Subjective and behavioral presence measurement and interactivity in the collaborative augmented reality game TimeWarp

Presence is usually assessed via a variety of subjective and objective measures. However, constraints often result in subjective measurements using questionnaires as a key method of data collection. In this paper we present a study of 44 participants of a collaborative augmented reality game known as TimeWarp which used both subjective and objective behavioral measures. Behavior as coded from video recordings of one scene of the game and self-reports about feelings of presence were compared. Our findings indicate that pointing behavior and verbal responses to the virtual content are correlated negatively to sense of presence. We further investigated the influence of subjectively perceived interactivity on perceived presence. We found that the interaction possibilities perceived by the participants predicted their experience of social presence with the virtual characters in the game. Furthermore, playing together with another person did not result in decreased social presence of the virtual characters. Implications for presence research are discussed.     

Genetic optimization of a vehicle fuzzy decision system for intersections

This paper presents a case study in which an autonomous vehicle must cooperate with a supposedly manually driven one to carry out a cross-roads man?uvre without risk. The main difference with other intersection systems is that the manual vehicle is driven without paying attention to the controlled one, so a cooperative coordination between vehicles is not possible. In this case is the autonomous vehicle the responsible of adapting its speed to the state of the manually driven, for finalizing the man?uvre both in a safe and efficient way.For this purpose, a three layer hierarchical fuzzy rule-based system (FRBS) is developed with the aim of dealing with such a situation: the first layer is in charge of detecting the kind of man?uvre that will be necessary; the second, in the case that an intersection is going to be crossed, is in charge of determining the suitable speed to do so without risk; and the third acts on the vehicle’s real speed. The first two layers are implemented by means of fuzzy decision systems, with the second being optimized by a genetic algorithm (GA). The GA evaluates candidates in random simulated scenarios taking into account different factors to calculate the fitness. These factors are: implementing a free collision policy, avoiding unnecessary stops, and terminating the man?uvre as rapidly as possible.     

Population Aging and Labour Market Participation of Old Workers in Sri Lanka

Sri Lanka??s population is predicted to age very fast during the next 50 years, bringing a potential slowdown of labor force growth and after 2030 its contraction. Based on a large and detailed survey of old people in Sri Lanka, conducted in 2006, the paper examines labor market consequences of this process, focusing on employment outcomes of old workers and the reasons and determinants of labor market withdrawal. The paper finds that a vast majority of Sri Lankan old workers are engaged in the informal sector, work long hours, and are paid less than younger workers. Moreover, using hard evidence, it shows that labour market duality characterizing most developing countries carries over to old age: (i) previous employment is the most important predictor of the retirement pathway; (ii) older workers fall into two categories: formal sector workers, who generally stop working before age 60 because of mandatory retirement regulations, and casual workers and the self-employed, who, due to poverty, work till very old ages and stop working primarily because of poor health; and (iii) the option of part-time work is used primarily by former formal sector workers.     

Application of ultrasonic methods to determine elastic anisotropy of polycrystalline copper processed by equal-channel angular pressing

Anisotropy of elastic properties of ultrafine-grained polycrystalline copper after one, two and four passes of equal-channel angular pressing (ECAP) is investigated by means of ultrasonic methods. For each material, Young’s and shear moduli in the principal processing directions are evaluated and the symmetry and orientation of the anisotropy are identified. The relation between the determined symmetry and the processing mechanisms is discussed. It is shown that the material after one and two passes of ECAP exhibits a measurable anisotropy, while the material after the fourth pass behaves isotropically. Within the discussion, it is shown that the origin of the observed anisotropy may be attributed to the spatial arrangement of grain boundaries rather than to the crystallographic texture. In the light of this conclusion, the obtained results correspond well with optical and transmission electron microscopy observations of the microstructures of ECAPed materials documented in the literature.     

Design of product polar quantizers for A/D conversion of measurement signals with Gaussian distribution

In this paper, a design of product polar quantizers for A/D (analog-to-digital) conversion of measurement signals and an analysis of their performances in the wide range of variances are considered, in a general manner, i.e. for any compression function. Special attention is devoted to the design of robust product polar quantizers, applying the developed theory on μ-law logarithmic compression function, which is very important since a lot of measurement signals are nonstationary. The proposed quantizers achieve much better performances than scalar quantizers (they have higher the maximal SQNR (signal-to-quantization noise ratio) for about 2.5 dB and they are more robust), without increasing of complexity. Theory is proved by simulation. These quantizers can be applied for many different types of measurement signals and can be used in many measurement systems (telemetry, telemedicine, wireless sensor networks, etc.).     

On-line learning of a fuzzy controller for a precise vehicle cruise control system

Usually, vehicle applications need to use artificial intelligence techniques to implement control strategies able to deal with the noise in the signals provided by sensors, or with the impossibility of having full knowledge of the dynamics of a vehicle (engine state, wheel pressure, or occupants’ weight).This work presents a cruise control system which is able to manage the pedals of a vehicle at low speeds. In this context, small changes in the vehicle or road conditions can occur unpredictably. To solve this problem, a method is proposed to allow the on-line evolution of a zero-order TSK fuzzy controller to adapt its behaviour to uncertain road or vehicle dynamics.Starting from a very simple or even empty configuration, the consequents of the rules are adapted in real time, while the membership functions used to codify the input variables are modified after a certain period of time. Extensive experimentation in both simulated and real vehicles showed the method to be both fast and precise, even when compared with a human driver.     

Modeling profile and kinematic analysis of two circular-arc cams

The paper presents a methodology for modeling profile of two circular-arc cams, which is based on the application of homogeneous coordinate transformation method. Analytical expressions that allow complete determining of all design parameters and coordinates of all the points of two circular-arc cams profile are defined. Also, analytical expressions for determining the kinematic performance such as displacement, velocity, acceleration and jerk are derived. The defined methodology is applied on concrete examples for which the analysis of the kinematic performance is also performed. Additionally, it is shown that a proper choice of the design parameters can significantly affect the improvement of the kinematic performance, especially the reduction of jerk as one of the most unfavorable occurrences in these mechanisms. The given methodology allows very efficient determination of all input data for parametric modeling and production of two circular-arc cams on numerical machines. This approach allows the fulfillment of one of the most important requirements of modern production–reduction of time necessary for design and manufacturing which causes reduction of costs.