• 한국염색가공학회지
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• 제14권2호
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• pp.33-39
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• 2002

A study has been made of the dry-jet-wet spinning of PAN copolymer fibers using 60% aqueous zinc chloride solution as solvent and 25∼40% aqueous zinc chloride solution as non-solvent. The technological characteristics of this method were that small streams of dope were extruded from the die and allowed to pass through a short distance of air gap(about 10mm) before entering the spinning bath for full coagulation. This work showed the importances which coagulation condition, stretch ratio and fiber tenacity up to 10.5 g/d could be obtained with elongation of 11∼16%. Individual fibers were evaluated on the basis of density and mechanical properties such as tenacity and elongation etc.

• 한국연초학회지
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• 제11권2호
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• pp.211-224
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• 1989

10. Three major factors, freeness, filler and blend ratio that exercised considerable influence on physical properties of cigarette papers were chosen for the sake of their optimization at this experiment. An optimization of those above factors in paper manufacturing was investigated using response surface analysis. Optimum beating degree for Kenaf, Flax and NBKP showed around 72。SR, 68。SR and 85 SR, respectively, in considering of five quality index such as porosity, tensile strength, stretch, whiteness and opacity. The best blending ration of reciprocal pulps treated under optimum beating degree were diversified and combination scope of the bast fiber (Kenaf, Flax) to the NBKP was range from 30% to 65% in case of the Kenaf, from 25 to 40% in Flax at the same receipe. The optimum range of calcium carbonate content revealed 25%~30% in Kenaf mixed NBKP and 24%~31% in Flax mixed NBKP.

• 한국산업융합학회 논문집
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• 제12권3호
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• pp.137-142
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• 2009

Burning velocity of methane-air mixtures with water vapor have been measured to study the process of flame propagation using schlieren photographs and computation. The computations were carried out for the burning velocity using premix code of Chemkin program to compare the experimental results. The quantity of water vapor contained were changed 5% and 10% of total mixtures, and equivalence ratio of mixtures between 0.8 and 1.2 were tested under the ambient temperature 323K and 373K. The results showed little difference between these two methods, the burning velocity was decreased by increasing the water vapor contents due to the interruption of flame development. And, the effect of ambient temperature was less significant by increasing the water contents on the burning velocity.

• 한국해양공학회지
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• 제14권1호
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• pp.44-51
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• 2000

Safety and integrity are required for reactor pressure vessels because they are operated in high temperature. There are single specimen method multiple specimen method and load ratio analysis method which used as evaluation of safety and integrity for reactor pressure vessels. In this study the fracture resistance curve(J-R curve) elastic-plastic fracture toughness($J_{IC}$) and material tearing modulus ($T_{mat}$) of SA 508 class 3 alloy steel used as reactor pressure vessel steel are measured and evaluated at room temperature 20$0^{\circ}C$ and 30$0^{\circ}C$ according to unloading compliance method and load ration analysis method. And then the comparison with experimental $J_{IC}$ and theoretical$J_{IC}$ by local fracture strain is managed.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.165-168
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• 2015

To measure laminar burning velocity in methane/air/ethylene mixture flame, propagating centrally ignited spherical premixed flame to radial direction was measured by high-speed schlieren images with elevated pressure. In this study, The experimentally measured unstretched laminar burning velocities of methane was compared with GRI mech 3.0 to validate experimental data and choose the radius range, respectively. numerical prediction using the PREMIX code with GRI mech 3.0, USC mech II,, and Wang mech were evaluated through comparison with experimental burning velocity with consideration of extrapolation on linear/nonlinear model.

• 한국염색가공학회지
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• 제33권3호
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• pp.120-130
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• 2021

The condition of covering process using thermoplastic polyetherester elastomeric fibers(TPEE) was established. Two types of core yarn(TPEE, Spandex) and one type of effect yarn(PET) were used as materials to confirm the change in physical properties of covering yarn under various covering conditions. In addition, the effects of the treatment temperature on the elongation at break of covering yarn after heat treatment was analyzed. Through this analysis, it was confirmed that the elastic recovery of TPEE which is used as the core yarn was increased with the draw ratio, but decreases when it exceeds 1:2.5. And the elongation at break of the covering yarn could be increased by increasing the twist per meter of it. Additionally, it was confirmed that the elastic recovery of TPEE which is used as a core yarn, could be increased by applying heat treatment.

