Numerical Investigation of Plunging Density Current

When a buoyant inflow of higher density enters a reservoir, it sinks below the ambient water and forms an underflow. Downstream of the plunge point, the flow becomes progressively diluted due to the fluid entrainment. The entrainment rate is strongly dependent on the Richardson number and reaches a constant value well downstream of the plunge point. This study is concerned with the analysis of the plunging phenomenon and the determination of the entrainment. A k-ε model including buoyancy effects, both in a sloping and a diverging channel, is used to reproduce the main flow characteristics. A relation between the depth at the plunge point in a channel of constant width and in a diverging channel is established, and theoretical results for the calculation of the dense layer thickness are provided. The latter indicates that the spreading rate of the dense layer in a diverging channel is a function of both the entrainment rate and the channel width. The predictions of the plunge line location are in agreement with most semiempirical equations.     

Examinations with the Cardiff Acuity Test

Intestinal epithelial cells (IEC) can exist as polarized cells and are capable of secreting interleukin-6 (IL-6), yet it has not been determined if this IL-6 is secreted in a polarized fashion. Using the non-transformed rat IEC-6 intestinal epithelial cell line grown on microporous membrane inserts, we have determined that these cells were capable of secreting IL-6 preferentially to the basal surface when stimulated basally with IL-1 beta. In contrast, stimulation of the cells with TNF-alpha resulted in an equal level of IL-6 secretion to the apical and basal surfaces, regardless of whether the cells were stimulated by the apical or basal route. Experiments designed to test the permeability of the IEC-6 cell layer to apically added sodium fluorescein confirmed that neither IL-1 beta nor TNF-alpha altered the integrity of the cell layer after three days. These results suggest that IEC may have the capacity to secret IL-6 in different patterns depending upon the stimulation received. This would allow communication between the IEC and lamina propria cells via basal secretion and rapid communication between IEC via apical secretion.     

Computer-assisted diagnosis of acute azotemia

We designed a computer program to make diagnostic suggestions in cases of acute azotemia. The performance of the program was tested in a retrospective manner on 63 patients with acute azotemia. The program correctly identified 90 of 94 diagnoses and made 20 false positive diagnostic suggestions. A revised version of the program correctly identified 94 of 94 diagnoses and made 4 false negative suggestions. The justification for this kind of diagnostic aid is discussed.     

FaSa: A fast and stable quadratic placement algorithm

Placement is a critical step in VLSI design because it dominates overall speed and quality of design flow.In this paper,a new fast and stable placement algorithm called FaSa is proposed.It uses quadratic programming model and Lagrange multiplier method to solve placement problems.And an incremental LU factorization method is used to solve equations for speeding up.The experimental results show that FaSa is very stable,much faster than previous algorithms and its total wire length is comparable with other algorithms.     

Enhanced chain dynamics in loop-sorting-systems by means of layout optimization and a kinematic model of the polygon action

Poor dynamics owing to polygon action is a known concern in mechanical applications of closed articulated chains. In this paper a kinematic model of the polygon action in large chains of loop-sorting-systems is proposed. Through optimization techniques the chain dynamics is improved by minimizing the polygon action using a parametric model of the track layout as design variables. Three formulations of the kinematic polygon action are tested on an average sized planer tracks layout to find a superior model. Verification of the proposed optimization method is performed using a state-of-the-art multi-body simulation model of the chain dynamics.     

Fast and Highly Sensitive Ionic‐Polymer‐Gated WS2–Graphene Photodetectors

The combination of graphene with semiconductor materials in heterostructure photodetectors enables amplified detection of femtowatt light signals using micrometer‐scale electronic devices. Presently, long‐lived charge traps limit the speed of such detectors, and impractical strategies, e.g., the use of large gate‐voltage pulses, have been employed to achieve bandwidths suitable for applications such as video‐frame‐rate imaging. Here, atomically thin graphene–WS₂ heterostructure photodetectors encapsulated in an ionic polymer are reported, which are uniquely able to operate at bandwidths up to 1.5 kHz whilst maintaining internal gain as large as 10⁶. Highly mobile ions and the nanometer‐scale Debye length of the ionic polymer are used to screen charge traps and tune the Fermi level of the graphene over an unprecedented range at the interface with WS₂. Responsivity R = 10⁶ A W^?1 and detectivity D* = 3.8 × 10¹¹ Jones are observed, approaching that of single‐photon counters. The combination of both high responsivity and fast response times makes these photodetectors suitable for video‐frame‐rate imaging applications.     

Achieving large transport bandgaps in bilayer graphene

Since opening sizable bandgaps in bilayer graphene (BLG) was proven possible, BLG has attracted considerable attention as a promising high-mobility candidate material for many electronic and optoelectronic applications. However, the bandgaps observed in the transport experiments reported in the literature are far smaller than both the theoretical predictions and the bandgaps extracted from optical measurements. In this study, we investigate the factors preventing the formation of large bandgaps and demonstrate that a ~200-meV transport bandgap can be opened in BLG by scaling the gate dielectric and employing a ribbon channel to suppress the percolative transport. This is the largest transport bandgap that has been achieved in BLG to date.

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Magnetron sputtering of TiOxNy films

This article reports on the characterization and preparation of N-doped titanium dioxide (TiO₂) films by reactive magnetron sputtering from Ti(99.5) targets in a mixture of Ar/O₂/N₂ atmosphere on unheated glass substrates. A dual magnetron system supplied by a dc bipolar pulsed power source was used to sputter the TiO_xN_y films. The amount of N in the TiO_xN_y film ranges from 5 to 40 at%. Its structure was measured using X-ray diffraction (XRD), the optical band gap was calculated from Tauc plots and the decrease of the water contact angle α_ir after the film activation by UV irradiation was investigated as a function of at% of N in the TiO_xN_y film. The yellow-coloured TiO_xN_y films with high (≈8 at%) amount of N exhibited a strong decrease of the band gap E_g down to 2.7 eV. A significant decrease of the water contact angle α_ir after UV irradiation has been observed for 2 μm thick transparent nanocrystalline (anatase+rutile) N-doped TiO₂ films containing less than 6 at% of N.