A multi-attribute decision making approach of mix design based on experimental soil characterization

The clay mineral composition is one of the major factors that governs the physical properties of silty sand subgrade. Therefore, a thorough knowledge of mineral composition is essential to predict the optimum engineering properties of the soil, which is generally characterized by different indices like maximum dry density (MDD), California bearing ratio (CBR), unconfined compressive strength (UCS) and free swelling index (FSI). In this article, a novel multiattribute decision making (MADM) based approach of mix design has been proposed for silty sand–artificial clay mix to improve the characteristic strength of a soil subgrade. Experimental investigation has been carried out in this study to illustrate the proposed approach of selecting appropriate proportion for the soil mix to optimize all the above mentioned engineering properties simultaneously. The results show that a mix proportion containing approximately 90% silty sand plus 10% bentonite soil is the optimal combination in context to the present study. The proposed methodology for optimal decision making to choose appropriate combination of bentonite and silty sand is general in nature and therefore, it can be extended to other problems of selecting mineral compositions.     

Insights into evolutionary trends in molecular biology tools in microbial screening for biohydrogen production through dark fermentation

Access to clean energy is vital to combat global warming and climate change, and nothing but hydrogen could better deliver it with ease to secure future energy needs. Biohydrogen could be produced in different routes including photolysis, water-gas shift reaction, dark, photo-fermentation and combination of both. Dark fermentative hydrogen production (DFHP) is efficient in comparison with photo-fermentation and utilizing organic waste ensures land usage and water for agriculture. Several microbes are involved in the process of biohydrogen production via dark fermentation and characterizing them at molecular level unveils holistic approach and understanding. Limited resources were available in terms of molecular tools for microbial characterization and this paper attempts to review the evolution of advanced molecular techniques including their merits and demerits. Understanding the composition of micro-flora is important in DFHP and could be classified as pure, co-cultures, enriched mixed cultures and mixed microbiota. These cultures act as seed sources for batch and continuous fermentations that help in understanding the efficiency of these methods. The schematics and systematic assessment of the various molecular tools (cloning, PCR-DGGE, FISH, NGS, CE-SSCP) for quantification, identification, detection and characterization of the microbial cell activity have been elaborated. Lastly, a comparative tabulation recapitulates the merits and drawbacks of each technique discussed. This provides valued information for choosing the right kind of microbial and molecular assessment tool for future characterization. Such analysis aids in suitable identification and characterization of microflora as potential biocatalysts for biohydrogen production through dark fermentation.     

Electrical impedance spectroscopic study of mandarin orange during ripening

Electrical impedance spectroscopy (EIS) as non-destructive investigation has been conducted to study the electrical impedance variations during ripening of mandarin orange. The objective of the work is to study the electrical impedance variations and variations in weight of the orange fruit with different ripening state. Electrical equivalent circuit has been modeled relative to the Nyquist plot obtained during the ripening of orange by non-linear curve fitting technique. EIS studies on orange fruit have been conducted by applying a small amount of alternating current through an array of Ag/AgCl electrodes attached to the orange fruit. The impedance and phase angles of orange fruit are measured at frequency sweep from 50 Hz to 1 MHz for 100 frequency points. The results revealed that the impedance, real part and imaginary part of the impedance all are increased and the weight of orange are decreased with the increase in ripening state. It is observed that the electrical equivalent circuit of orange fruit contains a constant phase element.     

Enhanced photoluminescence and photoconductivity of ZnO nanowires with sputtered Zn

We have sputtered Zn onto quasi-one-dimensional ZnO nanowires (NWs) in order to investigate the effect of Zn diffusion on the photoluminescence and photoconduction properties of ZnO NWs. Elemental mapping clearly indicates higher Zn concentration in the NWs due to diffusion of Zn. The Zn-sputtered NWs show an enhanced ultraviolet emission with 7 nm red shift. Since the ionization energy of Zni is 51 meV, the enhanced PL emission with a red shift is correlated to the coupling between free exciton and zinc interstitials (Zni) defects. The photocurrent transients show almost 20 times more photocurrent generation in Zn/ZnO NWs compared to the as-grown NWs. In contrast, the thin film shows no significant change in the photoluminescence and photoconductivity. Based on the photoconductivity and photoluminescence results, we predict that Zn diffusion in the NWs occurs easily compared to the films because of the smaller dimensions of the NWs.     

