基于正态信息扩散原理的极值型工程参数概率分布推断方法

在工程可靠度分析中存在大量的极值型工程参数,为了获得这类参数的最优概率分布,提出基于正态信息扩散原理的极值型工程参数概率分布推断方法。在考虑偏度的"3σ"统计原理的截尾区间下,以年最大标准风压和内摩擦角样本为例,分别利用正态信息扩散分布和极值型分布拟合2组样本,并运用K-S方法进行假设检验。为了考察样本个数对2种分布在拟合精度方面的影响,利用Monte-Carlo方法生成母函数为极值型分布的8组模拟样本,样本个数分别为15,20,30,50,100,200,500和1 000,并采用K-S检验法对不同样本个数下推断得到的概率分布进行检验。结合正态信息扩散分布的拟合优势,将其应用于核管道工程最大腐蚀深度预测。研究结果表明:不论是实际工程样本还是模拟样本,正态信息扩散分布和极值型分布均通过K-S检验,其中正态信息扩散分布的检验值均低于极值型分布的检验值;随着样本个数增加,正态信息扩散分布表现出更好的收敛优势。正态信息扩散分布的累积概率在10-4误差量级上表现出等于1的效果,而极值型分布的累积概率在同样的误差量级上达不到1。算例结果表明:利用正态信息扩散分布作为核管道腐蚀深度的预测模型,能够更加精确地预测其最大腐蚀深度。

向量值参数型Marcinkiewicz积分交换子的有界性

证明了向量值参数型Marcinkiewicz积分交换子μb,Ω,rρ是(Lp,.Fp,β∞)和(Lp,Ls)有界的,其中Ω满足某类Lq-Dini条件,拓广了以往的结果.

环形螺旋桨几何形状的数学表达方法

[目的]环形螺旋桨因其独特的外形,可有效减少梢涡泄出,有利于降低水动力噪声,提高推进效率,但同时也因其复杂的外形,难以采用常规螺旋桨的数学表达方法来对其几何外形进行建模,因此,需研究新型环形螺旋桨几何形状的数学表达。[方法]首先,详细介绍环形螺旋桨的结构特点和优势;然后,在参考常规螺旋桨几何形状数学表达的基础上,引入轴距、外侧角、侧倾角和竖直角等几何参数,以几何型值参数沿轴距方向分布的方式,详细推导环形螺旋桨的三维坐标数学公式,从而建立环形螺旋桨的数学表达方法;最后,以某一环形螺旋桨的型值为例,验证所提环形螺旋桨数学表达方法的可行性。[结果]结果显示,采用所提方法能够光顺地建立环形螺旋桨的几何外形。[结论]所提方法可用于快速进行环形螺旋桨的三维建模,能为进一步研究环形螺旋桨的物理特性和科学问题奠定坚实的基础。

Cross-section distortion and springback characteristics of double-cavity aluminum profile in force controlled stretch-bending

3D elastic-plastic FE model for simulating the force controlled stretch-bending process of double-cavity aluminum profile was established using hybrid explicit−implicit solvent method.Considering the computational accuracy and efficiency,the optimal choices of numerical parameters and algorithms in FE modelling were determined.The formation mechanisms of cross-section distortion and springback were revealed.The effects of pre-stretching,post-stretching,friction,and the addition of internal fillers on forming quality were investigated.The results show that the stress state of profile in stretch-bending is uniaxial with only a circumferential stress.The stress distribution along the length direction of profile is non-uniform and the maximum tensile stress is located at a certain distance away from the center of profile.As aluminum profile is gradually attached to bending die,the distribution characteristic of cross-section distortion along the length direction of profile changes from V-shape to W-shape.After unloading the forming tools,cross-section distortion decreases obviously due to the stress relaxation,with a maximum distortion difference of 13%before and after unloading.As pre-stretching and post-stretching forces increase,cross-section distortion increases gradually,while springback first decreases and then remains unchanged.With increasing friction between bending die and profile,cross-section distortion slightly decreases,while springback increases.Cross-section distortion decreases by 83%with adding PVC fillers into the cavities of profile,while springback increases by 192.2%.

