International Journal of Engineering
Volume:21 Issue: 2, Aug 2008

Hydroxyapatite nanorods aligned with ultrahigh crystallinity and high-yield were successfully synthesized through a hydrothermal approach. In this experiment, a new composition of cetyltrimethylammonium bromide ((CH3(CH2)15N+(CH3)3Br-) was designated as CTAP)/Ca(NO3)2/(NH4)2HPO4/NaOH and distilled water under hydrothermal condition, to synthesize single crystalHAp nanorods with diameter of 20 ± 10 nm and length of 80 ± 20 nm, was introduced. Crystal phases were determined by X-ray diffraction (XRD). Scanning electron microscope (SEM) was applied to investigate the morphology. The microstructure of the HAp products were further observed by transmission electron microscope (TEM) and high resolution transmission electron microscope(HRTEM) with energy-dispersive X-ray spectroscopy (EDX). The purity and chemical composition of the as-synthesized powder was analyzed by FTIR and inductively coupled plasma atomic emissionspectroscopy (ICP).

In this study, two thermodynamic models (regular solution theory and equation of state) were applied to obtain carotenoid solubility in the supercritical carbon dioxide solvent. Theoretical data obtained from the models were compared with the experimental data extracted from a published paper. The use of equation of state as an empirical correlation for collating and predicting liquidliquid and liquid-dense fluid equilibrium is discussed. It is concluded that the estimation of some parameters required for these calculations would be difficult if the solute (carotenoid) was a complex substance in which little information was known, apart from its structural formula. An alternativeprocedure is to apply activity coefficient expression of the regular solution equations for each phase.Calculations along these lines are described and the physical basis for applying these methods underthe relevant conditions was also presented. The regular solution theory approach in particular hasbeen found to be encouraging for the mutual miscibility calculations for heavy components (such ascarotenoid) particularly substances that are sensitive to temperature, though the interaction parametersfor the prediction activity coefficients must be regarded as pressure dependent.

Fructose is utilized as a common sweetener in many food industries. Today, a large amount of HFCS (high fructose corn syrup, an equilibrium mixture of glucose and fructose) is produced by glucose isomerase, immobilized enzymes from corn starch. There are a lot of date palms in Iran. Date is a favorable source of carbohydrates, and a suitable source for HFDS (high fructose date syrup) production. In this investigation, date syrup properties were first determined and the operational conditions for glucose isomerase application were optimized respectively. Ion exchange chromatography has been utilized for carbohydrate separation. Fructose obtained fromchromatographic column reached 90 % fructose syrup and glucose obtained was converted to fructose (42 % conversion) in a fixed bed glucose isomerase enzyme reactor. A mixture of this equilibriumsyrup with fructose syrup obtained from chromatographic column produced 55 % fructose syrup.

Many countries in the word have loose and unstable soils encompassing a wide range ofgeological materials, which when inundated, may collapse and cause very significant distress to the structure. Stone columns have been used to strengthen such soils; even so, there are still cases where failure has occurred. In this technical note, the process and causes of stone column failure in reinforcing collapsible soils is examined. A behavior analysis of a typical element of soil in the vicinity of column during inundation was studied. The difference between the behavior of a stone column in a collapsible fill and a column in a non-collapsible fill is reported in this paper. Also asolution for the problem of stone column failure is suggested.

Upper Gotvand dam is constructed on the Karun River located in the south west of Iran. In this paper, 2D and 3D models of the dam together with the foundation and abutments were constructed and several seepage analyses were carried out. Then the gypsum veins scattered throughout the foundation ground and also the seepage pattern were included in the models, hence the dissolution law of gypsum, was analyzed. It was disclosed that, the discharge fluxes obtained from 2D and 3D analyses are not similar and the discharge flux in 3D model is about 4 times the size of 2D model. Also, the 3D model localizes the phreatic surface some what higher than the 2D model does. This means that the 2D model estimates lower pore water pressure pattern in comparison with the 3D model. These may be attributed to the fact that with 2D model the lateral components of vectors of seepage velocity are ignored. In spite of the fact that the grout curtain is designed to be some 170 meters deep, however, complete dissolving of gypsum will severely increase the discharge flux through the foundation ground.