Reliability of ultra thin ZrO2 films on strained-Si

Ultra thin high-k zirconium oxide (equivalent oxide thickness 1.57 nm) films have been deposited on strained-Si/relaxed-Si_0.8Ge_0.2 heterolayers using zirconium tetra-tert-butoxide (ZTB) as an organometallic source at low temperature (<200 °C) by plasma enhanced chemical vapour deposition (PECVD) technique in a microwave (700 W, 2.45 GHz) plasma cavity discharge system at a pressure of 66.67 Pa. The trapping/detrapping behavior of charge carriers in ultra thin ZrO₂ gate dielectric during constant current (CCS) and voltage stressing (CVS) has been investigated. Stress induced leakage current (SILC) through ZrO₂ is modeled by taking into account the inelastic trap-assisted tunneling (ITAT) mechanism via traps located below the conduction band of ZrO₂ layer. Trap generation rate and trap cross-section are extracted. A capture cross-section in the range of 10⁻¹⁹ cm² as compared to 10⁻¹⁶ cm² in SiO₂ has been observed. The trapping charge density, Q_ot and charge centroid, X_t are also empirically modeled. The time dependence of defect density variation is calculated within the dispersive transport model, assuming that these defects are produced during random hopping transport of positively charge species in the insulating layer. Dielectric breakdown and reliability of the dielectric films have been studied using constant voltage stressing. A high time-dependent dielectric breakdown (TDDB, t_bd > 1500 s) is observed under high constant voltage stress.     

Design of Coaxial Couplers for High Efficiency Helix TWT

The main objective of the paper is to make an efficient design of the input and output coaxial coupler for a helix TWTs. An approach has been developed for the efficient design and analysis of the coaxial couplers in the practical situation. Normally multi-section impedance transformer approach is used for any wide band coupler. For a space helix TWT, coupler should be wide bandwidth and small size. In this case coupler is matched with helix slow wave structure and the standard 50-ohm connectors. The simulated return loss (dB) profile for different type of couplers is obtained by using Ansoft HFSS, CST microwave studio and compares those with experimental results. The tip loss design at sever ends for the input and the output section has been also optimized.     

Formulation and in vitro characterization of long-acting PLGA injectable microspheres encapsulating a peptide analog of LHRH

The present study aimed to formulate triptorelin acetate(TA)into poly(D,L-lactic-co-glycolic)acid(PLGA)based injectable sustained-release microspheres(TA-PLGA-MS)by usingdouble emulsion solvent extraction/evaporation(DESE)technique and investigate the effects of various material attributes and process parameters on the quality attributes such as size,shape,surface morphology,encapsulation efficiency(EE)and in vitro release behavior of these microspheres.Variable compositions of the outer water phase,type of the organic solvents,volume ratios of inner water phase to oil phase,PLGA concentrations,and the powers for emulsification in the preparation of the microspheres showed an influence on their quality attributes.An optimal formulation(F-2)obtained from this univariate approach possess an excellent EE value of 63.5%±3.4%and an average volumetric particle size of 35.3±1.8μm.This formulation was further accomplished with different solidification rates assisted by variable incubation temperatures,which exhibited an impact on the shape/surface and inner morphology of the microspheres.The resultant microspheres also displayed different in vitro release patterns.The matrices processed with a high incubation temperature conferred the fastest and the most complete drug release profile over the period of 63 days.Thus,the solidification rate could be identified as one of the critical process parameters that affected the quality of the PLGA based injectable microspheres specifically designed for the prolonged delivery of TA.     

Vertically Stacked SiGe Nanowire Array Channel CMOS Transistors

We demonstrate, for the first time, the fabrication of vertically stacked SiGe nanowire (NW) arrays with a fully CMOS compatible technique. Our method uses the phenomenon of Ge condensation onto Si and the faster oxidation rate of SiGe than Si to realize the vertical stacking of NWs. Gate-all-around nand p-FETs, fabricated using these stacked NW arrays as the channel (L_gges0.35 mum), exhibit excellent device performance with high I_ON/I_OFF ratio (~10⁶), near ideal subthreshold slope (~62-75 mV/dec) and low drain induced barrier-lowering (~20 mV/V). The transconductance characteristics suggest quantum confinement of holes in the [Ge]-rich outer-surface of SiGe for p-FETs and confinement of electrons in the core Si with significantly less [Ge] for n-FETs. The presented device architecture can be a promising option to overcome the low drive current restriction of Si NW MOSFETs for a given planar estate     

RF Behavior of Cylindrical Cavity Based 240 GHz, 1 MW Gyrotron for Future Tokamak System

In this paper, we present the RF behavior of conventional cylindrical interaction cavity for 240 GHz, 1 MW gyrotron for futuristic plasma fusion reactors. Very high-order TE mode is searched for this gyrotron to minimize the Ohmic wall loading at the interaction cavity. The mode selection process is carried out rigorously to analyze the mode competition and design feasibility. The cold cavity analysis and beam-wave interaction computation are carried out to finalize the cavity design. The detail parametric analyses for interaction cavity are performed in terms of mode stability, interaction efficiency and frequency. In addition, the design of triode type magnetron injection gun is also discussed. The electron beam parameters such as velocity ratio and velocity spread are optimized as per the requirement at interaction cavity. The design studies presented here confirm the realization of CW, 1 MW power at 240 GHz frequency at TE_46,17 mode.