• 천문학회보
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• 제16권
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• pp.8.1-8.1
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• 1991

• 대한기계학회논문집A
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• 제33권1호
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• pp.34-41
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• 2009

In this paper, a novel MR brake with permanent magnet is developed. This system consists of rotary disk, permanent magnet, spring and MR fluid. Permanent magnets are attached to the rotary disk and moves in the direction of radius. The magnets are linked to rotor axis by spring. As rotation speed increases, the magnets move outward from the center of the system by centrifugal force in the MR fluid. A proper design of stator or case makes the system have unique torque characteristics. The research is performed like following procedures. First, the electromagnetic characteristic of the system is analyzed using Maxwell. Next, torque is calculated using the results of the electromagnetic analysis. Finally, the performance of various types of the brake systems are investigated and compared with each other.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.413-418
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• 2004

Recently, the development of mobile devices demands information storage systems to use micro drive devices. 1-inch micro drive hard disk uses the load/unload(L/UL) technology to increase area recording density and reduce power consumption. Because micro drive has light actuator, effects of the flexible cable that is ignored in 3.5-inch hard disk drive is important to load/unload performances. In this paper, effects of flexible cable on load/unload performances are studied.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.586-591
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• 2004

A load/unload mechanism is applied to most small form factor hard disk drives. Loading velocity is ones of the most important factors to ensure the reliability of the load/unload operations. Especially, the lower the flying height of the head becomes, the more important the accuracy of the loading velocity control becomes. Because there is no sensor during the load/unload operations, BEMF voltage is used to sense the head velocity. To measure BEMF voltage, a simple circuit is added to the load/unload HDD control system. Overall acceptable results are obtained by using the simple PI controller but the errors from the target velocity occur when the head moves along the ramp and then reaches the disk. Feedforward profile and disturbance observer are used to remove those errors effectively.

• Imaging Science in Dentistry
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• 제36권4호
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• pp.199-206
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• 2006

Purpose: The purpose of this study was to evaluate comparison of static MRI and pseudo-dynamic (cine) MRI in temporomandibular joint (TMJ) disorder patients. Materials and Methods: In this investigation, 33 patients with TMJ disorders were examined using both conventional static MRI and pseudo-dynamic MRI. Multiple spoiled gradient recalled acquisition in the steady state (SPGR) images were obtained when mouth opened and closed. Proton density weighted images were obtained at the closed and open mouth position in static MRI. Two oral and maxillofacial radiologists evaluated location of the articular disk, movement of condyle and bony change respectively and the posterior boundary of articular disk was obtained. Results: No statistically significant difference was found in the observation of articular disk position, mandibular condylar movement and posterior boundary of articular disk using static MRI and pseudo-dynamic MRI (P<0.05). Statistically significant difference was noted in bony changes of condyle using static MRI and pseudo-dynamic MRI (P<0.05). Conclusion: This study showed that pseudo-dynamic MRI didn't make a difference in diagnosing internal derangement of TMJ in comparison with static MRI. But it was considered as an additional method to be supplemented in observing bony change.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.151-152
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• 2013

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.799-800
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• 2012

• 분석과학
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• 제11권5호
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• pp.321-331
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• 1998

기체크로마토그래피/질량분석법(GC/MS)을 이용하여 물시료 중에 미량으로 함유된 19종의 여러고리방향족탄화수소류에 대한 액체-액체 추출법, disk추출법 및 고체상 추출법을 이용한 시료 매트릭스로부터 분리, 추출하는 방법을 조사하였다. GC/MS의 오븐온도프로그램을 $80{\sim}310^{\circ}C$까지 단계적으로 변화시킨 결과 19종의 PAH류를 분리할 수 있었다. 액체-액체 추출법에 의한 물시료 중 PAH류의 회수율은 71.3~109.5% 범위로 나타났고, filtration에 의한 $C_{18}$ disk추출법의 회수율은 80.7~94.9% 범위로 높게 나타났다. 그러나 $C_{18}$ Sep-Pak을 사용한 고체상 추출법의 회수율은 51.8~77.9%범위이었다. 이상의 추출법에 대한 추출 회수율, 재현성 및 실험의 편리성 등 장단점을 비교한 결과, $C_{18}$ disk를 사용한 거르기법이 PAH류의 추출에 가장 적합한 방법임을 확인하였다. 각 추출법의 검출한계(S/N=5)는 액체-액체 추출법 및 고체상 추출법의 경우 0.25~6.25 ppb, disk추출법은 0.05~1.25 ppb 범위이었다.

