Small size monopole antenna with tri-band notch characteristics for broadband application

In this research article, the design of a broadband monopole antenna with triband notch characteristics is proposed. Notch characteristics are achieved by using an E-shaped slot on the patch and a U-shaped slot on the 50 Ω microstrip feed line. An E-shaped slot is introduced on the metal patch to reject one frequency band of 6.6 − 7.5 GHz and when an additional U-shaped slot is introduced on the microstrip feed line, it provides two-notch frequency bands of 4.8 − 5.7 GHz and 14.2 − 17.5 GHz. The notch bands are effectively used to avoid undesired interference from the WLAN, C band, and Ku band. The proposed antenna provides a very broad frequency range from 3.3 − 19.5 GHz except for three notch bands. The antenna is small in size and easy to design with only a volume of 29 mm × 21mm × 1.6 mm. The antenna is useful for broadband applications.

Efficient prediction of construction equipment exterior and cabin interior noise over broad frequency range using novel SEA method

Statistical Energy Analysis (SEA) is commonly used for the prediction of interior cabin noise from construction equipment such as excavators, dump trucks, or graders. While traditional SEA method is computationally efficient and effective for the prediction of total radiated noise, it isn't suitable for prediction of sound diffraction around machinery and evaluation of spatial variations in sound field. As a result, prediction of cabin airborne interior noise transmission using SEA method typically requires experimental measurements in order to estimate incident sound field over the exterior boundary of the cab which makes it unsuitable for use in early stage design where test data isn't available. A novel SEA method that accounts for spatial gradients in the reverberant field has been developed and is introduced in this paper. It's usage for prediction of both exterior and cab interior noise over broad frequency range is demonstrated along with experimental validation for construction equipment under operating conditions.

Ultrahigh energy-dissipation elastomers by precisely tailoring the relaxation of confined polymer fluids

Energy-dissipation elastomers relying on their viscoelastic behavior of chain segments in the glass transition region can effectively suppress vibrations and noises in various fields, yet the operating frequency of those elastomers is difficult to control precisely and its range is narrow. Here, we report a synergistic strategy for constructing polymer-fluid-gels that provide controllable ultrahigh energy dissipation over a broad frequency range, which is difficult by traditional means. This is realized by precisely tailoring the relaxation of confined polymer fluids in the elastic networks. The symbiosis of this combination involves: elastic networks forming an elastic matrix that displays reversible deformation and polymer fluids reptating back and forth to dissipate mechanical energy. Using prototypical poly (n-butyl acrylate) elastomers, we demonstrate that the polymer-fluid-gels exhibit a controllable ultrahigh energy-dissipation property (loss factor larger than 0.5) with a broad frequency range (10−2 ~ 108 Hz). Energy absorption of the polymer-fluid-gels is over 200 times higher than that of commercial damping materials under the same dynamic stress. Moreover, their modulus is quasi-stable in the operating frequency range.

Pre-selection of the candidate fields for deep imaging of the epoch of reionization with SKA1-low

ABSTRACT The Square Kilometre Array (SKA) will be the first low-frequency instrument with the capability to directly image the structures of the epoch of reionization (EoR). Indeed, deep imaging of the EoR over five targeted fields of 20 sq deg each has been selected as the highest priority science objective for SKA1. Aiming at preparing for this highly challenging observation, we perform an extensive pre-selection of the ‘quietest’ and ‘cleanest’ candidate fields in the southern sky to be suited for deep imaging of the EoR using existing catalogues and observations over a broad frequency range. The candidate fields should meet a number of strict criteria to avoid contaminations from foreground structures and sources. The candidate fields should also exhibit both the lowest average surface brightness and smallest variance to ensure uniformity and high-quality deep imaging over the fields. Our selection eventually yields a sample of 7 ‘ideal’ fields of 20 sq deg in the southern sky that could be targeted for deep imaging of the EoR. Finally, these selected fields are convolved with the synthesized beam of SKA1-low stations to ensure that the effect of sidelobes from the far-field bright sources is also weak.

Propagation of waves with a wide range of frequencies in digital core samples and dynamic strain anomaly detection: carbonate rock as a case study

SUMMARY Recent advancements in various types of seismic measurement methods, such as sonic logging, vertical seismic profiling (VSP) and surface seismic surveys, have allowed the high-quality measurement of seismic wave propagation over a broad frequency range. To elucidate the relationship between seismic wave propagation captured by various seismic methods at widely different frequencies and in highly heterogeneous zones (e.g. fractures, vuggy zones) developed in carbonate reservoirs, laboratory measurements have been conducted over a broad frequency range. However, existing laboratory methods measure the effective properties over an entire core sample. Furthermore, there are few laboratory measurements of individual fracture stiffnesses. We propose a method to indirectly estimate the local properties caused by local anomalies (e.g. fractures) in a core sample over a broad frequency range from the dynamic elastic properties of a dry core sample using synthetic seismic waveforms generated from a digital volume of the core sample. 3-D numerical simulations were conducted over a broad frequency range using a digital core model produced by X-ray computed tomography. The proposed method was applied to numerical models and two types (fractured and vuggy) of carbonate core plugs acquired in an Abu Dhabi oil field, with the frequency ranging from 200 Hz to 100 kHz in the tests. Local strain anomalies and their frequency dependencies were successfully detected in the fractured core plug. Such frequency-dependent local responses could be associated with the micromechanics of incomplete solid–solid contacts at fractures or the heterogeneity of core samples, and thus with the frequency-dependent fracture stiffness. It was also demonstrated that the heterogeneity-induced local strain in a vuggy core plug may affect the accuracy of existing low-frequency laboratory measurements.

Elegant design of carbon nanotube foams with double continuous structure for metamaterials in a broad frequency range

A CNT foam-based metamaterial was successfully designed with a bicontinuous phase structure and pressure-adjustable negative permittivitty and permeability.