• 한국의상디자인학회지
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• 제21권4호
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• pp.55-67
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• 2019

This study analyzed the fabric and product size of the burn patient's custom compression garment and measured the pressure applied by the garment to assess whether proper pressure is being delivered for treatment. The test clothes were presented to the market by body size and commissioned with the same design. The subjects selected four people close to the average body size of men in their 20s determined by 7th Size Korea. The experiment was conducted by wearing a compression suit, performing activities and measuring changes in the pressure of the garment according to changes in posture. The fabric used for the compressive clothing was not ruptured even at 216 kPa, the elasticity recovery rate was measured between 80.5 and 94.5%. The product dimensions of the experimental clothing varied by up to 8cm from brand to brand, requiring the standardization of compression clothing. The experiment showed that four types of compression suit varied in pressure, and the pressure range, excluding the gastric arm (17.9mmHg), was between 2.5-14.1mmHg, which failed to meet the level of pressurization for treatment purposes. The clothing pressure in the chest area dropped when performing movements rather than standing still. This was interpreted to be a result of reduced the adhesion of the compression suit during operation. The peak pressure (31.68mmHg) and the lowest pressure (2.2mmHg) was noted in the scapula, indicating that no pressure was being transmitted on the vertebrae. The pressure of the garment on the right shoulder blade was elevated in a supine position. Because much time is spent laying down, it is necessary for the pattern design to accommodate for the increased clothing pressure on the shoulder blades. Standardization of the level of pressurization for burn patient's custom-made pressure suits for each stage of treatment is urgently required.

• 한국정보처리학회논문지
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• 제4권7호
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• pp.1900-1906
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• 1997

본 논문에서는 FPGA에 회로를 설계할 때, 일괄검사가 가능한 BIST의 효율적인 BILBO(이하 EBILBO)를 설계한다. 제안된 일괄검사 알고리즘은 회로의 복잡도와 규모가 큰 회로에서 하나의 핀(pin)으로 정상속도에서 회로검사가 가능하다. BIST 설계에서, 필요한 검사패턴은 의사 랜덤패턴으로 생성하고, 출력은 다중 입력 쉬프트 레지스터에 의한 병렬 신호분석으로 검사하였다. 제안된 알고리즘은 VHDL로 동작적 기술하므로 검사패턴 생성과 응답분석 및 압축에 대한 모델을 용이하게 변경할 수 있다. FPGA상에 설계된 회로에서, 구현된 BIST의 EBILBO의 면적과 성능은 ISCAS89 벤치마크 회로를 통하여 평가하였다. 600 셀(cell) 이상의 회로에서 EBILBO 면적은 30% 이하로 감소하고, 검사패턴은 500K 정도로 신축성 있게 생성되고, 고장검출률의 범위는 88.3%에서 100%임을 확인하였다. 일괄검사의 BIST를 위한 EBILBO 동작은 정상모드와 병행하여 실시간으로 검사모드를 $s+n+(2^s/2^p-1)$시간 내에 동시에 수행할 수 있다.(CUT의 PI 수;n, 레지스터 수;s, p는 다항식의 차수). 제안된 알고리즘은 VHDL 코딩으로 설계와 검사가 병행될 수 있는 라이브러리로 구축되어 DFT에 광범위하게 응용되어질 수 있다.

• Geomechanics and Engineering
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• 제20권1호
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• pp.55-66
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• 2020

The damage or failure of coal rock is accompanied by energy accumulation, dissipation and release. It is crucial to study the energy evolution characteristics of coal rock for rock mechanics and mining engineering applications. In this paper, coal specimens sourced from the Xinhe mine located in the Jining mining area of China were initially subjected to uniaxial compression, and the micro-parameters of the two-dimensional particle flow code (PFC^2D) model were calibrated according to the experimental test results. Then, the PFC^2D model was used to subject the specimens to substantial uniaxial compression, and the energy evolution laws of coal specimens with various schemes were presented. Finally, the elastic energy storage ratio m was investigated for coal rock, which described the energy conversion in coal specimens with various arrangements of preformed holes. The arrangement of the preformed holes significantly influenced the characteristics of the crack initiation stress and energy in the prepeak stage, whereas the characteristics of the cumulative crack number, failure pattern and elastic strain energy during the loading process were similar. Additionally, the arrangement of the preformed holes altered the proportion of elastic strain energy U_e in the total energy in the prepeak stage, and the probability of rock bursts can be qualitatively predicted.

