• Title/Summary/Keyword: High Temperature Application

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A pilot study on the application of environmental DNA to the estimation of the biomass of dominant species in the northwestern waters of Jeju Island (제주도 서북 해역에서의 우점종 생물량 추정에 환경 유전자의 적용에 관한 시범 연구)

  • KANG, Myounghee;PARK, Kyeong-Dong;MIN, Eunbi;LEE, Changheon;KANG, Taejong;OH, Taegeon;LIM, Byeonggwon;HWANG, Doojin;KIM, Byung-Yeob
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.58 no.1
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    • pp.39-48
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    • 2022
  • Using environmental DNA (eDNA) in the fisheries and oceanography fields, research on the diversity of biological species, the presence or absence of specific species and quantitative evaluation of species has considerably been performed. Up to date, no study on eDNA has been tried in the area of fisheries acoustics in Korea. In this study, the biomass of a dominant species in the northwestern waters of Jeju Island was examined using 1) the catch ratio of the species from trawl survey results and 2) the ranking ratio of the species from the eDNA results. The dominant species was Zoarces gillii, and its trawl catch ratio was 68.2% and its eDNA ratio was 81.3%. The Zoarces gillii biomass from the two methods was 7199.4 tons (trawl) and 8584.6 tons (eDNA), respectively. The mean and standard deviation of the acoustic backscattering strength values (120 kHz) from the entire survey area were 135.5 and 157.7 m2/nm2, respectively. The strongest echo signal occurred at latitude 34° and longitude 126°15' (northwest of Jeju Island). High echo signals were observed in a specific oceanographic feature (salinity range of 32-33 psu and the water temperature range of 19-20℃). This study was a pilot study on evaluating quantitatively aquatic resources by applying the eDNA technique into acoustic-trawl survey method. Points to be considered for high-quality quantitative estimation using the eDNA to fisheries acosutics were discussed.

The Influence of the Systematic Analogies Used at the Interpretation of Experimental Results on High School Students' Conceptual Change of Enzymes (실험 결과 해석 과정에서 사용한 체계적 비유가 고등학생들의 효소 개념 변화에 미친 영향)

  • Lee, Won-Kyung;Kim, Heui-Baik
    • Journal of The Korean Association For Science Education
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    • v.27 no.7
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    • pp.663-675
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    • 2007
  • Chemical reactions in cells are so complicated and abstract that students have difficulty in understanding them. In this study, classes with the application of systematic analogies used at the interpretation of experimental results were taught to 10th-grade students in order to help them to understand the concept of enzymes, which play an important role in chemical reactions in cells. Effects of the classes on their understanding of the concept of enzymes and the role of systematic analogies were analyzed. The gap of understanding between the test group and the control group was significant at 0.05, indicating that systematic analogies are effective for students' understanding of the concept of enzymes. Looking into the concept of enzymes by individual element, the effect of systematic analogies was shown to be large for equilibrium-like processes, such as the enzyme structure change caused by temperature and pH; and the continuous and random actions of enzymes, which students have difficulty in understanding. For these processes, systematic analogies played a positive role in improving their conceptual status. The visualizations and familiarity of analogs increased their intelligibility regarding the concept of enzyme. Also, the systematic analogies increases their plausibility by helping to connect phenomena, taking place in the enzyme reaction experiments, with scientific concepts as scaffold. Accordingly, it was possible to explain experimental results as scientific concepts in a consistent manner. In addition, analogies familiar to students played a positive role from the affective perspective by promoting students' interest and helping them to approach hard scientific concepts.

