雷酸家族史话

通过雷酸自我介绍的方式来介绍雷酸及雷酸盐的发现、结构的解析以及在社会生活中的应用。从早期炼金术士发现雷酸汞,到结构分析中同分异构体概念的提出,再到诺贝尔采用雷酸汞研制炸药的成功,雷酸家族的故事为科学与技术彼此交融、共同进步提供了一个很好的例子。

GRACE observed mass loss in the middle and lower Yangtze basin

Anthropogenic architectures have a significant impact to the environment. The Three Gorges Dam(TGD),as the largest dam in the world, is a typical example, and has influenced the mass anomalies transported by the flow downstream in the Yangtze River since June 2003. However, the evidence of TGD influence on downstream mass transportation is not documented. In this study, we analyze the monthly gravity solutions from GRACE to investigate the downstream mass variations of Yangtze River. From our results,the considerable mass loss is detected in the downstream of TGD. By comparing our estimations with the in situ water level data of TGD, we find that the mass variations derived from GRACE at Datong station decreases shortly after the impoundment of TGD. This confirms a strong connection between them.Furthermore, by comparing with the in situ sediment load and river discharge at Yichang and Datong gauging stations, we find that the sediment load data shows a similar mass loss signature while the river discharge of both stations has stay at a relative stable level. This indicates that further study is still needed to understand the mechanism better.

Backward rescattered photoelectron holography in strong-field ionization

By numerically solving the time-dependent Schr¨odinger equation, we observe a remarkable strong-field interference pattern in the photoelectron momentum distribution of a hydrogen atom ionized by a few-cycles laser pulse. This interference pattern is joined together with the familiar near-forward strong-field photoelectron holographic interference. By applying the strong-field approximation theory, we investigate the formation of this interference pattern, which arises from the interference between the backward rescattered part and the direct part of the tunneling ionized electron wave packet. We demonstrate that this backward rescattered photoelectron holographic interference can also be observed in a more realistic parallel two-color laser field. These results pave a new way to look into the atomic and molecular structure with ultrafast timescale.

Recommendations for Promoting High Quality Development of Sericulture Industry in Dongtai City

With many years of benign development,Dongtai City has established a complete technical system for the sericulture industry,an advanced industrialized operation mode,a mature operation mechanism of trade,industry and agriculture,and a perfect social service mode.The production level of sericulture in Dongtai City is constantly improved. However,there are still problems such as small scale of individual household,slow technological progress,low level of industrial mechanization and labor saving,and hidden dangers in safe production of sericulture. It is recommended to fully build mulberry gardens and lay a solid foundation for the sericulture industry; implement compound operations to increase the level of income growth; deepen three major innovations,break through the bottlenecks; expand industrial functions,promote integrated development,and accelerate the high quality development of the sericulture industry in Dongtai City.

Single Adatom Adsorption and Diffusion on Fe Surfaces

Using Embedded-atom-method (EAM) potential, we have performed in detail molecular dynamics studies on a Fe adatom adsorption and diffusion dynamics on three low miller index surfaces, Fe (110), Fe (001), and Fe (111). Our results present that adatom adsorption energies and diffusion barriers on these surfaces have similar monotonic trend: adsorption energies, Ea(110) Ea(001) Ea(111), diffusion barriers, Ed(110) Ed(001) Ed(111). On the Fe (110) surface, adatom simple jump is the main diffusion mechanism with relatively low energy barrier;nevertheless, adatoms exchange with surface atoms play a dominant role in surface diffusion on the Fe (001).

神经重症患者气管插管拔除失败的风险因素分析

目的识别气管插管大于48 h且通过脱机试验的神经重症患者拔管的独立风险因素,并建立拔管风险预测模型。方法收集2020年4月至2023年8月安徽医科大学第一附属医院神经重症监护病房中接受规范化监护及治疗的83例神经重症患者的病例资料。根据拔管后96 h内是否需要再次插管或气管切开将83例患者分为拔管成功组(61例)和拔管失败组(22例)。比较两组患者的一般资料、神经功能、气道保护能力情况以及生理生化指标,最终通过多因素回归分析建立预测模型。进一步绘制受试者工作特征(ROC)曲线,检验研究结果的预测价值、敏感度和特异度,并采用Z检验对各评分的曲线下面积(AUC)进行比较。结果83例患者中有61例(73.5%)成功拔管,22例(26.5%)在拔管后96 h内呼吸障碍再次插管。两组患者格拉斯哥昏迷量表评分的运动子项(GCS-M)得分、肌力分级、拔管前意识水平、呛咳反应、吞咽功能、拔管后吸氧方式、拔管前体温、血钠离子浓度、Godet's评分、VISAGE评分和呼吸功能不全量表-插管(RIS-i)评分比较,差异均有统计学意义(P均<0.05)。将GCS-M得分、拔管前意识水平、呛咳反应、吞咽功能及拔管前体温纳入多因素logistic回归分析,结果显示拔管前的GCS-M得分<4分[比值比(OR)=8.835,95%置信区间(CI)(1.638,47.659),P=0.011]、呛咳反应>Ⅱ级[OR=10.281,95%CI(2.366,44.129),P=0.002]、体温≥37℃[OR=4.506,95%CI(1.024,19.833),P=0.046]是神经重症患者拔管失败的危险因素。进一步根据OR值对每个独立危险因素进行赋分,并建立神经危重拔管失败风险预测量表,总分为5分,ROC曲线分析显示本研究量表评分>1分预测拔管失败(高失败风险)的敏感度为77.3%,特异度为85.2%,AUC为0.850[95%CI(0.775,0.919),P<0.001]。Z检验结果显示,当前量表的预测价值高于Godet's评分(Z=2.050,P=0.040)、VISAGE评分(Z=1.990,P=0.047)。结论该临床预测评分可为神经重症患者脱机后拔管提供指导价值。

