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This paper presents the experimental and numerical investigation on deformation and fracture of the large-scale welded thin-walled AA 6061 panels under Mode I loading. The proposed model is able to successfully capture crack initiation, initial growth, as well as a more complicated phenomenon where the crack undergoes a sudden jump to a new location and steadily propagates. The fracture process was explained by an in-depth analysis of the local stress and strain fields along the crack path.

As a critical part of a comprehensive study on fracture of welded thin-walled aluminum structures for train safety, a material testing procedure was developed to calibrate heterogeneous weldments for plasticity and fracture. This technique eliminates the need for machining and testing of miniature tensile specimens, cut from different zones within the weldment. The material characterization for plasticity and fracture of each of the material zones within the weld is reported, as a combination of experimental and numerical studies. The material data were applied in further investigation on large-scale Mode I and Mode III test as presented in the two accompanying papers [Zheng L, et al., Mode I fracture of large scale welded thin-walled AA 6061 extruded panels, submitted as an accompanying paper; Zheng L, et al., Mode III fracture of large scale welded thin-walled AA 6061 extruded panels. Thin-Walled Structures 2008; 46(11): 1262–73].

As part of the research on deformation and fracture of the large-scale welded thin-walled AA 6061 panels, this paper presents the experimental and numerical investigation on its fracture under Mode III loading. The proposed local fracture approach is applied by incorporating the calibrated damage input data into the finite element model. The investigations demonstrate that the present finite element model can successfully predict the global force–deflection response, the deformation modes, as well as the crack formation and propagation, in this quite sophisticated problem involving welded joints.

Details are presented of the Whipple Observatory’s 10 m atmospheric Cherenkov telescope and camera, as it evolved during the period 1997 until 2006. The design of the telescope and camera’s optical and electronic systems is discussed together with a detailed description of the four-stage GRANITE (Gamma-RAy New Imaging TElescope) upgrade program, undertaken during the same time period. The objective of the upgrade was to improve the telescope’s sensitivity for the detection of very-high-energy gamma-rays. Results from the program are provided and are briefly discussed in the context of the design of VERITAS.

Currently, the ICE cab cars in Europe are of all-aluminum construction for durability and low weight. Several serious train collisions involving this type of train raised questions about their integrity under accidental loads. A typical aluminum cab car is assembled from extruded aluminum panels, which are MIG welded, forming long seam lines. In this work, crushing characteristics of full scale sandwich panels under a 4-point bending load configuration were studied experimentally and numerically. Tests were run all the way to first fracture which occurred inside buckling induced dimples on the compressive side. The force–deflection response and fracture initiation were predicted by the finite element method and compared with experimental results. The location of the first fracture and the corresponding load was predicted with great accuracy using a newly developed fracture criterion. Based on a simplified beam model, a closed form analytical solution of the force–deflection response for the pre-fracture stage was also developed.

The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is the major next generation imaging atmospheric Cherenkov γ-ray telescope in the western hemisphere and will be located in southern Arizona nearby Kitt Peak National Observatory. The VERITAS observatory will provide unprecedented sensitivity to photon energies between 50 GeV and 50 TeV. The first stage is an array of four telescopes to be fully operational in early 2006, with an expansion to seven telescopes envisioned for 2008. The construction of a prototype telescope is underway, for which first light is expected in Fall 2003. The technical concept is outlined and a progress report is given.

In some experiments photomultiplier based multichannel detectors are used to measure short light flashes in self-trigger mode in the presence of a significant background illumination. This background can induce a sizeable afterpulse rate. Contrary to published data the afterpulses can have rather large amplitudes and might be interpreted as genuine signals. This is the case with current imaging air Cherenkov telescopes in cosmic ray experiments. We found that due to the simple trigger logic of contemporary telescopes it is not the light of the night sky (LONS), but the afterpulsing which sets the trigger threshold. Afterpulsing features for 5 types of photomultiplier tubes are presented.

An optimized method is presented for the reconstruction of air shower directions for scintillator arrays. The method takes into account that both the expectation value and the spread of the measured arrival times not only depend on the distance of a counter from the shower axis, but also on the number of particles registered in that counter. It also takes into account that the distributions of the measured arrival times are not Gaussian. For showers recorded with the HEGRA scintillator array above the threshold energy of E thres = 20 TeV the mean angular resolution obtained with this method is 〈 σ 63% θ 〉 = 1.0°, and above the threshold E thres = 50 TeV it is 〈 σ 63% θ 〉 = 0.6°. Comparing the new procedure with the HEGRA standard procedure the angular resolution has improved on average by a factor of 1.33. The mis-pointing has been determined with an accuracy of 0.15°. The method is developed using experimental data.

With systems of atmospheric Cherenkov telescopes, providing stereo images of air showers, the shower parameters, such as the direction, core location, and height of shower maximum can be determined event by event. Techniques for the reconstruction of air showers are introduced, and are demonstrated using data from the first two HEGRA Cherenkov telescopes. Applied to observations of the Crab nebula, a clear signal is observed; the angular distribution of the excess events is consistent with Monte Carlo simulations of the expected resolution.

The results of observations of the Crab Nebula by the second HEGRA imaging atmospheric Cherenkov telescope during the period 1994/1995 are presented. The signal, detected at a level of 10 σ , allows one to estimate the flux and the spectral index of the γ -ray energy spectrum above 1 TeV. The analysis, based on the comparison of measurements with comprehensive Monte Carlo simulations, reveals a γ -ray flux F γ (≥ 1 TeV) ⋍ 8 × 10 −12 photons cm −2 s −1 , and indicates a rather steep integral spectrum in the energy region 1–3 TeV with a power-law index α ⋍ 1.6–1.8.

The first atmospheric Cherenkov telescope of VERITAS (the Very Energetic Radiation Imaging Telescope Array System) has been in operation since February 2005. We present here a technical description of the instrument and a summary of its performance. The calibration methods are described, along with the results of Monte Carlo simulations of the telescope and comparisons between real and simulated data. The analysis of TeV $\gamma$-ray observations of the Crab Nebula, including the reconstructed energy spectrum, is shown to give results consistent with earlier measurements. The telescope is operating as expected and has met or exceeded all design specifications., Comment: Accepted by Astroparticle Physics

Resume Quarante-huit patients presentant des lesions de l'appareil extenseur de la main ont ete traites par reparation primaire avec mobilisation post-operatoire assistee par une orthese dynamique d'extension a profil bas. Ils sont repartis en trois groupes : 25 plaies simples des tendons extenseurs des doigts longs ; 14 plaies simples des tendons extenseurs du pouce ; 9 plaies complexes. La mobilite de la suture tendineuse et l'elongation du cal ont ete etudies par implantation de reperes metalliques peroperatoires. Une etude electromyographique fonctionnelle en cours de reeducation nous a permis d'affiner la technique de reeducation limitant le secteur de flexion des articulations interphalangiennes proximales. Les resultats sont classes en 4 categories et repartis de la facon suivante : excellent 33 (60 %), bon 9 (16,4 %), moyen 4 (7,3 %), mauvais 9 (16,4 %). Aucune complication (infection, lâchage de suture, algodystrophie) n'est a deplorer dans cette courte serie preliminaire. Cette technique sophistiquee n'apporte que peu d'amelioration par rapport aux methodes traditionnelles dans le groupe des lesions simples. Sa principale indication est constituee par les lesions complexes ou elle a ameliore nos resultats.