MPLS 망을 통한 Video Streaming Service의 성능 개선에 관한 연구

김충현,김영범,Kim Choong-Hyun,Kim Young-Beom 한국융합신호처리학회 2006 융합신호처리학회 논문지 (JISPS) Vol.7 No.2

대표적인 비디오 스트리밍 서비스인 MPEG은 특성상 영상에 따라 프레임의 데이터 크기가 변동하며 QoS를 만족하기 위한 대역폭이 시간에 따라서 변동하게 된다. 따라서 인터넷을 통한 비디오 스트리밍 서비스에 있어서 망 관리 측면에서 비디오 스트리밍 서비스의 우선순위를 높게 부여하더라도 예기치 못한 혼잡상황에서는 순간적인 대역폭 부족으로 인하여 영상이 끊어지는 현상이 발생할 수 있다. 본 논문에서는 MPEG 특성에 맞는 대역폭 할당 및 트래픽 엔지니어링 방안을 고찰하였다. 인터넷 트래픽 양의 시간적 변동패턴을 기반으로한 LSP 설정과 고정 대역폭 할당을 통하여 지연시간을 단축과 전송효율 향상을 기하고 인입 라우터에서 CQ_LLQ 방식을 적용한 트래픽 shaping 과정을 통해 QoS를 만족할 수 있도록 하였고 OPNET을 이용한 컴퓨터 시뮬레이션을 통하여 제안한 방안의 성능을 확인하였다. In typical video streaming services such as MPEG encoded video, the transmission data sizes change depending on the frame types and the required bandwidth for QoS support also changes as time passes. Accordingly, in video streaming services using the Internet it could happen that the video services stop occasionally due to instantaneous deficiencies of the required bandwidth under unexpected congestion even if the highest priority is allocated to the service by network administration. In this paper, we investigate several methods for bandwidth allocation and traffic engineering to support MPEG video traffic and propose a new method to reduce the transmission delay and enhance the throughput, there by provisioning the QoS requirements. In the proposed scheme, LSPs are established based on temporal variation patterns of the Internet traffic and the CQ_LLQ policing scheme is applied for traffic shaping at the ingress routers. Finally we verified the performance of the proposed scheme via computer simulations using OPNET.

성상세포성 종양에서 MIB-1증식지수와 예후의 연관성

김충현,백광흠,김재민,고용,오석전,홍은경,Kim, Choong Hyun,Bak, Koang Hum,Kim, Jae Min,Ko, Yong,Oh, Suck Jun,Hong, Eun Kyung 대한신경외과학회 2001 Journal of Korean neurosurgical society Vol.30 No.4

Objective : The proliferative potential of intracranial glioma affects the histological malignancy and prognosis of patients with these tumors. In this study, we present the relationship between MIB-1 labeling index(LI) and clinical variables which might play the major role in determining the prognosis of patient with astrocytic tumors. Patients and Methods : Excised tumor specimens from a total of 52 patients were stained to detect monoclonal MIB-1-Ki-67 antibody by avidin-biotin complex immunohistochemistry. The MIB-1 LI was evaluated with histological grades, demograpghic data, and survival time. The statistical significance of their correlation was analyzed by Pearson correlation test. Results : The 52 patients included 30 male patients and 22 female patients. The tumors according to the criteria of the World Health Organization(WHO) classification were verified as pleomorphic xanthoastrocytoma in one, pilocytic astrocytomas 4, astrocytomas 1, anaplastic astrocytomas 3, and glioblastomas 31. MIB-1 LI in astrocytic ttumors showed no correlation with age and gender. However, the patients under 10 years had the longest survival time, whereas short survival time was observed in the older patients. The mean MIB-1 LI of different tumor grades were as follows : pleomorphic xanthoastrocytoma, $4.40{\pm}0.00$ ; pilocytic astrocytoma, $4.53{\pm}3.09$ ; astrocytoma, $5.50{\pm}6.03$ ; anaplastic astrocytoma, $12.68{\pm}12.50$ ; Glioblastoma, $21.31{\pm}19.63$. Although the levels of MIB-1 LI were varied in individual tumors, the MIB-1 LI was increased in parallel with the histological grades. Glioblstomas showed significantly higher MIB-1 LI compared with that of anaplastic astrocytomas and low grade astrocytomas (p = 0.001). The mean survival time of entire group of patients was also well correlated with MIB-1 LI in astrocytic tumors(p = 0.015). Moreover, the mean survival time of the entire group of patients with Lis < 10 was $125.33{\pm}113.57weeks$, and the mean survival of those with $Lis{\geq}10$ was $60.71{\pm}62.58weeks$. This difference was also statistically significant(p = 0.004). Conclusion : The results of this study suggest that MIB-1 LI correlates with histological grades and might play a significant role in predicting the survival of patients with astrocytic tumors.

