Introduction/purpose: The Euler-Sombor index (EU) is a new vertex- degree-based graph invariant, obtained by geometric consideration. It is closely related to the Sombor index (SO). The actual form of this relation is established. Methods: Combinatorial graph theory is applied. Results: The inequalities between EU and SO are established. Conclusion: The paper contributes to the theory of Sombor-index-like graph invariants.
Introduction/purpose: This paper introduces the concept of β - F-weak contraction by using the concepts of F-weak contraction and α - ψ - contraction. Methods: The use of the β - F-weak contraction proves some fixed points theorems in the framework of S-metric spaces. Results: The obtained results on fixed points in S-metric spaces generalize some known results in the literature. Conclusions: The β - F-weak contraction generalizes some important contraction types and examines the existence of a fixed point in S-metric spaces. The results are used to solve a non-linear Fredholm integral equation.
Introduction/purpose: Chemical structures are conveniently represented by graphs where atoms are nodes (vertices) and chemical bonds are branches (lines) in the graph. A graphical representation of a molecule provides a lot of useful information about the chemical properties of the molecule. It is known that numerous physical and chemical properties of molecules are highly correlated with theoretical invariants of graphs, which we call topological indices. One such theoretical invariant is the dominance number. The aim of this research is to determine the k-dominance numberfor cyclooctane chains ���1n, ���2n, ���3n and ���4n, for k ∈ {1,2,3}, n ∈ �. Methods: The cyclooctane chain is a chain of octagons connected by a single line. The vertices of the octagon are treated as nodes of the graph, and the sides and the line connecting them, as branches in the graph. Using mathematical methods, k-dominance was determined on one octagon, k∈{1,2,3}. Then, by representing the cyclooctane chains ���1n, ���2n, ���3n and ���4n, in a convenient, isomorphic way, we determined their k- dominance number, k∈{1,2,3}. Results: Determining k-dominance, k∈{1,2,3}, for 4 cyclooctane chains ���1n, ���2n, ���3n and ���4n, we obtained 12 different formulas to calculate their k-dominance number. All formulas are composed of several alternative algebraic expressions, the selection of which is conditioned by the divisibility of the number n by the number 2, 3 or 4, depending on the type of cyclooctane chain and k-dominance to be determined. The results of the research are fully presented in the paper through mathematically proven theorems and graphical representations.Conclusion: The results show that the k-dominance numbers, k∈{1,2,3}, on cyclooctane chains ���1n, ���2n, ���3n and ���4n, are determined and� � �explicitly expressed by mathematical expressions. They also indicate the possibility of their application in molecular graphs of cyclooctane rings, in computational chemistry, chemical and biological industry.
Introduction/purpose: Destabilization of critical resources (CRs) or critical infrastructure (CI) important for the stability of the state can be dangerous for society, economy, and especially national security. Disruption of one CI object or one of its parts often affects and causes disruption of other dependent CI, because the modern society has become a "networked society". The paper proposes a model for quantifying and defining the interdependence between different CIs and their priorities, based on statements of experts. Methods: The proposed methods that combine the Laboratory for Testing and Evaluation of Decision Making (DEMATEL) and the Analytical Network Process (ANP) have been successfully modified by fuzzy logic theory in this work. Results: Integrating multiple methods into a unique input data analysis model significantly affects the change in ranking. Conclusion: The work contributes to military science in making strategic decisions related to national security management through increasing the resilience of CRs and the societies that rely on them.
