• Journal of Environmental Health Sciences
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• 제48권2호
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• pp.86-95
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• 2022

Background: As high concentrations of uranium and radon have been detected in some areas in Korea, it is considered necessary to investigate natural radioactive materials in the Gwangju area. Objectives: This study aimed to identify the hydrochemical characteristics of groundwater in Gwangju and investigate the distribution characteristics of uranium and radon, which are naturally radioactive substances. Methods: To determine the uranium and radon concentrations in groundwater according to the geology of the Gwangju area, we measured 62 groundwater wells. A geological distribution map of uranium and radon content was prepared for this study. Results: The groundwater type, defined using a Piper diagram, was mainly Ca-HCO₃. The concentration of uranium in the groundwater ranged from 0 to 29.3 ㎍/L, with a mean of 3.3 ㎍/L and a median of 0.9 ㎍/L. The median concentration of uranium in groundwater was highest in alluvium, granitic gneiss, and biotite granite (classified by geological unit), in that order. The concentration of radon in the groundwater ranged from 4.8 to 313.2 Bq/L, with a mean of 75.6 Bq/L and a median of 59.6 Bq/L. The median concentration of radon in groundwater was highest in biotite granite, alluvium, and granitic gneiss, in that order. As a result of the correlation analysis of groundwater in the study area, there was no significant correlation between uranium and radon. Conclusions: In this study area, uranium was shown to be far below the concentrations allowed by drinking water quality standards, but radon concentrations exceeded drinking water quality monitoring standards in 11% of the samples. It was judged that appropriate measures, such as the installation of radon reduction facilities, will be required after a thorough review of high-concentration radon detection sites of in the research area.

• Journal of the Korean Institute of Gas
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• 제22권3호
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• pp.84-90
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• 2018

We researched the way to minimize the damage when the chlorine-leak accident take place in a purification plant. Since the level of risk based on the Off-site Risk Assessment(ORA) is a combination of proportional to the number of residents in the damaged area and frequency of accidents, we suggested the adequate conditions to reduce the number of residents in the damaged area by means of the operating temperature of a handling facility, installation of a emergency shut-off valve, and the analysis of the variation of the damaging range in accordance with the type of enclosure. The coverage of damage was calculated by the 'KORA(Korea Off-site Risk Assessment Supporting Tool) program. The research shows that the lower operating temperature gets, the more emergency shut-off valve being installed and the higher enclosure level of facility becomes, the extent of damage gets decreased. The decreasing rate of worst case was 17.6%, 71%, 34.5% respectively, the decreasing rate of alternative case was 31.6%, 69.0%, 34.8% respectively.

• The Journal of Korean Academy of Prosthodontics
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• 제36권2호
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• pp.258-272
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• 1998