In this paper, an adaptive nonlinear controller is designed for rotor Surface Permanent Magnet Synchronous Motor (SPMSM) drive on the basis of Input-Output Feedback Control (IOFC), and Recursive Least Square (RLS) method. The RLS estimator detects the motor electromechanical parameters, including the motor iron loss resistance online. Moreover, a Sliding-Mode (SM) observer is developed for online estimation of the rotor speed and rotor position. In this control scheme, the torque reference signal is generated by a conventional speed PI controller. The effectiveness and feasibility of the proposed control approach is tested by simulation. Computer simulation results show that the errors in the estimated quantities asymptotically converge to zero. These results also show that the drive system is stable and robust against the parameter uncertainties and external load torque disturbance.

In this research the effects of; increasing the amount of nickel and adding aluminum to create and prolong sulfidation resistance of Fe-Ni-Cr alloys have been investigated. Sulfidation tests were carried out at 1100°C in S/O bearing atmosphere. Prior to the tests, the specimens were annealed in argon at 1250°C for 8 hrs. Weight changes were measured and corroded deposits were analyzed byscanning electron microscope, X-ray diffraction, energy dispersive spectrometry and optical microscope. The results showed that, sulfidation resistance decreases as nickel content increase.Aluminum addition has good sulfidation resistance effect for these alloys, since alumina layer is more protective than chromia.

Lanthanum hydroxide (La(OH)3) nanostructures, including elliptical nanoparticles, octahedral rods and irregular nanoparticles were prepared chemically in NaOH and KOH solutions with 10 M concentration. The obtained powders were characterized with XRD, SEM, TEM and DTA. Crystallinities, morphologies and thermal behavior of the obtained nanostructure powders were investigated under the influence of above mentioned solvents. The effect of chemical''s temperature was also determined in one of the solvents (i.e. NaOH). The formation of growth in nanostructure mechanism under the influence of alkali solutions (i.e., KOH and NaOH) have been discussed considerably in this paper.

In this paper the electrodeposition of nickel on n-Si(111):H substrate, in the presence of sulphuric acid, was studied. Cyclic voltammetry has been used to characterize the electrochemical behavior of the system. The nickel deposits had a flower-like morphology with the sphericalnanostructure nucleus, distributed uniformly on the surfaces of the prepared n-Si(111) substrate.

Thermoacoustics describes energy conversion processes, activated by interaction temperature oscillation, accompanying the pressure oscillation in a sound wave, with solid boundaries. In ordinary experience this interaction of sound and heat cannot be observed, because of the very low temperature differences, but under suitable conditions, it can be emphasized and amplified to create remarkable thermodynamic effects such as, steep thermal gradients, powerful convective heat fluxes, and strong sound fields. We designed and constructed a simple thermoacoustic refrigerator with an adjustable mechanical resonator, coupled with the acoustic resonator. Our experimental data showed about % 10 increase in the efficiency of the refrigeration in comparison with a simple thermoacoustic refrigerator with no mechanical resonator.

In this research longitudinal shrinkage of two steel plates with identical thickness that are joint together through butt welding and another steel plate with bead welding. This study begins withthe introduction of a model, in which the thermoelastoplastic zones near the weld line is simulated with a thermoelastoplastic flat bar, and full-elastic areas beyond the weld line is simulated with a fullelastic springs, by proposing the physical terms of the model and favorite presumptions, the related equations are solved and eventually the conclusion is a relation which can be used to calculate the amount of longitudinal shrinkage with acceptable accuracy.

The work presented in this paper is an attempt to evaluate the exhaust emission characteristics of a hydrogen-ethanol dual fuel combination with different percents of hydrogen substitutions (i.e. 0-80 % by volume and of 20 % increment) at three different compression ratios of 7:1, 9:1 and 11:1. Experimental investigations have been carried out on a computer interfaced with; four-stroke cycle, single-cylinder, compression ignition (CI) engine, which was converted to spark ignition (SI) and carburetion, to suit ethanol fuel and a provision was made at the inlet manifold of the said engine to induct hydrogen gas. The effect of hydrogen substitutions on CO, HC, NOx emissions at 7, 9 and 11 compression ratios were determined. It was found that, at 100 % load, the percentage ofhydrogen substitution varied from zero to 80 % and the NOX emissions increased by 58.62, 59.3, 62.74 % for 7, 9, 11 compression ratios respectively. When the effect of compression ratio changed from 7:1 to 11:1 the same change took place in the percentage of substitution which was a reduction of CO and HC by 30.4 and 21.67 %.