Design improvements on rotary valve particle feeders used for obtaining suspended airflows

The back repulsion of low density particles, sticking of particles in feeder valve and interlocking and cohesive archs of particles in feeder hopper have been widely observed problems of a conventional rotary valve feeder used for feeding of granular particles into an airflow line. In this study, these problems of the rotary valve feeders were isolated by means of novel modifications to its conventional design. Results of the modifications showed that the modified feeder can be sensitively used to feed granular particles with mass feeding rates ranging between 5±0.15 and 85±0.85 g/s without encountering problems experienced with conventional rotary valves.     

Investigation of drag reduction performance of half NACA 0009 and 0012 airfoils placed over a trailer on the flow around truck-trailer

Journal of Mechanical Science and Technology - The drag reduction performance of a half airfoil attached to a trailer and the roof fairing at different positions was experimentally investigated in...     

Photooxidation of Some Mono-, Di-, and Tri-chlorophenols in Aqueous Solution by Hydrogen Peroxide/UV Combinations

A number of chlorophenols, namely 2-, 3-, and 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol, have been decomposed in aqueous solution by using hydrogen peroxide as the oxidizing agent under UV radiation emitted by a 400 W high-pressure mercury lamp in a thermostatted Pyrex-glass column photoreactor, and the organic-bound chlorine has been converted into the environmentally harmless inorganic chloride. For H₂O₂/chlorophenol mole ratios between 1: 1 and 16: 1, the photooxidation reaction approached pseudo-first order kinetics, and the rate constants increased with increasing ratio of the oxidant. A theoretical model for the degradation pathway is proposed. The fact that the reaction order was not simply unity could be attributed to the complex reaction sequence processing via a radical mechanism through colored intermediates possibly comprising hydroquinone, catechol and resorcinol.     

Predicting preferences of university students for prepaid vs post paid cell phone service plans

Information and communication technologies have recently become widely used, especially among the younger population. In this study, the factors affecting the preference of undergraduate students for prepaid or postpaid cell phone service plans were analyzed and a multi-layer perceptron type feed forward neural network model was developed to predict the preferences. Using the responses to the questionnaire administered to a group of undergraduate students in Istanbul University, the factors determining the preference for service plan were determined with χ2 test for independence. A classification model based on multi-layer perceptron type neural networks was developed. The classification accuracy of this model was compared to linear regression, LDA, QDA, Naive Bayes and decision tree approaches and shown to be superior.     

Analysis of interaction between tunnels in soft ground by 3D numerical modeling

Tunnels are increasingly being excavated in soft ground conditions when services are required in urban environments, and it is now common to have tunnels crossing at various elevations. As the tunnel excavations are undertaken at different levels, there will be an interaction which can have a significant influence on stress distributions and consequently deformations within the tunnels and surface settlement. As multi-layer tunnelling is a three dimensional phenomenon in nature, 3D numerical solutions must be utilized for perpendicularly crossing tunnels at various levels. This paper reports the investigations into the changes in stress distribution, deformations and surface settlements which may be expected when the twin Tohid Tunnels pass beneath the Line 4 metro tunnel in Tehran.     

The effect of par‐baking and frozen storage time on the quality of cup cake

The effects of frozen storage and initial baking time of par‐baked cake on baking loss, volume, moisture, colour and textural properties of cake obtained after thawing and rebaking were investigated. Cakes, par‐baked at 175 °C for 15, 20 and 25 min, were stored at ?18 °C for 3, 6 and 9 months. After storage, par‐baked cakes were thawed and rebaked at 175 °C for 10, 15 and 20 min. Baking loss, moisture content, L and +b colour values, firmness, gumminess and chewiness of the resulting full‐baked cakes were significantly affected by both par‐baking and frozen storage time, while specific volume, cohesiveness, springiness and resilience values were significantly affected by frozen storage time. The increase in the time of frozen storage of the par‐baked cake leads to a decrease in the quality of the rebaked cake, namely an increase of baking loss and cake crumb firmness, and a loss in the moisture content and specific volume. Moisture of cake crumb, L and +b colour values, firmness, gumminess and chewiness significantly increased as the par‐baking time increased. However, regarding baking loss, specific volume, moisture content and textural properties, 3‐month intermediate storage at ?18 °C and 20‐min initial baking time gave the best result among the cakes produced by using the two‐step baking procedure.     

