Enhanced tribological behaviors of sintered polycrystalline diamond by annealing treatment under humid condition

The tribological behaviors of the 700 °C annealed sintered polycrystalline diamond (PCD) at various relative humidity (RH) levels were systematically investigated. The comparison of tribological behaviors between the 700 °C annealed PCD and the pristine PCD was made to further understand the tribological mechanisms. The results reveal that the friction inducing carbonaceous transfer film and oxidation and hydrolysis induced tribochemistry reaction dominant the tribological behaviors of the annealed PCD at various RH levels. The low coefficient of friction (COF) obtained in dry environments is attributed to carbonaceous transfer film on the worn Si₃N₄ surface, which was formed by the layers shearing action of massive tiny diamond grains exfoliated from the annealed PCD surface. The graphitization, oxidation and stress relaxation of the PCD induced by the 700 °C annealing treatment make the tiny diamond grains more easily to exfoliate and be grinded on the Si₃N₄ interface. It facilitates the formation of friction reducing carbonaceous transfer film, and finally results in the 30% lower COFs than those of pristine PCD at low RH levels (5%–50% RH). Meanwhile, an enhanced wear resistance of PCD can be achieved after 700 °C annealing treatment. The tribochemistry reaction induced by the oxidation and hydrolysis of Si₃N₄ governs the tribological behaviors of the annealed PCD at high RH levels (60%–99.9% RH). It reveals higher COFs accompanied with serious wear of Si₃N₄ ball and nearly no wear loss of annealed PCD. The produced SiO₂ and silicic acid embeds into massive spalling pits on the annealed PCD surface, resulting in slighter wear of the PCD and Si₃N₄ than that of the pristine PCD/Si₃N₄. These results propose that the tribological behaviors of PCD under humid environment can be significantly improved by the 700 °C annealing treatment.     

Experimental investigation on gasification characteristics of polycarbonate (PC) microplastics in supercritical water

In order to solve the problem of marine microplastics and realize the harmless resource utilization of plastics, the gasification experiments of polycarbonate (PC) microplastics were carried out in supercritical water and a novel seawater gasification of microplastic experiment was investigated. In this paper, the effects of different operating conditions (temperature, time, feedstock concentration, pressure) on gasification performance were discussed. The gasification kinetic of microplastics in supercritical water was calculated. The experimental results showed that the increase in gasification temperature and time enhanced the cracking reaction and free radical reaction of the microplastics to increase the gasification efficiency, while the reduction in feedstock concentration improved the gasification efficiency by increasing the gasification level of unit feedstock. The change in pressure had no significant effect on gasification due to the fact that the properties of the supercritical water were not significantly changed. It was found that the valuable results that all alkali metal salts in seawater promote hydrogen conversion, while in terms of carbon conversion, only KCl, CaCl₂, NaHCO₃ and seawater had a significant catalytic effect on the gasification. Seawater gasification of microplastics was a potential resource utilization method. Finally, it was considered that the PC plastic gasification conformed to the random nucleation and subsequent growth model (n = 3), and the reaction activation energy was 230.45 kJ/mol, which was smaller than that of traditional pyrolysis.     

Smart firefighting construction in China: Status,problems, and reflections

“Smart firefighting” construction as a part of the “smart city” has been a concern of the public security and fire agencies at all levels. In this study, the status, problems, and reflections of “smart firefighting” construction in China are discussed. A recent survey indicates that China has launched its smart firefighting construction and initially created a new perspective on its regional smart firefighting work based on three main aspects: intelligent disaster perception by Internet of Things (IoT) construction, intelligent disaster prevention by big data construction, and intelligent disaster disposal by emergency rescue platform construction. However, the current smart firefighting construction in China still has some prominent problems such as the data interconnectivity and normalized management of various platforms, the extensibility of smart firefighting platforms, and the intelligent level of smart firefighting researches, which need to be solved urgently. Therefore, we argue that smart firefighting construction in China should establish data interconnectivity, industrial normalized management, 2D/3D geographic information interaction and extension, high-integration fire protection theory, and many other aspects in the near future and truly realize firefighting visualization and efficient data applications for 4D time space. This study could provide valuable reference for smart firefighting and smart city construction.     

A new method of predicting the saturation pressure of oil reservoir and its application

Saturation pressure is a vital parameter of oil reservoir which can reflect the oilfield characteristics and determine the oilfield development process, and it is determined by experiments in the laboratory in general. However, there was only one well with saturation pressure test in this target reservoir, and it is necessary to determine whether this parameter is right or not.In this work, we present a new method for quickly determining saturation pressure using machine learning algorithms, including random forest regressor (RF), support vector machine (SVM), decision trees (DT), and artificial neural network (ANN or NN). Using these approaches, saturation pressure was obtained by using the initial solution gas-oil ratio (GOR), temperature, API gravity and other reservoir-fluid data available in the oilfields. Compared with the empirical formula for saturation pressure calculation, the calculated result shows that the accuracy given from machine learning is higher than that from other formulas at home and abroad, and has a good match with the lab test. On the basis of the calculated saturation pressure, it can determine whether the reservoir enters into the stage of dissolved gas drive or not, which also provides the basis for maintaining the reservoir pressure by water injection in advance, rational development decision-making and work over measures.This approach above can provide technical guidance for predicting the saturation pressure in the development of different kinds of reservoirs, including the sandstone reservoirs and carbonate reservoirs.     

