Multiple Turbo Codes for Satellite Communications

Satellite communication channel has the characteristic of power limited, band abundance, and powerful error correcting ability FEC scheme is needed. For its near Shannon limit error correcting capability, Turbo codes may be suitable for satellite communication systems. The multiple Turbo codes can utilize channel capacity sufficiency and overcome the disadvantages of power limited for satellite communication systems. Force on the needed for satellite communication systems, multiple Turbo codes is adopted and server decoding schemes were proposed with simulation. Simulation results show that, the schemes proposed can get near channel capacity error correcting performance with short code block.     

Arch Axis Optimization of New Type Arch Bridge with Diagonal Web Cables Based on Geometric Nonlinear Mechanical Analysis

There are obvious geometric nonlinear mechanical characteristics in new type arch bridge with diagonal web cables. Meanwhile, the convergence of the existing arch axis iterative optimization method is not good. In order to solve new type arch bridge axis iteration convergence problem considering geometric nonlinear mechanical analysis, an arch axis iteration optimization method was proposed based on the iteration basis finite element model with two hinge arch model in main arch ring. A 600m span arch bridge with diagonal web cables was selected as an example to test the convergence performance and applicability of proposed method. The results showed that the bending moment of proposed method had better distribution along arch span, and it is about 35% smaller in maximum bending moment, 17% smaller in minimum bending moment and 23% smaller in bending strain energy compared to the results of linear iteration optimization method. Convergence analysis results demonstrated that proposed method had better iteration performance than the existing method. Meanwhile, different initial arch axis can converge to stable results.     

不同失稳判据下边坡稳定性的规律性

以塑性区贯通、位移增量突变、计算不收敛3种边坡失稳判据为依据,采用强度折减有限元法和重度增加有限元法对简单边坡进行了分析。结果表明：以边坡潜在滑动面上某点位移增量突变作为边坡失稳判据是准确的;对于不同土体强度参数下,以位移增量关系曲线突变为判据得到的边坡的安全系数较另外两种方法稳定;对应于塑性区贯通、位移增量曲线突变和计算不收敛的3种判据,边坡潜在滑动面依次向深层发展,边坡的安全系数依次增加。     

Asynchronous Parallel Algorithm for Finding All Zeros of a Polynomial

Parallel Halley iteration method, based on circular arithmetic for finding all zeros of a polynomial, avoids troublesome circular extraction operation,and the approximation with error estimation of all zeros of a polynomial can be obtained at the same time with it, and it has higher convergence rate , while it was synchronous parallel algorithm. The asynchronous parallel algorithm was constructed with circular arithmetic in order to find all zeros of a polynomial, and the convergence theory was established under the similar condition of Halley iteration method. The algorithm not only retain the advantage of Halley iteration method, but has better parallelism.     

Two-level Safety Evaluation and Structural Optimization of Steel Truss Bridge

A robust method for determining the component safety factor and structural safety factor of steel truss bridge is developed based on elastic modulus reduction method (EMRM). A procedure of two-level safety analysis and structural optimization is presented by means of the linear FEA iteration and the generalized yield criterion to take multiple internal forces into consideration. The strategy of elastic modulus adjustment is derived according to the principle of conversation of energy. The element bearing ratio (EBR) in every step can be obtained, and the first and last EBRs are employed to determine component safety factor and the structural safety factor for two-level structural safety evaluation of steel truss bridge. Those components with higher or lower EBR than the referenced EBR can be identified. By taking the quantitative relationship of the two level safety factors, a structural optimization scheme with better distribution of the EBR and saving material consumption can be achieved by adjusting the sectional strength of components with higher and lower EBR. Numerical examples show that the proposed method is promising with satisfying accuracy. The analysis of structural safety and optimization can be implemented by using the linear iteration while complicated nonlinear analysis in classical scheme is avoided.     

