MC-CDMA上下行链路扩频序列设计及仿真研究

分析了MC-CDMA上下行链路发送端的基带系统模型,给出了发送信号峰均功率比和用户扩频序列非周期自相关函数之间的关系,对上下行链路采用不同类型扩频序列集的PAPR性能进行了仿真.仿真结果表明在MC-CDMA的上下行链路中采用正交Golay序列均具有优异的PAPR性能,和常用基于walsh序列的MC-CDMA系统相比具有更强的实用意义.     

基于802.16的OFDM同步算法分析及其仿真实现

OFDM是一种新的高效的多载波调制技术，能够有效地对抗多径传播；但是，OFDM系统对定时和频偏很敏感。对一种具有802．16帧结构的OFDM系统定时同步和频率偏移估计算法进行了分析并通过MATLAB进行仿真实现。仿真结果表明算法适用于具有802．16帧结构的OFDM系统。     

一种高效的迭代OFDM频偏估计算法

提出了一种改进的正交频分复用（Orthogonal Frequency Division Multiplexing,OFDM）载波频率偏移估计算法并通过MATLAB进行仿真.仿真结果表明算法对小数载波频率偏移估计精度高并且其算法复杂度低.     

基于主波峰的自适应波形重跟踪算法研究

构建基于主波峰的自适应波形重跟踪算法（AMWRT）。首先提取主波峰,然后对主波峰分别应用经典的重心偏移法（OCOG）及阈值法（threshold）进行波形重跟踪,并进行精度比较,得到最优的观测水位。将AMWRT、OCOG和threshold法应用于长江中游地区,结果表明：1）测高卫星观测的长时间水位序列与水文站实测数据趋势较为一致;2）AMWRT算法相较于OCOG法及threshold法表现良好,比其中表现最好的经典threshold_0.5法的精度提高了30%,其绝对平均误差（MAE）和均方根误差（RMSE）分别降低至0.55 m和0.72 m。     

结构化查询语言向Mapbox表达式转换方法

当前,Mapbox-GL地图渲染引擎使用类似于表处理语言(LISP)的条件表达式语法实现要素的过滤,数理逻辑强,过于抽象,不具备自然语言逻辑,可读性差,配图作业中批量构建要素筛选任务时较为复杂,影响了配图效率和数据筛选的准确性.因此,本文提出一种使用SQL表达式向Mapbox表达式的转换方法,使用结构化查询语言代替Mapbox-GL过滤器参与到配图工作,在不改变表达式语义信息的情况下实现SQL运算符到Mapbox表达式的等价转换和语法映射,并设计开发原型系统进行验证.验证实验和实际应用均表明该算法有效降低了要素选择的难度和错误发生率,可以显著提高配图效率.     

一种新的基于模糊分析观测信息的局地化方法

地球表层系统是一个极其复杂的巨系统,为了更精确地表达地球表层系统各种过程的动态演进,解决数据同化系统观测误差的估计与处理已经成为地球科学领域备受关注的问题之一。在地球科学系统数值模拟中,一般采用集合数据同化来探讨地学变量预报时的各种误差。集合类卡尔曼滤波通常会由于集合数过小而带来欠采样、协方差低估、滤波发散和远距离虚假相关等问题。针对背景误差协方差被低估问题,局地分析方法（Local Analysis, LA）在一定程度上能起到抑制作用,但无法彻底解决背景误差协方差的虚假相关问题。因此,本文在集合卡尔曼滤波的算法框架下提出了一种与模糊逻辑控制算法相耦合的局地化分析方法（Fuzzy Analysis, FA）。在强非线性Lorenz-96模型中,对不同模型误差下的LA和FA方法进行了性能优劣方面的探讨,并比较分析了2种方法在集合数、观测数和观测位置、放大因子以及强迫参数变化时的同化性能。实验采用均方根误差作为算法评判依据,同时用功率谱密度（Power Spectral Density, PSD）更直接地对2种算法性能优劣作出了评价。结果表明：在完美模型下,FA相对于LA降低了17.5%的均方根误差（Root Mean Square Error, RMSE）;随着模型误差增大,RMSE减小的百分比和减小幅度都在降低;在严重模型误差下,FA降低了8.6%的RMSE。总体而言,新算法FA的有效性和鲁棒性都得到了验证,并且在EnKF同化基础下有效改进了传统的局地化分析方案,优化了观测误差处理,为今后的数据同化研究提供了一个较为全面的观测误差研究平台。     

