• Journal of the Korean Wood Science and Technology
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• v.35 no.2
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• pp.16-22
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• 2007

The behavior of ramie fibers and some wood elements in the early stage of alkali swelling was examined. When the fibers were treated with alkali solution, they significantly shrank in length and swelled in wall thickness. Ramie fibers showed a shrinkage averaging 23% in length and a swelling averaging 92% in width in 100 seconds treating time. Dimensional changes showed different fashion in each element of woods. The tracheids of latewood especially in Pinus densiflora and Larix kaempferi woods swelled intensively and showed balloon swelling, but in the case of Cryptomeria japonica, it was hardly observed. The swelling morphology of libriform fibers was similar to that of tracheids. The walls of vessel elements and parenchyma cells also swelled considerably in thickness but, no balloon swelling was found in both elements. The differences of swelling in different elements can be interpreted in terms of the differences of organization and/or chemical components of the cell walls.

• Journal of Korea Foresty Energy
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• v.22 no.2
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• pp.26-35
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• 2003

Bamboo strand board (BSB) was made with Phyllostachys banbusoides growing in Damyang district. Physical and mechanical properties of this BSB were summarized as follows; The specific gravity of BSB was 0.63∼0.79. Specific gravity decreased slightly with the thickness and length of BSB. Moisture content of BSB manufactured was 5.8∼6.9%. The absorption ate of BSB (42∼48%) did not show any relationship with the thickness and length of BSB. The thickness swelling rate of BSB was 13.9∼17.0%, relatively higher than any other panel products. Thickness swelling rate increased with the thickness of BSB, showing the strand thickness influenced much more on the rate of thickness swelling of BSB than the length of strand. The 3-point bending strength of BSB was 98∼126kgf/$\textrm{cm}^2$. Bending strength of showed the tendency of increase with the increased length of BSB, but with the decreased thickness. In particular, the length of BSB showed more effect on the increase of bending strength of BSB than the thickness of BSB. The compression strength perpendicular to BSB surface was 411 ∼ 465 kgf/$\textrm{cm}^2$, and the optimal length of strand for the 1mm- and 2mm-thickness of strand was 40mm and 60mm, respectively. Compression strength paralleled to BSD was 160∼221kgf/$\textrm{cm}^2$ and the optimal length of strand for the 2mm-thickness of strand appeared to be 60mm. The present work showed that appearance, physical and mechanical strength of BSB appeared quite positive in terms of board qualities, suggesting that bamboo would be appropriate for the production of board materials. In addition, our work showed that the crucial factor for determining the mechanical characteristics of BSB was the dimension of strand.

• Elastomers and Composites
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• v.51 no.4
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• pp.342-349
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• 2016

Characteristics of the swelling-induced wrinkles on the surfaces of natural rubber (NR) film were investigated. The wrinkle structure was generated by swelling of NR film pre-stretched and firmly bonded onto an aluminum substrate in hexane. A novel experimental method was adopted to replicate the swelling-induced wrinkles on the NR film using an epoxy-hardener system. To get insight into the wrinkle parameters; the wrinkle length (L), wrinkle distance (D), wrinkle height (H) and the angle between two consecutive wrinkles (${\theta}$), the cross-sections of the replicas obtained from saturated swollen NR film were examined using an optical microscopy (OM). From the OM images, the wrinkling parameters were measured as a function of the thickness of NR film from 0.42 to 1.76 mm. Also, it was evaluated that the effects of swelling time on the wrinkling parameters. The length (L), distance (D) and height (H) of wrinkles increased as the thickness of the NR film and the swelling time increased. However, the angle between the wrinkles (${\theta}$) showed a sharp decrease up to a swelling time of 200 minutes and slightly decreased afterwards.

• Journal of the Korean Wood Science and Technology
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• v.13 no.3
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• pp.3-26
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• 1985

