• Korean Journal of Materials Research
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• v.8 no.4
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• pp.328-336
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• 1998

In metal-carbon system with no mutual solubility between matrix and alloying elements as solid or liquid phases, Cu-C-X nanocomposite metal powders were prepared by high energy ball milling for solid-lubricating bronze bearings. Elemental powder mixtures of Cu-lOwt.%C- 5wt. %Fe and Cu- lOwt. %C- 5wt. %Al were mechanically alloyed with an attritor in an argon atmosphere, and then microstructural evolution of the Cu-C-X nanocomposite metal powders was examined. It has been found that after 10 hours of MA, the approximately 10$\mu\textrm{m}$ sized Cu-C- X nanocomposite metal powders can be produced in both compositions. Morphological characteristics and microstructural evolution of the Cu-C-X powders have shown a similar MA procedure compared to those of metal-metal system. As a result of X - ray diffraction analysis, diffraction peaks of Cu and C were broaden and peak intensities were decreased as a function of MA time. Especially, the gradual disappearance of C peaks in the X- ray spectra is proved to be due to the lower atomic scattering factor of C. The calculated Cu crystallite sizes in Cu- C- X nanocomposite metal powders by Williamson- Hall equation were about lOnm size, on the other hand, the observed ones by TEM were in the range of 10 to 30nm.

• Korean Journal of Materials Research
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• v.2 no.5
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• pp.353-359
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• 1992

Thermal oxidation and plasma enhanced chemical vapor deposition of tantalum oxide thin films on p-type (100) Si substrates were studied to examine the dielectric nature of T$a_2O_5$ as a Al/T$a_2O_5$/p-Si capacitor. Microstructure and dielectric properties of the capacitors were investigated by XRD, AES, high frequency C-V analyzer, I-V meter and TEM. XRD analysis showed that the structure of T$a_2O_5$ films were amorphous, but the films were crystallized to hexagonal $\delta$-T$a_2O_5$ by 65$0^{\circ}C$ thermal oxidation treatment. It was found that the stoichiometry of the films was more or less close to 2 : 5. Leakage current density and relative dielectric constant of thermal oxidation T$a_2O_5$ film at 60$0^{\circ}C$ was 5.0${ imes}10^{-6}$/A/c$m^2 and 31.5, respectively. In the case of PECVD T$a_2O_5$film deposited at 0.47W/c$m^2 they were 2.5${ imes}10^{-5}$/A/$ extrm{cm}^2$ and 24.0, respectively. The morphology of the films and interfaces were investigated by TEM.

• Korean Journal of Materials Research
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• v.21 no.7
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• pp.384-390
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• 2011

Ti-6Al-4V ELI (Extra Low Interstitial) alloy has been widely used as an alternative to bone due to its excellent biocompatibility. However, it still has many problems, including a high elastic modulus and toxicity. Therefore, nontoxic biomaterials with a low elastic modulus should be developed. However, the fabrication of a uniform coating is challenging. Moreover, the coating layer on Ti and Ti alloy substrates can be peeled off after implantation. To overcome these problems, it is necessary to produce bulk Ti and Ti alloy with hydroxyapatite (HA) composites. In this study, Ti, Nb, and Zr powders, which are biocompatible elements, were milled in a mixing machine (24h) and by planetary mechanical ball milling (1h, 4h, and 6h), respectively. Ti-35%Nb-7%Zr and Ti-35%Nb-7%Zr-10%HA composites were fabricated by spark plasma sintering (SPS) at $1000^{\circ}C$ under 70MPa using mixed and milled powders. The effects of HA addition and milling time on the biocompatibility and physical and mechanical properties of the Ti-35%Nb-7%Zr-(10%HA) alloys have been investigated. $Ti_2O$, CaO, $CaTiO_3$, and $Ti_xP_y$ phases were formed by chemical reaction during sintering. Vickers hardness of the sintered composites increases with increased milling time and by the addition of HA. The biocompatibilty of the HA added Ti-Nb-Zr alloys was improved, but the sintering ability was decreased.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.4
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• pp.89-94
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• 2008

