• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.350-355
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• 2012

Past few years have seen the growing importance of micro shock tubes in various engineering applications. A pharma ballistic technique is one such application which uses micro shock tube to accelerate drug particles and penetrate into skin, thus avoiding the usual injection drug delivery system. But for the efficient design of such instruments requires the detailed knowledge of shock characteristics and flow field inside a micro shock tube. Due to many factors such as boundary layer, low Reynolds number and high Knudsen number shock propagation inside micro shock tubes will be quite different from that of the well established macro shock tubes. In the present study, experimental studies were carried out on a micro shock tube of 3 mm diameter to investigate flow characteristics and shock propagation. Pressure values were measured at different locations inside the driven section. From the experimental values other parameters like shock velocity, shock strength were found and shock wave diagram was constructed.

• Structural Engineering and Mechanics
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• v.8 no.2
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• pp.165-180
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• 1999

The cost effectiveness of using steel roof systems for residential buildings is becoming increasingly apparent with the decrease in manufacturing cost of steel components, reliability and efficiency in construction practices, and the economic and environmental concerns. While steel has been one of the primary materials for structural systems, it is only recently that its use for residential buildings is being explored. A comprehensive system for the design of residential steel roof truss systems is presented. In the first stage of the research the design curves obtained from the AISI-LRFD code for the manufactured cross-sections were verified experimentally. Components of the truss systems were tested in order to determine their member properties when subjected to axial force and bending moments. In addition, the experiments were simulated using finite element analysis to provide an additional source of verification. The second stage of the research involved the development of an integrated design approach that would automatically design a lowest cost roof truss given minimal input. A modified genetic algorithm was used to handle sizing, shape and topology variables in the design problem. The developed methodology was implemented in a software system for the purpose of designing the lowest cost truss that would meet the AISI code provisions and construction requirements given the input parameters. The third stage of the research involved full-scale testing of a typical residential steel roof designed using the developed software system. The full scale testing established the factor of safety while validating the analysis and design procedures. Evaluation of the test results indicates that designs using the present approach provide a structure with enough reserve strength to perform as predicted and are very economical.

• Food Science and Preservation
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• v.18 no.3
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• pp.279-287
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• 2011

The purpose of this research is to develop bellflower (Platycodon grandiforum) root Jeonggwa as a health food. The Omija (Schizandra chinensis Baillon) water extract with 0-8% (w/w) Jeonggwa added was stored at $25^{\circ}C$ for 12 weeks. The quality characteristics of Jeonggwa during storage were investigated. The Jeonggwa showed a lower pH and a higher acdity as the amount of Omija water extract that was added increased. The moisture content of Jeonggwa were rose from 15-18% to 16-22% within 2 weeks of storage, and remained at that level up to the end of storage. The total viable cells of bellflower root Jeonggwa were 2.1~2.3 log CFU/g and increased in number during storage but never exceeded 4 log CFU/g. The shelf life of the Jeonggwa was extended when the Omija extract was added. The lightness (L), redness (a) and yellowness (b) of the Jeonggwa during its storage at $25^{\circ}C$ were highest in control samples, and the values decreased with the increase in the Omija extract concentration (p<0.001). The mechanical evaluation of the Jeonggwa showed that various tested parameters fell during the storage at $25^{\circ}C$. The hardness and strength of the Jeonggwa significantly decreased as the Omija extract concentration rose (p<0.05). In the ensory evaluation tests, the acceptability of the Jeonggwa was optimal when 4~6% of Omija extract was added to it.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.9
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• pp.1234-1243
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• 2021

This study intends to provide a forecast of the diffusion of countries participating in a newly proposed G to G mechanism named as the "International Defense Industry Cooperation Program of Korea", modeled after the U.S. Foreign Military Sales(FMS). For this purpose, the study analyses 40 years of statistical data of U.S. FMS customers to find two parameters, coefficient of innovation and imitation, which explain the diffusion in FMS customers. Furthermore, the study forecasts the diffusion in international participation to the proposed mechanism taking account of the differences in the level of government competitiveness and the strength of defense industrial base of Korea and the U.S. This study also provides recommendations for accelerating the desired outcomes under the new program. While Korea is likely to have relative advantages over 'imitators' in the international market, it will need to gain competitiveness in high-level capabilities going beyond the realm of medium-high level systems, and present attractive alternatives for offsets.

• Journal of the Korea Society for Simulation
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• v.27 no.4
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• pp.69-77
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• 2018

Launching system is designed to store the payload, withstand the rigors, and prevent it from rusting and damaging. The behavior during initial deployment of the missile is determined by production, assembly and insertion condition of a launching tube and a missile. The purpose of this research is to confirm the safety of a launching tube by statistically analyzing behavior of the missile, during initial deployment stage. Error parameters which effect initial behavior of the missile are selected and analyzed through Monte-Carlo Simulation. Based on the result of simulation, tip-off and stress distribution between rail and shoe is predicted by using the commercial analysis program called Recurdyn. Lastly, the safety factor is calculated based on yield strength of the material and maximum stress of the rail during the process of launching. The safety of the launching system is verified from the result of the safety factors.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.283-291
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• 2018

This study intends to develop an analytical model of unreinforced masonry(URM) walls for the nonlinear static analysis which has been generally used to evaluate the seismic performance of a building employing URM walls as seismic force-resisting members. The developed model consists of fiber elements used to capture the flexural behavior of an URM wall and a shear spring element implemented to predict its shear response. This paper first explains the configuration of the proposed model and describes how to determine the modeling parameters of fiber and shear spring elements based on the stress-strain curves obtained from existing experimental results of masonry prisms. The proposed model is then verified throughout the comparison of its nonlinear static analysis results with the experimental results of URM walls carried out by other researchers. The proposed model well captures the maximum strength, the initial stiffness, and their resulting load - displacement curves of the URM walls with reasonable resolution. Also, it is demonstrated that the analysis model is capable of predicting the failure modes of the URM walls.

