• Journal of Korean Society of Forest Science
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• v.87 no.2
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• pp.121-130
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• 1998

This study was carried out to investigate working time, productivity, and heart rate during thinning using chain saw in Japanese larch(Larix leptolepis) plantation site for analysis of physical work load, and to investigate maximal oxygen uptake of worker for analysis of maximal work capacity. The real working time was 366 minutes in a day ; about 192 minutes in the a.m., 174 minutes in the p.m.. The ratio of real working time per total working time was approximately 90%. The rate of moving(Mo) to real working times was 26.3, which was the largest one of work elements. Average maximal oxygen uptake, as an asset of personnel performance, was $2.42{\ell}/min$($46.5m{\ell}/kg/min$). During the real working time, average productivity, the mean rate of increase of heart rate, and the mean work load index was $2.62m^3/hr$, 93.2%, and 41.9%, respectively.

• Korean Journal of Agricultural and Forest Meteorology
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• v.1 no.1
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• pp.29-35
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• 1999

Soil structure and organic matter have been known to strongly affect water flow and solute transport, yet little information is available concerning soil hydraulic properties related to soil physical and chemical properties in the forest site. The purpose of this study was to quantify the spatial variability and spatial correlation of the measured parameter values from the plots established with the rainfall simulator on Japanese larch(Larix leptolepis) dominated site in Kwangju. Kyunggi-Do. Measurement of soil water flux and retention were made with the inherent soil texture, soil structure, and organic matter. The method was based on the observation that when water was applied at a constant rate to the soil surface on each plot. The method was simple to apply and consists of following steps: (i) Wet the soil from a rainfall simulator with several known discharge rates on a relatively leveled soil surface with and without organic matter. (ii) Once the borders of the ponded zone were steady, saturated hydraulic conductivity( $K_{s}$) and the matric flux function(F) was evaluated from a regression of flux vs. the reciprocal of the ponded area. A conductivity of the form $K_{i+}$$_1$ $_{c}$= $K_{i}$( $_{c}$) [1-d /dz] where flux continuity implies. For this, continuity of matric potential at the interface at all times are as follows: $_1$( $Z_{c}$) = $_2$( $Z_{c}$) = $_{c}$ for steady state intake from water ponded on the soil surface. Results of this investigation showed the importance of understanding spatial variability in wide differences of water retention and saturated hydraulic conductivity with respect to pore geometry and organic matter contents which influenced the water flux throughout the soil profile.l profile.ile.

• Journal of Korean Society of Forest Science
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• v.99 no.4
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• pp.633-637
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• 2010

This study was conducted to evaluate various effects of kinds of culture medium, concentrations of abscisic acid (ABA) or /kinds of osmotica on maturation of somatic embryos (SEs) with four (LL-L, LL-K, LL-P and LL-N) embryogenic tissue lines (ETLs) in Japanese larch (Larix leptolepis). In comparison of two culture medium, the LL-P produced the highest number of the cotyledon-staged SE (134.9/90 mg tissue) in 1/2LM medium. In contrast, no SEs were obtained except the LL-P (32.9) in medium of BLG. Effects of two concentrations of ABA in the medium with four ETL for SEs maturation were also compared. In the test of 60 or 100 ${\mu}M$ ABA, the highest result was obtained in 60 ${\mu}M$ ABA (142.9). However, the influence of ABA had little on SEs production except the LL-N regardless of concentrations of ABA. In comparison of different kinds/concentrations of osmotica, the best response was obtained from the treatment of 0.2 M maltose, the LL-K (540.5). In conclusion, the effects of production of SEs were greatly rely on the ETLs, rather than kinds of medium, concentrations of ABA or osmotica which were used in maturation of SEs.

