Automatic modulation classification (AMC) for overlapped sources plays an important role in spectrum monitoring and signal interception. In this paper, we propose a feature-based AMC framework for ...multiple overlapped sources. The framework first separates the overlapped sources via blind channel estimation and then conducts novel maximum-likelihood-based multicumulant classification (MLMC) for each of the sources. MLMC employs multiple cumulants of arbitrary orders and arbitrary lags as discriminating features and a maximum likelihood ratio test for decision making. Hence, MLMC maximizes the probability of correct classification under the condition that the selected cumulants are utilized. Moreover, both the case with perfect channel estimation and the practically more relevant case with blind channel estimations, called fast independent component analysis and natural gradient independent component analysis, are presented to facilitate the signal separation process. Extensive simulations are also conducted to verify the validity and the superiority of the proposed framework and the MLMC algorithm.
The rapid development of modern electronic technology has provided high efficiency for social production, but it also brings serious electromagnetic interference (EMI). Although traditional metals ...and their alloys can serve as good electromagnetic shielding materials, their heavy weight, high cost as well as poor corrosion resistance limit their application in EMI shielding. Therefore, electromagnetic shielding materials with lightweight are gradually attracting more and more attention to meet the trend of lightweight and highly integrated electronic equipment. Polymers are widely used in EMI shielding materials because of their unique characteristics, such as lightweight, high flexibility and excellent corrosion resistance. This review is focused on the well-studied polymer-based lightweight composites, with the aim of providing a comprehensive review of the existing EMI shielding mechanism, preparation and application of polymer-based lightweight composites, along with retrieving new general insights into the advantages and limitations associated with the different measurement and prediction techniques, as well as the EMI shielding effectiveness of polymer-based lightweight composites including metal-containing composites, intrinsic conductive polymers, filler-containing polymers and newly discovered materials. These lightweight materials with fine EMI shielding performance will find more and more potential applications in communications, electronics, aerospace, military, environmental protection, etc.
Graphical abstract
Academic engagement plays an undeniable role in students' leaning outcome. Therefore, identifying the influential antecedents of promoting students' academic engagement is extremely crucial. Despite ...previous empirical studies have delved into the part played by several student-related and teacher-related factors in triggering Chinese students' academic engagement, the exploration on the roles of teacher support and teacher-student rapport is still scant. Thus, this study attempts to concentrate on the influence of teacher support and teacher-student rapport on undergraduate students' academic engagement in China. Three scales of the questionnaire-one each for teacher's support, student-teacher rapport, and the level of academic engagement-were completed by a total of 298 undergraduate students. Spearman Rho test was adopted to detect the correlations between the variables. Following that, multiple regression analysis was used to estimate the predictive power of the dependent variables. The result found that teacher support and teacher-student rapport exert a tremendous influence on boosting Chinese students' academic engagement. The leading implications and future directions are also presented.
Estimating directions of arrival (DOA) without knowledge of the source number is regarded as a challenging task, particularly when coherence among sources exists. Researchers have trained deep ...learning (DL)-based models to attack the problem of DOA estimation. However, existing DL-based methods for coherent sources do not adapt to variable source numbers or require signal independence. Herein, we put forward a new framework combining parallel DOA estimators with Toeplitz matrix reconstruction to address the problem. Each estimator is constructed by connecting a multi-label classifier to a spatial filter, which is based on convolutional-recurrent neural networks. Spatial filters divide the angle domain into several sectors, so that the following classifiers can extract the arrival directions. Assisted with Toeplitz-based method for source-number determination, pseudo or missed angles classified by the estimators will be reduced. Then, the spatial spectrum can be more accurately recovered. In addition, the proposed method is data-driven, so it is naturally immune to signal coherence. Simulation results demonstrate the predominance of the proposed method and show that the trained model is robust to imperfect circumstances such as limited snapshots, colored Gaussian noise, and array imperfections.
Water-soluble chelated calcium has been widely used in agriculture as a fertilizer to improve the absorption and utilization of calcium by plants. This paper prepared a new organic mineral ...fertilizer, based on fulvic acid-like substance chelated calcium (PFA-Ca2+ complex), using optimal parameters (i.e., pH, time, temperature, and Ca2+ concentration) to achieve a high chelation efficiency. The absorption, utilization, and distribution of the PFA-Ca2+ complex in rice roots were analyzed using laser scanning confocal microscopy (LSCM). Our results demonstrated that the optimal PFA-Ca2+ complex chelating efficiency (87%) was achieved at an initial Ca2+ concentration of 0.1 mol L−1, an equilibration time of 120 min, a pH of 5.0, and a temperature of 40 °C. The chelating reaction of a fulvic acid-like substance with Ca2+ primarily occurred on phenol hydroxyl, alcohol hydroxyl, and carboxyl groups. The PFA-Ca2+ complex was primarily enriched in the roots' pericycle, cortical, and epidermis cells, in both chelating and non-chelating forms. To our knowledge, this is the first report investigating how the PFA-Ca2+complex affects transformation in plants, which has significant implications for research on plant nutrition and nutrient distribution.
