Spatial Variations in Particle Size,Heavy Mineral Assemblage and Magnetic Concentration of Dark-reddish Sands on Cedar Beach,Western Lake Erie,Ontario,Canada

Environmental magnetic research on beaches and shoreline processes is limited.Therefore,we carried out environmental magnetic studies on the heavy mineral-enriched,dark-reddish sands on Cedar Beach of western Lake Erie(41.68°N,82.40°W).Magnetite has been identified as the dominant magnetic mineral of these sands.This study reveals a spatial variation in concentration of magnetite particles,distribution of

Feeding habit and seasonal variation of stomach contents of sand dabs, Pseudopleuronectes yokohamae, in the South Bohai Sea

Sand dabs, an important commercial flatfish in the Bohai Sea, has recently decreased gradually in biomass, resulting from overfishing and marine pollution. Artificial culture and multiplication of sand dabs are essential and practical in China. The present paper examines the food habitof this fish to provide detailed information for its culture and multiplication.

Spatiotemporal variations of benthic macrofaunal community in the Xiamen Amphioxus Nature Reserve, eastern South China Sea

In order to realize the spatiotemporal variations of benthic macrofaunal communities at the"Amphioxus Sand"habitat,six surveys including four seasons and three consecutive summers(i.e.,2014,2015 and 2016)were conducted in two core sites,i.e.,Huangcuo(HC)and Nanxian-Shibaxian(NX),in the Xiamen Amphioxus Nature Reserve in China.A total of 155 species of macrofauna were recorded,therein,polychaetes were dominant in terms of species number and density.Significant spatiotemporal variations of macrofaunal communities were observed.The density of polychaetes and the biomass of molluscs in the HC site were higher than those in the NX site.Macrofauna were more diverse and abundant in the cold seasons(winter and spring)than that in the warm seasons(summer and autumn).The annual variations of macrofaunal communities may be attributed to the changes in sediment texture among the three years of the survey.The variations in macrofaunal communities were mainly related to the proportion of polychaetes within the community.In addition,the density of amphioxus(include Branchiostoma japonicum and B.belcheri)was negatively correlated to that of polychaetes,bivalves,and crustaceans.Amphioxus was less likely to be found in the sediments with higher silt and clay content.Five biotic indices including Margaref’s richness index(d),Peilou’s evenness index(J′),Shannon-Wiener diversity index(H′),AMBI and M-AMBI were calculated in the present study.AMBI seems suitable in assessing benthic health at the"Amphioxus Sand"habitat,and a potential risk of ecological health in Xiamen Amphioxus Nature Reserve should be aware.

Seasonal variation in dust events and the causes of the variation in the Tarim Basin,China

We analyzed dust event occurrence and its seasonal distribution at 16 sites in the Tarim Basin,China.Although the overall frequency of dust events was the highest in spring in this region,its variation in other seasons could be classified into three patterns:(1) frequency of dust events in autumn > that in summer > that in winter(at the Kashi and Kuche sites);(2) frequency in summer > that in winter > that in autumn(at the Ruoqiang site);and(3) frequency in summer > that in autumn > that in winter(at all other areas of the Tarim Basin).The frequency of dust events and their seasonal variations in the Tarim Basin were mainly controlled by wind speed and locally available dust sources;the former was the key control when dust sources did not differ significantly.The seasonal variation in evaporation had a smaller,but still significant effect on the frequency of dust events.

Research on testing method of resin sand high temperature compressive strength

High temperature compressive strength is one of the most important performances of resin sand; its value directly concerns the quality of castings. In order to seek the best testing method of resin sand high temperature compressive strength, a self-developed instrument was used to carry out experiments, and the sample shape and size were designed and studied. The results show that a hollow cylinder sample can reflect the strength difference of different resin sands better than a solid cylinder sample, and its data is stable. The experiments selected φ20/5×30 mm as the size of the hollow cylinder samples. The high temperature compressive strengths of phenol-formaldehyde resin coated sand, furan resin self-setting sand, and TEA resin sand were each tested. For the resin sand used for cast steel and cast iron, 1,000 ℃ was selected as the test temperature; for the resin sand used for cast non-ferrous alloy, 800 ℃ was selected as the test temperature; and for all the resin sand samples, 1 min was selected as the holding time. This testing method can truthfully reflect the high temperature performance of three kinds of resin sand; it is reproducible, and the variation coefficients of test values are under 10%.

