电厂SCR空气雾化喷嘴的雾化特性研究

SCR是当前世界上公认的成熟控制氮氧化物技术,喷嘴是其喷射系统的关键部件。空气雾化喷嘴是一种广泛应用的雾化装置,具有雾化效果好、供给系统简单等优点。设计了新型外混式空气雾化喷嘴,并对其雾化性能进行了实验研究。实验研究主要分析了空气压力、液体压力及测量位置不同时,新型外混式空气雾化喷嘴喷雾的SMD、平均轴向速度、平均径向速度、液滴通量等特性参数沿喷嘴径向的分布情况。实验结果表明,空气雾化喷嘴具有良好的雾化效果。     

不封底PCC能量桩与传统能量桩换热效率对比研究

PCC能量桩是一种基于PCC桩的新型能量桩技术,目前针对PCC能量桩在制冷和供热过程中的换热效率及热传导特性的研究仍相对较少。基于模型试验方法,开展循环温度作用下不封底PCC能量桩、传统能量桩的温度响应测试,实测获得桩身、桩周土热响应变化规律;继而,结合数值模拟方法,对比分析进/出水温度等因素对不封底PCC能量桩换热效率的影响规律。研究结果表明,本文试验条件下,夏季制冷模式下不封底PCC能量桩的热响应略大于传统能量桩,而冬季供热模式下差异不大;相同条件下,夏季制冷模式下不封底PCC能量桩的换热效率较传统能量桩高出24%,而冬季供热模式下仅高7%。     

Lack of population structure in the fiddler crab Uca annulipes along an East African latitudinal gradient: genetic and morphometric evidence

Phylogeographic patterns in Uca annulipes sampled from 30 locations across an East African latitudinal gradient were investigated using mitochondrial DNA cytochrome oxidase I sequences and analysed together with patterns of morphometric differentiation. Four hundred and four specimens along the east African coast were sampled, and 18 haplotypes were encountered. Haplotype and nucleotide diversity values were very low and the phylogenetic analysis did not reveal any clear phylogeographic structure. Furthermore, the analysis of molecular variance and pairwise Φ _ST values showed no significant spatial population differentiation. Mismatch analyses and tests of neutrality supported the hypothesis that this species has undergone a fairly recent demographic expansion. Our results, therefore, failed to demonstrate significant geographical structure in the pattern of genetic variation, indicating that populations of U. annulipes are capable of extensive gene flow among mangroves along the coast. The genetic structure of this species could be panmictic due to a high amount of gene flow along the geographical gradient in study during the planktonic larval phase, when larvae are carried along stream by the dominant currents. Moreover, the morphometric analysis performed did not reveal differences of shape differentiation according to a geographical pattern, although significant differences among the sampling areas were found.     

Reproduction and growth of the freshwater prawn, Palaemon paucidens (Decapoda: Palaemonidae) in a lake of Korea

This study analyzed the reproduction and growth of freshwater prawn, Palaemon paucidens De Haan 1844 from Suk-dang lake(Korea). The analysis of the sex ratio showed a higher proportion of males than that of females. The average size of the eggs was 6.12 (+/-0.55) mm3 in the non-eyed stage (stageA) and 7.20 (+/-0.86)mm3 in the eyed stage (stage B). The reproductive output (RO) calculated with the dried-body weight of an incubating female and the weight of the eggs in dried condition was 26.97% (n = 17) of the average females weight. Incubating prawn appeared in April, and the gonadosomatic indices(GSI) showed the highest value during three months from January to March. Based on the month when there was a high proportion of incubating females with a high GSI, the estimated spawning season of P. paucidens was April. The maturity of the female was evaluated by the development of the ovaries and the existence of eggs. The average body length when 50% of the females in the group reached maturity was 8.55 (+/-2.74) mm. The analysis of the length-frequency distribution showed that the life span of P. paucidens ranged from 12 to 13 months. Females mature faster than males.     

Evaluating the sources of potential migrant species: implications under climate change

As changes in climate become more apparent, ecologists face the challenge of predicting species responses to the new conditions. Most forecasts are based on climate envelopes (CE), correlative approaches that project future distributions on the basis of the current climate often assuming some dispersal lag. One major caveat with this approach is that it ignores the complexity of factors other than climate that contribute to a species' distributional range. To overcome this limitation and to complement predictions based on CE modeling we carried out a transplant experiment of resident and potential-migrant species. Tree seedlings of 18 species were planted side by side from 2001 to 2004 at several locations in the Southern Appalachians and in the North Carolina Piedmont (U.S.A.). Growing seedlings under a large array of environmental conditions, including those forecasted for the next decades, allowed us to model seedling survival as a function of variables characteristic of each site, and from here we were able to make predictions on future seedling recruitment. In general, almost all species showed decreased survival in plots and years with lower soil moisture, including both residents and potential migrants, and in both locations, the Southern Appalachians and the Piedmont. The detrimental effects that anticipated arid conditions could have on seedling recruitment contradict some of the projections made by CE modeling, where many of the species tested are expected to increase in abundance or to expand their ranges. These results point out the importance of evaluating the potential sources of migrant species when modeling vegetation response to climate change, and considering that species adapted to the new climate and the local conditions may not be available in the surrounding regions.     

