Arbitrary Width Research Articles

Inhibition of Rayleigh-Plateau instability on a unidirectionally patterned substrate

A fundamental process of surface energy minimization is the decay of a wire into separate droplets initiated by the Rayleigh-Plateau instability. Here we study the linear stability of a wire deposited on a unidirectionally patterned substrate with the wire being aligned with the pattern. We show that the wire is stable when a criterion that involves its width and the local geometry of the substrate at the triple line is fulfilled. We present this criterion for an arbitrary shape of the substrate and then give explicit examples. Our result is rationalized using a correspondence between the Rayleigh-Plateau instability and the spinodal decomposition. This work provides a theoretical tool for an appropriate design of the substrate's pattern in order to achieve stable wires of, in principle, arbitrary widths.

Asymptotic description of chirped Gaussian pulse propagation of arbitrary initial width in a causally dispersive dielectric

The combined influence of dispersion and absorption in chirped Gaussian pulse propagation of arbitrary initial width in a causal dielectric is shown to be intrinsically related to the dynamics of the saddle points of the phase function appearing in the unified, exact integral expression of the propagated field. The employed asymptotic approach provides, from the slowly varying envelope to the sub-cycle regime, an accurate description of the dynamical evolution of the propagated field, which is comprised of pulse components each being due to the asymptotic contribution of a relevant saddle point.

A first-principles study of a single C-chain doped AlN nanoribbons

Under the generalized gradient approximation (GGA), the structural and electronic properties are studied for both zigzag (ZAlNNRs) and armchair (AAlNNRs) AlN nanoribbons terminated with H atoms at both edges by using the first-principles projector-augmented wave (PAW) potential within the density function theory (DFT) framework. The results show that the Al–N, Al–C and Al–H bonds are ionic bonds while the C–C and C–H bonds are typical covalent bonds, and the N–C and N–H bonds have a degree covalent character. The systems of both perfect 7-ZAlNNR and perfect 7-AAlNNR with a single C-chain doped are still nonmagnetic semiconductors, and the C-chain reduces the band gap. The C-chain can change the band gap of 7-ZAlNNR from direct to indirect independent of the position of the C-chain, which is important in the practical application as light emitting devices. For NZ-ZAlNNR-C(n) with NZ=3, 5, 6, 10, the band gap decrease successively for C-chain position n from 2 to 3, 5, 6, 7 and 10, respectively. For NA-AAlNNR-C(n) of arbitrary width NA, except NA-AAlNNR-C(1) and NA-AAlNNR-C(n=NA) have a larger band gap, the band gap of the rest of the NA-AAlNNR-C(n) are about 2.0eV. Furthermore, the maximum band gap gradually decrease with the increase of the width NA. The C-chain substituting Al–N chain process is endothermic for both 7-ZAlNNR and 7-AAlNNR.

인공 신경망을 이용한 광대역 과정의 피로 손상 모델 개발

For the frequency-domain spectral fatigue analysis, the probability density function of stress range needs to be estimated based on the stress spectrum only, which is a frequency domain representation of the response. The probability distribution of the stress range of the narrow-band spectrum is known to follow the Rayleigh distribution, however the PDF of wide-band spectrum is difficult to define with clarity due to the complicated fluctuation pattern of spectrum. In this paper, efforts have been made to figure out the links between the probability density function of stress range to the structural response of wide-band Gaussian random process. An artificial neural network scheme, known as one of the most powerful system identification methods, was used to identify the multivariate functional relationship between the idealized wide-band spectrums and resulting probability density functions. To achieve this, the spectrums were idealized as a superposition of two triangles with arbitrary location, height and width, targeting to comprise wide-band spectrum, and the probability density functions were represented by the linear combination of equally spaced Gaussian basis functions. To train the network under supervision, varieties of different wide-band spectrums were assumed and the converged probability density function of the stress range was derived using the rainflow counting method and all these data sets were fed into the three layer perceptron model. This nonlinear least square problem was solved using Levenberg-Marquardt algorithm with regularization term included. It was proven that the network trained using the given data set could reproduce the probability density function of arbitrary wide-band spectrum of two triangles with great success.