Effect of Pyrolysis Fuel Oil Based Carbon Coating onto CFX Cathode on High-rate Performance of Lithium Primary Batteries (불화탄소 전극의 열분해 연료유 기반 탄소 코팅이 리튬일차전지의 고율속 성능에 미치는 영향)

  • Sangyeop Lee;Naeun Ha;Seongjae Myeong;Chaehun Lim;Sei-Hyun Lee;Young-Seak Lee
    • Applied Chemistry for Engineering
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    • v.35 no.4
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    • pp.321-328
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    • 2024
  • The performance of carbon fluoride-based lithium primary batteries (Li/CFX) is limited due to poor rate capability resulting from the low conductivity of carbon fluoride, which is used as the active material. Therefore, in this study, we applied a carbon coating using pyrolysis fuel oil on carbon fluoride to overcome this limitation and considered its electrochemical performance. An amorphous carbon layer was formed on the surface of the carbon fluoride through carbon coating, and the surface physicochemical properties of the carbon fluoride were meticulously considered based on the heat treatment temperature. The advanced research chemical 1000 heat treated at 450 ℃ (ARC@C450) sample, which was commercial carbon fluoride heat-treated at 450 ℃, showed the largest increase in the concentration of sp2 carbon bonds (62%) and the highest formation of semi-ionic C-F bonds. Also, the primary battery using the ARC@C450 sample as a cathode active material exhibited stable discharge capability at the highest rate of 5 C (392 mAh/g), and the Rct value was reduced by 53% compared to the untreated sample. Therefore, we proposed pyrolysis fuel oil-based carbon coating as a method to overcome the low conductivity of carbon fluoride, and the carbon-coated carbon fluoride showed excellent rate performance, suggesting its potential application in high-power primary batteries.

Simulation of Detailed Wind Flow over a Locally Heated Mountain Area Using a Computational Fluid Dynamics Model, CFD_NIMR_SNU - a fire case at Mt. Hwawang - (계산유체역학모형 CFD_NIMR_SNU를 이용한 국지적으로 가열된 산악지역의 상세 바람 흐름 모사 - 화왕산 산불 사례 -)

  • Koo, Hae-Jung;Choi, Young-Jean;Kim, Kyu-Rang;Byon, Jae-Young
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.11 no.4
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    • pp.192-205
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    • 2009
  • The unexpected wind over the Mt. Hwawang on 9 February 2009 was deadly when many spectators were watching a traditional event to burn dried grasses and the fire went out of control due to the wind. We analyzed the fatal wind based on wind flow simulations over a digitized complex terrain of the mountain with a localized heating area using a three dimensional computational fluid dynamics model, CFD_NIMR_SNU (Computational Fluid Dynamics_National Institute of Meteorological Research_Seoul National University). Three levels of fire intensity were simulated: no fire, $300^{\circ}C$ and $600^{\circ}C$ of surface temperature at the site on fire. The surface heat accelerated vertical wind speed by as much as $0.7\;m\;s^{-1}$ (for $300^{\circ}C$) and $1.1\;m\;s^{-1}$ (for $600^{\circ}C$) at the center of the fire. Turbulent kinetic energy was increased by the heat itself and by the increased mechanical force, which in turn was generated by the thermal convection. The heating together with the complex terrain and strong boundary wind induced the unexpected high wind conditions with turbulence at the mountain. The CFD_NIMR_SNU model provided valuable analysis data to understand the consequences of the fatal mountain fire. It is suggested that the place of fire was calm at the time of the fire setting due to the elevated terrain of the windward side. The suppression of wind was easily reversed when there was fire, which caused updraft of hot air by the fire and the strong boundary wind. The strong boundary wind in conjunction with the fire event caused the strong turbulence, resulting in many fire casualties. The model can be utilized in turbulence forecasting over a small area due to surface fire in conjunction with a mesoscale weather model to help fire prevention at the field.

