• Journal of Korean Neurosurgical Society
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• v.29 no.5
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• pp.644-649
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• 2000

Objective : Acute hydrocephalus can be caused by many pathologic conditions such as sub- arachnoid hemorrhage, intraventricular hemorrhage, inflammatory diseases. External ventricular drainage(EVD) through trephination of the skull is essential procedure for progressing or persistent symptomatic acute hydrocephalus. If the EVD can not be removed in short period, the chance of ventriculitis increases and periodic transposition of the draining catheter should be considered. Shunt procedure can not be performed in acute hemorrhage or infectious condition because of the risk of shunt malfunction or intra-abdominal spreading of the infection, respectively. The authors replaced EVD with continuous lumbar drainage(CLD) for the purpose of controlling acute hydrocephalus and preventing ventriculitis simultaneously, or treating ventriculitis more effectively in case of infection which had already broken out. CLD has many advantages over EVD, although, it can complicate disastrous downward brain herniation in patients with elevated intracranial pressure. The authors performed CLD with EVD maintained and then tested the possibility of the brain herniation with quite simple method. If the CLD was proven as safe through the test, EVD could be replaced with it without terrible herniation. Material and Method : Between September 1998 and April 1999, 10 patients underwent CLD in replacement of EVD. Among them, 5 were patients with aneurysmal subarachnoid hemorrhage, 2 were patients with thalamic hematoma and intraventricular hemorhage and 3 were patients with traumatic intracranial hemorrhage. Results : In eight of them the replacements were successfully done and one of them died on account of medical illness. In two of them the replacement could not be performed because of the risk of herniation and all expired owing to ventriculitis. Two patients required permanent shunt operation. Conclusion : This article provides a valuable alternative method of treatment for persistent symptomatic hydrocephalus which can not be managed with shunt operation immediately.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.143-154
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• 2016

This study investigated the occurrences, causes, and mitigation of the recent ground subsidence and underground cavity generation events in Korea. Two main causes of ground subsidence are (1) the soil erosion by seepage during tunneling and earth excavation and (2) the damage of underground pipes. The main cause of the soil erosion during tunneling was the uncontrolled groundwater flow. Especially, when excavating soft grounds using a tunnel boring machine (TBM), the ground near TBM operation halt points were found to be the most vulnerable to failure. The damage of underground pipes was mainly caused by poor construction, material deterioration, and differential settlement in soft soils. The ground subsidence during tunneling and earth excavation can be managed by monitoring the outflow of groundwater and eroded soils in construction sites. It is expected that the ground subsidence by the underground pipe damage can be managed or mitigated by life cycle analysis and maintenance of the buried pipes, and by controlling the earth pressure distribution or increasing the bearing capacity at the upper ground of the buried pipes.

• Journal of the Korean Professional Engineers Association
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• v.34 no.2
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• pp.167-173
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• 2001

Through alkaline hydrothermal activation processes, Na-A type zeolite was synthesized as a single phase withfunnel-glass waste from a television tube factory. The autoclaving was performed in a closed teflon vessel in therange of 80~95"C. The silica-rich solution as a starting material was hydrothermally synthesized with quartz in INNaOH by heating 350"C under the pressure of 1,500 atm. NaA102 was made from NaOH and Al(OH)3 by heating95"c for 2~3 hours and the molar ratios of it were Na20/A1203=1.4 and H20Ha20=8. The equi-dimensional Atype zeolite (1 ~2 U) was formed by the simple mixing of'the silica-rich solution, glass waste and NaA102 for I~3hours-heating at 80"C. The characterization of the reaction product shows Na-A as a single phase. The synthesizedzeolite has cube-dodecahedral form and Ca2+ ion exchange capacity of the Na-A was in the range of 215~220mequivalent/100 g.20mequivalent/100 g.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.107-114
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• 2017

