甲基苯基有机硅低聚体改性环氧树脂的韧性及热残重

以二甲基二乙氧基硅烷、甲基三乙氧基硅烷、苯基三乙氧基硅烷为单体原料,通过水解、缩聚的方法合成了甲基苯基有机硅低聚体(PMPS)。然后用其与双酚A型环氧树脂(E51)发生共聚反应,并且引入柔性环氧树脂(DER732),制备出一系列PMPS改性环氧树脂。红外光谱表明,PMPS接枝在环氧树脂上。探讨了PMPS含量对改性树脂拉伸强度、断裂伸长率、冲击强度、微观形貌、热残重的影响。结果表明,当m(E51)∶m(DER732)∶m(PMPS)=40∶20∶40时,改性树脂的断裂伸长率为49.63%,冲击强度为12.07 kJ/m2,600℃的热残重为27.19%,分别比未改性的环氧树脂提高了42.78%,8.41 kJ/m2和21.83%。

铝电解槽残极余热回收利用研究

铝电解过程中残极带走大量的热量,同时新极又需吸收熔体内的热量来加热。本文提出了利用热残极加热新极的设想,设计了相应的换热装置,并对换热效果进行了模拟计算。计算发现,换热箱内放置一组冷的双阳极和一组热的残极,8小时后,热残极可冷却到230OC以下,新极被加热到100～140OC之间,平均温升近100OC,折合能量节省为16kWh/t-Al。另外,经计算发现,对于本文设计的换热箱,换热8小时后,体系内的温度基本稳定,继续拉长换热时间,意义将不大。

Activation and afterheat analysis for CH HCSB TBM

With an activation calculation code FDKR and decay chain data library AF-DCDLIB, the radioactivity, afterheat decay and Biological Hazard Potential (BHP) from activation products have been analyzed in the CH HCSB TBM. The calculation results show that the total radioactivity inventory, heat decay and BHP are 2.10×1016Bq、5.06×10?3 MW、68.6 km3·(kW)?1, respectively, at shutdown after a continuous irradiation over 0.53 years with 500 MW fusion power. It shows that there isn’t seriously environmental safety issue in the TBM.

Oxidation behavior of C/C composites with SiC/ZrSiO_4-SiO_2 coating

A SiC/ZrSiO4？SiO2 （SZS） coating was successfully fabricated on the carbon/carbon （C/C） composites by pack cementation, slurry painting and sintering to improve the anti-oxidation property and thermal shock resistance. The anti-oxidation properties under different oxygen partial pressures （OPP） and thermal shock resistance of the SZS coating were investigated. The results show that the SZS coated sample under low OPP, corresponding to the ambient air, during isothermal oxidation was 0.54% in mass gain after 111 h oxidation at 1500 ° C and less than 0.03% in mass loss after 50 h oxidation in high OPP, corresponding to the air flow rate of 36 L/h. Additionally, the residual compressive strengths （RCS） of the SZS coated samples after oxidation for 50 h in high OPP and 80 h in low OPP remain about 70% and 72.5% of those of original C/C samples, respectively. Moreover, the mass loss of SZS coated samples subjected to the thermal cycle from 1500 ° C in high OPP to boiling water for 30 times was merely 1.61%.

Finite element analysis of stress distribution and burst failure of SiC_f/Ti-6Al-4V composite ring

A three-dimensional cyclic symmetry finite element model of titanium-matrix composites（TMCs） ring was developed to investigate the stress distribution and burst failure. The effects of fiber volume fractions, reinforced areas, thermal residual stresses and two different temperatures on stress distribution were studied. The burst speed was obtained through analyzing the hoop tensile stresses under a series of rotating speeds. The results indicate that at the two different temperatures, the influences of fiber volume fractions and reinforced areas on stress level and distribution are different. Some proposals are provided for the structure design of the TMCs ring. With regard to thermal residual stresses, a larger reinforced area is an advisable choice for design of the ring at higher temperature.

