Lam e-mode miniaturized quartz temperature sensors

Lam e-mode is very useful for realization of a miniaturized quartz crystal resonator because its resonant frequency principally depends only on the contour dimensions. Because the heat capacitance for the miniaturized quartz crystal resonator is small and the frequency response versus temperature is very rapid, the quartz crystal resonator is useful for application in temperature sensors. In addition, because a Lam e-mode quartz crystal resonator has zero temperature coefficients, designated LQ(1) cut and LQ(2) cut, and, particularly, the resonator for LQ(1) cut has a comparatively large value of the second-order temperature coefficient beta, a Lam e-mode quartz crystal resonator can be obtained with the large first-order temperature coefficient or when beta=0. In this paper, when cut angles phi=45 degrees and theta=45 degrees , alpha has a value of 44.6x10(-6)/ degrees C in the calculation and 39.9x10(-6)/ degrees C in the experiments with beta=0; when phi=51.5 degrees and theta=45 degrees , alpha=68.1x10(-6)/ degrees C in the calculation and 62.0x10(-6)/ degrees C in the experiments with a value of beta larger than that of phi=45 degrees and theta=45 degrees . For both cut angles, the calculated frequency change vs. temperature is found to be sufficiently large and slightly larger than the measured one.     

Doubly rotated resonators for sensing the properties of liquids

When a doubly rotated resonator is operated in a liquid, the displacement of the surface is partly out of the plane of the plate of the resonator. The out-of-plane component of the displacement propagates a damped compressional wave into the liquid, and the in-plane component propagates a damped shear wave. In this paper, we report the measurements of the series resonant frequency and the motional arm resistance of doubly rotated quartz resonators (theta approximately 35 degrees and phi = 7 degrees) in liquids to compare with singly rotated AT-cut resonators (theta approximately 35 degrees and phi = 0 degrees). A modified Butterworth-Van Dyke (BVD) equivalent circuit model is suggested to analyze doubly rotated cut resonators under liquid loading.     

QCM露点传感器水粘性影响的抑制方法研究

为了解决基于主控温式的石英晶体微天平（Quartz Crystal Microbalance, QCM）露点测量系统中冷凝水粘弹特性影响露点识别准确性的问题,对QCM电极进行疏水处理,改善凝结特性,减小水粘性引起的频率耗散,实现液态水质量变化引起的谐振频率偏移测量。在QCM电极上制备静态水接触角为133° ± 2°的疏水层并对其进行表征,将疏水电极与未经处理的电极用于露点识别实验,并与精密露点仪获得的标准露点进行比对。实验证明,通过疏水处理电极凝结面的方法能够有效提升QCM露点传感器的露点识别精度,为主控温式露点传感器结构的优化设计提供理论和实验依据。     

Quartz crystal microbalance studies of polymer gels and solutions in liquid environments

Spreading of liquids and soft solids on a rigid surface in a surrounding liquid medium is investigated by utilizing the lateral sensitivity of the quartz crystal microbalance (QCM). While the QCM has been used extensively to study systems with spatial variations in the direction normal to the crystal's electrodes, few studies have exploited the QCM's ability to sense changes in loading in the plane of the electrodes. We propose equations to describe the predicted response of the QCM to a generalized viscoelastic material spreading at the QCM surface at the expense of the surrounding liquid medium. Several experimental examples are given in order to support the validity of the proposed equations, including situations where the spreading material is a Newtonian liquid, a viscoelastic liquid, or one of two viscoelastic solids. The first viscoelastic solid is a physically cross-linked gel based on a styrene/ethylene-butene/styrene triblock copolymer in mineral oil, and the second is a cross-linked poly(ethylene glycol) hydrogel.     

A model for the quartz crystal microbalance frequency response to wetting characteristics of corrugated surfaces

We consider the effect of surface roughness, and its unique wetting behavior, on the response of a quartz crystal microbalance (QCM) resonator operating in contact with a fluid. The rough surface is modeled as sinusoidally corrugated particular to the case of a fixed relationship between amplitude and periodicity, as would arise from polishing with monodisperse spherical particles. The penetration of fluid into the troughs of the corrugations and the resulting meniscus are determined as a competition between surface tension and compression of the trapped gas. Liquid contained below the corrugation peaks, but above the gas/liquid meniscus, is trapped and behaves as an ideal mass layer, contributing a frequency shift that adds to that arising from liquid entrainment. This model allows QCM responses on rough surfaces to be described as a function of liquid properties and contact angle. This permits responses on hydrophobic surfaces to be understood in terms of incomplete surface wetting.     

