Linear Track Estimation Using Double Pulse Sources for Near-Field Underwater Moving Target

双脉搏来源(DPS ) 方法在这个工作为线性轨道评价被介绍。在在水下的移动的噪音鉴定的领域里指向， Doppler 将弄歪散发的噪音的频率和振幅。消除这，轨道评价是必要的。在 DPS 方法，我们首先估计通过放方法的基线在动人的目标安装的二正弦曲线脉搏来源的轴承。同时，每脉搏的射出并且记录的时间也被获得。然后，线性磁道参数将在两倍来源间距的帮助下基于几何学模式被完成。模仿的结果证实 DPS 改进以前的双来源间距方法的表演。模仿的实验用一辆动人的电池汽车被执行进一步评估它的表演。当目标离开是 4060m 时，实验结果证明那轨道方位角并且垂直偏导 DPS 的距离分别地在 0.6o 和 3.4m 下面。并且估计的速度的平均偏差在 0.25m/s 附近。

Application and Residue Pollution of Mulching Films in Xinjiang

In order to study current situation of application,recycling and residue pollution of mulching films in Xinjiang,and accurately grasp pollution degree of residue of mulching films,this paper made an empirical analysis on residue of mulching films in 31 typical counties and cities in Xinjiang. Results indicate that( i) use of mulching films in Xinjiang is wide and there is great difference in use and residue recycling between cities and counties. Planting area and planting structure jointly influence use of mulching films,and the use of mulching films is significantly correlated with recycling of mulching films,but not correlated with recycling rate of mulching films.( ii) There are significant differences in distribution of residue of mulching films,highest in North Xinjiang and South Xinjiang,followed by East Xinjiang,and the lowest in West Xinjiang.( iii) There are significant differences in distribution of residue of mulching films between different crop fields. Residue of mulching films in cotton field is the key problem of pollution.

Low frequency acoustic properties of bilayer membrane acoustic metamaterial with magnetic oscillator

A bilayer membrane acoustic metamaterial was proposed to overcome the influence of the mass law on traditional acoustic materials and obtain a lightweight thin-layer structure that can effectively isolate low frequency noise. The finite element analysis（FEA） results agree well with the experimental results.It is proved that the sound transmission losses（STLs） of the proposed structures are higher than those of same surface density acoustic materials. The introduction of the magnetic mass block is different from the traditional design method, in which only a passive mass block is fixed on the membrane. The magnetic force will cause tension in the membrane, increase membrane prestress, and improve overall structural stiffness. The effects of the geometry size on the STLs are discussed in detail. The kind of method presented in this paper can provide a new means for engineering noise control.

Sound absorption characteristic of micro-helix metamaterial by 3D printing

We present the design of micro-helix metamaterial supporting high sound absorption characteristic by 3D printing. The sample structure which is fabricated out of polylactide （PLA） material, many micro-helix are arranged by periodic arrays on XY plane. Experiment measurement results show that different geometrical dimensions of helix vestibule and cavity depth have a great effect on sound absorption coefficient. Physical mechanism depends on the friction and viscosity between the air and the helix vestibule. This work shows great potential of micro-structure metamaterial in noise control applications require light weight and large rigid of sound absorption.

Experimental investigation of sound absorption in a composite absorber

A composite absorber made of a polyurethane sponge and multi-layer micro-perforated plates is pre-sented in this study.Results from an acoustic impedance tube test show that the polyurethane sponge can exhibits higher low-frequency sound absorption in front of the micro-perforated plate,while sound absorption at medium and high-frequencies remains low.The physical mechanism behind this is that the micro-perforated plate increases the denpth cavity.If the polyurethane sponge is placed behind the micro-perforated plate,the amplitude of the original absorption peak will remain constant,but the ab-sorption peaks will shift to lower frequencies.The reason for this phenomenon is that porous materials with low flow resistance can be approximately equivalent to fluid,which not only does not affect the res-onance absorption coefficient of micro-perforated plate,but also makes the peaks move to low frequency.This study has the potential applications in the sound absorption design of composite structure.

Molecular diversity of arbuscular mycorrhizal fungi at a large-scale antimony mining area in southern China

Arbuscular mycorrhizal fungi （AMF） have great potential for assisting heavy metal hyperaccumulators in the remediation of contaminated soils. However, little information is available about the community composition of AMF under natural conditions in soils contaminated by antimony （Sb）. The objective of this study was to investigate the characteristics of AMF molecular diversity, and to explore the effects of Sb content and soil properties on the AMF community structure in an Sb mining area. Four Sb mine spoils and one adjacent reference area were selected from around the Xikuangshan mine in southern China. The association of AMF molecular diversity and community composition with the rhizosphere soils of the dominant plant species was studied by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis （PCR-DGGE）. Results from all five studied sites showed that the diversity of AMF decreased with increasing Sb concentration. Principal component analysis （PC_A） indicated that the AMF community structure was markedly different among these groups. Further redundancy analysis （RDA） showed that Sb contamination was the dominating factor influencing the AMF community structure in the Sb mine area. However, the multivariate analysis showed that, apart from the soil Sb content, extractable nitrogen content and organic matter content also attributed to AMF sequence distribution type. Some AMF sequences were only found in the highly contaminated area and these might be ideal candidates for improving phytoremediation efficiency in Sb mining regions. Gene sequencing analysis revealed that most species were affiliated with Gloraus, suggesting that Glomus was the dominant AMF genus in the studied Sb mining area.

Insights into simultaneous adsorption and oxidation of antimonite[Sb(III)]by crawfish shell-derived biochar:spectroscopic investigation and theoretical calculations

Removal of antimonite[Sb(Ⅲ)]from the aquatic environment and reducing its biotoxicity is urgently needed to safeguard environmental and human health.Herein,crawfish shell-derived biochars(CSB),pyrolyzed at 350,500,and 650℃,were used to remediate Sb(Ⅲ)in aqueous solutions.The adsorption data best fitted to the pseudo-second-order kinetic and Langmuir isotherm models.Biochar produced at 350℃(CSB350)showed the highest adsorption capacity(27.7 mg g^(−1)),and the maximum 78%oxidative conversion of Sb(Ⅲ)to Sb(V).The adsorption results complemented with infrared(FTIR),X-ray photoelectron(XPS),and near-edge X-ray absorption fine structure(NEXAFS)spectroscopy analyses indicated that the adsorption of Sb(Ⅲ)on CSB involved electrostatic interaction,surface complexation with oxygen-containing functional groups(C=O,O=C-O),π-πcoordination with aromatic C=C and C-H groups,and H-bonding with-OH group.Density functional theory calculations verified that surface complexation was the most dominant adsorption mechanism,whilstπ-πcoordination and H-bonding played a secondary role.Furthermore,electron spin resonance(ESR)and mediated electrochemical reduction/oxidation(MER/MEO)analyses confirmed that Sb(Ⅲ)oxidation at the biochar surface was governed by persistent free radicals(PFRs)(•O_(2)^(−)and•OH)and the electron donating/accepting capacity(EDC/EAC)of biochar.The abundance of preferable surface functional groups,high concentration of PFRs,and high EDC conferred CSB350 the property of an optimal adsorbent/oxidant for Sb(Ⅲ)removal from water.The encouraging results of this study call for future trials to apply suitable biochar for removing Sb(Ⅲ)from wastewater at pilot scale and optimize the process.