International Journal of Engineering
Volume:23 Issue: 3, Dec 2010

In this paper, we have fabricated a new microphone with lateral slotted diaphragmpositioned over the back plate electrode using 8 anchors. It consists of a 3μm thick aluminum (Al) as a diaphragm, a 0.5μm as a back plate electrode and 1.3 μm thick resist (AZ1500) as a sacrificial layer on 4 inches silicon wafer. The novelty of this method relies on diaphragm which includes some lateral slots to reduce the effect of residual stress and stiffness of diaphragm for increasing the microphone sensitivity and also air damping in the gap has been reduced laterally. By this way, it is not needed to make acousticholes in back plate, thus the effective surface of diaphragm has been increased and it causes to increase the microphone capacitance. Compared with previous works, the chip size of this microphone is reduced, the complex and expensive fabrication process can be avoided and the sensitivity can be increased. The measured zero bias capacitance of microphone is 17.5 pF, and its pull-in voltage is 25 V. The capacitance of the microphone was measured as a function of the applied bias voltage using C-V analyzer. The capacitance increased with increasing bias voltage due to the decrease in the air gap thickness as the Al membrane is electrostatically pulled towards the back plate. The microphone has been tested with external amplifier and speaker, the external amplifier was able to detect the sound waves from microphone on speaker and oscilloscope. The maximum amplitude of output speech signal of amplifier is 45 mV, and the maximum output of MEMS microphone is 1.125 μV.

In this paper, a modified auto zeroed integrator is used to design and simulate a low-voltage high-Q switched capacitor pseudo 2-path filter. The filter is a sixth–order Chebyshev band-pass filter operating at sampling frequency of 1MHz and center frequency of 250 kHz with a quality factor of 50. The proposed filter has both low-voltage and high speed properties of the auto zeroed integrators and accurate center frequency of N-path band-pass filters. The operating voltage is 1.5v with no use of voltage bootstrapper circuit. Simulation is done using HSPICE and 0.25μm CMOS technology.

Ag-Cu solid solutions prepared via ball milling process were subsequently milled for 30h and investigated by X-ray diffraction technique for Cu-20%Ag, Cu-3.64%Ag and Cu-80%Ag. It was noted that the solid solubility level increased by increasing initial solute content in composition. Results showed peak positions of silver and copper changed with milling time. By heating up to 700 K, the nanocrystalline supersaturated solid solution Cu (Ag) alloy was decomposed to nanophase composite of Ag and Cu. XRD pattern showed that the grain size of Ag and Cu phases increased obviously after heating but grain size was in nanometer range. Then, ultimate compressive strength and electrical conductivity of samples were determined that Cu-20%Ag-Cu had the highest ultimate compressive strength and also the highest electrical conductivity.

In this paper, the problem of forced convection over a horizontal flat plate under condition of variable plate temperature is presented and the homotopy perturbation method (HPM) is employed tocompute an approximation to the solution of the system of nonlinear differential equations governing the problem. This paper provides good supplements to the existing literature and generalizes the previous investigation of the problem under condition of fixed plate surface temperature. It is shown that HPM is accurate and reliable with high acceleration in converging.

The growth of slant cracks by fretting fatigue of a half plane in contact with a flat rounded pad was studied. The mode I and mode II stress intensity factors for cracks of various lengths and directions were calculated using the semi-analytical method of the distribution of dislocations, and their cumulative effect on the crack growth was investigated using the strain energy density criterion. The results showed dominance of mode I fracture on crack growth, and based on the observation of strain energy density factor versus crack orientation, the results also suggest that depending on the crack length, the most critical orientations of cracks are at 00 to 200 outward the contact zone. Good agreement was observed between the results of this semi-analytical approach, and the corresponding results from finite element method, for selected crack lengths and orientations.

