干旱区荒漠植被动力学及恢复对策调控指标分析

干旱区贫瘠土壤和植被单一是立地质量的重要指标,在水平结构上表现为一种有、无植被及不同种群组成的镶嵌分布,镶嵌分布具有的不均匀性在尺度变换下具有不变性特征;立地质量决定了抵抗破坏力度和恢复力度均弱,因而原生植被破坏时残存的幼苗或幼树经长期恢复形成了顶级单优结构。这就为应用生态学最著名的种群模型来研究其动力学行为奠定了基础。对动力学模型中的控制参数利用多种调控因子的组合分析,定量化地进行了受控变化研究,通过深入调试各种调控因子的数值范围、最佳指标的数值域和危险指标的数值域后,可提供便于操作的具体数据范围。     

基于NDVI的农牧交错区植被覆盖度变化研究——以宁夏盐池县为例

为了解农牧交错区植被覆盖度变化,以宁夏盐池县为例,基于NDVI和植被覆盖度遥感定量模型,提取了植被覆盖等级图。在此基础上对盐池县1989年、1999年、2003年的植被覆盖度等级图进行对比分析,结果表明两个时间段的植被盖度都呈增加趋势,后期（1999~2003年）年均变化明显高于前期（1989~1999年）年均变化,这主要归功于荒漠化治理措施（包括退耕还林、禁牧封育等）以及降水增加等多种因素。与此同时,在生态环境建设过程中,原有中、高覆盖度植被发生退化。因此,今后的治理工作应该加大对中、高盖度植被地区的保护工作。     

宁夏盐池县土地生产潜力评价研究

为了更好的解决荒漠化地区土地利用存在的问题,确定合理的土地利用规划,该文以位于半干旱区农牧交错区的宁夏盐池县为例,探讨该区土地潜力,建立了半干旱区农牧交错区土地潜力评价系统和指标体系,并筛选出评价主导因子,依据区域内的土地利用现状,将该区域分为17个地块,在地理信息系统下建立其属性数据库,结合有关专家判断,根据权重法对每一地块的土地潜力等级进行了评价.盐池县是宁夏沙化土地面积最大,风沙危害最严重的地区,沙化土地面积达5.6万hm²,占全县土地面积的75.14%.     

棉田与相邻荒漠过渡带节肢动物群落特征的初步研究

对南疆喀什地区莎车县恰热克镇棉田及相邻的荒漠-绿洲过渡带节肢动物群落进行初步研究明确了棉田及与之相邻的荒漠过渡带节肢动物群多样性和稳定性,了解不同生境节肢动物群落之间的关系.     

Temporal Logic and Concurrent Program

At first , temporal logic based on Manna Pnueli framework and concurrent program(transition diagrams) model based on shared variable are introduced, and mapping the model into basic transition systems; second,describing concurrent program and their properties(fairness, safety, liveness) by combing temporal logic with FTS model; at last,we point out temporal logic are more suitable than FSM and Petri net for specifies concurrent program.     

Formal Models for Hybrid Systems

Hybrid systems are reactive systems that intermix discrete and continuous components. Usually, the continuous components are modeled by differential equations, while the discrete components are modeled by discrete event systems or automata. Several important formal models for specifying hybrid systems are introduces, and a new computational model of hybrid systems hybrid transition system(HTS) is presented by extends fair transition systems(FTS).     

非均匀温差下埋地双层管道过渡段长度的计算

在管道输送介质过程中,由于管内温度和周围环境温度的差别,热量传播不可避免,温差沿管道的分布是变化 的。引入了温度衰减长度概念,在温差沿管道均匀分布时过渡段长度计算方法的基础上。     

