• 한국분무공학회지
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• 제11권3호
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• pp.161-167
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• 2006

As the exhaustion of petroleum resources and air pollution problems are getting serious recently, there are growing interests in premixed diesel engines which have the potential of achieving a more homogeneous mixture near TDC compared to conventional diesel engines. Early studies have shown that the fuel injection frequency and spray angle affected the mixture formation and combustion in a HCCI(Homogeneous Charge Compression Ignition) engine. Therefore, the purpose of this study is to investigate the relationship between combustion and mixture formations by injection timing and frequency using a narrow angle injector, NADI (Narrow Angle Direct Injection). In this study, we found that the fuel injection timing and injection frequency affect the mixture formations and then affect combustion in the HCCI engine.

• Steel and Composite Structures
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• 제12권1호
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• pp.53-72
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• 2012

In this study, the physically-based failure models for matrix and fibers in compression and tension loading are introduced. For the 3D stress based fiber kinking model a modification is proposed for calculation of the fiber misalignment angle. All of these models are implemented into the finite element code by using the advantage of damage variable and the numerical results are discussed. To investigate the matrix failure model, purely in-plane transverse compression experiments are carried out on the specimens made by Glass/Epoxy to obtain the fracture surface angle and then a comparison is made with the calculated numerical results. Furthermore, shear failure of $({\pm}45)_s$ model is investigated and the obtained numerical results are discussed and compared with available experimental results. Some experiments are also carried out on the woven laminated composites to investigate the fracture pattern in the matrix failure mode and shown that the presented matrix failure model can be used for the woven composites. Finally, the obtained numerical results for stress based fiber kinking model and improved ones (strain based model) are discussed and compared with each other and with the available results. The results show that these models can predict the kink band angle approximately.

• 한국엔터테인먼트산업학회논문지
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• 제14권4호
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• pp.401-409
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• 2020

본 연구는 테라테인먼트 물리적 요소를 적용하여 종아리 혈압, 발목 각도, 종아리 둘레에 미치는 영향을 알아보고자 하였다. 20대의 정상 여성 대학생을 대상으로 온열치료군(hot therapy group, 20명), 한랭 치료군(cold therapy group, 20명), 압박치료군(compression therapy group, 20명)으로 나누었다. 선행 논문을 근거로 하여 온열치료 20분, 한랭치료 15분, 압박치료 30분과 강도 100mmHg을 적용하였고, 왼쪽 다리에 적용 후 1시간 휴식을 취한 뒤 오른쪽 다리에 적용하였다. 각 군별로 종아리 혈압, 발목 각도, 종아리 둘레를 평가하였다. 본 연구결과, 온열 및 압박 치료에 종아리 혈압과 발목 각도의 적용은 혈압의 감소와 발목 각도의 증가에 유의한 효과가 있었으나(p<.05) 한랭 치료에서는 유의한 효과가 없었고, 모든 군에서 종아리 둘레의 부분에서는 통계학적으로 유의한 효과가 없었다. 따라서 종아리의 혈압의 감소와 종아리와 관련된 발목의 각도 증가를 위해서 온열치료와 압박치료를 권장하고, 다리에서 발생하는 여러 가지 문제점을 해결하는데 활용되길 기대한다.

• 한국자동차공학회논문집
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• 제14권4호
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• pp.20-25
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• 2006

Recently, there has been an interest in premixed diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to conventional diesel engines. Early studies are shown that in a HCCI(Homogeneous Charge Compression Ignition) engine, the fuel injection timing and injection angle affects the mixture formations. Thus the purpose of this study was to investigate relationship of combustion and mixture formations according to injection timing and injection angle in a common rail direct injection type HCCI engine using a early injection method called the PCCI(Premixed Charge Compression Ignition). From this study, we found that the fuel. injection timing and injection angle affect the mixture formations and in turn affects combustion in the PCCI engine.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.103-107
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• 2009

Recently, injection/compression molding process became more popular than ever to produce many transparent optical products of high precision. Especially, optical disk for read/write is the best example. But those optical disks can cause sensorial problems because of high birefringence or deformation from the residual stresses in the media. Therefore, it is necessary to study the effects of various process conditions on the final birefringence structure in injection-only and injection/compression molded disks for producing precision injection-molded products. In the present paper we have focused on the effect of injection, holding and compression processes on the optical anisotropy(i.e. birefringence) remaining in the MOD by examining the gapwise distribution of birefringence and extinction angle. The effect of holding pressure was found to form the inner two birefringence peaks. But the effect of compression pressure on the birefringence distribution was found to make the uniform distribution near the center in the gapwise direction and inversion of extinction angle far from the gate.

