• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2009년도 추계학술대회 논문집
• /
• pp.227-230
• /
• 2009

In order to predict failure behavior of advanced high-strength steel sheets (AHSS) in hole expansion tests, damage model was developed considering surface condition sensitivity (with specimens prepared by milling and punching: 340R, TRIP590, TWIP940). To account for the micro-damage initiation and evolution as well as macro-crack formation, the stress triaxiality dependent fracture criterion and rate-dependent hardening and ultimate softening behavior were characterized by performing numerical simulations and experiments for the simple tension and V-notch tests. The developed damage model and the characterized mechanical property were incorporated into the FE program ABAQUS/Explicit to perform hole expansion simulations, which showed good agreement with experiments.

• 대한수학회보
• /
• 제55권3호
• /
• pp.679-698
• /
• 2018

In this paper, with optimal normalized constants, the asymptotic expansions of the distribution and density of the normalized maxima from generalized Maxwell distribution are derived. For the distributional expansion, it shows that the convergence rate of the normalized maxima to the Gumbel extreme value distribution is proportional to 1/ log n. For the density expansion, on the one hand, the main result is applied to establish the convergence rate of the density of extreme to its limit. On the other hand, the main result is applied to obtain the asymptotic expansion of the moment of maximum.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제7권
• /
• pp.11-21
• /
• 1999

The capillary tube and short tube orifice have been widely used as an expansion device in the refrigeration and air-conditioning system. To improve the system performance, expansion devices need to be optimized with the components of a refrigeration system. In the present study, a numerical model for a capillary, which could predict the flow rate and properties along a tube, was developed by assuming homogeneous two-phase flow. A semi-empirical flow model for evaluation of the flow rate through a short tube orifice was also developed by using the experimental data. Finally, the results of the numerical model for a capillary was compared with those of the semi-empirical model for a short tube orifice to identify the dominant flow factors for the expansion devices.

• 설비공학논문집
• /
• 제10권1호
• /
• pp.118-128
• /
• 1998

Capillary and short tube orifice have been widely used as an expansion device in refrigeration and air-conditioning system. To improve the system performance, expansion devices need to be optimized with the components of a refrigeration system. In the present study, a numerical model for a capillary, which can predict properties along a tube and flow rate through a tube, was developed by assuming homogeneous two-phase flow, A semi-empirical flow model that can be used to evaluate the flow rate through a short tube orifice was also developed by summarizing the experimental data. Finally, the results of the numerical model for capillaries were compared with those of the semi-empirical model for short tube orifices to verify dominant flow factors for the expansion devices.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2008년도 추계 학술논문 발표대회
• /
• pp.117-120
• /
• 2008

The Purpose of this is properties of CFT filled with expansion concrete. CFT(concrete filled steel tube) is the structure that circle shape steel column filled with concrete. 3 kinds of expansive additives and variation of replacement rate. we changed expansive additive from 0%, 10%, 20%, 30% of ratio of addition rate are selected for this experiment. Merits of CFT are concrete internal force rising influenced by steel shape restriction, reinforcing the local buckling, excellent resistance to transformation. Generally, High rise building using CFT utilize the high strength and fluidity concrete for packing the tube inside. As the result a steel tube charged expensive concrete has stiffness 1.5times more than a steel tube not charged concrete. Increase of resisting power about compressive stress by binding expansion of expansive concrete affects strength increase and softness.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집A
• /
• pp.603-608
• /
• 2001

Recently, cold expansion of fastener holes is commonly used in the aerospace industry to increase the fatigue endurance of airframes. Cold expansion process is used as the retardation of crack initiation in the hole. This treatment leads to an improvement of fatigue behavior due to the compressive residual stresses developed on the hole surface. The residual stress profile depends on the cold expansion ratio. In the present paper, it is shown that residual stress is redistributed due to the application of cold expansion process for CT specimen. It is further shown that residual stress increases in proportion to cold expansion ratio. It is thought that crack growth rate increases as cold expansion ratio.

