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A Study on Recognition of Operating Condition for Hydraulic Driving Members
Park, Heung-Sik,Kim, Young-Hee,Kim, Dong-Ho,Cho, Yon-Sang,Park, Jae-Sang Korean Society for Precision Engineering 2003 International Journal of the Korean Society of Pre Vol.4 No.6
The morphological analysis of wear debris can provide early a failure diagnosis in lubricated moving system. It can be effective to analyze operating conditions of oil-lubricated tribological system with shape characteristics of wear debris in a lubricant. But, in order to predict and recognize an operating condition of lubricated machine, it is needed to analyze and to identify shape characteristics of wear debris. Therefore, If the morphological characteristics of wear debris are recognized by computer image analysis using the neural network algorithm, it is possible to recognize operating condition of hydraulic driving members. In this study, wear debris in the lubricating oil are extracted by membrane filter (0.45$\mu\textrm{m}$), and the quantitative values of shape parameters of wear debris are calculated by the digital image processing. This shape parameters are studied and identified by the artificial neural network algorithm. The result of study could be applied to prediction and to recognition of the operating condition of hydraulic driving members in lubricated machine systems.
Park, Heung-sik 한국통계학회 2000 Communications for statistical applications and me Vol.7 No.3
Using simulation, we compare the perturbation analysis estimate and the forward difference estimate for the first and second derivatives of performance measures in a Markov renewal process. We find the perturbation analysis estimate has much les mean squared error than the traditional forward difference estimate.
DERIVATION OF A PRICE PROCESS FOR MULTITYPE MULTIPLE DEFAULTABLE BONDS
Park Heung-Sik The Korean Statistical Society 2006 Journal of the Korean Statistical Society Vol.35 No.2
We consider a zero coupon bond that is at the risk of multitype multiple defaults. Assuming defaults occur according to k Cox processes, we find a price process for zero coupon bonds. To derive this process we follow the Lando (1998)'s method which uses conditional expectations instead of the traditional methods.
Effect of A Sinusoidal Field in a Switching Magnet for a Proton Beam Accelerator
Heung-Sik Kang,Chun-Kil Ryu,이희석,Hong-Gi Lee,Hong-Sik Han,Hyung-Seok Suh,Jinhyuk Choi,Ki-Hyeon Park,MunGyung Kim,Seong-Hun Jeong,Tae-Yeon Lee,Young-Gyu Jung 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.4
The 100-MeV Proton Engineering Frontier Project (PEFP) proton linac will provide two proton beam extraction lines at the 20-MeV and the 100-MeV end for users’ experiments. Each extraction line will be branched to 5 beamlines. To distribute the proton beam to each beamline, a switching magnet will be used. A conventional resonant AC-type power supply for the switching magnet, which supplies a current with a sinusoidal variation, causes some problems of sinusoidal field variation during the beam pulse duration and of magnet hysteresis. The effect of sinusoidal field variation is analyzed with the TRACE code by using the equivalent Twiss parameters. The effect of the magnet hysteresis is also described, and its solution is proposed.8消
Estimation for the Time-t Discounted Price of Multiple Defaultable Zero Coupon Bond
Park, Heung-Sik The Korean Statistical Society 2009 Communications for statistical applications and me Vol.16 No.3
We consider a multiple defaultable zero coupon bond. Assuming defaults occur according to a marked point process, we explain how to estimate the time-t discounted price of zero coupon bond by simulation. For the special case of a given specific random face value, we show that the real probability measure is the risk neutral probability measure. In this case the time-t discounted conditional price can be obtained by observing a single sample path upto the time t in the real world. Furthermore the time-t discounted price can be estimated by observing real situations or by simulation under the real probability measure.
Microsurgical Experience with Supraorbital Keyhole Operations on Anterior Circulation Aneurysms
Park, Heung-Sik,Park, Sang-Kyu,Han, Young-Min The Korean Neurosurgical Society 2009 Journal of Korean neurosurgical society Vol.46 No.2
Objective: Conventional pterional approach is a commonly used neurosurgical technique for the treatment of cerebral aneurysms. However, this technique requires more extensive brain exposure than other key hole approaches and is sometimes associated with surgical traumatization or cosmetic problems. The aim of this study was to compare the postoperative outcome between pterional and supraorbital keyhole approaches in the patients with anterior circulation aneurysms. Methods: The authors reviewed patients with anterior circulation aneurysms who underwent aneurysm clipping via pterional or supraorbital keyhole approach at a single institute over a period of 2 years. Ninety-eight patients harboring 108 aneurysms were included in this study. Various outcomes were recorded, which included clinical grade, cosmetic problems, patients' satisfaction and complications such as chewing discomfort, frontal muscle weakness, hyposmia, infection. Results: The supraorbital approach exhibited a shorter operation time compared with the pterional approach. Complications such as chewing discomfort occurred less frequently in the supraorbital approach group. Moreover, the cosmetic outcome was significantly better in the supraorbital group than in the pterional group. Conclusion: The supraorbital keyhole approach reduced intra- and postoperative complications, including chewing discomfort and cosmetic disturbances, compared with the conventional pterional approach.
Park, Heung-Sik,Chang, Dong-Kyu,Han, Young-Min The Korean Neurosurgical Society 2009 Journal of Korean neurosurgical society Vol.46 No.4
Objective : We investigated the locations of compressing vessels in hemifacial spasm. To approach compression sites, we described and evaluated the efficacy of the infranuchal infrafloccular (INIF) approach. Methods : A retrospective review of 31 consecutive patients who underwent microvascular decompression (MVD) through INIF with a minimum follow-up of 1 year was performed. Along the intracranial facial nerve, we classified the compression sites into the transitional zone (TRZ), the central nervous system (CNS) segment and the peripheral nervous system (PNS) segment. The INIF approach was used to inspect the CNS segment and the TRZ. Subdural patch graft technique was used in order to achieve watertight dural closure. The cranioplasty was performed using polymethylmethacrylate. The outcome and procedure-related morbidities were evaluated. Results : Twenty-nine patients (93%) showed complete disappearance of spasm. In two patients, the spasm was resolved gradually in 2 and 4 weeks, respectively. Late recurrence was noted in one patient (3%). The TRZ has been identified as the only compression site in 19 cases (61.3%), both the TRZ and CNS segment in 11 (35.5%) and the CNS segment only in 1 (3.2%). There was no patient having a compressing vessel in the PNS segment. Infection as a result of cerebrospinal fluid leak occurred in one patient (3%). Delayed transient facial weakness occurred in one patient. Conclusion : The TRZ and the CNS segment were more vulnerable area to the compression of vessels. We suggest that surgical avenue with the INIF approach provides early identification of this area.