拟合方式对酸碱滴定法测定土壤酸缓冲容量准确性的影响

酸碱滴定法是测定土壤酸碱缓冲容量的主要方法。该方法中酸碱滴定数据点的拟合方式对测得的土壤酸碱缓冲容量结果影响极大。为此,采用酸碱滴定法对38个酸性紫色土的酸缓冲容量进行测定,分别采用4种拟合方式(整段多项式曲线拟合、突跃范围内线性拟合、酸段多项式曲线拟合、酸段线性拟合)对酸碱滴定数据进行拟合并计算得到土壤的酸缓冲容量,比较分析了不同拟合方式计算得到的土壤酸缓冲容量的可靠性和准确度。结果表明:不同拟合方式获得的酸缓冲容量差异较大;不同拟合方式获得的曲线方程的决定系数(R^(2))不同,酸段线性拟合方式得到的R^(2)显著低于其他三种拟合方式,计算得到的酸缓冲容量的准确度较低;整段多项式曲线拟合方式获得的方程对酸碱滴定数据的拟合度最佳。进一步分析发现,4种拟合方式计算得到的酸缓冲容量与交换性盐基总量(r_(1))和有效阳离子交换量(ECEC,r_(2))间的相关性由大到小依次为:整段多项式曲线拟合(r_(1)=0.486^(**),r_(2)=0.525^(**))、突跃范围内线性拟合(r_(1)=0.223,r_(2)=0.245)、酸段多项式曲线拟合(r_(1)=0.183,r_(2)=0.220)、酸段线性拟合(r_(1)=-0.219,r_(2)=0.002),整段多项式曲线拟合算得的酸缓冲容量与土壤当前所处的阳离子交换和硅酸盐缓冲关系最为密切。综合得出,4种拟合方式中,整段多项式曲线拟合计算得到的酸缓冲容量的可靠性和准确度最好,有助于土壤酸减缓冲性能的准确测定。

一类非线性灰色微分方程的拟合方式

给出了形如dxdt+axα=b的一类非线性微分方程拟合的形式 ,对于非负离散点列 ,根据离散点列的凹凸性 ,讨论了选取α的方法 ,然后确定未知参数a、b .

GPS水准拟合方式的统计分析及拟合方式的选择

结合工程实际 ,对几个测区已有的资料采用各种拟合方式所得的成果进行统计分析 ,发现同一个测区、同一组起算数据采用不同的拟合方式 ,与水准测得的成果有着显著的差异。为此 ,提出一些通过检验拟合结果以选择拟合方式来获得较为可靠的成果的方法。

基于改进弗雷歇算法的虚拟直流电机等效惯量计算

伴随高密度分布式电源接入,电网惯量水平持续下降,尤其是在新能源独立供电条件下,其惯量远远低于最低惯量需求。通过对端口换流器施加虚拟直流电机控制策略,可以利用控制参数灵活调整系统惯量,减少电网惯量差额,增强电网的稳定性。但该控制方法虚拟出的等效惯量大小暂不明确,虚拟惯量对等效惯量的影响也有待进一步探究。据此,文中首先在虚拟直流电机模型的基础上,利用小信号模型分析虚拟惯量与等效惯量对系统动态特性的影响,指出两者的惯量等效关系。其次,基于虚拟惯量与等效惯量的对应关系,提出一种利用弗雷歇算法度量电压曲线相似度的等效惯量计算方法,明确虚拟直流电机控制的等效惯量大小。然后,引入相关性约束与曲线特征约束,提出一种改进弗雷歇算法,保证等效惯量计算的正确性。最后,采用最优拟合方式实现惯量等效关系的函数化,给出虚拟惯量与等效惯量间的数量关系。仿真结果验证了文中所提等效惯量计算方法的有效性。

