• Journal of the Korean Wood Science and Technology
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• v.50 no.4
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• pp.237-245
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• 2022

This study examined the structural performance of experimental parallel strand lumber (PSL) from a Larch veneer strand. The prototype of PSL from a Larch veneer strand was manufactured in the experimental laboratory and tested. The bending and dowel bearing strength were determined from the modulus of elasticity (MOE), modulus of rupture (MOR), and dowel bearing strength based on a 5% offset yield load. The test results indicated that the average MOR of PSL was higher than that of 2 × 4 dimension lumber, and the average MOE of PSL was lower than that of 2 × 4 dimension lumber. A linear relationship was observed between the MOR and MOE. The allowable bending stress of PSL was derived as specified in ASTM D2915 and compared with other research. The dowel bearing strength of PSL in parallel to the grain was approximately double that perpendicular to the grain of PSL. A comparison of several theoretical calculations based on each national code for the dowel bearing strength was conducted, and some theoretical equations produced results closer to the experimental results when it was parallel to the grain, but the difference was higher in the case perpendicular to the grain. The test results showed that PSL made with Japanese larch veneer strands appeared to be suitable for a raw material of structural composite lumber (SCL) appeared to be used as a raw material for SCL.

• Journal of the Korean Wood Science and Technology
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• v.43 no.1
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• pp.36-42
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• 2015

This study examined true modulus of elasticity (MOE) and modulus of rigidity (G) for domestic woods with different slenderness ratios (L/D) using the static bending and stress wave tests. Bending properties of small clear wood specimen of three domestic wood species were determined at 12% moisture content. The results of this study indicated that both MOR and MOE of domestic woods were affected by the slenderness ratio. As the slenderness ratio increased, MOR and MOE increased. G and true MOE of domestic timber beams were obtained at different slenderness ratios by flexure test and stress wave test. The values reported here can be useful if these species woods are used for structural purposes. However, the reported values are only indicative and do not represent the true average of wood species due to the limited number of specimens tested.

• Journal of the Korean Wood Science and Technology
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• v.43 no.2
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• pp.168-176
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• 2015

This study was performed to investigate the effects of heat treatment the on mechanical properties of two species of wood under different heating conditions including at $180^{\circ}C$ for 12 h and 24 h, and at $210^{\circ}C$ for 3 h and 6 h. Two species of wood, Pinus densiflora and Larix kaempferi, were exposed to different heat treatments to assess the effects on the volume change, bending properties in static and dynamic mode and compressive strength. The results showed heat treatment caused significant changes in mechanical properties such as the static and dynamic moduli of elasticity ($MOE_d$ and $MOE_s$), and the modulus of rupture (MOR). The volume of the wood after heat treatment decreased as the heating temperature and time were increased. The bending strength performance of the wood after heat treatment decreased as the heating temperature and time were increased. The effect of heat treatment at a high temperature on the bending MOR was greater in both species than that for a long time. However, the compressive strengths of all the heat-treated samples were higher than the control sample. Furthermore, highly significant correlations between $MOE_d$ and MOR, and $MOE_s$ and MOR were found for all heating conditions.

• Animal Bioscience
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• v.34 no.10
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• pp.1600-1606
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• 2021

Objective: This study was conducted to enhance our understanding of nitrogen (N) metabolism and mammary amino acid (AA) utilization in lactating cows with divergent phenotypes of residual feed intake (RFI). Methods: Fifty-three multiparous mid-lactation Holstein dairy cows were selected for RFI measurements over a 50-d experimental period. The 26 cows with the most extreme RFI values were classified into the high RFI (n = 13) and low RFI (n = 13) groups, respectively, for analysis of N metabolism and AA utilization. Results: Compared with the high RFI cows, the low RFI animals had lower dry matter intake (p<0.01) with no difference observed in milk yield between the two groups (p>0.10). However, higher ratios of milk yield to dry matter intake (p<0.01) were found in the low RFI cows than in the high RFI cows. The low RFI cows had significant greater ratios of milk protein to metabolizable protein (p = 0.02) and milk protein to crude protein intake than the high RFI cows (p = 0.01). The arterial concentration and mammary uptake of essential AA (p<0.10), branched-chain AA (p<0.10), and total AA (p<0.10) tended to be lower in the low RFI cows. Additionally, the low RFI cows tended to have a lower ratio of AA uptake to milk output for essential AA (p = 0.08), branched-chain AA (p = 0.07) and total AA (p = 0.09) than the high RFI cows. Conclusion: In summary, both utilization of metabolizable protein for milk protein and mammary AA utilization are more efficient in cows with lower RFI than in the high RFI cows. Our results provide new insight into the protein metabolic processes (related to N and AA) involved in feed efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1395-1401
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• 2004

In The objective of this paper is to apply blind minimum output energy multiuser detection method to multicarrier direct sequence code division multiple access system. The performance of MC/DS-CDMA is reduced due to multiple access. To increase the performance of system, we need to cancel multiple user components. Blind interference canceller is able to detect the desired's information with the only minimal information of the desired user. We evaluate the performance of the proposed receiver under Gaussian channel. Simulation results show that the proposed receiver has about 6［dB］ gain of signal to noise ratio without multiple user interference and has about 3［dB］ gain of SNR with multiple user interference. Also, the result of comparing the capacity of the active users shows that the proposed method has about 2 times capacity more than conventional method. As a conclusion, simulation results show that the proposed method has better performs better than conventional method.

