• Transactions of the Korean Society of Mechanical Engineers
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• 제11권1호
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• pp.82-87
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• 1987

In this study a method of shape optimization is applied to two dimensional heat transfer system. For this the optimization problem is defined in a functional form including cost, constraints and the system governing equation. Then the material derivative concept in continuum mechanics and the adjoint variable method are employed for the shape design sensitivity analysis. With the sensitivity analysis results, an optimum is sought with the gradient projection optimization algorithm. The two dimensional isoparametric finite elements are used for accurate analysis and sensitivity calculations. The above method is employed to find the boundary shape to achieve a desired temperature distribution along a segment of the boundary subject to the maximum area constraint.

• Korean Journal of Soil Science and Fertilizer
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• 제32권3호
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• pp.268-273
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• 1999

To measure the precision of Soiltek$^{(R)}$ KA-1 spectrophotometric measurement of soil available phosphate, standard deviation, C;V, and relative sensitivity were investigated, comparing to Lancaster method. Available phosphate concentration measured by Soiltek$^{(R)}$ KA-1 spectrophotometric method was highly correlated with Lancaster method($r=0.998^{***}$) and the slop of regression equation was close to 1.0. There were no differences in standard deviation. CV, and relative sensitivity for soil available phosphate concentrations measured by two methods. Regarding to convenience of experimental procedure and instrumental operation, and time saving analysis, Soiltek$^{(R)}$ KA-1 spectrophotometric measurement for soil available phosphate is highly recommended.

• Korean Journal of Agricultural and Forest Meteorology
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• 제9권3호
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• pp.170-178
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• 2007

Rapid increases in the concentrations of greenhouse gases and many other chemically important trace gases have occurred over the last several centuries. For understanding the roles of these important gases in global change, it is essential to identify their sources and sinks, to characterize biogenic gas fluxes between the biosphere and atmosphere, and to understand the processes that control them. In this paper, enclosure-based measurements are described in a practical manner for field experiments. Theoretical reviews of mass balance equation in the enclosure and sensitivity of the flow-through dynamic flux chamber technique are presented; specifically for the case of NO flux measurements from soil surface. The physical system and theory behind the flow-through dynamic flux chamber method are examined. New calculation flux formula was introduced by considering NO chemical loss on chamber wall and uncertainties of the NO flux calculation were discussed.

• Journal of the Korean Institute of Gas
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• 제13권2호
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• pp.23-29
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• 2009

This study investigated sensitivity of the gas sensor to chemical weapons with the sensor material doped with catalysts. The nano-sized SnO2 powder mixed with metal oxides (TiO2) was doped with transition metals(Pt, Pd and In). Thick film of nano-sized SnO2 powder with TiO2 was prepared by screen-printing method onto Al2O3 substrates with platinum electrode and chemical precipitation method. The physical and chemical properties of sensor material were investigated by SEM/EDS, XRD and BET analyzers. The measured sensitivity to simulant toxic gas is defined as the percentage of resistance of value equation, [(Ra-Rg)/$Ra\;{\times}100$)], that of the resistance(Ra) of SnO2 film in air and the resistance(Rg) of SnO2 film in acetonitrile gas. The best sensitivity and selectivity of these thick film were shown with 1wt.% Pd and 1wt.% TiO2 for acetonitile gas at the operating temperature of $250^{\circ}C$.

• Journal of Digital Convergence
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• 제14권6호
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• pp.425-430
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• 2016

The goal of this study is to explore the factors that influence on intention to use UHDTV Service. Research problems has been designed to Structural equation model by Technology Acceptance Model. The Perceived quality, Price sensitivity, Innovativeness are adopted as independent variables. And Perceived usefulness, Perceived ease of use are adopted as intervening variables. A result of analysis, Perceived quality and Price sensitivity influenced the Intention to use via Perceived usefulness and Perceived ease of use. But in case of Innovativeness, it did not influence the Perceived usefulness while it influenced the Perceived ease of use. Meanwhile, the influence of Perceived quality to Perceived usefulness had more impact than the other path between the other factors.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제21권3호
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• pp.239-245
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• 2008

A level set based topological shape optimization using extended B-spline basis functions is developed for steady-state heat conduction problems. The only inside of complicated domain identified by the level set functions is taken into account in computation, so we can remove the effects of domain outside parts in heat conduction problem. The solution of Hamilton-Jacobi equation leads to an optimal shape according to the normal velocity field determined from the sensitivity analysis, minimizing a thermal compliance while satisfying a volume constraint. To obtain exact shape sensitivity, the precise normal and curvature of geometry need to be determined using the level set and B-spline basis functions. Using topological derivative concept, the nucleation of holes for topological changes can be made whenever and wherever necessary during the optimization.

