• Journal of Korean Society of Industrial and Systems Engineering
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• 제21권48호
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• pp.123-132
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• 1998

The group formation problem of the machine and part is a very important issue in the planning stage of cellular manufacturing systems. This paper investigates Self-Organizing Map(SOM) neural networks approach to machine-part grouping problem. We present a two-phase algorithm based on SOM for grouping parts and machines. SOM can learn from complex, multi-dimensional data and transform them into visually decipherable clusters. Output layer in SOM network is one-dimensional structure and the number of output node has been increased sufficiently to spread out the input vectors in the order of similarity. The proposed algorithm performs remarkably well in comparison with many other algorithms for the well-known problems shown in previous papers.

• Transactions of the Korean Society of Machine Tool Engineers
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• 제12권4호
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• pp.70-76
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• 2003

Braiding machines of maypole type have complex guide tracks. It is not easy to speed up drivers while carriers are moving at high speed. This paper presents a new design approach using dynamic analysis and modeling for moving carriers on the guide tracks. The proposed approach will be shown to be effective by using simulation tool, WORKING MODEL $2D^{\circledR}$, for high speed drivers on new models of braiding machines of maypole type.

• International journal of advanced smart convergence
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• 제5권3호
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• pp.40-46
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• 2016

The internet allows the information to flow at anywhere in anytime easily. Unfortunately, the network also becomes a great tool for the criminals to operate cybercrimes such as identity theft. To prevent the issue, using a very complex password is not a very encouraging method. Alternatively, keystroke dynamics helps the user to solve the problem. Keystroke dynamics is the information of timing details when a user presses a key or releases a key. A machine can learn a user typing behavior from the information integrate with a proper machine learning algorithm. In this paper, we have proposed mini-batch ensemble (MIBE) method which does the preprocessing on the original dataset and then produces multiple mini batches in the end. The mini batches are then trained by a machine learning algorithm. From the experimental result, we have shown the improvement of the performance for each base algorithm.

• Journal of Korean Society of Industrial and Systems Engineering
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• 제19권37호
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• pp.201-210
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• 1996

Although FMS implementation in Korea is not yet mature, the worldwide empirical data shows the diffusion of FMS is inevitable in near future. As the reletionships between the high capital cost and the relative benefits and advantages are complex to analyse, it is rather beneficial to prepare the effective operation strategies which exploit the FMS flexibility, such as machine loading with alternative routing and dispatching rules. This paper shows the formulation applying a goal programming model for the loading problem with objectives of minimizing the production cost and maximizing the machine utilization, including constraints such as machine tool capacity and demands, etc. A realistic random FMS model is developed for illustration. Since loading and dispatching are a composite of two interdependent tasks, simulation is made to investigate the interactions between the two.

• Journal of the Korea Safety Management & Science
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• 제3권1호
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• pp.127-137
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• 2001

Because of the inherent flexibility in their design for improved material properties, composites have wide applications in aerospace vehicles and automobiles. The purpose of this study is to investigate the energy absorption characteristics of CFRf (Carbon Fiber Reinforced Plastics) tubes on static and impact tests. Static compression tests have been carried out using the static testing machine(Shin-gang buckling testing machine) and impact compression tests have been carried out using the vertical crushing testing machine. When such tubes were subjected to crushing loads, the response is complex and depends on the interaction between the different mechanisms that control the crushing process. The collapse characteristics and energy absorption were examined. Trigger and interlaminar number affect the energy absorption capability of CFRP tubes.

• Journal of Electrical Engineering and Technology
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• 제8권2호
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• pp.197-205
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• 2013

Real time transient stability assessment mainly depends on real-time prediction. Unfortunately, conventional techniques based on offline analysis are too slow and unreliable in complex power systems. Hence, fast and reliable stability prediction methods and simple stability criterions must be developed for real time purposes. In this paper, two new methods for real time determining critical clearing time based on clustering identification are proposed. This article is covering three main sections: (i) clustering generators and recognizing critical group; (ii) replacing the multi-machine system by a two-machine dynamic equivalent and eventually, to a one-machine-infinite-bus system; (iii) presenting a new method to predict post-fault trajectory and two simple algorithms for calculating critical clearing time, respectively established upon two different transient stability criterions. The performance is expected to figure out critical clearing time within 100ms-150ms and with an acceptable accuracy.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 한국공작기계학회 1999년도 춘계학술대회 논문집
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• pp.105-110
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• 1999

Wire electrical discharge machining (WEDM) is one of the unconventional machining processes, which is utilizing electrical energy to remove work-piece. In recent years WEDM used widely in die-sinking industry because WEDM can machine any hard materials if only it has conductivity and can machine accurately to the complex geometry, for fine wire is used in WEDM for the tool electrode. However WEDM is non-contact machining process, which is utilizing discharge phenomena occurring between two electrodes, the size of the machined part is larger than that of the tool electrode size. It is called discharge gap or clearance the difference size between the tool electrode and the machined part in WEDM. By the experiment clearances according to the machining condition was investigated.

• Journal of Korean Society of Industrial and Systems Engineering
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• 제20권43호
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• pp.81-89
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• 1997

This study is concerned with the scheduling problems in flexible manufacturing systems(FMSs). The scheduling problem in FMSs is a complex one when the number of machines and jobs are increased. Thus, a heuristic method is recommended in order to gain near-optimal solutions in a practically acceptable time. The purpose of this study is to develope a machine and AGV dispatching algorithm. The proposed dispatching algorithm is a on-line scheduling algorithm considering the due date of parts and the status of the system in the scheduling process. In the new machine and AGV dispatching algorithm, a job priority is determined by LPT/LQS rules considering job tardiness. The proposed heuristic dispatching algorithm is evaluated by comparison with the existing dispatching rules such as LPT/LQS, SPT/LQS, EDD/LQS and MOD/LQS. The new dispatching algorithm is predominant to existing dispatching rules in 100 cases out of 100 for the mean tardiness and 89 cases out of 100 for the number of tardy jobs.

• Proceedings of the KIEE Conference
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.2052-2053
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• 2007

Recently, the importance of supplying the reliable electric power is increasing. Breaking insulation of stator winding is major cause of fault in rotator machine. On-line PD detecting is useful technique to diagnose rotator machine. However, interpretation of its results in time domain is very complex because of the mixed results with PD(Partial Discharge) and noise signal. Therefore, the results were analyzed in frequency domain by FFT (Fast Fourier Transform) to detect precise PD signals. The purpose of this paper is to describe the optimal frequency range to discriminate the PD and noise signal.

• Proceedings of the KIEE Conference
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.98-100
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• 2005

DSPs used at motor control are usually fixed point processor. They need scaling because they cannot excute floating point calculation. Scaling for floating point calculation makes the DSP's speed down, complex coding and etc. Therefore the IQ math is adopted. IQ math makes the fixed point processor possible to calculate the floating point math. In addition, IQ math can reduce memory usage and be more faster than that without IQ math. It seems that IQ math is appropriate in motor position control. In comparison of the position calculation between the IQ math, math function and the sine table, the method using IQ math is superior than other methods.