离心旋流式喷嘴雾化特性实验研究

目的进一步优化低温多效蒸馏技术中的喷淋布液方式,提高海水淡化换热效率。方法采用马尔文激光粒度分析仪、高速摄像机和翻转水量仪对不同口径的CJ-9型离心旋流式喷嘴进行研究。结果同一口径的喷嘴,随着水流压力的增加,液滴粒径分布的均匀性显著提高。随着水压的增加,同一个喷嘴液体破碎的纹路变密,同时液膜破碎的长度变短,破碎效果越好,雾化性能越好。同一口径的喷嘴,入口压力越大,其边缘流峰值越高,空心化率现象越明显。同一压力下不同口径的喷嘴,口径越大,其形成双波峰的跨度越短;同一口径的喷嘴,入口压力越大,其形成双波峰的跨度越长,其边缘流峰值越高。结论液滴粒径分布的均匀性随着水压的增加或孔径的减小而显著提高,喷淋密度在直径方向上存在两个峰值,运用"峰谷叠加"原理,来满足低温多效蒸发器布液均匀的整体要求。     

钢铁行业袋式除尘用滤料孔径与微细粉尘捕集特性关系研究

选用钢铁行业袋式除尘用滤料,采用泡点法进行孔径及孔径分布测试,并进行了除尘滤料冷静态过滤性能测试。通过对实验数据分析得到:针刺滤料平均孔径为22.22~26.83μm,孔径分散程度较高;覆膜针刺过滤材料平均孔径仅为1.0μm左右,孔径分布较为集中;针刺滤料的孔径会影响到其透气性,透气性随着最大孔径的增加而增加;针刺滤料孔径及孔径分布对过滤效率有直接的影响,孔径越大,孔径分布分散程度越高,过滤效率越低,过滤阻力越小;过滤风速为1.0 m/min时覆膜滤料对微细颗粒物的捕集效率达到80%左右,约为普通针刺毡滤料的2~4倍,阻力约为普通针刺毡滤料的14~32倍。     

不同粒径钨尾砂中重金属的含量及形态研究

以江西省赣南地区牛孜石、画眉坳、西华山钨矿尾砂库为研究对象,采集钨尾砂样品3份,使用标准筛将其细分为7个粒径等级(450μm)。以BCR连续提取法对重金属进行形态提取,ICP-OES测定不同粒径钨尾砂颗粒物中Cr、Mn、Cu、Zn、Cd、As、Pb、Ni重金属各形态的含量。研究结果表明:不同粒径的尾砂中重金属的含量差异明显,Cu、Zn元素在粒径>380μm的颗粒物中含量较高,Cr、Cd、Pb、Ni、Mn元素则在粒径<25μm的颗粒物中有着很高的含量,特别是Pb,该粒径中的含量远高于其他任何粒径区间。重金属形态随尾砂粒径分布表明:不同矿区同一粒径的尾砂各形态重金属所占比例差异明显,但相同的是,粒径大于450μm的颗粒物中Cu、Zn可交换态形式所占比例较高,而粒径小于25μm的极细颗粒物中,可溶态的Ni含量很高,需要采取有效管理措施以遏制可能发生的污染。     

The role of life histories and trophic interactions in population recovery

Factors affecting population recovery from depletion are at the focus of wildlife management. Particularly, it has been debated how life‐history characteristics might affect population recovery ability and productivity. Many exploited fish stocks have shown temporal changes towards earlier maturation and reduced adult body size, potentially owing to evolutionary responses to fishing. Whereas such life‐history changes have been widely documented, their potential role on stock's ability to recover from exploitation often remains ignored by traditional fisheries management. We used a marine ecosystem model parameterized for Southeastern Australian ecosystem to explore how changes towards “faster” life histories might affect population per capita growth rate r. We show that for most species changes towards earlier maturation during fishing have a negative effect (3–40% decrease) on r during the recovery phase. Faster juvenile growth and earlier maturation were beneficial early in life, but smaller adult body sizes reduced the lifetime reproductive output and increased adult natural mortality. However, both at intra‐ and inter‐specific level natural mortality and trophic position of the species were as important in determining r as species longevity and age of maturation, suggesting that r cannot be predicted from life‐history traits alone. Our study highlights that factors affecting population recovery ability and productivity should be explored in a multi‐species context, where both age‐specific fecundity and survival schedules are addressed simultaneously. It also suggests that contemporary life‐history changes in harvested species are unlikely to increase their resilience and recovery ability.     