Introduction/purpose: Simulated annealing is a powerful technique widely used in optimization problems. One critical aspect of using simulated annealing effectively is a proper and optimal adjustment of its parameters. This paper presents a novel approach to efficiently adjust the parameters of simulated annealing to enhance its performance and convergence speed. Methods: Since the simulated algorithm is inspired by the cooling Metropolis process, the basic idea is to simulate and analyze this process using a mathematical model. The proposed work tends to properly imitate the Metropolis cooling process in the algorithmic field. By intelligently adjusting the temperature schedule, temperature reduction and cooling rate, the algorithm optimizes the balance between exploration and exploitation, leading to improved convergence and higher-quality solutions. Results: To evaluate the effectiveness of this approach, it was applied first on a chosen sample function to be minimized, and then on some usual known optimization functions. The results demonstrate that our approach, called Optimal Adjusting of Simulated Annealing parameters (OASA), achieves superior performance compared to traditional static parameter settings and other existing approaches, showing how to well adjust the parameters of the simulated annealing algorithm to improve its efficiency in terms of solution quality and processing time. Conclusion: Adjusting the algorithm parameters could have a significant contribution in the optimization field even for other metaheuristics.
Introduction/purpose: Data Envelopment Analysis (DEA) is commonly used to calculate the efficiency of similar Decision-Making Units (DMUs), which as such are elements of one set. In the article, it is considered that each such element of a set (of similar elements) is at the same time an element of a system (of various elements). An example of DMUs are 27 railway stations in the Republic of Serbia (RS) as an element of a set of railway stations and as an element of the railway transportation system, in the function of transporting goods, after division of the company Serbian Railways in 2015 (into "passengers" and "goods"). For the sake of better service, attraction and retention of clients, in the newly opened, free, transport market, the purpose of this article is to find the efficiency of the RS stations iin the period of 2018-2022. Methods: Set-systemic-model comparative DEA analysis of railway stations as a DMUs. A unit is an element of the set, a unit is an element of the system, and a unit is the subject of the mathematical DEA- CCR/BCC/SE model. Results: The final efficiency, the average of all average values, is 0.7666, as a result of a triple comparative DEA analysis: 27 DMU, three DEA models and five years of functioning. Conclusion: Stations are functionally different in terms of efficiency and each station functionally differs by years and by model. The final aim is an input-output balance and the 27/27 option which is achieved with corrective actions - reduction/addition, input or output.
Introduction/purpose: This article presents the bending examination of advanced-generation composite structures with specific properties exposed to different loads. Methods: This paper thus proposes and introduces a new generalized five- variable shear strain theory for calculating the static response of functionally graded rectangular plates made of ceramic and metal. Notably, our theory eliminates the need for a shear correction factor and ensures zero-shear stress conditions on both the upper and lower surfaces. Numerical investigations are introduced to interpret the influences of loading conditions and variations of power of functionally graded material, modulus ratio, aspect ratio, and thickness ratio on the bending behavior of FGPs. These analyzes are then compared to the results available in the literature. Results: Preliminary results include a comparative analysis with standard higher-order shear deformation theories (PSDPT, ESDPT, SSDPT), as well as Mindlin and Kirchhoff theories (FSDPT and CPT). Conclusion: Our theory contributes alongside established theories in the field, providing valuable insights into the static thermomechanical response of functionally graded rectangular plates. This encompasses the influence of volume fraction exponent values on nondimensional displacements and stresses, the impact of aspect ratios on deflection, and the effects of the thermal field on deflection and stresses. Numerical examples of the bending examination of advanced-generation composite structures with specific properties exposed to different loads demonstrate the accuracy of the present theory.
Introduction/purpose: All data exchanged over the Internet as well as other computer networks should be considered exposed to various types of security threats. In light of this, the transmission of voice over applications that do not use any type of crypto-protection allows anyone to discern the content of communication. Since voice transmission requires as little delay as possible, various protocols are used to enable crypto protected real-time communication. This paper presents one solution in a desktop application variant. Methods: The essence in voice exchange systems as well as in other systems where real-time communication is necessary is the establishment of a crypto-protected session which is a virtual secure channel for communication to which only the communicating parties have access. Voice sessions in the application are established with the SIP (Session Initiation Protocol) protocol. The sessions are further protected using the ZRTP (Zimmerman Real-time Transport Protocol) protocol. FusionPBX was used as the SIP server (registrar) for testing purpouses. The application is developed in C++ language using the Qt framework. Results: The final version of the application demostrates that ZRTP and SIP protocols are well suited for establishing crypto protected voice communications with low delay. Conclusion: This solution provides cryptographic functions for data secrecy and the management of cryptographic keys. Improving the solution with digital signatures and certificates will result in additional cryptographic functions: data integrity and personal identification. With this improvement, this solution will be able to withstand modern security threats with low delay.
