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易地扶贫搬迁对贫困户生计资本和生计策略的影响——基于8省16县的3期微观数据分析

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中国人口·资源与环境 2020年第10期30卷 143-153页

作者：王君涵李文冷淦潇仇焕广清华大学经济管理学院北京100084 中国人民大学农业与农村发展学院北京100872

坚决打赢脱贫攻坚战是党中央、国务院的一项重要战略部署,2020年是我国精准扶贫战略的验收之年。易地扶贫搬迁是精准扶贫战略的重要组成部分,该文基于可持续生计框架与空间贫困观两种理论,阐述了易地扶贫搬迁打破贫困陷阱的机理。本文利... 详细信息

坚决打赢脱贫攻坚战是党中央、国务院的一项重要战略部署,2020年是我国精准扶贫战略的验收之年。易地扶贫搬迁是精准扶贫战略的重要组成部分,该文基于可持续生计框架与空间贫困观两种理论,阐述了易地扶贫搬迁打破贫困陷阱的机理。本文利用8省16县2176户易地扶贫搬迁农户3期跟踪调查数据,通过PSM-DID、Heckman两阶段方法实证检验了易地扶贫搬迁对农户生计资本和生计策略的长期和短期影响,并采用多期DID等方法进行了稳健性检验。研究结果表明:①易地扶贫搬迁切实改善了农户的生计资本和生计策略,打破了原本由于制约性资源存量过低而无法跳出的贫困陷阱,使农户进入一个新的可持续生计循环中,即搬迁时间越长,生计资本积累越多。②易地扶贫搬迁在短期对家畜养殖有负向影响,对外出务工有正向影响;长期对农林种植有负向影响,对非农自营有正向影响。③对于搬迁后的农户而言,不同生计策略依赖于不同的生计资本。农林种植依赖于自然资本、物质资本、人力资本和金融资本,家畜养殖依赖于物质资本和社会资本,外出务工依赖于物质资本和人力资本,非农自营依赖于人力资本和金融资本。根据研究结果,提出以下政策建议:一是短期应及时稳定保证房屋基建、水电气网、交通道路设施等物质资本的供给,并根据当地产业特色提供技能培训、工作获取等帮扶措施,切实保障搬迁人口的策略转变。二是长期应持续地通过教育、医疗卫生等措施增强其文化素养和健康水平,同时提供便利的金融服务与税收优惠政策,支撑搬迁人口非农策略的可持续发展,实现长期稳定的脱贫。

关键词：易地扶贫搬迁生计资本生计策略贫困陷阱 PSM-DID

Research on cubic polynomial acceleration and deceleration control model for high speed NC machining

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第3期9卷 358-365页

作者： Hong-bin leng Yi-jie WU xiao-hong PAN Institute of Modern Manufacture Engineering Zhejiang University Hangzhou 310027 China

To satisfy the need of high speed NC (numerical control) machining, an acceleration and deceleration (acc/dec) control model is proposed, and the speed curve is also constructed by the cubic polynomial. The proposed control model provides continuity of acceleration, which avoids the intense vibration in high speed NC machining. Based on the discrete characteristic of the data sampling interpolation, the acc/dec control discrete mathematical model is also set up and the discrete expression of the theoretical deceleration length is obtained furthermore. Aiming at the question of hardly predetermining the deceleration point in acc/dec control before interpolation, the adaptive acc/dec control algorithm is deduced from the expressions of the theoretical deceleration length. The experimental result proves that the acc/dec control model has the characteristic of easy implementation, stable movement and low impact. The model has been applied in multi-axes high speed micro fabrication machining successfully.

关键词： High speed NC machining Acceleration and deceleration (acc/dec) control model Cubic speed curve Discrete mathematical model Adaptive acceleration and deceleration control algorithm

Integrated high-performance and accurate shaping technology of low-cost powder metallurgy titanium alloys: A comprehensive review

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International Journal of Minerals,Metallurgy and Materials 2024年第3期31卷 413-426页

作者： Xuemeng gan Shaofu Li Shunyuan xiao Yafeng Yang State Key Laboratory of Mesoscience and Engineering Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Science and Technology on Particle Materials Chinese Academy of SciencesBeijing 100190China