Simulation of thermocapillary flow in a two dimensional cavity with lattice Boltzmann method

Thermocapillary flow driven by an unbalanced surface tension plays the most important role for mass and heat transport in floating zone melt crystal growth under microgravity. The authors develop both a serial and a parallel codes with lattice Bhatnagar-Gross-Krook(BGK) model using two distribution functions, and numerically study the thermocapillary flow in a two dimensional square cavity with a single free surface under microgravity condition. The serial code is developed by combining collision and propagation step, using a temporary array to continuously read distribution functions, and its performance is improved two times faster than the code with separating the collision and propagation step. The MPI parallel code is proposed utilizing one dimensional partitioning and non-blocking communication. The accurate and reliable results are achieved with both the serial and parallel codes by comparing with CFD results simulated by the finite volume method; the MPI parallel code has high performance.     

Pressure-Dependent Analysis of Water Supply Network Damaged by Earthquake Based on Emitter Model

When the water supply network suffered earthquake damages, pipeline leaks and bursts may occur. In the period in post-earthquake emergency rescue and repair, the network is supplying water with additional outflow of damages (leaks and breaks), which result in pressure deficient. According to the frictional head loss along the break pipeline, a model with additional emitter at the endpoint of the disconnect pipeline was proposed to simulate the break, which simplifies the modeling of breaks. The pressure-dependent demand relationship was adopted in the process of pressure-deficient hydraulic simulation to avoid node negative pressure. Meanwhile a backtracking and line search procedure was utilized to control the iteration step of pipeline network nonlinear equations, which ensure the global convergence of the hydraulic simulation. The effectiveness of the proposed method was verified by a case study.     

Simulation of the constant modulus blind equilibrium algorithm with variable step size based on the mean square error

The mathematic models and basic theory of constant modulus algorithm (CMA) for blind channel equalization are introduced. An improved algorithm with variable step size is proposed based on CMA. The improved algorithm uses the mean square error (MSE) to obtain the new variable step size to solve the contradiction between the convergence rate and accuracy in traditional CMA with fixed step. To smooth the MSE learning curve for easy comparison, an ensemble average technique is used to analyze the performance of convergence with different step sizes. The theoretical analysis and the simulation results show that the improved algorithm is superior to the traditional constant modulus(CM) in terms of convergence speed and residual error.     

Application of Symmetric Galerkin Boundary Element Method in Limit Analysis of Plane Problems

Based on Melan's theorem, the symmetric Galerkin boundary element method (SGBEM) is used to discretize two dimensional structures and a computational formulation of structural limit analysis is established. The self equilibrium stress field is constructed by linear combination of several basic vectors, which are the stress differences between different iteration steps at the same increment using the traditional elastoplastic incremental method. Then the complex method is used to solve the nonlinear programming directly, so that the lower bound load multiplier of two dimensional structures is obtained. The validation of the present method has been confirmed by some numerical examples.     

An edge detection method based on a good point set genetic algorithm

In order to improve the convergence rate of genetic algorithms based on edge detection, a novel edge detection method based on a good point set genetic algorithm (GGA) was proposed. The proposed method designed the crossover operation with the theory of good point set in which the progeny inherits the common genes of the parents which represent its family so as to improve the convergence rate of the genetic algorithm. Furthermore, before the algorithm was used for edge detection, the feature space of the image grey level was transformed into the feature space of the fuzzy entropy. Dissimilarity enhancement processing next was applied to the image by using a fuzzy entropy theory to filter the non edge pixels so as to reduce the scale of the solution domain. This approach offered another efficient way to improve the convergence rate. Experimental results show the proposed algorithm performs very well in terms of convergence rate. The detected edge image is well localized, thin, and robustly resistant to noise.     

