Original System Research Articles

Resonance response and chaotic analysis for an irrational pendulum system

We propose a novel rotating pendulum system with irrational nonlinearity, bi-stable phenomenon and quasi-zero stiffness characteristic, which bears a transition from standard double well dynamics to discontinuous double well dynamics by adjusting a geometric parameter. Nonlinear dynamical behaviors of the proposed irrational pendulum system subjected to viscus damping and periodic excitation are studied. To analytically demonstrate the primary resonance response for this perturbed irrational pendulum system, we introduce an approximate irrational system which is significant parallels with the original pendulum system from the perspective of qualitative analysis and quantitative calculation. Averaging method is applied to investigate the dynamic response of the perturbed irrational pendulum system with quasi-zero stiffness at origin. The effect of the internal and external parameters on the response curves are discussed. Numerical fitting technique and semi-analytical Melnikov method are used to detect the chaotic boundaries of the perturbed irrational pendulum system with two types of homoclinic orbits. Different types of periodic solutions and chaos are clarified in the perturbed irrational pendulum system by using numerical simulations. It is found that a class of chaos with oscillatory and rotational motions bears significant similarities to paroxysmal chaos due to sudden rotational motion and two chaotic motions formed by period-doubling bifurcation merge into one chaos.

Hopf bifurcation in an age-structured predator–prey system with Beddington–DeAngelis functional response and constant harvesting

In this paper, an age-structured predator–prey system with Beddington–DeAngelis (B–D) type functional response, prey refuge and harvesting is investigated, where the predator fertility function f(a) and the maturation function β(a)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta (a)$$\\end{document} are assumed to be piecewise functions related to their maturation period τ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ au $$\\end{document}. Firstly, we rewrite the original system as a non-densely defined abstract Cauchy problem and show the existence of solutions. In particular, we discuss the existence and uniqueness of a positive equilibrium of the system. Secondly, we consider the maturation period τ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ au $$\\end{document} as a bifurcation parameter and show the existence of Hopf bifurcation at the positive equilibrium by applying the integrated semigroup theory and Hopf bifurcation theorem. Moreover, the direction of Hopf bifurcation and the stability of bifurcating periodic solutions are studied by applying the center manifold theorem and normal form theory. Finally, some numerical simulations are given to illustrate of the theoretical results and a brief discussion is presented.

A Multiple Scale Approach to Nonlinear Vibrations and Stability of Doubly Curved Shells/Panels Under External and Parametric Excitations

This study focuses on nonlinear vibrations and stability of doubly curved shells/panels. The thin-walled shell structure is assumed to be acted upon by external loads as well as parametric excitation. Using the first-order shear deformation Fülgge theory assumptions, governing equations of motion are derived for a general doubly curved geometry. Nonlinear components which are compatible with the Von-Karman kinematic assumptions are retained in the formulation and the rest of nonlinear components are neglected due to the fact that strains are assumed to be small and rotations to be moderate. The formulation can be readily reduced to any geometry including cylindrical shells and spherical panels, as benchmark examples in this study. Employing the Galerkin discretization approach and applying a modification to the Volmir assumption, a reduced order form of the original system is determined, which is shown to be a great representative of the original system with much more computational advantages. Using the method of multiple scales, the reduced order nonlinear governing equations are solved to discover the primary resonance, forced vibration characteristics and stability margins of thin-walled shells/panels under the action of parametric excitation. Several interesting findings on nonlinear behavior of cylindrical shells and spherical panels (as benchmark geometries) are presented while giving a demonstration of the accuracy and computational advantages of the proposed model.

