• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.264-264
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• 2010

Single-walled carbon nanotubes (SWCNTs) were grown on a Si wafer by using thermal chemical vapor deposition (t-CVD). We investigated the effect of the catalyst deposition rate on the types of CNTs grown on the substrate. In general, smaller islands of catalyst occur by agglomeration of a catalyst layer upon annealing as the catalyst layer becomes thinner, which results in the growth of CNTs with smaller diameters. For the same thickness of catalyst, a slower deposition rate will cause a more uniformly thin catalyst layer, which will be agglomerated during annealing, producing smaller catalyst islands. Thus, we can expect that the smaller-diameter CNTs will grow on the catalyst deposited with a lower rate even for the same thickness of catalyst. The 0.5-nm-thick Fe served as a catalyst, underneath which Al was coated as a catalyst support as well as a diffusion barrier on the Si substrate. The catalyst layers were. coated by using thermal evaporation. The deposition rates of the Al and Fe layers varied to be 90, 180 sec/nm and 70, 140 sec/nm, respectively. We prepared the four different combinations of the deposition rates of the AI and Fe layers. CNTs were synthesized for 10 min by flowing 60 sccm of Ar and 60 sccm of $H_2$ as a carrier gas and 20 sccm of $C_2H_2$ as a feedstock at 95 torr and $810^{\circ}C$. The substrates were subject to annealing for 20 sec for every case to form small catalyst islands prior to CNT growth. As-grown CNTs were characterized by using field emission scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, UV-Vis NIR spectroscopy, and atomic force microscopy. The fast deposition of both the Al and Fe layers gave rise to the growth of thin multiwalled CNTs with the height of ${\sim}680\;{\mu}m$ for 10 min while the slow deposition caused the growth of ${\sim}800\;{\mu}m$ high SWCNTs. Several radial breathing mode (RBM) peaks in the Raman spectra were observed at the Raman shifts of $113.3{\sim}281.3\;cm^{-1}$, implying the presence of SWCNTs (or double-walled CNTs) with the tube diameters 2.07~0.83 nm. The Raman spectra of the as-grown SWCNTs showed very low G/D peak intensity ratios, indicating their low defect concentrations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.363-363
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• 2008

The development of dry etching process for sapphire wafer with plasma has been key issues for the opto-electric devices. The challenges are increasing control and obtaining low plasma induced-damage because an unwanted scattering of radiation is caused by the spatial disorder of pattern and variation of surface roughness. The plasma-induced damages during plasma etching process can be classified as impurity contamination of residual etch products or bonding disruption in lattice due to charged particle bombardment. Therefor, fine pattern technology with low damaged etching process and high etch rate are urgently needed. Until now, there are a lot of reports on the etching of sapphire wafer with using $Cl_2$/Ar, $BCl_3$/Ar, HBr/Ar and so on [1]. However, the etch behavior of sapphire wafer have investigated with variation of only one parameter while other parameters are fixed. In this study, we investigated the effect of pressure and other parameters on the etch rate and the selectivity. We selected $BCl_3$ as an etch ant because $BCl_3$ plasmas are widely used in etching process of oxide materials. In plasma, the $BCl_3$ molecule can be dissociated into B radical, $B^+$ ion, Cl radical and $Cl^+$ ion. However, the $BCl_3$ molecule can be dissociated into B radical or $B^+$ ion easier than Cl radical or $Cl^+$ ion. First, we evaluated the etch behaviors of sapphire wafer in $BCl_3$/additive gases (Ar, $N_2,Cl_2$) gases. The behavior of etch rate of sapphire substrate was monitored as a function of additive gas ratio to $BCl_3$ based plasma, total flow rate, r.f. power, d.c. bias under different pressures of 5 mTorr, 10 mTorr, 20 mTorr and 30 mTorr. The etch rates of sapphire wafer, $SiO_2$ and PR were measured with using alpha step surface profiler. In order to understand the changes of radicals, volume density of Cl, B radical and BCl molecule were investigated with optical emission spectroscopy (OES). The chemical states of $Al_2O_3$ thin films were studied with energy dispersive X-ray (EDX) and depth profile anlysis of auger electron spectroscopy (AES). The enhancement of sapphire substrate can be explained by the reactive ion etching mechanism with the competition of the formation of volatile $AlCl_3$, $Al_2Cl_6$ or $BOCl_3$ and the sputter effect by energetic ions.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.778-784
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• 2003

