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. 퇴적물 음파전달속도 측정은 전통적으로 신호투과빙식을 이용한 수은기둥 방법을 응용하여 사용하여 왔다. 그러나 이 방법은 시료 및 표준물질을 통과한 신호를 오실로스코프상에서 자료처리를 할 수 없으며, 육안으로 펄스신호를 구분해야 하고, 측정자에 따라 속도값의 차이가 나타날 수 있고, 동일인이 측정할 경우에도 반복된 연습에 의한 숙련이 필요하다. 또한 수은기둥을 자주 보정해 주어야 하는 등의 단점이 있다. 이러한 문제를 해결하기 위해 퍼스널컴퓨터와 음파전달속도 측정장치인 오실로스코프 사이를 GPIB(General Purpose Interface Bus) 카드를 이용하여 연결한 다음 컴퓨터상에서 커서를 움직여 퇴적물의 음파전달속도를 측정하는 새로운 측정기법을 개발하였다. 새로운 측정방법의 검증을 위해서 동일시료에 대해 기존 수은기둥 방법과 병행하여 측정한 결과 측정 오차를 넘지 않는 거의 유사한 값을 보였다. 따라서 새로운 측정기법은 해양퇴적불의 속도측정에 이용될 수 있게 되었으며 입력된 양질의 파형을 이용하여 신호처리(FFT)를 함으로서 장래에 다른 음향특성(감쇠)까지도 구할 수 있는 장점을 갖게 되었다.

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. Physical and acoustic properties of the Southeastern Yellow Sea Mud (SEYSM) of Korea were studied by using 10 piston cores. The data were also compared with mudbelt sediments in the South Sea and the East Sea (southeastern inner shelf) of Korea. The sediments were mainly composed of homogeneous silt. Sandy mud and mud were minor components. The major source of sediment in the study area is probably the Keum River. Finegrained sediments discharged from the river are transported southward by coastal current, resulting in a gradual southward increase in porosity and a decrease in wet bulk density and sound velocity. The mean grain size especially appears to be the most important variable to determine the physical properties and velocity. The variations of physical properties with burial depth are dependent more strongly on sediment texture (especially, silt content) than compaction and/or consolidation. Correlations between the physical properties and the sediment texture show slight deviations from those of the East Sea and the South Sea of Korea in spite of similar pattern within the limiting values. This is probably due to the differences in silt contents, sedimentary environments, mineral compositions, and gas contents.

Compressional Wave Velocity and Electrical Resistivity in Hemipelagic Clay-rich Sediment, Northwestern Pacific

김대철,김기현,Kim, Dae Choul,Kim, Kee Hyun The Korean Society of Oceanography 1988 韓國海洋學會誌 Vol.23 No.3

Properties of porosity, compressional wave velocity, velocity anisotropy, electrical resistivity, and resistivity anisotropy are measured and calculated for two DSDP clay-rich hemipelagic sequences in the northwestern Pacific. Velocity and resistivity increase with burial depth at the expense of decreasing porosity. Profiles of velocity anisotropy and resistivity anisotropy show almost the same trend. Horizontally developed low aspect ratio pores may generate velocity and resistivity anisotropy. The preferred orientation of clay minerals is also believed to be responsible for the observed anisotropy.

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.

농업기계 신뢰성 현황

김대철,남요상,강영선,Kim, Dae-Cheol,Nam, Yo-Sang,Gang, Yeong-Seon 대한기계학회 2007 기계저널 Vol.47 No.9

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. 한국 남동해역 내대륙붕 음향혼탁층이 잘 발달된 이토대(mudbelt) 퇴적물의 음파전달속도와 전기비저항에 대해연구하기 위하여 총 9개 정점에서 피스톤시추기를 이용하여 해저퇴적물을 채취하였다. 각 코어별 10 cm 깊이로 퇴적물의 음파전달속도, 전기비저항, 공극율 및 전밀도를 측정하였고 연엑스선 촬영을 통해 퇴적구조를 관찰하였다. 연구지역의 해저지층은 고해상도 해저지층탐사기를 이용하여 조사하였다. 고해상도 해저지층탐사결과 음향혼탁층의 분포를 알 수 있었으며,코어시료의 연엑스선분석 결과 가스에 의해 형성된 균열구조(degassying structure)를 확인할 수 있었다. 코어시료의 내부구조, 음파전달속도, 전기비저항 및 물성 값을 토대로 연구지역 퇴적물을 가스함유퇴적물(gassy sediment)과 무가스함유퇴적물(non-gassy sediment)로 구분하였다. 퇴적물의 깊이에 따른 속도, 전기비저항, 공극율 및 전밀도 차이는 퇴적물 조직과 관련된 퇴적구조에 영향을 받으며, 가스의 함유유무와 그에 수반되는 균열구조에 의해 음파전달속도와 전기비저항 값이 큰 차이를 나타냈다. 이들 자료의 수직적인 단면도와 상관관계를 통해 연구지역에서는 가스함유 유무에 따라 음파전달속도와 전기비저항 값이 크게 반응하며 이중 음파전달속도가 더 민감하게 반응하는 것으로 나타났다.

