Theory Method Research Articles

Identifying Performance Assessment Indicators for Agricultural Small-scale Machinery

The use of small-scale machinery proves to be common for agricultural, transportation and other types of work on small-scale farms, peasant farms, family gardens, farmsteads, on hilly lands and inconvenient areas, where the use of traditional powerful machinery is impossible or economically impractical. Small-scale machinery as well as powerful agricultural machinery rarely passes state tests. One of the main reasons for that is a lack of indicator systems for agrotechnical, operational and technological, reliability, economic and ergonomic assessment. The necessity of determining such systems (sets, criteria, indicators) is argued to be important. (Research purpose) The research aims to identify performance assessment indicators for agricultural small-scale machinery by capitalizing on the existing indicators for powerful machines and hands-on experience of exploiting mini-machinery in small farms of Uzbekistan. (Materials and methods) The primary materials are the performance indicators for the agricultural machinery, provided by the existing state and industry standards. The study uses the methods of system analysis, logical thinking, monographic observation and set theory. (Results and discussion) As a result of ranking, several performance indicator systems were selected for the agrotechnical, operational-technological, reliability, economic and ergonomic assessment of small-scale machinery. (Conclusions) It was found out that for the general assessment of the structure parameters, the quality of the technological process and the functionality of small-scale machinery prototypes, it is reasonable to use 26 main and 14 auxiliary indicators. At the same time, a reduction in material and labor resources is expected in the process of testing.

A retrial queueing system with processor sharing and impatient customers

Objectives. The problem of constructing and investigating a mathematical model of a stochastic system with processor sharing, repeated calls, and customer impatience is considered. This system is formalized in the form of a queueing system. The operation of the queue is described in terms of multi-dimensional Markov chain. A condition for the existence of a stationary distribution is found, and algorithms for calculating the stationary distribution and stationary performance characteristics of the system are proposed.Methods. Methods of probability theory, queueing theory and matrix theory are used.Results. The steady state operation of a queueing system with repeated calls, processor sharing and two types of customers arriving in a marked Markovian arrival process is studied. The channel bandwidth is divided between two types of customers in a certain proportion, and the number of customers of each type simultaneously located on the server is limited. Customers of one of the types that have made all the channels assigned to them busy leave the system unserved with some probability and, with an additional probability, go to the orbit of infinite size, from where they make attempts to get service at random time intervals. Customers of the second type, which caused all the channels assigned to them to be busy, are lost. Customers in orbit show impatience: each of them can leave orbit forever if the time of its stay in orbit exceeds some random time distributed according to an exponential law. Service times of customers of different types are distributed according to the phase law with different parameters. The operation of the system is described in terms of a multi-dimensional Markov chain. It is proved that for any values of the system parameters this chain has a stationary distribution. Algorithms for calculating the stationary distribution and a number of performance measures of the system are proposed. The results of the study can be used to simulate the operation of a fixed capacity cell in a wireless cellular communication network and other real systems operating in the processor sharing mode.

On the dynamics of the axisymmetric circular system via an exact continuum elasticity theory and discrete singular convolution method

The vibration for the circular sector plates made of reinforced composite with carbon nanotubes based on a 3D-poroflexibility theory is presented in this research. A discrete singular convolution integration method (DSC-IM) is used. By using the renowned rule of mixtures, the effective mechanical properties are related to reinforced composites. The present results, formulations, and solution procedures are verified. The novelty of this work considers the effects of 3D- elasticity theory’s initial radial and environmental stresses and various boundary conditions via DSC-IM. Consequently, the outcomes demonstrate that in-plane boundary conditions, CNT’s volume fraction, Biot’s coefficient, and radial and circumferential initial stresses greatly impact the vibration frequency of the circular sector plates. Also, the effect of initial circumferential stress is more prominent than radial ones in determining the vibration frequency. Also, in higher open-angle, the impact of volume fraction related to CNTs on the vibrational frequency of the system is more apparent.

