• Journal of the Korean GEO-environmental Society
• /
• v.9 no.6
• /
• pp.21-29
• /
• 2008

As household and industrial wastes continue to rapidly increase every year, the demands for landfill sites are also increasing. However, the construction of landfill sites causes many problems due to the high costs of liners, while the leachate from the landfills generates secondary contamination of surrounding lands and groundwater. The purpose of this study is to determine the proper mixing ratio to meet the liner conditions (must be less than $1{\times}10^{-7}cm/sec$), using the local soil as the main material and using fly ash, bentonite, and cement as the mixing materials. The possibility of using this mixture as the liner for landfill sites was examined. To determine the proper mixing ratio, this study conducted basic physical properties tests, compaction tests, consolidation tests, and uniaxial compression tests. It was found that the higher the ratio of bentonite, the lower the coefficient of permeability, and the higher the ratio of fly ash, the higher the coefficient of permeability. The reason for this is that, while bentonite expands and fills pores, fly ash cannot fill the pores because the particles have a round shape and do not have adhesion. In conclusion, the optimum coefficient of permeability that meets the landfill liner condition was obtained when the ratio of bentonite was 15% or higher. If fly ash was mixed, the landfill liner condition was met when the ratio of bentonite was 15% or higher and the ratio of fly ash was 20% or lower.

• The Journal of Korean Academy of Prosthodontics
• /
• v.43 no.6
• /
• pp.751-763
• /
• 2005

Statement of problem. To improve a direct implant fixation to the bone, various strategies have been developed focusing on the surface of materials. The surface quality of the implant depends on the chemical, physical, mechanical and topographical properties of the surface. The different properties will interact with each other and a change in thickness of the oxide layer may also result in a change in surface energy, the surface topography and surface, chemical composition. However, there is limited the comprehensive study with regard to changed surface and biologic behavior of osteoblast by anodization. Purpose of study. The aim of this study was to analyze the characteristics of an oxide layer formed and to evaluate the cellular biologic behaviors on titanium by anodic oxidation (anodization) by cellular proliferation, differentiation, ECM formation and gene expression. And the phospholipase activity was measured on the anodized surface as preliminary study to understand how surface properties of Ti implant are transduced into downstream cellular events. Methods and Materials. The surface of a commercially pure titanium(Grade 2) was modified by anodic oxidation. The group 1 samples had a machined surface and other three experimental specimens were anodized under a constant voltage of 270 V(Group 2), 350 V(Group 3), and 450 V(Group 4). The specimen characteristics were inspected using the following five categories; the surface morphology, the surface roughness, the thickness of oxide layer, the crystallinity, and the chemical composition of the oxide layer. Cell numbers were taken as a marker for cell proliferation. While the expression of alkaline phosphatase and Runx2 (Cbfa1) was used as early differentiation marker for osteoblast. The type I collagen production was determined, which constitutes the main structural protein of the extracellular matrix. Phospholipase $A_2$ and D activity were detected. Results. (1) The anodized titanium had a porous oxide layer, and there was increase in both the size and number of pores with increasing anodizing voltage. (2) With increasing voltage, the surface roughness and thickness of the oxide film increased significantly (p<0.01), the $TiO_2$phase changed from anatase to rutile. During the anodic oxidization, Ca and P ions were more incorporated into the oxide layer. (3) The in vitro cell responses of the specimen were also dependant on the oxidation conditions. With increasing voltage, the ALP activity, type I collagen production, and Cbfa 1 gene expression increased significantly (p<0.01), while the cell proliferation decreased. (4) In preliminary study on the relation of surface property and phospholipase, PLD activity was increased but $PLA_2$ activity did not changed according to applied voltage. Conclusion. The anodized titanium shows improved surface characteristics than the machined titanium. The surface properties acquired by anodization appear to give rise more mature osteoblast characteristics and might result in increased bone growth, and contribute to the achievement of a tight fixation. The precise mechanism of surface property signaling is not known, may be related to phospholipase D.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.22 no.4
• /
• pp.329-340
• /
• 2006

