排序方式： 共有139条查询结果，搜索用时 0 毫秒
81.
Rukiye Ayan Mine Isiksal-Bostan 《International Journal of Mathematical Education in Science & Technology》2019,50(1):65-81
The purpose of this study was to examine middle school students’ proportional reasoning, solution strategies and difficulties in real life contexts in the domain of geometry and measurement. The underlying reasons of the difficulties were investigated as well. Mixed research design was adopted for the aims of the study by collecting data through an achievement test from 935 sixth, seventh and eighth grade students. The achievement test included real life problems that required proportional reasoning, and were related to the measurement of length, perimeter, area and volume concepts. In addition, task-based interviews were conducted on 12 of these students to collect more comprehensive data and to support the findings of the achievement test. Findings revealed that although students were mostly successful in giving correct answers, their reasoning lacked a clear argument of the direct and indirect proportional relationships between the variables and that they approached the problems by superficial characteristics of the problems. 相似文献
82.
Ram Nandan Kumar Jeeban Kumar Nayak Subhasish Dutta Gupta Nirmalya Ghosh Ayan Banerjee 《Laser u0026amp; Photonics Reviews》2024,18(2):2300189
The spin-orbit interaction (SOI) of light generated by tight focusing in optical tweezers is regularly employed in generating angular momentum - both spin and orbital - the effects being extensively observed in trapped mesoscopic particles. Specifically, the transverse spin angular momentum (TSAM), which arises due to the longitudinal component of the electromagnetic field generated by tight focusing is of special interest, both in terms of fundamental studies and associated applications. This study provides an effective and optimal strategy for generating TSAM in optical tweezers by tightly focusing first-order radially and azimuthally polarized vector beams with no intrinsic angular momentum (AM) into a refractive index stratified medium. The choice of such input fields ensures that the longitudinal spin angular momentum (LSAM) arising from the electric (magnetic) field for the radial (azimuthal) polarization is zero. As a result, the effects of the electric and magnetic TSAM are exclusively observed separately in the case of input first-order radially and azimuthally polarized vector beams on single optically trapped birefringent particles. This research opens up new and simple avenues for exotic and complex particle manipulation in optical tweezers. 相似文献
83.
In the search of suitable anode candidates with high specific capacity, favorable potential, and structural stability for lithium-ion batteries (LIBs), transition-metal phosphorus trisulfides (TMPS3) can be considered as one of the most promising alternatives to commercial graphite. Here, it was demonstrated that the limitations of commercial anode materials (i.e., low specific capacity, large volume change, and high lithium diffusion barrier as well as nucleation) can be circumvented by using TMPS3 monolayer surfaces. The study revealed that lithium binds strongly to TMPS3 monolayers (−2.31 eV) without any distortion of the surface, with Li@TMPS3 exhibiting enhanced stability compared with other 2D analogues (graphene, phosphorene, MXenes, transition-metal sulfides and phosphides). The binding energy of lithium was overwhelmingly enhanced with vacancy defects. The vacancy-mediated TMPS3 surfaces showed further amplification of Li binding energy from −2.03 to −2.32 eV and theoretical specific capacity of 441.65 to 484.34 mAh g−1 for MnPS3 surface. Most importantly, minimal change in volume (less than 2 %) after lithiation makes TMPS3 monolayers a very effective candidate for LIBs. Additionally, the ultralow lithium diffusion barrier (0.08 eV) compared with other existing commercial anode material proves the superiority of TMPS3. 相似文献
84.
Dr. Debashrita Sarkar Dr. Sagar Ganguli Ayan Mondal Prof. Venkataramanan Mahalingam 《ChemElectroChem》2022,9(5):e202101140
Electrochemical water splitting is one of the most desirable techniques for combatting the global challenge of sustainable fuel generation. The generation of highly active electrocatalysts for efficient oxygen evolution reaction (OER) requires the rational design of a precatalyst that can enhance the number density of the active catalyst generated during water splitting. In this work, we report sulfurincorporated iron-doped cobalt silicate (CoFeSiO−S) nanoparticles, which exhibit a unique ability to show gradual improvement in the electrocatalytic behavior with time. The precatalyst could reach a low overpotential of 267±6 mV at benchmark current density of 10 mA/cm2 and 300 mV at 100 mA/cm2 current density after applying chronopotentiometry for 30 h. The exceptional OER performance is further evidence by a low Tafel slope of 37.0±0.5 mV/dec with a very high TOF value of 1.05 s−1. This improved activity is attributed to 1) facilitation of Co2+/Co3+ by Fe doping, 2) faster catalyst activation due to lower metal-sulfur bond energy compared to metal-oxygen bond energy, 3) higher pore diameter that enables faster diffusion of reactants and products, 4) lower charge transfer resistance of sulfur incorporated iron-doped cobalt phyllosilicate than pristine, and 5) silicate anion etching in the electrolyte. This work establishes a fundamental understanding of the surface reconstruction occurring during the OER process where silicates are employed as precatalyst. 相似文献
85.