The practical engineering applications of powder metallurgy (PM) Ti alloys produced through cold compaction and pressure-less sintering are impeded by poor sintering densification, embrittlement caused by excessive O impurities, and severe sintering deforma-tion resulting from the use of heterogeneous powder mixtures. This review presents a summary of our previous work on addressing the above challenges. Initially, we proposed a novel strategy using reaction-induced liquid phases to enhance sintering densification. Near- complete density (relative density exceeding 99%) was achieved by applying the above strategy and newly developed sintering aids. By focusing on the O-induced embrittlement issue, we determined the onset dissolution temperature of oxide films in the Ti matrix. On the basis of this finding, we established a design criterion for effective O scavengers that require reaction with oxide films before their dissol-ution. Consequently, a ductile PM Ti alloy was successfully obtained by introducing 0.3wt% NdB6 as the O scavenger. Lastly, a powder- coating strategy was adopted to address the sintering deformation issue. The ultrafine size and shell-like distribution characteristics of coating particles ensured rapid dissolution and homogeneity in the Ti matrix, thereby facilitating linear shrinkage during sintering. As a result, geometrically complex Ti alloy parts with high dimensional accuracy were fabricated by using the coated powder. Our fundament-al findings and related technical achievements enabled the development of an integrated production technology for the high-performance and accurate shaping of low-cost PM Ti alloys. Additionally, the primary engineering applications and progress in the industrialization practice of our developed technology are introduced in this review.

关键词： powder metallurgy titanium sintering densification oxygen scavenging accurate shaping

Microstructure and dry sliding wear behavior of cast Al-Mg_2Si in-situ metal matrix composite modified by Nd

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Rare Metals 2013年第3期32卷 284-289页

作者： xiao-Feng Wu Guan-gan Zhang Fu-Fa Wu School of Materials Science and Engineering Liaoning University of Technology

The microstructure and dry sliding wear behav- ior of cast Al-18 wt% MgaSi in-situ metal matrix com- posite modified by Nd were investigated. Experimental results show that, after introducing a proper amount of Nd, both primary and eutectic Mg2Si in the Al-18 wt% Mg2Si composite are well modified. The morphology of primary Mg2Si is changed from irregular or dendritic to polyhedral shape, and its average particle size is signifi- cantly decreased. Moreover, the morphology of the eutectic MgzSi phase is altered from flake-like to very short fibrous or dot-like. The wear rates and friction coefficient of the composites with Nd are lower than those without Nd. Furthermore, the addition of 0.5 wt% Nd changes the wear mechanism of the composite from the combination of abrasive, adhesive, and delamination wear without Nd into a single mild abrasion wear with 0.5 wt% Nd.

关键词： Al/Mg2Si composites Nd modification Microstructure Dry sliding wear behavior

Novel radiation pattern reconfigurable antenna with six beam choices

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The Journal of China Universities of Posts and Telecommunications 2012年第2期19卷 123-128页

作者： CAI xiao-tao WANG An-guo MA Ning leng Wen School of Electronic Information Engineering Tianjin UniversityTrianjin 300072China

This article presents a novel radiation pattern reconfigurable antenna with six beam choices, which works in 5.2 GHz wireless local area network （WLAN） frequency band. The designed antenna has good impedance matching at the resonant frequency. The beam can be reconfigured to six different directions, and each main lobe of six azimuth patterns has a half power beam width （HPBW） of about 60°. The antenna can cover all directions in the azimuth plane （XY-plane） by controlling the states （ON or OFF） of six switches. Simulation and measurement have been carried out to validate the design and experimental results demonstrate that the proposed antenna has the capacity to provide the pattern reconfigurability.

关键词： antenna pattern reconfigurability parasitic patch WLAN

A CLASS OF TWO-STEP CONTINUITY RUNGE-KUTTA METHODS FOR SOLVING SINGULAR DELAY DIFFERENTIAL EQUATIONS AND ITS STABILITY ANALYSIS

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Journal of Computational Mathematics 2005年第6期23卷 647-656页

作者： Xin leng De-gui Liu xiao-qiu Song Li-rong Chen Beijing Institute of Computer Application and Simulation Technology 100854 China Beijing Institute of Applied Physics and Computational Mathematics 100088 China

In this paper, a class of two-step continuity Runge-Kutta（TSCRK） methods for solving singular delay differential equations（DDEs） is presented. Analysis of numerical stability of this methods is given. We consider the two distinct cases：（i）τ≥ h, （ii）τ 〈 h, where the delay τ and step size h of the two-step continuity Runge-Kutta methods are both constant. The absolute stability regions of some methods are plotted and numerical examples show the efficiency of the method.

