• Tunnel and Underground Space
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• v.18 no.4
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• pp.280-288
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• 2008

Since blast-induced vibration may cause serious problem to the rock mass as well as the nearby structures, the prediction of blast-induced vibration and the stability evaluation must be performed before blasting activities. Dynamic analysis using measurement vibration waveform which is measured by bore hole blasting or test blasting has been increased recently in order to analyze the effect of the blast-induced vibration. The waveform made by bore hole blasting has the similar vibration level and duration to those the waveform of sing hole has. However, there can be a little difference in attenuation characteristics with the blast induced vibration waveform in the field. Through the superposition modeling of single hole waveform, I obtained the vibration waveform on the blasting condition changes and conducted dynamic analysis using this waveform in this study.

• Structural Engineering and Mechanics
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• v.63 no.3
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• pp.347-359
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• 2017

Blast resistant gates are required to be lightweight and able to mitigate extreme loading effect. This may be achieved through innovative design of a gate and its supporting frame. The first is well covered in literature while the latter is often overlooked. The design of supporting frame depends mainly on the boundary conditions and corresponding reaction forces. The later states the novelty and the aim of this paper, namely, the analysis of reaction forces in supporting structure of rectangular steel gates subjected to "far-field explosions". Flat steel plate was used as simplified gate structure, since the focus was on reaction forces rather than behaviour of gate itself. The analyses include both static and dynamic cases using analytical and numerical methods to emphasize the difference between both approaches, and provide some practical hints for engineers. The comprehensive study of reaction forces presented here, cover four different boundary conditions and three length to width ratios. Moreover, the effect of explosive charge and stand-off distance on reaction forces was also covered. The analyses presented can be used for a future design of a possible "blast absorbing supporting frame" which will increase the absorbing properties of the gate. This in return, may lead to lighter and more operational blast resistant gates.

• Explosives and Blasting
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• v.36 no.2
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• pp.1-9
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• 2018

In this paper, AUTODYN blasting simulation of single blast hole were conducted to evaluate the blasting effects of Polymer Gel. The coupling mediums used as the filling material around an explosive charge were air and gelatin. each simulation case was D I(decoupling index) 1.0, 1.25, 1.56 with air or polymer gel coupling materials. In order to evaluate blast effects full charge model was used as a reference for evaluation of blasting effects. The results of numerical analysis showed that fragmentation of a limestone model of were much more fractured by polymer gel medium than by air medium. As expected, the transmitted peak pressure was higher polymer gel coupled model than in air medium.

• The Plant Pathology Journal
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• v.16 no.5
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• pp.257-263
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• 2000

Infection with rice blast fungus (Magnaporthe grisea) significantly reduced foliar net photosynthesis (A) of rice cultivars: Ilpoom, Hwasung, and Choochung in greenhouse experiments. By measuring the amount of diseased leaf area with a computer image analysis system, the relation between disease severity (DS) and net photosynthetic rate was curvilinearly correlated (r=0.679). Diseased leaves with 35% blast symptom can be predicted to have a 50% reduction of photosynthesis. The disease severity was linearly correlated (r=0.478) with total chlorophyll (chlorophyll a and chlorophyll b) per unit leaf area(TC). Light use efficiency was reduced by the fungal infection according to the light response curves. However, dark respiration (Rd) did not change after the fungal infection (p=0.526). Since the percent of reduction in photosynthesis greatly exceeded the percent of leaf area covered by blast lesions, loss of photosynthetic tissue on an area basis could not by itself account for the reduced photosynthesis. Quantitative photosynthetic reduction can be partially explained by decreasing TC, but cannot be explained by decreasing Rd. By photosynthesis (A)-internal CO$_2$ concentration (C$_i$ curve analysis, it was suggested that the fungal infection reduced ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity, ribulose-1,5-bisphosphate (RuBP) regeneration, and inorganic phosphate regeneration. Thus, the reduction of photosynthesis by blast infection was associated with decreased TC and biochemical capacity, which comprises all carbon metabolism after CO$_2$ enters through the stomata.