Purpose: To observe the high temperature creep test and the fracture surface of the samples of 9% Ni alloy steel generally used for all kinds of mahine parts and predict the durability of that by determining a constant of C with a Larson-Miller variable. Methods: The equipment of this test was made into lever-beam style designed by Andrade and F. Garofalo et al.. The condition of creep test was set under 16 kinds of conditions after fixing 4 kinds of temperature condition and 4 kinds of stress condition to check how it effects the samples. Results: The temperature of creep test was increased, the stress index (n) of creep deformation was gradually decreased from 3.97 to 3.55. The activation energy of creep deformation was decreased from 90.39 to 83.64 kcal/mol when the stress was increased. A constant of C value by calculation of larson-Miller variable was about 22 and if temperature for use is suggested, the durability could be calculated. Conclusions: By analyzing the fracture phenomenon and suggesting the observation result of the fracture surface of the samples and creep test of 9% Ni alloy steel, the basic design data for the practical use of accessories in the field of equipment could be constructed and used to predict the durability of the equipment.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.22 no.3
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• pp.257-264
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• 2012

Objectives: This study's aims were to evaluate the effects of load center of gravity within an object lifted and feet placements on peak EMG amplitude acting on bilateral low back muscle groups, and to suggest adequate foot strategies with an aim to reducing low back pain incidence while lifting asymmetric load. Methods: The hypotheses that asymmetric load imposes more peak EMG amplitude on low back muscles contralateral to load center of gravity than symmetric load and maximum peak EMG amplitude out of bilateral ones can be relieved by locating one foot close to load center of gravity in front of the other were established based on biomechanics including safety margin model and previous researches. 11 male subjects were required to lift symmetrically a 15.8kg object during 2sec according to each conditions; symmetric load-parallel feet (SP), asymmetric load-parallel feet (AP), asymmetric load-one foot contralateral to load center of gravity in front of the other (AL), and asymmetric load-one foot ipsilateral to load center of gravity in front of the other (AR). Bilateral longissimus, iliocostalis, and multifidus on right and left low back area were selected as target muscles, and asymmetric load had load center of gravity 10cm deviated to the right from the center in the frontal plane. Results: Greater peak EMG amplitude in left muscle group than in right one was observed due to the effect of load center of gravity, and mean peak EMG amplitudes on both sides was not affected by load center of gravity because of EMG balancing effect. However, the difference of peak EMG amplitudes between both sides was significantly affected by it. Maximum peak EMG amplitude out of both sides and the difference of peak EMG amplitude between both sides could be reduced with keeping one foot ipsilateral to load center of gravity in front of the other while lifting asymmetric load. Conclusions: It was likely that asymmetric load lead to the elevated incidence of low back pain in comparison with symmetric load based on maximum peak EMG amplitude occurrence and greater imbalanced peak EMG amplitude between both sides. Changing feet positions according to the location of load center of gravity was suggested as one intervention able to reduce the low back pain incidence.

• The Journal of Internal Korean Medicine
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• v.22 no.3
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• pp.299-307
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• 2001

Objectives: Fatigue is a common symptom experienced by many people who visit Oriental medical clinics or hospital. However, there has been little study about the fatigue in the Oriental medical academic world. For this reason, we attempted to investigate the present status of fatigue of outpatients, and its relation with Health Practice Index(HPI). Methods: The subjects were 63 outpatients who visited the Tonification Clinic in Kyunghee Oriental Medical Center between January 1, 2001 and July 31, 2001. Their chief complaint was fatigue and they did not have any physical or mental problem. They were given a questionnaire which included questions reflecting general characteristics, fatigue degree and health habits. We measured degree of fatigue by Chalder scale et al. Health habits were investigated about 5 articles out of 'Breslow 7 Health habits'. Results: Among the subjects, 48 people(76.2%) were considered as 'fatigue patients' by the Chalder scale. Of this 48 fatigue patients, 27 people(56.3%) had manifested fatigue for more than 6 months. The average of scale II for all the patients was 14.05, which indicates moderate degree of fatigue. They complained fatigue, drowsiness and general weakness, dryness and discomfort of the eyes, headache, shoulder pain and neck stiffness, dizziness, heat in the upper part of the body, and poor concentration. There were no differences in degree of fatigue according to Health habits including exercise or not, smoking or not, the frequency of drinking, hours of sleeping, and body mass index. Conclusions: Many people complain fatigue symptom. Therefore doctors should have more interest in fatigue and care. This study can provide standards of prognosis of fatigue patients. Also prospective studies are needed to find relationship between health habits and fatigue degree.

