黄土沟壑区黑麦草植被冠层与根系坡面水沙效益及水力特性

基于野外人工模拟降雨试验和黑麦草全植被结构、根系结构及裸坡结构,通过设置不同雨强(30 mm·h-1、60 mm·h-1和90 mm·h-1)和不同下垫面坡度(1°、3°和5°),对坡面产流产沙特征、水力参数分布变化及坡面侵蚀特征和水力特征关系进行了分析,揭示了不同草被结构类型下坡面产流产沙特征与水力特性.结果表明:随...     

长壁工作面巷顶沿空掘巷围岩应力分析

镇城底矿工作面的回采巷道一条沿顶板掘进,一条沿底板掘进,相邻两工作面在端头搭接,沿底板掘进的巷道形成巷顶沿空掘巷。通过理论分析、相似模拟、数值模拟及现场实测对巷顶沿空掘巷围岩结构及应力环境进行了研究。得到如下结论：该巷道不受超前和固定支承压力影响,大结构下方的矸石垫层可起到能量和应力耗散的作用,避免了动载和冲击影响,应力低且稳定;岩层移动形成的垮落角对采空区应力大小和分布（尤其采空区边缘）有重要影响;垮落角越小,采空区应力越小,该巷道围岩应力越小,采空区恢复至原岩应力的距离越大;垮落角对岩体塑性区发育方向起控制和导向作用;该巷道围岩应力大幅低于原岩应力,卸压程度大;实测该巷道竖向和横向位移均比非沿空巷道小,即顶底板和两帮应力环境均得到改善。研究对维护具有冲击倾向的高应力巷道具有一定意义。     

基于C2阶连续函数的广义Hoek-Brown强度准则屈服面与塑性势面棱角圆化方法

Hoek-Brown强度准则的屈服面与塑性势面在棱角处导数无定义,具有数值奇异性,采用圆角进行光滑过渡只能满足一阶导数连续性,而二阶导数仍然无定义,使得棱边上一致切线模量矩阵无法正确计算,导致有限元总体平衡方程组Newton-Raphson隐式迭代二阶收敛性丧失。提出基于C2阶连续函数的广义Hoek-Brown准则屈服面与塑性势面棱角圆化方法,使得棱角处函数曲面二阶连续可导,棱边上一致切线模量矩阵可精确计算。基于ABAQUS数值开发平台,采用FORTRAN语言编制Hoek-Brown准则理想弹塑性UMAT用户子程序,通过数值算例验证所提方法的正确性。     

Incorporating economics into fisheries management frameworks in Australia

A large gap has been identified between the current and optimal economic performance of wild-capture commercial fisheries in Australia. Economic approaches have the potential to assist fisheries to bridge this gap, such as bio-economic models that combine biology with fishing costs to evaluate the economic performance of a broad range of management measures. Economic objectives are prevalent in overarching Australian fisheries legislation, however economic data is often not collected and economic analyses or instruments not broadly applied. This paper reviews selected Australian fisheries to demonstrate the accrued economic benefits from applying formal bio-economic models and conducting empirical analyses of the impact of supply on product value. Challenges to the implementation and continued use of economic analyses and instruments are discussed including: (i) short-term transition costs and associated trade-offs between ecological, economic, social and political objectives; (ii) scarce logistical and financial capacity to collect and analyse economic data; (iii) a lack of desire among industry to change and transition to economic targets such as maximum economic yield (MEY), particularly when it is associated with lower catches; and (iv) a lack of economic literacy among fisheries managers and industry. It is contended that many of these challenges initially arise from an absence of clearly identified and prioritised objectives within overarching legislation and management plans. Once objectives are prioritised, limited resources can be allocated more efficiently to improve data collection, economic analysis and increase awareness as well as education of managers and industry.     

Distribution,abundance and population structure of Hexaplex trunculus and Bolinus brandaris (Gastropoda: Muricidae) in offshore areas of the Gulf of Gabès,southern Tunisia

The banded murex Hexaplex trunculus and purple dye murex Bolinus brandaris are frequently caught as bycatch by bottom trawlers operating in the Gulf of Gabès, southern Tunisia. Although these muricid gastropods might importantly constitute an additional source of income for fishermen as well as help to diversify local shellfish production, information on their catches is relatively scarce. Hence, the present study aimed to assess the status of local populations of H. trunculus and B. brandaris, including data on their spatial and depth distributions, abundance, biomass, population structure and mortality. Fishing surveys using bottom trawls were performed between May 2006 and June 2007 in offshore areas of the Gulf of Gabès. In total, 198 fishing hauls were analysed, corresponding to a total fishing duration of 333.3 hours and a total prospecting area of 1 534 ha at depths of 20–86 m. Altogether, 3 026 H. trunculus and 3 599 B. brandaris of a broad size range (22.9?91.1 and 22.4?97.0 mm shell length, respectively) were sampled during the study period. GIS-produced maps were employed to determine the species’ spatial and bathymetric distributions by extrapolating their estimated fishing yield (bycatch per unit effort), abundance, biomass and mortality in relation to the total area surveyed in the gulf. The results provide valuable baseline information that may be applied to management proposals for regulating this untargeted resource, ultimately assisting sustainable exploitation and long-term preservation of this alternative fishing resource in the offshore areas of the Gulf of Gabès.     

