A methodology for measuring in situ lattice strain of bulk polycrystalline material under cyclic load

The material response of polycrystalline materials under cyclic loading is not fully understood. Even during uniaxial loading, individual grains embedded within the polycrystalline material can experience complicated strain histories. By quantifying the deformation state at the crystal level, we can begin to understand the conditions that lead to fatigue failure. An in situ powder diffraction method was developed and employed at the Cornell High Energy Synchrotron Source to measure the aggregate crystal response at various points in a material's life using synchrotron x ray. A set of experiments was conducted using a load frame capable of exerting cyclic uniaxial loads on a specimen. A high speed x-ray shutter was developed to synchronize the x-ray beam and the loading cycle. Using the high speed shutter, the evolution of the lattice strains for the families of crystallographic planes was measured while the aggregate was under cyclic uniaxial loading, thus monitoring a live evolution of lattice strain in a cyclically loaded specimen. The methodology is demonstrated using uniaxial cyclic specimens machined from oxygen free conductivity (OFHC) copper sheet.     

Microstructure-Based Estimation of Strength and Ductility Distributions for $$\alpha +\beta $$ Titanium Alloys

Titanium alloys are processed to develop a wide range of microstructure configurations and therefore material properties. While these properties are typically measured experimentally, a framework for property prediction could greatly enhance alloy design and manufacturing. Here a microstructure-sensitive framework is presented for the prediction of strength and ductility as well as estimates of the bounds in variability for these properties. The framework explicitly considers distributions of microstructure via new approaches for instantiation of structure in synthetic samples. The parametric evaluation strategy, including the finite element simulation package FEpX, is used to create and test virtual polycrystalline samples to evaluate the variability bounds of mechanical properties in Ti-6Al-4V. Critical parameters for the property evaluation framework are provided by measurements of single crystal properties and advanced characterization of microstructure and slip system strengths in 2D and 3D. Property distributions for yield strength and ductility are presented, along with the validation and verification steps undertaken. Comparisons between strain localization and slip activity in virtual samples and in experimental grain-scale strain measurements are also discussed.

     

Effect of Phellinus linteus extract supplementation on cortisol and related cytokines in young male adults

This study investigated the anti-inflammatory effects of Pellinus linteus (PL) extract supplementation in healthy young men. The subjects were 18 healthy young males 20 years of age that were given 1.5 L of 0.12% PL extract orally (n=8) or a placebo (control group, n=10) daily for 4 weeks. The body composition, the white blood cell (WBC) count and differential as well as the serum cortisol, interleukin (IL)-1β, and IL-6 concentrations were measured before and after the supplementation. Serum concentrations of cortisol and IL-1β at rest after oral supplementation were significantly decreased compared to before treatment (p<0.01, p<0.05, respectively). However, there was no change in the IL-6. And also, these factors in PL extract supplement group were significantly reduced after performing the exercise compared to control group. These results suggest that oral PL extract supplements for 4 weeks had a significant effect on inhibition of inflammatory markers in healthy young men.     

An 87 fJ/conversion-step 12 b 10 MS/s SAR ADC using a minimum number of unit capacitors

This work proposes a 12 b 10 MS/s 0.11 μm CMOS successive-approximation register ADC based on a C-R hybrid DAC for low-power sensor applications. The proposed C-R DAC employs a 2-step split-capacitor array of upper seven bits and lower five bits to optimize power consumption and chip area at the target speed and resolution. A V_CM-based switching method for the most significant bit and reference voltage segments from an insensitive R-string for the last two least significant bits minimize the number of unit capacitors required in the C-R hybrid DAC. The comparator accuracy is improved by an open-loop offset cancellation technique in the first-stage pre-amp. The prototype ADC in a 0.11 μm CMOS process demonstrates the measured differential nonlinearity and integral nonlinearity within 1.18 LSB and 1.42 LSB, respectively. The ADC shows a maximum signal-to-noise-and-distortion ratio of 63.9 dB and a maximum spurious-free dynamic range of 77.6 dB at 10 MS/s. The ADC with an active die area of 0.34 mm² consumes 1.1 mW at 1.0 V and 10 MS/s, corresponding to a figure-of-merit of 87 fJ/conversion-step.     

