• Industrial Engineering and Management Systems
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• v.15 no.1
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• pp.99-109
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• 2016

During the last two decades, impact factor has been widely used as a journal evaluation metric that differentiates the influence of a specific journal compared with other journals. However, impact factor does not provide a reliable metric between journals in different subject categories. For example, higher impact factors are given to biology and general sciences than those assigned to other traditional engineering and social sciences. This study initially analyzes the trend of the time series of the impact factors of the journals listed in Journal Citation Reports during the last decade. This study then proposes new journal evaluation metrics that adjust the impact factors across different subject categories. The proposed metrics possibly provides a consistent measure to mitigate the differences in impact factors among subject categories. On the basis of experimental results, we recommend the most reliable and appropriate metric to evaluate journals that are less dependent on the characteristics of subject categories.

• Journal of the Korea Convergence Society
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• v.9 no.7
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• pp.9-16
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• 2018

The purpose of this study is to prevent the malicious user from breaking the door-lock due to physical impact. If it matches the analog displacement value set in the door-lock system, it protects the body and property by transmitting damage information in real time to the manager smart phone. The research suggests a system that transmits damage information in real time to registered users when door-lock is damaged by physical impact. Then compare the impact information sensed by the door lock with the data of the sensitivity control unit. In the web server of the proposed system, after impact information transmitted from Door-Lock is stored in the DB, if the impact information is larger than the shock detection transmission reference value stored in the DB, it is transmitted to the administrator in real time by SMS module so that illegal access information.

• Journal of the Korea Institute of Military Science and Technology
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• v.1 no.1
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• pp.211-218
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• 1998

As a part of trajectory modulation to increase system survivability and terminal effectiveness, impact angle control is required in the terminal phase of tactical missile systems. The missile systems are not allowed to have high altitude to reduce probability of detection by sensors of missile defense systems. In this paper, an analytic form of a time-optimal control law is suggested in the case of constrained missile maneuverability and impact angle under the assumption of a zero-lag autopilot. The control law is obtained by establishing optimal missile-target engagement geometry in the vertical plane. Extension of the law for missiles with autopilot response lags requiring a numerical solution is studied by introducing an iterative algorithm for optimal switching time determination of which the initial switching instants are obtained from the analytic solution. Also suggested is a closed-form impact angle control law derived by an energy-optimal approach. The performances of the proposed guidance laws are evaluated by a series of computer runs.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1134-1143
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• 1994

A study of adiabatic shear band formation and propagation of 4340 steel was done using the stepped speciment which was subjected to high velocity impact. The high velocity impact was performed on compression Hopkinson bar impact machine. After the controlled impact, the specimen was prepared for visual inspection. Numerical simulation was also performed with same geometrical dimension using explicit time integration finite element code. Experimental results were then compared with the numerical prediction. It was found that the numerical prediction is quite accurate, average thickness of adiabatic shear band is about $10{\mu}m$, the macro crack around shoulder is due to folding, and the deformation control ring is effective to freeze the propagation of adiabatic shear band.

• Industrial Engineering and Management Systems
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• v.4 no.2
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• pp.192-197
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• 2005

Among many amplitude parameters, Kurtosis (4-th normalized moment of probability density function) is recognized to be the sensitive good parameter for machine diagnosis. Kurtosis has a value of 3.0 under normal condition and the value generally goes up as the deterioration proceeds. In this paper, simplified calculation method of kurtosis is introduced for the analysis of impact vibration with one sided affiliated impact vibration which occurs towards the progress of time. That phenomenon is often watched in the failure of such as bearings’ outer race. One sided affiliated impact vibration is approximated by one sided triangle towards the progress of time and simplified calculation method is introduced. Varying the shape of one sided triangle, various models are examined and it is proved that new index is a sensitive good index for machine failure diagnosis. Utilizing this method, the behavior of kurtosis is forecasted and analyzed while watching machine condition and correct diagnosis is executed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.8
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• pp.93-98
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• 2022

Adiabatic blanking is a method to improve productivity through an autocatalytic cycle that occurs repeatedly through plastic deformation and thermal softening caused by impact energy. In this study, an axisymmetric analysis model comprising a punch, die, holder, and specimen was developed to confirm the temperature and deformation characteristics caused by an impact load. Through this, the impact energy, diameter of the punch, gap between the punch and die, and the effect of the fillet were analyzed. Because this process occurs in a very short time, adiabatic analysis can be performed using the explicit time-integration method. The analysis, confirmed that it is necessary to design a structure capable of increasing the local temperature and plastic deformation by controlling the impact energy, working area, gap, and the fillet.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1341-1344
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• 2003

Studies on impact damage of composite laminate shells were fewer compared with those on impact behaviors to analyze time-load, displacement-load and impact energy - energy absorption. Up to date the studies were not enough to demonstrate suitability of their results because they were dependent on theories and numerical analyses. In particular, it is a well-known fact that there was a correlation between initial peak load and damage resistance of composite material flat plates imposed with low-speed impact, but studies on composite material shells with curvature were also very few. Actually structures such as wings or moving bodies of airplanes, motor cases and pressure containers of rockets are circular. And as low-speed impact load is imposed for optimal design of take-off and landing, and containers of airplanes, it is very important to analyze evaluation of behaviors and damaged areas. Therefore, in this paper to evaluate the impact characteristics of the CFRP laminate shell according to size of curvature quantitatively, it was to identify energy absorption and impact damage instruments according to change of impact speed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.51-59
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• 2004

An experimental procedure to identify failure modes of impact damage using sensor signals and to analyze their general features is examined. A series of low-velocity impact tests from low energy to damage-induced high energy were performed on the instrumented drop weight impact tester to monitor the stress wave signals due to failure modes such as matrix cracking, delamination, and fiber breakage. The wavelet transform(WT) and Short Time Fourier Transform(STFT) are used to decompose the piezoelectric sensor signals in this study. The extent of the damage in each case was examined by means of a conventional ultrasonic C-scan. The PVDF sensor signals are shown to carry important information regarding the nature of the impact process that can be extracted from the careful signal processing and analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.311-316
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• 2004

For the location estimation in the conventional LPMS(Loose Parts Monitoring System), it is popular to employ a group delay among the acoustic sensors installed within a 3 ft range from the impact source. However, there exists inherent error in determining the arrival time differences of the generated wave group among the neighboring sensors. To overcome this problem in this study, the two dimensional approach has been proposed and applied to effectively estimate the arrival time differences by using a continuous wavelet transform which is one of the linear time-frequency analysis methods. The experiment has been performed to both the plate model and the real steam generator in a nuclear power plant. It is expected that the reliability of the location estimation could be enhanced when the proposed time-frequency method is introduced into the LPMS system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.3
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• pp.197-204
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• 2021

If a failure or an abnormal maneuver occurs during the flight test of a missile, the missile is deliberately self-destructed so as not to continue the flight. At this time, debris are produced and it is important to estimate the impact area in real-time whether it is out of the safety area. In this paper, we propose a method to estimate the debris dispersion area and falling time in real-time using a Fully-Connected Neural Network (FCNN). We applied the Unscented Transform (UT) to generate a large amount of training data. UT parameters were selected by comparing with Monte-Carlo (MC) simulation to secure reliability. Also, we analyzed the performance of the proposed method by comparing the estimation result of MC.