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Investigation and Analysis of Data Rate for Free Space Optical Communications System Under Dust Conditions
摘要： In this study, the performance of free-space optics (FSO) communication link under dust conditions was analysed. The data were modulated by the non-return-to-zero technique. The optical link was investigated with varying data rates under the effect of dust conditions. The performance of the FSO system was tested in terms of the bit error rate (BER), Q-factor and received power at the maximum link. Simulation results were obtained to compare between two transmit data rates (0.3 and 0.7 Gbps). The system has a high BER at a high data rate. In the meantime, it has a high Q-factor at a low data rate.
关键词： OptiSystem 7.0,Atmospheric transmittance,FSO,BER,Dust concentration,Attenuation,Q-factor,Propagation,WDM
更新于2025-09-23 15:19:57
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Estimation of the performance limits of a concentrator solar cell coupled with a micro heat sink based on a finite element simulation
摘要： Concentrated photovoltaic (CPV) technology makes use of cheap optical elements to amplify the irradiance and focus it on small-sized solar cells enabling the extraction of higher amounts of electricity. However, increasing the solar concentration raises the temperature of the PV cell which can deter its performance and can also cause its failure. To combat this issue both active and passive cooling mechanisms are utilized for different types of CPV systems. In this study, we determine the limits of passive cooling systems and establish when an active cooling system is needed based on the recommended operating temperature of the solar cell. We investigate the temperature characteristics of the solar cells bonded to three different substrate materials under different solar concentrations. Results showed that cell temperature is linearly dependent on the concentration ratio and ambient temperature independent of the substrate material. Further, the integration of a micro-finned heatsink results in higher heat dissipation by 25.32%, 23.13%, and 22.24% in comparison with a flat plate heatsink for Direct Bonded Copper (DBC), Insulated Metal Substrate (IMS), and Silicon Wafer (Si wafer) substrates respectively. The low thermal resistance of the IMS substrate compared to the DBC and the Si wafer substrates result in the best thermal performance in terms of maintaining the cell temperature < 80 °C and allowing a wider range of high concentration ratio.
关键词： Concentration Ratio,Passive cooling,micro fin heat-sink,finite element,Concentrating Photovoltaic,flat-plate heat-sink
更新于2025-09-23 15:19:57
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Myosin II Filament Dynamics in Actin Networks Revealed with Interferometric Scattering Microscopy
摘要： The plasma membrane and the underlying cytoskeletal cortex constitute active platforms for a variety of cellular processes. Recent work has shown that the remodeling acto-myosin network modifies local membrane organization, but the molecular details are only partly understood because of difficulties with experimentally accessing the relevant time and length scales. Here, we use interferometric scattering microscopy to investigate a minimal acto-myosin network linked to a supported lipid bilayer membrane. Using the magnitude of the interferometric contrast, which is proportional to molecular mass, and fast acquisition rates, we detect and image individual membrane-attached actin filaments diffusing within the acto-myosin network and follow individual myosin II filament dynamics. We quantify myosin II filament dwell times and processivity as functions of ATP concentration, providing experimental evidence for the predicted ensemble behavior of myosin head domains. Our results show how decreasing ATP concentrations lead to both increasing dwell times of individual myosin II filaments and a global change from a remodeling to a contractile state of the acto-myosin network.
关键词： actin networks,ATP concentration,interferometric scattering microscopy,membrane organization,myosin II filament dynamics
更新于2025-09-23 15:19:57
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Optical fiber sensors for measurement of heavy metal ion concentration: A review
摘要： With the increasing of water pollution problems, detection of heavy metal ion concentration in water environment becomes significant. Optical fiber sensor, with its particular advantages of small-size, anti-electromagnetic interference, chemical inertness, remote and real-time monitoring ability, has become an ideal platform for detection of heavy metal ion concentration. In this paper, we briefly review the current research progress of heavy metal ion sensors based on optical fiber technology. Five main measurement methods are described, including optical absorbance method, fiber grating method, modal interference method, plasmonic method, and fluorescence method. The sensing mechanisms, sensing structures, sensing materials, and sensing characteristics of different kinds of measurement methods are introduced and summarized. Furthermore, the advantages and disadvantages of each measurement method are analyzed. Finally, the future development directions of optical fiber heavy metal ion sensors are also discussed.
