• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.172-185
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• 2009

This paper presents case histories and research projects related to geotechnical challenges at waste landfill sites in Japan. Due to the limitation of inland space available to waste disposal, coastal landfills and the associated containment systems are important considerations, particularly for metropolitan areas. Experimental works on heavy metals mobility using a large column to simulate the redox potential at the coastal landfill sites are introduced. After the closure of landfill sites, they are expected to be utilized as new land space, since new space is difficult to find in urban area. In the redevelopment of such closed landfill sites, there are possibilities of environmental risks, such as generation of toxic gas and leachate, differential settlement of the waste layer, damage to the lining system. Whether the pile installation through the clay layer acting as a landfill bottom barrier is environmentally acceptable or not has been a great concern in the redevelopment of closed waste landfill sites in particular coastal landfill sites. An analytical study to evaluate the cost-effective remedial option for a dumped waste site located along a landslide area, where cut-off wall keyed into the aquitard might elevate groundwater level and thus may not be employed, is presented.

• Journal of the Korean Geotechnical Society
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• v.36 no.10
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• pp.33-39
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• 2020

A geological repository has been considered as an option for the disposal of high-level radioactive waste (HLW). The HLW is disposed in a host rock at a depth of 500~1,000 meters below the ground surface based on the concept of engineered barrier system (EBS). The EBS is composed of a disposal canister, buffer material, backfill material, and gap-filling material. The compacted bentonite buffer is very important since it can restrain the release of radionuclide and protect the canister from the inflow of ground water. The saturation of the buffer decreases because high temperature in a disposal canister is released into the surrounding buffer material, but saturation of the buffer increases because of the inflow of ground water. The unsaturated properties of the buffer are critical input parameters for the entire safety assessment of the engineered barrier system. In Korea, Gyeongju bentonite can be considered as a candidate buffer material, but there are few test results of the unsaturated properties considering temperature variation. Therefore, this paper conducted experiment of soil-water characteristic curve for the Gyeongju compacted bentonite considering temperature variation under a constant water content condition. The relative error showed approximately 2% between test results and modified van-Genuchten model values.

• Journal of Korean Neurosurgical Society
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• v.53 no.2
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• pp.65-71
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• 2013

Objective : In order to develop a novel nerve guidance channel using porcine small intestinal submucosa (SIS) for nerve regeneration, we investigated the possibility of SIS, a tissue consisting of acellular collagen material without cellular immunogenicity, and containing many kinds of growth factors, as a natural material with a new bioactive functionality. Methods : Left sciatic nerves were cut 5 mm in length, in 14 Sprague-Dawley rats. Grafts between the cut nerve ends were performed with a silicone tube (Silicon group, n=7) and rolled porcine SIS (SIS group, n=7). All rats underwent a motor function test and an electromyography (EMG) study on 4 and 10 weeks after grafting. After last EMG studies, the grafts, including proximal and distal nerve segments, were retrieved for histological analysis. Results : Foot ulcers, due to hypesthesia, were fewer in SIS group than in Silicon group. The run time tests for motor function study were 2.67 seconds in Silicon group and 5.92 seconds in SIS group. Rats in SIS group showed a better EMG response for distal motor latency and amplitude than in Silicon group. Histologically, all grafts contained some axons and myelination. However, the number of axons and the degree of myelination were significantly higher in SIS group than Silicon group. Conclusion : These results show that the porcine SIS was an excellent option as a natural biomaterial for peripheral nerve regeneration since this material contains many kinds of nerve growth factors. Furthermore, it could be used as a biocompatible barrier covering neural tissue.

• Tuberculosis and Respiratory Diseases
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• v.69 no.2
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• pp.75-80
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• 2010

The year of 2009~2010 brought a number of concepts and new ideas were evaluated with promising results. However, some studies that challenged many beliefs. In acute respiratory distress syndrome (ARDS), recent clinical studies took into consideration of pathophysiologic changes of respiratory system compliance. Meta-analysis of positive end-expiratory pressure trials showed survival benefit of high positive end-expiratory pressure in ARDS. Until now, prone positioning did not show survival benefit in patients with ARDS. Extracorporeal membrane oxygenation (ECMO) based management improved survival in patients with severe ARDS. ECMO can be a management option in severe ARDS. Sedation is a standard practice in critically ill patients needing mechanical ventilation. However, Danish group reported less sedation of critically ill patients receiving mechanical ventilation was associated with an increase in days without ventilation. Although this single center study has some limitations, the overall results are promising. Use of maximal sterile barrier precautions (mask, sterile gown, sterile gloves, and large sterile drapes) with chlorhexidine-impregnated dressing reduced central venous catheter related infection. Selective oropharyngeal decontamination (application of topical antibiotics in the oropharynx) reduced the mortality rate of an intensive care unit (ICU) population. Normoglycemia in Intensive Care Evaluation and Survival Using Glucose Algorithm Regulation (NICE-SUGAR) trial reported intensive glucose control increased mortality among adults in the ICU. Some of the results of above papers are promising. However, some ideas may need for more frequent individual assessment and increase the workload of ICU staffs. Before implementation of new practice in ICU, we should take into consideration of individual hospital situation including human and material resources.

