挤压的热平衡及温度变化

温度是挤压工艺的最重要的参数之一。提高温度,金属变形抗力减小,但同时易于导致局部温度过高,引起低熔点共晶和多相组织熔化,以及制品表面粗糙,限制了最大挤压速度。挤压过程中温度的变化取决于:锭坯加热湿度,锭坯向挤压筒的热传导以及变形和摩擦热效应。     

金属板材成形中拉深损伤模拟的两种求解方法

讨论用数值模拟预测板材成形中发生拉深损伤破坏的两种不同的求解方法。第一种是采用完全耦合的弹塑性破坯模型的动力显式数值方法。基于状态参量的不可逆热力学过程 ,完全耦合的本构方程考虑各向同性强化和拉深。这些已引入有限元软件ABAQUS/E用于对金属成形的模拟。在数值技术方面 ,隐式积分方法被用来对本构方程的局部时间积分 ,动力显式技术用于求解总体平衡方程。第二种方案是采用简化的损伤模型的方法 ,被称为逆法 (InveseApprch)。I.A被限定在考虑各向同性强化和损伤的塑性全量理论基础上的简单的本构关系。做比例加载和临界损伤达到以后的损伤饱和假定 ,可以得到损伤演化方程的封闭解。这两种损伤模型在编程中的实施采用两种方式 :计算中考虑或不考虑损伤作用 ,也就是耦合的或非耦合的计算。文中给出一些算例来说明每种损伤模型的优点     

Desiderata for Languages to be Used in the Defnition of Reference Business Processes

In many modern enterprises, explicit business process de nitions facilitate the pursuit of business goals in such ways as best practice reuse, process analysis, processe ciency improvement, and automation. Most real-world business processes are large and complex. Successfully capturing, analysing, and automating these processes requires process de nition languages that capture a variety of process aspects with a wealth of details. Mostcurrent process modelling languages, such as Business Process Modelling Notation (BPMN),focus on structural control ows among activities while providing inadequate support for other process de nition needs. In this paper, we rst illustrate these inadequacies through our experiences with a collection of real-world reference business processes from the Aus-tralian lending industry. We observe that the most signi cant inadequacies include lack of resource management, exception handling, process variation, and data ow integration.These identi ed shortcomings led us to consider the Little-JIL language as a vehicle forde ning business processes. Little-JIL addresses the afore-mentioned inadequacies with a number of innovative features. Our investigation concludes that these innovative features are e ective in addressing a number of key reference business process de nition needs.     

Electrolytic cell engineering and device optimization for electrosynthesis of e-biofuels via co-valorisation of bio-feedstocks and captured CO2

Utilizing CO₂ in an electro-chemical process and synthesizing value-added chemicals are amongst the few viable and scalable pathways in carbon capture and utilization technologies.CO₂ electro-reduction is also counted as one of the main options entailing less fossil fuel consumption and as a future electrical energy storage strategy.The current study aims at developing a new electrochemical platform to produce low-carbon e-biofuel through multifunctional electrosynthesis and integrated co-valorisation of biomass feedstocks with captured CO₂.In this approach,CO₂ is reduced at the cathode to produce drop-in fuels(e.g.,methanol)while value-added chemicals(e.g.,selective oxidation of alcohols,aldehydes,carboxylic acids and amines/amides)are produced at the anode.In this work,a numerical model of a continuous-flow design considering various anodic and cathodic reactions was built to determine the most techno-economically feasible configurations from the aspects of energy efficiency,environment impact and economical values.The reactor design was then optimized via parametric analysis.     

Improvement of porous polyvinylidene fluoride-co-hexafluropropylene hollow fiber membranes for sweeping gas membrane distillation of ethylene glycol solution

Porous polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) hollow fiber membranes were fabricated through a wet spinning process. In order to improve the membrane structure, composition of the polymer solution was adjusted by studying ternary phase diagrams of polymer/solvent/non-solvent. The prepared membranes were used for sweeping gas membrane distillation (SGMD) of 20 wt% ethylene glycol (EG) aqueous solution. The membranes were characterized by different tests such as N₂ permeation, overall porosity, critical water entry pressure (CEP_w), water contact angle and collapsing pressure. From FESEM examination, addition of 3 wt% glycerol in the PVDF-HFP solution, produced membranes with smaller finger-likes cavities, higher surface porosity and smaller pore sizes. Increasing the polymer concentration up to 21 wt% resulted in a dense spongy structure which could significantly reduce the N₂ permeance. The membrane prepared by 3 wt% glycerol and 17 wt% polymer demonstrated an improved structure with mean pore size of 18 nm and a high surface porosity of 872 m^-1. CEP_w of 350 kPa and overall porosity of 84% were also obtained for the improved membrane. Collapsing pressure of the membranes relatively improved by increasing the polymer concentration. From the SGMD test, the developed membrane represented a maximum permeate flux of 28 kg·m^-2·h^-1 which is almost 19% higher than the flux of plain membrane. During 120 h of a long-term SGMD operation, a gradual flux reduction of 30% was noticed. In addition, EG rejection reduced from 100% to around 99.5% during 120 h of the operation.     

Synthesis and optimization of high surface area mesoporous date palm fiber-based nanostructured powder activated carbon for aluminum removal

Date palm fiber (DPF) derived from agrowaste was utilized as a new precursor for the optimized synthesis of a cost-effective, nanostructured, powder-activated carbon (nPAC) for aluminum (Al3+) removal from aqueous solutions using carbonization, KOH activation, response surface methodology (RSM) and central composite design (CCD). The optimum synthesis condition, activation temperature, time and impregna-tion ratio were found to be 650 ℃, 1.09 hour and 1:1, respectively. Furthermore, the optimum conditions for removal were 99.5％and 9.958 mg·g-1 in regard to uptake capacity. The optimum conditions of nPAC was analyzed and characterized using XRD, FTIR, FESEM, BET, TGA and Zeta potential. Moreover, the adsorption of the Al3+ conditions was optimized with an integrated RSM-CCD experimental design. Regression results revealed that the adsorption kinetics data was well fitted by the pseudo-second order model, whereas the adsorption isotherm data was best represented by the Freundlich isotherm model. Optimum activated carbon indicated that DPF can serve as a cost-effective precursor adsorbent for Al3+removal.     