Introduction/purpose: The paper explores the implementation of two-factor authentication (2FA) in computer systems, addressing the increasing need for enhanced security. It highlights the vulnerabilities of password-based authentication and emphasizes the advantages of 2FA in mitigating digital threats. The development of the VoiceAuth application, integrating 2FA through a combination of password and voice authentication, serves as a practical illustration. Methods: The research adopts a three-tier architecture for the VoiceAuth application, encompassing a database, server-side REST API, and client- side single-page application. Speaker verification is employed for voice authentication, analyzing elements like pitch, rhythm, and vocal tract shapes. The paper also discusses possibilities for future upgrades, suggesting enhancements such as real-time voice verification and additional 2FA methods. Results: The application's implementation involves a detailed breakdown of the REST API architecture, Single Page Applications (SPAs), and the Speaker Verification service. Conclusion: The research underscores the crucial role of two-factor authentication (2FA) in bolstering the security of computer systems. The VoiceAuth application serves as a practical demonstration, showcasing the successful integration of 2FA through a combination of password and voice authentication. The modular architecture of the application allows for potential upgrades.
Introduction/purpose: The study of vehicle suspension is a challenge for researchers in the field of vehicles regarding the impact of the suspension system on vehicle performances such as ride comfort, road holding, and working space. This paper presents the simulation of the Land Rover Defender 110 vehicle in the roll plane (half vehicle) in Simulink/MATLAB. The obtained results were compared with the results obtained in the ADAMS/CAR software package of the Land Rover Defender 110 simulation model previously experimentally validated. The Defender 110 vehicle has a dependent suspension system in both axles and a passive suspension type with four degrees of freedom (4 DOF). Methods: The equations of the system can be solved mathematically with a scheme in Simulink/MATLAB while half-vehicle modeling has been done in ADAMS/CAR. Results: The comparison of the vehicle characteristics obtained by the two simulation methods was done for three different scenarios, and it was noticed that there is a good correlation between them. Conclusion: It was concluded that the Defender 110 vehicle simulation model in Simulink/MATLAB is validated. The validated model can be used to perform suspension system optimization in future work.
Introduction/purpose: In recent times, with the tendency to develop new types of armor-piercing ammunition, constant investments in the development of new types of armored obstacles is necessary. Obstacles made of high-alloy steel plates are still the best form of protection against larger caliber ammunition. There are a number of factors to consider when selecting an alloy, including the weight, dimensions, intended use, desired ballistic performance, and costs. According to that, a numerical analysis of penetration of a 30mm armor-piercing fin-stabilized discarding sabot projectile into the steel alloy Weldox 460 plates of different thicknesses at a distance of 1000m with a velocity of 1300m/s is presented in this paper. Methods: The stresses and deformations of the penetration effect were calculated through numerical analysis and finite element modeling. To specify material characteristics, the Johnson-Cook material model and the fracture of materials model have been utilized. In order to define models and carry out numerical calculations, the software packages FEMAP and LS Dyna have been used in this paper. Results: For a numerical analysis of the penetration process of this projectile type against armor obstacle, four different armor plate thicknesses are calculated: 10mm, 50mm, 100mm, and 110mm. For each of them, the results are shown in a form of stress and displacement, so that the interaction phenomena between the sub-projectile and the armor plate can be described. Conclusion: Modeling the impact on armor-piercing obstacles is extremely difficult, time-consuming, and complex, and the resulting models very successfully (or with some deviation) approximate the real problem of projectile penetration. One of the most effective methods for solving problems of this kind and others of a similar nature in recent times is the finite element method analysis. The material and the target dimensions, as well as the ballistic parameters and the material of the projectile have the biggest influence on projectile penetration. The target's resistance to penetration increases when all input parameters are maintained at the same level and its thickness is increased, and vice versa.
