高速铁路精密工程测量技术标准问题的探讨

文章从阐述明确告诉铁路建设中相关测量技术标准的必要性入手,对其精密工程中测量技术标准的相关内容展开了具体分析,并对测量精度控制的要点展开了相应研究。     

Recycling Bacteria for the Synthesis of LiMPO4 (M = Fe,Mn) Nanostructures for High‐Power Lithium Batteries

In this work, a novel waste‐to‐resource strategy to convert waste bacteria into a useful class of cathode materials, lithium metal phosphate (LiMPO₄; M = Fe, Mn), is presented. Escherichia coli (E. coli) bacteria used for removing phosphorus contamination from wastewater are harvested and used as precursors for the synthesis of LiMPO₄. After annealing, LiFePO₄ and LiMnPO₄ nanoparticles with dimensions around 20 nm are obtained. These particles are found to be enveloped in a carbon layer with a thickness around 3–5 nm, generated through the decomposition of the organic matter from the bacterial cell cytoplasm. The battery performance for the LiFePO₄ is evaluated. A high discharge capacity of 140 mAh g^?1 at 0.1 C with a flat plateau located at around 3.5 V is obtained. In addition, the synthesized particles display excellent stability and rate capabilities. Even under a high C rate of 10 C, a stable discharge capacity of 75.4 mAh g^?1 can still be achieved.     

One‐Pot Synthesis of Tunable Crystalline Ni3S4@Amorphous MoS2 Core/Shell Nanospheres for High‐Performance Supercapacitors

Transition metal sulfides gain much attention as electrode materials for supercapacitors due to their rich redox chemistry and high electrical conductivity. Designing hierarchical nanostructures is an efficient approach to fully utilize merits of each component. In this work, amorphous MoS₂ is firstly demonstrated to show specific capacitance 1.6 times as that of the crystalline counterpart. Then, crystalline core@amorphous shell (Ni₃S₄@MoS₂) is prepared by a facile one‐pot process. The diameter of the core and the thickness of the shell can be independently tuned. Taking advantages of flexible protection of amorphous shell and high capacitance of the conductive core, Ni₃S₄@amorphous MoS₂ nanospheres are tested as supercapacitor electrodes, which exhibit high specific capacitance of 1440.9 F g^?1 at 2 A g^?1 and a good capacitance retention of 90.7% after 3000 cycles at 10 A g^?1. This design of crystalline core@amorphous shell architecture may open up new strategies for synthesizing promising electrode materials for supercapacitors.     

基于二次特征提取与SVM的异常步态识别

长期以异常步态行走将导致人体足部、踝关节、大腿疼痛乃至身体骨骼疾病.针对目前普遍采用的基于计算机视觉的步态识别技术对数据采集环境要求严苛、视频图像分析受环境影响较大等问题,基于人行走时的足底压力变化特征进行步态识别,足底压力数据经由穿戴式步态采集器,可以不受环境限制且能实现较远距离的步态识别.并提出一种基于二次特征提取与支持先向量机的异常步态识别方法.该方法采用主成分分析法对从足底压力变化曲线中提取出来的步态特征进行二次提取.获取包含样本数据信息的主要特征信息,通过多分类支持向量机模型对步态进行识别.实验结果表明:该方法对异常步态的平均识别率达到92.625 5%,具有较高的识别精度.     

超高层建筑电梯群节能控制方案设计

提出一种基于能量回馈原理设计的超高层建筑电梯群的节能控制方案.对4台电梯变频器直流侧并联控制系统进行设计,并分析其工作原理;设计控制系统的主电路并阐述其工作原理.     

Carbon Nanotube‐Encapsulated Noble Metal Nanoparticle Hybrid as a Cathode Material for Li‐Oxygen Batteries

Although Li‐oxygen batteries offer extremely high theoretical specific energy, their practical application still faces critical challenges. One of the main obstacles is the high charge overpotential caused by sluggish kinetics of charge transfer that is closely related to the morphology of discharge products and their distribution on the cathode. Here, a series of noble metal nanoparticles (Pd, Pt, Ru and Au) are encapsulated inside end‐opened carbon nanotubes (CNTs) by wet impregnation followed by thermal annealing. The resultant cathode materials exhibit a dramatic reduction of charge overpotentials compared to their counterparts with nanoparticles supported on CNT surface. Notably, the charge overpotential can be as low as 0.3 V when CNT‐encapsulated Pd nanoparticles are used on the cathode. The cathode also shows good stability during discharge–charge cycling. Density functional theory (DFT) calculations reveal that encapsulation of “guest” noble metal nanoparticles in “host” CNTs is able to strengthen the electron density on CNT surfaces, and to avoid the regional enrichment of electron density caused by the direct exposure of nanoparticles on CNT surface. These unique properties ensure the uniform coverage of Li₂O₂ nanocrystals on CNT surfaces instead of localized distribution of Li₂O₂ aggregation, thus providing efficient charge transfer for the decomposition of Li₂O₂.     

雪峰山西侧海相碳酸盐岩沉积间断古岩溶发育规律研究

雪峰山西侧地区加里东期不整合面表现为寒武系牛蹄塘组与震旦系灯影组不整合及上寒武统与奥陶系之间的假整合。由于研究区经历了多期的构造运动,形成了多个区域不整合面,不同时期不同沉积间断的时间长短控制了碳酸盐岩岩溶发育的强度,发育的岩溶缝洞系统的充填程度进而影响了其连通性。不整合面在研究区内出露相对较少,该文主要针对野外调查发现的两处典型露头,即牛蹄塘组—灯影组、上寒武统—下奥陶统之间的不整合面对古岩溶的控制性作用进行分析研究。     

扭带结构影响管内传热与熵产的研究进展

随着工业技术不断发展,传统换热管的传热方式已经无法满足高热流密度下的热量输运要求。扭带插入物是一种能够有效提高换热管传热效率的强化传热元件,以其结构简单、加工容易的特点受到了很多学者的关注和研究。管内流体的传热性能及熵产往往作为评价换热管性能的重要参数,因此扭带结构与流动工质对这些参数的影响成为近年来研究的重点。本文主要综述了近十年来不同结构扭带对管内传热与熵产影响的研究进展。首先,将文献中研究的扭带按照几何结构进行分类,阐述和分析了不同类型扭带对换热管的传热、熵产以及综合性能的影响,试图找出几何结构与换热管传热性能以及熵产之间的联系。其次,介绍了扭带与纳米流体复合传热技术的研究进展。最后,归纳了研究人员为达到传热性能最大化以及熵产最小化而建立的传热和熵产模型,并对模型的优缺点进行了评价。     

Anti-Swelling,High-Strength,Anisotropic Conductive Hydrogel with Excellent Biocompatibility for Implantable Electronic Tendon

As hydrogels rapidly advance for diverse technologies, their practical applications as implantable artificial tendon becomes promising, yet challenging. It requires similar anisotropic fibril structures, matching water content, high mechanical strength, good biocompatibility, and stable performance under physiological conditions. Furthermore, the capabilities of real-time joint motion monitoring and implant condition are extremely important for the precise assessment of rehabilitation processes. However, it is challenging to realize all these properties simultaneously. Herein, this work reports an intelligent implantable artificial tendon based on strong and conductive anisotropic hydrogel, by coupling prestretching-induced ordered structure with drying-enabled strengthening. The fiber structure fixed during drying/rehydration produces a dense and stable network with a hierarchically anisotropic structure. The resulting anisotropic hydrogel presents excellent anti-swelling ability (<3%), high tensile strength (3.71 MPa), and toughness (9.86 MJ m⁻³) upon hydration, at a tendon-matching water content of 72.5 wt%. The in vitro and in vivo tests demonstrate its excellent biocompatibility with significant protein resistance. With reliable strain sensing, the hydrogel can act as an intelligent artificial tendon to restore and real-time monitor joint motion in an in vitro model. The SD rats with tendon defects display restored motor function after implantation of the hydrogel as tendon substitutes, facilitating malfunction tissue therapeutics and rehabilitation.