• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1688-1690
• /
• 2002

The unpredictable threat of lightning surge is ever increasing in today's low-voltage power supplies. Thus Surge protection devices for AC mains are more widely used. The false-tripping of the earth leakage breaker (ELB) can be caused by the installation of surge protection devices with MOV. In order to examine the cause of malfunction, the malfunction characteristics of ELBs applied by lightning surge were investigated experimentally. As a result, all of them brought about malfunctions under 7 kV of the impulse voltage. The suitable position of MOV and use of zener diode were suggested to eliminate the problems.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1999.11a
• /
• pp.146-153
• /
• 1999

A numerical dynamic simulation is necessary to investigate the capacity of the HDD. The slider surface become more and more complicated to make the magnetized area smaller and readback signal stronger. So a numerical dynamic simulation must be preceded to develop a new slider in HDD. The dynamic simulations of air-lubricated slider bearing have been peformed using FIFD(Factored Implicit Finite Difference) method. The governing equation, Reynolds equation Is modified with Fukui and Kaneko model(FK model) which includes the first and the second-order slip. The equations of motion for the slider bearing are solved simultaneously with the modified Reynolds equation for the case of three degrees of freedom. The slider transient response for disk step bump and slider impulse force is given for various case and for iteration algorithm and new algorithm.

• The Korean Journal of Health Service Management
• /
• v.10 no.1
• /
• pp.117-129
• /
• 2016

Objectives : This study investigated the prevalence of unmet health care needs among Korean adults and related factors. Methods : The study participants were adults over the age of 20 mental health experience from the Korea Health Panel in 2012(n=4,730). Statistical analysis methods used in this study were the ${\chi}^2$-test, Logistic Regression Analysis and other basic statistics such frequency-and percentage using SPSS version 22.0. Results : (1)Significant variables of stress: Factors were age, economic activity, subjective health status, and activity limitation. (2)Significant variables of depression: Factors were age, income class(low) and activity limitation. (3)Significant variables of suicidal impulse: Factors were age, chronic diseases, income class, and activity limitation. Conclusions : Stress, depression, and suicidal impulse can be unmet medical factors; therefore improvement measures and mental health counseling programs in response to suicide impulses, should be developed. Thus there is a need for a health sciences approach.

• Journal of the Korean Chemical Society
• /
• v.7 no.3
• /
• pp.203-206
• /
• 1963

The eddy diffusion in the pulsed wetted wall column, where the spherical balls are consecutively arrayed along the axis of the column and turbulence is caused around the balls by pulsation, has been studied both theoretically and experimentally. A diffusion equation is solved for a longitudinal column where a concentration impulse is given at the top of the column, and the experimental results, which are the impulse response measurements at the half of the total height of the column, have shown a good agreement with the developed theory. A method of measuring the eddy diffusivity, which is based on the slope of concentration vs. time in the particular interval of concentration, is proposed and the measured diffusivity is used as a criterion of comparing the theory and the experiment. The eddy diffusion is remarkably increased as the amplitude and the frequency of the pulsation increase but the increasing rate is decreased as the pulsation increases.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1997.10a
• /
• pp.42-49
• /
• 1997

In this paper, the method for soil-structure interaction analyses in the time domain is proposed. The far field soil region which is the outside of the artificial boundary is modeled by using explicit frequency-dependent two dimensional infinite elements which can include multiple wave components propagating into the unbounded medium. Since the dynamic stiffness matrix of the far field soil region using the proposed infinite elements is obtained explicitly in terms of exciting frequencies and constants in the frequency domain, the matrix can be easily transformed into the displacement unit-impulse response matrix, which corresponds to a convolution integral of it in the time domain. To verify the proposed method for soil-structure interaction analyses in the time domain, the displacement responses due to an impulse load on the surface of a soil layer with the rigid bed rock are compared with those obtained by the method in the frequency domain and those by models with extend finite element meshes. Good agreements have been found between them.

