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Variable stiffness surgical robots are capable of adapting to different surgical scenarios, providing enhanced stability during minimally-invasive surgeries. Prevalent methods for achieving variable stiffness, such as lockable mechanisms, granular jamming, and phase transition materials, have inherent weaknesses including difficulties in downsizing and issues related to excessive temperatures. In this paper, a novel lockable mechanism based on electrostatics is proposed, along with a tendon-driven surgical robot prototype that utilizes this locking mechanism to achieve variable stiffness. The proposed mechanism involves the installation of graphite electrode sheets at each joint, with silica gel being used as the dielectric material. By applying a high voltage to the electrode sheets, adjacent joints automatically absorb and restrict relative sliding, effectively preventing joint rotation and ensuring complete joint locking. An electrostatic adhesive braking force model for the robot is presented. Simulations and experiments conducted based on the robot prototype have been carried out to validate the locking capability of the proposed mechanism and the accuracy of the electrostatic adhesive braking force model. [ABSTRACT FROM AUTHOR]

• Multi-scale fusion neural network is proposed to solve the elliptical interface problem. • Multi-scale fusion neural network can better capture "sharp turns" on the interface. • Solutions by multi-scale fusion neural network can better preserve the C 0 continuity while keeping the flux jumps. • We apply multi-scale fusion neural network to calculate the electrostatic potential of immersed biomolecules. In this paper, we construct a novel multi-scale fusion network as a new deep learning structure to solve the elliptic interface problem. Compared with the results of the fully connected neural network and ResNet, the new multi-scale fusion network is shown to be able to better capture "sharp turns", leading to the improved accuracy. Furthermore, its numerical solutions can preserve the C 0 continuity of the solution while keeping the flux jumps passing through different interfaces, thus maintaining the physics of the differential equation. Then, as an application, the new method is applied to solve the three-dimensional Poisson-Boltzmann equations to calculate the electrostatic potential of immersed biomolecules. Numerical experiments demonstrate the effectiveness of our new method compared to the results obtained by the finite element method. [ABSTRACT FROM AUTHOR]

In this paper, the local and nonlocal Poisson–Boltzmann equations are studied on their linear and nonlinear models with spherical symmetry. In particular, the exact solutions of the linear and nonlinear modes are obtained in either analytical expressions or simplified boundary value problems, whose solutions can be found easily via the Maple procedure dsolve for example. Numerical results confirm the derived solution properties, and show that the two new linear models proposed in this paper can have higher accuracy than the two conventional linear models in approximation to the local and nonlocal nonlinear models, respectively. [ABSTRACT FROM AUTHOR]

Abstract The electrostatically controlled deployable membrane antenna (ECDMA) is expected to become one of the next generation spaceborne antennas due to its lightweight, large-aperture and high-precision advantages. However, form-finding of the ECDMA is a challenge that related to the cable-membrane structure and electrostatic force. This paper presents an extended force density method (EFDM) that identifying the equivalent cable force density to replace the orthotropic membrane element stress by the virtual work principle. Then the force density equilibrium equations of the cable-membrane electrode structure and the membrane reflective surface of the ECDMA are deduced based on the EFDM and the corresponding form-finding strategies are given, respectively. Simulations and experiments show that the EFDM presented in this paper is effective for the form-finding design of the ECDMA. Highlights • The EFDM is applicable to the form-finding of orthotropic membrane structure. • The form-finding design of the cable-membrane electrode structure and the membrane surface need different strategies. • The parabolic membrane reflective surface wrinkling is worth of study. [ABSTRACT FROM AUTHOR]

• FWVM module has 2 stages of Cock-Croft Walton voltage multiplier circuit. • The FWVM unit is fed by a center tapped, 20 kHz high voltage transformer. • The maximum ground fault current is 50 A as per simulation results. • The 100 kV, 100 mA FWVM module is designed, fabricated and tested at 100 kV. The 100 kV, 100 mA DC full-wave voltage multiplier (FWVM) modular unit is being developed for accelerator power supply and other plasma applications at Institute for Plasma Research (IPR). The high voltage engineering design involved in fabrication architecture and assembly of 100 kV, 100 mA DC FWVM module is the main focus of this paper. This FWVM module has 2 stages of Cock-Croft Walton voltage multiplier circuit considering the required optimum number of stages for final 500 kV voltage output. The FWVM unit is fed by a center tapped High Voltage High Frequency (HVHF) transformer. Electrical circuit simulations have been carried out to ensure the electrical performance parameters. The maximum value of the fault current during ground fault is 50 A as per simulation results. The 100 kV, 100 mA FWVM module is designed, fabricated and tested at 100 kV. Simulation Results, fabrication details, engineering design details and test results have been presented in this paper. [ABSTRACT FROM AUTHOR]

Understanding the behavior and properties of spherical polyelectrolyte brushes (SPEBs), which are polyelectrolyte brushes grafted to a spherical core, is fundamental to many applications in biomedical, chemical and petroleum engineering as well as in pharmaceutics. In this paper, we study the pH-responsive electrostatics of such SPEBs in the decoupled regime. In the first part of the paper, we derive the scaling conditions in terms of the grafting density of the PEs on the spherical core that ensure that the analysis can be performed in the decoupled regime. In such a regime the elastic and the excluded volume effects of polyelectrolyte brushes (PEBs) can be decoupled from the electrostatic effects associated with the PE charge and the induced EDL. As a consequence the PE brush height, assumed to be dictated by the balance of the elastic and excluded volume effects, can be independent of the electrostatic effects. In the second part, we quantify the pH-responsive electrostatics of the SPEBs – we pinpoint that the radial monomer distribution for a given brush molecule exhibit a non-unique cubic distribution that decays away from the spherical core. Such a monomer distribution ensures that the hydrogen ion concentration is appropriately accounted for in the description of the SPEB thermodynamics. We anticipate that the present analysis, which provides possibly one of the first models for probing the electrostatics of pH-responsive SPEBs in a thermodynamically-consistent framework, will be vital for understanding the behavior of a large number of entities ranging from PE-coated NPs and stealth liposomes to biomolecules like bacteria and viruses. [ABSTRACT FROM AUTHOR]

