• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.78.1-78.1
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• 2016

상호작용 하는 쌍성계의 진화과정 중 질량이동에 의한 궤도 변화에는 아직 풀리지 않은 수수께끼가 남아있다. 예를 들면 바륨별 (Ba Star)의 경우, 관측된 궤도 이심률은 평균 0.2, 1000일 단위의 주기를 보여주고 있다. Population Synthesis시뮬레이션으로 이를 재현할 경우 관측된 궤도 성질을 맞추지 못하거나, 바륨별의 형성 개수를 맞추지 못하는 문제점이 있다. 비슷한 문제가 청색낙오성 (Blue Straggler Star)의 시뮬레이션 결과에서도 나타나고 있는데, 이 문제의 핵심은 Roche Lobe Over Flow (RLOF)를 통한 질량 이동이 결과적으로 Common Envelope (CE)으로 이어지기 때문에 각운동량을 크게 잃게 되어 궤도가 원형화 되기 때문인 것으로 판명이 되었다. 따라서 이번 연구에서는 RLOF를 통한 질량이동 중 CE 과정을 효과적으로 피해갈 수 있는 질량이동 과정을 제안하고, 이를 시뮬레이션에 적용하여 관측자료를 설명할 것이다. 최종적으로는, 위의 질량이동 과정을 오픈 소스 항성진화 프로그램인 MESA에 포함시켜, 쌍성계 궤도와 그 별들의 표면 원소 분포 사이의 상관관계를 정량적으로 설명하려고 한다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.53-54
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• 2011

The facilities producing the nuclear energy chosen for resolving the recent global energy problem have been increasingly constructed, and hence more frequent durability tests on radiation shielding concrete are required due to NPP(Nuclear Power Plant) life extension and increase of radioactive waste repositories. Bulk dry density is one of the critical factors ensuring the durability and performance of the radiation shielding concrete because the design of the radiation shielding reinforced concrete structures for NPPs is based on the bulk dry density of the concrete. Bulk density of unconsolidated shielding concrete can be calculated utilizing a test assuring to satisfy the bulk dry density, or existing credible data set. This study evaluated correlation between bulk density and bulk dry density of the concrete used for Korean NPPs (y=1.0913X-0.2458) and developed a correlation expression considering standard deviation of bulk dry density (y=1.0913X-0.3358).

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.413-422
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• 2001

In this study, the effect of hydrodynamic masses is investigated in the dynamic characteristics and earthquake response analyses of the submerged HANARO flow tubes. First, the consistent hydrodynamic masses of the surrounding water are obtained by finite element method. Then, modal analyses and response spectrum analyses are performed and verified by comparing the results with those measured from an experiment. Arbitrary cross-sections of submerged structures and boundary conditions of the surrounding fluid can be considered by using the general benefits of a finite element method comparing with the conventional analytical methods. Practical criteria based on parametric studies are proposed to evaluate the dynamic characteristics of HANARO flow tubes including the hydrodynamic masses.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2000.05a
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• pp.134-139
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• 2000

Crab shell의 중금속 제거 가능성과 그 효율을 검토하기 위하여 chemical sorbent인 cation exchange resin(CER), zeolite, granular activated carbon(GAC), powdered activated carbon(PAC)의 중금속 제거능을 비교한 결과 다음과 같은 결론을 도출할 수 있었다. 1) 0.1 mM～l.0 mM의 초기 중금속 농도에서 중금속 제거량에 미치는 영향을 비교해 보았을 때 중금속 제거의 평형에 도달하는 시간은 농도가 높을수록 오래 걸렸으며 단위 흡착제 질량당 중금속 제거량은 초기 중금속 농도가 높을수록 증가하였다. 특히 구리 이온 제거 실험에서는 낮은 농도에서 crab shell의 구리 이온 제거량이 CER의 경우보다 조금 떨어지는 경향을 보였으나, 대부분의 중금속 제거에 있어서는 crab shell이 다른 chemical sorbent에 비해 뛰어난 중금속 제거능력을 보였다. 2) 흡착 등온 모델에 적용해 보았을 때, 단위 흡착제 질량당 중금속 최대 흡착량이 crab shell > CER > zeolite > PAC =GAC의 순으로, 모든 중금속 제거 실험에서 crab shell이 가장 뛰어난 것으로 나타났다. 실제 폐수처리 공정에서는 GAC나 PAC가 많이 이용되고 있는데, 수중의 중금속을 보다 효율적이고 경제적으로 처리할 수 있는 crab shell을 폐수처리 공정에 응용할 수 있는 방안을 검토할 필요성이 있을 것으로 판단된다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.218-219
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• 2018

