PMU measurements based short-term voltage stability assessment of power systems via deep transfer learning

Deep learning has emerged as an effective solution for addressing the challenges of short-term voltage stability assessment (STVSA) in power systems. However, existing deep learning-based STVSA approaches face limitations in adapting to topological changes, sample labeling, and handling small datasets. To overcome these challenges, this paper proposes a novel phasor measurement unit (PMU) measurements-based STVSA method by using deep transfer learning. The method leverages the real-time dynamic information captured by PMUs to create an initial dataset. It employs temporal ensembling for sample labeling and utilizes least squares generative adversarial networks (LSGAN) for data augmentation, enabling effective deep learning on small-scale datasets. Additionally, the method enhances adaptability to topological changes by exploring connections between different faults. Experimental results on the IEEE 39-bus test system demonstrate that the proposed method improves model evaluation accuracy by approximately 20% through transfer learning, exhibiting strong adaptability to topological changes. Leveraging the self-attention mechanism of the Transformer model, this approach offers significant advantages over shallow learning methods and other deep learning-based approaches.Comment: Accepted by IEEE Transactions on Instrumentation & Measuremen

From Federalism, Chinese Style to Privatization, Chinese style

In 1994 China began a profound reform of its state-owned enterprises. We first describe and characterize this progress in two areas: privatization of small state-owned enterprises at the county level and mass layoffs of excess state workers at the city level. Local governments have initiated these reforms, which are proceeding in economically and politically sensible ways. We then argue that privatization, Chinese style, rests on an adequate economic and political foundation - federalism, Chinese style. We suggest a range of incentives that propel local governments toward SOE reform, including their harder budget constraints and increased competition from the non-state sector. In this sense, federalism, Chinese style, has induced privatization, Chinese style.http://deepblue.lib.umich.edu/bitstream/2027.42/39516/3/wp126.pd

From Federalism, Chinese Style to Privatization, Chinese style

In 1994 China began a profound reform of its state-owned enterprises. We first describe and characterize this progress in two areas: privatization of small state-owned enterprises at the county level and mass layoffs of excess state workers at the city level. Local governments have initiated these reforms, which are proceeding in economically and politically sensible ways. We then argue that privatization, Chinese style, rests on an adequate economic and political foundation - federalism, Chinese style. We suggest a range of incentives that propel local governments toward SOE reform, including their harder budget constraints and increased competition from the non-state sector. In this sense, federalism, Chinese style, has induced privatization, Chinese style.privatization, restructuring, federalism, local governments, China

Multi-nanolayered VO2/Sapphire Thin Film via Spinodal Decomposition

Abstract Coating of VO2-based thin film has been extensively studied for fabricating energy-saving smart windows. One of the most efficient ways for fabricating high performance films is to create multi-nanolayered structure. However, it has been highly challenge to make such layers in the VO2-based films using conventional methods. In this work, a facile two-step approach is established to fabricate multilayered VO2-TiO2 thin films. We first deposited the amorphous thin films upon sputtering, and then anneal them to transform the amorphous phase into alternating Ti- and V-rich multilayered nanostructure via a spinodal decomposition mechanism. In particular, we take advantage of different sapphire substrate planes (A-plane (11–20), R-plane (1–102), C-plane (0001), and M-plane (10-10)) to achieve different decomposition modes. The new approach has made it possible to tailoring the microstructure of the thin films for optimized performances by controlling the disorder-order transition in terms of both kinetic and thermodynamic aspects. The derived thin films exhibit superior optical modulation upon phase transition, significantly reduced transition temperature and hysteresis loop width, and high degradation resistance, these improvements indicate a high potential to be used for fabricating the next generation of energy saving smart windows

Phase behavior and hydrocarbons distribution in shale oil during EOR with nano-confinement effect