Thermal residual stress of polycrystalline diamond compacts

Thermal residual stresses in polycrystalline diamond compact(PDC)cutter arising from the difference in thermal expansion between the polycrystalline diamond(PCD)and the supporting tungsten carbide substrate after sintering at high pressure and high temperature were investigated using finite element simulation,laboratory tests and theoretical analysis.The obtained results show that although compressive residual stresses exist both in the interface of PCD table and in the most region of PCD table surface, the tensile residual stress,which is a fatal shortage to PDC,can also occur near the outer diameter area of PCD table,and the maximum value is 690 MPa.Distribution of tensile stress in the PCD table is given through experimental results,which is well consistent with the numerical results.This finding may be significant in designing new PDC cutters with lower residual stress and high cutting behavior.

Crop residue incorporation and nitrogen fertilizer effects on greenhouse gas emissions from a subtropical rice system in Southwest China

Crop residue incorporation has been widely accepted as a way to increase soil carbon(C) sequestration and sustain soil fertility in agroecosystems. However, effect of crop residue incorporation on greenhouse gas(GHG) emissions in rice paddy soils remains uncertain. A field experiment was conducted to quantify emissions of CH_4 and N_2O and soil heterotrophic respiration(RH) from a paddy rice field under five different crop residue treatments(i.e., 150 kg N ha^(-1) of synthetic N fertilizer application only [NF], 150kg N ha^(-1) of synthetic N fertilizer plus 5.3 Mg ha^(-1) wheat residue [NF-WR1], 150 kg N ha^(-1) of synthetic N fertilizer plus 10.6 Mg ha^(-1) wheat residue [NF-WR2], 75 kg N ha^(-1) of synthetic N fertilizer plus 10.6 Mg ha^(-1) wheat residue [50%NF-WR2] and 150 kg N ha^(-1) of synthetic N fertilizer plus 21.2 Mg ha^(-1) wheat residue [NF-WR3]) in southwest China. Our results showed that crop residue incorporation treatments(NF-WR1, NF-WR2, 50%NF-WR2, NF-WR3) significantly increased CH_4 emissions by at least 60%, but N_2O emissions were not enhanced and even suppressed by 25% in the NF-WR3 treatment as compared to the NF treatment. Soil RH emissions were comparable among experimental treatments, while crop residue incorporation treatments significantly increased soil carbon sequestrations relative to the NF treatment. Overall, CH_4 emissions dominated total global warming potentials(GWP) across all experimental treatments. The average yieldscaled GWPs for the NF and NF-WR1 treatments were significantly lower than for the NF-WR2, 50%NFWR2 and NF-WR3 treatments. Given the comparable yield-scaled GWPs between the NF and NF-WR1 treatments, the NF-WR1 treatment could gain net carbon sequestration as compared with the NF treatment with net soil carbon loss. Our findings suggest that the NF-WR1 treatment should be an effective option to sustain rice production while mitigating GHG emissions from the rice field in China.

天津市挤塑聚苯板薄抹灰外墙外保温系统应用研究

挤塑聚苯板薄抹灰外墙外保温系统在天津市建筑保温节能工程上应用已有多年,出现的质量问题较多,在业内引起不少争议,本文就这些问题以及应对方法进行探讨。

The effect of hot intermittent cupping on pain,stiffness and disability of patients with knee osteoarthritis

