• Journal of Welding and Joining
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• 제19권6호
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• pp.643-651
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• 2001

A new waveform control technique has been developed for suppressing the spatter generation in the repelled transfer mode of high current $CO_2$ welding. Based on the spatters in repelled transfer, a waveform concept of concept was established in a way to drop the welding current to lower level right before the pendant weld drop detatchment so that the explosion force associating with drop detatchment was decreased. There were several variables to be controlled such as the moment of current drop, the base current and the time of retention at the base current. Either at lower base current or at longer retention time, the more instantaneous shot circuits were int개duced and thus the spatter generation rates were increased. With optimizing the control variables, the amount of spatter generated was decreased by about 30%.

• Tribology and Lubricants
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• 제11권5호
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• pp.122-127
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• 1995

The heat generations of angular contact ball bearings are studied experimentally with numerical simulations. The temperature variations of inner and outer races and the temperature increase distributions are measured by using thermocouples for the spindle rotational speeds, preloads, viscosity of oils, and lubrication methods. The measured values from experiments are used to estimate the heat generation rates. The heat generation is focused mainly on the dominant sources which are robbings due to spin and gyro-moments of bearing balls, applied load and viscous friction. Oil-jet and oil-air lubrication methods are adopted using oils with different viscosities.

• 한국가스학회지
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• 제23권1호
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• pp.36-40
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• 2019

본 연구에서는 최근 4년간(2015년~2018년)의 하절기 기간(6월~8월)에 생산한 발전량 및 발전설비용량 데이터를 기반으로 천연가스, 석탄, 원자력, 신재생에너지 상호간의 가동률에 대해 비교 분석한 것이다. 기저발전을 담당하는 원자력 발전과 석탄 발전은 발전설비용량에 비해 실제로 생산한 발전량이 60% 정도로 높게 유지되었기 때문에 경제성을 확보한 것이다. 반면에 천연가스 발전과 신재생에너지 발전은 발전설비 투자 대비 실제 가동률이 29.5%와 27.3%로 대단히 낮아 발전원가를 낮추기 어려운 구조이다. 그러나 석탄 발전은 온실가스와 미세먼지 발생량 측면에서 구조적인 문제점을 갖고 있다. 반면에 천연가스 발전은 상대적으로 온실가스 발생량이 적고 안전해도 첨두발전 체계에 묶여 경제성을 확보하기 어려운 구조이다. 따라서 발전정책의 변화가 있어야 에너지원간의 균형발전이 가능할 것으로 예상된다.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.281-285
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• 2002

The photophysical properties and the singlet oxygen generation efficiencies of meso-tetraphenyl-trithiasapphyrin $(S_3TPS)$ and meso-tetmkis(p-methoxy phenyl)-trithiasapphy rin ((p-MeO)-$S_3TPS$) have been investigated, utilizing steady-state and time-resolved spectroscopic methods to elucidate the possibility of their use as photosensitizers for photodynamic therapy (PDT). The observed photophysical properties were compared with those of other porphyrin-like photosensitizers in geometrical and electronic structural aspects, such as extended ${\pi}$ conjugation, structural distortion, and internal heavy atoms. The steady-state electronic absorption and fluorescence spectra were both red-shifted due to the extended ${\pi}$-conjugation. The fluorescence quantum yields were measured as very small. Even though intersystem crossing rates were expected to increase due to the increment of spin orbital coupling, the triplet quantum yields were measured as less than 0.15. Such characteristics can be ascribed to the more enhanced internal conversion rates compared with the intersystem crossing rates. Furthermore, the triplet state lifetimes were shortened to -1.0 ${\mu}s$ as expected. Therefore, the singlet oxygen quantum yields were estimated to be near zero due to the fast triplet state decay rates and the inefficient energy transfer to the oxygen molecule as well as the low triplet quantum yields. The low efficiencies of energy transfer to the oxygen molecule can be attributed to the lower oxidation potential and/or the energetically low lying triplet state. Such photophysical factors should be carefully evaluated as potential photosensitizers that have extended ${\pi}$-conjugation and heavy core atoms synthesized for red-shifted absorption and high triplet state quantum yields.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2018년도 추계학술대회
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• pp.25-25
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• 2018

