• Journal of the Korean Society of Systems Engineering
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• v.14 no.2
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• pp.49-57
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• 2018

The main objective of this paper is come up with methodology approach for FPGA-based system in verification and validation lifecycle regarding software reliability using system engineering approach. The steps of both reverse engineering and re-engineering are carried out to implement an FPGA-based of safety critical system in Nuclear Power Plant. The reverse engineering methodology is applied to elicit the requirements of the system as well as gain understanding of the current life cycle and V&V activities of FPGA based-system. The re-engineering method is carried out to get a new methodology approach of software reliability, particularly Software Reliability Growth Model. For measure the software reliability of a given FPGA-based system, the following steps are executed as; requirements definition and measurement, evaluation of candidate reliability model, and the validation of the selected system. As conclusion, a new methodology approach for software reliability measurement using software reliability growth model is developed.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1519-1528
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• 2004

Atmospheric Re-Entry guidance is divided as longitudinal and lateral. This paper proposes a longitudinal reference trajectory and control law using the inverse dynamics method with pseudospectral Legendre method. Application of this method into Re-Entry problem forces a power of calculation time-reduction due to unnecessary of integration or any iteration as well as sufficient accuracy convergence. The used guidance scheme is time-to-go.

• Journal of Aerospace System Engineering
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• v.14 no.2
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• pp.28-35
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• 2020

In this paper, we present a design for a retraction-type actuator (ReACT) that has the characteristics of both thermomechanical metamaterials and displacement amplification mechanisms. The ReACT consists of an actuating bar, a diamond-shaped displacement amplification (DA) structure, and a slot for loading thin-film heaters formed through the actuating bar. When power is supplied to the thin film heater, the actuating bars contacting the heater thermally expand, and the diamond-shaped DA structures retract in the longitudinal direction. The performance characteristics of the ReACT, such as temperature distribution and retracting displacement, were calculated with thermomechanical analysis methods using the finite element method (FEM). Subsequently, the ReACTs were fabricated using a polymer-based 3D printer that can easily execute complex structures, and the performance of the ReACT was evaluated through repeated tests under various temperature conditions. The results of the performance evaluation were compared with the results of the FEM analysis.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.47
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• pp.125-138
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• 1998

In this paper, we investigate the effect of re-entrance to the same work station in a job shop with multiple identical machines. System A is defined as the system in which re-entrance is not permitted, and system B is defined as the system in which re-entrance is permitted. By the analytical result of the queueing network, we find that the two systems have the same queue length distributions and utilizations under FIFO dispatching rule when all parameters are same. Simulation models are developed for various comparisons between the two systems, and simulation experiments are conducted for the combinations of five dispatching rules, two average workloads and two due date allowances. Five performance measures are selected for the comparison. The simulation results show that permitting re-entrance affects for some combinations of system environments.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.115-120
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• 1998

The surface chemistry of $Re_2(CO)_{10}$ deposition for preparing highly dispersed rhenium catalysts and the formation of active site for the metathesis were studied. Alumina as support was treated at 1223K(DA) and 773k(PDA), respectively. The metathesis activity of the catalysts at 298K was measured by using pure propene under atmospheric pressure. The oxidation number of rhenium on PDA was very high, and that on DA was zero-valent with highly dispersed state. The prepared Re/DA catalyst was easily activated by treating with oxygen gas at low temperatures after thermal decomposition at high temperatures. The activity of Re/DA catalyst, even with very low rhenium loading, was much higher than that of Re/PDA or conventional $Re_2O_7/Al_2O_3$ catalysts. Therefore, rhenium carbonyl was effective for preparing a highy active metathesis catalyst with very low rhenium loading. Rhenium ion on Re/DA catalyst seemed to be bonded to two oxygen atoms on DA surface, that is, two-valent. The two-valent rhenium ion was changed to about six-valent by treating with oxygen. It could be considered that propene metathesis occurred through carbene complex which was formed on the six-valent rhenium ions.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.2065-2069
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• 2004

This paper presents an adaptive equalizer using finite impulse response (FIR) filter and least-mean square (LMS) algorithm. Herein, the variable step-size technique (VSLMS) for compensating the amplitude of chrominance signal is utilized. The proposed equalizer can be enhanced and compressed the chrominance signal at color subcarrier. The LMS algorithm employed in simplicity structure but gives slow convergence speed. Thus, the variable step-size is very attractive algorithm due to its computational efficiencies and the speed of convergence is improved. In addition, experimental results are carried out by using the modulated 20T sine squared test signal. It is shown here that the adaptive equalizer can be equalized the amplitude chrominance distortion in color television transmission without relative delay distortion.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1084-1089
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• 2004

This paper describes the improvement of web cache server by scoping in replacement algorithm of data which are collected from the clients. We have found that each replacement algorithm is suitable for each type of data in the web pages. Therefore, we introduce the mechanism to select the replacement algorithm depending on the size of data called the Replacement Algorithm Selection Mechanism (RASM). RASM allows the web cache server to have the suitable replacement algorithm for each type of data. As the result, the byte hit ratio of web cache server can be increased and the congestion in the network can be alleviated.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1132-1136
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• 2005

In this paper, adaptive equalizer receiver for a turbo code direct sequence code division multiple access (DSCDMA) by using least mean square (LMS) adaptive algorithm is presented. The proposed adaptive equalizer is using soft output of decision feedback adaptive equalizer (DFE) to examines the output of the equalizer and the Log- maximum a posteriori (Log-MAP) algorithm for the turbo decoding process of the system. The objective of the proposed equalizer is to minimize the bit error rate (BER) of the data due to the disturbances of noise and intersymbol interference (ISI)phenomenon on the channel of the DS-CDMA digital communication system. The computer program simulation results shown that the proposed soft output decision feedback adaptive equalizer provides a good BER than the others one such as conventional adaptive equalizer, infinite impulse response adaptive equalizer.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.307-310
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• 1996

In this paper, we deal with some numerical analyses of a re-entry vehicle in a 2-dimensional plane as an optimal control problem. To reduce the dynamic load, the heat load and the oscillation in the trajectory, we researched the trajectories in which the load factor or the rate of flight path angle was minimized during re-entry. In addition to that, taking advantage of the monotonous subarc method and the folded time-axis method, we tried to find the heat-less and load-less trajectory with combinations of some sectional functionals so that we can achieve more comfortability.

• Journal of electromagnetic engineering and science
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• v.7 no.1
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• pp.7-11
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• 2007

PCB Power-Bus (comprising power/ground planes) impedance and fields are evaluated by an efficient series expansion method that is suggested in this paper. It is used to investigate the structure's radiated emission(RE) levels and find acceptable ways of loading the power/ground planes such as decoupling capcitor(DeCap)s, balanced feeding and slits, in order to reduce the interferences. Also, the calculations and measurements of a proposed geometry are verified by vector fitting as a analysis model to check the behavior of the slit.