• Nuclear Engineering and Technology
• /
• 제50권1호
• /
• pp.35-42
• /
• 2018

This article presents clean core criticality calculations and control rod worth calculations for TRIGA (Training, Research, Isotope production-General Atomics) Mark II research reactor benchmark cores using Winfrith Improved Multi-group Scheme-D/4 (WIMS-D/4) and Program for Reactor In-core Analysis using Diffusion Equation (PRIDE) codes. Cores 133 and 134 were analyzed in 2-D (r, ${\theta}$) and 3-D (r, ${\theta}$, z), using WIMS-D/4 and PRIDE codes. Moreover, the influence of cross-section data was also studied using various libraries based on Evaluated Nuclear Data File (ENDF/B-VI.8 and VII.0), Joint Evaluated Fission and Fusion File (JEFF-3.1), Japanese Evaluated Nuclear Data Library (JENDL-3.2), and Joint Evaluated File (JEF-2.2) nuclear data. The simulation results showed that the multiplication factor calculated for all these data libraries is within 1% of the experimental results. The reactivity worth of the control rods of core 134 was also calculated with different homogenization approaches. A comparison was made with experimental and reported Monte Carlo results, and it was found that, using proper homogenization of absorber regions and surrounding fuel regions, the results obtained with PRIDE code are significantly improved.

• 대한의용생체공학회:의공학회지
• /
• 제32권3호
• /
• pp.207-217
• /
• 2011

Electrode impedances are measured to quantitatively characterize the electrode-electrolyte or cell-electrode interfaces. In the case of high-density microelectrode arrays(MEAs) that have been developed for brainmachine interface applications, the characterization process becomes a repeating and time-consuming task; a system that can perform the measurement and analysis in an automated fashion with accuracy and speed is required. However, due to the large number of channels, parasitic capacitance and off-capacitance components of the switching system become the major factors that decreased the accuracy for the measurement of high impedance microelectrodes. Here we investigated the implementation of automatic impedance measurement system with analyzing the causes of possible measurement-related problems in multichannel switching configuration. Based on our multi-channel measurement circuit model, we suggest solutions to the problems and introduce a novel impedance measurement scheme using electro-mechanical relays. The implemented measurement system could measure |Z| < 700 $k{\Omega}$ of impedance in - 10% errors, which can be widely applicable to high density neural recording MEAs.

• Asian-Australasian Journal of Animal Sciences
• /
• 제17권6호
• /
• pp.794-798
• /
• 2004

An attempt was made to improve the efficiency of growth and lactation performance of dairy heifers subjected to a stair-step growth scheme using rice straw as the sole roughage source. Twenty-four young Holstein heifers were randomly assigned to either control or test group. The control diet met the National Research Council (NRC) requirement, with heifers calving at 24 to 26 mo of age. The test group was individually fed according to a schedule of 3, 2, 4, 2, 5 and 2 mo in which feed intake was alternately 20% below or 25% above the NRC requirements. Heifers on the stair-step growth pattern gained more body weight and consumed less dry matter (10.80 and 11.22%, respectively), resulting an increasing growth efficiency compared with the control. Body condition, first estrus, first conception, services per conception and calving difficulty (data not shown) were not affected. Milk yield of the test group was 8.5% higher than that of the control group. During the early lactation period, the milk yield was significantly higher in the stair-step group than in that of the control group (p<0.05). Milk composition was not affected by compensatory growth induced by the stair-step scheme. Also, weight at calving and calf growth performance was not affected by stair-step growth. The results indicate that using rice straw as a sole roughage source in a stair-step compensatory growth scheme can contribute to the improvement of growth efficiency and early lactation performance.

