• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.6
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• pp.949-958
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• 2001

A semi-infinite interfacial crack propagated with constant velocity in two bonded anisotropic strips under out-of-plane clamped displacements is analyzed. Using Fourier integral transform the problem is formulated and the Wiener-Hopf equation is derived. By solving this equation the asymptotic stress and displacement fields near the crack tip are obtained, where the results get more general expressions applicable not only to isotropic/orthotropic materials but also to the extent of the anisotropic material having one plane of elastic symmetry for the interfacial crack. The dynamic stress intensity factor is obtained as a closed form, which is decreased as the velocity of crack propagation increases. The critical velocity where the stress intensity factor comes to zero is obtained, which agrees with the lower value between the critical values of parallel crack merged in the material 1 and 2 adjacent to the interface. Using the near tip fields of stresses and displacements, the dynamic energy release rate is also obtained as a form of the stress intensiy factor.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.63-64
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• 2023

Indoor Air Quality is crucial in hospital projects to ensure the health and safety of patients, staff, and visitors. The research methodology comprises an comprehensive literature review, then a comprehensive questionnaire survey conducted among stakeholders involved in Vietnamese hospital projects. 15 variables were identified and categorized into four distinct groups, elucidating their influence on the adoption of advanced IAQ-enhancing technology. This study uses factor analysis, a mean score method and hypothesis test to analyze the factor result from the survey. two-step process, including an in-depth literature review and questionaire survey. The study's findings culminated in the ranking, examination, and categorization of these 15 variables, which were clustered into four essential categories: economic factors, design elements, governance strategies, and technical requirements. Additionally, the research explored viable solutions to improve indoor air quality in Vietnam's unique environmental context, examining the factors that impact the selection of such solutions. The study's outcomes yield practical recommendations for architects, engineers, and hospital administrators in enhancing IAQ within healthcare facilities. Furthermore, it presents a framework attuned to local environmental factors and building materials, contributing significantly to the existing body of knowledge on IAQ within hospital projects, particularly in the Vietnamese context.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.7
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• pp.911-917
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• 1999

The sonic nozzle is widely used as reference device for calibrating flowmeters In gas flow measurement and its use requires the Critical Flow Factor(CFF) based on the thermodynamic properties of the gas at the nozzle throat. ISO-9300 provides the calculating method of the factor. But since the CFF from this method show an error over ${\pm}0.5%$ In specific conditions and of ${\pm}0.1{\sim}{\pm}0.2%$ in common Natural Gas(NG) custody transfer condition. this method cannot be applied for gas flow measurement with sonic nozzle. Each research bodies or organizations of the world have joined in order to calculate the CFF more accurately. They have performed these works using their own method and compared the results with each other under the management of ISO. KOGAS have joined those works, because the high-pressure natural gas flow calibration facility of KOGAS will be constructed in late 1999, and then had necessities to calculate a CFF accurately. The calculation method of KOGAS was using the equation of state from AGA-8('94), high accuracy model of ideal gas properties and the solutions of thermodynamic equations. The evaluation results have had a very good consistency within ${\pm}0.05%$ in most NO custody transfer conditions compared to the speed of sound for methane and also shown that the CFF was within ${\pm}0.1%$ compared to the results of other works of the world.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3003-3008
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• 2007

Critical nozzle has been frequently employed to measure the flow rate of various gases, but hydrogen gas, especially being at high-pressure condition, was not nearly dealt with the critical nozzle due to treatment danger. According to a few experimental data obtained recently, it was reported that the discharge coefficient of hydrogen gas through the critical nozzle exceeds unity in a specific range of Reynolds number. No detailed explanation on such an unreasonable value was made, but it was vaguely inferred as real gas effects. For the purpose of practical use of high-pressure hydrogen gas, systematic research is required to clarify the critical nozzle flow of high-pressure hydrogen gas. In the present study, a computational fluid dynamics(CFD) method has been applied to predict the critical nozzle flow of high-pressure hydrogen gas. Redlich-Kwong equation of state that take account for the forces and volume of molecules of hydrogen gas were incorporated into the axisymmetric, compressible Navier-Stokes equations. A fully implicit finite volume scheme was used to numerically solve the governing equations. The computational results were validated with some experimental data available. The results show that the coefficient of discharge coefficient is mainly influenced by the compressibility factor and the specific heat ratio, which appear more remarkable as the inlet total pressure of hydrogen gas increases.

