• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1458-1465
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• 2010

A lot of dredging and reclaming projects are recently under way in Korea for the efficient use of limiting land space. Saemanguem area is special case of reclaiming by dredged soil. In case of a confined disposal of dredged soils by a pump dredger, generally coarse grained soils are separated from fines with dropping at the near part of the pump dredger. This kind of seperation of fine contents could be a factor of liquefaction by earthquake. In Korea, recently, earthquakes with magnitude of 3.0 or higher are distinctively increasing in 1990. In this study, cyclic shear characterics of Saemanguem Dredged sand depending on fine content were analyzed. A series of undrained cyclic triaxial test with cyclic stress ratio ($\sigma_d/{2\sigma_{{\upsilon}c}}'$) were performed on both isotropic consolidated specimen and sand with fine contents of 0%, 5%, 15%, 30%, 40% under the effective vertical stress of 100kPa and 50% and 60%, 70% of relative density for fine content of 0%, respectively. In the test results, cyclic shear strength increased by increasing of cyclic stress ratio($\sigma_d/{2\sigma_{{\upsilon}c}}'$) with increasing the relative density at the same number of cyclic under the effective confining pressure of 100kPa. It is almost highest the double amplitude(DA) 1%, 3%, 5%, 7.5% and 10% at fine content of 15% between Cyclic stress ratio($\sigma_d/{2\sigma_{{\upsilon}c}}'$) value at cyclic number five and fine content. Number of cyclic is 30 under the effective vertical stress of 100kPa, 70% of relative density for fine content of 15%. when the cyclic stress ratio at each relative density was compared at cyclic number five, the double amplitude(DA) 1%, 3%, 5%, 7.5% and 10%, and the pore-pressure ratio (${\Delta}u/{\sigma'}_c$) 0.95 value were compared; under the relative density of 70% and the effective confining pressure of 100kPa. The pore-pressure ratio (${\Delta}u/{\sigma'}_c$) 0.95 value showed a similar trend to the double amplitude (DA) 5% line.

• Safety and Health at Work
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• v.6 no.1
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• pp.18-24
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• 2015

Background: In 2006, three farmers died at the bottom of an agricultural shallow well where the atmosphere contained only 6% oxygen. This study aimed to document the variability of levels of oxygen and selected hazardous gases in the atmosphere of wells, and to identify ambient conditions associated with the low-oxygen situation. Methods: A cross-sectional survey, conducted in June 2007 and July 2007, measured the levels of oxygen, carbon monoxide, hydrogen sulfide, and explosive gas (percentage of lower explosive limit) at different depths of the atmosphere inside 253 wells in Kamphaengphet and Phitsanulok provinces. Ambient conditions and well use by farmers were recorded. Carbon dioxide was measured in a subset of wells. Variables independently associated with low-oxygen condition (<19.5%) were identified using multivariate logistic regression. Results: One in five agricultural shallow wells had a low-oxygen status, with oxygen concentration decreasing with increasing depth within the well. The deepest-depth oxygen reading ranged from 0.0% to 20.9%. Low levels of other hazardous gases were detected in a small number of wells. The low-oxygen status was independently associated with the depth of the atmosphere column to the water surface [odds ratio (OR) = 13.5 for 8-11 m vs. <6 m], depth of water (OR = 0.17 for 3-<8 m vs. 0-1 m), well cover (OR = 3.95), time elapsed since the last rainfall (OR = 7.44 for >2 days vs. <1 day), and location of well in sandy soil (OR = 3.72). Among 11 wells tested, carbon dioxide was detected in high concentration (>25,000 ppm) in seven wells with a low oxygen level. Conclusion: Oxygen concentrations in the wells vary widely even within a small area and decrease with increasing depth.

