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( Won Seok Oh ),( Yong Seuk Lee ),( Byung Kak Kim ),( Jae Ang Sim ),( Beom Koo Lee ) 대한슬관절학회 2016 대한슬관절학회지 Vol.28 No.2
Purpose: To analyze the contact mechanics of the femoral component and polyethylene of the Low Contact Stress rotating platform (LCS-RP) in nonweight bearing and weight bearing conditions using full flexion lateral radiographs. Materials and Methods: From May 2009 to December 2013, 58 knees in 41 patients diagnosed with osteoarthritis and treated with total knee arthroplasty (TKA) were included in this study. TKA was performed using an LCS-RP knee prosthesis. Full flexion lateral radiographs in both weight bearing and nonweight bearing condition were taken at least one month postoperatively (average, 28.8 months). Translation of femoral component was determined by the contact point between the femoral component and polyethylene. Maximum flexion was measured as the angle between the lines drawn at the midpoint of the femur and tibia. Results: Posterior shift of the contact point in LCS-RP TKA was observed under weight bearing condition, which resulted in deeper flexion compared to LCS-RP TKA under nonweight bearing condition Conclusions: In the LCS-RP TKA, the contact point between the femoral component and polyethylene moved posteriorly under weight bearing condition, and the joint was more congruent and maximum flexion increased with weight bearing.
Koo, Min Ye,Shin, Hon Chung,Kim, Won-Seok,Lee, Gyo Woo 한국탄소학회 2014 Carbon Letters Vol.15 No.4
Multi-walled carbon nanotube reinforced epoxy composites were fabricated using shear mixing and sonication. The mechanical, viscoelastic, thermal, and electrical properties of the fabricated specimens were measured and evaluated. From the images and the results of the measurements of tensile strengths, the specimens having 0.6 wt% nanotube content showed better dispersion and higher strength than those of the other specimens. The Young's moduli of the specimens increased as the nanotube filler content was increased in the matrix. As the concentrations of nanotubes filler were increased in the composite specimens, their storage and loss moduli also tended to increase. The specimen having a nanotube filler content of 0.6 wt% showed higher thermal conductivity than that of the other specimens. On the other hand, in the measurement of thermal expansion, specimens having 0.4 and 0.6 wt% filler contents showed a lower value than that of the other specimens. The electrical conductivities also increased with increasing content of nanotube filler. Based on the measured and evaluated properties of the composites, it is believed that the simple and efficient fabrication process used in this study was sufficient to obtain improved properties in the specimens.
Won So Yeon,Cha Jihoon,Choi Hyun Seok,Kim Young Dae,Nam Hyo Suk,Heo Ji Hoe,Lee Seung-Koo 대한영상의학회 2022 Korean Journal of Radiology Vol.23 No.3
Objective: Intracranial atherosclerotic stroke occurs through various mechanisms, mainly by artery-to-artery embolism (AA) or branch occlusive disease (BOD). This study evaluated the spatial relationship between middle cerebral artery (MCA) plaques and perforating arteries among different MCA territory infarction types using vessel wall magnetic resonance imaging (VW-MRI). Materials and Methods: We retrospectively enrolled patients with acute MCA infarction who underwent VW-MRI. Thirty-four patients were divided into three groups according to infarction pattern: 1) BOD, 2) both BOD and AA (BOD-AA), and 3) AA. To determine the factors related to BOD, the BOD and BOD-AA groups were combined into one group (with striatocapsular infarction [BOD+]) and compared with the AA group. To determine the factors related to AA, the BOD-AA and AA groups were combined into another group (with cortical infarction [AA+]) and compared with the BOD group. Plaque morphology and the spatial relationship between the perforating artery orifice and plaque were evaluated both quantitatively and qualitatively. Results: The plaque margin in the BOD+ group was closer to the perforating artery orifice than that in the AA group (p = 0.011), with less enhancing plaque (p = 0.030). In the BOD group, plaques were mainly located on the dorsal (41.2%) and superior (41.2%) sides where the perforating arteries mainly arose. No patient in the AA group had overlapping plaques with perforating arteries at the cross-section where the perforator arose. Perforating arteries associated with culprit plaques were most frequently located in the middle two-thirds of the M1 segment (41.4%). The AA+ group had more stenosis (%) than the BOD group (39.73 ± 24.52 vs. 14.42 ± 20.96; p = 0.003). Conclusion: The spatial relationship between the perforating artery orifice and plaque varied among different types of MCA territory infarctions. In patients with BOD, the plaque margin was closer and blocked the perforating artery orifice, and stenosis degree and enhancement were less than those in patients with AA.