MIMO OFDM短波无线通信同步技术的研究

多输入多输出（MIMO）技术是最近几年发展起来的无线通信技术。目前利用MIMO技术提高短波通信的传输速率和可靠性的研究已经开展。着重研究了MIMO OFDM（交频分复用）短波无线通信的同步技术，利用截断的Suehiro序列构成的训练符号完成了系统的同步捕获。仿真结果标明，与Mody算法相比，该方案在性能相近的情况下可提高系统的频谱效率。     

用冻融结合超声波法辅助提取浒苔多糖的工艺条件

浒苔(Enteromorpha prolifera)多糖具有多种生物学活性,一种高效并对生物学活性影响小的多糖提取工艺对其生物学活性研究有重要意义。用冻融结合超声波法研究浒苔多糖的提取工艺,在单因素实验的基础上,选择水料质量比、超声波功率、提取时间、冻融-超声波次数进行4因素3水平的正交实验提取浒苔多糖。结果表明:浒苔多糖最佳提取条件为水料质量比55、超声波功率600 W、超声波作用时间8 min、冻融-超声波2次,浒苔多糖得率为19.124%。     

格形编码的正交频分复用技术在时间色散信道中的应用

提出了一种格形编码的正交频分复用 (TC OFDM )方案 ,研究把正交频分复用(OFDM )和格形编码 (TCM )有机地结合 ,来克服时间色散信道中的频率选择性和多径衰落。对码率 2 / 3格形编码的 8DPSK OFDM在时间色散信道中的误码率性能进行了分析和模拟 ,讨论了不同正交载波数情况下格形编码的设计。结果表明 ,在比特误码率BER为 10 - 3时采用TC OFDM方案与未编码系统相比可以提供 6dB的编码增益。     

环境示踪剂（3H、Cl）在干旱半干旱区地下水补给研究中的应用

地下水补给资源估算是地下水资源可持续开发利用的重要依据,传统地下水资源评价工作往往是采取水均衡法或达西定律等评价地下水补给资源,很少采用环境示踪剂方法。环境示踪剂在地下水补给研究中具有重要价值,特别是在干旱半干旱地区是一种非常简单可靠的评价方法。本文介绍了两种常见的环境示踪剂（3H、Cl）方法氚峰法和氯质量平衡法的基本原理及其在地下水补给研究中的主要应用,其中氯质量平衡法不仅可以估算地下水的补给量,而且可以研究植被覆盖变化对地下水补给影响和示踪地下水补给历史及气候变化。     

Impacts of salinity parameterizations on temperature simulation over and in a hypersaline lake

In this paper,we introduced parameterizations of the salinity effects(on heat capacity,thermal conductivity,freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecasting model coupled with the Community Land Model(WRF-CLM). This was done to improve temperature simulation over and in a saline lake and to test the contributions of salinity effects on various water properties via sensitivity experiments. The modified lake scheme consists of the lake module in the CLM model,which is the land component of the WRF-CLM model. The Great Salt Lake(GSL) in the USA was selected as the study area. The simulation was performed from September 3,2001 to September 30,2002. Our results show that the modif ied WRF-CLM model that includes the lake scheme considering salinity effects can reasonably simulate temperature over and in the GSL. This model had much greater accuracy than neglecting salinity effects,particularly in a very cold event when that effect alters the freezing point. The salinity effect on saturated vapor pressure can reduce latent heat flux over the lake and make it slightly warmer. The salinity effect on heat capacity can also make lake temperature prone to changes. However,the salinity effect on thermal conductivity was found insignificant in our simulations.     

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利用EMD阈值消噪改进MW组合周跳探测性能

分析MW组合观测值的噪声特性,评价其实际周跳探测性能,提出利用EMD阈值消噪方法进行降噪。对于EMD的端点效应问题,在MW递推均值上增加虚拟噪声构成虚拟观测值对数据进行延拓。估计MW组合经EMD分解后各层分量的阈值,削弱噪声影响。分析消噪后含周跳MW组合所发生的变化,指出周跳具有"扩散"现象,提出基于消噪后MW组合的探测方案。     

一种基于Ohta-Okamoto签名的门限群签名方案

在修改的Ohta_Okamoto数字签名方案基础上,设计出了一个新的(t,n)门限签名方案。该方案具有可验证性和防止内部成员合谋攻击;而且验证者在验证群签名的有效性计算的复杂性与一般个人签名方案一样。该方案的安全性是基于大整数的因式分解,因此在计算上是安全的。     

A VOF-based numerical model for breaking waves in surf zone

This paper introduces a numerical model for studying the evolution of a periodic wave train, shoaling, and breaking in surf zone. The model can solve the Reynolds averaged Navier-Stokes (RANS) equations for a mean flow, and (he k-s equations for turbulence kinetic energy k and turbulence dissipation rate e. To track a free surface, the volume of fluid (VOF) function, satisfying the advection equation was introduced. In the numerical treatment, third-order upwind difference scheme was applied to the convection terms of the RANS equations in order to reduce the effect of numerical viscosity. The shoaling and breaking processes of a periodic wave train on gently sloping beaches were modeled. The computed wave heights of a sloping beach and the distribution of breaking wave pressure on a vertical wall were compared with laboratory data.     

