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Ferromagnetic states of p-type silicon doped with Mn
Yunusov, Z. A.,Yuldashev, Sh. U.,Igamberdiev, Kh. T.,Kwon, Y. H.,Kang, T. W.,Bakhadyrkhanov, M. K.,Isamov, S. B.,Zikrillaev, N. F. Korean Physical Society 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.10
In this work, the ferromagnetic states of Mn-doped p-type silicon samples were investigated. Two different types of ferromagnetic states have been observed in Si (Mn, B). The samples with a relatively high concentration of Mn revealed a ferromagnetic state with a Curie temperature above room temperature, and that ferromagnetism was due to the Mn (x) B (y) ferromagnetic clusters. The samples with a moderate concentration of Mn at low temperatures revealed a ferromagnetic state that was mediated by carriers (holes). The samples demonstrated the anomalous Hall effect at temperatures below 100 K and had a negative magneto-resistivity peak at a temperature close to the Curie temperature. The thermal diffusivity measurements demonstrated the existence of a second-order phase transition in the samples with a moderate Mn concentration. The specific heat's critical exponent alpha = 0.5, determined from the thermal diffusivity measurements, confirmed the long-range nature of the magnetic exchange interaction in these samples.
Yunusov Khaydar Ergashovich,Turakulov Fozil Mamaraim Ugli,Sarymsakov Abdushkur Abdukhalilovich,Yuldoshov Sherzod Abdullaevich,Rashidova Sayyora Sharafovna,Guohua Jiang 대한화학회 2024 Bulletin of the Korean Chemical Society Vol.45 No.3
In this study, selenium nanoparticles (SeNPs) were synthesized and stabilized by reducing sodium selenite using ascorbic acid in an aqueous solution of sodium carboxymethylcellulose (Na‐CMC) with a degree of substitution of 0.97 and a degree of polymerization of 810. IR‐Fourier spectroscopy revealed that coordination bonds between functional groups in Na‐CMC and SeNPs resulted in the development of polymer‐metal complexes. UV–Vis spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and dynamic light scattering (DLS) methods were used to determine the SeNP sizes in the structure of the nanocomposite film. Investigation of the stabilization and nonstabilization of SeNPs over several cycles has shown that the effect of the polymer matrix of Na‐CMC on the stabilization of nanoparticles was achieved for 672 h, which was confirmed by the unchanged size distribution and resistance to change of the SeNPs synthesized in Na‐CMC solutions. In this study, selenium nanoparticles (SeNPs) were synthesized and stabilized by reducing sodium selenite using ascorbic acid in an aqueous solution of sodium carboxymethylcellulose (Na-CMC) with a degree of substitution of 0.97 and a degree of polymerization of 810. IR-Fourier spectroscopy revealed that coordination bonds between functional groups in Na-CMC and SeNPs resulted in the development of polymer-metal complexes. UV–Vis spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and dynamic light scattering (DLS) methods were used to determine the SeNP sizes in the structure of the nanocomposite film. Investigation of the stabilization and nonstabilization of SeNPs over several cycles has shown that the effect of the polymer matrix of Na-CMC on the stabilization of nanoparticles was achieved for 672 h, which was confirmed by the unchanged size distribution and resistance to change of the SeNPs synthesized in Na-CMC solutions.
Band gap engineering of ZnMnO diluted magnetic semiconductor by alloying with ZnS
Yunusov, Z.A.,Yuldashev, Sh. U.,Kwon, Y.H.,Kim, D.Y.,Lee, S.J.,Jeon, H.C.,Jung, H.,Kim, A.,Kang, T.W. North-Holland Pub. Co 2018 Journal of magnetism and magnetic materials Vol.446 No.-
<P><B>Abstract</B></P> <P>In this paper we report the results on the fabrication of diluted magnetic semiconductors Zn<SUB>1−x</SUB>Mn<SUB>x</SUB>O<SUB>1−y</SUB>S<SUB>y</SUB> thin films with manganese x=0.05 and sulfur 0≤y≤0.15 compositions, respectively, by using ultrasonic spray pyrolysis method. The influence of the sulfur concentration on the band gap energy, structural and magnetic properties have been studied by using optical transmission, X-ray diffraction and superconducting quantum interference device (SQUID) measurements, respectively. The morphology and composition of samples were studied by using Scanning Electron Microscope (SEM) and X-ray photoelectron spectroscopy (XPS). With increasing of the sulfur concentration the band gap energy of composition decreases, while the magnetization increases proportional to the sulfur concentration.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effect of the sulfur dopant concentration on the structural, optical and magnetic properties. </LI> <LI> Band gap energy of the films decreases from 3.2eV to 2.96eV with increasing the sulfur dopant concentration. </LI> <LI> The SQUID and Hall Effect measurements demonstrate the room temperature ferromagnetism in the sulfur doped ZnMnO thin films. </LI> </UL> </P>
Integration of IP traceback with DDoS detection systems
Laziz Yunusov,Young-Tak Kim 한국통신학회 2009 한국통신학회 학술대회논문집 Vol.2009 No.6
In this paper, we introduce a security management architecture which integrates IP traceback mechanism with currently deployed Intrusion Detection System (IDS)/Intrusion Prevention System (IPS). A model is presented to extend IP traceback mechanism with distribution of attack traffic patterns to prevent new attacks at edge traceback-enabled routers. Current state of the arts in research on DDoS detection and IP traceback mechanisms is discussed, and existing commercial solution of DDoS attack detection and mitigation are described.