The carbonation of concrete is one of the major factors that cause durability problems in concrete structures. The rate of carbonation depends largely upon the diffusivity of carbon dioxide in concrete. The purpose of this study is to identify the diffusion coefficients of carbon dioxide for various concrete mixtures. To this end, several series of tests have been planned and conducted. The test results indicate that the diffusion of carbon dioxide reached the steady-state within about five hours after exposure. The diffusion coefficient increases with the increase of water-cement ratio and decreases with the increase of relative humidity at the same water-cement ratio. The content of aggregates also influences the diffusivity of carbon dioxide in concrete. It was found that the diffusion coefficient of cement paste is larger than that of concrete or mortar. The experimental study of carbon dioxide diffusivity in this study will allow more realistic assessment of carbonation depth in concrete structures.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.63-69
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• 1999

The electrical properties of rf-magnetron sputtered $Ba_{0.5}Sr_{0.3}TiO_3$ (BST) capacitors were investigated by varying annealing temperature and atmosphere of the rapid thermal annealing (RTA). The electrical properties of Pt/BST/Pt capacitors were found to strongly depend on the RTA condition. It seems that the dependence of the electrical properties of the Pt/BST/Pt capacitors on the RTA condition is related to the oxygen vacancies in BST thin films. In order to clarify the relation between the oxygen vacancies and the electrical properties of Pt/BST/Pt capacitors, we have examined the two different annealing methods. One annealing method was performed in $O_2$ gas and the other was done in $O_2$-plasma at the same condition of 450$^{\circ}C$, 20 mtorr. It was found that the leakage current densities of $O_2$-plasma annealed capacitor were much lower than those of $O_2$ annealed capacitor. The dielectric constants of $O_2$ annealed capacitor decreased about 14% comparing with those of as-deposited. In contrast, there was no decrease in the dielectric constant of $O_2$-plasma annealed. These results indicate that $O_2$-plasma annealing is very effective in compensation the oxygen vacancies in BST thin films. It can be also concluded that the oxygen vacancies greatly affect the electrical properties of Pt/BST/Pt capacitors.

• Journal of Environmental Health Sciences
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• v.29 no.2
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• pp.50-55
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• 2003

3,3-dichlorobenzidine is suspected to be cancinogenic in experimental animal and human. Several studies have investigated excretion of metabolites in urine, hemoglobin adduction and cancer incidence among workers occupationally exposed to 3,3'-dichlorobenzidine. In these researches, metabolites of 3,3'-dichlorobenzidine had a very important role, and were required as highly purity. The purpose of this study was synthesis and isolation of its metabolites from 3,3'-dichlorobenzidine. 3,3'-dichlorobenzidine was partially dissolved in benzene, ether, ethanol and methanol, and completely dissolved in 70% acetic acid on mixtures of citric acid containing less than 1% DCB, pyridine, a mixture of 0.5N NaOH and toluene(1:2), and phenol saturated with 20 mM TRIZA base. DCB, monoacetyl-DCB and diacetyl-DCB were measured by using gas chromatography/mass spectrometry(GC/MS). Detection for checking them was nitrogen phosphorous detection mode(NPD), and for identifying them was selected ion monitoring mode(SIM). The base peaks were 252 m/z in DCB, 252, and 294 m/z in monoacetyl-DCB, and 252, 294 and 336 m/z in diacetyl-DCB, respectively. Diacetyl-DCB was synthesized by titrating DCB solution of pyridine with sufficient acetyl chloride. Precipitation was diacetyl-DCB, which was purity of 98.7%. And its supernatant was composed of DCB, monoacetyl-DCB and diacetyl-DCB. By using acetic acid as controller of acetylation, monoacetyl-DCB was isolated from diacetyl-DCB . And residual pyridine was removed by using acetone. The purity of monoacetyl-DCB was 98.8%.

