Search results for: dynamic systems perspective

Authors: Zaouche Mohammed, Amini Mohammed, Foughali Khaled, Hamissi Aicha, Aktouf Mohand Arezki, Boureghda Ilyes

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In this paper, we present a piloting law based on the adaptive differentiators via high order sliding mode controller, by using an aircraft in virtual simulated environment. To deal with the design of an autopilot controller, we propose a framework based on Software in the Loop (SIL) methodology and we use Microsoft^TM Flight Simulator (FS-2004) as the environment for plane simulation. The aircraft dynamic model is nonlinear, Multi-Input Multi-Output (MIMO) and tightly coupled. The nonlinearity resides in the dynamic equations and also in the aerodynamic coefficients' variability. In our case, two (02) aircrafts are used in the flight tests, the Zlin-142 and MQ-1 Predator. For both aircrafts and in a very low altitude flight, we send the piloting control inputs to the aircraft which has stalled due to a command disconnection. Then, we present the aircraft’s dynamic behavior analysis while reestablishing the command transmission. Finally, a comparative study between the two aircraft’s dynamic behaviors is presented.

Keywords: adaptive differentiators, second order sliding modes, dynamic adaptation of the gains, microsoft flight simulator, Zlin-142, MQ-1 predator

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Authors: Peikun Zhang, Chunhua Cui

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Photoelectrochemical (PEC) water splitting provides a promising pathway to convert solar energy into renewable fuels. However, the main and seemingly insurmountable obstacle is that the sluggish kinetics of oxygen evolution reaction (OER) severely jeopardizes the overall efficiency, thus exploring highly active, stable, and appreciable catalysts is urgently requested. Herein a competitive coordination strategy was demonstrated to form a reversible hybrid homo-heterogeneous catalyst for efficient OER in alkaline media. The dynamic process involves an in-situ anchoring of soluble nickel–bipyridine pre-catalyst to a conductive substrate under OER and a re-dissolution course under open circuit potential, induced by the competitive coordination between nickel–bipyridine and nickel-hydroxyls. This catalyst allows to elaborately self-modulate a charge-transfer layer thickness upon the catalytic on-off operation, which affords substantially increased active sites, yet remains light transparency, and sustains the stability of over 200 hours of continuous operation. The integration of this catalyst with exemplified state-of-the-art Ni-sputtered Si photoanode can facilitate a ~250 mV cathodic shift at a current density of 20 mA cm-2. This finding helps the understanding of catalyst from a “dynamic” perspective, which represents a viable alternative to address remaining hurdles toward solar-driven water oxidation.

Keywords: molecular catalyst, oxygen evolution reaction, solar energy, transition metal complex, water splitting

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Authors: Ruoyu Mao

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The fast-paced and high-stress lifestyle of modern cities is an important cause of mental health problems and chronic physical diseases, and at the same time, all kinds of health problems will react to physical and mental stress, further aggravating the health risks; therefore, stress adjustment should be considered as an important perspective of the spatial environment to intervene in the health of the population. The purpose of this paper is to analyse the structural and therapeutic characteristics of the built environment of urban parks, to analyse the path of its effect on the stress adjustment of the population, and to summarise the mechanism of the built environment of urban parks to intervene in the health of the population from the perspective of stress adjustment.

Keywords: stress adjustment, health interventions, urban parks, built environments

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Authors: Bochra Khiari, Lamia Labed

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In the new digital marketplace, organizations are striving for a proactive position by leveraging the great potential of disruptive technologies to seize the full opportunity of the digital revolution in order to reshape their customer value propositions. New technologies such as big data analytics, which provide prediction of future events based on real-time information, are being integrated into BPM which urges the need for additional core values like capabilities for dynamic adaptation, autonomic behavior, runtime reconfiguration and post-deployment activities to manage unforeseen scenarios at runtime in a situated and changeable context. Dynamic Software Product Lines (DSPL) is an emerging paradigm that supports these runtime variability mechanisms. However, few works exploiting DSPLs principles and techniques in the BPM domain have been proposed so far. In this paper, we propose a conceptual approach DynPL4CBPM, which integrates DSPLs concepts along with the entire related dynamic properties, to the whole BPM lifecycle in order to dynamically adapt business processes according to different context conditions in an individual environment.

