Thermal expansion coefficient tailoring of LAS glass-ceramic for anodic bondable low temperature co-fired ceramic application

The Li–Al–Si glass-ceramics were prepared by conventional glass-ceramic fabrication method. The influences of Na₂O content on the sintering property, microstructure, and coefficient of thermal expansion were investigated. The results show that the coefficient of thermal expansion of LAS glass-ceramics can be tailored to match that of silicon by the addition of Na₂O content. Na₂O has a remarkable influence on the crystallinity of Li–Al–Si glass-ceramic. The coefficient of thermal expansion of Li–Al–Si glass-ceramic is thus tunable between that of glass phase and crystal phase. The Si–O bond length change in stretch vibration modes introduced by Na₂O also contributes to the variation of coefficient of thermal expansion of the Li–Al–Si glass-ceramics. The coefficient of thermal expansion of the Li–Al–Si glass-ceramic with 1.5 wt% Na₂O addition is about +3.34 ppm/°C at 350 °C and shows a good compatibility to that of silicon in a wide temperature range, which makes it a promising candidate for anodic bondable low temperature co-fired ceramic substrate applications.     

平面桁架构建的定日镜面形支撑结构优化及实验

针对反射面成型的复杂影响因素，提出平面桁架构建的定日镜面形支撑结构优化技术路线. 利用模拟仿真、数值计算和优化算法等方法，解析20 m²定日镜面形定义技术路线的4个组成环节：面形规格及宽高比、上弦杆的截面矩、平面桁架组间距的最优值、机加工中工艺控制要点的量化. 试制小型定日镜进行实验，分析光斑形状和能流密度分布特性，并与理想球面形光斑比较，两者的拟合优度大于0.98. 实验结果表明，当反射镜宽高比取1.2，上弦杆截面矩取40 000 mm⁴，桁架组间距取950 mm，上弦杆和斜杆的开孔公差小于0.9 mm时，反射面形的质量提升. 研究从原理和实践上证明了该优化技术路线的可行性.     

干熄炉斜道区莫来石-红柱石砖的损毁研究

测试并比较了使用4年后干熄炉斜道区莫来石-红柱石过梁砖不同部位(炉腔侧、风道侧和芯部)砖体的体积密度、显气孔率、耐压强度、化学组成,利用XRD和SEM分别分析了其物相组成和显微结构变化,并对其损毁机制进行了探讨。结果表明:1)莫来石-红柱石砖原始强度较低,易遭受炉体结构应力和热应力破坏;2)与砖体芯部相比,炉腔侧和风道侧受环境气氛影响更大,结构更为疏松,强度下降更明显;3)高温下红柱石莫来石化导致的体积膨胀、低熔点相侵入形成的新物相以及弱还原气氛下SiO2的分解破坏了材料的结合体系,造成了材料致密度的降低和强度大幅下降,是除了炉体结构应力、热应力等因素外,导致干熄炉斜道区莫来石-红柱石砖破坏的不可忽略的因素。     

Inhibition of counterflow methane/air diffusion flame by water mist with varying mist diameter

In the present study, the effect of fine water mist on extinguishment of a methane–air counterflow diffusion flame was investigated to understand the underlying physics of fire extinguishment of highly stretched diffusion flame by water mist. Twin-fluid atomizers were used to generate polydisperse water mist of which Sauter mean diameters were 10, 20, 40, and 60 μm. When water mist is not added, the critical stretch rate at extinguishment is 439 s⁻¹ as compared to the theoretical value of 460 s⁻¹. For the case with water mist addition, when the stretch rate is small enough, almost all the water mist evaporates within the flame zone. On the other hand, for high stretch rate case, large mist droplets pass through the flame zone and can reach the stagnation plane. However, no oscillatory motion was found around the stagnation plane. Critical stretch rate at extinguishment decreases monotonously with the mass fraction of water mist independently of the mist diameter within the range of D₃₂ from 10 μm to 60 μm. On the other hand, with increase in the surface area parameter, the critical stretch rate at extinguishment decreases rapidly and becomes less sensitive at large surface area parameter, of which tendency is qualitatively in good agreement with theoretical predictions. For a constant surface area parameter, the critical stretch rate decreases with mist diameter because the mass fraction of water mist should increase in proportion to the mist diameter to keep the surface area parameter constant. When the water mist evaporates completely in the flame zone as in the present study, the mass fraction of the water mist is the dominant factor for fire extinguishment, rather than the surface area parameter. Therefore, an appropriate combination of stretch rate and water mist mass fraction should be provided to suppress effectively a given fire with a small amount of water mist.     