This investigation evaluated patients who received Steri-Oss implants from the Dental Hospital of Chosun University during the period from March 1989 to August 1997. 346 fixtures of 127 patients were included in this study. The results were as follows ; 1.The follow-up period was defined as the period between the surgical placement of the implants and the last follow-up examination. The mean follow-up period was $2.17{\pm}1.21$ years. 2.The period between fixture installation and second surgery was $0.71{\pm}0.44$ years in the maxilla and $0.46{\pm}0.21$ years in the mandible. 3.The number of fixtures which were installed in the upper jaw(112) was less than that in the lower jaw(234) and in the posterior region(260) was more than in the anterior region(86). 4.The length of fixture which was most frequently used was 12 mm and least was 8mm. Screw implants were installed more than cylindrical implants. 3.8mm implant was the most common implans, followed by 4.5mm and 3.25mm. 5.The number of augmentation cases was more than that of non-augmentation cases and the rate of augmentation cases in the maxilla was more than that in the mandible. 6.Implant restorations for partial edentulos patients(94cases) were more than single- tooth implant restorations(33cases) or implant restorations for complete edentulos patients(10cases). 7.Free-standing prostheses for partially edentulous patients were more commom than any other type of connection between implants and natural teeth. 8.Plaque Index($0.95{\pm}0.74$) and Gingival Index($0.31{\pm}0.52$) were very similar around the natural teeth and reflected an acceptable level of plaque and gingivitis control. Mean value for keratinized mucosa index($1.93{\pm}1.20$) remained fairly constant around level 2(1-2 mm keratinized epithelium). 9.Patients were generally satisfied with implant in terms of comfort, function, speech and esthetics. 10.There was not a statistically significant differences in overall survial rate between implants placed in the maxilla (91.5%) and those placed in the mandible (93.8%). Fourteen implants lost before the prosthetic rehabilitation and eleven implants lost following variable periods in function after the prosthetic phase of the treatment. 11.Cause of implant failures was exfoliation or removal of fixture due to non-osseointegration before the prosthetic rehabilitation or due to fracture of fixture, masticatory pain after the prosthetic rehabilitation. 12.The survival rate of Steri-Oss implants using the Kaplan-Meier statistical analysis was 93.8% at 2 year and 86.6% at 5 year, In all cases, implant losses occured predominantly in the healing period. There was a steep decline in the rate of implant loss after the first year. 13.The survival rate of Steri-Oss implants in the anterior region was 94.8% at 2 year and 94.8% at 5 year and that in the posterior region was 92.8% at 2 year and 75.9% at 5 year. In conclusion, this study revealed a number of parameters and guidelines for achieving an optimal success rate in osseointegration.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제32권6호
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• pp.511-520
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• 2010

Purpose: This study was conducted in order to compare the efficacy of osseointegration of three different calcium metaphosphate (CMP) coated implants in the rabbit's femur. Materials and Methods: Twenty four rabbits and three different type of CMP coated implants and RBM implants were used in this study. The animals were divided into 4 groups on the basis of implant surface characteristics. Two implants were installed into the condyle of femur of each rabbits. The animals were sacrificed at 2 and 4 weeks after installation. The undecalcified specimens were prepared for histological, radiological examination and histomorphometric analysis of implant-bone contact ratios (BIC) and bone area ratio (BA). Results: Two implants were failed to osseointegrate and implant success rate was 95.2%. There were not any significant inflammatory response in all groups. Fluorescent image at 4 weeks shows that remodeling is slower in RBM group than CMP group. CMP III showed more active remodeling than CMP I, II. In histomorphologic analysis, BIC ratio at 2 weeks was lower than 4 weeks. Conclusion: The results suggest that the ratios of CMP coated implants were higher than that of RBM control group but there is no significantly difference between RBM group and CMP group. In conclusion, CMP coated implant had more clinical availability than RBM implants.

• Journal of the Korean Society of Environmental Restoration Technology
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• 제14권3호
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• pp.115-141
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• 2011

In urban space, public space is publicly or privately owned space freely accessible by the public. Privately owned public space to the public hosts small-scale rest facilities to serve the public in buildings of certain purposes and sizes for the sake of pleasant urban environment. The Building Act and building ordinances formulate a set of criteria for management and easement of construction standards as well as the area. When creating privately owned public space, one can get incentives through the easement of floor space index and height limit. The purposes of this study were to investigate and analyze privately owned public open space, which is freely accessible by the public, and its adjacent streets and to propose plans to improve the regulations for securing privately owned public space for more rational and practical legal applications. The study then proposed some plans to help to increase the quality of privately owned public space including applying the coefficient to suggest the type of privately owned public space fit for the features of the streets and measure the appropriate utility level differently and distinguishing the mandatory items according to the facility regulations in privately owned public space from the ones qualified for additional points in case of installation. The types of privately owned public open space should be applied differently and the content of facilities intended should be different according to whether it will serve as a resting place or grant more importance on traffic by walking, depending on the features of its adjacent streets. The privately owned public space, the frontage space of building, and the adjacent sidewalks should become a whole and be regarded as one space from the integrated perspective. The results of the study claim further significance in that it investigated privately owned open space and roadside across Seoul. They will serve as useful data to solve the problems with the privately owned public space of the city, which destroys spatial continuity by focusing on the quantitative increase of privately owned open space and creating individual privately owned open spaces and builds high-rise buildings alienated from the existing spaces, and to increase the quality of future privately owned public space.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제38권4호
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• pp.204-211
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• 2012