关键词： Water pollution,Optical fiber sensor,Concentration measurement,Heavy metal ion sensor
更新于2025-09-23 15:19:57
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Gas-vapor Interplay in Plasmonic Bubble Shrinkage
摘要： The understanding of the shrinkage dynamics of plasmonic bubbles formed around metallic nanoparticles immersed in liquid and irradiated by a resonant light source is crucial for the usage of these bubbles in numerous applications. In this paper we experimentally show and theoretically explain that a plasmonic bubble during its shrinkage undergoes two different phases: first, a rapid partial bubble shrinkage governed by vapor condensation and, second, a slow diffusion-controlled bubble dissolution. The history of the bubble formation plays an important role in the shrinkage dynamics during the first phase, as it determines the gas-vapor ratio in the bubble composition. Higher laser powers lead to more vaporous bubbles, while longer pulses and higher dissolved air concentrations lead to more gaseous bubbles. The dynamics of the second phase barely depends on the history of bubble formation, i.e. laser power and pulse duration, but strongly on the dissolved air concentration, which defines the concentration gradient at the bubble interface. Finally, for the bubble dissolution in the second phase, with decreasing dissolved air concentration, we observe a gradual transition from a R(t) ∝ (t0 ? t)1/3 scaling law to a R(t) ∝ (t0 ? t)1/2 scaling law, where t0 is the lifetime of the bubble and theoretically explain this transition.
关键词： dissolved air concentration,laser power,pulse duration,plasmonic bubbles,vapor condensation,shrinkage dynamics,diffusion-controlled dissolution
更新于2025-09-23 15:19:57
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Impact of CsI concentration, relative humidity, and annealing temperature on lead-free Cs2SnI6 perovskites: Toward visible light photodetectors application
摘要： Physical, electrical, and photodetection properties of stable, lead-free Cs2SnI6 (CSI) perovskite thin films prepared on thermally oxidized Si (SiO2, 100 nm) substrates via direct solution spin coating process are reported. XRD, XPS, and EDS analysis reveal that initial CsI rich-concentration, higher RH% levels (>40%) have an impact on phase formation of CSI films. The porous, sub-lm sized rods of fabricated CSI films are confirmed by FEG-SEM analysis. Contact resistance (Rc) and sheet resistance (Rsh) for CSI films, annealed at 150 (cid:1)C, are decreased up to 37% and 85%, respectively, as compared with those of films processed at 75 (cid:1)C. The photoresponsivity (6 mA/W) and specific detectivity (2.00 (cid:1) 109 Jones) for two-terminal CSI photodetectors are achieved with annealing condition of 100℃ and at a bias voltage of 1 V as well. The preliminary photodetection properties for CSI devices processed at low temperatures indicate that they can be potentially applicable to a flexible, visible light photodetector.
关键词： Electrical and photodetection properties,RH% levels,CsI concentration,Annealing temperature,Structural
更新于2025-09-23 15:19:57
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Synergy of adsorption and photocatalysis on removal of high-concentration dye by Ag/AgCl/Bi6O4(OH)4(NO3)6·H2O nanocomposite using Bi12O17Cl2 as bismuth source
摘要： Novel basic bismuth nitrite nanocomposite-Ag/AgCl/Bi6O4(OH)4(NO3)6·H2O has been applied to remove high-concentration methyl orange (MO). The nanocomposite was prepared by a two-step method with Bi12O17Cl2 as bismuth source. XRD, TEM, HRTEM and IR analyses were performed to clarify the composition and microstructure. TEM and HRTEM images reveal that the nanocomposite is consisted of plate-stacking Bi6O4(OH)4(NO3)6·H2O ultrathin nanosheets, where monodispersed AgCl (3-7 nm) and Ag (10-120 nm) nanoparticles are uniformly distributed. Influences of contact time, MO concentration and solution pH on adsorption capacity have been studied. Adsorption capacity is 349 mg g-1 at natural state, 740 mg g-1 at pH=3, and 141 mg g-1 at pH=9. Visible-light photocatalytic performance was evaluated by degradating high-concentration MO of 500 mg L-1 at natural state, 1500 mg L-1 at acidic condition, and 300 mg L-1 at the alkaline condition. Combining with distinct composition and structure of the nanocomposite, removal mechanism is proposed based on the synergy of adsorption and photocatalysis.
