Neutron emission from electromagnetic dissociation of Pb nuclei at √ s NN = 2.76 TeV measured with the ALICE ZDC

The ALICE Zero Degree Calorimeter system (ZDC) is composed of two identical sets of calorimeters, placed at opposite sides with respect to the interaction point, 114 meters away from it, complemented by two small forward electromagnetic calorimeters (ZEM). Each set of detectors consists of a neutron (ZN) and a proton (ZP) ZDC. They are placed at zero degrees with respect to the LHC axis and allow to detect particles emitted close to beam direction, in particular neutrons and protons emerging from hadronic heavy-ion collisions (spectator nucleons) and those emitted from electromagnetic processes. For neutrons emitted by these two processes, the ZN calorimeters have nearly 100% acceptance. During the √ sNN = 2.76 TeV Pb-Pb data-taking, the ALICE Collaboration studied forward neutron emission with a dedicated trigger, requiring a minimum energy deposition in at least one of the two ZN. By exploiting also the information of the two ZEM calorimeters it has been possible to separate the contributions of electromagnetic and hadronic processes and to study single neutron vs. multiple neutron emission. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at √ s NN = 2.76 TeV, with neutron emission, are σ single EMD = 187:4 ± 0.2 (stat.)-11.2 +13.2 (syst.) b and σmutual EMD = 5.7 ± 0.1 (stat.) ±0.4 (syst.) b, respectively [1]. This is the first measurement of electromagnetic dissociation of 208Pb nuclei at the LHC energies, allowing a test of electromagnetic dissociation theory in a new energy regime. The experimental results are compared to the predictions from a relativistic electromagnetic dissociation model'701st International Conference on New Frontiers in Physics, ICFP 20122012-06-10Kolymbari, Crete; Greecesem informaçã

Model investigations of Strouhal number of iced cable of cable-stayed bridge

W artykule przedstawiono sposób i wyniki badań liczby Strouhala nieruchomego modelu oblodzonego cięgna mostu podwieszonego. Badania wykonano w tunelu aerodynamicznym z komorą klimatyczną Laboratorium Czeskiej Akademii Nauk w Telc. W komorze klimatycznej wykonano doświadczalne oblodzenie modelu cięgna o osi nachylonej pod kątem 300 do płaszczyzny poziomej. Kształt oblodzonej powierzchni zarejestrowano metodą fotogrametrii cyfrowej. Do badań w tunelu aerodynamicznym wykonano nowy model sekcyjny oblodzonego cięgna metodą druku 3D. Liczbę Strouhala wyznaczono w zakresie wartości liczby Reynoldsa od 28 do 122 na podstawie pomiaru częstości odrywania się wirów w śladzie aerodynamicznym za modelem.The paper presents the method and results of wind tunnel investigations of Strouhal number of stationary iced cable model of cable-stayed bridge. The investigations were performed in a Climatic Wind Tunnel Laboratory of the Czech Academy of Sciences in Telc. The experimental icing of the inclined cable model in the climatic chamber of the laboratory was made. The shape of the iced model was registered by a numerical photogrammetry method. For the aerodynamic tunnel investigations, the new iced cable model was made by using 3D printing method. The Strouhal number was determined within the range of the Reynolds number between 28·103 and 122·103, on the basis of the dominant vortex shedding frequency measured in the flow behind the model