Optimized synthesis and photovoltaic performance of TiO2 nanoparticles for dye-sensitized solar cell

This paper presents response surface methodology （RSM） as an efficient approach for modeling and optimizing TiO2 nanoparticles preparation via co-precipitation for dye-sensitized solar cell （DSSC） perfor- mance. Titanium （IV） bis-（acetylacetonate） di-isopropoxide （DIPBAT）, isopropanol and water were used as precursor, solvent and co-solvent, respectively. Molar ratio of water, aging temperature and calcina- tion temperature as preparation factors with main and interaction effects on particle characteristics and performances were investigated, Particle characteristics in terms of primary and secondary sizes, crys- tal orientation and morphology were determined by X-ray diffractometry （XRD） and scanning electron microscopy （SEM）. Band gap energy and power conversion efficiency of DSSCs were used for perfor- mance studies. According to analysis of variance （ANOVA） in response surface methodology （RSM）, all three independent parameters were statistically significant and the final model was accurate. The model predicted maximum power conversion efficiency （0.14%） under the optimal condition of molar ratio of DIPBAT-to-isopropanol-to-water of 1 ： 10：500, aging temperature of 36 C and calcination temperature of 400 ℃. A second set of data was adopted to validate the model at optimal conditions and was found to be 0.14 ± 0.015%, which was very close to the predicted value. This study proves the reliability of the model in identi（ving the optimal condition for maximum performance.     

Design optimization of guide vane for mitigating elbow erosion using computational fluid dynamics and response surface methodology

A 90° elbow equipped with guide vanes was developed with the intent of reducing elbow erosion. Numerical models were formed to predict the maximum erosion rate of elbow and Face-1, and the response surface methodology was used to study the relationship between the erosion rate and structural parameters of guide vane. A second-order response surface model was established to determine the relationship between R₁ and variables, and a reduced cubic (RC) polynomial model was obtained to reveal the relationship between R₂ and the three factors. The numerical results show that the low-speed region is expended and the maximum discrete particle matter (DPM) concentration is reduced after installing the guide vane. This internal component provides a shelter for the elbow from the direct impact of high-speed solids.     

Modeling and optimization of the parameters affecting the in-situ microencapsulation process for producing epoxy-based self-healing anti-corrosion coatings

Micro/nanocapsules of urea–formaldehyde resin loaded with linseed oil, which are a self-healing agent in glass flake epoxy anti-corrosion paint, were prepared using a combination of ultrasonic homogenization and in-situ polymerization. The main objective of this study was to model and optimize the microencapsulation process. Five-level central composite design was used to design, model, and optimize the microencapsulation process. A quadratic model was constructed to show the dependency of the percentage of encapsulated linseed oil and capsule size, as model responses, on the studied independent variables (the rotational speed of the agitator and the power and duration of sonication). Analysis of variance showed that all of the variables have significant effects on the encapsulated linseed oil percentage, while the rotational speed of the agitator and sonication time is effective variables for controlling the capsule size. Under the determined optimum conditions, a maximum encapsulated linseed oil percentage (ELO%) of 93.9% and a minimum micro/nanocapsule size of 0.574 μm were achieved at 594 rpm agitation, 350 W sonication power, and 3 min sonication time. Validation of the model was performed. The percentage relative errors between the predicted and experimental values of the ELO% and micro/nanocapsule size are 1.28% and 3.66%, respectively. The efficacy of the optimum micro/nanocapsules in healing cracks in a glass flake epoxy paint and corrosion protection was investigated by the salt spray test and Tafel polarization technique.     

Experimental and statistical assessments of the mechanical strength reliability of gamma alumina catalyst supports

The mechanical strength of solid catalysts is considered an important factor in terms of ensuring the reliable performance of industrial reactors. In this work, a pelletizing method was used to form gamma alumina support for catalysts. Response surface methodology (RSM) was employed to analyze and model the effects of various manufacturing parameters on the crushing strength of the supports. These parameters were binder concentration, compaction pressure, calcination temperature, and drying mode. The suggested model was verified by applying an analysis of variance to assess its validity with regard to crushing strength. The mechanical reliability of various supports was also determined by calculating their Weibull modulus values through linear regression of the Weibull equation. The material with the highest mechanical strength reliability will have both a high mean crushing strength and a high Weibull modulus, and the best values obtained for a support in this work were 70.7 MPa and 6.63, respectively. The conditions used to form this sample were: 20 mass% binder concentration, 861 MPa compaction pressure, 466 °C calcination temperature, and gentle drying.     

