• Communications for Statistical Applications and Methods
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• 제9권3호
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• pp.809-824
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• 2002

we propose two methods which separate the variable selection step and the split-point selection step. We call these two algorithms as CHITES method and F&CHITES method. They adapted some of the best characteristics of CART, CHAID, and QUEST. In the first step the variable, which is most significant to predict the target class values, is selected. In the second step, the exhaustive search method is applied to find the splitting point based on the selected variable in the first step. We compared the proposed methods, CART, and QUEST in terms of variable selection bias and power, error rates, and training times. The proposed methods are not only unbiased in the null case, but also powerful for selecting correct variables in non-null cases.

• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.103-106
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• 2003

The short circuit current problem is one of the operational problems that need to be solved by power system engineers in Korea. It is an important issue in the Seoul metropolitan area especially because of highly meshed configuration. Currently, it is regulated by changing 154 kV system configuration from loop connection to radial system, by splitting of the bus where load balance can be achieved, and by upgrading circuit breaker rating. A development project for 154 kV/2 KA SFCL application to 154 kV transmission system after 2010 is proceeding. In this paper, a feasibility study of superconducting fault current limiter (SFCL) is carried out in Seoul metropolitan area to find out the effects of its application and feasibility. This study shows that it can reduce fault current considerably, and as it can minimize the upgrading of circuit breaker rating, the economic potential of SFCL is evaluated positively.

• 한국자기공명학회논문지
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• 제24권1호
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• pp.16-22
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• 2020

Based on quantum transport theory, we investigated theoretically the magnetic field dependence of the quantum optical transition of quasi 2-dimensional Landau splitting system, in CdS and ZnO Through the analysis of the current work, we found the increasing properties of the cyclotron resonance line-profiles (CRLPs) which show the absorption power and the cyclotron resonance line-widths (CRLWs) with the magnetic field in CdS and ZnO We also found that that CRLWs, γ_total(B) of CdS < γ_total(B) of ZnO in the magnetic field region B < 15 Tesla.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권2호
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• pp.108-113
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• 2013

This paper describes a low power asynchronous successive approximation register (SAR) type 12b analog-to-digital converter (ADC) for biomedical applications in a 0.35 ${\mu}m$ CMOS technology. The digital-to-analog converter (DAC) uses a capacitive split-arrays consisting of 6-b main array, an attenuation capacitor C and a 5-b sub array for low power consumption and small die area. Moreover, splitting the MSB capacitor into sub-capacitors and an asynchronous SAR reduce power consumption. The measurement results show that the proposed ADC achieved the SNDR of 68.32 dB, the SFDR of 79 dB, and the ENOB (effective number of bits) of 11.05 bits. The measured INL and DNL were 1.9LSB and 1.5LSB, respectively. The power consumption including all the digital circuits is 6.7 ${\mu}W$ at the sampling frequency of 100 KHz under 3.3 V supply voltage and the FoM (figure of merit) is 49 fJ/conversion-step.

• 한국수소및신에너지학회논문집
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• 제31권2호
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• pp.242-249
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• 2020

The Kalina cycle (KC) is considered as one of the most efficient systems for recovery of low grade heat. Recently, Kalina based power and cooling cogeneration cycles (KPCCCs) have been suggested and attracted much attention. This paper presents an energy and exergy analysis of a recently suggested KPCCC with flexible loads. The cycle consists of a KC (KCS-11) and an aqua-ammonia absorption refrigeration cycle. By adjusting the splitting ratios, the cycle can be operated with four modes of pure Kalina cycle, pure absorption cooling cycle, Kalina-cooling parallel cycle, and Kalina-cooling series cycle. The effects of system variables and the operating modes on the energetic and exergetic performances of the system are parametrically investigated. Results show that the system has great potential for efficient utilization of low-grade heat source by adjusting loads of power and cooling.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.421-423
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• 2004

As power system grows more complex and power demands increase, the fault current tends to gradually increase. In the near future, the fault current will exceed a circuit breaker rating for some substations, which is an especially important issue in the Seoul metropolitan area because of its highly meshed configuration. Currently, the Korean power system is regulated by changing the 154kV system configuration from a loop connection to a radial system, by splitting the bus where load balance can be achieved, and by upgrading the circuit breaker rating. A development project applying 154kV Superconducting Fault Current Limiter(SFCL) to 154kV transmission systems is proceeding with implementation slated for after 2010. In this paper, the expected price of SFCL in order to assure the economic feasibility is evaluated comparing with upgrading cost of ciui.1 breakers. The results show that the SFCL should be developed under seven times of price of circuit breaker to be competitive against upgrading circuit breakers.

