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생체 세라믹스용 마모시험장비의 제작 및 정방정지르코니아의 마모특성
김성호,류득배,문병규,이수완 선문대학교 중소기업기술지원연구소 2001 선문공대 연구/기술 논문집 Vol.6 No.1
생체 세라믹스용 마모시험장비를 제작하였다. 마모시험기는 lever system을 이용하여 하중인가가 되게 설계되었으며 step motor를 사용하여 회전수 조절이 용이하게 하였다. DAQ (Data Acquisition System)을 이용하여 하중을 측정하여 마찰계수를 측정할 수 있게 하였다. 성능평가를 위해 정방정지르코니아를 Ringer's solution에서 선속도 40 mm/s, 인가하중 10, 20, 30 N에서 마모시험 하였다. Grooving, crack networking등의 마모기구가 관찰되었다. A wear testing machine for bioceramics was designed and made, which loading and rotating parts consisted of a lower systemed and a step motor, respectively. Friction coefficient was determined by DAQ(Data Acquisition System). Wear resistance of tetragonal zirconia was measured under linear velocity of 40 mm/sec, applied load of 10, 20, 30 N in Ringer's solution, which showed grooving, crack networking on worn surfaces.
선형등화기를 이용한 다중-사용자 복조 혼합 TDMA/CDMA 시스템
문영득,김상규 부산 외국어 대학교 2002 外大論叢 Vol.24 No.-
In this paper, we studied for multi-user detection system, which hold the merit of CDMA system and can enhance the system capacity. We designed actually realizable quasi-optimal multiuser detection system by use of linear equalizer on the concept that multiuser detection algorithm can be reduced by combination TDMA with CDMA, we call this the hybrid TDMA/CDMA system. And we proposed multiuser detection system, which can use PSAD and MSDD channel estimation method. As a result of performance analysis, we acquired equal or much better performance by use of linear multichannel equalizer in the case of not so many user. And on the occasion of many user within cell we can also acquired much better performance in comparison with conventional single user detection system by use of hybrid TDMA/CDMA system.
척추성형술 또는 풍선 척추성형술 시행 후 발생하는 추체의 재압박
전득수 ( Deuk Soo Jun ),문도현 ( Do Hyun Moon ),고영규 ( Young Kyu Ko ),최장석 ( Jang Seok Choi ),안병근 ( Byoung Keun An ),백제원 ( Je Won Paik ),박민호 ( Min Ho Park ) 대한골절학회 2015 대한골절학회지 Vol.28 No.2
Purpose: The purpose of this study was to examine incidence of recompression and risk factors in the patients with osteoporotic vertebral compression fracture (OVCF) after vertebroplasty or kyphoplasty. Materials and Methods: This study was conducted on 179 vertebral bodies of 126 patients who underwent vertebroplasty or kyphoplasty on OVCF from January 2004 to August 2013. Results: When anterior vertebral height of fractured vertebrae declined by more than 3 mm from the height immediately after vertebroplasty or kyphoplasty, it was judged that recompression had occurred. Recompression was observed in a total of 58 vertebrae (32.4%). Recompression occurrences were found to be decreasing significantly when fractured vertebrae were the thoracic spine. In addition, osteonecrosis occurred in the preoperative vertebrae and restoration degree of anterior vertebral height immediately after vertebroplasty or kyphoplasty affected recompression occurrences significantly. The other factors (age, sex, bone mineral density, steroid medication history, follow-up duration, cement volume, vertebroplasty or kyphoplasty, and approach method) were compared, but no statistical significance was found. Conclusion: The risk of vertebral recompression is more common, especially when osteonecrosis occurred in preoperative vertebrae or when vertebroplasty or kyphoplasty achieved remarkable restoration of anterior vertebra height. When performing vertebroplasty or kyphoplasty, such conditions should be considered carefully.
