登录

双语推荐：四流球谐函数

进入期刊文章
为了在不大幅度增加计算成本的情况下提高大气辐射传输计算的精度，利用单层四流球谐函数结合多层二流累加法，构造了可用于多层大气的四流球谐函数算法。为了比较与其他辐射传输算法的差异，引入48流离散纵坐标算法作为比较标准，Eddington 近似、四流离散纵坐标算法作为比较对象。在真实大气廓线条件下，计算了晴空和有云大气顶向上辐射通量、地表向下辐射通量以及加热率廓线。得出以下结论：在晴空情况下，与作为标准的48流离散纵坐标法相比，Eddington 近似、四流离散纵坐标法和新构造的四流球谐函数方法加热率绝对误差都小于0.3 K／d；向上、向下辐射通量的相对误差分别小于1％和0.6％。这表明在晴空情况下，3种算法对加热率的计算精度差别不大；对辐射通量的计算精度，两种四流近似算法比传统的 Eddington 近似更为精确。在有云情况下，与48流离散纵坐标法相比，四流球谐函数和四流离散纵坐标法计算的云顶加热率相对误差小于1％，而 Eddington 近似计算的云顶加热率相对误差大于5％。结果表明：新构造的四流球谐函数算法可用于大气辐射传输模式，在不大幅度增加计算成本的同时，提高了晴空大气的整体辐射计算精度和有云大气辐射加热率的计算精度。
In order to increase the accuracy of radiative transfer calculation without increasing calculation cost,a method using the singleˉlayer fourˉstream spherical harmonic expansion approximation combining with the twoˉstream adding algorithm has been built in this paper.Then,the fourˉstream spherical harmonic expansion approximation was compared with the traditional Eddington approximation and the fourˉstream discrete ordinate approximation by using the 48ˉstream discreteˉordinate approxiˉ mation method as a standard reference.The results of the upward and downward radiative fluxes as well as the heating rates in the real atmosphere have been shown.For clear sky,the differences between the Eddington method,fourˉstream spherical harˉ monic expansion approximation,fourˉstream discreteˉordinate approximation,and the standard results are all less than 0.3 K/d for heating rates,and less than 1% and 0.6% for the upward and downward radiative fluxes,respectively.It shows tha

[ 可能符合您检索需要的词汇 ]

进入期刊文章
利用南极地区40多个GPS跟踪站2010年全年的实测数据,实现了极区电离层TEC建模,对多项式模型、广义三角级数函数模型、低阶球谐函数模型、改进的球谐函数模型以及球冠谐函数模型等五种电离层经验模型进行了比较,并评估了其在极区的适用性情况。结果表明,各个模型在极区都可以取得比较好的拟合精度,残差均值在0.1TECU以内,均方根误差在2 TECU以内。
Total electron content (TEC)were derived from GPS measurements collected from more than 40 continuously operating stations in Antarctica during 201 0,and then were modeled using five commonly used regional models:the poly model (POLY ),the generalized trigonometric series function model (GTSF ),the low-degree spherical harmonic function model (LSH),the adjusted spherical harmonic function model (ASHF)and spherical cap har-monic analysis (SCHA).The five models were compared with assessing their applicability in polar regions.The re-sults showed that all five models performed well in Antarctica,with 0.1 TECU of residual mean value and 2 TECU of root mean square error.

[ 可能符合您检索需要的词汇 ]