A Fully Digital Automatic Gain Control System with Wide Dynamic Range Power Detectors for DVB-S2 Application (넓은 동적 영역의 파워 검출기를 이용한 DVB-S2용 디지털 자동 이득 제어 시스템)

  • Pu, Young-Gun;Park, Joon-Sung;Hur, Jeong;Lee, Kang-Yoon
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.46 no.9
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    • pp.58-67
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    • 2009
  • This paper presents a fully digital gain control system with a new high bandwidth and wide dynamic range power detector for DVB-S2 application. Because the peak-to-average power ratio (PAPR) of DVB-S2 system is so high and the settling time requirement is so stringent, the conventional closed-loop analog gain control scheme cannot be used. The digital gain control is necessary for the robust gain control and the direct digital interface with the baseband modem. Also, it has several advantages over the analog gain control in terms of the settling time and insensitivity to the process, voltage and temperature variation. In order to have a wide gain range with fine step resolution, a new AGC system is proposed. The system is composed of high-bandwidth digital VGAs, wide dynamic range power detectors with RMS detector, low power SAR type ADC, and a digital gain controller. To reduce the power consumption and chip area, only one SAR type ADC is used, and its input is time-interleaved based on four power detectors. Simulation and measurement results show that the new AGC system converges with gain error less than 0.25 dB to the desired level within $10{\mu}s$. It is implemented in a $0.18{\mu}m$ CMOS process. The measurement results of the proposed IF AGC system exhibit 80-dB gain range with 0.25-dB resolution, 8 nV/$\sqrt{Hz}$ input referred noise, and 5-dBm $IIP_3$ at 60-mW power consumption. The power detector shows the 35dB dynamic range for 100 MHz input.

Effect of Soil Temperature, Seedtime, and Fertilization Rate on the Secondary Growth in the Cultivation of the Big Bulbils of Namdo Garlic (Allium sativum L.) (남도마늘 대주아 재배시 지온, 파종시기 및 시비량이 이차생장에 미치는 영향)

  • Choi, Hak-Soon;Yang, Eun-Young;Chae, Won-Byoung;Kwack, Yong-Bum;Kim, Hong-Lim
    • Journal of Bio-Environment Control
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    • v.18 no.4
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    • pp.454-459
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    • 2009
  • The secondary growth of garlic depreciates the quality of a bulb and, in the worse cases, makes it difficult to be used as a seed bulb due to many insertions of small cloves in the seed bulb. Therefore, the effect of soil temperature, seedtime, and fertilization rate on the secondary growth of the big bulbils of Namdo garlic has been examined. When we analyzed into the growth characteristics of big bulbils of Namdo garlic under different fertilizer application levels (50% increased fertilization, experimental fertilization and 50% decreased fertilization), the plant height, numbers of leaf, sheathe diameter, leaf length, and leaf width were the best in 50% increase of the test rate of fertilizer. The occurrence rates of secondary growth were 34.2% in 50% decrease of the test rate of fertilizer, 44.3% in the test rate, and 54.1% in 50% increase of the test rate of fertilizer. In other words, the occurrence rate of secondary growth increased by increasing the fertilization rate. While the average harvested bulb weight were 34.1g in 50% decrease of the test rate of fertilizer, 35.1g in the test rate of fertilizer, and 33.9g in 50% increase of the test rate of fertilizer, there were no changes in the number of cloves under different fertilization rates. As the correlation diagram between the soil temperature and occurrence of the secondary growth showed very high relation with 0.892~0.997, the secondary growth in cultivation of Namdo garlic big bulbils had considerably close correlation with the soil temperature. As the earlier the seedtime was, the growth of the above-groundparts including the plant height, numbers of leaf, and sheath diameter were the better. The averages of bulb weight were 36g in the mid September sowed seed bulb, 29.6g in the late September sowed seed bulb, and 27.9g in the early October sowed seed bulb. Overall, our results showed that the bulb size is dependent on the seedtime and the seedtime has no particular effects on the secondary growth.