Antenna Array Pattern Synthesis via Coordinate Descent Method

This paper presents an array pattern synthesis algorithm for arbitrary arrays based on coordinate descent method (CDM). With this algorithm, the complex element weights are found to minimize a weighted L2 norm of the difference between desired and achieved pattern. Compared with traditional optimization techniques, CDM is easy to implement and efficient to reach the optimum solutions. Main advantage is the flexibility. CDM is suitable for linear and planar array with arbitrary array elements on arbitrary positions. With this method, we can configure arbitrary beam pattern, which gives it the ability to solve variety of beam forming problem, e.g. focused beam, shaped beam, nulls at arbitrary direction and with arbitrary beam width. CDM is applicable for phase-only and amplitude-only arrays as well, and furthermore, it is a suitable method to treat the problem of array with element failures.

Axial magnetic resonances of rotationally symmetric high-permittivity dielectric particles of arbitrary shape

We develop a simple semi-analytical approach for calculating the magnetic response of rotationally symmetric high-permittivity dielectric particles to an axially applied magnetic field. By using this approach, magnetic resonances of dielectric rings of arbitrary width and thickness and of dielectric cones with arbitrary height-to-diameter aspect ratio are studied. The approach is validated by a comparison with the results of rigorous numerical simulations using the Maxwell equations.

Acquisition System for the Arbitrary Pulse Width and Position Signals Application in Ultrasound

Acquisition System for the Arbitrary Pulse Width and Position Signals Application in Ultrasound

Anisotropic zero-index waveguide with arbitrary shapes.

We design a series of waveguides composed of uniform anisotropic epsilon-near-zero media. Unlike normal waveguides in which the transmission rate strongly depends on the width and the boundary shape, such waveguides can achieve high transmission with almost arbitrary width and boundary shapes, leading to applications such as unusual waveguides, wave expanders and compressors, splitters, bends, and devices with combined purposes. The physical origin of such high transmission can be explained by using transformation optics and the condition for total transmission is derived. Numerical simulations with multilayers consisting of dielectric and negative-permittivity materials proved our theory. Our work provides a unified physical picture for waveguide structures based on anisotropic epsilon-near-zero media.

Multimode behavior of electron Zitterbewegung induced by an electromagnetic wave in graphene

Electrons in monolayer graphene in the presence of an electromagnetic (or electric) wave are considered theoretically. It is shown that the electron motion is a nonlinear combination of Zitterbewegung (ZB, trembling motion) resulting from the periodic potential of graphene lattice and the driving field of the wave. This complex motion is called "Multi-mode Zitterbewegung". The theory is based on the time-dependent two-band Hamiltonian taking into account the graphene band structure and interaction with the wave. Our theoretical treatment includes the rotating wave approximation and high-driving-frequency approximation for narrow wave packets, as well as numerical calculations for packets of arbitrary widths. Different regimes of electron motion are found, depending on relation between the ZB frequency $\omega_Z$ and the driving frequency $\omega_D$ for different strengths of the electron-wave interaction. Frequencies and intensities of the resulting oscillation modes are calculated. The nonlinearity of the problem results in a pronounced multi-mode behavior. Polarization of the medium is also calculated relating our theoretical results to observable quantities. The presence of driving wave, resulting in frequencies directly related to $\omega_Z$ and increasing the decay time of oscillations, should facilitate observations of the Zitterbewegung phenomenon.

Automated modular high energy evaluation system for experimental thyristor devices

A high energy, modular, completely automated test bed with integrated data acquisition and characterization systems was successfully designed in order to perform both safe operating area as well as very high volume reliability testing on experimental silicon carbide Super Gate Turn Off (SGTO) thyristors. Although the system follows a modular design philosophy, with each functional block acting as a peripheral to a main control module and can be adapted to arbitrary power and pulse width levels, for the specific SGTO devices initially evaluated it was configured to have the device discharge variable current levels of up to 6 kA into a 0.5 Ω resistive load with a relatively square pulse fixed at 100 μs full width at half maximum delivering energy levels up to 1.8 kJ to the load.

Forwarding metamorphosis

In Software Defined Networking (SDN) the control plane is physically separate from the forwarding plane. Control software programs the forwarding plane (e.g., switches and routers) using an open interface, such as OpenFlow. This paper aims to overcomes two limitations in current switching chips and the OpenFlow protocol: i) current hardware switches are quite rigid, allowing ``Match-Action'' processing on only a fixed set of fields, and ii) the OpenFlow specification only defines a limited repertoire of packet processing actions. We propose the RMT (reconfigurable match tables) model, a new RISC-inspired pipelined architecture for switching chips, and we identify the essential minimal set of action primitives to specify how headers are processed in hardware. RMT allows the forwarding plane to be changed in the field without modifying hardware. As in OpenFlow, the programmer can specify multiple match tables of arbitrary width and depth, subject only to an overall resource limit, with each table configurable for matching on arbitrary fields. However, RMT allows the programmer to modify all header fields much more comprehensively than in OpenFlow. Our paper describes the design of a 64 port by 10 Gb/s switch chip implementing the RMT model. Our concrete design demonstrates, contrary to concerns within the community, that flexible OpenFlow hardware switch implementations are feasible at almost no additional cost or power.

