• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.9
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• pp.893-899
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• 2015

In the design of injection molds, the temperature distribution and deformation of the mold is one of the most important parameters that affect the flow characteristics, flash generation, and surface appearance, etc. Plastic injection analyses have been carried out to predict the temperature distribution of the mold and the pressure distribution on the cavity surface. As the input loads, we transfer the temperature and pressure results to the structural analysis. We compare the structural analysis results with the thermal expansion effect using the actual flash and step size of a smartphone cover part. To reduce the flash problem, we proposed a new mold design, and verified the results by performing simulations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.279-289
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• 2000

Residual stress induced in U-bending and tube-to-tubesheet joint processes of PWR's row-1 heat exchanger tube was measured by X-ray method and Hole-Drilling Method(HDM). Compressive residual stresses(-) at the extrados surface were induced in U-bending, and its maximum value reached -319 MPa in axial direction at the position of $\psi$ = $0^{\circ}$. Tensile residual stresses(+) of $\sigma_{zz}$ = 45 MPa and $\sigma_{\theta\theta}$ = 25 MPa were introduced in the intrados surface at the position of $\psi$ = $0^{\circ}$. Maximum tensile residual stress of 170 MPa was measured at the flank side at the position of $\psi$ = $90^{\circ}$, i.e., at apex region. It was observed that higher stress gradient was generated at the irregular transition regions (ITR). The trend of residual stress induced by U bending process of the tubes was found to be related with the change of ovality. The residual stress induced by the explosive joint method was found to be lower than that by the mechanical roll method. The gradient of residual stress along the expanded tube was highest at the transition region (TR), and the residual stress in circumferential direction was found to be higher than the residual stress in axial direction.

• Korean journal of food and cookery science
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• v.26 no.4
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• pp.398-405
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• 2010

In this study, white bread was prepared containing 1.5, 3.0, 4.5 or 6.0% barley leaves tea powder (BLTP). The samples along with a control were then compared regarding their quality characteristics, including pH, total titratable acidity, fermentation power of dough expansion, specific volume, baking loss, moisture content, color, textural characteristics, internal surface appearances and sensory qualities, all to determine the optimal ratio of BLTP. As the BLTP content increased, the pH of the dough and bread and the lightness decreased, whereas the total titratable acidity increased. The fermentation power of dough expansion increased with a longer incubation time. The control group was evidenced by a significantly higher specific volume and baking loss than that observed in the BLTP samples. However, greenness and yellowness evidenced the opposite effect. Hardness was highest at a substitution level of 1.5% and lowest at a level of 4.5%. Fracturability and resilience were not significantly different among the samples. For the internal surface appearance, darkness and greenness increased both increased at higher BLTP content. In the sensory evaluation, color, flavor and overall acceptability were highest in the control bread samples but minimal at a substitution level of 6.0%. Softness was the highest at the 3.0% substitution level and lowest in the control bread samples. Barley leaf flavor, astringency, bitterness and off-flavor increased as the BLTP content increased. Delicious taste was not significantly different among the samples. In conclusion, the results demonstrated that 4.5% BLTP may prove quite useful as a substitute for wheat flour in the production of white bread and may provide favorable nutritional and functional properties.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.8
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• pp.1270-1277
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• 2003

The extrusion conditions of the soymilk residue and corn grits mixtures were optimized. The experiment was designed according to the D-optimal design of response surface methodology (RSM), which shows 18 experimental points including 4 replicates for three independent variables (screw speed, water content and die temperature). The responses variables such as bending force, expansion ratio, bulk density, water solubility index (WSI), water absorption index (WAI), and color values (L＊, a＊, b＊) were evaluated using response surface analysis. Expansion ratio and WSI decreased with increasing water content, whereas bulk density tended to increase with increasing water content. While greater screw speeds enhanced WSI and yellowness, higher moisture contents decreased the expansion ratio and WSI value. However, die temperature did not influence upon the response variables. The optimum extrusion conditions by numerical and graphical methods were similar: the screw speed, water content, and die temperature were 250 rpm, 22.43% and l28.16$^{\circ}C$ by the numerical method; 250 rpm, 22.43%, and 128.02$^{\circ}C$ by graphical method.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.644-648
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• 2004

