누적손상이론을 이용한 기계류부품의 가속수명시험법 개발

김대철,이근호,김형의,Kim, Dae-Cheol,Lee, Geun-Ho,Kim, Hyeong-Ui 한국기계연구원 2002 硏究論文集 Vol.32 No.-

This study was performed to develop accelerated life test method of machanical parts using cumulative damage theory that used to model the fatigue of parts that receive variable load. The cumulative damage theory was introduced, and the estimation of life and calculation of accelerated life test time was illustrated. As the actual application example, accelerated life test method of agricultural tractor transmission was described. Life distribution of agricultural tractor transmission was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 3,000 hours and 90% reliability for one test sample. According to the cumulative damage theory, because test time can shorten in case increase test load, test time could be reduced by 482 hours when we put the load 1.1 times of rated load than 0.73 times of rated load that is equivalent load calculated by load spectrum of the agricultural tractor. This time, acceleration coefficient was 11.7. This accelerated test method was used to develop accelerated test method of gear reducer, hydraulic hose and bearing as well as agricultural tractor transmission and it is considered to be applied comprehensively to machanical parts the fatigue of which is happened by load or pressure etc.

물리화학적 성적을 근거로한 선택적 요침사검사의 유용성에 관한 고찰

김대철,김경동,김정숙 대한임상검사정도관리학회 1991 臨床檢査와 精度管理 Vol.13 No.2

가스함유퇴적물에서의 음파전달속도 및 전기비저항 특성: 한국남동해역 이토대 퇴적물의 분석결과

김대철,박수철,서영교,Kim, Dae-Choul,Park, Soo-Chul,Seo, Young-Kyo 한국해양학회 2001 바다 Vol.6 No.4

Compressional wave velocity and electrical resistivity of muddy sediments in the southeastern inner shelf of Korea were studied using nine piston core samples. The acoustic and physical properties were measured with 10 cm depth interval. Sediment structures were examined by x-radiographs of the cored sediments. Subbottom profiles were obtained by a high-resolution acoustic subbottom profiler. Acoustic turbid layers are clearly seen on the profiles, and x-radiographs of the sediments showed degassying structures formed by gas escaping. On the basis of x-radiographic images, velocities, electrical resistivities and physical properties, the sediments are divided into gassy and non-gassy sediments. The presence of gas and degassying structures result in a marked variation in velocity and electrical resistivity. It can be concluded that velocity and electrical resistivity arep arameter to recognize gassy sediment. The velocity is important parameter to indicate gassy sediment.

황해 남동부 니질대의 물리적 성질: 동해 및 남해 니질대와의 비교

김대철,김신정,서영교,정자헌,김양은,김길영,Kim, Dae-Choul,Kim, Shin-Jeong,Seo, Young-Kyo,Jung, Ja-Hun,Kim, Yang-Eun,Kim, Gil-Young 한국해양학회 2000 바다 Vol.5 No.4

황해 남동부 니질대(mudbelt)퇴적물의 물리적 성질을 연구하기 위하여 총 10개 정점에서 해저 퇴적물을 채취하였다. 그 자료는 동해(남동 내대륙붕)및 남해니질대 자료와 비교하였다. 시추퇴적물들의 대부분은 실트질이 우세하며, 그 외 사질니 및 니로 구성되어 있다. 연구지역 표층퇴적물은 주로 금강에서 유입된 세립질 퇴적물이 연안류에 의해 남쪽으로 이동하여 분급화되면서 평균입도, 속도 및 습윤전밀도값은 점진적으로 감소하고 공극율은 증가하는 경향을 잘 보인다. 평균입도가 물성 및 음파전달속도를 결정하는데 주요한 변수로 나타났고, 수직적인 변화도 다져 짐작용이나 고화작용에 의한 영향보다는 퇴적물 조직 (주로 실트함량)의 변화 경향을 잘 반영하는 것으로 나타났다. 조직 및 물성간의 상관관계를 보면 비교모델로 사용한 남해 및 동해역 퇴적물과 가벼운 편차는 있으나 전반적인 경향은 유사하다 다만 가벼운 편차가 나타나는 것은 실트함량의 차이, 퇴적환경, 광물조성의 차이 및 가스의 함량 등 복합적인 결과로 보인다.

