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Strain Effects on the Band Gap and Diameter of CdSe Core and CdSe/ZnS Core/Shell Quantum Dots at Any Temperature
摘要： We present the results of an experimental study about strain effects on the core band gap and diameter of spherical bare CdSe core and CdSe/ZnS core/shell quantum dots (QDs) synthesized by using a colloidal technique at varying temperatures. Structural characterizations were made by using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) techniques. Optical characterizations were made by using UV-Vis absorption and fluorescence emission spectroscopies. The XRD analysis suggests that the synthesized bare CdSe core and CdSe/ZnS core/shell QDs have zinc blende crystal structure. HRTEM results indicate that the CdSe core and CdSe/ZnS QDs have average particle sizes about 3.50 nm and 4.84 nm, respectively. Furthermore, compressive strain causes an increase (decrease) in the core band gap (diameter) of spherical CdSe/ZnS core/shell QDs at any temperature. An elastic strain-modified effective mass approximation (EMA) predicts that there is a parabolic decrease (increase) in the core band gap (diameter) of QDs with temperature. The diameter of spherical bare CdSe core and CdSe/ZnS core/shell QDs calculated by using the strain-modified EMA, with core band gap extracted from absorption spectra, are in excellent agreement with the HRTEM data.
关键词： diameter,quantum dots,band gap,CdSe,strain effects,CdSe/ZnS,temperature
更新于2025-09-12 10:27:22
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Polarization-Dependent Lateral Optical Force of Subwavelength-Diameter Optical Fibers
摘要： It is highly desirable to design optical devices with diverse optomechanical functions. Here, we investigate lateral optical force exerted on subwavelength-diameter (SD) optical fibers harnessed by input light modes with different polarizations. It is interesting to find that input light modes of circular or elliptical polarizations would bring about lateral optical force in new directions, which has not been observed in previous studies. By means of finite-difference time-domain (FDTD) simulations, detailed spatial distributions of the asymmetric transverse force density are revealed, meanwhile dependence of optical force on input light polarizations, fiber diameters, and inclination angles of fiber endfaces are all carefully discussed. It is believed that polarization-sensitive reflection, refraction, and diffraction of optical fields occur at the interface, i.e., fiber oblique endfaces, resulting in asymmetrically distributed optical fields and thereafter non-zero transverse optical force. We believe our new findings could be helpful for constructing future steerable optomechanical devices with more flexibility.
关键词： circular polarization,elliptical polarization,optical force,subwavelength-diameter optical fiber
更新于2025-09-12 10:27:22
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Comparison of 9.0 and 9.2?mm Flap Diameter Options of Femtosecond Laser In-Situ Keratomileusis for Hypermetropia and Hypermetropic Astigmatism
摘要： Aim. To compare the postoperative one-year outcomes of asphericity (Q) and high order aberration (HOA) values of 9.0 and 9.2 mm diameter ?ap groups in hypermetropia and hypermetropic astigmatism subjects who underwent femtosecond laser in-situ keratomileusis (LASIK). Materials and Methods. The study included 68 eyes of 34 patients. A femtosecond laser platform (Allegrato Wave, Wavelight AG, Erlangen, Germany) was used for ?ap cutting. Corneal stroma was ablated using Wavelight EX500 with wavefront-optimized pro?le (WaveLight GmbH, Erlangen, Germany). 9.0 mm ?ap diameter was randomly chosen for one eye, and 9.2 mm ?ap diameter was chosen for the fellow eye. Two eyes of the patients who used two di?erent ?ap diameters were enrolled into two di?erent groups. Corneal stroma was ablated using Wavelight EX500 with wavefront-optimized pro?le (WaveLight GmbH, Erlangen, Germany). Postoperative one-year outcomes of Q and HOA values of 9.0 and 9.2 mm diameter ?ap groups were compared statistically. Results. The preoperative manifest refraction spherical equivalents of the 9.0 and 9.2 mm diameter ?ap groups were 1.86 ± 1.81 D and 1.69 ± 1.99 D (p ? 0.754). No intraoperative or postoperative complications were observed. At postoperative one-year, Q values were 0.98 ± 0.13 D and 0.91 ± 0.15 D (p ? 0.029). HOAs including horizontal and vertical coma, horizontal and vertical trefoil, spherical aberration, and second order vertical coma were not signi?cantly di?erent (p > 0.05 for all). Total HOA values were 1.62 ± 0.14 and 1.40 ± 0.16, in the 9.0 and 9.2 mm diameter ?ap groups, respectively (p < 0.001). Conclusion. Both the 9.0 and 9.2 mm diameter ?ap options in femtosecond LASIK are equally safe and e?ective. Many of the HOA values are similar in both options, and better results were provided in terms of total HOA and Q values with the 9.2 mm diameter ?ap option. This study was registered with trial registration number 118-011.
