Parallel-Transmission: A New Usage of Multi-Radio Diversity in Wireless Mesh Network

To fully utilize the diversity of multi-radio, a new parallel transmission method for wireless mesh network is proposed. Compared with conventional packet transmission which follows “one flow on one radio”, it uses the radio diversity to transmit the packets on different radios simultaneously. Three components are presented to achieve parallel-transmission, which are control module, selection module and schedule module. A localized selecting algorithm selects the right radios based on the quality of wireless links. Two kinds of distributed scheduling algorithms are implemented to transmit packets on the selected radios. Finally, a parallel-adaptive routing metric is presented. Simulation results by NS2 show that this parallel-transmission scheme could enhance the average throughput of network by more than 10%.

Wolbachia Infection in Populations of Ostrinia furnacalis: Diversity, Prevalence, Phylogeny and Evidence for Horizontal Transmission

Wolbachia are maternally inherited endosymbiotic bacteria infecting a wide range of arthropods and filarial nematodes. They can induce various reproduction alterations in their hosts, including thelytokous parthenogenesis, cytoplasmic incompatibility （CI）, feminization of genetic males and male killing. Here we investigated diversity and prevalence patterns of Wolbachia infection in 43 geographical populations of the Asian corn borer, Ostriniafurnacalis, in China and one population in North Korea. Based on Wolbachia surface protein gene （wsp） sequences, nine strains of Wolbachia （wFurl-wFur9）, belonging to supergroups A and B, were identified in populations of O. furnacalis with an average infection rate of 10.5%. Superinfection commonly appeared in individuals of O. furnacalis and coinfection patterns were very complex. There was no specific pattern for the prevalence and distribution of the nine Wolbachia strains suggesting an intricate evolutionary history of Wolbachia infection in this species. The genetic similarity of the wFurl-wFur9 strains with those detected in two parasitoids of O. furnacalis, Macrocentrus cingulum and Lydella grisescens, strongly suggests host-parasitoid horizontal transmission.

HIV Diversity and Classification, Role in Transmission

The hallmark of HIV-1 is its extensive genetic diversity that emanates mainly from high mutations. Phylogenetically, HIV can be classified into geographically confined groups, types, subtypes and circulating recombinant forms (CRFs) that are however subject to change over time. HIV genetic diversity may partially explain the observed heterogeneity in HIV prevalence and has also been reported to impact on viral transmissibility and differential rates of disease progression. The aim of this review is to present a simple overview of the principles and concepts of HIV diversity and classification. Tracking the presence of new HIV strains is not only important for surveillance purposes but is also critical in facilitating personalized targeted therapy as well as forming the basis for development of the much anticipated effective vaccines against this scourge.

Transmission restriction and genomic evolution co-shape the genetic diversity patterns of influenza A virus

Influenza A virus(IAV)shows an extensive host range and rapid genomic variations,leading to continuous emergence of novel viruses with significant antigenic variations and the potential for cross-species transmission.This causes global pandemics and seasonal flu outbreaks,posing sustained threats worldwide.Thus,studying all IAVs'evolutionary patterns and underlying mechanisms is crucial for effective prevention and control.We developed FluTyping to identify IAV genotypes,to explore overall genetic diversity patterns and their restriction factors.FluTyping groups isolates based on genetic distance and phylogenetic relationships using whole genomes,enabling identification of each isolate's genotype.Three distinct genetic diversity patterns were observed:one genotype domination pattern comprising only H1N1 and H3N2 seasonal influenza subtypes,multi-genotypes cocirculation pattern including majority avian influenza subtypes and swine influenza H1N2,and hybrid-circulation pattern involving H7N9 and three H5 subtypes of influenza viruses.Furthermore,the IAVs in multi-genotypes cocirculation pattern showed region-specific dominant genotypes,implying the restriction of virus transmission is a key factor contributing to distinct genetic diversity patterns,and the genomic evolution underlying different patterns was more influenced by host-specific factors.In summary,a comprehensive picture of the evolutionary patterns of overall IAVs is provided by the FluTyping's identified genotypes,offering important theoretical foundations for future prevention and control of these viruses.

