• Journal of Korean Society of Forest Science
• /
• v.96 no.3
• /
• pp.325-337
• /
• 2007

Illegal slash-and-bum fields and slash-and-bum farmers in Korea had increased in spite of Japanese Joseon Government's strong regulations and clearance measures, and land reform after the 1945 Liberation of Korea until 1970s. This study is to inquire into the necessary and sufficient conditions to disappear entirely the matters from 1974 to 1979 that illegal slash-and-bum fields and slash-and-burn farmers continued long in existence until the early 1970s. The findings are as follows; Firstly, the population pressure to agricultural lands that main factor of generation of illegal slash-and-bum fields had decreased rapidly because the rural populations and less income farmers have decreased after 1967. Especially, the decrease of the rural populations had never seen to the 1970s. It is recognised that the social condition for the success in 1970s. Secondly, the continuous economic growth from the early 1960s enabled the Korean government to solve the matter through the sufficient financial investment from the Government. For example, the gross national product (GNP) and the government budget in 1974 increased around 25 times after 1960. It is recognised that the economic condition for the success in 1970s. Finally, it was enabled to remove the concealment from the slash-and-bum farmers and to monitor illegal re-cultivation thoroughly because the development of forest inventory technique using an aerial photograph and the expansion of road facilities. It is recognised that the technical condition for the success in the 1970s.

• Ocean and Polar Research
• /
• v.25 no.spc3
• /
• pp.361-371
• /
• 2003

The effect of bottom friction on the steady wind-driven circulation in the Yellow Sea and the East China Sea (YSECS) has been studied using a two-dimensional numerical model with and without tidal forcing. Upwind flow experiment in YSECS has also been carried out with a schematic time variation in the wind field. The surface water setup and circulation pattern due to steady wind forcing are found to be very sensitive to the bottom friction. When the effects of tidal currents are neglected, the overall current velocities are overestimated and eddies of various sizes appear, upwind flow is formed within the deep trough of the Yellow Sea, forming a part of the topographic gyre on the side of Korea. When tidal forcing is taken into account, the wind-induced surface elevations are smoothed out due to the strong tide-induced bottom friction, which is aligned almost normal to the wind stresses; weak upwind flow is farmed in the deep trough of the Yellow Sea, west and south of Jeju. Calculation with wind forcing only through a parameterized linear bottom friction produces almost same results from the calculation with $M_2$ tidal forcing and wind forcing using a quadratic bottom friction, supporting Hunter (1975)'s linearization of bottom friction which includes the effect of tidal current, can be applied to the simulation of wind-driven circulation in YSECS. The results show that steady wind forcing is not a dominant factor to the winter-time upwind flow in YSECS. Upwind flow experiment which considers the relaxation of pressure gradient (Huesh et al. 1986) shows that 1) a downwind flow is dominant over the whole YSECS when the northerly wind reaches a maximum speed; 2) a trend of upwind flow near the trough is found during relaxation when the wind abates; 3) a northward flow dominates over the YSECS after the wind stops. The results also show that the upwind flow in the trough of Yellow Sea is forced by a wind-induced longitudinal surface elevation gradient.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.44 no.5
• /
• pp.92-102
• /
• 2016

While there have many completions of large parks recently under development, there has been a dearth of quality assessments. Studies focused on post-evaluation have been made to resolve this, but most of these are biased toward user satisfaction after completion and therefore behaviour analysis has limitations on solving problemsduring the actual design implementation processes. Therefore, this study examined the internal phenomenon and structure of the implementation process of design competition through the ground theory and microscopic independent perspective. As a result, maintaining the identity and differentiation of parks derived from the preserved design competition scheme contributed greatly to completeness and satisfaction. Outcomes were mainly caused by the trust of public officials as the ordering organization, the will of policy decision-makers, and the competence of operational enterprises, etc. Negative factors such as undermining the whole concept of the park and landscape occurred as external pressure and related subjects intruded on change design factors due to variations in social conditions. Additionally, illogical construction processes occurred, such as a reinvestigation of the budget for restoration after damaging on original landscape. There have been needs for the improvement of the work processing system. On balance, an interventional role is very important in the park construction process, especially the PA and operation committee in terms of maintaining the basic direction, landscape design supervision for detailed designs, and expert construction management on LA in terms of rational work management in the field. The study, using the microscopic perspective of the designer and ground theory, deliver significant meaning as an early study by suggesting alternative methods for the after-evaluation of large parks and structurally looking into main influence factors driven during the construction process.

