Design patterns for real-time distributed control system benchmarking

In this paper, we describe the design and development of a simulation–agent interface for real-time distributed control system benchmarking. This work is motivated by the need to test the feasibility of extending agent-based systems to the physical device level in manufacturing and other industrial automation systems. Our work focuses on the development of hybrid physical/simulation environment that can be used to perform tests at both the physical device level, as well as the planning and scheduling level of control. As part of this work, we have extended the proxy design pattern for this application. This paper focuses on the resulting software design pattern for distributed control system benchmarking and provides examples of its use in our hybrid physical/simulation environment.     

A new hybrid mutation operator for multiobjective optimization with differential evolution

Differential evolution has become one of the most widely used evolutionary algorithms in multiobjective optimization. Its linear mutation operator is a simple and powerful mechanism to generate trial vectors. However, the performance of the mutation operator can be improved by including a nonlinear part. In this paper, we propose a new hybrid mutation operator consisting of a polynomial-based operator with nonlinear curve tracking capabilities and the differential evolution’s original mutation operator, for the efficient handling of various interdependencies between decision variables. The resulting hybrid operator is straightforward to implement and can be used within most evolutionary algorithms. Particularly, it can be used as a replacement in all algorithms utilizing the original mutation operator of differential evolution. We demonstrate how the new hybrid operator can be used by incorporating it into MOEA/D, a winning evolutionary multiobjective algorithm in a recent competition. The usefulness of the hybrid operator is demonstrated with extensive numerical experiments showing improvements in performance compared with the previous state of the art.     

Annealing effects in H- and O-terminated P-doped diamond (111) surfaces

The annealing induced effects on hydrogen (H)- and oxygen (O)-terminated P-doped (111) diamond surfaces were investigated by X-ray photoelectron spectroscopy (XPS). Thermally triggered systematic shift of carbon 1s (C1s) peaks was observed for both the surface terminations. The shift is characterized by H- and O-desorption kinetics until a clean surface is produced and then by the non-diamond carbon layer formation on the diamond surface. Desorption induced shift of binding energy (BE) in H-terminated surface is larger than O-terminated diamond surface since the surface bonding configuration of H and O is different. The clean surface emerges at a lower temperature for O-terminated surface than it turned out in H-terminated surface. The growth of non-diamond carbon layer was analysed through loss spectrum of C1s core levels.     

Navigation and discovery in 3D CAD repositories.

Due to increasing product design complexities and the ever-expanding variety of product parts, the amount of information that designers must catalog has exploded. Accordingly, capable CAD tools to help designers create engineering artifacts are now pervasive. The volume of such engineering artifacts generated has increased exponentially and enterprises spend huge resources to organize and archive them into repositories. In these large design repositories, traditional text-based searches prove unwieldy and impractical, and are thus insufficient for individuals seeking 3D content. The paper explains that while traditional text-based searches are impractical for users seeking 3D content in large repositories, existing 3D search systems present search results in a 1D list, which is hard to search. A new interaction paradigm lets users navigate results in 2D and 3D spaces and easily find 3D models that are similar overall or in a single orientation.     

Direct sampled I/Q beamforming for compact and very low-cost ultrasound imaging

A wide variety of beamforming approaches are applied in modern ultrasound scanners, ranging from optimal time domain beamforming strategies at one end to rudimentary narrowband schemes at the other. Although significant research has been devoted to improving image quality, usually at the expense of beamformer complexity, we are interested in investigating strategies that sacrifice some image quality in exchange for reduced cost and ease in implementation. This paper describes the direct sampled in-phase/quadrature (DSIQ) beamformer, which is one such low-cost, extremely simple, and compact approach. DSIQ beamforming relies on phase rotation of I/Q data to implement focusing. The I/Q data are generated by directly sampling the received radio frequency (RF) signal, rather than through conventional demodulation. We describe an efficient hardware implementation of the beamformer, which results in significant reductions in beamformer size and cost. We present the results of simulations and experiments that compare the DSIQ beamformer to more conventional approaches, namely, time delay beamforming and traditional complex demodulated I/Q beamforming. Results that show the effect of an error in the direct sampling process, as well as dependence on signal bandwidth and system f number (f#) are also presented. These results indicate that the image quality and robustness of the DSIQ beamformer are adequate for low end scanners. We also describe implementation of the DSIQ beamformer in an inexpensive hand-held ultrasound system being developed in our laboratory.     

Modeling of combustion and ignition of solid-propellant ingredients

Techniques for modeling energetic-material combustion and ignition have evolved tremendously in the last two decades and have been successfully applied to various solid-propellant ingredients. There has been a paradigm shift in the predictive capability of solid-propellant combustion models as the field has advanced from a simple and global-kinetics approach to a detailed approach that employs elementary reaction mechanisms in the gas phase, and accommodates thermal decomposition and subsequent reactions in the condensed phase. The detailed models not only allow calculation of propellant burning-rate characteristics, such as pressure and temperature sensitivities, but also of the surface conditions and entire combustion-wave structure, including the spatial variations in temperature and species concentrations.

