Seasonal and Interannual Variations of Carbon Exchange over a Rice–Wheat Rotation System on the North China Plain

Rice-wheat （R-W） rotation systems are ubiquitous in South and East Asia, and play an important role in modulating the carbon cycle and climate. Long-term, continuous flux measurements help in better understanding the seasonal and interannual variation of the carbon budget over R-W rotation systems. In this study, measurements of CO2 fluxes and meteorological variables over an R-W rotation system on the North China Plain from 2007 to 2010 were analyzed. To analyze the abiotic factors regulating Net Ecosystem Exchange （NEE）, NEE was partitioned into gross primary production （GPP） and ecosystem respiration. Nighttime NEE or ecosystem respiration was controlled primarily by soil temperature, while daytime NEE was mainly determined by photosythetically active radiation （PAR）. The responses of nighttime NEE to soil temperature and daytime NEE to light were closely associated with crop development and photosynthetic activity, respectively. Moreover, the interannual variation in GPP and NEE mainly depended on precipitation and PAR. Overall, NEE was negative on the annual scale and the rotation system behaved as a carbon sink of 982 g C m 2 per year over the three years. The winter wheat field took up more CO2 than the rice paddy during the longer growing season, while the daily NEE for wheat and rice were -2.35 and -3.96 g C m-2, respectively. After the grain harvest was subtracted from the NEE, the winter wheat field became a moderately strong carbon sink of 251-334 g C m-2 per season, whereas the rice paddy switched to a weak carbon sink of 107-132 per season.

Profile Measurement of Ion Temperature and Toroidal Rotation Velocity with Charge Exchange Recombination Spectroscopy Diagnostics in the HL-2A Tokamak

This paper deals with the profile measurement of impurity ion temperature and toroidal rotation velocity that can be achieved by using the charge exchange recombination spectrum （CXRS） diagnostics tool built on the HL-2A toknmak. By using CXRS, an accurate impurity ion temperature and toroidal plasma rotation velocity profile can be achieved under the condition of neutrM beam injection （NBI） heating. Considering the edge effect of the line of CVI 529.06 nm （n= 8-7）, which contains three lines （active exciting spectral line （ACX）, passivity exciting spectral line （PCX） and electron exciting spectral line （ICE））, and using three Gaussian fitted curves, we obtain the following experimental results： the core ion temperature of HL-2A device is nearly thousands of eV, and the plasma rotation velocity reaches about 104 m· s^-1. At the end of paper, some explanations are presented for the relationship between the curves and the inner physical mechanism.

A Brief Study on pH, Exchangeable Ca²⁺and Mg²⁺in Farmlands under Tobacco-Rice Rotation in Xuancheng City of South Anhui

pH, exchangeable Ca2+ and Mg2+ of soil can influence the yield and quality of flue-cured tobacco. Xuancheng city is the dominant tobacco-planting region in Anhui province since 2008. A general soil survey was conducted in Xuancheng city to understand the current situations of pH, exchangeable Ca2+ and Mg2+ of farmlands under tobacco-rice rotation and to decide whether continuous applying dolomite powders to abate soil acidification. In total 124 topsoil samples (0-20 cm) were collected from the typical farmlands and soil pH, exchangeable Ca2+ and Mg2+ were measured. The results showed that soil pH and Ca2+ and Mg2+ in Xuancheng city were generally in the suitable grades, pH ranged from 4.56 to 8.42 with an average of 5.87, exchangeable Ca2+ ranged from 1.01 cmol(1/2Ca2+) kg-1 to 100.55 cmol(1/2Ca2+) kg-1 with an average of 11.07 cmol(1/2Ca2+) kg-1, and exchangeable Mg2+ ranged from 0.14 cmol(1/2Mg2+) kg-1 to 2.86 cmol(1/2Mg2+) kg-1 with an average of 0.81 cmol(1/2Mg2+) kg-1, all spanned from the low grades to the high grades. To the whole Xuancheng city, 37.10%, 62.10% and 72.58% of the surveyed farmlands were in the low grades of pH, exchangeable Ca2+ and Mg2+, respectively, while 52.42%, 25.00% and 20.97% of the farmlands were in the suitable grades, respectively. pH had an extremely significantly positive Napierian logarithm correlation with exchangeable Ca2+ and an extremely significantly positive power correlation with exchangeable Mg2+. In total about 338.2 kg·hm-2 of Ca2+ and 202.4 kg·hm-2 of Mg2+ are annually input into the farmlands, while about 110.4 kg·hm-2 of Ca2+ and 7.4 kg·hm-2 of Mg2+ are annually moved out from the farmlands, exchangeable Ca2+ and Mg2+ were annually increased by 225.2 kg·hm-2 and 187.6 kg·hm-2 in the farmlands, respectively. It is necessary to monitor the farmlands dynamically in order to decide whether continuous applying dolomite powders which should be dependent upon the specific conditions of individual farmlands.

