Evidence of sedimentation inequality along riparian areas colonised by Impatiens glandulifera (Himalayan balsam)

Soil loss from riparian areas supporting the annual invasive weed, Impatiens glandulifera (Himalayan balsam), was measured and compared with equivalent values recorded at nearby, topographically similar areas supporting perennial vegetation over a cumulative seven-year period, along sections of two separate river systems; one in Switzerland, and one in the UK. Soil loss from colonised locations was significantly greater than from reference locations in four of the seven measurement periods. Despite contrasting results, standard deviations, based on soil losses and gains, were predominantly higher for colonised areas at both rivers over most monitoring periods. These findings indicated that areas colonised by Himalayan balsam experience higher sediment flux in comparison with areas free of invasion. Here, we test those original interpretations by reinterrogating the datasets using a more robust analysis of inequality. Nine datasets were tested, five of which (i.e. 56%) showed that sediment flux was significantly greater at Himalayan balsam-invaded areas than at reference areas. Three datasets showed no difference in sediment flux between invaded and reference areas (33%), and one (11%) showed higher sediment flux at reference areas. Most results uphold our original interpretations and support our hypothesis that hydrochory probably dictates where colonisation initially occurs, by depositing Himalayan balsam seeds in slack or depressional areas along river margins. Once Himalayan balsam becomes established and sufficient perennial vegetation is displaced, seasonal die-off and depleted vegetation cover may increase the risk that some areas will experience significantly higher sediment flux.     

工程机械新型传动系统的特性分析

介绍了静液压传动这一新型动力传动系统的特点.通过详细分析该系统液压元件类型的选择、排量与传动变速比关系及该类系统特性参数之间的关系,得出了在实际使用中,为了保证工程机械在大功率工况下,不降低经常工况的效率,提高传动变速比与其它传动形式的匹配方案.通过对匹配方案的分析为工程车辆的开发设计提供理论基础和方法.     

桥头跳车原因与防治措施

本文从路在沉降、施工方法和结构体系上对桥头跳车病害进行原因分析,提出减少病害防治措施。     

Economic Benefit Analysis of Sedimentation Reduction by Forests in Miyun Watershed, Beijing

Soil erosion causes the loss of the fertilized surface soil. The eroded soil can be transported into rivers, lakes and reservoirs. The sedimentation raises the riverbed. It also reduces the flood discharge ability of rivers and the storage ability of reservoirs(Sun Lida, et al, 1995; Yu Zhimin, et al, 1999). Various researches proved that forests could reduce soil erosion. Forests in the watershed can decrease the sedimentation of the reservoir (Guo Zhongwei, et al, 1998; Qing Yongsheng, 2…     

二次调节静液储能拖拉机传动系统

二次调节静液储能拖拉机传动系统是由柴油机，液压蓄能器，液压泵/马达（二次元件），差动变速器和驱动轴等组成，该系统充分利用了液压蓄能功率密度大，二次元件具有较高的控制质量，可实现四象限工作等特点；实现了柴油机和拖拉机行驶载荷的分离，工作过程中当外负载扭矩发生变化时，将引起二次元件的转速变化，从而引起二次元件排量的变化，通过调节液压马达的变量机构使其与工作负载所需转速相适应。     

The Warrumbungle Post‐Fire Recovery Project—raising the profile of soils

The impacts of a wildfire and subsequent rainfall event in 2013 in the Warrumbungle National Park in New South Wales, Australia were examined in a project designed to provide information on post‐fire recovery expectations and options to land managers. A coherent suite of sub‐projects was implemented, including soil mapping, and studies on soil organic carbon (SOC) and nitrogen (N), erosion rates, groundcover recovery and stream responses. It was found that the loss of SOC and N increased with fire severity, with the greatest losses from severely burnt sandstone ridges. Approximately 2.4 million t of SOC and ~74,000 t of N were lost from soil to a depth of 10 cm across the 56,290 ha affected. Soil loss from slopes during the subsequent rainfall event was modelled up to 25 t ha^?1, compared to a long‐term mean annual soil loss of 1.06 t ha^?1 year^?1. Groundcover averages generally increased after the fire until spring 2015, by which time rates of soil loss returned to near pre‐fire levels. Streams were filled with sand to bank full levels after the fire and rainfall. Rainfall events in 2015–2016 shifted creek systems into a major erosive phase, with incision through the post‐fire sandy bedload deposits, an erosive phase likely related to loss of topsoils over much of the catchment. The effectiveness of the research was secured by a close engagement with park managers in issue identification and a communications programme. Management outcomes flowing from the research included installation of erosion control works, redesign of access and monitoring of key mass movement hazard areas.     