Thermal Quench in HTS Double Pancake Race Track Coil
Jae-deuk Lee,Young-kil Kwon,Seung-kyu Baik,Eon-yong Lee,Young-chun Kim,Tae-sun Moon,Heui-ju Park,Woon-sik Kwon,Jung-pyo Hong,Minwon Park,Inkeun Yu,Young-sik Jo Institute of Electrical and Electronics Engineers 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>In large scale applications, such as SMES, motors and generators, High Temperature Superconducting (HTS) magnets are constructed with many stacks of the double-pancake coils connected in series. In spite of its higher thermal stability, HTS magnet can experience a severe quench, which can resulted from a very small portion. From HTS magnet design point of view, it is very important to predict the possibility of occurrence quench in the designed magnet to provide a suitable quench protection device. In this paper a highly instrumented HTS race track double-pancake coil was prepared to examine the quench development characteristics. It is wound using the Bi-2223 tape. Many voltage taps, cryogenic thermocouples and heater were installed in the winding. Conduction cooling method is adapted for the convenience of temperature. Quench development in the coil was measured under different operating current. The experimental details and results are presented in this paper.</P>
Design and Analysis of 1 MW Synchronous Machine via 3D Magnetic Field Calculation
Seung-Kyu Baik,Young-Kil Kwon,Eon-Young Lee,Jae-Deuk Lee,Jung-Pyo Hong,Yeong-Chun Kim,Tae-Sun Moon,Heui-Joo Park,Woon-Sik Kwon Institute of Electrical and Electronics Engineers 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>A 1 MW class superconducting synchronous rotating machine has been designed as a draft based on 2-dimensional (2D) magnetic field distribution considering several conditions such as superconducting wire length, machine efficiency, size and so on. By the way from 2D design it is not possible to consider the effect of end coils and end portions of stator iron yoke especially in superconducting machine with air-cored structure which increases magnetic field difference between 2D and 3D analysis. In this paper electrical design based on the 3D magnetic field distribution is conducted to get more proper design result and reduce design errors from 2D design approach. As the machine has larger capacity, the superconducting machine will show the advantages more and more over the conventional machine. Although the advantages at 1MW rating are not so great, the 3D design approach to get more optimized result would be very helpful for larger superconducting synchronous machine design. Through 3D analysis such as EMCN (equivalent magnetic circuit network) method and Flux-3D FEM (finite element method), we could get smaller machine size, higher efficiency, and smaller Bi-2223 HTS (high temperature superconducting) wire length than the 2D design result. Moreover influence of an important parameter, synchronous reactance, has been analysed on the machine performances such as voltage variation and output power.</P>
Byong-Kyu Kim,Deuk-Young Nah,Kang Un Choi,Jun-Ho Bae,Moo-Yong Rhee,Jae-Sik Jang,Keon-Woong Moon,Jun-Hee Lee,Hee-Yeol Kim,Seung-Ho Kang,Woo hyuk Song,Seung-Uk Lee,Byung-Ju Shim,Hangjae Chung,Min Su Hyo 대한심장학회 2020 Korean Circulation Journal Vol.50 No.11
Background and Objectives: The relationship between the hospital percutaneous coronary intervention (PCI) volumes and the in-hospital clinical outcomes of patients with acute myocardial infarction (AMI) remains the subject of debate. This study aimed to determine whether the in-hospital clinical outcomes of patients with AMI in Korea are significantly associated with hospital PCI volumes. Methods: We selected and analyzed 17,121 cases of AMI, that is, 8,839 cases of non-ST-segment elevation myocardial infarction and 8,282 cases of ST-segment elevation myocardial infarction, enrolled in the 2014 Korean percutaneous coronary intervention (K-PCI) registry. Patients were divided into 2 groups according to hospital annual PCI volume, that is, to a high-volume group (≥400/year) or a low-volume group (<400/year). Major adverse cardiovascular and cerebrovascular events (MACCEs) were defined as composites of death, cardiac death, non-fatal myocardial infarction (MI), stent thrombosis, stroke, and need for urgent PCI during index admission after PCI. Results: Rates of MACCE and non-fatal MI were higher in the low-volume group than in the high-volume group (MACCE: 10.9% vs. 8.6%, p=0.001; non-fatal MI: 4.8% vs. 2.6%, p=0.001, respectively). Multivariate regression analysis showed PCI volume did not independently predict MACCE. Conclusions: Hospital PCI volume was not found to be an independent predictor of in-hospital clinical outcomes in patients with AMI included in the 2014 K-PCI registry.
Kim Dong Kyu,Kwon Joon Ho,Han Kichang,Kim Man-Deuk,Kim Gyoung Min,Moon Sungmo,Park Juil,Won Jong Yun,Kim Hyung Cheol,Chun Sei Hyun,Choi Seung Myeon 대한영상의학회 2023 Korean Journal of Radiology Vol.24 No.5
Objective: To assess the safety and efficacy of balloon dilatation under dual guidance using fluoroscopy and bronchoscopy for treating bronchial stenosis following lung transplantation (LT), and to elucidate the factors associated with patency after the procedure. Materials and Methods: From September, 2012, to April, 2021, 50 patients (mean age ± standard deviation, 54.4 ± 12.2 years) with bronchial stenosis among 361 recipients of LT were retrospectively analyzed. The safety of balloon dilatation was assessed by evaluating procedure-related complications. Efficacy was assessed by evaluating the technical success, primary patency, and secondary patency. Primary and secondary cumulative patency rates were calculated using the Kaplan-Meier method. The factors associated with patency after the procedure were evaluated using multivariable Cox hazard proportional regression analysis. Results: In total, 65 bronchi were treated with balloon dilatation in 50 patients. The total number of treatment sessions was 277 and the technical success rate was 99.3% (275/277 sessions). No major procedure-related complications were noted. During the mean follow-up period of 34.6 ± 30.8 months, primary patency was achieved in 12 of 65 bronchi (18.5%). However, the patency rate improved to 76.9% (50 of 65 bronchi) after repeated balloon dilatation (secondary patency). The 6-month, 1-year, 3-year, and 5-year secondary patency rates were 95.4%, 90.8%, 83.1%, and 78.5%, respectively. The presence of clinical symptoms was a significant prognostic factor associated with reduced primary patency (adjusted hazard ratio [HR], 0.465; 95% confidence interval [CI], 0.220–0.987). Early-stage treatment ≤ 6 months (adjusted HR, 3.588; 95% CI, 1.093– 11.780) and prolonged balloon dilatation > 5 min (adjusted HR, 3.285; 95% CI, 1.018–10.598) were associated with significantly higher secondary patency. Conclusion: Repeated balloon dilatation was determined to be safe and effective for treating bronchial stenosis following LT. Early-stage treatment and prolonged balloon dilatation could significantly promote long-term patency.