Thermoelastic analysis of laminated composite and sandwich shells considering the effects of transverse shear and normal deformations

Abstract

In the present study, thermoelastic analysis of laminated composite and sandwich shells (cylindrical/spherical) is presented using fifth-order shear and normal deformation theory. The significant characteristic of the present theory is that it includes the effects of both transverse shear and normal deformations. The mathematical formulation uses the principle of virtual work to derive the variationally consistent governing equations and traction free boundary conditions. To obtain the static solution, these governing equations are solved by employing Navier’s solution technique. The shell is subjected to a mechanical/thermal load sinusoidally distributed over the top surface of the shell. The thermal load linearly varies across the thickness of the shell. The present results are compared with other higher-order models and 3D elasticity solution wherever possible. Thermal stresses presented in this study will act as a benchmark for the future work.     

Changes in phenolics,soluble solids,vitamin C,and antioxidant capacity of various cultivars of hardy kiwifruits during cold storage

Food Science and Biotechnology - Hardy kiwifruits (Actinidia arguta) contain various bioactive compounds such as vitamin C and phenolics and can withstand cold temperatures. Changes in soluble...     

基于模糊分析法的合肥市水资源承载力评价

以合肥市为例,选取人均水资源量、年产水模数、人均供水量、植被覆盖率、日生活用水量、万元GDP用水量、万元工业增加值需水量、人口密度、城市化率、农田灌溉定额、水资源开发利用率、人均GDP、污水排放达标率、水功能区达标率、生态用水率15个指标,在建立合肥市水资源承载力评价指标体系及等级标准体系的基础上,构建模糊分析模型并借助Matlab工具计算隶属度、确定指标权重,进而计算2013~2017年水资源承载等级,获得了合肥市水资源承载力情况,计算结果对合肥市水资源开发利用具有一定的参考意义。     

Shear and extensional rheology of selected polysaccharides

Rheology is used for the elucidation of the flow properties of polysaccharide solutions. For a given polysaccharide, both shear and extensional rheological experiments should be performed for the full characterisation of its flow properties. The provided information will facilitate the efficient exploitation of a polysaccharide in various applications. Although shear rheology is widely used in polysaccharides’ characterisation, there are only limited extensional rheology studies due to lack of reliable techniques in the formation of pure extensional flow. However, recently, several commercial extensional rheometers have been developed and thus, accurate extensional experiments can now be performed. The present work initially presents the principles and concepts of both shear and extensional rheology and then reports rheological findings for solutions of various polysaccharides and their derivatives. Xanthan and various members of the galactomannan, cellulose and alginate families were selected.     

不同粒径改性粉煤灰对磷酸根吸附性能的影响

废水排放过量的磷导致水体污染日益严重，将粉煤灰通过化学改性制备成了水化硅酸钙吸附剂，研究了改性吸附剂对磷酸根的吸附效果。利用XRD, SEM及BET比表面积等手段对粒度分级前后的吸附剂进行表征，研究不同粒级吸附剂对磷酸根的吸附性能，并考察其吸附机理。结果表明，不同粒级的吸附剂其化学成分出现了明显的偏析现象，孔隙结构也差异显著。相比其他粒径下的吸附剂颗粒，颗粒粒径在50?75 μm时，吸附剂中钙和硅含量较多，铝、铁和镁含量较低，水化硅酸钙组分含量最高，且伴有含铝的托贝莫来石晶体出现，钙离子的增加使其可以与更多的磷酸根结合形成沉淀。同时此粒径下具有较高的比表面积及孔隙度，疏松多孔的结构为钙离子提供更多活性位点。当使用粒径在50?75 μm的吸附剂吸附磷酸根时，磷的饱和吸附量可达到17.1 mg/g，比未分级的吸附剂高19.58%。     

乙炔发生發发气能力不足的原因及对策

分析了乙炔发生器发气能力低的原因,对发生器温度、发生器压力及发生器耙齿等方面进行了改进,提高了发气量。     

Structural,microstructural and electrochemical studies on LiMn2-x(GdAl)xO4 with spinel structure as cathode material for Li-ion batteries

Gd and Al co-doped LiMn_2-x(GdAl)_xO₄ (x?=?0, 0.01, 0.02, 0.03, 0.04 and 0.05) materials with spinel structure were synthesized by sol–gel method. Powder X-ray diffraction results confirm the formation of cubic spinel structure and average particle sizes are found to be between 80 and 110?nm from FE-SEM and TEM analysis. Decrease in peak potential difference as a function of doping in Cyclic Voltammetry results establishes enhancement in Li⁺ intercalation and de-intercalation. Electrochemical Impedance Spectroscopy (EIS) results showed that accumulation of charges on electrode has improved with doping over pristine samples. At a doping of x?=?0.02 charge transfer resistance values were found to be least. First cycle charge–discharge profiles for LiMn_1.96(GdAl)_0.02O₄ shows 139.2?mAh/g discharge capacity over other doped derivatives and pure LiMn₂O₄ (119.6?mAh/g) in aqueous Li₂SO₄ electrolyte. Doping of x?=?0.02 exhibit good cycling performance with only a total 4% capacity loss after 30 cycles.     

An approach to measure infill matric suction of irregular infilled rock joints under constant normal stiffness shearing

Rock joints infilled with sediments can strongly influence the strength of rock mass. As infilled joints often exist under unsaturated condition, this study investigated the influence of matric suction of infill on the overall joint shear strength. A novel technique that allows direct measurement of matric suction of infill using high capacity tensiometers (HCTs) during direct shear of infilled joints under constant normal stiffness (CNS) is described. The CNS apparatus was modified to accommodate the HCT and the procedure is explained in detail. Joint specimens were simulated by gypsum plaster using three-dimensional (3D) printed surface moulds, and filled with kaolin and sand mixture prepared at different water contents. Shear behaviours of both planar infilled joints and rough joints having joint roughness coefficients (JRCs) of 8–10 and 18–20 with the ratios of infill thickness to asperity height (t/a) equal to 0.5 were investigated. Matric suction shows predominantly unimodal behaviour during shearing of both planar and rough joints, which is closely associated with the variation of unloading rate and volumetric changes of the infill material. As expected, two-peak behaviour was observed for the rough joints and both peaks increased with the increase of infill matric suction. The results suggest that the contribution of matric suction of infill on the joint peak normalised shear stress is relatively independent of the joint roughness.     

Experimental study on the behavior of eccentrically loaded circular footing model resting on reinforced sand

In this study, an experimental investigation has been conducted on a circular footing model subjected to eccentric load resting on the geonet-reinforced sand. To this end, five series of tests were carried out in order to evaluate the effect of reinforcement dimension and eccentricity on the bearing capacity, settlement, and rotation of the footing. Results show that the bearing capacity ratio (BCR) is in direct relationship with eccentricity and the impact of soil reinforcement at low settlements is much more significant in the case of eccentric loading. Additionally, the bearing capacity interaction diagram and variation in the position of rotation line at different load levels for reinforced and unreinforced conditions are presented.