一种用分光光度计精确测量白度的方法

采用分光光度计对不透明白色物体的在各个波长的反射率进行测定,选取D65照明体与CIE1931观察者光谱三刺激值,根据亨特白度公式计算出不透明白色物体的白度值,由于不受主观因素的干扰,是一种非常客观、准确的白度评价方法.     

继电保护抗干扰分析

继电保护作为保证电力系统正常运行的重要安全防线,其可靠性尤为关键.但在继电保护系统运行过程中,受继保装置本身、外部环境等多个因素的影响,会出现各种干扰问题,进而影响保护动作的正确执行,产生误动作或者不动作,对电力系统安全运行产生不良影响,因此,对继电保护各种干扰及抗干扰措施的研究具有重要的意义.本文基于继电保护系统速动性、灵敏性及可靠性考虑,根据日常工作经验归纳出了继电保护系统常见的几种干扰,并提出了综合性的抗干扰措施,具有一定的实践指导价值.     

带有同道干扰的MIMO系统性能分析

鉴于已有评估MIMO系统性能的方法没有引入同道干扰而导致评估数据不准确,给出了一种准确评估MIMO系统性能的方法,并且通过K-best检测算法检验该方法的准确性.进而利用此估计方法评估了带有同道干扰的MIMO系统性能,并分析了同道干扰对系统性能的影响.仿真结果表明,随着干扰源的增加,同道干扰对MIMO系统的影响愈加明显.由于考虑了系统的同道干扰,故给出的估计方法更准确地评估了MIMO系统的性能.     

应用时频分析进行高频雷达射频干扰抑制

射频干扰是困扰高频雷达工作的难题之一.本文基于雷达基带采样信号中射频干扰和有用目标信号的时频分布的差异,提出了一种新的射频干扰抑制方法.将该方法应用于高频地波雷达的回波信号处理中,能有效地抑制射频干扰却不损失目标信号,从而使回波距离-多普勒谱的质量得到改善,大大提高了系统的抗干扰能力.该方法也可视为自动实时选频系统的一种软实现.     

激光制导武器光电干扰可视化仿真系统的设计与实现

针对光电对抗战术研究和教学的实际需求,设计并实现了一套以战场环境为背景,集激光制导武器飞行和光电干扰运用于一体的可视化仿真系统,解决了观察者对视点的实时控制,实现了战场环境、特殊效果的逼真模拟.     

基于SARSA学习的跳频系统智能抗干扰决策算法

为了提高在干扰多变电磁环境下跳频通信系统的抗干扰性能,提出一种基于改进SARSA学习的智能抗干扰决策算法。试错是强化学习最重要的特征,它可以影响算法的长期总收益,而试错的优劣由算法探索和利用的表现决定,故文中将基于置信度上界的动作选择策略和优先遍历思想应用于SARSA学习,以平衡智能体对状态-动作空间的探索和利用。另外,针对多种干扰并存的电磁环境以及跳频通信系统的跳速、信道划分间隔和跳频序列等可调节参数,设计了相应的系统模型、决策目标、状态-动作空间和奖赏函数。在不同干扰环境下所提算法都优于三种对比算法,表明基于置信度上界的动作选择策略和优先遍历思想的加入较好地协调了探索与利用的矛盾,提升了收敛速度和稳态性能,加强了SARSA学习对干扰环境的适应性。     

分布式干扰系统对雷达干扰的布阵方法

分布式干扰系统对敌方雷达进行干扰是一种常见的电子对抗手段.通过分析影响分布式干扰系统干扰效果的主要因素,研究了分布式干扰机对单部雷达及组网雷达干扰时的布阵方法,对分布式干扰系统的作战应用具有一定意义.     

光码分多址多用户干扰抑制方法研究

综述了光码分多址(CDMA)多用户干扰的问题及其抑制方法,指出目前光CDMA系统中多用户干扰主要影响发送比特为"0"时的误码率.提出了一种基于最大值判决的并行干扰抑制方法,进行误码性能仿真.仿真结果表明采用上述多用户干扰抑制方法的新型系统比常规系统的误码性能改善10个数量级以上.     

WCDMA与其它蜂窝系统共存时电磁兼容性能研究

通过系统级仿真对WCDMA与相邻频段其它蜂窝系统的电磁兼容问题进行了研究.基于系统级蒙特卡罗仿真技术,提出了一个完整的系统共存仿真容量方案,研究由于射频干扰造成的WCDMA系统的容量损失情况.在计算系统间干扰时,提出了一种称为等效技术的方法,大大提高了仿真速度.给出了可能存在的四种蜂窝系统的干扰造成的容量损失结果.     

