scholarly journals A Novel Sensor Prototype with Enhanced and Adaptive Sensitivity Based on Negative Stiffness Mechanism

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4644
Author(s):  
Lijun Liu ◽  
Yongzhong Nie ◽  
Ying Lei
Keyword(s):  
Low Frequency ◽  
High Sensitivity ◽  
Negative Stiffness ◽  
Micro Electro Mechanical Systems ◽  
Enhanced Sensitivity ◽  
Landslide Hazards ◽  
Negative Stiffness Mechanism ◽  
Low Sensitivity ◽  
Electric Filed ◽  
Design And Manufacture

Loess–mudstone/soil-rock interfacial landslide is one of the prominent landslide hazards that occurs in soil rock contacting zones. It is necessary to develop sensors with high sensitivity to weak and low frequency vibrations for the early warning of such interfacial landslides. In this paper, a novel monitoring sensor prototype with enhanced and adaptive sensitivity is developed for this purpose. The novelty of the sensitive sensor is based on the variable capacitances and negative stiffness mechanism due to the electric filed forces on the vibrating plate. Owing to the feedback control of adjustable electrostatic field by an embedded micro controller, the sensor has adaptive amplification characteristics with high sensitivity to weak and low frequency input and low sensitivity to high input. The design and manufacture of the proposed sensor prototype by Micro-Electro-Mechanical Systems (MEMS) with proper packaging are introduced. Post-signal processing is also presented. Some preliminary testing of the prototype and experimental monitoring of sand interfacial slide which mimics soil–rock interfacial landslide were performed to demonstrate the performance of the developed sensor prototype with adaptive amplification and enhanced sensitivity.

scholarly journals An Air Spring Vibration Isolator Based on a Negative-Stiffness Structure for Vehicle Seat

2021 ◽  
Vol 11 (23) ◽  
pp. 11539
Author(s):  
Cong Hung Nguyen ◽  
Cong Minh Ho ◽  
Kyoung Kwan Ahn
Keyword(s):  
Vibration Isolation ◽  
Dynamic Stiffness ◽  
Low Frequency ◽  
Negative Stiffness ◽  
Vibration Isolator ◽  
Air Spring ◽  
Nonlinear Force ◽  
Mechanical Spring ◽  
Negative Stiffness Mechanism ◽  
Vehicle Seat

This research introduces an air spring vibration isolator system (ASVIS) based on a negative-stiffness structure (NSS) to improve the vehicle seat’s vibration isolation performance at low excitation frequencies. The main feature of the ASVIS consists of two symmetric bellows-type air springs which were designed on the basis of a negative stiffness mechanism. In addition, a crisscross structure with two straight bars was also used as the supporting legs to provide the nonlinear characteristics with NSS. Moreover, instead of using a vertical mechanical spring, a sleeve-type air spring was employed to provide positive stiffness. As a result, as the weight of the driver varies, the dynamic stiffness of the ASVIS can be easily adjusted and controlled. Next, the effects of the dimension parameters on the nonlinear force and nonlinear stiffness of ASVIS were analyzed. A design process for the ASVIS is provided based on the analytical results in order to achieve high static–low dynamic stiffness. Finally, numerical simulations were performed to evaluate the effectiveness of the ASVIS. The results obtained in this paper show that the values of the seat displacement of the ASVIS with NSS were reduced by 77.16% in comparison with those obtained with the traditional air spring isolator without NSS, which indicates that the design of the ASVIS isolator with NSS allows the effective isolation of vibrations in the low-frequency region.

Stress and frequency analysis of silicon diaphragm of MEMS based piezoresistive pressure sensor

2019 ◽  
Vol 33 (07) ◽  
pp. 1950040 ◽  
Author(s):  
Samridhi ◽  
Manish Kumar ◽  
Sachin Dhariwal ◽  
Kulwant Singh ◽  
P. A. Alvi
Keyword(s):  
Frequency Analysis ◽  
Pressure Sensor ◽  
Dynamic Environment ◽  
High Sensitivity ◽  
Vibrational Modes ◽  
Piezoresistive Effect ◽  
Micro Electro Mechanical Systems ◽  
Enhanced Sensitivity ◽  
Piezoresistive Pressure Sensor ◽  
Frame Work