Seasonal differences in climatic controls of vegetation growth in the Beijing–Tianjin Sand Source Region of China

Launched in 2002, the Beiing–Tianjin Sand Source Control Project (BTSSCP) is an ecological restoration project intended to prevent desertification in China. Evidence from multiple sources has confirmed increases in vegetation growth in the BTSSCP region since the initiation of this project. Precipitation and essential climate variable-soil moisture (ECV-SM) conditions are typically considered to be the main drivers of vegetation growth in this region. Although many studies have investigated the inter-annual variations of vegetation growth, few concerns have been focused on the annual and seasonal variations of vegetation growth and their climatic drivers, which are crucial for understanding the relationships among the climate, vegetation, and human activities at the regional scale. Based on the normalized difference vegetation index (NDVI) derived from MODIS and the corresponding climatic data, we explored the responses of vegetation growth to climatic factors at annual and seasonal scales in the BTSSCP region during the period 2000–2014. Over the study region as a whole, NDVI generally increased from 2000 to 2014, at a rate of 0.002/a. Vegetation growth is stimulated mainly by the elevated temperature in spring, whereas precipitation is the leading driver of summer greening. In autumn, positive effects of both temperature and precipitation on vegetation growth were observed. The warming in spring promotes vegetation growth but reduces ECV-SM. Summer greening has a strong cooling effect on land surface temperature. These results indicate that the ecological and environmental consequences of ecological restoration projects should be comprehensively evaluated.

琵琶柴的防风固沙作用数值模拟

植物固沙是北方干旱、半干旱区防治风沙灾害的重要措施之一,其中琵琶柴(Reaumuria soongorica)为荒漠区分布最广泛的半灌木,具有重要的应用价值。本文利用计算平台Fluent对琵琶柴植株附近的流场进行数值模拟,分析风速特征和积沙特征。结果表明:(1)在10 m·s^(-1)初始风速下,植株前后皆会形成涡流,其高度和强度与距植株远近有关,整体低于0.25 m。(2)数值模拟结果表明,气流水平方向速度的变化多呈“N”和“W”型曲线,而垂直方向的气流速度变化则为“V”型曲线。(3)在较低风速下,非生长季琵琶柴的阻风效能要优于生长季,株后防护距离4 m;当风速大于6 m·s^(-1)时,双排生长季琵琶柴株后风速降低幅度可大于94.45%。(4)琵琶柴具有良好的阻沙效果,在初始风速为6 m·s^(-1)时,大部分沙粒堆积在植株前后底部;当风速增至10 m·s^(-1)时,生长季琵琶柴阻沙良好,沙粒主要沉积在株后1.5~3 H,沙粒堆积高度小于0.1 m;当初始风速为15 m·s^(-1)时,生长季琵琶柴株后积沙主要分布在株后2~3.5 H,而非生长季琵琶柴沙粒堆积范围则在株后1~10 H。无论何种生长季琵琶柴均能有效降低风场内气流速度,并对气流所携带的沙粒具有良好的沉降作用,在植物治沙工程中起重要作用。

南方主要河流水沙变化及人类活动的影响

为了解我国南方河流的水沙变化及主要成因,利用Mann-Kendall检验法和水文量累积曲线法,分析了南方主要河流代表站径流量和输沙量的变化特征,探讨了影响南方河流水沙变化的主要因素。结果表明,长江、珠江、钱塘江和闽江等南方河流代表站年径流量都没有显著的变化态势;除钱塘江代表站外年输沙量都有显著减少趋势;钱塘江2016—2020年为平水平沙期,2011—2020年为平水多沙期,其他河流2016—2020年和2011—2020年均为平水少沙期;影响南方河流水沙变化的人类活动包括水库拦沙、水土保持措施、河道采砂、流域过度建设等,其中水库拦沙是南方河流减沙的主要措施,水土保持措施在南方河流减沙过程中发挥了重要作用,河道采砂对河道减沙也发挥了一定的作用。

