压电层合板的结构特性及优化分析

基于三维弹性和压电理论 ,用幂级数展开方法得到了压电层合板静态特性的三维解 ;给出了压电层与基体之间剪应力、位移、电势的三维分布图 ;讨论了工程中常用的 2类压电材料在感知和作动情况下沿压电材料厚度方向电势的分布情况 ,分析了电势可看作线性分布的条件 ;讨论了压电层及粘结层厚度变化对层合板变形的影响 ,并作了优化分析 .     

Climate change and hydrologic process response in the Tarim River Basin over the past 50 years

Climate change and hydrologic process response in the Tarim River Basin over the past 50 years are the focus of more and more researchers＇ attention. In this paper, both temperature and precipitation time series were found to present a monotonic increasing trend using nonparametric tests. Noticeably, a significant step change in both temperature and precipitation time series occurred in 1986. By contrasting the trends of natural water process in headstream and mainstream, we found that it was anthropogenic activities not climate change that caused the river dried up and vegetation degenerated in the lower reaches of Tarim River. The results of gray correlation analysis show that the runoff of higher latitude distributing river is more closely associated with winter snow stocking, while that of lower latitude is more closely related to summer temperature. Runoff in the headstream is more sensitive to precipitation, while that in the mainstream is more sensitive to evaporation. The strong evaporation caused by increasing temperature weakened runoff to some extent in spite of the fact that precipitation increased over the past 50 years.     

农业技术商品化问题思考

农业技术商品化问题思考@范秀荣@曹建武@王雅鹏...     

陕西省中长期食物结构发展研究

根据城乡居民的膳食营养标准，采用运筹学、弹性理论等方法，系统地分析了陕西４０年来食物结构发展的规律和特点，提出了未来食物发展的趋势和解决供需矛盾的对策措施。     

Response of the accumulation of proline in the bodies of<Emphasis Type="Italic">Populus euphratica</Emphasis> to the change of groundwater level at the lower reaches of Tarim River

The content of proline in the plant bodies is closely related to the converse-succession-resistant capability of plants. Under the drought stress, the proline accumulates rapidly in the plant bodies for maintaining a certain mois-ture content and an expanding-pressure momentum in cells through the osmoregulation, thus the drought-resis- tant capability and the converse-succession-resistant ca-pability of plants are increased[1,2]. Many researches on the relationship between the proline and the…     

农业科技供需双重不足分析——以粮食安全为例

我国农业发展的科技支撑力度不够,存在农业科技供给和需求双重不足的矛盾。导致这种现象的表层原因是科技供需双方缺乏有效的沟通机制,深层原因在于农业科研、农业推广体系以及对农民相关支持体系中的制度缺失。在粮食安全问题上面这种矛盾尤为突出,只有围绕这些问题进行制度创新,才能为我国发展现代农业提供有力的科技保障。     

Daily variation of carbon flux in soils of Populus euphratica forests in the middle and lower reaches of the Tarim River

In order to lucubrate the daily variation of respiration in soils of Populus euphratica forests and analyze its relationship with environmental factors in the middle and lower reaches of the Tarim River, the LI-8100 instrument of soil CO2 flux system was used to measure the parameters of soil carbon flux and air temperature 10 cm above ground surface along the profiles of Usyman, Archy River, Yengisu and Karday, and the relationships between the soil carbon flux and the soil moisture content were analyzed. The nonlinear regression analysis was carried out with the software SPSS13.0. We observed that: (1) soil respiration began to be restrained when the air temperature was up to 30℃10 cm above the ground surface; (2) the rates of soil respiration under the forests of Populus euphratica were significantly different at various moisture contents, the soil carbon flux was high along the Usyman profile, which has a high soil moisture content, and it was low along the profiles of Archy River, Yengisu and Karday, which has a low soil moisture content; (3) the exponential model can be used to explain the relationship between soil respiration and air temperature 10 cm above the ground surface. The average Q10 values along the profiles of Usyman, Archy River, Yengisu and Karday are 0. 61, 0.16, 0. 22 and 0. 35 respectively, much lower than the average of the world; (4) there is a positive correlation between the soil carbon flux and the soil moisture content.     

文旅融合背景下石窟寺景区的游客情感分析——以洛阳龙门石窟为例

石窟寺是我国宝贵的历史文化遗产,文旅融合是保护与利用石窟寺的重要路径,探讨石窟寺景区的游客情感有助于推进"文化遗产活起来",以增强石窟寺的文化影响力.以洛阳龙门石窟景区为例,通过网络文本采集器获取了携程网、美团网、去哪儿网和驴妈妈网关于龙门石窟景区游客的在线评论6 208条,利用ROST CM 6软件对网络文本进行分词...     

SCFST柱框架-支撑结构恢复力模型

通过对SCFST柱框架-支撑结构进行拟静力性能研究发现,支撑、梁、柱依次发生破坏,结构破坏机制合理,滞回曲线呈梭形,无捏拢现象,耗能能力良好,骨架曲线的下降过程较为平缓,延性较好,结构在整体上表现出较好的抗震性能,有限元数值模拟与试验结果符合程度较高,验证了有限元模型的正确性。主要研究支撑两边柱的轴压比、单肢柱不同组合截面形式和框架-支撑结构中支撑钢管的刚度等因素,基于大量的有限元数值模型对其进行分析,得到了SCFST柱框架-支撑抗侧力结构的恢复力模型。运用回归分析方法建立结构的三折线骨架模型,明确了SCFST柱框架-支撑结构的滞回和退化规律,建立了此体系框架-支撑结构简化的滞回模型,并与试验结果进行对比分析,二者骨架曲线基本一致,滞回环形状均呈近似的平行四边形,吻合度较高。