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In near-field imaging of dense layered media, the forward model is complicated by material discontinuities, multi-reflections, refractions, antenna pattern effects, and coupling effects between the antenna and layers. Overcoming the non-uniformities caused by the antenna gain pattern and discontinuous media in the imaging function, a fast uniform near-field algorithm is developed to obtain smooth...
A 2-D near-field uniform diffraction tomographic (UDT) imaging algorithm is formulated to generate images of targets embedded in a layered structure. The conventional diffraction tomography (DT) improperly applies the stationary phase method for stratified environments to reduce the innermost spectral integral. In DT, the large argument is assumed to be the depth, which is not appropriate for near-field...
To realize image generation in real time with a portable radar system, a uniform diffraction tomographic (UDT) imaging algorithm is proposed to investigate objects buried in planar stratified media. Unlike conventional diffraction tomography (DT), UDT provides smoothly continuous images through layered structures, and like DT, the fast Fourier transform (FFT) is applied to generate images in real...
In this paper, a fast imaging algorithm based on the layered Green's function is applied to generate images of planar stratified media. Imaging results with a gap between blocks inside the wall are analyzed based on different polarizations. 2D FDTD simulations and measurements are used to generate near-field synthetic aperture backscatter data.
An efficient algorithm is proposed to reconstruct the 3D image of objects embedded in a multi-layered medium. Under the first-order Born approximation, the spectral domain dyadic Green's function for an arbitrary layered medium is used to obtain a linear relation between the spatial Fourier transform of the object function and the scattered field. The algorithm is efficiently implemented using the...
The growing size of modern storage systems is expected to exceed billions of objects, making metadata scalability critical to overall performance. Many existing distributed file systems only focus on providing highly parallel fast access to file data, and lack a scalable metadata service. In this paper, we introduce a middleware design called Index FS that adds support to existing file systems such...
Parallel file systems are often characterized by a layered architecture that decouples metadata management from I/O operations, allowing file systems to facilitate fast concurrent access to file contents. However, metadata intensive workloads are still likely to bottleneck at the file system control plane due to namespace synchronization, which taxes application performance through lock contention...
A matrix embedding (ME) code was developed as a commonly used steganographic technique by using a parity check matrix to perform embedding. In this paper, we propose a new approach to embedding algorithm using convolutional codes to improve the embedding efficiency. Higher embedding efficiency brings to better steganographic security. The proposed algorithm uses the time-varying convolutional codes...
Emulation of mechanical loads plays an important role in testing and verifying the control strategy of motor drive systems which consists of static and dynamic performance. During the test, the emulation system is required to provide load torque in accordance with the static and dynamic performances. And speed-torque characteristics should be taken in to consideration in the emulation of dynamic performance...
Event extraction plays an important role in improving complex natural language processing (NLP) applications. The Bio-Event extraction in GE shared task is important to understand biological processes. Although some researches and GE extraction systems have made great progress in biomedical event extraction from literatures, the methods still need to be studied and the performance of existing systems...
Modern cluster file systems provide highly scalable I/O bandwidth along the data path by enabling highly parallel access to file data. Unfortunately metadata scaling is lagging far behind data scaling. We propose a filesystem design that inherits the scalable data bandwidth of existing cluster file systems and adds support for distributed and high-performance metadata operations. Our idea is to integrate...
We analyze Hadoop workloads from three different research clusters from an application-level perspective, with two goals: (1) explore new issues in application patterns and user behavior and (2) understand key performance chal- lenges related to IO and load balance. Our analysis sug- gests that Hadoop usage is still in its adolescence. We see underuse of Hadoop features, extensions, and tools as well...
We analyze Hadoop workloads from three different research clusters from an application-level perspective, with two goals: (1) explore new issues in application patterns and user behavior and (2) understand key performance chal- lenges related to IO and load balance. Our analysis sug- gests that Hadoop usage is still in its adolescence. We see underuse of Hadoop features, extensions, and tools as well...
Conventional file systems are optimzed for large file transfers instead of workloads that are dominated by metadata and small file accesses. This paper examines using techniques adopted from NoSQL databases to manage file system metadata and small files, which feature high rates of change and efficient out-of-core data representation. A FUSE file system prototype was built by storing file system metadata...
Based on the Crescent Vector single-frequency and single-system testing OEM board with external GPS twin antennas to achieve real-time attitude determination. Take aerial photogrammetry for example, built a GPS twin antennas real-time yaw angle correction system based on MUC. The System acquires data through the OEM board, and real-time control the DC motor by the MCU to real-time achieve the correction...
As an ideal clean energy, solar energy has been used widely in cooking applications. The shape designing and color analysis of solar picnic products are carried out in the light of the heating principle of the box-type solar cookers. The problem of the inconvenience in bringing the spices, water, and mess kit in a picnic is solved by the intensive design concept, which also help to achieve the rational...
This paper proposes a digital intermediate frequency (D-IF) receiver for inter-vehicle communications. Bandpass sampling is employed to lower the sampling rate. Appropriate selection of sampling rate and equivalent digital IF frequency results in a simplified Digital down converter (DDC). Meanwhile, the simplified DDC makes the combination of DDC and the following low pass filter (LPF) possible. This...
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