关键词： Adsorption,Photocatalysis,Synergy,High-concentration methyl orange,Ag/AgCl/Bi6O4(OH)4(NO3)6·H2O
更新于2025-09-23 15:19:57
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Influence of solvent solubility parameter on the power law exponents and critical concentrations of one soluble polyimide in solution
摘要： Solvent species influence the interactions of dissolved polymers in solution and consequently induce changes in solution properties. A soluble polyimide was synthesized through polycondensation, and four solvents, namely, N,N-dimethylacetamide (DMAc), N-methyl pyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), were selected to investigate systematically the influence of solubility parameter on solution power law behaviors. The power law relationship between specific viscosity and concentration was established using rheology and applying concepts from the Zimm, Rouse-Zimm, and Doi-Edwards models. All power law exponents were higher than theoretical predictions, and in the three concentration regions, i.e. dilute, semidilute unentangled, and semidilute entangled, the exponents increase, decrease, and increase, respectively, with respect to solubility parameter. Arguments derived from the listed models are proposed to explain these trends. The influences of solubility parameter on the overlap and entanglement concentrations are also discussed.
关键词： Solubility parameter,Critical concentration,Polyimide,Power law exponent,Solution property
更新于2025-09-19 17:15:36
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Combined solar concentration and carbon nanotube absorber for high performance solar thermoelectric generators
摘要： Solar thermoelectric generators (STEGs) is one of the most important technologies for solar energy conversion. However, the inefficiency due to coupling constraints such like low working temperature and dimensionless figure of merit of the thermoelectric materials, also known as material’s ZT value, has been hampering the development of STEGs for a time. Here we demonstrate a high performance STEG system combined with solar concentrators and carbon nanotubes (CNTs) absorber, which can greatly improve the solar-thermal conversion process. The proposed STEG system enables a peak efficiency of 4.3% with solar concentration of 78, and a maximum power of 11.2 W at 106× suns. The enhanced efficiency is ensured by the optimized system thermodynamics due to the combination of solar concentration devices and CNT based solar absorber. Our design provides a universal prototype of solar thermal energy recovery system for distributed energy harvesting and deep-space explorations.
关键词： Thermodynamics,Carbon nanotube,Solar concentration,Thermoelectricity,Energy harvesting
更新于2025-09-19 17:15:36
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Selectively Photocatalytic Oxidation of Low Concentration Methane over Graphitic Carbon Nitride Decorated Tungsten Bronze Cesium
摘要： Although the traditional thermal catalysis is usually used to convert the methane into value-added products, its high reaction temperature results in low performance-price ratio in conversion of low concentration methane. In this regard, we synthesized a series of mace-like g-C3N4 decorated Cs0.33WO3 nanocomposites for photocatalytic conversion of low concentration methane under mild conditions. The optimized g-C3N4@Cs0.33WO3 (weight ratio = 3:7) photocatalyst selectively converted low concentration methane (1000 ppm) into methanol with yield of 4.38 μmol/h/g under light irradiation and at room temperature. Both performance experiments and trapping experiments verified that the methane activation and methyl oxidation involved in photocatalytic conversion process of methane. The ?O2- firstly activated the methane to methyl on the surface of the g-C3N4 in the composite and then the photogenerated electrons from the Cs0.33WO3 in the composite inhibited the peroxidation and increased the generation of methanol. This research provides a new route to design and synthesize photocatalysts for converting methane into value-added chemicals.
关键词： Selective Conversion,Low concentration methane,Tungsten Bronze Cesium,Photocatalytic Methane Conversion,Graphic Carbon Nitride
更新于2025-09-19 17:15:36