Characterization,dielectric and electrical behaviour of BaTiO3 nanoparticles prepared via titanium(IV) triethanolaminato isopropoxide and hydrated barium hydroxide

A new sol-precipitation technique for the preparation of nano BaTiO₃ crystallite has been developed by reacting 0·2 M each of Ti(IV) triethanolaminato isopropoxide and hydrated barium hydroxide in methanol such that the molar ratio of Ba : Ti is 1·02 at 80 °C under stirring (1200 rpm) for one hour in alkaline media using tetra methyl ammonium hydroxide (TMAH). It was calcined at 100 °C for 12 h. Structural and compositional properties were investigated by XRD, SEM, EDX, TEM, SAED and DLS techniques. FT–IR and TG–DTA were used to characterize its purity and the thermal stability. The BaTiO₃ particles prepared were found to be spherical, homogeneous and cubic in structure. The particle size was found to be 23–31 nm. The dielectric constant and dissipation factor after sintering at 400 °C were 5379 and 0·63, respectively at 100 Hz frequency. The a.c. conductivity (σ _a.c.) was found to be 2 × 10^–5 S-cm^–1 at room temperature (30 °C). It increased with increasing temperature up to 50 °C and decreased with further increase in temperature. The impedance was 3·37 × 10⁵ ohms at room temperature. It decreased with increasing frequency.     

Comparative study of natural calcium stilbite and magnesium exchanged stilbite for ethanol sensing

Natural stilbite (Ca-stilbite) zeolites have been collected from the queries near Pashan area, Pune, Maharashtra, India. The calcium ions in the Ca-stilbite structure are partially exchanged by magnesium ions using ion exchange process. The Ca-stilbite and Mg- stilbite samples are characterized by XRD, EDS, FTIR and TG/DTA techniques and are used as the functional materials for the preparation of thick films using screen printing technique. The screen printed films, deposited on glass substrates, are then sintered at 650 °C for proper adhesion to take place. These thick films are used as sensors to test ethanol. The XRD profiles and FTIR spectra reveal that the sensor material is a stilbite zeolite. EDS data shows that the magnesium ions are exchanged in the stilbite structure. TG/DTA study shows the thermal behavior of the samples wherein the structural breakdown occurs at 520 °C and weight loss due to desorption of water molecules can be revealed by exo & endo peaks. Ethanol sensing studies show that both the Ca-stilbite and Mg-stilbite films are sensitive to ethanol. In case of Mg-stilbite films, the operating temperature and ethanol response are found to be dependent on magnesium concentration. Lower the magnesium concentration lower is the operating temperature and higher is the ethanol sensitivity. Mg-stilbite films with specific concentration (0.05 M) shows the consistent ethanol sensing performance in comparison to Ca-stilbite film wherein response to ethanol decreases after repetitive use. The study reveals that Mg-stilbite thick film (0.05 M) is stable ethanol sensor which can be operated at 65 °C with reproducible characteristics.     

Multiple bandgap combination of thin film photovoltaic cells and a photoanode for efficient hydrogen and oxygen generation by water splitting

The objective of this research is to develop cheaper and more efficient photoelectrochemical (PEC) cells for the production of highly pure hydrogen and oxygen by water splitting. FSEC PV Materials Lab has developed PEC set up consisting of two thin film photovoltaic (PV) cells, a RuS₂ photoanode for efficient oxygen evolution and a platinum cathode for hydrogen evolution. A p-type transparent-conducting layer is prepared at the back of PV cell to transmit unabsorbed infrared photons onto the photoanode for efficient oxygen evolution. This paper presents the preparation and characterization of p- type ZnTe:Cu transparent conducting back layer and PEC cell.     

Characterization of Ti schottky diodes on epi-regrown 4H-SiC

The electrical characteristics of Schottky diodes fabricated on n-type epi layers regrown over an n-drift layer and regrown over a drift layer with selective boron-implanted p-type regions have been evaluated and compared to those on virgin, as-grown commercial epi-drift layers. Slightly lower (0.1–0.2 eV) Schottky barrier heights and larger ideality factors (1.2 vs. 1.03) were extracted for the regrown diodes from forward current-voltage and capacitance-voltage measurements. Although more than 1–2 orders higher reverse leakage current were also observed, our epi-regrowth process is still considered adequate for novel power device realization.     

