The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this paper, a novel approach to high resolution underwater acoustic imaging is proposed for limited aperture. The proposed imaging approach is based on cross-correlation and high resolution is achieved by using ultra-wideband (UWB) signals in combination with cross-correlation processing. The idea of the proposed imaging approach is that cross-correlation of a pair of the received UWB signals can...
A spherical hydrophone is developed. The equivalent circuit model and finite element model about the thin piezoelectric spherical shells have been built to predict its major performances. Some hydrophone prototypes have been fabricated and the corresponding tests in the anechoic tank have been finished. The results show that the above two way to design and simulate the thin piezoelectric spherical...
Synthetic basis functions method (SBFM) is a high order frequency domain algorithm. Compared to traditional method of moment (MoM), SBFM uses a series of synthetic functions (SFs) in place of low order functions to discretize vector integral equations which leads to a drastic decrease in memory cost. In traditional methods, the number of SFs is determined by the ratio between the last SF's singular...
A wideband omnidirectional dielectric resonator antenna (DRA) has been proposed. The simulated results show that the reflection coefficient of the DRA is less than −10dB in the frequency band of 1.61GHz-2.92GHz (57.8%), which can cover the 2G/3G/LTE bands simultaneously. In order to improve the omnidirectionality of the DRA array, a novel method to arrange the feeding coaxial cable is proposed. Based...
Accurate global observations from space are a critical part of the needed knowledge base for global climate change study. However, atmospheric temperature trends derived from space-borne microwave instruments remains a subject of debate, mainly due to uncertainty arise from calibration error and long-term drift and degradation of instrument. In this study, a new method was developed for assessing...
Spaceborne radiometers have provided critical information of atmospheric water vapor and precipitation through sounding channels around 183 GHz. Understanding the performance and characteristics of these channels is important for hardware assessment, refining radiative transfer model, and improving science product. Whereas atmospheric water profiles from ancillary operational or reanalysis data are...
Recently, the advanced coastline inflection point method (CIPSD) was developed to retrieve the instrument boresight pointing error of Suomi National Polar-orbiting Partnership (SNPP) Advanced Technology Microwave Sounder (ATMS). Because of the use of mathematical model and separate-domain technique, this algorithm can retrieve the boresight pointing error in terms of Euler angles efficiently. But...
The data-based parameter identification is an efficient way for the modeling of Wind Turbine Generation System (WTGS) which only reveals the external characteristic. However the inner characteristic is unknown. In practice the parameters of the mechanism model are changing with time. Thus in the paper the grey-box modeling approach which utilizes the operation data and operating mechanism together...
With the rapid development of economy, the proportion of cooling load and heating load grows into an important share of the total load. These loads formed the peak load and had great demand response potential. The effective demand response strategy becomes greatly significant to achieve peak load shifting, load rate improving and electricity cost reducing, which is developed on studying users load...
This paper presents a miniaturized Vivaldi antenna in order to meet the practical requirements of antenna array applications. Compared to the conventional Vivaldi antenna (CVA), the width of the modified Vivaldi antenna aperture is reduced 38.05% by adding regular slot edges (RSE), which will prevent the antenna array from generating the grating lobes. Additionally, the RSE has improved the radiative...
An aperiodic phased array antenna architecture for space-borne Synthetic Aperture Radar (SAR) is presented. The proposed array antenna possesses several advantages compare to traditional periodic arrays, including using phase-only control to fit different beam shaping and steering requirements, and consuming fewer RF energy to generate same receiving signal power level. An executive approach for the...
A new type of compact multibeam longitudinal slot array antenna fed by Rotman lens in composite construction of microstrip and substrate integrated waveguide (SIW) technology is proposed for mobile satellite communications. The antenna is constructed in the form of two layers, which is a highly integrated approach to reducing the size. A novel parallel-coupled SIW slot coupler is designed to connect...
In this paper, basic principles, advantages and disadvantages, development and applications of different types of fault current limiter (FCL) are described. Effects on safety and stability of power grid and optimization configuration are also expounded with the application of FCL in aspects of relay protection, reclosure, transient power angle and voltage stability. In addition, several key problems...
In this paper, the method of installing fault current limiters (FCLs) near DC converter station is proposed, which is aimed at the commutation failure caused by short circuit fault of the DC inverter side in AC/DC power system. Influence mechanism of FCLs on suppressing commutation failure is analyzed. What's more, effects of FCLs in different locations on commutation failure are compared. In addition,...
A novel reflectarray construction composited with dielectric and metal is demonstrated as a possible low-loss and low-cost solution for a dual-polarization antenna. This construction is working based on optical principle, where the phase shift is realized by varying the height of the dielectric-metal slab. And then, a conical-horn antenna is utilized as the primary feed. With the proposed unit-cell...
To improve the stopband attenuation performance, a modified Chebyshev filter based on transmission zeros is proposed. In the improved design process, several transmission zero-points out of passband is introduced to make stopband steeper, meanwhile, the network transformation is used to eliminate parasitic parameters in actual project realization, thus enhancing the performance of suppression outside...
Mutual radiation impedance attracts more and more attention in acoustic array research as inherent acoustic characteristic. For the measurement of the mutual radiation impedance, the curve fitting method is proposed based on the analysis of the relationship between the ideal and the practical directivity patterns. Simulation and experiments were carried out to validate the practicability of the method...
Holographic reconstruction is an inversion method with which the sound radiation characteristics of the sound source can be reconstructed by using nearfield acoustic holography. In this paper, the sound field holographic reconstruction method is researched based on the sound field reconstruction model of nearfield acoustic holography. Using MATLAB and LabVIEW virtual instrument software platform,...
The advantages of broad band and high efficiency make CBSA (cavity-backed slot antenna) a potential alternative for modern SAR (Synthetic Aperture Radar) systems. Therefore, a broadband CBSA is proposed for dual-polarization SAR system. By adopting double-layer wide slots and strip-lines feed, dual-polarization is achieved while still maintaining broad bandwidth. To enhance the antenna integration,...
A new constellation comprising of eight microwave small satellites is proposed in this study. This constellation is capable of covering the entire globe every two hours. With six more satellites added and properly arranged, a constellation is able to provide hourly observations of fast-evolving severe weather systems like hurricanes. Compared to current polar-orbiting satellite which normally carries...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.