101 research outputs found
Propagation of Coupled Acoustic, Electromagnetic and Spin Waves in Saturated Ferromagnetoelastic Solids
We study the propagation of plane waves in an unbounded body of a saturated
ferromagnetoelastic solid. The equations by Tiersten for small fields
superposed on finite initial fields in a saturated ferromagnetoelastic material
are employed, with their quasistatic magnetic field extended to dynamic
electric and magnetic fields for electromagnetic waves. Dispersion relations of
the plane waves are obtained. The cutoff frequencies and long wave
approximation of the dispersion curves are determined. Results show that
acoustic, electromagnetic and magnetic spin waves are coupled in such a
material. For YIG which is a cubic crystal without piezoelectric coupling, the
acoustic and electromagnetic waves are not directly coupled but they can still
interact indirectly through spin waves
An Analysis of Thickness-shear Vibrations of an Annular Plate with the Mindlin Plate Equations
The Mindlin plate equations with the consideration of thickness-shear
deformation as an independent variable have been used for the analysis of
vibrations of quartz crystal resonators of both rectangular and circular types.
The Mindlin or Lee plate theories that treat thickness-shear deformation as an
independent higher-order vibration mode in a coupled system of two-dimensional
variables are the choice of theory for analysis. For circular plates, we
derived the Mindlin plate equations in a systematic manner as demonstrated by
Mindlin and others and obtained the truncated two-dimensional equations of
closely coupled modes in polar coordinates. We simplified the equations for
vibration modes in the vicinity of fundamental thickness-shear frequency and
validated the equations and method. To explore newer structures of quartz
crystal resonators, we utilized the Mindlin plate equations for the analysis of
annular plates with fixed inner and free outer edges for frequency spectra. The
detailed analysis of vibrations of circular plates for the normalized frequency
versus dimensional parameters provide references for optimal selection of
parameters based on the principle of strong thickness-shear mode and minimal
presence of other modes to enhance energy trapping through maintaining the
strong and pure thickness-shear vibrations insensitive to some complication
factors such as thermal and initial stresses.Comment: Paper to be presented to the 2015 IEEE International Frequency
Control Symposium and European Frequency and Time Forum, Denver, CO, USA.
April 12-16, 201
Higher-Order Overtone Thickness-Shear Vibrations of Multilayered Thin-Film Acoustic Wave Resonators and Angular Rate Sensing
We propose a new structure for piezoelectric gyroscopes. It is made from multilayered thin films of AlN or ZnO with alternating c-axes along the film thickness. It is shown theoretically that when such a film is electrically driven into higher-order overtone thickness-shear vibration in one of the two in-plane directions of the film and is rotating about the film normal, the Coriolis force due to the rotation causes a higher-order overtone thicknessshear vibration in a perpendicular direction with an electrical output that can be used to measure the angular rate of the rotation. Different from existing thickness-shear mode piezoelectric gyroscopes which are based on the fundamental or the second overtone thickness-shear mode, the proposed gyroscope operates with higher-order overtone thickness-shear modes with higher frequencies and hence potentially higher sensitivity. Because of the overtone modes, the Coriolis force acting on the gyroscope forms a self-equilibrated system and does not transmit a net force or torque to the mounting structure. This implies higher device quality factor and better performance
Thickness-shear Frequencies of an Infinite Quartz Plate with Material Property Variation Along the Thickness
Properties of the quartz crystal blank of a resonator is assumed homogeneous,
uniform, and perfect in design, manufacturing, and applications. As end
products, quartz crystal resonators are frequently exposed to gases and liquids
which can cause surface damage and internal degradation of blanks under
increasingly hostile conditions. The combination of service conditions and
manufacturing process including chemical etching and polishing can inevitably
modify the surface of quartz crystal blanks with changes of material
properties, raising the question of what will happen to vibrations of quartz
crystal resonators of thickness-shear type if such modifications to blanks are
to be evaluated for sensitive applications. Such questions have been
encountered in other materials and structures with property variations either
on purpose or as the effect of environmental or natural processes commonly
referred to as functionally graded materials, or FGMs. Analyses have been done
in applications as part of studies on FGMs in structural as well as in acoustic
wave device applications. A procedure based on series solutions has been
developed in the evaluation of frequency changes and features in an infinite
quartz crystal plate of AT-cut with the symmetric material variation pattern
given in a cosine function with the findings that the vibration modes are now
closely coupled. These results can be used in the evaluation of surface damage
and corrosion of quartz crystal blanks of resonators in sensor applications or
development of new structures of resonators.Comment: This is to be presented and published with the 2014 IEEE
International Frequency Control Symposium, May 19-22, 2014, Taipei
International Convention Center, Taipe
Thickness-shear Vibration Frequencies of an Infinite Plate with a Generalized Material Property Grading along the Thickness
For quartz crystal resonators of thickness-shear type, the vibration
frequency and mode shapes, which are key features of resonators in circuit
applications, reflect the basic material and structural properties of the
quartz plate and its variation with time under various factors such as erosive
gases and liquids that can cause surface and internal damages and degradation
of crystal blanks. The accumulated effects eventually will change the surface
conditions in terms of elastic constants and stiffness and more importantly,
the gradient of such properties along the thickness. This is a typical
functionally graded materials (FGM) structure and has been studied extensively
for structural applications under multiple loadings such as thermal and
electromagnetic fields in recent years. For acoustic wave resonators, such
studies are equally important and the wave propagation in FGM structures can be
used in the evaluation and assessment of performance, reliability, and life of
sensors based on acoustic waves such as the quartz crystal microbalances (QCM).