한국꿩의 20주령 체중 및 육성기 체측정치에 대한 유전력과 유전상관

김대철,양영훈 ( D . C . Kim,Y . H . Yang ) 한국축산학회 1998 한국축산학회지 Vol.40 No.2

This study was carried out to estimate the heritabilities of body weight, shank length and shank width and to investigate the genetic correlation between the body weight at 20 wks and the other body measurements in growing period for pheasant(phasianus colchicus). The heritability estimates were in the range of 0.44∼0.73 for body weight, 0.27∼0.79 for shank length and 0.45∼0.71 for shank width in the growing period. The heritability estimates of body weight, shank length and shank width for male were slightly heigher than those for female at 4 wks old while the estimates at 12 wks and 20 wks were heigher for female than those for male. The heritability of daily body weight gains during 1-d to 4 wks, 5 to 12 wks, and 13 to 20 wks of age were 0.51, 0.46 and 0.30 for male and 0.39, 0.59 and 0.36 for female, respectively. The phenotypic and genetic correlation coefficients between the 20 wks body weight and other body measurements in the growing period were 0.24∼0.70 and 0.36∼0.85, respectively. Phenotypic and genetic correlation coefficients of 20 wks body weight with daily body weight gain during 5 to 12 wks were heigher than any other estimates with the daily weight gains.

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.

홈 서버 기반의 안정적이고 확장성 있는 지능형 관측/제어 로봇 시스템의 설계 및 구현

김대철 ( D. C. Kim ),오범석 ( B. S. Oh ),나대영 ( D. Y. Na ),안성현 ( S. H. An ),김대영 ( D. Y. Kim¸ ),이창민 ( C. M. Lee ),김우길 ( W. G. Kim ),홍종민 ( J. M. Hong ),전흥석 ( Heung Seok Jeon ) 한국정보처리학회 2006 한국정보처리학회 학술대회논문집 Vol.13 No.2

최근 기존의 단일 시스템 기반의 지능형 로봇이 가지는 한계를 극복하기 위해 네트워크기반 지능형 로봇에 관한 연구가 활발히 진행되고 있다. 네트워크기반 지능형 로봇은 로봇에 집중되는 기억 장치 및 컴퓨팅 자원을 네트워크를 통한 서버에 분산시키면서 로봇 자체의 단가는 낮춘 반면 고도의 서비스를 제공할 수 있게 한다. 그러나 네트워크기반 지능형 로봇 시스템은 서버의 과부하 부담 문제와 다양한 매체로 서비스하기 위한 일관성 있는 인터페이스 개발 문제 등 기술적으로 해결해야 할 몇 가지 문제를 가지고 있다. 본 논문에서는 홈 서버를 이용하여 이러한 문제들을 해결하면서 원격에서 모바일 로봇의 관측 및 제어가 가능한 지능형 로봇 시스템을 제안한다.

논문 : 노외기계시스템공학 ; 농업용 트랙터의 연료 소비량 예측 모델

김대철 ( D. C. Kim ),김경욱 ( K. U. Kim ),김수철 ( S. C. Kim ) 한국농업기계학회 2010 바이오시스템공학 Vol.35 No.1

A mathematical model was developed to predict the fuel consumption rate consumed by agricultural tractors under arbitrary loaded conditions. The model utilizes the measured data on the fuel consumptions at the full load and at the rated engine speed with partial loads, which can easily be obtained from the official OECD tractor test reports. It was found from the analysis of the measured fuel consumption data that the fuel consumptions at two different speeds does not change with power. The model was developed based on this fact and validated with the measured data of the 159 tractor test reports. The fuel consumptions predicted by the model were compared with those measured under the partially loaded conditions specified in the official OECD tractor test code II. The percent errors of the predicted fuel consumptions were in a range from 0.36 to 2.86% which assured that the developed fuel consumption model can be used practically to predict the fuel consumptions at any speed and power combinations. It was also shown that the developed model predicts the fuel consumption rate better than the Grisso`s model.