• Transactions on Electrical and Electronic Materials
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• 제18권5호
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• pp.287-297
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• 2017

Novel power system stabilizers (PSSs) have been proposed to effectively dampen low frequency oscillations (LFOs) in multi-machine power systems and have attracted increasing research interest in recent years. Due to this attention, recently, fractional order controllers (FOCs) have found new applications in power system stability issues. Here, a tilt-integral-derivative power system stabilizer (TID-PSS) is proposed to enhance the dynamic stability of a multi-machine power system by providing additional damping to the LFOs. The TID is an extended version of the classical proportional-integral-derivative (PID) applying fractional calculus. The design of the proposed three-parameter tunable TID-PSS is systematized as a nonlinear time domain optimization problem in which the tunable parameters are adjusted concurrently using a modified group search optimization (MGSO) algorithm. An integral of the time multiplied squared error (ITSE) performance index is considered as the objective function. The proposed stabilizer is simulated in the MATLAB/SIMULINK environment using the FOMCON toolbox and the dynamic performance is evaluated on a 3-machine 6-bus power system. The TID-PSS is compared with both classical PID-PSS (PID-PSS) and conventional PSS (CPSS) using eigenvalue analysis and time domain simulations. Sensitivity analyses are performed to assess the robustness of the proposed controller against large changes in system loading conditions and parameters. The results indicate that the proposed TID-PSS provides the better dynamic performance and robustness compared with the PID-PSS and CPSS.

• 대한본초학회지
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• 제20권3호
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• pp.43-49
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• 2005

Objectives : The present study was carried out to determine if Glycyrrhizae Radix extract exerts beneficial effect against the ischemia-induced acute renal failure in rabbits. Glycyrrhizae Radix was known to reinforce the function of the spleen and replenish Qi, remove heat and counteract toxicity, dispel phlegm and relieve cough, alleviate spasmodic pain, and to moderate drug actions. It's indications are weakness of the spleen and the stomach marked by lassitude and weakness; cardiac palpitation and shortness of breath; cough with much phlegm: spasmodic pain in the epigastrium, abdomen and limbs: carbuncles and sores. It is often used for reducing the toxic or drastic actions of other drugs. Methods : Antioxidative effect of 3% concentration of Glycyrrhizae Radix extract was measured. Rabbits were treated with Glycyrrhizae Radix extract via i.v., followed by renal ischemia/reperfusion, and the changes of urine volume, serum creatinine levels, glomerular filtration rate(GFR), fractional Na+ excretion$(FE\;Na^+)\;and\;K^+\;excretion(FE\;K^+)$ in ischemia/reperfusion induced acute renal failure were measured. Results : Renal ischemia/reperfusion caused increase of serum creatinine level, which was accompanied by a reduction in glomerular filtration rate(GFR). The fractional excretion of $Na^+\;and\;K^+$ increased in ischemia-induced animals, which was partially prevented by Glycyrrhizae Radix extract treatment. Conclusions : These results indicate that lipid peroxidation plays a critical role in ischemia-induced acute renal failure. Glycyrrhizae Radix extract exerts the protective effect against acute renal failure induced by renal ischemia/reperfusion, and its effect may be attributed to an antioxidant action.

• 한국진공학회지
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• 제7권4호
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• pp.374-380
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• 1998

글로벌 모델을 사용하여 $CF_4$ 플라즈마 내부에서의 각 중성 및 이온 라디칼 밀도를 계산하였다. 중성 입자로서는 플루오린 원자가 가장 많고, 높은 입력 전력 조건의 경우 CF 나 $CF^+$와 같은 저 분자 해리종이 주종을 이룬다. 압력이 증가 할수록 하전 입자의 밀도는 증가하나 전자 온도의 감소로 이온화율은 감소한다. 공급 가스인 $CF_4$의 해리율은 압력에 따 라 증가한후 다시 감소하는 양상을 보인다. 전자 온도 및 밀도는 입력유량에 대해서 거의 변화가 없다. $CF_4$의 해리율은 유량 증가에 따라 선형적으로 감소하며 이는 $CF_3$의 증가와 CF의 감소로 이어진다. 식각 실험 결과와의 비교를 통해 플루오로 카본 이온종 및 높은 C/F비를 갖는 중성 라디칼의 상대적 밀도 증가가 $SiO_2$/Si식각 선택도 향상에 주요함을 알 수 있다.

