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This paper contains the comparative study of elasto-mechanical, electronic and optical properties of pyrochlores. These structures are first optimized and second order-independent cubic elastic constants C11, C12and C44are computed using the optimized data. These computed cubic elastic constants are further used to check the mechanical stability, Poisson's ratio, Pugh's ratio and Cauchy pressure which depicts the flexible and ductile nature of both materials. Kleinman ratio is more significant for La2Zr2O7, so it has excellent bond stretching minimization phenomena. Young's modulus and lame's constants describe that Nd2Zr2O7is stiffer and difficult to compress than La2Zr2O7. Debye temperature and sound velocities are also calculated for both oxides. Due to the high melting temperature, Nd2Zr2O7is suitable for high-temperature environments and is used in aerospace and construction industries. Band structures reveal that these oxides are metallic as there appears no gap in electronic dispersion relations. Analysis of the density of states reveals the magnetic nature of these oxides as the density of states is not the perfect image of each other in both spin channels. The imaginary part of the dielectric function also shows the optically metallic nature and suitability for sensors and opto-electronic devices.

The objectives of this paper are twofold: (1) to present a new method of approximation such that the function and some of its derivatives are simultaneously approximated; and (2) to investigate the potential applications of this new method in the field of satellite geodesy by deriving a numerical solver of ordinary differential equations. To fulfill both the objectives, Sobolev polynomials are used. Explicit formulas for these polynomials are presented. A quadrature rule is derived based on the explicit forms of these polynomials. Solution of first order ordinary differential equations is presented based on the numerical integration method by the new quadrature rule. To present the applications of the results, three problems are investigated in the field of satellite geodesy. In the first application, orbit propagated by the numerical solution of orbital equations is compared with the Keplerian motion. It is shown that the new method for solving ordinary differential equations can be used alongside any other method, including the adaptive Runge-Kutta and Adams-Bashforth-Moulton integration methods. The comparison of this new method with the adaptive Runge-Kutta, Adams-Bashforth-Moulton, and the powerful and newly established adaptive Gaussian numerical integration methods reveals that it is at least 580, 666667, and 72 times more accurate than the mentioned methods, respectively, in any given absolute tolerance and time increment. The method is fast, stable, consistent, and capable of handling high accuracy, even with large time increment and low absolute tolerance, which is shown in this application. In the second application, the Gravity Recovery and Climate Experiment (GRACE) satellites' orbits are propagated using both the Ensemble Kalman Filter (EnKF) with stochastic updates and smoothing for the position and the Sobolev numerical integration. The orbits are then compared with the observed positions of the satellites. It is shown that the Sobolev polynomials work better in this problem, being more than 2 times more accurate. In the third application, the precision orbit determination problem for the Low Earth Orbit (LEO) CubeSats is investigated in the reduced dynamic form. A case study is presented for a pico-nano CubeSat in China. It is shown that the reduced dynamic orbit is approximately 32 percent more accurate than either of the kinematic or static Precise Point Positioning (PPP),representing a maximum error of 3.4 cm, with respect to the observation of the ground tracking stations.

Hybrid-resonant switched-capacitor (SC) converters have gained traction as a way to increase efficiency and power density in high conversion ratio dc-dc applications. However, there is still room to improve passive component utilization and performance by exploiting resonant behavior and the unique circuit networks in hybrid topologies. This article explores a nominally 3:1 step-down resonant SC dc-dc converter that uses a high-Q multiphase LC resonator. The resonator combines flying capacitors and inductor(s) into a single component, leveraging advantages of each to improve the performance (efficiency and power density) of the overall structure. A hardware prototype is presented that achieves over 97% efficiency at >100 W in a 48-V:16-V step-down configuration. The prototype is used to highlight an interesting direction for future research in intermediate-bus converters for data center applications.

This paper is aimed at the derivation of a discrete data smoothing function for the discrete Dirichlet condition in a regular grid on the surface of a spheroid. The method employed here is the local L2−semi-norm minimization, through Euler-Lagrange method, for the Beltrami operator. The method results in a weighted average of the surrounding points in a template based on the first order Taylor expansion of the unknown function under consideration. The coefficients of the weighted average are calculated and used to smooth the Geoid height data in Iran, derived from the EGM2008 geopotential model.

This paper is aimed at introducing the concept of Spherical Interpolating Moving Least Squares to the problems in geodesy and geophysics. Based on two previously known methods, namely Spherical Moving Least Squares and Interpolating Moving Least Squares, a simple theory is formulated for using Spherical Moving Least Squares as an interpolant. As an application, a case study is presented in which gravity accelerations at sea surface in the Persian Gulf are derived, using both the approximation and interpolation mode of the Spherical Moving Least Squares. The roles of the various elements in the methods-weight function, scaling parameter, and the degree of spherical harmonics as the basis functions-are investigated. Then, the results of approximation and interpolation are compared with the field data at sea surface, collected by shipborne gravimetry approach. Finally, the results are compared with another independent interpolation method-spline interpolation. It is shown that in this particular problem, SMLS approximation and SIMLS interpolation present a better accuracy than spherical splines.

