• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.4
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• pp.63-71
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• 2014

As power consumption increases, more power utilities are required to satisfy the demand and consequently results in tremendous cost to build the utilities. Another issue in construction of power utilities to meet the peak demand is an inefficiency caused by surplus power during non-peak time. Therefore, most power company considers power demand management with time-based electricity rate policy which applies different rate over time. This paper considers an optimal machine operation problem under the time-based electricity rates. In TOC (Theory of Constraints), the production capacities of all machines are limited to one of the bottleneck machine to minimize the WIP (work in process). In the situation, other machines except the bottleneck are able to stop their operations without any throughput loss of the whole manufacturing line for saving power utility cost. To consider this problem three integer programming models are introduced. The three models include (1) line shutdown, (2) block shutdown, and (3) individual machine shutdown. We demonstrate the effectiveness of the proposed IP models through diverse experiments, by comparing with a TOC-based machine operation planning considered as a current model.

• Journal of Families and Better Life
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• v.14 no.2
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• pp.127-138
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• 1996

The purpose of this study is to show farm women's stress under productive activity role multiple overload through family characteristic (pattern and number) and characteristic(type working time and involvement proportion) of productive activity. The outline of the study is as follow; 1. Stress by pattern and number of a family is highest in a four generation family and increases according as the number of the family increases. 2. The characteristic of productive activity : 1) Stress based on type of productive activity is highest in Type III of the most multiple overload roles. 2) in light of stress based working time area of household task activity is in inverse proportion to working time but area of farming and wage earning activity are approximately in direct proportion to it. The two-way ANOVA analysis show that stress in Type I of area of household task increases but in Type IV it decreases as working time increases 3) In stress based on involvement proportion to it. The wo-way ANOVA analysis show that stress in Type I of area of household task increases but in Type IV it decreases as working time increases. 3) In stress based on involvement proportion in three as working time increases 3). In stress based on involvement proportion in three activity areas the more the involvement proportion the less of the stress : an inverse ratio.

• ETRI Journal
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• v.46 no.2
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• pp.333-346
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• 2024

Various techniques for noninvasively focus microwave energy on lesions have been proposed for thermotherapy. To focus the microwave energy on the lesion, a focusing parameter, which is referred to as the magnitude and phase of microwaves radiated from an external array antenna, is very important. Although the finite-difference time-domain (FDTD)-based time-reversal (TR) focusing algorithm is widely used, it has a long processing time if the focusing target position changes or if optimization is needed. We propose a technique to obtain multistatic data (MSD) based on Green's function and use it to derive the focusing parameters. Computer simulations were used to evaluate the electric fields inside the object using the FDTD method and Green's function as well as to compare the focusing parameters using FDTD- and MSD-based TR focusing algorithms. Regardless of the use of Green's function, the processing time of MSD-based TR focusing algorithms reduces to approximately 1/2 or 1/590 compared with the FDTD-based algorithm. In addition, we optimize the focusing parameters to eliminate hotspots, which are unnecessary focusing positions, by adding phase-reversed electric fields and confirm hotspot suppression through simulations.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.3
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• pp.281-292
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• 2014

We propose a novel cooperative guidance law design method based on the finite time disturbance observer (FTDO) for multiple near space interceptors (NSIs) with impact time control. Initially, we construct a cooperative guidance model with head pursuit, and employ the FTDO to estimate the system disturbance caused by target maneuvering. We subsequently separate the cooperative guidance process into two stages, and develop the normal acceleration command based on the super-twisting algorithm (STA) and disturbance estimated value, to ensure the convergence of the relative distance. Then, we also design the acceleration command along the line-of-sight (LOS), based on the nonsingular fast terminal sliding mode (NFTSM) control, to ensure that all the NSIs simultaneously hit the target. Furthermore, we prove the stability of the closed-loop guidance system, based on the Lyapunov theory. Finally, our simulation results of a three-to-one interception scenario show that the proposed cooperative guidance scheme makes all the NSIs hit the target at the same time.

