• Journal of Korean Neurosurgical Society
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• v.67 no.2
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• pp.186-193
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• 2024

Objective : The treatment paradigm for acute ischemic stroke has undergone several major changes in the past decade, contributing to improved patient prognosis in clinical practice. However, the extent to which these changes have affected patient prognosis in the real-world is yet to be clarified. This study aimed to evaluate the real-world impact of modern reperfusion therapy for acute ischemic stroke using data from the National Health Insurance Service in Korea. Methods : This study included patients aged 18-80 years who were admitted via the emergency room with an I63 code between 2011 and 2020. The rates of intravenous thrombolysis use and endovascular treatment according to the year of admission were investigated. Furthermore, the rates of decompressive craniectomy and 3-month mortality were also analyzed. The 10-year observational period was divided into three periods based on the 2015 guideline change as follows : prior, 2011-2014; transitional, 2015-2016; and modern, 2017-2020. Results : A total of 307117 patients (mean age, 65.7±10.9 years) were included, and most patients were male (59.7%). The rate of endovascular treatment gradually increased during the study period from 0.71% in the prior period to 1.32% in the transitional period and finally to 1.85% in the modern period. Meanwhile, the 3-month mortality rate gradually decreased from 4.78% in the prior period to 4.03% in the transitional period and to 3.71% in the modern period. Conclusion : In Korea, the mortality rate decreased as the rate of modern reperfusion therapy increased in patients with acute ischemic stroke. Overall, technical and scientific advances in reperfusion therapy have improved the outcome of patients with acute ischemic stroke in Korea.

• Journal of Cerebrovascular and Endovascular Neurosurgery
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• v.25 no.4
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• pp.420-428
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• 2023

Objective: Intraprocedural rupture (IPR) is a fatal complication of endovascular coiling for cerebral aneurysms. We hypothesized that contrast leakage period may be related to poor clinical outcomes. This study aimed to retrospectively evaluate the relationship between clinical outcomes and contrast leakage period. Methods: Data from patients with cerebral aneurysms treated via endovascular coiling between January 2010 and October 2018 were retrospectively assessed. The enrolled patient's demographic data, the aneurysm related findings, endovascular treatment and IPR related findings, rescue treatment, and clinical outcome were analyzed. Results: In total, 2,859 cerebral aneurysms were treated using endovascular coiling during the study period, with IPR occurring in 18 (0.63 %). IPR occurred during initial frame coiling (n=4), coil packing (n=5), stent deployment (n=7), ballooning (n=1), and microcatheter removal after coiling (n=1). Tear sites included the dome (n=14) and neck (n=4). All IPRs were controlled and treated with coil packing, with or without stenting. Flow arrest of the proximal balloon was not observed. Temporary focal neurological deficits developed in two patients (11.1%). At clinical follow-up, 14 patients were classified as modified Rankin Scale (mRS) 0, three as mRS 2, and one as mRS 4. The mean contrast leakage period of IPR was 11.2 min (range: 1-31 min). Cerebral aneurysms with IPR were divided into late (n=9, mean time: 17.11 min) and early (n=9, mean time: 5.22 min) control groups based on the criteria of 10 min of contrast leakage period. No significant between-group differences regarding clinical outcomes were observed after IPR (p=1). Conclusions: In our series, all patients with IPR were controlled with further coil packing or stenting without proximal balloon occlusion within 31 min of contrast leakage. There was no difference in clinical outcomes when the long contrast leakage period group and short contrast leakage period group were compared.

• Clinical and Experimental Pediatrics
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• v.45 no.7
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• pp.828-835
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• 2002