Bonded-particle model calibration using response surface methodology

The bonded-particle model (BPM) is commonly used in numerical analysis of the mechanical behavior of rock samples. Constructing a BPM model requires specification of a number of microstructural parameters, including the parallel-bond tensile strength, parallel-bond cohesion strength, parallel-bond effective modulus, parallel-bond friction angle, and parallel-bond stiffness ratio. These parameters cannot be easily measured in the laboratory or directly related to either measurable or physical material parameters. Hence, a calibration process is required to choose the values to be used in simulations of physical systems. In this study, response surface methodology along with the central composite design approach is used to calibrate BPMs. The sensitivities of the microparameters related to the uniaxial compressive strength (UCS) and elasticity modulus (i.e., the macroscopic responses of the models) are thoroughly scrutinized. Numerical simulations are performed to carefully assess the performance of the model. It is found that the elasticity modulus is highly correlated with the parallel-bond effective modulus. In addition, the parallel-bond tensile and cohesion strengths are the two most significant microparameters with a considerable effect on the UCS. The predicted values determined by the proposed approach are in good agreement with the observed values, which verifies the applicability of the proposed method.     

基于响应面方法的桁架截面敏度分析和优化

把响应面方法引入桁架截面优化中,将应力和位移约束近似表达为桁架截面倒变量的线性函数。为拟合响应面,基于中心复合和单纯形试验设计方法开发了中心对称和拟单纯形试验设计两种方法,既可保证约束近似精度,又降低了结构分析计算量。对于桁架结构重量目标函数,直接推出倒变量的二阶形式,以桁架重量最小为目标的优化问题构造为标准的二次规划模型。将响应面方法计算的位移对设计变量的敏度与莫尔积分方法的近似显式进行了对比。以MSC.Patran为平台的数值算例表明:结合响应面方法,应用序列二次规划对问题进行寻优,其收敛精度及稳定性都可获得保障。     

Composite microcapsules with enhanced mechanical stability and reduced active ingredient leakage

A calcium shellac (CS) matrix was used to encapsulate polymeric melamine formaldehyde microcapsules (A) or CaCO₃ nanoparticles-stabilized microcapsules (B), both of which encapsulated an oil-based active ingredient, producing A–CS or B–CS composite microcapsules. The mechanical properties and oil release profiles of the composite microcapsules were evaluated. The composite microcapsules showed enhanced mechanical stability and reduced leakage of the active ingredient by one order of magnitude.     

海上溢油迁移转化的双层数学模型

海上溢油的双层数学模型将泄漏在海域中的溢油考虑为表层油膜和分布在整个水体中的悬浮 油滴两层组成. 采用Lagrangian追踪法模拟油膜的输移扩散. 在此方法中,油膜可用大量的小油滴表示,对每个油滴都规定随时间而变化的坐标系,油滴 的运动受到风、潮流和周围油的浓度影响. 油的迁移过程包括对流、扩展、湍动扩 散、附着在岸边以及沉降到海底等过程. 转化过程包括挥发、溶解、乳化等. 此外,光化学反应、生物降解能够改变油的特征以及减小油的污染. 该模型可以用于瞬时和连续溢油的情况,不仅可以用于模拟油,也可以模拟其它与油的密度 相近的有害物质的泄漏. 水动力学模型采用美国普林斯顿海洋模式(POM). 该溢油模型已应用于渤海海峡突发性溢油事故的模拟与预报.     

Hydrodynamics of a tandem fish school with asynchronous undulation of individuals

We perform numerical simulations using immersed boundary method for flow over a single and two fish in tandem performing traveling wave like motion for a range of Strouhal numbers. We investigate the hydrodynamic performance of single- and tandem-fish configurations using unsteady profiles of lateral side-force and drag coefficients, their time-averaged values, and wake behind these bodies. We present the spectra of hydrodynamic forces and find that the nature of these forces for a single fish resembles to those of stationary/oscillating bluff bodies and oscillating airfoils. For tandem cases, we vary the phase speed of undulatory motion of the rear fish while keeping the free-stream velocity constant. We show that hydrodynamic forces of the upstream and rear fish contain harmonics which are produced by nonlinear interaction of the oscillation frequencies of both fish. We find that the wake and time-averaged drag of the upstream fish remain almost independent of the undulating frequency of the rear fish at a certain Strouhal number. We also relate this observation with the absence of oscillation frequency of the rear fish in the Fourier spectra of hydrodynamic forces of the upstream fish. For the complete range of parameters, it is inferred that swimming in a tandem configuration seems more beneficial for the upstream fish. It happens due to wake-splitting effect of the rear fish that causes an enhancement of pressure in its wake. For the rear fish, it gains an advantage of drafting under certain conditions and its performance deteriorates at Strouhal numbers greater than 0.40.     

