• 대한기계학회논문집B
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• 제36권8호
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• pp.821-828
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• 2012

CPU의 발열량 증가는 서버를 통과하는 배출공기와 유입공기와의 상당한 온도차를 발생시키고 이로 인해 배출공기의 재순환 현상과 유입공기의 바이패스 현상이 발생한다. 이는 데이터센터 냉각시스템의 효율저하를 발생시킨다. 따라서 CRAC의 제어를 통해 유입공기와 배출공기를 분리하는 것이 데이터센터 냉각시스템의 중요한 목표이다. 본 연구에서는 CFD 해석 코드인 ICEPAK을 이용하여 데이터센터에 대한 수치해석을 진행하였다. 실내부로 유입되는 공기유량의 변화에 따른 CPU의 온도와 실 전체의 온도분포를 분석하였다. 이를 통해 CPU의 발열량에 따른 최적 유입유량을 선정하였다. CPU 발열량이 100, 120, 140 W인 경우 유입유량이 $0.15m^3/s$인 지점에서 발열제거와 온도분배가 가장 잘 이루어졌다. RTI 성능지표를 이용하여 해석결과를 검증하였고 RTI 값이 81인 경우 가장 안정적인 결과를 보였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권3호
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• pp.348-363
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• 2013

The use of I-Core sandwich panel has increased in cruise ship deck structure since it can provide similar bending strength with conventional stiffened plate while keeping lighter weight and lower web height. However, due to its thin plate thickness, i.e. about 4~6 mm at most, it is assembled by high power $CO_2$ laser welding to minimize the welding deformation. This research proposes a volumetric heat source model for T-joint of the I-Core sandwich panel and a method to use shell element model for a thermal elasto-plastic analysis to predict welding deformation. This paper, Part I, focuses on the heat source model. A circular cone type heat source model is newly suggested in heat transfer analysis to realize similar melting zone with that observed in experiment. An additional suggestion is made to consider negative defocus, which is commonly applied in T-joint laser welding since it can provide deeper penetration than zero defocus. The proposed heat source is also verified through 3D thermal elasto-plastic analysis to compare welding deformation with experimental results. A parametric study for different welding speeds, defocus values, and welding powers is performed to investigate the effect on the melting zone and welding deformation. In Part II, focuses on the proposed method to employ shell element model to predict welding deformation in thermal elasto-plastic analysis instead of solid element model.

• 한국산학기술학회논문지
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• 제19권5호
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• pp.451-458
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• 2018

본 연구는 소방직공무원들의 수면의 질을 평가하고, 이들의 일반적 특성, 건강습관특성 및 직업적 특성과 수면의 질과의 관련성을 규명하고자 시도하였다. 조사는 2016년 10월에 D광역시의 5개 소방서에 근무하고 있는 남성 소방직공무원 600명을 대상으로 Pittsburgh대학에서 개발한 수면의 질에 관한 질문 표(PSQI)를 사용한 자기기입식 설문조사에 의하였다. 연구결과, 전체 조사대상자의 13.2%는 "수면의 질이 좋은 군"으로, 86.8%는 "수면의 질이 좋지 않은 군"으로 나타났다. 일반적 특성 및 건강습관 특성별 수면의 질은 주관적인 건강상태가 좋지 않을수록, 흡연군보다 비흡연군에서, 주관적인 수면의 질이 높다는 군보다 낮다는 군에서 "수면의 질이 좋지 않다는 군"의 비율이 유의하게 높았다. 직업적 특성별 수면의 질은 다른 업무보다 화재진압을 한다는 군에서, 비교대근무군보다 교대근무군에서, 업무의 신체적 부담이 낮은 군보다 높은 군에서, 업무에 대한 만족도가 높은 군보다 낮은 군에서, 업무에 대한 적성도가 높은 군보다 낮은 군에서, 현재의 소방직에 대한 직업전환의사가 없다는 군보다 있다는 군에서 "수면의 질이 좋지 않다는 군"의 비율이 유의하게 높았다. 다중회귀분석결과, 수면의 질에 영향을 미치는 요인으로는 주관적 건강상태, 음주상태, 주관적인 수면의 질, 근무경력, 직위, 업무의 신체적 부담정도가 유의한 변수로 선정되었으며 이들의 설명력은 24.4%이었다. 위와 같은 연구결과는 소방직공무원들의 수면의 질은 일반적 특성, 건강습관 특성 및 직업적 특성의 여러 요인들과 유의한 관련성이 있음을 시사하고 있다.

• 한국정보통신학회논문지
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• 제10권7호
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• pp.1188-1195
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• 2006

본 논문은 개량된 분기한정법(branch-and bound method)을 이용하여 고속연산이 가능한 2차원 상태공간 디지털 필터의 설계방법을 제안하였다. 설계된 디지털 필터가 갖는 계수행렬의 모든 요소 값들은 오직 2개의 2의 멱수 (powers-of-two) 의 합으로만 표현되어진다. 따라서 제안된 방법으로 설계한 2 차원 상태공간 디지털필터는 간단한 가산연산만으로 수행이 이루어지므로 고속연산이 가능하고, 또한 구조가 간단하며 저가격으로 실현이 가능하다는 장점을 가진다 . 본 논문에서 제안된 방법의 타당성을 설계예시를 통해 고찰한 결과, 설계된 디지털 필터의 근사오차와 군지연특성이 동일한 설계사양으로 연속계수공간에서 설계되어진 디지털필터와 비교하여 유사한 결과를 얻을 수 있었다.