Activities for road transport enterprises on indicators of workers and rolling stock productivity planning

Introduction. The emphasis is placed on modern requirements in the development of transport industry by improving the planning of the activities of road transport enterprises in terms of indicators that determine the productivity of workers and rolling stock, which are a function of the demand for transportation. The results of the activities of road transport enterprises depend on the labour productivity of each employee performing a specific function for the implementation of a specific contract and making a profit.Materials and methods. Planning is carried out using the conceptual provisions of the current planning of the work of a trucking company, taking into account the relationship of activities and the demand for transportation, methods of probability theory and mathematical statistics, scientific principles of education and training of workers for the transport industry.Results. The application of a new approach to planning is to combine the productivity of workers and the production of rolling stock of the Motor Transport Enterprises (MTE). This made it possible to develop a mathematical model and methodology, which takes into account that the productivity of workers must ensure the receipt of the planned income for each contract and its value will be planned within the confidence limits. When planning, probabilistic events are taken into account that occur during the development of sectors of the economy of the Russian Federation and affect the need for skilled staff. Mathematical modeling is carried out in relation to the real operating conditions of cargo transportation and specific functions of employees. The number of rolling stock and the required number of employees are determined by the development of rolling stock, by the development of a specific production function by an employee in modern conditions of contractual relations.Discussion and conclusions. The results of the study are intended for the practice of road transport enterprises at the stage of determining indicators of labor productivity of workers and rolling stock.

МОДЕЛЬ И АЛГОРИТМ УПРАВЛЕНИЯ СОВОКУПНОСТЬЮ СБОРОЧНОГО ОБОРУДОВАНИЯ СИСТЕМЫ ОБЕСПЕЧЕНИЯ МЕХАНИЧЕСКОЙ СБОРКИ

The aim of the study is to optimize the control of the assembly equipment of the organizational and technological system for ensuring mechanical assembly based on threaded connections of the automated assembly process control system at an automotive cluster enterprise. The article solves the problem of considering the assembly equipment of an organizational and technological system for providing mechanical assembly based on threaded connections of an automated control system for the technological assembly process at an automotive cluster enterprise. Models, classifiers and an algorithm for optimal control of this set are being developed. Research methods of control theory; of the set-theoretical approach; decision-making methods; methods of mathematical analysis are used in the article. The novelty of the work is to develop the classifiers of assembly equipment of the organizational and technological system for ensuring mechanical assembly based on threaded connections depending on the design and degree of the facility automation and the possibility of its calibration. The main distinguishing characteristic of the proposed algorithm is to use the reduced cost of the assembly operation, which makes it possible to form an optimal set of the assembly equipment. As a result of the research a set-theoretic model of an element and a set of assembly equipment are proposed. The classifiers of the elements that make up the assembly equipment are developed. An algorithm for forming an optimal set of assembly equipment at an utomotivecluster enterprise is introduced. The developed algorithm is used in forming the assembly equipment at an automotive cluster enterprises and at the enterprises with a similar organizational and technological system for providing mechanical assembly. The findings of the research state that the proposed set-theoretic model of an assembly facility element allows accumulating and saving information about the elements of assembly equipment which is necessary for the effective management of assembly production at an automotive cluster enterprise. The developed classifiers are applied to decompose the set of equipment used in the assembly based on threaded connections and are necessary for solving the problems of automated control of the organizational and technological system for providing mechanical assembly based on threaded connections of the automated control system for the assembly process at the automotive cluster enterprise.

Optical and Electrical Modeling of DSSC with Light Scattering Layer

The dye-sensitized solar cell is one of the most promising solar cells as an alternative to conventional silicon-based solar cells. The advantages of DSSC compared to conventional silicon-based solar cells are the easy fabrication process and low cost. In general, DSSC consists of semiconductor materials and dye as a photoanode, a catalyst at the counter electrode, and an electrolyte. The problem is that the DSSC performance is not optimal in the light utilization process. One of the ways to improve DSSC performance is by increasing photon absorption. A method that can increase photon absorption on DSSC is by adding a light scattering layer (LSL) using TiO2 microparticles. The technique used in this study for the optical model is the scattering theory and numerical methods using the Finite Differential Time Domain (FDTD). The scattering intensity and incident photon intensity are used for the electron generation process. The result of electron generation is used to model electrically to obtain the value of the short circuit current density and the open-circuit voltage with the diffusion differential equation. DSSC with LSL has higher efficiency than DSSC without LSL. The results obtained from this study DSSC with LSL has an efficiency of 5.5%, Jsc 16 mA/cm2, and an open-circuit voltage of 0.6184 volts. DSSC without LSL has an efficiency of 4.9%, Jsc of 14.5 mA/cm2, and an open-circuit voltage of 0.6073 Volt.