Benzene imine (1) ⇌ 1H-azepine (2) isomerization occurs through sequential valence and endo–exo isomerism. Quantum chemical and quasiclassical trajectory (QCT) simulations reveal the coupled reaction pathway – ring-expansion followed by N-inversion to the most stable isomer, exo-1H-azepine (Exo-2). Direct-dynamics produce a mixture of endo- and exo-1H-azepine stereoisomers and govern the endo-1H-azepine (Endo-2) ⇌ exo-1H-azepine (Exo-2) ratio. Exo-2 is computationally identified as the most stable product while Endo-2 is fleetingly stable with a survival time (ST) ∼50 fs. N-Methyl substitution exclusively results in an exo-1-methyl-1H-azepine isomer. F-substitution at the N-site increases the barrier for N-inversion and alters the preference by stabilizing Endo-2. Interestingly, the exo-1-fluoro-1H-azepine (minor product) is formed through bifurcation via non-statistical dynamics. A highly concaved Arrhenius plot for 1a → 2a highlights the influence of heavy-atom tunneling on valence isomerism, particularly at low temperatures. Heavy-atom tunneling also results in a normal N–H(D) secondary KIE above 100 K even though the increase in hybridization from sp2 to sp3 at nitrogen should cause an inverse KIE classically.Non-classical processes such as heavy-atom tunneling and post transition-state dynamics govern stereoselectivity for benzene imine ⇌ 1H-azepine. 相似文献
86.
Pritam Chattopadhyay Ayan Mitra Goutam Paul Vasilios Zarikas 《Entropy (Basel, Switzerland)》2021,23(4)
Quantum cycles in established heat engines can be modeled with various quantum systems as working substances. For example, a heat engine can be modeled with an infinite potential well as the working substance to determine the efficiency and work done. However, in this method, the relationship between the quantum observables and the physically measurable parameters—i.e., the efficiency and work done—is not well understood from the quantum mechanics approach. A detailed analysis is needed to link the thermodynamic variables (on which the efficiency and work done depends) with the uncertainty principle for better understanding. Here, we present the connection of the sum uncertainty relation of position and momentum operators with thermodynamic variables in the quantum heat engine model. We are able to determine the upper and lower bounds on the efficiency of the heat engine through the uncertainty relation. 相似文献
87.
Biprajit Paul Ayan Mukherjee Deepak Bhuyan Samit Guha 《Journal of heterocyclic chemistry》2021,58(10):2033-2038
Construction of synthetic macrocyclic host that can bind with neutral molecules and anions has potential applications in supramolecular chemistry. Herein, we have designed and synthesized blue light emitting an unsymmetrical neutral bis-urea macrocyclic host. This macrocycle can bind with neutral DMF molecule (1:1) as well as Cl− ion (1:1) through noncovalent interactions. X-Ray crystal structure, 1H NMR titrations with Job's Plot, HRMS with isotropic distribution pattern, FT-IR, and density functional theory analysis revealed the binding of bis-urea macrocyclic host with the guest molecule. 相似文献
88.
Ayan Dasgupta Katarína Stefkova Rasool Babaahmadi Lukas Gierlichs Alireza Ariafard Rebecca L. Melen 《Angewandte Chemie (International ed. in English)》2020,59(36):15492-15496
Herein we report a facile, mild reaction protocol to form carbon–carbon bonds in the absence of transition metal catalysts. We demonstrate the metal‐free alkenylation reactions of aryl esters with α‐diazoesters to give highly functionalized enyne products. Catalytic amounts of tris(pentafluorophenyl)borane (10–20 mol %) are employed to afford the C=C coupled products (31 examples) in good to excellent yields (36–87 %). DFT studies were used to elucidate the mechanism for this alkenylation reaction. 相似文献
89.
Possibilities of generation of lower order and higher order intermodal entanglement in four‐wave mixing (FWM) process are rigorously investigated using Sen‐Mandal perturbative technique. The investigation has revealed that for a set of experimentally realizable parameters, one can observe lower order and higher order intermodal entanglement between pump and signal modes and signal and idler modes in a FWM process. In addition, trimodal entanglement involving pump, signal and idler modes is also reported. 相似文献
90.