• Journal of Korean Society of Transportation
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• v.28 no.2
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• pp.161-169
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• 2010

The amount of energy consumed by a transportation system in a city is influenced not just by a transportation system itself but also by city's spatial character. Yet there have been very limited studies on this subject. This study investigates the factors that influence the energy consumption by a transportation system and city's spatial character. The model of an urban area confined within a definite boundary is assumed in order to develop the relationships between the energy consumption and the transportation system. Various assumptions on the character of a city and activities are made. An equation for computation of the energy consumption is derived with such factors as modal split, densities of residents and workers, as well as technological development. Using the equation, sensitivity analyses are performed in order to identify the relationships between energy consumption and influencing factors. It is found that the modal split is the most powerful factor that determines the energy consumption by the transportation system. Yet it is also found that the densities of residents and workers and the technological factors are very important in determining the amount of energy consumption as well.

• Journal of Periodontal and Implant Science
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• v.52 no.4
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• pp.325-337
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• 2022

Purpose: The aim of this study was to investigate the effect of (1) the size of the bony access window and (2) collagen membrane coverage over the window in sinus floor elevation in a rabbit sinus model. Methods: Small bony access windows (SW; ø 2.8 mm) were made in 6 rabbits and large windows (LW; ø 6 mm) in 6 other rabbits. Both sinuses in each rabbit were allocated to groups with or without coverage of a collagen membrane (CM) on the window, resulting in 4 groups: SW, LW, SW+CM, and LW+CM. After 4 weeks of healing, micro-computed tomographic, histologic, and histomorphometric analyses were performed. Results: Bony healing in the window area was incomplete in all groups, but most bone graft particles were well confined in the augmented cavity. Histologically, the pattern of new bone formation was similar in all groups. Histomorphometrically, the percentage of newly formed bone was greater in the groups with CM than in the groups without CM, and in the groups with SW than in the groups with LW (12.92%±6.40% in the SW+CM group, 4.21%±7.73% in the SW group, 10.45%±4.81% in the LW+CM group, 11.77%±3.83% in the LW group). The above differences were not statistically significant (P>0.05). Conclusions: The combination of a small bony access window and the use of a collagen membrane over the window favored new bone formation compared to other groups, but this result should be further investigated due to the limitations of the present animal model.

• Journal of the Korean Geographical Society
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• v.29 no.1
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• pp.65-83
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• 1994

Sevaral problems of administrative area sysem in Korea have been brought up for a long time. Because its frame has remained since Chosun and Japanese colonial period in spite of changing local administrative environment in accordance with rapid industrialization and urbanization. Recent reform of city (Shi)- county (Gun) integration is derived from this argument. But problems which permeate deeply overall system cannot be solved by partial reorganization of Shi-Gun. They may be rationalized only through the reform of the whole system. The aims of this study are to analyze problems of administrative area system entirelr and to discuss the direction of its reform from that point of view. Major problems of administrative area system are summed up into the followings. Firstly, it is found that administrative hierarchies are too many levels. Contemporary administrative hierarchical structure is 4 levels: regional autonomous government (Tukpyolshi, Jik'halshi, Do), local autonomous government (Shi, Gun), two leveis of auxiliary administrative area (Up, Myun and Ri). These hierarchies were established in late period of Chosun which transportation was undeveloped and residential activity space was confined. But today developing transportion and expanding sphere of life don't need administrative hierarchical structurl with many levels. Besides developing administrative technology reduces administrative space by degrees. Many levels of contemporary administrative hierarchical structure are main factor of administrative inefficency, discording with settlement system. Second problem is that Tukpyolshi and Jik'halshi - cities under direct control of the central government as metropolitan area - underbounded cities. Underbounded city discomforts residential life and increases external elects of local pulic services. Especially this problem is Seoul, Pusan and Daegu. Third problem is that Do-areas are mostly two larger in integrating into single sphere of life. In fact each of them consistes of two or three sphere of life. Fourth Problem is metropolitan government system that central city is seperated from complementary area, i.e. Do. It brings about weakening the economic force of Do. Fifth problem is that several cities divided single sphere of life. It is main factor of finantial inefficency and facing difficult regional administration. Finally necessity of rural parish (Myun.) is diminished gradually with higher order center oriented activty of rural residents. First of all administrative area system should corresponds with substantial sphere of life in order to solve these problems. Followings are some key directions this study proposes on the reform of administrative area system from that standpoint. 1. Principles of reorgnization -- integration of central dty with complementary area. -- correspondence of administrative hierarchical structure with settlement system. -- correspondence of boundary of administrative area with sphere of life. 2. Reform strategy -- Jik'halshi is integrated with Do and is under the contol of Do. -- Small Seoul shi (city) which have special functions as captal is demarcated in Seoul tukpyolshi and 22 autonomous distrcts of Seoul tukpyolshi is integrated into 3-4 cities. -- Neighboring cities (Shies) in single sphere of life are intrgrated into single city (Shj). -- Myun and Ri are abolished in rural region and new unit of local administrative area on the basis of lowest order sphere of life into which 3-4 Ries are integrated replaces them.

