• Journal of Korean Society of Forest Science
• /
• v.80 no.1
• /
• pp.72-81
• /
• 1991

This study was carried out to provide necessary information for improving quarrying industry management in Korea. The results of the study are summarized as follows : 1. In aggregate and building-stone quarrying firms the managers over 40 years of age are 97% and 89.1%, the ones above education level of high school are 90% and 85% and the ones not more than 10 years of quarrying experience are 70% and 52%, respectively. Accordingly it can be pointed out that most of the managers of two types of firms are relatively old, have high educational background, while quarrying experiences of building-stone firm managers are longer than that of aggregate firm managers. 2. Most of the management forms are social corporation(60%) for aggregate quarry firms and private management(76%) for building-stone firms. Average areas of permitted stone-pits of aggregate and building-stone quarries are about 2.86ha and 1.66ha respectively. That is, aggregate quarrying firms are carried on a larger scale than building-stone quarrying firms. 3. The yearly average product of aggregate quarrying firms has increased steadily from $88.961m^3$ in 1985 to $144.028m^3$ in 1988, while, in case of building-stone quarry firms, it has significantly increased from $4.155m^3$ to $19.462m^3$ from 1985 to 1987, but reduced to $13.400m^3$ in 1988. Unstable production activities of building-stone quarrying firms may require continuous government support. 4. Major cost items are equipment rental, depreciation, salaries, repair, maintenance for aggregate quarrying firms, and salaries, depreciation, fuel, tax for building-stone quarrying firms. The yearly average rate of return is about 9.7% for aggregate quarry firms and 2.6% for building-stone quarry firms. It can be pointed out that aggregate quarrying firms is better managed than building-stone quarrying firms. 5. The production elasticity of salary for aggregate quarrying firms is 0.495, that of employees is 0.559, and that of capital service is 0.513. The sum of the elasticities is 1.257>1. Fur building-stone quarrying firms, that of employees is 0.492, that of variable costs is 0.192, and that of capital service is 0.498. The sum of elasticities is 1.172>1, thus denotes the increasing returns to scale for both types quarrying firms. 6. The ratio of marginal value product to opportunity cost of empolyees is 2.54, that of variable costs is 3.62, and that of capital service is 1.45, in aggregate quarrying firms. That of employees is 2.47, that is variable costs was 2.34, and that of capital service is 19.67 in building-stone quarrying firms. Therefore the critical factors for more expansion of management scale in aggregate quarrying firms are variable cost and employees, and are capital service in building-stone quarry ing firms. 7. The break-even points of stone sales are about 0.587 billion won and 0.22 billion won in aggregate and building-stone quarrying firms respectively. The optimum sales Level for profit maximization are about 2.0 billion and 0.5 billion in aggregate and building-stone quarry firms respectively.

• The Journal of Engineering Geology
• /
• v.23 no.4
• /
• pp.493-502
• /
• 2013

This study investigates the design parameters for riverbed filtration (RBF) based on the geochemistry of river water and groundwater. The study area consists of alluvium, and the area is readily affected by non-point sources of chemical contaminants in the surface environment; this is expected to affect the design parameters for RBF. River and groundwater samples were collected at three points along the river flow and at nine points along a transect normal to the river, respectively. The geochemical data indicate that the sources of individual chemical contaminants are industrial facilities and agricultural activity near the study area. In addition, The samples are mainly Ca-Na-$HCO_3$, Ca-Cl, and Ca-$HCO_3$-Cl type waters. The design parameters of RBF in the study area should consider K, $HCO_3$, $NO_3$, and Cl. We divided the study area into three regions based on the concentrations of stable nitrogen isotopes: Region A, the origin of the river and denitrification; Region B, denitrification in the flow direction of tributaries; and Region C, the origin of natural soil, sewage, and anthropogenic pollution.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.12
• /
• pp.6447-6454
• /
• 2013

Seawater intake systems have significant problems due to seawater pollution, suspended solids, unstable intake and maintenance etc. An underground type seawater intake system was newly developed to overcome the existing weaknesses and was facilitated in Gyukpo port. In this study, to check the performance of the new system, the samples for water quality and the 3-D numerical modeling test were conducted. The five times test included the COD, total nitrogen, total phosphorus, pH, and suspended solid for the intake system. The analyses show that the COD, total nitrogen, total phosphorus, PH showedminor changes before and after. On the other hand, the change in suspended solids was significant and water was purified below 5 mg/l, first level fisheries water, after. The numerical model adopted the RNG $k-{\epsilon}$ algorithm and the CFX model based on the finite volume method. The porosity algorithm was used to reproduce filtered-sand, outer diameter, and thickness. The numerical results showed that the double pipe is advantageous in that it provides a uniform pressure between the inner and outer pipe for the flow to be stable. In addition, the use of multiple intake pipes did not interfere with the discharge reduction of 0.98 at the both intake pipes compared with the central intake pipe.

