Analysis of stiffness and elastic deformation of a 2(SP+SPR+SPU) serial–parallel manipulator

A 2(SP+SPR+SPU) manipulator is a serial–parallel manipulator, which includes an upper manipulator and a lower manipulator. Its stiffness and elastic deformation are studied systematically in this paper. Firstly, a 2(SP+SPR+SPU) manipulator is constructed and its characteristics are analyzed. Secondly, the formulae for solving the elastic deformation and the compliance matrix of the active legs are derived and the elastic deformation and the total stiffness matrix of this manipulator are solved and analyzed. Finally, a finite element model of this manipulator is constructed and its elastic deformations are solved. The analytic solutions of elastic deformations of this manipulator are coincident with that of its finite element model.     

Coupling characteristics of rigid body motion and elastic deformation of a 3-PRR parallel manipulator with flexible links

Modeling of multibody dynamics with flexible links is a challenging task, which not only involves the effect of rigid body motion on elastic deformations, but also includes the influence of elastic deformations on rigid body motion. This paper presents coupling characteristics of rigid body motions and elastic motions of a 3-PRR parallel manipulator with three flexible intermediate links. The intermediate links are modeled as Euler–Bernoulli beams with pinned-pinned boundary conditions based on the assumed mode method (AMM). Using Lagrange multipliers, the fully coupled equations of motions of the flexible parallel manipulator are developed by incorporating the rigid body motions with elastic motions. The mutual dependence of elastic deformations and rigid body motions are investigated from the analysis of the derived equations of motion. Open-loop simulation without joint motion controls and closed-loop simulation with joint motion controls are performed to illustrate the effect of elastic motion on rigid body motions and the coupling effect amongst flexible links. These analyses and results provide valuable insight to the design and control of the parallel manipulator with flexible intermediate links.     

Position and stiffness analysis of a new asymmetric 2PRR–PPR parallel CNC machine

In this paper, structural stiffness analysis of a new 3-axis asymmetric planar parallel manipulator, a 2 P RR–P P R structural kinematic chain, is investigated. The manipulator is proposed as a tool holder for a 5-axis hybrid computer numerical control (CNC) machine. First, the structure of the robot is introduced and inverse kinematics solution is presented. Secondly, stiffness matrix of the robot is determined using a continuous method based on Castigliano’s theorem and calculation of strain energy of the robot components. This method removes the need for commonly used simplifying assumptions and, therefore, results in good accuracy. For this purpose, force and strain energy for each segment of the robot are analyzed. Finally, to verify the analytical results, commercial FEM software is used to simulate the physical structure of the manipulator. A numerical example is presented which confirms the correctness of the analytical formulations.     

Log-Linear Convergence and Divergence of the Scale-Invariant (1+1)-ES in Noisy Environments

Noise is present in many real-world continuous optimization problems. Stochastic search algorithms such as Evolution Strategies (ESs) have been proposed as effective search methods in such contexts. In this paper, we provide a mathematical analysis of the convergence of a (1+1)-ES on unimodal spherical objective functions in the presence of noise. We prove for a multiplicative noise model that for a positive expected value of the noisy objective function, convergence or divergence happens depending on the infimum of the support of the noise. Moreover, we investigate convergence rates and show that log-linear convergence is preserved in presence of noise. This result is a strong theoretical foundation of the robustness of ESs with respect to noise.     

Design and realization of a high resolution (640 × 480) SWIR image acquisition system

A new image acquisition system module for extracting signals of high-resolution short wave infrared (SWIR) from a focal plane array (FPA) is presented in this study. The short wave infrared (SWIR—with wavelength about 900–1,700 nm) images have been proven its unique values in many applications such as military, semiconductor inspection and aviation security. The designs for the SWIR data acquisition system module consists of digitization and acquisition of FPA signals, design of synchronous dynamic random access memory controller and real-time image signal transformation and display. Three major steps involved towards a successful SWIR module—(1) Selection of hardware ICs according to specification for the FPA; (2) Design of a timing generator for the image acquisition system to control FPA and other ICs by Verilog HDL programming; (3) Integrate the individual modules on a PCB. The SWIR image output signals are successfully generated in the format of National Television System Committee (NSTC), which can be displayed on a common NTSC monitor, flat panel displays with an AV input terminal or a CRT display in a favorable speed of frame rate at 30 per second.     

