Long-Term Bending Behaviour of Prestressed Glulam Bamboo-Wood Beam Based on Creep Effect

Creep is an important characteristic of bamboo and wood materials under long-term loading.This paper aims to study the long-term bending beha-viour of prestressed glulam bamboo-wood beam(GBWB).For this,14 pre-stressed GBWBs were selected and subjected to a long-term loading test for 60 days.Then,a comparative analysis was performed for the effects of pre-tension values,the number of pre-stressed wires,and long-term load on the stress variation of the steel wire and the long-term deflection of the beam midspan.The test results showed that with the number of prestressed wires increasing,the total stress of the steel wire in the beam midspan and the ratio of the long-term deflec-tion to the total deflection decreases decreased,but when the number of steel wires exceeded 4,the total stress and long-term deflection was less infuenced;with the pre-tension value increasing,the ratio of the total stress of the steel wire in the beam midspan and the ratio of the long-temm deflection to the total deflec-tion also decreased,but when the prestress force was greater than 3.975 kN,the:total stress and long-term deflection were less affected;with the other parameters unchanged,when the value of the long-term load increased,the total stress of the steel wire decreased,and the long-temm deflection of the beam midspan increased,which shall be more significant with the long-term load greater than 30%of the standard ultimate bearing capacity.After the test,the experimental data were fitted,and the creep coefficient was given.Finally,the long-term stiffness calcula-tion fommula of the pre-stressed GBWB based on creep effect was proposed.The research findings have certain theoretical significance and engineering value.

Experimental Study on Permeability Characteristics of Geotubes for Seepage Analysis on Safety Assessment of Dams

Geotubes are heterogeneous structures composed of filling sand and bag material,and its pemeability characteristics are different from that of flling sand.The uncertainty of geotubes permeability characteristics results in the failure of seepage analysis of geotube dams,which restricts the safety assessment of the dams.As the basis of the study on the seepage mechanism of the geotubes,the influence of particle grading on pemeability cofficient of flling sand and sand covered with geotextiles were explored by the pemmeability tests of flling sand with different particle grading under the condition of sand covered with or without geotextiles.And the infuence of geotextiles on the permeability coefficient was analyzed by comparing permeability coefficient of sand covered with and without geotextiles.The test results show that the influence of single particle size content on permeability coe ficient is consistent under the condition of sand covered with and without geotextiles.The content of powder,fine,medium and coarse particles is linearly related to their respective permeability cofficients.And the content of powder,fine,medium particles is negatively correlated with their permeability coefficients,while the content of coarse particles is positively correlated with the permeability coefficient.But the pemeability coefficient of sand covered with geotextiles is smaller than that of flling sand under the same conditions.Finally,the parameter d2 50 Cc/Cu was selected as a variable representing the particle grading to fit the empirical formula of permeability coefficient of flling sand and sand covered with geotextiles.

Moving-window bis-correlation coefficients method for visible and near-infrared spectral discriminant analysis with applications

The moving window bis corelation coefficients(MW BiCC)was proposed and employed for the discriminant analysis of transgenic sugarcane leaves and B-thalassemia with visible and near-infrared(Vis NIR)spectroscopy.The well-performed moving window principal component analysis linear discriminant analysis(MWPCA-LDA)was also conducted for comparison.A total of 306 transgenic(positive)and 150 nont ransgenic(negative)leave samples of sugarcane were collected and divided to calibration,prediction,and validation.The diffuse reflection spectra were corected using Savitzky-Golay(SG)smoothing with first-order derivative(d=1),third-degree polynomial(p=3)and 25 smpothing points(m=25).The selected waveband was 736-1054nm with MW-BiCC,and the positive and negative validation recognition rates(V_REC^(+),VREC^(-))were 100%,98.0%,which achieved the same effect as MWPCA-LDA.Another example,the 93 B-thalassemia(positive)and 148 nonthalassemia(negative)of human hemolytic samples were colloctod.The transmission spectra were corrected using SG smoothing withd=1,p=3 and m=53.Using M W-BiCC,many best wavebands were selected(e.g.,1116-1146,17941848 and 22842342nm).The V_REC^(+)and V_REC^(-)were both 100%,which achieved the same effect as MW-PCA-LDA.Importantly,the BICC only required ca lculating correlation cofficients between the spectrum of prediction sample and the average spectra of two types of calibration samples.Thus,BiCC was very simple in algorithm,and expected to obtain more applications.The results first confirmed the feasibility of distinguishing B-thalassemia and normal control samples by NIR spectroscopy,and provided a promising simple tool for large population thalassemia screening.