氟代苯阳离子的理论研究

用B3LYP方法及 6 3 11G (d ,p)和 6 3 11+G (d ,p)基组 ,对十二种氟代苯阳离子做了理论研究 ,优化了它们的电子基态的结构 ,计算了对应分子的垂直电离势 (VIP)和绝热电离势 (AIP) .依据Jahn Teller理论 ,计算确定了 1,3 ,5 C6H3 F+ 3 和C6F+ 6离子分别具有C2v( 2 B1 )和D2h( 2 B2g)结构 (对应分子分别为D3h和D6h结构 ) .其余十个离子的构型的对称点群与对应分子相同 ,但构型参数值有明显差别 .自然布居分析计算表明这些离子的正电荷主要分布在与F原子相连的C原子和各H原子上 .B3LYP/6 3 11+G (d ,p)

PARAMETRIC SENSITIVITY AND RUNAWAY IN FIXED BED REACTORS

This paper presents a comprehensive treatment of the parametric sensitivity and runaway in fixed bed reactors with one dimensional pseudo homogeneous dispersion model (ODDM). In this case, we find the existence of multiplicity and determine the runaway criterion through the critical isodisper sion curve. The calculated results indicate when the axial dispersion is relatively small, the impact of the axial dispersion on the parametric sensitivity may be neglected; but when the axial dispersion is large, this impact must be considered.

Numerical method for estimation of kinematical parameters for articulated rovers on loose rough terrain

Based on the study of passive articulated rover,a complete suspension kinematics model from wheel to inertial reference frame is presented,which uses D-H method of manipulator and presentation with Euler angle of pitch,roll and yaw.An improved contact model is adopted aimed at the loose and rough lunar terrain.Using this kinematics model and numerical continuous and discrete Newton's method with iterative factor,the numerical method for estimation of kinematical parameters of articulated rovers on loose and rough terrain is constructed.To demonstrate this numerical method,an example of two torsion bar rocker-bogie lunar rover with eight wheels is presented.Simulation results show that the numerical method for estimation of kinematical parameters of articulated rovers based on improved contact model can improve the precision of kinematical estimation on loose and rough terrain and decrease errors caused by contact models established based on general hypothesis.

Six—Parameter Exponential—Type Potential and the Identity for the Exponential—Type Potentials

We propose a six-parameter exponential-type potential (SPEP), which has been shown to be a shape-invariant potential with a translation of parameters. For this reducible potential, the exact energy levels are obtained byusing the supersymmetric shape invariance technique. Choosing appropriate parameters, four classes of exponential-typepotentials and their exact energy spectra are reduced from the SPEP and a general energy level formula, respectively.Each class shows the identity except for the different definitions of parameters.

Analysis of characteristic functions for equivalent circuit model in monolithic transformer

A model of monolithic transformers is presented, which is analyzed with characteristic functions. A closed- form analytical approach to extract all the model parameters for the equivalent circuit of Si-based on-chip transformers is proposed. A novel de-coupling technique is first developed to reduce the complexity in the Y parameters for the transformer, and the model parameters can then be extracted analytically by a set of characteristic functions. Simulation based on the extracted parameters has been carried out for transformers with different structures, and good accuracy is obtained compared to a 3-demensional full-wave numerical electro- magnetic field solver. The presented approach will be very useful to provide a scalable and wide-band compact circuit model for Si-based RF transformers.

Deformation features and failure mechanism of steep rock slope under the mining activities and rainfall

Underground mining activities and rainfall have potential important influence on the initiation and reactivation of the slope deformations,especially on the steep rock slope. In this paper,using the discrete element method(UDEC),numerical simulation was carried out to investigate deformation features and the failure mechanism of the steep rock slope under mining activities and rainfall. A steep rock slope numerical model was created based on a case study at the Wulong area in Chongqing city,China. Mechanical parameters of the rock mass have been determined by situ measurements and laboratory measurements. A preliminary site monitoring system has been realized,aiming at getting structure movements and stresses of unstablerock masses at the most significant discontinuities. According to the numerical model calibrated based on the monitoring data,four types of operation conditions are designed to reveal the effect of mining excavation and extreme rainfall on the deformation of the steep rock slope.

