• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.12
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• pp.1071-1078
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• 2010

The objective of this study is to investigate the heat transfer characteristics of evaporators that have various fin configurations and are used in household refrigerators. The frosting and defrosting characteristics of a spirally coiled circular fin-tube evaporator, a discrete-plate fin-tube evaporator, and a continuous-plate fin-tube evaporator were measured and compared. Under non-frosting conditions, the heat transfer coefficient of the spirally coiled circular fin-tube evaporator was 22.3% and 40.2% higher than the coefficients of the discrete- and continuous-plate fin-tube evaporators, respectively. Under frosting conditions, the heat transfer coefficient of the spirally coiled circular fin-tube evaporator was 27.0% and 46.3% higher than the coefficients of the discrete- and continuous-plate fin-tube evaporators, respectively. In addition, the defrosting water amount of the spirally coiled circular fin-tube evaporator was 3.2% and 9.4% lower than the amounts in the case of the discrete- and continuous-plate fin-tube evaporators, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.9-17
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• 2021

Curved beams are increasingly used in buildings, vehicles, ships, and aircraft, which has resulted in considerable effort being directed toward developing an accurate method for analyzing the dynamic behavior of such structures. The stability behavior of elastic circular arches has been the subject of a large number of investigations. One of the efficient procedures for the solution of ordinary differential equations or partial differential equations is the differential quadrature method DQM. This method has been applied to a large number of cases to overcome the difficulties of the complex computer algorithms, as well as excessive use of storage due to conditions of non-linear geometries, loadings, or material properties. This study uses DQM to analyze the in-plane vibration of the circular arches considering the effects of midsurface extension and rotatory inertia. Fundamental frequency parameters are calculated for the member with various parameter ratios, boundary conditions, and opening angles. The solutions from DQM are compared with exact solutions or other numerical solutions for cases in which they are available and given to analyze the effects of midsurface extension and rotatory inertia on the frequency parameters of the circular arches.

• Journal of Korean Dental Science
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• v.15 no.1
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• pp.51-60
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• 2022

Purpose: The aim of this study was to evaluate the bio-durability and bone regeneration capacity of the non-cross-linked collagen membrane in rabbit calvarial defect models. Materials and Methods: Four circular defects with 8 mm diameter were made in each of calvarium of 10 male rabbits. The following groups was randomly assigned to each defect - 1) Control, 2) membrane group containing non-cross-linked collagen membrane only (M), 3) bone graft group (B), 4) bone graft with membrane group (B+M). Animals were sacrificed and samples were harvested at 2 weeks (n=5) and 8 weeks (n=5). Histologic sections were prepared and histomorphometric analysis was performed. Result: Histologic results showed well adaptation of the non-cross-linked membrane on each defect and normal healing response at 2 weeks. At 8 weeks, the membranes were partially biodegraded. Histomorphometrically, B and B+M group showed the significantly greater total augmented area (B+M group, 10.44±1.49, P=0.016; B group, 9.13±0.53, P=0.032) and new bone formation (B+M group, 2.89±0.93, P=0.008; B group, 2.85±1.15, P=0.008) compared to control group. Collapsing of the central portion of the membrane, membrane group showed greater value in new bone formation at 8 weeks (1.78±0.68, P=0.032). Conclusion: Within the limitations of this study, the non-cross-linked collagen membrane fabricated using the improved decellularized method was shown to be effective for the regeneration of calvarial bone defects. In addition, prolonged barrier function might be provided using this collagen membrane.

• Journal of Korean Society of Steel Construction
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• v.10 no.3 s.36
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• pp.525-536
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• 1998

This paper is concerned with a theoretical study on the local load-carrying capacities of Concrete-Filled Circular Tubular(CFCT) column to H-beam connections by yield line theory. In this paper, the three cases which are assumed the yield line are involved. The first model is a simplified yield line model. The second model is modified by x and kx factors. The last one is a Morita's model. The local load-carrying capacities of CFCT column to H-beam connections has been studied both experimentally and theoretically using the yield line theory. The purpose of this paper is to suggest the basic data for developing the non-diaphragm connection.

• Physical Therapy Korea
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• v.12 no.4
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• pp.7-11
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• 2005

The purposes of this study were to investigate the effects of variability of training on the acquisition of motor skill of closed loop type tracking task using Rotary Pursuit, and to determine if there was a bilateral transfer effect to the non-dominant hand following practice with the dominant hand. Twelve healthy volunteer students (5 males and 7 females, aged 25 to 37) were randomly divided into a constant practice group and a variable practice group. A photoelectric rotary pursuit apparatus with stop clock and repeat cycle timer by Lafayette Instrumentation Co. was used for this study. Rotary pursuit is a closed loop task in which a subject attempts to keep a photoelectric stylus on a lighted target in motion. Subjects performed the clockwise circular pursuit task while standing. Experimental procedure was divided into three sessions, namely, pre-test, training, and post-test. The constant group practiced all 60 trials at 30 rpm. Variable practice group did a varied practice session with 15 trials at speeds of 20 rpm, 26 rpm, 34 rpm, and 46 rpm. No one in either group practiced with their non-dominant arm. A Mann-Whitney test and a Wilcoxon Signed Ranks test were used for statistical analyses. The results of this study showed no different training effect between groups on the post-test with the dominant hand. However, bilateral transfer effect of rotary pursuit task between hands was demonstrated. Possible mechanisms are discussed.