Keywords: adaptive processes, context aware business process management, customer centric business process management, dynamic software product lines

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Authors: Wojciech Sas, Emil Soból, Katarzyna Gabryś, Andrzej Głuchowski, Alojzy Szymański

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Depleting of natural resources is forcing the man to look for alternative construction materials. One of them is recycled concrete aggregates (RCA). RCA from the demolition of buildings and crushed to proper gradation can be a very good replacement for natural unbound granular aggregates, gravels or sands. Physical and the mechanical properties of RCA are well known in the field of basic civil engineering applications, but to proper roads and railways design dynamic characteristic is need as well. To know maximum shear modulus (GMAX) and the minimum damping ratio (DMIN) of the RCA dynamic loads in resonant column apparatus need to be performed. The paper will contain literature revive about alternative construction materials and dynamic laboratory research technique. The article will focus on dynamic properties of RCA, but early studies conducted by the authors on physical and mechanical properties of this material also will be presented. The authors will show maximum shear modulus and minimum damping ratio. Shear modulus and damping ratio degradation curves will be shown as well. From exhibited results conclusion will be drawn at the end of the article.

Keywords: recycled concrete aggregate, shear modulus, damping ratio, resonant column

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Authors: Maria Bashutkina

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In seeking to identify marketing factors that influence company’s performance, product management as well as new technology configuration, this study adopts resource based theory and applies it to the Swiss watchmaking companies. This paper presents results of qualitative research based on semi-structured interviews with CEO and marketing managers among watchmaking companies. This paper provides empirical evidences illustrating the link between the use of dynamic marketing capabilities and competitive advantage. We also present a set of propositions that outline how dynamic marketing capabilities could benefit product management and technological change in the Swiss independent watchmaking company, revealing competitive advantage in the highly competitive and turbulent market.

Keywords: dynamic marketing capabilities, luxury marketing, resource based theory, product management, Swiss watchmaking

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Authors: Julio Cesar Torres Rocha

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The present study is a three-stage action research that aims at raising EFL teachers’ awareness of World Englishes (WE) within a critical perspective of inquiry. Through a taught module on English and its varieties, a survey, a reflection paper, and a semi-structured interview were used to collect the data. The results of the study showed that there was a clear change of conception, at the theoretical level, in teachers’ papers. However, WE was regarded as future possibility for action. On the one hand, all of the participants said the module changed their conception of other varieties of English different from British and American ones. They all went from identifying themselves with either American or British variety, a celebratory perspective, to acknowledging and accepting other English varieties, a critical perspective of English as an international language (EIL).

Keywords: teachers’ s awareness, English as an international language, introducing world Englishes, critical applied linguistics

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Authors: Maciej Major, Izabela Major

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The aim of this paper is a numerical analysis of three-layered block design to walls construction subjected to the dynamic load. The block consists of the layers: concrete with rubber pads in shape of crosses, space filled with air and concrete with I-shape rubber pads. The main purpose of rubber inserts embedded during the production process is additional protection against the transversal dynamic load. For the analysis, as rubber, the Zahorski hyperelastic incompressible material model was assumed. A concentrated force as dynamic load applied to the external block surface was investigated. The results for the considered block observed as the stress distribution plot were compared to the results obtained for the solid concrete block. In order to estimate the percentage damping of proposed composite, rubber-concrete block in relation to the solid block the numerical analysis with the use of finite element method based on ADINA software was performed.

Keywords: dynamics, composite, rubber, Zahorski

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Authors: Cristina Schreiner, Romeo Ciobanu, Marius Pislaru

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This paper aims to build a system based on fuzzy models that can be implemented in the assessment of ecological systems, to determine appropriate methods of action for reducing adverse effects on environmental and implicit the population. The model proposed provides new perspective for environmental assessment, and it can be used as a practical instrument for decision-making.

