• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1158-1166
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• 2013

SAR calculation method following the Mobi-Kids study protocol is analyzed and evaluation method of cumulative RF dose from mobile phones which have been used by a subject of case and control groups is proposed. An SAR database is built by calculating SAR distributions in 4 head models at different ages for representative phone models with the same conducted power. To obtain SAR distribution in a subject's head for a specific commercial phone which had/have been used by him/her, an SAR correction factor using SAR compliance test results is determined. Cumulative dose is calculated by considering mobile phone characteristics and use pattern such as call time and laterality(right and left).

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.4
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• pp.483-490
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• 2010

The objectives of this study were to measure particle size and evaluate the effect of increasing alfalfa hay particle size on production characteristics in lactating Holstein dairy cows. Ninety multiparous Holstein cows in early to mid-lactation were randomly assigned in a complete randomized design for a 30-day period. Animals were offered one of the three diets, which were identical in energy, protein, and chemical composition, but differed only in particle size of alfalfa hay. The treatments were A) total mixed ration (TMR) in which only fine chopped alfalfa hay was incorporated in the ration, B) the same diet in which half of the alfalfa hay was fine chopped and incorporated in the mixed ration and half was long hay and offered as a top dressing, and C) the same diet with long hay alfalfa offered as a top dressing. Distribution of particle size of rations was determined through 20,000, 8,000 and 1,000 ${\mu}m$ sieves. The new method of quantitative determination of manure index was examined for each cow on different treatments. The geometric mean length of particle size in the rations was 5,666, 9,900 and 11,549 ${\mu}m$ for treatments A, B and C, respectively. Fat corrected milk (4%), milk fat percentage and production were significantly different (p<0.05) in treatment A versus B and C (fat corrected milk (FCM, 4%)) 28.3 vs. 35.2 and 32.3 kg/d, fat percentage 2.89, 4.04 and 3.62; but the change of ration particle size had no significant effect on milk production (p>0.05). Blood concentration of cholesterol in treatment A was significantly higher (p<0.05) than treatment B and C (181.0 vs. 150.0 and 155.2 mg/dl). Manure index in treatment C was significantly different (p<0.05) from treatment B (15.86 vs. 17.67). Based on these experimental findings, it is concluded that an increase in the ration particle size can increase milk fat percentage due to providing more physically effective fiber, which in turn could effect changes in manure consistency.

• Journal of computational fluids engineering
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• v.21 no.2
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• pp.112-119
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• 2016

NEXTSat-1 is the next-generation small-size artificial satellite system planed by the Satellite Technology Research Center(SatTReC) in Korea Advanced Institute of Science and Technology(KAIST). For the control of attitude and transition of the orbit, the system has adopted a RHM(Resisto-jet Head Module), which has a very simple geometry with a reasonable efficiency. An axisymmetric model is devised with two coil-resistance heaters using xenon(Xe) gas, and the minimum required specific impulse is 60 seconds under the thrust more than 30 milli-Newton. To design the module, seven basic parameters should be decided: the nozzle shape, the power distribution of heater, the pressure drop of filter, the diameter of nozzle throat, the slant length and the angle of nozzle, and the size of reservoir, etc. After quasi one-dimensional analysis, a theoretical value of specific impulse is calculated, and the optima of parameters are found out from the baseline with a series of multi-physical numerical simulations based on the compressible Navier-Stokes equations for gas and the heat conduction energy equation for solid. A commercial code, COMSOL Multiphysics is used for the computation with a FEM (finite element method) based numerical scheme. The final values of design parameters indicate 5.8% better performance than those of baseline design after the verification with all the tuned parameters. The present method should be effective to reduce the time cost of trial and error in the development of RHM, the thruster of NEXTSat-1.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.7
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• pp.589-594
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• 2014

Recently, higher capacity and energy density of lithium ion batteries are increasingly demanded for enhancing their performance in view of the rise in the commercial distribution of electric and hybrid vehicles. Computational analysis of a porous structure of vanadium pentoxide cathode was performed, employing a phase field model. The incipient model was designed as a spherical structure with cylindrical-shaped pores. Modifying the diameters and lengths of the pore cylinder and the number of pores, we considered different conditions for the porous vanadium pentoxide cathodes for analyzing their effect on the amount of lithium ion intercalated to them. Subsequently, we optimized the porous structure to contain the largest amount of intercalated lithium ion during discharge.

• The Journal of Engineering Geology
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• v.14 no.2
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• pp.147-168
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• 2004

Purpose of this study is to quantitatively characterize the fracture roughness which was measured with a confocal laser scanning microscope. The roughness discrete data measured by confocal laser microscope were analyzed by spectral analysis and fast Fourier transform (FFT).The roughness data by used noise reduction filter were applied for fractal analysis to describe roughness features quantitatively. Artificial fractures created by Brazilian test on granites were used to measure fracture roughness under the confocal laser scanning microscope. Measurements were performed along three scan lines on each fracture surface. 36 scan lines were determined on 12 specimens in total. Features of roughness showed that coarse and medium grained granites tend to more rough features than those of fine grained granites. Continuous analog data of roughness is possible to described as discrete data of measure roughness with a fixed interval under the confocal laser microscope. Results of FFT with the measured data showed the highest values on the second harmonics. Distribution of average amplitude of second harmonics was observed 0.9853 in coarse grained granite, 1.0792 in medium grained granite and 0.6794 in fine grained granite. This indicates that the larger roughness has the higher energy of harmonics as the result of fractal analysis in low frequency zone.

