The origin of low-order and high-order impedance-coupled resonant modes in piezoelectric-excited millimeter-sized cantilever (PEMC) sensors: Experiments and finite element models

The characteristics of both low-order and high-order resonant modes exhibited by piezoelectric-excited millimeter-sized cantilever (PEMC) sensors were investigated to determine the coupling between electrical impedance and resonant modes observed experimentally. Experimentally measured frequency response spectra correlated well (<5% difference; n = 10 sensors) with three-dimensional (3D) finite element model (FEM) calculations. FEM frequency response and eigen frequency analyses revealed the sensor's resonant modes were complex, and characterized by combinations of transverse, torsional, longitudinal, buckling, and lateral motion. The magnitude of average integrated charge and current density change in the piezoelectric (lead zirconate titanate; PZT) layer at resonance directly correlated with coupling of resonant modes to electrical impedance measurement. Of the 32 resonant modes predicted by eigen frequency analysis in the frequency range 0-1 MHz, only a subset of 17 modes produced charge and current density changes in the PZT layer greater than off-resonance values. Thus, only the subset of resonant modes was coupled to electrical impedance changes and could be exploited for sensing. Transverse, longitudinal, and lateral motion of the piezoelectric layer coupled strongly with the PZT electrical impedance, while torsional and buckling motion did not. Electrically decoupled resonant modes were made measurable by introducing minor geometric asymmetry in composite layer alignment. High-order modes were shown experimentally to exhibit sub-femtogram sensitivity to mass-changes in air. Such modes consisted of combinations of transverse and longitudinal modes in both sensor layers.     

Nature of sensitive high-order resonant modes in piezoelectric excited millimeter sized cantilever (PEMC) sensors

High-order resonant modes of piezoelectric-excited cantilever (PEMC) sensors were previously shown to be very highly sensitive at 0.3-2 fg/Hz for in-liquid applications. The purpose of this work is to show experimentally and with finite element model (FEM) simulations that such sensitive modes are strongly influenced by the sensor width, suggesting that the sensitive modes are torsional or buckling modes. From experimental observations the resonant frequency of high-order modes had a strong dependence on width, where a sensor with a smaller width had resonant modes at a higher frequency. Also the FEM simulations indicate that in this frequency range there are resonant modes with a buckling nature that change for a decrease in width, consistent with experimental observations. In order to establish that the width-dependent modes are mass-sensitive in liquids, resonant frequency change to density changes in flow experiments under fully liquid-immersed conditions were determined. Average frequency shifts of 475 ± 49 Hz (n = 5), 533 ± 31 Hz (n = 5), 715 ± 103 Hz (n = 5) and 725 ± 37 Hz (n = 5) were obtained for the four designs investigated in response to a density change of 0.0118 g/cm³. The results show that the resonant frequency response to variations in the geometry provides insightful data on the role of width in PEMC sensor design.     

振弦式传感器的频率敏感机理与应用

分析振弦式传感器的频率敏感机理,理论上说明这类传感器的传感原理。论述这类传感器使用过程中的关键———激振方式选择的理论依据。比较2类振弦式传感器的特点及使用要点,理论推导和实际运用结合起来,实际使用说明了理论分析的正确性。     

压电换能器谐振频率动态检测的研究

超声波换能器串联谐振频率的检测和研究都是基于静态分析,因而存在无法对实际应用电路进行动态参数的识别和实时跟踪的缺点.基于压电换能器的等效电路,结合导纳圆分析,提出了一种检测换能器谐振频率和相关参数的方法.该方法对超声波电源实现自动识别、跟踪以及动态匹配压电换能器谐振频率等具有非常重要的参考作用.动态检测结果表明,该方法可以较好地检测出压电换能器的谐振频率.     

