Robust AOA-Based Target Localization for Uniformly Distributed Noise via ℓp-ℓ1 Optimization.

This paper addresses the problem of robust angle of arrival (AOA) target localization in the presence of uniformly distributed noise which is modeled as the mixture of Laplacian distribution and uniform distribution. Motivated by the distribution of noise, we develop a localization model by using the ℓp-norm with 0≤p<2 as the measurement error and the ℓ1-norm as the regularization term. Then, an estimator for introducing the proximal operator into the framework of the alternating direction method of multipliers (POADMM) is derived to solve the convex optimization problem when 1≤p<2. However, when 0≤p<1, the corresponding optimization problem is nonconvex and nonsmoothed. To derive a convergent method for this nonconvex and nonsmooth target localization problem, we propose a smoothed POADMM estimator (SPOADMM) by introducing the smoothing strategy into the optimization model. Eventually, the proposed algorithms are compared with some state-of-the-art robust algorithms via numerical simulations, and their effectiveness in uniformly distributed noise is discussed from the perspective of root-mean-squared error (RMSE). The experimental results verify that the proposed method has more robustness against outliers and is less sensitive to the selected parameters, especially the variance of the measurement noise.

Optimal 3D Angle of Arrival Sensor Placement with Gaussian Priors.

Sensor placement is an important factor that may significantly affect the localization performance of a sensor network. This paper investigates the sensor placement optimization problem in three-dimensional (3D) space for angle of arrival (AOA) target localization with Gaussian priors. We first show that under the A-optimality criterion, the optimization problem can be transferred to be a diagonalizing process on the AOA-based Fisher information matrix (FIM). Secondly, we prove that the FIM follows the invariance property of the 3D rotation, and the Gaussian covariance matrix of the FIM can be diagonalized via 3D rotation. Based on this finding, an optimal sensor placement method using 3D rotation was created for when prior information exists as to the target location. Finally, several simulations were carried out to demonstrate the effectiveness of the proposed method. Compared with the existing methods, the mean squared error (MSE) of the maximum a posteriori (MAP) estimation using the proposed method is lower by at least 25% when the number of sensors is between 3 and 6, while the estimation bias remains very close to zero (smaller than 0.15 m).

Debate on the compositions of influenza B in northern hemisphere seasonal influenza vaccines.

Background: Annual influenza vaccination is the most effective way to prevent influenza. Influenza vaccines have traditionally included the hemagglutinins (HA) and neuraminidases (NA) from the two A viruses (H1N1 and H3N2) and either B Yamagata or B Victoria. Mismatches between circulating isolates of influenza B and the vaccines are very common. Taking 2017/2018 winter in northern hemisphere as an example, this study was designed to find out the reasons for mismatch between the trivalent influenza vaccine (TIV) and most of the epidemic isolates at that time, and to discuss if there are some optimized programs for seasonal influenza vaccines. Methods: HA and NA sequences of the seasonal isolates circulating from December 1, 2017 to February 28, 2018, and in the previously other 7 winters in northern hemisphere from Global Initiative on Sharing All Influenza Data (GISAID) and the influenza database of National Center for Biotechnology Information (NCBI). Phylogenetic trees and genetic distances were constructed or calculated by using MAFFT and MEGA 6.0 software. Results: Influenza B composition in the TIV recommendation mismatched most of circulating viruses in 2017/2018 winter; the vaccine strain was from the B/Victoria lineage, while most of epidemic isolates were from the B/Yamagata lineage. The epidemic lineage of influenza B reached its peak a little late in the previous winter might be responsible for this mismatch. During 2010-2018, the mean genetic distances between epidemic isolates of influenza A (H1N1 and H3N2) and the vaccines were no higher than 0.02375 ± 0.00341 in both HA and NA. However, concerning influenza B virus, when forecasting done well, the mean genetic distances between epidemic isolates and the vaccines were no higher than 0.02368 ± 0.00272; otherwise, the distances could reach 0.13695 ± 0.00238. Conclusion: When applying quadrivalent influenza vaccines (QIVs) for vaccination, the recommendations of compositions for influenza B could be altered and assessed once in 3 or 4 years; when economic burden was considered intensively and TIVs were utilized, the recommended compositions for influenza B could be announced in April or May, rather than in February or March as now.

Evolutionary dynamics of the H7N9 avian influenza virus based on large-scale sequence analysis.

Since 2013, epidemics caused by novel H7N9 avian influenza A viruses (AIVs) have become a considerable public health issue. This study investigated the evolution of these viruses at the population level. Compared to H7 and N9 before 2013, there were 18 and 24 substitutions in the majority of novel H7N9 AIVs, respectively. Nine of these in HA and six in NA were rare before 2013, and four of these in HA and two in NA displayed host tropism. S136(128)N and A143(135)V are located on the receptor binding sites of the HA1 subunit and might be important factors in determining the host species of novel H7N9 AIV. On an overall scale, the evolution of H7 and N9, both in terms of time distribution and host species, is under negative selection. However, both in HA and NA, several sites were under positive selection. In both the overall epidemics and the human-derived H7N9 AIVs, eight positive selection sites were identified in HA1, with some located within the known antigen epitopes or the receptor binding site(RBS) domain. This may induce variations in H7N9 AIV with positive selection. It is necessary to strengthen the surveillance of novel H7N9 AIVs, both in human and bird population to determine whether a new virus has emerged through selection pressure and to prevent future epidemics from occurring.

Semiaquatic mammals might be intermediate hosts to spread avian influenza viruses from avian to human.

