北疆复播地膜玉米的气候适应性初探     

唐凤兰  谢国辉  李辉  孔祥耀 《沙漠与绿洲气象(新疆气象)》2005,28(5):28-29

北疆乌兰乌苏的地膜玉米分期复播田间试验表明:随着复播日期的推迟,收获籽粒的百粒重和单穗籽粒干重呈下降趋势。7月5日前播种,90d以上的生长期,≥10℃活动积温2000℃·d,才能保证复播地膜玉米承单3号的正常成熟。  相似文献   

Scaling of strength reduction factors for degrading elasto‐plastic oscillators     

Arindam Chakraborti  Vinay K. Gupta 《地震工程与结构动力学》2005,34(2):189-206

The inelastic (design) spectra characterizing a seismic hazard are generally obtained by the scaling‐down of the elastic (design) spectra via a set of response modification factors. The component of these factors, which accounts for the ductility demand ratio, is known as the strength reduction factor (SRF), and the variation of this factor with initial period of the oscillator is called an SRF spectrum. This study considers scaling of the SRF spectrum in the case of an elasto‐plastic oscillator with strength and stiffness degradation characteristics. Two models are considered: one depending directly on the characterization of source and site parameters and the other depending on the normalized design spectrum characterization of the seismic hazard. The first model is the same as that proposed earlier by the second author, and is given in terms of earthquake magnitude, strong‐motion duration, predominant period, geological site conditions, ductility demand ratio, and ductility supply‐related parameter. The second model is a new model proposed here in terms of the normalized pseudo‐spectral acceleration values (to unit peak ground acceleration), ductility demand ratio and ductility supply‐related parameter. For each of these models, least‐square estimates of the coefficients are obtained through regression analyses of the data for 956 recorded accelerograms in western U.S.A. Parametric studies carried out with the help of these models confirm the dependence of SRFs on strong‐motion duration and earthquake magnitude besides predominant period and site conditions. It is also seen that degradation characteristics make a slight difference for high ductility demands and may lead to lower values of SRFs, unless the oscillators are very flexible. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Cyclic tests of post‐tensioned precast CFT segmental bridge columns with unbonded strands     

Chung‐Che Chou  Yu‐Chih Chen 《地震工程与结构动力学》2006,35(2):159-175

Two ungrouted post‐tensioned, precast concrete‐filled tube (CFT) segmental bridge columns were tested under lateral cyclic loading to evaluate the seismic performance of the column details. The specimens included a load stub, four equal‐height circular CFT segments, and a footing. Strands were placed through the column and post‐tensioned to provide a precompression of the column against the footing. One specimen also contained energy‐dissipating devices at the base to increase the hysteretic energy. The test results showed that (1) both specimens could develop the maximum flexural strength at the design drift and achieve 6% drift with small strength degradation and residual displacement, (2) the proposed energy‐dissipating device could increase energy dissipation in the hysteresis loops, and (3) the CFT segmental columns rotated not only about the base but also about the interface above the bottom segment. This study proposed and verified a method to estimate the experimental flexural displacement using two plastic hinges in the segmental column. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

同位素稀释质谱法测定塑料闪烁体中掺杂锂同位素含量   总被引：1，自引：0，他引：1  

刘雪梅龙开明  贾宝亭汤磊 《岩矿测试》2006,25(3):243-245

介绍了用同位素稀释质谱法（IDMS）测定塑料闪烁体中掺杂^6Li含量的方法。建立了样品的灰化、溶解程序，并对质谱条件进行了探索。实验表明，在300oC碳化2h，升温至500℃灰化5h后，用浓硝酸可以将样品完全溶解，在质谱测量时采用磷酸作为发射剂，可以得到大而稳定的离子流。在优化的实验条件下，塑料闪烁体中掺杂^6Li定量分析测定结果的相对标准偏差小于0．4％（n=11）。  相似文献   

