Toward Long-Term Sailing Robots: State of the Art From Energy Perspectives

Sailing robots can contribute significantly to maritime surface exploration, due to its potential for long-range and long-duration motions in the environment with abundant wind. However, energy, the critical factor for their long-term missions, shall be carefully investigated, so as to achieve sustainability in distance and time. In this survey, we have conducted a comprehensive investigation on numerous sailing robots, developed in academia and industry. Some of them have achieved long-term operation, and some are motivated by, but still on the way to this ambitious goal. Prototypes are grouped in each team, so as to view the development path. We further investigate the existing design and control strategies for energy sufficiency from three perspectives: actuation, harvesting, and energy management. In propulsion and steering, i.e., two major actuations, researchers have accumulated effective sail and rudder designs. The motorized propeller and wave-glider–inspired mechanism also contribute as compliments for propulsion. Electricity harvesting based on solar or wind energies is also discussed to gather more power from nature. Pros and cons in strategies of energy management, which are valuable tools to enhance power utilization efficiency, are elaborated. This article is hoped to provide researchers in long-term robotic sailing with a comprehensive reference from the perspectives of energy.

Influence of Particle Size of River Sand on the Decontamination Process in the Slow Sand Filter Treatment of Micro-Polluted Water

Slow sand filters (SSFs) have been widely used in the construction of water plants in rural areas. It is necessary to find river sand of suitable particle size to improve SSF treatment of micro-polluted water so as to ensure the effective and long-term operation of these plants. In this study, SSF1# (particle size of 0.1–0.5 mm), SSF2# (particle size of 0.5–1 mm), and SSF3# (particle size of 1–1.5 mm) were selected. The physical absorption, CODMn and NH4+-N removal effect, and microbial community were analyzed. According to Langmuir and Freundlich adsorption model fitting, the smaller the particle size of the river sand, the more pollutants are adsorbed under the same conditions. SSF1# has the shortest membrane-forming time, highest CODMn and NH4+-N removal rate, and highest Shannon estimator, indicating that there are more abundant microbial species in the biofilm. Mesorhizobium, Pannonibacter, Pseudoxanthomonas, Aquabacterium, Devosia, and other bacteria have different proportions in each system, each forming its own stable biological chain system. The effluent quality of the three SSFs can meet drinking water standards. However, river sand with a particle size range of 0.1–0.5 mm is easily blocked, and thus the recommended size range for SSF is 0.5–1 mm.

Method of Selecting Energy-Efficient Parameters of an Electric Asynchronous Traction Motor for Diesel Shunting Locomotives—Case Study on the Example of a Locomotive Series ChME3 (ЧMЭ3, ČME3, ČKD S200)

One of the assumptions made during the modernization process of diesel shunting locomotives is the replacement of a diesel traction motor with a DC generator with an electric asynchronous traction motor. The article aimed to develop a method of selecting energy-efficient parameters of an asynchronous electric traction motor for diesel shunting locomotives, which will ensure that its operating energy efficiency will be as high as possible. The method was verified on the example of a locomotive series ChME3 (ЧMЭ3, ČME3, ČKD S200). It has been found that using a traction asynchronous electric drive on a ChME3 locomotive, its efficiency increases in comparison with DC electric motors by 3–5% under the long-term operation modes and by 7–10% during locomotive operation with traction at the adhesion limit. Using a new traction gearbox with a higher gear ratio expands the speed range in which the asynchronous traction drive operates with a high-efficiency factor. It is effective to use a traction asynchronous electric drive to modernize ChME3 diesel locomotives in case of their use under the modes requiring the implementation of maximum traction forces at low speeds. A further increase in the efficiency of the traction asynchronous electric drive is possible based on the optimal design of the wheel-motor unit and the asynchronous traction electric drive.

Bifunctional manganese oxide–silver nanocomposites anchored on graphitic mesoporous carbon to promote oxygen reduction and inhibit cathodic biofilm growth for long-term operation of microbial fuel cells fed with sewage

Manganese oxide–silver nanocomposites anchored on graphitic mesoporous carbon were synthesized for enhancing oxygen reduction and inhibiting cathodic biofilm growth for the long-term operation of microbial fuel cells.