Guidance-plate-covered electrostatic precipitators (GPC-ESPs), which are ESPs with perforated guidance plates that cover their collecting electrodes, have been experimentally proven to have higher collection efficiencies than their traditional counterparts. The key to the GPC-ESP׳s success in high collection efficiency is that particles that enter the gaps between the guidance plate and the collecting electrode have lower chances of returning to the environment. This paper presents the characteristics of the GPC-ESPs, and discusses how the parameters of interest affect collection efficiency. The numerical model is carried out by modeling the particle transport, flow field, and electric field. Results show that when the diameters of the holes on the guidance plate are larger, the flow recirculation is stronger and allows for more particles to easily enter the gaps through these holes. The electrical characteristics are dependent on the repelling voltage and the diameter of the holes. The collection efficiency is also discussed in terms of two dimensionless parameters: the Stokes numbers (the ratio of inertia force to viscous drag force) and the electrostatic numbers (the ratio of electrostatic force to viscous drag force). Results show that a lower Stokes number and a higher electrostatic number results in a higher collection efficiency. The collection efficiency remains numerically unchanged when the electrostatic number stays the same. This paper also demonstrates a set of simulations to simulate particle re-entrainment. Results show that when particle re-entrainment happens at the collecting electrode, none of the particles reenter the environment through the holes of the guidance plate. When particle re-entrainment happens at the guidance plate, some of the particles escape the collector, but most of the particles enter the gaps and are recaptured at the collecting electrode, due to either flow recirculation or induced electrostatic forces. [ABSTRACT FROM AUTHOR]

In this paper, we analyze and give experimental evidence of the efficiency of pulsed-mode actuation for the characterization of capacitive MEMS resonators. In particular, we show how to process the output signal in pulsed mode to eliminate parasitic feedthrough effects and characterize the resonator. We test our approach on a pressure sensor, developed by THALES Avionics, used for avionics applications. Contrary to the existing state-of-the-art techniques, the method described in this paper can be used to characterize an electrostatic MEMS without a spectrum analyzer or high-performance ADC. [ABSTRACT FROM AUTHOR]

Abstract: This survey paper describes NCLab (Network Computing Laboratory), a novel cloud computing service that is pioneering free web browser access to finite element simulations. Presently, these include general second-order linear partial differential equations, linear elasticity problems, and electrostatics problems (all in two spatial dimensions). The modeling process consists of geometry definition in the web browser, mesh generation on a remote server, specification of material parameters and boundary conditions in the web browser, computation on a remote server, and visualization in the web browser. The module supports curvilinear elements and higher-order finite element discretizations. In this paper we present the modeling process using a sample electrostatics problem. Numerical results are provided. [Copyright &y& Elsevier]

• Gold and silica nanoparticles interact differently with the plasma membrane. • Variation in nanoparticle-membrane van der Waals interactions causes the difference. • This difference affects the specific and non-specific adhesion of the nanoparticles. • Choice of the ligands and the nanoparticle cytotoxicity effects are also affected. Making a nanoparticle (NP) approach and interact with a plasma membrane (PM) through the receptor-ligand interaction is key for applications like targeted drug delivery, cellular imaging, and theranostics. In this paper, we show that the van der Waals (vdW) interactions dominate the electrostatics ensuring that a gold NP approached the PM more spontaneously as compared to a silica NP. The negative σ (charge density) of a PM induces a negative electrostatic potential at the surface of the approaching gold NP and the silica NP; however, there is very little difference between these induced values due to a small electric double layer at the physiological salt concentration (c ∞). Hence there is very little difference in the electrostatic repulsion between the two cases, while the PM-NP vdW attraction is much more for the gold NP as a result of a larger Hamaker constant. Therefore, in comparison to the gold NP, the silica NP would (a) undergo a promotion of the specific adhesion and a prevention of the non-specific adhesion simultaneously for a larger σ − c ∞ phase space including the physiological conditions, (b) necessitate a larger length of the ligands to trigger spontaneous receptor-ligand interactions, and (c) require a larger driving force for force-driven receptor-ligand interactions. [ABSTRACT FROM AUTHOR]

Abstract Due to the complex and harsh operation conditions, like corrosion, aging cable and static electricity, of electrical traction drive system, ground fault will generate large short circuit current to harm the key components. Effective fault diagnosis is important, but also challenging. The conventional method used for ground fault detection only takes advantage of voltage measurements of DC-link. Other measurements onboard are also available, which are correlated with the voltage measurements. Taking the correlation into account will improve the detection performance. To this end, this paper presents a data-driven solution, which makes full use of the correlation between the voltage measurements with other measurements onboard. The proposed method consists of two components: (1) a canonical correlation analysis-based fault detection method, which takes into account the correlation within measurements; (2) a fault isolation method by means of the fault direction, which can be obtained with the available faulty data stored in the long-term operation. The developed method is applied to a traction drive system. It is shown that the proposed approach is able to improve the fault detection and isolation performance significantly with respect to three performance indicators, namely fault detection rate, detection delay and correct isolation rate, in comparison with the conventional method, which only uses the voltage measurements of DC-link. Highlights • Introduce characteristics of typical ground faults in the electrical traction system. • An CCA solution is proposed using the correlation between the measurements onboard. • A fault isolation method is proposed using the residual and fault direction info. [ABSTRACT FROM AUTHOR]

Abstract This study presents a novel control scheme for voltage regulation of a negative output cascade ultra-lift Luo converter (NOCULLC). Due to the complicated high order model of the converter, its performance is degraded against large load variations, input voltage changes and parametric uncertainties. In order to enhance the converter behavior, a PI compensator and a sliding mode current controller are combined to control the fourth order NOCULLC worked in a wide range of operating conditions. Because of the non-minimum phase structure of the converter, the output voltage of the converter is indirectly regulated by enforcing the input inductor current to track its reference signal. The sliding mode current controller improves the dynamic and static performances of the converter by minimizing the inrush current of the input inductor of the converter and also, the PI controller eliminates the steady state error of the output voltage of the converter. The closed loop system stability is demonstrated by using sliding mode theory. Furthermore, this paper proposes a systematic procedure to compute the gains of the controller based on the stability constraints which guarantees robustness of the developed controller. The experimental results show the robustness and effectiveness of the proposed controller against parametric variations and uncertainties of the converter. Also, a comprehensive comparison of the general aspects of the properties between the developed method and other existed controllers is provided. Highlights • Operation analysis of a NOCULL converter. • A PI and HM sliding mode current controller is designed for converter. • Experimental results of the converter under the proposed controller are illustrated. • Comparison between the proposed controller and a simple controller is presented. [ABSTRACT FROM AUTHOR]

