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1.
Processing, Microstructure, and Wear Behavior of Silicon Nitride Hot-Pressed with Alumina and Yttria 总被引:3,自引:0,他引:3
Ajoy Zutshi Richard A. Haber Dale E. Niesz Jane W. Adams John B. Wachtman Mattison K. Ferber Stephen M. Hsu 《Journal of the American Ceramic Society》1994,77(4):883-890
Commercial silicon nitride powder with A12 O3 and Y2 O3 additives was hot-pressed to complete density. The resulting microstructure contained elongated grains with no trace of remaining α-Si3 N4 . The aspect ratio of the elongated grains increased with increasing soak time at a fixed hot-pressing temperature. X-ray diffraction analysis showed that the crystalline phase in the hot-pressed samples was β-sialon (Si6−z Alz Oz N8−z ) with z values that increased with soak time. The fracture strength and fracture toughness of the samples increased as the aspect ratio of the grains increased. The Vickers hardness decreased slightly as the soak time was increased, which was attributed to a grain size effect. Wear tests of silicon nitride against silicon nitride were conducted on a reciprocating pin-on-disk apparatus with paraffin oil as a lubricant. Correlation studies of wear with microstructure and mechanical properties were performed. The wear rate increased rapidly with increasing soak time in spite of the increased strength and toughness. This was attributed to increased third-body wear caused by pullout of pieces from the wear surface. The pullout mechanism was not conclusively identified. However, TEM examination showed clear evidence of dislocation motion under the wear scar. Grain boundary microstresses caused by the anisotropic thermal expansion and elastic properties of the elongated grains may have contributed to the observed pullout. 相似文献
2.
Ajoy K. Datta Lawrence L. LarmorePriyanka Vemula 《Theoretical computer science》2011,412(40):5541-5561
A silent self-stabilizing asynchronous distributed algorithm, SSLE, is given for the leader election problem in a connected unoriented (bidirectional) network with unique IDs. SSLE also constructs a BFS tree on the network rooted at that leader. SSLE uses O(logn) space per process and stabilizes in O(n) rounds, against the unfair daemon, where n is the number of processes in the network. 相似文献
3.
The contribution of this paper is threefold. First, we present the paradigm of snap-stabilization. A snap- stabilizing protocol guarantees that, starting from an arbitrary system configuration, the protocol always behaves
according to its specification. So, a snap-stabilizing protocol is a time optimal self-stabilizing protocol (because it stabilizes
in 0 rounds). Second, we propose a new Propagation of Information with Feedback (PIF) cycle, called Propagation of Information with Feedback and Cleaning (). We show three different implementations of this new PIF. The first one is a basic cycle which is inherently snap-stabilizing. However, the first PIF cycle can be delayed O(h
2) rounds (where h is the height of the tree) due to some undesirable local states. The second algorithm improves the worst delay of the basic
algorithm from O(h
2) to 1 round. The state requirement for the above two algorithms is 3 states per processor, except for the root and leaf processors
that use only 2 states. Also, they work on oriented trees. We then propose a third snap-stabilizing PIF algorithm on un-oriented
tree networks. The state requirement of the third algorithm depends on the degree of the processors, and the delay is at most
h rounds. Next, we analyze the maximum waiting time before a PIF cycle can be initiated whether the PIF cycle is infinitely
and sequentially repeated or launch as an isolated PIF cycle. The analysis is made for both oriented and un-oriented trees.
We show or conjecture that the two best of the above algorithms produce optimal waiting time. Finally, we compute the minimal
number of states the processors require to implement a single PIF cycle, and show that both algorithms for oriented trees
are also (in addition to being time optimal) optimal in terms of the number of states.
WARNING: The concept of snap-stabilization was first introduced in [12]. The concept evolved over the last eight years. We
take this evolution in consideration in this paper, which includes the early results published in [10] and [12]. In particular,
infinite repetition of computation cycles is a requirement of self-stabilizing systems. This is not required in snap-stabilization because snap-stabilization ensures that the first completed computation cycle is executed according to the
specification of the problem. The correctness proofs conform to this basic property. 相似文献
4.
