• ETRI Journal
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• 제31권6호
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• pp.695-702
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• 2009

We propose a lens-drive unit composed of an ionic polymer-metal composite (IPMC) for an auto-focus compact camera module in cellular phones to solve the power consumption problem of voice coil motors which are widely used in commercial products. In this research, an IPMC incorporated into a lens-drive unit is designed to implement a large displacement in low-power consumption by using an anisotropic plasma treatment. Experimental results show that a camera module containing IPMCs can control and maintain the position of the lens by using proportional integral derivative control with a photo-reflective position sensor despite the non-linear actuation behavior of IPMCs. We demonstrate that the fabrication and commercialization of a lens actuator that has a large displacement and low power consumption using IPMCs is possible in the near future.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1058-1063
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• 2004

This paper presents a new approach regarding thermal characteristics associated with a design of the high efficiency motor. Electrical conduction materials, such as coil and aluminum embedded in the core generate high heat exerting negative influence on both lifetime and performance of machine. Thus, it is necessary to design high efficiency motor considering heat transfer in order to improve motor performance and to be protected against overheating. In this paper, firstly, numerical analysis of electromagnetic field is carried out by the nonlinear transient finite element method (FEM). Secondly, the linear static FEA of magneto-thermal field is implemented by applying source current computed by the nonlinear transient analysis. FE results are validated in terms of electromagnetics and heat transfer by experiments. And then, the pseudo-transient topology optimization using a multi-objective function is performed. The proposed method is applied to a squirrel cage single-phase induction motor of the scroll compressor.

• 한국생산제조학회지
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• 제18권6호
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• pp.652-657
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• 2009

MPW(Magnetic Pulse Welding) is a technologies for welding of metals by means of repulsive force on account of the interaction between electro-magnetic field of coil and current induced in outer pipe. These MPW is one of the most useful welding process of welding ability of the dissimilar metal in which cylindrical materials, such as pipe, tube. As the quality of a weld joint is strongly influenced by process parameters during the welding process and the success of the welding to evaluated according to the leakage pressure. Generally, the process parameters is magnetic pressure, the gap between outer pipe and inner pipe, and the ratio of thickness to diameter of pipe(D/T) in MPW. Therefore, the goal of this study was to explain the effect of parameters on the weld joint leakage pressure. For these purposes, FFD(Fractional Factorial Design) were used for the experiment. The measured data were analyzed by regression analysis and verification experiments with random condition were conducted to confirm the suggested experimental model.

• 한국자기공명학회논문지
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• 제23권1호
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• pp.12-19
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• 2019

A former study has shown that the spin-lattice relaxation time ($T_1$) in cancerous prostate tissue had enhanced contrast at an ultra-low magnetic field, $132{\mu}T$. To study the field dependence and the origin of the contrast we measured $T_1$ in pairs of ex-vivo prostate tissues at the Earth's magnetic field. A portable and coil-based nuclear magnetic resonance (NMR) system was adopted for $T_1$ measurements at $40{\mu}T$. The $T_1$ contrast, ${\delta}=1-T_1$ (more cancer)/$T_1$(less cancer), was calculated from each pair. Additionally, we performed pathological examinations such as Gleason's score, cell proliferation index, and micro-vessel density (MVD), to quantify correlations between the pathological parameters and $T_1$ of the cancerous prostate tissues.

• 대한영상의학회지
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• 제85권3호
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• pp.668-675
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• 2024

대동맥 문합부 누출은 급성 대동맥 박리의 치료인 상행 대동맥 치환술 후 발생할 수 있는 흔하지 않은 합병증이다. 대동맥 문합부 누출의 치료로는 재수술이 전통적인 치료 방법으로 추천되나 높은 사망률과 이환율을 보인다. 최근에는 몇 건의 증례 보고에서 중재 시술이 대안적인 접근방식으로 시도되고 있다. 이에 저자들은 A형 대동맥박리의 치료인 대동맥 이식편치환술 후 봉합선 열개에 의한 대동맥 문합부 누출을 코일과 N-butyl cyanoacrylate로 색전술을 시행한 증례와 혈관마개로 성공적으로 치료한 증례를 보고하고자 한다.

