Non-uniform Ring Research Articles

Dual-Band 180.DEG. Coupler with Arbitrary Power Division Ratio

An improved dual-band design method is presented for the 180° coupler. It uses the non-uniform impedance ring structure for the arbitrary power division and a π-shaped branch for the dual-band operation The increased design freedom offered by the proposed structure helps to extend the useful dual-band operation range.

Quadra-quantum dots grown on quantum rings having square-shaped holes: Basic nanostructure for quantum dot cellular automata application

Preferable quantum dot (QD) nanostructure for quantum computation based on quantum cellular automata (QCA) is laterally close-packed quantum dot molecular (QDM) having 4 QDs at the corners of square configuration. We called this 4 QDs-set as quadra-quantum dots (QQDs). Aligned QQDs with 2 electron-confinements work like a wire for digital information transmission by Coulomb repulsion force which is high speed and consumes little power. Combination of QQDs in line and their cross-over work as logic gates and memory bits. We have developed a Molecular Beam Epitaxial (MBE) growth technique call “Droplet Epitaxy” for several quantum nanostructures such as quantum rings (QRs), quantum dot rings (QDRs). In this presentation, we prepare QRs with 20 ML In-Ga (15:85) droplet at 390 °C and droplet growth rate of 1ML/s. Arsenic flux (7–8 × 10 −6 Torr) is then exposed for InGaAs crystallization at 200 °C for 5 min. During droplet epitaxy at high value of droplet thickness and high temperature, out-diffusion from the centre of droplets occurs under anisotropic stain. This leads to quantum ring structures having non-uniform ring stripes and deep square-shaped nanoholes. Using these peculiar QRs as templates, 4 QDs situating at each corner of square shape are regrown. Two of these 4 QDs are aligned either [1 1 ¯ 0] or [1 1 0] which are preferable crystallographic directions of QD alignment in general.

Macroscopic superposition states in rotating ring lattices

We investigate the effects of rotation on one-dimensional ultracold bosons confined to optical ring lattices. First, we show that there exists a critical rotation frequency at which the ground state of a weakly interacting and integer-filled atomic gas is fragmented into a macroscopic superposition state with different circulation. Second, we point out several advantages of using slightly non-uniform ring lattices. Finally, we demonstrate that different quasi-momentum states can be distinguished in time-of-flight absorption imaging and propose to probe correlations via the many-body oscillations induced by a sudden change in the rotation frequency.

Generation of macroscopic superposition states in ring superlattices

Ultracold bosons in rotating ring lattices have previously been shown to form macroscopic superpositions of different quasimomentum states. We demonstrate that the generation of this kind of state using slightly nonuniform ring lattices has several advantages: the energy gap decreases less severely with increasing number of particles, the sensitivity to detunings from the critical rotation frequency is reduced, and the scheme is not limited to commensurate filling. We show that different quasimomentum states can be distinguished in time-of-flight absorption imaging and propose to probe correlations via the many-body oscillations induced by a sudden change in the rotation frequency.

Energy Efficient Non-uniform Clustering Division Scheme in Wireless Sensor Networks

Wireless sensor networks can be used to monitor the interested region by multi-hop communication. Since sensor nodes are equipped with energy-limited batteries, energy conservation in such networks is of paramount importance in order to prolong the network lifetime. In this paper, considering the constrained radio range of node, we propose an energy efficient clustering division scheme from the viewpoint of energy consumption. The difference between our scheme and previous schemes is that ours is a non-uniform clustering hierarchy. With the algorithm that is proposed by this paper, we can divide the cluster into multiple non-uniform concentric rings and obtain the optimal thickness of each ring. Motivated by the derived results, every sensor node can adjust its radio range for transmission. Our extensive simulation results indicate that the proposed non-uniform clustering division scheme outperforms the conventional uniform clustering division schemes in terms of energy consumption and lifetime. The future research that should be explored is also discussed finally.

Attractive forces inside a thin nonuniform meteor ring

Attractive forces inside a thin nonuniform meteor ring are found and their features are revealed.

Free vibration of rotating ring stiffened cylindrical shells with non-uniform stiffener distribution

In this research, the free vibration analysis of simply supported rotating cylindrical shells with circumferential stiffeners, i.e. rings with non-uniform stiffeners eccentricity and non-uniform stiffeners spacing distribution is investigated. Ritz method is applied while stiffeners are treated as discrete elements. In strain energy formulation, by adopting Sander's theorem, stretching and bending characteristics of shells are considered. Also stretching, bending and wrapping effects of stiffeners are investigated. The translational inertia in three directions for shell and stiffeners, and rotary inertia for stiffeners are considered. The effects of initial hoop tension, centrifugal and Coriolis forces due to the rotation of shell are studied. The polynomial functions are used for Ritz functions. Natural frequency results for rings with uniform spacing and constant eccentricity have been compared with analytical and experimental results of other researchers, which showed good agreement. Fortunately, the agreements of the presented analytical results with the experimental values are better than the analytical values. At constant total mass of stiffeners, the effects of non-uniform eccentricity distribution and non-uniform rings spacing distribution (separately and simultaneously) on natural frequencies are investigated. Moreover, the influence of rotating speed on natural frequencies for the so-called non-uniform stiffeners distribution is studied.

