Specific Features of Mycorrhizal Symbiosis Formation in the Ontogeny of Orchids of the Temperate Zone

The study of relationships between symbiotic fungi and germinating seeds of the Orchidaceae showed that the effect of a fungus on germination depends on the presence of seed dormancy and its pattern. The specificity of symbiosis varies widely. The development of symbiotic sprouts in situand in vitro differs only in the rate, whereas the morphogenesis of asymbiotic sprouts is characterized by several anomalies.     

REACH SCALE HYDRAULIC ASSESSMENT OF INSTREAM SALMONID HABITAT RESTORATION1

ABSTRACT: This study investigates the use of a two‐dimensional hydrodynamic model (River2D) for an assessment of the effects of instream large woody debris and rock groyne habitat structures. The bathymetry of a study reach (a side channel of the Chilliwack River located in southwestern British Columbia) was surveyed after the installation of 11 instream restoration structures. A digital elevation model was developed and used with a hydrodynamic model to predict local velocity, depth, scour, and habitat characteristics. The channel was resurveyed after the fall high‐flow season during which a bankfull event occurred. Pre‐flood and post‐flood bathymetry pool distributions were compared. Measured scour was compared to predicted shear and pre‐flood and post‐flood fish habitat indices for coho salmon (Oncorhynchus kisutch) and steelhead trout (O. mykiss) were compared. Two‐dimensional flow model velocity and depth predictions compare favorably to measured field values with mean standard errors of 24 percent and 6 percent, respectively, while areas of predicted high shear coincide with the newly formed pool locations. At high flows, the fish habitat index used (weighted usable area) increased by 150 percent to 210 percent. The application of the hydrodynamic model indicated a net habitat benefit from the restoration activities and provides a means of assessing and optimizing planned works.     

HICKORY CREEK DRY RESERVOIR: A COMPRAOMISE DESIGN FOR BOTH FLOOD CONTROL AND NATURAL AREA PROTECTION1

Abstract: The proposed Hickory and Spring Creeks Flood Control and Recreation Project of the Illinois State Division of Water Resources and the Will County Forest Preserve District is desinged to provide flood control for Joliet, Illinos, and areas of the watershed to the east of the city and to provide open-space recreational land upstream from the Hickory Breek Dry Reservoir embankement. A viable forest ecosytem in the reservoir flood pool following construction is of major importance to the project. Factors of the environment influencing tree distribution and flood tolerance and a process for determining the best operational design to provide both flood control and the maintenance of a natural streamside forest ecosystem are described.     

LOCAL FLOW ACCELERATIONS IN RIVERS1

The geometry and formation of and the energy dissipation in flow accelerations in short steep reaches have been assessed, the latter as to its contribution to the energy expenditure in a long channel reach. An analysis of river gradients, aerial photos and additional field surveys has shown that flow accelerations can (1) originate naturally and sequentially from bars across a channel and nonsequentially from channel abandonment and channelside deposits and (2) be induced by a bankside groyne.     

基于FLACS CFD的不同气油比油气混输管道泄漏火灾后果对比

不同气油比的油气混输管道泄漏后果危害形式和风险差异的准确判断对于管道泄漏应急处置至关重要。以中国西部某油田集输管道为研究对象,针对不同气油比管道泄漏的火灾危害进行了对比分析,构建了FLACS CFD模型,并研究了油气混输管道原油泄漏形成池火的火灾特征和影响范围,以及天然气泄漏形成喷射火的高温分布和影响规律。研究结果表明:应急处置应考虑不同气油比下池火与喷射火危害的差异。在油气混输管线泄漏10 min形成稳定火焰的场景中,气油比低于100 m3/t时,原油池火为火灾危险的主要影响因素;气油比高于200 m3/t时,天然气喷射火为主要影响因素;气油比超过250 m3/t,高温覆盖距离不再明显增加;40 m为此场景下混输油气泄漏喷射火致死距离上限,120 m为温度影响上限。     

基于模糊保护层的池火灾事故风险分析

为计算引发池火灾事故的风险值,提高事故风险的量化水平,判断现有风险控制措施是否满足风险容忍度的要求,为制定减缓风险措施提供依据,给出了新的池火灾风险评估模型。基于传统的保护层分析模型(LOPA),结合模糊集合理论,引入模糊风险矩阵进行风险评估,构建适用于引发池火灾事故的模糊保护层(fL OPA)风险分析模型。该模型的特点是将模糊逻辑和保护层分析结合,减少了传统保护层分析方法计算过程中的不确定性因素,引入严重度减少指数(SRI)概念,使严重度计算、风险评估更加准确。运用该模型对原油储罐泄漏池火灾事故风险进行分析,给出风险决策方案,判断现有保护措施是否能控制风险在可容忍范围内,实例验证了模型的可行性。     

