Frication of high vowels has three levels in auditory impression,including non-frication,low frication,and high frication.The aim of this study was to study the acoustic characteristics and social variability of the t...Frication of high vowels has three levels in auditory impression,including non-frication,low frication,and high frication.The aim of this study was to study the acoustic characteristics and social variability of the three levels via the method of multivariate statistical modeling.We estimated the weighting of each parameter by fitting the model of Boosted Logistic Regression to obtain the optimal parametric set.Pattern recognition then quantified the social variability with the optimal set.It showed that the acoustic characteristics of the vowel frication are mainly reflected in the formants,of which the second bandwidth (B2) plays the most prominent role in distinguishing the three levels.Three dimensional diagrams further illustrated that the high frication group has the greatest B2 value,with the smallest first formant (F1) and skewness,while the non-frication group is completely the opposite.Results of pattern recognition showed that the degrees of variation in age and gender are both close to 19%,where the higher the frication level is,the greater the variability is.This paper thus suggested that low frication variants should be treated as fricative approximants,instead of fricative vowels as reported in the literature.展开更多
The negative transfer of native language influences the English acquisition process of the college students from Yantai in a great degree,both in the segmental and suprasegmental level,while the consonants in the segm...The negative transfer of native language influences the English acquisition process of the college students from Yantai in a great degree,both in the segmental and suprasegmental level,while the consonants in the segmental level are influenced most.The paper makes an experimental phonetic contrastive study on [d?],[t?],[?] in the aspect of frication between native English speakers from America and English learners from Yantai basing on processing a large number of English word corpora by using PRAAT.It is found that the degree of frication of [d?],[t?],[?] in American English is strong,while Yantai weak.展开更多
It is now over half a century since Keulegan conducted his open channel flow experiments. Over the past decades, many empirical formulae were proposed based on his results, however, there is still not a combined expre...It is now over half a century since Keulegan conducted his open channel flow experiments. Over the past decades, many empirical formulae were proposed based on his results, however, there is still not a combined expression to describe the effects of friction over all hydraulic regions in open channel flows. Therefore, in this letter, based on the analysis of the implicit model and the logarithmic matching method, the results of Keulegan (for authentic experiment data are no longer available, here we adopt the analytical solutions given by Dou) are rescaled into one monotone curve by combining the Reynolds number and the relative roughness of the river bed. A united expression that could cover the entire turbulence regions and be validated with Dou's analytical solutions is suggested to estimate the friction factor throughout the turbulent region in open channel flows, with higher accuracy than that of the previous formulas.展开更多
Achieving low friction and wear of poly(phenylene sulfide)(PPS) without using fillers or blending is a challenging task, but one of considerable practical importance. Here we describe how neat PPS with high tribologic...Achieving low friction and wear of poly(phenylene sulfide)(PPS) without using fillers or blending is a challenging task, but one of considerable practical importance. Here we describe how neat PPS with high tribological performance is achieved by manipulating processing parameters(pressure, flow and temperature). The key to achieving high tribological performance is comparatively high molecular chain orientation, realized in neat PPS, at high shear rates and low pressure. The friction coefficient and wear rate are as low as ~0.3 and~10^(-6) mm^(3)·N^(-1)·m^(-1), respectively, which break the record for neat PPS. These values are even better than those for PPS-based blends and comparable to PPS composites. Further studies show, for the first time, that wear rate decreases exponentially with increasing molecular chain orientation, prompting us to revise the classical Archard's law by including the effect of molecular chain orientation. These findings open the possibility of using neat PPS in highly demanding tribological applications.展开更多
基金supported by the National Social Science Foundation of China(19BYY048)the Major Program of the National Social Science Foundation of China(19ZDA307)
文摘Frication of high vowels has three levels in auditory impression,including non-frication,low frication,and high frication.The aim of this study was to study the acoustic characteristics and social variability of the three levels via the method of multivariate statistical modeling.We estimated the weighting of each parameter by fitting the model of Boosted Logistic Regression to obtain the optimal parametric set.Pattern recognition then quantified the social variability with the optimal set.It showed that the acoustic characteristics of the vowel frication are mainly reflected in the formants,of which the second bandwidth (B2) plays the most prominent role in distinguishing the three levels.Three dimensional diagrams further illustrated that the high frication group has the greatest B2 value,with the smallest first formant (F1) and skewness,while the non-frication group is completely the opposite.Results of pattern recognition showed that the degrees of variation in age and gender are both close to 19%,where the higher the frication level is,the greater the variability is.This paper thus suggested that low frication variants should be treated as fricative approximants,instead of fricative vowels as reported in the literature.
文摘The negative transfer of native language influences the English acquisition process of the college students from Yantai in a great degree,both in the segmental and suprasegmental level,while the consonants in the segmental level are influenced most.The paper makes an experimental phonetic contrastive study on [d?],[t?],[?] in the aspect of frication between native English speakers from America and English learners from Yantai basing on processing a large number of English word corpora by using PRAAT.It is found that the degree of frication of [d?],[t?],[?] in American English is strong,while Yantai weak.
基金supported by the National Natural Science Foun-dation of China(Grant Nos.51479007,11172218 and 11372232)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20130141110016)
文摘It is now over half a century since Keulegan conducted his open channel flow experiments. Over the past decades, many empirical formulae were proposed based on his results, however, there is still not a combined expression to describe the effects of friction over all hydraulic regions in open channel flows. Therefore, in this letter, based on the analysis of the implicit model and the logarithmic matching method, the results of Keulegan (for authentic experiment data are no longer available, here we adopt the analytical solutions given by Dou) are rescaled into one monotone curve by combining the Reynolds number and the relative roughness of the river bed. A united expression that could cover the entire turbulence regions and be validated with Dou's analytical solutions is suggested to estimate the friction factor throughout the turbulent region in open channel flows, with higher accuracy than that of the previous formulas.
基金financially supported by the National Natural Science Foundation of China (Nos. 21676217, 52003215, 21978240 and 52003219)Youth Project of Basic Research Program of Natural Science in Shaanxi Province (No. 2020JQ179)+1 种基金the Fundamental Research Funds for the Central Universities (Nos. 3102018AX004 and 3102017jc01001)the Open Testing Foundation of the Analytical & Testing Center of Northwestern Polytechnical University (No. 2020T020)。
文摘Achieving low friction and wear of poly(phenylene sulfide)(PPS) without using fillers or blending is a challenging task, but one of considerable practical importance. Here we describe how neat PPS with high tribological performance is achieved by manipulating processing parameters(pressure, flow and temperature). The key to achieving high tribological performance is comparatively high molecular chain orientation, realized in neat PPS, at high shear rates and low pressure. The friction coefficient and wear rate are as low as ~0.3 and~10^(-6) mm^(3)·N^(-1)·m^(-1), respectively, which break the record for neat PPS. These values are even better than those for PPS-based blends and comparable to PPS composites. Further studies show, for the first time, that wear rate decreases exponentially with increasing molecular chain orientation, prompting us to revise the classical Archard's law by including the effect of molecular chain orientation. These findings open the possibility of using neat PPS in highly demanding tribological applications.