• 정보처리학회논문지D
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• 제15D권1호
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• pp.31-40
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• 2008

유사 시퀀스 매칭에서는 고차원인 시퀀스를 저차원의 점으로 변환하기 위하여 저차원 변환을 사용한다. 그런데, 이러한 저차원 변환은 시계열 데이터의 종류에 따라 인덱싱 성능에 있어서 큰 차이를 나타낸다. 즉, 어떤 저차원 변환을 선택하느냐가 유사 시퀀스 매칭의 인덱싱 성능에 큰 영향을 주게 된다. 이 문제를 해결하기 위하여, 본 논문에서는 하나의 인덱스에서 두 개 이상의 저차원 변환을 통합하여 사용하는 하이브리드 접근법을 제안한다. 먼저, 하나의 시퀀스에 두 개 이상의 저차원 변환을 적용하는 하이브리드 저차원 변환의 개념을 제안하고, 변환된 시퀀스간의 거리를 계산하는 하이브리드 거리를 정의한다. 다음으로, 이러한 하이브리드 접근법 사용하면 유사 시퀀스 매칭을 정확하게 수행할 수 있음을 정형적으로 증명한다. 또한, 제안한 하이브리드 접근법을 사용하는 인덱스 구성 및 유사 시퀀스 매칭 알고리즘을 제시한다. 다양한 시계열 데이터에 대한 실험 결과, 제안한 하이브리드 접근법은 단일 저차원 변환을 사용하는 경우에 비해서 우수한 성능을 보이는 것으로 나타났다. 이 같은 결과를 볼 때, 제안한 하이브리드 접근법은 다양한 특성을 지닌 다양한 시계열 데이터에 두루 적용될 수 있는 우수한 방법이라 사료된다.

• Geomechanics and Engineering
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• 제23권1호
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• pp.1-13
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• 2020

To give a solution for seismic stability of tunnel faces subjected to earthquake ground shakings, the pseudo-dynamic approach is originally introduced to analyze tunnel face stability in this study. In the light of the upper-bound theorem of limit analysis, an advanced three-dimensional mechanism combined with pseudo-dynamic approach is proposed. Based on this mechanism, the required support pressure on tunnel face can be obtained by equaling external work rates to the internal energy dissipation and implementing an optimization searching procedure related to time. Both time and space feature of seismic waves are properly accounted for in the proposed mechanism. For this reason, the proposed mechanism can better represent the actual influence of seismic motion and has a remarkable advantage in evaluating the effects of vertical seismic acceleration, soil amplification factor, seismic wave period and initial phase difference on tunnel face stability. Furthermore, the pseudo-dynamic approach is compared with the pseudo-static approach. The difference between them is illustrated from a new but understandable perspective. The comparison demonstrates that the pseudo-static approach is a conservative method but still could provide precise enough results as the pseudo-dynamic approach if the value of seismic wavelengths is large or the height of soil structures is small.

• 대한산업공학회지
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• 제30권1호
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• pp.44-49
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• 2004

The aim of this study is to compare the methods in analyzing bio-signals representing measure driver's psychophysiological staus. This study has considered three approaches: first, the deterministic approach calculating the mean and standard deviation of bio-signal, second, probabilistic approach converting driver's bio-signal values to probability density function and identifying individual state relative to overall distribution, and third, diagnostic approach identifying the pattern change of signal over certain period of time. For evaluation of analysis methods, driver's bio-signal was collected under various road conditions, and three analysis approaches were applied respectively. In result, the deterministic approach was found to be simple to use, but generated a large variability of bio-signal. The probabilistic approach provide a relative status of individual driver among overall population, but too much affected by temporal variability of individual driver. The diagnostic approach seemed to reasonably find driver's psychophysiological change over certain period of time, but still needs to develop quantification method of the bio-signal.

• 대한전기학회논문지
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• 제41권7호
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• pp.809-822
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• 1992

A mathematical approach to solving the time-varying obstacle avoidance problem is pursued. The mathematical formulation of the problem is given in robot joint space(JS). View-time concept is used to deal with time-varying obstacles. The view-time is the period in which a time-varying obstacles. The view-time is the period in which a time-varying obstacle is viewed and approximated by an equivalent stationary obstacle. The equivalent stationary obstacle is the volume swept by the time-varying obstacle for the view-time. The swept volume is transformed into the JS obstacle that is the set of JS robot configurations causing the collision between the robot and the swept volume. In JS, the path avoiding the JS obstacle is planned, and a trajectory satisfying the constraints on robot motion planning is planned along the path. This method is applied to the collision-free motion planning of two SCARA robots, and the simulation results are given.

• 대한산업공학회지
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• 제27권2호
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• pp.140-149
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• 2001

The paper discusses the problem of finding the Origin-Destination(O-D) shortest paths in internodal transportation networks with time-schedule constraints. The shortest path problem on the internodal transportation network is concerned with finding a path with minimum distance, time, or cost from an origin to a destination using all possible transportation modalities. The time-schedule constraint requires that the departure time to travel from a transfer station to another node takes place only at one of pre-specified departure times. The scheduled departure times at the transfer station are the times when the passengers are allowed to leave the station to another node using the relative transportation modality. Therefore, the total time of a path in an internodal transportation network subject to time-schedule constraints includes traveling time and transfer waiting time. In this paper, a genetic algorithm (GA) approach is developed to deal with this problem. The effectiveness of the GA approach is evaluated using several test problems.

