Using Dynamic Runtime Testing for Rapid Development of Architectural Simulators

Architectural simulator platforms are particularly complex and error-prone programs that aim to simulate all hardware details of a given target architecture. Development of a stable cycle-accurate architectural simulator can easily take several man-years. Discovering and fixing all visible errors in a simulator often requires significant effort, much higher than for writing the simulator code in the first place. In addition, there are no guarantees that all programming errors will be eliminated, no matter how much effort is put into testing and debugging. This paper presents dynamic runtime testing, a methodology for rapid development and accurate detection of functional bugs in architectural cycle-accurate simulators. Dynamic runtime testing consists of comparing an execution of a cycle-accurate simulator with an execution of a simple and functionally equivalent emulator. Dynamic runtime testing detects a possible functional error if there is a mismatch between the execution in the simulator and the emulator. Dynamic runtime testing provides a reliable and accurate verification of a simulator, during its entire development cycle, with very acceptable performance impact, and without requiring complex setup for the simulator execution. Based on our experience, dynamic testing reduced the simulator modification time from 12–18 person-months to only 3–4 person-months, while it only modestly reduced the simulator performance (in our case under 20 %).     

Development of the ReaxFF reactive force field for mechanistic studies of catalytic selective oxidation processes on BiMoO x

We have developed a new reactive force field, ReaxFF, for use in molecular dynamics (MD) simulations to investigate the structures and reactive dynamics of complex metal oxide catalysts. The parameters in ReaxFF are derived directly from QM and have been validated to provide reasonable accuracy for a wide variety of reactions. We report the use of ReaxFF to study the activation and conversion of propene to acrolein by various metal oxide surfaces. Using high-remperature MD-simulations on metal oxides slabs exposed to a propene gas phase we find that (1) Propene is not activated by MoO₃ but it is activated by amorphous Bi₂O₃ to form allyl which does not get oxidized by the surface; (2) Propene is activated by Bi₂Mo₃O₁₂ to form an allyl-radical and the hydrogen gets abstracted by a Mo=O bond, which is bridged via an O to a Bi-site; (3) Propene is activated over V₂O₅ to form an allyl, which is then selectively oxidized on the surface to form acrolein. The propene reations on V₂O₅ occur at lower temperatures than on Bi₂O₃ or Bi₂Mo₃O₁₂. The results are all consistent with experimental observations, encouraging us that such investigations will enhance our mechanistic understanding of catalytic hydrocarbon oxidation sufficiently to suggest modifications for improving efficiency and/or selectivity.     

Failure characterization of polypropylene block copolymer welded joints

The failure behavior of polypropylene block copolymer double-V welded joints was investigated. Joints were prepared using the hot-gas welding technique at varying gas temperatures in the range of 230–260°C. Uniaxial tensile tests, fracture mechanics experiments, several microscopy techniques, and complementary FEM analysis were carried out to assess the quality of filler rods and welding interfaces. The developed interfaces were weaker than the parent material as a consequence of polymer chains segregation during the welding process. The hot-gas temperature had a marked effect on the failure behavior of the welds. The highest interface toughness was attained at the highest gas welding temperature used at which, polymer chains were able to quickly diffuse into the parent material enlarging the distance of penetration and hence the micro-deformation capability of the joint. POLYM. ENG. SCI., 47:1062–1069, 2007. © 2007 Society of Plastics Engineers     

Lot Streaming Flow Shop with a Heterogeneous Machine

Abstract

It is possible to obtain greater productivity of a production system by overlapping the operations required to process a manufacturing order. This methodology, known as lot streaming, requires dividing the production order (lot) into smaller sublots. In this article, we study production systems that include machines that operate in batch mode (processing a group of units at the same time) and single processing machines (processing one unit at a time) arranged in a flow shop configuration, that is all jobs must go through the same production stages in the same order. The obtained results show that addressing the problem with consistent sublots (a common sublot size used for the whole process) is inefficient. On the other hand, addressing the problem considering the sizing of sublots for each machine (variable sublots) greatly improves the quality of the solution but is computationally intensive (limiting the size of the problem that can be solved). Therefore, a decomposition procedure is proposed on the decision of sublots sizing. This procedure greatly improves the solution obtained using consistent sublots and does so with lower computational requirements than the variable sublots approach.     

