• Journal of the Korean Society of Safety
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• v.9 no.3
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• pp.13-21
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• 1994

Effects of tensile and compression residual stresses in the welded SS41 and A17075-76 on fatigue crack propagation behavior are investigated when a crack propagates from residual stresses region. We propose the fatigue crack growth equation on tensile and compression residual stresses in welded metal. The results obtained in this experimental study are summarized as follows . 1 ) A fatigue crack growth equation which applied fatigue fracture behavior of the welded metal is proposed. (equation omitted) where, $\alpha$, $\beta$, ${\gamma}$ and $\delta$ are constants, and R$_{eff}$ is effective stress ratio [R$_{eff}$=(Kmin+Kres)/(Kmax+Kres)], Kcf is critical fatigue stress intensity factor. The constants are obtained from nonlinear least square method. The relation between crack length and number of cycles obtained by integrating the fatigue crack growth rate equation is in agreement with the experimental data. 2) The experimental results confirmed that the cause of crack extension and retardation by residual stresses has relation to the phenomenon of crack closure. 3) The relaxing trend of residual stresses by the crack propagation was greater In case of compressive residual stress than that of tensile residual stress in the welded metal.tal.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.38 no.2 s.115
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• pp.1-8
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• 2006

In this study a process simulation method was used to analyze the accumulation phenomena of anionic starch in the process white water as the closure level of a fine paper making process is increased. A pilot paper machine was used as a model process. Dynamic simulations of the influence of white water usage ratio and uncoated broke addition ratio on the variation of process variable was monitored as a function of time. Results from the dynamic simulations showed that the volume of reservoirs affected the dynamic behavior of the process. The dynamic behavior of flow rate and dissolved starch concentration in process units were different from each other. The speed of the change of dissolved starch concentration in process units was depend on the starting point of the change of dissolved starch concentration, the length of circulation loop, and the volume of reservoirs.

• Wind and Structures
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• v.30 no.1
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• pp.99-117
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• 2020

This paper focuses on the processes of wind flow in atmospheric boundary layer, to produce realistic full scale pressures for design of low-rise buildings. CFD with LES turbulence closure is implemented on a scale 1:1 prototype building. A proximity study was executed computationally in CFD with LES that suggests new recommendations on the computational domain size, in front of a building model, apart from common RANS-based guidelines (e.g., COST and AIJ). Our findings suggest a location of the test building, different from existing guidelines, and the inflow boundary proximity influences pressure correlation and reproduction of peak loads. The CFD LES results are compared to corresponding pressures from open jet, full scale, wind tunnel, and the ASCE 7-10 standard for roof Component & Cladding design. The CFD LES shows its adequacy to produce peak pressures/loads on buildings, in agreement with field pressures, due to its capabilities of reproducing the spectral contents of the inflow at 1:1 scale.

• Geomechanics and Engineering
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• v.22 no.1
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• pp.11-23
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• 2020

In this study, a new analytical-numerical procedure is developed to give the stresses and strains around a circular tunnel in rock masses exhibiting different stress-strain behavior. The calculation starts from the tunnel wall and continues toward the unknown elastic-plastic boundary by a finite difference method in the annular discretized plastic zone. From the known stresses in the tunnel boundary, the strains are calculated using the elastic-plastic stiffness matrix in which three dimensional Hoek-Brown failure criterion (Jiang and Zhao 2015) and Mohr-Coulomb potential function with proper dilation angle (i.e., non-associated flow rule) are employed in terms of stress invariants. The illustrative examples give ground response curve and show correctness of the proposed approach. Finally, from the results of a great number of analyses, a simple relationship is presented to find out the closure of circular tunnel in terms of rock mass strength and tunnel depth. It can be valuable for the preliminary decision of tunnel support and for prediction of tunnel problems.

• KIEAE Journal
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• v.15 no.2
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• pp.69-78
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• 2015

Purpose: The aim of this study was to analyze the elementary schoolchildren's the fear of crime in pedestrian environment of elementary school for providing the basic design resource. Method:In order to deal with that, the questionnaire survey on the elementary schoolchildren's the fear of crime were conducted in 5 elementary schools in Ilsan new town. The results of the 293 questionnaires survey were analyzed through SPSS program. Result: The main results were as follows. The level of fear of crime in pedestrian environment differed in these 5 elementary schools because of the width of pedestrian path, the concealed place around pedestrian path, the nearness of park, the height/shape/interval of trees, the number of car and the closure-watching in the school caused by fence and trees and so on. The level of fear of crime in pedestrian environment differed between that of boy groups and that of girls groups because of the number of emergency bell/telephon, the shape of pedestrian path, the number of security office, the number of car and the concealed place around pedestrian path and so on.

