Predicting Tensile and Compressive Moduli of Structural Lumber

Nondestructive bending modulus of elasticity (MOE) of lumber is commonly used as input data to estimate mechanical properties of glued lumber or laminated timber components. Many standard and nonstandard test methods exist to determine MOE. However, when glued components are loaded, the stresses imposed on the lumber subcomponents are quite different from stresses used in determining MOE of the lumber. It is well known that the bending MOE of lumber is somewhat different from its tensile and compressive moduli. Therefore, defining the differences and relationships between bending MOE and tensile and compressive moduli is important. This study predicted the tensile and compressive modulus from dynamic and static bending MOE of major softwood structural lumber in Korea. The measured MOE and tensile and compressive moduli from the same specimens by various test methods were found to differ. In particular, the tensile modulus was twice the compressive modulus for the same specimen. Edgewise bending MOE, which showed the highest correlation with tensile and compressive moduli, was suggested as a suitable input parameter for predicting tensile and compressive moduli. Predicting tensile and compressive moduli from dynamic or flatwise bending MOE of structural lumber is also possible, although with a different relationship. With better prediction of tensile and compression moduli, it is expected that the properties of engineered wood or timber structures can be more accurately estimated

Improvement of Prediction Accuracy of Glulam Modulus of Elasticity by Considering Neutral Axis Shift in Bending

There is a discrepancy between the estimated modulus of elasticity (MOE) of glulam based on the dynamic MOE of laminates and measured MOE. The discrepancy is greater for glulam manufactured with mixed species. This study was undertaken to reduce the discrepancy between those MOE values. The error rate of predicting MOE of glulam by the transformed section method, without considering tension and compression modulus differences, was about 30%. To estimate the MOE of glulam more accurately, the differences between compression and tension modulus should be taken into account in the transformed section method. The measured tensile and compressive strain at the center of glulam under a bending load showed the movement of neutral axis toward the tension side of glulam. Therefore, the compression and tension modulus differences for each species should be identified before estimating the MOE of glulam. The prediction of glulam MOE was improved significantly by reflecting the ratio of compression and tension modulus vs dynamic MOE of laminates. The outermost of laminates in the compression side under bending load experienced plastic behavior and failure. This caused the neutral axis to move to the tension side and increased tension stress to cause the glulam to fail abruptly in tension. To improve the bending performance of glulam, reinforcing compression laminates need to be considered

Use of Adjacent Knot Data in Predicting Bending Strength of Dimension Lumber by X-Ray

In a previous study, the knot depth ratio (KDR) evaluation method was proposed to quantify the area of knots in a cross-section. That study reported that bending strength can be predicted by KDR analysis. However, the KDR model did not take into consideration the additional strength reduction caused by adjacent knots. It was found that the prediction of lumber strength was improved when adjacent knots were taken into consideration. Analysis using the KDRA (KDR adding knots) model revealed that the optimum cross-sectional interval, an input variable, is directly affected by knot size parallel to lumber length (KSPLL). KSPLL depends on the sawing method and log characteristics, and for species containing large knots, the cross-sectional interval is likely to be extremely wide. This can cause several adjacent small knots to be excluded from the analysis, requiring modification of the KDRA model algorithm. This modification resulted in improvement in the precision of the strength prediction, although the input variable of the cross-sectional interval was not used. The R2 values obtained using this method were 0.60 and 0.56 for Japanese larch and red pine, respectively

Improvement of Wood CT Images by Consideration of the Skewing of Ultrasound Caused by Growth Ring Angle

For the purpose of removing distortions in ultrasonic computerized tomographic (CT) images of wood, this study proposes a technique for taking into account the skewing effect in reconstructing the image. First, it was experimentally confirmed that an ultrasonic wave is refracted because of the anisotropic characteristics of wood. Transmission paths of an ultrasonic wave through a cross-section of wood were predicted by considering the change in wave velocity based on the annual ring angle and the presence of juvenile wood. Then, the methodology of the application of the predicted paths to CT image reconstruction was proposed and verified. The accuracy of defect detection in wood was significantly improved by the proposed technique

Moisture Content Prediction Below and Above Fiber Saturation Point by Partial Least Squares Regression Analysis on Near Infrared Absorption Spectra of Korean Pine

This study was performed to predict the surface moisture content of Korean pine (Pinus koraiensis) with low moisture content (approximately 0%) and high moisture content above the FSP using near IR spectroscopy. Near IR absorbance spectra of circular specimens were acquired at various moisture contents at 25°C. To enhance the precision of the regression model, mathematical preprocessing was performed by determining the three-point moving average and Norris second derivatives. After preprocessing, partial least squares regression was carried out to establish the surface moisture content prediction model. We divided the specimens into two groups based on their moisture contents. For the first group, which possessed moisture contents less than 30%, the R2 values and root mean squared error of prediction (RMSEP) of the model were 0.96 and 1.48, respectively. For the second group, which possessed moisture contents greater than 30%, the R2 values and RMSEP of the model were 0.94 and 4.88, respectively. For all moisture contents, the R2 and RMSEP were 0.96 and 5.15, respectively. As the range of moisture contents included in the prediction model was expanded, the error of the model increased. In addition, the peak positions of the water absorption band (1440 and 1930 nm) shifted to longer wavelengths at higher moisture contents

