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Sensitivity analysis of an in-plane MEMS vibratory gyroscope
No full textThis paper aims to put forward a detailed sensitivity analysis of an in-plane MEMS gyroscope with respect to various performance criteria that are very critical for use of the sensor in different applications ranging from platform stabilization to micro UAVs. Sensitivity analysis involves selecting key design parameters and critical performance criteria and studying the effect of variation of each design parameter on each of the performance criteria. The five key design parameters of the MEMS gyro are the drive stiffness k (d) , sense stiffness k (s) , drive mass m (d) , sense mass m (s) and the sense damping coefficient C (s) . The four critical gyro performance criteria selected are scale factor, bandwidth, resolution and dynamic range. The influence of variations in different geometric dimensions of the structure on the design parameters of the gyro is also established. The critical geometric dimensions are identified that are then suitably modified allowing faster convergence of the design to meet the desired performance specifications. This study is relevant on two counts (1) the fine tuning of the design to meet all the desired performance criteria with minimum variation in geometric dimensions and with no change in the footprint of the sensor die and (2) the influence of geometric dimensional variations induced during the fabrication of the MEMS gyro structure
Defining the Functionally Important Domain and Amino Acid Residues in Mycobacterium tuberculosis Integration Host Factor for Genome Stability, DNA Binding, and Integrative Recombination (vol 199, e00357-17, 2017)
No full textIron(III) Complexes of Vitamin B-6 Schiff Base with Boron-Dipyrromethene Pendants for Lysosome-Selective Photocytotoxicity
No full textIron(III) complexes of a vitamin B-6 Schiff base and NNN-donor ligands with pendant boron-dipyrromethene (BODIPY) moieties; namely, Fe(L1-3)(L-4,L-5)](NO3) (1-4), where L-1 is benzyl-bis(pyridin-2-yl)methyl]methanamine (bzdpa in 1), L-2 is a noniodinated BODIPY-appended dipicolylamine ligand (in 2, 3), L-3 is the diiodinated BODIPY analogue in 4, L-4 is a vitamin B-6 Schiff base, namely 3-hydroxy-5(hydroxymethyl)-4-{(2-hydroxyphenyl)imino]methyl}-2-meth ylpyridine (in 1, 3, and 4), and L-5 is 2-(2-hydroxyphenylimino)-methyl]phenol (in 2) as a nonpyridoxal Schiff base, were prepared, characterized, and their cellular localization and cytotoxic activity in light and in the dark were studied. The diiodo-BODIPY complex 4 displays remarkable photoinduced cytotoxicity in visible light (400-700 nm), with IC50 values within 0.11-0.25 mu m and about 200-fold lower dark toxicity. Complex 3, being fluorescent, was used for cellular imaging by confocal microscopy. Complex 4 shows supercoiled pUC19 DNA cleavage activity through the generation of singlet oxygen (O-1(2)) as the reactive oxygen species (ROS). Selective uptake of the complexes is observed from competitive cellular incorporation assays in cancer and noncancer cells. The complexes also show no apparent toxicity up to 100 mu m in the immortal human lung epithelial cells HPL1D in both light and the dark. Complex 3 shows preferential accumulation in lysosomes, giving a Pearson's correlation coefficient value of about 0.7
Inhomogeneous Dirichlet boundary condition in the a posteriori error control of the obstacle problem
No full textWe study a posteriori error control of finite element approximation of the elliptic obstacle problem with nonhomogeneous Dirichlet boundary condition. The results in the article are two fold. Firstly, we address the influence of the inhomogeneous Dirichlet boundary condition in residual based a posteriori error control of the elliptic obstacle problem. Secondly by rewriting the obstacle problem in an equivalent form, we derive a posteriori error bounds which are in simpler form and efficient. To accomplish this, we construct and use a post-processed solution (u) over tilde (h) of the discrete solution u(h) which satisfies the exact boundary conditions sharply although the discrete solution u(h) may not satisfy. We propose two post processing methods and analyze them, namely the harmonic extension and a linear extension. The theoretical results are illustrated by the numerical results. (C) 2017 Elsevier Ltd. All rights reserved
Deformation mechanisms and texture evolution of in-situ magnesium matrix composites containing polymer derived SiCNO dispersoids during hot compression
