• Journal of the Korean Society of Combustion
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• v.21 no.3
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• pp.7-15
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• 2016

The fuel in conventional liquid fuel combustor is atomized by spray method for high efficiency and low emissions. To improve the overall fuel efficiency and lower pollutant emissions in liquid fuel combustion systems, the effective spatial and temporal separation of droplet evaporation from normal spray process is needed. In this paper, the recuperation of high temperature burnt gas for fuel evaporation was proposed to develop a cylindrical premixed combustor. The recuperation process using U shaped tube is effective to evaporate the liquid fuel. The results show that the flame mode is changed into red radiation flame, blue flame and lift off flame with decreasing equivalence ratio as gas fuel combustion mode. In particular, the blue flame is found to be very stable at heating load 9.2 kW and equivalence ratio 0.731. NOx was measured blow 105 ppm ($O_2$ zero base) from equivalence ratio 0.705 to 0.835. CO which is a very important emission index in liquid fuel combustor was observed below 5 ppm ($O_2$ zero base) under the same equivalence region.

• Health Policy and Management
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• v.15 no.4
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• pp.81-109
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• 2005

According to many recent studies suggesting that cash flow analysis method tends to be more effective than traditional financial index analysis method to predict corporate bankruptcy, this study applies the cash flow analysis method to hospital business to identify the significant variables which can distinguish between superior hospitals and bankruptcy hospitals. The author analyzed recent 3 years, i.e. from the year of 2000 to the year of 2002, financial statements of 31 bankrupt hospitals In 2003, and the same number of superior hospitals through using Multiple Discriminant Analysis and Logit Analysis. The results are belows; First, the study releases that Logit Analysis is more likely to be effective than Multiple Discriminant Analysis. Second, this research also shows that traditional financial index analysis method is more superior compare to cash flow analysis method for hospital bankruptcy predict model. Finally, this study suggest that the significant variables, which can distinguish superior hospitals from bankrupt hospitals, are Operating/Current Liabilities$(Y_2)$, CFO/Equity$(Y_5)$ for cash flow analysis method and Net Worth to Total Assets Ratio$(X_1)$, Quick Ratio $(X_3)$, Return on Assets$(X_6)$, Growth Rate of Patient Revenues$(X_{16})$ for traditional financial index analysis method.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.355-360
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• 2005

The properties of contaminants, contaminated soil, and the elapsed time are important factors to in-situ soil remediation. Gabr et. al. (1996) derived the solution equation of contaminant concentration ratio as initial one $(C/C_0)$ with time and spatial changes in contaminated area with vertical drains. The contaminant concentration ratio $(C/C_0)$ is analyzed with time and spatial changes as varying the effective diameter, porosity, shape factor, density of contaminated soil and temperature in ground and unit weight, viscosity of contaminants by using FLUSH1 model. Results from numerical analysis indicate that the most important factor to the in-situ soil remediation using vertical drains is the effective diameter of contaminated soil. It also shows that the viscosity of contaminants, porosity of soil, shape of soil, temperature in ground, unit weight of contaminants are, in order, affected to the soil remediation but density of soil is insignificant to the soil remediation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.90-98
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• 2014

The shear behavior of reinforced concrete structure is one of difficult problems that are not clearly identified theoretically despite the efforts of researchers for several years. Since bending and shear strength of hollow slab may decrease due to hollow part inside slab, prediction of such structure performance is very important. Presently the formulas of shear designing standard expressions of each country are formulas by experiment for hollow slab. In this study, the shear behavior of one-way hollow slab by reinforcement ratio were analyzed through experiment to conduct studying on estimation of shear strength, and then shear strength formulas of hollow slab were compared and analyzed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.2
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• pp.200-211
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• 1998

Heat transfer performance improvement by fin and groovs is studied for condensation of R-11 on integral-fin tubes. Eight tubes with trapczodially shaped integral-fins having fin density from 748 to 1654fpm(fin per meter) and 10, 30 grooves are tested. A plain tube having the same diameter as the finned tubes is also used for comparison. R-11 condensates at saturation state of 32 $^{\circ}C$ on the outside tube surface coded by inside water flow. All of test data are taken at steady state. The heat transfer loop is used for testing singe long tubes and cooling is pumped from a storage tank through filters and folwmeters to the horizontal test section where it is heated by steam condensing on the outside of the tubes. The pressure drop across the test section is measured by menas pressure gauge and manometer. The results obtained in this study is as follows : 1. Based on inside diameter and nominal inside area, overall heat transfer coefficients of finned tube are enhanced up to 1.6 ~ 3.7 times that of a plain tube at a constant Reynolds number. 2. Friction factors are up to 1.6 ~ 2.1 times those of plain tubes. 3. The constant pumping power ratio for the low integral-fin tubes increase directly with the effective area to the nominal area ratio, and with the effective area diameter ratio. 4. A tube having a fin density of 1299fpm and 30 grooves has the best heat transfer performance.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.3096-3101
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• 2008