Numerical analysis of emergency river restoration scheme for Qingping mega debris flow

The mega debris flow occurred on August 13 th 2010 in Qingping town,China(hereafter called ’8.13’ Debris Flow) have done great damage to the local habitants as well as to the re-construction projects in the quake-hit areas,and the channel-fill deposit problem caused by the debris flow was the most destructive.Moreover,it is of high possibility that an even severe deposit problem would reappear and result in worse consequences.In order to maximize risk reduction of this problem,relevant departments of the government established a series of emergency river restoration schemes,for which the numerical analysis is an important procedure to evaluate and determine the optimized one.This study presents a numerical analysis by applying a twodimensional debris flow model combined with a relevant water-sediment model to simulate the deposit during the progress of the debris flow,and to calculate and analyze the river flow field under both the present condition and different restoration conditions.The results show that the debris flow model,which takes the confluence of the Wenjia Gully to the main river into account,could simulate the deposit process quite well.In the reproduced debris flow from the simulation of the ’8.13’ Debris Flow,the original river flow path has switched to a relatively lower place just along the right bank with a high speed of near 7m.s-1 after being blocked by the deposit,which is highly hazardous.To prevent this hazard,a recommended scheme is derived through inter-comparison of different restoration conditions.It shows that the recommended scheme is able to reduce the water level and as well to regulate the flow path.Based on the given conditions of the mainstream and the tributary confluence for the simulated ’8.13’ Debris Flow,when encountering a debris flow with deposit volume less than 0.5 million m3,the river channel can endure a 20-year return flood;however,when the deposit volume increases to 2 million m3,the flood capacity of the river will be greatly impacted and the scheme becomes invalid.The recommended scheme supported by the present study has been applied to the emergency river restoration after this mega-debris flow.     

Fuzzy Sliding Mode Active Disturbance Rejection Control of an Autonomous Underwater Vehicle-Manipulator System

In this paper, a fuzzy sliding mode active disturbance rejection control(FSMADRC) scheme is proposed for an autonomous underwater vehicle-manipulator system(AUVMS) with a two-link and three-joint manipulator. First, the AUVMS is separated into nine subsystems, and the combined effects of dynamic uncertainties, hydrodynamic force, unknown disturbances, and nonlinear coupling terms on each subsystem are lumped into a single total disturbance. Next, a linear extended state observer(LESO) is presented to estimate the total disturbance. Then, a sliding mode active disturbance rejection control(SMADRC) scheme is proposed to enhance the robustness of the control system. The stability of the SMADRC and the estimation errors of the LESO are analyzed. Because it is difficult to simultaneously adjust several parameters for a LESO-based SMADRC scheme, a fuzzy logic control(FLC) scheme is used to formulate the FSMADRC to determine the appropriate parameters adaptively for practical applications. Finally, two AUVMS tasks are illustrated to test the trajectory tracking performance of the closed-loop system and its ability to reject and attenuate the total disturbance. The simulation results show that the proposed FSMADRC scheme achieves better performance and consume less energy than conventional PID and FLC techniques.     

Impact of convective momentum transport by deep convection on simulation of tropical intraseasonal oscillation

This paper focuses on the impacts of convective momentum transport (CMT) on simulations of the tropical intraseasonal oscillation (TIO) in SAMIL. Two sets of experiments are performed, which give different reality of the Madden-Julian Oscillation (MJO). The Tiedtke cumulus parameterization scheme is used for all experiments. It is found that simulations of the TIO can be influenced by CMT, and the impacts on the simulated TIO depend on the model capability in simulating the MJO. CMT tends to have large influences to the model that can simulate the eastward propagation of the MJO. CMT can further influence the long-term mean of zonal wind and its vertical shear. Zonal wind suffers from easterlies biases at low level and westerlies biases at upper level when CMT is introduced. Such easterlies biases at low level reduce the reality of the simulated tropical intraseasonal oscillation. When CMT is introduced in the model, MJO signals disappear but the model’s mean state improves. Therefore, a more appropriate way is needed to introduce CMT to the model to balance the simulated mean state and TIO signals.