On the issue of limiting nutrient and predictions of cyanobacteria in aquatic systems

This study aims at bridging the gap between freshwater and marine eutrophication studies by presenting (1) a cross-system analysis of the relationship between chlorophyll and the total nitrogen (TN) to total phosphorus (TP) ratio (2) a general model to predict concentrations of cyanobacteria from data on TP, the TN/TP ratio, salinity and temperature, and (3) a general trophic level classification for aquatic systems based on chlorophyll classes (for oligo-, meso-, eu- and hypertrophic systems). The data compiled in this study concerns more than 500 lakes and coastal areas covering a very wide domain in terms of nutrient concentrations and salinity. There was no simple relationship between the TN/TP ratio and empirical chlorophyll concentrations or concentrations of cyanobacteria. Variations in TP rather than TN generally seem to be more important to predict variations among systems in chlorophyll-a and cyanobacteria. Different "bioavailable" forms of the nutrients (DIN, DIP, phosphate, nitrate, etc.) have been shown to have very high coefficients of variation (CV), which means that many samples are needed to obtain reliable empirical data which are necessary in models aiming for high predictive power and practical usefulness.     

A novel sediment gas sampler and a subsurface gas collector used for measurement of the ebullition of methane and carbon dioxide from a eutrophied lake

A novel sediment bubble gas sampler and a subsurface bubble gas collector were designed to measure the ebullition of gases from profundal sediments of aquatic ecosystems. The sediment gas sampler was constructed to collect bubble gas samples directly from the uppermost sediment layers for gas composition analysis. The floating subsurface gas collector, designed to trap the bubbles released naturally from sediments, permitted the measurement of both the volume and the composition of the bubble gas. Due to its low cost, light weight and rapid sampling capability, the gas collector is ideal for studies requiring many replicate collectors. These devices were used for measurement of the ebullition of methane (CH4) and carbon dioxide (CO2) during an open water period from hypereutrophic Lake Postilampi, situated within the midboreal zone in Finland. The bubble gas obtained from the sediment with the sediment gas sampler had higher concentrations of CH4 and CO2 than the bubbles trapped in the gas collectors. This indicated that the bubble gas composition changed, either naturally during the migration of the bubbles from the sediment through the water column to the gas collectors, and/or during their storage in the collectors prior to sampling. The mean CH4 ebullition from Lake Postilampi was estimated to be in the range from 36 to 46 mg m(-2 d(-1), based on the bubble gas CH4 concentrations measured from the gas collectors and sediment, respectively. The bubbles contained only 0.02-0.57% of CO2 and thus, the ebullition had no significance in the release of CO2 from the lake.     

浅谈高层建筑外部的尺度设计

从城市环境、建筑及其构成要素等方面进行了分析,将高层建筑的外部尺度进行了分层,通过参考人的尺度与视觉感,对高层建筑外部尺度设计原则加以阐述,以期创造优美的高层建筑外部造型。     

ZnO-Al_2O_3-B_2O_3-SiO_2系微晶玻璃与可伐合金的润湿性能

研制了一种新型的与可伐熔封的ZnO-Al_2O_3-B_2O_3-SiO_2系微晶玻璃,研究了不同工艺条件下微晶玻璃与可伐合金间的润湿角大小,结果表明,熔封气氛和熔封温度对润湿性能影响很大,熔封时间影响最小.采用最佳的工艺条件,其润湿性能与现有的其它玻璃润湿性能相似.同时发现玻璃与可伐合金间的润湿角保持在10°～30°之间能得到质量良好的熔封产品.在基本不改变传统工艺制度的条件下,可完成锌铝硼硅系微晶玻璃与可伐合金的熔封,即利用排蜡过程同时完成微晶玻璃的形核,熔封后在稍低温度保温或减慢冷却速度可以完成微晶玻璃的结晶过程.锌铝硼硅系微晶玻璃与预氧化可伐合金的封接依靠玻璃中的SiO_2与FeO或Fe_3O4发生界面反应形成牢固的结合.     

