Prediction of sediment,particulate nutrient and dissolved nutrient concentrations in a dry tropical river to provide input to a mechanistic coastal water quality model

A Generalised Additive Modelling (GAM) approach is applied to prediction of both particulate and dissolved nutrient concentrations in a wet-tropical river (the Fitzroy River, Queensland, Australia). In addition to covariant terms considered in previous work (i.e. flow, discounted flow and a rising-falling limb term), we considered several new potential covariates: meteorological and hydrological variables that are routinely monitored, available in near-real time, and were considered to have potential predictive power. Of the additional terms considered, only flows from three tributaries of the Fitzroy River (namely, the Nogoa, Comet and Isaac Rivers) were found to significantly improve the model. Inclusion of one or more of these additional flow terms greatly improved results for dissolved nitrogen and dissolved phosphorus concentrations, which were not otherwise amenable to prediction. In particular, the Nogoa sub-catchment, dominated by pasture for cattle, was found to be important in determining dissolved inorganic nitrogen and phosphorus concentrations reaching the river mouth. This insight may direct further research, including future refinement of processed-based catchment models. The GAMs described here are used to provide near real-time river boundary conditions for a complex coupled hydrodynamic and biogeochemical model of the Great Barrier Reef Lagoon, and can be coupled with a forecasting hydrological model to allow integrated forecasting simulations of the catchment to coast system.     

Optimal tracing and replay for debugging message-passing parallel programs

A common debugging strategy involves reexecuting a program (on a given input) over and over, each time gaining more information about bugs. Such techniques can fail on message-passing parallel programs. Because of nondeterminacy, different runs on the given input may produce different results. This nonrepeatability is a serious debugging problem, since an execution cannot always be reproduced to track down bugs. This paper presents a technique for tracing and replaying message-passing programs. By tracing the order in which messages are delivered, a reexecution can be forced to deliver messages in their original order, reproducing the original execution. To reduce the overhead of such a scheme, we show that the delivery'order of only messages involved inraces need be traced (and not every message). Our technique makes run-time decisions to detect and trace racing messages and is usuallyoptimal in the sense that the minimal number of racing messages is traced. Experiments indicate that only 1% of the messages are often traced, gaining a reduction of two orders of magnitude over traditional techniques that trace every message. These traces allow an execution to be reproduced any number of times for debugging. Our work is novel in that we adaptively decide what to trace, and trace only those messages that introduce nondeterminacy. With our strategy, large reductions in trace size allow long-running programs to be replayed that were previously unmanageable. In addition, the reduced tracing requirements alleviate tracing bottle-necks, allowing executions to be debugged with substantially lower execution time overhead.This work was supported in part by National Science Foundation grants CCR-8815928 and CCR-9100968, Office of Naval Research grant N00014-89-J-1222, and a grant from Sequent Computer Systems, Inc.     

Deterministic secure quantum communication without unitary operation based on high-dimensional entanglement swapping

By analysis of the basic properties of entanglement swapping of high-dimensional Bell states,a universal and general deterministic secure quantum communication(DSQC)protocol is proposed,in which unitary operation is not required.By making use of the results of high-dimensional Bell measurement,the sender and the receiver can encode and decode the message respectively by performing the modular addition and subtraction.Two mutually complementary bases are constructed;and according to the property of mutual complement,a method for checking security of the high-dimensional quantum channel is put forward.Some common attack strategies are analyzed,and the corresponding error rates are calculated.Then the upper bound of the threshold of error rate is deduced.     

基于横纵向联合控制的多目标优化车辆跟驰研究

为解决车辆在拥堵环境中因车速波动较大所带来的跟驰平稳性较差、跟踪无效或不安全等问题,提出了基于车辆模型和深度强化学习的多目标优化跟驰方案。首先基于车辆横纵向动力学建立车辆跟驰模型,然后根据车间距误差、速度误差、横向偏差及相对偏航角等,利用深度确定性策略梯度算法得到跟驰车的加速度和转向角,以更平稳安全地控制跟驰车辆。经NGSIM公开驾驶数据集进行测试与验证,该方案可有效地提升跟驰车辆的稳定、舒适与安全性,对保证交通安全和提升道路通行能力具有重要意义。     

片上网络路由算法分析与评估

本文对片上网络中的确定性XY路由算法和基于拐弯模型的4种自适应路由算法进行分析,并采用Noxim模拟器在6种合成通信模式下对5种路由算法的性能进行评估。实验结果表明,在均匀随机通信模式下,XY路由算法的性能优于自适应路由算法;在置换1和混洗通信模式下,奇偶路由算法的性能优于其他路由算法;在置换2、位反和蝶形通信模式下,负向优先路由算法的性能优于其他路由算法。     

证券市场中庄家与散户间的确定性微分博弈

基于确定性微分博弈理论,建立了一种庄家与散户间的连续时间的博弈模型.首先将所有散户作为一个整体与庄家进行博弈,以博弈双方持股率的动态关系作为动态系统方程,并以此构建了一个确定性微分博弈模型; 然后运用开环纳什均衡和反馈纳什均衡分别求解出满足共态函数的常微分方程组和满足价值函数的Issacs - Bellman偏微分方程,以此得到庄家与散户博弈的开环纳什均衡策略和反馈纳什均衡策略.该结果可为金融监管部门监管证券市场和证券市场投资者买卖股票提供参考.     

轴流压气机旋转失速建模与检测II: 基于北航低速压气机试验台的实验研究

轴流压气机旋转失速和喘振的提前检测对于提高压气机工作效率和稳定性具有重要的意义.本文以北京航空航天大学航空发动机重点实验室的低速轴流压气机实验台为研究对象,基于确定学习理论及动态模式识别方法,开展旋转失速初始扰动近似准确建模和快速检测研究.首先,在压气机机匣壁面周向布置多个动态压力传感器,获取压气机失速前和失速先兆的动态压力信号,基于确定学习理论对旋转失速初始扰动的内部系统动态进行建模;其次,基于以上建模,利用微小振动故障检测方法实现对旋转失速的离线和在线提前检测.实验结果表明,本文所提方法能够在不同转速情况下,提前0.3 s~1 s实现对旋转失速的实时在线检测.     

基于特征迭代的云存储数据即时确定性删除方法

传统数据删除方法易受到云存储环境中大量近似特征的影响,产生冗余数据,导致加解密时间过长、密钥可用率较低,为此提出一种基于特征迭代的云存储数据即时确定性删除方法。首先,提取云存储数据中的冗余数据特征,对云存储下冗余数据进行分类,迭代直至收敛,实现冗余数据高性能删除;其次,采用加密机制实现云存储数据在网络用户间的安全共享,将原始数据密文切分为剩余密文和采样密文;最后,把不完整的剩余数据密文上传至云端,同时引入可信任第三方对取样密文进行保存,通过销毁取样密文实现数据即时确定性删除。实验结果表明,所提方法的数据密文拆分所用时间较短,且密钥可用率较高,可达90%,说明其方法能够有效满足云存储系统中对冗余数据或过期数据的确定性删除要求。     

虚拟机动态迁移方法

对虚拟机动态迁移方法的研究背景、研究意义以及研究现状进行综述,分别介绍了内存预拷贝迁移、内存后拷贝迁移、内存混合复制迁移和基于日志跟踪重现的迁移方法,对其算法思想、关键技术、实现机制以及性能等进行概括、分析和比较,并针对当前主流的预拷贝迁移的优化策略予以分类阐述。最后,对动态迁移方法有待深入的研究热点和发展趋势进行展望。