Tested Frequency Range Research Articles

Electromagnetic properties of Ni and La doped strontium hexaferrites in the microwave region

The complex permeability and permittivity spectra of novel Ni and La substituted SrCo 2Fe 16O 27 W-type hexaferrites are studied in the 2–18 GHz microwave band. While permittivity exhibits practically no dispersion in the specific testing frequency range, both doping elements yield an increase of dielectric polarization. The permeability of composite specimens is governed by the inherent tendency of Ni and La to induce the anisotropy transformation from planar to axial configuration. Actually, the decrease of the in-plane and out-of-plane anisotropy fields H ϕ and H θ , along with the high saturation magnetization M s, for low substitution rates, result in the significant rising of μ max ″ and its shift to substantially lower frequencies. Thus, the alteration of the Ni or La proportion enables the tuning of the magnetic loss peak over the range 5.8–16.7 GHz with maximum values as high as 0.85. Moreover, with the aim to investigate the impact of anisotropy on the dynamic magnetic properties, some essential formulations are reviewed. Through this analysis, the minimization of H ϕ of the intermediate compounds in the vicinity of the anisotropy transition, which indicates the existence of an isotropic easy magnetization surface, is highlighted as a basic design requirement for the fabrication of soft hexagonal ferrites with increased μ′ and μ″ values.

Electromagnetic Shielding Effectiveness of Cement Based Materials with Scrap Tires Wire - FeCuNbSiB Amorphous Alloy Powder

Replacement of steel fiber by scrap tires wire as shielding agent in cement-matrix composites was discussed in this paper. The electromagnetic shielding effectiveness (SE) of cement based composites materials containing FeCuNbSiB amorphous alloy powder and scrap tires wire were measured with coaxial planar－spectrum analyzer method. Results show scrap tires wire can effectively enhance the SE of cement composites in tested frequency range. The shielding effectiveness at 1.5GHz is 14.1 dB at a scrap tires wire content of 1.3 vol.% in cement paste. The SE of composites that simultaneously contain scrap tires wire and FeCuNbSiB powder is higher than singly use these shield agents.

Polygenic inheritance of sensorineural hearing loss ( Snhl2, -3, and -4) and organ of Corti patterning defect in the ALR/LtJ mouse strain

Progressive sensorineural hearing loss in humans is a common and debilitating impairment. Sensorineural deafness in inbred strains of mice is a similarly common and genetically diverse phenotype providing experimental models to study the underlying genetics and the biological effects of the risk factors. Here, we report that ALR/LtJ mice develop early-onset profound sensorineural hearing loss as evidenced by high-to-low frequency hearing threshold shifts, absent distortion-product otoacoustic emissions, and normal endocochlear potentials. Linkage analyses of a segregating backcross revealed three novel quantitative trait loci named sensorineural hearing loss ( Snhl) - 2, -3, and -4. The QTLs achieved very high LOD scores with markers on chromosome 1 ( Snhl2, LOD: 12), chromosome 6 ( Snhl3, LOD: 24) and chromosome 10 ( Snhl4, LOD: 11). Together, they explained 90% of the phenotypic variance. While Snhl2 and Snhl3 affected hearing thresholds across a broad range of test frequencies, Snhl4 caused primarily high-frequency hearing loss. The hearing impairment is accompanied by an organ of Corti patterning defect that is characterized by the ectopic expression of supernumerary outer hair cells organized in rows along the abneural site of the sensory epithelium in the presence of unaltered planar polarity and otherwise normal cochlear duct morphology. Cloning the Snhl2, -3, and -4 genes in the ALR/LtJ mice may provide important genetic and mechanistic insights into the pathology of human progressive sensorineural deafness.