Introduction/purpose of the research: Latent fingermarks can be found on the crime scene on various surfaces and made visible by different forensic methods. As this evidence can often be found on brass surfaces (ammunition casings, decorative items, etc.) the paper discusses the possibilities of applying electrochemical deposition of nickel on brass. The condition for the application of this technique is the existence of a conductive substrate. Fatty components of latent fingermarks have insulating properties and prevent the electrodeposition process. Methods: Experimental thin rectangular pieces of brass foil were used as substrates for latent fingermarks. Samples were degreased in acetone and ethyl alcohol, rinsed in deionized water, and dried in a stream of compressed air before leaving the fingermarks. To enhance the presence of sweat on friction ridges, the hand was placed in the silicone glove for five minutes. A slight touch of the index finger was left on the tiles. Fingermarks were developed on brass samples by fingerprint powder and the electrochemical deposition of nickel on another brass surface simultaneously. In order to obtain the best possible evidence, the parameters affecting the deposition rate (current density, deposition time) were changed until a clear fingermark was obtained. Results: The fingermarks were compared visually using a magnifying glass with illumination to observe the contrast between the papillary lines and the interpapillary space and the characteristic details (minutiae). The optimal results were achieved with the current density (deposition rate) of 50mA/cm2 for 10s. Conclusion: Electrochemical deposition of nickel on brass is an applicable technique for developing latent fingermarks with certain limitations.
Introduction/purpose: Cutting is a typical material process. However, an appropriate solution for simultaneous optimization of material machinability and tool life in material cutting processes has not been obtained yet. In this article, probabilistic multi-objective robust design (PMORD) is expounded and the robust design problem in the simultaneous optimization of material machinability and tool life is analyzed by taking the machining of ferrite-bainite dual-phase steel as an example. Methods: According to PMORD, the arithmetic mean and its deviation of various performance and utility indexes of alternative schemes are evaluated as twin independent responses, which respectively contribute a part of the partial preferable probability to the performance indexes. In the evaluation, the arithmetic average of the utility index is taken as the representative of the utility attribute, and the evaluation is made in accordance with the function or preference of the utility index. However, the deviation term is generally used as an unbeneficial type of the index (that is, the smaller the better) to participate in the evaluation. The product of the two parts of partial preferable probability is the actual partial preferable probability of the corresponding performance index. The product of the partial preferable probability of all performance utility indexes gives the total preferable probability of the corresponding scheme, which is the only index for each scheme to participate in the competition in robust design. Results: The optimization result of this example is that the tool life is 1297.3333 s (standard deviation is 2.0817 s) and the surface roughness is2.22μm (standard deviation is 0.2μm), while the corresponding working conditions are that the heat treatment temperature of the material is 790°C, the cutting speed is 150m/min, the feed speed is 0.15mm/rev, and the cutting depth is 0.2mm. Conclusion: The example of the parameter optimization of cutting of ferrite-bainite dual-phase steel by means of PMORD indicates the rationality of the appropriate solution.
Introduction/purpose: During the 1999 NATO attack on Yugoslavia, three new weapons were used and tested for the first time. The first is the strategically invisible B-2 bomber, the second is the new JDAM (Joint Direct Attack Ammunition) and the third is the "soft bomb", or the blackout bomb, made of thin electrically conductive fibers. The aim of the paper is to present the new combat devices used during the aggression on the FRY and to quantitatively detect the elements of electrically conductive fibers. The paper also presents the lawsuit of the Federative Republic of Yugoslavia (FRY) to the International Criminal Tribunal for the former Yugoslavia (ICTY) in The Hague. The lawsuit was rejected. Methods: Physical and chemical analyzes of the fibers were performed. An electron microscope, SEM JSM Jeol 6610LV, was used to analyze the physicochemical characteristics of electrically conductive fibers. It providesthe information on the morphology of the sample surface, resulting in a high- resolution image.The microscope is equipped with an X-ray detector (Oxford Instrumets X-Max 20 mm2) for EDS analysis (Energy Dispersive Spectroscopy). It enables the determination of the chemical composition of the material in the analyzed sample volume, based on the interaction between the directed electron beam and the sample atom. Results: The characteristics of the B-2 stealth aircraft used to bomb the FRY are shown. The JDAM bomb is an improved ordinary MK bomb with electronic devices added to guide the bomb via satellites. A semi- quantitative analysis of the fibers was performed on the SEM, confirming that the metal layer of the fiber predominantly consists of aluminum, and the non-metallic layer has the highest proportion of silicon dioxide. The fiber is carcinogenic. Conclusion: In 1999, the territory of Yugoslavia was a testing ground for new combat weapons of NATO aviation - B-2 and JDAM guided bombs. Blackout bombs were dropped on the electrical power systems of Yugoslavia leaving the whole Serbia without electricity for hours. Not only was the bombing-caused environmental pollution radiological and chemical but it was also caused by glass-aluminum electrically conductive fibers as pollutants.
