• Polymer(Korea)
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• v.25 no.4
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• pp.575-586
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• 2001

Stabilized polyacrylonitrile (PAN) fibers can be transformed into quasi-carbon fibers with different properties depending on heat-treatment processing parameters at lower temperatures than temperature for the fabrication of carbon fibers. It has been investigated from the preliminary work that appropriate quasi-carbonization processes at about 1100$^{\circ}C$ strongly influence various properties of quasi-carbon fiber/polymer composite as well as quasi-carbon fiber itself. The objective of the present work is to prepare quasi-carbon fibers from stabilized PAN fibers using various quasi-carbonization cycles and to examine their properties. Two temperature regions, up to 800$^{\circ}C$ and above 1000$^{\circ}C$, were used for quasi-carbonization processes. The chemical composition, physical properties, thermal stability, microstructure, mechanical properties and electrical resistivity of the quasi-carbon fibers prepared with different final heat-treatment temperatures, heating rates, holding times, heating steps, and purging gas purity were extensively examined. The results were also compared with those from stabilized PAN fiber and commercial PAN-based carbon fiber. The present study showed that a variety of properties of quasi-carbon fibers significantly depended on several quasi-carbonization process parameters.

• Journal of the Korean Chemical Society
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• v.45 no.3
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• pp.256-263
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• 2001

The STS contents, emphasized in the 6th curriculum, in the chemistry parts of general science textbooks were analyzed. The STS contents of textbooks showed average of 24.4%. The chapter in "modern science and technology" were included 45.5% in STS contents, 38.7% in "environment", 29.1% in energy, and 14.0% in "materials". When the STS contents were analyzed by STS topics of Piel, the results are as follows; 38.3% on environmental quality and utilization of natural source, 29.6% on effect of technological developments, 7.9% on energy, and 0.6% on human engineering. However, there were no topics on population, space research and national defense. When the STS contents were analyzed by student activities of SATIS, most of the activities were research and case study. There were few field activities of role play, problem solving and decision making, and research design.

• Korean Journal of Food Science and Technology
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• v.29 no.3
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• pp.516-521
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• 1997

Effect of amylose content on the physical properties of resistant starches (RS) from autoclaved maize starches (with starch:water=1:3.5, at $121^{\circ}C$) which were repeated up to 4 times heating-cooling cycles, were investigated by water uptake, scanning electron microscope (SEM) and differential scanning calorimetry (DSC). Amylose content of waxy maize starch (Amioca), common maize starch (PFP), high amylose starch(Amaizo, Amylomaize VII) were 0%, 29%, 50%, and 72%, respectively. Yield of RS increased as amylose content increased. Water uptake of all kinds of native starch was higher than that of RS, but lower than that of autoclaved starch. By SEM, RS showed some small particles on surface but the size of particles was different with amylose content. Single endothermic transition peak exhibited at $40{\sim}70^{\circ}C$ in autoclaved Amioca and PFP (crystalline melting of amylopectin) and at $132{\sim}169^{\circ}C$ in autoclaved Amaizo and Amylomaize VII(crystalline melting of amylose) by DSC. RS from all kinds of autoclaved starches except Amioca showed single endothermic peak over $155^{\circ}C$ but the enthalpy was not related to amylose content.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.3
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• pp.64-69
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• 2007

Motion control of the system is a position control of motor. Motion control of an uncertain robot system is considered as one of the most important and fundamental research directions in the robotics. Some distinguished works using linear control, adaptive control, robust control strategies based on computed torque methodology have been reported. However, it is generally recognized within the control community that these strategies suffer from the following problems : the exact robot dynamics are needed and hard to implement, the adaptive control cannot guarantee the performance during the transient period for adaptation under the variation, the robust control algorithms such as the sliding mode control need information on the bounds of the possible uncertainty and disturbance. And it produces a large control input as well. In this dissertation, a motion control for the unmanned intelligent robot system using disturbance observer is studied. This system is affected with an impact vibration disturbance. This paper describes a stable motion control of the system with the consideration of external disturbance. To obtain the stable motion independently against the external disturbance, the disturbance rejection is strongly required. To address the above issue, this paper presents a Disturbance OBserver(DOB) control algorithm. The validity of the suggested DOB robust control scheme is confirmed by several computer simulation results. And the experiments with a motor system is performed to give the validity of applicability in the industrial field. This results make the easier implementation of the controller possible in the field.

• Korean Journal of Food Science and Technology
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• v.44 no.4
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• pp.493-497
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• 2012

The objective of this study was carried out in order to evaluate the antioxidative activities of n-hexane fractions from medicinal herbs. Certain parts from 6 species of edible and medicinal herbs were extracted with methanol. Radical scavenging activity of the n-hexane fractions against DPPH and ABTS radicals were observed to be high in Psoralea corylifolia, and Scutellsria barbata; it also significantly increased (p<0.05). For a comparison of the effect of various concentration of fractions, as the concentration of treatment increased, the antioxidative effects on radical scavenging activity also oncreased; yet it was not significant. The antioxidative effect of medicinal plants was dependent on the concentration but was not significant. Therefore, these results indicate that edible wild plants, such as Psoralea corylifolia, and Scutellsria barbata may be useful as potential antioxidant sources for improving the human antioxidant defense system against disease.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.5
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• pp.35-42
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• 2014

