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Background: The aim of this study is to search for the predictive value of 3D fat analysis and calculation technique (FACT) and intravoxel incoherent motion (IVIM) parameters in identifying osteoporosis in women. Methods: We enrolled 48 female subjects who underwent 3.0 T MRI, including 3D FACT and IVIM sequences. Bone mineral density (BMD) values and Fracture Risk Assessment (FRAX) scores were obtained. Proton density fat fraction (PDFF) in the bone marrow and the real diffusion (D) value of intervertebral discs were measured on 3D FACT and IVIM images, respectively. Accuracy and bias were assessed by linear regression analysis and Bland–Altman plots. Intraclass correlation coefficients were used to assess the measurements’ reproducibility. Spearman’s rank correlation was applied to explore the correlation. MRI-based parameters were tested for significant differences among the three groups using ANOVA analyses. A receiver operating characteristic (ROC) analysis was performed. Results: The PDFF of the vertebral body showed a negative correlation with BMD (R = −0.393, p = 0.005) and a positive correlation with the FRAX score (R = 0.706, p < 0.001). The D value of intervertebral discs showed a positive correlation with BMD (R = 0.321, p = 0.024) and a negative correlation with the FRAX score (R = −0.334, p = 0.019). The area under the curve values from the ROC analysis showed that the 3D FACT and IVIM sequences could accurately differentiate between normal and osteoporosis (AUC = 0.88 using the PDFF; AUC = 0.77 using the D value). The PDFF value demonstrated a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 78.6%, 89.5%, 84.6%, and 85.0%, respectively, in its ability to predict osteoporosis. The D value had a sensitivity, specificity, PPV, and NPV of 63.16%, 92.9%, 65.0%, and 77.8%, respectively, for predicting osteoporosis. Conclusions: The 3D FACT- and IVIM-measured PDFF and D values are promising biomarkers in the assessment of bone quality and fracture risk.

In order to improve the positioning accuracy of high resolution remote sensing satellite without ground control points, the accuracy of payload pointing determination must be improving. In this paper, the development of high accuracy payload pointing determination technology of satellite is introduced, and the main methods that achieve high accuracy are analyzed. There are two implementations, one is the highly stable structural design and the integrated configuration design which provides common installation reference for both attitude sensors and payloads, the other is measurement of the relative changes between the attitude sensors and the payloads in orbit and to achieve high precision payload pointing determination by compensation processing. Based on the investigation results, this paper proposes a pointing determination system design for multiple payloads, which realizes the high precision transmission from the measuring sensors to the pointing monitoring payloads from the system level, and can solve the pointing change caused by the internal changes of payloads such as the camera and LIDAR system. The design method can provide a reference for the future development of the satellite with high performance.

This paper proposes a method using the deep neural network for satellite remote sensing image detection. This paper improves its network structure base on the YOLO-v3 network, which includes reshaping multi-scale feature maps, improving the network structure, improving the detection ability of weak targets in remote sensing images, reducing the number of convolution channels in CNN, and improves the detection speed. In this paper, the target database is established based on satellite remote sensing images such as GF-2 and ZY-3. The results of this paper show that the proposed algorithm has excellent performance in target detection accuracy and efficiency.

The internal structure of off-axis three-mirror system is commonly complex. The mirror installation error in assembly always affects the imaging line-of-sight and further degrades the image quality. Due to the complexity of the optical path in off-axis three-mirror optical system, the straightforward theoretical analysis on the variations of imaging line-of-sight is extremely difficult. In order to simplify the theoretical analysis, an equivalent single-mirror system is proposed and presented in this paper. In addition, the mathematical model of single-mirror system is established and the accurate expressions of imaging coordinate are derived. Utilizing the simulation software ZEMAX, off-axis three-mirror model and single-mirror model are both established. By adjusting the position of mirror and simulating the line-of-sight rotation of optical system, the variations of imaging coordinates are clearly observed. The final simulation results include: in off-axis three-mirror system, the varying sensitivity of the imaging coordinate to the rotation of line-of-sight is approximately 30 um/″; in single-mirror system, the varying sensitivity of the imaging coordinate to the rotation of line-of-sight is 31.5 um/″. Compared to the simulation results of the off-axis three-mirror model, the 5p relative error of single-mirror model analysis highly satisfies the requirement of equivalent analysis and also verifies its validity. This paper presents a new method to analyze the installation error of the mirror in the off-axis three-mirror system influencing on the imaging line-of-sight. Moreover, the off-axis three-mirror model is totally equivalent to the single-mirror model in theoretical analysis.

International audience; Nowadays, how to make a human-computer interaction system which can take into account large-area display, high precision tracking and multi-user operation at the same time is a hot research topic. This paper presents a novel low cost pen-based projective interaction system that can write or draw like writing brush. The system is composed of infrared scanning projector, digital pen, projector, screen, wireless receiver module and computer. The infrared scanning projector is designed to achieve fast projection, which is to track the pen’s two dimensional location accurately along with the digital pen. The system has the advantage of multi-user supported, high tracking precision, and has the function of identity recognition and writing calligraphy.