In many industrial processes, electrostatic charges are inevitable and affect the hydrodynamic behavior and heat transfer ability of chemical equipment. A comprehensive study of the electrostatic effect on bubble behavior, particle fluctuation velocity and heat transfer coefficient in the fluidized bed with a central jet has been evaluated in this paper by Eulerian-Eulerian two-fluid model coupled with electrostatic model and energy model. The simulated voidage profiles at different positions, bubble detachment time and initial bubble diameter are compared with experimental results from the literature without charge. The bubble behaviors including bubble frequency and bubble numbers, combined with particle fluctuation parameters are analyzed in both charged and uncharged system. The electrostatic effect on two kinds of heat transfer coefficients is quantitatively compared, namely bubble to emulsion phase heat transfers based on the gas throughflow velocity and gas-solid local heat transfer coefficient. Simulation results show that electrostatic charges decrease bubble numbers and granular temperature, whereas the averaged heat transfer coefficients are enhanced. Overall, the electrostatic effect on the hydrodynamic and heat transfer characteristics can be revealed. [ABSTRACT FROM AUTHOR]

Abstract This paper deals with the mathematical and numerical analysis of a nonlinear 2D transient magnetic model when the source data are given in terms of the voltage drop excitations in conductors and the remanent magnetic flux for permanent magnets. The formulation consists of a distributed nonlinear magnetostatic model with time appearing as a parameter, and a circuit equation linking currents and voltage drops. This last equation is used to express the problem as an implicit ODE system whose operator involves the resolution of the distributed model. The model is spatially discretized using a finite element method and an implicit Euler scheme is employed for time discretization. We perform the mathematical analysis of the problem at both the continuous and discrete levels and obtain an error estimate that is illustrated with some numerical results. [ABSTRACT FROM AUTHOR]

Highlights • A nonlinear pedal like FGM microresonator under electrostatic actuation is modeled. • Both softening-type and hardening-type behaviors are observed in the system. • Pull-in voltages are calculated for various FG material profiles and gap distances. • Internal resonance of 1:2 ratio between the two modes of the system is studied. • Using FG material provides a wider frequency bandwidth during design process. Abstract In this paper a nonlinear pedal like microresonator made of Functionally Graded material is introduced and modeled. Using Lagrangian formulation nonlinear equations of motion of the system are derived and the natural frequencies and mode shapes are extracted by linear analysis. The effects of various parameters such as geometry, FG material index and DC voltages on the natural frequencies and mode shapes are investigated. Static pull-in voltages of the system are obtained and it is found that depending on the type of actuation, both softening and hardening behaviors can be observed in the system. The results are compared with previous studies and finite element method where a good agreement is achieved. A two-mode reduced order model along with first-order averaging technique is implemented to derive the asymptotic dynamic equations of motion. The effects of different parameters including AC actuation level, damping and material power index on the dynamic response of the system are studied around resonance conditions. It is observed that when the system parameters are adjusted properly, the directly excited in-plane mode, in turn excites the out-of-plane torsional mode of the structure through internal resonance of 1:2 ratio within a specific frequency bandwidth. A wide range of frequency will be available by changing only the power index of the material and the system can be manipulated to be used in various MEMS applications such as mass sensors and RF filter-mixer devices. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

This paper takes a detailed look at the operation of the electrostatic soot sensor and its potential use to monitor motor vehicle particulate matter emissions. Charged soot particles entering the sensor are trapped and grow into dendritic soot structures aligned with the electric field. Above a critical length, the electrostatic force fractures the dendrites, producing fragments that carry sufficient charge between the electrodes to generate nanoamp level currents. While proportional to soot concentration, this current also responds to flow variations, which limits the sensor's application in areas such as motor vehicle on-board diagnostics. The present work demonstrates that this flow dependence is closely related to the sensor's response to variations in electric field. The measured response to step changes in applied voltage agrees very well with a kinetic model of electric field induced dendrite growth and fragmentation. Variations in flow induce fluctuations in sensor current as dendrites reorient in response to the drag force and find themselves above or below the critical length for fragmentation. This mechanism qualitatively fits the experimental data. In engine exhaust applications, variation of exhaust flow with engine operation interferes with time resolved soot measurement. This interference partially cancels out when averaged over time, rendering the electrostatic soot sensor a potentially viable means to distinguish diesel particulate filter performance. [ABSTRACT FROM AUTHOR]

• The novel Modified-Extended Pitzer-Debye-Hückel term is applied with the UNIversal QUAsi-Chemical model in aqueous ionic liquids. • Three developments of the Pitzer-Debye-Hückel equation are tested and compared. • Binary interaction parameters are systematically reduced keeping comparable modeling performance. Recently an improved long-range model for electrolyte solutions was developed that is applicable from infinite dilution to pure salt. This paper tests this claim for the first time applying it to the calculation of liquid-liquid equilibria for mixtures of different ionic liquids (ILs) and water. The conventional Pitzer-Debye-Hückel (PDH) equation is compared to two of its new, thermodynamically consistent extensions. Both development stages, the extended PDH term and the modified-extended PDH, account for concentration dependent mixture properties instead of using solvent properties. The latter one additionally introduces a modified parameter of closest approach which improves the overall performance of the model for high electrolyte concentrations in systems with variable or low permittivities. To account for the short-range interactions, these long-range models are coupled with the UNIversal QUAsi-Chemical (UNIQUAC) model. Three modeling strategies were tested for the short-range contribution. First, the UNIQUAC parameters were adjusted to each system individually, then the binary interaction parameters were the same for each binary interaction type for all the systems and lastly a linear function of the carbon number was used where possible. For all systems and all modeling strategies tested, the predictive performance increased from PDH to E-PDH and then to ME-PDH. Overall, an introduction of concentration dependent properties and the modification added to ME-PDH enhanced modeling performance when describing these systems, showing the general applicability of this novel long-range term. [ABSTRACT FROM AUTHOR]

In this paper, we review the importance of long-range zeolite framework interactions in theoretical predictions for a variety of zeolite-catalyzed processes, and we show why such interactions must be determined accurately in order to reproduce experimentally measured adsorption and activation energies. We begin with an overview of the different strategies that have been used to account for long-range coulombic and dispersive interactions of zeolite framework atoms with species adsorbed at an active site. These methods include full periodic-DFT calculations and multi-layer hybrid techniques. Electrostatic interactions are observed to have a more significant impact than dispersive interactions on the geometries of ion-pair transition states and adsorbed species. Stabilization of the TS relative to reactant complexes is also dictated by electrostatic interactions. Dispersion effects are found to significantly stabilize both transition and reactant states for adsorbed species, especially those which have dimensions that provide good fits within the zeolite pore or cavity. We also show that the relevance of particular active site configurations can be missed, if the effects of long-range interactions are neglected. As a case in point, we demonstrate that a site previously considered inactive for ethane dehydrogenation, [GaH 2 ] + may in fact be more active than previously thought, when the impact of long-range interactions on the predicted activation energy is taken into account. Finally, the use of hybrid quantum mechanics/molecular mechanics approaches on extended, finite zeolite clusters has emerged as an accurate, highly cost-effective, and versatile alternative towards overcoming some of the present-day limitations of periodic calculations. [ABSTRACT FROM AUTHOR]