인체 뇌종양조직에서 텔로머레이즈의 발현과 세포사멸

김충현,정진환,백광흠,김재민,고용,오석전,Kim, Choong Hyun,Cheong, Jin Hwan,Bak, Koang Hum,Kim, Jae Min,Ko, Yong,Oh, Suck Jun 대한신경외과학회 2001 Journal of Korean neurosurgical society Vol.30 No.2

Objective : Telomerase, a ribonucleoprotein adds telomere repeats to the ends of telomeres to compensate for the progressive loss. A favorable prognosis associated with low or no telomerase activity in some tumors, and cells transfected with antisense human telomerase lost telomeric repeats and die. We studied about the relationship between telomerase activity and apoptosis in the human brain tumors. Material and Methods : Between July 1998 and December 1999, 62 patients with brain tumors underwent surgery and their surgical specimens were obtained. Telomerase activity was investigated by telomeric repeats amplification protocol(TRAP) assay. Apoptosis was also evaluated by DNA fragmentation analysis. Differences and correlation in data were analyzed using Mann-Whitney test and Wilcoxon-signed rank test. Results : Expression rate of telomerase activity and apoptosis were 80% and 30% in malignant gliomas, 33% and 0% in low grade gliomas, 63% and 38% in meningiomas, 67% and 33% in pituitary adenomas, 33% and 33% in metastatic tumors, 67% and 17% in acoustic neurinomas, 100% and 100% in pineoblastomas, 100% and 0% in the hemangioblastoma, respectively. There was no significant difference of telomerase activity and apoptosis between histological types. But a significant difference was noted in the expression of telomerase activity between malignant gliomas and low grade gliomas(p = 0.022). Brain tumors with telomerase activity expressed the lower rate of apoptosis. A significant correlation was also found between telomerase activity and absence of apoptosis in the human brain tumors(p = 0.005). Conclusions : Our data suggests that telomerase may protect from apoptosis of the human brain tumors and also may play an important role in the biological malignancy of the gliomas.

SEM을 이용한 나일론피니언의 마멸특성 고찰

김충현,안효석,정태형,Kim, Choong-Hyun,Ahn, Hyo-Sok,Chong, Tae-Hyong 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.6

Power-transmission Nylon pinions against steel gears fur different pitch line velocities was studied with a power circulating gear test rig under unlubricated condition by SEM(Scanning Electron Microscope). The wear characteristics of Nylon pinions varied significantly with the pitch line velocity and applied load. Wear occurred most severely at the regions including pitch circle and root circle of Nylon pinions. It is confirmed that Nylon pinions are able to be used fer power-transmission under limited conditions.

일자리 불일치의 선행변수 및 결과변수에 대한 연구

김충현(Kim Choong Hyun),이재훈(Rhee Jae hoon) 한국경영교육학회 2013 한국경영교육학회 학술발표대회논문집 Vol.2013 No.12

