Ractions of SiC with H2/H2O/Ar Mixtures at 1300°C

The reactions of a sintered α-SiC with 5% H₂/H₂O/Ar at 1300°C were studied. Thermomchemical modeling indicates that three reaction regions are expected, depending on the initial water vapor or equivalently oxygen content of the gas stream. A high oxygen content ( P (O₂) > 10⁻²² atm) leads to a SiO₂ formation. This generally forms as a protective film and limits consumption of the SiC (passive oxidation). An intermediate oxygen content (10⁻²² atm > P (O₂) > 10⁻²⁶ atm) leads to SiO and CO formation. These gaseous products can lead to rapid consumption of the SiC (active oxidation). Thermogravimetric studies in this intermediate region gave reaction rates which appear to be controlled by H₂O gas-phase transport to the sample and reacted microstructures showed extensive grain-boundary attack in this region. Finally, a very low oxygen content ( P (O₂) < 10⁻²⁶ atm) is thermochemically predicted to lead to selective removal of carbon and formation of free silicon. Experimentally low weight losses and iron silicides are observed in this region. The iron silicides are attributed to reaction of free silicon and iron impurities in the system.     

Implementation of Envelope Analysis on a Wireless Condition Monitoring System for Bearing Fault Diagnosis

 Envelope analysis is an effective method for characterizing impulsive vibrations in wired condition monitoring (CM) systems. This paper depicts the implementation of envelope analysis on a wireless sensor node for obtaining a more convenient and reliable CM system. To maintain CM performances under the constraints of resources available in the cost effective Zigbee based wireless sensor network (WSN), a low cost cortex-M4F microcontroller is employed as the core processor to implement the envelope analysis algorithm on the sensor node. The on-chip 12 bit analog-to-digital converter (ADC) working at 10 kHz sampling rate is adopted to acquire vibration signals measured by a wide frequency band piezoelectric accelerometer. The data processing flow inside the processor is optimized to satisfy the large memory usage in implementing fast Fourier transform (FFT) and Hilbert transform (HT). Thus, the envelope spectrum can be computed from a data frame of 2048 points to achieve a frequency resolution acceptable for identifying the characteristic frequencies of different bearing faults. Experimental evaluation results show that the embedded envelope analysis algorithm can successfully diagnose the simulated bearing faults and the data transmission throughput can be reduced by at least 95% per frame compared with that of the raw data, allowing a large number of sensor nodes to be deployed in the network for real time monitoring.     

A method for evaluating rigor and industrial relevance of technology evaluations

One of the main goals of an applied research field such as software engineering is the transfer and widespread use of research results in industry. To impact industry, researchers developing technologies in academia need to provide tangible evidence of the advantages of using them. This can be done trough step-wise validation, enabling researchers to gradually test and evaluate technologies to finally try them in real settings with real users and applications. The evidence obtained, together with detailed information on how the validation was conducted, offers rich decision support material for industry practitioners seeking to adopt new technologies and researchers looking for an empirical basis on which to build new or refined technologies. This paper presents model for evaluating the rigor and industrial relevance of technology evaluations in software engineering. The model is applied and validated in a comprehensive systematic literature review of evaluations of requirements engineering technologies published in software engineering journals. The aim is to show the applicability of the model and to characterize how evaluations are carried out and reported to evaluate the state-of-research. The review shows that the model can be applied to characterize evaluations in requirements engineering. The findings from applying the model also show that the majority of technology evaluations in requirements engineering lack both industrial relevance and rigor. In addition, the research field does not show any improvements in terms of industrial relevance over time.     

Multivariate Median Filters and Partial Differential Equations

Multivariate median filters have been proposed as generalizations of the well-established median filter for gray-value images to multichannel images. As multivariate median, most of the recent approaches use the \(L^1\) median, i.e., the minimizer of an objective function that is the sum of distances to all input points. Many properties of univariate median filters generalize to such a filter. However, the famous result by Guichard and Morel about approximation of the mean curvature motion PDE by median filtering does not have a comparably simple counterpart for \(L^1\) multivariate median filtering. We discuss the affine equivariant Oja median and the affine equivariant transformation–retransformation \(L^1\) median as alternatives to \(L^1\) median filtering. We analyze multivariate median filters in a space-continuous setting, including the formulation of a space-continuous version of the transformation–retransformation \(L^1\) median, and derive PDEs approximated by these filters in the cases of bivariate planar images, three-channel volume images, and three-channel planar images. The PDEs for the affine equivariant filters can be interpreted geometrically as combinations of a diffusion and a principal-component-wise curvature motion contribution with a cross-effect term based on torsions of principal components. Numerical experiments are presented, which demonstrate the validity of the approximation results.     

A Parallelization Approach for Hard Real-Time Systems and Its Application on Two Industrial Programs

Applications in industry often have grown and improved over many years. Since their performance demands increase, they also need to benefit from the availability of multi-core processors. However, a reimplementation from scratch and even a restructuring of these industrial applications is very expensive, often due to high certification efforts. Therefore, a strategy for a systematic parallelization of legacy code is needed. We present a parallelization approach for hard real-time systems, which ensures a high reusage of legacy code and preserves timing analysability. To show its applicability, we apply it on the core algorithm of an avionics application as well as on the control program of a large construction machine. We create models of the legacy programs showing the potential of parallelism, optimize them and change the source codes accordingly. The parallelized applications are placed on a predictable multi-core processor with up to 18 cores. For evaluation, we compare the worst case execution times and their speedups. Furthermore, we analyse limitations coming up at the parallelization process.     

