• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.3
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• pp.358-364
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• 2013

Borosilicate glass(GVB-Solutions in glass, 2mm, Germany) was prepared in the composition of $80.4SiO_2-4.2Na_2O-2.4Al_2O_3-13.0B_2O_3$. The 2-step crystallization was performed around $584^{\circ}C$ of glass transition temperature ($T_g$), and $774^{\circ}C$ of crystallization temperature($T_c$). The maximum nucleation rate was $8.8{\time}10^9/mm^3{\cdot}hr$ at $600^{\circ}C$ and the maximum crystal growth rate was 3.5nm/min at $750^{\circ}C$. The maximum mechanical properties were observed at 22.8% of volume fraction, the strength, hardness and fracture toughness was 555MPa, $752kg/mm^2$, $1.082MPa{\cdot}mm^{1/2}$. The crystal size of 177nm which has volume fraction of 22.8% showed maximum strength of 562MPa, it is about 157% higher than parent borosilicate glass. From these results, the crystallized borosilicate glass can be applied weight lighting of bullet proof materials.

• Advances in environmental research
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• v.5 no.4
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• pp.251-262
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• 2016

The biodegradability and decomposition efficiencies increase with the pre-treatment of sludge in a digestion process. In this study, the feasibility of ultrasound coupled with potassium permanganate oxidation as a disintegration method and digestibility of aerobic reactor fed with disintegrated sludge with ultrasound coupled potassium permanganate were investigated. The first stage of the study focused on determining the optimum condition for ultrasonic pre-treatment for achieving better destruction efficiency of sludge. The second part of the study, the aerobic digestibility of sludge disintegrated with ultrasound and potassium permanganate oxidation alone and combined were examined comparatively. The results showed that when 20 min of ultrasonic pre-treatment applied, the specific energy output was 49384 kJ/kgTS with disintegration degree of 58.84%. During the operation of aerobic digester, VS/TS ratios of digesters fed with disintegrated sludge decreased indicating that disintegration methods could obviously enhance aerobic digestion performance. The highest reduction in volatile solids was 75% in the digester fed with ultrasound+potassium permanganate disintegrated sludge at the end of the operation compared to digester fed with raw sludge. Total Nitrogen (TN) and Total Phosphorus (TP) levels in sludge supernatant increased with this combined method significantly. Besides, it promoted the production of ${\bullet}OH$, thus enhancing the release of Carbon (C), Nitrogen (N) and Phosphorus (P) from the sludge. Disintegration with all methods used in this study could not improve Capillary Suction Time (CST) reduction in disintegrated digesters during the operation. The results demonstrated that the combined ultrasound treatment and potassium permanganate oxidation method improves the biodegradability compared to control reactor or their single application.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.142-143
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• 2017

As weapons systems are fused with advanced technologies, many of the expenses for research and development are favorites, and that group demands high reliability of weapons systems before the lifecycle. However, empirical studies on the reliability of defense weapons systems are restricted to lack of attention and limitation of data. In this research, we proposed the process of collecting field operation specifications based on the experience gathered by visiting directly to the weapons system operator's trap, strategy and maintenance support force (COMROKFLT, Naval Logistics Command, Naval Shipyard, production company). We used this to derive the operation MTBF of the solubility inducing bullet shooting system and compared it with the target value at the time of development.

• Journal of Life Science
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• v.24 no.9
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• pp.1012-1018
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• 2014