Effect of solids concentration on bacterial leaching of heavy metals from sewage sludge

Microbial metal leaching from sewage sludge (2-9% w/v) was carried out with the iron-oxidizing bacterium Thiobacillus ferrooxidans. Measurements of pH, oxidation-reduction potential, and concentration of Fe2+ indicated that T. ferrooxidans was effective in removing metals from an incubation bath containing less than 5% sludge solids concentration. Specifically, Cu leaching was completely suppressed at a high solids concentration of 9% (w/v). Results indicated that the deactivation of T. ferrooxidans at a high sludge content was mainly due to the presence of inhibiting materials such as organic matter. A mixed culture of sulfur-oxidizing bacteria was obtained by enrichment from anaerobically digested sewage sludge to enhance the efficiency of the microbial leaching process. These bacteria were much more effective in metal leaching than was iron-oxidizing T. ferrooxidans. At 9% (w/v) solids concentration, the leaching efficiencies of Zn and Cu were 78% (2.66 g/kg dry sludge) and 59% (1.36 g/kg dry sludge), respectively. Therefore, when removing heavy metals from the anaerobically digested sewage sludge, the indigenous sulfur-oxidizing bacteria isolated in the current study were more efficient than T. ferrooxidans, especially at high sludge solids concentrations.     

Management Objective Importance in Fisheries: An Evaluation Using the Analytic Hierarchy Process (AHP)

In determining the importance of criteria in the management of fisheries, two key issues stand out—the definition of a succinct set of criteria and the determination of which interest groups play a defining role in the management development process. This is indeed the case for all natural resource management problems, and many other environmental problems as well. The analytic hierarchy process (AHP) provides an effective framework for such an analysis. The AHP is generally used to evaluate importance amongst criteria based on the concept of paired comparison. This paper considers the development of a representative criteria hierarchy, and uses data obtained from a pairwise comparison survey based on the UK fisheries of the English Channel to investigate priorities that exist among different interest groups in the fisheries. The implementation of the AHP in this application provides a useful tool for analysis of criteria amongst groups involved in the management process with diverse interests.     

Using the multiple cell balance method to solve the problem of two-dimensional groundwater flow and contaminant transport with nonequilibrium sorption

The problem of large-scale contamination of groundwater by relatively low levels of organic contaminants is most frequently addressed by extracting and treating the impacted groundwater. This pump-and-treat strategy is often unsuccessful because of difficulties encountered in recovering the contaminants from relatively immobile zones within the porous medium. These zones can exist at the particle scale, as intraparticle or intra-aggregate porosity, and at the larger scales, as low-permeability layers or lenses interspersed in substantially more permeable layers. This work focuses on achieving an efficient numerical solution to a system of groundwater flow and contaminant transport equations that sufficiently captures the dynamics of slow desorption in a two-dimensional porous medium. The conceptual model and governing equations are presented. A numerical method for solving the governing equations, the upstream-weighted, multiple cell balance (UMCB) method, is proposed. The UMCB algorithm has been employed previously for the case of solute transport with equilibrium sorption, and is extended here to the nonequilibrium case. The approach employs a finite-element basis function and a finite-difference local mass balance, and is designed to reduce computational and storage requirements, while minimizing the mass balance error. The computational grid is formed by division of the flow domain into triangular elements. An invented node at the center of each element divides the element into three subtriangular regions. By linking the center of each triangular element and the mid-point of each elemental side, a multiangular region, referred to as an exclusive subdomain, is defined. The discretized system of governing equations is derived from the integral form that describes the mass balance in the exclusive subdomain of each node. The paper details the application of the numerical method, and demonstrates that the method is reasonably accurate and computationally efficient for a two-dimensional domain subject to nonequilibrium sorption.     

安全工程的大实践──铁路行车安全车机联控与劳动安全站区联控

叙述了广州铁路集团公司行车安全车机联控与劳动安全站区联控的基本做法和主要经验，提出了发展和完善“双联控”，使之成为铁路运输管理的一项基本制度和管理模式需要解决的问题。     

Biochemical responses of the mycorrhizae in Pinus massoniana to combined effects of Al, Ca and low pH

Biochemical responses of Pinus massoniana, with and without the inoculation mycorrhizal fungus Pisolithus tinctorius at the root, to artificial acid rain (pH 2.0) and various Ca/Al ratios were investigated. Some enzymes associated with the nutritive metabolism, such as acid phosphatase, alkaline phosphatase, nitrate reductase, mannitol dehydrogenase and trehalase, in the roots, stems and leaves of plant were obviously inhibited by the artificial acid rain and Al. After treatment with pH 2.0 + Ca/Al (0/1 or 1/10) artificial acid rain, the protein content in the organs was decreased. However, the activities of superoxide dismutase (SOD) and peroxidase (POD) and glutathione (GSH) concentrations were induced. It demonstrated that acid rain and Al could induce oxygen radicals in plant. Compared with the treatments with lower pH or Al, respectively, the combination of lower pH and Al concentration was more toxic to P. massoniana. Al toxicity could be ameliorated by the addition of Ca and the amelioration was the most when the ratio was 1/1 among the various Ca/Al ratio. Infection with mycorrhizal fungus P. tinctorius at the root of P. massoniana increased the ability of the plant to resist the toxicity of artificial acid rain and Al stress.