Statement of problem: Damping of the peak force transmitted to implants has been reported by in vitro studies using impact forces on resin-veneered superstructures. Theoretical assumptions suggest that use of acrylic resin for the occlusal surfaces of a prosthesis would protect the connection between implant and bone. Therefore, the relationship between prosthesis materials and the force transmitted through the implant system also needs to be investigated under conditions that resemble the intraoral mechanical environment. Purpose: The purpose of this study was to analyze the fracture strength and modes of temporary prosthesis when a flange or occlusally extended structure were connected on the top of the abutment. Material and method: Modified abutments of winged and bulk design were made by casting the desired wax pattern which is made on the UCLA type plastic cylinder. Temporary crowns were made using templates on the modified abutments, and its fracture toughness and strain were compared to the traditional temporary prosthesis. To evaluate the effect of aging, 5.000 times of thermocycling were performed, and their result was compared to the 24hours specimen result. Results: The following conclusions were drawn from this study: 1. In the fracture toughness test, temporary crown's fracture line located next to the screw hole while modified designs with metal support showed fracture line on the metal and its propagation along the metal-resin interface. 2. Wing and bulk structure didn't show significant difference in the fracture toughness (p>0.05), but wing structure showed stress concentration on the screw hole area compared to bulk structure which showed even stress distribution. 3. In the fracture toughness test after thermocycling, wing and bulk structure showed increased or similar results in metal supported area while off-metal area and temporary crown showed decreased results. 4. In the strain measurement after thermocycling, its value increased in the temporary and bulk structure. However, wing structure showed decreased value in the loading point while increased value in the screw hole area. Conclusion: Wing type design showed compatible result to the bulk type that its application with composite resin prosthesis to the implant dentistry is considered promising.

• Journal of the Korean Data and Information Science Society
• /
• v.27 no.2
• /
• pp.395-407
• /
• 2016

This study aims to apply the G-theory for estimation of reliability of evaluation scores between raters on Taekwondo Poomsae rating categories. Selecting a number of game days and raters as multiple error sources, we analyzed the error sources caused by relative magnitude of error variances of interaction between the factors and proceeded with D-study based on the results of G-study for optimal determination of measurement condition. The results showed below. The estimated outcomes of variance component for accuracy among the Taekwondo Poomsae categories with G-theory showed that impact of error was the biggest influence factor in raters conditions and in order of interaction in subjects and between subjects, also impact of variance component estimation error on expression category was the major influence factor in interaction and in order of the between subjects and raters. Finally, the result of generalizability coefficient estimation via D-study showed that measurement condition of optimal level depend on the number of raters was 8 persons of raters on accuracy category, and stable reliability on expression category was gained when the raters were 7 persons.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.4
• /
• pp.349-360
• /
• 2017

In concrete construction work, formwork is an important process that accounts for 10% of the total construction cost. Recent buildings are becoming bigger and higher. In order to maximize the efficiency and safety of this formwork, the system of formworking has been systematized. However, the human accidents and the noise complaints arise from dismantling processes frequently occur. In order to solve these problems, most of them are dependent on foreign technology, but they do not take into consideration the conditions of domestic construction site. In this study, we developed a table type multi-drop system form for a slab and beam which can improve the process, safety and reduction of disassembly noise, and evaluated the physical properties of the main members which are used in the system. The results of this study show that there is sufficient strength to be used as a slab and a laying material for both a yoke beam and a supporting post. The noise level is improved compared to existing method.

