• Title/Summary/Keyword: Material properties

Search Result 18,097, Processing Time 0.05 seconds

The synthesis of dextran from rice hydrolysates using Gluconobacter oxydans KACC 19357 bioconversion (Gluconobacter oxydans 생물전환을 통한 쌀 가수분해물 유래 dextran 합성)

  • Seung-Min Baek;Hyun Ji Lee;Legesse Shiferaw Chewaka;Chan Soon Park;Bo-Ram Park
    • Food Science and Preservation
    • /
    • v.31 no.1
    • /
    • pp.149-160
    • /
    • 2024
  • Dextran is a glucose homo-polysaccharide with a predominantly α-1,6 glycosidic linkage of microbial source and is known to be produced primarily by lactic acid bacteria. However, it can also be obtained through the dextran dextrinase of acetic acid bacteria (Gluconobacter oxydans). The dextrin-based dextran was obtained from rice starch using G. oxydans fermentation of rice hydrolysate, and its properties were studied. Both dextrin- and rice hydrolysate-added media maintained the OD value of 6 after 20 h of incubation with acetic acid bacteria, and the gel permeation chromatography (GPC) analysis of the supernatant after 72 h of incubation confirmed that a polymeric material with DP of 480 and 405, which was different from the composition of the substrate in the medium, was produced. The glucose linkage pattern of the polysaccharide was confirmed using the proton nuclear magnetic resonance (1H-NMR) and the increased α-1,4:α-1,6 bond ratio from 0.23 and 0.13 to 1:2.37 and 1:4.4, respectively, indicating that the main bonds were converted to α-1,6 bonds. The treatment of dextrin with a rat-derived alpha-glucosidase digestive enzyme resulted in a slow release of glucose, suggesting that rice hydrolysate can be converted to dextran using acetic acid bacteria with glycosyltransferase activity to produce high-value bio-materials with slowly digestible properties.

Assessment of Methane Production Rate Based on Factors of Contaminated Sediments (오염퇴적물의 주요 영향인자에 따른 메탄발생 생성률 평가)

  • Dong Hyun Kim;Hyung Jun Park;Young Jun Bang;Seung Oh Lee
    • Journal of Korean Society of Disaster and Security
    • /
    • v.16 no.4
    • /
    • pp.45-59
    • /
    • 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.

Studies on the Physical Properties of Major Tree Barks Grown in Korea -Genus Pinus, Populus and Quercus- (한국산(韓國産) 주요(主要) 수종(樹種) 수피(樹皮)의 이학적(理學的) 성질(性質)에 관(關)한 연구(硏究) -소나무속(屬), 사시나무속(屬), 참나무속(屬)을 중심(中心)으로-)

  • Lee, Hwa Hyoung
    • Journal of Korean Society of Forest Science
    • /
    • v.33 no.1
    • /
    • pp.33-58
    • /
    • 1977
  • A bark comprises about 10 to 20 percents of a typical log by volume, and is generally considered as an unwanted residue rather than a potentially valuable resourses. As the world has been confronted with decreasing forest resources, natural resources pressure dictate that a bark should be a raw material instead of a waste. The utilization of the largely wasted bark of genus Pinus, Quercus, and Populus grown in Korea can be enhanced by learning its physical and mechanical properties. However, the study of tree bark grown in Korea have never been undertaken. In the present paper, an investigative study is carried out on the bark of three genus, eleven species representing not only the major bark trees but major species currently grown in Korea. For each species 20 trees were selected, at Suweon and Kwang-neung areas, on the same basis of the diameter class at the proper harvesting age. One $200cm^2$ segment of bark was obtained from each tree at brest height. Physical properties of bark studied are: bark density, moisture content of green bark (inner-, outer-, and total-bark), fiber saturation point, hysteresis loop, shrinkage, water absorption, specific heat, heat of wetting, thermal conductivity, thermal diffusivity, heat of combustion, and differential thermal analysis. The mechanical properties are studied on bending and compression strength (radial, longitudinal, and tangential). The results may be summarized as follows: 1. The oven-dry specific gravities differ between wood and bark, further more even for a given bark sample, the difference is obersved between inner and outer bark. 2. The oven-dry specific gravity of bark is higher than that of wood. This fact is attributed to the anatomical structure whose characters are manifested by higher content of sieve fiber and sclereids. 3. Except Pinus koraiensis, the oven-dry specific gravity of inner bark is higher than that of outer bark, which results from higher shrinkage of inner bark. 4. The moisture content of bark increases with direct proportion to the composition ratio of sieve components and decreases with higher percent of sclerenchyma and periderm tissues. 5. The possibility of determining fiber saturation point is suggested by the measuring the heat of wetting. With the proposed method, the fiber saturation point of Pinus densiflora lies between 26 and 28%, that of Quercus accutissima ranges from 24 to 28%. These results need be further examined by other methods. 6. Contrary to the behavior of wood, the bark shrinkage is the highest in radial direction and the lowest in longitudinal direction. Quercus serrata and Q. variabilis do not fall in this category. 7. Bark shows the same specific heat as wood, but the heat of wetting of bark is higher than that of wood. In heat conductivity, bark is lower than wood. From the measures of oven-dry specific gravity (${\rho}d$) and moisture fraction specific gravity (${\rho}m$) is devised the following regression equation upon which heat conductivity can be calculated. The calculated heat conductivity of bark is between $0.8{\times}10^{-4}$ and $1.6{\times}10^{-4}cal/cm-sec-deg$. $$K=4.631+11.408{\rho}d+7.628{\rho}m$$ 8. The bark heat diffusivity varies from $8.03{\times}10^{-4}$ to $4.46{\times}10^{-4}cm^2/sec$. From differential thermal analysis, wood shows a higher thermogram than bark under ignition point, but the tendency is reversed above ignition point. 9. The modulus of rupture for static bending strength of bark is proportional to the density of bark which in turn gives the following regression equation. M=243.78X-12.02 The compressive strength of bark is the highest in radial direction, contrary to the behavior of wood, and the compressive strength of longitudinal direction follows the tangential one in decreasing order.

