Effect of strain rate on yielding strength of a Zr-based bulk metallic glass

Uniaxial tension and compression experiments were performed on a typical Zr52.5Cu17.9N44.6Al10Ti5 (Vit 105) bulk metallic glass over a wide range of strain rates at room temperature. It is found that the strain rate effect of the yielding strength will change from insensitive to negative with increasing strain rate above a critical value. This phenomenon can be quantitatively described by a modified cooperative-shear model of shear transformation zones that takes the adiabatic temperature rise into account. The model predicts well the present and other experimental data

A reconstructed discontinuous Galerkin method based on a Hierarchical WENO reconstruction for compressible flows on tetrahedral grids

A reconstructed discontinuous Galerkin (RDG) method based on a hierarchical WENO reconstruction, termed HWENO (P1P2) in this paper, designed not only to enhance the accuracy of discontinuous Galerkin methods but also to ensure the nonlinear stability of the RDG method, is presented for solving the compressible Euler equations on tetrahedral grids. In this HWENO (P1P2) method, a quadratic polynomial solution (P-2) is first reconstructed using a Hermite WENO reconstruction from the underlying linear polynomial (P-1) discontinuous Galerkin solution to ensure the linear stability of the RDG method and to improve the efficiency of the underlying DG method. By taking advantage of handily available and yet invaluable information, namely the derivatives in the DG formulation, the stencils used in the reconstruction involve only von Neumann neighborhood (adjacent face-neighboring cells) and thus are compact. The first derivatives of the quadratic polynomial solution are then reconstructed using a WENO reconstruction in order to eliminate spurious oscillations in the vicinity of strong discontinuities, thus ensuring the nonlinear stability of the RDG method. The developed HWENO (P1P2) method is used to compute a variety of flow problems on tetrahedral meshes to demonstrate its accuracy, robustness, and non-oscillatory property. The numerical experiments indicate that the HWENO (P1P2) method is able to capture shock waves within one cell without any spurious oscillations, and achieve the designed third-order of accuracy: one order accuracy higher than the underlying DG method

Crystallization Kinetics in Polymorphic Organic Compounds

Polymorphism is frequently encountered in many pharmaceutical, chemical, and food products. Polymorphs have the same chemical composition but different crystal structures, and therefore differ in their physicochemical properties such as stability, solubility, and bioavailability. These property differences can influence the product performance. Thus, the production of specific and well-defined polymorphs is crucial, especially in the pharmaceutical industry. This thesis focuses on how to establish control over the polymorph formation. Crystallization kinetics, especially nucleation kinetics and thermodynamics, were studied to improve the understanding of polymorphic crystallization behavior. Using the improved fundamental understanding, control over the polymorphism of model organic compounds has been successfully established.Process and EnergyMechanical, Maritime and Materials Engineerin

An Energy-Efficient 3.7-nV/√ Hz Bridge Readout IC With a Stable Bridge Offset Compensation Scheme

This paper describes an energy-efficient bridge readout IC (ROIC), which consists of a capacitively coupled instrumentation amplifier (CCIA) that drives a continuous-time delta–sigma modulator (CTM). By exploiting the CCIA’s abilityto block dc common-mode voltages, the bridge’s bias voltage may exceed the ROIC’s supply voltage, allowing these voltages to be independently optimized. Since bridge output is typically much smaller than bridge offset, a digital to analog converter (DAC) is used to compensate this offset before amplification andthus increase the CCIA’s useful dynamic range. Bridge loading is reduced by using a dual-path positive feedback scheme to boost the CCIA’s input impedance. Furthermore, the CCIA’s output is gated to avoid digitizing its output spikes, which would otherwise limit the ROIC’s linearity and stability. The ROIC achieves an input-referred noise density of 3.7 nV/Hz, a noise efficiency factor (NEF) of 5, and a power efficiency factor (PEF) of 44, which both represent the state of the art. A pressure sensing system, built with the ROIC and a differential pressure sensor (AC4010), achieves 10.1-mPa (1) resolution in a 0.5-ms conversion time. The ROIC dissipates about 30% of the system’s power dissipation and contributes about 6% of its noise power. To reduce the sensor’s offset drift, a temperature compensation scheme based on an external reference resistor is used. After a two-point calibration, this scheme reduces bridge offset drift by 80× over a 50 °C range.Accepted Author ManuscriptElectronic InstrumentationMicroelectronic

Reliability Analysis of Heterogeneous Slope Considering Effect of Distribution Types

The effect of probability distributions on the slope reliability is highlighted in this study since the lognormal distribution is often used to characterize the variability of soil properties to avoid negative values. A multiple response-surface based MCS method for slope reliability analysis in spatially variable soils is proposed. A heterogeneous slope consisting of three soil layers (including a weak layer) is studied to demonstrate the validity of the proposed method and explore the effect of probability distributions for soil shear strength parameters on the reliability of the heterogeneous slope. The results indicate that the proposed method provides a practical tool for evaluating the reliability of heterogeneous slopes in spatially variable soils. The difference in the probabilities of failure of the heterogeneous slope associated with the lognormal, normal, gamma and beta distributions is significant when the spatial variability of multiple soil properties is incorporated. In general, the probability of failure may be underestimated as the lognormal distribution is used for characterization of the random fields of soil properties

A Power-Efficient Readout for Wheatstone-Bridge Sensors With COTS Components

This paper presents a direct digital converter for Wheatstone bridge sensors, which is realized with commercial off-the-shelf components. The power efficiency of the readout is enhanced by embedding the bridge sensor in a second-order continuous-time sigma-delta modulator (CTDeltaSigmaM). By directly digitizing the output signal of a Wheatstone bridge in the current mode, the noise performance is dominated by the operational amplifier in the first integrator and the bridge sensor. To demonstrate the performance of the proposed circuit, an MEMS piezoresistive differential pressure sensor is used. Measurement results show that a resolution of 12.7 mParms (0.41 mOhmrms), with a 0.5-ms conversion time, can be achieved. Powered by 5 V, the circuit and the bridge sensor draw 9.55 and 7.58 mW, respectively.Accepted Author ManuscriptElectronic Instrumentatio

31.3 A 0.14mm²16MHz CMOS RC Frequency Reference with a 1-Point Trimmed Inaccuracy of ±400ppm from -45°C to 85°C

Recently, rapid strides have been made in improving the accuracy of RC-based frequency references [1 -3]. Inaccuracies better than \pm 500ppm from -45^{\circ}C to 85^{\circ}C have been achieved, but typically at the expense of a costly and time-consuming 2-point trim to compensate for RC spread and temperature dependence. This paper describes a 16MHz RC-based frequency reference that achieves \pm 400ppm inaccuracy over the industrial temperature range with a single room-temperature (RT) trim. The prototype draws 88\muA from a1.8V supply and occupies 0.14mm^{2}, which represents a 2\times improvement in both power and area compared to the state of the art [2].Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationMicroelectronic