Nash Equilibria and the Price of Anarchy for Flows over Time

We study Nash equilibria in the context of flows over time. Many results on static routing games have been obtained over the last ten years. In flows over time (also called dynamic flows), flow travels through a network over time and, as a consequence, flow values on edges are time-dependent. This more realistic setting has not been tackled from the viewpoint of algorithmic game theory yet; but there is a rich literature on game theoretic aspects of flows over time in the traffic community.     

Resource bisimilarity and graded bisimilarity coincide

Resource bisimilarity has been proposed in the literature on concurrency theory as a notion of bisimilarity over labeled transition systems that takes into account the number of choices that a system has. Independently, g-bisimilarity has been defined over Kripke models as a suitable notion of bisimilarity for graded modal logic. This note shows that these two notions of bisimilarity coincide over image-finite Kripke frames.     

Resource bisimilarity and graded bisimilarity coincide

Resource bisimilarity has been proposed in the literature on concurrency theory as a notion of bisimilarity over labeled transition systems that takes into account the number of choices that a system has. Independently, g-bisimilarity has been defined over Kripke models as a suitable notion of bisimilarity for graded modal logic. This note shows that these two notions of bisimilarity coincide over image-finite Kripke frames.     

微管道内的剪应力传感器

制作了一个微管道内的剪应力传感器,该传感器通过热传递的原理工作.采用硅微加工技术制作微管道,在玻璃上通过溅射方法形成钛铂合金热膜,最后将两者键合封装,形成埋置了热膜的封闭微管道.测量了热膜的电阻温度系数,确定了热膜处于不同输入功率下的过热比.对该剪应力传感器进行了方波实验,确定其工作在不同过热比下的时间常数.对传感器进行实验标定,得到不同进出口压差下,微管道内的壁面剪应力大小.     

RIP Bill

In the UK, the two distinct issues that are addressed by the RIP Bill are that keys to encryption have to be handed over on demand, and secondly that once keys have been handed over, the informant cannot tell other correspondents and colleagues — or even the head of the organization — that their security has been compromised.     

双足机器人在动态环境中步态规划研究

在双足机器人跨越迎面而来的动态障碍物的问题中,由于障碍物的高度,和速度是不可预测等因素,机器人的迈步步长和迈步高度决定了其能否实现成功跨越.介绍一种双足机器人步态规划方法,应用模糊Q学习算法对迈步高度进行学习,将迈步的起始点、落点和迈步高度作为特征点,利用三次样条对特征点进行插值得到摆动腿运动轨迹,最后通过摆动角间的几何关系得出各关节处摆动角的变化规律,控制机器人跨越动态障碍物.仿真结果表明,通过进行的步态规划,机器人可以成功跨越动态障碍物,并且各关节处的摆动角变化曲线平缓无畸变.     

Evaluating the performance of the space‐borne SAR sensor systems for oil spill detection and sea monitoring over the south‐eastern Mediterranean Sea

Synthetic Aperture Radar (SAR) images have been extensively used for the detection of oil spills in the marine environment as they are independent of local weather conditions, cloudiness and sun illumination. The objective of the study was to provide the users with specific knowledge on SAR image availability over a target area and assess the monitoring capability (visibility of an area) with respect to the requirements for oil‐spill detection and marine environment protection over the south‐eastern part of the Mediterranean Sea. For this purpose, a web GIS tool has been implemented, enabling the users to submit their queries and receive answers in the form of reports and statistics, concerning the current image acquisition capability over the area of interest. It also provides the user with graphic representations of the sensors' swath coverages over the same geographic location. The system has been tested over the Hellenic Seas and the resulting figures denoting the temporal resolution in the observation are analysed and discussed. The analysis shows that the operation of the Envisat satellite, in conjunction with ERS‐2 and Radarsat satellites, has significantly improved the monitoring capability. As shown, the increase in the number of observations over a target location can reach theoretically a level of 130%. In conclusion, the study provides the user with an assessment of the remaining technological gaps and unmet user needs in the domain of marine environment protection.     