Formation of CaZrO3 at the interface between CaO–SiO2–MgO–CaF2(–ZrO2) slags and magnesia refractories: Computational and experimental study

The formation behaviour of calcium zirconate (CaZrO₃) at the interface between the CaO–SiO₂–MgO–CaF₂(–ZrO₂) slags (B$B$(=(mass% CaO) /(mass% SiO₂)) = 2.0) used in the AOD converter and the MgO refractories has been computed by employing a commercial thermodynamic software. The solubility of zirconia (ZrO₂) in the liquid CaO–SiO₂-7 mass% MgO slag phase is relatively small, viz. about 2–3 mass% and the CaZrO₃ phase is formed at about B>1.5$B>1.5$. The region of fully liquid phase extends to the composition saturated by dicalcium silicate (Ca₂SiO₄) and cubic ZrO₂ (B∼1.2$B\sim 1.2$). The effect of 7 mass% CaF₂ addition on the solubility of ZrO₂ in the liquid slag phase was computed to be negligible, while the liquid phase exists through the entire compositions. In addition, the region of fully liquid phase extends to the more basic composition range (B∼1.5$B\sim 1.5$), where the saturating phases are the Ca₂SiO₄ and CaZrO₃. The thermodynamic calculations indicate CaZrO₃ not to form at (mass% ZrO₂) /(mass% MgO) ((=Z/M))<0.6. In the “ Liquid+Ca₂SiO₄+MgO” region, the activity of SiO₂ in the liquid phase is nearly fixed because the activity of CaO in the liquid phase is unaffected by the activity of ZrO₂. However, with higher ZrO₂ activity from the increase in the Z/M ratio, the activity of CaO in the liquid phase is expected to decrease due to the formation of CaZrO₃. The formation behaviour of CaZrO₃ in the slags, computed based on the Gibbs energy minimization principles, could experimentally be confirmed by employing the XRD and SEM–EDS analysis.     

New solitary wave solutions of (2+1)-dimensional space–time fractional Burgers equation and Korteweg–de Vries equation

In this article, via the improved fractional subequation method, the fully analytical solutions of the (2+1)-dimensional space–time fractional Burgers equation and Korteweg–de Vries equation involving Jumarie’s modified Riemann–Liouville derivative have been derived. As a result, with the aid of symbolic computation, many types of new analytical solutions are obtained, which include new solitary wave, periodic wave and rational wave solutions. The graphical representations show that these gained solutions have abundant structures.     

Analytical Expansion and Numerical Approximation of the Fermi–Dirac Integrals F j(x) of Order j=−1/2 and j=1/2

This paper uses properties of the Weyl semiintegral and semiderivative, along with Oldham's representation of the Randles–Sevcik function from electrochemistry, to derive infinite series expansions for the Fermi–Dirac integrals _j (x), –j=–1/2, 1/2. The practical use of these expansions for the numerical approximation of _–1/2(x) and _1/2(x) over finite intervals is investigated and an extension of these results to the higher order cases j=3/2, 5/2, 7/2 is outlined.     

Critical evaluation and thermodynamic modeling of the Fe–V–O (FeO–Fe2O3–VO–V2O3–VO2–V2O5) system

Critical evaluation and optimization of the Fe–V–O ternary oxide system was carried out based on all the available phase equilibria and thermodynamic property data at 1 atm total pressure. The Fe₃O₄–FeV₂O₄ spinel solid solution was described within the framework of Compound Energy Formalism considering the cation distribution between tetrahedral and octahedral sites. The wüstite phase, corundum phase, and VO₂ solid solution were described using a simple random mixing model. The Modified Quasichemical Model was used to describe liquid oxide solution in consideration of all multivalence states of Fe and V (Fe²⁺, Fe³⁺, V²⁺, V³⁺, V⁴⁺ and V⁵⁺). The variation of phase equilibria depending on the oxygen partial pressures and thermodynamic data in the system were well reproduced in the present study.     

Effect of MgO on the liquid/spinel/matte/gas equilibria in the Si–Fe–Mg–O–Cu–S system at controlled P(SO2) 0.3 and 0.6 atm

In this study, the effect of MgO on the phase equilibria of iron silicate slags in equilibrium with Fe₃O₄ spinel and matte of fixed 72 wt % Cu were identified at controlled P(SO₂) 0.3 and 0.6 atm. The experimental process includes equilibration, quenching and Electron Probe X-ray Micro Analysis (EPMA). Spinel (Fe₃O₄) substrates were applied to confirm the equilibrium was achieved in the primary phase field of spinel. It was found that the presence of MgO increases the liquidus temperature of slag under a constant SiO₂ content, i.e., more SiO₂ is required to be fluxed to keep a stable smelting temperature with MgO. The effects of CaO and MgO on the liquidus of the system were further compared and found that the influence of MgO is stronger than CaO at 1250 °C under the same weight content while opposite situation occurs at 1200 °C, which is different from the FactSage predictions. Thus, the present study provides important information not only for the industrial smelting process but also for the thermodynamic modelling.     

