• Journal of Korean Society of Environmental Engineers
• /
• v.36 no.5
• /
• pp.342-351
• /
• 2014

The present paper investigates the performance of direct wet mineral carbonation technology to fix carbon dioxide ($CO_2$) from relatively high $CO_2$ concentration feeding gas using wollastonite ($CaSiO_3$)-water (and 0.46 M acetic acid) suspension solution. To minimize the energy consumed on the process, the carbonation in this work is carried out at atmospheric pressure and slightly higher room temperature. As a result, carbon fixation is confirmed on the surface of $CaSiO_3$ after carbonation with wollastonite-water suspension solution and its amount is increased according to the $CO_2$ composition in the feeding gas. The leaching and carbonation ratio of wollastonite-water suspension system obtained from the carbonation with 50% of $CO_2$ composition feeding gas is 13.2% and 10.4%, respectively. On the other hand, the performance of wollastonite-acetic acid in the same condition is 63% for leaching and 1.39% for carbonation.

• Journal of the Korea Concrete Institute
• /
• v.19 no.2
• /
• pp.153-161
• /
• 2007

This paper investigates the lap splice performance of structural steel bars embedded in high performance fiber reinforced cementitious composite(HPFRCC) with various matrix ductilities. Matrix ductility is governed fiber type and fiber volume fraction. Fiber types were polypropylene(PP), polyethylene(PE) and hybrid fiber[polyethylene fiber+steel cord(PE+SC)]. The lap splice length$(l_d)$ was calculated according to the relevant ACI code requirements for reinforcing bars in normal concrete. As the result of tests, lap splice strength of HPFRCC using PE1.5 and hybrid fiber increased by up to $82{\sim}91$ percent more than that of concrete. Splice strength and energy absorption capacity of PE0.75+SC0.75 or PE1.5(fiber volume fraction 1.5%) specimen increased more than that of PP2.0(fiber volume fraction 2.0%) specimen. Therefore lap splice performance depends on fiber tensile strength and Young's modulus more than fiber volume fraction. Also, HPFRCC appear multiple crack and ductile postpeak behavior due to bridging of fiber in cementitious composite.

• Journal of Radiation Protection and Research
• /
• v.32 no.1
• /
• pp.1-8
• /
• 2007

A model for radiological dose assessment in an urban environment, METRO-K has been developed. Characteristics of the model are as follows ; 1) mathematical structures are simple (i.e. simplified input parameters) and easy to understand due to get the results by analytical methods using experimental and empirical data, 2) complex urban environment can easily be made up using only 5 types of basic surfaces, 3) various remediation measures can be applied to different surfaces by evaluating the exposure doses contributing from each contamination surface. Exposure doses contributing from each contamination surface at a particular location of a receptor were evaluated using the data library of kerma values as a function of gamma energy and contamination surface. A kerma data library was prepared fur 7 representative types of Korean urban buildings by extending those data given for 4 representative types of European urban buildings. Initial input data are daily radionuclide concentration in air and precipitation, and fraction of chemical type. Final outputs are absorbed dose rate in air contributing from the basic surfaces as a function of time following a radionuclide deposition, and exposure dose rate contributing from various surfaces constituting the urban environment at a particular location of a receptor. As the result of a contaminative scenario for an apartment built-up area, exposure dose rates show a distinct difference for surrounding environment as well as locations of a receptor.

• Applied Chemistry for Engineering
• /
• v.24 no.3
• /
• pp.305-313
• /
• 2013

In this study, we investigated effects of thermal annealing on the thermal properties and microphase separation behaviors of glycidyl azide-based thermoplastic polyurethane elastomers (ETPE). The GAP-based ETPEs were characterized by attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and gel permeation chromatography (GPC). The effects of annealing temperature conditions ($80{\sim}130^{\circ}C$, 1 h or 24 h) on the properties of the ETPEs were investigated. The intensity of azide group absorption peak of ATR-FTIR spectra and the solubility of ETPE for methylene chloride and dimethylformamide solvent decreased after the annealing at $130^{\circ}C$ for 1 h and at $105^{\circ}C$ for 24 h. With increasing the annealing temperature from $80^{\circ}C$ to $110^{\circ}C$, the high temperature rubbery plateau region of storage modulus curves from DMA thermogram for GAP-based ETPEs was extended to the higher temperature.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.3
• /
• pp.32-38
• /
• 2020

