• Korean Journal of Mathematics
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• 제28권1호
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• pp.65-73
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• 2020

This article concerns a property of local rings and domains. A ring R is called weakly local if for every a ∈ R, a is regular or 1-a is regular, where a regular element means a non-zero-divisor. We study the structure of weakly local rings in relation to several kinds of factor rings and ring extensions that play roles in ring theory. We prove that the characteristic of a weakly local ring is either zero or a power of a prime number. It is also shown that the weakly local property can go up to polynomial (power series) rings and a kind of Abelian matrix rings.

• Journal of Information Technology Applications and Management
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• 제17권3호
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• pp.43-56
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• 2010

Completely Automated Public Turing test to tell Computers and Humans Apart or CAPTCHA has received remarkable attention. Deciphering distorted texts is still a human task. The current CAPTCHA mainly requires users to read English alphabets. As such, Thai CAPTCHA may be the choice for Thai online practitioners. However, no published work has examined how Thai online practitioners perceive CAPTCHA. This study thus attempts to fill this void. Based on the 112 number of usable online questionnaire submission, Thai online practitioners are all aware of CAPTCHA. Also, nine out of ten samples identified correctly the prime benefits of CAPTCHA. Using exploratory factor analysis, their attitude towards CAPTCHA was classified into two dimensions. They perceived (1) drawback of general CAPTCHA and (2) feasibility of Thai CAPTCHA. In addition to extending our insight into application of CAPTCHA, policy-makers responsible for electronic commerce in Thailand could initiate plans in response to Thai online practitioners' perception.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.217-220
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• 1996

This study presents a R&D performance monitoring system (RDMS) that is applicable for managing nuclear program in KAERI. The prime goal of RDMS is to furnish project manager with reliable and accurate information on status of progress, performance and resource allocation, and attain traceability and visibility of project implementation for effective project management. In this study, the work breakdown structure (WBS) as the governing factor for integration of scope, schedule, resource data was derived, and the above parameters were loaded personal computer. A RDMS is comprised of about 12,000 R&D activities of the 16 goverment-led projects. The Primavera software was used to monitor the progress, evaluate the performance and analyze the resource distribution to activities.

• 한국터널지하공간학회 논문집
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• 제17권6호
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• pp.615-621
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• 2015

In this paper diamond wire cutting method has been proposed to cut the rock in the tunnel face. Diamond wire saw method could cut the rock from tunnel face with very minor vibration and noise. In this study rock cutting process has been simulated with FEM method by using LS-DYNA explicit non-linear finite element code. Normal load act as an prime factor when cutting the rock surface. For observing the effect of normal load on bead, several experiments has been conducted by varying normal loads on the bead. From each experiment, cutting rate has been calculated to compare the cutting rate with different load conditions. By increasing the normal load on bead, cutting rate increases drastically.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.410-415
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• 2000

A diesel engine is one of the major prime movers to its high thermal efficiency. But due to the recent attention far the environmental pollution, the emissions of diesel engine became to a important problem. So it is needed to understand the characteristics of diesel spray injected into a combustion chamber. The factor which controls the diesel spray are the injection pressure, the nozzle diameter, the impinging angle and the variation of pressure and temperature. In this paper, experiments were conducted far the variation of the environmental temperature(273k, 373k, 573k), free spray and impinging spray. And the notions of penetration, spray angle, axial distance for free spray, and axial distance, spray thickness from impinging wall fur impinging spray.

• Structural Engineering and Mechanics
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• 제21권3호
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• pp.333-350
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• 2005

This paper presents results of an experimental study to evaluate a new retrofit technique for strengthening shear deficient short concrete beams and columns. In this technique a mortar jacket reinforced with expanded steel meshes is used for retrofitting. Twelve short reinforced concrete specimens, including eight retrofitted ones, were tested. Six specimens were tested under a constant compressive axial force of 15% of column axial load capacity based on original concrete gross section, $A_g$, and the concrete compressive strength, ${f_c}^{\prime}$. Main variables were the spacing of ties in original specimens and the volume fraction of expanded metal in jackets. Original specimens failed before reaching their nominal calculated flexural strength, $M_n$, and had very poor ductility. Strengthened specimens reached their nominal flexural strength and had a ductility capacity factor of up to 8 for the beams and up to 5.5 for the columns. Based on the test results, it can be concluded that expanded steel meshes can be used effectively to strengthen shear deficient concrete members.