• Journal of Korean Society of Forest Science
• /
• v.76 no.2
• /
• pp.127-137
• /
• 1987

This study was conducted to examine the effects of trampling on the changes in soil and vegetation around the trails. The study areas were established both on the trails and in the forested areas located in Ui and Jeongnung valleys at Pukhansan National Park. Soil core sampling, measurements of vegetations and counts of persons visited per hour were done during the period from April 6 to October 9, 1986. The physical properties of soils became better with increasing distances from the trail, and the best conditions were observed in the forested areas. The differences were not significant among the zones within the trailside. More number of individuals and basal area (or coverage) in woody plants were observed in the forested areas than at trailsides. For the herb layer, however, more number of individuals and coverage were shown at the trailside. In the Ui valley, the quantitative measures of herbaceous plants decreased as the bulk density and penetration resistance increased. In the Jeongnung valley, however, only bulk density was negatively related to the quantitative measures. The fact that there were poor relations between soil factors and quantitative measures of herbaceous plants in Jeongnung valley might be influenced by other factors rather than soil compaction. Thus, more research would be needed to understand the critical factors affecting the vegetational changes in recreation areas.

• Journal of the Korean School Mathematics Society
• /
• v.13 no.3
• /
• pp.459-483
• /
• 2010

This study aims to develop materials related to math education for the aged and to identify the effects of application as part of active measures to the aging society with its growing elderly population which is one of the greatest changes in our society. In this purpose, the necessity and objectives for development of materials of 'Silver Math' as education for the aged are explained. Developing and disseminating materials with a role as a program for intelligent needs and physical and spiritual health of the aged presents standards for development of more systemic and meaningful educational materials at this point of time when the importance of education of the aged increases to help the old enjoy qualitatively successful lives in later years in the perspective of lifelong education. Also it aims to present standards of contents and requirements in learning that are adequate and meaningful to old learners at the actual learning sites where education takes place only in terms of making good use of spare time while at the same time suggesting plans of teaching and learning as well as conditions for learning environment. Next, the effectiveness of 'Silver Math' are explored by applying developed materials to the aged. materials of 'Silver Math' for the aged with contents that are appropriate to the definitive and cognitive level of the aged are presented. The developed materials for mathematical activities are divided into 'computation of basic numbers' for those wishing to learn calculation and concepts of numbers, 'active math' that corresponds to definitive factors of old learners, facilitates leisure time through mathematical activities, and Improves communication abilities through cooperative learning among learners, and 'math with thinking power' to solve simple calculation problems by applying to various actual situations.

• The Journal of Engineering Geology
• /
• v.26 no.1
• /
• pp.79-85
• /
• 2016

A concrete silo plays an important role in subsurface low- and intermediate-level waste facilities (LILW) by limiting the release of radionuclides from the silo geosphere. However, due to several physical and chemical processes the performance of the concrete structure decreases over time and consequently the concrete loses its effectiveness as a barrier against groundwater inflow and the release of radionuclides. Although a number of processes are responsible for degradation of the silo concrete, it is determined that the main cause is corrosion of the reinforcing steel. Therefore, the time it takes for the silo concrete to fail is calculated based on two factors: the initiation time of corrosion, defined as the time it takes for chloride ions to penetrate through the concrete cover, and the propagation time of corrosion. This paper aims to estimate the time taken for concrete to fail in a LILW disposal facility. Based on the United States Department of Energy (DOE) approach, which indicates that concrete fails completely once 50% of the volume of the reinforcing steel corrodes, the corrosion propagation time is calculated to be 640 years, which is the time it takes for corrosion to penetrate 0.640 cm into the reinforcing steel. In addition to the corrosion propagation time, a diffusion equation is used to calculate the initiation time of corrosion, yielding a time of 1284 years, which post-dates the closure time of the LILW disposal facility if we also consider the 640 years of corrosion propagation. The electrochemical conditions of the passive rebar surface were modified using an acceleration method. This is a useful approach because it can reduce the test time significantly by accelerating the transport of chlorides. Using instrumental analysis, the physicochemical properties of corrosion products were determined, thereby confirming that corrosion occurred, although we did not observe significant cracks in, or expansion of, the concrete. These results are consistent with those of Smartet al., 2006 who reported that corrosion products are easily compressed, meaning that cracks cannot be discerned by eye. Therefore, it is worth noting that rebar corrosion does not strongly influence the hydraulic conductivity of the concrete.