Objectives: Dental implants installation in patients with diabetes remains controversial as altered bone healing around implants has been reported. And little is known about the biological factors involved in bone healing around implants. The present study aimed to investigate the biological markers around immediately placed implants in rats with controlled and uncontrolled diabetes. Materials and Methods: Twenty rats (40 sites) were divided into the control, insulin-treated and diabetic groups. The rats received streptozotocin (60 mg/kg) to induce diabetes; animals in the insulin-treated group also received three units of subcutaneous slow-release insulin. Two threaded titanium alloy implant ($1.2{\times}3mm$) were placed in the extraction socket of the both maxillary first molars and allowed for healing. Bone blocks including implant were harvested at 3 days, 1, 2 and 4 weeks. The levels of bone morphogenetic protein (BMP)-4, transforming growth factor (TGF)-${\beta}1$, osteocalcin (OC) and osteonectin (ON) were measured in the peri-implant osseous samples by RT-PCR. Results: The BMP-4 level increased immediately in all groups by day 3, then decreased abruptly in the control and the insulin-treated groups. However, by week 4, all groups showed mostly the same amount of BMP-4 expression. The level of TGF-${\beta}1$ also instantly increased by day 3 in the insulin-treated group. This level elevated again reaching the same values as the control group by week 4, but was not as high as the diabetic group. In addition, the expression of OC and ON in the control and insulin-treated groups was higher than that of the diabetic group at 2 weeks and 4 weeks, indicating active bone formation in these groups. Conclusion: The immediate placement of titanium implants in the maxilla of diabetic rat led to an unwanted bone healing response. Conclusively, the results of this study suggest that immediate implant insertion in patients with poorly controlled diabetes might be contraindicated.

• Proceedings of the Korea Crystallographic Association Conference
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• 한국결정학회 2002년도 정기총회 및 추계학술연구발표회
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• pp.5-6
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• 2002

The new spectrometer for X-ray Induced Electron Emission Spectroscopy (XIEES) .has been recently developed in KRISS in collaboration with PTI (Russia). The spectrometer allows to perform research using the XAFS, SXAFS, XANES techniques (D.C.Koningsberger and R.Prins, 1988) as well as the number of techniques from XIEES field(L.A.Bakaleinikov et all, 1992). The experiments may be carried out with registration of transmitted through the sample x-rays (to investigate bulk samples) or/and total electron yield (TEY) from the sample surface that gives the high (down to several atomic mono-layers in soft x-ray region) near surface sensitivity. The combination of these methods together give the possibility to obtain a quantitative information on elemental composition, chemical state, atomic structure for powder samples and solids, including non-crystalline materials (the long range order is not required). The optical design of spectrometer is made according to Johannesson true focusing schematics and presented on the Fig.1. Five stepping motors are used to maintain the focusing condition during the photon energy scan (crystal angle, crystal position along rail, sample goniometer rail angle, sample goniometer position along rail and sample goniometer angle relatively of rail). All movements can be done independently and simultaneously that speeds up the setting of photon energy and allows the using of crystals with different Rowland radil. At present six curved crystals with different d-values and one flat synthetic multilayer are installed on revolver-type monochromator. This arrangement allows the wide range of x-rays from 100 eV up to 25 keV to be obtained. Another 4 stepping motors set exit slit width, sample angle, channeltron position and x-ray detector position. The differential pumping allows to unite vacuum chambers of spectrometer and x-ray generator avoiding the absorption of soft x-rays on Be foil of a window and in atmosphere. Another feature of vacuum system is separation of walls of vacuum chamber (which are deformed by the atmospheric pressure) from optical elements of spectrometer. This warrantees that the optical elements are precisely positioned. The detecting system of the spectrometer consists of two proportional counters, one scintillating detector and one channeltron detector. First proportional counter can be used as I/sub 0/-detector in transmission mode or by measuring the fluorescence from exit slit edge. The last installation can be used to measure the reference data (that is necessary in XANES measurements), in this case the reference sample is installed on slit knife edge. The second proportional counter measures the intensity of x-rays transmitted through the sample. The scintillating detector is used in the same way but on the air for the hard x-rays and for alignment purposes. Total electron yield from the sample is measured by channeltron. The spectrometer is fully controlled by special software that gives the high flexibility and reliability in carrying out of the experiments. Fig.2 and fig.3 present the typical XAFS spectra measured with spectrometer.