Modeling Coherent Backscattering Errors in Fiber Optic Gyroscopes for Sources of Arbitrary Line Width

We present a new model of the noise and drift induced by coherent backscattering in a fiber optic gyroscope (FOG) interrogated with a light source of arbitrary temporal coherence. This study is critical to understand whether a FOG driven with a laser instead of a broadband source can attain high sensitivity and stability, which would have the overwhelming benefit of improving the FOG scale factor stability by at least ten-fold and would enable the use of FOGs for inertial navigation of aircrafts. Analytical and numerical solutions bring to light two significant new predictions. First, coherent-backscattering noise can be made negligibly small by utilizing a laser with a very narrow linewidth (less than ~ 20 kHz), although in this regime the drift is high. Second, by using a laser with a broad linewidth (greater than ~ 10 MHz), both the noise and the drift are low enough for aircraft inertial navigation. The dependencies of the noise and drift on fiber loss, loop coupling coefficient, and backscattering coefficient are also presented to define the optimum mode of operation of this new class of FOGs.

Measurement of Radiative Proton Capture onF18and Implications for Oxygen-Neon Novae

The rate of the 18F(p,γ)19Ne reaction affects the final abundance of the γ-ray observable radioisotope 18F, produced in novae. However, no successful measurement of this reaction exists and the rate used is calculated from incomplete information on the contributing resonances. Of the two resonances thought to play a significant role, one has a radiative width estimated from the assumed analogue state in the mirror nucleus, 19F. The second does not have an analogue state assignment at all, resulting in an arbitrary radiative width being assumed. Here, we report the first successful direct measurement of the 18F(p,γ)^19Ne reaction. The strength of the 665 keV resonance (Ex=7.076 MeV) is found to be over an order of magnitude weaker than currently assumed in nova models. Reaction rate calculations show that this resonance therefore plays no significant role in the destruction of ^{18}F at any astrophysical energy.

Time-transformation approach to pulse propagation in nonlinear dispersive media: Inclusion of delayed Raman nonlinearity

We extend our time-transformation technique to include the delayed Raman response and use it to study propagation of ultrashort, few-cycle, optical pulses inside a dispersive nonlinear medium. Our technique deals directly with the electric field associated with an optical pulse and can be applied to pulses of arbitrary widths, as it does not make use of the slowly varying envelope approximation. We apply it to optical pulses containing several optical cycles and launched such that they form a third-order optical soliton. We vary the number of optical cycles within the pulse from 1 to 10 and study how the features such as soliton fission, intrapulse Raman scattering, and dispersive-wave generation depend on pulse width and soliton order. We find that for a fixed soliton order, the Raman-induced frequency shift becomes smaller, while the fraction of energy transferred to the dispersive wave increases, as pulse width is reduced. In the special case of a single-cycle pulse, the most dominant effect is self-steepening and it leads to dramatically different features in both the shape and spectrum of output pulses.

Microscopic theoretical study of Raman spectra in charge and spin ordered cuprate systems

Raman scattering is one of the most powerful methods to investigate the electron as well as the phonon excitations in the systems. In this communication, we present a theoretical study of Raman scattering in the normal state of the high-TC systems in the under-doped region displaying the interplay of the spin-density-wave (SDW) and charge-density-wave (CDW) interactions. The SDW order arises from the repulsive Coulomb interaction of electrons, while the CDW order arises due to strong electron–phonon interaction giving rise to Fermi surface instability. We calculate phonon response function in order to examine the possibility of observing the SDW excitation mode in presence of the CDW interaction present in the same conduction band. The Raman scattering intensity is calculated from the imaginary part of the phonon Green’s function assigning an arbitrary spectral width. The spectral density function displays two mixed modes of excitation peaks at energies 2(Δc±Δs). The evolution of excitation peaks are investigated by varying CDW coupling, SDW coupling and the phonon momentum transfer energy.

