基于滑动地址序列的IPv6网络拓扑发现引擎

为满足IPv6网络的拓扑发现需求,提出了一种基于滑动地址序列的IPv6网络拓扑发现算法。算法根据并发进行的分布式探针数量,将待探测的目标地址集等分为若干子集,在每个周期内每个探针只按序针对其中的一个子集进行探测,同时探针之间互相通告各自探测的结果;此后每个探针按序对下一个子集进行探测,如果发现过程抵达前面的探测周期中其他探针已经发现的共同路径时,则停止继续向前探测。基于本算法实现的系统对一个真实的纯IPv6主干网环境进行了全面发现实验。实验结果表明,该引擎减少了约35%的IPv6探测报文,达到设计目的。     

Preventing IP Source Address Spoofing: A Two-Level, State Machine-Based Method

A signature-and-verification-based method, automatic peer-to-peer anti-spoofing (APPA), is proposed to prevent IP source address spoofing. In this method, signatures are tagged into the packets at the source peer, and verified and removed at the verification peer where packets with incorrect signatures are filtered. A unique state machine, which is used to generate signatures, is associated with each ordered pair of APPA peers. As the state machine automatically transits, the signature changes accordingly. ...     

基于声波测井资料的疏松砂岩可压性研究

出砂是疏松砂岩油藏开采中遇到的难题之一,目前常用防砂方法是高压挤压砾石充填防砂技术.为了对该技术实施后地层近井形态进行科学描述,为现场施工参数的优化提供可靠依据,在缺少物模获取相关参数的前提下,根据高压挤压砾石充填地层受力特点,借鉴声波测井资料,建立数学模型,并推导出基于测井资料的挤压模量计算公式.提出疏松砂岩岩层可压性概念,明确岩层挤压指数来表述疏松砂岩可压性,并根据其数值范围划分软、硬地层.采用挤压模量计算公式对具有完整测井资料的多口防砂施工井进行编程计算,并将得到的各施工井挤压模量加权平均后进行拟合.与高压挤压砾石充填施工实际数据对比,计算结果准确、可靠.     

基于MIMO模式选择的IEEE802.11n节能算法

多入多出(multiple input multiple output,MIMO)是IEEE 802.11n的重要特征,其利用空分复用技术提升系统吞吐量,但同时也带来了新的问题,即MIMO技术的使用会大幅增加通信终端的能耗。IEEE 802.11n标准中增加了空分复用节能机制,但该机制只针对接收端的节能,对于发送端没做任何规定。针对这一问题,该文研究了IEEE 802.11n发送端的能耗问题,提出了一种基于MIMO模式选择的发送端节能算法。该算法以单位比特能耗为优化目标,根据聚合帧大小和已有速率自适应模块的统计信息预测每个MIMO模式的单位比特能耗,据此为每一个待发送的聚合帧动态地选择能效最优的MIMO模式,进而达到优化发送端能耗的效果。基于真实实验数据的数值分析结果表明:该算法能够很好地优化发送能耗,同时降低对系统吞吐量的影响。     

Whole-genome analysis informs breast cancer response to aromatase inhibition

To correlate the variable clinical features of oestrogen-receptor-positive breast cancer with somatic alterations, we studied pretreatment tumour biopsies accrued from patients in two studies of neoadjuvant aromatase inhibitor therapy by massively parallel sequencing and analysis. Eighteen significantly mutated genes were identified, including five genes (RUNX1, CBFB, MYH9, MLL3 and SF3B1) previously linked to haematopoietic disorders. Mutant MAP3K1 was associated with luminal A status, low-grade histology and low proliferation rates, whereas mutant TP53 was associated with the opposite pattern. Moreover, mutant GATA3 correlated with suppression of proliferation upon aromatase inhibitor treatment. Pathway analysis demonstrated that mutations in MAP2K4, a MAP3K1 substrate, produced similar perturbations as MAP3K1 loss. Distinct phenotypes in oestrogen-receptor-positive breast cancer are associated with specific patterns of somatic mutations that map into cellular pathways linked to tumour biology, but most recurrent mutations are relatively infrequent. Prospective clinical trials based on these findings will require comprehensive genome sequencing.     

