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Synthetic Impulse and Aperture Radar (SIAR) is a kind of Multiple Input Multiple Output (MIMO) radar. It is a four‐dimensional radar that has advantages against stealth targets, multi targets, anti‐radiated missile, reconnaissan...
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Synthetic Impulse and Aperture Radar (SIAR) is a kind of Multiple Input Multiple Output (MIMO) radar. It is a four‐dimensional radar that has advantages against stealth targets, multi targets, anti‐radiated missile, reconnaissance and interference, as well as valuable features in high range resolution and high detection probability. SIAR uses special frequency coding separately in each antenna. This code has an essential function in SIAR, such as separating frequency bandwidth, satisfying orthogonality in transmitted signals, suppressing range‐angle and range‐Doppler frequency coupling. Pulse‐to‐pulse frequency code agility is a kind of radar signal coding that is used to suppress the sidelobes in range‐Doppler frequency. In this study, a design method is suggested to transmit waveform based on non‐sequential positive, negative and random carrier frequency coding with the dot product approach in pulse‐to‐pulse frequency code agility, to reduce sidelobes in range‐Doppler frequency coupling. The simulation results showed that this method could effectively remove the strong coupling between range‐Doppler frequency. Removing coupling in the range‐Doppler frequency decreases the sidelobes.
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Synthetic impulse and aperture radar (SIAR) is an orthogonal multiple input multiple output radar. It has several advantages, including the ability to detect multiple targets, Antiradiated Missiles (ARM), and stealth targets. Desp...
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Synthetic impulse and aperture radar (SIAR) is an orthogonal multiple input multiple output radar. It has several advantages, including the ability to detect multiple targets, Antiradiated Missiles (ARM), and stealth targets. Despite its four-dimensional (4-D) nature, it exhibits a strong coupling between range and angle, which dictates how well SIAR performs in the range-angle domain. Not only does the SIAR use frequency codes to separate the antennas, but also to ensure orthogonality. They can, however, mitigate the strong coupling between range and angle. Pulse-to-pulse frequency code agility is a technique for suppressing the SIAR radar's sidelobes. In this letter, we propose a method for reducing the coupling between range and angle by combining sequential positive, negative and random code with the dot product. The idea of coupling reduction presented in this letter is based on the ratio of each antenna position and frequency codes, which is referred to $\alpha $k, and multiple $\alpha $k in an array provides new advantages for target detection. This technique has the potential to significantly reduce the sidelobe levels.
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In recent years there have been numerous studies that have sought to understand the factors that determine the frequency of accidents on roadway segments over some period of time, using count data models and their variants (negati...
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In recent years there have been numerous studies that have sought to understand the factors that determine the frequency of accidents on roadway segments over some period of time, using count data models and their variants (negative binomial and zero-inflated models). This study seeks to explore the use of random-parameters count models as another methodological alternative in analyzing accident frequencies. The empirical results show that random-parameters count models have the potential to provide a fuller understanding of the factors determining accident frequencies.
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In this paper; dynamical resource allocation scheme is proposed to improve throughput and fairness in the modern broadband wireless systems such as IEEE 802.16 Worldwide Interoperability for Microwave Access. To assign the subcarr...
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In this paper; dynamical resource allocation scheme is proposed to improve throughput and fairness in the modern broadband wireless systems such as IEEE 802.16 Worldwide Interoperability for Microwave Access. To assign the subcarriers to users, dynamic fractional frequency reuse is used. In dynamic fractional frequency reuse, each cell is partitioned into two regions, one called super region and another called regular region. Regular region is divided into 3 parts which correspond to the three sectors. In this method, a utility function is firstly used for the subcarrier allocation to the geographical regions and then opportunistic scheduling is applied for the assignment subcarriers to users in each cell. In order to increase the throughput of the system, adaptive modulation and coding techniques are used. Using dynamic fractional frequency reuse reduces fairness among users of a cell. Therefore a random access sub-band is applied to improve the fairness of the system.
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In a network application, channel coding alone is not sufficient to reliably transmit a message of finite length K from a source to one or more destinations as in, e.g., file transfer. To ensure that no data is lost, it must be co...
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In a network application, channel coding alone is not sufficient to reliably transmit a message of finite length K from a source to one or more destinations as in, e.g., file transfer. To ensure that no data is lost, it must be combined with rateless erasure correcting schemes on a higher layer, such as a time-division multiple access (TDMA) system paired with automatic repeat request (ARQ) or random linear network coding (RLNC). We consider binary channel coding on a binary symmetric channel (BSC) and q-ary RLNC for erasure correction in a star network, where Y sources send messages to each other with the help of a central relay. In this scenario RLNC has been shown to have a throughput advantage over TDMA schemes as K→∞ and q→∞. In this paper we focus on finite block lengths and compare the expected throughputs of RLNC and TDMA. For a total message length of K bits, which can be subdivided into blocks of smaller size prior to channel coding, we obtain the channel code rate and the number of blocks that maximize the expected throughput of both RLNC and TDMA, and we find that TDMA is more throughput-efficient for small message lengths K and small q.
