Abstract—An accurate prediction of bed level variation and especially of the mechanism of local scour hole development around bridge abutments is of paramount importance, in river engineering, for a safe design of the construction. In the present research work, a two-dimensional, explicit, finite-volume numerical algorithm, which combines the hydrodynamic equations of viscous, unsteady, free-surface flow in rivers with the continuity equation for the conservation of sediment mass is used to simulate scour depth variation in the region of vertical wall abutments. The capabilities of the applied numerical model are demonstrated by comparing the computed results with available measurements of bed formation in the region of three orthogonal abutments, with different widths, normal to the flow direction. All the experimental results were conducted in a laboratory flume in Technological Educational Institute of Thessaly and scouring depths were obtained in the vicinity of each construction, for different inflow discharges and flow duration. Numerical simulation results of the maximum scour depth and of the developed scour whole area are satisfactorily compared with the experimental measurements. Comparisons show the accuracy and the validity of the applied two dimensional, movable bed numerical techniques.
Keywords—Abutment, Local scour, Two-dimensional sediment transport model.
Material characterisation and parameter effects on bulk solid dissolution rate of paracetamol in a stirred tank vessel using an in situ UV-ATR probe
Abstract— The progress from batch to continuous manufacture of pharmaceuticals has highlighted the requirement for dosing solid feed material directly, efficiently and accurately into continuous flow systems. Solids are currently dissolved in batch vessels before feeding into a flow system. This study focuses on gaining scientific understanding on rate kinetics of solid dissolution and parameters affecting solid dosing in current batch systems as a starting point; the knowledge gained will inform future continuous solid dosing work. Paracetamol was the model compound and the mixtures of water/ IPA the solvent systems. An in situ UV spectrometer was used to quantify the concentration of solute in solution during dissolution. In this paper, we present the dissolution kinetics results from a parametric study of effects of temperature, solvents, mixing and particle sizes on dissolution characteristics in a stirred tank vessel. The dissolution profiles from our system are similar to that of published work, with the fastest kinetics for the micronised particles, albeit problematic when dosing as a single shot. Dissolution rate is increased with increasing temperature, solvent content (solubility), mixing intensity and decreasing particle size.
Keywords— Dissolution, Solid dosing, Continuous Work up, Batch manufacturing, Continuous Pharmaceutical Manufacture, Stirred tank reactor, UV Spectrometry.
Abstract— Thermodynamic properties of the Al-Fe–Ni system and its constituent’s binary systems in a wide temperature range of 1873-1973 K and the whole range of concentrations have been studied using the FactSage.
Keywords— Al-Fe-Ni, FactSage, thermodynamic properties.
Abstract— Cold plasma exhibits many advantages in environmental treatment without additive reagent required. The 2,4,6-Trinitrophenol (TNP) might be degraded with high efficiency using cold plasma. The main factors influencing the TNP degradation have been studied. The kinetics of the TNP process proposed fits to the pseudo- first order reaction. The overall reaction rate expression was established to be - r= 0.024CTNP at low TNP concentration
Keywords— Cold plasma, 2,4,6-Trinitrophenol, degradation by plasma.
Abstract— Copper-based shape memory alloy with zinc and aluminum was manufactured, plastically deformed, heat treated and characterized in terms of physico-mechanical, structural and micro-structural investigation. Typical martensitic microstructure with twins is revealed by optical and electron microscopy. The presence of the martensite in the structure was further confirmed through X-ray diffraction. Toughness and hardness of the alloy are investigated too. Optimal properties are obtained for the condition of the alloy that was subjected to heat treatment according to the following scheme: annealing at 850 0C and 900 0C (10 min) + quenched in water + aging at 400 0C (1 hour) + air cooling.
Keywords— shape memory, SEM-EDS, hardness, copper-zinc-aluminum alloy, martensitic structure.
