The observation of a bright X-ray source by the Chandra X-ray Observatory's High Energy Transmission Grating Spectrometer (HETGS) can be compromised by photon pile-up in the CCD leading to false absorption features in the observed spectrum. A method for removing the e ects of pile-up in a dispersed grating spectrum is presented. The e ectiveness of the technique is demonstrated through its appl...

The ion pile-up region in the comet Halley ionosphere observed on the inbound leg of the Giotto trajectory is accompanied by a decrease of the magnetic field strength. This magnetic field dip is explained by means of a diamagnetic effect of the plasma density increase in the pile-up region. Maximum of the plasma pressure seems to coincide with the maximum of the ion density. We arrived at the c...

Pile-up and dead-time are two main causes of nonlinearity in the response of a PET scanner as a function of activity in the field of view (FOV). For a given scanner and acquisition system, pile-up effects depend on the material and size of the object being imaged and on the distribution of activity inside and outside the FOV, because these factors change the singles-to-coincidences ratio (SCR)....

Finite element modeling has been used to study the development of surface deformation during indentation with a Vickers indenter. A wide range of materials with different elastic modulus and yield stresses are examined. Results show that in a pyramidal indentation process, for a perfectly plastic material, sinking-in during loading can change to pile-up in unloading. This phenomenon depends on ...

The high creep resistance of dispersion-strengthened metals is the result of a threshold stress, which is determined in existing models by considering the interaction of a single dislocation with dispersoids. This paper presents a new model which takes into account the effect of dislocation pile-ups upon the detachment threshold stress of dispersion-strengthened metals. First, it is shown that ...

Pile foundations have been the subject of interest for earthquake engineers since last several decades. The devastations caused in major earthquakes of the world can be the reason enough to carry out the research on the topic of seismic behavior of piles. One definite concern is liquefaction induced ground movement after the shaking in an earthquake, causing extra lateral loads acting on piles....

We study one event of reconnection onset associated to a small substorm on 27 September 2006 by using Cluster observations at inter-spacecraft separation of about 10 000 km. We focus on the acceleration of suprathermal electrons during different stages of reconnection. We show that several distinct stages of acceleration occur: (1) moderate acceleration during reconnection of pre-existing plasm...

Nanoindentation morphologies of crystalline copper have been probed at the grain scale. Experimental tests have been conducted on nanocrystalline (NC), ultrafine-grained (UFG), and coarse-grained (CG) copper samples with a new Berkvoich indenter at the strain rate of 0.04/s without holding time at an indentation depth of 2000 nm at room temperature. As the grain size increases, the height of th...

Pulsed power technology and appropriate boundary conditions have been used to create simulations of magnetically driven astrophysical jets in a laboratory experiment. The experiments are quite reproducible and involve a distinct sequence. Eight initial flux tubes, corresponding to eight gas injection locations, merge to form the jet which lengthens, collimates, and eventually kinks. A model dev...

At room temperature, the indentation morphologies of crystalline copper with different 13 grain size including nanocrystalline (NC), ultrafine-grained (UFG) and coarse-grained (CG) copper 14 were studied by nanoindentation at the strain rate of 0.04/s without holding time at indentation 15 depth of 2000 nm. As the grain size increasing, the height of the pile-up around the residual 16 indentati...