Effects of imperfect automation on decision making in a simulated command and control task

OBJECTIVE: Effects of four types of automation support and two levels of automation reliability were examined. The objective was to examine the differential impact of information and decision automation and to investigate the costs of automation unreliability. BACKGROUND: Research has shown that imperfect automation can lead to differential effects of stages and levels of automation on human performance. Method: Eighteen participants performed a "sensor to shooter" targeting simulation of command and control. Dependent variables included accuracy and response time of target engagement decisions, secondary task performance, and subjective ratings of mental work-load, trust, and self-confidence. RESULTS: Compared with manual performance, reliable automation significantly reduced decision times. Unreliable automation led to greater cost in decision-making accuracy under the higher automation reliability condition for three different forms of decision automation relative to information automation. At low automation reliability, however, there was a cost in performance for both information and decision automation. CONCLUSION: The results are consistent with a model of human-automation interaction that requires evaluation of the different stages of information processing to which automation support can be applied. APPLICATION: If fully reliable decision automation cannot be guaranteed, designers should provide users with information automation support or other tools that allow for inspection and analysis of raw data.     

Snap-stabilization and PIF in tree networks

The contribution of this paper is threefold. First, we present the paradigm of snap-stabilization. A snap- stabilizing protocol guarantees that, starting from an arbitrary system configuration, the protocol always behaves according to its specification. So, a snap-stabilizing protocol is a time optimal self-stabilizing protocol (because it stabilizes in 0 rounds). Second, we propose a new Propagation of Information with Feedback (PIF) cycle, called Propagation of Information with Feedback and Cleaning (). We show three different implementations of this new PIF. The first one is a basic cycle which is inherently snap-stabilizing. However, the first PIF cycle can be delayed O(h ²) rounds (where h is the height of the tree) due to some undesirable local states. The second algorithm improves the worst delay of the basic algorithm from O(h ²) to 1 round. The state requirement for the above two algorithms is 3 states per processor, except for the root and leaf processors that use only 2 states. Also, they work on oriented trees. We then propose a third snap-stabilizing PIF algorithm on un-oriented tree networks. The state requirement of the third algorithm depends on the degree of the processors, and the delay is at most h rounds. Next, we analyze the maximum waiting time before a PIF cycle can be initiated whether the PIF cycle is infinitely and sequentially repeated or launch as an isolated PIF cycle. The analysis is made for both oriented and un-oriented trees. We show or conjecture that the two best of the above algorithms produce optimal waiting time. Finally, we compute the minimal number of states the processors require to implement a single PIF cycle, and show that both algorithms for oriented trees are also (in addition to being time optimal) optimal in terms of the number of states. WARNING: The concept of snap-stabilization was first introduced in [12]. The concept evolved over the last eight years. We take this evolution in consideration in this paper, which includes the early results published in [10] and [12]. In particular, infinite repetition of computation cycles is a requirement of self-stabilizing systems. This is not required in snap-stabilization because snap-stabilization ensures that the first completed computation cycle is executed according to the specification of the problem. The correctness proofs conform to this basic property.     

Effect of nitrogen addition on the microstructure and mechanical behavior of 317L and 904L austenitic stainless steel welds

A systematic study of the effect of nitrogen addition on the microstructure and mechanical behavior of two different austenitic stainless steel welds, namely, 317L and 904L was carried out. For this, nitrogen content of the welds was altered by introducing different proportions of nitrogen gas into the argon shielding gas during welding. Nitrogen addition to 317L weld changed solidification mode from primary ferrite to primary austenite. As 904L weld solidify by primary austenitic mode, no change in the solidification mode was found with N addition. The results showed that, with rise in nitrogen content of the welds, various mechanical properties like ultimate tensile strength and ductility had improved significantly and that the welds prepared with 1 vol% N₂ in the shielding gas indeed failed in the base alloy making the weld stronger than the parent metal. It was noticed that the effect of N towards improving the mechanical properties 904L weld was higher than that found in the case of 317L weld.     

A parallel hp‐FEM infrastructure for three‐dimensional structural acoustics

This paper describes a parallel three‐dimensional numerical infrastructure for the solution of a wide range of time‐harmonic problems in structural acoustics and vibration. High accuracy and rate of error‐convergence, in the mid‐frequency regime,is achieved by the use of hp‐finite and infinite element approximations. The infrastructure supports parallel computation in both single and multi‐frequency settings. Multi‐frequency solves utilize concurrent factoring of the frequency‐dependent linear algebraic systems and are naturally scalable. Scalability of large‐scale single‐frequency problems is realized by using FETI‐DP—an iterative domain‐decomposition scheme. Numerical examples are presented to cover applications in vibratory response of fluid‐filled elastic structures as well as radiation and scattering from elastic structures submerged in an infinite acoustic medium. We demonstrate both the numerical accuracy as well as parallel scalability of the infrastructure in terms of problem parameters that include wavenumber and number of frequencies, polynomial degree of finite/infinite element approximations as well as the number of processors. Scalability and accuracy is evaluated for both single and multiple frequency sweeps on four high‐performance parallel computing platforms: SGI Altix, SGI Origin, IBM p690 SP and Linux‐cluster. Results show good performance on shared as well as distributed‐memory architecture. Copyright © 2006 John Wiley & Sons, Ltd.     