Simultaneous analysis of nitro compounds by Voltammetric method combined with the partial least squares (PLS) and the principal component regression (PCR)
Abstract— Nitro aromatic compounds exhibit a strong electrochemical behavior on hanging mercury drop electrodes (HMDE). The ability to simultaneously determine 6 nitro compounds including nitrobenzene (NB), 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP), 2,4- dinitrophenol (DNP) and trinitrophenol (TNT) in the same samples was investigated by differential pulse Voltammetry. The method is based on the electrochemical process at HMDE in acetate buffer of pH 4.6. It was found that peak potentials of voltammetric reduction waves of NB, 2-NP, 3-NP and 4-NP appeared at - 0.332, - 0.281, - 0.311 and - 0.387 V respectively. Under the same conditions there are three peak potentials at -0.131, - 0.227, - 0.332 V for TNT and two peaks at tại - 0.221, - 0.332V for DNT. The peaks of these compounds are very close together. Due to the serious overlapping of Voltammetric peaks of these compounds in the mixtures, so that by a conventional Voltammetry it not possible to individually determine each compound. In this study, linear multivariate regression methods such as partial least squares (PLS), principal component regression (PCR) was used to resolve the overlapped Voltammograms. The obtained relative standard errors of both methods are within ± 10%. The PLS (10.8% RSEt) results in data better than PCR (11.8% RSEt).
Keywords— Nitrobenzene, 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, Dinitrotoluene, Trinitrotoluene.
Abstract— The exploited fish populations and the fishery dependent on them require regular monitoring and periodical stock assessment. The resource evaluation is crucial for definition of appropriate management strategies for rational exploitation and long-term sustainable development of the exploited stocks.
The determination of the current state of a given stock is directly related to analysis of historical and present data concerning specific stock parameters which indicates the current status of the stock and suggests relevant definition of healthy exploitation levels. Such key stock parameters are growth and mortality rates, abundance indices, carrying capacity, maturity and reproduction, catch composition and recruitment [1,3,4,6,13,14].
The present article introduces a program system - MATLAB-based standalone application specifically developed to facilitate length-weight relationship of fish analysis outcome, growth and mortality parameters estimates and their confidence limits, normality tests of length-weight-frequency sample data, used in analysis. The proposed system incorporates statistical analysis of the overall significance of the mathematical models and results delivered, as well as methodology to overcome added computational errors in numerical analysis.
Keywords— fish stocks, growth and mortality parameters, MATLAB programming environment, standalone application, stock assessment.
Abstract—The flow acting in a T-junction channel is present in several industrial applications, such as air conditioning systems, water cooling circuits, gas exhaust systems and others. In order to numerically simulate this case, the Average Reynolds Navier-Stokes (RANS) equation is used for a two-dimensional stationary flow using the k-ε model together with wall functions such as standard wall function, Enhanced and Menter-Lechner wall treatments. The moment ratio used is = 2 and the Reynolds number at the inlet of the flow parallel to the channel is Re = 15,000. The results were compared with the literature data using Large Scale Simulation (LES). The results obtained for k-ε model Enhanced and Menter-Lechner wall treatment were satisfactory and close to that found by the LES simulation, however, results obtained from k-ε model standard wall function presented large deviation to literature, mainly in the boundary layer and K production profiles. In general, the results presented small distortions for the profiles of turbulent kinetic energy production near walls, however, they illustrate in an analogous manner to the literature the production of turbulent kinetic energy K concentrated in the shear layers between flows. The main results analyzed in this paper are the length of the recirculation bubble, boundary layer profile, mean velocity magnitude and kinetic energy production k.
Keywords—Turbulence, RANS, k-ε, T-Junction, Channel, LES.
Design of RF Transmitter with high speed for Magnetic Resonance Imaging (MRI) using 8-Core DDS System of FPGA
Abstract— An overall goal of the research is to investigate a new approach to the MRI RF Transmitter. Design a high-speed MRI RF transmitter. The goal is to explore the potential of a built-in DDS core of an FPGA chip to generate a dual-channel output at a 1 GHz sampling frequency of each. This output will be processed by a dual-input DAC chip for a total of 2 GHz sampling rate. The entire system should be able to generate the output signal ranging from 100 kHz to 750MHz. To accomplish this goal, it is necessary to study and to investigate the structures of these features to see how they could be utilized as a main core in a pulse generator
According to the datasheet provided by Xilinx, a DDS core has a single sine or/ and cosine output signal. The DDS core can operate at a maximum clock of 250 MHz. A 250 MHz clock speed is insufficient to generate outputs at 1 GHz sampling frequency. Consequently, the proposed custom DDS system is expected to quadruple the clock speed of the system by implementing multiple DDS core modules within the system.
Keywords— Direct Digital Synthesis.