Cascade position control of a single pneumatic artificial muscle–mass system with hysteresis compensation

The inherent hysteresis in a pneumatic artificial muscle (PAM) makes it difficult to control accurately the position of the PAM’s end effector. This hysteresis causes energy loss and the area of the hysteresis loop is dependent on the amplitude of the motion and on the underlying causes of the hysteresis phenomenon. This means that if the hysteresis energy loss is properly compensated, a more accurate positioning would be achieved. In this paper, the pressure/length hysteresis of a single PAM is modeled by using a Maxwell-slip model. The obtained model is used in the feedforward path of a cascade position control scheme, in which the inner loop is designed to cope with the nonlinearity of the pressure buildup inside the PAM, whereas the outer loop is designed to cope with the nonlinearity of the PAM dynamics itself. The experimental results show that position control of a single PAM–mass system with hysteresis compensation (HC) is effectively improved compared to a control without HC, and the control system shows high robustness to load changes.     

Experimental determination of the derivative of the current–voltage characteristic of a nonlinear semiconductor structure using modulation Fourier analysis

The derivative of the nonlinear current–voltage characteristic of two antiparallel p–n junctions is experimentally obtained by the method of modulation Fourier analysis. The derivative of the current–voltage characteristic is reconstructed using the current dependences of the first and higher voltage harmonics. The advantage of modulation Fourier analysis over numerical differentiation is experimentally validated for the first time. The applied technique has no limitations on the current modulation amplitude. Large amplitudes make it possible to identify the nature of the nonlinearity of the dependence under study and to determine the contribution of the nonlinear fraction against the background of significant linearity.     

Diffraction of a plane electromagnetic wave by a circular dielectric cylinder with a finite-length perfectly conducting metal strip on the Cylinder’s lateral surface

The diffraction of E-and H-polarized plane electromagnetic waves by a circular dielectric cylinder with a finite-length perfectly conducting metal strip on the cylinder’s lateral surface is considered. The diffraction problem is solved with the use of the method of singular integral equations. The distributions of the surface current on the metal strip are calculated. The patterns of the reflected electromagnetic field are determined from these distributions for various incidence angles of the plane electromagnetic wave. It is shown that the pattern of the diffracted field strongly depends on the angle of the wave incidence on the metal strip.     

Transition times between the extremum points of the current–voltage characteristic of a resonant tunneling diode with hysteresis

A numerical solution to the problem of transient processes in a resonant tunneling diode featuring a current–voltage characteristic with hysteresis is found for the first time in the context of a coherent model (based on the coupled Schrödinger and Poisson equations) taking into account the Fermi distribution of electrons. The transitions from the high-current to the low-current state and vice versa, which result from the existence of hysteresis and are of great practical importance for ultrafast switches based on resonant tunneling diodes, are studied in detail. It is shown that the transition times for such processes initiated by the application of a small voltage can significantly exceed the characteristic time ?/Γ (where G is the width of the resonance level). It is established for the first time that the transition time can be reduced and made as short as the characteristic time ?/Γ by applying a sufficiently high voltage. For the parameters of the resonant-tunnelingdiode structure considered in this study, the required voltage is about 0.01 V.     

Generation of surface electron states with a silicon–ultrathin-oxide interface under the field-induced damage of metal–oxide–semiconductor structures

The high-frequency capacitance–voltage characteristics of metal–oxide–semiconductor structures on n-Si substrates with an oxide thickness of 39 Å are studied upon being subjected to damage by field stress. It is shown that the action of a high, but pre-breakdown electric field on an ultrathin insulating layer brings about the formation of a large number of additional localized interface electron states with an energy level arranged at 0.14 eV below the conduction band of silicon. It is found that, as the field stress is increased, the recharging of newly formed centers provides the accumulation of excess charge up to 8 × 10¹² cm^–2 at the silicon–oxide interface. The lifetime of localized centers created under field stress is two days, after which the dependences of the charge localized at the semiconductor–insulator interface on the voltage at the gate after and before field stress are practically the same.     

