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Emerging photoluminescence from defective vanadium diselenide nanosheets

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Photonics Research 2018年第4期6卷 244-253页

作者： AMIR ghobadi TURKAN GAMZE ULUSOY ghobadi ALI KEMAL OKYAY EKMEL OZBAY NANOTAM-Nanotechnology Research Center Bilkent University Department of Electrical and Electronics Engineering Bilkent University UNAM-Institute of Materials Science and Nanotechnology Bilkent University Department of Physics Bilkent University

In this paper, for the first time to our knowledge in the literature, we demonstrate photoluminescence from two-dimensional(2D) vanadium diselenide(VSe_2) nanosheets(NSs). The preparation of these nanostructures is carried out with a combinational method based on nanosecond pulsed laser ablation(PLA) and chemical exfoliation. For this aim, VSe_2 bulk is first ablated into nanoparticles(NPs) inside a water solution. Afterward,NPs are chemically exfoliated into NSs using lithium intercalation via ultrasonic treatment. Although VSe_2 is a semimetal in its bulk form, its nanostructures show photo-responsive behavior, and it turns into a strongly luminescent material when it is separated into NSs. Based on the obtained results, the surface defects induced during the PLA process are the origin of this photoluminescence from NSs. Our findings illustrate that this new material can be a promising semiconductor for photovoltaic and light emitting diode applications.

关键词： Semiconductors Optical materials Photoluminescence

Magneto-Transport and Nanomagnet Dynamics in MgO-Based Magnetic Tunnel Junctions(MTJs)

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Communications in Theoretical Physics 2016年第2期65卷 254-258页

作者： Nader ghobadi Reza Daqiq Faculty of Science Department of PhysicsMalayer University

We investigate bias and different barrier thicknesses effects on quantities related to spin and charge currents in MgO-based magnetic tunnel junctions. Using the non-Equilibrium Green's function formalism, we demonstrate that the in-plane and out-of-plane components of the spin-transfer torque have asymmetric and symmetric behaviors respectively. Magneto-resistance also decreases with increasing barrier thickness. The Landau–Lifshits–Gilbert equation describes the dynamics of the magnetization made by spin transfer torque. Increasing in spin current above its critical value or smaller the magnet reduces the switching time which is major result for making of new memory devices.

关键词： magnetic tunnel junctions spin-transfer torque magneto-resistance nanomagnet dynamics

A Robust Tracking Controller for Electrically Driven Robot Manipulators: Stability Analysis and Experiment

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International Journal of Automation and computing 2015年第1期12卷 83-92页

作者： Mohamadreza Homayounzade Mehdi Keshmiri Mostafa ghobadi Department of Mechanical Engineering Isfahan University of Technology (IUT) Department of Mechanical Engineering University at Buffalo SUNY

In this paper, a robust controller for electrically driven robotic systems is developed. The controller is designed in a backstepping manner. The main features of the controller are: 1) Control strategy is developed at the voltage level and can deal with both mechanical and electrical uncertainties. 2) The proposed control law removes the restriction of previous robust methods on the upper bound of system uncertainties. 3) It also benefits from global asymptotic stability in the Lyapunov sense. It is worth to mention that the proposed controller can be utilized for constrained and nonconstrained robotic systems. The effectiveness of the proposed controller is verified by simulations for a two link robot manipulator and a four-bar linkage. In addition to simulation results,experimental results on a two link serial manipulator are included to demonstrate the performance of the proposed controller in tracking a given trajectory.

关键词： Electrically driven robots Lyapunov stability parametric uncertainty robust control uncertain actuator dynamics

Algorithms for Handoff Minimization in Wireless Networks

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Journal of Computer Science & Technology 2019年第4期34卷 887-900页

作者： Mansoor Davoodi Esmaeil Delfaraz Sajjad ghobadi Mahtab Masoori Institute for Advanced Studies in Basic Sciences Zanjan 45137-66731Iran Gran Sasso Science Institute L'Aquila 67100Italy

This study focuses on the problem of handoff minimization for a set of users moving in a wireless *** problem is analyzed by considering two cases for the user's movement under access point capacity constraints:1)all users move together,and 2)each user can have their chosen path within the *** the first case,we propose an optimal competitive ratio algorithm for the ***,in the second case,having the connectivity assumption,that is,"if a user is connected to an access point so long that the received signal strength of the access point is not less than a specified threshold,the user should continue his/her connection",we prove that no approach can reduce the number of unnecessary handoffs in an offline ***,without connectivity assumption,we present an optimal deterministic algorithm with the competitive ratio of n?for this problem under online setting,where n is the number of users and?is the maximum number of access points which cover any single point in the ***,we prove that the randomized version of the algorithm achieves an expected competitive ratio of O(log△).