Consequences of ignoring dispersal variation in network models for landscape connectivity

Habitat loss and fragmentation can negatively influence population persistence and biodiversity, but the effects can be mitigated if species successfully disperse between isolated habitat patches. Network models are the primary tool for quantifying landscape connectivity, yet in practice, an overly simplistic view of species dispersal is applied. These models often ignore individual variation in dispersal ability under the assumption that all individuals move the same fixed distance with equal probability. We developed a modeling approach to address this problem. We incorporated dispersal kernels into network models to determine how individual variation in dispersal alters understanding of landscape-level connectivity and implemented our approach on a fragmented grassland landscape in Minnesota. Ignoring dispersal variation consistently overestimated a population's robustness to local extinctions and underestimated its robustness to local habitat loss. Furthermore, a simplified view of dispersal underestimated the amount of habitat substructure for small populations but overestimated habitat substructure for large populations. Our results demonstrate that considering biologically realistic dispersal alters understanding of landscape connectivity in ecological theory and conservation practice.     

Responses of Seed‐Dispersing Birds to Amount of Rainforest in the Landscape around Fragments

Habitat loss and fragmentation alter the composition of bird assemblages in rainforest. Because birds are major seed dispersers in rainforests, fragmentation‐induced changes to frugivorous bird assemblages are also likely to alter the ecological processes of seed dispersal and forest regeneration, but the specific nature of these changes is poorly understood. We assessed the influence of fragment size and landscape forest cover on the abundance, species composition, and functional properties of the avian seed disperser community in an extensively cleared, former rainforest landscape of subtropical Australia. Bird surveys of fixed time and area in 25 rainforest fragments (1–139 ha in size across a 1800 km² region) provided bird assemblage data which were coupled with prior knowledge of bird species’ particular roles in seed dispersal to give measurements of seven different attributes of the seed disperser assemblage. We used multimodel regression to assess how patch size and surrounding forest cover (within 200 m, 1000 m, and 5000 m radii) influenced variation in the abundance of individual bird species and of functional groups based on bird species’ responses to fragmentation and their roles in seed dispersal. Surrounding forest cover, specifically rainforest cover, generally had a greater effect on frugivorous bird assemblages than fragment size. Amount of rainforest cover within 200 m of fragments was the main factor positively associated with abundances of frugivorous birds that are both fragmentation sensitive and important seed dispersers. Our results suggest a high proportion of local rainforest cover is required for the persistence of seed‐dispersing birds and the maintenance of seed dispersal processes. Thus, even small rainforest fragments can function as important parts of habitat networks for seed‐dispersing birds, whether or not they are physically connected by vegetation. Respuestas de Aves Dispersoras de Semillas al Incremento de Selvas en el Paisaje Alrededor de Fragmentos     

A spatially explicit estimate of the prewhaling abundance of the endangered North Atlantic right whale

The North Atlantic right whale (NARW) (Eubalaena glacialis) is one of the world's most threatened whales. It came close to extinction after nearly a millennium of exploitation and currently persists as a population of only approximately 500 individuals. Setting appropriate conservation targets for this species requires an understanding of its historical population size, as a baseline for measuring levels of depletion and progress toward recovery. This is made difficult by the scarcity of records over this species’ long whaling history. We sought to estimate the preexploitation population size of the North Atlantic right whale and understand how this species was distributed across its range. We used a spatially explicit data set on historical catches of North Pacific right whales (NPRWs) (Eubalaena japonica) to model the relationship between right whale relative density and the environment during the summer feeding season. Assuming the 2 right whale species select similar environments, we projected this model to the North Atlantic to predict how the relative abundance of NARWs varied across their range. We calibrated these relative abundances with estimates of the NPRW total prewhaling population size to obtain high and low estimates for the overall NARW population size prior to exploitation. The model predicted 9,075–21,328 right whales in the North Atlantic. The current NARW population is thus <6% of the historical North Atlantic carrying capacity and has enormous potential for recovery. According to the model, in June–September NARWs concentrated in 2 main feeding areas: east of the Grand Banks of Newfoundland and in the Norwegian Sea. These 2 areas may become important in the future as feeding grounds and may already be used more regularly by this endangered species than is thought.     

