• 대한기계학회논문집A
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• 제34권3호
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• pp.369-374
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• 2010

리니어 모터는 동력전달장치가 필요 없는 직접구동 방식으로 접촉 식의 비선형 효과를 크게 줄일 수 있고 구조 또한 간단하다. 그러나 리니어 모터는 동력전달장치를 제거함으로 인해 파라미터 변화와 외란 등에 둔감한 동력전달장치의 장점을 잃게 되어 모델의 불확실성이나 외란에 민감할 뿐만 아니라 마찰과 리플의 특성에 쉽게 영향을 받는다. 본 논문은 리니어 모터의 두 축을 대상으로 위치제어에 악영향을 주는 대표적인 비선형 함수인 마찰력과 리플력을 추정하여 이를 보상하며 개선된 교차 축 연동제어기를 통해 축 간의 윤곽정밀도를 향상시켰다. 기존의 연구된 제어기들은 위치추종과 윤곽추종을 위해 개별적인 제어기를 설계하였으나 제안된 제어기는 하나의 안정한 제어기로 두 축의 위치정밀도와 윤곽정밀도를 동시에 향상시켰다. 제안된 비선형 적응제어기는 모의실험을 통하여 기존의 제안된 교차 축 연동제어기와 비교검증을 함으로써 제안된 제어시스템의 성능을 검증하였다.

• 한국공작기계학회논문집
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• 제16권6호
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• pp.146-152
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• 2007

An active micro-mixer, which was composed of an oscillating micro-stirrer in the microchannel to provide rapid, effective mixing at high flow, rates was analyzed. The effects of molecular diffusion and disturbance by the stirrer were considered with regard to two types of mixer models: the simple straight microchannel and microchannel with an oscillating stirrer. Two types of mixer models were studied by analyzing mixing behaviors such as their interaction after the stirrer. The mixing was calculated by Lattice Boltzmann methods using the D2Q9 model. In this study, the time-averaged mixing index formula was used to estimate the mixing performance of time-dependent flow. The mixing indices of the two models compared. From the results, it was found that the mixer with an oscillating stirrer was much more enhanced and stabilized. Therefore, an optimum design for a dynamic micro-mixer with an oscillating stirrer was performed using Taguchi method in order to obtain a robust solution. The design parameters were established as the frequency, the length and the angle of the stirrer and the optimal values were determined to be 2, 0.8D and ${\pm}75^{\circ}$, respectively. It was found that the mixing index of the optimal design increased 80.72% compared with that of the original design.

• 한국공작기계학회논문집
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• 제17권5호
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• pp.95-100
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• 2008

An active micro-mixer, which is composed of an oscillating micro-stirrer in the micro-channel to provide effective mixing was optimized. The effects of molecular diffusion and disturbance by the stirrer were considered with regard to two types of mixer models: the simple straight micro-channel and micro-channel with an oscillating stirrer. Two types of mixer models were studied by analyzing mixing behaviors such as their interaction after the stirrer. The mixing was calculated by Lattice Boltzmann methods using the D2Q9 model. In this study, the time-averaged mixing index formula was used to estimate the mixing performance of time-dependent flow. The mixing indices of the two models were compared. From the results, it was found that the mixer with an oscillating stirrer was much more enhanced and stabilized. Therefore, an approximate optimization of an active micro-mixer with an oscillating stirrer was performed using Kriging method with OLHD(Optimal Latin Hypercube Design) in order to determine the optimal design variables. The design parameters were established as the frequency, the length and the angle of the stirrer. The optimal values were obtained as 1.0346, 0.66D and $\pm45^{\circ}$, respectively. It was found that the mixing index of the optimal design increased by 88.72% compared with that of the original design.

• 한국환경생태학회지
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• 제10권1호
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• pp.87-102
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• 1996

한반도 난대기후대의 식생구조를 연구하기 위하여 남해안 도서지방의 상록활엽수림 지역에 52개 조사구를 설치하였다. 난대상록활엽수림은 지리적 격리와 인위적 교란에 의해 지역간 식생구조가 매우 상이하였다. 조사지의 식생들은 대체적으로 자연적 식생천이가 이루어진 상록활엽수림 집단, 장기간 훼손되었거나 관리되어온 상록활엽수림 집단, 그리고 상록활엽수종으로 천이되고 있는 조림식생 집단으로 구분되었다. 52개 조사구에서 80% 이상의 상재도를 보인 수종은 후박나무, 사스레피나무, 마삭줄, 생달나무, 광나무 등이었다. 난대기후대의 극상군락이라고 추정되는 육박나무군락은 주도와 애도에 잔존하고 있었다. 과거 교란이 있었던 해안지역에서는 구실잣밤나무로 이차천이가 예상된다.

