An efficient current-based logic cell model for crosstalk delay analysis

Logic cell modelling is an important component in the analysis and design of CMOS integrated circuits, mostly due to nonlinear behaviour of CMOS cells with respect to the voltage signal at their input and output pins. A current-based model for CMOS logic cells is presented, which can be used for effective crosstalk noise and delta delay analysis in CMOS VLSI circuits. Existing current source models are expensive and need a new set of Spice-based characterisation, which is not compatible with typical EDA tools. In this article we present Imodel, a simple nonlinear logic cell model that can be derived from the typical cell libraries such as NLDM, with accuracy much higher than NLDM-based cell delay models. In fact, our experiments show an average error of 3% compared to Spice. This level of accuracy comes with a maximum runtime penalty of 19% compared to NLDM-based cell delay models on medium-sized industrial designs.     

A coupled Thermal‐mechanical FE Model of Flow Localization during the Hot Torsion Test

The hot torsion test (HTT) has been extensively used to analyse and physically model the flow behaviour and microstructure evolution of materials and alloys during hot deformation processes. The geometry of the specimen is a key factor for obtaining reliable results. In the present work, a thermo‐rigid viscoplastic FE code, THORAX.FOR, was developed to describe the interaction of thermal‐mechanical conditions and geometries of the HTT specimens. This was used to recommend the conditions for avoiding flow localization during HTT of API‐X70 microalloyed steel. The simulation results show how an inappropriate choice of both test specimen geometry and twist rate of deformation could lead to a significant temperature raise in the middle of the gauge section and temperature gradient in the radial and longitudinal direction of the specimen. This consequently causes flow localization during the test. Therefore, assumptions of isothermal forming conditions or uniform strain softening may not be valid in many test scenarios. These assumptions could introduce significant errors in the post results of the test such as flow curve and interpretation of microstructure evolution. Recommendations on proper specimen geometry for a specified strain rate will be given to avoid flow localization during the hot torsion test.     

Dynamics and vibrations of particle-sensing MEMS considering thermal and electrostatic actuation

Microsystem Technologies - The dynamic behavior of micro-cantilevers and micro-bridges under electrostatic and thermal base actuations is investigated in this paper. To solve the equation...     

Thermal actuation and confinement of water droplets on paper-based digital microfluidics devices

In this paper, the thermocapillary actuation is implemented to manipulate and confine the fluid droplets in a paper-based digital microfluidics (PB-DMF) device. The main advantage of using the thermocapillary actuation over the traditional electrowetting-on-dielectric actuation in the DMF devices is its ability to work with lower operating DC voltages. The proposed device is fabricated by the low-cost screen printing method using very low-cost materials. In order to overcome the weak controllability of the device over the droplets, a new thermal confinement technique is proposed which simply embedded in the device electrode pattern. A new thermally actuated valve is also designed to work based on thermocapillary actuation for switching on or off the droplets. The fabricated DMF device and the thermal valve are both combined with a microfluidics paper-based analytical device to form a hybrid paper chip in which the droplets are driven by both channel-based and droplet-based devices. The device operation is tested by using a biochemical glucose colorimetric detection assay.     

Hybridizing electromagnetism-like mechanism algorithm with migration strategy for layout and size optimization of truss structures with frequency constraints

The optimal design of a truss structure with dynamic frequency constraints is a highly nonlinear optimization problem with several local optimums in its search space. In this type of structural optimization problems, the optimization methods should have a high capability to escape from the traps of the local optimums in the search space. This paper presents hybrid electromagnetism-like mechanism algorithm and migration strategy (EM–MS) for layout and size optimization of truss structures with multiple frequency constraints. The electromagnetism-like mechanism (EM) algorithm simulates the attraction and repulsion mechanism between the charged particles in the field of the electromagnetism to find optimal solutions, in which each particle is a solution candidate for the optimization problem. In the proposed EM–MS algorithm, two mechanisms are utilized to update the position of particles: modified EM algorithm and a new migration strategy. The modified EM algorithm is proposed to effectively guide the particles toward the region of the global optimum in the search space, and a new migration strategy is used to provide efficient exploitation between the particles. In order to test the performance of the proposed algorithm, this study utilizes five benchmark truss design examples with frequency constraints. The numerical results show that the EM–MS algorithm is an alternative and competitive optimizer for size and layout optimization of truss structures with frequency constraints.     

Structural sensitivity reanalysis formulations based on the polynomial-type extrapolation methods

Structural and Multidisciplinary Optimization - This paper presents new structural sensitivity reanalysis formulations based on the polynomial-type extrapolation methods. In these formulations, the...     

Fumaryl chloride and maleic anhydride–derived crosslinked functional polymers for nonlinear optical waveguide applications

The synthesis, processing, and characterization of new crosslinked functional polymer thin films derived from fumaryl chloride and maleic anhydride is presented. Experimental data demonstrated that this is a versatile, convenient, and cost‐effective method of fabricating ultrastructure crosslinked and functional polymer thin films for potential nonlinear optical (NLO) or other applications where molecular orientation is required. The unsaturated and processable polyester thin films are capable of crosslinking in air to form a hardened lattice under a variety of conditions, including both thermal and photoinitiated crosslinking. The thermal stability of the second harmonic (SHG) signal for a crosslinked NLO thin film was stable at temperatures up to 150°C, which is in contrast to uncrosslinked polymers whose SHG signals typically decreased over 50% below 100°C. Because of the lack of NH/OH groups and their vibrational overtones in the polymer, these crosslinked polyester systems have a great potential for low optical loss applications at 1550 nm communication wavelength. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 317–322, 2004     

Electrically conductive semi‐IPNs based on polyaniline and crosslinked polyvinylacetate

Electrically conductive semi‐IPNs based on polyaniline and crosslinked polyvinylacetate were prepared. Polyaniline successfully percolated through the crosslinked PVAc networks and the resulting semi‐IPNs show a continuous network morphology. The conductivity of the semi‐IPN increases with increasing content of polyaniline and increasing acidity used during the polymerization of the polyaniline. The conductivity of the semi‐IPN is 0.13 S/cm, with the highest polyaniline content of 19.3 wt %. The depression of polyaniline with temperature change is smallest followed by the depression of semi‐IPN of the polyaniline/crosslinked polyvinylacetate, which is considerably smaller than the depression of crosslinked polyvinylacetate. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2287–2293, 2002