• Journal of Welding and Joining
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• 제11권3호
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• pp.34-47
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• 1993

Finite element models were developed for thermal and residual stress analysis for the specific welding problems. They were used to evaluate the effectiveness of the various welding heat input models, such as ramp heat input function and lumped pass models. Through the parametric studies, thermal-mechanical modeling sensitivity to the ramp function and lumping techniques was determined by comparing the predicted results with experimental data. The kinetics for residual stress formation during welding can be developed by iteration of various proposed mechanisms in the parametric study. A ramp heat input function was developed to gradually apply the heat flux with variable amplitude to the model. This model was used to avoid numerical convergence problems due to an instantaneous increase in temperature near the fusion zone. Additionally, it enables the model to include the effect of a moving arc in a two-dimensional plane. The ramp function takes into account the variation in the out of plane energy flow in a 2-D model as the arc approaches, travels across, and departs from each plane under investigation. A lumped pass model was developed to reduce the computation cost in the analysis of multipass welds. Several weld passes were assumed as one lumped pass in this model. Recommendations were provided about ramp lumping techniques and the optimum number of weld passes that can be combined into a single thermal input.

• The Journal of Korean Academy of Sensory Integration
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• 제11권1호
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• pp.39-49
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• 2013

Objective : We studied adolescent's sensory processing characteristics and classification of the depending on the adolescent's sensory processing characteristics degree. And we studied depending on sensory processing characteristics the difference of the general characteristics; sex, health status, hospital visit, the usual sensory problem. In addition, we investigated differences in each group; sensory processing characteristics, stress, depression, and self-esteem. Methods : We have collected 310 for students in Busan, Gyeongsangnam-do region of high school to distribute the questionnaire; Adolescent / Adult sensory profile (AASP), the Korean version Daily Stress Assessment (K-DSI), Beck Depression Inventory (BDI), and Self-Esteem Scale (SES). The questionnaire used in the final study part 310 to part 288 of which corresponds to 92% of the total questionnaire. The data analysis was used SPSS for windows 18.0 statistical analysis. Results : Sensory Seeking of sensory processing characteristics of adolescents in the study was low score. The higher stress score, Sensory Sensitivity and Sensation Avoiding score were higher, and the higher depression score, Low Registration and Sensation Avoiding score were higher. The lower self-esteem score, Sensation Avoiding and Sensory Sensitivity score was higher whereas Sensation Seeking score was lower. Conclusions : Study about Korean's mean in the next studies should be investigate. In addition, a lot of study about adolescents with sensory processing problems should be investigate.

• Journal of the Korean Society of Food Science and Nutrition
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• 제36권1호
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• pp.124-130
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• 2007

The purposes of this study were (1) to analyze price sensitivity, (2) to define the range of acceptable prices for each foreign segment, and (3) to provide a price model for Korean traditional restaurants. From October to November, 2006, a total of 781 foreigners responded to individual surveys. Statistical analyses on the survey data were performed using descriptive statistics and Price Sensitivity Measurement (PSM). Major findings from the study are as follows: First, the ranges of the acceptable prices were $98$\sim$$130 for fine dining/gourmet restaurants, $70$\sim$$90 for theme/ambience restaurants, $40$\sim$$60 for popular/family restaurants, and $18$\sim$$30 for convenience/fast food restaurants. Second, the convenience/fast food restaurants showed the highest price sensitivity. Third, a low stress level and wide range of the acceptable price were observed for the fine dining/gourmet restaurants, suggesting that the price sensitivity of the fine dining/gourmet restaurants was quite low. Finally, the price sensitivity indicated by the Japanese was higher than by the other groups. In consequence, the research findings suggest that the managers of the Korean traditional restaurants should strategically plan prices by understanding different customers' price sensitivity within and between customer segments. Through additional research, marketers can compare perceptions of specific brands, the competition, and variations within a product line.

• International Journal of Automotive Technology
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• 제7권4호
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• pp.485-492
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• 2006

The AA5182/polypropylene/AA5182(AA/PP/AA) sandwich sheets have been developed for application to automotive body panels in future lightweight vehicles with significant weight reduction. It has been reported that the AA5182 aluminum sheet shows $L\"{u}ders$ band because of dissolved Mg atoms that cause fabrication process problem, especially surface roughness. The examination of serration behavior has been made after the tensile deformation of the AA/PP/AA sandwich sheets as well as that of the AA5182 aluminum skins at room and elevated temperatures. All sandwich sheets and the AA5182 aluminum skin showed serration behavior on their flow curves. However, the magnitude of serration was significantly diminished in the sandwich sheet with high volume fraction of the polypropylene core. According to the results of the analysis of the surface roughness following the tensile test, $L\"{u}ders$ band depth of the sandwich sheet evidently showed lower than that of the AA5182 aluminum skin. The strain rate sensitivity, m-value, of the AA5182 aluminum skin was -0.006. By attaching these skins to the polypropylene core, which has relatively large positive value of 0.050, m-value of the sandwich sheets changed to the positive value. The serration mechanism of the sandwich sheets was quantitatively investigated in the point of the effect on polypropylene thickness variation, that on the strain rate sensitivity and that on the localized stress state.

• Journal of Korean Society of Steel Construction
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• 제17권5호통권78호
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• pp.519-526
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• 2005

During summer, very high compressive force occurs on the continuous welded rail (CWR) track because of the increase of rail temperature (max. $60^{\circ}C$). This extreme temperature stress can cause the CWR track to buckle. Among many CWR parameters affecting the track buckling, the influence of the lateral and longitudinal ballast resistance was investigated on the stability of the CWR track in this study. Also, the sensitivity of the track irregularity such as the alignment defect and the gauge irregularity was investigated.