A turbocharger is an engine supercharger that is driven by exhaust gas. It improves the output and fuel efficiency by increasing the charging efficiency of the mixture gas, which is achieved by changing the rotatory power of the turbine connected to the exhaust passage. It is important to control the supercharging for this purpose. A nozzle slide joint is one of the core parts. Austenitic stainless steel is currently used as the material for this part, and its excellent mechanical properties include high heat resistance and corrosion resistance. However, because of its poor machinability, there are many difficulties in producing products with complicated shapes. Machining is used in the production of nozzle slide joints for high dimensional accuracy after metal powder injection molding. As design variables in this study, we investigated the sintering temperature, product stress, deformation rate, radius of curvature of the punch, and angle of the chamfer punch, which are related to the strain and shapes. The goal is to suggest a forming process using Nitronic 60 that does not require machining to manufacture a nozzle slide joint for a turbocharger. Accordingly, we determined the best process environment using finite-element analysis, the signal-noise ratio, and the Taguchi method for experiment design. The relative density and hydrostatic pressure of the final product were in accordance with the results of the finite element analysis. Therefore, we conclude that the Taguchi method can be applied to the design process of metal powder injection molding.

• Journal of Korean Society of Environmental Engineers
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• v.38 no.3
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• pp.144-149
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• 2016

The metal-impregnated activated carbon was produced from bamboo activated carbon by soaking method of metal nitrate solution. The carbonization and activation of raw material was conducted at $900^{\circ}C$. The specific surface area and pore size distribution of the prepared activated carbons were measured. Also, NO and activated carbon reaction were conducted in a thermogravimetric analyzer in order to use as de-NOx agents of used activated carbon. Carbon-NO reactions were carried out with respect to reaction temperature ($20^{\circ}C{\sim}850^{\circ}C$) and NO gas partial pressure (0.1 kPa~1.8 kPa). As results, the specific volume and surface area of bamboo activated carbon impregnated with copper were decreased with increasing Cu amounts of activated carbon. In NO reaction, the reaction rate of Cu impregnated bamboo activated carbon[BA(Cu)] was promoted to compare with that of bamboo activated carbon[BA]. But the reaction rate of Ag impregnated bamboo activated carbon[BA(Ag)] was retarded. Measured reaction orders of NO concentration and activation energy were 0.63[BA], 0.92[BA(Cu)], and 80.5 kJ/mol[BA], 48.5 kJ/mol[BA(Cu)], 66.4 kJ/mol[BA(Ag)], respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.3
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• pp.578-584
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• 2017

$SiO_2$ buffer layer (100 nm) has been deposited on PET substrate by electron beam evaporation. And then, IZTO (In-Zn-Sn-O) thin film has been deposited on $SiO_2$/PET substrate with different RF power of 30 to 60 W, working pressure, 1 to 7 mTorr, by RF magnetron sputtering. Structural, electrical and optical properties of IZTO thin film have been analyzed with various RF powers and working pressures. IZTO thin film deposited on the process condition of 50 W and 3 mTorr exhibited the best characteristics, where figure of merit was $4.53{\times}10^{-3}{\Omega}^{-1}$, resistivity, $4.42{\times}10^{-4}{\Omega}-cm$, sheet resistance, $27.63{\Omega}/sq.$, average transmittance (400-800 nm), 81.24%. As a result of AFM, all the IZTO thin film has no defects such as pinhole and crack, and RMS surface roughness was 1.147 nm. Due to these characteristics, IZTO thin film deposited on $SiO_2$/PET structure was found to be a very compatible material that can be applied to the next generation flexible display device.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.522-529
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• 2014

Circulating fluidized bed system consists of SEWGS reactor - lower loop seal - regeneration reactor - riser - cyclone - upper loop seal has been used for solid circulation between the SEWGS reactor and the regeneration reactor in a SEWGS system for pre-combustion $CO_2$ capture. A vertical type lower loop seal has been used in current system but this lower loop seal requires high gas flow rate through the lower loop seal for fluidization and smooth solid circulation, and consequently, causes slugging behavior sometimes. To overcome these disadvantages, inclined type lower loop seal was proposed by this study. Solid circulation characteristics with change of lower loop seal geometry were measured and compared in a bubbling - bubbling - riser type circulating fluidized bed using $CO_2$ absorbent (P-78) as bed material at ambient temperature and pressure. We could conclude that the inclined lower loop seal is better than the vertical type lower loop seal from the viewpoints of minimum flow rate requirement for stable solid circulation and solid height change during solid circulation.

