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排序方式: 共有173条查询结果,搜索用时 0 毫秒
81.
Cristina I. Muresan Clara M. Ionescu Eva H. Dulf Roxana Rusu-Both Silviu Folea 《化学工程与技术》2018,41(10):1936-1948
The process of enriching the 13C isotope, performed in trains of cryogenic distillation columns, exhibits large settling times, nonlinearities, large dead‐times, and are difficult to model precisely. Such equipment has been developed in Romania, with concentration increasing up to 70 %. A control analysis for a single unit has already been done including a decentralized multivariable PI controller and two decoupling control algorithms based on the internal model control (IMC) approach. Here, a multivariable predictive controller, the extended prediction self‐adaptive controller is proposed. The simulation results, considering significant modeling errors, demonstrate that this represents a more suitable choice than the previously designed strategies. Comparisons are included to support this idea. 相似文献
82.
A novel graphene-on-organic film fabrication method that is compatible with a batch microfabrication process was developed and used for electromechanically driven microactuators. A very thin layer of graphene sheets was monolithically integrated and the unique material characteristics of graphene including negative thermal expansion and high electrical conductivity were exploited to produce a bimorph actuation. A large displacement with rapid response was observed while maintaining the low power consumption. This enabled the successful demonstration of transparent graphene-based organic microactuators. 相似文献
83.
Marin Cernea Bogdan Stefan Vasile Vasile Adrian Surdu Roxana Trusca Cristina Bartha Floriana Craciun Carmen Galassi 《Journal of Materials Science》2018,53(20):14160-14171
One of the most promising ways for the realization of multi-functional materials is the integration of oxides with different properties in artificial heterostructures. In this paper, a novel piezoelectric–ferromagnetic heterostructure consisting of 0.92Na0.5Bi0.5TiO3–0.08BaTiO3 (abbreviated as BNT–BT0.08) and CoFe2O4 layers is fabricated on Si–Pt substrate, by sol–gel method coupled with spin-coating technique. The composite thin film shows only perovskite Bi0.5Na0.5TiO3-like rhombohedral phase and CoFe2O4 cubic phase. The thickness of CoFe2O4 and BNT–BT0.08 layers is ~?280 and?~?400 nm, respectively. BNT–BT0.08/CoFe2O4 heterostructure thin film shows a saturation magnetization of 0.11 emu/g at 5 K and 0.07 emu/g at 295 K, dielectric constant of 235 at 1 kHz and tunability of 70% at 1 kHz and an electric field E?=?110 kV/cm. The results reveal that the investigated hybrid piezoelectric/ferromagnetic structure shows piezoelectric behavior, good ferroelectric and ferromagnetic properties. This bilayer composite can be used in miniature low-frequency magnetic sensor and piezoelectric sensor for biomedical domain. 相似文献
84.
Rajesh Kumar Dhanaraj Lalitha Krishnasamy Oana Geman Diana Roxana Izdrui 《计算机、材料和连续体(英文)》2021,68(2):1949-1965
In Wireless Body Area Networks (WBANs) with respect to health care, sensors are positioned inside the body of an individual to transfer sensed data to a central station periodically. The great challenges posed to healthcare WBANs are the black hole and sink hole attacks. Data from deployed sensor nodes are attracted by sink hole or black hole nodes while grabbing the shortest path. Identifying this issue is quite a challenging task as a small variation in medicine intake may result in a severe illness. This work proposes a hybrid detection framework for attacks by applying a Proportional Coinciding Score (PCS) and an MK-Means algorithm, which is a well-known machine learning technique used to raise attack detection accuracy and decrease computational difficulties while giving treatments for heartache and respiratory issues. First, the gathered training data feature count is reduced through data pre-processing in the PCS. Second, the pre-processed features are sent to the MK-Means algorithm for training the data and promoting classification. Third, certain attack detection measures given by the intrusion detection system, such as the number of data packages trans-received, are identified by the MK-Means algorithm. This study demonstrates that the MK-Means framework yields a high detection accuracy with a low packet loss rate, low communication overhead, and reduced end-to-end delay in the network and improves the accuracy of biomedical data. 相似文献
85.
In this paper, we use results from the Hotelling model of non-renewable resources to examine the mainstream view among economists that improvements in recovery technology can offset declines in petroleum reserves. We present empirical evidence from two well-documented mega-oilfields: the Forties in the North Sea and the Yates in West Texas. Patterns of depletion in these two fields suggest that technology temporarily increases the rates of production at the expense of more pronounced rates of depletion in later years—in line with Hotelling's predictions. Insofar as our results are generalizable, they call into question the view of most economists that technology can mitigate absolute resource scarcity. This raises concerns about the capacity of current mega-fields to meet future oil demand. 相似文献
86.
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88.
Medana Zamfir Iulia‐Roxana Stefan Mihaela‐Marilena Stancu Silvia‐Simona Grosu‐Tudor 《International Journal of Food Science & Technology》2016,51(10):2164-2170
Lactococcus lactis 19.3 produces a bacteriocin with a wide inhibitory spectrum, including the food pathogen Listeria monocytogenes. The producing strain was able to grow and produce similar amounts of bacteriocin in MRS medium, cow's milk and soya milk, respectively. The mode of action of this bacteriocin was further investigated using two indicator strains, Lactobacillus delbrueckii subsp. bulgaricus LMG 6901T and Listeria monocytogenes ATCC 1911‐1. The bacteriocin displayed a bactericidal effect, causing a rapid decrease of the cell viability. Bacteriocin treatment of the sensitive strains resulted in major morphological changes, including pore formation, as shown by scanning electron microscopy. Finally, the bacteriocin‐encoding gene was identified by sequencing. The presence of nisin gene was confirmed. Based on all our data gathered so far, L. lactis 19.3 is a good candidate for a starter or protective culture in the manufacturing of both fermented dairy and vegetarian food products. 相似文献
89.
Teodora Gratiela Tihan Mioara Daniela Ionita Roxana Gabriela Popescu Dana Iordachescu 《Materials Chemistry and Physics》2009,118(2-3):265-269
The purpose of this study is to put in evidence the correlation between hydrophilic/hydrophobic balance and biocompatibility of PMMA–HA composites, in order to select the best composites for futures clinical applications. For this purpose, PMMA–HA cements with different compositions were prepared and static contact angle measurements, water absorption and gingival fibroblasts cell culture were performed and discussed. 相似文献
90.
Roxana Fekri Alireza Aliahmadi Mohammad Fathian 《The International Journal of Advanced Manufacturing Technology》2009,41(11-12):1240-1260
Successful development of the new product (NPD) is one of the most critical tasks in manufacturing process and challenging issues that managers usually face. In response to unanticipated changes in volatile markets, agile NPD is a focus to manufacturing companies. Identifying the causal relationships between the main factors of agile NPD process as a complex system, can influence the effectiveness of managers’ decision making, and the productivity of actions in this kind of process. This study reports the results of an empirical research done on the main factors affecting the agile NPD process and the relationships between them in Iranian manufacturing enterprises. These factors are identified and categorized in six main groups by explanatory factor analysis method, and the relationships between them are introduced with the simple fuzzy cognitive map method. 相似文献