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Percutaneous Sacroplasty : Effectiveness and Long-Term Outcome Predictors
Lee, Jaehyung,Lee, Eugene,Lee, Joon Woo,Kang, Yusuhn,Ahn, Joong Mo,Kang, Heung Sik The Korean Neurosurgical Society 2020 Journal of Korean neurosurgical society Vol.63 No.6
Objective : To evaluate the effectiveness and long-term outcome predictors of percutaneous sacroplasty (PSP). Methods : This single-center study assessed 40 patients with sacral insufficiency fractures using the short-axis technique under C-arm flat-panel detector computed tomography (CT). Two radiologists reviewed the patients' magnetic resonance and CT images to obtain imaging findings before PSP and determine technical success, respectively. The short-term outcomes were visual analog scale score changes and opioid usage reductions. Long-term outcomes were determined using telephone interviews and the North American Spine Society (NASS) patient-satisfaction index at least one year after PSP. Results : Technical success was achieved without any significant complications in 39 patients (97.5%). Telephone interviews were possible with 12 patients and failed in 10 patients; death was confirmed in 18 patients. Fifteen patients (50%) re-visited the hospital and received conservative treatment, including spinal injections. Nine patients reported positive satisfaction (NASS patient-satisfaction index 1 or 2), while the negative satisfaction group (NASS patient-satisfaction index 3 or 4, n=3) showed a higher incidence of compression fractures at the thoracolumbar spine level (66.7% vs. 22.2%) and previous spinal injection history (66.7% vs. 33.3%). The poor response group also showed higher incidences of facet joint arthrosis (100% vs. 55.6%), central canal stenosis (100% vs. 22.2%), neural foraminal stenosis (33.3% vs. 22.2%), scoliosis (100% vs. 33.3%), and sagittal malalignment (100% vs. 44.4%). Conclusion : PSP was effective for sacral insufficiency fractures and showed good long-term outcomes. Combined compression fractures in the thoracolumbar spine and degenerative lumbar pathologies could be possible poor outcome predictors.
이재형(Jaehyung Lee),이하림(Harim Lee),이성주(Sungju Lee),김영민(Youngmin Kim) 대한전기학회 2021 대한전기학회 학술대회 논문집 Vol.2021 No.10
본 논문에서는 7 V 배터리 전원으로 동작하는 대기압 플라즈마 발생 소자의 제작과 특성을 보고하고 있다. 글로우 방전(glow discharge)을 mesh 형태의 전극으로 발생시켜 대기압 플라즈마를 안정적으로 유발할 수 있었으며, 대기압 플라즈마 발생 중 빈번히 나타나는 sputtering 에 의한 전극 손상을 유전체 방전 (dielectric barrier discharge)을 통해 최소화 할 수 있었다. 또한 대기압 플라즈마의 전기적 특성 결과를 측정하여 제시하고 있다.
Robust Fundamental Frequency Estimation Combining Contrast Enhancement and Feature Unbiasing
Jaehyung Lee,Soo-Young Lee IEEE 2008 IEEE signal processing letters Vol.15 No.1
<P>A high-performance fundamental frequency estimator inspired by the human auditory system is presented. It uses a cubic-root transform and contrast enhancement on the spectral domain to enhance weak harmonics and suppress noise. The proposed weighted unbiasing process reduces multiple or submultiple pitch errors efficiently. Evaluation is performed under the presence of white noise, babble noise, and telephone channel distortion. The results show that the proposed method performs equivalent to or better than previous state-of-the-art methods in the majority of the noise and channel conditions.</P>
Real Options Analysis of Groundwater Extraction and Management with Water Price Uncertainty
Lee, Jaehyung Korean Resource Economics Association 2018 자원·환경경제연구 Vol.27 No.4
This paper analyses the investment options of groundwater development project under water price uncertainty. The optimal investment threshold price which trigger the investment are calibrated base on monopolistic real options model. Stochastic dynamic model is set to reflect the uncertainty of water price which follows the GBM (Geometric Brownian Motion) process. Our finding from non-cooperative investment decision model is that uncertainty of water price could deter the groundwater investment by considering the existence of option values. For policy markers, it is easy to manage 'charges for utilization of groundwater' rather than 'performance guarantee ratio' when managing groundwater investment with pricing policy. And it is necessary to make comprehensive and well-designed policies considering the characteristics of regional groundwater reservoir and groundwater developers.
Real Options Analysis of Groundwater Extraction and Management with Water Price Uncertainty
( Jaehyung Lee ) 한국환경경제학회·한국자원경제학회(구 한국환경경제학회) 2018 자원·환경경제연구 Vol.27 No.4
This paper analyses the investment options of groundwater development project under water price uncertainty. The optimal investment threshold price which trigger the investment are calibrated base on monopolistic real options model. Stochastic dynamic model is set to reflect the uncertainty of water price which follows the GBM (Geometric Brownian Motion) process. Our finding from non-cooperative investment decision model is that uncertainty of water price could deter the groundwater investment by considering the existence of option values. For policy markers, it is easy to manage ‘charges for utilization of groundwater’ rather than ‘performance guarantee ratio’ when managing groundwater investment with pricing policy. And it is necessary to make comprehensive and well-designed policies considering the characteristics of regional groundwater reservoir and groundwater developers.
Vibration of a Vehicle Body Due to Road Roughness
Jaehyung Lee,Sang-Woo Bae,Hong Hee Yoo,Jang Moo Lee 한국자동차공학회 1999 한국 자동차공학회논문집 Vol.7 No.1
This paper presents a computational method to analyze the frequency characteristics of the vehicle system that includes vehicle body, suspension components and tires. With the modal synthesis technique, a coupled formulation was obtained for the substructure systems in which rubber bushings for body mount are modeled as tri-axial scalar springs. Equations of motion for the system are derived based on the modal synthesis method. Vibration modes and forced response characteristics of the system can be obtained by solving the system equation.<br/> To verify the accuracy of the simulation results obtained by the presented method, the bench test of quarter car and the modal test of the experimental vehicle are performed. Test results are in good agreement with the computational results obtained by the present method.<br/>