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141.
Summary The thermal behavior of several formulations consisting of ethylene-propylene elastomers and acrylonitrile-butadiene rubber
was investigated by differential scanning calorimetry. The sample compositions cover the whole concentration range of ((EPDM,
EPR)/NBR = 100/0, 20/80, 40/60, 60/40, 80/20 and 0/100). The evaluation of molar enthalpies for studied polymer blends allowed
to calculate molar capacities at various temperatures from 335 K up to 450 K. Due to the lack of additivity in the molar capacities
of studied blends, the contributions of each component to the overall values of Cp are calculated. The dependency of component contributions on their concentrations follows a first order function, which explains
the existence of a certain interaction between components. 相似文献
142.
The present paper is a theoretical contribution to the field of iterative methods for solving inconsistent linear least squares problems arising in image reconstruction from projections in computerized tomography. It consists on a hybrid algorithm which includes in each iteration a CG-like step for modifying the right-hand side and a Kaczmarz-like step for producing the approximate solution. We prove convergence of the hybrid algorithm for general inconsistent and rank-deficient least-squares problems. Although the new algorithm has potential for more applied experiments and comparisons, we restrict them in this paper to a regularized image reconstruction problem involving a 2D medical data set. 相似文献
143.
In this work, an originally bio-inspired cryptosystem is developed. It is based on the use of cellular automata (CAs) as pseudorandom bit generators and programmable cellular automata (PCA) to construct the block ciphering functions of the proposed enciphering scheme. The cryptosystem is featured by resistance on different types of attacks and high speed due to the cellular automata's parallel information processing property. The proposed architecture could be efficiently implemented in reconfigurable hardware like field programmable gate arrays (FPGAs) and could be applied in high-speed data communication. The project was implemented in two experimental hardware platforms based on Spartan 3 XC3S400fg456-4 and XILINX Spartan 3E XC3S500E. 相似文献
144.
This paper considers a gradient type of iterative algorithm applied to the open loop control for nonlinear affine systems. The convergence of the algorithm relies on the control signal in each iteration be nonsingular. We present an algorithm for computing the singular control for a general class of nonlinear affine systems. Various nonlinear mechanical systems, including nonholonomic systems, are included as examples. 相似文献
145.
Pritpal Dang Prasanna Ballal Frank L. Lewis Dan O. Popa 《Journal of Intelligent and Robotic Systems》2008,51(2):235-257
A novel approach for relative and absolute localization of wireless sensor nodes using a potential field method is presented.
The main idea of our work is to develop relative and absolute localization algorithms for the position estimate of stationary
unattended ground sensor (UGS) nodes using a potential field method. A dynamical model is derived for each sensor node to
estimate the relative and absolute position estimates under the influence of a certain fictitious virtual force. In the algorithm
the sensor nodes do not move physically, but a virtual motion is carried out to generate optimal position estimates. The convergence
of the estimator system to a least squares solution is guaranteed using Lyapunov theory. Separate control algorithms for relative
and absolute localization are developed which guarantee the convergence of the position estimates. The relative localization
algorithm assumes that distance (i.e. range) measurements between UGS nodes are available and for absolute localization algorithm,
uninhabited aerial vehicles (UAV) are available with on board GPS such that they have absolute position information together
with range measurement information. In the relative localization algorithm the UGS nodes are localized with respect to an
internal co-ordinate frame. In absolute localization the UGS nodes are localized with respect to the known absolute position
of UAV in the air–ground network. The effectiveness of the control algorithm is highlighted by the real time implementation
results. 相似文献
146.
Iulian Munteanu Antoneta Iuliana Bratcu Maria Andreica Seddik Bacha Daniel Roye Joël Guiraud 《Simulation Modelling Practice and Theory》2010,18(9):1342-1354
This paper focuses on exploring a new method of real-time replication of the dynamic behaviour of prime movers that drive rotating generators involved in energy conversion chains. Their behaviour depends on the mover’s mechanical characteristics and dynamical properties, such as inertia or friction coefficient, which are seldom known precisely. Being also dependent on the variations of the primary energy resource, not always controllable in its natural environment, this behaviour must be simulated by using a smaller and cheaper mover, whose model is sufficiently known such that to render it fully controllable. This paper explores the possibility that the desired real-time replication be achieved by means of a new method of tracking the mover’s rotational speed. To this end, various controllers, both linear and nonlinear can be employed. The design steps are provided for a PI controller, as well as for two nonlinear controllers, while focusing on the practical aspects of controller implementation. Their performance results are assessed comparatively on an experimental rig for two types of prime movers: one whose mechanical torque-speed characteristic is linear and a cross-flow water turbine, having a nonlinear torque-speed characteristic. 相似文献
147.
