To improve the self-cleaning ability of aquaculture tank and the efficiency of circulating water,physical and numerical experiments were conducted on the influence of inlet structure on sewage discharge in a rounded s...To improve the self-cleaning ability of aquaculture tank and the efficiency of circulating water,physical and numerical experiments were conducted on the influence of inlet structure on sewage discharge in a rounded square aquaculture tank with a single inlet.Based on the physical model of the tank,analysis of how inlet structure adjustment affects sewage discharge efficiency and flow field characteristics was conducted to provide suitable flow field conditions for sinkable solid particle discharge.In addition,an internal flow field simulation was conducted using the RNG k-εturbulence model in hydraulic drive mode.Then a solid-fluid multiphase model was created to investigate how the inlet structure affects sewage collection in the rounded square aquaculture tank with single inlet and outlet.The finding revealed that the impact of inlet structure is considerably affecting sewage collection.The conditions of C/B=0.07-0.11(the ratio of horizontal distance between the center of the inlet pipe and the tank wall(C)to length of the tank(B))andα=25°(αis the angle between the direction of the jet and the tangential direction of the arc angle)resulted in optimal sewage collection,which is similar to the flow field experiment in the rounded square aquaculture tank with single inlet and outlet.An excellent correlation was revealed between sewage collection and fluid circulation stability in the aquaculture tank.The present study provided a reference for design and optimization of circulating aquaculture tanks in aquaculture industry.展开更多
The collective motion of rounded squares with different comer-roundness ζ is studied by molecular dynamlcs （MD） simulation in this work. Three types of translational collective motion pattern are observed, includin...The collective motion of rounded squares with different comer-roundness ζ is studied by molecular dynamlcs （MD） simulation in this work. Three types of translational collective motion pattern are observed, including＇, gliding, hopping and a mixture of gliding and hopping. Quantitatively, the dynamics of each observed ordered phase is characterized by both mean square displacement and van Hove functions for both translation and rotation. The effect of corner-roundness on the dynamics is further studied by comparing the dynamics of the rhombic crystal phases folmed by different comer-.rounded particles at a same surface fraction. The results show that as ζ increases from 0.286 to 0.667, the translational collective motion of particles changes from a gliding-dominant pattern to a hopping-dominant patte;n, whereas the rotational motion pattern is hopping-like and does not change in its type, but the rotational hopping becomes much more frequent as increases （i.e., as particles become more rounded）. A simple geometrical model is proposed to explain the trend of gliding motion observed in MD simulations.展开更多
The mutual relationships of three effective factors, the diameter D/d （d is the diameter of exit） of obstructed plate, exit densimetric Froude number and the distance Hid of the plate from jet orifice for obstructed...The mutual relationships of three effective factors, the diameter D/d （d is the diameter of exit） of obstructed plate, exit densimetric Froude number and the distance Hid of the plate from jet orifice for obstructed buoyant jet in static ambient, are analyzed to explain normal and abnormal rounded flowing （reverberated and bifurcated flowing）. The critical Froude numbers for obstructed buoyant jets with H/d=2, 4, 6, 8 which distinguished normal and abnormal flowing pattern are obtained. Normal rounded flowing is found only for a plate under a special value of H/d. A fitted formula of critical Froude numbers with H/d and D/d is presented to distinguish rounded flowing types. The occurring of reverberated or bifurcated flowing in abnormal rounded flow is analyzed. Based on the results of obstructed buoyant jets with D/d=1, normal rounded flowing occurred only for all conditions and axial dilution behind the plate under different H/D is obtained.展开更多
Preface Throughout history,women have played an essential role in shaping human civilization and have made immense contributions to social progress.But the paths towards gender equality and women's well-rounded de...Preface Throughout history,women have played an essential role in shaping human civilization and have made immense contributions to social progress.But the paths towards gender equality and women's well-rounded development across the world have been long and arduous.Since its founding in 1921,the Communist Party of China(CPC)has remained committed to women's liberation and development and gender equality.展开更多
BACKGROUND Colorectal cancer(CRC)is the second leading cause of cancer-related deaths worldwide with an alarming rise in early-onset CRC(eoCRC)over the past several decades.Unlike late-onset CRC,the drivers behind eoC...BACKGROUND Colorectal cancer(CRC)is the second leading cause of cancer-related deaths worldwide with an alarming rise in early-onset CRC(eoCRC)over the past several decades.Unlike late-onset CRC,the drivers behind eoCRC remain less clear.While certain risk factors such as obesity and smoking have demonstrated a relatively strong association with eoCRC in the literature,some studies have challenged these associations,emphasizing the need for additional studies.METHODS This cross-sectional study used de-identified data from the National Health and Nutrition Examination Survey(1999-2023),including 30321 United States adults aged 18 to 49 years.Participants with missing key variables were excluded.Standardized protocols were used to collect demographic,lifestyle,anthropo-metric[body mass index(BMI),body roundness index(BRI),waist circumference(WC)],and self-reported CRC data.Logistic regression and propensity score matching assessed associations between obesity-related parameters and eoCRC.Statistical analyses were performed in R and Stata,with P<0.05 defined as significant.RESULTS Of 30321 participants,48 received a diagnosis of eoCRC.Patients with eoCRC were older(mean age 39.96 years vs 34.36 years;P<0.001)and had higher WC and BRI.None of the eoCRC patients were heavy drinkers(P=0.006).Unadjusted models demonstrated significant associations of eoCRC with BRI quartiles,as well as BMI-defined obesity,WC,and smoking.In unadjusted models,BRI remained the strongest independent predictor;those in the highest BRI quartiles had over 10-fold greater odds of eoCRC.In fully adjusted models,BRI remained significant,but BMI-and waist-based obesity were not.CONCLUSION BRI is a stronger predictor of eoCRC risk compared to other obesity indices and is a superior tool for identifying young individuals at higher risk of CRC.展开更多
