• Journal of Soil and Groundwater Environment
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• v.6 no.3
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• pp.53-59
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• 2001

There is a lot of method to manage the insanitary landfill but vertical cutoff walls have been widespreadly used and were installed into the subsurface to act as a barrier to horizontal groundwater flow, The stabilized material such as specialized cement or mixed soil with additives has been generally applied for the materials of the deep soil mixing barrier in korea. The amount of the stabilized material is dependent on the field conditions, because the mixing ratio of the material and the field soil should achieve a requirement in the coefficient of permeability, lower than 1.0$\times$$10^{7}$cm/sec. This study determined the quantity and optimized function ratio of the stabilized material in the formation process of the mixed barrier that was added with stabilized material on the field soil classified into SW-SC under USCS (Unified Soil Classification System). After that the fly ash and lime were selected as an additives an that could improve the function of the stabilized material and then the method to improve the functional progress in the usage of putting into the stabilized material as an appropriate ratio was studied and reviewed. The author used the flexible-wall permeameter for measuring the permeability and unconfined compressive strength tester for compressive strength, and in the view of environmental engineering the absorption test of heavy metals and leaching test regulated by Korean Waste Management Act were performed. As the results, the suitable mixing ratio of the stabilized material in the deep soil mixing barrier was determined as 13 percent. To make workability easy, the ratio of stabilized material and water was proven to be 1 : 1.5. With the results, the range of the portion of the additives(fly ash : lime= 70 : 30) was proven to be 20-40% for improving the function of the stabilized material, lowering of permeability. In heavy metal absorption assessment of the mixing barrier system with the additives, the result of heavy metal absorption was proved to be almost same with the case of the original stabilized material; high removal efficiency of heavy metals. In addition, the leaching concentration of heavy metals from the leaching test for the environmental hazard assessment showed lower than the regulated criteria.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.4
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• pp.241-248
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• 2010

This paper deals with the performance analysis and design of the Darrieus-type vertical axis turbine to evaluate the effect of key design parameters such as number of blade, blade chord, pitch and camber. The commercial CFD software FLUENT was employed as an unsteady Reynolds-Averaged Navier-Stokes (RANS) solver with k-e turbulent model. Grid system was modelled by GAMBIT. Basic numerical methodology of the present study is appeared in Jung et al. (2009). Two-dimensional analysis was mostly adopted to avoid the barrier of massive calculation required for parametric study. It was found that the highly efficient turbine model could be designed through the optimization of design parametrrs.

• 한국해양학회지
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• v.21 no.3
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• pp.146-155
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• 1986

Zooplankton samples of upper 50m layer in May, 1985 and of various depth intervals depending on thermal structure in October, 1985 were analyzed. Standing stock represents mean of 538inds/㎥ in spring and 267 inds/㎥ and 508inds/㎥ of whole column mean and surface layer in fall, respectively. A total of 55 and 104taxa is identified in each season and accumulated data list at least 123 species inhabiting in the study area. Copepods dominate in the zooplankton community, followed by protozoans and appendicularians in both seasons. In surface layer, distribution of subtropical species and standing stock seems to illuminate the effects of the Tsushima Current and the North Korean Cold Watermass in cold season, whereas only standing stock shows discernable variation in warm season. Concerning whole water column, depth of permanent thermocline bottom, at about 120m in fall 1985, plays significant role as a barrier to the distribution of mesopelagic cold water species. Serial sampling in October, 1985 does not reveal any perceivable diel vertical migration, which is considered to confirm the earlier suggest that owing to the lack of true abyssal species zooplankton biomass of deeper gayer is very poor, so that diel vertical migration of the East Sea is weak.

• Magazine of the Korean Society of Agricultural Engineers
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• v.30 no.1
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• pp.38-49
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• 1988