The size-modified Poisson–Boltzmann equation (SMPBE) is one important variant of the popular dielectric model, the Poisson–Boltzmann equation (PBE), to reflect ionic size effects in the prediction of electrostatics for a biomolecule in an ionic solvent. In this paper, a new SMPBE hybrid solver is developed using a solution decomposition, Schwartz’s overlapped domain decomposition, finite element, and finite difference. It is then programmed as a software package in C , Fortran , and Python based on the state-of-the-art finite element library DOLFIN from the FEniCS project. This software package is well validated on a Born ball model with analytical solution and a dipole model with known physical properties. Numerical results on six proteins with different net charges demonstrate its high performance. Finally, this new SMPBE hybrid solver is shown to be numerically stable and convergent in the calculation of electrostatic solvation free energy for 216 biomolecules and binding free energy for a DNA-drug complex. [ABSTRACT FROM AUTHOR]

Carbonaceous materials served as functional units have trigged tremendous fundamental and practical interest in preparing electronic composites especially in meta-composites. In this paper, carbon functional nano-units were built by electrostatic self-assembly of carbon nanotubes (CNTs) and carbon black (CB). Three-dimension carbon networks hosted in CaCu 3 Ti 4 O 12 (CCTO) matrix were constructed by randomizing CNTs/CB nano-units. Negative permittivity was observed when increasing CNTs/CB nano-units contents exceeded the percolation threshold. The negative permittivity behavior considered as deriving from the low frequency plasma oscillation of delocalized electrons in carbon networks was analyzed by Drude model and equivalent circuit model. Besides, the electrical properties influenced by percolating phenomenon including ac conductivity, dielectric loss, and impedance were investigated. This work presents a novel meta-composites with negative permittivity built by CNTs/CB nano-units filling in low-temperature sintering CCTO matrix which extends the fields of meta-composites and will greatly facilitate its practical applications. [ABSTRACT FROM AUTHOR]

In this paper, an electrostatic vibration energy harvester is proposed and fabricated with both broad bandwidth and high normalized power density (NPD, harvested power/volume/acceleration 2 ). The device is made up of two parts, top movable plate and bottom fixed plate, both of which are fabricated from silicon wafers using advanced micro-electro-mechanical system (MEMS) technology. A CYTOP polymer layer is spray coated for an electret material as well as an adhesive layer for low temperature wafer bonding. The air damping effect in energy harvesting has been investigated. At a low pressure of 3 Pa in a vacuum chamber, maximum power output of 4.95 μW has been harvested at low vibration amplitude of 0.09 g, resulting in a bandwidth of 12 Hz and NPD of 3 mW/cm 3 /g 2 , which outperforms most of the previous harvesters. A high harvester effectiveness of 67.9% is therefore achieved. The response on random vibrations is also tested. An average output power of 2.22 μW is harvested when random vibration is applied at a frequency range of 160 ± 12.5 Hz with RMS acceleration of 10.5 m/s 2 . The excellent overall performance gives promising application for energy harvesting from random sources and multi-device stack for wireless sensor networks. [ABSTRACT FROM AUTHOR]

In this paper, a size-dependent model of clamped-clamped composite laminated electrostatic Euler–Bernoulli microbeams with piezoelectric layers attached was proposed based on a new modified couple stress theory for anisotropic elasticity. With the aid of Hamilton's principle, the nonlinear differential governing equation was established and solved by utilizing the generalized differential quadrature method. The present model, which can be reduced to the isotropic beam model takes the residual stresses, fringing effects and midplane stretching effects into consideration. A good agreement exists between numerical results of the present reduced model and those of available literature. Numerical analysis reveals that the size effect is significant when geometry sizes of a beam are comparable to the internal material length scale parameter (hereafter referred to as MLSP). Furthermore, the pull-in voltage dependence of the residual stress, midplane stretching, MLSP as well as the voltage applied to the piezoelectric layers are also investigated. The present model can accurately predict the static behavior and guide the design of composite laminated micro-beam actuated by both the electrostatic and piezoelectric forces. [ABSTRACT FROM AUTHOR]

The Ion Source of the ITER Heating Neutral Beam Injector (HNB) is polarized at −1MVdc to ground. A large-1MVdc air-insulated Faraday cage (12.5 m (L) × 8.4 m (W) × 9.6 m (H)), called High Voltage Deck 1 (HVD1), hosts the Ion Source and Extractor Power Supplies (ISEPS) and the associated HNB diagnostics; the HVD1 is interfaced with a SF 6 insulated Transmission Line (connecting the main power supplies to the HNB) through a High Voltage (HV) Bushing Assembly (HVBA) carrying inside ISEPS power conductors and diagnostics. The HVD1 and HVBA are unique devices for size, electrostatic and mechanical features. This paper presents the main design choices adopted to comply with the challenging technical requirements and the supporting electrostatic, seismic and thermal analyses. Finally, next procurement steps and definition of special tests to verify the key design choices are also reported. [ABSTRACT FROM AUTHOR]

This paper reports a turn-on theranostic fluorescent nanoprobe P-CDs/HA-Dox obtained by electrostatic assembly of polyethylenimine (PEI)-modified carbon dots (P-CDs) and Hyaluronic acid (HA)-conjugated doxorubicin (Dox) for hyaluronidase (HAase) detection, self-targeted imaging and drug delivery. P-CDs/HA-Dox show weak emission in a physiological environment. By utilizing the high affinity of HA to CD44 receptors overexpressed on many cancer cells, P-CDs/HA-Dox are capable of targeting and penetrating into cancer cells, where they are activated by HAase. As a result, HA-Dox can be digested into small fragments, causing the release of Dox and thereby restoring the fluorescence of P-CDs. The theranostic fluorescent nanoprobe can effectively distinguish cancer cells from normal cells. The as-prepared nanoprobe achieves a sensitive assay of HAase with a detection limit of 0.65 U mL −1 . Furthermore, upon Dox release, the Dox could efficiently induce apoptosis in HeLa cells, as confirmed by MTT assay. The design of such a turn-on theranostic fluorescent probe provides a new strategy for self-targeted and image-guided chemotherapy. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic pull-in instability and bifurcation characteristics of circular nanoplate subjected to electrostatic and Casimir forces are studied. Surface effect originates from high surface/volume ratio of nanostructures, where atoms at a free surface experience distinct local environments with respect to those in the bulk material. Thus, the surface free energy being negligible in classical elastic theory, becomes significant in dynamic behaviors of nanostructures. Based on Eringen's nonlocal elasticity and Gurtin-Murdoch surface model, the nonlinear governing equation of electrically actuated circular nanoplate is derived in polar coordinate. The closed-form solution of dynamic frequency and electrostatic voltage is obtained by utilizing the homotopy perturbation method (HPM). Furthermore, the coupling effects of nonlocal parameter and surface characteristics on the dynamic pull-in instability of circular nanoplate are investigated, and the nonlinear dynamics behaviors, time histories and phase diagrams of electrically actuated circular nanoplate are discussed. Some new results obtained in this work could be helpful in design of 2-D circular nanoplate-type actuator considering size-dependency and quantum vacuum fluctuation effects. [ABSTRACT FROM AUTHOR]