Antioxidant and Protective Effects of Bupleurum falcatum

Bupleuri Radix (BR), the dried roots of Bupleurum falcatum L., has been used in folk medicine as an antiinflammatory and antioxidative agent. The aqueous extract of BR was evaluated for its possible ameliorative effect in the regulation of hyperthyroidism in l-thyroxine- (LT4-) induced rat model. After oral administration of 300, 150, and 75 mg/kg of BR extracts, once a day for 15 days from 12th LT4 treatments, changes on the body, thyroid gland, liver, and epididymal fat pad weights, serum triiodothyronine, thyroxine, thyroid-stimulating hormone, asparte aminotransferase and alanine aminotransferase concentrations, hepatic lipid peroxidation, glutathione contents, superoxide dismutase, and catalase activities were investigated with thyroid gland, liver, and epididymal fat histopathological changes. The effects of BR extracts were compared with that of propylthiouracil, a standard antithyroid drug 10 mg/kg (intraperitoneally). In this experiment, BR extracts dose dependently reversed LT4-induced hyperthyroidisms, and these effects indicating their potential in the regulation of hyperthyroidism. Further, the BR extract normalized LT4-induced liver oxidative stresses, and also reduced liver and epididymal fat pad changes. BR extracts 150 mg/kg showed comparable effects on the LT4-induced rat hyperthyroidism as compared with PTU 10 mg/kg. These effects of BR may help the improvement of hyperthyroidisms and accompanied various organ damages

Epidemiologic survey of head and neck cancers in Korea.

Head and neck cancers have never been systematically studied for clinical purposes yet in Korea. This epidemiological survey on head and neck cancer patients was undertaken from January to December 2001 in 79 otorhinolaryngology resident-training hospitals nationwide. The number of head and neck cancer patients was 1,063 cases in the year. The largest proportion of cases arose in the larynx, as many as 488 cases, which accounted for 45.9%. It was followed by, in order of frequency, oral cavity (16.5%), oropharynx (10.0%), and hypopharynx (9.5%). The male:female ratio was 5:1, and the mean age was 60.3 yr. Surgery was the predominant treatment modality in head and neck cancers: 204 (21.5%) cases were treated with only surgery, 198 (20.8%) cases were treated with surgery and radiotherapy, 207 cases (21.8%) were treated with combined therapy of surgery, radiotherapy, and chemotherapy. Larynx and hypopharynx cancers had a stronger relationship with smoking and alcohol drinking than other primary site cancers. Of them, 21 cases were found to be metastasized at the time of diagnosis into the lung, gastrointestinal tract, bone, or brain. Coexisting second primary malignancies were found in 23 cases. At the time of diagnosis, a total of 354 cases had cervical lymph node metastasis accounting for 42.0%

Suppression of Structural Fatigue by Doping in Spinel Electrode Probed by In Situ Bending Beam Method

The onset of a Jahn-Teller effect at the surface of LiMn2O4 particles during cycling in the 4 V range was previously reported to be one of the causes for the capacity fading. Furthermore, it has been reported that the Jahn-Teller effect in the 4 V range may be suppressed by the substitution of the Mn ions by either Li or other transition metal ions. However, no direct evidence has yet been reported. This study provides evidence for the onset of a Jahn-Teller effect in thin film 4 V LiMn2O4 and its suppression caused by substituting the Mn ions with Co31 and Ni21 ions using in situ bending beam method ~BBM!. The deflectograms are measured simultaneously with galvanostatic charge/discharge or cyclic voltammograms, and the onset of the Jahn-Teller effect is investigated by means of the differential strain peak which is observed at around 3.90-3.95 V during cyclic voltammetry, and the slope variation observed in the strain curves during galvanostatic charge/discharge. The suppression of the Jahn-Teller effect in the doped spinel leads to the magnitude of the differential strain peak resulting from the Jahn-Teller effect being reduced in comparison with the other two pairs of peaks, which correspond to the current peaks of the cyclic voltammogram.This work was supported by KOSEF through the Research Center for Energy Conversion and Storage (RCECS), Korea Science and Engineering Foundation (no. 2000-2-30100-012-3) and by the Ministry of Information and Communication of Korea (Support Project of University Information Technology Research Center supervised by KIPA). The authors thank Cheil Industries, Inc., for the supporting electrolytes