최근 심각한 고용난과 함께 취업자의 일자리불일치가 사회적 문제로 대두되고 있다. 이에 본 연구에서는 현재 기업종사자들을 대상으로 직무와 관련된 숙련불일치와 종업원 개인의 취업시 희망 일자리 수준과 실제 기업제공 수준간의 괴리감의 발생으로 인한 일자리-기대 불일치에 대한 이론적 고찰과 측정척도를 개발하고, 이들 두 가지 불일치의 선행변수와 결과변수에 대한 분석을 시도하였다.연구 결과, 먼저 숙련불일치의 경우 개인의 업무경험, 자격증보유가 유의적인 영향을 미치는 것으로 나타났으며, 일자리-기대불일치의 경우, 직업탐색요인 중 구직기간과 구직경로가 그리고, 조직특성 중 업무강도, 임금수준, 복지후생, 고용안정성이 일자리-기대 불일치에 영향을 미치는 것으로 나타났다. 그리고 숙련불일치와 일자리-기대불일치는 종업원의 직무만족(내·외적), 조직몰입, 이직의도에 유의적인 영향을 미치는 것으로 나타났다.이상의 연구결과에 기초하여 조직구성원의 일자리 불일치에 대한 지각정도를 파악하고, 일자리 불일치 해결을 위한 개인 및 기업차원의 효과적인 인적자원관리방안에 대한 시사점을 제공하였다. Along with a serious unemployment crisis, employees' job mismatch has also become another problem in Korea.This study, whose major research targets are current employees after employment, is aimed at developing measures for job-expectancy mismatch caused by skill mismatch and difference between employees' expectation about job levels they're looking for and real levels of jobs provided. We also tried to find out antecedents and consequences of those two types of mismatch.Antecedent variables include human capital, job searching, job characteristics and organizational environmental characteristics while consequence variables do containing satisfaction, organizational commitment and turnover intention.Results showed that number of certificates, job-searching duration and job-searching channels among job-seeking factors and work strength, wage level, welfare, job insecurity among organization characteristics have significant effects on job-expectancy mismatch. Besides, both skill mismatch and job-expectancy mismatch have a strongly significant affect on job satisfaction, organizational commitment and intention of changing jobs.This study not only tried to grasp our perception with job mismatch, but also provided some implications of effective human resource management in order to solve those problems regarding two mismatches. Finally, limitations of the study and suggestions for future studies are presented in the conclusion.

튜닝포크를 이용한 액체밀도의 계측

김충현(Choong Hyun Kim),이용복(Yong-Bok Lee),이성철(Sung-Chul Lee) 한국생산제조학회 2007 한국생산제조학회지 Vol.16 No.1

노인 낙상 후 충격량 측정 및 기립여부 판단 시스템 구현

김충현(Choong Hyun Kim),이영재(Young-Jae Lee),이필재(Pil-Jae Lee),이정환(Jeong-Whan Lee) 대한전기학회 2011 전기학회논문지 Vol.60 No.6

In this study, we proposed the system that calculates the algorithm with an accelerometer signal and detects the fall shock and it’s direction. In order to gather the activity patterns of fall status and attach on the subject’s body without consciousness, the device needs to be small. With this aim, it is attached on the right side of subject’s waist. With roll and pitch angle which represent the activity of upper body, the fall situation is determined and classified into the posture pattern. The impact is calculated by the vector magnitude of accelerometer signal. And in the case of the elderly keep the same posture after fall, it can distinguish the situation whether they can stand by themselves or not. Our experimental results showed that 95% successful detection rate of fall activity with 10 subjects. For further improvement of our system, it is necessary to include tasks-oriented classifying algorithm to diverse fall conditions.

중소제조기업의 인력부족요인 및 전략적 선택행위에 대한 연구

김충현(Choong hyun Kim) 한국인사관리학회 2018 한국인사관리학회 학술대회 발표논문집 Vol.2018 No.1

본 연구는 지역의 중소제조기업의 노동력 부족원인을 분석하고, 이를 바탕으로 중소기업의 경영자가 인력 부족현상을 해결하기 위한 전략적 행위를 도출하고자하였다. 선행연구를 통해 도출된 인력부족의 주요 결정요인으로 사회적 인식, 기업 요인, 지역 요인, Job Mismatch 요인을 독립변수로 활용하여, 이들과 인력부족정도간의 관계를 분석하였다. 먼저 본 연구에서 독립변수로 설정한 인력부족원인변수와 종속변수인 인력부족간의 회귀분석 결과, 4가지 측면의 변수 중 사회적 인식 변수와 지역요인변수가 중소기업의 인력부족에 유의미한 영향을 미치는 것으로 나타났다. 그리고 지역 중소기업의 인력부족과 이를 해결하기 위한 중소기업 경영자의 전략적 선택행위를 분석한 결과, 기업 특성(혹은 노동시장)에 따라 중소기업의 경영자는 기업의 인력부족을 해소하기 위하여 다양한 전략적 행위를 취하는 것으로 나타났으며, 기업규모가 규모가 크거나 근로자의 연령대가 고령화 될수록 신규인력의 채용을 선호하고, 인력부족상태가 심각할수록 기존인력을 활용하는 전략적 행위를 추구함을 확인할 수 있다. 본 연구는 지역의 중소기업을 대상으로 조사를 실시하였기 때문에, 지역의 중소기업의 인력부족의 심각성을 경각시켜 줄 뿐만 아니라, 지역 기업에서도 인력부족을 해결하기 위한 전략을 선택하는데에도 도움이 되리라 예상된다. The purpose of this study is to analyze the causes of labor shortage in local SMEs and to solving the strategic choice behaviors of managements of SMEs. The main determinants of the shortage of labor derived through previous studies are social awareness, corporate factors, regional factors, and Job Mismatch factors as independent variables and analyzed the relationship between these factors and shortage of labor. First of all, regression analysis between the labor shortage cause variable and the dependent variable, labor shortage variable set as independent variables in this study showed that social cognition variables and regional factor variables had a significant impact on the shortage of SMEs. And as a result of analyzing the lack of labor in the local SMEs and the strategic choice behavior of the SME managers in response to them, managers of SMEs have taken various strategic actions in order to solve the labor shortage. The larger the firm size is, or the older the worker ages, the more favorable the recruitment of new workforce. This study is expected to help not only the seriousness of the lack of workforce in the local SMEs but also the strategies to solve the labor shortage in the local enterprises.

