Optimal oscillation parameters of vibrating screens

Ferenc Safranyik,Bela M. Csizmadia,Attila Hegedus,Istvan Keppler 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5

Optimal oscillation parameters of vibrating screens are determined using analytical methods by investigating movement of a single spherical grain particle in the vibrating sieve’s non-inertial reference frame. Dimensionless parameters determining the efficiency of screening process are defined. Effect of interactions between multiple numbers of particles moving on the screen is analyzed using discrete element method. By comparing the analytical and numerical results, it can be seen, that the analytical evaluation of screening efficiency can be used until a given contaminant size unlimitedly in the examined range of screen angle. Additionally in case of this minimal contaminant size there is a maximal screening angle value. Above this angle it seems, that the use of our discrete element based evaluation of screening efficiency is unavoidable.

Testing red blood cell deformability of laboratory animals by slit-flow ektacytometry in various viscosity media: Inter-species and gender differences

Ferenc Kiss,Erika Sajtos,Lili Matyas,Zsuzsanna Magyar,Istvan Furka,Iren Miko,Norbert Nemeth 한국유변학회 2010 Korea-Australia rheology journal Vol.22 No.2

Viscosity of the suspending medium can be a determinant contributor to the effective measurements of red blood cell deformability using ektacytometry. Deformability of erythrocyte is known to show inter-species and gender differences, therefore the evaluation of the effects and the standardized usage of the suspending media are important in animal experiments. For evaluating the differences using various viscosity media, we aimed to test male and female Sprague-Dawley rats and beagle dogs. Blood samples were collected and red blood cell deformability was tested by a RheoScan-D200 slit-flow ektacytometer using parallel measurements in PVP solutions at viscosity of 15, 20 and 30mPa.s. The lowest elongation index values were measured in 15mPa.s solution in both species and genders. The inter-species differences were obvious: rats had higher elongation index values. Gender differences were found only in 20 and 30mPa.s samples: in rats males, while in dogs females had better red blood cell deformability. The standard usage of PVP solutions is essential for comparative studies, because the results obtained from different viscosity PVP solutions are not comparable to each other. In Sprague-Dawley rats and beagle dogs the relatively less viscous media (<20mPa.s) may result in less informative data.

An Oligopoly Model of Commercial Fishing

Ferenc Szidarovszky,Koji Okuguchi 서울대학교 경제연구소 1998 Seoul journal of economics Vol.11 No.3

Population dynamics and oligopoly theory are combined to formulate international fishery under imperfect competition. It is assumed that fish harvesting countries behave as oligopolist, but their costs depend on their harvest rates as well as on the total fish stock, which is governed by the biological growth law. e show that the number of nonextlnct equilibria is 0, 1, or 2, and characterize the dynamic behavior of the fish stock in terms of model parameters and initial fish stock level. Finally, We analyze how the steady state equilibrium fish stock is affected by entry of a new fishing country.

Export Markets for Ginseng Products

Ference, Don The Korean Society of Ginseng 1991 Journal of Ginseng Research Vol.15 No.3

The current size, characteristics. and channels of distribution of the offshore export (non North American) market for ginseng products are described. The apparent size of the worlds export market for ginseng products in 1987 is 3,363 tonnes. The major export markets for ginseng are Hong Kong (1,972.4 tonnes) and Japan (540.9 tonnes). The volume of ginseng imported into Hong Kong has doubled over the past five years from 976.3 tonnes in 1983 to 1,972.4 tonnes in 1987. This increase is reflective of an expanding Chinese market. In terms of products forms, the toast majority of ginseng imported into China is in root form, while Japan imports both red and white ginseng as well as ginseng beverages and medical products. Hong Kong is the destination of over 86f; of the volume of North American ginseng exported between 1983 and 1987. North American ginseng products are distributed by ginseng brokers or importers/exporters.

