Criterion Of Maximum Efficiency Research Articles

ПІДВИЩЕННЯ ЕНЕРГЕТИЧНОЇ ЕФЕКТИВНОСТІ РЕГУЛЬОВАНОГО ЕЛЕКТРОПРИВОДУ ОДНОЦИЛІНДРОВОГО ПОРШНЕВОГО КОМПРЕСОРА

The peculiarities of the operation of closed systems of adjustable electric drives of single-cylinder reciprocating compressors due to the presence of a non-linear dependence between the motor load torque and the angular movement of its rotor are considered. The method of synthesis of the regulator of the amplitude of the supply voltage of an induction motor of such an electric drive at a fixed value of the supply frequency is proposed. According to the results of research, it was found that the effect of increasing energy efficiency (reducing the difference in efficiency for constant and periodic loads) due to the use of a voltage regulator increases with a decrease in the power supply frequency. It is shown that the optimization of the transmission coefficient of the voltage regulator of electric drives with a non-linear dependence between the motor load torque and the angular movement is expedient to be carried out according to the criterion of maximum efficiency. References 25, figures 10, table 1.

ENERGY CHARACTERISTICS OF THE ELECTROMAGNETIC VIBRATION DRIVE WITH PULSE POWER SUPPLY OF VIBRATOR COILS

Vibrating equipment provides various technological processes, such as transportation, separation, compaction of mixtures. The electromagnetic drive is usually used in vibrating conveyors, feeders and other devices where vibration parameters are automatically controlled. Increasing the energy efficiency of such devices is an important task. The paper examines the influence of the power supply voltage on the energy characteristics of the electromagnetic vibration drive and determines the most effective voltage form. To do this, an analysis of factors affecting the efficiency of the drive was carried out. It was found that one of the factors is the time interval between the maximum current and the minimum value of the air gap, and increasing the efficiency is possible by reducing this interval by forming bipolar rectangular voltage pulses with maximum amplitude, which create narrow sharp pulses of the vibrator coil current. As a result of the numerical modeling of the processes in the drive, it was found that with increasing power, current pulses cause short-term deep saturation of steel, which leads to increased losses and reduced efficiency. Therefore, a zero voltage interval was added between the positive and negative voltage pulses, which limits the peak current values. The simulation of the processes in the vibration drive with the voltage supply of the proposed form was carried out, its energy characteristics were calculated: the dependence of the efficiency on the frequency at different load values, the dependence of the maximum values of the efficiency on the power. It was established that the use of pulsed power supply makes it possible to increase the efficiency of the drive up to 80% in the power range from 0.25 of the nominal value to the nominal one, which is on average 10% more compared to sinusoidal voltage. The dependences of frequency and zero voltage interval optimal values (according to the criterion of maximum efficiency) on power, which can be used in automatic control of the drive, have been obtained. References 10, figures 9, tables 2.

MODERN ECONOMIC AND ORGANIZATIONAL IMPERATIVES OF CONSTRUCTION DEVELOPMENT IN PROJECTS FOR THE ADMINISTRATION OF STRATEGIC CHANGES IN ENTERPRISES

The article is devoted to the study of modern concepts that influence the cognitive mechanisms of project management in construction. The conducted analysis proved that obtaining a greater effect from the use of the knowledge of the participants in the implementation of the construction project is possible under the condition of the joint implementation of three modern concepts: enterprise integration, information modeling in construction and big data management. In addition to an effectively working communication system within the project, an important condition is the availability of effective knowledge management tools. Knowledge management tools are technologies used to improve and ensure the implementation of knowledge management sub-processes. Information modeling technologies in construction can become an important tool for analyzing big data, generating information and knowledge, because after the completion of each stage of the implementation of a construction project, large data sets remain. Accumulated data can be a corporate asset, the acquisition and use of which allows you to make better forecasts and make the right management decisions. In addition, the knowledge that arose in the project and was tested by practice can be considered more reliable in comparison with data from experiments or simulations, because they contain more fundamental knowledge about reality. The developed methods and models allow: solving the task of choosing the optimal network organizational structure based on the criterion of maximum efficiency in the use of information connections between project participants; carry out an assessment of the effect of the joint introduction of information modeling in construction and the integrated implementation of the construction project; to carry out a comprehensive study and optimization of the information and communication network of the participants in the implementation of the construction project; start the process of introducing information modeling in public procurement in the construction industry of Ukraine. The obtained results can be used by scientific institutions, enterprises and organizations - key participants in the implementation of construction projects, authorities at various levels, and also form the basis for further theoretical, methodological and applied research.

