• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.37 no.5
• /
• pp.905-914
• /
• 2017

We examine 554 state basic districts and 1832 householders in Busan metropolitan city to see whether the physical and walkable characteristics of housing influence apartment housing prices. We use two-level models modeling for a more accurate analysis. Walkable characteristics in level 2 state basic districts potentially explain 77% of the variation in housing values, with the highest impact on crime safety characteristics. Overall, our spatial multi-level analysis based on new state basic districts in Korea explained price variation better than previous studies, which considered each householder. The results provide policy opportunities for planners and citizen groups to pursue strategies that encourage the development of walkable and sustainable neighborhoods.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.13 no.4
• /
• pp.586-593
• /
• 2010

In this paper, I have proposed that the 1st and 2nd AC-DC transformation methods using multi-level pulsating currents and selection switches. Through making the rectified voltage of the proposed AC-DC translation which is similar to reference voltage by selecting from multi-level pulsating currents, the proposed translation has dramatically reduced the ripple voltage. I have compared the performance of the DC voltage, the ripple voltage and the peak to peak voltage of the proposed method with the conventional method. The simulation results show that the proposed 2nd method has the better performance than the 1st method in the point of average DC voltage drop and peak to peak voltage increase.

• Journal of Power Electronics
• /
• v.9 no.4
• /
• pp.593-603
• /
• 2009

This paper proposes and describes the design and operational principles of a three-phase three-level nine switch voltage source inverter. The proposed topology consists of three bi-directional switches inserted between the source and the full-bridge power switches of the classical three-phase inverter. As a result, a three-level output voltage waveform and a significant suppression of load harmonics contents are obtained at the inverter output. The harmonics content of the proposed multilevel inverter can be reduced by half compared with two-level inverters. A Fourier analysis of the output waveform is performed and the design is optimized to obtain the minimum total harmonic distortion. The full-bridge power switches of the classical three-phase inverter operate at the line frequency of 50Hz, while the auxiliary circuit switches operate at twice the line frequency. To validate the proposed topology, both simulation and analysis have been performed. In addition, a prototype has been designed, implemented and tested. Selected simulation and experimental results have been provided.

• Health Policy and Management
• /
• v.30 no.3
• /
• pp.355-365
• /
• 2020

Background: This study is aimed to verify individual and regional-level factors affecting the depression of Koreans and to develop social programs for improving the depressive status. Methods: This study used individual-level variables from the Korean Community Health Survey (2018) and used the e-regional index of the Korean Statistical Information Service as the regional-level variable. A multi-level logistic regression was executed to identify individual and regional-level variables that were expected to affect the extent of depressive symptoms and to draw the receiver operating characteristic curve to compare the volume of impact between variables from both levels. Results: The results of the multi-level logistic regression analysis in regards to individual-level factors showed that older age, female gender, a lower income level, a lower education level, not having a spouse, the practice of walking, the consumption of breakfast higher levels of stress, and having high blood pressure or diabetes were associated with a greater increase in depressive symptoms. In terms of regional factors, areas with fewer cultural facilities and fewer car registration had higher levels of depressive symptoms. The comparison of area under the curve showed that individual factors had a greater influence than regional factors. Conclusion: This study showed that while both, individual and regional-level factors affect depression, the influence of the latter was relatively weaker as compared to the first. In this sense, it is necessary to develop programs focused on the individual, such as social prescribing at the local or community-level, rather than the city and nation-level approach that are currently prevalent.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.14 no.6
• /
• pp.143-153
• /
• 2019

This study This study analyzed the effectiveness of Corporate Entrepreneurship, using Human Capital Corporate Panel (HCCP) data from 2017. The attitude of workers, which is main link in the process of corporate entrepreneurship, has been studied at a singular level at individual and organizational levels due to the lack of data and analysis methods. Multi-level analysis using hierarchical and linear modeling was performed to improve the accuracy of the relationship estimation between variables. In addition, this study examined the moderating effect of the organizational level in the process of entrepreneurship. As a result, corporate entrepreneurship has had a positive effect on job satisfaction and turnover, which is due to the employees attitude and organization. Organizational trust in the process has been shown to perform an important role in the relationship between the corporate entrepreneurship and job satisfaction, and that the relationship between the corporate entrepreneurship and turnover has not been controlled. Based on these results, the implications, limitations, and future research tasks of the study are discussed.

