• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.5
• /
• pp.1150-1160
• /
• 1993

The behavior of polystyrene in the strip cavity during the packing and cooling stages for an injection molding process is examined numerically. The mathematical model is based on the unified post-filling model and finite element/finite difference methods are used to solve simultaneously the continuity, momentum and energy equations coupled to an equation of state. Simulated results show that the density of the molded parts is lower in the core than at the skin, and that the hotter the melt or the higher the packing pressure, the higher the density in the core. The density variation during the packing stage comes up to 50% compared with the total density variation. Also, the density variation after gate sealing and the effect of cooling rate on the equation of state are negligible.

• Composites Research
• /
• v.26 no.1
• /
• pp.42-47
• /
• 2013

In this study, an economical and effective processing technique to form multiple dimples on the surface of a composite part, which are known to be useful to improve aerodynamic performance and heat dissipation. Forming dimples on the surface using molds is an expensive processing because forming multiple tiny positive spheres on the surface of the mold requires much time and effort. In this study, plates with multiple round holes are utilized as a core to form dimples on the carbon/epoxy composite skin covering the core. A vacuum bagging process is used to apply pressure on the surface while curing. Composite parts which have multiple dimples on the surface can be utilized in the field which needs high aerodynamic performance and heat dissipation ability such as high speed sports car bodies.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.2 s.257
• /
• pp.166-173
• /
• 2007

Fatigue fracture behavior of a hybrid bolted joint was evaluated in comparison to the case of static fracture. Two kinds of specimens were fabricated for the mechanical tests; a hybrid bolted joint specimen for the shear test and a hybrid joint part specimen applied in the real tilting car body for the bending test. Characteristic fracture behaviors of those specimens under cyclic toads were obviously different from the case under static loads. For the hybrid bolted joint specimen, static shear loading caused the fracture of the bolt body itself in a pure shear mode, whereas cyclic shear loading brought about the fracture at the site of local tensile stress concentration. For the hybrid joint part specimen, static bend loading caused the shear deformation and fracture in the honeycomb core region, while cyclic bend loading did the delamination along the interface between composite skin and honeycomb core layers as well as the fracture of welded joint part. Experimental results obtained by static and fatigue tests were reflected in modifications of design parameters of the hybrid joint structure in the real tilting car body.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.6 no.1
• /
• pp.151-161
• /
• 2014

In this study, an experimental investigation has been made of the applicability of outer-layer vertical blades to real ship model. After first devised by Hutchins and Choi (2003), the outer-layer vertical blades demonstrated its effectiveness in reducing total drag of flat plate (Park et al., 2011) with maximum drag reduction of 9.6%. With a view to assessing the effect in the flow around a ship, the arrays of outer-layer vertical blades have been installed onto the side bottom and flat bottom of a 300k KVLCC model. A series of towing tank test has been carried out to investigate resistance (CTM) reduction efficiency and improvement of stern wake distribution with varying geometric parameters of the blades array. The installation of vertical blades led to the CTM reduction of 2.15~2.76% near the service speed. The nominal wake fraction was affected marginally by the blades array and the axial velocity distribution tended to be more uniform by the blades array.

• Journal of Fashion Business
• /
• v.25 no.2
• /
• pp.127-142
• /
• 2021

This study aims to organize the prototype design method of compression wear for women professional soccer players. Despite the excellent performance of female soccer players in world competition, most functional wear has been developed mainly for men, so professional female athletes have fewer choices. Soccer is a sport requiring core and lower body muscle strength, and muscular endurance for long periods of playing or walking on the field. Female soccer players did not differ much in upper body compared to other women, but their lower body had a smaller hip circumference than waist circumference and a larger thigh circumference, requiring compilation considering the physical characteristics and movement of athletes. Female soccer players wear sports bras while playing but regular bras and compression wear during normal exercise because they sweat on under their breast, which irritates sensitive skin. For core muscles in the upper body and to support for thigh and hip muscles in the lower body, the uniform in this study was designed by reducing the body size of a professional female soccer player in her 20s and the actual measurements of commercial compilation software to 81% of the chest circumference, 95% of the waist circumference, and 78% of the hip circumference. The design experiment in this study was a simple exercise and did not produce produce results for long-term exercise and performance improvement, but can be used to design a composition pattern system for other professional female athletes.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.844-847
• /
• 2005

A seamless analysis of complex geometry is one of greatly interesting topic. However, there are still gaps between the industrial applications and fundamental academic studies owing to time consuming modeling process. To resolve this problem, an auto mesh generation program based on grid-based approach has been developed for IT-product in the present study. At first, base mesh and skin mesh are generated using the information of entities which extracted from IGES file. Secondly the provisional core mesh with rugged boundary geometry is constructed by superimposing the skin mesh as well as the base mesh generated from the CAD model. Finally, the positions of boundary nodes are adjusted to make a qualified mesh by adapting node modification and smoothing techniques. Also, for the sake of verification of mesh quality, the hexahedral auto mesh constructed by the program is compared with the corresponding tetrahedral free mesh and hexahedral mapped mesh through static finite element analyses. Thereby, it is anticipated that the grid-based approach can be used as a promising pre-processor for integrity evaluation of various IT-products.