• Hip & pelvis
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• 제35권4호
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• pp.246-252
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• 2023

Purpose: The aim of this study was to compare short-term results from use of the direct anterior approach (DAA) and the conventional posterolateral approach (PLA) in performance of bipolar hemiarthroplasty for treatment of femoral intertrochanteric fractures in elderly patients. Materials and Methods: A retrospective review of 100 patients with intertrochanteric fractures who underwent bipolar hemiarthroplasty was conducted. The PLA was used in 50 cases from 2016 to 2019; since that time we have used the DAA in 50 cases from 2019 to 2021. Measurements of mean operative time, blood loss, hospitalization period, and ambulation status, greater trochanter (GT) migration and stem subsidence were performed. And the incidence of complications was examined. Results: Operative time was 73.60±14.56 minutes in the PLA group and 79.80±8.89 minutes in the DAA group (P<0.05). However, after experiencing 20 cases using DAA, there was no statistically difference in operative time between two groups (P=0.331). Blood loss was 380.76±180.67 mL in the PLA group and 318.14± 138.51 mL in the DAA group (P<0.05). The hospitalization was 23.76±11.89 days in the PLA group and 21.45 ±4.18 days in the DAA group (P=0.207). In both groups, there were no progressive GT migration, intraoperative fractures or dislocations, although there was one case of infection in the PLA group. Conclusion: Although use of the DAA in performance of bipolar hemiarthroplasty required slightly more time in the beginning compared with the PLA, the DAA may well be an alternative, safe surgical technique as a muscle preserving procedure in elderly patients with intertrochanteric fractures.

• 대한치과의사협회지
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• 제54권12호
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• pp.1045-1054
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• 2016

Purpose : Aim of this study is to describe and compare clinical results and complications epending on the surgical approaches for the mandibular subcondyle fracture Materials and methods : The patients who had been diagnosed as the mandibular subcondyle fracture and underwent open reduction and internal fixation from May 2009 to December 2014 were included. They were divided into two groups depending on the surgical approaches; endoscopically assisted transoral approach and retromandibular approach. Association between the preoperative fracture classification and post-operative results was reviewed depending on the surgical approaches. Results : The number of patients selected in this study was 33. Eighteen patients (male 7, female 11) underwent open reduction and internal fixation via retromandibular approach and fifteen patients (male 12, female 3) underwent open reduction and internal fixation via endoscopically assisted transoral approach. The mean age, follow up period, and operation time were $44.29{\pm}15.19years$, $9.97{\pm}7.82months$, and $161{\pm}89.44minutes$. Post-operative results were all "good" state in the retromandibular approach group regardless of the fracture classification but two patients in the endoscopically assisted transoral approach group underwent re-operation due to "poor" results. The fracture types of two were classified as displacement and lateral override at the same time. There was no statistically significant difference between two groups. Three patients in the retromandibular approach group had experienced facial nerve palsy (17%) temporarily. No one showed malocclusion in this study. There was no significant difference on the complications such as temporomandibular disorder, local infection, and condyle resorption depending on the surgical approaches. Conclusion : In this study, there was no significant difference on the complications between the two groups but retromandibular approach has advantage over endoscopically assisted transoral approach in case of the severely displaced subcondyle fracture.

• 한국멀티미디어학회논문지
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• 제22권8호
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• pp.887-896
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• 2019

In this paper, we discuss an optimization approach for time-synchronizations in networked simulators. This method is a sub-technology that is required to combine heterogeneous simulators into a single simulation. In previous time-synchronization studies, they had built a network system among networked simulators. The network system collects network packets and adds time-stamps to the networked packets based on the time that occurs in events of simulation objects in the individual simulators. Then, it sorts them in chronological order. Finally, the network system applies time-synchronization to each simulator participating in interworking sequentially. However, the previous approaches have a limitation in that other participating simulators should wait for while processing an event in a simulator in a time stamp order. In this paper, we attempt to solve the problem by optimizing time-synchronizations in networked simulation environments. In order to prove the practicality of our approach, we have conducted an experiment. Finally, we discuss the contributions of this paper.

• 대한수학회보
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• 제39권1호
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• pp.23-31
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• 2002

A scale parameter is the principal parameter to be estimated, since it corresponds to one of the main reliability characteristics, namely the average time to failure. To provide robustness of scale estimators to gross errors in the data, we apply the Huber minimax approach in time to failure models of the statistical reliability theory. The minimax valiance estimator of scale is obtained in the important particular case of the exponential distribution.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.458-463
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• 1997

In this paper, we propose a variable structure control approach for the system with matched and unmatched uncertainty. By using time-varying sliding mode, the reaching mode is removed, and the design methodology represents a realistic design approach with quadratic criterion for systems incorporating both matched and unmatched uncertainties. The criterion contains states and linear part of input for all time. The practical application of the control strategy is presented in the design of a stability augmentation system for an aircraft is presented.