• Journal of Korean Society of Environmental Engineers
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• v.38 no.12
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• pp.647-655
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• 2016

Lead dioxide ($PbO_2$) is an electrode material that is effective for organic pollutant degradation based on hydroxyl radical ($^{\bullet}OH$) attack. Representative parameters for $PbO_2$ electrodeposition are summarized to current, temperature, reaction time, concentration of Pb(II) and electrolyte agent. In this study, $Ti/PbO_2$ electrodes were fabricated by electrodeposition method under controlled reaction time, current density, temperature, concentration of $HNO_3$ electrolyte. Effects of deposition parameters on $^{\bullet}OH$ evolution were investigated in terms of electrochemical bleaching of p-Nitrosodimethylaniline (RNO). As major results, the $^{\bullet}OH$ evolution was promoted at the $PbO_2$ that was deposited in longer reaction time (1-90 min), lower current density ($0.5-50mA/cm^2$), higher temperature ($5-65^{\circ}C$) and lower $HNO_3$ concentration (0.01-1.0 M). Especially, the $PbO_2$ which was deposited in 0.01 M of lowest $HNO_3$ concentration by applying $20mA/cm^2$ for above 10 min was most effective on $^{\bullet}OH$ evolution. The performance gap between $PbO_2$s that was best and worst in $^{\bullet}OH$ evolution was about 41%. Among the properties of $PbO_2$ related on $^{\bullet}OH$ evolution performance, conductivity of $Ti/PbO_2$ significantly influenced on $^{\bullet}OH$ evolution. The increase in conductivity promoted $^{\bullet}OH$ evolution. In addition, the increase in crystal size of $PbO_2$ interfered $^{\bullet}OH$ evolution at surface of some $PbO_2$ deposits.

• Journal of Biomedical Engineering Research
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• v.24 no.5
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• pp.401-410
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• 2003

This study investigates the biomechanical efficacies of various cement augmentation techniques with or without pressurization for varying degrees of osteoporotic femur. For this study, a biomechanical analysis using a finite element method (FEM) was undertaken to evaluate surgical procedures, Simulated models include the non-cemented(i.e., hip screw only, Type I), the cement-augmented(Type II), and the cemented augmented with pressurization(Type III) models. To simulate the fracture plane and other interfacial regions, 3-D contact elements were used with appropriate friction coefficients. Material properties of the cancellous bone were varied to accommodate varying degrees of osteoporosis(Singh indices, II∼V). For each model. the following items were analyzed to investigate the effect surgical procedures in relation to osteoporosis of varying degrees : (a) von Mises stress distribution within the femoral head in terms of volumetric percentages. (b) Peak von Mises stress(PVMS) within the femoral head and the surgical constructs. (c) Maximum von Mises strain(MVMS) within the femoral head, (d) micromotions at the fracture plane and at the interfacial region between surgical construct and surrounding bone. Type III showed the lowest PVMS and MVMS at the cancellous bone near the bone-construct interface regardless of bone densities. an indication of its least likelihood of construct loosening due to failure of the host bone. Particularly, its efficacy was more prominent when the bone density level was low. Micromotions at the interfacial surgical construct was lowest in Type III. followed by Type I and Type II. They were about 15-20% of other types. which suggested that pressurization was most effective in limiting the interfacial motion. Our results demonstrated the cement augmentation with hip screw could be more effective when used with pressurization technique for the treatment of intertrochanteric fractures. For patients with low bone density. its effectiveness can be more pronounced in limiting construct loosening and promoting bone union.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.858-863
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• 2010