This paper presented as follows results of laboratory model tests with various shaped footings on soil bed reinforced with the strips on the base of behaviour of soil structure according to the loads and triaxial test results reinforced with geotextiles. Their parameters studied were the effects on the bearing capacity of a footing of the first layer of reinforcement, horizontal and vertical spacing of layers, number of layers, tensile strength of reinforcement and iclination load to the vertical 1.Depending on the strip arrangement, ultimate bearing capacity values could be more improved than urreinforced soil and the failure of soil was that the soil structure was transfered from the macrospace to microspase and its arrangement, from edge to edge to face to face. 2.The reinforcement was produced the reinforcing effects due to controlling the value of factor of one and permeable reinforcement was never a barrier of drainage condition. 3.Strength ratio was decreased as a linear shape according to increment of saturation degree of soil used even though at the lower strength ratio, the value of M-factor was rot influenced on the strength ratio but impermeable reinforcement decreased the strength of bearing capacity. 4.Ultimate bearing capacity under the plane-strain condition was appeared a little larger than triaxial or the other theoretical formulars and the circular footing more effective. 5.The maximum reinforcing effects were obtained at U I B=o.5, B / B=3 and N=3, when over that limit only acting as a anchor, and same strength of fabric appeared larger reinforcing effects compared to the thinner one. 6.As the LDR increased, more and more BCR occurred and there was appeared a block action below Z / B=O.5, but over the value, decrement of BCR was shown linear relation, and no effects above one. 7.The coefficient of the inclination was shown of minimum at the three layers of fabrics, but the value of H / B related to the ultimate load was decreased as increment of inclination degree, even though over the value of 4.5 there wasn't expected to the reinforcing effects As a consequence of the effects on load inclination, the degree of inclination of 15 per cent was decreased the bearing capacity of 70 per cent but irnproved the effects of 45 per cent through the insertion of geotextile.

• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.167-171
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• 2013

PURPOSE. The purpose of this case series was to evaluate the effect of guided bone regeneration using demineralized allogenic bone matrix with calcium sulfate. MATERIALS AND METHODS. Guided bone regeneration using Demineralized Allogenic Bone Matrix with Calcium Sulfate ($AlloMatrix^{TM}$, Wright. USA) was performed at the time of implant placement from February 2010 to April 2010. At the time of the second surgery, clinical evaluation of bone healing and histologic evaluation were performed. The study included 10 patients, and 23 implants were placed. The extent of bony defects around implants was determined by measuring the horizontal and vertical bone defects using a periodontal probe from the mesial, distal, buccal, and lingual sides and calculating the mean and standard deviation of these measurements. Wedge-shaped tissue samples were obtained from 3 patients and histologic examination was performed. RESULTS. In clinical evaluation, it was observed that horizontal bone defects were completely healed with new bones, and in the vertical bone defect area, 15.1% of the original defect area remained. In 3 patients, histological tests were performed, and 16.7-41.7% new bone formation was confirmed. Bone graft materials slowly underwent resorption over time. CONCLUSION. $AlloMatrix^{TM}$ is an allograft material that can be readily manipulated. It does not require the use of barrier membranes, and good bone regeneration can be achieved with time.

• Journal of Periodontal and Implant Science
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• v.31 no.2
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• pp.437-449
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• 2001

The socket preservation procedure was a simple and effective technique, and has better prognosis for implantation. The socket preservation usually used barrier membrane in combination with/without alloplastic bone materials. A recently study had shown that a regenerative therapy to tooth extraction utilizing growth factors made better results. Platelet-rich plasma was clinically easy method that acquired the growth factors, and is known that accelerated new bone formation and mineralization of bone graft materials. The purpose of this study was to evaluate clinical and histopathologic results which occur following socket preservations using platelet-rich plasma and bovine bone powder. Twelve patients who required extraction of one or more teeth for implantation at the department of periodontics in Dankook University Dental Hospital were selected. Extraction sockets were treated by using platelet-rich plasma and bovine bone powder. 3 months later, we observed clinical and histopathological results as follows: 1. Internal vertical measurement was an average of 7.33mm preoperatively and statistically significantly decreased to an average of 1.42mm postoperatively(p<0.05). 2. External vertical measurement was an average of 3.33mm preoperatively and decreased to an average of 2.75mm postoperatively; therefore there was no significant difference. 3. Horizontal measurement was an average of 7.75mm preoperatively and statistically decreased to an average of 6.08mm postoperatively(p<0.05). 4. Osteocyte-like cells and new bone formation connected with bovine bone grafts were observed in histopathologic examination. This study implied that platelet-rich plasma and bovine bone powder grafts were effective treatment for socket preservation and regeneration of severe bony defect made by implantation failure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.79-93
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• 2008

Water quality simulations on the Saemangeum inner reservoir have been carried out using EFDC model to understand water quality variations caused by abrupt physical changes due to closing of tidal barrier. According to hydrodynamic simulation, model reproduces not only outer regional dynamics but also inner superelevation very well. Calibration and verification of water quality models accomplished using observed data taken before closing. Also sensitivity tests regarding riverine discharges and tidal flats were done. Due to enlarging of always wet zone caused by super elevation on inner tidal flats, predicted DO decreases at that region as a result of SOD. Moreover shrink of mixing zone after closing of dike causes deteriorating of water quality showing DO as 2 mg/L during summer at Mangyeong and Dongjin estuaries, however it does not spread to middle part of the reservoir. Vertical stratification occurs after closing and shows vertical differences in DO concentration at least 6 mg/L to 7 mg/L in summer season. Most part of the reservoir is getting stratified and it leads to an oxigen deficit zone near bottom.

