• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.17-25
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• 2013

Performance of DI diesel engine with high fuel injection method is directly related to the emission characteristics and fuel consumption. At present, diesel injection system with piezo element is replacing conventional solenoid type due to their faster electro-mechanical properties. In this study, it was investigated the sensitivity characteristics regarding internal hydraulic modeling based on the AMESim environment of piezo-driven injector The analytic parameter for this study defined such as In/Out orifice, injection hole's diameter and driven voltage on piezo stack. As the results, it was shown that these parameter influence on a fast response characteristics of piezo-driven injector. Also we found fuel pressure recovery time is faster about 0.1 ms due to larger IN orifice diameter. And larger OUT orifice diameter occurs maximum pressure drop with faster its timing of about 0.2 ms.

• Journal of the Korea Society of Computer and Information
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• v.23 no.1
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• pp.33-39
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• 2018

In this paper, We studied the possibility of SoC(System On Chip) design using infrared image processing IP(Intellectual Property). And, we studied NUC(Non Uniformity Correction), BPR(Bad Pixel Recovery), and CEM(Contrast Enhancement) processing, the infrared image processing algorithm implemented by IP. We showed the logic and timing diagram implemented through the hardware block designed based on each algorithm. Each algorithm was coded as RTL(Register Transfer Level) using Verilog HDL(Hardware Description Language), ALTERA QUARTUS synthesis, and programed in FPGA(Field Programmable Gated Array). In addition, we have verified that the image data is processed at each algorithm without any problems by integrating the infrared image processing algorithm. Particularly, using the directly manufactured electronic board, Processor, SRAM, and FLASH are interconnected and tested and the verification result is presented so that the SoC type can be realized later. The infrared image processing IP proposed and verified in this study is expected to be of high value in the future SoC semiconductor fabrication. In addition, we have laid the basis for future application in the camera SoC industry.

• Journal of Physiology & Pathology in Korean Medicine
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• v.26 no.6
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• pp.929-933
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• 2012

This study was done to examine the prognosis according to onset and duration of treatment in acute ischemic cerebral infarction patients. We analysed NIHSS(National Institutes of Health Stroke Scale) score of acute ischemic cerebral infarction patients who visited department of Internal Korean Medicine, one medical center in Busan from January to December 2009. We divided patients into two groups by the initial time of treatment. Group A is admitted within 7 days, Group B is admitted from 7 to 14 days. We used NIHSS for functional recovery after 3 weeks later from admission day, and analyzed prognostic factor by analysis of covariance. All patients showed statistically significant improvement after 1week, 2weeks, 3weeks from admission, and between 1st week and 2nd week. However, there was no significant difference between 2nd week and 3rd week. NIHSS recovery score after 3weeks were analysed according to the timing of treatment. There was a statistically significant difference between two groups. The percentage of aggravated patients showed no statistically significant difference between the two groups. This study suggests that earlier admission care has an effect on functional recovery of patients with acute ischemic cerebral infarction. Further research on the large scale and long-term follow up is required.

• Journal of Korean Neurosurgical Society
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• v.29 no.8
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• pp.1126-1135
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• 2000

Objectives : The goal of surgical management of cerebral arteriovenous malformation(AVM) is elimination of the lesion without development of new neurological deficits. To improve the management results of cerebral AVMs in the future, this article discusses about surgical complications of the AVM and their management. Material and Methods : During the past 18 years, 116 patients with cerebral AVMs were managed by surgery. Among these cases, 7 cases died, 7 cases developed new neurological deficits, 11 cases residual AVM and 5 cases intracerebral hematoma(ICH) after surgery. The author analyzes the causes of those complications and investigates the methods to minimized those complications based on the review of the literatures. Results : One stage removal of AVM and ICH in the poor neurological state were performed in 5 of 7 death cases. Subtotal removal of ICH followed by delayed AVM surgery after recovery is regard as one method to improve the outcome of patient with large ICH. Postoperative new neurological deficits developed owing to normal perfusion pressure breakthrough(NPPB) in 3, judgement error in 2, preoperative embolization in 1 and cortical injury in 1 case(s). Proper management of NPPB, accurate anatomical knowledge and physiological monitoring during operation, and well trained skill for embolization are regard as methods to minimize those complications. Residual AVMs after surgery were noticed in 11 cases, in which unintended 6 cases due to inaccurate dissection of peripheral margin of AVM, and intended 3 cases due to massive brain swelling during operation, 1 cases due to diffuse type and 1 case due to multiple type of AVM. Accurate dissection of peripheral margin of AVM and mild hypotension during operation may help to avoid this complication. Postoperative hemorrhage occurred in 3 cases due to rupture of the residual AVM and in 2 cases due to oozing from the AVM bed. Complete resection of AVM, complete control of bleeding points at AVM bed and mild hypotension during early postoperative period are the methods to avoid this complication. Conclusion : A precise but flexible therapeutic strategy and refined skill for endovascular, radiosurgical and microsurgical techniques are required to successful treatment of cerebral AVM. Adequate timing of AVM resection, accurate anatomical knowledge, proper management of NPPB and accurate dissection of peripheral margin of AVM are the key points for avoiding complications of the AVM surgery.