Founder Effects,Inbreeding, and Loss of Genetic Diversity in Four Avian Reintroduction Programs

Abstract: The number of individuals translocated and released as part of a reintroduction is often small, as is the final established population, because the reintroduction site is typically small. Small founder and small resulting populations can result in population bottlenecks, which are associated with increased rates of inbreeding and loss of genetic diversity, both of which can affect the long‐term viability of reintroduced populations. I used information derived from pedigrees of four monogamous bird species reintroduced onto two different islands (220 and 259 ha) in New Zealand to compare the pattern of inbreeding and loss of genetic diversity among the reintroduced populations. Although reintroduced populations founded with few individuals had higher levels of inbreeding, as predicted, other factors, including biased sex ratio and skewed breeding success, contributed to high levels of inbreeding and loss of genetic diversity. Of the 10–58 individuals released, 4–25 genetic founders contributed at least one living descendent and yielded approximately 3–11 founder–genome equivalents (number of genetic founders assuming an equal contribution of offspring and no random loss of alleles across generations) after seven breeding seasons. This range is much lower than the 20 founder–genome equivalents recommended for captive‐bred populations. Although the level of inbreeding in one reintroduced population initially reached three times that of a closely related species, the long‐term estimated rate of inbreeding of this one population was approximately one‐third that of the other species due to differences in carrying capacities of the respective reintroduction sites. The increasing number of reintroductions to suitable areas that are smaller than those I examined here suggests that it might be useful to develop long‐term strategies and guidelines for reintroduction programs, which would minimize inbreeding and maintain genetic diversity.     

基于农业生态地带模型的中国粮食产能动态评估

随着人口增加和人们生活水平的不断提高,我国粮食消费需求将继续呈刚性增长,使得粮食品种和区域结构性矛盾加剧,而粮食产能的动态评估能够让我们加深认识我国粮食供需平衡,对制定适宜于我国经济社会发展同时保障粮食安全的粮食可持续发展战略具有重要意义.论文选取农田生产力作为我国粮食产能的指标,通过改进农业生态地带(AEZ)模型,动态嵌入不同县域水平的管理和投入水平的限制性因子,集成县级截面数据估计投入系数权重,并基于此估算了全国2000-2010年间农田生产力水平.研究发现,2000年以来,我国农田生产力虽年际间存在波动,但总体呈现增长的态势,且区域差异性显著.农田生产力水平存在从沿海到内陆、从南向北及从东向西的递减的梯度,而局部地区农田生产力变化明显,表现出明显的东西分异规律,其次是南北分异规律.而对各个地区农田生产力平均值统计发现,东部沿海地区与南部省份的农田生产力要高于内陆省份,西部地区农田生产力普遍低于东部和中部地区.2000、2005、2010年全国分县统计的粮食产量数据与动态估算结果进行精度验证,其相关系数分别达到0.82、0.76和0.89,实际产量为估算结果的69.4％、73.4％、67.2％,较好的反映了我国农田生产力的基本状况.最后,基于我国农田生产力时空变化规律和局部差异性特征,以及我国经济区水平上的中国农田生产力的变化规律,从耕地数量保障、农业管理和投入水平提高以及适宜的农业区划方面,提出适宜于我国自然环境状况和社会经济发展的农田生产力保障策略,对保障我国的农田生产力的稳定增长方面的规划决策与政策制定具有参考价值.     

Dynamic evaluation of land productivity in China

For making rational and scientific land-use planning,an inventory indicator of land productivity subject to biophysical limitations and human disturbance is required.This study introduces agricultural land productivity(ALP)as the dynamic indicator to measure land productivity,involving factors that affect agricultural production,such as characteristics of climate,soil,and terrain.As a case study of this dynamic indicator,ALP was estimated at county level and aggregated into provincial level in the whole of China.The result shows that ALP increased during 2000-2010 in China,and the ratios of ALP to the actual grain yield were 65.40%and 66.38%in the years 2000 and 2005,respectively.The ALP is an effective dynamic indicator to estimate the land productivity and to represent the basic conditions about the supply of water,energy,nutrients,and the physical basis for plant growth,as well as the local input.ALP estimation could provide supporting information for policy-making about land production planning and land-use management.