• ETRI Journal
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• 제30권6호
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• pp.871-873
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• 2008

In this letter, we investigate the spectral efficiency of IEEE 802.22 wireless regional area network (WRAN) spectrum overlay when it is used in TV white space. Since 2004, when the FCC published the notice of proposed rule making 04-186 to make use of unused TV spectrum, the IEEE 802.22 working group has been standardizing specifications for WRAN operations. There have been a few papers investigating the spectral efficiency of this, but their analyses were limited to the cases for various guard distances between WRAN base stations. Since WRAN base station (BS) power for WRAN service may differ from country to country, it is important to analyze the spectral efficiency for various WRAN BS powers. In this letter, we analyze the spectral efficiency of WRAN spectrum overlay as a function of the power of WRAN BSs. The simulation results show that spectral efficiency decreases as the power of WRAN BSs and guard distances increase.

• 한국의류학회지
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• 제19권6호
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• pp.866-886
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• 1995

The purpose of this study is to analyze the pattern and the meaning of textiles, and decorative techniques of ikat weaving and dyeing in Indonesia. The textile design also analyzes by examining the method of ikat techniques such as warp ikat, weft ikat and double ikat, and by classifying the style of regions. The most common motifs are geometric designs of spirals, meanders, straight lines, triangles, and circles which are influenced by outside world. Although these motifs or symbols have been evident since prehistoric times, their design and meaning have been continually reinterpreted as changes in the ceremonies and rituals. While motifs such as reptiles, birds, and human figures, depicted in spiral, hooked and rhomb configurations, have been identified among the most resilient features of Indonesian textile design, new meanings have been added to these ancient forms, and designs have been transformed and reinterpreted to suit local conceptions. Since textiles are a visual expression of Indcufsian life, textiles place the individual symbolically within social milieu, identifying rank, family, locality and religious affiliations. Textiles represent a link between the human and the spiritual realm, and a vehicle for the display of sacred and secular potency Ikat textiles play to embody special transforming powers and sacred mediating qualities, providing protection and evoking life-enriching forces for individuals or social group.

• 복식
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• 제56권5호
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• pp.89-104
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• 2006

The purpose of this study is to explain how a power group in a society forms features of sexuality in dress. As for the research methodology, first, historical research was undertaken to study in socioeconomic context in which sexuality has been formed and transformed. Second, demonstrative studies on sexual-image styles were undertaken through the analysis of pictures and photos. Third, analysis of the relationship between the power and sexuality in dress was done by literature research. Masculinity in dress, such as simplicity and concealment, corresponds to the attributes of the viewer, and femininity in dress, such as decoration and exposure, corresponds to the attributes of the viewee. Power struggle is the complex process of forming of the viewer-viewee relationship. The one who grasps the power becomes the viewer. In the shift from the Industrial Society to the Information and Technology Society, powers are horizontally spread over the society and the stereotype of sexuality in both women's and men's dress is fading out. In the field of design, standards and certainty described by absolute power are losing their importance. The 'chaotic' view of a world filled with mutual exchange of masculinity and femininity and uncertainty of sexuality will be sure to be a dominant trend in fashion.

• Communications for Statistical Applications and Methods
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• 제25권3호
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• pp.321-328
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• 2018

In clinical trials with repeated measurements, the time-averaged difference (TAD) may provide a more powerful evaluation of treatment efficacy than the rate of changes over time when the treatment effect has rapid onset and repeated measurements continue across an extended period after a maximum effect is achieved (Overall and Doyle, Controlled Clinical Trials, 15, 100-123, 1994). The sample size formula has been investigated by many researchers for the evaluation of TAD in two treatment groups. For the evaluation of TAD in multi-arm trials, Zhang and Ahn (Computational Statistics & Data Analysis, 58, 283-291, 2013) and Lou et al. (Communications in Statistics-Theory and Methods, 46, 11204-11213, 2017b) developed the sample size formulas for continuous outcomes and count outcomes, respectively. In this paper, we derive a sample size formula to evaluate the TAD of the repeated binary outcomes in multi-arm trials using the generalized estimating equation approach. This proposed sample size formula accounts for various correlation structures and missing patterns (including a mixture of independent missing and monotone missing patterns) that are frequently encountered by practitioners in clinical trials. We conduct simulation studies to assess the performance of the proposed sample size formula under a wide range of design parameters. The results show that the empirical powers and the empirical Type I errors are close to nominal levels. We illustrate our proposed method using a clinical trial example.

• Nuclear Engineering and Technology
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• 제17권2호
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• pp.98-104
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• 1985

가압중수로인 CANDU의 노심에는 많은 반응도 조절장치들이 분포되어 있어 출력분포와 잉여반응도를 조절하며, 이러한 장치들의 효자는 노심해서에서 증분격자상수로 나타낸다. 격자코드인 WIMS를 사용하여 2군 군정수를 계산하고 이를 이용하여 SUPERCELL코드로 증분 격자상수를 생산하였다. 증분격자상수는 조정봉과 지역조절장치에 대해 노심해석을 통해 평가하였으며 반응도가와 채널출력을 참고 자료와 비교하였다. 반응도가와 최대채널출력 오차가 참고값에 대해 각각 0.97%와 0.6% 범위 내에서 나타났다.

• Journal of Welding and Joining
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• 제35권3호
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• pp.28-34
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• 2017

The authors derived the criteria on the process parameters of laser depositions with metal powers(SUS316L & IN718) by evaluating the surface and cross-section properties of the deposition layers. The surface characteristics of the deposition layer are investigated through optical microscopy by controlling the process parameters of laser output, powder feeding rate and gas feeding rate. The cross-section characteristics were also analyzed after polishing and chemical etching process. As the gas feeding rate increased, the amount of powder loss increased and the difference in the dilution ratio and heat affected zone depending on laser outputs was observed. In addition, the powder feeding rate used in the experiment did not interfere with the energy absorption of the base material.