Power Consumption Prediction in Real-Time Multitasking Systems

The paper presents a practical methodology for the prediction of power consumption of a multitask real-time system. The authors briefly recall the structure of the original multitasking time-predictable system. The system has a regular and scalable architecture. It consists of many cores based on pipeline processing with threads’ interleaving mechanism. In previous works, the authors have presented a number of issues related to the methodology of designing a time-predictable system and the scheduling of hardware threads with different design goals and constraints. The current article presents an accurate method for measuring the dynamic power dissipated in a system for various scenarios and the system configuration. The proposed approach is based on continuous monitoring of the power consumed by the FPGA, transmitting the measurements to the computer from the measuring device, and online analysis of the obtained results. The authors based their power estimation method on the original task frequency factor (TF). A theoretical analysis was made, and a series of practical experiments were carried out. The results obtained enable accurate estimation of the power requirements for the tasks performed in the real-time system. The presented technique can be useful during the design stage of multitasking real-time systems.

High-gain observer design for auxiliary systems of non-minimum phase nonlinear systems

To a non-minimum phase nonlinear system, it was supposed that, if there is an output feedback control that stabilizes the auxiliary system, then there is an output feedback that stabilizes the original system. The existing methods base designing output feedback for non-minimum phase nonlinear system on the hypothesis that there exists output feedback for auxiliary system. However, the auxiliary system could be unobservable. Alternatively, this study aims to create a way to design output feedback for auxiliary systems in unobservable situation. An output state is constructed in the last equation of auxiliary system, which artificially makes the internal dynamics of the auxiliary system observable. Then, a cascade high-gain observer is designed for the auxiliary system, consisting of an extended high-gain observer for external dynamics and a high-gain observer for internal dynamics of the auxiliary system. Therefore, the output feedback control for auxiliary system can be designed via the cascade high-gain observer and a state feedback. Finally, the proposed method is demonstrated by an academic example and an inverted pendulum on a cart in the simulation.

ПРО ОДИН ПІДХІД ДО ПЕРЕТВОРЕННЯ ЧИСЕЛ У СИСТЕМАХ ЗАЛИШКОВИХ КЛАСІВ ІЗ РІЗНИМИ МОДУЛЯМИ

The purpose of the study is an analytical consideration of the system of residual classes for the implementation of the operation of converting numbers from one system of residual classes to another. System analysis, number theory, and the Chinese remainder theorem are tools of the research methodology. The method uses the representation of the number both by its remainders and in the polyadic code. The methodology is based on determining the positional characteristics for this module on the basis of the received positional characteristics for the remaining modules of the original system, with the subsequent construction on their basis of the residuals for the modules of the sought system. The theoretical justification of the approach for obtaining an effective solution of this non-modular operation is performed. The considered solutions have high speed and can be effective in the development of modular computing structures for promising information technologies.

On evaluation of reliability increase in fault-tolerant multi processor systems

The work is devoted to the problem of evaluating the reliability increase of a fault-tolerant multiprocessor system by adding an extra processor to the system. It is assumed that the behavior of the modified system in the failure flow, in the case of the extra processor failure, does not differ from the behavior of the original system. The article describes both k-out-of-nsystems, and more complex ones, including hierarchical systems.An important feature of the proposed approach is that it involves the preliminary calculation of someadditionalauxiliaryvalues that do not depend on the reliability parameters of the added processor.Further, the reliability increase is assessed by substituting these parameter values into basicexpressions, which simplifies the selection of the optimal processor from the available set, sufficient to achieve the required level of system reliability, or confirms the impossibility of this.The proposed approach is compatible with any methods of calculating the reliability parameters of fault-tolerant multiprocessor systems but is particularly relevant for methods based on statistical experiments with models of system behavior in the failure flow, in particular, such as GL-models, due to the significant computational complexityof such calculations. In addition, for the simplest cases considered, k-out-of-nsystems with identical processors, a simple expression is proposed for an approximate estimateof the ratio of failure probabilities of the original and modified systems.Thehigher the reliability of the system processors, the higher the accuracy of such an assessment. Examples are given that prove the practical correctness of the proposed approaches.The calculation of the reliability system parameters, as well as auxiliary expressions, was based on conducting statistical experiments with corresponding GL-models.

