• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.10
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• pp.862-871
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• 2012

The numerical simulations on 500-N class rocket engine using 96% hydrogen peroxide and kerosene have been conducted, considering atomization, evaporation, mixing and combustion of its propellants. The grid containing 1/6 part of combustion chamber has been generated and it is assumed that 3 kinds of liquid-phase propellants (kerosene, hydrogen peroxide and water) were injected as hollow cone spray pattern, using Rosin-Rammler function for distribution of droplet diameter. For the calculation of combustion the eddy-dissipation model was applied. Owing to small size of combustion chamber and large specific heat / latent heat of hydrogen peroxide and water the propulsion characteristics were highly influenced by the size of droplet particles, and in this analysis the engine with droplet particles of 30 micron in average has shown the best propulsion performance.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.1
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• pp.1-12
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• 1995

Isothermal and thermal-mechanical fatigue characteristics of 12Cr heat resisting steel used for high temperature applications were investigated including hold time effects. Isothermal low cycle fatigue test at $600^{\circ}C$ and in-phase, out-of-phase thermal-mechanical fatigue test at 350 to $600^{\circ}C$ were conducted using smooth cylindrical hollow specimen under strain-control with total strain ranges from 0.006 to 0.015. Regardless of thermal-mechanical and isothermal fatigue tests, cyclic softening behavior was observed and much more pronounced in the thermal-mechanical fatigue tests with hold times due to the stress relaxation during the hold time. The phase difference between temperature and strain in thermal-mechanical fatigue tests resulted in significantly shorter fatigue life for out-of-phase compared to in-phase. The differences in fatigue lives were dependent upon the magnitudes of plastic strain ranges and mean stresses. During the hold time in the strain-controlled fatigue tests, the increase in the plastic strain range and the stress relaxation were observed. It appeared that the increase in plastic strain range per cycle and the introduction of creep damage made important contributions to the reduction of thermal-mechanical fatigue life with hold time, and the life reduction tendency was more remarkable in the in-phase than in the out-of-phase thermal-mechanical fatigue. Isothermal fatigue tests performed under the combination of fast and slow strain rates at $600^{\circ}C$ showed that the fatigue life decreased as the strain rate and frequency decreased,especially for the low strain ranges.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.1 s.244
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• pp.84-89
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• 2006

A wireless capsule endoscope has been developed to replace the conventional endoscope. However, the commercialized capsule endoscope moves passively by peristaltic waves, which has some limitations for doctors to diagnose more thoroughly and actively. In order to solve this problem, a locomotive mechanism is proposed for wireless capsule endoscopes. Based on the tests of various actuators, a piezo actuator is selected as a micro actuator for capsule endoscope. In general, piezo actuators are known to have limited displacement with high voltage supply. In order to overcome the limitation of common piezo actuator, the impact based piezo actuator, is developed to realize long stroke up 11mm. By using the impact based piezo actuator, a prototype of an earthworm-like locomotive mechanism was developed. In addition, the proposed locomotive mechanism has engraved clamps mimicked the claw of an insect. The earthworm-like locomotive mechanism has 15 mm in diameter and 30mm under retraction stage and 41 mm under elongation stage in total length. Hollow space is allocated to comprise essential endoscope components such as a camera, a communication module, bio sensors, and a battery. For the feasibility test of proposed locomotive mechanism, a series of experiments were carried out including in-vitro tests. Based on results of the experiments, we conclude that the proposed locomotive mechanism is effective to be used for micro capsule endoscopes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.10a
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• pp.190-190
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• 2003