• Current Optics and Photonics
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• 제5권4호
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• pp.391-401
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• 2021

In the present study, a hyperelastic constitutive model is built by complying with a simplified hyperelastic strain energy function, which yields the numerical solution for a deformed polydimethylsiloxane (PDMS) membrane in the case of axisymmetric hydraulic pressure. Moreover, a nonlinear equilibrium model is deduced to accurately express the deformation of the membrane, laying a basis for precise analysis of the optical transfer function. Comparison to experimental and simulated data suggests that the model is capable of accurately characterizing the deformation behavior of the membrane. Furthermore, the stretch ratio derived from the model applies to the geometrical optimization of the deformed membrane.

• 대한기계학회논문집B
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• 제21권2호
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• pp.195-201
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• 1997

Static and non-static flame methods were used to measure the laminar burning velocity of methane, ethane and natural gas. The flame slot angle and velocity of unburned gas mixture were determined by Schlieren method and LDV, respectively, for static flame. The diameter of nozzle was selected as 11 mm. The experimental results containing the stretch effect showed that the maximum burning velocities were 41.5 for natural gas, 40.8 for methane and 43.4 cm/sec for ethane on equivalence ratio of 1.1. Constant volume combustion chamber was also used for non-static flame. The propagation process of flame front was visualized by high speed camera during constant pressure. The maximum burning velocity of natural gas was determined as 42.1 cm/sec on equivalence ratio of 1.15.

• 국제물리치료학회지
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• 제10권1호
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• pp.1706-1710
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• 2019

Background: Despite frequent shoulder injuries of rotator cuff muscle of golfers by the result of overuse and poor swing mechanics, there is little research on shoulder specific rehabilitation exercises for injured rotator cuff muscle and golf swing Objective: To examined the effect of rehabilitation exercise for golfers on the X factor and ground reaction force (GRF) according to phase of the golf swing. Design: Crossover study Methods: The participants were 13 amateur golfers selected for a 4 week rehabilitation exercise for golfers. A rehabilitation exercise for golfers consisting of 5 steps and 4 items (sleeper stretch, full side plank, push up to plank, high plank knee unders) were applied to all participants. A three dimensional motion analyzer and force platform (SMART-E, BTS, Italy) were used to measure the X factor (angle between shoulder and pelvis at top of back swing) and GRF according to phase of the golf swing. All dependent variables were measured before and after exercise. The collected data was analyzed using the paired t test and SPSS 21.0. Results: The GRF had a statistically significant increase in the impact phase and ratio impact/weight after rehabilitation exercise for golfers (p<.05). The X-factor, GRF in top of back swing and finish were no significant differences between before and after exercise (p>.05). Conclusions: These results suggested that rehabilitation exercise for golfers was effective for increasing GRF in the impact phase and ratio impact/weight for amateur golfer.

• 한국정밀공학회지
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• 제10권3호
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• pp.198-204
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• 1993

The study is concerned with finite element analysis and design of axisymmetric deep drawing by local heating. When the bottom shape of a cup is not flat but in complex-shaped, i.e., hemispherical, the cup cannot be drawn in one or two processes in the conventional deep drawing process and the limit drawing ratio is limited as well. By introducing local heating selectively with regards to the heating position, the formability of the sheet metal can be greatly increased with the reduced number of processes. In the Process analysisthe rigid- viscoplastic finite element method is employed and the temperature effect is incorporated. Bishop's step-wise decoupled method is employed to analyze the thermomechanical interaction between deformation and heat transfer. Axisymmetric deep drawing of a hemisphere-bottomed cup has been analyzed for various combinations of heat application in the punch and the die. At the first stage of deep drawing stretch forming is practically carried out by firmly pressing the blankholder with the punch and the die heated at various levels of temperature. Then at the second stage the same cup is drawn for the saame or different combination of temperature. From the computation, it has thus been shown that the fromability of a cup is greatly increased in two-stage deep drawing with increased limet drawing ratio.