• Journal of Korean Society of Forest Science
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• v.100 no.4
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• pp.693-697
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• 2011

This study was conducted to examine effects of concentrations of abscisic acid (ABA) or /kinds of osmotica on induction of somatic embryos (SEs), germination and plantlet regeneration in Japanese larch (Larix kaempferi). In comparison of duration of culture, concentrations of ABA and osmoticum, the highest induction number (191/g tissue) of the SE was showed in $60{\mu}M$ ABA+0.2 M sucrose for 4 weeks culture. However, the lowest number (3.5~23.5) of SEs was induced from $4{\mu}M$ ABA+0.1 M sucrose, regardless of culture duration for SEs induction. In comparison of germination efficiency of SEs, the highest induction frequencies of cotyledon (90.9%), hypocotyl (95.8%) and root (96.5%), respectively, were obtained from the SEs that cultured from the treatment of $60{\mu}M$ ABA+0.2 M sucrose with 5 weeks culture. In contrast, the lowest germination response was showed in SEs that induced from the treatment of $4{\mu}M$ ABA+0.1 M sucrose. In comparison of effect of different kinds/concentrations of osmotica for germination and plantlet regeneration, the best response was obtained from the treatment of 0.2 M sucrose with induction of cotyledon (98.3%), hypocotyl (78.4%), root (57.5%) and plantlet regeneration (54.8%), respectively.

• Journal of the Korean Wood Science and Technology
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• v.40 no.1
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• pp.26-37
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• 2012

Recently, the demand and supply on the Hanok have been increased. However, Hanok should be requested larger section of structural members because of excessive roof weight. So, structural skin-timber was manufactured to get a lightweight structural member. The structural skin-timber has exterior shape with larger section but a great volume of wood be removed. The reduced strength of structural skin-timber can be supplemented by hybridizaion of structural member. Japanese larch and Domestic pine were used to manufacture the structural skin-timber. Structural skin-timbers of rectangular shape and cylinder shape were manufactured and tested to evaluate the bending properties. The intended strength property could not be obtained because member had been suffered severe damage by precision deficiency of manufacturing machine. However, if precision of manufacturing machine would be improved and additional hybridizaion of structural skin-timber would be done, lightweight structural member will be able to be manufactured. Structural skin-timber did not showed statistical significancy between two species, so it is possible to use pine mixed with larch. Only MOR of larch showed statistical significancy between rectangular shape and cylinder shape, so it is necessary to use of those as separate things. However, the rest of skin-timber can be judged mixed using because of non statistical significancy. The objective of this study was the development of lightweight larger structural member with relatively strength. If hybrid member of skin-timber could be developed with wood-ceramics, lightweight steel and more, it can be possible to be used as a building material of Hanok, interior material, post & beam construction material and more.

• Journal of the Korean Wood Science and Technology
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• v.45 no.4
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• pp.409-418
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• 2017

This work attempted to manufacture glued-laminated timber (Glulam) bonded with melamine-urea-formaldehyde (MUF) resin adhesives at various melamine contents from 20% to 50% under high frequency (HF) heating for a very short time. Two preparation methods were employed to prepare MUF resin adhesives with different melamine contents: one-batch method of synthesizing MUF resins in a single batch, and two-batch method of mixing urea-formaldehyde (UF) resin with melamine-formaldehyde (MF) resin that had been synthesized separately. As the melamine content increased, the gelation time and peak temperature of MUF resins decreased. The adhesion performance of plywood showed that the one-batch MUF resin adhesive with 50% melamine content only satisfied the standard requirement of water resistance. Thus, the one-batch MUF resin adhesive with 50% melamine content was applied for bonding wood lamina from four softwood species such as Japanese larch, Korean red pine, Korean pine and Japanese cedar to manufacture Glulam under HF heating. All Glulam samples bonded with the one-batch MUF resin adhesives with 50% melamine content except those from Korean Red Pine satisfied the requirement in water soaking or boiling water delamination test as an exterior grade Glulam. The presence of rosin in Korean Red Pine was believed to be responsible for its poor adhesion. These results showed that the one-batch MUF resin adhesives with 50% melamine content provided acceptable water resistance with exterior grade Glulam manufactured under HF heating.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.16 no.5
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• pp.83-92
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• 2013

