• Journal of KIISE:Computer Systems and Theory
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• v.35 no.6
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• pp.273-283
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• 2008

Many embedded real-time systems have adopted processors supported with dynamic voltage scaling(DVS) recently. Power is one of the important metrics for optimization in the design and operation of embedded real-time systems. We can save considerable energy by using slowdown of processor supported with DVS. In this paper, we propose heuristic algorithms to calculate task slowdown factors for an efficient energy consumption in embedded real-time systems with task synchronization. The previous algorithm has a following constraint : given the tasks are ordered in a nondecreasing order of their relative deadline, the task slowdown factors computed are in a nonincreasing order. In this paper, we relax the constraint and propose heuristic algorithms which have the same time complexity that previous algorithm has and can save more energy. Experimental results show that the proposed algorithms are energy efficient.

• Proceedings of the KIEE Conference
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• 1979.08a
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• pp.26-28
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• 1979

The optimal selection of Prime Implications for the multi-output switching function is difficult task, as the input variables increase. This paper is concerned with the technique for the minimization of the multi-output switching function using the intersection table. This procedure is applicable to both manual and computer-programmed realization without complexity.

• Journal of the korean Society of Automotive Engineers
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• v.26 no.1
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• pp.76-82
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• 2004

In this paper, the trend of quality management system that suppliers in the automotive industry are adopting, the classification system of suppliers and car manufacturers requirements for quality are described. Due to the complexity of the requirements for quality, the introduction of an active quality management system which can meet all conditions is a difficult task. Thus, to cope with this difficulty, this paper shows the optimal requirements that suppliers have to consider when they are introducing quality management system and the discriminated strategies to assure parts quality by supplier model.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.04a
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• pp.187-190
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• 2003

Due to complexity of diverse features in urban area, accurate feature extraction is laborious task in aerial and satellite imagery. Especially occlusion by buildings, and image distortion of shadow effects make processing more difficult work. In this study, algorithm was presented to correct of shadow effects in aerial color images. This algorithm enables user to accurately interpretate urban information by correction of shadow effects in aerial color images

• Journal of Navigation and Port Research
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• v.34 no.6
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• pp.503-509
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• 2010

Remarshaling is referred to a preparatory task of rearranging containers piled up in a stacking yard to improve the efficiency of loading. Selective remarshaling is required because the time for remarshaling known as large time-consuming task is not enough to remarshal all containers. In this research, we compare two previous researches in more objectively way: heuristic and genetic algorithm based approaches. In addition, we prove the effect of iterative reselection method on dwindling the gap between plan and execution due to the uncertainty of crane operation during execution. Simulation experiments under realistic uncertainty model show that heuristic approaches which have few computational complexity can cope with the uncertainty well when reselection interval is short, but genetic algorithm based approach has advantages when reselection interval that can ensure appropriate number of evolutions is given because of computational complexity for search.

• The Transactions of the Korea Information Processing Society
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• v.6 no.6
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• pp.1678-1685
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• 1999

In most of the existing real-time schedulers producing the total value as large as possible, the service times for all schedulable tasks are computed at each time a new task arrives. If all scheduled tasks would be executed completely before a new task arrives, the schedule may produce the greatest total value. But this is not always true in real situations. In many cases, (a) new tasks arrive(s) before all the scheduled tasks are executed completely. In this paper, we propose a unique scheduling algorithm for real-time tasks. The proposed algorithm determines the service times only for some tasks with earlier deadlines while the existing algorithms determine the service times for all tasks. This partial computation decreases the average scheduling complexity ramatically, even though, in the worst case, the complexity of the proposed algorithm becomes O(N2), which is equal to that of a previous algorithm that has been known as a less complicated one.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.744-750
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• 2009

According to the result of related studies, the degradation of human performance has been revealed as one of the most significant causes resulting in the safety of any human-involved system. This means that preventing the occurrence of accidents/incidents through avoiding the degradation of human performance is prerequisite for their successive operation. To this end, it is necessary to develop a plausible tool to evaluate the complexity of a task, which has been known as one of the decisive factors affecting the human performance. For this reason, in this paper, the complexity of tasks to be conducted by KTX drivers was quantified by TACOM measure that is enable to quantify the complexity of proceduralized tasks being used in nuclear power plants. After that, TACOM scores about the tasks of KTX drivers were compared with NASA-TLX scores that are responsible for the level of a subjective workload to be felt by KTX drivers.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.5
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• pp.427-436
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• 2010

This paper deals with a task assignment problem of multiple UAVs performing multiple tasks on multiple targets. The task assignment problem of multiple UAVs is a kind of combinatorial optimization problems such as traveling salesman problem or vehicle routing problem, and it has NP-hard computational complexity. Therefore, computation time increases as the size of considered problem increases. To solve the problem efficiently, approximation methods or heuristic methods are widely used. In this study, the problem is formulated as a mixed integer linear program, and is solved by a mixed integer linear programming and a genetic algorithm, respectively. Numerical simulations for the environment of the multiple targets, multiple tasks, and obstacles were performed to analyze the optimality and efficiency of each method.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.5
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• pp.542-554
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• 1997

In this paper, we present a resource conscious approach to designing distributed real-time systems as an extension of our original approach [8][9] which was limited to single processor systems. Starting from a given task graph and a set of end-to-end constraints, we automatically generate task attributes (e.g., periods and deadlines) such that (i) the task set is schedulable, and (ii) the end-to-end timing constraints are satisfied. The method works by first transforming the end-to-end timing constraints into a set of intermediate constraints on task attributes, and then solving the intermediate constraints. The complexity of constraint solving is tackled by reducing the problem into relatively tractable parts, and then solving each sub-problem using heuristics to enhance schedulability. In this paper, we build on our single processor solution and show how it can be extended for distributed systems. The extension to distributed systems reveals many interesting sub-problems, solutions to which are presented in this paper. The main challenges arise from end-to-end propagation delay constraints, and therefore this paper focuses on our solutions for such constraints. We begin with extending our communication scheme to provide tight delay bounds across a network, while hiding the low-level details of network communication. We also develop an algorithm to decompose end-to-end bounds into local bounds on each processor of making extensive use of relative load on each processor. This results in significant decoupling of constraints on each processor, without losing its capability to find a schedulable solution. Finally, we show, how each of these parts fit into our overall methodology, using our previous results for single processor systems.

• The Transactions of the Korea Information Processing Society
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• v.5 no.5
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• pp.1151-1161
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• 1998

In this paper, we are considering a heterogeneous processor system in which each processor may have different performance and reliability characteristics. In other to fully utilize this diversity of processing power it is advantageous to assign the program modules of a distributed program to the processors in such a way that the execution time of the entire program is minimized. This assignment of tasks to processors to maximize performance is commonly called load balancing, since the overloaded processors can perform their own processing with the performance degradation. For the task assignment problem, we propose a new objective function which formulates this imbalancing cost. Thus the task assignment problem is to be carried out so that each module is assigned to a processor whose capabilities are most appropriate for the module, and the total cost is minimized that sum of inter-processor communication cost and execution cost and imbalance cost of the assignment. To find optimal assignment is known to be NP-hard, and thus we proposed an efficient heuristic algorithm with time complexity $O(n^2m)$ in case of m task modules and n processors.