• 대한토목학회논문집
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• 제8권2호
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• pp.89-98
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• 1988

본 연구는 도금공장에서 생산된 슬러지를 시멘트 고형화방법을 이용하여 처리할 때 고형화에 영향을 미치는 인자들 중에 모래/시멘트 비, 물시멘트 비, 젖은 슬러지의 양, 그리고 중금속 용출방지제를 네가지의 인자로 하여 압축강도와 용출량의 변화를 살펴 보았다. 모래/시멘트 비는 Cr(VI) 용출에 가장 큰 영향을 미치는 인자이며, 물/시멘트 비는 Zn와 압축강도에 가장 큰 영향을 미치는 인자였다. Cr(VI)는 Zn보다 시멘트 고형화에서 leachability가 더 적었다. 현장에서의 Cr(VI)과 Zn 그리고 압축강도를 예측하기 위한 모델을 계발하였으며, 고체화의 3급 Brick으로의 이용을 위해 혼합조건을 제시하였다. 그리고 30g의 건조슬러지를 고형화할 때 최적조건은 모래/시멘트 비, 물/시멘트 비, 그리고 중금속 용출방지제의 양은 각각 1, 1.5, 1.075g이었다.

• 한국해양환경ㆍ에너지학회지
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• 제16권2호
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• pp.61-70
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• 2013

조류발전용 수직축터빈(VAT)의 3차원적인 유체동력학적 성능을 효과적으로 예측할 수 있는 연구를 진행하였다. 수치해석은 2차원과 3차원으로 수행하였으며 이를 통해 물리적 유동현상의 차이를 파악하였다. 3차원 효과는 주로 날개 끝단에서 발생하는 날개끝 보오텍스가 주된 원인으로서, 이로 인해 터빈 날개가 내어주는 양력이 손실되고 회전하는 터빈은 토크가 감소하였다. 이러한 현상은 본 연구에서 채택한 통상적인 수직축 터빈의 스팬-직경비 범위에서 상당한 수준으로 나타남을 확인하였다. 본 연구에서는 대상 터빈을 선정하고 2차원으로 성능해석 후 3차원 효과를 보정하는 비교적 간단하고 효과적인 방법을 제안하였다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.484-488
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• 1997

Three-dimensional finite element analyses were used to compare the stress distribution and the stability of the fixation among seven different tibial components and to investigate the effect due to implant materials in total knee arthroplasty. The components included an intact tibia(Type I), Cemented Cobalt-Chromium tibial tray implanted with a PMMA cemented Co-Cr stem(Type II), Cemented Co-Cr tibial tray with a uncemented Co-Cr stem(Type III), Cemented Ultra High Molecular Weight Polyethylene (UHMWPE) tibial tray with a cemented UHMWPE stem (Type IV), Cemented UHMWPE tray with a uncemented UHMWPE stem(Type V), Cemented Co-Cr tray without a stem(Type VI), and Cemented UHMWPE tray without a stem(Type VII). Uncemented components were assumed to have complete bony in growth and a rigid state of fixation between component and bone. The interface between bone/cement/component of cemented components was also assumed to be fully bonded. Bi-condylar forces were applied. The results indicated that Uncemented stem components provided lower bone stress shielding and stress concentration. The UHMWPE tray and stem component showed better agreement with the intact tibia than the Co-Cr Alloy tray and stem components. If the implant tray can be fixed firmed without a stem, Cemented PE tray without a stem(Type VII) may be recommended to give the best characteristics in the sense of stress distribution and stability.