关键词： hypermetropic astigmatism,asphericity,femtosecond laser,LASIK,high order aberration,hypermetropia,flap diameter
更新于2025-09-11 14:15:04
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Diode-pumped neodymium:yttrium aluminum garnet laser effects on the visceral pleura in an <i>ex vivo</i> porcine lung model?
摘要： Management of tree plantations needs information on the number, time, intensity and type of thinnings, and the length of the rotation. Economically optimal plantation management depends on discount rate and site fertility. This study proposed a new approach to developing management instructions for tree plantations, simultaneously for all discount rates and site classes. The method was applied to larch (Larix olgensis A. Henry) plantations in northeast China. Instead of optimizing the management of individual stands, instructions for thinning basal area, thinning intensity and rotation diameter were optimized. The instructions consisted of three equations, the first indicating the basal area at which the stand should be thinned, the second showing the optimal thinning intensity, and the third model indicating the mean diameter of trees at the moment of clear-felling. Particle swarm optimization (PSO) was employed to simultaneously optimize the coefficients of these three equation models. PSO maximized the average net present value of the management schedules of 29 larch sample plots. The obtained instructions corresponded to earlier results on the effects of different factors on optimal stand management. Management based on the instructions developed in this study resulted in almost equally profitable management as in the case where the management of every plot was optimized separately.
关键词： thinning,particle swarm optimization,tree plantations,management instructions,rotation diameter
更新于2025-09-11 14:15:04
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Quantification of source specific black carbon scavenging using an aethalometer and a disdrometer
摘要： Aerosol black carbon (BC) is the second strongest contributor to global warming, after CO2, and it is linked to many adverse health effects. A sampling campaign of 15 months was carried out in León (Spain) in order to evaluate the scavenging of BC with an ensemble aethalometer-disdrometer. The aethalometer provides the concentration of equivalent black carbon (eBC), and the disdrometer, the raindrop size distribution. A total of seventy-five rain events were studied and in 73% of them there was an effective (eBCinitial > eBCfinal) scavenging, with a mean decrease of 48 ± 37% in long rain events (>8 h) and 39 ± 38% in short rain events. The scavenging of BC is strongly related to its source. Thus, the scavenging coefficient (SC) mean value of the BC from fossil fuel (eBCff) for short and long rain events was 5.1 10-5 and 1.3 10-5 s-1, respectively. For the BC from biomass burning (eBCbb), the SC values were 1.6 10-4 and 2.8 10-5 s-1 in short and long events, respectively. There was a significant positive correlation between the SC and the number of drops with diameters between 0.375 and 2.5 mm. Rain scavenging of eBC was analyzed depending on the air mass origin obtaining an effective scavenging for air masses from Atlantic, Arctic and Africa. A linear model (R2=0.72) was built to estimate the ?eBC values with variables from an aethalometer, a disdrometer and a weather station: eBC concentration before rain, swept volume and precipitation accumulated. A Kolmogorov-Smirnov statistical test confirmed the goodness of fit of the model to the measured data.
关键词： BC scavenging estimation model,rainfall,scavenging coefficient,Black carbon,raindrop diameter,wet deposition
更新于2025-09-10 09:29:36
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Tailoring Physical Properties of Carbon Nanotube Threads During Assembly
摘要： Spinnable carbon nanotubes (CNTs) are useful formats for studying physical properties of CNT fiber assemblies in their pristine states. They are free of catalyst, uniform in length, with a comparatively narrow diameter distribution, and their assembly into thread does not require additional chemicals or solvents. Good quality drawable CNT arrays can be readily assembled into uniform diameter threads with great control over the number of CNTs incorporated into the thread assembly. This uniformity allows study the physical properties that result from changes that occur during thread formation. Here, we report trends of electrical resistivity and mechanical strength that resulted from alterations in their manufacturing parameters, allowing to change intrinsic physical properties of a material such as electrical resistivity. We correlate the electrical resistivity and mechanical strength as a function of diameter, density, and turns/meter. Understanding the effects of dry-spinning parameters will allow a better design of the physical properties of CNT threads for specific applications, such as strain or electrochemical sensors.