In this paper we prove the Liouville type theorem for stable solution of the p -Laplace equation (0.1) − Δ p u = f ( x ) | u | q − 1 u , x ∈ R N , where f ( x ) is a continuous and nonnegative function in R N ∖ { 0 } such that f ( x ) ≥ a 0 | x | a as | x | ≥ R 0 > 0 , where a > − p and a 0 > 0 . The results hold true for 1 ≤ p − 1 < q = q c ( p , N , a ) . Here q c is a new exponent, which is infinity in low dimension and is always larger than the classical critical one. [ABSTRACT FROM AUTHOR]

This paper resolves an ostensible inconsistency in the literature in calculating the evaporation rate for sessile drops in a quiescent environment. The earlier models in the literature have shown that adapting the evaporation flux model for a suspended spherical drop to calculate the evaporation rate of a sessile drop needs a correction factor; the correction factor was shown to be a function of the drop contact angle, i.e. f ( θ ). However, there seemed to be a problem as none of the earlier models explicitly or implicitly mentioned the evaporation flux variations along the surface of a sessile drop. The more recent evaporation models include this variation using an electrostatic analogy, i.e. the Laplace equation (steady-state continuity) in a domain with a known boundary condition value, or known as the Dirichlet problem for Laplace's equation. The challenge is that the calculated evaporation rates using the earlier models seemed to differ from that of the recent models (note both types of models were validated in the literature by experiments). We have reinvestigated the recent models and found that the mathematical simplifications in solving the Dirichlet problem in toroidal coordinates have created the inconsistency. We also proposed a closed form approximation for f ( θ ) which is valid in a wide range, i.e. 8 ° ≤ θ ≤ 131°. Using the proposed model in this study, theoretically, it was shown that the evaporation rate in the CWA (constant wetted area) mode is faster than the evaporation rate in the CCA (constant contact angle) mode for a sessile drop. [ABSTRACT FROM AUTHOR]

A rotating circular disk with variable thickness under thermal environment is investigated in this paper. The circular disk is made of functionally graded magneto-electro-elastic (FGMEE) material, which is a mixture of piezoelectric (PE) and piezomagnetic (PM) materials, and the material properties are assumed to vary along the radius of the disk exponentially. In order to study the thermo-magneto-electro-elastic behavior of the FGMEE circular disk, equations of heat conduction, electrostatics and magnetostatics are established, and the governing equation expressed by displacement is finally solved utilizing a semi-analytical method. Numerical results separately show the effect of material properties, material components, geometric shapes and rotating speeds on the thermo-magneto-electro-elastic behaviors of the FGMEE circular disk. In the discussions of influences of various parameters to the results, material property parameters are the temperature change index and functionally graded index, material component parameter is the volume fraction of PE material, and geometric parameters are the inner-outer thickness ratio, thickness change index and inner-outer radius ratio. Results in this study may be useful for the optimal design of rotating FGMEE circular disks with variable thickness. [ABSTRACT FROM AUTHOR]

A helicopter flying through an atmosphere containing particulates may accumulate high electrostatic charges which can challenge its operational safety. In this paper we elaborate and validate a triboelectric charging model to predict the electrification experienced by a helicopter while hovering in dusty air. We employed Large Eddy simulations to describe the turbulent structures inherent in the flow around the rotorcraft. The dust particles were tracked individually in a Lagrangian framework. A model accounting for the triboelectric charge transfer when a particle hits the helicopter was introduced. The results demonstrate the accuracy of the proposed approach and allow a detailed analysis of the location of the charge accumulation. [ABSTRACT FROM AUTHOR]

In this paper, the distribution of 210 Po after high temperature processes in six units of coal-fired power plants (CFPs) were evaluated. The coal, bottom ashes, fly ashes from electrostatic precipitators (ESP), and flue gases from stacks were sampled from four CFPs and analyzed for 210 Po contents. The results showed that 210 Po was mainly captured by the ESP, with little left in the bottom ash, and a small fraction of 210 Po was directly discharged into the environment through the stacks, accounting for 0.06%–0.6%, which was consistent with the reported data. It was also found that part of the 210 Po could not be accounted for in the mass balance analysis for the whole combustion process in CFPs, which was also in line with the reported data. The results obtained in this study provided essential basic data for environmental radiological risk analysis for CFPs. [ABSTRACT FROM AUTHOR]

Viscoelastic phenomena widely exist in MEMS materials, which may have certain effects on quasi-static behaviors and transition mechanism of nonlinear jumping phenomena. The static and dynamic behaviors of a doubly clamped viscoelastic microbeam actuated by one sided electrode are investigated in detail, based on a modified couple stress theory. The governing equation of motion is introduced here, which is essentially nonlinear due to its midplane stretching effect and electrostatic force. Through quasi-static analysis, the equilibrium position, pull-in voltage and pull-in location of the system are obtained with differential quadrature method and finite element method. The equivalent geometric nonlinear parameter is presented to explain the influence of the scale effect on the pull-in location. Different from elastic material, there are two kinds of pull-in voltages called as instantaneous pull-in voltage and the durable pull-in voltage in viscoelastic system. Then, Galerkin discretization and the method of multiple scales are applied to determine the response and stability of the system for small vibration amplitude. A new perturbation method to deal with viscoelastic term is presented. Theoretical expressions about the parameter spaces of linear-like vibration, hardening-type vibration and softening-type vibration are then deduced. The influence of viscoelasticity and scale effect on nonlinear dynamic behavior is studied. Results show that the viscoelasticity can reduce the effective elastic modulus and make the system tend to softening-type vibration; the scale effect can increase effective elastic modulus and make the system tend to hardening-type vibration. And most of all, simulation results of case studies are used to realize parameter optimization. Then parameter conditions of linear-like vibration, which is desired for many applications, are obtained. In this paper, the results of multi-physical field coupling simulation are used to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

