• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
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• pp.325-326
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• 2009

본 연구에서는 물-시멘트 비에 따른 시멘트계 재료인 시멘트 페이스트, 모르터 및 콘크리트의 pH 저하 저항성을 평가하였다. 우선 시멘트 페이스트에 대해 물-시멘트 비 30%, 40%, 50% 인 보통 포틀랜드 시멘트 페이스트의 산 증가에 따른 pH를 측정하였다. 또한, 페이스트의 pH 저하 저항성에 대한 골재의 영향에 대해 알아보기 위해서 콘크리트, 모르터, 페이스트의 pH 저하 저항성 측정 실험도 수행하였다. 실험결과, 산이 증가할수록 pH는 감소하였으며 특히 pH 10 정도에서 급격한 pH 저하가 발생되었다. 산 증가에 따른 pH 감소정도는 산중화능력으로 나타내었으며 시멘트 수화물에 의해 특정 pH에서 산중화능력이 물-시멘트비에 따라 높게 나타났다.

• 약학회지
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• 제44권3호
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• pp.205-212
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• 2000

The effect of BRL 34915, a $K^{+}$ channe$Na^{+}$l opener, on renal function was investigated in anesthetized dog. BRL 34915, when given into the vein, elicited the decrease of urine volume accompanied with the reduction of renal plasma flow (RPF), osmolar clearance ($C_{osm}$) and amounts of sodium excreted into urine ($E_{na}$), whereas reabsorption rate of sodium in renal tubules ($R_{na}$), ratio of $K^{+}$ against $Na^{+}$ in urine ($K^{+}$ /$Na^{+}$) were elevated significantly with a partial fall of mean arterial pressure (MAP). BRL 34915 injected into a renal artery produced the diuretic action along with the increase in RPF $C_{osm}$, $E_{na}$ and amounts of potassium excreted in urine ($E_{k}$), and the decrease in $R_{na}$, reabsorption rate of potassium in renal tubules ($R_{k}$), free water clearance ($C_{H20}$) and $K^{+}/Na^{+}$ ratio in only ipsilateral kidney, however changes of the renal function were not observed in control kidney. BRL 34915 given into carotid artery exhibited the same aspect as changes of renal function induced by intravenous BRL 34915. These results suggest that BRL 34915 has dual effects, renally acting diuretic and centrally acting antidiuretic action.n.

• 천문학회지
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• 제40권4호
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• pp.157-160
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• 2007

I present a model to explain the mass segregation and shallow mass functions observed in the central parts of starburst stellar clusters. The model assumes that the initial pre-stellar cores mass function resulting from the turbulent fragmentation of the proto-cluster cloud is significantly altered by the cores coalescence before they collapse to form stars. With appropriate, yet realistic parameters, this model based on the competition between cores coalescence and collapse reproduces the mass spectra of the well studied Arches cluster. Namely, the slopes at the intermediate and high mass ends, as well as the peculiar bump observed at $6M_{\bigodot}$. This coalescence-collapse process occurs on a short timescale of the order of the free fall time of the proto-cluster cloud (i.e., a few $10^4$ years), suggesting that mass segregation in Arches and similar clusters is primordial. The best fitting model implies the total mass of the Arches cluster is $1.45{\times}10^5M_{\bigodot}$, which is slightly higher than the often quoted, but completeness affected, observational value of a few $10^4M_{\bigodot}$. The model implies a star formation efficiency of ${\sim}30$ percent which implies that the Arches cluster is likely to a gravitationally bound system.

• 천문학회보
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• 제42권1호
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• pp.55.3-55.3
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• 2017

The L1641 cloud in Orion is an active site of star formation. We mapped a square region of 60 arcmin by 60 arcmin in the continuum emission from 0.89 mm to 2.0 mm wavelength using MUSIC mounted on the Caltech Submillimeter Observatory 10.4 m telescope. Eight sources were detected in at least two wavelength bands, and all the detected emission comes from thermal dust continuum radiation of dense cloud cores. Their spectral energy distributions were characterized. The dust emissivity spectral index is beta = 1.3 on average, within the range of typical cores in nearby star-forming regions. Two cores, V380 Ori NE and HH 34 MMS, have unusually low emissivity index of beta = 0.3. These cores may contain millimeter-sized dust grains, which suggests that the lifetime of some dense cores can be much longer than the free-fall timescale.

• 천문학회보
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• 제42권1호
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• pp.38.1-38.1
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• 2017

We report the results of three-dimensional radiation hydrodynamic simulations of star cluster formation in turbulent molecular clouds, with primary attention to how stellar radiation feedback controls the lifetime and net star formation efficiency (SFE) of their natal clouds. We examine the combined effects of photoionization and radiation pressure for a wide range of cloud masses (10^4 - 10^6 Msun) and radii (2 - 80 pc). In all simulations, stars form in densest regions of filaments until feedback becomes strong enough to clear the remaining gas out of the system. We find that the SFE is primarily a function of the initial cloud surface density, Sigma, (SFE increasing from ~7% to ~50% as Sigma increases from ~30 Msun/pc^2 to ~10^3 Msun/pc^2), with weak dependence on the initial cloud mass. Control runs with the same initial conditions but without either radiation pressure or photoionization show that photoionization is the dominant feedback mechanism for clouds typical in normal disk galaxies, while they are equally important for more dense, compact clouds. For low-Sigma clouds, more than 80% of the initial cloud mass is lost by photoevaporation flows off the surface of dense clumps. The cloud becomes unbound within ~0.5-2.5 initial free-fall times after the first star-formation event, implying that cloud dispersal is rapid once massive star formation takes place. We briefly discuss implications and limitations of our work in relation to observations.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.254-260
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• 2000

