• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.5
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• pp.615-623
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• 2016

The paper describes a hysteretic buck converter including a differentiator and an adaptive hysteresis window controller. Differentiating the feedback signal achieves ultra-fast switching of the buck converter. The adaptive hysteresis window control allows a monotonous operation with predictable noise spectrum, and gives way to efficient design for variable supply and output voltages. The measurement results in a $0.13-{\mu}m$ CMOS process indicated that the switching frequency became double times higher, and the voltage ripple was reduced by up to 69%. They also indicated that the normalized switching frequency variation was reduced by 74% with variable $V_{DD}$ and by 63% with variable $V_{OUT}$. The power efficiency was improved by 3.5% depending on loading condition.

• The Korean Journal of Applied Statistics
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• v.23 no.2
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• pp.357-366
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• 2010

Many tree algorithms have been developed for regression problems. Although they are regarded as good algorithms, most of them suffer from loss of prediction accuracy when there are many noise variables. To handle this problem, we propose the multi-step GUIDE, which is a regression tree algorithm with a variable selection process. The multi-step GUIDE performs better than some of the well-known algorithms such as Random Forest and MARS. The results based on simulation study shows that the multi-step GUIDE outperforms other algorithms in terms of variable selection and prediction accuracy. It generally selects the important variables correctly with relatively few noise variables and eventually gives good prediction accuracy.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.4
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• pp.9-17
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• 1996

This paper develops a sequential updating method of the Euler parameter generalized coordinates for the machine kinematics and dynamics, The Newton's method is slightly modified so as to utilize the Jacobian matrix with respect to the virtual rotation instead of this with repect to the Euler parameters. An intermediate variable is introduced and the modified Newton's method solves for the variable first. Relational equation of the intermediate variable is then solved for the Euler parameters. The solution process is carried out efficiently by symoblic inversion of the relational equation of the intermediate variable and the iteration equation of the Euler parameter normalization constraint. The proposed method is applied to a kinematic and dynamic analysis with the Generalized Coordinate Partitioning method. Covergence analysis is performed to guarantee the local convergence of the proposed method. To demonstrate the validity and practicalism of the proposed method, kinematic analysis of a motion base system and dynamic analysis of a vehicle are carried out.

• Journal of Biosystems Engineering
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• v.22 no.2
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• pp.105-116
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• 1997

Using the design variables and conditions reported in the rut part of this paper, an analysis and optimum design of the tractor-rotary power driveline were carried out. The optimum design method involved 1 variable, 2 variable and multiple variable analysis performed as requested in the design process. In order to evaluate the effects of the design variables on the power transmission performance a sensitivity analysis were also conducted. the results indicated that the length and link point of the upper link, the upper hitch point of the implement master and the location of the implement input connection affect most significantly the driveline performance. The optimum design improved the performance of an exampled tractor-rotary driveline by 93% in terms of cosine ratio.

• International Journal of Automotive Technology
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• v.6 no.5
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• pp.467-473
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• 2005

A continuously variable transmission (CVT) with an inner spherical traction drive was conceptually designed for bicycle usage. The range of the overall speed ratio is from 1.0 to 4.5. The rated power and pedal speed are 100 Watts and 6 rad/s, respectively. The peculiar packageability, high-level power efficiency and high torque capacity were considered in the design process. A compact CVT that can be installed within a $244\times125\times160mm^3$ space and is above 0.9 in efficiency for the rated values was numerically designed. The distribution of efficiency according to the input torque and input speed were calculated. Gradeability in the prescribed operation mode was simulated.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.257-261
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• 2008

The Digital Radio Mondiale (DRM) system is a digital broadcasting standard designed for use in the LF, MF and HF bands of the broadcasting bands below 30 MHz. The system provides both superior audio quality and improved user services / operability compared with existing AM transmissions. In this paper, we propose a variable point Prime Factor FFT design method for Digital Radio Mondiale (DRM) system. Proposed method processes a various size IFFT/FFT of Robustness Mode on DRM standard efficiently by composing Radix-Prime Factor FFT Processing Unit of form similar to Radix-4 by insertion of a variable Prime Factor Twiddle Factor and Garbage data. So, we improved limitation that cannot process 112/176/256/288 FFT of each mode of DRM system with a existent Radix Processor and increase memory size and memory access time for IFFT/FFT processing by software processing in case of implementation with a existent high speed DSP.

• Communications for Statistical Applications and Methods
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• v.26 no.1
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• pp.69-78
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• 2019

A structured model with both single-index and varying coefficients is a powerful tool in modeling high dimensional data. It has been widely used because the single-index can overcome the curse of dimensionality and varying coefficients can allow nonlinear interaction effects in the model. For high dimensional index vectors, variable selection becomes an important question in the model building process. In this paper, we propose an efficient estimation and a variable selection method based on a smoothing spline approach in a partially linear single-index-coefficient regression model. We also propose an efficient algorithm for simultaneously estimating the coefficient functions in a data-adaptive lower-dimensional approximation space and selecting significant variables in the index with the adaptive LASSO penalty. The empirical performance of the proposed method is illustrated with simulated and real data examples.

• Proceedings of the Materials Research Society of Korea Conference
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• 2001.05a
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• pp.139-139
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• 2001

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1994.04a
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• pp.79-79
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• 1994

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.7 no.2
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• pp.233-246
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• 1996

There have been great deal of studies on adult stress but comprehensive studies on adolescent stress are not sufficient. Because adolescents have different developmental tasks from adult's, and because they spend most of their time in a structured environment such as school, the research on adolescent stress is necessary. So, this study empirically investigated the types of stress and coping which students experience and their coping mechanisms in a stressful situation. In this study, perceived social support was considered as stuructural variable, and cognitive appraisal as a process variable, while existing researches tried to explain the coping mechanism only from the viewpoint of structure, or hypothesized the structure variable in the process term. The relation ships between cognitive appraisal and perceived social support on coping behavior were evaluated. Survey on 519 high school students in Seoul showed that cogitive appraisal was a structural variable which varied across the types of stress, and that perceived social support was a structure variable which was independent of the type of stress. Cognitive appraisal was related more to the qualitative process of stress appraisal than coping behavior, and perceived social support was an important structure which influenced both the appraisal process and coping behavior.