• Tribology and Lubricants
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• 제34권3호
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• pp.84-92
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• 2018

Bearings are essential for reducing vibration and wear, in order to achieve high durability and increase longevity. White metal treatment of tilting pads via centrifugal casting method has the possibility of increasing durability. However, this manufacturing method has drawbacks such as long processing time, high defect rate, and harmful health effects. Laser cladding deposition technique is a powerful method that can address these issues by decreasing the processing time and providing good adhesion. In this study, we suggest optimum conditions for laser cladding deposition that can be used in industrial applications. We deposited a soft white metal layer on SCM440 that is primarily used in shafts to minimize wear of bearing pads. During the laser deposition process, we controlled factors such as laser power, powder feed rate, and laser head speed to determine the optimum conditions. In addition, we measured the hardness using micro Vickers, and performed field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and friction tests to investigate the mechanical properties and surface characteristics for different parameters. Based on the experimental results, we suggest that laser power, powder feed rate, and laser head speed of 1.3 kW, 2.5 rpm, and 10 mm/s, respectively, constitute the optimum conditions for producing white metals using laser cladding.

• Journal of Chest Surgery
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• 제25권11호
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• pp.1318-1326
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• 1992

Backgroud. To determine the influence of age at operation upon surgical outcome in patients with isolated secundum atrial septal defect, retrospective clinical analysis was done. Material and method. From June, 1976 to December, 1991, 146 patients, 63 male and 83 female patients ranging in age from 13 months to 56 years, were operated on for isolated secundum atrial septal defect. The patients were divided into 3 groups according to their age at operation: Group I [<20 years old], 91 patients[62.3%]; Group II [21 to 40 years old], 44 patients[30.1%]; GroupIII[>41 years old], 11 patients[7.6%]. Significant differences in clinical features, hemodynamic function, early and late results between age groups were speculated. Results. One hundred thirty-one patients[89.6%] were symptomatic at the time of operation, the most common symptoms being dyspnea on exertion, recurrent respiratory infection, palpitation and chest pain. Patients in NYHA class III or IV were 3.3% in group I, 25% in groupIII, and 54.5% in group Ill. Hemodynamic data was available for 138 patients [94.5%]. Significant pulmonary hypertension [MPA systolic pressure $^3$ 40mmHg] was noted in 22 patients [15.9%]. Patients with pulmonary vascular disease [Rp/Rs>1.25] were 2% in group I, 7.3% in group Il, and 9.1% in groupIII. But there were no significant differences between the age groups in the size of the shunt or the ratio of pulmonary to systemic flow. Atrial septal defects were closed with direct suture in 144 patients and patch repair was performed in 2 patients with high defect. Atrial arrhythmia [8.2%] was the most common postoperative complication. The mean [LSD] duration of follow-up in all patients was 16$\pm$22 months [range, 1~96 months]. Functional result was excellent regardless of the age groups. During follow-up period, late cardiovascular events were arrhythmia [7 cases], reoperation for recurrent ASD [2 cases], and premature late death due to bacterial endocarditis [1 case]. Incidence of preoperative and late atrial fibrillation was significantly higher in older age group. Conclusion. Age at operation is one of the most important predictor of early and late surgical outcome with its impact on the following factors : 1] hemodynamic alterations and ventricular dysfunction due to longstanding volume and pressure overload, 2] pulmonary vascular disease, and 3] atrial arrhythmia including atrial fibrillation as a result of atrial dilatation. Therefore, among patients with surgically repaired atrial septal defects, those operated on over the age of 20 require careful supervision on the long-term basis.

• 천문학회지
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• 제50권6호
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• pp.167-178
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• 2017

We present a study of the inexplicit connection between radio jet activity and ${\gamma}$-ray emission of BL Lacertae (BL Lac; 2200+420). We analyze the long-term millimeter activity of BL Lac via interferometric observations with the Korean VLBI Network (KVN) obtained at 22, 43, 86, and 129 GHz simultaneously over three years (from January 2013 to March 2016); during this time, two ${\gamma}$-ray outbursts (in November 2013 and March 2015) can be seen in ${\gamma}$-ray light curves obtained from Fermi observations. The KVN radio core is optically thick at least up to 86 GHz; there is indication that it might be optically thin at higher frequencies. To first order, the radio light curves decay exponentially over the time span covered by our observations, with decay timescales of $411{\pm}85$ days, $352{\pm}79$ days, $310{\pm}57$ days, and $283{\pm}55$ days at 22, 43, 86, and 129 GHz, respectively. Assuming synchrotron cooling, a cooling time of around one year is consistent with magnetic field strengths $B{\sim}2{\mu}T$ and electron Lorentz factors ${\gamma}$ ~ 10 000. Taking into account that our formal measurement errors include intrinsic variability and thus over-estimate the statistical uncertainties, we find that the decay timescale ${\tau}$ scales with frequency ${\nu}$ like ${\tau}{\propto}{\nu}^{-0.2}$. This relation is much shallower than the one expected from opacity effects (core shift), but in agreement with the (sub-)mm radio core being a standing recollimation shock. We do not find convincing radio flux counterparts to the ${\gamma}$-ray outbursts. The spectral evolution is consistent with the 'generalized shock model' of Valtaoja et al. (1992). A temporary increase in the core opacity and the emergence of a knot around the time of the second ${\gamma}$-ray event indicate that this ${\gamma}$-ray outburst might be an 'orphan' flare powered by the 'ring of fire' mechanism.