Design and implementation of a novel two stage mechanical–magnetic variable stiffness actuator (M²-VSA)

This paper presents the design and implementation of a novel joint-based magnetic actuator for robotic manipulators using variable stiffness mechanism. This new actuator prototype, namely M²-VSA, is developed as an improvement over previous actuators in its class. The robotic arm with M²-VSA joint can safely interact with human operators and work in hazardous conditions. The main novelty in this work is the use of magnetic force in accompanying with springs in a novel arrangement to adjust the joints’ stiffness and mitigate the effect of impact. The theoretical framework and advantages of the design are discussed in detail. Experimental studies through various tests show the effectiveness and efficiency of mechanical–magnetic joint as a safe mechanism in environments where human and robotics have interaction.     

Effect of CaO on the liquid/spinel/matte/gas equilibria in the Si–Fe–O–Cu–S system at controlled P(SO2) 0.3 and 0.6 atm

Herein the phase equilibria in the Si–Fe–Ca–O–S–Cu system in equilibrium with matte at controlled P(SO₂) of 0.3 and 0.6 atm and fixed matte grade of 72 wt % Cu were experimentally investigated in the spinel primary phase field. The high-temperature equilibrations were realized in spinel substrate and the sample after quenching were characterized using Electron Probe Micro-analysis (EPMA). The effect of CaO on the liquidus temperature of slags was quantified with varying CaO content from 0 to 6 wt %. It was found that, the presence of CaO increased the liquidus temperature of slags and moreover, the increment effect got enhanced with increasing CaO content in the present range. The influence of P(SO₂) was further clarified and it was found that, the equilibrium SiO₂ content in the liquid phase, at the same temperature, remarkably increased with increasing P(SO₂). The present study will not only deepen the understanding of the equilibration in the present liquid/spinel/matte/gas system, but also provide useful guidance for the industrial operations.     

Spatiotemporal mapping of a large mountain glacier from CryoSat-2 altimeter data: surface elevation and elevation change of Bering Glacier during surge (2011–2014)

CryoSat-2 radar altimeter data have been applied to map surface elevations of the Greenland and Antarctic ice sheets, and of Arctic icecaps. In this article we investigate the feasibility of using CryoSat-2 data for spatiotemporal analysis of surface elevation of a large mountain glacier. Bering Glacier, Alaska (which is 8–20 km wide and approximately 80 km long) is selected as a study area because it surges and hence shows short-term elevation changes. The approach includes a correction method, geostatistical analysis, and several methods for error assessment. A time series of digital elevation models (DEMs) is derived for six-month increments from Summer 2011 to Winter 2013/2014. DEMs have, on average, numerical Kriging errors of 1.65 + 3.19 m and Kriging estimation standard deviations of 11.32 + 1.01 m. A crossover analysis with airborne laser altimeter data from the fall months of 2011, 2012, and 2013 produced differences of 5.03 + 13.67 m compared to respective CryoSat-2 data sets. Difference maps are derived from the DEMs and are used to infer dynamical changes associated with the recent surge. In conclusion, CryoSat-2 data can be employed for spatiotemporal mapping of the evolution of surface elevation in Bering Glacier and other mountain glaciers of similar width, while providing key insight into large-scale elevation change over relatively short time periods.     

Characterization of mesoscale spatio‐temporal patterns and variability of remotely sensed Chl a and SST in the Interior Sea of Chiloe (41.4–43.5° S)

This study characterizes the spatial and temporal distribution of chlorophyll a (Chl a) and sea surface temperature (SST) in the Interior Sea of Chiloe in Chile at a moderate spatial resolution using SeaWiFS and MODIS‐Aqua time series data from the Goddard Earth Science (GES) Data and Information Services Center (DISC) imported into the GES DISC Interactive Online Visualization and Analysis System (‘Giovanni’). The Interior Sea of Chiloe is home to Chile's salmon farming industry, the world's second largest salmonid producer. This study undertakes the characterization of the main patterns of spatial and temporal variability of Chl a and SST in the Interior Sea of Chiloe using a continuous set of time series ocean colour and SST data. Both Chl a and SST exhibit a marked spatial and temporal distribution, with values being significantly higher in the northern area (41.4–42.7° S; total area 41.4–43.5° S) and during the spring–summer period. Peak Chl a concentrations tend to occur in a temporal interval from October to April (austral spring–austral autumn), whereas monthly averaged peak SST values occur consistently in the month of February (austral summer). Chl a concentrations exhibit strong interannual variations, with monthly averaged peak Chl a concentrations experiencing a twofold increase between the year with the lowest and highest Chl a peak concentration in the time series. Results suggest that at the present scale of analysis two spatial domains can be distinguished, regarding the differential behaviour of SST and Chl a in the northern and southern areas of the Interior Sea of Chiloe. The concurrent analysis of Chl a time series data with accumulated rainfall time series data as a proxy of solar radiation, on the other hand, supports previous hypothesis suggesting solar radiation to be a limiting factor for phytoplankton development in the Interior Sea of Chiloe. The role of geomorphological factors on pattern formation and the results presented in this study in relation to results from seasonal oceanographic cruises in the area are briefly discussed.     

