普通旋风除尘器结构尺寸优化设计

以Ｌｅｉｔｈ设计法为基础，考虑除尘效率和压降等因素的影响，以除尘效率为理想目标，以一些流体力学特性和实际限制、经验值为约束，建立数学模型，用数学规划论的方法进行旋风除尘器结构尺寸的优化，以此设计的旋风除尘器应用到现场既可节约投资，又可降低能耗，设计方法通用性好．     

热带海—气的相互作用与地球自转—用天文方法预测ENSO事件

本文介绍了热带海洋、大气的相互作用,着重描述了它们与地球自转年际速率变化的关系和物理过程的联系,以及用天文观测的日长变化资料预测ENSO事件的方法和尝试.     

Phytoremediation of petroleum hydrocarbons in tropical coastal soils I. selection of promising woody plants

GOAL, SCOPE AND BACKGROUND: This glasshouse study is aimed at evaluating tropical plants for phytoremediation of petroleum hydrocarbon-contaminated saline sandy subsurface soils. Tropical plants were selected for their ability to tolerate high salinity and remove No. 2 diesel fuel in coastal topsoil prior to further investigation of the phytoremediation feasibility in deep contaminated soils. The residual petroleum-hydrocarbon contaminant at the John Rogers Tank Farm site, a former petroleum storage facility, at Hickam Air Force Base, Honolulu, Hawaii, is located in a coastal area. It lies below a layer of silt in the subsurface, in loamy sand characterized by moderate salinity and high pH. Little is known regarding the ability of tropical plants to remediate petroleum hydrocarbon-contaminated subsurface soil in Hawaiian and other Pacific Island ecosystems although suitable plants have been identified and utilized for bioremediation in surface soil or marine sediments. METHODS: The experiments were conducted in long narrow pots under glasshouse conditions in two phases. A preliminary experiment was done with nine tropical plants: kiawe (Prosopis pallida), milo (Thespesia populnea), common ironwood (Casuarina equisetifolia), kou (Cordia subcordata), tropical coral tree (Erythrina variegata), false sandalwood (Myoporum sandwicense), beach naupaka (Scaevola sericea), oleander (Nerium oleander), and buffelgrass (Cenchrus ciliaris). These plants were screened for resistance to high salinity treatment (2% NaCl) and two diesel fuel levels (5 and 10 g No. 2 diesel fuel/kg soil) in separate treatments. Plants that showed good tolerance of both factors were further evaluated in a second phase for their efficacy in the phytoremediation of diesel-fuel petroleum hydrocarbons under moderate salinity treatment (1% NaCl). RESULTS: Tropical coral tree and buffelgrass were susceptible to either 2% NaCl or diesel fuel at 10 g/kg soil, but tolerant of diesel fuel at 5 g/kg soil. Kiawe, milo, kou, common ironwood, N. oleander, beach naupaka and false sandalwood were tolerant of high salinity (2% NaCl) or high diesel fuel level (10 g/kg soil). These seven plants were also tolerant of the combined adverse effects of a moderate salinity (1% NaCl) and 10 g diesel fuel/kg soil. Three trees, kiawe, milo and kou significantly accelerated the degradation of petroleum hydrocarbons in the soil spiked with 10 g diesel fuel/kg soil under a moderate salinity treatment (1% NaCl). CONCLUSION: Thus the tropical woody plants, kiawe, milo and kou showed potential for use in phytoremediation of petroleum hydrocarbons in coastal tropical soils. RECOMMENDATIONS AND OUTLOOK: Two fast growing trees, milo and kou, appeared promising for further phytoremediation evaluation in experiments that simulate the soil profile at the field site.     

