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Adaptive Tracking Algorithm of Weak GNSS Signal
Full text linkThe receiver of a global navigation satellite system (GNSS) is likely to lose tracking for a GNSS signal in some degraded environments. To solve this problem, this paper analyzes both the bandwidth and the dynamic stress errors of the carrier tracking loop (CTL) of a GNSS receiver, and then designs a new adaptive tracking algorithm for GNSS signals. First, we design an error extraction module to extract phase errors so that a CTL can estimate phase errors without using a loop discriminator, which can reduce the requirements of the carrier-to-noise ratio (CNR) of GNSS signals. Second, we design a motion detection module to detect the real-time movement status of GNSS receivers. Then, using its detecting results as inputs, we design an algorithm to automatically make the CTL switch between a second-order loop and a third-order loop. Third, we design a bandwidth-adjusting module to adjust the bandwidth of CTL, according to the CNR and the movement status of a GNSS receiver. Finally, a simulation is performed to verify that our adaptive carrier tracking algorithm can effectively improve the precision of CTL, as well as enhance its dynamic range
The Role of Venture Capital Investment Trusts in Startup Financing: Financial Performance Analysis Using Entropy and TOPSIS Methods
Full text linkThis study assesses the financial performance of eight Venture Capital Investment Trusts in Türkiye over 2021-2024 using an Entropy-TOPSIS multi-criteria decision-making framework. Twelve financial ratios representing liquidity, profitability, leverage, and efficiency dimensions are used to construct annual decision matrices. Entropy results indicate that liquidity indicators carry the highest weights, while leverage-related measures are least influential; profitability maintains moderate importance, and efficiency gains greater prominence in 2023–2024. Using these objective weights, the TOPSIS analysis shows that Hub consistently achieves the highest performance, followed by Gözde VCIT, whereas Bulls VCIT and İş VCIT display weaker and more volatile results. The dataset is derived from independently audited annual reports retrieved from the Borsa Istanbul Public Disclosure Platform. Overall, the findings demonstrate the usefulness of the Entropy–TOPSIS approach for transparent, multidimensional performance assessment in a regulated emerging market and provide a practical quantitative framework for policymakers and investors
Small Solar Installations
Full text linkAbstract: The paper considers small solar installations, which are developed and created at the Institute of Materials Science of the Academy of Sciences of the Republic of Uzbekistan. The authors of the article operate a Large Solar Furnace with a thermal power of 1000 kW and have extensive experience in operating and building solar high-temperature furnaces. Small solar installations are simple, cheap and easy to operate
Fabrication of PVDF/PMMA Polymer for Sustainable Energy Harvesting
Full text linkAbstract: The synthesis of blends that combine properties of two or more polymeric materials is increasingly investigated due to the versatility of the synthesis and its growing potential for many applications, including sustainability. Their characteristics are defined mainly by the synthesis conditions. Therefore, this paper details the synthesis process of easy-to-handle films using mixing method. The procedures and drawbacks found during the preparation of composite films are described. Polymeric compounds formed by the mixture of polyvinylidene fluoride (PVDF) and polymethyl methacrylate (PMMA) are addressed, varying the concentration, and evaluating their impact on the piezoelectric capacity. Films were formed through the spin-coating technique and characterized by optical and holographic microscopes. The results showed that composites with a concentration of 50 wt.% or larger of PVDF in the blend acquire a morphology with a granular appearance, however at lower concentrations they present a homogeneous morphology similar to that of PMMA. A homogeneous distribution of PVDF in the PMMA stands out. However, excessive contents of PMMA are associated to peaks and non-uniformities detected like multicolored regions by digital holography. Controlled strength-strain laboratory tests allowed to evaluate the film blends performance. The results indicate noticeable improvements in voltage output for a composition 70wt% PVDF and 30 wt% PMMA
Crystal Engineering for Achievement of Functional Materials Through Facile Intercalation of Lamella Mineral Kaolinite
Full text linkAbstract: Kaolinite, a layered clay mineral, has attracted widely attention due to its versatile advantages including low cost, environmentally friendly processing and easy modification. By comparison of the wide studies of the intercalation processes of kaolinite via the replacement of diverse intercalated agents, the multiple functional properties of intercalated kaolinites are ignored as well as such kind of study is very limited. In this review, we have summarized a series of intercalated compounds of kaolinites with organic molecules or organic salts by means of a simple intercalation strategy. Additionally, their multiple functional properties (such as dielectricity, ferroelectricity and ionic conductivity) will also be mentioned
The Numerical Simulation of Welding Residual Stress of Dissimilar Transparent Thermoplastics with MZA Powder Absorbent
Full text linkAbstracts: There are residual stresses in the joint caused by swift temperature variation in the process of laser transmission welding with metal absorbent. However, the related forming process is hard to detect through experimental methods. Herein, a physical model is established to describe the evolution of stress during the welding of polyarylsulfone (PASF) and polycarbonate (PC). The evolution of heat stress and the forming of residual stress is analyzed through the method of heat-force sequential coupling. In this process, the condensate transition, metal powder deformation, and clamping forces are involved in the mathematical model of stress-strain. In this model, the stress history can be divided into n time intervals according to the principle of superimposed stresses. The results revealed a significant correlation between the thermal history and stress evolution. Furthermore, the maximum von-mises stress appeared at the time of 1.7 s, then there was a decreasing tendency and stabled at 9 s. The von-mises stress was considered as residual stress after that time and the related stress distribution was investigated. The findings of this study provide a comprehensive understanding of residual stress on the joint