• Tuberculosis and Respiratory Diseases
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• v.49 no.1
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• pp.93-98
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• 2000

Acute respiratory distress syndrome (ARDS) has been reported to be associated with a variety of medical and surgical conditions, including All-trans-retinoic acid (ATTA). ATRA is very efficaceous drug to acute promyelocytic leukemia (APL). This drug can induce complete remission at APL without fatal risk of disseminated intravascular coagulation. But ATRA treatment, sometimes, produces the symptoms of fever, weight gain and acute respiratory distress, renal function impairment. The causes of these symptoms are not fully proved, but supposed as the result of leukostasis and capillary leak syndrome from excessive leukocyte differentiation and cytokines release. Recently, we experienced a 24-year-old woman who complained gum bleeding for 6 days. At bone marrow biopsy, she was diagnosed as APL. 2 days after ATRA treatment, she was suffered from the symptoms of dyspnea and general ache. At laboratory examination, total leukocyte count was 50,400/$mm^3$, $PaO_2$ was 42.5 mm Hg and chest PA revealed the findings compatible with ARDS. Treatment with low dose ara-C, corticosteroid and general supportive cares were tried. Within 3 days after treatment, the patient recovered from ARDS by evidence of arterial blood gas study and chest radiographs. She has acquired complete remission of APL with maintenance of A TRA. And so, we present this case with a review of related literatures.

• Tuberculosis and Respiratory Diseases
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• v.54 no.3
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• pp.304-310
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• 2003

Background : Recent discoveries on the physiology of an erection have demonstrated that the organic causes of impotence are more common, and psychogenic impotence is correspondingly less common than was formally believed. The incidence of sexual dysfunctions in chronic obstructive pulmonary disease (COPD) patients is largely unknown or may be perfunctorily attributed to the associated illness or to aging. This study investigated whether or not the impotence was related to the COPD itself as well as whether or not it nay stem from organic causes in a notable proportion of such patients. Methods : The sexual function was evaluated in 10 COPD patients and 10 normal control subjects. A nocturnal Rigi Scan was performed to evaluate the erectile function of each group. The level of hormones such as the free testosterone, prolactin and thyroid stimulating hormone (TSH) was measured, and a pulmonary function test and arterial blood gas analysis was performed. Results : The time duration and frequency of a penile erection were significantly lower in COPD patients than the controls (p<0.05). In addition, the $PaO_2$ levels correlated with the time duration of the penile erection. Conclusion : These results suggest that COPD is one of the causes of organic erectile dysfunction.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.277-277
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• 2011

