Tailoring n-ZnO/p-Si Branched Nanowire Heterostructures for Selective Photoelectrochemical Water Oxidation or Reduction

Kargar, Alireza,Sun, Ke,Jing, Yi,Choi, Chulmin,Jeong, Huisu,Zhou, Yuchun,Madsen, Kristian,Naughton, Perry,Jin, Sungho,Jung, Gun Young,Wang, Deli American Chemical Society 2013 Nano letters Vol.13 No.7

<P>We report the fabrication of three-dimensional (3D) branched nanowire (NW) heterostructures, consisting of periodically ordered vertical Si NW trunks and ZnO NW branches, and their application for solar water splitting. The branched NW photoelectrodes show orders of magnitudes higher photocurrent compared to the bare Si NW electrodes. More interestingly, selective photoelectrochemical cathodic or anodic behavior resulting in either solar water oxidation or reduction was achieved by tuning the doping concentration of the p-type Si NW core. Specifically, n-ZnO/p-Si branched NW array electrodes with lightly doped core show broadband absorption from UV to near IR region and photocathodic water reduction, while n-ZnO/p<SUP>+</SUP>-Si branched NW arrays show photoanodic water oxidation with photoresponse only to UV light. The photoelectrochemical stability for over 24 h under constant light illumination and fixed biasing potential was achieved by coating the branched NW array with thin layers of TiO<SUB>2</SUB> and Pt. These studies not only reveal the promise of 3D branched NW photoelectrodes for high efficiency solar energy harvesting and conversion to clean chemical fuels, but also developing understanding enabling rational design of high efficiency robust photocathodes and photoanodes from low-cost and earth-abundant materials allowing practical applications in clean renewable energy.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2013/nalefd.2013.13.issue-7/nl304539x/production/images/medium/nl-2012-04539x_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl304539x'>ACS Electronic Supporting Info</A></P>

3D Branched Nanowire Photoelectrochemical Electrodes for Efficient Solar Water Splitting

Kargar, Alireza,Sun, Ke,Jing, Yi,Choi, Chulmin,Jeong, Huisu,Jung, Gun Young,Jin, Sungho,Wang, Deli American Chemical Society 2013 ACS NANO Vol.7 No.10

<P>We report the systematic study of 3D ZnO/Si branched nanowire (b-NW) photoelectrodes and their application in solar water splitting. We focus our study on the correlation between the electrode design and structures (including Si NW doping, dimension of the trunk Si and branch ZnO NWs, and b-NW pitch size) and their photoelectrochemical (PEC) performances (efficiency and stability) under neutral conditions. Specifically, we show that for b-NW electrodes with lightly doped p-Si NW core, larger ZnO NW branches and longer Si NW cores give a higher <I>photocathodic</I> current, while for b-NWs with heavily doped p-Si NW trunks smaller ZnO NWs and shorter Si NWs provide a higher <I>photoanodic</I> current. Interestingly, the photocurrent turn-on potential decreases with longer p-Si NW trunks and larger ZnO NW branches resulting in a significant photocathodic turn-on potential shift of ∼600 mV for the optimized ZnO/p-Si b-NWs compared to that of the bare p-Si NWs. A photocathode energy conversion efficiency of greater than 2% at −1 V <I>versus</I> Pt counter electrode and in neutral solution is achieved for the optimized ZnO/p-Si b-NW electrodes. The PEC performances or incident photon-to-current efficiency are further improved using Si NW cores with smaller pitch size. The photoelectrode stability is dramatically improved by coating a thin TiO<SUB>2</SUB> protection layer using atomic-layer deposition method. These results provide very useful guidelines in designing photoelectrodes for selective solar water oxidation/reduction and overall spontaneous solar fuel generation using low cost earth-abundant materials for practical clean solar fuel production.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-10/nn404170y/production/images/medium/nn-2013-04170y_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn404170y'>ACS Electronic Supporting Info</A></P>

Mathematical modeling of smart nanoparticles-reinforced concrete foundations: Vibration analysis

Masood Kargar,Mahmood Rabani Bidgoli 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.4

In this research, vibration and smart control analysis of a concrete foundation reinforced by SiO₂ nanoparticles and covered by piezoelectric layer on soil medium is investigated. The soil medium is simulated with spring constants and the Mori-Tanaka low is used for obtaining the material properties of nano-composite structure and considering agglomeration effects. With considering first order shear deformation theory, the total potential energy of system is calculated and by means of Hamilton.s principle in three displacement directions and electric potential, the six coupled equilibrium equations are obtained. Also, based an analytical method, the frequency of system is calculated. The effects of applied voltage, volume percent and agglomeration of SiO₂ nanoparticles, soil medium and geometrical parameters of structure are shown on the frequency of system. Results show that with applying negative voltage, the frequency of structure is increased.