Compositional Variation of Arsenopyrites in Arsenic and Polymetallic Ores from the Ulsan Mine, Republic of Korea, and their Application to a Geothermometer (울산광산산(蔚山鑛山産) 유비철석(硫砒鐵石)의 조성변화(組成變化) 및 지질온도계(地質溫度計)에 대(對)한 적용(適用))

  • Choi, Seon-Gyu;Chung, Jae-Ill;Imai, Naoya
    • Economic and Environmental Geology
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    • v.19 no.3
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    • pp.199-218
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    • 1986
  • Arsenopyrite in arsenic and polymetallic ores from calcic Fe-W skarn deposit of the Ulsan mine, Republic of Korea, has been investigated by means of electron microprobe analysis and X-ray diffractometry. As a result, it is revealed that the Ulsan arsenopyrite may be classified into the following three species with different generation on the basis of its mode of occurrence, chronological order during polymetallic mineralization and chemical composition; arsenopyrites I, II and III. 1) Arsenopyrite I-(Ni, Co)-bearing species belonging to the oldest generation, which has crystallized together with (Ni, Co)-arsenides and -sulpharsenides in the early stage of polymetallic mineralization. In rare cases, it contains a negligible amount of antimony. It occurs usually as discrete grains with irregular outline, showing rarely subhedral form, and is diffused in skarn zone. The maximum contents of nickel and cobalt are 10.04 Ni and 2.45 Co (in weight percent). Occasionally, it shows compositional zoning with narrow rim of lower (Ni+Co) content. 2) Arsenopyrite II-arsenian species, in which (Ni+Co) content is almost negligible, may occur widely in arsenic ores, and its crystallization has followed that of arsenopyrite I. It usually shows subhedral to euhedral form and is closely associated with $l{\ddot{o}}llingite$, bismuth, bismuthinite, chalcopyrite, sphalerite, bismuthian tennantite, etc. It is worthy of note that arsenopyrite II occasionally contains particles consisting of both bismuth and bismuthinite. 3) Arsenopyrite III-(Ni, Co)-free, S-excess and As-deficient species is close to the stoichiometric composition, FeAsS. It occurs in late hydrothermal veins, which cut clearly the Fe-W ore pipe and the surrounding skarn zone. It shows euhedral to subhedral form, being extremely coarse-grained, and is closely associated with pyrite, "primary" monoclinic pyrrhotite, galena, sphalerite, etc. Among three species of the Ulsan arsenopyrite, arsenopyrite I does not serve as a geothermometer, because (Ni+Co) content always exceeds 1 weight percent. In spite of the absence of Fe-S minerals as sulphur-buffer assemblage, the presence of $Bi(l)-Bi_2S_3$ sulphur-buffer enables arsenopyrite II to apply successfully to the estimation of either temperature and sulphur fugacity, the results are, $T=460{\sim}470^{\circ}C$, and log $f(S_2)=-7.4{\sim}7.0$. With reference to arsenopyrite III, only arsenopyrite coexisting with pyrite and "primary" monoclinic pyrrhotite may serve to restrict the range of both temperature and sulphur fugacity, $T=320{\sim}440^{\circ}C$, log $f(S_2)=-9.0{\sim}7.0$. These temperature data are consistent with those obtained by fluid inclusion geothermometry on late grandite garnet somewhat earlier than arsenopyrite II. At the beginning of this paper, the geological environments of the ore formation at Ulsan are considered from regional and local geologic settings, and physicochemical conditions are suspected, in particular the formation pressure (lithostatic pressure) is assumed to be 0.5kb (50MPa). The present study on arsenopyrite geothermometry, however, does not bring about any contradictions against the above premises. Thus, the following genetical view on the Ulsan ore deposit previously advocated by two of the present authors (Choi and Imai) becomes more evident; the ore deposit was formed at shallow depth and relatively high-temperature with steep geothermal gradient-xenothermal conditions.