• Proceedings of the KOR-BRONCHOESO Conference
• /
• 1978.06a
• /
• pp.9.1-10
• /
• 1978

Recently the authors have observed various wave-forms by insertion of induction coil into the scala tympani as well as attached outer device in the outside of the body in damaged hair cells of the cats. In the cochlear nerve. action potential indicated different polarities induced by examination of the bundle of the cochlear nerve fibers. Impulse wave-form as a result of excitation of cohlear nerve fibers showed bipolar wave-form such as negative 1 and positive 1. Therefore action potential showed also bipolar wave-form as above mentioned. We can obtained suitable response with above mentioned outer and inner device as an exact oscillogram.

• Proceedings of the KIEE Conference
• /
• 1998.11a
• /
• pp.97-99
• /
• 1998

This paper presents a numerical study of the behavior of the transformer winding, when stressed by the standard impulse voltage. The mathematical model of the transformer takes several points into the account. Capacitance of not adjacent winding as well as adjacent winding, eddy current loss caused by self and mutual inductance given as the functions of frequency. Not like the previous approach where calculation of capacitance is performed, in average sense. In this paper, capacitance of both adjacent and not adjacent winding is calculated using the numerical approach(B.E.M.), so they can get the more accurate value of capacitance. Because of frequency dependency of inductance, numerical-laplace-transform technique is required. Finally, to validate this approach, a simple test winding is simulated.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.18 no.3
• /
• pp.470-487
• /
• 1996

The purpose of this study was to investigate the dynamic response of the mandible to impact and provide insight into the fracture mechanism of the mandible, by 3-dimensional finite element method. The finite element model of the mandible was developed and calculated using NASTRAN/XL (MSC co. U.S.A.) and the linear dynamic transient analysis was performed according to the impulsive force direction, force type and impulse time to the mandible. At first, the load was applied on the mandibular symphysis, body, angle and subcondylar area in the horizontal mandibular plane and the computed stress-time histories at 14 locations of the mandible were obtained. Secondly, the impulsive force was directed to the symphyseal area with changing the force magnitude and impulse time, and calculated the node displacement at 8 locations of mandible. The conclusions from from this study were as follows. 1. The appearance of impulsive energy transmission was different to the direction of impulse to the mandible. 2. The impulsive stress and deformation were larger in lingual or medial side than buccal or lateral in the mandible. 3. The velocity, appearance of energy transmission and the fracture pattern in mandible were affected rather impulse time than force. 4. The horizontal impact to the one side of mandible did not have effect on the stress and displacement of contralateral mandible. From the above results, fracture pattern in symphysis can be showed as simple or comminuted, multiple or associated in body and angle and solitary in subcondyle area.

• Journal of the Korean Data Analysis Society
• /
• v.20 no.6
• /
• pp.2953-2966
• /
• 2018

Housing prices are closely related to various variables that indicate macroeconomic conditions. In this paper, empirical analysis based on data is performed referring to previous studies. Focusing on the policy interest rate among the factors affecting the housing price, the non-linear impulse responses of other variables to the interest rate shock are analyzed. Using the random forest algorithm, the variable importance scores of the macroeconomic variables presented in the previous studies are calculated. After selecting the variables through this process, the impulse responses are calculated using a model that can capture non-linearity. According to the model, the responses of housing prices to the policy rate is only significant when the rate is raised. Especially, the impulse response is amplified when the shock increases due to the non-linear characteristics that can not be captured by the traditional VAR methodology. The analysis results suggest that the interest rate as a policy instrument should be approached from a more cautious perspective.

• Journal of Technology Innovation
• /
• v.24 no.2
• /
• pp.91-113
• /
• 2016

The purpose of this study is to examine the causal relationship among R&D spending and variables of technology trade, and to explore promoting R&D activities and revitalizing technology trade. To analyze the causal relationship, we built a multivariate model that consists of government R&D spending, private R&D spending, technical importation and export of techniques, and employed the Granger-causality test based on an error correction model. The results show that there are five Granger-causality relationship among them in the short run, as well as there are eleven Granger-causality relationship among a total of twelve causal relationship, excluding only a unidirectional causality relationship from the government R&D spending to the export of techniques, in the long run. Besides, we attempted the impulse-response analysis on them to observe the reaction of any dynamic system in response to some external change. The significance of this paper is to make sure the causal relationship between R&D investments and the technology trade by analyzing empirically, and to suggest several implications for promoting the R&D activities and revitalizing the technology trade.