Microwave Drying of Scots Pine Lumber:Structure Changes,Its Effect on Liquid Permeability

Microwave(MW)drying method was adopted to enhance the liquid permeability of Scots pine lumber.Structure changes were characterized by stereoscope microscope,scanned electron microscope(SEM)and transmission electron microscope(TEM)examination.Pore parameters before and after MW treatment were detected by mercury intrusion porosimetry(MIP)method,and the effect of structure changes on liquid permeability were analyzed.As stereoscope microscope,SEM and TEM examination results showed,macro and micro checks mainly developed at intercellcular of tracheids,intercellular of ray parenchyma and tracheid,while these checks extend main along the radial-longitudinal plane.Pit border destruction,aspirated pits’orus translocation and micro-checks in tracheid cell wall were also observed.MIP test shown that pore volume and pore area increased as macro and micro checks generated to form new cavities.Microstructure changes would increase the quantity of pores or enlarge the pore diameter.Liquid flow pathways increased as macro and micro checks generated,aspirated pits reopened to form new pathways;liquid flow efficiency improved as porosity,pore volume and pore diameter increased which facilitated the liquid flow.

Assessment of flexural properties of different grade dimension lumber by ultrasonic technique

The dimension lumber （45mm×90mm×3700mm） of plantation Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） was graded to four different classes as SS, No. 1, No.2 and No.3, according to national lumber grades authority （NLGA） for structure light framing and structure joists and planks. The properties of apparent density was determined at 15% moisture content, bending strength and stiffness were tested according to American Society for Testing and Materials （ASTM） D198-99, and dynamic modulus of elasticity （Eusw） was measured by ultrasonic technique, for predicting the flexural properties of different grade lumbers. The results showed that Eosw was larger than the static MOE. The relationship between Eusw and static MOE was significant at 0.01 level, and the determination coefficients （R2） of the four grade lumbers followed the sequence as R^2No.2 （0.616）〉 R^2ss （0.567）〉 R^2No1 （0.366）〉 R^2No.3 （0.137）. The R^2 of Fusw and MOR were lower than that of the Etru and MOR for each grade. The Eusw of all the grade lumbers, except No.3-grade, had significant correlation with the static MOE and MOR, thus the bending strengthof those grade lumbers can be estimated by the E The Etru valuesof four grade lumbers followed a sequence as No.2-grade （10.701 GPa） 〉 SS-grade （10.359 GPa） 〉 No.l-grade （9.840 GPa） 〉 No.3-grade （9.554 GPa）. For the same grade dimension lumber, its Eusw value was larger than static MOE. Mean values of MOR for four grade lumbers follow a sequence as No.2-grade （48.67 MPa） 〉 SS-grade （48.16 MPa） 〉 No.3-grade （46.55 MPa） 〉 No. 1-grade （43.39MPa）.

Liquid penetration of freeze-drying and air-drying wood of plantation Chinese fir

A comparative study was conducted on liquid penetration of the freeze-drying and air-drying sapwood and heartwood lumber of plantation Chinese fir （Cunninghamia lanceolata）. The maximum amount of dyeing solution uptake by the capillary rise method was used to evaluate the liquid penetration properties of the treated wood. The pit aspiration ratio was determined by semithin section method. Changes in wood microstructure were investigated using scanning electron microscopy. The results showed that compared with air drying, the freeze drying had a significant effect on liquid penetration of sapwood and heartwood of Chinese fir. The liquid penetration of sapwood is significantly higher than that of the heartwood for both drying treatments. Low pit aspiration ratio and cracks of pits membrane of some bordered pits are the main reasons for increasing liquid penetration after freeze drying treatment.

