• 대한수의학회지
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• 제51권3호
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• pp.227-231
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• 2011

This study was undertaken to assess the lateral ventricle, which was some portion of brain and related to congenital anomalies, from 1, 2, 4, and 8 months of age in healthy micropigs. They were induced general anesthesia and performed magnetic resonance imaging (MRI) with a 0.3 Tesla magnet. Each age group was evaluated by three subjects such as lateral ventricular volume, ventricular volume ratio and asymmetry. T1 weighted transverse images were acquired for calculation of lateral ventricular and corresponding brain parenchyma areas. The ratio of bilateral ventricle areas used to analyze the asymmetry. The mean ventricular volumes of each month were $676.74{\pm}25.58mm^3$ (1 month-old), $630.64{\pm}143.84mm^3$ (2 month-old), $992.12{\pm}106.03mm^3$ (4 month-old) and $1172.62{\pm}237.57mm^3$ (8 month-old), respectively. The ventricular volume ratio was the smallest at 2 month-old and re-increased from that age. The ratio was significantly different between 2 month-old and other age groups (p < 0.05). The value of bilateral area ratio showed within 1.5 in all experimental animals. Consequently the lateral ventricle showed a positive correlation with aging and symmetric shapes in both sides. The developmental pattern of the lateral ventricle provides basic data in micropigs as an experimental animal model for physiological and neurosurgical approach.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.37-37
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• 1999

KSTAR(Korea Superconducting Tokamak Advanced Research) 핵융합 토카막 실험 장치의 플라즈마 가열을 위한 수소 중성입자빔 수송라인 내에 설치되는 collimator에 가해지는 열속 및 플라즈마에 전달되는 빔의 통과율을 해석하였다. 43cm$\times$12cm 크기의 이온원으로부터 방출되는 이온빔의 공간적 분산은 기본적으로는 Gaussian 분산(수직바향으로 1.2$^{\circ}$, 수평방향으로 0.5$^{\circ}$)의 형태를 가지지만 이온 가속 전장의 공간적 불균일로 인해 Gaussian 분산에서 다소 벗어나는 형태를 띠게 되는데, 이의 영향을 고려할 수 있는 수학적 모델을 정립하였다. 해석에 고려된 요소들은 다음과 같다. 이온원을 수많은 점원의 집합으로 가정하여 각각의 점원으로부터 주어진 공간적 분산을 가지는 이온들이 방출되는 것으로 가정하였으며, 방출된 이온은 중성화 과정을 거쳐 40%의 이온만이 중성입자화되며, 중성화되지 않은 60%의 이온들은 bending magnet에서 ion dump로 유도되어 사라지며, 나머지 중성입자들은 직진 운동을 하게 된다. 빔 진행 도중 빔 중앙에서 크게 벗어나는 일부 중성입자들은 여러 겹으로 존재하는 빔 collimator에 의해 단계적으로 제거되며, 일부 중성입자들은 잔류 수소기체에 의한 재이온화 과정을 거치기도 한다. 여기서는 정립된 수학적 모델을 이용하여 이들 collimator에서 제거되는 양 및 재이온화 손실들을 고려하여 최종적으로 플라즈마에 입사되는 중성입자 빔을 계산하였다. 한편, 빔 수송라인 설치시에 발생할 수 있는 설치 오차를 이온원 설치시의 오차와 빔 collimator 설치상의 오차로 구분하여 이들의 의한 영향도 계산하였다. Gaussian 분산을 가정하였을 경우, 이온원에 가장 근접하여 설치되는 collimator에 가해지는 수직성분의 열속은 9.7kW/cm2로 계산되었다. 이 열속을 제어 가능한 수준으로 낮추기 위해서 collimator는 빔 라인과 거의 나란하게 설치될 것이다. 빔의 통과율은 약 33%로서 하나의 이온원에서 방출된 7.8MW 중 2.5 MW만이 플라즈마에 전달되는 것을 알 수 있었다. Non-Gaussian 분산의 경우, 최대 열속은 9.1kW/cm2로 다소 낮아졌으나, 빔통과율은 28%정도로 더욱 낮아졌다. 설치상의 오차에 의한 영향을 살펴보면, 이온원이 1$^{\circ}$ 정도 기울어지게 설치된다면 collimaor에 가해지는 최대 열속 및 빔통과율은 약 15kW/cm2, 16.6% 정도로 나타나 매우 심각한 결과를 초래함을 알 수 있었다. 이에 비해 collimator 설치상의 오차의 영향은 이보다 훨씬 작아 5mm 오차가 발생했을 경우에도 최대 열속은 12kW/cm2까지 증가했으나, 빔 통과율의 변화는 거의 없었다.