• Journal of Trauma and Injury
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• 제18권2호
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• pp.107-111
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• 2005

Backgrounds: To evaluate the effectiveness of conservative treatment in osteoporotic thoraco-lumbar compression fractures and to identify the factors influencing the progression of compression. Materials and Methods: From January 2003 to October 2004, Patients who were admitted to our hospital for osteoporotic thoraco-lumbar compression fractures were reviewed retrospectively with follow-up more than 12 months (ave. 14.6 months). With simple x-ray lateral view, we evaluate wedge compression ratio (WCR) and kyphotic angle (KA) at initial and final follow-up. We separate the patients into two groups baesed on the amount of progression of vertebral compression and evaluate a relation with BMD, vertebral fracture level, initial WCR, initial KA. All datas were statistically analyzed. Results: An average of T-score was -3.5 and the changes of KA between initial and final follow-up were average $3.5^{\circ}$. Compression of anterior column were progressed to 8.5%. The changes between initial and final WCR in Group I (N=24) was 17.8%, and Group II (N=18) was 3.3%. T-score in group I was -3.4 and group II was -3.8 (p=0.228). vertebral fracture level were 10 T12, 12 L1, 2 L2 in group I; 6 T12, 6 L1, 6 L2 in group II (p=0.156). Initail WCR was 0.74 in group I, 0.63 in group II, and there was statistical difference between two groups(p=0002). Initial kyphotic angle was $13.9^{\circ}$in group I, $16.2^{\circ}$in group II repectively (p=0.392). Conclusion: The conservative treatment with short-term bed rest and early embulation is effective and valuable method to patients who have osteoporotic thoraco-lumbar compression fractures. There was no statistical difference between two groups according to BMD, vertebral fracture level, KA. But in comparison with initail WCR between two groups, there was statistical difference. That means, in the case of small initial compression of anterior column, the progression of compression was bigger than else. In these patients, more strict use of appropriate brace and careful follow-up should be needed.

• 한국컴퓨터정보학회논문지
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• 제24권11호
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• pp.179-185
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• 2019

이 연구는 심폐소생술 중 거울을 활용한 시각적 효과를 이용했을 때 가슴압박의 질을 비교함으로써, 좀 더 나은 물리적 요소를 제공하여 효과적인 심폐소생술을 할 수 있도록 하는데 기초자료를 제공하고자 시행 되었다. 무작위 교차방법(Randomized Crossover Design)에 의한 실험 연구로 BLS Health Care-Provider 자격을 이수한 28명을 대상으로 가슴압박 시행 시 깊이, 속도, 압박 대이완의 비율, 팔의 각도, 용이성 등을 측정하였다. 수집된 자료는 SPSS Ver. 23.0 for Win 통계프로그램을 이용하여 분석하였다. 본 연구의 결과를 종합해 보면 심폐소생술에서 가슴압박 시행 시 거울을 활용한 가슴압박 방법을 이용한다면 효율적인 가슴압박을 할 수 있었고, 가슴압박의 평균 깊이, 압박 대 이완 비율, 팔의 각도, 구조자의 자세가 나아져 가슴압박의 질적 지표가 향상되었음을 알 수 있었다. 하지만 거울을 활용한 가슴압박 방법에 대해 다양한 환경요소 및 직군에 대하여 추가적인 연구를 통해 임상적 활용의 가능성을 확인하는 것이 필요 할 것이다.

• Journal of Mechanical Science and Technology
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• 제20권9호
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• pp.1475-1482
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• 2006

Wet compression means the injection of water droplets into the compressor of gas turbines. This method decreases the compression work and increases the turbine output by decreasing the compressor exit temperature through the evaporation of water droplets inside the compressor. Researches on wet compression, up to now, have been focused on the thermodynamic analysis of wet compression where the decrease in exit flow temperature and compression work is demonstrated. This paper provides thermodynamic and aerodynamic analysis on wet compression in a centrifugal compressor for a microturbine. The meanline dry compression performance analysis of centrifugal compressor is coupled with the thermodynamic equation of wet compression to get the meanline performance of wet compression. The most influencing parameter in the analysis is the evaporative rate of water droplets. It is found that the impeller exit flow temperature and compression work decreases as the evaporative rate increases. And the exit flow angle decreases as the evaporative rate increases.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.420-423
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• 2003

A low temperature difference model Stirling engine is a small Stirling engine running with several degree of temperature difference without power output. In this study, the design parameters to give maximum power are discussed. As results, the phase angle is about 100 degree, and compression ratio is 1.5% of the ratio of heat source temperatures at maximum power condition.

• Geomechanics and Engineering
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• 제17권6호
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• pp.553-564
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• 2019

This paper presents experimental results of rock-concrete bi-material discs under cyclically diametrical compression. It was found that both specimens under cyclical and static loading failed in three typical modes: shear crack, tensile crack and a combined mode of shear and wing crack. The failure modes transited gradually from the shear crack to the tensile one by increasing the interface angle between the interface and the loading direction. The cycle number and peak load increased by increasing the interface angle. The number of cycles and peak load increased with the interface groove depth and groove width, however, decreased with increase in interface groove spacing. The concrete strength can contribute more to the cycle number and peak load for specimens with a higher interface angle. Compared with the discs under static loading, the cyclically loaded discs had a lower peak load but a larger deformation. Finally, the effects of interface angle, interface asperity and concrete strength on the fatigue strength were also discussed.