C72DA盘条拉拔断裂分析

针对C72DA盘条拉拔过程中产生笔尖状和斜劈状断口的现象,对盘条进行化学成分分析,并采用金相检验和扫描电镜观察相结合的方法,研究出现断裂的原因。结果表明,C72DA盘条轧制或中丝热处理不当使索氏体含量偏低,是造成盘条拉拔断丝呈笔尖状断口的主要因素;盘条内部出现显微孔洞缺陷也是造成笔尖状断口的因素。盘条边部存在异常组织或拉拔不当易形成斜劈状断口。提出应加强生产过程控制,防止出现粗片状珠光体、莱氏体及高温淬火等异常组织,以提高产品质量。     

LX72A帘线钢盘条开发

介绍LX72A帘线钢盘条开发过程。通过改良LF炉精炼渣系及优化连铸二冷参数等工艺手段,有效降低钢水中的夹杂物含量,缓解连铸方坯的碳偏析;在轧制过程中,通过优化加热炉的空燃比,以弱还原性气氛缓解方坯表面脱碳现象,使盘条表面局部总脱碳层厚度小于0.05 mm,采用开轧温度960～1 000℃,入精轧温度850～880℃,吐丝温度880～910℃,辊道速度0.95 m/s的轧制工艺,使盘条索氏体化率超过85%。生产的5.5 mm热轧盘条抗拉强度为1 040～1 100 MPa,伸长率不小于15%,断面收缩率大于44%,其综合质量通过了贝卡尔特测评机构的专业测评,盘条顺利拉拔至0.22 mm,经捻制合股后完全满足钢帘线使用要求。     

VS2005下昆虫飞行磨数据分析软件设计

利用通信控件(MSComm)实现PC机与设备之间串行通信,应用图表控件(TeeChart)和表格控件(UltimateGrid72)实现显示、对比等分析功能,对昆虫飞行数据进行收集,设计了基于普通计算机的飞行磨软件.本软件也可用于其他数据的收集及控制.     

Hydrogen production by methane decomposition: Origin of the catalytic activity of carbon materials

A wide variety of carbon materials (ordered mesoporous carbons, carbon blacks, activated carbon, carbon nanotubes, coke and graphite) have been investigated as catalysts for hydrogen production by methane decomposition, with the aims of identifying the carbon properties which control in a greater extension the catalytic activity and determine the nature of the active sites involved in the reaction.The catalytic activity of the different carbon materials was determined and compared using temperature-programmed experiments in a thermobalance. The initial activity was followed through the threshold temperature, defined as the temperature at which hydrogen production starts being detected, whereas the average reaction rate was also calculated and compared. The lowest threshold temperature was observed with ordered mesoporous carbons (CMK materials), followed by activated carbon and carbon blacks. On the other hand, at long reaction times activated carbon was quickly deactivated yielding a relatively low average reaction rate. The deactivation process seems to be greatly linked to the presence of micropores while the long-term activity is retained in those materials with ordered mesoporosity (CMKs) or formed by nanoparticles (carbon blacks), which make them more resistant to deactivation by the formation of carbonaceous deposits.Whereas no clear dependence is observed between the threshold temperature and the surface area neither with the presence of polar groups in the carbon catalysts, characterization of these materials by XPS shows that a direct relationship exists with the amount of defects present on the graphene layers. This fact strongly supports that these defects are the main active sites for methane decomposition over carbon catalysts.     

Cavitation erosion behaviour of 20SiMn low alloy steel in Na2SO4 and NaHCO3 solutions

Most of the former studies on cavitation erosion (CE) in corrosive media were carried out in NaCl solutions. In contrast, the effects of and ions, which are dominant anions in most rivers of China, on cavitation erosion have not been investigated systematically. In this paper, the cavitation erosion behaviour of 20SiMn low alloy steel in Na₂SO₄ and NaHCO₃ solutions was investigated by using a magnetostrictive-induced CE facility. The micrographs of damaged surfaces were observed by scanning electron microscope (SEM). It was found that the CE rate of 20SiMn low alloy steel in 0.003% Na₂SO₄ solution was higher than that in 0.003% NaCl solution, but in 0.03%, 0.3%, and 3% solutions their CE rate was almost the same. The CE rate of 20SiMn low alloy steel in 0.003-3% NaHCO₃ solutions was higher than that in the equivalent 0.003-3% Na₂SO₄ and 0.003-3% NaCl solutions, which may be related to stress corrosion cracking or corrosion fatigue mechanism in NaHCO₃ solutions. The role of corrosion was analyzed by using polarization curves, electrochemical impedance spectroscopy (EIS), linear polarization resistance and the corrosion potential with or without cavitation. Independent of the test media, cavitation shifted the corrosion potential in the positive direction and strongly enhanced the cathodic current density in the polarization curves. In the interaction of cavitation erosion and corrosion, the corrosion-induced erosion component was predominant. Cavitation also greatly reduced the magnitude of impedance though the initial impedance under cavitation conditions in 3% NaHCO₃ solution was almost one order larger than that in 3% Na₂SO₄ solution.     