This paper provides a comprehensive review of recent advances in the modeling and simulation of various solid-propellant ingredients over a wide range of ambient conditions. The specific materials of concern include nitramines (RDX, HMX), azides (GAP), nitrate esters (NG, BTTN, TMETN), ADN, and AP monopropellants, as well as homogeneous mixtures representing binary (RDX/GAP, HMX/GAP, and AP/HTPB) and ternary (RDX/GAP/BTTN) pseudo-propellants. Emphasis is placed on the steady-state combustion and laser-induced ignition of nitramines. The capabilities and deficiencies of existing approaches are addressed. In general, the detailed gas-phase reaction mechanisms developed so far represent the chemistry of monopropellants and associated mixtures consistently well, and help understand the intricate processes of solid-propellant combustion. The reaction mechanisms in the condensed phase, however, still pose an important challenge. Furthermore, the current knowledge of the initial decomposition of molecules emerging from the propellant surface is insufficient to render the models fully predictive. Modeling is thus not yet a predictive tool, but it is a useful guide. In the near future, it is likely that detailed combustion models can assist in the formulation of advanced solid propellants meeting various performance and emission requirements.     

Microstructural characterization and pore structure analysis of nuclear graphite

Graphite will be used as a structural and moderator material in next-generation nuclear reactors. While the overall nature of the production of nuclear graphite is well understood, the historic nuclear grades of graphite are no longer available. This paper reports the virgin microstructural characteristics of filler particles and macro-scale porosity in virgin nuclear graphite grades of interest to the Next Generation Nuclear Plant program. Optical microscopy was used to characterize filler particle size and shape as well as the arrangement of shrinkage cracks. Computer aided image analysis was applied to optical images to quantitatively determine the variation of pore structure, area, eccentricity, and orientation within and between grades. The overall porosity ranged between ∼14% and 21%. A few large pores constitute the majority of the overall porosity. The distribution of pore area in all grades was roughly logarithmic in nature. The average pore was best fit by an ellipse with aspect ratio of ∼2. An estimated 0.6-0.9% of observed porosity was attributed to shrinkage cracks in the filler particles. Finally, a preferred orientation of the porosity was observed in all grades.     

Copper‐Catalyzed Oxidative Transformation of Secondary Alcohols to 1,5‐Disubstituted Tetrazoles

A mild and convenient oxidative transformation of secondary alcohols to 1,5‐disubstituted tetrazoles is uncovered by employing trimethylsilyl azide (TMSN₃) as a nitrogen source in the presence of a catalytic amount of copper(II) perchlorate hexahydrate [Cu(ClO₄)₂^.6 H₂O] (5 mol%) and 2,3‐dichloro‐5,6‐dicyano‐para‐benzoquinone (DDQ) (1.2 equiv.) as an oxidant. This reaction is performed under ambient conditions and proceeds through C C bond cleavage.

     

Path switching: a technique to tolerate dual rail routing imbalances

Dual Rail Precharge (DRP) circuits, which are theoretically secure against differential power analysis attacks, suffer from an implementation problem: balancing the routing capacitance of differential signals. To solve this, four proposals have been put forward: Divided Wave Dynamic Differential Logic (DWDDL) (Tiri and Verbauwhede in DATE ’04, pp. 246–251, [2004]), FatWire (Tiri and Verbauwhede in Cardis 2004, pp. 143–158, [2004]), Backend Duplication (Guilley et al. in Lecture Notes in Computer Science, vol. 3659, pp. 383–397, [2005]) and Three Phase Dual Rail (Bucci et al. in Lecture Notes in Computer Science, vol. 4249, pp. 232–241, [2006]). Of these, three (DWDDL, FatWire, Backend Duplication) proposals alter the routing mechanism of Standard Place and Route tools, which in turn introduces an additional step. The other proposal introduces a third phase which reduces the system’s performance. In this paper we propose a new countermeasure, Path Switching, to address the routing problem in DRP circuits. From SPICE simulations we show that our proposal does not reveal the secret key for up to 300,000 traces, an increase of 75 times over normal Dual Rail circuits and 3000 times over normal single rail circuits.     

Highly Efficient Rubrene–Graphene Charge‐Transfer Interfaces as Phototransistors in the Visible Regime

Atomically thin materials such as graphene are uniquely responsive to charge transfer from adjacent materials, making them ideal charge‐transport layers in phototransistor devices. Effective implementation of organic semiconductors as a photoactive layer would open up a multitude of applications in biomimetic circuitry and ultra‐broadband imaging but polycrystalline and amorphous thin films have shown inferior performance compared to inorganic semiconductors. Here, the long‐range order in rubrene single crystals is utilized to engineer organic‐semiconductor–graphene phototransistors surpassing previously reported photogating efficiencies by one order of magnitude. Phototransistors based upon these interfaces are spectrally selective to visible wavelengths and, through photoconductive gain mechanisms, achieve responsivity as large as 10⁷ A W^?1 and a detectivity of 9 × 10¹¹ Jones at room temperature. These findings point toward implementing low‐cost, flexible materials for amplified imaging at ultralow light levels.