The Fukushima Daiichi Nuclear Power Plant accident in March 2011 caused severe radioactive contamination in the surrounding environment. Since the accident, much attention has been paid to the biological and genetic consequences of organism inhabiting the contaminated area. The effect of radiation exposure on genetic mutation rates is little known, especially for low doses and in situ conditions. Evaluating DNA mutation by low levels of radiation dose is difficult due to the rare mutation event and lack of sequence information before the accident. In this study, correlations with air dose levels and somatic DNA mutation rates were evaluated using Next Generation Sequencer for the clonal plant, Phyllostachys edulis. This bamboo is known to spread an identical clone throughout Japan, and it has the advantage that we can compare genetic mutation rate among identical clone growing different air dose levels. We collected 94 samples of P. edulis from 14 sites with air dose rates from $0.04{\sim}7.80{\mu}Gy/h$. Their clonal identity was confirmed by analysis using 24 microsatellite markers, and then, sequences among samples were compared by MIG sequence. The sequence data were obtained from 2,718 loci. About ~200,000 bp sequence (80 bp X 2,718 loci) were obtained for each sample, and this corresponds to about 0.01% of the genome sequence of P. edulis. In these sequences, 442 loci showed polymorphism patterns including recent origin mutation, old mutation, and sequence errors. The number of mutations per sample ranged from 0 to 13, and did not correlate with air dose levels. This result indicated that DNA mutations have not accumulated in P. edulis living in the air doses levels less than $10{\mu}Gy/h$. Our study also suggests that mutation rates can be assessed by selecting an appropriate experimental approach and analyzing with next generation sequencer.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.781-781
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• 2009

We demonstrate that trasition metal catalyst nanoparticle (NP) attached to carbon nitride nanotubes (CNNTs) show selective catalytic activities on hydrogen generation from the water solution including chemical hydride negative ions. The natural bonding orbitals (NBO) obtained from the first-principle calculations shows that the catalysts attached on CNNTs are quite differently polarized when they play for hydrogen generation from chemical hydride ions and hydrogen of water. For Co and Ni nanoparticles attached on CNNTs, their charges are more positively polarized when they interact with $BH_4^-Na^+$ and $H_2O$ while Pt atoms are less positively charged. In this matter, the increased positive charges on catlyst nanoparticles are proven to be more efficient in attracting hydride negative ions, thus improving hydrogen generate rates. Consequently, this result implies that these different charge polarization leads to selective catalytic activities of NPs-CNNTs. In the hydrogen generation experiments, Co-CNNTs shows the highest hydrogen generation rate when the similar amounts of catalyst nanoparticles (Co, Ni, and Pt) are dispersed on the sidewalls of CNNTs.

• Nuclear Engineering and Technology
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• 제40권4호
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• pp.299-304
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• 2008

A detection system was set up to measure the neutron generation rate of a recently developed D-D neutron generator. The system is composed of a Si detector, He-3 detector, and electronics for pulse height analysis. The neutron generation rate was measured by counting protons using the Si detector, and the data was crosschecked by counting neutrons with the He-3 detector. The efficiencies of the Si and He-3 detectors were calibrated independently by using a standard alpha particle source $^{241}Am$ and a bare isotopic neutron source $^{252}Cf$, respectively. The effect of the cross-sectional difference between the D(d,p)T and $D(d,n)^3He$ reactions was evaluated for the case of a thick target. The neutron generation rate was theoretically corrected for the anisotropic emission of protons and neutrons in the D-D reactions. The attenuations of neutron on the path to the He-3 detector by the target assembly and vacuum flange of the neutron generator were considered by the Monte Carlo method using the MCNP 4C2 code. As a result, the neutron generation rate based on the Si detector measurement was determined with a relative uncertainty of ${\pm}5%$, and the two rates measured by both detectors corroborated within 20%.

• 대한토목학회논문집
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• 제6권2호
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• pp.45-55
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• 1986

