• Journal of the Microelectronics and Packaging Society
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• v.24 no.2
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• pp.23-27
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• 2017

This paper proposes an approach to predict the reliability of high temperature heaters by identifying their primary failure modes and mechanisms in the field. Test specimens were designed to have the equivalent stress conditions with the high temperature heaters in the field in order to examine the effect of stress conditions on the solder joint failures. There failures often result from cracking due to intermetallic compound (IMC) or void formation within a solder joint. Aging tests have been performed by exposing the test specimens to a temperature of $170^{\circ}C$ in order to reproduce solder joint failures in the field. During the test, changes in IMC formation were investigated by scanning electron microscopy (SEM) on the cross-sections of the test specimens, while changes in void formation were monitored both by resistance spectroscopy and by micro-computed tomography (microCT), alternately. The test results demonstrated the void volume within the solder increased as the time at the high temperature increased. Also, the phase shift of high frequency resistance was found to have high correlation with the void volume. These results implied the failure of high temperature heaters can be non-destructively predicted based on the correlation.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.153-153
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• 2010

p-i-n 형 비정질 실리콘 박막 태양전지에서 p층은 창물질(window material)로서 전기 전도도가 크고, 빛 흡수가 적어야한다. p층의 두께가 얇으면 p층 전체가 depletion layer가 되고 충분한 diffusion potential을 얻을 수 없어 open-circuit voltage ($V_{oc}$)가 작아진다. 반대로 p층 두께가 두꺼워지면 빛 흡수가 증가하고, 표면 재결합이 문제가 되어 변환효율이 감소한다. 밴드갭이 큰 물질로 창층을 제작하게 되면 보다 짧은 파장의 입사광이 직접 i층을 비추므로 Short-circuit current ($I_{sc}$) 와 fill factor를 증가시킬 수 있다. 하여 본 연구에서는 기존의 창층으로 사용되는 Boron을 doping한 p-type a-Si:H 대신에 $N_2O$를 첨가한 p-type a-$SiO_x$:H의 $N_2O$ flow rate에 따른 밴드갭의 변화에 관한 연구를 수행하였다. p-type a-$SiO_x$:H Layer는 $SiH_4$, $H_2$, $N_2O$, $B_2H_6$ 가스를 혼합하여 증착하게 되는데 $SiH_4$, 가스와 $H_2$ 가스의 혼합비는 1:20, $B_2H_6$ 농도는 0.5%로 고정 하였으며 $N_2O$의 flow rate을 가변하며 증착하였다. $N_2O$의 가변조건은 5에서 50sccm으로 가변하여 증착하며 일반적으로 사용되는 RF-PECVD (13.56MHz)를 이용하였고 증착 온도는 175도, 전극간의 거리는 40mm, 파워와 압력은 30W, 700mTorr로 고정하여 진행하였다. 전기적 특성을 알아보기 위해 eagle 2000 Glass를 사용하였고 구조적 특성은 p-type wafer를 사용하여 각각 대략 200nm의 두께로 증착하였다. 증착 두께는 Ellipsometry를 이용하였으며 전기 전도도는 Agilent사의 4156c를 구조적특성은 FT-IR을 사용하여 측정하였다. Conductivity(${\sigma}_d$)는 $N_2O$가 증가함에 따라 $8.73\;{\times}\;10^{-6}$에서 $5.06\;{\times}\;10^{-7}$으로 감소하였고 optical bandgap ($E_{opt}$)은 1.71eV에서 2.0eV로 증가함을 알 수 있었다. 또한 reflective index(n)의 경우는 4.32에서 3.52로 감소함을 나타내었다. 기존의 p-type a-Si:H에 비해 상당한 $E_{opt}$을 가지므로 빛 흡수에 의한 손실을 줄임으로서 $V_oc$를 향상 시킬 수 있으며 동시에 짧은 파장에서의 입사광이 직접 i층을 비추므로 $I_{sc}$와 FF를 향상 시킬 수 있으리라 예상된다. 다소 낮은 전도도만 개선한다면 고효율의 박막 태양전지를 제작 할 수 있을 것으로 기대된다.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.2
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• pp.313-321
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• 1996