An EPR Study on Intramolecular Spin Exchange and Rotational Mobility of Nitroxides Linked by a Long-chain

The effects of pressure and solvent on the intramolecular spin exchange of biradicals having two nitroxide fragments linked by a long flexible chain were studied by means of highpressure EPR technique.It was found that the intramolecular exchange interaction between nitroxides of biradical took place through the direct contact between them.By analyzing the observed EPR spectra,we have estimated the ratio(in/out)value of the average lifetime of the radical fragments inside a cage(in)to that outside the cage(out).The in/out values decreased with decreasing temperature and increasing pressure.The results suggest that the nearly cyclic conformation in a cage is favorable in solution.Further,the rotational correlation time of individual nitroxide was estimated from the anisotropic EPR signal,and the information on the segmental motion of the nitroxide group in biradical was obtained.

The rotational anisotropies in the ferromagnetism/antiferromagnetism 1/ antiferromagnetism 2 exchange bias structures

The rotational anisotropies in the exchange bias structures of ferromagnetism/antiferromagnetism 1/antiferro- magnetism 2 are studied in this paper. Based on the model, in which the antiferromagnetism is treated with an Ising mean field theory and the rotational anisotropy is assumed to be related to the field created by the moment induced on the antiferromagnetic layer next to the ferromagnetic layer, we can explain why in experiments for ferromag- netism （FM）/antiferromagntism 1 （AFM1）/antiferromagnetism 2 （AFM2） systems the thickness-dependent rotational anisotropy value is non-monotonic, i.e. it reaches a minimum for this system at a specific thickness of the first anti- ferromagnetic layer and exhibits oscillatory behaviour. In addition, we find that the temperature-dependent rotational anisotropy value is in good agreement with the experimental result.

The Hysteretic Behavior of Angular Dependence of Exchange Bias in NiFe/granular-FeMn-MgO Bilayers

We investigate the hysteretic behavior of the angular dependence of exchange bias for a series of polycrystalline NiFe/(FeMn)_(1-x)(MgO)_(x) bilayers with varying x.For x=0.025,the antiferromagnetic layer is of the largest degree of the fcc(111)preferred texture.At the same x,both the exchange field and blocking temperature acquire maximal values.In particular,the hysteretic behavior of the angular dependence between clockwise and counter-clockwise rotations shows minimal angular shift.These results can be explained in terms of the thermal activation model.

What They Learned Won't Go Away:The Impacts ofan International Exchange Program on Chinese Teacher Candidates' Understanding of and Practice in Science Education

Purpose:The Canadian university where this study took place has established an international exchange program in teacher education with a large Chinese university.This study was designed to examine how the international exchange program influenced Chinese science teacher candidates'understanding of science education and how such learning impacted their teaching in China.Design/Approach/Methods:The study adopted a qualitative research design with interview and reflective journal as the main approaches for data collection.Findings:Participants greatly appreciated the opportunity of exchange.They reported an improved understanding of Canadian school education and its science curriculum and pedagogy,which changed many aspects of their original values about the relationship between the teacher and students,classroom environment,and so on.Although they faced many constraints to implement what they learned from the exchange in Chinese science classrooms,what they learned had never been forgotten.Participants tried to apply them here and there at the level they could control.Originality/Value:There are many reported studies in the literature about Chinese international students on Western campuses.However,research on Chinese students who participate in international exchange programs is very rare.The findings of this study can inform policymakers and education practitioners about student international exchange programs and benefit future exchange participants.

