HotSpot: a compact thermal modeling methodology for early-stage VLSI design

This paper presents HotSpot-a modeling methodology for developing compact thermal models based on the popular stacked-layer packaging scheme in modern very large-scale integration systems. In addition to modeling silicon and packaging layers, HotSpot includes a high-level on-chip interconnect self-heating power and thermal model such that the thermal impacts on interconnects can also be considered during early design stages. The HotSpot compact thermal modeling approach is especially well suited for preregister transfer level (RTL) and presynthesis thermal analysis and is able to provide detailed static and transient temperature information across the die and the package, as it is also computationally efficient.     

A brief review of the ionic conductivity enhancement for selected oxide electrolytes

The advantages of lowering the operation temperature of SOFCs have attracted great interest worldwide. One of the major barriers to decreasing the operation temperature is the ohmic loss of the electrolyte. Maximizing the electrolyte ionic conductivity is of significant importance, especially in the absence of new electrolyte materials. The ionic conductivity of electrolytes can be influenced by many parameters. There has been an enormous effort in the literature for the improvement of the electrolyte ionic conductivity. From a practical point of view, this paper reviews various approaches to enhancing the ionic conductivity of polycrystalline zirconia- and ceria-based oxide electrolytes in the light of composition, microstructure, and processing. Suggestions are given for future work.     

Silicon oxide thin films prepared by a photo-chemical vapour deposition technique

Wide band gap a-SiO_x:H films have been prepared by the photochemical decomposition of a SiH₄, CO₂ and H₂ gas mixture. Deposition parameters namely the CO₂ to SiH₄ gas flow ratio, H₂ dilution and chamber pressure were optimized in order to achieve highly photoconducting (1 × 10^-6 S cm^-1) films with an optical gap of 1.99 eV. The optical gap was found to increase with an increase in the CO₂ to SiH₄ flow ratio. A decrease in the photoconductivity, refractive index, spin g-value and a simultaneous increase in the spin density are attributed to an incorporation of oxygen into the films. Upon hydrogen dilution the photoconductivity of a-SiO_x:H films was observed to improve along with an increase of the optical gap. The spin density of a-SiO_x:H films was of the order of 10¹⁷ cm^-9. The optoelectronic properties of the films have been correlated with the bonding configurations in the film, deposition parameters and the growth kinetics. This revised version was published online in November 2006 with corrections to the Cover Date.     

Fatigue characteristics of pulsed MIG-welded Al-Zn-Mg alloy

Pulse-current MIG welding of Al-Zn-Mg alloy was carried out using an extruded section of base material and Al-Mg (5183) filler wire. During welding the pulse parameters such as the mean current and pulse frequency were varied and their effect on the geometry and porosity content of weld deposit as well as the fatigue life of the weldment was studied. The pulse parameters were found to affect significantly the geometry and porosity content of weld deposit and consequently the fatigue life of the weldment. For a comparative study, weldments were also prepared by using conventional continuous current MIG-welding process, where welding currents equivalent to the mean currents of pulsed process were used. The fatigue life of the weldment was correlated with the geometry and porosity content of weld deposit.     

Turbulent natural convection heat transfer from a vertical plate to the power-law fluid at high prandtl numbers

A simple analytical technique for turbulent natural convection heat transfer from an isothermal vertical plate to a power-law fluid is developed. The model is based on the assumption that the turbulent heat transfer rate is controlled by the flow characteristic near the surface in the limit of large Prandtl numbers. The formulation proposed in this work agrees well with the correlations available in the literature.     

Structure of nitric oxide synthase oxygenase dimer with pterin and substrate

Crystal structures of the murine cytokine-inducible nitric oxide synthase oxygenase dimer with active-center water molecules, the substrate L-arginine (L-Arg), or product analog thiocitrulline reveal how dimerization, cofactor tetrahydrobiopterin, and L-Arg binding complete the catalytic center for synthesis of the essential biological signal and cytotoxin nitric oxide. Pterin binding refolds the central interface region, recruits new structural elements, creates a 30 angstrom deep active-center channel, and causes a 35 degrees helical tilt to expose a heme edge and the adjacent residue tryptophan-366 for likely reductase domain interactions and caveolin inhibition. Heme propionate interactions with pterin and L-Arg suggest that pterin has electronic influences on heme-bound oxygen. L-Arginine binds to glutamic acid-371 and stacks with heme in an otherwise hydrophobic pocket to aid activation of heme-bound oxygen by direct proton donation and thereby differentiate the two chemical steps of nitric oxide synthesis.