Two-tone nonlinear electrostatic waves in the quantum electron–hole plasma of semiconductors

Longitudinal electrostatic waves in the quantum electron–hole plasma of semiconductors are considered taking into account the degeneracy of electrons and holes and the exchange interaction. It is found in the framework of linear theory that the dispersion curve of longitudinal waves has two branches: plasmon and acoustic. An expression for the critical cutoff frequency for plasma oscillations and an expression for the speed of sound for acoustic vibrations are derived. It is shown that the plasma wave always exists in the form of a superposition of two components, characterized by different periods and wavelengths. Two nonlinear solutions are obtained within nonlinear theory: one in the form of a simple superposition of two tones and the other in the form of beats.     

Detection of a random process with the use of a δ-doped Schottky diode

The problem of finding the mean value and variance of the output process that occur in the course of noninertial detection of a random stationary process with the use of a δ-doped Schottky diode has been studied with the feedback taken into account. The dependences of the output parameters on the input parameters have been obtained within a Gaussian approximation. The effect of the inertia of the detecting system using the δ-doped Schottky diode on the simple statistical characteristics of the output process have been analyzed.     

A Simple Variant of the Merkle–Damg?rd Scheme with?a?Permutation

We propose a new composition scheme for hash functions. It is a variant of the Merkle–Damg?rd construction with a permutation applied right before the processing of the last message block. We analyze the security of this scheme using the indifferentiability formalism, which was first adopted by Coron et al. to the analysis of hash functions. We also study the security of simple MAC constructions out of this scheme. Finally, we discuss the random oracle indifferentiability of this scheme with a double-block-length compression function or the Davies–Meyer compression function composed of a block cipher.     

CVD-growth of CNT with the use of catalutic Ct–Me–N–O thin films incorporated in the technology

The process of the formation of carbon nanotube arrays on Ct–Me–N catalytic alloys of low nickel content (10–20 at %) by chemical vapor deposition, where Ct is a catalytic metal from the group of Ni, Co, Fe, and Pd, and Me is a transition metal of group IV–VII of the periodic table, was investigated. It is shown that CNT grow effectively when the alloy contains Ti, V, Cr, Zr, Hf, Nb, and Ta. The addition of nitrogen and oxygen to the alloy’s composition gives rise to a buildup of oxynitrides, expelling of the catalyst, and formation of its clusters on the surface. The replacement of metals in the alloy has an effect on the diameter of the CNT. Moreover, the alloy films 10–500 nm thick can be used for the CNT growth, which is responsible for high degree of homogeneity and the repeatability of the process. CNT growth was not observed when the alloy contained W and Re.     

Temperature dependence of the contact resistance of ohmic contacts to III–V compounds with a high dislocation density

A new mechanism describing the rise in the contact resistance ?? _c of ohmic contacts to n-n ⁺-n ⁺⁺-GaAs(GaP, GaN, InP) structures with increasing measurement temperature T, experimentally observed in the temperature range 100?C400 K, is suggested on the basis of a theoretical analysis of the temperature dependence of ?? _c . Good agreement between the experimental and theoretical ?? _c (T) dependences is obtained and explained for a case where there is a high density of dislocations (on which metallic shunts are localized) in the near-contact region of the semiconductor.     

Controllable synthesis of Sm2O3 crystallites with the assistance of templates by a hydrothermal–calcination process

Sm₂O₃ crystallites were controllably synthesized by the hydrothermal–calcination process with the assistance of different templates. The phase compositions, morphologies and optical properties of the as-prepared samples were characterized by X-ray diffraction, scanning electron microscope and ultraviolet–visible spectrophotometer. It is investigated that the influence of different templates on the structural and optical properties of Sm₂O₃ samples. Results showed that Sm₂O₃ crystallites with ribbon-like, granular and flake-like morphologies were obtained when NaNO₃, trisodium citrate and polyvinyl-pyrrolidone (PVP) were used as template agents. These templates effectively controlled the microstructure and optical properties of the as-prepared samples. The monoclinic phase Sm₂O₃ crystallites with ribbon-like morphology were prepared by using NaNO₃ as the template agent, which energy gap is only 4.827 eV.     

Technique for the Electrochemical Capacitance–Voltage Profiling of Heavily Doped Structures with a Sharp Doping Profile

Semiconductors - The specific features of applying electrochemical capacitance–voltage profiling to investigate heavily doped structures with a sharp doping profile are considered. Criteria...     

