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151.
L. G. Mendonça-Filho R. L. B. Rodrigues R. Rosato E. B. F. Galante 《Journal of Energetic Materials》2013,31(3):293-308
ABSTRACTNew formulations of nitrocellulose-based propellants were evaluated aiming less-toxicity-and-less-erosivity. Three original ingredients of M-14 propellant – dinitrotoluene, dibutyl phthalate, and diphenylamine – were replaced. The new formulations, with ballistic performances similar to M-14, were based on ethylcentralite, akardite-II, RDX, diethylene glycol dinitrate, triethylene glycol dinitrate, and acetyl tributyl citrate (ATBC). The toxicities of the crude ingredients were analyzed. The H2 content in the combustion products was a key point in the analysis. The best results were found to the compositions based on ATBC and akardite-II only. The work can be used to guide future works related to new formulations of propellants. 相似文献
152.
André O. Menezes Michelly T. Rodrigues Adriana Zimmaro Luiz E.P. Borges Marco A. Fraga 《Renewable Energy》2011,36(2):595-599
Aqueous-phase reforming of oxygenated hydrocarbons for hydrogen production presents several advantages as feed molecules can be easily found in a wide range of biomass, there is no need for its vaporization and the process allows thorough exploitation of the environmental benefits of using hydrogen as an energy carrier. The use of glycerol in particular is motivated due to its availability as a consequence of increasing biodiesel production worldwide. In this contribution, the performance of Pt-based catalysts supported on different oxides (Al2O3, ZrO2, MgO and CeO2) is studied on glycerol reforming. All catalysts led to a hydrogen-rich gas phase. However, a good potential activity with high production of hydrogen and low concentration of undesired hydrocarbons was accomplished over the catalysts supported on MgO and ZrO2. The high electron donating character of such oxides indicates the influence of the nature of the support in catalytic performance for glycerol reforming. 相似文献
153.
Zuzana Dimitrovová Hélder C. Rodrigues 《Structural and Multidisciplinary Optimization》2010,42(3):325-340
The contribution of optimization has been essential to the more recent developments in design of new mechanical structures
and materials. The objective of this work is to apply the models of material and structural optimization to the design of
passive vibration isolators. A computational tool to identify the optimal viscoelastic characteristics of a nonlinear one-dimensional
isolator was developed. The cost functional involves the minimization of a weighted average of the maximum transient and steady
state response amplitudes for a set of predefined dynamic loads. The optimal isolator behaviour is obtained by a simulated
annealing method. The solutions obtained are analyzed and discussed concerning their dependence on the applied forces and
objective function selection. The results obtained can facilitate the design of elastomeric materials with improved behaviour
in terms of dynamic stiffness for passive vibration control. 相似文献
154.
155.
Tânia Tomé Áttila L. Rodrigues Mário J. de Oliveira 《Computer Physics Communications》2009,180(4):536-539
We study by numerical simulations the time correlation function of a stochastic lattice model describing the dynamics of coexistence of two interacting biological species that present time cycles in the number of species individuals. Its asymptotic behavior is shown to decrease in time as a sinusoidal exponential function from which we extract the dominant eigenvalue of the evolution operator related to the stochastic dynamics showing that it is complex with the imaginary part being the frequency of the population cycles. The transition from the oscillatory to the nonoscillatory behavior occurs when the asymptotic behavior of the time correlation function becomes a pure exponential, that is, when the real part of the complex eigenvalue equals a real eigenvalue. We also show that the amplitude of the undamped oscillations increases with the square root of the area of the habitat as ordinary random fluctuations. 相似文献
156.
157.
dos Santos Ferreira M.F. Rodrigues Ferreira da Rocha J. de Lemos Pinto J. 《Quantum Electronics, IEEE Journal of》1992,28(4):833-841
A theoretical analysis is performed of the frequency noise in tunable two- and three-section distributed Bragg reflector (DBR) laser diodes (LDs), taking into account the nonlinear gain compression effect. For a two-section DBR LD the frequency noise is shown to depend significantly on the tuning current, particularly at low frequencies (below the gigahertz range) and for low and moderate values of the grating coupling coefficient. For high values of this coefficient the tuning dependence is generally negligible when the tuning is performed only through the DBR section, but it becomes significant when using the phase control current in a three-section device. It is shown that the enhancement factor for the spontaneous emission rate due to the longitudinal field dependence increases significantly with tuning for low values of the grating coupling coefficient 相似文献
158.
C.C. Chin D. Derdall J. Sebesta F. Jiang P. Dindo G. Rodrigues D. Bond S.-K. Pan A. R. Kerr E. Lauria M. Pospieszalski J. Zhang T. Cecil A. Lichtenberger 《Journal of Infrared, Millimeter and Terahertz Waves》2004,25(4):569-600
We have built a 100 GHz sideband-separating receiver. The receiver, a breadboard for the band 3 cartridges for ALMA, achieves a SSB noise temperature of 6hf/k with a 4–8 GHz IF. We show that it is possible to meet the ALMA specifications. The design of the receiver is reviewed and the relationships between the receiver noise temperature and properties of the components used in the receiver are discussed. 相似文献
159.
There are a number of possibilities for local and vascularized bone transfer when a small amount of cortico-cancellous bone is required in the hand and fingers. The authors describe the dissection technique and a clinical application of a reverse dorsal metacarpal osteocutaneous flap to reconstruct the proximal phalanx of a fifth finger. They emphasise the bone vascularisation, studied 48 hours postoperatively with a bone scan and confirmed with bone healing 4 weeks later. The advantages are: it is a compound flap, easy to dissect under tourniquet in one operation, it can be done in an emergency care situation and it does not require ligation of an important vascular axis. The essential precaution is to visualise the patency of the fourth dorsal metacarpal artery before flap dissection, acknowledging that in only 63% of cases is there a vascular pattern that allows flap dissection with a long arc of rotation. 相似文献
160.
Intrusion Detection System for Wireless Sensor Networks Using Danger Theory Immune-Inspired Techniques 总被引:1,自引:0,他引:1
Helio Mendes Salmon Claudio M. de Farias Paula Loureiro Luci Pirmez Silvana Rossetto Paulo Henrique de A. Rodrigues Rodrigo Pirmez Flávia C. Delicato Luiz Fernando R. da Costa Carmo 《International Journal of Wireless Information Networks》2013,20(1):39-66
An IDS framework inspired in the Human Immune System to be applied in the wireless sensor network context is proposed. It uses an improved decentralized and customized version of the Dendritic Cell Algorithm, which allows nodes to monitor their neighborhood and collaborate to identify an intruder. The work was implemented and tested both in simulation and in real sensor platform scenarios, comparing them to each other and was also compared to a Negative Selection Theory implementation in order to demonstrate its efficiency in detecting a denial-of-sleep attack and in energy consumption. Results demonstrated the success of the proposal. 相似文献