低渗透水平气井流入动态研究

借助数值模拟方法 ,结合我国最大的长庆低渗透气田实际 ,对低渗透气田水平气井的流入动态进行了研究 ,系统地分析了气藏流体、储层物性以及水平井性质参数对水平气井流入动态 (IPR曲线 )的影响 ,总结出相应规律。并将二项式IPR曲线与指数式IPR曲线相结合 ,提出了一种新型的水平气井IPR曲线拟合方式和预测模型。在长庆低渗透气田的应用结果表明 ,用该曲线形式和预测模型对水平气井流入动态的拟合结果明显好于二项式拟合方式 ,预测结果令人满意。

磷全尾砂胶结体强度规律的试验研究

以宜昌某磷矿山全尾矿为原料,设计了全尾砂充填胶结体的力学性质与料浆浓度、灰砂比和养护时间三因素关系间的试验方案,并制作灰砂比为1∶4~1∶10、料浆浓度为68%~75%的充填体试件,分别养护3、7、14和28d后进行单轴抗压强度试验,并通过线性、多项式和指数三种拟合方式探究强度与三因素间的定量关系。充填体强度与灰砂比表征出多项式函数关系,与料浆浓度表征出多项式函数关系,与养护时间表征出指数函数关系。强度随灰砂比减小而递减且递减趋势变缓,随料浆浓度增大而递增且递增趋势更明显,随养护时间增高而递增但递增趋势渐缓。该研究成果可为同类磷矿山全尾砂胶结充填物强度的确定提供参考。

GPS与重力测量在东海大桥高程控制测量中的应用

在东海大桥的高程控制测量中,最困难的是将上海陆地上的高程传递到小洋山岛,两者直线间距近30km,施工前又无中间平台可利用。将GPS测量与传统的重力测量相结合,通过选择合理的积分半径,采用拟合方式确定了大地水准面,完成了高程传递。通过全年潮位观测,验证了本次高程传递的精度是可靠的。

数字示波器计量校准与应用中须注意的若干问题

数字示波器的某些参数的测试结果在计量校准和实际应用中,采用不同的采用率、采样方式、拟合方式所得到的结果是不同的,这种差异在我们的计量校准和实际应用中是不容忽视的,必须加以考虑。本文就在用数字示波器进行计量校准和实际应用中进行信号测试时,选用不同的带宽、采用率、采样方式、拟合方式及打开通道数目的不同,对校准和测试结果的影响。

数字示波器计量校准与实际应用中若干问题讨论

本文就在用数字示波器进行计量校准和实际应用中进行信号测试时,选用不同的带宽、采样率、采样方式、拟合方式及打开通道数目的不同,对校准和测试结果的影响。

酸性紫色土盐基饱和度和pH值的关联分析及分类学意义

探讨酸性紫色土pH值和盐基饱和度(Base Saturation,BS)间的关联性,为酸性紫色土BS的估算及分类提供科学参考及建议.在重庆市采集24个典型酸性紫色土剖面的77个发生层土样,测定其机械组成、pH值、BS和有机质等理化性质,采用回归模型和BP神经网络两种模型,对pH值和BS数据进行拟合分析.回归模型的拟合结果表明,一元二次拟合方程的拟合效果优于一元线性方程拟合效果.BP神经网络模型中随着输入与BS相关数据类型的增加,拟合准确度更高.基于拟合模型,假设BS的取值为50%时,得到pH值的范围为5.11~5.21.采用一元二次拟合方程y=-0.02024x 2+0.34642x-0.74023(y为BS,x为pH值),能够较好实现酸性紫色土BS的估算,在开展紫色土系统分类高级单元划分时,建议优先采用BS<50%为“酸性”诊断标准,若需使用pH值为“酸性”检索条件,建议将原标准pH<5.5调整为pH<5.1.

