879,698 research outputs found
A priority based routing protocol for wireless sensor networks
Recently, the demands on wireless sensor networks have switched from low traffic rate and static topology to more challenging requirements in order to meet the rapid expansion of WSN into various domain applications. This paper proposes a seamless cross layer solution that integrates network layer and medium access control to accommodate some of the new challenges. This new solution allows routing paths being generated dynamically to meet the requirement of potential mobile nodes. Higher data throughput and flow control are part of the new demands required to be addressed urgently. The proposed solution integrates a priority based MAC to handle congestion and packet loss problems which commonly happened in WSN when an occurrence of event spread into wide are
High-Dimensional Data Reduction, Image Inpainting and their Astronomical Applications
Technological advances are revolutionizing multispectral astrophysics as well as the detection and study of transient sources. This new era of multitemporal and multispectral data sets demands new ways of data representation, processing and management thus making data dimension reduction instrumental in efficient data organization, retrieval, analysis and information visualization. Other astrophysical applications of data dimension reduction which require new paradigms of data analysis include knowledge discovery, cluster analysis, feature extraction and object classification, de-correlating data elements, discovering meaningful patterns and finding essential representation of correlated variables that form a manifold (e.g. the manifold of galaxies), tagging astronomical images, multiscale analysis synchronized across all available wavelengths, denoising, etc. The second part of this paper is dedicated to a new, active area of image processing: image inpainting that consists of automated methods for filling in missing or damaged regions in images. Inpainting has multiple astronomical applications including restoring images corrupted by instrument artifacts, removing undesirable objects like bright stars and their halos, sky estimating, and pre-processing for the Fourier or wavelet transforms. Applications of high-dimensional data reduction and mitigation of instrument artifacts are demonstrated on images taken by the Spitzer Space Telescope
Some results of test beam studies of Transition Radiation Detector prototypes at CERN
Operating conditions and challenging demands of present and future
accelerator experiments result in new requirements on detector systems. There
are many ongoing activities aimed to develop new technologies and to improve
the properties of detectors based on existing technologies. Our work is
dedicated to development of Transition Radiation Detectors (TRD) suitable for
different applications. In this paper results obtained in beam tests at SPS
accelerator at CERN with the TRD prototype based on straw technology are
presented. TRD performance was studied as a function of thickness of the
transition radiation radiator and working gas mixture pressure
Lead-free piezoceramics - Where to move on?
Lead-free piezoceramics aiming at replacing the market-dominant lead-based ones have been extensively searched for more than a decade worldwide. Some noteworthy outcomes such as the advent of commercial products for certain applications have been reported, but the goal, i.e., the invention of a lead-free piezocermic, the performance of which is equivalent or even superior to that of PZT-based piezoceramics, does not seem to be fulfilled yet. Nevertheless, the academic effort already seems to be culminated, waiting for a guideline to a future research direction. We believe that a driving force for a restoration of this research field needs to be found elsewhere, for example, intimate collaborations with related industries. For this to be effectively realized, it would be helpful for academic side to understand the interests and demands of the industry side as well as to provide the industry with new scientific insights that would eventually lead to new applications. Therefore, this review covers some of the issues that are to be studied further and deeper, so-to-speak, lessons from the history of piezoceramics, and some technical issues that could be useful in better understanding the industry demands. As well, the efforts made in the industry side will be briefly introduced for the academic people to catch up with the recent trends and to be guided for setting up their future research direction effectively.ope
Wireless industrial monitoring and control networks: the journey so far and the road ahead
While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks
2D Detectors for Particle Physics and for Imaging Applications
The demands on detectors for particle detection as well as for medical and
astronomical X-ray imaging are continuously pushing the development of novel
pixel detectors. The state of the art in pixel detector technology to date are
hybrid pixel detectors in which sensor and read-out integrated circuits are
processed on different substrates and connected via high density interconnect
structures. While these detectors are technologically mastered such that large
scale particle detectors can be and are being built, the demands for improved
performance for the next generation particle detectors ask for the development
of monolithic or semi-monolithic approaches. Given the fact that the demands
for medical imaging are different in some key aspects, developments for these
applications, which started as particle physics spin-off, are becomming rather
independent. New approaches are leading to novel signal processing concepts and
interconnect technologies to satisfy the need for very high dynamic range and
large area detectors. The present state in hybrid and (semi-)monolithic pixel
detector development and their different approaches for particle physics and
imaging application is reviewed
Operating-system support for distributed multimedia
Multimedia applications place new demands upon processors, networks and operating systems. While some network designers, through ATM for example, have considered revolutionary approaches to supporting multimedia, the same cannot be said for operating systems designers. Most work is evolutionary in nature, attempting to identify additional features that can be added to existing systems to support multimedia. Here we describe the Pegasus project's attempt to build an integrated hardware and operating system environment from\ud
the ground up specifically targeted towards multimedia
Robot-sensor synchronization for real-time seamtracking in robotic laser welding
The accuracy requirements of laser welding put high demands on the manipulator that is used. To use industrial six-axis robots for manipulating the laser welding optics, sensors measuring the seam trajectory close to the focal spot are required to meet the accuracy demands. When the measurements are taken while the robot is moving, it is essential that they are synchronized with the robot motion. This paper presents a synchronization mechanism between a seam-tracking sensor and an industrial 6-axis robot, which uses Ethernet-based UDP communication. Experimental validation is carried out to determine the accuracy of the proposed synchronization mechanism. Furthermore, a new control architecture, called trajectory-based control is presented, which embeds the synchronization method and allows various sensor-based applications like teaching of a seam trajectory with a moving robot and real-time seam-tracking during laser welding
Exploiting rules and processes for increasing flexibility in service composition
Recent trends in the use of service oriented architecture for designing, developing, managing, and using distributed applications have resulted in an increasing number of independently developed and physically distributed services. These services can be discovered, selected and composed to develop new applications and to meet emerging user requirements. Service composition is generally defined on the basis of business processes in which the underlying composition logic is guided by specifying control and data flows through Web service interfaces. User demands as well as the services themselves may change over time, which leads to replacing or adjusting the composition logic of previously defined processes. Coping with change is still one of the fundamental problems in current process based composition approaches. In this paper, we exploit declarative and imperative design styles to achieve better flexibility in service composition
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