Factor Graphs Based Turbo Codes Decoding

Beth turbo codes and LDPC codes can achieve the Shannon limited performance. The constituent RSC codes in turbo codes are more structural and this lends the encoding problem easier with shift_register circuit.While the encoding of LDPC codes is performed via matrix multiplication, it is more complex than it appears for capacity_approaching LDPC codes. On the other hand,the soft_input soft_output BCJR algorithm,or the sub_optimal version of it,used for turbo_decoding is rather complex while sum_product algorithm used for LDPC decoding lends itself to parallel implementation and is computationally simpler. Combining the turbo codes encoding and LDPC decoding,a new scheme based on factor graphs and sum_product algorithm is developed, Which can reduce the decoding complexity of turbo codes greatly,and also has some guides in the designing of interleaver and the choosing of RSC constituent codes. Simulation shows the correctness of the scheme.     

Nonlinear Aerostatic Stability of Suspension Bridge with Spatial Main Cables

The three component coefficients of section model of You Cha Bridge were obtained by using two five component balances.And the three dimensional aerostatic stability of You Cha Bridge was analyzed based on the modified increment and inner outer iteration method implemented in ANSYS.It is indicated that the aerostatic stability of You Cha Bridge with spatial main cables is more excellent compared with those of suspension bridges which have two parallel main cables.A full aero elastic model with geometrical scale of 1:90.35 was designed and used to experimentally determine the wind velocity inducing aerostatic divergence in smooth wind.And it is found that the critical wind velocity for attendant bridge is higher than the design wind velocity.     

Quadrature Methods and Their Extrapolations for Solving Boundary Integral Equations of Steady Navier-Stokes Problems

This paper presents an iteration method of solving non linear boundary integral equations (BIE) of the plane Navier Stokes problem,which each step of the iteration is to solve a linear BIE of nonhomogeneous Stokes problem. Using the quadrature methods of [1],we give a new algorithm with a high order accuracy.The algorithm not only saves work,but also the accuracy can be improved by Richardson extrapolation.     

基于主成分分析的BP神经网络估算藏北高寒草地覆盖度变化

藏北高寒牧区草地是中国高寒草地分布面积最大的地区。为了及时准确地获得该区域草地覆盖度的变化趋势,本研究利用多年气象数据、社会统计数据、GIMMS、MODIS两种归一化植被指数（NDVI）数据作为参数,构建 BP神经网络模型,估算2010—2014年藏北高寒草地年际变化趋势,并用主成分分析方法优化参数来改进模型。结果表明,① BP神经网络模型及其改进模型对藏北高寒草地覆盖度年际变化趋势与遥感值的相关系数为0.16、0.47,表明通过主成分分析优化参数后的BP神经网络模型具有较好的模拟效果。 ②两种BP神经网络估算的植被指数值与NDVI值平均误差率分别为2.36%、2.20%。均有较高的模拟精度。③从神经网络训练步数上看,BP神经网络结果训练收敛步长为5000,基于主成分分析的BP神经网络模型训练收敛步长为454,表明后者提高了计算效率,体现出良好的收敛性。因此,无论从年际变化趋势拟合程度、植被指数估算值精度、还是从计算效率来看,改进的BP神经网络模型对于估算藏北高寒草地覆盖度变化更加行之有效。     

Analysis of Global Stability of Soil Nailing Bracing Structures in Non-homogeneous Soil

Based on Swedish slices limited equilibrium method, a new computation formula of stability safety factor is presented for interior stability analysis of soil nailing wall in non-homogeneous soil. A new genetic algorithm is put forward by adopting dynamic self-adaptive technology and nonstandard genetic operators. Applying the dynamic self-adaptive technology and nonstandard genetic operators into the field of soil-nailing wall interior stability analysis, the dynamic adaptive genetic algorithm for searching the arbitrary critical slip surface is established. It is shown that the dynamic adaptive genetic algorithm has better performance in finding optimal solution, quicker convergence than traditional algorithm as well as more reasonable results.     

热管管外结冰过程研究

通过对热管制冰传热过程的理论分析,得出影响结冰速率的主要因素是热管的温度与半径.建立了管外结冰一维传热模型,分别以半径和时间为步长对结冰速率进行迭代求解,并利用半径微元法得出了不同温度以及不同圆管半径下的制冰速率曲线.与试验结果相比,所得理论模型能够较好地与其吻合.     