Influence of Cl-, Br-, NO 3 - and SO 4 2- ions on the corrosion behaviour of 6061 Al alloy

The effects of anions like Cl^-, Br^-, NO ₃ ^- and SO ₄ ^2- on the anodic dissolution of the monolithic Al 6061 alloy have been investigated at neutral pH through immersion testing and electrochemical techniques like potentiodynamic polarization and a.c. impedance spectroscopy. Scanning electron microscopy was employed to characterize the corroded surface and to observe the extent of pitting in different media. From the evaluated corrosion parameters it was found that the dissolution of the matrix was extensively reduced in presence of aqueous solutions containing Br^-, NO ₃ ^- and SO ₄ ^2- ions while Cl^- ions aggravated corrosion by penetrating into the barrier oxide film on the surface of the material. Pronounced effect of pitting was observed in presence of Cl^- and the level of pitting in NO ₃ ^- and Br^- were mild. In presence of SO ₄ ^2- ions passivity was extended over a wide potential range and breakdown of passivity occurs when the material was polarized beyond pitting potential. The departure of capacitive behaviour towards resistive behaviour was clearly observed through impedance measurements when investigations were conducted in Cl^- media and in presence of the other electrolytes. Corrosion rates were, however, controlled during prolonged exposure in the electrolytic media, specially in case of chloride media, due to the predominance of film repair kinetics.     

Benchmarking nanotechnology for high-performance and low-power logic transistor applications

Recently there has been tremendous progress made in the research of novel nanotechnology for future nanoelectronic applications. In particular, several emerging nanoelectronic devices such as carbon-nanotube field-effect transistors (FETs), Si nanowire FETs, and planar III-V compound semiconductor (e.g., InSb, InAs) FETs, all hold promise as potential device candidates to be integrated onto the silicon platform for enhancing circuit functionality and also for extending Moore's Law. For high-performance and low-power logic transistor applications, it is important that these research devices are frequently benchmarked against the existing Si logic transistor data in order to gauge the progress of research. In this paper, we use four key device metrics to compare these emerging nanoelectronic devices to the state-of-the-art planar and nonplanar Si logic transistors. These four metrics include: 1) CV/I or intrinsic gate delay versus physical gate length L/sub g/; 2) energy-delay product versus L/sub g/; 3) subthreshold slope versus L/sub g/; and 4) CV/I versus on-to-off-state current ratio I/sub ON//I/sub OFF/. The results of this benchmarking exercise indicate that while these novel nanoelectronic devices show promise and opportunities for future logic applications, there still remain shortcomings in the device characteristics and electrostatics that need to be overcome. We believe that benchmarking is a key element in accelerating the progress of nanotechnology research for logic transistor applications.     

Synthesis and Optical Studies of Superconducting MgB2 Thin Films

Synthesis and optical transmission of MgB₂ thin films on optically transparent glass are reported. In the 400–1000 nm regime as deposited films show high metallic reflectivity and very little transmission. After deposition, the films were annealed ex situ and rendered superconducting with T _c of 38 K, approaching that of the bulk material. The reaction conditions where quite soft ∼10 min at 550°C. The optical absorption coefficient, α and photon energy, E followed a Tauc-type behavior, = _T (E - E_g )(\alpha E)^{1/2} = \beta _T (E - E_{\rm g} ). The band gap (E _g) was observed to peak at 2.5 eV; but, the slope parameter β _T behaved monotonically with reaction temperature. Our results indicate that an intermediate semiconducting phase is produced before the formation of the superconducting phase; also optical measurements provide valuable information in monitoring the synthesis of MgB₂ from its metallic constituents. In addition these films have interesting optical properties that may be integrated into optoelectronics.     

Impact of applying pre-processing techniques for improving classification accuracy

Image denoising is a procedure aimed at removing noise from images while retaining as many important signal features as possible. Many images suffer from poor contrast due to inadequate illumination or finite sensitivity of the imaging device, electronic sensor noise or atmospheric disturbances. This paper proposes a hybrid directional lifting technique for image denoising to retain the original information present in the images. The primary objective of this paper is to show the impact of applying preprocessing techniques for improving classification accuracy. In order to classify the image accurately, effective preservation of edges and contour details of an image is essential. The discrete wavelet transform-based interpolation technique is developed for resolution enhancement. The image is then classified using support vector machine classifier, which is well suitable for image classification. The efficiency of the classifier is analyzed based on receiver operating characteristic (ROC) curves. The quantitative performance measures peak signal to noise ratio and ROC analysis show the significance of the proposed techniques.