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81.
结合工程实例介绍了灌注桩工程中有关成孔体积、混凝土灌注量与钢筋笼重量等内容的精确计算公式,这些公式对灌注桩前期概算及施工后期工程量计算具有指导意义。 相似文献
82.
Experimental modelling of an aggrading braided river has allowed investigation of the relationship between the frequency of channel avulsion ( A f ), the duration of time that the braidplain is occupied by flow, the spatial pattern of braidplain sedimentation and how these respond to a change in sediment supply ( S s ). Model results demonstrate a strong, positive relationship between S s and A f and that there is no downstream change in A f over the short braidplain distances ( ca 100 m) modelled herein. Although A f is strongly dependent on S s , the degree of channel switching does not influence the rate, or spatial pattern, of braidplain sedimentation. All experiments used a single, central input for water and sediment, and the channels occupied the centre of the alluvial basin for a longer period of time than the margins for all sediment supply rates and distances downstream. Despite this spatio-temporal pattern in flow occupancy, braidplain sedimentation rates were nearly uniform both downstream and across the basin, and increased at approximately the same rate as increases in S s . As a consequence, less frequent, and possibly short-lived, flows at the margins of the braidplain deposited and preserved more sediment per unit time in comparison with the centre of the basin where flow occupancy was higher. An approximate order of magnitude change in sediment supply resulted in only a factor of two change in bed slope, probably due to both an increase in channelization and adjustment of the channel form that maintained sediment transport through the basin. This result suggests that linear diffusion models are unlikely to be applicable in landscape evolution models that possess aggrading multi-thread rivers, which are capable of self-adjustment in channel number and form. 相似文献
83.
84.
We use a three-dimensional mixed-wet random network model representing Berea sandstone to extend our previous work on relative permeability hysteresis during water-alternating-gas (WAG) injection cycles [Suicmez, VS, Piri, M, Blunt, MJ, 2007, Pore-scale simulation of water alternate gas injection, Transport Porous Med 66(3), 259–86]. We compute the trapped hydrocarbon saturation for tertiary water-flooding, which is water injection into different initial gas saturations, Sgi, established by secondary gas injection after primary drainage. Tertiary water-flooding is continued until all the gas and oil is trapped. We study four different wettability conditions: water-wet, weakly water-wet, weakly oil-wet and oil-wet. We demonstrate that the amounts of oil and gas that are trapped show surprising trends with wettability that cannot be captured using previously developed empirical trapping models. We show that the amount of oil that is trapped by water in the presence of gas increases as the medium becomes more oil-wet, which is opposite from that seen for two-phase flow. It is only through a careful analysis of displacement statistics and fluid configurations that these results can be explained. This illustrates the need to have detailed models of the displacement processes that represent the three-phase displacement physics as carefully as possible. Further work is needed to explore the full range of behavior as a function of wettability and displacement path. 相似文献
85.
86.
为探明陆基养殖和离岸养殖尖吻鲈(Lates calcarifer)形态性状与体质量的关系及形态差异,在海南省陵水县室内车间及南沙美济礁深水网箱对同一批次15月龄尖吻鲈的体质量Y和头长X1、躯干长X2、体长X3、全长X4、体高X5、眼径X6、吻长X7、尾柄高X8、尾柄长X9等9个形态性状进行了测量,并进行了相关分析、通径分析和回归分析。结果显示,2个养殖条件下尖吻鲈在眼径和吻长等2个方面无显著差异,但在体质量、头长、躯干长、体长、全长、体高、尾柄高、尾柄长和体高与全长的比值等方面呈极显著差异(P<0.01)。陆基养殖尖吻鲈各主要性状间的相关关系达到显著(P<0.05)或极显著水平(P<0.01);除眼径X6与吻长X7无显著相关性外,美济礁离岸养殖尖吻鲈的其他各性状间的相关性达到显著(P<0.05)或极显著水平(P<0.01)。通径分析结果表明,陆基养殖群体的X4和X5对尖吻鲈体质量的直接作用达显著水平(P<0.05),而X3、X5和X9对美济礁离岸养殖群体体质量的直接作用达显著(P<0.05)或极显著水平(P<0.01)。决定系数分析显示,陆基养殖群体的X4和X5对体质量的共同决定系数之和为0.971,美济礁离岸养殖群体的X3、X5和X9对体质量的共同决定系数之和为0.864,说明2个尖吻鲈养殖群体的体质量分别主要由这些形态性状决定;通过逐步回归分析,建立了2个养殖群体尖吻鲈多元回归方程:Y陆基养殖=-1 128.61+3.143X4+6.418X5,Y美济礁离岸养殖=-2 054.81+7.377X3+9.196X5-10.041X9。研究表明,2种养殖模式下尖吻鲈的形态存在显著差异,美济礁离岸养殖尖吻鲈在体型上更具优势。 相似文献
87.