Keywords: ecosystem model, environmental security, fuzzy logic, sustainability of habitable regions

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Authors: Xu Chen, Zhao Caiqi

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In addition to the advantages of light weight, resistant corrosion and ease of processing, aluminum is also applied to the long-span spatial structures. However, the elastic modulus of aluminum is lower than that of the steel. This paper combines the high performance aluminum honeycomb panel with the aluminum latticed shell, forming a new panel-and-rod composite shell structure. Through comparative analysis between the static and dynamic performance, the conclusion that the structure of composite shell is noticeably superior to the structure combined before.

Keywords: combination of aluminum honeycomb panel, rod latticed shell, dynamic performence, response spectrum analysis, seismic properties

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Authors: Tariq Aljuneidi, Akif Asil Bulgak

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Remanufacturing may be defined as the process of bringing used products to “like-new” functional state with warranty to match, and it is one of the most popular product end-of-life scenarios. An efficient remanufacturing network lead to an efficient design of sustainable manufacturing enterprise. In remanufacturing network, products are collected from the customer zone, disassembled and remanufactured at a suitable remanufacturing facility. In this respect, another issue to consider is how the returned product to be remanufactured, in other words, what is the best layout for such facility. In order to achieve a sustainable manufacturing system, Cellular Manufacturing System (CMS) designs are highly recommended, CMSs combine high throughput rates of line layouts with the flexibility offered by functional layouts (job shop). Introducing the CMS while designing a remanufacturing network will benefit the utilization of such a network. This paper presents and analyzes a comprehensive mathematical model for the design of Dynamic Cellular Remanufacturing Systems (DCRSs). In this paper, the proposed model is the first one to date that consider CMS and remanufacturing system simultaneously. The proposed DCRS model considers several manufacturing attributes such as multi-period production planning, dynamic system reconfiguration, duplicate machines, machine capacity, available time for workers, worker assignments, and machine procurement, where the demand is totally satisfied from a returned product. A numerical example is presented to illustrate the proposed model.

Keywords: cellular manufacturing system, remanufacturing, mathematical programming, sustainability

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Authors: T. Penkova, A. Korobko, V. Nicheporchuk, L. Nozhenkova, A. Metus

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This paper presents an approach of on-line control of the state of technosphere and environment objects based on the integration of Data Warehouse, OLAP and Expert systems technologies. It looks at the structure and content of data warehouse that provides consolidation and storage of monitoring data. There is a description of OLAP-models that provide a multidimensional analysis of monitoring data and dynamic analysis of principal parameters of controlled objects. The authors suggest some criteria of emergency risk assessment using expert knowledge about danger levels. It is demonstrated now some of the proposed solutions could be adopted in territorial decision making support systems. Operational control allows authorities to detect threat, prevent natural and anthropogenic emergencies and ensure a comprehensive safety of territory.

Keywords: decision making support systems, emergency risk assessment, natural and anthropogenic safety, on-line control, territory

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Authors: Talha Ali Khan

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This paper presents an adaptive neuro-fuzzy interference system (ANFIS), which is applied to a hybrid stepper motor (HSM) to regulate its speed. The dynamic response of the HSM with the ANFIS controller is studied during the starting process and under different load disturbance. The effectiveness of the proposed controller is compared with that of the conventional PI controller. The proposed method solves the problem of nonlinearities and load changes of the HSM drives. The proposed controller ensures fast and precise dynamic response with an excellent steady state performance. Matlab/Simulink program is used for this dynamic simulation study.

Keywords: stepper motor, hybrid, ANFIS, speed control

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Authors: Mohammad Shams Esfand Abadi, Mehrdad Zalaghi, Reza ebrahimpour

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In this paper, we propose a sign adaptive filter algorithm with the ability of dynamic selection of subband filters which leads to low computational complexity compared with conventional sign subband adaptive filter (SSAF) algorithm. Dynamic selection criterion is based on largest reduction of the mean square deviation at each adaption. We demonstrate that this simple proposed algorithm has the same performance of the conventional SSAF and somewhat faster than it. In the presence of impulsive interferences robustness of the simple proposed algorithm as well as the conventional SSAF and outperform the conventional normalized subband adaptive filter (NSAF) algorithm. Therefore, it is preferred for environments under impulsive interferences. Simulation results are presented to verify these above considerations very well have been achieved.

