Exploration and Practice of“Guiding Interactive”Teaching in Advanced Geochemistry Courses from the Perspective of Constructivist Theory

The construction of geochemical disciplines has brought new vitality to the development of traditional geology.In the new round of“Double First-Class”discipline construction at Central South University,the course of Advanced Geochemistry has effectively stimulated students’interest in learning and further improved their scientific thinking and research innovation skills through the implementation of“Guiding Interactive”teaching reform measures,which has important theoretical significance and practical value.

A Study on the Implementation Path of the Blended Teaching Model in Geological Hazards Investigation and Evaluation

Geological Hazards Investigation and Evaluation is the core course of Environmental Geological Engineering,aiming to cultivate skilled talents with solid theoretical knowledge and excellent practical skills.At present,the course faces several issues,including a teaching environment disconnected from real-world work scenarios,course content that deviates from job-related tasks,a lack of digital teaching resources,and reliance on a single teaching method,leading to students’poor feedback from employers.Based on the concept of outcome-based education,the course team of Geological Hazards Investigation and Evaluation establishes a“five-step double-rotation”blended teaching model with the help of a Small Private Online Course platform.The program is designed to improve the teaching environment and expand the digitalized teaching resources in order to improve students’learning motivation,enhance learning effectiveness,and cultivate skillful talents who meet employers’satisfaction.

The Insights and Influence of the Sydney Accord on the Teaching Reform of Vocational Education in China: A Case Study of Professional Curriculum Achievement Evaluation

Scientific curriculum evaluation methods are critical for achieving talent training objectives.The Sydney Accord,one of the three major engineering education certification agreements,focuses on the training of“engineering technologists.”Its logical system and three core principles align well with the connotation development of professional construction in China’s higher vocational colleges,offering significant insights for promoting reform and development in engineering education in Chinese colleges and universities.By incorporating the core principles,elements,and graduate quality defined in the Sydney Accord and focusing on the evaluation of curriculum achievement against“graduation requirements,”the quality of vocational education can be enhanced,making it an important direction for future teaching reforms in vocational education.

The Role and Positioning of Digital Textbooks in Vocational Education in Relation to Teachers

In recent years,with the rapid advancement of digital technologies,digitization in vocational education has become a major trend.Among these advancements,digital textbooks have emerged at the forefront of digitization,significantly impacting both their form and content.This article aims to analyze the existing issues in the use of digital textbooks in vocational education and emphasize the importance of recognizing the vital role of teachers in the wave of digital textbook innovation.It is crucial to clarify the role and positioning of teachers to avoid inadvertently diminishing their classroom significance while prioritizing technological innovations.Teachers should fully leverage the role of digital textbooks as tools for organizing classroom activities and recognize the core and essence of classroom teaching as digital technologies enter the scope of vocational education.By doing so,teachers can contribute to the high-quality development of modern vocational education.

Gini Coefficient-based Task Allocation for Multi-robot Systems With Limited Energy Resources

Nowadays, robots generally have a variety of capabilities, which often form a coalition replacing human to work in dangerous environment, such as rescue, exploration, etc. In these operating conditions, the energy supply of robots usually cannot be guaranteed. If the energy resources of some robots are consumed too fast, the number of the future tasks of the coalition will be affected. This paper will develop a novel task allocation method based on Gini coefficient to make full use of limited energy resources of multi-robot system to maximize the number of tasks. At the same time, considering resources consumption,we incorporate the market-based allocation mechanism into our Gini coefficient-based method and propose a hybrid method,which can flexibly optimize the task completion number and the resource consumption according to the application contexts.Experiments show that the multi-robot system with limited energy resources can accomplish more tasks by the proposed Gini coefficient-based method, and the hybrid method can be dynamically adaptive to changes of the work environment and realize the dual optimization goals.

Controllable wave propagation in a weakly nonlinear monoatomic lattice chain with nonlocal interaction and active control

The one-dimensional monoatomic lattice chain connected by nonlinear springs is investigated, and the asymptotic solution is obtained through the Lindstedt-Poincar′e perturbation method. The dispersion relation is derived with the consideration of both the nonlocal and the active control effects. The numerical results show that the nonlocal effect can effectively enhance the frequency in the middle part of the dispersion curve.When the nonlocal effect is strong enough, zero and negative group velocities will be evoked at different points along the dispersion curve, which will provide different ways of transporting energy including the forward-propagation, localization, and backwardpropagation of wavepackets related to the phase velocity. Both the nonlinear effect and the active control can enhance the frequency, but neither of them is able to produce zero or negative group velocities. Specifically, the active control enhances the frequency of the dispersion curve including the point at which the reduced wave number equals zero, and therefore gives birth to a nonzero cutoff frequency and a band gap in the low frequency range. With a combinational adjustment of all these effects, the wave propagation behaviors can be comprehensively controlled, and energy transferring can be readily manipulated in various ways.

Two-Year Observation of Fossil Fuel Carbon Dioxide Spatial Distribution in Xi’an City

The need for atmospheric carbon dioxide(CO2)reduction in the context of global warming is widely acknowledged by the global scientific community.Fossil fuel CO2(CO2ff)emissions occur mainly in cities,and can be monitored directly with radiocarbon(14 C).In this research,annual plants[Setaria viridis(L.)Beauv.]were collected from 26 sites in 2013 and2014 in the central urban district of Xi’an City.The△14C content of the samples were analyzed using a 3 MV Accelerator Mass Spectrometer,and CO2ff concentrations were calculated based on mass balance equations.The results showed that the CO2ff mixing ratio ranged from 15.9 to 25.0 ppm(part per million,equivalent toμmol mol-1),with an average of 20.5 ppm in 2013.The range of measured values became larger in 2014,from 13.9 ppm to 33.1 ppm,with an average of 23.5 ppm.The differences among the average CO2ff concentrations between the central area and outer urban areas were not statistically significant.Although the year-to-year variation of the CO2ff concentration was significant(P<0.01),there was a distinctly low CO2 ff value observed in the northeast corner of the city.CO2 ff emiissions from vehicle exhaust and residential sources appeared to be more significant than two thermal power plants,according to our observed CO2 ff spatial distribution.The variation of pollution source transport recorded in our observations was likely controlled by southwesterly winds.These results could assist in the optimal placement of regional CO2 monitoring stations,and benefit the local government in the implementation of efficient carbon emission reduction measures.

