再论波动方程反演波速问题——波的反射与透射公式

本文是文[1]的续篇,讨论由波动方程(?)Q/(?)t~2=v~2(x)△Q 反演波速v(x)的方法是否近似可用。作者指出,在非均匀介质条件下用此波动方程不能正确描述波的传播特性,因它不能保证弹性力在间断面上连续。以双层介质为例,分别从此方程及原始波动方程出发推导波的反射与透射公式,得到不同的反射系数与透射系数表达式。二者相差很大,不可能是近似关系,因此从波动方程直接反演波速函数的方法是不可取的。     

对可控硅调压整流电路若干问题的分析

本文比较了两种可控硅整流电路,在这两种电路中把反并联可控硅接入阳极变压器。文章介绍了电路的过压和过流的保护方法并给出了电路的计算公式和经验数据。     

Multiple statistical approaches for the discrimination of mangrove species of Rhizophoraceae using transformed field and laboratory hyperspectral data

This study aims at discriminating eight mangrove species of Rhizophoraceae family of Indian east coast using field and laboratory spectra in spectral range (350–2500 nm). Parametric and non-parametric statistical analyses were applied on spectral data in four spectral modes: (i) reflectance (ii) continuum removed, (iii) additive inverse and (iv) continuum removed additive inverse. We introduced continuum removal of inverse spectra to utilize the advantage of continuum removal in reflectance region. Non-parametric test gave better separability than parametric test. Principal component analysis and stepwise discriminant analysis were applied for feature reduction and to identify optimal wavelengths for species discrimination. To quantify the separability, Jeffries–Matusita distance measure was derived. Green (550 nm), red edge (680–720 nm) and water absorption region (1470 and 1850 nm) were found to be optimal wavelengths for species discrimination. The continuum removal of additive inverse spectra gave better separability than the continuum removed spectra.     

降雨资料Kriging与IDW插值对比分析—以漓江流域为例

降水空间化信息在很多领域都具有重要意义,而进行空间插值方法形成降水空间化信息是当代较为常用的方式。面对众多的插值方法其插值精度成为我们是否采用的关键,就kirging插值法与IDW(Inverse Distance Weighting)插值进行研究以探讨其插值效果,为此类科学研究提供依据。研究以漓江流域内各气象站点降水统计资料为基础分别采用上述两种方法进行插值处理,通过与预留实测站点比较评判方法的插值效果的优劣。结果表明,多年月平均降水量作为时间步长时,降水丰沛的月份使用kriging插值法较优于IDW插值法,而枯水月份则使用IDW插值法较优于kriging插值法。     

梯级水库设计洪水最可能地区组成法计算通式

利用Copula函数建立各分区洪水的联合分布,基于联合概率密度最大原则,推导得到最可能地区组成法的计算通式,并用来推求梯级水库下游断面的设计洪水。选择清江流域水布垭-隔河岩-高坝洲梯级水库为例,开展了验证和方法比较研究。结果表明:最可能地区组成法计算得到的设计洪水值位于同频率地区组成法多方案计算结果的区间之内;受清江梯级水库调洪的影响,宜都断面设计洪水的削峰率十分显著,最可能地区组成法推求100年一遇设计洪水的削峰率达到30.2%。该法具有较强的统计基础,组成方案唯一,结果合理可行,为复杂梯级水库设计洪水的计算提供了一种新途径。     

流速仪法测流最小水深计算公式推导

在<河流流量测验规范>中,规定了流速仪法测流垂线、流速测点的分布位置和布置测点时的最小水深,[1]也有这方面的刊载,并列举了部分计算公式,但公式考虑不够全面,而且还不符合规范要求.本文依据规范,按流速仪测点布置情况,分析推导出了具体完整的计算公式,并对测点布置方案选择提出了相应的建议.     

Parameter identification for lined tunnels in a viscoplastic medium

This paper is dedicated to the identification of constitutive parameters of elasto‐viscoplastic constitutive law from measurements performed on deep underground cavities (typically tunnels). This inverse problem is solved by the minimization of a cost functional of least‐squares type. The exact gradient is computed by the direct differentiation method and the descent is done using the Levenberg–Marquardt algorithm. The method is presented for lined or unlined structures and is applied for an elastoviscoplastic constitutive law of the Perzyna class. Several identification problems are presented in one and two dimensions for different tunnel geometries. The used measurements have been obtained by a preliminary numerical simulation and perturbed with a white noise. The identified responses match the measurements. We also discuss the usage of the sensitivity analysis of the system, provided by the direct differentiation method, for the optimization of in situ monitoring. The sensitivity distribution in space and time assess the location of the measurements points as well as the time of observation needed for reliable identification. Copyright © 2002 John Wiley & Sons, Ltd.     

Pile driving formulas based on pile wave equation analyses

Pile driving formulas, which directly relate the pile set resulting from a hammer blow to the static load capacity of the pile, are often used to decide whether a pile will have the required design capacity. However, existing formulas do not consider soil or pile type, and do not, in general, reliably predict pile capacity. In this paper, an advanced model for dynamic pile driving analysis was used to develop accurate pile driving formulas. The proposed driving formulas are validated through well-documented case histories. Comparisons of predictions from the proposed formulas with results from static and dynamic load tests show that they produce reasonably accurate predictions of pile capacity based on pile set observations.     

正、反演结合对川东石炭系储层地震响应特征的分析

川东地区石炭系碳酸盐岩储层是油气勘探开发的重点及难点储层之一。该储层以厚度小且变化大、低孔、低渗、非均质特点强为特征；地震响应上表现为典型的薄层响应特点。这里综合考虑了石炭系储层和上覆梁山组地层不同的地质特征，建立了地质、测井分析控制下的精细模型及正、反演，探讨了檀木场气田石炭系储层的地震响应特征。其正演结果表明，梁山组地层对石炭系的地震响应具有重要的影响，时差较振幅更为敏感。在正演结论指导下，运用考虑了时差和梁山组地层的初始模型，获得了较高精度的反演结果。     

直流电阻率法与工作面透明化

通过先进的勘探设备与技术实现综采工作面的透明化,使煤层信息更加全面、准确,可为综采工作面的智能化生产奠定坚实的基础。直流电阻率法是矿井物探常用方法,其稳定性好、抗干扰能力强,对低阻体和高阻体都有灵敏的反映能力,因此直流电阻率法是实现工作面透明化的关键手段之一。为探究直流电阻率法在工作面透明化中的应用效果,对工作面探明含水构造、巷道迎头超前探测等问题,分别使用不同的工作方法对两种问题的响应特征进行三维正、反演。结果表明在对应的工作方法下得到的三维直流反演数据分布规律与初始模型基本一致,有良好的高、低阻体区分能力。对实际工程中直流电阻率法在工作面透明化中的应用有一定指导作用。