Shiva Bejugama Shibu Chameettachal Falguni Pati Ajoy Kumar Pandey 《Ceramics International》2021,47(2):1594-1601
Niobia (1 mol. %) doped Ceria Stabilized Zirconia (NbCSZ) powders were synthesized using a co-precipitation method. The synthesized powders were uniaxially compacted and sintered in air. The two-step sintering method was adopted to sinter the samples, and the sintering schedule was optimized based on density, grain size, the phase present, and the hardness of the sintered sample. It was observed that the two-step sintering method effectively suppressed the grain growth of NbCSZ samples and helped in achieving a finer grain size of 1.57 μm along with the hardness of 1195 HV10 and optimum fracture toughness value 6.20 MPa m1/2. The Low-Temperature Degradation (LTD) behavior of the sintered samples was estimated through an accelerated hydrothermal aging test, which revealed that the samples are highly resistant to LTD and shown no phase change even after 150 h of study. Moreover, the cytocompatibility of the NbCSZ was tested by culturing MG63 cells on the samples for 7 days. The NbCSZ was found to be highly biocompatible as evident from cell viability and metabolic activity assay. 相似文献
5.
15–25 wt% zirconia (stabilized with 14 mol% ceria) toughened alumina was synthesized by co-precipitation technique. The synthesized powders were calcined at different temperatures, compacted and conventionally sintered following two steps sintering process. Uniformly distributed submicron sized grains with Vickers' hardness value up to 1730±6HV20 were achieved after conventional sintering. In order to assess the ageing behaviour, samples were hydrothermally treated (in vitro) at 134 °C under 0.2 MPa in presence of simulated body fluid. Rietveld refinement of the X-ray diffraction patterns was carried out to estimate the phase content after calcination, sintering and after different stages of hydrothermal treatment. No significant phase change (only ∼3%) was observed even after 100 h of hydrothermal treatment. Very few bulged grains (resulted from the tetragonal to monoclinic phase transformation) on the surface and slight decrease in hardness value were observed after hydrothermal treatment. Fretting wear in dry condition was carried out taking ball on flat geometry for 105 cycles at different loads before and after hydrothermal treatment. Wear volumes were directly estimated from the surface scanning of the wear scar using profilometer. Transition of wear and its related mechanisms at different loads along with the effect of ageing on wear were discussed. 相似文献
6.
7.
Ajoy Raman 《电子设计技术》2007,14(11):124-124,128
本设计实例能以最少的元件数实现利用单变压器推挽DC/DC转换器的固有倍压特性的宽范围倍压器.它采用高压达林顿晶体管阵列驱动器ULN2023A来实施.该电路具有5V~30V的较宽输入电压范围,并能以适宜的效率提供了1W~4W的典型电源输出. 相似文献
8.
Shrimp aquaculture constitutes a major economic activity of some middle- and low-level economies in the world. Though it is practiced by around 70 countries, it is primarily dominated by China, Thailand, Indonesia, Vietnam, Ecuador and India. These six countries account for 80 % of the global shrimp production. The study has highlighted the role of research in the development of the industry by taking the examples of Penaeus vannamei and P. monodon. In case of the former, a seven time rise in quantum of research (studied by the number of publications as a proxy) could induce five time increase in production, whereas, in the latter case similar pattern was not noticed. The study has observed that based on shrimp production and research contribution; the major 30 countries associated with shrimp aquaculture could be categorized as: (i) high production, high-research contribution, (ii) low production, high-research contribution and (iii) high production, low-research contribution. The countries under the third category are at great risk and may suffer huge economic losses in the event of outbreak of any disease. By generating network map of research linkage across different countries the study has highlighted the potential countries for strengthening the existing linkage and fostering new linkage for knowledge consolidation. The study has given some suggestion for policy formulation for achieving a rapid growth of shrimp aquaculture in the world. 相似文献
9.
Ajoy Kumar Ray 《Journal of Materials Engineering and Performance》2018,27(6):2609-2609
10.