参数可变AR干扰建模及实现

在抗干扰仿真系统中,需要建立不同的干扰模型来测试系统的性能.自回归(AR)干扰模型是一种使用非常广泛的干扰模型.在深入分析自回归AR干扰模型的特性、分析方法和参数求解算法的基础上,提出了一种功率和带宽等参数可变AR干扰建模的方法,通过对AR模型带宽、功率的控制和调整,建立不同特性的干扰,以达到对抗干扰仿真系统的测试.仿真实验结果说明,该方法简单,有效,使系统性能检测的实现更加灵活,在实际的工程中能够得到广泛的应用.     

完整性条件下无干扰模型

以Rushby的无干扰工作为基础,对完整性条件下的无干扰模型进行了研究:指出了Rushby所定义的视图划分系统和基于引用监视器假设的系统在完整性条件下和机密性条件下一样,都是满足无干扰的;给出了Biba模型的无干扰解释;提出了动作等价关系,并利用动作等价关系研究了完整性条件下的信息流释放问题;提出了等价自动机和纯化等价自动机的观点,并说明了如何利用这2个图形化的工具帮助进行完整性无干扰推演。     

A nonfunctional approach to system integrity

Systems provide integrity protection by ensuring that there is no unauthorized modification of information. Traditional models of protection tend to define integrity in terms of ad hoc authorization techniques whose effectiveness is justified more on the basis of experience and "best practice," rather than on any common theoretical foundation. A formal definition of integrity is proposed that is independent of any particular implementation mechanism. A series of simple examples is used to demonstrate that existing integrity mechanisms such as separation of duties, well-formed transactions, and so forth, can be regarded as implementation techniques for achieving integrity. The proposed characterization of integrity is nonfunctional, that is, it falls into the same category of properties as noninterference and its relatives. As a consequence, validating that a system has integrity can be expected to be as challenging as validating that a system upholds noninterference.     

可移动系统安全模型统一框架

本文的主要工作是利用可移动进程的形式化模型π演算为工具,考虑系统的移动性(Mobility),将系统安全属性的刻画归结为特定系统进程等价的验证,提出一种新的安全模型框架.在此框架下,可以方便表示不同的不干涉安全属性,并对其进行强弱对比;针对不同安全需求,可定义新的安全属性.并且,该框架建立一个新的安全属性研究的平台,可广泛地适用于具有移动进程的分布式系统的安全分析.     

Identifying effective initiators in OSNs: from the spectral radius perspective

In this paper, we focus on maximizing the influence of online social networks (OSNs). Particularly, we try to answer how to select proper information initiators such that information can propagate as widely as possible. We stress our attention on the susceptible‐infected model, a type of epidemic models, to describe the process of information diffusion. In general, OSNs can be classified into two categories, Facebook‐like OSNs and Twitter‐like OSNs. The former ones require bidirectional connections, while the latter do not, so we use the undirected unweighted graph and directed unweighted graph to describe them, respectively. We also pay additional attention to the nonidentity of the link probability on information transmission and build the weight graph, which can also cover both the two types of OSNs. In order to determine values of weight graph's weights, we introduce a learning method to obtain useful factors from raw data for assessing the true link probability on information transmission. Based on spectral analysis within the three graphs, our investigations on the information diffusion show that the spectral radius of the graph adjacency matrix can reflect the capability of information propagation, according to which we could determine effective initiators. We conduct our simulations on real OSNs. Experimental results show that our approach could effectively discover the initiators that spread information widely. Copyright © 2016 John Wiley & Sons, Ltd.     

信息安全体系模型研究

信息安全体系是信息安全解决方案和工程实施的依据和参照。作为信息安全建设的指导方针,安全体系的设计应该体现出可靠性、完备性、可行性和可扩展性等项原则。通过对信息安全体系发展历程的研究,分析不同体系的优缺点,提出了一种新的信息安全体系模型,并简要介绍了该模型的设计思想,以及与现有信息安全体系模型的关系。这种信息安全体系模型更加符合信息安全体系设计的要求,可以作为各类组织信息安全建设的参考。     