Diversity and toxigenicity among members of the Bacillus cereus group

Members of the Bacillus cereus group were isolated from rice products by centrifugation-plating and conventional spread-plating methods. Random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) results showed broad diversity among the strains and revealed some associations among isolates from raw and cooked rice samples, at the genotypic level. A comparatively greater diversity among strains was observed in isolates from raw rice than those from cooked rice and, generally, the RAPD profiles of isolates from raw and cooked rice were different, with only a few of them common to both types of rice. The toxigenic potential of the isolates was also determined by molecular and immunoassay analyses. The results revealed that most isolates from the B. cereus group were potentially or actually toxigenic, and some isolates could produce both diarrhoeal and emetic toxins. Generally, isolates belonging to the B. cereus group with the same RAPD pattern were shown to have a similar profile of enterotoxigenicity.     

A 14–10 b dual-mode low-noise pipeline ADC for high-end CMOS image sensors

This work proposes a low-noise four-stage pipeline ADC operating at 14 b 50 MS/s and 10 b 70 MS/s for high-end CIS applications. In the 10 b 70 MS/s mode, the last-stage MDAC and flash ADC are turned off rather than the first-stage MDAC and flash ADC for the same input-referred noise in both modes. The proposed ADC shares a single amplifier for the first- and second-stage MDACs to reduce power consumption and chip area. The amplifier thermal noise of the SHA and MDACs is minimized by adjusting the trans-conductance of input and current-source transistors while two separate reference voltage drivers for the MDACs and the flash ADCs reduce the switching noise. The prototype ADC in a 0.13 μm CMOS technology providing 0.35 μm thick-gate-oxide transistors shows the measured DNL and INL within 0.79 and 2.54 LSB in the 14 b mode, and 0.53 and 0.44 LSB in the 10 b mode, respectively. The ADC shows the maximum SNDR and SFDR of 68.5 and 86.7 dB in the 14 b 50 MS/s mode, and the SNDR and SFDR of 60.5 and 77.8 dB for the 10 b 70 MS/s mode, respectively. The ADC with the measured input-referred noise of 1.20 LSB_rms/14 b consumes 192.9 mW at the 14 b 50 MS/s, and 184.9 mW in the 10 b 70 MS/s mode with 3.3/1.2 V dual supplies.     

In situ characterization of residual stress evolution during heat treatment of SiC/SiC ceramic matrix composites using high-energy X-ray diffraction

Volumetric strains were measured in silicon carbide/silicon carbide melt-infiltrated ceramic matrix composites (CMCs) at ambient and high temperatures using high-energy synchrotron X-ray diffraction (XRD). Both silicon and silicon carbide constituents were interrogated utilizing a broad spectrum of diffracting planes that would be largely inaccessible to common laboratory XRD equipment. Residual room-temperature principal strains in the melt-infiltrated silicon phase were found to be approximately 1100 με in compression, corresponding to stresses of approximately 300 MPa using simplifying constitutive assumptions. Residual room-temperature principal strains in silicon carbide particles found throughout the matrix were approximately 500 με in tension, corresponding to approximately 300 MPa. Residual strains were found to decrease considerably as temperatures increased from ambient temperature to 1250°C. Residual strains returned to approximately preheat treatment values after cool-down to ambient temperature. Strain measurements in the silicon phase were found to be significantly affected by dissolved boron dopant levels causing contraction of the silicon lattice. This contraction must be accounted for in high-temperature experiments for accurate calculation of stresses in the silicon phase.     

A Coupled Small and Wide-Angle X-Ray Scattering Study of Phase Transformation Mechanisms in U-6Wt Pct Nb

Metallurgical and Materials Transactions A - The elevated temperature phase transformation kinetics of U-6wt&nbsp;pct Nb in both wrought and cast conditions were investigated using in-situ...     

Electrical and magnetic properties of electro-oxidative polymerized poly(tris(thienylphenyl)amine)s

Electro-oxidative polymerized poly(tris(thienylphenyl)amine)s, which have the hyperbranched (dendritic) structure (PTPA) and linear type (PMeTPA), were investigated for their electrical and magnetic properties. The conductivity PTPA showed was almost one order higher than that of PMeTPA. From the solid state ESR measurements of the polymers, observation of ESR signal at g = 2.0027 and 2.0030 indicated the formation of a triphenylamine cation radical. The normalized magnetization plots (M/M_s) for PTPA and PMeTPA are close to the theoretical Brillouin curves for S = 1, indicating a magnetic interaction between the spin centers in PMeTPA. The spin concentrations determined by the M_s values of PTPA and PMeTPA were 7.3–7.4 and 1.3–1.4%, respectively. This large difference in the spin concentration of the polymers according to the structure resulted from a different spin conformation by the radical structure.