Long-term analysis of the urban heat island effect using multisource Landsat images considering inter-class differences in land surface temperature products.

It is imperative to quantitatively analyze the long-term temporal and spatial characteristics of the urban heat island (UHI) effect on cities for applications, such as urban expansion and environmental protection. Owing to the high spatial resolution and availability of long time-series data, remote sensing images from Landsat satellites are widely used for land surface temperature (LST) retrieval. However, limited by the satellite revisit cycle and image quality, the use of multisource Landsat images in a long-term study of the UHI effect is inevitable.

Geometric modeling of attitude jitter for three-line-array imaging satellites.

Attitude jitter causes image motion and degrades geometric accuracy of high-resolution satellite images. This work studies the mechanism of the attitude jitter effect on the imaging geometry of three-line-array push-broom sensors onboard satellites, which is a typical configuration used for topographic mapping. Based on a rigorous physical imaging model, we derived quantitative models of the geometric effect of attitude jitter in the roll, pitch, and yaw angles on the image distortions of the forward, nadir, and backward view sensors, and the accuracy of the derived models is validated through comprehensive experiments and analyses.

Spatiotemporal spread pattern of the COVID-19 cases in China.

The COVID-19 pandemic is currently spreading widely around the world, causing huge threats to public safety and global society. This study analyzes the spatiotemporal pattern of the COVID-19 pandemic in China, reveals China's epicenters of the pandemic through spatial clustering, and delineates the substantial effect of distance to Wuhan on the pandemic spread. The results show that the daily new COVID-19 cases mostly occurred in and around Wuhan before March 6, and then moved to the Grand Bay Area (Shenzhen, Hong Kong and Macau).

A mathematical simulation of the tip-apex distance and the calcar-referenced tip-apex distance for intertrochanteric fractures reduced with lag screws.

Background: As a predictor of the risk of lag screw cutout, it was recommended that keeping tip-apex distance (TAD)<25mm and placing the screw centrally or inferiorly, but positioning the lag screw too inferiorly in the head would produce TAD>25mm. We aim to simulate various positions of the lag screw in the femoral head and identify whether 25mm is a suitable cut-off value that favours all sizes of femoral heads with intertrochanteric fractures of the hip.

Methods: Using a general mathematical software, the positions of the screw tip points were simulated.