Keywords: acoustic echo cancellation (AEC), normalized subband adaptive filter (NSAF), dynamic selection subband adaptive filter (DS-NSAF), sign subband adaptive filter (SSAF), impulsive noise, robust filtering

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Authors: Michael Lognoul

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In April 2021, the European Commission released its AI Act Proposal, which is the first policy proposal at the European Union level to target AI systems comprehensively, in a horizontal manner. This Proposal notably aims to achieve an ecosystem of trust in the European Union, based on the respect of fundamental rights, regarding AI. Among many other requirements, the AI Act Proposal aims to impose several generic transparency obligationson all AI systems to the benefit of natural persons facing those systems (e.g. information on the AI nature of systems, in case of an interaction with a human). The Proposal also provides for more stringent transparency obligations, specific to AI systems that qualify as high-risk, to the benefit of their users, notably on the characteristics, capabilities, and limitations of the AI systems they use. Against that background, this research firstly presents all such transparency requirements in turn, as well as related obligations, such asthe proposed obligations on record keeping. Secondly, it focuses on a legal analysis of their scope of application, of the content of the obligations, and on their practical implications. On the scope of transparency obligations tailored for high-risk AI systems, the research notably notes that it seems relatively narrow, given the proposed legal definition of the notion of users of AI systems. Hence, where end-users do not qualify as users, they may only receive very limited information. This element might potentially raise concern regarding the objective of the Proposal. On the content of the transparency obligations, the research highlights that the information that should benefit users of high-risk AI systems is both very broad and specific, from a technical perspective. Therefore, the information required under those obligations seems to create, prima facie, an adequate framework to ensure trust for users of high-risk AI systems. However, on the practical implications of these transparency obligations, the research notes that concern arises due to potential illiteracy of high-risk AI systems users. They might not benefit from sufficient technical expertise to fully understand the information provided to them, despite the wording of the Proposal, which requires that information should be comprehensible to its recipients (i.e. users).On this matter, the research points that there could be, more broadly, an important divergence between the level of detail of the information required by the Proposal and the level of expertise of users of high-risk AI systems. As a conclusion, the research provides policy recommendations to tackle (part of) the issues highlighted. It notably recommends to broaden the scope of transparency requirements for high-risk AI systems to encompass end-users. It also suggests that principles of explanation, as they were put forward in the Guidelines for Trustworthy AI of the High Level Expert Group, should be included in the Proposal in addition to transparency obligations.

Keywords: aI act proposal, explainability of aI, high-risk aI systems, transparency requirements

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Authors: Anu Malhotra, Rahul Malhotra

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This review paper is focused on achievement ability analysis of perspective teachers and students of technical education of Haryana. It is well known that women have higher verbal achievement, while men have higher achievement in non-verbal and scientific achievement. Chi-square analyses were performed to evaluate the effect of information and communication technology tools on the scientific, verbal and non-verbal achievement of the controlled and uncontrolled group of 204 students of Haryana. The computed value of expected count, which is more than 5, shows that there is a significant improvement in achievement ability of students of the controlled group when compared to the uncontrolled group. The research analyzes that the Information and communication technology tools play an important role in enhancing student’s achievement.

