• Journal of Electrical Engineering and Technology
• /
• 제11권2호
• /
• pp.329-337
• /
• 2016

With the increasing deployment of distributed generators in the distribution system, a very large search space is required when dynamic programming (DP) is applied for the optimized dispatch schedules of voltage and reactive power controllers such as on-load tap changers, distributed generators, and shunt capacitors. This study proposes a new optimal voltage and reactive power scheduling method based on dynamic programming with a heuristic searching space reduction approach to reduce the computational burden. This algorithm is designed to determine optimum dispatch schedules based on power system day-ahead scheduling, with new control objectives that consider the reduction of active power losses and maintain the receiving power factor. In this work, to reduce the computational burden, an advanced voltage sensitivity index (AVSI) is adopted to reduce the number of load-flow calculations by estimating bus voltages. Moreover, the accumulated switching operation number up to the current stage is applied prior to the load-flow calculation module. The computational burden can be greatly reduced by using dynamic programming. Case studies were conducted using the IEEE 30-bus test systems and the simulation results indicate that the proposed method is more effective in terms of saving electric charges and improving the voltage profile than loss minimization.

• Earthquakes and Structures
• /
• 제10권5호
• /
• pp.1067-1087
• /
• 2016

In this paper, a decoupled proportional-integral-derivative (PID) control approach for seismic control of smart structures is presented. First, the state space equation of a structure is transformed into modal coordinates and parameters of the modal PID control are separately designed in a reduced modal space. Then, the feedback gain matrix of the controller is obtained based on the contribution of modal responses to the structural responses. The performance of the controller is investigated to adjust control force of piezoelectric friction dampers (PFDs) in a benchmark base isolated building. In order to tune the modal feedback gain of the controller, a suitable trade-off among the conflicting objectives, i.e., the reduction of maximum modal base displacement and the maximum modal floor acceleration of the smart base isolated structure, as well as the maximum modal control force, is created using a multi-objective cuckoo search (MOCS) algorithm. In terms of reduction of maximum base displacement and story acceleration, numerical simulations show that the proposed method performs better than other reported controllers in the literature. Moreover, simulation results show that the PFDs are able to efficiently dissipate the input excitation energy and reduce the damage energy of the structure. Overall, the proposed control strategy provides a simple strategy to tune the control forces and reduces the number of sensors of the control system to the number of controlled stories.

• 소성∙가공
• /
• 제9권5호
• /
• pp.512-525
• /
• 2000

Designers are frequently faced with multiple quality issues in injection molded parts. These issues are usually In conflict with each other, and thus tradeoff needs to be made to reach a final compromised solutions. The objective of this study is to develop an automated injection molding design methodology, whereby part defects such as warpage and weld line are optimized. The features of the proposed methodology are as follows: first, Utility Function approach is applied to transform the original multiple objective problem into single objective problem. Second is an implementation of a direct search-based Injection molding optimization procedure with automated consideration of process variation. The Space Reduction Method based on Taguchi's DOE(Design Of Experiment) is used as a general optimization tool in this study. The computational experimental verification of the methodology was partially carried out for a can model of Cavallero Plastics Incorporation, U. S. A. Applied to production, this study will be of immense value to companies in reducing the product development time and enhancing the product quality.

• 로봇학회논문지
• /
• 제18권1호
• /
• pp.1-9
• /
• 2023

This paper presents an optimal path planning strategy for aerial searching and surveying of a user-designated area using multiple Unmanned Aerial Vehicles (UAVs). The method is designed to deal with a single unseparated polygonal area, regardless of polygonal convexity. By defining the search area into a set of grids, the algorithm enables UAVs to completely search without leaving unsearched space. The presented strategy consists of two main algorithmic steps: cellular decomposition and path planning stages. The cellular decomposition method divides the area to designate a conflict-free subsearch-space to an individual UAV, while accounting the assigned flight velocity, take-off and landing positions. Then, the path planning strategy forms paths based on every point located in end of each grid row. The first waypoint is chosen as the closest point from the vehicle-starting position, and it recursively updates the nearest endpoint set to generate the shortest path. The path planning policy produces four path candidates by alternating the starting point (left or right edge), and the travel direction (vertical or horizontal). The optimal-selection policy is enforced to maximize the search efficiency, which is time dependent; the policy imposes the total path-length and turning number criteria per candidate. The results demonstrate that the proposed cellular decomposition method improves the search-time efficiency. In addition, the candidate selection enhances the algorithmic efficacy toward further mission time-duration reduction. The method shows robustness against both convex and non-convex shaped search area.