Improvement and performances of DV hop localization algorithm in wireless sensor networks

In order to improve the node localization precision of Range Free based DV Hop localization algorithm in wireless sensor networks (WSNs) with randomly distributed nodes and dynamic topology, the improved algorithm is proposed. After analyzing the DV Hop algorithm, considering the obvious errors of the estimated node coordinates calculated by Polygon based method in traditional DV Hop algorithm, the numerical iterative algorithm is constructed by employing Taylor series expansion, and simulation studies for the improved DV Hop algorithm are conducted. The selection criteria for the convergent threshold of iterative step is determined, the localization performance of the improved localization algorithm is analyzed by comparing with the traditional DV Hop algorithm under the same condition of selected convergent threshold and simulation parameters, while the calculation amount and convergence rate of the improved algorithm are also measured by the statistic iterations. The simulation results show that by selecting reasonable iterative threshold values and appropriately increasing calculation amount for node localization, the improved DV Hop localization algorithm greatly improves the localization precision and the error stability, which is feasible for node localization in WSNs with both randomly distributed nodes and dynamic topology.     

粒子群优化的神经网络在夏季降水预测中的应用

降水短期气候预测是一个非常复杂、重要的研究课题。为了提高其预测能力,拟采用1959—2011年逐月74项大气环流特征量序列、月平均500 hPa高度场和月平均海温场,选取预测因子;用主分量分析方法提取样本数据中主要信息为综合因子。用粒子群优化人工神经网络方法,建立宣城市夏季降水短期气候预测模型。对2007—2011年宣城市夏季降水预报检验结果表明,粒子群优化人工神经网络收敛速度快,迭代次数少;试报平均绝对误差是66.5 mm,绝对值平均相对误差10.5%,预测精度高,具有很好的应用推广前景。     

A new pattern recognition method of gas sensor array detection

BP neural network based gas sensor array detection pattern recognition has some disadvantages, such as slow convergence and local minimum problem. A modified immune neural network model which combines BP algorithm and immune algorithm is proposed to enhance global search capability and improve the performance of the neural network model. Orthogonal test is adopted to design the study samples of neural network. This ensures the accuracy of neural network while reducing the number of samples. The simulation results show that the proposed pattern recognition method solves the cross sensitivity of gas sensor effectively, overcomes the disadvantages of traditional BP neural network and improves the learning speed and detection accuracy.     

四川省农业与旅游业融合发展评价及障碍因素分析

推动农业与旅游业的深度融合发展,对当前推进农业供给侧结构性改革、农业农村产业融合发展具有重要的意义,而科学评价农业与旅游业融合发展、把握融合发展的阶段特征和主要障碍十分必要。通过文献分析,从资源禀赋条件、融合创新水平、融合发展效应3个方面构建农业与旅游业融合发展的评价指标体系,并采用AHP、熵权法、障碍度评价等对四川省进行实证分析。结果显示:（1）2005—2016年,四川省农业与旅游业融合发展指数总体呈上升趋势,总体趋好;（2）融合创新指数呈现出逐年下降的趋势,非农资源导向的旅游产品大大降低了农业主题旅游产品的市场份额;（3）融合发展的综合效应指数变化呈显著增长,但融合发展的综合效应尚处于起步阶段;（4）总体而言,四川省农业与旅游业的融合发展尚处于资源依托型向产品（业务）融合型的发展模式过渡;（5）现阶段,融合创新水平是持续影响四川省农业与旅游业融合发展的主要障碍因素,且障碍度呈现逐年递增的态势。四川省农业与旅游业的融合发展必须走精品化发展之路,要推动农业与旅游业资源的协同化、精品化开发,要利用新技术进一步扩大旅游知识的扩散和拓展多元主体参与的渠道,以全面提升融合发展的质量和水平。