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541.
水果渣改性絮凝剂的性能表征 总被引:3,自引:0,他引:3
对化学改性天然高分子絮凝剂的制备及絮凝效果进行了初步研究。以来源丰富的水果渣为原料,分别与氯乙酸、丙烯腈、丙烯酰胺在不同的条件下醚化、聚合,制得多种絮凝剂,用于处理造纸废水。 相似文献
542.
543.
George M. Leigh William S. Hearn Kenneth H. Pollock 《Environmental and Ecological Statistics》2006,13(1):89-108
Instantaneous natural mortality rates and a nonparametric hunting mortality function are estimated from a multiple-year tagging
experiment with arbitrary, time-dependent fishing or hunting mortality. Our theory allows animals to be tagged over a range
of times in each year, and to take time to mix into the population. Animals are recovered by hunting or fishing, and death
events from natural causes occur but are not observed. We combine a long-standing approach based on yearly totals, described
by Brownie et al. (1985, Statistical Inference from Band Recovery Data: A Handbook, Second edition, United States Fish and Wildlife Service, Washington, Resource Publication, 156), with an exact-time-of-recovery
approach originated by Hearn, Sandland and Hampton (1987, Journal du Conseil International pour l’Exploration de la Mer, 43, 107–117), who modeled times at liberty without regard to time of tagging. Our model allows for exact times of release
and recovery, incomplete reporting of recoveries, and potential tag shedding. We apply our methods to data on the heavily
exploited southern bluefin tuna (Thunnus maccoyii). 相似文献
544.
JAIME BOSCH§ PEDRO A. RINCÓN LUZ BOYERO† IÑIGO MARTÍNEZ-SOLANO‡ 《Conservation biology》2006,20(1):180-189
Abstract: Amphibians are declining worldwide because of multiple factors, including human-mediated introduction of fishes into naturally fishless areas. Although several studies have focused on the effect of exotic fishes on native amphibians breeding in ponds or lakes, little is known about their effects on stream-breeding species. We studied the effects of introductions of native brown trout ( Salmo trutta ) and exotic brook trout ( Salvelinus fontinalis ) on the stream-breeding, endemic Iberian frog ( Rana iberica ) in a protected area in central Spain. We assessed occurrence patterns of tadpoles and salmonids and compared habitat use of the three species. We also determined experimentally whether chemical cues from salmonids elicited antipredator behavior in tadpoles. Finally, we assessed the relative influence of tadpole habitat preferences, differences in salmonid species, and invasion geography on tadpole occurrence. Despite widely overlapping habitat preferences, tadpoles and trout did not coexist, with the former restricted to fishless habitats. Tadpoles detected chemical cues from both trout species and reacted by decreasing their activity, although the response toward the native brown trout was stronger. The residual distribution of Iberian frogs in Peñalara is better explained by the geography of fish invasions than by the fish species involved. Measures such as fish extirpation from certain areas, aimed at recovering lost habitat and improving connectivity among remaining populations of Iberian frogs, seem critical for the species' long-term survival in central Spain. 相似文献
545.
根据胶体光学吸收行为研究Zn~(2+)-S~(2-)胶体反应测定Zn~(2-)双波长新光度分析方法。该方法简单方便、曲线稳定、精密度(RSD)<3%,加标回收率为93%~103%,检出限:0.3mg/L.适合于0~10.0μg/ml天然水测定。 相似文献
546.
针对难以迅速扑灭的隧道甲醇火灾场景,在截面积9.14 m~2,长38 m的全尺寸隧道内开展了一系列实验,研究了不同通风条件下多喷头细水雾系统对隧道甲醇火灾的抑制作用。通过分析火源周围温度分布、火源下风向隧道温度分布及隧道能见度等参数,综合评估了通风条件下细水雾系统抑制隧道火灾的效果。结果表明:纵向通风降低隧道温度的同时易引起人眼高度处温度升高;细水雾能迅速控制火灾发展并有效降低隧道温度,但细水雾雾滴的扩散与沉降易造成隧道能见度的下降。在本文条件下,风速为4.98 m/s的纵向通风和10 MPa压力下的6喷头细水雾系统共同作用能够有效降低火源周围温度和隧道温度,并显著提高隧道能见度。 相似文献
547.
A broad and objective perspective of ecological and socioenomic knowledge is required to underlie a scientific approach to
the problems of terrestrial restoration ecology. Uncertainty associated with limited scientific knowledge highlights the crucial
importance of the interaction between science and policy in weighing ecological restoration alternatives in relation to other
management options. In this paper, we provide a pragmatic definition for restoration ecology that is suitable for extensive
terrestrial applications and present a decision framework to help organize and clarify different phases of the decision process
as it is related to ecological restoration. We argue that restoration planning should include a wider spectrum of participants
and decisions than have traditionally been employed. 相似文献
548.
解放以来我国农业灾害综述 总被引:4,自引:0,他引:4
本文根据现有数据,浅析了解放以来我国农业灾害,特别是水、旱灾害的变化及其原因;分析了成灾比例与减灾工作状况之间存在着内在的联系,指出成灾比例可以在一定程度上反映减灾工作的好坏。旨在为客观评价我国农业减灾现状,合理配置减灾力量,提供信息和决策依据。 相似文献
549.
550.
灾害与锡林郭勒草地退化,沙漠化 总被引:2,自引:1,他引:2
锡林郭勒盟是我国北方重要的畜牧业基地,它以拥有约0.197亿hm2天然草地而著称于世。然而,由于自然灾害和人为不正确的利用而发生了严重退化.到目前,全盟退化草地已占48.63%,它不仅为畜牧业生产带来了困难,同时也使一些重要的草地生态因子发生了变化,直接危及了人们的生产和生活。对于退化、沙漠化和草地整治已刻不容缓,应该引起国家有关部门和各级领导的足够重视. 相似文献