Objective:The aim of this study was to investigate the effect of hot intermittent cupping on pain,stiffness and inability of patients with knee osteoarthritis(KO).Methods:The present study was a clinical trial,which was performed on 38 patients with KO referring to Gonabad Rheumatology Specialty Clinic.Based on permutation block method,the research units were divided into cupping therapy and control groups.For the cupping therapy group,four sessions of cupping therapy were performed every four days.To collect data,the form of demographic information,Visual Analogue Scale(VAS)and the Western Ontario and McMaster(WOMAC)osteoarthritis scale were used,and the data were analyzed by SPSS software v.16 using descriptive statistics and independent t-test,paired t-test,Chi-square test and Fishers exact test with a significance level of P<0.05.Results:Findings showed that there was no significant difference between the cupping therapy and control groups in terms of demographic characteristics and they were homogeneous.Findings indicated that,based on VAS,the mean pain intensity in the left(P<0.001)and the right knees(P<0.001),as well as based on WOMAC,stiffness(P=0.006),pain intensity(P<0.001)and disability(P<0.001)in the cupping therapy group significantly decreased compared to the control group.Conclusion:Findings showed that hot intermittent cupping therapy reduced the pain intensity,stiffness and disability in patients with KO.

Effect of Extractive Removal on the Calorific Value of Brazilian Woods Residues

In wood processing, the production of residues is an unavoidable aspect to be considered. The use of wood residues is gaining importance due to the large amount generated and improper disposal, which can seriously harm environment. Burning of wood residues to energy generation is an increasingly usual practice. However, wood residues hold chemical substances that could be recovered before burning. These substances are the wood extractives, which may have many uses as natural dyes for fabrics, foods and cosmetics, as well as potential medicines. Thus, it is of great interest to study the effect of extractive removal on the calorific value of wood residues. In this work, the calorific value of three Brazilian wood species commonly used in sawmills （hymenaeacourbaril, jatoba; cedrelingacatenaeformis, cedroarana; tabebuiasp, ipe） and residues of urban trees pruning （caesalpiniaechinata, Brazil wood） were evaluated before and after extraction in hot water. In woods studied, the calorific value showed three patterns of behavior after removal of extractives soluble in hot water. For Brazil wood, the removal of extractives caused no significant change in calorific value. For cedroarana and jatoba, extractive removal led to a decrease in wood calorific value of 161.3 kcal.kg1 and 40. l kcal.kg^-1, respectively, which indicates that the extractives from these species have a positive energy potential. Finally, for ipe, the removal of extractives resulted in an increase in calorific value of wood （67.6 kcal.kg^-1）, which might encourage the recovery of extractives from wood residues before burning for energy generation.

Computational Analysis for Residue-Specific CDK2-Inhibitor Bindings

Cyclin-dependent kinase 2 (CDK2) is a key macromolecule in cell cycle regulation. In cancer cells, CDK2 is often overexpressed and its inhibition is an effective therapy of many cancers including breast carcinomas, leukemia, and lymphomas. Quantitative characterization of the interactions between CDK2 and its inhibitors at atomic level may provide a deep understanding of protein-inhibitor interactions and clues for more effective drug discovery. In this study, we have used the computational alanine scanning approach in combination with an efficient interaction entropy method to study the microscopic mechanism of binding between CDK2 and its 13 inhibitors. The total binding free energy from the method shows a correlation of 0.76?0.83 with the experimental values. The free energy component reveals two binding mode in the 13 complexes, namely van der Waals dominant, and electrostatic dominant. Decomposition of the total energy to per-residue contribution allows us to identify five hydrophobic residues as hot spots during the binding. Residues that are responsible for determining the strength of the binding were also analyzed.

Research on numerical welding experiment of a thick spherical shell structure

In this paper, in order to predict the residual deformation of thick spherical structure, a welding program is compiled in APDL language based on Ansys and a numerical welding experiment of a welding example is carried out. The temperature field of welding was simulated firstly, then a thermal-structure coupling analysis was carried out, and at last the residual stress and deformation after welding were got. After that, the numerical experiment result was compared with physical experiment one. The comparative analysis shows that the numerical simulation fits well with physical experiment. On the basis of that, a three-dimensional numerical experiment of a thick spherical shell structure was carried out to get the changing rule of stress and deformation of a thick spherical shell structure during welding. The research is of great value to the prediction of residual deformation and high precision machining.