CHOICE OF LOCOMOTIVE PARK MAINTENANCE STRATEGY WHEN INTRODUCING THE SERVICE

In operation, sometimes there are situations of uncertainty in assessing the technical condition of locomotive equipment and at the same time choosing the optimal strategy for its maintenance, including the possibility of using the service. Application of the concept of service gives the chance to stimulate work of all divisions of locomotive economy, to save all kinds of resources for operation of locomotives. According to this, the article substantiates the choice of strategy for maintaining the locomotive fleet using the provisions of the theory of statistical solutions. Game theory approaches were used to theoretically substantiate the transition to a service for decision-making in conflict situations and to determine the optimal strategy of behavior of each of the participants in this situation. Approaches to the choice of strategy for the maintenance of the locomotive fleet during the introduction of the service on the basis of the provisions of the theory of strategic games on the criterion of maximum efficiency were considered. It is shown on examples of the decision of some problems of a choice of maintenance strategy of locomotives for various industrial situations. It is concluded that a mixed strategy describes different situations best and allows to made rational decisions. It is also noted that the most effective approach to concretize the algorithm of actions is the complex application of the theory of strategic decisions, the theory of fuzzy sets, the theory of pattern recognition.

OPTIMIZATION TECHNIQUE OF DRIVING DISC PARAMETERS

Flat circular discs in powered operation mode create driving forces. These forces enable to decrease the wheel slippage of the energy saturated tractor of tillage unit and to reduce the specific energy consumption. The objective of this study was to develop a technique that enables to determine the driving disc optimal parameters for maximum efficiency criterion. The earlier developed mathematical model of soil-disc interaction was used for this purpose. Soil properties in the model are characterized by means of two empirical constants. The relative depth and the kinematic parameter determine the disc operation mode. It was shown that the driving disc can operate with high efficiency, if the disc operates at the optimal values of the parameters. The driving disc efficiency can achieve the value about fifty percent. The experimental results confirmed the adequacy of the technique. The discrepancy between the predicted and field experimental values of driving forces and applied moments was about 25%. The proposed technique can be modified to optimize the parameters of other powered rotary tools of tillage machines and units.

РАЗРАБОТКА И ИССЛЕДОВАНИЕ АЛГОРИТМА ФОРМИРОВАНИЯ КОНТУРОВ УПРАВЛЕНИЯ

The article deals with a long-term strategy of the control loop generation involving controlled objects (CO), surveillance facilities (SF) and environment objects (EO). It describes an assigned 3D problem of allocation that leads to the maximum efficiency criterion due to an optimum allocation of CO and SF in EO. The optimization of CO and SF adjustable parameters requires solving the 3D problem of allocation for many times that takes much more time. The article describes a mathematical optimization model of adjustable parameters of the control loop objects and proposes an algorithm of random searching for the solution of 3D problem of allocation. The random searching based on a random generation of CO and SF numbers, and the composition change of relative loops. Some experimental studies for different dimension problems were carried out using the proposed algorithm. The numbers of derangements in the algorithm and solution time were defined, when the efficiency criterion reached its maximum. The article gives an approximate time to solve the problem with one optimized adjustable parameter and different number of control loop objects.

Parametric optimization of supercritical power plants using gradient methods

Gradient nonlinear optimization methods are among the most effective approaches to determine the optimal parameters of thermal power plants. These methods allow us to consistently optimize a large number of thermodynamic and design parameters and mass flow rates of actuation fluids and of heat-transfer fluids. This paper proposes an original gradient method to optimize the parameters of a 660 MW supercritical coal-fired power unit. The specific feature of the method is that it can start from a point where there is no solution of the combined equation defining the plant. The exact solution of the nonlinear combined equation is achieved only at the optimal point, consequently the calculation time is reduced. The method provides better convergence and greater accuracy of solving the nonlinear combined equation defining the processes in the power unit. Optimization is carried out according to the criterion of maximum efficiency, minimum specific plant investments and minimum cost of electricity at different fuel prices. The austenitic and nickel alloys are considered for superheater and reheater tubes of a steam generator. Co-optimization of the thermodynamic and design parameters of the power unit by the criterion of the minimum cost of electricity allowed us to get original solutions that combine the high temperature (615–622 °C) and low pressure (16.7–18.1 MPa) of live steam.