Increased methylation variation in epigenetic domains across cancer types

Tumor heterogeneity is a major barrier to effective cancer diagnosis and treatment. We recently identified cancer-specific differentially DNA-methylated regions (cDMRs) in colon cancer, which also distinguish normal tissue types from each other, suggesting that these cDMRs might be generalized across cancer types. Here we show stochastic methylation variation of the same cDMRs, distinguishing cancer from normal tissue, in colon, lung, breast, thyroid and Wilms' tumors, with intermediate variation in adenomas. Whole-genome bisulfite sequencing shows these variable cDMRs are related to loss of sharply delimited methylation boundaries at CpG islands. Furthermore, we find hypomethylation of discrete blocks encompassing half the genome, with extreme gene expression variability. Genes associated with the cDMRs and large blocks are involved in mitosis and matrix remodeling, respectively. We suggest a model for cancer involving loss of epigenetic stability of well-defined genomic domains that underlies increased methylation variability in cancer that may contribute to tumor heterogeneity.     

高速网络性能测试负载生成多流发送调度算法

测试负载生成是网络性能测试的重要环节之一.为了在测试过程中模拟复杂的数据流量环境,常常通过组合大量特征各异的流来近似实际网络流量.流的重要属性是其速率与突发程度,文中将此定义为流模式.在使用多个流来模拟复杂的网络环境时,一个重要问题是如何调度多个流,以保证各个流的流模式.提出了一种调度方法GRR(grouping round robin), 将所有流分成若干小组后分别在组内和组间两级轮询调度,可在较低的时间和空间复杂度内实现调度目标.算法已在一个高速网络性能测试系统IP-TEST中得到应用,达到了1 Gb/s的线速发送速率,并且支持突发流模式.     

An asymmetric solar wind termination shock

Voyager 2 crossed the solar wind termination shock at 83.7 au in the southern hemisphere, approximately 10 au closer to the Sun than found by Voyager 1 in the north. This asymmetry could indicate an asymmetric pressure from an interstellar magnetic field, from transient-induced shock motion, or from the solar wind dynamic pressure. Here we report that the intensity of 4-5 MeV protons accelerated by the shock near Voyager 2 was three times that observed concurrently by Voyager 1, indicating differences in the shock at the two locations. (Companion papers report on the plasma, magnetic field, plasma-wave and lower energy particle observations at the shock.) Voyager 2 did not find the source of anomalous cosmic rays at the shock, suggesting that the source is elsewhere on the shock or in the heliosheath. The small intensity gradient of Galactic cosmic ray helium indicates that either the gradient is further out in the heliosheath or the local interstellar Galactic cosmic ray intensity is lower than expected.     

混合液回流比对A/A/O工艺处理城市污水反硝化除磷脱氮效果的影响

试验以小试规模的传统A/A/O工艺处理某城市污水处理厂的进水为研究对象,在污泥回流比为100%的条件下,探讨了混合液回流比为100%、200%、300%时系统对反硝化除磷脱氮效果的影响。结果表明,随着混合液回流比的增加,系统对TP的去除呈现出先升高后降低的趋势,在混合液回流比为200%时,TP的去除率达到93.3%,出水TP的平均值为0.47mg/L;COD的去除基本不随混合液回流比的变化而变化,始终保持了良好的去除效果,平均去除率达到94.6%,出水平均值为18.2mg/L;系统对TN的去除效果较差,这可能与缺氧区较短的水力停留时间有关,但是,在混合液回流比为200%时TN的去除率相对稳定。所以,在本试验条件下以回流比为200%时的除磷脱氮效果最佳。