• Archives of Craniofacial Surgery
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• v.11 no.2
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• pp.91-94
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• 2010

Purpose: For the best possible aesthetic reconstruction after craniofacial bone tumor resection, pasteurization has been adopted to devitalize neoplastic cells while maintaining osteoinductive properties and mechanical strength. This case report aims to demonstrate a long-term follow-up result of a monostotic fibrous dysplasia in frontal bone which was reconstructed by pasteurized tumoral autograft in situ. Methods: A 14-year-old girl presented with a hard, nontender, slowly growing mass of 6-year duration on her left supraorbital area. CT showed $5{\times}4{\times}3cm$ sized well defined bony mass confined to frontal bone with heterogeneous density. Tumor was excised completely through bicoronal approach and reimplanted to its original site after pasteurization at $60^{\circ}C$ for 30 minutes. The pathologic examination confirmed fibrous dysplasia. Results: She revisited our clinic 5 years later after suffering some assault on her face. On CT examination, pasteurized tumoral autograft was incorporated to host bone except the fractured upper orbital rim without any evidence of recurrence. She has been satisfied with the result. Conclusion: Pasteurization offers a simple, reliable, cosmetic, economic, and durable reconstruction method for craniofacial skeletal tumor. It has advantages of both biologic incorporation ability and mechanical strength without risk of recurrence. So, it should be considered as one of the primary options in benign as well as resectable malignant tumors of craniofacial skeleton.

• Journal of Information Processing Systems
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• v.1 no.1 s.1
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• pp.70-74
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• 2005

Sensor networks have emerged as an interesting and important research area in the last few years. These networks require that time be synchronized more precisely than in traditional Internet applications. In this paper, we compared and analyzed the performance of the RBS and TDP mechanisms in the view of the number of generated messages and the synchronization accuracy. The reason that we chose be RBS ad the TDP mechanism to be compared is because the RES is an innovative method to achieve the high accurate synchronization. And TDP is a new method taking over the NTP method which has been used widely in the Internet. We simulated the performance of two methods assuming the IEEE 802.11 CSMA/CA MAC. As for the number of nodes in the sensor networks, two situations of 25 (for the small size network) and 100 (for the large size network) nodes are used. In the aspect of the number of messages generated for the synchronization, TDP is far better than RBS. But, the synchronization accuracy of RBS is far higher than that of TDP. We cm conclude that in a small size sensor networks requiring very high accuracy, such as an application of very high speed objects tracking in a confined space, the RBS is more proper than TDP even though the RBS may generate more traffic than TDP. But, in a wide range sensor networks with a large number of nodes, TDP is more realistic though the accuracy is somewhat worse than RBS because RBS may make so many synchronization messages, and then consume more energies at each node. So, two mechanisms may be used selectively according to the required environments, without saying that the one method is always better than the other.

