Biodiversity metrics on ecological networks: Demonstrated with animal gastrointestinal microbiomes

Biodiversity has become a terminology familiar to virtually every citizen in modern societies.It is said that ecology studies the economy of nature,and economy studies the ecology of humans;then measuring biodiversity should be similar with measuring national wealth.Indeed,there have been many parallels between ecology and economics,actually beyond analogies.For example,arguably the second most widely used biodiversity metric,Simpson(1949)’s diversity index,is a function of familiar Gini-index in economics.One of the biggest challenges has been the high“diversity”of diversity indexes due to their excessive“speciation”-there are so many indexes,similar to each country’s sovereign currency-leaving confused diversity practitioners in dilemma.In 1973,Hill introduced the concept of“numbers equivalent”,which is based on Renyi entropy and originated in economics,but possibly due to his abstruse interpretation of the concept,his message was not widely received by ecologists until nearly four decades later.What Hill suggested was similar to link the US dollar to gold at the rate of$35 per ounce under the Bretton Woods system.The Hill numbers now are considered most appropriate biodiversity metrics system,unifying Shannon,Simpson and other diversity indexes.Here,we approach to another paradigmatic shift-measuring biodiversity on ecological networks-demonstrated with animal gastrointestinal microbiomes representing four major invertebrate classes and all six vertebrate classes.The network diversity can reveal the diversity of species interactions,which is a necessary step for understanding the spatial and temporal structures and dynamics of biodiversity across environmental gradients.

Spatial coherence resonance induced by coloured noise and parameter diversity in a neuronal network

Spatial coherence resonance in a two-dimensional neuronal network induced by additive Gaussian coloured noise and parameter diversity is studied. We focus on the ability of additive Gaussian coloured noise and parameter diversity to extract a particular spatial frequency （wave number） of excitatory waves in the excitable medium of this network. We show that there exists an intermediate noise level of the coloured noise and a particular value of diversity, where a characteristic spatial frequency of the system comes forth. Hereby, it is verified that spatial coherence resonance occurs in the studied model. Furthermore, we show that the optimal noise intensity for spatial coherence resonance decays exponentially with respect to the noise correlation time. Some explanations of the observed nonlinear phenomena are also presented.

Network coding with diversity and outdated channel state information

Physical-layer network coding （PNC） has the potential to significantly improve the throughput of wireless networks where the channels can be modeled as additive white Gaussian noise （AWGN） channel. As extending to mul- tiple channels, this technique requires both amplitude and phase compensation at each transmitter and will lead to inef- ficient systems yielding no diversity even with perfect channel state information （CSI）. In order to avoid these limita- tions, we apply network coding with diversity （NCD） to achieve a form of selection diversity and extend NCD to coop- erative multiple access channels in this paper. However, in practical wireless communication systems, the CSI could become outdated due to the difference between the CSI used in the relay selection and data transmission phases. Hence, the selected relay may not be the best one during data transmission phase due to the dynamic change in the wireless channels. Therefore, we first explore the relation between the present and past CSIs. Exploiting this relationship, the NCD scheme with outdated CSI is investigated based on the past CSI. To evaluate the performance of this scheme, an information-theoretic metric, namely the outage capacity, is studied under this condition.

Synchronization performance in time-delayed random networks induced by diversity in system parameter

Synchronization rhythm and oscillating in biological systems can give clues to understanding the cooperation and competition between cells under appropriate biological and physical conditions. As a result, the network setting is appreciated to detect the stability and transition of collective behaviors in a network with different connection types. In this paper, the synchronization performance in time-delayed excitable homogeneous random networks（EHRNs） induced by diversity in system parameters is investigated by calculating the synchronization parameter and plotting the spatiotemporal evolution pattern, and distinct impacts induced by parameter-diversity are detected by setting different time delays. It is found that diversity has no distinct effect on the synchronization performance in EHRNs with small time delay being considered. When time delay is increased greatly, the synchronization performance of EHRN degenerates remarkably as diversity is increased. Surprisingly, by setting a moderate time delay, appropriate parameter-diversity can promote the synchronization performance in EHRNs, and can induce the synchronization transition from the asynchronous state to the weak synchronization. Moreover, the bistability phenomenon, which contains the states of asynchronous state and weak synchronization,is observed. Particularly, it is confirmed that the parameter-diversity promoted synchronization performance in time-delayed EHRN is manifested in the enhancement of the synchronization performance of individual oscillation and the increase of the number of synchronization transitions from the asynchronous state to the weak synchronization. Finally, we have revealed that this kind of parameter-diversity promoted synchronization performance is a robust phenomenon.

