Fuel combustion test in constant volume combustion chamber with built-in adaptor

Combustion tests of pre-mixture of methane and air in constant volume combustion chamber(CVCC) have been carried out by means of flame propagation photo and gas pressure measurement,the effects of CVCC body temperature,intake pressure of pre-mixture of methane and air,equivalence ratio and location of the built-in adaptor have been investigated.The whole combustion chamber can be divided into two parts,i.e.the upper combustion chamber and the lower combustion chamber,by the built-in adaptor with through hol...     

铝合金ADC12Z高压铸造过程中铸件与铸型间界面热交换系数的研究

通过采集高压铸造过程中铸型内部温度的变化曲线,采用热传导反算法,求解了以铝合金ADC12Z为铸件材料的铸件-铸型界面换热系数,分析了该界面换热系数随铸件厚度的变化规律.计算及分析结果表明:在压铸过程中,铸件-铸型界面换热系数迅速升至最大值,随后下降,凝固结束后趋于稳定.铸件厚度增大不仅提高了换热系数,而且对换热系数的变化趋势也有很大影响.同时,不同厚度的铸件,其固相率和冷却速率的变化规律也有较大区别.     

基于动态特性的剑杆织机共轭凸轮开口机构的设计方法

重新建立了共轭凸轮开口机构的动力学模型,组成相应的弹性振动微分方程.用矩阵摄动法分析该微分方程,并设计织机的开口机构.与传统的求解方法相比,计算时间减少20%,减小综框的振动以及降低断纬频率达到65%以上.     

Shop-floor scheduling at shipbuilding yards using the multiple intelligent agent system

The intelligent agent system has become a typical approach to research distributed artificial intelligence and distributed problem solving. However, despite its various technical advantages, the distribution and expansion of the intelligent agent system approach has been limited because existing methodologies rely on specialized applications and therefore require intensive investment to develop new systems. In an attempt to conquer these difficulties, a standardized methodology to construct intelligent agent systems is proposed. This approach deviates from current agent system approaches of repeatedly constructing new and customized expert systems. Specifically, it provides an economical method for developing intelligent agent systems by investigating the possibility of standardizing message communication protocols in linguistics speech-act theory and by supplementing traditional algorithmic systems with intelligent segments using, among others, expert system tools. To verify effectiveness, the shop-floor scheduling system of a large-scale shipbuilding yard has been redesigned, developed, and tested using this approach. This shop-floor scheduling system requires the scheduling of when and where to process block construction under various constraints. It is a difficult four-dimensional time and space allocation problem involving traditional NP-complete search spaces. The tested intelligent agent system proposes an innovative method for reducing the search space into three levels: the algorithm level, the agent intelligence level, and the level of cooperation among agents. It also provides methods for solving deadlock occurrence and non-uniformity problems resulting from parallel processing. Test results demonstrate applicability and economy, among other technical advantages.     

Study on photocatalysis of TiO 2 nanotubes prepared by methanol-thermal synthesis at low temperature

TiO₂ nanotubes were synthesized by the solvothermal process at low temperature in a highly alkaline water–methanol mixed solution. Their characteristics were identified by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), specific surface area (BET), Fourier transform infrared spectroscopy (FTIR) and UV–Vis absorption spectroscopy. The as-prepared samples were tested by the photodegradation reaction of methylene blue (MB) dye under visible-light irradiation. The ratios of methanol and water, as well as calcination temperature, affected the morphology, nanostructure and photocatalytic performance. The methanol solvent plays an important role in improving crystallization of the anatase phase, which affects the photocatalytic reaction. Titanate nanotubes were synthesized in methanol–water volume ratios of 10:90, 20:80 and 30:70 which still had high absorbability. Titania nanotubes formed at a calcination temperature of 300 °C using methanol–water volume ratio of 30:70 showed highest photocatalytic performance, much higher than that using water solvent and TiO₂–P25 powder.     

Milling parameter optimization through a discrete variable transformation

Although milling is one of the most common chip metal removal processes, little has been done to aid in identifying the optimum operational conditions for milling processes. In this paper, a mathematical model for milling operations is developed and the five primary control variables identified. The model is then decomposed and an efficient optimization procedure developed for control variable identification.     

Etching characteristics of thin SiON films using a liquefied perfluorocarbon precursor of C6F12O with a low global warming potential

Perfluorocarbon gas is widely used in the semiconductor industry. However, perfluorocarbon has a negative effect on the global environment owing to its high global warming potential (GWP) value. An alternative solution is essential. Therefore, we evaluated the possibility of replacing conventional perfluorocarbon etching gases such as CHF₃ with C₆F₁₂O, which has a low GWP and is in a liquid state at room temperature. In this study, silicon oxynitride (SiON) films were plasma-etched using inductively coupled CF₄ +C₆F₁₂O+O₂ mixed plasmas. Subsequently, the etching characteristics of the film, such as etching rate, etching profile, selectivity over Si, and photoresist, were investigated. A double Langmuir probe was used and optical emission spectroscopy was performed for plasma diagnostics. In addition, a contact angle goniometer and x-ray photoelectron spectroscope were used to confirm the change in the surface properties of the etched SiON film surface. Consequently, the etching characteristics of the C₆F₁₂O mixed plasma exhibited a lower etching rate, higher SiON/Si selectivity, lower plasma damage, and more vertical etched profiles than the conventional CHF₃ mixed plasma. In addition, the C₆F₁₂O gas can be recovered in the liquid state, thereby decreasing global warming. These results confirmed that the C₆F₁₂O precursor can sufficiently replace the conventional etching gas.     

铝合金压铸过程铸件/铸型界面换热行为的研究Ⅱ.工艺参数对界面换热的影响

基于本文第1部分的数学模型,求解了各种工艺参数下铸件/铸型间的界面热流和换热系数,重点研究不同工艺参数对于界面热流和换热系数的影响.在现有的"阶梯"块铸件的条件下,计算结果表明:压铸过程各种工艺参数对于铸件/铸型界面热流和换热系数有着不同的影响规律.铸型初始模腔表面温度对于界面热流的峰值有着很大的影响,随着铸型初始模腔表面温度的上升,热流峰值不断下降.对于较厚的"阶梯"面,铸型初始模腔表面温度对于界面换热系数的影响较大,随着该温度的上升,界面换热系数的峰值不断下降;对于较薄的"阶梯"面,各种工艺参数对于界面换热系数的影响不大.