In this letter, the weighted fractional Fourier transform (WFRFT) is performed on the chaotic sequence to enhance the security of the chaotic direct sequence spread spectrum (CD3S) communication, and a WFRFT-CD3S system that spreads the information bits through the WFRFT-chaotic sequence is proposed. In the proposed system, the transmitter scrambles the phase space trajectory of the chaotic sequence through WFRFT and make the distribution of the transmitted signal be Gaussian-like. The receiver synchronizes the WFRFT-chaotic sequence through bidirectional correlation search and demodulates the information through the synchronized local WFRFT-chaotic sequence. Simulations are implemented to evaluate the security performance, synchronization performance, and demodulation performance of the proposed system.
Phytohormones have an essential ability to adapt to abiotic stresses, including drought stress (DS), by mediating physiological and molecular processes. Arbuscular mycorrhizas (AMs) can enhance tolerance of DS, but the information regarding phytohormone changes in AM plants exposed to DS is little known. Trifoliate orange (Poncirus trifoliata) seedlings colonized by an AM fungus Funneliformis mosseae were subjected to DS and well-watered for 6 weeks. Plant growth performance, gas exchange, indole-acetic acid (IAA), gibberellins (GAs), brassinosteroids (BRs), abscisic acid (ABA), methyl jasmonate (MeJA) and zeatin riboside (ZR) were determined. The 6-week DS treatment strongly restricted root mycorrhizal colonization. Mycorrhizal inoculation significantly increased plant growth parameters under DS, as compared with non-mycorrhizal treatment. Mycorrhizal treatment also induced significantly higher leaf-relative water content, net photosynthetic rate, transpiration rate and stomatal conductance but lower intercellular CO2 concentration and leaf temperature under DS, compared with non-mycorrhizal treatment. Mycorrhizal plants under DS condition represented significantly higher leaf ABA, IAA, GAs, BRs and ZR levels than non-mycorrhizal plants. The study, hence, suggested that mycorrhizal inoculation induced the changes of gas exchange and endogenous phytohormone levels to enhance drought tolerance in trifoliate orange.
The main advantage of tail-sitter unmanned aerial vehicle (UAV) are introduced. Three design solutions of rotor tail-sitter lift system of UAV have been presented and the respective control strategies and characteristics of three solutions are also analyzed in the paper, through the related experiments the design of twin-rotor lift system is verified, and its feasibility is proved. The characteristics and the applying background of the twin-rotor tail-sitter UAV are described in detail. Some useful conclusions of the lift system for tail-sitter UAV are obtained.
Nitrogen is an important nutrient for the yield formation of winter wheat, and the rich spectral and texture information of UAV ultra-high resolution imagery provides an important technical approach for nitrogen accurate prediction. In this study, based on the spectral and texture features extracted from UAV remote sensing images of winter wheat during the key growth stages (jointing stage, booting stage, flowering stage, and filling stage), the LASSO method was introduced to screen feature variables to eliminate the collinearity among the feature variables, and ridge regression, least-squares regression, and LASSO regression were used to construct the nitrogen prediction model in winter wheat plants. When the regularization parameter λ took the value of 0.08, 17 sensitive feature variables such as Nir, RERDVI, NGBDI, con_G, ent_R, mean_R, and mean_Nir were screened out. Based on the screened sensitive characteristic variables, the nitrogen prediction models established by the three methods of ridge regression, least squares regression, and LASSO regression all achieved significant differences at the 0.05 level. The accuracy of the three nitrogen prediction models was highly consistent with R2 of 0.76, 0.77, and 0.78, respectively, and the RMSEs of 3.55g/m2, 3.79g/m2, and 3.79g/m2, respectively. This indicates that the LASSO feature screening method introduced in this study not only makes the model concise but also the model constructed by the sensitive variables screened by LASSO is robust and provides technical support for precise monitoring and management of nitrogen in smart agriculture.
Diagnosing neonatal asphyxia solely according to Apgar score may lead to misdiagnosis. The aim of this study was to explore new and more accurate diagnostic criteria for neonatal asphyxia.Totally 10 376 live born neonates in our hospital were consecutively enrolled into the study. The following five items related to birth asphyxia, i.e., antepartum high-risk factors, Apgar scores, umbilical artery blood pH, organ injury, differential diagnosis on the causes of low Apgar score cases were examined and registered. The relationship among the first 4 items were analyzed. By differential diagnosis, the sensitivity and specificity of each index on diagnosing asphyxia and their complementary value on each other were investigated.The items correlated well with each other (P < 0.01 or < 0.05) but were not entirely parallel and consistent; they could complement but could not substitute for each other. The sensitivity of antepartum high-risk factors, low Apgar scores, umbilical artery blood pH < 7.00 and organ injury was 100%, 100%, 44.44% and 100%, while the specificity was 17.99%, 98.90%, 96.05% and 96.62%, respectively. Of the 230 low Apgar score cases in this series only 50.9% coincided with asphyxia. For the 230 cases, when low Apgar score was combined with umbilical artery blood pH < 7.00, the sensitivity and specificity were 41% and 99.1% and when low Apgar score was combined with umbilical artery blood pH < 7.20, the sensitivity and specificity were 100% and 29.20%, respectively. After organ injury was added, the specificity was increased to 65.49%. When differential diagnosis was further added to exclude the other causes of low Apgar score cases, the misdiagnosis rate was minimized.Up to now, no single accurate index for diagnosing neonatal asphyxia is available. In order to increase diagnostic bases and reduce misdiagnosis, the criteria of sole Apgar score should be replaced by multi-index diagnostic criteria. Based on the present study, a set of integrated diagnostic criteria for neonatal asphyxia is proposed: (1) prenatal high-risk factors, (2) low Apgar scores (respiratory depression must present), (3) umbilical artery blood pH < 7.00, if only pH < 7.20, the items (2) (4) (5) must be present, (4) hypoxic-ischemic organ injury (at least one organ dysfunction), (5) the other causes of low Apgar scores should be excluded. The last 4 indexes should all be met and the first one serves as reference. If multi-organ (three or more organs) dysfunction and (or) hypoxic-ischemic encephalopathy are present, severe asphyxia can be diagnosed.
This paper explores the relevance theory's account for the perception of an utterance, and attempts to offer a neurophysiological justification for some key hypotheses in RT. Meanwhile a crucial proposal for neurocognitive understanding of language perception is brought forward.
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