Assessment of reliability and criteria for improving the quality of rock cutting equipment of tricone drilling bits for well-boring especially hard rock

One of the options for solving the problem - a comprehensive improvement in the quality of the bit was proposed. The most widespread damages that are caused by premature failure of the rock cutting equipment of tricone rock drilling bit when we have been process well-boring by especially hard rocks are analyzed. The main idea is to develop a step-logical model. Such model is created on the basis of reasons that bring to a failure of tricone drilling bit, which are rock cutting equipment. It is prescribed that the failure of rock cutting equipment is the reason of the logical sequence of the most probable events, and the criterion of failure is the minimum cross-section in the failure model. This article presents a stepwise logical analysis, which makes it possible to establish the nature of the relationship between the basic factors that are taken into account when making decisions. Researches were conducted on the basis of mathematical planning of experiments in the real production of drill bits. One example is shown of how modules can be used that describe one of the possible reasons for the failure of a rock cutting equipment's tricone drilling bit. The three main factors are the basic events. This is determined by the analysis that in all cases, in the failure models of the bit. These main factors are the initial material properties and design parameters set at the design and construction stage, as well as technological factors that are formed at the stages of design and implementation of manufacturing processes. A step-by-step analysis makes it possible to detect the relationship between under control factors and failures. A scheme is proposed for determining the parameters of technological system element, with the help of which it is possible to establish quality indicators of insert rock cutting equipment of tricone drilling bits. The choice of the optimal variant of parameters is carried out in accordance with the criterion of maximum efficiency. Thus, the application of step-logic models makes it possible not only to find out the reasons for the failure of rock cutting equipment for tricone drilling bit, but also to make correct and substantiated decisions for quality assurance of processes at the main stages of the lifecycle for manufacturing tricone drilling bit.

Investigation of the influence of centrifugal pump wet part geometry on hemolysis index

The present study focuses on the influence of the circulatory support pump wet part geometry on the level of damage experienced by blood cells in it. The object of the study is a centrifugal pump: axial input, impeller and volute. The values of density and viscosity are constant and are close to the physiological parameters of blood of a healthy human. In order to estimate hemolysis blood cells are considered as spherical particles, which do not interact with each other. At each point of the trajectory of the particle equivalent shear stress is calculated according to Huber-Mises criterion. Hemolysis is then calculated in accordance with Lagrangian approach to particle movement in a flow. As an experimental hemolysis curve a power law of equivalent shear stress depending on the time the particle has experienced this stress was chosen. For a wet part optimization criterion of maximum efficiency and minimum hemolysis are considered.

Modeling of Fast-Permeant Component Removal from Gas Mixture in a Membrane Module with Pulsed Retentate

The process of unsteady-state membrane gas separation (fast-permeant impurity removal) with a pulsed retentate flow operation was considered. A semiempirical mathematical algorithm was developed to describe this process taking into account its kinetic characteristics (total cycle time, stripping time and withdrawal time, withdrawal velocity) using the MathCad® software package. Based on the developed algorithm, the basic operational parameters that affect the separation efficiency of the unsteady-state process were analyzed. It was shown that the optimal ratio of the stripping time and the withdrawal one determined by the maximum efficiency criterion more corresponds to the minimum retentate concentration than to the maximum productivity. However, the developed algorithm allows to set the productivity minimum limit by introducing additional initial data into the calculation procedure. The mathematical modeling results correlate well with the experimental data.

Optimization of signal-code constructions using the maximum efficiency criterion

Signal-code constructions based on some known and new formats of digital signal modulation have been studied. It was established that the signal-code constructions based on the amplitude modulation of many components were characterized by larger information efficiency as compared with the case of using the quadrature amplitude modulation.

Features of ballistic design of ARKON-1 remote-sensing space system for optoelectronic earth observations

SC orbit parameters are selected and substantiated based on the maximum efficiency criterion based on the requirements of comprehensiveness, periodicity, and the immediacy of data acquisition using the example of the ballistic design of the ARKON-1 space system for the optoelectronic observation of Earth developed by NPO Lavochkin.