随机变量和、差、积、商的相关分析(续完)

２ 积〔ｚ＝ｘｙ〕 乘数与被乘数可以互换而不影响其积。因此，对于由两变量之积与其中一个变量，无论是乘数或被乘数所得到的相关系数表现形式是相同的。由“随机变量积、商的统计参数计算公式”一文中①可知，变量ｘ、ｙ乘积的均值、均方差计算式为：均值 ｚ＝ｘ...

Monte Carlo and phantom study in the brain edema models

Because the brain edema has a crucial impact on morbidity and mortality,it is important to develop a noninvasive method to monitor the process of the brain edema effectively.When the brain edema occurs,the optical properties of the brain will change.The goal of this study is to access the feasibility and reliability of using noninvasive near-infrared spectroscopy(NIRS)monitoring method to measure the brain edema.Specifically,three models,including the water content changes in the cerebrospinal fuid(CSF),gray matter and white matter,were explored.Moreover,these models were numerically simulated by the Monte Carlo studies.Then,the phantom experiments were performed to investigate the light intensity which was measured at different detecting radius on the tissue surface.The results indicated that the light intensity correlated well with the conditions of the brain edema and the detecting radius.Briefly,at the detect ing radius of 3.0 cm and 4.0 cm,the light intensity has a high response to the change of tissue parameters and optical properties.Thus,it is possible to monitor the brain edema noninvasively by NIRS method and the light intensity is a reliable and simple parameter to assess the brain edema.

Quantification of glucose and glycerol diffusion in myocardium

The results on determination of glucose and glycerol difusion cofficients in myocardium tissuse are presented.The method is based on the measurement and analysis of temporal dependence of tissue optical collimated transmittance umder action of a hyperosmotic agent.This temporal tissue response is related to the rate of the agent and water diffusion in a tissue.The diffusion coefficients for tssue fAuid fluxes at glucose and glycerol application to the myocardium at 20℃ have been estimated as(4.75±3.40)×10^(-7) and(7.71±4.63)×10^(-7) cm^(2)/s,respectively.

ALL ADMISSIBLE LINEAR ESTIMATES OF REGRESSION COEFFICIENTS UNDER MATRIX LOSS

The necessary and sufficient conditions for a linear estimator of a linear estimable functionof regression coefficients in a general fixed effects linear model with the assumptions of normality to beadmissible in the class of all estimators under matrix liss function are given.For a general randomeffects or mixted effects linear model the necessary and sufficient conditions are obtained too.

Pressure Loss Through Sharp 180 deg Turn in a Relatively Short Two－Pass Smooth and Rib－Roughened Channel

The local pressure distributions and resistance coefficients (f1 and f2) through the sharp 180 deg turn in a relatively short (L/De = 4) two-pass smooth and rib-roughened channel were investigated for a Reynolds number range of 1.0 × 103 - 9.0 × 103. The rib pitch-to-height ratios (p/e) were 5,10, and 20. The rib height-to-hydraulic diameter ratios (e/De) were 0.025, 0.050 and 0.10, and the rib angles of attack (α) were 90, 45, 60, -45, and -60 deg. Ribs were installed not only in before and after turn regions but also in turn region. The results show that the resistance coefficients remain approximately constant when Reynolds number is more than 3.0×104. The effects of the rib condguration (rib spacing, rib height, and rib orientation) on the inlet straight duct resistance coefficient (f2) were significant, however, their effects on the overall resistance coefficient (f1) were diluted by the sharp-180 turn. For this relatively short channel (L/De=4), the overall resistance coefficient (f1) was greatly affected by the sharp turn. Correlations for the overall resistance (f1) and inlet straight duct resistance coefficient (f2) are presented.