• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.738-744
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• 2018

This paper proposes a low cost hot swap operation circuit of a parallel operation power supply for servers. Hot swap function for server power system is essential in 24 hour operation system such as internet data center, server, factory and etc. Server power supplies used in internet data centers have two or more parallel operations with the hot swap operation. However, the cost of the power supply is high because the controller IC for hot swap operation is very expensive. Therefore, this paper proposes a parallel-operated power supply with a low-cost hot swap controller for servers. The proposed system can operate hot swap function by using discrete devices and reduce the cost by more than 50%. A 1.2kW prototype system is implemented to verify the proposed low cost hot swap controller.

• Journal of Korea Multimedia Society
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• v.13 no.9
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• pp.1272-1284
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• 2010

As the mobile computers are becoming powerful and are used like general-purpose computers, operating systems for mobile computers also require swap system functionality that utilizes main memory efficiently. Flash memory is widely used as storage device for mobile computers but current linux swap system does not consider flash memory. Swap system is tightly related with process execution since it stores the contents of process in execution. By taking advantage of this characteristics, in this paper, we study a new linux swap system called PASS(Process-Aware Swap System), which allocates the different flash memory blocks to each process. Trace-driven experimental results show that PASS outperforms existing linux swap system with existing garbage collection schemes in terms of garbage collection cost.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.5
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• pp.476-484
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• 2015

Due to the recent advances in non-volatile memory technologies such as PCM, a new memory hierarchy of computer systems is expected to appear. In this paper, we explore the performance of PCM-based swap systems and discuss how this system can be managed efficiently. Specifically, we introduce three management techniques. First, we show that the page fault handling time can be reduced by attaching PCM on DIMM slots, thereby eliminating the software stack overhead of block I/O and the context switch time. Second, we show that it is effective to reduce the page size and turn off the read-ahead option under the PCM swap system where the page fault handling time is sufficiently small. Third, we show that the performance is not degraded even with a small DRAM memory under a PCM swap device; this leads to the reduction of DRAM's energy consumption significantly compared to HDD-based swap systems. We expect that the result of this paper will lead to the transition of the legacy swap system structure of "large memory - slow swap" to a new paradigm of "small memory - fast swap."

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.399-399
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• 2021

최근 전세계적으로 발생하고 있는 기후변화로 인해 가뭄, 홍수, 태풍 등 자연재해의 빈도가 증가하고 있다. 특히, 강수량의 변동성이 커지면서 가뭄과 홍수가 단기간에 번갈아 가며 발생하는 경우가 자주 발생하고 있다. 가뭄과 홍수가 짧은 기간 동안에 교차해서 발생하는 급변사상은 예측하기 어려우며, 갑작스럽게 중첩되는 재난으로 인명과 재산피해 뿐 아니라 생태계에까지 심각한 영향을 미칠 것이다. 본 연구에서는 일 강수량 자료를 바탕으로 표준가중평균강수지수(Standard Weighted Average Precipitation, SWAP)를 산정하고 한강 유역의 가뭄-홍수 급변사상에 대한 특성을 분석하였다. 1966년부터 2018년까지의 한강유역 중권역별 면적평균강수량과 가중치, 이전 강수량의 영향을 받는 일수를 바탕으로 SWAP를 산정하였다. SWAP 지수가 10일 연속 -1 미만일 때를 가뭄이라 정의하고, 이후 SWAP 지수가 7일 연속 0.5 이상이면 가뭄사상이 종료된다고 판정하였다. 또한 SWAP 지수가 10일 연속 +1 초과일 때를 홍수라고 정의하고, SWAP 지수가 7일 연속 -0.5 이하가 되면 홍수사상이 종료된다고 판정하였다. 가뭄-홍수 급변사상이란 가뭄의 종료시점과 홍수의 시작시점의 차이가 5일 이내일 경우에 해당한다. 급변사상의 전·후로 강수량이 얼마나 급격하게 차이 나는지를 판단하기 위하여 급변 시점 전·후 5일의 누적 SWAP 지수인 심각도 K(Severity)를 분석지표로 활용하였다. K를 통해 한강유역 가뭄-홍수 급변사상의 시·공간적 분포를 분석하고 미래의 급변사상의 발생가능성을 예측할 수 있다. 본 연구 결과, 한강 유역의 24개 중권역 중에서 18개의 중권역이 가뭄-홍수 급변사상의 심각도가 점점 상승하는 추세이고, 가장 심각도 상승폭이 높은 중권역은 홍천강(1014)으로 첫 사상인 1967년부터부터 2015년의 마지막 사상까지 약 55% 정도 상승하였다.

