The digital twin is widely known as a tool for digitalization of a product, but there is no common definition concerning this term. This article discusses the definition and utilization of digital twin. Areas of use, it's implementation in the product lifecycle and most importantly it's benefits. The lack of a standardized concept of a digital twin leads to a misunderstanding between mathematical models and digital twin. Several definitions of digital twin were analyzed and compared with the definition of mathematical model and simulation modelling. The basic concept of areas of use for digital twin is introduced. The differences and similarities between the two definitions were found. The article aims first of all to help the management of digital twins in practical application.

The article discusses the process of development an imitational model of the outlet. This model is created to validate calculation algorithms in the workforce management information system by evaluating the effectiveness of the some count of schedules, which are built with this system. If this schedules are more effective than the previous algorithm’s schedules, so new algorithm is more effective than previous version. Model is needed because calculation algorithms can not be used for validation themselves. Validation with real client’s outlet is so long and expensive, and is check only one or pair the calculation’s algorithms results, so in fact it can’t be used. Imitation model provide a chance to imitate works different types of outlets with many variants results of new version the calculation algorithms. AnyLogic was chosen because it is superior in functionality to the alternative despite the rather high cost of an official license. The text contains the results of the work performed, a brief description of the stages is given. Keywords: simulation modeling, AnyLogic, validation, information systems, workforce management

This research consists in the creation of a hardware-software complex for the rehabilitation of stroke patients. The device is designed for rehabilitation of patients after acute disorders of cerebral blood circulation with severe neurotraumas. The device is based on two existing rehabilitation technologies: the method of transcranial brain stimulation with the help of a magnetic neurostimulator, and the development of hand motility with the help of gloves. The combination of these two methods will allow patients to recover effectively, even at home, after they was suffering from neurotrauma. Keywords: stroke, ischemic, rehabilitation, biofeedback, paresis, brain, computer, mechanized glove, hardware, and software complex, CNS diseases, integration, TMS, magnetic neurostimulator

The paper defines the models of the objective tree and the current reality tree. Such models allow to define problems on the basis of cause-effect relations. The paper provides general recommendations for the application of these models. It describes their application on the example of an information system, a compound program complex. The information is accompanied by visual images in the form of diagrams. The information system is used in the field of retail to solve many different problems. The paper explains the need to identify problems. Within the framework of the example, the system's stakeholders are defined and their interaction with the objective tree is given. After that, a certain objective is considered and the reason for that is given. As a result of using the current reality tree, the paper compiles a list of root problems. At the end, it proves the connection between the solution of low-level problems and the implementation of high-level objectives. Finally, it provides recommendations for further work related to the selected list of problems.