Combining interaction and context design to support collaborative argumentation using a tool for synchronous CMC

Abstract Empirical studies and theory suggest that educational dialogue can be used to support learners in the development of reasoning, critical thinking and argumentation. This paper presents an educational design for synchronous online peer discussion that guides student dialogue in ways that lead to improved argumentation and collaborative knowledge development. This design includes a mediating interface – or tool, linked to a broader set of online educational activities – a designed local context, where the latter aims to provide conditions that support argumentation. The approach is based on collaborative working and dialogue game approaches to discussion. Preliminary findings with UK Open University students showed the argumentation process was more coherent, varied, deeper and extended when using our interaction design compared with the use of a simple unstructured interface.     

HIPed Tailored Hollandite Waste Forms for the Immobilization of Radioactive Cs and Sr

Hot isostatically pressed tailored hollandite waste forms were used to demonstrate the immobilization of Cs and Sr are separable from spent nuclear fuel, as well as Ba and Rb. Four hollandite formulations were investigated, two samples with ∼12 wt% waste loading (on an oxide basis) and two with ∼18 wt% waste loading. Two of the samples were Al-substituted and the other two contained Mg. The hollandite in the Al-substituted samples contained all the waste cations, as designed, but this was not the case in the Mg-substituted samples. The hollandite in the Mg-substituted samples did not contain all the waste cations, with ∼50% of the Sr forming SrTiO₃ as a secondary phase. This resulted in waste forms that were not as durable, with respect to Cs, as their Al counterparts. The formation of SrTiO₃ had little effect on the Sr release rates and was not detrimental to the Mg-substituted hollandite waste form. For the Al-substituted samples, the MCC-1 normalized release rates were <0.06 g·(m²·day)⁻¹ at 0–28 days for all elements, while the Cs release rates remained at 2.0 g·(m²·day)⁻¹ at 0–28 days for the Mg-substituted samples.     

Trust, power and interorganizational information systems: the case of the electronic trading community TransLease

This paper focuses on Cap Gemini’s electronic commerce system, TransLease. TransLease is an interorganizational information system (IOS), which facilitates electronic commerce between motor vehicle leasing and repair companies. During our investigation, the system was used by approximately 1000 repair agents working for seven of the UK’s leading vehicle leasing and contract hire companies. This system was originally developed by AT&T and acquired by Cap Gemini in July 1998. At the time of acquisition, the system was seen as being of high strategic value, although it was also seen as underperforming. This paper reports the results of an action research project, which formed one element of the process by which Cap Gemini investigated the former problem. In the paper, TransLease is described as a complex electronic community, dependent upon the existence of symbiotic relationships. As such, the problems that the system users and developers experienced can be attributed to factors that impeded the mutual benefit accruing from participation in the system. The efficacy of the terms of exchange and the degree to which participants mutually benefit through electronic interaction is determined by the complex interplay of a number of relational and organizational factors. The research therefore illustrates the importance of the ‘soft’ organizational issues in IOS management and development, and suggests a conceptual model of the factors relevant in this case. At the time of this study, TransLease was still in the early stages of its life cycle, having only been available in the marketplace for approximately 18 months. During this time, through recognizing the complex problems and issues detailed in this paper, Cap Gemini accordingly redressed the way in which the system was managed and maintained. TransLease is now seen as having matured into a highly successful example of an IOS – a view reflected by its position as market leader in the industry. As this paper will show, the key to improving the existing service has been the emphasis Cap Gemini now places on managing the ‘soft’ aspects of the electronic community.     

APACS: a system for the automatic analysis and classification of conceptual patterns

Many existing inductive learning systems have been developed under the assumption that the learning tasks are performed in a noise-free environment. To cope with most real-world problems, it is important that a learning system be equipped with the capability to handle uncertainty. In this paper, we first identify the various sources of uncertainty that may be encountered in a noisy problem domain. Next, we present a method for the efficient acquisition of classification rules from training instances which may contain inconsistent, incorrect, or missing information. This algorithm consists of three phases: ( i ) the detection of inherent patterns in a set of noisy training data; ( ii ) the construction of classification rules based on these patterns; and ( iii ) the use of these rules to predict the class membership of an object. The method has been implemented in a system known as APACS (automatic pattern analysis and classification system). This system has been tested using both real-life and simulated data, and its performance is found to be superior to many existing systems in terms of efficiency and classification accuracy. Being able to handle uncertainty in the learning process, the proposed algorithm can be employed for applications in real-world problem domains involving noisy data.     

Timoshenko精确法在悬臂梁适应性分析中的应用

利用有限元、小网格及其他数字技术求解端部加载悬臂梁的挠度及应力,这种方法证明了自适应程序的能力。但是在许多情况下,并没有符合这种精确求解方法的边界条件,因此影响了自适应程序的有效性。事实上,作为一个探索性的问题,这种精确解并不适用于自适应程序,因为完全精确的网格都是相同的。本文对此问题进行了讨论,强调了由于边界条件不匹配精确解而产生的一些错误,用一种更符合实际的悬臂梁模型与之做了对比;同时还讨论了程序的有效性。