The two-dimensional liquid gratings have diffraction properties on light. This experiment designed and fabricated an orthogonal two-dimensional liquid grating. Based on the experimental design and principal analysis, the multiple diffraction patterns were obtained by experiments for different light sources. This device was employed to measure the speed of ultrasound in the clear water. Furthermore, the study examined how the speed of ultrasound in clear water varies with temperature and was contrasted with theoretical values. The experimental results attain a remarkably high level of measurement precision.
The rise in greenhouse gas concentrations has been identified as a primary driver of global warming, leading to adverse effects such as rising sea levels and droughts. In response, understanding the dynamics of greenhouse gas concentration changes has become pivotal in the quest to effectively combat climate change and mitigate the adverse effects of global warming. This study utilizes data from the GOSAT satellite to analyze the trends in global CO2 and CH4 concentrations from 2010 to 2022. Furthermore, the time series and seasonal variation characteristics of greenhouse gas concentrations of CO2 and CH4 in the Hefei area were studied, combined with the geographical environment of Hefei. To enhance comprehension, the article also assembles an HYSPLIT backward trajectory model to scrutinize the latent influences exerted by monsoon transport and atmospheric boundary layer conditions on greenhouse gas distributions. Over the course of the decade from 2010 to 2022, greenhouse gas concentrations in the Hefei region exhibited an unwavering upward trajectory, punctuated by conspicuous seasonal fluctuations, showcasing distinct seasonal variations that aligned with the observations of the ground-based observation network TCCON. The concentrations of CO2 surged from 391.05 ppm to 417.98ppm, signifying a net gain of 26.930ppm, corresponding to an annual growth rate of approximately 2.4 ppm. Similarly, CH4 concentrations underwent a net increase of 72 ppb, characterizing an annual growth rate of about 10.4 ppb. These figures underscore the relentless ascent of greenhouse gas concentrations, warranting immediate attention and action. The concentrations of greenhouse gases are subjected to a plethora of factors, encompassing both local biogenic and non-biogenic sources, the intricate patterns of monsoon-driven atmospheric transport, and the unique characteristics of the atmospheric boundary layer. The findings emanating from this comprehensive study are poised to serve as the bedrock upon which Hefei City can formulate and refine its strategies for greenhouse gas emission reduction. Furthermore, the study emphasizes the impact of monsoon transport patterns and atmospheric boundary layer conditions, which can significantly affect the dispersion and accumulation of greenhouse gases in the region. Understanding these factors is crucial for devising effective strategies to mitigate greenhouse gas emissions.
Based on the solution to the rate equations of interactions between laser and sodium atoms, the excitation probability of sodium atoms is achieved. The return photons at 330 nm are numerically calculated for the 1 W laser power at the sodium layer in the mesosphere. Results show that a long pulse laser with a few microsecond durations and 1000 Hz repetition rates can well excite the polychromatic laser guide star to obtain no less return photons at 330 nm than that by the continuous-wave laser in a given condition. In order to obtain enough return photons to satisfy the requirement of tip-tilt detection, the parameters of linewidth, durations, repetition rates, polarization and launch diameters of the laser should be properly chosen. And effects of the laser launch diameters and the atmospheric turbulence on the return photons are slight. For the wonderful vertical atmospheric transmittance T0=0.5 at the Starfire Optical Range, Mauna Kea and Paranal, considering the effects of geomagnetic field, when the power of launch laser varies from 10 W to 25 W with the zenith angles from 0° to 40°, the return photons at 330 nm reach 104 ph/m2/s.
The circular-polarized laser can excite Sodium Laser Guide Star (SLGS) to obtain a large number of the return photons. Re-pumping technology can further enhance the return photon flux of SLGS. But laser propagating in the atmosphere suffers the atmospheric turbulence which causes the stochastic distributions of laser intensity in mesosphere. This leads to the fluctuations of return photon flux as the strength of atmospheric turbulence. We study effects of atmospheric turbulence on the return photon flux of SLGS under the Hufnagle-vally5/7(HV5/7), Greenwood and Mod-HV models by numerical simulation. Results show that both the return photon flux and fluctuations under the strong atmospheric turbulence are more than those under the weak one. Comparing re-pumping with no re-pumping, increment of the return photon flux under the three atmospheric turbulence models increase with the decreasing strength of atmospheric turbulence. But the fluctuations of the return photon flux greatly decrease for re-pumping.
Based on the relative intensity distributions of Sodium Laser Beacon (SLB) and analysis of the on-axis imaging of incoherent light, considering the effects of atmospheric turbulence and the changes of telescope receiving diameter on the short-exposure SLB imagings on the focal plane, imagings of an extended source SLB are simulated under the three atmospheric turbulence models. Results indicate that sharpness and peak strehl ratio of SLB imagings increase but sharpness radius decrease with the decrease of atmosphere turbulence strengths. Moreover, the changes of telescope diameter from 3.0m to 1.5m cause the decrease of sharpness and peak strehl ratio but the increase of sharpness radius.
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