Keywords: achievement, ICT, perspective teacher, verbal achievement

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Authors: Dong Jiang

Abstract:

Turnout is the essential equipment on the railway, which also belongs to one of the strongest demanded infrastructural facilities of railway on account of the more seriously frog rail failures. In cooperation with Germany Company (DB Systemtechnik AG), our research team focuses on the quantitative analysis about the frog rails to predict their lifetimes. Moreover, the suggestions for the timely and effective maintenances are made to improve the economy of the frog rails. The lifetime of the frog rail depends strongly on the internal damage of the running surface until the breakages occur. On the basis of Hertzian theory of the contact mechanics, the dynamic loads of the running surface are calculated in form of the contact pressures on the running surface and the equivalent tensile stress inside the running surface. According to material mechanics, the strength of the frog rail is determined quantitatively in form of the Stress-cycle (S-N) curve. Under the interaction between the dynamic loads and the strength, the internal damage of the running surface is calculated by means of the linear damage hypothesis of the Miner’s rule. The emergence of the first Breakage on the running surface is to be defined as the failure criterion that the damage degree equals 1.0. From the microscopic perspective, the running surface of the frog rail is divided into numerous segments for the detailed analysis. The internal damage of the segment grows slowly in the beginning and disproportionately quickly in the end until the emergence of the breakage. From the macroscopic perspective, the internal damage of the running surface develops simply always linear along the lifetime. With this linear growth of the internal damages, the lifetime of the frog rail could be predicted simply through the immediate introduction of the slope of the linearity. However, the superficial abrasion plays an essential role in the results of the internal damages from the both perspectives. The influences of the superficial abrasion on the lifetime are described in form of the abrasion rate. It has two contradictory effects. On the one hand, the insufficient abrasion rate causes the concentration of the damage accumulation on the same position below the running surface to accelerate the rail failure. On the other hand, the excessive abrasion rate advances the disappearance of the head hardened surface of the frog rail to result in the untimely breakage on the surface. Thus, the relationship between the abrasion rate and the lifetime is subdivided into an initial phase of the increased lifetime and a subsequent phase of the more rapid decreasing lifetime with the continuous growth of the abrasion rate. Through the compensation of these two effects, the critical abrasion rate is discussed to reach the optimal lifetime.

Keywords: breakage, critical abrasion rate, frog rail, internal damage, optimal lifetime

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Authors: Agnieszka Kałdonek-Crnjaković

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Research on Attention-Deficit/Hyperactivity Disorder (ADHD) is abundant but not in the field of applied linguistics and foreign or second language education. To fill this research gap, the present study aimed to investigate the effect of ADHD on skills and systems development in a second and foreign language from the teacher's perspective. The participants were 51 English as a foreign language (EFL) teachers in Poland working in state pre-, primary, and high schools. Research questions were as follows: Do ADHD-type behaviors affect EFL learning of the individual with the condition and their classmates to the same extent considering different educational settings and specific skills and systems? And To what extent do ADHD-type behaviors affect ESL/EFL skills and systems considering different ADHD presentations? Data were collected by means of a questionnaire distributed via a Google form. It contained 14 statements on a six-point Likert scale related to the effect of ADHD on specific language skills and systems in the context of an individual with the condition and their classmates and situations related to inattention and hyperactivity/impulsivity presentations of the condition, where the participants needed to identify skills and systems affected by the given ADHD manifestation. The results show that ADHD affects all language skills and systems development in both the individual with the condition and their classmates, but this effect is more significant in the latter. However, ADHD affected skills and systems to a different degree; writing skills were reported as the most affected by this disorder. Also, the effect of ADHD differed depending on the educational setting, being the highest in high school and lowest in the first three grades of primary school. These findings will be discussed in the context of foreign/second language teaching in the school context, considering different phases of education as well as future research on ADHD and language learning and teaching.

Keywords: ADHD, EFL teachers, foreign/second language learning, language skills and systems development

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Authors: Ghania Zidani, Said Drid, Larbi Chrifi-Alaoui, Abdeslam Benmakhlouf, Souad Chaouch

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In this paper, we focus on the study for path tracking control of unicycle-type Wheeled Mobile Robots (WMR), by applying the Backstepping technic. The latter is a relatively new technic for nonlinear systems. To solve the problem of constraints nonholonomics met in the path tracking of such robots, an adaptive Backstepping based nonlinear controller is developed. The stability of the controller is guaranteed, using the Lyapunov theory. Simulation results show that the proposed controller achieves the objective and ensures good path tracking.

