The new three-phase 5-level current-source inverter (CSI) proposed in this paper was developed by connecting three separate single-phase 5-level CSIs in series, and its operational principle was analyzed. There are tw...The new three-phase 5-level current-source inverter (CSI) proposed in this paper was developed by connecting three separate single-phase 5-level CSIs in series, and its operational principle was analyzed. There are two major problems existing in current-source multilevel inverters, one is the complex PWM control method (2-logic to 3-logic conversion), and the other is the problem of current-unbalance between different levels. A simple current-balance control method via DC current feedback is applied in each single-phase 5-level CSI cell to implement the current-balance control between different levels. And to reduce the output current harmonics, POD PWM control technique was used. Simulation and experimental results showed that this new three-phase 5-level CSI topology operates correctly.展开更多
Implementing acoustic emission experiments with large rock samples, LURR (Load/Unload Response Ratio) theory was studied. The loading conditions in the experiments were designed to simulate the complicated loading pro...Implementing acoustic emission experiments with large rock samples, LURR (Load/Unload Response Ratio) theory was studied. The loading conditions in the experiments were designed to simulate the complicated loading process of underground rocks. The damages emerging inside the rock samples were recorded by the acoustic emission technique during the loading process. The experimental results were consistent with prediction by LURR theory. Integrating the changing processes of LURR value Y and the location process of acoustic emission events showed agreement between the variation of LURR value Y and the damage evolution inside the rocks. Furthermore, the high value of Y emerged before the complete breakdown of materials. Therefore, the damage evolution of rock specimen can be quantitatively analyzed with LURR theory, thus the failure of the rock materials and the earthquake occurrence may be predicted. The experimental results gave a further verification of LURR theory.展开更多
A new method of estimating the frequency-known signals from the strong background noise was presented first. Then the new method was used in the demodulation of the digital frequency modulation (FSK) signals. The new ...A new method of estimating the frequency-known signals from the strong background noise was presented first. Then the new method was used in the demodulation of the digital frequency modulation (FSK) signals. The new demodulation method can complete the demodulation of the FSK signals only with the carrier frequency and without any carrier phase information. The simulation results show that the performance of anti-noise of the new method is better than that of the incoherent demodulation method and the fluctuation of the carrier phase has little effect on the new method. So the new demodulation method has a fine prospect in the practical applications.展开更多
Attracting released hatchery-reared fish to designated areas during the growth process is vital to realize the objectives of sea ranching. Based on the bottom artificial reefs and surface kelp culture facilities in th...Attracting released hatchery-reared fish to designated areas during the growth process is vital to realize the objectives of sea ranching. Based on the bottom artificial reefs and surface kelp culture facilities in the Xiangshan Bay sea ranch, we proposed systematic techniques related to acoustic conditioning of the black seabream(Sparus macrocephalus). Experiments conducted in 12 m × 10 m × 1.6 m ponds on Xixuan Island showed that black seabream was positively sensitive to 500–600 Hz periodic signals. Conditioned responses were apparent after 8 d. Two to three days were required for recovery of the memory of a conditioned response after a 20-day interval. According to the practical application requirements in the open sea, unattended acoustic conditioning equipment was developed. The ranching equipment was used in 12 m × 12 m × 2.5 m cages, and the behavior of black seabream juveniles was successfully guided after 7 days. Of the 16000 released fish, 82.5% of them were conditioned with a flexible grading net. To avoid inducing a stress response, the juveniles were released into the sea ranch in situ from the net cage. The acoustic conditioning equipments were moved into the open sea and the aggregation phenomenon of the released fish was observed when the sound was played. After 6 months of investigation and based on Sr+ marking, only one acoustically conditioned fish was found outside the 3.5-km^2 sea ranch area, thereby reached the goal of guiding activity. The practical effect in the Xiangshan Bay sea ranch showed the validity of the acoustic conditioning system, which may contribute to improve the operation of the sea ranches in the East China Sea.展开更多