Vibration analysis of spherical sandwich panels with MR fluids core and magneto-electro-elastic face sheets resting on orthotropic viscoelastic foundation

Javad Kargar,Ali Ghorbanpour Arani,Ehsan Arshid,Mohsen Irani Rahaghi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.5

The current study considers free vibration of the spherical panel with magnetorheological (MR) fluids core and magneto-electro-elastic face sheets. The panel is subjected to electro-magnetic loads and also is located on an orthotropic visco- Pasternak elastic foundation. To describe the displacement components of the structure, the first-order shear deformation theory (FSDT) is used and the motion equations are extracted by employing Hamilton’s principle. To solve the motion differential equations, Navier’s method is selected as an exact analytical solution for simply supported boundary conditions. Effect of the most important parameters such as magnetic field intensity, loss factor, multi-physical loads, types of an elastic medium, geometrical properties of the panel, and also different material types for the face sheets on the results is considered and discussed in details. The outcomes of the present work may be used to design more efficient smart structures such as sensors and actuators.

ON A CLASS OF STARLIKE FUNCTIONS RELATED WITH BOOTH LEMNISCATE

R. KARGAR,J. SOKOL,A. EBADIAN,L. TROJNAR-SPELINA 장전수학회 2018 Proceedings of the Jangjeon mathematical society Vol.21 No.3

Let A be the class of normalized analytic functions. We study the class BS(α) as follows BS(α) := { f ∈ A : (zf'(z)/ f(z) - 1) ≺ z/1-αx2, |z| < 1}, where "≺" is the subordination relation and 0 ≤ α < 1. Also, we consider the class BK(α), including of all functions f ∈ A such that zf'(z) ∈ BS(α). In the present article, some properties of the classes BS() and BK() are investigated.

High Prevalence of Class 1 to 3 Integrons Among Multidrug-Resistant Diarrheagenic Escherichia coli in Southwest of Iran

Mohammad Kargar,Zahra Mohammadalipour,Abbas Doosti,Shahrokh Lorzadeh,Alireza Japoni-Nejad 질병관리본부 2014 Osong Public Health and Research Persptectives Vol.5 No.4

Objectives: Horizontal transfer of integrons is one of the important factors that can contribute to the occurrence of multidrug-resistant (MDR) bacteria. This study aimed to determine the prevalence of integrons among MDR Escherichia coli strains isolated from stool specimens and investigate the associations between the existence of integrons and MDR properties in the southwest of Iran. Methods: There were 164 E. coli strains isolated from January 2012 to June 2012. Fecal specimens identified as E. coli by the conventional methods. Subsequently the antibiotic resistance was assessed using Clinical and Laboratory Standard Institute criteria. The presence of class 1-3 integrons and embedded gene cassettes was verified using specific primers by multiplex polymerase chain reaction assay. Results: Among a total of 164 studied samples, 69 (42.07%) isolates were multidrug resistant. Class 1 and class 2 integrons were present in 78.26% and 76.81% MDR isolates, respectively. For the first time in Iran, class 3 integron was observed in 26.09% MDR isolates. Significant correlations were identified between: class 1 integron and resistance to amikacin, gentamicin, chloramphenicol, ampicillin, tetracycline, nalidixic acid, and co-trimoxazole; class 2 integron and resistance to aminoglycosides, co-trimoxazole, cefalexin, ampicillin, and chloramphenicol; and class 3 integron and resistance to gentamicin, kanamycin, and streptomycin. Conclusion: Our results indicate that integrons are common among MDR isolates and they can be used as a marker for the identification of MDR isolates. Therefore, due to the possibility of a widespread outbreak of MDR isolates, molecular surveillance and sequencing of the integrons in other parts of the country is recommended.