一种提高电阻式传感器灵敏度的双传感器电路

提出一种双传感器电路,其原理是利用1个传感器在气氛变化时电阻的变化,改变通过另1个传感器的电流,使得后一传感器在气氛变化时电流和电阻的同时变化,使灵敏度得到极大提高。以SrFeO3薄膜传感器考察了这种双传感器电路的实际效果。     

An experimental study of Love-wave acoustic sensors operating in liquids

It has been shown that properly designed Love-wave acoustic sensors are very promising for sensing in gaseous and liquid environments because of their high sensitivity. Since Love-wave devices do not incur a radiative loss when used in a liquid, they have many potential applications in biosensing. We have successfully manufactured a range of 40 μm wavelength Love-wave devices based on SiO₂/ST-quartz, with the SiO₂ thickness ranging from 0 to 7.3 μm. The relationship of the mass-loading sensitivity to the thickness of the SiO₂ layer has been obtained experimentally. High sensitivity (≥ 300 cm⁻² g⁻¹) is achieved at an SiO₂ thickness between 3.5 and 6.5 μm. The Love-wave oscillators have operated efficiently in various liquids with excellent stability and low noise. In this paper, we report the experimental results for the devices operating in various liquids. The mass sensitivity, insertion loss, oscillation frequency stability, noise level, liquid viscous loading and acoustoelectric coupling have been studied. The influence of the thickness of the SiO₂ layer on some of these properties has also been investigated.     

气体传感器在感度测试自动鉴爆中的应用

针对感度测试自动鉴爆的要求,选用合适的气体传感器,组建测试系统,实时采集感度试验时特定气体的生成量,进行预处理和特征量提取,再利用BP算法在线进行计算,根据鉴别准则进行鉴别。试验证明:提出的方法能实现爆炸鉴别的自动化,操作简单、识别率高。     

高灵敏度QCM在阻尼介质中的分辨率改进

为改进晶体谐振器在阻尼介质中频率的稳定性和分辨率,研究了分辨率和干扰频率的理论关系,采用D触发器设计混频电路来减小回路的噪音干扰,由此分析了石英晶片上附着微小质量和液体时的等效电路,并制作了QCM传感器,得到了电路响应曲线;取4MHz、10MHz的谐振器在液体中进行了试验。结果表明:提高晶体谐振器的分辨率,减小噪音在谐振器中的出现比提高频率更有效。     

含几何缺陷的均质材料悬臂薄板的自由振动

以TC4钛合金均质材料悬臂薄板为研究对象.基于经典板壳理论,通过Rayleigh-Ritz法,根据悬臂板边界条件预设模态函数,求得包括全局、局部的函数型几何缺陷的悬臂板的前四阶固有频率.探究了悬臂板的缺陷类型、尺寸、位置等多种因素对自由振动的影响.     

Design of a broadband dielectric resonator antenna and its application in low sensitivity frequency beam‐scanning array with wide scanning angle and suppressed sidelobes

In this paper, a broadband dielectric resonator antenna (DRA) with a simple H‐slot feeding structure is proposed. The broad bandwidth (~45%) and uni‐directional radiation enable this DRA suitable to work as a radiation element in the construction of a beam‐scanning array with not only low frequency sensitivity which is important for accurate angle estimation of in‐coming targets, but also a wide scanning range. Moreover, stable coupling coefficients are established around all the above three resonances with respect to its corresponding feeding line, ensuring a low sidelobe level (SLL) across the whole operating frequency range. In order to realize such a DRA, a latticed rectangular structure is utilized to generate the lower two resonances, while the upper resonance is generated by its H‐shaped feeding slot. The shape of the latticed dielectric resonator is also modified according to a 3‐D printed fixing structure for an accurate installation. A 20‐element beam‐scanning prototype is demonstrated and manufactured. The range of scanning angle is from ?36° to +13° within the bandwidth of 10 to 16 GHz, corresponding to a frequency sensitivity of only 122.5 MHz/^o. The achieved SLL are smaller than 19 dB for all scanning beams. The above performance indicates that, this array is very suitable for near‐range radar systems requiring an accurate angle estimation.     

Global asymptotic stability of steady states in a chemotaxis-growth system with singular sensitivity

This paper deals with a fully parabolic chemotaxis-growth system with singular sensitivity

under homogeneous Neumann boundary conditions in a smooth bounded domain $\Omega ?{\mathbb{R}}^2$, where the parameters $\chi ,\mu >0$ and $r\in \mathbb{R}$. Global existence and boundedness of solutions to the above system were established under some suitable conditions by Zhao and Zheng (2017). The main aim of this paper is further to show the large time behavior of global solutions which cannot be derived in the previous work.     