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%.

A Novel Practical Cooperative Diversity Method for the Power-Limited Wireless Sensor Network

A novel practical cooperative diversity method for power-limited wireless sensor network system was proposed. At first, the system model was presented and the cooperation problem is formulated under the minimum outage probability criterion, then the focus was put on the power efficiency of system, such as the relay selection, cooperation strategy and power allocation etc. At last the uniform procedure of the proposed method was given. The results of the simulation clearly demonstrate that our method not only has the properties of simple operation and wide applying scope, but also outperforms those of current classical methods on the aspect of outage probability under the basis of the same power limitation.

A CROSS-LAYER STRATEGY FOR COOPERATIVE DIVERSITY IN WIRELESS SENSOR NETWORKS

We investigate the problem of how to minimize the energy consumption in multi-hop Wireless Sensor Network (WSN),under the constraint of end-to-end reliability Quality of Seervice (QoS) requirement.Based on the investigation,we jointly consider the routing,relay selection and power allocation algorithm,and present a novel distributed cross-layer strategy using opportunistic relaying scheme for cooperative communication.The results show that under the same QoS requirement,the proposed cross-layer strategy performs better than other cross-layer cooperative communication algorithms in energy efficiency.We also investigated the impact of several parameters on the energy efficiency of the cooperative communication in WSNs,thus can be used to provide guidelines to decide when and how to apply cooperation for a given setup.

煤矿区土壤细菌群落结构及其对不同复垦模式的响应

科学揭示不同复垦模式土壤细菌群落稳定性及其潜在互作关系对于复垦土地差异化管理及可持续利用至关重要。本文以挖深垫浅、煤矸石充填和粉煤灰充填3种模式复垦土壤为研究对象,基于高通量Illumina Miseq 16S rRNA测序技术,采用方差分析、Spearman相关性等分析方法,研究不同复垦模式下的土壤细菌群落结构和多样性。通过构建分子生态网络模型,揭示不同复垦模式下土壤细菌群落的稳定性及菌群间潜在互作关系,明晰对细菌群落结构稳定性起关键作用的微生物种群。结果表明:①不同复垦模式土壤细菌群落的多样性与丰富度水平有显著差异(P<0.05),均表现为挖深垫浅>煤矸石充填>粉煤灰充填;不同复垦模式土壤细菌群落组成相似,变形菌门、酸杆菌门、放线菌门和拟杆菌门是所有模式土壤中的优势菌门,在各复垦模式土壤细菌群落中的占比之和均达70%以上。②不同复垦模式下土壤细菌群落的显著影响因子不同,部分优势细菌门与影响因子间的变化趋势不同,有机质含量是影响挖深垫浅复垦土壤细菌群落组成的主要影响因素,pH是影响煤矸石与粉煤灰充填复垦土壤细菌群落组成的主要影响因素。③挖深垫浅复垦土壤细菌网络复杂,群落联系紧密,能更好地传递物质、能量和信息;煤矸石充填复垦土壤细菌网络内部节点间的连通度低,但菌群信息交换速度慢,拥有4个关键节点,网络相对稳定;粉煤灰充填复垦的土壤细菌网络规模最小,节点连通度不高,在外界环境发生变化时反应快,网络稳定性最差。3种复垦模式土壤细菌群落间关系均以协同合作为主导,煤矸石充填复垦土壤细菌群落间的协同合作关系占比最高。本文揭示了3种不同复垦模式下土壤细菌群落结构与分子生态网络差异,研究结果可为高潜水位采煤塌陷区土地复垦模式的优选以及人为干预方式的选择提供支撑。

