• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.911-916
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• 2012

It is important to identify dynamic characteristics of nuclear fuel components. Since the fuel always exposed to turbulent flow, the dynamic contact between grids and rods is one of the fuel failure modes. The dynamic behavior of grids in nuclear fuels is quite complex, since two pairs of spring support are placed in the limited space. The strap in a cell has single spring and double dimples and this paper focuses on investigation of the grid strap(Test Fuel Strap, TFS) vibration in one cell. To identify the grid strap vibration, modal analysis of the strap is performed using Finite Element Method (FEM). Modal testing on a $5{\times}5$ grid structure without rods is performed. The modal testing results are compared to analytic results. In addition, random test considering rod effect is performed about a $5{\times}5$ grid with rods under real contact condition in the air. Finally, the strap vibration of a $5{\times}5$ fuel bundle in INvestigation of Flow INduced vIbraTion(INFINIT) facility is measured in real fluid velocity condition without heating. It is shown that modal frequencies from the test are almost equal to those peak frequencies in the INFINIT test.

• Restorative Dentistry and Endodontics
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• 제23권2호
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• pp.597-606
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• 1998

The purpose of this study was to evaluate the shear bond strength of the Compoglass Carvifil bonded on the dentin surface according to etching or non-etching and two time application or three time application of single component. Human non-carious 60 extracted 3rd molar were used. The occlusal dentin surfaces of all teeth were exposed with Diamond Wheel Saw and polished with Lapping & Polishing machine(South Bay Technology Co., U.S.A). The teeth were then distributed randomly into four groups of 15 teeth each and dentin surface were conditioned as following. Control group : Non-etching, two times application of Syntac Single Component. (According to manufacture's instruction) Experimental group 1 : Non-etching, three times application of Syntac Single Component. Experimental group : 2 Etching, two times application of Syntac Single Component. Experimental group 3 : Etching, three times application of Syntac Single Component. Compoglass were bonded to exposed dentin surfaces and all samples were placed in distilled water for 7 days. The shear bond strengths were measured by universal testing machine (SHIMADAZU AUTOGRAPH, AGS-4D., Japan). The results were as follows : 1. Experimental group 3 revealed the highest value (30.75${\pm}$4.74 MPa) and control group revealed the lowest value(14.85${\pm}$2.69 MPa). There was significant difference of shear bond strength among four groups(P<0.01) 2. The acid-etching groups (experimental group 2, 3) had higher shear bond strengths than non etching groups(control group and experimental group 1). 3. The additional application of Syntac single component groups revealed a higher bond strength than two times application groups (control group and experimental group 2).

• 방사선산업학회지
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• 제9권2호
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• pp.85-90
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• 2015

Purpose: Time of operation has been reduced and accuracy of operation has been improved since C-arm, which offer real-time image of patient, was introduced in operation room. However, because of the contamination of patient, C-arm could not be used more appropriately. Therefore, this study is to know factors of controlling exposure dose, image quality and the exposed dose of health professional in operation room. Materials and methods: Height of Wilson frame (bed for operation) was fixed at 130 cm. Then, Model 76-2 Phantom, which was set by assembling manual of Fluke Company, was set on the bed. Head/Spine Fluoroscopy AEC mode was set for exposure condition. According to detector size of C-arm, the absorbed dose per min was measured in the 7 steps OFD (cm) from 10 cm to 40 cm (10, 15, 20, 25, 30, 35, 40 cm). In each step of OFD, the absorbed dose per min of same diameter of collimation was measured. Moreover, using Nero MAX Model 8000, exposure dose per min was measured according to 3 step of distance from detector (20 cm, 60 cm, 100 cm). Finally, resolution was measured by CDRH Disc Phantom and magnification of each OFD was measured by aluminum stick bar. Result: According to detector size of C-arm, difference of absorbed dose shows that the dose of 20 cm OFD is 1.750 times higher than the dose of 40 cm OFD. It means that the C-arm, which has smaller size of detector, shows the bigger difference of absorbed dose per min (p<0.05). In the difference of absorbed dose in the same step of OFD (from 20 cm to 40 cm), the absorbed dose of 9 inch detect or C-arm was 1.370 times higher than 12 inch' s (p<0.05). When OFD was set to 20 cm OFD, the absorbed dose of non-collimation case was approximately 0.816 times lower than the absorbed dose of collimation cases (p<0.05). When the distance was 20 cm from detector, exposed does includes first-ray and scatter-ray. When the distance was 60 cm and 100 cm from detector, exposed does includes just scatter-ray. So, there was the 2.200 times difference of absorbed does. Finally, when OFD was increased, spatial resolution was 4 to 5 step was increased. However, low contrast resolution was not relative. Moreover, there was 1.363 times difference of magnification (p<0.05). Conclusion: When C-Arm is used, avoiding contamination of patient is more important factor than reducing exposed dose of health professional in operation room. Just controlling exposure time is just way to reduce the exposed does of workers. However, in the case, non-probability influence could be occurred. Therefore, this study proved that the exposed dose will be reduced if the factors such as using small detector size of C-arm, setting OFD from 20 cm to 25 cm and non-collimating. Moreover, dose management of C-arm in the non-interesting area will be considered additionally.

