Estimation of Sea State Parameters from Ship Motion Responses Using Attention-based Neural Networks

On-site estimation of sea state parameters is crucial for ship navigation systems' accuracy, stability, and efficiency. Extensive research has been conducted on model-based estimating methods utilizing only ship motion responses. Model-free approaches based on machine learning (ML) have recently gained popularity, and estimation from time-series of ship motion responses using deep learning (DL) methods has given promising results. Accordingly, in this study, we apply the novel, attention-based neural network (AT-NN) for estimating sea state parameters (wave height, zero-crossing period, and relative wave direction) from raw time-series data of ship pitch, heave, and roll motions. Despite using reduced input data, it has been successfully demonstrated that the proposed approaches by modified state-of-the-art techniques (based on convolutional neural networks (CNN) for regression, multivariate long short-term memory CNN, and sliding puzzle neural network) reduced estimation MSE by 23% and MAE by 16% compared to the original methods. Furthermore, the proposed technique based on AT-NN outperformed all tested methods (original and enhanced), reducing estimation MSE by up to 94% and MAE by up to 70%. Finally, we also proposed a novel approach for interpreting the uncertainty estimation of neural network outputs based on the Monte-Carlo dropout method to enhance the model's trustworthiness.Comment: 14 page

Improved parametrized multiple window spectrogram with application in ship navigation systems

In analyzing non-stationary noisy signals with time-varying frequency content, it's convenient to use distribution methods in joint, time and frequency, domains. Besides different adaptive data-driven time-frequency (TF) representations, the approach with multiple orthogonal and optimally concentrated Hermite window functions is an effective solution to achieve a good trade-off between low variance and minimized stable bias estimates. In this paper, we propose a novel spectrogram method with multiple optimally parameterized Hermite window functions, with parameterization which includes a pair of free parameters to regulate the shape of the window functions. The computation is performed in the optimization process to minimize the variable projection (VP) functional problem. The proposed parametrized distribution method improves TF concentration and instantaneous frequency (IF) estimation accuracy, as shown in experimental results for synthetic signals and real-life ship motion response signals. With the optimization of nonlinear least-squares approximation of the ship response signals, the Hermite spectra are centralized, and only up to 15 basis functions are sufficient for concentration improvement in the TF domain

Biomechanical analysis of three-point shot in basketball

Background: A precise three-point shot (3S) is considered a key parameter of success in a basketball game, and therefore the factors that affect its success have always attracted the attention of researchers. Aim: The aim of this research was a biomechanical-mathematical analysis of 3S in basketball, in order to determine the key parameters for performing a 3S. Results: The research shows a model of shooting a basketball player from the central position of the shot with 6.75 m. The modeling led to the conclusion that the height of the throw, the speed and the angle of the throw of the ball have a positive and direct relationship with the angle at which the ball falls into the basket when it comes to a shot for three points. Conclusion: The height of the throw, the speed and the angle of the ball have a positive and direct relationship with the angle at which the ball hits the basket when it comes to a shot for three points. Anthropometric characteristics of the player, such as the length of the arm, and the height of the player, directly lead to a positive relationship with the throwing angle

DVOSTRUKO NAPAJANI ASINKRONI STROJ ZA VJETRONAPONSKE SUSTAVE

U ovom radu obrađena je tematika korištenja dvostruko napajanog asinkronog stroja kao jednog od koncepata upravljanja u vjetronaponskim sustavima. Teorijski su opisane sve komponente suvremenog vjetronaponskog sustava te je objašnjen način pretvorbe energije vjetra u električnu energiju uz dobivanje maksimalne izlazne snage. Navedene su sve prednosti korištenja ovog koncepta upravljanja te je isti uspoređen s ostalim konceptima upravljanja u smislu načina djelovanja, učinkovitosti i cijene. Dan je način djelovanja asinkronog stroja uz pripadajući matematički model u mirujućem i rotirajućem koordinatnom sustavu te je razrađeno načelo toka aktivne i reaktivne snage u slučaju sinkronog, nadsinkronog i podsinkronog načina rada. Kako bi se ispitale karakteristike mehaničkih i električnih veličina izveden je model upravljanja dvostruko napajanog asinkronog generatora u PLECS programskom paketu. Također su opisani svi elementi korištenog upravljačkog sustava kao i njihova hijerarhija djelovanja unutar strukture vektorskog upravljanja s orijentacijom statorskog toka i mrežnog napona. Simulacijom karakterističnih pojava tijekom ustaljenog stanja rada, prijelaznog stanja ubrzanja i usporavanja brzine vrtnje rotora te stanja kvara pada mrežnog napona, ispitana su međudjelovanja električnog i mehaničkog pogonskog sklopa. Analizom rezultata za različita pogonska stanja utvrđeno je kako predstavljeni sustav ima izrazito povoljne dinamičke karakteristike i potvrđena su sva teorijska razmatranja koja opisuju način djelovanja tog koncepta upravljanja.This paper deals with double fed induction generator as one of the concepts of wind energy conversion systems. All components of the modern systems are presented and an explanation about wind power to electric power conversion with maximum power coefficient is given. All the advantages of using this control concept are listed and compared with other common control concepts in terms of performance, efficiency and cost. The principle of the induction machine's work with the corresponding mathematical model in the stationary and rotating coordinate system is described and the principle of active and reactive power flow in the case of synchronous, supersonic and sub-synchronous mode of operation is elaborated. In order to examine the characteristics of mechanical and electrical variables, model of double fed induction generator is created in the PLECS program package. All elements of the control systems used as well as their hierarchical actions within the structure of vector control with stator flux orientation and network voltage orientation are described too. By simulating the system during steady state of operation, transient acceleration state and rotor speed deceleration, as well as failure of network, electrical and mechanical drive circuit interactions were examined. Simulations for different operating conditions confirms that the presented system has well dynamic performances according to theoretical considerations of this control concept