• 한국기후변화학회지
• /
• 제8권3호
• /
• pp.221-230
• /
• 2017

There are two main policies to meet the national goal of reducing Greenhouse Gases (GHGs) emissions in Korea towards Paris Agreement. From 2012 to 2014, Target Management System (TMS) was operated and the Emissions Trading Scheme (ETS) has been established since 2015. To compare the impact of TMS and ETS on reducing GHGs, we collected annual GHGs emission reports submitted by individual business entities, and normalized them using a z-variant normalized function. In order to evaluate the impact of those policies, we calculated the amount of GHGs emissions of 73 business entities from 15 business sectors. Those entities emitted $508million\;CO_2eq$, which is 74% of total national GHGs emissions in 2014. The main results of analysis indicate that accumulated GHGs emissions during the period 2012 to 2014 affected by TMS was higher than the national goal of GHGs emission reduction, and only the GHGs emissions in 2014 were in the range of allowed GHGs emissions, set by the Government. In 2015, when ETS initiated, total GHGs emission trading was $4.84million\;tCO_2eq$, which is only 0.9% of total allowance in 2015. However, more than 50% of business entities, who got the allowance of GHGs emission given by the Government, met the goal of GHGs emissions. Particularly, 27 of 73 business entities reduced GHGs more under the ETS rather than the TMS. Even though we analyzed only 4 years' data to demonstrate the impact of TMS and ETS, it is expected to commit the national goal of GHGs reduction target by TMS and ETS.

• 대한자기공명의과학회:학술대회논문집
• /
• 대한자기공명의과학회 2002년도 제7차 학술대회 초록집
• /
• pp.133-133
• /
• 2002

Purpose： The purpose of paper is to implement software to visualize brain fiber tract using a 24-bit color coding scheme and to test its feasibility. Materials and Methods： MR imaging was performed on GE 1.5 T Signa scanner. For diffusion tensor image, we used a single shot spin-echo EPI sequence with 7 non-colinear pulsed-field gradient directions： (x, y, z)：(1,1,0),(-1,1,0),(1,0,1),(-1,0,1),(0,1,1),(0,1,-1) and without diffusion gradient. B-factor was 500 sec/$\textrm{mm}^2$. Acquisition parameters are as follows： TUTE=10000ms/99ms, FOV=240mm, matrix=128${\times}$128, slice thickness/gap=6mm/0mm, total slice number=30. Subjects consisted of 10 normal young volunteers (age：21∼26 yrs, 5 men, 5 women). All DTI images were smoothed with Gaussian kernel with the FWHM of 2 pixels. Color coding schemes for visualization of directional information was as follows. HSV(Hue, Saturation, Value) color system is appropriate for assigning RGB(Red, Green, and Blue) value for every different directions because of its volumetric directional expression. Each of HSV are assigned due to (r,$\theta$,${\Phi}$) in spherical coordinate. HSV calculated by this way can be transformed into RGB color system by general HSV to RGB conversion formula. Symmetry schemes： It is natural to code the antipodal direction to be same color(antipodal symmetry). So even with no symmetry scheme, the antipodal symmetry must be included. With no symmetry scheme, we can assign every different colors for every different orientation.(H =${\Phi}$, S=2$\theta$/$\pi$, V=λw, where λw is anisotropy). But that may assign very discontinuous color even between adjacent yokels. On the other hand, Full symmetry or absolute value scheme includes symmetry for 180$^{\circ}$ rotation about xy-plane of color coordinate (rotational symmetry) and for both hemisphere (mirror symmetry). In absolute value scheme, each of RGB value can be expressed as follows. R=λw｜Vx｜, G=λw｜Vy｜, B=λw｜Vz｜, where (Vx, Vy, Vz) is eigenvector corresponding to the largest eigenvalue of diffusion tensor. With applying full symmetry or absolute value scheme, we can get more continuous color coding at the expense of coding same color for symmetric direction. For better visualization of fiber tract directions, Gamma and brightness correction had done. All of these implementations were done on the IDL 5.4 platform.

