Field investigations of soil hydrological properties of fen soils in North‐East Germany

To investigate the changes of hydrological properties of peat soil in course of soil development, field measurements at 84 fen sites (Histosols) in 19 fen regions of North‐East Germany were carried out. Capillary water supply at all the stages of soil development was not limited up to 70 cm of ground water level. Worsening of plant water supply was the result of mud accumulation in the capillary fringe, ground water levels located deeper than 70 cm below soil surface, low hydraulic conductivity in the ground water zone, and hysteresis effects, affected by high dynamics of ground water level during the day.     

基于非线性预测的机床主轴温升特性快速辨识

提出了一种快速辨识数控机床主轴温升特性的方法,该方法通过基于支持向量机回归的非线性预测技术,利用短时间实际采集主轴的温升数据,预测长达数小时的主轴温升曲线,并辨识出主轴的稳态温度、热平衡时间等温升特性参数。该方法可大大缩短数控机床主轴热平衡试验的时间。试验研究表明基于支持向量机回归的非线性预测方法快速辨识的主轴温升特性与热平衡试验结果相吻合,验证了本文方法的有效性与可行性。     

中国梨（晚香和秋香）树上成熟特性的研究

研究了梨的成熟特性，代表品种是晚香梨和秋香梨．实验结果表明，两种梨果重随成熟进展一直在增加，晚香梨果重在８月份和９月份增重快，果实的横径生长一直稍大于纵径生长，果近似球形．秋香梨花树上成熟时即通过呼吸跃变期出现乙烯峰，晚香在９月中旬采收后贮藏到１１月１５日才出现与乙烯峰相平行的呼吸高峰．在成熟期间两种梨果实硬度不断降低，秋香梨下降最快，采后两周组织已分解软化；晚香梨硬度下降缓慢．果实硬度下降伴随有ＰＧ活性的上升．可溶性固形物，总糖在成熟期间不断增加，其中主要是果糖，葡萄糖次之，蔗糖含量很少．可滴定酸在成熟过程中不断下降。     

边缘城市如何融入都市圈——以安徽省铜陵市为例

随着中心城市经济辐射功能的完善,都市圈周边城市将获得良好的发展机遇。以铜陵市为例,研究都市圈周边城市如何融入都市圈实现自身经济发展。铜陵紧邻长三角,有着良好的工业基础,近年来经济发展迅速,已经进入国际公认的经济起飞阶段。面对长三角扩容的机遇,铜陵应该积极争取融入长三角,正确定位,努力成为“长三角经济后花园,”实现在中部率先崛起。     

柴油污染土壤中毛细水上升规律研究

通过室内土柱模拟试验,对柴油残留时土壤的毛细水上升规律进行了研究。结果表明,柴油污染砂土和壤粘土的毛细水上升速率随时间变化关系可用乘幂方程拟合。污染土壤毛细水上升高度和上升速率均随柴油质量分数的增加而减小,污染砂土的毛细水上升高度与含油率呈规律的负线性相关。疏水性石油污染物产生所谓“莲花效应”是土壤毛细水上升高度减小的...     

The 10 Australian ecosystems most vulnerable to tipping points

We identify the 10 major terrestrial and marine ecosystems in Australia most vulnerable to tipping points, in which modest environmental changes can cause disproportionately large changes in ecosystem properties. To accomplish this we independently surveyed the coauthors of this paper to produce a list of candidate ecosystems, and then refined this list during a 2-day workshop. The list includes (1) elevationally restricted mountain ecosystems, (2) tropical savannas, (3) coastal floodplains and wetlands, (4) coral reefs, (5) drier rainforests, (6) wetlands and floodplains in the Murray-Darling Basin, (7) the Mediterranean ecosystems of southwestern Australia, (8) offshore islands, (9) temperate eucalypt forests, and (10) salt marshes and mangroves. Some of these ecosystems are vulnerable to widespread phase-changes that could fundamentally alter ecosystem properties such as habitat structure, species composition, fire regimes, or carbon storage. Others appear susceptible to major changes across only part of their geographic range, whereas yet others are susceptible to a large-scale decline of key biotic components, such as small mammals or stream-dwelling amphibians. For each ecosystem we consider the intrinsic features and external drivers that render it susceptible to tipping points, and identify subtypes of the ecosystem that we deem to be especially vulnerable.     

