Experimental determination of sediment transport capacity of rill flow over sandified loess slope

Rill erosion is affected by the sand particle content in soil, especially in the wind and water erosion transition region of the Loess Plateau. The sediment transport capacity (STC) is a key parameter in rill erosion research, assessing the impact of aeolian sand intrusion on the STC of rill flow is of importance for a better understanding of rill erosion. This study aimed to assess the effect of aeolian sand intrusion on the STC on sandified loess slopes, with typical slopes and flow discharges, using a flume system which consisting of a sediment-feeding and a sediment-supply/settlement flume. The sediment feeding flume was jointed by 10° higher than that of the sediment measurement flume section. Three flow discharges (2, 4, and 8 L min⁻¹) and four slope gradients (5°, 10°, 15°, and 25°) were used to represent the natural hydrological conditions under three intrusion rates (SIR) of aeolian sands (10%, 20%, and 50%). The results show that STC increased with slope gradient and flow discharge, and the relationship between the STC and the SIR was significantly affected by the slope gradient; the STCs decreased with the SIR on a slope of 5° but increased with the SIR on steep slopes of 15°–25°, implying a significant impact of slope gradient on the relationship between SIR and STC. The SIR of 50% resulted in the highest sediment concentration nearly 1200 kg m⁻³ on slopes of 25°. On sandified loess slopes of 10%, 20%, and 50% SIR, the STC were about 30%, 46%, and 57% higher than on loess slopes, indicating an increased erosion rate by sand particle intrusion into loess soil. These results highlight the impact of sand intrusion on STC of rill flow and provide deeper insights into the soil loss process on the sandified loess slope.     

一种基于隐马尔可夫链的网络入侵检测研究

提出了一种基于HMM的网络异常入侵建模方法,使用隐马尔可夫模型中的Baum-welch算法识别攻击者攻击意图,给出了计算P(O|λ)和阈值的算法。仿真实验数据基于林肯实验室提供的入侵检测数据集,对系统进行了测试与性能分析,并与Snort系统比较,具有一定的应用价值。     

Identification of salt tolerant baldcypress (<Emphasis Type="Italic">Taxodium distichum</Emphasis> (L.) Rich) for planting in coastal areas

Coastal baldcypress (Taxodium distichum) forests are being killed in the southern United States as a result of saltwater intrusion. Tank studies have indicated substantial intraspecific variation in salt tolerance within baldcypress populations, but only one field study has been conducted and it used a limited seed source. The major objective of this project was to expand the collection range of baldcypress across the southeastern United States and determine if there are baldcypress populations that can survive and grow in saltwater damaged areas. Seeds were collected in 1996 from eight estuarine areas (James River = VA; Cape Fear River = NC; Winyah Bay = SC; Ogeechee River = GA; Ochlockonee River = FL; Mobile Bay = AL; Biloxi River=MS; Chalmette = LA). Seeds were stratified and planted, and seedlings were grown for 2 years before planting in two abandoned ricefields on Hobcaw Barony near Georgetown, South Carolina in 1999. Salinity levels reached 18.5ppt during 2001 at the peak of the worst drought on record. By 2002, the only seedlings surviving were those from LA, AL, and FL. After 5 years in the field, LA seedlings were the best performers with a mortality rate of only 27%. More detailed analyses of the biologic and genetic characteristics of trees growing in the LA site need to be completed to determine if they represent a source of baldcypress seed possessing greater tolerance to saline conditions. If so, seeds need to be collected and nurseries established to grow seedlings to help restore degraded wetland swamp areas along the Gulf and Atlantic coasts.     

青岛市海水入侵现状与防控措施研究

通过对青岛市海水入侵概况、影响因素以及危害的分析,提出了相应的补救措施,为青岛市海水入侵的防治提供了新的思路。     

基于CDAN技术与BP算法的棉花病虫害入侵检测-预报系统模型

为了提高棉花生产的信息化和棉花病虫害预报的效率与智能性,针对棉花病虫害入侵产生因素的多维性,对棉花叶面信息表现的时序、棉花叶面的状态在时间和空间域中表现出的紧密相关性进行了分析,把人工神经网中的BP神经网络算法和信息安全领域中的入侵检测技术CDAN引进来,构造成基于CDAN技术与BP神经网络的棉花病虫入侵检测一预报系统.     