Experimental determination of axial compressive strength of crimped cold-formed channels

This paper presents experimental axial compressive failure loads of 33 cold-formed regular channels and 51 cold-formed crimped channels varying in sizes, lengths, and end conditions. Strain gauges and mechanical dial gauges were used during the centering of the specimens in the test frame. For some specimens, the failure loads of regular channels were greater than those of the crimped channels. In other cases, the crimped channels were stronger. Therefore, statistical analysis (Student's t-test) was carried out and the null hypothesis that there is no difference between the compressive strength of regular and crimped channels was accepted at 0.01 significance level. Thus, the compressive strength of crimped channels can be calculated using the formulas applicable for regular channels.     

Comparison of the single-bubble-class and modified two-bubble-class models of bubble column reactors

Gas phase conversions and product selectivities predicted by the single-bubble-class and modified two-bubble-class models of bubble column reactors are compared for a multistep gas-liquid reaction involving series/parallel steps. A situation is considered where the first reaction step is fast and occurs in the interfacial region while the other reaction steps are slow and occur only in the liquid bulk. Equivalent hydrodynamic and transport parameters provide a common basis for the comparison. The differences in the gas phase conversions predicted by these models are insignificant. However, the two models predict very different values of selectivities for the intermediate products. This analysis enables us to judge the range of applicability of the single-bubble-class model in design and scale-up of bubble column reactors.     

A linear rate control model for better target buffer level tracking in H.264

An improved rate control scheme with better buffer level tracking and more accurate mean absolute difference (MAD) prediction for H.264 video encoding is proposed in this work. Compared to the existing H.264 rate control scheme, the proposed scheme gives better buffer regulation with improved peak signal-to-noise ratio for basic unit level rate control. The bits required for encoding header information account for a significantly high percentage of the total bits, especially at lower bit rate and for low motion sequences. A linear relation between coded mean absolute difference and header bits is proposed for achieving effective rate control. The proposed scheme estimates the mean absolute difference adaptively from temporally colocated regions and INTER16x16 mode decision process. The estimated mean absolute difference is then used for calculating the quantization parameter for better target matching. A new linear rate control model is proposed, which works well especially for low motion sequences. The experimental results show that the proposed improvement in rate control algorithm significantly reduces the difference between actual and target buffer level while improving the quality of encoded video sequences.     

High-throughput biomarker segmentation on ovarian cancer tissue microarrays via hierarchical normalized cuts

We present a system for accurately quantifying the presence and extent of stain on account of a vascular biomarker on tissue microarrays. We demonstrate our flexible, robust, accurate, and high-throughput minimally supervised segmentation algorithm, termed hierarchical normalized cuts (HNCuts) for the specific problem of quantifying extent of vascular staining on ovarian cancer tissue microarrays. The high-throughput aspect of HNCut is driven by the use of a hierarchically represented data structure that allows us to merge two powerful image segmentation algorithms-a frequency weighted mean shift and the normalized cuts algorithm. HNCuts rapidly traverses a hierarchical pyramid, generated from the input image at various color resolutions, enabling the rapid analysis of large images (e.g., a 1500 × 1500 sized image under 6 s on a standard 2.8-GHz desktop PC). HNCut is easily generalizable to other problem domains and only requires specification of a few representative pixels (swatch) from the object of interest in order to segment the target class. Across ten runs, the HNCut algorithm was found to have average true positive, false positive, and false negative rates (on a per pixel basis) of 82%, 34%, and 18%, in terms of overlap, when evaluated with respect to a pathologist annotated ground truth of the target region of interest. By comparison, a popular supervised classifier (probabilistic boosting trees) was only able to marginally improve on the true positive and false negative rates (84% and 14%) at the expense of a higher false positive rate (73%), with an additional computation time of 62% compared to HNCut. We also compared our scheme against a k-means clustering approach, which both the HNCut and PBT schemes were able to outperform. Our success in accurately quantifying the extent of vascular stain on ovarian cancer TMAs suggests that HNCut could be a very powerful tool in digital pathology and bioinformatics applications where it could be used to facilitate computer-assisted prognostic predictions of disease outcome.