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排序方式: 共有2099条查询结果,搜索用时 78 毫秒
981.
Arturo Pacheco-Vega Claudia Ruiz-Mercado Kevin Peters Luis Enrique Vilchiz 《传热工程》2013,34(14):1208-1215
We have developed a fuzzy-rule-based controller to perform on-line temperature control of a concentric-tube heat exchanger facility. The rules for the controller were derived from dynamical values of the mass flow rates and fluid temperatures in the heat exchanger. The fuzzy controller was embedded in a closed-loop, single-input single-output system to control the outlet temperature of the cold fluid. The development of the controller was done in two phases, the difference between the phases being the information about the system that was used to build the corresponding control scheme. To validate this fuzzy controller, a series of experiments, corresponding to regulation and tracking of a setpoint, was carried out for maintaining specific values of the outlet temperature under different perturbations. Results from this investigation demonstrate that the fuzzy-rule-based controller is able to effect control of the system, and that the amount of information about the plant provided to it is important in terms of accuracy and efficiency. 相似文献
982.
983.
Dow MP Bakke LJ Cassar CA Peters MW Pursley JR Smith GW 《Reproduction (Cambridge, England)》2002,123(5):711-719
The serine proteinases, tissue-type (tPA) and urokinase (uPA) plasminogen activator, are implicated in the ovulatory processes via their ability to convert plasminogen to its active form, plasmin. One mechanism for regulation of plasmin-directed ovarian extracellular matrix remodelling during follicle rupture and corpus luteum formation is through inhibition of plasminogen activation by the plasminogen activator inhibitors (PAI-1 and PAI-2). The effect of the preovulatory gonadotrophin surge on the temporal and spatial regulation of expression of PAI-1 and PAI-2 mRNA and PAI activity in preovulatory bovine follicles and new corpora lutea collected at 0, 6, 12, 18, 24 and 48 h after a GnRH-induced gonadotrophin surge was examined. Both PAI-1 and PAI-2 mRNAs were upregulated markedly after the gonadotrophin surge, with the highest expression observed in follicles collected at about the time of ovulation (24 h) and in corpora lutea (48 h). PAI-1 mRNA was localized primarily to the thecal layer of preovulatory follicles. In contrast, PAI-2 mRNA was localized specifically to the granulosa cell layer. Significant PAI activity was detected in follicle extracts, but temporal or spatial differences in PAI activity were not detected in response to the gonadotrophin surge. These results indicate that PAI-1 and PAI-2 mRNAs are upregulated in preovulatory bovine follicles after the gonadotrophin surge in a cell-specific way. Regulation of PAI-1 and PAI-2 may help to control plasminogen activator activity associated with ovulation and early corpus luteum formation. 相似文献
984.
B. Denkena L. Overmeyer K. M. Litwinski R. Peters 《The International Journal of Advanced Manufacturing Technology》2014,73(5-8):989-998
This paper presents a rigid body machine tool simulation that is real-time capable and used in machine tool controls to estimate dynamic dislocations. The rigid body model is parameterized by static stiffness measurements and compared with a simulation in a customary software system RecurDyn. Based on the theoretical consideration, a modal analysis is examined in order to determine the damping properties of the test rig and to verify the control model dynamically. The investigated model of the test rig is afterwards implemented in a Kalman filter and transferred into the machine tool control. The performance of this control is assessed by linear movements. Finally, the dependency of the machine tool behavior on the position and load mass is considered by using the control model. 相似文献
985.
Mammary secretions (n = 34 cows) and mammary phagocytes (n = 18 cows) were collected throughout the nonlactating (dry) period to determine changes in intramammary phagocytic defense mechanisms. Mammary secretions were evaluated for their ability to support phagocytosis of Staphylococcus aureus by neutrophils from donor cows and mammary phagocytes for phagocytic and chemiluminescence activity. Ability of secretions to support phagocytosis decreased with advancing length of the dry period. This effect was more pronounced when dry cow secretions constituted 50% of the phagocytic mixture. Phagocytic activity of mammary phagocytes decreased with advancing dry period when autologous secretion was used in the incubation mixture. With homologous secretion, the percentage of phagocytosis increased 5 to 6 d after drying off compared with before drying off and then gradually decreased throughout the remainder of the dry period. Chemiluminescence activity (log10 counts per minute) of mammary phagocytes was lower during the dry period and decreased with advancing dry period. Results indicated diminishing ability of secretions to support phagocytosis and diminished phagocytic and bactericidal mechanisms during the dry period. 相似文献
986.
Manuel Weber Wolfgang Frey Ren Peters 《Advanced Synthesis \u0026amp; Catalysis》2012,354(8):1443-1449
Masked and activated highly enantioenriched α,α‐disubstituted α‐amino acids with an additional adjacent stereocenter were formed by a tandem reaction involving five steps using racemic unprotected amino acid substrates. Key step is the 1,4‐addition of in‐situ generated azlactones to a broad number of enones. The products of this step‐economic route can, e.g., be useful for a divergent and rapid access to biologically interesting unnatural glutamic acid derivatives. 相似文献
987.
Peters CH Sachs-Quintana IT Mateker WR Heumueller T Rivnay J Noriega R Beiley ZM Hoke ET Salleo A McGehee MD 《Advanced materials (Deerfield Beach, Fla.)》2012,24(5):663-668
Degradation in a high efficiency polymer solar cell is caused by the formation of states in the bandgap. These states increase the energetic disorder in the system. The power conversion efficiency loss does not occur when current is run through the device in the dark but occurs when the active layer is photo-excited. 相似文献
988.
Ivanov SS Rangelov AA Vitanov NV Peters T Halfmann T 《Journal of the Optical Society of America. A, Optics, image science, and vision》2012,29(3):265-269
Driving on an analogy with the technique of composite pulses in quantum physics, we propose highly efficient broadband polarization converters composed of sequences of ordinary retarders rotated at specific angles with respect to their fast-polarization axes. 相似文献
989.
Laura Peters 《集成电路应用》2008,(3):50-55
由45纳米过渡到32纳米技术节点,除了可能在一些关键的材料方面发生改变,另一个主要的变化是在关键工艺层中采用双重成像光刻技术。何去何从,成本因素和产品需求将起到决定性的作用。 相似文献
990.
Quantitative systems analysis as a strategic planning approach for metropolitan water service providers. 总被引:2,自引:0,他引:2
Sydney Water selected life cycle assessment (LCA) to inform a review of its overall strategic planning document: WaterPlan 21. This assessment covered the entire business and has enabled ecological sustainability to be assessed in terms of quantitative indicators. The LCA was performed by firstly examining a base case which would eventuate if Sydney Water maintained its current operations with only the modifications, augmentations and upgrades planned for implementation between now and 2021. We then performed a number of scenario analyses to examine the benefits of additional demand management, energy efficiency, energy generation, supply augmentation and effluent quality initiatives. The results indicated significant improvements are available and that some of these measures are more desirable than others. We also examined a scenario for the alternative delivery of water and wastewater services in new urban areas. This showed quantitatively that, since connecting new fringe suburbs to the existing system requires significant expenditure on energy for pumping, major improvements in the sustainability of water and wastewater systems can be achieved by using localised, water-saving alternatives. 相似文献