• 대한기계학회논문집A
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• 제37권11호
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• pp.1423-1428
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• 2013

본 논문은 1.2kW 급 BLDC 모터의 분석을 위하여 열 발산 측정 시스템을 제작하였다. 온도증가는 모터절연체의 문제를 일으켜 모터 수명과 연결되므로 모터의 온도를 아는 것은 중요하다. 실험에서 모터의 부하를 설정하기 위해 자동차용 제너레이터를 장착하였고, 부하의 변경을 위해 165W~495W를 변화를 주었다. 다양한 부하조건하에 분당 모터 회전 수를 2000~4000 까지 변경하면서 모터 각 부분에 열전대로 시간에 따른 온도변화를 측정하였다. 실험 결과로서 자연대류조건하에서는 모터의 회전 수 및 부하가 증가할수록 온도는 수렴하지 않으며 모터코일의 온도가 최고 $120^{\circ}C$ 이상까지 증가하였으나, 강제 대류조건하에서는 4000s 이상에서 $84^{\circ}C$에 수렴하였다. 모터의 최대/최소 온도 차이는 회전 수 및 부하가 증가할수록 최소 $10^{\circ}C{\sim}26^{\circ}C$의 차이를 보였다. 온도의 분포는 모터코일(1 번채널), 모터외부옆면(5 번채널), 모터내부 캡(2 번채널), 모터외부상부(4 번채널), 모터내부벽면(3 번채널)순으로 나타났다.

• 한국정보통신학회논문지
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• 제14권5호
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• pp.1209-1216
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• 2010

당뇨 합병증 등으로 인한 말초혈류 및 신경장애, 수족냉증 및 손가락 관절염, 통증 질환이 증가하고 있으며, 이러한 문제를 개선할 수 있는 손가락 질환 전용 치료기기가 전무한 상태로 이와 관련된 치료기의 개발이 필요하다. 본 연구에서는 시변 미약자기장을 이용하여 비침습적으로 말초혈류/신경개선과 손가락 류마티스 치료를 위한 솔레노이드 원통형 코일을 제작하고, 다양한 치료목적에 사용하기 위해서 3가지 자극모드(N, S, N/S)와 자극주파수(0.25, 0.5, 1hz)를 선택할 수 있는 시스템을 설계하였다. 자속밀도 측정 프로브를 솔레노이드의 중심에서부터 거리를 0 ~ 3cm 단계로 자극방식과 주파수별로 자속밀도를 측정하였다. 자속밀도를 측정한 결과, 모든 자극방식과 주파수에서 솔레노이드 내부의 중심(0cm)에 근접할수록 자속밀도가 급격히 증가하였다. 솔레노이드 중심 자속밀도는 N자극 (294.3mT)과 S자극(293.8mT)에서는 1Hz, N/S자극(275.4mT)에서는 0.25Hz에서 가장 높게 측정되었다. 본 논문에서는 다양한 패턴과 강도의 자기장을 이용하여 다양한 손가락 질환을 치료할 수 있는 솔레노이드형 치료기기를 개발하였다. 솔레노이드 내부 자속밀도를 측정함으로써 손가락 말초질환 개선을 위한 미약자기장 시스템의 임상 적용 가능성을 확인하였다.

• Journal of Korean Neurosurgical Society
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• 제64권5호
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• pp.751-762
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• 2021