• Aerospace Engineering and Technology
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• v.2 no.2
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• pp.124-132
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• 2003

This paper described the structural design and the fabrication procedure of KSR-III composite pressure tank. The type of the composite pressure tank was COPV(Composite Overwrapped Pressure Vessel). A non-load sharing liner was made of aluminum 6061-0 and the liner provided a helium gas seal. The composite pressure tank was winded using T700 carbon/epoxy on the liner. Because the aluminum liner was thin, multiple cure cycles were applied to the filament winding technique. The multiple cure cycles prevented the liner-cylinder from losing a circular shape. A fitting force at the metallic boss was spread to the carbon fiber by a boss ring. The boss ring also prevented a local deformation at the boss part.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.240-244
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• 2005

In this study a simple model is developed that predicts impact damage in a composite laminate using an analytical model. The model uses a non-linear approximation method (Rayleigh-Ritz) and the large deflection plate theory to predict the number of failed plies and damage area in a quasi-isotropic composite circular plate (axisymmetric problem) due to a point impact load at its centre. It is assumed that the deformation due to a static transverse load is similar to that occurred in a low velocity impact. It is found that the model, despite its simplicity, is in good agreement with FEM predictions and experimental data for the deflection of the composite plate and gives a good estimate of the number of failed plies due to fibre breakage. The predicted damage zone could be used with a fracture mechanics model developed by the second investigator and co-workers to calculate the compression after impact strength of such laminates. This approach could save significant running time when compared to FEM solutions.

• Journal of Pharmaceutical Investigation
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• v.13 no.1
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• pp.10-22
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• 1983

The interactions of ${\alpha}-cyclodextrin({\alpha}-CyD)$ and ${\beta}-cyclodextrin({\beta}-CyD)$ with several non-steroidal antiinflammatory drugs were studied on the effects of ${\alpha}-$ and ${\beta}-CyD$ on the solubility of the drugs in aqueous medium. Indoprofen, niflumic acid, alclofenac, and naproxen were chosen as representatives of antiinflammatory drugs. The solubility of all drugs studied increased with the addition of ${\beta}-CyD$, while not with glucose or ${\alpha}-CyD$. The increase of the solubility with ${\beta}-CyD$ was considered due mainly to the formation of inclusion complexes between ${\beta}-CyD$ and drugs. From the solubility data, the apparent stability constants K of the complex could be calculated. Ultraviolet absorption and circular dichroism confirmed the inclusion of indoprofen, niflumic acid and naproxen with ${\beta}-CyD$ in the molar ratio of 1 : 1. Inclusion complexes in solid powder form were obtained by the freeze-drying method and the inclusion formation was confirmed again by infrared, diffential thermal analysis, and X-ray diffraction measurements.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.4 s.148
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• pp.494-503
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• 2006

Inherent damage zone model is presented to explain the fatigue properties near the fatigue limit and the crack growth threshold consistently Inherent damage zone model assumes that the stress at a point which is located at a small distance, $r_0$, an inherent length of the material that represents the size of effective damage zone, from the crack initiation position governs the fatigue characteristics regardless of the geometric configuration of the specimen; smooth specimen, notched specimen or cracked specimens with short and long crack length. A special feature of the paper is using the exact stress distributions of notched and cracked specimens at the strength evaluations. Analytical elastic solutions by Neuber and Westergaard are employed for this purpose Relationship between fatigue limit of smooth specimen and threshold stress of cracked specimen, occurrence condition of non-propagating crack at the root of elliptic notch and circular hole and relationship between stress concentration factor and fatigue notch factor are discussed quantitatively based on the proposed model.

• Journal of Mechanical Science and Technology
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• v.19 no.4
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• pp.947-957
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• 2005

In this study a simple model is developed that predicts impact damage in a composite laminate avoiding the need of the time-consuming dynamic finite element method (FEM). The analytical model uses a non-linear approximation method (Rayleigh-Ritz) and the large deflection plate theory to predict the number of failed plies and damage area in a quasi-isotropic composite circular plate (axisymmetric problem) due to a point impact load at its centre. It is assumed that the deformation due to a static transverse load is similar to that oc curred in a low velocity impact. It is found that the model, despite its simplicity, is in good agreement with FEM predictions and experimental data for the deflection of the composite plate and gives a good estimate of the number of failed plies due to fibre breakage. The predicted damage zone could be used with a fracture mechanics model developed by the second investigator and co-workers to calculate the compression after impact strength of such laminates. This approach could save significant running time when compared to FEM solutions.