Truthful and Secure Routing in Ad Hoc Networks with Malicious and Selfish Nodes

Mehdi Kargar,Mohammad Ghodsi 보안공학연구지원센터 2009 International Journal of Security and Its Applicat Vol.3 No.1

Cooperation among nodes is important in ad hoc networks since in such networks nodes depend on each other for forwarding packets. However, cooperation in such operations consumes nodes energy and recourses. Therefore, it is necessary to design incentive mechanisms to enforce nodes to forward packets when the source and destination of the packet are other nodes in the network. We study routing in ad hoc and wireless networks from a game theoretic view point. Based on this view, the network consists of selfish and greedy nodes who accept payments for forwarding data for other nodes if the payments cover their individual costs incurred by forwarding data. Also, route falsification attacks are easy to launch by malicious nodes in ad hoc networks. These nodes falsify data and routes in the network. Thus, mitigating this attack is vital for the performance of the whole network. Previous routing protocols in ad hoc networks inspired by game theory just consider that network consists of selfish nodes. In this work, we consider that the network consists of malicious nodes too. Here we present a truthful and secure mechanism for routing in ad hoc networks that cope malicious and selfish nodes.

Molecular Investigation of Quinolone Resistance of Quinolone Resistance-Determining Region in Streptococcus pneumoniae Strains Isolated from Iran Using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism Method

Mohammad Kargar,Fataneh Moein Jahromi,Abbas Doosti,Somayeh Handali 질병관리본부 2014 Osong Public Health and Research Persptectives Vol.5 No.5

Objectives: The resistance of Streptococcus pneumoniae to the recently available antibiotic treatment has been a growing problem. The aim of the study was to determine the quinolone-resistant strains and detect the presence of mutations in the quinolone resistance-determining regions of the gyrA, parE, and parC genes. Methods: In this study, for the first time in Iran, the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used to investigate the presence of mutations at quinolone resistance-determining regions of topoisomerase IV and DNA gyrase on 82 S. pneumoniae strains, among them 45 clinical samples were from patients and 37 from healthy carriers (control group). Results: In clinical samples, 34 (75.56%) strains contained mutations in the parC gene, 31 (68.89%) carried mutations in the gyrA gene, and 14 (31.11%) had parE gene mutations. Antibiotic susceptibility test was performed using the CLSI (Clinical and Laboratory Standards Institute) criteria on three different generations of quinolone family, with nalidixic acid (82.22%) showing the highest resistance and levofloxacin (42.22%) the least resistance. Conclusion: Results indicated that there is a significant correlation between quinolone resistance development and mutations in the parE gene as well as in the parC and gyrA genes.

On Water CuSO₄. 5H₂O-catalyzed Synthesis of 2-amino-4H-chromenes

Behbahani, Farahnaz Kargar,Maryam, Sadeghi Korean Chemical Society 2013 대한화학회지 Vol.57 No.3

Sustainable development is a balance between environment and development. Sustainable development requires sustainable supplies of clean, affordable, and renewable energy sources that do not cause negative impact to the society. This article introduces a green chemistry method to synthesize 2-amino-4H-chromenes that reduces or eliminates the use and generation of hazardous substances in the design, manufacture, and application of chemical products. This method is described using copper (II) sulfate pentahydrate, as a green and reusable catalyst on water. The products were obtained at very good yields, short reaction time, and at lower cost than other reported procedures.

Shape and Orifice Optimization of Airbag Systems for UAV Parachute Landing

Alizadeh, Masoud,Sedaghat, Ahmad,Kargar, Ebrahim The Korean Society for Aeronautical and Space Scie 2014 International Journal of Aeronautical and Space Sc Vol.15 No.3

An airbag is an important safety system and is well known as a safety system in cars during an accident. Airbag systems are also used as a shock absorber for UAVs to assist with rapid parachute landings. In this paper, the dynamics and gas dynamics of five airbag shapes, cylindrical, semi-cylindrical, cubic, and two truncated pyramids, were modelled and simulated under conditions of impact acceleration lower than $4m/s^2$ to avoid damage to the UAV. First, the responses of the present modelling were compared and validated against airbag test results under the same conditions. Second, for each airbag shape under the same conditions, the responses in terms of pressure, acceleration, and emerging velocity were investigated. Third, the performance of a pressure relief valve is compared with a fixed-area orifice implemented in the air bag. For each airbag shape under the same conditions, the optimum area of the fixed orifice was determined. By examining the response of pressure and acceleration of the airbag, the optimum shape of the airbag and the venting system is suggested.