Control of a permanent magnet synchronous motor fed by a direct AC-AC converter

This paper presents a Simulink model for the field orientation control of a three-phase permanent magnet synchronous motor (PMSM) fed by a direct AC-AC converter. In the field control scheme, the current and speed controllers are designed using the Internal Model Control (IMC) technique. This means that a time-consuming design procedure is avoided. Field weakening control is also applied to the drive system. Simulation results for the input of the converter with unity input displacement factor are given in addition to the output results. Promising results illustrate that a high performance PMSM fed by an AC-AC converter is achievable.     

Oil recovery from lime‐treated wastewater of olive mills

Olive mill wastewater is a by‐product of olive oil production and generates a major environmental problem in the Mediterranean area. The amount of oil and grease, which is one of the parameters used for the characterization of this wastewater, cannot be determined easily using a standard method. Therefore some modifications of the standard method were investigated in this study. To this end wastewater was first treated with lime, without using diatomaceous‐silica, then acidified, filtered through muslin cloth only, and finally extracted with an organic solvent. However, the results obtained by the modified method didn't differ significantly from those obtained by the standard method. Furthermore some tests were conducted to recover the remaining oil, which may be economically important, in these waste products. The oil could be recovered in the range of 70.6 to 96.4% if the wastewater was treated with lime while air was passed through the mixture, filtered using a muslin cloth disk, dried, and extracted with an organic solvent.     

Realization and simulation of wall shear stress integrated sensors

In this paper we present the impact of hot wire geometry and fluid characteristics on the efficiency of a hot wire to be used as a wall shear stress sensor. Finite differences and finite elements modelling based simulators were used in order to evaluate the thermal performances of hot wire wall shear stress sensor. Several structures were explored including simple conductor or suspended above a cavity (free and sealed with an oxide membrane). It is found out that wire length, wire section and the dimensions of the micro-cavity lying below the hot wire are of fundamental importance on the thermal exchanges occurring between the hot wire and the fluid.     

Application of ANN in the prediction of the pore concentration of aluminum metal foams manufactured by powder metallurgy methods

In this work, the effect of fabrication parameters on the pore concentration of aluminum metal foam, manufactured by the powder metallurgy process, has been studied. The artificial neural network (ANN) technique has been used to predict pore concentration as a function of some key fabrication parameters. Aluminum metal foam specimens were fabricated from a mixture of aluminum powders (mean particle size 60 μm) and NaCl at 10, 20, 30, 40(wt)% content under a pressure of 200, 250, and 300 MPa. All specimens were then sintered at 630°C for 2.5 h in argon atmosphere. For pore formation (foaming), sintered specimens were immersed into 70°C hot running water. Finally, the pore concentration of specimens was recorded to analyze the effect of fabrication parameters (namely, NaCl ratio, NaCl particle size, and compacting pressure) on the foaming behavior of compacted specimens. It has been recorded that the above-mentioned fabrication parameters are effective on pore concentration profile while pore diameters remain unchanged. In the ANN training module, NaCl content (wt)%, NaCl particle size (μm), and compacting pressure (MPA) were employed as inputs, while pore concentration % (volume) of compacts related to fabrication parameters was employed as output. The ANN program was successfully used to predict the pore concentration % (volume) of compacts related to fabrication parameters.     

Direction finding of moving ferromagnetic objects inside water by magnetic anomaly

The remote sensing methods by the use of magnetic anomaly are gaining importance in applications of defense technologies and industrial purposes recently. In this study, it is aimed to determine the remote detection, the variation of characteristic of the voltage in the sensor relative to the motion, the effects of material length, magnetic permeability and direction of motion of the object on this characteristic and to convert them to a useful mathematical expression by using magnetic anomaly of ferromagnetic objects such as submarines moving inside water. For this purpose, first of all, a water tank of 1 m³ is prepared and approximately a homogeneous magnetic field of 10⁻³ T is created within this water tank. Ferromagnetic materials with six different lengths and permeabilities are moved in three different directions relative to the position of the sensor by means of a computer controlled x–y scanner designed for this experiment inside this magnetic field. The magnetic change caused by this motion at the point where the sensor is positioned is detected as the output voltage of the sensor. A mathematical expression is formulated taken into account the variations of the sensor output voltage with respect to the length, magnetic permeability and the direction of motion of the material and it is validated by the experimental results. This study clearly shows that the existence and the direction of motions of ferromagnetic objects with different lengths and magnetic permeabilities inside water can be detected with high accuracy.     

