Analysis on the Cause of Twisting Defects Occurred in Sheet Panel Formed Through Local Embossing and Edge Bending

Keecheol Park,Jongyoun Park 한국소성가공학회 2010 기타자료 Vol.2010 No.6

Recently, significantly thinner sheet steels are tested and applied in digital display equipment than previous ones, therefore many cases of shape defects such as twisting, oil canning and curvatures in stamped panels are reported from stamping factories. In order to study the cause of twisting defects of stamped panel, simulative tests by 800×500 and 240×180 size blank and numerical simulation were done and analyzed the effects of forming conditions and material characteristics on twisting defects. It was found that the residual stress in stamped panel is the source of twisting and it increases as the difference between residual stress in panel center (positive stress component due to emboss forming) and marginal regions (negative stress value) increases. Both the residual stress difference in blank and twisting deformation increased in dense emboss formed cases than sparse embossing cases. Twisting deformation was increased if thinner blank, more curved blank and higher yield stress sheet applied cases.

Job Tenure and Wage Growth

Keecheol Ryoo(柳基喆) 영남대학교 산경연구소 1993 영상저널 Vol.1 No.-

Industry-Specific Human Capital and Wage Determination

Keecheol Ryoo(柳基喆) 영남대학교 산경연구소 1995 영상저널 Vol.3 No.-

Industry-Specific Human Capital and Wage Determination

Ryoo, Keecheol 嶺南大學校 産經硏究所 1995 産經硏究 Vol.3 No.-

미끄럼 속도가 공구와 강판 사이의 마찰 특성에 미치는 영향 및 이에 따른 강판의 딥 드로잉 성형성 변화

박기철(Keecheol Park),김석년(Seoknyeon Kim) 한국소성가공학회 2017 한국소성가공학회 학술대회 논문집 Vol.2017 No.5

취업형태의 지속성에 관한 연구

류기철 한국노동경제학회 2001 勞動經濟論集 Vol.24 No.1

본 논문에서는 취업형태를 정규직 임금근로, 비정규직 임금근로 및 자영업의 세 유형으로 구분하여 한국노동패널 자료에 포함된 남자근로자들의 전직에 따른 취업형태의 변화를 살펴보았으며, 또한 경쟁적 위험도 모형을 추정함으로써 이들의 재취업시의 취업형태의 결정에 영향을 미치는 요인들에 대한 분석을 행하였다. 분석 결과에 의하면 퇴직한 일자리에서의 취업형태가 새 일자리에서의 취업형태를 결정하는 데에 중요한 영향을 미치며, 또한 직장이동이 반복되는 경우 그 영향력이 점차로 약화되기는 하나 직전 직장 이전에 취업했던 일자리에서의 취업형태도 새 직장에서의 취업형태의 결정에 영향을 미치는 것으로 나타났다. 즉 직전 직장에서 비정규직으로 근무하다 실직한 근로자는 전직 이전의 직장에서 정규직으로 취업했던 근로자에 비해 정규직에 재취업할 가능성은 크게 낮은 반면, 또다시 비정규직에 재취업할 가능성은 크게 높은 것으로 분석되었다. 마찬가지로 퇴직한 직장에서의 취업형태가 자영직이었던 근로자는 전직 이전의 직장에서 정규직으로 취업했던 근로자에 비해 정규직에 재취업할 가농성은 크게 낮은 반면, 또다시 자영직에 재취업할 가능성은 크게 높은 것으로 분석되었다. 이러한 분석결과는 우리나라 남자근로자의 경우 비정규직 또는 자영직 일자리가 막다른 일자리로서의 성격을 가진다고 단정할 수는 없다고 하더라도 일단 비정규직 또는 자영직에 취업한 근로자가 전직을 통해 정규직 일자리로 옮겨가기가 쉽지 않음을 보여주는 것이라 생각된다. 이와 함께 실업률이 높아질수록 정규직과 자영직에의 취업 가능성은 낮아지나 비정규직에의 취업 가능성은 오히려 높아지는 것으로 나타났는데, 이는 노동시장에서의 수급조건이 근로자에게 불리할수록 노동시장의 비정규화가 빠른 속도로 진행될 수 있음을 의미하는 것으로 해석된다. This paper uses the Korean Labor Panel data to investigate changes in the employment types of male workers following their job changes with the classification of workers into three categories: regular wage workers, non-regular wage workers, and self-employed workers. It also estimates a competing-risks hazard model to analyze the determinants of employment types of workers. The results show that the type of employment of a worker at an immediate previous job has a critical importance in determining his employment type at a new job and that the types of employment at jobs other than the immediate previous job also play some role in determining the type of employment at a new job, although their impact declines as the number of intervening jobs increases. A job loser, who worked as a non-regular worker at his immediate previous job, for example, is considerably less likely to find a regular job, but more likely to get reemployed at another non-regular job than one who worked as a regular worker at his immediate previous job. Similarly, a worker who quit self-employment is much less likely to find a regular job but more likely to restart his own business than one who worked as a regular worker at his immediate previous job. These findings suggest that it is not easy at all for a worker who worked as either a non-regular worker or self-employed worker to become a regular worker, although it might be premature to assert that non-regular jobs or self-employed jobs are dead-end jobs. Another interesting finding of this analysis is that a high unemployment rate lowers a probability of reemployment at either regular jobs or self-employed jobs, but raises a non-regular job reemployment probability, which strongly implies that as labor market conditions become adverse to workers the proportion of non-regular employment can rise rapidly.