旋风静电除尘器流场分布测试研究

利用五孔探针系统对直筒式旋风静电除尘器模型的三维流场进行了测定与分析。结果表明：随着入口风速、供电电压增加，旋风静电除尘器内气流的切向和径向速度分别增加，各截面轴向速度沿半径的分布基本相似；与旋风除尘器相比，旋风静电除尘器内气流的切向速度和径向速度的变化更为平缓，入口风速为8．5m／s时，在0．3～0．5倍简体直径时，切向速度达最大。     

APPLICATION OF BIOLOGICAL MEASURES FOR STREAM INTEGRITY ASSESSMENT IN SOUTH-EAST BRAZIL

The sensitivity of eleven metrics using macroinvertebrate assemblages were evaluated in an environmental gradient in a tropical river in south-east Brazil. Eight sites were sampled in an altitudinal range of 160–650 m.a.s.l. during 1999 (April and August) and 2000 (February). Four substrates were sampled at each site: riffle litter, pool litter, stony substrates and sediment. Correspondence Analysis indicated that assemblages were primarily more influenced by physical changes (like deforestation and erosion processes) than the water chemistry. The sensitivity of each metric was evaluated through the application of box-and-whisker plot method by its power to assess impairment (metrics should be able to discriminate reference sites from impaired sites) and natural variability (metrics should not discriminate two reference sites). Metrics that failed in at least one of the above premises were not considered as sensitive. In this study, the most sensitive metrics were Shannon index, BMWP-ASPT, %_EPT, and relative abundance of EPT to Chironomidae.     

辽宁地区一次暴雨过程成因的位涡诊断分析

2003年8月5—6日，受东移北上的华北气旋的影响，辽宁省大部分地区出现暴雨天气，其中彰武、本溪等地出现局地大暴雨。应用MM5非静力中尺度模式对这次暴雨过程进行了数值模拟，在模拟结果的基础上，利用位涡分析方法对这次过程进行了诊断分析。结果表明，在对流层低层有正位涡扰动存在，对强对流天气具有触发作用；对流层中低层的相对高位涡中心和对流层高层的较强低位涡中心相配合，有利于形成低层辐合与高层辐散，使得气旋得以维持和发展，从而为对流性降水提供了必要条件；在对流层中低层，出现高位涡中心地区可能形成暴雨中心。     

旋风除尘器的压力损失及减阻措施

通过探讨引起旋风除尘器阻力损失的原因，提出了相应的减阻措施－安装导向板和内筒。     

Long-term impacts of land-use change on dynamics of tropical soil carbon and nitrogen pools

Land-use changes, especially the conversion of native forest vegetation to cropland and plantations in tropical region, can alter soil C and N pools and N availability for plant uptake. Deforestation, followed by shifting cultivation and establishment of rubber tree plantation, is a common land-use change in Xishuangbanna, southwest China. However the influence of this kind of land-use change on soil C and N dynamics in this region remains poorly understood, This study was conducted to assess the effects of land-use change on soil C and N pools. Soil samples were collected on five adjacent plots, which belong to three land-use types including secondary forest-an acuminate banana( Musa itinerans) secondary forest and a male bamboo( Dendrocalamus membranaceae) secondary forest, shifting cultivation, and rubber tree ( Hevea brasiliensis (H. B. K. ) Muell. Arg. ) plantation(one plot is 3-year-old, and another is 7-year-old). We measured soil bulk density (BD), pH value, moisture content and concentrations of soil organic carbon(SOC), total soil nitrogen(TSN), and inorganic N(NO3^- -N and NH4^ -N) at 0--3, 3--20, 20--40 and 40--60cm depths, and calculated C and N pools in 0--20, 20--40, 40--60, and 0--60 cm soil layers. Compared with the adjacent secondary forests, shifting cultivation and establishment of rubber tree plantations resulted in significant decline in concentrations and stocks of SOC and TSN in 0--20 and 0--60cm soil layers, and increase in pH and bulk density at 0--3, 3--20, and 20--40cm depths. Soil moisture content decreased only in 0--20cm surface soils in shifting cultivation and plantations. The dynamics of mineral N was much more complex, which had different trends among depths and ecosystems. Compared with the secondary forests, SOC stocks in 0--20cm surface soils in shifting cultivation and rubber tree plantations(3-year-old plantation and 7-year-old plantation) decreased by 34.0%, 33%, and 23% ; and TSN stocks decreased by 32.2%, 20.4%, and 20.4%, respectively,whereas the decreases of SOC and TSN stocks in 0--60cm soil layers were much less. The results indicated that C and N losses were mainly occurred in 0--20cm surface soil, followed by 20--40cm layer.     