  • PDF

Effects of Formaldehyde/Urea Molar Ratio on Bonding Strength of Plywood and Properties of Sliver-PB and Strand-PB (F/U 몰비의 변이가 합판의 접착성과 Sliver-PB, Strand-PB의 물성에 미치는 영향)

  • Park, Heon;You, Young-Sam
    • Journal of the Korean Wood Science and Technology
    • /
    • v.27 no.2
    • /
    • pp.38-45
    • /
    • 1999
  • This study was to figure out proper Formaldehyde/Urea molar ratio of UF resin with satisfactory bonding strength of plywood and properties of particleboard. The six kinds of UF resins were manufactured with F/U molar ratio 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0. The boards were made of three kinds of raw materials : Veneer, Sliver-Particle and Strand-Particle. Manufacturing condition of plywood : amount of mixing resin was 150g/$m^2$. The fourty secs/mm simple-pressing schedule in the pressure 10kgf/$m^2$ was applied for 480mm${\times}$700mm board at the temperature of $110^{\circ}C$ in a hot press. Manufacturing condition of particleboard : Target density was 0.65g/$cm^2$. The stepwise 9 minutes- multi-pressing schedule in the maximum pressure 40kgf/$cm^2$, the minimum pressure 15kgf/$cm^2$ was applied for $480mm{\times}634mm{\times}12mm$ board at the temperature of $150^{\circ}C$ in a hot press. The results are as follows : I. In bonding strength, plywood which was made by F/U molar ratio 1.2 showed the highest value. Other molar ratio resin also gave the satisfied value of KS standard, 7.5kgf/$cm^2$. 2. In internal bond strength of particleboard, Sliver-Particleboard(SLPB) and Strand-Particleboard(STPB) varied respectively from 5.9kgf/$cm^2$ to 4.8kgf/$cm^2$, from 6.7kgf/$cm^2$ to 5.4kgf/$cm^2$. SLPB with F/U=1.2 and STPB with F/U=1.6 had higher IB value. Also, both SLPB and STPB showed lower IB value in F/U molar ratio 2.0 and 1.0. 3. SLPB and STPB with six kinds of UF resin respectively satisfied bending strength of KS standard 150 Type(130kgf/$cm^2$) and 200 Type(180kgf/$cm^2$). Bending strength data for both of SLPB and STPB showed little or no loss from F/U=1.8 to F/U=1.2. Also, STPB was approximately two times higher than that of SLPB. Therefore, the raw material's shape had more effect on bending strength than the FlU molar ratio. 4. F/U=1.6 and 1.4 showed the lower thickness swelling in SLPB and STPB. All of STPBs satisfied thickness swelling of KS standard, under 12%.

  • PDF

An Examination into the Illegal Trade of Cultural Properties (문화재(文化財)의 국제적 불법 거래(不法 去來)에 관한 고찰)

  • Cho, Boo-Keun
    • Korean Journal of Heritage: History & Science
    • /
    • v.37
    • /
    • pp.371-405
    • /
    • 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.

