Aging Studies on Conducting Polypyrrole

Kaynak, Akif The Korean Fiber Society 2001 Fibers and polymers Vol.2 No.4

Change of tensile properties, electrical conductivity and microwave shielding of electrochemically synthesized polypyrrole films with time are presented. Highly doped films had good electrical stability, retaining high microwave reflectivity throughout the aging period. Lightly doped films were less stable and partially reflective and absorptive of microwaves. FT-IR spectral observations revealed a progressive increase in intensity of an unsaturated conjugated carbonyl peak, which was not observed in the highly doped films, suggesting that the concentration of the dopant had an influence on mechanism of degradation of conductivity.

Characterization of Conductive Polypyrrole Coated Wool Yarns

Kaynak, Akif,Wang, Kijing,Hurren, Chris,Wang, Xungai The Korean Fiber Society 2002 Fibers and polymers Vol.3 No.1

Wool yams were coated with conducting Polypyrrole by chemical synthesis methods. Polymerization of pyrrole was caned out in the presence of wool yarn at various concentrations of the monomer and dopant anion. The changes in tensile, moisture absorption, and electrical Properties of the yam upon coating with conductive polypyrrole are Presented. Coating the wool yams with conductive Polypyrrole resulted in higher tenacity, higher breaking strain, and lower initial modulus. The changes in tensile properties are attributed to the changes in surface morphology due to the coating and reinforcing effect of conductive Polypyrrole. The thickness of the coating increased with the concentration of p-toluene sulfonic acid, which in turn caused a reduction in the moisture regain of the wool yin. Reducing the synthesis temperature and replacing p-toluenesulfonic acid by anthraquinone sulfonic acid resulted in a large reduction in the resistance of the yam.

터어키 政治와 9月 12月 쿠데타

Altan Kaynak 한국외국어대학교 1982 한국외국어대학교 논문집 Vol.15 No.1

Neuro-adaptive sliding-mode tracking control of robot manipulators

Topalov, Andon V.,Kaynak, Okyay,Aydin, Gokhan John Wiley Sons, Ltd. 2007 International journal of adaptive control and sign Vol.21 No.8

<P>In this work, a new dynamical on-line learning algorithm for robust model-free neuro-adaptive control of a class of nonlinear systems with uncertain dynamics is proposed and experimentally tested in order to evaluate its performance and practical feasibility in industrial settings. The control application studied is the trajectory tracking control task for the first three joints of an open architecture articulated robot manipulator. The control scheme makes use of variable structure systems theory and the feedback-error-learning concept. An inner sliding motion is established in terms of the neurocontroller parameters, aiming to lead the error in its control signal towards zero. The outer sliding motion bears on the system under control, the state tracking error vector of which is simultaneously driven towards the origin of the phase space. The existing relation between the two sliding motions is shown. Experimental results illustrate that the proposed neural-network-based controller possesses a remarkable learning capability to control complex dynamical systems, virtually without requiring a priori knowledge of the plant dynamics and laborious start-up procedures. Copyright © 2007 John Wiley & Sons, Ltd.</P>

An Oscillator and a Mixer for 140-GHz Heterodyne Receiver Front-End based on SiGe HBT Technology

Yoon, Daekeun,Song, Kiryong,Kaynak, Mehmet,Tillack, Bernd,Rieh, Jae-Sung The Institute of Electronics and Information Engin 2015 Journal of semiconductor technology and science Vol.15 No.1

This paper reports a couple of key circuit blocks developed for heterodyne receiver front-ends operating near 140 GHz based on SiGe HBT technology. Firstly, a 123-GHz oscillator was developed based on Colpitts topology, which showed -5 dBm output power and phase noise of -107.34 dBc/Hz at 10 MHz. DC power dissipation was 25.6 mW. Secondly, a 135 GHz mixer was developed based on a modified Gilbert Cell topology, which exhibited a peak conversion gain of 3.6 dB at 1 GHz IF at fixed LO frequency of 134 GHz. DC power dissipation was 3 mW, which mostly comes from the buffer.

Analysis of the Turkish Education System: A System Dynamics Approach on Dropouts and Deficiencies in Job Market

( Rhythima Shinde ),( Duygu Kaynak ) 한국시스템다이내믹스학회 2016 한국시스템다이내믹스 연구 Vol.17 No.4

The education system has always been a controversial issue in the Turkish Republic history. Contrary to developed countries, educational institutions, teaching activities and high school and university entrance exams are regularly changed disruptively by the authorities. Despite many interventions with the purpose of improving the public education system, it was found that education policies do not meet expectations: dropouts are still high and students do not gain necessary knowledge and skills to meet the industry needs. This study focuses on modelling the education system and job market while generating policies to increase the quality of the education system and meeting industry expectations. Simulation results point out to the fact that the government should invest on the improvement of current universities rather than opening new universities. Moreover, industry support to vocational schools should be stimulated to increase number of vocational school students and create new job opportunities for them. Finally, the policies are tested under uncertain parameters and their robustness is verified.

