As photosynthetically active radiation (PAR) variability and PAR estimating methods play an important role in climate change and ecological process research, PAR variation trends and broadband global solar radiation (...
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As photosynthetically active radiation (PAR) variability and PAR estimating methods play an important role in climate change and ecological process research, PAR variation trends and broadband global solar radiation (R (s) ) ratios (PAR/R (s) ) in the North China Plain (NCP) are examined using in situ PAR and R (s) observed data for 2005 to 2011. The annual average PAR value found in the NCP is 22.9 mol m(-2) d(-1). The highest and lowest values were recorded at Changwu and Luancheng sites, respectively. The highest PAR/R (s) value was found in Jiaozhouwan due to large water vapor volumes present in this area. PAR/R (s) levels have increased in the NCP due to a decrease in fine aerosols and increase in water vapor concentration. From these analysis results, a parameterization model that can be applied to all sky conditions was checked. Empirical estimation model comparisons for obtaining PAR values indicate that model was least accurate when R (s) was used independently. When the model included R (s), the clearness index (K (s)) and the solar zenith angle, the model estimated PAR values with acceptable accuracy. A parameterization model was constructed by considering K (s) and attenuation factors of PAR under clear weather conditions (rho (clear)). The improved parameterization model more accurately predicts values for local sites and for various observation sites.
Bimanual mobile manipulation significantly enhances the capabilities of field robots that interact with diverse dynamic environments and expands the range of possible manipulation actions. This paper introduces a robu...
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Bimanual mobile manipulation significantly enhances the capabilities of field robots that interact with diverse dynamic environments and expands the range of possible manipulation actions. This paper introduces a robust shared control architecture for remote manipulation of the Collaborative Dual-arm Robot Manipulator (CURI), aimed at stable object transportation. Given that stable contact is pivotal for successful object transportation, our focus is on stabilizing the contact between the robot end-effectors and the object using a contact servoing strategy. To maintain stable contact, it is essential that the contact wrenches consistently stay within the predefined friction cones throughout the task. We propose a novel shared control strategy to stabilize the contact using the contact parameterization model. This model formulates the contact stability manifold using a set of unconstrained reparameterized variables through a bijective mapping function, ensuring that the controller derived from these unconstrained reparameterized variables consistently maintains contact stability. The efficacy of the proposed approach is convincingly demonstrated through a series of experiments involving representative bimanual transportation tasks within a logistics context. Both theoretical analysis and experimental validations confirm that our proposed control strategy not only ensures the stable transportation of objects by CURI but also substantially enhances the overall robustness of the shared control system.
Surface downward longwave radiation (SDLR) is crucial for maintaining the global radiative budget balance. Due to their ease of practicality, SDLR parameterization models are widely used, making their objective evalua...
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Surface downward longwave radiation (SDLR) is crucial for maintaining the global radiative budget balance. Due to their ease of practicality, SDLR parameterization models are widely used, making their objective evaluation essential. In this study, against comprehensive ground measurements collected from more than 300 globally distributed sites, four SDLR parameterization models, including three popular existing ones and a newly proposed model, were evaluated under clear- and cloudy-sky conditions at hourly (daytime and nighttime) and daily scales, respectively. The validation results indicated that the new model, namely the Peng model, originally proposed for SDLR estimation at the sea surface and applied for the first time to the land surface, outperformed all three existing models in nearly all cases, especially under cloudy-sky conditions. Moreover, the Peng model demonstrated robustness across various land cover types, elevation zones, and seasons. All four SDLR models outperformed the Global Land Surface Satellite product from Advanced Very High-Resolution Radiometer Data (GLASS-AVHRR), ERA5, and CERES_SYN1de-g_Ed4A products. The Peng model achieved the highest accuracy, with validated RMSE values of 13.552 and 14.055 W/m2 and biases of -0.25 and -0.025 W/m2 under clear- and cloudy-sky conditions at daily scale, respectively. Its superior performance can be attributed to the inclusion of two cloud parameters, total column cloud liquid water and ice water, besides the cloud fraction. However, the optimal combination of these three parameters may vary depending on specific cases. In addition, all SDLR models require improvements for wetlands, bare soil, ice-covered surfaces, and high-elevation regions. Overall, the Peng model demonstrates significant potential for widespread use in SDLR estimation for both land and sea surfaces.
Measurements of ozone concentrations, and meteorological and surface parameters were carried out over a flat green grassland in northwest Spain, in July 1995. Turbulent parameters and sensible and latent heat fluxes w...
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Measurements of ozone concentrations, and meteorological and surface parameters were carried out over a flat green grassland in northwest Spain, in July 1995. Turbulent parameters and sensible and latent heat fluxes were calculated using the gradient technique. Fluxes and deposition velocity and resistances were evaluated assuming that the diffusivity for heat fluxes was equal to pollutant diffusivity. The daily average value of dry deposition velocity was 6 mm s(-1) but it was influenced by wind velocity and atmospheric stability. Resistances have been calculated according to a simple resistance model and a comparison between theoretical and measured values has been made.
In general practical applications, the point spread function (PSF) of the imaging system, the imaging process, and the observation noise, are unknown a priori information. Therefore, the identification of the PSF is a...
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ISBN:
(纸本)9780819473639
In general practical applications, the point spread function (PSF) of the imaging system, the imaging process, and the observation noise, are unknown a priori information. Therefore, the identification of the PSF is a challenging and difficult problem in the world. The algorithm of identification of the PSF and the restoration of the blurred images based on the priori blur models (known as the PBM algorithm) is proposed. In practical application, the priori models of the PSF mainly consist of the linear motion blur, out of focus blur and the Gaussian blur. In the situation of that the degradation process is formed by the one of the above point spread functions, the PSF can be formulated in parametric model. The corresponding parameters of the model are determined by the algorithm proposed in this paper. Thus, the PSF is obtained according to the parameter of the model consequently. First, the parameter changing scope and the increment step length of the parameters are provided based on the original guess. Second, the criterion that the Euclid length of the difference between the observed image and blurred image corresponding to the PSF is minimized is incorporated in order to determine the parameter of the PSF. Therefore, the PSF is identified by the parametric model and the original image is estimated via the ordinary image restoration algorithms. In this paper, we applied the Wiener filter to restore the original images. The experimental results show that the identified result of the PSF is reliable and accurate and the restoration effect with the identified PSF is better when the observed image have high signal to noise ratio (SNR).
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