DETERMINATION OF THE SPIN COUPLING CONSTANTS IN THE ^(87)Rb^(129)Xe VAN der WAALS MOLECULE

The measurement of the ratio of the repolarization signal to the optical pumping signal of the Rb atoms has been used to determine the ratio c of the spin rotation coupling constant to the spin exchange coupling constant of the ^(87)Rb^(129)Xe Van der Waals molecule.The value c=3.4±0.1 is inferred from these studies.The author has also given the magnitudes of the spin rotation and spin exchange interactions.

Effects of Coordinate Rotation on Turbulent Flux Measurements during Wintertime Haze Pollution in Beijing, China

Eddy-covariance observations from the Beijing 325-m meteorological tower are used to evaluate the effects of coordinate rotation on the turbulent exchange of momentum and scalars during wintertime haze pollution(January-February 2013). Two techniques are used in the present evaluation; namely, the natural wind coordinate(NWC) and the planar fit coordinate(PFC), with the latter being applied by means of two methods for linear regression(i.e., overall and sector-wise). The different techniques show a general agreement in both turbulent fluxes and transport efficiencies, especially evident at the lower, 140-m level above the ground(compared to the higher, 280-m level), perhaps implying that the selection of a technique for coordinate rotation(NWC or PFC) is less of a concern for a sufficiently low level, despite the complexities of urban terrain. Additionally, sector-wise regression is a recommended approach for practical application of the PFC in a complex urban environment subjected to particulate pollution, because this method is found to produce a better correlation between the mean vertical velocity at the 140- and 280-m heights.

政策感知、职业认同与教师交流轮岗政策遵从

教师对交流轮岗政策的遵从意愿直接影响政策实施成效。为探析政策感知、职业认同是否及如何影响教师交流轮岗政策遵从意愿,本研究采用有序Probit模型对比分析1487份教师调查问卷数据。研究发现:教师整体上对交流轮岗政策遵从意愿处于中等偏上水平,政策感知、职业认同对政策遵从呈多通道的差异化影响。具体表现为:在政策感知方面,政策了解和认可程度高的教师更倾向于遵从交流轮岗政策;职业认同方面,工作回报、角色价值和工作成就感对政策遵从有正相关性,而工作保障和工作氛围则对政策遵从有负相关性。深入分析后认为:良好的工作保障和氛围可能强化了教师对稳定性的期望,减少了对人事变革的接受度,进而对交流轮岗政策遵从意愿产生负向影响。

教师交流轮岗制度:逻辑转向与实践路径——基于专业资本的视角

教师交流轮岗制度是优化师资配置、缩小城乡教育差距、促进义务教育优质均衡发展的重要举措。现行教师交流轮岗制度遵循资源配置的逻辑理路,面临“补偿”取向下目标与手段存在一定的倒置、人力资源工具化认识下教师个体理性的隐匿等困境。当前义务教育进入新发展阶段,教师交流轮岗制度的价值诉求应从“岗位流动”过渡到“提供优质教育”共享。交流轮岗实质是教师专业资本的跨域流动与增值,专业资本理论可以为解读教师交流轮岗制度提供新的思路。基于专业资本视角,将轮岗教师专业发展作为交流轮岗制度与义务教育优质均衡的中间变量,从价值旨归、教师定位、均衡模式、驱动机制等应然层面探析教师交流轮岗制度的逻辑转向。在此基础上,从人力资本扩散、社会资本积聚、决策资本生成等方面提出相应的实践路径,进一步提升教师交流轮岗制度的实施效果。