汽车正向开发中车门玻璃曲面的设计与校核

研究了在全新车型正向开发过程中车门玻璃曲面的设计方法。介绍了两种不同的曲面拟合方式,并总结了其优缺点。同时,从人机工程、玻璃面升降空间、玻璃面透光高度等角度,对造型车门玻璃曲面的校核方法及评判标准进行了系统性地阐述。

示波器测量上升时间的动态误差评估

就使用示波器进行上升时间测量时,选用不同的带宽、采用率、采样方式、拟合方式及打开通道数目的不同对测量结果所产生的动态误差进行了评估,最后说明了探头、反射、非线性对测试结果的影响。

Woolen Textile Simulation by Synthesis Mapping

This paper proposes a new rapid and efficient method for woolen textile simulation- mapping synthesize. This method uses a stochastic function to simulate fuzz on some types of wool textile. The wool yarns are simulated on the basis of Phong illumination model. In order to obtain a visual effect of the wool textile with fuzz, the light intensity of fuzz is synthesized as a color parameter in the Phong illumination model after the yams have been simulated. The model of woolen textile with fuzz can be built eventually.With synthesis mapping methods, user can choose his favorite fuzz density on the wool by controlling some appropriate parameters.

Min-max partitioning problem with matroid constraint

In this paper, we consider the set partitioning problem with matroid constraint, which is a generation of the k-partitioning problem. The objective is to minimize the weight of the heaviest subset. We present an approximation algorithm, which consists of two sub-algorithms-the modified Edmonds' matroid partitioning algorithm and the exchange algorithm, for the problem. An estimation of the worst ratio for the algorithm is given.

Measuring Carbon Dioxide Sink of Betung Bamboo （Dendrocallamus asper （Schult f.） Backer ex Heyne） by Sinusoidal Curves Fitting on Its Daily Photosynthesis Light Response

Planting plant such as Betung bamboo （Dendrocalamus asper （Schult f.） Backer ex Heyne） is one of the best ways for reducing global warming effect. Betung bamboo is giant grass （Poaceae） which has been traditionally used by Indonesian people for construction material since a long time ago. Poaceae family commonly has better carbon sink ability than trees because of its Ca photosynthesis mechanisms, but bamboo sub-family （Bambusoideae） lacks the Ca photosynthetic pathway and anatomy. In the absence of this feature the maximum possible productivity of bamboos is unlikely to greatly exceed that of other bioenergy crops with C3 photosynthesis such as fast growing tree species. This research proposed a sinusoidal equation as a basic equation for plant＇s daily photosynthesis light response curve fitting. The sinusoidal equation was success for Betung bamboo＇s daily photosynthesis light response curve fitting （R2 〉 60%）. It had similar result in estimating carbon sink （82.35 kg/clump/year） compared to those which calculated by annual increment （69.01-107.82 kg/clump/year）. It is better to choose sinusoidal equation than quadratic or cubic Betung bamboo is a good choice to be planted in order to resist the global warming effect because it has superior carbon sink capability （82.35 kg/clump/year） than slow growing tree, and equal to fast growing tree species, besides many other advantages.

Simulation of Land-use Scenarios for Beijing Using CLUE-S and Markov Composite Models

This study investigated and simulated land use patterns in Beijing for the year 2000 and the year 2005 from the actual land use data for the year 1995 and the year 2000,respectively,by combining spatial land allocation simulation using the CLUE-S model,and numerical land demand prediction using the Markov model.The simulations for 2000 and 2005 were confirmed to be generally accurate using Kappa indices.Then the land-use scenarios for Beijing in 2015 were simulated assuming two modes of development:1) urban development following existing trends;and 2) under a strict farmland control.The simulations suggested that under either mode,urbanized areas would expand at the expense of land for other uses.This expansion was predicted to dominate the land-use conversions between 2005 and 2015,and was expected to be accompanied by an extensive loss of farmland.The key susceptible to land-use changes were found to be located at the central urban Beijing and the surrounding regions including Yanqing County,Changping District and Fangshan District.Also,the simulations predicted a considerable expansion of urban/suburban areas in the mountainous regions of Beijing,suggesting a need for priority monitoring and protection.