进入期刊文章
基于 ARGO 浮标的剖面数据，提出了八阶的 Chebyshev 多项式拟合方法，分别拟合温度、盐度和声速的深度梯度变化，并通过拟合多项式计算各个深度层的海水声速，实现观测数据的标准化。为了分析全球的三维声速场，提出了基于面球谐函数展开表示全球海水声速场的模型，并通过最小二乘拟合方法直接估计面球谐函数展开系数，计算结果显示面球谐函数表示的海水声速场模型的准确、直观。
ARGO profile data are discrete temperature and salinity gradients with depth,which cannot be directly used in global seawater temperature model and salinity model.In order to normalize the ARGO profile data,an eight-order Chebyshev polynomials fitting approach,which can calculate the temperature and salinity at any depth,is suggested.Because sound speed is a function of temperature,salinity and pressure of seawater,global sound speed field can be constructed by normalized ARGO profile data.Based on surface spherical harmonic function(SHF)expansion,a new global sound speed field model,which can be used to analyze the horizontal gradient in any direction,is proposed.By least square estimating,the coefficients of the SHF can be resolved at different depth,which can construct a three-dimension global sound speed field model.Numerical results show SHF-based global sound speed model has a very good precision and visualization.

[ 可能符合您检索需要的词汇 ]

进入期刊文章
采用球谐函数与有限元相结合的方法(即球谐有限元法),对二维介质内辐射换热问题进行研究。以规则和非规则形状几何体辐射问题为例,使用球谐有限元法可得到较准确的计算结果,且与其它数值计算方法(如球谐有限差分法、离散坐标有限元法等)相比具有以下优势:球谐有限元法方法简单,计算速度快,适用于大型工程应用;球谐有限元法可用于计算各种形状的几何体,计算应用范围广。
The spherical harmonics finite element method, which combines the spherical harmonics method and the finite element method together, has been applied to deal with two dimensional radiative transfer prob-lems. Taking the regular and irregular geometry cases as examples, better results are obtained with the spheri-cal harmonics finite element method. Compared with other numerical methods, such as the spherical harmon-ics finite difference method and the discrete-ordinate finite-element method, the spherical harmonics finite el-ement method has some advantages. Firstly, the method is simple and the calculation speed is fast, and it is ap-propriate for engineering application. Secondly, the spherical harmonics finite element method can be applied to all kinds of geometry shapes, the range of application is wide.

[ 可能符合您检索需要的词汇 ]

进入期刊文章
为了提高三轴光电跟踪系统的指向精度,针对三轴光电跟踪系统的光机结构提出了一种具有明确物理意义的指向误差修正模型。首先,根据四元数的旋转变化方法详细分析了各轴系误差对空间目标指向误差的映射关系表达式,然后,通过这些关系式建立三轴光电跟踪系统的指向误差修正模型。实验结果表明,该方法可以将有效的修正系统指向误差,且外符合修正精度高于球谐函数指向误差修正模型,同时该方法在装配调试阶段对预估指向精度具有一定的参考指导作用。
In order to modify the pointing error of three-axis optoelectronic tracking systems, a new method based on the optical-mechanical structure of three-axis systems was proposed. Firstly, related equations which show the impaction of axis errors to the pointing error of spatial target were analyzed based on the rotation transform theory of quaternion. Then, a new modification model of three-axis optoelectronic tracking system was obtained thought all the different equations. Experimental results show that the method can reduce the pointing error effectively, and the exterior-error modified capability of this method is higher than spherical-function modification model. At the same time, the method would have a certain reference guide to estimate the pointing precision during assemblage and debugging.

[ 可能符合您检索需要的词汇 ]

进入期刊文章
夹层板壳结构由于其优异的力学特性在工程中被广泛使用，但有关其非线性振动特性的研究还不够完善，其精确解答一般很难得到。本文对具有软夹心和极薄表层夹层矩形板的非线性自由振动方程进行简化，并将振型设成时间和空间函数的分离形式，时间函数取谐函数，空间函数未知。将假定的振型函数带入微分方程，得到对边简支梁式夹层板无量纲化的空间模态控制方程。采用修正迭代法和伽辽金法对其进行求解，得到了梁式夹层板振型的一个解析解，以及梁式夹层板非线性振动的振幅和振频的解析关系式，并进一步分析了夹层板剪切参数对非线性振动特性的影响。
The sandwich plates and shells are widely used in engineering because of their excellent mechanical characteristic. How-ever, researches about their nonlinear vibration characteristics, of which the accurate solution is difficult to achieve, are still not perfect.In this paper,the fundamental equations of the nonlinear free vibration for rectangular sandwich plates with the soft interlayer and the extremely thin surface are simplified firstly. And the vibration mode are assumed as the separate form of time and space function, the time function employs the simple harmonic, the space function is unknown. The assumed vibration mode function is substituted into the differential equation to get the dimensionless control equation of the space modality for the beam sandwich plate with two opposite edges simply supported. The equations are solved with the aid of the modified iteration method and the Gal-erkin method to achieve an analytical solution for the vibration mode of the beam sandwich

