3,487 research outputs found
Sherman-Morrison Regularization for ELAA Iterative Linear Precoding
The design of iterative linear precoding is recently challenged by extremely
large aperture array (ELAA) systems, where conventional preconditioning
techniques could hardly improve the channel condition. In this paper, it is
proposed to regularize the extreme singular values to improve the channel
condition by deducting a rank-one matrix from the Wishart matrix of the
channel. Our analysis proves the feasibility to reduce the largest singular
value or to increase multiple small singular values with a rank-one matrix when
the singular value decomposition of the channel is available. Knowing the
feasibility, we propose a low-complexity approach where an approximation of the
regularization matrix can be obtained based on the statistical property of the
channel. It is demonstrated, through simulation results, that the proposed
low-complexity approach significantly outperforms current preconditioning
techniques in terms of reduced iteration number for more than in both
ELAA systems as well as symmetric multi-antenna (i.e., MIMO) systems when the
channel is i.i.d. Rayleigh fading.Comment: 7 pages, 5 figures, IEEE ICC 202
Power Allocation for FDMA-URLLC Downlink with Random Channel Assignment
Concerning ultra-reliable low-latency communication (URLLC) for the downlink
operating in the frequency-division multiple-access with random channel
assignment, a lightweight power allocation approach is proposed to maximize the
number of URLLC users subject to transmit-power and individual user-reliability
constraints. Provided perfect channel-state-information at the transmitter
(CSIT), the proposed approach is proven to ensure maximized URLLC users.
Assuming imperfect CSIT, the proposed approach still aims to maximize the URLLC
users without compromising the individual user reliability by using a
pessimistic evaluation of the channel gain. It is demonstrated, through
numerical results, that the proposed approach can significantly improve the
user capacity and the transmit-power efficiency in Rayleigh fading channels.
With imperfect CSIT, the proposed approach can still provide remarkable user
capacity at limited cost of transmit-power efficiency.Comment: 6 pages, 6 figures, published on the conference of PIMRC 202
Tris(2-amino-1,3-thiaÂzole-κN 3)(7-oxaÂbicycloÂ[2.2.1]heptane-2,3-dicarboxylÂato-κ3 O 2,O 3,O 7)cadmium(II) dihydrate
In the crystal structure of the title complex, [Cd(C8H8O5)(C3H4N2S)3]·2H2O, the CdII atom exhibits a slightly distorted octaÂhedral CdO3N3 coordination, defined by the bridging O atom of the bicycloÂheptane unit, two O atoms from the carboxylÂate groups and by three N atoms from three 2-aminoÂthiaÂzole ligands. Uncoordinated lattice water molÂecules are also present in the crystal structure. N—H⋯O and O—H⋯O hydrogen-bonding interÂactions link the components into a three-dimensional structure
The Arabidopsis NLP7 gene regulates nitrate signaling via NRT1.1-dependent pathway in the presence of ammonium.
Nitrate is not only an important nutrient but also a signaling molecule for plants. A few of key molecular components involved in primary nitrate responses have been identified mainly by forward and reverse genetics as well as systems biology, however, many underlining mechanisms of nitrate regulation remain unclear. In this study, we show that the expression of NRT1.1, which encodes a nitrate sensor and transporter (also known as CHL1 and NPF6.3), is modulated by NIN-like protein 7 (NLP7). Genetic and molecular analyses indicate that NLP7 works upstream of NRT1.1 in nitrate regulation when NH4+ is present, while in absence of NH4+, it functions in nitrate signaling independently of NRT1.1. Ectopic expression of NRT1.1 in nlp7 resulted in partial or complete restoration of nitrate signaling (expression from nitrate-regulated promoter NRP), nitrate content and nitrate reductase activity in the transgenic lines. Transcriptome analysis revealed that four nitrogen-related clusters including amino acid synthesis-related genes and members of NRT1/PTR family were modulated by both NLP7 and NRT1.1. In addition, ChIP and EMSA assays results indicated that NLP7 may bind to specific regions of the NRT1.1 promoter. Thus, NLP7 acts as an important factor in nitrate signaling via regulating NRT1.1 under NH4+ conditions
Nanocarbon-Based Flame Retardant Polymer Nanocomposites.
In recent years, nanocarbon materials have attracted the interest of researchers due to their excellent properties. Nanocarbon-based flame retardant polymer composites have enhanced thermal stability and mechanical properties compared with traditional flame retardant composites. In this article, the unique structural features of nanocarbon-based materials and their use in flame retardant polymeric materials are initially introduced. Afterwards, the flame retardant mechanism of nanocarbon materials is described. The main discussions include material components such as graphene, carbon nanotubes, fullerene (in preparing resins), elastomers, plastics, foams, fabrics, and film–matrix materials. Furthermore, the flame retardant properties of carbon nanomaterials and their modified products are summarized. Carbon nanomaterials not only play the role of a flame retardant in composites, but also play an important role in many aspects such as mechanical reinforcement. Finally, the opportunities and challenges for future development of carbon nanomaterials in flame-retardant polymeric materials are briefly discussed.post-print8100 K
Poly[bisÂ(1H-imidazole)bisÂ(μ2-1H-imidazolido)bisÂ(μ2-7-oxabicycloÂ[2.2.1]heptane-2,3-dicarboxylÂato)trizinc(II)]
The title polymer, [Zn3(C8H8O5)2(C3H3N2)2(C3H4N2)2]n, was formed by the reaction of zinc acetate with imidazole and 7-oxabicycloÂ[2.2.1]heptane-2,3-dicarboxylic anhydride (norcanÂtharidine). One of the two crystallographically unique ZnII atoms is four-coordinated by three N atoms of three imidazole ligands, two of which are deprotonated, and by one carboxylÂate O atom of the demethylÂcantharate anion. The second ZnII atom is situated on an inversion centre and is six-coordinated by the bridging O atoms of two symmetry-related demethylÂcantharate anions and by four carboxylÂate O atoms of the corresponding carboxylÂate groups. The polymeric crystal structure is additionally stabilized by N—H⋯O hydrogen bonding between the imidazole ligands and carboxylÂate O atoms
Surface Modification of Ammonium Polyphosphate for Enhancing Flame-Retardant Properties of Thermoplastic Polyurethane.
Currently, the development of efficient and environmentally friendly flame-retardant
thermoplastic polyurethane (TPU) composite materials has caused extensive research. Ammonium
polyphosphate (APP) is used as a general intumescent flame retardant to improve the flame retardancy
of TPU. In this paper, we developed a functionalized APP flame retardant (APP-Cu@PDA). Adding
only 5 wt% of APP-Cu@PDA into TPU can significantly improve the flame-retardant’s performance
of the composite material, reflected by a high LOI value of 28% with a UL-94 test of V-0 rating.
Compared with pure TPU, the peak heat release rate, total heat release, peak smoke release rate, and
total smoke release were reduced by 82%, 25%, 50%, and 29%, respectively. The improvements on
the flame-retardant properties of the TPU/5%APP-Cu@PDA composites were due to the following
explanations: Cu2+-chelated PDA has a certain catalytic effect on the carbonization process, which
can promote the formation of complete carbon layers and hinder the transfer of heat and oxygen.
In addition, after adding 5% APP-Cu@PDA, the tensile strength and elongation at the break of
TPU composites did not decrease significantly. In summary, we developed a new flame-retardant
APP-Cu@PDA, which has better flame-retardant properties than many reported TPU composites,
and its preparation process is simple and environmentally friendly. This process can be applied to
the industrial production of flame retardants in the future.post-print4370 K
- …