고장력볼트로 체결되는 철판 사이의 미끄럼계수

김충현(Choong Hyun Kim) 한국트라이볼로지학회 2008 한국윤활학회지(윤활학회지) Vol.24 No.6

Tensile test results using three kinds of steel structure specimens are measured and compared. Slip coefficient between shot blasted steel plates was greater than 0.6. For the case of the plates coated with Super zinc, it revealed that the coefficients were greater than 0.5. On the other hand, Super epoxy coating decreased its slip coefficient less than 0.25. Steel plates coated with Super zinc are proved to be practically applicable to the steel structures with anti-corrosion characteristics and clean surfaces.

스카프 패치로 수리한 복합재 단일겹침 체결부의 파손 특성 연구

김충현 ( Choong-hyun Kim ),유재승 ( Jae-seung Yoo ),변창석 ( Chang-seok Byeon ),주현우 ( Hyun-woo Ju ),박민영 ( Min-young Park ),최진호 ( Jin-ho Choi ),권진회 ( Jin-hwe Kweon ) 한국복합재료학회 2016 Composites research Vol.29 No.3

본 연구에서는 스카프 패치로 수리한 복합재 단일겹침 체결부의 파손강도를 시험과 해석으로 연구하였다. 스카프 비, 모재의 적층패턴, 결함크기를 달리 하며 총 45개의 시편에 대한 시험을 수행하여 파손강도와 파손 모드를 분석하였다. 다양한 형상의 시편에 대한 시험 결과, 한 경우를 제외하고는 수리 후의 체결부가 결함이 없는 체결부 강도 이상의 강도를 회복하며, 체결부 인자에 따른 특별한 차이는 나타나지 않는 것을 확인하였다. 파손강도가 낮게 나타난 한 경우에 대한 파손면 분석결과 모재의 표면층인 평직층의 표면처리가 충분치 않은 것이 원인인 것으로 판단되었다. 시험 결과의 분석을 위해 3차원 유한요소해석을 수행하였는데, 유한요소해석에서도 고려한 체결부 인자가 상하부 모재와 패치, 접착층에서의 응력에 큰 영향을 미치지 않는 것을 확인하였다. 이는 단일겹침 체결부의 경우 외부 인장하중이 겹침영역을 통과하면서 상하부 모재로 분산되기 때문인 것으로 판단된다. 시험과 해석 결과 모재 중앙에 결함이 존재하는 단일겹침 체결부의 경우 절차에 따라 패치 접착이 이루어지고, 모재의 표면처리가 충분히 이루어진다면 수리를 통해 손상 전 강도를 회복할 수 있는 것으로 판단된다. The failure strength of composite single-lap joint repaired using scarf patch was investigated by test and finite element method. A total of 45 specimens were tested changing scarf ratio, stacking pattern, and defect size to study the failure strength and mode. Except for one case, all repaired specimens showed the equal or higher strength than the sound specimens and the effect of considered repair parameters was not remarkable. It was found through the failure mode inspection that the surface treatment for bonding was not enough in the case which failed at the lower load than the sound specimen. Three-dimensional finite element analysis was conducted to verify the test results. It was confirmed that the considered repair parameters do not significantly affect the stress distribution of the specimens. It was also observed that the applied tensile load is relieved passing through the overlapped region thickness of which is almost double. From this study, it is concluded that if the bonding procedure for adherends and patch including surface treatment for fabric layer is thoroughly followed, the strength of repaired single-lap joint can be restored up to the strength of sound one.