1,657 research outputs found

    On reducing uncertainty on the Elliptical Plane modal identification method

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    The Elliptical Plane has been recently introduced as a modal identification method that uses an alternative plot of the receptance. The method uses the dissipated energy per cycle of vibration as a starting point. For lightly damped systems with conveniently spaced modes, it produces quite accurate results, especially when compared to the well-known method of the inverse. When represented in the Elliptical Plane, the shape of the receptance is elliptical near resonant frequencies. The modal damping factor can be determined from the angle of the ellipse鈥檚 major axis with the horizontal axis, whereas the real and imaginary parts of the modal constants can be determined from numerical curve-fitting (as in the method of the circle - Nyquist plot). However, the lack of points that can be used near the resonance (due to limitations in the frequency resolution, and effects from other modes near each resonance) and the fact that measurements are polluted by noise, bring uncertainty to the numerical curve-fitting. This paper aims at providing the first steps on the improvement of the quality of the modal identification of the receptance in the Elliptical Plane. The method and results are discussed with a multiple degree-of-freedom numerical example

    Calorimeters for Precision Timing Measurements in High Energy Physics

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    Current and future high energy physics particle colliders are capable to provide instantaneous luminosities of 1034 cm^(-2)s^(-1) and above. The high center of mass energy, the large number of simultaneous collision of beam particles in the experiments and the very high repetition rates of the collision events pose huge challenges. They result in extremely high particle fluxes, causing very high occupancies in the particle physics detectors operating at these machines. To reconstruct the physics events, the detectors have to make as much information as possible available on the final state particles. We discuss how timing information with a precision of around 10 ps and below can aid the reconstruction of the physics events under such challenging conditions. High energy photons play a crucial role in this context. About one third of the particle flux originating from high energy hadron collisions is detected as photons, stemming from the decays of neutral mesons. In addition, many key physics signatures under study are identified by high energy photons in the final state. They pose a particular challenge in that they can only be detected once they convert in the detector material. The particular challenge in measuring the time of arrival of a high energy photon lies in the stochastic component of the distance to the initial conversion and the size of the electromagnetic shower. They extend spatially over distances which propagation times of the initial photon and the subsequent electromagnetic shower which are large compared to the desired precision. We present studies and measurements from test beams and a cosmic muon test stand for calorimeter based timing measurements to explore the ultimate timing precision achievable for high energy photons of 10 GeV and above. We put particular focus on techniques to measure the timing with a precision of about 10 ps in association with the energy of the photon. For calorimeters utilizing scintillating materials and light guiding components, the propagation speed of the scintillation light in the calorimeter is important. We present studies and measurements of the propagation speed on a range of detector geometries. Finally, possible applications of precision timing in future high energy physics experiments are discussed

    A simple current control strategy for a four-leg indirect matrix converter

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    In this paper the experimental validation of a predictive current control strategy for a four-leg indirect matrix converter is presented. The four-leg indirect matrix converter can supply energy to an unbalanced three-phase load whilst providing a path for the zero sequence load. The predictive current control technique is based on the optimal selection among the valid switching states of the converter by evaluating a cost function, resulting in a simple approach without the necessity for modulators. Furthermore, zero dc-link current commutation is achieved by synchronizing the state changes in the input stage with the application of a zero voltage space vector in the inverter stage. Simulation results are presented and the strategy is experimentally validated using a laboratory prototype

    Predictive current control with instantaneous reactive power minimization for a four-leg indirect matrix converter

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    This paper presents the experimental valida卢tion of a predictive current control strategy with minimiza卢tion of the instantaneous reactive input power for a Four-Leg Indirect Matrix Converter (4Leg-IMC). The topology includes an input matrix converter stage, which provides the dc voltage for a four-leg voltage source converter (VSC) output stage. The VSC鈥檚 fourth leg provides a path for the zero sequence load current. The control technique is based on a finite control set model predictive control (FCS-MPC) strategy, whereby the switching states for the input and out卢put converters are selected by evaluating a predictive cost function. This results in a simpler approach than that seen in other well-known modulation methods, such as three-dimensional space vector modulation (3D-SVM). Positive dc voltage, (a requirement for the safe operation of the IMC) and minimization of the instantaneous input reactive power are obtained, while maintaining good tracking of the load reference currents. Furthermore, soft switching is achieved by synchronizing the state changes in the input stage with the application of zero voltage space vectors in the inverter stage. The control strategy is experimentally verified using a laboratory prototype

