• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.1
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• pp.60-65
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• 2000

The virtual mass of net is an important parameter in the analysis and control of net movement in the water. This experiment was performed with the purpose of getting a relation on the quantity of netting and virtual mass of trawl nets using the circulating water channel that can control flow speed. Twelve types of conical nets were examined. Resistance of the conical net at the steady and acceleration state was recorded as text on the personal computer through the tension meter and current meter. The results were obtained as follows ;1. Resistance(R) of the conical net is proportional to the degree of attack angle in the sam e amount of twine material.2. Coefficient of the resistance(Cd)could be defined by the following regression model as a function of Reynolds Number(Re). Cd=0.039Re-0.14743. Resistance(R) is proportional to TSA(Twine surface area) and defined as follows; R=21.398TSA-0.12194. Coefficient of virtual mass(CM) could be calculated by the following first order regression model. CM=37.557U-8.96845. Virtual mass is directly proportional to Volume of net(V) or d/l.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.11
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• pp.1009-1014
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• 2013

In the present study, using a variation of rib height, the transient response and the performance are investigated. The cell voltage is acquired according to the current density change($0.8A/cm^2$ to $1.0A/cm^2$) under same stoichiometry and relative humidity. The different level of undershoots appeared at the different clamping pressure(1.5MPa and 2.0MPa) and different rib height. At 1.5MPa clamping pressure, rib manufactured cut at $100{\mu}m$ height goes to steady state faster than reference plate and has lower maximum undershoot voltage. But performance is lower than reference plate due to increasing contact resistance.

• Journal of Veterinary Clinics
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• v.24 no.1
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• pp.5-9
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• 2007

The purpose of this study was to examine the allometric analysis of roxithromycin using pharmacokinetic data. The pharmacokinetic parameters used were $half-life(t_{1/2})$, mean residence time (MRT), clearance (Cl) and volume of distribution at steady state $(V_{ss})$. Relationships between body weight and the pharmacokinetic parameter were based on the empirical formula $Y=aW^b$, where 'Y' is $t_{1/2}$, MRT, Cl, or $V_{ss}$, W the body weight and 'a' is an allometric coefficient (intercept) that is constant for a given drug. The exponential term, 'b', is a proportionality constant that describes the relationship between the pharmacokinetic parameter of interest and body weight. As results of the allometric analyses, the logarithms of $t_{1/2}$, MRT, Cl, and $V_{ss}$ were linearly related to the logarithms of body weight. Results of the current analyses could provide information on appropriate doses of roxithromycin for all species.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.2
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• pp.71-82
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• 1984

A programme, called BIPOLE, for the numerical analysis of twotimensional n-p-n bipolar transistors was developed. It has included the SRH and Auger recolnbination processes, the mobility dependence on the impurity density and the electric field, and the band-gap narrowing effect. The finite difference equations of the fundamental semiconductor equations are formulated using Newton's method for Poisson's equation and the divergence theorem for the hole and electron continuity equations without physical restrictions. The matrix of the linearized equations is sparse, symmetric M-matrix. For the solution of the linearized equations ICCG method and Gummel's algorithm have been employed. The programme BIPOLE has been applied to various kinds of the steady-state problems of n-p-n transistors. For the examples of applications the variations of common emitter current gain, emitter and diffusion capacitances, and input and output characteristics are calculated. Three-dimensional representations of some D.C. physical quantities such as potential and charge carrier distributions were displayed. This programme will be used for the nome,rical analysis of the distortion phenom ana of two-dimensional n-p-n transistors. The BIPOLE programme is available for everyone.

• Bulletin of the Korean Chemical Society
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• v.27 no.1
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• pp.65-70
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• 2006

An amperometric glucose biosensor has been developed based on the use of the nanoporous composite film of sol-gel-derived zirconia and perfluorosulfonated ionomer, Nafion, for the encapsulation of glucose oxidase (GOx) on a platinized glassy carbon electrode. Zirconium isopropoxide (ZrOPr) was used as a sol-gel precursor for the preparation of zirconia/Nafion composite film and the performance of the resulting glucose biosensor was tuned by controlling the water content in the acid-catalyzed hydrolysis of sol-gel stock solution. The presence of Nafion polymer in the sol-gel-derived zirconia in the biosensor resulted in faster response time and higher sensitivity compared to those obtained at the pure zirconia- and pure Nafion-based biosensors. Because of the nanoporous nature of the composite film, the glucose biosensor based on the zirconia/Nafion composite film can reach 95% of steady-state current less than 5 s. In addition, the biosensor responds to glucose linearly in the range of 0.03-15.08 mM with a sensitivity of 3.40 $\mu$A/mM and the detection limit of 0.037 mM (S/N = 3). Moreover, the biosensor exhibited good sensor-to-sensor reproducibility (~5%) and long-term stability (90% of its original activity retained after 4 weeks) when stored in 50 mM phosphate buffer at pH 7 at 4 ${^{\circ}C}$.