Design and Engineering of Open Weave Jute Soil Saver for Potential Application in the Field of Soil Erosion Control and Hill Slope Management

Out of several natural agents causing extensive damages to roads, landslides can claim to be a major destroyer. There are several causes for landslides such as hazardous ground conditions, landform configuration adversities, occasionally occurring natural physical forces and anthropogenic impact on the environment. In such vulnerable situations the top soil on hill slopes get disintegrated due to intensive precipitation or shaking due to tremors and eventually flows down rapidly down the slope. The situation deserves the search for a biocover which can reduce the velocity of overland flow and entrap detached soil particles thereby controlling top soil loss. Jute Geotextile (JGT) if properly designed can fulfill the said criteria besides facilitating growth of vegetation. This paper discusses optimization of property parameters of open weave Jute Geotextile in tune with different parameters of design concerning protection of hill slope along with comparative analysis of the results of different tests on one hand and determination of tolerance limit of the prime property parameters of the developed JGT samples, on the other, which have been employed in different case studies to prove their potentiality and technoeconomic viability.     

Amide-containing segmented copolymers

This review highlights the synthesis, physical properties, and emerging technologies of state-of-the-art segmented copolymers containing amide hydrogen bonding sites. Amide hydrogen bonding plays a crucial role in the physical properties associated with amide-containing segmented copolymers. Amide hard segments are accessible in many different forms from amorphous alkyl amides to crystalline aramids and greatly influence copolymer morphology and mechanical properties. Variations in copolymer structure allow for the fine tuning of physical properties and the ability to predict mechanical performance based upon structural modifications. This review includes various synthetic methods for producing well-defined amide-containing segmented copolymers as well as common applications. Also, the morphological and mechanical properties associated with modifications in copolymer structure are discussed.     

测井曲线标准化方法研究

由于长岭凹陷区经过近60年的勘探开发,再加上井场井眼条件的差异、测井系列、仪器刻度、测量时间及操作者不同等因素,使得各测井曲线存在系统误差。因此在开展储层参数研究和有效厚度划分时,为消除这些非地层因素对原始资料的影响,有必要对测井曲线进行标准化,以保证解释结果的合理性与可靠性。测井曲线标准化方法可以分为定性和定量两种类型。其中定性方法主要包括直方图法标准化校正、均值法标准化校正和重叠图法标准化校正;定量方法则为趋势面分析校正法。本论文利用Matlab软件,采用趋势面方法对研究区域内的井进行测井曲线标准化。结果表明经过趋势面法标准化校正能够消除不利因素,准确的提取出测井曲线中的各种有用地质信息。     

Impact behavior and fractographic study of carbon nanotubes grafted carbon fiber-reinforced epoxy matrix multi-scale hybrid composites

Carbon nanotubes are the most promising reinforcement for high performance composites. Multiwall carbon nanotubes were directly grown onto the carbon fiber surface by catalytic thermal chemical vapor deposition technique. Multi-scale hybrid composites were fabricated using the carbon nanotubes grown fibers with epoxy matrix. Morphology of the grown carbon nanotubes was investigated using field emission scanning electron microscopy and transmission electron microscopy. The fabricated composites were subjected to impact tests which showed 48.7% and 42.2% higher energy absorption in Charpy and Izod impact tests respectively. Fractographic analysis of the impact tested specimens revealed the presence of carbon nanotubes both at the fiber surface and within the matrix which explained the reason for improved energy absorption capability of these composites. Carbon nanotubes presence at various cracks formed during loading provided a direct evidence of micro crack bridging. Thus the enhanced fracture strength of these composites is attributed to stronger fiber–matrix interfacial bonding and simultaneous matrix strengthening due to the grown carbon nanotubes.     

超大面积混凝土地面结构无缝施工数值模拟研究

随着科技的发展和社会的进步,各种建筑物的规模都在大幅度提升,随之产生的大面积混凝土整体地面在建筑工程中得到了广泛的应用。为了预防和控制大面积混凝土地面裂缝的出现,无缝施工技术得到了越来越广泛的认可。该文以实际工程为依托,对短距离释放应力无缝施工技术进行了研究,利用有限元软件ABAQUS模拟分析施工过程中混凝土水化热与温度的关系,探究相邻混凝土浇筑块的温度传导关系,以期能对类似工程无缝施工起到一定借鉴作用。     

Study of using a multi-touch tabletop technology to facilitate collaboration,interaction, and awareness in co-located environment

This study aimed to evaluate how differently co-located users perform and interact while solving problems by using existing and newly developed interaction mechanisms of a multi-touch tabletop system on a large-size tabletop display. Furthermore, this study aimed to investigate users’ perceived situation awareness due to the system. This study conducted one experiment and introduced three newly developed interaction mechanisms: two-way rubber band, drag-and-response, and centre collection area. Two-way rubber band enables users not only to send but also to request digital objects. Drag-and-response allows users to accept or to reject digital objects sent by others; therefore, it eliminates conflicting situations and interference. Centre collection area stores, organises, and manages shared digital resources on a surface of a tabletop display, so that users have an overall picture of available resources. This paper discusses results of an experiment, research findings, and implications along with conclusions and several suggestions for future development and research.