Decentralized fault diagnosis approach without a global model for fault diagnosis of discrete event systems

Diagnosability property ensures that a predefined set of faults are diagnosable by a centralized diagnoser built using a global model of the system, while co-diagnosability guarantees that these faults are diagnosed in decentralized manner using a set of local diagnosers. A fault must be diagnosed by at least one local diagnoser by using its proper local observation of the system. The aim of using decentralized diagnosis approaches is to overcome the space complexity and weak robustness of centralized diagnosis approaches while at the same time preserving the diagnostic capability of a centralized diagnosis. However, co-diagnosability property is stronger than diagnosability property. If a system is co-diagnosable, then it is diagnosable, while a diagnosable system does not ensure that it is co-diagnosable. Therefore, the challenge of decentralized diagnosis approaches is to perform local diagnosis and to verify that it is equivalent to the centralized one without the need for a global model. In this paper, an approach is proposed to obtain co-diagnosable decentralized diagnosis structure of discrete event systems without the use of a global model. This approach is based on the synchronization of local diagnosis decisions in order to solve the ambiguity between local diagnosers. This synchronization allows obtaining local diagnosis equivalent to the global one without the use of a global model.     

Search strategies along the academic lifecycle

Understanding how individual scientists build a personal portfolio of research is key to understanding outcomes on the level of scientific fields, institutions, and systems. We lack the scientometric and statistical instruments to examine the development over time of the involvement of researchers in different problem areas. In this paper we present a scientometric method to map, measure, and compare the entire corpus of individual scientists. We use this method to analyse the search strategies of 43 condensed matter physicists along their academic lifecycle. We formulate six propositions that summarise our theoretical expectations and are empirically testable: (1) a scientist’s work consists of multiple finite research trails; (2) a scientist will work in several parallel research trails; (3) a scientist’s role in research trail selection changes along the lifecycle; (4) a scientist’s portfolio will converge before it diverges; (5) the rise and fall of research trails is associated with career changes; and (6) the rise and fall of research trails is associated with the potential for reputational gain. Four propositions are confirmed, the fifth is rejected, and the sixth could not be confirmed or rejected. In combination, the results of the four confirmed propositions reveal specific search strategies along the academic lifecycle. In the PhD phase scientists work in one problem area that is often unconnected to the later portfolio. The postdoctoral phase is where scientists diversify their portfolio and their social network, entering various problem areas and abandoning low-yielding ones. A professor has a much more stable portfolio, leading the work of PhDs and postdoctoral researchers. We present an agenda for future research and discuss theoretical and policy implications.     

Algorithms to Minimize Data Transfer for Code Update on Wireless Sensor Network

In Wireless Sensor Networks, the preloaded program code and data on sensor nodes often need to be updated due to changes in user requirements and environmental conditions. Sensor nodes are severely restricted by energy constraints. It is especially energy consuming for sensor nodes to transfer data through wireless radios. To efficiently reprogram sensor nodes through radio, we propose an algorithm, Minimum Data transferred by Copying and Downloading (MDCD) and its extension E-MDCD, to minimize the number of bytes needed to be transferred from the host machine to the sensor nodes. Experimental results show that the E-MDCD algorithm reduces the number of bytes transferred by 93.25 % for small code change compared with the Rsync based algorithm. In average, E-MDCD can reduce 59.82 % compared with the existing the Rsync based algorithm and 16.14 % compared with the Vdelta algorithm.     

Technique to Measure 3D Work-of-Fracture of Concrete in Compression

A high-resolution 3D scanning technique called X-ray microtomography was applied to measure internal damage and crack growth in small mortar cylinders loaded in compression. Synchrotron-based microtomography allows us to resolve internal features that are only a few microns in size. Multiple tomographic scans were made of the same specimen at different levels of deformation using a custom-built loading frame. 3D image analysis was used to measure internal crack growth during each deformation increment. Measured load-deformation curves were used to calculate the nonrecoverable work of the external load on the specimen. Nonrecoverable work of load was related to measured incremental change in crack surface area to estimate work-of-fracture in three dimensions. Initial results indicate a nearly constant work-of-fracture for the early stages of crack growth. These results show that basic fracture mechanics principles may be applied to concrete in compression; however, we must think in terms of 3D multiple crack systems rather than traditional 2D single crack systems.     