The electrical conductivity is an important property of nanofluids that has not been widely studied. To study both the effects of temperature and concentration, the electrical conductivity of water-based Al2O3 nanofluids with 12?nm diameter particles is measured. Conventional models, such as the Maxwell model and Bruggemann correlation, were considered for comparison and disagreement were noticed. Experimental results showed the Al2O3 nanofluids increased their electrical conductivity with increasing volume fraction as compared to that of the base fluid, as well as with temperature increasing. A stronger influence on volume fraction was noticed. Electrical conductivity measurements for these nanofluids indicate an enormous enhancement (390.11?%) at 60?°C for a volume fraction of 4?%in distilled water. Furthermore, at higher volume fractions, the electrical conductivity enhancement begins to level off, which is attributed to ion condensation effects in the high-surface charge regime. A 3D statistical analysis was also considered to obtain an empirical correlation. 相似文献
148.
Ingmar A. J. van Hengel Melissa W. A. M. Tierolf Lidy E. Fratila-Apachitei Iulian Apachitei Amir A. Zadpoor 《International journal of molecular sciences》2021,22(7)
Patients receiving orthopedic implants are at risk of implant-associated infections (IAI). A growing number of antibiotic-resistant bacteria threaten to hamper the treatment of IAI. The focus has, therefore, shifted towards the development of implants with intrinsic antibacterial activity to prevent the occurrence of infection. The use of Ag, Cu, and Zn has gained momentum as these elements display strong antibacterial behavior and target a wide spectrum of bacteria. In order to incorporate these elements into the surface of titanium-based bone implants, plasma electrolytic oxidation (PEO) has been widely investigated as a single-step process that can biofunctionalize these (highly porous) implant surfaces. Here, we present a systematic review of the studies published between 2009 until 2020 on the biomaterial properties, antibacterial behavior, and biocompatibility of titanium implants biofunctionalized by PEO using Ag, Cu, and Zn. We observed that 100% of surfaces bearing Ag (Ag-surfaces), 93% of surfaces bearing Cu (Cu-surfaces), 73% of surfaces bearing Zn (Zn-surfaces), and 100% of surfaces combining Ag, Cu, and Zn resulted in a significant (i.e., >50%) reduction of bacterial load, while 13% of Ag-surfaces, 10% of Cu-surfaces, and none of Zn or combined Ag, Cu, and Zn surfaces reported cytotoxicity against osteoblasts, stem cells, and immune cells. A majority of the studies investigated the antibacterial activity against S. aureus. Important areas for future research include the biofunctionalization of additively manufactured porous implants and surfaces combining Ag, Cu, and Zn. Furthermore, the antibacterial activity of such implants should be determined in assays focused on prevention, rather than the treatment of IAIs. These implants should be tested using appropriate in vivo bone infection models capable of assessing whether titanium implants biofunctionalized by PEO with Ag, Cu, and Zn can contribute to protect patients against IAI. 相似文献
149.
Daniela Spridon Luminita Panaitescu Daniel Ursu Constantin V. Uglea Iuliana Popa Raphael M. Ottenbrite 《Polymer International》1997,43(2):175-181
A series of maleic anhydride (MA)–vinyl acetate (VA), MA–methyl methacrylate (MM) and MA–styrene (S) copolymers were prepared and characterized. By employing various amounts of initiator, MA–VA, MA–MM and MA–S copolymers with molecular weights ranging between 18 000 and 219 000 were obtained. The ‘in vivo’ and ‘in vitro’ tests performed on K562 cellular cultures (human chronic myeloid leukaemia) and also on Westar rats (inoculated with the Walker 256 carcinosarcome) showed that, as a function of the molecular weight, the copolymers synthesized had a 50% in vitro cytotoxicity and a mean tumour regression of a maximum of 68%. © 1997 SCI. 相似文献
150.
E. De Bona L. Balice L. Cognini M. Holzhäuser K. Popa O. Walter M. Cologna D. Prieur T. Wiss G. Baldinozzi 《Journal of the European Ceramic Society》2021,41(6):3655-3663
Three different spark plasma sintering (SPS) treatments were applied to highly sinteractive, near-stoichiometric UO2.04 nanocrystalline (5 nm) powders produced by U(IV) oxalate hydrothermal decomposition at 170 °C. The sintering conditions for reaching 95 % theoretical density (TD) in regular SPS, high pressure SPS (HP-SPS), and, for the first time, two-step SPS (2S-SPS), were determined. Densification to 95 % TD was achieved at 1000 °C in regular SPS (70 MPa applied pressure), 660 °C in HP-SPS (500 MPa), and 650?550 °C in 2S-SPS (70 MPa). With the goal of minimising the grain growth during densification, the sintering treatments were optimised to favour densification over coarsening, and the final microstructures thus obtained are compared. Equally dense UO2 samples of different grain sizes, ranging from 3.08 μm to 163 nm, were produced. Room-temperature oxidation of the powders could not be avoided due to their nanometric dimensions, and a final annealing treatment was designed to reduce hyperstoichiometric samples to UO2.00. 相似文献