• Archives of Pharmacal Research
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• 제18권3호
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• pp.183-188
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• 1995

Polymeric reinforcement and coatings of alginate beads were carried out to control the release rate of drug from alginate beads. A poorly water-soluble ibuprofen (IPF) was selected as a model drug. A commercially available $Eudragit^{\circledR}$ RS100 was also used as a polymer. Effects of polymeric contents, the presence of plasticizers and amount of drug loading on the release rate of drug were investigated. The release rate of drug from alginate beads in the simulated gastric fluid did not occur within 2 h but released immediately when dissolution media were switched to the simulated intestinal fluid. No significant difference of release rate from polymer-reinforced alginate bead without plasticizers was observed when compared to plain (simple) beads. However, the release rate of drug from polymer-reinforced alginate beads was further sustained and retarded when aluminium tristearate (AT) as a plasticizer was added to polymer. However, polyethylene glycol 400 (PEG400) did not change the release rate of drug from alginate beads although PEG400 was used to improve dispersion of polymer and sodium alginate, and plasticize $Eudragit^{\circledR}$ RS100 polymer. The presence of plasticizer was crucial to reinforce alginate gel matrices using a polymer. As the amount of drug loading increased, the release rate of drug increased as a result of decreasing effects of polymer contents in matrices. The significantly sustained release of drug from polymer-coated alginate beads occurred as the amount of polymer increased because the thickness of coated membrane increased so that cracks and pores of the outer surface of alginate beads could be reduced. The sustained and retarded action of polymer-reinforced and coated beads may result from the disturbance of swelling and erosion (disintegration) of alginate beads. From these findings, polymeric-reinforcement and coatings of alginate gel beads can provide an advanced delivery system by retarding the release rate of various drugs.

• 한국군사과학기술학회지
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• 제21권2호
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• pp.246-254
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• 2018

Psychological stress and physical fatigue, such as anxiety, fear, sleep disturbance, etc., caused by exposure to the war, can lead to post-traumatic stress syndrome(PTSD) or war syndrome. The military has also prepared for drug use to minimize war syndrome and preserve combat strength. However, efforts to prevent war syndrome are still lacking. This study was conducted to identify biomarkers that can track psychophysiological changes. Psychophysiological changes associated with PTSD can be divided into four main categories. The four categories are behavioral changes, changes in brain cognition, neuroimmunological changes, and changes in innate immunity. This study suggest that biomarker profile can be made by the distance moved and the anxiety-like behavior in the open field for behavior category, brain BDNF levels in the brain cognition category, serum corticosterone in the neuroimmunology category, and inflammatory cytokine levels in the innate immunity category.

• 한국재난관리표준학회지
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• 제4권1호
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• pp.29-37
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• 2011

최근 고성토 도로건설 구간에서 거주민들이 고성토 도로가 생활환경에 영향과 경제적인 피해를 최소화 해 줄 것을 요구하는 민원이 급격하게 증가하는 실정이다. 본 연구에서는 고성토 도로와 교량이 건설되는 도로구간을 연구 대상지역으로 선정하고, 3차원 미기후모델 'Envi-met'을 이용하여 도로의 건설 전과 후에 온도장과 바람장의 변화에 대한 수치해석을 수행하였다. 그 결과를 요약하면 다음과 같다. 바람장의 분석 결과, 고성토 구간의 도로가 기류의 흐름 방해하여 바람장의 급격한 변화를 나타내었으며, 대부분 분석공간에서 풍속의 감소를 나타내었다. 그러나 교량 구간의 도로는 풍향에 미치는 영향이 크지 않았고, 풍속의 감소에 미치는 영향도 상대적으로 낮게 나타났다. 온도장의 분석 결과, 고성토 도로가 기류의 유동과 혼합을 방해하여 분석공간의 내부에서 미세한 온도의 변화가 나타났다. 이러한 결과는 도로건설 사업에서 수치모사의 이용이 미기후 변화와 교통사고 등과 같은 재난 가능성을 최소화하는데 필요한 유용한 정보를 제공할 수 있음을 나타내었다.