This paper reports the stress and frequency analysis of dynamic silicon diaphragm during the simulation of micro-electro-mechanical-systems (MEMS) based piezoresistive pressure sensor with the help of finite element method (FEM) within the frame work of COMSOL software. Vibrational modes of rectangular diaphragm of piezoresistive pressure sensor have been determined at different frequencies for different pressure ranges. Optimal frequency range for particular applications for any diaphragm is a very important so that MEMS sensors performance should not degrade during the dynamic environment. Therefore, for the MEMS pressure sensor having applications in dynamic environment, the diaphragm frequency of 280 KHz has been optimized for the diaphragm thickness of 50 [Formula: see text]m and hence this frequency can be considered for showing the better piezoresistive effect and high sensitivity. Moreover, the designed pressure sensor shows the high linearity and enhanced sensitivity of the order of ([Formula: see text]0.5066 mV/psi).

scholarly journals Enhanced sensitivity for light and electron microscopic in situ hybridization with multiple simultaneous non-radioactive oligodeoxynucleotide probes.

1995 ◽  
Vol 43 (8) ◽  
pp. 829-841 ◽  
Author(s):  
A Trembleau ◽  
F E Bloom
Keyword(s):  
In Situ Hybridization ◽  
Fluorescent Dyes ◽  
General Procedure ◽  
Simultaneous Detection ◽  
High Sensitivity ◽  
Electron Microscopic Level ◽  
Electron Microscopic ◽  
Enhanced Sensitivity ◽  
Low Sensitivity

Although oligonucleotide probes are useful for in situ hybridization, their low sensitivity compared to riboprobes and cDNA remains a problem. We have systematically examined the protocols to provide a general procedure that increases the sensitivity of oligoprobes for light and electron in situ hybridizations by using mixtures of multiple non-overlapping oligonucleotides (multi-oligoprobes). The protocol achieves these improvements with both radioactive and non-radioactive oligoprobes. With 33P-labeled probes in a semiquantitative assay, we found that mixtures of up to six vasopressin-directed multi-oligoprobes, each employed at saturating concentration, led to an additive signal with no significant increase of the background. Using this approach with non-radioactive oligoprobes, we were able to detect in the hypothalamus several low or moderately abundant mRNAs, such as vasopressin heterogeneous nuclear RNA and the galanin, dynorphin, and tyrosine hydroxylase mRNAs. Moreover, we showed that multi-oligoprobes used in a pre-embedding procedure were suitable for studying the ultrastructural compartmentalization of moderately abundant mRNAs. Finally, with the same basic approach we demonstrated that two sets of multi-oligoprobes can be combined for simultaneous detection of two different mRNAs using fluorescent dyes, making this approach suitable for high-resolution confocal analyses. Overall, our data demonstrate that multi-oligoprobes provide a sensitive tool of choice for various applications in which both well-preserved morphology and high sensitivity are needed. In particular, these probes appear ideal for study of the comparative subcellular localization of mRNAs at both the light and the electron microscopic level.

Design of Low Frequency Hydrophone Based on PVDF Piezoelectric Materials

2014 ◽  
Vol 513-517 ◽  
pp. 3085-3089 ◽  
Author(s):  
Zhu En Chen ◽  
Zhou Wan ◽  
Yi Yang Li ◽  
Hao Hua Liu ◽  
Xi Cun You
Keyword(s):  
Piezoelectric Materials ◽  
Low Frequency ◽  
High Sensitivity ◽  
Fast Response ◽  
Piezoelectric Film ◽  
Frequency Range ◽  
Sensitive Material ◽  
Frequency Signal ◽  
Low Sensitivity ◽  
Sensor Stability

In view of the existing of low frequency hydrophone in signal detection problems such as low sensitivity, frequency range is small, In this paper, application of PVDF piezoelectric film as sensitive material of low frequency hydrophone, use its advantages as fast response, high sensitivity, good mechanical properties, and so on [1], designed a kind of low frequency hydrophone, experiments are carried out to study the detection of low frequency signal. This paper introduces the structure, material and size of the hydrophone, and analyzes the experimental data. Experiments show that the sensor stability and high sensitivity, can effectively detect the low frequency acoustic wave in the water.

scholarly journals A Bioinspired Tilt Sensor Model with Adaptive Gain and Enhanced Sensitivity

