4,238 research outputs found

    Downlink beamforming concepts in UTRA FDD

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    This article gives a comparison of beamforming concepts. Adaptive beamforming and fixed beam switching in WCDMA-FDD-mode are compared from a system level perspective, ordinary sectorization (three 120° sectors) serves as a basis for comparison. Pilot channels P-CPICH (Primary Common Pilot Channel) and S-CPICH (Secondary CPICH) are considered as additional interference. For adaptive beamforming channel estimation has to be based on the pilot bit sequence on DPCCH (Dedicated Physical Control Channel) which leads to degradation especially for high mobile velocities and large angular dispersions of the multipath channel

    Quasi-randomness and algorithmic regularity for graphs with general degree distributions

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    We deal with two intimately related subjects: quasi-randomness and regular partitions. The purpose of the concept of quasi-randomness is to express how much a given graph “resembles” a random one. Moreover, a regular partition approximates a given graph by a bounded number of quasi-random graphs. Regarding quasi-randomness, we present a new spectral characterization of low discrepancy, which extends to sparse graphs. Concerning regular partitions, we introduce a concept of regularity that takes into account vertex weights, and show that if G=(V,E)G=(V,E) satisfies a certain boundedness condition, then GG admits a regular partition. In addition, building on the work of Alon and Naor [Proceedings of the 36th ACM Symposium on Theory of Computing (STOC), Chicago, IL, ACM, New York, 2004, pp. 72–80], we provide an algorithm that computes a regular partition of a given (possibly sparse) graph GG in polynomial time. As an application, we present a polynomial time approximation scheme for MAX CUT on (sparse) graphs without “dense spots.

    Design and fabrication of a low cost implantable bladder pressure monitor

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    In the frame of the Flemish Community funded project Bioflex we developed and fabricated an implant for short term (< 7 days) bladder pressure monitoring, and diagnosis of incontinence. This implant is soft and flexible to prevent damaging the bladder's inner wall. It contains a standard flexible electronic circuit connected to a battery, which are embedded in surface treated silicone to enhance the biocompatibility and prevent salt deposition. This article describes the fabrication of the pill and the results of preliminary cytotoxicity tests. The electronic design and its tests, implantation and the result of the in-vivo experimentation will be presented in other articles

    Low Voltage Control for the Liquid Argon Hadronic End-Cap Calorimeter of ATLAS

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    At the ATLAS detector a SCADA system surveys and controls the sub- detectors. The link is realized by PVSS2 software and a CanBus hardware system. The low voltages for the Hadronic Endcaps of the liquid argon calorimeter are produced by DC/DC-converters in the power boxes and split into 320 channels corresponding to the pre- amplifier and summing boards in the cryostat. Six units of a prototype distribution board are currently under test. Each of it contains 2 ELMBs as CanBus interface, a FPGA of type QL3012 for digital control and 30 low voltage regulators for the individual fine adjustments of the outputs

    Using Geospatial Information Technologies to Identify Factors Affecting Grazing Distribution on Grasslands

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    The relationship between environmental and management factors and grazing livestock distribution is fundamental to understanding and improving grazing systems. With the advent of geospatial information technologies, global positioning systems (GPS) and geographic information systems (GIS) have been used to improve the efficiency and effectiveness of quantifying the distribution of livestock grazing in response to various independent variables (Bailey et al., 2001). The specific objective of this project was to develop a tool that enables managers and students to identify and study the effect of management and environmental factors on grazing livestock distribution

    Upgrade of the Cold Electronics of the ATLAS HEC Calorimeter for sLHC

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    The signal amplification and summation electronics of the ATLAS Hadronic End-cap Calorimeter (HEC) is operated at the circumference of the HEC calorimeters inside the cryostats in liquid argon. The present electronics is designed to operate at irradiation levels expected for the LHC. For operation at the sLHC the irradiation levels are expected to be a factor 10 higher, therefore a new electronic system might be needed. The technological possibilities are investigated. From irradiation tests of the present HEC electronics it is known that it will operate up to a dose of 55 kGy of ionizing radiation and up to a neutron fluence of 3 * 10**14 n/cm**2, where it shows some degradation of performance. This matches well the requirements of up to 1.5 * 10**13 n/cm**2 for 10 years of LHC operation, including safety factors. For a subsequent sLHC running phase with 10 times higher expected irradiation levels, a more radiation hard HEC electronics will be needed. Therefore generic studies of different technologies have been carried out at the transistor level to understand the radiation hardness up to integrated neutron fluxes of ~2*10**16 n/cm**2 and the behaviour during operation at cryogenic temperatures. The S-parameter technique has been used to monitor the performance e.g. of gain and linearity during irradiation at room temperature. In addition, DC measurements before and after irradiation have been compared. Results of these tests and of accompanying noise tests are reported. In addition, results of S-parameter measurements will be reported operating the transistors in liquid nitrogen. Conclusions are drawn and the potential is assessed on the viability of using the tested technologies for carrying out the design of new HEC cold electronics for the sLHC
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