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1.
针对现实中土壤水分含量测定困难的问题,应用回归分析方法,找到反映土壤水分含量的相关因素,推导出回归方程,从而计算出土壤水分含量.这样简便了测定方法,便于在实际中运用.  相似文献   

2.
黄媛  陈晓春 《经济数学》2019,36(4):75-81
基于1997-2016年中国30个省级地区的数据,建立面板分位数回归模型考量对外贸易与经济增长对不同分位水平二氧化碳排放的影响.研究发现:在各分位点对外贸易对碳排放的影响为负,但仅在高分位点显著,并且对外贸易的减排效应表现出随碳排放量增加而增加的趋势.经济增长在50%分位点以外的其他分位点对碳排放具有显著的促进作用,但环境库兹涅茨假说只在低排放省份和高排放省份有效;进一步研究显示,对外贸易通过促进经济增长对碳排放产生的正向间接影响大于负向直接影响,对外贸易总体上加剧了环境污染,验证了"污染天堂假说".  相似文献   

3.
为了研究水中悬浮隧道在近场非接触爆炸荷载作用下的动力响应规律,将悬浮隧道简化为等截面等刚度的Bernoulli-Euler弹性支撑梁,建立悬浮隧道在爆炸冲击作用下的动力学模型,使用Galerkin法求解振动微分方程,结合一个悬浮隧道待建工程对其进行参数分析,讨论炸药量、爆心距、锚索竖向刚度对位移、速度、加速度的影响规律,并利用其结果对隧道和人体进行损伤分析.结果表明:爆心距对悬浮隧道运动学参数的影响显著,就位移而言随爆心距的增加隧道最大位移近似呈反比例下降趋势,与10 m爆心距相比,20 m和30 m工况下位移分别下降了50.7%,66.6%;炸药量对悬浮隧道运动学参数的影响显著,就位移而言随炸药量的增加隧道最大位移近似呈低阶幂函数上升趋势,与20 kg炸药量相比,40 kg和60 kg的峰值位移分别增加了29.8%,51.3%;锚索竖向刚度对悬浮隧道运动学参数的影响显著,就位移而言随锚索刚度的增加隧道的最大位移近似呈阶梯状下降趋势,与5×10~5 N/m的锚索刚度相比,5×10~6 N/m和5×10~7N/m工况下的隧道最大位移分别下降了53.0%,86.2%,但锚索刚度存在一个高效作用区间,当刚度在区间内,能显著地改变隧道管体的位移,当处在区间外(或大或小)时,对位移的影响不明显.  相似文献   

4.
在"产品包邮"策略下,考虑电商平台服务水平以及物流成本的影响,构建了分散决策和联合决策的电商供应链运作模型,研究了最优决策并设计了"佣金联合物流价格"协调机制,最后采用数值算例证明了结论.研究表明:1)分散决策下,销售价格随佣金和物流成本的增加而增加;服务水平随佣金的增加而提升,但与物流成本的变化无关;物流费用随佣金的增加而减少,随物流成本的增加而增加;制造商以及物流运营商的利润随佣金和物流成本的增加而减少;电商平台的利润随佣金的增加而增加,随物流成本的增加而减少.2)联合决策下,销售价格和服务水平与佣金的变化无关;但是销售价格随物流成本的增加而增加;服务水平随物流成本的增加而下降.3)联合决策是系统最优的一种运行模式,与分散模式相比,产品销售价格较低,电商平台的服务水平较高,电商供应链系统的总利润较高.借助设计的"佣金联合物流价格"协调机制可以实现这种模式.  相似文献   

5.
研究管输条件下胶凝原油颗粒的融化特性对原油集输及停输再启动等具有重要的意义,基于宽相变区,采用数值分析方法研究了球形胶凝原油颗粒在管道中的融化特性.利用Fluent软件,模拟分析了油水温差为40、50、60°、水流速度为0.1、0.2、0.3m/s、半径为5、10、15mm胶凝原油的温度场及液相云图,得到不同初始条件下球形胶凝原油的总融化时间及温度变化曲线.结果表明:受导热机制作用,原油为同心融化;原油中心附近三个监测点的融化过程分为五个阶段,且相变前后换热速率发生显著变化;颗粒半径每增加5mm原油融化时间增加的幅度升高、油水温差每增加10°原油融化时间减少的幅度降低、水流速度每增加0.1m/s原油融化时间减少的幅度升高.  相似文献   

