不同组合间距的尼龙阻沙网积沙形态特征对比

在塔克拉玛干沙漠腹地垄间平沙地,布设了两条尼龙阻沙网水平组合防沙实验,组合间距分别为2H、5H、10H、15H(H为阻沙网高度),一个风季中对实验设置的地形及纵断面蚀积量进行了动态观测。结果表明:(1)各尼龙阻沙网组合形成有规律的地表蚀积空间分布格局:形成以阻沙网为核心的积沙区,其上下风侧分布有较稳定的风蚀区,两条阻沙网之间存在临时的风蚀区。(2)在阻沙网前后形成与阻沙网高度相近的积沙体,在第一条阻沙网上风侧区域,积沙厚度与水平距离呈指数函数关系,在阻沙网背风侧,积沙厚度与水平距离呈二次函数关系。(3)2H和5H积沙体纵断面呈单峰状,风季中后期形似"几"字形,而10H和15H呈双峰状,风季中后期形似"M"字形。(4)阻沙网组合间距越小,积沙分布就越集中,形体越高大,反之则越分散,风季末阻沙网积沙体地形起伏度、平均坡降、积沙体积比、积沙断面面积轮廓比大小排序均为2H>5H>10H>15H。(5)阻沙网积沙体积具有随阻沙网间距增大而降低的趋势,观测断面最大积沙体积5HH>2H>15H>10H,5H、2H、15H分别较10H大13.20%、12.34%、3.78%,可见,5H防沙效果最优。

广州市南沙区万顷沙网河区排涝调蓄演算研究

快速城市化进程改变了城市地区原有下垫面,不透水层面积增加,暴雨期间汇流时间缩短,洪峰流量加大,进而导致城市内涝加剧,严重影响城市的防洪安全。本研究以广州市南沙区万顷沙网河区为研究对象,基于水量平衡的调蓄演算方法,对研究区域蓄排设施的规模进行分析;构建MIKE11一维网河模型,对涝区水情进行模拟,校核排涝工程规模,并对工程布局与规模进行了优化。结果表明:(1)万顷沙网河区在典型水文组合情况下,内河涌最高水位6.15 m,泵站抽排历时约11 h,抽排流量65 m3·s-1,满足排涝需求;(2)结合片区泵站排水能力,可使片区达到20年一遇24 h暴雨不成灾的规划防洪标准,片区水闸和泵站参数选取合适;(3)在50年一遇超标准情况下,万十涌水位最高约6.33 m,超过片区管控水位,表明当防洪标准提升,片区需合理增设排涝泵站规模,以满足管控水位要求。研究成果可为沿海城市的排涝减灾和实现水系综合整治提供科学依据。

巧用塑料除沙网扩座

小蚕期用塑料除沙网扩座较用其他方法,不仅简单、省时、省工,而且可减少蚕体受伤,保证蚕儿健康。具体操作方法如下。收蚁的当天上午,整理蚕座张种蚁蚕面积达蚕匾的一半,即0.4m^2。把抬出的蚁蚕靠蚕匾的一边放。

双排尼龙阻沙网-草方格联合沙障防风效应的风洞实验

为了解双排尼龙阻沙网-草方格联合沙障的防风效应,进行孔隙度为40%、45%、55%的双排尼龙阻沙网-草方格联合沙障风洞实验,研究在6、10、14 m·s^(-1)等3种风速下的风速加速率等值线、防风效能和风速廓线指标。结果表明:(1)在不同风速条件下,双排尼龙阻沙网-草方格联合沙障防风效应随着来流风速增大而明显降低;(2)40%孔隙度双排尼龙阻沙网-草方格联合沙障防风效应较好,而45%孔隙度时防风效应较差,55%孔隙度防风效应最差;(3)双排尼龙阻沙网-草方格联合沙障在防风效应方面存在累加。因此,建议在实际应用中采用40%孔隙度双排尼龙阻沙网-草方格联合沙障,以获得最佳防风效应。

塔克拉玛干沙漠4种结构尼龙阻沙网的防风阻沙效益对比

常用尼龙阻沙网的孔隙度为均匀分布,而风沙流结构在垂直方向上是非均匀分布的。通过设计4种孔隙度非均匀分布的尼龙阻沙网:大条带上疏下密式(A)、大条带上密下疏式(B)、小条带疏密相间式(C),将其布设在塔克拉玛干沙漠腹地的垄间平地,以均匀结构阻沙网为对照(CK)。对4种阻沙网前后的风速变化、防风效能、积沙形态、积沙量进行对比。结果表明:①B阻沙网有效防护距离最短,仅为6H(H为阻沙网的高度),其余3种结构有效防护距离差别不大,均为15H;在网后10H处0.15 m、0.3 m和0.5 m 3个观测高度,风速削弱程度的平均值存在明显差异,呈C>A>B>CK。②在风季后期,4种结构阻沙网前后积沙量B最小,其余3种类型差别不大。③综合考虑防风和阻沙效益,C阻沙网提供了一个较好的结构模式,防护效益最好,B阻沙网最差,A和CK阻沙网效益相差不大。研究结果为高立式沙障结构优化设计提供了参考依据。