• 한국산학기술학회논문지
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• 제16권4호
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• pp.2777-2783
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• 2015

전력 피크 감소는 전력 공급자 뿐 아니라 사용자에게도 점점 중요한 기술이 되고 있다. 전기 부하 스케줄링은 기기의 주기적 작동 시간을 여러 개의 시간 조각들로 분리하고 여러 기기들에 대해 작동 시간 조각들을 통합적으로 교차 배치하여 전력 피크를 줄이는 기법이다. 본 논문에서는 부하 스케줄링 알고리즘인 EDF, LSF, TCBM, lazy 스케줄러의 성능을 분석하고 개선 방안을 제시한다. 분석을 위해 스케줄링 정책들을 분산제어 시뮬레이션 환경에서 구현하고, 실제 전력 사용 데이터를 이용한 광범위한 실험을 통해 전력 편차, 스위칭 횟수, 온도 범위 위반 비율 등의 관점에서 스케줄링 정책별 성능 특성을 논한다. 또한, 과도한 스위칭 방지를 위해 제한적 선점 기능을 제안하고 그 효과를 입증한다. 실험결과, 스케줄러 용량을 실제 전력 요구에 맞춰 설정하면 성능이 극대화됨을 확인하였으며, 스케줄링을 통해 150W 보다 큰 전력편차를 가지는 비율이 원래 21.5%에서 3.2%까지 감소함을 알 수 있었다.

• 한국통신학회논문지
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• 제37권8B호
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• pp.677-686
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• 2012

In the presence of a high power cellular network, picocells are added to a Macro-cell layout aiming to enhance total system throughput from cell-splitting. While because of the different transmission power between macrocell and picocell, and co-channel interference challenges between the existing macrocell and the new low power node-picocell, these problems result in no substantive improvement to total system effective throughput. Some works have investigated on these problems. Pico Cell Range Expansion (CRE) technique tries to employ some methods (such as adding a bias for Pico cell RSRP) to drive to offload some UEs to camp on picocells. In this work, we propose two solution schemes (including cell selection method, channel allocation and serving process) and combine new adaptive frequency partitioning reuse scheme to improve the total system throughput. In the simulation, we evaluate the performances of heterogeneous networks for downlink transmission in terms of channel utilization per cell (pico and macro), call blocking probability, outage probability and effective throughput. The simulation results show that the call blocking probability and outage probability are reduced remarkably and the throughput is increased effectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권6호
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• pp.2094-2114
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• 2022

Due to the wide application of fifth generation communication, wireless sensor networks have become an indispensable part in our daily life. In this paper, we analyze physical layer security for two-way relay with energy harvesting (EH), where power splitter is considered at relay. And two kinds of combined methods, i.e., selection combining (SC) and maximum ratio combining (MRC) schemes, are employed at eavesdropper. What's more, the closed-form expressions for security performance are derived. For comparison purposes, this security behaviors for orthogonal multiple access (OMA) networks are also investigated. To gain deeper insights, the end-to-end throughput and approximate derivations of secrecy outage probability (SOP) under the high signal-to-noise ratio (SNR) regime are studied. Practical Monte-Carlo simulative results verify the numerical analysis and indicate that: i) The secure performance of SC scheme is superior to MRC scheme because of being applied on eavesdropper; ii) The secure behaviors can be affected by various parameters like power allocation coefficients, transmission rate, etc; iii) In the low and medium SNR region, the security and channel capacity are higher for cooperative non-orthogonal multiple access (NOMA) systems in contrast with OMA systems; iv) The systematic throughput can be improved by changing the energy conversion efficiency and power splitting factor. The purpose of this study is to provide theoretical direction and design of secure communication.

• 한국위성정보통신학회논문지
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• 제11권2호
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• pp.55-59
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• 2016

기존 무선에너지 하비스팅시스템에서 유저는 하나의 Hybirid-AP (H-AP)로부터 에너지와 정보를 동시에 받았다. 하지만 무선에너지 하비스팅은 거리가 멀수록 감쇄가 심하기 때문에 H-AP에서 거리가 먼 유저들은 낮은 하비스팅 효율 가진다 (이중 근거리/원거리 문제). 이러한 문제를 해결하기 위해서 본 논문은 Power beacon (PB)을 통해 유저에게 별도의 파워를 공급하는 비결합 무선에너지 하비스팅 네트워크를 시스템 모델로 사용하였다. 이 논문의 주된 목적은 다양한 제약 조건과 Quality of service (QoS), 그리고 Quality of harvested power (QoP)를 만족하면서 목적 함수인 Energy efficiency (EE)를 최대화 하는 것이다. 제안된 시스템은 라그랑지안 쌍대 분해법 이론을 기반으로 EE 최대화를 위한 최적의 시간 스케줄링 알고리즘을 제안한다. 이 알고리즘을 통해 프레임 분해 요소, H-AP의 송신파워, 그리고 PB의 송신파워의 최적 값과 EE의 최대값을 구할 수 있다. 모의 실험 결과는 제안된 알고리즘으로 파라미터가 최적 값으로 빠르게 수렴하고 제안된 모델의 성능이 기존의 시스템 모델보다 우수하다는 것을 증명한다.