• Journal of Physiology & Pathology in Korean Medicine
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• v.21 no.3
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• pp.605-610
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• 2007

This experimental study was performed to evaluate the effects of ehtanol extract of Purple Solanum tuberosum L(EPSTL) on obesity and hyperlipidemia in rats induced by high fat diet. Sprague-Dawley rats were divided into normal group, control group, EPSTL (100 mg/kg and 200 mg/kg) treated group. EPSTL was orally administered to the obese rats by high fat diet for 6 weeks. The effect of EPSTL on obesity and hyperlipidemia were examined in vitro and in vivo as follows : EPSTL effectively inhibited the differentiation of 3T3-L1 adipocytes in a concentration dependent manner. EPSTL significantly lowered body weight of rats fe high fat diet for 6 weeks from 4 weeks treatment compared with untreated control. EPSTL significantly reduced the weight of retroperitoneal fat only at 100 mg/kg and epididymal fat pad in rats fed high fat diet for 4 weeks at 100 and 200 mg/kg. EPSTL significantly reduced the level of triglyceride at 200 mg/kg, while EPSTL tended to lower the levels of total lipid and phospholipid in rats fed high fat diet for 4 weeks with no significance. EPSTL significantly attenuated the level of total cholesterol, LDL and atherosclerosis index (Al) as well as increased the level of HDL at 200 mg/kg. EPSTL significantly reduced the levels of total lipid and triglyceride of hepatic tissues in rats fed high fat diet for 4 weeks at 200 mg/kg. EPSTL significantly lowered the level of insulin, while it did not affect leptin compared with untreated control. Taken together, these results suggest that EPSTL can be used for the treatment or prevention of hyperlipidemia and obesity.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2001.04a
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• pp.115-126
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• 2001

1988년 Reaven이 인슐린저항성증후군(insulin resistance syndrome)의 개념을 처음 소개한 후 전세계적으로 관심이 증가하고 있다. 인슐린저항성증후군은 대사성증후군 (metabolic syndrome), X 증후군(syndrome X)이라고도 하며, 인슐린 저항성에 따른 고인슐린혈증, 내당능장애(impaired glucose tolerance)와 2형 당뇨병(인슐린 비의존형 당뇨병), 이상지질혈증(dyslipidemia), 고혈압 등 일련의 질환은 동일인에서 흔히 병발하고, 이들은 모두 죽상경화증(atherosclerosis)의 위험인자라는 관점에서 상호연관성을 갖는 질환군이라는 개념이다. 2형 당뇨병은 인슐린에 대한 말초조직의 저항성과 상대적으로 감소된 인슐린 분비능의 결과라고 할 수 있다. 또한 상당수의 2형 당뇨병은 비만, 특히 복부비만을 동반하고 있으며, 비만은 그 자체로 인슐린 저항성을 유발한다. 결국 인슐린 저항성이 장기간 개선되지 못하게 되면 2형 당뇨병이 유발되게 된다. 따라서 2형 당뇨병에 대한 최선의 치료는 혈당조절 뿐만 아니라 인슐린 저항성과 관련된 심혈관계 위험인자를 개선시키는 것을 목표로 해야 한다. 그 증거로 당뇨병 조절과 관련한 대규모 전향적 연구인 UKPDS(United Kingdom Prospective Diabetes Study)의 결과를 보면, 2형 당뇨병에서 설폰요소제(sulfonylurea)나 인슐린으로 10년동안 혈당조절을 했을 때 미세혈관 합병증은 의미있게 감소시켰으나 대혈관 합병증의 발생률은 의미있는 감소를 보이지 못하였다. 반면 대혈관 합병증이 미세혈관 합병증보다 사망에 기여하는 비율이 70배 이상이라는 사실은 당뇨병의 치료가 혈당조절에만 초점이 맞추어져서는 안 되며 심혈관계 위험인자를 개선시키는 치료가 동시에 진행되어야 한다는 점을 시사한다.시료에서 매우 드물게 관찰된다. 음극선발광(cathodoluminescence) 영상의 해석을 통해 저어콘 결정의 성장사를 유추하였으며, 이를 바탕으로 이온현미분석 점(spot)을 정하였다. U-Pb-Th 자료는 퍼스(Perth) 저어콘 스탠다드 (CZ3, 564 Ma, $^{206}$Pb/$^{238}$U=0.0914)를 사용하였다. 아래에 기술하는 연대는 모두 $^{206}$Pb/$^{238}$U 연대에 해당된다. 두 개의 화강암질 편마암 시료로부터 구한 U-Pb 저어콘 연대는 각각 812 $\pm$ 14 Ma(1006-8)와 822 $\pm$ 17 Ma(1006-9)로 분석오차 내에서 서로 일치한다. 이 결과는 춘천 및 전곡 지역의 석류석 각섬암에서 보고된 Sm-Nd 전암연대(852 $\pm$ 24 Ma 및 824 $\pm$ 143 Ma; Lee and Cho, 1995; Ree et al., 1996)와 잘 부합한다. 따라서 후기 원생대 기간 중 화성활동이 한반도에서 광범위하게 일어났음을 시사한다. 한편, 1006-9 시료에서는 예외적으로 한 개의 저어콘 입자 주변부(rim)에서 매우 얇은 과성장띠가 관찰되었으며, 두 개의 점 분석으로부터 구한 U-Pb 저어콘 연대는 약 235 Ma이다. 이 띠는 또한 변성기원의 저어콘에서 흔히 관찰되는 작은 W (<0.05) 비를 보인다. 1006-5 시료는 위 두 시료로부터 수 km 떨어진 지점에서 채집하였으나, 저어콘 연대는 상이한 기록을 보여준다. 즉 매우 작은 Th/U (<0.01) 값을 갖는 저어콘의 주변부에서 223 $\pm$ 5 Ma의 연대가 잘 정의되며, 이는 1006-9 시료에서 관찰된 결과와