Inhibition of Hepatitis C virus (HCV) Core protein- induced Cell Growth by Non-structural Protein 4A (NS4A) is Mediated by Mitochondrial Dysregulation

Hepatitis C virus (HCV) is a significant health problem facing the world. More than 170 million people are infected with HCV worldwide. HCV encodes a large polyprotein precursor that is processed into at least 10 distinct products including structural (core, E1 and E2) and non-structural (NS2, NS3, NS4A, NS4B, NS5A and NS5B). Besides its importance in virus replication, NS4A functions as a cofactor for NS3 and contributes to viral pathogenesis by influencing cellular functions. Here, we investigated the effect of NS4A protein on the growth rate induced by core protein in liver cells. Using our established tetracycline inducible system, we demonstrated the ability of NS4A protein to inhibit core protein-induced cell growth in Hepatoma cell line, HepG2. Induction of both core and NS4A proteins in HepG2- core/NS4A transfectants inhibited core-induced growth advantage in HepG2-core transfectants and blocked NS4A protein-induced cell growth inhibition in HepG2-NS4A transfectants. Using both immune fluorescence staining and Western blot analysis, we confirmed the localization of NS4A protein to the mitochondria in HepG2-NS4A transfectants expressing NS4A protein. Data obtained from flow cytometry analysis, using JC-1 demonstrated the loss of mitochondrial membrane potential (ΔΨ^ by the expression of NS4A protein in HepG2-NS4A transfectants, but not by the expression of core protein in HepG2-core transfectants. Whereas, the induction of the expression of both core and NS4A proteins in HepG2-core/NS4A transfectants blocked NS4A-induced loss of ΔΨm in HepG2 cells. Taken together, our data suggest an important role for mitochondria in the modulation HCV NS4A-induced inhibition of HCV core-mediated cell growth

Ružička days : International conference 19th Ružička Days “Today Science – Tomorrow Industry” : Proceedings

Dear colleagues, we are extremely honoured to present to you the Proceedings of the international conference 19th Ružička Days, which was successfully held on September 21–23, 2022, in Vukovar, Croatia, in the hometown town of our famous Croatian scientist and first Nobel laureate, professor Leopold (Lavoslav) Ružička. The main goals of the Conference were to promote excellence, originality and innovation of interdisciplinary scientific research as well as the practical application of the obtained results through collaboration with industry, emphasizing thus the recognizable slogan of the Ružička Days conference: "Today Science – Tomorrow Industry". In addition, the Conference gave the opportunity for meetings, exchanging the ideas, opinions, experiences and cooperation among participants from different working surroundings. It is also important to point out that since 2008, within the international conference Ružička Days, Meeting of Young Chemists has also been held, where high school students, with the help of their mentors, present papers in the field of chemistry, with the aim to direct students and young people to the technical and natural sciences, especially chemistry. In its seventh issue (2011, 2013, 2015, 2017, 2019, 2021) the Proceedings publishes scientific and professional full papers of high quality in the following sections: Chemical analysis and synthesis (10), Chemical and biochemical engineering (3), Food technology and biotechnology (4), Chemistry in agriculture and forestry (1), Environmental protection (9) and 8th Meeting of Young Chemists (3). Full-length papers were subjected to an international review procedure done by eminent experts from the corresponding fields, to whom we express our gratitude, but they were not subjected to linguistic proofreading. On behalf of the Scientific and Organizing Committee of the 19th Ružička Days we cordially thank all the authors, reviewers, participants, lecturers, organizers, especially the international organizers EuCheMS and EHEDG, auspices and sponsors, and all the others who, in any way, supported the Conference and contributed to the preparation of the Proceedings, especially to our highly skilled and committed associates, who have put a lot of effort in the preparation of these Proceedings. At the very end, special thanks to our young, future scientists and their mentors who are faithful participants of the Meeting of Young Chemists of the Ružička Days conference. Enjoy the extremely interesting scientific and professional papers contained in these Proceedings, until the next 20th jubilee of Ružička Days in 2024! We are looking forward to meeting you again in Vukovar! Yours sincerely, Chief Editors Jurislav Babić Vesna Ocelić Bulatović Dajana Kučić Grgi