Modeling of industrial accidents with liquefied toxic and flammable gases

Modeling of industrial accidents with liquefied toxic and flammable gases is considered. Propagation of nonreacting heavy gas clouds over complex terrains is described by a two-dimensional model with averaging over the cloud height. A numerical simulation of a toxic accident initiated by the release of chlorine in the urban environment has been performed and the number of injured people has been computed. A two-dimensional axisymmetric model based on the Favre-averaged Navier-Stokes equations is used to model the fireballs occurring upon combustion of hydrocarbon fuel-air clouds. Zones of various thermal hazards for people have been obtained.     

On the degree of boundary slip over nonplanar surfaces

The breakdown of the no-slip boundary condition at a fluid–solid interface has been recognized in micro/nanofluidics for many years. However, the relationship between the curvature of the surface and the degree of boundary slip has not been understood sufficiently well. The present study reveals that the degree of slip depends effectively on the surface curvature, which is having an opposing effect over rotating concave and convex surfaces. The results show that as surface curvature increases, the boundary slip becomes negligible over a concave surface, while it becomes increasingly important over a convex surface. In addition, boundary slip formulae are proposed that can accurately predict the boundary slips over convex and concave surfaces. These formulae are found to be in very good agreement with DSMC data for a range of accommodation coefficients and boundary curvatures. The present study then explains the mechanism of the intriguing phenomenon of velocity inversion which has, until the present study, often been mistakenly attributed solely to the effects of boundary curvature.     

应用于工业长距离实时控制的高速接口设计

工业实时控制中大量的数据传输和远端控制对数据传输速度提出了极高的要求,本文提出了一种以高速串／并转换器件ＩＭＳ Ｃ０１１为核心的可满足工业实时控制的高速接口电路,数据传输速率在使用光缆时可达２０Ｍｂｉｔｓ／Ｓｅｃ,本文以此接口电路为依据,实现了工业两相流测量过程层析成象系统（电阻层析成象系统和电磁层析成象系统）的连续控制和数据采集,获得较高的数据采集速率。     

Spatial and temporal variability of soil moisture over India using IRS P4 MSMR data

The brightness temperature data measured by the multi‐frequency scanning microwave radiometer (MSMR) data has been analysed over the Indian subcontinent to deduce the seasonal and monthly variations of soil moisture. The present results show the spatial variations of soil moisture over the Indian region which is affected by the monsoon and show strong variability over different geological terrains.     

Book review

Thermal inertia is a measure of the resistance power of a material to changes in temperature, and this property of a material is very important from the aspects of hydrological and geological studies. Generation of thermal inertia images and their possible geological application has been attempted over the Indian peninsula and its surroundings using INSAT-1D (Indian National Satellite) VHRR (Very High Resolution Radiometer) day-time and consecutive nighttime data. Using the concepts of energy balance computation and also using the procedures involved in albedo computation and the digital registration of day time and pre-dawn imagery, a thermal inertia map over the whole peninsula and its surroundings has been generated. An attempt has been made to correlate the thermal inertia anomalies with sub-surface structures. The analysis done over the subcontinent shows the possibility of delineation of subsurface structures by thermal inertia mapping.     

Formalisation of the computation of the echelon form of a matrix in Isabelle/HOL

In this contribution we present a formalised algorithm in the Isabelle/HOL proof assistant to compute echelon forms, and, as a consequence, characteristic polynomials of matrices. We have proved its correctness over Bézout domains, but its executability is only guaranteed over Euclidean domains, such as the integer ring and the univariate polynomials over a field. This is possible since the algorithm has been parameterised by a (possibly non-computable) operation that returns the Bézout coefficients of a pair of elements of a ring. The echelon form is also used to compute determinants and inverses of matrices. As a by-product, some algebraic structures have been implemented (principal ideal domains, Bézout domains, etc.). In order to improve performance, the algorithm has been refined to immutable arrays inside of Isabelle and code can be generated to functional languages as well.     

