• Advances in nano research
• /
• v.9 no.4
• /
• pp.251-261
• /
• 2020

In this article, vibration attributes of single walled carbon nanotubes based on Galerkin's method have been investigated. The influence of power law index subjected to different end supports has been overtly examined. Application of the Hamilton's variational principal leads to the formation of partial differential equations. The effects of different physical and material parameters on the fundamental frequencies are investigated for armchair and zigzag carbon nanotubes with clamped-clamped, simply supported and clamped-free boundary conditions. By using volume fraction for power law index, the fundamental natural frequency spectra for two forms of Single-Walled Carbon Nanotubes (SWCNTs) are calculated. The influence of frequencies against length-to-diameter ratios with varying power law index are investigated in detail for these tubes. MATLAB software package has been utilized for extracting tube frequency spectra. The obtained results are confirmed by comparing with available literature.

• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.218-223
• /
• 1999

A piezoelectric flextentional deep-water sonar transducer has been simulated using a coupled FE-BEM. The dynamics of the sonar transducer is modelled in three dimensions and is analyzed with extern리 electrical excitation conditions as well as external acoustic pressure loading conditions. Different results are available such as steady-state frequency response for RX and TX, displacement modes, directivity patterns, back-scattering patterns, resonant frequencies, bandwidths, quality factors, transmitting voltage (TV) responses, input receiving sensitivity (RS) responses. White the present barrel-stave typed sonar transducer of the piezoelectric material is being simulated, the external surface of the transducer is modified in order to allow the same water pressure to be applied to the inner and the outer surfaces of the transducer. With this modification for deep-water application, the resonance frequency of the modified flextentional sonar transducer becomes much lower than that of the unmodified flextentional sonar transducer. The results of the present sonar transducer modelling are also compared with those of a commercial package such as ATILA.

• Journal of the Korean Society for Railway
• /
• v.3 no.3
• /
• pp.117-124
• /
• 2000

The rubber wheel-type AGT has two major kinds of bogie; one is the bogie type and the other steering one. Both are important vehicular structure to support the whole running vehicle and passenger loads. This paper deals with the static analysis for the two types of bogie frame subjected to combined external forces, as well as independent ones specified in UIC 515-4. Furthermore, the dynamic analysis is performed under vibrational loading conditions so as to compare dynamic characteristics, Numerical results by using commercial packages, I-DEAS and NASTRAN show that maximum stresses do not exceed the yield strength level of material used for both bogies. From an overall viewpoint of strength, the bogie type turns out to be superior to the steering type except for the case of a lateral loading. It is also observed that the steering type shows a characteristics of low frequency behavior during a course of searching for structurally weak areas to be stiffened. The vibrational fatigue analysis for each bogie frame depends on the loading time history conditions which is applied. Time History Central Database List in the NASTRAN package. Subsequent1y, the fatigue life of bogie type is longer than the steering type.

• Journal of Welding and Joining
• /
• v.21 no.6
• /
• pp.71-76
• /
• 2003

For the purpose of clarifying the influence of welding residual stress to the fatigue crack propagations behaviour, an analytical investigation based on finite element method is performed to examine the opening behaviour of tip-closed crack in the compressive residual stress. A finite element model comprised of contact elements for the crack plane and plane stress elements for the base material is used to evaluate crack opening stress of the crack existing in the residual stress field. Also an analytical method based on the superposition principle to estimate the length of opened part of tip closed crack and the stress distribution adjacent to the crack during uploading is applied to the finite element model. The software for the analysis is ABAQUS, which is a general purpose finite element package. The results show that stresses distributed on the crack surfaces are reduced and approached to zero as the applied stresses are increased up to crack tip opening stress and no mechanical discontinuity is found at the boundary of contact elements and plane stress elements. It is verified that the opening behavior of the fatigue crack in the residual stress can be predicted by finite element method with the proposed analytical method.

• Journal of Technologic Dentistry
• /
• v.33 no.4
• /
• pp.283-289
• /
• 2011

Purpose: The purpose of this study was to evaluate flexural strength of full zirconia crown using block after clinical work. Methods: The three point bending test was used to measure the flexural strength of zirconia block. Statistical analysis was done using the Statistical Package for Social Sciences version 19.0 for Windows. As for the analysis methods, the study used analysis of variance, Tukey's test. Results: The ave Rage value of flexural strengths of WIELAND, Zirkonzahn, Hass, D-MAX were 516.2 MPa, 612.6MPa, 566.2MPa, 744.6MPa. The ave Rage value of Surface Roughness of WIELAND, Zirkonzahn, Hass, D-MAX were 0.39Ra, 0.33Ra, 0.33Ra, 0.47Ra. Conclusion: Flexural strength of zirconia block decreased after clinical work. Flexural strength of zirconia block is equal to or higher than flexural strength of dental metal, so zirconia block can be used as dental material.