Compression Behaviors of Parallel Bamboo Strand Lumber Under Static Loading

In order to investigate the influence of length and compression directions upon behaviour of parallel bamboo strand lumber(PBSL)specimens,240 axial compression tests have been performed.With three similar one different typical failure modes,the mechanical performance for PBSL specimens under compression parallel to grain and perpendicular to grain are different as a whole.From the point of the characteristic values,the compression strength parallel to grain is 2.1 times of the compression strength perpendicular to grain.The elastic modulus for compression parallel to grain is 3.64 times of the compression strength perpendicular to grain.While the compression ratios along two compression directions are equal to each other.The bigger Poisson ratios for one typical side surface is 3.93 times of that for another typical side surface for PBSL specimens under compression perpendicular to grain,and the bigger value is equal to that for PBSL specimens under compression parallel to grain.Length can influence the mechanical properties of the PBSL specimens.The size 50 mm×50 mm×100 mm should be good choice for the standard or code to measure the compression strength.PBSL materials have better ductility under compression parallel to grain than that under compression perpendicular to grain.Stress-strain relationship models were proposed for PBSL specimens under compression parallel to grain and perpendicular to grain,respectively.These proposed models gave a good agreement with the test results.

A Review of Basic Mechanical Behavior of Laminated Bamboo Lumber

Over the past decade,the physical and mechanical performances of laminated bamboo lumber(LBL)–a bamboo-based structural material,have been extensively studied using experimental,analytical,and numerical approaches.This paper presents a review of existing knowledge in the literature about the mechanical properties of LBL.The paper involved the review of the response of LBL to different types of loading such as tension,bending,compres-sion,and shear.Based on results of the literature reviewed,the strength of LBL parallel to grain was 90–124 MPa with MOE of 10700 MPa in tension,29.55–72.60 MPa,and MOE of 8396–11022 MPa in compression,63.87–128.4 MPa,and MOE of 8320–10912 MPa in bending,and 7.15–17.5 MPa in shear.The average strength of LBL was similar and in some cases exceeded the average values of bamboo-or wood-based materials,while the variability of its mechanical parameters was lower.The variability in strength values of LBL was affected by bamboo species,density and thickness of bamboo strips,growth portion,type of treatment,strips arrange-ments,and type of adhesive which in turn calls for classification of LBL by strength grades,degree of hardness,the capability of impregnation and penetration,as well as by areas of application in construction.The study pro-vided and discussed concluding observations,the current research gap,and future research directions on the mechanical properties of LBL.

Measurement of lumber moisture content based on PCA and GSSVM

Lumber moisture content(LMC) is the important parameter to judge the dryness of lumber and the quality of wooden products.Nevertheless the data acquired are mostly redundant and incomplete because of the complexity of the course of drying,by interference factors that exist in the dryness environment and by the physical characteristics of the lumber itself.To improve the measuring accuracy and reliability of LMC,the optimal support vector machine(SVM) algorithm was put forward for regression analysis LMC.Environmental factors such as air temperature and relative humidity were considered,the data of which were extracted with the principle component analysis method.The regression and prediction of SVM was optimized based on the grid search(GS) technique.Groups of data were sampled and analyzed,and simulation comparison of forecasting performance shows that the main component data were extracted to speed up the convergence rate of the optimum algorithm.The GS-SVM shows a better performance in solving the LMC measuring and forecasting problem.

Analysis of factors affecting diagonal tension and compression capacity of corner joints in furniture frames fabricated with dovetail key

This study was conducted to analyze the effect of joint type, and numbers and types of dovetail keys on diagonal tension and compression performance of corner joints in a furniture frame. Joint members were cut from white fir lumber. Butted and mitered joints were constructed with one and two dovetail key（s） with butterfly and H shapes. Joints were glued by polyvinyl acetate （PVAc） and cynoacrylate （CA）. Compression capacity of joints was higher than diagonal tension. Mitered joints were stronger than butted ones. Butterfly dovetail keys were superior to H shape keys. Double keys performed better than single key. Experimental joints glued with PVAc were stronger than those glued with CA glue and control specimens. In terms of strength, butterfly dovetailed joints were comparable with doweled joints.