RESEARCH OF THE FEATURES OF DIGITAL SIGNAL FORMATION IN SATELLITE COMMUNICATION LINES

Context. Remote sensing of the Earth is now widely used in various fields. One of the challenges of remote sensing is the creation of inexpensive satellite systems operating in polar circular orbits. These systems require the development of a receptiontransmission system that allows tens of gigabits of video information to be transmitted to an earth receiving station within ten minutes. That is, there is a need to create a communication system that provides high speed data transmission from small satellites weighing up to 50 kg.
 Objective. The aim of the work is to study the features of digital signal formation in modern satellite communication lines and to develop a communication system with a high data transfer rate (usually 300 Mbit/s), which can be applied to small Earth Observation satellites.
 Method. Proposed concept for building a high-speed data transmitter from a remote sensing earth satellite using commercially available off-the-shelf technology. Calculations of the power flow density created at the input of the receiving earth station were performed to find out the possible power of the on-board transmitter.
 Results. A diagram of a communication system based on the DVB-S standard using the technology of commercially available off-the-shelf products has been developed. The high-speed data transmitter is implemented on a Xilinx® Zynq Ultrascale+ ™ MPSoC FPGA microchip, which is located on an Enclustra Mercury XU8 module with a high-performance dual 16-bit AD9174 DAC. The on-board transmitter with a power of up to 2 W meets the requirements of the ITU Radio Regulations for the power flux density on the surface of the Earth, which is created by the radiation of the space station EESS in the range 8025–8400 MHz. It is shown that the energy reserve of the communication line of 3 dB is achieved for various commands for coding and modulation changes with an increase in the elevation angle, which allows to increase the speed of information transmission.
 Conclusions. An original receiving-transmitting system was developed for use in small satellites for remote sensing of the Earth. It is shown that the function of adaptive modeling of ACM of the DVB-S standard allows you to automatically change the transmission parameters in real time depending on the changing conditions of the channel, providing opportunities for more flexible and effective data transmission in various conditions, which will allow to increase the volumes of information transmitted by communication session. The proposed system operates in the X-band and is built using commercially available off-the-shelf products. An antenna with double circular polarization is used as the emitter. Two physical channels represent two polarization modes: right circular polarization and left circular polarization, each of which has three frequency channels.

The World Must Put Hunger to Shame: The Hidden Story of Homowo, Ngmayem and Ngma

This message calls our world to put hunger to shame using the revealed examples of Homowo and ngmayem, an original ethnic food systems in Ghana. The occurrence of hunger over the centuries can be understood from hunger’s proverbial mood. The results of hunger on humans due to its numerous causes and it associated lessons compelled early Ga-Adangbe settlers in Ghana to independently initiate the concepts of ‘Homowo’ (hoot at hunger) and ‘Ngmayem’ (celebrate life foods) as food systems. The hidden systems and basics in these unique food systems of ‘hoot at hunger’ and that of ‘celebrate life foods’ was studied. Some notable findings from the concept of ‘hoot at hunger’ involves a comprehensive layout of hooting at hunger using sustainable agriculture and the following principles: an appropriate food with or without therapeutic effect, applicable technology, basic knowledge in food and nutrition, building a suitable organizational system driven by skilled humans across several communities, by recalling historical records of hunger in society, a set day of remembrance, eating good foods all day, by the story of who we are and where we come from, with unity of purpose as a community lead by honest leaders, and also by proper symbols, designs and expressions. A remarkable outcome from ‘celebrate life foods’ norm was that it showed a notable historical record about a people, their decisions, actions, dealings and group effort in time during a hunger crisis. Once again, both concepts call for the establishment of specialized centers for advanced studies on unique food systems of old and hunger around the world with a museum chronicling the past stories of hunger challenges among a people, district, nation and the world, their probable causes and its impact on their health, and how they invented exceptional systems and products to solve those problems. All these concepts are intended to transform or strengthen food systems.

