一种含Ru镍基单晶高温合金的组织特征

对一种含3%Ru(质量分数,下同)的第四代镍基单晶高温合金的热处理态组织中的γ′相尺寸及分布情况、亚晶及嵌镶结构、γ/γ′两相点阵错配度、γ′相体积分数等进行了表征.X射线衍射实验结果表明,该合金不是一种完整的单晶合金,而是由许多相邻平均取向偏差为0.5°左右、最大取向偏差为3°左右的亚晶组成,亚晶存在亚晶界.每一个亚晶又是由大量的嵌镶结构组成,嵌镶结构之间的取向偏差为0.1°-0.2°.实验结果表明,这种合金的热处理态组织中存在明显的组织不均匀现象,呈枝晶状分布.该合金的平均γ′相尺寸为0.39μm,平均γ′相体积分数为69.5%,平均γ/γ′两相点阵错配度为-2.0×10~3.讨论了这种合金热处理态组织的演变规律.     

Influence of CuO nanoparticles in enhancing the thermal conductivity of water and monoethylene glycol based nanofluids

In this paper the effect of CuO nanoparticles on the thermal conductivity of base fluids like mono ethylene glycol and water was studied. Both the base fluids showed enhancement in effective thermal conductivity. This enhancement was investigated with regard to various factors; concentration of nanoparticles, types of base fluids, sonication time and settlement time. For both the base fluids, an improvement in thermal conductivity was found as concentration of nanoparticles increased due to interaction between particles. It was also found that as the sonication time was increased, there was furthermore an improvement in the thermal conductivity of the base fluids. Effect of base fluids is the complex idea to understand. Lower base fluid's viscosities are supposed to contribute grater enchantment, but another factor of fluid nanoparticles surface interaction also more important. The experimentally measured thermal conductivities of base fluid's nanoparticles suspension were compared to a variety of models (Maxwell, Hamilton–Crosser and Bruggeman Model). It is observed that none of the mentioned models were found to predict accurately the thermal conductivities of nanofluids.     

压力变化对洗涤室内气泡特性影响的数值模拟研究

为了更好地揭示洗涤冷却室内气体穿越液池时的气液两相的传热和传质特性,尤其是压力对气泡特性的影响这一至今尚未解决的关键问题,运用流体体积（VOF）模型进行了动态数值模拟。建立了从数值模拟结果中提取湿周和气含率信息的方法,并对压力影响进行了系统的分析研究,研究结果表明：总湿周随压力的升高而显著加长;同一压力下,液池中的平均气含率和平均湿周长从池底向上逐渐地升高;同一高度上,平均气含率和平均湿周随压力的升高而增加。获得了洗涤过程中湿周随压力的变化规律。     

Study of the relationship between nanofluid＇s stability and conductivity

基于Maxwell电磁理论中电解质悬浮液中粒子质量分数和电导率之间的关系,提出了一种判定纳米流体悬浮稳定性的方法,并进行了实验验证。实验中,采用＂两步法＂经超声振荡制备了CuO/去离子水纳米流体。利用电导率仪测量了不同质量分数时纳米流体的电导率,建立了质量分数与电导率的关系,同时研究了温度对电导率的影响。结果表明电导率随着颗粒质量分数的增加而增加,随着质量分数的减小而减小;随着温度的增长,电导率只有微小变化,可以忽略温度对电导率的影响。     

纳米流体悬浮稳定性和电导率的关系研究

基于Maxwell电磁理论中电解质悬浮液中粒子质量分数和电导率之间的关系,提出了一种判定纳米流体悬浮稳定性的方法,并进行了实验验证。实验中,采用"两步法"经超声振荡制备了CuO/去离子水纳米流体。利用电导率仪测量了不同质量分数时纳米流体的电导率,建立了质量分数与电导率的关系,同时研究了温度对电导率的影响。结果表明电导率随着颗粒质量分数的增加而增加,随着质量分数的减小而减小;随着温度的增长,电导率只有微小变化,可以忽略温度对电导率的影响。     

