Experimental research on air film formation behavior of air cushion belt conveyor with stable load

In this paper, the air film formation behavior of air cushion belt conveyor with stable load is studied. The air cushion field is analyzed by means of theoretical derivation, numerical simulation and experimental research. An intelligent experiment platform is developed. Three dimensional pressure distribution of air film and the air film thickness distribution along the conveyor belt in the width direction are obtained. The experimental result is analyzed by comparing with theoretical calculation and numerical simulation. The numerical and theoretical results are in good agreement with those obtained from experiments. The air film formation behavior pattern of air cushion belt conveyor with stable load is presented. The optimized film thickness and pore distribution are obtained based on the comprehensive energy consumption. This study provides a basis for the optimization design of air cushion belt conveyor.     

基于Copula函数的失效相关构件可靠度计算

相关性可靠度的计算是可靠性工程的重点和难点。利用刻画相关性最有力的工具Copula函数,给出关于失效相关构件可靠度计算的新方法(Copula-Reliability算法),验证多模式失效的机械零件可靠度值是介于独立假设理论计算值和薄弱环节理论计算值之间的一个连续变化过程,克服Dietlevsen窄界、主次失效模式、独立性假设等方法的局限性。该方法不需要确定n种失效模式的联合密度函数,且用n重差分运算代替n重积分运算,简化了计算。通过实例与别的方法进行比较,说明方法的有效性、精确性。     

港中浅层低电阻率油层成因及识别方法

针对港中浅层存在的低电阻率油层现象开展研究,分析了构造、岩性、地层水性质及钻井液性能等影响地层电阻率的主要因素,探讨了评价低电阻率油层的技术对策。通过综合利用测井、测试及地质资料开展精细地层对比,分析各套油水系统的分布规律,有针对性地进行油水层综合评价,突破传统油层评价观念束缚,充分挖掘各类油气信息,重新制定了该区的油气层解释图板,现场实施取得了比较好的效果,为该区类似油气层的重新评价提供了借鉴。     

动态调整技术在注聚开发中的应用与探讨

对下二门油田注聚区块不同生产阶段所采用的各种动态调整技术进行了研究和探讨,现场应用效果良好,提高了聚驱开发效果,对其它同类油田的聚驱开发具有借鉴意义.     

Crystalline structure and morphology in uniaxially oriented polypropylene film modified with nanosilica

Silica‐polypropylene (PP) composite resins were prepared with nanosilica particles and PP resin through melt blending. This composite resin was used to prepare uniaxially oriented PP film under certain conditions. Surface and cross‐section morphologies of the PP films were analyzed by SEM, while the crystalline phase, crystalline orientation, and grain size of the PP films were analyzed by X‐ray diffraction (XRD). Crystallinity was analyzed by differential scanning calorimetry (DSC). The mechanical properties, heat resistance, and barrier properties of the film were tested and analyzed. The PP melts formed shish‐kebab structure when subjected to shearing or stretching at near‐melting temperatures. The ratio of the intensity of the XRD of 040 crystal surface to that of the 110 crystal surface was greater than 0.71. The modified polypropylene melt was subjected to tensile action at 30°C on a cooling roller, resulting in a specially oriented structure. However, the ratio of the intensity of the XRD of the 040 crystal surface to that of the 110 crystal surface did not change. Under the same processing conditions (ie, low cooling temperature and high unidirectional tension), a transverse 040 wafer was formed on the surface of the unmodified film, but polypropylene film modified by nanosilica was not found. The fiber‐like shish‐kebab structure with regular arrangement appeared on the film. The change in the microstructure of the modified polypropylene film resulted in a material with excellent mechanical properties, toughness, barrier property, and heat resistance.     

玉米秸秆微晶纤维素的制备及其性质

以玉米秸秆为原料,研究其提取制备微晶纤维素的工艺及产品性能。探讨酸解温度、硫酸体积分数、酸解时间对微晶纤维素聚合度及得率的影响,并对微晶纤维素的理化性质进行了分析。结果表明:玉米秸秆微晶纤维素最佳制备工艺条件为:反应温度85℃,硫酸体积分数8%,水解时间90 min,此时制得微晶纤维素聚合度为292,纯度92.6%,得率76.48%,结晶度为74.5%。在此条件下,玉米秸秆微晶纤维素在保留形态结构的同时具有较高的结晶度和热稳定性,具备较好的应用性能和价值。     

基于属性和图形匹配的案例检索技术的研究与应用

为了实现弹体案例的快速准确检索,文章将用于互联网3D图形搜索技术引用到案例检索过程中来,并且将其与传统的基于属性的匹配算法结合起来,提出了一种新的综合匹配算法。与现有的案例检索算法相比,基于属性和图形的综合匹配算法可以更加全面地反映出案例之间的相似性。通过案例研究表明,该算法可以快速、方便地对弹体成形工艺案例库进行检索。     

Applying vermiculite‐modified polypropylene film to flexible packaging material

This article presents a process for preparing organovermiculite by ball‐milling expanded vermiculite (EVMT) in water‐based ethylene vinyl acetate (EVA) latex. In this process, the vermiculite (VMT) is exfoliated to prepare a kind of EVMT/EVA modifying agent, in which EVA serves as both intercalating polymer into VMT and compatibilizer between VMT and polypropylene (PP). During melt blending between EVMT/EVA and PP, shear force exfoliates VMT sheets, dispersing them relatively well in the PP matrix. Compared with raw PP, EVMT‐modified cast polypropylene (CPP) are better when EVMT loading ranged from 0.5 to 1.0%, with improvement in both the strength and toughness of the EVMT/EVA‐modified CPP film. Specifically, tensile strength was increased by 44–54%, yield stress increased by 26%, stress at break increased by 37–43%, energy at break (toughness) increased by 29–34%, oxygen transmission rate decreased by 6.2–12.9%, the water vapor transmission rate was not significantly affected, the peel bond strength of laminated CPP film increased by 18–27%, and the processability and melt flow index (MFI) of EVMT/EVA/PP composites were improved as well. Increasing MFI attributes facilitated the processing and formation of EVMT/EVA/PP. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40954.     

Numerical simulation of gurney flaps lift-enhancement on a low reynolds number airfoil

Two-dimensional steady Reynolds-averaged Navier-Stokes(RANS) equations with transition shear stress transport(SST) model were solved to investigate the effects of Gurney flaps on the aerodynamic performance of a low Reynolds number airfoil. This airfoil was designed for flight vehicles operating at 20 km altitude with freestream velocity of 25 m/s. The chord length(C) of this airfoil is 5 m and the corresponding Reynolds number is 7.76×10~5. Gurney flaps with the heights ranging from 0.25%C to3%C were investigated. It has been shown that Gurney flaps can enhance not only the prestall lift but also lift-to-drag ratio in a certain range of angles of attack. Specially, at cruise angle of attack(3°), Gurney flap with the height of 0.5%C.can increase lift-to-drag ratio and lift coefficient by 1.6% and 12.8%, respectively. Furthermore, the mechanisms of Gurney flaps to improve the aerodynamic performance were illustrated by analyzing the surface pressure distribution, streamlines and trailing-edge flow structure for this low Reynolds number airfoil. Specially, distinguished from some other numerical researches, the flow details such as the laminar separation bubble and transition phenomena for low Reynolds number airfoil with Gurney flaps were investigated and it was found that Gurney flaps can delay the transition onset position at small angles of attack(≤2°). However, with the increase of angles of attack, Gurney flaps will promote the boundary layer transition.