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排序方式: 共有822条查询结果,搜索用时 15 毫秒
811.
Mahdi Rezaei-Sameti 《Physica B: Condensed Matter》2012,407(1):22-26
In this work, an armchair model of the (4,4) boron phosphide nanotubes (BPNTs) with a 1-nm length and consisting of 32 B and 32 P atoms is considered to study the influence of doping three atoms of aluminum in sites of boron (B3AlPNTs) and three atoms of nitrogen in sites of phosphors (BP3NNTs) on the electrostatic structure properties. The mouths of nanotubes are capped by hydrogen atoms in order to saturate the dangling bonds of the boundaries and to decrease the calculation time. The structures of BPNTs, B3AlPNTs and BP3NNTs are optimized by performing the level of density functional theory (DFT) using 6-31G? basis set. The optimized structures are used for calculating the chemical shielding (CS) tensors and nuclear magnetic resonance parameters such as isotropic chemical shielding (CSI) and anisotropic chemical shielding (CSA). The results reveal that in both models of B3AlPNTs and BP3NNTs by doping N atoms the chemical shielding parameters of P and B atoms, which are directly connected to the Al and N atoms decreased and the other sites significantly changed. 相似文献
812.
H.K. Hisham A.F. Abas G.A. Mahdiraji M.A. Mahdi A.S. Muhammad Noor 《Optics & Laser Technology》2012,44(6):1698-1705
A unified and comprehensive study on the small-signal intensity and frequency modulation characteristics of a fiber Bragg grating Fabry–Perot (FBG–FP) laser are numerically investigated. The effect of injection current, temperature, external optical feedback (OFB), nonlinear gain compression factor, fiber grating (FG) parameters and spontaneous emission factor on modulation response characteristics are presented. The rate equations of the laser model are presented in the form that the effect of temperature (T) and external optical feedback (OFB) are included. The temperature dependence (TD) of laser response is calculated according to the TD of laser cavity parameters instead of directly using the well-known Parkove equation. It is shown that the optimum external fiber length (Lext) is 3.1 cm and the optimum range of working temperature for FGFP laser is within ±2 °C from the FBG reference temperature (To). Also, the antireflection (AR) coating reflectivity and the linewidth enhancement factor have no significant effect on the modulation spectra. It is also show that modulation response is extremely sensitive to the OFB level, high injection current and gain compression factor. The study indicates clearly that good dynamic characteristic can be obtained by system parameters optimization. 相似文献
813.
H.K. Hisham A.F. Abas G.A. Mahdiraji M.A. Mahdi A.S. Muhammad Noor 《Optics & Laser Technology》2012,44(6):1995-1998
Zhang et al. [Opt. Laser Technol. 39 (2007) 997–1001], through theoretical calculation, have shown that the turn-on time delay can be reduced by increasing any of the non-radiative (Anr), radiative (B), and/or Auger recombination (C) coefficients at a constant injection current over threshold current. Here, we explain that the results presented by that paper are incorrect and the turn-on time delay increases by increasing any of the carrier recombination rate coefficients. 相似文献
814.
N. S. Shahabuddin H. Mohamad M. A. Mahdi Z. Yusoff H. Ahmad S. W. Harun 《Laser Physics》2012,22(1):212-215
A simple multi-wavelength source is demonstrated based on spectral slicing of supercontinuum (SC) light using a Sagnac loop
mirror. A mode locked fiber laser with pulse width of 800 fs is employed to generate the SC in photonic crystal fiber (PCF).
The SC light extending from 1200 nm up to the wavelength region above 1750 nm is obtained at the amplified pulse pump power
of 30 dBm. By slicing the SC with a loop mirror, a multiwavelength comb spectrum is obtained with different channel spacing
for different operating wavelength region. Spacings of 1.5, 2.3, and 2.9 nm are shown at wavelength regions of 1220, 1450,
and 1730 nm, respectively. It is also observed that the signal to noise ratio (SNR) increases from 15 to 20 dB as the operating
wavelength increases from 1220 to 1730 nm region. 相似文献
815.