동력 전달용 구동부품에 있어서 중공 플랜지 형상의 부품은 흔히 찾아 볼 수 있으며, 이는 높은 강도를 요구하기 때문에 강도향상을 위하여 단조에 의한 제품의 성형 방법이 많이 연구되고 있다. 중공 플랜지형상을 갖는 제품의 제조 방법으로서는 중실 플랜지 형상으로 단조하여 내경부를 절삭가공하는 방법, 중실 소재를 후방압출하여 중공 플랜지형상으로 단조하는 방법, 또는 중공의 초기소재를 사용하여 중공 플랜지형상으로 단조하는 방법이 일반적이다. 본 연구에서는 Fig. 1에 나타낸 것과 같이 중공 플랜지 형상을 갖는 기계 부품의 단조방법에 대해 연구하였으며, 중공 관의 내경을 $d^1$, 외경을 $d^2$, 플랜지부의 외경을 $D^0$, 중공 관의 두께를 t, 플랜지부의 두께를 T로 정의하였다. 중공 플랜지 형상에 있어서 공정 설계의 변수는 다양하겠으나, 본 연구에서는 중공관의 외경과 내경의 형상비 $\alpha$(=$d^2$/$d^1$), 플랜지의 폭과 중공관의 두께비 $\beta$(=B/t) 및 중공관의 두께와 플랜지의 두께비 r(=T/t)의 변화에 따른 성형조건에 관해 고찰하였다. 중공 플랜지 형상의 성형방법으로 Fig. 2에 나타낸 것과 같은 $\circled1$중실소재를 이용한 후방압출단조(backward extrusion forging)방법, $\circled2$중공 소재를 이용한 엎셋(upset forging)방법, $\circled3$중공 소재를 이용한 압조법(injection forging), $\circled4$중실소재를 이용한 압조-압출(injection-extruding forging)법의 4가지의 단조 방법을 제시 하였다. 또한, 유한요소해석을 수행하여 소성유동 형태, 유효변형률, 단조하중을 검토하고. 모델재료인 납을 이용한 실험을 통하여 이를 검증하였다. 이를 바탕으로 산업 현장에서 경험에 의존하였던 공정 설계를 보다 효과적으로 개선하기 위한 단조법을 제시하고자 하였다. 또한 중실 소재를 이용한 중공 플랜지 형상의 단조 방법 중 보다 적절한 단조방법인 압조 단조에 있어서 일반적으로 사용되고 있는 SM10C에 대한 유한요소 해석을 수행하였으며, 제품의 형상비에 따라 폴딩 결함의 발생 유무를 검토하고, 폴딩 결함 없이 단조하기 위한 중공 플랜지의 형상한계 비를 제시하였다.

• Journal of Trauma and Injury
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• v.33 no.1
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• pp.38-42
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• 2020

Purpose: Immediate post-laparotomy hypotension (PLH) is a precipitous drop in blood pressure caused by a sudden release of abdominal tamponade after laparotomy in cases of severe hemoperitoneum. The effect of laparotomy on blood pressure in patients with significant hemoperitoneum is unknown. Methods: In total, 163 patients underwent laparotomy for trauma from January 1, 2013 to December 31, 2015. Exclusion criteria included the following: negative laparotomy, only a hollow viscous injury, and hemoperitoneum <1,000 mL. After applying those criteria, 62 patients were enrolled in this retrospective review. PLH was defined as a decrease in the mean arterial pressure (MAP) ≥10 mmHg within 10 minutes after laparotomy. Results: The mean estimated hemoperitoneum was 3,516 mL. The incidence of PLH was 23% (14 of 62 patients). The MAP did not show significant differences before and after laparotomy (5 minutes post-laparotomy, 67.5±16.5 vs. 68.3±18.8 mmHg; p=0.7; 10 minutes post-laparotomy, 67.5±16.5 vs. 70.4±18.8 mmHg; p=0.193). The overall in-hospital mortality was 24% (15 of 62 patients). Mortality was not significantly higher in the PLH group (two of 14 [14.3%] vs. 13 of 48 [27.1%]; p=0.33). No statistically significant between-group differences were observed in the intensive care unit and hospital stay. Conclusions: PLH may be less frequent and less devastating than it is often considered. Surgical hemostasis during laparotomy is important. Laparotomy with adequate resuscitation may explain the equivalent outcomes in the two groups.

• Conservation Science in Museum
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• v.9
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• pp.31-49
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• 2008

We have investigated and conserved three small Buddha statues dating from Joseon period that were purchased by the National Museum of Korea. Chemical analysis and investigation of internal structures were enabled us to identify its compositions and hollow spaces which have various materials just like fabrics, silver ornaments, beads and wood fragments. The fabrics date from the early years of the Joseon dynasty to the middle one. The compositions of matrix of the Buddha statues vary 80-90 wt% Ag and 7-15 wt% Cu. And its surface layers were gilt with amalgam. Mechanical and chemical cleaning with EDTA-2Na were applied together during the cleaning process.

• ALGAE
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• v.25 no.4
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• pp.187-195
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• 2010

The genus Rosenvingea is well known in the tropics. Four species have been reported from Pacific Mexico: R. floridana, R. antillarum, R. intricata and R. sanctae-crucis. We collected a plant (Boca del Cielo, Chiapas) that we identified as Rosenvingea orientalis, a species not previously reported from Pacific Mexico. We were able to characterize the life cycle of this species for the first time in laboratory culture. It reproduced exclusively by plurilocular sporangia (plurangia). The mature plants were up to 6 cm long with cylindrical to compressed fronds (to 2 mm wide) with dichotomous branches in the upper half of the thallus. The medulla was hollow with 2-3 layers of large inflated colourless cells at the periphery. The cortex was comprised of 1 layer of small cells, each with a single chloroplast and pyrenoid. Linear plurangial sori with phaeophycean hairs formed along the mature fronds. Zoospore germlings developed into prostrate filamentous systems, each with a single phaeophycean hair that gave rise to a single erect shoot with multiple hairs arising near the tip. Molecular phylogeny using the psaA gene placed this isolate within the Scytosiphonaceae. It does not confirm the exact identification of R. orientalis, although its placement close to other Rosenvingea sequences was confirmed and morphological evidence supports its placement in R. orientalis. Our culture investigations indicated that it has an asexual life cycle. Further collections are needed to resolve the full generic and specific relationships of Rosenvingea and related taxa, and their reproductive patterns.

