International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

The research proposes a newsvendor-like model that enables determining the optimal timing for renting machinery with its operators before the arrival of the raw material, and derives an optimal manufacturing strategy. The research includes a case study with a comprehensive analysis for a blueberry harvester that demonstrates the applicability of the proposed model. The rigorous theoretical analysis of the optimal harvesting strategy is validated by numerical experiments. The presented results may help researchers and agriculture practitioners in planning mechanical-manual integrated manufacturing.

This research considers the problem of sequential quality control and presents different methods for the quick detection, with low false alarm rate, of a change in a stochastic system. The paper focuses on recently proposed control schemes called Nested Plans. These schemes include two unknown parameters that essentially impact their efficiency. The research presents a way to find the optimal values of the parameters, and shows that Nested Plans with the correct choice of the parameters are very efficient, robust and simple for practical applications.

This paper analyzes a simple project with two activities. The activities can be executed in a serial mode (separately), in a parallel mode (overlapping), or in a mixed mode (partly in a serial mode and partly in a parallel mode). There is interdependence between the activities and the duration-budget tradeoffs functions of the activities are defined differently for each execution strategy. The paper presents a deterministic duration-budget tradeoff model that takes into account the interdependence between the activities in order to determine the optimal execution-mode and the budget distributions among the project activities. A stochastic extension of the proposed model is also considered. The presented analysis can help project managers and practitioners in choosing the optimal overlapping strategy for different objective functions and constraints.

This paper presents a multinomial model for a special case of the machine interference problem (MIP), where each of N identical machines randomly requests several different service types. The model allows the calculation of the expected interference time in the queue for each service type. The extended version of the model allows calculation of the exact distribution function of the steady state waiting time and total service time for each type of requested service. In addition, the model can be adjusted for the case where the service is provided by a group of K identical operators, each operator is capable to handle all types of service, but each service type has a different priority.

This research analyzes the optimal harvesting policy and the optimal timing for ordering a rented self-propelled blueberry harvester for maximizing the total expected profit. The paper proposes a stochastic model that takes into account two types of uncertainties:
1) the exact date when the crop will be ready for harvesting (fruition) is unknown; 2) the exact quantity of the crop in the field is unknown. Another factor that is taken into account is the decreasing price of the crop during the harvesting season.