• Communications of the Korean Mathematical Society
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• v.33 no.3
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• pp.985-999
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• 2018

This paper is devoted to the existence and uniqueness of $L^p$ (p > 1) solutions for general time interval multidimensional backward stochastic differential equations (BSDEs for short), where the generator g satisfies a ($p{\wedge}2$)-order weak monotonicity condition in y and a Lipschitz continuity condition in z, both non-uniformly in t. The corresponding stability theorem and comparison theorem are also proved.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1748-1753
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• 2011

In this paper, we consider the stability of linear systems with an interval time-varying delay. It is known that the adoption of decomposition of delay improves the stability result. For the interval time-delay case, they applied it to the interval of time-delay and got less conservative results. Our basic idea is to apply the general decomposition to the low limit of delay as well as interval of time-delay. Based on this idea, by using the modified Lyapunov-Krasovskii functional and newly derived Lemma, we present a less conservative stability criterion expressed as in the form of linear matrix inequality(LMI). Finally, we show, by well-known two examples, that our result is less conservative than the recent results.

• Bulletin of the Korean Mathematical Society
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• v.52 no.2
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• pp.483-504
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• 2015

This paper is devoted to solving a multidimensional backward stochastic differential equation with a general time interval, where the generator is uniformly continuous in (y, z) non-uniformly with respect to t. By establishing some results on deterministic backward differential equations with general time intervals, and by virtue of Girsanov's theorem and convolution technique, we prove a new existence and uniqueness result for solutions of this kind of backward stochastic differential equations, which extends the results of [8] and [6] to the general time interval case.

• Management Science and Financial Engineering
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• v.4 no.2
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• pp.1-13
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• 1998

The Shortest Path Problem in Time-dependent Networks, where the travel time of each link depends on the time interval, is not realistic since the model and its solution violate the Non-passing Property (NPP:often referred to as FIFO) of real phenomena. Furthermore, solving the problem needs much more computational and memory complexity than the general shortest path problem. A new model for Time-dependent Networks where the flow speeds of each link depend on time interval, is suggested. The model is more realistic since its solution maintains the NPP. Solving the problem needs just a little more computational complexity, and the same memory complexity, as the general shortest path problem. A solution algorithm modified from Dijkstra's label setting algorithm is presented. We extend this model to the problem of Minimum Expected Time Path in Time-dependent Stochastic Networks where flow speeds of each link change statistically on each time interval. A solution method using the Kth-shortest Path algorithm is presented.

• Journal of the Korean Operations Research and Management Science Society
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• v.14 no.2
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• pp.105-114
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• 1989

The actual working time of jobs, in general, is different to the standard time of jobs. In this paper, in order to analyze the actual working time of each job in production, we use the total production amount and the encessary total working time. The method which analyzes the actual working time is as follows. In this paper, we propose the interval regression analysis for obtaining an interval linear regression model with constraint conditions with respect to interval parameters. The merits of this method are the following.1) it is easy to obtain an interval linear model by solving a LP problem to which the formulation of proposed regression analysis is reduced, 2) it is easy to add constraint conditions about interval parameters, which are a sort of expert knowledge. As an application, within a case which has given certain data, the actual working time of jobs and the number of workers in a future plan are estimated through the real data obtianed from the operation of processing line in a heavy industry company. It results from the proposed method that the actual working time and the number of workers can be estimated as intervals by the interval regression model.

• Journal of Advanced Navigation Technology
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• v.20 no.5
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• pp.475-481
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• 2016

In this paper, the new stability condition of linear discrete interval time-varying systems with time-varying delay time is proposed. The considered system has interval time-varying system matrices for both non-delayed and delayed states with time-varying delay time within given interval values. The proposed condition is derived by using Lyapunov stability theory and expressed by very simple inequality. The restricted stability issue on the interval time-invariant system is expanded to interval time-varying system and a powerful stability condition which is more comprehensive than the previous is proposed. As a results, it is possible to avoid the introduction of complex linear matrix inequality (LMI) or upper solution bound of Lyapunov equation in the derivation of sufficient condition. Also, it is shown that the proposed result can include the many existing stability conditions in the previous literatures. A numerical example in the pe revious works is modified to more general interval system and shows the expandability and effectiveness of the new stability condition.

• Journal of Korean Neurosurgical Society
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• v.63 no.5
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• pp.598-606
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• 2020

