Improvement of a grass-clover silage-fed biogas process by the addition of cobalt

Batch assays were performed with samples from a silage-fed mesophilic biogas process accumulating acetate to examine if the addition of single trace elements (iron, nickel, cobalt and molybdenum) or a mixture of trace elements could improve the process. The results from the batch assays led to the addition of cobalt to reach a concentration of 0.2 mg L⁻¹. This made it possible to increase the organic loading rate (OLR) above that in a parallel process not receiving any extra cobalt. Problems with low gas production and decreasing pH were overcome by the daily supply of this single element in small amounts. Acetate conversion to methane was improved, which was confirmed by increased specific methanogenic activity (SMA) with acetate as a substrate. As a consequence, an OLR of 7.0 g VS L⁻¹ day⁻¹ was achieved at a hydraulic retention time (HRT) of 20 days with an equivalent increase in methane production. Without cobalt addition, an OLR of 5.0 g VS L⁻¹ day⁻¹ with an HRT of 20 days was reached after 70 weeks operation.     

美国硬木的等级

1 美国硬木资源概况 美国硬木产品已经在整个亚洲广泛使用多年,向东南亚地区出口硬木贸易额从2001年的7700万美元上升至2005年的1亿4000万美元,而在此期间,中国市场的需求从2.3亿美元上升到4.78亿美元.中国家具业年产值达到420亿美元,产品销往国际国内两个市场.     

Power assisted fuel cell

A hybrid fuel cell demonstrated pulse power capability at pulse power load simulations synonymous with electronics and communications equipment. The hybrid consisted of a 25.0 W Proton Exchange Membrane Fuel Cell (PEMFC) stack in parallel with a two-cell lead-acid battery. Performance of the hybrid PEMFC was superior to either the battery or fuel cell stack alone at the 18.0 W load. The hybrid delivered a flat discharge voltage profile of about 4.0 V over a 5 h radio continuous transmit mode of 18.0 W.     

Using Survey Data and Mathematical Modeling to Prioritize Water Interventions in Developing Countries

Water Resources Management - A traditional cost-benefit analysis of potential water interventions in a given locality is a laborious and time-intensive process. To help decision makers identify...     

Book reviews

A Fourth Way? Privatization, Property and the Emergence of New Market Economies. Gregory S. Alexander & Grazyna Skapska (Eds). London, Routledge, 1994, xxiii + 336 pp., ISBN 0415906970 (HB), 0415906989 (PB)

From Public Housing to the Social Market. Rental Policy Strategies in Comparative Perspective. Jim Kemeny. London and New York, Routledge, 1995, 194 pp., £40.00

European Housing Finance. Single Market or Mosaic?. Will Bartlett & Glen Bramley (Eds). Oxford, The Alden Press, School for Advanced Urban Studies (SAUS) publication 12 (Bristol) 1994, 282 pp., £19.95, paperback, ISBN 1 873575 63 7

Housing, Financial Markets and the Wider Economy. David Miles. Chichester, John Wiley & Sons, 1994, 228 pp., £35.00

Women in the Housing Service. Marion Brion. London, Routledge, 1994, ISBN 0 415 08094 £45.00 Hardback

Slippery Customers: Estate Agents, The Public and Regulation. Michael Clarke, David Smith & Michael McConville. London, Blackstone Press, 1994, 295 pp., £19.95     

纵波-转换横波联合反演技术在页岩气藏勘探中的应用

近几年的页岩油气开发实践表明,页岩非均质性及水平井段的方位对页岩气单井产量、采收率及页岩气开采的经济性影响较大,而页岩非均质性主要受到天然微裂缝的影响。因此,开展页岩内天然微裂缝研究,寻找页岩储层“甜点”等是成功部署高产气井、提高页岩气开采经济效益的必然选择。基于美国阿巴拉契亚盆地Marcellus页岩区的3C/3D高分辨率地震资料,利用快/慢速转换横波（PSV-1/PSV-2）反射时间厚度差法,对Marcellus地层的天然微裂缝发育带进行了探测。应用纵-转换横波（PP-PS）联合反演技术,结合联合反演密度、纵横波速度比（v_P/v_S）等组合属性参数,对天然微裂缝的开闭性及张性天然微裂缝孔隙空间的含气性分别进行了识别和检测,并利用实钻井资料对地球物理方法预测的页岩储层“甜点”（含气张性微裂缝）进行验证,取得较好效果。实际应用表明,纵-横波联合反演技术对于张性天然微裂缝的识别及含气性检测具有突出优势,能有效降低钻探风险。     

Taming Charge Transport in Semiconducting Polymers with Branched Alkyl Side Chains

The solid‐state packing and polymer orientation relative to the substrate are key properties to control in order to achieve high charge carrier mobilities in organic field effect transistors (OFET). Intuitively, shorter side chains are expected to yield higher charge carrier mobilities because of a denser solid state packing motif and a higher ratio of charge transport moieties. However our findings suggest that the polymer chain orientation plays a crucial role in high‐performing diketopyrrolopyrrole‐based polymers. By synthesizing a series of DPP‐based polymers with different branched alkyl side chain lengths, it is shown that the polymer orientation depends on the branched alkyl chain lengths and that the highest carrier mobilities are obtained only if the polymer adopts a mixed face‐on/edge‐on orientation, which allows the formation of 3D carrier channels in an otherwise edge‐on‐oriented polymer chain network. Time‐of‐flight measurements performed on the various polymer films support this hypothesis by showing higher out‐of‐plane carrier mobilities for the partially face‐on‐oriented polymers. Additionally, a favorable morphology is mimicked by blending a face‐on polymer into an exclusively edge‐on oriented polymer, resulting in higher charge carrier mobilities and opening up a new avenue for the fabrication of high performing OFET devices.     

Low energy ballasted flotation

A novel process which involves the replacement or supplementation of bubbles in the dissolved air flotation process with low density beads is presented. The work comprised a series of bench-scale flotation trials treating three commonly encountered algal species (Microcystis, Melosira and Chlorella) that were removed in a flotation cell configured as either: conventional dissolved air flotation (DAF); ballasted flotation using low density 70 μm glass beads with a density of 100 kg m⁻³; or a hybrid process of ballasted flotation combined with conventional DAF. Results indicated that the bead only system was capable of achieving better residual turbidity than standard DAF at bead concentrations of 500 mg L⁻¹. Addition of beads in combination with standard DAF reduced turbidity further to even lower residual turbidity levels. Algae removal was improved when glass beads were dosed, but removal was dependent on algal species. Microcystis was removed by 97% for bead only systems and this removal did not change significantly with the addition of air bubbles. Melosira was the next best removed algae with bead only dosed systems giving similar removals to that achieved by standard DAF using a 10% air recycle ratio (81 and 76% removal respectively). Chlorella was the least well removed algae by bead only systems (63% removal). However, removal was rapidly improved to 86% by the addition of air bubbles using only a 2% recycle ratio. Energy estimations suggested that at least a 50% energy reduction could be achieved using the process offering a potential route for future development of low energy separation processes for algae removal.     

安全仪表系统的网络安全考虑：最先还是最后？

对于完整的控制和安全系统，建立强大的防护体系是否是一项可以确保安全仪表系统商业连续性的必要投资？