• 대한치과의사협회지
• /
• 제12권1호
• /
• pp.37-42
• /
• 1974

To ascertain if the ultrasonic cleaning technique caused any dimensional changes in heat and cold curing and fluid resin denture bases and in addition to evaluate the dimensional changes of the resin denture bases stored in water and air, the author measured the distance between the outsides of two pins embedded in methyl methacrylate test denture bases by mean of 12 inch vernier caliper, accurate to 0.02mm. The results were as follows; (1) Ultrasonic cleaning didn't cause any permanent dimensional changes, but only affected temporary dimensional expansion in 16 test denture bases. (2) Temporary expansion rate caused by 10 minutes' ultrasonic cleaning was 0.29% and at the maximal temperature of the cleaning solution it was 0.64%. (3) The half of the denture bases stored in water showed the dimensional expansion rate of 0.47% while the others stored in air showed the dimensional shrinkage rate of 0.15% after 4 months.

• 대한기계학회논문집
• /
• 제14권5호
• /
• pp.1311-1319
• /
• 1990

본 연구에서는 작동유체로서 습증기와 거동이 유사한 습증기를 대기흡입식 간 헐 초음속 풍동을 이용하여, 팽창율이 일정한 노즐을 통하여 팽창시키는 경우에 대하 여 비평형 응축영역내 입치하는 경우에 대하여, 정체점 상태량의 변화에 기인되는 응 축 및 응축형격파가 경사형격파의 형상과 변화에 미치는 영향을 다음의 관점으로부터 연구하였다.

• 대한가정학회지
• /
• 제26권2호
• /
• pp.1-13
• /
• 1988

The purpose of this study was to classify somatotype of males, to show changes of the body skin surface by the somatotype. The size of sample was 156 males between age 20 and 24. Somatotype classified into Bending somatotype, Standard somatotype, Turning over somatotype. And according to the somatotype, changing of the upper part of the body by the arm movements analyzed through gypsum experiment. The result obtained from this study were as follows; 1. the variation of the upper part of the body form by changing the am movements, by the increasing of movements, shoulder-point ws moved to be inside or upside, the anterior armpit point & armpit point were moved to the upside. 2. As a result of investigating into the rate of the expansion and contraction of the basic lines and body surface area by the arm movements, the rate of expansion and contraction of the basic lines by the arm movements, the side sea length showed the maximum rate of extension in 135 degrees, the shoulder length showed the maximum rate of contraction in 135 degrees. The rate of expansion and contraction on the body surface area by the arm movements showed the phenomenon of contraction, of items F1, F6, B1, B9 showed the phenomenon of extension, of items F3, F4, F8, F9, B8, B9. 3. According to somatotypes, items which show the significant difference were, of items f3, f8, b3, b8, F2, F7, F8, B3, B7, in all movements.

• 대한전자공학회논문지TC
• /
• 제47권11호
• /
• pp.14-18
• /
• 2010

M-ary와 PN 확산의 조합이 존재하는 CDMA 시스템에서 성능분석 방법을 제안하였다. M-ary와 PN 확산에 의한 전체 대역폭 확장이 같더라도 두 블럭의 대역폭 확장의 조합에 따라 시스템 성능이 달라진다. 따라서 M-ary와 PN 확산이 이루는 CDMA 시스템 전체 대역폭 확장이 아니라, 각각의 대역폭 확장을 사용하여 시스템 성능을 분석하였다. 그리고 SINR이 높을수록 M-ary에 의한 대역폭 확장이 PN 확산에 의한 대역폭 확장보다 비트오율을 더 많이 감소시키는 것을 볼 수 있었다. 제안한 성능분석 방법이 M-ary에 의한 성능개선의 효과를 반영했기 때문에 전체 대역폭 확장만을 사용한 방법보다 더 정확한 성능분석을 할 수 있었다.