• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.64-70
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• 2007

Preparation and characterization of carbon-slurry fuel with high dispersion have been carried out. Carbon-slurry fuel was obtained by mixing Jet A-1 liquid fuel with appropriate carbon powders and additives. Dispersion of carbon in Jet A-1 was affected by various factors such as mixing temperature, characteristics of carbon powders, and type and amount of additives. Among these factors, the stability of the slurry fuel was most dependent on the type of additive. A variety of additives such as anionic, cationic, and nonionic additives was tested for the dispersion of carbon in Jet A-1. It was found that anionic additives based on sodium salts showed the highest dispersion of carbon-slurry fuels. The degree of dispersion could be monitored by measuring the luminosity.

• Korean Journal of Materials Research
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• v.5 no.5
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• pp.598-605
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• 1995

Thin films of $YB_{2}Cu_{3}O_{7-d}$ were prepared on various substrated of MgO(100), $SrTiO_{3}$, and $LaAlO_{3}$ by using off-axis magentron sputtering methods and annealing in-situ. The prarameters of film fabrication processes had been optimized through a "follow the lcoal maxima" strategy to yield good quality films in therms of the critical temperature $T_{c}$ and the critical current density $J_{c}$. Optimizedproecsses employing a plane magndtron and an cylindrical magnetron yielded $T_{c}$>90K along with $J_{c}$$10^{6}$A/$\textrm{cm}^2$ at 77K and > 2${\times}$$10^{7}$A/$\textrm{cm}^2$ at 5K. The sampels, however, showed degradationinthe properties, after chemical etching for fabrication of microbridges with the line width of 2-10 mocrons. In particular, the value of $T_{c}$ for the microbridges of 2microns was as small as 80%. The degradation was strongly dependent on the line width through a formula : $T_{c}$(e)=$T_{c}$)b) [1-a exp(-1000 bL)} where $T_{c}$(e) and $T_{c}$ (b) are the values of $T_{c}$ in the absolute scale measured after and before chemical etching, respectively and L is the line width in mm. By utilizing a best fitting technique, the proper constant values of a and to b were found as exp(-1.2) and 0.22, respectively. This formula was very useful in estimatiing the upper limit of the device operationtemperature.

• Smart Structures and Systems
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• v.20 no.6
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• pp.709-728
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• 2017

This disquisition proposes a nonlocal strain gradient beam theory for thermo-mechanical dynamic characteristics of embedded smart shear deformable curved piezoelectric nanobeams made of porous electro-elastic functionally graded materials by using an analytical method. Electro-elastic properties of embedded curved porous FG nanobeam are assumed to be temperature-dependent and vary through the thickness direction of beam according to the power-law which is modified to approximate material properties for even distributions of porosities. It is perceived that during manufacturing of functionally graded materials (FGMs) porosities and micro-voids can be occurred inside the material. Since variation of pores along the thickness direction influences the mechanical and physical properties, so in this study thermo-mechanical vibration analysis of curve FG piezoelectric nanobeam by considering the effect of these imperfections is performed. Nonlocal strain gradient elasticity theory is utilized to consider the size effects in which the stress for not only the nonlocal stress field but also the strain gradients stress field. The governing equations and related boundary condition of embedded smart curved porous FG nanobeam subjected to thermal and electric field are derived via the energy method based on Timoshenko beam theory. An analytical Navier solution procedure is utilized to achieve the natural frequencies of porous FG curved piezoelectric nanobeam resting on Winkler and Pasternak foundation. The results for simpler states are confirmed with known data in the literature. The effects of various parameters such as nonlocality parameter, electric voltage, coefficient of porosity, elastic foundation parameters, thermal effect, gradient index, strain gradient, elastic opening angle and slenderness ratio on the natural frequency of embedded curved FG porous piezoelectric nanobeam are successfully discussed. It is concluded that these parameters play important roles on the dynamic behavior of porous FG curved nanobeam. Presented numerical results can serve as benchmarks for future analyses of curve FG nanobeam with porosity phases.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.2
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• pp.66-73
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• 2017

This study was to evaluate the influential parameters such as intial Cs concentration, reaction temperature, contact time and pH variation of solution on Cs adsorption. Using the experimental data, adsorption kinetics, isotherms and thermodynamic properties were analyzed. The Cs ion adsorption of the zeolite X was effective in the range from pH 5 to 10 and reached equilibrium after 60 minutes. The adsorption kinetics and isotherms of Cs ion with the zeolite X was described well by the pseudo-second-order kinetic and Langmuir isotherm model. The maximum adsorption capacities of Cs ion calculated from Langmuir isotherm model at 293~333 K were from 303.03 mg/g to 333.33 mg/g. It was found that thermodynamic property of Cs ion absorption on the zeolite X was spontaneous and endothermic reaction. The experimental data were fitted a second-order polynomial equation by the multiple regression analysis. The values of the dependent variable calculated by this best fitted model equation were in very good agreement with the experimentally obtained values.

