潞安矿区煤田钻井造浆土实验研究

针对潞安矿区煤田钻探造浆用土进行了室内实验测试与分析,通过造浆率的测试和造浆改性实验,得出其造浆率极低、利用常规的方法不能调节现场造浆土造浆性能的结论;实验研究了现场造浆土的矿物成分、粒度成分及其造浆后的失水量、胶体率和比重,得出现场土不适合作为泥浆造浆用土,进而对潞安矿区煤田钻孔造浆土进行了推荐。     

The effect of anode bed geometry on the hydraulic behaviour of PEM fuel cells

The influence of the anode bed geometry on the hydraulic behaviour of PEM fuel cells is assessed. Three basic geometrical patterns are studied, namely the interdigitated, the parallel and the serpentine ones, in their original, as well as in modified forms of them, in which their angles have been smoothed. Issues concerning the anode flow field of a fuel cell, the influence of the Reynolds number on pressure drop, the mass flowrate distribution along the anode bed channels and the residence time of the fluid inside the fuel cell are investigated. All different geometries are studied by means of 3D numerical flow simulations. The results indicate that the pressure drop, flowrate nonuniformity in bed channels and residence time increase as the flow Reynolds number increases. The effect of geometry smoothing on the results is also assessed.     

Microstructure and oxidation behaviour of Ir-rich Ir–Al binary alloys

In the current study, alloys of Ir–11Al, Ir–23Al, Ir–30Al, Ir–41Al and Ir–45Al (at.%) were prepared to investigate the microstructure and oxidation behaviour of Ir-rich Ir–Al alloys. Ir(Al)_ss and/or β-IrAl intermetallic phases were found to exist in the prepared alloys. During isothermal oxidation at 1100 °C, the Ir(Al)_ss and β-IrAl individually changed to porous and dense Al₂O₃. The microstructure of the oxide scale formed on Ir–23Al was similar to that of its former alloy which possessed a dendrite-like configuration. It was found that the mass change of Ir–45Al followed a parabolic law, showing the best oxidation resistance among the Ir–Al alloys.     

ZWB-10（6.3）kV线路无功功率自动补偿器的使用

采油二厂现有30条6 kV配电线路,每条线路的功率因数各不相同,有的达到标准,有的没有达到标准。众所周知,如果线路的功率因数低,就会造成线路电流增大,电能损耗增加,用电量也随之增加,电量的增加也就带来了企业成本的增加。因此,提高配电线路的功率因数是目前所有供电部门的一项非常重要的工作。     

The nanometre-scale physiology of bone: steric modelling and scanning transmission electron microscopy of collagen�Cmineral structure

The nanometre-scale structure of collagen and bioapatite within bone establishes bone''s physical properties, including strength and toughness. However, the nanostructural organization within bone is not well known and is debated. Widely accepted models hypothesize that apatite mineral (‘bioapatite’) is present predominantly inside collagen fibrils: in ‘gap channels’ between abutting collagen molecules, and in ‘intermolecular spaces’ between adjacent collagen molecules. However, recent studies report evidence of substantial extrafibrillar bioapatite, challenging this hypothesis. We studied the nanostructure of bioapatite and collagen in mouse bones by scanning transmission electron microscopy (STEM) using electron energy loss spectroscopy and high-angle annular dark-field imaging. Additionally, we developed a steric model to estimate the packing density of bioapatite within gap channels. Our steric model and STEM results constrain the fraction of total bioapatite in bone that is distributed within fibrils at less than or equal to 0.42 inside gap channels and less than or equal to 0.28 inside intermolecular overlap regions. Therefore, a significant fraction of bone''s bioapatite (greater than or equal to 0.3) must be external to the fibrils. Furthermore, we observe extrafibrillar bioapatite between non-mineralized collagen fibrils, suggesting that initial bioapatite nucleation and growth are not confined to the gap channels as hypothesized in some models. These results have important implications for the mechanics of partially mineralized and developing tissues.     

时尚风向标--游泳健身

游泳作为一项时尚的运动，对人们的身心健康有很大的益处。从游泳运动理论和实际练习等方面系统阐述了游泳健身，并指导人们用科学方法游泳健身。     

On electromagneto-thermoelastic plane waves under Green–Naghdi theory of thermoelasticity-II

The present work attempts to investigate the propagation of one-dimensional electromagneto-thermoelastic plane waves in an isotropic unbounded thermally and electrically conducting media with finite conductivity in the context of the theory of thermoelasticity of Green and Naghdi type-II. The heat conduction equation is affected with the Thomson coe?cient. Basic governing equations are modified by using Green–Naghdi theory of type-II. Our problem formulation derives two different systems. The first system is found to be coupled with the thermal field and represents the longitudinal wave. However, the second system represents transverse wave that is uncoupled with the thermal field. In both the cases, we identify waves that are affected with the magnetic field. Asymptotic expansions of dispersion relation solutions and various components of plane waves such as phase velocity, specific loss, and penetration depth are derived analytically for high- and low-frequency values in all cases. Analytical results predicting the limiting behavior of longitudinal and transverse waves are verified with the numerical results. The results of the present study are compared with the results of the thermoelastic case, and a detailed analysis of the effects of presence of the magnetic field under this theory has been presented.     

Packet loss visibility across SD,HD, 3D,and UHD video streams

The trend towards video streaming with increased spatial resolutions and dimensions, SD, HD, 3D, and 4kUHD, even for portable devices has important implications for displayed video quality. There is an interplay between packetization, packet loss visibility, choice of codec, and viewing conditions, which implies that prior studies at lower resolutions may not be as relevant. This paper presents two sets of experiments, the one at a Variable BitRate (VBR) and the other at a Constant BitRate (CBR), which highlight different aspects of the interpretation. The latter experiments also compare and contrast encoding with either an H.264 or an High Efficiency Video Coding (HEVC) codec, with all results recorded as objective Mean Opinion Score (MOS). The video quality assessments will be of interest to those considering: the bitrates and expected quality in error-prone environments; or, in fact, whether to use a reliable transport protocol to prevent all errors, at a cost in jitter and latency, rather than tolerate low levels of packet errors.     

Automatic measurement and warning of tension force reduction in a PT tendon using eddy current sensing

Post-tensioning (PT) using a bundle of pre-stressed strands is a critical process for assembling pre-fabricated and modularized bridge members. However, the tension force gradually diminishes over time due to such factors as corrosion, creep, and steel relaxation. Such changes compromise the overall safety of such structures. In this study, an eddy-current-based tension-force-loss warning (EC-TFLW) technique is proposed to detect and warn automatically of excessive loss of tension force in a PT tendon. A ring-type eddy-current sensor (ECS) is mounted on the outer surface of a wedge holding a tendon, and the level of eddy current measured by the ECS is related to the tension force of the tendon. The advantages of the proposed technique include: (1) low power consumption, (2) low cost, (3) simple installation, and (4) automated warning. The performance of the proposed EC-TFLW technique was validated experimentally in a full-scale lab test of a 3.3-m long, 15.2-mm diameter, mono-strand tendon that was tensioned using a universal testing machine (from 20 to 180 kN). Statistical hypothesis testing using the chi-square distribution was applied to the measured eddy current signals, and if the decline in tension exceeded a certain level, a warning was sent out automatically.