Electromagnetic Shielding Effectiveness of Carbon Black -Carbon Fiber Cement Based Materials

The electromagnetic shielding effectiveness (SE) of cement based composites filled with carbon black and carbon fiber were discussed in this paper. Results show the SE of cement composites will get obvious improvement as the carbon black mass fraction increases beyond 6%. Carbon fiber is a much more effective additive than carbon back. The shielding effectiveness were gradually improved with the increase of content of carbon fiber, the maximum attained 21 dB at 1.5GHz. Adding carbon black and carbon fiber, SE of the cement based materials get more upward gradient, the maximum SE reached 27 dB in tested frequency range.

Salicylate induced neural changes in the primary auditory cortex of awake cats

Systemic administration of salicylate at high doses can induce reversible tinnitus and hyperacusis in humans and animals. For this reason, a number of studies have investigated the salicylate-induced changes of neural activity in the auditory cortex (AC); however, most previous studies of the AC were conducted on brain slices or anesthetized animals, which cannot completely represent the actual conditions. Few efforts have been made to examine the neural activity of awake animals, and only recorded the local field potential (LFP) of the AC. In this study, we recorded neural spike activities from chronically implanted electrodes in the primary AC (A1) of awake cats, and investigated the changes of neural responses to pure-tone and click-train stimuli after systemic injection of 200 mg/kg salicylate. We found that sound-evoked spike activities were significantly increased from 1 h after salicylate administration, and the increase of neural responses lasted longer than 3 days with a peak at 12 h. Salicylate not only increased the amplitude of transient responses at the onset and offset of pure-tone stimuli, but also induced a sustained response during the prolonged stimulus period and a late response at ∼100 ms after stimulus offset. The significant enhancement of neural responses was observed over the entire tested frequency range (0.1–16 kHz) with a relative peak in the band of 3.2–9.6 kHz. The capability of exhibiting spikes synchronizing with successive clicks was also enhanced. All these effects were more apparent when the neurons were driven by high intensity sounds. Salicylate-administration also decreased the mean spontaneous rate in A1 units, and the decrease of spontaneous rate was larger in the units with a high initial spontaneous rate. Our data confirm that salicylate can modulate the neural activity at the cortical level and provide more information for understanding the mechanism of salicylate-induced tinnitus.

The Study on Piezoelectric Impedance Technique Used in Loading Damage Identification

The superiority and feasibility of piezoelectric impedance method used in damage detecting was expounded, and the research status of the technical was summarized. Then, the rationale of the basic theory of the technique used in damage identification and health monitoring was analyzed here. The experiment of the damage change of loaded beam was researched. The experiment of the beam which was loaded by a material property, the value of the beam was got by an impedance analyzer, while the beam with different pull force. The research indicates that while the testing frequency range should elect as 300k-800k, with the increasing of loading force, the value of real part impedance is descending, the damage index of beam is increasing. PZT can sensitively catch the influence brought by stress varying

The Influence of Electroless-Silver Coated Cenosphere Powders on the Electromagnetic Shielding Interference Effectiveness and Mechanical Properties of the Silicone Rubber

Silver plating cenosphere powders were developed by electroless plating method. After being mixed with silver plating cenosphere powders and curing agent, silicone rubber composites was obtained. The surface morphology, microstructure and cross-section of Ag-coated cenosphere powders and composites were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The influence of different concentration of Ag-coated cenosphere powders on the conductivity, electromagnetic shielding interference effectiveness and mechanical properties of the silicone rubber was discussed from the point of view of condition of Ag-coated cenosphere powders and silicone rubber. The results showed that the smooth and compact silver coating was deposited on the surface of cenosphere powders. The Ag-coated cenosphere powders possessed good oxidation resistance and enough strength to resist being crushed during the preparation of composites. The adhension between the silver film and cenosphere powders was good. There existed the extreme shielding effectiveness (SE) of silicone rubber composites filled with Ag-coated cenosphere powders. The electrical conductivity no longer plays an important role in enhancing the SE of composites when the SE of composites reaches the extremum. When the content of the Ag-coated cenosphere powders was 180 parts per hundred of rubber (phr), the SE values of composites were typically above 80 dB and close to the extremum across the tested frequency range from 2.6 GHz to 3.95 GHz. And the mechanical properties of composites with 180 phr were not degraded obviously.