해양퇴적물의 자동음파전달속도 측정장치

김대철,김길영,서영교,하덕호,하인철,윤영석,김정창,Kim, Dae-Choul,Kim, Gil-Young,Seo, Young-Kyo,Ha, Deock-Ho,Ha, In-Chul,Yoon, Young-Seok,Kim, Jeng-Chang 한국해양학회 1999 바다 Vol.4 No.4

The conventional mercury delay method to measure compressional wave velocity of unconsolidated sediment is inconvenient because the signal must be analyzed on the oscilloscope and the mercury column has to be calibrated between measurements. We developed an automated compressional wave velocity measurement technique by connecting an oscilloscope and a PC with a GPIB (General Purpose Interface Bus) card. The GPIB card buses signals from the oscilloscope to the PC where the signal from a sample is analyzed and compared to the input pulse thereby the compressional wave velocity of the sample is computed and recorded automatically. Differences between the mercury delay method and the automated measurement technique are negligible except the slightly greater velocity in the automated measurement technique. We concluded that the new technique can be used to measure the velocity for unconsolidated marine sediment. It also has an advantage to calculate sediment attenuation through the processing of waveform using the spectral ratio technique.

A Lagrangian Relaxation Method for Parallel Machine Scheduling with Resource Constraints

김대철,Kim, Dae-Cheol Korean Institute of Industrial Engineers 1998 산업공학 Vol.11 No.3

This research considers the problem of scheduling jobs on parallel machines with non-common due dates and additional resource constraints. The objective is to minimize the total absolute deviation of job completion times about the due dates. Job processing times are assumed to be the same. This problem is motivated by restrictions that occur in the handling and processing of jobs in certain phases of semiconductor manufacturing and other production systems. We examine two problems. For the first of these, the number of different types of additional: resources and resource requirements per job are arbitrary. The problem is formulated as a zero-one integer linear programming and the Lagrangian relaxation approach is used. For the second case, there exists one single type of additional resource and the resource requirements per job are zero or one. We show how to formulate the problem as an assignment problem.

Laboratory/In situ Sound Velocities of Shelf Sediments in the South Sea of Korea

김대철,김길영,정자헌,서영교,Roy H. Wilkens,유동근,이광훈,김정창,이희일,Gunay Cifci 한국수산과학회 2008 Fisheries and Aquatic Sciences Vol.11 No.2

Compressional sound velocities of shelf sediments in the South Sea of Korea, were measured in situ and in the laboratory for six cores. In situ sound velocity was measured using the Acoustic Lance (frequency of 7.5-15kHz), while laboratory velocity was measured by the pulse transmission technique (frequency of 1MHz). Physical properties were relatively uniform with sediment depth, suggesting little effect of sediment compaction and/or consolidation. Average in situ velocity at each core site ranged from 1,457 to 1,488 m/s, which was less than the laboratory velocity of 1503 and 1604 m/s. In muddy sediments the laboratory velocity was 39-47 m/s higher than in situ velocity. In sandy sediments, the difference was greater by an average of 116 m/s. Although the velocity data were corrected by the velocity ratio method based on bottom water temperature, the laboratory velocity was still higher than the in situ velocity (11-21 m/s in muddy sediments and 91m/s in sandy sediments). This discrepancy may be caused by sediment disturbance during core collection and/or by the pressure of Acoustic Lance insertion, but wass most likely due to the frequency difference between in situ and laboratory measurement systems. Thus, when correcting laboratory velocity to in situ velocity, it is important to consider both temperature and frequency.

