Istanbul Technical University

About: Istanbul Technical University is a education organization based out in Istanbul, Turkey. It is known for research contribution in the topics: Fuzzy logic & Large Hadron Collider. The organization has 12889 authors who have published 25081 publications receiving 518242 citations. The organization is also known as: İstanbul Teknik Üniversitesi & Technical University of Istanbul.

OFDM-Subcarrier Index Selection for Enhancing Security and Reliability of 5G URLLC Services

Abstract: An efficient physical layer security technique, referred to as OFDM with subcarrier index selection (OFDM-SIS), is proposed for safeguarding the transmission of OFDM-based waveforms against eavesdropping in 5G and beyond wireless networks. This is achieved by developing a joint optimal subcarrier index selection (SIS) and adaptive interleaving (AI) design, which enables providing two levels (sources) of security in time division duplexing (TDD) mode: one is generated by the optimal selection of the subcarrier indices that can maximize the signal-to-noise ratio at only the legitimate receiver, while the other is produced by the AI performed based on the legitimate user’s channel that is different from that of the eavesdropper. The proposed scheme not only provides a remarkable secrecy gap, but also enhances the reliability performance of the legitimate user compared with the standard OFDM scheme. Particularly, a gain of 5–10 dB is observed at a bit error rate value of 10−3 compared with standard OFDM as a result of using the adaptive channel-based subcarrier selection mechanism. Moreover, the proposed technique saves power, considers no knowledge of the eavesdropper’s channel, and provides secrecy even in the worst security scenario, where the eavesdropper can know the channel of the legitimate link when an explicit channel feedback is used as is the case in frequency division duplexing systems. This is achieved while maintaining low complexity and high reliability at the legitimate user, making the proposed scheme a harmonious candidate technique for secure 5G ultra reliable and low latency communications (URLLC) services.

A new method for dynamic analysis of mistuned bladed disks based on the exact relationship between tuned and mistuned systems

Abstract: A new method for the dynamic analysis of mistuned bladed disks is presented. The method is based on exact calculation of the response of a mistimed system using response levels for the tuned assembly togeher with a modification matrix constructed from the frequency response function (FRF) matrix of the tamed system and a matrix describing the mistuning. The train advantages of the method are its efficiency and accuracy, which allow the use of large finite element models of practical bladed disk assemblies in parametric studies of mistuning effects on vibration amplitudes. A new method of calculating the FRF matrix of the tuned system using a sector model is also developed so as to improve the efficiency of the method even further, making the proposed method a very attractive tool for mistuning steadies. various numerical aspects of the proposed method are addressed and its accuracy and efficiency are demonstrated using representative test cases

Synthesis and Characterization of Macrophotoinitiators of Poly(∊-caprolactone) and Their Use in Block Copolymerization

Abstract: Novel end-chain and midchain functional macrophotoinitiators of poly(-caprolactone) have been synthesized. For this purpose, mono- and dihydroxy functional photoinitiators namely, benzoin (B) and 2-hydroxy-2-methyl-1-phenyl propan-1-one (HMPP), Darocure 1173, and 2-hydroxy-1-(4-(2-hydroxy- ethoxy)phenyl)-2-methyl propan-1-one (HE-HMPP), Irgacure 2959, respectively, were used as initiators for the stannous-2-ethylhexanoate (Sn(Oct)2) catalyzed living ring-opening polymerization of -caprolactone. The gpc and IR, H NMR, UV, and fluorescence spectroscopic studies revealed that low-polydispersity poly(-caprolactone) with desired photoinitiator functionality at the end or in the middle of the chain were obtained. These prepolymers were used to induce radical polymerization of methyl methacrylate (MMA) upon irradiation via R-cleavage of the incorporated phenyl ketone groups. While end-chain functional macrophotoiniators led to the formation of both homo and block copolymers, only block copolymers of -CL and MMA were formed with midchain functional macrophotoinitiator. Successful blocking has been confirmed by a strong change in the molecular weight of the prepolymer and the block copolymer as well as by NMR spectral measurements.