Effect of Isovalent Doping on the Magnetic Properties of ZnMnO Diluted Magnetic Semiconductors
Ziyodbek A. Yunusov,Shavkat U. Yuldashev,강태원,이승주,권영해,전희창 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.2
The magnetic properties of a ZnMnO diluted magnetic semiconductor isovalently doped with Mg and S have been successfully studied. ZnMnO alloys were prepared with dierent concentrations of magnesium and sulfur by using ultrasonic spray pyrolysis technique; additionally, the lms were doped for free charge carriers by using nitrogen. For ZnMnO doped with 5% of Mg, the Curie temperature reached 104 K, and second-phase magnetic precipitates were observed with increasing Mg concentration. On the other hand, the sulfur doped ZnMnO showed an increased Curie temperature higher than room temperature due to increased number of holes which mediated the magnetic exchange interaction between magnetic ions.
Development of a Low-cost Industrial OCR System with an End-to-end Deep Learning Technology
Subedi, Bharat,Yunusov, Jahongir,Gaybulayev, Abdulaziz,Kim, Tae-Hyong Institute of Embedded Engineering of Korea 2020 대한임베디드공학회논문지 Vol.15 No.2
Optical character recognition (OCR) has been studied for decades because it is very useful in a variety of places. Nowadays, OCR's performance has improved significantly due to outstanding deep learning technology. Thus, there is an increasing demand for commercial-grade but affordable OCR systems. We have developed a low-cost, high-performance OCR system for the industry with the cheapest embedded developer kit that supports GPU acceleration. To achieve high accuracy for industrial use on limited computing resources, we chose a state-of-the-art text recognition algorithm that uses an end-to-end deep learning network as a baseline model. The model was then improved by replacing the feature extraction network with the best one suited to our conditions. Among the various candidate networks, EfficientNet-B3 has shown the best performance: excellent recognition accuracy with relatively low memory consumption. Besides, we have optimized the model written in TensorFlow's Python API using TensorFlow-TensorRT integration and TensorFlow's C++ API, respectively.
Development of a Work Management System Based on Speech and Speaker Recognition
Gaybulayev, Abdulaziz,Yunusov, Jahongir,Kim, Tae-Hyong Institute of Embedded Engineering of Korea 2021 대한임베디드공학회논문지 Vol.16 No.3
Voice interface can not only make daily life more convenient through artificial intelligence speakers but also improve the working environment of the factory. This paper presents a voice-assisted work management system that supports both speech and speaker recognition. This system is able to provide machine control and authorized worker authentication by voice at the same time. We applied two speech recognition methods, Google's Speech application programming interface (API) service, and DeepSpeech speech-to-text engine. For worker identification, the SincNet architecture for speaker recognition was adopted. We implemented a prototype of the work management system that provides voice control with 26 commands and identifies 100 workers by voice. Worker identification using our model was almost perfect, and the command recognition accuracy was 97.0% in Google API after post- processing and 92.0% in our DeepSpeech model.
Critical behavior of the resistivity of GaMnAs near the Curie temperature
Yuldashev, Sh.U.,Yunusov, Z.A.,Kwon, Y.H.,Lee, S.H.,Ahuja, R.,Kang, T.W. Pergamon Press ; Elsevier Science Ltd 2017 Solid state communications Vol.263 No.-
<P>The effect of the magnetization fluctuations on the resistivity of GaMnAs near the Curie temperature T-C was experimentally studied. It is shown that the determination of T-C from the maximum of the temperature derivative of the resistivity is valid for the samples with a high concentration of free carries. Whereas, for the samples with low concentration of free carriers the T-C coincides with the resistivity maximum. The magnetic specific heat for T > T-C demonstrates the crossover from the one dimensional to the three dimensional critical behavior when the temperature become closer to the Curie temperature. This is explained by the formation of the ferromagnetic phase in the paramagnetic side of the phase transition which is started from Mn-Mn dimers oriented along one direction.</P>