五种淡水鱼对固定气泡幕反应初探

观察了尼罗罗非鱼(Tilapia nilotica),鲢(Hypophthalmichthys moli-trix)、鳙(Aristichthys nobilis)、草鱼(Ctenopharyngodon idellus)和鲫鱼(Caras-sius auratus)等五种淡水鱼对固定气泡幕的反应,气泡幕对这五种鱼均有一定的阻拦作用,但阻挡效果不理想,阻拦率分别为:罗非鱼53％,鲢44.6％,鳙27.6％,草鱼23.3％,鲫鱼21.7％,该五种鱼对气泡幕均有明显的适应现象,随着实验时间的延长和实验重复次数的增加,阻拦率常呈下降趋势。     

Proliferation and differentiation into endothelial cells of human bone marrow mesenchymal stem cells （MSCs） on poly DL-lactic-co-glycolic acid （PLGA） films

Autologous, allograft and synthetic vessels currently used in clinical vessel replacement have many defi- ciencies, especially in the area of small caliber vessel replacement. The supply of autologous arteries or veins may not be sufficient or suitable fo…     

Experimental measurement of the electrical conductivity of single crystal olivine at high temperature and high pressure under different oxygen fugacities

At 1.0?4.0 GPa and 1123?1473 K and under oxygen fugacity-controlled conditions (Ni+NiO, Fe+Fe₃O₄, Fe+FeO and Mo+MoO₂ buffers), a YJ-3000t Model six-anvil solid high-pressure apparatus and a Sarltron-1260 Impedance/Gain-Phase analyzer were employed to conduct an in situ measurement of the electrical conductivity of single crystal olivine. Experimental results showed that: (1) within the range of experimentally selected frequencies (10³?10⁶ Hz), the electrical conductivity of the sample is of great dependence on the frequency; (2) with the rise of temperature (T), the electrical conductivity (σ) will increase, and the Arrenhius linear relationship is established between lgσ and 1/T; (3) under the control of oxygen buffer Fe+Fe₃O₄, with the rise of pressure, the electrical conductivity tends to decrease whereas the activation enthalpy and independent-of-temperature preexponential factor tend to increase, with the activation energy and activation volume of the sample estimated at (1.25±0.08) eV and (0.105±0.025) cm³/mol, respectively; (4) under given pressure and temperature conditions, the electrical conductivity tends to increase whereas the activation energy tends to decrease with increasing oxygen fugacity; and (5) the mechanism of electrical conduction of small polarons can provide insight into the behavior of electrical conduction of olivine under high pressure and high temperature.     

磷钼钒多酸基固体酸催化剂高效加氢精制FCC汽油

以目前国际上两大研究热点杂多酸和纳米晶沸石为研究的活性组分和载体,采用浸渍法制备了镍盐(以NiO计2.5%)促进的单钒取代磷钼酸(10%)基纳米HZSM—5复合固体酸催化剂,IR和UV-Raman表征的结果显示单钒取代磷钼酸以Keggin结构存在于载体纳米晶HZSM—5上.在连续固定床反应器上以劣质催化裂化汽油加氢精制为探针反应评价了制备催化剂的反应性能.评价结果表明,在温和的反应条件下[汽油,2.2mL/h;WHSV,0.8h-1;反应温度285℃;VH2∶V油=300;系统压力2.1MPa;催化剂装填量2.1g],产物组成经碱洗和乙醇调和后可达到93#汽油国V排放标准,催化剂显示出了良好的低温芳构化、加氢脱硫反应性能和催化活性的稳定性.催化剂具有可循环使用、制备方法简单和加氢精制活性高等优势,具有一定应用前景.     

