• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.89-92
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• 2009

고농도 과산화수소를 추진제로 이용하는 연구가 활발해짐에 따라서 고농도 과산화수소의 국내 생산을 위한 과산화수소 증류에 관한 연구가 필요하게 되었다. 과산화수소의 열분해를 막기 위하여 진공 증류법을 이용하였으며, 증류 압력은 Raoult's law를 이용하여 $40^{\circ}C$ 이하에서 증류가 이루어 질 수 있도록 30 torr로 선정하였다. 실험을 위한 변수로는 증류 온도를 선정하였으며, 증류에 걸린 시간과 증류 후에 계산한 수득율을 성능 평가 대상으로 선정하였다. 실험 결과, 대체로 증류에 소요된 시간이 짧을수록 수득율이 낮으며, 리시버 내의 물의 과산화수소 농도도 더 높은 것을 확인하였다. 또한 비슷한 시간 동안 증류를 수행하였을 경우, 증류 온도가 높을수록 더 높은 농도에 도달하며, 수득율이 낮은 경향을 보였다.

• 진공이야기
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• 제1권1호
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• pp.11-16
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• 2014

A variety of metal vacuum systems displays the celebrated 1/t pressure, namely, power-law dependence on time t, with the exponent close to unity, as to the origin of which there has been long-standing controversy. Here we propose a chemisorption model for water adsorbates, based on the argument for 2D fermion behavior of water adsorbed on a metal surface, and obtain analytically the power-law behavior of pressure with an exponent unity. Further, the model predicts that the pressure should depend on the temperature T according to $T^{1.5}$, which is indeed confirmed by our experiment.

• Computers and Concrete
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• 제3권4호
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• pp.249-260
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• 2006

Self-consolidating concrete (SCC) in the fresh state is known for its excellent deformability, high resistance to segregation, and use, without applying vibration, in congested reinforced concrete structures characterized by difficult casting conditions. Such a concrete can be obtained by incorporating either mineral or chemical admixtures. This paper presents the results of an investigation to asses the applicability of Abram's law in predicting the compressive strength of SCC to any given age. Abram's law is based on the assumption that the strength of concrete with a specific type of aggregate at given age cured at a prescribed temperature depends primarily on the water-to-cement ratio (W/C). It is doubtful that such W/C law is applicable to concrete mixes with mineral or chemical admixtures as is the case for SCC where water to binder ratio (W/B) is used instead of W/C as the basis for mix design. Strength data of various types of SCC mixtures is collected from different sources to check the performance of Abram's law. An attempt has been made to generalize Abram's law by using various optimization methodologies on collected strength data of various SCC mixtures. A set of generalized equations is developed for the prediction of SCC strength at various ages. The performance of generalized equations is found better than original Abram's equations.

• 대한화학회지
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• 제53권2호
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• pp.175-188
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• 2009

본 연구에서는 학교 현장에 적용 가능한 ‘샤를의 법칙’ 실험방법을 개발하였다. 교과서 및 문헌 분석을 통하여 실험 장치 및 방법을 구성하는데 필요한 요소를 분석하였다. 전체 부피를 결정하는 부분 으로 단순 구조인 주사기를 사용할 때 보다 바이알과 부피 변화를 관찰하는 부분으로 유리관을 연결한 구조를 사용하였을 때 온도 변화에 따른 기체의 부피 변화를 쉽게 측정할 수 있었고, 비커 같은 큰 부피 의 물중탕 기구 보다 눈금실린더를 이용한 물중탕 방법이 냉각 시간에 있어서 이점을 보여주었다. 부피 변화 부분에서 저항이 최소화된 형태로 액체 마개 형태가 이용되었다. 액체 마개로 물방울을 사용할 경 우 측정 초반에 증발에 의해 기체 부피변화에 큰 영향을 주는데, 글리세롤을 사용할 경우 이 같은 영향 은 거의 없었다. 제안된 실험방법으로 대략 1 시간 이내의 실험 시간을 소요하여 높은 선형 상관계수($R^2$ = 0.999)를 갖는 결과를 얻을 수 있었고, 부피가 0이 되는 온도가 $-216.7\;{^{\circ}C}$로 예측되는 정도로 매우 정확 한 결과를 보여주었다. 본 연구를 통해 개발된 샤를의 법칙 실험은 학교 급별 교육과정에 따라 수준을 조절하여 실시할 수 있을 것으로 예상한다.