• Intestinal research
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• 제11권3호
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• pp.155-160
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• 2013

Behçet's disease (BD) is a systemic immunological disorder characterized by recurrent mucosal ulcerative lesions including oral and genital ulcerations in association with skin and ocular involvements. BD also can involve the gastrointestinal tract. Gastrointestinal involvement of BD is one of the major causes of morbidity and mortality for this disease. However, clinical data are quite limited because of the rarity of intestinal BD. Therefore, the management of intestinal BD is heavily dependent on expert opinions and standardized medical treatments of intestinal BD are yet to be established. In this brief review, the authors summarized the currently available medical treatments such as 5-aminosalicylic acids, corticosteroids, immuno-modulators, and anti-TNF agents. Moreover, we sought to suggest a treatment algorithm for intestinal BD based on the recently published and updated data.

• 한국의류학회지
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• 제44권6호
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• pp.1189-1204
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• 2020

Population aging and longevity have compelled major worldwide consumer markets to focus on senior citizens who exhibit a desire to nurture their appearance and obtain related products such as cosmetics. This trend signals an increasing need for in-depth research on elderly consumers in the color cosmetics market. This study identified the characteristics of seniors in the pre-elderly stage ("new seniors") based on their lifestyle and market segments. It employed online surveys with participants consisting of pre-elderly Korean women born between 1955 and 1963 who reside in the greater Seoul and Gyeonggi area. The study used SPSS 23.0 for factor analysis, reliability verification, cluster analysis, ANOVA, Duncan's test, and cross-analysis. The results show that new seniors could be classified into four groups based on lifestyle: Prime Seniors, Potential Seniors, Rational Seniors, and Slump Seniors. Each group has distinct characteristics. The findings suggest that the senior market requires further segmentation and is no longer a single uniform market. This study also confirms that the lifestyles of the elderly is an instrumental variable for their segmentation.

• 한국발생생물학회지:발생과생식
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• 제27권4호
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• pp.221-226
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• 2023

A stem cell niche provides an environment that governs stem cell maintenance and division. Thus, the development of a proper niche is of prime importance to stem cell behaviors. Mechanisms of niche development are beginning to be revealed in the Drosophila male gonad. Niche cells are initially dispersed throughout the gonad, then assemble at its apical tip through the anterior migration of posteriorly located niche cells. The molecular mechanisms of this migration and assembly are still poorly understood. Here we show evidence suggesting that Lin28, an RNA-binding protein and regulator of let7 genesis, might be an intrinsic factor for the anterior migration of niche cells. We found that a dispersed, ectopic niche, a phenotype observed with anterior migration defects, occurs in lin28 mutant gonads. This phenotype is rescued by expression of lin28 in the niche cells. These findings suggest that Lin28 might be required for the anterior migration of niche cells.

• 대한전자공학회논문지
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• 제13권5호
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• pp.17-23
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• 1976

고속열중성자로에서 정상 운전중인 원자로를 운전정지하였다가 재가동할 때 가장 문제가 되는 것은 핵분열 생성물인 Xe135의 독소작용이다. 이것은 Xe135가 원자로 출력에 영향을 주는 열중성자에 대한 흡수단면적이 크고 그의 반감기가 길기 때문이다. 그러므로 원자로의 일시적 운전정지가 요구될 때 이의 재가시에는 반듯이 이 독소를 능과할 수 있는 충분한 초과반응도를 가해 주던지, Xe135가 붕괴되어 그의 농도가 줄어든 이후에야 원자로의 재가동이 가능하게 된다. 위와 같은 문제는 사실상 원자로 운전시 안전성 뿐만 아니라 경제성에도 큰 영향을 주고 있다. 본 논문에서는 이 점을 고려하여 Pontoyagin의 최대원리를 이용하여 운전정지를 최적화시키므로서 언제든지 원자로를 전출력으로 재가동할 수 있도록 운전정지 방법을 개선하였다. 그러나 제어과정에서나 그 이후에도 X, 농도는 제어된 허용치를 넘지 않고 최소시간 이내에 모든 제어를 끝내도록 하였다. The buildup of fission product, i.e. Xe-135 poisoning, is a prime factor in restarting a nuclear reactor from the shutdown, which was under normal operation in the high flux thermal reactor, It is caused by the high absorption crosssection of Xe-135 to thermal neutrons and its long half life, from which the thermal power is affected. It is then possible to restart a nuclear reactor after the sufficient excess reactivity to override this poisoning must be inserted, or its concentration is decreased sufficiently when its temporary shutdown is required. As ratter of fact, these have an important influence not only on reactor safety but also on economic aspect in operation. Considering these points in this study, the shutdown process was cptimized using the Pontryagin's maximum principle so that the shutdown mirth[d was improved as to restart the reactor to its fulpower at any time, but the xenon concentration did not excess the constrained allowable value during and after shutdown, at the same time all the control actions were completed within minimum time from beginning of the shutdown.