• Journal of Korean Society of Steel Construction
• /
• v.20 no.2
• /
• pp.289-301
• /
• 2008

Double skin composite (DSC) wall is a structural wall that is filed with concrete between two steel plate skins connected by tie bars. This type of wall was developed to enhance the structural performance of wall, to reduce wall thickness, and to enhance constructibility, eliminating the use of formwork and re-bars. In this study, cyclic tests were performed to investigate the inelastic behavior and earthquake resistance of isolated and coupled DSC walls with rectangular and T-shapedcross-sections. The DSC walls showed stable cyclic behaviors, exhibiting excellent energy dissipation capacity. The te st specimens failed by the tensile fracture of welded joints at the wall base and coupling beam and by the severe local buckling of the steel plate. The deformation capacity of the walls varied with the connection details at the wall base and their cross-sectional shapes. The specimens with well-detailed connections at the wall base showed relatively god deformation capacity ranging from 2.0% to 3.7% drift ratio. The load-carrying capacities of the isolated and coupled wall specimens were evaluated considering their inelastic behavior. The results were compared with the test results.

• Korean Journal of Rural Living Science
• /
• v.7 no.2
• /
• pp.99-108
• /
• 1996

This study has intended to suggest fundamental data to develope and choose appropriate shoes for upland farming in order to prevent health deterioration of women workers and improve work effectiveness and reduce fatigue by wearing appropriate shoes. During 1995. 4. 28 - 5. 10, Fifty women workers in hot pepper farming were observed and major shoe types, which were rubber shoes, walking shoes, slippers, and rubber boots, were selected for the study. During 1995. 10. 9 - 31, two subjects were tested by wearing those shoes in the laboratory where the temperature was 24$\pm$1$^{\circ}C$ and relative humidity 50$\pm$5%RH. And the temperature & humidity on sole and in the shoes, the rectal temperature, skin temperature, blood pressure, pulse, lactate concentration of blood, Flickers' value and subjective sensation were measured. The results were as follows : 1. 84% of women workers mentioned that they need shoes improvement and the order of most frequent shoe types to be worn was rubber shoes, walking shoes, slippers, rubber boots. 2. The rate of women who were unsatisfied with shoes for upland farming is 38 percentages. The reason of unsatisfaction was that feet were in a sweat and alien substances were let into shoes. 3. The temperature & humidity on sole were the lowest in rubber boots during experiment(p＜0.01). 4. The relative humidity in the shoes was the highest in rubber boots by 90% and the lowest in walking shoes by 72% during rest And the humidity in slippers and walking shoes were significantly low in experiment(p＜0.001). 5. Rubber boots showed the highest rise in rectal temperature by 0.2$^{\circ}C$ showing increase of core temperature (p＜0.05). 6. The mean skin temperature during experiment was highest in rubber boots by 33.8$^{\circ}C$(p＜0.001).

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.37 no.6
• /
• pp.567-575
• /
• 2013

A POD analysis based on time-resolved PIV measurements in a circulating water channel has been conducted to identify the skin friction reduction mechanism of outer-layer vertical blades. A recent PIV measurement indicated 2.73% and 7.95% drag reduction in the blade plane and the blade-in-between plane, respectively. In the present study, the influence of vertical blades array upon the characteristics of the turbulent coherent structures was analyzed by the POD method. It is observed that the vortical structures are cut and deformed by the blades array and that their temporal evolution is strongly associated with the skin-friction drag reduction mechanism in the turbulent boundary layer flow.

• The Journal of the Korea Contents Association
• /
• v.8 no.8
• /
• pp.111-118
• /
• 2008

Nowadays, people get images from various media like TV, magazines, newspaper, internet. Such images directly influence people's thoughts and lives, either consciously or unconsciously. In the past, reproduction devices have been mainly used in reproducing an original scene accurately. Lately, the cognitive preference became a key value in the scene reproduction, and it was affected by the surrounding media. Recently, the most commonly used device in reproducing an original scene is the camera. The core of an image is the light, in other words, the exposure. Most digital cameras are set to adjust exposure automatically in order to reproduce a scene physically as identical as possible. However, physically right exposure does not always give images that people prefers. Numbers of tests were done to find the exposure value that makes an image cognitively more preferred. Skin tones which are highly sensitive to color and changes in density has been used in the tests. A male and a female model have been used to classify changes in cognitive preference due to gender differences.