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Wear Resistance of Amorphous-Crystalline Coatings Under Boundary Friction
Full text linkThe results of tests under boundary friction conditions are present detonation coatings Zr-Al-B in a wide range of changes in friction conditions.
The obtained results were compared with the parallel tested coatings based on tungsten carbide type WK-15, also with samples of 30HGSNA steel and BrOCS6-6-3 bronze.
The qualitative and quantitative composition of surface layers participating in boundary friction conditions was assessed using modern physical methods of analysis. Profilograms and microphotographs of friction surfaces of amorphous-crystalline coatings are presented, showing that under boundary friction conditions, coating samples are smoothed, which leads to a decrease in roughness.
Installed the presence of the formation of solid solutions of oxygen interstitialization in zirconium, which corresponds to the formation of secondary structures of the first type on friction surfaces, the characteristic feature of which is their surface localization, ultra-dispersed structure, the ability to minimize destruction and screen unacceptable adhesive phenomena. Using Auger electron microscopy, it was confirmed that oxygen completely replaces sulfur in surface structures.
It is shown that the studied detonation coatings Zr-Al-B, developed for practice, have high tribotechnical characteristics in the entire range of tests under boundary friction conditions. At the same time, as a result of studies of the mechanism of tribochemical transformations of hydrocarbons and the properties of transformed surface films, it was established that they retain lubricating properties and provide high antifriction characteristics of the friction system in the entire wide range of changes in boundary friction conditions
Evaluation of Mechanical Properties and Hydrophilicity of Alkaline and Plasma Treated Abaca Fiber Epoxy Composite with Mineral Waste as Fillers
Full text linkAbstract: Natural fiber composites (NFC) are increasingly recognized for their sustainability and versatility. Abaca fiber is one of the prominent natural fibers that are sourced from the leaf sheaths of the abaca plant. This study provides an overview of the comparison of the mechanical properties and water uptake behavior of surface-modified N2 plasma and alkali treated abaca fiber-reinforced epoxy composites with granite powder used as fillers. It mentions the use of varying filler content (0 wt.%, 10 wt.%, 20 wt.%, and 30 wt.%) in both the pre-treated composites and compares their properties. Plasma-treated granite filler samples showed superior tensile strength and flexural properties, despite a negative effect on impact properties. A lower water absorption is observed in plasma-treated composites with fillers compared to those without fillers. Overall, the potential of surface modification techniques with granite-based mineral fillers is apparent in improving the performance of N2 plasma treated NFCs, thus expanding their applications across different industries aiming for the good mechanical hygroscopic properties
Lethal Autonomous Weapon Systems: Ethical Dilemmas and Legal Compliance in the Era of Military Disruptive Technologies
Full text linkLethal Autonomous Weapon Systems (LAWS) have emerged as one of the most significant advancements in military technology, leveraging artificial intelligence (AI) and machine learning to execute missions without direct human control. As these systems become central to modern warfare, they raise critical questions about their compliance with International Humanitarian Law (IHL) and International Human Rights Law (IHRL). This paper delves into the legal and ethical debates surrounding LAWS with particular attention to the discussions within the Group of Governmental Experts on LAWS (GGE on LAWS). We analyze whether these technologies can adhere to fundamental human rights while maintaining their operational efficacy. Through the application of the Autonomy Spectrum Framework to real-world scenarios, the study highlights both the strategic advantages of LAWS and the risks of dehumanizing warfare. The need for robust legal frameworks to ensure accountability and human oversight remains paramount
Research Progress of Fixed Bed Dehumidification System: A Mini Review
Full text linkAbstract: In recent years, the fixed bed dehumidification system has received extensive attention. Research shows that the fixed bed can be combined with the vapor compression refrigeration system to replace the traditional air conditioning (A/C) system, improve the dehumidification efficiency of the system and reduce energy consumption of A/C. In this study, the optimization and improvement methods of the fixed bed dehumidifier in recent years are introduced in detail firstly. It points out that adding heating/cooling devices to the fixed bed can greatly improve the dehumidification capacity and efficiency of the system, which is the main method to improve the fixed bed currently; Optimizing the structure of fixed bed is also an effective method, but the current research results have limited improvement on dehumidification performance; Optimizing the regeneration mode of fixed bed can improve the utilization rate of renewable energy and improving the overall dehumidification efficiency of the system, but the research in the direction is still insufficient; The parallel double packed bed structure can ensure the continuous operation of the fixed bed to improve the dehumidification efficiency of the system, but such systems are large in scale and high in cost. Then the dehumidification performances of various systems are summarized and comprehensively compared. Finally, the future optimization and improvement direction of the fixed bed is pointed out
Technical and Economic Assessment of the Use of an Autonomous Photoelectric Water Lift Installation in the Karakum Desert
Full text linkAbstract: One of the urgent problems of Turkmenistan is the development of desert territories, which occupies 80%. The task of scientific research is to analyze the problems of energy supply and water supply for the development of the desert and the desertification of this territory. One of the priority energy supply is the use of renewable energy sources, water supply, the use of groundwater. The article considers the eco-energy resources and potentials of solar energy for lifting water from the depths, using technical and economic methods to evaluate capital investments, investment costs and energy efficiency of solar photovoltaic water lifting stations in the Karakum Desert. The given methodology for technical and economic calculations, capital investments, investment costs and evaluation of the effectiveness of operational parameters for use in transhumance will be useful in the preparation of a feasibility study (feasibility study). On the basis of solar - energy resources, calculate, draw up an energy map of the rise of water from the depth of occurrence and evaluate the technical and economic indicators for the development of the Karakum desert and the development of transhumance
