• 한국연소학회:학술대회논문집
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• 한국연소학회 2013년도 제46회 KOSCO SYMPOSIUM 초록집
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• pp.25-28
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• 2013

This study presents both experimental and numerical investigation of ignition characteristics of n-heptane and n-butanol mixture. The $O_2$ concentration was fixed to 9-10% to make high exhaust gas recirculation(EGR) rate condition. Experiments were performed using a rapid compression machine. In addition, a numerical study of the ignition delay time was performed using CHEMKIN codes to validate experimental results and predict chemical species after combustion process. The results showed that the ignition delay time increased with increasing n-butanol ratio and the reactivity decreased by low $O_2$ concentration.

• Steel and Composite Structures
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• 제49권4호
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• pp.441-456
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• 2023

Aiming at the development trend of light weight and high strength of engineering structures, this paper experimentally investigated the seismic performance of circular-in-square high-strength concrete-filled double skin steel tubular (HCFDST) stub columns with out-of-code width-to-thickness (B/t) ratios. Typical failure mode of HCFDST stub columns appeared with the infill material crushing, steel fracture and local buckling of outer tubes as well as the inner buckling of inner tubes. Subsequently, the detailed analysis on hysteretic curves, skeleton curves and ductility, energy dissipation, stiffness degradation and lateral force reduction was conducted to reflect the influences of hollow ratios, axial compression ratios and infill types, e.g., increasing hollow ratio from 0.54 to 0.68 and 0.82 made a slight effect on bearing capacity compared to the ductility coefficients; the higher axial compression ratio (e.g., 0.3 versus 0.1) significantly reduced the average bearing capacity and ductility; the HCFDST column SCFST-6 filled with concrete obviously displayed the larger initial secant stiffness with a percentage 34.20% than the column SCFST-2 using engineered cementitious composite (ECC); increasing hollow ratios, axial compression ratios could accelerate the drop speed of stiffness degradation. The out-of-code HCFDST stub columns with reasonable design could behave favorable hysteretic performance. A theoretical model considering the tensile strength effect of ECC was thereafter established and verified to predict the moment-resisting capacity of HCFDST columns using ECC. The reported research on circular-in-square HCFDST stub columns can provide significant references to the structural application and design.

• Structural Engineering and Mechanics
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• 제48권6호
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• pp.791-807
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• 2013

Ultra High Performance Cementitious Composites with compressive strength 200MPa (UHPCC-200) is proposed for the structural design of super high hybrid wind turbine tower to gain durability, ductility and high strength design objectives. The minimal wall thickness is analyzed using basic bending and compression theory and is modified by a toque influence coefficient. Two cases of wall thickness combination of middle and bottom segment including varied ratio and constant ratio are considered within typical wall thickness dimension. Using nonlinear finite element analysis, the effects of wall thickness combinations with varied and constant ratio and prestress on the structural stress and lateral displacement are calculated and analyzed. The design limitation of the segmental wall thickness combinations is recommended.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.442-445
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• 1997

With increasing use of high strength concrete tied columns in structural engineering, it becomes necessary to examine the applicability of related sections of current design codes. High strength concrete has an advantage of strength capacity and stiffness especially for column elements. This paper presents an experimental study of high strength concrete tied columns subjected to eccentric loading. The main variables included in this test were concrete compressive strength, steel amount, eccentricity, and slenderness ratio. The concrete compressive strength varied from 34.9Mpa(356kg/$\textrm{cm}^2$ ) to 93.2Mpa(951kg/$\textrm{cm}^2$ ) and the longitudinal steel ratios were between 1.1% and 5.5%. The eccentricity was selected for the different failure modes, i.e., compression control, balanced point, and tension control. The slenderness ratio varied from 19 to 61. The column specimens with same slenderness ratio but with different concrete compressive strength were constructed and tested. The purpose of this paper is to show failure modes of high strength reinforced concrete columns.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.450-453
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• 2004

The present study is a basic experiment on the estimation of the compression strength of high strength concrete, aiming at estimating the compression strength of mass test pieces of high strength concrete by giving the temperature hysteresis of the mass test pieces to managerial test pieces. Thus, this study made concrete test pieces in an optimal mix ratio for each strength level, and also created adiabatic curing tank and managerial test pieces. Then it carried out comparative analysis in relation to core strength and suggested equipment and a technique that can control the strength of high strength concrete mass more conveniently and accurately.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.586-588
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• 2005

The MSC (Multi Spectral Camera) system is a remote sensing payload to obtain high resolution ground image. This system uses lossy image compression method for &Direct mission& that transmit whole image during one contact. But some image degradation occurred especially at high compression ratio. To reduce this degradation, the MSC uses NUC (Non-uniformity Correction) Unit. This unit correct CCD (Charge Coupled Device)'s high-frequency non-uniformity. So high frequency contents of image can be minimized and whole system SNR can be maximized. But NUC has some disadvantage either. It decreases entire system reliability by adding one electronic system. Adding NUC also led to difficulty of electronic design, assembly and testability. In this paper, the comparison is performed between on-orbit non-uniform correction and on ground correction. by evaluating NUC advantage for the point of view of image quality. Using real MSC parameter and proper model, considerable reference point for the system design came to possible.