Performance Evaluation of Flows with Diverse Traffic and Transmission Rates in IEEE 802.11 WLAN

IEEE 802.11 WLAN cannot guarantee the QoS of applications, thus admission control has been proposed as an essen-tial solution to enhance the QoS. Packet delay and throughput are commonly employed as assessment criterions to determine whether a new connection can be admitted into the WLAN. Considering the real network condition, the analytical model is presented in this paper, which is aimed to evaluate the packet delay and throughput performance of IEEE 802.11 WLAN in nonsaturated conditions, taking into account diverse transmission rates and diverse traffic flows (i.e. flows with different packet sizes and arrival rates) simultaneously. This model is based on Markov chain and the theoretical predictions are verified by simulation in OPNET 14.5. We also analyze the influences of transmission rate diversity and traffic flow diversity on throughput performance. It is observed that, the presence of even one station with lower transmission rate can cause a considerable degradation in throughput performance of all the stations when they have the same packet size and arrival rate. Higher system throughput can be achieved if lower transmission rate stations transmit packets with smaller size or arrival rate.

Performance analysis of space-time transmit diversity techniques for multi-antenna WCDMA systems

Several space-time coding based transmit diversity techniques for wideband code division multiple access (WCDMA) systems with four transmitter antennas are investigated. Performances of the rake receivers are analyzed and compared with those of the multi-antenna receive diversity techniques. Theoretical analysis shows that the multi-antenna transmit diversity techniques provide considerable performance gain at the mobile receiver in the wireless channel with less inherent multipath diversity, especially the G4 coding based scheme. Compared with the multi-antenna receive diversity techniques with the same diversity order, the transmit diversity techniques introduce much more multi-access plus multipath interference and require measures of interference suppression in the multi-user environments.

Viral evolution and transmission effectiveness

Different viruses transmit among hosts with different degrees of efficiency. A basic reproductive number(R0) indicates an average number of cases getting infected from a single infected case. R0 can vary widely from a little over 1 to more than 10. Low R0 is usually found among rapidly evolving viruses that are often under a strong positive selection pressure, while high R0 is often found among viruses that are highly stable. The reason for the difference between antigenically diverse viruses with low R0, such as influenza A virus, and antigenically stable viruses with high R0, such as measles virus, is not clear and has been a subject of great interest. Optimization of transmissibility fitness considering intra-host dynamics and inter-host transmissibility was shown to result in strategies for tradeoff between transmissibility and diversity. The nature of transmission, targeting either a na?ve children population or an adult population with partial immunity, has been proposed as a contributing factor for the difference in the strategies used by the two groups of viruses. The R0 determines the levels of threshold heard immunity. Lower R0 requires lowerherd immunity to terminate an outbreak. Therefore, it can be assumed that the outbreak saturation can be reached more readily when the R0 is low. In addition, one may assume that when the outbreak saturation is reached, herd immunity may provide a strong positive selection pressure that could possibly result in an occurrence of escape mutants. Studies of these hypotheses will give us an important insight into viral evolution. This review discusses the above hypotheses as well as some possible mechanistic explanation for the difference in transmission efficiency of

Morphological and phylogenetic diversity of magnetotactic bacteria and multicellular magnetotactic prokaryotes from a mangrove ecosystem in the Sanya River,South China

