Line-of-sight task-space sensing methodology for the localization of robotic end-effectors

In this paper, the implementation of a line-of-sight (LOS) task-space sensing methodology is presented for guidance-based microlocalization of robotic end-effectors. The novelty of the overall system is its applicability to cases that do not allow for the direct proximity measurement of the end-effector's pose (position and orientation). The mobility of the localization application dictates the minimum number and the type (planar or spatial) of the LOS that would be necessary to use and, consequently, the exact configuration of the sensing system. Although the main focus of the paper is the presentation of the proposed LOS sensing system, a brief discussion of a robot-guidance method, which relies on the use of this sensing system, is also included. Extensive experiments conducted for a high-precision 3-DOF (degrees of freedom) planar robotic platform utilizing the overall guidance system validated our research.     

Storage of hydrogen in nanostructured carbon materials

Recent developments focusing on novel hydrogen storage media have helped to benchmark nanostructured carbon materials as one of the ongoing strategic research areas in science and technology. In particular, certain microporous carbon powders, carbon nanomaterials, and specifically carbon nanotubes stand to deliver unparalleled performance as the next generation of base materials for storing hydrogen. Accordingly, the main goal of this report is to overview the challenges, distinguishing traits, and apparent contradictions of carbon-based hydrogen storage technologies and to emphasize recently developed nanostructured carbon materials that show potential to store hydrogen by physisorption and/or chemisorption mechanisms. Specifically touched upon are newer material preparation methods as well as experimental and theoretical attempts to elucidate, improve or predict hydrogen storage capacities, sorption–desorption kinetics, microscopic uptake mechanisms and temperature–pressure–loading interrelations in nanostructured carbons, particularly microporous powders and carbon nanotubes.     

Acquisition of high-precision images for non-contact atomic force microscopy

The atomic force microscope (AFM) system has evolved into a useful tool for direct measurements of intermolecular forces with atomic-resolution characterization that can be employed in a broad spectrum of applications. The distance between cantilever tip and sample surface in non-contact AFM is a time-varying parameter even for a fixed sample height, and typically difficult to identify. A remedy to this problem is to directly identify the sample height in order to generate high-precision atomic-resolution images. For this, the microcantilever (which forms the basis for the operation of AFM) is modeled as a single mode approximation and the interaction between the sample and cantilever is derived from a van der Waals potential. Since in most practical applications only the microcantilever deflection is accessible, we will use merely this measurement to identify the sample height. In most non-contact AFMs, cantilevers with high-quality factors are employed essentially for acquiring high-resolution images. However, due to high-quality factor, the settling time is relatively large and the required time to achieve a periodic motion is long. As a result, identification methods based on amplitude and phase measurements cannot be efficiently utilized. The proposed method overcomes this shortfall by using a small fraction of the transient motion for parameter identification, so the scanning speed can be increased significantly. Furthermore, for acquiring atomic-scale images of atomically flat samples, the need for feedback loop to achieve setpoint amplitude is basically eliminated. On the other hand, for acquiring atomic-scale images of highly uneven samples, a simple PI controller is designed to track the desired constant sample height. Simulation results are provided to demonstrate the feasibility of the approach for both sample height identification and tracking the desired sample height.     

A Critical Study of the Compressible Lattice Boltzmann Methods for Riemann Problem

In this paper, the discrete velocity model proposed by Kataoka and Tsutahara (Phys. Rev. E 69(5):056702, 2004) for simulating inviscid flows is employed. Three approaches for improving the stability and the accuracy of this model, especially for high Mach numbers, are suggested and implemented in this research. First, the TVD scheme (Harten in J. Comput. Phys. 49:357?C393, 1983) is used for space discretization of the convective term in the Lattice Boltzmann equation. Next, the modified Lax-Wendroff with artificial viscosity is employed to increase the robustness of the method in supersonic flows. Finally, a combination of TVD and the 2nd order derivative of the distribution function is employed using a differentiable switch. It is found that the recent technique is a more suitable approach for a wide range of Mach numbers. Moreover, the WENO scheme for space discretization has been applied and compared with these newly applied methods.     