Sasa quelpaertensis Nakai (Korean name, Jeju-Joritdae) is one of the most abundant plants on Mt. Halla, Jeju Island, and it has long been used in traditional medicines. Recent studies have reported it as possessing various beneficial functions, including anti-inflammatory, anti-diabetic, anti-hypertension, anti-gastritis, anti-oxidant, and anti-cancer effects. However, the molecular mechanisms of its anti-cancer activity have not been clearly elucidated. In this study, we investigated the anti-cancer effects and mechanism of S. quelpaertensis on human colon cancer HT-29 cells. Cell growth inhibition by S. quelpaertensis was determined by MTT assay. Apoptosis was performed by DNA fragmentation, flow cytometry with propidium iodide staining (PI), and reverse transcription-polymerase chain reaction (RT-PCR) to confirm the anti-apoptotic factors, such as inhibitor of apoptosis (IAP) family members. $NO^{\bullet}$ production was determined by Griess assay. S. quelpaertensis treatment resulted in the time- and dose-dependent inhibition of the cell viability of HT-29 cells by inducing apoptosis, as evidenced by the accumulation of the sub-G1 cell population stained by PI, as well as the ladder-like DNA fragmentation in a dose-dependent manner. S. quelpaertensis-inducing apoptosis was accompanied by the induction of S cell cycle arrests, increasing $NO^{\bullet}$ concentrations, and the down-regulation of IAPs, including X-chromosome-linked IAP (XIAP), cellular IAP-1 (cIAP-1), cIAP-2, and survivin. Taken together, these findings have important implications for future clinical developments of S. quelpaertensis in colon cancer treatment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.12
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• pp.936-941
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• 2010

In this study, we have investigated the effects of Mn dopant on the bulk trap levels and grain boundary characteristics of $Bi_2O_3$-based ZnO (ZB) varistor using admittance spectroscopy and dielectric functions (such as $Z^*,\;Y^*,\;M^*,\;\varepsilon^*$, and $tan\delta$). Admittance spectra and dielectric functions show two bulk traps of $Zn_i^{..}$ (0.20 eV) and $V^{\bullet}_o$ (0.29~0.33 eV) in ZnO-$Bi_2O_3-Mn_3O_4$ (ZBM). The barrier of grain boundaries in ZBM could be electrochemically single type. However, its thermal stability was slightly disturbed by ambient oxygen because the apparent activation energy of grain boundaries was changed from 0.79 eV at lower temperature to 1.08 eV at higher temperature. The grain boundary capacitance $C_{gb}$ was decreased slightly with temperature as 1.3~1.8 nF but resistance $R_{gb}$ decreased exponentially. The relaxation time distribution can result from the heterogeneity of the barriers constituting the varistor. It is revealed that Mn dopant in ZB reduced the heterogeneity of the barrier in grain boundaries and stabilized the barrier against the ambient temperature.

• Journal of the Korean Professional Engineers Association
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• v.17 no.3
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• pp.6-21
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• 1984

A rock slide in amount of 100 tons in weight happened at 7: 10 a.m., 4th October 1982, on the southwestern ridge of Mt. Seunghag, Busan City. The original rock mass of the rock slide is located 850m west from the Dangri Crushed Stone Quarry. The geology of the area consists of agglomerate, andesite, andesitic tuff, and shale hornfels of the Cretaceous Yucheon Group. The rock blocks were first shifted along the steep joint plane on an andesite outcrop at the site and then to the eastern foot of the mountain slope where some private houses are placed. The mountain slope is covered with thick superficial soil. A slided monolithic-block with 83 tons in weight from the rock slide met with an accident of striking against a house with a tremendous force, to which much damage was done as much as its half was destroyed. The rock-slided block pierced the board-floored room only posited at the center and by the bedroom of the house making a pass like a bullet hole, and hence cut a big pine tree with 24 centimeters in diameter at a distance of 26 meters down the house. However nobody was killed or injured in the stricken house, though seven family members were stayed therein at the very time of accident. They really met a rare opportunity in an unhappy disaster. Measurements of the rock slide were made in the course of the field survey. The monolithic mass was transported by way of saltation, rolling, and sliding to a distance of 300 meters down along the slope dipping 30$^{\circ}$ east. It took about 16 seconds front tile outcrop to the terminal. The acceleration value of the monolithic rock slide is 2.35m/sec$^2$.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.4
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• pp.447-455
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• 2018

If a hidden enemy is shooting, there is a threat against soldiers in recent conflicts. This paper aims to improve the localization of a muzzle using microphone array. Gunshot noise can provide information about the location of muzzle with two signals, the muzzle blast from the gun barrel and the projectile sound from the bullet. Two signals arrive to the microphone array with different arrival time and angle. If the arrival angles of the two signals are estimated, distance between sniper location and the microphone array can be calculated by using geometric principles. This method was established in 2003 by Pare. But this method has a limitation that it cannot calculate the distance when the arrival angles of the two signals are same. Also it has an error when the angle difference of arrival is small. In order to overcome this limitation, a new method is proposed that uses the change of characteristic of the projectile sound with respect to vertical distance from the trajectory. The proposed method estimates the distance correctly when the arrival angle of two signals are same, and when the angle difference between two signals is increased, the estimation error increases with respect to the angle. Therefore these two methods can be selected according to the angle difference between two signals to estimate the distance of the muzzle. Below the threshold of the angle difference, the proposed method can be used to estimate distance with smaller error than the existing method. This was demonstrated by shooting tests using actual sniper rifles.