• Archives of Craniofacial Surgery
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• v.20 no.3
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• pp.176-180
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• 2019

Background: Parotidectomy is the treatment of choice in many parotid tumors. Due to the extensive nature of the procedure, unfavorable complications such as gustatory sweating, surgical site depression are common. Various techniques using fascia, muscle or AlloDerm have been developed but debate still remains regarding its availability and affordability. We applied a newly developed acellular dermal matrix (Insuregraf) to the parotidectomy field to act as a physical barrier and to provide adequate filling effect for prevention of functional and aesthetic complications. Methods: From March 2010 to March 2017, 30 patients with parotid tumors underwent superficial parotidectomy. Twenty patients underwent only superficial parotidectomy. Ten patients had Insuregraf applied to the surgical site after superficial parotidectomy. We evaluated the incidence of Frey's syndrome, surgical site depression, and patient satisfaction rate in both groups. Results: The incidence of Frey's syndrome was lower in the Insuregraf group (0 vs. 2). Surgical site depression was also lower in the Insuregraf group (2 vs. 20). Satisfaction score for facial contour in Insuregraf group was 9.2 out of 10, which was comparable to 6.2 out of 10 in the control group. Conclusion: Application of Insuregraf after superficial parotidectomy is an effective surgical procedure to prevent complications such as Frey's syndrome and surgical site depression. This technique is affordable and safe with no immune reactions. Above all this surgical method should be considered as an option for patients who are concerned about the contour of the face after surgery.

• Journal of Soil and Groundwater Environment
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• v.14 no.3
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• pp.40-46
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• 2009

The applicability of a well-type autotrophic sulfur-oxidizing reactive barrier (L $\times$ W $\times$ D = $3m\;{\times}\;4\;m\;{\times}\;2\;m$) as a long-term treatment option for nitrate removal in groundwater was evaluated. Pilot-scale (L $\times$ W $\times$ D = $8m\;{\times}\;4\;m\;{\times}\;2\;m$) flow-tank experiments were conducted to examine remedial efficacy of the well-type reactive barrier. A total of 80 kg sulfur granules as an electron donor and Thiobacillus denitrificans as an active bacterial species were prepared. Thiobacillus denitrificans was successfully colonized on the surface of the sulfur granules and the microflora transformed nitrate with removal efficiency of ~12% (0.07 mM) for 11 days, ~24% (1.3 mM) for 18 days, ~45% (2.4 mM) for 32 days, and ~52% (2.8 mM) for 60 days. Sulfur granules attached to Thiobacillus denitrificans were used to construct the well-type reactive barrier comprising three discrete barriers installed at 1-m interval downstream. Average initial nitrate concentrations were 181 mg/L for the first 28 days and 281 mg/L for the next 14 days. For the 181 mg/L (2.9 mM) plume, nitrate concentrations decreased by ~2% (0.06 mM), ~9% (0.27 mM), and ~15% (0.44 mM) after $1^{st}$, $2^{nd}$, and $3^{rd}$ barriers, respectively. For the 281 mg/L (4.5 mM) plume, nitrate concentrations decreased by ~1% (0.02 mM), ~6% (0.27 mM), and ~8% (0.37 mM) after $1^{st}$, $2^{nd}$, and $3^{rd}$ barriers, respectively. Nitrate plume was flowed through the flow-tank for 49 days by supplying $1.24\;m^3/d$ of nitrate solution. During nitrate treatment, flow velocity (0.44 m/d), pH (6.7 to 8.3), and DO (0.9~2.8 mg/L) showed little variations. Incomplete destruction of nitrate plume was attributed to the lack of retention time, rarely transverse dispersion, and inhibiting the activity of denitrification enzymes caused by relatively high DO concentrations. For field applications, it should be considered increments of retention time, modification of well placements, and intrinsic DO concentration.