The blueberry farming requires the soil condition of well-drainage, pH of 4.5 to 5.2, and high in organic matters for stable growth and development. Most of soil type of cultivated land in Korea, however, belongs to alkaline soils with low organic matter content and poor drainage. Therefore, the blueberry farmers use peat moss heavily to improve the soil condition, but the guideline on the effective and economic ratio of peat moss is not established yet. This study was performed to determine the cost effective peat moss ratio for amending soils, and to investigate the feasibility of using sawdust and coco peat as soil amendments. Peat moss, coco peat and sawdust are mixed with soil at the ratio of 0, 12.5, 50 and 100% (v/v). Among 3 organic materials with various mixture ratios, the pH of soil was the lowest in 100% peat moss and sawdust mixtures (pH 3.67 and pH 3.73, respectively), followed by pH 5.30 at 50% peat moss. The soil organic matter content are directly proportional to the mixture ratios in all three organic materials and the same trend was observed in the variation of content of exchangeable potassium in the coco peat treatments. On the contrary, the content of available phosphate, exchangeable calcium and magnesium decreased with increasing the ratio of organic materials. The nitrogen content in the leaves decreased as increasing the ratio of peat moss and coco peat in soil, but not of sawdust. The content of phosphate decreased but potassium increased as the ratio of sawdust and coco peat increased. There was no clear difference in the contents of magnesium and calcium among 3 organic materials. The plant height, stem diameter and dry weight of blueberry plants were the highest in 50 % peat moss, followed by 12.5% peat moss and 12.5% coco peat. The plants in 100% peat moss showed very poor growth. It can be concluded that peatmoss, when applied and managed appropriately, will be a good material for improving soil condition as well as securing desirable growth for blueberry. Upon coupling economic aspect, the optimum mixing ratio of peatmoss for blueberry farming is approximately 25-50%.

• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.3
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• pp.77-91
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• 2015

This study aims to suggest adequate soil management through the analysis of physicochemical properties of soil in the planting grounds of Incheon International Airport, which was constructed on a massive land reclamation site. Study areas were 5 sites at the international business complex, the passenger terminal, the airport support complex, the free trade zone, and the access road. Soil profile analysis showed that 9 plots out of the 27 plots were hardpan and heterospere within 80cm from the soil surface. The earth laid on the ground was categorized as gravel based soil(4 plots), dredged soil from the sea bottom and mixed reclamation materials(2 plots), clay with poor permeability(3 plots) and waste construction material(1 plot). Average soil hardness was $11.5kg/cm^2$ and soil textures were sandy soil, sandy loam and loamy sand. Average soil pH was 6.7 and average organic matter content was 0.7%. Electrical conductivity was 0.0dS/m and exchangeable cation concentrations were $Ca^{2+}$ 3.4cmol/kg, $Mg^{2+}$ 1.5cmol/kg, $K^+$ 0.3cmol/kg and $Na^+$ 1.0cmol/kg. Average cation exchange capacity was 11.0cmol/kg. Although average figures in Solum mostly meet the landscape design criteria, properties of each soil layer showed various values sometimes over the limit. Base saturations were $Ca^{2+}$ 29.9%, $Mg^{2+}$ 13.3% and $K^+$ 3.7% for lower soil, $Ca^{2+}$ 33.3%, $Mg^{2+}$ 17.0% and $K^+$ 2.7% for mid-soil and $Ca^{2+}$ 32.6%, $Mg^{2+}$ 12.2% and $K^+$ 1.9% for upper soil. Exchangeable sodium percentages were 16.4% for lower soil, 7.5% for mid-soil and 4.7% upper soil. Sodium adsorption rates were 0.8 for lower soil, 0.3 for mid-soil and 0.2 for upper soil. Factors affecting to the vegetation growth were heterogeneity and poorness of solum, disturbance of dredged soils, high soil hardness including hardpan in the subsurface soil layer and shallow effective soil depth, high soil acidity, imbalance of base contents, low organic matter content and low available phosphate levels in the soil.

• Korean Journal of Food Science and Technology
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• v.26 no.6
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• pp.670-678
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• 1994