This study examined the problems of existing vehicles to propose alternatives to improve the crashworthiness of railway freight cars through collision acceleration analysis using a one-dimensional collision analysis method. A collision scenario of railway shunting and crash accidents was selected from the collision accident cases and international standards. A one-dimensional collision simulation using LS-DYNA was performed according to those scenarios. As a result, the acceleration level of the freight wagon was calculated to be under 2g and was predicted to meet the EN 12663 standard in the shunting situation. On the other hand, the result of crash simulation with an impact velocity between 10 and 15 km/h revealed the shock absorber capacity of the railway coupler to be insufficient in a crash situation, resulting in increased acceleration, and carbody deformation could be predicted. As a method of improving the crashworthiness, a deformation tube-type energy absorber was applied to the coupler system, and collision analysis was performed again with new energy absorption strategy. Overall, the simulation showed that the acceleration level was decreased by 12% of the conventional freight-car energy absorption system.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.119-120
• /
• 2011

Kawazoe는 1997년 p-type TOS를 만들기 위해서는 3가지가 충족되어야 한다고 언급한바 있다. 첫 번째, 가시광영역에서 투명하기 위해서 cation의 d10s0이 가득 차야 한다. 가득 차지 않은 d10 shell은 광 흡수가 가능하여 투과도를 떨어뜨린다. N-type을 예로 들어 ZnO, TiO, In2O3가 각각 Zn2+, Ti4+, In3+가 되어 d shell을 가득 차게 만드는 것을 볼 수 있다. 두 번째, cation d10s0 shell은 산소의 2p shell과 overlap 되어야 한다. 이 valence band는 홀 전도를 더욱 좋게 한다. 예를 들어 Cu1+(3d), Ag1+(4d)가 해당한다. 세 번째로, 양이온과 산소간의 공유결합을 강하게 하기 위해서 결정학적 구조는 매우 중요하다. Delafossite 구조는 산소가 pseudo-tetrahedral 구조로서 공유결합에 유리하다. 이러한 환경은 O2- (2p6)을 형성하고 홀의 이동도를 증가시킨다. 예를 들어 Cu2O의 경우 앞의 2가지를 만족시키지만 광학적 특성에서 좋지 않다. 그 이유가 3번째 언급한 결정학적인 요인에 있다. 결정 계의 환경은 Cu2O를 따라가면서 3차원적인 연결을 2차원적으로 변형된 delafossite 구조에서는 quantum well이 형성되어 band gap이 커진다. 본 연구에서는 전기적 이방성을 가지고 있는 delafossite CuCrO2 상에서 우선배향을 일으키는 인자 중 기판을 변화시켜 실험을 진행하였다. 결과적으로 기판변화를 통해 우선배향조절이 가능하였으며 CuCrO2 박막을 시켰으며, 결정방향에 따른 전기적 물성의 이방성에 관한 연구는 계속 진행 중에 있다. c-plane sapphire 기판위에는 [00l]로 성장하는 반면, c-plane STO 기판 위에는 [015] 방향으로 성장하는 것을 확인하였다. 이러한 원인은 기판과 증착되는 박막간의 mismatch를 최소화 하여 strain을 줄이고, 계면에서의 Broken boning 수를 줄여 계면에너지를 낮추는 방법이기 때문일 것으로 예상된다. C-plane sapphire 기판위에 증착될 경우 증착온도가 증가함에 따라 c-축으로의 성장이 온전해지며 이에 따라 캐리어농도의 감소와 모빌리티의 증가가 급격하게 변하는 것을 확인할 수 있다. 반면 c-plane STO 기판에서는 증착온도에 따른 박막의 배향변화가 없으며 전기적 물성 변화 또한 비교적 작은 것을 간접적으로 확인하였다.