Stable double spacing multiwavelength Brillouin-Erbium doped fiber laser based on highly nonlinear fiber 总被引:1,自引:0,他引:1
A double frequency spaced multiwavelength Brillouin-Erbium doped fiber laser (BEDFL) with figure-of-eight cavity have been
successfully developed and tested. Double frequency spacing is achieved by using a piece of 2 km of highly nonlinear fiber
(HNLF) as a gain medium. Figure-of-eight configuration removes the odd order Stokes signals via a four-port circulator. Fifteen
Stokes channels are simultaneously generated with a spacing of 0.154 nm that is around 20 GHz, when the Brillouin pump and
980 nm pump powers are fixed at the optimized values of 6 dBm and 40 mW, respectively. Fourteen anti stoke channels are also
obtained, which are generated through four wave mixing (FWM) process in the laser cavity. The output is smooth triangular
comb. The BEFL can also be tuned from 1526.5 to 1567.5 nm. 相似文献
816.
Aida Esmaeilian-Marnani Ahmad Fauzi Abas Mohd Adzir Mahdi Khairulmizam Samsudin 《Optical Review》2012,19(2):71-77
Propagation of temporal 50 femtosecond pulse and pulse stream, which is realized by substituting each input pulse with reduced-order
overlapping soliton pair, is investigated through short standard single-mode fiber. For the pulse stream the initial inter-pulse
delay is selected to be 227 fs and the pulses are to be perturbed to avoid collision with the neighboring pulses. This method
reduces the pulse time delay and properly retains the amplitude despite tradeoff between these two. This is a significant
improvement in the low power femtosecond pulse and pulse stream propagation. 相似文献
817.
Let (m, n) ∈ ℕ2, Ω an open bounded domain in ℝm , Y = [0, 1]m ; uε in (L2(Ω))n which is two-scale converges to some u in (L2(Ω × Y))n . Let φ: Ω × ℝm × ℝn → ℝ such that: φ(x, ·, ·) is continuous a.e. x ∈ Ω φ(·, y, z) is measurable for all (y, z) in ℝm × ℝn , φ(x, ·, z) is 1-periodic in y, φ(x, y, ·) is convex in z. Assume that there exist a constant C1 > 0 and a function C2 ∈ L2(Ω) such that
818.
Mahdi Shahriarinour Faten Divsar Fereshteh Kamalpour Dahka Sharareh Nezamivand Chegini Mohamad Mahani Arash Moeini Pierfrancesco Cerruti 《Molecules (Basel, Switzerland)》2022,27(1)
The release of pharmaceutical wastewaters in the environment is of great concern due to the presence of persistent organic pollutants with toxic effects on environment and human health. Treatment of these wastewaters with microorganisms has gained increasing attention, as they can efficiently biodegrade and remove contaminants from the aqueous environments. In this respect, bacterial immobilization with inorganic nanoparticles provides a number of advantages, in terms of ease of processing, increased concentration of the pollutant in proximity of the cell surface, and long-term reusability. In the present study, MCM-41 mesoporous silica nanoparticles (MSN) were immobilized on a selected bacterial strain to remove alprazolam, a persistent pharmaceutical compound, from contaminated water. First, biodegrading microorganisms were collected from pharmaceutical wastewater, and Pseudomonas stutzeri was isolated as a bacterial strain showing high ability to tolerate and consume alprazolam as the only source for carbon and energy. Then, the ability of MSN-adhered Pseudomonas stutzeri bacteria was assessed to biodegrade alprazolam using quantitative HPLC analysis. The results indicated that after 20 days in optimum conditions, MSN-adhered bacterial cells achieved 96% biodegradation efficiency in comparison to the 87% biodegradation ability of Pseudomonas stutzeri freely suspended cells. Kinetic study showed that the degradation process obeys a first order reaction. In addition, the kinetic constants for the MSN-adhered bacteria were higher than those of the bacteria alone. 相似文献
819.
In this study the Zweifach-Fung effect is investigated in a Y-shaped bifurcation when the clearance between the rigid spherical particle and the walls is small ... 相似文献
820.