• 동의생리병리학회지
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• 제20권1호
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• pp.98-102
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• 2006

The present stuby was carried out to determine if Radix Glycyrrhizae extract exerts beneficial effect against the ischemia-induced acute renal failure in rabbits. Radix Glycyrrhizae was known to reinforce the function of the spleen and replenish Qi, remove heat and counteract toxicity, dispel phlegm and relieve cough, alleviate spasmodic pain, and to moderate drug actions. It's indications are weakness of the spleen and the stomach marked by lassitude and weakness; cardiac palpitation and shortness of breath; cough with much phlegm; spasmodic pain in the epigastrium, abdomen and limbs; carbuncles and sores. It is often used for reducing the toxic or drastic actions of other drugs. Rabbits were treated with Radix Glycyrrhizae extract via i.v., followed by renal ischemia/reperfusion. Fractional excretion of glucose and phosphate, lipid peroxidation and light microscopy were done to evaluate the beneficial effect of Radix Glycyrrhizae extract on ischemia/reperfusion induced acute renal failure. Renal ischemia/reperfusion caused increase of fractional excretion of glucose and phosphate increased in ischemia-induced animals, which was partially prevented by Radix Glycyrrhizae extract treatment. Ischemia/reperfusion increased lipid peroxidation, which was prevented by Radix Glycyrrhizae extract administration. And the beneficial effect of Radix Glycyrrhizae extract on ischemia/reperfusion induced kidney injury was shown through the light micrographic observation. These results indicate that lipid peroxidation plays a critical role in ischemia-induced acute renal failure. Radix Glycyrrhizae extract exerts the protective effect against acute renal failure induced by renal ischemia/reperfusion.

• 국제학술발표논문집
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• The 5th International Conference on Construction Engineering and Project Management
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• pp.467-474
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• 2013

Construction contactors must continuously seek to improve their cash flows, which reside at the heart of their financial success. They require careful planning, analysis, and optimization to avoid the risk of bankruptcy, remain profitable, and secure long-term growth. Sources of cash include bank loans and retained earnings, which are conceptually similar in that they both incur a cost of capital. Financial management therefore requires accurate yet customizable modeling capabilities that can quantify all expenses, including said cost of capital. However, currently existing cash flow models in construction engineering and management have strongly simplified the manner in which interest is assessed, which may even lead to overstating it at a disadvantage to contractors. The variable nature of cash balances, especially in the early phases of construction projects, contribute to this challenging issue. This research therefore extends a new cash flow model with an accurate interest calculation. It utilizes singularity functions, so called because of their ability to flexibly model changes across any number of different ranges. The interest function is continuous for activity costs of any duration and allows the realistic case that activities may begin between integer time periods, which are often calendar months. Such fractional interest calculation has hitherto been lacking from the literature. It also provides insights into the self-referential behavior of compound interest for variable cash balances. The contribution of this study is twofold; augmenting the corpus of financial analysis theory with a new interest formula, whose strengths include its generic nature and that it can be evaluated at any fractional value of time, and providing construction managers with a tool to help improve and fine-tune the financial performance of their projects.

• Wind and Structures
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• 제38권4호
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• pp.261-275
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• 2024

Before performing an experimental study on the downburst-generated wave, it is necessary to examine the scale effects and corresponding corrections or compensations. Analysis of similarity is conducted to conclude the non-dimensional force ratios that account for the dynamic similarity in the interaction of downburst with wave between the prototype and the scale model, along with the corresponding scale factors. The fractional volume of fluid (VOF) method in association with the impinging jet model is employed to explore the characteristics of the downburst-generated wave numerically, and the validity of the proposed scaling method is verified. The study shows that the location of the maximum radial wind velocity in a downburst-wave field is a little higher than that identified in a downburst over the land, which might be attributed to the presence of the wave which changes the roughness of the underlying surface of the downburst. The impinging airflow would generate a concavity in the free surface of the water around the stagnation point of the downburst, with a diameter of about two times the jet diameter (D_jet). The maximum wave height appears at the location of 1.5D_jet from the stagnation point. Reynolds number has an insignificant influence on the scale effects, in accordance with the numerical investigation of the 30 scale models with the Reynolds number varying from 3.85 × 10⁴ to 7.30 × 10⁹. The ratio of the inertial force of air to the gravitational force of water, which is denoted by G, is found to be the most significant factor that would affect the interaction of downburst with wave. For the correction or compensation of the scale effects, fitting curves for the measures of the downburst-wave field (e.g., wind profile, significant wave height), along with the corresponding equations, are presented as a function of the parameter G.