Enhancing electrochromic properties of polypyrrole by silsesquioxane nanocages

A new monomer, octa(thiophenephenyl)silsesquioxane (OThiophenePS) was synthesized via click chemistry. The chemical structure of OThiophenePS was characterized by nuclear magnetic resonance (¹H NMR) and Fourier transform infrared (FT-IR) spectroscopies. Electrochemical polymerization of pyrrole with OThiophenePS was performed resulting in polypyrrole-attached, polyhedral oligomeric silsesquioxane (OPS–PPy). The spectroelectrochemical studies show that the electrochromic properties of (OPS–PPy) are superior to those of polypyrrole (PPy). This great improvement can be attributed to the more accessible doping sites and the facile ion movement during the redox switching brought by the loose packing of the PPy chains.     

Performance analysis of gas liquefaction cycles

Relations are developed for first‐ and second‐law analyses of the simple Linde–Hampson cycle used in gas liquefaction systems. An expression for the minimum work requirement, which is applicable to any gas liquefaction system, is developed with the help of a Carnot refrigerator. It is shown that the minimum work depends only on the properties of the incoming and outgoing gas streams and the environment temperature. Numerical calculations are performed to obtain the performance parameters of different gases while parametric studies are done to investigate the effects of liquefaction and inlet gas temperatures on various first‐ and second‐law performance parameters. As the liquefaction temperature increases and the inlet gas temperature decreases, the liquefied mass fraction, the coefficient of performance (COP) and the exergy efficiency increase while actual and reversible work consumptions decrease. The exergy efficiency values appear to be low, indicating significant potential exists for improving efficiency and thus decreasing the required work consumption for a specified amount of liquefaction. Copyright © 2007 John Wiley & Sons, Ltd.     

Thermo‐economic optimization of superheating and sub‐cooling heat exchangers in vapor‐compressed refrigeration system

In this study, superheating and sub‐cooling heat exchangers in vapor‐compressed refrigeration system are analyzed from thermodynamics and economical (refrigeration system operation cost, investment cost) viewpoints. Using four different refrigerants (R22, R502, R134a and R404a), the temperature of condenser at the interval of (35–55°C) and temperature of evaporator at the interval of (?10 to 10°C) have been obtained from the calculation process. The second law analysis (analysis of irreversibility) of a refrigeration system is carried out and then the whole system is optimized thermo‐economically. As a result of calculations, optimum superheating and sub‐cooling temperatures of heat exchanger (superheating, sub‐cooling) areas corresponding to these temperatures are obtained. Copyright © 2007 John Wiley & Sons, Ltd.     

Modeling a ground-coupled heat pump system by a support vector machine

This paper reports on a modeling study of ground coupled heat pump (GCHP) system performance (COP) by using a support vector machine (SVM) method. A GCHP system is a multi-variable system that is hard to model by conventional methods. As regards the SVM, it has a superior capability for generalization, and this capability is independent of the dimensionality of the input data. In this study, a SVM based method was intended to adopt GCHP system for efficient modeling. The Lin-kernel SVM method was quite efficient in modeling purposes and did not require a pre-knowledge about the system. The performance of the proposed methodology was evaluated by using several statistical validation parameters. It is found that the root-mean squared (RMS) value is 0.002722, the coefficient of multiple determinations (R²) value is 0.999999, coefficient of variation (cov) value is 0.077295, and mean error function (MEF) value is 0.507437 for the proposed Lin-kernel SVM method. The optimum parameters of the SVM method were determined by using a greedy search algorithm. This search algorithm was effective for obtaining the optimum parameters.The simulation results show that the SVM is a good method for prediction of the COP of the GCHP system. The computation of SVM model is faster compared with other machine learning techniques (artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS)); because there are fewer free parameters and only support vectors (only a fraction of all data) are used in the generalization process.