Badawy, Safa A.Su, RuiFadda, Ahmed A.Abdel-Latif, Ehab...
10页
查看更多>>摘要：Four novels (N-benzothiazolyl)-cyanoacetamide-based metal-free dyes SA17-20 with D-pi-A architecture were designed and synthesized as co-sensitizers for HD-2 for dye-sensitized solar cells (DSSCs). They contain strong donating moieties of trimethoxybenzene and N,N-dimethylaniline conjugated with the nitrile function of cyanoacetamide part (NHCOCH2CN) as an anchoring group. The role of donor/acceptor in the cyanoacetamide-based structure motifs of SA17-20 in the co-adsorption properties was characterized and their influence on the optical and electrochemical properties was discussed. Consistent with the experimental results, the equilibrium molecular geometries calculated using density functional theory (DFT), at the B3LYP/ 6-31 G (d, p) level, demonstrated the effect of (N-benzothiazolyl)-cyanoacetamide structures on the photovoltaic performance. Co-sensitization technique mainly depends on the uniqueness of the donor-acceptor unit of the co-sensitizer being used. Using (N-benzothiazolyl)-cyanoacetamide cosensitizers with HD-2 showed improved power conversion efficiency (PCE) than HD-2 alone. HD2 was used because of its high efficiency, molar extinction coefficient and photocurrent densities. While HD-2 sensitizer alone displayed PCE of (7.46%), among the co-sensitizers, SA20, containing methoxythiazole and trimethoxybenzene as a donor part attached to (CN) and (CO) as anchoring components, exhibited the best PCE of (8.27%) with Jsc (19.25 mA/cm2) and Voc (0.68 V). These results demonstrated that (N-benzothiazolyl)-cyanoacetamide dyes SA17-20 are promising candidates for efficient DSSCs.
查看更多>>摘要：The high luminescent CdTe/CdS core/shell quantum dots in a stable, aqueous medium have been synthesized and their structural and optical properties of CdTe/CdS core/shell quantum dots have been scrutinized. The results indicate that by changing the shell thicknesses of 10 and 16 nm, the emission spectra of CdTe/CdS structures can span from 530 nm to 560 nm and the wavelength tunability is achieved. Moreover, the 10 nm shell thickness for CdS yields a high photoluminescence quantum yield of 32%, an average fluorescence lifetime of 18.4 ns, and a nonradiative decay rate of 0.3 x 108 s-1. An enhancement in the optical nonlinearities has been observed for CdTe/CdS core/shell quantum dot with a shell thickness of 10 nm compared to CdTe quantum dot and CdTe/CdS core/shell quantum dot with the thickness of 16 nm. This can be explained by the core surface passivation, decreasing of the surface trap density, and increased quantum confinement effects. Our results represent a valuable step towards the development of random lasers, optical limiters, and high-performance optoelectronic applications.
查看更多>>摘要：This letter reports on the design of an ultra-compact echelle grating (EG) demultiplexer in O-band for Coarse wavelength division multiplexing (CWDM) systems based on silicon-on-insulator (SOI) and proposes an optimization idea. The correlation between optical performance and design parameters of EG device is analyzed based on the theory of Finite-difference time-domain (FDTD), providing a more accurate optimization reference. Further optimization is achieved by secondary adjustment of the blaze angle of grating facets and the position of output waveguides according to the simulated field distribution. The device has four channels with channel spacing of 20 nm and a small footprint of only 140x100 mu m(2). The simulated insertion loss for all channels is lower than 2 dB with insertion loss uniformity of below 1dB, and the crosstalk is better than 40 dB.
查看更多>>摘要：In the current work, we consider the Fokas system that describes the nonlinear pulse propagation in monomode optical fibers. By employing the Exp-function method, we succeed in constructing six families(eleven sets) of the exact soliton solutions. And the behaviors of the real, imaginary and absolute parts of the solutions are described through the 3-D contours. It reveals that the Expfunction method is an effective method to construct abundant exact solutions for the partial differential equations arising in optics.
Salehpoor, MohammadrezaVahid, HosseinFard, Ali HeidaryFallah, Hamidreza...
10页
查看更多>>摘要：The main idea of this work is to design a notch filter structure with a narrow notch width and maximum reflection while reducing fabrication challenges. In addition, using anti-reflection layers in the outermost part of the designed structure, the pass-band ripples are reduced. In this study, we considered [(nHnL)(s) (mHmL)(p) (nHnL)(z)] structure with n=5 and m=3. Using this form of design and combining 3 and 5 quarter-wave coefficients instead of 1 and 3, we could reach a narrower NW in fewer periods of HL layers. The stability of the deposition conditions and the density of the layers affect their quality and consequently the result of environmental tests. Hence, to construct the designed structure, we employed the sputtering method with RF and DC sources. In our experiments, we showed that the use of a simple shield prevents the oxidation of targets' surfaces as well as reduces the deposition rate and increases the stability of deposition processes. Fabricated Samples have been subjected to a variety of environmental tests, including humidity, hard and soft abrasion, temperature, and adhesion tests with satisfactory results.
