The experimental study on vibration characteristics of high-speed turbine generator bearing rotor system

This study investigates the effect of gas supply pressure on power frequency amplitude, critical speed of rotation, whirl frequency and its corresponding power frequency, as well as on whip frequency and its corresponding power frequency on the basis of a high-speed turbine generator bearing-rotor system supported by a gas bearing and with changes in bearing gas supply pressure. Experimental results show that the optimization of gas supply pressure will reduce power frequency amplitude, improve critical speed, and delay the occurrence of whirl and whip. Under these conditions, the stability of the bearing-rotor system is improved, thus providing an experiment basis for the on-line monitoring and control of high-speed turbine generator operation

Stability Assessment of the PET-Based Distributed Grid

The penetration of renewables has been increasing nowadays. The traditional transformer can no longer meet the requirements of utilities. For this reason, a power electronic transformer (PET) is proposed as one of the promising alternatives. However, there are coupling issues between the PET and the connected converters in the low-voltage grid. To study the issues effectively, this article developed impedance models of the PQ node, PV node, and PET. Based on the models, the system stability under different scenarios is assessed by the generalized Nyquist criterion. The effects of the line impedance and control parameters on system stability are studied. Moreover, a comprehensive parameter sensitivity analysis was carried out to reveal the coupling mechanism between converters. Simulations are given to validate the effectiveness of the theoretical analyses

Protein Hydrogel Microbeads for Selective Uranium Mining from Seawater

Practical methods for oceanic uranium extraction have yet to be developed in order to tap into the vast uranium reserve in the ocean as an alternative energy. Here we present a protein hydrogel system containing a network of recently engineered super uranyl binding proteins (SUPs) that is assembled through thiol-maleimide click chemistry under mild conditions. Monodisperse SUP hydrogel microbeads fabricated by a microfluidic device further enable uranyl (UO₂²⁺) enrichment from natural seawater with great efficiency (enrichment index, <i>K</i> = 2.5 × 10³) and selectivity. Our results demonstrate the feasibility of using protein hydrogels to extract uranium from the ocean

Shore Power Optimal Scheduling Based on Gridding of Hybrid Energy Supply System

In order to reduce the environmental pollution near the port and save the cost of power supply, it is necessary to use shore power technology to power the ships that dock. This paper studies a power distribution strategy based on hybrid energy supply system. Through the establishment of wind power generation subsystem, photovoltaic power generation subsystem, and then combined with the national grid system to form a hybrid energy onshore power supply system, using the hybrid energy power supply system to power the ship. Without considering the power connection device, the whole shore power system was gridding processing. The objective function is established with the lowest cost of power supply system, and the grid node coefficient is calculated with different optimization algorithms to realize power distribution of port shore power supply system. The results showed that the power supply cost of the hybrid power supply system obtained by genetic algorithm (GA) and particle swarm optimization algorithm (PSO) is lower than the traditional power supply cost, and the power distribution is realized according to the distribution node coefficient. It provides a theoretical basis and application reference for the optimization scheme of energy management combined with port power and distributed power supply and the construction and management of new shore power

Study on Roof-Coal Caving Characteristics with Complicated Structure by Fully Mechanized Caving Mining

With mining technology and mechanization degree being improving, fully mechanized caving mining technology (FCM) has become a main method for thick coal seam extraction in China. However, roof-coal caving characteristics in turn restrict its recovery efficiency, especially for the coal seam with complicated structure (CCS), that is, the coal seam comprises hard or soft coal and gangue. In order to explore the key factors influencing the roof-coal caving and recovery characteristics, related research work has been conducted as follows: firstly, a mechanical model of CCS has been established, which indicates the strength of the coal and gangue will directly affect the roof-coal recovery. Meanwhile, based on the geological settings of Qinyuan coal mine, numerical simulation on roof-coal caving law under different thicknesses of hard or soft coal and gangue has been performed using UDEC software. The results show that the maximum principal stress will increase with the increase of mining depth, making the roof-coal to break easily. Furthermore, the range of the plastic zone of the top coal and the damage degree of the top coal increase with the increase of mining depth. Physical modeling results show that when an extraction-caving ratio is 1, the number of times the coal arch forms is 0.43 at every caving, up to a maximum of 3; the number of times coal arch forms with an extraction-caving ratio of 2 is 4.65 times larger than that with an extraction-caving ratio of 1. The probability of coal arch formation with an extraction-caving ratio of 3 is minimal, about 0.4, which is due to that the arch span is large and the curvature is small, so it is difficult to form a stable arch structure. According to the mechanical characteristics of roof-coal in Qinyuan coal mine, deep-hole blasting technique has been used to reduce the fragments of roof-coal crushed. The results show that this technique can effectively improve the recovery of roof-coal

Versatile Engineered Protein Hydrogels Enabling Decoupled Mechanical and Biochemical Tuning for Cell Adhesion and Neurite Growth

Development of engineered protein materials with wide-ranging mechanical strength and stiffness while maintaining the biofunctionality of protein molecules within remains a big challenge. Here we demonstrate the synthesis of protein hydrogels by photochemically cross-linking recombinant mussel foot protein-3 (Mfp3). The hydrogels’ stiffness can be broadly tuned by adjusting the concentration of protein polymers or co-oxidants, or light intensity needed for the chemical cross-linking. The protein polymers were also designed to contain SpyCatcher domains, which enabled postgelation decoration with diverse folded globular proteins under mild physiological conditions. Not only did the resulting hydrogels support the adhesion and proliferation of a variety of cell lines, but they were also able to activate the JAK/STAT3 pathway and induce neurite growth via the covalently immobilized leukemia inhibitory factor (LIF). These results illustrate a new strategy for designing bioactive materials for regenerative neurobiology

B₁₂-Dependent Protein Oligomerization Facilitates Layer-by-Layer Growth of Photo/Thermal Responsive Nanofilms

We report the robust growth of an entirely protein-based, photo- and thermoresponsive Layer-by-Layer nanofilm using genetically encoded SpyTag/SpyCatcher chemistry. The process was facilitated by AdoB₁₂-induced tetramerization of photoreceptor proteins. Protein cargos can be released from the film in a light-dependent manner, showing its potential for therapeutic protein delivery

Effect of Tool Coatings on Machining Properties of Compacted Graphite Iron

Compacted graphite iron (CGI) has become the most ideal material for automotive engine manufacturing owing to its excellent mechanical properties. However, tools are severely worn during processing, considerably shortening their lifespan. In this study, we prepared a series of cemented carbide-coated tools and evaluated their coating properties in cutting tests. Among all tested coatings, PVD coating made of AlCrN (AC) presented with the best surface integrity and mechanical properties, achieving the best comprehensive performance in the coating test. The AC-coated tool also exhibited the best cutting performance at a low speed of 120 m/min, corresponding to a 60% longer cutting life and the lowest workpiece surface roughness relative to other coated tools. In the cutting test at a high speed of 350 m/min, the CVD double-layer coated tool (MT) with a TiCN inner layer of and an Al2O3 outer layer had a 70% longer cutting life and the lowest workpiece surface roughness relative to other coated tools