A generalized formulation for coagulation of charged particles is presented in this paper. The governing equations can be solved semi-implicitly for a number of discrete size and charge bins. The computationally efficient mechanism gives volume and charge conserved solution with time. A distinct way of handling electrostatic dispersion in dynamic model has been used in this work. The scheme has been tested for charged, nebulized aerosol particles by model studies and also compared with experimental observations. The model simulated results show that charge can significantly affect the coagulation dynamics if charge level is higher than the Boltzmann equilibrium charge limit for less than 1 μm particles. It was found that for the bipolar charge case, there was a significant effect on the enhancement of the coagulation process. For the case of unipolar charge, electrostatic dispersion was seen to play a role in the depletion of number concentration. The model was then validated against results of six controlled experiments in which electrical low pressure impactor (ELPI) was used for measurement of charge and number size distribution. Our model results were found to be in reasonable agreement with observed values. The developed model is fast (independent of time step) and numerically stable. It can be used for several applications involving coagulation dynamics of charged aerosol particles. [ABSTRACT FROM AUTHOR]

Electrons injected into the build envelope during powder bed electron-beam additive manufacturing can accumulate on the irradiated particles and cause them to repel each other. Under certain conditions, these electrostatic forces can grow so large that they drive the particles out of the build envelope in a process known as “smoking”. In the present work, we investigate the causes of powder bed charging and smoking during electron-beam additive manufacturing. In the first part of the paper, we characterize the surface chemistry of a common feedstock material—gas-atomized Ti-6Al-4V powder—and find that a thick, electrically insulating oxide overlayer encapsulates the particles. Based on these experimental results, we then formulate an analytical model of powder bed charging in which each particle is approximated as a capacitor, where the particle and its substrate are the electrodes and the oxide overlayer is the dielectric. Using this model, we estimate the charge distribution in the powder bed, the electrostatic forces acting on the particles, and the conditions under which the powder bed will smoke. It is found that the electrical resistivity of the oxide overlayer strongly influences the charging behavior of the powder bed and that a high resistivity promotes charge accumulation and consequent smoking. This analysis suggests new quality control and process design measures that can help suppress smoking. [ABSTRACT FROM AUTHOR]

The paper reports a simple electrostatic self-assembly method to fabricate the gold nanoparticles/graphene oxide (Au NPs@GO) films which present superior SERS activity. The Au NPs@GO films with different layers construction and surface compositions (with Au NPs or GO as the outer layer) are obtained simply by changing the self-assembly cycles. Results indicate that the film with two assembly cycles (F-2 film) exhibits the best SERS activity towards R6G molecules compared with that of one assembly cycle (F-1 film) and three assembly cycles (F-3 film) due to the high loadings of the absorbed Au NPs exposed on the surface of the film. Meanwhile, the Raman enhancement effect of the F-2 film with the outer layer of Au NPs is better than that of the outer layer covering with GO sheets (F-2-GO) possibly owing to the optimal synergetic effect of Au NPs and GO. Furthermore, our fabricated Au NPs@GO films present favorable reproducibility and high stability, which are significant for the practical application of these SERS substrates. [ABSTRACT FROM AUTHOR]

Thus far, Computational Fluid Dynamics (CFD) simulations fail to predict the electrostatic charging of particle–gas flows reliably. The lack of a predictive tool leads to powder operations prone to deposits and discharges, making chemical plants unsustainable and prime candidates for explosions. This paper reviews the rapid progress of numerical models in recent years, their limitations, and outlines future research. In particular, the discussion includes CFD models for the physics and chemistry of particle electrification. The condenser model is most popular today in CFD simulations of powder flow electrification but fails to predict most of its features. New experiments led to advanced models, such as the non-uniform charge model, which resolves the local charge distribution on non-conductive particle surfaces. Further, models relying on the surface state theory predicted bipolar charging of polydisperse particles made of the same material. While these models were usually implemented in CFD tools using an Eulerian–Lagrangian strategy, recently Eulerian methods successfully described powder charging. The Eulerian framework is computationally efficient when handling complete powders; thus, Eulerian methods can pave the way from academic studies to application, simulating full-scale powder processing units. Overall, even though CFD models for powder flow charging improved, major hurdles toward a predictive tool remain. • Simulating powder flow charging is an unsolved multi-scale and -physics problem. • Highly resolved Lagrangian simulations reveal the particle charging dynamics. • The particle charging model is the largest contributor to the simulation error. • New experiments and nano-scale models capture same-material and bipolar charging. • Eulerian simulations can cover complete conveyors but struggle with polydispersity. [ABSTRACT FROM AUTHOR]

The dynamic response of a MEMS accelerometer can be influenced by several multi-physics effects, especially if the gaps between the shuttle and the stator attain sub-micrometric values. The present paper aims at tackling the aforementioned issues by means of a suitable experimental procedure, which has been purposely devised for the problem at hand, and through the execution of numerical analyses (based on the Finite Element Model). The effect of parasitic electrostatic forces and hydrodynamic forces is clearly demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, a new box iterative method for solving a class of nonlinear interface problems is proposed by intermixing linear and nonlinear boundary value problems based on a special seven-overlapped-boxes partition. It is then applied to the construction of a new finite element and finite difference hybrid scheme for solving the Poisson–Boltzmann equation (PBE) — a second order nonlinear elliptic interface problem for computing electrostatics of an ionic solvated protein. Furthermore, a modified Newton minimization algorithm accelerated by a multigrid preconditioned conjugate gradient method is presented to efficiently solve each involved nonlinear boundary value problem. In addition, the analytical solution of a Poisson dielectric test model with a spherical solute region containing multiple charges is expressed in a simple series of Legendre polynomials, resulting in a new PBE test model that works for a large number of point charges. The new PBE hybrid solver is programmed as a software package, and numerically validated on the new PBE test model with 892 point charges. It is also compared to a commonly used finite difference scheme in the accuracy of computing solution and electrostatic free energy for three proteins with up to 2124 atomic charges. Numerical results on six proteins demonstrate its high performance in comparison to the PBE finite element program package reported in Xie (2014). [ABSTRACT FROM AUTHOR]

