• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.39.1-39.1
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• 2013

We use high-resolution hydrodynamic simulations to study nonlinear gas responses to imposed non-axisymmetric stellar potentials in barred-spiral galaxies. The gas is assumed to be infinitesimally thin, isothermal, and unmagnetized. We consider various spiral-arm models with differing strength and pattern speed, while fixing the bar parameters. We find that the extent and shapes of spiral shocks as well as the related mass drift depend rather sensitively on the pattern speed. In models where the arm pattern is rotating more slowly than the bar, the gaseous arms extend from the bar ends all the way to the outer boundary, with a pitch angle slightly smaller than that of the stellar counterpart. The arms drive mass inflows at a rate of ${\sim}0.5-2.5M{\odot}/yr$ to the bar region to which the shock dissipation, external torque, and self-gravitational torque contribute about 50%, 40%, and 10%, respectively. About 85% of the inflowing mass is added to bar substructures such as an inner ring, dust lanes, and a nuclear ring. while the remaining 15% encircles the bar region. On the other hand, models where the arms corotate with the bar exhibit mass outflows, rather than inflows, over most of the arm region. In these models, spiral shocks are much more tightly wound than the stellar arms and cease to exist in the region where $M{\bot}/sinp*{\geq}25-40$, where $M{\bot}$ denotes the Mach number of a rotating gas perpendicular to the arms with pitch angle p*. We demonstrate that the distributions of line-of-sight velocities and densities can be a useful diagnostic tool to distinguish if the arms and bar corotate or not.

• Journal of the Korean Data and Information Science Society
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• v.21 no.1
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• pp.11-20
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• 2010

The purpose of this study is to analyze the images of the Military Academy, Naval Academy, Air Force Academy, Police Academy, and Armed Forces Nursing Academy using multidimensional scaling method. For this research, we surveyed 363 applicants to special purpose academies including Military Academies and Police College. The study showed that the Military, Naval, and Air Force Academies had stronger image than the Police Academy in the area of physical strength, tradition, and fellowship between senior and junior. On the other hand, the Police Academy had better image in the area of social activity and applicant's academic achievement. The Military Academy had been evaluated the best school among the three Academies in the area of applicant's academic achievement, educational environment, faculty, tradition, and fellowship between senior and junior.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.2
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• pp.174-180
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• 2017

Recently, the world faces the environmental problem such as air pollution due to harmful gas discharged from car and abnormal climate due to the green-house gases increased by the discharge of $CO_2$. Compressed Natural Gas (CNG), one of alternative for this problem, is less harmful, compared to the existing fossil fuel, as gaseous fuel, and less carbon in fuel ingredients and carbon dioxide generation rate relatively favorable more than the existing fuel. However, CNG fuel has the weakness of slow flame propagation speed and difficult fast burn. On the other hand, hydrogen does not include carbon in fuel ingredients, and does not discharge harmful gas such as CO and HC. Moreover, it has strength of quick burning velocity and ignition is possible with small ignition energy source and it's has wide Lean Flammability Limit. If using this hydrogen with CNG fuel, the characteristics of output and discharge gas is improved by the mixer's burning velocity improved, and, at the same time, is possible to have stable lean combustion with the reduction of $CO_2$ expected. Therefore, this research tries to identify the characteristics of engine and emission gas when mixing CNG fuel and hydrogen in each portion and burning them in spark igniting engine, and grasp the lean combustion limit and emission gas characteristics according and use it as the basic data of hydrogen-CNG premixed engine.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.3
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• pp.427-433
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• 2013

This study was designed to examine changes in the physicochemical properties of extruded corn fibers with different amounts of feed moisture (30, 40, and 50%). The screw speed and die temperature were fixed to 200 rpm and $140^{\circ}C$, respectively. The crude ash, fat, and protein in corn fiber decreased from the extrusion process. The insoluble dietary fiber in corn fibers decreased, while soluble dietary fiber increased at a feed moisture of 30%. The specific length of the extruded corn fiber increased while the specific mechanical energy input, density, breaking strength, and elastic modulus decreased. The water absorption index (WAI) and reducing sugar content of the corn fibers did not significantly change, but the water soluble index (WSI) decreased as the feed moisture content of the corn fiber increased. On the other hand, the WAI of de-starched corn fiber decreased while WSI and reducing sugars increased as the feed moisture content of the corn fiber increased.

• Journal of the Korean Society for Heat Treatment
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• v.7 no.4
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• pp.244-252
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• 1994

The morphological changes of primary solid particles as a fuction of process time on Al-Si alloys during semi-solid state processing with a shear rate of 200s were studied. In hypereutectic Al-15.5wt%Si alloy, it was observed that primary Si crystals are fragmented in the early stage of stirring and morphologies of primary Si crystals change from faceted to spherical during isothermal shearing for 60 minutes. In quaternary Al-12.5wt%Si-2.9wt%Cu-0.7wt%Mg alloy system, it was observed both primary silicon and ${\alpha}$-alumunum particles. Microstructural evolution of primary Si crystals was similar to that of the hypereutectic Al-Si alloy but equiaxed ${\alpha}$-Al dendrites are broken into nearly spherical at the early stage of shearing and later stage of the isothermal shearing ${\alpha}$- Al particles are slightly coarsoned by Ostwald ripening. Mechanical properties of Al-Si-Cu-Mg alloy were compared to those from other processes (squeeze casting and gravity casting). After T6 heat treatment, comparable values of hardness were obtained while slightly lower compressive strength values were observed in rheocast alloy. The elongation, on the other hand, exhibited significant increasement of 15% over gravity cast alloy.