基于模糊综合分析法的引调水工程水质响应关系分析

为提升引调水工程的环境改善效果,须对水体的自身连通水平、水质现状、水环境主要影响因子进行分析。以太湖流域跃进联圩为研究对象,利用图论连通度理论对研究区域静态基流连通性进行评价,探索圩内水系连通性的空间差异及变化特性。同时,开展短期引调水实验,结合模糊综合分析法评价引调水带来的圩内水质变化情况及规律,研究圩内水环境和水系连通性的响应关系。结果表明,模糊综合评价法在引调水环境改善分析中具有适用性,可实现对圩内各监测点位水质变化的全面分析;水体流动性是影响圩区内水质的重要环境因素,高锰酸盐指数是导致圩内水质恶化的主要影响因子。引调水工程对圩区水环境具有一定的持续改善性作用,但对基流连通性较差的区域,改善效果有限。

平原河网水动力优化调度与水环境改善的响应关系研究

平原河网河道流动性较差是引起水环境污染严重的主要原因,引调水是改善平原河网地区水环境的重要措施之一。本文以佛山市三山围为例,基于实测资料构建了河网水动力水质耦合模型,采用15天的连续水动力水质监测数据对模型进行了验证,并将NSE和RMSE模型评价指标用于模型评价。同时结合地势、潮汐规律和景观水位等设计了4种闸控模式和7种景观控制水位,共28种模拟工况,模拟分析了不同条件下的水动力水质改善与内外江潮位变化、引排水流量及其空间分布、闸控方式和景观水位等综合响应机理。结果表明:构建的模型合理可靠。研究区域受引排水路径的影响,河道流动性差异较为显著。综合考虑河道流量分布、水流路径、分汊河道分流作用和外江污染物浓度等对河道水质的作用效果并有效结合潮汐河网的动态水环境容量和污染源排放的时空分布对水环境的改善作用将非常显著。与低景观控制水位相比,高景观控制水位的内江动态水环境容量相对较大,污染物浓度较低。景观控制水位从0.2 m上升至0.8 m时,不同引调水路径的引水流量上升28.00%~64.70%,断面氨氮浓度削减了0.85~5.50 mg/L,削减比例达到28.89%~67.23%。本研究为平原潮汐河网水环境优化调度研究提供了新的思路,为相关部门对平原河网的水环境改善提供了重要的参考。

南水北调立法对国家水网引调水工程建设的启示研究

南水北调工程是在中国乃至世界范围内规模最大的跨流域引调水工程,国家出台《南水北调工程供用水管理条例》(以下简称《条例》),作为规范其运行管理的专门立法,有效保障了工程水量调度、水质保障、供水管理、工程设施管理和保护等运行实践。文章系统总结了南水北调立法需要协调的关系,梳理了《条例》重点规范的制度及实施情况,整理了针对《条例》开展的配套制度建设情况。针对国家水网相关规划中提出的推进实施一批重大引调水工程,从及早谋划工程立法建设、强化水量统一调度、突出规范工程运行涉及的重要内容、强化对生态环境的保护等方面,对国家水网相关的引调水工程立法建设提出了建议,可为引调水工程法规制度建设提供有益参考。

信息网络地位与产业结构升级

数字技术发展促使信息流动打破时空局限,形成信息网络并深刻影响经济主体效率。以往研究通过交通基础设施、企业生产等形成的城市网络,研究信息在城市之间流动对产业结构的影响,但这并非衡量城市信息网络的最直接方式。本文基于2011—2017年中国城市之间的日频百度搜索数据,构建了城市间信息网络,并用信息联系强度、信息多样性刻画信息网络地位特征,并讨论其对产业结构升级的影响。结果发现,信息联系强度和信息多样性促进了城市产业结构升级,且仅在中西部地区显著;省间信息网络作用大于省内;促进知识溢出、带动城市创业是信息网络产生影响的重要渠道。本文为中国构建网络空间命运共同体提供了经验依据,也为数字经济时代城市提升产业结构提供了可行路径。

一种随机森林增强的车载容迟网络路由算法

针对车载容迟网络(Vehicular Delay Tolerant Network,VDTN)中车辆节点高速移动造成的通信链路不稳定性问题,利用车辆节点的移动模式,提出了一种随机森林增强的VDTN路由算法.首先,引入与车辆节点运动相联系的属性并利用动态相遇奖励机制对车辆节点进行分类,以此构建初始随机森林模型.接着,从决策树的分类性能和多样性两个方面优化模型,选择分类性能好、多样性高的决策树构造改进的随机森林模型,其中,决策树的分类性能和多样性分别根据每棵树分类错误率及相应的惩罚权重和由不合度量定义的决策树之间的相似度来衡量.最后,根据改进的随机森林模型提出新的VDTN路由算法.仿真实验证明,所提出的路由算法能显著提高消息的投递率,降低消息的投递时延,从而验证了其有效性.

