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寒旱区内陆河流域碳通量年际变化控制机制

地球科学 2024年第5期49卷 1907-1919页

作者：王同红王旭峰张松林谭俊磊张阳任志国白雪洁西北师范大学地理与环境科学学院甘肃兰州730000 中国科学院西北生态环境资源研究院黑河遥感试验研究站甘肃兰州730000

为了解寒旱区内陆河流域碳通量的年际变化及其控制机制,使用涡度相关技术和气象观测系统同步对黑河流域典型生态系统(草地、农田、湿地、荒漠、森林)的碳通量和气象环境要素进行了长期定位观测.分析观测数据显示:黑河流域内农田(玉米)... 详细信息

为了解寒旱区内陆河流域碳通量的年际变化及其控制机制,使用涡度相关技术和气象观测系统同步对黑河流域典型生态系统(草地、农田、湿地、荒漠、森林)的碳通量和气象环境要素进行了长期定位观测.分析观测数据显示:黑河流域内农田(玉米)生长季净生态系统生产力(NEP)与总初级生产力(GPP)最大(729.81 g C/m^(2)/a与1184.60 g C/m^(2)/a),戈壁荒漠最小(94.18 g C/m^(2)/a与134.97 g C/m^(2)/a);湿地生长季生态系统呼吸(Reco)最大(460.22 g C/m^(2)/a),戈壁荒漠最小(41.18 g C/m^(2)/a).黑河上游高寒生态系统温度对NEP、GPP和Reco年际变化的解释度明显高于黑河中下游干旱生态系统,而上游高寒生态系统土壤水分对NEP、GPP和Reco年际变化的解释度低于中下游干旱生态系统.在上游的高寒生态系统中,各站点间温度与NEP、GPP和Reco为正相关,而在中下游则为负相关.浅层土壤水分在黑河流域内高寒区和干旱区均与生态系统的NEP、GPP和Reco为正相关,上游高寒区浅层土壤水分与NEP、GPP和Reco的相关性要高于深层土壤水分,而中下游干旱区则是深层土壤水分与NEP、GPP和Reco的相关性更高.

关键词：碳黑河流域总初级生产力净生态系统生产力生态系统环境地质

Web C: toward a portable framework for deploying legacy code in web browsers

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Science China(Information Sciences) 2015年第7期58卷 113-127页

作者： YIN Jie TAN Gang bai XiaoLong HU ShiMin Department of Computer Science and Technology Tsinghua University Department of Computer Science and Engineering Lehigh University

For security, most web applications are developed in some type-safe language, such as Java Script or Java. However, there is a huge amount of legacy codes developed in unsafe languages, which provide rich functionality and are more efficient than their type-safe counterparts. To allow browsers to incorporate type-safe components in a secure way, previous approaches use the software-based fault isolation(SFI) to isolate untrusted legacy code. The SFI approach performs machine-code transformation for security, but the downside is the loss of architecture independence. We propose Web C, a system that allows legacy code transmitted over the web via the Low Level Virtual Machine(LLVM) bitcode format. The untrusted bitcode is transformed by Web C into code in the Web C security language, which enforces both memory isolation and control-flow integrity. Compared with previous approaches, Web C is more portable, provides stronger security, and allows more flexible memory management. Experimental results show that the average runtime overhead of Web C is modest.

关键词： Web C software fault isolation symbol link shadow memory area portable

Inertial gravity wave parameters for the lower stratosphere from radiosonde data over China

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Science China Earth Sciences 2017年第2期60卷 328-340页

作者： bai ZhiXuan BIAN JianChun CHEN HongBin CHEN Lei Key Laboratory of Middle Atmosphere and Global Environment Observation Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China College of Earth Sciences University of Chinese Academy of SciencesBeijing 100049China Northwest Institute of Nuclear Technology Urumqi 841700China

Characterization of gravity wave （GW） parameters for the stratosphere is critical for global atmospheric circulation models. These parameters are mainly determined from measurements. Here, we investigate variation in inertial GW activity with season and latitude in the lower stratosphere （18-25 km） over China, using radiosonde data with a high vertical resolution over a 2-year period. Eight radiosonde stations were selected across China, with a latitudinal range of 22°-49°N. Analyses show that the GW energy in the lower stratosphere over China has obvious seasonal variation and a meridional distribution, similar to other regions of the globe. The GW energy is highest in winter, and lowest in summer; it decreases with increasing latitude. Velocity perturbations with longitude and latitude are almost the same, indicating that GW energy is horizontally isotropic. Typically, 85% of the vertical wavelength distribution is concentrated between elevations of 1 and 3 km, with a mean value of 2 kin; it is almost constant with latitude. Over 80% of all the horizontal wavelengths occur in the range 100-800 km, with a mean value of 450 km; they show a weak decrease with increasing latitude, yielding a difference of about 40 km over the 22°-49°N range. The ratio of horizontal wavelength over vertical wavelength is about 200：1, which implies that inertial GWs in the lower stratosphere propagate along nearly horizontal planes. Ratios of their intrinsic frequency to the Coriolis parameter decrease with increasing latitude; most values are between 1 and 2, with a mean value of 1.5. Study of the propagation directions of GW energy shows that upward fractions account for over 60% at all stations. In contrast, the horizontal propagation direction is significantly anisotropic, and is mainly along prevailing wind directions; this anisotropy weakens with increasing latitude.

关键词： Inertial gravity wave Lower stratosphere Energy density Intrinsic frequency Propagation direction SeasonalVariation Latitudinal variation Velocity perturbations

Synthesis and characterization of magnetic polymer microspheres with a core-shell structure

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China Particuology 2007年第1期5卷 180-185页

作者： Ming Lu Shu bai Kun Yang Yan Sun Department of Biochemical Engineering School of Chemical Engineering and Technology Tianjin University Tianjin 300072 China

Non-porous magnetic polymer microspheres with a core-shell structure were prepared by a novel micro-suspension polymerization technique. A stable iron oxide ferrofluid was used to supply the magnetic core, and the polymeric shell was made of glycidyl methacrylate （GMA monomer） and ethylene dimethacrylate （cross-linker）. In the preparation, polyvinyl alcohol was used as the stabilizer, and a lauryl alcohol mixture as the dispersant. The influence of various conditions such as aqueous phase volume, GMA and initiator amounts, reaction time and stirring speed on the character of the microspheres was investigated. The magnetic microspheres were then characterized briefly. The results indicate that the microspheres with active epoxy groups had a narrow size distribution range from 1 to 10 μm with a volume-weighted mean diameter of 4.5 μm. The saturation magnetization reached 19.9 emu/g with little coercivity and remanence.

关键词： Ferrofluid Micro-suspension polymerization Magnetic microspheres Particle size Magnetization

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借入队流程增强少先队员组织光荣感

教学与管理 2024年第26期 20-23页

作者：白梓琪赵荣辉吴静静内蒙古师范大学教育学院

组织光荣感是增强少先队组织凝聚力的重要前提。增强少先队员组织光荣感是少先队教育的最基本内容,也是进行少先队教育的最本质要求,更是当前少先队改革的重要命题。队前教育、入队仪式、队内活动和后期反馈构成完整的入队流程,以队前... 详细信息

组织光荣感是增强少先队组织凝聚力的重要前提。增强少先队员组织光荣感是少先队教育的最基本内容,也是进行少先队教育的最本质要求,更是当前少先队改革的重要命题。队前教育、入队仪式、队内活动和后期反馈构成完整的入队流程,以队前教育激活组织光荣感,借入队仪式增强组织认同感、队内活动增强组织归属感、反馈小组增强组织责任感,在整体上增强少先队员的组织光荣感,为培养有理想、有道德、有文化、有纪律的社会主义接班人贡献力量。

关键词：入队流程组织光荣感少先队少先队员

Dynamic Modeling and Experiment of a New Type of Parallel Servo Press Considering Gravity Counterbalance

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Chinese Journal of Mechanical Engineering 2013年第6期26卷 1222-1233页

作者： HE Jun GAO Feng bai Yongjun WU Shengfu State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong University China First Heavy Industries

The large capacity servo press is traditionally realized by means of redundant actuation, however there exist the over-constraint problem and interference among actuators, which increases the control difficulty and the product cost. A new type of press mechanism with parallel topology is presented to develop the mechanical servo press with high stamping capacity. The dynamic model considering gravity counterbalance is proposed based on the virtual work principle, and then the effect of counterbalance cylinder on the dynamic performance of the servo press is studied. It is found that the motor torque required to operate the press is a lot less than the others when the ratio of the counterbalance force to the gravity of ram is in the vicinity of 1.0. The stamping force of the real press prototype can reach up to 25 MN on the position of 13 mm away from the bottom dead center. The typical deep-drawing process with 1 200 mm stroke at 8 strokes per minute is proposed by means of five order polynomial. On this process condition, the driving torques are calculated based on the above dynamic model and the torque measuring test is also carried out on the prototype. It is shown that the curve trend of calculation torque is consistent to the measured result and that the average error is less than 15%. The parallel mechanism is introduced into the development of large capacity servo press to avoid the over-constraint and interference of traditional redundant actuation, and its dynamic characteristics with gravity counterbalance are presented.