When scientific research began in early twentieth-century China,a key issue was the acquisition of reliable empirical information through objective and precise observations.This article examines a specific case where ...When scientific research began in early twentieth-century China,a key issue was the acquisition of reliable empirical information through objective and precise observations.This article examines a specific case where a scientist grappled with such an issue:the linguist Chao Yuen Ren’s application of mechanical means in his phonetic studies.In the 1920s–1930s,Chao conducted a series of field and lab studies on the dialects in southern and central China.In contrast to traditional scholars’exclusive reliance on sharp ears and rhyme books,Chao employed mechanical devices to inscribe and analyze the spectrographs of dialectical tones and used phonographs to record the articulations of his subjects.It is demonstrated that Chao’s machines not only provided a new method of observation;they also altered the theoretical understanding of certain fundamental categories in Chinese phonology,such as tones.Moreover,Chao did not aim to replace human perception with automatic mechanisms in empirical investigations.Rather,the use of machines in his research called for an active and engaged scientific persona.展开更多
Objective To obtain a general overview of gallstone disease in Shanghai. Methods 3415citizens aged >20 in the community of Shanghai were randomly selected to undergo a clinical epidemiological study and an ultrasou...Objective To obtain a general overview of gallstone disease in Shanghai. Methods 3415citizens aged >20 in the community of Shanghai were randomly selected to undergo a clinical epidemiological study and an ultrasound examination to screen for cholelithiasis. Results Overall prevalence rate of gallstones was 6.5% (8.6% in women and 5.1% in men). Among the 3415 persons investigated, 65 had already undergone cholecystectomy. The percentage of asymptomatic gallstone was 70 .5% . Prevalence of gallstone diseases (gallstones plus cholecystectomy) increased with age significantly. Conclusion Compared to the research in Shanghai ten years ago, especially for the persons older than 50 years, the gallstone disease has become more frequent. The proportion of asymptomatic gallstones and the awareness is increasing.展开更多
A model-independent 3-D texture synthesis of physical and stochastic algorithms,based on an amplitude modulation method,is presented to realize 3-D fabric dynamic simulation.The physical functions are built to simulat...A model-independent 3-D texture synthesis of physical and stochastic algorithms,based on an amplitude modulation method,is presented to realize 3-D fabric dynamic simulation.The physical functions are built to simulate fabric basic deformation.The stochastic functions,generated by Perlin noise,are used to simulate fabric natural motion in the wind.The two kinds of functions are synthesized by method of amplitude modulation.As the arithmetic uses stochastic functions in stead of recursive algorithm,it is capable of simulating the fabric material,the wind force and direction in real-time.Given the fabric material and wind strength,the stochastic functions can be created to simulate fabric motion in the wind and this model can be adjusted by controlling some certain parameters to achieve a good simulation effect.This method is conceptually intuitive,computationally fast and efficient.Furthermore,the combination of fabric physical and statistic motion characteristics provides an attractive way to improve the display effect and rate.展开更多
Valeo, involved in engine cooling fan system design for many years, is interested in noise prediction tools for axial fans. Thus, this paper describes a two-part study of tonal noise computation. The first part deals ...Valeo, involved in engine cooling fan system design for many years, is interested in noise prediction tools for axial fans. Thus, this paper describes a two-part study of tonal noise computation. The first part deals with the prediction of tonal noise using analytical models. As for the second part, it describes a hybrid approach for predicting tonal noise where the sources are extracted from an Unsteady Reynolds-Averaged Naviers-Stocks （URANS） simulation and then propagated into the far, free field using the Ffowcs Williams and Hawkings＇ acoustic analogy. The computational domain is meshed with 46 million polyhedral elements and the simulation takes into account the exact geometry of the rotor blades, the stator blades and the shroud. The results from the first part show that analytical models can be used for comparisons between different fan geometries, but are unable to provide accurate noise predictions compared to experimental results. The simulation shows non-periodic blade loading over a whole fan revolution, and different blade loading between the blades. This introduces some bias in the assessment of the acoustic performance of the fan. Overall, the results from the hybrid method are in accordance with the experimental results.展开更多