• 대한방사선기술학회지:방사선기술과학
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• 제21권2호
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• pp.19-25
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• 1998

By analyzing each part of expsure condition and the status of an entrance dose which is exposed to patients, this study reached the following conclusion. Since there is no standard in setting up an exposure condition, the technology practiced in each facility varies tremendously, and the entrance dose increased especially due to the improper selection of screen and grid and the shortage of a total amount of filtration in leaching the standard filtration amount. Entrance dose was, generally, turned out to be $2{\sim}3$ times as much as that of advanced countries, and there was big difference between facilities ; approximately 52 times inlateral of cervical vertebrae, 35 times in A-P of femur, 33 times in chest A-P, and 11 times in lumber A-P. Therefore, to minimize the entrance dose of a patient with thegreatest amount of image information, acquirement of technological know-how necessary for standardization of exposure condition for each part can be an important research task.

• 한국작물학회지
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• 제40권1호
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• pp.9-15
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• 1995

본 실험은 단마의 번식기관별 재식거리 및 시비량이 마의 생육 및 수량에 미치는 영향을 구명코져 1992년부터 1993년까지 경북농림진흥원 북부시험장에서 수행하였던 바 그 결과를 요약하면 다음과 같다. 1. 출아일수는 절편묘 42~56일, 여두묘 37~46일, 영여자묘 50~56일로 나타나 여두묘가 가장 빨랐으며, 시비량이 많을 수록 출아가 지연되는 경향이었다. 2. 지상부 생육은 사용한 종묘가 절편묘, 여두묘, 영여자묘 순으로 아장이 길었으며, 밀식하면 마디수가 다소 적은 경향을 보였고, 전체적인 지상부의 생육은 절편묘를 종근으로 하여 재식거리 60${\times}$20cm에 N$P_2O_2K_2O$를 56-56-64kg/10a로 시용하는 것이 가장 양호하였다. 3. 지하부의 생육은 괴근장, 괴근폭, 괴근수 및 괴근중 모두 절편묘, 여두묘, 영여자묘의 순으로 양호하였고, 재식거리에 따른 괴근생장은 밀식할수록 괴근장, 괴근폭, 괴근중이 적어지는 경향이었고, 시비량이 많을 수록 개체당 무게가 증가하였다. 4. 수량은 절편묘를 30${\times}$20cm로 밀식하면 60${\times}$20cm에 비해 평균적으로 19%의 증수효과가 있었고, 여두묘는 45${\times}$15cm에 비해 30${\times}$15cm가 10% 증수되었으며, 영여자묘는 30${\times}$10cm에 비해 10${\times}$10cm가 10%정도 증수되었다. 적품성은 절편묘, 여두묘, 영여자묘 순으로 우수하였으며 시비량에 있어서는 N-$P_2O_2K_2O$＝28-28-32kg/10a에 비해 56-56-64kg/10a 처리가 37~47%감수되었다. 따라서 단마 재배시 다식밀식으로 재배하는 것이 수량증수의 효과가 있었으나 적품성을 고려할 때 절편묘는 45${\times}$20cm, 여두묘는 30${\times}$15cm, 영여자묘는 20${\times}$10cm로 재배하는 것이 유리하다고 판단된다.

