甲基睾丸酮在罗非鱼体内的消解规律

研究了在现实养殖环境中,采用含甲基睾丸酮200 mg/kg的饲料持续投喂罗非鱼成鱼3 d,随后将其转移到养殖池塘中体内甲基睾丸酮的消解规律。应用高效液相色谱法检测不同时间肌肉和鱼皮中甲基睾丸酮的残留量,结果发现肌肉和鱼皮中甲基睾丸酮残留量趋势为指数递减,组织中甲基睾丸酮残留量在停药后1164 h,即49 d时才无检出。     

A feature selection method combined with ridge regression and recursive feature elimination in quantitative analysis of laser induced breakdown spectroscopy

In the spectral analysis of laser-induced breakdown spectroscopy,abundant characteristic spectral lines and severe interference information exist simultaneously in the original spectral data.Here,a feature selection method called recursive feature elimination based on ridge regression(Ridge-RFE) for the original spectral data is recommended to make full use of the valid information of spectra.In the Ridge-RFE method,the absolute value of the ridge regression coefficient was used as a criterion to screen spectral characteristic,the feature with the absolute value of minimum weight in the input subset features was removed by recursive feature elimination(RFE),and the selected features were used as inputs of the partial least squares regression(PLS) model.The Ridge-RFE method based PLS model was used to measure the Fe,Si,Mg,Cu,Zn and Mn for 51 aluminum alloy samples,and the results showed that the root mean square error of prediction decreased greatly compared to the PLS model with full spectrum as input.The overall results demonstrate that the Ridge-RFE method is more efficient to extract the redundant features,make PLS model for better quantitative analysis results and improve model generalization ability.     

A hidden line elimination method for curved surfaces

An algorithm for displaying curved surfaces with hidden lines eliminated is described. The surfaces are displayed as rectangular grids of straight segments which approximate those surfaces. The algorith is essentially one of brute force. However, it divides the screen space into small 3D boxes to reduce the number of subpatches to be checked to determine the visibility of each grid point. It turned out that this division process made this algorithm about 10 times faster than the algorithm which had no use of the division.Expanding the algorithm for making contour drawings is very easy. Some methods for drawing silhouette lines are considered.     

节点优化编号的改进最小度算法

为了提高节点优化编号的效果与效率,文中提出了改进的最小度算法.最小度编号算法MD(minimum degree)中,与任意节点相连的节点的总数称为该节点的度,将与任意节点相连的所有节点的度的总和称为该节点的量度.文中提出MD中,在度最小的前提下,将量度最小的节点先行消去,可实现注入元更少.另外,选取主元后,利用不换行不...     

高速电压随动电源的发展及面临的挑战

随着3G通信时代的到来,新的数字调制方式使功率放大器的射频输入信号表现出高带宽和"非恒定包络"的特点,如果功率放大器仍采用传统的恒定电压供电,则将产生较大的功率损耗。因此,为提高其工作效率,高速电压随动电源的应用是发展趋势。本文阐述了高速电压随动电源的概念和应用背景,对现有包络线跟踪变换器的电路系统结构进行分类和归纳总结,指出各结构的优势、适用场合和直接应用于高速电压随动电源时的不足。最后,文章指出合理的系统架构、高频高效驱动电路的设计以及对寄生参数效应的考虑是高速电压随动电源的设计所面临的主要挑战。     

肉桂酰杯[4]芳烃的合成及清除自由基活性

杯[4]芳烃经醚化、氨解得到了含酰肼基团的中间体3,在PEG-400存在下,肉桂酰氯与3反应获得了含肉桂酰基的杯[4]芳烃衍生物4;4-经基肉桂酸与氯甲酸乙酯形成的混合酐与3反应,得到了相应的化合物5。用^1H NMR,^13C NMR及IR对4,5进行了结构表征,用MS对4进行了结构确证。DPPH·法测定4,5清除有机自由基活性的结果表明,4,5的自由基清除率约为19％,比杯[4]芳烃母体及肉桂酸都有所提高。     

EDA技术在"数字逻辑"课程触发器教学中的应用

在"数字逻辑"课程触发器理论教学中,根据触发器工作原理,利用EDA技术的原理图设计和时序波形仿真,在课堂上结合现代电化教学手段,通过理论基础分析和电路波形仿真结果两方面的课程内容,让学生真正了解"不确定"现象、"一次翻转"现象以及"去抖动"现象,这样可以提高课堂教学效果.     

胶球清洗在余热电站试投时存在的问题及对策

胶球清洗系统的正常投运,可提高电站机组凝汽器的真空度,降低传热端差.分析了胶球清洗装置投运时存在的问题,对清洗系统的二次滤网和凝汽器水室的涡流区进行了结构改进,提高了胶球的回收率.胶球清洗系统的投运关系到机组的效率及出力,通过消缺方案的实施,取得了明显效果,恢复了清洗装置原有的性能指标.     

稀疏信号表示中的幅度偏差及消除方法

在稀疏信号表示的并行选取字典算法中,当频率不在栅格点上时,对应的幅度估计可能会有很大的偏差.为了消除这个偏差,本文先求得较精确的频率估计值,然后在其邻域内进行进一步寻优,得到幅度估计.将此方法用于各种信噪比下的仿真信号,都能得到较好的幅度估计性能.因此此方法是一种能有效消除稀疏信号表示中幅度偏差的方法.     

新型单相低谐波饱和式可控电抗器

提出了一种新型的单相饱和式可控电抗器拓扑,将可控电抗器的控制绕组和辅助消谐绕组有机地统一起来。新的拓扑结构将控制绕组通过一个半桥控制电路和一个电压型的逆变器连接到和主绕组紧密耦合的辅助消谐绕组。消谐绕组在抑制谐波的同时担负从系统传递能量给控制绕组的功能。针对单相应用条件下,基于新的拓扑结构,利用能量平衡原理,检测系统侧的电流,在控制可控电抗器的等值电抗的同时,通过逆变器的输出电流,使可控电抗器在不同的工作状态下所产生的谐波得到补偿,从而使单相饱和式可控电抗器的谐波水平大为降低。仿真结果验证了新型拓扑结构的有效性和可行性。