Magnetotactic bacteria(MTB)are morphologically and phylogenetically diverse prokaryotes commonly able to produce magnetic nanocrystals within intracellular membrane-bound organelles(i.e.,magnetosomes)and to swim along geomagnetic field lines.We studied the diversity of MTB in the samples collected from a mangrove area in the Sanya River,Hainan,South China,using microscopic and microbial phylogenetic methods.Results of microanalysis and observation in microscopy and energy dispersive X-ray spectroscopy(EDXS)reveal a highly morphological diversity of MTB including unicellular cocci,vibrios,rod-shaped bacteria,and three morphotypes of multicellular magnetotactic prokaryotes(MMPs).In addition,analysis of the 16S rRNA gene showed that these MTB were clustered into 16 operational taxonomic units affi liated to the Alpha-,Delta-,and Gamma-proteobacteria classes within the Proteobacteria phylum.Meanwhile,by using the coupled fluorescence and transmission electron microscopy analysis,rodshaped bacteria,vibrio,and cocci were phylogenetically and structurally identified at the single-cell level.This study demonstrated highly diverse MTB communities in the mangrove ecosystem and provide a new insight into the overall diversity of MTB.

Global patterns of phylogenetic diversity and transmission of bat coronavirus

Bats are reservoirs for multiple coronaviruses(Co Vs).However,the phylogenetic diversity and transmission of global bat-borne Co Vs remain poorly understood.Here,we performed a Bayesian phylogeographic analysis based on 3,594 bat Co V Rd Rp gene sequences to study the phylogenetic diversity and transmission of bat-borne Co Vs and the underlying driving factors.We found that host-switching events occurred more frequently forα-Co Vs than forβ-Co Vs,and the latter was highly constrained by bat phylogeny.Bat species in the families Molossidae,Rhinolophidae,Miniopteridae,and Vespertilionidae had larger contributions to the cross-species transmission of bat Co Vs.Regions of eastern and southern Africa,southern South America,Western Europe,and Southeast Asia were more frequently involved in cross-region transmission events of bat Co Vs than other regions.Phylogenetic and geographic distances were the most important factors limiting Co V transmission.Bat taxa and global geographic hotspots associated with bat Co V phylogenetic diversity were identified,and bat species richness,mean annual temperature,global agricultural cropland,and human population density were strongly correlated with the phylogenetic diversity of bat Co Vs.These findings provide insight into bat Co Vevolution and ecological transmission among bat taxa.The identified hotspots of bat Co V evolution and transmission will guide early warnings of bat-borne Co V zoonotic diseases.

Generalized Block Markov Superposition Transmission over Free-Space Optical Links

In free-space optical(FSO) communications, the performance of the communication systems is severely degraded by atmospheric turbulence. Channel coding and diversity techniques are commonly used to combat channel fading induced by atmospheric turbulence. In this paper, we present the generalized block Markov superposition transmission(GBMST) of repetition codes to improve time diversity. In the GBMST scheme, information sub-blocks are transmitted in the block Markov superposition manner, with possibly different transmission memories. Based on analyzing an equivalent system, a lower bound on the bit-error-rate(BER) of the proposed scheme is presented. Simulation results demonstrate that, under a wide range of turbulence conditions, the proposed scheme improves diversity gain with only a slight reduction of transmission rate. In particular, with encoding memory sequence(0, 0, 8) and transmission rate 1/3, a diversity order of eleven is achieved under moderate turbulence conditions. Numerical results also show that, the GBMST systems with appropriate settings can approach the derived lower bound, implying that full diversity is achievable.

Genetic diversity of RNA viruses infecting invertebrate pests of rice

Invertebrate species are a natural reservoir of viral genetic diversity,and invertebrate pests are widely distributed in crop fields.However,information on viruses infecting invertebrate pests of crops is limited.In this report,we describe the deep metatranscriptomic sequencing of 88 invertebrate samples covering all major invertebrate pests in rice fields.We identified 296 new RNA viruses and 13 known RNA viruses.These viruses clustered within 31 families,with many highly divergent viruses constituting potentially new families and genera.Of the identified viruses,13 RNA viruses clustered within the Fiersviridae family of bacteriophages,and 48 RNA viruses clustered within families and genera of mycoviruses.We detected known rice viruses in novel invertebrate hosts at high abundances.Furthermore,some novel RNA viruses have genome structures closely matching to known plant viruses and clustered within genera of several plant virus species.Fortyfive potential insect pathogenic RNA viruses were detected in invertebrate species.Our analysis revealed that host taxonomy plays a major role and geographical location plays an important role in structuring viral diversity.Cross-species transmission of RNA viruses was detected between invertebrate hosts.Newly identified viral genomes showed extensive variation for invertebrate viral families or genera.Together,the large-scale metatranscriptomic analysis greatly expands our understanding of RNA viruses in rice invertebrate species,the results provide valuable information for developing efficient strategies to manage insect pests and virus-mediated crop diseases.

