面向学生的高校智能管理系统的设计与实现

随着网络技术的快速发展,高校对学生信息化的建设和管理愈加重视。高校智能管理系统是高校信息化建设的重要展现。本文针对学生日常的生活轨迹和生活信息,进行相关的数据分析和挖掘,采用Python语言和MySQL数据库技术,在Flask框架上进行改进,实现了以学习管理、健康管理和生活管理三大功能模块的轻量级Web和安卓应用,将面向学生的高校智能管理系统打造成一个集成化的平台,以提升校园管理的工作效率和提供健康安全保障。     

Lie group method for solving viscous barotropic vorticity equation in ocean climate models

In studying the problem of the nonlinear viscous barotropic non-divergent vorticity equation on $f$- and $\beta$- planes, the method of Lie group has been applied. The method reduces the number of independent variables by one, and consequently, for the case of three independent variables we applied the method successively twice and the nonlinear partial differential equation reduces to ordinary differential equation. Investigation of exact solutions of the viscous barotropic non-divergent vorticity equation on $f$- and $\beta$- planes, via the application of Lie group, provides large classes of new exact solutions which include both Rossby and Rossby–Haurwitz waves as special cases. Also, The Lie symmetries of the viscous barotropic non-divergent vorticity equation with two parameters $F$ and $\beta$, are determined. The possible reductions of the viscous barotropic vorticity equation with two parameters $F$ and $\beta$ have been investigated by means of one- dimensional Lie subalgebras.     

Manual Therapy Facilitates Homeostatic Adaptation to Bone Microstructural Declines Induced by a Rat Model of Repetitive Forceful Task

The effectiveness of manual therapy in reducing the catabolic effects of performing repetitive intensive force tasks on bones has not been reported. We examined if manual therapy could reduce radial bone microstructural declines in adult female Sprague–Dawley rats performing a 12-week high-repetition and high-force task, with or without simultaneous manual therapy to forelimbs. Additional rats were provided 6 weeks of rest after task cessation, with or without manual therapy. The control rats were untreated or received manual therapy for 12 weeks. The untreated TASK rats showed increased catabolic indices in the radius (decreased trabecular bone volume and numbers, increased osteoclasts in these trabeculae, and mid-diaphyseal cortical bone thinning) and increased serum CTX-1, TNF-α, and muscle macrophages. In contrast, the TASK rats receiving manual therapy showed increased radial bone anabolism (increased trabecular bone volume and osteoblast numbers, decreased osteoclast numbers, and increased mid-diaphyseal total area and periosteal perimeter) and increased serum TNF-α and muscle macrophages. Rest, with or without manual therapy, improved the trabecular thickness and mid-diaphyseal cortical bone attributes but not the mineral density. Thus, preventive manual therapy reduced the net radial bone catabolism by increasing osteogenesis, while rest, with or without manual therapy, was less effective.     

从欧美日标准看我国不锈钢钢管制造业的现状及发展前景(上)

介绍了欧、美、日不锈钢钢管标准的特点。详细对比欧、美、日不锈钢钢管新标准中钢种类别、制造方法、供货状态、规格范围等有关内容。指出我国不锈钢钢管制造业应在不断扩大产量的同时,加大新钢种研发力度,完善产品规格范围,开发不锈钢钢管制造新工艺,注重产品外观质量,增加我国不锈钢钢管行业的国际竞争力。     

Stability of Flip-Chip Interconnects Assembled with Al/Ni(V)/Cu-UBM and Eutectic Pb-Sn Solder During Exposure to High-Temperature Storage

