• Smart Structures and Systems
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• 제12권3_4호
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• pp.345-361
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• 2013

Locating and assessing the severity of damage in large or complex structures is one of the most challenging problems in the field of civil engineering. Considering that the wavelet packet transform (WPT) has the ability to clearly reflect the damage characteristics of structural response signals and the artificial neural network (ANN) is capable of learning in an unsupervised manner and of forming new classes when the structural exhibits change, this paper investigates a multi-stage structural damage diagnosis method by using the WPT and ANN based on "energy-damage" theory, in which, the wavelet packet component energies are first extracted to be damage sensitive feature and then adopted as input into an improved back propagation (BP) neural network model for damage diagnosis in a step by step mode. To validate the efficacy of the presented approach of the damage diagnosis, the benchmark structure of the American Society of Civil Engineers (ASCE) is employed in the case study. The results of damage diagnosis indicate that the method herein is computationally efficient and is able to detect the existence of different damage patterns in the simulated experiment where minor, moderate and severe damages corresponds to involving in the loss of stiffness on braces or the removal bracing in various combinations.

• 한국정밀공학회지
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• 제10권3호
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• pp.198-204
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• 1993

The study is concerned with finite element analysis and design of axisymmetric deep drawing by local heating. When the bottom shape of a cup is not flat but in complex-shaped, i.e., hemispherical, the cup cannot be drawn in one or two processes in the conventional deep drawing process and the limit drawing ratio is limited as well. By introducing local heating selectively with regards to the heating position, the formability of the sheet metal can be greatly increased with the reduced number of processes. In the Process analysisthe rigid- viscoplastic finite element method is employed and the temperature effect is incorporated. Bishop's step-wise decoupled method is employed to analyze the thermomechanical interaction between deformation and heat transfer. Axisymmetric deep drawing of a hemisphere-bottomed cup has been analyzed for various combinations of heat application in the punch and the die. At the first stage of deep drawing stretch forming is practically carried out by firmly pressing the blankholder with the punch and the die heated at various levels of temperature. Then at the second stage the same cup is drawn for the saame or different combination of temperature. From the computation, it has thus been shown that the fromability of a cup is greatly increased in two-stage deep drawing with increased limet drawing ratio.

• 대한화학회지
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• 제35권5호
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• pp.534-538
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• 1991

흡착 분리 방법을 이용하여 고순도 삼염화실란(TCS) 중의 미량 붕소 농도를 분광광도법적으로 측정하는 방법을 제안하였다. TCS중의 붕소 화합물과 복합체를 잘 형성하고 황산-quinalizarin계 발색 시약에 잘 녹으며 측정시 간섭 효과를 나타내지 않는 Lewis 염기성 물질로 NaCl이 선택되었다. 이러한 흡착 분리 방법을 통해 TCS분석 도중에 실리카겔 및 기포가 생성되는 문제를 방지할 수 있었는데, 반도체급 TCS중의 붕소 농도는 ${\pm}$20%의 표준편차 범위내에서 6.1 ${\mu}$g/l로 측정되었다. 반면 NaCl로 붕소화합물을 제거시킨 정제된 TCS 중의 붕소 농도는 0.2 ${\mu}$g/l이어서 NaCl의 우수한 흡착 성능을 확인할 수 있었다. 또한 NaCl이 TCS 정제 중 붕소 제거에 효과적임을 다른 잘 알려진 흡착제들과 비교 분석하였다.

• 소성∙가공
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• 제15권6호
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• pp.445-452
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• 2006

In most of automobile body panel manufacturing, trimming process is generally performed before flanging. To find feasible trimming line is crucial in obtaining accurate edge profile after flanging. Section-based method develops blank along manually chosen section planes and find trimming line by generating loop of end points. This method suffers from inaccurate results of edge profile. On the other hand, simulation-based method can produce more accurate trimming line by iterative strategy. In this study, new fast simulation-based method to find feasible trimming line is proposed. Finite element inverse method is used to analyze the flanging process because final shape after flanging can be explicitly defined and most of strain paths are simple in flanging. In utilizing finite element inverse method, the main obstacle is the initial guess generation for general mesh. Robust initial guess generation method is developed to handle genera] mesh with very different size and undercut. The new method develops final triangular mesh incrementally onto the drawing tool surface. Also in order to remedy mesh distortion during development, energy minimization technique is utilized. Trimming line is extracted from the outer boundary after finite element inverse method simulation. This method has many advantages since trimming line can be obtained in the early design stage. The developed method is verified by shrink/stretch flange forming and successfully applied to the complex industrial applications such as door outer flanging process.

• Journal of Microbiology and Biotechnology
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• 제27권12호
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• pp.2199-2210
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• 2017

Soil burial is the most widely used disposal method for infected pig carcasses, but composting has gained attention as an alternative disposal method because pig carcasses can be decomposed rapidly and safely by composting. To understand the pig carcass decomposition process in soil burial and by composting, pilot-scale test systems that simulated soil burial and composting were designed and constructed in the field. The envelope material samples were collected using special sampling devices without disturbance, and bacterial community dynamics were analyzed by high-throughput pyrosequencing for 340 days. Based on the odor gas intensity profiles, it was estimated that the active and advanced decay stages were reached earlier by composting than by soil burial. The dominant bacterial communities in the soil were aerobic and/or facultatively anaerobic gram-negative bacteria such as Pseudomonas, Gelidibacter, Mucilaginibacter, and Brevundimonas. However, the dominant bacteria in the composting system were anaerobic, thermophilic, endospore-forming, and/or halophilic gram-positive bacteria such as Pelotomaculum, Lentibacillus, Clostridium, and Caldicoprobacter. Different dominant bacteria played important roles in the decomposition of pig carcasses in the soil and compost. This study provides useful comparative date for the degradation of pig carcasses in the soil burial and composting systems.