气温对栉孔扇贝浮游幼虫浮游状态的影响

气温对栉孔扇贝浮游幼虫浮游状态的影响在于水、气温高于水温时，幼虫集群；气温低于水温２￣３℃时，幼虫不集群，但尚能上浮，气温比水温更低时，幼虫不上浮，这可能与幼虫的趋温性有关。与病态的浮游幼虫下沉相比，低气温造成的浮游幼虫下沉可逆性要大得多。只有提高气温才能解决。     

Communal pair spawning behaviour of vendace (Coregonus albula) in the dark

Mating in nature is rarely random, and most fish species have refined mating systems. The vendace (Coregonus albula) is a short‐lived, small‐sized, cold‐water‐adapted pelagic schooling species that is known to spawn in groups, but the actual mating system of this species, like many other group‐spawning fishes, has not been described in detail. Vendace typically spawn in the littoral or sublittoral zones of lakes in late autumn, and the hatching of larvae occurs close to icebreak in the following spring. In our large study lake, vendace larvae were caught in 93% of 1,149 random sampling locations lake‐wide. We examined the courtship and mating of vendace under experimental conditions by nonintrusive observation of the natural behaviour, to clarify whether spawning activity is associated with illumination and to assess the postspawning mortality of vendace. Here, we describe and document in detail for the first time the spawning behaviour of vendace: they spawn in the dark, and females release a small portion of their eggs (on average 1% of mean total individual fecundity) when the female and male, side by side, dart from near the bottom up towards the surface, that is perform a spawning rise. Males and females had several spawning rises (on average 1,200). Our results showed high postspawning mortality (56%). The spawning stress seems to be a potential component of mortality regulating the lifespan duration of vendace.     

高转速行星齿轮止推垫圈流体动压润滑特性

以直齿行星排的行星轮止推垫圈为对象,为了减小其与行星齿轮之间因轴向力而导致的磨损,通过对止推垫圈加工径向沟槽的方法,对其进行流体动压润滑设计,使止推垫圈与行星轮间有相对运动时产生流体动压承载力,从而使两者之间实现非接触而减小磨损.因结构的对称性,允许正反向旋转且加工容易而选择径向直线矩形槽.建立了定常雷诺方程的模型,应用有限体积法对其进行离散求解.分析了槽数、槽宽比、槽深和径向宽度等结构参数对垫圈流体动压力承载性能、润滑油流量和温升的影响规律.考虑到工程应用,着重对较少油槽数量（2～12）情况下的润滑特性进行了分析.结果表明：槽数约为20时,油膜具备最大的承载力;油槽数量介于10～60时具备较大的承载力;槽区角度与周期槽角度之比约为0.5时具有最佳承载力,径向宽度越大则承载力越大;槽数越多、槽深越大、径向宽度越大,流量越大,反之减小;槽宽比增大能使流量减小;降低润滑油温升的措施为增加垫圈槽数、增大径向宽度,使槽深处于10～40μm.     

Influence of Cement Fineness and Components on Temperature Rise of Concrete

Adiabatic temperature rise of mass concrete is effected by many factors. Among those factors, the analysis of cement fineness and components is lacking. Influences of cement fineness, alkali content, replacement of fly ash, and gypsum content on temperature rise of concrete were investigated. The test results show that, temperature rise and temperature rise rate are improved with the increment of specific surface area of cement. When alkali content is ranging from 0.4% to 1.2%, the maximum temperature is reduced with the increment of alkali content, and the temperature-time will be extended whether too high or too low alkali content in cement. The increment of replacement of fly ash and gypsum content is good for reducing temperature rise of concrete.