Free vibration of non-uniformly ring stiffened cylindrical shells using analytical, experimental and numerical methods

In this research, the free vibration analysis of cylindrical shells with circumferential stiffeners, i.e. rings with non-uniform stiffeners eccentricity and unequal stiffeners spacing is investigated using analytical, experimental and finite elements (FE) methods. Ritz method is applied in analytical solution while stiffeners treated as discrete elements. The polynomial functions are used for Ritz functions and natural frequency results for simply supported stiffened cylindrical shell with equal rings spacing and constant eccentricity is compared with other's analytical and experimental results, which showed good agreement. Also, a stiffened shell with unequal rings spacing and non-uniform eccentricity with free–free boundary condition is considered using analytical, experimental and FE methods. In experimental method, modal testing is performed to obtain modal parameters, including natural frequencies, mode shapes and damping in each mode. In FE method, two types of modeling, including shell and beam elements and solid element are used, applying ANSYS software. The analytical and the FE results are compared with the experimental one, showing good agreements. Because of insufficient experimental modal data for non-uniformly stiffeners distribution, the results of modal testing obtained in this study could be as useful reference for validating the accuracy of other analytical and numerical methods for free vibration analysis.

Stationary-phase slip state in quasi-one-dimensional rings

The nonuniform superconducting state in a ring in which the order parameter vanishing at one point is studied. This state is characterized by a jump of the phase by $\pi$ at the point where the order parameter becomes zero. In uniform rings such a state is a saddle-point state and consequently unstable. However, for non-uniform rings with e.g. variations of geometrical or physical parameters or with attached wires this state can be stabilized and may be realized experimentally.

Post-buckling of a non-uniform ring subjected to uniform external pressure

Rigid plastic analysis is used to find the post-buckling response of a non-uniform circular ring subjected to uniform external pressure. The non-uniform ring has a section of reduced thickness over part of its circumference. A five plastic hinge model is used to describe the non-axisymmetric post-buckling collapse. The principle of virtual work and upper bound theorem are applied to find the collapse pressure and mode of collapse. Depending on the non-uniformity, two modes of collapse can occur: global and snap-through buckling. Global buckling occurs when the angular extent is greater than 90 degrees. When the angular extent is less than 90 degrees and the thickness reduction is large, snap-through buckling takes place. Closed-form expressions for the variation of the collapse load with respect to non-uniformity of the ring are derived.

Vibrations of non-uniform rings studied by means of the differential quadrature method

Abstract The vibrational behavior of ring-like structures is of interest in several technological situations: from automotive and aircraft tires to electric motors and transformers. This study deals with the solution of the governing sixth order differential equation by using the differential quadrature method. The fundamental frequency of in-plane, inextensional vibration is thus determined and compared with the value predicted by the optimized Rayleigh-Ritz method.

Leader election in uniform rings

A self-stabilizing leader election protocol is proposed here for uniform rings of primal size. A ring of processors is said to be uniform if no distinguished leader processor exists. Having the proposed protocol as the first phase, all self-stabilizing protocols for nonuniform rings can be implemented as the second phase. Dijkstra's self-stabilizing mutual exclusion protocol for nonuniform rings is superimposed as an example on the leader election protocol. The result is a two-phase self-stabilizing mutual exclusion protocol for uniform rings. Let the size of the ring be n. Our self-stabilizing mutual exclusion protocol uses 3n states for each processor, which improves a previous result that uses approximately (n 2 /ln n) states

A note on free flexural vibrations of a non-uniform ring with fixed supports

An approximate solution for the title problem is obtained by using the “optimized” Rayleigh-Ritz method. The fundamental mode shape is approximated by means of polynomial co-ordinate functions which contain two exponential optimization parameters. Since the Rayleigh-Ritz method provides upper bounds, the fundamental frequency coefficient is determined by minimizing the lowest root of the frequency equation with respect to the optimization parameters. Continuous and discontinuous variation of the ring thickness are considered. Results are presented for a circular ring with two opposite, infinitely rigid supports.

Resonance splitting in nonuniform ring resonators

The frequency response of a microstrip ring resonator with small terminal couplings is discussed. For resonators consisting of nonuniform lines, there is shown to be resonance splitting in the transfer function.

Asymptotic solution for pressurized noncircular cylinders with nonuniform rings

Abstract : An asymptotic expansion procedure is used to analyze hydrostatically loaded noncircular cylindrical shells. The asymptotic solution is combined with a solution for singly symmetric oval rings with variable cross-sectional properties to obtain the solution for pressurized noncircular cylinders with nonuniform rings. Numerical results are compared with existing solutions for doubly symmetric oval shells reinforced by uniform rings. The cross sections of these cylinders range from circular to ovals having a major-to-minor axis ratio of 1.3. Numerical results are also presented for oval cylinders reinforced by nonuniform oval rings. Cases of both singly and doubly symmetric rings are considered. (Author)

Stresses in Eccentric Nonuniform Rings Reinforcing Cylindrical Shells

Bending and membrane stresses are determined in nonuniform frames of an infinitely long reinforced circular cylindrical shell subjected to hydrostatic pressure. The Donnell shell equations and deep-ring theory are used to solve the interaction problem. The frames, periodically spaced along the shell, are composed of two uniform but different sections. Each section of each frame has a different centroidal radius. Analyses of bending and membrane stress distributions in the frames are presented. Approximate solutions of different degrees of simplicity and accuracy are also given.