Keywords: Backstepping control, kinematic and dynamic controllers, Lyapunov methods, nonlinear control systems, Wheeled Mobile Robot (WMR).

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Authors: L. Srikanth, D. Neelima Satyam

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The transmission line towers are one of the important life line structures in the distribution of power from the source to the various places for several purposes. The predominant external loads which act on these towers are wind and earthquake loads. In this present study tower is analyzed using Indian Standards IS: 875:1987 (Wind Load), IS: 802:1995 (Structural Steel), IS:1893:2002 (Earthquake) and dynamic analysis of tower has been performed considering ground motion of 2001 Bhuj Earthquake (India). The dynamic analysis was performed considering a tower system consisting two towers spaced 800m apart and 35m height each. This analysis has been performed using numerical time stepping finite difference method which is central difference method were employed by a developed MATLAB program to get the normalized ground motion parameters includes acceleration, frequency, velocity which are important in designing the tower. The tower is analyzed using response spectrum analysis.

Keywords: response spectra, dynamic analysis, central difference method, transmission tower

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Authors: Nadjah Chergui, Narhimene Boustia

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Intrusion Detection Systems are an essential tool for network security infrastructure. However, IDSs have a serious problem which is the generating of massive number of alerts, most of them are false positive ones which can hide true alerts and make the analyst confused to analyze the right alerts for report the true attacks. The purpose behind this paper is to present a formalism model to perform correlation engine by the reduction of false positive alerts basing on vulnerability contextual information. For that, we propose a formalism model based on non-monotonic JClassicδє description logic augmented with a default (δ) and an exception (є) operator that allows a dynamic inference according to contextual information.

Keywords: context, default, exception, vulnerability

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Authors: Zaki Ahmad Khan, Jamshed Siddiqui, Abdus Samad

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The Scheduling and mapping of tasks on a set of processors is considered as a critical problem in parallel and distributed computing system. This paper deals with the problem of dynamic scheduling on a special type of multiprocessor architecture known as Linear Crossed Cube (LCQ) network. This proposed multiprocessor is a hybrid network which combines the features of both linear type of architectures as well as cube based architectures. Two standard dynamic scheduling schemes namely Minimum Distance Scheduling (MDS) and Two Round Scheduling (TRS) schemes are implemented on the LCQ network. Parallel tasks are mapped and the imbalance of load is evaluated on different set of processors in LCQ network. The simulations results are evaluated and effort is made by means of through analysis of the results to obtain the best solution for the given network in term of load imbalance left and execution time. The other performance matrices like speedup and efficiency are also evaluated with the given dynamic algorithms.

Keywords: dynamic algorithm, load imbalance, mapping, task scheduling

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Authors: Boualem Chetti

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The dynamic characteristics of a three-lobe journal bearing lubricated with micropolar fluids are determined by the linear stability theory. Lubricating oil containing additives and contaminants is modeled as micropolar fluid. The modified Reynolds equation is obtained using the micropolar lubrication theory and the finite difference technique has been used to solve it. The dynamic characteristics in terms of stiffness, damping coefficients, the critical mass and whirl ratio are determined for various values of size of material characteristic length and the coupling number. The computed results show compared with Newtonian fluids, that micropolar fluid exhibits better stability.

Keywords: three-lobe bearings, micropolar fluid, dynamic characteristics, stability analysis

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Authors: Lan Nguyen, Kien Le Tan, Bao Nguyen Pham Gia

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Due to the high cost, specialized dynamic measurement devices for industrial lands are difficult for many colleges to equip for hands-on teaching. This study connects a dynamic measurement sensor and receiver utilizing an inexpensive Raspberry Pi 4 board, some 24-bit ADC circuits, a geophone vibration sensor, and embedded Python open-source programming. Gather and analyze signals for dynamic measuring, ground vibration monitoring, and structure vibration monitoring. The system may wirelessly communicate data to the computer and is set up as a communication node network, enabling real-time monitoring of background vibrations at various locations. The device can be utilized for a variety of dynamic measurement and monitoring tasks, including monitoring earthquake vibrations, ground vibrations from construction operations, traffic, and vibrations of building structures.