• Structural Engineering and Mechanics
• /
• 제20권2호
• /
• pp.241-257
• /
• 2005

A numerical approach combining the finite element method with two different stability criteria namely the Budiansky and the phase-plane buckling criteria is used to study the dynamic buckling phenomena of plate and shell structures subjected to sudden applied loading. In the finite element analysis an explicit time integration scheme is used and the two criteria are implemented in the Finite Element analysis. The dynamic responses of the plate and shell structures have been investigated for different values of the plate and shell imperfection factors. The results indicate that the dynamic buckling time, which is normally considered in predicting elasto-plastic buckling behavior, should be taken into consideration with the buckling criteria for elastic buckling analysis of plate and shell structures. By selecting proper control variables and incorporating them with two dynamic buckling criteria, the unique dynamic buckling load can be obtained and the problems of ambiguity and contradiction of dynamic buckling load of plate and shell structure can be resolved.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.57-61
• /
• 2006

In the single-phase switched reluctance motor (SRM) drive, the required DC source is generally supplied by the circuit consisting of bridge rectifier and large filter capacitor connected with DC line terminal. Due to the large capacity of the capacitor, the charged time of capacitor is very short from the AC source. Lead to the bridge rectifiers draws pulsating current from the AC source side, which results in reduction of power factor and low system efficiency. Therefore a novel single-phase SRM drive system is presented in this paper, which includes drive circuit realizing reduction of torque ripple and improvement of power factor with a novel switching topology. The proposed drive circuit consists of one switching part and diode, which can separate the output of AC/DC rectifier from the large capacitor and supply power to SRM alternately, in order to realize the torque ripple reduction and power factor improvement through the switching scheme. In addition, the validity of the proposed method is tested by some simulations and experiments.

• 대한전기학회논문지
• /
• 제35권7호
• /
• pp.296-303
• /
• 1986

The active filter of current injection type is the device which eliminates the harmonics in ac line by injecting the harmonic compensating current into the ac side. And its harmonic reduction performance is entirely dependent on the control scheme of the current-fed inverter and the harmonic compensating current becomes the PWM wave by the inverter. This PWM compensating current can be determined by selecting the switching function properly which eliminates the harmonics up to any order with using no independent sources. The new injection current model is derived by the proposed method which is called the optimized injection method. The overall characteristics of the proposed method are investigated through digital computation and the feasibility is proved with experimental results obtained from the Z-80 microcomputer control of the active filter.

• 대한전기학회논문지
• /
• 제36권5호
• /
• pp.352-359
• /
• 1987

The cycloconverter operating on a circulating current-free mode has many zero crossing points. If an exact zero crossing points are not detected, the three phase-unbalanced currents will flow in a motor. In this paper, the current feedback using a current reference wave is proposed to improve the problems of zero crossing detection, three phase-unbalanced voltages, currents, and torgue ripples. To prevent the saturation of the air gap flux and keep the torque constant, the constant voltage / hertz control with IR compensation is adopted. The PI-controller is designed using the linearized model of the cycloconverterinduction motor system. Alsi, Z-80A single board computer has been used to implement the proposed scheme which results in the performance improvement of cycloconterter-fed induction motor speed control system.

• 한국지능시스템학회:학술대회논문집
• /
• 한국퍼지및지능시스템학회 2003년도 ISIS 2003
• /
• pp.492-495
• /
• 2003

Fuzzy Min-Max Neural Network(FMMNN) is a powerful classifier, It has, however, some problems. Learning result depends on the presentation order of input data and the training parameter that limits the size of hyperbox. The latter problem affects the result seriously. In this paper, the new approach to alleviate that without loss of on-line learning ability is proposed. The committee machine is used to achieve the multi-resolution FMMNN. Each expert is a FMMNN with fixed training parameter. The advantages of small and large training parameters are used at the same time. The parameters are selected by performance and independence measures. The Decision of each expert is guided by the gating network. Therefore the regional and parametric divide and conquer scheme are used. Simulation shows that the proposed method has better classification performance.