Analytical solution for fixed-end beam subjected to uniform load

A bi-harmonic stress function is constructed in this work. Ariy stress function methodology is used to obtain a set of analytical solutions for both ends fixed beams subjected to uniform load. The treatment for fixed-end boundary conditions is the same as that presented by Timoshenko and Goodier （1970）. The solutions for propped cantilever beams and cantilever beams are also presented. All of the analytical plane-stress solutions can be obtained for a uniformly loaded isotropic beam with rectangular cross section under different types of classical boundary conditions.     

Preparation and characterization of N-isopropylacrylamide/carboxymethylated chitosan hydrogel

Poly （N-isopropylacrylamide） （PNIPAAm）/carboxymethylated chitosan （CMCH） hydrogels were prepared by irradiating the aqueous solution mixture of NIPAAm and CMCH by 60 Co γ-ray.The effects of feed ratio of NIPAAm and CMCH,temperature,pH and ionic strength on the swelling ratio of PNIPAAm/CMCH hydrogels were studied.The results show that the addition of CMCH shifts the lower critical solution temperature （LCST） of the PNIPAAm hydrogel to higher temperature.The PNIPAAm/CMCH hydrogel displays not only pH-and thermo-sensitivity,but also ion-sensitivity.Differential scanning calorimetry （DSC） was applied for the determination of the LCST of the hydrogel.     

Science Letters： Analytical solutions for a uniformly loaded circular plate with clamped edges

A bi-harmonic potential function was constructed in this study. Love solution was employed to obtain analytical solutions of uniformly loaded plates with two different types of clamped edges. The treatment of clamped boundary conditions was the same as that adopted by Timoshenko and Goodier （1970）. The analytical solution for the first type of clamped boundary condition is identical with that obtained by Luo et al.（2004）, and the solutions for both types were compared with the FEM results and the calculations of thin plate theory.     

Multi-group ant colony algorithm based on simulated annealing method

To overcome the default of single search tendency, the ants in the colony are divided into several sub-groups. The ants in different subgroups have different trail information and expectation coefficients. The simulated annealing method is introduced to the algorithm. Through setting the temperature changing with the iterations, after each turn of tours, the solution set obtained by the ants is taken as the candidate set. The update set is obtained by adding the solutions in the candidate set to the previous update set with the probability determined by the temperature. The solutions in the candidate set are used to update the trail information. In each turn of updating, the current best solution is also used to enhance the trail information on the current best route. The trail information is reset when the algorithm is in stagnation state. The computer experiments demonstrate that the proposed algorithm has higher stability and convergence speed.     

Unified analytical solutions for a circular opening based on non-linear unified failure criterion

Unified analytical solutions are presented for the predictions of the stresses and displacements around a circular opening based on nonqinear unified failure criterion and the elastic-brittle-plastic softening model. Unified analytical solutions not only involve generally traditional solutions which are based on the Hock-Brown （H-B） failure criterion or the non-linear twin-shear failure criterion, but also involve other new results. The results of the radius of plastic zone, radial displacements and stresses are obviously different using three rock masses when different values of the unified failure criterion parameter or different material behavior models are used. For a given condition, the radius of plastic zone and radial displacements are reduced by increasing the unified failure criterion parameter. The latent potentialities of rock mass result from considering the effect of intermediate principal stress. It is shown that proper choices of the failure criterion and the material behavior model for rock mass are significant in the tunnel design.     

Solution of nonlinear cubic-quintic Duffing oscillators using He’s Energy Balance Method

In this study, He＇s Energy Balance Method （EBM） was applied to solve strong nonlinear Duffing oscillators with cubic-quintic nonlinear restoring force. The complete EBM solution procedure of the cubic-quintic Duffing oscillator equation is presented. For illustration of effectiveness and convenience of the EBM, different cases of cubic-quintic Duffing oscillator with different parameters of α,β and y were compared with the exact solution. We found that the solutions were valid for small as well as large amplitudes of oscillation. The results show that the EBM is very convenient and precise, so it can be widely appli- cable in engineering and other sciences.     

