Parametric study of instantaneous heat transfer based on multidimensional model in direct-injection hydrogen-fueled engine

This paper presents a parametric study on instantaneous heat transfer of a direct-injection hydrogen-fueled engine using a multidimensional model. A simplified single-step mechanism was considered for estimating the reaction rate of hydrogen oxidation. The modified wall-function was used for resolving the near-wall transport. An arbitrary Lagrangian–Eulerian algorithm was adopted for solving the governing equations. Experimental measurements were implemented to verify the developed model. They show that the instantaneous heat-transfer model is sufficiently accurate. The influence of engine speed, equivalence ratio, and the start of injection timing were investigated. The flow fields appeared to have greater size vectors and coarser distribution with an increase of engine speed. A heterogeneous distribution was obtained for an ultra-lean mixture condition (φ ≤ 0.5), which decreased with an increase of equivalence ratio. There was no pronounced influence of the start of injection on the flow field pattern and mixture homogeneity. Thermal field analysis was used to demonstrate trends in the instantaneous heat transfer. It was observed that there was a crucial distinction between the lean and ultra-lean mixtures as well as the engine speed. Furthermore, a non-uniform behavior was found for the impact of the equivalence ratio on temperature distribution. It is clear that the developed models are powerful tools for estimating the heat transfer of the hydrogen-fueled engine. The developed predictive correlation is highly accurate in predicting the heat transfer of the hydrogen-fueled engine, focusing on the equivalence ratio as a governing variable.     

Stabilization of Tl-1223 Phase by Arsenic Substitution

Systematic studies on the Tl_1−x As _x Ba₂Ca₂Cu₃O_9−δ system, with 0.0≤x≤0.3, were carried out to investigate the effect of arsenic on the superconductivity of Tl-1223 phase. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), electron dispersive X-ray (EDX) and electrical resistivity measurements. XRD studies indicated that the tetragonal structure of Tl-1223 phase does not change by arsenic substitution whereas the lattice parameters a and c do. The elemental compositions analysis, determined from EDX, indicated that the arsenic was successfully introduced into the microstructure of Tl-1223 phase. The superconducting transition temperature T _c , determined from electrical resistivity data, increased from 122 to 127 K as x increased from 0.0 to 0.025 and then it suppressed with further increase in x. This means that the lower As-content may stabilize the Tl-1223 phase. In order to study the effect of arsenic substitution on the thermodynamic fluctuations of the Cooper pairs, above T _c , the excess conductivity analysis were performed using Aslamazov–Larkin (AL) theory. The results clarified that there are four regions appeared as the temperature increases namely critical (cr), three-dimensional (3D), two-dimensional (2D), and short-wave (sw) fluctuations. The zero-temperature coherence length along c-axis, the effective layer thickness of the two dimensional system, and the interlayer coupling strength were estimated as a function of the As-content. Furthermore, the thermodynamics critical field, lower critical magnetic field, upper critical magnetic field, critical current density, and Fermi energy were calculated from the above measurements.     

Time-averaged heat transfer correlation for direct injection hydrogen fueled engine

This paper presents the development of an empirical correlation for the prediction of time-averaged heat transfer for a direct-injection hydrogen fueled engine. Computer simulation based on one-dimensional gas dynamics approach was used to perform the time-averaged analysis for the in-cylinder heat transfer. Simulation was performed for 1800 ≤ rpm ≤ 5000, 0.2 ≤ φ ≤ 1.2 and 130 deg before top dead center (BTDC) ≤ SOI ≤ 70 deg BTDC. Experimental measurements were used to verify the developed model, during which the engine performance could be determined to a reasonable accuracy of 10%. The equivalence ratio (φ) was considered as a governing variable, through the new correlation for the time-averaged heat transfer. A nonlinear regression approach was used to develop the new correlations. In the case of all the simulation data, the proposed correlations have a satisfactory performance with the determination coefficient (R²) of about 0.99. A relative error of 10% was found in more than 95% of the simulation data. However, the relative error was reduced to about 50% in the newly developed correlations, which increased its reliability to more than the Taylor's correlation for representing the actual data. Due to the general form, hydrocarbon fuel is suitable for the newly developed correlations that are theoretically made.     

Experimental Investigation and Analysis of the Settlement Funnel in Beds Supporting Different Types of Foundations

A solution is given for determination of the stresses in a foundation bed, which is represented by a linearly deformable half space and intended for foundations with circular or square lower surfaces extending beyond the limits of the loaded area. Experimental data on the settlement funnel in homogeneous and layered beds are presented. The dependence of the spread of the settlement funnel on the dimensions of the plate is established.     