Mapping of tubular woven composite preforms on to doubly-curved surfaces

This paper deals with the drape behaviour of tubular woven fabric hoses over doubly curved mould surfaces. The primary aim of this analysis is to predict the alignment of the constituent fibres over the mould surface, which in composites-based applications directly influences the quality of the final product in terms of its structural homogeneity and mechanical properties. Previous work in the area has resulted in algorithms to map the fibres of a flat woven fabric over open surfaces using the shear deformation theory of a woven lamina. The present paper first applies these algorithms to map a flat fabric on to a doubly curved tubular surface and determines the outline of an equivalent tubular fabric preform needed to cover the surface. It is noted that using such a mapping, even to produce a simple u-bend tube requires the tubular preform to have varying cross-section, which is difficult to manufacture. Subsequently, specific algorithms are developed to map a straight tubular hose over a bent and twisted tubular section. Using basic principles of mechanics, models have been derived to map the mesh of fibres over geodesic paths on the curved surface. It is noted that shear deformation plays little or no role but fabric extension and buckling play major roles. The resulting mapping algorithm has been applied to several shapes of varying complexity and experimental validations have been performed.     

Corner layer flow: optimazation of numerical method of solution

The axial corner flow problem has been studied using an ADI method. An optimization study of the method has been carried out in order to maximise the solution convergence rate while maintaining is stability and accuracy. The results obtained by the present method are in good agreement with the available results due to the Gauss-Seidel explicit method.The influence of symmetry boundary on the solution convergence rate has been studied and the approximate manner of specifying this boundary condition for numerical computation has been established. The boundary condition on the vorticity function at the wall has been analysed, and the advantages of the implicit treatment of this boundary condition over explicit treatment are presented. The supriority of the ADI method over the Gauss-seidel explicit method is clearly demonstrated.     

Experiments on string matching in memory structures

Various string matching algorithms have been designed and some experimental work on string matching over bounded alphabets has been performed, but string matching over unbounded alphabets has been little investigated. We present here experimental results where symbols are taken among potentially infinite sets such as integers, reals or composed structures. These results show that, in most cases, it is better to decompose each symbol into a sequence of bytes and use algorithms which assume that the alphabet is bounded, and use heuristics on symbols. © 1998 John Wiley & Sons, Ltd.     

Studies on land surface temperature over heterogeneous areas using AVHRR data

The study addresses the use of the split-window method in tropical regions for estimation of surface temperature over heterogeneous surfaces from satellite sensor data. An attempt has been made to derive emissivity in the thermal channels using the NDVI in conjunction with fractional vegetation cover at pixel level. The estimated surface temperature values are compared with the in situ data over the region and are found to be within error limits of +/- 1.8°C. The utility of fractional vegetation cover in controlling surface temperature has been studied for the selected features over the area. The results suggest the utility of emissivity estimated from the NDVI in land surface temperature estimation.     

Approximate polynomial GCD over integers

Symbolic numeric algorithms for polynomials are very important, especially for practical computations since we have to operate with empirical polynomials having numerical errors on their coefficients. Recently, for those polynomials, a number of algorithms have been introduced, such as approximate univariate GCD and approximate multivariate factorization for example. However, for polynomials over integers having coefficients rounded from empirical data, changing their coefficients over reals does not remain them in the polynomial ring over integers; hence we need several approximate operations over integers. In this paper, we discuss computing a polynomial GCD of univariate or multivariate polynomials over integers approximately. Here, “approximately” means that we compute a polynomial GCD over integers by changing their coefficients slightly over integers so that the input polynomials still remain over integers.     

LMI searches for anticausal and noncausal rational Zames–Falb multipliers

Given a linear time-invariant plant, the search for a suitable multiplier over the class of Zames–Falb multipliers is a challenging problem which has been studied for several decades. Recently, a new linear matrix inequality search has been proposed over rational and causal Zames–Falb multipliers. This letter analyzes the conservatism of the restriction to causality on the multipliers and presents a complementary search for rational and anticausal multipliers. The addition of a Popov multiplier to the anticausal Zames–Falb multiplier is implemented by analogy with the causal search. As a result, a search over a noncausal subset of Zames–Falb multipliers is obtained. A comparison between all the search methods proposed in the literature is given.     

Can Worms Be Good?

Since 1999 programmers and security analysts all over the world have been engaged in a debate over the use of malicious techniques for “constructive” purposes. The use of viral techniques as a means of solving problems implies certain risks. Here are some examples.