Chemical Engineerng

The room temperature nitriding of titanium is accomplished by utilizing nitrogen ion beams delivered by a 2.3 kJ plasma focus discharge. Titanium samples are exposed to ions at different axial positions (3, 5, 7 and 9 cm from the focus) in order to correlate their surface properties with ion beam parameters such as energy, number density, current density and energy flux (energy deliverance per unit time per unit volume). A BPX65 photodiode detector is employed to measure the ion beam parameters by using the time of flight technique. X-ray diffraction analysis as well as field emission scanning electron microscopy along with the energy dispersive x-ray spectroscopy is carried out to explore the structural, morphological and compositional profiles of the treated samples. The results demonstrate the formation of nanocrystalline TiN thin film with surface features strongly dependent on ion beam energy flux. A Vickers microindentation measurement reveals that the surface hardness is improved 4-5 times for typical nitrided samples.

Correlation of neutron emission with plasma electron temperature in a low-energy (2.3 kJ) plasma focus is investigated. To determine the plasma temperature by continuum X-ray analysis, cobalt is selected as the filter, which discriminates the line radiation from the background impurities like carbon, nitrogen, and oxygen, or the copper of which plasma focus electrodes are made. For a pressure range of high neutron emission (1-4 mbar), the neutron yield is found to correlate with the plasma temperature. The highest temperature recorded is 5 keV at 2.5 mbar, the filling pressure for the highest neutron emission in this device.

Neutron emission from a small Mather-type plasma focus facility operated by a single 32 ~tF, 15 kV capacitor is studied. Specifically, the effects of insulator sleeve length and a "ceiling" introduced in front of the central electrode on the neutron yield and on the fluence anisotropy are investigated.

The effects of insulator sleeve length and anode length variation on the pressure range of neutron emission in a low energy plasma focus are investigated. It is found that the proper choice of the two parameters broadens the pressure range of the high neutron yield and hence improves the shot to shot reproducibility of the system. The experiment also demonstrates that the bulk of the neutrons are emitted from a region within 2 cm above the anode top and that, in turn, reflects on the nature of the dominant production mechanism.

A low-energy (2.3 kJ) plasma focus energized by a single 32-μF capacitor charged at 12 kV with filling gases hydrogen, neon, and argon is investigated as an X-ray source. Experiments are conducted with a copper and an aluminum anode. Specifically, attention is given to tailoring the radiation in different windows, e.g., 1.2–1.3 keV, 1.3–1.5 keV, 2.5–5 keV, and Cu-Kα line radiation. The highest X-ray emission is observed with neon filling and the copper anode in the 1.2–1.3 keV window, which we speculate to be generated due to recombination of hydrogenlike neon ions with a few eV to a few 10s of eV electrons. The wall-plug efficiency of the device is found to be 4%. The other significant emission occurs with hydrogen filling, which exhibits wall-plug efficiency of 1.7% for overall X-ray emission and 0.35% for Cu-Kα line radiation. The emission is dominated by the interaction of electrons in the current sheath with the anode tip. The emission with the aluminum anode and hydrogen filling is up to 10 J, which corresponds to wall-plug efficiency of 0.4%. The X-ray emission with argon filling is less significant.

A self-compensating scheme is described that eliminates the need for temperature control devices employed in many LED-based optical test and measurement instruments to ensure optical signal stability. Thermal behavior of GaAlAs LED sources is exploited to provide an optical wavelength band signal with 0.1 %P C power level stability.

Abstrucf-In general LED based dual wavelength referenced intensity-modulated optical fiber sensors do not take account of the thermal drifts of the LED source(s). An optical design concept termed wavelength thermal matching is described that can be applied to extract a pair of stable optical signals from the emission of a single LED. This strategy ensures the selection of two separate wavelength bands within which the optical signal variations due to LED thermal effects will be very similar. Hence the application of wavelength thermal matching principle in the design of a dual wavelength referenced system provides referencing effectiveness against both the optical propagation losses and the optical source fluctuations.

Linear crosstalk due to interchannel spectral overlapping in wavelength division multiplexed (WDM) systems employing spectrally-sliced LED sources is examined with the aid of a new analytical approach. Mathematical expressions are obtained that predict that, in general, the crosstalk in such WDM systems will be approximately six times the square of the channel separation expressed as a fraction of the spectral bandwidth of the channels. Experimental optical crosstalk measurements are also reported for a dual-channel spectrally-sliced LED sourced WDM system that support the theoretical predictions.

In a low energy (2.3kJ) Mather-type plasma focus with stainless steel anode, neutron and X-ray emission is investigated by employing timeintegrated and time resolved detectors. A neutron yield of 3.5 x 10' is observed, which is almost double the yield when a copper anode is used. It is speculated that a low sputtering yield of the anode material lowers the impurity concentration in the plasma and thus enhances the neutron yield. One may therefore conclude that a proper choice of electrode material is essential to achieve enhanced radiation yield from plasma focus devices. At a pressure of 2.0mbar, the neutron yield is found to be the highest and almost isotropic. Further, multiple foci are also observed. The neutron fluence isotropy and the high yield are attributed to trapping of magnetic flux lines and of energetic deuterons between the two current sheaths.

