A Conformable High Temperature Nitride Coating for Ti Alloys

There are many applications including aeroengine design where one would like to operate Ti or its alloys at higher temperatures, but the threat of oxidation or fire remains a longstanding challenge. Here, we have designed a bilayer nitride coating for Ti and its alloys produced by magnetron sputter deposition of a SiAlN coating (1.2 μm thick) with a Mo interlayer. We have taken advantage of interdiffusion and inter-reaction at the interface during cyclic oxidation at 800°C to form a layered nitride coating system comprising: a SiAlN top layer, a TiN0.26 and Ti5Si3 mixed phase interlayer, and a Ti-Mo solid solution. The novel TiN0.26 interlayer exhibits adaptive conformability via mechanical twinning, thereby accommodating the thermal mismatch strain between the coating and substrate. This, along with high adhesion, confers excellent thermal cycling life with no cracking, spallation and oxidation of the coating evident after hundreds of hours of cyclic oxidation (>40 cycles) in air at 800°C. This work provides a design pathway for a new family of coatings displaying excellent adhesion, adaptive conformability and superior environmental protection for Ti alloys at high temperature

Sciences for The 2.5-meter Wide Field Survey Telescope (WFST)

The Wide Field Survey Telescope (WFST) is a dedicated photometric survey facility under construction jointly by the University of Science and Technology of China and Purple Mountain Observatory. It is equipped with a primary mirror of 2.5m in diameter, an active optical system, and a mosaic CCD camera of 0.73 Gpix on the main focus plane to achieve high-quality imaging over a field of view of 6.5 square degrees. The installation of WFST in the Lenghu observing site is planned to happen in the summer of 2023, and the operation is scheduled to commence within three months afterward. WFST will scan the northern sky in four optical bands (u, g, r, and i) at cadences from hourly/daily to semi-weekly in the deep high-cadence survey (DHS) and the wide field survey (WFS) programs, respectively. WFS reaches a depth of 22.27, 23.32, 22.84, and 22.31 in AB magnitudes in a nominal 30-second exposure in the four bands during a photometric night, respectively, enabling us to search tremendous amount of transients in the low-z universe and systematically investigate the variability of Galactic and extragalactic objects. Intranight 90s exposures as deep as 23 and 24 mag in u and g bands via DHS provide a unique opportunity to facilitate explorations of energetic transients in demand for high sensitivity, including the electromagnetic counterparts of gravitational-wave events detected by the second/third-generation GW detectors, supernovae within a few hours of their explosions, tidal disruption events and luminous fast optical transients even beyond a redshift of 1. Meanwhile, the final 6-year co-added images, anticipated to reach g about 25.5 mag in WFS or even deeper by 1.5 mag in DHS, will be of significant value to general Galactic and extragalactic sciences. The highly uniform legacy surveys of WFST will also serve as an indispensable complement to those of LSST which monitors the southern sky.Comment: 46 pages, submitted to SCMP

中国人色素性乾皮症患者の遺伝的相補性群の解析

京都大学0048新制・課程博士博士(医学)甲第7732号医博第2085号新制||医||708(附属図書館)UT51-99-G326京都大学大学院医学研究科生理系専攻(主査)教授 宮地 良樹, 教授 佐々木 正夫, 教授 池永 満生学位規則第4条第1項該当Doctor of Medical ScienceKyoto UniversityDA

Nest-Like MnO2 Nanowire/Hierarchical Porous Carbon Composite for High-Performance Supercapacitor from Oily Sludge

In the aim to go beyond the performance tradeoffs of classic electric double-layer capacitance and pseudo-capacitance, composites made out of carbon and pseudo-capacitive materials have been a hot-spot strategy. In this paper, a nest-like MnO2 nanowire/hierarchical porous carbon (HPC) composite (MPC) was successfully fabricated by a controllable in situ chemical co-precipitation method from oily sludge waste. Due to the advantages of high surface area and fast charge transfer for HPC as well as the large pseudo-capacitance for MnO2 nanowires, the as-prepared MPC has good capacitance performance with a specific capacitance of 437.9 F g−1 at 0.5 A g−1, favorable rate capability of 79.2% retention at 20 A g−1, and long-term cycle stability of 78.5% retention after 5000 cycles at 5 A g−1. Meanwhile, an asymmetric supercapacitor (ASC) was assembled using MPC as the cathode while HPC was the anode, which exhibits a superior energy density of 58.67 W h kg−1 at the corresponding power density of 498.8 W kg−1. These extraordinary electrochemical properties highlight the prospect of our waste-derived composites electrode material to replace conventional electrode materials for a high-performance supercapacitor