Influence of crack closure on the stress intensity factor in bending plates — A classical plate solution

Based on the classical plate theory in conjunction with the assumption of line contact at the compressive edge of a crack face, closed form solutions were presented for a through-the-thickness central crack in an infinite plate subjected to all around bending. The complete solutions were obtained by superposing the membrane components due to the contact forces at the crack face to the non-closure bending components. The distribution of the contact forces was found uniform by considering the contact condition which prevents mutual penetration of the crack faces at the compressive edges. The results showed that the closure of the crack faces tends to reduce the crack opening displacement at the tension side and, consequently, reduce the stress intensity factor. The finite element method was also used to investigate the present problem. The modified crack closure method in combination with the finite element method was used to find the stress intensity factors. Close agreement between the finite element and the analytical solutions was observed.     

Analytical study of the principal angle used in optical experiments

An analytical method has been developed for directly calculating the principal angle theta(p) at which the phase difference between the two reflection coefficients is equal to 90 degrees and at which the ratio of /r(p)/ to /r(s)/ is equal or close to a minimum. The equations given here can be used in many optical applications. For example, ellipsometric data measured at an incidence angle theta(p) will have higher precision than data measured at other incidence angles. theta(p) is the principal angle. Instead of three principal angles, there is only one principal angle, which can be found in the region of 0 < or = theta(p) < or = 90 degrees for most metallic materials used in applications. Results show good agreement between the measured and the calculated spectra of delta(p) and rho(po).     

Effects of flow rate on sensitivity and affinity in flow injection biosensor systems studied by 55-MHz wireless quartz crystal microbalance

In this paper, we developed a 55-MHz wireless-electrodeless quartz crystal microbalance (QCM) and systematically studied the effects of flow rate on the sensitivity to the detection of proteins and on the affinity between biomolecules evaluated by the flow injection system. Brownian motion of proteins in liquid suggests a low probability of meeting, and the convection effect plays an important role in the sensitivity and the affinity in the flow cell injection system. The wireless quartz crystal was isolated in the QCM cell, and flow rates between 50 and 1000 microL/min were used for monitoring binding reactions between human immunoglobulin G and Staphylococcus aureus protein A. The sensitivity was significantly increased as the flow rate increased, while the affinity value remained unchanged. However, the affinity value was affected by the reaction time for a large-concentration analyte, indicating the need of a high-sensitivity biosensor system for accurate evaluation of affinity. The electrode effect on the QCM sensitivity was also theoretically investigated, showing that the electrode significantly deteriorates the QCM sensitivity and makes the Sauerbrey equation invalid.     

QCM Operation in Liquids: An Explanation of Measured Variations in Frequency and Q Factor with Liquid Conductivity

Recently, several reports have shown that when one side of a quartz crystal microbalance (QCM) is exposed to a liquid, the parallel (but not the series) resonant frequency is influenced by the conductivity and dielectric constant of the liquid. The effect is still controversial and constitutes a serious complication in many applications of the QCM in liquid environments. One suggestion has been that acoustically induced surface charges couple to charged species in the conducting liquid. To explore this effect, we have measured the parallel and the series mode resonance frequencies, and the corresponding Q factors, for a QCM with one side facing a liquid. These four quantities have all been measured versus liquid conductivity, using a recently developed experimental setup. It allows the simultaneous measurement of the resonant frequency and the Q factor of an oscillating quartz crystal, intermittently disconnected from the driving circuit. Based on these results, a simple model together with an equivalent circuit for a quartz crystal exposed to a liquid is presented. The analysis shows that it is not necessary to infer the existence of surface charges (or other microscopic phenomena such as electrical double layers) to account for the influence of the liquid's electrical properties on the resonant frequency. Our results show that the contacting conductive liquid, in effect, enlarges the electrode area on the liquid side and thereby changes the parallel resonant frequency. By proper design of the QCM measurement, perturbing effects due to the liquid's electrical properties can be circumvented.     

