• Journal of KIISE:Computer Systems and Theory
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• v.27 no.6
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• pp.599-607
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• 2000

This paper suggests an efficient reachability analysis method of bounded petri nets. Reachability analysis is a fundamental basis for studying the dynamic properties of any discrete event systems. However, it takes at least exponential execution time and memory space to verify in general petri nets. That is, state space explosion problem may occur. In this paper, we attack problems of previous approaches - state space explosion and restrictions to applicable petri net classes - by formulating the reachability problem as set operation over structural relations among places on an unfolding.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.6
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• pp.333-342
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• 2022

The blast analysis method entails the use of an empirical equation and application of the pressure-time history curve as an explosive load. Although this method is efficient owing to its simple model and short run time, previous studies indicate that it may not be appropriate for near-field explosions. In this study, we investigated why different results were observed for the analysis method by considering an RC beam under near-field explosion conditions with the scaled distance of 0.4-1.0 as an example. On this basis, we examined the application range of the empirical analysis method by using the finite element analysis program LS-DYNA. The results indicate that the empirical analysis method based on data from far-field explosion tests underestimates the impulse. Thus, the calculated deflection of the RC beam would be smaller than the measured deflection and arbitrary Lagrangian-Eulerian (ALE) analysis result. The ALE analysis method is more suitable for near-field explosion conditions wherein the structural responses are large.

• Explosives and Blasting
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• v.27 no.2
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• pp.56-60
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• 2009

In view of physics, energy is defined as the ability to work. The use of natural gas and nuclear power have been increased since 1980s to replace fossil fuels such as coal and petroleum. Recently, solar energy, wind power, tidal power, and geothermal energy have been considered as promising alternative energy sources to overcome environmental pollution. However, their energy efficiencies are much lower than those of chemical energies such as nuclear power, explosive, and petroleum gas. In this study, the present situation of the green energy was reviewed to seek out the way to overcome the limit of the environmental (alternative) energy. Also, purification, application and development trend of the highly efficient alternative energy sources were investigated.

• Journal of Korean Society for Quality Management
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• v.43 no.3
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• pp.327-340
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• 2015

Purpose : Recently, many quality issues are aroused in military forces, such as failures in K-series weapons, combat uniforms' defects and 40mm ammunition explosion accident. To address these problems, Defense Agency for Technology and Quality(DTaQ) introduced new systems such as Manufacturing Readiness Assessment(MRA), Test Report Information System(TRIS) and so on. However, these activities require the human and time resources which cannot be increased in short period. In this paper, we suggest more practical and efficient product examination method. Methods : The most popular and widely used government's quality assurance technique is a sampling method to examine the product. In this research, we first reviewed the DTaQ's quality assurance regulation, then identified several possible problems and finally suggested more efficient and effective sampling plans. Results : We have suggested new sampling framework and evaluated its performance on two military supplies by comparing with other sampling method, and observed that the number of tested samples can be substantially reduced. Therefore, required quality assurance time can be saved. Conclusion : In this paper, we first reviewed the product examination frameworks of DTaQ, PPQMS and DCMA. Then we identified several possible problems which can cause the loss of objectivity and time. To handle these problems, we suggested the new product examination framework and tested the framework to verify the performance.

• Journal of The Korean Astronomical Society
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• v.43 no.2
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• pp.25-39
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• 2010

We perform kinetic simulations of diffusive shock acceleration (DSA) in Type Ia supernova remnants (SNRs) expanding into a uniform interstellar medium (ISM). Bohm-like diffusion due to self-excited $Alfv\acute{e}n$ waves is assumed, and simple models for $Alfv\acute{e}nic$ drift and dissipation are adopted. Phenomenological models for thermal leakage injection are considered as well. We find that the preshock gas temperature is the primary parameter that governs the cosmic ray (CR) acceleration efficiency and energy spectrum, while the CR injection rate is a secondary parameter. For SNRs in the warm ISM of $T_0\lesssim10^5K$, if the injection fraction is $\xi\gtrsim10^{-4}K$, the DSA is efficient enough to convert more than 20% of the SN explosion energy into CRs and the accelerated CR spectrum exhibits a concave curvature flattening to $E^{-1.6}$, which is characteristic of CR modified shocks. Such a flat source spectrum near the knee energy, however, may not be reconciled with the CR spectrum observed at Earth. On the other hand, SNRs in the hot ISM of$T_{0}\approx10^{6}K$ with a small injection fraction, $\xi$<$10^{-4}$, are inefficient accelerators with less than 10% of the explosion energy getting converted to CRs. Also the shock structure is almost test-particle like and the ensuing CR spectrum can be steeper than $E^{-2}$. With amplified magnetic field strength of order of $30{\mu}G$ $Alfv\acute{e}n$ waves generated by the streaming instability may drift upstream fast enough to make the modified test-particle power-law as steep as $E^{-2.3}$, which is more consistent with the observed CR spectrum.

