High impedance fault arcing on sandy soil in 15 kV distributionfeeders: contributions to the evaluation of the low frequency spectrum

The measured values of current harmonics at a staged high-impedance ground fault on sandy soil are presented. The measured low-frequency spectrum is compared with current harmonics recorded continuously for one week at the substation. This comparison was carried out to determine to what extent 120 Hz and 180 Hz components can be used to help detect a high-impedance fault. The field measurements are supported by a simple theoretical model and laboratory measurements. It is concluded that, for the studied feeder, detection of high-impedance arcing faults may be possible by monitoring of the second-harmonic current     

Interaction of certain oxides,carbides and high-melting metals at high temperatures

Conclusions The greatest stability in contact with BeO is shown by tungsten: with MgO, by molybdenum and tungsten; and with stabilized zirconium oxide, by molybdenumThe most resistant material in contact with the molybdenum up to 2100° is tantalum carbide, and the interaction between molybdenum and zirconium, hafnium and niobium carbide begins at 1800–2200°.     

The practical implementation of time-optimal control for robotic manipulators

This paper presents experimental results for time-optimal control of robotic manipulators along specified paths. The implementation of time-optimal control represents several unique problems: (1) the control is generally discontinuous (bang-bang), (2) actuator dynamics are usually ignored in order to reduce the system order, and (3) the optimal control leaves no control authority to compensate for tracking errors caused by unmodeled dynamic and the delays introduced by the on-line feedback controller. To overcome these difficulties, we compensate for motor dynamics using a simplified friction model, and account for the dynamics of the feedback controller using trajectory preshaping. Implemented for the UCLA Direct Drive Arm, this is shown to drastically reduce the tracking errors compared to the errors obtained with no preshaping and no compensation for motor dynamics. The experimental results demonstrate the merit of time optimal control for reducing motion time as well as for increasing tracking accuracy.     

Patterns of emotion expression during separation in the strange-situation procedure.

The facial expressions of 28 13-mo-old middle-class children were videotaped during the 3-min separation episode of the Ainsworth strange-situation procedure (ASSP). Facial behavior was analyzed to determine the patterns of emotional expressions during separation and to assess the relations between these patterns and types of attachment as assessed by the ASSP. Findings reveal that anger was the dominant negative emotion expressed by the majority of Ss in each of 3 ad hoc groups determined by level of negative emotion. Some high-negative emotion expressers displayed predominantly anger and others mainly sadness. Patterns of emotion expression varied with type of attachment; Ss who showed an insecure-resistant attachment pattern displayed less interest and more sadness than Ss in the securely attached groups. The proportion of time anger was expressed did not differ significantly with type of attachment. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Navigation Among Moving Obstacles Using the <Emphasis Type="Italic">NLVO</Emphasis>: Principles and Applications to Intelligent Vehicles

Vehicle navigation in dynamic environments is a challenging task, especially when the motion of the obstacles populating the environment is unknown beforehand and is updated at runtime. Traditional motion planning approaches are too slow to be applied in real-time to this problem, whereas reactive navigation methods have generally a too short look-ahead horizon. Recently, iterative planning has emerged as a promising approach, however, it does not explicitly take into account the movements of the obstacles.This paper presents a real-time motion planning approach, based on the concept of the Non-Linear Vobst (NLVO) (Shiller et al., 2001). Given a predicted environment, the NLVO models the set of velocities which lead to collisions with static and moving obstacles, and an estimation of the times-to-collision. At each controller iteration, an iterative A* motion planner evaluates the potential moves of the robot, based on the computed NLVO and the traveling time. Previous search results are reused to both minimize computation and maintain the global coherence of the solutions.We first review the concept of the NLVO, and then present the iterative planner. The planner is then applied to vehicle navigation and demonstrated in a complex traffic scenario.Frédéric Large is a member of the French National Consortium on road automation, namely LaRA (“La Route Automatisée”), in the eMotion (formely known as Sharp) research project-team at INRIA (French National Institute for Research on Computer Science and Control). He holds an engineer degree in artificial intelligence (1998) and a master and his Ph.D. in computer science (2003) from the University of Savoie in the Rhône-Alpes (France). Dr. Large works on modelling and reasonning for mobile service-robots and intelligent vehicles. In particular, he specialises on autonomous navigation in environments shared by moving obstacles whose future behaviour is uncertain.Christian Laugier is Research Director at INRIA (French National Institute for Research on Computer Science and Control), and leader of the robotics project-team at INRIA Rhône-Alpes since 1984. He received the Ph.D. and “State Doctor” degrees in Computer Science from Grenoble University (France) in 1976, and 1987 respectively. His current research interests mainly lies in the areas of Motion Autonomy, Intelligent Vehicles, Decisional Processes, and Virtual Reality. In 1997, he was awarded the Nakamura Prize for his contribution to the advancement of the technology on Intelligent Robots and Systems. Pr. Christian Laugier is a member of several scientific national and international committees (several French scientific committees, Adcom of IROS, Adcom of the EURON European Network, etc.), and he is regularly involved in the organizing committees of the major international conferences in Robotics (e.g. IEEE ICRA and IEEE/RSJ IROS). In addition to his research and teaching activities, he participated in the start-up of four industrial companies in the fields of Robotics, Computer Vision, and Computer Graphics.Zvi Shiller is a Professor, founder and head of the Department of Mechanical Engineering-Mechatronics at the College of Judea and Samaria in Ariel, Israel. He received the B.Sc. (‘76) from Tel Aviv University, and the M.Sc. (‘84) and Sc.D. (‘87) from the Massachusetts Institute of Technology, all in Mechanical Engineering. Before joining the College of Judea and Samaria in 2001, he served fourteen years on the faculty of the Department of Mechanical and Aerospace Engineering at UCLA. Professor Shiller’s current research interests include trajectory planning, multi-robot coordination, navigation of autonomous off-road vehicles and active safety of intelligent road vehicles.     

Syringe filtration methods for examining dissolved and colloidal trace element distributions in remote field locations

It is well-established that sampling and sample processing can easily introduce contamination into dissolved trace element samples if precautions are not taken. However, work in remote locations sometimes precludes bringing bulky clean lab equipment into the field and likewise may make timely transport of samples to the lab for processing impossible. Straightforward syringe filtration methods are described here for collecting small quantities (15 mL) of 0.45- and 0.02-microm filtered river water in an uncontaminated manner. These filtration methods take advantage of recent advances in analytical capabilities that require only small amounts of waterfor analysis of a suite of dissolved trace elements. Filter clogging and solute rejection artifacts appear to be minimal, although some adsorption of metals and organics does affect the first approximately 10 mL of water passing through the filters. Overall the methods are clean, easy to use, and provide reproducible representations of the dissolved and colloidal fractions of trace elements in river waters. Furthermore, sample processing materials can be prepared well in advance in a clean lab and transported cleanly and compactly to the field. Application of these methods is illustrated with data from remote locations in the Rocky Mountains and along the Yukon River. Evidence from field flow fractionation suggests that the 0.02-microm filters may provide a practical cutoff to distinguish metals associated with small inorganic and organic complexes from those associated with silicate and oxide colloids.