Proximity effect in quartz crystal microbalance

When an object approaches a vibrating quartz crystal microbalance (QCM) the resonant frequency changes. This "proximity effect" was seen at the distance of 10 mm in air and became more pronounced as the distance decreased. This effect depends on the quality factor (Q-factor) value of a QCM, conductivity of the object, and electrical connection of the object to QCM electrodes. A special setup was constructed to test the impact of the proximity effect on a QCM. Damping fluid was placed on one side of QCM, to change the Q-factor. A conducting metal disk was brought close to the other side of the QCM exposed to air. By varying the distance between the QCM and an object (metal disk), a shift in frequency was observed. This proximity effect was largest (>200 Hz for 10 MHz QCM) when the Q-factor was low and a conducting metal disk (e.g., Cu) was electrically shorted to the proximal (nearest) QCM electrode. The finite element modeling showed that the proximity effect was likely due to interaction of the object with the fringing electromagnetic field of the QCM. A simple modified Butterworth Van-Dyke model was used to describe this effect. It must be recognized that this effect may lead to large experimental artifacts in a variety of analytical QCM applications where the Q-factor changes. Therefore, in order to avoid artifacts, QCM and similar mass acoustic devices should not operate in the low Q-factor (<1000) regime.     

Low-loss birefringent spectral filters comprising three identical retarders

Basic fan or folded arrangements comprising three identical retarders in cascade between parallel or crossed polarizers are presented for constructing birefringent spectral filters without an internal polarizer. The retarders' axes are oriented with an angle increment of theta or -theta preferably with /theta/ 相似文献   

How are glories formed?

Mie theory can be used to generate full-color simulations of atmospheric glories, but it offers no explanation for the formation of glories. Simulations using the Debye series indicate that glories are caused by rays that have suffered one internal reflection within spherical droplets of water. In 1947, van de Hulst suggested that backscattering (i.e., scattering angle theta = 180 degrees) could be caused by surface waves, which would generate a toroidal wavefront due to spherical symmetry. Furthermore, he postulated that the glory is the interference pattern corresponding to this toroidal wavefront. Although van de Hulst's explanation for the glory has been widely accepted, the author offers a slightly different explanation. Noting that surface waves shed radiation continuously around the droplet (not just at theta = 180 degrees), scattering in a specific direction theta = 180 degrees - delta can be considered as the vector sum of two surface waves: one deflecting the incident light by 180 degrees - delta and the other by 180 degrees + delta. The author suggests that the glory is the result of two-ray interference between these two surface waves. Simple calculations indicate that this model produces more accurate results than van de Hulst's model.     

Effects of interface slip and viscoelasticity on the dynamic response of droplet quartz crystal microbalances

In the present paper we first present a derivation based on the time-dependent perturbation theory to develop the dynamical equations which can be applied to model the response of a droplet quartz crystal microbalance (QCM) in contact with a single viscoelastic media. Moreover, the no-slip boundary condition across the device-viscoelastic media interface has been relaxed in the present model by using the Ellis-Hayward slip length approach. The model is then used to illustrate the characteristic changes in the frequency and attenuation of the QCM with and without the boundary slippage due to the changes in viscoelasticity as the coated media varies from Newtonian liquid to solid. To complement the theory, experiments have been conducted with microliter droplets of aqueous glycerol solutions and silicone oils with a viscosity in the range of 50 approximately 10,000 cS. The results have confirmed the Newtonian characteristics of the glycerol solutions. In contrast, the acoustic properties of the silicones oils as reflected in the impedance analysis are different from the glycerol solutions. More importantly, it was found that for the silicone oils the frequency steadily increased for several hours and even exceeded the initial value of the unloaded crystal as reflected in the positive frequency shift. Collaborative effects of interfacial slippage and viscoelasticity have been introduced to qualitatively interpret the measured frequency up-shifts for the silicone oils. The present work shows the potential importance of the combined effects of viscoelasticity and interfacial slippage when using the droplet QCM to investigate the rheological behavior of more complex fluids.     

Effect of interfacial free energy anisotropy on silicon whisker growth

Data are presented which demonstrate that the {111} and {100} surfaces of a silicon whisker in contact with a liquid metal solvent droplet are more anisotropic than those in contact with the vapor phase. Melting of metal solvent particles on a silicon substrate is accompanied by wettability anisotropy: the (111) close-packed faces of silicon are more poorly wetted by liquid solvent droplets than are the other faces.     