基于捐赠土壤种子库方法的沙丘植被恢复模拟实验

退化沙地土壤种子库数量不足限制了其自然恢复能力,传统的种子库添加植被恢复技术措施存在添加物种数量、配比难以确定的限制,针对上述问题,提出了捐赠土壤种子库的植被恢复方法,即从邻近植被生境相似的长期稳定群落转移包含土壤种子库的表层土壤进行受损区植被恢复的方法。该方法在受损湿地、草地和林地的恢复方面取得了较好的应用效果,但是该方法能否用于荒漠化区域的植被恢复尚未见报道。采用室内盆栽和模拟降雨相结合的实验办法,以长期稳定的固定沙丘为捐赠土壤种子库源区,以流动沙丘和半固定沙丘为受捐对象,对比分析了捐赠固定沙丘土壤种子库对流动沙丘和半固定沙丘植被恢复的效果,并模拟了降雨变化对恢复效果的影响作用。结果表明:1)捐赠土壤种子库显著提高了半固定沙丘和流动沙丘模拟处理的种子萌发数量和幼苗地上生物量,有利于促进流动沙丘和半固定沙丘向固定沙丘进行演替;2)捐赠土壤种子库方法在半固定沙丘的植被恢复效果优于流动沙丘;3)捐赠土壤种子库可以增加流动沙丘实现跨越式恢复的可能性,加快其向固定沙丘的演替进程;4)小幅度的降雨量增减对受捐区种子萌发数量和地上生物量无显著影响;5)极端降雨可以显著提高受捐区种子萌发数量和地上生物量。综上所述,在模拟实验条件下,捐赠土壤种子库技术可以有效地促进退化沙丘植被恢复,极端降雨事件对捐赠土壤种子库实施后的恢复效果影响更加显著。研究为捐赠土壤种子库在退化沙地植被恢复的野外实际应用提供了理论支持。

螺纹桩加固风积沙地基液化特征试验研究

研究目的:随着我国的西部交通建设不断发展,线路工程将难以避免地穿越风积沙河谷地区,路基工程将面临地基液化的问题。螺纹桩作为近年来出现的新型桩基,在地震作用下加固可液化场地的桩土相互作用力学机制和抗液化效果的研究相对较少。本文通过振动台试验,首次从小波包能量变异角度研究了螺纹桩加固风积沙地基的液化特征,并验证了其适用性。进一步分析了螺纹桩复合地基液化易发部位的时频-能量演化规律,并探讨了风积沙的微观液化过程。研究结论:(1)在地震作用下,螺纹桩能提高风积沙地基的刚度和整体抗液化能力,抑制风积沙骨架结构的变化或重组;(2)小波包能量变异特征与孔压响应呈现的液化规律联系紧密,评价地基液化具有适用性;(3)螺纹桩可将风积沙地基的液化易发区从中部转移到浅层,有利于通过地基加固人为干预地基液化;(4)螺纹桩-风积沙复合地基未发生液化时,震动响应能量主要集中在第一频带(0.1~6.26 Hz),而发生液化时,低频(2~5 Hz)积聚的能量逐渐向高频(10~15 Hz)发散,并伴随在时间节点上出现新的能量尖点;(5)在微观层面,风积沙液化过程是剪胀剪缩循环交替的过程,颗粒排布从紧密接触到相互分离,而螺纹桩桩身的螺纹对风积沙的体积应变有抑制作用,降低其液化势;(6)本研究成果可为液化地基螺纹桩加固技术设计提供一定参考。

金沙江下游梯级水库对三峡水库消落期水沙条件的影响

金沙江下游梯级水库蓄水运行对三峡库区水沙条件产生明显影响,进而引起航道条件的改变。利用实测水沙资料,分析金沙江下游梯级水库对三峡水库消落期水沙条件的影响。结果表明,2015年1—5月向家坝下泄流量增大,平均增幅37%,朱沱站、寸滩站流量也随之增加34%和26%;向家坝站输沙量减少约98%,由占寸滩站沙量比重58%以上减少为1%~5%。水沙条件的改变有利于改善三峡库区航道条件,特别是朝天门以上库尾河段枯水期的航道最小维护水深由1—4月的2.7 m提升至12月的2.9 m,而朝天门以下河段航道条件受向家坝下泄流量的影响相对较小。

