基于经验模态分解提高太赫兹频率分辨率的方法

太赫兹频率分辨率是影响物质鉴别的重要因素,但是由于太赫兹时域光谱系统中存在器件反射,使得参考信号和测量信号出现多个反射峰,时域信号长度截断导致频率分辨率很低。为了去除反射峰的影响,提出基于经验模态分解去除时域反射峰,从而提高太赫兹频率分辨率的方法。通过与太赫兹主峰的互相关定位时域反射峰,计算反射峰的上下包络和求平均值,获取本征模函数并代替反射峰,增加时域信号有效长度,提高太赫兹频域分辨率。空气中水蒸汽的太赫兹透射谱实验结果表明,该方法具有自适应去除多个反射峰的能力,对太赫兹时域信号修复效果良好,频率分辨率提高了12倍,而且未丢失有用的吸收谱信息,吸收峰的位置和个数与真实谱一致,很好地保留了太赫兹谱的鉴别能力。     

Eigentime identity for asymmetric finite Markov chains

Two kinds of eigentime identity for asymmetric finite Markov chains are proved both in the ergodic case and the transient case.     

关于两类矩阵最佳逼近问题

１．引言与引理 设Ｒｍ×ｎ表示所有ｍ×ｎ阶实矩阵的集合;ＳＲｎ×ｎ是所有ｎ阶实对称矩阵的全体;ＯＲｎ×ｎ是所有ｎ阶实正交矩阵的全体;Ｉｎ是ｎ阶单位矩阵;ＡＴ是矩阵Ａ的转置;ｒａｎｋＡ表示矩阵 Ａ的秩;‖·‖是矩阵的Ｆｒｏｂｅｎｉｕｓ范数．此外,对于 　　　　,Ａ＊Ｂ表示 Ａ与 Ｂ的 Ｈａｄａｍａｒｄ积,其定义为　　　　　　　　　　　　　,现考虑如下问题： 问题 Ⅰ给定　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　,使得 　　　　　,求 问题Ⅱ给定 ,求 ,使得 本文运用矩阵对…     

线性流形上矩阵方程BTXB=F的双对称最小二乘解

1引言令R~(n×m)、OR~(n×n)、SR~(n×n)(SR_0~(n×n))分别表示所有n×m阶实矩阵、n阶实正交阵、n阶实对称矩阵(实对称半正定阵)的全体,A~ 表示A的Moore-Penrose广义逆,I_k表示k阶单位矩阵,S_k表示k阶反序单位矩阵。R(A)表示A的列空间,N(A)表示A的零空间,rank(A)表示矩阵A的秩。对A=(a_(ij)),B=(b_(ij))∈R~(n×m),A*B表示A与     

多孔二氧化钛对三氯甲烷光催化氧化的影响

报道 了以多孔 二氧化钛 为光催 化剂光催 化降解 水环境中 三氯甲烷 的一些 结果． 在所选定的实验 条件下 经１５ ｈ 光照, Ｃ Ｈ Ｃｌ３ 光催 化分解率 可达８０ ％ 左右 ． 此 结果 有利 于今 后进 一步 开展实用性 光催化 净化反应 器的研制     

A covariant representation of the Ball–Chiu vertex

In nonabelian gauge theory the three-gluon vertex function contains important structural information, in particular on infrared divergences, and is also an essential ingredient in the Schwinger–Dyson equations. Much effort has gone into analyzing its general structure, and at the one-loop level also a number of explicit computations have been done, using various approaches. Here we use the string-inspired formalism to unify the calculations of the scalar, spinor and gluon loop contributions to the one-loop vertex, leading to an extremely compact representation in all cases. The vertex is computed fully off-shell and in dimensionally continued form, so that it can be used as a building block for higher-loop calculations. We find that the Bern–Kosower loop replacement rules, originally derived for the on-shell case, hold off-shell as well. We explain the relation of the structure of this representation to the low-energy effective action, and establish the precise connection with the standard Ball–Chiu decomposition of the vertex. This allows us also to predict that the vanishing of the completely antisymmetric coefficient function S   of this decomposition is not a one-loop accident, but persists at higher-loop orders. The sum rule found by Binger and Brodsky, which leads to the vanishing of the one-loop vertex in N=4$N=4$ SYM theory, in the present approach relates to worldline supersymmetry.     