• The Journal of the Korea Contents Association
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• 제19권3호
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• pp.590-599
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• 2019

The purpose of this study is to identify the mediated effects of social support in relation to college students' emotional control ability and rejection sensibility, and to provide basic data to intervene in students with high resistance sensibility. To this end, a survey of 449 university students was conducted and the hypothesis of this study was verified using a structural equation model. The analysis results are as follows. First, the relationship between emotional control ability, rejection sensibility and social support perceived by university students through correlation analysis showed significant correlation between emotional control ability, social support and rejection sensitivity. Second, in the structural model of social support in relation to emotional control ability and rejection sensibility, it was confirmed that social support played a role between emotional control ability and rejection sensibility. Based on the results of this study, some suggestions for the application and follow - up studies were discussed.

• The Journal of the Korea Contents Association
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• 제19권5호
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• pp.363-370
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• 2019

The purpose of this paper is to investigate motivational factors and consequence of the herd behavior of adolescent consumers under the buying decision process in the connected era of internet. For such purpose, this study built a research model and examined how sensitivity to fads, interaction and inaccuracy affect the disequilibrium consumption of adolescents. We also examined the relationship between disequilibrium consumption and consumption happiness. The survey method was used for this paper, and data from a total of 142 students were used for the analysis. And structural equation model was used to analyze the data. The results of this empirical study is summarized as followings. First, sensitivity to fads and interaction have direct effect on the disequilibrium consumption of adolescents. Second, disequilibrium consumption has a positive effect on adolescents' consumption happiness. This implies that the importance of herd behavior in designing rational choice in adolescents' consumption behaviors.

• Journal of Oral Medicine and Pain
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• 제26권2호
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• pp.133-146
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• 2001

This study was performed to predict the conservative treatment outcome of TMD patients by investigating the prognostic factors ; symptom duration, history of previous treatment, history of previous medication, history of trauma, disability of daily activity, severity of pain, noise, limitation of mouth opening(LOM) and maximum comfortable opening(MCO). Two hundreds and fifty-four subjects were selected for this study among the TMD patients who had visited the Dept. of Oral Medicine BNUH and been treated conservatively with medication, physical therapy, behavioral treatment, and splint therapy from 1991 to 2000. The subjects were divided into two groups improved or unimproved according to the treatment response following six months of conservative treatment. Those who showed less than 1 on NAS for pain, TMJ noise, and opening limitation belonged to the improved group and those who showed more than 2 on NAS belonged to the unimproved group. The two groups were compared with respect to symptom severity, number of diagnosis, history of trauma, previous treatment, previous medication, and disability of daily activity. A prognostic equation with the factors revealed to be significantly related to the prognosis of conservative treatment was obtained. The obtained results were as follows ; 1. In improved group, mean duration of history was 12 months, mean treatment duration of a patient was 4 months an mean number of treatment was about 10 times. In other words, in unimproved group, mean duration of history was 27.4 months, mean treatment duration of patient was 10.5 months and mean number of treatment was 19 times. 2. In unimproved group, multiple diagnosis, chronicity, disability of daily activity were significantly greater than that of the improved group. 3. Patients in unimproved group revealed severe noise at first visit and smaller maximum comfortable opening comparatively. 4. Prognostic factors such as duration of treatment, number of treatment, multiplicity, and chronicity and disability of daily activity showed a significant relation in prediction of improvement. 5. Prognostic equation with significant variables is as follows ; Y = 1.984 - 0.251Noise + 0.068MCO - 0.673Multiplicity. - 0.958Chronicity - 0.065Disability. Classification accuracy of 70.3 %, sensitivity of 71.4% and specificity of 66.7% were shown. 6. Prognostic equation with all factors is as follows : Y = 1.599 - 0.038Pain - 0.256Noise - 0.006Limitation + 0.068MCO - 0.580Multiplicity - 1.025Chronicity - 0.720Disability - 0.329Medication - 0.087Treatment + 0.740Trauma. Classification accuracy of 70.3 %, sensitivity of 73% and specificity of 64.3% were shown. 7. Prognostic value of the improved group with significant factors was $1.0446{\pm}1.0726$ and prognostic value of the unimproved group with significant factors was $-0.013{\pm}1.0146$. Prognostic value of the improved group with all factors was $1.0465{\pm}1.0849$ and prognostic value of the unimproved group with all factors was $-0.057{\pm}1.0611$.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제27권1호
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• pp.1-8
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• 2014

Using the level set and the meshfree methods, we develop a topological shape optimization method applied to linear elasticity problems. Design gradients are computed using an efficient adjoint design sensitivity analysis(DSA) method. The boundaries are represented by an implicit moving boundary(IMB) embedded in the level set function obtainable from the "Hamilton-Jacobi type" equation with the "Up-wind scheme". Then, using the implicit function, explicit boundaries are generated to obtain the response and sensitivity of the structures. Global nodal shape function derived on a basis of the reproducing kernel(RK) method is employed to discretize the displacement field in the governing continuum equation. Thus, the material points can be located everywhere in the continuum domain, which enables to generate the explicit boundaries and leads to a precise design result. The developed method defines a Lagrangian functional for the constrained optimization. It minimizes the compliance, satisfying the constraint of allowable volume through the variations of boundary. During the optimization, the velocity to integrate the Hamilton-Jacobi equation is obtained from the optimality condition for the Lagrangian functional. Compared with the conventional shape optimization method, the developed one can easily represent the topological shape variations.