融合麻雀搜索算法和柯西变异策略的沙猫群优化算法

针对原始的沙猫群优化算法在迭代后期搜索效率低,容易陷入局部最优的问题,提出了一种多策略改进的沙猫群优化算法(ISCSO).首先,通过融合麻雀搜索算法的搜索机制策略,提高了沙猫靠近和捕获猎物的速度,有效地提升了算法后期的搜索能力.其次,为避免算法出现早熟收敛现象,引入limit阈值判断算法是否陷入局部最优.最后,采用柯西变异策略,改变个体所处位置,提高种群多样性,使算法跳出局部最优.通过在6种不同类型的基准测试函数上进行仿真,对实验结果进行数值分析,结果表明:改进后的沙猫群优化算法在求解高维复杂问题上具有精度高、收敛速度快、鲁棒性强等优势.

基于改进沙猫群算法优化CNN-BiLSTM的热负荷预测

针对传统热负荷预测精度不高、无法满足换热站及热网优化调控需求的问题,提出一种VMD-ISCSO-CNN-BiLSTM的热负荷预测模型。首先,利用变分模态分解(VMD)对原始供热负荷数据进行降噪处理,降低数据的不稳定性;其次,由K-means算法改进种群初始化,由演变机制改进寻优能力和由变异机制改进跳出局部最优能力,利用改进沙猫群算法(ISCSO)对卷积神经网络、双向长短期记忆神经网络(CNN-BiLSTM)超参数进行寻优,建立热负荷预测模型;最后通过实例进行分析。结果表明,数据降噪后模型预测精度更高,R^(2)提升1.1%;由ISCSO优化的模型比其他算法优化的模型预测效果更好,拟合度达到99.4%;VMD-ISCSO-CNN-BiLSTM的组合预测模型相较于单一模型,RMSE降低18.5%,MAE降低13.8%,R^(2)提升15.8%,并有更好的拟合度,泛化性强,满足工程实际要求。

3D立体格栅–砂界面剪切性状试验研究

为探究土工格栅–砂界面的剪切律、强度律和体变律,基于3 D打印技术制作的土工格栅,通过改进的应变控制式直剪仪进行了不同横肋数量的土工格栅与不同干湿类型的标准砂间的界面剪切试验。结果表明:法向应力越大,剪切应力弱化现象越明显,界面抗剪强度及其指标与横肋数量成正比例关系;3 D立体格栅–湿砂界面粘聚力随着横肋数量的增多而减小。3 D立体格栅–干砂界面抗剪强度及其指标比3 D立体格栅–湿砂界面大,剪胀特性更明显。干砂和湿砂均表现出剪胀的体变行为,且横肋数量越多,剪胀特性越明显。研究成果可为探究3 D土工格栅在实际工程中的应用提供参考。

不同发育期小玉竹种子大小变异特性及萌发规律

【目的】种子是植物繁衍的基础,探究小玉竹种子不同采收期形态特征和萌发规律,以期揭示小玉竹种子的形态特征及变异、适宜采收期,为培育小玉竹优质种苗提供科学依据。【方法】以吉林市东团山野生小玉竹种子为研究对象,精确测定其不同发育期长径、宽径、纵径、形态指数、大小指数、千粒重等大小特征指标,利用标准主轴估计法分析种子形态特征的异速生长关系;低温沙藏处理30 d并通过培养皿纸上发芽方法进行种子发芽规律研究。【结果】不同发育期小玉竹种子大小各性状变异均为连续分布的数量性状,发育期变异系数:重量>纵径>宽径>长径,分别集中在在成熟期变异系数:重量>长径>纵径>宽径。4℃沙藏30 d显著提升发芽率、发芽势。【结论】小玉竹种子近似椭圆形,在三维角度下越大越立体饱满形状趋于“圆球”。种子重量变异最大,可以利用此特性进行分级,9月底采收更合适,4℃沙藏30 d,发芽更快更整齐,发芽率可达87.78%。研究结果可以指导小玉竹的产业实践,促进小玉竹有性繁殖发展。