• Wind and Structures
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• v.7 no.3
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• pp.159-172
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• 2004

The study of how buildings affect wind flow is an important part of the research being conducted on urban climate and urban air quality. NJU-UCFM, a standard $k-{\varepsilon}$ turbulence closure model, is presented and is used to simulate how the following affect wind flow characteristics: (1) an isolated building, (2) urban canyons, (3) an irregular shaped building cluster, and (4) a real urban neighborhood. The numerical results are compared with previous researchers' results and with wind tunnel experiment results. It is demonstrated that the geometries and the distribution of urban buildings affect airflow greatly, and some examples of this include a changing of the vortices behind buildings and a "channeling effect". Although the mean air flows are well simulated by the standard $k-{\varepsilon}$ models, it is important to pay attention to certain discrepancies when results from the standard $k-{\varepsilon}$ models are used in design or policy decisions: The standard $k-{\varepsilon}$ model may overestimate the turbulence energy near the frontal side of buildings, may underestimate the range of high turbulence energy in urban areas, and may omit some important information (such as the reverse air flows above the building roofs). In ideal inflow conditions, the effects of the heights of buildings may be underestimated, when compared with field observations.

• Speech Sciences
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• v.15 no.3
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• pp.145-156
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• 2008

The goal of this study was to investigate acoustic and physiologic characteristics of two phonation types of 'Khoomei' which is a traditional singing style of people who live around the Altai mountains or Mongolia region. It can be produced two pitches simultaneously - high melody pitch can be perceived along with a low drone pitch. Sygyt and kargyraa styles are the most popular and identifiable styles and they can be recognized as the different sounds depending on the method of voice production. Two trained Mongolians participated and have used at least 5 - 6 years. The characteristics of this voice production were measured by using flexible fiberscope, Stroboscopy, Lx Speech studio, Spead, and Doctor Speech. In Sygyt style, very high vocal fold closure (71.50%) with both true and false vocal folds contact and strong breathing support was observed. They also showed that tongue height and harmonics were increased (around 10dB) with resonance cavity movement. In contrast, it was found that Kargyraa sound had very low pitch with relaxed stomach, less laryngeal tension and lower vocal fold contact (69.50%) than hard Sygyt style sound without raising the tongue during phonation. 'Khoomei' phonation can be made by strong contact of both true and false vocal folds and by increasing the harmonics as well.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.3
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• pp.597-601
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• 1997

This paper presents improper use of latex-elastic ring in movement of teeth and its consequence. Simple orthodontic movement of teeth including closure of diastema may be achieved by the use of simple method with fixed or removable appliance associated with latex-elastic ring. But, if it is used alone, it acts as a local irritant and then produces localized periodontitis. In case of localized periodontitis resulting from latex-elastic ring, diagnosis is difficult because the patient is usually unaware of the presence of the rings on the roots of the involved teeth and because the ring is not probed and is radiolucent and therefore not discernible radiographically and clinically. Occasionally, surgery is requred for the detection. This case emphasizes the necessity that the use of latex-elastic ring in closing diastema should be accompanied with removable or fixed appliance as well as close professional supervision. Its use without adequate provision for stabilization or retention on the crowns of teeth results in destruction of periodontal support and the teeth may be lost.

• The Korean Fashion and Textile Research Journal
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• v.10 no.1
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• pp.68-75
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• 2008

Demands and attempts to express Korean traditional beauty are increasing. Some schools choose the uniform in designs expressing the image of Hanbok, but recently there is a few increment of wearing the uniforms. For the improvement of the uniforms, first of all, the shape and the clothing materials of the uniforms should be considered. We have compared and analyzed the shape and the clothing materials of the uniforms reflecting the image of Hanbok, according to seasons and clothing items. The uniforms reflecting the image of Hanbok were worn in eight schools and all of them are Saenghwal Hanbok style. The shape of Saenghwal Hanbok school uniforms showed both Korean style and western style characteristics. Korean style characteristics were expressed through the appearance-related parts while western style characteristics showed through the performance-related parts such as open/closure method, armhole pattern and straight sleeve line. It was shown that girls' uniforms are more diverse and similar to the western style uniforms than boys' uniforms. It was found that most of the clothing material were synthetic fiber or mixture of natural/synthetic fiber, and polyester was shown to be used most.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.4
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• pp.266-274
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• 2016

Many researchers have been trying to improve the propulsion efficiency of a propeller. In this study, the numerical analysis is carried out for the POW(Propeller Open Water test) performance of a propeller equipped with an energy saving device called PHVC(Propeller Hub Vortex Control). PHVC is aimed to control the propeller hub vortex behind the propeller so that the rotational kinetic energy loss can be reduced. The unsteady Reynolds Averaged Navier-Stokes(URANS) equations are assumed as the governing flow equations and are solved by using a commercial CFD(Computational Fluid Dynamics) software, where SST k-ω model is selected for turbulence closure. The computed characteristic values, thrust, torque and propulsion efficiency coefficients for the target propeller with and without PHVC and the local flows in the propeller wake region are validated by the model test results of KRISO LCT(Large Cavitation Tunnel). It is concluded from the present numerical results that CFD can be a good promising method in the assessment of the hydrodynamic performance of PHVC in the design stage.