The influence of an aggressive environment (0.6 M, aerated NaCl solution) on short fatigue crack initiation and growth behaviour has been studied. The study involved three major test series, namely: air fatigue, corrosion fatigue, and intermittent air fatigue/corrosion fatigue. The above tests carried out under filly reversed torsional loading conditions at a frequency of 5 Hz, showed that it was the nonmetallic inclusions which took part in crack initiation resulting from debonding at metal matrix/inclusion interface and pitting of inclusions in both air and corrosive environments, respectively. Short fatigue crack growth results in these two environments obtained by using plastic replication technique, indicated a large effect of microstructure i.e. prior austenite grain boundaries. The stage/stages at which the environmental contribution was dominant has been discussed by considering the results achieved from intermittent tests. However, the mechanisms involved in corrosion fatigue short crack growth have also been described in the light of results obtained from further investigations carried out by conducting corrosion fatigue tests under applied cathodic potential conditions and tests on hydrogen pre-charged specimens under air fatigue and uniaxial tension conditions.

Fatigue tests have been conducted both in laboratory air and using an intermittent air/corrosion fatigue sequential cycling technique. All tests were performed on smooth specimens made from a quenched and tempered steel and subjected to fully reversed torsional loading. Crack initiation and growth behaviour was recorded using a surface replication technique. Debonding at the metal matrix/ inclusion interface appears to be the main cause of the formation of short cracks. The growth of these short cracks dominates the fatigue lifetime, being significantly influenced by the material microstructure. Empirical models for short and long crack growth were developed by employing elastic plastic fracture mechanics parameters to predict the total fatigue life of a specimen. Later, these crack growth equations derived from air fatigue tests conducted at stresses above the fatigue limit were applied to the crack growth results obtained from intermittent air fatigue/corrosion fatigue tests carried out at sub-fatigue limit stress levels. A reasonable agreement was observed between predicted and experimental crack growth rates (

ABSTRACT The structural stability, mechanical, electronic and thermodynamic properties of the cubic sodium based fluoro-perovskite NaXF3 (X=Mg, Zn) have been studied using density functional theory (DFT). The generalized gradient approximation of Perdew–Burke and Ernzerhof (GGA-PBE) is used for modeling exchange-correlation effects. In addition, the alternative form of the GGA proposed by Engel and Vosko (GGA-EV) is also used to improve the electronic band structure calculations. The results show that both compounds are stable in the cubic Pm3m structure. From Poisson׳s ratio, it is inferred that cubic anti-perovskite NaXF3 are ductile in nature and that bonding is predominantly of ionic in nature. The electronic band structure calculations and bonding properties show that anti-perovskites have an indirect energy band gap (M–Г) with a dominated ionic character. The thermal effects on thermal expansion coefficient, Debye temperature and Grüneisen parameter were predicted using the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The calculations are found to be in good agreement with other results.

A generalized dielectric constant for the electron Bernstein waves using non-Maxwellian distribution functions is derived in a collisionless, uniform magnetized plasma. Using the Neumann series expansion for the products of Bessel functions, we can derive the dispersion relations for both kappa and the generalized ͑r , q͒ distributions in a straightforward manner. The dispersion relations now become dependent upon the spectral indices and ͑r , q͒ for the kappa and the generalized ͑r , q͒ distribution, respectively. Our results show how the non-Maxwellian dispersion curves deviate from the Maxwellian depending upon the values of the spectral indices chosen. It may be noted that the ͑r , q͒ dispersion relation is reduced to the kappa distribution for r = 0 and q = + 1, which, in turn, is further reducible to the Maxwellian distribution for → ϱ.

Kelley's solution for the incompressible viscous flow past an infinite walI, with time dependent suction, is extended for an idealized elastico-viscous liquid. The effect of the presence of the elasticity on the velocity field and the skin friction is examined. It is found that the back-flow at the wall is enhanced by the elasticity parameter. The phase angle of the skin friction is also found to decrease with increasing the unsteady part of the suction velocity.

Diabetes mellitus occurs throughout the world but is more common in developed countries. More than 150 million people were found with diabetes in 2004. In 2005, there were about 20.8 million people with diabetes in United State alone. While an estimated 14.6 million have been diagnosed with diabetes, unfortunately 6.2 million were unaware that they have diabetes. To focus on the adverse effects of drugs prescribed for the treatment of diabetes mellitus, a search about data regarding side effects of drugs used in the treatment of diabetes was made using "pubmed", "medline" and "google" published during 1970 to 2011. These drugs included: insulin, metformin, glibenclamide and glimpiride. Search was made by using the terms given in "keywords" and some other terms given in article. Eighty research articles of these drugs were found. The side effects of these drugs were compared with each other to avoid duplication of data. Out of 20 articles of each drug, percentage of hypoglycemic effect produced by insulin, glibenclamide, glimpiride and metformin was 90, 80, 40 and 0%, respectively, while hypersensitivity reactions showed a percentage of 50, 15, 10 and 5%, respectively. Percentage of hepato-toxicity produced by these drugs was 0, 35, 10 and 10%, respectively. Only metformin produced lactic acidosis and vitamin B12 deficiency and percentage of these effects are 60 and 30%, respectively. It is necessary to focus on the side effects of the drugs prescribed for the treatment of diabetes mellitus.

Aiming at the exploration of herbal use by society, crude extracts of the seeds of some commonly used medicinal plants (Vitis vinifera, Tamarindus indica and Glycin max) were screened for their free radical scavenging properties using ascorbic acid as standard antioxidant. Free radical scavenging activity was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical. The overall antioxidant activity of grape seeds (Vitis vinifera) was the strongest, followed in descending order by soybean (Glycin max) and tamarind (Tamarindus indica). The seeds extract of Vitis vinifera, Glycin max and Tamarindus indica showed 85.61%, 83.45% and 79.26%, DPPH scavenging activity respectively.