两条尼龙阻沙网不同组合间距的积沙量对比分析

在塔克拉玛干沙漠腹地垄间平沙地布设了两条尼龙阻沙网4种水平组合间距(2H、5H、10H、15H,H为阻沙网间距)的防沙实验,分析两条尼龙阻沙网的积沙量大小和空间分布,及其与阻沙网组合间距的关系。实验结果表明:1阻沙网积沙量与组合间距呈弱线性负相关,其中2H和5H积沙量最大,但两者差异不大,10H最小,15H居中,与常规认识不同。2不同组合模式的积沙量空间分配格局也明显不同,2H主要堆积在下风侧,而5H、10H、15H则均位于网间和下风侧,上风侧和下风侧积沙量与组合间距呈线性负相关,而网间积沙量与组合间距呈线性正相关。3两条尼龙阻沙网积沙量及其空间分布差异主要与特殊的近地表流场结构有关,但其分异机制还需要深入研究。

不同间距双排尼龙阻沙网防风效应的风洞模拟

为揭示风速和间距对双排尼龙阻沙网防风效应的影响,开展对2H、5H、10H、15H(H为尼龙网高度)间距尼龙阻沙网在6、9、12m·s-1风速下的风洞模拟试验,对不同风速、间距下加速率等值线、变化趋势和防风效能进行对比分析。结果表明:1风速和间距对双排尼龙阻沙网加速率极小值出现的相对位置基本无影响,但后排网后极小值小于前排网后,两排尼龙网对风场的影响存在累加效应。2双排尼龙阻沙网防风效应随来流风速增大而明显降低。32H、5H间距双排尼龙阻沙网防风效应相对较好,5H最优,10H最差。该结果与相同间距设置的野外实验相一致。实际应用中尼龙阻沙网的布设应综合考虑风况、布设间距等因素,笔者建议双排尼龙阻沙网布设间距采用5H。

高立式阻沙网的阻沙效果对比

设计了高120cm的4种结构HDPE阻沙网:均匀结构阻沙网(a)、大条带上疏下密式阻沙网(b,60cm宽条带)、小条带疏密相间式阻沙网(c,20或10cm宽条带)和中条带上密下疏式阻沙网(d,40cm宽条带),布设在塔克拉玛干沙漠腹地的垄间平地。阻沙试验结果表明:(1)4种结构阻沙网积沙纵断面的蚀积形态均呈单峰,但积沙宽度和高度不同,3种非均匀结构的阻沙网积沙高度均高于均匀结构阻沙网,积沙高度c>b>d>a。(2)4种结构阻沙网积沙量c>a>b>d,积沙量均集中在下风侧分布,但b和c阻沙网积沙在上风侧的积沙量高于a和d阻沙网。(3)不同结构阻沙网积沙量及其空间分布差异主要与阻沙网结构的特殊风场结构有关。

不同高度双行尼龙阻沙网的合理间距研究

双排、多排高立式沙障其高效的防风阻沙作用在线路工程风沙防治中被广泛关注,阻沙网布设间距是沙障布设中首要解决的问题。基于阻沙网风速流场和输沙量测定结果,对乌兰布和沙漠穿沙公路间距12m高度为60cm、80cm、100cm和120cm阻沙网布设的合理性进行了研究。结果表明:(1)从风速流场分析,双排流场形式主要以"双峰型"为主,第二排阻沙网后的风速加速率极小值均小于第一排阻沙网后的风速加速率,即双排之间存在叠加效应。(2)从集沙仪0~50cm的输沙量分析,近地表风速与输沙量之间符合幂函数关系为Q=0.00004V5.9337,且4种高度的中间过渡区集沙仪输沙量均在4~8m范围内出现先下降后上升的趋势。(3)在低风速(<12m·s-1)平坦的流沙环境下,双排阻沙网的合理布设间距分别为4m、5.5m、6.5m和8m。建议铺设带数可依据实际风况与线性沙害程度调整为:60cm及以下3~4带,80-100cm高2~3带,120cm高1~2带。

