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Numerical investigation and potential tunability scheme on e^+e^- and π^+π^- stimulated pair creation from vacuum using high intensity laser beams

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High Power Laser Science and Engineering 2016年第4期4卷 1-7页

作者： i.Ploumistakis S.D.Moustaizis i.Tsohantjis Technical University of Crete Laboratory of Matter Structure and Laser Physics National and Kapodistrian University of Athens Faculty of PhysicsDepartment of Nuclear and Particle Physics

Numerical estimates for electrons and mesons particle–antiparticle creation from vacuum in the presence of strong electromagnetic fields are derived, using the complete probability density relation of Popov's imaginary time method(Popov, JETP Lett. 13, 185(1971); Sov. Phys. JETP 34, 709(1972); Sov. Phys. JETP 35, 659(1972); Popov and Marinov, Sov. J. Nucl. Phys. 16, 449(1973); JETP Lett. 18, 255(1974); Sov. J. Nucl. Phys. 19, 584(1974));(Popov,Phys. Let. A 298, 83(2002)), and within the framework of an experimental setup like the E144(Burke et al., Phys. ***. 79, 1626(1997)). The existence of crossing point among pair creation efficiency curves of different photon energies and the role of odd/even multiphoton orders in the production rates are discussed. Finally a kind of tunability process between the two creation processes is discussed.

关键词： high intensity lasers multiphoton processes pair production

improving the reconstruction efficiency of sparsity adaptive matching pursuit based on the Wilkinson matrix

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Frontiers of information Technology & Electronic Engineering 2018年第4期19卷 503-512页

作者： Rasha SHOiTAN Zaki NossaiR i.i.iBRAHiM Ahmed TOBAL Computer and Systems Department Electronic Research Institute Electronics Communicationsand Computer DepartmentHelwan University

Sparsity adaptive matching pursuit(SAMP)is a greedy reconstruction algorithm for compressive sensing *** reconstructs signals without prior information of sparsity and presents better reconstruction performance for noisy signals compared to other greedy ***,SAMP still suffers from relatively poor reconstruction quality especially at high compression *** the proposed research,the Wilkinson matrix is used as a sensing matrix to improve the reconstruction quality and to increase the compression ratio of the SAMP ***,the idea of block compressive sensing(BCS)is combined with the SAMP technique to improve the performance of the SAMP *** simulations have been conducted to evaluate the proposed BCS-SAMP technique and to compare its results with those of several compressed sensing *** results show that the proposed BCS-SAMP technique improves the reconstruction quality by up to six decibels(d B)relative to the conventional SAMP *** addition,the reconstruction quality of the proposed BCS-SAMP is highly comparable to that of iterative ***,the computation time of the proposed BCS-SAMP is less than that of the iterative techniques,especially at lower measurement fractions.

关键词： Block compressive sensing Sparsity adaptive matching pursuit Greedy algorithm Wilkinson matrix

Conditions for formation and trapping of the two-ion Coulomb cluster in the dissipative optical superlattice

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Chinese Physics B 2015年第6期24卷 305-313页

作者： i.V.Krasnov institute of Computational Modeling Siberian DivisionRussian Academy of Sciences

Conditions have been studied under which a polychromatic optical superlattice can form and trap the Coulomb cluster of two strongly interacting ions. in our previous work （Krasnov i V and Kamenshchikov L P 2014 Opt. Comm. 312 192） this new all-optical method of obtaining and confining the Coulomb clusters was demonstrated by numerical simulations for special values of the optical superlattice parameters and in the case of Yb ions. in the present paper the conditions are explicitly formulated, under which the long-lived two-ion cluster in the superlattice cell is formed. The peculiarity of these conditions is the renormalization of the ion-ion Coulomb interaction. Notably, the renormalized Coulomb force is determined by the effective charge which depends on the light field parameters and can strongly differ from the ＂bare＂ ion charge. This result can be accounted for by the combined manifestation of the quantum fluctuations of optical forces, nonlinear dependence of these forces on the velocity, and non-Maxwellian （Tsallis type） velocity distribution of the ions in the optical superlattice. Explicit analytical formulas are also obtained for the parameters of the optical two-ion cluster.

关键词： optical trap ion trap rectified gradient force Coulomb clusters

Analysis of highly efficient perovskite solar cells with inorganic hole transport material

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Chinese Physics B 2019年第12期28卷 393-399页

作者： i Kabir S A Mahmood Department of Electrical and Electronics Engineering Bangladesh University of Engineering and Technology

Organo-halide perovskites in planar heterojunction architecture have shown considerable promise as efficient light harvesters in solar cells. We carry out a numerical modeling of a planar lead based perovskite solar cell(PSC) with Cu2ZnSnS4(CZTS) as the hole transporting material(HTM) using the one-dimensional solar cell capacitance simulator(SCAPS-1 D). The effects of numerous parameters such as defect density, thickness, and doping density of the absorber layer on the device performance are investigated. The doping densities and electron affinities of the electron transporting material(ETM) and the HTM are also varied to optimize the PSC performance. it has been observed that a thinner absorber layer of220 nm with a defect density of 1014 cm-3 compared to the reference structure improves the device performance. When doping density of the absorber layer increases beyond 2×1016 cm-3, the power conversion efficiency(PCE) reduces due to enhanced recombination rate. The defect density at the absorber/ETM interface reduces the PCE as well. Considering a series resistance of 5 ?·cm2 and all the optimum parameters of absorber, ETM and HTM layers simultaneously, the overall PCE of the device increases significantly. in comparison with the reference structure, the PCE of the optimized device has been increased from 12.76% to 22.7%, and hence the optimized CZTS based PSC is highly efficient.