패밀리 레스토랑의 샐러드 바 서비스품질이 고객만족, 재방문의도 구전효과에 미치는 영향 : 서울 및 수도권 프랜차이즈 패밀리 레스토랑을 중심으로

김대철,성혜진,고재윤 한국호텔관광학회 2007 호텔관광연구 Vol.9 No.3

Recently sea food restaurants become popular among customers. This study analyzes the effect of the service quality of family restaurants' salad bar on customer' satisfaction, revision intention and oral transmitting intention. This study researched 300 workers from family restaurant and used 256 questionnaires to analyze results. As a result, first, as for the effect of the service quality on customer' satisfaction, human service satisfaction is found to influence empathy factor, reliability factor, tangibles factor, responsiveness factor and assurance factor. Also, material service satisfaction is found to influence oral transmitting intention. Second, customer satisfaction influences revising intention and Word of Mouth intention, System service satisfaction influences revising intention and oral transmitting intention, and material service satisfaction is found to influence oral transmitting intention. Third, as for the influence of service quality on revising intention and Word of Mouth intention, revising intention influences reliability factor, tangibles factor and assurance factor. Word of Mouth influences empathy factor, reliability factor and assurance factor. Finally, when customers choose salad bar, the quality and variety of menu, and taste influence them. Customers get information of salad bar from people around them.

담낭암종에서의 p53, Heat Shock Protein 70과 TopoisomeraseIIα 의 발현

김대철,노미숙,정진숙 대한병리학회 2006 Journal of Pathology and Translational Medicine Vol.40 No.6

The present study was designed to investigate the expression of p53, Heat Shock Protein 70 (HSP70), and Topoisomerase (Topo) IIα in the preneoplastic lesions and carcinomas of the gallbladder (GB) and to assess the correlation between the expression of these proteins and the clinicopathologic parameters by performing immunohistochemistry. Methods : The immunohistochemical expressions of p53, HSP70 and Topo IIα were evaluated in 38 gallbladder carcinomas and 3 adenomas. Fifteen CISs and 8 dysplasias that were located adjacent to invasive carcinomas were also studied. Results : A p53 expression was identified in 22 (57.9%) of the 38 GB carcinomas, in 9 (64.3%) of 14 CISs, and in none of the 8 dysplasias and 3 adenomas. A HSP70 expression was found in 11 (29%) of the 38 carcinomas, in 11 (78.6%) of 14 CISs, and in 4 (57.2%) of 7 dysplasias. A Topo IIα expression was present in 36 (94.7%) of the 38 carcinomas, in 13 (92.9%) of 14 CISs, in 7 (100%) of 7 dysplasias and in 3 (100%) of 3 adenomas. p53 overexpression was related to the T stage of the primary tumor, while HSP70 and Topo IIα were not related to any of the clinicopathologic parameters. Conclusion : p53 may be involved in GB carcinogenesis and in the progression of cancer. p53 may be also helpful for making the differential diagnosis between dysplasia and CIS. A further large study is needed to better elucidate the roles of HSP70 and Topo IIα in GB carcinogenesis.

Habit modification of tamoxifen crystals using antisolvent crystallizations

김대철,여상도 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.5

The crystal habit of tamoxifen was modified using antisolvent crystallization techniques. Tamoxifen was crystallized from organic solvents using two different antisolvents (water and carbon dioxide). The habit of the precipitated crystals was modified by changing the process conditions, such as the solution and antisolvent mixing rate, the organic solvent, the presence of ultrasonic waves, and the addition of external additives. Particle size, crystal habit, particle aspect ratio and powder XRD patterns of the precipitated tamoxifen crystals were measured. With water as the antisolvent, the particle size of tamoxifen was significantly reduced compared to that of the raw material. When the antisolvent was carbon dioxide, the particle size was an order of magnitude greater than that of the raw material. The average aspect ratio of the tamoxifen crystals ranged from 1.8 to 16.2. The presence of ultrasonic waves caused a significant reduction in the aspect ratio, as well as the particle size. Furthermore, the addition of external additives was found to influence the crystal habit of tamoxifen.