纳米银/聚丙烯酰胺/乙烯-醋酸乙烯酯共聚物复合材料的电性能

Nano-Ag particles/polyacrylamide （PAM） composites were synthesized by γ irradiation method and then blended with ethylene vinyl acetate （EVA）. Dielectric behaviors of the Ag/PAM/EVA composites are investigated as a function of both the concentration and size of Ag particles. When concentration of the Ag fillers is rarely low, dielectric anomalies were first observed in contrast to the traditional percolation theory. As concentration of Ag increases, volume resistivity and breakdown field strength are enhanced, loss tangent （tan δ） reduced and dielectric constant kept invariable. In addition, the above variation became larger when the diameter of the Ag nano-particles is smaller. Such dielectric anomalies may be understood by considering the unique ＂Coulomb Blockade Effect＂ of the nano-sized Ag particles.     

Expansion of spherical cavity of strain-softening materials with different elastic moduli of tension and compression

An expansion theory of spherical cavities in strain-softening materials with different moduli of tension and com-pression was presented. For geomaterials,two controlling parameters were introduced to take into account the different moduli and strain-softening properties. By means of elastic theory with different moduli and stress-softening models,general solutions cal-culating Tresca and Mohr-Coulomb materials' stress and displacement fields of expansion of spherical cavity were derived. The effects caused by different elastic moduli in tensile and compression and strain-softening rates on stress and displacement fields and development of plastic zone of expansion of cavity were analyzed. The results show that the ultimate expansion pressure,stress and displacement fields and development of plastic zone vary with the different elastic moduli and strain-softening prop-erties. If classical elastic theory is adopted and strain-softening properties are neglected,rather large errors may be the result.     

Coupling reaction mechanism of 2-(2-bromo-4-fluoro-phenyl)-1-cyclohexen-1-yl trifluoromethane-sulfonate

The detailed mechanism of CuI-catalyzed C-O intramolecular coupling reaction of 2-（2-bromo-4-fluoro-phenyl）-l- cyclohexen-1-yl trifluoromethane-sulfonate was studied with the density functional theory （DFT）. The geometries of the reactants, transition states, intermediates and products were optimized at the B3LYP/6-31 ＋G＊ level. Meanwhile, the single point energy of species involved in gas and solvent at B3LYP/6-31 I＋G＊ level was individually investigated. Polarizable continuum models （PCM） were applied to the dioxane and water solutions at the same level, respectively. Results show that the rate-limiting step, M3→TS3, does not change in different solutions. However, the activation energy in a dioxane solution is lower than that in water, which explains the previous experimental results. Compared with the non-catalyzed reaction process, the activation energy of the rate- limiting step is reduced by 56.53 kJ mo1-1 in gas and 44.84 kJ mol-l in solvent, demonstrating a high catalytic efficiency of CuI.     

五朔节(英文)

The first day of the month of May is known as May Day. It is the time of year when warmer weather begins and flowers and treesstart to blossom. It is said to be a time of love and romance. It is when people celebrate the coming of summer with lots of different customs that are expressions of joy and hope after a long winter.     

反相乳液聚合法合成聚丙烯酸纳米及微米颗粒

采用反相乳液聚合方法,合成纳米及微米级尺寸的聚丙烯酸吸水性颗粒.将Span-80和Twoon-80组成的协同乳化体系分散于烷烃介质,使聚合体系稳定化.聚合初期,单体存在于乳化液滴和胶束中.在自由基引发下,聚合得到的聚丙烯酸颗粒大小均一,且其尺寸取决于引发剂的类型.若使用水溶性引发剂,如过硫酸铵,得到微米级的颗粒;若使用油溶性的偶氮二异丁腈作引发剂,由于丙烯酸的齐聚物分子链在油性连续相中溶解受限,则得到纳米级颗粒.     

聚二甲基硅烷与聚二甲基硅氧烷链特征比分析比较

应用构象统计方法和改进的侧基旋转异构态模型,推导了对称取代基链的均方回转半径特征比《S2》/2xl2公式,可研究聚二甲基硅烷链的柔顺性,根据特征比与链长的关系,得到聚二甲基硅烷链长链特征比值0.94,结果还与聚二甲基硅氧烷链前期计算值作了比较.     