An Oscillator and a Mixer for 140-GHz Heterodyne Receiver Front-End based on SiGe HBT Technology

윤대근,송기룡,Mehmet Kaynak,Bernd Tillack,이재성 대한전자공학회 2015 Journal of semiconductor technology and science Vol.15 No.1

This paper reports a couple of key circuit blocks developed for heterodyne receiver front-ends operating near 140 GHz based on SiGe HBT technology. Firstly, a 123-GHz oscillator was developed based on Colpitts topology, which showed -5 dBm output power and phase noise of -107.34 dBc/Hz at 10 MHz. DC power dissipation was 25.6 mW. Secondly, a 135 GHz mixer was developed based on a modified Gilbert Cell topology, which exhibited a peak conversion gain of 3.6 dB at 1 GHz IF at fixed LO frequency of 134 GHz. DC power dissipation was 3 mW, which mostly comes from the buffer.

A SiGe BiCMOS Amplifier-Frequency Doubler Chain Operating for 284–328 GHz

유정환,김정수,윤종원,Kaynak Mehmet,이재성 한국전자파학회 2022 Journal of Electromagnetic Engineering and Science Vol.22 No.2

This work describes the development of an amplifier frequency doubler chain (AFDC) operating at around 300 GHz based on SiGe BiCMOS technology. The driver amplifier is based on the differential cascode configuration, which employs coupled-line transformers for compact design. The frequency doubler is based on the class-B topology, which is known for exhibiting a large output power with low DC power consumption. The integrated AFDC, which consists of the frequency doubler and the preceding driver amplifier, exhibited a measured peak output power and DC-to-RF efficiency of -0.9 dBm and 0.97%, respectively, along with a conversion gain of -0.1 dB. It operates from 284 to 328 GHz with a 0-dBm input signal, consuming a total DC power of only 84 mW. The chip size is 720 × 310 μm2, excluding RF and DC pads.

Uniform Micellization: The Key to Enhanced Mechanical Strength and Swelling Efficiency of Chitosan Hydrogel

Bijan Nasri-Nasrabadi,Akif Kaynak,Cynthia Wong,Pejman Heidarian,Khashayar Badii,Abbas Z. Kouzani 한국섬유공학회 2019 Fibers and polymers Vol.20 No.1

The fabrication of hydrophilic porous hydrogel, with high mechanical strength and good uptake capacity is desirable for a broad range of applications such as drug delivery and liquid sensors. The usual methods are limited to the production of structures with high density of covalently crosslinked networks that restricts the polymer chain rearrangement, resulting in non-uniformed pore size distribution. Covalent networks also limit the activity of functional groups and influence the uptake properties of the polymer. In this study, we proposed simple cyclic cryogelation for the fabrication of hydrogels with uniform pore sizes via controlling the micellization and crystal formation. The chitosan based hydrogels ionically crosslinked with 8 % (w/v) of tripoli phosphate sodium (TPP) displayed high Young’s modulus (63 MPa) after cyclic freezethawing. The liquid uptake capacity of the samples treated with 8 % (w/v) TPP solution at pH 4 showed a slight decrease of about 29 % in comparison to that of non-cyclic processed samples (36 %).

Correlating the Fineness and Residual Gum Content of Degummed Hemp Fibres

Beltran, Rafael,Hurren, Christopher J.,Kaynak, Akif,Wang, Xungai The Korean Fiber Society 2002 Fibers and polymers Vol.3 No.4

It is well known residual gum exists in degummed or rotted hemp fibers. Gum removal results in improvement in fiber fineness and the properties of the resultant hemp yams. However, it is not known what correlation if any exists between the residual gum content in retted hemp fibers and the fiber fineness, described in terms of fiber width in this paper. This study examined the mean width and coefficient of variation (CV) of fiber width of seventeen chemically rotted hemp samples with reference to residual gum content. The mean and CV of fiber width were obtained from an Optical fiber diameter analyser (OFDA 100). The linear regression analysis results show that the mean fiber width is directly proportional to the residual gum content. A slightly weaker linear correlation also exists between the coefficient of variation of fiber width and the residual gum content. The strong linear co-relation between the mean of fiber width and the residual gum content is a significant outcome, since testing for fiber width using the OFDA is a much simpler and quicker process than testing the residual gum content. Scanning Electron Microscopy (SEM) reinforces the OFDA findings. SEM micrographs show a flat ribbon like fiber cross-section hence the term \"fiber width\" is used instead of fiber diameter. Spectral differences in the untreated dry decorticated skin samples and chemically treated and subsequently carded samples indicate delignification. The peaks at $1370cm^{-1}$, $1325cm^{-1}$, $1733cm^{-1}$, and $1600cm^{-1}$ attributed to lignin in the untreated samples are missing from the spectra of the treated samples. The spectra of the treated samples are more amine-dominated with some of the OH character lost.cter lost.