• Journal of Electrochemical Science and Technology
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• v.8 no.4
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• pp.331-337
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• 2017

A simple strategy is proposed herein for attaining uniform current distribution in direct methanol fuel cells by varying the catalyst loading over the electrode. In order to use the same total catalyst amount for a serpentine flow field, three spatial variation types of catalyst loading were selected: enhancing the cathode catalyst loading (i) near the cathode outlet, (ii) near the cathode inlet, and (iii) near the lateral areas. These variations in catalyst loading are shown to improve the homogeneity of the current distribution, particularly at lower currents and lower air-flow rates. Among these three variations, increased loading near the lateral areas was shown to contribute most to achieving a homogenous current distribution. The mechanism underlying each catalyst loading variation method is different; very high catalyst-loading is shown to decrease the homogeneity of the distribution, which may be caused by water management in the thick catalyst layer thereof.

• Journal of Distribution Science
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• v.14 no.1
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• pp.7-15
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• 2016

Purpose - The purpose of this paper is to study the relationships among store image, customer satisfaction, behavioral intentions (BI) and fast distribution in shahrvand chain super market in Tehran. Research design, data, and methodology - The 300 samples were from all the customers of Shahrvand chain stores. Since the present study aimed to explore the relationship between store image, customers' satisfaction, customers' behavioral intentions, and the proximity of shops to customers with considering determination for the influence of each factor, the customers of Shahrvand chain stores were randomly asked to comment on this issue. Results - Attitude to services and merchandising are positively associated with their positive store image. Besides, positive store image has a positive relationship with customers' behavioral intentions and customers'satisfaction. The relationship between fast distribution and customers' satisfaction is significantly positive. Conclusions - Several studies have shown that, in general, store image is important to attract and retain customers. This paper depicts the specific influences of image specifically on customer satisfaction and behavioral intention. Factors related to image have been discussed as their attitudes which touch areas of organizational behavior that have been embedded in the model, and it contributes to the originality or the value of the study.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.4
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• pp.54-61
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• 2015

Recently, DC-based power system is being paid attention as the solution for energy efficiency. As the example, HVDC (High Voltage DC) transmission system is utilized in the real power system. On the other hand, researches on LVDC (Low Voltage DC) distribution system, which are including digital loads, are not enough. In this paper, reliability in LVDC distribution system is analyzed according to the specific characteristics such as the arrangement of DC/DC converters and the number of poles. Furthermore, power quality is also taken account of since LVDC distribution system includes multiple sensitive loads and electric power converters. In order to achieve this, LVDC distribution systems are modeled using ElectroMagnetic Transient Program (EMTP) and both the minimal cut-set method and Customer Interruption Cost (CIC) are used in the reliability analysis.

• Journal of The Korean Astronomical Society
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• v.30 no.1
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• pp.95-106
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• 1997

We investigate the velocity distribution of dark matter in the disk of a galaxy like the Milky Way at the solar radius. Using N-body simulations with the total mass and z-component of angular momentum conserved, we calculate the response of a dissipationless dark matter galactic halo during the dissipational collapse of the baryonic matter in spiral galaxy formation. The initial distribution of dark matter and baryonic particles is assumed to be a homogeneous mixture based on a King model. The baryonic matter is assumed to contract, forming the final luminous components of the galaxy, namely the disk and, in some cases, a bulge and central point. Both slow and fast growth of the luminous components are considered. We find that the velocity distribution of dark matter particles in a reference frame rotating slowly about the galaxy center in the plane of the disk is similar to a Maxwellian, but it is somewhat boxier, being flatter at the peak and truncated in the tails of the distribution. We tabulate parameters for the best-fitting Maxwellian and modified-Maxwellian distributions. There is no significant difference between slow collapse and fast collapse for all these results. We were unable to detect any effect of disk formation on the z-dependence of the dark matter density distribution.

• Korea-Australia Rheology Journal
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• v.15 no.1
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• pp.35-41
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• 2003

It is expected that particle size distribution of any portion obtained through screening, is of more uniform than that of the original mixture, typically following such as log-normal, Rosin-Rammler distributions and so on. In this study, therefore, a new relation between parameters of the uniform distribution and flow characteristics of the coarse particle suspensions is derived based on the continuous polydisperse model (Ookawara and Ogawa, 2002b), which is derived from the discrete polydisperse model (Ookawara and Ogawa,2002a). The derived model equation predicts a linear increase of viscosity with shear rate, viz., dilutant flow characteristics. Further, the increase of viscosity is expected to be proportional to the square of volume fraction of particles, and to show the linear dependency on density and average diameter of particles. It is also shown that the uniform distribution model includes additional term that expresses the effect of distribution width. For verification of the model, the experimental results of Clarke (1967) are cited as well as in our previous work for the monodisperse model (Ookawara and Ogawa,2000) since most parameters were varied independently in his work. It is suggested that the newly introduced term expands the applicable range compared with the monodisperse model.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.6
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• pp.475-486
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• 1997