Keywords: sensors, FFT, signal processing, real-time data monitoring, ground propagation wave, python, raspberry Pi 4

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Authors: V. Geza, J. Vencels, G. Zageris, S. Pavlovs

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One of the most perspective methods to produce SoG-Si is refinement via metallurgical route. The most critical part of this route is refinement from boron and phosphorus. Therefore, a new approach could address this problem. We propose an approach of creating surface waves on silicon melt’s surface in order to enlarge its area and accelerate removal of boron via chemical reactions and evaporation of phosphorus. A two dimensional numerical model is created which includes coupling of electromagnetic and fluid dynamic simulations with free surface dynamics. First results show behaviour similar to experimental results from literature.

Keywords: numerical modelling, silicon refinement, surface waves, VOF method

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Authors: Ghada Mohamed Rashad, Doaa Ayoub Elimy, Mohamed Hussein Elgendy, Ahmed Mohamed Fathi Elshiwi, Mahmoud Ghazy

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Background: Flat feet cause changes in foot mobility, foot posture, and load distribution under the foot which influences dynamic balance, that is essential in activities of daily living and for optimal performance in sports activity. Purpose: To investigate the effect of flat feet on dynamic balance including overall stability index (OAI), anteroposterior stability index (APSI) and mediolateral stability index (MLSI). Study Design: The design of the study was an experimental design. Subjects: Forty subjects from both sexes were selected from the Faculty of Physical Therapy, Cairo University, their mean age (23.55 ± 1.74 ) years, divided into two groups, group A (8 males and 12 females) with flat feet, and group B (9 males and 11 females) with normal feet. Methods: The Navicular Drop Test was used to determine if the feet were pronated and Biodex Balance System was used to assess dynamic balance at level 8 and level 4 for both groups. Results: There was no significant difference in dynamic balance including (OSI, APSI and MLSI) of the Biodex at stability level (8) (most stable) (p = 0.56). While there was a significant difference between both groups in all dependent variables at stability level (4) (less stable level) (p = 0.0001). Conclusion: It may be concluded that flat feet have an effect on dynamic balance and there is balance affection in subjects with flat feet.

Keywords: flat feet, dynamic balance, postural stability, types of flat feet, eversion strength

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Authors: Chitsanzo Isaac

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Across the world, the ongoing Covid-19 pandemic has challenged urban systems and policy frameworks, highlighting societal vulnerabilities and systemic inequities among many communities. Measures of confinement and social distancing to contain the Covid-19 virus have fragmented the physical and social fabric of cities. This has caused urban dwellers to reassess how they engage with their urban surroundings and maintain social ties. Urbanists have presented strategies that would allow communities to survive and even thrive, in extraordinary times of crisis like the pandemic. Tactical Urbanism, particularly the 15-Minute City, has gained popularity. It is considered a resilient approach in the global north, however, it’s transferability to the global south has been called into question. To this end, this paper poses the question: to what extent is the 15-Minute City framework integral sustainable design, and are there processes that make it adoptable by cities in the global south? This paper explores four issues using secondary quantitative data analysis and convergence analysis in the Paris and Blantyre urban regions. First, it questions how the 15-Minute City has been defined and measured, and how it impacts urban dwellers. Second, it examines the extent to which the 15-minute city performs under the lens of frameworks such as Wilber’s integral theory and Fleming’s integral sustainable design theory. Thirdly this work examines the processes that can be transferred to developing cities which foster community resilience through the perspectives of experience, behaviors, cultures, and systems. Finally, it reviews the principal ways in which a multi-perspective reality can be the basis for resilient community design and sustainable urban development. This work will shed a light on the importance of a multi-perspective reality as a means of achieving sustainable urban design goals in developing urban areas.

