排序方式: 共有9条查询结果,搜索用时 15 毫秒
1
1.
将自适应技术应用于多用户正交频分复用系统,能够提高频谱利用率,降低系统发射功率,从而使系统的整体性能达到最优;针对多用户OFDM系统,将其信道分配和比特分配相结合,提出了更优的多用户OFDM自适应组合调制比特分配算法(MCABA)。根据信道特性的瞬时估计值,自适应地为各用户分配子信道和比特,在给定误码率的条件下使总的发送功率最小,仿真结果表明,该算法计算简单,优化效率高,可以达到接近理论上的最优水平。 相似文献
2.
3.
《Intermetallics》2000,8(7):721-728
The authors formerly found that introduction of nitrogen gas into milling atmosphere improved drastically production yield of γ-based TiAl powder by mechanical alloying of a powder mix of Ti and Al. In this report, the role of nitrogen gas on the improvement in production yield of γ-based TiAl powder was investigated by three series of milling experiments. As a result, the authors found that: (1) nitrogen gas affects the formation of TiAl powder after milling in argon for a certain period; (2) TiAl powder formed by mechanical alloying has the crystal structure of Al supersaturated α-Ti phase; (3) the content of nitrogen gas in the milling atmosphere has a great influence on the yield; (4) concerning the mechanism, it is presumed that a layer of Al supersaturated α-phase was formed during milling in argon, and transformed into a solid-solution with nitrogen during milling under the existence of nitrogen gas, and thereby became brittle and was broken into the fine powder. 相似文献
4.
大规模光伏电站的不断接入为电力系统的安全稳定运行带来了巨大挑战。为解决光伏电站出力不确定性所造成的功率波动问题,提高光伏电站在并网点处电压的稳定性,文章采用由蓄电池与超级电容组成的复合储能一体化控制方法,提高光伏并网点电压稳定水平。首先研究由光伏电源、复合储能构成的典型复合储能系统拓扑结构下储能双层优化控制策略;其次,在不同储能介质的荷电状态与充放电特性模型基础上,研究基于不同光伏并网点电压波动场景的多储能介质组合电压波动抑制优化控制模型及其求解算法;最后,以并网光伏电站数据为基础,建立光伏复合储能电压波动优化控制仿真模型。仿真结果及其分析表明,文章所提出的基于复合储能的并网点电压波动抑制模型能够有效提升并网点电压稳定性能。 相似文献
5.
跨流域调水是解决北方天然缺水的必然选择,却往往由于水价机制不合理,长期亏损,无法稳定地发挥供水效益。因此,跨流域调水工程应该推行更科学、合理的两部制水价。本文分析了适用于跨流域调水不同环节的两部制水价,并提出了可行的计算方法,以期水价管理部门提供水价制定和调整的方法支持。 相似文献
6.
7.
8.
传统基于肌电(Electromyography,EMG)的运动识别方法多是利用训练后的固定参数模型,分类已预先定义的有限个目标动作,但对肌肉疲劳导致的肌电变化,以及未定义的外部动作等干扰因素无能为力.针对这一问题,提出一种自更新混合分类模型(Self-update hybrid classification model,SUHC),该模型融合了用于排除外部动作干扰的一类支持向量机(Support vector machine,SVM),以及用于分类目标动作数据的多类线性判别分析(Linear discriminant analysis,LDA),并引入自更新机制以对抗肌电时变性干扰.通过手部动作识别实验验证提出方法的效果,在肌电大幅变化干扰下,SUHC的目标动作识别精度达到89%,对比传统的支持向量机、多层感知器(Multiple layer perceptron,MLP)和核线性判别分析(Kernel LDA,KLDA),提高了约18%,并且SUHC具备排除外部动作干扰能力,排除精度高达93%. 相似文献
9.
《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2004,217(1):97-103
We have investigated the distribution and amount of nitrogen implanted in tin oxide films using SIMS and XPS depth profiling. The amount of nitrogen was found to increase with increasing ion dose and energy. In the nitrogen depth profile a peak was observed indicating the position of the maximum nitrogen concentration and the result was verified using theoretical calculations. The relative distribution of nitrogen compared to tin was found to decrease continuously with increasing depth of the film. 相似文献
1