Elimination of lock-in phenomenon in vortex-induced vibration by passive modal control

Theoretical analysis and numerical results have shown that frequency lock-in in vortex-induced vibration (VIV) is caused by the instability of the structural mode rather than a resonant response to external excitations. However, there is a lack of experimental evidence supporting relevant theoretical research findings. This study investigates VIV suppression with a passive modal controller (PMC) for a circular cylinder at Reynolds numbers $Re = 60$ and $Re = 40$ , using experiments to distinguish the effects of stable and unstable wake modes. Comparative analysis before and after the implementation of the PMC reveals significant reduction in the vibration amplitude and the disappearance of the lock-in phenomenon at $Re = 60$ . The vibration frequency closely follows the vortex shedding frequency after control, while dynamic mode decomposition of the flow field indicates that the wake mode is dominant. For $Re = 40$ , the vibration is eliminated and the flow becomes steady. Additionally, the root loci of the coupled system are investigated before and after the PMC implementation via linear stability analysis. The results indicate that the PMC can alter the dynamic characteristics of the original system, causing the structural mode and PMC mode to couple when approaching the PMC frequency. Then, the interaction typically improves the stability of the structural mode. Finally, a parametric study is conducted in the experiment, as well as a linear stability analysis. The study provides experimental evidence that stability control of the structural mode is the key to suppressing VIV and eliminating the lock-in phenomenon.

Interobserver Reliability of Milan and Modified Milan System for Reporting Salivary Gland Cytopathology: An Institutional Experience.

In 2018, the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) was published, defining a diagnostic categorization scheme. However, this system of classification was criticized due to its suboptimal diagnostic accuracy and low interobserver reliability. For these reasons, the modified Milan system was recently proposed by a few authors claiming it to be more clinically reliable. The present study aimed to analyze the interobserver reliability of MSRSGC and modified MSRSGC. A total of 100 salivary gland fine-needle aspirations were reviewed over a 1-year period and classified by two independent observers according to MSRSGC and modified MSRSGC. Interobserver reproducibility was estimated using observed agreement and chance-corrected agreement (Cohen's kappa). An overall chance corrected agreement of 0.37 (fair) was obtained for the original Milan system and 0.41 (moderate) for the modified one. In addition, subcategories of modified MSRSGC performed better than the MSRSGC in terms of interobserver reliability. The present study suggests that modified MSRSGC should be accepted worldwide as the clinical relevance of any categorization scheme requires diagnostic accuracy along with excellent interobserver reproducibility.

A PRAGMATICALLY ORIENTED APPROACH TO GENERATIVE LINGUISTICS

The annotated paper examines the possibility of creating an original grammatical system when teaching a new language. The pragmatic approach to generative linguistics was the methodology of language acquisition using a unified model of the Russian sentence. The article discusses algorithms of sentence modelling at two levels: external and internal, based on the theories of N.Chomsky and L.Teniers. The external level includes the construction of a unified sentence structure from the deep structure to the surface structure according to N.Chomsky. And the internal level includes the structural correlation of model elements as the content of the unified sentence structure itself -according to L.Tenier. The theories of N.Chomsky and L.Teniers defined all models as a union of components and reflected in the same models the relations of hierarchy between the components. The study demonstrates a way of teaching foreign speakers the language with the help of the author’s theory of algorithmic syntax.

Statistical Methods for Detecting Recycled Electronics: From ICs to PCBs and Beyond

<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Globalization of semiconductor industry has led to unprecedented challenges in design, verification, test, security and trustworthiness of contemporary electronics. With parts sourced from various suppliers across the globe, who are beyond the auspices of the original designers and system integrators, serious concerns arise regarding integrity and trustworthiness of electronic circuits, which can be compromised by malicious actors at any stage of the component manufacturing and system assembly process. Among the variety of such concerns, recycled electronics sold as new by malicious suppliers/vendors pose a key threat to mission-critical end applications such as military systems, financial institutions, transportation security, and poser distribution infrastructure. Recycled electronics may experience performance degradation due to aging and, more importantly, may have shorter-than-expected lifetime, thereby raising serious reliability and safety issues. To combat this problem, statistical methods have been proposed in the past decade as a time-efficient and cost-effective approach to identify recycled electronics sold as new. Initially demonstrating in the context of detecting recycled Integrated Circuits (ICs), such methods are based on using statistics and machine learning to outline the parametric signatures of known brand-new ICs and, thereby, weed out ICs that do not fit the expected profile. This article summarizes the current state of knowledge in recycled IC detection schemes and discusses how these methods have inspired, over time, the development of similar solutions in a plethora of domains, including identification of recycled Field Programmable Gate Arrays (FPGAs), recycled hardware components in a network, and recycled Static Random-Access Memories (SRAMs)/Flash memories</i> .