• Korean Journal of Optics and Photonics
• /
• v.28 no.4
• /
• pp.153-157
• /
• 2017

An infrared camera and laser common-path optical system is applied to DIRCM (directional infrared countermeasures), to increase boresighting accuracy and decrease weight. Thermal effects of a laser beam in a common-path optical system are analyzed and evaluated, to predict any degradation in image quality. A laser beam with high energy density is absorbed by and heats the optical components, and then the surface temperature of the optical components increases. The heated optical components of the common-path optical system decrease system transmittance, which can degrade image quality. For analysis, the assumed simulation condition is that the laser is incident for 10 seconds on the mirror (aluminum, silica glass, silicon) and lens (sapphire, zinc selenide, silicon, germanium) materials, and the surface temperature distribution of each material is calculated. The wavelength of the laser beam is $4{\mu}m$ and its output power is 3 W. According to the results of the calculations, the surface temperature of silica glass for the mirror material and sapphire for the lens material is higher than for other materials; the main reason for the temperature increase is the absorption coefficient and thermal conductivity of the material. Consequently, materials for the optical components with high thermal conductivity and low absorption coefficient can reduce the image-quality degradation due to laser-beam thermal effects in an infrared camera and laser common-path optical system.

• Journal of the Korean Wood Science and Technology
• /
• v.37 no.4
• /
• pp.330-339
• /
• 2009

The material properties of Cedar (Cryptomeria japonica) were evaluated according to heat treatment conditions. The special focus was made on the color control of cedar wood by heat treatment. The difference of color between sapwood and heartwood could be reduced by heat treatment at a temperature above $170^{\circ}C$. Long heating time was more effective in reducing the difference. The Equilibrium Moisture Content (EMC) of heat-treated wood was as low as 50 percent. The result obviously indicates that heat-treated wood is more dimensionally stable in the change of moisture condition than the control. The heat-treated wood was also effective in increasing the durability against wood rotting fungi. However, more study is required to develop heat treatment as an environmentally-friendly technology for wood preservation without chemical. The mechanical properties of heat-treated wood showed relatively higher performance than the control in general. Meanwhile the dramatic decrease in impact bending stress due to the loss of ductility may limit uses of heat-treated wood in certain cases. There were no significant changes in microscopic structure which may cause changes in mechanical properties. Further study on the chemical analysis of heat-treated wood is needed to scrutinize the causes of changes of material properties.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.15 no.5
• /
• pp.175-181
• /
• 2005

Ingots of rutile single crystals were grown by the skull melting method, and their characteristics were compared in terms of melt-dwelling time for each melt. The method is based on direct inductive heating of an electrically conducted melt by an alternating RF field, and the heating is performed by absorption of RF energy. $TiO_2$ is an insulator at room temperature but its electric conductivity increases elevated temperature. Therefore, titanium metal ring(outside diameter : 6cm, inside diameter : 4cm, thickness 0.2cm) was embedded into $TiO_2$, powder (anatase phase, CERAC, 3N) for initial RF induction heating. Important factors of the skull melting method are electric resistivity of materials at their melting point, working frequency of RF generator and cold crucible size. In this study, electric resitivity of $TiO_2$, $(10^{-2}\~10^{-1}\;{\Omega}{\cdot}m)$ at its melting point was estimated by compairing the electric resitivities of alumina and zirconia. Inner diameter and height of the cold crucible was 11 and 14cm, respectively, which were determined by considering of the Penetration depth $(0.36\~1.13cm)$ and the frequency of RF generator.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.7 no.2
• /
• pp.99-106
• /
• 1987

Annealing were performed to investigate the behaviors of the residual stress remaining on the member of a steel structure. According to the fatigue test, the welding part has higher fatigue crack growth rate than the base metal part because the hardening of welding part reduce fracture toughness. However, the heat treatment decrease the hardness and increase the resistance to failure. Thus, the fatigue crack growth rate is improved and it reaches the minimum at $650^{\circ}C$. Elber' s equation includes the effect of the crack-close so that this equation provides a lower the fatigue crack growth rate than Paris-Erdogan' s equation, the Elber's curves show no significant difference to indentify the effect of the residual stress. The Pop loading along the crack length increases as the hardness goes higher. The heat treatment not only decrease the hardness, and the fatigue crack growth rate, but increase the absorption energy and fracture toughness on the member of a steel structure. As the result, the heat treatment produces the resistant ability to cracking which can reduce the degree of danger to failure.