• 대한의용생체공학회:의공학회지
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• 제29권2호
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• pp.114-121
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• 2008

Within 2 to 5 months after stroke, patients recover variable degrees of function, depending on the initial deficit. An impaired hand function is one of the most serious disability in chronic stroke patients. Therefore, to evaluate the extent of motor dysfunction in the hemiplegic hand is important in stroke rehabilitation. In this paper, motor recoveries in 8 chronic stroke patients with Fugl-Meyer (FM) and white matter changes before and after the training program with a designed bilateral symmetrical arm trainer (BSAT) system were examined. The training was performed at 1 hr/day, 5 days/week during 6weeks. In all patients, FM was significantly improved after the 6-week training. Diffusion tensor imaging (DTI) results showed that tractional anisotropy ratio (FAR) and fiber tracking ratio (FTR) in the posterior internal capsule were significantly increased after the training. It seemed that the cortical reorganization was induced by the 6 week training with the BSAT. In all parameters proposed this study, a significant correlation was found between these parameters (FAR and FTR) and motor recoveries. This study demonstrated that DTI technique could be useful in predicting motor recovery in chronic hemiparetic patients.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
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• pp.117-128
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• 1999

The removal of nitrogen oxides(NOx) from $N_{2}/O_{2}$ gas using a pulsed corona discharge was investigated as a function of the reduced electric field(E/N) and the energy density(J/L). A kinetic model was developed to characterize the chemical reactions taking place in a pulsed corona discharge reactor. The model calculates the fractional concentrations of radical species at each pulse-on period and utilizes the radicals to remove NOx for the subsequent pulse-off period. Electron collision reaction data are calculated using ELENDIF program to solve Boltzmann equation for electron energy distribution function, and the subsequent chemical reactions are calculated using CHEMKIN-II program to solve stiff ODE(ordinary differential equation) problems for species concentrations. The corona discharge energy per pulse and the time-space averaged E/N were obtained by fitting the model to experimental data. The model calculation shows good agreement with the experimental data, and predicts the formation of other species such as $NO_{2}$, $O_{3}$ and $N_{2}O$.

• 대한기계학회논문집A
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• 제29권7호
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• pp.921-929
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• 2005

This paper presents an accelerated life test for burnout of tungsten filament of incandescent lamp. From failure analyses of field samples, it is shown that their root causes are local heating or hot spots in the filament caused by tungsten evaporation and wire sag. Finite element analysis is performed to evaluate the effect of vibration and impact for burnout, but any points of stress concentration or structural weakness are not found in the sample. To estimate the burnout life of lamp, an accelerated life test is planned by using quality function deployment and fractional factorial design, where voltage, vibration, and temperature are selected as accelerating variables. We assumed that Weibull lifetime distribution and a generalized linear model of life-stress relationship hold through goodness of fit test and test for common shape parameter of the distribution. Using accelerated life testing software, we estimated the common shape parameter of Weibull distribution, life-stress relationship, and accelerating factor.

• Kyungpook Mathematical Journal
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• 제53권1호
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• pp.13-23
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• 2013

In this present work, the authors obtain Fekete-Szeg$\ddot{o}$ inequality for certain normalized analytic function $f(z)$ defined on the open unit disk for which $$\frac{{\lambda}{\beta}z^3(L(a,c)f(z))^{{\prime}{\prime}{\prime}}+(2{\lambda}{\beta}+{\lambda}-{\beta})z^2(L(a,c)f(z))^{{\prime}{\prime}}+z(L(a,c)f(z))^{{\prime}}}{{\lambda}{\beta}z^2(L(a,c)f(z))^{{\prime}{\prime}}+({\lambda}-{\beta})z(L(a,c)f(z))^{\prime}+(1-{\lambda}+{\beta})(L(a,c)f(z))}\;(0{\leq}{\beta}{\leq}{\lambda}{\leq}1)$$ lies in a region starlike with respect to 1 and is symmetric with respect to the real axis. Also certain applications of the main result for a class of functions defined by Hadamard product (or convolution) are given. As a special case of this result, Fekete-Szeg$\ddot{o}$ inequality for a class of functions defined through fractional derivatives are obtained.