Our laboratoy has been participated in Proficiency Analytical Testing (PAT) program which is operated by the Americal Industrial Hygiene Association in cooperation with the National Institute for Occupational Safety and Health (NIOSH). The program is designed to assist a laboratory improve its analytical performance by providing samples on a quarterly basis, evaluating the results, and providing reports on how well the laboratory performed. Evaluation of the results reported here covers five rounds of the PAT program (round 121~round 125). The way a laboratory is evaluated by PAT program is as follows: 1) There is no overall proficiency rating given to a laboratory. 2) A proficiency rating is given for each type of analyze (i.e., metals, silica, asbestos, solvents) that a laboratory analyzed. 3) Proficiency is rated acceptable ("A") if Z score lies between -3 and +3, and unacceptable if Z score is either higher than +3 ("H") or lower than -3 ("Lo"). Z score = (reported data - reference value) / standard deviation 4) For a laboratory to be rated proficient it must either have had no outliers over the most recent two rounds or of the samples actually analyzed over the past year (past four rounds), 75 % or more of the analyze sample results must be acceptable. According to the above rating criteria of PAT program, performance of metals including cadmium, lead, chromium and zinc, and asbestos sample analyses were rated acceptable ("A"). For silica analyses, all samples except one out of four samples in round 122 was rated high("H") were acceptable showing 95 % of ing 95 % of acceptance rate (19/20) throughout the rounds. Analyses of organic solvents were done on 52 samples in 9 types including methanol(MOH), 1,1,1-trichloroethane(MCM), tetrachloroethylene(PCE), trichloroethylene(TCE), benzene(BNZ), o-xylene(OXY), toluene(TOL), chloroform(CFM), 1,2-dichloroethane(DCE). All samples analyzed were rated acceptable except 2 samples that were rated high; one out of each four MCM and TCE samples in round 121, and one that was low out of four o-xylene analyses in round 122 indicating 94 % of acceptance rate(49/52) throughout the rounds. According to the laboratory rating criteria, our laboratory is rated proficient so far for all types of contaminants.

• Journal of the Korea Institute of Building Construction
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• v.21 no.3
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• pp.213-219
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• 2021

Change orders that occur frequently during the construction phase, af ect the construction performance in terms of cost, time, quality, safety and environment, and place a huge burden for stakeholders of given projects. This study analyzed the causes of change orders and their impact on the basis of 721 cases and a questionnaire of 164 domestic U.S. military construction participants in a total of 24 U.S. military projects. Important factors for change orders in the US military construction projects were engineering change due to design errors (348 cases, 48.3%), user requests change(86 cases, 11.9%), and different site conditions (69 cases, 9.6%). In addition, due to the change orders, construction cost increased by 6.56% on average and construction period was extended by 21.1% compared to the original schedule. As a result, it is anticipated that domestic construction companies can obtain a better understanding of change orders and construction performance, which may be difficult due to accessibility and limitations to military facilities. Also, it is proposed a successor study that guides in the right direction for the U.S. Military Construction.

• Korean Journal of Breeding Science
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• v.42 no.4
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• pp.407-412
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• 2010

Recently, peoples are greatly concerned with global temperature change because global warming can be a potential serious effect on agriculture production such as yield reduction and poor grain quality. On the other hand, it can bring some beneficial effects through twice cultivation of rice in temperate region. In order to overcome this situation, we developed extremely early-maturing rice 'Milyang255' which heading date was similar with 'Jinbuolbyeo'. Based on agronomic characteristics of 'Milyang255', it has very short stature as 65 cm of culm length and slightly lower spikelets number per panicle compared with that of 'Jinbuolbyeo'. However, the grain appearance, palatability and other items were better than those of 'Jinbuolbyeo' in panel test of cooked rice. The milled rice yield of 'Milyang255' is 3.94 MT/ha at the early transplanting. Especially, its grain filling rate was higher and faster than Jinbuolbyeo and the head rice ratio in milled rice was also higher. Thus, 'Milyang255' can efficiently reduce the growth duration of rice cultivation and also be useful material for research on twice cultivation of rice in Korea.