• Korean journal of food and cookery science
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• v.24 no.2
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• pp.188-197
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• 2008

This study was carried out to determine the optimal cooking conditions for various rice cultivars (Ilpoom, Saechucheong, Sindongjin, and Sura-top rice) using trial preparations with different soaking times (0, 30, and l20min) and cooking equipment (electric pressure cookers, electric cookers, gas pressure cookers, iron pots, and stone pots). In adddition, the texture and sensory characteristics of the rice prepared with the electric pressure cookers, gas pressure cookers, and stone pots were analyed. The results showed that the moisture, amylose and physicochemical compositions of the four rice varieties were similar. According to RVA, the Sura, cultivar had generally high viscosity, and the Ilpoom, cultivar presented the highest hot and peak viscosities. Saechucung had the highest initial gelatinizing temperature and Sindongjin showed the greatest setback. The optimal amounts of added water as well as heating conditons were dependent on the rice varieties, soaking times, and cooking equipment. A longer soaking time reduced the hardness of the cooked rice, amount of added water, and the heating time. The pressure cooking equipment provided the best cooked rice texture, reduced the affect of the soaking time, and decreased the heating time. In general, all the variaties of cooked rice had high overall acceptability, which tended to increase when the rice was soaked for 30min prior to cooking, had a 1.2-fold amount of water to rice added, and was cooked in the pressure equipment.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.749-754
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• 2006

This study performed of a water cooling system by using a steam ejector and jet condenser to drop the temperature of the water in aquafarm by about $5^{\circ}C$ from $25^{\circ}C$ or higher in this research, to replace the present water cooling system, Ive focused on a water cooling system operated by latent heat of evaporation, thus this system needs a vacuum pressure to evaporate the water in enclosed tank. The water cooling effects are dependent on the vacuum pressure in the enclosed tank, and the cooling water is generated by evaporation. As the experimental results, the absolute vacuum pressure obtained was about $5{\sim}8mmHg$ using a steam driven ejector with jet condenser in experiments. The obtained results are respectively ${\Delta}T=7^{\circ}C$, ${\Delta}T=5^{\circ}C$ and ${\Delta}T=5.5^{\circ}C$ at heat exchanger flow rate 4L/M. The obtained results are respectively ${\Delta}T=5.5^{\circ}C$, ${\Delta}T=5.5^{\circ}C$ and ${\Delta}T=5.5^{\circ}C$ at heat exchanger flow rate 4.5L/M.

• Journal of the Optical Society of Korea
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• v.17 no.6
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• pp.548-558
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• 2013

In this work, laser induced breakdown spectroscopy (LIBS) is used to investigate soil samples collected from different desert areas of Riyadh city in Saudi Arabia. Both qualitative analysis and plasma parameters are studied via the observed LIBS spectra. These experiments have been done using a Spectrolaser-7000 system with 50 mJ fundamental wavelength of Nd:YAG laser and detection delay time of 1 microsecond. Many spectral lines are highly resolved for many elements like Al, Fe, Mg, Si, Mn, Na, Ca and K. The electron temperatures Te and electron densities Ne, for the constituent of generated LIBS plasma, are determined for all the collected samples. It is found that both Te and Ne vary from one desert area to other. This variation is due to the change of the elemental concentration in different desert areas that affects the sample's matrices. Time dependent measurements have also been performed on the soil samples. While the signal-to-base ratio (SBR) reached its optimal value at 1 microsecond, the plasma parameters Ne and Te reach values of $4{\times}10^{17}cm^{-3}$ and 9235 K, respectively, at 2.5 microsecond. The later indicate that the plasma cooling processes are slow in comparison to the previously observed results for metallic samples. The observed results show also that in the future it is possible to enhance the exploitation of LIBS in the remote on-line environmental monitoring application, by following up only the values of Ne and Te for one element of the soil desert sample using an optical fiber probe.

• Analytical Science and Technology
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• v.20 no.5
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• pp.370-382
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• 2007

In this study, solid-phase microextraction (SPME) technique using GC/FID was studied as a possible alternative to liquid-liquid extraction for the analysis of EGBE, DGBE, DBM and TGME in water, and an optimization condition of trace analysis of EGBE, DGBE, DBM and TGME using the factorial design was described. Experiments used a fractional factorial design method followed by central composite design allowing optimization of a number of factors as well as statical analysis of results. The response surface analysis showed that the extraction efficiency can be described by a second-order polynomial equation in which the salts concentration, extraction temperature, extraction time and sonication time are the major influences. Using DOE, a new data-dependent method was developed that improved the quantity of confidently analyzed EGBE, DGBE, DBM and TGME in water samples.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.10
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• pp.973-978
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• 2010

The emission of volatile organic compounds (VOCs) from building materials is one of great concerns due to maintain airtight condition of a building to reduce energy consumption, and it causes the deterioration of indoor air quality. Therefore, the emission characterization of VOCs from building materials is necessary to improve indoor air quality. Emission characteristics of VOCs from a plywood flooring that is one of the most commonly used materials in an under-heating system, and from an adhesive that is generally used to stick a plywood flooring to a concrete floor were investigated using an emission chamber test in this study. It was found that the VOCs emission factor was dependent upon and proportional to indoor temperature, and the emission characteristics were closely related to the existing places and conditions of VOCs sources inside the building materials. Maximum emission factors of hexane and toluene from building materials were generally observed at the beginning, however, only that of toluene from a plywood flooring was shown after 6 hours from the beginning. It could be considered that the existing place and condition of toluene source inside a plywood flooring could influence on the VOCs emission. From this study, bake-out time more than 72 hours could be recommended before moving in to avoid the exposure to high concentration of VOCs emitted from an under-heating system.

• Journal of Climate Change Research
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• v.4 no.1
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• pp.41-49
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• 2013

Recent findings have revealed that black carbon is one of the substantial materials affecting climate change along with greenhouse gases. Usually, black carbon is generated by incomplete combustion of biomass and deposited on snow and ice surface, resulting in increasing adsorption of radiant energy and accelerating ice melting. However, it is still questionable what the emission characteristics of black carbons from biomass combustion is. We investigated the emission characteristics of black carbon generated from a wood stove in this study. We found that the emission of black carbon was highly dependent upon combustion temperature and the amount of combustion air supplied. The emission factors were 1.01 g-BC/kg-Oak for fireplace wood burning under incomplete combustion, 0.37 g-BC/kg-Oak for fireplace wood burning under complete combustion and 0.29 g-BC/kg-Oak for small wood-stove burning.