• Fire Science and Engineering
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• v.30 no.2
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• pp.35-42
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• 2016

The membrane structure provides high satisfaction with lightweight, improved workability, reduced cost, and a free shape. Thus, its applications expanding. On the other hand, in an architectural membrane that is vulnerable to fire, the development of various architectural membranes with flame resistance is in demand. Therefore, this study applied basalt woven fabric safety for flame resistance, excellent heat insulation and thermal properties on an architectural membrane. The PTFE- coated basalt woven fabric membrane was compared with a PTFE coated glass fiber membrane by DSC/TGA, strength properties, flammability, and incombustibility properties. In addition, this study confirmed the membrane applicability of basalt woven fabric and basalt-glass hybrid woven fabric through a comparison with existing architectural membranes.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.2
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• pp.157-164
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• 2011

This work is devoted to the technique application of lock-in infrared Thermography in the shipbuilding and ocean engineering industry. For this purpose, an exploratory study to find the optimized test conditions is carried out by the design of experiments. It has been confirmed to be useful method that the phase contrast images were quantified by a reference image and weighted by defect hole size. Illuminated optical intensity of lower or medium strength give a good result for getting a phase contrast image. In order to get a good phase contrast image, lock-in frequency factors should be high in proportion to the illuminated optical intensity. The integration time of infrared camera should have been inversely proportional to the optical intensity. The other hand, the difference of specimen materials gave a slightly biased results not being discriminative reasoning.

• The Journal of Korean Physical Therapy
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• v.24 no.5
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• pp.362-369
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• 2012

Purpose: This study examined the effects of an elastic band resistance exercise program on the body functions and Glycosylated hemoglobin (HbA1c) of elderly people with type 2 diabetes. Methods: Twenty-seven elderly patients with type 2 diabetes were enrolled in this study (exercise group 14, control group 13). The subjects in the exercise group participated in the program for 60 minutes a day, three times a week, for 12 weeks. All the subject's body functions, HbA1c were measured to compare the following: before the intervention, at the completion of the 12 weeks intervention, and eight weeks after the intervention. Results: Compared to the control group, the exercise group showed significant improvements in the 12 week and follow-up measurement after the intervention in body function, such as the strength of the upper and lower limbs, agility and limit of stability. The body functions of the exercise group improved as the period of intervention progressed. On the other hand, the HbA1c level at each follow-up measurement was similar in the two groups. Conclusion: The 12 week elastic band exercise program is recommended as an effective intervention for improving the body functions of elderly people with type 2 diabetes. Nevertheless, a combined intervention of steady exercise, diet therapy and drug therapy will be needed for further active prevention and management of type 2 diabetes.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.265-276
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• 2003

The objective of this research is to provide basic data for improving athletic performances, suggesting methods that can be utilized at games and coaching movements in the snatch, by analyzing the level of contribution of muscles to the movements of the snatch lift through three-dimensional imaging and EMG analysis between skilled and unskilled lifters. To this end, three high school students (the skilled group), three middle school student (the unskilled group) were selected; two digital video cameras and electromyography were used. The muscles measured by an EMG include gastrocnemius muscle, biceps femoris muscle, erector spinae, latissimus dorsi muscle, trapezius muscle, and brachioradialis. Based on the Ariel Performance Analysis System (APAS) program, the results of the analysis are summarized as follows. 1. In performing snatch pulls, the skilled lifters were found to simultaneously move the weight centers of the body and the barbell close to vertical, close to the shoulders in the pulling portion; in snatching and grabbing the barbell from a sited position, it was observed that the shorter the time for adjusting to change in the height of the barbell by using rotational inertia, the better it is to perform the movements. 2. The skilled lifters were observed to perform stable and efficient movements in grabbing the bar in a sited position, by moving the barbell and weight center of the body close to vertical and moving the shoulder joint under the bar fast. 3. The results of the EMG analysis of the entire movements from the snatching portion to the portion of grabbing the bar in a sited position show that when the skilled lifters lifted the barbell vertically during the pulling portion, their shoulder joints were extended to put more weight on biceps femoris muscle and brachioradialis; and in snatching and grabbing the bar from a sited position, it was found desirable to increase the myoelectrical activity of erector spinae in order to achieve a balance in the movements of the hip joint between font and rear, as the weight centers of the body and the barbell move higher. On the other hand, the unskilled lifters were found that in response to change in posture, they increase their muscular strength inefficiently in performing the movements throughout the entire lifting process.

• Tribology and Lubricants
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• v.36 no.3
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• pp.124-132
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• 2020

The effect of the stoichiometry on the sliding wear properties of NiAl coatings has been investigated. Three different powder mixtures with the compositions of Ni-50at%Al, Ni-54at%Al and Ni-42at%Al were diepressed respectively, and which were subsequently coated on mild steel through combustion synthesis in an induction heating system. Sliding wear behavior of the coatings was examined against an alloyed tool steel using a pin-on-disc type sliding wear test machine. As results, it could be seen that powder mixture(Ni-54at%Al) with displaying Al-rich deviations from the stoichiometry of NiAl(Ni-50at%Al) was promoted the most the synthetic reactivity. The microstructure of the coating layer with the compositions of Ni-54at%Al exhibits the porous NiAl single phase structure. However, the microstructure of the coating layer of the compositions of Ni-42at%Al exhibits the denser multi-phase structure containing several intermediate phases in addition to NiAl. Densification of the coating layer was enhanced by increasing the reacting temperature. On the other hand, the wear properties of the coating layers showed that the wear mode at speeds of around 1 m/s was severe wear, regardless of the stoichiometry and reacting temperature. However, wear properties of coating layer with the compositions of Ni-42at%Al were superior to those of coating layer with the compositions of Ni-54at%Al. This would be attributed by the fact that coating layer with the compositions of Ni-42at%Al develops little void and much intermediate phases with high strength.