Effect of austenite dispersion on phase transformation in dual phase steel

It was observed that ferrite carbide aggregate formation suppressed to cooling rates below 1 °C/s and a significant amount of austenite transformed to martensite even at the cooling rate of 0.1 °C/s (furnace cooling). The critical cooling rates for carbide formation is so low, compared with previous studies.     

可拓逻辑和可拓思维对决策树算法的分析与优化

为从理论层次上深度解析决策树分类算法的逻辑可行性,根据可拓理论中可拓逻辑和可拓思维的全新视角,对构建决策树过程中节点的选择、规则提取和预测等步骤,进行理论上的分析和评价.以可拓思维中的菱形思维模式来分析决策树算法中节点的选择,以可拓逻辑中基元变换理论来评价决策树算法的规则提取,以可拓逻辑中的基元发散规则来解释决策树算法的预测步骤,在验证决策树算法各个步骤符合可拓理论处理矛盾问题的思维模式的同时,也对决策树算法的分类结果建立了基于可拓理论的评价体系.     

高速内冷铣孔空蚀机理的数值模拟与实验研究

目的预测高速内冷铣孔过程中空蚀的发生,并初步揭示高速内冷铣削过程中铣刀空蚀失效机理及已加工工件表面的空蚀损伤机理。方法采用三维数值分析与实验相结合的方法,在建立高速内冷铣削封闭流场的基础上进行数值计算,搭建了高速内冷空蚀试验平台并进行实验,通过粗糙度仪对分段后工件样条的已加工表面进行测定,通过电子显微镜对实验后的分段工件样条已加工表面和铣刀形貌进行分析。结果仿真分析发现用40 mm立铣刀以14500 r/min转速铣削60 mm 50 mm孔时,流场中的含气率达到10%左右,预测了高速内冷铣削过程中空蚀现象的存在,空蚀后楔形发散区的孔壁粗糙度Ra为0.311~0.478 m,楔形收缩区的孔壁粗糙度Ra为0.138~0.317 m。工件已加工表面出现麻点和海绵状为主的空蚀针孔,铣刀侧后面出现蜂窝状和鱼鳞状的空蚀坑。结论仿真分析和实验共同验证了高速内冷铣削过程中空蚀现象的存在,空蚀位置可能出现在内冷铣刀侧后刀面及部分工件已加工表面,且铣刀侧后刀面空蚀程度远超工件已加工表面,为高速内冷切削加工过程中空蚀机理的研究提供依据。     

基于湛江地域文化的创意产品设计研究

目的探析湛江的地域文化资源,为设计开发具有显著湛江地域文化特色的文创产品提供有力的参考和支持。方法以湛江的地域文化为核心,对湛江文化资源进行分类;研究文创产品的具体属性,对湛江文创产品进行设计梳理;构建基于湛江地域文化的创意产品设计模型,并通过具体的设计案例进行展示。结论通过对湛江地域文化资源进行挖掘、整理、归纳,探析文化创意产品的属性,构建设计模型,为湛江地域文化创意产品的设计提供思路,有利于提升湛江地域文化和文创产品的双重价值。     

无机元素对生物质焦炭-CO2气化反应性的催化/抑制作用研究及模型构建

基于简单碰撞理论，建立了含有无机元素影响的焦炭气化反应动力学模型。建模过程中，考虑了七种无机元素含量、催化/抑制能力以及单一无机元素饱和催化倍率对焦炭反应性的影响。实验部分，选取四种生物质样品置于微型流化床反应器中测试了焦炭反应性，并与模型计算值进行了对比，结果表明模型能够较好预测焦炭反应性，同时表现出对不同样品的适应性。该模型能够通过输入样品特性参数和反应工况条件实现焦炭反应性的定量预测。该模型的建立表明固体燃料通用气化反应的规律是存在的，可以为进一步阐明气化反应规律提供理论参考。     