• Journal of the Korean Geotechnical Society
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• v.23 no.10
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• pp.33-45
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• 2007

In this study, the blast-induced vibration effects on the structural stability of the adjacent tunnel were estimated with respect to the allowable peak particle velocity (PPV). The blasting distance from the tunnel satisfying the allowable PPV was estimated based on the analytical solutions, United States Bureau of Mines (USBM) suggestions, and the equations used in the subway in Seoul. The allowable blasting distance was estimated by using finite difference analysis (FDA) and the behavior of the concrete lining and rock bolts was examined and the stability of those was estimated during the blast. Research results show that the blast-induced vibration effects on the structural stability are negligible for the concrete lining but relatively large for the rock bolts.

• Journal of Korean Association for Spatial Structures
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• v.23 no.1
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• pp.25-34
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• 2023

This paper presents a computational fluid dynamics (CFD) analysis to investiagate the effect of expansion chamber on overpressure reduction in protective tunnels subjected to detonation of high explosives. A commercial CFD code, Viper::Blast, was used to model the blast waves in a protective tunnel with a length of 160 m, width of 8.9 m and height of 7.2 m. Blast scenarios and simulation matrix were establihsed in consideration of the design parameters of expansion chamber, including the chamber lengths of 6.1 m to 12.1 m, widths of 10.7 m to 97 m, length to width ratios of 0.0 to 5.0, heights of 8.0 m and 14.9 m, and ratios of chamber to tunnel width of 1.2 to 10.9 m. A charge weight of TNT of 1000 kg was used. The mesh sizes of the numerical model of the protective tunnel were determined based on a mesh convergence study. A parametric study based on the simulation matrix was performed using the proposed CFD tunnel model and the optimized shape of expansion chamber of the considered tunnel was then proposed based on the numerical results. Design recommendations for the use of expansion chamber in protective tunnel under blast loads to reduce the internal overpressures were finally provided.

• Journal of Korean Institute of Industrial Engineers
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• v.23 no.4
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• pp.687-698
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• 1997

In this paper, a Variation of Blast with Go-Back-N(V-BGBN) protocol is proposed, which differs from Blast with Go-Back-N(BGBN) and Blast with Full Retransmission on Error(BFRE) protocols in the retransmission strategy of packets. Performances of these three protocols under correlated packet errors are analyzed. Throughput efficiency of an arbitrary packet is obtained under the assumption that the round trip delay and the packet length are respectively constant. Recursive formula and difference equations are used as analytical tools. Correlation of packet errors is modelled by a two state Markov chain. The throughput efficiencies under these protocols are compared. V-BGBN protocol is shown to be superior to other two protocols in high speed network.

• Steel and Composite Structures
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• v.23 no.1
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• pp.107-114
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• 2017

Design of stepwise foam claddings subjected to air-blast is performed based on random Voronoialgorithm. FE models are constructed using the random Voronoialgorithm, and numerical analysis is carried out to simulate deformation mode and energy absorption of the cladding by the ABAQUS/Explicit software. The FE model is validated by test result, and good agreement is achieved. The deformation patterns are presented to give an insight into the influences of distribution on deformation mechanisms. The energy absorbed by the stepwise foam cladding is examined, and the parameter effects, including layer number, gradient, and blast loading, are discussed. Results indicate that the energy absorption capacity increases with the number of layer, gradient degree, and blast pressure increasing.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.32-33
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• 2016

This purpose of this study is to find the properties of pore structure and length change of blast furnace slag cement added alkali powder stimulant on shrinkage reducing agent presence. In length change, the specimen added alkaline stimulant was smaller than normal blast furnace slag concrete. And the specimen added shrinkage reduction agent was confirmed to show smaller rate of length change than the length. In MIP analysis of 1day-age, 0.1㎛ subsequent pore amount of the specimen added alkaline stimulant was significantly smaller value the normal blast furnace slag concrete specimen.

• Journal of Digital Contents Society
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• v.5 no.4
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• pp.264-268
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• 2004

MIMO(Multi-Input Multi-Output)) system, which can increase the channel capacity by in multiple transmit and/or receive antennas, has been intensively studied for higher data rates and better quality in wireless communications. This paper treats the MIMO channel modeling and analyze the performance of V-BLAST system with ZF receiver and MMSE reciver, using OSUS algorithm respectively, over MIMO channel.