167 research outputs found

    Projeto de filtros digitais IIR com tÊcnicas de computação evolucionåria

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    IIR digital filter design is classic problem in Electrical Engineering. Digital filter have many applications, and dozens of different behaviors. There are many specialist methods in literature, each with specific differences and characteristics. But most of these methods are not flexible, preventing one from fixing all parameters, because some of them are a sub-product of the calculation process. Therefore, this problem is also solved in literature with Evolutionary Computing techniques. Several works were found with this approach, but in almost all, the focus was in the evolutionary algorithm rather than on the filter problem, using this only as a benchmark function. Moreover, the filter stability - prerequisite for the filter application - is neglected in almost all of them. So, this work proposes a new fitness function, as well as a new codification, in order to obtain good filters, obedient to the specifications, with Evolutionary Computing algorithms in the canonic form, this is, without structural modifications. The proposed fitness function tries to correct distortions caused by the traditional one, which does not takes into account the filter gain specifications. The new coding maps the search space only to the stable solutions, not excluding any valid solution in the transformation. Moreover, a post-processing allows the filter phase equalization, this is, to make the pass band phase delay linear. This property is necessary in many types of applications, specially the telecommunication ones. The modifications performance is compared to the classic approaches found in the literature, and the most efficient set is use to compare the two most used Evolutionary Computing algorithms, GA and PSO. After this, extensive parameter tuning experiments were made, producing a final version of the method to compare with the specialist one. The chosen specialist method was the Elliptic filter, because the filter response has similarities with the one found by the proposed algorithm, and also because it is the most powerful one. Results showed excellent filters found with the proposed modifications, with a specification obedience rate well above the ones obtained with the classical approaches. Comparing with the specialist method, a similar performance was achieved, showing that IIR filter design with Evolutionary Computing can be used in real systems. Future work will address new modifications in the fitness function, and the performance of different EC algorithms in this problem. The application in online systems is promising, so the behavior of this approach with non-stationary specifications coming from channel estimation techniques should also be investigated.O projeto de filtros digitais do tipo IIR Ê um problema clåssico da engenharia. Filtros digitais possuem diversas aplicaçþes, e muitas variantes de comportamento. Existem vårios mÊtodos especialistas consagrados na literatura, cada um com suas peculiaridades e adequaçþes a diferentes casos. PorÊm, a maior parte destes mÊtodos não Ê flexível, impedindo a especificação de todos os parâmetros importantes de um filtro, pois alguns desses são um sub-produto do processo de cålculo. Por isso, este problema tambÊm Ê atacado na literatura atravÊs de tÊcnicas de computação evolucionåria. Diversos estudos foram encontrados com esta abordagem, mas em quase todos, o enfoque era dado no algoritmo evolucionårio em vez de no filtro, utilizando este apenas como uma função de \emph{benchmark}. AlÊm disso, a estabilidade do filtro - condição imprescindível para a utilização do mesmo - Ê desprezada em quase todos os trabalhos. Portanto, este trabalho propþe uma função de \emph{fitness} e uma nova codificação para este problema, de forma a possibilitar a obtenção de bons filtros, dentro das especificaçþes, com algoritmos de Computação Evolucionåria na forma canônica, isto Ê, sem modificaçþes estruturais. A função de \emph{fitness} proposta busca corrigir distorçþes causadas pela função tradicional, que não leva em conta a obediência às especificaçþes do filtro. A codificação mapeia o espaço de busca apenas para as soluçþes eståveis, sem excluir nenhuma solução vålida nesta transformação. AlÊm disso, um pós-processamento permite equalizar a resposta em fase do filtro, isto Ê, tornar o atraso de fase na banda de passagem linear, condição necessåria para a utilização em diversos sistemas, especialmente os de telecomunicaçþes. O desempenho das modificaçþes Ê comparado com as abordagens clåssicas utilizadas na literatura, e o conjunto escolhido como o mais eficiente Ê utilizado para comparar os dois algoritmos mais utilizados em Computação Evolucionåria, o PSO e o AG. Após esse passo, experimentos extensivos de ajuste de parâmetros foram realizados, para que a versão final fosse comparada com o mÊtodo especialista mais poderoso, que Ê o cålculo de filtros elípticos. Os resultados mostraram que o conjunto de modificaçþes proposto fez com que excelentes filtros fossem obtidos, com uma taxa de obediência às especificaçþes muito superior à obtida sem o mesmo. Comparando com o mÊtodo especialista, o desempenho foi semelhante, com pontos a favor e contra cada um, mostrando que o projeto de filtros IIR atravÊs de Computação Evolucionåria pode ser utilizado em sistemas reais. Em trabalhos futuros poderão ser estudadas novas modificaçþes na funçao de \emph{fitness}, alÊm do desempenho obtido com outros algoritmos evolucionårios. A utilização em sistemas \emph{online} Ê uma aplicação promissora, e o comportamento deste mÊtodo com especificaçþes não-estacionårias, oriundas de informaçþes de estimação de canal tambÊm deve ser investigado