The object of this study was to investigate the effects on physical and mechanical properties of wood particle and sawdust board combined with wire net. Conventional forming, press-lam, and veneer comply boards combining one to four wire net sheets were made from wood particle and sawdust with different spacings (8, 10, 12, and 18 Mok) and different wire diameters (0.35, 0.50, and 0.80mm) composing wire net. They were compared and analyzed statistically with specific gravity, thickness swelling, length swelling, bending properties (modulus of rupture, modulus of elasticity, work to proportional limit, and total work), internal bonding strength, and screw holding strength between wood particle and sawdust boards. The results obtained at this study as cording to the discussions might be concluded as follows; 1. In specific gravity, both particle and sawdust boards by press-lam method were higher than by conventional forming and veneer comply method, and the boards containing more wire net sheets also showed higher value. But the wire net spacings(Mok) had no influence on specific gravity. In general, particle board showed higher specific gravity than sawdust board. Veneer comply board showed lowest specific gravity values. 2. Both particle and sawdust boards by press-lam method was slightly lower than by conventional forming and veneer comply method in thickness swelling. The sawdust board containing 8, 12. and 18 Mok wire net showed lower thickness swelling than the corresponding particle board, but both sawdust and particle boards containing the T8 and 10 Mok wire net showed higher and similar thickness swelling. 3. Both particle and sawdust boards containing wire net showed no difference in MOR and MOE of bending. Comply board was the highest and particle board showed slightly higher than sawdust board in MOR and MOE values. 4. In work to proportional limit and total work in bending, both particle and sawdust boards containing thicker wire diameter and more wire net sheets showed higher value. From these facts, it is conceivable that boards with thicker wire diameter and more wire net sheets show increasing resistance against external force. But there was no significant difference between particle and sawdust borads. 5. In resistance against delamination (internal bonding strength), both sawdust and particle boards containing wire net showed lower value than control, and also showed decreasing tendency with more number of wire net sheet composed. Particle board showed higher resistance against delamination than sawdust board. 6. In screw holding strength, sawdust board containing thicker wire diameter and more wire net sheets showed higher value, but particle board by press-lam method was higher than by conventional forming and veneer comply method. Screw holding strength of particle board was higher than that of sawdust board.

• Journal of the Korean Wood Science and Technology
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• v.24 no.4
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• pp.56-63
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• 1996

This study was to manufacture thinned wood of Larix leptolepis Gordon into Oriented Strand Board(OSB) with Urea-Formaldehyde Resin. The OSB was made of four kinds of strand in slenderness ratio 150 ; thickness $0.3{\pm}0.05mm$, $0.4{\pm}0.05mm$, $0.5{\pm}0.05mm$ and $0.6{\pm}0.05mm$, respectively length 45mm, 60mm, 75mm and 90mm. Target densities were 0.65gr/$cm^3$, 0.75gr/$cm^3$ and 0.85gr/$cm^3$. The stepwise 9 minutes-multi-pressing schedule in the maximum pressure 40kgf/$cm^2$, the minimum pressure 10kgf/$cm^2$ was applied for $400mm{\times}390mm{\times}12mm$ board at the temperature of $150^{\circ}C$ in a hot press. In MOR The OSB of thin strand thickness $0.3{\pm}0.05mm$(length 45mm) and density 0.85gr/$cm^3$ was the highest. The strand thickness had more effect on MOR than the strand length. In strand thickness $0.4{\pm}0.05mm$(length 60mm) and density 0.85gr/$cm^3$ was the highest MOE. The strand thickness and length had adverse effects on MOE each other. At internal bonding. The OSB of strand thickness $0.3{\pm}0.05mm$(length 45mm) and board density 0.75gr/$cm^3$ showed the highest value. OSB had higher IB value with thinner strand thickness. The thinner strand thickness showed the lower thickness swelling in turn $0.3{\pm}0.05mm$(length 45mm), $0.4{\pm}0.05mm$(length 60mm), $0.5{\pm}0.05mm$(length 75mm). $0.6{\pm}0.05mm$(length 90mm). Target densities 0.75gr/$cm^3$ 0.65gr/$cm^3$, 0.85gr/$cm^3$ showed in turn lower value. Finally, The OSB made of thinned wood of Larix leptolepis Gordon showed good results in laboratory experiment.

• Journal of the Korean Wood Science and Technology
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• v.13 no.3
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• pp.49-53
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• 1985