Investigation of pressure wave behaviors in the rotational speed effects on a pressure-exchange wave rotor

A wave rotor is suitable for compact and efficient pressure-exchange between gas flows.This work measured the circumferential pressure distribution of the rotor/stator interfaces and utilized a CFD method to simulate the unsteady pressure waves.The experimental and CFD results showed some slopes in the circumferential pressure distributions,and the slopes indicated the traces of specific unsteady pressure waves.Such traces varied regularly if the rotational speed varied within a range from-11%to+11%off the baseline value,but they were seriously disturbed if the rotational speed varied by-45%from the baseline value.It verified that a pressure wave in a wave rotor tended to keep its pressure ratio and propagation velocity unchanged if the rotational speed varied by a small extent,and that the pressure wave could not keep its propagation patterns if the rotational speed varied by a large extent.Because of the pressure wave behaviors,the wave rotor demonstrated specific regulations of the rotational speed effects on its operational states.

Understanding the Outcomes of the China-England Mathematics Teacher Exchange:Observations ofa Shanghai Teacher

Highlights This study examines the China-England Mathematics Teacher Exchange program to identify and evaluate the differences in Chinese approach to mathematics education.There are numerous differences in terms of national mathematics curricula,organization of mathematics teaching,and evaluation objectives and methods due to different educational and learningcultures.China has made great achievements in mathematics education and student academic performance but has much to learn from England.

Eddy Current Test for Detection of Foreign Material using Rotating Probe

There are several elements that affect on the integrity of steam generator tubes. One of the elements is loose parts located on outside of the tubes. It causes erosion which is possible to lead fatal defect like crack on the outside surface of the tubes. In this study, artificial loose parts on Inconel 690 tube are demonstrated and eddy current testing data of the region is acquired using rotating probe. Ferromagnetic and nonmagnetic foreign materials were used to demonstrate artificial loose parts. Eddy current channel of 100 KHz frequency shows definite signals of those foreign materials but stainless steel was not clearly detected. This result can be explained based on the electrical conductivity of the materials and it can be confirmed with lissajous window and C-scan. In addition, no indication was detected when the distance of the gap between the foreign materials and the tube is increased to more than 3 mm under this test condition. Based on these experimental inspections, we were able to find suitable methods for analyzing the signals obtained under various conditions that could occur when conducting steam generator eddy current test in NPP.

中国城乡教师交流轮岗政策的历史变迁、演进逻辑与未来走向

乡村教师作为教育教学活动的主体,直接影响着乡村教育教学质量,更关系到乡村振兴的人才根基。中国城乡教师交流轮岗政策大致经历了初步探索、规范建制、制度深化三个阶段。在此过程中,城乡教师交流轮岗政策的动力机制、价值取向、过程保障和话语体系有着自身的演进逻辑。该政策的未来走向将以“省域统筹、县管校聘、弱势补偿”为动力机制、以确立城乡师资优质均衡发展为价值取向、以健全城乡交流轮岗教师在地化发展为过程保障、以契合多元主体的利益诉求为政策话语,从而构成未来城乡教师交流轮岗政策的新框架。

政策网络视角下县域教师交流政策的执行困境与破解路径——基于辽宁省T县的案例研究

教师交流是促进义务教育均衡发展的关键举措。本研究立足于辽宁省T县义务教育教师交流政策执行调研实况,利用政策网络理论分析框架,分析教师交流政策主体间的互动关系对政策执行成效的影响机制。研究发现,县域教师交流政策网络主体主要包括政策社群网络、府际网络、校际网络和议题网络,各网络主体之间的互动关系对县域教师交流政策执行成效具有显著影响作用。县域教师交流政策执行面临着政策社群网络内部的部门协同不畅、政策社群网络与府际网络间的利益取向冲突、校际网络内部的资源流动不畅、议题网络的参与程度不高等四大困境。基于此,破解县域教师交流政策执行中所面临的困境应畅通政策社群网络内部的跨部门合作通道,稳固跨部门合作关系;按照纵向职责同构原则,明确政策社群网络和府际网络的职责分工;调整校际网络内部的互动模式,疏通县乡学校交流渠道;畅通议题网络参与渠道,激发议题网络规模效应;调整校际网络内部的互动模式,疏通县乡学校交流渠道;畅通议题网络参与渠道,激发议题网络的规模效应。

