• 한국정밀공학회지
• /
• 제25권4호
• /
• pp.47-52
• /
• 2008

Recently, the study for filling imbalance in thermoplastic polymer has gradually been increased. However, it is hard to find the researches for filling imbalance of thermoplastic elastomer(TPE). The experiment of filling imbalance was conducted for the three kinds of thermoplastic vulcanizes(TPVs) and PP polymer in the mold with geometrically balanced runner system(Unary Branch Type Runner System). In this experiment, the effects of the melt temperature, injection pressure and injection speed on the filling imbalance were investigated. There was also the imbalance in TPV injection molding process as well as in conventional injection molding with plastics. The tendency of filling imbalance in TPV injection molding specially decreased by taking place the hesitation of TPV melt.

• Design & Manufacturing
• /
• 제2권4호
• /
• pp.5-10
• /
• 2008

Recently, the study for filling imbalance in thermoplastic polymer has gradually been increased. However, it is hard to find the researches for filling imbalance of thermoplastic elastomer(TPE). The experiment of filling imbalance was conducted for the three kinds of thermoplastic vulcanizes(TPVs) and PP polymer in the mold with geometrically balanced runner system(Unary Branch Type Runner System). In this experiment, the effects of the melt temperature, injection pressure and injection speed on the filling imbalance were investigated. There was also the imbalance in TPV injection molding process as well as in conventional injection molding with plastics. The tendency of filling imbalance in TPV injection molding specially decreased by taking place the hesitation of TPV melt.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
• /
• pp.11-12
• /
• 2016

The contemporary buildings are becoming super-taller gradually as the industry evolves. Accordingly, winter concrete also became an important element for the year-round construction since shortening of a construction duration became important. Accordingly, this research team once developed a double bubble sheet as concrete cover curing compound during winter. But since there is no proper countermeasure for the exposed reinforcement bars, it is worried that the concrete can be damaged by exposed frozen reinforcement bars at a low temperature during the initial period. Therefore, in this study, it is intended to review the temperature history of the reinforcement bars depending on changes of the covering methods of the exposed reinforcement bars by using bubble sheets.

• 설비공학논문집
• /
• 제8권3호
• /
• pp.413-422
• /
• 1996

Freezing of water in von-$K{\acute{a}}rm{\acute{a}}n$ swirling flow is considered. The transient behavior of the temperature distribution in both solid and liquid phases and freezing rate are determined. The fluid flow induced by the rotation of solid strongly inhibits the freezing process. The thickness of frozen layer is inversely proportional to the square root of the angular velocity of solid. As the angular velocity or initial liquid temperature becomes larger, the freezing process is more strongly inhibited by the fluid flow. When phase change is present, the transient heat transfer rate is greater than the case with no phase change.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2002년도 춘계 학술대회논문집
• /
• pp.109-114
• /
• 2002

The effect of nose radius on aerodynamic heating are investigated by using the Wavier-Stokes code extended to thermochemical nonequilibrium airflow. A spherical blunt body, whose radius varies from 0.003048 m to 0.6096 m, flying at Mach 25 at an altitude of 53.34 km is considered. Comparison of heat flux at stagnation point with the solution of Viscous Shock Layer and Fay-Riddell are made. Obtained result reveals that the flow chemistry for very small radius is nearly frozen, and therefore the contribution of heat flux due to chemical diffusion is smaller than that of translational energy. As the radius becomes larger, the portion of diffusion heat flux becomes greater than translational heat flux and approaches to a constant value.

• Advances in biomechanics and applications
• /
• 제1권2호
• /
• pp.77-83
• /
• 2014

Creep phenomenon at the scale of bone tissue (small specimens) is known to be present and demonstrated for low strains. Here creep is demonstrated on a pair of fresh-frozen human femurs at the organ level at high strains. Under a constant displacement applied on femur's head, surface strains at the upper neck location increase with time until fracture, that occurs within 7-13 seconds. The monotonic increase in strains provides evidence on damage accumulation in the interior (probably damage to the trabeculae) prior to final fracture, a fact that hints on probable damage of the trabecular bone that occurs prior to the catastrophic fracture of the cortical surface layer.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2005년도 금형가공,미세가공,플라스틱가공 공동 심포지엄
• /
• pp.9-12
• /
• 2005

The rapid thermal response (RTR) molding is a novel process developed to raise the temperature of mold surface rapidly to the polymer melt temperature prior to the injection stage and then cool rapidly to the ejection temperature. The resulting filling process is achieved inside a hot mold cavity by prohibiting formation of frozen layer so as to enable thin wall injection molding without filing difficulty. The present work covers flow simulation of thin wall injection molding using the RTR molding process. In order to take into account the effects of thermal boundary conditions of the RTR mold, coupled analysis with transient heat transfer simulation is suggested and compared with conventional isothermal analysis. The proposed coupled simulation approach based on solid elements provides reliable thin wall flow estimation fur both the conventional molding and the RTR molding processes