Sulphur removal by pyrolysis of Turkish lignites

Modes of distribution of sulphur have been determined in eleven lignite samples from major reserves in Turkey. Total sulphur contents have been found to vary 0.91%–10.32% on dry basis. The lignites contain relatively high amounts of organic sulphur. Distributions of sulphur have been determined in chars from the pyrolysis of lignites at 440 °C. Reductions in combustible sulphur contents have been found to vary 15.7%–72.0%. No correlation has been found between the extent of desulphurization by pyrolysis and the relative amounts of forms of sulphur in the parent lignites.     

Photocatalytic Selective Oxidation of 4‐Methoxybenzyl Alcohol to Aldehyde in Aqueous Suspension of Home‐Prepared Titanium Dioxide Catalyst

The photocatalytic oxidation of 4‐methoxybenzyl alcohol to p‐anisaldehyde (PAA) was performed in water with organic‐free suspensions of home‐prepared and commercial titanium dioxide (TiO₂) catalysts. The nanostructured TiO₂ samples were synthesised by boiling aqueous solutions of titanium tetrachloride (TiCl₄), under mild conditions, for different times. The crystallinity increased with the boiling time. The 4‐methoxybenzyl alcohol oxidation rate followed the same pattern but the highest yield (41.5 % mol) to PAA was found for the least crystalline sample, that showed a quantum efficiency of 0.116 %. A comparison with two commercial TiO₂ samples showed that all the home‐prepared catalysts exhibited a PAA yield higher than that of commercial ones. The only by‐products present were traces of 4‐methoxybenzoic acid and aliphatic products, carbon dioxide being the other main oxidation product.     

Extraction of molybdenum,nickel and aluminium from spent Ni–Mo hydrodesulphurization (HDS) catalyst in oxalic acid solutions

ABSTRACT

Dissolution behaviour of metals in Ni–Mo hydrodesulphurization catalyst waste was investigated in a 1?L jacketed glass reactor. Samples were roasted at 500°C in a tube furnace for the removal of C and S prior to the dissolution experiments. It was determined that roasted samples consisted of mainly 27.692% Al, 20.238% Mo, 5.267% Ni and 4.331% P. Unmilled samples were used for dissolution experiments because dissolution experiments carried out with milled and unmilled samples showed that milling has no significant effect on the dissolution rate. Oxalic acid solutions with 0.25–1 M, reaction temperatures of 25–70°C and solid to liquid ratios of 10–100?g?L^?1 were used as experimental parameters. It was found that the dissolution behaviour of Ni is different from Al, Mo and P. 92% of Mo, 19% of Ni, 28% of Al and 72% of P were dissolved at optimum dissolution conditions.     

Increasing Lightning Strength of Optical Ground Conductors

In this article, testing and improvement stages of AA6101 and 6201 materials used in manufacturing of new generation optical ground conductors (OPGW) installed against lightning strike have been presented. The designed and manufactured prototype composite conductor OPGW for Turkey’s transmission lines is composed of six galvanized steel wires, one stainless steel tube with multi glass fibers and 12 aluminium alloy wires. Test samples prepared from prototype failed in first trial of lightning strike due to spot melting of conductor outer surface. The amplitude of the arc current was adjusted to 200A. The duration of the arc was 500 ms with 100C total charge. It caused breaking of excessive aluminium alloy wires at outer layer. Thus material improvement by inoculation with AlB₂ compound into molten metal was applied at continuous casting line. Its aim is to obviate destroying effects of lightning strike by the increasing conductivity of the base conductive part composed of alloy AA6101 and 6201 wires. Conductivity increases were made by transforming detrimental transition impurities Ti, V, Cr and Zr into diborides as TiB₂, ZrB₂, CrB₂, and VB₂. After all OPGW composite conductor manufactured with improved aluminium alloy wires passed lightning strike tests perfectly.     

Capacitive solvent sensing with interdigitated microelectrodes

Microsystem Technologies - We were able to quantify dielectric properties of solvents such as DI water, isopropyl alcohol, and acetone using interdigitated microelectrodes (IMEs). IMEs were...