• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.445-449
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• 2009

With the recent increase in the demand for the net-shape forming, numerical simulations are being commonly adopted to increase the efficiency and effectiveness of design of bulk metal forming processes. Proper consideration of tribological problems at the contact interface between the tool and workpiece is crucial in such simulations. In other words, lubrication and friction play important roles in metal forming by influencing the metal flow, forming load and die wear. In order to quantitatively estimate such friction condition or lubricant characteristic, the constant shear friction model is widely used for bulk deformation analyses. For this, new friction testing method based on the forward or backward extrusion process is proposed to predict the shear friction factor in this work. In this method, the tube-shaped punch pressurizes the workpiece so that the heights at the center and outer of punch (or mandrel) become different according to the friction condition. That is, the height at the center of punch is higher than that at the outer of the punch when the friction condition at the contact interface is severe. From this founding, the proposed friction testing method can be applied to effectively evaluate the friction condition in bulk metal forming processes.

• Journal of Korean Society of Transportation
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• v.6 no.1
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• pp.55-64
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• 1988

Prior to using any computer model, the program-embedded palameters showing significant differences from real world should be calibrated. This is especially true when the model is expected to be used fro various roadway and traffic condition. The calibration of TRANSYT model was conducted for the parameters of start-up delay, and lag, stop penalty(K), platoon dispersion factor, and saturation flow rate. The values of the parameters were obtained by theoretical methods from actual field measurements for discharging and arrival pattern. The sites elected for the study was an intersection of Dongil-Ro and Hwarang-Ro, and a 334 meter downstrean section from the intersection stop line on westbound Hwarang-Ro. The study results showed that the start-up delay was 2.6 sec, end lag was 1.0 sec, saturation flow rate was 2287 pcphgpl, platoon dispersion factor was 0.2-03, and stop penalty(K) was 32. However, since these parameters re apt to depend on traffic and roadway condition, it is doubtful whether the obtained values will be applicable to the area-wide situation other than this particular site.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.808-815
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• 2001

The three-phase diode rectifier with a capacitive filter is highly sensitive to line voltage unbalance, and may cause significantly unbalanced line currents even under slightly unbalanced voltage condition. This paper presents an analysis of this 'unbalance amplification' effect for an ideal rectifier circuit without ac-and dc-side inductors. The voltage unbalance is modeled by introducing a deviation voltage superimposed on balanced three-phase line voltages. With proper approximations, closed-form expressions for symmetrical components of the line current and current unbalance factor are derived in terms of the voltage unbalance factor, filter reactance, and load current. The validity of analytical predictions is confirmed by simulation.

• Journal of applied mathematics & informatics
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• v.34 no.5_6
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• pp.435-441
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• 2016

Let G be a graph, and let g, f be two nonnegative integer-valued functions defined on V (G) with g(x) ≤ f(x) for each x ∈ V (G). A graph G is called a fractional (g, f, n)-critical graph if after deleting any n vertices of G the remaining graph of G admits a fractional (g, f)-factor. In this paper, we obtain a binding number condition for a graph to be a fractional (g, f, n)-critical graph, which is an extension of Zhou and Shen's previous result (S. Zhou, Q. Shen, On fractional (f, n)-critical graphs, Inform. Process. Lett. 109(2009)811-815). Furthermore, it is shown that the lower bound on the binding number condition is sharp.

• The Journal of Korean Academy of Prosthodontics
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• v.9 no.1
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• pp.59-62
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• 1969

The causes of periodontal disease have been descried as malocclusion, trauma from occlusion, local irritants and poor oral hygien. The systemic factor has also been considered as a etiologic factor of periodontal disease. On the other aspect systemic condition could be affected by periodontal disease. For the study of relationships between periodontal disease and systemic condition, twenty patients with periodontal disease and twenty persons with no periodontal involvement were evaluated for inorganic elements and organic materials in the blood. The results of the blood analysis of the two groups were as follows. : Phosphorus and alkline-phoshatase in the group with periodontal disease showed slightly increased phenomenon compared to the control group, and on the other hand calcium and calcium-phosphorus ratio decreased phenomenon. But there is no any significant alteration in the content of each element between the two groups.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1151-1156
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• 2003

The dynamic properties of short-fiber reinforced Chloroprene rubber for vibration isolators have been studied as functions of interphase conditions and fiber content. The loss factor showed the maximum at strain amplitude 2%, and increased 0.09 for matrix, 0.05 for reinforced rubber with increasing frequency respectively. The dynamic ratio rapidly decreased with increasing strain amplitude, and some increased with increasing frequency. The better interphase condition showed the lower dynamic ratio. Therefore, the short-fiber reinforced rubber could have the better isolation in frequency ratio(${\sqrt{2}}min$.) compared to frequency ratio(${\sqrt{2}}max$.). And we have investigate the possibility of applying short-fiber reinforced rubber to automotive engine mount.