• Journal of the Korean Wood Science and Technology
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• v.22 no.4
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• pp.43-50
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• 1994

본 연구는 침엽수재를 사용한 손가락결합부재의 강도 및 감쇠특성을 측정함으로서 문창틀재로의 사용가능성을 시험하기 위하여 수행하였다. 손가락결합부 시험편의 형태는 손가락부분의 길이와 경사도에 따라서 다섯가지로 제작하였다. 하중은 4개의 하중단계를 갖는 양방향휨으로 가하였으며 각각의 하중단계는 3개의 하중주기로 구성되었다. 손가락결합부의 파괴특성을 분석하기 위하여 감쇠시험 과정에 AE신호를 측정하였다. MOE는 시험편의 형태와 뚜렷한 관련을 갖고 있지 않으나, MOR은 손가락부분의 경사도가 증가될수록 감소되는 뚜렷한 관계를 나타내었다. 감쇠비는 하중단계가 증가될수록 감소되었으나 파괴직전의 단계에서는 증가되는 경향을 나타내었다. 하중방향에 대하여 수직한 방향의 손가락결합부재가 수평방향부재보다 더 높은 강도를 나타내었다. 60dB 이상의 AE신호는 목재 또는 접착층의 파괴에 의하여 발생되는 것으로 분석되었다. 완전한 파괴가 발생하는 경우에는 100dB 이상의 AE신호가 발생하였다.

• Smart Structures and Systems
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• v.22 no.5
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• pp.611-620
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• 2018

In this research the effect of bedding layer angle and bedding layer thickness on the shear failure mechanism of concrete has been investigated using PFC3D. For this purpose, firstly calibration of PFC3d was performed using Brazilian tensile strength. Secondly shear test was performed on the bedding layer. Thickness of layers were 5 mm, 10 mm and 20 mm. in each thickness layer, layer angles changes from $0^{\circ}$ to $90^{\circ}$ with increment of $25^{\circ}$. Totally 15 model were simulated and tested by loading rate of 0.016 mm/s. The results shows that when layer angle is less than $50^{\circ}$, tensile cracks initiates between the layers and propagate till coalesce with model boundary. Its trace is too high. With increasing the layer angle, less layer mobilize in failure process. Also the failure trace is very short. It's to be note that number of cracks decrease with increasing the layer thickness. The minimum shear test strength was occurred when layer angle is more than $50^{\circ}$. The maximum value occurred in $0^{\circ}$. Also, the shear test tensile strength was increased by increasing the layer thickness.

• Structural Engineering and Mechanics
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• v.68 no.4
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• pp.507-517
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• 2018

In this research the effect of bedding layer angle and bedding layer thickness on the shear failure mechanism of concrete has been investigated using PFC3D. For this purpose, firstly calibration of PFC3d was performed using Brazilian tensile strength. Secondly punch shear test was performed on the bedding layer. Thickness of layers were 5 mm, 10 mm and 20 mm. in each thickness layer, layer angles changes from $0^{\circ}$ to $90^{\circ}$ with increment of $25^{\circ}$. Totally 15 model were simulated and tested by loading rate of 0.016 mm/s. The results show that when layer angle is less than $50^{\circ}$, tensile cracks initiates between the layers and propagate till coalesce with model boundary. Its trace is too high. With increasing the layer angle, less layer mobilizes in failure process. Also, the failure trace is very short. It's to be note that number of cracks decrease with increasing the layer thickness. The minimum shear punch test strength was occurred when layer angle is more than $50^{\circ}$. The maximum value occurred in $0^{\circ}$. Also, the shear punch test tensile strength was increased by increasing the layer thickness.

• Journal of the Korean Wood Science and Technology
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• v.33 no.2 s.130
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• pp.40-55
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• 2005

This study was carried out to discuss the feasibility of wood and plastic wastes as the raw materials for wood particle-plastic composites. For this purpose, composites were manufactured from coarse and fine wood particles and polypropylene fibers by nonwoven web process. And the effect of wood particle size on the performance of the composites were analyzed according to ASTM D 1037-93. In the physical properties of composites, water absorption decreased with the increase of target density and polypropylene fiber content. And the composites with fine wood particles appeared to have slightly lower water absorption than those with coarse wood particles. Thickness swelling did not vary significantly with the increase of target density but increased with the increase of wood particle content. And the composites with fine wood particles were significantly lower in thickness swelling than those with coarse wood particles. In the mechanical properties of composites, dry and wet MOR showed the increasing tendency with the increase of polypropylene fiber content and target density. Dry and wet MOE showed the increasing tendency with the increase of target density but only wet MOE exhibited the increasing tendency with the increase of polypropylene fiber content. Composites with fine wood particles appeared to be generally higher in wet MOR and MOE than those with coarse wood particles. In conclusion, composites with fine wood particles showed generally higher performance than those with coarse ones. Also, composites were significantly superior to control particleboards in the performance, especially in water absorption and thickness swelling.

• Structural Engineering and Mechanics
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• v.68 no.4
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• pp.497-505
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• 2018

Three points bending flexural test was modeled numerically to study the crack propagation in the pre-cracked beams. The pre-existing edge cracks in the beam models were considered to investigate the crack propagation and coalescence paths within the modeled samples. The effects of particle size on the single edge-notched round bar in bending test were considered too. The results show that Failure pattern is constant by increasing the ball diameter. Tensile cracks are dominant mode of failure. These crack initiates from notch tip, propagate parallel to loading axis and coalescence with upper model boundary. Number of cracks increase by decreasing the ball diameter. Also, tensile fracture toughness was decreased with increasing the particle size. In the present study, the influences of particles sizes on the cracks propagations and coalescences in the brittle materials such as rocks and concretes are numerically analyzed by using a three dimensional particle flow code (PFC3D). These analyses improve the understanding of the stability of rocks and concretes structures such as rock slopes, tunnel constructions and underground openings.