Repeated annual drought has minor long‐term influence on δ13C and alkane composition of plant and soil in model grassland and heathland ecosystems

As a result of global climate change the incidence of drought conditions in Europe is predicted to increase in the future, which also influences plant resistance. Lipids are important plant constituents that protect plants against drought stress and contribute to the intermediate stable carbon (C) pool in soil. However, the extent to which drought influences lipid cycling in the plant–soil system is unknown and, therefore, it remains questionable how the ecosystem recovers after drought. We focused on plant and soil samples from two different plant communities (temperate grassland and heathland) that had been exposed to 5 years of 4.5–6.0 weeks repeated annual drought. They were sampled one year after the last drought to check the recovery of the plant–soil system. Samples were analyzed for their bulk C, stable C and nitrogen (N) isotope (δ¹³C, δ¹⁵N) and lipid composition. Contrary to our expectation, no strong influence of five years of repeated annual drought was observed for above‐ground biomass, roots and soils in the model ecosystems with respect to elemental (C and N concentrations, C : N ratio) bulk isotope (δ¹³C, δ¹⁵N) composition and the total extractable lipid concentration. Thus, plants did not sustain a significant change in their C and lipid concentration as well as their composition after five years of repeated annual drought. This might be related to the comparatively short drought period related to the overall growth season and provides evidence for recovery of the C and lipid dynamics in temperate grassland and heathland model ecosystems exposed to annual drought.     

气动肌肉肘关节MPI迟滞模型与补偿控制

针对气动肌肉驱动的四连杆肘关节输入气压与输出角度间的迟滞进行分析。建立肘关节迟滞的PrandtlIshlinskii(PI)模型,采用Levenberg-Marquardt方法辨识模型参数;选择改进Play算子合适的包络函数,设计一种可描述非对称迟滞现象的改进PI(Modified PI,MPI)模型,相较于传统PI模型(Classical PI,CPI),MPI模型对非对称迟滞曲线拟合度更高。基于MPI模型,设计前馈积分逆补偿器,并与PID组成积分逆补偿控制器(MPI-I-I-PID);完成了MPI-I-I-PID、PID与基于CPI模型的积分逆补偿PID控制器(CPI-I-I-PID)的位置控制仿真。仿真结果表明,MPI-I-I-PID可以减小跟踪误差,提高跟踪精度。在不同负载下进行了控制实验,实验结果表明,随着负载增加,补偿效果减弱,为此在补偿器中加入分段PID,MPI-I-I-pPID可减小抖动幅度,降低肘关节跟踪误差,提高位置控制精度和稳定性,验证了迟滞补偿器的有效性。     

低温胁迫对决明属牧草苗期活性氧化谢及其自适性响应的研究

试验研究低温胁迫对决明属牧草“CPI86134”品系苗期活性氧代谢及其自适性响应结果表明,随低温胁迫强度的提高和低温胁迫时间的延长,植株体内活性氧净产生速率、过氧化氢和丙二醛含量、叶片电解质渗透率均增加;植株体内活性氧清除酶超氧化物歧化酶、过氧化物酶、抗坏血酸过氧化物酶活性在0~48h胁迫时间内以较快速率提高,48h后其提高速率趋缓。活性氧清除酶活性的提高是“CPI86134”品系对低温胁迫伤害的一种自适性反应,活性氧、过氧化氢大量积累最终导致“CPI86134”植株体膜脂过氧化和膜系统的损伤。     

Variability in pattern and hydrogen isotope composition (δ2H) of long-chain n-alkanes of surface soils and its relations to climate and vegetation characteristics: A meta-analysis

The average chain length (ACL), carbon preference index (CPI), and hydrogen isotope composition (δ²H) of long-chain n-alkanes in sediments have been used to retrieve information about the paleoclimate. Despite their importance as in-between media from leaves to sediments, n-alkanes of surface soils have not been systematically analyzed at large scale. Such an investigation of the spatial variation of n-alkane properties in soil and their dependence on climatic and botanic (e.g., vegetation type) factors could provide a rationale for a better estimation of the past environment. We synthesized the patterns and δ²H of long-chain n-alkanes in soil (δ²H^n-alkanes) with regard to vegetation types (cropland, grassland, shrubland, and woodland) and environmental factors using data from peer-reviewed papers. Our results showed that the ACL and CPI of soil C₂₇–C₃₃ n-alkanes were not suitable indicators for differentiating vegetation types at large scale; instead, ACL significantly correlated with water conditions such as mean annual precipitation (MAP) and Palmer drought severity index (PDSI), and CPI significantly correlated with temperature without significant influence of vegetation type. The variation (i.e., standard deviation) of fractionation between the δ²H values in annual precipitation and in soil n-alkanes (ε_rain-soil) was smaller than that reported in leaves; therefore, soils were better suited to quantifying the general growing conditions of plants at a certain site. The fractionation ε_rain-soil correlated with climatic conditions as described by the PDSI and relative humidity (RH). This correlation agreed with the change in leaf water enrichment with changing RH taken from the literature and was independent of the vegetation type at large scale. This meta-analysis may provide useful information for the variations of the patterns and δ²H_n-alkanes values in surface soils.     

