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排序方式: 共有1718条查询结果,搜索用时 0 毫秒
41.
MIN Jiahua SHI Zhubin QIAN Yongbiao SANG Wenbin ZHAO Hengyu TENG Jianyong LIU Jishan 《核技术(英文版)》2009,20(1):46-50
CdZnTe (CZT) capacitive Frisch grid detectors can achieve a higher detecting resolution.The anode structure might have an important role in improving the weighting potential distribution of the detectors.In this paper,four anode structures of capacitive Frisch grid structures have been analyzed with FE simulation,based on a 3-dimensional weighting potential analysis.The weighting potential distributions in modified anode devices (Model B,C and D) are optimized compared with a square device (Model A).In model C and D,the abrupt weighting potential can be well modified.However,with increased radius of the circular electrode in Model C the weighting potential platform away from the anode becomes higher and higher and in Model D,the weighting potential does not vary too much. 相似文献
42.
43.
Xuan Lian Hiroaki Miyoshi Yuki Mitsuya Kenji Shimazoe 《Journal of Nuclear Science and Technology》2018,55(7):805-811
The liquid crystal display (LCD) technology allows several simple circuits to be built using thin film transistors, thus making fabrication of compact, integrated, large-area, and low-cost micro-pattern gaseous detectors possible. In this work, a single-grid-type micro-strip gas chamber (S-MSGC) using transparent electrodes based on the LCD technology was fabricated and successfully operated in several gas mixtures. The detector was coupled with a multi-pixel photon counter to detect an optical signal through the transparent substrate in Ar/CF4 gas. Both electrical and optical signals were measured and the light yield of the detector was acquired. Successful operation of the S-MSGC can be considered the very important first step for development of the next target of integrated devices. 相似文献
44.
《International Journal of Hydrogen Energy》2023,48(75):29367-29390
Airlines are faced with the challenge of reducing their environmental footprint in an effort to push for climate-neutral initiatives that comply with international regulations. In the past, the aviation industry has followed the approach of incremental improvement of fuel efficiency while simultaneously experiencing significant growth in annual air traffic. With the increase in air traffic negating any reduction in Greenhouse Gas (GHG) emissions, more disruptive technologies such as hydrogen-based onboard power generation are required to reduce the environmental impact of airline operations. However, despite initial euphoria and first conceptual studies for hydrogen-powered aircraft several decades ago, there still has been no mass adoption to this day. Besides the challenges of a suitable ground infrastructure, this can partly be attributed to uncertainties with the associated maintenance requirements and the expected operating costs to demonstrate the economic viability of this technology. With this study, we address this knowledge gap by estimating changes towards scheduled maintenance activities for an airborne hydrogen storage and distribution system. In particular, we develop a detailed system design for a hydrogen-powered, fuel-cell-based auxiliary power generation and perform a comparative analysis with an Airbus A320 legacy system. That analysis allows us to (a) identify changes for the expected maintenance effort to enhance subsequent techno-economic assessments, (b) identify implications of specific design assumptions with corresponding maintenance activities while ensuring regulatory compliance and (c) describe the impact on the resulting task execution. The thoroughly examined interactions between system design and subsequent maintenance requirements of this study can support practitioners in the development of prospective hydrogen-powered aircraft. In particular, it allows the inclusion of maintenance implications in early design stages of corresponding system architectures. Furthermore, since the presented methodology is transferable to different design solutions, it provides a blueprint for alternative operating concepts such as the complete substitution of kerosene by hydrogen to power the main engines. 相似文献
45.
Lisa Biasetto Rachele Bertolini Hamada Elsayed Andrea Ghiotti Stefania Bruschi 《Ceramics International》2019,45(5):5941-5951
Rods of commercially pure titanium were machined using standard oil-based emulsion and cryogenic cooling, and were then coated with sphene (CaTiSiO5) bioceramic by spray coating using an automatic airbrush. The sphene bioceramic was synthesized in-situ starting from a suspension of polysiloxane that used as SiO2 precursor, CaCO3 and TiO2 nanoparticles. The suspension was deposited on the machined substrates, which were heat treated up to 950?°C in order to promote the formation of sphene ceramic. The produced coated prototypes were characterized to evaluate the effect of the machining conditions on surface roughness and microstructure of the substrate, and thereby their effect on coating adhesion. Nanoindentation tests were employed to determine the hardness and elastic modulus of the coating through its thickness. Results showed that the reduced amount of defects on the surface of the cryo-machined substrates, contributed to increase the hardness, elastic modulus and adhesion strength of the coating-substrate interfaces compared to standard machined samples, therefore improving adhesion of the coating to the underlying substrate. 相似文献
46.