직교식 기준 페이지 선택 기법을 이용한 웹 탐색 성능 향상

李基哲,李善愛 弘益大學校 科學技術硏究所 2002 科學技術硏究論文集 Vol.13 No.-

The web world is getting so huge and untractable that without an intelligent information extractor we would get more and more helpless. Conventional web spidering techniques for general purpose search engine may be too slow for the specific search engines, which concentrate only on specific areas or keywords. In this paper a new model for improving web spidering capabilities is suggested and experimented. How to select adequate reference web pages from the initial web page set relevant to a given specific area (or keywords) can be very important to reduce the spidering speed. Our reference web page selection method dynamically and orthogonally selects web pages, and it can also decide the appropriate number of reference pages, using a newly defined measure. Even for a very specific area, this method worked comparably well almost at the level of experts. If we consider that experts cannot work on a huge initial page set, and they still have difficulty in deciding the optimal number of the reference web pages, this method seems to be very promising. We also applied reinforcement learning to web environment, and our method-based reinforcement learning experiments shows that our method works quite favorably in terms of both the number of hyper links and time.

가용성과 작업의 균등분배를 위한 JMX기반 클러스터 서버시스템

李基哲,蔡熙星 弘益大學校 科學技術硏究所 2003 科學技術硏究論文集 Vol.14 No.-

Information demands are fast rising, and today's computer system servers need to serve as many users and as many kinds of applications as possible, Therefore, a clustering system is mainly the internal structure of a server. Technically the server needs to be designed to load balance well. In this paper, a new clustering scheme is suggested for easy construction and maintenance of a server using Java Management Extensions. Recent Java technologies such as J2ME, J2EE, JMX, Jini and JDMK made it possible to integrate existing system functionalities based on the Java technology. Moreover, the adoption of application servers based on EJB technology speeds up rapidly. Recently, the demand of supporting on-line multimedia contents which have multiple terabytes size data increases. To address this problem, a clustering system which interconnects multiple computers with moderate price range seems to be very popular as an alternative to a single, high performance server. Experiments show that our system is easy to construct, expand, and load balance well even for dynamic situations of node additions, deletions, and malfunctions.

수동형 해양 시역전 수중음향장벽과 수중탐지에의 응용

신기철,김재수,Shin, Keecheol,Kim, Jeasoo 한국음향학회 2012 韓國音響學會誌 Vol.31 No.8

시역전 기술을 활용한 수중음향장벽에 의한 수중물체 탐지는 능동소나와 수동소나의 기법과 이론적 배경이 명확한 시역전 처리의 개념을 포함하고 있다. 본 논문에서는 수동형 해양 시역전에 의한 수중탐지의 개념과 이론을 수립하였다. 또한 수중음향 전파모델을 활용하여 모델링을 통해 수동형 시역전 수중음향장벽의 성능 예측을 수행하였다. 본 연구의 결과는 수동형 시역전 개념을 이용한 수중음향장벽 탐지시스템의 설계 시 유용한 성능예측 도구로 활용될 수 있다. Target detection by acoustic barrier method includes active and passive sonar technique and time reversal process whose theoretical background is already well defined. In this paper, the concept and theory of underwater detection by passive ocean time reversal is established. Also, the reason that this study was conducted was to investigate feasibility of complex mathematical modeling to provide some predictive capability for underwater acoustic barrier with passive time reversal. It may eventually lead to a useful predictive tool when designing underwater acoustic barrier detection system using the passive time reversal concept.

A 2018 Samsung Smart TV Data Acquisition Method Analysis

Terrence Nemayire,Alex Ogbole,Sungmi Park,Keecheol Kim,Yeonseok Jeong,장윤식 한국디지털포렌식학회 2019 디지털 포렌식 연구 Vol.13 No.3

Internet of Things (IoT) has brought a fair share of challenges for Digital forensics and Law Enforcement Agencies in carrying out their investigative duties. The authors of this paper studied the current trends and noticed an increase in crimes that require digital evidence from Smart TVs. Smart TVs are not only a probable source for digital evidence, but have become an integral part in most digital investigations, since they have the ability to connect to the Internet, store digital materials and are able to be synced with various user cloud accounts. This paper marks out the changes in results when using past well-known acquisition methods on the recent Smart TV device and proposes a general investigation procedure model for data acquisition and probable digital evidence for Smart TVs using Chip-Off methods. Regarding the lack of generally applicable methods for Smart TV forensics, this work for a new model will contribute to collective efforts as a whole.