Human-centered control scheme for delayed bilateral teleoperation of mobile robots

Teleoperation task performance strongly depends on how well the human operator’s commands are executed. In this paper, we propose a control scheme for delayed bilateral teleoperation of mobile robots that considers user’s commands execution in order to achieve a high-performance teleoperation system in some important aspects like time to complete the task, safety, and operator dependence. We describe some evaluation metrics that allow us to address these aspects and a quantitative metric is proposed and incorporated in the control scheme to compensate wrong commands. A force feedback is applied to the master at the local site as a haptic cue. In addition, the system stability is analyzed taking into consideration the master and remote robot dynamic models and the asymmetric time-varying delays of the communication channel. Multiple human-in-the-loop simulations were carried out and the results of the evaluation metrics were discussed. Additionally, we present experiments where a user teleoperates a mobile robot via the Internet connection between Argentina and Italy.     

Usability,user experience and mental workload in a mobile Augmented Reality application for digital storytelling in cultural heritage

Virtual Reality - Augmented Reality (AR) has become an increasingly used technology to support and enhance the enjoyment of cultural heritage. Particularly relevant is its importance for...     

Mobrex: visualizing users' mobile browsing behaviors.

This paper deals with the Mobile Browsing Explorer (Mobrex) to give analysts a set of interactive visualizations that highlight various aspects of how users browse an information space. Here, we describe the tool and demonstrate its support of a user study of three browsing techniques for mobile maps. Although we mainly focus here on PDAs and mobile map browsing, Mobrex can easily support analysts studying user interaction with other information spaces and other devices, including mobile phones and desktop computers.     

Layout design in dynamic environments: analytical issues

The paper discusses the layout problem for a productive environment affected by variability of demand (dynamic environment). A conceptual framework of the layout flexibility is discussed, according to the concept of layout robustness. An analytical approach extends the technique adopted for the optimal layout determination from the static to the dynamic context. For an assigned layout problem, an example shows how the analytical approach may be applied to the calculation of the probability distribution of the cost function. From this basis, a measure of the layout robustness is proposed and commented on, in order to give useful advice to those in charge of layout planning and control and to highlight the potential use of the theoretical issues discussed.     

Material-Based Construction Site Image Retrieval

The technological advancements in digital imaging, the widespread popularity of digital cameras, and the increasing demand by owners and contractors for detailed and complete site photograph logs have triggered an ever-increasing growth in the rate of construction image data collection, with thousands of images being stored for each project. However, the sheer volume of images and the difficulties in accurately and manually indexing them have generated a pressing need for methods that can index and retrieve images with minimal or no user intervention. This paper reports recent developments from research efforts in the indexing and retrieval of construction site images in architecture, engineering, construction, and facilities management image database systems. The limitations and benefits of the existing methodologies will be presented, as well as an explanation of the reasons for the development of a novel image retrieval approach that not only can recognize construction materials within the image content in order to index images, but also can be compatible with existing retrieval methods, enabling enhanced results.     

Revisitation of formaldehyde-aniline condensation. III. The Cyclic Tetramer of N-Methyleneaniline: An X-ray diffraction structure determination

The cyclic tetramer of N -methyleneaniline, one of the products from the condensation between formaldehyde and aniline under neutral condition, has been characterized as 1.3.5.7-tetraphenyltetrazocine ( 3 ) and its crystal structure elucidated by X-ray diffraction.     

