螺距对螺旋慢波系统色散和耦合阻抗的影响

螺距是慢波系统的一个重要参数,直接影响螺旋慢波系统的色散特性和耦合阻抗.严格求解螺距对慢波系统色散和耦合阻抗的影响是不方便的,而通过计算机模拟可以方便快速地研究螺距对慢波系统色散和耦合阻抗的影响.模拟结果表明,对于工程项目当螺距变化小于4%时,螺距对色散和耦合阻抗的影响是很小的.     

Mid-Basal-to-Ceiling Versus Mid-Ceiling-to-Basal Elicitation of Maximum Phonational Frequency Range

The purpose of this study was to investigate if there was an effect of task on the determination of maximum phonational frequency range (MPFR). Two tasks commonly used to elicit MPFR in clinical voice evaluations were compared. Normal adult females (n = 30) were examined. No statistically significant effect of task was found. Both tasks (mid-basal-to-ceiling and mid-ceiling-to-basal) were found to have a high positive correlation (0.89). Implications of the use on one task to determine maximum phonational frequency range are discussed, as is the possibility of a task effect on determination of other voice parameters.     

Can listeners hear who is singing? A comparison of three-note and six-note discrimination tasks

Timbre is typically investigated as a perceptual attribute that differentiates a sound source at one pitch and loudness. Yet the perceptual usefulness of timbre is that it allows the listener to recognize one sound source at different pitches. This paper investigated the ability of listeners to identify which pitch in an ascending or descending sequence of three or six stimuli was sung by a different singer. For three-note sequences, the task was extremely difficult, and with rare exceptions, listeners chose the most dissimilarly pitched stimulus as coming from the oddball singer. For six-note sequences, the detection of the oddball singer was much improved in spite of the added complexity of the task. These results support the idea that timbre should be understood as a transformation that connects the different sounds of one source and that a "rich" set of sounds is necessary to discover the trajectory.     

基于小波变换的清浊音分类及基音周期检测算法

该文提出了一种基于小波变换的鲁棒性基音周期检测方法。检测前在小波域上用Teager能量算子对语音信号进行清浊音判决,对浊音段采用空域相关函数提取基音周期。实验表明,与传统的小波变换算法和自相关法相比,该方法鲁棒性好,具有更高的准确性。     

低速率WI编码器中4~6bit基音量化算法研究

基音在语音编码中通常采用7bit无失真均匀量化。由于浊音段语音的基音普遍具有缓慢渐变的特点,为了更有效地去除前后帧基音之间存在的相关性,该文基于Eriksson和Kang提出的4bit基音量化算法,针对汉语语音进行研究,实现了一套4~6bit基音量化算法。该算法计算简单,无需码书存储。将此基音量化方案应用于WI模型和WI编码器,主观A/B听力测试结果表明,该方案在高效量化基音的同时保证了合成语音质量几乎没有损失,完全满足低速率WI编码器对量化基音的要求。     

一种2.4kbps改进型MBELP编码

该文给出了一种改进的2.4kb/s多带激励线性预测(IMBELP)语音编码算法。与传统的MBELP算法相比,本算法在基音提取和清/浊音判决上采取了一些改进措施,使得合成语音质量有一定的提高。本文详细介绍了改进后的MBELP算法,并将其在基音提取和清/浊音判决的结果与传统的MBELP进行比较。     

语音压缩编码中的两种基音预测器

本文研究了语音压缩编码中基音预测器的两种情形,即开环和闭环结构。提出了一些简化基音预测器求解方法,比较了几种条件下的基音预测器性能。给出了计算机仿真结果。     

煤精制软沥青庚烷不溶甲苯可溶族结构的光谱分析

以高温煤焦油为原料制备软化点为32℃煤焦油精制软沥青,再以庚烷、甲苯为溶剂超声萃取得庚烷不溶甲苯可溶物。蒸气压渗透法测定庚烷不溶甲苯可溶物平均分子量为349;元素分析与平均分子量结合得平均分子式C26.65H17.62N0.12S0.06O0.51,平均分子中杂原子总数0.68;红外分析结果表明：其杂原子氧以R—O—R,Ar—O—R结构存在,氮以R—NH—R和—N=结构存在,且以—N=为主;采用改进的Brown-Lander模型得其平均结构是六环稠环;紫外分析表明,线性排列为主、面性排列为辅,即庚烷不溶甲苯可溶族的化学结构以渺位缩合为主,迫位缩合为辅。