No full textIn-situ magnesium matrix composite was fabricated by injecting a liquid polymer directly into, and having it converted into 2.5 vol% SiCNO ceramic dispersoids, within molten Mg using a stir-casting method. The deformation mechanisms and texture evolution for these as-cast composites were investigated in a strain rate range of 10(-3) - 1 s(-1) within a temperature range of 150-350 degrees C under uniaxial compression. It was observed that the deformed composites follow a power-law creep having a stress exponent, n = 8 and activation energy, Q = 149 kJ mol(-1) which suggest that deformation mechanism is controlled by lattice self-diffusion for constant structure creep. It was found that in the range of 150-250 degrees C, with a ratio of rate of work-softening to rate of work-hardening of about 0.80, twinning induced shear bands nucleate and propagate along the direction of maximum shear stress. When the temperature approaches 350 degrees C, the plastic flow is dominated by dislocation assisted slip. Analysis of Zener-Hollomon parameter (Z) revealed that the transition from twinning into dislocation slip dominated deformation progresses at 10(13) s(-1) < Z < 10(13) s(-1). Macro-textural studies confirm that while basal plane assists deformation by twinning mechanism, the non-basal prismatic planes favor significant plastic deformation by dislocation assisted slip for the in-situ composites
Study on dynamic actuation in double microcantilever-based electrostatic microactuators with an in-house experimental set-up
No full textThis paper investigates the effect of dynamic excitation and its utility for enhancement of stable displacement range for a double cantilever-based electrostatic microactuator. A coupled electromechanical problem has been formulated using Galerkin method and solved considering dynamic actuation. The effect of excitation frequency is analyzed thoroughly to estimate the maximum stable displacement range of the actuator. Extensive studies illustrate that for suitable ac voltage-frequency combination, the maximum stable tip deflection for the cantilevers can be obtained even in the range of 50% to 90% of initial gap under specific damping. Such inherent dynamic characteristic of the actuator has been exploited here to achieve larger travel range. Furthermore, the theoretical observation has been experimentally demonstrated with a double microcantilever-based structure fabricated using silicon-on-insulator based process. The experimentation has been carried out using a developed in-house set-up. The major advantage in the present study is that unlike reported literature, the extended range has been achieved here without any additional complex circuits or design modifications. The proposed concept can be extended further to improve the displacement range of other microstructures toward different applications. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE
Tracking and Erosion Resistance of LSR and HTV Silicon Rubber Samples under Acid Rain Conditions
No full textAssessment of the material degradation in laboratory similar to field conditions is still a challenge. In the present work an attempt is made to study the effect of environment conditions in service life of polymeric insulators on tracking and erosion resistance. Evaluation of tracking and erosion resistance of Silicone Rubber insulating samples of high temperature vulcanized (HTV) rubber and liquid silicone rubber (LSR) are carried out under AC and positive polarity DC voltage. The samples are treated under normal contaminants as per IEC 60587 and acidic contaminant solution simulating acid rain. The conditions of pollution/contamination severity level are taken into consideration by maintaining the conductivity approximately 2.5 mS/cm for both solution to observe the effect of acidity alone on the samples, the acidity level is varied to understand the material behavior under acidic case with AC and DC stress application. A new experimental arrangement is set up based on IEC 60587 and ASTM D-2303 standards. The constant voltage method is employed to find the relative tracking performance of silicone rubber samples for different chemical composition. Physico-chemical analysis involving SEM, EDAX and FTIR is carried out on treated samples to understand the surface morphology and chemical changes. A comparative analysis is carried out for the acid rain solution and the standard solution of NH4Cl. Further leakage current performance and analysis is carried under both AC and DC stress
Excited state intramolecular proton transfer emission in bent core liquid crystals