• 한국초전도ㆍ저온공학회논문지
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• 제18권1호
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• pp.10-13
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• 2016

In this study, we developed a new volume reduction technique for cesium contaminated soil by magnetic separation. Cs in soil is mainly adsorbed on clay which is the smallest particle constituent in the soil, especially on paramagnetic 2:1 type clay minerals which strongly adsorb and fix Cs. Thus selective separation of 2:1 type clay with a superconducting magnet could enable to reduce the volume of Cs contaminated soil. The 2:1 type clay particles exist in various particle sizes in the soil, which leads that magnetic force and Cs adsorption quantity depend on their particle size. Accordingly, we examined magnetic separation conditions for efficient separation of 2:1 type clay considering their particle size distribution. First, the separation rate of 2:1 type clay for each particle size was calculated by particle trajectory simulation, because magnetic separation rate largely depends on the objective size. According to the calculation, 73 and 89 % of 2:1 type clay could be separated at 2 and 7 T, respectively. Moreover we calculated dose reduction rate on the basis of the result of particle trajectory simulation. It was indicated that 17 and 51 % of dose reduction would be possible at 2 and 7 T, respectively. The difference of dose reduction rate at 2 T and 7 T was found to be separated a fine particle. It was shown that magnetic separation considering particle size distribution would contribute to the volume reduction of contaminated soil.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.609-617
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• 2016

Belt-driven Starter Generator (BSG) differs from other mild hybrid systems as the crankshaft of vehicle are not run off. Motor permits a low-cost method of adding mild hybrid capabilities such as start-stop, power assist, and mild levels of regenerative braking. Wound rotor synchronous motor (WRSM) could be adopted in BSG system for HEV e-Assisted application instead of the interior permanent magnet synchronous motor (IPMSM). In practice, adequate torque is indispensable for starter assist system, and energy conversion should be taken into account for the HEV or EV as well. Particularly, flux weakening control is possible to realize by adjusting both direct axis components of current and field current in WRSM. Accordingly, this paper present an off-line current acquisition algorithm that can reasonably combine the stator and field current to acquire the maximum torque, meanwhile the energy conversion is taken into consideration by losses. Besides, on account of inductance influence by non-uniform air gap around rotor, nonlinear inductances and armature flux linkage against current variation are proposed to guarantee the results closer to reality. A computer-aided method for proposed algorithm are present and results are given in form of the Look-up table (LUT). The experiment shows the validity of algorithm.

• 조명전기설비학회논문지
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• 제19권1호
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• pp.70-79
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• 2005

본 논문은 축소차원 상태방정식을 사용한 전차원 관측기를 이용하여 저속도 영역에서의 운전 성능 개선방법을 제안하였다. 축소차원 상태방정식을 사용한 전차원 관측기는 간단한 모터속도 및 외란토크 관측기이다. 제안한 알고리즘은 약 1.9[rpm]의 저속도에서 매우 안정적인 결과를 보였다. 모터구동 시스템에서 외란토크는 저속도 영역에서 속도제어 성능을 저하시킨다. 제안한 알고리즘은 모터속도와 외란토크를 모두 추정한다. 추정된 외란 토크는 속도제어기의 출력에 전향보상 값으로 사용되며, 그 결과 저속도 영역(1.9rpm)에서 부하토크 응답특성이 향상된 것을 확인하였다.

• 조명전기설비학회논문지
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• 제19권3호
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• pp.66-74
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• 2005

최근 급속도로 발전되고 있는 산업분야에서 서보시스템은 빠른 응답특성과 고도의 정밀성이 요구되고 있다. 이러한 특성의 요구로 인하여 산업용 서보전동기 구동시스템에 고정자 혹은 회전자 자속벡터의 순시위치와 고정자 전류를 검출하여 좌표변환에 의해 고정자 전류를 여자성분과 토크성분으로 분리 제어하는 벡터제어 이론이 많이 적용되고 있다. 벡터제어에서는 좌표변환과 SVPWM 발생을 위해 많은 연산을 요구하므로 디지털 제어시스템에서 DSP에 많은 부담을 주고 있다. 그러나 직접토크제어(DTC) 알고리즘은 디지털 제어 구조로 토크와 고정자 자속 성분의 전류제어에 룩업 테이블을 사용하므로 벡터제어처럼 많은 제어기와 복잡한 연산을 필요로 하지 않고, 동적 응답특성이 전동기의 정수변화에 영향이 적으면서 직접 전동기의 토크와 고정자 자속을 독립적으로 제어할 수 있는 장점을 가진다. 따라서 본 논문에서는 표면 부착형 영구자석 동기전동기(SPMSM)를 사용하여 DTC에 의한 서보 전동기 제어와 벡터제어에 의한 서보 제어시스템 결과를 비교하여 직접토크제어 알고리즘의 산업용 서보 시스템으로의 적용 가능성을 확인하였다.