Biodegradable Materials Used in FDM 3D Printing Technology: A Critical Review
Full text linkAbstract: Three-dimensional (3D) printing is a flexible technique that has attracted increasing interest in recent years. 3D printing has powerful biodegradable materials that are important for environmental protection and emergencies such as COVID-19. To achieve better compatibility for customized and enhanced material characteristics, a variety of ways have been used. Companies and researchers are increasingly interested in biodegradable polymers and composites due to their easy production, eco-friendly, and suitability for a variety of applications. One small step toward protecting the world around us is the use of natural resources to produce fully or partially biodegradable composite materials. PHA (Polyhydroxyalkanoates), PLA (Polylacticacid), High impact polystyrene (HIPS), and PHB (Polyhydroxybutyrates) are examples of bioplastics that are produced and have similar functionality to conventional plastics while also being biodegradable. These materials have the potential to reduce our reliance on petroleum-based plastic, which may present environmental risks. Every country desperately needs to develop bioplastic usage and proper waste management for a pollution-free world. This review is expected to provide a general overview for 3D-printed biodegradable polymer and their applications using fused deposition modelling (FDM) technology
A Provisional Model for the Optimal Management of a Charging Station Assisted by Photovoltaic Panels for Plug-In Electric Vehicles
Full text linkThere is a strongly increasing diffusion of Electric Vehicles (EV) and Plug-in Hybrid Electric Vehicles (PHEV), in order to reduce air pollution in urban environment and to mitigate the global warming issues. Anyway, the achievement of this latter goal strictly depends on the source of primary energy used to generate electrical energy. In the paper, a model for the optimal design and operation of a charging station for EV and PHEV assisted by a PhotoVoltaic (PV) plant is presented. A provisional model for the estimation of the incoming insolation, based on cloudiness prevision, is integrated with a nonlinear constrained optimization algorithm, in order to satisfy the load while minimizing the recourse to electrical grid for battery storage charging. Simulations on different locations and charging loads for various size of PV plant and battery capacity are presented, and the benefits in terms of CO2 reduction discussed
An Improved Clustering Using by Likely Attributable Function and Informed Selection in WSN for Science of Management and Engineering
Full text linkWireless sensors networks (WSNs) are traditionally composed of large number of tiny homogenous sensors nodes connected through a wireless network that gather data to be treated locally or relayed to the sink node through multi-hop wireless transmission. The low-energy adaptive clustering hierarchy (LEACH) protocol is one of the Famous protocols used in the wireless sensor networks (WSNs). The LEACH protocol in wireless sensor network suffers from many Bugs and many researchers proposed different methods to mitigate them. In this paper, we propose two ideas in a format for improving leach protocol. For Cluster head selection we used a Likely Attributable Function that in this function used from a factor. This factor that we called the informed selection factor helps to farther nodes not selection for cluster head. This significantly decreases the energy consumption and increases the lifetime of associated nodes. Simulation is conducted in using MATLAB results are analyzed for energy consumption
A UAV for Triage Assessment of Chronic Illness in a GPS-Denied Environment
Full text linkIn this paper we conduct an extensive review of the literature toward an autonomous Unmanned Aerial Vehicle (UAV) for application in home healthcare. Based on the research findings, a system is proposed towards such a UAV for the purpose of patient care in an indoor environment, specifically in triage care for people living with chronic conditions. Our system seeks to provide an innovative solution for healthcare at home and to facilitate independent living as well as reduce over triaging through personalized robotics. The development of advanced navigation systems for UAVs has aroused extensive interest recently because of its enormous potential. In comparison to outdoor flight, GPS-denied navigation poses several distinct challenges in stability and control for quadcopter operability, including object detection and avoidance, real-time wireless client-server communications, stability and safety concerns. Medical Decision Support Systems (DSSs), which have been developed largely in the triage component of health assessment, care and decision making, also pose separate research challenges in terms of accuracy, consistency, response (processing) time and degree of automatic operation. As a single system, a drone-based DSS for chronic illness triage assessment poses unique challenges. For this application, the DSS requires voice-based responses, occurring in real-time and classified according to a dynamic and adaptive decision support engine that operates automatically; that is, with no human input and using non-invasive patient analysis. Existing healthcare systems of this nature have not yet been produced. Furthermore, patient recognition through real-time image fused with voice data in a noisy, GPS-denied environment has yet to be achieved. While path planning, navigation, control and stability concerns have been extensively addressed, accuracy for these systems can be improved and the technology as well as applied algorithms must be adapted to application-based requirements, in terms of weight, processing and dedicated communication requirements