Two-level optimal scheduling of source–storage-load interactive distribution network based on particle swarm optimization algorithm

In response to the difficulties of grid integration and consumption of a high proportion of new energy generation, as well as the high pressure on traditional thermal power generation to regulate peak loads, this paper constructs a wind-solar-fire-water complementary power generation system with “dual energy storage” and proposes a two-layer scheduling optimization strategy for this system. The scheduling model’s higher layer uses the system’s complementary power generation system’s maximum benefit as its objective function. The lower tier model has the minimization of the system’s cost of regulating load peaks as the objective function, and the model is solved by the improved adaptive immune particle swarm optimization algorithm considering various constraints. Taking the improved IEEE30 node system as an example for analysis, according to the operation of the original power system and the different characteristics of pumped storage and storage power plants, pumped storage and energy storage power stations are gradually added to the system for scheduling comparative analysis, and different capacities are configured, respectively. Through the analysis of examples, it is verified that the proposed dual-storage joint scheduling optimization strategy can effectively improve the overall operation of the system, reduce the peaking pressure of thermal power units, and achieve the expected goal of maximizing economic benefits. It also improves the new energy consumption in the region and alleviates the thermal power peaking pressure.

Improved continuous measurement system for atmospheric total peroxy and total organic nitrate under the high NOx condition.

We improved the thermal dissociation cavity attenuated phase shift spectroscopy (TD-CAPS) instrument to measure atmospheric total peroxy nitrates (PNs) and organic nitrates (ONs) continuously under the condition of high NOx. In TD-CAPS, PNs and ONs are dissociated in heated quartz tubes to form NO2, and the NO2 concentration is measured by cavity attenuated phase shift spectroscopy (CAPS). The original TD-CAPS system overestimates PN and ON concentrations in the presence of high NO concentrations. Our laboratory experiments and numerical simulations showed that the main cause of the overestimation was NO oxidation to NO2 by peroxy radicals generated in the heated quartz tubes. In the improved system, NO was converted to NO2 by adding excess O3 after the quartz tubes so that CAPS detected NOx (NO and NO2) instead of NO2. The uncertainty of the improved system was less than 20% with ∼15 parts per billion by volume (ppbv) NO and ∼80ppbv NO2. The estimated detection limit (3σ) was 0.018ppbv with an integration time of 2minin the presence of 64ppbv NO2. The improved system was tested for measurement of PNs and ONs in an urban area, and the results indicated that interference from NO was successfully suppressed.

Composite Observer of a Linear Time-Varying Singularly Perturbed System with Quasidifferentiable Coefficients

For a linear time-varying singularly perturbed system with a small parameter µ for a part of derivatives and quasi-differentiable coefficients, existence conditions are established and µ-asymptotic composite full- and reduced-order observers are constructed. The error in estimating a state with an arbitrary predetermined exponential decay rate converges to an infinitesimal value of the same order of smallness as the small parameter. The observer gain vector are expressed in terms of the gain vectors of subsystems of smaller dimension than the original one and independent of the small parameter, and the parameters of the original system are subject to weaker requirements than those previously known. A constructive algorithm for calculating the gain vector of a composite observer is presented.

Observer-based finite-time H∞ control for discrete-time singular Markovian jump systems with asynchronous modes

The asynchronous observer-based finite-time [Formula: see text] control problem for discrete-time singular Markovian jump systems with time-varying delays is studied, where the asynchronism of the controller and observer with respect to the original system is fully taken into consideration. By the use of finite-time analysis theory and the construction of suitable Lyapunov-Krasovskii functionals, sufficient conditions to determine the closed-loop error system is singular stochastic finite-time boundedness are given with [Formula: see text] performance level. Then, by applying linear matrix inequalities, the desired observer parameters and controller parameters can be computed. Finally, the effectiveness of our proposed method is confirmed by simulation.

