Pairs of Positive Periodic Solutions of Second Order Nonlinear Equations

, M.Sc. Thesis Sharif University of Technology Fattahpour, Haniyeh (Author) ; Hesaaraki, Mahmoud (Supervisor)

Abstract

In this thesis we study the problem of existence and multiplicity of positive periodic solution to the scalar ODE , , where is a positive function on , super linear at zero and sub linear at infinity, and is a -periodic and sign indefinite weight with negative mean value. We first show the nonexistence of solution for some classes of nonlinearities when is small. Then, using critical point theory, we prove the existence of at least two positive -periodic solutions for large. Then, we prove the existence of a pair of positive -periodic solutions as well as the existence of positive sub harmonic solutions of any order for the scalar second order ODE where is same as above,...

The Study of Kinematic Dipole and Clustering Dipole Magnitudes using Large-Scale Structure Data and the Effects of Modified Gravity

, M.Sc. Thesis Sharif University of Technology Tadayyoni, Haniyeh Sadat (Author) ; Baghram, Shant (Supervisor) ; Rahvar, Sohrab (Supervisor)

Abstract

The dipole in the angular distribution of the cosmic microwave background (CMB) is typically attributed to the Doppler effect and our motion relative to the CMB rest frame. It is expected that observations of large-scale structures (LSS) would also exhibit a related kinematic dipole, helping to confirm the kinematic origin of the CMB dipole. However, numerous studies of the LSS dipole have shown significant discrepancies with predictions based on the CMB. In this study, we assume that the CMB dipole is due to our motion relative to the CMB frame, and using radio source data from NVSS, we calculate the dipole induced by local large-scale structures across different redshift ranges....

Preparation of nanostructured and nanosheets of MoS2 oxide using oxidation method

, Article Ultrasonics Sonochemistry ; Volume 39 , 2017 , Pages 188-196 ; 13504177 (ISSN) Amini, M ; Ramazani S. A. A ; Faghihi, M ; Fattahpour, S ; Sharif University of Technology

2017

Abstract

Molybdenum disulfide (MoS2), a two-dimensional transition metal has a 2D layered structure and has recently attracted attention due to its novel catalytic properties. In this study, MoS2 has been successfully intercalated using chemical and physical intercalation techniques, while enhancing its surface properties. The final intercalated MoS2 is of many interests because of its low-dimensional and potential properties in in-situ catalysis. In this research, we report different methods to intercalate the layers of MoS2 successfully using acid-treatment, ultrasonication, oxidation and thermal shocking. The other goal of this study is to form S[dbnd]O bonds mainly because of expected enhanced...

Investigation of the effect of nanosilica on rheological, thermal, mechanical, structural, and piezoelectric properties of poly(vinylidene fluoride) nanofibers fabricated using an electrospinning technique

, Article Industrial and Engineering Chemistry Research ; Volume 56, Issue 44 , 2017 , Pages 12596-12607 ; 08885885 (ISSN) Haddadi, S. A ; Ahmad Ramazani, S. A ; Talebi, S ; Fattahpour, S ; Hasany, M ; Sharif University of Technology

2017

Abstract

The effects of different nano-SiO2 contents on the rheological properties of poly(vinylidene fluoride) (PVDF) solution and mechanical, thermal, structural, and piezoelectric properties of composite nanofibers were investigated. Results showed an increase in fiber diameter (∼125 to 350 nm) and ∼450% increase in tensile strength as the content of nano-SiO2 particles increased. The degree of crystallinity decreased by 19% as the nano-SiO2 content increased by 2% (w/w). Further investigation demonstrated that silica could significantly improve the piezoelectric properties of PVDF nanofibers as the output voltage showed an increase in the presence of silica attributed to change in the crystalline...

A misbehavior‐tolerant multipath routing protocol for wireless Ad hoc networks [electronic resource]

, Article International Journal of Research in Wireless Systems (IJRWS) ; Vol. 2, Issue 9, pp. , Sep. 2013 Sedghi, H. (Haniyeh) ; Pakravan, Mohammad Reza ; Aref, Mohammad Reza ; Sharif University of Technology

Abstract

Secure routing is a major key to service maintenance in ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. As a result of the resource limitations in such networks nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a novel data redirection method to mitigate the impact of node misbehavior on network...