• 한국안전학회지
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• 제12권4호
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• pp.15-20
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• 1997

This study is to investigate the behavior of fatigue crack growth with ATOS 55 steel which can be applied to the commercial car Dump Frame. It is to obtain the material coefficients after tensile and fatigue crack growth test with the variation of thickness or heat treatment. Also, that is proved the Pari's law by experiment. The summarized results are as follows ; 1) Increasing thickness, tensile and yield strength measured highly regardless to heat treatment and measured lowly as variation of heat treatment temperature. 2) Specimen of thickness 8.0㎜ measured the faster of crack growth rate than another thickness according to the results of experiment. It was the different of stress conditions in crack tip. 3) It was found that the experimental constant m was range of 2∼5 to the relationship between fatigue crack growth rate and stress intensity factor range. Also, it was to prove the Paris's law by the experiment.

• 한국표면공학회지
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• 제19권3호
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• pp.109-120
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• 1986

The electroless nickel plating on high alumina ceramics was performed in the bath containing nickel chloride, sodium hypophosphite and mono- or bi-carboxylic acid as a complexing agent in order to examine the empirical rate law as well as the effects of the complexing agent, plating temperature and pH on the rate of deposition. Adding the carboxylic acid to the plating bath, the rate of deposition was increased considerably, and each of the complexing agents showed a maximum deposition rate plateau around a particular concentration of the complexing agent. The rate of deposition was increased with increasing either temperature or pH, but microstructure of the surface became more rough. Furthermore, empirical rate law of the elecltroless nickel deposition on high alumina ceramics was discussed with the activation energy and other rate parameters calculated.

• Advances in aircraft and spacecraft science
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• 제9권3호
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• pp.243-261
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• 2022

Broad writing on the examination of sandwich structures mirrors the significance of incorporating thermal loadings during their investigation stage. In the current work, an endeavor has been made to concentrate on sandwich FGM beams' bending behaving under thermal loadings utilizing shear deformation theory. Temperature-dependent material properties are used during the analysis. The formulation includes the transverse displacement field, which helps better predict the behavior of thick FGM beams. Three-different thermal profiles across the thickness of the beam are assumed during the analysis. The study has been carried out on both symmetric and unsymmetric sandwich FGM beams. It has been observed that the bending behavior of sandwich FGM beams is impacted by the temperature profile to which it is subjected. Power-law exponent and thickness of core also affect the behavior of the beam.

• Steel and Composite Structures
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• 제16권1호
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• pp.77-96
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• 2014

In this paper, magneto-thermo-elastic problem of a thick truncated conical shell immersed in a uniform magnetic field and subjected to internal pressure is investigated. Material properties of the shell including the elastic modulus, magnetic permeability, coefficients of thermal expansion and conduction are assumed to be isotropic and graded through the thickness obeying the simple power law distribution, while the poison's ratio is assumed to be constant. The temperature distribution is assumed to be a function of the thickness direction. Governing equations of the truncated conical shell are derived in terms of components of displacement and thermal fields and discretised with the help of differential quadrature (DQ) method. Results are obtained for different values of power law index of material properties and effects of thermal load on displacement, stress, temperature and magnetic fields are studied. Results of the present method are compared with those of the finite element method.

• Nuclear Engineering and Technology
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• 제52권9호
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• pp.2041-2046
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• 2020

The present article investigates the influence of hydrogen concentration on the creep performance of cold-worked stress-relieved unirradiated Zircaloy-4 cladding tube using nanoindentation technique. The as-received Zircaloy-4 tube is hydrided to the concentrations of 600 ppm and 900 ppm using gaseous hydrogen charging method. Constant load indentation creep tests are performed for a dwell period of 600 s in the temperature range of 300℃-500 ℃ at 1000 μN, 2000 μN, and 3000 μN. The impact of hydrogen is evaluated in terms of steady state power law creep exponent and activation energy. The power law creep exponent decreases with increase in hydrogen concentration, however, it remains fairly constant with increase in temperature up to 500 ℃. Moreover, activation energy too decreases significantly with increase in hydrogen concentration. The mean stress exponent and activation energy are found to be 3.58 and 28.67 kJ/mol, respectively, for as-received sample.

• 대한기계학회논문집A
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• 제21권8호
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• pp.1175-1187
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• 1997

Densification behavior and grain growth of zirconia powder compacts are investigated under high temperature. Experimental data are obtained for zirconia powder under pressureless sintering, sinter forging and hot isostatic pressing. The constitutive equations by Kwon et al. are used for diffusional creep and grain growth. The constitutive equations by McMeeking and co-workers are also included to study the effect of power-law creep. These constitutive equations are implemented into a finite element program (ABAQUS) to investigate the friction effect during sinter forging and the canning effect during hot isostatic pressing. The agreements between experimental data and finite element results are very good in pressureless sintering and hot isostatic pressing, but not as good in sinter forging.