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Lijun Liu ◽  
Ying Lei
Keyword(s):  
Dynamic Range ◽  
Inertial Sensors ◽  
High Sensitivity ◽  
Negative Stiffness ◽  
Mechanical Stimuli ◽  
Enhanced Sensitivity ◽  
Sensor Model ◽  
Broad Dynamic Range ◽  
Tilt Sensor ◽  
Tilt Sensors

Although various types of tilt sensors have been proposed in the past decade, it is still essential to develop rugged, cheap, simple-structured tilt sensors with wide measuring range and high sensitivities for efficient monitoring of infrastructures and early warning of natural disasters. It has been investigated that stereocilia in some fishes’ inner ear organs are the basic sensory units of nature’s inertial sensors and are highly sensitive over broad dynamic range because of a combination of adaptation and negative stiffness mechanisms. In this paper, a bioinspired tilt sensor model is proposed that mimics the mechanism of stereocilia in adaptive signal amplification to mechanical stimuli, leading to high sensitivity to weak input and low sensitivity to high input, thus expanding the dynamic range through adaptive amplification. The negative stiffness mechanism is implemented by magnet forces. The tilt motion is measured by the strain gauge at the end of the flexible cantilever beam element in the model. Measurements of both static and dynamics tilt motion are investigated. Numerical simulation results are used to demonstrate the capability of the proposed model for the measurements of tilt motions with adaptive amplification and enhanced sensitivity.

Design and experiments of a quasi–zero-stiffness isolator with a noncircular cam-based negative-stiffness mechanism

2020 ◽  
Vol 26 (21-22) ◽  
pp. 1935-1947
Author(s):  
Ming Li ◽  
Wei Cheng ◽  
Ruili Xie
Keyword(s):  
Harmonic Balance ◽  
Experimental Studies ◽  
Approximation Error ◽  
Low Frequency ◽  
Harmonic Balance Method ◽  
Negative Stiffness ◽  
Restoring Force ◽  
Stiffness Characteristic ◽  
Physical Prototype ◽  
Negative Stiffness Mechanism

This article presents a quasi–zero-stiffness isolator with a cam-based negative-stiffness mechanism, where the cam has a user-defined noncircular profile to generate negative stiffness to counterbalance the positive stiffness of the vertical spring and yield the quasi–zero-stiffness characteristic around the equilibrium position. Unlike previous studies, the proposed quasi–zero-stiffness isolator has the preferable feature that the desired cubic restoring force can be directly obtained through the well-designed profile of the cam in the negative-stiffness mechanism with the friction considered during the model design, rather than through the Taylor expansion and friction-ignoring assumption, which can avoid the approximation error between the theoretical design and the specific realization. The pure-cubic nonlinear differential equation of motion of the quasi–zero-stiffness isolator is derived and solved with the harmonic balance method, followed by the discussion of the relevant dynamic characteristics. Experimental studies are carried out based on the physical prototype of the quasi–zero-stiffness isolator. The results show that the quasi–zero-stiffness isolator can greatly extend the isolation frequency bandwidth and has a much lower resonance peak. In the low-frequency band, the quasi–zero-stiffness isolator greatly outperforms the corresponding linear system but is equivalent or even inferior in the high-frequency range with the increase of excitation force.

Vibration control through the robust nonlinear absorber with negative stiffness and internal resonance creation

2022 ◽  
pp. 107754632110623
Author(s):  
Peiman Harouni ◽  
Nader Khajeh Ahmad Attari ◽  
Fayaz Rahimzadeh Rofooei
Keyword(s):  
Internal Resonance ◽  
Vibration Suppression ◽  
Low Frequency ◽  
Multiple Scale ◽  
Harmonic Excitation ◽  
Negative Stiffness ◽  
Primary System ◽  
Nonlinear Absorber ◽  
Negative Stiffness Mechanism ◽  
Stiffness And Damping

