• 대한환경공학회지
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• 제28권7호
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• pp.731-737
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• 2006

미국 Oak Ridge 연구소 관리지역에서 Inceptisol(Inc) 및 Utisol(Ult)이 지배적으로 분포된 토양층의 A- 및 B-층으로부터 채취한 물리화학적 특성이 잘 규명된 4종의 토양시료에 As(III) 및 As(V)를 흡착시킨 후 토양시료에 대한 추출용액의 비 1:100 조건에서 pH를 1.5로 고정시킨 생리학적 추출용액을 이용한 추출시험을 통하여 초기 노화조건에서의 비소의 생접근도(bioaccessibility) 및 As(III) 산화정도와 6개월간의 노화시간 경과에 따른 비소의 생접근도를 조사하였다. 토양시료에 As(C)를 주입시킨 후 48시간이 경과되었을 때 모든 토양시료에서, 특히 Ult-B, 빠르고도 강한 As(V)의 고정화(sequestration) 현상이 일어났다. 그렇지만 3개월이 지난 후에는 As(V)의 고정화에 큰 변화가 없었다. 동일한 토양시료에 As(III)를 인위적으로 오염시킨 후 48시간이 경과되었을 때 Inc-A 및 Ult-A 토양시료에서는 상당 분율의 As(III)가 As(V)로 산화되었다. 이러한 As(III)의 산화정도는 토양시료내의 망간 함량과 비례관계가 있는 것으로 나타났다. As(III)를 오염시킨 Inc-B 및 Ult-B 토양시료에서의 노화시간 경과에 따른 총비소의 생접근도 감소는 Inc-A 및 Ult-A 토양시료에서 얻어진 값보다 더 크게 나타났다. 이러한 경향은 철 함량이 풍부한 Inc-B 및 Ult-B 토양들이 As(III)로부터 산화된 As(V)를 지속적으로 고착화시킴에 따른 것으로 여겨지며 As(V)로 오염시킨 토양시료에서 얻어진 As(V) 고착화 정도와 유사한 경향을 나타내었다.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.54-61
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• 2004

The engine-out flow is highly transient and hot, and may place tremendous thermal and inertial loads on a closed-coupled catalyst. Therefore, time-dependent and detailed flow and thermal field simulation may be crucial. The aim of this study is to develop combined chemical reaction and multi-dimensional fluid dynamic mathematical model and to study the effect of unsteady pulsating thermal and flow characteristics on thermal reliability of closed-coupled catalyst. The effect of cell density on the conversion performance under real running condition is also investigated. Unlike previous studies, the present study focuses on coupling between the problems of pulsating flow pattern and catalyst thermal response and conversion efficiency. The results are expressed in terms of temporal evolution of flow, pollutant and temperature distribution as well as transient characteristics of conversion efficiency. Fundamental understanding of the flow and thermal phenomena of closed-coupled catalyst under real running condition is presented. It is shown that instants of significantly low values of flow uniformity and conversion efficiency exist during exhaust blowdown and the temporal varaition of flow uniformity is very similar in pattern to one of conversion efficiency. It is also found that the location of hot spot in monolith is directly affected by transient flow pattern in closed-coupled catalyst.

• Corrosion Science and Technology
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• 제5권2호
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• pp.69-76
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• 2006

Premature cracking of the epoxy coatings applied on ship's ballast tanks(BT) can lead to damage of ship's hulls. To avoid this, it's important to have clear understanding of the underlying mechanism and primary factors of the coating crack. In this study, the efforts were made to clarify the integrated effects of main factors, i.e., initial coating shrinkage, thermally induced strain, steel-structural strain and the intrinsic coating flexibility at the initial and after aging, to the early cracking phenomena of epoxy coating in the ship's ballast tank. The coating crack is caused by combination of thermal stress, structural stress, and internal stresses which is closely related to chemical structures of the coatings. On the other hand, thermal stresses and dimensional stabilities would rarely play a major role in coating crack for ballast tank coatings with rather large flexibility. Crack resistance of the coatings at early stages can be estimated roughly by measuring internal stress, FT-IR and $T_g$ value of the coatings. A new screening test method was also proposed in this study, which can be possibly related to the long-term resistance of epoxy-based paints to cracking.

• 한국전기전자재료학회논문지
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• 제30권9호
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• pp.551-557
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• 2017

It is extremely important to improve methodologies for the lifetime assessment of porcelain insulators. While there has been a considerable amount of work regarding the phenomena of lifetime distributions, most of the studies assume that aging distributions follow the Weibull distribution. However, the true underlying distribution is unknown, giving rise to unrealistic inferences, such as parameter estimations. In this article, we review several distributions that are commonly used in reliability and survival analysis, such as the exponential, Weibull, log-normal, and gamma distributions. Some properties, including the characteristics of failure rates of these distributions, are presented. We use a Bayesian approach for model selection and parameter estimation procedures. A well-known measure, called the Bayes factor, is used to find the most plausible model among several contending models. The posterior mean can be used as a parameter estimate for unknown parameters, once a model with the highest posterior probability is selected. Extensive simulation studies are performed to demonstrate our methodologies.