• Journal of the Society of Naval Architects of Korea
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• 제44권2호
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• pp.130-138
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• 2007

A coupled variational equation for fluid-structure interaction (FSI) problems is derived from a steady state Navier-Stokes equation for incompressible Newtonian fluid and an equilibrium equation for geometrically nonlinear structures. For a fully coupled FSI formulation, between fluid and structures, a traction continuity condition is considered at interfaces where a no-slip condition is imposed. Under total Lagrange formulation in the structural domain, finite rotations are well described by using the second Piola-Kirchhoff stress and Green-Lagrange strain tensors. An adjoint shape design sensitivity analysis (DSA) method based on material derivative approach is applied to the FSI problem to develop a shape design optimization method. Demonstrating some numerical examples, the accuracy and efficiency of the developed DSA method is verified in comparison with finite difference sensitivity. Also, for the FSI problems, a shape design optimization is performed to obtain a maximal stiffness structure satisfying an allowable volume constraint.

• Journal of the Korean Society for Heat Treatment
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• 제33권4호
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• pp.161-172
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• 2020

The tensile property of A5082 and A6060 aluminium wrought alloys was investigated, in terms of the strain rate sensitivity on alloy conditions by heat treatment and bake hardenability on pre-strain prior to strain ageing. The tensile test was carried out in a range of strain rate of 4.17 × 10^-5 s^-1 ~ 4.17 × 10^-5 s^-1 in room temperature and the nominal range of pre-strain was 3.0 ~ 10.5%. The tensile deformation of A5082 alloys is characterized as typical case of dynamic strain ageing with negative strain rate sensitivity for all conditions, and the tensile strength indicates a similar level regardless of alloy conditions, except only in full annealed condition. The stress-relief annealing on A6060 alloys can induce practical decrease in strength level of over approximately 100 MPa without any ductility loss, compared to as-rolled condition, while a full annealed and aged condition leads remarkable strengthening effect with the decrease of tensile elongation. Additionally, the bake hardenability of A5082 alloy by strain ageing indicates a negative dependence upon the increase of pre-strain, while A6060 alloy exhibits a positive sign even in low level relatively compared with conventional SPCC.

• Transactions of the Korean Society of Mechanical Engineers A
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• 제25권3호
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• pp.520-528
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• 2001

This paper investigates a resonant microaccelerometer that measures acceleration using a built-in micromechanical resonator, whose resonant frequency is changed by the acceleration-induced axial force. A set of design equations for the resonant microaccelerometer has been developed, including analytic formulae for resonant frequency, sensitivity, nonlinearity and maximum stress. On this basis, the sizes of the accelerometer are designed for the sensitivity of 10$^3$Hz/g in the detection range of 5g, while satisfying the conditions for the maximum nonlinearity of 5%, the minimum shock endurance of 100g and the size constraints placed by microfabrication process. A set of the resonant accelerometers has been fabricated by the combined use of bulk-micromachining and surface-micromachining techniques. From a static test of the cantilever beam resonant accelerometer, a frequency shift of 860Hz has been measured for the proof-mass deflection of 4.3${\pm}$0.5$\mu\textrm{m}$; thereby resulting in the detection sensitivity of 1.10${\times}$10$^3$Hz/g. Uncertainty analysis of the resonant frequency output has been performed to identify important issues involved in the design, fabrication and testing of the resonant accelerometer.

• Journal of Korean Society for Quality Management
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• 제39권4호
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• pp.507-515
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• 2011

MIL-HDBK-217 has played a pivotal role in reliability prediction of electronic equipments for more than 30 years. Recently, RIAC developed a new methodology $217Plus^{TM}$which officially replaces MIL-HDBK-217. Sensitivity analysis of the 217Plus component models to various parameters has been performed and meaningful observations have been drawn in this study. We first briefly reviewed the $217Plus^{TM}$ methodolog and compared it with the conventional model, MIL-HDBK-217. We then performed sensitivity analysis $217Plus^{TM}$ component models to various parameters. Based on the six parameters and an orthogonal array selected, we have performed indepth analyses concerning parameter effects on the model. Our result indicates that, among various parameters, operating temperature and temperature rise during operation have the most significant impacts on the life of a component, and thus a design robust to high temperature is the most importantly required. Next, year of manufacture, duty cycle, and voltage stress are weaker but may be significant when they are in heavy load conditions. Although our study is restricted to a specific type of diodes, the results are still valid to other cases. The results in this study not only figure out the behavior of the predicted failure rate as a function of parameters but provide meaningful guidelines for practical applications.

• KSCE Journal of Civil and Environmental Engineering Research
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• 제5권3호
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• pp.137-144
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• 1985

This paper deals with the adjoint variable method in design sensitivity analysis that is essential to the structure optimization. The method is shown to be much simpler than the conventional method in structure optimization by applying it to the optimal design of finite dimensional structures. Design sensitivity analyses and their numerical solutions for the principal constraints, i.e., displacement and stress constraints under static loads are obtained. Furthermore, it is proved that optimization can be carried out efficiently by applying the optimization algorithm. Structure optimization problems of minimizing the volumes of the truss structures(finite dimensional structures) under the appropriate boundary conditions, loading conditions and constraints are considered.