Experimental evaluation of sensitivity and non-linearity in polysilicon piezoresistive pressure sensors with different diaphragm sizes

MEMS-based piezoresistive pressure sensors are widely popular due to advantages such as small size, low cost, simple fabrication, and DC output. In this work, the design simulation, fabrication process, and characterization of four pressure sensors with square diaphragms of edge-length 1,060, 1,280, 1,480, and 1,690 µm are reported. Several design principles such as appropriate boundary condition, piezoresistor placement, and fracture stress are considered in the design phase. The sensors have novel shaped polysilicon piezoresistors and equal diaphragm thickness of 50 µm. The sensors are fabricated simultaneously by putting the different designs on the same mask set so that the best design can be determined after characterization. The uncompensated and unamplified output response of the different sensors are reported at three temperatures (?5, 25 and 55 °C). Out of the four sensors with different diaphragm sizes, the sensor with a diaphragm edge length of 1,280 μm is found to have optimum characteristics. For the diaphragm with edge-length of 1,280 µm, in the pressure range of 0–30 Bar, sensitivity of 3.35–3.73 mV/Bar, non-linearity of <0.3 %, and hysteresis of <0.1 % are obtained. The different sensors can be used in the specified pressure range for suitable applications.     

A reliable measure of footwear upper comfort enabled by an innovative sock equipped with textile pressure sensors

Footwear comfort is essential and pressure distribution on the foot was shown as a relevant objective measurement to assess it. However, asperities on the foot sides, especially the metatarsals and the instep, make its evaluation difficult with available equipment. Thus, a sock equipped with textile pressure sensors was designed. Results from the mechanical tests showed a high linearity of the sensor response under incremental loadings and allowed to determine the regression equation to convert voltage values into pressure measurements. The sensor response was also highly repeatable and the creep under constant loading was low. Pressure measurements on human feet associated with a perception questionnaire exhibited that significant relationships existed between pressure and comfort perceived on the first, the third and the fifth metatarsals and top of the instep.

Practitioner Summary: A sock equipped with textile sensors was validated for measuring the pressure on the foot top, medial and lateral sides to evaluate footwear comfort. This device may be relevant to help individuals with low sensitivity, such as children, elderly or neuropathic, to choose the shoes that fit the best.     

双压电结构乐甫波激发效率和液体传感的仿真

乐甫波器件适于液体检测,但在工程上经常因为激发效率较低而影响应用。与“压电基底-非压电薄膜”的单压电结构乐甫波器件相比,双压电结构的特点是薄膜也选用压电材料,以期增大器件整体的压电效应。在建立理论模型的基础上,通过空气中和液体检测时双压电结构乐甫波与声表面波、单压电结构乐甫波的机电耦合系数仿真并对比,表明对于某些压电基底和薄膜,双压电结构具有更高的乐甫波激发效率。并且,以液体介电常数检测为例,仿真结果还表明了双压电结构乐甫波比单压电结构具有更高的灵敏度。     

低刚度高谐振频率的新型微压电悬臂梁探针的结构设计

以超高密度信息存储技术为应用背景,设计了低刚度高谐振频率的新型微压电悬臂梁探针,并安排了探针加工工艺流程.通过建立更接近真实结构的悬臂梁模型,推导出了非矩形不等截面多层材料复合悬臂梁的弹性常数和谐振频率计算公式,并算出设计的悬臂梁探针的弹性常数和谐振频率分别为4 N/m和245 kHz.通过悬臂梁几何参数对力学性能影响的分析,从力学性能的角度对用于超高密度信息存储的悬臂梁探针进行了几何尺寸的优化.     