Fullering process is a type of open die forging. In this research, elongation and maximumsideways spread in final shape of a billet after the first blow of a fullering process are predicted by designing a back propagation multilayer perceptron neural network. Several experiments are conducted using lead as the model material. Billets with three different square cross-sections are used in these experiments. These fullering physical investigations are performed to simulate the elongation and maximum sideways spread in the final shape of the billet at the end of the first blow of the process. In addition, ring compression tests are undertaken in the quantitative determination of the friction coefficient for three kinds of lubricants. In the training of neural network width of billet, friction coefficient, height of the final shape, and die length are used as the input data. Elongation and maximum sideways spread in the final shape of the billet are the specified outputs. As a result of the specified parameters, the program is able to estimate the elongation and maximum sideways spread for any given input variables instead of time consuming experimental processes or finite element simulations.

In this investigation, a mathematical model for studying oscillatory flow of blood in astenosed artery under the influence of transverse magnetic field through porous medium has been developed. The equations of motion of blood flow are solved analytically. The analytical expressions for axial velocity, volumetric flow rate, pressure gradient, resistance to blood flow and shear stress have been derived. These expressions reveal significant alterations in blood flow due to stenosis. It is seen that magnetic field significantly controls the flow patterns. We have incorporated the magnetic field perpendicular to the flow of blood. The concept of porous medium is also taken into consideration which takes care of the suction factor. The effects of various parameters particularly magnetic number and porosity constant on the blood flow through stenosis have been examined. To validate the analytical results, numerical experiment is performed. The results obtained in the investigation are in reasonably good agreement with experimental findings existing in the literature.

In this article, we survey machine repair problems (MRP) with an emphasis on historicaldevelopments of queuing models of practical importance. The survey proceeds historically, starting with developments in 1985, when the first published review on machine interference models appeared. We attempt to elaborate some basic MRP models of the real life congestion situations. The brief survey of some notable contributions done in the area of machining system has been provided. Many concepts have been incorporated while discussing the machine repair problems under consideration. The purpose of this article is to expose queuing theorists and applied probability analysts to the real time problems that arise in machine repair modeling. This survey may also be useful for machine repair modeling to the practitioners as well as to the researchers.

Estimation of ore reserves is one of the most critical aspects of mining geology. Theaccurate assessment of the tonnage and grade of run of mine may be the difference between a healthy profitable operation and an expensive early mine closure. The first step in ore reserve estimation is to determine the boundary of ore body or ore/waste contacts. This paper presents a specific mining application to estimate ore/waste boundaries, which uses usual chemical variables. In the suggested procedure, the geostatistical method of Indicator Kriging (IK) was used to determine the boundary of ore body in Choghart iron mine of Iran. Assuming a cutoff grade in terms of the iron content mode, all data values transformed to either 1 or 0. An IK estimation of transformed data was performed. These values must always lie in the interval [0, 1], and can be interpreted as the probability that the grade is above the specified indicator. Then, the estimated probability plans were compared to the extracted plans. Results showed that blocks with the estimated probability of equal to or more than 0.85 are laid within the ore body boundary and blocks with the probability less than 0.15 should be considered as waste. This rule was then applied to the remaining ore deposit and its reserve was estimated to be about 75 million tons.

In the present paper, we have studied immunglobulin (IgG) of epileptic children,migraineous and paralytic patients. We have compared our results with normal healthy controls. We found that the bands ranges from 1151.94 to 1168.28 cm-1 due to phospholipids (P-O-C) group appear in some of the migraineous and paralytic patients only. These bands are absent in normal and epileptic patients. The vibrational energy of these phospholipid bands is almost constant and is approximately equal to 13.87kJ mole-1. The force constant is found in the range of 455.04 to 468.04 cm-1. Amide A band is intact and found in all the normal and diseased samples. Hydrocarbon, carbide and peroxide were also present in all the diseased and healthy controls. The absence of few bands in these disorders is the distinct features of these samples. Amide IV band is also found in paraplegic patient at 767.76 and 771.97 cm-1. The vibrational energy is found 9.18 kJ mole-1 and 9.23 kJ mole-1 and force constant is found 32.30 Nm-1 and 32.65 Nm-1.