Variation in the reaction zone and its effects on the strength of diffusion bonded titanium–stainless steel couple

Solid state bonding was carried out between commercially pure titanium and 304 stainless steel at 850 °C temperature for 30–150 min under uniaxial load in vacuum. The transition joints were characterized using optical and scanning electron microscopes and revealed the presence of reaction layers in the diffusion zone. The chemical composition of these reaction products was determined by energy dispersive spectroscopy and the presence of phase/phase mixtures σ, -Fe + χ, χ + λ, λ + FeTi + β-Ti and β-Ti were predicted. Their existence was also confirmed by X-ray diffraction technique. The concentration–penetration plots for Ti, Fe, Cr and Ni are obtained from electron probe microanalysis, which also exhibit concentration gaps in the profile indicating formation of intermetallics in the diffusion zone. The width of intermetallic phases attains its maximum for 90 min joining time, then drops and again rises for 150 min bonding time. The maximum bond strength of 76% of that of titanium was achieved for the assemblies processed for 90 min owing to better coalescence of the mating surfaces, though the volume fraction of intermetallics is high.     

ARC: an integrated admission and rate control framework for competitive wireless CDMA data networks using noncooperative games

The competition among wireless data service providers brings in an option for the unsatisfied customers to switch their providers, which is called churning. The implementation of Wireless Local Number Portability (WLNP) is expected to further increase the churn rate (the probability of users switching the provider). However, the existing resource management algorithms for wireless networks fail to fully capture the far-reaching impact of this unforeseen competitiveness. From this perspective, we first formulate noncooperative games between the service providers and the users. A user's decision to leave or join a provider is based on a finite set of strategies. A service provider can also construct its game strategy set so as to maximize their utility (revenue) considering the churn rate. Based on the game theoretic framework, we propose an integrated admission and rate control (ARC) framework for CDMA-based wireless data networks. The admission control is at the session (macro) level while the rate control is at the link layer packet (micro) level. Two admission control modes are considered - one-by-one mode and batch processing mode, in which multiple users are admitted at a time. We show that: 1) for the one-by-one mode, the Nash equilibrium using pure strategy can be established for both under-loaded and fully-loaded systems and 2) for batch processing mode, there is either an equilibrium in pure strategy or a dominant strategy exists for the service provider. Therefore, the providers have clearly defined admission criteria as outcome of the game. Users are categorized into multiple classes and offered differentiated services based on the price they pay and the service degradation they can tolerate. We show that the proposed ARC framework significantly increases the provider's revenue and also successfully offers differentiated QoS to the users.     

Thalamic thought disorder: on being "a bit addled"

Humans can generate and maintain relatively coherent trains of thought in natural discourse. The neural mediation of this ability and the phenomenology of its breakdown are not well understood. We report a case of a woman with paramedian thalamic strokes involving the mammillothalamic tract, intralaminar nuclei, parts of the dorsomedial and ventral lateral nuclei bilaterally. She presented with a dense amnesia and confusion typical of the syndrome of bilateral paramedian thalamic infarcts. Her Tc-99m HMPAO brain SPECT scan showed decreased thalamic and basal ganglia blood flow. General diminution of cerebral blood flow and areas of further diminution in the right frontal, left temporal and left temporoparietal regions were also observed. Although her amnesia was characteristic of diencephalic amnesia, her most striking clinical feature was a bizarre, disconnected and at times incoherent speech output. Analysis of her speech revealed relatively preserved lexical and morpho-syntactic linguistic production. By contrast, analysis of the macrostructure of her discourse revealed frequent unpredictable topic shifts that were completely unconstrained by contextual factors. Many of her shifts were intrusions from previous topics. We interpret her severely disordered speech output as representing the surface manifestations of a thought disorder (rather than as a language disorder per se) characterized by an inability to maintain and appropriately shift themes that normally guide discourse. Median and intralaminar thalamic nuclei appear to be critical for the neurophysiologic regulation of thalamocortical and striatocortical circuits, which in turn may be critical for the functional regulation of contextually appropriate transitions of thought.     

Local vascular complications after heart catheterization

BACKGROUND: A prospective study was carried out to clarify the efficacy of an endoscopic screening program for detecting superficial colorectal neoplasias by color changes such as faint redness or discoloration, which have been described as a key finding of these lesions in the literature. METHODS: We enrolled 716 consecutive cases in this study, but more than half of them did not reveal any abnormalities colonoscopically. RESULTS: Of the 716 cases, 48 (7%) were examined by magnifying colonoscopy with a dye spraying technique, following the detection of superficial color changes. Sixteen neoplastic lesions (in 16 cases) were detected among the 48 cases and the detection rate was calculated as 2.2% (16/716) in the total number of cases and 33% (16/48) in those showing color abnormalities. Histologically, all of the 16 were adenomas. These neoplastic lesions were most frequent (52%; 11/21) in those showing faint redness in an oval shape, whereas 14 (94%) of the 15 lesions were non-specific in those showing faint redness with unclear margin. CONCLUSIONS: These results may confirm the diagnostic utility of color abnormality, particularly faint redness in an oval shape, for endoscopic screening of superficial colorectal neoplasias.     

Effect of microstructure on hydrogen embrittlement of weld-simulated HSLA-80 and HSLA-100 steels

HSLA-80 and HSLA-100 steels have been subjected to weld-simulated grain-coarsened heat-affected zone (GCHAZ) and grain-refined heat-affected zone (GRHAZ) treatments at peak temperatures of 1350 °C and 950 °C, respectively, followed by varying cooling rates to approximate the weld heat inputs of 10 to 50 kJ/cm. Subsequent slow strain rate testing in synthetic seawater has been employed to assess the hydrogen embrittlement (HE) propensity of the materials. It is indicated that in spite of an increase in strength after weld simulation, further ductility deterioration, compared to the base material under similar testing conditions, did not occur in GCHAZ HSLA-100 steel and for low heat input condition of GRHAZ HSLA-80. This has been attributed to their HE resistant microstructures. Predominant acicular ferrite or lath martensite or a combination of both imparts resistance to HE, as observed in the case of grain-coarsened HSLA-100 and for the low heat input grain-refined HSLA-80 steels. The deleterious effect of bainitic-martensitic microstructure has been reflected in the ductility values of grain-coarsened HSLA-80, which is in agreement with the observation of higher susceptibility of the as-received HSLA-100 steel having a similar structure. However, contrary to its beneficial effect in the as-received HSLA-80, an acicular ferrite structure has shown vulnerability toward HE for high heat input grain-refined HSLA-80. This has been attributed to the presence of polygonal ferrite and to the development of an HE susceptible substructure on GRHAZ weld simulation.     

Parametric study of latchup immunity of deep trench-isolated, bulk,nonepitaxial CMOS

The improvement of latchup immunity in bulk, nonepitaxial CMOS with deep trench isolation has been demonstrated using numerical simulation. Through a proper design of trench dimensions and layout, it is shown that the holding voltage can be increased to a level above the power supply voltage (3.3 V in deep-submicrometer CMOS), yielding latchup-free CMOS even for nonepitaxial substrates. The holding voltage is strongly influenced by the current flow patterns in the conductivity-modulated well and substrate regions, which are affected by trench depth, layout parameters, and the tank and p⁺/n⁺ emitter doping concentrations. The deep trench makes the current flow patterns two-dimensional, and this causes parametric dependencies that cannot be explained from simple trench-isolation techniques. Design issues that are unique to deep trench isolation have been identified