• Plant Biotechnology Reports
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• 제4권2호
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• pp.117-123
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• 2010

We used a flow cytometer to investigate the variations in endopolyploidy (the frequencies of nuclei with DNA contents equivalent to 4C through 16C) during the short period of the early growing stage in vigorously growing young tissues of maize seedlings. We examined different portions of the root and leaves that had been growing for 7 (day 7) and 13 (day 13) days after germination. Endoreplication showed two opposing phenomena without aging. In one case, the endopolyploidy of the first leaf was higher on day 13 than on day 7. In the latter case, endopolyploidy decreased, as clearly revealed by a comparison of the endopolyploidy of the second leaves and the 160-170 mm portion of the seminal root on days 7 and 13. Endopolyploidy was also lower in the top of the leaf. In roots, endopolyploidy was increased by the exogenous application of abscisic acid for only 1 day. The levels of endopolyploidy increased without an increase in cell size in the roots. These results showed that endoreplication occurs in actively growing and young tissue and that the variation can be induced in the short period examined.

• 한국의류학회지
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• 제33권10호
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• pp.1530-1540
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• 2009

Life expectancy has increased and people are more concerned with keeping their 'youth'. Appearance is a competitive edge and people are caught up in a baby face fad that has expanded into a culture and beauty trend. This study examined the definitions and phrenological characteristics of a baby face and the causes of the baby face fad in a review of the baby face as a "sociocultural and beauty cultural code" based on literature, journals, previous papers, and Internet materials. Anatomically speaking, a "baby face" refers to a face that keeps the features of a child's face without aging signs. The baby face fad gained momentum due to the influences of the digital culture, the encouragement of the mass media, changes to the social structure, dietary improvements, new living styles, and an evolving aesthetic sense. The results reveal the sociocultural backgrounds behind the "baby face fad" settling down as a part of culture in addition to the phrenological characteristics of a baby face. It is also estimated that the baby face fad could affect the beauty culture and trends as a social phenomena.

• 한국실내디자인학회논문집
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• 제25권5호
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• pp.63-70
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• 2016

Modern society is suffering from the phenomena of low-fertile, ultra-aging, and low-growth. On this social flow, most social classes undergo vulnerable situation and their overall housing and living condition have difficulties. So far many housing guidelines for diverse population were developed, recently, inclusive 'Customized Housing Design Guideline for Childcare Families' in terms of maintaining family and society has been completed. The purpose of this study is to analyze User Benefit Characteristics of 'Customized Housing Design Guideline for Childcare Families'. The research subjects are essential 140 guidelines appropriate to children's development and parents' care. The research method is contents analysis and the analysis criterion are 4 concepts of the User Benefit Criteria- 'Behavioral Facilitation (BF)', 'Physiological Maintenance (PhM)', 'Perceptual Maintenance (PM)', 'Social Facilitation (SF)'. 3 people inter-raters reliability was established. Altogether, the guidelines were rated in the order of PhM>PM>BF>SF, and these characteristics are similar as common universal design guidelines. This showed the supportability of spatial characteristics in the guidelines related to user's special behaviors. Also, the results show the importance of outdoor space planning for safe social interactions. The supportable characteristics of 'Customized Housing Design Guideline for Childcare Families' could be expected to efficiently apply for new housing development in the future.

• Structural Engineering and Mechanics
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• 제48권5호
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• pp.615-642
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• 2013

In this paper a study on prestressed concrete slab bridges is presented. A design philosophy based on the concept of load balancing through prestressing is proposed in order to minimize the effects of delayed deformations due to creep. Aspects related to the stress redistribution inside these bridges for time-dependent phenomena are analyzed and discussed, by applying the principles of aging linear visco-elasticity. Prestressing is seen as an equivalent external load which counterbalances the permanent loads applied to the bridge, nullifying the elastic deflections due to sustained loads, and thus avoiding the related delayed deformations. An optimization of the structural behavior through the use of one-way prestressing is achieved. The determination of a convenient variable depth of slab bridges and the correspondent layout of tendons is considered as a useful means for applying the load balancing concept in actual cases of structures like long cantilevers or bridge decks. A case-study related to the slab bridges built 30 years ago at Jeddah in Saudi Arabia is presented and discussed, in order to show the effectiveness of the proposed approach to the conceptual design of prestressed concrete bridges.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.413-416
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• 2005

고분자경화제를 사용한 라이너와 HTPB 추진제의 접착력 및 접착공정을 개선연구를 수행하였다. HTPB와 TDI를 반응시켜 제조된 고분자경화제를 라이너에 사용하면, 접착계면에서 경화제의 이동현상이 줄어든다. 따라서 연소관 준비공정에서 내열재 연마 및 물질이동방지제 도포공정의 생략이 가능하며 HTPB 추진제와 라이너의 접착력이 증가되었다. 또한 가속노화 시험결과 접착력의 저하현상이 관찰되지 않았다.

• 전자공학회논문지B
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• 제31B권9호
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• pp.101-111
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• 1994

The human face can provide a great deal of information in regard to his/her race, age, sex, personality, feeling, psychology, mental state, health condition and ect. If we pay a close attention to the aging process, we are able to find out that there are recognizable phenomena such as eyelid drooping, cheek drooping, forehead furrowing, hair falling-out, the hair becomes gray and etc. This paper proposes that the method to estimate the age by analyzing these feature components for the facial image. Ang we also introduce the method of facial image synthesis in accordance with the cange of age. The feature components according to the change of age can be obtainec by dividing the facial image into the 3-dimensional shape of a face and the texture of a face and then analyzing the principle component respectively using 3-dimensional model. We assume the age of the facial image by comparing the extracted feature component to the facial image and synthesize the resulted image by adding or subtracting the feature component to/from the facial image. As a resurt of this simulation, we have obtained the age changed ficial image of high quality.