Objective : The purpose of this study was to evaluate the impact of time interval between index event and stenting on the periprocedural risk of stenting for symptomatic carotid stenosis and to determine the optimal timing of stenting. Methods : This retrospective study included 491 (322 symptomatic [65.6%] and 169 asymptomatic [34.4%]) patients undergoing carotid stenting. The symptomatic patients were categorized into Day 0-3, 4-7, 8-10, 11-14, 15-21, and >21 groups according to the time interval between index event and stenting. Periprocedural (≤30 days) risk for clinical (any neurological deterioration) and radiological (new infarction on postprocedural diffusion-weighted imaging) events of stenting in each time interval versus asymptomatic stenosis was calculated with logistic regression analysis adjusted for confounders, and provided as odds ratio (OR) and 95% confidence interval (CI). Results : Overall clinical event rate (4.3%) of stenting for symptomatic carotid stenosis was higher than that for asymptomatic stenosis (1.2%; OR, 3.979 [95% CI, 1.093-14.489]; p=0.036). Stenting in Day 0-3 (13.2%; OR, 10.997 [95% CI, 2.333-51.826]; p=0.002) and Day 4-7 (8.3%; OR, 6.775 [95% CI, 1.382-33.227]; p=0.018) was associated with high risk for clinical events. However, the clinical event rates in stenting after 7 days from index event (Day 8-10, 1.8%; Day 11-14, 2.5%; Day 15-21, 0%; Day >21, 2.9%) were not different from that in stenting for asymptomatic stenosis. Overall radiological event rate (55.6%) in symptomatic stenosis was also higher than that in asymptomatic stenosis (35.5%; OR, 2.274 [95% CI, 1.553-3.352]; p<0.001). The high risk for radiological events was maintained in all time intervals (Day 0-3 : 55.3%; OR, 2.224 [95% CI, 1.103-4.627]; p=0.026; Day 4-7 : 58.3%; OR, 2.543 [95% CI, 1.329-4.949]; p=0.005; Day 8-10 : 53.6%; OR, 2.096 [95% CI, 1.138-3.889]; p=0.018; Day 11-14 : 57.5%; OR, 2.458 [95% CI, 1.225-5.021]; p=0.012; Day 15-21 : 55.6%; OR, 2.271 [95% CI, 1.099-4.764]; p=0.028; Day >21 : 54.8%; OR, 2.203 [95% CI, 1.342-3.641]; p=0.002). Conclusion : This study showed that as stenting was delayed, the periprocedural risk for clinical events decreased. The clinical event risk was high only in stenting within 7 days and comparable with that for asymptomatic stenosis in stenting after 7 days from index event, although the radiological event risk was not affected by stenting timing. Therefore, our results suggest that delayed stenting after 7 days from symptom onset is a safe strategy for symptomatic stenosis.

• Journal of Trauma and Injury
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• v.34 no.2
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• pp.105-111
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• 2021

Purpose: Open extremity fractures require prompt antibiotic medication and initial debridement surgery to reduce the infection rate and restore functional stabilization. We aimed to report the effects and positive outcomes of a trauma team approach on the management of open extremity fractures in polytrauma patients. Methods: This retrospective review included all polytrauma patients with open extremity fractures admitted between March 2009 and December 2019. Patients were divided into two groups according to whether they were treated before or after the implementation of the trauma team approach (March 2014). We analyzed the outcomes in each group with respect to the time interval until the doctor's arrival, total length of stay in the emergency department, the time interval until initial antibiotic treatment and operation, whether the initial operation was performed within 24 hours, and the rate of deep infections. Results: A total of 123 patients met the inclusion criteria. There were no statistically significant differences in demographic characteristics. The time interval until the doctor's arrival (64.12±49.2 minutes vs. 19.82±15.23 minutes; p=0.035) and initial antibiotic treatment (115.47±72.12 minutes vs. 48.78±30.12 minutes; p=0.023) significantly improved after implementing the trauma team approach. The union rate was not significantly different. However, the time interval until initial debridement, opportunity for initial debridement within 24 hours, and the rate of deep infections demonstrated better results. Conclusions: The reduced time interval until initial antibiotic treatment and debridement could be attributed to the positive effect of the trauma team approach on the management of open extremity fractures in polytrauma patients.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.4
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• pp.502-508
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• 2014

In this paper, a delay-dependent $H_{\infty}$ filtering problem is investigated for discrete-time delayed nonlinear systems which include a more general sector nonlinear function instead of employing the commonly used Lipschitz-type function. By using the Lyapunov-Krasovskii functional approach, a less conservative sufficient condition is established for the existence of the desired filter, and then, the corresponding solvability condition guarantee the stability of the filter with a prescribed $H_{\infty}$ performance level. Finally, two simulation examples are given to show the effectiveness of the proposed filtering scheme.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.3
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• pp.285-294
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• 2012

Using bearing measurement only, target motion state is not directly obtained so that TMA (Target Motion Analysis) is needed for this situation. TMA is a nonlinear estimation technique used in passive SONAR systems. Also it is the one of important techniques for underwater combat management systems. TMA can be divided to two parts: batch estimation and sequential estimation. It is preferable to use sequential estimation for reducing computational load as well as adaptively to target maneuvers, batch estimation is still required to attain target initial state vector for convergence of sequential estimation. Selection of batch time interval which depends on observability is critical in TMA performance. Batch estimation in general utilizes predetermined batch time interval. In this paper, we propose a new method called the BTIS (Batch Time Interval and Initial State Estimation). The proposed BTIS estimates target initial status and determines the batch time interval sequentially by using a bank of GMM-TS (Gaussian Mixture Measurement-Track Splitting) filters. The performance of the proposal method is verified by a Monte Carlo simulation study.