• Macromolecular Research
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• 제11권2호
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• pp.104-109
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• 2003

A microcellular, which combines a rubber with the conventional formulation of styrene/divinylbenzene/sorbitan monooleate/water system, was prepared using high internal phase emulsion (HIPE) polymerization. Although the open microcellular foam with low density from the conventional HIPE polymerization shows highly porous characteristics with fine, regular and isotropic structure, the one having much smaller cell size is desirable for various applications. In this study, a polybutadiene was introduced to reduce the cell size with comparable properties. Major interests were focused on the effects of rubber concentration and agitation speed on the cell sizes and compression properties. Scanning electron microscopy was used to observe the microcellular morphology and compression tests were conducted to evaluate the stress-strain behaviors. It was found that the cell size decreased as rubber concentration increased, reflecting a competition between the higher viscosity of continuous phase and the lower viscosity ratio of dispersed to continuous phases due to the addition of high molecular weight rubber into the oil phase of emulsion. A correlation for the average cell size depending on agitation speed was attempted and the result was quite satisfactory.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제9권6호
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• pp.646-661
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• 2003

웹환경에서 모든 클라이언트 컴퓨터에 방대한 볼륨데이타를 저장하여 놓고 이것을 인터랙티브하게 가시화하는 것은 쉽지 않다. 한 가지 해결 방법은 볼륨데이타를 압축하여 데이타베이스 서버에 보관하여 놓고 요구에 맞추어 네트워크를 통하여 클라이언트 컴퓨터에 전송하여 가시화하는 것이다. 이러한 경우 압축에 많이 사용하는 알고리즘이 웨이블릿 변환이다. 이 논문에서는 서버 컴퓨터에서 볼륨데이타를 웨이블릿 알고리즘을 이용하여 압축하여 놓고 클라이언트 컴퓨터로 전송하여 디렉트볼륨렌더링하는 패러다임에 적합한 웨이블릿과, 압축률을 구하기 위한 실험을 한다. Engine, CThead, Bentum 볼륨데이타를 Har, Daubechies4, 12, 20 웨이블릿을 이용하여 각각 전체 데이타의 50%, 10%, 5%, 1%, 0.1%, 0.03%로 압축하여 디렉트볼륨렌더링을 이용하여 가시화한 후 육안 및 영상평가지표를 이용하여 평가하였다. 성능은 압축률이 낮은 범위에서는 Harr 웨이블릿이 우수하였고 압축률이 높은 곳에서는 Daubechies4와 Daubechies12 웨이블릿이 우수하였다. 바람직한 압축률은 육안으로 평가한 경우는 전체 데이타의 약 1%이고 영상평가지표를 이용하여 평가한 경우는 전체 데이타의 약 5-10%이었다.

• 한국자동차공학회논문집
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• 제15권2호
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• pp.8-14
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• 2007

Compression ignition of homogeneous charges in IC engines indicates possibilities of achieving the high efficiency of DI diesel engines with low level of NOx and particulate emissions. The objectives of this study are to further understand the characteristics of the HCCI(Homogeneous charge compression ignition) combustion and to find ways of extending the rich HCCI operation limit in an engine-like environment. DME fuel is supplied either in the form of premixture with air or directly injected in the combustion chamber of a rapid compression and expansion machine under the conditions of various equivalence ratio and injection timing. The cylinder pressure is measured and the rate of heat release is computed from the measured pressure for the analysis of the combustion characteristics. The experimental data show that the RCEM can operate without knock on mixtures of higher equivalence ratio, when DME is directly injected in the combustion chamber than introduced as a fraction of a perfect or nearly perfect premixture. Very early fuel injection timings usually employed in HCCI operation are seen to have only insignificant effects in control of ignition timing.

• 한국의류산업학회지
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• 제21권3호
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• pp.336-345
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• 2019

This study evaluated the preference and wearing characteristics of existing fitness compression wear for elderly women and identified the problems and improvements of existing fitness apparel. Preference and wearing characteristics for 6 types (A-F) of upper and lower fitness compression wear were evaluated. Photos and drawings as well as the preferred designs and details were investigated after presenting the evaluation clothing. Evaluations were made on a 5 point Likert scale for the fitness, allowance, pressure, ease of movement, fabric material, and overall satisfaction after wearing. The design preference indicated that B type (26.6%) and C type (23.4%) were preferred in the top with C, E and F type preferred to the same ratio of 19.4% in the slacks. The fitness and allowance amount of the top B type were the most appropriate (${\geq}4$), the C type was in close contact (2.86), and the F type was inadequate in the neck circumference (1.77). The feeling of pressure was high in the waist, abdomen, thighs, and knees. The area where the elderly people want to improve their strength was the legs; in addition, a pattern design was needed to strengthen leg muscles when designing fitness compression wear. However, a design with excessive adhesion due to a muscle support band was shown to be not preferred. Therefore, depending on the activity, it is necessary to develop a fitness compression wear that applies an optimum stretching ratio of fabric based on body surface area changes.