• Proceedings of the KIPE Conference
• /
• 2016.07a
• /
• pp.333-334
• /
• 2016

This paper proposes a new cascoded configuration for hybrid energy storage system (HESS) which consists of batteries and supercapacitor (SC) for Electric Vehicle applications. In this configuration,a resonant LLC converter is interfacedin series with a battery module and it converts a part of the energy from the batteries and transfer it to the dc-link bus. The LLC converter is controlled by a phase-shift angle between the primary and secondary switches to maintain a constant dc-link voltage and obtain soft-switching conditions for all the primary switches. By placing the SC moduleina cascoded concept, the rated voltage of SC can be reduced significantly compared with the conventional topologies. It helps save the cost and reduce the number of SC cells. The proposed configuration can operate with four different modes: feeding load, acceleration, regenerative braking andSC charging. A scaled-down prototype converter (2 kW, 600V output) is designed and tested to verify the advantages of the proposed topology. The maximum efficiency obtained with the proposed topology is 99%.

• Journal of Korean Neurosurgical Society
• /
• v.47 no.5
• /
• pp.392-394
• /
• 2010

Trochlear nerve palsy associated with spontaneous subarachnoid hemorrhage (SAH) is known to be a rare malady. We report here on a patient who suffered with left trochlear nerve palsy following rupture of a right posterior communicating artery aneurysm. A 56-year-woman visited our emergency department with stuporous mental change. Her Hunt-and-Hess grade was 3 and the Fisher grade was 4. Cerebral angiography revealed a ruptured aneurysm of the right posterior communicating artery. The aneurysm was clipped via a right pterional approach on the day of admission. The patient complained of diplopia when she gazed to the left side, and the ophthalmologist found limited left inferolateral side gazing due to left superior oblique muscle palsy on day 3. Elevated intracranial pressure, intraventricular hemorrhage or a dense clot in the basal cisterns might have caused this trochlear nerve palsy.

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.75-75
• /
• 2013

Recent observations have shown that some massive globular clusters (GCs) host multiple stellar populations having different heavy element abundances enriched by supernovae. They usually accompany multiple red giant branches (RGBs) in the color-magnitude diagrams (CMDs), and are distinguished from most of the other GCs which display variations only in light element abundances. In order to investigate the star formation histories of these peculiar GCs, we have constructed synthetic CMDs based on the updated versions of Yonsei.Yale ($Y^2$) isochrones and horizontal branch evolutionary tracks which include the cases of enhancements in both helium and the total CNO abundances. To estimate ages and helium abundances of subpopulations in each GC, we have compared our models with the observations on the Hess diagram by employing a ${\chi}^2$ minimization technique. In this talk, we will present our progress in the population modeling for these GCs with multiple RGBs.

• Journal of Korean Neurosurgical Society
• /
• v.39 no.1
• /
• pp.36-39
• /
• 2006

Objective : The present study attempts to address the change of management results over time during the past 13 years in good-grade patients with intracranial aneurysm. Methods : Six hundred twenty five [Hunt-Hess grade I to III] out of 826 patients with ruptured intracranial aneurysms operated by the same operator within 3 days after the attack from 1990 to 2002 were selected. Since 1998, endovascular aneurysmal occlusion was done in selected cases of 21 patients. The change of management results over time, including rebleeding rate, delayed ischemic neurologic deficit[DIND] as a cause of morbidity and mortality and surgical outcome were examined. Results : The ratio of poor-grade patients in all patients tended to decrease over the years. The early rebleeding rate declined from 5.0% to 1.2% with the use of tranexamic acid and computed tomography angiogram DIND as a cause of mortality and morbidity has decreased from 12.5% in 1990 to approximately 0% currently. Surgical outcome began to improve significantly in 1994 [poor outcome : 25% in 1990, 12.2% in 1994,6.8% in 2002]. Conclusion : These results suggest that the advances in care and increased experience of the operator significantly affect the change of overall outcome, and early detection of the aneurysm is needed for reducing the ratio of poor-grade patients.

• Journal of Korean Neurosurgical Society
• /
• v.29 no.7
• /
• pp.923-928
• /
• 2000

Objective : The reliability of transcranial doppler sonography(TCD) for predicting delayed ischemic neurologic deficit( DIND) was investigated in patients with aneurysmal subarachnoid hemorrhage(SAH). Methods : The velocity of blood flow through the middle cerebral artery was measured by TCD in 70 patients treated surgically within 72 hours due to ruptured cerebral aneurysm. A correlation between measured maximal mean blood flow velocities and clinical factors including age, hypertension, Hunt-Hess grade, Fisher grade, DIND, and outcome was made. Results : An age-dependent reduction of the measured maximal mean velocities was found(r＝-0.4043, p<0.001). Flow velocities in hypertensive patients were significantly lower than in the normotensive individuals(two-tailed T test, p<0.05). There was no significant difference between the flow velocities and evaluated other clinical factors. When the flow velocities of 14 patients who developed DIND were compared with those of patients without deficits, no significant difference was seen. A significant increase in flow velocities in the days before the onset of DIND was found only in 4 of 14 cases. High flow velocities did not necessarily mean impending neurological deficits : 6 of 70 patients tolerated flow velocities over 160cm/s. Conclusion : We suggest that TCD readings have limited utility for predicting DIND following SAH, especially in older or hypertensive patients. More direct measurements of blood flow are necessary to adequately predict which patients are at high risk of DIND.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.5
• /
• pp.1934-1944
• /
• 2017