• The Korean Journal of Mycology
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• v.16 no.4
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• pp.230-234
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• 1988

Ganoderma lucidum, a divine mushroom, beared the nonbasidiocarpus basidiospore without the normal basidiocarp. The fungus formed the basidial stroma from the aerial mycelium on agar media, and the basidium was developed from apical cells of the mycelium on the surface of the basidial stroma. One to four basidiospores were observed on a basidium. The nonbasidiocarpous basidiospores formed on the basidial stroma were similar to the normal basidiospores in morphology, although the nonbasidiocarpus basidiospores were slightly smaller in size. However, the number of hollow on the spore surface was remarkably smaller than that of the normal spore. The formation of nonbasidiocarpous basidiosproes was influenced by the genetic factor and the environmental factors such as light, temperature and ventilation.

• Journal of Pharmaceutical Investigation
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• v.18 no.2
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• pp.61-67
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• 1988

The influence of different suppository bases on the dissolution, and the bioavailability of aspirin suppositories in rabbits and humans was investigated using Witepsol H15 (WIT), WIT-Tween 80 (TWE), WIT-sodium lauryl sulfate (SLS), polyethylene glycol (PEG), hollow WIT (WIT-HOLL) and capsule incorporated into WIT (WIT-CAP). The results obtained were as follows: 1) Dissolution rates of aspirin suppositories with different bases in distilled water were faster in the order of WIT-TWE >WIT-SLS >PEG >WIT-HOLL >WIT >WIT-CAP. 2) The maximum blood levels $(C_{max})$ of aspirin in rabbits and humans were highest in WIT-TWE and WIT-SLS bases, but $C_{max}$ from WIT base was lower than that in oral administration of aspirin suspension. 3) The times reaching the maximum blood levels $(T_{max})$ in rabbits were 1 hr for oral administration, 1.5-2.5 hr for WIT-TWE, WIT-SLS, PEG, and WIT bases, and 2.5-4.0 hr for WIT-HOLL and WIT-CAP bases, but $T_{max}$ in humans were 1 hr for oral administration and WIT-TWE base, and 2-4 hr for WIT and WIT-HOLL bases. 4) Relative bioavailability (RBA) of aspirin suppositories in rabbits was higher in WIT-SLS, WIT-TWE and PEG bases than that in oral administration, and RBA of aspirin suppositories in humans was higher in the order of WIT-TWE >PEG >WIT-HOLL >oral >WIT bases tested. 5) Good correlation between dissolution rates and $C_{max}$ was obtained: y = 0.60x+32.23 (r = 0.96) for rabbits, and y = 0.60x+35.74 (r = 0.97) for humans.

• Korean journal of food and cookery science
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• v.10 no.4
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• pp.405-411
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• 1994

This study was conducted to know the quality of chou made with flour pastes which were stored at different conditions of quick freezing, slow freezing, cold and room temperature. Also, this study included investigation of the chou properties such as expansion, sensory evaluation, degree of gelatinization, and physical and structural properties of paste were observed. There were not significant differences m diameter, height, volume, appearance, hollow formation, and sensory evaluation between the chou made with the paste stored at freezing condition and chou directly baked after pasting. Quick and slow freezing storages did not significantly affect the properties of chou, and the same results were obtained among the chou made with pastes thawed at room temperature and in microwave ovenrange. The chou of pastes stored at room temperature and in microwave ovenrange. The chou of pastes stored at room temperature and stored in refrigerator showed lowed expansion and value of sensory evaluation than those of frozen pastes. The paste stored at room temperature had the lowest hardness and viscosity compared with the other storage conditions. According to the observation of light microscope. the lipid bodies of the paste of freezing storage smaller those of the room temperature and refrigerator storage. The expantion of chou made with paste stored at room temperature was greatly decreased due to the high coalescence of lipid bodies, and also the paste components such as lipid, starch granule gluten at room temperature had inferior dispersion condition. The general tendency of the degree of gelatinization of chou were low in all treatments of paste. The values were 23.5%~46.0% in freezing, 77.3% in room temperature, 68.7% in directly baked after pasting, and 61.0% in cold storage, respectively. The formation and the taste of chou made with frozen paste were similar to those of chou directly baked pasting.