Nodes Effect on the Bending Performance of Laminated Bamboo Lumber Unit

This research studied the ultimate bearing capacity of laminated bamboo lumber(LBL)unit and thereby calculated the maximum bending moment.The load-displacement chart for all specimens was obtained.Then the flexural capacity of members with and without bamboo nodes in the middle section was coMPared.The bending experiment phenomenon of LBL unit was concluded.Different failure modes of bending components were analysed and concluded.Finally,the bending behaviour of LBL units is coMPared with other bamboo and timber products.It is shown that the average ultimate load of BS members is 866.1 N,the average flexural strength is 101 MPa,the average modulus of elasticity is 8.3 GPa,and the average maximum displacement is 17.02 mm.The average ultimate load of BNS members is 1008.1 N,the average flexural strength is 118.02 MPa,the average modulus of elasticity is 9.9 GPa,and the average maximum displacement is 18.26 mm.Laminated bamboo lumber(LBL)unit without bamboo nodes(BNS)has relatively higher flexural strength coMPared with LBL unit with bamboo nodes(BS).The presence of bamboo nodes reduces the strength of the entire structure.Three failure modes were concluded for BS members,and two failure modes were observed for BNS members during the experimental process.According to a coMParison between the LBL unit and other products,the flexural strength and bending modulus of elasticity of the LBL unit are similar as bamboo scrimber and raw bamboo components,which is much higher than timber components.

Slenderness Ratio Effect on the Eccentric Compression Performance of Chamfered Laminated Bamboo Lumber Columns

Eccentric compression tests on 15 chamfered laminated bamboo lumber(LBL)columns with a height ranging from 600 to 3000 mm were conducted in order to study the eccentric mechanical performance.The failure of all specimens was caused by the crack of bamboo fiber in the tensile region.When the ultimate strength was reached,except specimens with a height of 600 mm,all other specimens could bear large deformation,showing good ductility.The lateral displacements of the specimens under eccentric compression were approximately para-bolic in the direction of column height.The ultimate bending moment of LBL columns with different slenderness ratios under compression with the same initial eccentricity was a fixed value.The relationship between ultimate capacity,axial displacement,lateral displacement,and slenderness ratio was analyzed based on test results.It was found that the plane section assumption could be used to express the stress and strain distribution of chamfered LBL columns under eccentric compression.A method for calculating the ultimate bearing capacity was proposed using a constitutive model based on the Ramberg-Osgood relation and the empirical formula for calculating the ultimate capacity was given on the basis of the former research as well as the test results in this paper.

Effects of salinity on the nail-holding power of dimension lumber used in light-frame wood building

We studied the effect of salinity on nail-hold- ing power in wood construction. In saline solution, the holding power of nails was less than in purified water. With the increase of salt concentration, the surface and side nail- holding power of the wood specimens both declined, but the differences between salinity treatments were not sig- nificant. However, compared to the surface and side nail- holding power, the power on the edge was generally less and the difference was not obvious in different salt con- centrations. In the same salt concentration, with the extension of the processing cycle, the performance of holding power of nails showed a downward trend, expect the temporary rise in the middle.

The Relationship between Neck and Shoulder Pain and the Sagittal Alignment of the Spine in Standing in Younger Generation

Background: The relationship between chronic neck and shoulder pain and posture remains controversial. The purpose of this study was to investigate the relationship between chronic neck and shoulder pain and spinal sagittal alignment in standing posture in younger generation. Methods: Subjects included 57 females and 32 males (average age, 29.9 ± 5.7 years). All subjects were 20s or 30s. Spinal curvature was assessed using SpinalMouse. The subjects were also divided into a normal group (VAS zero group) and a pain group by VAS results. Statistical analysis was performed by Student’s t-test. Significance was defined as p < 0.05. Results: The normal group and pain group included 29 and 60 subjects, respectively. In terms of location of pain, thirty-one subjects felt neck pain, 50 felt pain above the scapula, and 17 felt pain between the thoracic spine and scapula. Thoracic kyphosis and lumbar lordosis in the pain group were significantly higher than those in the normal group (p = 0.013 and p = 0.020, respectively). Thoracic kyphosis in subjects with neck pain or pain above scapula was significantly higher than that in subjects without pain (p = 0.0075 and p = 0.025, respectively). Lumbar lordosis in subjects with pain above the scapula or interscapula was significantly higher than that in subjects without pain (p = 0.016).

Effect of heating methods on drying quality of small-diameter birch lumbers

Following a normal low temperature drying schedule, the small-diameter Birch lumbers （ 1 000mm× 45mm ×30mm） were dried with consecution-heats or intermittent-heating, visual drying defects （bow, crook, twist, check along grain and end check） were measured, and then statistical analyses were performed. It was found that the drying quality of small-diameter Birch lumbers could be improved with intermittent-heating, but the intermittent time should be prolonged. Prolonging intermittent time helped to weaken or even avoid wood distortion and drying checks. It wash＇ t helpful in avoiding crook. The drying quality of small-diameter Birch lumbers with all kinds of drying methods reached the second class of the Chinese National Standard. The drying quality reached the first class of the Chinese National Standard with the intermittent-heating in the area of visual wood defects.