关键词： competitive ratio handoff minimization offline algorithm online algorithm wireless network

Excellent electrocatalytic activity of benzil for direct reduction of CO2 as well as indirect reduction of pyridine:A kinetic view of the electrocarboxylation process

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Journal of Energy Chemistry 2017年第3期26卷 569-573页

作者： Kobra ghobadi Hamid R.Zare Hossein Khoshro Abbas A.Jafari Department of Chemistry Faculty of ScienceYazd UniversityYazd 89195-741Iran

Benzil,1,2-diphenylethane-1,2-dione, was used as an excellent electrocatalyst for reduction of carbon dioxide, CO. The reduction overpotential of COwas reduced about 900 m V in the presence of a benzil mediator. The chemical reaction of the product of the electrocatalytic reduction of CO,(activated CO,CO) with pyridine at a glassy carbon electrode, GCE, surface and in an acetonitrile-ButNClOsolution was investigated by cyclic voltammetry, chronoamperometry and controlled potential *** chronoamperometry, the catalytic rate constant, k, for the electron transfer between benzil and COwas obtained as 8.1 ± 0.4 Ms. The results indicate that pyridine has a strong interaction with the activated CO. The coulometry method was used to obtain the product of the pyridine chemical reaction with CO. The spectral characterizations of FTIR,H andC NMR of the coulometry experiment product proved that the pyridine anion radical, Py, was carboxylated by CO, and isonicotinic acid is the final major product.

关键词： Carbon dioxide Benzil Pyridine electrocarboxylation Catalytic rate constant Isonicotinic acid

Tuning the metal filling fraction in metal-insulator-metal ultra-broadband perfect absorbers to maximize the absorption bandwidth

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Photonics Research 2018年第3期6卷 168-176页

作者： AMIR ghobadi HODJAT HAJIAN ALIREZA RAHIMI RASHED BAYRAM BUTUN EKMEL OZBAY NANOTAM-Nanotechnology Research Center Bilkent University Department of Electrical and Electronics Engineering Bilkent University Department of Physics Bilkent University UNAM-Institute of Materials Science and Nanotechnology Bilkent University

In this paper, we propose a methodology to maximize the absorption bandwidth of a metal-insulator-metal(MIM) based absorber. The proposed structure is made of a Cr-Al_2O_3-Cr multilayer design. At the initial step,the optimum MIM planar design is fabricated and optically characterized. The results show absorption above 0.9 from 400 nm to 850 nm. Afterward, the transfer matrix method is used to find the optimal condition for the perfect light absorption in an ultra-broadband frequency range. This modeling approach predicts that changing the filling fraction of the top Cr layer can extend light absorption toward longer wavelengths. We experimentally proved that the use of proper top Cr thickness and annealing temperature leads to a nearly perfect light absorption from 400 nm to 1150 nm, which is much broader than that of a planar design. Therefore, while keeping the overall process lithography-free, the absorption functionality of the design can be significantly improved. The results presented here can serve as a beacon for future performance-enhanced multilayer designs where a simple fabrication step can boost the overall device response without changing its overall thickness and fabrication simplicity.

关键词： Tuning the metal filling fraction perfect absorbers maximize the absorption bandwidth MIM

Pharmacological activity of Mentha longifolia and its phytoconstituents

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Journal of Traditional Chinese Medicine 2017年第5期37卷 710-720页

作者： Mohammad Hosein Farzaei Roodabeh Bahramsoltani Ali ghobadi Fatemeh Farzaei Fariba Najafi Medical Biology Research Center Kermanshah University of Medical Sciences Kermanshah *** Iran Pharmaceutical Sciences Research Center Kermanshah University of Medical Sciences Kermanshah *** Iran Department of Traditional Pharmacy School of Traditional Medicine Tehran University of Medical Sciences Tehran *** Iran School of Traditional Medicine Iran University of Medical Sciences Tehran *** Iran Kermanshah University of Medical Sciences Kermanshah *** Iran

Current paper reviews the pharmacological activities, therapeutic indications and phytochemicals of M. longifolia. This herb has been consumed traditionally for the treatment of various diseases, including gastrointestinal disorders, respiratory disorders, infectious diseases, inflammatory diseases, as well as menstrual disorders. In the modern era, various pharmacological activities have been confirmed for M. longifolia, such as anti-parasitic, antimicrobial, anti-insect, antimutagenic, antinociceptive, anti-inflammatory, antioxidant, keratoprotective, hepatoprotective, anti-diarrhea, and spasmolytic effects. The plant showed therapeutic benefits in irritable bowel syndrome, amenorrhea and oligomenorrhea, and oxidative stress-associated diseases as well. A vast variety of natural components such as flavonoids, phenolic acids, cinnamates, ceramides, sesquiterpenes, terpenes, and terpenoids have been suggested to be responsible for the pharmacological action of M. longifolia. These natural products can be considered as novel medicinal sources for developing new drugs. Further investigations to explore therapeutic efficacy, tolerability,and pharmaceutical properties of M. longifolia phytochemical agents are recommended.