鳙鱼酶解物体外抗氧化的研究

利用碱性蛋白酶Alcalase对鳙鱼进行控制酶解,制备出具有清除自由基活性的酶解物并比较其还原能力和对脂肪氧合酶活性的影响,并考察其对红细胞溶血、肝线粒体肿胀的影响,结合不同处理后肝脑组织中MDA浓度的测定以对鳙鱼酶解物在模拟体系中的抗氧化活性进行综合评价。结果表明三种鳙鱼酶解物的肽提取率均在70%以上且主要由寡肽(含5～6个氨基酸残基)组成,三种酶解物均具有一定的还原能力,在较高浓度时能抑制脂肪氧合酶的活性并可在体外抑制因H2O2引发的新西兰家兔红细胞溶血和由FeSO4和Vc诱导的肝线粒体肿胀,同时降低肝脑组织中MDA的产生。说明鳙鱼酶解物在一定浓度范围内具有抗氧化作用,比较三种酶解物的抗氧化特性可知酶解物C具有较强的综合抗氧化能力,可作为后续研究的材料。     

OFDM系统中频域同步技术及FPGA实现

针对OFDM系统频域中的整数倍频率偏移、小数倍频率偏移、采样钟频率偏移和定时偏移等问题,本文提出了相应的解决方案,并采用FPGA对各方法进行硬件电路实现.这些硬件实现方法巧妙,估计精确,能节省大量硬件资源.通过实际的电路时序波形仿真验证,证明了这些方法的实用性.     

海藻酸钠-壳聚糖复合膜中溶氧扩散性能研究

氧气在微胶囊膜中的扩散行为将直接决定微囊内细胞的生长代谢行为.以海藻酸钠-壳聚糖聚电解质复合平板膜为研究模型,利用渗透池法,重点考察溶氧在膜中的扩散行为及其影响因素.结果显示:复合膜的扩散系数和孔隙率均低于海藻酸钙,复合膜中溶氧扩散系数为(7～13)×10-10m2·s-1,为水中的23.3％～43.3％,孔隙率为93％～97％;扩散系数随海藻酸钠特性黏度的增大而减小,随壳聚糖分子量的增大而减小.微胶囊膜是氧传质主要的阻力部位,孔隙率、三维结构和材料极性是影响扩散性能的重要因素,改变海藻酸钠特性黏度和壳聚糖分子量可以改变膜孔隙率、结构和材料极性,进而调节膜扩散性能.     

钢筋钢纤维混凝土连梁的变形特点

通过4个不同钢纤维体积率的钢筋混凝土连梁在低周反复荷载作用下的试验,测试了连梁在低周反复荷载作用下钢筋应变和侧向位移,分析了钢纤维对连梁中钢筋应变和侧向位移的影响规律.研究结果表明:钢纤维对连梁的纵向钢筋应变、箍筋应变和侧向位移影响明显;随着钢纤维体积率的增大,钢筋的极限应变和连梁的极限位移都显著增大.     

Symbolic representation for analog realization of a family of fractional order controller structures via continued fraction expansion

This paper uses the Continued Fraction Expansion (CFE) method for analog realization of fractional order differ-integrator and few special classes of fractional order (FO) controllers viz. Fractional Order Proportional-Integral-Derivative (FOPID) controller, FO[PD] controller and FO lead–lag compensator. Contemporary researchers have given several formulations for rational approximation of fractional order elements. However, approximation of the controllers studied in this paper, due to having fractional power of a rational transfer function, is not available in analog domain; although its digital realization already exists. This motivates us for applying CFE based analog realization technique for complicated FO controller structures to get equivalent rational transfer functions in terms of the controller tuning parameters. The symbolic expressions for rationalized transfer function in terms of the controller tuning parameters are especially important as ready references, without the need of running CFE algorithm every time and also helps in the synthesis of analog circuits for such FO controllers.