This paper addresses the nonlinear Schrödinger equation (NLSE) with Kerr law nonlinearity and perturbation terms in optical fibre. A class of grey and black optical solitary wave solutions of this equation are retrieved by adopting an appropriate solitary wave ansatz solution. These types of solitary waves play a vital role in understanding various physical phenomena in nonlinear systems. This lead to a constraint condition on the solitary wave parameters which must hold for the solitary waves to exist. Moreover, the modulation instability (MI) analysis of the model is studied by employing the concept of linear-stability analysis (LSA) and the MI gain spectrum is got. Physical interpretations of the acquired results are demonstrated. It is hoped that the results reported in this paper can enrich the nonlinear dynamical behaviours of the equation. 相似文献
MXenes, a fast-growing family of two-dimensional (2D) transition metal carbides/nitrides, are promising for electronics and energy storage applications. Mo2CTx MXene, in particular, has demonstrated a higher capacity than other MXenes as an anode for Li-ion batteries. Yet, such enhanced capacity is accompanied by slow kinetics and poor cycling stability. Herein, it is revealed that the unstable cycling performance of Mo2CTx is attributed to the partial oxidation into MoOx with structural degradation. A laser-induced Mo2CTx/Mo2C (LS-Mo2CTx) hybrid anode has been developed, of which the Mo2C nanodots boost redox kinetics, and the laser-reduced oxygen content prevents the structural degradation caused by oxidation. Meanwhile, the strong connections between the laser-induced Mo2C nanodots and Mo2CTx nanosheets enhance conductivity and stabilize the structure during charge–discharge cycling. The as-prepared LS-Mo2CTx anode exhibits an enhanced capacity of 340 mAh g−1 vs 83 mAh g−1 (for pristine) and an improved cycling stability (capacity retention of 106.2% vs 80.6% for pristine) over 1000 cycles. The laser-induced synthesis approach underlines the potential of MXene-based hybrid materials for high-performance energy storage applications. 相似文献
Flight controllers for micro-air UAVs are generally designed using proportional-integral-derivative (PID) methods, where the tuning of gains is difficult and time-consuming, and performance is not guaranteed. In this paper, we develop a rigorous method based on the sliding mode analysis and nonlinear backstepping to design a PID controller with guaranteed performance. This technique provides the structure and gains for the PID controller, such that a robust and fast response of the UAV (unmanned aerial vehicle) for trajectory tracking is achieved. First, the second-order sliding variable errors are used in a rigorous nonlinear backstepping design to obtain guaranteed performance for the nonlinear UAV dynamics. Then, using a small angle approximation and rigorous geometric manipulations, this nonlinear design is converted into a PID controller whose structure is naturally determined through the backstepping procedure. PID gains that guarantee robust UAV performance are finally computed from the sliding mode gains and from stabilizing gains for tracking error dynamics. We prove that the desired Euler angles of the inner attitude controller loop are related to the dynamics of the outer backstepping tracker loop by inverse kinematics, which provides a seamless connection with existing built-in UAV attitude controllers. We implement the proposed method on actual UAV, and experimental flight tests prove the validity of these algorithms. It is seen that our PID design procedure yields tighter UAV performance than an existing popular PID control technique. 相似文献
□ In conventional metal cutting process, materials are assumed to be homogeneous and isotropic structure. However, some materials with a single crystal or coarse elongated polycrystalline demonstrate strong anisotropic behavior in physical and mechanical properties in machining of some superalloy materials. The anisotropic structure always leads to variation at machinability properties of the material. In this study, machinability properties of ferritic superalloy PM2000, which had elongated a few coarse grains, were investigated. These properties were determined by investigation of chip formation, cutting forces and surface roughness. Machinability was assessed by single-point turning on a CNC lathe and turning forces were measured by using a Kistler Lathe Dynamometer. The chip formation mechanisms in machining of PM2000 at various cutting speeds were determined by using a quick-stop device (QSD). Chip roots and machined surfaces were analyzed by means of scanning electron microscopy (SEM). The results indicated that the machinability properties of the PM2000 were changed by orientated coarse grain structure. Three types chip formation mechanism were determined at the same cutting conditions. Also, surface roughness on the machined each grain changed with changing the grain to be cut. Surface roughness and force fluctuations decreased with increasing the cutting speed; however, tool wearing increased. 相似文献
In this paper, a 9-bit 1.3 GS/s single channel SAR ADC is presented. In conventional SAR ADCs, the capacitive DAC size grows exponentially with respect to converter resolution. This results in both signal bandwidth and conversion speed reduction. The proposed architecture implements binary search through a redundant capacitive DAC for the 5 first MSBs and through programmable comparator thresholds for the remaining 4 LSBs. The DAC capacitance at the front-end remains small enough to achieve high sampling rate with increased input bandwidth. Two asynchronously clocked alternate comparators are used additionally to improve conversion speed. The ADC is designed and simulated in 28 nm FD-SOI CMOS. It consumes 4.1 mW from a 1 V supply, while achieving a SNDR of 52.1 dB and a Figure-of-Merit of 11.4 fJ/conversion-step. 相似文献
Capturing and modelling 3D information of the built environment is a big challenge. A number of techniques and technologies are now in use. These include EDM, GPS, and photogrammetric application and also remote sensing applications. In this paper, we discussed 3D laser scanning technology, which can acquire high density point data in an accurate, fast way. Besides, the scanner can digitize all the 3D information concerned with a real world object such as buildings, trees and terrain down to millimetre detail Therefore, it can provide benefits for refurbishment process in regeneration in the Built Environment.