• 한국조경학회지
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• 제32권1호
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• pp.47-56
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• 2004

Rapid economic development in Korea caused functions of city functions such as concentration of population, deterioration of the quality of living environment and traffic congestion. Korean cities have lost their identity becausr they are merged functionally and physically with neighboring cities, forming one mesa-city. Unified shape and disorganized streets of cities often cause confusion among foreigners and visitors. It is very difficult for them to find their image in strange cities. It is, however, important to correctly analyze the image and meaning of cities for understanding its identity. The purpose of this study is to develop a method to analyze the city image by focusing on some of the main cities in Korea. For this purpose, the adjective questionnaire and multi-dimension scaling (MDS) are applied to the analysis of city image. Image analysis graph by MDS can visually present the general and integrate images. The results of this study are summarized as follows: The important factors for interpretation of city image are historical and industrial character. Seoul, Taegu and Pusan have industrial and complex city images. Kongju has historical city image, while Changwon has a modern image. Chuncheon belongs to a soft and small image. Each city has an alternative solution against a negative image, according to the image analysis graph.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVII)
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• pp.287-292
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• 2005

The crude polysaccharides(C-CPF, C-CPM, C-CPB) derived from fruiting body, mycelia and mycelia free broth of cordyceps militaris were obtained by ethanol precipitation of hot water extracts. After a batch fermentation of C. militaris was carried out in a 5 L jar vessel, endo-polysaccharide and exo-polysaccharide were obtained. They were demonstrated as the hetero polysaccharides which were composed of glucsose, galactose and mannose by performed with HPAEC(high pH anion exchange chromatography) and conformation of random coil by its complex forming ability with congo red reagent. They were purified by ion exchange (DEAE-cellulose) and gel filtration chromatography. They were monitered by phenol-sulfuric acid method and Bradford method. The NO induction activities of crude polysaccharides and purified polysaccharides derived from mycelia free broth were enhanced rather than LPS(lipo polysaccharide) which was used as a general NO inducer. These effects presumably contibute to the antitumor activities. The homogenieties and molecular weights of polysaccharides were determined by using Sepharose CL-6B. The yield, molecular weights and NO induction activities of C-CPFN Fr.III, C-CPMN Fr.III, C-CPBN Fr.II were 0.387, 0.408 and 0.153, 127 K 210 K and 36 K, 40.79%, 88.72%, and 104.17%, respectively.

• Journal of Advanced Marine Engineering and Technology
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• 제34권2호
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• pp.303-309
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• 2010

유한요소법을 통하여 유성압연기(planetary rolling mill)에 의한 동관 압연공정을 연구하였다. 이 압연은 3개의 롤에 의해 만네스만 공법으로 동관을 성형하는 공정이고, 냉간가공으로 시작하여 열간가공으로 종료되며, 기존의 압출방식에 비해 공정의 단축과 원가 절감의 장점을 갖고 있다. 압연공정은 다양하고 복합적인 공정변수 들을 포함하고 있고, 각각의 변수들은 성형결과에 영향을 미친다. 그러므로 동관압연의 모든 공정변수가 고려되어져야 한다. 동관 압연공정은 성공적으로 시뮬레이션 되었고 최적의 압연조건을 결정하는데 유용할 것이다.

• 소성∙가공
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• 제24권2호
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• pp.121-129
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• 2015

A net-shape forming of small and complex-shaped metal parts by metal injection molding (MIM) has economic advantages in mass production, especially for STS 316L valve fitting. STS 316L offers excellent corrosion resistance, but it has poor machinability, which is a limitation in using it for a cost-effective production where both forging and machining are employed. Simulation and experimental analysis were performed to develop a MIM STS 316L 90° elbow fitting minimizing trial and error. A Taguchi method was used to determine which input parameter was the most sensitive to possible defects (e.g. sink mark depth) during the injection molding. The final prototype was successfully built. The results indicate that the simulation tool can be used during the design process to minimize trial and error, but the final adjustment of parameters based on field experience is essential.

• 한국분말재료학회지
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• 제28권1호
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• pp.51-58
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• 2021

The conversion of carbon preforms to dense SiC by liquid infiltration is a prospectively low-cost and reliable method of forming SiC-Si composites with complex shapes and high densities. Si powder was coated on top of a 2.0wt.% Y2O3-added carbon preform, and reaction bonded silicon carbide (RBSC) was prepared by infiltrating molten Si at 1,450℃ for 1-8 h. Reactive sintering of the Y2O3-free carbon preform caused Si to be pushed to one side, thereby forming cracking defects. However, when prepared from the Y2O3-added carbon preform, a SiC-Si composite in which Si is homogeneously distributed in the SiC matrix without cracking can be produced. Using the Si + C → SiC reaction at 1,450℃, 3C and 6H SiC phases, crystalline Si, and Y2O3 were generated based on XRD analysis, without the appearance of graphite. The RBSC prepared from the Y2O3-added carbon preform was densified by increasing the density and decreasing the porosity as the holding time increased at 1,450℃. Dense RBSC, which was reaction sintered at 1,450℃ for 4 h from the 2.0wt.% Y2O3-added carbon preform, had an apparent porosity of 0.11% and a relative density of 96.8%.