Compression-Dependent Viscoelastic Behavior of Human Cervix Tissue

We have characterized the viscoelastic properties of human cervical tissue through a range of precompressional loads and testing frequencies. Mechanical testing is necessary to develop robust elasticity-based techniques for the diagnosis of cervical abnormalities. The storage modulus (E') and material damping (tan 6) were measured in 13 patients, 40 to 76 years old. Our results showed that E' increased monotonically from approximately 4.7 to 6.3 kPa over the precompression range (1-6%) for a testing frequency of 1 Hz. Increases in precompressions of 4% or greater significantly increased E' obtained after dynamic compression testing when data were normalized to 1% precompression. Tan delta remained fairly constant (approximately 0.35) and was not significantly affected by changes in precompression. E' and tan delta increased significantly with frequency. E 'monotonically increased from 4.7 to 7.9 kPa for the 1-3% compression range (lowest precompression for 2% amplitude) and from 6.3 to 10.3 kPa for the 6-8% range (highest precompression for 2% amplitude) when increasing frequency from 1 to 30 Hz. Tan delta increased montonically from 0.35 to 0.45 for 2% amplitude compressions from 1 to 30 Hz regardless of initial precompression. Our results show that precompression and testing frequency must be taken into account in order to obtain consistent measurements in mechanical diagnostic tests developed for cervical abnormalities.

Acoustic-induced motion of the bushcricket (Mecopoda elongata, Tettigoniidae) tympanum

Bushcrickets have a tonotopically organised hearing organ, the so-called crista acustica, in the tibia of the forelegs. This organ responds to a frequency range of about 5-80 kHz and lies behind the anterior tympanum on top of a trachea branch. We analyzed the sound-induced vibration pattern of the anterior tympanum, using a Laser-Doppler-Vibrometer Scanning microscope system, in order to identify frequency-dependent amplitude and phase of displacement. The vibration pattern evoked by a frequency sweep (4-79 kHz) showed an amplitude maximum which would correspond to the resonance frequency of an open tube system. At higher frequencies of about 30 kHz a difference in the amplitude and phase response between the distal and the proximal part of the tympanum was detected. The inner plate of the tympanum starts to wobble at this frequency. This higher mode in the motion pattern is not explained by purely acoustic characteristics of the tracheal space below the tympanum but may depend on the mechanical impedance of the tympanum plate. In accordance with a previous hypothesis, the tympanum moves over the whole tested frequency range in the dorso-ventral direction like a hinged flap with the largest displacement in its ventral part and no higher modes of vibration.

The impact of concentration, temperature and pH on dynamic rheology of psyllium gels

Structural aspects of the psyllium gum prepared from the seed husk of the plant of Plantago ovata Forsk was characterized by dynamic rheology and microscopy. Dynamic rheological properties of psyllium gel in the linear viscoelastic region, as a function of concentration (2, 2.5 and 3% w/w), temperature (5–95 °C) and pH (2.5–10) were investigated. Mechanical spectra of the psyllium gels were obtained by frequency sweep measurement classified into that of weak gels because G′ was larger than G″ throughout the tested frequency range and the separation of the two moduli (tan δ) was greater than 0.1. The phase angle increased with temperature and a peak associated with gel melting appeared at about 40 °C. All gels at different pH presented a typical weak gel spectrum. Scanning electron microscopy showed porous structures with different pore-size distribution for psyllium gels under different conditions in terms of concentration, pH and temperature.