• 한국안전학회지
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• 제26권2호
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• pp.13-19
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• 2011

The magnetic polishing is the useful method to finish using magnetic power of magnet. That method is one of precision polishing techniques and has an aim of the clean technology using for the pure of gas and inside of the clean pipe. The magnetic abrasive polishing method is not so common for machine that it is not spreaded widely. There are rarely researcher in this field because of non-effectiveness of magnetic abrasive. Therefore, in this paper deals with development of the magnetic abrasive using Sr-Ferrite. In this development, abrasive grain GC used to resin bond fabricated low temperature. And Sr-Ferrite of magnetic abrasive powder fabricated that Sr-Ferrite was crused into 200 mesh. The XRD analysis result show that only GC abrasive and Sr-Ferrite crystal peaks detected which explains resin bond was not any more chemical reaction. From SEM analysis it is found that GC abrasive and Sr-Ferrite were strong bonding with each other by bond. The magnetic polishing is performed by polishing the surface of pipe by attracting magnetic abrasives with magnetic fields. This can be widely applied for finishing machinery fabrications such as various pipes and for other safety processes. In this paper, we could have investigated in to the changes of the movement of magnetic abrasive grain. In reference to this result, we could have made the experiment which is set under the condition of the magnetic flux density, polishing velocity according to the form of magnetic brush.

• 성인간호학회지
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• 제20권6호
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• pp.950-959
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• 2008

Purpose: The present study was conducted in order to examine claustrophobia, noise sensitivity and vital signs according to anxiety sensitivity level in patients who have Magnet Resonance Imaging(MRI). Methods: With 100 outpatients, we measured anxiety sensitivity, claustrophobia, noise sensitivity and vital sign before and after MRI. Measuring tools were ASI, CLQ-M, and NSI. Data were collected from February to March, 2008. Results: The ASI score was higher in women than in men(p < .05), and no statistically significant difference was observed according to age, region of scanning, experience in MRI, and the use of contrast agent. Both men and women patients showed the same ASI score and decrease in CLQ M and NSI between before and after MRI. In women, ASI, CLQ M and NSI were in positive correlation with one another(p < .001), and in men, there was no correlation between ASI and CLQ M, and positive correlation was observed with NSI(p < .05). In comparison according to ASI level, blood pressure and pulse rate were not different in men and women. CLQ M was not different in men, but was different in women(p < .001). NSI was different in both men and women(men p < .05; women p < .001). Conclusion: MRI may cause claustrophobia in patients with high anxiety sensitivity, and noise appears to aggravate anxiety. In particular, claustrophobia was more serious in women than in men. Therefore, it is necessary to develop nursing interventions to reduce anxiety sensitivity particularly for female patients, and to make plans to educate and lower noise before MRI in order to reduce claustrophobia.

• Smart Structures and Systems
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• 제26권5호
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• pp.619-629
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• 2020

Solar towers, which often has a large aspect ratio and low fundamental natural frequency, were extremely prone to large amplitude of wind-induced vibrations, especially Vortex-Induced Vibration (VIV). A tiny Tuned Mass Damper (TMD) with conveniently adjustable eddy current damping was specially designed and manufactured for elastic wind tunnel tests of a solar tower. A series of numerical simulations by using the COMSOL software were conducted to determine three key parameters, including the thickness of the back iron plate and the conductive plate (T_b and T_c), the distance between the magnet and the conductive plate (T_d). Based on the results of numerical simulations, a tiny TMD was manufactured and its structural parameters were experimentally identified. The optimized values of the tiny TMD can be conveniently realized. The tiny TMD was installed at the top of the elastic test model of a 243-meter-high solar tower, and a series of wind tunnel tests were carried out to examine the effectiveness of the TMD in suppressing wind-induced responses of the test model. The results showed that the wind-induced responses could be obviously reduced by the TMD, especially in the cross-wind direction. The cross-wind RMS and peak responses at the critical wind velocity can be reduced by about 86% and 75%, respectively. However, the maximum reduction of the responses at the design wind velocity is about 45%, obviously less than that at the critical wind velocity.

• Asian-Australasian Journal of Animal Sciences
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• 제14권2호
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• pp.155-162
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• 2001

Effect of the north (N) or south pole (S) of a magnet and dithiothreitol (DTT) or heparin sodium (H) on the orientation of bull sperm were studied. Sperm were collected from four Japanese Black bulls of Okinawa Prefectural Livestock Experimental Station were treated with various concentrations of DTT or H during the first and sixth days and were then exposed them to N or S with a magnetic field of 3,000 Gauss for 24 hours. Experimental results showed that both N and S significantly increased the perpendicular oriented percentage of bull sperm in most treatments not treated or treated with DTT or H. Anisotropy of magnetic field of bull sperm was the main cause which induced them to orient perpendicular to the magnetic direction. The results of the experiment also showed that, in most cases, the two polarities had the same effect on the orientation of bull sperm. However, in some cases, N exerted a stronger effect on the perpendicular percentage of bull sperm than S, such as with the 20 mM DTT treatment at the first and sixth days and the 100 units H treatment at the sixth day. These cases showed that the perpendicular oriented percentage of bull sperm at N was significantly higher than that of S. It was only the 100 units heparin treatment at S both at the first and sixth days that upward perpendicular orientation was higher than that at N. This might be due to the fact that protamin-DNA structure of a small number of bull sperm nuclei slightly changed because of heparin action.