Policy analysis of the ‘MPA‐process’ in temperate continental shelf areas

• 1. The decision to designate, implement and manage marine protected areas (MPAs) is often made ad hoc without clear guiding procedures. This study evaluates the process of establishment and management of MPAs in temperate soft‐bottom marine areas, including identification of objectives, site selection, designation, implementation, ecological effectiveness and socio‐economic impacts.
• 2. For the first time, literature about marine conservation strategies in soft‐bottom temperate areas is brought together in one ‘systems approach’, which is visualized in a flow chart including three phases: setting policy objectives, making decisions and evaluating the eventual effects of the MPA. Policy objectives are generally easy to identify and in most cases national policy objectives are driven by international and regional legal obligations. The decision making process is the most complex phase, as the acceptance of MPAs has to be balanced against the human activities that take place in the area.
• 3. The relation between fisheries and MPA‐management appears to be most challenging in soft‐bottom temperate marine areas because of conflicting interests and institutional differences. Activities limited in space and not relying directly on ecosystem functions (e.g. offshore energy production and aggregate extraction) are generally easier to manage than fisheries.
• 4. The conceptual mapping exercise presented here serves as a basis for a systems approach for MPAs and has been tested for the Belgian coastal environment. In the Belgian ‘MPA‐process’, the application of the systems approach proves to be useful in providing insight into the complex interactions of various authorities with scattered jurisdictions.
• 5. The unified and simplified representation of the various aspects is (1) a useful communication tool for policy makers and managers to inform other sectors and the public at large and (2) a valuable support during the ‘MPA‐process’ that considerably enhances the prospects for success.

Copyright © 2008 John Wiley & Sons, Ltd.     

人为侵入体对城市绿地土壤水分入渗特征的影响

在快速城市化过程中,人为侵入体大量混入绿地,改变了土壤的三相组成及孔隙特征,但其对城市绿地土壤的入渗影响仍不清楚。基于一维垂直土柱入渗模拟,以典型人为侵入体砖块和混凝土碎块为例,研究其对城市绿地土壤水分入渗的影响特征。结果表明:(1)人为侵入体的混入均会抑制城市绿地土壤水分下渗,导致其稳定入渗速率降低,累积入渗量、湿润锋距离和土壤体积含水量减小,深层土壤水分变化滞后。同一配比下,以混凝土碎块对土壤水分入渗的抑制作用更为明显(P0.1);(2)随着人为侵入体配比从10%增加到20%,土壤稳定入渗率、累积入渗量、湿润锋距离和土壤体积含水量仍持续减小或略有增加,但差异均不显著(P0.1),其对土壤水分下渗的抑制作用渐趋减弱。(3)不同类型人为侵入体及配比下,城市绿地土壤水分的入渗量随时间变化更加符合Kostiakov模型。研究结果可为未来海绵城市的高效建设提供科学依据。     

《建筑抗震设计规范》中抗震计算方法的归纳

《建筑抗震设计规范》（GB50011-2010）第5.1.2条,明确列出了各类建筑结构的抗震计算方法,归纳有三种方法,即底部剪力法、振型分解反应谱法和时程分析法,本文对此展开分析。     

播种时期和浸种对君迁子出苗的影响

对君迁子(Diospyros lotus.l.)种子播前浸种和浇底水处理,于不同时期播种试验。结果表明:自然条件下,君迁子在1月底之前播种出苗较好;土壤持水量低时,播前应浸种,播种时应浇底水,可保证出苗率。君迁子种子休眠不明显,只要水分充足,4月初以前播种均可获得理想的育苗效果。     

大亚湾不同波浪、水深与坡度条件下车叶型人工鱼礁的安全重量

基于小振幅波和力学理论,以车叶型鱼礁为对象,对其在大亚湾不同波浪(台风、十年一遇、二十五年一遇、五十年一遇)、不同水深(6～20 m)、不同海床坡度(10-1、30-1、50-1)及附着生物等多种条件下的安全性进行了研究分析,确定了车叶型鱼礁的安全重量和大亚湾海域适于其投放的水深范围.结果表明,安全重量在深于12 m的水深范围内变化平稳,而在较浅的水深特别是在波浪发生破碎的前后过程大小差异明显,表现出随水深变浅先变大后变小的波动特征,二十五年一遇的波浪条件下3种坡度的安全重量最大值分别为42.4、22.4和20.3 t,对应水深为10、12和14 m.坡度对礁体安全重量的影响非常明显,坡度越小,安全重量越轻,各种波浪条件下30-1与50-1下的安全重量随水深的变化特征相似,而10-1与30-1的差异远大于30-1与50 -1的差异.礁体的安全重量与波浪条件、水深和海床坡度有直接关系,水深过浅或海床坡度过大均可能导致礁体在较大波浪下失稳.从礁体稳定性与航道安全性两方面考虑,应选择大亚湾12 m以深、坡度平缓的水域,投放设计重量为22.4 t的车叶型人工鱼礁.