软土地区某深基坑工程变形控制措施的有限元分析

软土地区深基坑开挖过程中对周边环境保护的要求越来越高,目前在实际工程设计施工中已有很多基坑加强加固措施用于控制深基坑的变形,但变形控制效果差异较大,且不同工程之间由于支护条件和环境情况差异较大,没有严格的可比性.结合某基坑工程的基坑支护设计、施工、监测情况,对比该基坑不同位置设置被动区土体裙边加固、加厚支护挡墙对基坑工程变形控制的效果,通过采用有限元数值模拟方法对这些基坑工程加强加固措施进行研究分析,得出这些措施能有效控制基坑工程变形量,得出了一些有利于指导深基坑工程设计及施工的建议和结论.     

约束线性系统关于非凸评价泛函的最优控制

研究一类约束线性系统关于非凸评价泛函的最优控制问题,该最优控制问题的评价泛函的被积函数中含有关于控制变量的非凸二次函数.由Pontryagin极值原理建立球约束下非凸二次优化问题,并利用倒向微分流求解该问题,进而求解一组微分边值问题以得到原问题的最优控制.同时把数学过程转化为求解的算法,并给出了一个数值计算的例子.     

隋唐宋时期浙江采石格局及其环境驱动

采石与地理环境之间的互动是区域人地关系的重要组成部分.根据浙江省现代采石场、古采石场遗址调查数据,结合浙江省地质、交通、水系、古气候变化及历史地理背景,探讨了浙江省隋唐宋时期采石格局及其驱动因素.研究表明:隋唐宋三朝,浙江古采石遗址数量增加明显,为历史时期采石活动的鼎盛期;期间杭州湾沿岸、浙东沿海、钱塘江流域三大采石中心相继出现并发展,是历史采石格局由分散→单一中心→多中心演化的重要时期.隋唐宋时期采石格局的形成和采石业的发展受该时期凿建运河、围堰建闸、兴筑海塘、建设港口、修建都城等工程建设和岩性、水系、古气候变化等自然环境因子的共同驱动.     

高性能高黏改性沥青高低温性能研究

为进一步提升材料的黏结能力与耐久性,特研发HVA-H高黏改性剂,使用此种改性剂与SBS改性沥青在合理剪切工艺下,制备出一种高黏改性沥青。通过荧光显微镜观察HVA-H高黏改性剂掺量分别为4%、6%、8%、10%时高黏改性沥青的分散性,确定最佳掺量,并将其与试验室原有的高黏改剂和其它厂家高黏改性剂进行对比分析研究。结果表明：HVA-H高黏改性剂最佳掺量为8%,HVA-H高黏改性沥青高低温性能优于HVA高黏改性沥青和其它厂家高黏改性沥青;且拉伸柔量指标与BBR试验结果之间存在相关性,可精确评价改性沥青的低温性能;Carreau模型比Cross模型拟合精度更高,在实际应用中可通过Carreau模型拟合零剪切黏度,对研究改性沥青高温性能有较好的指导作用。     

时延-多普勒频移对伪码捕获影响的性能分析

在扩频信号处理中,伪码的捕获一般通过相关来实现。以m序列为研究对象,首先针对一种典型的相关过程分析了其时延、多普勒频移对相关的联合影响,结论表明两者耦合影响非常小,几乎可忽略不计。在此基础上提出另一种利用FFT进行能量积累的伪码捕获方法,该方法相对一般相关可对多普勒进行补偿,并可得到时延-多普勒频移的联合二维估计。     

Experimental study on absorption of blade vibration of honeycomb seal and shunt injection

Honeycomb seals and shunt injection have been proposed to weaken the blade vibration. Honeycomb seals, as well as, smooth seals were tested with different seals' clearances and shrouded blades. The shunt injection was sprayed to the blade tip clearance in the reverse direction of the main flow. Experimental results showed that both honeycomb seals and shunt injection had the damping effect for blade vibration, and the blade vibration magnitude could be reduced by more than 25% and 17%, respectively. When the two methods were adopted synchronously, more than 1/3 of the blade vibration could be reduced. Consequently, adopting honeycomb seal and superinducing proper shunt injection are two useful ways to minimize vibration of the blade from the viewpoints of avoiding blade rupture and improving the rotor stability.