Use of a mathematical model in the analysis of survival curves of Daphnia magna exposed to toxicants

Chronic toxicity tests carried out on species of the genus Daphnia (Crustacea: Cladocera) are bioassays commonly used in ecotoxicology. Mortality in the cohorts exposed to toxicants can be examined by the analysis of survival curves. The shape of these curves may be very different because of inter-individual heterogeneity: the less rectangular is the shape the more different is the probability of dying of daphnids in the cohort. Aim of this paper is to analyze the characteristics-in particular the shape-of survival curves of cohorts of Daphnia magna exposed to heavy metals in chronic toxicity tests. Experimental curves were fitted by a mathematical model recently proposed, which puts emphasis just on this heterogeneity, described by the parameter of the model S(0). The information contained in S(0) is very useful for the present purposes: the higher the value of S(0) the less rectangular the shape of the curve and, as a consequence, the higher the age-at-death heterogeneity of the cohort is thought to be. The model contains a second parameter, omega, representing the maximum potential ability of the individuals to survive in a specific environment and is related with the maximal life span. The model fitted well the survival curves in most cases and both S(0) and omega showed statistically different values between treatments, useful for comparisons. It was concluded that S(0) provides a quantitative estimation of curve "rectangularization", useful to check different sensitivities to a specific toxicant concentration among daphnids belonging to the same cohort, while omega provides an estimate of maximal life span.     

On the lack of comonotonicity between likert scores and Rasch-based measures

The Rating Scale Model (RSM) and the Partial Credit Model (PCM) are fairly well-known examples of Rasch models for polytomously scored items. In addition to a number of threshold parameters, both the models contain two scalar parameters characterizing item and person location on a common interval-level scale. The rank order of items and persons defined by the Likert summative scores (i.e. the raw total scores) is compared with that obtained from the Rasch-based measures (i.e. the maximum likelihood estimates of person and item parameters). It is proved that: 1) the property of comonotonicity between Likert summative scores and Rasch-based measures holds for both the person and item parameters of the RSM; 2) the property of comonotonicity between Likert summative scores and Rasch-based measures holds for the PCM only with reference to the person parameters; 3) violations of comonotonicity are possible, for particular datasets, for the item parameters of the PCM.     

Mixed micelles containing lipophilic gadolinium complexes as MRA contrast agents

Mixed micelles for MRA are multicomponent systems containing a phospholipid, a biocompatible non-ionic surfactant (e.g. Synporonic^(k) F-108) and a lipophilic gadolinium complex. A variety of lipophilic gadolinium complexes were designed taking into account features such as: (i) nature of ligand (cyclic versus acyclic); (ii) lipophilic moiety; (iii) global charge of the complex; and (iv) nature of bond connecting the complex to the lipophilic moiety. All the lipophilic gadolinium complexes after formulation as mixed micelles show high relaxivities in water and in blood (rat). Mixed micelles containing gadolinium complexes bearing only one aliphatic chain cannot be used as MRA contrast agents because they have a high haemolytic effect. Furthermore, in rats they are quickly eliminated from the blood stream. These drawbacks are completely circumvented using gadolinium complexes bearing two aliphatic chains. Mixed micelles containing such complexes show high relaxivities. no haemolytic effect and long blood permanence. This makes them promising candidates as MRA contrast agents. However, elimination, which occurs exclusively through the liver, is not complete, even after 7 days. Complexes containing labile (e.g. ester) bonds between the lipophilic moieties and the chelate subunit are eliminated through both the liver and the kidneys. However, elimination is stiil not complete after 7 days.     

Catalytic flameless combustion of methane over perovskites prepared by flame–hydrolysis

A set of perovskite-type catalysts of general formula LaBO_3±δ (B=Co, Mn, Fe) and a sample of La₂NiO_4±δ were prepared by means of a recently proposed innovative flame–hydrolysis procedure. The catalysts were characterised by nanometer-size particles (20–60 nm), relatively high surface area (ca. 20 m²/g), high thermal stability and high phase purity. Their high activity for the catalytic flameless combustion of methane confirmed the validity and versatility of the preparation method.

Temperature-programmed -desorption and -reaction, coupled with mass spectrometric analysis, allowed to better understand some aspects of the catalytic behaviour shown by the present samples for the cited reaction. In particular, an interesting correlation between the availability of oxygen at various temperatures, as revealed by the so-called and β oxygen desorption peaks, and reaction mechanism was found for the different B metals.