WO_3掺杂NiO的气敏性能研究

用水热法制备出NiO纳米粉体,对其进行了WO3系列掺杂。利用XRD对产物晶相结构进行表征,测试了掺杂材料的气敏性能。结果表明:适量WO3的掺杂明显改善了NiO材料的气敏性能,其中,掺杂质量分数为6%的气敏元件性能最好,350℃时对Cl2的灵敏度可达到37.5,200℃时对H2S的灵敏度可达30.4。说明该元件在不同温度下对不同气体具有选择性,且该元件对H2S响应恢复快。     

外力对逆磁致伸缩索力传感器影响研究

基于索力传感理论模型和环式结构的索力传感器,对索力测量原理做了推导,传感器输出感应电压与激励磁场变化、外力变化、某一激励磁场下的材料磁导率及空气间隙尺寸、线圈密度等有关.重点分析了加载外力对传感器输出的影响.在稳恒直流激励下,当外力缓慢变化时可通过感应积分电压反映外力;当外力交流变化时,可通过感应电压求得外力,感应电压幅值与加载外力的频率成正比.最后,确定模拟实验参数,对传感器进行了仿真.结果表明当外力缓慢变化时,感应积分电压与外力成线性关系,传感器的灵敏度与线圈匝数.材料逆磁致伸缩系数成正比.     

静电刚度式谐振微加速度计设计

运用梁的横向振动特性分析了梁振动频率与平行板电容形成的静电刚度的关系,并以此设计了静电刚度式谐振微加速度计。在加速度作用下,检测质量产生的惯性力使电容器极板发生位移来改变电容结构的间隙大小,从而使谐振频率发生变化,通过检测频率变化量来测量输入加速度的大小。根据加速度计的工作原理说明检测过程中梁的机械刚度保持不变,只与产生静电刚度的电容间隙变化相关,减小了检测信号对机械误差与残余应力的依赖性。运用加工参数进行理论计算得出加速度计的灵敏度为21．17Hz／gn,在CoventorWare2005中进行仿真表明：加速度计的固有频率为23．94kHz,灵敏度约为20Hz／gn,与理论设计值相近。     

绝缘电阻对圆柱型换能器噪声接收灵敏度影响研究

研究装艇条件下绝缘电阻对圆柱型换能器噪声接收灵敏度的影响.推导装艇条件下圆柱型换能器噪声接收灵敏度的表达式,并进行理论计算验证.仿真结果表明,当绝缘电阻大于100 时,对圆柱型换能器噪声接收灵敏度没有影响;当绝缘电阻小于10 时,在频率低于4 时,对圆柱型换能器噪声接收灵敏度影响明显,在大于6 时,基本没有影响.     

Soft sensing modelling based on optimal selection of secondary variables and its application

The composition of the distillation column is a very important quality value in refineries, unfortunately, few hardware sensors are available on-line to measure the distillation compositions. In this paper, a novel method using sensitivity matrix analysis and kernel ridge regression （KRR） to implement on-line soft sensing of distillation compositions is proposed. In this approach, the sensitivity matrix analysis is presented to select the most suitable secondary variables to be used as the soft sensor＇s input. The KRR is used to build the composition soft sensor. Application to a simulated distillation column demonstrates the effectiveness of the method.     

Optimization of dynamic response using a monolithic-time formulation

The design of systems for dynamic response may involve constraints that need to be satisfied over an entire time interval or objective functions evaluated over the interval. Efficiently performing the constrained optimization is challenging, since the typical response is implicitly linked to the design variables through a numerical integration of the governing differential equations. Evaluating constraints is costly, as is the determination of sensitivities to variations in the design variables. In this paper, we investigate the application of a temporal spectral element method to the optimization of transient and time-periodic responses of fundamental engineering systems. Through the spectral discretization, the response is computed globally, thereby enabling a more explicit connection between the response and design variables and facilitating the efficient computation of response sensitivities. Furthermore, the response is captured in a higher order manner to increase analysis accuracy. Two applications of the coupling of dynamic response optimization with the temporal spectral element method are demonstrated. The first application, a one-degree-of-freedom, linear, impact absorber, is selected from the auto industry, and tests the ability of the method to treat transient constraints over a large-time interval. The second application, a related mass-spring-damper system, shows how the method can be used to obtain work and amplitude optimal time-periodic control force subject to constraints over a periodic time interval. This research was performed while the first author held a National Research Council Research Associateship Award at the Air Force Research Laboratory. An early version of this paper was presented at the 46th AIAA Aerospace Sciences Meeting and Exhibit, Jan 7–10, 2008, Reno, Nevada.     

GPS接收装置的射频干扰分析

工程实际中,具有GPS接收功能的装置会与其它设备的射频源共存,这些射频源包括GSM、UMTS、WLAN、Bluetooth.指出这些射频源对GPS接收装置的干扰程度,明确哪种射频源对GPS接收装置的阻塞影响最大,同时提出相应的解决方案是关键.验证方法主要是基于Texas Instrument的GPS接收装置,接收由GPS卫星模拟器发出的GPS信息,由具备GSM、UMTS、WLAN、Bluetooth功能的外部设备分别对GPS接收装置发出不同的射频干扰信号.结果证明,工作在UMTS频段的设备,对GPS接收装置的阻塞影响最大,改善GPS接收装置中的带通滤波器性能,对抑制UMTS干扰信号有很好的作用.     

基于观测的POMDP 优化算法及其仿真

在分析马尔可夫决策过程（Markov Decision Process, MDP）性能灵敏度的基础上,讨论了部分可观 测马尔可夫决策过程（Partially Observable Markov Decision Process, POMDP）的性能优化问题．给出了POMDP 性能灵敏度分析公式,并以此为基础提出了两种基于观测的POMDP 优化算法：策略梯度优化算法和策略迭 代优化算法．最后以准许控制问题为仿真实例,验证了这两个算法的有效性．     

Ka频段高灵敏度检波器研制

介绍了一种高电压灵敏度、低切线灵敏度检波器的设计方法。在建立检波二极管简化物理模型的基础上,进行了检波二极管Ka频段阻抗参数的提取,再根据提取的阻抗参数,通过仿真优化了射频匹配网络,使得检波器能够较好地工作在23～34 GHz。实测表明,在1.2 kHz视频带宽下,当输入功率为-30 dBm时,23～34 GHz范围内电压灵敏度高于6 000 mV/mW,切线灵敏度优于-56 dBm,对应等效噪声功率(Noise Equivalent Power, NEP)估算为11.5～36 pW/Hz^1/2。对比实测与仿真结果较为一致,证明了阻抗参数提取的有效性。     

考虑同步机调差系数灵敏度与频率约束的机组组合

为解决高比例新能源并网带来的系统惯量水平降低及频率安全问题,有必要从同步机的角度出发,进一步发挥同步机组的调频能力,提高系统的频率稳定。考虑系统中各同步机组频率支撑能力的不同,基于灵敏度的方法分析不同机组调差系数的改变对最大频率偏差的影响程度。综合考虑同步机与风机参与调频,推导最大频率偏差的解析表达式。在考虑频率安全约束的基础上,提出考虑同步机调差系数灵敏度的多目标机组组合模型,并采用快速非支配多目标优化算法(non-dominated sorting genetic algorithms-II, NSGA-II)进行模型求解。仿真结果表明,所提模型在考虑频率约束的机组组合模型基础上,进一步发挥了同步机组的调频能力,抑制了最低点频率的跌落,改善了系统的频率响应。