Laser Beam Build-Up Welding: Precision in Repair,Surface Cladding,and Direct 3D Metal Deposition

Surface coating, repair, and rapid design changes of high-value components and tools are demanding challenges of modern manufacturing technology. In this field, advanced laser-based techniques are of outstanding importance for the related applications in mould and tool, aircraft and aerospace, as well as automotive industry. Many laser cladding solutions have been transferred into industrial series production within the last years. The motivations for the raising interest are given by the typical features of the technology: on the base of closed CAD/CAM chains, a quick and comprehensive treatment even of complex shaped and highly stressed components is possible. The heat input into the workpiece is less compared to TIG or PTA welding, although a metallurgical bonding to the substrate is guaranteed. Furthermore, the precise material deposition even at small partial areas is an advantageous characteristic. The coating materials include metal alloys (Co, Ni, Cu basis, Titanium, and steel), hard metals (e.g., WC/Co, TiC, and VC with metallic binders), and oxide ceramics (Al₂O₃/TiO₂). Typical base materials are steel, cast iron, and lightweight metal alloys based on Aluminum, Titanium, and Magnesium. The accuracy of the produced 3D structures in the range of 0.1 mm is the highest possible in the group of welding techniques. On the other hand, the available system technology (lasers, powder feeders and nozzles, CAD/CAM systems) permits a very easy and successful integration of the laser technology into manufacturing systems. Examples of application are the surface protection of lightweight automotive motor components, repair and quick modifications of metal forming tools as well as the complete restoration of damaged blades and disks of aero engines and gas turbines.     

Similarity of prior trauma exposure as a determinant of chronic stress responding to an airline disaster.

The cumulative effects of trauma were examined in 108 workers at the site of a major air disaster at 4 time points over a year following the crash. The influence of trauma history on chronic distress and physiological arousal associated with the crash were examined. Stress levels were expected to differ on the basis of the similarity of prior trauma exposure to work at the crash site. Prior traumatic exposure that was "dissimilar" to this type of work was associated with greater vulnerability to crash-related stress, that is, more distress and crash-related intrusions during the year following the crash. Accumulation of a variety of different traumatic experiences appeared to sensitize workers to the new stressor and to perpetuate chronic stress. Understanding the role of trauma history is important for improving intervention efforts aimed at alleviating stress following a trauma. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quantitative representation of the anisotropy and tension/compression asymmetry of the critical resolved shear stress of an L12-ordered intermetallic

The anomalous anisotropy and tension (t)/compression (c)-asymmetry of the critical resolved shear stress τ_o of the L1₂-long-range ordered intermetallic γ′_NIM are analysed in the light of a published (Miner RV, Gabb TP, Gayda J, Hember, KJ. Met Trans A 1986; 17A: 507) analytical expression

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. Particles of γ′_NIM strengthen the commercial nickel-base superalloy NIMONIC 105. characterises the orientation of the specimen, and T_o≈300 K and T_peak≈ 1000 K mark the temperature (T) range in which τ_o is anomalous. Except for γ′_NIM-single crystals with the [011]-orientation, the formula describes the anisotropy and (t/c)-asymmetry of the critical resolved shear stress satisfactorily.     

Evaluation of a hybrid method for refrigerant flow balancing in multi-circuit evaporators

A companion paper [Kim, J.-H., Braun, J.E., Groll, E.A., 2009. A hybrid method for refrigerant flow balancing in multi-circuit evaporators: upstream versus downstream control. International Journal of Refrigeration doi:10.1016/j.ijrefrig.2009.01.013 presented a hybrid approach for providing control of refrigerant flow distribution in evaporators that involves the use of small balancing valves in each circuit along with a primary expansion device to control the overall superheat from the evaporator. Furthermore, the companion paper demonstrated that the flow balancing valves should be located upstream rather than downstream of the evaporator in order to realize significant benefits. The current paper utilizes the model presented in the companion paper to more fully evaluate the effects of uneven air and refrigerant flow distributions and the benefits of upstream hybrid control in response to these effects.     

