Sea-urchin-like ZnO nanomaterials were successfully synthesized by decomposition of zinc acetate precursor in the presence of sodium hydroxide and ethylene glycol(EG)in an ethanol solution using a solvothermal method at 180℃ for 12h.The crystalline phase and morphology of the resultant nanomaterials were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),selected-area electronic diffraction(SAED)and high-resolution electron microscopy(HRTEM).Interestingly,the sizes and prod length of the samples can be easily tuned by changing the amount of directing agent EG and keeping other reaction conditions unchangeable.On the basis of our experimental outcomes,EG-controlled-nucleation-growth formation mechanism was proposed to correspond for the sea-urchin-like ZnO growth processes.And the photoluminescence(PL)spectra of the as-selected samples were measured at room temperature,presenting two emission peaks centered at～388 and 480 nm....

Mesoporous polyethylene glycol-resorcinol and formaldehyde(PEG-RF) carbon xerogels were prepared by a new polymer blend method in which PEG-RF mixed organic xerogels were synthesized by blending thermally unstable polyethylene glycol with organic monomers, resorcinol and formaldehyde and then subjected to pyrolization at 1 000 ℃. The influences of mass ratio of PEG to the theoretical yield of RF xerogel, m(PEG)/m(RF) and the relative molecular mass of PEG on the pore structure and electric double layer capacitance(EDLC) performance of PEG-RF carbon xerogels were investigated. The results show that PEG under different conditions leads to the difference of phase separation structure of the polymer blend and thus the change of pore structure of PEG-RF carbon xerogels. Specific surface area and capacity of PEG-RF carbon xerogels in 30% H2SO4 solution can reach 755 m2/g and 150 F/g, respectively. Their surface can be fully utilized to form electric double layer. However, the pore structure differences of PEG-RF carbon xerogels result in their different EDLC performances. The distributed capacitance effect increases with decreasing the pore size of PEG-RF carbon xerogels....

Using the direct method for a coupled KdV system, six types of the similarity reductions are obtained. The group explanation of the results is also given. It is pointed out that, in order to find all the results by nonclassical Lie approach, two additional condition equations should be satisfied at the same time together with two original equations....

A numerical analysis based on the boundary element method (BEM) was presented for the hydrodynamic performance of a high skew propeller (HSP) which is employed by an underwater vehicle (UV).Since UVs operate at two different working conditions (surface and submerged conditions),the design of such a propeller is a cumbersome task.This is primarily due to the fact that the resistance forces as well as the vessel efficiency under these conditions are significantly different.Therefore,some factors are necessary for the design of the optimum propeller to utilize the power at the mentioned conditions.The design objectives of the optimum propeller are to obtain the highest possible thrust,minimum torque,and efficiency.In the current study,a 5-bladed HSP was chosen for running the UV.This propeller operated at the stem of the UV hull where the inflow velocity to the propeller was non-uniform.Some parameters of the propeller were predicted based on the UV geometrical hull and operating conditions.The computed results include the pressure distribution and the hydrodynamic characteristics of the HSP in open water conditions,and comparison of these results with those of the experimental data indicates good agreement.The propeller efficiency for both submerged and surface conditions was found to be 67％ and 64％,respectively,which compared to conventional propellers is a significantly higher efficiency....

A set of constrained Newton methods were developed for static traffic assignment problems.The Newton formula uses the gradient of the objective function to determine an improved feasible direction scaled by the second-order derivatives of the objective function.The column generation produces the active paths necessary for each odgin-destlnation pair.These methods then select an optimal step size or make an orthogonal projection to achieve fast,accurate convergence.These Newton methods based on the constrained Newton formula utilize path information to explicitly implement Wardrop's principle in the transport network modelling and complement the traffic assignment algodthms.Numedcal examples are presented to compare the performance with all possible Newton methods.The computational results show that the optimal-step Newton methods have much better convergence than the fixed-step ones,while the Newton method with the unit step size is not always efficient for traffic assignment problems.Furthermore,the optimal-step Newton methods are relatively robust for all three of the tested benchmark networks of traffic assignment problems....

Based on the classical response surface method (RSM), a novel RSM using improved experimental points (EPs) is presented for reliability analysis. Two novel points are included in the presented method. One is the use of linear interpolation, from which the total EPs for determining the RS are selected to be closer to the actual failure surface;the other is the application of sequential linear interpolation to control the distance between the surrounding EPs and the center EP, by which the presented method can ensure that the RS fits the actual failure surface in the region of maximum likelihood as the center EPs converge to the actual most probable point (MPP). Since the fitting precision of the RS to the actual failure surface in the vicinity of the MPP, which has significant contribution to the probability of the failure surface being exceeded, is increased by the presented method, the precision of the failure probability calculated by RS is increased as well. Numerical examples illustrate the accuracy and efficiency of the presented method....