    Performance and Operation of the CMS Electromagnetic Calorimeter

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    The operation and general performance of the CMS electromagnetic calorimeter using cosmic-ray muons are described. These muons were recorded after the closure of the CMS detector in late 2008. The calorimeter is made of lead tungstate crystals and the overall status of the 75848 channels corresponding to the barrel and endcap detectors is reported. The stability of crucial operational parameters, such as high voltage, temperature and electronic noise, is summarised and the performance of the light monitoring system is presented

    Measurement of the underlying event activity in pp collisions at √s = 0.9 and 7 TeV with the novel jet-area/median approach

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    Open Access: This article is distributed under the terms of the Creative Commons Attribution License.-- Chatrchyan, S. et al.The first measurement of the charged component of the underlying event using the novel >jet-area/median> approach is presented for proton-proton collisions at centre-of-mass energies of 0.9 and 7 TeV. The data were recorded in 2010 with the CMS experiment at the LHC. A new observable, sensitive to soft particle production, is introduced and investigated inclusively and as a function of the event scale defined by the transverse momentum of the leading jet. Various phenomenological models are compared to data, with and without corrections for detector effects. None of the examined models describe the data satisfactorily. © 2012 SISSA.Acknowledge support from BMWF and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); MoER, SF0690030s09 and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France);BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); MSI (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MON, RosAtom, RAS and RFBR (Russia); MSTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); ThEP, IPST and NECTEC (Thailand); TUBITAK and TAEK (Turkey); NASU (Ukraine); STFC (United Kingdom); DOE and NSF (USA). Individuals have received support from the Marie-Curie program and the European Research Council (European Union); the Leventis Foundation; the A. P. Sloan Foundation; the Alexander von Humboldt Foundation; the Austrian Science Fund (FWF); the Belgian Federal Science Policy Office; the Fonds pour la Formation à la Recherche dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the Agentschap voor Innovatie door Wetenschap en Technologie (IWTBelgium); the Ministry of Education, Youth and Sports (MEYS) of Czech Republic; the Council of Science and Industrial Research, India; the Compagnia di San Paolo (Torino); and the HOMING PLUS program of Foundation for Polish Science, cofinanced from European Union, Regional Development Fund.Peer Reviewe

    Calibration of the CMS Drift Tube Chambers and Measurement of the Drift Velocity with Cosmic Rays

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    Search for physics beyond the standard model in events with a Z boson, jets, and missing transverse energy in pp collisions at √s̅ = 7 TeV

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    Alignment of the CMS silicon tracker during commissioning with cosmic rays

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    This is the Pre-print version of the Article. The official published version of the Paper can be accessed from the link below - Copyright @ 2010 IOPThe CMS silicon tracker, consisting of 1440 silicon pixel and 15 148 silicon strip detector modules, has been aligned using more than three million cosmic ray charged particles, with additional information from optical surveys. The positions of the modules were determined with respect to cosmic ray trajectories to an average precision of 3–4 microns RMS in the barrel and 3–14 microns RMS in the endcap in the most sensitive coordinate. The results have been validated by several studies, including laser beam cross-checks, track fit self-consistency, track residuals in overlapping module regions, and track parameter resolution, and are compared with predictions obtained from simulation. Correlated systematic effects have been investigated. The track parameter resolutions obtained with this alignment are close to the design performance.This work is supported by FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTDS (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)

    Commissioning and performance of the CMS pixel tracker with cosmic ray muons

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    This is the Pre-print version of the Article. The official published verion of the Paper can be accessed from the link below - Copyright @ 2010 IOPThe pixel detector of the Compact Muon Solenoid experiment consists of three barrel layers and two disks for each endcap. The detector was installed in summer 2008, commissioned with charge injections, and operated in the 3.8 T magnetic field during cosmic ray data taking. This paper reports on the first running experience and presents results on the pixel tracker performance, which are found to be in line with the design specifications of this detector. The transverse impact parameter resolution measured in a sample of high momentum muons is 18 microns.This work is supported by FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTDS (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)

    Performance of the CMS drift-tube chamber local trigger with cosmic rays

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    The performance of the Local Trigger based on the drift-tube system of the CMS experiment has been studied using muons from cosmic ray events collected during the commissioning of the detector in 2008. The properties of the system are extensively tested and compared with the simulation. The effect of the random arrival time of the cosmic rays on the trigger performance is reported, and the results are compared with the design expectations for proton-proton collisions and with previous measurements obtained with muon beams

    Search for Supersymmetry at the LHC in Events with Jets and Missing Transverse Energy

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    A search for events with jets and missing transverse energy is performed in a data sample of pp collisions collected at root s = 7 TeV by the CMS experiment at the LHC. The analyzed data sample corresponds to an integrated luminosity of 1: 14 fb(-1). In this search, a kinematic variable alpha(T) is used as the main discriminator between events with genuine and misreconstructed missing transverse energy. No excess of events over the standard model expectation is found. Exclusion limits in the parameter space of the constrained minimal supersymmetric extension of the standard model are set. In this model, squark masses below 1.1 TeV are excluded at 95% C. L. Gluino masses below 1.1 TeV are also ruled out at 95% C. L. for values of the universal scalar mass parameter below 500 GeV
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