Keywords: 15-minute city, developing cities, global south, community resilience, integral sustainable design, systems thinking, complexity, tactical urbanism

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Authors: Paul G. Bolz, Paul G. Lindner, Frohmut Wellner, Christian Schulze, Joern Huebelt

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Concrete, as a result of its use as a construction material, is not only subject to static loads but is also exposed to variables, time-variant, and oscillating stresses. In order to ensure the suitability of construction materials for resisting these cyclic stresses, different test methods are used for the systematic fatiguing of specimens, like the cyclic indirect tensile test. A procedure is presented that allows the estimation of the degradation of cylindrical concrete specimens during the cyclic indirect tensile test by measuring the dynamic modulus of elasticity in different states of the specimens’ fatigue process. Two methods are used in addition to the cyclic indirect tensile test in order to examine the dynamic modulus of elasticity of cylindrical concrete specimens. One of the methods is based on the analysis of eigenfrequencies, whilst the other one uses ultrasonic pulse measurements to estimate the material properties. A comparison between the dynamic moduli obtained using the three methods that operate in different frequency ranges shows good agreement. The concrete specimens’ fatigue process can therefore be monitored effectively and reliably.

Keywords: concrete, cyclic indirect tensile test, degradation, dynamic modulus of elasticity, eigenfrequency, fatigue, natural frequency, ultrasonic, ultrasound, Young’s modulus

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Authors: Liliia N. Butymova, Vladimir Y. Modorsky, Nikolai A. Shevelev

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Prediction of vibration processes in gas transmittal units (GTU) is an urgent problem. Despite numerous scientific publications on the problem of vibrations in general, there are not enough works concerning FSI-modeling interaction processes between several deformable blades in gas-dynamic flow. Since it is very difficult to solve the problem in full scope, with all factors considered, a unidirectional dynamic coupled 1FSI model is suggested for use at the first stage, which would include, from symmetry considerations, two blades, which might be considered as the first stage of solving more general bidirectional problem. ANSYS CFX programmed multi-processor was chosen as a numerical computation tool. The problem was solved on PNRPU high-capacity computer complex. At the first stage of the study, blades were believed oscillating with the same frequency, although oscillation phases could be equal and could be different. At that non-stationary gas-dynamic forces distribution over the blades surfaces is calculated in run of simulation experiment. Oscillations in the “gas — structure” dynamic system are assumed to increase if the resultant of these gas-dynamic forces is in-phase with blade oscillation, and phase shift (φ=0). Provided these oscillation occur with phase shift, then oscillations might increase or decrease, depending on the phase shift value. The most important results are as follows: the angle of phase shift in inter-blade oscillation and the gas-dynamic force depends on the flow velocity, the specific inter-blade gap, and the shaft rotation speed; a phase shift in oscillation of adjacent blades does not always correspond to phase shift of gas-dynamic forces affecting the blades. Thus, it was discovered, that asynchronous oscillation of blades might cause either attenuation or intensification of oscillation. It was revealed that clocking effect might depend not only on the mutual circumferential displacement of blade rows and the gap between the blades, but also on the blade dynamic deformation nature.

Keywords: aeroelasticity, ANSYS CFX, oscillation, phase shift, clocking effect, vibrations

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Authors: C. Gebauer, C. Henke, R. Vossen

Abstract:

Within the Mohamed Bin Zayed International Robotics Challenge (MBZIRC) 2020, a team of unmanned aerial vehicles (UAV) is used to capture intruder drones by physical interaction. The challenge is motivated by UAV safety. The purpose of this work is to investigate the agility of a quadcopter being controlled visually. The aim is to track and follow a highly dynamic target, e.g., an intruder quadcopter. The following is realized in close range and the opponent has a velocity of up to 10 m/s. Additional limitations are given by the hardware itself, where only monocular vision is present, and no additional knowledge about the targets state is available. An image based visual servoing (IBVS) approach is applied in combination with a Linear Quadratic Regulator (LQR). The IBVS is integrated into the LQR and an optimal trajectory is computed within the projected three-dimensional image-space. The approach has been evaluated on real quadcopter systems in different flight scenarios to demonstrate the system's stability.

Keywords: image based visual servoing, quadcopter, dynamic object tracking, linear-quadratic regulator

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