• Explosives and Blasting
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• v.22 no.4
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• pp.7-15
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• 2004

An explosion modeling technique was developed by using the spherical discrete element code, PFC3D, which can be used to model the dynamic stress wave propagation phenomenon. The modeling technique is simply based on an idea that the explosion pressure should be applied to a PFC3D particle assembly not in the form of an external force (body force), but in the form of a contact force (surface force). According to this concept, the explosion pressure is applied to the wall particles by the scheme of radius expansion/contraction of inner-hole particles. The output wall force is compared to the input hole pressure in every time step, and a correction routine is activated to control the radius multiplier of the inner-hole particles. A comparative blast simulation far a cement mortar block of $80\times90\times80mm$ was conducted by using the conventional explosion modeling method and the new one. The results of the simulation are presented in a qualitative fashion.

• Korean Journal of Food Science and Technology
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• v.22 no.3
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• pp.266-271
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• 1990

Yukwa(Korean traditional puffed rice snack) puffed by vegetable oil was evaluated its shelf-life and monitored its physicochemical changes during long term storage. And air puffing instead of oil was tested for substitution of puffing medium. The shelf-life of oil puffed Yukwa was less than 4 weeks at $30^{\circ}C$ by peroxide value and negligible changes in physical texture was detected after 9 weeks storge. There was a possibility to apply air puffing method for Yukwa making and its optimum temperature was around $250^{\circ}C$. Air puffed Yukwa was a little less expansion rate, same level of hardness and high brittleness compared with oil puffed . Sensory evaluation of air puffed Yukwa was as same as air puffed in odour, firmness and texture but overall taste was less score probably causing by oil used which need a impovement for air puffed Yukwa. No differences in structure of both Yukwa observed by SEM was showed.

• Korean Journal of Food Science and Technology
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• v.20 no.4
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• pp.470-475
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• 1988

The extrusion-cooking method was used to make gelatinized rice extrudate from rice grits of the Chuchung and the Samgang varieties. The water contents of raw rice grits varied from 15% to 25%, and the physicochemical properties of extrudates were evaluated. Low moisture content showed high expansion ratio in rice extrudate and resulted in some decrease in gelatinization, bulk density and break strength. Increasing the water content to 25% resulted in increase in water absoption index but decrease in water solubility index. With regards to Brabender Amylograph values and rheological patterns, higher moisture content in raw materials revealed stronger pseudoplastic flow behavior with lower viscogram property. Hunter's color values of rice flours extruded at low water content were low in b values. Scanning electron microscopy demonstrated the break-down of starch granules during extrusion.

• Journal of Korean Society for Geospatial Information Science
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• v.17 no.3
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• pp.41-48
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• 2009

This study investigated the characteristics of spatial expansion/centralization and the spatial structural change of urban. The data used in analysis were urban population, employment, building floor area, and land price. The analysis was performed for the data of 1995, 2000, and 2005 during 10 years after 1995. The method of research was as follows; The movement of mean center and standard distance/standard deviation ellipse was estimated to investigate the urban growth change. The result of Moran's I analysis showed a clustered pattern, not a dispersed pattern, however; the effect was not significant. The town area requires the well-ordered urban planning such as land use. The contours map demonstrates that a monopole structure was generally transformed into a multicentralization structure. The development of mutural connection axis among central street roads was fragile.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2008.04a
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• pp.203-208
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• 2008

The purpose of the study is to establish the concept of residential standard, and at the same time to investigate the area of the minimum residential standard in the countries of the world through the preceding studies. In addition, it also aims at establishing the objective residential standard by comparing the residential standard of Korea with that of foreign countries, examining the problems and finding out the matters to be improved through the comparison of the residential standard in advanced countries with the minimum residential standard of Korea. The standard residential area, derived from the process of examining the minimum residential standard, will be used as the basic material for the calculation of the reasonable area in the surface plan for the study of low-cost housing development. The method of the study is to establish the concept of residential standard and at the same time to find out the problems in the minimum residential standard of Korea and improvement methods through the comparison of the residential standards in other countries. As the result of the studies focused on the area among the residential standards, it is found out that the Korea's residential area per capita is established as the least in comparison with that of advanced countries. The real area decided depending on the size of social space suitable for living can play a role in improving the degree of satisfaction in the person's living in the residential area. Therefore, it is urgently necessary to make a depth study on the surface area of the minimum residential standard, and it is also required to propose the residential standard and directions for the improvement of the qualitative level rather the quantitative expansion of residential structures.