Investigation into electrical conductivity and electromagnetic interference shielding effectiveness of silicone rubber filled with Ag-coated cenosphere particles

In this paper, silver film on the surface of cenosphere particles was obtained by an electroless plating method. The Ag-coated cenosphere particles were used as conductive filler in silicone rubber for electromagnetic interference (EMI) shielding applications. The effect of Ag-coated cenosphere particle content on the electrical conductivity and shielding effectiveness (SE) of the silicone rubber composite was investigated. The results indicated that the Ag-coated cenosphere particles mixed in the silicone rubber were not broken and were evenly distributed. The silver film was not oxidized during preparation of the composite. The volume resistivity of the composites decreased and SE was enhanced with increase of the Ag-coated cenosphere particle content. When the Ag-coated cenosphere particle content reached 240 parts per hundred of rubber (phr), the SE values of the silicone rubber composite were typically above 80 dB across the tested frequency range from 100 KHz to 1.5 GHz.

Picosecond electric pulse excitation of three-branch ballistic nanodevices

Picosecond electrical pulse excitation of the ballistic three-branch junctions (TBJs) was performed to investigate the electrical response at terahertz frequencies. The generation of picosecond electrical pulses and the signal detection with sub-picosecond temporal resolution were achieved by a photoconductive switch and the time-resolved electro-optical sampling technique, respectively, with the help of the femtosecond Ti:Sapphire laser system. The electrical response of a TBJ rectifier to the 1.75-ps-wide incident pulse was successfully measured and its frequency spectrum was not degraded in the tested frequency range, as compared to the incident excitation.

Absorption properties of carbonyl-iron/carbon black double-layer microwave absorbers

Double-layer materials were devised in order to improve the absorbing properties of electromagnetic wave absorbing plates. The double-layer wave absorbing materials are composed of a matching layer and an absorption layer. The matching layer is the surface layer through which most of the incident waves can enter, and the absorption layer beneath it plays an important role in incident wave attenuation. The total thickness of the double layer is the sum of the thicknesses of these two layers. Carbonyl iron (CI) and carbon black (CB) were used as absorbents in the matching and absorption layers, respectively. The structures of the CI and CB particles were analyzed using scanning electron microscopy and transmission electron microscopy; the dielectric properties and absorption mechanisms were also studied. In the testing frequency range 2–18 GHz, the results show that the double-layer absorbers have two absorption peaks, and the positions and values of these peaks change with the content level of the absorbents. When the mass fraction of CI in the matching layer is 50% and the total thickness of the absorber is 4 mm, the effective absorption band (below −8 dB) reaches 5.5, 5.8, and 6.5 GHz. Where the mass fraction of CB is 50% or 60% and the mass fraction of CI is 70%, the bandwidth with reflection loss below −4 dB is larger than 10 GHz.

Nonlinear Identification of Mechanical Parameters in a Squeeze Film Damper With Integral Mechanical Seal

End seals in squeeze film dampers (SFDs) aid to increase their damping capability while maintaining low lubricant flow rates and reducing the severity of air ingestion. This paper presents measurements of the forced response in a SFD integrating a contacting end seal and with closed flow ports, i.e., no lubricant through flow. The system motion is nonlinear due to the dry-friction interaction at the mechanical seal mating surfaces. Single parameter characterization of the test system would yield an equivalent viscous damping coefficient that is both frequency and motion amplitude dependent. Presently, an identification method suited for nonlinear systems allows determining simultaneously the squeeze film damping and inertia force coefficients and the seal dry-friction force. The identification procedure shows similar (within 10%) force coefficients than those obtained with a more involved two-step procedure that first requires measurements without any lubricant in the test system. The identified SFD damping and inertia force coefficients agree well with model predictions that account for end flow effects at recirculation grooves. The overall test results demonstrate that the nonrotating end seal effectively eliminates side leakage and avoids air ingestion, thus maintaining a consistent damping performance throughout the test frequency range. The nonlinear identification procedure saves time and resources while producing reliable physical parameter estimations.