Localization of Plastic Deformation in the Copper and Stainless Steels Samples, Irradiated with Neutrons

The reduction of ductility of austenitic stainless steels as a result of long-term operation in the nuclear reactor core is an important problem of modern radiation materials science. Understanding the mechanisms of the effect of neutron irradiation on the mechanical properties of austenitic steels is impossible without research of localization processes occurring during the deformation. In this paper, it was found that the value of the true local deformation corresponding to the onset of neck formation in face-centered cubic structured metals decreases with an increase in the radiation dose, while the true stress remains almost constant. Additional hardening of AISI 304 steel due to the intensive formation of the martensitic α’-phase increases not only the stress at which a neck is formed in this alloy, but also the true local deformation. As a result, the uniform elongation increases and remains high after neutron irradiation to 0.05 dpa. The forehanded formation of the martensitic α’-phase in sufficient quantity before the necking onset can be considered as an additional deformation mechanism that will increase the ability of the material to deform uniformly.

NITRO CELLULOSE POWDER CHARGES OF LONG SERVICE LIFE: PROBLEMS AND THEIR POSSIBLE SOLUTIONS

One of the components of the problem of Ukraine's national security is the loading of warehouses with a variety of ammunition with an expired guaranteed storage period. The experience of storing ammunition shows that during long-term storage, propylene powder used in ammunition is capable of spontaneously undergoing various physical and chemical transformations, which negatively affects the ballistic characteristics of ammunition. The lack of ammunition production in Ukraine has led to the fact that ammunition is currently in operation, the storage time of which reaches 25-30 years or more. This article analyzes publications devoted to scientific research related to the problems of ballistic stability of propellants. A number of factors are presented that affect the physicochemical stability of powder charges during their long-term operation. The generalizing data on changes in the main ballistic characteristics of ammunition at different periods of their storage are presented. It is assumed that one of the ways to improve the ballistic and energy characteristics of ammunition with long service lives can be the regeneration of nitrocellulose powder charges. It is shown that at present there are no methods for the regeneration of propellant charges of long service life. However, there are encouraging data on the treatment of propellants with hydrogen peroxide, on the basis of which a technology can be developed for the complete or partial restoration of the ballistic and energy characteristics of the propellant charge. It is presented that the predictive assessment of changes in the characteristics of ammunition with long service lives does not correspond to their real indicators. It has been determined that the problem of nitrocellulose propellants of long service life is complex and, on the basis of its solution, theoretical and methodological foundations of the regeneration of nitrocellulose propellant charges can be developed to homologate the ballistic and energy characteristics of ammunition.

Experiences in long-term operation of a green hydrogen production plant using wind power in Germany - a possible model for Vietnam

Hydrogen is considered as "the green fuel of the 21st century" and forecasted to play a leading role in the energy transition. The article introduces the processes of green hydrogen production in Energiepark Mainz, the first wind power hydrogen production plant with a capacity of 6 MW in Germany. The article describes the production, storage, transportation, and consumption (gas, fuel for bus and industries) of green hydrogen through the continuous operation of the plant. Based on that, the author analyses opportunities and challenges when applying Energiepark Mainz's model to the green hydrogen production strategy in Vietnam.

Towards dynamic property control of bridge spans

Regulation of the dynamic properties of bridge spans is a priority field of this research, which solves the problem of increasing the obsolescence and physical periods of bridge structures manifested both at the design stage of the load redistribution in the load bearing and during long-term operation.Over the past 40 years, technical bridge diagnostics has shown that the durability and safe long-term operation can be ensured by the improved calculations, operation and stress and strain control under the excess and over-calculated live loads.The aim of this work is to control the dynamic deformation and amplitude-frequency characteristics of bridge spans under harmonic random (non-stationary) oscillations of the span-vehicle system due to changes in the energy and stress state of the structure. The dynamic behavior of the span-vehicle system is based on the control for the amplitude-frequency characteristics of random oscillations by averaged values, the required spectral density being provided.The use of dynamic dampers for the system element control and the rigidity of junctions provide antiphase oscillations of the bridge span elements such as beams and decks, that leads to the unaccounted inertial forces.Another important element of the joint work imbalance of the bridge span elements during the dynamic load, are various defects, both in the deck design and load-bearing elements. It is assumed that the deck is a transfer layer (element) of vibrations induced by a vehicle in the beams. It is shown that the control for the dynamic properties is required in the case of a coincidence between the vehicle and beam stiffness and mass at the center of the system rigidity.The attention is paid to the conditions and dependencies between the dynamic load parameters and the stress-strain state of the bridge beams at the elastic and elastoplastic stages, with respect to the additional inertia of the system. This approach is the pilot in the Russian and foreign bridge construction in terms of experimental studies and testing of bridges for continuous random traffic.The dynamic testing of bridge spans for random traffic flow contributes to the creation of vibration diagnostic express laboratories necessary for the operation and maintenance of bridges.