Simulation of the current distribution in lead-acid batteries to investigate the dynamic charge acceptance in flooded SLI batteries

Measurements show that the dynamic charge acceptance (DCA) of flooded SLI lead-acid batteries during micro-cycling in conventional and micro-hybrid vehicles is strongly dependent on the short-term history, such as previous charge or discharge, current rate, lowest state of charge in the last 24 h and more. Factors of 10 have been reported. Inhomogeneous current distribution, especially as a result of acid stratification, has been suggested to explain the DCA variability.This hypothesis was investigated by simulation of a two-dimensional macrohomogeneous model. It provides a spatial resolution of three elements in horizontal direction in each electrode and three elements in vertical direction. For an existing set of parameters, different current profiles were analyzed with regard to the current distribution during charging and discharging.In these simulations, a strong impact of the short-term history on current, charge and acid density distribution was found as well as a strong influence of micro-cycles on both charge distribution and acid stratification.     

On the wideband EMI response of a rotationally symmetric permeableand conducting target

A simple and accurate model is presented for computation of the electromagnetic induction (EMI) resonant frequencies of canonical conducting and ferrous targets, in particular, finite-length cylinders and rings. The imaginary resonant frequencies correspond to the well known exponential decay constants of interest for time-domain EMI interaction with conducting and ferrous targets. The results of the simple model are compared to data computed numerically, via method-of-moments (MoM) and finite-element models. Moreover, the simple model is used to fit measured wideband EMI data from ferrous cylindrical targets (in terms of a small number of parameters). It is also demonstrated that the general model for the magnetic-dipole magnetization, in terms of a frequency-dependent diagonal dyadic, is applicable to general rotationally symmetric targets (not just cylinders and rings)     

Fast Simultaneous Angle,Wedge, and Beam Intensity Optimization in Inverse Radiotherapy Planning

We present a new fast radiotherapy planning algorithm which determines approximatively optimal gantry and table angles, kinds of wedges, leaf positions and intensities simultaneously in a global way. Other parameters are optimized only independently of each other. The algorithm uses an elaborate field management and field reduction. Beam intensities are determined via a variant of a projected Newton method of Bertsekas. The objective function is a standard piecewise quadratic penalty function, but it is built with efficient upper bounds which are calculated during the optimization process. Instead of pencil beams, basic leaf positions are included. The algorithm is implemented in the new beam modelling and dose optimization module Homo OptiS.Supported by the Ministry of Education, Science, and Culture of Mecklenburg-Vorpommern.     

Construction and in vivo efficacy of a replication-deficient recombinant adenovirus encoding murine growth hormone

We have constructed a recombinant, replication-deficient, first-generation adenovirus-encoding mouse GH (mGH), AdCMVmGH. This virus directed mGH production from an epithelial cell line in vitro in a dose-dependent manner. When injected into the quadriceps muscle or submandibular ducts of mGH-deficient Snell dwarf mice, AdCMVmGH resulted in the production of significantly elevated serum mGH levels. Furthermore, after i.m. injection, dwarf mice increased in weight by 8% over 4 days and close to 100% by 30 days. When AdCMVmGH was administered to 3- to 4-week-old rats by i.v. injection to assess general metabolic responses, serum mGH, insulin-like growth factor 1, triglycerides and cholesterol levels were significantly elevated. AdCMVmGH should be a valuable experimental tool for the controlled, directed expression of mGH in preclinical mouse model studies.     

Attenuation of low-frequency electromagnetic fields in permeableand conducting chimneys

For practical reasons shielded rooms cannot be manufactured perfectly closed; openings are necessary to enable an exchange of data and transport of energy and air through the shielding walls. To avoid a severe degradation of the overall shielding efficiency, the openings are often equipped with tubes, sometimes also called chimneys. It is beyond the scope of this paper to perform an exact calculation of the total field excited by a special source distribution. However, analytical expressions for the decay constants of the electromagnetic field inside a permeable and conducting semi-infinite tube with rectangular cross section are derived. The decay constants of the different modes that are excited corresponding to the symmetry properties of the exciting field are compared to identify the dominant mode with the lowest decay constant. It characterizes the shielding efficiency