    A Binary Fruit Fly Optimization Algorithm to Solve the Set Covering Problem

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    The Set Covering Problem (SCP) is a well known NP-hard problem with many practical applications. In this work binary fruit fly optimization algorithms (bFFOA) were used to solve this problem using different binarization methods. The bFFOA is based on the food finding behavior of the fruit flies using osphresis and vision. The experimental results show the effectiveness of our algorithms producing competitive results when solve the benchmarks of SCP from the OR-Library

    A Comparison of Three Recent Nature-Inspired Metaheuristics for the Set Covering Problem

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    The Set Covering Problem (SCP) is a classic problem in combinatorial optimization. SCP has many applications in engineering,including problems involving routing, scheduling, stock cutting, electoral redistricting and others important real life situations. Because of its importance, SCP has attracted attention of many researchers. However,SCP instances are known as complex and generally NP-hard problems.Due to the combinatorial nature of this problem, during the last decades,several metaheuristics have been applied to obtain efficient solutions.This paper presents a metaheuristics comparison for the SCP. Three recent nature-inspired metaheuristics are considered: Shuffled Frog Leaping,Firefly and Fruit Fly algorithms. The results show that they can obtainn optimal or close to optimal solutions at low computational cost

    Design and performance of the Fermilab Constant Fraction Discriminator ASIC

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    We present the design and performance characterization results of the novel Fermilab Constant Fraction Discriminator ASIC (FCFD) developed to readout low gain avalanche detector (LGAD) signals by directly using a constant fraction discriminator (CFD) to measure signal arrival time. Silicon detectors with time resolutions less than 30 ps will play a critical role in future collider experiments, and LGADs have been demonstrated to provide the required time resolution and radiation tolerance for many such applications. The FCFD has a specially designed discriminator that is robust against amplitude variations of the signal from the LGAD that normally requires an additional correction step when using a traditional leading edge discriminator based measurement. The application of the CFD directly in the ASIC promises to be more reliable and reduces the complication of timing detectors during their operation. We will present a summary of the measured performance of the FCFD for input signals generated by internal charge injection, LGAD signals from an infrared laser, and LGAD signals from minimum-ionizing particles. The mean time response for a wide range of LGAD signal amplitudes has been measured to vary no more than 15 ps, orders of magnitude more stable than an uncorrected leading edge discriminator based measurement, and effectively removes the need for any additional time-walk correction. The measured contribution to the time resolution from the FCFD ASIC is also found to be 10 ps for signals with charge above 20 fC

    Desarrollo de un sistema de gesti贸n para pymes

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    Lo que se quiere mostrar en este proyecto es un desarrollo de un sistema de gesti贸n para Pymes, que supra las necesidades de la obtenci贸n de la informaci贸n del control presupuestal e indicadores de gesti贸n que asistan a la toma de decisiones y cambios en el mercado. Con la facilidad de consulta en cualquier parte del mundo, pues tiene el beneficio que los usuarios teniendo a mano un computador, internet y adquiriendo con antelaci贸n su contrase帽a, puedan consultar en la plataforma del sistema todos los informes que requieran a cualquier hora

    Desarrollo de un sistema de gesti贸n para pymes

    Get PDF
    Lo que se quiere mostrar en este proyecto es un desarrollo de un sistema de gesti贸n para Pymes, que supra las necesidades de la obtenci贸n de la informaci贸n del control presupuestal e indicadores de gesti贸n que asistan a la toma de decisiones y cambios en el mercado. Con la facilidad de consulta en cualquier parte del mundo, pues tiene el beneficio que los usuarios teniendo a mano un computador, internet y adquiriendo con antelaci贸n su contrase帽a, puedan consultar en la plataforma del sistema todos los informes que requieran a cualquier hora

    Entangled Photon Pair Source Demonstrator using the Quantum Instrumentation Control Kit System

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    We report the first demonstration of using the Quantum Instrumentation and Control Kit (QICK) system on RFSoCFPGA technology to drive an entangled photon pair source and to detect the photon signals. With the QICK system, we achieve high levels of performance metrics including coincidence-to-accidental ratio exceeding 150, and entanglement visibility exceeding 95%, consistent with performance metrics achieved using conventional waveform generators. We also demonstrate simultaneous detector readout using the digitization functional of QICK, achieving internal system synchronization time resolution of 3.2 ps. The work reported in this paper represents an explicit demonstration of the feasibility for replacing commercial waveform generators and time taggers with RFSoC-FPGA technology in the operation of a quantum network, representing a cost reduction of more than an order of magnitude
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