In the present study were examined numerically and experimentally the off-design performance characteristics on an axisymmetric plug nozzle with variable throat area. In this nozzle concept, its throat area can be changed by translating the plug into the axial direction. First, a mixed-expansion plug nozzle, in which two expansion parts are arranged both inside and outside, was designed by means of the method of characteristics. Second, the CFD analysis was verified by the cold-flow wind tunnel test. Third, its performance characteristics were evaluated over a wide range of pressure ratio from half to double throat area through the design point, using the CFD code verified by the wind tunnel tests. It was made clear from the study that not so critical thrust efficiency losses were found and the maximum thrust efficiency loss was at most approximately 5 % under off-design conditions without external flow. This result shows that a plug nozzle can give the altitude compensation even under off-design geometry operations. However, shock waves were observed in the inner expansion part under the doubled throat area operation and thus some thermal problems may be caused on the plug surface. Furthermore, collapse of cell structure on the plug surface was observed with external flow (around Mach number 2.0) as it became lower pressure ratio below the design point and the fact may result in big efficiency loss regardless of geometrical configuration.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.4
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• pp.482-487
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• 2008

In case of flooding, the underwater flight vehicle (UFV) executes the blowing by blowing ballast tanks off using high pressure air (HPA), while it also uses control planes and a propulsion unit to reduce the overshoot depth caused by a flooding and blowing sequence. However, the conventional whole HPA blow-off method lets the body on the surface after blowing despite slight flooding. This results in the unnecessary mission failure or body exposure. Therefore, it is necessary to keep the body at the near surface by the blowing control while reducing the overshoot depth. To solve this problem, an adaptive blowing control algorithm, which is based on the decomposition method expanding the expert knowledge in depth control and the adaptive method using fuzzy basis function expansion (FBFE), is proposed. To verify the performance of the proposed algorithm, the blowing control of UFV is performed. Simulation results show that the proposed algorithm effectively solves the problems in the UFV blowing control system online.

• Composites Research
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• v.34 no.6
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• pp.426-433
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• 2021

The carbon fiber reinforced plastic manufacturing process has a problem in that a dimensional error occurs due to thermal deformation such as residual stress, spring-in, and warpage. The main causes of thermal deformation are various, including the shape of the product, the chemical shrinkage, thermal expansion of the resin, and the mold effect according to the material and surface condition of the mold. In this study, a viscoelastic model was applied to the plate model to predict the thermal deformation. The effects of chemical shrinkage and thermal expansion of the resin, which are the main causes of thermal deformation, were analyzed, and the analysis technique of the 3-D viscoelastic model with and without mold was also studied. Then, the L-shaped mold effect was analyzed using the verified 3D viscoelastic model analysis technique. The results show that different residual deformation occurs depending on the surface condition even when the same mold is used.

• Journal of the Korean Wood Science and Technology
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• v.44 no.3
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• pp.302-314
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• 2016

This study was carried out to confirm the effects of the knife-incising and kerfing pretreatment on the moisture content and surface check occurrence of Douglas-fir heavy timber. In the case of moisture content, the moisture gradient that formed in the inner part of the specimen was observed in all specimens. In addition, the moisture gradient was formed differently from the surface layer to 72 mm depending on the pretreatment conditions, and it was formed gradually in the kerfing than the knife-incising. In addition, it was found that the solid volume should be considered when measuring the average moisture content. In the case of surface check, the surface check occurrence was reduced in the knife-incising, kerfing, and the combination of knife-incising and kerfing than the control. In particular, the kerfing treatment was shown that the expansion of surface check width was effectively suppressed. In the case of knife-incising treatment, although the surface check was less than the control, the preventive effect on the surface check occurrence did not reach the level of the kerfing treatment.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.6
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• pp.1031-1040
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• 1997

This study was done to analyze the body surface developments of armhole area. The major conclusions of this study are: 1. The body surface developments showed the characteristics of expansion and contraction of body at armhole area. By arm movements, front armhole lines on the body surface developments of upper arm were slow going, but back armhole lines were full and round. As a whole, armhole line of the back torso was swollen outside especially at backarmpit point area, it seemed like a line of raglan sleeve. 2. Regression Analysis was carried out to adapt armhole line on the upper arm and upper body to bodice and sleeve pattern, following the axillary circumference line and chest breadth line changed to the basic pattern form. As the result, armhole lines of 90$^{\circ}$ and 135-180$^{\circ}$ movements deviated from those of standard posture. U-type, clear armhole curve of standard posture turned to V-type, slanting line by arm movements.

• Journal of the Korean Society of Clothing and Textiles
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• v.22 no.7
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• pp.892-900
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• 1998

This study was done to analyze the surface development of upper arm for planning sleeve armhole line. The major conclusions of this study are: 1. The surface development by arm movements made the expansion and contraction of upper arm surface changes easily visible. Armhole lines of 90$^{\circ}$and 135$^{\circ}$~180$^{\circ}$movements deviated from those of standard posture. 2. According to regression analysis, armhole lines on the upper arm were adapted to sleeve patten, following the axillary circumference line changed to biceps line. Sleeve cap length ranged from armhole/4+2.5cm to armhole/4$\pm$0.5cm. 3. Compared to Rim's pattern method, ascending and descending amounts of armhole lines were represented as fixed values.