Purpose : The outcomes of infants weighing less than 1,500 gm(very low birth weight infant : VLBWI) reflect recent progress in neonatal intensive care. In this study, we analyzed changes over time in survival rate and morbidity of VLBWIs during the past seven years. Methods : A retrospective review of medical records was analyzed for VLBWIs admitted to the neonatal intensive care unit of Samsung Medical Center within three days from birth. We compared the outcomes of previous corresponding data(period I : Oct. 1994 to Sept. 1996), with the outcomes of period II(Oct. 1996 to Dec. 1998) and period III(Jan. 1999 to Dec. 2000). Results : As shown in Tables 1 and 3, the distribution of birth weight, gestational age(GA), gender, and inborn admissions did not change during the 7-year study. The overall survival rate of VLBWI increased significantly over time(period I : 72% vs period III : 88.3%, P<0.05). Between period I and period II, the birth weight-specific survival rate increased by 23.6%(75% vs 92.7%, P<0.05) for infants 1,000 to 1,249 gm. Between period II and period III, the birth weight-specific survival rate increased three times(20% vs 66.7%, P<0.05) for infants <750 gm. The survivors of lowest birth weight included infants at 624 gm(GA : $26^{+5}$ weeks), 667 gm(GA : $25^{+6}$ weeks) and 480 gm(GA : $26^{+2}$ weeks) in each period. The gestational age-specific survival rate in period III increased significantly in GA 25-26 weeks and 29-30 weeks(vs period I & period II, P<0.05). The survivors of lowest gestational age included infants at GA 26 weeks(970 gm), GA $23^{+5}$ weeks(791 gm) and GA $24^{+1}$ weeks(740 gm) in each period. The incidence of severe IVH(grade III, IV) and the early death rate(< seven days) decreased in period III(vs period I; P<0.05), reflecting improvements in neonatal intensive care. Conclusion : The survival rate of VLBWI continues to increase, particularly for BW < 750 gm, GA < 26 weeks. This increase in survival is not associated by any increase in major morbidities.

• Journal of the Chungcheong Mathematical Society
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• v.25 no.4
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• pp.747-752
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• 2012

When the service time distribution has a finite exponential moment, we present a large deviations result for the busy period distribution in the M/G/1 queue without the assumption of Abate and Whitt (1997) and Kyprianou (1971).

• Proceedings of the Korean Statistical Society Conference
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• 2002.11a
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• pp.273-277
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• 2002

In this paper, with martingale argument we derive the explicit formula for the Laplace transform of the busy period of M/M/1 queue with bounded workload which is also called finite dam. Much simpler derivation than appeared in former literature provided.

• Journal of architectural history
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• v.7 no.4 s.17
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• pp.165-173
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• 1998

The Fort of Han and Jin period was not only a defence-system of military purpose, but also a production-system of national economy, and a administration-system of the state as well. So it took a great role in the protection of social order and the preservation of Chinese culture.

• Journal of applied mathematics & informatics
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• v.28 no.3_4
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• pp.553-568
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• 2010

By making use of minimax theory and pseudo $Z_p$ index theory, some results on the existence and multiplicity of periodic solutions with minimal period to nonconvex superquadratic discrete Hamiltonian systems are obtained.

• Journal of the Chungcheong Mathematical Society
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• v.36 no.4
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• pp.215-221
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• 2023

We characterize a rational period function q(z) for Γ⁺₀ (3) which has a pole only at 0.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.9
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• pp.76-85
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• 2007

An optical rotary encoder is easy to implement for automatic control applications. In particular, the output of the encoder has a digital form pulse, which is also easy to be connected to a popular digital controller. By using the encoder, there are various angular velocity detecting methods, M-, T-, and M/T-method. Each of them has a property of its own. They have common limitation that the angular velocity detection period is strongly subject to the destination velocity magnitude in case of ultimate low range. They have ultimate long detection period or cannot even detect angular velocity at near zero velocity. This paper proposes a dual encoder system with two encoders of normal resolution. The dual encoder system is able to keep detection period moderately at near zero velocity and even detects zero velocity within nominal period. It is useful for detecting velocity in case of changing rotational direction at which there occurs zero velocity. In this paper, various experimental results are shown for the dual encoder system validity.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.2
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• pp.321-323
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• 2012

Cognitive radio has been recently proposed to dynamically access unused-spectrum. Since the spectrum availability for opportunistic access is determined by spectrum sensing, sensing is identified as one of the most crucial issues of cognitive radio networks. The PHY-layer sensing, as a part of spectrum sensing in cognitive radio, concerns the sensing mechanism to determine channel to be sensed and to access. One of the important issues in the PHY-layer sensing control is to find an available sensing period and trade-off between spectrum sensing and data transmission. In this paper, we show the relationship between spectrum sensing and data transmission according to the sensing period. We analyze and propose the new scheme to evaluate optimal sensing period.