Selective Catalytic Reduction (SCR) technology is well-known to be effective for the reduction of NOx emission. So car manufacturers has adopted Ures-SCR system to be satisfied with emission regulation. This paper discusses the effective of $NH_3/NOx$ ratio and SCR catalyst temperature in the $NH_3$-SCR reactor on DeNOx performance. So it is shown the characteristic of NOx conversion and ammonia slip using the $NH_3$ instead of Urea-Solution. From the result of this study, it is found to optimize $NH_3/NOx$ ratio to have the best case of high NOx conversion and low ammonia slip at variable SCR catalyst temperatures. Lastly, it is also found the characteristics of NOx conversion and ammonia slip with compared with Urea.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.297-304
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• 2002

This study is about penetrability of Micro Cement(MC) used for ground improvement. In this study, the characteristics of chemical grouting such as solidification, penetrability were analyzed experimentally by changing permeability of ground, grain size and relative density of grout material. For evaluating applicability of grout material, solidification test and penetrability test were performed. From the results of the tests, effective solidification ratio and penetrability ratio of MC was each 75%, 86% to be excellent when ground permeability was in the range of 10$^{-2}$ and 10$^{-4}$ cm/sec. Otherwise, those of Ordinary Portland Cement(OPC) were both lower than 50% to be poor. When penetrability of grout material is needed for improvement of dam foundation and soft ground, application of MC Is much superior to that of the other materials. The results of the grouting tests in the water flowing ground show that solidification effect of long gel-time grout material is excellent as injection pressure increases when groundwater velocity is relatively low. But when groundwater velocity is relatively high, solidification effect of long gel-time grout material is very poor because most grout materials are outflowed. Therefore, as groundwater velocity is high, effective solidification ratio of long gel-time grout material is better than that of short gel-time grout material, also penetration distance of long gel-time grout material is longer than that of short gel-time grout material.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.243-252
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• 1987

The propagation and closure behavior of surface crack initiated at a sharply notched specimens were investigated in 5083-H113 aluminium alloy under constant amplitude of tension load by the unloading elastic compliance method. The crack shape (aspect ratio) was found to be approximately semicircular during the crack was being small and to be changed to semi-elliptical during it was being long. The propagation rate of a surface crack initiated from notch root decelerated with increasing crack length when the crack was small and then accelerated when it was large. The effect of stress ratio was large in lower .DELTA.K range, but the effective stress intensity factor range .DELTA.K$_{eff}$ was found to diminish the difference of the crack propagation rate. By considering the increase in crack closure stress with crack length and examining the microphotographs, plasticity-induced and roughness-induced crack closure mechanisms were predominant in the range of this study.y.

• Steel and Composite Structures
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• v.42 no.3
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• pp.375-388
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• 2022

In this work, limit elastic speed analysis of functionally graded porous rotating disks has been reported. The work proposes an effective approach for modeling the mechanical properties of a porous functionally graded rotating disk. Four different types of porosity models namely: uniform, symmetric, inner maximum, and outer maximum distribution are considered. The approach used is the variational principle, and the solution has been achieved using Galerkin's error minimization theory. The study aims to investigate the effect of grading indices, aspect ratio, porosity volume fraction, and porosity types on limit angular speed for uniform and variable disk geometries of constant mass. To validate the current study, finite element analysis has been used, and there is good agreement between the two methods. The study yielded a decrease in limit speed as grading indices and aspect ratio increase. The porosity volume fraction is found to be more significant than the aspect ratio effect. The research demonstrates a range of operable speeds for porous and non-porous disk profiles that can be used in industries as design data. The results show a significant increase in limit speed for an exponential disk when compared to other disk profiles, and thus, the study demonstrates a range of FG-based structures for applications in industries that will not only save material (lightweight structures) but also improve overall performance.

• Physical Therapy Rehabilitation Science
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• v.11 no.1
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• pp.88-96
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• 2022

Objective: Purpose of this study was to compare muscle activity ratio of multifidus to erector spinalis according to various cueing including tactile stimulation to provide an effective strategy to provide verbal and tactile feedback during exercise to provoke multifidus muscle activation. Design: Cross-sectional study. Methods: Participants of this study included 28 healthy adults. Muscle activities of the multifidus and erector spinalis were measured while the participants performed tasks according to the three different methods of verbal cueing and three different tactile stimulation. Surface EMG was used to measure the muscular activity of the muscles during all the tasks. Results: Tactile stimulation to abdomen and lumbar vertebrae showed no significant difference in the muscle activity ratio (p>0.05). However, muscle activity ratio of the multifidus in relation to the erector spinalis was increased when subjects were given verbal instructions to make lumbar curvature with little force and to make lumbar curvature while pulling navel (p<0.05). However, it was decreased when they were provided with verbal instruction to make lumbar curvature with strong force (p<0.05). Conclusions: According to the results, proper verbal instruction was an effective tool to increase the muscular activity of multifidus. This study aimed to find and provide the most appropriate verbal cueing while doing exercises to activate multifidus.