姿控飞轮轴承供油器设计与精准供油分析

姿控飞轮转子系统是飞行器飞行姿态的重要控制部件,对轴承精准润滑与供油可靠性提出了严格要求。基于固体间隙密封的反向设计原理,本文设计了一种依靠离心力自动调节轴承供油率的微型供油器,充分利用两个轴承之间的狭小空间,结构简单且可靠性高。首先建立了供油速率的流固耦合理论分析模型,得到了供油速率的半解析解,研究了供油器过盈接触面的几何参数等对供油速率的影响规律,发现供油器的供油速率与供油量可以通过优化过盈配合界面的几何尺寸、表面粗糙度和过盈配合压力等来实现精确控制,供油速率与过盈接触界面名义间隙的立方和周向长度成正比,与润滑油粘度和接触面轴向宽度成反比。供油率与轴承转速的平方成正比,使得轴承在高速运转时可以自动得到足够的润滑油。此技术可以应用于航天航空器的精密姿控飞轮系统以及其他各类精密轴承转子系统的供油设计。     

On Bone Mechanics,Modelling and Optimization

Analysis, evolution and layout in bone mechanics are described as seen from an optimal design and solid mechanics perspective. Anisotropic behaviour and three-dimensional modelling are necessary and focus is therefore put on the aspects of dealing with a large number of material parameters. The tools of homogenization, inverse homogenization and some basic results from optimal structural design are described.     

Numerical study of a well boat operating at a fish farm in long-crested irregular waves and current

The dynamic response of a coupled well boat–fish farm system in irregular long-crested waves and current is analyzed numerically in the time domain. The main purpose is to investigate the influence of the well boat on the fish farm and then to determine the operational conditions of the well boat.The numerical study of slow-drift sway motion of the well boat is performed at first. Hydrodynamic and statistical theories are briefly introduced. The cross-flow principle is assumed valid for evaluating the transverse viscous loads and the needed cross-sectional drag coefficients are estimated empirically and validated against available experiments. The mean value and standard deviation of the slow-drift motion from time domain agree well with those from frequency domain when equivalent linearized drag damping is incorporated.The coupled system with the well boat placed at the weather side of the fish farm is then analyzed in detail. Special attention is paid to two critical response variables, i.e., maximum anchor-line loads and maximum floating collar stresses. Numerical results show that the examined two variables will increase more than 300% due to the well boat in moderate exposure sea states. A sensitivity analysis is also carried out to identify the important parameters influencing these two response variables. Cross-sectional drag coefficients for the well boat and fish-farm related parameters (pretension load in the anchor lines and anchor-line stiffness) have moderate influence on the two variables. Simplifying the modeling of the coupled system, for instance neglecting the net cage and the first-order motion, has more effect on the maximum anchor load than on the maximum floating-collar stress and reduced sensitivity is observed in current, especially for the latter variable.Lastly, the operational conditions of the well boat are determined through systematic simulations. Numerical results show that the maximum loads in the mooring lines are moderate compared with the corresponding breaking limits even in high exposure sea states, while for the maximum stress in the floating collar can be close to the yield stress when operating in moderate exposure regions.     

Drying of porous oil shales

Rate processes including change of phase are modelled analytically for a half-space porous substance exposed to a jump in external temperature. The model predicts, in a closed form, the pressure build-up and the rate of evaporation of volatiles from a porous matrix. It assumes two distinct regions separated by a moving interface where the change of phase takes place. One region maintains its initial concentration of volatiles while the second is devoid of volatiles. Different thermophysical properties are considered for the two regions. The model was applied for the evaporation of moisture from oil-shale. Results are given in a parametric form     

Optimization of energy extraction in transverse galloping

A numerical method to analyse the stability of transverse galloping based on experimental measurements, as an alternative method to polynomial fitting of the transverse force coefficient C_z, is proposed in this paper. The Glauert–Den Hartog criterion is used to determine the region of angles of attack (pitch angles) prone to present galloping. An analytic solution (based on a polynomial curve of C_z) is used to validate the method and to evaluate the discretization errors. Several bodies (of biconvex, D-shape and rhomboidal cross sections) have been tested in a wind tunnel and the stability of the galloping region has been analysed with the new method. An algorithm to determine the pitch angle of the body that allows the maximum value of the kinetic energy of the flow to be extracted is presented.     

Optimization of jet parameters to control the flow on a ramp

This study deals with the use of optimization algorithms to determine efficient parameters of flow control devices. To improve the performance of systems characterized by detached flows and vortex shedding, the use of flow control devices such as oscillatory jets are intensively studied. However, the determination of efficient control parameters is still a bottleneck for industrial problems. Therefore, we propose to couple a global optimization algorithm with an unsteady flow simulation to derive efficient flow control rules. We consider as a test case a backward-facing step with a slope of 25°, including a synthetic jet actuator. The aim is to reduce the time-averaged recirculation length behind the step by optimizing the jet blowing/suction amplitude and frequency.     

