휴대폰 앱을 통한 철도인접지역의 열차진동 사용성평가

정영석,윤성원,Jung, Young-Seok,Yoon, Sung-Won 한국공간구조학회 2016 한국공간구조학회지 Vol.16 No.4

Recently, with development of city traffic network planning, there are various effects with living space from vibration of railway. But, study which about effect from vertical vibration in floor slab in nearing structure is lack in nowadays. This thesis have analysed result from acceleration response per distance as well as proceed with serviceability evaluation and extracted natural frequency from measuring vibration of railway using mobile phone application which is oriented for building which have distances about 5m to 22m from railway.

휴대폰 애플리케이션을 통한 초대형 구조물의 동적특성 분석

정영석,윤성원,Jung, Young-Seok,Yoon, Sung-Won 한국공간구조학회 2015 한국공간구조학회지 Vol.15 No.4

The serviceability design of the high-rise building is affected by the wind response vibration such as the acceleration, at this time it is important to calculate the natural frequency correctly. Since the suggestion equation of the natural frequency being used in the design phase is not the regression equation obtained from the vibration measurement of the high-rise building, the verification to use for the serviceability design of the high-rise building is necessary. This thesis conducted an ambient vibration measuring on the high-rise building through the mobile-phone application to calculate the natural frequency and suggested a natural frequency approximate expression following the building's height, and compared with the domestic/foreign standard and the result of the eigen-value analysis.

무선 센서 네트워크에서 저밀도 센서 노드에 대한 간접 위치 추정 알고리즘

정영석,우매리,김종근,Jung, Young-Seok,Wu, Mary,Kim, Chong-Gun 한국융합신호처리학회 2012 융합신호처리학회 논문지 (JISPS) Vol.13 No.1

센서 네트워크에서의 각 노드들은 지리적 위치에 기반을 둔 정보를 처리해야할 경우에 다양한 방법으로 자신의 위치를 알 수 있다. GPS를 이용한 위치 획득 방법은 전파의 가시성을 요구하므로 위치 정보를 획득할 수 없는 경우가 존재하고 비용이 많이들며, 전력소모가 많다. GPS 없이 센서 노드들의 위치를 알아내는 방법은 복잡한 수학적 알고리즘을 요구하며, 위치 추정의 정확도 측면에서 불리하다는 단점을 가지고 있다. AHLoS는 GPS를 이용한 위치 측정과 위치 추정 알고리즘을 모두 사용하는 혼합 방식이다. AHLoS에서 GPS 노드는 GPS로부터 수신한 자신의 위치를 자신과 인접한 GPS 기능이 없는 일반 노드로 방송한다. 일반 노드는 최소한 3개 이상의 이웃 노드의 위치 정보를 수신할 경우 삼각 측량 위치 계산 알고리즘의 반복 수행을 통해 자신의 위치를 계산할 수 있다. 그러나, 센서 네트워크에서 노드 이동성 네트워크 밀도 지리적 조건에 따라 노드가 3개 이상의 이웃 신호를 수신하지 못할 경우가 존재한다. 본 연구에서는 GPS 노드로부터 위치 정보를 3개 이상 직접 수신하기 어려운 저밀도 환경에서 각 센서 노드가 간접적으로 자신의 위치를 획득하는 방법을 제안한다. Each sensor node can know its location in several ways, if the node process the information based on its geographical position in sensor networks. In the localization scheme using GPS, there could be nodes that don't know their locations because the scheme requires line of sight to radio wave. Moreover, this scheme is high costly and consumes a lot of power. The localization scheme without GPS uses a sophisticated mathematical algorithm estimating location of sensor nodes that may be inaccurate. AHLoS(Ad Hoc Localization System) is a hybrid scheme using both GPS and location estimation algorithm. In AHLoS, the GPS node, which can receive its location from GPS, broadcasts its location to adjacent normal nodes which are not GPS devices. Normal nodes can estimate their location by using iterative triangulation algorithms if they receive at least three beacons which contain the position informations of neighbor nodes. But, there are some cases that a normal node receives less than two beacons by geographical conditions, network density, movements of nodes in sensor networks. We propose an indirect localization scheme for low-density sensor nodes which are difficult to receive directly at least three beacons from GPS nodes in wireless network.