• Korean Journal of Clinical Pharmacy
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• v.19 no.1
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• pp.50-60
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• 2009

Highly variable drugs (within-subject variability greater than 30%) have been difficult to meet current regulatory acceptance criteria using a reasonable number of study subjects. In this study, we reviewed previous studies presenting alternative approaches for bioequivalence evaluation of highly variable drugs, and focused on an approach for widening the bioequivalence acceptance limits using within-subject variability. We discussed the suggested five solutions for highly variable drug including the deletion of $C_{max}$ of the bioequivalence criteria, direct expansion of bioequivalence limit, multiple dose studies in steady state, bioequivalence assessment on the metabolite, add-on study, and widening the bioequivalence acceptance limits based on reference variability. The methods for widening of bioequivalence limits based on reference variability are scaled average bioequivalence containing within-subject variability on reference drug (${\sigma}_{WR}$), population bioequivalence derived from total variability on reference drug (${\sigma}_{TR}$) and test drug (${\sigma}_{TT}$), and individual bioequivalence derived from subject by formulation interaction variability (${\sigma}_D$) and within subject variability on reference drug (${\sigma}_{WR}$) and test drug (${\sigma}_{TR}$). To apply these methods, the switching variability (${\sigma}_0$) will have to be set by the regulatory authorities. The proposals of bioequivalence evaluation approach for the highly variable in Korea are presented for both of new drug and reevaluation drug.

• Journal of Communications and Networks
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• v.15 no.1
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• pp.77-86
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• 2013

Cognitive radio (CR) has emerged as one of effective methods to enhance the utilization of existing radio spectrum. Main principle of CR is that secondary users (SUs) are allowed to use the spectrum unused by primary users (PUs) without interfering PU's transmissions. In this paper, PUs operate on a slot-by-slot basis and SUs try to exploit the slots unused by PUs. We propose OSA protocols in the single channel and we propose an opportunistic spectrum access (OSA) protocols in the multi-channel cognitive radio networks with one control channel and several licensed channels where a slot is divided into contention phase and transmission phase. A slot is divided into reporting phase, contention phase and transmission phase. The reporting phase plays a role of finding idle channels unused by PUs and the contention phase plays a role of selecting a SU who will send packets in the data transmission phase. One SU is selected by carrier sense multiple access / collision avoidance (CSMA/CA) with request to send / clear to send (RTS/CTS) mechanism on control channel and the SU is allowed to occupy all remaining part of all idle channels during the current slot. For mathematical analysis, first we deal with the single-channel case and we model the proposed OSA media access control (MAC) protocol by three-dimensional discrete time Markov chain (DTMC) whose one-step transition probability matrix has a special structure so as to apply the censored Markov chain method to obtain the steady state distribution.We obtain the throughput and the distribution of access delay. Next we deal with the multi-channel case and obtain the throughput and the distribution of access delay by using results of single-channel case. In numerical results, our mathematical analysis is verified by simulations and we give numerical results on throughput and access delay of the proposed MAC protocol. Finally, we find the maximum allowable number of SUs satisfying the requirements on throughput and access delay.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.356-362
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• 2005

In this paper, in order to develop a simple and high efficient ballast without an external ignitor, a half-bridge type ballast with a coupled inductor and a frequency controlled synchronous rectifier is proposed. The Internal LC resonance of the buck converter is used to generate a high voltage pulse for the ignition, and the coupled inductor filter is used for steady state ripple cancellation. Also, a synchronous buck converter is applied for the DC/DC converter stage. In order to improve the efficiency of the ballast, a frequency control method is proposed. This scheme reduces a circulation current and trun off loss of the MOSFET switch on the constant power operation, which results in increase of the efficiency of the ballast system about 4$\%$, compared to a fixed frequency control. It consists a 2-stage version ballast with a PFC circuit. The results are verified nth hardware experiments.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.3
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• pp.147-154
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• 2003

This paper presents a high-frequency boost type ZVS-PWM chopper-fed DC-DC power converter with a single active auxiliary edge-resonant snubber at the load stage which can be designed for power conditioners such as solar photovoltaic generation, fuel cell generation, battery and super capacitor energy storages. Its principle operation in steady-state is described in addition to a prototype setup. The experimental results of boost type ZVS-PWM chopper proposed here, are evaluated and verified with a practical design model in terms of its switching voltage and current waveforms, the switching v-i trajectory and the temperature performance of IGBT module, the actual power conversion efficiency, and the EMI of radiated and conducted emissions, and then discussed and compared with the hard switching scheme from an experimental point of view. Finally, this paper proposes a practical method to suppress parasitic oscillation due to the active auxiliary resonant switch at ZCS turn-off mode transition with the aid of an additional lossless clamping diode loop, and can be reduced the EMI conducted emission.

• Journal of Power Electronics
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• v.13 no.3
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• pp.369-380
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• 2013

Direct torque control based on space vector modulation (SVM-DTC) protects the DTC transient merits. Furthermore, it creates better quality steady-state performance in a wide speed range. The modified method of DTC using SVM improves the electrical magnitudes of asynchronous machines, such as minimizing the stator current distortions, the stator flux with electromagnetic torque without ripple, the fast response of the rotor speed, and the constant switching frequency. In this paper, the proposed method is based on two new control strategies for direct torque control with space vector modulation. First, fuzzy logic control is used instead of the PI torque and a PI flux controller to minimizing the torque error and to achieve a constant switching frequency. The voltages in the direct and quadratic reference frame ($V_d$, $V_q$) are achieved by fuzzy logic control. In this scheme, the switching capability of the inverter is fully utilized, which improves the system performance. Second, the close loop of stator flux estimation based on the voltage model and a low pass filter is used to counteract the drawbacks in the open loop of the stator flux such as the problems saturation and dc drift. The response of this new control strategy is compared with DTC-SVM. The experimental and simulation results demonstrate that the proposed control topology outperforms the conventional DTC-SVM in terms of system robustness and eliminating the bad outcome of dc-offset.