2-Hydroxy-1, 4-napthoquinone solubilization,thermodynamics and adsorption kinetics with surfactant

2-Hydroxy-1,4-napthoquinone(lawsone) natural red-orange dye was extracted from fresh henna(Lawsonia inermis) leaves in an alkaline media.The lawsone-surfactant solubilization constants(K_(LS))were calculated for the first time by using cationic cetyltrimethylammonium bromide(CTAB) and anionic sodium dodecyl sulphate(SDS).The standard free energy,concentration of solubilized lawsone and number of lawsone molecules solubilized into micelles were calculated and discussed.Surface excess,minimum surface area per molecule,surface pressure,free energy(adsorption and aggregation) and equilibrium constants of different states were determined from tensiometry.Different metal ions(Ag~+,Co~(2+),Cu~(2+),Ni~(2+),Fe~(3+),Zn~(2+) and Al~(3+)) were used to determine the complex forming ability with lawsone.Out of these,Ag~+ ions have strong binding capacity with lawsone.The adsorption of lawsone on the surface of glass with silver ions in presence of CTAB was also observed at pH 9.0.The pseudo-first, secondorder kinetic equation,intraparticles diffusion and Elovich models were used to determine the kinetics of lawsone adsorption onto the surface of glass and a probable mechanism has been discussed.Lawsone adsorption followed second-order kinetic equation(k_2=0.019 g·mg~(-1)·min~(-1)).     

Sulfamic acid functionalized slag for effective removal of organic dye and toxic metal from the aqueous samples

Surface functionalization of blast furnace slag with sulfamic acid(a zwitterion) was performed for the removal of Cr~(3+) and methylene blue dye(MB) from water samples. The slag functionalization process was optimized using Response Surface Methodology Design. Statistical analysis of the parameters that include the sulfamic acid amount(A), reaction time(B), and temperature(C) revealed that(A) increase had a negative effect on the adsorption of both pollutants by the zwitterion slag, whereas(B) and(C)increase presented a positive impact. At the optimum condition of 2 g sulfamic acid amount, 50 min reaction time and 37 °C temperature, the prepared slag showed a removal efficiency of more than 90% for both Cr~(3+) and MB. Surface characterization by SEM/EDS, FTIR, XPS and surface area analyser, showed an improvement in surface properties and the incorporation of zwitterionic NH_2~+ and S@O groups of sulfamic acid. Adsorption isotherm and kinetic studies conducted with the zwitterion slag showed the adsorption process was suited to Freundlich isotherm model and pseudo-second-order kinetic model.The thermodynamic study conducted revealed the spontaneity of the process based on the calculated negative DG(Gibb's free energy) values. The prepared zwitterion slag offered easy regeneration with dilute HCl solution and showed a considerable removal(Cr3+: 65% and MB: 80%) for both pollutants even after 3 cycles of usage.     

Radiation-absorption,chemical reaction,Hall and ion slip impacts on magnetohydrodynamic free convective flow over semi-infinite moving absorbent surface

The investigation of radiation-absorption,chemical reaction,Hall and ion-slip impacts on unsteady MHD free convective laminar flow of an incompressible viscous,electrically conducting and heat generation/absorbing fluid enclosed with a semi-infinite porous plate within a rotating frame has been premeditated.The plate is assumed to be moving with a constant velocity in the direction of fluid movement.A uniform transverse magnetic field is applied at right angles to the porous surface,which is absorbing the fluid with a suction velocity changing with time.The non-dimensional governing equations for present inves-tigation are solved analytically making use of two term harmonic and non-harmonic functions.The graphical results of velocity,temperature and concentration distributions on the analytical solutions are displayed and discussed with reference to pertinent parameters.It is found that the velocity profiles decreased with an increasing in Hartmann number,rotation parameter,the Schmidt number,heat source parameter,while it increased due to an increase in permeability parameter,radiation-absorption param-eter,Hall and ion slip parameters.However,the temperature profile is an increasing function of radiation-absorption parameter,whereas an increase in chemical reaction parameter,the Schmidt num-ber Sc or frequency of oscillations decrease the temperature profile on cooling.Also,it is found that the concentration profile is decreased with an escalating in the Schmidt number or the chemical reaction parameter.     

Densities and excess molar volumes of mixtures containing diesel,biodiesel and alkanols at temperatures from 288.15 to 313.15 K

The present work is focusing on the synthesization and physico-chemical properties of Jatropha curcas biodiesel with diesel and alcohols.The densities of binary diesel (2)+1-alkanols (C_3 or C_4)(3) and ternary Jatropha curcas biodiesel (1)+diesel (2)+1-alkanols (C_3or C_4)(3) blends have been reported over full range of composition at temperatures within range 288.15 to 313.15 K.Also densities of Jatropha curcas biodiesel (1)+diesel or 1-alkanols (C_3 or C_4)(2) blends have been measured at 313.15 K.Excess molar volumes,V~E,V~E_(123)of binary and ternary blends were calculated from the measured data and the derived properties were correlated to composition using Redlich–Kister equation.A reasonable agreement was found between the measured and estimated values.Further,densities and excess molar volumes data were reasoned to discuss molecular interactions taking into consideration effect of composition and temperature.