Charging damage from plasma enhanced TEOS deposition

Serious n-channel transistor hot-carrier lifetime degradation due to plasma-charging damage during PETEOS deposition is reported for the first time. Contrary to conventional wisdom, a dielectric film thickness dependent damage is observed. A new mechanism for charging-damage during plasma deposition of dielectric is proposed. This new mechanism uses photoconduction to explain why the antennae continue to charge up after a layer of dielectric is deposited on top. Some numerical estimation is provided     

Reaction Sintering of Polycarbosilane-Impregnated Compact of Silicon Carbide Hollow Particles and the Resultant Thermoelectric Properties

Porous SiC ceramics fabricated from hollow particles and polycarbosilane (PSC) are promising materials for high-temperature thermoelectric energy conversion. Reaction sintering of PCS-impregnated compacts of SiC hollow particles gave rise to porous microstructures with the hollow shape remaining. The repetition of the PCS-impregnation and sintering process resulted in only a slight increase in density but in a great improvement in thermoelectric properties.     

Instantaneous frequency of an arbitrary signal

This paper defines the non-negative pointwise instantaneous frequency (pIF) and pointwise instantaneous amplitude (pIA) of an arbitrary time signal to be the circular frequency and radius of curvature of the signal’s instantaneous trajectory on the complex plane consisting of the signal and its conjugate part from the Hilbert transform. One analytical and three computational methods are derived to prove and validate this concept. The analytical method is derived based on the definition of pIF and circle fitting. A five-point frequency tracking method is developed to eliminate the incapability of the original four-point Teager–Kaiser algorithm (TKA) for obtaining pIF of signals with moving averages. A three-point conjugate-pair decomposition (CPD) method is derived based on circle fitting using a pair of conjugate harmonic functions for frequency tracking. Moreover, the Hilbert–Huang transform (HHT) uses the empirical mode decomposition (EMD) to sift a signal’s instantaneous dynamic component from its sectional moving average (sMA) as the first intrinsic mode function, and then Hilbert transform is used to compute the first IMF’s frequency and amplitude as the sectional instantaneous frequency (sIF) and sectional instantaneous amplitude (sIA). Because finite difference is used in the five-point TKA, its accuracy is easily destroyed by noise. On the other hand, because CPD uses a constant and a pair of windowed regular harmonics to fit data points and estimate pIF and pIA, noise filtering is an implicit capability of CPD and its accuracy increases with the number of processed data points. Numerical simulations confirm that pIF and pIA are non-negative and physically meaningful and can be used for frequency tracking and accurate characterization of complex signals. However, sIF and sIA from HHT are more useful for system identification because the IMFs sifted by EMD often correspond to actual vibration modes.     

Stability of tri-taper journal bearings under dynamic load using a non-linear transient method

Stability of a tri-taper journal bearing which is subjected to steady, periodic and variable rotating loads is studied theoretically using a non-linear transient approach. The hydrodynamic forces are initially obtained by solving the Reynolds equation, satisfying the Reynolds boundary conditions. Further, the transient behavior of rotor bearing system is predicted by substituting these hydrodynamic forces in the equations of motion and then solving them by fourth order Runge Kutta method. Stability of the rotor bearing system is determined from the journal locus. Comparative studies predict that the dynamic performance is superior for a bearing with high ramp size and aspect ratio.     

柔性MEMS衬底材料及其在传感器上的应用

概述了MEMS器件衬底材料的功用及分类(刚性材料和柔性材料)。根据其使用柔性衬底材料的不同,将其分为有机聚合物材料(聚酰亚胺、硅橡胶、聚对苯二甲酸乙二醇酯和聚对二甲苯、硅树脂)和金属及陶瓷材料(不锈钢和氧化铝)。重点阐述了材料的特性,并结合国内外专家学者的研究,例举了其在MEMS传感器方面的应用,分析了它们的特点及优越性。指出在MEMS器件衬底材料领域,对柔性材料和新型Si基材料的研究与开发是未来研究工作的重点和热点。     

