中国楷膜藻科(红藻门)新记录——掌状美叶藻

掌状美叶藻(Callophyllis palmata Yamada)分布于日本,北美洲西海岸等地,最近发现在中国大连广鹿岛有分布,属于我国新记录种.掌状美叶藻属于红藻门(Rhodophyta)楷膜藻科(Kallymeniaceae)美叶藻属(Callophyllis),主要特点为藻体颜色鲜红,生有根丝细胞.该种与贴生美叶藻C.adnata区别在于直立生长,分枝顶端呈二叉状凹陷;与附着美叶藻C.adhaerens区别在于分枝幅度较宽,可达10 mm以上.     

层次分析法在雷达模拟器标绘评估中的应用

根据国际海事组织关于雷达模拟器标绘评估的要求,分析了目前标绘评估方法的不足和层次分析法在评估中的适用性.提出了标绘评估标准的层次结构和基于层次分析法的标绘评估方法,实际应用表明,该方法能对雷达模拟器标绘训练进行比较客观的评估,在一定程度上弱化了评估过程中主观判断的影响.     

Nodal signals pattern vertebrate embryos

Vertebrate embryonic patterning requires several conserved inductive signals–including Nodal, Bmp, Wnt and Fgf signals. Nodal, which is a member of the transforming growth factor β (TGFβ) superfamily, activates a signal transduction pathway that is similar to that of other TGFβ members. Nodal genes, which have been identified in numerous vertebrate species, are expressed in specific cell types and tissues during embryonic development. Nodal signal transduction has been shown to play a pivotal role in inducing and patterning mesoderm and endoderm, and in regulating neurogenesis and left-right axis asymmetry. Antagonists, which act at different steps in the Nodal signal transduction pathway, have been shown to tightly modulate the inductive activity of Nodal. Received 20 October 2005; received after revision 15 November 2005; accepted 25 November 2005     

极端干旱条件下岷江上游古溪沟流域地下水-地表水环境特征及地下水资源战略储备选址适宜性评价

古溪沟流域是岷江上游汇入紫坪铺水库重要的补水单元,为研究极端干旱条件下流域内地下水-地表水化学特征和影响因素,探讨地下水资源战略储备选址适宜性,共采集16个地下水样和2个地表水样,综合运用Gibbs图、离子比值、绝对主成分-多元线性回归模型(APCS-MLR)等方法分析水化学及其影响因素;运用熵权水质指数(EWQI)进行地下水水质评价;采用层次分析法(AHP)构建流域地下水资源战略储备选址适宜性指标评价体系,探讨地下水资源战略储备选址的适宜性。结果表明,古溪沟流域地下水-地表水中主要阳离子为Ca₂₊^、M_g2+^、Na₊^、K₊^,主要阴离子为HCO_3-^、SO_42-^、Cl_-^,地下水化学类型以HCO₃-Ca、HCO₃-Ca.Mg、HCO₃.SO₄-Ca为主;Gibbs图、离子比值、APCS-MLR模型等解译出水化学组分主要来源为水-岩作用(44.08%)、工业活动(12.17%)、原生地质环境叠加工业活动(11.83%)、农业活动叠加生活污染(9.04%),水-岩相互作用主导了地下水水质形成的水文地球化学过程的同时还受到人为活动因素和自然环境等其他因素的影响;熵权水质指数(EWQI)评价地下水质量为I级和Ⅱ级分别占比56.25%和18.75%,Ⅲ级的占比为6.25%,Ⅳ级和Ⅴ级分别占比12.50%和6.25%,地表水上游为I级,下游为IV级,整体出现沿地下水径流途径,水质逐渐变差的现象,表明地下水-地表水已受到人类活动一定程度的影响;流域地下水资源战略储备选址综合适宜性指数(AI)介于1.0~9.8之间,适宜区面积占比48.57%,分布在流域中-东部下游区域,不适宜占比51.43%,不适宜区分布在流域上游区域,研究成果可在极端条件下为古溪沟流域-紫坪铺水库-都江堰的水资源安全开发利用及地下水资源战略储备选址布局提供参考。     

考虑压敏效应的低渗透油藏CO2辅助重力驱合理配产方法

高倾角低渗透油藏在进行水驱开发时,在油藏高部位存在大量剩余油,采收率较低,采用CO2辅助重力驱,可以充分利用高倾角的地质特征,有效提高该类油藏的采出程度。但是由于CO2对原油物性影响要远大于水对原油物性的影响,CO2驱替过程中流体的渗流过程更加复杂,因此有必要对低渗透油藏CO2重力驱合理配产优化进行研究。首先,依据油藏中任意一点压力与最小混相压力的关系,分别建立了考虑压敏效应的低渗透油藏CO2重力驱混相和非混相模型;其次,运用Python对模型进行求解,同时分析了压敏系数、地层倾角、注采井距和注气速度对油藏配产的影响;最后,结合现有工作制度法和增产倍数法,对比本模型计算结果,运用tNavigtor软件对三种方法进行采收率预测。研究结果表明：运用本文方法对油藏进行合理配产具有较好的开发效果,油藏采收率相对较高,研究成果对该类低渗油藏的开发具有较好的借鉴意义。     