基于改进沙猫群算法的微电网日前优化调度

微电网系统包括多种分布式能源,为降低微电网综合发电成本,提高供电的可靠性和安全性,合理安排微电网日前调度计划,以运行成本和环境保护成本最低为目标函数,首先,建立由水、光、微型燃气轮机、储能装置组成的微电网日前优化调度模型;然后,将反向学习策略和柯西变异算子融入到沙猫群算法中,提出一种改进沙猫群算法求解上述模型;最后,通过与其他算法进行调度的结果对比,结果表明改进沙猫群算法能更合理地安排各机组的出力计划,明显降低微电网运行综合成本,同时减少二氧化碳排放量,实现了微电网的经济环保优化调度。

沙坡头人工固沙植被土壤水分空间异质性

利用传统统计学和地统计学相结合的方法对沙坡头人工固沙植被区0～200cm之间的各层土壤水分的空间变异性进行研究．结果表明，1）土壤水分相对变异较大的层是在160～180cm层和180～200cm层，变异系数分别为0．72和0．73．表层0～5cm层的相对变异也较大，变异系数为0．66．2）半方差函数分析结果表明，各层土壤水分均具有明显的空间变异性，各层土壤水分自相关部分的空间异质性占总空间异质性的程度很高，所占比例在87．7％～99．9％范围内．各层土壤水分的有效变程大小有较大差异，最小值出现在60～80cm层（7．04m），最大值出现在20～40cm层（19．71m），土壤水分有效变程从表层到深层没有明显的变化规律；3）土壤水分插值图反映出0～140cm之间相邻各层土壤水分变化较大，140～200cm各层土壤水分变化较小；4）土壤水分在0°、45°、90°、135°四个方向的半方差函数基本上是一条直线，表明在这四个方向上半方差和距离的相关性较低，土壤水分变化是独立、随机的，是同质性的．

戈壁风沙流结构特性及其意义

通过砾质戈壁风沙流野外实测数据的分析以及风洞模拟实验研究发现:戈壁风沙流结构具有与沙漠风沙流完全不同的风沙流特征,戈壁风沙地表的粗糙度随风速的增大而增加,其表面风沙流输沙量高度分布表现出独特的"象鼻"效应,在一定高度处呈现最大值,并随风速的增加而增高。该"象鼻"效应导致戈壁风沙流结构特征值λ远大于1,不论风速多大,风沙流都处于未饱和状态的非堆积搬运状态。这种特殊性质比较清楚地解释了敦煌莫高窟千年来不被沙山埋没的谜底。并且在风沙防治工程实践中,采用砾石压沙措施,构造类似与砾质戈壁的下垫面,人工促使风沙流结构呈现"象鼻"形状,可使防沙工程达到理想的输导作用。

塔里木盆地沙尘天气的季节变化及成因分析

选取了塔里木盆地周边16个站点,详细分析了沙尘天气的季节变化特征。结果表明:各站点沙尘天气频率虽均以春季最高,但其他3个季节沙尘日数的分布可以分为3种类型:第一种以秋季最高,夏季次之,冬季最低,如喀什和库车地区;第二种以夏季最高,冬季次之,秋季最低,如若羌地区;第三种以夏季最高,秋季次之,冬季最低,这一种类型是塔里木盆地沙尘天气季节分布的主要特征。沙尘天气的季节变化主要受风速和沙源季节变化的影响。当沙尘来源相似时,风速是控制沙尘释放强度的主要因素。

人工采砂对东江干流局部河段河床冲淤的影响研究

基于水动力学方法、泥沙输移原理,建立了一维河流河床冲淤数学模型,并应用于东江干流岭下站～博罗站河段河床冲淤变化分析和预测研究。根据1972-1999年历史地形、水文、采砂资料进行河床冲淤变化分析,在1972-1999年期间,河床整体呈下切状态,人工采砂对河床冲淤变化有重大影响。在此基础上预测未来10年-20年河床冲淤变化状况,如果不考虑人工采砂影响,河床整体以淤积为主,下游河床淤积更明显,如果考虑人工采砂影响,河床则整体呈下切状态。这一研究结果表明:人工采砂直接影响研究河段河床冲淤变化形态,对河道通航和引水工程等都有很大的影响。同时,该研究结果也可为建立合理的采砂制度和建设有效的工程措施提供依据。