中国人类世科学研究新进展

国际地层委员会人类世工作组决议人类世应由全球界线层型剖面和点位(“金钉子”)定义为一个正式的地质年代单位。20世纪中叶以来人类活动突变式增强,改变了原有的地球演化速率和方向,对地球环境造成极为显著的影响,并在地质记录中留下清晰的具有全球同步特性的物理、化学和生物印记,为识别这一年代地层单位的底界提供了最佳选择。当前,全球共有12个人类世“金钉子”候选剖面和点位参评。与此同时,中国学者在人类活动代用指标体系构建、人类世候选“金钉子”研究与国际对比方面取得了突出进展,发现人工放射性核素、微塑料、δ^(13)C、δ^(15)N和硅藻等均可作为人类活动理想的标志物,且远离城市和人类活动影响的中国四海龙湾玛珥湖沉积物剖面对全球信号敏感,^(239,240)Pu浓度于1953年快速增加,多环芳烃、^(129)I、烟炱^(14)C、碳球粒、DNA、δ^(13)C和重金属等指标在1953年前后均存在系统性变化,因此提出1953年作为人类世底界。中国四海龙湾湖沉积物剖面与日本别府海湾沉积物剖面被人类世工作组提议作为人类世“金钉子”辅助剖面。未来人类世科学研究的最终目标应是在阐明人类活动对地球系统影响的基础上,深化人地系统耦合与适应的可持续发展理论和技术创新。

Mechanism of accelerated dissolution of mineral crystals by cavitation erosion

Cavitation,a phenomenon produced by a moving fluid,is ubiquitous in the water environment of the Earth's surface and its related mechanical action in the process of cavitation leads to the widespread erosion of rock in nature.Although the mechanical action of flowing water body that accelerates the rock mass loss and fragmentation of rock(abrasion,erosion,and etching)and other phenomena have been much studied,its acceleration of mineral crystal dissolution is rarely reported.The physical mechanism of effect is not yet clear.The cavitation bubble produced in the cavitation process is at the micron level,and its related mechanical action leading to the accumulation of rock mineral dissolution is manifested in time and space in the process of the chemical element's migration between water and rock minerals.Cavitation erosion may be one of the important driving forces for the migration of geochemical elements within the lithosphere and hydrosphere.In this paper,based on the crystal dissolution stepwave dynamic theory and the theoretical derivation and calculation of Gibbs free energy change of the mineral crystals plastic deformation which caused by the mechanical action of cavitation erosion,we give the possible mechanism of accelerating the transient dissolution of mineral crystals by cavitation erosion—the cavitation bubbles on the surface of the near crystal release the high speed micro-jet and shock wave perpendicular to the surface during the collapsing,in which the water hammer pressure produced by micro-jet at the solid–liquid interface causes instantaneous plastic deformation on the crystal surface under the condition that it is larger than the yield stress of the crystal.Under the influence of the thermal effect of the plastic deformation process and the change of Gibbs free energy(the dislocation elastic strain energy of plastic deformation on the crystal surface may be included),the local instantaneous dissolution rate of the mineral surface is accelerated.The continuous cavitation erosion eventually causes fracture and breaking of the mineral crystal,meanwhile,the Gibbs–Thomson effect may enhance the dissolution of mineral crystals more prominently.At the same time,the correctness of the mechanism is verified qualitatively by the acoustic cavitation experiment with the same erosion mechanism.

Preface to Special Topic on Atmospheric Greenhouse Gas Measurement and Application in China

China initiated a national carbon trading market in December 2017.Commitments and actions to reduce greenhouse gas(GHG)emissions require consistent,reliable and timely information on GHG emissions.GHG monitoring and modeling studies provide GHG emission estimates to evaluate and guide progress towards emission reductions.GHG monitoring has mainly focused on global-scale background networks over the last few decades,while recent efforts have been made on regional and urban scales,such as projects in the Beijing-Tianjin-Hebei city cluster,in Paris,Washington-Baltimore.

超材料中的弹性波及其调控

超材料是一类具有微结构的人工复合材料.通过巧妙的微结构设计,力学超材料可实现很多难以在自然界中发现的力学性能,包括低频禁带、准直聚能、单向传输、声波隐身和拓扑态等.这些反常力学性能使力学超材料得以突破传统材料的力学性能极限,为低频振动与波动的控制带来了颠覆性的技术革命.

Evidence for Asian summer monsoon precipitation instability of the Younger Dryas phase

The loess and desert transitional zone of China responses sensitively to the Asian monsoon fluctuations. A high resolution loess-dust and aeolian sand-paleosols section records the climatic history of the Younger Dryas. Based upon AMS 14C dating of pollen concentrates and proxy climate indices including magnetic susceptibility, organic carbon content and grain size, it is demonstrated that the Asian monsoon climate manifests not only cooling as in other regions of the Northern Hemisphere, but also unusual oscillations in precipitation which were probably associated with atmospheric interactions between both the Northern and Southern Hemispheres and atmospheric pressure anomalies of topic Pacific Ocean （ENSO）.