• Journal of Korea Soil Environment Society
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• v.5 no.2
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• pp.87-97
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• 2000

The effects of environmental conditions, initial dissolved oxygen concentrations, pH, and the presence of electron carrier vitamin $B_{12}$, on the reduction rate of Tn by $Fe^0$ was quantitatively analyzed using a batch reactor In all experiments, TNT reduction was best described with a first order reaction and the reduction rate decreased with the increase in the initial DO concentration. However, the specific reaction rate did not decrease linearly with the increase in the initial DO concentration. In the presence of HEPES buffer 0.2 and 2.0 mM(pH 5.7$\pm$0.2), the specific reaction rate increased more than 5.8 times, which showed reduction rate is rather significantly influenced by the pH of the solution. To test the possibility of reaction rate enhancement, well-known electron carrier(or mediator) , vitamin $B_{12}$, has augmented besides $Fe^0$. In the presence of 8.0 $mu\textrm{g}$/L of vitamin $B_{12}$, the specific reaction rate increased as much as 14.6 times. The results indicate that the addition of trace amount of vitamin $B_{12}$ can be a promising rate controlling option for the removal of organics using a $Fe^0$ filled permeable reactive barrier.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.1
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• pp.23-28
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• 2009

There is several ways of recycling methods for waste FRP boats. The main one is mechanical recycling that is one of the simple and technically proven methods. It recently has been reported that FRP can be recycled by separating into laminated glass fiber layers instead of crushing into powder. Even though the mechanical recycling is a good way for the eligibility of laminated glass fiber reinforced material, the system should have another option which can collect resin of FRP. Because the resin is still very useful renewable energy source, that cannot be discarded, But FRP is made up of laminated glass fiber(roving cloth layer) which is fire retardant substances and very hard to break into each layer. Due to the high cost of fossil energy the waste plastics should be regenerated to the source of renewable energy. Laminated glass fiber which is recyclable in a very limited way, is currently a serious barrier to waste FRP boat regenerating. This study is to propose a new extracting method which is efficient and environment friendly FRP waste regenerating system. The recycled glass fiber which is obtained by the separation of the roving layer from FRP waste has been found to be useful for concrete(FRC) products or concrete(FRC) structures as fiber reinforced material. And it can be successively applied to renewable energy applications using the waste resins of FRP residue without laminated glass fiber.

• Korean Journal of Social Welfare Studies
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• v.40 no.3
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• pp.181-211
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• 2009

Asian Americans are one of the fastest growing minority groups in the United States. One of the stereotypes associated with Asians is that they are more likely to choose careers in science, medicine, and engineering rather than social science, inclusive of social work, mass communication, or humanities (Leong & Serafica, 1995; Tang et al., 1999). This occupational stereotyping of Asians is not just a myth in that only a few Asians choose social work as a career (Lennon, 2005; NASW, 2006). Few studies exist on Asian Americans who do not choose Asian stereotypical career choices, such as social work. Acknowledging this lack of research, the present study was developed to explore the relationships between factors that may influence Asian Americans who choose social work as their career. Based on Social Cognitive Career Theory (Lent, Brown, & Hackett, 1994), it was hypothesized that acculturation and family immigration status influenced parental involvement, disapproval by significant others as a perceived career barrier among Asian American social workers. A cross-sectional survey design was used in this study. The sample was derived from the members'database of the National Association of Social Workers (NASW). A total of 900 were randomly chosen among 1,802 of Asian American social workers in the NASW database, and 370 Asian American social workers participated in this study with 41 percent of a return rate. Quantitative data were collected through standardized measurements: Suinn-Lew Asian Self-Identity Acculturation Scale (Suinn, Rickard-Figueroa, Lew, & Vigil, 1987); Career Barriers Inventory Revised (Swanson, et al., 1996); and eight items from Tang et al.'s (1999) Asian American Career Development Questionnaire. The data were collected through a combined method of an online survey with option of a paper mail-return questionnaire. Results of the study found significant group differences among family immigration status groups on parental involvement, and perceived likelihood and hindrance of disapproval by significant others. The group of the 2nd generation reported the highest scores of parental involvement among the family immigration status groups. Also, Asian American social workers who represented the 3rd and higher generation of immigration reported lowest perceived likelihood and hindrance scores of disapproval by significant others. However, there was no significant multivariate effect of acculturation on parental involvement, and perceived likelihood and hindrance of disapproval by significant others. Implications and limitations of this study, as well as suggestions for future research, are discussed.