Introduction/purpose: Concrete, mortar, and cement pastes are materials that have become central in various fields of construction, structures, and civil engineering. About 7 billion cubic meters of concrete are implemented. Concrete is generally considered a homogeneous material, but that is not always the case given its rheological behavior, which can be due to heterogeneous phenomena of segregation and bleeding. Methods: The study tested a concrete column's physical and mechanical characteristics and deformation in elevation. The tests included measuring absolute and apparent density, porosity, capillary absorption, permeability, speed of propagation, compressive strength, and static and dynamic modulus of elasticity. For this purpose, the standards of non-destructive testing (sclerometer, ultrasound, etc.) were used to take the average of a series of points located at different levels of the element to be tested. Results: The results indicate that changes in the column's height affect its physical and mechanical properties, either increasing or decreasing them (such as porosity, absorbency, permeability, compressive strength, and the static and dynamic modulus of elasticity). These changes are influenced by various factors, including the inherent properties of the concrete implementation (such as vibration and curing) and the climate conditions during construction. Conclusion: The findings of this study emphasize the importance of a nuanced approach to testing and evaluating variations in concrete properties by taking into account the multifaceted impact of changes in column height.
Introduction: The experimental area of brain-computer interfaces (BCIs) is expanding to include movement actions, which play a crucial part in deciphering cognitive processes. Without the need for any kind of exterior stimulation, motor imagining (MI) can be used as a powerful model for brain- computer interfaces (BCIs). A natural method of operating exterior devices is to imagine moving various joints in the same arm. These envisioned motions have similar spatial images in the motor brain, making it difficult to differentiate MI of various joints of the same leg based on EEG data. Method: A pre-existing data collection of 25 participants was utilized in this study. The participants visualized using their right limbs to carry out three different activities: visualize yourself manipulating your right hand, visualize bending your right arm, and close your eyes while you relax. To assign categories to these impulses, we turned to the adaptive neuro-fuzzy reasoning system. Results: The average level of accuracy was 90%. Conclusion: The findings demonstrate that this technique is crucial for correctly categorizing EEG data. The data collection used in this investigation consists of EEG measurements of the same limb used in muscular imaging. The new categorization method will be applied to these signals to draw conclusions.
Introduction/purpose: Starting from general relativity, black hole generation and effects are investigated. Method: Einstein’s equation and its Schwarzschild solution are employed to study black holes. Quantum mechanics is used to obtain Hawking’s radiation. Results: Black holes are actually not completely black - they radiate energy during their lifetime. Conclusions: Black holes could evaporate and this effect is observable if their mass is sufficiently small. Their entropy scales differently with respect to their mass from that of other objects in thermodynamics.