Preservation of cochlear function in Cd39 deficient mice

Signalling actions of extracellular nucleotides via P2 receptors influence cellular function in most tissues. In the inner ear, P2 receptor signaling is involved in many processes including the regulation of hearing sensitivity and the cochlea’s response to noise stress. CD39 (NTPDase1/ENTPD1) is an ectonucleotidase (ecto-nucleoside triphosphate diphosphohydrolase) that can hydrolyse purine and pyrimidine nucleoside tri- and di-phosphates to generate monophosphate nucleosides. Mice null for Cd39 exhibit major alterations in haemostasis and profound alterations in inflammatory and thrombotic reactions. Studies in the cochlea have suggested the involvement of purinergic-type signals that could be modulated by CD39 in regulation of cochlear blood flow and also auditory neurotransmission. This study aimed to determine the auditory phenotype of adult Cd39 null mice on the C57BL6 background . Auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE) were unaffected in Cd39-deficient mice across the range of test frequencies, suggesting normal neural and outer hair cell function. Mutant mice also showed little difference to wild type mice in vulnerability to acoustic trauma. Gene expression analysis of other membrane-bound NTPDases with comparable hydrolytic activity demonstrated an up-regulation of Entpd2 and Entpd8 in the cochleae of Cd39 deficient mice. These findings suggest that Cd39 deletion alone does not adversely affect cochlear function, possibly as compensatory up-regulation of other surface located NTPDases may offset predicted alterations in cochlear homeostasis.

Reflections on ‘The effect of elevated temperature and environment on the fatigue crack growth characteristics of Ti‐6Al‐2Sn‐4Zr‐2Mo‐0.1Si’ by J. A. Ruppen and A. J. McEvily, FFEMS, Vol 2, Issue 1, 1979, pp. 63–72

A principal finding of the study was that at 538 °C fatigue crack growth tests in air and in vacuum showed that oxidation rather than creep was more important in affecting the fatigue crack growth rate in the range of test frequencies from 1 to 30 Hz. Similar results have also been found for steel, as shown in Fig. 1. Effect of testing conditions on the fatigue crack growth behaviour of a 9Cr-2Mo steel.1 Figure 2 shows long crack growth behaviour as a function of Eq. (2) and R value. The transition in growth behaviour occurs where the plastic zone size is about equal to the grain size of the α-phase, 10 μm. The rate of fatigue crack growth in Ti-6Al-4V as a function of (ΔKeff−ΔKeffth)2, modified for static modes of separation which occur at the highest value of the parameter. A comparison of experimental and predicted values of the fatigue strength, σw, as a function of the initial flaw size, a0.4 Note that the smallest flaw is but 15 μm in length. After some 60 year of intense research by many investigators, it is beginning to look as though we can deal with fatigue crack propagation on a quantitative basis, based upon the understanding of the basic mechanisms involved.

Mechanical anti-aliasing acoustic low-pass filtering fiber-optic hydrophones with side cavities

A novel mechanical anti-aliasing fiber-optic hydrophone with an acoustic low-pass filter of side cavities has been reported，to the best of our knowledge，for the first time. The low frequency lumped parameters model and the effective acoustic circuit of the hydrophone is constructed based on the theories of electro-acoustic analogy，and the acoustic performance is predicted by the circuit analysis methods. Theoretical results show that the hydrophone has three resonant frequencies and one inverse resonant frequency induced by the side cavities，and the hydrophone has good high frequency attenuation properties. A hydrophone with side cavities，designed and fabricated by us，is tested in a standing-wave tube filled with water. The measured frequency response curve，on the whole，has identical form as that predicted by theory, over the test frequency range of 50 to 7000 Hz. To be speaific，the low frequency responses are in good accordance，and the acoustic sensitivity is about -140 dB re 1 rad/μPa. The high frequency responses have obvious difference，which is mainly induced by the operation limitation of the low frequency model. It is expected that this new type of fiber-optic hydrophone will work as an important class of sensors used to eliminate the aliasing in the future fiber-optic sonar systems.