Performance and cost modelling taking into account the uncertainties and sensitivities of current and next-generation PEM water electrolysis technology

This paper presents a bottom-up approach to the assessment of model performance and costs of a proton-exchange-membrane electrolysis considering cell, stack and process levels. The cell voltage is modelled dependent on current density and detailed models for stack, investment and hydrogen costs are developed. Taking into account current research on PEM electrolysis, such as the use of thinner membranes or low precious metal loading on the electrodes, allows the prediction of next generation's efficiency and costs. By comparison of a current and next-generation PEM electrolysis, the effectiveness of individual development steps was assessed and remaining space for efficiency and cost improvement was identified. This can help to prioritize and to focus on development steps which are most effective.In the next generation, efficiency will be increased even at higher current density operation. Thus, specific stack costs will drop to less than half of present day costs which is decisive to achieve lower hydrogen production costs in the next generation. Specific installed costs and hydrogen production costs of the current and next generation are calculated for plant sizes up to 100 MW_DC and reveal significant cost decrease for plant capacities up to 25 MW_DC while only changing slightly for capacities larger than this.Costs are always subject to uncertainties due to model assumptions and boundary conditions that need to be defined. Uncertainties and the sensitivities of the model are estimated and assessed to provide an indication of the actual cost range. Main cost model uncertainties are identified to arise from membrane electrode and stack assembly costs, civil engineering and construction surcharge as well as the electrical system. Hydrogen costs are dominated by operating costs and therefore are highly sensitive to the annual operating hours and the electricity price, which have a greater impact on the hydrogen costs than the model assumptions for capital costs.     

Interface engineering and heterometal doping Co–Mo/FeS for oxygen evolution reaction

The sluggish kinetics of the oxygen evolution reaction (OER) limits the development of water electrolysis technology and the long-term efficiency of hydrogen energy production. In addition, it is important to evaluate the reconstruction performance of OER catalysts for actual water electrolysis. We created a self-supported electrode with FeS film coated Fe foam as a substrate, ordered resoluble molybdate (MoO₄²⁻) anions in interlayers, and Co-doped as a catalytically active phase for the OER. The catalyst is capable of electrochemical self-reconstruction (ECSR). With the dissolution of molybdate and sulfur ions, the catalyst surface cobalt iron oxide (CoFe₂O₄) forms an active amorphous FeCoOOH, which is favorable for alkaline OER. We realized the introduction of new active sites in the catalyst reconstruction process. Finally, the composite CoFeO_x catalyst increased the specific surface area, promoted bubble transport, and enhanced electron mass transfer. The synergistic coupling effect of the catalyst makes it have excellent OER activity and stability. Remarkably, Co–Mo/FeS nanosheets afforded an electrocatalytic OER with a current density of 100 mA cm⁻² at a low overpotential of 321 mV. These discoveries open up new opportunities for the application of doping and template-directed surface reconfiguration, which holds promise as an effective electrocatalyst for the OER.     

Hierarchically porous carbon from biomass tar as sustainable electrode material for high-performance supercapacitors

The byproduct tar from biomass gasification process had seriously impeded development and applications of this technology, thus novel path for biomass tar valorization is had been continuously pursued. Given its high carbon content, this work attempted to convert biomass tar into hierarchically porous carbon by thermal activation with acetate potassium. The optimal product produced with mass ratio of biomass tar to acetate potassium of 1:3 and activation temperature at 800 °C was revealed as excellent electrode material for high-performance supercapacitor, which demonstrated electrochemical capacitance up to 310.4 F/g at 0.2 A/g, whilst preserved 91% of initial capacitance after 5000 charge-discharge circles at current density of 5 A/g. These excellent properties had arisen from the open and hierarchical porosity and large surface area. This work disclosed the great potential of biomass tar as sustainable and competent candidate for fabricating high-performance electrode material for electrochemical energy devices, and may bring up new opportunities to development of biomass gasification technologies.