• Journal of the Korea Organic Resources Recycling Association
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• 제26권1호
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• pp.55-64
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• 2018

The purpose of this study is to provide a design and operation technical guideline for meeting the appropriate design criteria to biogas utilization treating organic wastes. In accordance with the government's mid-to long-term policies on bio-gasification and energization of organic wastes, the expansion of the waste-to-energy (WTE) facilities is being remarkably promoted. However, because of the limitation of livestock manure containing low-concentration of volatile solids, there has been increased in combined bio-gasification without installing new anaerobic digestion facilities. The characteristics and common problems of each treatment processes were investigated for on-going 11 bio-gasification facilities. The seasonal precision monitoring of chemicophysics analysis on anaerobic digestor samples was conducted to provide guidelines for design and operation according to the progress of biogas utilization. Consequently, Major problems were investigated such as large deviation of organic materials depending on seasons, proper dehumidification of biogas, pretreatment of hydrogen sulfide, operation of power generation and steam. This study was conducted to optimize biogas utilization of type of organic waste(containing sewage sludge and food waste, animal manure), research the facilities problem through field investigation.

• Journal of Korean Society of Forest Science
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• 제96권6호
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• pp.652-660
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• 2007

The study was intended to investigate the changes of construction types of 216 non-national forest roads, which were completed between 1989 and 2005 in Jeollabuk-do, by analyzing their drawing and specification. It was found that the mean length of yearly construction has been significantly reduced after the Policy of Green Forest Roads compared with before the policy. Soil cut-off of earth work was changed from bulldozer to a combination of bulldozer and excavator. Soils were transported by truck in all design, but establishment of spoil-bank was not designed at all. The design of slope revegetation works was developed from turfing and Bastard indigo planting to seed spray, combination of seed spray and belt-sodding, and mulching with coir net and rice straw. In design of the culvert, the average interval of culvert installation was reduced to 92m in step 3, the dimension of culverts was expanded to over 600 mm after step 2, and all drainpipes were corrugated steel pipes. The design length of concrete pavement increased from 40 m/km of step 1 to 240 m/km of step 3. Thanks to the enormously increased amount of concrete pavement, the stability and functionality of forest roads could be improved. Stone masonry was the main work drawn for slope stability, and concrete retaining wall and gabion have been drawn for same object since 1999.

• Journal of the Korea Organic Resources Recycling Association
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• 제26권2호
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• pp.95-103
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• 2018

As a guideline for desulfurization and dehumidification pretreatment facility for optimizing utilization of biogas, the $H_2S$ concentration is set at 150 % which can be treated with iron salts, dehumidification is the optimum value for generator operation, and the relative humidity applied at the utilization of biogas in EU is set at 60 %. We have set up the generator facility guidelines to optimize utilization of biogas. The appropriate amount of biogas should be at least 90 % of the total gas generation, and the capacity of generator facility should be set at 20~30 %. In order to equalize the pressure of the incoming gas the generator, a gas equalization tank should be installed and the generator room average temperature should be kept at $45^{\circ}C$ or less. Since the gas is not produced at a certain methane concentration in the digester, the efficiency is lowered. Therefore, it is required to install an air fuel ratio control system according to the change in methane concentration. Therefore, it is necessary to compensate for the disadvantages of biogasification facilities of organic waste resources and optimize utilization of biogas and improve operation of facilities. This study was conducted to optimize biogas utilization of type of organic waste(containing sewage sludge and food waste, animal manure), investigate the facilities problem and propose design, operation guidelines such as pre-treatment facilities and generators.