• Journal of Sensor Science and Technology
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• v.23 no.4
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• pp.245-250
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• 2014

When the charged particle travels in transparent medium with a velocity greater than that of light in the same medium, the electromagnetic field close to the particle polarizes the medium along its path, and then the electrons in the atoms follow the waveform of the pulse which is called as Cerenkov light or radiation. This type of radiation can be easily observed in a spent fuel storage pit. In optical fibers, the Cerenkov light also can be generated due to their dielectric components. Accordingly, the radiation-induced light signals can be obtained using optical fibers without any scintillating material. In this study, to measure the intensities of Cerenkov radiation induced by gamma-rays, we have fabricated the fiber-optic Cerenkov radiation sensor system using silica optical fibers, plastic optical fibers, multi-anode photomultiplier tubes, simulated spent fuel assembly and a scanning system. To characterize the Cerenkov radiation generated in optical fibers, the intensities of Cerenkov radiation generated in the silica and plastic optical fibers were measured. Also, we measured the longitudinal distribution of gamma rays emitted from the Ir-192 isotope by using the fiber-optic Cerenkov radiation sensor system and simulated spent fuel assembly.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.195-204
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• 2012

Biomineralization has been explored for geochemical cycles and microbial tolerance mechanisms to metal toxicity. Here, we are introducing NanoFermentation which enables economic, environmentally friendly, requiring low input energy, and scalable manufacturing of nano-dimensioned magnetite. We are also focusing on controlling factors of crystallite size which can determine superparamagnetism and ferrimagnetism. Controlling factors are such as microbial species, temperature, incubation time, medium composition, substituted elements and their concentration, precursor type, reaction volume, precursor concentration density and their combinations. Crystallite size distribution of biomagnetite depends on the balance between nuclei generation and crystal growth. Biomineralization will elucidate elemental cycles on earth crust and microbial ecology as well as it will be applied to material sciences and devices via massive production of nanomaterials.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.12
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• pp.1171-1179
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• 2008

LES analysis was conducted with in-house CFD code to investigate the turbulence evolution and interaction due to turbulence ring and splash plate in the gas generator. The calculation results show that the installation of turbulence ring can introduce additional turbulences and significantly improve turbulent mixing in the downstream flow. However, the addition of splash plate in the downstream of TR(Turbulence Ring) brings totally different shape of perturbation energy and enstrophy distribution into turbulent mixing. This enhancement can be done by the formation of the intensively strong vorticity and mixing behind the plate. Pressure drop was found to be a reasonable level of about 1% or less of initial pressure in all calculation cases. Also, calculation results revealed that the variation of shape and intrusion length of TR did not greatly affect the characteristics of turbulent mixing in the chamber. Even though the effect of installation location of splash plate on the turbulent mixing was not investigated yet, calculation results conclude the addition of splash plate leads to the increase in turbulent mixing with an acceptable pressure drop.

• The Korean Journal of Food And Nutrition
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• v.25 no.4
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• pp.762-769
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• 2012

In order to study the cooking characteristics of four rice cultivars of Seolhyangchal, Baegjinju, Ilpum and Haiami, we investigated the relationship between the textures of cooked rice and their physicochemical properties. Different levels in grain weight. length/width ratio and amylose content were observed among the four rice cultivars. There was no significant difference in the amylopectin chain length distribution among the cultivars. Water absorptions of rice grains during soaking were completed between 30 and 40 min, with Haiami showing the slowest absorption. Significant differences in the viscosity properties of rice flour were found by a Rapid Visco Analyser. Baegjinju with low amylose content had the highest viscosity in paste breakdown. According to the DSC results of rice starches, there were significant differences in the onset, peak and conclusion temperatures of the endothermic peak. Gelatinization enthalpy showed energy content changes between 4.20 and 6.97 J/g, with the lowest change in Haiami. Texture properties of cooked rice were assessed using a Texture Analyzer, which showed that the hardness of cooked rice was decreased with soaking than without soaking. However, this finding was not applicable for Haiami rice.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.147-158
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• 2004

For stiffened plates composed of composite materials, many researchers have used a finite element method which connected isoparametric plate elements and beam elements. However, the finite element method is difficult to reflect local behavior of stiffener because beam elements are transferred stiffness for nodal point of plate elements, especially the application is limited in case of laminated composite structures. In this paper, for analysis of laminated composite stiffened plates, 3D shell elements for stiffener and plate are employed. Reissner-Mindlin's first order shear deformation theory is considered in this study. But when thickness will be thin, isoparamatric plate bending element based on the theory of Reissner-Mindlin is generated by transverse shear locking. To eliminate the shear locking and virtual zero energy mode, the substitute shear strain field is used. A deflection distribution is investigated for simple supported rectangular and skew stiffened laminated composite plates with arbitrary orientation stiffener as not only variation of slenderness and aspect ratio of the plate but also variation of skew angle of skew stiffened plates.