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Designing a multiplexing metasurface to exhibit diverse functionalities has been a trend in electromagnetics, acoustics, and mechanics. Here, we report a simple method to design the 2-bit coding acoustic metasurface by combining t...
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Designing a multiplexing metasurface to exhibit diverse functionalities has been a trend in electromagnetics, acoustics, and mechanics. Here, we report a simple method to design the 2-bit coding acoustic metasurface by combining the Helmholtz resonator-like structures. Each meta-atom has four coding modes to independently modulate the wave fronts at two different frequencies. The equivalent circuit principle and decoupling effect are theoretically and numerically analyzed to clarify the underlying physical mechanism of our design. We filter and suppress the redundant diffraction beams to realize perfect negative reflection by controlling the number of outgoing diffraction modes. Considering the impact of loss, we simulate the scattered pressure and directivity of far field radiation for oblique illumination at two predesigned frequencies, the results of which show good agreement with the predicted ones. Our work may have potential in the design of multiplexing, frequency-selective, and programmable acoustic devices. (C) 2021 Published by Elsevier B.V.
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We show that expander codes, when properly instantiated, are high-rate list recoverable codes with linear-time list recovery algorithms. List recoverable codes have applications to constructing efficiently list-decodable codes, as...
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We show that expander codes, when properly instantiated, are high-rate list recoverable codes with linear-time list recovery algorithms. List recoverable codes have applications to constructing efficiently list-decodable codes, as well as in compressed sensing and group testing. Previous list recoverable codes with linear-time decoding algorithms have all had rate at most 1/2; in contrast, our codes can have rate 1-epsilon for any epsilon > 0. We can plug our high-rate codes into a construction of Alon and Luby (1996), recently highlighted by Meir (2014) to obtain linear-time list recoverable codes of arbitrary rates R, which approach the optimal trade-off between the number of non-trivial lists provided and the rate of the code.A slight strengthening of our result would imply linear-time and optimally list-decodable codes for all rates. Thus, our result is a step in the direction of solving this important problem. (C) 2018 Elsevier Inc. All rights reserved.
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This paper describes a project that was undertaken using naturalistic driving data collected via Global Positioning System (GPS) devices to demonstrate a proof-of-concept for proactive safety assessments of crash-prone locations. ...
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This paper describes a project that was undertaken using naturalistic driving data collected via Global Positioning System (GPS) devices to demonstrate a proof-of-concept for proactive safety assessments of crash-prone locations. The main hypothesis for the study is that the segments where drivers have to apply hard braking (higher jerks) more frequently might be the "unsafe" segments with more crashes over a long-term. The linear referencing methodology in ArcMap was used to link the GPS data with roadway charactetistic data of US Highway 101 northbound (NB) and southbound (SB) in San Luis Obispo, California. The process used to merge GPS data with quarter-mile freeway segments for traditional crash frequency analysis is also discussed in the paper. A negative binomial regression analyses showed that proportion of high magnitude jerks while decelerating on freeway segments (from the driving data) was significantly related with the long-term crash frequency of those segments. A random parameter negative binomial model with uniformly distributed parameter for ADT and a fixed parameter for jerk provided a statistically significant estimate for quarter-mile segments. The results also indicated that roadway curvature and the presence of auxiliary lane are not significantly related with crash frequency for the highway segments under consideration. The results from this exploration are promising since the data used to derive the explanatory variable(s) can be collected using most off-the-shelf GPS devices, including many smartphones. (C) 2017 Elsevier Ltd. All rights reserved.
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The Letter is concerned with the optimisation of coded frequency and phase modulation (FPM). Two approaches to optimisation are presented and their improvements over the normal coded FPM are investigated. The analytic and simulati...
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The Letter is concerned with the optimisation of coded frequency and phase modulation (FPM). Two approaches to optimisation are presented and their improvements over the normal coded FPM are investigated. The analytic and simulation results show that the additional gains due to optimisation can be achieved with little or no loss.
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The genetic code of living organisms is inscribed into so called Open Reading Frames (ORFs) positioned in chromosomes. The code uses 20 amino acids as building blocks for the inscribed information. We show that the number of appea...
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The genetic code of living organisms is inscribed into so called Open Reading Frames (ORFs) positioned in chromosomes. The code uses 20 amino acids as building blocks for the inscribed information. We show that the number of appearances of a given amino acid in ORFs on a yeast chromosome may be described in a highly satisfactory manner by the Negative Binomial (NB) distribution. The fit is surprisingly good. We show the results for ORFs found in four yeast chromosomes, namely no. 4, 7, 11 and 13. The negative binomial fit is shown (1) graphically; (2) considering the Kolmogorov statistic; (3) performing a chi-square test and (4) using simulated samples. The applicability of the Kolmogorov test to the analysed data is discussed.
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