基于知识元引用网络的细分领域演化特征研究

[目的/意义]理解科学知识发展演化过程有助于促进科学研究,从微观视角追踪知识在细分领域中的结构与演化特征对知识评估和知识服务具有重要意义。[方法/过程]以医学信息学中知识元为例,利用语义类型界定每种疾病的治疗相关细分领域,构建125种疾病不同时刻的知识元引用网络,采用Leiden算法识别知识群落,从群落知识演化、群落知识竞争状态等维度揭示疾病个体的演化特征;提出丰富度、均衡性与差异度三种测度指标,揭示疾病个体与整体的多样性特征。[结果/结论]研究表明,知识元引用网络中的群落能够反映出疾病知识结构与演进状态。整体层次的疾病知识多样性特征包括:疾病知识群落数量不断增加,群落间规模与组成差异不断扩大;不同疾病表现出常规型、早期争议型、泛指型演化模式;研究较早的疾病普遍均衡性较低、差异度较高。

基于生成对抗网络的非织造布二维图像重建

非织造布纤维结构的准确表征是其性能分析的重要基础。为了解决基于近似模拟的表征结果中纤维形态、结构与真实样本不一致的问题,提出了一种基于生成对抗网络的非织造布二维图像重建方法。使用全自动光学显微镜对非织造布图像进行抓取,并在此基础上构建纤维生成对抗网络(Fiber generation adversarial network,FGAN)对图像样本进行建模。针对高分辨率图像重建时存在的失真问题,采用多尺度训练策略,同时引入权重多样性损失。采用图像质量评估指标FID作为实验评价指标,分别与DCGAN、WGAN-GP、BEGAN、PROGAN等生成模型进行对比实验。结果表明:FGAN重建的非织造布图像质量更高;消融实验证明,多尺度训练策略与权重多样性损失函数中FID数值分别降低24.52%、20.31%。FGAN模型的提出,使非织造布结构分析摆脱对近似模拟方法的依赖,提供了准确的纤维分布信息,对非织造布的质量评估、性能优化等应用具有重要意义。

基于参考文献的论文跨学科性、跨时域性及其影响力研究

本文在跨学科性概念的基础上,提出了跨时域性的测度框架,并将其量化为时域丰富性、时域非均衡性、时域差异性和时域深度4个维度。本文对微软学术数据库中1950—2020年38879575篇论文的跨学科性和跨时域性的时间趋势、分布特征以及科学家的生涯演化模式进行了细致分析,并进一步研究了跨学科性、跨时域性与科学影响力的关系。研究发现:①论文的跨学科性和跨时域性呈现一致的增长趋势和不一致的领域分布;②跨学科性和跨时域性指标具有无标度分布等异质性分布特征,且跨学科性和跨时域性的相关性并不强;③科学家生涯中后期的跨学科性和跨时域性明显增强,这种趋势在很大程度上可以归因于其引用行为的变化;④跨学科性和跨时域性对科学影响力有着相反的作用效应,即跨学科性显著促进科学影响力,跨时域性显著抑制科学影响力,较强的跨学科性和较弱的跨时域性组合成为颠覆性热点论文的概率最高。本文提出的跨时域性测度框架丰富了知识融合和跨学科理论,并为科技政策和学术评价提供了启示。

公司治理水平与数字化转型:来自上市公司的证据

基于股东、董事和高管视角,构建了包含股东网络、股权集中度、董事会多样性和传统技术导向型高层管理团队在内的公司治理水平指标,以中国3040家沪深A股上市公司为样本,探讨公司治理水平对数字化转型的作用机制。研究发现:公司治理水平是企业进行数字化转型的关键驱动因素;另外,公司治理水平不同维度指标的影响机制表明,股东网络降低了企业的融资约束,股权集中度增加了企业的风险承担,董事会多样性增加了企业的创新能力,从而推动了企业的数字化转型;而传统技术导向型高层管理团队降低了企业的战略执行,阻碍了企业的数字化转型。