Avian influenza A viruses (AIVs) can occasionally transmit to mammals and lead to the development of human pandemic. A species of mammal is considered as a mixing vessel in the process of host adaptation. So far, pigs are considered as a plausible intermediate host for the generation of human pandemic strains, and are labelled 'mixing vessels'. In this study, through the analysis of two professional databases, the Influenza Virus Resource of NCBI and the Global Initiative on Sharing Avian Influenza Data (GISAID), we found that the species of mink (Neovison vison) can be infected by more subtypes of influenza A viruses with considerably higher α-diversity related indices. It suggested that the semiaquatic mammals (riverside mammals), rather than pigs, might be the intermediate host to spread AIVs and serve as a potential mixing vessel for the interspecies transmission among birds, mammals and human. In epidemic areas, minks, possibly some other semiaquatic mammals as well, could be an important sentinel species for influenza surveillance and early warning.

An Outlier Detection Method Based on Mahalanobis Distance for Source Localization.

This paper addresses the problem of localization accuracy degradation caused by outliers of the angle of arrival (AOA). The problem of outlier detection of the AOA is converted into the detection of the estimated source position sets, which are obtained by the proposed division and greedy replacement method. The Mahalanobis distance based on robust mean and covariance matrix estimation method is then introduced to identify the outliers from the position sets. Finally, the weighted least squares method based on the reliable probabilities and distances is proposed for source localization. The simulation and experimental results show that the proposed method outperforms representative methods when unreliable AOAs are present.

A DFT study of the unimolecular decomposition of 1,2,4-butanetriol trinitrate.

To improve understanding of the unimolecular decomposition mechanism of 1,2,4-butanetriol trinitrate (BTTN) in the gas phase, density functional theory calculations were performed to determine various decomposition pathways at the B3LYP/6-311G** level. Two main mechanisms for the unimolecular decomposition of BTTN were found. In the first, homolysis of one of the O-NO2 bonds occurs to form •NO2 and CH2ONO2CHONO2CH2CH2O•, which subsequently decomposes to form CH3CHO + •CHO + 3NO2 + HCHO. In the second, successive HONO elimination reactions yield three HONO and OHCCH2CHONO2CH2ONO2 fragments, which subsequently decompose to form CH3CHO + 2CO + 3HONO. We also found that the first pathway has a slightly lower activation energy than the second. The results show that the pathway involving O-NO2 cleavage is slightly more energetically favorable than that involving HONO elimination.

[The analysis of hantavirus S gene in Apodemus agrarius in Changbai area].

To gain more insights into epidemiologic characteristics and genotype of hantavirus in Apodemus agrarius in Changbai Area. Complete hantavirus S segment sequences were amplified by RT-PCR and sequenced. The phylogenetic trees were constructed for analysis of genetic characters of hantavirus. A total of 58 Apodemus agrarius were trapped in the epidemic areas, and complete hantavirus S segment sequences were obtained from 4 lung samples of these rodents (6. 90%0). Phylogenetic analysis of the four S segment sequences indicated that all viruses isolated from Apodemu sagrarius were closely related to genotype 6 of Hantaan virus (95. 8%-96. 3%, nucleotide identity; 98. 6%-99. 5%, amino acid identity), all of them had a specific S387 different from other genotypes of Hantaan virus.

Complete Genome Sequence of Wohlfahrtiimonas chitiniclastica Strain SH04, Isolated from Chrysomya megacephala Collected from Pudong International Airport in China.

Wohlfahrtiimonas chitiniclastica bacilli that live in the larvae of a parasitic fly were recently isolated and are speculated to be the cause of fulminant sepsis. Here we report and analyze the complete genome sequence of Wohlfahrtiimonas chitiniclastica strain SH04. No complete genome sequence of a Wohlfahrtiimonas chitiniclastica isolate has been documented previously.

Theoretical studies on the unimolecular decomposition of nitroglycerin.

To improve the understanding of the unimolecular decomposition mechanism of nitroglycerin (NG) in the gas phase, density functional theory calculations were performed to determine various decomposition channels at the B3LYP/6-311G** level. For the unimolecular decomposition mechanism of NG, we find two main mechanisms: (I) homolytic cleavage of O-NO2 to form •NO2 and CH2ONO2CHONO2CH2O•, which subsequently decomposes to form •CHO, •NO2, and 2CH2O; (II) successive HONO eliminations to form HONO and CHO-CO-CHO, which subsequently decomposes to form CH2O + 2CO2 and •CHO + CO. We also find that the former channel has slightly smaller activation energy than the latter one. In addition, the rate constants of the initial process of the two decomposition channels were calculated. The results show that the O-NO2 cleavage pathway occurs more easily than the HONO elimination.

Prediction of the properties and thermodynamics of formation for energetic nitrogen-rich salts composed of triaminoguanidinium cation and 5-nitroiminotetrazolate-based anions.

Density functional theory and volume-based thermodynamics calculations were performed to study the effects of different substituents and linkages on the densities, heats of formation (HOFs), energetic properties, and thermodynamics of formation for a series of energetic nitrogen-rich salts composed of triaminoguanidinium cation and 5-nitroiminotetrazolate anions. The results show that the -NO(2), -NF(2), or -N(3) group is an effective substituent for increasing the densities of the 5-nitroiminotetrazolate salts, whereas the effects of the bridge groups on the density are coupled with those of the substituents. The substitution of the group -NH(2), -NO(2), -NF(2), -N(3), or the nitrogen bridge is helpful for increasing the HOFs of the salts. The calculated energetic properties indicate that the -NO(2), -NF(2), -N(3), or -N=N- group is an effective structural unit for improving the detonation performance for salts. The thermodynamics of formation of the salts show that all the salts may be synthesized easily by the proposed reactions. The structure-property relationships provide basic information for the molecular design of novel high-energy salts.