Value of Small Patches in the Conservation of Plant-Species Diversity in Highly Fragmented Rainforest

Abstract:  We evaluated the importance of small (<5 ha) forest patches for the conservation of regional plant diversity in the tropical rainforest of Los Tuxtlas, Mexico. We analyzed the density of plant species (number of species per 0.1 ha) in 45 forest patches of different sizes (1–700 ha) in 3 landscapes with different deforestation levels (4, 11, and 24% forest cover). Most of the 364 species sampled (360 species, 99%) were native to the region, and only 4 (1%) were human-introduced species. Species density in the smallest patches was high and variable; the highest (84 species) and lowest (23 species) number of species were recorded in patches of up to 1.8 ha. Despite the small size of these patches, they contained diverse communities of native plants, including endangered and economically important species. The relationship between species density and area was significantly different among the landscapes, with a significant positive slope only in the landscape with the highest deforestation level. This indicates that species density in a patch of a given size may vary among landscapes that have different deforestation levels. Therefore, the conservation value of a patch depends on the total forest cover remaining in the landscape. Our findings revealed, however, that a great portion of regional plant diversity was located in very small forest patches (<5 ha), most of the species were restricted to only a few patches (41% of the species sampled were distributed in only 1–2 patches, and almost 70% were distributed in 5 patches) and each landscape conserved a unique plant assemblage. The conservation and restoration of small patches is therefore necessary to effectively preserve the plant diversity of this strongly deforested and unique Neotropical region.     

Water budget and the consequent duration of canopy carbon gain in a teak plantation in a dry tropical region: Analysis using a soil–plant–air continuum multilayer model

A soil–plant–air continuum multilayer model was used to numerically simulate canopy net assimilation (A_n), evapotranspiration (ET), and soil moisture in a deciduous teak plantation in a dry tropical climate of northern Thailand to examine the influence of soil drought on A_n. The timings of leaf flush and the end of the canopy duration period (CDP) were also investigated from the perspective of the temporal positive carbon gain. Two numerical experiments with different seasonal patterns of leaf area index (LAI) were carried out using above-canopy hydrometeorological data as input data. The first experiment involved seasonally varying LAI estimated based on time-series of radiative transmittance through the canopy, and the second experiment applied an annually constant LAI. The first simulation captured the measured seasonal changes in soil surface moisture; the simulated transpiration agreed with seasonal changes in heat pulse velocity, corresponding to the water use of individual trees, and the simulated A_n became slightly negative. However, in the second simulation, A_n became negative in the dry season because the decline in stomatal conductance due to severe soil drought limited the assimilation, and the simultaneous increase in leaf temperature increased dark respiration. Thus, these experiments revealed that the leaflessness in the dry season is reasonable for carbon gain and emphasized the unfavorable soil water status for carbon gain in the dry season. Examining the duration of positive A_n (DPA) in the second simulation showed that the start of the longest DPA (LDPA) in a year approached the timing of leaf flush in the teak plantation after the spring equinox. On the other hand, the end appeared earlier than that of all CDPs. This result is consistent with the sap flow stopping earlier than the complete leaf fall, implying that the carbon assimilation period ends before the completion of defoliation. The model sensitivity analysis in the second simulation suggests that a smaller LAI and slower maximum rate of carboxylation likely extend the LDPA because soil water from the surface to rooting depth is maintained longer at levels adequate for carbon gain by decreased canopy transpiration. The experiments also suggest that lower soil hydraulic conductivity and deeper rooting depth can postpone the end of the LDPA by increasing soil water retention and the soil water capacity, respectively.