• Journal of Nutrition and Health
• /
• v.35 no.6
• /
• pp.668-680
• /
• 2002

The purpose of this study was to investigation the importance and categorization of task elements of school food service dietician and to provide the useful data for standard model of the dietician′s tasks of school foodservice. This study was conducted in school food services nationwide in method of written questionnaire. The questionnaires were mailed to the dieticians of 3 type school foodservice system-conventional, commissary, joint management. Of the 660 schools that participated in this study, the responses from 212 conventional system and 212 commissary system and 200 joint management system were selected for analysis. Statistical analysis was performed with SAS/Win 6.12 package program for descriptive analysis, T-test, ANOVA, factor analysis using. The main results of this study can be summarized as follows Importance level was more than 4 score out of 5 scale in most of the task elements. The result was indicative of the appropriateness of definition of the 61 task elements. Of 61 task elements, importance level on ′nutrition education′ and on ′evaluation of foodservice operation management′ indicated the most significant difference between present and ideal situation. Through factor analysis, 61 task elements were regrouped into 7 dimensions; "Duty dimension of cooking and distribution management", "Duty dimension of cost management", "Duty dimension of raw material management", "Duty dimension of education management", "Duty dimension of menu management", "Duty dimension of record keeping of foodservice", "Duty dimension of general management (others)".

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.2
• /
• pp.133-138
• /
• 2005

The deformation of sheet metal due to the residual stress during blanking or piercing process, is numerically simulated by means of a commercial finite element code. Two dimensional plain strain problem is solved and then its result is applied to the deformation analysis of the lead frame. The plain strain element is applied to the 2D problem to observe the Von Mises equivalent stress concentration at the both shearing edges. As the punch penetrates into the sheet material, the stress concentration generated on both edges is getting increased to be the shearing surface. The limits of the punching depth applied to the simulation is 16% and 24% of the sheet thickness for the plain strain element and the hexahedral element, respectively. The hexahedral element and the limit of punching depth were applied to the deformation analysis of the lead frame for the blanking process. The FEM results for the lead deformation were very good agreement with the experimental ones. This paper shows that the coarse mesh has enabled to analyze the lead deformation generated due to the blanking mechanism. This simple approach to save the calculation time will be very effective to the design of the blanking tools in industries.

• Journal of Fashion Business
• /
• v.16 no.4
• /
• pp.1-12
• /
• 2012

This study made an analysis on the relation and influence between outdoor wear benefit, clothing selection criteria and purchasing satisfaction. Survey was conducted targeting 20s-30s males and females who have experience of purchasing outdoor wear and 335 sheets of questionnaire were used for final analysis. And statistics package SPSS16.0 was used for analysis of collected materials. A group seeking the trendy brand turned out to give considerable thought to the brand and trend and purchase less than 100,000won at the discount outlet. A group pursuing functional practicality puts an emphasis on the activity and use, and purchases at the internet shopping mall or department store. Regarding material, function, design, style and color as important, a group pursuing individuality and appearance turned out to purchase clothing at various places such as discount outlet, specialty store and internet. A group that is indifferent to clothing appeared not to care about specific elements when selecting outdoor wear. The result of study showed that consumers of outdoor wear show purchasing satisfaction in respect of design, style, color or trend.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.23 no.4
• /
• pp.89-101
• /
• 2015

In this study, it examined whether recognized career barriers among students of majoring in aviation affected career stress and career decision level, and career stress moderated the impact of career barriers on career decision level. For this purpose, it conducted a survey of aviation-related college students in C university from Sep. 21th. 2015 to Oct. 8th. 2015. A total of 225 questionnaires were analyzed using SPSS 21.0 statistical package program and frequency analysis, factor analysis, reliability analysis, regression analysis, and correlation analysis were conducted. Findings indicated that career barriers partly influenced the career stress and career decision level. Also, career stress had an negative effect on career decision level. Lastly, career stress moderated the impact of career barriers on career decision level. The implication of this paper would be used as a fundamental material to guide for career direction to students majoring in aviation.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.12
• /
• pp.25-33
• /
• 2003

A burr has been defined as undesirable projection of material formed as a result of plastic flow from a cutting or shearing operation. It is unavoidable in all kinds of machining operation. As a result, burr makes troubles on manufacturing process due to deburring cost, quality of products and productivity. In this study, the primary interest is about exit burr. The burr formation mechanism in each type of burr is classified. Data bases are developed to predict burr formation result. In the milling operation, we develop an algorithm to analyze the burr formation mechanism by the geometrical analysis on the multi featured workpiece with multi cutting path. The algorithm includes three steps, i. e., the feature identification, the cutting condition identification, and the analysis on exit burr formation. We can predict which portion of workpiece would have the exit burr in advance so that we can manage to find a way to minimize the exit burr formation in an actual cutting. Also, this algorithm can be implemented in a commercial CAM package so that we can simulate the NC code to review the burr formation in advance.