The characteristics of atmospheric aerosols were investigated as a function of particle size and water solubility. The atmospheric aerosols were sampled with classifying into 12 size ranges by the use of Andersen low-pressure impactor. Collected aerosol particles were extracted by ultrapure water and filtered to be separated into water-soluble and insoluble components. The concentrations 12 elements in both components were determined by PIXE analysis. And the concentrations of 8 ions in the soluble component were analyzed by ion chromatography. In general, the mass size distribution of particulate matter was represented as a bimodal distribution. The mass size distributions of S$(SO_4^{2-}), K(K^+), Zn and NH_4^+$ skewed to the smaller size range and those of Si, Ca$(Ca^{2+}), Fe, Na^+ and Mg^{2+}$ skewed to the larger size range. They had roughly one peak in the fine and coarse particle region,respectively. On the other hand, the mass size distribution of Ti, Mn, Ni, Cu, $Cl^- and NO_3^-$ were represented as the bimodal distribution. Fe and Si in the aerosol particles extracted into pure water are existing in high insoluble state. Conversely, almost the whole of S is dissolved in water.

• Korean Journal of Ecology and Environment
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• v.52 no.4
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• pp.340-347
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• 2019

The red swamp crayfish (Procambarus clarkia) originated from the North America distribute widely as invasive species throughout the world including Europe, Asia, Africa, North America and South America. The red swamp crayfish is also an invasive species in South Korea. We aimed to characterize the occurrence and distribution pattern of the red swamp crayfish, and evaluate the potential distribution of this species in South Korea. In South Korea, the red swamp crayfish was firstly reported in Seoul in 1996, and recently its occurrence is frequently reported at streams or reservoirs at different regions, showing the expansion of its distribution area. The red swamp crayfish has high potential to occur in the nationwide scale in South Korea because of their biological adaptation, effects of climate change, changes of their habitat condition, and various types of human activities. Finally, our results revealed the necessary to conduct an extensive field survey, to keep up a monitoring program for the occurrence of alien species, and to implement a strategy to prevent the dispersal of alien species in the natural ecosystems.

• Communications for Statistical Applications and Methods
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• v.24 no.5
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• pp.519-531
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• 2017

We consider goodness-of-fit test statistics for Weibull distributions when data are randomly censored and the parameters are unknown. Koziol and Green (Biometrika, 63, 465-474, 1976) proposed the $Cram\acute{e}r$-von Mises statistic's randomly censored version for a simple hypothesis based on the Kaplan-Meier product limit of the distribution function. We apply their idea to the other statistics based on the empirical distribution function such as the Kolmogorov-Smirnov and Liao and Shimokawa (Journal of Statistical Computation and Simulation, 64, 23-48, 1999) statistics. The latter is a hybrid of the Kolmogorov-Smirnov, $Cram\acute{e}r$-von Mises, and Anderson-Darling statistics. These statistics as well as the Koziol-Green statistic are considered as test statistics for randomly censored Weibull distributions with estimated parameters. The null distributions depend on the estimation method since the test statistics are not distribution free when the parameters are estimated. Maximum likelihood estimation and the graphical plotting method with the least squares are considered for parameter estimation. A simulation study enables the Liao-Shimokawa statistic to show a relatively high power in many alternatives; however, the null distribution heavily depends on the parameter estimation. Meanwhile, the Koziol-Green statistic provides moderate power and the null distribution does not significantly change upon the parameter estimation.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.2
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• pp.217-223
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• 2014

In order to suggest the methodology for improving the equity of flow distribution in open channel with multiple outlet, CFD simulations were carried out for actual scale distribution channel being operated in domestic G_WTP(Water Treatment Plant). Also, before and after installing the longitudinal multi hole(diameter=250 mm, 116 holes) baffle suggested by this research, turbidity measurements data were collected for evaluating the effects of hydraulic modification for inlet flow equity. From the both results, total turbidity of settled water was lowered by 30 % and equity of flow distribution was improved about 60 % compared with before hydraulic structure modification.

• Korean Journal of Medicinal Crop Science
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• v.23 no.6
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• pp.431-438
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• 2015

Background : This study was conducted to determine out the effect of storage temperature on the quality of fresh ginseng (Panax ginseng C. A. Meyer) during distribution. Methods and Results : Fresh ginseng was washed, packed in $30{\mu}m$ low density polyethylene (LDPE) film, then stored at 0, -2 and $-4^{\circ}C$. After 4 weeks of storage, ginseng was then stored at $5^{\circ}C$, as a simulation of the distribution process. Ginseng stored at $-4^{\circ}C$ showed higher respiration rate, ethylene production and electrolyte conductivity during the distribution phase than those stored at 0 and $-2^{\circ}C$. Decay and browning rate rapidly increased following 3 weeks of distribution in samples stored $-4^{\circ}C$. However ginseng stored $-2^{\circ}C$, which is below freezing point, for 4 weeks did not show the physiological change or quality deterioration. Ginsenoside contents decreased during storage for all plant, but did not differ significantly between storage temperatures. Conclusions : Storage at temperatures below $-2^{\circ}C$ can negatively affect respiratory characteristics and electrolyte leakage and increase quality deterioration and decay rates during distribution.