• Journal of KIISE:Software and Applications
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• v.35 no.1
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• pp.12-21
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• 2008

As the usage of computer systems is increasing in our lives, the reliability and safely of these systems need to be thoroughly checked through the verification techniques. As a basic formalism for several modeling methods, the finite state machine (FSM) is widely used in specification and verification of system models. And there is a technique for ing internal events of FSM in order to effectively analyze the system. However, this technique does not handle the state explosion problem since it can be applied after completely generating all the state space of the system. In this research, we provide a new approach for efficiently representing concurrent properties of FSM, the slice model and provide an efficient transition reduction method based on the slice model. Our approach is effective in time and space perspective since it is peformed by partially generating the needed system states while the existing abstraction technique can be applied to all the system states.

• Journal of Multimedia Information System
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• v.9 no.3
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• pp.219-226
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• 2022

The advancement of realistic visual effects technology provides increasingly immersive experiences and consumer satisfaction with content. The explosion and destruction effects in live-action films and animations are some of the most frequently used visual effects, but they are relatively difficult to execute, so it is challenging to make them look realistic. This study tested a method of effectively realizing computer-generated explosions and destruction. Experiments for this study are as follows: first, the interlink according to density accumulation of the fluid; second, the interlink according to the temperature accumulation of the fluid; and third, the interlink according to the distance between the fluid and the involved objects. This study was conducted to identify an optimal solution for producing computer-generated explosions and destruction.

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.11-18
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• 2018

To interact with a virtual object in immersive virtual environment, the target object should be selected quickly and accurately. Conventional 3D ray casting method using a direction of user's hand or head allows the user to select an object quickly. However, accuracy problem occurs when selecting an object using conventional methods among occlusion of objects. In this paper, we propose a region of interest based selection method that enables to select an object among occlusion of objects using a combination of gaze tracking and hand gesture recognition. When a user looks at a group of occlusion of objects, the proposed method recognizes user's gaze input, and then region of interest is set by gaze input. If the user wants to select an object among them, the user gives an activation hand gesture. Then, the proposed system relocates and visualizes all objects on a virtual active window. The user can select an object by a selecting hand gesture. Our experiment verified that the user can select an object correctly and accurately.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.845-851
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• 2013

Because the existing control system has been operating for about 20 years, it is necessary to upgrade the system for stable and efficient operation. But, there is a difficulty in maintenance by difference of manufacturer of each main control systems for boiler, turbine and generator. This developed IMCS(Integrated Monitoring and Control System) consists of more than 10,000 inputs and outputs for large scale thermal power plant. This paper consists of the development journey of IMCS MBC(mill and burner control) ; core binary protection & monitoring logic including prevention circuit of boiler explosion & implosion. In this project, the IMCS for boiler, turbine and generator was developed on basis of one communications platform. In this paper, the whole journey of development of IMCS MBC is dealt with designing software and hardware, coding application software, and validating software and hardware.

• Animal Bioscience
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• v.35 no.9
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• pp.1367-1378
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• 2022

Objective: The present study was conducted to examine the gas production, fermentation characteristics, nutrient degradation, and methanogenic community composition of a rumen fluid culture with Broussonetia papyrifera (B. papyrifera) subjected to ensiling or steam explosion (SE) pretreatment. Methods: Fresh B. papyrifera was collected and pretreated by ensiling or SE, which was then fermented with ruminal fluids as ensiled B. papyrifera group, steam-exploded B. papyrifera group, and untreated B. papyrifera group. The gas and methane production, fermentation characteristics, nutrient degradation, and methanogenic community were determined during the fermentation. Results: Cumulative methane production was significantly improved with SE pretreatment compared with ensiled or untreated biomass accompanied with more volatile fatty acids production. After 72 h incubation, SE and ensiling pretreatments decreased the acid detergent fiber contents by 39.4% and 22.9%, and neutral detergent fiber contents by 10.6% and 47.2%, respectively. Changes of methanogenic diversity and abundance of methanogenic archaea corresponded to the variations in fermentation pattern and methane production. Conclusion: Compared with ensiling pretreatment, SE can be a promising technique for the efficient utilization of B. papyrifera, which would contribute to sustainable livestock production systems.