Flow boiling of FC-72 from a screen laminate extended surface matrix

An investigation is conducted to assess the thermal performance of multi-layered screen laminates when used as porous extended surface matrices (ESMs) in vertical up flow boiling. A dielectric coolant (FC-72) is used as the working fluid. Four specimens are constructed having different mesh-geometries and/or number of layers. Channel Reynolds numbers are varied from 2700 to 8500 and ESM base superheats are varied from 0 to 40 °C.Results indicate that devices equipped with this technology can tolerate steady heat fluxes in excess of 100 W/cm² (based on the base cross section area of the ESM) with corresponding ESM base superheats below 30 °C. Thermal performance (the increase in heat flux at a given superheat) increases by as much as 30% for a 3-fold increase in Reynolds number. The total capacity of the ESM (the product of heat flux and base cross section area) increases approximately linearly with ESM thickness. A feature of this technology is that it greatly extends the heat flux working range over an unenhanced surface.     

Compositions of invariant fuzzy implications

We examine sup-min compositions in a finite family of fuzzy implications. Since the composition of invariant fuzzy implications is an invariant function, then we get a kind of `multiplication table' for such implications. A multistage proof of such table is presented. As a result we obtain examples of finite semigroups of fuzzy implications.     

基于ST72F324的强排式燃气热水器控制系统

意法(ST)半导体公司的ST系列单片机近年来刚被引入我国,其在综合性能方面有一定特色,其中ST72F324是一款性价比很高的8位flash单片机.本方案充分利用了ST72F324的各种资源,简化了硬件设计,为燃气式热水器控制器提供了一种低成本高可靠性的解决方案.     

D72树脂催化合成柠檬酸三丁酯

以D72树脂为催化剂,以柠檬酸和正丁醇为原料合成柠檬酸三丁酯,对影响反应的因素进行研究。实验表明,柠檬酸三丁酯合成反应的最佳条件是：在n（正丁醇）：n（柠檬酸）=5：1,催化剂用量为20%（以柠檬酸质量计算）,反应6.5 h的条件下,产物的收率可达94.3%,催化剂重复使用5次。     

Urban sprawl and municipal budgets in Spain: A dynamic panel data analysis

Urban sprawl has recently become a matter of concern throughout Europe, but it is in southern countries where its environmental and economic impact has been most severe. This low‐density, spatially expansive urban development pattern can have a highly marked impact on municipal budgets. Thus, local governments may see sprawl as a potential source of finance, in terms of building‐associated revenues and increased transfers from upper tiers of government. At the same time, sprawl leads to increased levels of expenditure, as it may raise the provision costs of certain local public goods and requires greater investment in extending basic infrastructure for new urban development. What, therefore, is the net fiscal impact of urban sprawl? Do local governments consider the long‐run net fiscal impact of new urban growth or do they simply focus on its short‐term benefits, ignoring future development costs? This paper addresses these questions by analysing the dynamic relationship between urban sprawl and local budget variables. To do so, we estimate a panel vector autoregressive model using data for 4,000 Spanish municipalities for the period 1994–2005. Computed generalized impulse response functions show: (i) that sprawl considerably increases demand for new infrastructure; (ii) that the capital deficit generated by this new infrastructure is covered in the main by intergovernmental transfers and, to a lesser extent, by revenues linked to the real estate cycle; and (iii) that sprawl leads to a short‐term current surplus, as the increase in current revenues offsets the increase in current expenditures due to public service provision for new developments. Overall, these findings point to a moral hazard problem for local governments in which inordinate intergovernmental transfers and development revenues encourage excessive urban sprawl.