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排序方式: 共有219条查询结果,搜索用时 15 毫秒
131.
In this paper, we introduce a foundation for computable model theory of rational Pavelka logic (an extension of ?ukasiewicz logic) and continuous logic, and prove effective versions of some related theorems in model theory. We show how to reduce continuous logic to rational Pavelka logic. We also define notions of computability and decidability of a model for logics with computable, but uncountable, set of truth values; we show that provability degree of a formula with respect to a linear theory is computable, and use this to carry out an effective Henkin construction. Therefore, for any effectively given consistent linear theory in continuous logic, we effectively produce its decidable model. This is the best possible, since we show that the computable model theory of continuous logic is an extension of computable model theory of classical logic. We conclude with noting that the unique separable model of a separably categorical and computably axiomatizable theory (such as that of a probability space or an Lp Banach lattice) is decidable. 相似文献
132.
Tavakoli Mohammad Reza Ali Akbari Omid Mohammadian Anoushiravan Khodabandeh Erfan Pourfattah Farzad 《Journal of Thermal Analysis and Calorimetry》2019,135(2):1119-1134
Journal of Thermal Analysis and Calorimetry - The current study investigates the laminar and two-phase nanofluid flow inside a two-dimensional rectangular microchannel with the ratio of length to... 相似文献
133.
In this paper, an entropy-consistent flux is developed, continuing from the work of the previous paper. To achieve entropy consistency, a second and third-order differential terms are added to the entropy-conservative flux. This new flux function is tested on several one dimensional problems and compared with the original Roe flux. The new flux function exactly preserves the stationary contact discontinuity and does not capture the unphysical rarefaction shock. For steady shock problems, the new flux predicts a slightly more diffused profile whereas for unsteady cases, the captured shock is very similar to those produced by the Roe- flux. The shock stability is also studied in one dimension. Unlike the original Roe flux, the new flux is completely stable which will provide as a candidate to combat multidimensional shock instability, particularly the carbuncle phenomenon. 相似文献
134.
The dynamic nature of the ion wake formed downstream a dust particle immersed in a plasma with flowing ions has been investigated via Particle-in-Cell simulation. It is found that the wake oscillates in time and the motion is characterized by some dominant frequencies. By means of signal processing analysis, three harmonics are detected (two at low frequencies and one at high frequencies) and compared to the characteristic plasma frequencies given by the dispersion relations for ions and electrons. Good matching is found between the high frequency harmonic and the electron plasma frequency, and between the low frequency harmonics and the ion acoustic and ion plasma frequencies. 相似文献
135.
Pourfattah Farzad Sabzpooshani Majid Toghraie Davood Asadi Amin 《Journal of Thermal Analysis and Calorimetry》2021,143(1):203-211
Journal of Thermal Analysis and Calorimetry - Lignin-based polycaprolactone (PCL) graft copolymers with various graft ratios were prepared by ring-opening reaction in order to design new lignin... 相似文献
136.
Babak Heidary Alizadeh Alireza Foroumadi Farzad Kobarfard Mina Saeedi Abbas Shafiee 《Journal of heterocyclic chemistry》2015,52(6):1693-1698
In this work, (R)‐4‐(3,4‐dimethoxybenzyl)dihydrofuran‐2(3H)‐one was prepared though an efficient and novel method starting from (S)‐5‐((benzyloxy)methyl)dihydrofuran‐2(3H)‐one. Then, it was utilized as a versatile starting material for the synthesis of novel dimethylmatairesinol analogues; dibenzylbutyrolactone derivatives, via the reaction of the later compound and various aromatic aldehydes. 相似文献
137.
By combining the sensing capabilities of nanoscale magnetic relaxation switches (MRS) within multi-reservoir structures, a potentially powerful implantable multiplexed sensor has been developed. MRS are magnetic nanoparticles that decrease the transverse relaxation time (T(2)) of water in the presence of an analyte. The switches encased in polydimethylsiloxane (PDMS) devices with polycarbonate membranes (10 nm pores) have demonstrated in vitro sensing of the beta subunit of human chorionic gonadotrophin (hCG-beta), which is elevated in testicular and ovarian cancer. Devices showed transverse relaxation time (T(2)) shortening by magnetic resonance imaging (MRI) when incubated in analyte solutions of 0.5 to 5 microg hCG-beta mL(-1). The decrease in T(2) was between 9% and 27% (compared to control devices) after approximately 28 h. This prototype device is an important first step in developing an implantable sensor for detecting soluble cancer biomarkers in vivo. 相似文献
138.
Farzad Kobarfard Joel M. Kauffman Walter J. Boyko 《Journal of heterocyclic chemistry》1999,36(5):1247-1251
It appeared that a key intermediate for 2-amino-3-fluorothiophene ( 1 ), methyl 3-fluorothiophene-2-carboxylate ( 5 ), had been prepared by a Schiemann reaction of the 3-diazonium salt ( 6 ) in xylenes. This report was not correct. Gomberg coupling products 7 with o-xylene are actually formed. We were able to prepare 5 by using special conditions for the Schiemann reaction. The hydrazide derivative of 5 failed to give 1 under Curtius reaction conditions. Two new acetamidofluorothiophene compounds were prepared using SelectfluorTM as the fluorinating agent, but no aminofluorothiophenes 1-3 or salts could be obtained by acidic hydrolysis of either amide. 相似文献
139.
Khajeh-Khalili Farzad Honarvar M. Amin Naser-Moghadasi Mohammad Dolatshahi Mehdi 《Journal of Infrared, Millimeter and Terahertz Waves》2021,42(11-12):1078-1093
Journal of Infrared, Millimeter, and Terahertz Waves - In this paper, a multiple-input and multiple-output (MIMO) antenna with high gain and high isolation based on the metamaterial concept is... 相似文献
140.
ABSTRACTThis article investigates wave propagation behavior of a multi-phase nanocrystalline nanobeam subjected to a longitudinal magnetic field in the framework of nonlocal couple stress and surface elasticity theories. In this model, the essential measures to describe the real material structure of nanocrystalline nanobeams and the size effects were incorporated. This non-classical nanobeam model contains couple stress effect to capture grains micro-rotations. Moreover, the nonlocal elasticity theory is employed to study the nonlocal and long-range interactions between the particles. The present model can degenerate into the classical model if the nonlocal parameter, couple stress and surface effects are omitted. Hamilton’s principle is employed to derive the governing equations which are solved by applying an analytical method. The frequencies are compared with those of nonlocal and couple stress-based beams. It is showed that wave frequencies and phase velocities of a nanocrystalline nanobeam depend on the grain size, grain rotations, porosities, interface, magnetic field, surface effect and nonlocality. 相似文献