• Journal of the Korean Professional Engineers Association
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• v.16 no.2
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• pp.11-17
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• 1983

This work presents a method for the determination of the safety factor of a slope based on the theory of the calculus of variations. The method allows for the determination of the critical sliding line (The one giving the minimum safety factor) without the necessity of guessing about its shape, which leads to a considerable economy of time and effort. Furthermore it gives the actual safety factor of the slape and consequently a more complete knowledge of the safety of the slope is obtained.

• International Commerce and Information Review
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• v.9 no.2
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• pp.19-40
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• 2007

In recent, T-commerce is widely dispersed as alternative type of commerce. It is forecasted that t-commerce system is used more than e-commerce system. Therefore more and more t-commerce-related industries are also recognizing that t-commerce is a critical business model. It is needed to understand the concept of t-commerce and develop the t-commerce marketing strategy. CEO analyses consumer's behaviors according to the data about buyers and applies the advantage of t-commerce to the communication with customers. This t-commerce system plays an important role in maximizing customer satisfaction and affecting their intention to reuse it. Therefore this paper attempts to identify T-commerce critical success factors and divide between use-intention group and unuse-intention group by taking out a discriminant function by the discriminant analysis. This lays a foundation in developing T-commerce strategy. According to the discriminant function extracted, convenience factor, amusement factor, system quality factor, product perception factor are significant in the sequence of influential degree. However, usefulness factor and speedy connection factor are not significant. In result, the target hitting rate is 77.9% in the first unuse-intention group and it is 95.2% in the second use-intention group. The total discriminant target hitting rate is computed to higher value, 86.55%. The statistic package, SPSS 12.0, is used to survey and analyse data and test the hypothesis. The validity and reliability of variables are verified by both reliability analysis and factor analysis. The discriminant analysis is used to tell the difference between use-intention group and unuse-intention group.

• Journal of the Korea Society of Computer and Information
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• v.5 no.4
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• pp.211-217
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• 2000

The Curriculum Determinant Factors of Information Management are identified Manpower Demand Factor, Department Associate Perception Factor, Imitation Factor, Education Demand Factor. The result of This Study proposed that Computer Science Field, IT Field, Internet Field had to Include to Curriculum of Information management. In Addition, The Result of This Study is identified that Curriculum Determinant Factor is related to Composition Factor. Manpower Demand factor Department Associate Perception Factor are important to Curriculum Determinant. And IT Field, Computer Science Field are critical to curriculum of Information Management.

• Journal of Korean Association for Spatial Structures
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• v.13 no.1
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• pp.87-96
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• 2013

This study investigated characteristics of buckling load and effective buckling length by member rigidity of dome-typed space frame which was sensitive to initial conditions. A critical point and a buckling load were computed by analyzing the eigenvalues and determinants of the tangential stiffness matrix. The hexagonal pyramid model and star dome were selected for the case study in order to examine the nodal buckling and member buckling in accordance with member rigidity. From the numerical results, an effective buckling length factor of adopted models was bigger than that of Euler buckling for the case of fixed boundary. These numerical models indicated that the influence of nodal buckling was greater than that of member buckling as member rigidity was higher. Besides, there was a tendency that the bifurcation appeared on the equilibrium path before limit point in the member buckling model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.416-427
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• 1998

Unidirectional commingled-yarn-based carbon fiber(CF)/polyamide(PA) 6 composite was fabricated under molding pressures of 0.4, 0.6 and 1.0 MPa to study its flexural deformation and fracture behavior. Fiber/matrix interfacial bonding area became larger with an increase of molding pressure from 0.4 to 0.6 MPa. For molding pressures .geq. 0.6 MPa, good flexural performance of similar magnitudes was attained. For the fracture test, four kinds of notch direction were adopted : edgewise notches parallel (L) and transverse (T) to the major direction of fiber bundles, and flatwise notches parallel(ZL) and perpendicular(ZT) to this direction. Nominal bend strength for L and ZL specimens exhibited high sensitivity to notching. ZL specimens revealed the lowest values of the critical stress intensity factor $K_c$ which was slightly superior to those of unfilled PA6 matrix. Enlargement of the compression area for T specimens was analyzed by means of the rigidity reduction resulting from the fracture occurrence.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1520-1526
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• 2002

The Charpy and Izod impact tests are the most prevalent techniques used to characterize the effects of high impulse loads on ploymeric materials. An analysis method for rubber toughened PVC is suggested to evaluate critical dynamic strain energy release rates(G$\_$c/) from the Charpy impact energy measurements. An instrumented Charpy impact tester was used to extract ancillary information concerning fracture parameters in addition to total fracture energies and maximum critical loads. The dynamic stress intensity factor Kid was computed for varying amounts of rubber contents from the obtained maximum critical loads and also toughening effects were investigated as well.