• 대한방사선기술학회지:방사선기술과학
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• 제15권2호
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• pp.3-9
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• 1992

In an experiment using chest radiography, the authors measured the scattered ray content ratio and exposed skin dose giving varieties to the object thickness, tube voltage, additional filters and gird. The result was as follows, In the 80 kV the required mAs for the density 1.8 was $10{\sim}20$ times as much as in the 140 kV, and when 10 : 1 grid was used the required mAs was $3{\sim}5$ times as much as when grid was not used. Under the same tube voltage the scattered ray content ratios were increased as the additional filter thickness became thicker. And when 10 : 1 grid was used the ratio could be decreased $2{\sim}5$ times as much as when grid was not used. Skin doses exposed to the patients were increasing as the thickness of the object became thicker, and were decreasing as filters became thicker while showing slow the decreasing effects above the 1/8 VL. And when the grid was used skin doses were increased $2{\sim}4$ times as much as when not used. In order to improve the image qualities while reducing the exposures in the chest radiography, the authors suggest followings. The additional filters up to the 1/2 VL will be suitable according to the thickness of the objects in the 80kv, while the 10 : 1 grid and additional filter of 1/8 VL will be suitable in the 140 kV.

• Toxicological Research
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• 제29권1호
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• pp.69-79
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• 2013

The purpose of this study was to investigate the current status of metal pollution in the sediment from rivers, lakes, and streams in active gold mining districts in Ghana. Two hundred and fifty surface sediment samples from 99 locations were collected and analyzed for concentrations of As, Hg, Cr, Co, Cu, Fe, Zn, Pb, Cd, Ni, and Mn using inductively coupled plasma-mass spectroscopy (ICP-MS). Metal concentrations were then used to assess the human health risks to resident children and adults in central tendency exposure (CTE) and reasonable maximum exposure (RME) scenarios. The concentrations of Pb, Cd, and As were almost twice the threshold values established by the Hong Kong Interim Sediment Quality Guidelines (ISQG). Hg, Cu, and Cr concentrations in sediment were 14, 20, and 26 times higher than the Canadian Freshwater Sediment Guidelines for these elements. Also, the concentrations of Pb, Cu, Cr, and Hg were 3, 11, 12, and 16 times more than the Australian and New Zealand Environment and Conservation Council (ANZECC) sediment guideline values. The results of the human health risk assessment indicate that for ingestion of sediment under the central tendency exposure (CTE) scenario, the cancer risks for child and adult residents from exposure to As were $4.18{\times}10^{-6}$ and $1.84{\times}10^{-7}$, respectively. This suggests that up to 4 children out of one million equally exposed children would contract cancer if exposed continuously to As over 70 years (the assumed lifetime). The hazard index for child residents following exposure to Cr(VI) in the RME scenario was 4.2. This is greater than the United States Environmental Protection Agency (USEPA) threshold of 1, indicating that adverse health effects to children from exposure to Cr(VI) are possible. This study demonstrates the urgent need to control industrial emissions and the severe heavy metal pollution in gold mining environments.

• Safety and Health at Work
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• 제5권3호
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• pp.131-135
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• 2014

Background: Cassava and corn milling is a growing small-scale enterprise in Africa. We aimed to determine the incidence of hand-arm musculoskeletal complaints among vibration-exposed Congolese cassava and corn millers in the previous 12 months. Methods: A cross-sectional study was conducted, prior to a follow-up study, from March to May 2013 among cassava/corn millers in Lubumbashi, Democratic Republic of Congo, in which 365 millers age-matched to 365 civil workers anonymously answered a questionnaire. Results: Overall incidence of hand-arm musculoskeletal complaints was 25.8% in millers (vs. 5.2% in civil workers; p < 0.001). The risk of experiencing musculoskeletal symptoms was seven times higher in millers [vs. civil workers; odds ratio (OR) = 7.10; 95% confidence interval (CI): 4.03-12.50; p < 0.0001]; 2.4 times higher in smoking millers (vs. smoking civil office workers; OR = 2.36; 95% CI: 1.42-3.88; p < 0.001); 3.6 times higher in millers with longer daily exposure (> 8 hours; vs. those working ${\leq}8$ hours; OR = 3.56; 95% CI: 1.93-3.61; p = 0.026); and 7.4 times higher in young millers (vs. older millers, OR = 7.39; 95% CI: 1.29-75.52; p < 0.001). Smoking, number of cigarettes, and daily exposure duration were positively correlated with musculoskeletal complaints. Conclusion: This study revealed a relatively high incidence of musculoskeletal complaints among African cassava and corn millers. The use of anti-vibration protective equipment and the regulation of this hazardous occupation may reduce the burden of musculoskeletal disorders in millers.