무선 단말기 위치 예측 기반의 대역폭 예약을 이용한 멀티미디어 호 수락 알고리즘

정영석,Jung Young-Seok 한국융합신호처리학회 2006 융합신호처리학회 논문지 (JISPS) Vol.7 No.1

In this paper, we proposed the multimedia call admission control algorithm with the bandwidth reservation based on the prediction of wireless terminal's location to guarantee quality of service for multimedia applications in cellular networks. This algorithm aims at minimizing possible errors In predicting the moving direction of terminals using a mobility prediction scheme. This prediction reduces the size of bandwidth reserved redundantly. In order to evaluate the performance of the algorithm, the blocking rate of new calls and the forced termination rate of hand-off calls are measured and compared the results with those of existing schemes. The results of the experiment revealed that the algorithm presented in this paper achieved better performance with lower call blocking rates and forced-termination rates than those of other methods. 본 논문에서는 무선 이동통신망에서 멀티미디어 응용 프로그램의 서비스 품질 보장을 위하여 무선 단말기의 이동성을 예측하기 위하여 무선 단말기 위치 예측에 기반을 둔 대역폭 예약 알고리즘을 제안한다. 제안된 알고리즘은 이동성 예측 기법을 이용하여 단말기의 이동 방향에 대한 예측 오류를 최소화하는 것을 목적으로 한다. 이러한 예측은 불필요하게 중복되어 예약된 대역폭의 크기를 줄인다. 알고리즘의 성능 평가를 위해서, 신규호의 탈락률과 핸드오프호의 강제종료율을 측정하고 기존에 제안된 기법들의 성능 평가 결과와 비교한다. 그 결과 본 논문에서 제시된 알고리즘이 기존의 방법들에 비해 낮은 호 탈락률 및 강제종료율을 가지는 우수한 성능을 나타내었다

1-methyl-4-phenylpyridinium($MPP^+$)로 유도된 파킨슨병의 세포손상에 대한 황백의 신경세포 보호효과

정영석,정혜미,서운교,Jung, Young-Seok,Jung, Hye-Mi,Seo, Un-Kyo 대한한방내과학회 2009 大韓韓方內科學會誌 Vol.30 No.1

Background and Objective : The prospects for developing an anti-apoptotic natural component or a compound that exerts a neuroprotective effect with few or no side effects for the treatment of neurodegenerative disease appear favorable. In the present study, we evaluated the effects of the methanol extract of Phellodendri Cortex (PC extract) on 1-methyl-4-phenyl pyridinium($MPP^+$)-induced apoptosis in PC-12 cells. Materials and Methods : We used the methanol extract of Phellodendri Cortex (PC extract). PC-12 cells were cultured by RPMZ-1640. We found the PC extract's gene expression (Bax, Bcl-2) by using RT-PCR. We examined the PC extract's protein expression (Bcl-2, Bax, cytochrome c, poly (ADP-ribose) polymerase (PARP), caspase-3) by SDS-PAGE and Western blot. Results : Apoptosis in $MPP^+$-induced PC-12 cells was accompanied by an increased Bax/Bcl-2 ratio, release of cytochrome c to the cytosol and the activation of caspase-3. PC extract inhibited the down-regulation of Bcl-2 and the up-regulation of Bax, as well as the release of mitochondrial cytochrome c into the cytosol. In addition, PC extract attenuated caspase-3 activation and cleavage of poly (ADP-ribose) polymerase (PARP). Conclusion : These results suggest that the neuroprotective potentials of PC extract against $MPP^+$-induced apoptosis can be. at least partially, ascribed to its anti-apoptotic effects in PC-12 cells.

저노이즈형 진동계측 앱을 통한 MEMS 센서의 계측성능분석

정영석,윤성원,Jung, Young-Seok,Yoon, Sung-Won 한국공간구조학회 2017 한국공간구조학회지 Vol.17 No.1

With increasing number construction of high-rise building which has about 40 to 60 floors there have been many kinds of problem which related with usage from vibration. To predict response acceleration, it is important to assess correct natural frequency. However, due to the noise of MEMS sensor, it is difficult to measure dynamic characteristic such as natural frequency when measuring ambient vibration using MEMS sensor within cell phone. Therefore, a comparative analysis on vibration measuring applications was performed after measuring ambient vibration of 2 skyscrappers which have height between 133.5~244.3m that are located in Seoul and Observation tower using I-jishin APP with noise reduction function of MEMS sensor in order to verify the effectiveness of low noise type vibration measurement APP.