直压立式纱网沙障不同取样季节输沙量变化特征

[目的]对不同规格纱网沙障春季、夏秋季的输沙量变化特征进行定位连续测定,为进一步评价纱网沙障的固沙效果提供科学依据。[方法]采用野外定位、定期观测方法,研究不同季节纱网沙障的输沙量变化特征。[结果]无论是春季,还是夏秋季,设置2 m×2 m,3 m×3 m,3 m×4 m和4 m×4 m的纱网沙障对风沙流的拦截效果随着网格变小而增加,且输沙量随高度变化趋势线均呈现指数关系。来自西北风方向的输沙量大于东南风方向的输沙量,且春季输沙量大于夏秋季输沙量。和对照相比,春季3 m×4 m纱网沙障0—60 cm高度拦截的净输沙量降低了85.98%,而夏秋季降低了79.56%。[结论]纱网沙障输沙量主要集中在地表20 cm及以下高度范围,并随着纱网沙障规格增加其降低输沙量能力减少。设置纱网沙障能有效减少风沙流危害。

纱网黄瓜制种的栽培管理要点

纱网黄瓜制种是一种科技含量高、繁种程序多、技术复杂的瓜菜制种方法,它需要纱网扣棚隔离、父母本栽培、人工对花授粉等十几项技术。宁阳县白马镇自1986年从天津农科院黄瓜研究所引进这一繁种技术后,

A FVCOM-Based Unstructured Grid Wave, Current,Sediment Transport Model,I.Model Description and Validation

An effort was made to couple FVCOM (a three-dimensional (3D),unstructured grid,Finite Volume Coastal Ocean Model) and FVCOM-SWAVE (an unstructured grid,finite-volume surface wave model) for the study of nearshore ocean processes such as tides,circulation,storm surge,waves,sediment transport,and morphological evolution.The coupling between FVCOM and FVCOM-SWAVE was achieved through incorporating 3D radiation stress,wave-current-sediment-related bottom boundary layer,sea surface stress parameterizations,and morphology process.FVCOM also includes a 3D sediment transport module.With accurate fitting of irregular coastlines,the model provides a unique tool to study sediment dynamics in coastal ocean,estuaries,and wetlands where local geometries are characterized by inlets,islands,and intertidal marsh zones.The model was validated by two standard benchmark tests: 1) spectral waves approaching a mild sloping beach and 2) morphological changes of seabed in an idealized tidal inlet.In Test 1,model results were compared with both analytical solutions and laboratory experiments.A further comparison was also made with the structured grid Regional Ocean Model System (ROMS),which provides an insight into the performance of the two models with the same open boundary forcing.

Analysis of the Estonian Forest Conservation Area Network

Estonian Forestry Development Programme set in 2003 ambitious goal that area of strictly protected forests should increase at least to 10% from total forest area in Estonia before 2010 by expanding the area of old-growth under protection, improving the representativeness of conservation areas and establishment of large conservation sites. Inventory of forests was carried out on existing and possible new conservation areas within the Estonian Forest Conservation Area Network project （EFCAN） in 1999-2001. EFCAN project had remarkable results. The share of strictly protected forests has increased to 7.8% of total forest area by 2009 and the network of conservation areas is quite well covering all forest ecosystems in Estonia. Several selected areas are still not protected for different reasons. These areas should still be considered for protection as the areas may lose their conservation value. Several forest types （meso-eutrophic, eutrophic boreo-nemoral and eutrophic paludifying forests） should have larger area for conservation and large disturbance areas （wind damage, forest fire） should be also included into the network.

Social Networks Among Migrants in Saudi Arabia （SA）： Opportunities and Implications

This paper presents results of a pilot research conducted among social networks of both Sudanese and Egyptians in Jeddah city, Saudi Arabia （SA）. The main objectives of the research are focused into four interrelated issues： （1） to analyse the structural-function of the social networks of Sudanese and Egyptian migrants; （2） to explain the opportunities and challenges confronting the social networks; （3） to examine the elements of implications on SA society as perceived by the networks; and （4） to identify perceived future visions of the social network members in the context of their social and economic remittances in both countries. The research has applied a qualitative method and a structured interview sheet was used for data collection. The Sudanese sample focused on members from a Nubian social network in ]eddah who resemble skilled, semi-skilled, and unskilled labours, while the Egyptian sample selected randomly from semi-skilled youth labours and unskilled labours as informal groups. The research has found some differences in the structural functions of both groups. There are many similarities shared between the two groups in relation to conserving social ties, support and cooperation as one homogeneous socio-ethnic groups in the hosting country. Also, the results show that both groups follow similar strategies of social and economic remittances to home land. Moreover, both groups are suffering and facing many shared challenges regarding economic security and sustainability in the hosting country. While, the Sudanese group has clear vision in respect of the betterment of the migrants in SA, the Egyptian group perceives the future as gloomy and uncertain.