• Journal of the Korean Vacuum Society
• /
• v.17 no.1
• /
• pp.51-57
• /
• 2008

we have demonstrated structural evolution and optical properties of Si-nanowires (NWs) synthesized on Si (111) substrates with nanoscale Au-Si islands by rapid thermal chemical vapor deposition (RTCVD). The Au-Si nano-islands (10-50nm in diameter) were employed as a liquid-droplet catalysis to grow Si-NWs via vapor-liquid-solid mechanism. The Si-NWs were grown by a mixture gas of SiH4 and H2 at a pressure of 1.0 Torr and temperatures of $500{\sim}600^{\circ}C$. Scanning electron microscopy measurements showed that the Si-NWs are uniformly sized and vertically well-aligned along <111> direction on Si (111) surfaces. The resulting NWs are ${\sim}60nm$ in average diameter and ${\sim}5um$ in average length. High resolution transmission microscopy measurements indicated that the NWs are single crystals covered with amorphous SiOx layers of ${\sim}3nm$ thickness. In addition, the optical properties of the NWs were investigated by micro-Raman spectroscopy. The downshift and asymmetric broadening of the Si main optical phonon peak were observed in Raman spectra of Si-NWs, which indicates a minute stress effects on Raman spectra due to a slight lattice distortion led by lattice expansion of Si-NW structures.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.9
• /
• pp.626-633
• /
• 2020

This study examined the behavior of the ground by comparing the methods using the results of the Terzaghi formula and the ground investigation data and method considering the dilatancy effect for a circular tunnel using the finite element method. In the case of the Terzaghi formula, the tunnel load can be overestimated and cause overdesign. The method using the results of the ground investigation data cannot be applied when a reasonable coefficient of earth pressure is not determined. This is because it behaves completely differently from the actual behavior, and unexpected problems can occur. In the case of the method considering the dilatancy effect, however, both the strength enhancement effect can be considered through the dilatancy angle and relative density. Therefore, the tunnel load was calculated most reasonably using the method considering dilatancy. Finite element analysis using the geotechnical survey results showed that the tensile stress acts at the top of the tunnel when the upper soil of the tunnel is shallow. On the other hand, additional verification is necessary, such as a comparison with the field measurement results. Through additional research, if normalized, the tunnel load can be calculated reasonably at the time of tunnel design, and safe and economical design is possible.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.1 no.1
• /
• pp.86-98
• /
• 1998

In order to provide an information as input data of possible storm surges in advance, the typhoon center and maximum wind position analysis scheme must be developed for the initialization of pressure and wind field.This study proposes a semi-automatical and objective analysis method and a procedure on a real time basis using the satellite TBB data of the GMS IR1, NOAA satellite CH4 and CH5, and shows the result of an experimental analysis. It includes a simple method of determining the parameters of the typhoon using minimum top temperature of the convective cloud near the inner eyewall. The method analyzing the isotropic cross sectional variation of TBB gradient from center to environment was developed to determine the center of Rmax of typhoon. This position of intense eyewall from typhoon center can be considered as the position of maximum wind. The results of estimation of typhoon center show very good agreement to the results of synoptic analysis. It is found that the Rmax is approximately 50-200km. From the comparison of the GMS and NOAA IR TBB data, it is found that the Rmax from NOAA data tends to be longer than those from GMS data.

• Journal of the Korean Geosynthetics Society
• /
• v.6 no.2
• /
• pp.1-8
• /
• 2007

Recently, the demand for industrial and residental land are increasing with economic growth, but it is difficult to acquire areas for development with good ground condition. For efficient and balanced development of land, new development projects are being carried out not only the areas with inland but those with the soft ground as well. As soft grounds have complex engineering properties and high variations such as ground subsidence especially when their strength is low and depth is deep, we need to accurately analyze the engineering properties of soft grounds and find general measures for stable and economic design and management. Vertical drain technology is widely used to accelerate the consolidation of soft clay deposits & dredged soil under pre-loading and various types of vertical drain are used with there discharge capacity. Under field conditions, discharge capacity is changed with various reason, such as soil condition, confinement pressure, long-term clogging and folding of vertical drains and so on. Therefore, many researcher and engineer recommend the use of required discharge capacity. In this paper, the experiment study were carried out to obtain the discharge capacity of four different types of vertical drains by utilizing the large-scale model tests and the required discharge capacity was calculated by several methods.