The effects of amylase addition during extrusion cooking of rice on the physico-chemical properties of the extrudates were investigated in order to develop rice-based Korean style weaning food products. A laboratory-built single screw extruder was used, the enzymes used were Termamyl 120LS(amylase from Bacillus licheniformis, NOVO Co.), BAN 240L(amylase from Bacillus amylolichuefaciens, NOVO Co.) and malt powder. By the addition of enzymes, the water soluble index of the extrudates increased by 3 times compared to that of the extrudates without enzyme and the concentration of reducing sugar in the extrudates increased drastically at 28 feed moisture. The gel permeation chromatographic pattern showed that the large molecular starch fractions diminished by the addition of enzyme during extrusion and the low molecular fraction increased. The residual enzyme activity in the extrudate were 27% for the most thermo-resistance enzyme by treating at $140^{\circ}C$ in the metering section of the extruder. The sediment volume of the extrudate dispersion increased as the metering section temperature increased to $140^{\circ}C$ . By the addition of enzymes the viscosity of extrudate dispersion was redused $1/4{\sim}1/200$ of that of the extrudates without enzyme. It allowed to use 1.8 times of solid material to the weaning food formulation to attain the same level of consistency as the commercial products. It proves that the addition of amylase during rice extrusion is effective to increase the energy density of weaning food by starch degradation, which results in the increases of water solubility, reducing sugar content, dispersibility and fluidability.

• The Korean Journal of Food And Nutrition
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• v.25 no.3
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• pp.564-569
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• 2012

Selenium was initially considered toxic to humans, but it was then discovered that selenium is essential for normal life processes. Selenium plays important roles in antioxidants. It is expected that chitosan microcapsules containing nano-selenium will be able to be used as a key material in bio-medical and cosmetic applications. The high concentration of chitosan derivatives guarantees increased antioxidative activity. Both inorganic and organic forms of selenium can be nutritional sources. The antioxidant properties of selenoproteins help prevent cellular damage from free radicals. The objective of this experiment was to study the antioxidative activity of chitosan nano-selenium. Our experiments were divided into five groups, in the presence of various concentrations(0.1%, 0.3%, 0.5%, 0.7%, and 0.9%) of chitosan. We performed an assessment of the antioxidant properties and cytotoxicity of respective concentrations of chitosan nano-selenium. The antioxidant activity was examined by the free radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl(DPPH) assay. The cytotoxicity effect was measured by means of 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay. As a result, the electron donating abilities of 0.1%, 0.3%, 0.5%, 0.7%, and 0.9% of chitosan nano-selenium exhibited effective andioxidant scavenging activity at 12.5 ${\mu}g/m{\ell}$ against DPPH radicals. 0.3% chitosan nano-selenium did not show cytotoxicity on human keratinocytes. In general, the cytotoxicity of 0.1% and 0.9% chitosan nano-selenium showed the lowest effects. Though low cytotoxicity of 0.5% and 0.7% chitosan nano-selenium exhibited 29.67% and 38.4% against human keratinocytes on adding 100 ${\mu}g/m{\ell}$ and 50 ${\mu}g/m{\ell}$, respectively, cell vitality was recovered with 200 ${\mu}g/m{\ell}$. These findings support the notion that chitosan nano-selenium may be useful as a new active ingredient source for bioactive compounds.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.2
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• pp.182-206
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• 2003

