Removal of hexavalent chromium from aqueous solution by agricultural waste biomass

In the present study adsorption of Cr(VI) from aqueous solutions onto different agricultural wastes, viz., sugarcane bagasse, maize corn cob and Jatropha oil cake under various experimental conditions has been studied. Effects of adsorbent dosage, Cr(VI) concentration, pH and contact time on the adsorption of hexavalent chromium were investigated. The concentration of chromium in the test solution was determined spectrophotometrically. FT-IR spectra of the adsorbents (before use and after exhaustion) were recorded to explore number and position of the functional groups available for the binding of chromium ions on to studied adsorbents. SEMs of the adsorbents were recorded to explore the morphology of the studied adsorbents. Maximum adsorption was observed in the acidic medium at pH 2 with a contact time of 60min at 250rpm stirring speed. Jatropha oil cake had better adsorption capacity than sugarcane bagasse and maize corn cob under identical experimental conditions. The applicability of the Langmuir and Freundlich adsorption isotherms was tested. The results showed that studied adsorbents can be an attractive low cost alternative for the treatment of wastewaters in batched or stirred mode reactors containing lower concentrations of chromium.     

A general higher-order shell theory for compressible isotropic hyperelastic materials using orthonormal moving frame

The primary objective of this study is threefold: (1) to present a general higher-order shell theory to analyze large deformations of thin or thick shell structures made of general compressible hyperelastic materials; (2) to formulate an efficient shell theory using the orthonormal moving frame, and (3) to develop and apply the nonlinear weak-form Galerkin finite element model for the proposed shell theory. The displacement field of the line normal to the shell reference surface is approximated by the Taylor series/Legendre polynomials in the thickness coordinate of the shell. The use of an orthonormal moving frame makes it possible to represent kinematic quantities (e.g., the determinant of the deformation gradient) in a far more efficient manner compared with the nonorthogonal covariant bases. Kinematic quantities for the shell deformation are obtained in a novel way in the surface coordinate described in the appendix of this study with the help of exterior calculus. Furthermore, the governing equation of the shell deformation has been derived in the general surface coordinates. To obtain the nonlinear solution in the quasi-static cases, we develop the weak-form finite element model in which the reference surface of the shell is modeled exactly. The general invariant based compressible hyperelastic material model is considered. The formulation presented herein can be specialized for various other nonlinear compressible hyperelastic constitutive models, for example, in biomechanics and other soft-material problems (e.g., compressible neo-Hookean material, compressible Mooney–Rivlin material, Saint Venant–Kirchhoff model, and others). A number of numerical examples are presented to verify and validate the formulation presented in this study. The scope of potential extensions are outlined in the final section of this study.     

Improving injection efficiency of gate modulation ROIC interface for HgCdTe IR photodiodes

Microsystem Technologies - A new interface circuit for readout of HgCdTe Infrared photodiodes is proposed that can be used for efficient transfer of photocurrent from the photodiodes to the...     

Silver nanoparticle/r-graphene oxide deposited mesoporous-manganese oxide nanocomposite for pollutant removal and supercapacitor applications

Mesoporous manganese oxide was prepared by a non-ionic surfactant route using Triton X-100, followed by Ag nanoparticle (NP) and graphene oxide incorporation by an ultra-sonication-assisted process. Fine Ag NPs were incorporated into the tubular texture of mesoporous manganese oxide. The crystalline phase, particle size, and morphology of the prepared materials were characterized by X-ray diffraction (XRD), Barrett–Joyner–Halenda–Brunauer–Emmett–Teller analysis, scanning electron microscopy–energy dispersive X-ray analysis, and high-resolution transmission electron microscopy (HR-TEM). The XRD results confirmed the formation of the Mn₂O₃ phase for the as-prepared mesoporous manganese oxide and its nanocomposite. Very fine Ag NPs (<5–10 nm) were obtained. The mesoporous MnO₂ and graphene-incorporated Ag NPs/meso-MnO₂ had a tubular structure and “flaky pastry”-type morphology for the synthesized nanocomposites. HR-TEM images further confirmed the beautiful structural formation upon graphene addition and spherical/dot-shaped NP incorporation into the matrix of MnO₂. Improved surface area was obtained for the Ag NPs and graphene-incorporated mesoporous MnO₂ as compared to bulk MnO₂. The Cr(VI) removal analysis was performed using a batch technique, and enhanced removal of Cr(VI) was achieved (>98% removal of Cr(VI) within 1–2 h of reaction time) for Ag NP-incorporated mesoporous MnO₂. Efficient activity was observed because of the fine Ag NPs present in mesoporous manganese oxide, as opposed to the case of graphene oxide-doped meso-MnO₂ and pristine mesoporous meso-MnO₂.     