关键词： resistivity,threads,and twist angle.,fibers,yarns,Carbon nanotubes,diameter control
更新于2025-09-10 09:29:36
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On the Influence of Collector Size on the Solar Chimneys Performance
摘要： Performance of solar chimney power plant system is highly influenced by the design geometries. The collector size is logically enhances the solar chimney performance, but the trend of enhancement is not yet investigated. In the present work, experimental and numerical investigations have been carried out to ascertain, in terms of qualitative and quantitative evaluation, the effect of the collector diameter. Daily thermal efficiency has been determined at four different collector diameter. Two different collector diameters, 3.0 and 6.0 m, have been investigated experimentally, and then scaled up, to 9.0 and 12.0 m, by numerical simulation using ANSYS-FLUENT?15 software. Results demonstrated that collector diameter has effectively influenced the system performance. Larger collector diameter imposed increase in the velocity, temperature and the daily average thermal efficiency of the system. From the experimental results, increasing the collector diameter from 3.0 to 6.0 m has increased the daily average thermal efficiency of the collector from 9.81 to 12.8. Simulation results at 800 W/m2 irradiation revealed that the velocity in the chimney have increased from 1.66 m/s at 3.0 m collector diameter to 2.34, 2.47 and 2.63 m/s for 6.0, 9.0 and 12.0 m collector diameters, respectively.
关键词： experimental investigation,thermal efficiency,solar chimney,numerical simulation,collector diameter
更新于2025-09-10 09:29:36
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The investigation of the diameter dimension effect on the Si nano-tube transistors
摘要： The vertical gate-all-around (V-GAA) Si nano-tube (NT) devices with different diameter dimensions are studied in this work with the promising device performance. The V-GAA structure makes the transistor easy to be scaled down continuously to meet the complementary metal-oxide-semiconductor (CMOS) scaling requirements of the 7/10 nm technology node and beyond. The Si NT device with the hollow structure is demonstrated to have the capability to “deplete” and “screen-out” the out-of gate control carriers in the center of the NT and further result in the better device short channel control. Based on the study in this work, the V-GAA Si NT device with the optimized diameter dimension (= 20 nm) can benefit the Ion-state current and reduce the Ioff-state stand-by power simultaneously, due to the less surface roughness scattering and the better short channel control characteristics. The proposed V-GAA Si NT device is regarded as one of the most promising candidates for the future application of the sub-7/10 nm logic era.
关键词： diameter dimension effect,Si nano-tube transistors,short channel control,surface roughness scattering,vertical gate-all-around
更新于2025-09-10 09:29:36
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Flow through polydisperse pores in an anodic alumina membrane: A new method to measure the mean pore diameter
摘要： We describe a novel technique for the characterization of the mean pore radius of self-ordered porous anodic alumina membranes. We have studied the flow of liquids through cylindrical membrane pores under conditions of very low Reynolds number (Re ? 1). We find that the flow data are well-described by Poiseuille’s law. Characterization is achieved through the application of the H?gen-Poiseuille equation on flow measurements conducted in a simple and compact experimental setup. This setup allows for the monitoring of flow as a result of the pressure difference between the two sides of the membrane without the use of sophisticated and costly laboratory equipment. The proposed method has been tested by flow experiments using liquids of various viscosities. Good agreement is found between the results obtained from the flow data and the pore radii measured by scanning electron microscopy. Consistent results for the mean pore radius for the same membrane have been obtained in all cases.
关键词： Poiseuille’s law,scanning electron microscopy,anodic alumina membrane,mean pore diameter,flow measurement
更新于2025-09-10 09:29:36
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The effects of ranibizumab injections on fluorescein angiographic findings and visual acuity recovery in age-related macular degeneration
摘要： The objective of the study reported here was to evaluate the effect of ranibizumab on retinal circulation times and vessel caliber and to analyze the correlation of these factors with visual acuity (VA) prognosis in patients with age-related macular degeneration (AMD).
关键词： central macular thickness,prognosis,retinal arteriole diameter,vessel caliber,retinal vein diameter
更新于2025-09-09 09:28:46