6.
研究的是唐家山地震次生灾害引发的堰塞湖问题.首先对数字高程地图进行等高图像分析求解了堰塞湖不同高程水位对应的湖区面积,建立了蓄水量体积与堰塞湖水位高程的离散化模型,然后建立了神经网络模型和多元线性回归模型研究了北川降雨量与堰塞湖入库流量的关系,继而求解得到不同降雨量下每日堰塞湖水位高程.在研究泄洪过程时,首先通过对泄洪过程和溃坝过程内在机理的研究分别建立了正交多项式逼近模型和仿真模型得到溃坝时的溃口流量随时间变化的关系,继而分析求解得到溃坝时其他参数随时间变化的关系.针对淹没区的问题,综合数字高程地图和行政区域地图,利用数字地图计算了洪水到达各被淹没区域的时间,淹没范围,以便于确定撤离方案.  相似文献   

7.
说明:本卷含超量题满分110分,考试时间100分钟·一、选择题(在下列各题的四个备选答案中,只有一个是正确的,请把你认为正确的答案的字母代号填入括号里.本大题每小题2分,满分20分)1、一个圆桶,底面直径为9cm,高12cm,则桶内所能容下的最长木棒为()·A.10cmB.15cmC.18cmD.20cm2、  相似文献   

8.
脑内有数种内源性吗啡样物质,它们的分布和功能意义不尽相同.为阐明内源性吗啡样物质与针刺镇痛的关系有必要对它们分别进行研究.本文采用灵敏和专一的放射免疫分析法测定了家兔和大白鼠在针麻过程中各脑区及脑脊液中两种脑啡肽的含量变化.主要结果为:(1)针刺镇痛过程中下丘脑及纹状体两种脑啡肽均明显升高;(2)家兔侧脑室注射杆菌肽能够显著增强针效和提高脑内及脑脊液中脑啡肽的含量;(3)蛋白合成抑制剂环己亚胺可以削弱针刺升高脑啡肽含量的作用,说明加速生物合成是针刺增加脑啡肽含量的机制之一;(4)手术游离下丘脑后大白鼠电针效应削弱,提示下丘脑参与了针刺镇痛过程.  相似文献   

9.
利用已建立的四能级理论模型对提出的Cs Sr中的两个激光感生碰撞过程进行了数值计算 ,得到了碰撞跃迁几率随碰撞参数的变化关系及碰撞截面随转换激光失谐量的变化关系 ,并与三能级近似理论模型的计算结果进行了比较 .通过比较四能级理论与三能级近似理论模型的计算结果 ,进一步证实了理论的分析 :当 |ω2 1|值与 |ω43 |相近时 ,三能级理论的计算结果将存在着很大的误差 ,而四能级理论模型则适合于计算各种条件下的激光感生碰撞过程 .  相似文献   

10.
首先计算了四个 n 值命题逻辑系统L*,Luk,G(o)d及Ⅱ中一个典型公式户p1→p2真度;然后比较了公式p1→p2在这四个逻辑系统中真度的大小并分析了真度差异的原因;最后,研究了每个逻辑系统中公式p1→p2的真度随 n 变化的情况.  相似文献   

11.
Depth variations of environmental tritium and of soil moisture in the unsaturated zone of the semi-arid alluvial tracts of northern Gujarat (India) are measured and utilised to evaluate vertical groundwater recharge. Results obtained from the two different experiments carried out at an interval of two years are found to be in fair agreement. An average of recharge amounting to about 5 per cent is indicated. The observed depth variation of tritium gives support to the view that the movement of soil moisture in this region is layered.  相似文献   

12.
The paper deals with the study of rate of soil moisture movement and recharge to groundwater system at Indian Agricultural Research Institute (IARI) farm for the years 1973, 1974 and 1975. The utility of artificially injected tritium, experimental techniques adopted and a quantitative determination of recharge and moisture movement rates are discussed. Corrections for upward movement of moisture after the end of monsoon have been used to calculate the average rates of water movement below the injection level and groundwater recharge. Average rates of soil moisture movement and recharge are 9.4 mm/d and 27.4% (193 mm) of monsoon precipitation for three years respectively. Under favourable conditions the diffusion coefficients for soil water system are calculated assuming Gaussian distribution of tritium concentrations in the soil profiles. The average value of diffusion coefficient is 2.5 × 10?5 cm2/s for the sandy loam soils. The variation in recharge is mainly due to inherent variability in soil physical properties and vegetative cover. The technique is not found reliable for higher water table conditions on account of lateral flow.  相似文献   

13.
In this work we present a mathematical model describing the coupled heat and moisture transport in paper. The model is solved numerically and the numerical solution is used to study the interdependency of the moisture and temperature distribution in paper. The results show that variation with temperature of the saturated water vapor concentration and the sorption isotherm parameters are both important for inducing moisture desorption. It is also found that for steep relative humidity ramps moisture sorption generates temperature increments that slow down the sorption process itself. The model is also used to study the moisture gradients in a paper sheet inside a printer from Océ Technologies, which contains a warm print surface. The results predict changes in moisture content of only 0.2%, which suggests that no deformations are induced on the printed sheet.  相似文献   