• Korean journal of applied entomology
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• v.56 no.2
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• pp.195-201
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• 2017

The entomopathogenic fungus Zoophthora radicans (Entomophthorales: Entomophthoraceae) was found to infect Cnaphalocrocis medinalis, Plutella xylostella, Myzus persicae and one unidentifed species. Samples of the fungus were collected from three areas (Jinan, Gimje, and Iksan) in Jeollabuk-do, Korea. Infected insects appeared in July and September, during which time population infection rate of Z. radicans on C. medinalis reached up to 46%. Zoophthora radicans hyphal bodies are rod-like to hyphoid, and primary conidia are bullet-shaped to long ovoid. The fungus was isolated from the surfaces of larvae and cultured in Sabouraud dextrose agar with yeast extract (SDAY). The optimal temperature range for mycelial growth was $20{\sim}28^{\circ}C$. Mycelium growth on SDAY supplemented with egg yolk and milk (SDAY-EM) was higher than on SDAY alone. Zoophthora radicans may play an important role in controlling insect population density using naturally induced epizootics.

• The Journal of the Korea Contents Association
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• v.20 no.11
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• pp.368-377
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• 2020

In this paper, the transmission and the phases of the memories in the novels dealing with Vietnam War have been studied. As a research method, Aleida Assmann's memory theory which plays a role in culturoloy theory is utilized. This study shows firstly that the others' voices excluded from the official memories of Vietnam War have emerged. Vietnam War novels released after 1990s actively reflecting the others' voices transmitted fresh the cultural memories. As the stories of civilian massacre, defoliant victims, and children of mixed bloods, Lai Daihan excluded from the official memories have emerged as a main them in the Vietnam War novels, they have become resistant memories. Existence and Formality, a Vietnam War novel by Bang Hyeonsuk brings up how to remember Vietnam War. His another novel, Time to Eat Lobster shows that without the fundamental retrospect and introspection of Vietnam War, Korea can't help but have the identity of America. Secondly, this paper shows that the tragedy of Vietnam War remains as a trauma that human bodies remember. White War by Ahn Jeonghyo shows that the memory moves back to the past in the process of struggle. In the novel, Slow Bullet by Lee Daehwan the phases of demage from defoliants lead to the family's tragedy. The Red Ao Dai by O Hyeonmi shows how a Korean-Vietnamese overcomes negation of his father and win his identity. In A Sad Song in Saigon shows that a mixed blood, Sairang who suffered from the confusion of his identity and his story fell down to a romance novel because of the weakness of narrative.

• The Journal of the Korea Contents Association
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• v.16 no.5
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• pp.698-709
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• 2016

Free Learning Semester, the new education policy of middle schools in Korea, will be completely implemented in 2016. The purpose of this study was to explore the school experiences of middle-school students in the Free Learning Semester through qualitative approach. In-depth interview was conducted with 8 middle-school students from the purposive sampling. As a result of the analysis, 10 essential themes were identified. Themes were as follows: 'Struggling from the performance evaluation with biting the bullet', 'Great pressure on final examination that is only once a year', 'Inconvenience of career education experience', 'Higher level of friendship', 'Double face of discrimination and respect', 'Chance to adaptation between elementary and middle-school', 'Regret about fleeting time without thought', 'Ambivalence of freedom and suppression', 'Warm place with peer', 'Being pushed rehearsal wearing other's cloth'. In conclusion, the nature of lived experience of middle-school students in the Free Learning Semester is based on ambivalence of various aspects, but is predominant in 'higher level of friendship'. It suggested that the Free Learning Semester can be a positive alternative to existing education system that made students to compete each other. It is expected to be able to discuss the future policy direction using the result of this study which explored the nature of lived experience related to the Free Learning Semester.