• Clean Technology
• /
• v.23 no.3
• /
• pp.270-278
• /
• 2017

This study introduces a method to easily fabricate highly monodisperse pectin hydrogel microfibers in a microfluidic device by using partial gelation. The hydrodynamic parameters between the pectin aqueous solution and the calcium ions containing oil solution are precisely controlled to form a stable elongation flow of the pectin aqueous solution, and partial gelation of the pectin aqueous solution is performed by the chelating of the calcium ions at the interface between the two phases. The partially gelled pectin aqueous solution is phase-separated from the oil solution in an aqueous calcium chloride solution outside the microfluidic device and is completely gelled to produce monodisperse pectin hydrogel microfibers. The thickness of the pectin hydrogel microfiber is controlled in a reproducible manner by controlling the volumetric flow rate of the initially injected pectin aqueous solution. The pectin hydrogel microfibers were 200 to 500 micrometers in diameter and had a coefficient of variation below 5% under all thickness conditions, indicating that the pectin hydrogel microfibers produced by partial gelation are highly monodisperse. In addition, biomaterials can be immobilized to the pectin hydrogel microfibers produced by a single process, demonstrating the possibility that our pectin hydrogel microfiber can be used as carriers for biomaterials or tissue engineering.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.10
• /
• pp.42-47
• /
• 2017

In this study,we conducted an injection molding analysis of metal powder materials for the development of flanges, which are necessary adapters for optical communication. The metal powder injection molding process is a technique for producing an injection molded article having a complicated shape by mixing ceramic or stainless powder and binders. It is used to produce products which require complex processing technology or for which the productivity is low. The purpose of this study is to minimize the manufacturing processing of products which are manufactured through existing mechanical processing procedures. For the injection molding analysis, we mixed stainless STS316 metal powder with binders at a ratio of 6 to 4 to make molding materials consisting of granular pellets. Then, three-dimensional modeling and meshing were carried out to obtain the optimal injection molding analysis conditions(molding temperature, melting temperature, injection time, injection temperature, injection pressure, packing time and cooling time). As a result of the analysis, it was discovered that the inlet became available 13.29 seconds after the first injection. Also, as the flowing and packing in the melt through the sprue, runner and gate were stable, it is expected that good molds can be manufactured.

• Journal of Plant Biotechnology
• /
• v.37 no.1
• /
• pp.25-46
• /
• 2010

The demand for fuel and energy resources continues to grow due to increased consumption and emerging economies in all parts of the world. With this increase in demand, crude oil prices in the international market has jumped dramatically. Global warming, which is a consequence of increasing greenhouse gas (GHG) emissions, has become scientific, social, and political concerns. To cope with global warming and energy crisis, cost-competitive biofuels are urgently needed. In addition, development of an infrastructure, which supplies energy stably and diversifies energy resources, as well as new cost-saving technologies should be developed to reduce the costs of producing biofuels. Due to high oleic acid content, rapeseed (Brassica napus L.) is currently the potential feedstock for biodiesel production in temperate zone region and the production and use of rapeseed oil is already commercialized in Europe. In Korea double-cropping (rice and rapeseed) became more prevalent because it reduces competitions from land constraints. Production of rapeseed as a biodiesel feedstock may reduce the influence of rising oil prices and nation's dependence on imported petroleum and increase job opportunities and farm incomes.

• The Journal of the Korea Contents Association
• /
• v.19 no.1
• /
• pp.445-462
• /
• 2019

This paper illustrated the use of focus groups with adolescents and youth experts to enhance knowledge of anger, anger expression, and its coping strategies. Nine youth experts and 9 adolescents participated in the study. Analysis of the findings identified 12 meaningful elements, 34 sub-elements, and 138 descriptions. The meaningful elements were as follow: the lack of stable care, anger-provoking situations, a relationship between distorted thoughts and anger, physical and psychological symptoms, different types of anger expression, suppressed anger, difficulty of anger control, youth efforts to control anger, needs to implement appropriate anger expression, psychological mechanism of anger, effective ways to cope with anger, suggested by youth experts, needs of alternative anger management programs. Based on these findings, the study suggests various anger management alternatives, including ICT based cognitive-behavior anger management programs.

