Impact of dams on point bar habitat: a case for the extirpation of the Sacramento Valley Tiger Beetle,C. hirticollis abrupta

Quantitative analyses of flow and stage data, remote sensing and geographic information systems analysis, and field studies were used to assess the impact of dams and diversions on the point bar habitat of the Sacramento Valley Tiger Beetle (Cicindela hirticollis abrupta). The reaches of interest include sites of known historic populations of C. h. abrupta along the Sacramento River from approximately 8 km north of Colusa southward to the confluence with the Feather River and along the Feather River between Yuba City and its confluence with the Sacramento River. The results from this study show that construction of two major dams has altered flows such that prolonged and increased flows during summer, fall, and early winter have most likely disrupted life cycles, flooded larvae, drowned overwintering adults and led to high mortality. Additionally, habitat availability has decreased over time because point bars have decreased in number and area causing increased distances between populations and isolation of populations. Moreover, point bar armouring, channel scouring, altered flows, redirected flows through weirs, and lithologic controls have produced a bimodal distribution of mean grain sizes in the Sacramento River in which the more northern bars contain gravel deposits and more southern bars possess fine sands. These conditions negatively alter moisture retention and sediment compaction and, consequently, burrowing conditions needed by this tiger beetle. Additionally, more stabilized flows (reduced variability) and increased fine‐grained deposition have enabled development and encroachment of vegetation onto the sand bars. Finally, human stresses, such as foot traffic and vehicular traffic may have interfered with burrowing, ovipositing, and foraging. The combination of these stress factors has most likely led to a reduction in source populations and, ultimately, the apparent extirpation of the entire metapopulation. Copyright © 2006 John Wiley & Sons, Ltd.     

双层堤基的井涌破坏与无害管涌

双层堤基水文地质结构特殊，堤基承压水常具独特的“渗而不流”特征。在“不流”条件下，堤后盖层薄弱处受超高承压水头顶裂破坏，产生的局部冒水孔实属承压自流井，由此形成的管涌实质为井涌。底部进水的承压井流影响范围不大，井涌的破坏范围更小，据此可区分出有害管涌与无害管涌。前者局限于堤脚附近，小范围压渗为首选方案；对后者，既无需专门防治，更不必追求根治。     

论服务性企业的内部信息流管理——从服务质量管理角度

不同类型的服务性企业，其产品的种类、顾客化程度、顾客参与性程度和劳动密集程度等特征各有不同，但由于服务产品的某些共同特性，形成了企业内部信息流管理的共同规律。也决定了服务性企业内部信息流管理的必然性和特殊性。企业的信息流管理是企业加强顾客和企业之间以及企业各部门之间沟通的重要基石。掌握信息流管理原理，应对顾客意见，保持信息的容易获得性、流转顺畅性、对改变的自适应性和信息反馈机制，对不断提高服务质量、提高顾客满意度至关重要。     

荆江门弯道近期滩槽演变特点及影响因素分析

三峡水库运用改变了下泄水沙条件,坝下游弯曲河型均呈现“凸冲凹淤”演变规律,以致碍航问题日益突出。为研究弯曲河型滩槽演变特点及其成因,以下荆江河段荆江门弯道为例,利用三峡蓄水后近15 a实测地形资料,采用逻辑推理及统计分析方法分析其影响因素并预测了航道变化趋势。结果表明:三峡工程运用后,凸岸边滩年际间呈持续冲刷趋势,冲刷位置不断下移导致河段展宽引起航道条件恶化;在平滩流量(20 000~25 000 m³/s)持续时间＞15 d的年份,凸岸边滩冲刷后退,反之淤长;冲淤幅度与年均来沙量,尤其细沙(d≤0.125 mm)含量密切相关,基本呈同步变化趋势;荆江一期工程实施后,在当前水沙条件下凸岸边滩会继续受冲,形成枯水双槽,航道条件将恶化。水沙过程的改变是弯曲河型滩槽演变的主要原因,遇大水且来沙量较少的年份,荆江门河段很可能出浅碍航,这可为下荆江弯曲河段航道治理提供一定的参考价值。     

基于计算机仿真的堆石坝坝面流水施工方案研究

根据流水施工的基本原理和堆石坝填筑的施工特点，利用计算机仿真技术对堆石坝施工交通运输系统进行模拟，考虑了堆石坝土石方挖运对其坝面流水施工的影响，合理确定出坝面流水施工方案，使其既能够满足施工进度所要求的填筑强度，又能够保证各分区可以进行流水施工。     

利率风险管理的重要免疫工具:持续期模型

利率市场化进程的加快凸现利率风险管理的重要性和迫切性.作为一种利率风险管理的重要免疫工具,持续期配比策略在近些年来有了较大发展.本文在深入探讨Macaulay持续期的三种重要含义的基础上,详细地分析和比较了近期提出的几种主要持续期即:方向持续期、 部分持续期和近似持续期,最后简单讨论了将这些持续期模型及其免疫策略用于中国市场应注意的问题.     

基于久期缺口的商业银行利率风险免疫策略及实证分析

随着利率市场化的深入，利率风险越来越成为影响商业银行绩效的主要风险，因此，如何对商业银行利率风险进行计量及管理，日益成为国内外学术界高度关注的重要课题。通过建立久期缺口模型，提出了商业银行利率风险免疫策略，并进行实证分析表明：通过确立目标项目，调整资产与负债结构，可以较好地实现商业银行的利率风险免疫。     

某城区排涝泵站设计流量计算方法初探

采用平均排除法、最大24 h雨型洪水流量时程分配法和产流汇流法3种方法分别计算了某城区电排站的设计流量,并将3种方法的计算结果进行对比分析,选用合适电排站的设计流量,可为类似工程设计流量的确定提供参考。     

Default- and call-adjusted duration for corporate bonds

Call and default can potentially alter the timing and amounts of promised cashflows for callable, corporate bonds. While prior research has indicated the theoretical importance of adjusting Macaulay duration for the impacts of default and call, the question of their relative impact remains a matter of debate [The High Yield Debt Market, Dow Jones Irwin, New York, 1990, p. 18; J. Finan. 53 (1998) 2225]. We develop a theoretical analysis incorporating both default and call effects on duration and test its implications employing a previously unexplored data base of Canadian, investment grade, corporate bond indices containing an unusual provision making it possible to identify callable and noncallable indices.     

区域金融生态系统基本性状模型研究

金融生态环境概念是我国金融学术界的首创。金融生态环境作为一个全新的理论范畴,其区域空间属性还是一个探索性的初创领域。本文以科学发展观作为指导原则,通过采用状态空间系统分析方法,把区域生态系统的基本特征表达为一个集合即开放性、闭路循环性、根植性和可持续性;并通过采用结构分析方法,揭示了上述基本特征范畴的因果关系路径和测量方程。相对于以往文献的描述性方法而言,本文从提出概念假说到推导立论均体现了一种逻辑论证的科学方法,从而保证了所得出命题及其结论的准确性和可行性。