• 한국전산유체공학회:학술대회논문집
• /
• 2011.05a
• /
• pp.259-260
• /
• 2011

Using modern techniques from scientific computing and numerical analysis, natural phenomena or scientific experiment can be simulated effectively with a computer and used for computer graphics, for example as special effects for the film industry, manufacturing the thin film, multi-phase simulation and image processing. The Level Set method can make those things happen without a lot of difficulties. This method was devised by Osher and Sethian(1988) to represent dynamically moving interfaces as the zero level set of a scalar function that evolves in time. Since then, many researchers have worked on many applications using a Level Set Method. I will give a talk about the applications of the Level Set Method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.489-493
• /
• 2007

Mmulti-domain noise analysis method using Power Flow Boundary Element Method(PFBEM) has been developed successfully. Some applications are introduced. several examples. PFBEM is a numerical analysis method formulated by applying Boundary Element Method(BEM) to Power Flow Analysis(PFA). PFBEM is very powerful in predicting noise level in medium-to-high frequency ranges. However there are restrictions in analyzing the coupled structures and multi-media. In this paper, an analysis method for multi-domain acoustic problems in the diverse acoustic fields is suggested. And the developed method is applied to the car interior and exterior multi-domain noise analysis.

• The Journal of Korean Association of Computer Education
• /
• v.16 no.1
• /
• pp.51-61
• /
• 2013

This study is to investigate the effecting factors on using ICT ability, and using computers for learning through PISA 2009 Korean data. Multi-level analysis is adapted to hierarchical nested data. Results show as follows: First, using ICT ability is affected by variables on the student level, but not on the school level, except in ESCS. Second, using computers for the purpose of learning at home is also affected by variables on the student level, but not on the school level, except in ESCS and in the size of region. Third, using computers for learning at the school is more influenced by variables on the school level like ESCS, the size of region, the ratio of computers, and the student-teacher ratio. The results suggest planning a computer education policy with considering both personal and school differences based on the multi-level approach.

• Structural Engineering and Mechanics
• /
• v.64 no.2
• /
• pp.195-204
• /
• 2017

Analytical and experimental studies of the innovative pipe in pipe damper have been recently investigated by the authors. In this paper, by adding lead or zinc infill or slit diaphragm inside the inner pipe, it is tried to increase the equivalent viscous damping ratio improving the cyclic performance of the recently proposed multi-level control system. The damper consists of three main parts including the outer pipe, inner pipe and added complementary damping part. At first plastic deformations of the external pipe, then the internal pipe and particularly the added core and friction between them make the excellent multi-level damper act as an improved energy dissipation system. Several kinds of added lead or zinc infill and also different shapes of slit diaphragms are modeled inside the inner pipe and their effectiveness on hysteresis curves are investigated with nonlinear static analyses using finite element method by ABAQUS software. Results show that adding lead infill has no major effect on the damper stiffness while zinc infill and slit diaphragm increase damper stiffness sharply up to more than 10 times depending on the plate thickness and pipe diameter. Besides, metal infill increases the viscous damping ratio of dual damper ranging 6-9%. In addition, obtained hysteresis curves show that the multi-level control system as expected can reliably dissipate energy in different imposed energy levels.

• Journal of Advanced Marine Engineering and Technology
• /
• v.23 no.4
• /
• pp.574-582
• /
• 1999

This paper discusses the multi-level optimization method in dynamic optimization problems through stiffened plate of ship structures. In structural optimization the computational cost increases rapidly as the number of design variables increases. And we need a great amount of cal-culation and time on problems of modified dynamic characteristics of large and complicated struc-tures. In this paper the multi-level optimization is proposed which decreases computational time and cost. the dynamic optimum designs of stiffened plate that control the natural frequency and minimize weight subjected to constraints condition are derived. The way to apply the multi-level optimization methods in this study follow: In the first step the dynamic characteristics is controlled for the two-dimensional model of stiffened plate by sensitivity analysis and quasi-least squares methods. In the second step the cross-section of the stiffener is decided so that the weight is minimized under needed constraints by the steepest descent or ascent method. In the third the three-dimensional model is made based on the results of the first step and the second step confirmation and finer tuning of the objective function are carried out. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate.