GPSS World Research Articles

Simulation Model of One-Parameter Selective Assembly of Two Elements With Multivariate Set-Making

Analytical and simulation methods are used to model assembly processes and technological systems in order to determine and optimize their performance and functioning parameters. The first one, describes an object or process using mathematical relationships indirectly. Simulation modelling is one of the modern methods of production system experimental research, allowing to take the presence of various components in the system, nonlinear characteristics, non-determinism and dynamism of ongoing processes into account. This work is devoted to the simulation model development of the technological process of multivariate one-parameter selective assembly of two elements. Multivariate set-making is defined by generalized rules with a set of weights which elements are set the distribution of elements between sets of different types. Selectively assembled elements have parameters determined by the manufacturing stage, which are independent random variables with known probabilistic characteristics. It is assumed that the input-output relationship is linear with given coefficients, the set-making equations linking the numbers of selective groups and assembly sets are known. A simulation model of the assembly process was built in the GPSS World, which, in contrast to the known one, operates with multivariate set-making rules for the case of assembly of two elements. The model allows to determine the quantitative indicators of the assembly process, in particular, the probabilities of assembly set formation, work-in-progress and preliminary rejects. As an example, the process of multivariate set-making of two parts forming a precision engineering product is considered. The data of parts distributions of both types by selective groups before assembly are given, the technological process indicators are calculated. Based on the modelling results the advantages and disadvantages of the multivariate set-making process are outlined.

ANALYSIS OF THE RESULTS OF SIMULATIVE MODELLING OF THE INFORMATION SECURITY SYSTEM IN THE CORPORATE NETWORKS OF HIGHER EDUCATION INSTITUTIONS

The analysis shows that the insufficient level of information security in service networks is the main cause of huge losses for enterprises. Despite the appearance of a number of works to solve this problem, there is currently no unified system for assessing information security. This shows that this problem has not yet been sufficiently studied and relevant. This work is one of the steps towards creating a system for assessing information security in service networks. The purpose of the work is to develop an algorithm and simulation model, analyze the results of the simulation model to determine the main characteristics of the information security system (ISS), providing the ability to completely close all possible channels of threats by controlling all unauthorized access (UA) requests through the protection mechanism (PM). To solve the problem, a simulation method was applied using the principles of queuing systems (QS). This method makes it possible to obtain the main characteristics of the ISS from the UA with an unlimited amount of buffer memory (BM). Models, an algorithm and a methodology for the development of ISS from UA are proposed, which is considered as a single-phase multi-channel QS with an unlimited volume of BM. The process of obtaining simulation results was implemented in the GPSS World modeling system and comparative analyzes of the main characteristics of the ISS were carried out for various laws of distribution of output parameters. At the same time, UA requests were the simplest flows, and the service time was subject to exponential, constant and Erlang distribution laws. Conducted experiments based on the proposed models and algorithm for analyzing the characteristics of the ISS from the UA as a single-phase multi-channel QS with unlimited waiting time for requests in the queue confirmed the expected results. The results obtained can be used to build new or modify existing ISS in corporate networks for servicing objects for various purposes. This work is one of the approaches to generalizing the problems under consideration for systems with an unlimited volume of BM. Prospects for further research include research and development of the principles of hardware and software implementation of ISS in service networks.

Selecting a transport and forwarding company for meeting a customer’s needs when organizing international road cargo transportation

The object of this study is the process of planning the work of a manufacturing enterprise that needs transport and forwarding services when exporting goods to counterparties in different countries of the world. The problem being solved is predetermined by the need to devise recommendations for choosing a transport and forwarding company when serving an individual customer, based on its individual needs and conditions of cooperation. A simulation model for the selection of a transport and forwarding company was constructed and implemented to meet the customer’s needs when exporting goods, applying the GPSS World simulation automation package. The model provides for the optimization of the choice of a transport and forwarding company for servicing counterparties based on the assessment of their activity indicators over previous periods of cooperation. When building the model, the types of commercial conditions of the exporter’s cooperation with the transport and forwarding company, indicators of the quality assessment of the basic level of service and the duration of service at all stages of the foreign trade operation were taken into account. The application of the constructed model in practice will enable exporters and importers to choose a transport and forwarding company depending on the individual needs of customers in the delivery of goods. The simulation results reflect the performance indicators of the provision of transport and forwarding services by various specialized enterprises. This will make it possible to involve in the transport and forwarding service of a separate counterparty an organization that will meet all the requirements of goods buyer in accordance with the terms of the international economic contract. At the same time, the duration of choosing and agreeing the terms of cooperation could be reduced by 12–15 % while the efficiency of transport and forwarding services would increase by 13–16 %

Simulation Modeling of QS with Hyper-Erlang and Erlang Distributions

The article is devoted to the construction of simulation models of customer delay in the queue in the form of a queuing system (QS) described by both ordinary and right-shifted hyper-Erlang and second-order Erlang distributions. This article is a logical continuation of previous works devoted to the construction of numerical-analytical QS models with shifted distribution laws. In the article, the Erlang distribution is considered as a special case of the more general Gamma distribution law, in contrast to the normalized Erlang distribution. These two forms of the Erlang distribution differ in numerical characteristics, except for the coefficient of variation. To solve the problem, the system of discrete-event modeling GPSS WORLD was used.

Methodology for Optimizing the Headcount Based on Simulation Modeling

The article discusses the advantages of simulation modeling of the number of sales personnel in order to increase the economic efficiency of the organization. Headcount optimization aims to generate savings while meeting the organization’s goals. This example considers the activities of one of the leading players in the regional food market. In accordance with the general structure of the processes of receiving and servicing customers in the organization, their simulation model was developed in the GPSS World software environment. The obtained conclusions are economically substantiated.

Methodology for optimizing the headcount based on simulation modeling

The article discusses the advantages of simulation modeling of the number of sales personnel in order to increase the economic efficiency of the organization. Headcount optimization aims to generate savings while meeting the organization’s goals. This example considers the activities of one of the leading players in the regional food market. In accordance with the general structure of the processes of receiving and servicing customers in the organization, their simulation model was developed in the GPSS World software environment. The obtained conclusions are economically substantiated.

Development of a simulation model of the activities of a transport and forwarding enterprise in the organization of international road cargo transportation

The object of this study is the process of planning the work of a transport and forwarding company when serving different categories of customers who need organizational support for the delivery of goods by road transport in international traffic. The solved problem is due to the need to devise recommendations for organizing the work of forwarders when interacting with customers of transport and forwarding services that export or import different categories of cargo. A simulation model of the transport and forwarding company’s work in customer service was developed and implemented in the GPSS World simulation automation package. The model provides for the optimization of organizational and management processes in cooperation with customers of transport and forwarding services. When developing the model, the duration of the types of work in which freight forwarders are involved in the export and import of goods by road transport was taken into account. The model also predicts the probability of errors in the forwarder’s work and the duration of their elimination. The application of the developed model in practice will enable the owners of transport and forwarding companies to plan the full-time number of forwarders and the duration of service provision under different conditions of interaction with customers. The simulation results reflect the performance indicators of the enterprise in serving different categories of customers. This will make it possible to optimize the work of the enterprise by planning personnel support. At the same time, the duration of transport and forwarding services will be reduced by 10–15 %, the capacity of the enterprise will increase by 6–11 %, and the reliability of service provision will increase by 8–14 %

Логико-временная формализация имитационных моделей систем железнодорожной автоматики и телемеханики

The purpose of the article is to present the results of developing a method for formalizing simulation models of railway automation and remote control systems as queuing systems with a rigidly regulated sequence of using service devices while processing streams of requests of various types. For the software implementation of simulation models with such properties, the GPSS World tool is traditionally used. The logical time formalization is proposed, and the concept of the proposed formalization of simulation models is formulated. Its main provisions include: the type of request is determined solely by the composition and sequence of occupation and release of servicing devices; the use of transaction parameters to organize their multiphase processing for each type of request; checking the value of Boolean functions for each procedure of processing requests for each type; the regulated time in the procedure of processing requests is considered as one of the many logical conditions of Boolean functions; logical and parametric description of the modeled system should be performed at the level of initial data without changing the text of the modeling program. Objects in GPSS World sufficient for implementing this concept have been identified. Using the selected objects, an alphabet has been compiled, and logical diagrams of modeling algorithms have been developed in the obtained alphabet. This serves as a demonstration of the application of the logical time concept for the formalization of simulation models of complex queuing systems. A GPSS program has been developed to confirm the possibility and feasibility of using the proposed method for formalizing simulation models of railway automation systems with a rigid structure.

SOFTWARE GENERATORS IN THE GPSS WORLD ENVIRONMENT FOR DISTRIBUTIONS-PROBABILITY MIXTURES WITH QUALITYASSESSMENT RESULTS

This article presents quality assessment results for the software generators of pseudo-random sequences (PRS) presented in [1; 2] for QS simulation, including second-order hyper-Erlang and hyper-exponential distributions of the second order, that flows organically from these works. These distribution laws are in demand in queuing theory as it provides a big range of changes in the variation coefficient which plays an important role in the average queue delay calculating. There is no data on such generators neither in scientific literature, no in the GPSS WORLD library. Software generator quality evaluation, regardless of the programming language, is usually made according to statistical tests. In this case, chi-squared and Kolmogorov-Smirnov’s tests are used. In addition, the comparison between theoretical and statistical aspects of the corresponding order is provided. Unlike simple distribution laws, for which the use of the above mentioned statistical tests is provided for in well-known software products and does not cause any difficulties, in our case automatic testing is impossible. The well-known packages STATISTICA, STATGAPHICS, Matlab/Simulink, etc. do not provide for the use of the hyper-Erlang and hyper-exponential distribution laws we consider. Therefore, the Pearson statistical test is calculated and checked manually. The presented results should be useful for professionals of discrete event modeling in the GPSS WORLD environment.

SIMULATION MODEL OF A QS WITH HYPEREXPONENTIAL DISTRIBUTION IN THE GPSS WORLD ENVIRONMENT

This article presents results obtained on the development of a pseudo-random sequence generator for simulation modeling of queueing system (QS) with second-order hyperexponential input distribution. In the scientific literature on GPSS WORLD, including web resources, the authors did not find any data in this subject area. The GPSS WORLD library includes many generators of various distribution laws, but there are no generators for such important composite distributions according to the queuing theory. It is known that the hyperexponential distribution concept provides a wide range of changes in the random variable variation coefficient from unity to an arbitrarily large value. Due to the fact that the variation coefficients of arrival and service intervals play an important role in estimating the delay of queue claims in queuing systems, thus this distribution concept plays a special role in modeling of QS. For a hyperexponential distribution of the second order, the authors previously obtained numerical-analytical results based on the Lindley integral equation spectral solution method. The article describes a developed algorythm and a program on GPSS WORLD to simulate the functioning of QS with hyperexponential input distribution incl. description of operation of logical switches. The difference between analytical and simulation modeling of the two-phase representation of a given distribution concept is explained on the example of the developed model. The adequacy of the obtained results was confirmed by comparing the simulation results with the results of numerical simulation in the Mathcad environment.

Effeciency assessment of IoT devices control with Teletraffic theory

In connection with the global decarbonization program until 2050, the transition to clean green energy, the growth of the Internet of Things (IoT) number, and energy distribution and control across the load are being raised. The relevance of the work is confirmed that there has been significant growth of the industrial IoT for years, significantly changing the mechanism of industrial enterprise management programs. The object of the research is the IoT device control system for efficient energy distribution using a Queuing Theory, namely the Teletraffic Theory. The novelty of the work is that the Teletraffic Theory, which deals with the mathematical modeling and analysis of traffic patterns in communication networks, can be explicitly applied to IoT device control. The authors developed a mathematical model of IoT control using the Teletraffic Theory and, based on it, created a simulation model of a network router and a transition schedule in the "GPSS World" software. The obtained results of the work were 16 states and a balance equation in which all probabilities were found. Probabilities were used to calculate nodes and network characteristics. 100,000 requests from IoT devices coming to two routers were simulated. The study results showed that the first node's load is 63.2 % with an average processing time per transaction of M=1.436 sec., and the load of the second node is 32 % with M=0.914 sec. The created network router model worked with minimal losses during transactions. Accordingly, the IoT control system developed in this study has shown its effectiveness and is applicable for practical use in controlling IoT devices in Smart Grid. It is planned to research the possibility of using Teletraffic Theory in energy distribution control systems in Smart Grids

Construction of a simulation model of goods delivery in international road transportation taking into account the functioning efficiency of logistics supply chain

The object of this study is the process of goods delivery in international road transport using various types of logistics chains. The problem being solved is due to the need to develop recommendations for exporters of goods to reformat or design new supply chains during wartime. The expediency of organizing foreign trade operations by the cargo owners' own forces or with the involvement of enterprises providing logistics consulting services is considered. A simulation model of goods delivery in international road traffic was built and implemented in the GPSS World simulation automation package. The model involves the optimization of organizational and technological processes related to the activity of both a separate link and the entire supply chain. The study takes into account the components of the time characteristics of the performance of preparatory work when establishing cooperation with institutions and organizations, as well as the direct service of the exporter. The application of the developed model in practical activities will provide an opportunity for exporters to obtain information about the duration and reliability of the stages of a foreign trade operation and the feasibility of involving consulting enterprises in cooperation. At the same time, the simulation results reflect the performance indicators of the proposed supply chains when delivering goods by road transport along various routes. The proposed simulation model will make it possible to reduce the time spent searching for links in the formation of a supply chain by 8–12 %, and the duration of a foreign trade operation by 10–14 %. Thus, the reliability of cooperation with intermediary organizations will increase by 8–11 %

THE PROBLEM OF GENERATING PSEUDORANDOM SEQUENCES OF COMPOSITE DISTRIBUTIONS FOR QS SIMULATION

This article presents the results obtained on developing a pseudo-random sequence generator for simulation modeling of a QS with a hyper-Erlangian input distribution of the second order. In foreign and Russian-language scientific literature, including web resources, data on this domain were not found by the authors. It is known that this distribution law is the most general distribution of a continuous nonnegative random variable within a wide range of variation coefficients. The latter plays an important role in estimating a delay of requests in a queue in queuing systems, since an average delay of requests in a queue is related to the coefficients of variation of arrival and service intervals via the quadratic dependence. Using this higher order distribution is difficult to derive a solution for an average waiting time due to the increasing computational complexity. For the hyper-Erlangian distribution law of the second order, the authors previously obtained some numeric and analytic results based on the method of spectral solution to the Lindley's integral equation. The article presents the obtained algorithm and program on GPSS WORLD for simulating the functioning of a QS with a hyper-Erlangian input distribution. The adequacy of the obtained results was confirmed by comparing the simulation results with the results of numerical simulation in the Mathcad environment. The authors hope that the presented results will be in demand by specialists in the field of simulation modeling in the GPSS WORLD environment.

Имитационное моделирование систем массового обслуживания на основе составных распределений – вероятностных смесей

This article presents the results obtained on the development of software pseudo-random sequence generators for QS simulation in the GPSS WORLD discrete-event simulation system with hyper-Erlang (HE2) and hyper-exponential (H2) input distributions. Data in this subject area, neither in foreign nor in domestic scientific literature, were found by the authors. There are no such generators in the GPSS WORLD library either. It is known that the distributions of HE2 and H2 are the most general and provide a large range of the coefficient of variation. The latter play an important role in estimating the delay of requests in the queue in queuing systems, since the average queue delay is directly proportional to their squares. For the distributions of HE2 and H2, the authors previously obtained numerical-analytical results based on the method of spectral solution of the Lindley integral equation. The article presents the obtained algorithms and programs on GPSS WORLD to simulate the functioning of the QS with the specified input distributions. The adequacy of the obtained results was confirmed by comparing the simulation results with the results of numerical simulation in the Mathcad environment. The authors hope that the presented results will be in demand by specialists in the field of simulation modeling in the GPSS WORLD environment.

Features of building hybrid simulation models in Actor Pilgrim

In recent years, simulation has been actively used to study socio-economic processes in order to test various management decisions (for analyzing risks, projects, regional processes, logistics, etc.). Today, three simulation systems (Actor Pilgrim, AnyLogic, GPSS World), each of which has its own areas of application, are the most widespread in Russia. So, the system Actor Pilgrim is most suitable for modeling socio- economic processes. The first version of this system was developed by a group led by Professor Alexander Anatolyevich Yemelyanov more than 35 years ago to solve experimental problems in the direction of "Flexible automated production". It was based on a new modeling paradigm, which was built on the actor-network theory. The transition to solving new problems, primarily in the economics, led to the need for its further system development through the implementation of temporal, financial and spatial dynamics. Currently, the system development is carried out through the construction of hybrid simulation models, which is associated with the introduction of various analysis methods. So, when modeling actual technical and economic processes (for example, import substitution of high- tech products), it is proposed to use artificial intelligence methods that allow you to get informed decisions in conditions of information uncertainty. Models that include fuzzy logic methods and swarm algorithms (in particular, bacterial optimization) have shown good results. For example, fuzzy logic methods have been used to assign "fair" priorities to option projects through a detailed analysis of the factors of the internal and external environment of enterprises that will implement them. Bacterial optimization algorithms have been used to search for "promising" areas for the implementation of the projects of import substitution of high-tech products. These swarm algorithms are distinguished by the ability to simultaneously study favorable and negative factors, i. e. allow taking into account various risk situations. The modern version of Actor Pilgrim is intended for systems analysts, economists-mathematicians and other professionals who are familiar with programming, but are not professional programmers.

SCHEDULING TECHNIQUE OF ROUTE VEHICLES ON DUPLICATING STRETCHES

Schedule optimization is a proven strategy to improve service quality for public transport networks. However, current research mostly optimizes schedule design using prior knowledge of users’ routings, ignoring the optimization of public transport schedules on duplicating stretches of route vehicles. This article presents a new alignment technique of time intervals between consecutive vehicles of different routes on duplicating stretches, considering existing public transport networks in attaining optimization of public transport schedule. Scheduling technique of route vehicles on duplicating stretches includes some steps: analysis of public transport network and determining a lot of duplicating stretches, calculation of the optimal time intervals among arrivals of route vehicles and alignment of these intervals among consecutive route vehicles on duplicating stretches, realization simulation model of urban passenger transport within the simulation modeling system of GPSS World. Furthermore, testing the optimization technique of route vehicle scheduling, analysis of the quality of adjusted schedule with route vehicles of different kinds included, and determining the optimization efficiency for duplicating stretches. The adjusting technique of urban passenger transport schedule allows to increase movement steadiness of consecutive vehicles of different routes on duplicating stretches, adjust traffic intervals for each route, shorten the traffic load on stations, reducing idle time and queue lengths of route vehicles in front of transport stops and also minimize waiting time for route vehicle by those passengers who can be transported along several routes. Improving the bus schedule on duplicating stretches in Gomel is illustrated demonstrating the technique developed. This scheduling technique can be used by carriers and transport operators to improve the quality of services provided.

Development of a simulation model of a cargo customs complex operation as a link of a logistic supply chain

The main link in the logistics supply chain is the cargo customs complex. It provides customs and logistics services to cargo owners during the export and import of goods, complex services, placement of goods in a customs warehouse and a temporary storage warehouse. To substantiate the choice of the optimal logistics supply chain and optimize the work of the cargo customs complex, it is proposed to use simulation modeling. The model of operation of the logistics chain and the cargo customs complex is presented in a general form. The proposed model is implemented in the GPSS World simulation automation package. Testing the simulation model involved checking its adequacy. Checking the adequacy of the simulation model, which showed the maximum value of the t-statistic of 1.424 with a critical value of 1.85, proved its compliance with the work of a real object. After completing the adequacy check, the simulation error was estimated, which was 3 % with an allowable 5 %, due to the presence of pseudo-random number generators in the simulation model. Thus, the simulation error is insignificant for this study. For the cargo customs complex, an example of the simulation results is given. Based on the results of simulation modeling, it is possible to determine: the optimal type of the logistics supply chain and the optimal structure of the cargo customs complex. A wide range of tasks that the proposed simulation model can solve is presented. Thus, the developed simulation model will make it possible to analyze and improve the modes of operation of the cargo customs complex. In addition, it will allow to get an informed decision regarding the use of a certain type of logistics supply chain

Efficiency assessment of optimizing the schedule of urban passenger transport on duplicate sections

Introduction. One of the quality indicators of urban passenger transport services is regularity of route vehicles, which directly depends on a well-designed schedule. An urgent task is to optimize urban passenger transport schedule in response to the improvement in passenger service quality. The purpose of this work is to develop alignment technique of time intervals between consecutive vehicles of different routes on duplicate sections and efficiency assessment of its application.Materials and methods. Optimization technique includes some steps: analysis of public transport network, determining a lot of duplicate sections and their characteristics, calculation the optimal time intervals among arrivals of route vehicles and alignment this intervals among consecutive route vehicles on duplicate sections, analysis of the quality of adjusted schedule of route vehicles and calculating the effect. The simulation model of urban passenger transport within simulation modelling system GPSS World is realized. It allows testing optimization technique of route vehicle scheduling.Conclusions. Adjusting technique of urban passenger transport schedule allows to increase movement steadiness of consecutive vehicles of different routes on duplicate sections, adjust traffic intervals for each route, shorten the traffic load on stations, reducing idle time and queue lengths of route vehicles in front of transport stops and also minimize waiting time for route vehicle by those passengers, who can be transported along several routes.Application. The described technique was tasted in the existing transport network of Gomel.Value. The obtained optimization results can be used by carriers and transport operators to improve the quality of services provided.

Modeling of an interactive distance learning platform by means of modern information technologies

According to the requirements of the Ministry of Science and Education, teachers of various qualifications are required to regularly improve their professional skills. Using the distance learning platform allows you to automate the learning process, starting with the paperwork, ending with the final testing and obtaining a diploma. The problem is that during the course of training, you have to wait a long time for a response from a consultant on the subject or on the course support. The study of this problem was carried out on the basis of the existing database of the company "InfoTeacher". To determine the most promising courses, we used cluster data analysis using the R software environment. At the beginning, we calculated the optimal number of clusters according to the criterion of rocky scree, and then continued the cluster analysis using the k-means method. Thus, the main input parameters for building an interactive simulation model were identified. This model is a queuing system and was implemented in the GPSS World programming language. The parameters of the model were selected so that it was effective: to minimize the queues for consultation with the curator, while the curators should be loaded by at least 50%.

ОСОБЕННОСТИ ИСПОЛЬЗОВАНИЯ ИМИТАЦИОННОГО МОДЕЛИРОВАНИЯ ДЛЯ ПРИНЯТИЯ УПРАВЛЕНЧЕСКИХ РЕШЕНИЙ ПО РАЗВИТИЮ ПРЕДПРИНИМАТЕЛЬСКОЙ ДЕЯТЕЛЬНОСТИ НА ПРИМЕРЕ ТОРГОВОЙ КОМПАНИИ

Currently, for the effective development of any company, modern information technologies and information systems are used, including for making up-to-date decisions on the management of processes and personnel. In the context of the digitalization of the economy, special attention is paid to the business processes of interaction with clients of companies whose main goal is to increase the client base. In modern economic conditions, small business in Russia is developing steadily. Particularly relevant is the use of modern information technologies, which contribute to increasing the company's competitiveness, making new economic decisions, forming relevant strategies for the production and sale of products, goods, services, and building and retaining a customer base. To improve interaction with customers and the development of small businesses, the use of simulation modeling of queuing systems is of particular importance. In this study, used the GPSS World Student modeling environment, which allowed us to analyze the queuing system using the example of a grocery store. Computational experiments using the prepared simulation model have shown the direction of optimizing the number of points of payment for purchases when interacting with customers. Also, a preliminary forecast of the economic efficiency of the company with a different amount of used cash registers was carried out.