• 한국가금학회지
• /
• 제29권1호
• /
• pp.45-52
• /
• 2002

계육 surimi에서 trehalose와 oligosaccharide의 단백질 냉동변성 방지효과를 구명하기 위하여 본 실험을 실시하였다. 기계발골노계육에 0.5% 소금물(고기:용액, 1:4)로 2회, 증류수로 1회 수세하여 surimi를 제조하였다. Trehalose와 oligosaccharide를 각각 8%씩 혼합한 후 $-18^{\circ}C$에서 10주간 냉동저장하였다. 모든 Surimi의 적색도(a*)는 냉동기간동안 감소하였다. 냉동기간중에 trehalose, oligosaccharide, 무첨가 순으로 명도가 높고 적색도와 황색도가 낮아 색택 안정성이 있는 것으로 나타났다. 냉동기간중 surimi의 gel 강도(압착력, 경도, 탄성, 점착성)는 감소하였지만, trehalose와 oligosaccharide 첨가가 무침가구에 비해 유의적으로 높은 수준을 유지하였다. 냉동기간중에 부착성은 trehalose 첨가가 가장 높았다. 따라서 이들 당류가 계육 surimi에 단백질 냉동변성방지제로 효과가 인정되었으며, trehalose는 감미도가 기존 설탕보다 낮고 색깔 및 물성에서 oligosaccharide 보다 더 우수한 것으로 판단되었다.

• 한국항공우주학회지
• /
• 제30권1호
• /
• pp.114-123
• /
• 2002

케로신/액체산소 추진기관을 갖는 초음속 로켓의 플룸 유동장을 9 화학종 14 반응 모델과 연계된 레이놀즈 평균 Navier-Stokes 방정식을 이용하여 해석하였다. 유한속도 화학반응이 플룸 유동장에 미치는 영향을 고찰하기 위하여 그 결과를 화학적 동결유동 해석 결과와 비교하였다. 계산은 상용 CFD 소프트웨어인 FLUENT 5를 이용하여 수행하였다. 반응 유동 해석 결과는 노즐 내부에서의 화학반응에 따른 연소가스의 온도 증가로 인해 전체적으로 동결유동에 비해 더 높은 온도장을 나타내었다. 플룸에서의 모든 화학반응은 전단류와 배럴 충격파 반사지점 후방의 고온 영역에 국한되어 일어났으며 본 해석의 경우 플룸내에서의 유한속도 화학반응이 유동에 미치는 영향은 미약한 것으로 나타났다. 그러나 본 연구에서 이루어진 유한속도 화학반응을 고려한 플룸 해석을 통하여 플룸에서의 주된 화학 반응 및 이들의 반응 메커니즘을 확인할 수 있었다.

• Geomechanics and Engineering
• /
• 제27권5호
• /
• pp.433-445
• /
• 2021

Artificial ground freezing (AGF) is a commonly used geotechnical support technique that can be applied in any soil type and has low environmental impact. Experimental and numerical investigations have been conducted to optimize AGF for application in diverse scenarios. Precise simulation of groundwater flow is crucial to improving the reliability these investigations' results. Previous experimental research has mostly considered horizontal seepage flow, which does not allow accurate calculation of the groundwater flow velocity due to spatial variation of the piezometric head. This study adopted vertical seepage flow-which can maintain a constant cross-sectional area-to eliminate the limitations of using horizontal seepage flow. The closure time is a measure of the time taken for an impermeable layer to begin to form, this being the time for a frozen soil-ice wall to start forming adjacent to the freeze pipes; this is of great importance to applied AGF. This study reports verification of the reliability of our experimental apparatus and measurement system using only water, because temperature data could be measured while freezing was observed visually. Subsequent experimental AFG tests with saturated sandy soil were also performed. From the experimental results, a method of estimating closure time is proposed using the inflection point in the thermal conductivity difference between pore water and pore ice. It is expected that this estimation method will be highly applicable in the field. A further parametric study assessed factors influencing the closure time using a two-dimensional coupled thermo-hydraulic numerical analysis model that can simulate the AGF of saturated sandy soil considering groundwater flow. It shows that the closure time is affected by factors such as hydraulic gradient, unfrozen permeability, particle thermal conductivity, and freezing temperature. Among these factors, changes in the unfrozen permeability and particle thermal conductivity have less effect on the formation of frozen soil-ice walls when the freezing temperature is sufficiently low.