Given that many operational satellite sensors are not calibrated, while a handful of research sensors are, cross-calibration between the two types of sensor is a cost-effective means of calibration. A new method of sensor cross-calibration is demonstrated here using the Chinese Multi-channel Visible Infrared Scanning radiometer (MVIRS) and the US Moderate Resolution Imaging Spectrometer (MODIS). MVIRS has six channels, equivalent to the current National Oceanic and Atmospheric Administration's (NOAA) Advanced Very High Resolution Radiometer (AVHRR) and four additional ones for remote sensing of ocean colour and moisture. The MVIRS on-board China's polar-orbiting meteorological satellite (FY-1D) was launched on 15 May 2002 with an earlier overpass time than Terra. The sensor has no on-board calibration assembly. This study attempts to calibrate MVIRS against the well-calibrated MODIS, by taking a series of measures to account for their differences. Clear-sky measurements made from the two sensors in July-October 2002 were first collocated. Using the 6S radiative transfer model, MODIS reflectances measured at the top-of-the atmosphere were converted into surface reflectances. They were corrected to the viewing geometry of the MVIRS using the bidirectional reflectance distribution function (BRDF) measured on the ground. The spectral response functions of the two sensors were employed to account for spectral discrepancies. After these corrections, very close linear correlations were found between radiances estimated from the MODIS and the digital readings from the MVIRS, from which the calibration gains were derived. The gains differ considerably from the pre-launch values and are subject to degradation over time. The calibration accuracy is estimated to be less than 5%, which is compatible to that obtained by the more expensive vicarious calibration approach.
The efficient separation of photogenerated electron–hole pairs is a critical challenge that hampers the performance of photocatalytic systems. In this work, a NiCo2S4/ZnCdS (NiCo2S4/ZCS) Schottky junction was constructed by a simple physical mixing method. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results proved that NiCo2S4 is an amorphous material, and density functional theory (DFT) calculations confirmed the metallic nature of NiCo2S4. The light absorption capacity of the NiCo2S4/ZCS heterojunction is significantly enhanced with the NiCo2S4 loading. The formation of Schottky junctions between NiCo2S4 and ZnCdS results in photogenerated electron transfer and spatial separation and prevents the recombination of charge carriers. Therefore, the optimized 20% NiCo2S4/ZCS exhibits a remarkable photocatalytic hydrogen evolution (PHE) activity of 25 mmol g–1 h–1, which is 4.79 and 150.6 times higher than that of ZnCdS alone and NiCo2S4. This work provides a successful strategy for preparing a ZnCdS-based Schottky junction to promote PHE activity.
Manual apple harvest by seasonal migrant workers throughout the U.S. using ladder-bucket method. Though it is known that apple harvest would cause occupational injuries to workers, few studies have been conducted to quantify the levels of occupational injuries. Applying the rapid upper limb assessment (RULA) method, this study comprehensively evaluated the harvest process by dividing it into different activities. To alleviate occupational injuries in apple harvest, a low-cost harvest-assist unit has been developed, and its performance on reducing occupational injuries was further evaluated. Experimental results showed that seven out of 11 activities in the ladder-bucket harvest method would lead to occupational injuries, and the adoption of ladders and buckets was mainly responsible for causing occupational diseases. It has been demonstrated that adoption of the harvest-assist unit for high level apples harvest would not result in occupational injuries. Using the combined method (conventional for low level apples + harvest-assist unit for high level apples) to harvest apples would significantly reduce the occupational injury potential by cutting down the uncomfortable time ratio from 64 to 29%. This study demonstrated that combining the conventional harvest method for low level apples and the harvest-assist unit for high level apples harvest would significantly reduce the potential of occupational injuries. Thus, the newly developed apple harvest-assist unit supplies a solution to apple growers to alleviate harvest employees' occupational injuries.
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