- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
On the attenuation of fluida??structure coupled modes in a non-planar waveguide
摘要： In this article, the attenuation of ?uid–structure coupled modes of non-planar waveguide involving cavities is discussed. The physical problem is modeled to illustrate the scattering behavior of acoustic waves in a ?exible waveguide composed of thin elastic elements having edges or joints and structural discontinuities. The ?uid–structure coupled waveforms scatter after interacting with the discontinuities and edges of the underlying structure. An appropriate choice of edges offers scattering or resonance processes, which also guide ?uid–structure coupled waves. The mode-matching technique, together with low-frequency approximation, is used to determine velocity potentials. The guiding structure is then analyzed and validated through scattering energy functionals by varying the dimensions of the cavities and the wave frequency. The results are formulated and analyzed by tuning the device using an appropriate choice of edge conditions, dimension of cavities, and wave frequencies, thereby validating the obtained solutions. These descriptions are very useful for the active control measure of structural vibrations.
关键词： cavities,mode-matching,Attenuation,non-planar waveguide,?uid structure
更新于2025-09-23 15:19:57
-
Upgraded CdZnTe Based on the Infrared Attenuation Spectrum
摘要： According to the infrared attenuation spectrum, we can know the conduction type and major point defect of CdZnTe crystals. Based on point defect modelling, an appropriate modus of atmosphere annealing was described in this paper. In this paper, annealing with Cd pressure control technology was used to upgrade p-CdZnTe and n-CdZnTe, respectively. Characterizations reveal that the optical and electrical performance of the CZT crystals is patently improved after annealing. Employment of the infrared attenuation spectrum as the annealing guideline has been veri?ed to be feasible and effectual in this paper.
关键词： CdZnTe,atmosphere annealing,infrared attenuation spectrum,free carrier absorption
更新于2025-09-19 17:15:36
-
Synergistic effect of β-Bi2O3 and graphene/MWCNT in silicone-based polymeric matrices on diagnostic X-ray attenuation
摘要： The prolonged exposure of high-energy ionizing radiations during treatment of cancer/tumour and radiological examinations is hazardous to occupational workers and patients. Lead-incorporated composite materials are traditionally used as radiopaque fabrics, but are heavy, bulky and hence often cause inconvenience to users. Therefore, superior radiopaque protective wears that are preferably lead-free, light weight and flexible are being explored. Towards this goal, we study here the synergistic effect of graphene nanoplatelets and multi-walled carbon nanotube (MWCNT) on the X-ray attenuation property of polymer nanocomposites containing β-Bi2O3 nanofillers. The effect of graphene and MWCNT at different concentrations on Bi2O3-based polymer nanocomposites is studied to attain optimal compositions with respect to its X-ray attenuation property and thermal stability. Surface topography and surface roughness of the nanocomposite blocks are studied using an atomic force microscope (AFM). The effect of the density of polymer on the curing, thermal stability and X-ray attenuation property is also studied by using silicone polymers of density 1.7 (G1) and 1.04 g/cm3 (G2). The X-ray attenuation property of nanocomposites with G1 polymer matrix is found to be better than that of G2. The G1-based nanocomposite containing β-Bi2O3 and graphene is found to be better than the one with G1 polymer containing β-Bi2O3 and MWCNT. Thermal stability of multifiller nanocomposites is found to be better than the one without nanofillers. AFM topography images show a variation in surface roughness of nanocomposites with different fillers, which contributes to the different micro- and nano-structural architectures due to polymer–nanofiller interaction, thereby, affecting the X-ray attenuation of the nanocomposites. Our study shows that the multifiller nanocomposite containing β-Bi2O3 and graphene nanoplatelets offer greater potential for the development of efficient radiopaque fabric materials.