受限空间脉冲细水雾灭火数值模拟

为研究脉冲细水雾灭火效果和灭火机理,采用FDS软件对连续和脉冲细水雾熄灭受限空间油盘火进行了数值模拟。通过模拟和理论分析确定了脉冲细水雾周期为8 s开启、8 s暂停,并设置了冷却和窒息两种灭火条件,对两种细水雾熄灭不同尺寸的柴油池火进行了研究。结果表明:连续细水雾无法熄灭直径15 cm和20 cm的小尺寸油盘火,对直径25 cm中尺寸油盘火的灭火机理为冷却,对直径为30cm和35 cm大尺寸油盘火的灭火机理为窒息;脉冲细水雾能够熄灭不同尺寸的油盘火,且灭火效率高,火焰熄灭均发生在喷头暂停喷水期间,灭火机理为水雾蒸发稀释氧气而窒息。     

大型原油储罐泄漏隔堤池火灾后果研究

为了研究储罐大孔泄漏后可能产生的隔堤局部面状液池火灾,以10万立方大型原油储罐为例,采用计算流体力学软件FLUENT和火灾模拟软件FDS计算储罐在真实泄漏场景下的液池区域,模拟发生隔堤池火的分布特征及对临罐热辐射影响。研究结果表明:储罐原油泄漏后将在隔堤内形成相对稳定面积的液池,在储罐不同方位处泄漏形成的液池面积与储罐壁距雨水收集槽长度相关;储罐正下方的隔堤池火对储罐造成的热辐射极大;风对临罐受到的池火热辐射强度影响明显,指向罐组中心方向的来风对临罐热辐射强度影响较大。     

Second organic aerosol formation from the ozonolysis of α-pinene in the presence of dry submicron ammonium sulfate aerosol

An indoor chamber facility is described for investigation of atmospheric aerosol chemistry. Two sets of α-pinene ozonolysis experiments were conducted in the presence of dry ammonium sulfate seed particle: ozone limited experiments and α-pinene limited experiments. The concentration of gas phase and particle phase species was monitored continuously by on-line instruments and recorded automatically by data sampling system. The evolution of size distribution was measured by a scanning mobility particle sizer ...     

川西米亚罗地区亚高山针叶林建群种云杉土壤种子库研究

对川西米亚罗地区天然亚高山针叶林云杉种群的种子雨和土壤种子库进行了研究 .结果表明 :云杉种子雨过程从 2 0 0 2年 10月初到翌年 1月初 ,种子雨雨量 (n)为 5 79.99± 110 .84粒 /m2 ,其中种子下落主要集中在 11月 ,占种子雨总量的 5 7.80 % .种子雨分布格局呈集群分布 .于 2 0 0 3年春季 (3月 )和夏季 (8月 )两次对该天然云杉林土壤种子库取样 ,土壤种子库大小分别为 4 72 .8± 74 .82粒 /m2 和 185 .5± 89.95粒 /m2 ;腐烂种子分别为 39.6 0± 13.2 4粒 /m2和 12 0 .0± 6 3.39粒 /m2 ,腐烂种子比例由 8.39%增加到 6 4 .6 9% ;空粒种子分别为 118.8± 4 4 .6 6粒 /m2 和 6 5 .5± 2 6 .4 8粒 /m2 ,所占比例从 2 5 .14 %增加到 35 .31% .两次取样结果都表明 ,种子库种子主要集中在枯枝落叶层 ,分别占6 6 .17%和 6 6 .0 3% ,0～ 2cm层占 2 4 .73%和 2 3.4 5 % ,2～ 5cm层占 9.10 %和 10 .5 1% .到 8月 ,土壤中几乎所有云杉种子都失去活力 ,说明云杉种子库属于Thompson和Grime定义的第Ⅱ类型 ,即土壤种子库仅在冬季存在 ,在春季萌发 .土壤中春、夏、秋季种子很少或几乎没有 .林下云杉幼苗在 2 0 0 3年 6月 3号开始出现 ,在 6月中旬左右到达出苗高峰 ,累计平均幼苗数 4 .35株 /m2 .在川西米亚罗地区天然