乡村地域主导功能的转型与乡村发展阶段的划分

乡村地域功能是乡村地域对促进区域经济、社会、文化发展以及生态环境保护所承担的职能,它与城市地域功能在一定程度上实现了广义上的"地域分工"。乡村地域功能是客观存在的,但在不同的经济发展阶段下,不同功能的相对价值则有差异,文中在对乡村地域功能进行定义的基础上,对其各功能的特征进行了阐述。同时在钱纳里一般标准工业化模型的框架下,分析了在不同工业化发展阶段城市地域功能与乡村地域功能的转型轨迹,并以此将乡村发展阶段划分为维持生计型,产业驱动型与多功能主导型三个阶段。按照新修订一般工业化发展阶段的划分标准,2009年中国总体上处于产业驱动型乡村发展阶段,若干大都市区的郊区已进入了多功能主导型乡村发展阶段,也有一些省区乡村仍将长时间的处于产业驱动型乡村发展阶段。     

鲢幼鱼非疲劳贴网及姿态转换行为研究

流速是影响鱼类生存与繁衍栖息的重要因子。为了了解鱼类在中等流速区的游泳行为,探究其对水流的适应特征,利用鱼类游泳能力测定装置,以鲢(Hypophthalmichthys molitrix)幼鱼[体重(9.82±3.81) g,体长(8.56±1.11) cm)]为对象,采用递增流速法,分析了游泳过程中的非疲劳贴网行为与姿态转换行为。结果表明,在22℃水温条件下,鲢幼鱼平均相对临界游泳速度(critical swimming speed,U_(crit))相比其体长(body length,BL)为(6.00±0.93)BL/s;其非疲劳贴网速度(no-fatigue impingement speed,U_(imp))与临界游泳速度呈线性正相关,U_(crit)=1.03 U_(imp)+1.26 (R~2=0.86,P0.01);姿态转换速度(gait transition speed,U_(tran))与临界游泳速度呈线性正相关,U_(tran)=0.59 U_(crit)+1.55 (R~2=0.43,P0.01);非疲劳贴网速度与姿态转换速度呈线性正相关,U_(tran)=0.51U_(imp)+2.72 (R~2=0.41,P0.001)。在中等流速范围内(2～4 BL/s),实验鱼摆尾频率(tail beat frequency, TBF)和单次摆尾周期前进距离(stride length, SL)均随流速增加而增大。首次出现非疲劳贴网的流速为4.62 BL/s,流速增至5.08 BL/s时出现姿态转换行为。发生姿态转换后,TBF开始下降,而SL随流速增加快速增大。研究显示,鲢幼鱼非疲劳贴网行为对游泳能力和姿态转换速度有显著影响,且非疲劳贴网行为与姿态转换行为之间也存在相互影响。研究结果可为自然环境中鱼类生态行为研究、鱼类资源保护及渔业管理提供参考。     

DNA barcoding reveals clear delineation between spawning sites for neritic versus oceanic fishes in the Gulf of Mexico

We combined research‐vessel cruises of opportunity with DNA barcoding to survey planktonic, percomorph fish eggs at 40 stations distributed across and around the Gulf of Mexico (GoM). The objectives were (a) to determine whether eggs of fishes that are potential candidates for the daily egg production method (DEPM) can be readily barcoded, (b) to identify taxa that are spawning in the GoM, (c) to determine encounter rates for eggs of economically valuable taxa, and (d) to characterize individual egg taxa as being primarily neritic, primarily oceanic, or primarily mixed (i.e., both neritic and oceanic). Of the 1,144 eggs that were individually barcoded, 709 (62%) were definitively identified to species (62 species from 42 families), with an additional 20 taxa identified to genus or subfamily level. The eggs of 15 economically important species were identified, most of which had intermediate encounter rates and moderately dispersed spatial distributions, as indicated by an index of aggregation. SIMPROF analysis of stationwise cluster analysis identified eight significant groups within the 35 stations that yielded percomorph eggs; a corresponding specieswise analysis identified six groups of stations as having a neritic egg community and two groups as having an oceanic community, with a community transition located at the shelf break. Although the neritic and oceanic stations did not share important species, it remains possible that coastal pelagic species have mixed neritic–oceanic distributions. Together, these results indicate DEPM fish‐egg surveys based on DNA barcoding are feasible at the large marine ecosystem scale.