Moving beyond ‘more crop per drop’: insights from two decades of research on agricultural water productivity

ABSTRACT

Concern over increasing water scarcity has led to the introduction of the concept of agricultural water productivity and an emphasis on interventions to achieve ‘more crop per drop’. Yet, a strong debate continues on how the concept is to be defined and used. Drawing largely from the irrigation literature, the origins of the concept and its methodological developments are reviewed, and its use in applied work over two decades is discussed. Based on this analysis of conceptual and applied research, key insights into the concept’s contributions and limitations are presented, as well as opportunities for further refinements.     

南水北调中线水源区浮游植物群落结构 及其生物多样性

为探究南水北调中线水源区丹江口水库浮游植物群落结构变化及其生物多样性，于 2014—2015 年对丹江 口水库进行为期 1 年的调查和分析。发现浮游植物共 8 门 76 属 101 种，其中，绿藻门、蓝藻门及硅藻门占总种数 90.10%，绿藻门种类数最多（45 种），其次是蓝藻门（26 种）和硅藻门（20 种）。浮游植物群落结构随季节变化有所 不同：夏秋季节生物量明显高于冬春季节；优势种在冬季以颗粒直链藻、颗粒直链藻极狭变种、铜绿微囊藻和小 环藻为主，春季以球衣藻、薄甲藻属及小环藻为主，夏季以简单颤藻、单胞衣藻原变种和球衣藻为主，秋季以类颤 藻鱼腥藻、简单颤藻、球衣藻和小环藻为主。应用 Shannon-Wiener 多样性指数 H′、Pielou 均匀度指数 J′、Margalef 丰富度指数 Dm评价水质结果表明：丹江口水库夏秋季水体营养化程度更高。典型对应分析表明：水温、透明度、 总氮、总磷等是影响浮游植物群落结构的主要环境因子，夏秋季受温度影响蓝藻、绿藻数量逐渐增多，一定程度 上增加了受水区生态变化风险。本研究可为南水北调中线水源区丹江口水库生态环境变化及生物迁移风险提供 数据支持。     

掘进工作面瓦斯分级治理的技术研究

余吾煤业公司作为高瓦斯矿井,瓦斯吸附能力强,属低透气性难抽放煤层。矿井目前处于新旧采区重叠期、瓦斯含量双向变化重叠期,需要立足当前、分类施策,提升采掘效率。为进一步规范掘进工作面瓦斯治理,建立规范的瓦斯治理程序,介绍了掘进工作面瓦斯分级治理相关措施,确保掘进工作面安全生产有序进行。     

Waste sugar solution polymer-derived N-doped carbon spheres with an ultrahigh specific surface area for superior performance supercapacitors

Waste sugar solution (WSS), a waste by-product of manufacturing vitamin C, contains abundant waste acids and organics. In this work, a N/O-enriched copolymer was synthesized via a facile polymerization via the hydrogen bonding of O-containing functional groups and melamine and the crosslinking of aldehyde groups. Subsequently, N-doped carbon spheres were prepared by a typical carbonation/activation method. Remarkably, benefiting from an ultrahigh specific surface area (3612 m²/g) and rich heteroatom content (4.3% for N, 8.8% for O), the carbon spheres deliver a high specific capacitance of 387 F/g at 50 mA/g and 283 F/g at 5 A/g with 6 M KOH in two-electrode system. The assembled symmetric electric double-layer capacitor exhibits high energy density of 10.83 Wh/kg at 11.10 W/kg. This research provides a facile method for preparing N/O-doped carbon spheres by WSS, and confirms the excellent electrochemical performance of WSS-derived carbons in energy storage applications.     

Experimental and computational study on the separation performance of an electrostatic precipitator with curved transvers collecting plates

Aiming at the problems of low collection efficiency of fine particulate matter and large area occupied by existing electrostatic precipitators (ESP), a new type of horizontal electrode ESP is proposed. It has the advantages of accelerating turbulent coalescence, increasing the effective dust collecting area and increasing the particle driving speed. The performance of the new type of ESP is systematic studied through simulation and experiment at the same time, and the results matches well. By comparing the dust removal effect of the horizontal electrode ESP and the conventional ESP, it can be concluded that the horizontal electrode ESP has a better dust removal efficiency, and can still maintain a better dust removal effect under high air velocity. The dust removal efficiency of new ESP can reach above 98% under the experimental conditions.     

加工精度对方便米饭理化性质的影响

过度"精、细、白"的大米加工方式造成大量的粮食和营养浪费。为促进我国粮食适度加工政策的实施,研究大米加工精度(DOM)对方便米饭复水性质(水分含量和水分分布)、形态特征(长宽比、延长率和体积膨胀率)、颜色(L值、b值和ΔE值)、质构(硬度和黏度)和微观结构的影响及规律。结果表明,当DOM≥3%时,方便米饭的水分吸收速率、水分分布和形态特征与精白米方便米饭(DOM 12%)相近。当DOM升至6%时,方便米饭的形态特征、总体颜色ΔE值、硬度和微观结构也与精白米方便米饭相近。当DOM达到9%时,方便米饭的黏度已与精白米方便米饭无显著差异。由此可见,生产方便米饭的大米DOM范围宜为6%～9%。用此DOM范围的大米生产方便米饭,可以保留部分糠层营养物质,节约3%～6%的粮食。