This study analyzed the unit weight and compressive strength properties of lightweight concrete using high volume blast furnace slag powder by the mixing ratio of lightweight coarse aggregate to investigate the properties of lightweight concrete using domestic artificial lightweight aggregate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.215-216
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• 2019

Recently, due to abnormal climate phenomena caused by greenhouse gas, flood damage such as local torrential rain has been emerging in Korea. Accordingly, there is a growing need for porous blocks capable of permeability in concrete, but there are limitations in commercialization due to problems such as high unit weight and flexural strength development limitations. This study investigates the unit weight and strength properties of porous blocks using bottom ash as an alternative to aggregate as part of a study to improve the light weight of porous blocks.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.765-772
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• 2011

The present study summarizes a series of compressive tests on concrete cylinder in order to examine the stressstrain relationship of alkali-activated (AA) slag concrete. The compressive strength and unit weight of concrete tested ranged from 8.6 MPa to 42.2 MPa and from $2,186kg/m^3$ to $2,343kg/m^3$, respectively. A mathematical equation representing the complete stress-strain curve was developed based on test results recorded from 34 concrete specimens. The modulus of elasticity, strain at peak stress, slopes of ascending and descending branches of stress-strain curves were generalized as a function of compressive strength and unit weight of concrete. The mean and standard deviation of the coefficient of variance between measured and predicted curves were 6.9% and 2.6%, respectively. This indicates that the stress-strain relationship of AA slag concrete is represented properly with more accuracy in the proposed model than in some other available models for ordinary portland cement (OPC) concrete.

• Resources Recycling
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• v.22 no.2
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• pp.62-70
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• 2013

Electric arc furnace slag is made in ironworks during steel refining, it is been increasing chemical and physical resistibility using ageing method of unstable state of melting steel slag for using concrete's fine aggregates. Which is been changing stable molecular structure of aggregates, it restrains moving of ion and molecule. In Korea, KS F 4571 has been prepared for using the electric arc furnace slag to concrete aggregates. In this study, Electric arc furnace slag is used in the PMC(Polymer Modified Concrete) which is applied a bridge pavement of rehabilitation, largely. In that case, this study evaluates the structural safety about increasing the specific weight. The 4-type bridges(RC slab bridge, RC rigid-frame bridge, PSC Beam bridge, Steel box girder bridge) pavement's increasing the total dead load is in 1 ~ 2%. Design moments in a load combination are increased less then 2%. safety factor is decreased less than 3%. Therefore, the structural safety has no problem for applying the electric arc furnace slag within PMC in bridge.

• Journal of The Korean Association For Science Education
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• v.20 no.1
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• pp.1-11
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• 2000

This study investigated both elementary and middle school students' abilities of reading scales and students' conceptions of measuring instruments and units. Seventy two students with 5th grade, sixty nine students with 7th grade, and eighty students with 9th grade were participated. Performance tests and written questionnaires were used. To assess their scale reading abilities, individual performance test was used. Every student should measure length of an envelope, temperature of water, volume of water, etc. And to find out students' conceptions related with measuring instruments and units, written questionnaires with pictures and photographs were used. Some of the students' abilities of reading scales were considerably poor. The results of a two-plate-balance and measuring-cylinder were worse than those of a ruler, a spring-balance, and a thermometer. Many of the students had misconceptions related with measuring instruments. Some of them did not know exactly the meaning of volume, or mass, or force. So they did not know what to measure with the measuring instruments. Also students were confused with several units of volume, force, weight and mass.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.101-110
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• 2022

In this study, water content tests were performed on various fresh concretes subjected to different binder compostions to review the estimation errors and reliability of water content test methods. Micro-oven drying method, air-meter method, capacitance method and microwave penetration method were used to estimate water content of fresh concrete. Errors in water content estimation were analyzed by each test method. Regardless of the test method of water content, the estimation error was less than 5 %, and in the case of the test using mortar, the error in the estimation value was relatively large. In addition, based on the test results of water content of various concrete, the probability density function in which the estimation error for each test method becomes the population was analyzed. Water content test methods of fresh concrete which using concrete samples showed high estimate reliability of 97 % within the estimation error range of ± 10 kg/m³. On the other hand, the reliability of water content test method using mortar samples was lower.