Introduction/purpose: This work provides a comprehensive overview of blockchain technology, elucidating its foundational principles and how it ensures transparency, immutability, and decentralization. The integration of Solidity with blockchain is explored through theoretical approach. Methods: This work meticulously dissects blockchain principles, elucidating transparency, immutability, and decentralization, while exploring Solidity integration in a theoretical framework, ensuring a comprehensive understanding of their intricate relationship and contributing to a broader comprehension of modern distributed ledger technology. Results: The resulting product of this paper will be getting useful knowledge about the technology that practically shapes the world. Conclusion: In conclusion, the adoption of Solidity as a programming language in blockchain technology has proven to be pivotal, enhancing smart contract functionality and overall system security. Its specialized features make it an indispensable tool for developers navigating the complexities of decentralized applications.
Introduction/purpose: Information systems represent a set of people, data, processes and information technologies related to the purpose of data collection, processing, storage and their filtering into useful information needed for supporting organizations or decision making. The information system is developed as a Web application with the help of the Javascript programming language, Node.js, and React.js, while in the background it relies on data storage and communication with the SQL database. Methods: Modern web application development tools are used and tested on low budget hardware. Results: Effective software for a car park with low maintenance cost and great reliability has been developed. Conclusion: The software made work easier, increased access to data and facilitated data review, reducing the possibility of error. The application described in this article and made for research shows how modern commercial technologies can be used for military purposes.
Introduction/purpose: This paper conducts a comprehensive analysis of a potential implementation of Voice over Internet Protocol (VoIP) systems, focusing on network architecture, VoIP phones, and servers. The study explores potential vulnerabilities and proposes solutions. The paper concludes by advocating for a holistic approach to securing VoIP systems, incorporating supplementary services to ensure the confidentiality, integrity, and availability of voice communications in the digital landscape. Methods: Review of the underlying theory, analysis of the end-user needs and potential solutions, practical viability assesment. Results: The theoretical points discussed were proven in practice, using commercially available resources. Communication was established in an expected manner. Conclusions: Implementing solutions similar to the one presented in the paper would be a relatively inexpensive way to make diverse improvements to the operation of tactical level units, both in peacetime and during war.
Introduction/purpose: This paper seeks to provide a review of the applications of the fifth (5G) and the next, the sixth (6G), generation of mobile wireless communications in the military environment. Methods: Analyzes and syntheses were used to consider various aspects, challenges, developments, and implementations of the fifth (5G) generation as well as the sixth (6G) generation mobile wireless communications for military purposes. Results: The background and the state of the art of 5G and 6G mobile wireless communications are presented. Next, 5G military impact and initiatives are described. The paper also presents future prospectives of 6G for its usage in the military. Finally, possible 6G military applications are presented. Conclusion: 5G had achieved the first deployment by 2020 and completed the first phase of its evolution in 2022. The 5G Advanced starts as a version towards the sixth generation in a way to find different solutions for implementation not only for commercial, but also for military purposes. With the platform approach to connectivity, 5G military networks contain different requirements, range of implementation options with spectral efficiency, latency, and reliability as primary performance metrics. Toward 6G, machine learning (ML) and artificial intelligence (AI) methods have proposed new approaches to modeling, design, optimization, and implementation in military systems.
Introduction/purpose: The research aimed to analyze the key aspects of human-computer interaction, studying the evolution of this field from its beginnings to contemporary trends. Focusing on different aspects of this interaction, it studied how methods, technologies and principles have evolved over time and shaped our experiences in the digital environment. Methods: The research methodology was based on the analysis of relevant literature and research papers devoted to human-computer interaction. Systematic review and evaluation of sources identified the key information on the evolution of user interaction with computers. Through evaluation of available studies, changes in interface design methods, interaction technologies and understanding of user needs over time were identified. Results: Based on data synthesis, the key aspects of human-computer interaction were identified. An analysis of the literature revealed changes in interface design methods, interaction technologies, and understanding of user needs over time. Specific results included information on the evolution of interaction aspects, including improvements in efficiency, intuitiveness and personalization of experiences. Conclusion: The key conclusion of the research is that innovations and evolution of technology have significantly influenced the way users interact with computer systems. Improvements in interface design, recognition technologies, and personalization of experiences are key factors in creating better user experiences and optimizing human-computer interaction. The research points to the continuous development and changes in the field of human-computer interaction, emphasizing the need for further research and innovation in this area.