• ETRI Journal
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• v.35 no.6
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• pp.960-968
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• 2013

To implement a cloud game service platform supporting multiple users and devices based on real-time streaming, there are many technical needs, including game screen and sound capturing, audio/video encoding in real time created by a high-performance server-generated game screen, and real-time streaming to client devices, such as low-cost PCs, smart devices, and set-top boxes. We therefore present a game service platform for the running and management of the game screen, as well as running the sound on the server, in which the captured and encoded game screen and sound separately provide client devices through real-time streaming. The proposed platform offers Web-based services that allow game play on smaller end devices without requiring the games to be installed locally.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.3
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• pp.263-272
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• 2008

We implemented a real-time servo system for a manipulator based on Laser Range Finder (LRF). and established algorithms for grasping a moving cylinder. We devised a manipulator mechanism and driving hardware based on a system board equipped with Xscale Processor with real-time operating system RTAI on Linux. The manipulator motor driver is connected to the system board via CAN communication link, and LRF is connected via RS-232C. We implemented real-time software including CAN device driver, RS-232C device driver, manipulator trajectory generator, and LRF control software. A typical application experiment for grasping a cylinder with circle motion demonstrated our system's real-time performance.

• Journal of KIISE:Software and Applications
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• v.30 no.10
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• pp.983-991
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• 2003

The Web-based instruction on the internet provides lots of learners with the related information and knowledge beyond time and space. But in the Web-based instruction, there is a problem that the teaming process statuses for learners can be known only through an exam. This paper introduces a web monitoring method to check whether the learner has some problems in learning process and to be able to find out the students with the problems. In the method this paper proposes a learning time prediction model for predicting the proper next study time intervals based on the learner`s learning times and grades on Previous learning units. This method provides the educator with the learning Process statuses for learners. The Loaming prediction model for web-based monitoring can be used to stimulate learners to take the good teaming processes by sending automatically alerting messages if their real teaming times exceeds on his predicted learning time interval. The results of the estimation through case study on the web-based monitoring to use the teaming time prediction model show that most of on-line learners with Poor teaming process statuses get poor grades. In addition, the results show that learner`s poor habits keep going on without change.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.6
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• pp.550-556
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• 2009

In an application of a time reversal(TR) focusing of array transducer on a defect inside the test material, we employ a new time delay focusing technique based the TR process. In order to realize this idea, a multi-channel ultrasonic system is constructed capable of applying necessary time delays to each channel. The TR-based focusing procedure first measures the backscattered signals after firing one of the array elements. A phase slope method is then used to determine the time-of-flights of the backscattered signals received by all elements of the array. These time delays are used to adjust the time of excitation of the elements for transmission focusing on the defect. In addition to the TR focusing, the classical phased array focusing is also considered for comparison. Experimental results show that the TR-based time delay focusing produces much stronger backscattered signals than the phased array focusing, demonstrating the enhanced capability of the TR focusing.

• Journal of Intelligence and Information Systems
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• v.4 no.2
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• pp.23-34
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• 1998

Travel time forecasting, especially public bus travel time forecasting in urban areas, is a difficult and complex problem which requires a prohibitively large computation time and years of experience. As the network of target area grows with addition of streets and lanes, computational burden of the forecasting systems exponentially increases. Even though the travel time between two neighboring intersections is known a priori, it is still difficult, if not impossible, to compute the travel time between every two intersections. For the reason, previous approaches frequently have oversimplified the transportation network to show feasibilities of the problem solving algorithms. In this paper, forecasting of the travel time between every two intersections is attempted based on travel time data between two neighboring intersections. The time stamps data of public buses which recorded arrival time at predetermined bus stops was extensively collected and forecast. At first, the time stamp data was categorized to eliminate white noise, uncontrollable in forecasting, based on wavelet conversion. Then, the radial basis neural networks was applied to remaining data, which showed relatively accurate results. The success of the attempt was confirmed by the drastically reduced relative error when the nodes between the target intersections increases. In general, as the number of the nodes between target intersections increases, the relative error shows the tendency of sharp increase. The experimental results of the novel approaches, based on wavelet conversion and neural network teaming mechanism, showed the forecasting methodology is very promising.

• Journal of Korean Society for Quality Management
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• v.42 no.1
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• pp.33-41
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• 2014

Purpose: The purpose of this paper is estimate response quality of three major portal in Korea based on the response time. In addition to response time, the response time by 1Kbyte will be analysed. Methods: Data was collected from July 2010 to November 2013 using Firebug. For comparing averages, ANOVA will be used. For comparing distributions, Chisquare test and Kolmogov-Smirnov test will be used for parametric and non parametric test respectively. Results: For response quality based on response time, Daum gets the first place, Naver the second place, and Nate the third place. But the order of the response time per 1Kbyte is different. The order is Naver, Daum and Nate. Conclusion: The response quality may be estimated using various factors. Response time is the most important factor. Daum provides the shortest response time. We could say Daum provides the best response quality. But Naver provides the shortest response time per 1Kbyte. From these results, we know reducing packets is very important thing in response time.