Non-linear properties of nitride-based nanostructures for optically controlling the speed of light at 1.5 μm

Future bandwidth demand in optical communications requires all-optical devices based on optical non-linear behavior of materials. InN, with a room temperature direct bandgap well below 0.82 eV (1.5 μm) is very attractive for these applications. In this work, we characterize the non-linear optical response and recombination lifetime of the interband transition of InN layers grown on GaN template and Si(1 1 1) by molecular beam epitaxy. Non-linear characterization shows a decrease of the third-order susceptibility, χ⁽³⁾, and an increase of recombination lifetime when decreasing the energy difference between the excitation and the apparent optical band-gap energy of the analysed samples. Taking into account the non-linear characterization, an optically controlled reduction of the speed of light by a factor S=4.2 is obtained for bulk InN at 1.5 μm. The S factor of InN (5 nm)/In_0.7Ga_0.3N (8 nm) multiple quantum well heterostructures at the same operation wavelength is analysed, predicting an increase of this factor of three orders of magnitude. This result would open the possibility of using InN-based heterostructures for all-optical devices applications.     

振动挤出对HDPE管材耐慢速裂纹增长性能的影响

使用自制的电磁动态塑化挤出机挤出高密度聚乙烯(HDPE)管材。对稳态挤出和振动挤出的HDPE管材耐慢速裂纹增长性能进行了测试。采用DSC、WAXD分析研究了振动力场对HDPE管材耐慢速裂纹增长性能的影响。结果表明:振动挤出的HDPE管材结晶度提高,熔点升高,晶片变厚,晶粒尺寸变大,结晶完善,耐慢速裂纹增长性能提高。     

转动设备现场动平衡技术与应用

汽车车身是汽车整体结构中重要的组成部分，材料一般以钢板、碳纤维、铝、强化塑料等为主。针对于不同用途的汽车车身而言构成材料也具有一定的差异性，同时也带来了不同的属性。本文对汽车车身材料的现状进行了分析并对其发展趋势进行了展望，提出了相关观点，供以参考。     

Role of microstructure and testing conditions in sulphide stress cracking of X52 and X60 API steels

The resistance of X52 and X60 API steels to sulphide stress cracking (SSC) was tested by tensile tests at a constant load and also by slow strain rate tensile (SSRT) tests. Both steels were tested after hot-rolling, when they had a microstructure which consisted predominantly of ferrite and pearlite. They were then tested after laboratory quenching and tempering, when their microstructure was predominantly of tempered bainite or martensite. The results showed that the resistance of the steel to SSC depended strongly on the microstructure when it was tested under a constant load. In this case, the quenching and tempering considerably increased the resistance of the steel to SSC. The results of SSRT tests were similar regardless of the heat treatment used. Non-metallic inclusions seemed to play an important role as crack initiation sites during the SSRT tests; this may be due to the hydrogen–deformation interaction. The resistance to SSC varied as a function of the specimen's orientation during the SSRT tests. This may be related to the geometric characteristics of the non-metallic inclusions.     

森林土壤有机碳库组分定量化研究

用一级动力学方程研究了贵州省黎平县森林土壤活性、缓效性和惰效性有机碳库的变化及分解速率,模拟结果表明:各土壤剖面的土壤活性碳库一般占总有机碳的0.5%~7.6%,平均驻留时间(M ean Residue Tim e,MRT)为41~64天;缓效性碳库占总有机碳的45%~71%,平均驻留时间为3~30年;采用酸水解法测定惰效性碳库的库容,一般占总有机碳的20%~50%。活性碳库的变化规律为混交林>阔叶林>针叶林,缓效性碳库中混交林最大,其它两种林分规律不明显;不同林龄的杉木(8年,16年,40年),非活性碳库(缓效性碳库和惰效性碳库之和)的含量变化规律为40年>16年>8年,说明40年生的杉木下土壤固碳能力比8年和16年的强;16年的又比8年的强。     

电路中不连续振动的物理基础

在本文中,通过对电路中的微小寄生参数能否忽略的规律研究,阐明脉冲和数字电路中不连续振动的物理基础,并导出一条能简化非线性振动系统微分方程的定理,借此可分析各种不连续振动的电路。     

切换线性系统稳定性研究进展

切换线性系统的稳定性分析和稳定化设计是近年来研究的热点.为此,对近期关于这一问题研究所得到的主要成果进行综述.首先给出任意切换以及带约束切换两种情况下系统稳定性分析的主要结论;然后给出切换线性系统稳定化中的主要方法;最后简要概述目前切换系统的实用稳定性和有限时间稳定性问题,并就这一领域今后的发展方向进行了展望.     

Strain hardening modulus as a measure of environmental stress crack resistance of high density polyethylene

In this paper it is shown that the resistance to slow crack propagation in polyethylene can be predicted from a simple tensile measurement performed at 80 °C. It is shown that for different types of polyethylene homopolymers and copolymers the slope of a tensile curve above its natural draw ratio (i.e. strain hardening) correlates well with the measured stress crack resistance. The data presented in this paper confirm that the slow crack resistance in polyethylene is determined by the failure of the fibrils within the craze, which is shown to be determined by the strain hardening of a tensile curve. A material with a strong strain hardening will reduce the strain rate and consequently the time to failure will be strongly increased. Considering the fact that the slow crack resistance of polyethylene is usually assessed by tedious and time consuming testing methods performed on the notched samples in contact with specific fluids, the findings reported in this publication offer a possibility to assess the information on slow crack propagation in much simpler and faster way.     

高扬程抽水泵站水锤防护措施

高扬程抽水泵站事故停泵时易发生水锤及速率升高问题，现阶段最有效的办法是采用液控缓闭蝶阀，在高扬程抽水站管网设计阶段，应对工程及该阀的特性有充分的了解，避免在工程调试阶段或运行阶段出现不应有的问题，保证供水管网及水泵的安全运行。     

缓/控释肥对小麦增产与提高氮肥利用率的效果研究

以不施氮肥、尿素基施和尿素基追比5:5等3个处理做对照,对3种包膜缓/控释肥处理冬小麦产量、产量相关因子、不同时期植株含氮量及肥料利用率进行了分析比较。结果表明,缓/控肥处理的以上几个指标均接近于尿素基追比5:5处理。与尿素基施相比,包膜缓/控释肥增产10.03%～11.17%,有效穗数和穗粒数增加,返青-拔节期植株含氮量明显提高,氮肥利用率提高了6.18%～11.57%。3种缓/控释肥相比较,产量、产量因子、植株含氮量及肥料利用率没有显著性差异。