Investigating different types of fluids in pulsating heat pipes for improving heat transfer in an air-cooled heat exchanger

Air-cooled heat exchangers are utilized in various industries to cool process fluids. To have a better heat transfer, fins are used in the structure of exchangers. In this study, a set of experiments were performed to investigate the improvement in the amount of heat transfer in an air-cooled heat exchanger. For this purpose, a real case study was conducted on air-coolers in a natural gas compressor station; afterward, the finned tubes were replaced by pulsating heat pipes (PHPs), and a different type of fluid was applied to the pulsating heat pipes. The laboratory system was set up to measure the overall heat transfer coefficient under two conditions involving either finned tubes or a PHP with R134, R22, and filled acetone fluids. Finally, the results were verified by the theory method. The results showed that all the three fluid agents (R134, R22, and Acetone) with natural convection of 9.94 m/s, an inlet fluid velocity of 5.54 m/s, and an average feed velocity were able to enhance the heat transfer coefficient by 10, 13, and 11%, respectively. In addition, compared with finned tubes, R134, R22, and Acetone improved the natural convection heat transfer coefficient by 22.2, 18.6, and 21.7%, respectively.

Pedagogical documentation and the refusal of method: troubling dogmas and inviting collective obligations

ABSTRACT This article explores how pedagogical documentation, as the refusal of method, can be aligned with post qualitative inquiry, opening up possibilities for refuting dogmas and methods in early childhood pedagogy, theory, practice, and research. It delineates understandings of pedagogical documentation in the educational project of Reggio Emilia, and describes dogmatic (or unthought) practices which influence perceptions and uses of pedagogical documentation elsewhere: the dogma of children’s interests; the dogma of implementation; and the dogma of method. The article draws on the experience of a collective of academic-researchers and teacher-researchers working with pedagogical documentation in the context of an investigation into children’s relations with waste. Excerpts from interviews illuminate ‘voices troubling dogmas’, proposing an invitation to move forward from dogmas to imagining our collective obligations. Pedagogical documentation is thus conceived as a catalyst for helping us think collectively with the hope of making the dogmatic impossible.

On optimization of the mixed charging infrastructure of electric buses for urban routes

Objectives. When transition from a fleet of diesel buses to a fleet of electric buses, it is important to optimize the charging infrastructure, which combines the slow-charging technologies at the depot overnight and fast recharging at the terminals of the routes. The purpose of the study is to create models and methods for developing the cost-effective solutions for selecting this type of charging infrastructure for a fleet of electric buses serving the city route system, taking into account a number of specific conditions. The operation of the fleet and charging infrastructure is modeled both for the depot at night and for the terminal stops in the most representative period of the day, characterized by the highest intensity of passenger traffic and maximum power consumption.Methods. Methods of set theory, graph theory and linear approximation are used.Results. A mathematical model has been developed for the problem of optimizing a mixed-type charging infrastructure for an electric bus fleet. The total daily cost of charging stations, degradation of electric bus batteries and consumed electricity was chosen as the objective function. The model is formulated as a mixed integer linear programming problem.Conclusion. To solve the formulated problem, standard solvers like IBM ILOG CPLEX can be used. The solution of the problem lies in the choice of durations and schedules for charging electric buses at low-capacity charging stations in the depot at night and at high-capacity charging stations of terminal stops in a given range of peak hours.

Vibration characteristics of cracked FG-GRC plates in thermal environments based on phase field theory and meshless method

Stiffness degradation resulting from matrix cracking has a great impact on the vibrational behaviors of composite laminates. However, the vibration frequencies of functionally graded graphene-reinforced composite (FG-GRC) plates with crack defects remain largely unexplored. In this paper, the variational phase field theory is implemented to investigate the vibration characteristics of cracked FG-GRC plates subjected to thermal conditions. The effective elastic constants depending on the temperature of FG-GRC plates are characterized by the extended Halpin-Tsai model. The first-order shear deformation theory (FSDT) is employed to describe the displacement fields of the cracked FG-GRC plates. The meshfree kernel particle method is engaged to discretize governing equations over the computational domain and then the obtained governing eigen-equations are calculated using the Ritz methodology. The numerical results illustrate the influences of crack length, crack number, the strength of foundations, graphene distribution, temperature variation and geometric values on the vibration fundamental frequencies of the FG-GRC plates. The present work not only provides an alternative and feasible approach for solving the interaction problems between cracking and vibration, but also makes significant advances to characterize the vibrational behaviors of cracked functionally graded materials for engineering applications.