• Journal of Yeungnam Medical Science
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• 제8권2호
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• pp.138-149
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• 1991

흰쥐(Sprague-Dawley)의 방광에서 적출한 배뇨근절편을 적출 근편 실험조에 현수하고, 등척성 장력 측정기를 사용하여 그 수축력을 묘기하였다. 배뇨근 절편은 전기장자극에 의해 수축하였으며, 이 수축반응은 콜린에스테라제 억제약물인 physostigmine에 의해 증가하였고 신경말단에서의 choline 재흡수를 방해하는 hemicholinium에 의해 억제되었으며, 신경절봉쇄약물인 hexamethonium에 의해서는 영향을 받지 않았으나 신경축색전도 억제제인 tetrodotoxin에 의해서 소실되었다. 이러한 전기장자극유발 수축은 콜린성 무스카린성 수용체봉쇄약물인 atropine에 의해 부분적으로 길항되었으며, atropine에 의해 길항되지 않는 부분은 ATP 탈감작에 의해 완전히 소실되었다. 배뇨근 절편은 콜린성 무스카린성 수용체 흥분제인 bethanechol과 퓨린성 수용체 흥분제인 ATP에 의하여 농도의존적 수축력 증가를 나타내었으며, 이중 bethanechol 유발수축은 ATP 탈감작에 의해 영향을 받지 않았고, ATP 유발수축은 tetrodotoxin에 의하여 영향을 받지 않았다. 이상의 결과로 보아 흰쥐의 적출배뇨근에는 흥분성 신경전달체계로서 퓨린성 수용체와 콜린성 수용체가 존재하며, 이들은 서로 영향을 미침이 없이 독자적으로 배뇨근 수축에 기여하고 있다고 사료된다.

• Asian-Australasian Journal of Animal Sciences
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• 제23권10호
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• pp.1354-1363
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• 2010

This study compared the effect of four different feeding methods for gestating gilts on reproductive performance and growth of their progeny. A total of 40 F1 primiparous sows (Yorkshire${\times}$Landrace) were allotted to four treatments in a completely randomized design (CRD). For treatments, gestating period of sows was divided into three trimesters (0-35 d, 36-90 d and 91-110 d) and different amounts of feed were provided to each treatment group by Flat, Down-Up-Down (DUD), Up-Down-Up (UDU) and Down-Up-Up (DUU) feeding methods. The experimental diet was formulated to meet or exceed the standards of NRC (1998). Body weight gain of gestating gilts from d 0 to 110 was affected by feeding method (p<0.05). When gilts were fed constant feed ration (Flat feeding), less body weight loss was observed during lactation (-0.9 kg, p<0.05) and desirable backfat thickness (average 19.5 mm) was acquired at 110 days of gestation. Feed intake of lactating sows tended to be greater (4.22, 3.60, 3.97 and 4.13 kg/d, p>0.05) as sows in Flat feeding treatment had lower backfat thickness during gestation compared with other treatments (p<0.05). When gestating gilts were fed higher amount of feed during mid-trimester, the number of stillborn (1.4 piglet per litter, p<0.05) and mummies (0.8 piglet per litter, p = 0.25) were increased compared to other treatments. Feeding methods for gestating gilts had no effect on litter weight and gain of litter weight during the nursing period. Flat feeding method resulted in decreased plasma glucose concentration at 7 d postpartum (p<0.05), and increased LH concentration at 21 d postpartum (p<0.01) compared to other treatments. These results suggested that higher feed intake of gestating gilts resulted in detrimental effects on body condition and reproductive performance of sows. When gestating gilts consumed constant feed during gestation (2 kg/d), better reproductive performance and less body weight loss in lactation were observed because sows consumed more feed during the whole lactation period. Consequently, Flat feeding will be a desirable feeding strategy for gestating gilts to maximize reproductive performance, and better body condition of sows without any negative influence on the growth of their progeny.

