中国常用人工鱼礁流场效应的比较分析

不同结构的人工鱼礁在海中会产生不同的流场效应,为了对比分析不同结构人工鱼礁的流场效应差异,该文利用CFX软件,对6类礁型18种中国常用人工鱼礁进行了数值模拟。引入了2种相对评价方法(比礁高和比混凝土体积)和3个评价指标(礁体中垂面上的上升流面积、背涡流面积和上升流高度)。首先分析了评价指标适用的相对评价方法,然后对18种鱼礁进行比较研究,最后从每类礁型分别选出一个礁体为代表研究它们在不同流速下(0.2,0.4,0.6,0.8和1.0 m/s)上升流和背涡流的差异。结果表明:研究上升流和背涡流面积时比混凝土体积法更科学,研究上升流高度时比礁高法更有效;无论上升流还是背涡流,三角型礁的相对面积都为最大,复合型礁次之,框架性礁最小;上升流高度、上升流面积和背涡流面积都不随来流速度变化;最大上升流流速与来流速度呈线性关系,其斜率在不同礁体间存在差异;该研究以期为不同海域不同要求下人工鱼礁的选择和设计提供了参考。     

镂空方型增殖礁上升流特性的粒子图像测速试验

利用粒子图像测速技术（particle image velocimetry）对镂空方型增殖礁单体礁和组合礁的上升流流场特性进行分析,按照海区实测流速和礁区选址要求,设定5个不同的来流速度0.2、0.4、0.6、0.8、1.0 m/s,并计算出试验流速分别为0.045、0.090、0.135、0.180、0.225 m/s。结果表明：单体礁在任何一种迎流方式下,上升流的规模都随来流速度的增加而增大;而相同来流速度下,主视面90o迎流时,上升流规模最大;单体俯视面45o迎流时,上升流规模最小;礁体横向组合排列时,礁体间距在0.5L～1.0 L时所产生的上升流规模最大,礁体间的协同作用最强;礁体纵向组合排列时,在0.5L～1.5 L倍的间距时,礁体间的相互作用较强,形成的上升流规模最大。     

电白大放鸡渔场人工鱼礁投放海域资源环境状况评价

根据在电白大放鸡渔场开展人工鱼礁投放海域本底调查所获的海洋资源和环境资料及以往有关文献中对该海域的调查资料,对人工鱼礁礁区的生物资源、海水水质、底质等方面进行评价,认为电白大放鸡渔场人工鱼礁礁区滨海旅游基础好,海洋渔业资源种类繁多,浮游生物丰富,水质良好,底质多为沙、粗沙或粉沙黏土为主,具有营造游钓鱼礁,发展海洋（岛）生态旅游与娱乐游钓的得天独厚的自然条件.     

滩涂淤泥在人工藻礁制备中的应用

为了有效利用滩涂淤泥中的营养物质,加快人工藻场的构建进程,通过筛除、烘干等方法将滩涂淤泥制成人工藻礁的原料,按照不同比例与水泥混合(0.3∶1、0.5∶1、0.7∶1、0.9∶1)制备成人工藻礁礁块,采用一元线性回归方法对不同淤泥-水泥混合比藻礁中的营养盐溶出效果进行了分析,并测量了各混合比礁体的抗压强度。结果表明,各比例礁体中氮、磷的溶出规律基本符合线性模式(R20.73);各混合比礁体中营养盐的溶出效果符合缓释肥的释放规律,可持续向周边水体中溶出含有氮、磷的营养物质;铵盐的溶出效果随淤泥含量的增加呈上升趋势,且各混合比礁块之间有极显著差异(P0.01);磷酸盐的溶出效果随淤泥含量的增加呈上升趋势,但各混合比礁块之间并无显著差异(P0.05);此外,礁体的抗压强度随淤泥含量的增加呈下降趋势。该研究可为滩涂淤泥在人工鱼礁制作和人工藻场增殖中的应用提供理论依据和技术参考。     

浙江嵊泗人工鱼礁区小黄鱼生长特征与资源合理利用的初步研究

人工鱼礁是放置于海底以影响有关海洋生物资源的物理、生物或社会经济过程的人工设施, 具有修复生态环境、保护渔业资源的功能。本文根据2004年10月人工鱼礁拟投海域本底调查资料以及2005~2007年跟踪调查资料, 分析了小黄鱼的平均体长、平均体重、体长组成和体重组成随时间的变化趋势; 根据投礁前(2004年10月)和投礁后(2005年、2006年和2007年)的调查资料, 求解了小黄鱼的体长体重关系式和生长方程, 计算了体重生长的拐点年龄、临界年龄和总瞬时死亡率, 估算了人工鱼礁区小黄鱼的资源量。结果表明: 投礁后小黄鱼的平均体长和体重均呈上升趋势, 优势体长组和体重组均向高值移动; 同等体长情况下由投礁后体长体重关系式估算的体重比用投礁前的体长体重关系式估算的值大; 投礁后小黄鱼个体生长方程的参数L∞、W∞、K值分别从投礁前的140.5 mm、36.5 g和0.28 a^-1增加到186.0 mm、118.5 g和0.36 a^-1; 投礁后体长与体重生长速度与投礁前相比有所增大, 且体重生长的拐点年龄从投礁前2.55 a提高到2007年的2.58 a; 小黄鱼种群生物量增长的临界年龄从投礁前的3.21 a提高到3.77 a; 小黄鱼种群的总瞬时死亡率从投礁前的1.065 a^-1减小到0.75 a^-1; 鱼礁区小黄鱼资源量约131.5 t。并对人工鱼礁区小黄鱼生长特征和资源管理进行讨论。     