The effects of pre-treatments, the hot water extraction of wood meal and the addition of chemical ($CaCl_2$) to wood-cement water system on the properties of wood-cement composite such as modulus of rupture (MOR), modulus of elasticity (MOE), water sorption ratio and swelling ratio of resulting boards were studied in this experiment. The wood meals through 0.83mm(20 mesh) and retained on 0.42mm(35 mesh) screen were prepared from Pinus densiflora S. at Z. and Larix leptolepsis G. For hot water extraction, 500 grams of wood meal for each species were heated to boiling with 1,500ml of distilled water in 2-liter beaker for 6 hours. Every 2 hours, the wood meals were washed with boiling distil1ed water and reheated to boiling again. After 6 hours boiling, the boiled wood particles were collected by pouring this particles on 200 mesh screen. The collected particles then washed twice with hot distilled water and dried for 24 hours in an oven at $109{\pm}20^{\circ}C$. A mixture of 663.4 grams of cement with 331.7 grams of wood meal based on oven-dry weight were dry-mixed in a plastic vessel. The mixture was kneaded with 497.6ml of distilled water in the ratio of 1.5ml of water to a gram of wood meal. To add calcium chloride to the mixture as an accelerator, $CaCl_2$ 4% solution by weight per volume, was added to pine-or larch-cement board in the ratio of 3% to cement weight. To set wood-cement board, this mixture was clamped at 30cm ${\times}$ 30cm, in thickness of 1.5cm for 3 days at room temperature, declamped and then placed at open condition for 17 days. The target density was 1.0. The four specimens sized to 5cm in width and 28cm in length were used for MOR and MOE test for each treatment. After MOR test, the tested specimens were cut to the size of 5cm ${\times}$ 5cm for water sorption and swelling test. The twenty specimens used to measure the water sorption ratio (soaking 24 hours) and ten of these were used for swelling ratio measurement The results obtained were as follows: 1) Larch was not suitable for wood-cement boards because larch-cement board developed no strength, but pine showed 97.9kg/$cm^2$ by hot water extraction. 2) To increase MOR, hot water extraction was more effective than the addition of $CaCl_2$ in pine and larch because the $CaCl_2$ addition was seemed to speed up the ratio of cement hydration without reacting with the wood substances. 3) The water sorption ratio was lowered by the addition of $CaCl_2$ to wood-cement system because the chemical additive accelerated the rate of cement hydration. 4) In pine-cement board, the swelling ratio from 0.37 to 0.42 percent was observed in length and the swelling ratio from 0.88 to 2.0 percent in thickness. As a rule, the swelling ratio of wood-cement board was very low and the swelling ratio in thickness was higher than in length.

• Journal of the Korean Society of Tobacco Science
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• v.28 no.1
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• pp.23-30
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• 2006

In order to improve the final product quality, tobacco industry has gradually decreased the size and number of steams in the cigarette. Especially, steams bigger than $3{\times}3$ mm($length{\times}thickness$) and $2{\times}10$ mm($width{\times}length$) are not acceptable in the process as objectionable stems. A total number of 12 samples where the $length{\times}tickness$ samples were prepared by decreasing the present sample ($3{\times}3$ mm) with 1 mm up to $1{\times}1$ mm, and the $width{\times}length$ samples were prepared by decreasing the present sample ($2{\times}10$ mm) with 2 mm up to $2{\times}6$ mm for the stems in leaf and stems in expanded cut-tobacco were prepared to apply a fire ball drop test using stems. In addition, cigarettes were produced for these stems in order to analyze the forced fire ball drop including the burning, encapsulation and unencapsulation pressure drop and a single or unspecified direction combustion. Based on the results of the test, it was evident that the fire ball drop in the stems in expanded cut-tobacco presented a lower level than that of the stems in leaf. Also, the stems in expanded cut-tobacco presented a larger swelling and higher burning for a single direction than that of the stem in leaf. In addition, it was considered that the management criteria for objectionable stems should be changed as $3{\times}3$ mm and $2{\times}8$ mm for the $length{\times}thickness$ and $width{\times}length$ sample, respectively, in both steams in leaf and expanded cut-tobacco.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.32 no.2
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• pp.35-39
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• 2000

Refining is very important process of fibers treatment for proper paper properties. An extent of refining is usually measured by freeness, although freeness gives complicated meanings. One of a direct way of studying the refining effects on pulp fibers is making photomicrographs of beaten fibers. The conventional microscopy like light microscopy(LM) and scanning electron microscopy(SEM) require to preserve the wet structure of pulp fibers morphologically since most of papermaking process is carried out almost entirely in water. Recently developed microscopy, especially confocal laser scanning microscopy(CLSM), offers the possibility of examining fully hydrated pulp fibers. Cross-sectional images of wet pulp fibers are also generated using optical sectioning by CLSM and image analysis in order to verify and quantify the extent of fiber wall swelling indicating the internal fibrillation. At low beating load such as 2.5 kgf, in the same freeness, breaking length is higher than that of high beating load such as 5.6 kgf. fiber wall thickness at low beating load is greater than that at high beating load. This result is accounted for the fact that internal fibrillation in the low beating load was high.

• Journal of the Korean Wood Science and Technology
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• v.15 no.3
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• pp.44-55
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• 1987

In order to study the effect of sawdustboard combined with plastic chips, 0.5mm($T_1$), 1mm($T_2$), 1.4mm($T_3$) thick nylon fiber. polypropylene rope fiber(RP), and 0.23mm thick moth-proof polypropylene net fiber(NP) were cut into 0.5, 1, 2cm long plastic chips. Thereafter, sawdustboard combined with plastic chips prepared as the above and plastic non-combined sawdustboard(control) were manufactured into 3 types of one-, two-, and three layer with 5 or 10% combination level. By the discussions and results at this study, the significant conclusions of mechanical and physical properties were summarized as follows: 1. The MORs were shown in the order of 3 layer> 2 layer> 1 layer among plastic non-combined boards, and $T_3$ < $T_2$ < $T_1$ < RP (NP(5%) < NP(l0%) among plastic combined boards. In 2cm long plastic chip in 1 layer board, the highest strength through all the composition was recognized. 1 layer board showing the lower strength with 0.5cm plastic chip rendered to the bending strength improvement by 2 or 3 layer board composition. On the other hand, 2 or 3 layer combined with 1, 2cm long polypropylene net fiber chips incurred MOR's conspicuous decrease requiring optimum plastic chip combined level and consideration to combined type. 2. MOE in plastic non-combined 3 layer board exhibited sandwich construction effect by higher resin content application to surface layer in the order of 3layer>1layer>2layer with the highest stiffness of the board combined with polypropylene chip, while nylon chip-combined board had little difference from plastic non-combined board. In relevant to length and layer effect, 3 layer board combined with the 0.5cm long polypropylene net fiber chip in 5% and 10% combined level presented 34-43% and 44-76% stiffness increase against plastic non-combined board(control), respectively. Moreover, in 1 layer board, 30% stiffness increase with 10% against 5% combined level in the 1 and 2cm long polypropylene net fiber chip was obtained. 3. Stress at proportional limit(Spl) showing the fiber relationship (r: 0.81-0.97) between MOR presented in the order of 1 layer<2 layer<3 layer in plastic non-combined board. Correspondingly, combined effect by layer and plastic chip length was similar to MOR's. 4. Differently from previous properties(MOR, MOE, Spl). work to maximum load(Wml) of 2 layer board approached to that of 3 layer board. Conforming the above phenomenon. 2 layer combined with 0.5cm long polypropylene net fiber chip kept the greater work than 1 layer. The polypropylene combined board superior to nylon -and plastic non - combined board seemed to have greater anti - failing capacity. 5. Internal bond strength(IB), in contrast to MOR's tendency. showed in the order of T1

• Applied Microscopy
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• v.17 no.1
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• pp.47-64
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• 1987

Morphological difference of the renal glomerulus at different age groups have been studied in young (three month-old), adult (twelve month-old) and old (thirty month-old) Fisher strain 344 rats. Pieces of the tissues were taken from renal corticies prefixed with 2.5% glutaraldehyde-1.5% paraformaldehyde (0.1 M Millonig's phosphate buffer, pH 7.3), following by post-fixation with 1% osmium tetroxide (0.1 M Millonig's phosphate buffer, pH 7.3) and embedded within Araldite. The ultrathin sections contrasted with uranyl acetate and lead citrate were observed under a JEM 100CX electron microscope. The mean thickness of glomerular basal lamina and Bowman's capsule were determined by measuring the thinnest portion of basal lamina, and by taking the average of 50 readings from electron micrographs at different ages. The numerical changes of the slit pores were compared based upon the numbers over the length of 10um of glomerular basal lamina. The results were as follow: 1. The thickness of glomerular basal lamina is increased during aging; 140.4 nm in young rats, 270.0 nm in adult ones, and 437.8 nm in old ones. 2. The thickness of basal lamina of parietal cells of Bowman's capsule is 187.5 nm in young rats, 914.0 nm in adult ones, and 2850.0 nm in old ones. 3. The numbers of the slit pores of basal lamina are reduced during aging, 30.3 slit pores/$10{\mu}m$ in adult ones, and 24.2 slit pores/$10{\mu}m$ in old ones. 4. Accumulation of dense intracytoplasmic filamentous material in the parietal cells of Bowman's capsule is increased in the vicinity of the basal lamina during aging. The proximal tubule-like epithelial cell in Bowman's capsule is observed at one glomerulus in a young rat. 5. The endothelial cells are edematous and form balloon-like structure protruding into capillary lumen in young and old rats. 6. Cytoplasm of the podocyte shows a variety of alteration during aging, such as swelling of mitochondria and of endoplasmic reticulum, and increase of microtubules, microfilaments, lysosomes and lamellated myelin structures, etc. Accumulation of dense intracytoplasmic material in the foot processes is increased in the vicinity of the basal lamina during aging. The podocytic membrane-like structures are seen in young and o]d rats. 7. The mesangial matrices and mesangial cells are increased during aging, and slight swelling of endoplasmic reticulum and Golgi cisternae in young and old rats.