High-Tg porous polyimide films with low dielectric constant derived from spiro-(adamantane-2,9′(2′,7′-diamino)-fluorene)

Porous polyimide (PI) films with low dielectric constants and excellent thermal properties have been a pressing demand for the next generation of high-performance, miniature, and ultrathin microelectronic devices. A series of novel porous PI films containing fluorenyl-adamantane groups were prepared successfully via thermolysis of poly(ethylene glycol) (PEG) added in the PI matrix. The cross-sectional morphologies of porous PI films showed closed pores with diameters ranging from 135 to 158 nm, which were uniform and regular in shape without interconnectivity. These porous PI films exhibited excellent thermal properties with a glass-transition temperature at 376 °C whereas the 5% weight loss temperature in air excess of 405 °C due to enhanced rigidity afforded by fluorenyl-adamantane groups. Accompanied by thermolysis content of PEG increasing from 0 to 20 wt %, the density of porous PI films decreased, and the corresponding porosity grew significantly from 0 to 11.48%. Depending on porosity, the dielectric constant and dielectric loss of porous PI films significantly declined from 2.89 to 2.37 and from 0.050 to 0.021, respectively. These excellent properties benefit the as-prepared porous PI films for application as interlayer dielectrics, integrated circuit chips, or multichip modules in microelectronic fields. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47313.     

复合外加剂改性盐石膏的研究

盐石膏的主要成分为无水硫酸钙,其活性差、凝结硬化慢、强度低,需要添加活性剂来激发盐石膏的活性。通过复合外加剂对盐石膏加以改性,并通过XRD和SEM对其作用机理做了分析。结果表明,单掺脱硫石膏和建筑石膏均能缩短盐石膏的凝结时间,建筑石膏的效果较好,但掺量不宜过高。复掺建筑石膏和缓凝剂时,两者比例要控制得当,适宜的建筑石膏和缓凝剂掺量分别为50%和0.10%~0.12%（质量分数）。分析可知,大掺量建筑石膏会增加盐石膏硬化体中二水相和针棒状晶体的含量;缓凝剂掺量的增加,会降低盐石膏硬化体中二水相的含量,棱形晶体增多,从而降低了盐石膏的强度。     

一种改进的新三步搜索算法

在对三步法工作原理进行研究的基础上提出了新三步搜索算法（NITSS）。该方法充分利用视频序列运动矢量概率分布上的中心偏置特性．在三步搜索算法的基础上引入了十字型分布的4个点构成搜索点群。实验结果表明。新三步搜索算法解决了三步法的小运动估计效果较差问题．提高了搜索精度，保持了三步法的高效率。     

试论融资租赁项下的进口贸易

阐述了当前跨国公司在合同中普遍采用的融资租赁的性质及融资租赁项下的进口贸易特点。     

机械结构动态改进技术在电动机振动噪声防治中的应用

本文介绍了结构实验模态分析、灵敏度分析和局部结构改进分析等先进的结构动态改进技术的基本原理,并由此对Y112M-4型电动机的机座进行了计算和分析,确定出一个结构改进方案.经实际改进试验验证,这一改进可有效地抑制电动机电磁振动和电磁噪声的传递,具有明显的减振降噪作用.     

多量程数据采集记录装置的设计

通常的数据采集与记录装置不易实现多量程测量。通过对标度方程进行分析得知,要改变量程只须改变两个参数——标度因子和量程下限。我们设计了一个使用单片机的多量程数据采集和记录装置,能处理多达256种量程。本文叙述了算法分析、硬件和软件的设计以及该装置的性能指标。     

Sulfur distribution in coke and sulfur removal during pyrolysis

In order to investigate the mechanisms of coke desulfurization by blowing additional gas into coking chamber during pyrolysis process, some experiments were conducted to study the effects of some factors on the distribution of sulfur in coke. These factors include pyrolysis temperatures, the kinds of the blowing gases and the diameters of coking chamber. It was found that sulfur was mainly released at the range of 300–600 °C. Under this temperature range, the sulfur content in coke can be reduced by 0.05–0.06% by blowing N₂, CO or CH₄, and by 0.14% by blowing H₂ at a space velocity of 1.2 mm/s compared with the absolute sulfur content of 0.92% in the case without gas feeding. Obviously, H₂ is more effective on sulfur removal than N₂, CO or CH₄. The total, organic and inorganic sulfur contents in coke increase with increasing the diameter of coking chamber under identical pyrolysis conditions. Both organic and inorganic sulfur contents in coke increase regularly from the center to brim at identical height of a coke column for all the cases. In addition, the organic and inorganic sulfur contents at the cranny surface are higher than those in interior at the same sampling position. X-ray photoelectron spectroscopy (XPS) analyses suggest that the main contributions to the increase of inorganic and organic sulfur contents are due to the formation of negative bivalent sulfur and thiophenic compounds, respectively.     