• 산업경영시스템학회지
• /
• 제23권61호
• /
• pp.105-114
• /
• 2000

Job Shop Problem which consists of the m different machines and n jobs is a NP-hard problem of the combinatorial optimization. Each job consists of a chain of operations, each of which needs to be processed during an uninterrupted time period of a given length on a given machine. Each machine can process at most one operation at a time. The purpose of this paper is to develop the heuristic method to solve large scale scheduling problem using Constraint Satisfaction Problem method and Simulated Annealing. The proposed heuristic method consists of the search algorithm and optimization algorithm. The search algorithm is to find the solution in the solution space using CSP concept such as backtracking and domain reduction. The optimization algorithm is to search the optimal solution using SA. This method is applied to MT06, MT10 and MT20 Job Shop Problem, and compared with other heuristic method.

• 한국멀티미디어학회논문지
• /
• 제3권4호
• /
• pp.356-364
• /
• 2000

블록정합에 기초한 고속 움직임 추정 알고리듬은 탐색점의 수를 줄이기 위해 정해진 탐색패턴을 사용하며, 평균절대 오차 공간에서 오차는 전역 최소해 (global minimum)에 근접할수록 단조 감소한다는 가정을 바탕으로 하고 있다. 따라서, 탐색영역 내에 여러 최소점이 있는 다중 모달(multimodal) 해공간에서는 국소 최소해(local minima)에 고립될 가능성이 크며, 전역 최소해를 얻는 것은 초기 탐색점에 크게 의존한다. 이러한 현상은 서로 다른 여러 움직임이 공존하는 움직임 경계에서 더욱 부각된다. 이러한 문제점을 개선하기 위하여 본 논문에서는 시공간적으로 인접한 블록의 움직임 정보에 기초하여 탐색영역 내에 탐색 후보영역들을 정의하고, 국소 최소해로의 고립 가능성을 줄이기 위해 여러 후보영역들에 대한 다중 국소 탐색법(multiple local search method : MLSM)을 제안한다 또한, 다중 국소 탐색 법에서는 전체 후보영역들의 탐색으로 인한 부가적인 계산량을 줄이기 위해 탐색점 맵 상에 후보영역들을 표시하고 후보영역에 대한 중복탐색을 배제한다. 모의실험 결과 제안한 방법은 다른 경사법에 의한 결과보다 특히, 움직임 경계에서의 탐색에서 우수한 결과를 보였으며, PSNR에 대해서는 탐색점의 수를 증가시키지 않는 범위 내에서 전역 탐색법(full search : FS)에 의한 결과와 비슷한 결과를 얻을 수 있었다.

• Journal of Information Processing Systems
• /
• 제17권5호
• /
• pp.1020-1033
• /
• 2021

Nowadays, online or mobile social network services (SNS) are very popular and widely spread in our society and daily lives to instantly share, disseminate, and search information. In particular, SNS such as YouTube, Flickr, Facebook, and Amazon allow users to upload billions of images or videos and also provide a number of multimedia information to users. Information retrieval in multimedia-rich SNS is very useful but challenging task. Content-based media retrieval (CBMR) is the process of obtaining the relevant image or video objects for a given query from a collection of information sources. However, CBMR suffers from the dimensionality curse due to inherent high dimensionality features of media data. This paper investigates the effectiveness of the kernel trick in CBMR, specifically, the kernel principal component analysis (KPCA) for dimensionality reduction. KPCA is a nonlinear extension of linear principal component analysis (LPCA) to discovering nonlinear embeddings using the kernel trick. The fundamental idea of KPCA is mapping the input data into a highdimensional feature space through a nonlinear kernel function and then computing the principal components on that mapped space. This paper investigates the potential of KPCA in CBMR for feature extraction or dimensionality reduction. Using the Gaussian kernel in our experiments, we compute the principal components of an image dataset in the transformed space and then we use them as new feature dimensions for the image dataset. Moreover, KPCA can be applied to other many domains including CBMR, where LPCA has been used to extract features and where the nonlinear extension would be effective. Our results from extensive experiments demonstrate that the potential of KPCA is very encouraging compared with LPCA in CBMR.