Numerical study of unsteady flow and heat transfer of circular tangential direction jets flowing over the inner cylinder surface in the annular chamber

In order to understand the dynamics of vortices on heat transfer, the unsteady flow field of tangential direction jets flowing in the annular chamber is numerically investigated by scale-adaptive simulation (SAS). The jet Reynolds number is 332,000 based on the jet’s diameter and inflow velocity for a specific geometric model. The analogy theory is used to obtain the convective heat transfer coefficient distribution on the hub surface. Spectral analysis via fast Fourier transform (FFT) is used to analyze frequency information that flows inside the chamber. The proper orthogonal decomposition (POD) method is performed on the velocity field in the chamber and the convective heat transfer coefficient on the hub surface using a snapshot method. The fast Fourier transform helps find the dominant frequency of the unsteady flow in the chamber. The time sequence of velocity fields on the radial plane shows the presence of cyclic flapping of the jet. The proper orthogonal decomposition analysis indicates that the unsteady periodic flow phenomenon in the chamber and unsteady heat transfer on the hub surface are mainly related to the dynamics of the counter-rotating vortices caused by the jet.     

基于Adaboost-SVR模型的我国碳排放强度分析与预测

首先对我国1960-2017年的碳排放趋势分5个阶段分析,发现虽然在不同时期存在波动,但长期来看,我国碳排放强度呈逐步下降趋势.然后对差分平稳后的序列数据建立Adaboost-SVR预测模型,采用RMSE、MAPE、MAE、MSE四个评价指标比较Adaboost-SVR模型与Adaboost-DT、SVR、BP神经网络对碳排放强度的预测精度.结果表明,组合模型明显优于其他3种模型,对于碳排放强度预测具有很高的可靠性.另外,通过使用Adaboost-SVR模型进行后续年份预测,发现我国未来碳排放强度总体将继续缓慢下降.最后,基于二氧化碳排放量的LMID分解结果,提出调整能源产业结构, 促进可再生能源利用等节能减排建议.     

A note on continuously decomposed evolving exchange economies

It is routine to demonstrate in the exchange economy framework that small changes of individual preferences and endowments always result in small changes of the derived excess demand functions as one should expect. Though being as desirable for reasons of the consistency of the whole approach, however, a precise proof of the converse direction so far is still open to question. The present paper shows that it is actually true. We use a decomposition method for aggregate excess demand functions developed by Mas-Colell which is derived from the well-known decomposition method developed by Sonnenschein and perfected by Debreu and Mantel. Our result fills in a notorious gap in the line of economic justification usually given for this decomposition, or disaggregation, method in that comparative static analysis would be restricted if the decomposition of excess demand functions would not be continuous.     

Schwarz domain decomposition for the incompressible Navier–Stokes equations in general co‐ordinates

This paper describes a domain decomposition method for the incompressible Navier–Stokes equations in general co‐ordinates. Domain decomposition techniques are needed for solving flow problems in complicated geometries while retaining structured grids on each of the subdomains. This is the so‐called block‐structured approach. It enables the use of fast vectorized iterative methods on the subdomains. The Navier–Stokes equations are discretized on a staggered grid using finite volumes. The pressure‐correction technique is used to solve the momentum equations together with incompressibility conditions. Schwarz domain decomposition is used to solve the momentum and pressure equations on the composite domain. Convergence of domain decomposition is accelerated by a GMRES Krylov subspace method. Computations are presented for a variety of flows. Copyright © 2000 John Wiley & Sons, Ltd.