关键词： Nanofillers,Graphene,MWCNT,Nanocomposites,Bi2O3,X-ray attenuation
更新于2025-09-19 17:15:36
-
Radiation induced attenuation in pure silica polarization maintaining fibers
摘要： Radiation-induced attenuation (RIA) at λ = 1.55 μm is studied in polarization-maintaining (PM) pure-silica-core optical fibers of the Panda-type under γ-irradiation and upon pulsed-X-ray-irradiation. For the first time, the RIA spectrum is compared under γ-irradiation in a Panda and in a non-PM fiber drawn from the same preform before embedding the stress-applying rods. It is found out that the chief RIA origins in the near-IR range in both fibers are an extremely short-lived band centered at ~1 eV and the tails of the classical bands due to strain-assisted self-trapped holes (STHs) at 1.63 and 1.88 eV. The former band is found to be many times more intense in the Panda; the latter bands, somewhat more intense in the non-PM fiber. The ~1-eV band proved to be composed of two Gaussian sub-bands centered at 0.95 and 1.12 eV. Under γ-irradiation, the composite ~1-eV band is found to be photobleached virtually fully by 1.55-μm light of 5-mW power, which results in manifold reduction of the total RIA. Upon pulsed irradiation, RIA in Pandas at large post-pulse times (> 1 ms–1 s) is found to fall off below the record low level demonstrated elsewhere by a non-PM pure-silica-core fiber. This fact is explained as being due to a smaller concentration of strain-assisted STHs in Pandas than in non-PM fibers. The concentration of strain-assisted STHs in Pandas is shown to increase with increasing the value of birefringence.
关键词： Radiation-induced attenuation,Self-trapped holes,Polarization-maintaining fiber
更新于2025-09-19 17:15:36
-
Effect of attenuate light on polymerization of ceramic suspensions for stereolithography
摘要： Weak bonding strength between interlayers can seriously affect the quality of ceramic parts manufactured by stereolithography. Therefore, the possibility of using chemical bonds to strengthen the adhesion within these parts and the extent to which may be effective are of interest. Thus, a multi-exposure model was built to illustrate the state of this interface. The secondary conversion of a cured layer defined as conversion rate increment caused by decayed ultraviolet (UV) light in a subsequent exposure was selected to represent the extent of a chemical bond. The level of UV light attenuation occurred when travelling through a suspension layer was determined using the Attenuation Law. When decayed light illuminated a cured layer, it underwent further photopolymerization, which was detected by temperature change. The secondary conversion was affected by parameters including the incident energy dose and the propagating length. Optimization of these parameters helped to achieve higher chemical bond ratio.
关键词： Ceramic stereolithography,Secondary photopolymerization,Multi-exposure model,Light attenuation
更新于2025-09-19 17:15:36
-
[IEEE 2019 IEEE International Ultrasonics Symposium (IUS) - Glasgow, United Kingdom (2019.10.6-2019.10.9)] 2019 IEEE International Ultrasonics Symposium (IUS) - Simultaneous dictionary learning and reconstruction from subsampled data in photoacoustic microscopy
摘要： The Global Precipitation Measurement (GPM) Core Observatory will carry a Dual-frequency Precipitation Radar (DPR) consisting of a Ku-band precipitation radar (KuPR) and a Ka-band precipitation radar (KaPR). In this study, “at-launch” codes of DPR precipitation algorithms, which will be used in GPM ground systems at launch, were evaluated using synthetic data based upon the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) data. Results from the codes (Version 4.20131010) of the KuPR-only, KaPR-only, and DPR algorithms were compared with “true values” calculated based upon drop size distributions assumed in the synthetic data and standard results from the TRMM algorithms at an altitude of 2 km over the ocean. The results indicate that the total precipitation amounts during April 2011 from the KuPR and DPR algorithms are similar to the true values, whereas the estimates from the KaPR data are underestimated. Moreover, the DPR estimates yielded smaller precipitation rates for rates less than about 10 mm/h and greater precipitation rates above 10 mm/h. Underestimation of the KaPR estimates was analyzed in terms of measured radar re?ectivity ( ) of the KaPR at an altitude of 2 km. The underestimation of the KaPR data was most pronounced during strong precipitation events of (high attenuation cases) over heavy precipitation areas in the Tropics, whereas the underestimation was less pronounced when the (moderate attenuation cases). The results suggest that the underestimation is caused by a problem in the attenuation correction method, which was veri?ed by the improved codes.
关键词： simulation,spaceborne radar,rain,Global Precipitation Measurement (GPM),snow,Tropical Rainfall Measuring Mission (TRMM),Algorithms,attenuation
更新于2025-09-19 17:13:59
-
Design and achievement of hardware-in-the-loop simulation system for strapdown semi-active laser seeker
摘要： According to the work characteristics of semi-active laser-guided weapon system, at first, the optical characteristics of the laser received by seeker were analyzed; and mathematical model of the optical signal power received by seeker was established. Secondly, a hardware-in-the-loop simulation(HILS) system was designed for strapdown seeker. In order to simulate energy and laser spot’s continuous variations, a high-precision continuous dynamic laser energy attenuation system and a digital micromirror device(DMD) spot projection system were designed respectively. In the end, the HILS system was used to evaluate the performances of strapdown seeker and the seeker was tested for response coherence among the four quadrants, field of view(FOV), linear field of view, minimum received optical power, and angle measurement accuracy.
