An instructional robotics and machine vision laboratory

The US Naval Academy has assembled a laboratory consisting of 16 identical stations in support of several robotics and machine vision courses. Each station has an 80386-based microcomputer, a five degree-of-freedom robot arm, a video-rate vision system, and a speech synthesis system. The robot arms are capable of teach-pendant operation or control via the attached computer. Programs written in the robot control language can be downloaded into, stored in, and run from robot RAM. For greater flexibility, move instructions can be generated by the controlling computer (in any desired computer language) and transmitted to the arm for execution via an RS-232 link. Each joint of the robot (plus the gripper) has a dedicated microprocessor for closed-loop servo operation utilizing incremental drive-motor shaft encoders and micro-switches for “home” locations. The vision system includes an RS170-compatible video camera, a PC-compatible frame grabber board, and a video monitor. This configuration permits the utilization of 2D and 3D vision feedback in the robot control process. The laboratory is used in support of undergraduate courses that cover such topics as robot kinematics and task planning, elementary machine vision, and artificial neural networks     

Body loadings and health risk assessment of polychlorinated dibenzo-p-dioxins and dibenzofurans at an intensive electronic waste recycling site in China

This study is one of the very few investigating the dioxin body burden of a group of child-bearing-aged women at an electronic waste (e-waste) recycling site (Taizhou, Zhejiang Province) (24 +/- 2.83 years of age, 40% were primiparae) and a reference site (Lin'an city, Zhejiang Province, about 245 km away from Taizhou) (24 +/- 2.35 years of age, 100% were primiparae) in China. Five sets of samples (each set consisted of human milk, placenta, and hair) were collected from each site. Body burdens of people from the e-waste processing site (human milk, 21.02 +/- 13.81 pg WHO-TEQ1998/g fat (World Health Organization toxic equivalency 1998); placenta, 31.15 +/- 15.67 pg WHO-TEQ1998/g fat; hair, 33.82 +/- 17.74 pg WHO-TEQ1998/g dry wt) showed significantly higher levels of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/ Fs) than those from the reference site (human milk, 9.35 +/- 7.39 pg WHO-TEQ1998/g fat; placenta, 11.91 +/- 7.05 pg WHO-TEQ1998/g fat; hair, 5.59 +/- 4.36 pg WHO-TEQ1998/g dry wt) and were comparatively higher than other studies. The difference between the two sites was due to e-waste recycling operations, for example, open burning, which led to high background levels. Moreover, mothers from the e-waste recycling site consumed more foods of animal origin. The estimated daily intake of PCDD/Fs within 6 months by breastfed infants from the e-waste processing site was 2 times higher than that from the reference site. Both values exceeded the WHO tolerable daily intake for adults by at least 25 and 11 times, respectively. Our results implicated that e-waste recycling operations cause prominent PCDD/F levels in the environment and in humans. The elevated body burden may have health implications for the next generation.     

The cost of probabilistic agreement in oblivious robot networks

In this paper, we look at the time complexity of two agreement problems in networks of oblivious mobile robots, namely, at the gathering and scattering problems. Given a set of robots with arbitrary initial locations and no initial agreement on a global coordinate system, gathering requires that all robots reach the exact same but not predetermined location. In contrast, scattering requires that no two robots share the same location. These two abstractions are fundamental coordination problems in cooperative mobile robotics. Oblivious solutions are appealing for self-stabilization since they are self-stabilizing at no extra cost. As neither gathering nor scattering can be solved deterministically under arbitrary schedulers, probabilistic solutions have been proposed recently.The contribution of this paper is twofold. First, we propose a detailed time complexity analysis of a modified probabilistic gathering algorithm. Using Markov chains tools and additional assumptions on the environment, we prove that the convergence time of gathering can be reduced from O(n²) (the best known bound) to O(1) or , depending on the model of multiplicity detection. Second, using the same technique, we prove that scattering can also be achieved in fault-free systems with the same bounds.     

Shared WiFi-Communities – User Generated Infrastructure am Beispiel von FON

Shared WiFi-Communities emerge when users share their private Wireless Fidelity with others and in return get free internet access via community members’ internet connection. Supply of wireless capacity and demand for WLAN usually are coordinated by a central authority therewith users can find specific hosts within the community. Initial players that conduct commercial WiFi-Communities established their position in the market. The international market leader with 170,000 hotspots worldwide is FON. The commercial success of shared WiFi-communities (e.g. FON) depends on the adoption of a special router or modifications of the existing WLAN-infrastructure. More importantly it is essential that users permanently offer broadband capacity to the community. Only then net effects can durably generate enhanced usage benefits. A survey of 268 German FON users reveals that the community shows a high level of cohesion. Users barely vary from the default setting concerning shared bandwidth of the router. Additionally most interviewees offer their WLAN 24 hours a day. Despite the possibility of earning money with the wireless capacity most users do not offer bandwidth with a purely economic ambition. Although the market potential of shared WiFi communities appears tremendous legal obstructions and technical restraints exacerbate penetration.     