Won, Ho-Ryun,Chang, Jae Won,Kang, Yea Eun,Kang, Jae Yoon,Koo, Bon Seok Elsevier 2018 Oral oncology Vol.87 No.-
<P><B>Abstract</B></P> <P>The purpose of this systematic review and meta-analysis was to determine the optimal extent of lateral neck dissection in patients with well-differentiated thyroid carcinoma with clinically confirmed lateral neck lymph node metastases. All studies reporting the distribution of metastatic lymph nodes in level IIb or level V, complication rate, recurrence rate, or clinical outcomes according to the extent of lateral neck dissection were collected from MEDLINE and Embase databases. Two reviewers independently retrieved articles, extracted data, and assessed the quality of the studies. A total of 40 criteria-meeting studies were included in the systematic review and meta-analysis, representing a total of 6 027 patients. The distribution of metastatic lymph nodes was 13.7% (95% confidence interval [CI]: 8.2–21.9%) in level IIb and 22.1% (95% CI: 18.6–26.1%) in level V. Shoulder syndrome complication showed a tendency to increase when comprehensive neck dissection was performed. The recurrence rate was 11.2% (95% CI: 8.4–14.9%) in the comprehensive neck dissection group and 11.0% (95% CI: 4.2–26.1%) in the selective neck dissection group. Clinical outcomes showed no difference between groups. In conclusion, selective neck dissection may be considered in patients with well-differentiated thyroid carcinoma with lateral neck lymph node metastases without any other risk factors.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The optimal extent of lateral neck dissection in WDTC patients is under debate. </LI> <LI> The distribution of metastatic lymph nodes in levels IIb and V is relatively low. </LI> <LI> Shoulder syndrome incidence tends to be higher in comprehensive neck dissection. </LI> <LI> There is no difference in recurrence according to the extent of neck dissection. </LI> <LI> If there are no other risk factors, selective neck dissection may be considered. </LI> </UL> </P>
Design and Fabrication of Hyperabrupt Varactor Diode on GaAs substrate
Seok-Gyu Choi,Yong-Hyun Baek,Tea-Jong Baek,Sun-Woo Park,Do-Hyun Kim,Wan-Joo Kim,Won-Young Uhm,Soon-Sik You,Y-W Kim,Sam-Dong Kim,Jin-Koo Rhee 대한전자공학회 2008 ICEIC:International Conference on Electronics, Inf Vol.1 No.1
In this paper, we have designed and fabricated hyperabrupt varactor diodes. Capacitance variations of hyperabrupt-doped varactor diodes are larger than those of uniform-doped varactor diodes. We adopted sensitivity S for the design of the hyperabrupt varactor diodes. The large S means the larger capacitance variations with biasing voltages. The measured reverse breakdown voltage of the fabricated varactor diodes was about 20 V. Also, the leakage current was 13 ㎁ at 20 V of reverse bias. The ideality factor was 1.15 at 300 K. For the anode contact diameter of 50 ㎛, the maximum capacitance of the fabricated varactor diode was 2.1 pF and the minimum capacitance 0.44 ㎊. Therefore, the Cmax/Cmin ratio was 4.77. Also, for the anode contact diameter of 60 ㎛, the maximum and minimum capacitances were 2.9 and 0.62 ㎊, respectively. And, thus, the Cmax/Cmin ratio was 4.64. The sensitivity of the fabricated varactor diodes (D=60 ㎛) was 2.37.