• Journal of the Korea Society of Computer and Information
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• v.20 no.12
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• pp.75-82
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• 2015

Generally, the optimal solution of assignment problem can be obtained by Hungarian algorithm of two-sided optimization with time complexity $O(n^4)$. This paper suggests one-sided optimal assignment and swap optimization algorithm with time complexity $O(n^2)$ can be achieve the goal of two-sided optimization. This algorithm selects the minimum cost for each row, and reassigns over-assigned to under-assigned cell. Next, that verifies the existence of swap optimization candidates, and swap optimizes with ${\kappa}-opt({\kappa}=2,3)$. For 27 experimental data, the swap-optimization performs only 22% of data, and 78% of data can be get the two-sided optimal result through one-sided optimal result. Also, that can be improves on the solution of best known solution for partial problems.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.482-483
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• 2018

본 논문에서는 Hot-Swap 가능한 모듈라 ESS용 DC-DC 컨버터에서 ESS 모듈의 Hot-Swap 과정에서 발생하는 과도상태에 대해 컴퓨터 시뮬레이션을 통해 분석을 하고, 과도상태에서 과전류를 저감할 수 있는 방법에 대해 제시하고자 한다.

• Management Science and Financial Engineering
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• v.19 no.1
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• pp.49-52
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• 2013

In this paper we provide a valuation formula for a variance swap with regime switching. A variance swap is a forward contract on variance, the square of realized volatility of the underlying asset. We assume that the volatility of underlying asset is governed by Markov regime-switching process with finite states. We find that the proposed model can provide ease of calculation and be superior to the models currently available.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.308-309
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• 2020

본 논문은 추가적인 회로 없이 DVR 전원공급장치의 Hot-Swap 기능을 구현하는 방법을 제안한다. 기존에 사용하던 ORing Diode와 MOSFET의 추가 없이 LLC 컨버터 2차측 정류다이오드만의 바이어스 특성을 이용해 Hot-Swap 기능을 구현한다. 168W급 DVR 전원공급장치를 대상으로 제안한 회로의 타당성을 모의실험을 통해 입증한다.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.433-434
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• 2019

본 논문에서는 직렬형 Hot-Swap ESS(Energy Storage System)에서 하나의 DC-DC 컨버터 모듈이 순간적으로 추가 또는 제거되는 고장 상황에서의 과도 응답에 대해 이론적 분석을 진행하였고, 컴퓨터 모의실험을 통해 분석 결과의 유효성을 검증하였다.

• Communications for Statistical Applications and Methods
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• v.28 no.6
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• pp.655-671
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• 2021

This study analyzes the premium risk of insurers in Korea, which is expected to experience the fastest population aging in the world. Based on the Lee-Carter model, we generate 10,000 scenarios for the number of future survivors in the group of the 10,000 policyholders of life annuity. According to the result of simulation study, the probability of insurer's loss for both groups of male and female policyholders is very low. This result indicates that the premium risk of insurers is not as great as the insurer's concern. This study also suggests introduction of the longevity swap as an alternative to manage the premium risk for the insurer which sells life annuity products. The longevity swap allows insurers to hedge premium risk and reduce capital burden due to the premium risk inherent in life annuity. This study also shows through examples that the counterparty of swap deal may have excess profit in exchange for taking premium risk.