Идентификация компонентного состава твердой углеводородной фазы в пласте и оценка ее влияния на поведение подвижного флюида баженовской свиты в процессе разработки залежи

The purpose of the work is to identify the composition of the initial reservoir hydrocarbon (HC) system of the Bazhenov formation, as well as to assess the influence of the presence of a heavy solid hydrocarbon phase (bitumen) in the formation on the production of mobile fluids using PVT modeling methods. The article describes the necessary experiments to determine the component composition of the C81+ fraction and the PVT properties of the formation mobile fluid taken from the well and the bitumen extract from the rock, and also presents their results. In addition, the properties of fractions up to C81+ were calculated depending on the molecular weight for PVT modeling (extension of the Katz-Firuzabadi table). One of the important parts of the article is the assessment of the ratio of bound and free oil in the original reservoir system. Based on geochemical research data, an analysis was performed to assess the component composition of the original system (using the example of the Bazhenov Formation) using rock pyrolysis and studying formation fluid and bitumen. Using the results of studies of reservoir fluid samples, a PVT model was built and tuned. This PVT model was used to assess the properties of the initial reservoir hydrocarbon system and was adjusted to the fraction of the solid phase in the reservoir at the initial reservoir conditions. After this, based on the PVT model, an assessment was made of the influence of the presence of a solid phase in the composition of the reservoir system on the behavior of a mobile hydrocarbon fluid during reservoir development for depletion, as well as on the use of enhanced oil recovery methods (injection of associated petroleum gas and thermal methods of influencing the reservoir).

Supercritical carbon dioxide cycle thermodynamic and exergoeconomic improvements using a bidirectional coupling strategy

Supercritical carbon dioxide (SCO2) combined cycle power system, one of the potentially effective ways to achieve energy grade utilization of the medium and high-temperature heat sources, is vulnerable to ambient temperatures as the system performance is susceptible to the compressor inlet temperature. So far, most studies have been focused on the system performance analysis and optimization under ideal operation conditions while the mitigation of unfavorable ambient temperature is missed. In this work, a bidirectionally-coupled system is proposed to reduce the compressor inlet temperatures in the original SCO2 cycle power system so that the adverse effects of ambient temperature are alleviated. The proposal utilizes the low-grade waste heat in a SCO2 recompression reheat Brayton cycle (i.e., topping cycle) to drive an absorption refrigeration cycle (i.e., bottoming cycle) which in turn precools the compressor inlet of the topping cycle. The thermodynamic and exergoeconomic analyses have been conducted for the proposed bidirectionally-coupled combined SCO2 RRBC and ARC system, with the attention to the effects of ambient temperatures on the system performance. Our results show that the combined SCO2 RRBC and ARC system increases the energy efficiency relative to the standalone cycle power system by over 5% at the ambient temperatures of 303.15 K or above, while the exergy efficiency improves by 1.124%–3.574%. In terms of the exergoeconomic factor, the combined SCO2 RRBC and ARC system also exhibits superiority against standalone cycle power system. The current work proves that a conventional recuperated SCO2 cycle system can be improved both thermodynamically and economically by coupling it to an absorption refrigeration cycle, despite of the additional upfront costs for the components. The discovery could further promote the commercial application of the SCO2 cycle power systems in new generation plants.

An averaging result for fractional variable-order neutral differential equations with variable delays driven by Markovian switching and Lévy noise

In this paper, we derive new results on the averaging principle for a class of Caputo neutral stochastic system driven by Markovian switching and Lévy noise with variable delays and time-varying fractional order. Under a set of appropriate conditions, we showed that solutions of the averaged stochastic systems approach the solutions of the original stochastic systems in the sense of both convergences in mean square and convergence in probability. Finally, we attach two examples with numerical simulations to justify the validity of our theory.