• 전자공학회논문지A
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• 제31A권8호
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• pp.46-52
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• 1994

DC and AC current crowding effects for microwave and high speed bipolar transistors are investigated in detail using a new and accurate measurement technique based on Z-parameter equationa. Using the new measurement technique dc and ac current crowding effects have been explained clearly in bipolar junction transistors. To model ac crowding effects a capacitive element defined as base capacitance (C$_b$), called ac crowding capacitance is added to base resistance in parallel thereby treating the base resistance(R$_b$) as base impedance Z$_b$. It is shown that base resistance decreases with increasing collector current due to dc current crowding and approaches to a certain limited value at high collector current due to current crowding and approaches to a certain limited value at high collector currents regardless of the emitter size. It is also observed that due to ac current crowding base capacitance increases with increasing collector current. To quantigy the ac crowding effects for SPICE circuit simulation the base capacitance(C$_b$) including the base depletion and diffusion components has been modeled with an analytical expression form.

• 대한전자공학회논문지SD
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• 제41권8호
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• pp.17-24
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• 2004

Density-gradient 방법을 이용하여 게이트의 양자효과가 double-gate MOSFET의 단채널 효과에 미치는 영향을 2차원으로 분석하였다. 게이트와 sidewall 산화막 경계면에서 발생하는 2차원 양자공핍 현상에 의하여 게이트 코너에 큰 전하 다이폴이 형성되며 subthreshold 영역에서 다이폴의 크기가 증가하고 classical 결과에 비하여 전자 농도와 전압 분포가 매우 다름을 알 수 있었다. Evanescent-nude분석을 통하여 게이트의 양자효과가 소자의 단채널 효과를 증가시키며 이는 기판에서의 양자효과에 의한 영향보다 크다는 것을 확인하였다. 양자효과에 의하여 게이트 코너에 형성되는 전하 다이폴이 단채널 효과를 증가시키는 원인임을 밝혔다.

• Journal of Power Electronics
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• 제13권3호
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• pp.390-399
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• 2013

As a result of the depletion of fossil fuels and environmental contamination, it has become important to use renewable energy. For the stable utilization of renewable energy sources, energy storage devices must be used. In addition, renewable and distributed power sources with energy storage devices must operate stably under grid-connected mode. This paper proposed dynamic response modeling for renewable power generation systems including a charger/discharger with an energy storage device in order to derive a method to guarantee stable operation while fully utilizing the energy from the energy storage device. In this paper, the principle operation and design guidelines of the proposed scheme are presented, along with a performance analysis and simulation results using MATLAB and PSIM. Finally, a hardware prototype of a 1kW power conditioning system with an energy storage device has been implemented for experimental verification of the proposed converter system.

• 센서학회지
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• 제24권5호
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• pp.353-357
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• 2015

A new SPICE-compatible model for a gate/body-tied PMOSFET photodetector (GBT PD) with an overlapping control gate is presented. The proposed SPICE-compatible model of a GBT PD with an overlapping control gate makes it possible to control the photocurrent. Research into GBT PD modeling was proposed previously. However, the analysis and simulation of GBT PDs is not lacking. This SPICE model concurs with the measurement results, and it is simpler than previous models. The general GBT PD model is a hybrid device composed of a MOSFET, a lateral bipolar junction transistor (BJT), and a vertical BJT. Conventional SPICE models are based on complete depletion approximation, which is more applicable to reverse-biased p-n junctions; therefore, they are not appropriate for simulating circuits that are implemented with a GBT PD with an overlapping control gate. The GBT PD with an overlapping control gate can control the sensitivity of the photodetector. The proposed sensor is fabricated using a $0.35{\mu}m$ two-poly, four-metal standard complementary MOS (CMOS) process, and its characteristics are evaluated.

• 대한지하수환경학회지
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• 제7권3호
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• pp.133-140
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• 2000

초정지역은 세계 3대 광천수 생산지의 하나로서 지하수 이용업체들이 집중적으로 지하수 개발을 하고 있어 지하수자원의 고갈이 우려되고 있다. 본 연구에서는 초정지역의 지속적인 개발로 인해 장래 예측되는 지하수 장애에 대처하기 위해 수치모형을 이용하여 초정지역의 지하수 유통해석을 수행하였다. 해석 결과 동북쪽에 위치한 산간유역의 수위의 변화에 비하여, 하류 구릉지역에서는 양수정들을 중심으로 수위 강하가 급격하게 일어나고 있다. 이는 하류 구릉지역에 공장들이 밀집하여 있고 생활용수와 농업용수 또한 많은 양을 양수를 하는데 기인한다. 따라서 향후 지하수자원의 고갈이 우려되며, 이에 대한 대책이 심각하게 요구된다.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1284-1288
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• 2021

In this work, we propose and design a GaN-based diode with a p-doped GaN (p-GaN) multi-well structure for high efficiency betavoltaic (BV) cells. The short-circuit current density (J_SC) and opencircuit voltage (V_OC) of the devices were investigated with variations of parameters such as the doping concentration, height, width of the p-GaN well region, well-to-well gap, and number of well regions. The J_SC of the device was significantly improved by a wider depletion area, which was obtained by applying the multi-well structure. The optimized device achieved a higher output power density by 8.6% than that of the conventional diode due to the enhancement of J_SC. The proposed device structure showed a high potential for a high efficiency BV cell candidate.

