附着力、内聚力、有效内聚力与润湿性

本文引进“有效内聚力”的概念,它是以简单方式所定义的“内聚力”的一半;指出真正表征液体内聚倾向强弱的应该是“有效内聚力”;然后对润湿性导出与传统判据不同的两条判据,并给出实例来证明判据的正确性.一基本假设 设固体对液体分子的引力有效作用距离为l1,液体分子间的引力有效作用距离为 l2,因此表面层和附着层的厚度分别为l2和e=Max(l1,l2). 在本文中,除非特别申明,我们将处处使用下达通常的“简化假设”[1]:①忽略重力;②将分子间斥力绝对化而用引力刚心模型(不必球对称)来描写液体分子;③用具有理想表平面的引力刚体来描写固体;④…     

基于无线传感网络的智能移动监控系统设计

为解决部分环境监控需要管理人员值守问题,提出了一种基于ZIGBEE与3G网络的环境智能移动监控系统。系统采用CC2530主控芯片,将传感器所采集到的数据通过ZIGBEE无线网络协议传输到PC终端。在3G网络环境中, VC编制的上位机与安卓智能移动设备根据TCP/IP通信协议进行数据通讯。实验结果表明：管理人员通过使用上位机或者安卓智能移动终端都能实时、准确、有效地监控被测环境因子数据。     

薄膜电弱点测试仪的研制

电气用塑料薄膜要求进行电弱点测试,研制的薄膜电弱点测试仪,具有多重保护功能及输出电压自动回归零位控制,保证了系统的安全性;放卷臂安装有磁粉制动控制器,保证了走膜均匀平稳;测试电压全量程线性显示及测试电压平滑、自动、精准调整及电弱点计数的合理性,保证了测试数据的真实性.     

GC/MS法测定室内空气中邻苯二甲酸酯类物质

针对室内空气中日益严重的邻苯二甲酸酯类污染,建立了固相萃取柱采样,GC/MS测定室内空气中16种邻苯二甲酸酯类物质的测试方法,可用于评价室内空气质量。     

微通道板结构参数对噪声因子的影响

采用对比测量方法研究了微通道板结构参数,即开口比、板厚、电极深度、离子阻挡膜、输入增强膜对其噪声因子的影响。结果表明,开口比增大,噪声因子减小;板厚增加,噪声因子增加;输入电极深度增加,噪声因子增加;离子阻挡膜会增加噪声因子;输入增强膜会降低噪声因子。其中,离子阻挡膜对噪声因子的影响最大,板厚对噪声因子的影响最小。微通道板的结构参数不仅对噪声因子产生影响,而且对其他参数,如增益、均匀性等性能均会产生影响。要降低微通道板噪声因子,比较可行的方法是将微通道板的开口比提高到68%,在此基础上,再在微通道板的输入端制作一层高二次电子发射系数的MgO2输入增强膜,使微通道板的噪声因子接近1,从而达到理想微通道板的水平。     

OPCM超声换能器的驱动性能及正交异性研究

研究了正交异性压电复合材料(OPCM)换能器的驱动特性,采用1-1型OPCM制备了换能器,对其驱动原理及正交异性进行了理论分析.通过数值仿真和实验测试了其在横观正交方向上不同的压电特性,即正交异性,并得出正交比,该特性可聚集特征信号的能量,从而提高结构损伤的定位精度.OPCM超声换能器模拟与实验测试结果一致,研究表明,这种新型换能器具有明显的正交异性,能在特定方向产生定向应力波,其驱动性能优于片状压电元件.     

基于人工蜂群优化的K-means航空客户价值分析

对客户价值进行分析,识别重要价值客户,对航空公司获利至关重要.提出了基于人工蜂群优化的K-means算法对航空客户价值进行分析的模型.首先,对航空客户的当前价值、潜在价值和客户忠诚度三个方面进行分析,建立了客户价值综合评价指标体系;然后,采用低方差滤波和高相关滤波的方法进行指标约简,根据约简后的决策系统完成客户价值初筛...     

Preliminary Frequency Comparison of Two 40^Ca^＋ Optical Frequency Standards

Frequency comparison is one of the most efficient ways to evaluate the performance of a frequency standard. Based on the pre-existing 40^Ca＋ optical frequency standard, we set up the second 40^Ca^＋ optical frequency standard, which has been improved in the materials and structure of ion traps for better control of the magnetic field. After the compensation, the residual magnetic field at the position of the ion is adjusted to be～500nT with a long time jitter of～10nT, which is better than the pre-existing 40^Ca^＋ optical frequency standard. We realize the ＇4-point-closed-loop locking＇ on the second 40^Ca＋ optical frequency standard after a series of preparatory works. Through half an hour of measurement time, the two frequency standards exhibited a stability of 2.1 × 10^-13.τ^1/2 and a relative frequency difference of 1.5 （2.9）Hz.     

思维地图在优化物理教学中的应用

随着“读图时代”的到来,知识可视化越来越受到教育研究者的关注,同时,越来越多的知识可视化工具被开发和研究,如概念图、思维导图、思维地图等。本文初步介绍了思维地图,并且具体列举了思维地图的8种类型在物理教学中的应用。     

Calculation and analysis of the number of return photons from sodium laser beacon excited by the long pulse laser with circular polarization

The number of return photons from sodium laser beacon（SLB） greatly suffers down-pumping, recoil, and geomagnetic field when the long pulse laser with circular polarization interacts with sodium atoms in the mesosphere. Considering recoil and down-pumping effects on the number of return photons from SLB, the spontaneous radiation rates are obtained by numerical computations and fittings. Furthermore, combining with the geomagnetic field effects, a new expression is achieved for calculating the number of return photons. By using this expression and considering the stochastic distribution of laser intensity in the mesosphere under different turbulence models for atmosphere, the number of return photons excited by the narrow-band single mode laser and that by the narrow-band three-mode laser are respectively calculated. The results show that the narrow-band three-mode laser with a specific spectrum structure has a higher spontaneous radiation rate and more return photons than a narrow-band single mode laser. Of note, the effect of the atmospheric turbulence on the number of return photons is remarkable. Calculation results indicate that the number of return photons under the HV5/7 model for atmospheric turbulence is much higher than that under the Greenwood and Mod HV models.