• 한국산학기술학회논문지
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• 제10권8호
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• pp.1824-1831
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• 2009

본 논문은 대규모 전력 송전망에서 발전기가 사고로 인해 순간적으로 전력공급을 중단하게 되었을 때 과도기간 동안 나타나는 전력계통 주파수의 급강하가 탈락된 발전기의 위치로부터 전력 송전망 전체로 파급되어 가는 전파속도를 분석한다. 이러한 전력계통 주파수 동요의 전파속도는 전력계통 고유의 특성에 따라 다르게 나타나기 때문에 광역적 측면에서 전력 수송망의 특성을 이해하는데 중요한 파라미터이며, 최근 미국의 전력 송전망을 대상으로 운영중인 광역 전력계통 주파수 감시스템(FNET)을 활용한 전력 IT 적용연구에서 중요한 파라미터로 활용되고 있다. 본 논문에서는 방대한 규모를 가진 미 동부의 전력송전 연계계통에 대해 최근의 동적모델을 사용하여 다양한 위치에서의 발전기 탈락을 모의한 후 이에 따른 전력계통주파수 동요의 전파 특성을 분석하고 그 전파속도를 제시한다.

• 한국물환경학회지
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• 제32권2호
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• pp.205-215
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• 2016

In order to improve water quality in the Paldang Lake, a riparian vegetation belt, treatment wetland, and artificial floating island were designed for introduction in the upland field, the estuary of tributaries, and the section of water facing mountainous land, respectively. We synthesized vegetation information collected from a reference river and found that herbaceous, shrubby, and tree vegetation zones tended to be dominated by Phragmites japonica, Phalaris arundinacea, etc.; Salix gracilistyla, S. integra, etc.; and S. koreensis, S. subfragilis, and Morus alba, respectively. In our plan, the herbaceous vegetation zone, which is established on floodplains with a high frequency of disturbance, will be left in its natural state. A shrubby vegetation zone will be created by imitating the species composition of the reference river in the ecotone between floodplain and embankment. A tree vegetation zone will be created by imitating species composition on the embankment slope. In the treatment wetland, we plan to create emerged and softwood plant zones by imitating the species composition of the Zizania latifolia community, the Typha orientalis community, the P. communis community, the S. integra community, and the S. koreensis community. The floating island will be created by restoring Z. latifolia and T. orientalis for water purification purposes.

• Nutrition Research and Practice
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• 제2권2호
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• pp.85-92
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• 2008

The present study was conducted to develop a Multi-dimensional Body Image Scale for Malaysian female adolescents. Data were collected among 328 female adolescents from a secondary school in Kuantan district, state of Pahang, Malaysia by using a self-administered questionnaire and anthropometric measurements. The self-administered questionnaire comprised multiple measures of body image, Eating Attitude Test (EAT-26; Gamer & Garfinkel, 1979) and Rosenberg Self-esteem Inventory (Rosenberg, 1965). The 152 items from selected multiple measures of body image were examined through factor analysis and for internal consistency. Correlations between Multi-dimensional Body Image Scale and body mass index (BMI), risk of eating disorders and self-esteem were assessed for construct validity. A seven factor model of a 62-item Multi-dimensional Body Image Scale for Malaysian female adolescents with construct validity and good internal consistency was developed. The scale encompasses 1) preoccupation with thinness and dieting behavior, 2) appearance and body satisfaction, 3) body importance, 4) muscle increasing behavior, 5) extreme dieting behavior, 6) appearance importance, and 7) perception of size and shape dimensions. Besides, a multidimensional body image composite score was proposed to screen negative body image risk in female adolescents. The result found body image was correlated with BMI, risk of eating disorders and self-esteem in female adolescents. In short, the present study supports a multi-dimensional concept for body image and provides a new insight into its multi-dimensionality in Malaysian female adolescents with preliminary validity and reliability of the scale. The Multi-dimensional Body Image Scale can be used to identify female adolescents who are potentially at risk of developing body image disturbance through future intervention programs.