优化偏最小二乘光度法同时测定铑铱钯的研究   总被引：6，自引：0，他引：6  

王洪艳  吴敬 《岩矿测试》1998,17(3):161-166

采用局部加权、随机矩阵法等步骤,使建立的校准模型能充分反映未知样品的数字结构特征,达到优化的目的,从而改善偏最小二乘法在处理实际未知样品数据时的解析能力,以提高计算结果的精度。用该优化偏最小二乘法对模拟地质样品中痕量贵金属Ｒｈ、Ｉｒ、Ｐｄ进行多组分光度测定,其分析结果的相对误差均小于１０％;分别测定９．５μｇ／Ｌ、３５．０μｇ／Ｌ、６６．０μｇ／Ｌ含量的Ｒｈ、Ｉｒ和Ｐｄ７次,其标准偏差Ｒｈ为０．２;Ｉｒ为１．１;Ｐｄ为２．０。  相似文献   

强夯加插板加固软基的试验研究   总被引：1，自引：1，他引：0  

郭红梅  马培贤 《世界地质》1998,17(3):86-90

采用强夯法加固地基上部吹,回填土,打设塑料排水板排水固结地基下部软土的联合施工工艺,对我国北方某地的软土地基处理进行了试验研究,通过分析试验小区的监测资料得知,该地基处理方法在技术上可靠,工艺上合理。  相似文献   

镁质粘土在碱性耐火材料工业应用的初步探索   总被引：1，自引：0，他引：1  

章人骏 《地球学报》1998,19(1):77-83

本研究项目的主要步骤是把镁质粘土和橄榄岩或焦油镁砂砖废料在箱式电炉里进行烧结试验（温度１２００～１２５０℃）。同时测定了原料、烧结样品和５种产品的物理性质和矿物组分。结果表明,产品里的矿物多是富镁的高熔点矿物,包括继承性的或新生的镁橄榄石和方镁石,少量钙镁橄榄石、镁黄长石以及痕量硅酸二钙。２号产品含较多的斜顽辉石,由滑石或海泡石转化而成,它的熔点较低。试验表明,妥善选择原料和配方是走向成功的第一步,而瘠性和塑性材料相配合,则是传统经验的重现。在这种场合,镁质粘土作为结合粘土,起了很大作用。利用氧气煤气火焰快速测定熔点也是有意义的尝试。  相似文献   

阻尼耗能在结构弹塑性地震反应中的作用   总被引：3，自引：2，他引：3  

蒋立志  林荫琦 《地震工程与工程振动》1996,16(3):30-38

本文用计算分析的方法研究了结构在弹塑悸地震反应过程中的阻尼耗能与塑性耗能的数量关系问题。  相似文献   

旱作带田-膜两用的水热效应及增产效益研究     

仇化民  王宁珍  马妮娜 《气象学报》1996,54(4):508-512

西北黄土高原，光照丰富，雨热同期。实施旱作带田一膜两用技术，可增温２—５℃，节水３０—４０ｍｍ以上，调水７０％左右。热量利用率高达０．９８７，降水利用效率１５．１５ｋｇ／（ｍｍ·ｈｍ２），气候生产力利用指数０．４９。增产效益明显，变作物一年一作为一年两作，总产可达８２５０—９０００ｋｇ／ｈｍ２，比单作增产４５％以上。  相似文献   

CO₂气肥固体发生剂在温棚室蔬菜栽培中的应用   总被引：2，自引：0，他引：2       下载免费PDF全文

赵国强  朱自玺  邓天宏  方文松  赵月萍  孙晖  宁松林 《气象》1997,23(10):53-57

温棚室内Ｃ炒足是影响温棚蔬菜生产的重要因素之一。温棚人工增施ＣＯ２的方法很多，但都有一定的局限性，作者根据现在温棚室的实际情况研制出一种新型高效的ＣＯ２发生剂－－固体气肥发生剂，对比试验表明，该发生剂能使蔬菜增产２５％以上，投入产比在１：６以上，并且具有无公害的特点。  相似文献