关键词： CH3NH3Pbi3 Cu2ZnSnS4(CZTS) SCAPS-1D absorption coefficient

Susceptibility to Hot Cracking and Weldment Heat Treatment of Haynes 230 Superalloy

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Journal of Materials Science & Technology 2006年第5期22卷 685-690页

作者： i.K.Lee Department of Mechatronic Technology National Taiwan Normal University TaipeiTaiwanChina

This study investigates the susceptibility of hot cracking and weldment heat treatment of Haynes 230 superalloy. The Varestriant test was conducted to evaluate this susceptibility. Welding was performed by gas tungsten arc welding （GTAW） and plasma arc welding （PAW） with stress relief heat treatment and solid solution heat treatment. A tensile test is then performed to measure the changes in the mechanical properties of the heattreated material. The results indicate that the number of thermal cycles does not affect the susceptibility of Haynes 230 superalloy to hot cracking. However, it does increase the strain. in weldment of heat treatment, stress relief annealing increases the yield strength and tensile strength of the welded parts. The section of the tensile specimens shows fibrous fractures on the welded parts, regardless of whether they are heat-treated.

关键词： Haynes 230 super alloy Varestriant test Hot cracking Susceptibility Stress relief annealing

Evaluation of Phytochemical Contents and Antimicrobial Activities of Pandiaka heudelotii

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Advances in Biological Chemistry 2024年第2期14卷 55-63页

作者： ikenna Obiora Alaekwe Uche Eunice Ekpunobi Vincent ishmel Egbulefu Ajiwe chinedu Chris Aguoma Jamilu Ahmad Department of Chemistry Federal University Gusau Gusau Nigeria Department of Pure and industrial Chemistry Nnamdi Azikiwe University Awka Awka Nigeria

The work investigated the secondary metabolites present in different parts of the Pandiaka heudelotii plant harvested from Ezira, Orumba south local government area of Anambra state, southeastern Nigeria as well as their antimicrobial activity. The objectives were to extract, determine the phytochemicals present, evaluate the antimicrobial potential and determine the zones of inhibition of the root, stem and leaf extracts of the plant. The emergence of antibiotics has decreased the spread and severity of a wide range of diseases. Plant extracts were tested for antibacterial and antifungal activities against Staphylococcus aureus, Escherichia coli, Proteus vulgaris, Streptococcus pyogenes, Bacillus subtelis, Pseudomonas aerogenes, Salmonella typhi, Aspergillus flavus, Aspergillus niger and Candida albicans. The zone of inhibition of extracts was compared with that of standard drugs like Erythromycin, Ciprofloxacin, Fulcin and Fluconazole. The result revealed the inhibition of bacterial and fungal growth with some test organisms. The microbial activity of the plant parts may be due to the presence of various secondary metabolites. The ethyl acetate extracts of Pandiaka heudelotii stood out with a minimum inhibitory concentration (MiC) range of 5 - 10 mg/mL and a minimum bactericidal concentration (MBC)/minimum fungicidal concentration (MFC) of 10 - 20 mg/ml against some test organisms. The plant can thus be worked upon to discover biologically active natural products that may serve as a prelude to the development of new pharmaceutical research undertakings.

关键词： Pharmaceuticals Secondary Metabolites Antibiotics Pandiaka heudelotii Bacteria

Chemoprotective activity of aqueous leaf extract of Acalypha wilkesiana against cyclophosphamide-induced toxicity in rats

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Asian Pacific Journal of Tropical Medicine 2019年第9期12卷 409-415页

作者： chinedu P.Anokwuru God’swill N.Anyasor Olutayo S.Shokunbi Babajide Sopekan Oyindamola K.Osinuga Olusola E.Afolabi Olamide B.Arojojoye Chibundu N.Ezekiel isaiah Di.Ramaite Department of Basic Sciences School of Science and TechnologyBabcock UnitersiyIlishan RemoOgun StateNgeria Department of Chemistry School of Mathematical and Natural SciencesUnirersity of VendaThohoyandou South Africa Department of Biochenistry Benjamin S.Carson(Snr)Schoo of MedicineCollege of Health and Medical ScienesBabcock Uniters Department of Microbiology School of Science and TchnlogyBabrock Unitersitslishan RemoNigera