• 한국멀티미디어학회논문지
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• 제22권6호
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• pp.676-683
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• 2019

Wireless Sensor Networks (WSNs) consist of multiple tiny and power constrained sensors which use radio frequencies to carry out sensing in a designated sensor area. To effectively design and implement reliable WSN, it is critical to consider models, protocols, and algorithms that can optimize energy consumption of all the sensor nodes with optimal amount of packet delivery. It has been observed that deploying a single sink node comes with numerous challenges especially in a situation with high node density and congestion. Sensor nodes close to a single sink node receive more transmission traffic load compared to other sensors, thus causing quick depletion of energy which finally leads to an energy hole and sink hole problems. In this paper, we proposed the use of multiple energy efficient sink nodes with brute force technique under optimized parameters to improve on the number of packets delivered within a given time. Simulation results not only depict that, deploying N sink nodes in a sensor area has a maximum limit to offer a justifiable improvement in terms of packet delivery ratio but also offers a reduction in End to End delay and reliability in case of failure of a single sink node, and an improvement in the network lifetime rather than deploying a single static sink node.

• 방사성폐기물학회지
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• 제18권4호
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• pp.481-496
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• 2020

After nuclear power plants are permanently shut down and decommissioned, the remaining irradiated metal components such as stainless steel, carbon steel, and Inconel can be used as neutron absorber. This study investigates the possibility of reusing these metal components as neutron absorber materials, that is burnable poison. The absorption cross section of the irradiated metals did not lose their chemical properties and performance even if they were irradiated over 40-50 years in the NPPs. To examine the absorption capability of the waste metals, the lattice calculations of WH 17×17 fuel assembly were analyzed. From the results, Inconel-718 significantly hold-down fuel assembly excess reactivity compared to stainless steel 304 and carbon steel because Inconel-718 contains a small amount of boron nuclide. From the results, a 20wt% impurity of boron in irradiated Inconel-718 enhances the excess reactivity suppression. The application of irradiated Inconel-718 as a burnable absorber for SMR core was investigated. The irradiated Inconel-718 impurity with 20wt% of boron content can maintain and suppress the whole core reactivity. We emphasize that the irradiated metal components can be used as burnable absorber materials to control the reactivity of commercial reactor power and small modular reactors.

• 디지털산업정보학회논문지
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• 제16권4호
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• pp.9-17
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• 2020

When IoT sensor nodes are deployed in areas where data collection is challenging, sensors must be relocated if sensing holes occur due to improper placement of sensors or energy depletion, and data collection is impossible. The sensing hole's cluster header transmits a request message for sensor relocation to an adjacent cluster header through a specific relay node. However, since a specific relay node is frequently used, a member sensor located in a specific cluster area adjacent to the sensing hole can continuously receive the movement message. In this paper, we propose a method that avoids the situation in which the sensing hole cluster header monopolizes a specific relay node and allows the cluster header to use multiple relay nodes fairly. Unlike the existing method in which the relay node immediately responds to the request of the header, the method proposed in this paper solves a ping-pong problem and a problem that the request message is concentrated on a specific relay node by applying a method of responding to the request of the header using a timer. OMNeT++ simulator was used to analyze the performance of the proposed method.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.3073-3084
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• 2022

The propagation of radiation source uncertainties in spent nuclear fuel (SNF) cask shielding calculations is presented in this paper. The uncertainty propagation employs the depletion and source term outputs of the deterministic code STREAM as input to the transport simulation of the Monte Carlo (MC) codes MCS and MCNP6. The uncertainties of dose rate coming from two sources: nuclear data and modeling parameters, are quantified. The nuclear data uncertainties are obtained from the stochastic sampling of the cross-section covariance and perturbed fission product yields. Uncertainties induced by perturbed modeling parameters consider the design parameters and operating conditions. Uncertainties coming from the two sources result in perturbed depleted nuclide inventories and radiation source terms which are then propagated to the dose rate on the cask surface. The uncertainty analysis results show that the neutron and secondary photon dose have uncertainties which are dominated by the cross section and modeling parameters, while the fission yields have relatively insignificant effect. Besides, the primary photon dose is mostly influenced by the fission yield and modeling parameters, while the cross-section data have a relatively negligible effect. Moreover, the neutron, secondary photon, and primary photon dose can have uncertainties up to about 13%, 14%, and 6%, respectively.