Thermal analysis properties and adhesive properties of self-healing agents were evaluated through differential scanning calorimetry, reaction heat measurement, and adhesive shear test. D1E0, D3E1, D1E1, D1E3, and D0E1, depending on the mixing ratio of DCPD and ENB, were considered as self-healing agents. The amount of Grubbs' catalyst, depending on the type of self-healing agents, was varied from 0.1 wt% to 1.5 wt%. In the case of DCPD, the polymerization reaction occurred faster and the stabilized adhesive strength increased as the amount of catalyst increased; however, a large amount of catalyst was required. ENB had excellent reactivity with a small amount of the catalyst; however, high reaction heat was observed at the early stage of polymerization. Thermal analysis properties and adhesive properties of self-healing agents can be controlled by varying a mixing ratio of DCPD and ENB. Among the self-healing agents used for this study, the D3E1 would be one of the most preferable candidates with regard to maximum adhesive strength, reaching time to maximum adhesive strength, stabilized adhesive strength, and reaction heat.

• Journal of Convergence for Information Technology
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• v.9 no.7
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• pp.85-93
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• 2019

The purpose of this study is to identify the influence of demographic characteristics such as inappropriate lifestyle, stress, and health status among health risk factors of early adolescents according to gender. There is a gender difference in the perception of mental and physical health of early adolescents, and the result can be different in behavior patterns between men and women. This study was conducted to identify the health risk factors as independent variables for early adolescents in Daegu and Gyeongbuk area, and to analyze the determinants of gender (male, female) differences by parents, family environment, friends, academic background, appearance, grade, location, school grades, family situation, and health status as demographic factors. And, the Odds Ratio of the early adolescents was analyzed through logit analysis and the differences according to the influence relationship of each of them were examined. As a result of the analysis, the more the sleep and physical activity, parents, home environment, friends, academic background, and appearance are increased, the more the influence is likely to become on the male students. On the contrary, the rest of the health risk factors can increase, and the threat to the health risk factors is likely to become severe to the female students.Among them, it is necessary to develop a pre-preventive program for early adolescents' health risk factors, provide basic data for practical application in the field, and seek a detailed program according to the gender of early adolescents.

• Clean Technology
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• v.25 no.3
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• pp.238-244
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• 2019

In this study, the ignition characteristics of petroleum-based aviation fuel (Jet A-1), bio aviation fuel (Bio-6308), and blended aviation fuel (50:50, v:v) were analyzed in accordance with change of temperature and pressure. The ignition delay time of each aviation fuel was measured by combustion research unit (CRU) and the compositions of the fuels were analyzed by GC/MS and GC/FID for qualitative and quantitative results. From the results, it was confirmed that the ignition delay times of all aviation fuels were shortened with increasing temperature and pressure. In particular, the effect of temperature was larger than the effect of pressure. Also, the ignition delay time of Jet A-1 was the longest at all measurement conditions, and it was judged that this result is because of the structurally stable characteristics of the benzyl radical generated during the oxidation reaction of the aromatic compound (about 22.48%) in Jet A-1. Also, it was confirmed that Jet A-1 had no section where the degree of shortening of ignition delay time was decreased by increasing temperature, which was because the benzyl radical inhibits the response that can affect the negative temperature coefficient (NTC). The ignition characteristics of blended aviation fuel (50:50, v:v) showed a similar tendency to those of Jet A-1, rather than to those of Bio-6308, so that the blended aviation fuel (50:50, v:v) can be applied to the existing system without any change.

• Journal of Navigation and Port Research
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• v.43 no.1
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• pp.33-41
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• 2019

In December 2012, a pile driving boat sunk off the coast of Ulsan port in Korea. The cause of capsizing of these boats was considered a complex problem. Although Korean Ship Safety Technology Authority concluded that leaders (cranes) of the vessel were designed with sufficient safety factors, National Forensic Service concluded that the capsizing was caused by the failure of leaders. This study reviewed the related laws, strength calculations, and structural analysis methods used by the Korea Ship Safety Technology Authority. In addition, numerical simulations were carried out on hydrodynamic analysis and structural analysis to analyze the cause of vessel capsizing based on the rules of the Korean Register of Shipping. The results were similar to those found by National Forensic Service. In conclusion, the study suggested that inspection especially for a pile driving boat subjected to the Korean Register of Shipping rules should be carried out to prevent the similar accident.

• The Journal of Korean Philosophical History
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• no.25
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• pp.315-332
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• 2009

This research shows that Mozi setting forth a military thoughts will be discussed and lighted up in modern value. Mozi's theory on a military was formed in order to protect weak people from the strong in the basis of his philosophy of not attacking. It is different from the art of war for attack. There are some merits in Mozi's strategy of war that we have to take notice of. First of all, Mozi indicated that married women, the old and children was provided with specific roles in the war times. Especially, married women' parts will be equal to men. The old and children should usually be respected for the government to offer them important roles in the war time. Therefore, this paper will be showed in the respect of Mozi's thoughts that is considered as human being's fundamental rights in terms of ensuring the weak's rights. Furthermore, Mozi's theories on technology from loving the civil was applied to defensive fight and his advanced arms was arranged in the actual fight. However, his arms could be useful to the only defensive fight. This case was reflected as Mojia's theories that science is sincerely useful toward the civil. There will be some small or large wars in the future. Mozi's theories based on a military peaceful thoughts that everyone ought to be loved without discrimination should be highly valued when all wars will take place for the purpose of their own profits.