Historical changes in bivalve growth rates indicate ecological consequences of human occupation in estuaries

1. Only 800 years ago, New Zealand became the last major land mass to be settled by humans, leading to environmental degradation and precipitating a decline in indigenous fauna. Such ecological downgrading can alter ecosystem processes and drive down the capacity for remnant ecosystems to withstand the anthropogenic pressures of today.
2. In New Zealand, these impacts are chronicled in a concise and remarkably complete archaeological record and are distinguishable from natural changes due to changing climate.
3. Estuaries are subject to strong environmental gradients that drive productivity and contain critical habitats for key life‐history phases for marine and terrestrial species. Linking land to sea, they host abundant, accessible human resources and are sensitive to anthropogenic environmental modification.
4. Austrovenus stutchburyi is a common filter feeding bivalve in New Zealand estuaries. An important food source for Māori, their shells are abundant in middens. Growth rates of A. stutchburyi are affected by multiple environmental factors, including temperature, salinity, nutrients, and sediment, and are recorded through time as easily measurable annual shell bands. Measuring spatial and temporal variation in growth rate of A. stutchburyi can be used to identify the timing of changes in estuarine conditions.
5. Growth bands were measured in archaeological and modern (AD 1300–present) A. stutchburyi shells from six sites around New Zealand with varying occupational histories. There were no increases in growth rate, and rates declined measurably over time at three sites (up to a 50% reduction in growth per year). This decline was greater at estuaries that had experienced greater catchment modification, indicating that sediment loading due to land clearance was a likely driver of this change.
6. New Zealand's coastline and marine resources are often perceived as wild and pristine. We propose that fundamental changes have occurred in the functioning of coastal marine ecosystems, which constrain its future.

     

Limnology of Macrobrachium amazonicum grow‐out ponds subject to high inflow of nutrient‐rich water and different stocking and harvest management

We evaluated the water characteristics and particle sedimentation in Macrobrachium amazonicum (Heller 1862) grow‐out ponds supplied with a high inflow of nutrient‐rich water. Prawns were subject to different stocking and harvesting strategies: upper‐graded juveniles, lower‐graded juveniles, non‐graded juveniles+selective harvesting and traditional farming (non‐grading juveniles and total harvest only). Dissolved oxygen, afternoon N‐ammonia and N‐nitrate and soluble orthophosphate were lower in the ponds in comparison with inflow water through the rearing cycle. Ponds stocked with the upper population fraction of graded prawns showed higher turbidity, total suspended solids and total Kjeldahl nitrogen than the remaining treatments. An increase in the chemical oxygen demand:biochemical oxygen demand ratio from inlet (4.9) to pond (7.1–8.0) waters indicated a non‐readily biodegradable fraction enhancement in ponds. The sedimentation mean rate ranged from 0.08 to 0.16 mm day^?1 and sediment contained >80% of organic matter. The major factors affecting pond ecosystem dynamic were the organic load (due to primary production and feed addition) and bioturbation caused by stocking larger animals. Data suggest that M. amazonicum grow‐out in ponds subjected to a high inflow of nutrient‐rich water produce changes in the water properties, huge accumulation of organic sediment at the pond bottom and non‐readily biodegradable material in the water column. However, the water quality remains suitable for aquaculture purposes. Therefore, nutrient‐rich waters, when available, may represent a source of unpaid nutrients, which may be incorporated into economically valued biomass if managed properly.     

黄河沙坡头连续弯道环流运动与冲淤特性实测数据分析

利用声学多普勒流速剖面仪、回声测深仪等测量仪器,对黄河沙坡头段连续弯道中10个典型断面的流速、水深、河床高程等进行了实测.通过分析各断面流速等值线、平面流场和近几年河床高程的变化情况.结果表明,弯道断面流场的主流分布与河床底部泥沙冲淤分布基本相一致,满足弯道水流的一般规律:凹岸冲刷,凸岸淤积.     

智能化超高压食品灭菌设备

设计了一套智能化超高压食品加工设备,分析并确定了水介质增压器、单向阀、卸压阀、容器密封和温控系统的结构和相关参数.试验表明,整机结构合理、操作方便、性能稳定、安全可靠.利用该设备在600 MPa处理鲜榨桃汁5 min,产品符合商业无菌要求.