冰雹冲击下塑料薄膜的损伤分析

塑料薄膜的力学性能分析是薄膜结构设计的主要方向。该研究采用试验和数值模拟结合的方式分析了冰雹冲击下塑料薄膜的破坏形式和损伤规律,并通过试验结果验证了数值模拟方法的有效性。通过数值模拟对冰雹在不同尺寸、不同冲击角度下单次和二次冲击塑料薄膜进行了分析,此外对薄膜厚度和两层薄膜之间的间距的影响进行了分析。结果表明：1）0.12 mm厚度的塑料薄膜可抵挡直径10 mm以下的冰雹冲击。但冰雹尺寸在30 mm以上时,塑料薄膜因拉伸应力波的作用导致薄膜发生破坏。2）冰球二次冲击塑料薄膜时会造成应力波的叠加,导致薄膜的加速破坏。3）在0°、30°、60°这3种冲击角度下,冰球冲击角度为60°时造成薄膜的破坏面积最大。4）双层薄膜的破坏面积随薄膜之间的间距增大而增大,当双层薄膜的间距控制在5 mm内可实现双层薄膜抗冰雹冲击效果优于厚度相同的单层薄膜。分析结果表明：改进薄膜结构的抗拉强度是提高薄膜抗冰雹冲击能力的主要方向。该研究可为薄膜结构设计和薄膜损伤分析提供参考。     

果蔬冷库进货期间货物温度稳定性的影响因素

温度是果蔬贮藏环境最重要的参数。为了研究果蔬进库过程中影响货物温度稳定性的因素,该文以西安某苹果冷藏库为研究对象,建立冷库环境三维非稳态数值求解模型,模拟了进货过程中新进货物摆放间距、进货温度和进货量对达到贮藏条件货物温度稳定性的影响。模拟结果表明,在实际运行管理中,存在适宜的进货温度和进货量,可使苹果贮藏环境受进货过程影响最小,进货效率最高;增大进货间距可以减小对货物温度场的影响,进货摆放间距并不是越大越好。该文研究的冷库,进货过程中货物应先预冷到3℃再进库,进货摆放间距为0.5 m,进货量不大于10%。     

新疆砾石地葡萄滴灌带合理设计及布设参数的数值分析

为了摸清新疆含砾石复杂土壤条件下土壤水分运动规律,优化葡萄滴灌系统设计中的各项设计参数及合理布设,该文通过田间交汇试验确定合适的滴头间距为30 cm,并借助Hydrus-2D数值模型确定了土壤水力参数,同时运用该数值模型模拟了不同滴头流量和滴灌带水平间距布设形式下地表滴灌土壤水分分布特征。根据土壤湿润体特征结合葡萄根系分布规律,确定新疆砾石地葡萄滴灌系统合理的滴头流量为2.5～3.0 L/h,滴灌带水平间距为60 cm。该结果可为新疆砾石地复杂土壤葡萄滴灌系统的科学设计和田间合理布设提供参考。     

不同进口高度排水管道用涡流装置截流特性模拟与试验

为研究不同进口高度h的涡流截流装置的截流特性,选用瞬态不可压缩流动的N-S方程和重整化群RNG k-ε湍流模型,采用欧拉模型中的VOF(volume of fluid)法对涡流截流装置进行了数值模拟,分析了进口高度h对涡流截流装置截流特性、截流效率的影响,并且研究了涡流装置内部流场分布特性,同时对涡流截流装置的截流特性进行了试验验证。结果表明,进口高度越小,截流能力越强;涡流截流装置的截流效率,随着高度h增大先减小后增大,转折点在3h/5~4h/5之间;当进口宽度固定时,为了保证不发生溢流或者堵塞,且能够实现较好截流,涡流截流装置的进口高度应选择4h/5~5h/5之间,此时,涡流装置的进口截面面积大于出口截面面积。涡流截流装置的截流主要是因为在装置内部形成了局部低压,静压力转换为流体运动的动压力,使流体产生高速旋流,发生了旋流截流。该研究可为城市污水截流装置提供新的可选设计方法,降低污水溢流或者内涝发生率。     

采用拦沙坝防护的浅基桥墩局部冲坑三维流场数值模拟

采用数值模拟的方法,针对典型工程,对桥墩周围河床局部冲刷的三维流场进行了研究.通过将数值模拟所得流速场和物理模型中用ADV流速仪在实体模型中的鼍测结果进行对比和相互验证,结果较为吻合,同时分析了流场分布及不同方向流速对冲坑形成的作用.本文所采用的桥墩局部冲刷流场数值模拟计算方法对于深入研究桥墩局部冲刷及复杂边界流场理论具有一定的参考价值,所得流速场分布结果为浅基桥梁工程防护设计提供了参考依据.     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.