• Fire Science and Engineering
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• v.33 no.4
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• pp.35-40
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• 2019

In this study, the mass flow rate of the heat release rate equation, which is the major factor of the oxygen consumption method, was analyzed for the fundamental investigation of the cone-calorimeter (5 m length and 0.3 m diameter). The shapes of a completely empty inside, 3 mm pore diameter mesh and pore diameter 10 mm honeycomb with 0.76 porosity were constructed using the cone-calorimeter. To calculate the mass flow rate, four bi-directional probes and thermocouples were installed in a uniform position in the vertical direction of flow. The velocity gradient and flow perturbation were measured from the increase in Reynolds number. As the flow capacity increased, the speed gradient increased in all three shapes relative to the turbulence intensity. In addition, the deviation of extended uncertainty to the mass flow was completely low in the order of empty space, mesh (d_p = 3 mm) and honeycomb (d_p = 10 mm and 𝜖 = 0.76) at the 95% confidence level. The results can be used in designs to improve the flow stability of the cone calorimeter.

• Journal of Korean Society of Forest Science
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• v.88 no.1
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• pp.38-46
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• 1999

Canopy structure conductances of a Norway spruce forest in the Solling Hills(Central Germany) and Central Forest Biosphere Reserve(320km to the north-west from Moscow) were derived from LE(latent heat flux) and H(sensible heat flux) fluxes measured(by Eddy correlation technique and energy balance method) and modelled(by one dimensional non-steady-state) SVAT(soil-vegetation-atmosphere-transfer) model(SLODSVAT) using a rearranged Penman-Monteith equation("Big-leaf" approximation) during June 1996. They were compared with canopy stomatal conductances estimated by consecutive intergrating the stomatal conductance of individual needles over the whole canopy("bottom-up" approach) using SLODSVAT model. The result indicate a significant difference between the canopy surface conductances derived from measured and modelled fluxes("top-down" approach) and the stomatal conductances modelled by the SLODSVAT("bottom-up" approach). This difference was influenced by some nonphysiological factors within the forest canopy(e.g. aerodynamic and boundary layer resistances, radiation budget, evapotranspiration from the forest understorey). In general, canopy surface conductances derived from measured and modelled fluxes exceeded canopy stomatal conductance during the whole modelled period, The contribution of the understorey's evapotranspiration to the total forest evapotranspiration was small (up to 5-9% of the total LE flux) and was not depended on total radiation balance of forest canopy. Ignoring contribution of the understorey's evapotranspiration resulted in an overestimation of the canopy surface conductance for a spruce forest up to 2mm/s(about 10-15%).

• Membrane Journal
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• v.12 no.1
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• pp.41-50
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• 2002

The streaming potential generated by the electrokinetic flow within electric double layer of charged microchannel is applied to determine the zeta potential of hollow-fiber membrane pore by using the general Helmholtz-Smoluchowski equation. The streaming potential is know to provide a useful real-time information on the surface property and the interaction between pore and particles in actual situations and physicochemical conditions. The influence of physicochemical parameters upon the filtration with hollow-fibers has been examined with an in-situ and simultaneously monitoring the streaming potential as well as permeate flux. In particular, the present study examined an experimental method to identify the effect of cake layer which can vary according to the axial position of a hollow-fiber and the progress of membrane fouling by measuring the position-dependent streaming potential. As the latex concentration increases, the permeate flux decreased but the streaming potential increased. The growth of cake layer has been mire developed with increasing latex concentration, however, the effect of surface charges of latexes deposited on the membrane surface leads to increase the streaming potential. With increasing ionic concentration of KCI, both the permeate flux and the streaming potential decrease. The increase of ionic concentration provides a compact cake layer due to the shrinkage of Debye length and the decreased streaming potential results from the weakened ionic flows owing to a thin diffusive double layer.

• Journal of Ginseng Research
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• v.26 no.2
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• pp.85-88
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• 2002

This study was carried out to obtain information of the photosynthetic rate at various temperature and light intensity, stomata, chlorophyll, specific leaf weight, characteristics of aerial part and root in ginseng new cultivars developed by pure line selection. The light saturation point of leaves in new cultivars and Jakyungjong were 15,000 lux, and the optimum air temperature on the photosynthesis of new cultivars and Jakyungjong were 20$\^{C}$. The photosynthetic rates were increased in order of Jakyungjong, Gopoong, Chunpoong and Yunpoong. The dark respiration rate of leaves in ginseng cultivars were increased according to the increasing of temperature, and the dark respiration rate of leaves of Yunpoong was the highest among cultivars. The specific leaf weight (SLW) were increased in order of Jakyungjong, Yunpoong, Gopoong, Chunpoong, but total chlorophyll contents were not different among cultivars. Stomata frequency of Yunpoong was the highest being 69.2ea among cultivars, while the length of stomata was reverse. Yunpoong was superior in aerial part among ginseng cultivars : the number of stem was 1.8ea, the number of palmately leaves was 7.7ea, the number of leaflets was 41.0ea, leaf area was 12.3 dm$^2$ The root weight were increased in order of Jakyungjong, Gopoong, Chunpoong and Yunpoong. Chunpoong and Gopoong hove good root shape the length of tap root in Chunpoong and Gopoong were the longest being 6.5 cm and 6.8 cm respectively, but that in Yunpoong was the shortest being 4.4 cm.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.24 no.2
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• pp.101-121
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• 2015