• 한국방사선학회논문지
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• 제12권6호
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• pp.785-791
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• 2018

최근 PACS에서 장기간 저장장치로 디스크 배열이 많이 사용되고 있으나, 디스크에 대한 년 간 불량률에 관해서 신뢰성이 부족한 실정이다. 2016년 10월부터 2017년 2월까지 PACS 판독기에서 의료영상을 읽거나 저장하면서 하드디스크의 직렬포트단자를 조사하였으며, PACS 영상저장 장치에 사용되었던 하드디스크 98대와 개인용 컴퓨터에 사용되었던 하드디스크 101대에 저장된 데이터에서 전송률을 산출하였다. PACS 판독기에서 CT영상을 읽었을 경우에는 수십 MB이하 단위로 읽기는 87.8%, 쓰기는 12.2%가 수행되었다. PACS 판독기에서 CT 영상을 저장할 때는 수십 MB이하 단위로 읽기는 11.4%, 쓰기는 88.6%가 수행되었다. 개인용 컴퓨터에서 엑셀 파일을 읽을 경우에는 3 MB 이하단위로 읽기는 75%, 쓰기는 25%가 수행되었다. 개인용 컴퓨터에서 엑셀 파일 저장을 진행하면서 하드디스크와의 통신은 3 MB이하단위로 읽기는 38%, 쓰기는 62%가 수행되었다. PACS내 영상저장장치에 사용되는 하드디스크의 전송률은 10 GB/h, 개인용 컴퓨터의 하드디스크의 전송률은 5 GB/h로 나타났다. PACS내 영상저장에 사용되던 하드디스크의 년간 불량률은 0.97 ~ 1.13%를 보였고, 개인용 컴퓨터 내 하드디스크의 년간 불량률은 0.51~0.7%를 보였다. 전송량이 높을수록 년 간 불량률도 높아졌다. 이러한 결과는 하드디스크의 수명예측이나 연간 고장률을 예측하기 위한 기초 자료로 활용될 것이다.

• 대한치과기공학회지
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• 제31권1호
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• pp.63-74
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• 2009

Partial or complete prosthesis is needed when teeth are lost due to various kinds of reason. Artificial teeth recover occlusion instead of natural teeth. Artificial teeth are required of esthetics, fragile resistance and abrasive resistance. Artificial tooth is made of acrylic resin or porcelain. Nowadays, acrylic resin artificial teeth are mainly used. Acrylic resin teeth are occluded with natural teeth, gold alloy, Ni-Cr alloy or porcelain etc. Acrylic resin teeth have similar translucency, gloss of natural teeth. And it has good chemical bond with denture base material, but it has low wear resistance. The aim of this study is to compare wear resistance among several denture teeth(Endura, SR-orthosit-PE, Planustar) and between artificial resin denture teeth and opposing 3 restorative materials(gold, Ni-Cr alloy, porcelain). Wear tests were conducted with a rotating wear testing apparatus(pin-on-disk type wear tester) under conditions of rpm 180, 75 minutes and constant loading of 50N. The upper part was the cusp of maxillary first molar and the lower part was a disk type restorative materials. To make similar oral environment, water was supplied continually. The acrylic resin teeth wear was determined by weighing the cusp each 5 minutes during 75 minutes test. Vicker's hardness tester was used to evaluate the surface hardness of test specimens. The SEM was used to evaluate the wear surfaces. The results were as follows: 1. Wear rates of acrylic resin teeth opposing to the restorative materials were high in order of Porcelain, Gold, Ni-Cr alloy (p<.05). 2. Wear resistance rate opposing to the Porcelain disk, was shown in order of Endura, SR-orthosit-PE, Planustar. The wear rate of opposing to porcelain disk was above two times more than that of other groups (p<.05). 3. Wear resistance rates opposing to the Gold, Ni-Cr alloy disk, was shown in order of Endura, SR-orthosit-PE, Planustar (p<.05). 4. A degree of the surface hardness is directly proportional to the degree of wear resistance. There are statistically significant differences between each groups (p<.05).