• 한국농촌건축학회논문집
• /
• 제18권4호
• /
• pp.17-24
• /
• 2016

Since the users have direct access to search and browse freely, the open access system has been employed to all the usual modern libraries. However, library space shortage problem created by the continuously increasing printed materials caused the degradation of usability and quality of the library space. Open Access system is superior in user convenience but is inferior in space efficiency. Keeping the open access system is considered as one of the reasons of the space shortage problem. Even though the closed access system does not provide free access or easy browsing for the uses, it's space efficiency is much higher than the open access system. The closed access system should be employed as a plan to relieve space shortage problem. Since the closed access system does not allow the public direct access to books, it is very economical. It also provides much better space efficiency with higher book shelving density. In this article, closed access library system models and their characteristics are examined as the reduction plans for the library space shortage problems.

• 한국시뮬레이션학회논문지
• /
• 제28권1호
• /
• pp.23-39
• /
• 2019

군 병력 감축, 인명중시 사상의 확산 그리고 4차 산업혁명을 통한 혁신 기술의 국방에서의 활용과 같은 시대적 요구 속에 드론-봇의 적극적인 활용이 요구되고 있다. 특히, 드론을 활용한 감시 및 정찰은 미래 전장에서 큰 역할을 할 것으로 예상된다. 하지만 정찰용 드론의 운용 개념, 특히 적을 찾기 위한 드론의 탐색 경로에 대한 연구는 많이 이루어지지 않았다. 본 연구에서는 정찰 목적용 드론의 효과적인 운용을 위한 탐색 방법을 시뮬레이션 분석을 통해 제안한다. 시뮬레이션에서 드론과 적은 연속공간에서 선형(First-Order)으로 움직이며, 적은 불확실성을 반영하여 랜덤워크 기법을 적용하였다. 연구는 먼저 기존에 군에서 주요하게 활용하던 탐색 방법(Parallel, Spiral)이 실제로 목표를 탐지하는 확률을 제시하며, 이어서 탐지자의 탐색반경과 속도가 탐지 확률에 미치는 영향을 분석한다. 마지막으로, 적이 랜덤하게 이동하지 않고 특정한 목표를 가지고 이동할 때 적용할 수 있는 새로운 탐지방법인 PS(Probability Search), PCS((Probability Circle Search), HS(Hamiltonian Search), HCS(Hamiltonian Circle Search) 방법을 소개하고 이에 대한 실험결과를 제시한다. 본 연구에서 제시한 탐색방법은 드론의 정찰 작전 시 활용도가 클 것으로 기대한다.

• 천문학회보
• /
• 제38권1호
• /
• pp.43.1-43.1
• /
• 2013

We present here the preliminary results of the fast variability of AGN radio light curves. The shortest time scale of minute in AGN light curves is needed to probe the AGN activity for a few reasons; First, to check if there is any kind of shortest time scale activity. Secondly, to find out what high frequency end of AGN spectra look like. For the last, to see the time delay at several wavelength bands and the change of the spectral index with time. The observation was conducted with three KVN(Korea VLBI Network) antennas with single dish cross scan mode. In order not to lose the target at any given time, whenever one station needs to observe the calibrator, the other station is on the target. Though the detailed data reduction is still going on, there might exist varying feature in the radio light curve. The more fine calibration will be done in near future and another good data set is ready for the reduction.