Application of global sensitivity analysis to a tire model with correlated inputs

When a vehicle equipped with tire is manoeuvred on the ground, the tires are submitted to a number of forces – longitudinal force when driving or braking torque is applied to the wheel and/or lateral force when the wheel is steered to turn at a corner. Pacejka model describes these forces that represent the reaction of the road onto the tire. This nonlinear model depends on correlated parameters such as the friction coefficient, the vertical load, and the cornering stiffness, which have to be identified from some measurements. The sensitivity of Pacejka model to these correlated parameters are studied using an approach based on polynomial chaos. It consists in decorrelating the parameters using the Nataf transformation and then, in expanding the model output onto polynomial chaos. The sensitivity indices are then obtained straightforwardly from the algebraic expression of the coefficients of the polynomial expansion.     

Impacts of uncertain project duration and asymmetric risk sensitivity information in project management

This paper investigates the impacts of uncertain project duration and asymmetric risk sensitivity information on the structure of incentive contract and profits in project management where a risk‐neutral project manager (she) engages a risk‐averse contractor (he) to complete a project. The project manager offers a duration‐based incentive contract to the contractor to ensure that he invests his effort to shorten the project duration and reports his risk sensitivity information truthfully. Within the framework of principal‐agent theory, we first develop a duration‐based incentive contract model, and then derive the optimal contract mechanism by solving its equivalent optimal control problem with Pontryagin maximum principle. We show that if the contractor is highly risk averse and the project duration is highly volatile, the project manager should lower the penalty term to motivate the contractor to make duration‐reduction efforts. Moreover, comparing with the symmetric information scenario, we find that the project manager distorts the penalty term for all contractor's risk types (but the lowest) downward. Our results show that the project manager is more willing to acquire the contractor's risk sensitivity information under the uncertain project duration. The results also suggest that from the project manager's perspective, it is beneficial to have better information about the contractor's risk sensitivity by using a numerical analysis.     

Method of stochastic sensitivity synthesis in a stabilisation problem for nonlinear discrete systems with incomplete information

A problem of the synthesis of the assigned probabilistic distribution near the equilibrium of stochastic nonlinear discrete-time system with incomplete state information is considered. We construct a static feedback regulator which provides a required stochastic sensitivity of this equilibrium. It is shown that this problem is reduced to the solution of some quadratic matrix equations. The solvability of these quadratic equations is analysed, and attainability sets are described. In the two-dimensional case, two variants of the control input are discussed and compared. These general results are applied to the suppression of large-amplitude oscillations around the equilibria of the stochastically forced Henon model with noisy observations. We show how suggested control technique, by minimising the stochastic sensitivity, allows us to suppress chaos and provide a structural stabilisation.     

数字预失真系统对各种误差的敏感度分析

大多数数字预失真（DPD）系统都是在各种理想假设条件下进行的理论验证和算法仿真。在真实的硬件系统中由于受到各种误差分量的影响, 仿真环境下所得的补偿效果与性能指标有时很难在实际系统中复现。针对DPD系统中常见的几种误差分量进行分析, 根据其数字域体现建立基带误差模型及数字域DPD仿真系统。通过大量细致的仿真实验, 归纳和分析了各种误差分量对DPD系统的影响, 最终为硬件系统各主要部件设计指标的提出提供了依据并同时降低了后期系统调试的工作量。     

Selling luxury fashion to conspicuous consumers in the presence of discount sensitivity behavior

In the luxury fashion industry, with the possibility of stockout, conspicuous consumers may purchase products at the full price rather than wait for any potential discount. However, in the presence of a possible future discount, conspicuous consumers may also feel regret to purchase at the full price if they find that the product is still available at the markdown price. Considering the possible stockout and future discount, in this paper, we evaluate the firm's pricing and production decisions on conspicuous consumers in the presence of discount sensitivity behavior. We build up an analytical model and consider that the customer purchasing utility decreases with discount sensitivity if she/he purchases at the full price. The firm can create scarcity in the market by reducing inventory to induce customers to purchase early. If the fraction of the customers with discount sensitivity is lower than a certain level, the firm should intentionally produce a large amount of products. Moreover, we find that product design enhancement can effectively weaken the negative effects of customer discount sensitivity on the quantity decisions. More managerial insights are discussed.