关键词： mechanical press parallel mechanism dynamic modeling virtual work principle

脓毒症患儿肠道菌群结构与炎症反应相关性的前瞻性队列研究

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中国当代儿科杂志 2024年第6期26卷 567-574页

作者：吕昭怡王六菊徐梅先白新凤曹利静河北省儿童医院重症医学一科河北石家庄050031

目的探讨脓毒症患儿肠道菌群结构特征及其与炎症反应的相关性。方法采用前瞻性队列研究方法,纳入2021年12月—2023年1月收治的脓毒症患儿为研究对象(设为脓毒症组),选择同期住院的感染非脓毒症患儿为对照(设为非脓毒症组)。比较两组... 详细信息

目的探讨脓毒症患儿肠道菌群结构特征及其与炎症反应的相关性。方法采用前瞻性队列研究方法,纳入2021年12月—2023年1月收治的脓毒症患儿为研究对象(设为脓毒症组),选择同期住院的感染非脓毒症患儿为对照(设为非脓毒症组)。比较两组患儿肠道菌群分布特征、外周白细胞(white blood cell,WBC)计数、C-反应蛋白(C-reactive protein,CRP)、细胞因子水平的差异,并将大便菌群相对丰度与WBC计数、CRP、细胞因子水平进行相关性分析。结果属水平上,脓毒症组阿克曼氏菌属、瘤胃球菌属及另枝杆菌属相对丰度低于非脓毒症组,肠球菌属、链球菌属、葡萄球菌属相对丰度高于非脓毒症组(P<0.05)。门水平上,脓毒症患儿小儿危重症评分≤70分组以变形菌门为优势菌门(37.46%),71~80分组和81~90分组优势菌门为厚壁菌门(分别为72.20%、43.88%)。属水平上,18例标本中5例标本单一菌群相对丰度超过50%。脓毒症组WBC计数、CRP、白介素(interleukin,IL)-6、IL-10、肿瘤坏死因子-α水平高于非脓毒症组(P<0.05)。Spearman秩相关性分析显示:在属水平上,脓毒症组瘤胃球属、另枝杆菌属、副萨特氏菌属相对丰度与WBC计数、CRP、IL-6水平均呈负相关(P<0.05);肠球菌属相对丰度与CRP水平呈正相关(P<0.01);链球菌属、葡萄球菌属等相对丰度与CRP、IL-6水平均呈正相关(P<0.05);链球菌属相对丰度与WBC计数呈正相关(P<0.05)。结论脓毒症患儿肠道菌群呈紊乱状态,且随病情程度不同具有特征性;脓毒症患儿肠道菌群结构改变与机体炎症反应具有相关性。

关键词：脓毒症肠道菌群炎症反应相关性儿童

Semiempirical equations of state of H_(2)O/CO_(2) binary mixtures in graphite nanoslits

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Science China(Physics,Mechanics & Astronomy) 2023年第8期66卷 83-92页

作者： Haoxuan Li Bin Zhao Chengzhen Sun Bofeng bai State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

The existence of confining walls limits the prediction accuracy of nanoconfined fluids using macroscopic equations of state(EOSs);moreover,appropriate EOSs for multicomponent mixture fluids in nanoconfined spaces are ***,we derive the EOS of multicomponent mixture fluids confined in nanospaces at high temperatures and pressures,mainly considering the nanoconfinement effect and the competitive adsorption effect between different ***,the EOSs are validated through comparison with the molecular dynamics-simulated Pv T data of CO_(2)/H_(2)O mixtures in graphite *** consider the above effects,we derive two EOSs via two modeling methods:EOS I is obtained through modification of the actual component occupation volume in the Peng-Robinson equation of state(PR EOS)by fitting the binary component interaction coefficient and the number of adsorbed molecules according to a selectivity coefficient,while EOS II is obtained by considering the decreased pressure of the fluids in PR EOS by adding an attractive term between components and *** the simulation results as a benchmark,the two EOSs exhibited good prediction accuracies under low CO_(2) concentrations,and generally,EOS II was more accurate than EOS *** study fills the gap in the EOSs of nanoconfined mixture fluids,and the obtained equations can help to further describe the thermodynamic properties of confined mixture fluids.

关键词： confined fluid mixtures equation of state nanoconfined spaces molecular dynamics simulation

Multiscale simulation of nanometric cutting of single crystal copper——effect of different cutting speeds

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Acta Metallurgica Sinica(English Letters) 2009年第6期22卷 440-446页

作者： Hongmin PEN Qingshun bai Yingchun LIANG Mingjun CHEN School of Mechatronics Engineering Harbin Institute of Technology Harbin 150001 China

A multiscale simulation has been performed to determine the effect of the cutting speed on the deformation mechanism and cutting forces in nanometric cutting of single crystal copper. The multiscale simulation model, which links the finite element method and the molecular dynamics method, captures the atomistic mechanisms during nanometric cutting from the free surface without the computational cost of full atomistic simulations. Simulation results show the material deformation mechanism of single crystal copper greatly changes when the cutting speed exceeds the material static propagation speed of plastic wave. At such a high cutting speed, the average magnitudes of tangential and normal forces increase rapidly. In addition, the variation of strain energy of work material atoms in different cutting speeds is investigated.

关键词： Multiscale simulation Nanometric cutting Single crystal copper Propagation speed of plastic wave