Numerical Simulation and Superplastic Forming of Ti-6Al-4V Alloy for a Dental Prosthesis

This article investigates superplastic forming (SPF) technique in conjunction with finite element (FE) simulation applied to dental repair. The superplasticity of Ti-6Al-4V alloys has been studied using a uniquely designed five-hole test with the aim of obtaining the modeled grain size and the flow stress parameters. The data from the five-hole test are subsequently put into the FE program for the simulation of a partial upper denture dental prosthesis (PUD4). The FE simulation of the PUD4 is carried out to set up appropriate input parameters for pressing due to the SPF process being fully automatic controlled. A variety of strain rates ranging from 2.4 × 10⁻⁵ to 1 × 10⁻³ s⁻¹ are selected for the characterization of superplastic properties of the alloy. The Superflag FE program is used to generate an appropriate pressure-time profile and provide information on thickness, grain size, and grain growth rate distribution. Both membrane elements and solid elements have been adopted in the simulation and the results from both types of elements are compared. An evaluation of predicted parameters for the SPF of the prosthesis is presented.     

Mechanical,thermal expansion,and flammability properties of co-extruded wood polymer composites with basalt fiber reinforced shells

Basalt fiber (BF) filled high density polyethylene (HDPE) and co-extruded wood plastic composites (WPCs) with BF/HDPE composite shell were successfully prepared and their mechanical, morphological and thermal properties characterized. The BFs had an average diameter of 7 μm with an organic surfactant surface coating, which was thermally decomposed at about 210 °C. Incorporating BFs into HDPE matrix substantially enhanced flexural, tensile and dynamic modulus without causing a noticeable decrease in the tensile and impact strength of the composites. Micromechanical modeling of tensile properties for the BF/HDPE composites showed a good fit of the selected models to the experimental data. Compared to neat HDPE, BF/HDPE composites had reduced linear coefficient of thermal expansion (LCTE) values. The use of the pure HDPE and BF/HDPE layers over a WPC core greatly improved impact strength of core–shell structured composites. However, the relatively less-stiff HDPE shell with large LCTE values decreased the overall composite modulus and thermal stability. Both flexural and thermal expansion properties were enhanced with BF reinforced HDPE shells, leading to well-balanced properties of core–shell structured material. Cone calorimetry analysis indicated that flammability performance of core–shell structured composites was improved as the BF content increased in the shell layer.     

Characterisation of the mechanical properties of pultruded fibre-reinforced polymer tube

This paper presents an investigation on the mechanical properties of pultruded fibre-reinforced polymer (FRP) tube. Unlike typical FRP tube, the investigated tube has additional ±45° glass fibre reinforcement making it suitable for several structural applications. Tests on coupons and full-scale specimens were undertaken to determine the mechanical properties of the tube. Moreover, a finite element (FE) analysis was carried to simulate the compressive and flexural behaviours of full-scale specimen. Experimental results showed that coupon and full-scale specimens exhibited linearly elastic up to failure. The maximum variation of the experimental data is up to 8% indicating that the reproducibility of the test is quite reasonable and that the experimental procedures were conducted within the acceptable margin of error. The comparison between the compressive and flexural peak load values obtained experiment and FE methods revealed that their difference is less than 5%. Furthermore, the compressive and flexure failure modes obtained from the experiment were fairly simulated in the FE analysis. These indicated that FE analysis predicted reasonably the actual compressive and flexural behaviours of the pultruded FRP tube.     

Hierarchical optimization of boiler–turbine unit using fuzzy stable model predictive control

This paper develops a hierarchical control system structure based on the Takagi–Sugeno fuzzy model to achieve an optimal control of a boiler–turbine unit. In the upper layer of the hierarchy, an optimal reference governor is designed to find the optimal operating point. A disturbance term is introduced to the fuzzy model to lump the modeling mismatch and unknown disturbance. Thus, the effect of plant behavior variation can be removed and the operating point found can be feasible to control. In the lower layer, a stable model predictive controller is developed to track the optimal set-points while guaranteeing the input-to-state stability of the system. Fuzzy Lyapunov function and appropriate slack and collection matrices are used to reduce the conservatism of stability design and improve the performance. Through the estimation of the disturbance term using an observer, the two layers in the hierarchy are coupled and the integrated system can realize a dynamic optimal control of the boiler–turbine unit, even in the case of severe plant behavior variations.     

Performance enhancement and load reduction of a 5 MW wind turbine blade

A wind turbine rotor blade, based on the U.S. National Renewable Energy Laboratory (NREL) 5 MW reference turbine, is optimized for minimum cost of energy through simultaneous consideration of aerodynamics and bend-twist coupling. Eighty-three total design variables are considered, encompassing airfoil shapes, chord and twist distributions, and the degree of bend-twist coupling in the blade. A recently developed method requiring significantly less computation than finite element analysis is used for planning and predicting the bend-twist coupling behavior of the rotor. Airfoil performance is computed using XFOIL, while the wind turbine loads and performance are computed using the NREL FAST code. The objective function is annual cost of energy (COE), where reductions in flapwise bending loads and blade surface area are assumed to decrease rotor cost through reduced material requirements. The developed optimization process projects decreased blade loads while maintaining wind turbine performance.     

Removal of several metal ions from aqueous solution using powdered stem of Arundo donax L. as a new biosorbent

Arundo donax L., a member of Poaceae, was washed, dried, selected, pulverized, and then used for removal of Cu(II), Cd(II), Ni(II), Pb(II) and Zn(II) from aqueous solution. Series batch experiments were conducted to investigate the effects of contact time, pretreatment, particle size of biomass and solution pH on the biosorption capability of A. donax L. powder. The desorption characteristics and renewability of the biomass were also studied. The applicability of Langmuir and Freundlich isotherms was examined for the experimental data, so did the pseudo-first-order, pseudo-second-order and Elovich kinetic models. Results showed that alkali-treated A. donax L. biomass was more appropriate to be the bio-material for biosorption when compared to acid-treated, washed and virgin A. donax L. Owing to its fast adsorption rate, high uptake capacity and the renewability of facility, stem of A. donax L. treated with NaOH seems to be a promising biosorbent for removal of heavy metals from wastewater.     

比较香港肝癌分期和巴塞罗那肝癌分期对TACE后生存的预测作用

【摘要】 目的 比较香港肝癌分期（HKLC）和巴塞罗那肝癌（BCLC）分期对TACE治疗原发性肝癌预后判断能力的差别。方法 回顾性分析2008年8月—2015年12月间182例初发的行TACE治疗的原发性肝癌患者，按两种分期方法完成分期评分，Kaplan- Meier分析计算两种分期方法各分期间的中位生存时间，并计算各分期系统似然比（LR）χ2值、赤池信息量准则（AIC）和Harrell C值。结果 两种分期方法各分期间的生存时间差异有统计学意义（P＜0.001）。HKLC分期系统的AIC、LR χ2及Harrell C值分别是1 360、66.6、0.813，而BCLC的AIC、LR χ2及Harrell C值分别为1365、61.8、0.772。结论 相对于BCLC分期，HKLC分期更适合预测国内行TACE治疗的原发性肝癌患者的生存时间。