关键词： Analysis of numerical stability Singular delay differential equations Two-step continuity Runge-Kutta methods

Detection for disease tipping points by landscape dynamic network biomarkers

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National Science Review 2019年第4期6卷 775-785页

作者： xiaoping Liu xiao Chang Siyang leng Hui Tang Kazuyuki Aihara Luonan Chen Key Laboratory of Systems Biology Center for Excellence in Molecular Cell Science Institute of Biochemistry and Cell Biology Shanghai Institutes for Biological Sciences Chinese Academy of Sciences School of Mathematics and Statistics Shandong University at Weihai Institute of Industrial Science the University of Tokyo Institute of Statistics and Applied Mathematics Anhui University of Finance & Economics School of Life Science and Technology Shanghai Tech University Center for Excellence in Animal Evolution and Genetics Research Center for Brain Science and Brain-Inspired Intelligence

A new model-free method has been developed and termed the landscape dynamic network biomarker(l-DNB) methodology. The method is based on bifurcation theory, which can identify tipping points prior to serious disease deterioration using only single-sample omics data. Here, we show that l-DNB provides early-warning signals of disease deterioration on a single-sample basis and also detects critical genes or network biomarkers(i.e. DNB members) that promote the transition from normal to disease states. As a case study, l-DNB was used to predict severe influenza symptoms prior to the actual symptomatic appearance in influenza virus infections. The l-DNB approach was then also applied to three tumor disease datasets from the TCGA and was used to detect critical stages prior to tumor deterioration using an individual DNB for each patient. The individual DNBs were further used as individual biomarkers in the analysis of physiological data, which led to the identification of two biomarker types that were surprisingly effective in predicting the prognosis of tumors. The biomarkers can be considered as common biomarkers for cancer, wherein one indicates a poor prognosis and the other indicates a good prognosis.

关键词： single-sample network dynamic network biomarkers tipping points of complex disease

Recent progress and future prospect of digital soil mapping： A review

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Journal of Integrative Agriculture 2017年第12期16卷 2871-2885页

作者： ZHANG gan-lin LIU Feng SONG xiao-dong State Key Laboratory of Soil and Sustainable Agriculture Institute of Soil Science Chinese Academy of Sciences Nanjing 210008 P.R China University of Chinese Academy of Sciences Beijing 100049 P.R. China

To deal with the global and regional issues including food security, climate change, land degradation, biodiversity loss, water resource management, and ecosystem health, detailed accurate spatial soil information is urgently needed. This drives the worldwide development of digital soil mapping. In recent years, significant progresses have been made in different aspects of digital soil mapping. The main purpose of this paper is to provide a review for the major progresses of digital soil mapping in the last decade. First, we briefly described the rise of digital soil mapping and outlined important milestones and their influence, and main paradigms in digital soil mapping. Then, we reviewed the progresses in legacy soil data, environmental covariates, soil sampling, predictive models and the applications of digital soil mapping products. Finally, we summarized the main trends and future prospect as revealed by studies up to now. We concluded that although the digital soil mapping is now moving towards mature to meet various demands of soil information, challenges including new theories, methodologies and applications of digital soil mapping, especially for highly heterogeneous and human-affected environments, still exist and need to be addressed in the future.

关键词： digital soil mapping soil-landscape model predictive models soil functions spatial variation

Blowing up of Solutions to the Cauchy Problem for the Generalized Zakharov System with Combined Power-Type Nonlinearities

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Acta Mathematica Sinica,English Series 2012年第9期28卷 1917-1936页

作者： Zai Hui gan Bo Ling GUO Chun xiao GUO College of Mathematics and Software Science Sichuan Normal University Institute of Applied Physics and Computational Mathematics Department of Mathematics China University of Mining and Technology Beijing

This paper deals with blowing up of solutions to the Cauchy problem for a class of general- ized Zakharov system with combined power-type nonlinearities in two and three space dimensions. On the one hand, for co = ＋oo we obtain two finite time blow-up results of solutions to the aforementioned 4 ≤ p 〈 N＋2/N-2 4 system. One is obtained under the condition a ≥ 0 and 1 ＋ 4/N or a 〈 0 and 1 〈 p 〈 1 ＋（N = 2,3）; the other is established under the condition N = 3, 1 〈 p 〈 N=2/N-2 and α（p - 3）〉 0. On the other hand, for co 〈＋∞ and α（p - 3）〉 0, we prove a blow-up result for solutions with negative energy to the Zakharov system under study.

关键词： Generalized Zakharov system blowing up combined power-type nonlinearities Lyapunov function in time