A Level-Crossing Analog-to-Digital Converter With Triangular Dither

In this paper, a level-crossing analog-to-digital converter is described. It can convert audio bandwidth signals with high resolution using few threshold levels and digital interpolation. Samples are generated at nonuniform time intervals and then interpolated to produce uniformly spaced output samples. A periodic triangular dither signal added to the input ensures that low-amplitude or slowly varying signals are sampled and converted accurately. The dither is estimated and removed digitally before interpolation. Simulations show that greater than 10-bit resolution can be achieved with only seven comparators when using a sixth-order polynomial interpolator.     

Constructal multi-scale cylinders in cross-flow

This paper reports a new concept for maximizing heat transfer density in assemblies of cylinders in cross-flow: the use of cylinders of several sizes, and the optimal placement of each cylinder in the assembly. The heat transfer is by laminar forced convection with specified overall pressure difference. The resulting flow structure has multiple scales that are distributed nonuniformly through the available volume. Smaller cylinders are placed closer to the entrance to the assembly, in the wedge-shaped flow regions occupied by fluid that has not yet been used for heat transfer. The paper reports the optimized flow architectures and performance for structures with 1, 2 and 3 cylinder sizes, which correspond to structures with 1, 2 and 4 degrees of freedom. The heat transfer rate density increases (with diminishing returns) as the optimized structure becomes more complex. The optimized cylinder diameters are relatively robust, i.e., insensitive to changes in complexity and flow regime (pressure difference). The optimized spacings decrease monotonically as the driving pressure difference increases. The multi-scale flow architectures optimized in this paper have features and qualities similar to tree-shaped (dendritic) designs, where the length scales are numerous, hierarchically organized, and nonuniformly distributed through the available space.     

Combining algorithms for automatic detection of optic disc and macula in fundus images

This paper proposes an efficient combination of algorithms for the automated localization of the optic disc and macula in retinal fundus images. There is in fact no reason to assume that a single algorithm would be optimal. An ensemble of algorithms based on different principles can be more accurate than any of its individual members if the individual algorithms are doing better than random guessing. We aim to obtain an improved optic disc and macula detector by combining the prediction of multiple algorithms, benefiting from their strength and compensating their weaknesses. The location with maximum number of detectors’ outputs is formally the hotspot and is used to find the optic disc or macula center. An assessment of the performance of integrated system and detectors working separately is also presented. Our proposed combination of detectors achieved overall highest performance in detecting optic disc and fovea closest to the manually center chosen by the retinal specialist.     

Entropy generation in MHD Williamson nanofluid over a convectively heated stretching plate with chemical reaction

This investigation focuses on the influence of thermal radiation on the magnetohydrodynamic flow of a Williamson nanofluid over a stretching sheet with chemical reaction. The phenomena at the stretching wall assume convective heat and mass exchange. The novelty of the present study is the thermodynamic analysis in the nonlinear convective flow of a Williamson nanofluid. The resulting set of the differential equations are solved by the homotopy analysis method. We explored the impacts of the emerging parameters on flow, heat, and mass characteristics, including the rate of entropy generation and the Bejan number through graphs, and extensive discussions are provided. The expressions for skin friction, Nusselt and the Sherwood numbers are also analyzed and explored through tables. It is concluded that the rate of mass transfer may be maximized with the variation of the Williamson and chemical reaction parameters. Moreover, the entropy generation rate and the Bejan number are augmented via increasing the Williamson parameter.     

Amino acid composition of guineafowl's egg

Samples of eggs from two breeds (White-breasted and Pearl) of guinea hens which were housed either on deep litter or in layer cages were analysed for their content of amino acids. The protein content of whole eggs ranged from 482 to 494 mg g^?1, with a mean of 487 mg g^?1. Concentrations of the various amino acids in the egg ranged from 118 mg (tryptophan) to 752 mg (glutamic acid) per g N. The mean concentration of total sulphur amino acids was 395 mg per g N. Overall the amino acid composition of guineafowl egg was not affected by either breed or housing system.     

Maximal heat transfer density: Plates with multiple lengths in forced convection

This paper shows that in a space filled with heat generating parallel plates and laminar forced convection, the heat transfer density can be increased beyond the level known for parallel plates with optimal spacing. The technique consists of inserting in every entrance region new generations of smaller plates, because smaller plates have thin boundary layers that fit in the unused (isothermal) entrance flow. This technique can be repeated several times, and the result is a sequence of multi-scale flow structures that have progressively higher heat transfer densities. The work consists of numerical simulations in a large number of flow configurations, one differing slightly from the next. The complete optimized architecture and performance of structures with one, two and three plate length scales are reported. Diminishing returns are observed as the number of length scales increases. This method can be used to develop multi-scale nonuniform flow structures for heat exchangers and cooled electronic packages.     

Towards a New MODDE of Improving Legal Decision Support Design

This paper contributes to the ebb and flow of innovations in decision support system design by presenting the MODDE methodology (Model Of Decision support system Design and Evaluation). It utilizes a simple conceptualisation of the software engineering process, and aims to provide computer consultants with guidance to the way they may include consideration of three qualitative dimensions of high level autonomous decision making. These three dimensions--discretion, consistency and resolution--have arisen directly from work in an applied legal domain. MODDE facilitates systematic attention to these dimensions in a way not previously done and thus complements existing software and requirements engineering practices.     

Operating conditions of an open and direct solar thermal Brayton cycle with optimised cavity receiver and recuperator

The small-scale open and direct solar thermal Brayton cycle with recuperator has several advantages, including low cost, low operation and maintenance costs and it is highly recommended. The main disadvantages of this cycle are the pressure losses in the recuperator and receiver, turbomachine efficiencies and recuperator effectiveness, which limit the net power output of such a system. The irreversibilities of the solar thermal Brayton cycle are mainly due to heat transfer across a finite temperature difference and fluid friction. In this paper, thermodynamic optimisation is applied to concentrate on these disadvantages in order to optimise the receiver and recuperator and to maximise the net power output of the system at various steady-state conditions, limited to various constraints. The effects of wind, receiver inclination, rim angle, atmospheric temperature and pressure, recuperator height, solar irradiance and concentration ratio on the optimum geometries and performance were investigated. The dynamic trajectory optimisation method was applied. Operating points of a standard micro-turbine operating at its highest compressor efficiency and a parabolic dish concentrator diameter of 16 m were considered. The optimum geometries, minimum irreversibility rates and maximum receiver surface temperatures of the optimised systems are shown. For an environment with specific conditions and constraints, there exists an optimum receiver and recuperator geometry so that the system produces maximum net power output.     

Nonlinear thermal radiation on MHD tangential hyperbolic hybrid nanofluid over a stretching wedge with convective boundary condition

In this study, two distinct nanoparticles: aluminum oxide (Al₂O₃) and copper (Cu) are chosen as nanomaterials to examine the effects of nonlinear electrically conducting magnetohydrodynamic radiation on the flow of tangential hyperbolic hybrid nanofluid across a nonlinearly stretched sheet with convective boundary conditions. The equations that regulate fluid flow are represented as partial differential equations. These equations are reduced to their equivalent ordinary differential equations, which are solved using the homotopy analysis approach with the help of similarity variables. The effect of essential physical factors on fluid velocity, temperature, skin friction coefficient, and local Nusselt number is investigated and discussed. Results ascertain that the heat transfer rate of Cu/H₂O nanofluid becomes high when equated to Cu–Al₂O₃/H₂O nanofluid. Furthermore, the temperature distribution enhances with the rise in solid volume fraction while it diminishes with improved magnetic field for both nanofluid and hybrid nanofluid.