Characterization of Welding Induced Anisotropy in Steel by Magnetic Barkhausen Noise

Residual stress continues to be important issues in shipbuilding. This paper demonstrates how the heat affected zone that results from welding could be identified nondestructively using MBN （magnetic Barkhausen noise） technique. A stress concentration region was created by placing a weld bead on a marine steel plate used in ship construction. MBN measurements were made on the back surface of the welded plate along the weld direction and perpendicular to it in a line that crosses the weld bead. The stress distribution as deduced from the MBN measurements was found to be anisotropic in the material of the heat affected zone. The heat induced anisotropy was completely eliminated by shot peening the HAZ material as revealed by MBN intensity. It was concluded that the directional MBN measurements could be used to characterize the induced anisotropy and hence assess the thermal residual stresses distribution near a localized stresses concentration regions imposed by welding.

Dimension Reduction Method in Thermodynamics of Multireaction Systems(Ⅱ)Residual Properties,Property Changes of Mixing and Excess Properties Relations

Based on the fundamental thermodynamic principle the relationships of the residual properties, the property changes of mixing and the excess properties between the hypothetical solution of unreacted independent species and the equilibrated solution of actual species have been established. The hypothetical solution provides a way of reducing the dimensionality of problem and simplifying the analysis.

Residual Effect of Long Term Application of Organic and Mineral Fertilizers on Selected Chemical Properties of a Savanna Alfisol

The residual effect of organic and mineral fertilizers on selected chemical properties of an Alfisol in the long term soil fertility trial established in 1950 at Samaru, Nigerian savanna was assessed. The trial was left fallow for fourteen years due to lack of funds. Topsoil was collected from plots that received three levels of cow dung （D）, nitrogen （N） and phosphorus （P） in all possible combinations. The soils were analyzed for selected chemical properties. Except for significant effect of applied P on available P, sole application of cow dung, N or P had no significant effect on all the measured soil properties. The interaction of D and P significantly affected the mean values of exchangeable Ca, Mg, K and ECEC in the range of 1.12-1.96, 0.62-1.11, 0.37-0.64 and 2.82-4.11 cmol/kg respectively. The most important results were the ability of the plot that received neither D nor P to significantly increase these parameters than the plots that received only one of the treatments. The results show that the fallow period has changed the effects of application of organic and mineral fertilizers on the soil chemical properties under continuous cultivation by modifying them towards those of a native savanna Alfisol.

FEM analysis on the effect of cobalt content on thermal residual stress in polycrystalline diamond compact(PDC)

Thermal residual stress in Polycrystalline Diamond Compacts （PDCs） is mainly caused by the mismatch in the Coefficients of Thermal Expansion （CTE） between the polycrystalline diamond （PCD） layer and WC-Co substrate. In the PCD layer, the CTE of cobalt exhibit magnitudes four times larger than those of diamond. Cobalt content in the PCD layer has important effects on the thermal residual stress of PDCs. In this work, the effects of cobalt content on thermal residual stress in PCDs were investi- gated by the Finite Element Method （FEM）. The simulation results show that the thermal residual stress decreases firstly, and then increases with increasing cobalt content （1 vo1.%-20 vol.%）, which reaches a minimum value when the cobalt content is about 10 vol.%. The FEM analysis results are in agreement with our experimental results. It will provide an effective method for further designing and optimizing PDC properties.

Theoretical model of double-walled carbon nanotube pullout from a composite matrix

A micromechanical model of double-walled carbon nanotube (DWCNT) pullout from a composite matrix is presented with the interfacial residual stress and van der Waals (vdW) forces taken into consideration.The interfacial residual stress induced by thermal expansion coefficient (TEC) mismatch is introduced via thermo-elastic constitutive relations.The influence of vdW interactions between two layers of DWCNT on the interfacial stress distributions of DWCNT and matrix is analyzed.The analytical expressions of interfacial shear stress and the axial stresses of DWCNT and matrix are derived,respectively.Furthermore,the influences of temperature change,interfacial friction coefficient,DWCNT aspect ratio,DWCNT volume fraction and the relative modulus between DWCNT and matrix are illustrated and discussed.