义务教育交流轮岗教师专业发展的理念、逻辑及路径

义务教育交流轮岗教师专业发展具有情境差异性、专业适应性和道德期望性的独特性,蕴含着深化、提升教师专业素养的基本理念,包括明晰交流轮岗教师的“新手—专家”型复合性角色、立足于交流轮岗对于专业发展的研修属性、践行交流轮岗专业服务均衡教育资源的伦理价值。交流轮岗促进教师专业发展的逻辑在于通过教育时空、对象的转变而对教师专业自主、知识、智慧形成挑战,诸如教师专业自主的构建与深化、专业知识的转化与再生、专业智慧的激活与创生。为此,需要通过教学实践落实均衡义务教育资源的专业伦理、构建教师交流轮岗的自我激励机制、提供支撑专业发展的教研活动平台。

气相旋转换热器壳程强化传热数值模拟

目前,针对大批量谷物干燥的换热器种类较少及现有换热器换热量小、换热效率和能源利用率低等问题,在前人研究的基础上改进了气相旋转换热器结构,并改变螺旋叶片螺距来强化壳程传热。采用计算流体力学软件FLUENT数值模拟方法,对气相旋转换热器壳程进行传热特性分析,得到气相旋转换热器壳程流场在两种螺距的螺旋叶片结构下的压力云图、温度云图和流体速度矢量图,并对比不同流量条件下以两种螺旋叶片螺距为变量的壳程压降、壳程出口温度。研究结果表明:在壳程进口流速为4m/s、进口温度为100℃工况下,对比螺旋叶片螺距为277.5mm及壳程螺距为412mm的螺旋叶片,壳程压降增加30.1%,努尔赛数提高为40.7%。

轮岗教师乡土情感的缺失表征、根源及文化形塑

基于文化唯物主义理论视域,轮岗教师的乡土情感具有深刻意蕴,具体体现于:轮岗教师是认同乡村生活方式的“局内人”、是推动乡村学校发展的“同行者”、是担负乡村社会责任的“新乡贤”。目前,在轮岗交流实践中,存在着部分轮岗教师对乡村学校发展持“事不关己”态度、对乡村生活方式难以或不愿认同、乡村社会责任担当意识薄弱等问题。其原因在于:轮岗教师的教学岗位变动较频繁,乡村公共文化生活吸引力不足,轮岗教师对自身的角色认知不到位。对此,需要通过以下举措形塑轮岗教师的乡土情感:健全乡村学校组织文化,增强轮岗教师的“主人翁”意识;重构乡村公共文化生活,提升轮岗教师的乡土认同感;明确乡村社会文化身份,引导轮岗教师的责任行为。

我国“县管校聘”教师流动政策的回顾与省思

我国“县管校聘”政策实施已十余年,历经“教师流动”与“县管校用”要素孵化、“县管校聘”政策落地发展两大阶段。基于多源流理论,本研究对“县管校聘”缘何从教师交流轮岗政策演变而成进行政策过程分析。研究发现:教师流动意愿与归属感“双低”、乡村教育新闻舆论聚焦点以及教师管理体制阻力难破为问题源流;各方建言献策、地方“县管校用”改革有成效为政策源流;学生家长诉求与教师配置问题矛盾突出、“努力办好人民满意的教育”“促进教育公平”执政理念为政治源流。三源流在耦合时机与动力“催化”下打开“县管校聘”政策之窗。据此建议增强问题意识、配套流动量化标准、补充评价考核机制、完善各项保障机制、考虑不同县(区)实施“县管校聘”的地方特殊性,同时加强乡村教育基础设施建设,以期“县管校聘”在各地实施更为合理、深入、有效。