• Journal of Photoscience
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• v.12 no.1
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• pp.17-23
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• 2005

Application of a new photocatalyst has been attempted to improve the efficiency and rates of photocatalytic degradation of azo dyes by using a model dye such as Methyl Orange. As a new photocatalyst, $TiO_2$ encapsulated EFAL-removed zeolite Y ($TiO_2$ /EFAL-removed zeolite Y) has been synthesized by ion-exchange in the mixture of EFAL-removed zeolite Y with 0.05 M aqueous [$(NH_4)_2 TiO(C_2O_4)_2.H_2O$] [$TiO(C_2O_4)_2.H_2O$]. This new photocatalyst has been characterized by measuring XRD, IR and reflectance absorption spectra as well as ICP analysis, and it was found that the framework structure of $TiO_2$ /EFAL-removed zeolite Y is not changed by removing the extra-framework aluminum (EFAL) from the normal zeolite Y and the $TiO_2$ inside the photocatalyst exists in the form of $(TiO^{2+})_n$ nanoclusters. Based on the ICP analysis, the Si/Al ratio of the $TiO_2$ /EFAL-removed zeolite Y and the weight of $TiO_2$ were determined to be 23 and 0.061g in 1.0g photocatalyst, respectively. It was also found that adsorption of the azo dye in the $TiO_2$ /EFAL-removed zeolite is very effective (about 80 % of the substrate used). This efficient adsorption contributes to the synergistic photocatalytic activities of the $TiO_2$ /EFAL-removed zeolite by minimizing the required flux diffusion of the substrate. Thus, the photocatalytic reduction of methyl orange (MO) was found to be 8 times more effective in the presence of $TiO_2$ /EFAL-removed zeolite Y than in the presence of $TiO_2$ /normal zeolite Y. Furthermore, the photocatalytic reduction of MO by using 1.0 g of the $TiO_2$ /EFAL-removed zeolite Y containing 0.061g of $TiO_2$ is much faster than that carried out by using 1.0 g of Degussa P-25.

• Journal of Preventive Medicine and Public Health
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• v.29 no.4 s.55
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• pp.853-861
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• 1996

Pneumoconiosis is one of the major problem in the field of occupational health at Korea. Therefore, the efficient diagnosis of pneumoconiosis is a hot issue on the occupational health program. The author executed this study to estimate the diagnostic value of high resolution computed tomography(HRCT) compared with chest radiography for screening of welder's lung. HRCT was introduced very recently for the diagnosis of pneumoconiosis, however, the diagnostic value for screening of welder's lung - principally nonfibrogenic and reversible - has not been evaluated. The subjects were fifty cases of welder's lung or suspected cases who had been collected between 1989 and 1994 from one shipyard and continuously followed-up on the basis of in-plant periodic health check program. We applied both chest radiography and HRCT on the same subjects from May 1 to 30, 1996. The images were evaluated by two careered radiologists independently. The findings of chest radiography were classified into four category by ILO classification, and the findings of HRCT according to the criteria of Bergin et al. The concordance between two radiologists expressed with Kendall's tau-b was 0.72 by chest radiography and 0.44 by HRCT- that is, interobserver variation of HRCT was bigger than that of chest radiography. The concordance between the two different methods was highly variable as 0.44 by radiologist A and 0.06 by radiologist B - that is, interobserver variation was very big. However, HRCT looked more detectable for the minor parenchymal change. These findings suggested that it is not appropriate to use HRCT routinely for screening of welder's lung due to lack of diagnostic criteria, and feasibility, acceptability and economic aspects. Nevertheless, HRCT might be recommendable in the case of equivocal parenchymal features on the chest radiography, unexplained respiratory symptoms, and/or lung function abnormalities suggestive of interstitial fibrosis.