New NO-donors with antithrombotic and vasodilating activities, Part 17. Arylazoamidoximes and 3-arylazo-1,2,4-oxadiazol-5-ones

Seven arylazoamidoximes (3), six phenoxycarbonyl derivatives (4), and six 1,2,4-oxadiazol-5-ones (5) have been prepared and their structure and purity established by spectroscopy and elemental analysis. In the EI mass spectra ready elimination of NO from the title amidoximes was observed. A new addition reaction of 3a with hydrochloric acid to 4-chlorophenylhydro-azoamidoxime 7 is described. The compounds were tested for nitric oxide dependent biological properties, i.e. platelet aggregation, antithrombotic effects, and decrease in blood pressure. In arterioles of rats 5/19 compounds inhibited the formation of thrombi with a laser beam by > or = 20% 2 h after oral administration of 60 mg/kg. Among these are three amidoximes (3a, 3e, 3f), one phenoxycarbonyl derivative (4a), and one oxadiazolone (5a). With the 4-chlorophenylazoamidoxime 3c a long lasting (24 h) decrease of blood pressure in spontaneously hypertensive rats was observed. Microsomal fractions of rat liver oxidize arylazoamidoximes and generate nitric oxide (e.g. 3a and 3b). NO was measured by the oxyhemoglobin assay. The influence of SOD, pretreatment of the rats with dexamethasone, as well as kinetic parameters were determined. Type 3 compounds, therefore, are a new class of NO donors. Type 4 and 5 compounds function as their prodrugs.     

Simulation and computer-aided kinematic design of three-degree-of-freedom spherical parallel manipulators

Parallel robotic manipulators are complex mechanical systems that lead to involved kinematic and dynamic equations. Hence, the design of such systems is in general not intuitive, and advanced simulation and design tools specialized for this type of architecture are highly desirable. This article discusses the kinematic simulation and computer-aided design of three-degree-of-freedom spherical parallel manipulators with either prismatic or revolute actuators. The kinematic analysis of spherical parallel manipulators is first reviewed. Solutions for the direct and inverse kinematic problems are given, and the expressions for the singularity loci are then introduced. The determination of the workspace of this type of manipulator is also addressed. Finally, a computer package developed specifically for the CAD of spherical parallel manipulators is presented. This package allows the interactive analysis of manipulators of arbitrary architecture including the representation of the workspace, the representation of singularities, and the graphic animation of trajectories specified either by the direct or the inverse kinematic module. It can be used for the design of any spherical parallel three-degree-of-freedom actuated mechanism, which can find many applications in high-performance robotic systems. © 3995 John Wiley & Sons, Inc.     

Transcranial ultrasound focus reconstruction with phase and amplitude correction

Therapeutic and diagnostic ultrasound procedures performed noninvasively through the skull require a reliable method for maintaining acoustic focus integrity after transmission through layered bone structures. This study used a multiple-element, phased-array transducer to reconstruct ultrasound foci through the human skull by amplitude and phase correction. It was previously demonstrated that adaptive phase correction using a multiple-element, focused transducer array yields a significant correction to an acoustic field that has been distorted by the heterogeneities of the skull bone. The introduction of amplitude correction, in a regime in which acoustic pressures from individual transducer array elements are adjusted to be normalized at the focus, has demonstrated a 6% (-0.27 dB) average decrease in acoustic sidelobe acoustic intensity relative to the focal intensity and a 2% (-0.09 dB) average decrease in the full-width-at-half-maximum (FWHM) of the acoustic intensity profile at the focus. These improvements come at the expense of significant ultrasound intensity loss--as much as 30% lower (-1.55 dB)--at the focus because the amplitude correction method requires that, at constant power, a larger proportion of energy is absorbed or reflected by regions of the skull that transmit less energy. In contrast, a second correction method that distributes pressure amplitudes such that the sections of the skull which transmit more ultrasound energy are exposed with higher ultrasound intensities has demonstrated an average sidelobe intensity decrease of 3% (-0.13 dB) with no change in the FWHM at the focus. On average, there was a 2% (0.09 dB) increase in the acoustic intensity at the focus for this inverse amplitude correction method. These results indicate that amplitude correction according to the transmission properties of various segments of the skull have a clear effect on ultrasound energy throughput into a target site within the brain parenchyma.     

Synthesis of linear aliphatic polycarbonate macroglycols using dimethylcarbonate

A series of linear aliphatic polycarbonate polyols were synthesized using dimethylcarbonate and a linear alkane diol or specific combinations of linear alkane diols. Polyol synthesis was carried out in a two‐stage process using dimethylcarbonate and a linear alkane diol to prepare a series of homopolymer polycarbonate polyols. Polyol grades were characterized using Fourier transform infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetery techniques. Suitable reaction conditions were developed to yield polycarbonate polyols of number average molecular weight between 700 and 1700. The crystallinity of the polycarbonate polyols was shown to reduce as the molecular weight of the alkane diols used in the polycarbonate synthesis was increased. These polymers offer the potential for use in the synthesis of ether free polyurethane elastomers for biomedical applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Behavior of RC columns strengthened with different CFRP systems under eccentric loading

The present study investigates the performance of eccentrically loaded columns externally strengthened with different carbon fiber-reinforced polymer (CFRP) systems. The 10 specimens were representative-scale square columns made of normal-strength concrete with substandard (internal) reinforcement details that were designed to represent old building structural columns. Eight columns were upgraded by four types of commercially available systems of external reinforcement, using plates, unidirectional or bi-directional composite fabrics. It was considered necessary to get information on a wide spectrum of carbon fiber-reinforcement systems in order to provide a satisfactory set of experimental data for validating future suitable retrofitting design methods. Experimental results presented in this paper show that a significant improvement of the strength capacity, deformation capacity and ductility of columns can result of the CFRP application, but the observed gains strongly depend on the reinforcement systems.