1,109 research outputs found

    Distributed Linear Convolutional Space-Time Coding for Two-Relay Full-Duplex Asynchronous Cooperative Networks

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    In this paper, a two-relay full-duplex asynchronous cooperative network with the amplify-and-forward (AF) protocol is considered. We propose two distributed space-time coding schemes for the cases with and without cross-talks, respectively. In the first case, each relay can receive the signal sent by the other through the cross-talk link. We first study the feasibility of cross-talk cancellation in this network and show that the cross-talk interference cannot be removed well. For this reason, we design space-time codes by utilizing the cross-talk signals instead of removing them. In the other case, the self-coding is realized individually through the loop channel at each relay node and the signals from the two relay nodes form a space-time code. The achievable cooperative diversity of both cases is investigated and the conditions to achieve full cooperative diversity are presented. Simulation results verify the theoretical analysis.Comment: 11 pages, 7 figures, accepted by IEEE transactions on wireless communication

    Power-Efficient Radio Resource Allocation for Low-Medium -Altitude Aerial Platform Based TD-LTE Networks

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    In order to provide an increased capacity, throughput and QoS guarantee for terrestrial users in emergency scenarios, a low-medium-altitude aerial platform based time-division-duplex long term evolution (TD-LTE) system referred to as Aerial LTE, is presented in this paper. Additionally a power-efficient radio resource allocation mechanism is proposed for both the Aerial LTE downlink and uplink, which is modeled as a cooperative game. Our simulation results demonstrate that the proposed algorithm imposes an attractive tradeoff between the achievable throughput and the power consumption while ensuring fairness among users

    Physicochemical Properties of a Red Soil Affected by the Longterm Application of Organic and Inorganic Fertilizers

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    Red soils are widespread throughout subtropical and tropical regions and are the most important resources for grain production in South China. Application of chemical fertilizers alone or chemical fertilizers combined with organic amendments is commonly practiced to improve physicochemical properties and fertility for red soils. This chapter summarizes the findings of a 22-year long-term field experiment conducted in the red soil region of south central China. Changes in soil pH, soil organic matter (OM), nitrogen (N), phosphorus (P), and aggregate distribution and stability as affected by the long-term fertilization treatments were examined and discussed. Combined application of chemical fertilizer and rice straw or pig manure significantly increased soil pH in the first 7 years, but soil pH decreased linearly at a rate of 0.04–0.07 unit yearly since then. Soil total N and total P content significantly increased during the long-term fertilization, and the effects of pig manure addition on N and P build-up were greater than that of rice straw addition. In contrast, soil total potassium (K) contents significantly decreased by the long-term fertilization. There was a significant difference between the effect of rice straw addition and pig manure amendment on various aggregate size distribution in the red soil

    Use of biochar as a soil amendment to reduce potentially toxic metals (PTMs) phytoavailability

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    The contamination of potentially toxic metals (PTMs) is widespread in the world and has negatively affected plants, humans, soil health, and environmental quality. Some metals are essential plant nutrients but they are also toxic to vegetation and aquatic live when present in high concentrations, such as Cu, Mn and Zn. Others (e.g., Pb, Cd, Cr, and As) are potential toxic metals for all organisms, and are not needed (or are toxic) for plant growth. This chapter summarizes the use of readily available biochars (BCs) to reduce PTMs phytoavailability in soils thus improving crop yields and to minimize its impact on the environment. The physicochemical and morphological properties of BCs as affected by feedstock sources and pyrolysis temperatures are discussed. The effectiveness of biochar rates on plant growth and metal fractions are also highlighted. Biochar has the potential to be used as a viable bioproduct for the remediation of contaminated soils since it reduces the phytoavailability of PTMs pollutants. Biochars produced from different feedstocks and at different pyrolysis temperatures present highly heterogeneous physicochemical and morphological properties, which can affect the effectiveness in the remediation of PTMs contaminated soils. Therefore, potential technologies need to be developed and research gaps still need to be overcome to optimize the use of BCs as a feasible alternative for remediation of metal contaminated soils.Plant and Soil Science

    S3^3FD: Single Shot Scale-invariant Face Detector

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    This paper presents a real-time face detector, named Single Shot Scale-invariant Face Detector (S3^3FD), which performs superiorly on various scales of faces with a single deep neural network, especially for small faces. Specifically, we try to solve the common problem that anchor-based detectors deteriorate dramatically as the objects become smaller. We make contributions in the following three aspects: 1) proposing a scale-equitable face detection framework to handle different scales of faces well. We tile anchors on a wide range of layers to ensure that all scales of faces have enough features for detection. Besides, we design anchor scales based on the effective receptive field and a proposed equal proportion interval principle; 2) improving the recall rate of small faces by a scale compensation anchor matching strategy; 3) reducing the false positive rate of small faces via a max-out background label. As a consequence, our method achieves state-of-the-art detection performance on all the common face detection benchmarks, including the AFW, PASCAL face, FDDB and WIDER FACE datasets, and can run at 36 FPS on a Nvidia Titan X (Pascal) for VGA-resolution images.Comment: Accepted by ICCV 2017 + its supplementary materials; Updated the latest results on WIDER FAC