纤维复合材料在调水工程长输管道中的应用

调水工程长距离输水管道的材料选择,对工程成本和输水线路的安全有着重要影响。纤维复合材料具有轻质高强、内壁光滑、耐腐蚀性好等特点,正逐步应用在输水管道中。文章分析了影响长距离输水管道材料选择的主要因素,介绍了钢管、球墨铸铁管、混凝土管等传统输水管道的材料特性,阐述了纤维复合材料在输水管道中的应用,重点分析了玻璃钢夹砂管的发展和特点,最后对纤维复合材料输水管道在产品升级、施工技术、安全防护和质量管理四个方面的发展进行了展望。

滇中引水工程中数字孪生技术的应用研究

为更好地采用信息化手段为滇中引水工程建设及运行管理提供更科学的决策,提出采用数字孪生技术构建智慧滇中引水体系的解决方案。在总结目前滇中引水工程信息化建设的基础上,对标水利工程数字孪生建设要求,搭建滇中引水工程数字孪生系统架构,从信息采集、数据传输、云计算中心和数字孪生平台几个方面全面系统地进行构建,并根据工程实际提出水源泵站、深埋隧洞和运行维护3个数字孪生运用场景。研究结果可有效提高滇中引水工程智能安全的建设管理水平和调水能力,也可供其他引水工程数字孪生建设借鉴。

导流式输水管网消能装置设计与影响因素研究

为了保障山区输水管网运行安全,设计导流式输水管网消能装置。装置由上壳体、消能空腔和下壳体组成,设置入口端和出口端,消能空腔内设有均匀间隔的消能板和导流孔。采用Fluent数值模拟和验证试验对试验方法进行验证,设置3种入口流速、3种导流孔径比例和有无导流片开展全因素试验,并对2种导流孔直径进行消能率对比试验。结果表明:在保证过流能力下,入口流速和导流孔径均对消能率起主导作用,入口流速越大,即流量越大,消能率越好。消能率与导流孔径负相关,导流孔径越小越有利于消能。当基础孔径相同时,为同时满足过流能力且确保消能达到较好效果,建议选择导流孔径比例保持不变布置方式。入口流速为1.0 m/s时,局部水头损失占总水头损失的96.3%,所以当计算总水头损失时,可以忽略沿程水头损失。当入口流速小于4.0 m/s时,选择不安装导流片,达到4.0 m/s时,有无导流片消能率基本持平,大于5.0 m/s后,选用安装导流片消能效果更优。

双层分流对冲穿孔管结构消声特性研究

发动机排气系统中的噪声特性为高频、宽频带,以及排气气流作用下产生的再生噪声,传统的消声结构不能有效地解决该噪声问题。因此,提出通过将锥形分流单元与双层穿孔管相结合的消声方法。首先通过一个锥形分流单元对进入消声器的气流进行分流,分流后的气流在第一层穿孔管外腔得到充分的减速,再经过第一层穿孔管进行初次消声,然后通过第二层穿孔管进行二次消声,最后通过第二层穿孔管上的小孔进入到对冲腔,使气流在对冲腔发生对冲,气流在对冲的过程中速度逐渐降低,再生噪声减小消声效果增强。通过对双层穿孔管结构的传递损失进行推导,分析结构参数对消声性能的影响,得到传递损失的影响因素与变化特性,并进行实验验证。实验结果表明:提出的消声方法能够在高频入射声波的情况下维持较高的传递损失和较宽的消声频带。