The pore structure of shale reservoirs leads to the complex phase behavior of shale reservoir fluids, which is aggravated due to changes in fluid composition during reservoir development. Effective prediction of changes in the phase behavior of fluids in shale reservoirs is important. This paper proposes a pore-size-dependent Peng-Robinson equation of state (PR-EOS) to describe phase behavior in nanopores. The approach considers the shift of critical parameters and the gas-liquid capillary pressure and compiles by MATLAB. The verification of the model is satisfying by matching the result with Tnavigator PVTi using the published date. The results show that fluids in nanoscale pores are more likely to exhibit near-critical or condensate states. We also compare the changes in phase behavior when fluids dissolve CO2 and CH4 and observe the phase transition (from gaseous to liquid phase) of the lighter crude oil sample that dissolved more gas during the differential liberation experiment (DL). Finally, we use CO2 pre-pad energized fracturing of a shale oil reservoir in northern China as an example to explain abnormal production performances, such as a majority of light hydrocarbons in the produced fluid of the well during the flow back stage, single gas phase production in the early production stage, and stable gas/oil ratio (GOR) in the process of development. Our novel methodology and phase behavior change mechanism can enhance our understanding of the phase behavior of fluids in shale oil reservoirs during enhanced oil recovery

Water Promotes Melting of a Metal–Organic Framework

Water is one of the most reactive and abundant molecules on Earth, and it is thus crucial to understand its reactivity with various material families. One of the big unknown questions is how water in liquid and vapor forms impact the fast-emerging class of metal–organic frameworks (MOFs). Here, we discover that high-pressure water vapor drastically modifies the structure and hence the dynamic, thermodynamic, and mechanical properties of MOF glasses. In detail, we find that an archetypical MOF (ZIF-62) is extremely sensitive to heat treatments performed at 460 °C and water vapor pressures up to ∼110 bar. Both the melting and glass transition temperatures decrease remarkably (by >100 °C), and simultaneously, hardness and Young’s modulus increase by up to 100% under very mild treatment conditions (<20 bar of hydrothermal pressure). Structural analyses suggest water to partially coordinate to Zn in the form of a hydroxide ion by replacing a bridging imidazolate-based linker. The work provides insight into the role of hot-compressed water in influencing the structure and properties of MOF glasses and opens a new route for systematically changing the thermodynamics and kinetics of MOF liquids and thus altering the thermal and mechanical properties of the resulting MOF glasses

Research and application on megawatt level intelligent fracturing pump system in coal mine

This paper presents the development of a megawatt-scale intelligent fracturing pump system for underground coal mines, designed to address the escalating demands for flow and pressure in large-scale regional fracturing applications, particularly in hard roof management and enhanced gas extraction permeability. The system integrates automatic control and variable frequency technology with the design of underground coal mine fracturing pumps, enabling dynamic collection of performance parameter data at various stages of hydraulic fracturing. It provides real-time analysis of the power matching for electrically driven fracturing pumps and achieves full automation of the fracturing process. Key technological challenges, such as the development of special materials for high-pressure, high-flow-rate fracturing pumps; the reliability of the transmission system and hydraulic ends for megawatt-level fracturing pumps; and intelligent control technology, have been successfully addressed. The research included: Development of high-strength, erosion-resistant martensitic precipitation hardening stainless steel suitable for extreme conditions with large flow, ultra-high pressure, and sand-mixed media, along with ultra-high pressure self-reinforcing treatment to enhance the fatigue life of the hydraulic ends of fracturing pumps; Investigation of critical reliability technologies, including high-strength welding for alloy steel, high-load-bearing, high-power-to-weight ratio gear transmission technology, and wear-resistant friction pairs of aluminum bronze alloy-cast iron, to ensure the reliability of the transmission system under high-power conditions; Creation of a high-durability metal plunger-combination seal fracturing fluid sealing pair, with the application of computer simulation technologies such as virtual prototyping, FEA, CFD, and hydraulic system simulation to optimize the structure, performance, and reliability of the fracturing pump’s fluid end suction and discharge systems; Mastery of technologies such as low-frequency variable flow sealing for deep boreholes, automatic identification of coal and rock layer fracturing, and cyclic fracturing control, enabling intelligent control throughout the fracturing process. The industrial trial of this system has been successfully conducted at the Caojiatan coal mine 122110 extra-thick coal mine working face for weak zone management of hard roof strata and at the Dongli coal mine 1250 gas control lane for high-efficiency extraction of anti-reflection gas in coal seam areas. Field tests demonstrated that at the Caojiatan coal mine, pre-splitting treatment for hard roofs achieved stable fracture expansion pressure with a maximum of 32.4 MPa and an average flow rate of 100 m3/h. At the Dongli Coal Mine, the gas permeability enhancement test revealed that after 10 days of hydraulic fracturing, the average pure gas extraction volume increased to 1.596 m3/min, approximately 29 times that of the conventional drilling extraction process