Research and Practice on the Crustal Deformation Mobile Monitoring Network Layout in the Hydropower Station Reservoir Area

According to the construction project of the crustal deformation mobile monitoring network in the cascade hydropower stations built in the lower reaches of Jinsha River,this paper analyzes the design ideas and layout principles of crustal deformation mobile monitoring used in the monitoring of reservoir induced earthquakes. This paper introduces three types of monitoring networks used in the Xiluodu reservoir and Xiangjiaba reservoir, as well as the work already undertaken,in order to provide a kind of reference for the related engineering construction and comprehensive monitoring of reservoir induced earthquakes.

The Jinsha River Groundwater Observation Network and Discussion about Its Earthquake Precursor Monitoring Capability

A groundwater observational network for monitoring seismic precursors has been established at the reservoirs on the lower reaches of the Jinsha River in southwestern China, where a series of hydropower stations are under construction. It is the second network in China that is operated by enterprises with the purpose to observe and study earthquake precursors in reservoir areas. This paper presents the layout and technical constitution of the network, features of its observational wells and aquifers and the preliminary result of its experimental operation. Its capability to monitor seismic precursor is evaluated based on an analysis of the well-aquifer system as well as the multiple-monthly, monthly, daily and hourly variations of water levels and water temperatures observed by this network.

Fine Measurements and Analysis of Temperature Gradients in the Wells of the Jinsha River Groundwater Observational Network

Fine measurements have been conducted to temperatures and their gradients of six wells of the Jinsha River Groundwater Observational Network.The results show that the influence depths of sun radiation heat are 50m to 125m,average temperature gradients in the wells range from 0.11 to 2.81℃/hm and most are 1～2℃/hm,and the temperature gradients on varied depth sections of one well are highly changeable.Lithology of strata and their integrity,particularly high-angle crashed fault zones,have imposed major effects on the influence depths of sun radiation heat and temperature gradients of the wells.The micro dynamic characteristics of water temperature,such as coseismic effects,tidal effects and anomalies of the wells prior to earthquakes,probably depend,to a large degree,on the temperature gradients of the depths at which the water temperature sensors are settled.

Use of Renewable Energy Sources in Saudi Arabia through Smart Grid

Even though Saudi Arabia is the world＇s largest producer and exporter of petroleum and petroleum based products, it is also blessed with high potential of renewable energy sources like solar and wind. Untapped wind and solar energy sources, which are abundant throughout the kingdom, can be connected and optimally integrated into the grid through the use of smart grid technologies and the expansion of transmission facilities. Smart grid is an auto-balancing, self-monitoring power grid that accepts power from any source of fuel like oil, sun or wind and delivers electricity from suppliers to consumers. It helps to control the use of appliances in order to save energy, reduces cost and increase reliability. This paper describes the attributes of a smart grid and how these act as driving force to modernize the electrical power grid. The necessity of conservation of oil in Saudi Arabia is argued. Moreover, the vast availability of renewable energy sources like solar and wind in Saudi Arabia and advantages in utilizing these sources through smart grid technologies are advocated in this paper.

高立式沙障不同叠加模式的阻沙量对比分析

为了解决尼龙阻沙网在沙埋情况下的防风阻沙,采用不同叠加模式的尼龙阻沙网进行防护。设置3种高立式沙障叠加模式方案,叠加位置分别位于迎风坡、阻沙网、背风坡,迎风坡与背风坡叠加的尼龙阻沙网与原有阻沙障距离和长度均相同,叠加的阻沙网高度为沙埋原有阻沙障的一半,且叠加的尼龙阻沙网需高出原有尼龙阻沙障。选择高1.2 m的沙埋阻沙障进行叠加,迎风与背风坡叠加的位置距原有阻沙障水平距离约45 cm。通过野外观测发现:①不同叠加模式的高立式沙障阻沙量不同,即阻沙网>迎风坡>背风坡;②3种不同叠加模式的积沙量都随着阻沙网的不断叠加而增加,且增加的阻沙量越来越大;③随着阻沙网的不断叠加,3种不同叠加模式的单位阻沙成本不断变化。迎风坡与阻沙网模式的单位阻沙成本不断降低,最后趋于平稳;背风坡模式有所不同,其单位阻沙成本先有所增加,然后再下降,最终趋于平稳。阻沙成本为:阻沙网<迎风坡<背风坡。