New Mathematical Model Based on Affine ransformation for Remote Sensing Image with High Resolution

This paper calculates the parameters of image position and orientation,proposes a mathematical model and adopts a new method with three steps of transformations based on parallel ray projection.Every step of the model is strict,and the map function of each transformation is the first order polynomials and other simple function.The final calculation of the parameters is for the linear equations with good status.As a result,the problem of the relativity of image parameter calculation is solved completely.Some experiments are carried out.

Research on an algorithm for solving parameter ranges in parametric drawing systems

To solve the problem that in parametric drawing systems, unreasonable parameter values in a parametric model often result in an improper shape of a geometric object, this paper proposes a novel algebraic algorithm for determining the valid range of parameter values in certain 2-dimensional parametric drawing systems. This algorithm can solve valid range of parameters such as radius and coordinate of centre points of parametric models with only linear segments and circles. The result of the study shows that all values within the valid range provided by this algorithm can ensure that the topological shape of a geometric object does not change after reconstruction, and to some extent, this algorithm can significantly promote the efficiency of parametric drawing system design and the intel- lectual level of human-computer interaction. The analysis shows that complexity of this algorithm is O（n2）.

Modeling of delta-wing type vortex generators

A numerical model of delta-wing type vortex generator was developed in two steps.The first step was to obtain a parameterized model of the shedding vortex based on delta-wing theory,which relates the geometry parameters and flow field parameters to the strength of shedding vortex which directly decides the source term.In the second step,a method was proposed to add source terms into the flow control equations so that the shedding vortex could be simulated numerically.As soon as the numerical model was completed,two cases:One for a plate and another for an airfoil segment were investigated for test.Comparison showed that the flow field structure and aerodynamic performance agreed well with those obtained from cases with real vortex generators.

Influences of non-isothermal atmospheric backgrounds on variations of gravity wave parameters

Because of the importance of gravity waves （GWs） in coupling different atmospheric regions, further studies are necessary to investigate the characteristics of GW propagation in a non-isothermal atmosphere. Using a nonlinear numerical model, we simulate the propagation of small amplitude GWs with various wavelengths in different non-isothermal atmospheres. Our re- sults show that the GW vertical wavelength undergoes sharp changes above the stratopause and mesopause region. Specifically for a GW with an initial vertical wavelength of 5 km, the seasonal background temperature structure difference at 50° latitude can cause the vertical wavelength to vary by -2 krn in the mesosphere and by as large as -4.5 km in the lower thermosphere. In addition, the GW paths exhibit great divergence in the height range of -65-110 kin. Our results also show that the variations of GW path, vertical wavelength and horizontal phase velocity are not synchronized in a non-isothermal atmosphere as in an isothermal atmosphere. Despite the fact that all GWs change their characteristics as they propagate upward in a non-isothermal atmosphere, the variations relative to the initial parameters at a reference height are similar for different initial vertical wavelengths. Our results indicate that the changing characteristics of a gravity wave in a non-isothermal atmosphere need to be considered when investigating the relationship of GWs at two different heights.

The role of constant optimal forcing in correcting forecast models

In this paper,the role of constant optimal forcing(COF) in correcting forecast models was numerically studied using the well-known Lorenz 63 model.The results show that when we only consider model error caused by parameter error,which also changes with the development of state variables in a numerical model,the impact of such model error on forecast uncertainties can be offset by superimposing COF on the tendency equations in the numerical model.The COF can also offset the impact of model error caused by stochastic processes.In reality,the forecast results of numerical models are simultaneously influenced by parameter uncertainty and stochastic process as well as their interactions.Our results indicate that COF is also able to significantly offset the impact of such hybrid model error on forecast results.In summary,although the variation in the model error due to physical process is time-dependent,the superimposition of COF on the numerical model is an effective approach to reducing the influence of model error on forecast results.Therefore,the COF method may be an effective approach to correcting numerical models and thus improving the forecast capability of models.