This paper reported an acoustic experiment examining the effect of topic structure and syntax on boundary pitch parameters. Simple discourses containing three sentences were constructed and the boundary between the fi...This paper reported an acoustic experiment examining the effect of topic structure and syntax on boundary pitch parameters. Simple discourses containing three sentences were constructed and the boundary between the first sentence and the second sentence of each discourse varied along the following parameters： （1） topic internal, clause; （2） topic shift, clause; （3） topic internal, sentence; and （4） topic shift, sentence. Seven native speakers of Standard Chinese read the short discourses aloud. The offset f0, f0 Max, and f0 Min of the first sentence and the onset f0, f0 Max, and f0 Min of the second sentence were measured. It was found that relative to topic internal condition, topic shift condition induced higher onset f0 following the boundary. Moreover, this higher onset f0 was caused by the raising of both f0 max and f0 min, suggesting pitch register raising rather than pitch range expansion following the boundary. Syntactic structure as index by clause or sentence was found to have no effect on boundary pitch parameters. These results provide strong evidence for a role of topic strucutre in speech production展开更多
基金Project (No. 50477033) supported by the National Natural Science Foundation of China
文摘The new three-phase 5-level current-source inverter (CSI) proposed in this paper was developed by connecting three separate single-phase 5-level CSIs in series, and its operational principle was analyzed. There are two major problems existing in current-source multilevel inverters, one is the complex PWM control method (2-logic to 3-logic conversion), and the other is the problem of current-unbalance between different levels. A simple current-balance control method via DC current feedback is applied in each single-phase 5-level CSI cell to implement the current-balance control between different levels. And to reduce the output current harmonics, POD PWM control technique was used. Simulation and experimental results showed that this new three-phase 5-level CSI topology operates correctly.
文摘Implementing acoustic emission experiments with large rock samples, LURR (Load/Unload Response Ratio) theory was studied. The loading conditions in the experiments were designed to simulate the complicated loading process of underground rocks. The damages emerging inside the rock samples were recorded by the acoustic emission technique during the loading process. The experimental results were consistent with prediction by LURR theory. Integrating the changing processes of LURR value Y and the location process of acoustic emission events showed agreement between the variation of LURR value Y and the damage evolution inside the rocks. Furthermore, the high value of Y emerged before the complete breakdown of materials. Therefore, the damage evolution of rock specimen can be quantitatively analyzed with LURR theory, thus the failure of the rock materials and the earthquake occurrence may be predicted. The experimental results gave a further verification of LURR theory.
基金the National Natural Science Foundation of China (60272077) the Science Foundation of Aeronautics (02F53030).
文摘A new method of estimating the frequency-known signals from the strong background noise was presented first. Then the new method was used in the demodulation of the digital frequency modulation (FSK) signals. The new demodulation method can complete the demodulation of the FSK signals only with the carrier frequency and without any carrier phase information. The simulation results show that the performance of anti-noise of the new method is better than that of the incoherent demodulation method and the fluctuation of the carrier phase has little effect on the new method. So the new demodulation method has a fine prospect in the practical applications.
基金financially supported by the Special Fund for Agro-scientific Research in the Public Interest (No. 201303047)the National Natural Science Foundation of China (No. 51309150)
文摘Attracting released hatchery-reared fish to designated areas during the growth process is vital to realize the objectives of sea ranching. Based on the bottom artificial reefs and surface kelp culture facilities in the Xiangshan Bay sea ranch, we proposed systematic techniques related to acoustic conditioning of the black seabream(Sparus macrocephalus). Experiments conducted in 12 m × 10 m × 1.6 m ponds on Xixuan Island showed that black seabream was positively sensitive to 500–600 Hz periodic signals. Conditioned responses were apparent after 8 d. Two to three days were required for recovery of the memory of a conditioned response after a 20-day interval. According to the practical application requirements in the open sea, unattended acoustic conditioning equipment was developed. The ranching equipment was used in 12 m × 12 m × 2.5 m cages, and the behavior of black seabream juveniles was successfully guided after 7 days. Of the 16000 released fish, 82.5% of them were conditioned with a flexible grading net. To avoid inducing a stress response, the juveniles were released into the sea ranch in situ from the net cage. The acoustic conditioning equipments were moved into the open sea and the aggregation phenomenon of the released fish was observed when the sound was played. After 6 months of investigation and based on Sr+ marking, only one acoustically conditioned fish was found outside the 3.5-km^2 sea ranch area, thereby reached the goal of guiding activity. The practical effect in the Xiangshan Bay sea ranch showed the validity of the acoustic conditioning system, which may contribute to improve the operation of the sea ranches in the East China Sea.