Evaluating instrumented Charpy impact strain signals using curve fitting equations

An effective and simple way to develop equations from impact strain signals was proposed.Little research has been performed in this area,but this equation is very important for evaluating input signals in finite element analysis impact tests and for obtaining additional information on material deformation and fracture processes under impact loading.For this purpose,dynamic impact responses were examined through signals obtained from a strain gauge installed on an impact striker connected to a data acquisition system.Aluminium 6061-T6 was used to extract strain responses on the striker during Charpy impact testing.Statistical analysis was performed using the I-kaz method,and curve fitting equations based on the equation for vibration response under a non-periodic force were used to evaluate the Charpy impact signals.The I-kaz coefficients and curve fitting equations were then compared and discussed with related parameters,such as velocities and thicknesses.Velocity and thickness were found to be related to the strain signal patterns,curve fitting equations and I-kaz coefficients.The equations developed using this method had R2 values greater than 97.7%.Finally,the constructed equations were determined to be suitable for evaluating Charpy impact strain signal patterns and obtaining additional information on fracture processes under impact loading.

Shear creep characteristics and constitutive model of limestone

The characters of limestone in weak interlayer of a high rocky slope in Xuzhou, China, are studied by shear static test and shear creep test. The results show that limestone specimens have attenuation creep properties and constant rate creep properties, almost have no accelerated creep properties. The exponential type empirical formula is selected to fit creep grading curves by polynomial regression analysis method, and the square sums of the fitting results residual are in the order of 10^(-7). Then grade creep curves at every shear loads are set up. Combining creep rate-time curve, the creep properties of limestone are analyzed. As the physical meaning of component model is clearer, the Poytin–Thomson model is set up. Through the least square method, the optimal parameters of Poytin–Thomson model are obtained,and the sums of squared residuals belong to 10^(-3)order of magnitude, which can meet the accuracy requirements of engineering calculation. So the Poytin–Thomson model can reflect the shear creep characteristics of limestone very well.

Polynomial Quasisolutions Method for Some Linear Differential Difference Equations of Mixed Type

The paper considers a scalar linear differential difference equation （LDDE） of mixed type x（t） = （a0 ＋ a1t）X（t） ＋ （b0 ＋ b1t）x（t - 1） ＋ （d0 ＋ d1tx（t ＋ 1） ＋ f（t）, t ∈ R, （＊） where f（t） = ∑n=0^F fn^tn. This equation is investigated with the use of the method of polynomial quasisolutions based on the representation of an unknown function in the form of polynomial x（t） = ∑n=0^N xn^tn. As a result of substitution of this function into equation （＊）, there appears a residual △（t） = 0（t^N）, for which an exact analytical representation has been obtained. In turn, this allows one to find the unknown coefficients xn and consequently the polynomial quasisolution x（t）. Several examples are considered.

Parameterization of height-diameter and crown radius-diameter relationships across the globe

The tree height-diameter at breast height(H-DBH)and crown radius-DBH(CR-DBH)relationships are key for forest carbon/biomass estimation,parameterization in vegetation models and vegetation-atmosphere interactions.Although the H-DBH relationship has been widely investigated on site or regional scales,and a few of studies have involved CR-DBH relationships based on plot-level data,few studies have quantitatively verifed the universality of these two relationships on a global scale.This study evaluated the ability of 29 functions to ft the H-DBH and CR-DBH relationships for six different plant functional types(PFTs)on a global scale,based on a global plant trait database.Results showed that most functions were able to capture the H-DBH relationship for tropical PFTs and boreal needleleaf trees relatively accurately,but slightly less for temperate PFTs and boreal broadleaf trees(BB).For boreal PFTs,the S-shaped Logistic function ftted the H-DBH relationship best,while for temperate PFTs the Chapman-Richards function performed well.For tropical needleleaf trees,the fractional function of DBH satisfactorily captured the H-DBH relationship,while for tropical broadleaf trees,the Weibull function and a composite function of fractions were the best choices.For CR-DBH,the ftting capabilities of all the functions were comparable for all PFTs except BB.The Logistic function performed best for two boreal PFTs and temperate broadleaf trees,but for temperate needleleaf trees and two tropical PFTs,some exponential functions demonstrated higher skill.This work provides valuable information for parameterization improvements in vegetation models and forest feld investigations.