哑铃湾网箱养殖海域沉积物中的氮 总被引:1,自引:0,他引:1
2003年1月采集了哑铃湾网箱养殖区和非养殖区的沉积物柱状样,对氮的垂直剖面和沉积物-海水界面的通量进行了比较研究。结果表明,养殖区和非养殖区氮的垂直剖面和通量存在很大差异。交换态NH4 -N和交换态氮养殖区随深度的增加而降低,非养殖区随深度的增加而增加;非交换态氮养殖区与非养殖区差异不大;其它各形态氮一般随深度的增加呈降低的趋势。除非交换氮以外,各形态氮的含量表层和近表层养殖区明显高于非养殖区,养殖年限越长含量越高。氮的通量,主要是氨氮的通量,养殖区为80.54mg/(m2.d),非养殖区仅为5.58mg/(m2.d),养殖较长时间现已停养的海区也达到了86.18mg/(m2.d)。 相似文献
88.
Numerical simulation of the influences of sinker weight on the deformation and load of net of gravity sea cage in uniform flow 总被引:11,自引:0,他引:11
1IntroductionThe fish farming and aquaculture industry areexpanding and the demand for suitable locations forfish farms is increasing.In the future,more of thefish farms will be located offshore,as the number ofsuitable nearshore locations is limited.Futu… 相似文献
89.
In light of growing urban traffic, car parking becomes increasingly critical for cities to manage. As a result, the prediction of parking occupancy has sparked significant research interest in recent years. While many external data sources have been considered in the prediction models, the underlying geographic context has mostly been ignored. Thus, in order to study the contribution of geospatial information to parking occupancy prediction models, road network centrality, land use, and Point of Interest (POI) data were incorporated in Random Forest (RF) and Artificial Neural Network (ANN, specifically Feedforward Neural Network FFNN) prediction models in this work. Model performances were compared to a baseline, which only considers historical and temporal input data. Moreover, the influence of the amount of training data, the prediction horizon, and the spatial variation of the prediction were explored. The results show that the inclusion of geospatial information led to a performance improvement of up to 25% compared to the baseline. Besides, as the prediction horizon expanded, predictions became less reliable, while the relevance of geospatial data increased. In general, land use and POI data proved to be more beneficial than road network centrality. The amount of training data did not have a significant influence on the performance of the RF model. The ANN model, conversely, achieved optimal results on a training input of 5 days. Likely attributable to varying occupancy patterns, prediction performance disparities could be identified for different parking districts and street segments. Generally, the RF model outperformed the ANN model on all predictions. 相似文献
90.
网箱养殖海区底泥产芽孢细菌多样性 总被引:2,自引:0,他引:2
采用培养与16S rRNA基因序列比对的方法,对海水网箱养殖区底泥中的可培养细菌进行研究。结果表明,网箱正下方的产芽孢细菌比例高达50%,随着离网箱距离的增加,产芽孢细菌的比例明显降低,200m远时,其比例降至17%。从3个采样点分离纯化出91株产芽孢细菌,对其菌落形态、菌体形态的研究和部分菌株16S rRNA基因的DGGE带型和序列分析表明,91株产芽孢细菌中,有85株属于芽孢杆菌属(Bacillus)的10个种,25个发育型;6株属于盐芽孢杆菌属(Halobacillus)的1个种,3个发育型。芽孢杆菌属的B.marisflavi、B.baekryungensis、B.aquaemaris、B.pumilu等4个种为优势类群。此外,接近半数的产芽孢细菌能代谢含硫化合物,部分菌株能够还原硝酸盐或分解无机磷化合物,仅有3株菌具有亚硝酸盐还原作用。 相似文献