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排序方式: 共有2973条查询结果,搜索用时 140 毫秒
1.
Brian Lawn David Marshall Rishi Raj Greg Hirth Trevor Page Julie Yeomans 《Journal of the American Ceramic Society》2021,104(1):23-26
Crystalline quartz has long been identified as among the weakest of abundant crustal minerals. This weakness is particularly evident around the α–β phase inversion at 573°C, in which Si–O bonds undergo a displacive structural transformation from trigonal to hexagonal symmetry. Here we present data using indentation testing methodologies that highlight the precipitous extent of the transformational weakening. Although the indentations are localized over relatively small specimen contact areas, the data quantify the essential deformation and fracture properties of quartz in a predominantly (but not exclusively) compressive stress field, at temperatures and pressures pertinent to conditions in the earth's crust. 相似文献
2.
Novel core-shell-like Ni-supported hierarchical beta zeolite catalysts on bioethanol steam reforming
《International Journal of Hydrogen Energy》2020,45(33):16409-16420
Hierarchical-Beta zeolites have been hydrothermally synthesized by adding a new gemini organic surfactant. The used gemini surfactant play the role of a “pore-forming agents” on the mesoscale, on the same time, providing alkaline environment for the system. With this hierarchical Beta zeolite as the core support, we successfully prepared a shell layer of Ni-containing (22 wt%) petal-like core-shell-like catalyst and applied it to bioethanol steam reforming. At the reaction temperature of 350 °C–550 °C, the conversion rate of ethanol and the selectivity of hydrogen were always above 85% and 70%. After reaction of 100 h on stream at 400 °C, there were not obvious inactivation could be observed on NiNPs/OH-MBeta catalyst. 相似文献
3.
Ruthenium colloidal particles prepared by the decomposition of a ruthenium acid sulfite complex increased the electrochemical reduction of benzene from 45% to 60% at room temperature and 10 psig of hydrogen. The reduction was carried out in a 21 mole % ethanol - 79 mole % hexamethylphosporamide. The significant increase in the percent of benzene reduced was accompanied by an apparent current efficiency of 98%. Comparison with analogous experiments employing colloidal platinum particles indicates that the above increase in benzene reduction can be attributed to direct catalytic hydrogenation by the ruthenium. 相似文献
4.
M. Loidl E. Leblanc T. Branger H. Rotzinger T. Daniyarov M. Linck A. Fleischmann C. Enss 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2004,520(1-3):73-75
We report on a feasibility study on precise determination of mass-specific activity of low-energy emitting radioisotopes. Conventional methods of activity measurement suffer from source self-absorption and a strong decrease in detection efficiency for low-energy electrons and photons. We propose a new method based on metallic magnetic microcalorimeters with the source embedded in the detector target in a 4π geometry. First results with a 55Fe source show that electrons and photons are detected with a detection efficiency close to unity and with little loss of energy for electrons. The aim of this study is to provide standards of activity with very low uncertainties in the framework of radiation metrology. 相似文献
5.
We have perforated a series of experiments to study cavitation in superfluid helium into which electrons are injected by field-emission from a sharp tip. The injected electrons force open small cavities in the liquid (“electron bubble”). These objects explode at a critical negative pressure P c, and in previous experiments we have studied the cavitation that resugts from these explosions. In the present experiments we have detected cavitation events that occur before a negative pressure as large as P c is reached. We suggest that these events may arise from a process in which two neutral helium dimers interact and an electron is injected into the liquid through Penning ionization. 相似文献
6.
Influence of coal forced oxidation on technological properties of cokes produced at laboratory scale
《Fuel Processing Technology》2005,87(1):1-10
The effect of coal oxidation in air at 140 °C on the technological properties of cokes obtained at laboratory scale from two medium volatile bituminous coals has been studied. The proximate and ultimate analyses do not show important changes with coal oxidation time. However oxidation clearly has a strong effect on the plastic properties of the coals in view of the fact that the Gieseler fluidity eventually disappears. From this point variations in plastic properties can still be detected by FSI. Other changes, such as a shortening of the length of the saturated fragments of the aliphatic chains, a decrease in the aliphatic hydrogen content and an increase in the oxygen-containing groups are detected by PA-FTIR. It was also found that the main coke quality indices (mechanical strength and reactivity to CO2) of both coke series are impaired with coal oxidation. A close relationship between reactivity to CO2 and the micropore specific surface area of the cokes has been corroborated. 相似文献
7.
8.
Although thoracoabdominal injuries are uncommon in the athlete, they can be catastrophic if unrecognized or if diagnosis and treatment are delayed. This article reviews thoracic, intrathoracic, abdominal, and groin injuries in the athlete, and how they can be diagnosed and managed. 相似文献
9.
10.
Julia Flanders 《Language Resources and Evaluation》1997,31(4):301-310
This paper discusses the contested role of images in electronic editions, and summarizes some of the chief arguments for their
inclusion. I then argue that, to truly determine the importance of images to the function of electronic editions, we must
understand the contribution the image makes to the form of textual knowledge provided by the edition. I suggest a distinction
between editions which are primarily pedagogical in their aims, those which aim above all at scholarly authority, and those
which attempt to provide textual information as high-quality data which can be analysed and processed. I conclude that the
latter represents the most significant future trend in electronic editing.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献