Cold Spray Deposition of Freestanding Inconel Samples and Comparative Analysis with Selective Laser Melting

Cold spray offers the possibility of obtaining almost zero-porosity buildups with no theoretical limit to the thickness. Moreover, cold spray can eliminate particle melting, evaporation, crystallization, grain growth, unwanted oxidation, undesirable phases and thermally induced tensile residual stresses. Such characteristics can boost its potential to be used as an additive manufacturing technique. Indeed, deposition via cold spray is recently finding its path toward fabrication of freeform components since it can address the common challenges of powder-bed additive manufacturing techniques including major size constraints, deposition rate limitations and high process temperature. Herein, we prepared nickel-based superalloy Inconel 718 samples with cold spray technique and compared them with similar samples fabricated by selective laser melting method. The samples fabricated using both methods were characterized in terms of mechanical strength, microstructural and porosity characteristics, Vickers microhardness and residual stresses distribution. Different heat treatment cycles were applied to the cold-sprayed samples in order to enhance their mechanical characteristics. The obtained data confirm that cold spray technique can be used as a complementary additive manufacturing method for fabrication of high-quality freestanding components where higher deposition rate, larger final size and lower fabrication temperatures are desired.     

梯度纤维多孔材料的吸声特性及结构优化

利用金属纤维为原料,制成内部具有梯度孔结构的金属纤维多孔吸声材料。梯度孔结构可分为孔隙度梯度和丝径梯度,分别研究了这2种梯度结构的吸声特性。结果表明,厚度在6~30 mm范围内时,孔隙度梯度结构按照孔隙度从大到小的顺序排列有利于提高全频的吸声性能;厚度为3 mm时,孔隙度梯度结构的排列顺序对吸声性能的影响规律恰好相反;丝径梯度结构的吸声特点是当厚度为3 mm时,细丝径纤维多孔材料在前,全频吸声性能较好;当厚度≥15mm时,粗丝径纤维多孔材料在前,全频吸声性能好;厚度在3~15 mm之间,2种排列方式的丝径梯度结构的吸声-频率曲线存在一个交点,随着厚度的增加,该交点逐渐向低频方向移动。     

碳纤维增强酚醛树脂/石墨复合材料双极板的性能

研究了碳纤维表面处理方法及其含量对碳纤维增强酚醛树脂／石墨复合材料导电性能与力学性能的影响。结果表明：空气氧化处理碳纤维表面形成微孔和刻蚀沟槽,容易形成应力集中,复合材料的强度不高;空气加液相氧化处理填充了碳纤维表面的微裂纹,对复合材料有一定的补强作用;液相氧化处理有利于提高碳纤维表面活性以及碳纤维的均匀分散性,使材料表现出较好的力学性能与导电性能;随碳纤维含量增多,材料电导率变小,材料强度开始增大,达到最大值后材料强度下降。对碳纤维进行液相氧化处理,碳纤维含量在3％～4％时复合材料的力学性能与导电性能最好。     

Design update,thermal and fluid dynamic analyses of the EU-HCPB TBM in vertical arrangement

In the frame of the activities of the EU Breeder Blanket Programme and of the Test Blanket Working Group of ITER, the Helium Cooled Pebble Bed Test Blanket Module (HCPB TBM) is developed in Forschungszentrum Karlsruhe (FZK) to investigate DEMO relevant concepts for blanket modules.The three main functions of a blanket module (removing heat, breeding tritium and shielding sensitive components from radiation) will be tested in ITER using a series of four TBMs, which are irradiated successively during different test campaigns. Each HCPB TBM will be installed, with a vertical orientation, into the vacuum vessel connected to one equatorial port. As the studies performed up to 2006 in FZK concerned a horizontal orientation of the HCPB TBM, a global review of the design is necessary to match with the new ITER specifications.A preliminary version of the new vertical design is proposed extrapolating the neutronic analysis performed for the horizontal HCPB TBM. An overview of the new HCPB TBM vertical designs, as well as the preliminary thermal and fluid dynamic analyses performed for the validation of the design, are presented in this paper. A critical review of the results obtained allows us, in the conclusion, to prepare a plan for the future detailed analyses of the vertical HCPB TBM.     

500 kV线路黄河大跨越桩基自平衡检测试验

开封变一新乡东 500kV线路黄河大跨越工程桩基 ,采用自平衡检测试验方法。该方法是一种新颖的、有效的桩基承载力检测方法 ,具有加载灵活、不受场地限制、加荷量大、周期短、经济性好等特点 ,根据试验结果确定桩基极限承载力。但该检测方法试验效果受自平衡点位置选择影响较大 ,在具体检测试验中应引起足够重视。