• 한국정밀공학회지
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• 제18권11호
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• pp.51-57
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• 2001

A light beam reflected from a machined surface generally containes information concerning about its surface roughness. This study examines and proposes a surface roughness measurement technique for on-machine measurement of machined surfaces. The technique is based on the measurement of a reflected laser beam pattern and the statistical analysis of its light intensity distribution. The surface roughness was found to be closely related to the standard deviation of the light intensity on the primary axis of the reflected pattern. An image acquisition device is made up of a laser diode, a half mirror, a screen, and a CCD camera. The exact image with the primary and secondary axes of a reflected laser beam pattern is calculated through such image processing algorithm as thresholding, edge detection, image rotation, segmentation, etc. A median filter and a surrounding light correction algorithm are improve the image quality and reduce the measuring error. Using the developed measuring device the effect of screen materials and workpiece and workpiece materials was investigated. Experimental results regarding to relatively high-quality surfaces machined by grinding, polishing, lapping processes have shown the measurement error is within 10% in the range of $0.1{mu}m~0.8{\mu}m R_q.$Therefore, the proposed method is thought to be effectively used when quick measurements is needed with workpieces fixed on the machine.

• Journal of Preventive Medicine and Public Health
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• 제46권1호
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• pp.1-9
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• 2013

Objectives: We examined the association between social expenditures of the local government and the mortality level in Korea, 2004 to 2010. Methods: We used social expenditure data of 230 local governments during 2004 to 2010 from the Social Expenditure Database prepared by the Korean Institute for Health and Social Affairs. Fixed effect panel data regression analysis was adopted to look for associations between social expenditures and age-standardized mortality and the premature death index. Results: Social expenditures of local governments per capita was not significantly associated with standardized mortality but was associated with the premature death index (decline of 1.0 [for males] and 0.5 [for females] for each expenditure of 100 000 Korean won, i.e., approximately 100 US dollar). As an index of the voluntary effort of local governments, the self-managed project ratio was associated with a decline in the standardized mortality in females (decline of 0.4 for each increase of 1%). The share of health care was not significant. Conclusions: There were associations between social expenditures of the local government and the mortality level in Korea. In particular, social expenditures per capita were significantly associated with a decline in premature death. However, the voluntary efforts of local governments were not significantly related to the decline in premature death.

• 대한치과보철학회지
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• 제44권4호
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• pp.363-373
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• 2006

Statement of Problem : The accuracy and dimensional stability of elastomeric impression materials have been the subject of numerous investigation. Few studies have addressed the effect of changes in time on the dimensional stability of impression materials. Purpose: The purpose of this investigation was to evaluate the effects of elastomeric impression materials and storage time on dimensional stability. Materials and methods: A total of 75 impressions were made of epoxy resin dies mimicked prepared 3-unit fixed partial denture. The dies had 1 buccolingual, 1 mesiodistal and 1 occlusogingival lines and interpreped dot. Impression materials investigated included two polyether impression materials and three polyvinylsiloxane impression material. 15 specimens were made of each impression material and poured by type IV stone over times (30 minutes, 24 hours, 72 hours) after mixing; the same examiner measured each specimen 3 times at a magnification of 3.5$\times$. All statistical tests were performed with the level of significance set at .05. Results : The results indicated that significant difference at any measuring point of stone dies of the polyether impression materials and when measurements at 30 minutes, 24 hours, and 72 hours were compared ; the length of measuring point increased significantly as time passed by. However this result is not significant clinically. Analysis also showed significant differences at any measuring point when polyvinylsiloxane and polyether impression materials were compared and significant differences clinically. Conclusion: Under the conditions of this study, the shrinkage rate of the polyvinylsiloxane and polyether impression materials significantly increased as time passed by. The polyether impression materials showed higher shrinkage significantly, while the shrinkage rate of all five materials showed a significant time-dependent increase.