• 대한금속재료학회지
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• 제50권2호
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• pp.100-106
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• 2012

This study was performed to fabricate porous titanium foam by three-dimensional layer manufacturing process, and to evaluate the porosities, compressive stress, Young's modulus and fracture pattern. Porous titanium foam was made of CP(Commercial Pure) titanium powder (${\leq}5{\mu}m$). Total porosities of titanium foam were in the range of 55-68%. Pore size distribution was $200-440{\mu}m$ for coarse pores, $50-100{\mu}m$ for intermediate pores and $5-10{\mu}m$ for fine pores. Compression elastic modulus and compression stress were decreased with increasing porosity. Young's modulus ranged from 1.04-5.62 GPa and maximum stress ranged from 20-241 MPa. Regarding the mechanical properties, 3D(Three Demensional) porous titanium fabricated layer manufacturing is a promising material for human bone replacement.

• Smart Structures and Systems
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• 제23권5호
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• pp.479-493
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• 2019

In this paper, the interaction between notch and micro pore under uniaxial compression has been performed experimentally and numerically. Firstly calibration of PFC2D was performed using Brazilian tensile strength, uniaxial tensile strength and biaxial tensile strength. Secondly uniaxial compression test consisting internal notch and micro pore was performed experimentally and numerically. 9 models consisting notch and micro pore were built, experimentally and numerically. Dimension of these models are 10 cm*1 cm*5 cm. the length of joint is 2 cm. the angularities of joint are $30^{\circ}$, $45^{\circ}$ and $60^{\circ}$. For each joint angularity, micro pore was situated 2 cm above the lower tip of the joint, 2 cm above the middle of the joint and 2 cm above the upper of the joint, separately. Dimension of numerical models are 5.4 cm*10.8 cm. The size of the cracks was 2 cm and its orientation was $30^{\circ}$, $45^{\circ}$ and $60^{\circ}$. Diameter of pore was 1cm which situated at the upper of the notch i.e., 2 cm above the upper notch tip, 2 cm above the middle of the notch and 2 cm above the lower of the notch tip. The results show that failure pattern was affected by notch orientation and pore position while uniaxial compressive strength is affected by failure pattern.

• 한국지반공학회지:지반
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• 제2권2호
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• pp.17-28
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• 1986

전북도내 3개시역에서 채취한 유기물함량 15%인 저유기질토(LL:95%)와 유기물함량 68%인 고유기질토(LL:400%)의 압밀특성을 조사분석하기 위해서 표준압밀시험과 단일하중압밀시험을 실시하였다. 공소비는 저유기질토 보다 고유기질토가 현저하게 큰 경향을 보였으며 e-log P 곡선에서 저유기질토는 하중이 증가함에 따라서 공소비 감소경향이 완만하였으나 고유기질토에서는 현저하게 감소하였다. 압밀량과 장기압밀시간과의 관계에서 고유기질토의 경우 약 5분경 부터 시간대수에 따라 직선적으로 증가하였고 저유기질토는 일반정성토와 같은 경향을 보였다. 고유기질토의 2차압밀표수는 상기추밀시간에 따라 일정한 경향을 나타내고 있으므로 장기롱밀량추정에 중요한 인자로 이용될 수 있다.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제5권3호
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• pp.155-164
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• 2016