Microsoft Word - 21410_0_art_file_1_1139507572.doc

Abstract This paper investigates the potential of various approaches for improving sweep in parts of the Daqing Oil Field that have been EOR targets. Possibilities included (1) gel treatments that are directed at channeling through fractures, (2) colloidal dispersion gels, (3) reduced polymer degradation, (4) more viscous polymer solutions, and (5) foams and other methods. Our studies indicated that the polymer flood should have provided excellent sweep throughout the vast majority of the patterns under consideration. However, since ASP flooding is being considered to increase recovery efficiency from the Daqing Oil Field, mobility control and sweep improvement will be especially important and challenging during implementation of any future ASP process. Fractures were present in a number of Daqing wells (both injectors and producers). Because the fractures were narrow far from the wellbore, severe channeling did not occur. On the contrary, fractures near the wellbore aided reservoir sweep. These near-wellbore fractures substantially increased the injectivity index during injection of polymer solutions and increased oil productivity index in the production wells. These observations may be valuable during implementation of future floods where very low-mobility chemical (i.e., ASP) banks must be injected to maintain mobility control. Several modes of polymer degradation were considered, with mechanical (shear) degradation being of most concern. Appropriate use of near-wellbore fractures may effectively mitigate mechanical degradation, as well as improving injectivity. Several new polymers show potential for cost-effective improvements at Daqing. Increased polymer concentration was also considered. A number of other approaches are (or have been) under investigation, including colloidal dispersion gels, foams, ASP foams, steam, microbes, and polymer solutions prepared with reduced salinity. Introduction Laboratory research began in the 1960s, investigating the potential of enhanced oil recovery (EOR) processes in the Daqing Oil Field. Use of polymer flooding was identified as a key method to improve areal and vertical sweep efficiency, as well as providing mobility control. 1 Consequently, the world's largest polymer flood was implemented at Daqing, beginning in 1996. 2,3 By 2004, 22.7% of total production from the Daqing Oil Field was attributed to polymer flooding. Polymer flooding should boost the ultimate recovery for the field to over 50% original oil in place (OOIP)-10% OOIP more than from waterflooding. Alkaline/surfactant/polymer flooding (ASP) has also experienced extensive laboratory testing in China. The ASP technique was gradually perfected for application at Daqing and has been pilot tested on a large scale. Although field tests of polymer and ASP flooding have been very successful at Daqing, concerns about sweep efficiency persist-particularly the possibility of channeling expensive chemical formulations through the reservoir. Therefore, the sweep efficiency at Daqing is receiving intense scrutiny, and possibilities for improvement are being considered. In this paper, we examine the nature of reservoir sweep in parts of the Daqing Oil Field that have been EOR targets. We investigate the potential of various approaches for improving sweep, including (1) gel treatments that are directed at channeling through fractures, (2) colloidal dispersion gels, (3) reduced polymer degradation, (4) more viscous polymer solutions, and (5) foams and other methods (e.g., thermal and microbial techniques). Our objective is to establish better options for improving sweep in the main producing zone in the future. Sweep Efficiency in the Daqing Oil Field Stratification. What is the nature of the sweep efficiency problem at Daqing? This study focused on the Eastern Berxi polymer flooding area of the Daqing field-specifically on 17 production wells and 8 injection wells. Layer PI, a principal target for EOR at Daqing, is composed of up to seven named "zones." The gross pay for Layer PI varied between 18 and 33 SPE 9944

Stress–Strain Properties and Gas Permeability Evolution of Hybrid Fiber Engineered Cementitious Composites in the Process of Compression

Polyvinyl alcohol (PVA)-steel hybrid fiber reinforced engineered cementitious composites (ECC) characterized by optimal combination of high strength and high ductility were developed recently. These composites exhibit even tighter crack width than normal ECC, showing great potential for lower permeability in cracked state, and consequently improving the durability of ECC structures. In addition, the wide variety of promising applications in underground or hydraulic structures calls for knowledge on the mechanical behavior and corresponding permeability properties of strained ECC under multiaxial stress, as they are essential for structural analysis and durability design. Experimental investigations into the compressive properties and the in-situ gas permeability of PVA-steel hybrid fiber ECC were performed in this study, with special focus on the impact of additional steel fiber content and confining pressure. The test results show that the presence of a low confinement level allows ECC to attain a substantial improvement on compressive behavior but impairs the enhancement efficiency of additional steel fiber. The permeability evolution of strained ECC corresponds to the variation of radial strains, both of which experience little change below the threshold stress but a rapid increase beyond the peak axial strain. Apart from exhibiting low permeability at relatively small strains in the pre-peak stage, ECC can also exhibit low permeability at higher levels of compressive strain up to 2.0%. However, unlike the case in tensile loading, impermeability of cracked ECC in compression would be weakened by additional steel fibers, especially in the post-peak stage. The present research is expected to provide insight into performance-based durability design of structures made of or strengthened with ECC

Effects of rare earth addition and service mode on surface integrity evolution of high-end machine tool spindle bearings under service

Machine tool spindle bearings used as supporting rotator parts play a very important role in machining industry. Keeping a good surface integrity is crucial to the long-time and high-efficiency work of the bearings. To find out the crucial factors for bearing failure, surface integrity evolutions on machine tool spindle bearings made from a normal bearing steel and a newly developed rare-earth-addition bearing steel were compared after benchtop tests in this work. Furthermore, surface integrity evolutions on bearings were analyzed under field service with more complex service conditions. The results show that the surface integrity changes under both benchtop testing and filed service, while the surface damages and changes in surface integrity on the inner rings are more significant than those on the outer rings. Meanwhile, the surface damage modes are mainly scratches and impressions on the benchtop bearings, while surface rolling contact fatigue predominates the damages on the field bearings. Furthermore, the addition of rare earth elements in bearing steels transfers the crack initiation mode from inclusion initiated to martensite initiated under service, possibly resulting in a higher stability of accuracy and longer life for bearings