不同年龄段人眼的视觉感知研究

为了探究不同年龄段人眼的视觉特性,采用立体色域的方法建立了显示系统中不同年龄人群的视觉感知模型,以基于CIEL^*A^*B^*颜色空间的立体色域作为标准,取得了不同年龄观察者的立体色域数据。结果表明,从光度学来看,观察者年龄的增长会导致其明视光谱发光效率函数的峰值响应有小幅度的降低,并且其峰值位置在波长轴上向长波方向移动;从色度学上来看,色域体积从20岁的1.73×10⁶到60岁的1.16×10⁶,减小了约1/3,且这种减小集中在中高亮度水平上;进一步分析波长与立体色域的关系,发现绿色光源对所有年龄观察者的立体色域影响最大,对于所有的观察者推荐520 nm的最佳波长选择。该研究可为显示系统针对不同年龄观察者的色域、波长和亮度之间提供设计指导。     

The use of visual search for knowledge gathering in image decision support

This paper presents a new method of knowledge gathering for decision support in image understanding based on information extracted from the dynamics of saccadic eye movements. The framework involves the construction of a generic image feature extraction library, from which the feature extractors that are most relevant to the visual assessment by domain experts are determined automatically through factor analysis. The dynamics of the visual search are analyzed by using the Markov model for providing training information to novices on how and where to look for image features. The validity of the framework has been evaluated in a clinical scenario whereby the pulmonary vascular distribution on Computed Tomography images was assessed by experienced radiologists as a potential indicator of heart failure. The performance of the system has been demonstrated by training four novices to follow the visual assessment behavior of two experienced observers. In all cases, the accuracy of the students improved from near random decision making (33%) to accuracies ranging from 50% to 68%.     

Sensorless Control of Induction Machines by a New Neural Algorithm: The TLS EXIN Neuron

This paper proposes two speed observers for high-performance induction machine drives, both adopting an online adaptation law based on a new total least-squares (TLS) technique: the TLS EXIN neuron. The first is a model reference adaptive system (MRAS) observer with a neural adaptive integrator in the reference model and a neural adaptive model trained online by the TLS EXIN neuron. This observer, presented in a previous article of the authors, has been improved here in two aspects: first, the neural adaptive integrator has been modified to make its learning factor vary according to the reference speed of the drive, second, a neural adaptive model based on the modified Euler integration has been proposed to solve the discretization instability problem in field-weakening. The second observer is a new full-order adaptive one based on the state equations of the induction machine, where the speed is estimated by means of a TLS EXIN adaptation technique. Both these observers have been provided with an inverter nonlinearity compensation algorithm and with techniques for the online estimation of the stator resistance of the machine. Moreover, a thorough theoretical stability analysis has been developed for them both, with particular reference to the field-weakening region behavior for the TLS MRAS observer and to the regenerating mode at low speeds for the TLS adaptive observer. Both speed observers have been verified in numerical simulation and experimentally on a test setup, and have also been compared experimentally with the BPN MRAS observer, the classic adaptive observer and with an open-loop estimator. Results show that both proposed observers outperform all other three observers in every working condition, with the TLS adaptive observer resulting in a better performance than the TLS MRAS observer     

A comparison of human and model observers in multislice LROC studies

Model and human observers have been compared in a series of localization receiver operating characteristic (LROC) studies involving single-slice and multislice image displays. The task was detection of Ga-avid lymphomas within single photon emission computed tomography (SPECT)-reconstructed transverse slices of a mathematical phantom, and the studies involved four reconstruction strategies: the filtered-backprojection (FBP) and ordered-subset expectation-maximization (OSEM) algorithms with two- and three-dimensional postreconstruction filtering. The human-observer data was drawn from studies performed by Wells et al. (2000), while multiclass versions of the nonprewhitening (NPW), channelized nonprewhitening (CNPW), and channelized Hotelling (CH) model observers, each capable of performing the tumor search task, were applied. The channelized observers were evaluated with multiple square-channel models and both with and without internal noise. For the multislice studies, two different capacities for integrating the slice information were also tested. The CH observer gave good quantitative agreement with the human data from both image-display studies when the internal-noise model was used. The CNPW observer performed similarly with the iterative strategies. Wells et al. had shown that human observers are imperfect integrators of multislice information, and this is characterized as increased internal noise with the model observers.     

Real-time information flow analysis

In previous work, we studied some noninterference properties for information flow analysis in computer systems on classic (possibilistic) labeled transition systems. In this paper, some of these properties, notably bisimulation-based nondeducibility on compositions (BNDC), are reformulated in a real-time setting. This is done by first enhancing the security process algebra proposed by two of the authors with some extra constructs to model real-time systems (in a discrete time setting), and then by studying the natural extension of these properties in this enriched setting. We prove essentially the same results known for the untimed case: ordering relation among properties, compositionality aspects, partial model checking techniques. Finally, we illustrate the approach through two case studies, where in both cases the untimed specification is secure, while the timed specification may show up interesting timing covert channels.