Statement of problem : Successful osseointegration of endosseous threaded implants is dependent on many factors. These may include the surface characteristics and gross geometry of implants, the quality and quantity of bone where implants are placed, and the magnitude and direction of stress in functional occlusion. Therefore clinical quantitative measurement of primary stability at placement and functional state of implant may play a role in prediction of possible clinical symptoms and the renovation of implant geometry, types and surface characteristic according to each patients conditions. Ultimately, it may increase success rate of implants. Purpose : Many available non-invasive techniques used for the clinical measurement of implant stability and osseointegration include percussion, radiography, the $Periotest^{(R)}$, Dental Fine $Tester^{(R)}$ and so on. There is, however, relatively little research undertaken to standardize quantitative measurement of stability of implant and osseointegration due to the various clinical applications performed by each individual operator. Therefore, in order to develop non-invasive experimental method to measure stability of implant quantitatively, the resonance frequency analyzer to measure the natural frequency of specific substance was developed in the procedure of this study. Material & method : To test the stability of the resonance frequency analyzer developed in this study, following methods and materials were used : 1) In-vitro study: the implant was placed in both epoxy resin of which physical properties are similar to the bone stiffness of human and fresh cow rib bone specimen. Then the resonance frequency values of them were measured and analyzed. In an attempt to test the reliability of the data gathered with the resonance frequency analyzer, comparative analysis with the data from the Periotest was conducted. 2) In-vivo study: the implants were inserted into the tibiae of 10 New Zealand rabbits and the resonance frequency value of them with connected abutments at healing time are measured immediately after insertion and gauged every 4 weeks for 16 weeks. Results : Results from these studies were such as follows : The same length implants placed in Hot Melt showed the repetitive resonance frequency values. As the length of abutment increased, the resonance frequency value changed significantly (p<0.01). As the thickness of transducer increased in order of 0.5, 1.0 and 2.0 mm, the resonance frequency value significantly increased (p<0.05). The implants placed in PL-2 and epoxy resin with different exposure degree resulted in the increase of resonance frequency value as the exposure degree of implants and the length of abutment decreased. In comparative experiment based on physical properties, as the thickness of transducer increased, the resonance frequency value increased significantly(p<0.01). As the stiffness of substances where implants were placed increased, and the effective length of implants decreased, the resonance frequencies value increased significantly (p<0.05). In the experiment with cow rib bone specimen, the increase of the length of abutment resulted in significant difference between the results from resonance frequency analyzer and the $Periotest^{(R)}$. There was no difference with significant meaning in the comparison based on the direction of measurement between the resonance frequency value and the $Periotest^{(R)}$ value (p<0.05). In-vivo experiment resulted in repetitive patternes of resonance frequency. As the time elapsed, the resonance frequency value increased significantly with the exception of 4th and 8th week (p<0.05). Conclusion : The development of resonance frequency analyzer is an attempt to standardize the quantitative measurement of stability of implant and osseointegration and compensate for the reliability of data from other non-invasive measuring devices It is considered that further research is needed to improve the efficiency of clinical application of resonance frequency analyzer. In addition, further investigation is warranted on the standardized quantitative analysis of the stability of implant.

• Economic and Environmental Geology
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• v.47 no.6
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• pp.563-569
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• 2014

Ruby is one of the most favor colored gem, for beautiful red tone, be high in scarcity value. However, rubies with high quality are produced in restricted regions, such as in Thailand, Sri Lanka, Myanmar, and Tanzania etc., and they have been gradually exhausted by mining for a long period. Therefore, improving qualities of low level rubies with various treatments is arising an alternative way to obtain better rubies. Gemological and mineralogical properties of the natural ruby from Tanzanian were studied with heat treatments. Those characteristics were compared between only heat and adding flux materials under heating. Tanzanian raw rubies were applied a heat treatment ($1,600^{\circ}C$ for 6 hours). However, chromameter and UV-Vis analyses found that a simple heat treatment is inappropriated for the Tanzanian ruby. Although $Cr^{3+}$ containing for red color in the ruby increased with heat treatment, the ruby displays dark medium red because of Fe in the ruby as a form of $Fe_2O_3$. The low transparency after heat treatment is attributed to the recrystallization of $SiO_2$ which has a low melting point. Chromameter confirmed adding Pb-containing flux under heating greatly improves the clarity and color of Tanzanian rubies with micro-fractures and cavities on the surface. EMPA results show that Pb as an additive fills the cavities and cracks on raw Tanzanian rubies during the heat treatment. As a rewult of it, the quality of the Tanzanian ruby raw dramatically improved. These results indicate that the heat treatment with an additive (Pb in this study) is an effective way to obtain better quality of the Tanzanian ruby. Consequently, this study suggests a suitable method to improve the properties of the Tanzanina ruby. The result of this study would provide useful information to upgrade the qualities of similar gem stones such as corundum and sapphire.

• Journal of Korean Society of Disaster and Security
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• v.16 no.4
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• pp.45-59
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• 2023