Effect of PP-g-MAH compatibilizer content in polypropylene/nylon-6 blends

A method commonly used to induce compatibility between polyamides and polyolefins is by chemical modification of the polyolefins. This concept has been employed to produce compatibilized blend of nylon 6 (N6) and polypropylene copolymer (PPCP) by adding maleic anhydride grafted polypropylene (PP-g-MAH) as a third component. The blends of N6, PPCP and PP-g-MAH were prepared using a twin screw extruder. TEM of the blends revealed better dispersion and reduction in the size of the dispersed phase. In case of N6 rich blends, about 25% increase in tensile strength was observed with just three phb of PP-g-MAH. The maximum impact strength and flexural modulus were observed at around 30% PPCP. The incorporation of PP-g-MAH increased the flexural modulus of N6/PPCP blends significantly.     

Simulation of a System of Product Knowledge Based on Catalog-Assisted Design

Conceptual models for catalog-assisted design are developed to improve semantic modeling in the automation of design problems and the extraction of knowledge from engineering documents. The conceptual models are presented graphically.     

Maximum temperature rise of fire plume ejected out of the compartment window with a horizontal eave

This study focuses on the maximum temperature rise of fire plume ejected out of the compartment window with a horizontal eave. Based on the symmetry of ejected plume and pictures recorded by the cameras in the study, the shape of ejected thermal plume out of the window under the eave is suggest as an isosceles trapezoid, and the ejected thermal plume rising at the edge of the eave is assumed to be a rectangular fire source. The dimensions of the rectangular fire source are theoretically deduced for compartment fire process of different window geometry, width of eave, and heat release rate, according to the conservation of plume mass. The previous predictive model for plume temperature proposed by Quintiere is popularized to the ejected flame above an eave by including the dimensions of the rectangular fire source as well as the width of eave. The results would provide theoretical guidance to the application of fireproof eave in high-rise building for fire protection designs.     

Lab scale optimization of various factors for photocatalytic hydrogen generation over low cost Cu0.02Ti0.98O2-δ photocatalyst under UV/Visible irradiation and sunlight

We have demonstrated earlier that maximum H₂ generated @ 1.167 l/h/m² over Cu_0.02Ti_0.98O_2-δ photocatalyst with apparent quantum efficiency, AQE of 7.5% and solar fuel efficiency, SFE of 3.9% under sunlight. With an aim to scale-up the solar photocatalytic hydrogen process to pilot plant, optimization studies at lab scale as well as in upscaled photoreactors were performed over Cu_0.02Ti_0.98O_2-δ, photocatalyst under UV/visible and sunlight. Cu_0.02Ti_0.98O_2-δ was synthesized by facile sol-gel route and characterized by relevant techniques. Several operational parameters were investigated in order to finalize the conditions which are most favourable for photocatalytic hydrogen yield. Factors such as photocatalyst loadings, v/v concentration of sacrificial reagent, replacement of methanol by industrial waste glycerol, role of different configuration of light source with reactor, effect of stirring during the photocatalytic reaction, effect of fluctuations of solar flux at hourly basis, illumination area on hydrogen yield were studied. Contribution of each factor in determining the hydrogen yield was quantified. Relative standard deviation in hydrogen yield as a function of each factor was estimated. Our findings suggest that in addition to catalyst loadings and sacrificial reagent, improved dispersion of photocatalyst obtained by stirring the reaction mixture in horizontal geometry resulted in enhanced H₂ yield. Hydrogen yield obtained at lab scale can be appropriately extrapolated with respect to illumination area instead of weight of photocatalyst. A relative standard deviation (RSD) of ± 3.82% and ± 4.53% in H₂ yield was calculated for sunny and cloudy days in time zone of 10.30–16.30 h IST. Deviation of H₂ yield was more on cloudy days and beyond 16:30 h. These studies have provided a daily window of 11:00–15:00 h to be utilized throughout the year for a commercial scaled up process, prohibiting the illumination during less productive hours of the day for shaping the improved economics of solar hydrogen generation. Our results obtained at lab scale would be useful to perform sunlight driven scaled –up photocatalytic process using low cost visible light efficient photocatalyst, Cu_0.02Ti_0.98O_2-δ.