Objective:To investigate the protective effect of aqueous leaf extract of Acalypha(A.)wilkesiana ***(Euphorbiaceae)against cyclophosphamide-induced toxicity in albino ***:Twenty male albino rats were randomly divided into five groups of four animals *** control group(Ⅰ)was fed with pellets and distilled water,while group Ⅱ was orally administered with only 20 mg/kg *** Ⅲ,Ⅳ and Ⅴ were coadministered with 20 mg/kg body weight cyclophosphamide and 110,220 and 440 mg/kg body weight *** leaf extract,respectively,for 7 *** treatment,liver and kidney function biomarkers,haematological parameters,liver antioxidants,and mitochondrial membrane permeability transition pore opening were ***:*** leaf extract significantly reduced(Pide-induced increase in plasma aspartate aminotransferase,alanine aminotransferase,creatinine,uric acid and *** increased superoxide dismutase,catalase,glutathione-S-transferase activities and reduced glutathione *** also increased packed cell volume count,hemoglobin concentration and white blood cell count while inhibiting the induction of mitochondrial ***:This study demonstrates that aqueous extract of *** leaf protected tissues against cyclophosphamide-induced oxidative damage.

关键词： Medicinal plants Oxidative stress Chemoprotective activity Cyclophosphamide Acalypha wilkesiana

Electrical and dielectric characterization of Au/ZnO/n-Si device depending frequency and voltage

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Chinese Physics B 2017年第2期26卷 477-483页

作者： i Orak A Kocyigit S Ahndal Bingol University Vocational School of Health Services 12000 Bingol Turkey Bingol University Faculty of Sciences and Arts Department of Physics 12000 Bingol Turkey igdir University Engineering Faculty Department of Electrical Electronic Engineering 76000 Igdir Turkey Gazi Universty Faculty of Sciences Department of Physics 06500 Ankara Turkey

Au/Zn O/n-type Si device is obtained using atomic layer deposition（ALD） for Zn O layer, and some main electrical parameters are investigated, such as surface/interface state（Nss）, barrier height（Φb）, series resistance（Rs）, donor concentration（Nd）, and dielectric characterization depending on frequency or voltage. These parameters are acquired by use of impedance spectroscopy measurements at frequencies ranging from 10 k Hz to 1 MHz and the direct current（DC） bias voltages in a range from-2 V to ＋2 V at room temperature are used. The main electrical parameters and dielectric parameters,such as dielectric constant（ε＂）, dielectric loss（ε＂）, loss tangent（tan δ）, the real and imaginary parts of electric modulus（M and M）, and alternating current（AC） electrical conductivity（σ） are affected by changing voltage and frequency. The characterizations show that some main electrical parameters usually decrease with increasing frequency because charge carriers at surface states have not enough time to fallow an external AC signal at high frequencies, and all dielectric parameters strongly depend on the voltage and frequency especially in the depletion and accumulation regions. Consequently, it can be concluded that interfacial polarization and interface charges can easily follow AC signal at low frequencies.

关键词： Au/ZnO/n–Si device dielectric properties polarization process frequency and voltage dependence

Experimental nuclear charge density and theoretical description of theabove-barrier light heavy-ion fusion process

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Chinese Physics C 2023年第8期47卷 64-74页

作者： i.i.Gontchar M.V.Chushnyakova Physics and Chemistry Department Omsk State Transport UniversityOmskRussia Physics Department Omsk State Technical UniversityOmskRussia

Theoretical modeling of nucleus-nucleus collisions is often based on the nucleus-nucleus *** of the advanced methods for constructing this potential is the semi-microscopical double-folding model with M3 YParis *** and neutron densities are significant components of this *** correct nucleon density(ND) must reproduce the experimental nuclear charge density(NCD).However,those who deal with modeling the fusion process typically disregard this *** aim to achieve a good description of both the nuclear charge density and above-barrier fusion cross sections of even-even light nuclei with Z=*** consider several versions of NDs available in literature and construct our own approximation for the ND of the even-even spherical nuclei^(12)C,^(16)O,and^(40)Ca,abbreviated as FE-density(Fermi+exponential).We carefully compare the NCDs resulting from different versions of NDs with the experimental *** finding the nucleus-nucleus potential using the double-folding model with the density dependent M3 Y-Paris NN-forces and FE densities,we evaluate the abovebarrier fusion cross sections for five reactions,^(12)C+^(12)C,^(12)C+^(16)O,^(16)O+^(16)O,^(16)O+^(40)Ca,and^(40)Ca+^(40)Ca,and40Ca+40Ca,for which experimental data are *** cross sections are calculated using two approaches:a) the barrier penetration model and b) the trajectory model with surface friction(TM).To find the transmission coefficients for the TM,the Langevin equations are *** all considered reactions,our TM typically reproduces the above-barrier experimental cross sections within 10-15%.The only adjustable parameter of the model,the optimal friction strength KRm,is found to be approximately 90 zs·GeV-1for the light reactions12C+12C,12C+16O,and16O+16O and approximately 15zs·GeV-1for the heavy reactions16O+40Ca and40Ca+*** latter findings are in reasonable agreement with the systematics found ***,the FE-recipe allows highly accurate and s

关键词： nuclear charge densities nucleon densities heavy-ion fusion surface friction double-fold-ing model