Zlatar Ski Center has an extremely high potential as a ski resort that could be among the most visited ones in Serbia. What characterizes this center is the proximity of Kokin Brod Lake, the Tara River and the like. Therefore, Zlatar should be considered both as a ski center and in terms of other diversities. The aim of this paper is to analyze the possibility of expanding the capacity of ski resorts by increasing the possible flow of skiers on new ski lifts and ski slopes. The methods used in this paper belong to operational research, specifically, the geometric interpretation of linear programming. It is also shown how to optimize the extended capacities. If the capacities of ski slopes are to be increased, it would initiate greater investment in accommodation capacities in the area of the municipality of Nova Varoš, which would affect its improvement in terms of tourism.

The paper presents the analysis of the transport plan by applying the geometric interpretation of linear programming, dual approach and simplex method to the optimization of the transport plan. The goal is to optimize the transport plan from the aspect of choosing the type of transport task, type and scope of engagement of transport means, in order to maximize the functions of the goal that represents the earnings. The approach to analysis is illustrated by a characteristic task that is solved in the paper in the described way. The main difference between this and the tasks analyzed so far is that the imposed restrictions represent a system of inequalities which, by introducing fictitious variables, is transformed into a system of equations to which the standard maximum problem is applied. The benefit of this approach is a simpler but also more comprehensive approach to the analysis of the transport plan. It is especially suitable for relatively small transport systems when there are a number of limitations and where it is not convenient to buy and use software packages. The emphasis in the paper is on maximizing earnings while meeting the imposed limits. The analysis yielded identical results in all three ways.

Introduction: An unknown primary tumor (UPT) is defined as a biopsy-proven malignancy whose anatomic origin remains unidentified after diagnostic evaluation. The estimated incidence of unknown primary tumors is 2-7% of all malignancies. Aim: The aim of this study was to determine the role of 18 FDG PET/CT in the evaluation of primary tumor and its influence on therapeutic management. Material and methods: This retrospective study included 56 patients, which were examined in the PET center of Center for Nuclear Medicine (Clinical Center of Serbia), from May 2011 until September 2017. Examinations using 18 FDG on PET/CT system were done on all patients using a 64 slice Biograph True 64 PET/CT hybrid imaging system (Siemens Medical Solutions, USA). Image acquisition was done at least 60 minutes after applying the radiopharmaceutical (18 FDG), which have been applied after proper preparation of each patient. Results: The primary site of tumor was found in 23 (41%) patients, which is a statistically significant value 23/56, χ 2 1.78, p < 0.05. Conclusion: Considering the acquired results, 18 FDG PET/CT represents a significant advancement when it comes to non-invasive diagnostics of UPT.

The topic of the paper is the application of dual approach in formulation and resolution of goods distribution tasks problems. The gap in previous goods distribution research is the absence of the methodologies and goods transportation calculation methods for manufacturing companies with not too large amount of goods distribution whereby goods distribution is not the core activity. The goal of this paper is to find a solution for transportation in such companies. In such cases it is not rational to procure a specific software for the improvement of goods transportation but rather apply the calculation presented in this paper. The aim of this paper from mathematical aspect is to show the convenience of switching from the basic geometric interpretation of linear programming applied on transportation tasks to dual approach for the companies with too many costs limitations per transport task but not enough available transportation means. Recent research studies that use dual approach in linear programming are generally not applied to transportation tasks although such approach is very convenient. The goal of the paper is also to resolve transportation tasks by both primal and dual approach in order to prove the correctness of the method.