关键词：药理活性阿里胃肠道疾病萜类化合物薄荷呼吸系统疾病抗寄生虫氧化应激

Effect of Silicon on Growth and Development of Strawberry under Water Deficit Conditions

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Horticultural Plant Journal 2018年第6期4卷 226-232页

作者： DEHGHANIPOODEH Safoora ghobadi Cyrus BANINASAB Bahram GHEYSARI Mahdi SHIRANIBIDABADI Siamak Department of Horticulture College of Agriculture Isfahan University of Technology IUT Water Engineering Department College of Agriculture Isfahan University of Technology

Water stress is a major factor that limits agricultural crop production. Silicon(Si) is generally considered as a beneficial element for the growth of higher plants, especially for those grown under stressful environment. This study was conducted to examine the effects of Si on growth and development of strawberry(Fragaria × ananassa ‘Camarosa') under water stress conditions. A factorial experiment, in a completely randomized design, was used to investigate the effects of three irrigation levels and four Si treatments consisting of 0, 5, 10, and 15 mmol·L^(-1) potassium silicate(K_2 SiO_3). The results showed that an increase in the levels of water stress caused a decrease in most of the quantitative characteristics such as specific leaf area, chlorophyll fluorescence, net photosynthesis rate, and stomata conductance; addition of Si significantly increased most of the mentioned factors; water stress increased electrolyte leakage, proline, and water use efficiency(WUE); Si treatment significantly decreased transpiration rate and improved chlorophyll content and WUE. Water stress stimulated mineral nutrient absorption whereas Si application decreased it under water stress. In conclusion, it was found that in most of the investigated factors, 10 mmol·L^(-1) potassium silicate had the best effect on growth and development of strawberry. Besides, Si application had beneficial effects on strawberry plants and the addition of it could alleviate water stress.

关键词： Fragaria×ananassa potassium silicate water stress photosynthesis mineral nutrient

Evaluation of anti-aphthous activity of decoction of Nicotiana tabacum leaves as a mouthwash： a placebo-controlled clinical study

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中医杂志：英文版 2016年第2期36卷 160-164页

作者： Siavash Vaziri Mahdi Mojarrab Mohammad Hosein Farzaei Farid Najafi Ali ghobadi Department of Infectious Disease Imam Reza Hospital Kermanshah University of Medical Sciences Kermanshah *** Iran Pharmaceutical Sciences Research Center Kermanshah University of Medical Sciences Kermanshah *** Iran Pharmaceutical Sciences Research Center Kermanshah University of Medical SciencesKermanshah *** Iran Kermanshah University of Medical Sciences Kermanshah *** Iran Department of Traditional Pharmacy School of Traditional Medicine Tehran University of Medical Sciences Tehran *** Iran

OBJECTIVE: To determine the effects of decoction derived from the leaves of Nicotiana tabacum(L.)as a mouthwash on minor recurrent ***: A randomized double-blinded placebo-controlled clinical trial was conducted on 60 patients with minor recurrent aphthous. Treatment comprised of application of tobacco or placebo mouthwash(10 m L 3 times a day) for 5 days. Clinical evaluation included pain level using a visual analog scale and ulcer size on days 1, 3, and 5 were measured. Adverse effects after mouthwash application were recorded, and the oral mucosa was examined by the investigator at each ***: A total of 54 subjects with the mean age(38 ± 10) years fulfilled the study. No minor and major adverse effects were observed. In the treatment group, ulcer pain score was decreased by 79.2%and 93.8% and ulcer size was reduced by 69.1%and 92.2%(days 3 and 5, respectively), which was significantly greater than the control group(P <0.01).CONCLUSION: The decoction prepared with of Nicotiana tabacum leaves, used as mouthwash are well-tolerated and safe, and can be used for the management of recurrent aphthous.

关键词：临床试验口腔黏膜漱口水活性评价烟草视觉模拟平均年龄不良反应