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A new method using gradient boosting regression tree(GBRT) which is optimized by logistic regression(LR) to predict working resistance of hydraulic support is proposed, avoiding shortcomings of current determining methods. Add learning rate to GBRT to limit the learning rate of sub-models and prevent over-fitting; using LR to optimize sample parameters to establish LR-GBRT regression prediction model; the model is applied to predict resistance of hydraulic support, and the prediction result is compared with linear regression(LR), support vector model(SVM), decision tree regression(DTR), elastic net regression(EN). The results show that the model has better generalization performance and higher prediction accuracy. It can effectively predict resistance of hydraulic support .

Constructing van der Waals (vdW) hetero-structures is an effective and feasible method to enhance two-dimensional (2D) materials with desired properties and to extend the application of the original materials. In this work, we establish a C2N/BlueP vdW hetero-structure and explore its photocatalytic water splitting performance by investigating the electronic structure, band edge alignment, charge transfer, optical absorption and strain response based on the density functional theory (DFT) method. Numerical results indicate that the C2N/BlueP hetero-structure possesses a proper direct bandgap and intrinsic type-II band alignment, which are beneficial to the space separation of photo-generated electron–hole pairs. The optical absorption of the hetero-structures is enhanced from the visible to ultraviolet light region compared with those of both individual monolayers. More importantly, the valence band maximum (VBM) is lower than the oxidation potential of water, and the conduction band minimum (CBM) is higher than the reduction potential of water, which indicates the proper photocatalytic potential for water splitting of the C2N/BlueP hetero-structure. By applying a small vertical pressure perpendicular to the hetero-structure with roughly 6% interlayer compression, both the band alignment and the optical absorption can be improved, which gives better performance of photocatalytic water splitting for the C2N/BlueP hetero-structure. [ABSTRACT FROM AUTHOR]

Recently, 2D carbon phosphides (PCs) have attracted much attention due to their superior electronic and photovoltaic properties suitable for potential applications in field effect transistors and photodetectors. In this work, we systematically investigate the stability, electronic properties, optical absorption and photocatalytic water splitting performance of few-layered PC3 by using the first principles calculation method. Numerical results indicate that both monolayered and bilayered PC3 can serve as efficient photocatalysts for overall water splitting due to their high stability, moderate band gaps, suitable band edge positions, anisotropic high carrier mobilities and strong capacity of solar absorption. Compared with monolayered PC3, bilayered PC3 displays higher carrier mobilities (2500-23 000 cm2 V-1 s-1) and a wider optical absorption spectrum. Moreover, by applying an in-plane biaxial strain, the utilization of solar energy and the pH range suitable for overall water splitting can be improved effectively for both monolayered and bilayered PC3. Our work reliably expands the potential application of 2D few-layered PC3 in the field of nano-electronics and nano-optoelectronics.

Constructing van der Waals (vdW) hetero-structures is an effective and feasible method to enhance two-dimensional (2D) materials with desired properties and to extend the application of the original materials. In this work, we establish a C 2 N/BlueP vdW hetero-structure and explore its photocatalytic water splitting performance by investigating the electronic structure, band edge alignment, charge transfer, optical absorption and strain response based on the density functional theory (DFT) method. Numerical results indicate that the C 2 N/BlueP hetero-structure possesses a proper direct bandgap and intrinsic type-II band alignment, which are beneficial to the space separation of photo-generated electron-hole pairs. The optical absorption of the hetero-structures is enhanced from the visible to ultraviolet light region compared with those of both individual monolayers. More importantly, the valence band maximum (VBM) is lower than the oxidation potential of water, and the conduction band minimum (CBM) is higher than the reduction potential of water, which indicates the proper photocatalytic potential for water splitting of the C 2 N/BlueP hetero-structure. By applying a small vertical pressure perpendicular to the hetero-structure with roughly 6% interlayer compression, both the band alignment and the optical absorption can be improved, which gives better performance of photocatalytic water splitting for the C 2 N/BlueP hetero-structure.

Objective: To determine the total blood loss and hidden blood loss associated with surgery for lumbar spinal stenosis and to identify risk factors for blood loss., Methods: From September 2002 to July 2006, the clinical data from 138 patients with lumbar spinal stenosis undergoing initial operation were analysed prospectively. There were 44 males and 94 females, aging 56-78 years (mean 66.7 years). A simple posterior lumbar spinal decompression was used in 26 cases; posterior spinal canal decompression, interbody distraction Cage, and bone graft between transverse process was used in 54 cases; pedicle screw fixation, posterior decompression and bone graft between transverse process was used in 32 cases; posterior decompression, pedicle screw fixation, interbody Cage, and graft between transverse process was used in 26 cases. Before operation, 23 patients took aspirin, and after operation 15 patients had gastrointestinal bleeding. Intraoperative blood loss was calculated by the aspirator and observed blood loss intraoperation. The whole estimated blood loss was calculated according to the level of hemoglobin, blood volume and blood transfusion at the time of admission and after 3 and 4 days of operation., Results: The blood loss intraoperation was (485.51 +/- 143.75) mL. The estimated blood loss was (1218.60 +/- 306.86) mL, which was significantly higher than the intraoperational blood loss (P < 0.001). There was significant difference between the estimated blood loss and observed blood loss during surgeries (P < 0.001). There were significant differences in the estimated blood loss and observed blood loss during surgery between patients treated with aspirin and without aspirin (P < 0.001), between patients with gastrointestinal bleeding and whiout gastrointestinal bleeding (P < 0.001)., Conclusion: The total blood loss after surgery for lumbar spinal stenosis is much greater than that of observed intra-operation. The type of surgery, treatment with aspirin and gastrointestinal bleeding or ulceration can all independently increase blood loss.