底水油藏水侵量计算新方法

针对底水油藏的开发,在缺乏试井数据的情况下采用常规油藏物质平衡法以及试井分析方法均难以确定水驱控制储量,进而无法获得水体参数和特征来计算油田的水侵量。为了更加准确的预测水驱油田水侵量,本文结合生产动态资料,选择符合的水驱特征曲线计算水驱控制储量。在此基础上,考虑油环油、溶解气、水体等因素,建立物质平衡方程,通过亏空体积曲线法计算获得水侵量。利用Fetkvoitch拟稳态模型,采用试错法,优化计算水体体积和水侵系数,保证Fetkvoitch拟稳态模型求解的水侵量和亏空体积曲线法求解的水侵量最接近,得到最优的水体体积和水侵系数对未来生产动态中水侵量进行预测。运用油藏数值模拟软件建立的模型与本文提出两种的计算方法拟合结果对比可知的水体体积的误差为2.6%、水侵指数的误差为2.2%,计算结果准确,为底水油藏计算水侵量提供了可靠的依据,并为预测水侵量提供了新的方法。     

Maximum likelihood estimator of the parameter for a continuous one-parameter exponential family under the optimal ranked set sampling

This paper studies a maximum likelihood estimator (MLE) of the parameter for a continuous one-parameter exponential family under ranked set sampling (RSS). The authors first find the optimal RSS according to the character of the family, viz, arrange the RSS based on quasi complete and sufficient statistic of independent and identically distributed (iid) samples. Then under this RSS, some sufficient conditions for the existence and uniqueness of the MLE, which are easily used in practice, are obtained. Using these conditions, the existence and uniqueness of the MLEs of the parameters for some usual distributions in this family are proved. Numerical simulations for these distributions fully support the result from the above two step optimizations of the sampling and the estimation method.     

DDFS spurious signals due to amplitude quantization in absence of phase-accumulator truncation

Spurious signals in direct digital frequency synthesizers (DDFSs) are partly caused by amplitude quantization and phase truncation, which affect their application to many wireless telecommunication systems. Thee signals are deterministic and periodic in the time domain, so they appear as line spectra in the frequency domain. Two types of spurious signals due to amplitude quantization are exactly formulated and compared in thetime and frequency domains respectively. Then the frequency spectra and power levels of the spurious signals due to amplitude quantization in the absence of phase-accumulator truncation are emphatically analyzed, and the effects of the DDFS parameter variations on the spurious signals are thoroughly studied by computer simulation. And several important conclusions are derived which can provide theoretical support for parameter choice and spurious performance evaluation in the application of DDFSs.     

High efficient moving object extraction and classification in traffic video surveillance

Moving object extraction and classification are important problems in automated video surveillance systems. A background model based on region segmentation is proposed. An adaptive single Gaussian background model is used in the stable region with gradual changes, and a nonparametric model is used in the variable region with jumping changes. A generalized agglomerative scheme is used to merge the pixels in the variable region and fill in the small interspaces. A two-threshold sequential algorithmic scheme is used to group the background samples of the variable region into distinct Gaussian distributions to accelerate the kernel density computation speed of the nonparametric model. In the feature-based object classification phase, the surveillance scene is first partitioned according to the road boundaries of different traffic directions and then re-segmented according to their scene localities. The method improves the discriminability of the features in each partition. AdaBoost method is applied to evaluate the relative importance of the features in each partition respectively and distinguish whether an object is a vehicle, a single human, a human group, or a bike. Experimental results show that the proposed method achieves higher performance in comparison with the existing method.     

城市疫情传播和复工强度建模及相关性分析

以多源大数据为基础构建模型,分析全国34个典型城市因疫情导致的人口迁徙变化和人力缺口,并通过迁徙基数推算其他各城市的复工强度。仿真结果证明SEIR仓室模型能够较好地模拟此次疫情发展趋势,利用其估计各城市内部新型冠状病毒感染肺炎的基本再生数,结合人力缺口对复工强度进行回顾性的矩阵分析,以总结我国此次抗疫经验。相关性分析阶段对K-means无监督聚类后的城市集群进行回归分析,结果表明对于大部分城市而言,复工强度的大小与其人力缺口、基本再生数以及人均GDP水平有明显的相关关系。