Synthesis of poly[methyl（3,3,3-trifluoropropyl）siloxane]-b-poly（ethylene oxide） block copolymers

A series of new amphiphilic poly[methyl（3,3,3-trifluoropropyl）siloxane]-b-poly（ethylene oxide） （PMTFPS-b-PEO） diblock copolymers with different ratios of hydrophobic segment to hydrophilic segment were prepared by coupling reactions of end-functlonal PMTFPS and PEO homopolymers. Copolymers were shown to be well defined and narrow molecular weight distribution （MWD） （1.07-1.3） by characterizations such as gel permeation chromatography （GPC） and ^1H-nudear magnetic resonance （^1H-NMR）.     

Low-Temperature Plasma Induced Grafting of 2-Methacryloyloxyethyl Phosphorylcholine onto Poly（tetrafluoroethylene） Films

Modification of poly(tetrafluoroethylene) (PTFE) films with 2-methacryloyloxyethyl phosphorylcholine (MPC) was performed by low-temperature plasma treatment and grafting polymerization. Surface properties of PTFE were characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra, X-ray photoelectron spectroscopy (XPS), and static contact angle. The results show that MPC has been grafted onto PTFE film surface successfully. Contact angle for the modified PTFE films in the water decreased from 108° to 58.25°, while surface energy increased from 17.52 mN/m to 45.47 mN/m. The effects of plasma treatment time, monomer concentration and grafting time on degree of grafting were determined. In the meanwhile, blood compatibility of the PTFE films was studied by checking thrombogenic time of blood plasma.     

薄膜涂层材料--聚对二甲苯

聚对二甲苯薄膜(N、C、D型)是一种性能优良的涂层材料,文章主要介绍聚对二甲苯薄膜的成膜原理、工艺流程、性能及广泛用途.     

Influence of Poly(methylmethacrylate) Dopant on Butadiene Derivative Electroluminescence

ＩｎｆｌｕｅｎｃｅｏｆＰｏｌｙ（ｍｅｔｈｙｌｍｅｔｈａｃｒｙｌａｔｅ）ＤｏｐａｎｔｏｎＢｕｔａｄｉｅｎｅＤｅｒｉｖａｔｉｖｅＥｌｅｃｔｒｏｌｕｍｉｎｅｓｃｅｎｃｅＷａｎｇＧｕａｎｇｍｉｎｇ１（王光明）ＷａｎｇＧｕａｎｇｍｉｎ２（王广民）ＹｕａｎＣｈｕ...     

表观黏度法研究聚丙烯酰胺与聚乙二醇在水中的相互作用

采用表观黏度法,以黏度增长因子R为指标,对聚丙烯酰胺(PAM)与聚乙二醇(PEG)在水中的相互作用进行研究,并考察PAM摩尔分数、PEG相对分子质量、剪切速率和温度对其相互作用的影响。结果表明:混合体系中PAM与PEG之间的相互作用表现为表观黏度的降低,主要为疏水、氢键及相互缠结作用等;当体系中PAM的摩尔分数为0.6时,相互作用最强;该作用随PEG相对分子质量的增大而略增强,随剪切速率的增加先增大后减小,随温度的升高先减小后增大。表观黏度法快捷简便,适用于溶液中聚合物分子间相互作用的研究。     

Influence of surfactant concentration on counter-ion induced solubility of poly（pyridine-2,5-diyl）

INTRODUCTION Preparation and electrical properties ofpoly(arylene)s having π-conjugation system along thepolymer chain are the subject of recent interest(Skotheim et al., 1997; Nalwa, 1997; Yamamoto,2002). Among the poly(arylene)s, poly(p-phenylene),poly(pyridine-2,5-diyl) and poly(thiophene-2,5-diyl)are the most fundamental polymers and had beenextensively studied (Skotheim et al., 1997; Yama-moto, 2002; Nurulla et al., 2001). However, thesepolymers show only…     

废聚酯醇解产物羟值的分析方法

采用乙酸酐 /吡啶回流法和乙酸酐 /高氯酸 /乙酸乙酯常温酰化法 ,分别测定了废聚醋醇解产物的羟值。结果表明 ,两种方法测定结果均准确可靠。乙酸酐 /吡啶回流法适用于所有的废聚酯醇解产物 ,但操作麻烦、费时。乙酸酐 /高氯酸 /乙酸乙酯常温酰化法用于深度醇解的醇解产物 ,操作简单、快捷