Simulation of residual stresses and their effects on thermal barrier coating systems using finite element method

Thermal barrier coating(TBC)systems are widely used in industrial gas-turbine engines.However,premature failures have impaired the use of TBCs and cut down their lifetime,which requires a better understanding of their failure mechanisms.In the present study,experimental studies of isothermal cycling are firstly carried out with the observation and estimation of microstructures.According to the experimental results,a finite element model is established for the analysis of stress perpendicular to the TBC/BC interface.Detailed residual stress distributions in TBC are obtained to reflect the influence of mechanical properties,oxidation,and interfacial roughness.The calculated results show that the maximum tensile stress concentration appears at the peak of TBC and continues to increase with thermal cycles.Because of the microstructural characteristics of plasma-sprayed TBCs,cracks initialize in tensile stress concentration(TSC)regions at the peaks of TBC and propagate along the TBC/BC interface resulting in the spallation of TBC.Also,the inclusion of creep is crucial to failure prediction and is more important than the inclusion of sintering in the simulation.

Thermal-induced transformation of wetting behaviors on laser-textured SiC surfaces

Thermal-induced transformation of wetting behaviors on laser-textured silicon carbide （SIC） surfaces was discussed in this work. To investigate the transformation, a quenching experiment was conducted and an X-ray diffractometer was used to measure the residual stress. The experimental results demonstrate that the significantly enhanced hydrophilicity was induced by the increasing thermal residual stress of SiC materials after the aqueous quenching. It was found that the decrease in the contact angle increased with the increasing quenching temperature. Quenching at 350℃ led to the change of contact angle from 89.28° to 70.88° for the smooth surface, while from 72.25° to 33.75° for the laser-textured surface with depth 8 μm. Further, the surface hydrophobicity was enhanced by the release of thermal residual stress after quenching, thereby leading to an increase in the contact angle over time. The transformation of wetting behaviors on laser textured SiC surfaces can be achieved mutually by the aqueous quenching method.

A novel microstructural design and heat treatment technique based on gradient control of carbon partitioning between austenite and martensite for high strength steels

Based on gradient control of carbon partitioning between martensite and austenite during heat treatment of steels,a stepping-quenching-partitioning(S-Q-P) process is developed for high strength steels.The S-Q-P process involves several quenching processes at progressively lower temperatures between martensite-start(Ms) and martensite-finish(Mf) temperatures,each followed by a partitioning treatment at either the initial quenching temperature or above that temperature.A novel microstructure is designed based on the S-Q-P process.Sizes and distributions of retained austenite and high-carbon martensite surrounded by martensite laths can be manipulated by the partitioning duration and temperature,and quenching temperature of the S-Q-P process.Alloying element Si is employed in the S-Q-P steel to suppress formation of carbides and create suitable amount of retained austenite.A steel of 0.39C-1.22Mn-1.12Si-0.23Cr(wt.%) treated by the S-Q-P process is endowed with some special microstructural characteristics:some strips of retained austenite located at edges of martensite blocks with high density of dislocations and between martensite laths,some small blocks of twinned martensites distributed among bundles of the low-carbon martensite lath.The mechanical properties of the medium carbon steel after the S-Q-P process can reach ultimate tensile strength(Rm) of 1240 MPa,total elongation(EI) of 25%,and product of strength and ductility(PSD) of 31.2 GPa% that are much more improved than those after the conventional quenching-tempering(Q-T) and currently prevailing quenching-partitioning(Q-P) treatments.The PSD of the tested steel after the S-Q-P process increases by 67% and 32% as compared with those after the Q-T and Q-P processes,respectively.