• Asian Pacific Journal of Cancer Prevention
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• 제15권13호
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• pp.5187-5194
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• 2014

Background: Numerous studies have suggested that selenium deficiency may be associated with an increased risk for several types of cancer, but few have focused on thyroid cancer. Materials and Methods: We examined the association between post-diagnostic fingernail selenium levels and differentiated thyroid cancer risk in a French Polynesian matched case-control study. Conditional logistic regression models were used to estimate odds ratios and 95% confidence intervals. Results: The median selenium concentration among controls was $0.76{\mu}g/g$. Significantly, we found no association between fingernail selenium levels and thyroid cancer risk after conditioning on year of birth and sex and additionally adjusting for date of birth (highest versus lowest quartile: odds-ratio=1.12, 95% confidence interval: 0.66-1.90; p-trend=0.30). After additional adjustment for other covariates, this association remained non-significant (p-trend=0.60). When restricting the analysis to thyroid cancer of 10 mm or more, selenium in nails was non-significantly positively linked to thyroid cancer risk (p-trend=0.09). Although no significant interaction was evidenced between iodine in nails and selenium in nails effect (p=0.70), a non-significant (p-trend =0.10) positive association between selenium and thyroid cancer risk was seen in patients with less than 3 ppm of iodine in nails. The highest fingernail selenium concentration in French Polynesia was in the Marquises Islands ($M=0.87{\mu}g/g$) and in the Tuamotu-Gambier Archipelago ($M=0.86{\mu}g/g$). Conclusions: Our results do not support, among individuals with sufficient levels of selenium, that greater long-term exposure to selenium may reduce thyroid cancer risk. Because these findings are based on post-diagnostic measures, studies with prediagnostic selenium are needed for corroboration.

• 대기
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• 제25권4호
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• pp.719-734
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• 2015

Korea is one of the country with the world's oldest meteorological observation records. Starting with first meteorological record of fog in Goguryeo in the year of 34 BC, Korea had left a great deal of quantitative observation records, from the Three Kingdoms Period to Goryeo to Joseon. During the Joseon Dynasty, with a great attention by kings, efforts were particularly made to measure rainfall in a systematic and scientific manner. In the 23rd year of King Sejong (1441), the world's first rain gauge called "Chugugi" was invented; in the following year (1442), a nationwide rainfall observation network was established. The King Sejong distributed Chugugi to 350 observation stations throughout the state, even to small towns and villages, for measuring and recording rainfall. The rainfall observation using Chugugi, initiated by King Sejong, had been in place for about 150 years, but halted during national disturbances such as Japanese invasion of Korea in 1592. Since then, the observation had been forgotten for a long time until the rainfall observation by Chugugi was resumed in the 48th year of King Yeongjo (1770). King Yeongjo adopted most of the existing observation system established by King Sejong, including the size of Chugugi and observation rules. He, however, significantly reduced the number of Chugugi observation stations to 14, and commanded the 352 local authorities such as Bu, Gun, Hyeon to conduct "Wootaek", a method of measuring how far the moisture had absorbed into the soil when it rains. Later on, six more Chugugi stations were established. If the number of stations of Chugugi and Wootaek are combined together, the total number of rainfall observation station in the late period of Joseon Dynasty was 372. The rainfall observation with Chugugi during the Joseon Dynasty is of significance and excellence in three aspects: 1) the standard size of Chugugi was so scientifically designed that it is as great as today's modern rain gauge; 2) rainfall was precisely measured, even with unit of Bun (2 mm); and 3) the observation network was distributed on a nationwide basis.

• 대한토목학회논문집
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• 제31권6C호
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• pp.251-258
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• 2011