滨海盐碱地苜蓿-小黑麦轮作对土壤细菌和真菌群落多样性与网络结构的影响

把豆科植物纳入作物轮作体系,不仅促进农业生态系统的可持续发展,而且为提高作物产量提供了一条关键途径,尤其是应用在低投入和低多样性农业系统时。然而,土壤微生物群落对于豆科作物轮作的响应仍鲜有研究。以典型滨海盐碱地为研究对象,利用高通量测序技术深入探究了土壤微生物群落结构和共现网络模式对于冬小黑麦(Triticosecale Wittmack)-夏玉米(Zea mays L.)和紫花苜蓿(Medicago sativa L.)-冬小黑麦两种轮作模式的响应。结果显示,相对于小黑麦-玉米轮作,苜蓿-小黑麦轮作对细菌群落多样性影响较小,但降低了真菌群落丰富度,这可能与土壤氮和磷含量的变化有关。非度量多维尺度分析(NMDS)结果显示,苜蓿-小黑麦轮作对细菌群落结构的影响较小,但改变了真菌群落结构,这可能与土壤pH和土壤有机碳含量的变化有关。共现网络分析结果表明,苜蓿-小黑麦轮作增加了细菌群落共现网络的复杂性和稳定性,具体表现在网络节点数、连接数、平均连接度、关键节点以及负连接数的增加,平均路径长度的降低。然而,真菌群落共现网络的复杂性和稳定性却表现出了相反的趋势。该研究表明,细菌和真菌对苜蓿轮作具有不一致的响应,在探究豆科作物轮作对土壤微生物的影响时,应当充分考虑这种不一致响应。

一种可降解半互穿网络暂堵剂的制备及性能

非均质性是油气储层的基本特征,酸化施工采用暂堵剂封堵高渗、促使酸液作用于低渗层,是提高非均质储层酸化改造效果的关键措施。为了解决现有高分子暂堵剂成胶时间不可控、残渣伤害严重等问题,采用生物材料海藻酸钠(SA)和黄原胶(XG)通过半互穿方式形成具有高强度可降解的新型暂堵剂SAXG。以变形量和成胶时间为目标优化了体系的最优质量百分比0.7%SA+0.3%XG,采用流变仪测试了凝胶的流变性以及延迟成胶效果,以残渣含量描述体系的可降解性,通过扫描电子显微镜(SEM)明确了SAXG半互穿网络与SA凝胶的区别,最后采用岩心流动实验验证了体系的转向酸化效果。研究结果表明,SAXG成胶时间范围为14~456 min;SAXG在盐水和酸液中可完全降解;暂堵酸化后岩心渗透率比常规酸化后提高了2.85倍;降解后岩心渗透率恢复率达98.6%。SAXG可有效促使酸液转向,从而提高酸化改造效果。

西藏热振国家森林公园土壤原生动物群落沿海拔分布格局及其与环境因子的关联特征

土壤原生动物是土壤中一类微型单细胞真核生物,是土壤的关键组成部分,对土壤环境质量动态变化具有重要的指示作用。为了解不同海拔土壤原生动物群落组成、多样性、分布格局及其与环境因子的耦合关系,于2021年7月根据西藏热振国家森林公园地理特征设置了3种不同海拔(低,LA;中,MA;高,HA)共9个样地,采用“非淹没培养法”、“活体观察法”和“Wilbert蛋白银法”对土壤原生动物进行培养和形态学鉴定。结果表明,研究区3种不同海拔共鉴定出土壤原生动物76种,隶属2门12纲23目32科46属,优势纲为动鞭纲(Zoomastigophorea),占总物种数的22.37%。其中,低海拔以动鞭纲为主,中高海拔以肾形纲(Colpodea)占据优势,这与肾形纲的生长方式为R-对策有关。Shannon-Wiener多样性指数、Pielou均匀度指数和Margalef丰富度指数在3种海拔段之间均无显著差异。土壤pH、含水量在低海拔和高海拔间存在差异。共发生网络分析显示,3个不同海拔土壤原生动物物种的共现网络节点间的关系主要为正相关。Mantel分析和冗余分析结果显示,总磷是影响土壤原生动物群落组成的主要驱动因子。该研究结果有助于了解西藏热振国家森林公园生态系统变化,为青藏高原生态环境保护和可持续发展提供基础数据支持。