Geodynamic modeling of thermal structure of subduction zones

During subduction processes, slabs continuously have heat exchange with the ambient mantle, including both conduction and advection effects. The evolution of slab thermal structure is one of the dominant factors in controlling physical and chemical property changes in subduction zones. It also affects our understanding of many key geological processes, such as mineral dehydration, rock partial melting, arc volcanism, and seismic activities in subduction zones. There are mainly two ways for studying thermal structure of subduction zones with geodynamic models: analytical model and numerical model. Analytical model provides insights into the most dominant controlling physical parameters on the thermal structure, such as slab age, velocity and dip angle, shear stress and thermal conductivity, etc. Numerical model can further deal with more complicated environments, such as viscosity change in the mantle wedge, coupling process between slabs and the ambient mantle, and incorporation of petrology and mineralogy. When applying geodynamic modeling results to specific subduction zones on the Earth, there are many factors which may complicate the process, therefore it is difficult to precisely constrain the thermal structure of subduction zones. With the development of new quantitative methods in geophysics and geochemistry, we may obtain more observational constraints for thermal structure of subduction zones, thus providing more reasonable explanations for geological processes related to subduction zones.

Detection of Charged Higgs Bosons in e^+e^-(γγ)→tφ^- Production at the ILC

Abstract In the context of the left-right twin Higgs （LRTH） model, we have studied the charged Higgs bosons production processes e＋e-（γγ） →tbФ- at the International Linear Collider （ILC）. It is found that the cross sections of these two processes could reach a few Fo with reasonable parameter values. With the yearly integrated luminosity of L 500 fb-1 expected at the ILC, one could collect hundreds up to thousands of charged ttiggs events via these two processes. Therefore, our researches in this paper can help us search for charged Higgs bosons, and furthermore, to test the LRTH model.

Keeping it simple: the value of an irreducibly simple climate model

Richardson et al. （Sci Bull, 2015. doi：10.1007/ sl1434-015-0806-z） suggest that the irreducibly simple climate model described in Monckton of Brenchley et al. （Sci Bull 60：122-135, 2015. doi：10.1007/s11434-014- 0699-2） was not validated against observations, relying instead on synthetic test data based on underestimated global warming, illogical parameter choice and near-in- stantaneous response at odds with ocean warming and other observations. However, the simple model, informed by its authors＇ choice of parameters, usually hindcasts observed temperature change more closely than the general-circu- lation models, and finds high climate sensitivity implausi- ble. With IPCC＇s choice of parameters, the model is further validated in that it duly replicates IPCC＇s sensitivity interval. Also, fast climate system response is consistent with near-zero or net-negative temperature feedback. Given the large uncertainties in the initial conditions and evolutionary processes determinative of climate sensitivity, subject to obvious caveats a simple sensitivity-focused model need not, and the present model does not, exhibit significantly less predictive skill than the general-circula- tion models.

A moving average Cholesky factor model in joint mean-covariance modeling for longitudinal data

Modeling the mean and covariance simultaneously is a common strategy to efficiently estimate the mean parameters when applying generalized estimating equation techniques to longitudinal data. In this article, using generalized estimation equation techniques, we propose a new kind of regression models for parameterizing covariance structures. Using a novel Cholesky factor, the entries in this decomposition have moving average and log innovation interpretation and are modeled as the regression coefficients in both the mean and the linear functions of covariates. The resulting estimators for eovarianee are shown to be consistent and asymptotically normally distributed. Simulation studies and a real data analysis show that the proposed approach yields highly efficient estimators for the parameters in the mean, and provides parsimonious estimation for the covariance structure.

Sequential Estimate for Generalized Linear Models with Uncertain Number of Effective Variables

For the generalized linear model,the authors propose a sequential sampling procedure based on an adaptive shrinkage estimate of parameter.This method can determine a minimum sample size under which effective variables contributing to the model are identified and estimates of regression parameters achieve the required accuracy.The authors prove that the proposed sequential procedure is asymptotically optimal.Numerical simulation studies show that the proposed method can save a large number of samples compared to the traditional sequential approach.