강관말뚝은 오랫동안 다양한 깊은 기초에 적용되어 왔으나 최근 강재가격의 상승으로 균질한 품질, 큰 강성, 용이한 시공 등의 장점에도 불구하고 기술자들이 자유롭게 적용 못하고 있다. 그러므로 강관말뚝으로 시공할 경우에는 초기 항타후 계획고 이상에서 절단된 강관을 재활용할 수 있다면 공사비를 절감하는데에 기여할 수 있다. 이러한 사유로 인하여 시공자들은 항타후 절단된 강관말뚝을 새롭게 시공할 말뚝과 함께 시공하고자 하나 명확한 정량적인 항타후 강관말뚝의 거동특성의 부재 및 재활용을 위한 적절한 대응방법과 기준의 부재로 인하여 말뚝의 건전도 문제, 문제 발생시의 대응방법 부재 등이 실제 현장에서 종종 발생하고 있다. 본 연구에서는 신규 강관말뚝과 사용자 하중 또는 극한 하중을 받은 강관말뚝에 대하여 현장에서 수행한 말뚝 동재하시험과 실내에서의 피로시험, 인장시험, 샤르피 충격시험을 실시하여 그 결과를 비교분석하였다. 시험결과로부터 허용응력 수준의 항타응력이 발생한 사용 하중조건에서는 항복강도의 변화가 2% 이하이며 최대 허용항타응력($0.9{\sigma}_y$)을 항타횟수가 3000회까지 받은 극한 하중조건에서는 항복강도의 변화가 5% 이하인 것을 확인할 수 있다. 또한 각 변수의 민감도를 확인하기 위하여 통계분석을 실시하였다. 모든 실험결과로부터 강관말뚝의 재활용 가능여부에 대한 판단 기준은 항복강도의 변화 보다는 오히려 샤르피충격에너지, 용접부에서의 강도변화 및 품질관리, 강관의 단면 변화, 항타후 강관의 국부좌굴에 기인하는 것을 확인할 수 있었다.

• Archives of Plastic Surgery
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• 제34권3호
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• pp.298-304
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• 2007

Purpose: This study was undertaken to investigate the osteogenic induction potential of PGA & FBS mixture on a calvarial defect in the rabbit. Methods: Twenty New zealand white rabbit, weighing from 3.5-4kg were allocated into each of the three groups. Four 8 mm sized bone defects were made on the parietal bone by drilling. In group I, the bony defects were implanted with $50{\mu}m$ thickness film containing mixture of PGA and FBS. In group II, with PGA only film, & in group III, the bony defects were left with no implants. Results were evaluated by using morphologic change, radiographic study, biochemical study and histologic examination at 1 week (group I n=7, group II n=7, group III n=14), 2 weeks (group I n=6, group II n=6, group III n=12) and 3 weeks (group I n=7, group II n=7, group III n=14) following implantation. Results: In the morphologic & radiographic study, the formation and corticalization of callus were observed earlier in group I than in groups II and III (p < 0.05). In histological examination, group I showed more abundant and faster new bone formation than in group II and III. In biochemical analysis, group I displayed more activity than in group II and III. Group I also showed more abundant osteopontin, osteocalcin than groups II and III. Conclusion: In conclusion, the results demonstrate that the mixture of PGA and FBS has an effect on osteoblastic formation in the rabbit model. It is considered that further evaluation of long term results on resorption, immunologic tissue reaction and response of applied mixture in the human model will be needed.

• Archives of Plastic Surgery
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• 제34권3호
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• pp.279-284
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• 2007

Purpose: The vein graft was considered as a useful conduit for nerve defect. But the problem is that it might be collapsed in long vein graft state. A new experimental model using vein graft filled with hyaluronic acid was considered. Methods: Thirty rats were used for the experimental animal. In group I, one side of the femoral nerve was exposed and a segment was removed about 15mm. The neural gap was connected with nerve graft. In group II, the nerve gap was connected with vein graft only. In group III, the nerve gap was connected with vein graft filled with hyaluronic acid. A walking track analysis was made periodically for 2 months and NCV(nerve conduction velocity) was executed at the end of the experiment. And morphologic studies were also done for all groups Results: In a walking track analysis, the toe-spread was widen and the foot-length was lengthened. The recovery of the toe-spread and foot length was checked 2 weeks interval, periodically for two months. The SFI (sciatic function index) was $-52.5{\pm}8.2$ in group I, $-68.1{\pm}4$ in group II, $-55.3{\pm}7.9$ in group III. In electrophysiological study, NCV(nerve conduction velocity) was $26.71{\pm}3.11m/s$ in group I, $17.94{\pm}4.35m/s$ in group II, $25.69{\pm}2.81m/s$ in group III. The functional recovery in group I and III was superior to that the group II statistically(p < 0.05) Under electromicroscopic study, the number of the myelinated axons were $1419.1{\pm}240$ in group I, $921.7{\pm}176.8$ in group II, $1322.2{\pm}318$ in group III. The number of the myelinated axons were much more in group I and III than group II statistically (p<0.05). Conclusion: This study suggested that the vein graft filled with hyaluronic acid is more effective than vein graft only for the conduit of the nerve gap. It was thought that the technique could be used in clinical cases with nerve defects as an alternative method to classical nerve grafts.