Defining project performance standards as parameters of the compliance risk regulatory system

Subject. This article discusses the problem of choosing the standards of project time and cash expenditures, taking into account their randomness. Objectives. The article aims to describe the task of setting standards for the values of project time and budget profiles, taking into account compliance risk, and analyze the dependence of the effectiveness of project profile norm setting on the compliance risk level. Methods. For the study, we used the methods of probability theory, mathematical statistics, and dynamic programming. Results. The article formulates a problem of project profile norm setting, taking into account compliance risk, and provides an algorithm for dynamic programming to establish standards and oversizes corresponding to risk appetite. It shows an example of the calculation of these design characteristics, where at each stage of the project there are fourteen types of independent random factors that negatively affect the costs of the project. The article also describes the dependence of efficiency and additional regulatory costs for managing compliance risk on the risk level. Conclusions. The task of project costs norm setting based on a risk-oriented approach is formulated and solved on the basis of the dynamic programming method. This can be used to design a compliance risk management system. For the example considered, we identify areas of unacceptable, acceptable and negligible risks.

Solution of one optimum control problem regarding the depletion of gas reservoir

Using the methods of the optimal control theory, the problem of determining the optimal technological mode of gas deposits’ exploitation under the condition of their depletion by a given point in time is solved. This task is of particular interest for the exploitation of offshore fields, the activity of which is limited by the service life of the field equipment. The considered problem is also of certain mathematical interest as an objective of optimal control of nonlinear systems with distributed parameters. The usefulness and importance of solving such problems are determined by the richness of the class of major tasks that have a practical result. As an optimality criterion, a quadratic functional characterizing the conditions of reservoir depletion is considered. By introducing an auxiliary boundary value problem, and taking into account the stationarity conditions for the Lagrange functions at the optimal point, a formula for the gradient of the minimized functional is obtained. To obtain a solution to this specific optimization problem, which control function is sought in the class of a piecewise continuous and bounded function with discontinuities of the first kind, the Pontryagin’s maximum principle is subjected. The calculation of the gradient of the functional for the original and adjoint problems with partial differential equations is carried out by the method of straight lines. The numerical solution of the problem was carried out by two methods – the method of gradient projection with a special choice of step and the method of successive approximations. Despite the incorrectness of optimal control problems with a quadratic functional, the gradient projection method did not show a tendency to «dispersion» and gave a convergent sequence of controls.

Spatial Linear Coding in Joint Radar and Multicast Communication Systems

Introduction. This paper presents optimization methods for the amplitude-phase distribution in a transmitting antenna array in a system with a common signal for multicast data transmission and radar sensing in a given sector of space. Two approaches are considered for the choice of an objective function for the optimization problem. The first approach involves minimizing the transmitted power for a given quality of user service and radar surveillance. The second approach involves optimizing the quality of service for the worst radar and communication channel under a given power budget. The value that determines the quality of service is the signal-to-noise ratio, for both communication and radar.Aim. Тo solve the optimization problem of spatial linear coding of signals in a joint multicast radar and communication system, which shares a common signal.Materials and methods. Optimization of spatial linear coding in a joint radio radar and communication system was carried out by the methods of statistical theory and optimization theory using the numerical solution of optimization problems. The performance characteristics of the system were analyzed by Monte Carlo simulation. Statistical simulation was performed in the MATLAB environment using standard tools, as well as the CVX package for the numerical solution of convex optimization problems.Results. Optimization problems were formulated based on the criteria of the minimum radiated power and the maximum signal-to-noise ratio in the worst channel. A limitation on the radiated power of individual antenna channels was used for both cases. Optimization problems were approximately reduced to convex problems with semidefinite constraints, which could be solved using the wellknown interior point algorithm with polynomial complexity. The performed statistical simulation produced optimal performance characteristics of a joint system, including the total power versus the threshold signal-to-noise ratio and the signal-to-noise ratio for the worst channel versus the power budget.Conclusion. The proposed numerical optimization methods for spatial linear coding in a transmitting antenna array can be recommended when designing joint radar communication systems.