柽柳丛枝植原体鉴定及16S rRNA基因多样性分析

【目的】研究柽柳丛枝病在新疆南疆地区的分布危害、分类、形态特征及病原物16S rRNA基因的遗传多样性,为该病害的检测和鉴定提供理论依据。【方法】调查新疆南疆地区柽柳丛枝病的分布及危害,采用形态学与分子生物学相结合的方法,对柽柳丛枝病病原物进行透射电镜观察、16S rRNA基因和rp基因扩增,研究其形态特征及分类地位,并对新疆南疆不同地区柽柳丛枝病病原物16S rRNA基因遗传多样性。【结果】柽柳丛枝病在新疆南疆地区的平均发病率为9.06%,平均病情指数为5.66;在柽柳丛枝韧皮部组织中观察到有植原体颗粒的存在;16S rRNA基因和rp基因巢式PCR分别获得1219 bp和1174 bp大小的条带,柽柳丛枝病属于植原体病害,在分类地位上属于植原体16SrXXX-A亚组;新疆南疆柽柳丛枝植原体主要可分为4个株系,16S rRNA基因核苷酸相似度在96.5%~99.8%。【结论】柽柳丛枝病在新疆南疆地区主要分布在阿克苏市、温宿县、巴楚县、图木舒克市、阿拉尔市、伽师县,阿拉尔市12团等地,且发生情况和危害程度均较轻,不同地区之间的发病率及病情指数存在显著差异性;柽柳丛枝病存在植原体颗粒并主要在韧皮部组织中,有球形、椭圆形和不规则形态,大小300~600 nm不等。

深度学习辅助的随机频率分集阵列下的三维无线安全传输

针对相控阵列辅助的无线通信系统中发射波束只依赖角度特性而导致的安全隐患问题,以及传统的迭代算法所带来的高计算复杂度问题,该文提出由深度学习(DL)和随机频率分集阵列(RFDA)辅助带有3维安全区域的安全传输方案。首先,推导在3维空间中带有安全区域的期望用户实现安全通信的传输条件。在此基础上,构建系统安全速率下界最大化问题。随后,提出基于深度学习的神经网络方案来设计最优的波束成形矢量和人工噪声(AN)矢量来降低计算复杂度。仿真结果表明:即便是在窃听者位于安全区域边缘的最差情况下,所提方案仍能够在实现3维安全传输,能够保证安全区域内接收到的信息不被窃听。

输变电工程对生物多样性影响评价——以河北滦河上游国家级自然保护区为例

针对输变电工程建设经过河北滦河上游国家级自然保护区,对保护区生物多样性进行了现状调查,选取景观/生态系统、生物群落、种群/物种、主要保护对象、生物安全以及社会因素等6项指标,对保护区生物多样性造成的影响进行了分析评价,得出了输变电工程建设对保护区生物多样性影响指数(BI)为52.10,影响程度为“中低度影响”等级,并提出了野生动植物保护、施工组织优化、水土保持等减缓影响的措施。

南水北调中线(驻马店段)环境岩土工程问题研究

以南水北调中线驻马店段为研究背景,采用现场调查、工程地质测绘以及钻探手段,查明输水管线沿线地层主要为第四系全新统上段冲湖积层、全新统下段冲湖积层和上更新统冲湖积层。结合设计要求,进一步查明项目施工和运行过程中可能存在地震效应、边坡稳定性、施工排水、水土流失以及泥沙冲刷与淤积等关键技术问题,提出了相应的处理建议。研究可为南水北调中线工程施工和运行过程中可能发生的环境岩土工程问题提供数据支撑。

OFDM系统下高速铁路通信选择分集传输技术的切换优化方案研究

本研究基于OFDM系统选择分集传输技术,设计了一种适用于高速列车的通信切换优化方案,保证列车在驶过不同小区时,能够保持通信的可靠与稳定。