Dam break flood wave under different reservoir’s capacities and lengths

Dam failure has been the subject of many hydraulic engineering studies due to its complicated physics with many uncertainties involved and the potential to cause many losses of lives and economical losses. A primary source of uncertainties in many dam failure analyses refers to prediction of the reservoir’s outflow hydrograph, which is studied in the present investigation. This paper presents an experimental study on instantaneous dam failure flood under different reservoir’s capacities and lengths in which the side slopes change within a range of 30°–90°. Thus, several outflow hydrographs are calculated and compared. The results reveal the role of the side slopes on dam break flood wave, such that lower side slope creates more catastrophic outflow. The reservoir capacity and length are also recognized to be important factors, such that they do affect peak discharge and time to peak of the outflow hydrograph. Finally, the paper presents two simple relations for peak discharge and maximum water level estimation at any downstream location.     

A Blue Photosensitizer Realizing Efficient and Stable Green Solar Cells via Color Tuning by the Electrolyte

Semitransparent dye-sensitized solar cells (DSCs) are appealing as aesthetically pleasing and colorful see-through photovoltaics. Green semitransparent DSCs have been presented, but the best ones rely on green zinc porphyrin photosensitizers and high volatile electrolytes. For potential outdoor applications, the zinc porphyrin DSCs employing ionic liquid electrolytes merely reached a power conversion efficiency (PCE) of 6.3% even with opaque mesoporous TiO₂ films. Herein, the new green DSC is realized by using a blue organic photosensitizer in conjunction with an orange ionic-liquid-based electrolyte, presenting a simple and an effective path for color tuning of photovoltaics. The new approach allows for broadly modulating the color from spring green to cyan by tuning the contributions of the light absorption by the dye-sensitized TiO₂ film and the electrolyte layer. The new semitransparent DSCs with spring green to cyan colors have PCEs ranging from 6.7% to 8.1% and show stability for 1000 h under accelerated ageing test at 80 °C, superior to the zinc porphyrin DSCs. The findings pave a new way to achieve efficient and stable colorful solar cells.     

Novel poly (vinyl chloride) matrix membrane electrodes for the determination of phenolic pollutants in waste water

The construction and electrochemical response characteristics of poly (vinyl chloride) matrix membrane sensors for seven phenolic compounds (phenol, o-cresol, p-cresol, p-chlorophenol, o-nitrophenol, alpha-naphthol and beta-naphthol) are described.The membranes incorporate ion association complexes of these seven phenolic anions with phenanthroline-iron(II) as electroactive materials.These sensors show linear response for phenol, o-cresol, p-cresol, p-chlorophenol, o-nitrophenol, alpha-naphthol, and beta-naphthol over wide concentration ranges, with an average anionic slope 54.3 mV per concentration decade.The suggested sensors exhibit fast response time (1 min), low determination limits (1 x 10(-5)M), good stability (2-3 weeks), reasonable selectivity to phenolic compounds in the presence of other water pollutants. The average percentage recovery was 99.78+/-0.088 for individual phenolates and 99.61+/-0.198 for phenolates in mixtures.The investigated sensors were successfully used for direct potentiometric determination of traces of these phenolic compounds in wastewater samples. Results with mean accuracy of 99.74+/-0.29%, 99.82+/-0.36%, 99.65+/-0.47%, 99.73+/-0.37%, 99.77+/-0.30%, 99.86+/-0.31% and 99.91+/-0.22% was obtained for the seven sensors, respectively.These results were compared with data obtained using the British pharamacopial method (The British Pharmacopoeia, Her Majesty's Stationary Office, London, 1993) and others (Clarke's Isolation and Identification of Drugs in Pharmaceuticals Body Fluids and Post-mortem Materials, 2nd Edition, The Pharmaceutical Press, London, 1998).     

A comparative review of dynamic neural networks and hidden Markov model methods for mobile on-device speech recognition

The adoption of high-accuracy speech recognition algorithms without an effective evaluation of their impact on the target computational resource is impractical for mobile and embedded systems. In this paper, techniques are adopted to minimise the required computational resource for an effective mobile-based speech recognition system. A Dynamic Multi-Layer Perceptron speech recognition technique, capable of running in real time on a state-of-the-art mobile device, has been introduced. Even though a conventional hidden Markov model when applied to the same dataset slightly outperformed our approach, its processing time is much higher. The Dynamic Multi-layer Perceptron presented here has an accuracy level of 96.94% and runs significantly faster than similar techniques.

     

Characterization of Biogenic Silica Generated by Thermo Chemical Treatment of Rice Husk

This study presents two routes to produce amorphous silica from an Egyptian rice husk under conditions optimized for least environmental impact and low cost. The first route includes thoroughly washing of the husk sample with water, dry milling and leaching with citric acid. The leaching process was applied in two stages, that is, at 323 K for 180 min and then at 353 K for 60 min. After washing and drying, the leached sample was subjected to a heat treatment in a muffles furnace at four sequential steps. The second route includes all the previously mentioned steps, except the citric acid leaching. The final products were characterized using x-ray fluorescence analysis, carbon content analysis, x-ray diffraction, differential thermal analysis, nitrogen adsorption, mercury intrusion, and scanning electron microscopy. The results show that the citric acid leaching has many advantages with respect to silica yield and porosity as well.     