As a key component of high-voltage power conversion system for electric vehicles (EVs), bidirectional DC/DC (Bi-DC/DC) is required to have high efficiency and light weight. Conventional design methods optimize the Bi-DC/DC at the maximum power dissipation point (MPDP). For EVs application, the work condition of the Bi-DC/DC is not strict as the MPDP, where the design method using MPDP may not be optimal during travel of EVs. This paper optimizes the Bi-DC/DC converter targeting efficiency and weight based on the driving cycle. By analyzing the two-phase interleaved Bi-DC/DC for hybrid energy storage systems (HESS) of EVs, its power dissipation is calculated, and an efficiency model is derived. On this basis, weight models of capacitor, inductor and heat sink are built, as well as a dynamic temperature model of heat sink. Based on these models, a method using New European Driving Cycle (NEDC) for optimal design of Bi-DC/DC which simultaneously considered efficiency and weight is proposed. The simulation result shows that compare with conventional optimization methods revealed that the optimization approach based on driving cycle allowed significant weight reduction while meeting the efficiency requirements.

• Journal of Korean Neurosurgical Society
• /
• v.44 no.6
• /
• pp.353-357
• /
• 2008

Objective : Many vascular neurosurgeons tend to remove bone flap in patients with large aneurysmal intracerebral hematomas (ICH). However, relatively little work has been done regarding the effectiveness of prophylactic decompressive craniectomy in a patient with a large aneurysmal ICH. Methods : Large ICH was defined as hematoma when its volume exceeded 25 mL, ipsilateral to aneurysms. The patients were divided into two groups; aneurysmal subarachnoid hemorrhage (SAH) associated with large ICH, January, 1994 - December, 1999 (Group A, 41 patients), aneurysmal SAH associated with large ICH, January, 2000 - May, 2005 (Group 8, 27 patients). Demographic and clinical variables including age, sex, hypertension, vasospasm, rebleeding, Hunt-Hess grade, aneurysm location, aneurysm size, and outcome were compared between two groups, and also compared between craniotomy and craniectomy patients in Group A. Results : In Group A. 21 of 41 patients underwent prophylactic decompressive craniectomy. In Group 8, only two patients underwent craniectomy. Surgical outcome in Group A (good 23, poor 18) was statistically not different from Group 8 (good 15, poor 12). Surgical outcomes between craniectomy (good 12, poor 9) and craniotomy cases (good 11, poor 9) in Group A were also comparable. Conclusion : We recommend that a craniotomy can be carried out safely without prophylactic craniectomy in patients with a large aneurysmal ICH if intracranial pressure is controllable with hematoma evacuation.

• Journal of Korean Neurosurgical Society
• /
• v.50 no.4
• /
• pp.327-331
• /
• 2011

Objective : The aim of this study is to investigate the clinical outcomes of surgery and coiling and analyze the predicting factors affecting the clinical outcomes of ruptured posterior inferior cerebellar artery (PICA) aneurysms. Methods : During the last 15 years, 20 consecutive patients with ruptured PICA aneurysms were treated and these patients were included in this study. The Fisher's exact test was used for the statistical significance of Glasgow Outcome Scale (GOS) according to initial Hunt-Hess (H-H) grade, treatment modalities, and the presence of acute hydrocephalus. Results : Eleven (55%) and nine (45%) patients were treated with surgical clipping and endovascular treatment, respectively. Among 20 patients, thirteen (65.0%) patients had good outcomes (GOS 4 or 5). There was the statistical significance between initial poor H-H grade, the presence of acute hydrocephalus and poor GOS. Conclusion : In our study, we suggest that initial H-H grade and the presence of acute hydrocephalus may affect the clinical outcome rather than treatment modalities in the ruptured PICA aneurysms.

• Journal of Korean Neurosurgical Society
• /
• v.29 no.12
• /
• pp.1657-1663
• /
• 2000

The authors report a case of a 72-year-old woman who presented with intraventricular and subarachnoid hemorrhage of Hunt and Hess grade IV after the rupture of a giant aneurysm arising from the right internal carotid artery. The aneurysm was clipped successfully with the aid of cardiopulmonary bypass(closed chest method), deep hypothermic circulatory arrest, and cerebral protection with barbiturate resulting in moderate disability. We discuss the usefulness and problems related to technique of circulatory arrest and cardiopulmonary bypass using closed chest method, and suggest the possible benefits of open chest method in elderly people and the importance of preoperative plan to coordinate anesthesia and operation.

• Archives of Plastic Surgery
• /
• v.42 no.5
• /
• pp.567-571
• /
• 2015

Background Bariatric surgeries performed in the USA has increased twelve-fold in the past two decades. The effects of rapid weight loss on facial features has not been previously studied. We hypothesized that bariatric surgery will mimic the effects of aging thus giving the patient an older and less attractive appearance. Methods Consecutive patients were enrolled from the bariatric surgical clinic at our institution. Pre and post weight loss photographs were taken and used to generate two surveys. The surveys were distributed through social media to assess the difference between the preoperative and postoperative facial photos, in terms of patients' perceived age and overall attractiveness. 102 respondents completed the first survey and 95 respondents completed the second survey. Results Of the 14 patients, five showed statistically significant change in perceived age (three more likely to be perceived older and two less likely to be perceived older). The patients were assessed to be more attractive postoperatively, which showed statistical significance. Conclusions Weight loss does affect facial aesthetics. Mild weight loss is perceived by survey respondents to give the appearance of a younger but less attractive patient, while substantial weight loss is perceived to give the appearance of an older but more attractive patient.