Viscoelastic Characteristics and Creep Prediction for Laminated Veneer Lumber

The viscoelastic characteristics of Aspen laminated veneer lumber (LVD were investigated with results revealing the dynamic creep behaviour under asymmetrical cyclic loading, which is analogous to solid wood under a static load. Curves for the creep indicated that after 10s cycles, the multiple correlation coefficient R2 for the 4-element, is more than 0. 98 in any instance, overwhelmingly well fitted to the data obtained. The mean square error of the 3-element viscoelastic model was 1 - 5 times higher than of the 4-ele-ment model under various cyclic loadings within a relative large loading range. The viscoelastic curves for LVL samples are nonlinear. They were linearized at some stress levels below 60% of their limited intensities. As loading was sustained for a longer period, the viscous flow was found to have a tendency of attenuation. The work absorbed by a specimen before the occurrence of creep failure, could be estimated in terms of failure appearance. Consequently, we could calculate the

Study of drying of small diameter Larch lumbers with intermittent heating

Intermittent heating for drying of small diameter Larch lumbers is investigated experimentally. The lumbers were dried using an experimental drying schedule. Moisture content (MC) of the lumber was continuously recorded and final drying defects were examined. The drying curves showed that the drying rate was a constant in the early stage of intermittent heating drying and decreased evidently when the MC was about 18% (intermittent 2h) and 20% (intermittent 6h). The drying quality reached the second (intermittent 2h) and first grade (intermittent 6h) of the Chinese National Standard. The visual drying defects, especially the check extent along grains were reduced with intermittent heating. When the intermittent time increased, the effect was more obvious.

Analysis of influencing factors of clinical effect of TCM treatment for degenerative lumbar spondylolisthesis

Objective:To explore the related factors that may affect the efficacy of traditional Chinese medicine in treating degenerative lumbar spondylolisthesis.Methods:A total of 535 patients with DLS who were treated in Wangjing Hospital of China Academy of Chinese Medical Sciences and other hospitals from June 2011 to October 2014 were selected.The central random system was used to randomly divide the treatment group and control group.This study included 267 patients in the treatment group using the traditional Chinese medicine program((lumbar spine reduction and lumbar spine rehabilitation),36 cases of severely missing data were excluded,and a total of 231 DLS patients were included.Observation indicators were selected using the Visual Analog Scale(VAS)and the Japanese Orthopaedic Association(JOA)for the evaluation of lumbar vertebral disorders.The clinical efficacy was evaluated using the JOA lumbar pain curative effect evaluation standard[7].[(Joa score after treatment-JOA score before treatment]/(out of 29 points-JOA score before treatment)]×100%.The JOA score and the change of the efficacy index of the patients were observed.According to the JOA efficacy index after the treatment,it was divided into significant effect(≥50%)and poor effect(<50%).Single-factor screening and multi-factor Logistic regression analysis were used.Gender,age,course of disease,BMI index,slip-off segment,slip-off direction,back pain VAS score,total JOA score,back pain-score,lower limb pain and numbness-score,walking ability-score,straight leg elevation test-score,Feeling-scoring,muscle strength-scoring,supine turn-scoring,standing action-scoring,washing action-scoring,standing posture and continuous standing-scoring,long sedentary-scoring,weight lifting and holding-scoring,walking-scoring 2.Bladder function-scores were assigned to logistic regression models for univariate analysis,and meaningful independent variables were screened for multivariate logistic regression.Results:No serious adverse reactions occurred in the patients included in this study.According to the comparison of JOA scores before and after treatment,the results of the index of efficacy index showed that the effective rate of DLS in this project was 96.6%,and a significant effect of 77.6%was achieved.Univariate Logistic regression analysis showed that the duration of disease,supine turn-scoring,washing action-scoring,prolonged sedentary-scoring,weight lifting and keeping-scoring had statistically significant effects on the inclusion of patients with significant efficacy(P<0.05);single factor logistic regression analysis of total score of JOA score before treatment was not statistically significant(P=0.215),but because it is important for evaluating the patient's condition,it was included in multifactor logistic regression analysis at the same time.Course of onset,supine turn-scoring,washing action-scoring,prolonged sedentary-scoring,weight lifting and holding-scoring,JOA score before treatment.Six independent variables were substituted into the two-class logistic regression model for multivariate analysis..Multivariate logistic regression analysis showed that the effects of total JOA score and supine turn-scoring before treatment on the efficacy of patients were statistically significant(P<0.05).There are many factors influencing the efficacy of traditional Chinese medicine treatment of DLS,and the probability of obtaining a significant effect for each additional point of JOA score and supine turn-score before treatment increases by 1.167 and 0.410 times,respectively.Conclusion:The clinical application of lumbar spine reduction combined with lumbar rehabilitation exercises in patients with degenerative lumbar spondylolisthesis with a higher total JOA score or a lower limit of supine turning can achieve better clinical results.This finding has certain guiding significance for the clinical application of this therapy in the treatment of DLS,and is beneficial to improving patient satisfaction and clinical effectiveness.