Electric and Mechanical Switching of Ferroelectric and Resistive States in Semiconducting BaTiO3–δ Films on Silicon

Materials that can couple electrical and mechanical properties constitute a key element of smart actuators, energy harvesters, or many sensing devices. Within this class, functional oxides display specific mesoscale responses which often result in great sensitivity to small external stimuli. Here, a novel combination of molecular beam epitaxy and a water‐based chemical‐solution method is used for the design of mechanically controlled multilevel device integrated on silicon. In particular, the possibility of adding extra functionalities to a ferroelectric oxide heterostructure by n‐doping and nanostructuring a BaTiO₃ thin film on Si(001) is explored. It is found that the ferroelectric polarization can be reversed, and resistive switching can be measured, upon a mechanical load in epitaxial BaTiO_3?δ /La_0.7Sr_0.3MnO₃/SrTiO₃/Si columnar nanostructures. A flexoelectric effect is found, stemming from substantial strain gradients that can be created with moderate loads. Simultaneously, mechanical effects on the local conductivity can be used to modulate a nonvolatile resistive state of the BaTiO_3?δ heterostructure. As a result, three different configurations of the system become accessible on top of the usual voltage reversal of polarization and resistive states.     

Complete autoencoders for classification with missing values

Neural Computing and Applications - It has been demonstrated that modified denoising stacking autoencoders (MSDAEs) serve to implement high-performance missing value imputation schemes. On the...     

Representative cross information potential clustering

This paper proposes an information-theoretic approach for clustering with a new measure of cross information potential and two clustering algorithms. Instead of using all points of the dataset, the proposed measure uses representative points to quantify the interaction between distributions without any loss of the original properties of cross information potential. This brings a double advantage. It decreases the cost of computing the cross information potential, thus drastically reducing the running time. Secondly, it captures the interaction among the data points by utilizing the underlying statistics of the space region centered around the representative points. With this, we have made it possible to use cross information potential in applications where it was not. We also proposed two algorithms for clustering which explore the idea of creating links between regions of the feature space that are highly correlated. We ran several tests and compared the results with single linkage hierarchical algorithm, finite mixture of Gaussians and spectral clustering in both synthetic and real image segmentation datasets. Experiments showed that our approach achieved better results compared to the other algorithms and it was capable of capture the real structure of the data in most cases regardless of its complexity. It also produced good image segmentation with the advantage of a tuning parameter that provides a way of refine segmentation.     

Long-term evaluation of a sequential batch reactor (SBR) treating dairy wastewater for carbon removal.

Many dairy industries have been using SBR wastewater treatment plants because they allow optimal working condition to be reached. However, to take advantage of SBR capabilities, strong process automation is needed. The aim of this work is to study the factors that influence SBR performance to improve modelling and control. To better understand the whole process we studied the kinetic modelling, the carbon removal mechanism and the relation between reactor performance, aerobic heterotrophic activity and bacterial population dynamics (by terminal restriction fragment length polymorphisms of 16S rDNA, T-RFLP). The heterotrophic activity values presented high variability during some periods; however, this was not reflected on the reactor performance. As sludge health indicator, the average activity in a period was better than individual values. Although all the carbon removal mechanisms are still unclear for this process, they seemed to be influenced by non-respirometric ways (storage, biosorption, accumulation, etc.). The variability of heterotrophic activity could be correlated with the bacterial population diversity over time. Despite the high variability of the activity, a simple kinetic model (pseudo ASM1) based on apparent constant parameters was developed and calibrated. Such modellisation provided a good tool for control purposes.