Zirconia polycrystalline (Y-TZP) showed better mechanical properties and superior resistance to fracture than other conventional dental ceramics. Zirconia-based ceramics have been successfully introduced into the clinic to fabricate fixed dental prostheses (FDPs), along with a dental computer-aided/computer-aided manufacturing (CAD/CAM) system. It has been clinically available as an alternative to the metal framework for fixed dental prostheses (FDPs). The most frequent clinical complication with zirconia-based FDPs was chipping of the veneering porcelain that was affected by many factors. Another option was full-contour zirconia FDPs using high translucent zirconia. Full-contour zirconia FDPs has many clinical advantages but it caused concern about the wear of antagonist enamel, because the hardness of Y-TZP was over double that of porcelain. However, many articles demonstrates that highly polished zirconia yielded lower antagonist wear compared with porcelains. In this article (1) advantages of full zirconia restorations, (2) clinical applications of zirconia restorations, (3) abutment preparation, (4) surface finish of zirconia restoration and antagonist enamel wear, (5) bond of zirconia with resin-based luting agents, (6) communication in clinical & lab.procedures for full zirconia restorations are reviewed.

• Journal of Applied Tourism Food and Beverage Management and Research
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• v.16 no.2
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• pp.1-15
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• 2005

This study was intended to make Korean type of sourdough bread using domestic wheat produced in Korea, while measuring and analyzing gluten content, pH level, TTA level and mixograph of wheat to extract the most excellent sourdough starter. Furthermore, this study also used CrumbScan to compare and analyze the properties of product as shown in making sourdough bread with the above starter. pH level ranged from 4.0 to 4.5 throughout all kinds of Korean wheat four, which were considered to be appropriately available as sourdough starter. As the result of analysis from mixogram, SF fit for making bread but korean wheat flour showed less level of mixing tolerance and content of protein, which were considered inappropriate for making bread. As the result of imaging analysis by CrumbScan, SF, KWF 5 and KWF 6 showed the higher fineness and elongation than any other kind of korean wheat flour, which were considered appropriate for making bread.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.264-269
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• 2012

Die slide injection marvelously reduces the cost and time in processing plastic products because they can simplify the conventional process through eliminating additional process. However, this process must resolve some defects like whitening, resin infiltration, blowhole, resin overflow, etc. In this study, the process parameters of the injection molding are optimized by using the finite element method and Taguchi method. The injection molding analysis is simulated by employing the Moldflow insight 2010 code and the 2nd injection is by adopting the Multi-stage injection code. The process parameters are optimized by using the $L_{16}$ orthogonal array and smaller-the-better characteristics of the Taguchi method that was used to produce an airtight container (coolant reservoir tank) from polypropylene (PP) plastic material.rodanwhile, the optimum values are confirmed to be similar in 95% confidence and 5% significance level through analysis of variance (ANOVA). rooreover, new products and old products were compared by mdasuring the dimensional accuracy, resulting in the improvement of dimensional stability more than 5%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.235-240
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• 2010

Transpiration cooling is the most effective cooling technique for liquid rocket and air-breathing engines operating in aggressive environments with higher pressures and temperatures. Combustor liners and turbine vanes are cooled by the coolant(air or fuel) passing through their porous walls and also the exit coolant acting as an insulating film. However, its practical implementation has been hampered by the limitations of available porous materials. The search for more practical methods of increasing the internal heat transfer within the walls has led to the development of multi-laminate porous structures, such as Lamilloy$^{(R)}$ and Transply$^{(R)}$. This paper reviews recent research activities of transpiration cooling for the propulsions of liquid rocket, gas turbine, and scramjet.

• Applied Chemistry for Engineering
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• v.24 no.4
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• pp.370-374
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• 2013

The effects of zinc chloride addition on pore development of porous carbon nanofibers prepared by polyacrylonitrile (PAN)/ N,N'-dimethylformamide (DMF) (10 wt%) electrospinning were investigated. The change of morphological and structural modification by zinc chloride activation was investigated by a scanning electron microscopy (SEM) analysis. $N_2$ adsorption isotherm characteristics at 77 K were confirmed by Brunauer-Emmett-Teller (BET) and Horvath-Kawazoe (H-K) equations, and the curves showed the Type I mode in the International Union of Pore and Applied Chemistry (IUPAC) classification, indicating that lots of micropores exist in the sample. In addition, specific surface areas and total pore volumes of porous carbons prepared by the zinc chloride activation were determined as 600~980 $m^2/g$ and 0.24~0.40 $cm^3/g$, respectively. As experimental results, many holes or demolished structures were found on the fiber surfaces after the zinc chloride activation as confirmed by a SEM analysis. It was also observed that various pore sizes were found to be depended on the adding content of zinc chloride in PAN/DMF solution in this system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.181-189
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• 2016

An analytical model was developed by Sim to estimate the two-phase damping ratio for upward two-phase flow perpendicular to horizontal tube bundles. The parameters of two-phase flow, such as void fraction and pressure loss evaluated in the model, were calculated based on existing experimental formulations. However, it is necessary to implement a few improvements in the formulations for the case of tube bundles. For the purpose of the improved formulation, we need more information about the two-phase parameters, which can be found through experimental test. An experiment is performed with a typical normal square array of cylinders subjected to the two-phase flow of air-water in the tube bundles, to calculate the two-phase Euler number and the two-phase friction multiplier. The pitch-to-diameter ratio is 1.35 and the diameter of cylinder is 18mm. Pressure loss along the flow direction in the tube bundles is measured with a pressure transducer and data acquisition system to calculate the two-phase Euler number and the two-phase friction multiplier. The void fraction model by Feenstra et al. is used to estimate the void fraction of the two-phase flow in tube bundles. The experimental results of the two phase friction multiplier and two-phase Euler number for homogeneous and non-homogeneous two-phase flows are compared and evaluated against the analytical results given by Sim's model.