Sallam, O. I.Zakaly, Hesham M. H.Issa, Shams A. M.Rashad, M....
13页
查看更多>>摘要：Structural, optical and electrical properties of developed (P2O5)(47)-(Na2O)(23)-(Al2O3)(6)-PbO(24-x)-(Sm2O3)(x) (where x = 0.5, 1 and 3 mol%) at different gamma irradiation doses (0, 10, 50 KGy) have been investigated. Melt-quenching method was used for synthesizing these glasses. XRD observations provide for the ampophosity of the as-prepared glasses. The effect of different gamma irradiation doses and Sm2O3 contents affect crystallinity of the developed samples. Moreover, the results show a decreasing in the transmittance light as the gamma doses increase from 0 to 50 kGy. The both calculated direct and indirect optical band gap were found to be affected by gamma irradiation doses for (P2O5)(47)-(Na2O)(23)-(Al2O3)(6)-PbO(24- x)-(Sm2O3)(x). On the other hand, the electrical activation energy and electrical conductivity of the glasses were affected by gamma irradiation doses for (P2O5)(47)-(Na2O)(23)-(Al2O3)(6)-PbO(24-x)-(Sm2O3)(x) (where x = 0.5, 1 and 3 mol%). These various studies forces to fabricate a glass material that could be utilized to attenuate or reduce gamma-radiation.
Ahmed, Ala F.Abdulameer, Mohammed R.Kadhim, Murad M.Mutlak, Falah A. -H....
9页
查看更多>>摘要：The current study aimed the syntheses and characterizations of Gold nanoparticles (Au NPs) using a laser ablation Q-switched Nd: YAG laser with a wave-length of 355 nm at a variety of laser pulse energies (E) and deposited on porous silicon (PS). Optical emission spectrometer was used to diagnosed medium air to study gold plasma characteristics and prepared Au nanoparticles. The laser pulse energy influence has been studied on the plasma characteristics in air. The data showed the emergence of the ionic (Au II) spectral emission lines in the gold plasma emission spectrum. XRD has been utilized to examine structural characteristics. Moreover, AFM results 37.2 nm as the mean value of the diameter that is coordinated in a shape similar to the rod that appears for Au NPs, in addition to that, TEM has been an indication of the fact that synthesized Au NPs were spherical with a mean size of particles, ranging from 25 nm to 30 nm. At high laser pulse energy, the intensity of all emission peaks in the air at atmospheric pressure was considerably greater. Finally, variations in the operating temperature associated with the NH3 gas sensor, created from the samples that have been prepared on the sensitivity of the sensor and response time have been evaluated, the maximal sensitivity is nearly 41% concerning Au NPs that have been ablated via laser energy (E) 400 mJ on the porous silicon of the NH3 gas.
查看更多>>摘要：A random-forest (RF)-assisted artificial-neural-network (ANN) method (RF-ANN method) was developed to improve the analytical performance of laser-induced breakdown spectroscopy (LIBS) in evaluating the composition of low-alloy steel. The RF algorithm was employed to identify the weight values of spectral variables in the quantitative analysis, and the weight values were used as the criteria to select the spectral variables. The selected variables were then used as inputs to train the ANN, which was then used as the analysis model. Compared to the calibration curve method, the RF-ANN method performs well in nonlinear fitting and utilizes an abundance of spectral information; moreover, it can accommodate large amounts of plasma data via filter spectral variables, thus overcoming the problem of the ANN training speed being too slow for practical use due to the redundancy in spectral variables. The results revealed an improvement in the analytical performance of LIBS using the RF-ANN method to predict the concentrations of chromium (Cr) and vanadium (V) in low-alloy steel samples. Specifically, the root-mean-square errors of cross-validation (RMSECV) for Cr and V were reduced from 0.060 and 0.042 wt% using the calibration curve method to 0.021 and 0.007 wt%, respectively, using the RF-ANN method.
查看更多>>摘要：The positive mass theorem in general relativity states that in an asymptotically flat spacetime, if the momentum-energy tensor is divergence-free and satisfies a dominant energy condition, then a total momentum-energy four-vector can be formed, of which the energy component is nonnegative. In this paper, we take the wave four-tensor of a plane light wave in free space as a counterexample to show that there is no guarantee that a total four-vector can be formed. Thus the theoretical framework for the positive mass theorem is flawed. In addition, it is also shown as well that the Lorentz covariance of Dirac wave equation is not compatible with Einstein mass-energy equivalence.
查看更多>>摘要：Understanding how to properly match an optical lens f-number (F/#) to a modern CCD/CMOS sensor is necessary to maximize the highest image quality and resolution. Even a perfect diffraction limited lens system will experience sensor limitations causing degradation in an image if the sensor is not properly matched with the system's F/#. We therefore propose a modern review of the Johnson image resolution criterion to accommodate modern CCD/CMOS sensors. This study will outline a new method for analyzing the modulation transfer function (MTF) as a method to better match the F/# and sensor via a new modified Johnson Criteria, and then how to incorporate radiometric pixel counting into the modified Johnson resolution definition to inform a more precise image resolution criteria.
NSTL
Elsevier