• Economic and Environmental Geology
• /
• v.38 no.2 s.171
• /
• pp.165-176
• /
• 2005

Natural gas in deep sediment may occur in three phases based on the physical and chemical conditions. If the concentration of gas in pore water is less than the solubility, gas is dissolved. If the concentration of gas is greater than its solubility (water is saturated or supersaturated with gas), gas occurs as a fee gas below the gas hydrate stability Lone (GHSZ) and is present as solid hydrate within the GHSZ. The knowledge of gas concentration in deep sediment appears critical to determine the phase of natural gases and to understand the formation and distribution of gas hydrate. However, reliable data on gas concentration are usually available only from the upper section of marine sediment by the headspace gas technique, which is widely used for sampling of gases from the sediments. The headspace gas technique represents only a fraction of gases present in situ because sediments release most of the gases during recovery and sampling. The PCS (Pressure Core Sampler) is a downhole tool developed to recover a nominal $1{\cal}m$ long, $4.32{\cal}cm$ diameter core containing $1,465cm^3$ of sediment, pore water and gas at in situ pressure up to 68.9 MPa. During Leg 204, the PCS was deployed at 6 Sites. In situ methane gas concentration and distribution of gas hydrate was measured by using PCS tool. Characteristics of methane concentration and distribution is different from site to site. Distribution of gas hydrate in the study area is closely related to characteristics of in situ gas concentration measured by PCS.

• Korean Journal of Digital Imaging in Medicine
• /
• v.14 no.1
• /
• pp.13-20
• /
• 2012

In a normal x-ray examination, the cooperation of a patient in positioning greatly influences the improvement of work performance, the quality of the images and the reduction in time spent on the examination. An attempt was made to discover the connection between an examination information printout and the effects of the examination by informing the patient before the examination on the examination positions in order to increase the level of cooperation by the patient and by surveying the degree of satisfaction of the patient during the examination proceedings. An examination information printout was prepared on five positions that patients consider to be difficult while receiving normal x-ray examinations and were shown to 257 male and female patients between the ages of 30 to 79 who had visited this hospital between January 1 to February 29, 2012 or to a person who had accompanied the patients before the examination to research the degree of satisfaction regarding the printout. In addition, the examination explanation printout was given to Radiologic Technologists with over 1 year experience in this hospital to use while taking the x-rays and the degree of satisfaction was surveyed and it was examined if the increase of the degree of satisfaction had an effect on the reduction in the examination time. The patients who utilized the examination information printout revealed results of approximately a 7.8% higher degree of satisfaction among the patients who had previous experience receiving x-ray examinations compared to those were having an x-ray for the first time. In the age groups between 30 to 70 years of age, the age group in the 30's revealed the lowest level of satisfaction at approximately 69% and the group in the 50's showed the highest degree of satisfaction of 87.94%. In the survey of the Radiologic Technologists, 85% responded that they were satisfied. In the question that stated "Will the examination information printouts reduce the time involved in unnecessary conversations with the patients?," the responses showed a 95% degree of satisfaction. The degree of satisfaction was high over the examination information printout by both the patients and the Radiologic Technologists. Although the effects of examination time reduction varied based on the ages of the patients and physical conditions that they were in and could not be given measurement values, it was able to be seen through the survey that reduction of the unnecessary communication between the patient and the Radiologic Technologists contributed to the increase in the degree of satisfaction. As a result, both the patients and the Radiologic Technologists had an increased degree of satisfaction over the examination information printout and it was possible for improvements to be made in the quality of medical service provided as well. Nevertheless, it is considered that a more developed manual in terms of quality and quantity must be produced using a more systematic approach and design.