垂直升降式天线杆承载通信天线的风负荷分析

针对垂直升降式天线杆在风力环境下进行升降操作存在安全盲目性问题,本文提供了一种在不同风力环境下,计算升降式天线杆承载通信天线的迎风面积以及计算允许承载风负荷能力的方法,同时给出了实际修正结果,作为操作训练的安全性参考依据。经应用表明,在具体的通信天线参数和所处的风力环境下,通过该方法计算的结果可有效指导用户使用天线杆进行安全性升降操作训练。     

QoS routing based on mobile agent for LEO satellite IP networks

Current quality of service (QoS) routing schemes for low earth orbit (LEO) satellites IP networks either neglect the varying population density or fail to guarantee end-to-end delay. As a remedy, QoS routing protocol based on mobile agent (QoSRP-MA) is proposed. QoSRP-MA is a source-based routing protocol. Once connection requests arrive, QoS mobile agents are dispatched from ingress satellite to explore routes, which migrate using satellite routing tables. Upon arriving in egress satellite, QoS mobile agents migrate back towards ingress satellite to reserve bandwidth. To construct satellite routing tables, load balancing routing algorithm based on mobile agent (LBRA-MA) is presented. In LBRP-MA, at regular intervals mobile agents launched on all satellites migrate autonomously to evaluate path cost and update routing tables. Moreover, path cost between source and destination is evaluated considering satellite geographical position as well as inter-satellite link (ISL) cost. Furthermore, ISL congestion index is considered to update routing table. Through simulations on a Courier-like constellation, it shows that QoSRP-MA can achieve guaranteed end-to-end delay bound with higher throughput, lower connection failing ratio and signaling overhead compared to high performance satellite routing (HPSR) scheme.     

轻载高效Buck转换器设计及其纹波控制方案

提出了一种峰值电流模式PWM下的轻载高效Buck DC-DC控制方案。该方案根据负载大小来自适应调节开关频率和电感电流峰值,实现宽负载范围内高的转换效率和对输出纹波的控制。把误差信号与负载自适应的门限相比较,以判定转换器工作模式。在轻载模式下,通过循环开启或者关闭振荡器来降低转换器的开关频率,降低开关损耗。详细推导了在保持输出电压纹波不变的情况下,负载自适应门限与负载大小之间的关系,并在典型应用下得到二者呈线性关系的结论。采用0.5μm BCD工艺进行仿真,结果显示,在输入电压12 V,输出电压3.3 V下,轻载时最高有94.2%的转换效率,在负载从10 mA到500 mA变化时,轻载模式纹波为120~140 mV,与理论分析的控制纹波130 mV较为符合。     

活性炭负载纳米TiO_2光催化降解甲醛废水研究

甲醛对人和温血动物的毒性很强,如果人类长期饮用被甲醛污染的水源,会引发头昏、贫血以及各种神经系统疾病.为此,研究学者对甲醛废水的处理进行了很多的试验研究.目前处理甲醛废水的主要方法有:芬顿法、光催化氧化法、湿式氧化处理等高级氧化技术,二氧化氯法,蒸汽吹脱法,氧化吸附法,SBR工艺等.     

划痕试验法对特殊薄膜系结合力的检测与评价

简要介绍了划痕试验法测量表面薄膜与基体结合力的测试原理和实验方法，讨论了影响临界载荷Lc测量值准确性的主要因素，通过对薄膜系的分类以及大量实际测量数据的总结和分析，认为被测薄膜以及基体的物理化学特性对临界载荷的测量具有重要的影响，单纯从声发射信号的变化来确定临界载荷的方法有可能存在较大误差，分析和讨论了某些特殊薄膜系的声发射信号与其实际临界载荷值之间存在较大偏差的现象和原因，并提出了针对不同膜系，合理利用声发射曲线，摩擦力斜率以及显微观测来正确判定临界载荷的必要性。     