On the contact surfaces of footwear loosely, moderately and strongly held particle fractions were separated and analyzed in an effort to detect different particle signals. Three environmental exposure sites were chosen to have different, characteristic particle types (soil minerals). Shoes of two types (work boots and tennis shoes) were tested, accumulating particles by walking 250m in each environment. Some shoes were exposed to only one environment; others were exposed to all three, in one of six different sequences. Sampling methods were developed to separate particles from the contact surface of the shoe based on how tightly they were held to the sole. Loosely held particles were removed by walking on paper, moderately held particles were removed by electrostatic lifting, and the most tightly held particles were removed by moist swabbing. The resulting numbers and types of particles were determined using forensic microscopy. Particle profiles from the different fractions were compared to test the ability to objectively distinguish the order of exposure to the three environments. Without exception, the samples resulting from differential sampling are dominated by the third site in the sequential footwear exposures. No noticeable differences are seen among the differential samplings of the loosely, moderately and strongly held particles: the same overwhelming presence of the third site is seen. It is clear from these results (1) that the third (final) exposure results in the nearly complete removal of any particles from prior exposures, and (2) that under the experimental conditions loosely, moderately and strongly held particles are affected similarly, without any detectable enrichment of the earlier exposures among the more tightly held particles. These findings have significant implications for casework, demonstrating that particles on the contact surfaces of footwear are rapidly lost and replaced. [ABSTRACT FROM AUTHOR]

Improving the dispersion of graphene nanosheets (GN) in a polymer matrix is a critical step in lowering the percolation threshold of nanocomposites. In this paper, an effective method based on an electrostatic assembly process is reported. Polystyrene (PS) latex was first prepared by using hexadecyl trimethyl ammonium bromide (CTAB) as a cationic surfactant, which created positive charges on the surface of the PS micelles. An in situ demulsification process was then conducted by adding negatively charged graphene oxide (GO) particles into the positively charged PS latex. Thus, GO sheets were attached spontaneously to the surfaces of PS particles through electrostatic adsorption. Followed by in situ reduction and hot pressing, the agglomeration of GN was largely prohibited by the PS microspheres and facilitated the formation of GN networks in the PS matrix. The obtained PS/GN nanocomposites exhibited excellent electrical properties with a percolation threshold as low as 0.054 vol.% GN. When the GN content reached 1.53 vol.%, the electrical conductivity was 46.32 S/m and the thermal conductivity 0.47 W/mk. This strategy represents a new environment-friendly pathway, which is also applicable for other polymer matrices, for large-scale production of polymer composites with fully interconnected graphene networks at ultra-low GN content. [ABSTRACT FROM AUTHOR]

In this paper we describe a novel method for delivering a precise, known amount of electric charge to a micron-sized solid target. Aerosolised microparticles passed through a plasma discharge will acquire significant electric charge. The fluid stability under evaporative stress is a key aspect that is core to the research. Initially stable charged aerosols subject to evaporation (i.e. a continually changing radius) may encounter the Rayleigh stability limit. This limit arises from the electrostatic and surface tension forces and determines the maximum charge a stable droplet can retain, as a function of radius. We demonstrate that even if the droplet charge is initially much less than the Rayleigh limit, the stability limit will be encountered as the droplet evaporates. The instability emission mechanism is strongly linked to the final charge deposited on the target, providing a mechanism that can be used to ensure a predictable charge deposit on a known encapsulated microparticle. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a modified active contour model based on p-Laplace equation for image segmentation. By combining the region information with the variable exponent p-Laplace energy, the modified model can fast and accurately segment the image with complex topological changes with flexible scheme of level set function initialization. Firstly, the region information is used to find the contours nearby the object boundaries. Secondly, the variable exponent p-Laplace energy is used for the regularization of the zero level contours that move to the accurate object boundaries with complex topological changes and deep depression. In addition, the Gaussian filter is used to keep the level set smoothing in the evolution process. Finally, the numerical scheme of the partial difference equation (PDE) based modified model is implemented via a simple finite difference method. And the scheme of level set function initialization can be chosen flexibly (i.e. a bounded constant function, a signed distance function(SDF) or a piecewise constant function). The experiment results on some synthetic and real images show that the modified model can segment complex object boundaries and the evolution of contours do not sensitive to the scheme of the level set function initialization. [ABSTRACT FROM AUTHOR]

Blending drug and carrier powders to produce homogeneous drug–carrier adhesive mixtures is a key step in the production of dry powder inhaler (DPI) formulations. Although the blending conditions can result in different conclusions or probably change the outcome of a study entirely if being selected differently, there is a scarcity of data on the influence of blending processes on the physicochemical properties of bulk powder formulations and the follow-on effects on DPI performance. This paper provides an overview of the interactions between variables related to blending conditions (e.g. blending equipment, time, speed and sequence as well as environmental humidity) and powder physicochemical properties (e.g. size distribution, shape distribution, density, anomeric composition, electrostatic charge, surface, and bulk properties), and their effects on the performance of adhesive mixtures for inhalation in terms of drug content homogeneity, drug–carrier adhesion, and drug aerosolisation behaviour. The relevance of carrier payload, batch size and segregation was also discussed. Challenges and future directions were identified. This review therefore contributes towards a better understanding of the blending process, powder physicochemical properties, and their interlinked effects on the fundamental understanding of adhesive mixtures for inhalation. The knowledge gained is essential to ensure optimum blending and thereby controlled functionality of DPIs. [ABSTRACT FROM AUTHOR]

The interaction between chitosans and Langmuir monolayers mimicking cell membranes has been explained with an empirical scheme based on electrostatic and hydrophobic forces, but so far this has been tested only for dimyristoyl phosphatidic acid (DMPA). In this paper, we show that the mode of action in such a scheme is also valid for dipalmitoyl phosphatidyl choline (DPPC) and dipalmitoyl phosphatidyl glycerol (DPPG), whose monolayers were expanded and their compressibility modulus decreased by interacting with chitosans. In general, the effects were stronger for the negatively charged DPPG in comparison to DPPC, and for the low molecular weight chitosan (LMWChi) which was better able to penetrate into the hydrophobic chains than the high molecular weight chitosan (Chi). Penetration into the hydrophobic chains was confirmed with polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) and sum frequency generation (SFG) spectroscopy. A slight reduction in conformational order of the lipid chains induced by the chitosans was quantitatively estimated by measuring the ratio between the intensities of the methyl (r + ) and methylene (d + ) peaks in the SFG spectra for DPPG. The ratio decreased from 35.6 for the closely packed DPPG monolayer to 7.0 and 6.6 for monolayers containing Chi and LMWChi, respectively. Since in both cases there was a significant phospholipid monolayer expansion, the incorporation of chitosans led to chitosan-rich and lipid-rich condensed domains, which mantained conformational order for their hydrophobic tails. The stronger effects from LMWChi are ascribed to an easier access to the hydrophobic tails, as corroborated by measuring aggregation in solution with dynamic light scattering, where the hydrodynamic radius for LMWChi was close to half of that for Chi. Taken together, the results presented here confirm that the same mode of action applies to different phospholipids that are important constituents of mammalian (DPPC) and bacterial (DPPG) cell membranes. [ABSTRACT FROM AUTHOR]

