Thermomechanical modelling the resistance welding of PbSb alloy

The analytical modelling of the PbSb alloy resistance spot welding process has been developed on the basis of mathematical analysis of thermomechanical conservation laws. The numerical solution of partial differential equations, obtained by such modelling, has been achieved by the finite element method. Thermomechanical equilibrium equations are derived, including specific properties, typical for PbSb alloys. The paper utilizes the basic experimentally proven assumption, that the temperature fields govern all processes during welding. Full agreement is evident between the experimental and analytical data

Evaluation of European railway companies efficiency: Application of a two-stage analysis

The aim of this paper is efficiency assessment of railway companies from larger Europe during the most recent time period, taking into account different input-output configurations. For this aim, two-stage analysis is employed, where efficiency scores are obtained by DEA in the first stage, while in the second stage different statistical tests are conducted and Tobit analysis is used in order to evaluate influence of different environmental factors. It has been found that railways were oriented either on passenger or freight transportation, with only few companies demonstrating high performance in both modes. While companies from Western Europe showed higher performance than companies from Central and Eastern Europe regarding passenger and overall transportation, this is not the case concerning freight transportation. Except for few companies, there are no clear trends in performance during the period observed, in terms of constant efficiency level increase or decrease. Great impact of factors selection on results has been identified

Different modeling technologies of hydraulic load simulator for thrust vector control actuator

Hidraulički simulatori su posebice važni u procesu verifikacije aktuacijskog sustava za kontrolu leta. Fleksibilni mlaznik ima niz specifičnosti u odnosu na druge komande leta, jer se opterećenje ne može opisati na klasičan način preko zglobnog momenta. Pored toga, klasičan hidraulički simulator, na bazi cilindra koji simulira opterećenje, nije dovoljan za potpunu simulaciju realnog opterećenja. Potrebno je napraviti mehaničko njihalo na koje deluje hidraulički cilindar i koje se oslanja na dva elastična oslonca kako bi se mogle simulirati i dopunske pojave koje postoje kod fleksibilnog mlaznika, a koji ne postoje kod drugih upravljačkih površina. Preko njihala se može zadati impulsna sila koja postoji u realnosti, a koju nije moguće generirati standardnim hidrauličkim simulatorom. U članku se pokazuje da se modeliranjem elastičnog opterećenja preko bond grafova simulator može projektirati bez preciznog razmatranja smjerova i pravaca sila u elastičnoj strukturi, već se samo energetski promatra unošenje sile u fleksibilnu strukturu preko mjesta djelovanja aktuacijske sile. Simulator s hidrauličkim cilindrom je pogodan u slučaju kad treba razmotriti rizik od vlastitih vibracija fleksibilne veze i mlaznika, to jest definirati takozvani notch filter. Tada hidraulički cilindar simulatora opterećenja može generirati oscilatorno gibanje, frekvenciju i amplitudu koje odgovaraju ovom dinamičkom slučaju opterećenja aktuatora fleksibilnog mlaznika koje je svedeno na njegovu klipnjaču, a da ne postoji rizik oštećenja fleksibilne strukture koja postoji u konstrukciji simulatora s njihalom.Hydraulic simulators are extremely important in the flight control actuator system’s verification process. Flexible nozzle has a number of specifics, comparing to other flight controls, because the load cannot be described, classically, by the hinge moment. Additionally, classical hydraulic simulator, in which the cylinder simulates the load, is not sufficient for performing a complete simulation of the real load. Building a mechanical pendulum, to which a hydraulic cylinder acts, and that rests on two elastic supports, enables simulation of additional phenomena that exist in flexible nozzle, but not in other control surfaces. Force from impulse that exists in reality, and which is impossible to be generated by standard hydraulic simulator, can be realized through the pendulum. This paper demonstrates that a simulator can be designed through modelling of the elastic load using bond graph, without a precise elaboration of direction of forces in elastic structure, just by observing, on energy level, the input of force in flexible structure over the point in which actuator force acts. Simulator with hydraulic cylinder is convenient to be used when there is a need for considering the risk of self-oscillation of flexible joint and nozzle, i.e. for defining the so-called notch filter. Then, the hydraulic cylinder of load simulator can generate the oscillation, frequency and amplitude that match this dynamic case of flexible nozzle actuator’s load that is being reduced to its piston rod, without a risk of damaging the flexible structure that exists in the construction of a simulator with pendulum

Search for neutral MSSM Higgs bosons decaying into a pair of bottom quarks

A search for neutral Higgs bosons decaying into a b (b) over bar quark pair and produced in association with at least one additional b quark is presented. This signature is sensitive to the Higgs sector of the minimal supersymmetric standard model (MSSM) with large values of the parameter tan beta. The analysis is based on data from proton-proton collisions at a center-of-mass energy of 8 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.7 fb(-1). The results are combined with a previous analysis based on 7 TeV data. No signal is observed. Stringent upper limits on the cross section times branching fraction are derived for Higgs bosons with masses up to 900 GeV, and the results are interpreted within different MSSM benchmark scenarios, m(h)(max), m(h)(mod+), m(h)(mod-), light-stau and light-stop. Observed 95% confidence level upper limits on tan beta, ranging from 14 to 50, are obtained in the m(h)(mod+) benchmark scenario

Search for a standard model-like Higgs boson in the mu(+)mu(-) and e(+)e(-) decay channels at the LHC