Objective : Endovascular treatment of intracranial aneurysms is challenging in case of wide-necked aneurysms because coils are prone to herniate into the parent artery, causing thromboembolic events or vessel occlusion. This study aims to compare long-term angiographic results of wide-necked aneurysms treated by stent-assisted, double-microcatheter, or single-microcatheter groups. Methods : Between January 2003 and October 2016, 108 aneurysms that were treated with endovascular coil embolization with a neck size wider than 4 mm and a follow-up period of more than 3 years were selected. We performed coil embolization with single-microcatheter, double-microcatheter, and stent-assisted techniques. Angiographic results were evaluated using the Raymond-Roy occlusion classification (RROC). All medical and angiographic records were reviewed retrospectively. Results : Clinical and angiographic analyses were conducted in 108 wide-necked aneurysms. The immediate post-procedural results revealed RROC class I (complete occlusion) in 66 cases (61.1%), class II (residual neck) in 36 cases (33.3%), and class III (residual sac) in six cases (5.6%). The final follow-up results revealed class I in 48 cases (44.4%), class II in 49 cases (45.4%), and class III in 11 cases (10.2%). Of a total of 45 (41.6%) radiologic recurrences, there were 21 cases (19.4%) of major recurrence that required additional treatment, and 24 cases (22.2%) of minor recurrence. The final follow-up angiographic results showed statistically significant differences between the stent-assisted group and the others (p<0.01). Conclusion : Long-term follow-up angiography demonstrated that the stent-assisted technique had a better complete occlusion rate than the other two techniques.

• Journal of Korean Neurosurgical Society
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• 제66권6호
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• pp.690-702
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• 2023

Objective : To analyze the outcomes of coil embolization (CE) for unruptured intracranial aneurysm (UIA) according to region and hospital size based on National Health Insurance Service data in South Korea. Methods : The incidence of complications, including intracranial hemorrhage (ICRH) and cerebral infarction (CI), occurring within 3 months and the 1-year mortality rates in UIA patients who underwent CE in 2018 were analyzed. Hospitals were classified as tertiary referral general hospitals (TRGHs), general hospitals (GHs) or semigeneral hospitals (sGHs) according to their size, and the administrative districts of South Korea were divided into 15 regions. Results : In 2018, 8425 (TRGHs, 4438; GHs, 3617; sGHs, 370) CEs were performed for UIAs. Complications occurred in 5.69% of patients seen at TRGHs, 13.48% at GHs, and 20.45% at sGHs. The complication rate in TRGHs was significantly lower than that in GHs (p=0.039) or sGHs (p=0.005), and that in GHs was significantly lower than that in sGHs (p=0.030). The mortality rates in TRGHs, GHs, and sGHs were 0.81%, 2.16%, and 3.92%, respectively, with no significant difference. Despite no significant difference in the mortality rates, the complication rate significantly increased as the number of CE procedures per hospital decreased (p=0.001; rho=-0.635). Among the hospitals where more than 30 CEs were performed for UIAs, the incidence of CIs (p=0.096, rho=-0.205) and the mortality rates (3 months, p=0.048, rho=-0.243; 1 year, p=0.009, rho=-0.315) significantly decreased as the number of CEs that were performed increased and no significant difference in the incidence of post-CE ICRH was observed. Conclusion : The complication rate in patients who underwent CE for UIA increased as the hospital size and physicians' experience in conducting CEs decreased. We recommend nationwide quality control policies CEs for UIAs.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제28권4호
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• pp.264-273
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• 2002

Pulsed electromagnetic field (PEMF) was used first to induce osteogenesis in 1974. The appliance which was consisted of the Helmholtz coil configuration have used to osteogensis. The objective of this study was to determine whether PEMF, a frequency of 100 Hz and magnetic field strength of 38 gauss applied to the calvarial defect in rabbit, could affect the induction of osteogenesis and the healing of the graft bone. This field should not produce excitation of nerve or muscle and heating the tissue. To evaluate the effect of PEMF on osteogenesis, 16 rabbit under the same condition was divided into 8 experimental groups and 8 control groups. 10 mm calvarial bone defects were formed around sagittal suture. The defect of left side was left without graft while the defect of right side was grafted by bone harvested from left side. A pulsed electromagnetic field was applied for 8 hours per day. Each group was sacrificed after 1 week, 2 weeks, 4 weeks, 8 weeks. Microscopic specimens were obtained from the calvarial bone defects and surrounding tissue using Hematoxylin-Eosin staining method. The results were as follows. 1. In the group which pulsed electromagnetic field was applied, new bone formation filled up the defect was observed after 4 and 8 weeks effectively. 2. There are no difference in the healing period for the fusion between the bone and graft bone. According to the result, the PEMF with 38 Gauss, 100 Hz was very effective in the healing of bone defect and new bone formation. So The PEMF will be useful in clinical aspect for oseteogenesis.