The thermal stability of flip-chip solder joints made with trilayer Al/Ni(V)/Cu underbump metalization (UBM) and eutectic Pb-Sn solder connected to substrates with either electroless Ni(P)-immersion gold (ENIG) or Pb-Sn solder on Cu pad (Cu-SOP) surface finish was determined. The ENIG devices degraded more than 50 times faster than the Cu-SOP devices. Microstructural characterization of these joints using scanning and transmission electron microscopy and ion beam microscopy showed that electrical degradation of the ENIG devices was a direct result of the conversion of the as-deposited Ni(V) barrier UBM layer into a porous fine-grained V₃Sn-intermetallic compound (IMC). This conversion was driven by the Au layer in the ENIG surface finish. No such conversion was observed for the devices assembled on Cu-SOP surface finish substrates. A resistance degradation model is proposed. The model captures changes from a combination of phenomena including increased (1) intrinsic resistivity, (2) porosity, and (3) electron scattering at grain boundaries and surfaces. Finally, the results from this study were compared with results found in a number of published electromigration studies. This comparison indicates that degradation during current stressing in the Pb-Sn bump/ENIG system is in part due to current-crowding-induced Joule heating and the thermal gradients that result from localized Joule heating.     

Subspace analysis of spatial time-frequency distribution matrices

Spatial time-frequency distributions (STFDs) have been previously introduced as the natural means to deal with source signals that are localizable in the time-frequency domain. Previous work in the area has not provided the eigenanalysis of STFD matrices, which is key to understanding their role in solving direction finding and blind source separation problems in multisensor array receivers. The aim of this paper is to examine the eigenstructure of the STFD matrices. We develop the analysis and statistical properties of the subspace estimates based on STFDs for frequency modulated (FM) sources. It is shown that improved estimates are achieved by constructing the subspaces from the time-frequency signatures of the signal arrivals rather than from the data covariance matrices, which are commonly used in conventional subspace estimation methods. This improvement is evident in a low signal-to-noise ratio (SNR) environment and in the cases of closely spaced sources. The paper considers the MUSIC technique to demonstrate the advantages of STFDs and uses it as grounds for comparison between time-frequency and conventional subspace estimates     

Anti‐Oxygen Leaking LiCoO2

LiCoO₂ is a prime example of widely used cathodes that suffer from the structural/thermal instability issues that lead to the release of their lattice oxygen under nonequilibrium conditions and safety concerns in Li‐ion batteries. Here, it is shown that an atomically thin layer of reduced graphene oxide can suppress oxygen release from Li_xCoO₂ particles and improve their structural stability. Electrochemical cycling, differential electrochemical mass spectroscopy, differential scanning calorimetry, and in situ heating transmission electron microscopy are performed to characterize the effectiveness of the graphene‐coating on the abusive tolerance of Li_xCoO₂. Electrochemical cycling mass spectroscopy results suggest that oxygen release is hindered at high cutoff voltage cycling when the cathode is coated with reduced graphene oxide. Thermal analysis, in situ heating transmission electron microscopy, and electron energy loss spectroscopy results show that the reduction of Co species from the graphene‐coated samples is delayed when compared with bare cathodes. Finally, density functional theory and ab initio molecular dynamics calculations show that the rGO layers could suppress O₂ formation more effectively due to the strong C? O_cathode bond formation at the interface of rGO/LCO where low coordination oxygens exist. This investigation uncovers a reliable approach for hindering the oxygen release reaction and improving the thermal stability of battery cathodes.     

Robust compensation of elastic deformations in ball screw drives

Elastic deformations occur in ball screw drives typically due to inertial forces, guideway friction, and cutting forces. This results in elongation and compression of the ball screw, which deteriorates the dynamic linear positioning accuracy. Closing the control loop with a linear encoder helps to alleviate this problem to a certain extent. However, linear scales cost significantly more than rotary encoders and their installation also brings about additional costs. This paper presents a new strategy for mitigating the detrimental effect of elastic deformations, in order to improve the translational accuracy of ball screw drives when only rotational feedback is available. A simple and physically intuitive model is developed, which is used to offset the position commands that are fed to the servo control law. Compensation is proposed using a closed-loop scheme, which is found to be robust against cutting forces, as well as variations in the table mass and guideway friction. These effects are detected as equivalent disturbances that cause an elastic deformation. The proposed closed-loop compensation strategy has been validated in machining and high-speed tracking experiments, as well as simulations, which demonstrate its effectiveness in terms of improving the ball screw drive’s final translational accuracy.