Chi-Seung LeeMin-Sung Chun Myung-Hyun KimJae-Myung Lee 《International Journal of Adhesion and Adhesives》2011,31(4):226-237
In the present paper, the debonding failure characteristics of epoxy and polyurethane adhesives embedded using a multi-laminated bonding system (MLBS) under cryogenic temperatures are evaluated. A series of pull-off and lap-shear tests under various temperatures (293, 163, and 110 K) are performed to identify the debonding failure characteristics of the MLBS. A modification of the Ramberg-Osgood constitutive model is carried out to predict the temperature-dependant elastic-inelastic stress-strain behaviour of the MLBS. The temperature-dependant material parameters are predicted using an empirical formulation. The debonding failure phenomenon is also studied. 相似文献
47.
We report on experimental results of the thermal conductivity k of
highly porous Si in the temperature range 4.2 to 20 K, obtained using the
direct current (dc) method combined with thermal finite element simulations. The
reported results are the first in the literature for this temperature range. It
was found that porous Si thermal conductivity at these temperatures shows a
plateau-like temperature dependence similar to that obtained in glasses, with a
constant k value as low as 0.04 W/m.K. This behavior is attributed
to the presence of a majority of non-propagating vibrational modes, resulting
from the nanoscale fractal structure of the material. By examining the fractal
geometry of porous Si and its fractal dimensionality, which was smaller than two
for the specific porous Si material used, we propose that a band of fractons
(the localized vibrational excitations of a fractal lattice) is responsible for
the observed plateau. The above results complement previous results by the
authors in the temperature range 20 to 350 K. In this temperature range, a
monotonic increase of k with temperature is observed, fitted with
simplified classical models. The extremely low thermal conductivity of porous
Si, especially at cryogenic temperatures, makes this material an excellent
substrate for Si-integrated microcooling devices (micro-coldplate).
PACS
61.43.-j; 63.22.-m; 65.8.-g 相似文献48.
Physical 3D models were established for corrugated packing used in the enrichment of the isotope 13C. Computational fluid dynamics (CFD) simulation results indicated that common corrugated packing was not well wetted when used for isotope distillation. It is concluded that liquid misdistribution in the packed tower results from the structure of the packing rather than from the height of the packing beds. The existence of entrainment was also demonstrated by CFD simulation. It is proved that mass transfer equations based on the Nusselt theory are not suitable for distillation calculation in such a corrugated packing system. By comparison, the recently developed structured packing model with a corrugation geometry based on the right‐angled triangle, known as Zigzag‐pak, describes vapor‐liquid distribution properties well and has significant advantages over common corrugated packing due to its better liquid distribution character. 相似文献
49.
《Ceramics International》2017,43(5):3970-3974
ZTA ceramics containing 20 wt% ZrO2 were fabricated at different sintering temperatures (1450, 1500 and 1550 °C) by SPS and HP processes, respectively. The influence of sintering process on the mechanical properties of ZTA ceramics at 298 K and 77 K was investigated. It can be seen that the bending strength and fracture toughness of samples prepared by the two processes both improved at cryogenic temperature. The stress-induced martensitic transformation toughening mechanism was confirmed by the in-situ Raman technique. The tetragonal ZrO2 would be even more easy to transform because of the residual stress generated when temperature decreased from 298 K to 77 K. Therefore, the transformation toughening effect would become stronger, result in the increase of mechanical properties. 相似文献
50.
《Ceramics International》2023,49(5):7913-7919
Developing novel optical thermometry with ultrahigh relative sensitivity and temperature resolution has become a cutting-edge topic. For this purpose, under obeying Boltzmann distribution, a series of Li2Zn0.9992-xAxGe3-yByO8:0.08% Cr3+ (B= Sc3+, In3+, A = Si4+) phosphors were studied, which the luminescence intensity ratio between the transition of 4T2g→4A2g emission and the R line based on thermally coupled energy levels constitutes a temperature sensing work with a relative sensitivity of 9.46% K?1, 9.73% K?1, and 10.38% K?1, respectively. It is worth mentioning that the luminescence intensity of the R line (peak 1) increases significantly with the increase of temperature, while the transition of 4T2g→4A2g (peak 2) with high intensity at low temperature gradually quenching, and this opposite trend is an important advantage for the design of excellent thermometers. Compared the best relative sensitivity of Li2Zn0.9992-xAxGe3-yByO8:0.08%Cr3+ (B= Sc3+, In3+, A = Si4+) with the crystal field Dq/B, it can be concluded that relative sensitivity increasing gradually with decreasing the intensity of crystal field. Finally, by testing the stability of the sample at 50 K, a thermal resolution of 0.082 K, 0.080 K and 0.077 K was obtained, respectively, which is one of the best thermal resolutions so far, while the repeatability of the sample stability at 50 K and 300 K cycles was higher than 99%. Our work is expected to provide guiding insights for optimizing the sensitivity of Cr3+-based luminescence intensity ratio thermometers. 相似文献