• Clinical and Experimental Pediatrics
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• v.45 no.2
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• pp.223-231
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• 2002

Purpose : We review our experience with pyeloplasty for unilateral ureteropelvic junction obstruction of moderate to severe hydronephrosis observed by prenatal ultrasonography to assess the appropriate timing of operation for recovery of renal function and obstruction. Methods : We retrospectively reviewed the records of the total 28 patients who underwent pyeloplasty between 1995 and 2001 at Asan Medical Center. We compared pre and postoperative differentials in renal function and diuretic renogram as measured by technetium-99m-mercaptoacetyl-triglycerine scan and the degree of hydronephrosis by renal ultrasonography. Results : In all 28 patients postoperative follow-up renal ultrasonography revealed significant improvement in hydronephrosis. In 10 poorly functioning hydronephrotic kidneys in which relative renal function function was less than 35%, renal function was improved postoperatively in 3 cases, but not improved in 7 cases. In all 28 patients postoperative follow-up diuretic renogram revealed significant improvement. Conclusion : We believe that the early pyeloplasty should be considered when ultrasonography and diuretic renography suggest obstruction because renal function does not improve significantly after pyeloplasty over preoperative value.

• Journal of Distribution Science
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• v.13 no.5
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• pp.53-60
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• 2015

Purpose - The purpose of this paper is to shed light on the importance of the slope and curvature of the volatility curve implied in option prices in the KOSPI 200 options index. A number of studies examine the implied volatility curve, however, these usually focus on cross-sectional characteristics such as the volatility smile. Contrary to previous studies, we focus on time-series characteristics; we investigate correlation dynamics among slope, curvature, and level of the implied volatility curve to capture market information embodied therein. Our study may provide useful implications for investors to utilize current market expectations in managing portfolios dynamically and efficiently. Research design, data, and methodology - For our empirical purpose, we gathered daily KOSPI200 index option prices executed at 2:50 pm in the Korean Exchange distribution market during the period of January 2, 2004 and January 31, 2012. In order to measure slope and curvature of the volatility curve, we use approximated delta distance; the slope is defined as the difference of implied volatilities between 15 delta call options and 15 delta put options; the curvature is defined as the difference between out-of-the-money (OTM) options and at-the-money (ATM) options. We use generalized method of moments (GMM) and the seemingly unrelated regression (SUR) method to verify correlations among level, slope, and curvature of the implied volatility curve with statistical support. Results - We find that slope as well as curvature is positively correlated with volatility level, implying that put option prices increase in a downward market. Further, we find that curvature and slope are positively correlated; however, the relation is weakened at deep moneyness. The results lead us to examine whether slope decreases monotonically as the delta increases, and it is verified with statistical significance that the deeper the moneyness, the lower the slope. It enables us to infer that when volatility surges above a certain level due to any tail risk, investors would rather take long positions in OTM call options, expecting market recovery in the near future. Conclusions - Our results are the evidence of the investor's increasing hedging demand for put options when downside market risks are expected. Adding to this, the slope and curvature of the volatility curve may provide important information regarding the timing of market recovery from a nosedive. For financial product distributors, using the dynamic relation among the three key indicators of the implied volatility curve might be helpful in enhancing profit and gaining trust and loyalty. However, it should be noted that our implications are limited since we do not provide rigorous evidence for the predictability power of volatility curves. Meaning, we need to verify whether the slope and curvature of the volatility curve have statistical significance in predicting the market trough. As one of the verifications, for instance, the performance of trading strategy based on information of slope and curvature could be tested. We reserve this for the future research.