A study on the efficiency of hardware Trojan detection based on path-delay fingerprinting

Hardware Trojan horses (HTHs) are among the most challenging treats to the security of integrated circuits. Path-delay fingerprinting has shown to be a promising HTH detection approach. However, previous work in this area incurs a large hardware cost or requires expensive testing techniques. Moreover, the relation between technology mapping and the efficiency of delay-based HTH detection have not yet been studied. In this paper, we present a HTH detection method which uses an effective test-vector selection scheme and a path-delay measurement structure. Furthermore, we demonstrate the large impact of technology mapping on the effectiveness of delay-based HTH detection. We also show that delay-based detection methods are highly scalable. In case of choosing an area-driven design strategy, the average HTH detection probability of our approach is about 63%, 78% and 90% if false alarm rate is 0%, 2% and 16%, respectively. However, with modifications in the technology mapping, the results show improvements to 85%, 94% and 99%, at the cost of about 20% area overhead. In addition, the efficiency of our method would not decrease for large benchmarks with thousands of gates.     

A guidance‐based motion‐planning methodology for the docking of autonomous vehicles

In this paper, a generic line‐of‐sight‐sensing (LOS)‐based guidance methodology is proposed for the docking of autonomous vehicles/robotic end‐effectors: A multi‐LOS task‐space sensing system is used in conjunction with a guidance algorithm in a closed‐loop feedback environment. The novelty of the overall system is its applicability to cases that do not allow for the direct proximity measurement of the vehicle's pose (position and orientation). In such instances, a guidance‐based technique must be employed to move the vehicle to its desired pose using corrective actions at the final stages of its motion. Namely, after the vehicle/end‐effector has failed to move to its desired docking pose within acceptable tolerances, LOS sensors initiate short‐range corrective motion commands. The objective of the proposed guidance method is, thus, to successfully minimize the systematic errors of the vehicle, accumulated after a long‐range motion, while allowing it to converge within the random noise limits. An additional advantage of the proposed system is its applicability to varying vehicle mobility requirements for high‐precision docking. The proposed system was successfully tested via simulation on a 6 degree‐of‐freedom (DOF) vehicle. Numerous simulation tests of the behavior of the vehicle under the command of the guidance algorithm were conducted, one of which is presented herein. © 2005 Wiley Periodicals, Inc.     

Effect of the liquid entrainment on the predicted pressure drop in vertical flow-boiling

Flow boiling in a vertical uniformly heated tube has been modelled employing the drift flux and two-fluid formulations. The governing equations are solved numerically and the results presented in the form of pressure drop versus mass flux curves are compared to previously obtained experimental results. The effect of the entrained liquid fraction at the transition from churn-turbulent to annular flow when a switch from the drift flux model to the two-fluid formulation is made is shown to affect the results and could improve the pressure drop predictions.     

APPLICATION OF MULTICOLUMN VALVE SWITCHING GAS CHROMATOGRAPHY FOR THE ANALYSIS OF NAPHTHA AND KEROSENE FRACTIONS OF SAUDI ARABIAN LIGHT CRUDE OIL

The straight run naphtha and kerosene fractions of Saudi Arabian Light crude oil were analyzed for paraffins, olefins, naphthenes and aromatics (PONA) using a gas chromatographic technique. This method is based upon group type separation according to carbon numbers using a programmed multiple valve switching sequence and employing multicolumn approach. The chromatographic operating conditions and carrier gas flow rates were selected to determine PONA contents of naphtha and kerosene fractions. These straight run fractions were produced by an automatic true boiling point (TBP) apparatus. Boiling range distributions of these fractions were determined using a standard ASTM method of simulated distillation. PONA results were compared with the literature. Total paraffins, naphthenes and aromatics agreed with each other.