• Geotechnical Engineering
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• v.13 no.4
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• pp.95-108
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• 1997

For normally consolidated clay, several researchers have developed a number of theoretical time factors to determine the coefficient of consolidation However, depending on the assumptions and analytical techniques, it could considerably vary even for a specific degree of consolidation. In this paper, a method is proposed to determine a consistent coefficient of consolidation over all ranges of degree of consolidation by applying the concept of the Optimum Design Technique. The initial excess pore pressure distribution is assumed to be obtainable by the successive spherical cavity expansion theory. The dissipation of pore pressure is simulated by means of two dimensional linear-uncoupled axisymmetric consolidation analysis. The minimization of the differences between the measured and the predicted excess pore pressures was carried by BFGS unconstrained optimum design algorithm with one dimensional golden section search technique. By analyzing numerical and real field examples, it can be found that the adopted optimum technique gives a consistent and convergent results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.857-864
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• 1998

The infuluence of Doppler effects on the tracking performance of a noncoherent second-order delay locked loop (DLL) operating on a data modulated signal is investigated. For the perfoermance analysis we consider the tracking accuracy (steady state error and jitter) of the linear DLL and the reliability of the nonlinear loop. The nonlinear analysis concerning the loop reliability makes use of an asympototic expansion for the MTLL(mean time to lose lock) which has been derived by applying the singular perturbation method. In particular, we give optimal loop parameters and the optimal bandwidth of the bandpass filter in the loop arms to achieve a maximum MTLL. Since Doppler effects can be producesd comparatively in LEO system, we can espect the more reliable DLL loop design. by using the results of the circuit simulation, the delay lock loop is synthesized in FPGA, and verified to get the GPS data from the STR-2770 GPS simulator system. So, the synthesized logic circuit is shown be accurately performed.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.3
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• pp.37-46
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• 2013

Recent years have witnessed the use of micro shock tube in various engineering applications like micro combustion, micro propulsion, particle delivery systems etc. The flow characteristics occurring in the micro shock tube shows a considerable deviation from that of well established conventional macro shock tube due to very low Reynolds number and high Knudsen number effects. Also the diaphragm rupture process, which is considered to be instantaneous process in many of the conventional shock tubes, will be crucial for micro shock tubes in determining the near diaphragm flow field and shock formation. In the present study, an axi-symmetric CFD method has been applied to simulate the micro shock tube, with Maxwell's slip velocity and temperature jump boundary conditions. The effects of finite diaphragm rupture process on the flow field and the shock formation was investigated, in detail. The results show that the shock strength attenuates rapidly as it propagates through micro shock tubes.

• Hwankyungkyoyuk
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• v.15 no.2
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• pp.1-13
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• 2002

The progress of environmental science and technology in the developed countries has been rapid in recent years. Particularly remarkable has been the advancement of various pollutant control measures, which have brought the pollution of inorganic factors such as air and water under control. In contrast, diversity of the ecosphere, of which man is a part, is being steadily impoverished and the biological community is getting unvaryingly uniform. These phenomena were brought about by the expansion of artificial environment such as new industrial complexes, transportation facilities and urban development. Man has constructed uniform and artificial environment, believing in the premise of confrontation with nature, to such a scale that the natural environment and biological community have lost their balance. This will increasingly endanger the soundness of the biotic environment of nature, which constitutes the potential foundation both for the survival environment of man as biological entity and for the development of human civilization. In order to guarantee the soundness of man's body, intelligence and sensitivity as wholesome gene pool on the earth and for the future of man, primarily important environmental education is the understanding of how man can everlasting exist in and with the survival environment. In view of this reality, it is vitally important to create ecologically diverse and well-balanced environment with living materials, i.e., vegetation in order to secure lasting survival environment for man. This task is urgently required in highly artificial environment where non-biological materials have forced the impoverishment of the biological community. Therefore, environmental education for the future should not be totally oriented to technology as that in the past nor it is limited to the medical aspect where well-being of human is the sole object of concern. That is to say, environmental education for the future should be one that provides knowledge that human can understand his place based on the ecological concept and thereby make him to have ethical consciousness that he can control his behavior within the reasonable level for ecological niche who he is located.

• Hwankyungkyoyuk
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• v.18 no.3 s.28
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• pp.75-90
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• 2005

The purpose of this study was to analyze middle school students' consumption lifestyle and develop a program for measuring Ecological Footprint (EF) for them. For this study, 200 male and female middle school students in large cities, medium & small cities were selected to analyze their consumption lifestyle. It was also that the existing programs for measuring EF were studied and basic rules of setting up new EF indicators were established based on the results of survey and literature study. 15 indexes was selected by dividing the life areas into food, housing, traffic, goods and services areas and than the delpi computer programming tools was used to develop program for measuring EF in this study. The program for measuring EF can be used as educational materials for consumers' environment education in the areas of social environment education and school environment education. The followings are suggestions coming out of this study. First, it is required to revise and complement program for measuring EF analyzing the problems that occur when applying it to middle school students actually. Second, some data that used during normalization of EF ate originally from the USA. So it is necessary to change the data to meet the Korean situation. Third, it is necessary to have design work that can invite interests of students with consumers' environmental education materials through cooperation between environmental education experts and computer programmers. Fourth, it is necessary to have practical research with consumers' environmental education adding educational contents into EF measurement program. Fifth, it is necessary to develop a method for distribution an expansion of the program for measuring EF to make it usable in different types of environmental education materials.