본 논문은 $CO_2$ 히트펌프용 모세관의 기초 설계자료를 제공하기 위해서 모세관 길이 예측에 대해서 이론 및 실험적으로 조사하였다. 본 연구에서 고려된 작동변수로는 증발온도, 가스냉각기 냉각압력, 냉매유량, 모세관의 관경 등이다. 몇몇연구자들의 자료를 바탕으로 $CO_2$ 모세관 길이를 예측할 수 있는 수학적 모델식을 작성하였다. 그리고 단열 모세관 팽창장치내 $CO_2$의 증발온도, 냉매유량, 냉각압력 등에 대해서 실험한 결과, Fig. 1에 나타낸 것처럼, 모세관 길이가 증가할수록 증발온도는 감소하는 것을 알 수 있다. 그리고 증발온도에 대한 실험값과 예측값의 비교 결과, 실험값이 예측값보다 약간 높게 나타났다. $CO_2$냉매가 모세관내를 통과할 때 플래쉬 가스(flash gas)의 발생으로 인해 액상의 양보다 기상의 양이 많아지고 액상의 압력강하보다 기상의 압력강하가 휠씬 더 크기 때문이다. 또한 증발온도에 대한 실험값과 예측값은 6.5~9.9% 이내에서 좋은 일치를 보였다. Fig. 2에 나타낸 것처럼, 모세관 길이가 증가할수록 냉매유량은 감소하는 것을 알 수 있다. 이는 전술한 바와 같이 모세관 길이가 증가할수록 냉매 압력강하가 더욱더 증가하기 때문이다. 그리고 냉매유량에 대한 실험값과 예측값의 비교 결과, 실험값이 예측값보다 약간 높게 나타났다. 이는 전술한 증발온도와 동일한 이유로 실제 $CO_2$냉매가 모세관내를 통과할 때 플래쉬 가스의 발생량이 많아지기 때문이다. 또한 냉매유량에 대한 실험값과 예측값은 0.64~10.9% 이내에서 좋은 일치를 보였다. Fig. 3에 나타낸 것처럼, 모세관 길이가 증가할수록 냉각압력은 증가하는 것을 알 수 있다. 이는 증발온도가 일정한 경우 모세관 길이가 증가할수록 냉매유량이 감소하여 압축기 토출측 온도(압력)가 상승하기 때문이다. 그리고 냉각압력에 대한 실험값과 예측값의 비교 결과, 실험값이 예측값보다 약간 낮게 나타났으며 실험값과 예측값은 1.04~3.7% 이내에서 좋은 일치를 보였다. 따라서 본 연구에서는 수송기계용 $CO_2$ 열펌프 단열 모세관에 대한 기초설계 자료로서, 냉각압력, 증발온도, 모세관 직경, 냉매유량 등의 조건으로부터 모세관 길이를 계산해낼 수 있는 예측 상관식을 제안하였다.

• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.456-470
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• 2013

Hollow-fiber membranes, is one of the new technologies that is growing rapidly in the past few decades. In addition, separation membranes using polymer materials, have attracted attentions in various fields including gas separation, fuel cells, water treatment, wastewater treatment, and organic separation. Nanofiltration (NF) membranes having the separation characteristics in the intermediate range between ultrafiltration and reverse osmosis (RO) membranes for liquid separation, with relatively low investment cost and operating pressure lower than that of RO membranes, have high permeance and rejection performance of multivalent ions as well as organic compounds of molecular weight between $200{\sim}1000gmol^{-1}$. In this paper, we would like to review the research trends on the various structure control and characterization of NF hollow fiber membranes with respect to materials and the methods of preparation (phase inversion method and interfacial polymerization method). Currently, most of NF membranes have been manufactured by plate and frame types or spiral wound types. But hollow fiber types have delayed in commercial products, because of the weak strength when to produce on the basis of the existing materials, therefore the development of new materials or improvement of existing materials will be needed. If improving manufacturing technology is available, hollow fiber types will replace spiral wound types and gradually show a higher market share.

• Fire Science and Engineering
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• v.24 no.5
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• pp.32-38
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• 2010

Multi-dimensional fire dynamics were studied numerically with the change in ventilation conditions in a full-scale ISO 9705 room. Fire Dynamic Simulator (FDS) was used for the identical conditions conducted in previous experiments. Flow rate and doorway width were changed to create over-ventilated fire (OVF) and under-ventilated fire (UVF). From the numerical simulation, it was found that the internal flow pattern rotated in the opposite direction for the UVF relative to the OVF so that a portion of products recirculated to the inside of compartment. Significant change in flow pattern with ventilation conditions may affect changes in the complex process of CO and soot formation inside the compartment due to increase in the residence time of high-temperature products. The fire behavior in the UVF created complex 3D characteristics of species distribution as well as thermal and flow structures. In particular, additional burning near the side wall inside the compartment significantly affected the flow pattern and CO production. The distribution of CO inside the compartment was explained with 3D $O_2$ distribution and flow patterns. It was observed that gas sampling at local positions in the upper layer were insufficient to completely characterize the internal structure of the compartment fire.