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Hamid Arian Zad 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.70 No.9
In the present work, we first verify pairwise quantum discord (QD) between half-spins of a mixed three-spin (1/2,1,1/2) system with Ising-XY model for which spins (1,1/2) have Ising interaction and spins (1/2,1/2) have both XY and Dzyaloshinskii-Moriya (DM) interactions. A single-ion anisotropy property is assumed for integer spin. This system is considered at the front of an external homogeneous magnetic field B in thermal equilibrium. Then, we investigate the pairwise entanglement between half-spins by using entanglement of formation (EoF) as functions of temperature T, magnetic field B and other introduced parameters. In this case, all parameters are independent of the temperature. We compare the QD and the EoF verified for the spins (1/2,1/2) and express some interesting temperature, magnetic and quantum correlation properties. Also, we study the anisotropy influences on the quantum correlation between such spins in detail, and we find that this parameter can be used as a quantum discord controller. In the second step, we investigate QD for the half-spins in a stochastic manner, i.e., when all parameters of the tripartite system are constant (independent of the temperature) except the anisotropy, which is considered as a random variable dependent on the temperature. Finally, we assume that all parameters are constant except the Ising coupling strength, which can change randomly with temperature. Ultimately, we conclude that in the experimental conditions under which some parameters may have stochastic behavior, the anisotropy can also be a good candidate to control QD.
Semimetallic Graphene for Infrared Sensing
Gul, Hamza Zad,Sakong, Wonkil,Ji, Hyunjin,Torres, Jorge,Yi, Hojoon,Ghimire, Mohan Kumar,Yoon, Jung Hyun,Yun, Min Hee,Hwang, Ha Ryong,Lee, Young Hee,Lim, Seong Chu American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.21
<P>Both photothermal and photovoltaic infrared (IR) detectors employ sensing materials that have an optical band gap. Different from these conventional materials, graphene has a conical band structure that imposes zero band gap. In this study, using the semimetallic multilayer graphene, IR detection at room temperature is realized. The relatively high Seebeck coefficient, ranging from 40 to 60 μV/K, compared to that of the metal, and the large optical absorption in the mid-IR region, in the wavelength range of 7-17 μm, enable graphene to detect IR without an absorber, which is essential for most IR detectors because the band gap of the sensing materials is much larger than the energy of IR and the incident IR can be absorbed directly by the sensing material. Thus, the incident IR can be absorbed directly by the sensing material in our device. The developed detector with a SiN membrane shows high responsivity and detectivity, which are 140 V/W and 5 × 10<SUP>8</SUP> cm·Hz<SUP>1/2</SUP>/W at 5 Hz, respectively. In addition, the IR sensor shows a response time of 600 μs. In the room-temperature operation of the IR sensor array without cooling, our sensors detect IR emitted from a human body and track the movement. The availability of large-area graphene in current technology opens new applications for metallic two-dimensional materials and a possibility for scale-up.</P> [FIG OMISSION]</BR>
Structural Investigation and Preparation of 14-alkyl-14H-dibenzo[a,j]xanthenes revised
Ahmad Khoramabadi-zad,Zahra Kazemi,Hadi Amiri Rudbari Korean Chemical Society 2002 대한화학회지 Vol.46 No.6
높은 순도의 14-알킬-14H-다이벤조[a,j]잔텐의 합성법과 AM1 SCF MO 계산을 보고하였다. Prepartion of the title compounds at 0-5$^{\circ}C$ is reported along with their AM1 SCF MO calculations. The advantage of this procedure is the hight purity of the produ cts.
Alireza Najigivi,Alireza Khaloo,Azam Iraji zad,Suraya Abdul Rashid 한국콘크리트학회 2013 International Journal of Concrete Structures and M Vol.7 No.3
In this study, a two-layer feed-forward neural network was constructed and applied to determine a mapping associating mix design and testing factors of cement?nano silica (NS)?rice husk ash ternary blended concrete samples with their performance in conductance to the water absorption properties. To generate data for the neural network model (NNM), a total of 174 field cores from 58 different mixes at three ages were tested in the laboratory for each of percentage, velocity and coefficient of water absorption and mix volumetric properties. The significant factors (six items) that affect the permeability properties of ternary blended concrete were identified by experimental studies which were: (1) percentage of cement; (2) content of rice husk ash; (3) percentage of 15 nm of SiO₂ particles; (4) content of NS particles with average size of 80 nm; (5) effect of curing medium and (6) curing time. The mentioned significant factors were then used to define the domain of a neural network which was trained based on the Levenberg?Marquardt back propagation algorithm using Matlab software. Excellent agreement was observed between simulation and laboratory data. It is believed that the novel developed NNM with three outputs will be a useful tool in the study of the permeability properties of ternary blended concrete and its maintenance.