Evaluation of E-sail parameters on central spacecraft attitude stability using a high-fidelity rigid–flexible coupling model

This study examines the impact of electric solar wind sail(E-sail)parameters on the attitude stability of E-sail’s central spacecraft by using a comprehensive rigid–flexible coupling dynamic model.In this model,the nodal position finite element method is used to model the elastic deformation of the tethers through interconnected two-node tensile elements.The attitude dynamics of the central spacecraft is described using a natural coordinate formulation.The rigid–flexible coupling between the central spacecraft and its flexible tethers is established using Lagrange multipliers.Our research reveals the significant influences of parameters such as tether numbers,tether’s electric potential,and solar wind velocity on attitude stability.Specifically,solar wind fluctuations and the distribution of electric potential on the main tethers considerably affect the attitude stability of the spacecraft.For consistent management,the angular velocities of the spacecraft must remain at target values.Moreover,the attitude stability of a spacecraft has a pronounced dependence on the geometrical configuration of the E-sail,with axisymmetric E-sails proving to be more stable.

Collision-avoidance strategy for a spinning electrodynamic tether system

Spinning electrodynamic tether systems(SEDTs)have promising potential for the active removal of space debris,the construction of observation platforms,and the formation of artificial gravity.However,owing to the survivability problem of long tethers,designing collision-avoidance strategies for SEDTs with space debris is an urgent issue.This study focuses on the design of collision-avoidance strategies for SEDTs with an electrodynamic force(Ampere force).The relative distance between the debris and the SEDT is first derived,and then two collision-avoidance strategies are proposed according to the two different cases.When debris collides closer to a lighter subsatellite,a stationary avoidance strategy is proposed to change the spatial position of the subsatellite by adjusting only the angular motion of the tether,which maintains the original orbit of the SEDT.When debris collides closer to a heavier main spacecraft,a comprehensive avoidance strategy is proposed to change the spatial position of the SEDT by slightly modifying the orbital height and changing the tether angular motion simultaneously.The numerical results illustrate that the proposed strategies promptly avoid potential collisions of an SEDT with space debris without significant changes in the orbital parameters of the SEDT.

Dynamics and de-spin control of massive target by single tethered space tug

This paper investigates the dynamics and de-spin control of a massive target by a single tethered space tug in the post-capture phase. The dynamic model of the tethered system is derived and simplified to a dimensionless form. Further, a decoupled PD controller is proposed, and the local stability of the controller is analyzed by linearization technique. Parametric studies of the dynamics and de-spin control of a massive target are conducted to characterize the dynamic process of de-spin with the proposed control law. It is shown that the massive target can be de-span by a single and small space tug with limited thrust within finite time. The thrust tangent with the tether de-spins the target while the thrust normal to the tether prevents the tether from winding up the target. The tether length has a positive contribution to the de-spin of a target. The longer tether leads to a faster de-spin process.

Robust formation control for missiles with obstacle avoidance

This paper investigates the robust formation control for missiles with obstacle avoidance.A sliding mode surface that is asymptotically stable is firstly presented by the collision avoidance potential function and hyperbolic tangent function.Based on the sliding mode surface,a robust formation controller with obstacle avoidance is designed for missiles.To improve the convergence rate,a finite-time controller which can deal with the formation control for missiles is given using an improved sliding mode surface.Finally,the effectiveness of the designed controllers for missiles is demonstrated by the Lyapunov theory and simulation results.

Energy-Efficient and Secure Power Allocation and Trajectory Optimization for UAV-Enabled Data Collection in Wireless Sensor Networks

Using unmanned aerial vehicles(UAVs)to collect data in wireless sensor networks(WSNs)has advantages of controllable mobility and flexible deployment.However,there are potential challenges of energy limitation and data security which may limit such applications.To cope with these challenges,a complicated and intractable optimization problem is formulated,which maximizes the performance metric of secrecy energy efficiency(EE)subject to the constraints of secrecy rate,maximum power,and trajectory.Then,an energy-efficient and secure solution is developed to improve the secrecy EE of the UAV-enabled data collection in the WSNs by joint optimizing the UAV’s trajectory and velocity along with the sensors’power.The proposed solution is an iterative algorithm based on the optimization approaches of alternating optimization,successive convex approximation,and fractional programming.Simulation results demonstrate that the proposed solution scheme is effective for improving the secrecy EE while guaranteeing the data security.

Knowing and doing of residents’ reading in rural areas in China: A survey of the current situation in the ethnic minority regions along the Nenjiang River

Concerning the problem of the lack of reading for the residents in Chinese rural areas,the existing studies mainly focus on developing rural reading facilities and improving the service models in use.Nevertheless,the problems,which arise from the fundamental characteristics of the rural residents(predominately farmers),have not been sufficiently studied.This paper reports on a research study,which aims to address these problems through a survey of 51