Ultrahigh and controllable drain current peak-to-valley ratio innegative resistance field-effect transistors with a strained InGaAschannel

Negative resistance field-effect transistor (NERFET) devices using either strained InGaAs or unstrained GaAs channel layers have been fabricated. The strained InGaAs channel NERFET's show strong negative differential resistance and large drain current peak-to-valley ratio. The peak-to-valley ratio of the InGaAs channel NERFET is more than 3000 at room temperature and larger than one million (10⁶) at 77 K. The peak-to-valley ratio is controllable by adjusting the collector voltage     

不锈钢网架(壳)技术及其应用

本文总结了多年来不锈钢网架的研究成果 ,并介绍了部分不锈钢网架的工程应用     

学习新版建筑工程施工质量验收规范的体会

结合新版建筑工程施工质量验收规范的学习和施工实践 ,介绍了新版标准与旧标准的差异和特点 ,并就如何贯彻实施新标准、准确掌握检验批等问题作了分析 ,提出了执行中的相关注意事项。     

用科学发展观推进水利“十个转变”

树立和落实科学发展观，除不断深化对科学发展观的科学性、必然性和战略性、指导性的认识，不断增强坚持和落实科学发展观的自觉性和坚定性外，更重要的是要将科学发展观付诸实践，见诸行动，贯穿到促进经济社会发展和推动改革开放的各项工作中去，在实践中将科学发展观转化为强大的物质力量。水利行业贯彻和落实科学发展观，关键在于认清形势，立足实际，把握重点，明确方向，在扎实推进“十个转变”上下功夫。     

^125I,^131I诱发小鼠精子畸形发生率比较

本文选用 ICR 雄性小鼠,经腹腔分别注射不同剂量的~(125)I 及~(131)I,观察并比较它们对小鼠精子畸形发生率的影响及染毒后睾丸中放射性活度的变化。实验结果表明:(1)~(125)I 染毒后4—5周,0、185、370和555 kBq 各组精子畸形发生率分别为9.00‰、9.57‰、11.6‰及13.9‰;~(131)I 染毒后4—5周,上述各组精子畸形发生率分别为8.50‰、12.5‰、14.7‰和15.5‰;在相同注入量下,~(125)I 与~(131)I 诱发小鼠精子畸形发生率的差异各组均不显著(X~2检验,p>0.05)。(2)~(125)I、~(131)I 染毒后2h 至7天内,两者在睾丸中的放射性活度及变化规律相似,即在染毒后2h 达最高值,每克睾丸中~(125)I 和~(131)I 的放射性活度分别占初始注入量(370 kBq)的0.72％和0.50％,然后迅速下降,至一周时,仅分别占初始注入量的0.035％和0.011％。     

浅析硫磺回收装置中的自动控制设计

大规模高含硫原油的炼制工艺必须配套设置脱硫和硫磺回收装置。笔者针对硫磺回收装置的特点,为确保装置的安全平稳运行,提出了该装置自动控制设计中需要严格监控的工艺参数及重点部位,叙述了仪表选型原则和精确测量与控制的原理和方法。     

Accurate higher-order analytical approximate solutions to nonconservative nonlinear oscillators and application to van der Pol damped oscillators

In general, this paper deals with general nonlinear oscillations of a nonconservative and single degree-of-freedom system with odd nonlinearity and, in particular, it presents accurate higher-order analytical approximate solutions to van der Pol damped nonlinear oscillators having odd nonlinearity and the Rayleigh equation. By combining the linearization of the governing equation with harmonic balancing and the method of averaging, we establish accurate analytical approximate solutions for the general weakly damped nonlinear systems. Unlike the classical harmonic balance method, simple linear algebraic equations instead of nonlinear algebraic equations are obtained upon linearization prior to harmonic balancing. The combination of these two methods results in very accurate transient response of the periodic solution. In addition and for the first time, this paper also presents a method for deducing fourth-, fifth- and higher-order linearized governing equations from the lower-order equations without the requirement of formulating the problem from the first principle. Three examples including the van der Pol damped nonlinear oscillator are presented to illustrate the excellent agreement with approximate solution using the exact frequency.