본(本) 연구(硏究)는 도시교통계획(都市交通計劃)에서 장래교통발생예측시(將來交通發生豫測時) 항상 문제(問題)로 되는 설명변수선택(說明變數選擇)의 애매성(曖昧性)을 해결(解決)하기 위하여 교통발생(交通發生)의 설명지표(說明指標)를 제안(提案)하는 동시(同時)에 최량(最良)의 도시교통발생(都市交通發生) Model을 작성(作成)하였다. 제안(提案)된 설명지표(說明指標)를 사용(使用)하여 목적별(目的別) 교통발생중회귀(交通發生重回歸) 모델을 작성(作成)하고, 단일변수(單一變數)로 설명(說明)이 가능(可能)한 것은 교통발생(交通발生)의 비손성(非負性)을 확보(確保)하기 위하여 단회귀(單回歸)모델로 수정(修正)하였다. 그러나 다변수(多變數)가 도입(導入)되어도 설명(說明)이 불충분(不充分)한 목적별(目的別) 교통(交通)(등교집중(等校集中)과 자유목적(自由目的)의 발생(發生)모델)은 동질(同質)의 토지이용활동(土地利用活動)으로부터 발생(發生)하는 교통(交通)의 발생특성(發生特性)이 유이(類似)함에 주목(注目)하여 각(各) zone을 특성별(特性別)로 분류(分類)하고 zone 군별(群別)로 교통발생(交通發生) 모델을 작성(作成)하여 통계적(統計的)으로 유의성(有意性)을 검토(檢討)하였다. 그리고 장래교통발생예측(將來交通發生豫測)은 단순(單純)하면서도 예측정도(豫測精度)의 제고(提高)가 바람직하므로 토지이용활동별(土地利用活動別)로 교통발생원단위(交通發生原單位)를 작성(作成)하고 안정성(安定性)을 고찰(考察)하여 교통발생예측시(交通發生豫測時) 실용가능(實用可能)한 원단위(原單位)를 제안(提案)하였다.

• Journal of Ecology and Environment
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• 제30권4호
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• pp.319-324
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• 2007

To investigate the impacts of transgenic rice on freshwater organisms, we conducted two life table experiments using Daphnia magna for fifteen and twenty days, respectively. We examined life history traits such as population growth rates (r), reproductive rates ($R_0$), generation times, and survivorship. In the first experiment, we used non-drought-stressed transgenic and non-transgenic rice harvested in 2005. In the second study, we used non-transgenic and transgenic rice harvested in 2006 following drought stress. Each experiment involved three treatments in which D. magna neonates were fed with Selenastrum capricornutum (control treatment) and S. capricornutum with 5% aqueous extracts of non-transgenic rice (N-T) and transgenic rice (T). In the first experiment, D. magna showed reduced population growth rates and lowered fecundity in the N-T and T treatments. In the second experiment, D. magna receiving both transgenic and non-transgenic rice extracts showed very high mortality, low population growth rates and reproduction rates. We could not detect any significant negative effects of extracts from transgenic rice on D. magna life history traits at 95%.

• Asian-Australasian Journal of Animal Sciences
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• 제22권7호
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• pp.969-976
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• 2009

Use of oocytes from prepubertal animals for in vitro embryo production holds potential application for reducing generation intervals and increasing genetic progress through embryo transfer. The objective of these studies was to compare the effect of three sperm pretreatments (prior to in vitro fertilization) and seven embryo culture protocols on fertilization rate and (or) subsequent development of in vitro fertilized embryos derived from oocytes harvested from ovaries of 1-6 month old prepubertal Boer goats in China. Cleavage rates were highest for embryos fertilized with heparin-treated versus calcium ionophore- or caffeine-treated sperm. Similar rates of blastocyst development were observed using heparin- and ionophore-treated sperm, which were higher than obtained with caffeine-treated sperm. No differences in cleavage or blastocyst rates were observed following embryo culture in basal medias (synthetic oviductal fluid (SOF), Charles Rosenkrans 1 (CR1) or tissue culture medium-199 (TCM-199)) containing 10% fetal bovine serum (FBS). Cumulus or oviductal cell co-culture did not enhance cleavage or blastocyst rates relative to culture in SOF+10% FBS. Replacement of FBS in SOF medium with 0.3% BSA increased cleavage rates, but did not increase rates of blastocyst development. Sequential culture in SOF+0.3% BSA followed by SOF+10% FBS increased blastocyst yield versus continuous culture in SOF+10% FBS and tended to increase blastocyst yield versus continuous culture in SOF+0.3% BSA. These results demonstrate a pronounced effects of sperm pretreatments and in vitro embryo culture systems on rates of blastocyst development and provide a potential protocol (sperm pretreatment with heparin and sequential embryo culture in SOF+0.3% BSA followed by SOF+10% FBS) for generation of the significant numbers of in vitro produced blastocysts from oocytes of prepubertal Boer goats necessary for application of embryo transfer in rural regions of China for distribution of Boer goat genetics.