An Interleaver With Arbitrary Passband Width Ratio Based on Hybrid Structure of Microring and Mach–Zehnder Interferometer

In order to improve transmission efficiency of optical-fiber communication system for hybrid 10 G/40 G system presently, and hybrid 40 G/100 G system in the future, a planar lightwave circuit-based optical interleaver with arbitrary passband width ratio is proposed and investigated, which is based on hybrid structure of microring and Mach-Zehnder interferometer and offers the advantages of compactness, ruggedness, and better compatibility with other integrated optical circuits. Most importantly, the interleaver we proposed can realize the 3-dB passband width ratio between two output ports from equal to any unequal proportion just by adjusting coupling coefficients of couplers involved. The simulation results of symmetrical and asymmetrical output spectra are presented and all of them are with a channel isolation more than 45 dB and a flat-top passband. Furthermore, the effects of some key parameters on the characteristics of output spectra are also analyzed.

Application of arbitrary pulse width and position trains for the correlation sidelobes reduction for narrowband transducers

Novel excitation technique is suggested which allows to reduce the correlation function sidelobes in case of narrowband channel. Application is planned for time of flight estimation using air coupled narrowband transducers. Time of flight is estimated by using the correlation function peak position. Narrowband signal has high level of correlation function sidelobes and therefore large signal to noise ratio cannot be fully exploited. Our investigation aimed to reduce the sidelobes by optimizing the signal. Novelty of the approach is that trains of arbitrary width and position square pulses are used. Such signals are easy to generate and to simulate in digital domain. The excitation signal spectrum was allowed to span beyond the passband, improving the envelope bandwidth in such way. The signal energy loss is caused by the attenuation of the out-of-band portion of the signal. Optimal balance between the energy loss and the sidelobes reduction had to be found. To predict the signal performance, the AC response of the transmission channel was measured and then used in simulation to predict the candidate signal’s performance: the expected sidelobes’ level and the energy. Monte Carlo technique was used to generate the candidate signals’ parameters for the simulation. The relative noise margin was suggested as optimum criteria to balance the loss of the energy and the sidelobes reduction. Performance of the optimal signals obtained in simulation was verified experimentally. It was concluded that reduction of the sidelobes’ is possible even for narrowband channel if some energy loss can be tolerated. An increase of 40% in relative noise margin, compared to the same length CW burst signals was achieved.

Nonparaxial traveling solitary waves in layered nonlinear media

A large class of exact analytical traveling solitary wave solutions in a variety of inhomogeneous structures consisting of linear and nonlinear layers is obtained. The solutions are related to a spatial resonance condition and describe reflectionless and radiationless beam propagation for arbitrary angles and spatial widths in the nonparaxial regime.

Application of Arbitrary Position and Width Pulse Trains Signals in Ultrasonic Imaging: Correlation Performance Study

Ultrasonic imaging requires both the accuracy and the resolution. Conventional imaging systems use the pulse signals to accomplish the task. But the energy attainable with such signals is limited. Spread spectrum, compressible signals allow to achieve the wide bandwidth even using long durations. Conventional signals do not offer full flexibility or, like nonlinear frequency modulation signals, lack the ease of properties control. We suggest using novel spread spectrum signals generation technique: trains of pulses of arbitrary pulse width and position (APWP). It is expected that APWP should have properties similar to chirp (wide, controllable bandwidth) and both the single pulse (low correlation sidelobes) signals. Study presented here was aimed at evaluating the correlation properties of APWP signals. It indicates that application of APWP signals allows obtaining the properties better or close to those of the conventional signals. It can be concluded that APWP signals offer a new perspective in imaging applications.DOI: http://dx.doi.org/10.5755/j01.eee.19.3.2690

Test

Ultrasonic imaging requires both the accuracy and the resolution. Conventional imaging systems use the pulse signals to accomplish the task. But the energy attainable with such signals is limited. Spread spectrum, compressible signals allow to achieve the wide bandwidth even using long durations. Conventional signals do not offer full flexibility or, like nonlinear frequency modulation signals, lack the ease of properties control. We suggest using novel spread spectrum signals generation technique: trains of pulses of arbitrary pulse width and position (APWP). It is expected that APWP should have properties similar to chirp (wide, controllable bandwidth) and both the single pulse (low correlation sidelobes) signals. Study presented here was aimed at evaluating the correlation properties of APWP signals. It indicates that application of APWP signals allows obtaining the properties better or close to those of the conventional signals. It can be concluded that APWP signals offer a new perspective in imaging applications. DOI: http://dx.doi.org/10.5755/j01.eee.19.3.2690