Now we studied the thickness-shear vibrations of FGM plates with properties of
AT-cut quartz crystal varying along the thickness in a general pattern
represented by a trigonometric function with both sine and cosine functions of
the thickness coordinate. The solutions are obtained by using Fourier expansion
of the plate deformation. We also obtained the frequency changes of the
fundamental and overtone modes which are strongly coupled for the evaluation of
resonator structures with property variation or design to take advantages of
FGM in novel applications.Comment: Paper for the proceedings of the 2015 IEEE International Frequency
Control Symposium and the European Frequency and Time Forum, Denver, CO, USA.
April 12-16, 201
Dietary supplementation with Dendrobium officinale leaves improves growth, antioxidant status, immune function, and gut health in broilers
BackgroundThe Dendrobium officinale leaves (DOL) is an underutilized by-product with a large biomass, which have been shown to exhibit immunomodulatory and antioxidant functions. The purpose of this research was to investigate the effects of DOL on broiler growth performance, antioxidant status, immune function, and gut health.MethodsOne hundred and ninety-two 1-day-old chicks were selected and divided into 4 groups at random, 6 replicates for each group and 8 in each. Chicks were given a basal diet supplemented with different amounts of DOL: 0% (control group, NC), 1% (LD), 5% (MD), or 10% (HD). During the feeding trial (70 days), broiler body weight, feed intake, and residual feeding were recorded. On d 70, 12 broilers from each group were sampled for serum antioxidant and immune indexes measurement, intestinal morphological analysis, as well as 16S rRNA sequencing of cecal contents and short-chain fatty acid (SCFA) determination.ResultsIn comparison to the NC group, the LD group had greater final body weight and average daily gain, and a lower feed conversion ratio (p < 0.05, d 1 to 70). However, in MD group, no significant change of growth performance occurred (p > 0.05). Furthermore, DOL supplementation significantly improved the levels of serum total antioxidant capacity, glutathione peroxidase, superoxide dismutase, and catalase, but reduced the level of malondialdehyde (p < 0.05). Higher serum immunoglobulin A (IgA) content and lower cytokine interleukin-2 (IL-2) and IL-6 contents were observed in DOL-fed broilers than in control chickens (p <0.05). Compared to the NC group, duodenal villus height (VH) and villus height-to-crypt depth (VH:CD) ratio were considerably higher in three DOL supplementation groups (p < 0.05). Further, 16S rRNA sequencing analysis revealed that DOL increased the diversity and the relative abundance of cecal bacteria, particularly helpful microbes like Faecalibacterium, Lactobacillus, and Oscillospira, which improved the production of SCFA in cecal content. According to Spearman correlation analysis, the increased butyric acid and acetic acid concentrations were positively related to serum antioxidant enzyme activities (T-AOC and GSH-Px) and immunoglobulin M (IgM) level (p < 0.05).ConclusionOverall, the current study demonstrated that supplementing the dies with DOL in appropriate doses could enhance growth performance, antioxidant capacity, and immune response, as well as gut health by promoting intestinal integrity and modulating the cecal microbiota in broilers. Our research may serve as a preliminary foundation for the future development and application of DOL as feed additive in broiler chicken diets
Virtual machine consolidated placement based on multi-objective biogeography-based optimization
The Thermal Infrared Visual Object Tracking VOT-TIR2015 challenge results
The Thermal Infrared Visual Object Tracking challenge 2015, VOT-TIR2015, aims at comparing short-term single-object visual trackers that work on thermal infrared (TIR) sequences and do not apply pre-learned models of object appearance. VOT-TIR2015 is the first benchmark on short-term tracking in TIR sequences. Results of 24 trackers are presented. For each participating tracker, a short description is provided in the appendix. The VOT-TIR2015 challenge is based on the VOT2013 challenge, but introduces the following novelties: (i) the newly collected LTIR (Link - ping TIR) dataset is used, (ii) the VOT2013 attributes are adapted to TIR data, (iii) the evaluation is performed using insights gained during VOT2013 and VOT2014 and is similar to VOT2015
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