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•An eco-friendly and bio-renewable functional fertilizer was prepared.•PFA-Ca2+ enhances rice root development and nutrient absorption.•The speciation and distribution of PFA-Ca2+ can be visually visualized in the root.
<正>Among various types of behaviors,locomotion is the foundation for exploration,navigation,foraging,and approaching.Proper locomotion enables animals to move from one place to another via a ...sequence of actions and is essential for their survival.An excess,paucity,or imbalance of movements is considered to be a movement disorder which can impair the quality of or threaten survival
The arousal state of the brain covaries with the motor state of the animal. How these state changes are coordinated remains unclear. We discovered that sleep-wake brain states and motor behaviors are ...coregulated by shared neurons in the substantia nigra pars reticulata (SNr). Analysis of mouse home-cage behavior identified four states with different levels of brain arousal and motor activity: locomotion, nonlocomotor movement, quiet wakefulness, and sleep; transitions occurred not randomly but primarily between neighboring states. The glutamic acid decarboxylase 2 but not the parvalbumin subset of SNr γ-aminobutyric acid (GABA)-releasing (GABAergic) neurons was preferentially active in states of low motor activity and arousal. Their activation or inactivation biased the direction of natural behavioral transitions and promoted or suppressed sleep, respectively. These GABAergic neurons integrate wide-ranging inputs and innervate multiple arousal-promoting and motor-control circuits through extensive collateral projections.
Fix a positive integer
N
and a real number
0
<
β
<
1
/
(
N
+
1
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. Let
Γ
be the homogeneous symmetric Cantor set generated by the IFS
{
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-
β
N
:
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=
0
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1
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,
N
}
.
For
m
∈
Z
+
...we show that there exist infinitely many translation vectors
t
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(
t
0
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t
1
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t
m
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with
0
=
t
0
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⋯
<
t
m
such that the union
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is a self-similar set. Furthermore, for
0
<
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<
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2
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+
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, we give a finite algorithm to determine whether the union
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=
0
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+
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is a self-similar set for any given vector
t
. Our characterization relies on determining whether some related directed graph has no cycles, or whether some related adjacency matrix is nilpotent.
Previous observational studies have shown that low back pain (LBP) often coexists with sleep disturbances, however, the causal relationship remains unclear. In the present study, the causal ...relationship between sleep disturbances and LBP was investigated and the importance of sleep improvement in the comprehensive management of LBP was emphasized.
Genetic variants were extracted as instrumental variables (IVs) from the genome-wide association study (GWAS) of insomnia, sleep duration, short sleep duration, long sleep duration, and daytime sleepiness. Information regarding genetic variants in LBP was selected from a GWAS dataset and included 13,178 cases and 164,682 controls. MR-Egger, weighted median, inverse-variance weighted (IVW), penalized weighted median, and maximum likelihood (ML) were applied to assess the causal effects. Cochran's
test and MR-Egger intercept were performed to estimate the heterogeneity and horizontal pleiotropy, respectively. Outliers were identified and eliminated based on MR-PRESSO analysis to reduce the effect of horizontal pleiotropy on the results. Removing each genetic variant using the leave-one-out analysis can help evaluate the stability of results. Finally, the reverse causal inference involving five sleep traits was implemented.
A causal relationship was observed between insomnia-LBP (OR = 1.954, 95% CI: 1.119-3.411), LBP-daytime sleepiness (OR = 1.011, 95% CI: 1.004-1.017), and LBP-insomnia (OR = 1.015, 95% CI: 1.004-1.026), however, the results of bidirectional MR analysis between other sleep traits and LBP were negative. The results of most heterogeneity tests were stable and specific evidence was not found to support the disturbance of horizontal multiplicity. Only one outlier was identified based on MR-PRESSO analysis.
The main results of our research showed a potential bidirectional causal association of genetically predicted insomnia with LBP. Sleep improvement may be important in comprehensive management of LBP.
In the absence of prophylactic therapy, cytomegalovirus (CMV) viremia is a common complication following allogeneic hematopoietic cell transplantation (allo-HCT) and represents a significant cause of ...morbidity and mortality. Approximately 25% of allo-HCT happen in China, where the development and refinement of the 'Beijing protocol' has enabled frequent and increasing use of haploidentical donors. However, refractory CMV infection (an increase by >1 log
in blood or serum CMV DNA levels after at least 2 weeks of an appropriately dosed anti-CMV medication) is more common among patients with haploidentical donors than with other donor types and has no established standard of care. Here, we review the literature regarding refractory CMV infection following allo-HCT in China.
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