Study on the Limitation of AVO Responses Shown in the Seismic Data from East-sea Gas Reservoir (동해 가스전 탄성파 자료에서 나타나는 AVO 반응의 한계점에 대한 고찰)

  • Shin, Seung-Il;Byun, Joong-Moo;Choi, Hyung-Wook;Kim, Kun-Deuk;Ko, Seung-Won;Seo, Young-Tak;Cha, Young-Ho
    • Geophysics and Geophysical Exploration
    • /
    • v.11 no.3
    • /
    • pp.242-249
    • /
    • 2008
  • Recently, AVO analysis has been widely used in oil exploration with seismic subsurface section as a direct indicator of the existence of the gas. In the case of the deep reservoirs like the gas reservoirs in the East-sea, it is often difficult to observe AVO responses in CMP gathers even though the bright spots are shown in the stacked section. Because the reservoir becomes more consolidated as its depth deepens, P-wave velocity does not decrease significantly when the pore fluid is replaced by the gas. Thus the difference in Poisson's ratio, which is a key factor for AVO response, between the reservoir and the layer above it does not increase significantly. In this study, we analyzed the effects of Poisson's ratio difference on AVO response with a variety of Poisson's ratios for the upper and lower layers. The results show that, as the difference in Poisson's ratio between the upper and lower layers decreases, the change in the reflection amplitude with incidence angle decreases and AVO responses become insignificant. To consider the limitation of AVO responses shown in the gas reservoir in East-sea, the velocity model was made by simulation Gorae V structure with seismic data and well logs. The results of comparing AVO responses observed from the synthetic data with theoretical AVO responses calculated by using material properties show that the amount of the change in reflection amplitude with increasing incident angle is very small when the difference in Poisson's ratio between the upper and lower layers is small. In addition, the characteristics of AVO responses were concealed by noise or amplitude distortion arisen during preprocessing. To overcome such limitations of AVO analysis of the data from deep reservoirs, we need to acquire precisely reflection amplltudes In data acquisition stage and use processing tools which preserve reflection amplitude in data processing stage.

Haptic Perception presented in Picturesque Gardens - With a Focus on Picturesque Garden in Eighteenth-Century England - (픽처레스크 정원에 나타난 촉지적 지각 - 18세기 영국 픽처레스크 정원을 중심으로 -)

  • Kim, Jin-Seob;Kim, Jin-Seon
    • Journal of the Korean Institute of Landscape Architecture
    • /
    • v.44 no.2
    • /
    • pp.37-51
    • /
    • 2016
  • Modern optical mechanisms slanted toward Ocular-centrism have neglected diverse functions of vision, judged objects in abstract and binary perspectives, and organized spaces accordingly, there by neglecting the function of eyes groping objects. Recently, various experiences have been induced through communication with other senses by the complex perception beyond the binary perception system of vision. Haptic perception is dynamic vision that induces accompanying bodily experiences through interaction among the various senses; it recognizes the characteristics of material properties and various sensitive stimulations of human beings. This study elaborates on the major features of haptic perception by examining the theoretical background of this concept, which stimulates the active experience of the subject and determines how characteristics of haptic perception are displayed in picturesque gardens. In order to identify the major features of haptic perception, this study examines how Adolf Hildebrand's theory of vision is developed, expanded, and reinterpreted by Alois Riegl, Wilhelm Worringer, Walter Benjamin, Maurice Merleau Ponty, and Gilles Deleuze in the histories of philosophy and aesthetics. Based thereon, the core differences in haptic perception models and visual perception models are analyzed, and the features of haptic perception are identified. Then, classical gardens are set for visual perception and picturesque gardens are set for haptic perception so that the features from haptic perception identified previously are projected onto the picturesque gardens. The research results drawn from this study regarding features of haptic perception presented in picturesque gardens are as follows. The core differences of haptic perception in contrast to visual perception can be summarized as ambiguity and obscureness of boundaries, generation of dynamic perspectives, induction of motility by indefinite circulation, and strangeness and sublime beauty by the impossibility of perception. In picturesque gardens, the ambiguity and obscureness of boundaries are presented in the irregularity and asymmetric elements of planes and the rejection of a single view, and the generation of dynamic perspectives results from the adoption of narrative structure and overlapping of spaces through the creation of complete views, medium range views, and distant views, which the existing gardens lack. Thus, the scene composition technique is reproduced. The induction of motility by indefinite circulation is created by branching circulation, and strangeness and sublime beauty are presented through the use of various elements and the adoption of 'roughness', 'irregularity', and 'ruins' in the gardens.