Critical evaluation and thermodynamic assessment of the R2O–P2O5 (R = Li,Na and K) systems

The R₂O–P₂O₅ (R = Li, Na and K) systems are thermodynamically optimized based on the evaluated phase equilibria and thermodynamic data by the CALPHAD method. Liquid phase is described by the Modified Quasichemical Model, which takes short-range ordering in liquid solution into account. All intermediate phases RPO₃, R₅P₃O₁₀, R₄P₂O₇ and R₃PO₄ are treated as stoichiometric compounds and the corresponding polymorphic transitions are considered. A set of self-consistent model parameters for describing the Gibbs free energy of each phase are obtained. The experimental phase equilibria, enthalpy of formation, entropy, heat capacity and activity are reproduced well within experimental error limits. The calculated liquidus around compounds become flatter with the increase of P₂O₅ content, suggesting that the degree of stability of phosphate increases as its composition approaches R₃PO₄. The calculated enthalpies of formation for intermediate compounds become more negative and entropies become more positive with the increase of atomic numbers of alkali metals.     

Topology optimization of neural networks based on a coupled genetic algorithm and particle swarm optimization techniques (c-GA–PSO-NN)

In this short paper, a coupled genetic algorithm and particle swarm optimization technique was used to supervise neural networks where the applied operators and connections of layers were tracked by genetic algorithm and numeric values of biases and weights of layers were examined by particle swarm optimization to modify the optimal network topology. The method was applied for a previously studied case, and results were analyzed. The convergence to the optimal topology was highly fast and efficient, and the obtained weights and biases revealed great reliability in reproduction of data. The optimal topology of neural networks was obtained only after seven iterations, and an average square of the correlation (R ²) of 0.9989 was obtained for the studied cases. The proposed method can be used for fast and reliable topology optimization of neural networks.

     

Simulation and comparative study on analog/RF and linearity performance of III–V semiconductor-based staggered heterojunction and InAs nanowire(nw) Tunnel FET

This paper presents the comparative study on linearity and analog/radio frequency presentation of an III–V staggered hetero-junction nanowire (NW) TFET with Si and InAs based NW TFET of same dimension. The device parameter of analog/RF performance for low power application such as transconductance (g_m), output resistance (R_O), intrinsic gain (g_mR₀), cut-off frequency (f_T), maximum frequency of oscillation (f_max), gain bandwidth product (GBW), VIP₂, VIP₃ as well as 1-dB compression point has been explored. There is a better improvement in analog/radio frequency presentation obtained from heterojunction NW TFET over Si and InAs TFET. The result reveals that heterojunction TFET provides superior intrinsic gain, higher cutoff frequency, higher GBW better linearity performance as compared to Si and InAs TFET.

     

Microfluidics assisted fabrication of microspheres by poly(2–hydroxyethyl methacrylate)-block-poly(l-histidine) hybrid materials and their utilization as potential drug encapsulants

A new series of synthetic polymer bioconjugate hybrid materials consisting of poly(2-hydroxyethyl methacrylate)[p(HEMA)]as a synthetic polymer block and poly(l-histidine) [p(His)] as a polypeptide block were synthesized by combining atom transfer radical polymerization of HEMA with ring opening polymerization of benzyl-N-carboxy-l-histidine anhydride. The resulting biocompatible p(HEMA)₂₅-b-p(His)_n (n = 15, 25, 35, and 45) hybrid polymers were investigated for their use as pH-sensitive drug delivery system. Highly uniform microspheres were fabricated by using the microfluidics assisted self-assembly of these block polymers and utilized them as carriers for a chemotherapeutic agent doxorubicin and a beta-lactam antibiotic ampicillin for the evaluation of the drug-loading and release behaviors according to pH, demonstrating the release is sensitive to pH. The capability of the new p(HEMA)-b-p(His) hybrid materials to self-assemble in microenvironments and to effectively encapsulate drug molecules serves as suitable carriers for the delivery of drug molecules with varying physiochemical properties.