Constitutive Equation of Laminated Veneer Lumber (LVL) at Large Deformation Condition

The stress-strain relation of laminated veneer lumber (LVL) was established by the method of regression, and its constitutive equation at large deformation and constant loading conditions was given to predict the static mechanical behaviors of LVL.

Clinical features and surgical treatment of the coexistence of cervical,thoracic and lumber degenerative disease

Objective To discuss clinical features and surgical treatment of the coexistence of cervical,thoracic and lumber degenerative disease. Methods From January 2004 to December 2008,79 cases with the coexistence of cervical,thoracic

Osteoblastoma Mimic Failed Back Surgery

A 44 year-old women with persistent back and irradiate pain after discectomy in L5-S1 lumbar level presented a osteoblastoma in L4-L5 level. The osteoblastoma mimic a failed back surgery. She was successfully treated by removing the tumour with instrumented posteroalateral fusion. This case warns people that a new disease (such as a tumour in this case), irrelevant to the original one, may happen simultaneously even if the original one has been successfully treated and should be differentiated from the previous disease or surgical failure and complications.

Dynamics of Lumber Production from Buttressed-Stumps of Logging Residues Using a Fuel Powered Horizontal Mobile Bandsaw Machine

Logging residue can be defined as any form of wood, which under the highest stage of technological development could be used in manufacturing but is left in the forest during logging. Lumber production from logging residues of a previous logging activity by a timber firm was undertaken with the objective of determining the suitability of utilizing buttressed-stumps as raw material for the timber industry. A horizontal mobile bandsaw machine was used to process the buttressed-stumps into lumber. The machine was characterized by a thin-kerr sawing technology （kerf-width 1.6 mm） compared to the conventional bandsaw machines of kerr-widths ranging from 3.0-4.5 mm. Lumber value and volume yields, fuel consumption rate, frequency of tool replacement and lumber production rate were assessed. Results indicated that there is the potential to increase timber production from logging residues by utilizing buttressed-stumps. Lumber value and volume yields of eight timber species investigated in this study ranged from 5%-31% and 34%-54% respectively. Fuel consumption rate which increased with increasing wood density, ranged from 5-14.5 liters/m3 of lumber produced. Frequency of saw replacement increased with increasing wood density. The number of saws required to produce one cubic meter of lumber, ranged from 1 to 7. Lumber production rate ranged from 0.10-0.38 m3/hour, increasing with decreasing wood density.

Effect of high temperature heat treatment on pH value of Masson Pine wood

Heat-treated wood has good dimensional stability,corrosion resistance and visual quality,but it is prone to mold,which limits its application.Based on the pH value of heat-treated wood,this study examines the factors affecting the pathogenesis causing heat-treated wood mold.Normally,the pH value of the heat-treated wood is between 4.38 and 5.10,which is suitable for the growth of mold.However,the pH of the heat-treated copper-containing material is between 6.63 and 7.12,which deviates the treated wood from the comfortable growth conditions for the mold,thereby reducing the occurrence of mold.