• Korean Journal of Breeding Science
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• v.41 no.2
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• pp.168-172
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• 2009

'Punghan' (Avena sativa L.), a winter oat for forage use, was developed by the breeding team at the Department of Rice and Winter Cereal Crop, NICS, RDA in 2008. It was derived from a cross between 'Beltsville 61-150 (IT133501)' and $F_1$ between 'Sikyonggwiri' and 'PA202-210'. A oat cultivar from USA, 'Beltsville 61-150', has a high cold tolerance, while the $F_1$ between 'Sikyonggwiri' and 'PA202-210' has early heading and high yielding with large-size grain. Subsequent enerations followed by the cross were handled in bulk and pedigree selection programs at Suwon and Yeoncheon, respectively. A line, 'SO99013-B-YB-31', was selected for earliness and good agronomic characteristics and designated as a line name of 'Gwiri 60'. The line 'Gwiri 60' was subsequently evaluated for winter hardiness, earliness, and forage yield in five locations, Yesan, Cheongwon, Iksan, Kimjae, and Jeju, from 2006 to 2008 and finally named as 'Punghan'. Over 3 years, the average forage dry matter yield of 'Punghan' harvested at milk-ripe stage was $14.5\;ton\;ha^{-1}$, compared with $13.6\;ton\;ha^{-1}$ of check cultivar 'Samhan'. 'Punghan' is about 2 days earlier in heading date than check cultivar. 'Punghan' is adapted primarily for winter planting use in the mid-southern regions of Korean peninsula.

• Journal of Yeungnam Medical Science
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• v.14 no.1
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• pp.168-174
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• 1997

Alphafetoprotein(AFP) is a glycoprotein synthesized by the fetus early in gestation by the yolk sac and later by the gastrointestinal tract and liver. The concentration of AFP is highest in fetal serum and amniotic fluid around 13th week, and 32nd week in maternal serum. Some conditions are associated with abnormal maternal serum AFP concentration. For examples, neural tube defects, omphalocele, renal anomalies are associated with elevated maternal serum AFP and fetal death, chromosomal trisomies are associated with low level of maternal serum AFP. So maternal serum AFP screening plays a significant role in assessing candidates for prenatal diagnosis and prenatal counselling in pregnant women. This study evaluates the normal ranges of AFP using enzyme immunoassay in normal pregnant women. We studied 500 normal pregnant women who visited the Department of Obstetrics & Gynecology, Yeungnam Medical Center, Yeungnam University during the period through January, 1993 to September, 1996. The group of the study were selected randomly at various gestational ages from 8 to 41 weeks. The results were summarized as follows: 1. The lowest level of AFP in our study group was 2.1ng/ml at 8 weeks of gestation. Thereafter serum alpha-fetoprotein concentrations rose rapidly to reach a peak value at 32nd week. 2. The mean levels of AFP in the primipara and multipara were $166.37{\pm}12.06ng/ml$, and $223.78{\pm}14.00ng/ml$, respectively, showing stastiscally significant difference between these two groups(p<0.01). 3. The mean levels of AFP between mothers who delivered male and female babies were $192.96{\pm}13.00ng/ml$, and $194.29{\pm}13.84ng/ml$, respectively, without statistically significant difference(p>0.05). 4. The normal ranges of maternal serum AFP according to each gestational week were evaluated.

• Journal of Yeungnam Medical Science
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• v.9 no.2
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• pp.359-381
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• 1992

This study was designed to investigate the effect of diazepam on the spontaneous contraction and oxytocin induced contraction of the isolated rat uterus. Female rat(Sprague-Dawley) pretreated with oophorectomy and 4 days administration of estrogen, weighing about 200 g, was sacrificed by cervical dislocation, and the uteruses were isolated. A longitudinal muscle strip was placed in temperature controlled($37^{\circ}C$) muscle chamber containing Locke's solution and myographied isometrically. Diazepam inhibited the spontaneous contraction and oxytocin induced contraction of the isolated rat uterus in a concentration-dependent manner. GABA, muscimol, a GABA A receptor agonist, bicuculline, a competitive GAGA A receptor antagonist, picrotoxin, a non competitive GABA A receptor antagonist, baclofen, a GABA B receptor agonist, and delta-aminovaleric acid, a GABA B receptor antagonist, did not affect on the spontaneous and oxytocin induced contraction of the isolated rat uterus. The inhibitory actions of diazepam on the spontaneous and oxytocin induced contraction were not affected by all the GABA receptor agonists and antagonists, but exceptionally potentiated by bicuculline. This potentiation-effect by bicuculline was not antagonized by muscimol. In normal calcium PSS, addition of calcium restored the spontaneous contraction preinhibited by diazepam and recovered the contractile of oxytocin preinhibited by diazepam. A23187, a calcium inophore, enhanced the restoration of both the spontaneous and oxytocin induced contraction by addition of calcium. In calcium-free PSS, diazepam suppressed the restoration of spontaneous motility by addition of calcium but allowed the recovery of spontaneous motility to a considerable extent. Diazepam could not inhibit some development of contractility by oxytocin in calcium-free PSS, but inhibited the increase in contractility by subsequent addition of calcium. These results suggest that the inhibitory action of diazepam on the rat uterine motility does not depend on or related to GABA receptors and that diazepam inhibits the extracellular calcium influx to suppress the spontaneous and oxytocin induced contractilities.