文摘When scientific research began in early twentieth-century China,a key issue was the acquisition of reliable empirical information through objective and precise observations.This article examines a specific case where a scientist grappled with such an issue:the linguist Chao Yuen Ren’s application of mechanical means in his phonetic studies.In the 1920s–1930s,Chao conducted a series of field and lab studies on the dialects in southern and central China.In contrast to traditional scholars’exclusive reliance on sharp ears and rhyme books,Chao employed mechanical devices to inscribe and analyze the spectrographs of dialectical tones and used phonographs to record the articulations of his subjects.It is demonstrated that Chao’s machines not only provided a new method of observation;they also altered the theoretical understanding of certain fundamental categories in Chinese phonology,such as tones.Moreover,Chao did not aim to replace human perception with automatic mechanisms in empirical investigations.Rather,the use of machines in his research called for an active and engaged scientific persona.
文摘Objective To obtain a general overview of gallstone disease in Shanghai. Methods 3415citizens aged >20 in the community of Shanghai were randomly selected to undergo a clinical epidemiological study and an ultrasound examination to screen for cholelithiasis. Results Overall prevalence rate of gallstones was 6.5% (8.6% in women and 5.1% in men). Among the 3415 persons investigated, 65 had already undergone cholecystectomy. The percentage of asymptomatic gallstone was 70 .5% . Prevalence of gallstone diseases (gallstones plus cholecystectomy) increased with age significantly. Conclusion Compared to the research in Shanghai ten years ago, especially for the persons older than 50 years, the gallstone disease has become more frequent. The proportion of asymptomatic gallstones and the awareness is increasing.
文摘A model-independent 3-D texture synthesis of physical and stochastic algorithms,based on an amplitude modulation method,is presented to realize 3-D fabric dynamic simulation.The physical functions are built to simulate fabric basic deformation.The stochastic functions,generated by Perlin noise,are used to simulate fabric natural motion in the wind.The two kinds of functions are synthesized by method of amplitude modulation.As the arithmetic uses stochastic functions in stead of recursive algorithm,it is capable of simulating the fabric material,the wind force and direction in real-time.Given the fabric material and wind strength,the stochastic functions can be created to simulate fabric motion in the wind and this model can be adjusted by controlling some certain parameters to achieve a good simulation effect.This method is conceptually intuitive,computationally fast and efficient.Furthermore,the combination of fabric physical and statistic motion characteristics provides an attractive way to improve the display effect and rate.
文摘Valeo, involved in engine cooling fan system design for many years, is interested in noise prediction tools for axial fans. Thus, this paper describes a two-part study of tonal noise computation. The first part deals with the prediction of tonal noise using analytical models. As for the second part, it describes a hybrid approach for predicting tonal noise where the sources are extracted from an Unsteady Reynolds-Averaged Naviers-Stocks （URANS） simulation and then propagated into the far, free field using the Ffowcs Williams and Hawkings＇ acoustic analogy. The computational domain is meshed with 46 million polyhedral elements and the simulation takes into account the exact geometry of the rotor blades, the stator blades and the shroud. The results from the first part show that analytical models can be used for comparisons between different fan geometries, but are unable to provide accurate noise predictions compared to experimental results. The simulation shows non-periodic blade loading over a whole fan revolution, and different blade loading between the blades. This introduces some bias in the assessment of the acoustic performance of the fan. Overall, the results from the hybrid method are in accordance with the experimental results.
文摘This paper reported an acoustic experiment examining the effect of topic structure and syntax on boundary pitch parameters. Simple discourses containing three sentences were constructed and the boundary between the first sentence and the second sentence of each discourse varied along the following parameters： （1） topic internal, clause; （2） topic shift, clause; （3） topic internal, sentence; and （4） topic shift, sentence. Seven native speakers of Standard Chinese read the short discourses aloud. The offset f0, f0 Max, and f0 Min of the first sentence and the onset f0, f0 Max, and f0 Min of the second sentence were measured. It was found that relative to topic internal condition, topic shift condition induced higher onset f0 following the boundary. Moreover, this higher onset f0 was caused by the raising of both f0 max and f0 min, suggesting pitch register raising rather than pitch range expansion following the boundary. Syntactic structure as index by clause or sentence was found to have no effect on boundary pitch parameters. These results provide strong evidence for a role of topic strucutre in speech production
