一种面向分簇无线传感器网络的多信道跨层协议

针对工业测控对传感器网络抗干扰性及通信实时性的要求,提出了一种面向分簇无线传感器网络的多信道跨层协议.该协议在簇内采用多信道配合时分复用机制,并通过高容忍度信道切换算法实时评估信道质量和自适应切换信道,以减小相邻簇和相邻频段协议的干扰,在簇间引入链路Q值评价路径状况,采用基于概率转发的多路径机制平衡网内数据流量,并控制和缓解拥塞,以减小数据流量大或变化快时因拥塞造成的丢包.该协议将簇内多信道和簇间多路径2种机制相结合以提升网络性能.仿真结果表明,相比传统的分簇协议,该协议能有效抵抗干扰并控制和缓解簇间拥塞,且可缩短约22％的簇间延时.     

一种高信道利用率的分簇传感器网络数据聚合协议

为了避免分簇无线传感器网络中簇内数据聚合时产生的簇间干扰,提高簇的信道利用率,提出了一种基于时分多址的无冲突数据聚合协议(IFDA).IFDA的帧分配算法采用一种概率调度策略.通过调度簇头进行广播,即在每个时隙中进行簇帧号分配,为相邻簇分配不同的时间帧聚合数据,与已有的协议的帧分配算法相比可降低广播的次数.同时,IFDA通过信道扩充(CE)算法来提高各个簇的信道利用率.CE算法中采用了一种基于时钟退避的调度策略,可均衡簇头间的信道利用率.仿真结果表明,IFDA协议中簇的平均信道利用率较已有的协议提高了约90%.     

一种高吞吐量的无线传感器网络多信道MAC协议

针对工业现场环境下无线传感器网络易受干扰而导致可靠性和吞吐量降低的问题,提出了一种基于单接口的多信道MAC层协议.该协议针对分簇式网络,采用改进的MMSN算法为各簇分配簇内通信基础信道,保证网内任意相邻簇信道互异,避免邻簇间的干扰,并在通信过程中根据实际信道质量和干扰强度动态分配簇内节点的通信信道,在抵御干扰的同时提高了信道的利用率.仿真结果表明,相比传统的MAC协议,该协议能有效提高无线传感器网络的吞吐量和抗干扰性.     

多射频多信道Ad hoc网络的信道分配与路由策略

文章针对多射频多信道ad hoc网络的特点,提出了一种信道分配方法和路由策略.新的信道分配方法在保持网络连通性的基础上能够简化信道分配,减少信道分配的冲突;新的路由策略综合考虑了带宽、信道差异、射频切换时延、信道间干扰等链路参数以及最小跳数等因素,更能准确地反映被选路由的链路质量.     

VANET中一种分布式路由协议MCCR

研究了VANET(Vehicular Ad-hoc Networks)中多信道环境下基于合作机制的路由选择问题.提出将发送时延和链路冲突数作为路由判据的主要参数的思路,设计了一种新的路由判据MCCM(Multi-Channel Contention-aware Cooperative Metirc),该判据综合考虑了路径内干扰和路径间干扰并反映出多信道环境对路由的影响.将MCCM路由判据应用到路由选择中,据此设计的路由算法能更好地适应VANET中的虚拟节点和虚拟链路,进而设计了一种全新的分布式路由选择协议MCCR(Multi-Channel Contention-awareCooperative Routing).模拟实验结果表明,在节点稠密、网络负载大时,MCCR路由算法能有效提高网络性能.     

超密集网络中基于分簇的干扰管理方案

在超密集网络中,全频复用能够提升网络的吞吐量,但是导致了严重的基站间干扰。为了降低基站间干扰,首先通过干扰权重值描述小基站间的干扰程度,建立合理的干扰图;然后将分簇问题转化为Max K-Cut问题,利用改进的次优化启发式算法对小基站进行分簇;最后通过信道分配算法为每个簇中的用户分配子信道。仿真表明,本文的干扰管理方案在降低小基站间干扰的同时,能够提升系统的频谱效率和平均吞吐量。     

无线Mesh网络逐层信道分配策略研究

网关是整个无线Mesh网络中数据流量汇聚的中心,网关周围的链路干扰将会制约整个网络的上下行吞吐量,然而在目前已有的信道分配方案中在进行信道分配时并未充分考虑到这一特点。提出一种以网关为中心的逐层多信道分配策略,在分配信道时尽可能优先考虑降低网关附件的冲突和干扰,从而达到提高整个网络性能的目标。仿真实验表明,本文算法在提高网络吞吐量方面达到了很好的效果。     

一种无线Mesh网络多播信道分配算法的研究

在无线Mesh网络中,多播是一种非常重要的技术,它要求在有限的带宽内提高网络吞吐量.在信道分配时最小化多播树的干扰可以提高网络吞吐量.本文提出一种多信道多播信道分配算法,该算法以链路上的数据流为指标来表征干扰度,考虑相同信道及相邻信道的干扰,通过减少干扰来提高无线Mesh网络的吞吐量.仿真结果表明,该算法可以达到更佳的网络吞吐量.     

效用最优的无线传感器网络退避算法研究

针对基于CSMA/CA协议的分簇传感器网络,提出了一种新的退避算法.首先通过把资源分配看成效用最大化的优化模型,说明了簇内传感器节点争用信道的退避窗口应该具有同样大小;然后在假定簇内各个节点有一样的退避窗口的基础上,通过最小化节点间的冲突概率,得到了簇内节点的最优退避窗口值和节点个数之间的关系.由此提出了一种基于最优共享退避窗口的重传算法,仿真结果表明本算法较传统的二进指数算法具有较少的冲突,能够减少传输时延、提高吞吐量,同时也是能量有效的.     

基于虚拟MIMO的无线传感网数据传输策略

基于无线传感网的虚拟多输入多输出(multi-input multi-output,MIMO)技术,结合分簇多跳传输模式进行全网的数据传输,根据分簇算法得到每一个簇的簇头,利用协作传输方式,将数据传输至相邻簇头.在进行数据传输时,综合考虑网络的电路能耗与传输能耗,推导出簇间传输的最小能耗为发送方簇的协作节点个数Mt的表达式,从而得到到达汇聚节点的最优路径.基于最小簇间能耗的协作虚拟MIMO多跳传输策略不需要接收端协同,避免了接收端协同的复杂性,同时从整个网络生存周期角度出发,节省更多的网络能耗.仿真结果表明,该策略在轮次增加或者簇间距离变化的情况下,都能得到较好的节能效果,从而延长网络的生存周期.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.