Effect of wettability on oil recovery and breakthrough time for immiscible gas flooding

The effect of wettability on oil recovery at higher water saturation is still not fully understood, especially in the case of mixed wettability. This study was conducted to examine the effects of wettability on oil recovery and breakthrough time through experiments for two wettability conditions (water-wet and mixed-wet) and three water saturations (20%, 40%, and 60%). Clashach sandstone core with a porosity of 12.8% and a permeability of 75 md was utilized as the porous media. Immiscible gas flooding was performed by injecting nitrogen gas into the core at room temperature and pressure. The results showed 54.3% and 48.8% of the initial oil in place (IOIP) as the ultimate oil recovery at 40% water saturation from mixed-wet core and water-wet core respectively. In contrast, the water-wet core displayed better results (32.6% of the IOIP) in terms of breakthrough time compared to the results of water-wet core (10.6% of the IOIP) at the same water saturation. In conclusion, oil recovery was found highly dependent on water saturation while breakthrough time was mainly affected by the wettability of the cores.     

The influence of temperature on the mechanical and fracture properties of a 20 vol% ceramic particulate-reinforced aluminium matrix composite

The influence of test temperature on the mechanical and fracture properties of a 20 vol% alumina particulate-reinforced 6061-aluminium matrix composite, in the peak-aged condition, was investigated in the temperature range 25–180 °C. Strength and stiffness were found to decrease but elongation to failure increased with increasing test temperature. However, the fracture toughness was relatively constant over this temperature range. The failure mechanism, the reaction zone around reinforcing particles, the number of debonded particles and void sizes were all significantly influenced by temperature. The role of the matrix/particle interface in the fracture process was also investigated.On leave at the Department of Mechanical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.     

Effect of multipath fading and multiple access interference on broadband code division multiple access systems

In this paper, the performance of uncoded uplink transmissions in a broadband code division multiple access (CDMA) system using tapped delay line (TDL) antenna array under multipath conditions is investigated. An expression for broadband CDMA system is derived to calculate the optimal weights of TDL antenna array. Using the derived broadband expression, the performance of TDL antenna array is investigated and compared with that of the already existing narrowband systems. Simulation results show that TDL antenna array can reduce multipath fading and multiple access interference (MAI). It is shown that if the signal‐to‐noise ratio (SNR) level is maintained at 20 dB and two‐ray channel model is used, two antennas with four taps each can support 30 users with a BER of 10^?3. If three‐ray channel model is used, the same antenna arrangement is not enough to support 30 users. To support these 30 users with BER of 10^?3, the number of taps needs to be increased to eight. Finally, the number of taps needs to be further increased to 16 if four‐ray channel model is used. Not only that, the SNR should also be increased to 25 dB to achieve the same BER. Copyright © 2011 John Wiley & Sons, Ltd.     

Helicopter radar return analysis: Estimation and blade number selection

The problem of helicopter parameter estimation and blade number selection is addressed. The parameters are estimated based on Maximum Likelihood methods and the corresponding Cramér-Rao bounds are derived. To avoid ambiguities in blade number estimation, we apply information theoretic criteria for blade number selection incorporating alternate penalty functions. We assume that a clutter filter essentially removes all of the clutter and also part of the signal returns, lowering the effective signal-to-noise-ratio. The fractional Fourier transform is used to separate the combined tail and main rotor signals into two different returns, allowing initial estimates of their corresponding rotor parameters. The proposed technique is validated by using returns from a helicopter observed experimentally with a pulse-Doppler radar.     

Continuous water treatment by adsorption and electrochemical regeneration

This study describes a process for water treatment by continuous adsorption and electrochemical regeneration using an air-lift reactor. The process is based on the adsorption of dissolved organic pollutants onto an adsorbent material (a graphite intercalation compound, Nyex^®1000) and subsequent electrochemical regeneration of the adsorbent leading to oxidation of the adsorbed pollutant. Batch experiments were carried out to determine the adsorption kinetics and equilibrium isotherm for adsorption of a sample contaminant, the organic dye Acid Violet 17. The adsorbent circulation rate, the residence time distribution (RTD) of the reactor, and treatment by continuous adsorption and electrochemical regeneration were studied to investigate the process performance. The RTD behaviour could be approximated as a continuously stirred tank. It was found that greater than 98% removal could be achieved for continuous treatment by adsorption and electrochemical regeneration for feed concentrations of up to 300 mg L⁻¹. A steady state model has been developed for the process performance, assuming full regeneration of the adsorbent in the electrochemical cell. Experimental data and modelled predictions (using parameters for the adsorbent circulation rate, adsorption kinetics and isotherm obtained experimentally) of the dye removal achieved were found to be in good agreement.