This paper examines the surprisingly large electrical current, nanoamps instead of picoamps, observed when sampling soot aerosol through an electrostatic trap. Aside from its fundamental interest, this phenomenon has potential practical application to motor vehicle on-board diagnostics of particulate matter emissions. The effect originates from the collection of electrically charged particles naturally present in flame produced soot onto the opposing polarity electrodes, but the measured current is ~10 3 times larger than carried by the soot. This amplified current is proportional to the flux of soot particles in steady state, but voltage and flow perturbations substantially magnify the effect. The amplification is not immediate; rather it follows a quiescent period, inversely proportional to soot concentration, which can last hundreds of seconds before climbing rapidly to tens of nanoamps. Concomitantly, large highly charged particles appear at the trap exit, of order 10 μm and carrying tens to hundreds of charges. In situ microscopy reveals that this coincides with the growth of dendritic structures aligned with the electric field, which collapse when it is turned off. As charged soot particles flow through the trap these structures exhibit vigorous apparent motion and detachment from one electrode and deposition onto the other. We present a kinetic model to explain this trap behavior. It is based on the assumption that the dendrites grow to a critical height at which the electric field force exceeds the binding force and the dendrites fragment. These highly charged fragments then deposit on the opposite electrode propagating a chain reaction of dendrite growth, fragmentation, and charge transport that produces the observed current amplification. [ABSTRACT FROM AUTHOR]

This paper examines the enhancement of static and dynamic travel range of electrostatically driven microbeams using shape optimization approach. Continuous functions of width and thickness are used for optimizing the geometry of both cantilever and fixed–fixed microbeams. Rayleigh–Ritz energy method is employed to compute the static and dynamic pull-in parameters. Particle swarm optimization and hybrid simulated annealing are used for shape optimization of microbeams. Constraints on design variables are imposed using penalty approach. Enhanced pull-in parameters obtained for variable geometry microbeams have been validated using 3-D finite element analysis. Optimized shapes of microbeams show significant improvement in static and dynamic travel range. Pull-in displacement is increased up to 54.92% for cantilever microbeam and 40.79% for fixed–fixed microbeam with hybrid simulated annealing. Effectiveness of particle swarm optimization is brought out through representative test cases. The convergence of the particle swarm optimization is approximately five times faster as compared to the hybrid simulated annealing, while maintaining the same level of accuracy. [ABSTRACT FROM AUTHOR]

The electrostatic forming membrane reflector antenna (EFMRA) is a promising scheme to construct large-size, high-precision and lightweight space deployable reflector antennas. A set of comprehensive structural optimization design procedures is presented for EFMRA in this paper. This procedure consists of four steps: Firstly, a synthesized form-finding method is introduced for the AstroMesh structure which is the structural foundation of the EFMRA. Based on the nonlinear force density method, a fast iterative format is derived, using which we can get a initial state in which the tensions of the front rear cable networks and one electrode membrane are completely uniform, and all the nodes of the front networks are on the ideal paraboloid. Secondly, based on the finite element theory, a structure-electrostatic coupled analysis model is established to take the coupled field problems into consideration. Thirdly, a technique is proposed to optimize the initial reflective membrane geometry. The shape of the membrane is expressed by a set of polynomials, and the polynomial coefficients are optimized to obtain optimal geometry of the reflective membrane. Moreover, the controlling voltage adjustment model is established, which is solved by sensitivity analysis. At length, these proposed methods are applied to the structural optimization design of an EFMRA. The results validate the effectiveness of this comprehensive optimization procedure and the feasibility of designing the EFMRA to compensate the errors introduced from manufacturing process and environmental changes. [ABSTRACT FROM AUTHOR]

We recently proposed a straightforward fluorescence microscopy technique to study adhesion of Giant Unilamellar Vesicles. This technique is based on dual observations which combine epi-fluorescence microscopy and total internal reflection fluorescence (TIRF) microscopy: TIRF images are normalized by epi-fluorescence ones. By this way, it is possible to map the membrane/substrate separation distance with a nanometric resolution, typically ~ 20 nm, with a maximal working range of 300–400 nm. The purpose of this paper is to demonstrate that this technique is useful to quantify vesicle adhesion from ultra-weak to strong membrane–surface interactions. Thus, we have examined unspecific and specific adhesion conditions. Concerning unspecific adhesion, we have controlled the strength of electrostatic forces between negatively charged vesicles and various functionalized surfaces which exhibit a positive or a negative effective charge. Specific adhesion was highlighted with lock-and-key forces mediated by the well defined biotin/streptavidin recognition. [ABSTRACT FROM AUTHOR]

The paper investigates some analytical and numerical aspects of the formation control exploited by means of inter-spacecraft electrostatic actions. The analysis is based on the evaluation and check of the stability issues by using a sequence of purposely defined Lyapunov functions. The same Lyapunov approach can also define a specific under-actuate control strategy for controlling selected “virtual links” of the formation. Two different selection criteria for these links are then discussed, showing the implications on the control chain. An optimal charge distribution strategy, which assigns univocally the charges to all the spacecraft starting from the charge products computed by the control, is also presented and discussed. Numerical simulations prove the suitability of the proposed approach to a formation of 4 satellites. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present conceptually newer design of electrostatically driven cantilever microbeams for enhancing their dynamic travel range. For dynamic analysis, Rayleigh's energy method is used. Design parameters defining width and thickness profiles are optimized using modified particle swarm optimization (MPSO) while satisfying imposed constraints. Results of test cases indicate maximum rise of around 50% in dynamic travel range is obtained compared to referential prismatic microbeam. Dynamic pull-in parameters obtained using modified particle swarm optimization show close agreement with those obtained using hybrid simulated annealing however, MPSO is almost five times faster while maintaining the same accuracy. [ABSTRACT FROM AUTHOR]

In this paper, the vibration suppression of micro- or nano-scale cantilever beams used in M/NEMS devices is studied. The beam is subjected to some nonlinear distributed forces, namely electrostatics force with first order fringing field correction, Casimir, and van der Waals forces. For the sake of precision, the beam is modeled by strain gradient elasticity theory capable of predicting the size effects in mechanical behavior of small-scale flexible structures. Since the governing partial differential equation of motion is nonlinear, the linearization approach is adopted to tackle the control problem. A novel control law is proposed that guarantees the exponential stability of the linearized closed-loop system and also the local stability of original nonlinear closed-loop system. To prepare the model for computer simulations, the continuous model is truncated to a set of nonlinear ordinary differential equations by using Kantorovich method. Simulation results show that the proposed controller not only suppresses the forced vibration of the beam before crossing dynamic pull-in threshold, but also it extends the dynamic pull-in criterion. [ABSTRACT FROM AUTHOR]