一种基于超声阻抗和回波能量的液位检测方法

针对超声波液位检测方法中,传感器和容器壁间的耦合度不佳所带来的稳定性和可靠性降低的问题,提出了一种基于阻抗法并利用回波能量来实现液位检测的方法.该方法利用液位上下方气液介质的阻抗不相等的特性,计算和比较两个接收传感器所接收到的回波能量之间的差异,以此来确定液位的位置.实验结果表明,该方法能够有效地克服因耦合条件不佳所带来的问题,检测精度满足应用需求.     

声表面波器件的反射特性及性能

为了准确分析反射型声表面波器件参数对其性能的影响,基于耦合模理论和P矩阵方法建立了器件的耦合模模型,分析得到器件的电反射特性即反射系数S11曲线,并在128°Y-X LiNbO3压电基片试制了频率为90 MHz的多种参数的器件,分析与测试结果表明:单个叉指换能器器件的S11中心频率为91.26 MHz,幅值为-20.58 dB,与理论分析结果91.44 MHz和-19.21 dB相近;带有反射栅的器件比单个叉指换能器件在中心频率处S11幅值增大约8.5 dB,谐振峰增多,时域曲线有明显的反射峰信号,验证了反射栅的反射特性;叉指换能器叉指对数减小使器件中心频率处的S11幅值减小,时域中的回波信号更尖锐,信噪比明显增大,表明对数较多的IDT具有较强的反射特性,对回波信号干扰较大,过小的叉指对数对器件声电转换效率影响很大,会使器件性能下降;较大的反射栅指条数对回波信号影响不大,但过小的指条数会降低反射栅反射系数,使得回波信号信噪比减小,纹波增多.     

机翼气动结构耦合数值分析方法

针对机翼的静气动弹性问题,为准确预测其气动特性,研究一种实用有效的气动结构耦合仿真方法.以客机机翼设计为例,通过机翼的静气动弹性问题分析和机翼的气动结构耦合分析流程的分解,建立参数化、自动化、模块化的气动结构耦合仿真分析平台.该平台的流程包括基于全速势方程的气动分析、基于MSC Nastran的结构仿真、应用MATLAB的载荷到结构模型的传递、结构变形向气动外形的映射等环节.算例表明该方法能较好地解决机翼的静气动弹性分析问题.     

自偏置低噪放的设计与改进

分析了贴片电容的非理想特性在C波段及以上频率的自偏置电路旁路应用中对低噪放设计的不利影响.分析表明,贴片电容用做自偏置旁路时将严重恶化电路的稳定性和噪声指标.提出了对自偏置电路的改进方法及工艺实现,从而避免了电容对指标的负面影响.为了验证改进电路的优势,采用改进的自偏置电路设计了6 GHz～9 GHz低噪放,实验结果很...     

耦合度模型的建立

该文从影响耦合度的因素出发,对其分析研究,给出度量模块耦合度的计算公式并建立模型。     

一种可用于军事领域上的压力光纤传感器

介绍了压力光纤传感器的原理 ,解决了光纤加工、耦合、排除干扰及降低功耗等一系列的问题。现场测试表明 :该传感器应用于军事领域是切实可行的     

Common coupling and pointer variables,with application to a Linux case study

Both common coupling and pointer variables can exert a deleterious effect on the quality of software. The situation is exacerbated when global variables are assigned to pointer variables, that is, when an alias to a global variable is created. When this occurs, the number of global variables increases, and it becomes considerably harder to compute quality metrics correctly. However, unless aliasing is taken into account, variables may incorrectly appear to be unreferenced (neither defined nor used), or to be used without being defined. These ideas are illustrated by means of a case study of common coupling in the Linux kernel.

磷酸酯类偶联剂对CaCO3／HDPE体系偶联效果的研究

研究了自制磷酸酯“W-893”偶联剂对轻质CaCO_3/HDPE的偶联效果。就力学性能(抗张强度、弯曲强度、冲击强度),流变学特性(流动曲线、表现粘度、剪切敏感性、温度敏感性、挤出胀大、压力振荡、熔体破坏)和比重测定的结果发现:“W-893”/CaCO_3/HDPE体系的冲击强度可以为HDPE(5000S)的2～3倍(325目),甚至3～4倍(1250目);弯曲强度提高33.3％,抗张强度下降2.5％,比铝酸酯、钛酸酯的偶联效果好。     

考虑流固耦合作用的双槽渡槽地震响应分析

为研究考虑流固耦合的大型双槽渡槽结构动力响应特性,采用空间8节点非协调元,基于流固耦合动力相互作用理论及弹性理论推导计算公式,编制了有限元计算程序。对南水北调中线双洎河渡槽的典型三跨进行了模态分析和地震时程响应计算,结果表明:槽内有水将大大增加渡槽结构质量矩阵中的数值,使结构自振频率明显降低,考虑流固耦合动力作用工况较空槽工况对应的地震响应值(包括位移、速度、加速度等)大,对结构整体抗震不利。     

THE NATURAL CONVECTION OF AQUIFERS WITH CONSTANT HEAT SOURCES AND ITS INFLUENCE ON TEMPERATURE FIELDS

By combining sand tank tests with numerical simulations, this paper studies the temperature fields around constant heat sources to reveal the mechanism of the natural convection and its influence on the temperature fields in the process of energy storage. Using the "24-channel temperature auto acquisition system" developed by our research group in the tests, the temperatures are recorded at measuring points within the research area in the tests, the revised Brinkman equation and a transfer-convection balance model are used for solving the aquifer water-thermal coupling problems, and through comparison of the test results with the calcula- tion results, it is discovered that the influence ranges and the variations of the two temperature fields are consistent, which validates the mathematical model. On the basis of this, we also study the influences of the heat source positions and the boundary conditions on the temperature fields, and the results show that, under the natural convection, the heat source positions may influence the distri- bution of the temperature fields, thus affect the energy storage. For the same energy storage layer, the temperature field for the top energy storage is characterized by a smaller heat influence range and a relatively concentrated temperature distribution. However, when the heat source is at the bottom, the range of a temperature field, and the temperature is relatively dispersed, which is not favorable to heat recycle, with the same heat source position, the boundary conditions determine the size of the critical Rayleigh number, and thus have an influence on the occurrence and the strength of the natural convection, and accordingly, on the temperature fields.