Influence of air gaps on the thermal–electrical–mechanical behavior of a copper metallization

Shrinking the IC dimensions the dielectric insulation between metal interconnects has become one of the major limits on increasing circuit speed. A lot of possible new low-k materials failed to meet specifications: too leaky, too soft, too unstable, and too expensive. Due to this air gaps beside the metallization are one solution. The reliability of ULSI multilevel copper metallizations under electro- and stress migration stress test conditions is investigated here with finite element analysis. A determination of the electrical and mechanical stress in a 3D copper metallization model based on the 45 nm technology node is carried out and the impact of a variation of the applied current density as well as geometrical parameters on the thermal–electrical and mechanical behavior is investigated. For a determination of the reliability the mass flux and mass flux divergence are separately calculated by a user routine. The influence of air gaps on single via structures and structures with a chain of four vias on the thermal–electrical–mechanical behavior is determined.     

Method of the Amplitude–Phase Synthesis of a Pareto-Optimal Planar Antenna Array

A method of the amplitude–phase multicriteria synthesis of a Pareto-optimal antenna array is proposed. The method is based on representation of the initial antenna array synthesis problem in the form of successively solved partial problems (subproblems) with small dimensionality. Each subproblem is reduced to determination of Pareto-optimal parameters of the amplitude–phase distribution of an additional beam added to the initial radiation pattern.     

The influence of a voltage ramp on the measurement of I–V characteristics of a solar cell

For convenience and efficiency the voltage applied to a Si solar cell is often fairly rapidly driven from zero to the open circuit value typically at a constant rate of 1 V per millisecond. During this time the values of the current are determined as a function of the instantaneous voltage thus producing an I–V characteristic. It is shown here that the customary expressions for the current as a function of cell parameters remain still valid provided that the diffusion length in the expression for the dark current is changed from its steady state value L to the effective diffusion length L_i given by

$\text{L}{}_1\text{= L}\text{1+}\text{q}\text{V}\text{?}\text{kT}{}^{\mathrm{\tau }}\text{,}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$

where V is the ramp rate considered constant and τ is the lifetime of minority carriers. This result is true to a very good approximation provided that low level injection prevails.     

Amplitude regeneration of NRZ–DPSK signal with a feed-forward control circuit

An optical-and-electrical hybrid-type amplitude regenerator for an NRZ–DPSK signal suffering from optical amplifier noise is described. The system is a feed-forward control circuit composed of a coupler, a photo detector, and an intensity modulator, and works to suppress intensity fluctuations in a DPSK signal while preserving phase information. A schematic explanation of how the DPSK transmission performance is improved with intensity noise suppression during transmission is presented, and an experiment to demonstrate its effect is conducted.     

Peculiarities of the Properties of III–V Semiconductors in a Multigrain Structure

The systematized results of studies of the properties of InAs, InSb, and GaAs semiconductors in a multigrain structure based on measurement and analysis of the current–voltage and spectral characteristics are presented. It is established that electron emission and injection are determined by the localization effects of states in the bulk and surface region of submicron grains. The phenomena of current limitation and lowfield emission characteristic of quantum dots are revealed and studied. The results can be used in studies and in the development of multigrain structures for gas and optical sensors, detectors, and emitters of infrared and terahertz ranges.     

Synthesis of a novel organic nonlinear optical chromophore and the Testing for μgβ Value

A novel second-order nonlinear optical chromophore (DCDHF-2-V) was synthesized from 3-Hydroxy-3-methyl-2-butanae,propanedinitrile and 4-diethylaminobenzaldehyde by aldol condensation reaction. Molecular structural characterization was investigated by elemental analysis,FTIR,and 1H-NMR spectra. The melting point obtained from DSC thermogram was almost 251 ℃,and the compound shows a thermal stability up to 270 ℃. Second-order NLO properties of the chromophore were measured by solvatochromic method. From the quantum-mechanical two-level model,it can be obtained that the μgβ value of DCDHF-2-V is 6520 × 10-48 esu atthe wavelength of 1064 nm.     

Synthesis of a novel organic nonlinear optical chromophore and the Testing for μgβ Value

Much attention has been devoted to nonlinear optica (NLO) materials over the past decade because of the poten tial applications in the field of telecommunications, optica signal processing, optical switching, and so forth. Organi NLO materials with high p…