基于切比雪夫最佳逼近意义下的CPI指数变化通道的原理与方法

中国2000-2015年的186组CPI指数所体现的变化规律，可以用通道原理来描述.通道类似于交通图中的道路，依据切比雪夫最佳逼近原理，以CPI函数为中心线，以极小化最大正负误差为边界线，包含了所有的CPI数据，是一条具有最大安全范围意义的数据通道.假设端点数据是建立在零误差基础上的最大权重数据，未来短期内CPI指数的变化不存在突变，或存在突变但其误差不大于通道内的最大正负误差，则通道的延伸可以预测未来CPI指数的变化，以及变化的波动范围.介绍了CPI通道的基本原理与方法、适用范围、判别法则、具体算法等.通过多个数据处理实例，说明了直线通道具有简单易懂、直观性强、计算方便、适用范围广、符合性较好等特点，验证了未来短期CPI指数变化基本是可知与可控的.     

X波段30W固态功率放大模块的设计

从国际范围来看,“固定篮子”指数理论仍然是编制CPI的主体框架,但透过我国CPI的编制方法可以得出其不但存在理论假设上的缺陷,且在抽样设计、权数确定以及计算公式方面均存在弊端。对此,尝试给出改进思路,以提高CPI的精度与信度。     

知识格在知识创新过程中的研究与应用

基于马尔可夫链模型,对我国物价波动走势进行的实证分析表明：虽然消费者价格指数增长率大于6％时的概率很小,但是它一旦进入这个状态,就会有一个较长的持续期,在短期内很难降下来,而当消费者价格指数增长率小于-2%时,它的持续期较短。增长率大于零小于2%这一状态是消费者价格指数一个相对比较稳定的状态。对于商品零售价格而言,增长率大于-2%小于0这一状态是商品零售价格指数一个相对比较稳定的状态,同时在这状态它还有较长的持续期。     

The Empirical Analysis of the Impact of Grain Price on CPI in Hubei Province

The paper analyzes the change trend of Hubei province grain price and its influence on CPI, based on data from1990-2014. The analysis results show that the grain price goes through a change of early rising and later reducing during1990-2014, and smoothly fluctuated in recent years with a downward trend; grain price and CPI fluctuations have a consistent trend, but the grain price volatility is ahead of CPI fluctuation; grain price has positive influences on the CPI; there is a longterm equilibrium relationship between them, namely,grain price is a significant cause of CPI fluctuation. Therefore, we should take various measures to stabilize grain price in order to stabilize the CPI.     

当前中国通货膨胀的成因及对策

20世纪08年金融危机后,全球经济历经两年多的时间缓慢复苏、回暖.中国在这次复苏中保持了较高的经济增长速度,伴随而来的是新一轮长时期的通货膨胀.通胀产生的原因有货币超量投放、高额的外汇占款、全球流动性泛滥,劳动力结构变化等诸多方面.缓解通胀,使物价回落的措施是控制货币的供给量；针对外汇占款的过度增长,政府应适度刺激进口...     

基于VAR模型的我国农产品生产价格指数与CPI关系的实证分析

CPI上扬与农产品价格上涨有着密不可分的关系,政府和相关部门也在利用农产品价格上涨的契机推动粮食、生猪等农产品产业结构调整,以确保农民增收.结合经济学原理和相关学者的研究对农产品价格和CPI的关系问题进行了经验分析,并选定时间序列数据,构建合适的VAR模型对农产品生产价格和CPI的关系进行实证分析,运用格兰杰因果检验来完善检验的结果,对农产品价格和CPI的关系进行定性和定量的分析,并提出相应的对策建议.