• Animal cells and systems
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• 제12권2호
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• pp.77-83
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• 2008

The canine fearfulness is a behavioral trait known to have a genetic basis. This research analyzed genetic effects of the dopamine D4 receptor polymorphism on this behavior by postulating a mixed model of inheritance. Genotyping for the three different repeat polymorphism found in the third exon of the receptor gene was carried out for the population of the Korean native dogs. Four hundred fifty eight dogs with known pedigree were genotyped, and 264 individuals were tested for their fear responses to an experimenter, in which four different behavioral paradigms were adopted. Since the results assessed by principal factor analysis revealed a major factor explaining 69% of the total phenotypic variance, the subsequent analyses were conducted for this quantity. Analyses of the factor scores by estimating their posterior means indicated that there is a fixed effect exerted by the three different repeat polymorphism found in the D4 receptor as well as sex, in addition to unidentified polygenic effects. The phenotypic contribution of the D4 genotype was roughly estimated to be about 2%, which is a fraction of the total genetic effects responsible for more than 20% of the total phenotypic variance.

• 청정기술
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• 제5권2호
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• pp.63-68
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• 1999

The activities of Ni(20wt%)/$La_2O_3$, Ni(20wt%)/${\gamma}-Al_2O_3$, and Ni(20wt%)/$SiO_2$ catalyst for $CO_2$ reforming of $CH_4$ were investigated in a fixed bed flow reactor under atmospheric condition. Catalyst characterization using XRD, TEM, SEM, BET analysis were also conducted. The catalytic activity of Ni(20wt%)/$La_2O_3$ catalyst has relatively superior to that of Ni(20wt%)/${\gamma}-Al_2O_3$ and Ni(20wt%)/$SiO_2$ catalyst. The good activity of Ni(20wt%)/$La_2O_3$ catalyst seems to depend on reduced $Ni^{\circ}$ phases of NiO($\rightarrow$ Ni + O), $LaNiO_3$($\rightarrow$ $Ni+La_2O_3$), Ni crystalline phases, and decoration of Ni phases by lanthanum species is also an important factor. Ni(20wt%)/${\gamma}-Al_2O_3$ and Ni(20wt%)/$SiO_2$ catalyst due to surface acidity resulted in the deposition of wisker type and encapsulate carbon on the surface of catalyst, but Ni(20wt%)/$La_2O_3$ catalyst did not show carbon on the surface of catalyst up to 8.5hr reaction.

• 한국재료학회지
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• 제19권3호
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• pp.151-155
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• 2009

Micro-scale copper bumps for build-up PCB were electroplated using a pulse-reverse method. The effects of the current density, pulse-reverse ratio and brightener concentration of the electroplating process were investigated and optimized for suitable performance. The electroplated micro-bumps were characterized using various analytical tools, including an optical microscope, a scanning electron microscope and an atomic force microscope. Surface analysis results showed that the electroplating uniformity was viable in a current density range of 1.4-3.0 A/$dm^2$ at a pulse-reverse ratio of 1. To investigate the brightener concentration on the electroplating properties, the current density value was fixed at 3.0 A/$dm^2$ as a dense microstructure was achieved at this current density. The brightener concentration was varied from 0.05 to 0.3 ml/L to study the effect of the concentration. The optimum concentration for micro-bump electroplating was found to be 0.05 ml/L based on the examination of the electroplating properties of the bump shape, roughness and grain size.

• 대한조선학회논문집
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• 제50권5호
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• pp.307-313
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• 2013

This paper presents a simulation for passenger ship evacuation considering determination of evacuating direction based on walking direction potential function. In order to determine walking direction of a passenger, his/her position in two dimensional plane was adopted as a design variable, and fixed boundaries such as walls and obstacles were adopted as constraints. To solve this optimum problem, a walking direction potential function was adopted as an objective function. This potential function was configured as a kind of penalty function and it contained two components. One is a potential function concerned with the distance to the destination, and other is a potential function based on the effect of walls and obstacles. To determine evacuating direction, this problem was solved by minimizing the walking direction potential function every unit time during the simulation. The crowd behavior of the passenger consisted of the flock behavior, a form of collective behavior of a large number of interacting passengers with a common group. With the proposed algorithm, the test problems in International Maritime Organization, Maritime Safety Committee/Circulation 1238(IMO MSC/Circ.1238) were implemented and the direction of passengers and total evacuation time was analyzed.