Graphene-CdSe quantum dot hybrid as a platform for the control of carrier temperature
Ghimire, Mohan Kumar,Gul, Hamza Zad,Yi, Hojoon,Dang, Dang Xuan,Sakong, Won Kil,Luan, Nguyen Van,Ji, Hyun Jin,Lim, Seong Chu Elsevier 2017 Flatchem Vol.6 No.-
<P><B>Abstract</B></P> <P>In a graphene and quantum dots (QDs) hybrid structure, the graphene is known to play the role of an electrode that conducts the photoexcited carriers from the QDs to the electrodes. Thus, the yield of photocurrent of the QD ensemble is greatly enhanced . However, in our study, the graphene provides a platform to control the energy relaxation of optically excited carriers from QDs. Thus, the temperature of photocarriers of QDs is controllable. Due to the moderate carrier temperature, the observed photocurrent from the hybrid structure reveals a photothermoelectric effect, which becomes even stronger when the Fermi energy, E<SUB>F</SUB>, is located near the charge neutrality point (CNP) of the graphene. However, the photothermoelectric behavior weakens with increased E<SUB>F</SUB>. Such a behavior originates from the varying electron-phonon coupling strength that is dependent upon E<SUB>F</SUB> of the graphene.</P> <P><B>Highlights</B></P> <P> <UL> <LI> In a graphene, the coupling strength of electron and optical phonon can be controlled by electrostatic gating. </LI> <LI> Hybridization of graphene and QDs provides a platform that we can control the carrier temperature. </LI> <LI> The carrier temperature ranges 0.03 to 1.6K above the graphene lattice temperature depending on the back gate bias. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Golnaz Sadoughi,Raheleh Mohammadpour,Azam Iraji zad,Nima Taghavinia,Shabnam Dadgostar,Mahmoud Samadpour,Fariba Tajabadi 한국물리학회 2013 Current Applied Physics Vol.13 No.2
The photoanodes of solid state dye sensitized solar cells (ss-DSCs) embedded with different contents of TiO2 hollow spheres (HSs) were prepared and the photovoltaic performances were systematically characterized. TiO2 hollow spheres were synthesized by a facile sacrificial templating method, grounded and added in different ratios to TiO2 nanoparticle (NP) paste, from which composite HS/NP electrodes were fabricated. The composite photoanodes include hollow spheres of 300e700 nm with enhanced light scattering characteristics in visible range which leads to improved light absorption in conventional thin film electrodes of ss-DSC. By optimizing the amount of HSs in the paste, 40% improvement in efficiency was obtained in comparison to ss-DSC utilized pure NP electrodes. By increasing the fraction of HSs in the electrode the current density increased by 56% (from 2.5 to 3.9 mA cm2). The improved photovoltaic performance of ss-DSC is primarily due to different morphology and altered charged trap distribution in HSs in comparison to NP which leads to significant enhancement in electron transport time and electron lifetime as well as charge collection efficiency and light absorption properties.
Metal-coated carbon fiber for lighter electrical metal wires
Kang, Sung Soo,Ji, Hyunjin,Gul, Hamza Zad,Sakong, Won Kil,Kim, Ji Yeon,Kim, Won Seok,Lee, Jhony,Han, Songhee,Park, Minyoung,Choi, Young Chul,Lim, Seong Chu Elsevier 2016 Synthetic metals Vol.222 No.2
<P><B>Abstract</B></P> <P>In this study, we plated thin conducting Cu layer in a thickness of 200–300nm on the surface of carbon fiber that was supposed to replace the core of Cu wire for weight reduction. The metal-coated carbon fibers (MCF) exhibit comparable electrical properties to the bulk Cu including the electrical conductivity of 5.9×10<SUP>−6</SUP> Ωcm, temperature coefficient of resistance (TCR) of 1.14×10<SUP>−3</SUP>/K, and featureless 1/f noises. In addition to electrical properties, the Joule heating of MCF revealed that the MCF terminated itself when the temperature of MCF significantly rose. This was due to the much lower burning temperature of carbon fiber, comparing to that of Cu, which can be beneficial in the prevention of a fire sparked by a hot metal wire.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Preparation of metal-coated carbon fiber for lighter electrical metal wires. </LI> <LI> Superb electrical properties of metal-coated carbon fiber along with lower weight. </LI> <LI> Excellent interfacial quality between copper and carbon fiber. </LI> </UL> </P>
Photocurrent Switching of Monolayer MoS<sub>2</sub> Using a Metal–Insulator Transition
Lee, Jin Hee,Gul, Hamza Zad,Kim, Hyun,Moon, Byoung Hee,Adhikari, Subash,Kim, Jung Ho,Choi, Homin,Lee, Young Hee,Lim, Seong Chu American Chemical Society 2017 NANO LETTERS Vol.17 No.2
<P>We achieve switching on/off the photocurrent of monolayer molybdenum disulfide (MoS2) by controlling the metal-insulator transition (MIT). N-type semiconducting MoS2 under a large negative gate bias generates a photocurrent attributed to the increase of excess carriers in the conduction band by optical excitation. However, under a large positive gate bias, a phase shift from semiconducting to metallic MoS2 is caused, and the photocurrent by excess carriers in the conduction band induced by the laser disappears due to enhanced electron-electron scattering. Thus, no photocurrent is detected in metallic MoS2. Our results indicate that the photocurrent of MoS2 controlling the MIT transition by means of gate bias.</P>