• Journal of Radiation Protection and Research
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• 제22권4호
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• pp.227-235
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• 1997

병원내 방사선 작업 종사자 51명(진단방사선과 18명, 치료방사선과 17명, 핵의학과 16명)에서 림프구의 염색체이상 빈도를 대조군 49명과 비교하여 저선량 만성피폭시 인체에 미치는 영향을 조사하였다. 종사자의 축적선량은 0.30-40.07 mSv 였으며 총축적선량 5 mSv 이하가 46%로 가장 많았다. 염색체 이상이 있는 세포수는 종사자군에서 1.275%로, 대조군에서의 0.677%에 비해 더 높았다(p<0.001). 염색분체형 이상은 종사자군이 약간 높은 경향은 있지만 통계적인 유의성은 없었으며, 염색체형 이상은 대조군 $0.344{\times}10^{-2}$/cell에 비해 종사자군이 $0.706{\times}10^{-2}$/cell로 2.1배 높았다(p<0.05). 이중 교환은 대조군 $0.083{\times}10^{-2}$/cell에 비해 종사자군 $0.245{\times}10^{-2}$/cell로 3.0배 높았다(p<0.05). 총축적선량, 최근 5년 및 최근 2년간의 선량은 염색체이상과 선량-반응 관계가 없었으나, 최근 1년간 피폭선량과 염색체형 교환 빈도사이에 유의한 상관관계가 있었다(p<0.05). 근무년수와 염색체 이상빈도와 선량-반응관계는 없었으며, 각 작업부서 별 염색체이상 빈도 및 대조군과의 비교시, 염색체형 교환이 핵의학과 $0.313{\times}10^{-2}$/cell로 가장 높았으며 (p<0.05), 치료방사선과 근무자 $0.265{\times}10^{-2}$/cell (p=0.0622), 진단방사선과 근무자 $0.167{\times}10^{-2}$/cell (p=0.1107)순이었다. 색체이상이 유발될 수 있음을 확인하였으며, 따라서 림프구 염색체이상은 매우 낮은 양의 방사선 피폭에 의하여도 발생함을 알 수 있었다.

• Natural Product Sciences
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• 제14권2호
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• pp.73-80
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• 2008

The authors screened the pharmacological effects of 50% ethanol extracts of Yacon on spermatogenesis in rats. Numbers of sperm in animals treated with 25, 50, or 100 mg/kg/day for 6 weeks of Yacon tuber extracts (YTE) were approximately 1.51, 1.61 and 1.78 times higher, respectively, than in the untreated control group. Moreover, the spermatogenic effect of Yacon leaf extract was found to be $1.03{\sim}1.38$ times higher than that of YTE. The ameliorative effect of Yacon tuber extracts on 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced toxicities in the rat were also investigated. Rats were assigned to three groups (6 rats/group), a control group, a TCDD exposed group, and a group treated with Yacon tuber extract (YTE) after TCDD exposure (TCDD/YTE group). 40 ${\mu}g/kg$ of TCDD was injected i.p., and 200 mg/kg/day of YTE was also administered for 4 weeks by oral gavage. The TCDD/YTE group showed a significant increase in sperm number as compared with the TCDD exposed group. In conclusion, TCDD induced testicular toxicity was significantly ameliorated by YTE. The results of the present study suggest that Yacon extract is a possible therapeutic for the treatment of spermatogenic disorder.