• Journal of Radiation Industry
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• v.8 no.3
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• pp.161-168
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• 2014

Increasing utilization of radiation and RI (Radioisotope) in nuclear industry including non-power area has achieved sustainable development of radiation industry. Industries are no longer confined by a single technology or abilities but expanded for application gradually. RI-Biomics fields are one of the convergence technology that is recognized on a high-tech industry. Unlike the conventional industry, RI-Biomics field needs to various specialists to perform related task. There is no domestic training program to educate the whole process. This study aims to suggest the plan for improvement of practical skills for specialists in RI-Biomics through development of our training program. For this purpose, we have first investigated the opinion about classification scheme from experts and then analyzed the results in order to reflecting our training program. Based on analyzed results, conformity assessment was executed to organize curriculum through status of constructed device and instructor in domestic. Our training program was performed jointly with KAERI (Korea Atomic Energy Research Institute). RI-Biomics center is prepared with facilities of overall experiment to improve quality of education. Due to the fact that specialists have routine task, we organized a five-day short course to reflect temporal difficulties. We performed a trial operation to 6 participants in RI-Biomics field. Through the survey for the specialists who participated in the program, we evaluated the efficiency of our training program. The results showed that participants were satisfied with the organized curriculum and educational materials. Therefore, our program is expected to be utilized as basic research data to develop feasible program for policy development and to improve practical skills in RI-Biomics.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.E
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• pp.17-28
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• 1999

Gas-liquid contact tests above a perforated-plate were conducted with air and water at flooding gas-flow conditions in order to study two-phase flow characteristics in a limestone-gypsum SO2 absorber. Gas layers were in the form of air pockets and confined to the limited areas around each duct pipe, while the remaining tary area were in the wet condition. The liquid above the tray was always in the flooded and even fluidized conditions at gas flows over the range studied, although vigorous bubbly or churn-turbulent two-phase regime was only observed in the immediate vicinity of the gas hole exit at low gas loads. The froth zone was extremely active to provide intimate contact between gas and liquid so that the necessary mass transfer operation can take place, which is the primary purpose of high-performance SO2 absorbers. Howefer, the absorber $\Delta$P was 250mmH2O for the initial water level at 150mm, which is an important issue to be resolved for economical operation of the SO2 absorber. It was seen in the liquid level-and gas flow-transient tests that changes in the absorber liquid inventory were much more pronounced for intimate gas-liquid contact than changes in the gas flow. Based on the 4- and 8-duct pipe test results, grouping the duct pipes near the center of the test tray seemed to promote better recirulation of liquid from gas-liquid contact zone back to the reaction tank so that the absorbed SO2 can be neutralized.

• Journal of Wetlands Research
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• v.7 no.2
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• pp.121-132
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• 2005

To classify the surface sedimentary facies using IKONOS image collected over Hwangdo tidal flat in Cheonsu Bay, the optical reflectance was compared for characterizing various sedimentary environments such as grain size, tidal channel pattern and area ratio of surface remnant water. The intertidal DEM (Digital Elevation Model) was generated by echo-sounder for analyzing the relationship between IKONOS image and sedimentary environments including topography. The boundary of the optical reflectance between mud-mixed facies and sand facies was distinct, and discrimination of the associated sandbar feature was also possible. The mud-mixed facies coupled with intricate tidal channels is confined to the relatively hi호 topography of Hwangdo tidal flat. The boundary between mud and mixed flat was indistinct in IKONOS optical reflectance but it would have a difference in the area ratio of surface remnant water. The dark area in the image represented the well developed sand facies having a lot of surface remnant water due to the relatively low surface topography. The overall accuracy of characterizing the surface sediment facies by maximum likelihood classification method was 86.2 %. These results demonstrate that high spatial resolution satellite imagery such as IKONOS coupled with knowledge of grain size, surface remnant water and tidal channel network can be effectively used to characterize the surface sedimentary facies (mud, mixed and sand) network of the tidal flat environments.