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A Study of Cleaning Technology for Zirconium Scrap Recycling in the Nuclear Industry (원자력산업에서 지르코늄 스크랩 재활용을 위한 세정기술에 관한 연구)

  • Lee, Ji-Eun;Cho, Nam-Chan;An, Chang-Mo;Noh, Jae-Soo;Moon, Jong-Han
    • Clean Technology
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    • v.19 no.3
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    • pp.264-271
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    • 2013
  • In this study, we optimized the removal condition of contaminants attached on the scrap surface to recycle the scrap generated from the Zr alloy tube manufacturing process back to the nuclear grade. The main contaminant is remnant of watersoluble cooling lubricant that is used in the pilgering manufacture during the tube production, and it is assumed to be compressed and carbonized on the surface of tube. Zirlo alloy tube of ${\phi}9.50mm$, which has high occurrence frequency of scrap, was selected as the object to be cleaned, and cleaning abilities of reagents were evaluated by measuring the characteristics of contaminants remained and by analyzing the surface of the tube after cleaning process. For evaluation of each cleaning agent, we selected two types of sodium hydroxide series and three types of potassium hydroxide series. Furthermore, to confirm dependence on tempe-rature and ultrasonic intensities, cleaning at the room temperature, $40^{\circ}C$, and $60^{\circ}C$ was conducted, and results showed that higher the cleaning temperature and higher the ultrasonic intensity, better the cleaning effect. As a result of the bare-eye inspection, while the use of sodium hydroxide provided satisfactory condition on the tube surface, the use of potassium hydroxide series provided satisfactory condition on the tube surface only when the ultrasonic intensity was over 120 W. In the cleaning effect analysis using the gravimetric method, cleaning efficiency of sodium hydroxide series was as high as 97.6% ($60^{\circ}C$, 120 W), but since the tube surface condition was poor after the use of potassium hydroxide, the gravimetric method was not appropriate. In the analytical result of surface contaminants on the tube surface, C, O, Ca, and Zr were detected, and mainly C and O dominated the proportion of contaminants. It was also found that the degree of cleaning on the tube affected the componential ratio of C and O; if the degree of cleaning is high, or if cleaning is well-conducted, the proportion of C is decreased, and the proportion of O is increased. Based on these results, optimal cleaning for application in the industry can be expected by categorizing cleaning process into three steps of Alkali cleaning, Rinsing, and Drying and by adjusting cleaning parameters in each step.

Stellite bearings for liquid Zn-/Al-Systems with advanced chemical and physical properties by Mechanical Alloying and Standard-PM-Route

  • Zoz, H.;Benz, H.U.;Huettebraeucker, K.;Furken, L.;Ren, H.;Reichardt, R.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2000.04a
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    • pp.9-10
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    • 2000
  • An important business-field of world-wide steel-industry is the coating of thin metal-sheets with zinc, zinc-aluminum and aluminum based materials. These products mostly go into automotive industry. in particular for the car-body. into building and construction industry as well as household appliances. Due to mass-production, the processing is done in large continuously operating plants where the mostly cold-rolled metal-strip as the substrate is handled in coils up to 40 tons unwind before and rolled up again after passing the processing plant which includes cleaning, annealing, hot-dip galvanizing / aluminizing and chemical treatment. In the liquid Zn, Zn-AI, AI-Zn and AI-Si bathes a combined action of corrosion and wear under high temperature and high stress onto the transfer components (rolls) accounts for major economic losses. Most critical here are the bearing systems of these rolls operating in the liquid system. Rolls in liquid system can not be avoided as they are needed to transfer the steel-strip into and out of the crucible. Since several years, ceramic roller bearings are tested here [1.2], however, in particular due to uncontrollable Slag-impurities within the hot bath [3], slide bearings are still expected to be of a higher potential [4]. The today's state of the art is the application of slide bearings based on Stellite\ulcorneragainst Stellite which is in general a 50-60 wt% Co-matrix with incorporated Cr- and W-carbides and other composites. Indeed Stellite is used as the bearing-material as of it's chemical properties (does not go into solution), the physical properties in particular with poor lubricating properties are not satisfying at all. To increase the Sliding behavior in the bearing system, about 0.15-0.2 wt% of lead has been added into the hot-bath in the past. Due to environmental regulations. this had to be reduced dramatically_ This together with the heavily increasing production rates expressed by increased velocity of the substrate-steel-band up to 200 m/min and increased tractate power up to 10 tons in modern plants. leads to life times of the bearings of a few up to several days only. To improve this situation. the Mechanical Alloying (MA) TeChnique [5.6.7.8] is used to prOduce advanced Stellite-based bearing materials. A lubricating phase is introduced into Stellite-powder-material by MA, the composite-powder-particles are coated by High Energy Milling (HEM) in order to produce bearing-bushes of approximately 12 kg by Sintering, Liquid Phase Sintering (LPS) and Hot Isostatic Pressing (HIP). The chemical and physical behavior of samples as well as the bearing systems in the hot galvanizing / aluminizing plant are discussed. DependenCies like lubricant material and composite, LPS-binder and composite, particle shape and PM-route with respect to achievable density. (temperature--) shock-reSistibility and corrosive-wear behavior will be described. The materials are characterized by particle size analysis (laser diffraction), scanning electron microscopy and X-ray diffraction. corrosive-wear behavior is determined using a special cylinder-in-bush apparatus (CIBA) as well as field-test in real production condition. Part I of this work describes the initial testing phase where different sample materials are produced, characterized, consolidated and tested in the CIBA under a common AI-Zn-system. The results are discussed and the material-system for the large components to be produced for the field test in real production condition is decided. Outlook: Part II of this work will describe the field test in a hot-dip-galvanizing/aluminizing plant of the mechanically alloyed bearing bushes under aluminum-rich liquid metal. Alter testing, the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed. Part III of this project will describe a second initial testing phase where the won results of part 1+11 will be transferred to the AI-Si system. Part IV of this project will describe the field test in a hot-dip-aluminizing plant of the mechanically alloyed bearing bushes under aluminum liquid metal. After testing. the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed.