In this paper an introduction of the moving least squares approach is presented in the context of data approximation and interpolation problems in Geodesy. An application of this method is presented for geoid height approximation and interpolation using different polynomial basis functions for the approximant and interpolant, respectively, in a regular grid of geoid height data in the region 16.0417∘≤ϕ≤47.9583∘and 36.0417∘≤λ≤69.9582∘, with increment 0.0833∘in both latitudal and longitudal directions. The results of approximation and interpolation are then compared with the geoid height data from GPS-Levelling approach. Using the standard deviation of the difference of the results, it is shown that the planar interpolant, with reciprocal of distance as weight function, is the best choice in this local approximation and interpolation problem.

Herein, we introduce the application of nickel hydroxide nanosheets on the electro-etched carbon fiber (ECF) formed via a direct electrodeposition, for fabrication of asymmetric supercapacitor. To confirm the practical applicability of prepared Ni(OH)2–ECF, an asymmetric device was assembled using Ni(OH)2–ECF in combination with an activated carbon (AC) electrode. Our results showed a substantial cycling stability (96% capacitance retention after 10000 cycles) and considerable rate capability at large discharge currents (60% capacitance retention at 8 A g− 1) for this asymmetric supercapacitor that may have originated from the good contact between Ni(OH)2and ECF. A maximum specific capacitance of 88.1 F g− 1was achieved for Ni(OH)2–ECF//AC/CF device and showed considerable rate capability at large discharge currents (60% capacitance retention at 8 A g− 1). The results of this study suggest the Ni(OH)2–ECF electrode is an excellent material for fabrication of supercapacitor electrodes.

This paper explores generalized output impedance models and develops a new performance-limit figure of merit (FOM) for switched-capacitor (SC) dc–dc converters that can be resonated or soft-charged with a single inductor. Compared to past work, the output impedance model is greatly simplified through a two-port charge multiplier treatment, yet it maintains accuracy across conversion ratios and is valid in both slow- and fast-switching operation. Building on previous analytical treatments of SC and ReSC converters, the model is expanded to derive optimizations that include both conduction and switching losses. The process is used to identify a new FOM for hybrid–resonant SC converters that can be used to identify the most suitable architectures for a given conversion ratio and relevant (energy or area) constraints on flying capacitors. This is used to highlight the active-device and capacitance utilizations of common topologies, as well as which are most favorable for hybrid–resonant operation.

In recent years, carbon nanoscrolls (CNSs) that have a tubular structure similar to that of the open multi-wall carbon nanotube have received significant attention. Graphene nanoscrolls (GNSs) have also attracted significant attention, owing to their unique properties. These nanoscrolls are obtained by systematically winding graphene sheets into a spiral, and are expected to have high mechanical strength, high carrier mobility, and high thermal conductivity. In the present work, an analytical model was used to determine the band energy of (16,0) GNS, and the normalized Fermi energies in the degenerate and non-degenerate regimes are modeled. The model revealed that degenerate and non-degenerate approximations can be used for normalized Fermi energies higher than 3 and lower than −3, respectively.

Concurrent orbit and attitude determination (COAD) plays a key role in reducing the cost of navigation and control subsystem for small satellites. This article is devoted to the problem of the COAD of satellites. A measurement package consisting of three axis magnetometer (TAM) and a sun sensor is shown to be sufficient to estimate the attitude and orbit information. To this end, an autonomous gyro-less COAD algorithm is proposed and implemented through the centralized data fusion of the TAM and the sun sensor. The set of nonlinear-coupled roto-translation dynamics of the satellite is used with a modified unscented Kalman filter (MUKF) to estimate the full satellite states. The MUKF is specially proposed to substantially cut the run time by minimizing the number of required sigma points. The results indicate that the adopted strategy fulfills the essential requirements of accuracy and the speed of state estimation. Local observability is demonstrated and an extensive Monte Carlo simulation has shown desirable stability characteristics for the proposed algorithm. Additionally, a sensitivity analysis on the orbital elements and sensor characteristics is performed to verify the feasibility and utility of the MUKF over a wider acceptable range of sensory and operating environments.