The spacer grid is one of the main structural components in fuel assembly, which supports the fuel rods, guides cooling water, and protects the fuel assembly from the external impact load such as earthquakes. The nonlinear dynamic impact analysis is conducted by using the finite element code ABAQUS/Explicit. Boundary condition for dynamic analysis is well applied to the test condition. Simulation results also similarly predict the local buckling phenomena. In addition to the buckling parameter, the local buckling cause is examined by both simulation and test method. It is found to correspond well with the test results. Impact tests are also carried out for some specimens of the spacer grid in order to compare the results between the test and the simulation. This test is accomplished by a free fall dummy weight onto the specimen. From this test, only the uppermost and lowermost layers of the multi-cell are buckled, which implies the local buckling at the weakest point of the grid structure.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.376-380
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• 2009

Peer-to-Peer content delivery technology recently begins to be used not only for file sharing applications such as eDonkey but also for every kind of content services. KBS, a broadcasting company in Korea, is aggressively driving to apply Peer-to-Peer technology to KBS's commercial internet video service but we found that there are two big huddles. First, end users may refuse to share their own resources for KBS's cost reduction using Peer-to-Peer content delivery technology. Second, it may cause that the number of free-riders increases and the efficiency of the overall system would fall. From commercial service provider's perspective, we have to avoid that end users have unfavorable impressions on the service and the usefulness of Peer-to-Peer technology decreases. In order to overcome these problems, we studied how to offer incentive to end users and how much incentive would be reasonable, and then applied the result to real service for verification.

• 자원환경지질
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• 제29권4호
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• pp.429-437
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• 1996

The purpose of this study is to correct the nodule abundance of FFG (Free Fall Grab) sampler on KODOS (Korea Deep Ocean Study) area in North-East Pacific Ocean. The image analysis of sea-floor photography was carried out for correcting the abundance of nodules, and the image enhancement techniques and edge detection method were used to discriminate between nodules and sediments. The trace of nodules on sediments was detected to reduce the fractionation effect in calculating the coverage of nodules. The three methods, using the coverage of nodules, using the volume density, and using corrected volume density, were utilized for the correction of the nodule abundance. The method using the coverage of nodules was more convenient and available for the correction of nodule abundance than the other two methods. The method using the corrected volume density had the highest confidence level compared with the other methods.

• 한국과학교육학회지
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• 제16권1호
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• pp.51-60
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• 1996

The purpose of this study is to develope and analyze a test for the assessment of physics inquiry experiment. To do this, three experiments about 'analysis of motion', 'the relation of force and acceleration', and 'free fall motion' in high school physics textbooks were chosen, and 5 scientific inquiry domains and 16 science process skills have been specified. For each experiments, test sheet of $29{\sim}44$ questions for assessing students' ability about physics inquiry experiment were developed on the basis of the scientific inquiry processes developed earlier. After instruction about 3 experiments mentioned above, a test was administered to the students who took experiment. After the adminstration of a test, the ratio of correct answers, discrimination index, and reliability were analyzed. Using the ratio of correct answers, we can determine item difficulty. Through the D.I(discrimination index), we can find which items can discriminate the students who took experiment well from those who took experiment badly, and we can also find the stability of a test result by the reliability analysis. The test developed in this study were also administered to the students who did not take experiments, and the results were compared with the those of the students who took experiments. With the comparison by chi-square method, we could find which items can discriminate the students who took experiments from those who did not take experiments.

• 한국동물학회지
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• 제37권1호
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• pp.76-87
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• 1994

High density lipophorin-L (HDLP-L) was purified from the hemolymph of Bombyx modi using KBr density gradient ultracentrifugation and gel permeation chromatographv (Sephadex G-2001. Lipophorin has native molecular weight of 730 Nd and consists of Apo-Lp I and Apo-Lp II with molecular weights of 250 Kd and 90 Kd, respectively. Lp contains large amounts of glutamine & glutamic acid, threonine, leucine but small amounts of cysteic acid & oxidized cystine, tyrosine, methionine. Lp also contains diacylglycerol, cholesterol, phosphatidylcholine, and phosphatidylethanolamine. Anti-lipophorin showed positive reaction with fat body and ovarial extracts and also revealed immunological identity with lipophorin of Fall webworm, Hyphantria cunea. Lipophorin maintains constant level during larval and pupal stapes but greatlv increases during adult stage in both male and female. Apo-Lp III was purified from adult hemolymph. Hemolymph was subjected to KBr ultracentrifusation and Lp-free fraction was submitted to cation exchange chromatosraphy after ammonium sulfate precipitation. Apo-Lp III has molecular weight of 17 Kd, and similar amino acid composition ar those of other species Lp but contains high amounts of tryptophan which other are tacking in.