A numerical model is developed by use of the boundary integral equation method to investigate the responses of a two-dimensional floating structure.The structure under consideration consisting of two pontoons,is connected by a rigid framework,and linked to the sea floor by a mooring system.The theoretical conception is based on potential theory with linear external forces,and applied to an arbitrarily shaped body and water depth.The discussion includes the influence of draft and space between pontoons on the responses of the floating structure.Finally,the validity of the method is adequately verified by experimental results....

Stress analysis for an infinite strip weakened by periodic cracks is studied. The cracks were assumed in a horizontal position, and the strip was applied by tension "p" in y-direction. The boundary value problem can be reduced into a complex mixed one. It is found that the EEVM ( eigenfunction expansion variational method) is efficient to solve the problem. The stress intensity factor at the crack tip and the T-stress were evaluated. From the deformation response under tension the cracked strip can be equivalent to an orthotropic strip without cracks. The elastic properties in the equivalent orthotropic strip were also investigated. Finally, numerical examples and results were given....

A magnetorheological (MR) fluids brake is a device to achieve brake by shear force of MR fluids. A MR rotary brake has the property that its braking torque changes quickly in response to an external magnetic field. In this study, the design method of the circular plate MR fluids brake is investigated theoretically. The equation of the torque transmitted by the MR fluids in the brake is derived to provide the theoretical foundation in the design of the brake. Based on this equation, after mathematically manipulated, the calculations of the volume, thickness and width of the MR fluids within the circular plate MR fluids brake are yield....

The microscopic analyses of polycrystalline material at high temperature were carried out. The crystal plasticity model proposed by Asaro and Needleman was applied to a polycrystal model in the finite element simulation and the crystal slip system was randomly provided for each crystal. The grain boundary sliding, which was characteristic at high temperature, was also taken into account. It was shown that the inhomogeneous deformation develops over the polycrystal and that the strain concentration appears around the triple point of crystal grain boundary....

The machining accuracy of workpiece is influenced by its orientation deviation,which is caused by the fixture-workpiece error.Based on the spatial coordinate theory,the orientation deviation of workpiece is measured by using an on-machine verification system,which can take into account the errors resulting from fixture manufacturing,installation and adjustment,location and clamping of workpiece.According to the least square method,the model of orientation deviation is built to determine the relationship between the theoretical and actual coordinate systems.The influence of orientation deviation on machining accuracy is quantified,and it is shown that the orientation deviation only affects the dimensional precision and position precision,rather than shape precision.In the experiment,the compensation processing ofrealtime errors was conducted,and the perpendicularity and inclination errors of the tetragonal part were reduced by 38.46％ and 47.06％,respectively....

The nonlinear dynamic control equation of a flexible multi-body system with definite moving attitude is discussed. The motion of the aircraft in space is regarded as known and the influence of the flexible structural members in the aircraft on the motion and attitude of the aircraft is analyzed. By means of a hypothetical mode, the deformation of flexible members is regarded as composed of the line element vibration in the axial direction of rectangular coordinates in space. According to Kane's method in dynamics, a dynamic equation is established, which contains the structural stiffness matrix that represents the elastic deformation and the geometric stiffness matrix that represents the nonlinear deformation of the deformed body. Through simplification the dynamic equation of the influence of the planar flexible body with a windsurfboard structure on the spacecraft motion is obtained. The numerical solution for this kind of equation can be realized by a computer....

On the basis of the deep geology and the geological structure of Huangtupo landslide, an ancient landslide in the reservoir of the Three Gorges, the geo-environmental model of the landslide is established to analyze quantitatively the sliding mechanism by using the discrete element method. It is concluded that interbedding structure of soft and hard formation consists of the main geological background,which induced the arching of the formation under gravity. Stability analysis of different loadings shows that the ground building weight on the middle slope may restrain the extension of shear sliding zone below, but may activate the foot area which will reduce the safety factor of the front....

A transient thermal model was developed for slab furnaces in Eregli Iron and Steel Worlds (Erdemir) in Turkey and the model was solved using the FlexPDE computer program. This program uses the finite element method. Program codes were written to solve the temperature distribution of slabs that are put into furnace at 25℃ and removed at about 1 250℃. To obtain the optimum slab exit temperature variation, the necessary air temperature inside the furnace was calculated to be 1 390℃. The slab temperature versus time and the temperature variation inside the slab were depicted....