Zr元素对CoCrCuFeMn高熵合金组织及耐磨性能的影响

高熵合金突破以一种或两种元素作为基元的传统合金设计理念,以等摩尔比或近等摩尔比制备出具有简单相结构且综合性能优异的多主元合金,有望使金属材料的性能极限和应用空间得到进一步拓展。为了研究元素掺杂对合金物相结构、显微组织和耐磨性能的影响机理,采用真空熔炼法制备出等摩尔比的CoCrCuFeMn和CoCrCuFeMnZr高熵合金。利用XRD、OM、SEM、EDS、显微硬度计和摩擦磨损试验机测试了Zr元素添加前后CoCrCuFeMn合金的物相结构、显微组织、硬度和耐磨性。研究发现：添加Zr元素后CoCrCuFeMnZr合金的物相结构由原来的两种FCC相转变为两种HCP相,显微组织明显细化,仍为典型的树枝晶结构。两种合金的摩擦曲线都呈现先增大后降低再稳定的变化趋势,添加Zr元素后合金的摩擦因数与质量损失率分别从原来的0.57、4.14%降低到0.47、0.49%,显微硬度从219.6HV提高到983.5HV。结果表明：合金相结构发生HCP转变主要与凝固过程中易于形成富含大原子半径Zr元素的粗糙固液界面和之字型为主的HCP位向关系有关。Cu在晶间区域富集的原因在于其熔点最低、电负性最大、原子半径仅次于Zr,且与除Zr外的所有合金元素均具有相应最大的正混合焓,故而使其在凝固最晚的晶间区域聚集。Mn元素偏析系数最小是由于其熔点仅高于Cu和具有除Zr外最大的电负性差,且与Co和Zr之间存在负的混合焓,而与Cu之间具有最大正混合焓,不利于其进行长程扩散和进入领先相的点阵格位所致。Zr元素添加使合金硬度和耐磨性大幅提高则是由于细晶强化、固溶强化和相结构转变所致。     

典型高耗能工业用户发用电经济优化建模及调节潜力研究

高能耗企业具有丰富的可调节资源,研究典型工业用户在分时电价下的发用电行为,可为价格型需求响应策略的制定起引导作用.首先,研究不同发电设备的生产约束,并且重点分析不同负荷之间的生产关系、时序关系与调节特性等问题,建立工业用户的发电成本、负荷转移成本与净电费成本模型,并形成典型工业用户发用电经济优化模型.其次,结合3类典型工业用户的生产特性,分别建立满足其特定约束条件下的发用电经济优化模型.最后,通过算例证明方法的有效性,并研究价格变化时不同工业用户的发用电调节策略,对比分析其调节潜力.     

SSLB500型高压电缆铝护套立式双轴连续包覆机的研制

金属护套是交联聚乙烯绝缘高压电缆的重要组成部分,介绍了高压电缆铝护套现有生产工艺及设备的特点;基于四通道连续包覆工艺,开发了SSLB500型高压电缆铝护套立式双轴连续包覆机,检测了挤出铝护套的尺寸和性能,分析了生产数据。研制结果表明:基于数值模拟优化结果设计的工模具结构合理,铝护套成型圆度达到99%,厚度偏差在±5%之内,焊合区域结合强度达到78.8 MPa,延伸率达到33.3%,与非焊合区性能相同;设备长时间运行稳定可靠,主轴转速在6~7.5 r/min时,平均产量达到738 kg/h,平均能耗440 k Wh/t,溢料率小于7%。综合数据表明,所开发的四通道连续包覆工艺及设备具有产品质量好、生产效率高、运行成本低的优点,满足电缆制造企业提质增效的需求。