L∞-algebras in Freedman–Townsend model and Batalin–Vilkovisky formalism

We present an [Formula: see text]-algebra description of the Freedman–Townsend tensor gauge theory with an emphasis on the Maurer–Cartan homotopy action form using cyclic inner product. It is explicitly shown that the gauge variations, the conservation law and the dynamics of the theory are all incorporated in the underlying [Formula: see text]-products. Also, following the more convenient method for reducible gauge theory, we propose the Batalin–Vilkovisky formalism of Freedman–Townsend model within the framework of [Formula: see text]-algebras.

Buckling of Bulk Structures With Finite Prebuckling Deformation

Abstract The prebuckling deformation of structures is neglected in most of the conventional buckling theory (CBT) and numerical method (CNM), because it is usually very small in conventional concepts. In the preceding paper (Su et al., 2019), we found a class of structures from the emerging field of stretchable electronics, of which the prebuckling deformation became large and essential for determining the critical buckling load, and developed a systematic buckling theory for 3D beams considering the effects of finite prebuckling deformation (FPD). For bulk structures that appear vastly in the advanced structures, a few buckling theories consider the effects of the prebuckling deformation in constitutive equations by energy method, which are significantly important but not straightforward and universal enough. In this paper, a systematic and straightforward theory for the FPD buckling of bulk structures is developed with the use of two constitutive models. The variables for the prebuckling deformation serve as the coefficients of the incremental displacements, deformation components, and stress in the buckling analysis. Four methods, including the CBT, CNM, DLU (disturbing-loading-unloading method) method and FPD buckling theory, are applied to the classic problems, including buckling of an elastic semi-plane solid and buckling of an elastic rectangular solid, respectively. Compared with the accurate buckling load from the DLU method, the FPD buckling theory is able to give a good prediction, while the CBT and CNM may yield unacceptable results (with 70% error for the buckling of an elastic semi-plane solid).

Research on Toy Design for Special Children Based on Sensory Integration Training, D-S Theory, and Extenics: Taking Physical Toys for ADHD Children as an Example

Based on sensory integration training, D-S theory and extenics, this paper discusses the innovation and development of ADHD children’s toys, so as to make the design scheme more real, scientific, and comprehensive and meet the internal needs of users. Considering the advantages of extenics and the D-S theory in dealing with uncertain and incompatible decision-making problems, an evaluation method of toy design scheme for special children based on extension analysis and the D-S theory is proposed. Through the combination of the D-S theory and extenics evaluation method and sensory integration training theory, the designed toy scheme has a certain auxiliary therapeutic effect on the rehabilitation of ADHD children. Through the design case of physical fitness for ADHD children, it is proved that the combination of the D-S theory and extenics based on the sensory integration training theory has a certain reference value for the generation of product scheme and makes the product design process more comprehensive and objective.

Calibration of Undrained Shear Strength Partial Factor Using Probability Theory

Design in accordance with Eurocode 7 applies the partial factors of geotechnical parameters to take into account uncertainties of various sources. The prescribed values of partial factors are unique, even though the degree of uncertainty can vary significantly. This can lead to an unequal reliability level of structures designed using the same procedures and methods. This paper analyses the influence of undrained shear strength variability on the reliability index (β), using reliability theory and statistical methods. Analyses were performed in the case of a shallow footing designed in accordance with Eurocode 7, design approach 3. It is shown that reliability indexes of a shallow footing could be lower than the target values prescribed in Eurocode. To meet these values, additional elaboration and calibration of undrained shear strength partial factor (γcu) was proposed.