마이크로크레딧의 국제적 동향과 한국 미소금융의 과제

정영석(Young Seok Jung),이기영(Kiyoung Lee) 한국경제발전학회 2013 經濟發展硏究 Vol.19 No.1

서민금융의 최대 과제는 저소득층의 신용거래에서 발생하는 정보불완전성과 높은 거래비용의 문제를 극복하는 것이다. 국제적으로 마이크로크레딧의 발전사례가 보여주는 교훈은 이러한 저소득층의 신용문제를 시장기능을 통하여 지속가능한 방식으로 해결할 수 있는 가능성을 보여주었다는 점이다. 본 연구는 미소금융재단의 출범으로 본격화되고 있는 우리나라 마이크로크레딧사업의 발전방향을 모색하기 위하여 해외 마이크로크레딧 기관들의 운영현황을 비용구조, 대출금리, 수익성 및 자립도, 신용위험, 자금조달구조 등 다양한 측면에서 살펴보고 은행과 NGO 등 기관의 유형별로도 비교 분석하였다. 현재 우리나라의 미소금융사업은 급속한 성장에도 불구하고 사회적 역할 만을 지나치게 강조함으로써 금리정책 등에 있어서 지속가능성이나 성장성을 확보하지 못하고 있는 문제점이 있다. 이에 본고는 “경제적 마이크로크레딧”과 “사회적 마이크로크레딧” 사업을 분리하여 별도의 성과지표, 심사기준 그리고 금리정책 등을 사용할 것을 제안하고, 특히 경제적 마이크로크레딧 사업에서는 회계적으로는 10~11%, 그리고 경제적 기회비용으로는 18%~19%로 추정되는 지속가능한 금리를 적용하여 서민금융시장의 왜곡을 막으면서 보다 적극적으로 금융접근성을 확대할 것을 제안하였다. 아울러 미소금융사업의 지배구조를 개선하고 경영정보의 투명성을 확보함으로써 사회적 관심과 민간의 참여를 유도하는 것이 중요하다. 그리고 공공정책은 마이크로크레딧을 포용적 금융제도의 일부로서 육성할 수 있도록 제도적으로 지원하고 서민금융의 인프라를 확충하는데 초점을 두어야 할 것으로 보인다(JEL: G210). Imperfect information and high transaction cost are two most important obstacles in financial services for low income and low credit individuals. The development of microcredit industry in the last 20 ~30 years shows a possibility that those structural problems could be resolved through market mechanism in a sustainable way. Korean microcredit industry begins to grow notably with the start of Smile Microcredit Bank (SMB) in 2009 with support from government. In order to learn lessons for the strategic direction of SMB which plays a central role in the development of Korean microcredit industry, this paper analyzes the performance of international microfinance industry over the last 10 years, specifically focusing on cost structure, interest rate, profitability, credit risk and financing structure depending upon the types of legal entity, and compares the international development pattern with SMB’s business model. Despite its fast growth in the last few years, SMB’s business model does not have sustainability and growth potential, as social purpose has been emphasized too much at the expense of commercial principles. Thus this paper recommends that SMB separate “economic microcredit” from “social microcredit”, and apply different performance measures, different underwriting standards, and different interest rate policies. Especially, in the case of economic microcredit, which should be performed not only by microcredit institutions but also by other financial institutions focusing on low income people, such as cooperative credit unions, it has to increase lending rate up to 10~11% in order to ensure sustainability on an accounting basis, and up to 18~19% to ensure sustainability on an economic opportunity cost basis, from the current 4.5%. Also, it is important to induce social investment from the private sector by enhancing its governance structure and transparency of management information. Public policy needs to focus on the legal and policy framework in the financial system to incorporate microfinance as one important part of inclusive financial system, and improvement of the infrastructure for the financial service for low income and low credit individuals.

평균전류모드제어를 이용하는 컨버터의 모델링 및 설계

정영석(Young-Seok Jung) 전력전자학회 2005 전력전자학술대회 논문집 Vol.- No.-

본 논문에서는 평균전류모드제어를 이용하는 컨버터의 연속시간 소신호 모델을 구한다. 평균전류 모드제어에 일반적으로 사용되는 보상기를 적용한 컨버터의 해석을 위해 샘플러를 전류루프에 포함시켜 해석한다. 기존 모델에서는 정확히 해석하기 어려웠던 전류루프 이득의 고주파 영역 해석이 제안한 모델을 이용함으로써 쉽게 해결할 수 있으며, 시스템의 안정성을 결정하는 고주파 영역에서의 주파수 응답 특성을 제안한 모델이 우수한 성능으로 예측 가능함을 보인다.

계통연계형 태양광발전시스템을 위한 고주파 DC 링크 인버터

정영석(Young-Seok Jung),유권종(Gwon-Jong Yu) 전력전자학회 2001 전력전자학술대회 논문집 Vol.2001 No.7

n investigation into power conditioners that interface with photovoltaic array and utilities has been completed. The rating for this investigation is residential systern(3-5kVA) that interface with a 220V single phase utility connection. As the result of this investigation, a 3kVA high frequency PWM IGBT inverter feeding a high frequency isolation transformer with a sinusoidal current wave was selected. The output of the transformer rectified with a diode bridge rectifier, four IGBT, used as 60Hz switched, reverse the polarity of the rectified current on every other half cycle of the utility voltage Even though the high frequency link system used more power semiconductors, a net size, weight, and parts cost saving result compared to the other systems due to elimination of 60Hz transformer.

