Rheological studies on Streptomyces fradiae ScF-5 in submerged fermentation

Studies on the rheology of Streptomyces fradiae ScF-5 in a 10-dm³ submerged fermenter for the production of intracellular glucose isomerase revealed that the apparent viscosity of the broth increased with increase in cell density up to 24 h and then declined while the density of the broth remained constant. The plot of shear stress versus shear rate at various fermentation periods showed the applicability of the Casson model. The yield stress and consistency index were found to increase gradually then decrease subsequently. In contrast, the flow behaviour index was less than unity and remained constant throughout the fermentation. The results contrast with the findings of other workers on the Newtonian and non-Newtonian character of fermentation broths and the applicability of the power law model to such systems.     

Photoconductivity of chemically deposited rare-earth-doped CdS films

Highly photosensitive films with photocurrent to dark current ratios of the order of 10⁵ have been prepared by doping CdS with Nd and Pr. The conditions for preparing such films with different fluxes are described and results of excitation spectra, transmission spectra and rise-decay curves are presented. Values of trap depths are also calculated.     

Dielectric and microstructural behaviour of strontium titanate borosilicate glass ceramic system

65(SrO·TiO₂)−35(2SiO₂·B₂O₃) wt% glass was synthesized. Differential thermal analysis study shows one exothermic peak which shifts towards higher temperature with increasing heating rate. Glass ceramics prepared by controlled crystallization of strontium titanate borosilicate glass produce uniform distribution of crystallites in a glassy matrix. Attempt was made to crystallize strontium titanate phase in this glass ceramic. Different phases precipitated out during ceramization have been identified by X-ray diffraction. It appears that due to high reactivity of SrO with B₂O₃, strontium borate crystallizes as principal phase followed by TiO₂ (rutile) and Sr₃Ti₂O₇ phases. Dielectric constant of these glass ceramics was observed to be more or less temperature independent over wide range of temperatures with low values of dielectric constant and dissipation factor.     

Surface film characteristics of Al-Li-Cu-Mg alloys in 0·1 N NaOH

The nature of surface films that form under free corrosion conditions, and their effect on the subsequent polarization behaviour of an Al-1·90Li-1·80Cu-1·00Mg-0·09Zr alloy in 0·1 mol/l NaOH solution at 35°C have been studied. The variation of open circuit potential (OCP) as a function of time is characteristic for the alloy in the electrolyte. It initially changes in the noble direction with the surface of the specimen being enveloped by a black coating, and, later, when the black coating is punctured at some localized regions, the OCP shifts and stabilizes at an active value of −1450 mV vs saturated calomel electrode (SCE). X-ray diffraction analysis of the surface film layer indicates that it consists of essentially lithium aluminum hydroxide at shorter immersion time, and lithium aluminum hydroxide and copper hydroxide after longer immersion time in the electrolyte. The scale morphology as a function of immersion time has also been studied by scanning electron microscopy. Polarization experiments conducted after 2 and 15 h of immersion revealed that the alloy exhibited active-passive type polarization behaviour in both the cases. The polarization behaviour of the specimen immersed for longer times has been explained by considering Cu ennoblement on the surface. It was also observed that the hydride LiAlH₄ forms on the surface regions of the alloy under free corrosion conditions.     

Shock-induced martensitic transformations in near-equiatomic NiTi alloys

Shock-impact generated tensile-stress pulses were used to induce B2-to-monoclinic martensitic transformations in two near-equiatomic NiTi alloys having different martensite transformation start (M _s ) temperatures. The NiTi-I alloy (M _s ≈+27 °C) impacted at room temperature at 2.0 and 2.7 GPa tensile stress-pulse magnitude, showed acicular martensite morphology. These martensite needles had a substructure containing microtwins, typical of “stress-assisted” martensite. The NiTi-II alloy (M _s ≈−45 °C) showed no martensite formation when shocked with tensile-stress pulses of 2 GPa. For tensile stresses of 4.1 GPa, the alloy showed spall initiation near the region of maximum tensile-stress duration. In addition, monoclinic martensite needles, with a well-defined dislocation substructure, typical of “strain-induced” martensite, were seen clustering around the spall region. No stress-assisted martensite was formed in this alloy due to its very low M _s temperature. The present article documents results of the use of a metallurgical technique for generating large-amplitude tensile stress pulses of finite duration for studies of phase transformations involving changes from a high density to a low density state.     

A novel parallel prefix adder for optimized Radix-2 FFT processor

Multidimensional Systems and Signal Processing - The Fast Fourier Transform (FFT) is the basic building block for DSP applications where high processing speed is the critical requirement. Resource...     

A fast-sensing readout circuit in 240 Hz enabled by code division multiple access (CDMA) implemented for an ultra-thin on-cell flexible capacitive touch panel

A new fast readout circuit employing the known coding scheme of code division multiple access (CDMA) is successfully designed and applied to a 7-inch ultra-thin, flexible on-cell touch screen panel (TSP). The adopted CDMA is known originally as a coding scheme for data communication, which is applied in this study to address the sensing electrodes of the ultra-thin flexible touch panel. Due to the orthogonality between the driving signals to the touch panel coded by Walsh transform, one type of CDMA, the interference noises between sensing electrodes can be reduced effectively to render accurate touch sensing results. The electromagnetic interference from the flexible display can also be filtered out as baseline component in the output signal. And the frame time of touch reporting can be substantially shortened. Following the sensing electrode is a new readout designed of the switched-capacitor (SC) circuit, to avoid distributing sample signals from parasitic capacitance and also to enlarge the voltage changes due to the capacitance changes caused by touches. A 12-bit analog-to-digital converter (ADC) is orchestrated after the SC circuit to transform the front-end analog signal to digital codes. The digital part of the designed readout adopts a correction algorithm to eliminate the background signals from the display, and also a moving average algorithm to minimize the higher-frequency noises from the display and other electrodes. Experiments are conducted to validate the expected performance. It is evidenced that the Walsh code driving algorithm improves the quality of the readout output signal to be in 42 dB SNR, the report rate to a fast 240 Hz, and a power consumption of 0.39 mW by each sensing channel.

     

Real-time monitoring of vehicle’s movement and damage avoidance cum repair system using Web Service Negotiation

Microsystem Technologies - The use of the automobiles increased tremendously in the last two decades, hence the vehicle collision and its impact emerged as the major problem, as safety of...