Overview of World Ginseng Production

Ference, Don The Korean Society of Ginseng 1991 Journal of Ginseng Research Vol.15 No.2

It is estimated that world ginseng production has increased from 3,200 tonnes In 1983 to 5,132 tonnes in 1987. China produced approximately hart of world ginseng production and South Korea's production amounts to 31.9% of world ginseng production. Canadian ginseng production of 114 tonnes in 1987 represents only 2.2% of estimated world production. World ginseng production is projected to increase to 6,856 tonnes by 1992. Canadian production as a proportion of total world production is expected to increase to 3.3% however, North American production overall is projected to decrease 12.0% of world production by 1992. Assuming that the value of each country's production is equal to average export price, the value of world ginseng production is estimated to be $ 443 million The estimated values of Korean, North Anerican and Canadian ginseng production represent $ 198.3million, 977.1 million, and $ 12.5 million, redpectively.

The power of slit-flow ektacytometry measurements for testing normal and heat treated red blood cells using various viscosity media in laboratory animals

Ferenc Kiss,Erika Sajtos,Timea Hever,Norbert Nemeth 한국유변학회 2010 Korea-Australia rheology journal Vol.22 No.1

Red blood cell (RBC) deformability values resulted from ektacytometry tests can be influenced by the viscosity of the medium in which the RBCs are suspended for measurement. To determine the power of measurements using various viscosity media in this study we used normal and heat treated RBCs from laboratory rats and beagle dogs. A RheoScan-D200 slit-flow ektacytometer was used to measure RBC deformability. Blood samples were taken from female Sprague-Dawley rats and inbred beagle dogs. Before and after heat treatment of RBC suspensions ektacytometry tests were performed using PVP solutions at viscosity of 15, 20and 30 mPa.s. Heat treatment caused impaired RBC deformability in both species and in every PVP solution. The difference between normal and heat treated RBCs was the highest in rats, while in dogs the magnitude of change was smaller, however being significant. Well comparable and stable results were found using 30 mPa.s media. The sensitivity of RBCs for heat treatment seems to be higher in rats. The suspending PVP medium at 30 mPa.s is recommended for testing RBC deformability by ektacytometry in laboratory rats and dogs, too, because this media resulted in the most stable data when comparing normal and rigid cells.

Measured and non-free vortex design results of axial flow fans

Ferenc Szlivka,Ildikó Molnár 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.10

The research is about the determination of developing flow pattern in the axial flow fan impeller. A measuring method and a sizing method of axial flow fans used in a research project have been studied. In this way it has been determined the spatial distribution of static pressure directly behind the impeller as well as the spatial distribution and direction of total pressure in a fixed system to the blade channel. There is an opportunity to identify the high loss region in the impeller: to determine the pressure loss and the hydraulic efficiency at each point. The article shows the results of comparison between the measurement data and the sizing results in the case of one in the agricultural-field utilized cooling fan. The impeller was designed by the help of the fore slanted blades in circumference direction as well as the non-free vortex theory. The basic theories of the design method of the blades and the realization of measurement results are analyzed, too.

New Directions in Linguistics for the 21st Century

Ferenc Kiefer(토론자),William Labov(토론자),Lee Chungmin(토론자),Stanley Peters(토론자),Park Byung-Soo(사회자) The Academy of Korean Studies 1992 Korea Journal Vol.32 No.3

Analytical approach of funnel flow discharge

Ferenc Safranyik,István Oldal 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.2

Design engineers often encounter problems because of the special mechanical behavior of granular materials. Such a typical problem is predicting discharge rate of silos and hoppers. This important design parameter must be known during the development of material transport devices attached to the container, but the calculation of this parameter may be challenging because well-known theories of hydrodynamics are not applicable. Several models are formed to evaluate discharge rate of silos, although most of them based on experimental observations are unable to explain physics of particle outflow. Oldal’s theory accounts for granular discharge of funnel flow, cylindrical silos with formation, and collapse of unstable arches above the orifice. It is applied to rectangular hoppers in this paper to generalize and prove this theory. An extended equation is derived by applying the original hypothesis that is validated using laboratory experiments and numerical simulations.

Global Stability Analysis of a Special Learning Process in Dynamic Oligopolies

Ferenc Szidarovszky 한양대학교 경제연구소 2004 JOURNAL OF ECONOMIC RESEARCH Vol.9 No.2