Fluorimetry was used to measure the amount of nicotinamide in plant samples. The nicotinamide was extracted and purified from plant tissues with ethyl acetate; converted to the fluorescent derivative, N1-methylnicotinamide, by reacting with methyl iodide; and quantified according to its fluorescent strength. The nicotinamide in the leaf tissue of ten kinds of plants was measured, and the results showed that the nicotinamide content for different plants varied from 0. 1 to 3.0 μg/g of fresh leaf weight. In addition, the crossing value of the fluorescent strength and the nicotinamide amount demonstrated that the linear correlation coefficient generally reached 0. 997, with a detectable limit of 0. 02 mg/L and the relative standard deviation of less than 9%. The results suggested that this method of quantifying nicotinamide in plants is useful and beneficial for functional research....

It is becoming possible to do detailed numerical analyses for the various mechanical behavior of braced excavation by researching and developing the numerical analysis technique such as the finite ele-ment method (FEM).However,the mechanical behavior of braced excavation has not been clanfied fully both in theory and in expedence.Therefore,improving the prediction accuracy during the prior design is very important for making the observational method of braced excavation more effective.In this paper,FEM analyses were performed for a model of braced excavation by using Geotechnical Finite Element Elasto-plastic Analysis Software,GeoFEAS (2D).As the constitutive law of ground,MC-DP model, and Dun-can-Chang model were applied.The results were compared and discussed with that of a site measurement,and the effects of the constitutive law of ground on the analyzed result were verified.For the difference be-tween the results,the reason was investigated by the analyses adjusting the elastic modulus of ground,and the appropriate application of the constitutive law was researched....

The mechanical performance of a flexible riser is more outstanding than other risers in violent environmental conditions.Based on the lumped mass method,a steep wave flexible riser configuration attached to a Floating Production Storage and Offloading(FPSO)has been applied to a global analysis in order to acquire the static and dynamic behavior of the flexible riser.The riser was divided into a series of straight massless line segments with a node at each end.Only the axial and torsional properties of the line were modeled,while the mass,weight,and buoyancy were all lumped to the nodes.Four different buoyancy module lengths have been made to demonstrate the importance of mode selection,so as to confirm the optimum buoyancy module length.The results in the sensitivity study show that the flexible riser is not very sensitive to the ocean current,and the buoyancy module can reduce the Von Mises stress and improve the mechanical performance of the flexible riser.Shorter buoyancy module length can reduce the riser effective tension in a specific range of the buoyancy module length when other parameters are constant,but it can also increase the maximum curvature of the riser.As a result,all kinds of the riser performances should be taken into account in order to select the most appropriate buoyancy module length....

Piano lessons are taught by a variety of different “methods”;individual teachers will have their preferences among the different methods.Each method has its own set of strengths and weaknesses.Our goal in pointing out both strong points and criticisms of teaching methods is to provide teachers with an overview of a given method's strengths and weaknesses.All teaching methods involve compromises and not every method works well for every student.You should evaluate these methods in light of your own needs and choose a teacher whose personal choice of a method or methods is consistent with your needs,wishes,and the way in which you learn most efficiently.Tips for teachers on choosing a teaching method can be found in our article....

Based on the nonlinear geometric relation between strain and displacement for flexible cable, the equilibrium equation under self-weight and influence of temperature was established and an analytical solution of displacement and tension distribution defined in Eulerian coordinate system was accurately obtained. The nonlinear algebraic equations caused by cable structure were solved directly using the modified Powell hybrid algorithm with high precision routine DNEQNE of Fortran. For example, a cable structure consisting of three cables jointly supported by a vertical spring and all the other ends fixed was calculated and compared with various methods by other scholars....

Being aimed at the inside wall wrinkling and sinking phenomenon of palladium-yttrium alloy thin wall spiral tube used for preparation of high purity hydrogen,extraction of hydrogen isotope,and purification and separation of hydrogen in the winding process,this article analyzed the reasons for above phenomena,established a numerical simulation model of winding process of above tube,using elastic-plastic Finite Element method analyzed the max.tensile stress and max.compression stress and their locations,thereby provides a theory base for the control of working forming course of thin wall spiral tube....

Ships and automobiles are fabricated from thin plates. To assemble parts, welding is commonly employed.However, welding distortion in large thin-plate panel structure is usually cased by buckling due to the residual stress. In this study, an elastic finite element method for predicting the welding distortion of three-dimensional thin-plate structures with considering welding sequence was proposed. In this method, the inherent strain was employed to model the local shrinkage due to welding itself, and the interface element was introduced to simulate the assembly process. The proposed method was applied to study the influence of welding sequence on the buckling distortion of the large thin-plate panel structure during assembly....