Numerical study of a well boat operating at a fish farm in current

Dynamic response of a well boat operating at a fish farm in current is investigated numerically. An objective is to determine the operational conditions of the well boat. In terms of the fish farm, a realistic set-up (with single cage) is considered, including a floating collar, an elastic sinker tube, a flexible-closed net cage and a complex mooring system. A time-domain solution is used to find the steady configuration and response. Transverse viscous current loads are estimated using the cross-flow principle. The drag coefficients are obtained empirically by considering cross-sectional details, free surface and three-dimensional (3D) flow effects. The drag force is experimentally validated. The effect of the ship wake on the net loading is also assessed.The most critical scenario with the well boat placed at the weather side of the fish farm is analyzed in detail. Critical response variables for operational limits are the maximum anchor-line tensions and floater stresses. Numerical results show that the anchor loads will increase more than 40% in small current velocities and up to 90% in high current velocities due to the viscous current loads on the boat. There is also a strong increase of the floating collar deformations and stresses when the well boat is in contact with the floating collar.A sensitivity analysis has been carried out to identify the physical parameters affecting the anchor loads and the maximum stress in the floating collar. From our studies, the anchor loads are more sensitive to current direction, bottom weight system, sinker tube depth and mooring line properties (pretension load, anchor chain weight, etc.) and less sensitive to other parameters such as floating collar stiffness and cross-sectional drag coefficients of the well boat. The shading effect of the well boat on the fish-farm inflow has been examined and appeared not negligible with 4% to 10% reduction of the anchor loads for the studied current conditions. The maximum stress in the floating collar is sensitive to well-boat loads related parameters (current direction, cross-sectional drag coefficient) and pretension load in the anchor line; not so sensitive to net loading related parameters such as sinker tube depth and sinker tube weight.Lastly, the operational conditions of the well boat at the fish farm were discussed. Numerical results show that the maximum stresses in the floating collar should be of major concern. The loads in the mooring lines are moderate compared with the corresponding breaking limits.     

Optimization and numerical investigation of an excavator carrier

The excavator carrier is a device for moving the excavator. There are many operational benefits in using this carrier to transport excavators safely, easily, and efficiently. An earlier model of this carrier is manufactured and in tests showed that the design needs to be improved. In this paper, a finite element method is used to model and analyze this carrier and optimize the design for better performance. The static and dynamic analysis is done to optimizing carrier design for removing the defect that identified in practical test. The goal of optimization is to increase the carrier's life, increase the safety of transportation, decrease the cost, and finally, commercialize the product. The results show that the carrier's weight is decreased by up to 30%. Also, a holder and lock system in the back of the carrier is designed for increasing the transportation safety and the stiffness of the carrier chassis. The effect of increasing a suspension system is studied, the idea is using leaf spring. The numerical results show that using the suspension system increases the carrier's life by up to 30% while adding a suspension system increases manufacturing costs by up to 10%.     

A numerical method for the evaluation of Fourier integrals

This paper suggests the use of spline function interpolation in the evaluation of Fourier integrals. At the same time, the numerical results of some common functions by various interpolation methods and a simplified method of construction of spline function for various boundary conditions are also presented.     

Optimization of LiMn2O4 electrode properties in a gradient- and surrogate-based framework

In this study, the effects of discharge rate and LiMn2O4 cathode properties (thickness, porosity, particle size, and solid-state diffusivity and conductivity) on the gravimetric energy and power density of a lithium-ion battery cell are analyzed simultaneously using a cell-level model. Surrogate-based analysis tools are applied to simulation data to construct educed-order models, which are in turn used to perform global sensitivity analysis to compare the relative importance of cathode properties. Based on these results, the cell is then optimized for several distinct physical scenarios using gradient-based methods. The comple-mentary nature of the gradient-and surrogate-based tools is demonstrated by establishing proper bounds and constraints with the surrogate model, and then obtaining accurate optimized solutions with the gradient-based optimizer. These optimal solutions enable the quantification of the tradeoffs between energy and power density, and the effect of optimizing the electrode thickness and porosity. In conjunction with known guidelines, the numerical optimization frame-work developed herein can be applied directly to cell and pack design.     

基于响应面模型的薄壁构件耐撞性优化设计

建立了薄壁构件的结构耐撞性优化模型，通过试验设计在设计空间中选择少量样本获得设计的响应特性，建立响应面模型，并应用Pareto遗传算法进行结构耐撞性的优化设计。