Real-Time Implementation of a Constrained MPC for Efficient Airflow Control in a PEM Fuel Cell

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Fuel cells represent an area of great industrial interest due to the possibility to generate clean energy for stationary and automotive applications. It is clear that the proper performance of these devices is closely related to the kind of control that is used; therefore, a study of improved control alternatives is fully justified. The air-supply control is widely used to guarantee safety and to achieve a high performance. This paper deals with this control loop, proposing and comparing two control objectives aimed at satisfying the oxygen starvation avoidance criterion and the maximum efficiency criterion, respectively. The control architecture is based on a constrained explicit model predictive control (MPC) law suitable for real-time implementation due to its low computational demands. The proposed controller is implemented and evaluated on a 1.2-kW polymer electrolyte membrane or proton exchange membrane fuel-cell test bench, thus obtaining real data which show that the maximum efficiency criterion does not conflict with the starvation avoidance criterion and allows system performance improvements of up to 3.46%. Moreover, experimental results utilizing the explicit MPC approach also show improved transient responses compared to those of the manufacturer's control law. </para>

ANAEROBIC BIOFILM REACTOR MODELING FOCUSED ON HYDRODYNAMICS

This work deals with an experimental and theoretical investigation of anaerobic biofilm reactors for treating wastewaters. Bioreactors are modeled as dynamic (gas-solid–liquid) three-phase systems. The anaerobic digestion model proposed by Angelidaki et al. (1999) was selected to describe the substrate degradation scheme and was applied to a biofilm system. The experimental setup consists of two mesophilic (36°±1°C) lab-scale anaerobic fluidized bed reactors (AFBRs) with sand as inert support for biofilm development. The experimental protocol is based on step-type disturbances applied on the inlet substrate concentration (glucose and acetate-based feeding) and on the feed flow rate considering the criterion of maximum efficiency. The predicted and measured responses of biological and hydrodynamic variables are investigated. Experimental data were used to estimate empirical values of biofilm detachment coefficients. Under the evaluated operating conditions, the proposed model for biofilm detachment rate, assumed as a first-order function of the energy dissipation parameter, is appropriate to represent the interaction between biofilm systems and fluidization characteristics in non-highly disturbed flow conditions. Model validation was carried out using the experimental data reported by Mussati et al. (2006). The results do not differ from those above. This seems to indicate that the proposed AFBR model is able to reproduce the main biological and hydrodynamic successes in the bioreactor.

Application of two anaerobic digestion models to biofilm systems

This work deals with a comparative analysis of two alternative anaerobic digestion models proposed by Batstone et al. [D.J. Batstone, J. Keller, I. Angelidaki, S.V. Kalyuzhnyi, S.G. Pavlostathis, A. Rozzi, W.T.M. Sanders, H. Siegrist, V.A. Vavilin, Anaerobic Digestion Model No. 1 (ADM1) IWA Task Group for Mathematical Modelling of Anaerobic Digestion Processes, IWA Publishing, London, UK, 2002] and Angelidaki et al. [I. Angelidaki, L. Ellegaard, B.K. Ahring, A comprehensive model of anaerobic bioconversion of complex substrates to biogas, Biotechnol. Bioeng. 63 (5) (1999) 363–372], and their application to biofilm systems. Bioreactors are modeled as dynamic (gas–solid–liquid) three-phase systems. The experimental set-up consists of two mesophilic (36 ± 1 °C) lab-scale anaerobic fluidized bed reactors, which were loaded with sand as inert support for biofilm development. The experimental protocol is based on step-type disturbances applied on the inlet substrate concentration (glucose and acetate-based feeding) and on the feed flow rate considering the criterion of maximum efficiency. The predicted and measured responses of total and soluble chemical oxygen demand (COD), volatile fatty acid concentrations, biogas production rate and pH are investigated. Under the operating conditions evaluated in this investigation, the anaerobic digestion model proposed by Angelidaki et al. [I. Angelidaki, L. Ellegaard, B.K. Ahring, A comprehensive model of anaerobic bioconversion of complex substrates to biogas, Biotechnol. Bioeng. 63 (5) (1999) 363–372] ensures the best prediction. Parameters related to non-active biomass composition, disintegration and hydrolysis should be revised to achieve a good agreement between experimental and predicted values using the model proposed by Batstone et al. [D.J. Batstone, J. Keller, I. Angelidaki, S.V. Kalyuzhnyi, S.G. Pavlostathis, A. Rozzi, W.T.M. Sanders, H. Siegrist, V.A. Vavilin, Anaerobic Digestion Model No. 1 (ADM1) IWA Task Group for Mathematical Modelling of Anaerobic Digestion Processes, IWA Publishing, London, UK, 2002].

