특성)

  • Lee, Byung-Gwan;Maeng, Ju-Cheul;Lee, Joung-Kyu;Yoon, Jung-Rag
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.4
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    • pp.617-621
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    • 2016
  • In addition to the energy storage facilities based on high power technologies, Electric double layer capacitors(EDLC) are today's candidate for power quality stabilization. However, its low energy density is often inhibiting factor for application of electric power industry. Hybrid supercapacitor is an promising energy storage device that positioned between conventional EDLC and Li-ion battery. This paper describes the preparation and characteristics of a hybrid supercapacitor and module for power quality stabilization. A cylindrical 3200F hybrid supercapacitor (60×74.5mm) was assembled by using the Li4Ti5O12 electrode as an anode and activated carbon as a cathode. It shows 2.5 times higher energy density than conventional EDLC with the same volume. In order to determine the characteristics of the hybrid supercapacitor Module for uninterruptible power supply (UPS), hybrid supercapacitor cells were connected in series with active balancing circuit. At even the high current density of 14A(10C), Module prepared by 18 cells showed the capacitance of 170F at 30~50V, suggesting the applicability for UPS.

Characteristics of direct laser micromachining of IC substrates using a nanosecond UV laser (나노초 UV 레이저 응용 IC 기판 소재 조성별 가공 특성)

  • Sohn, Hyon-Kee;Shin, Dong-Sig;Choi, Ji-Yeon
    • Laser Solutions
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    • v.15 no.3
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    • pp.7-10
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    • 2012
  • Dimensions (line/space) of circuits in IC substrates for high-end chips (e.g. CPU, etc.) are anticipated to decrease as small as 10μm/10μm in 2014. Since current etch-based circuit-patterning processes are not able to address the urgent requirement from industry, laser-based circuit patterning processes are under active research in which UV laser is used to engrave embedded circuits patterns into IC substrates. In this paper, we used a nanosecond UV laser to directly fabricate embedded circuit patterns into IC substrates with/without ceramic powders. In experiments, we engraved embedded circuit patterns with dimensions (width/depth) of abut 10μm/10μm and 6μm/6μm into the IC substrates. Due to the recoil pressure occurring during ablation, the circuit patterning of the IC substrates with ceramic powders showed the higher ablation rate.

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