• Journal of The Korean Association For Science Education
• /
• v.26 no.7
• /
• pp.856-869
• /
• 2006

J. J. Schwab is usually considered as the founder of the concept of scientific enquiry, perhaps the most important key word of science education of the 20th century. Mainly through the method of literature review, this study reappraises Schwab's life as a science educator as well as a curriculum scholar, and his ideas concerning several important issues about science and science education. Like other eminent science educators, before the 1950s, who were originally talented scientists but later became engaged in educational activities, Schwab were trained and known as a genetic scientist, but later he concentrated on university reform, curriculum studies and science education. His academic interest was very diverse across different disciplines, from biology and science in general to history, philosophy and education. The essence of his theory of scientific enquiry was 'to teach science as science', and the best way to do it was 'to teach science as enquiry'. With enquiry, however, he tried to deliver some important but differentiated meanings, for example by distinguishing 'science as enquiry' and 'teaching as enquiry', and 'static enquiry' and 'fluid enquiry'. Scientific enquiry was the core concept upon which many of his ideas concerning science education and education in general were based, such as the diversity of science, textbooks, curriculum and roles of teachers. In summary, Schwab can be characterized as a rational reformist of science education, who tried to identify the very nature and goals of the discipline and to bring its substantial changes with concrete and practical guidelines. Nevertheless, some of his ideas, like the diversity of science and conceptual invention, have been handed down by his followers frequently with considerable distortion.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.12
• /
• pp.1087-1093
• /
• 2010

Autotrophic denitrification is known as an effective and economical alternative for heterotrophic denitrification using external carbon sources such as methanol. In this study, we evaluated design and operation parameters for a sulfur denitrification reactor (SDR) treating high strength nitrogen wastewater. The SDR was filled with spherical sulfur media in connected to a pilot-scale nutrient removal process (daily flow rate, $Q=18\;m^3/d$) using moving spongy media. Total nitrogen (TN) concentration of the final effluent was below the 7.0 mg TN/L because nitrate was additionally removed through autotrophic denitrificationin without adding alkalinity (initial alkalinity was $169.4{\pm}20.8\;mg$ $CaCO_3$/L). During the test period, 60~80% of nitrogen in the influent was removed even in low temperature (below $15^{\circ}C$). The alkalinity consumption for nitrate removal in SDR was $4.09{\pm}1.29$ g $CaCO_3/g$ ${NO_3}^-$-N, and the residual alkalinity of influent of SDR was higher than that of theoretical requirements for full conversion of nitrate. The consumption of sulfur was 943.8 g S/d and it was 2.4 times higher than theoretical value (400.1 g S/d) due to abrasion and loss of sulfur media in backwash, etc.

• Journal of Animal Science and Technology
• /
• v.50 no.3
• /
• pp.343-354
• /
• 2008

The objective of this study was to investigate the effect of restricted feeding to pullet on growth and endocrine profile in layers(Isa brown). One thousand eighty brown-layer chicks were divided into three treatments; conventional feeding(ad libitum) and two restricted feedings(80% of conventional diet) for 70 weeks. One of restricted feeding started from seven to seventeen weeks of age, and the other started from twelve to seventeen weeks of age. Diets were formulated by NRC(1994) recommendation. Body weight and feed intake were measured every two weeks, and body composition and organ weight analyzed every week in rearing period and every eight weeks in laying period. Blood was collected at weighing body weight and was analyzed for the concentration of insulin-like growth factor-Ⅰand estradiol. Body weight and feed intake decreased as restriction of feeding begins comparing to ad libitum group(P<0.05), but reached to similar body weight and feed intake at 20 wk of age regardless of restriction. There were no significant differences in development of digestive tract and attached organs among the treatment groups. During rearing period, however, they were slightly higher in restricted group which was low in body weight. In terms of body composition, fat contents of restricted group were significantly lower(P<0.05) than that of ad libitum group around 1,000 grams of body weight. High concentration of IGF-Ⅰwas observed.