Switched-capacitor silicon compiler

A switched-capacitor (SC) silicon compiler will be described in this report. The input to this system is a set of specifications and a circuit description of an SC block. It has an opamp synthesis tool which is based on the selection and assembly of primitive modules. The opamp circuit topology is formed by searching through a set of styles yielding high performance opamp circuits serving a wide range of SC network applications. The layout strategy and architecture are such that they eliminate any crossover of sensitive signals by insensitive signals; Thus avoiding any special routing algorithm for sensitive routing. The results is a compact, parasitic-insensitive and "standard cell" type layout of an SC block with user-defined height. All blocks are placed and routed together by a general auto-placement and router tool

Glass transition investigated by a combined protocol using thermostimulated depolarization currents and differential scanning calorimetry

Relaxation times of bisphenol A polycarbonate around the glass transition temperature are estimated using the combination of differential scanning calorimetry (DSC) and thermostimulated depolarization currents (TSDC). These measurements are performed using samples with different thermal histories below and above the vitrification transformation. This protocol enables the extension of the range of equilibrium relaxation times measured by dielectric spectroscopy. By this mean we may recalculate the values of the Kauzmann temperature and fragility index

The evolution of anisotropies in the elastic response of an elastic-plastic material

The problem of determining the change in a material's symmetries as it undergoes an elastic-plastic deformation is considered. This is interpreted as the problem of evaluating the anisotropies of the current elastic response. The discussion is presented in the context of a particular form of constitutive equation which relates the Cauchy stress to the current value of the deformation gradient and a second order tensor quantity which is a function of the deformation gradient history. A sufficient condition is established for a transformation to be a material symmetry transformation of the current elastic response. This condition relates the minimum symmetries of the current elastic response to the initial material symmetry, the given deformation history, and the structure of the constitutive equation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30354/1/0000756.pd

Modeling the mechanical response of a material undergoing continuous isothermal crystallization

The gradual transition seen in polymer crystallization is modeled. A constitutive equation is developed to follow the mechanical behavior of a crystallizing polymer before, during, and after the completion of crystallization. The post-crystallization response of the material is studied and shown to be "elastic". The symmetries of the post-crystallization response are defined and calculated for crystallization under several deformation histories.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29975/1/0000338.pd

Ultrathin coding metasurface for underwater wave focusing, branching and self-bending generation with one single actuator

A novel metasurface is proposed that aims to generate underwater acoustic waves with various functions by only one actuator. Each metasurface unit consists of an air cavity sandwiched on one side by a vibration plate and connecting rubber supports. By properly selecting the ratio of the plate to unit lengths, a phase shift of π can be attained to constitute a binary coding metasurface. Three demonstrations, including focusing, branching and self-bending waves, are chosen to validate the functionality of the design. The design is also shown to work over a wide frequency range through changing the ratio. In addition, the design is extremely compact, with the thickness only about 1/100 of the target wavelength. Compared with commonly used phased array transducers that are utilized to generate underwater acoustic waves, this design offers has the advantage of needing only a single actuator as opposed to needing a lumped electrical control system

Dissipative elastic metamaterial with a lowfrequency passband

We design and experimentally demonstrate a dissipative elastic metamaterial structure that functions as a bandpass filter with a low-frequency passband. The mechanism of dissipation in this structure is well described by a mass-spring-damper model that reveals that the imaginary part of the wavenumber is non-zero, even in the passband of dissipative metamaterials. This indicates that transmittance in this range can be low. A prototype for this viscoelastic metamaterial model is fabricated by 3D printing techniques using soft and hard acrylics as constituent materials. The transmittance of the printed metamaterial is measured and shows good agreement with theoretical predictions, demonstrating its potential in the design of compact waveguides, filters and other advanced devices for controlling mechanical waves

Dissipative elastic metamaterial with a lowfrequency passband

We design and experimentally demonstrate a dissipative elastic metamaterial structure that functions as a bandpass filter with a low-frequency passband. The mechanism of dissipation in this structure is well described by a mass-spring-damper model that reveals that the imaginary part of the wavenumber is non-zero, even in the passband of dissipative metamaterials. This indicates that transmittance in this range can be low. A prototype for this viscoelastic metamaterial model is fabricated by 3D printing techniques using soft and hard acrylics as constituent materials. The transmittance of the printed metamaterial is measured and shows good agreement with theoretical predictions, demonstrating its potential in the design of compact waveguides, filters and other advanced devices for controlling mechanical waves

Changes in material symmetry associated with deformation: Uniaxial extension

When a material which is isotropic with respect to a reference configuration is deformed, it is anisotropic with respect to the deformed configuration. The nature of the anisotropy depends on the deformation. In this paper, we consider the special case of the change of a reference configuration by uniaxial extension. We first discuss the structure of the new material symmetry group, and show that it includes non-orthogonal unimodular transformations. Then using the general representation for the response functional of an isotropic material, we show how to construct a representation of the new response functional which satisfies the restrictions of the new material symmetry group.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27607/1/0000651.pd

Simulation of mechanical response in polymer crystallization

The problem of following the mechanical response of a polymer during crystallization is studied using a theory developed by Negahban and Wineman [1]. Elastic modulus, shear modulus, and Poisson's ratio are defined in the context of polymer crystallization. For unconstrained crystallization and crystallization under constant uniaxial stretching, the values of elastic modulus, shear modulus, poisons ratio, and residual stretch are evaluated. The proposed model is fit to data available for natural rubber and the predictions of the model are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31046/1/0000723.pd