The present study documented the characteristics of habitats and nests of Goshawk [Northern goshawk] Accipiter gentilis breeding in Gongju-si, Chungcheongnam-do and Haepyung, Kyungsangbuk-do, Eumsung-gun, Chungju-si, Chungcheongbuk-do from April 2007 to August 2011. Breeding habitat includes of mixes and deciduous trees and ravine forest, ranging from small to large areas and it used make a new nest and fix up the old nest at Goshawk. Goshawk make nests on Japanese larch Larix leptolepis, Japanese red pine Pinus densiflora and Pitch pine Pinus rigidae of $15.8{\pm}2.36m$ (range=7.4~18.7m) in height and $34.6{\pm}7.38cm$ (range=20.8~47.4cm) in diameter-at-breast height (DBH). It has $135.8{\pm}3.37cm$ in outer diameter of nest, $26.2{\pm}2.39cm$ in inner diameter, $7.1{\pm}1.41cm$ of depth, and $3.1{\pm}0.40Kg$ of weight. Breeding habitat (n=13) has 5~7 nests. It has 7 (53.8%) nest in fix up the old nest and 4 (30.8%)nests in make a new nest.

• Journal of the Korean Wood Science and Technology
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• v.34 no.3
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• pp.15-21
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• 2006

The objective of this research is to develop the technique for carbonization of wood pellet and analyze a possibility for the utilization of carbonized wood pellet. The properties of wood pellet charcoals, such as density, yield, elemental composition, higher heating value, and methyleneblue adsorption, were analyzed. Wood pellet was made of sawdust of Hyunsasi-poplar, Japanese larch, Korean pine, Korean red pine, and Jolcharn-oak (serrate oak), respectively. The high density charcoal ($0.5{\sim}0.7g/cm^3$) was yielded from densified wood pellet. The carbon contents and calorific values of wood pellet charcoals were increased with the increase of carbonization temperature. The methyleneblue adsorptivity of wood pellet charcoal was similar to that of wood charcoal.

• Journal of the Korean Wood Science and Technology
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• v.27 no.4
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• pp.20-29
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• 1999

Temperature has important effect on mechanical properties of wood. These effect needs to be understood and taken into account in the structural use of wood. Furthermore, the effect of cooling after exposing to high temperature must be explained. In this study, the effect of temperature, exposure time, specific gravity, and cooling on bending properties were investigated. The boundary temperatures at which bending MOE and MOR reduced rapidly were approximately $200^{\circ}C$ and $150^{\circ}C$, respectively. This boundary temperature was nearly constant with independence of species(specific gravity), exposure time, and cooling. Above the boundary temperature, the effect of exposure time was increased with temperature and the reduction of bending MOE and MOR for Japanese Larch with relatively higher specific gravity was smaller than that of Hem-fir. The recovery of bending MOE and MOR after cooling was also more significant above the boundary temperature than below. The degree of cooling effect was larger for MOR than MOE. Consequently, bending properties of wood in elevated temperatures should be considered in terms of the boundary temperature, $200^{\circ}C$ for bending MOE, $150^{\circ}C$ for MOR, and these boundary temperatures must be considered an important factor. Furthermore, to evaluate the safety of structure, the recovery after cooling should be considered.

• Journal of the Korean Wood Science and Technology
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• v.39 no.5
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• pp.437-443
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• 2011

In Korea, there has been a traditional post and beam wood construction with large roof load. Because a large friction is generated in wooden joint or members, it is important to evaluate the friction between wood members according to wood direction. Because most of studies have been concerned with friction between wood and steel, excluding effect of real area of contact, there are a few studies on the friction between wood members. The object of this study was to evaluate friction or coefficient of friction according to normal force and real area of contact of wood. With Japanese larch (Larix kaempferi) test specimens, five steps of normal force and combinations of test were prepared. Results indicated that normal force had almost no affection on the friction, however there was difference about friction or coefficient of friction according to real contact conditions of wood grain and contact area.