A series of scans externally and internally allows an accurate 3D model of the building to be produced. This model can be sliced through different planes to produce accurate 2D plans and elevations. This novel technology improves the efficiency and quality of construction projects such as maintenance of buildings or group of building that are going to be renovated for new services in the Built Environment. In addition, the laser scanner technology can be used in integration with differential GPS for terrain modelling for the analysis and inspection of terrain structure accurately.
In this paper, two case studies are introduced to demonstrate the use of laser scanner technology in Built Environment. These case studies are the Jactin House Building in East Manchester and the Peel building in the campus of University Salford. Through these case studies, while use of laser scanners are explained, the integration of it with various technologies and systems are also explored for professionals in both Built and Natural Environment. 相似文献
The literature on free vibration analysis of Bernoulli-Euler and Timoshenko piles embedded in elastic soil is plenty, but
that of Reddy-Bickford piles partially embedded in elastic soil with/without axial force effect is fewer. The soil that the
pile partially embedded in is idealized by Winkler model and is assumed to be two-layered. The pile part above the soil is
called the first region and the parts embedded in the soil are called the second and the third region, respectively. It is
assumed that the behaviour of the material is linear-elastic, that axial force along the pile length to be constant and the
upper end of the pile that is semi-rigid supported against rotation is modelled by an elastic spring. The governing differential
equations of motion of the rectangular pile in free vibration are derived using Hamilton’s principle and Winkler hypothesis.
The terms are found directly from the solutions of the differential equations that describe the deformations of the cross-section
according to the high-order theory. The models have six degrees of freedom at the two ends, one transverse displacement and
two rotations, and the end forces are a shear force and two end moments. Natural frequencies of the pile are calculated using
transfer matrix and the secant method for non-trivial solution of linear homogeneous system of equations obtained due to values
of axial forces acting on the pile, total and embedded lengths of the pile, the linear-elastic rotational restraining stiffness
at the upper end of the pile and to the boundary conditions of the pile. Two different boundary conditions are considered
in the study. For the first boundary condition, the pile’s end at the first region is semi-rigid connected and not restricted
for horizontal displacement and the end at the third region is free and for the second boundary condition, the pile’s end
at the first region is semi-rigid connected and restricted for horizontal displacement and the end at the third region is
fixed supported. The calculated natural frequencies of semi-rigid connected Reddy-Bickford pile embedded in elastic soil are
given in tables and compared with results of Timoshenko pile model. 相似文献
A uniform line integral representation is derived for edge-diffracted fields by using the modified theory of physical optics and uniform asymptotic evaluation methods. The method is applied to the problem of diffraction of plane waves by a semi-infinite edge, which creates tip-diffracted fields with edge-diffracted waves. The uniform diffracted fields are plotted and examined numerically. 相似文献
An alternative interpretation of the phenomenon of edge diffraction is proposed according to a new separation of the Fresnel function. The subfields are investigated in the problem of diffraction of a plane wave by a perfectly conducting half-plane, and the results are compared numerically with other interpretations. 相似文献