The global focus on mitigating climate change has traditionally centered on carbon dioxide, but recent attention has shifted towards methane as a crucial factor in climate change adaptation. Natural settings, particularly aquatic environments such as wetlands, reservoirs, and lakes, play a significant role as sources of greenhouse gases. The accumulation of organic contaminants on the lake and reservoir beds can lead to the microbial decomposition of sedimentary material, generating greenhouse gases, notably methane, under anaerobic conditions. The escalation of methane emissions in freshwater is attributed to the growing impact of non-point sources, alterations in water bodies for diverse purposes, and the introduction of structures such as river crossings that disrupt natural flow patterns. Furthermore, the effects of climate change, including rising water temperatures and ensuing hydrological and water quality challenges, contribute to an acceleration in methane emissions into the atmosphere. Methane emissions occur through various pathways, with ebullition fluxes-where methane bubbles are formed and released from bed sediments-recognized as a major mechanism. This study employs Biochemical Methane Potential (BMP) tests to analyze and quantify the factors influencing methane gas emissions. Methane production rates are measured under diverse conditions, including temperature, substrate type (glucose), shear velocity, and sediment properties. Additionally, numerical simulations are conducted to analyze the relationship between fluid shear stress on the sand bed and methane ebullition rates. The findings reveal that biochemical factors significantly influence methane production, whereas shear velocity primarily affects methane ebullition. Sediment properties are identified as influential factors impacting both methane production and ebullition. Overall, this study establishes empirical relationships between bubble dynamics, the Weber number, and methane emissions, presenting a formula to estimate methane ebullition flux. Future research, incorporating specific conditions such as water depth, effective shear stress beneath the sediment's tensile strength, and organic matter, is expected to contribute to the development of biogeochemical and hydro-environmental impact assessment methods suitable for in-situ applications.

• Korean Journal of Heritage: History & Science
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• v.37
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• pp.371-405
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• 2004

International circulation of cultural assets involves numerous countries thereby making an approach based on international law essential to resolving this problem. Since the end of the $2^{nd}$ World War, as the value of cultural assets evolved from material value to moral and ethical values, with emphasis on establishing national identities, newly independent nations and former colonial states took issue with ownership of cultural assets which led to the need for international cooperation and statutory provisions for the return of cultural assets. UNESCO's 1954 "Convention for the Protection of Cultural Property in the Event of Armed Conflict" as preparatory measures for the protection of cultural assets, the 1970 "Convention on the Means of Prohibiting and Preventing the Illicit Import and Transfer of Ownership of Cultural Property" to regulate transfer of cultural assets, and the 1995 "Unidroit Convention on Stolen or Illegally Exported Cultural Objects" which required the return of illegally acquired cultural property are examples of international agreements established on illegal transfers of cultural assets. In addition, the UN agency UNESCO established the Division of Cultural Heritage to oversee cultural assets related matters, and the UN since its 1973 resolution 3187, has continued to demonstrate interest in protection of cultural assets. The resolution 3187 affirms the return of cultural assets to the country of origin, advises on preventing illegal transfers of works of art and cultural assets, advises cataloguing cultural assets within the respective countries and, conclusively, recommends becoming a member of UNESCO, composing a forum for international cooperation. Differences in defining cultural assets pose a limitation on international agreements. While the 1954 Convention states that cultural assets are not limited to movable property and includes immovable property, the 1970 Convention's objective of 'Prohibiting and preventing the illicit import, export and transfer of ownership of cultural property' effectively limits the subject to tangible movable cultural property. The 1995 Convention also has tangible movable cultural property as its subject. On this point, the two conventions demonstrate distinction from the 1954 Convention and the 1972 Convention that focuses on immovable cultural property and natural property. The disparity in defining cultural property is due to the object and purpose of the convention and does not reflect an inherent divergence. In the case of Korea, beginning with the 1866 French invasion, 36 years of Japanese colonial rule, military rule and period of economic development caused outflow of numerous cultural assets to foreign countries. Of course, it is neither possible nor necessary to have all of these cultural properties returned, but among those that have significant value in establishing cultural and historical identity or those that have been taken symbolically as a demonstration of occupational rule can cause issues in their return. In these cases, the 1954 Convention and the ratification of the first legislation must be actively considered. In the return of cultural property, if the illicit acquisition is the core issue, it is a simple matter of following the international accords, while if it rises to the level of diplomatic discussions, it will become a political issue. In that case, the country requesting the return must convince the counterpart country. Realizing a response to the earnest need for preventing illicit trading of cultural assets will require extensive national and civic societal efforts in the East Asian area to overcome its current deficiencies. The most effective way to prevent illicit trading of cultural property is rapid circulation of information between Interpol member countries, which will require development of an internet based communication system as well as more effective deployment of legislation to prevent trading of illicitly acquired cultural property, subscription to international conventions and cataloguing collections.