Prolonging seal life with monolithic carbon design

A major petrochemical plant increased seal life from three months to one year by switching to a new seal design with narrow, monolithic carbon stationary faces that stay cool and in full contact under fluctuating conditions. The seals used before could not achieve reliable control of emissions below 1000 ppm. The monolithic carbon faces used in the new seals exhibit controlled thermal growth and maintain full face contact throughout cycling. The new seals also use a carbon grade that covers such a wide application range that it handles all applications in the plant, where carbon is compatible, thus reducing inventory and purchasing costs.     

Collision-free path planning for coordinate measurement machine probe

This paper focuses on the method of collision-free path of the coordinate measurement machine (CMM). In terms of the collision-free path, the cut face method is used to plan the displaced tracking along the boundary loop. In addition, the 'maximum angle between tangential vectors method' and the heuristic algorithm designated by the displacement characteristic among the feature faces are used to reduce the number of intermediary points. This can also reduce the distance of the displacement. The turning of the probe aims at the contact with the workpiece surface in the normal direction. If the contact position in the normal vector direction is impossible, the probe angle closest to the normal direction is adopted. The normal direction contact with the workpiece can, on the one hand, achieve better measuring position and, on the other hand, accompany with the cut face method and thus make a collision-free path possible.     

Design and fabrication of a length-extensional mode rectangular X-cut quartz resonator with zero temperature coefficient.

Rectangular X-cut quartz crystal resonators with cut angles theta > 5.0 degrees and aspect ratios Rzy (= width 2z0/length 2y0) from 0.3 to 0.5 are investigated. The resonators oscillate mode is a length-extensional mode. A semiempirical frequency equation was derived from the stress expressed in terms of the trigonometric and the hyperbolic transcendental functions with constants estimated by the regression curve fit to the stress simulated by the finite-element method (FEM). Contours on which a point satisfies a zero first order temperature coefficient condition are shown in a cut angle theta and Rzy diagram. We proved that a fabricated resonator with Rzy = 0.400 and theta = 16.0 degrees, whose design parameter is located in the area of the contour, had a zero temperature coefficient.     

Measuring the cross-anisotropy of hot-mix asphalt

This study measures the cross-anisotropy of gyratory, kneading and field-compacted hot-mix asphalt samples of two sizes. One set of cube samples were subjected to compression through the top face and the other set through the side face. In addition, two sets of beam samples were tested for flexure stiffness using load on both the top and side faces. Results show that the side faces can sustain an average compressive stress of 0.89, 0.91 and 0.77 times of the top faces for kneading, gyratory and field-compacted cube samples, respectively. The average flexure stiffness of the side face is 0.85 times of that of the top face. For comparison, finite element model (FEM) was developed to predict pavement stress–strain under wheel load. In addition, stress–strain data from a field-instrumented pavement section on Interstate 40 in New Mexico were collected. The FEM-simulated vertical stress shows a close match with collected stress at cross-anisotropy value of 0.8.     

Assessment of the accuracy of snow surface direct beam spectral albedo under a variety of overcast skies derived by a reciprocal approach through radiative transfer simulation

With radiative transfer simulations it is suggested that stable estimates of the highly anisotropic direct beam spectral albedo of snow surface can be derived reciprocally under a variety of overcast skies. An accuracy of +/- 0.008 is achieved over a solar zenith angle range of theta0 < or = 74 degrees for visible wavelengths and up to theta0 < or = 63 degrees at the near-infrared wavelength lambda = 862 nm. This new method helps expand the database of snow surface albedo for the polar regions where direct measurement of clear-sky surface albedo is limited to large theta0's only. The enhancement will assist in the validation of snow surface albedo models and improve the representation of polar surface albedo in global circulation models.     

Empirical equations for the principal refractive indices and column angle of obliquely deposited films of tantalum oxide, titanium oxide, and zirconium oxide

Values of the transmittance T(s) and the phaseretardation D were recorded in situ at two angles duringthe growth of thin films of tantalum oxide, titanium oxide, andzirconium oxide for deposition angles theta(nu) in the range40 degrees -70 degrees . Column angles for the same films were determinedex situ from scanning electron microscopy photographs ofdeposition-plane fractures. We show that the experimental columnangles are smaller than the corresponding values predicted by thetangent-rule equation psi = tan(-1)(0.5 tan theta(nu)) and that the experimental values fit a modifiedform of the equation psi = tan(-1)(E(1) tan theta(nu)) where E(1) is less than 0.5. We also show that theprincipal refractive indices are represented well by quadraticfunctions of the deposition angle, for example, n(1)(theta(nu)) = A(0) + A(2) theta(nu)(2).