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Properties and Suitability of Bark Extractives from Larix leptolepsis as a Bonding Agent (낙엽송(落葉松) 수피추출물(樹皮抽出物)의 특성(特性)과 접착제화(接着劑化)의 적합성(適合性))

  • Oh, Jung Do;Ahn, Won Yung
    • Journal of Korean Society of Forest Science
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    • v.77 no.3
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    • pp.294-302
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    • 1988
  • The experiment was carried out to investigate the properties of bark extractives form Larix epilepsies and to evacuate their suitability as a bonding agent. The yield and reactivity were measured to examine the influence of temperature and time and the effect of carbonation and sulfonation. To define the possibility of practical application as wood adhesives the viscosity and gelation time were measured at 33% concentration. The results obtained were summarized as follows : 1. As the both yield and reactivity were high, extraction for 2 hours at $80^{\circ}C$ was the optimal temperature and time. 2. The highest effect achieved at 1% $Na_2CO_3$ about carbonation and 1% $Na_2SO_3$ : $NaHSO_3$ and 0.25% $Na_2SO_3$ about sulfonation. The sulfonation of 0.25% $Na_2SO_3$ increased the yield and reactivity most highly. 3. By using hot water as extraction liquid the yield was 17.2%, while the addition of 1% and 5% NaOH to the extraction liquid increased the yield to 38.6% and 44.6%, respectively. 4. Hot water extracts showed the highest reactivity(68.8%). The addition of 1% and 5% NaOH led to decrease in reactivity(49.3% and 25.8%, respectively). 5. At 33% concentration of the extracts the viscosity appeared very variable. Significantly high values of viscosity was measured in 1% NaOH solution, while very low values appeared for 5% NaOH solution. 6. The shortest gelation time was determined at pH 7 to 10 and the highest at pH 4. The use of paraformaldehyde resulted in gelation times longer than those of 37% formaldehyde solution. 7. Except the sulfonation extracts of hot water and 1% NaOH, the other extracts were found unsuitable due to high viscosity(1% NaOH extracts, sulfonation extracts) or to curing inability(5% NaOH extracts, sulfonation extracts of 5% NaOH). 8. From the three extract solutions which appeared to be suitable for use as bonding agents the hot water extracts and the sulfonation extracts of hot water were superior in extract reactivity, while the sulfonation extracts of 1% NaOH exceeded the other two extracts in extract yield.

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