关键词： strapdown seeker,hardware-in-the-loop simulation,DMD spot projection,laser energy attenuation,semi-active laser-guided weapon
更新于2025-09-19 17:13:59
-
[IEEE 2019 IEEE 7th Workshop on Advances in Information, Electronic and Electrical Engineering (AIEEE) - Liepaja, Latvia (2019.11.15-2019.11.16)] 2019 IEEE 7th IEEE Workshop on Advances in Information, Electronic and Electrical Engineering (AIEEE) - Phase and Attenuation Characteristics of Models of GaAs Semiconductor Waveguides in Case of Two Layers
摘要： Models of cylindrical multilayer semiconductor-anisotropic-semiconductor dielectric-anisotropic-semiconductor waveguides are presented in this paper. We have selected n-GaAs semiconductor and TM-15 dielectric as a core of the presented waveguides. Anisotropic TM-15 and Rb1?x(ND4)D2PO4 dielectrics and n-InAs1-xSbx semiconductor we used for the external layers of waveguides. The influence of different core materials and temperature to the waves phase characteristics and attenuation was evaluated. Differential Maxwell’s equations, coupled mode, and boundary condition methods were used during the investigation. The density of electrons was constant and equal to N = 5·1019 m–3 during all investigations. The temperature has varied in the range of 125–200 K. Results have showed that material of the core, external layers and temperature has a big impact on the phase and attenuation characteristics of the waveguide and these types of waveguides could be used in the manufacture of phase shifters and attenuators.
关键词： phase characteristics,microwave devices,attenuation,semiconductor waveguides
更新于2025-09-19 17:13:59
-
[IEEE 2019 IEEE 2nd Ukraine Conference on Electrical and Computer Engineering (UKRCON) - Lviv, Ukraine (2019.7.2-2019.7.6)] 2019 IEEE 2nd Ukraine Conference on Electrical and Computer Engineering (UKRCON) - Radiating Unit Based on Inverted Dielectric Waveguide
摘要： The results of the experimental research of the radiating structure, based on inverted dielectric waveguide with metal plane and periodic sequence of auxiliary partially-metallized dielectric rods, are presented. The attenuation and VSWR measurements have been carried out in a wide frequency range. The near field amplitude has been measured through the moving probe method. The radiation energy characteristics have been measured.
关键词： VSWR,radiation pattern,inverted isolated dielectric waveguide,attenuation
更新于2025-09-16 10:30:52
-
Measurement of the local sound pressure on a Bias-flow liner using high-speed holography and tomographic reconstruction
摘要： Bias-?ow liners (BFL) are used as part of the cooling mechanism in airplane turbines and they also enable the reduction of noise emission. The attenuating principle is based on the interaction between sound waves and air ?ow. This turbulent aeroacoustic interaction occurs on a microscopic level and under harsh conditions. Therefore, in order to investigate local aeroacoustic phenomena, the distribution of the local sound ?eld impedance, de?ned as sound pressure over acoustic particle velocity, is measured non-invasively. This work focuses on the non-invasive measurement of the local sound pressure. A fast camera-based holographic measurement system for the two dimensional tomographic measurement of the local sound pressure with high spatial resolution is presented. It features a spatial resolution of 52 μm with a simultaneous acquisition of up to 1600 measuring points. This enables the observation of sub-mm aeroacoustic effects, which are expected in the near ?eld over the BFL’s surface, while reducing the measurement duration by three orders of magnitude compared to single point measurement systems. An experimental validation of the camera-based tomographic system is carried out by reference measurements. The system was applied at an acoustical model and an aeroacoustic model. The measured local sound pressure variations are discussed for both models. This work seeks to enable the non-invasive investigation of sound pressure, in order to further understand aeroacoustic effects, their sound attenuating properties and increase the attenuation capability of a BFL without degrading the overall performance of turbines.
关键词： optoacoustics,bias-?ow liner,Flow measurement,tomography,sound pressure,aeroacoustic attenuation
更新于2025-09-16 10:30:52