Coupling Effect of Nonlinear Stiffness of Tape Spring Hinges and Flexible Deformation of Panels during Orbit Maneuvers

Many solar panels for spacecrafts are deployed by Tape Spring Hinges (TSHs) which have changeable stiffness. The stiffness of TSH is small when panels are folded, and it becomes large quickly in its deployed status. Since the solar panel is a thin sheet, flexible deformation is easily generated by orbit maneuvers. The coupling effect between the nonlinear TSHs and the flexible panels generates obvious vibration which affects the operational stability of the satellite. To investigate this coupling effect, non-deformable, linear deformable and nonlinear deformable panels were modelled by rigid body, modal order reduction method (MORM) and finite element method (FEM), respectively. The driving torque of TSH was described as a function of the rotation angle and angular velocity. The nonlinear properties of the TSH were reflected by one angle-stiffness spline multiplied by one stiffness coefficient. Dynamic responses of a satellite in deployment and orbit steering were analyzed by numerical simulations. Analysis results indicate the local deformation of panels keeps the stiffness of the TSH within a large range which accelerates the orbit maneuvers. However, much vibration is generated by the coupling effect if the luck-up status is broken up. The coupling effect affects the sequence of deployment, overshoot phenomenon and acceleration magnitude of the panels. Although the MORM is more efficient than FEM in computation, we propose FEM is better suited in the design of TSH and in studying the precise control of spacecraft with flexible solar panels and TSHs.

Broadband Optical Constants and Nonlinear Properties of SnS2 and SnSe2

SnS2 and SnSe2 have recently been shown to have a wide range of applications in photonic and optoelectronic devices. However, because of incomplete knowledge about their optical characteristics, the use of SnS2 and SnSe2 in optical engineering remains challenging. Here, we addressed this problem by establishing SnS2 and SnSe2 linear and nonlinear optical properties in the broad (300–3300 nm) spectral range. Coupled with the first-principle calculations, our experimental study unveiled the full dielectric tensor of SnS2 and SnSe2. Furthermore, we established that SnS2 is a promising material for visible high refractive index nanophotonics. Meanwhile, SnSe2 demonstrates a stronger nonlinear response compared with SnS2. Our results create a solid ground for current and next-generation SnS2- and SnSe2-based devices.

Study and Analysis of Photonic Crystal Fiber for Broadband Laser Source Design

Photonic Crystal Fiber (PCF) has been a topic of extensive research in the field of nonlinear fiber optics. It is due to its combination of linear and nonlinear properties which ultimately results in the phenomenon having various types of applications. One of the phenomena is supercontinuum generation that has been extensively studied numerically and experimentally over the last few decades as it has important applications in the field of medical imaging and sensing. In this paper, we numerically analysed and studied PCF of hexagonal core with various parameters and propose our novel ‘Star in Hexagon’ design as a good candidate for the broadband supercontinuum generation and hence a broadband laser source. We numerically pumped a long 10 mm PCF of this kind at 3.1 um wavelength with a pulse having a power of 4000 W and a temporal width of 50 fs. A broadband supercontinuum ranging from 1.7 um to 18 um was obtained. The generated spectrum is quite well in the mid-infrared region. Hence it can be utilised for Mid – Infrared (MIR) applications.

Nonlinear vibrations of soil strata according to instrumental and numerical data

Исследования нелинейных явлений в грунтах, начатые в России почти 60 лет назад, явились стимулом современного развития исследований сейсмоаномальных явлений в комплексе геофизических показателей, наблюдающихся при сильных и разрушительных землетрясениях. Кроме чисто научных интересов большой интерес вызывает вопрос прогнозирования поведения грунтов и сооружений с точки зрения адекватности ожидаемому проявлению сейсмического воздействия. Адекватное изучение нелинейности, являющейся неотъемлемой характеристикой природных явлений, позволит приблизить соответствующее антисейсмические мероприятия к реальным особенностям проявлений сейсмического эффекта при сильных землетрясениях. Цельюработы являлось построение расчетной модели, описывающей явления, наблюдаемые в грунтовой среде при сильных сейсмических воздействиях и сопоставление расчетных данных с результатами инструментальных наблюдений. Методы. В работе анализируется иснтрументальная запись, полученная на слабых грунтах, на сонове вейвлет нанализа. Моделируются импульсы различной проолжитлеьности в среде с различной стпенью проявления нелинейных свойст (кртутизны нелиненйой заивисисмоти напряжение -деформация) методом конечных элементов. Результаты. В результате установлены различия в спектральном составе моделируемых импульсов. Сильное проявление нелинейных свойств характеризуется резкими изменениями фаз колебаний, в фазах высокой скорости нарастания амплитуд. В нелинейных спектрах происходит перераспределение энергии в более высокочастотную область, кратную основному пику, тем сильнее, чем сильнее нелинейность кривой наряжение-деформация. Studies of nonlinear phenomena in soils, which began in Russia almost 60 years ago, have stimulated the modern development of studies of seismically anomalous phenomena in the complex of geophysical indicators observed during strong and destructive earthquakes. In addition to scientific interests, the issue of forecasting the behavior of soils and structures from the point of view of adequacy to the expected manifestation of seismic impact is of great interest. An adequate study of nonlinearity, which is an integral characteristic of natural phenomena, will make it possible to bring the corresponding antiseismic measures closer to the real features of the manifestations of the seismic effect during strong earthquakes. Aim. The aim of the work was to build a computational model describing the phenomena observed in a soil medium under strong seismic effects and to compare the computed data with the results of instrumental observations. Methods.The paper analyzes an instrumental record obtained on soft soils using wavelet analysis. With the help of the finite element method pulses of different duration are modeled in a medium with different degrees of nonlinear properties manifestation (steepness of nonlinear stress-strain dependence). Results. As a result, differences in the spectral composition of the modeled pulses were determined. A strong manifestation of nonlinear properties is characterized by sharp changes in the phases of vibrations, in the phases of a high rate of amplitude rise. In nonlinear spectra, the energy is redistributed to a higher frequency region, which is a multiple of the main peak and the stronger the nonlinearity of the stress-strain curve is stronger.