대용량 데이터베이스의 빈도패턴 분석을 위해 기존의 Apriori 방식의 단점을 보완할 수 있는 새로운 트리 기반의 빈도 패턴 분석 알고리즘이 최근 다양하게 연구되고 있다. 그 중 FP-tree는 이러한 빈도 패턴을 분석하기 위해 빈도 패턴을 표현하는 트리 구조로 단 두 번의 전체 데이터베이스 스캔을 통해 빠르게 트리를 구성할 수 있으며 FP-grwoth를 통해 빈도 패턴을 분석할 수 있다. 이처럼 빈도 패턴 트리의 노드 수는 트리 자체의 메모리 할당량과도 연관이 있지만 그 후 growth의 메모리 자원 소비 및 처리 속도에도 영향을 미치게 된다. 따라서 빈도 패턴 트리의 노드 수의 감소는 트리 자체뿐만 아니라 빈도 패턴 분석에 있어서도 매우 중요하다. 하지만 FP-tree는 전체 아이템 수 라는 고정된 기준 문제로 인해 충분한 노드 수의 압축률을 갖지 못하고 있다. 본 논문에서는 이러한 FP-tree의 문제를 보완하여 좀 더 노드 수를 감소시킬 수 있도록 교집합 규칙이라는 새로운 패러다임을 적용한 빈도 패턴 트리인 IRFP-tree를 제시하고 실험을 통해 그 성능에 대해 증명하였다.

• Structural Engineering and Mechanics
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• 제60권6호
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• pp.939-952
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• 2016

A compression to tensile load transforming (CTT) device was developed to determine indirect tensile strength of concrete material. Before CTT test, Particle flow code was used for the determination of the standard dimension of physical samples. Four numerical models with different dimensions were made and were subjected to tensile loading. The geometry of the model with ideal failure pattern was selected for physical sample preparation. A concrete slab with dimensions of $15{\times}19{\times}6cm$ and a hole at its center was prepared and subjected to tensile loading using this special loading device. The ratio of hole diameter to sample width was 0.5. The samples were made from a mixture of water, fine sand and cement with a ratio of 1-0.5-1, respectively. A 30-ton hydraulic jack with a load cell applied compressive loading to CTT with the compressive pressure rate of 0.02 MPa per second. The compressive loading was converted to tensile stress on the sample because of the overall test design. A numerical modeling was also done to analyze the effect of the hole diameter on stress concentrations of the hole side along its horizontal axis to provide a suitable criterion for determining the real tensile strength of concrete. Concurrent with indirect tensile test, the Brazilian test was performed to compare the results from two methods and also to perform numerical calibration. The numerical modeling shows that the models have tensile failure in the sides of the hole along the horizontal axis before any failure under shear loading. Also the stress concentration at the edge of the hole was 1.4 times more than the applied stress registered by the machine. Experimental Results showed that, the indirect tensile strength was clearly lower than the Brazilian test strength.

• Smart Structures and Systems
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• 제29권4호
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• pp.535-547
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• 2022

Failure patterns of rock specimens represent valuable information about the mechanical properties and crack evolution mechanism of rock. Several kinds of research have been conducted regarding the failure mechanism of brittle material, however; the influence of brittleness on the failure mechanism of rock specimens has not been precisely considered. In the present study, experimental and numerical examinations have been made to evaluate the physical and mechanical phenomena associated with rock failure mechanisms through the uniaxial compression test. In the experimental part, Unconfined Compressive Strength (UCS) tests equipped with Acoustic Emission (AE) have been conducted on rock samples with three different brittleness. Then, the numerical models have been calibrated based on experimental test results for further investigation and comparing the micro-cracking process in experimental and numerical models. It can be perceived that the failure mode of specimens with high brittleness is tensile axial splitting, based on the experimental evidence of rock specimens with different brittleness. Also, the crack growth mechanism of the rock specimens with various brittleness using discrete element modeling in the numerical part suggested that the specimens with more brittleness contain more tensile fracture during the loading sequences.

• 한국자동차공학회논문집
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• 제10권1호
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• pp.67-75
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• 2002

A study to investigate the influence of combustion chamber shape, especially piston top face configuration, on the combustion stability is presented with CFD analysis and single cylinder GDI engine test. Initial configuration of the piston bowl was designed with CFD analysis and further parametric studies of the design factors on the piston top face were carried out through the single cylinder GDI engine test. It was found that both the geometry of piston top face and the compression ratio have great influences on the combustion stability. Of interest is that the design factors of the GDI piston to prevent mixture diffusion out of the piston bowl have important roles for the stable combustion at the stratified mixture condition. Also the relationship between spray impingement and flow pattern in a GDI piston bowl should be considered to design an optimal bowl configuration for stable stratified combustion.