• Resources Recycling
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• v.18 no.5
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• pp.19-25
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• 2009

Molybdenite concentrate ($MoS_2$) is the major mineral for the molybdenum industry, of which the industrial processing is first converted to technical grade molybdenum trioxide ($MoO_3$) by its oxidative roasting and purification, used as a raw material for manufacturing several molybdenum compounds. In the present work, detailed experimental results for the oxidative roasting of low grade Mongolian molybdenite concentrate are presented. The experiments were carried out in the temperature range of 793 to 823 K under an oxygen partial pressure range of 0.08 atm to 0.21 atm by using a thermogravimetric analysis technique. The molybdenite concentrate was an average particle size of $67\;{\mu}m$. In the oxidative roasting of low grade Mongolian molybdenite concentrate, more than 95% of molybdenite was converted to molybdenum trioxide in 60 min. at 828 K. The lander equation was found to be useful in describing the rates of the oxidative roasting and the reaction order with respect to oxygen concentration in a gaseous mixture with nitrogen was 0.11 order.

• Korean Journal of Materials Research
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• v.30 no.4
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• pp.176-183
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• 2020

The high-temperature stability of YSZ specimens fabricated by die pressure and cold isostatic press (CIP) is investigated in CaCl₂-CaF₂-CaO molten salt at 1,150 ℃. The experimental results are as follows: green density 46.7 % and 50.9 %; sintering density 93.3 % and 99.3 % for die press and CIP, respectively. YSZ foremd by CIP exhibits higher stability than YSZ formed by die press due to denseness dependency after high-temperature stability test. YSZ shows peaks mainly attributed to CaZrO₃, with a small t-ZrO₂ peak, unlike the high-intensity tetragonal-ZrO₂ (t-ZrO₂) peak observed for the asreceived specimen. The t-ZrO₂ phase of YSZ is likely stabilized by Y₂O₃, and the leaching of Y₂O₃ results in phase transformation from t-ZrO₂ to m-ZrO₂. CaZrO₃ likely forms from the reaction between CaO and m-ZrO₂. As the exposure time increases, more CaZrO₃ is observed in the internal region of YSZ, which could be attributed to the inward diffusion of molten salt and outward diffusion of the stabilizer (Y₂O₃) through the pores. This results in greater susceptibility to phase transformation and CaZrO₃ formation. To use SOM anodes for the electroreduction of various metals, YSZ stability must be improved by adjusting the high-density in the forming process.

• Journal of Chest Surgery
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• v.32 no.2
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• pp.138-143
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• 1999

Background: The endothelium-dependent vasorelaxation has been largely accounted for by the release of nitric oxide (NO). Three distinct isoforms of NO synthases (NOS) have been characterized, i.e., brain(bNOS), inducible (iNOS), and endothelial constitutive (ecNOS). Although hypertension hasbeen associated with a vascular endothelial dysfunction, changes in the vascular expression of NOS isoforms have not been established. The present study was aimed at exploring the vascular expression of NOS isozymes in hypertension. Material and Method: Two-kidney, one clip (2K1C) and deoxycorticosterone acetate (DOCA)-salt hypertension were induced in rats. The expression of different NOS isozymes in the thoracic aorta was determined by Western blot analysis. The vascular tissue contents of nitrites were measured by colorimetric assay. Result: Arterial blood pressure was significantly higher in experimental groups of 2K1C and DOCA-salt rats compared with their corresponding control rats. The vascular expression of bNOS as well as that of ecNOS was decreased in both models of hypertension. iNOS was not changed in DOCA-salt hypertension, but was also decreased in 2K1C hypertension. The vascular contents of nitrites were significantly decreased in DOCA-salt as well as in 2K1C hypertension. Conclusion: These results suggest that 2K1C and DOCA-salt hypertension are associated with decreases in the vascular expression of NOS isozymes and nitrite contents.