Study on the Silicone Contact Lens Using AA and BMA (AA(Acrylic acid)와 BMA(Butyl methacrylate)를 이용한 실리콘 콘택트렌즈에 관한 연구)

  • Kim, Tae-Hun;Yae, Ki-Hun;Kweon, Young-Seok;Sung, A-Young
    • Journal of Korean Ophthalmic Optics Society
    • /
    • v.11 no.3
    • /
    • pp.259-265
    • /
    • 2006
  • We polymerized material of AA(Acrylic acid) and BMA(butyl methacrylate) to make up for the weak points of hydrogel contact lens. The synthesis process of silicone synthesis is as follows. Acrylate-PDMS(Polydimethylsiloxane)-Urethane prepolymer was composed after Diisocynate reacted with HEMA(2-hydroxyethylmethacrylate) under the catalyst and it reacted again with bis(hydroxyalkyl) terminated poly(dimethylsiloxane) with high oxygen transmissibility characteristics. HEMA(2-hydroxyethylmethacrylate) was used to make prepolymer that can be polymerized and the urethane was used to improve elasticity and oxygen transmissibility, copolymerization was performed with conventional hydrogel contact lens materials to make silicone hydrogel contact lens with higher oxygen transmissibility. For manufacturing of contact lens, We added BMA(Butyl methacrylate) with better elasticity and flexibility, and AA(Acrylic acid) with higher moisturizing to used contact lens materials. AIBN (Azobis2-methylpropionitrile) as initiator and EGDMA(Ethylene Glycol Dimethacrylat) as crosslinking agent were used and the lens with higher oxygen transmissibility and better moisturizing were manufactured complying with basic contact lens properties, which have several combination trial of each monomer characteristics. Compounding SN which included SILICONE, HEMA, NVP and EGDMA etc was showed by swelling ratio of 9.38% and water content of 23.7%. SN was showed by swelling ratio of 9.38%, water content of 23.7% and a visible ray transmissibility of 89%. SB which added BMA in the SN was showed by swelling ratio of 12.50%, water content of 18.56% and a visible ray transmissibility of 88%. SAB which added both AA and BMA in the SN was showed by swelling ratio of 8.33%, water content of 12.93% and a visible ray transmissibility of 88%.

  • PDF

Effects of Electrodeposition Parameters on Electrochemical Hydroxyl Radical Evolution of PbO2 Electrode (이산화납 전극 제조 시 전기화학적 증착인자가 수산화라디칼 발생에 미치는 영향)

  • Shim, Soojin;Yoon, Jeyong
    • Journal of Korean Society of Environmental Engineers
    • /
    • v.38 no.12
    • /
    • pp.647-655
    • /
    • 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.

The Influence of Pesticides on Some Chemical and Microbiological Properties Related to Soil Fertility II. Effects of CNP Herbicide on Soil Microflora (농약제(農藥劑)의 시용(施用)이 토양(土壤)의 비옥성(肥沃性) 및 미생물상(微生物相)에 미치는 영향(影響) II. CNP 제초제시용(除草劑施用)이 토양미생물(土壤微生物) flora에 미치는 효과(效果))

  • Ryu, Jin-Chang;Araragi, Michio;Koga, Hiroshi
    • Korean Journal of Soil Science and Fertilizer
    • /
    • v.17 no.1
    • /
    • pp.67-76
    • /
    • 1984
  • This experiment was conducted to find out the changes in microflora of submerged soil uncultivated rice plant by application of CNP herbicide (2, 4, 6 - Trichlorophenyl-4-Nitrophenyl ether) under conditions applied with compost, rice straw, glucose or without organic material. The soil, sandy loam textured was incubated in green house for 66 days. Sampling and analysis of microorganisms were carried out during submergence periods. The results were summarilized as follows. 1. Number of aerobic total bacteria was increased by application of CNP herbicide during submerbed 50 days, afterthen, could not seen the difference. The application of rice straw increased number of aerobic bacteria regardless of CNP herbicide application or not, but glucose tended to decrease. 2. Number of Fungi was constantly maintained at $8-20{\times}10^3$ levels during period of submergence regardless of application of CNP herbicide and organic materials or not. 3. The CNP herbicide application tended to decrease the number of actinomycetes, particularly, in the treatments without organic substances and rice straw were remarkably decreased. 4. Anaerobic-and gram-negative bacteria populations were not showed any difference by application of herbicide and organic materials. 5. The ratios of aerobic bacteria to fungi and aerobic bacteria to actinomycetes appeared high values by application of herbicide and of organic substances. 6. At 66 days after submergence, the ratio of chromogenic actinomycetes to the total number of actinomycetes was lowered in application of herbicide. On the other hand, the percentage of both pretense-positive and cellulase-positive actinomycetes to the total isolates were higher in the treatment with herbicide than An without herbicide, particularly. The ratios of pretense-positive actinomycetes were high in the rice straw application regardless of herbicide application or not, but cellulase-positive actinomycetes was not remarkably difference.

  • PDF