Experimental Validation Through a Parallel Computation Algorithm for Evaluation Uncertainty of the Mathematical Model of Direct Expansion Solar Assisted Heat Pump
Full text linkThis paper presents the development of a mathematical model for a direct-expansion solar-assisted heat pump (DX-SAHP) operating in steady-state. The mathematical model was implemented using the scientific software EES and using a code written in Python. It was utilized a lumped parameter model for the heat exchangers and a semi-empirical model for the compressor. The mathematical model was validated using experimental data of a DX-SAHP running with R134a. Two hundred simulations were made combining different correlations for estimating the convective heat transfer coefficient in the evaporator/collector. The Mean Absolute Deviation (MAD) and the Mean Deviation (MD) between the theoretical and experimental values for the COP were 2.6±1.8 % and 0.9±1.8 %, respectively. The MAD and MD between the discharge temperature were 1.56±0.16 % and -1.45±0.16 %. The mean difference between the results using EES and Python were 1.4 %. The use of Python with parallel computing for uncertainty analyses, reduced the simulation time in 88 % if compared with EES. The model in Python is available as open-source through the platform Google Colaboratory
Structural Modeling and Thermal Conductivity of Graphite Film Reinforced Aluminum Matrix Laminated Composites
Full text linkAbstract: Excellent thermal conductivities of thermal management materials are expected to ensure the timely heat dissipation in lots of engineering applications and electronic devices. High in-plane thermal conductivity of laminated composites has become increasing significant for high energy and power density electronic devices. In this study, the continuous graphite film/aluminum (Gr film/Al) laminated composites were fabricated by vacuum hot pressing. In-plane and out-of-plane thermal conductivity of Gr film/Al laminated composites are tested. Two-dimensional structural models of Gr film/Al laminated composites are established, in which volume fraction, interfacial property, punching zone and orientation angle of Gr films can be controlled according to their actual composite microstructures. The effects of volume fraction and interfacial property on the thermal conductivity of Gr film/Al laminated composites are investigated. Two ways to reduce anisotropy of thermal conductivity are introduction of punching zones and control of Gr orientation, which are verified to be effective. On basis of the analysis above, a good understanding can be brought out for extensive thermal management applications of Gr/Al composites
Short-Time Effects on Compressive Strength of Residual Soils Due to Rainwater
Full text linkAbstract: The short-term effects of acid rain on the geotechnical properties of residual soil were investigated. Artificial acid rain (AAR) of pH values 2, 4 and 6 was created with an infiltration setup to replicate the interaction between acid rain and soil. The soil specimens were infiltrated with AAR for durations of 30mins and 60mins for each pH level of 2, 4 and 6 and a control sample using deionised water of pH 7.5. Unconfined compression test (UCS) and Atterberg limits test were performed on the treated samples to study the mechanical behaviour and the characteristics of the soil once contaminated with AAR. The results revealed that reducing the pH value of AAR led to a reduction in compressive strength and Young’s modulus and an increment in liquid limit while the plastic limit remained unchanged. The reduction in compressive strength due to acid rain was observed to be almost halved when the bulk unit weight of the soil was increased for the same infiltration period
Theoretical and Experimental Studies on Vibration Resistance of Composite Plates with Damping Coating
Full text linkAbstract: This study performs both theoretical and experimental studies on the vibration resistance of composite plates with damping coating subjected to impulse excitation load. A dynamic model is first proposed and the key differential equations are derived to solve the natural frequencies, time-domain vibration response, and dynamic stiffness at any vibration response point regarding the excitation point of such a coated structure. Then, a dynamic experiment system of two plate specimens with and without DC knocked by a hammer excitation is set up. The measured data indicates that the proposed dynamic model is trustworthy for predicting natural frequencies and dynamic stiffness results. Furthermore, based on the calculated dynamic stiffness data associated with the first four modes, the anti-vibration contribution of DC is quantitatively evaluated. It can be found that the coating can indeed improve the vibration resistance of the structure by up to 74.7%. In addition, the vibration suppression effect of DC is found to be closely related to the mode order of such a structure as well as the selected boundary condition
Mesoscopic Cohesive Crack Model of Microcapsule Self-Healing Concrete and Its Uniaxial and Triaxial Compression Simulation
Full text linkAbstract: In practical engineering structures, concrete is usually under a multiaxial stress state. Therefore, it is significant to investigate the mechanical behavior of microcapsule self-healing concrete under triaxial compression. In this study, a three-dimensional mesoscopic cohesive crack model of concrete based on the cohesive element is established to simulate uniaxial compression tests and conventional triaxial tests of concrete with different microcapsule content. The result shows that when the uniaxial compressive loading reaches , a small number of microcracks start to appear, leading to the nonlinear behavior of the stress-strain curve. When the uniaxial compression is loaded near the peak point (), the internal cracks of the sample begin to increase sharply. Different from the crack of the sample in uniaxial compression concentrated in the interfacial transition zone, the crack of the sample in triaxial compression is scattered in the interior of the mortar and the interfacial transition zone, and the greater the confining pressure, the more crack in the mortar