Метод определения оптимального времени профессиональной подготовки руководителей пожарно-спасательных подразделений

PURPOSE. The main goal of the research, the results of which are presented in the article, is to develop the method of determining optimal time required for professional training of fire-rescue units chiefs. In the given article incompetence refers to the state of professional and personal qualities of students (trainees) that characterizes the complete or partial lack of knowledge, abilities, skills, and experience in performing certain type of practical activities. It is assumed that the optimal time of training can be less than the amount of time currently spent without analytical or statistical assessment of the expediency of its spending. METHODS. As a mathematical apparatus, mathematical methods of reliability theory have been applied, as well as methods of probability theory and mathematical statistics. To prove the method feasibility numerical experiment has been carried out. FINDINGS. The presented method makes it possible to determine the minimum necessary time for a student (trainee) to master the required amount of managerial competence and develop firm professionally relevant qualities. To prove the method feasibility numerical experiment has been carried out. RESEARCH APPLICATION FIELD. The research results can be applied for improving teaching process for fire-rescue units chiefs as well as for heads of other organizational structures. CONCLUSIONS. The developed method makes it possible to establish the asymptotic dependence that shows the reduction of relative incompetence in a certain type of management performance depending on the time spent on study. A lemma has been proved about a point on function graph of dependence of relative incompetence on time corresponding to the optimal level of incompetence reduction and learning time.

Влияние наклона волноотражающего козырька на высоту защитной стенки резервуара типа «стакан в стакане»

PURPOSE. The article presents the results of experimental studies analysis on the influence of horizontal and inclined wave-reflecting visors proposed for installation on the protective wall of glass-in-glass tank type for reducing its height to or below the maximum possible level of liquid in the main tank. METHODS. In the process of the research work methods of similarity theory and hydraulic laboratory modeling, physical experiment, observation, comparison, finding empirical dependence based on mathematical processing of experimental data, description and generalization have been used. FINDINGS. It has been found that fitting a horizontal or inclined wave-reflecting visor on the protective wall of a “glass-in-glass” type tank is an effective method of reducing its height. At the same time, the best results are shown by a wave-reflecting visor at an angle of 135° to the protective wall which allows, in the interwalled distance ranged from 1.8 to 3 m given the length of its handling radius reducing the height of the protective wall to 85 % of the maximum possible level of liquid in the main tank. RESEARCH APPLICATION FIELD. The proposed method of reducing the height of the protective wall, design schemes and empirical dependencies can serve as the foundation for the development of a regulatory document on ensuring fire safety of “glass-in-glass” type tanks, as well as be used by design organizations to find optimal solutions for the design and placement of typical tanks with a nominal volume of 700 to 30.000 m3. CONCLUSIONS. The proposed design solution will allow designing and operating “glass-in-glass” type tanks, ensuring the required level of fire, industrial and environmental safety provided compliance with the requirements for stability of the protective wall and wave-reflecting visor to the effect liquid flow and collapsing structures in case of the accident of the main tank. At the same time, the application of an additional barrier is not required, since all liquid in case of possible destruction of the main tank will be held by the proposed structure of the protective wall with a wave-reflecting visor.

Effect of FA: X+3 (X = B, Al, and Ga) Color Centers on the Electronic and Optical Properties of LiF (001) Surface

The density functional theory and configuration interaction single excitations methods were used to study the effect of FA color centers on the electronic and optical properties of the LiF (001) surface. Three types of FA color centers were used, FA: B+3, FA: Al+3, and FA: Ga+3. The evaluated values of the ionization potential, chemical hardness, and softness indicate the stability of the investigated color centers. FA: B+3 is the most stable one. While the electron affinity values reveal that the FA: Al+3 center is the highest reactive one. The Ultraviolet-Visible spectra for FA: B+3, FA: Al+3, and FA: Ga+3 centers showed that the scrutinized centers have two absorption peaks. The highest absorption peak recorded for FA: B+3 center is located at 285 nm, while the highest absorption peaks recorded for FA: Al+3, and FA: Ga+3 centers are located at 173 and 165 nm, respectively. According to the light-harvesting efficiency values, FA: Al+3, and FA: Ga+3 centers have the highest efficiency to gather the energy during the pumping process than FA: B+3 centers. Stokes-shift values for FA: B+3, FA: Al+3, and FA: Ga+3 centers were 0.16, 0.37, and 0.33 eV, respectively, consequently, FA: Al+3 and FA: Ga+3 centers, are more suitable for laser production than FA: B+3 center.