Tuning of asymmetrical fuzzy logic control algorithm for SPV system connected to grid

Solar Photovoltaic (SPV) cells and hydrogen fuel cells are green and efficient Distributed Energy Resources (DERs) with minimal environmental impact. Integration of DERs with conventional grid through inverters has proven to be an accepted technique for a continuous and good quality power to end users. For an efficient use of an inverter, its control algorithm plays an important role. In this paper, asymmetrical Fuzzy Logic Control (FLC) algorithm is designed, developed and simulated for a SPV system connected to the grid. In proposed asymmetrical FLC algorithm, the fuzzy functions of error input close to zero are used for fine-tuning, and the error input away from zero are used for coarse tuning. The effectiveness of the proposed control algorithm is demonstrated for controlling the PV inverter in unity power factor mode while maintaining the power quality standards and load balancing. Further, the system steady-state and transient response with the asymmetrical FLC algorithm is analyzed for linear as well as non-linear loads using MATLAB along with Simulink toolbox. Finally, a comparative analysis of asymmetrical FLC algorithm with other algorithms is presented to establish the superiority of the proposed algorithm.     

Low power VLSI architecture design of BMC,BPSC and PC schemes

Line coding is used to tune the wave form based on the properties of the physical channel. Bi-Phase Mark Coding (BMC), Bi-Phase Space Coding (BPSC) and Phase Coding (PC) are used as Line coding techniques. The first objective of the proposed work is to design Generation and Degeneration operations of BMC, BPSC and PC techniques in a single chip. The second objective is to reduce the area and power consumption, by modifying the number of MOS devices used to design the system and by adjusting the width of the MOS devices. The proposed system is designed with 59 transistors and simulated using Cadence^® 90 nm technology. This occupies 1290 µm². Required power can be reduced up to 33% by using any one of the suitable coding among BMC, BPSC and PC based on the properties of the input data signal. If the input data has equal possibility of high and low level signals, PC technique will be suitable for power reduction. If the high level beats the low level, BPSC technique will be suitable. If the low level beats the high level, BMC technique will be suitable.     

Mixing crowded biological solutions in milliseconds

In vitro studies of biological reactions are rarely performed in conditions that reflect their native intracellular environments where macromolecular crowding can drastically change reaction rates. Kinetics experiments require reactants to be mixed on a time scale faster than that of the reaction. Unfortunately, highly concentrated solutions of crowding agents such as bovine serum albumin and hemoglobin that are viscous and sticky are extremely difficult to mix rapidly. We demonstrate a new droplet-based microfluidic mixer that induces chaotic mixing of crowded solutions in milliseconds due to protrusions of the microchannel walls that generate oscillating interfacial shear within the droplets. Mixing in the microfluidic mixer is characterized, mechanisms underlying mixing are discussed, and evidence of biocompatibility is presented. This microfluidic platform will allow for the first kinetic studies of biological reactions with millisecond time resolution under conditions of macromolecular crowding similar to those within cells.     

Feasibility study for reclamation of a secondary treated sewage effluent mainly from industrial sources using a dual membrane process

A feasibility study for reclamation of a secondary treated sewage effluent mainly from industrial sources (60%) in Singapore has been conducted using a dual membrane UF-RO process. The pilot system had a treatment capacity of 2 m³/h. The UF unit and RO unit were operated at 70–80% and 40% water recovery, respectively. Six-month run for the pilot was carried out to study the stability and fouling tendency of membranes.

The characteristics of the raw feed indicated that ammonia-N was consistently high at 30–50 mg/L. Very high fluctuations in iron (0.3–3.7 mg/L), turbidity (1–27.1 NTU) and TOC (3.2–56.7 mg/L) were observed. Nitrate was low at <0.2 mg/L. The results of the study showed that dosage of alum in the UF process significantly reduced organic foulants and phosphate scalants. The polymeric RO membrane could tolerate organics from industrial wastewater and performed >96% salt rejection at the end of the study after 6 months. The study concluded the dual membrane process was capable of reclaiming the sewage effluent mainly from industrial sources for industrial use.