Computer base and simulation technique have been applied for modeling the semi-solid die filling and part of the solidification process of aluminum A356 alloy. A fairly simple one-phase rheological model has been implemented into a fluid flow finite element software Procast, to solve the partial differential equations. This model is purely viscous nature and is implemented in the power law cut-off model of Procast. The constitutive parameters of this model were determined for a rheocast A356 alloy. Using these parameters and comparing the simulation results with experimental data showed good correlation with the model prediction. The designed die for rheocasting was applied for the production of a small propeller with thin section.

Microstructural evolution of the spray atomized and powder thixoformed hyper-eutectic A390 aluminum alloy was investigated. The spray atomized powder revealed homogeneous and very fine silicon particles distribution, due to the rapid solidification of the alloy. The semi-solid powders were extruded into a closed die cavity through a hole for the plastic deformation of the powder particles. A drop forge of 45kg weight at different heights was used in this investigation. Remarkable rearrangement and growth of the silicon rich phase was revealed in the final stage.

Globulization of the grain refined AZ91 magnesium alloy with Ca on a cooling slope was investigated. Dendritic morphology of the grains was transferred into round and well distributed small particles as a result of grain-refinement effect of Ca in the alloy. Semi-solid holding of the alloy was carried out at different temperatures to improve the spherecity of the globules. Results show that, remelting at 540 °C for 30 min provides the best shape factor for the alloy. The study of coarsening kinetic in this alloy showed lower growth rate alternative other research which used same condition for produce semi-solid billet just in using Ca.

A technique to achieve the globular weld structure using stirring the localized semisolid zone during butt-joining of zinc AG40A (Zamak-3) die cast alloy is reported. Since the semisolid temperature range of this alloy is very narrow, the accurate controlling of weld pool temperature must be considered. By presented process, globular microstructure of the weld zone can be achieved. Moreover the near weld zone would have the globular structure due to semisolid holding. A gas heating system was designed to heat up the nitrogen gas to desired temperature accurately. A heating element was embedded in a castable ceramic block while a stream of gas could pass closely around the hot element length. Hot nitrogen gas flow through a precise ceramic nozzle was used to create a localized semisolid pool. At this stage a fine stirrer was introduced into the weld seam in order to mix the two sides into a single uniform joint. Local mechanical properties of different zones show a good strength in the weld metal zone and heat affected zone by results of the shear punch tests and hardness tests. Air entrapment in the pool decreases by controlling the speed of substrate movement and stirrer rotation under the nozzle. The strengths of each zone show relative correspondence to the variation of the hardness values.

Although previous work has shown striking differences in radiobiological hypoxic fraction between KHT and RIF-1 murine sarcomas, intravascular oxyhaemoglobin (HbO2 saturations have revealed less substantial variations. Using quantitative histological techniques, we have also found minor differences in the distributions of distances between tumour cells and the nearest bloods vessel for KHT versus RIF-1 sarcomas. We report here, the results of an investigation of the inherent ability of these tumour cells to withstand conditions of hypoxia by in vitro culturing under aerobic and anoxic conditions. Tumours were dissociated, seeded into culture dishes, and placed in air-tight aluminium chambers. These chambers were repeatedly evacuated and refilled with a mixture of 95% N2 and 5% CO2 over a 2·5-h period. Following anoxic exposure, cells were removed and replated, and the in vitro plating efficiency (PE) was determined using a colony survival assay. After normalizing to aerobic controls, KHT tumour cells had a significantly lower PE, following a 16-hour exposure to anoxic conditions (0·4), than RIF-1 (0·6). Increasing the hypoxic exposure to 40 h resulted in normalized PEs of 0·07 for KHT versus 0·4 for RIF-1. Although these results support the hypothesis that the two tumour lines have different inherent abilities to withstand hypoxia, they do not explain the failure of direct measures of tumour oxygenation to correlate with the radiobiological hypoxic fraction. Additional factors such as differences in oxygen diffusivity or oxygen consumption rates between tumour lines may also be involved.

Abstract: It is desirable to reduce or eliminate the oxygen sensitivity of antimony pH microelectrodes in physiological applications because it is not possible to determine if changes in the electrode's EMF are associated with changes in pH or pO2. The oxygen sensitivity of electroplated antimony pH microelectrodes was experimentally determined for a factorial combination of (a) recessing the electrode tip, (b) saturating the medium with antimony axoide and (c) buffering the medium with phosphate. After establishing the baseline pH sensitivity in phosphate buffers, EMF was measured in a flow-through chamber using an electrometer, while the equilibrating gas was varied selectively from 5 per cent to 21 per cent oxygen. The investigation concluded that recessing the antimony pH microelectrode does not eliminate but does reduce the electrode's oxygen sensitivity. Saturating the medium with antimony oxide or buffering with phosphate do not reduce the oxygen sensitivity of the antimony pH microelectrode. Loss of electroplated antimony from the tip of the antimony pH microelectrode was associated with an increase in EMF.