No full textWe report the photophysics of two bent-core liquid crystals (BLCs), C56H67NO9 (BLC1) and C55H65NO9 (BLC2), containing a Schiff-base and two long alkyl chains at its two ends. The ground state dipole moment and the electronic structures of the BLCs were calculated using density functional theory (DFT). The dipole moments of the liquid crystals were estimated experimentally via solvatochromic shift of the absorption and fluorescence spectra. The dipole moments obtained experimentally are in quite good agreement with theoretically calculated values. In the fluorescence spectra of both the BLCs show an interesting feature, i.e., dual emission. This dual emission is explained via the presence of two tautomeric forms (keto and enol) of the BLCs in the excited state. The band at similar to 390-450 nm is assigned to the emission due to the keto-form, whereas the band at similar to 340-370 nm is due to the emission from the enol-form. Irrespective of the solvents used, the keto-band is more intense than the enol-emission-band. This intense emission from the keto-form of the tautomers is demonstrated via the excited state intramolecular proton transfer (ESIPT). From the time resolved fluorescence spectroscopy studies, a longer lifetime is obtained for the keto-band. The associated vibrational states observed in the emission spectrum are responsible for this longer lifetime. Our finding of the dual emissive nature of the liquid crystals in the visible range is potentially useful for high temperature liquid crystal display and sensing applications. (C) 2018 Elsevier B.V. All rights reserved
Magnetized advective accretion flows: formation of magnetic barriers in magnetically arrested discs
No full textWe discuss the importance of large-scale strong magnetic field in the removal of angular momentum outward, as well as the possible origin of different kinds of magnetic barrier in advective, geometrically thick, sub-Keplerian accretion flows around black holes. The origin of this large-scale strong magnetic field near the event horizon is due to the advection of the magnetic flux by the accreting gas from the environment, say, the interstellar medium or a companion star, because of flux freezing. In this simplest vertically averaged, 1.5-dimensional disc model, we choose the maximum upper limit of the magnetic field, which the disc around a black hole can sustain. In this so called magnetically arrested disc model, the accreting gas either decelerates or faces the magnetic barrier near the event horizon by the accumulated magnetic field depending on the geometry. The magnetic barrier may knock the matter to infinity. We suggest that these types of flow are the building block to produce jets and outflows in the accreting system. We also find that in some cases, when matter is trying to go back to infinity after knocking the barrier, matter is prevented being escaped by the cumulative action of strong gravity and the magnetic tension, hence by another barrier. In this way, magnetic field can lock the matter in between these two barriers and it might be a possible explanation for the formation of episodic jet
Instability Control by Actuating the Swirler in a Lean Premixed Combustor
No full textA detailed study concerning a novel, dynamic control strategy for mitigating thermoacoustic instability in a swirl-stabilized lean premixed, laboratory combustor configuration is presented in this paper. The mitigation strategy is realized by rotating the otherwise static swirler, which is primarily meant for stabilizing the lean premixed flame. The proposed strategy is tested over a range of bulk flow velocities, mixture equivalence ratios, and swirler rotation rates for validating the robustness of this concept. A prominent reduction in the fundamental acoustic mode amplitude by about 25dB is observed with this control technique for the cases that are studied. The physical mechanism responsible for the instability mitigation due to the rotating swirler is investigated by observing the distinct changes associated with the reacting flowfield using particle image velocimetry. An attempt is made to probe into the self-excited flame dynamics using high-speed intensified, chemiluminescence imaging and identifying the instability driving source locations from a spatial Rayleigh indices map. The rotating swirler induces vortex breakdown and increased turbulence intensity to decimate strongly positive Rayleigh indices regions (and eventually the acoustic energy source) to render quiet instability mitigated swirling flames