• Applied Chemistry for Engineering
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• v.28 no.3
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• pp.306-312
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• 2017

Changes in the cell growth and lipid accumulation of marine microalga Dunaliella tertiolecta were investigated in response to the combination of different stress factors including the variation of iron supply as a primary stress factor and different options in light irradiation and $CO_2$ supply as a secondary stress factor. High or limited Fe conditions could act as a stress for lipid synthesis. As a secondary stress factor, non-$CO_2$ condition was good for lipid accumulation, but the overall cell growth was sacrificed significantly after a long-time cultivation. Dark condition as a secondary stress factor also favored lipid accumulation and the extent of cell density reduction at the early period in the dark was small compared to other stress conditions. The two-stage cultivation strategy was necessary to maximize lipid production because tendencies of the cell growth and lipid content were not identical under the chosen stress condition. The first stage was for preparing a high cell density under the normal growth-favoring condition and the second stage was the stress condition to induce lipid accumulation in a short time. The short-term (12 h) incubation under the 5X Fe (3.25 mg/L) and dark conditions resulted in the best lipid productivity of 1.44 g/L/d providing 2 g/L inoculum at the second stage.

• Journal of Fashion Business
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• v.11 no.4
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• pp.1-17
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• 2007

The purpose of this study was to provide for the useful fundamental data to enterprise which produces the natural-dyed clothing products by investigating with the holding conditions and pursuit of wearing images. The subjects were females aged 20 to 59, a questionnaire was developed by the researcher and distributed to 237 females. A sample of 223 females responded to the questionnaire. Data analyses were processed by SPSS WIN 10.0 Program; Frequency count and percentage, $X^2-test$, ANOVA and Duncan's multiple range test were used for statistical analysis. The results of this study were as follows: First, there were significant differences in holding items, period and private ownership according to age, any academic background and a monthly income. Second, the result by classification of the pursuit of wearing images could be identified four factors: factor 1) sexual and feminine image, factor 2) simple and common image, factor 3) comfortable and natural image and factor 4) dynamic image.

• Tunnel and Underground Space
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• v.30 no.1
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• pp.63-75
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• 2020

When tunnel is excavated via drilling and blasting, the excessive overbreak is the primary cause of personal or equipment safety hazards and increasing the cost of the tunnel operation owing to additional ground supports such as shotcrete. The practical management of overbreak is extremely difficult due to the complex causative mechanism of it. The study examines the relationship between rock mass characteristics (unsupported face condition, uniaxial compressive strength, face weathering and alteration, discontinuities- frequency, condition and angle between discontinuities and tunnel contour) and the depth of overbreak through using feed-forward artificial neuron networks. Then, Overbreak Resistance Factor (ORF) has been developed based on the weights of rock mass parameters to the overbreak phenomenon. Also, a new concept of tunnel overbreak management system using ORF has been suggested.

• Journal of the Korean Society of Costume
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• v.58 no.9
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• pp.29-37
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• 2008

The purpose of this study was to investigate insulation of thermal clothing under still and dynamic air conditions(with 2.1m/sec air velocity) and decrease of insulation in both conditions, to analyze correlations among them, and to estimate insulation and decrease of insulation using factors, such as fabric insulation, fabric weight, clothing weight, air permeability, and water vapor resistance. A total of 25 kinds of clothing were tested(9 types for suits, 6 types of jacket, 5 types for shirts, and 5 types for trousers). The results of this study were as follows; Thermal resistance of clothing under the dynamic air condition decreased comparing to that of clothing under still air condition in all types of clothing. Decrease in shirts was the biggest(47.5%), followed by suits(39.51%), trousers(37.48%), and jackets(34.49%) in sequence. Thermal resistance of clothing under dynamic air condition showed very high correlation(0.98, p<0.01) with that of clothing under still air condition, followed by thermal resistance of fabric(0.86, p<0.01). Decrease in thermal resistance of clothing showed the highest correlation with air permeability. It didn't show correlation with other factors. Regression analysis showed that fabric thickness would be useful factor for estimating thermal resistance of clothing and air permeability also would be useful factor for estimating decrease in thermal resistance of clothing.