Evaluation of healthy and sensory indexes of sweetened beverages using an electronic tongue

Overconsumption of sugar-sweetened beverages may increase the risk of health problems and so, the evaluation of their glycemic load and fructose-intolerance level is essential since it may allow establishing possible relations between physiologic effects of sugar-rich beverages and health. In this work, an electronic tongue was used to accurately classify beverages according to glycemic load (low, medium or high load) as well to their adequacy for people suffering from fructose malabsorption syndrome (tolerable or not): 100% of correct classifications (leave-one-out cross-validation) using linear discriminant models based on potentiomentric signals selected by a meta-heuristic simulated annealing algorithm. These results may be partially explained by the electronic tongue’s capability to mimic the human sweetness perception and total acid flavor of beverages, which can be related with glycemic load and fructose-intolerance index. Finally, the E-tongue was also applied to quantify, accurately, healthy and sensory indexes using multiple linear regression models (leave-one-out cross-validation: R_adj > 0.99) in the following dynamic ranges: 4.7 < glycemic load ≤ 30; 0.4 < fructose intolerance index ≤ 1.5; 32 < sweetness perception < 155; 1.3 < total acid flavor, g L⁻¹ < 8.3; and, 5.8 < well-balanced flavor ≤ 74. So, the proposed electronic tongue could be used as a practical, fast, low-cost and green tool for beverage’s healthy and sensory evaluation.     

Some intriguing items in the history of scientific balances

The short survey covers the development of the balance since its invention in the Neolithic era. Scales have been used most probably first as tools in trading, but already in Old Egyptian papyrus its use in techniques is documented. Its theory was cleared by Aristotle and Archimedes and at least at that time it was used as a scientific instrument. Today the balance is still the most widely used instrument in science and there are still improvements.     

三维介孔氨基三亚甲基膦酸锆的合成及其担载铁催化剂的甲醛催化氧化活性

以氧氯化锆和氨基三亚甲基膦酸(ATMP)为原料合成了一种新型介孔材料氨基三亚甲基膦酸锆(NTAZP)。使用XRD、FTIR、TG-DTA和SEM等手段对所合成的介孔材料进行了结构表征和形貌分析。然后以NTAZP为载体,用Fe(NO3)3水溶液处理,得到担载Fe3+的氨基三亚甲基膦酸锆。研究结果表明,Fe3+被吸附到载体孔道中后,NTAZP结构未被破坏,Fe3+离子与NTAZP孔壁骨架上的N发生了配位作用。铁担载NTAZP(NTAZP-Fe3+)对甲醛氧化具有良好的催化活性,催化反应条件温和,催化剂稳定性良好。以载体NTAZP担载铁还避免了Fe3+进入水体,催化剂得以回收利用,避免造成二次污染。NTAZP-Fe3+是一种高效绿色的新型小分子醛类化合物氧化催化剂。     

浅谈变频器在中央空调系统节能改造中的运用

随着中国经济的快速发展,中央空调系统已在社会广泛应用,在为人们提供舒适的工作和生活环境的同时,中央空调系统也成为建筑的能耗大户。在全球推进低碳经济,节能减排的大趋势下,如何节能、高效地解决中央空调系统的节能减排问题,已经成为社会研究的热点。据国家能源局统计,我国建筑能耗约占全国总能耗的30%左右,而空调能耗又约占建筑总能耗的50%~65%,降低空调系统能耗对我国完成节能减排目标与推动建设为节约型社会具有非常重要的作用。     

电子管前级放大器中的电子管倒相电路分析

电子管功率放大器中,为了驱动互补推挽结构的功率输出电路,其前级放大电器需使用倒相电路。以电子管微变等效电路分析为基础．针对共阴武、分负载式、分压式、自平衡式4种常见倒相电路进行了理论计算,得出了单臂电压增益和双臂净输出电压增益的解析表达武,并利用仿真软件对这些结果进行了验证,为电子管前级放大器的设计提供了理论依据。