• Economic and Environmental Geology
• /
• v.43 no.2
• /
• pp.177-184
• /
• 2010

When cement grout is used for waterproofing of grounds, important roles are played by fluidity, particle size and bleeding. The most important element which determines their characteristics is the water/cement ratio of grout. Moreover in order to improve the efficiency of soil permeation, micro cement with a smaller average diameter is used in addition to ordinary portland cement. Besides the mixing ratio and cement diameter, the condition of ground is also of fundamental importance in the efficiency of permeation. In order to evaluate grout in terms of permeation ability into ground, we need a field test of grounting, which is cost and time consuming. In this paper we present a laboratory test method in which the suitability and efficiency of grouts are simply and more practically tested. In Korea neither a test standard nor devices are available to simulate grouting in a laboratory. We devised a grout injection equipment in which grouting was reproduced in the same condition with different materials, and suggested a standard for the production of specimens. Our tests revealed that the efficiency of injection increases with the water/cement ratio. We also found that more efficiently injected is the grout with the order of decreasing size; MS8000, micro cement, and ultra fine cements, and colloidal super cement.

• Tunnel and Underground Space
• /
• v.24 no.1
• /
• pp.67-80
• /
• 2014

Long-term stability and delayed failure of granite were evaluated through the laboratory test based on Wilkins method and Brazilian disc test (BDT) which yields tensile strength, mode I fracture toughness and subcritical crack growth parameters. Then, the long-term strength of granite was estimated by using analytical models and long-term stability of compressed air-energy storage (CAES) pilot cavern pressurized up to 5 ~ 6 MPa was evaluated using numerical code, FRACOD with the determined subcritical crack growth parameters. The results of test and analyses showed that the subcritical crack growth index, n was determined as 29.39 and the inner pressure of 5 ~ 6 MPa had an insignificant effect on the long-term stability of pilot cavern. It was also found that the measurement and analysis of acoustic emission events can describe the accumulation of damage due to subcritical crack growth quantitatively. That is, AE monitoring can provide the current status of rock under loading if we make an identical installation condition in the field with that of the laboratory test.

• Journal of Engineering Education Research
• /
• v.19 no.3
• /
• pp.35-43
• /
• 2016

The purpose of this study is to explore directions for improvement of teaching at college of engineering based on analysis of differences from course evaluation of students and instructors. Data was collected from 86 instructors' ratings on courses and their 3004 students' ratings on courses at college of engineering in a two-year, a three-year college and a University from 2010 to 2013. The results of the survey indicate significant differences in the statistics from the several questions between the instructors and the students as well as between the course in a two-year, a three-year college and in a University. First, instructors' self evaluation of the course is higher than students' satisfaction ratings of the course on the average. Instructors' self evaluation are high on the questions 'The subject was proper for the course', 'The course provided the latest theory and trend of the field', and 'Fairness and objectivity about the exams and the assignments'. Also, the difference between Instructors and students on the questions is significant in the statistics. The professor must make sure that students know well how to organize the course content and the method for feedback to test result and homework. Second, instructors have higher satisfaction ratings on the six questions and students have higher satisfaction ratings on the one question('Make students participate in the class effectively') at a two-year and a three-year college. However, students have higher satisfaction ratings on the three questions('Make students participate in the class effectively', 'Concern about students' learning process', and 'Use of E-learning and media equipments') and instructors have higher satisfaction ratings on the one question. It means instructors at a University feel pressure on a teaching and they are unsatisfied with their teaching skills. Third, the result of comparing six parts of the questions shows that students' satisfaction ratings are higher on 'Students participation' and 'Application of media equipments' parts whereas instructors' self evaluation are higher on 'Exams and assignments' part. Fourth, the question 'Make students participate in the class effectively' is significant in statistic based on comparison of instructors and students, and comparison of in a college and a University. Students' satisfaction ratings are higher than instructors' self evaluation.