Inverse Approach of Parameter Optimization for Nonlinear Meta-Model Using Finite Element Simulation

Accurate and efficient estimation and prediction of the nonlinear behavior of materials during plastic working is a major issue in academic and industrial settings. Studies on property meta-models are being conducted to estimate and predict plastic working results. However, accurately representing strong nonlinear properties using power-law and exponential models, which are typical meta-models, is difficult. The combination meta-model can be used to solve this problem, but the possible number of parameters increases. This causes a cost problem when using FE simulation. In this study, the accuracy of the nonlinear properties of materials and the number of iterations were compared for three typical meta-models and the proposed advanced meta-models considering stress–strain properties. A material property test was conducted using ASTM E8/E8M, and the meta-model was initialized using ASTM E646 and MATLAB Curve Fitting Toolbox. A finite element (FE) simulation was conducted for the meta-models, and the test and simulation results were compared in terms of the engineering stress–strain curve and the root-mean-square error (RMSE). In addition, an inverse method was applied for the FE simulation to estimate the true stress–strain properties, and the results were analyzed in terms of the RMSE and the number of iterations and simulations. Finally, the need for an advanced meta-model that exhibits strong nonlinearity was suggested.

NONLINEAR PROPERTIES OF STRUCTURAL HETEROGENEOUS PHOTONIC CRYSTAL FIBERS WITH As2Se3 SUBSTRATE

We examine the possibility of improving the nonlinear properties of photonic crystal fibers (PCFs) with As2Se3 substrates by creating a difference in the diameters of the air holes of the rings around the core. With the new design, all-normal dispersion properties, small effective mode area, high nonlinear coefficient, and low confinement loss were achieved in the long-wavelength range of 2.0–7.0 µm. The highest nonlinear coefficient is 4414.918 W-1.km-1 at 4.5 µm for the lattice constant (Ʌ) of 3.0 µm and the filling factor (d/Ʌ) of 0.85, while the lowest loss is 1.823´10-21 dB/cm with Ʌ = 3.5 µm and d/Ʌ = 0.8. Based on the numerical simulation results, the characteristics of two optimal structures have been analyzed in detail to guide the application in supercontinuum generation.

Synthesis, DFT calculations and optical nonlinear properties of two derived Schiff base compounds from ethyl-4-amino benzoate

Two Schiff base compounds viz., Ethyl (E)-4-((3-ethoxy-2-hydroxybenzylidene)amino)benzoate(EHB) and Ethyl (E)-4-(((2-hydroxynaphthalen-1-yl)methylene)amino)benzoate(ENB) are synthesized by condensation of ethyl-4-amino benzoate with 2-hydroxy-3-ethoxy benzaldehyde and 2-hydroxy-1-naphthaldehyde. The two compounds are studied and identified by FT-IR, UV-visible, Mass, 1H-NMR and 13C-NMR spectroscopies. The nonlinear refractive index (NRI) of the two compounds are determined, for ENB compound via the diffraction ring patterns (DRPs) and the Z-scan and via Z-scan for the EHB compound, using continuous wave (cw) low power laser beam, and founds of the order of 10-7 cm2/W due to the first technique and 10-8 cm2/W due to the second technique. The optical limiting (OLg) property of both compounds is studied too with OLg thresholds of 16.5 mW and 11 mW for the compounds EHB and ENB respectively, which makes these two compounds as candidates to be used as an optical limiter (OLr). The DRPs are numerically simulated based on the theory of Fresnel-Kirchhoff with reasonable agreement compare to the experimental findings.

Synchronization of Chaotic Systems: A Generic Nonlinear Integrated Observer-Based Approach

The purpose of this research is to study the synchronization of two integrated nonlinear systems with time delay and disturbances. A nonlinear system is a system in which the difference in output is not relative to the difference in input. A new control methodology for synchronization of the two chaotic systems master and slave is recognized by means of the unique integrated chaotic synchronous observer and the integrated chaotic adaptive synchronous observer. The instantaneous approximation states of the master and slave systems are accomplished by means of methods for suggesting observers for every one of the master and slave systems and by the production of error signals between these approximated states. This approximated synchronization error signal and state approximation errors meet at the origin by means of methods involving a particular observer-based feedback control signal to ensure synchronization and state approximation. Using Lyapunov stability theory, adaptive and nonadaptive laws for control systems, and nonlinear properties, the intermingling conditions for state approximation errors and approximated synchronization errors are established as nonlinear matrix inequalities. A solution to the resulting inequality constraints using a two-step linear matrix inequality (LMI)-based approach is introduced, giving essential and adequate conditions to extract values from the controller gain and observer gain matrices. Simulation of the suggested synchronization procedure for FitzHugh–Nagumo neuronal systems is demonstrated to expand the viability of the suggested observer-based control techniques.