In this study, a nonlinear absorber that works with a negative stiffness mechanism is suggested to mitigate vibration, and its effect on the reduction of vibration is investigated. The negative stiffness, which is inherently nonlinear, creates internal resonance; therefore, the vibration energy can be transmitted from low-frequency to high-frequency vibrating modes, causing vibration suppression. The nonlinear absorber is added to the primary nonlinear system, and when the main system is subjected to external resonance due to harmonic excitation, the negative stiffness parameter of absorber is so adjusted that autoparametric resonance occurs and vibration is reduced. First, the mathematical model of the system is presented and the governing differential equations of the motion are derived, and then, using the multiple scale method, the equations are solved for the case without, and with the 1:3 internal resonance. The responses and their stability are inspected, discussed, and compared. After that, the effect of negative stiffness and damping parameters on vibration amplitude reduction is investigated and the adequacy of the proposed absorber will be demonstrated by numerical analysis. Finally, the energy exchange between the primary system and the absorber will be demonstrated by plotting the responses in the state space and the displacement response Fourier spectrum.

scholarly journals Magnetoelastic Coupling and Delta-E Effect in Magnetoelectric Torsion Mode Resonators

Sensors ◽  
2021 ◽  
Vol 21 (6) ◽  
pp. 2022
Author(s):  
Benjamin Spetzler ◽  
Elizaveta V. Golubeva ◽  
Ron-Marco Friedrich ◽  
Sebastian Zabel ◽  
Christine Kirchhof ◽  
...  
Keyword(s):  
Low Frequency ◽  
High Sensitivity ◽  
Element Model ◽  
Mode Number ◽  
Frequency Change ◽  
General Description ◽  
Resonance Modes ◽  
Field Sensor ◽  
Magnetic Sensitivity ◽  
Bending Modes

Magnetoelectric resonators have been studied for the detection of small amplitude and low frequency magnetic fields via the delta-E effect, mainly in fundamental bending or bulk resonance modes. Here, we present an experimental and theoretical investigation of magnetoelectric thin-film cantilevers that can be operated in bending modes (BMs) and torsion modes (TMs) as a magnetic field sensor. A magnetoelastic macrospin model is combined with an electromechanical finite element model and a general description of the delta-E effect of all stiffness tensor components Cij is derived. Simulations confirm quantitatively that the delta-E effect of the C66 component has the promising potential of significantly increasing the magnetic sensitivity and the maximum normalized frequency change ∆fr. However, the electrical excitation of TMs remains challenging and is found to significantly diminish the gain in sensitivity. Experiments reveal the dependency of the sensitivity and ∆fr of TMs on the mode number, which differs fundamentally from BMs and is well explained by our model. Because the contribution of C11 to the TMs increases with the mode number, the first-order TM yields the highest magnetic sensitivity. Overall, general insights are gained for the design of high-sensitivity delta-E effect sensors, as well as for frequency tunable devices based on the delta-E effect.

scholarly journals Second harmonic generation correlation spectroscopy for characterizing translationally diffusing protein nanocrystals

2016 ◽  
Vol 72 (7) ◽  
pp. 849-859
Author(s):  
Ximeng Y. Dow ◽  
Christopher M. Dettmar ◽  
Emma L. DeWalt ◽  
Justin A. Newman ◽  
Alexander R. Dow ◽  
...  
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Unit Volume ◽  
Second Harmonic ◽  
Incident Beam ◽  
High Sensitivity ◽  
Correlation Spectroscopy ◽  
Optical Process ◽  
Active Nanoparticles ◽  
Low Sensitivity

Second harmonic generation correlation spectroscopy (SHG-CS) is demonstrated as a new approach to protein nanocrystal characterization. A novel line-scanning approach was performed to enable autocorrelation analysis without sample damage from the intense incident beam. An analytical model for autocorrelation was developed, which includes a correction for the optical scattering forces arising when focusing intense, infrared beams. SHG-CS was applied to the analysis of BaTiO3nanoparticles ranging from 200 to ∼500 nm and of photosystem I nanocrystals. A size distribution was recovered for each sample and compared with the size histogram measured by scanning electron microscopy (SEM). Good agreement was observed between the two independent measurements. The intrinsic selectivity of the second-order nonlinear optical process provides SHG-CS with the ability to distinguish well ordered nanocrystals from conglomerates and amorphous aggregates. Combining the recovered distribution of particle diameters with the histogram of measured SHG intensities provides the inherent hyperpolarizability per unit volume of the SHG-active nanoparticles. Simulations suggest that the SHG activity per unit volume is likely to exhibit relatively low sensitivity to the subtle distortions within the lattice that contribute to resolution loss in X-ray diffraction, but high sensitivity to the presence of multi-domain crystals.

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