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41.
Spin-dependent electronic transport through an open multiple-quantum-dot ring threaded by a magnetic flux is theoretically investigated by using the single particle Green?s function method. By introducing local Rashba spin–orbit interaction on an individual quantum dot and local magnetic moments on two of other quantum dots, we calculate the spin-polarization in the output lead. We find the spin-polarization can be tuned by manipulating magnetic moments, adjusting magnetic flux and setting the Rashba spin–orbit strength. It is also shown the system can operate as an efficient spin-inverter when the structure is adjusted properly. The analysis can be utilized in designing optimized nanodevices. 相似文献
42.
In this paper, we have theoretically studied dynamics of a semiconductor quantum dot (QD) laser for enhancing its small signal and large signal modulation as a function of compression gain. We have considered InGaAs/GaAs QD laser rate equations and solved this equation system numerically. We have revealed that a diminution in compression gain leads to an improvement in frequency bandwidth for this three state lasing system. We also have calculated turn on delay and output power that obviously indicates the effect of compression gain on relaxation oscillations. 相似文献
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Zahra Danesh Kaftroudi Esfandiar Rajaei Abolfazl Mazandarani 《Journal of Russian Laser Research》2014,35(2):124-137
We investigate the physics of an internal device for a high-performance, vertical-cavity surface-emitting laser operating at 1.305 μm. Experimental results are analyzed using as the simulation software a photonic-integrated-circuit simulator in 3D (PICS3D), which is a state-of-the-art 3D simulator for surface- and edge-emitting laser diodes, semiconductor optical amplifiers, and other similar active waveguide devices. The 2D/3D semiconductor equations are coupled to the optical modes in both lateral and longitudinal directions. Optical properties such as the quantum well/wire/dot optical gain and spontaneous emission rates are computed self-consistently. Careful adjustments of material parameters led to an excellent agreement between simulation and measurements. Simulation results show that the maximum output power is limited by electron leakage from quantum wells. 相似文献
46.
A coarse‐grained (CG) model for the simulation of nanoconfined water between graphene surfaces is developed. For this purpose, mixed‐grained simulations are done, in which the two‐site water model of Riniker and van Gunsteren [S. Riniker, W. F. van Gunsteren, J. Chem. Phys. 2011 , 134, 084110] is simulated between atomistically resolved graphene surfaces. In the developed pure CG model, the two interaction sites of water and a combination of eight carbon atoms in the graphene surface are grouped together to construct water and surface CG beads. The pure CG potentials are constructed by iteratively matching the radial distribution functions and the density profiles of water beads in the pore with the corresponding mixed‐grained distributions. The constructed potentials are shown to be pore‐size transferable, capable of predicting structural properties of confined water over the whole range of pore sizes, ranging from extremely narrow pores to bulk water. The model is used to simulate a number of nanoconfined systems of a variety of pore sizes at constant temperature, constant parallel component of pressure, and constant surface area of the confining surfaces. The model is shown to predict the layering of water in contact with the surfaces, and the solvation force is in complete agreement with the mixed‐grained model. It is shown that water molecules in the pore have smaller parallel diffusion coefficients compared to bulk water. Well‐organized layers beside the surfaces are shown to have lower diffusion coefficients than diffuse layers. More information on the dynamics of water in the pore is obtained by calculating the rate of water exchange between slabs parallel to the surfaces. The time scale to achieve equilibrium for this process, depending on the pore width and on the degree of layering of water beside the surfaces, is a few nanoseconds in nanometric pores. 相似文献
47.
Khosrow Jadidi Ramin Ghahremanzadeh Davoud Asgari Parisa Eslami Hamid Arvin-Nezhad 《Monatshefte für Chemie / Chemical Monthly》2008,141(7):1229-1232
The green reaction of isatoic anhydrides with α-amino acids in presence of the ionic liquid 1-butyl-3-methylimidazolium bromide
afforded 1,4-benzodiazepine-2,5-diones in excellent yields in absence of a catalyst. The reaction workup is simple and the
ionic liquid was easily recovered from the reaction and reused. The methodology was quite general and a range of cyclic and
acyclic α-amino acids were examined to produce 1,4-benzodiazepine-2,5-diones. 相似文献
48.
Khosrow Jadidi Ramin Ghahremanzadeh Davoud Asgari Parisa Eslami Hamid Arvin-Nezhad 《Monatshefte für Chemie / Chemical Monthly》2008,139(10):1229-1232
The green reaction of isatoic anhydrides with α-amino acids in presence of the ionic liquid 1-butyl-3-methylimidazolium bromide
afforded 1,4-benzodiazepine-2,5-diones in excellent yields in absence of a catalyst. The reaction workup is simple and the
ionic liquid was easily recovered from the reaction and reused. The methodology was quite general and a range of cyclic and
acyclic α-amino acids were examined to produce 1,4-benzodiazepine-2,5-diones.
Correspondence: Khosrow Jadidi, Department of Chemistry, Shahid Beheshti University, PO Box 1983963113, Tehran, Iran. 相似文献
49.
Habibollah Eskandari Abolfazl Bezaatpour Forogh Eslami 《Journal of the Iranian Chemical Society》2017,14(2):457-469
A new solid-phase extraction method was developed for trace determination of Hg(II) by using a small amount of naked magnetite nanoparticles as an adsorbent. The magnetite nanoparticles were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The adsorbed Hg(II)-dithizone complex was eluted with 1.0 mL aliquot of an acidic 1-propanol solution prior to electrothermal atomic absorption spectrometry. A huge positive effect was found on the mercury adsorption by ionic strength. Under optimized condition, a linear calibration curve was obtained for mercury in the range of 0.2–50 ng mL?1 with relative standard deviation in the range of 0.5–2.0%. The limit of detection and enrichment factor were 0.01 ng mL?1 and 98.3, respectively. The effects of coexisting ions were studied extensively, and a new clean-up procedure was used to remove the matrix effects by using a simple sample pretreatment step using a little amount of magnetite nanoparticles. The method was successfully applied to the determination of Hg(II) in different water and human urine samples and a commercial sodium nitrate. 相似文献
50.
Abbas Eslami Seyed Ghorban Hosseini 《Journal of Thermal Analysis and Calorimetry》2011,104(2):671-678
The lactose/KClO3 is a widely used pyrotechnic mixture to vaporize organic materials, such as smoke dyes. However, because of low ignition
temperature of this mixture, serious precaution should be taken into account to prevent its accidental self-ignition. In order
to find a safe and efficient alternative of this conventional mixture, KClO3 has been replaced by common oxidizing agents including KMnO4, KNO3, KClO4, Ba(NO3)2, PbO2 and NH4ClO4. TG and DTA analysis have been used to obtain thermal characteristic of the mixtures. Based on ignition temperature of the
pyrotechnic mixtures we can divide them into four categories as follows: (1) the mixture igniting at low temperature, i.e.,
at about 200 °C. (2) Moderate temperature igniting mixture, in which ignition occurs at 300–400 °C. (3) High temperature igniting
mixture with ignition temperature higher than 400 °C .(4) Not igniting mixtures. Also, the apparent activation energy (E), ΔG
#, ΔH
#, ΔS
# and critical ignition temperature (T
b
) of the ignition processes of low and moderate temperature igniting mixtures were obtained from the DSC experiments. Finally,
among the investigated mixtures, lactose/KNO3 can be considered as a safe and efficient pyrotechnic composition for vaporization of organic materials, such as smoke dyes,
due to its moderate safe ignition temperature. 相似文献