14.
The downward movement of water in the soil due to 1971 monsoon precipitation and supplemental surface irrigation has been traced at about forty-five sites in Western Uttar Pradesh, using a thin layer of moisture tagged with tritiated water. The tritiated layer was found to move down to different depths at different sites. The movement, averaged over the forty sites is found to be 96 cm, indicating that the average recharge for the year 1971 (a year of normal monsoon) was 21.5 cm of water.  相似文献   

15.
This paper utilizes Artificial Neural Networks (ANNs), standard Support Vector Regression (SVR), Least-Squares Support Vector Regression (LS-SVR), linear regression (LR) and a rain rate (RR) formula that meteorologists use, to estimate rainfall. A unique source of ground truth rainfall data is the Oklahoma Mesonet. With the advent of the WSR-88D network of radars data mining is feasible for this study. The reflectivity measurements from the radar are used as inputs for the techniques tested. LS-SVR generalizes better than ANNs, linear regression and a rain rate formula in rainfall estimation and for rainfall detection, SVR has a better performance than the other techniques.Mathematics Subject Classification: 30C40  相似文献   

16.
Rainfall forecasting by technological machine learning models   总被引:5,自引:0,他引:5  
Accurate forecasting of rainfall has been one of the most important issues in hydrological research. Due to rainfall forecasting involves a rather complex nonlinear data pattern; there are lots of novel forecasting approaches to improve the forecasting accuracy. Recurrent artificial neural networks (RNNS) have played a crucial role in forecasting rainfall data. Meanwhile, support vector machines (SVMs) have been successfully employed to solve nonlinear regression and time series problems. This investigation elucidates the feasibility of hybrid model of RNNs and SVMs, namely RSVR, to forecast rainfall depth values. Moreover, chaotic particle swarm optimization algorithm (CPSO) is employed to choose the parameters of a SVR model. Subsequently, example of rainfall values during typhoon periods from Northern Taiwan is used to illustrate the proposed RSVRCPSO model. The empirical results reveal that the proposed model yields well forecasting performance, RSVRCPSO model provides a promising alternative for forecasting rainfall values.  相似文献   

17.
Conclusion The above-developed method of studying the effect of uniaxial compressive and tensile loads on moisture absorption in polymers was tested on epoxy binder EDT-10. It was established experimentally for this material that tensile stresses up to 50 MPa significantly increase the equilibrium moisture content (up to 20% of the initial value). There is a corresponding increase in the rate of moisture absorption during the initial stage of the sorption process — up to 80% of the initial value. No changes in the diffusion coefficient were seen in this case. The application of compressive stresses of up to 40 MPa also had no effect on the kinetics of moisture absorption.Deceased.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 1, pp. 110–115, January–February, 1993.  相似文献   

18.
豫南山区落叶阔叶林生态系统水量平衡研究   总被引:2,自引:0,他引:2  
采用水量平衡方法和集水区技术,利用2006年至2009年的观测资料,研究了豫南低山区落叶阔叶林生态系统的水量平衡.结果表明:系统年平均输入降水为1200.2 mm,其中79%集中在4-9月,主要支出项为径流和蒸散,分别为444.4 mm和754.3 mm,各占降水的37.0%和62.9%,土壤蓄水变化量仅为1.5 mm;林冠层对降水的分配中,林冠截留量407.4 mm,截留率33.9%,穿透水和树干茎流量分别为761.7 mm和31.1 mm,各占降水量的63.5%和2.6%.集水区年均径流输出总量为444.4 mm,其中地下径流420.9 mm,地表径流仅23.5 mm.落叶阔叶林生态系统具有良好的水文生态效应。  相似文献   

19.
对近四十五年来中国漠河的气温变化作了一个初步分析.根据中国漠河1961~2005年逐日平均、最高、最低气温资料,求得了相应的年均温、年均高温和年均低温,分别对它们进行了线性拟合,结果表明它们在这45年都有所升高,并且由t检验得出线性趋势都是显著的.之后用线性回归模型拟合了年均温与年均高温和年均低温的关系,得出了拟合方程,并由F检验说明了线性回归关系的显著性.最后又采用变系数回归模型的局部线性拟合方法拟合了年均温与年均高温和年均低温的变化关系,从而揭示了年均高温和年均低温对年均温的影响随时间变化的规律,对研究年均温升高的原因具有一定的参考意义.  相似文献   

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