Jamming transition in a highly dense granular system under vertical vibration

The dynamics of the jamming transition in a three-dimensional granular system under vertical vibration is studied using diffusing-wave spectroscopy. When the maximum acceleration of the external vibration is large, the granular system behaves like a fluid, with the dynamic correlation function G(t) relaxing rapidly. As the acceleration of vibration approaches the gravitational acceleration g, the relaxation of G(t) slows down dramatically, and eventually stops. Thus the system undergoes a phase transition and behaves like a solid. Near the transition point, we find that the structural relaxation shows a stretched exponential behavior. This behavior is analogous to the behavior of supercooled liquids close to the glass transition.Comment: 5 pages, 5 figures, accepted by Phys. Rev.

Identification of the enclosed electro-thermal system with using dynamic thermal response

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.A methodology for modeling and simulating electro-thermal system in an enclosed electronic package is presented. The electro-thermal model was constructed by using system dynamics, particularly the bond graph methodology. The system model, in which the electrical domain and the thermal domain are coupled, is presented. The system model described its dynamic thermal behaviour of the system caused by heat generation from the electronic package which in located in the test enclosure chamber. The system model included the time-variant thermal parameters such as environment variation and with incoming heat flow variation. In detail, an effective way to identify the time-variant thermal parameters of the system with considering transient thermal behaviour using temperature difference between nodes was suggested. The system model contains the variation of heat flow derived by resistance change of resistive heater in electronic device increasing with temperature rise of heater, and the variation of ambient air temperature. The electro-thermal system model was validated when the system has time-variant thermal parameters such as variation of convection and contact resistance. The proposed system model shows good agreement with measured temperature response in the transient state corresponding to the variance of environment.vk201

Erratum

"Erratum on the article ‘A bi-level framework for pricing of high-occupancy toll lanes’." Transport, 29(4), p. 46

First Demonstration of Ultra-Thin SiGe-Channel Junctionless Accumulation-Mode (JAM) Bulk FinFETs on Si Substrate with PN Junction-Isolation Scheme

A SiGe-channel junctionless-accumulation-mode (JAM) PMOS bulk FinFETs were successfully demonstrated on Si substrate with PN junction-isolation scheme for the first time. The JAM bulk FinFETs with fin width of 18 nm exhibits excellent subthreshold characteristics such as subthreshold swing of 64 mV/decade, drain-induced barrier lowering (DIBL) of 40 mV/V and high Ion/Ioff current ratio ( \u3e 1 x 105). The change of substrate bias from 0 to 5 V leads to the threshold voltage shift of 53 mV by modulating the effective channel thickness. When compared to the Si-channel bulk FinFETs with fin width of 18 nm, Si and SiGe channel devices exhibits comparable subthreshold swing and DIBL. For devices with longer fin width, SiGe channel devices exhibits much lower DIBL, indicating superior top-gate controllability and robustness to substrate bias compared to the Si channel devices. A zero temperature coefficient point was observed in the transfer curves as temperature increases from -120 to 120°C, confirming that mobility degradation is dominantly affected by phonon scattering mechanism

Small and Medium Amplitude Oscillatory Shear Rheology of Model Branched Polystyrene (PS) Melts

Linear and nonlinear rheological properties of model comb polystyrenes (PS) with loosely to densely grafted architectures were measured under small and medium amplitude oscillatory shear (SAOS and MAOS) flow. This comb PS set had the same length of backbone and branches but varied in the number of branches from 3 to 120 branches. Linear viscoelastic properties of the comb PS were compared with the hierarchical model predictions. The model underpredicted zero-shear viscosity and backbone plateau modulus of densely branched comb with 60 or 120 branches because the model does not include the effect of side chain crowding. First- and third-harmonic nonlinearities reflected the hierarchy in the relaxation motion of comb structures. Notably, the low-frequency plateau values of first-harmonic MAOS moduli scaled with M$^{-2}$$_{w}$ (total molecular weight), reflecting dynamic tube dilution (DTD) by relaxed branches. Relative intrinsic nonlinearity Q$_{0}$ exhibited the difference between comb and bottlebrush via no low-frequency Q$_{0}$ peak of bottlebrush corresponding to backbone relaxation, which is probably related to the stretched backbone conformation in bottlebrush