The paper investigates the issue of volatility of stock index returns on the Warsaw Stock Exchange (WIG20 index returns volatility). The purpose of this review is to compare how other stock market indexes as HANG SENG, NIKKEI 225, FTSE 250, DAX, S&P 500 and NASDAQ 100 influance the volatility of WIG20 index returns. The innovation of this work is the usage of a new neural network with three different activation functions to predict future volatility of WIG20 index returns. The input for this network is the last 3 values of WIG20 index returns volatility and the last 3 values of one of the considered foreign index returns volatility. As measurements for the best forecasting performance of neural networks are taken common used forecast errors: ME (mean error), MPE (mean percentage error), MAE (mean absolute error), MAPE (mean absolute percentage error), RMSE (root mean square error). The study shows that the Polish stock market is mainly influenced by the European and US markets.

Introduction and objective: The medical records were examined of 222 patients of the Osteoporosis Treatment Clinic at the Central Clinical Hospital of the Medical University of Łódź, Poland. The influence was analyzed of 27 clinical risk factors on the occurrence of low-energetic fractures...

This paper suggests a numerical method of computing a confidence interval for one-step ahead. It eliminates the need for assumptions regarding the distribution of random values. In this article, a Monte Carlo simulation is performed to verify the presented new approach. Additionally, it is tested on the time series of the daily USD/EUR foreign exchange rate and exchange rate returns. To measure and compare the degree of predictive accuracy, the coverage rates are used. These metrics determine whether interval forecast covers the true value or not. Four tests: Kupiec’s POF and TUFF, Christoffersen test, and traffic light test are employed to validate the presented method and compare it with the classical historical method. The results of the tests confirm the desirability and effectiveness of the proposed method.

Allocation algorithms based on rankings are utilized in various situations, such as selecting appropriate tasks for workers, scheduling doctors’ appointments, or assigning children to schools.Amodified version of the standard Gale-Shapley algorithm is introduced and employed in Poland’s secondary school recruitment process. This algorithm relies on students’ school results and their priority lists. During the recruitment process, students are assigned to a school on the basis of their performance and preference list. However, this approach disadvantages weaker students, as they are only considered towards the end of the process. Consequently, they are often assigned to schools with a lower priority on their lists or, in some cases, remain unassigned. The proposed modification aims to improve opportunities for students to plan their educational future more fairly, considering their individual achievements.

The jump of the Milnor number of an isolated singularity $f_0$ is the minimal non-zero difference between the Milnor numbers of $f_0$ and one of its deformations $f_s$. We determinate the jump of quasihomogeneous singularities in the class of linear deformations.

Designing retaining structures depends on many factors, primarily the function of the retaining structure and soil conditions. It is not easy to choose the right retaining structure due to the great variety of their structural and material solutions. Preliminary numerical analyses in this case can be very useful. This article presents the results of numerical analyses of the behaviour of retaining structures and soil for various structural and material solutions as well as defined soil and water conditions. Six variants of retaining structures were analysed, in which the type of retaining walls, the materials used and the height of the walls were varied. The assessment was done basing on maps of stress and displacement of the retaining structure and soil. An additional factor in the selection of retaining structures are costs, durability and lead time. The finite element method allows the analysis of the behaviour of the structure - soil system. It enables comparison of various construction variants at the design stage and selection of the best solution in given soil and water conditions for the set selection criteria.