Oxidation of Fe-C alloys in the temperature range 600–850°C

The oxidation behavior of Fe-C alloys in the temperature range 600–850°C has been studied. CO ₂ evolved during oxidation was measured using an infrared gas analyzer. The presence of C lowers the oxidation rate relative to that of pure Fe and this has been related to the rejection of carbon at the alloy-scale interface causing poor contact between scale and alloy. As a result, the scale contains a higher proportion of magnetite, which reduces its overall growth rate. Very little carbon is lost to the atmosphere. The ease with which the rejected carbon is incorporated into the alloy depends on the alloy structure.     

Surface crystalline phases and nanoindentation hardness of explanted zirconia femoral heads

One new and nine explanted zirconia femoral heads were studied using glancing angle X-ray diffraction, scanning electron microscopy, and nanoindentation hardness techniques. All starting zirconia implants consisted only of tetragonal zirconia polycrystals (TZP). For comparison, one explanted alumina femoral head was also studied. Evidence for a surface tetragonal-to-monoclinic zirconia phase transformation was observed in some implants, the extent of which was varied for different in-service conditions. A strong correlation was found between increasing transformation to the monoclinic phase and decreasing surface hardness. Microscopic investigations of some of the explanted femoral heads revealed ultra high molecular weight polyethylene and metallic transfer wear debris.     

Robust Data Hiding in Audio Using Allpass Filters

A novel technique is proposed for data hiding in digital audio that exploits the low sensitivity of the human auditory system to phase distortion. Inaudible but controlled phase changes are introduced in the host audio using a set of allpass filters (APFs) with distinct parameters of allpass filters, i.e., pole-zero locations. The APF parameters are chosen to encode the embedding information. During the detection phase, the power spectrum of the audio data is estimated in the z-plane away from the unit circle. The power spectrum is used to estimate APF pole locations, for information decoding. Experimental results show that the proposed data hiding scheme can effectively withstand standard data manipulation attacks. Moreover, the proposed scheme is shown to embed 5-8 times more data than the existing audio data hiding schemes while providing comparable perceptual performance and robustness     

Engineering Interface Composition for Passivation of HgCdTe Photodiodes

A compositionally graded surface layer has been created for the passivation of Hg_1-xCd_xTe photodiodes. The graded CdTe-Hg_1-xCd_xTe interface was created by deposition of CdTe and subsequent annealing. It was found that the composition gradient and width of the graded region could be tailored by adopting a suitable annealing procedure. The effect of grading on the interface electrical properties and photoelectrical properties was studied by X-ray photoelectron spectroscopy (XPS), photoconductive decay, and C-V measurements. Insulator fixed-charge density and interface-trap density could be reduced to 3times10¹⁰ cm ^-2 and 2times10¹⁰ cm^-2middoteV^-1, respectively, by creating a graded interfacial composition. The interface conditions so engineered led to a low surface recombination velocity ~3000 cm/s. A direct correlation has been established between the process conditions, interfacial composition, and the electrical/photoelectrical properties of the CdTe-Hg_1-xCd_xTe heterostructures. The passivation layer formed by this method is shown to be suitable for the fabrication of high-performance infrared detectors     

The method of lines applied to crack problems including plasticity effect

To seek stress and strain distributions in flawed structures, the governing equations in elasto-plasticity are first derived in terms of displacement increments. The method of lines is then applied to derive the sets of ordinary differential equations with appropriate boundary conditions. Their solutions are sought along continuous lines of a discretized region. They are solved by a combination of power series and modal matrix method. A step by step integration is devised to determine the displacements at nodal points. Non-linear work-hardening is taken care of by the effective stress and strain approach. The cases of uncracked and cracked hollow cylinders of finite length under axisymmetrical loadings are studied in detail. The growth of plastic zone, crack-opening displacement and J-integral along various paths are illustrated.     

Hydrodynamic and micellar properties of sodium alkyl benzene sulphonates

This paper provides hydrodynamic data and micellar properties of some sodium alkyl benzene sulphonates. The free energy of micellisation. as deduced from experimental data, is compared with that calculated from the structural parameters and shows that these sulphonates form spherical and ellipsiodal micelles in aqueous medium. The ease of micellisation and micelle size increases as one goes from sodium decyl to sodium hexadecyl benzene sulphonates. The solubilisation data of n-octane and ethyl benzene in aqueous sodium alkyl benzene sulphonate solutions above the cmc indicates that aliphatic hydrocarbons when solubilised reside within the micellar core whereas aromatic hydrocarbons reside in the micellar core as well as in the annular space between hydrodynamic shear surface and surface of the micellar core,     

Capacitance Requirements for Isolated Self Excited Induction Generators

Capacitance requirements for isolated self excitd induction generators are discussed. It is shown that numerical methods based upon the steady state as well as operational equivalent circuit give similar predicted values. An analytical method is proposed to compute, Cmin, the minimun capacitance value required for self excitation under no load conditons. It is shown that Cmin is inversely proportional to the square of the speed. Furthermore, it is inversely proportional to the maximum saturated magnetizing reactance. The theoretical results are verified experimentally for a number of test machines and a good agreement is observed between the theoretical and the experimental values. The influence of load impedance and its power factor on the terminal capacitance required to maintain self excitation under steady state is also examined and it is shown that when machine is loaded, the terminal capacitance should be several times that required at no load. Furthermore, the influence of terminal capacitor upon the maximum available output power fron isolated induction generators is also examined.     

Critical micelle concentration of lauric acid-diethanolamine condensate by polarographic and spectrophotometric methods: A comparative study

The critical micelle concentration (cmc) values of surfactants obtained by different physical methods do not show any concordance especially in cases when determinations are made in presence of electrolytes. With lauric acid-diethanolamine condensate, the behavior is altogether different. A comparison of the spectrophotometric and polarographic determinations, with and without the presence of extraneous electrolytes reveals that the cmc values in both cases are almost similar. The results indicate that the cmc values of nonionic surfactants are not affected by acids, bases and salts when added in low concentrations.     

Interactions of "ultra-low" doses of naltrexone and morphine in mature and young male and female rats

Sex and age influence morphine analgesia in humans and animals. Mature rats show greater morphine analgesia in males than in females. Ultra-low doses of naltrexone enhance morphine analgesia. In mature rats (18-22 weeks), naltrexone (0.002-2.0 mg/kg)-morphine (2 mg/kg) cotreatment enhanced morphine analgesia in females, an effect inversely related to naltrexone dose. Conversely, in mature male rats, naltrexone tended to decrease morphine analgesia with increasing dose. In young rats (8-10 weeks), morphine analgesia was unrelated to sex and in both sexes the naltrexone-morphine interaction was negligible. These data show that dose, age, and sex alter the naltrexone-morphine interaction in rats.     

The stability of 100 ppb hydrogen sulfide standards

An experimental study has been performed to determine the factors affecting the stability of hydrogen sulfide calibration mixtures at concentrations below 1 ppm. Quantitative data was obtained that illustrates that material selection and surface treatment are major factors affecting the shelf life of low concentration reactive gas mixtures. With the proper material selection and surface treatment, hydrogen sulfide and carbonyl sulfide standard mixtures on the order of 50-100 ppb can be maintained for at least 18 months.