Real-time crowd motion planning

Real-time crowd motion planning requires fast, realistic methods for path planning as well as obstacle avoidance. In a previous work (Morini et al. in Cyberworlds International Conference, pp. 144–151, 2007), we introduced a hybrid architecture to handle real-time motion planning of thousands of pedestrians. In this article, we present an extended version of our architecture, introducing two new features: an improved short-term collision avoidance algorithm, and simple efficient group behavior for crowds. Our approach allows the use of several motion planning algorithms of different precision for regions of varied interest. Pedestrian motion continuity is ensured when switching between such algorithms. To assess our architecture, several performance tests have been conducted, as well as a subjective test demonstrating the impact of using groups. Our results show that the architecture can plan motion in real time for several thousands of characters.

Qualitative Ordinal Scales: The Concept of Ordinal Range

Many practical problems of quality control involve the use of ordinal scales. Questionnaires planned to collect judgments on qualitative or linguistic scales, whose levels are terms such as “good,” “bad,” “medium,” etc., are extensively used both in evaluating service quality and in visual controls for manufacturing industry. In an ordinal environment, the concept of distance between two generic levels of the same scale is not defined. Therefore, a population (universe) of judgments cannot be described using “traditional” statistical distributions since they are based on the notion of distance. The concept of “distribution shape” cannot be defined as well. In this article, we introduce a new statistical entity, the so-called ordinal distribution, to describe a population of judgments expressed on an ordinal scale. We also discuss which of the traditional location and dispersion measures can be used in this context and we briefly analyze some of their properties. A new dispersion measure, the ordinal range, as an extension of the cardinal range to ordinal scales, is then proposed. A practical application in the field of quality is developed throughout the article.     

Microchip laser-induced breakdown spectroscopy: a preliminary feasibility investigation

A commercial, 7 microJ/pulse, 550 ps microchip laser is used to induce plasma on Pb, Si, Cu, Fe, Ni, Ti, Zn, Ta, and Mo foils and a Si wafer. The measured plasma lifetime is comparable with the duration of the laser pulse (a few ns). The plasma continuum radiation is low, while some of the strong resonance lines (e.g., Zn 213.86 nm) show self-reversal. Quantitative analysis is possible using non-gated detectors but analytical lines should be chosen with care to avoid reduction in the linear dynamic range. The mass removed (0.5-20 ng/pulse) is sufficient to yield spectra that are detectable with portable grating spectrometers equipped with non-gated, non-intensified detector arrays. The spectrum of Cd is detected with a broadband portable spectrometer (200-950 nm). The combination of the broadband spectrometer and the microchip laser is very promising for material identification, especially in field applications.     

Ultraviolet curable epoxy acrylic resins — network flexibilization in the presence of reactive diluents

Different reactive diluents suitable for inducing network flexibilization of a typical ultraviolet curable epoxy resin based on bisphenol-A-diglycidyl-ether-diacrylate (BGEDA) were investigated. Firstly the influence of some monoacrylic reactive diluents, e.g. 2-ethylhexyl-acrylate (EHA) and 4-hydrocybutil-acrylate (HBA) and of a bis-acrylic diluent, polyethylene-glycol-diacrylate (PEGDA) was examined. Subsequently a systematic study was carried out on the properties of coatings resulting from mixtures of BGEDA and a poly(diethylene-glycol-carbonate) diacrylate (PGCDA) as reactive diluent. The main mechanical, dynamic-mechanical and technological properties of both free films and films coated on steel sheets, were evaluated. Interesting network flexibilization properties were observed when PGCDA was used as reactive diluent of BGEDA. The formulations investigated allowed us to obtain a broad range of flexibility for the resulting ultraviolet cured resins and to correlate the coating flexibility with other fundamental properties such asT _g, elastic modulus, abrasion resistance, hardness, adhesion, impact resistance, accelerated ageing and resistance to chemicals.