Design of Frequency Invariant Wideband Beamformer with Real and Symmetric FIR Filters

An approach to wideband beamformer with frequency invariant property is proposed by optimising the space-time two-dimensional finite impulse response (FIR) filters. Frequency invariant beam pattern brings some restrictions on frequency bandwith and filter length. Using the Landau-Pollak theorem to estimate the rank of wideband signals, we give the lower bound of filter length respect to array element numbers and the relative bandwidth of wideband signal. With the expression of beam pattern using real and symmetric FIR filters, we develop corresponding optimisation formation considering the robustness of beamformer as well, which can be easily solved by the least mean square (LMS) algorithm. A design example is provided to show the effectiveness of the proposed method.Defence Science Journal, 2012, 62(4), pp.243-247, DOI:http://dx.doi.org/10.14429/dsj.62.96

A Novel Technique Based on the Combination of Labeled Co-Occurrence Matrix and Variogram for the Detection of Built-up Areas in High-Resolution SAR Images

Interests in synthetic aperture radar (SAR) data analysis is driven by the constantly increased spatial resolutions of the acquired images, where the geometries of scene objects can be better defined than in lower resolution data. This paper addresses the problem of the built-up areas extraction in high-resolution (HR) SAR images, which can provide a wealth of information to characterize urban environments. Strong backscattering behavior is one of the distinct characteristics of built-up areas in a SAR image. However, in practical applications, only a small portion of pixels characterizing the built-up areas appears bright. Thus, specific texture measures should be considered for identifying these areas. This paper presents a novel texture measure by combining the proposed labeled co-occurrence matrix technique with the specific spatial variability structure of the considered land-cover type in the fuzzy set theory. The spatial variability is analyzed by means of variogram, which reflects the spatial correlation or non-similarity associated with a particular terrain surface. The derived parameters from the variograms are used to establish fuzzy functions to characterize the built-up class and non built-up class, separately. The proposed technique was tested on TerraSAR-X images acquired of Nanjing (China) and Barcelona (Spain), and on a COSMO-SkyMed image acquired of Hangzhou (China). The obtained classification accuracies point out the effectiveness of the proposed technique in identifying and detecting built-up areas

Tau pathology is associated with postsynaptic metabotropic glutamate receptor 5 (mGluR5) in early Alzheimer's disease in a sex-specific manner

INTRODUCTION To investigate the associations of metabotropic glutamate receptor 5 (mGluR5) with tau deposition and cognitive ability in patients with early Alzheimer's disease (AD). METHODS Twenty-six cognitively impaired (CI) and 14 cognitively unimpaired (CU) individuals underwent mGluR5 positron emission tomography (PET) ([18F]PSS232), amyloid PET ([18F]florbetapir), and tau PET ([18F]MK6240), and neuropsychological assessment. The relationships among mGluR5 availability, tau deposition, and neuropsychological assessment were analyzed using Spearman's correlation and mediation analyses. RESULTS CI patients had lower mGluR5 in the hippocampus than CU (standardized uptake value ratio [SUVr]: 2.03 ± 0.25 vs 1.79 ± 0.17, p = 0.003). Hippocampal mGluR5 was negatively associated with hippocampal tau deposition (r = ?.46, p = 0.003) and positively associated with cognitive performance, but only in women. Hippocampal tau deposition mediated the effect of mGluR5 on cognitive performance. DISCUSSION Reduced hippocampal mGluR5 is negatively related with tau deposition in most cortical regions and positively associated with cognitive performance, making it a promising biomarker for AD diagnosis and therapy. Highlights Cognitively impaired (CI) patients exhibited lower metabotropic glutamate receptor 5 (mGluR5) availability in the hippocampus than cognitively unimpaired (CU) subjects. Hippocampal mGluR5 availability was negatively associated with tau deposition in widespread cortex. Hippocampal mGluR5 availability was positively associated with cognitive performance. The close association of mGluR5 with tau and cognition performance exists only in females. Tau pathology mediated the relationship between mGluR5 availability and cognition

Microaerophilic Oxidation of Fe(II) Coupled with Simultaneous Carbon Fixation and As(III) Oxidation and Sequestration in Karstic Paddy Soil

Microaerophilic Fe(II)-oxidizing bacteria are often chemolithoautotrophs, and the Fe(III) (oxyhydr)oxides they form could immobilize arsenic (As). If such microbes are active in karstic paddy soils, their activity would help increase soil organic carbon and mitigate As contamination. We therefore used gel-stabilized gradient systems to cultivate microaerophilic Fe(II)-oxidizing bacteria from karstic paddy soil to investigate their capacity for Fe(II) oxidation, carbon fixation, and As sequestration. Stable isotope probing (SIP) demonstrated the assimilation of inorganic carbon at a maximum rate of 8.02 mmol C m-2 d-1. Sequencing revealed that Bradyrhizobium, Cupriavidus, Hyphomicrobium, Kaistobacter, Mesorhizobium, Rhizobium, unclassified Phycisphaerales, and unclassified Opitutaceas, were fixing carbon. Fe(II) oxidation produced Fe(III) (oxyhydr)oxides, which can absorb and/or co-precipitate As. Adding As(III) decreased the diversity of functional bacteria involved in carbon fixation, the relative abundance of predicted carbon fixation genes, and the amount of carbon fixed. Although the rate of Fe(II) oxidation was also lower in the presence of As(III), over 90% of the As(III) was sequestered after oxidation. The potential for microbially mediated As(III) oxidation was revealed by the presence of arsenite oxidase gene (aioA), denoting the potential of the Fe(II) oxidizing and autotrophic microbial community to also oxidize As(III). The results of this study demonstrate that carbon fixation coupled to Fe(II) oxidation can increase the carbon content in soils by microaerophilic Fe(II)-oxidizing bacteria, as well as accelerate As(III) oxidation and sequester it in association with Fe(III) (oxyhydr)oxides

Microsoft Word - 8278 Tamplate.

Abstract: With the developments of network communication, electronic commerce plays a more and more role in the trade business and industry structure. The requirement for the electronic commerce turns to be higher. In this study, we study current status about the cryptographic algorithms exploited in electronic commerce. We discuss the advantages and disadvantages about the symmetric and asymmetric algorithms and improve them. Then we give a new scheme that combines the improved symmetric algorithm and asymmetric algorithm. We give sound reasons to explain why our scheme is more secure. Finally, we carry the experiments to show the security of our scheme

Research of Cryptographic Algorithms Applied in Electronic Commerce

With the developments of network communication, electronic commerce plays a more and more role in the trade business and industry structure. The requirement for the electronic commerce turns to be higher. In this study, we study current status about the cryptographic algorithms exploited in electronic commerce. We discuss the advantages and disadvantages about the symmetric and asymmetric algorithms and improve them. Then we give a new scheme that combines the improved symmetric algorithm and asymmetric algorithm. We give sound reasons to explain why our scheme is more secure. Finally, we carry the experiments to show the security of our scheme