• Journal of Soil and Groundwater Environment
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• v.13 no.2
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• pp.12-20
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• 2008

This study was conducted to investigate the spatial distributions of chromated copper arsenate (CCA) metals in soils around three log structures and a sound barrier, all built with CCA-treated wood. Sixty-six surface and 35 profile soil samples were collected around the wood structures in addition to 13 background soil samples. The concentrations of chromium, copper, and arsenic in the soil samples collected in the vicinity of the structures were higher than those in the background samples, except in the case of one structure. The concentrations in the surface soils adjacent to the 3-year-old structures seemed to be higher than those in the soils adjacent to the 8-year-old ones. Although the lateral distributions of the metals varied with the structures, chromium and arsenic appeared to show concentration gradients within 20-60 cm and 40-100 cm, respectively. Copper seemed to be the least mobile, displaying concentration gradients only within 20 cm. Even though there were no explicit vertical concentration gradients for any of the metals according to the profile soil sample analysis, chromium and copper seemed to show concentration gradients only up to 5 and 10 cm, respectively, whereas arsenic showed gradients up to 35 cm. At study sites, it was evident that heavy metals leached into soil from CCA-treated wood were confined to neighboring areas both laterally and vertically, and that any plausible ecological impact may occur only within a small range.

• Tunnel and Underground Space
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• v.24 no.6
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• pp.405-417
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• 2014

In a high-level waste repository, the gap fill of the engineered barrier is an important component that influences the performance of the buffer and backfill. This paper reviewed the overseas status of R&D on the gap fill used engineered barriers, through which the concept of the gap fill, manufacturing techniques, pellet-molding characteristics, and emplacement techniques were summarized. The concept of a gap fill differs for each country depending on its disposal type and concept. Bentonite has been considered a major material of a gap fill, and clay as an inert filler. Gap fill was used in the form of pellets, granules, or a pellet-granule blend. Pellets are manufactured through one of the following techniques: static compaction, roller compression, or extrusion-cutting. Among these techniques, countries have focused on developing advanced technologies of roller compression and extrusion-cutting techniques for industrial pellet production. The dry density and integrity of the pellet are sensitive to water content, constituent material, manufacturing technique, and pellet size, and are less sensitive to the pressure applied during the manufacturing. For the emplacement of the gap fill, pouring, pouring and tamping, and pouring with vibration techniques were used in the buffer gap of the vertical deposition hole; blowing through the use of shotcrete technology and auger placement and compaction techniques have been used in the gap of horizontal deposition hole and tunnel. However, these emplacement techniques are still technically at the beginning stage, and thus additional research and development are expected to be needed.

• Journal of IKEEE
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• v.23 no.1
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• pp.193-199
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• 2019

In this study, we have proposed a floating metal guard ring structure based on TCAD simulation in order to enhance the breakdown voltage characteristics of gallium oxide ($Ga_2O_3$) vertical high voltage switching Schottky barrier diode. Unlike conventional guard ring structures, the floating metal guard rings do not require an ion implantation process. The locally enhanced high electric field at the anode corner was successfully suppressed by the metal guard rings, resulting in breakdown voltage enhancement. The number of guard rings and their width and spacing were varied for structural optimization during which the current-voltage characteristics and internal electric field and potential distributions were carefully investigated. For an n-type drift layer with a doping concentration of $5{\times}10^{16}cm^{-3}$ and a thickness of $5{\mu}m$, the optimum guard ring structure had 5 guard rings with an individual ring width of $1.5{\mu}m$ and a spacing of $0.2{\mu}m$ between rings. The breakdown voltage was increased from 940 V to 2000 V without degradation of on-resistance by employing the optimum guard ring structure. The proposed floating metal guard ring structure can improve the device performance without requiring an additional fabrication step.