• Journal of Drive and Control
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• v.16 no.3
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• pp.51-58
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• 2019

The objective of this study was to investigate a simulation technology for the AM field based on ANSYS Inc.. The introduction of metal 3D printing AM process, and the examining of the present status of AM process simulation software, and the AM process simulation processor were done in the previous study (part 1). This present study (part 2) examined the use of the AM process simulation processor, presented in Part 1, through direct execution of Topology Optimization, Ansys Workbench, Additive Print and Additive Science. Topology Optimization can optimize additive geometry to reduce mass while maintaining strength for AM products. This can reduce the amount of material required for additive and significantly reduce additive build time. Ansys Workbench and Additive Print simulate the build process in the AM process and optimize various process variables (printing parameters and supporter composition), which will enable the AM to predict the problems that may occur during the build process, and can also be used to predict and correct deformations in geometry. Additive Science can simulate the material to find the material characteristic before the AM process simulation or build-up. This can be done by combining specimen preparation, measurement, and simulation for material measurements to find the exact material characteristics. This study will enable the understanding of the general process of AM simulation more easily. Furthermore, it will be of great help to a reader who wants to experience and appreciate AM simulation for the first time.

• Korean Journal of Agricultural Science
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• v.46 no.3
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• pp.689-703
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• 2019

The term quality or freshness of eggs in industrial production still poses concerns regarding whether washing is necessary. Therefore, the aims of this study were to examine the effects of different storage times and temperatures and to perform a comparison between washed and unwashed eggs. A total of 1000 washed and 1000 unwashed egg samples were stored at three different temperatures (5, 10, and $25^{\circ}C$) for 0 - 8 weeks and were used for the data collection. On the designated day, the eggs were processed to evaluate their internal and external quality traits, such as the Haugh unit, airspace volume, eggshell strength, pH, and microbiological profile. Significant differences (p < 0.05) were observed between the washed and unwashed eggs for each quality trait. The results indicate that storage between 5 and $10^{\circ}C$ better preserved the quality of eggs compared with the storage at $25^{\circ}C$ throughout the days of the storage. Overall, this study suggests that the storage time and temperature have a vital role in maintaining the quality of eggs which were significantly affected during storage. In addition, all the quality parameters differed between the washed and unwashed samples which is further responsible for deteriorating the quality of the eggs.

• Journal of Preventive Medicine and Public Health
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• v.52 no.4
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• pp.242-249
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• 2019

Objectives: Elderly individuals with diabetes should maintain a normal body mass index (BMI) to help control their blood glucose levels. This study investigated barriers to physical activity (PA), self-efficacy to overcome those barriers, and PA self-efficacy among elderly individuals with diabetes in relation to BMI. Methods: This cross-sectional study included 56 participants. Data were collected by a questionnaire interview and direct measurements for anthropometric data. PA self-efficacy was measured using 8 questions describing different levels of PA, where participants rated the strength of their belief that they could engage in that activity. Self-efficacy to overcome barriers was measured using 10 questions capturing participants' confidence in their ability to engage in PA despite different possible barriers. Mean scores for these parameters were analyzed using the chi-square test and the independent t-test. Results: In total, 89.3% of participants had a low PA level and 58.9% had more than 3 hours of sedentary activity per day. Furthermore, 55.4% were obese and 14.3% were overweight. The mean scores for PA self-efficacy and self-efficacy to overcome barriers were $59.1{\pm}26.4$ and $52.5{\pm}13.8$, respectively. PA level was related to BMI (p<0.001; r=0.116) and sedentary activity (p<0.05; r=0.274). PA self-efficacy and age were not related to BMI. Barriers to PA were associated with PA levels (p<0.05). Conclusions: Physical inactivity was a major problem in elderly individuals with diabetes, and was correlated with higher BMI. Lower levels of PA might be mediated by sedentary activity.

• Geomechanics and Engineering
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• v.18 no.3
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• pp.315-328
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• 2019

This paper presents an investigation on bearing capacity, load-settlement behavior and safety factor of rock-soil slopes reinforced using geogrid-box method (GBM). To this end, small-scale laboratory studies were carried out to study the load-settlement response of a circular footing resting on unreinforced and reinforced rock-soil slopes. Several parameters including unit weight of rock-soil materials (loose- and dense-packing modes), slope height, location of footing relative to the slope crest, and geogrid tensile strength were studied. A series of finite element analysis were conducted using ABAQUS software to predict the bearing capacity behavior of slopes. Limit equilibrium and finite element analysis were also performed using commercially available software SLIDE and ABAQUS, respectively to calculate the safety factor. It was found that stabilization of rock-soil slopes using GBM significantly improves the bearing capacity and settlement behavior of slopes. It was established that, the displacement contours in the dense-packing mode distribute in a broader and deeper area as compared with the loose-packing mode, which results in higher ultimate bearing load. Moreover, it was found that in the loose-packing mode an increase in the vertical pressure load is accompanied with an increase in the soil settlement, while in the dense-packing mode the load-settlement curves show a pronounced peak. Comparison of bearing capacity ratios for the dense- and loose-packing modes demonstrated that the maximum benefit of GBM is achieved for rock-soil slopes in loose-packing mode. It was also found that by increasing the slope height, both the initial stiffness and the bearing load decreases. The results indicated a significant increase in the ultimate bearing load as the distance of the footing to the slope crest increases. For all the cases, a good agreement between the laboratory and numerical results was observed.