排序方式: 共有98条查询结果,搜索用时 343 毫秒
21.
Jalil Morshedian Hossein A. Khonakdar Sorour Rasouli 《Macromolecular theory and simulations》2005,14(7):428-434
Summary: A mechanical model was developed to describe qualitatively and quantitatively the stress‐strain‐time behavior of a prepared shape memory crosslinked polyethylene during hot stretching, stress relaxation under 200% strain at high temperature and strain recovery of the heat shrinkable polymer. The stress‐strain, the stress relaxation and the irrecoverable strain behavior of the model were established by driving the constitutive equation, which could qualitatively represent the behavior of the real material. By choosing significant values for the parameters of the proposed model, an excellent fit was obtained between the experimental behavior of the polymer and that predicted by the model. It was also revealed that the main source responsible for the imperfect recovery of the induced strain observed was the stress relaxation occurring during the stretch holding‐cooling time step.
22.
This paper addresses optimization of a high-speed digital feedback controller for a plasma position in Damavand tokamak. Damavand
tokamak discharges have plasma currents up to 40 kA with discharge duration greater than 15 ms and toroidal magnetic fields
up to 1.2 T. The plasma position is measured using saddle-loops and Rogowski coil and is controlled by electromagnetic forces
generated by passing currents through control coils placed around the plasma. A desired control objective is maintaining the
plasma in the center of vacuum vessel and to stabilize the plasma in the presence of disturbances in a time domain of the
order of few milliseconds. In order to achieve maximum performance it is essential to optimize the control system. In this
paper plasma position measurement and the details of implementing high-speed PID controllers based on a TMS320c25 digital
signal processor along with the system optimization are presented. 相似文献
23.
Faramarz Rostami-Charati Rahimeh Hajinasiri Seyyed Zahra Sayyed Alangi Saeid Afshari Sharif Abad 《Chemical Papers》2016,70(7):907-912
4-amino-2-iminodithiole derivatives were synthesised via multi-component reactions of tetramethyl thiourea, isothiocyanates and alkyl bromides in the presence of ZnO nanorods (ZnO-NR) as the catalyst in water at ambient temperature. These reactions provide low yields without catalysts. The catalyst exhibited significant reusable activity. 相似文献
24.
Rezayati Sobhan Jafroudi Mogharab Torabi Nezhad Eshagh Rezaee Hajinasiri Rahimeh Abbaspour Sima 《Research on Chemical Intermediates》2016,42(6):5887-5898
Research on Chemical Intermediates - An efficient and cost-effective procedure for preparation of Fe3O4 nanoparticles and supported Brønsted acidic ionic liquid... 相似文献
25.
The present methodology describes an efficient, environmentally friendly and simple protocol for the synthesis of some 4,4′-(arylmethylene)bis(1H-pyrazol-5-ol) derivatives through a one-pot pseudo-five-component reaction of hydrazine hydrate/phenyl hydrazine, ethyl acetoacetate, and various aromatic aldehydes catalyzed by guanidine hydrochloride. This condensation reaction was performed by tandem Knoevenagel–Michael reaction in water under refluxing conditions giving the title compounds in 82–92% yields. Atom economy, simple operation, easy work-up, using inexpensive organocatalyst, high yields in short times, clean transformation, and environmentally benign are some of the important features of this new protocol. 相似文献
26.
In this paper, we present the first model of co-opetition for a Hub Location Problem between two logistics service provider (LSPs) companies where the mother company is the owner of infrastructure. The LSPs would like to cooperate with each other by establishing joint edges with limited capacities connecting their service networks. Such services are in form of pendulum services (a direct service between two points) between nodes of different networks. Additional market can be generated as a result of joining the two networks. At the same time, a competition is taking place between the two operators to increase their share from the additional market generated. In order to solve this problem, we propose a matheuristic approach combining a local search algorithm and a Lagrangian relaxation-based approach. In our matheuristic algorithm, the neighbourhood solutions are evaluated using a Lagrangian relaxation-based approach. Numerical results of applying the proposed algorithm on a real case study of the problem are presented. 相似文献
27.
28.
S. M. M. Rasouli Mehrdad Farhoudi Nima Khosravi 《General Relativity and Gravitation》2011,43(10):2895-2910
We investigate the effects of a special kind of dynamical deformation between the momenta of the scalar field of the Brans–Dicke
theory and the scale factor of the FRW metric. This special choice of deformation includes linearly a deformation parameter.
We trace the deformation footprints in the cosmological equations of motion when the BD coupling parameter goes to infinity.
One class of the solutions gives a constant scale factor in the late time that confirms the previous result obtained via another
approach in the literature. This effect can be interpreted as a quantum gravity footprint in the coarse grained explanation.
The another class of the solutions removes the big bang singularity, and the accelerating expansion region has an infinite
temporal range which overcomes the horizon problem. After this epoch, there is a graceful exiting by which the universe enters
in the radiation dominated era. 相似文献
29.
Zinatossadat Hossaini Faramarz ROstami-Charati Rahimeh Hajinasiri Mohammad A.Khalilzadeh 《中国化学快报》2012,23(5):512-514
An efficient synthesis of methyl 4-hydroxy-6-oxo-1,6-dihydro-2-pyridine carboxylates is described.This involves three component reactions between primary alkyl amines,malonyl dichloride and methyl propiolates. 相似文献
30.
The structure and dynamics of early stage kinetics of pressure-induced phase separation of compressible polymer solutions via spinodal decomposition is analyzed using a linear Euler-Cahn-Hilliard model and the modified Sanchez Lacombe equation of state. The integrated density wave and Cahn-Hilliard equations combine the kinetic and structural characteristics of spinodal decomposition with density waves arising from pressure-induced couplings. When mass transfer rate is slower that acoustic waves, concentration gradients generate density waves that cycle back into the spinodal decomposition dynamics, resulting in oscillatory demixing. The wave attenuation increases with increasing mass transfer rates eventually leading to nonoscillatory spinodal demixing. The novel aspects of acousto-spinodal decomposition arise from the coexistence of stable oscillatory density dynamics and the unstable monotonic concentration dynamics. Scaling laws for structure and dynamics indicate deviations from incompressible behavior, with a significant slowing down of demixing due to couplings with density waves. Partial structure factors for density and density-concentration reflect the oscillatory nature of acousto-spinodal modes at lower wave vectors, while the single maximum at a constant wave vector reflects the presence of a dominant mode in the linear regime. The computed total structure factor is in qualitative agreement with experimental data for a similar polymer solution. 相似文献