• Journal of Power Electronics
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• v.15 no.3
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• pp.644-651
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• 2015

This paper introduces a novel digital one cycle control (DOCC) boost power factor correction (PFC) converter. The proposed PFC converter realizes the FPGA-based DOCC control approach for single-phase PFC rectifiers without input voltage sensing or a complicated two-loop compensation design. It can also achieve a high power factor and the operation of low harmonic input current ingredients over universal loads in continuous conduction mode. The trailing triangle modulation adopted in this approach makes the acquisition of the average input current an easy process. The controller implementation is based on a boost topology power circuit with low speed, low-resolution A/D converters, and economical FPGA development board. Experimental results demonstrate that the proposed PFC rectifier can obtain a PF value of up to 0.999 and a minimum THD of at least 1.9% using a 120W prototype.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.252-257
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• 1998

Two-stage power factor correction (PFC) converter with a single PWM controller for universal input voltage (90-264V) is proposed. It consists of a power factor pre-regulator cascaded by a DC/DC converter as in a conventional two-stage approach. However, a single PWM controller is used as in a single-stage, single-switch PFC approach. The switch in the PFC part is synchronized with the switch in the DC/DC converter with a fixed switching frequency. Employing an adaptive delay scheme the switch in the PFC part is controlled to limit the energy storage capacitor voltage within a designed range for the optimum efficiency, and to reduce input current harmonic distortion. The experimental results obtained on a 200W (5V/40A) prototype PFC converter are given to verify the effectiveness of the proposed control method.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.11
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• pp.63-71
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• 2010

FormFactors is one of the most critical design factors in early development of mobile phone, and proper selection of FormFactors is necessary for smoothness of product development and customer satisfaction. Especially, emergence of mobile convergence added so various functions besides its original call function that importance of selecting FormFactors has increased because multiform FormFactors are needed. However there is problem such as frequent change of decision making in existing process because established process picks out FormFactors sensibly and arbitrarily through idea pull and so forth. We proposed FormFactors selection process by Axiomatic Design, set approach method and block approach method for reasonable and systematical FormFactors selection. First of all, we set the purpose of mobile phone development, and it is examined by Axiomatic Design. FormFactors design matrix is deduced through this process, the numbers of axes and rails are proposed using set approach method, and then patterns of FormFactors are embodied by block approach method. Particularly process application was tried through case study of mobile phone development, and we ensured that new FormFactors can be presented to a designer by systematical verification if change of customer requirements occurs through our process.

• Asian Journal of Atmospheric Environment
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• v.4 no.3
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• pp.150-156
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• 2010

Inter-comparison of chemical transport models (CTMs) was conducted among four modeling research groups. Model performance of the ensemble approach to $O_3$ and $PM_{2.5}$ simulation was evaluated by using observational data with a time resolution of 1 or 6 hours at four sites in the Kanto area, Japan, in summer 2007. All groups applied the Community Multiscale Air Quality model. The ensemble average of the four CTMs reproduced well the temporal variation of $O_3$ (r=0.65-0.85) and the daily maximum $O_3$ concentration within a factor of 1.3. By contrast, it underestimated $PM_{2.5}$ concentrations by a factor of 1.4-2, and did not reproduce the $PM_{2.5}$ temporal variation at two suburban sites (r=~0.2). The ensemble average improved the simulation of ${SO_4}^{2-}$, ${NO_3}^-$, and ${NH_4}^+$, whose production pathways are well known. In particular, the ensemble approach effectively simulated ${NO_3}^-$, despite the large variability among CTMs (up to a factor of 10). However, the ensemble average did not improve the simulation of organic aerosols (OAs), underestimating their concentrations by a factor of 5. The contribution of OAs to $PM_{2.5}$ (36-39%) was large, so improvement of the OA simulation model is essential to improve the $PM_{2.5}$ simulation.

• Journal of the Optical Society of Korea
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• v.9 no.1
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• pp.6-12
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• 2005

The perturbation approach is applied to solve the nonlinear Schrodinger equation, and its valid range has been determined by comparing with the results of the split-step Fourier method over a wide range of parameter values. With γ= 2㎞/sup -1/mW/sup -1/, the critical distance for the first order perturbation approach is estimated to be(equation omitted). The critical distance, Z/sub c/, is defined as the distance at which the normalized square deviation compared to the split-step Fourier method reaches 10/sup -3/. Including the second order perturbation will increase Z/sub c/ more than a factor of two, but the increased computation load makes the perturbation approach less attractive. In addition, it is shown mathematically that the perturbation approach is equivalent to the Volterra series approach, which can be used to design a nonlinear equalizer (or compensator). Finally, the perturbation approach is applied to obtain the sinusoidal response of the fiber, and its range of validity has been studied.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.1
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• pp.75-84
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• 2013

In this paper, the guidance law for formation flight and collision avoidance of multiple Unmanned Aerial Vehicle (UAV)s is proposed. To construct the physically comprehensible guidance law for formation flight, the virtual structure approach is used. To develop a guidance law for collision avoidance considering both other UAVs and unknown static obstacles, a geometric approach using information such as a relative position vector is utilized. Through the Lyapunov theorem, the stability of the proposed guidance law is proved. To combine guidance commands, the concept of the elastic weighting factor inspired by the elastic behavior of shape memory polymer, which tends to regain its original shape after deformation, is introduced. By using the concept of elastic weighting factor, multiple UAVs are able to cope actively with the situation of a collision between both UAVs and static obstacles during the formation flight. To verify the performance of the proposed method, numerical simulations are performed.

• Communications for Statistical Applications and Methods
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• v.7 no.1
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• pp.141-150
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• 2000

In this paper we propose a method of computing Bayes factor to detect an outlier in a random effects model. When no information is available and hence improper noninformative priors should be used Bayes factor includes the unspecified constants and has complicated computational burden. To solve this problem we use the fractional Bayes factor (FBF) of O-Hagan(1995) and the generalized Savage0-Dickey density ratio of Verdinelli and Wasserman (1995) The proposed method is applied to outlier deterction problem We perform a simulation of the proposed approach with a simulated data set including an outlier and also analyze a real data set.

• Journal of the Korean Statistical Society
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• v.25 no.4
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• pp.577-588
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• 1996

The Bayes factor provides a possible hierarchical Bayesian approach for studying the change point problems. A hypothesis for testing change versus no change is considered using predictive distributions. When the underlying distribution is in one-parameter exponential family with conjugate priors, Bayes factors are investigated to the hypothesis above. Finally one example is provided .

• 한국데이터정보과학회:학술대회논문집
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• 2004.04a
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• pp.131-139
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• 2004

Robust parameter design is to identify appropriate settings of control factors that make the system's performance robust to changes in the noise factors that represent the source of variation. In this paper, we introduce a factor analysis approach to simultaneously optimize multiple quality characteristics in the robust parameter design. An example is illustrated to compare it with already proposed method.

• Korean Journal of Oriental Medicine
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• v.13 no.3
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• pp.21-27
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• 2007

Most of studies on tobacco have researched it as economic or cultural factor. These studies, certainly, have the value of their own. But from time to time these studies have brought about romantic view regarding tobacco, and have been an obstacle to approach it as a medical factor. Thus this thesis will introduce documents of tobacco as medical factor. Through it we will be able to furnish researchers with information to treat poison caused by tobacco.