Operational experience of 2 × 11,500m3d MSF seawater desalination plant

This paper outlines the operational experience with 2 × 11,500 m³ p.d. Multi Stage Flash desalination plants which were introduced to Bahrain in 1976. It attempts to place in perspective the problems which this technology presented, as it was new to Bahrain. The particular difficulties which resulted from use of bare carbon steel are identified. The corrective measures which were taken to minimise the rate of corrosion are stated. The paper concludes that careful specifications of materials for such plants is essential, and that the necessary expertise must be available at start up to achieve stable operation and to minimise down time.     

Novel technique for estimating metal semiconductor field effect transitor parasitics

A novel technique is developed for extracting the gate resistance, parasitic inductances, and pad capacitances for metal semiconductor field effect transistor devices. The parameters are extracted from two sets of S‐parameter measurements: cold measurements and pinch‐off measurements. The proposed technique gives rise to reliable results and it is insensitive to the unavoidable measurement errors over any frequency range. The technique is tested on hypothetical data and applied to S‐parameter measurements of a few metal semiconductor field effect transistor devices on the same wafer to provide a unique solution. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 62–73, 2003.     

Interactive Middleware Services for Heterogeneous Systems

Computing has become more invisible, widespread and ubiquitous since the inception of the Internet of Things (IoT) and Web of Things. Multiple devices that surround us meet user’s requirements everywhere. Multiple Middleware Framework (MF) designs have come into existence because of the rapid development of interactive services in Heterogeneous Systems. This resulted in the delivery of interactive services throughout Heterogeneous Environments (HE). Users are given free navigation between devices in a widespread environment and continuously interact with each other from any chosen device. Numerous interactive devices with recent interactive platforms (for example, Smart Phones, Mobile Phones, Personal Computer (PC) and Personal Digital Assistant (PDA)) are available in the market. For easy access to information and services irrespective of the device used for working and even at the drastic change of the environment, the execution of applications on a broad spectrum of computing devices is propelled by the availability of the above-mentioned platforms. Different applications that need interoperability to coordinate and correspond with each other should be facilitated. Using a standard interface and data format, HE must link various devices from various platforms together to communicate with each other. To aid the interactive services performed by a middleware framework that operates on Application Programming Interface (API) over HEs, this issue aims to endorse an Adaptable Service Application Programming Interface (ASAPI).     

Finite sample multivariate tests of asset pricing models with coskewness

Exact inference methods are proposed for asset pricing models with unobservable risk-free rates and coskewness; specifically, the Quadratic Market Model (QMM) which incorporates the effect of asymmetry of return distribution on asset valuation. In this context, exact tests are appealing given (i) the increasing popularity of such models in finance, (ii) the fact that traditional market models (which assume that asset returns move proportionally to the market) have not fared well in empirical tests, (iii) finite sample QMM tests are unavailable even with Gaussian errors. Empirical models are considered where the procedure to assess the significance of coskewness preference is LR-based, and relates to the statistical and econometric literature on dimensionality tests which are interesting in their own right. Exact versions of these tests are obtained, allowing for non-normality of fundamentals. A simulation study documents the size and power properties of asymptotic and finite sample tests. Empirical results with well-known data sets reveal temporal instabilities over the full sampling period, namely 1961-2000, though tests fail to reject the QMM restrictions over 5-year sub-periods.     

Rapid assessment of neoformed compounds in nuts and sesame seeds by front-face fluorescence

The potential of a rapid spectral method, based on front-face fluorescence, to monitor lipid neoformed compounds (NFC) during processing of nuts and sesame seeds was investigated. Fluorescence fingerprints were obtained from front-face fluorescence acquisition directly on crushed nuts and sesame seed samples obtained at different stages of processing. Fluorescence was very sensitive to physicochemical changes induced by the heat process, namely roasting. Parallel factor (PARAFAC) analysis of the fluorescence landscapes revealed four main fluorescence profiles in the nuts, and five in the sesame seeds. These were associated with peptidic tryptophan, tocopherols and process derived products. Various regression models between fluorescence spectra and NFC appearing during the process, carboxymethyllysine (CML) and trans fatty acids (tFA) showed good correlations (R > 0.89) and satisfactory prediction errors (RMSECV < 1.67). When applied to indicators of lipid peroxidation, good regression models were also obtained allowing prediction of the pAV (p-anisidine value) and TBARs (thiobarbituric acid reactive substances): R = 0.73 and 0.96 in nuts and sesame seeds, respectively, with prediction errors lower than 0.78. This study demonstrates the interest of front-face fluorescence as a promising tool for quality control of nuts and seeds roasting.