Time-Evolving Measures and Macroscopic Modeling of Pedestrian Flow

This paper introduces a new model of pedestrian flow, formulated within a measure-theoretic framework. It consists of a macroscopic representation of the system via a family of measures which, pushed forward by some flow maps, provide an estimate of the space occupancy by pedestrians at successive times. From the modeling point of view, this setting is particularly suitable for treating nonlocal interactions among pedestrians, obstacles, and wall boundary conditions. In addition, the analysis and numerical approximation of the resulting mathematical structures, which are the principal objectives of this work, follow more easily than for models based on standard hyperbolic conservation laws.     

A combined analytical approach applied to Medieval wall paintings from Puglia (Italy): The study of painting techniques and its conservation state

A combined analytical approach has been applied to the wall paintings, dated from 10th to 14th centuries, of the Santi Stefani crypt at Vaste (Lecce, Southern Italy). These paintings are a precious testimony of Medieval art in Southern Italy. However, the church shows problems of damp as well as clear evidences of flora, fungi and mold presence, and there is little knowledge of the pictorial methodologies used. Raman spectroscopy allowed to determine the palette and to reconstruct the worksite and the chronological sequence of the various paint layers. Kaolinite, calcite, carbon black, hematite, massicot, goethite, indigo and azurite were identified as pigments along with synthetic pigments, like phthalocyanine blue and chrome yellow. Attenuated total reflectance‐Fourier transform infrared spectroscopy suggested the presence of egg as a binder in some pictorial layers. The conservation state of the crypt is poor, and detachments of pigmented layers are frequent because of the presence of subflorescence and efflorescence: nitrate, sulfate and chloride salts have been identified spectroscopically and quantified by ion chromatography. The extensive use of kaolinite in Santi Stefani, actually not uncommon in Medieval art, is observed for the first time in a crypt of Puglia: its use to stabilize some pigments and to improve their adhesion on substrate is proposed. Copyright © 2015 John Wiley & Sons, Ltd.     

Construction of infinite unimodular sequences with zero autocorrelation

Unimodular waveforms x are constructed on the integers with the property that the autocorrelation of x is one at the origin and zero elsewhere. There are three different constructions: exponentials of the form e^{2 pi na q},e^{2 \pi i n^\alpha \theta}, sequences taken from roots of unity, and sequences constructed from the elements of real Hadamard matrices. The first is expected and elementary and the second is based on the construction of Wiener. The third is the most intricate and is really one of a family of distinct but structurally similar waveforms. A natural error estimate problem is posed for the last construction. The analytic solution is not as useful as the simulations because of the inherent counting problems in the construction.     

A unifying approach to abstract matrix algebra preconditioning

In earlier papers Tyrtyshnikov [42] and the first author [14] considered the analysis of clustering properties of the spectra of specific Toeplitz preconditioned matrices obtained by means of the best known matrix algebras. Here we generalize this technique to a generic Banach algebra of matrices by devising general preconditioners related to “convergent” approximation processes [36]. Finally, as case study, we focus our attention on the Tau preconditioning by showing how and why the best matrix algebra preconditioners for symmetric Toeplitz systems can be constructed in this class. Received April 25, 1997 / Revised version received March 13, 1998     

Understanding deadlock and livelock behaviors in Hybrid Control Systems

This paper introduces a formal definition and a categorization of Deadlock and Livelock behaviors for a general class of deterministic Hybrid Control Systems (HCS), thus extending the classical notion known for (uncontrolled) discrete transition systems. This characterization hinges on three important aspects: (1) the concept of composition (or interconnection) of HCSs; (2) the notion of control-dependent specification, and that of composition of specifications; (3) the dynamical structure of an HCS and its related behaviors. The first notion is introduced in a novel manner, by including aspects from the literature of discrete transition systems, as well as accounting for classical concepts such as that of feedback interconnection of dynamical systems. The second point allows us to formally express general properties that are of interest from a systems and control theory perspective. The third part discriminates between the different and possibly pathological behaviors that are characteristic to HCSs. After commenting on the issues of Deadlock and Livelock prevention and verification, the article concludes with two case studies.     

煤粉燃烧中NOx和SOx生成的详细反应机理模拟

采用详细化学反应机理与CFD方法耦合的煤粉燃烧数值模拟程序,计算了煤粉燃烧过 程中CO, NOx和SOx等的浓度分布特性. 通过与实验对照,验证了数值模拟方法的 可靠性,并分析了燃烧温度和煤粉细度等因素对于NO生成的影响. 结果表明温度对于NO的 生成影响较大,随着温度的增加,NO的生成浓度明显增加;对于不同煤种,可能存在一个温 度点,这时NO的生成速率将非常快;在计算范围内,温度对SO2的最终生成浓度没有 明显影响,而只影响SO2的释放过程. 煤粉细度对于NO生成有较小的影响.