A search is presented for a standard model-like Higgs boson decaying to the mu(+)mu(-) or e(+)e(-) final states based on proton-proton collisions recorded by the CMS experiment at the CERN LHC. The data correspond to integrated luminosities of 5.0 fb(-1) at a centre-of-mass energy of 7 TeV and 19.7 fb(-1) at 8 TeV for the mu(+)mu(-) search, and of 19.7 fb(-1) at 8 TeV for the e(+)e(-) search. Upper limits on the production cross section times branching fraction at the 95% confidence level are reported for Higgs boson masses in the range from 120 to 150 GeV. For a Higgs boson with a mass of 125 GeV decaying to mu(+)mu(-), the observed (expected) upper limit on the production rate is found to be 7.4 (6.5(-1.9)(+2.8)) times the standard model value. This corresponds to an upper limit on the branching fraction of 0.0016. Similarly, for e(+)e(-), an upper limit of 0.0019 is placed on the branching fraction, which is approximate to 3.7 x 10(5) times the standard model value. These results, together with recent evidence of the 125 GeV boson coupling to tau-leptons with a larger branching fraction consistent with the standard model, confirm that the leptonic couplings of the new boson are not flavour-universal. (C) 2015 CERN for the benefit of the CMS Collaboration. Published by Elsevier B.V

Search for the production of dark matter in association with top-quark pairs in the single-lepton final state in proton-proton collisions at root s=8 TeV

A search is presented for particle dark matter produced in association with a pair of top quarks in pp collisions at a centre-of-mass energy of root s = 8TeV. The data were collected with the CMS detector at the LHC and correspond to an integrated luminosity of 19.7 fb(-1). This search requires the presence of one lepton, multiple jets, and large missing transverse energy. No excess of events is found above the SM expectation, and upper limits are derived on the production cross section. Interpreting the findings in the context of a scalar contact interaction between fermionic dark matter particles and top quarks, lower limits on the interaction scale are set. These limits are also interpreted in terms of the dark matter-nucleon scattering cross sections for the spin-independent scalar operator and they complement direct searches for dark matter particles in the low mass region

Search for the associated production of the Higgs boson with a top-quark pair

A search for the standard model Higgs boson produced in association with a top-quark pair (t (t) over barH) is presented, using data samples corresponding to integrated luminosities of up to 5.1 fb(-1) and 19.7 fb(-1) collected in pp collisions at center-of-mass energies of 7 TeV and 8 TeV respectively. The search is based on the following signatures of the Higgs boson decay: H - GT hadrons, H - GT photons, and H - GT leptons. The results are characterized by an observed t (t) over barH signal strength relative to the standard model cross section, mu = sigma/sigma(SM), under the assumption that the Higgs boson decays as expected in the standard model. The best fit value is mu = 2.8 +/- 1.0 for a Higgs boson mass of 125.6 GeV

Search for third-generation scalar leptoquarks in the t tau channel in proton-proton collisions at root s=8 TeV

A search for pair production of third-generation scalar leptoquarks decaying to top quark and tau lepton pairs is presented using proton-proton collision data at a center-of-mass energy of root s=8TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb(-1). The search is performed using events that contain an electron or a muon, a hadronically decaying tau lepton, and two or more jets. The observations are found to be consistent with the standard model predictions. Assuming that all leptoquarks decay to a top quark and a tau lepton, the existence of pair produced, charge -1/3, third-generation leptoquarks up to a mass of 685 GeV is excluded at 95% confidence level. This result constitutes the first direct limit for leptoquarks decaying into a top quark and a tau lepton, and may also be applied directly to the pair production of bottom squarks decaying predominantly via the R-parity violating coupling lambda(333)

Search for long-lived particles that decay into final states containing two electrons or two muons in proton-proton collisions at root s=8Tev

A search is performed for long-lived particles that decay into final states that include a pair of electrons or a pair of muons. The experimental signature is a distinctive topology consisting of a pair of charged leptons originating from a displaced secondary vertex. Events corresponding to an integrated luminosity of 19.6 (20.5) fb(-1) in the electron (muon) channel were collected with the CMS detector at the CERN LHC in proton-proton collisions at root s TeV. No significant excess is observed above standard model expectations. Upper limits on the product of the cross section and branching fraction of such a signal are presented as a function of the long-lived particles mean proper decay length. The limits are presented in an approximately model-independent way, allowing them to be applied to a wide class of models yielding the above topology. Over much of the investigated parameter space, the limits obtained are the most stringent to date. In the specific case of a model in which a Higgs boson in the mass range 125-1000 GeV/c(2) decays into a pair of long-lived neutral bosons in the mass range 20-350 GeV= c(2), each of which can then decay to dileptons, the upper limits obtained are typically in the range 0.2-10 fb for mean proper decay lengths of the long-lived particles in the range 0.01-100 cm. In the case of the lowest Higgs mass considered (125 GeV/c(2)), the limits are in the range 2-50 fb. These limits are sensitive to Higgs boson branching fractions as low as 10(-1)

Performance of photon reconstruction and identification with the CMS detector in proton-proton collisions at root s=8TeV

A description is provided of the performance of the CMS detector for photon reconstruction and identification in proton-proton collisions at a centre-of-mass energy of 8 TeV at the CERN LHC. Details are given on the reconstruction of photons from energy deposits in the electromagnetic calorimeter (ECAL) and the extraction of photon energy estimates. The reconstruction of electron tracks from photons that convert to electrons in the CMS tracker is also described, as is the optimization of the photon energy reconstruction and its accurate modelling in simulation, in the analysis of the Higgs boson decay into two photons. In the barrel section of the ECAL, an energy resolution of about 1% is achieved for unconverted or late-converting photons from H - GT gamma gamma decays. Different photon identification methods are discussed and their corresponding selection efficiencies in data are compared with those found in simulated events