[ 可能符合您检索需要的词汇 ]

进入期刊文章
参考ISO 3381-2005 标准,对运营中速度等级为300 km/h 的某型高速列车进行车间连接处车内噪声测试,给出了车间连接处车内噪声的频谱特性及其空间分布规律.进而,基于球谐函数声场分解和重构的球形阵列声源识别原理,采用球形阵列声源识别系统,对车间连接处车内噪声进行声源识别,明确了车间连接处车内噪声的源强和分布特性.最后,参考TB 3094-2004 标准,对典型的车间连接风挡结构进行隔声特性测试.综合上述测试结果,对车间连接处噪声的产生机理进行了综合的分析.结果表明,现有高速列车风挡结构不单有隔声不足的问题,还存在较显著的结构振动声辐射,对风挡结构的优化设计需同时考虑上述两大因素.
According to the standard ISO 3381-2005, the interior noise of the gangway in a certain type of high-speed trains at 300 km/h speed level is tested. The spectral characteristics and the spatial distribution of the interior noise are ob-tained. Furthermore, based on the theory of spherical harmonic decomposition and reconstruction, a spherical array sound source recognition system is employed to recognize the sound sources of the interior noise at the gangway. Then the intensity and distribution characteristics of the interior noise are obtained. Finally, according to the standard TB 3094-2004, the sound insulation characteristic of the windshield structure of a typical gangway is tested. According to the test results, the mecha-nism of the interior noise of the gangway is analyzed comprehensively. It is shown that the existing windshield structures have not only the deficiencies in sound insulation, but also the significant noise radiation due to the structural vibration. So,

[ 可能符合您检索需要的词汇 ]

进入期刊文章
利用GNSS数据反演电离层空间结构的理论和方法是近年来相关学者研究的热点之一。基于电离层中电子分布受地磁、太阳热辐射和地壳变动等影响较大,利用球谐函数能有效反映电离层空间面分布关系的特点,结合Champan函数是描述电离层垂直剖面密度的理想模型,建立了一种层析电离层三维空间结构模型—SHCF。根据电离层静日下E层和F层的分布高度,合理地确定了模型中的参数。以中国区域GPS CORS2008年9月4日两时间段的实测数据为例,计算出模型在两时间段内估计的残差分别为0.247 m和0.196 m;并通过不同位置垂直方向的密度分布图和三维残差分布图进一步验证了模型的有效性和可靠性;同时,对新模型与球谐单层模型估计后的残差受高度角的影响也进行了对比分析。由于该模型不受先验条件的约束,因此,具有较大的应用价值。
GNSS data can be used to inversely derive the theory and method of ionospheric spatial structure. Since the distribution of electrons in the ionosphere is significantly influenced by geomagnetic, solar radiation, crustal movement etc., this paper analyzes the characteristic of spherical-harmonic function which can reflect the characteristic of ionospheric spatial lay-distribution, and studies this Champan function which is an ideal model to describe distribution of vertical ionosphere. A new three-dimension SHCF model for tomography spacial ionosphere is established. Based on the height distribution of static subsolar ionospheric E layer and F layer, the constant parameters of the model are determined. The measured data from GPS CORS in Chinese region at September 4, 2008 is used to illustrate the new algorithm, and the estimated residuals of the algorithm in two time periods are 0.247 m and 0.196 m respectively. And its reliability and accuracy are further verified by the vertical den

[ 可能符合您检索需要的词汇 ]