球化退火工艺对高碳马氏体不锈钢8Cr13MoV组织及性能的影响

为了优化高碳马氏体不锈钢8Cr13MoV的球化热处理工艺,提高其退火后的冷加工性能,采用微观组织分析法以及拉伸力学分析法研究了球化退火过程中奥氏体化保温时间和冷却速率对8Cr13MoV钢的球化效果影响。结果表明, 随着奥氏体保温时间的增加,组织中细颗粒状碳化物数量减少,索氏体数量增多,试样硬度先降低后升高,但断后伸长率持续增加;随冷却速率增加,试样组织中细颗粒状碳化物和索氏体数量、硬度和强度增加,断后伸长率降低。综合对比,奥氏体保温时间ϕ90 min时试样综合力学性能较好,冷却速率应控制在25 ℃·h^-1以内。与奥氏体保温时间相比,冷却速率对力学性能的影响更加显著。     

A novel fast distance relay for series compensated transmission lines

This paper presents a fast distance relay for series compensated transmission lines based on the R–L differential-equation algorithm using the theory of equal transfer process of transmission lines. The measuring distances based on the proposed algorithm can fast approach the actual value of fault distance when a fault occurs in front of the series capacitor. When a fault occurs behind of the series capacitor, the fault loop, including the series capacitor, does not match the R–L transmission line model, so the measuring distances fluctuate severely. Based on this, the relative position of the fault with respect to the series capacitor can be judged effectively according to the fluctuation range of the measuring distances, and the accurate fault location can be obtained fast. A variety of PSCAD/EMTDC simulation tests show that the new relay has fast operating speed and high accuracy when applied to the long series compensated transmission lines.     

Three Ln(III)-2,3,5-trichlorobenzoate coordination polymers (Ln = Tb,Ho and Er): Syntheses,structures and magnetic properties

Three novel lanthanide polymers, [Ln(III)(L)₃EtOH]_n (Ln = Tb(1), Ho(2), Er(3), HL = 2,3,5-trichlorobenzoic acid), have been solvothermal synthesized and characterized by single-crystal X-ray diffraction, infrared spectroscopy and element analyses. The three polymers crystallize in triclinic space group P-1. The Ln(III) ions are in turn bridged by double and quadruple carboxylate of L⁻ ligands to form one-dimensional (1D) chains. Magnetic studies reveal that polymer 1 demonstrates dominant ferromagnetic behavior, polymer 2 shows antiferromagnetic behavior, and polymer 3 present spin-canting behavior.     

Microstructure and mechanical properties of laser beam welded Al–Li alloy 2060 with Al–Mg filler wire

Alloy 2060-T8 is a newly developed high-strength Al–Li alloy for applications in aircraft industry. Crack-free welds were obtained in laser beam welding with 5087 filler wire under optimized welding conditions. In this paper, fusion zone microstructure and joint mechanical properties were investigated. Microstructure typical for the weld metal consists of α-Al matrix with a few nanoscale precipitates inside and a coarse icosahedral quasicrystalline T₂ phase at the dendritic and grain boundaries. The quasicrystalline occurred normally in Al–Li–Cu alloys with higher Li contents. Our investigations show that the icosahedral quasicrystalline phase T₂ phase forms in the laser-welded Al–Li alloy 2060 with lower Li content as a result of segregation and replacement of Mg element. The joint tensile strength in as-welded condition is around 317 MPa, about 63% of that of the base metal, and fracture occurs within the fusion zone.     

Next POI Recommendation Based on Location Interest Mining with Recurrent Neural Networks

Journal of Computer Science and Technology - In mobile social networks, next point-of-interest (POI) recommendation is a very important function that can provide personalized location-based...     

Mechanism of mid-spatial-frequency waviness removal by viscoelastic polishing tool

Nanoscale roughness with ultra-precise form control can be readily achieved using compliant finishing methods such as bonnet polishing. However, their weak point lies in the difficulty of removing mid-spatial-frequency (MSF) waviness in the typical range from 0.1 to 5.0 mm wavelength. To overcome this shortcoming, a bonnet tool filled with viscoelastic fluid is developed and a comprehensive model is established to disclose its distinct removal behavior in the MSF range. The model considers tool viscoelasticity, stress distribution and workpiece topography. Experiments show high consistency with theoretical predictions, and show that MSF waviness can be effectively reduced using the proposed method.