• Journal of Yeungnam Medical Science
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• v.10 no.1
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• pp.68-76
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• 1993

Pregnancy induced hypertension is multifaceted syndrome with variable involvement of several key organ systems, so sensitive and specific laboratory tests for predicting severity and prognosis, and early diagnosis of this disease are required. Because heme catabolism results in equimolar production of carboxyhemoglobin, iron and bilirubin, a concomittant rise of these parameters would provide confirmation of increased heme catabolism. Microangiopathic hemolytic anemia may occurs in severe preeclampsia, but it is not known whether increased red cell turnover occurs with mild preeclampsia as complication. The purpose of this study was to confirm that increased heme catabolism also occurs in patients with mild preeclampsia. The analysis of data was done on 23 cases with mild preeclampsia and 35 normal pregnant women, who were admitted to Yeungnam University Hospital from October 1992 to March 1993. The results were as follows. 1. The mean antepartum serum iron concentration was significantly higher in the group with mild preeclampsia($86.5{\pm}6.1{\mu}g/dl$) than in the controls($53.2{\pm}5.3{\mu}g/dl$). 2. The mean antepartum and postpartum carboxyhemoglobin concentrations were significantly higher in the group with mild preeclampsia(antepartum : $2.55{\pm}0.42{\mu}g/dl$, postpartum : $1.21{\pm}0.4{\mu}g/dl$) than the controls(antepartum : $0.61{\pm}0.2{\mu}g/dl$, postpartum $0.53{\pm}0.2{\mu}g/dl$) 3. During postpartum, carboxyhemoglobin concentration in preeclampsia reduced significantly from antepartum level, but, there was no difference between antepartum and postpartum carboxyhemoglobin concentrations among controls. 4. Bilirubin concentrations were similar in both groups.

• Journal of Yeungnam Medical Science
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• v.2 no.1
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• pp.221-227
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• 1985

Thirty-four patients with suspected ectopic pregnancy whose serum hCG levels had been measured by beta-hCG EIA before surgery were evaluated retrospectively. The results were as follows: 1. Final diagnosis of thirty-four patients with suspected ectopic pregnancy comprised twenty- eight tubal pregnancy, five ruptures of hemorrhagic corpus luteum and, one tubo-ovarian abscess. One of the five patients with rupture of hemorrhagic corpus luteum was accompanied by missed abortion. 2. Range of serum hCG levels in twenty-eight patients with tubal pregnancy was 59-21,980 mIU/ml and that of four patients with rupture of hemorrhagic corpus luteum and one patient with tubo-ovarian abscess was 0.6-6.6mIU/ml. Serum hCG level of a patient with rupture of hemorrhagic corpus luteum who was accompanied by missed abostion was 200 mIU/ml. 3. Serum hCG levels in twenty-two of twenty-eight patients with tubal pregnancy were lower than 3,000 mIU/ml. Low serum hCG level below 100mIU/ml and high serum hCG level above 6,500 mIU/ml were noticed in four and six patients with tubal pregnancy, respectively. 4. Mean serum hCG levels (${\pm}SD$) of twelve patients with tubal pregnancy who had intra-abdominal free blood of less than 500ml and sixteen patients with tubal pregnancy who had intra-abdominal free blood of more than 500ml were 4,131 (${\pm}7,801$) mIU/ml and 3,208 (${\pm}5,081$) mIU/ml, respectively. There was no statistical difference in the mean level of serum hCG between both group (P>0.05). 5. Mean serum hCG levels (${\pm}SD$) of thirteen patients with unruptured tubal pregnancy and fifteen patients with ruptured tubal pregnancy were 2,628 (${\pm}5,448$) mIU/ml and 4,449 (${\pm}6,938$) mIU/ml, respectively. Mean level of serum hCG was statistically higher in ruptured tubal pregnancy (P<0.01). 6. Positive rate of urine pregnancy test in the diagnosis of ectopic pregnancy was 64% (16/25) and mean range of serum hCG level of nine patients with false negative result were 353 mIU/ml and 59-933 mIU/ml.