Evaluation of Measurement Systems with a Small Number of Observers

The standard R&R study for evaluation of measurement systems assumes that participating observers constitute a random sample. Often there are only a few observers, all of them included in the study. An alternative measure for the gauge R&R is proposed for this situation, and it is shown that this may improve the perception of the quality of the measurement system markedly, especially with only a few observers. Finally it is shown that a simple estimator can be used, with a bias limited to just a few percent.     

Analysis of rDNA Regions of Five Freshwater Unionid Mussel Species in Presque Isle Bay,Southeastern Lake Erie

Population structure and fecundity of freshwater mussels can be difficult to assess due to the benthic habitat and complex life cycles of these organisms. However, rapid and reliable classification of unionids can be accomplished with polymerase chain reaction if species-specific DNA primers are established. In this report we describe the sequence analysis of the ITS1 and ITS2 regions from five mussel species (Amblema plicata, Fusconia flava, Lampsilis siliquoidea, Ligumia nasuta, and Pyganodon grandis) isolated from a refuge in Lake Erie. Sequence comparison revealed strong similarities between A. plicata and F. flava and between L. siliquoidea and L.nasuta. P. grandis contained regions of additional DNA not present within the other species. Our study confirmed the placement of Ligumia nasuta within the Lampsilinae. The analysis also revealed DNA sequences within the ITS1 and ITS2 regions that are species-specific. Thus, the development of species-specific PCR primers can be utilized for analysis of adult populations and for glochidia on host fish.     

Light aversion in mice depends on nonimage-forming irradiance detection.

Detection of light in the eye underlies image-forming vision, but also regulates adaptive responses in physiology and behavior. Typically these adaptive responses do not involve image-forming vision, but depend on a relatively absolute measure of brightness (nonimage-forming irradiance detection). The goal of this study was to further understand how image-forming vision and nonimage-forming irradiance detection contribute to the effects of light on behavior. Three light dependent behaviors were assessed in wild-type, Rpe65-/- and rd1 mice. In Rpe65-/- mice, nonimage-forming irradiance detection is severely attenuated, but rod based visual acuity is relatively preserved. In rd1 mice visual acuity is nonrecordable, but nonimage-forming responses are less severely attenuated than Rpe65-/-. Positive masking, an image-forming vision dependent increase in wheel running, was absent in rd1 and restricted to higher irradiances in Rpe65-/-. Negative masking, a suppression of wheel running sensitivity with nonimage-forming irradiance detection input, was increased in rd1, but reduced in Rpe65-/- mice. By contrast, light aversion, an avoidance of brightly lit areas, was abolished in both Rpe65-/- and rd1. This shows that image-forming vision is not sufficient for light aversion, suggesting nonimage-forming irradiance detection motivates this behavior. Further, the differing effects of disease suggest that negative masking and light aversion are distinct responses with specialized nonimage-forming irradiance detection pathways. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Testing of a sodium/nickel chloride (ZEBRA) battery for electric propulsion of ships and vehicles

One of the promising future batteries for electric propulsion of vehicles and ships is the sodium/nickel chloride or ZEBRA (Zero Emission Battery Research Activities) battery. Despite some disadvantages with respect to the high temperature, the advantages with respect to specific energy and energy density are such that, especially in applications where the battery is used on a more or less continuous basis (e.g., in delivery vans and taxies) it is an interesting candidate battery. Another interesting application is on board of ships, like submarines or future electrical surface ships with electric propulsion. In 1995 a 2 year feasibility study, including experimental testing of a 10 kW h battery, was completed. This investigated the naval applicability of the sodium/sulphur battery, which is also a high temperature battery. Here the limited, experimentally proven, life-time of the batteries of about 1.5 years and this made naval application almost impossible. A paper about this study was presented at the 19th International Power Sources Symposium held at Brighton, England, in April 1995 [R.A.A. Schillemans, C.E. Kluiters, Sodium/sulphur batteries for naval applications, in: A. Attewell, T. Keily (Eds.), Power Sources 15, International Power Sources Symposium Committee, Crowborough UK, 1995. p. 421.]. Because of the more or less comparable specifications on specific energy and the more promising results of the life-time and field tests with sodium/nickel chloride batteries, a ZEBRA battery from AEG Anglo Batteries has been tested for naval applications. This was done by simulating the charge and discharge as it occurs in practice for the applications investigated. With respect to the electrical ship application (investigated for the Royal Netherlands Navy) the power versus time taken from the battery was simulated as well as the charge procedures. The same can be done for the vehicle application: in this case typical drive cycles for a van or taxi are translated to power versus time taken from the battery. The results of the tests for application of the battery in naval ships are very promising.