水氮耦合对膜下滴灌棉花产量效应的探讨

为了探讨膜下滴灌棉花水肥耦合效应,于2003-2004年在新疆北疆雨水较少地区开展不同水氮条件对棉花产量效应的大田试验研究。结果表明,在该试验条件下,土壤水分对产量的作用最大,氮肥次之;水氮耦合的产量效应表现为适宜土壤水分中施肥量效果最高,高土壤水分中施肥量次之,低土壤水分低施氮量最低;水氮交互大小的顺序是水氮耦合＞土壤水分＞施氮量;获得最高籽棉产量5253kg/hm2的灌水量为4190m3/hm2,施氮量为276kg/hm2。     

地面气象观测数据文件的全程质量控制

利用山西省1983年-2006年暴雨洪涝、干旱、冰雹、霜冻、连阴雨等气象灾害受灾面积资料和农作物产量资料,采用灰色关联分析方法,对山西省主要气象灾害对农业的危害大小进行了分析。结果表明,影响山西农作物产量最严重的4种气象灾害依次是干旱、暴雨洪涝、冰雹和霜冻。     

Simulating the Impacts of Global Warming on Wheat in China Using a Large Area Crop Model

Temperature is one of the most prominent environmental factors that determine plant growth,development, and yield.Cool and moist conditions are most favorable for wheat.Wheat is likely to be highly vulnerable to further warming because currently the temperature is already close to or above optimum.In this study,the impacts of warming and extreme high temperature stress on wheat yield over China were investigated by using the general large area model(GLAM) for annual crops.The results showed that each 1℃r...     

中原腹地气候变化对冬小麦产量的影响——以商丘地区为例

为探明气候变化对商丘地区冬小麦产量的影响,根据1991～2010商丘市气候资料和小麦产量资料,利用数学统计与Thornthwaite Memoriae模型,结合未来气候预测结果定量分析了气候变化对冬小麦产量的影响。结果表明,冬小麦产量整体上呈波动上升趋势;主成分分析表明,气温、降水量、蒸发量与极端温度为影响冬小麦产量的主要气候因子,蒸发量过大及极端低温对冬小麦生产不利。商丘地区"暖湿型"气候有利于冬小麦生产力的提高,"冷干型"气候对冬小麦生产最为不利;未来几十年内气候可能将向"暖湿型"变化,对商丘地区粮食作物产量的提升较为有利。     

Reconstructing high-magnitude/low-frequency landslide events based on soil redistribution modelling and a Late-Holocene sediment record from New Zealand

A sediment record is used, in combination with shallow landslide soil redistribution and sediment-yield modelling, to reconstruct the incidence of high-magnitude/low-frequency landslide events in the upper part of a catchment and the history of a wetland in the lower part. Eleven sediment cores were obtained from a dune-impounded wetland at Te Henga, west Auckland, northern New Zealand. Sediment stratigraphy and chronology were interpreted by radiocarbon dating, foraminiferal analysis, and provisional tephrochronology. Gradual impoundment of the wetland began c. 6000 cal yr BP, coinciding with the start of a gentle sea-level fall, but complete damming and initial sedimentation did not begin until c. 1000 cal yr BP. After damming, four well-defined sediment pulses occurred and these are preserved in the form of distinct clay layers in most of the sediment cores. For interpreting the sediment pulses, a physically based landslide model was used to determine spatially distributed relative landslide hazard, applicable at the catchment scale. An empirical landslide-soil redistribution component was added and proved able to determine the volumes and spatial pattern of eroded and deposited soil material, sediment delivery ratio and the impact on total catchment sediment yield. Sediment volumes were calculated from the wetland cores and corresponding landslide scenarios are defined through back-analysis of modelled sediment yield output. In general, at least four major high-magnitude landslide events, both natural and intensified by forest clearance activities, occurred in the catchment upstream of Te Henga Wetland during the last c. 1000 years. The spatial distribution of modelled critical rainfall values for the catchment can be interpreted as an expression of shallow landslide hazard. The magnitude of the sediment pulses represented in the wetland can be back-calculated to critical rainfall thresholds representing a shallow landslide model scenario.