서민금융기관의 대출금리, 비용구조 및 수익성에 관한 연구: 해외의 영리 마이크로 파이넌스 기관을 활용한 실증분석

정영석 ( Young Seok Jung ),이기영 ( Ki Young Lee ) 한국금융연구원 2012 금융연구 Vol.26 No.2

Structural issues in the lending market for low income and less creditworthy individuals could be summarized into two topics. The first is market inefficiency, that is, adverse selection and moral hazard caused by imperfect information, and the second is high unit cost of loans to service customers with small loan amount. Although there were many researches about financial access and availability of credit for less creditworthy individuals recently in Korea, they focused mostly on the institutional aspect of the lending market, and rigorous economic analyses were not performed enough to support policies in that area. The purpose of this paper is to provide an empirical knowledge of this special lending market, based on a theoretical model of lenders` behavior. The theoretical model is developed by extending the historical research of Stiglitz and Weiss (1981) on credit rationing to the specific decision making process of lenders under imperfect credit information. Based on the lending market model, authors test the model using international commercial microfinance institutions, and interpret the results to enhance understanding of the lending market for low income and less creditworthy individuals. Economic models of loan loss rate, interest rate and profitability are theoretically derived, and they are tested as a simultaneous equation system. Also, cost structure of the loan is analyzed focused on the impact of economies of scale in operating cost. Although the empirical test is performed with data from international microfinance institutions, the analysis demonstrates a possibility of developing the special lending market based on commercial principles, and provides lessons for the related policy in the area, as well as a rigorous test of the theoretical model. In chapter 2, under the assumption of imperfect information, a theoretical model of lenders behavior is developed for lending interest rate, loan loss rate, and profitability. The models are developed by applying the original model of Stiglitz and Weiss (1981) on credit rationing. But it is extended by incorporating lender`s decision making process under imperfect information with specific consideration of important variables in banking, such as error rate in the credit decision making process, default rate, recovery rate, and market competition etc. Chapter 3 and 4 summarize previous researches in this area, and describe data and methodology of this research. Most of the previous researches came from microfinance industry in relation with its commercialization and outreach. But despite their significant contribution, they have limitation in some areas, such as the scope of data and method of empirical test. To address those issues, this paper adopts a differentiated approach. At first, different from the previous researches that estimated interest rate and loan loss rate as separate variables, this paper builds theoretical and empirical models as a simultaneous equation system, and adopts an appropriate econometric methodology. Secondly, previous researches on microfinance industry included all types of institutions including small NGOs. But, this paper uses only for-profit bank and nonbank financial institutions in order to focus on the economic behavior and opportunities in the market. Thirdly, a panel data is created to cover 182 microfinance institutions over six year period from 2005 to 2010 with Mix`s public data. Six year sample which is consistent with one credit cycle will provide an unbiased view of those financial institutions` performance in the long term. Also, this data set makes possible a panel regression methodology, which is more useful than a simple cross sectional approach adopted by other researches. In Chapter 5, results of the empirical test are summarized. Using the panel data, two approaches are taken. The first is a regression analysis on the simply pooled data without consideration of uniqueness of each individual institution. The second is a random effect panel regression which incorporates unique values of each individual institution in each regression. The regression analysis of the simply pooled data shows an evidence of strong form of adverse selection, that is, a decreasing profitability of loans over a threshold interest rate, as well weak form adverse section, that is, an increasing loan loss rate with interest rate. But, in the random effect panel regression, the effect of interest rate on both loan loss rate and profitability is reduced to only marginally significant level. Also, the average loan loss rate of all sample turned out to be in the range of 1.5~2.5%, and average ROA was over 1%, both of which are better than general perception of the lending market for the poor. Based on those findings, authors contend that market inefficiencies caused by imperfect information is not such a serious barrier in extending financial access for the low income borrowers, at least in the observable range of lending interest rates. On the other hand, the most important factor in the high interest rates of small loans for low income borrowers was found to be the high operating cost, and the determinants of operating cost were analyzed focused on the impact of economies scales in two dimensions, that is, average loan size and number of outstanding loans. In addition to the average loan size, the number of loans outstanding was proved to have very significant impact of economies of scales, over a size of an institution which had been believed to have a maximum benefit of economies of scale. Also, market competition which was proxied by the ratio of total commercial bank credit over GNP was proved to reduce lending rate directly and indirectly through operating cost. Despite all the favorable findings to support development of credit market for low income borrowers based on market mechanism, very high volatility of loan loss rate and ROA should be seriously noted in the management and supervision of those financial institutions focusing on lending for less creditworthy and low income customers.