Performance optimisation of reciprocating heat engine cycles with internal irreversibility

In the present study, an optimal performance analysis based on maximum power (MP) and maximum efficiency criterion including internal irreversibility for steady state operation has been performed for the air standard Dual cycle. It is shown that the effect of internal irreversibility such as friction on MP may be characterised by the cycle irreversibility parameter representing the ratios of entropy differences for the cycle. The presence of this parameter in the equations for the MP and the corresponding efficiency shows that an engine with internal irreversibility delivers less power and has a lower efficiency than a reversible engine. The effect of the design parameters such as pressure ratio, cut off ratio and extreme temperature ratio of the cycles has also been investigated under the MP and maximum efficiency conditions on the basis of having the internal irreversibility. Also in the present study, performance analysis has been extended to the Otto and Diesel cycles which may be considered as special cases of the Dual cycle.

Scale-free foraging by primates emerges from their interaction with a complex environment.

Scale-free foraging patterns are widespread among animals. These may be the outcome of an optimal searching strategy to find scarce, randomly distributed resources, but a less explored alternative is that this behaviour may result from the interaction of foraging animals with a particular distribution of resources. We introduce a simple foraging model where individual primates follow mental maps and choose their displacements according to a maximum efficiency criterion, in a spatially disordered environment containing many trees with a heterogeneous size distribution. We show that a particular tree-size frequency distribution induces non-Gaussian movement patterns with multiple spatial scales (Lévy walks). These results are consistent with field observations of tree-size variation and spider monkey (Ateles geoffroyi) foraging patterns. We discuss the consequences that our results may have for the patterns of seed dispersal by foraging primates.

Modelling of GaAs solar cells under wide angle cones of homogeneous light

A new theoretical model is presented for the performance of solar cells when light in the shape of a cone impinges on them. This is the case for concentration applications. The model is applied to 1000 sun concentrator p/n heteroface GaAs solar cells for the general purpose of a cone angle of between 0° and 90°. A multidimensional optimization of the whole GaAs solar cell structure (antireflecting coatings + ohmic contacts + semiconductor structure) is carried out. It is the first time that the whole structure has been simultaneously optimized under a maximum efficiency criterion. This is thanks to the dual consideration of the opto-electrical characteristics of the window layer. An assessment of GaAs solar cells working inside optical concentrators is also derived. Copyright © 1999 John Wiley & Sons, Ltd.

Resolving the Siting Impasse: Modeling social and Environmental Locational Criteria with a Geographic Information System

Abstract This site suitability study examines the representation of social criteria for locating a recycling center, and demonstrates how traditional overlay approaches to “McHargian” site suitability analysis can be extended to include these social criteria through the use of a geographic information system. The social criteria, characterized in terms of “closeness” and distance, are examined in relation to siting policy objectives of effectiveness and equity. One social representation is made by transforming a range of the distances between population concentrations and a waste facility into a map of attitudes of opposition towards the facility, using empirical estimates of attitudes. This social representation is combined with environmental criteria to identify solutions that both satisfy environmental concerns and are the best choices according to social criteria of being implementable and feasible, rather than only according to the traditional criterion of maximum efficiency.

Estimation of the parameters of the Rice distribution

This paper deals with the problem of estimating the parameters of the Rice distribution. The distribution has applications in sonar and radar signal processing and a proper estimation procedure with associated confidence intervals is important. Using the sample second moment as an estimate of the second moment of the distribution, two techniques, viz., methods of moments and maximum likelihood are applied to synthetic envelope data of known signal-to-noise ratios, in order to estimate the parameter from different sample sizes. It is concluded that the sample second moment is an unbiased estimate of the theoretical second moment and for the signal-to-noise ratio parameter both methods work without any significant bias and satisfy the criterion of maximum efficiency. However, the method of moments is simpler, easier to apply and therefore recommended as the method of choice.