• Journal of The Korean Society of Clinical Toxicology
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• v.16 no.2
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• pp.86-92
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• 2018

Purpose: Cardiovascular or respiratory complications of acute intoxication are the most common causes of mortality. Advanced cardiac life support (ACLS) or specific antidotes help manage these cardiac or respiratory complications in acute intoxication. On the other hand, some cases do not respond to ACLS or antidotes and they require some special treatment, such as extracorporeal life support (ECLS). ECLS will provide the chance of recovery from acute intoxication. This study examined the optimal timing of ECLS in acute intoxication cases. Methods: This paper is a brief report of a case series about ECLS in acute poisoning. The cases of ECLS were reviewed and the effects of ECLS on the blood pressure and serum lactate level of the patients were analyzed. Results: A total of four cases were reviewed; three of them were antihypertensive agent-induced shock, and one was respiratory failure after the inhalation of acid. The time range of ECLS application was 4.8-23.5 hours after toxic exposure. The causes of ECLS implementation were one for recurrent cardiac arrest, two for shock that did not respond to ACLS, and one for respiratory failure that did not respond to mechanical ventilator support. Three patients showed an improvement in blood pressure and serum lactate level and were discharged alive. In case 1, ECLS was stared at 23.5 hours post toxic exposure; the patient died due to refractory shock and multiple organ failure. Conclusion: The specific management of ECLS should be considered when a patient with acute intoxication does not recovery from shock or respiratory failure despite ACLS, antidote therapies, or mechanical ventilator support. ECLS improved the hemodynamic and ventilator condition in complicated poisoned patients. The early application of ECLS may improve the tissue perfusion state and outcomes of these patients before the toxic damage becomes irreversible.

• The Journal of the Acoustical Society of Korea
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• v.31 no.7
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• pp.441-448
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• 2012

Spread spectrum provides the minimized inter-symbol interference, the low probability of intercept and the multiple access capability. This paper presents a direct sequence spread spectrum with carrier/timing recovery and equalizer which compensates the delay spread caused by multipath transmission. When the sea trials were performed in Korean East Sea, the bit error rates of QPSK and direct sequence spread spectrum are $1.46{\times}10^{-2}$ and $5.17{\times}10^{-4}$ at 3 km source-receiver range, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.8
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• pp.715-720
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• 2014

In order to maximize the effect of left ventricular assist device (LVAD) on ventricular unloading, the therapy should be begun at appropriate level of heart failure severity. We predicted pumping efficacy of LVAD according to the severity of heart failure theoretically. We used 3 dimensional finite element model of ventricle coupled with 6 Wind-kessel compartmental model of vascular system. Using the computational model, we predicted cardiac responses such as contractile ATP consumption of ventricle, left ventricular pressure, cardiac output, ejection fraction, and stroke work according to the severity of ventricular systolic dysfunction under the treatments of continuous LVAD. Contractile ATP consumption, which indicates the ventricular energetic loading condition decreased maximally at the $5^{th}$ level heart-failure under LVAD therapy. We conclude that optimal timing for LVAD treatment is $5^{th}$ level heart-failure when considering LVAD treatment as "bridge to recovery".

• Journal of Korean Neurosurgical Society
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• v.38 no.4
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• pp.281-286
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• 2005

Objective : The authors report our experience of urokinase thrombolysis in treating patients harboring nonaneurysmal spontanesous intraventricular hemorrhage[IVH] and evaluated complications, safety and feasibility of this procedure retrospectively. Methods : Fifty-three patients with nonaneurysmal IVH>15mL without underlying structural etiology or coagulopathy were recruited. The patients with Glasgow Coma Scale[GCS]<5 were excluded. A catheter was directed into the IVH. Hematoma aspiration was followed by instillation of urokinase at the ear level of drainage bag under intracranial pressure monitoring system. This was repeated every 6hours until half of its initial volume. For analysis of prognostic factors, we classified the patients into two groups by Glasgow outcome scale[GOS]; good [$GOS\;{\ge}3$] and bad [GOS<3] prognosis group, and performed comparative analysis between two groups. Results : Mean age was 60.2years. The baseline hematoma size ranged 16 to 72mL. IVH volume reduction was done by an average of 74.2%. As complications, there were 3cases of rebleeding and 2cases of ventriculitis. No intracranial adverse effects were observed during thrombolytic theraphy. At 6months after the procedure, 29patients had achieved a good recovery, 15remained vegetative. 9patients died in hospital. The main good prognostic factors were young age, small IVH volume, and high GCS. Conclusion : The results of this study suggest that this relatively easy and safe method of treatment will improve the prognosis. However, further clinical studies also must assess optimal thrombolytic dosage, frequency, and timing of urokinase instillation for safety and effectiveness and must include controlled comparisons of mortality, disability outcome, quality of life, time until convalescence, and cost of care in treated and untreated patients.