The effect of pectin concentration on viscoelastic and sensory properties of processed cheese

SummaryThe effect of pectin addition on viscoelastic properties of model processed cheeses with 40% w/w dry matter and 50% w/w fat in dry matter after 42 days of storage at temperature 6 ± 2 °C has been investigated using dynamic oscillation rheometry (plate–plate geometry; frequency range 0.1–50.0 Hz; temperature 20 °C). The role of pectin concentration (0.2%, 0.4%, 0.6% and 0.8% w/w) has been studied. Also, the sensory evaluation of samples has been made to assess cheese appearance, rigidity, spreadability and flavour. All samples with the pectin addition were more rigid and less spreadable compared with processed cheeses without pectin. With the increasing concentration of pectin the storage (G′) and loss (G″) moduli rose at the whole tested frequency range (0.1–50.0 Hz). Growing pectin content resulted in the decrease in loss tangent (the nature of gel was changed to more elastic material). The dependence of processed cheese rigidity on pectin concentration (in range 0–0.8% w/w) was not linear. The appearance and flavour were not worse by pectin addition.

Active Vibration Control Using Delay Compensated LMS Algorithm by Modified Gradients

Active vibration control (AVC) based on adaptive finite impulse response (FIR) filters inhere delays in conditional signal dispersion. Reasons for these delays are geometrical arrangements, and computational time in analog digital converters (ADCs) and in digital analog converters (DACs). The delays represent a phase shift in periodic signals. These delays avoid instant feedback of the signals through the least mean square (LMS) algorithm. This can lead to instability and even divergence. This study presents a modification of the LMS algorithm by adjusting the underlying gradient descent algorithm. Using analytic considerations, it shows the conditions of convergence for the stepsize as well as the gradient. The result is that all delays occurring can be compensated entirely. Unlike the delayed LMS algorithm, the introduced method considers possible delays analytically and furnishes the possibility for a perfect delay compensation. Modifications are easy to put into practice and were researched and verified using various simulations. Measurements on a duct in a range from 100 Hz to 1000 Hz confirm the success of adjustment and show an excellent convergence over the whole tested frequency range. Signal manipulation, for example, with a low-pass filter, which allows reverse phase shifts between – π and π, results only in a small frequency range and may be omitted by using the delay compensated LMS algorithm. The analytic mathematical derivation of the required modification can be implemented easily.

Representations of Cat Meows and Human Vowels in the Primary Auditory Cortex of Awake Cats

Previous investigation of neural responses to cat meows in the primary auditory cortex (A1) of the anesthetized cat revealed a preponderance of phasic responses aligned to stimulus onset, offset, or envelope peaks. Sustained responses during stationary components of the stimulus were rarely seen. This observation motivates further investigation into how stationary components of naturalistic auditory stimuli are encoded by A1 neurons. We therefore explored neuronal response patterns in A1 of the awake cat using natural meows, time-reversed meows, and human vowels as stimuli. We found heterogeneous response types: approximately 2/3 of units classified as "phasic cells" responding only to amplitude envelope variations and the remaining 1/3 were "phasic-tonic cells" with continuous responses during the stationary components. The classification was upheld across all stimuli tested for a given cell. The differences of phasic responses were correlated with amplitude-envelope differences in the early stimulus portion (<100 ms), whereas the differences between tonic responses were correlated with ongoing spectral differences in the later stimulus portion. Phasic-tonic cells usually had a characteristic frequency (CF) <5 kHz, which corresponded to the dominant spectral range of vocalizations, suggesting that the cells encode spectral information. Phasic cells had CFs across the tested frequency range (<16 kHz). Instantaneous firing rates for natural and time-reversed meows were different, but mean rates for different categories of stimuli were similar. Evidence for cat's A1 preferring conspecific meows was not found. These functionally heterogeneous responses may serve to encode ongoing changes in sound spectra or amplitude envelope occurring throughout the entirety of the sound stimulus.