Observations of sampling are often subject to rounding, but are modeled as though they were unrounded. This paper examines the impact of rounding errors on parameter estimation with multi-layer ranked set sampling. It...Observations of sampling are often subject to rounding, but are modeled as though they were unrounded. This paper examines the impact of rounding errors on parameter estimation with multi-layer ranked set sampling. It shows that the rounding errors seriously distort the behavior of covariance matrix estimate, and lead to inconsistent estimation. Taking this into account, we present a new approach to implement the estimation for this model, and further establish the strong consistency and asymptotic normality of the proposed estimators. Simulation experiments show that our estimates based on rounded multi-layer ranked set sampling are always more efficient than those based on rounded simple random sampling.展开更多
提出了一种基于混沌遗传算法的计算圆度误差的新方法.它利用混沌优化方法的遍历性和随机性,通过混沌扰动操作可克服传统遗传算法中的早熟问题,确保算法的全局收敛性.该方法满足最小条件原理,其计算结果的精确度非常高,理论上可以获得全...提出了一种基于混沌遗传算法的计算圆度误差的新方法.它利用混沌优化方法的遍历性和随机性,通过混沌扰动操作可克服传统遗传算法中的早熟问题,确保算法的全局收敛性.该方法满足最小条件原理,其计算结果的精确度非常高,理论上可以获得全局最优解.实例计算表明,这种算法简单明确,具有精度高、收敛速度快、易于计算机程序实现和推广应用等特点.
Abstract：
A new method for calculating the roundness error based on chaos genetic algorithms is proposed. The system utilizes the ergodicity and randomness of chaos optimal method and by means of chaos stir operation, which can overcame the problem of premature convergence in traditional genetic algorithms and ensured an convergence of the algorithms. The method satisfies the principle of the least condition, the precision of calculating result is very high and can find .the global optimal solution. An actual calculated example showed that this method is simple and clear and it has features of high precision and fast convergent speed as well as using computer easily and popularizing application easily.展开更多
In this paper, an aeronautical thin-walled part with a complex geometry which has several sharp bends and curvatures in different directions was investigated. This kind of part is difficult to be manufactured only in ...In this paper, an aeronautical thin-walled part with a complex geometry which has several sharp bends and curvatures in different directions was investigated. This kind of part is difficult to be manufactured only in one stage. Therefore, an innovative multi-stage active hydroforming process assisted by the rigid forming method was designed. In addition, an optimized blank geometry is obtained. In fact, the main focused point of this paper is to propose a new small radius rounded corner forming technique and analyze the mechanism. Two kinds of forming modes of changing a big rounded corner into a small one, which are related to different tangential positions of the die in the process of calibration, are analyzed theoretically. Meanwhile, the stress and strain states of the deformation region are compared. The relationships between the minimum relative radii of rounded corners I and II in the first stage and the hydraulic pressure are calculated by the bending theory. Finally, the influences of the tensile-bulging effect and the interface condition of the double-layer sheet on the forming quality of the specimen are investigated. The achieved results can make a foundation for utilizing the proposed method in forming of thin-walled parts with very small radii.展开更多
Automatic speech recognition (ASR) is vital for very low-resource languages for mitigating the extinction trouble. Chaha is one of the low-resource languages, which suffers from the problem of resource insufficiency a...Automatic speech recognition (ASR) is vital for very low-resource languages for mitigating the extinction trouble. Chaha is one of the low-resource languages, which suffers from the problem of resource insufficiency and some of its phonological, morphological, and orthographic features challenge the development and initiatives in the area of ASR. By considering these challenges, this study is the first endeavor, which analyzed the characteristics of the language, prepared speech corpus, and developed different ASR systems. A small 3-hour read speech corpus was prepared and transcribed. Different basic and rounded phone unit-based speech recognizers were explored using multilingual deep neural network (DNN) modeling methods. The experimental results demonstrated that all the basic phone and rounded phone unit-based multilingual models outperformed the corresponding unilingual models with the relative performance improvements of 5.47% to 19.87% and 5.74% to 16.77%, respectively. The rounded phone unit-based multilingual models outperformed the equivalent basic phone unit-based models with relative performance improvements of 0.95% to 4.98%. Overall, we discovered that multilingual DNN modeling methods are profoundly effective to develop Chaha speech recognizers. Both the basic and rounded phone acoustic units are convenient to build Chaha ASR system. However, the rounded phone unit-based models are superior in performance and faster in recognition speed over the corresponding basic phone unit-based models. Hence, the rounded phone units are the most suitable acoustic units to develop Chaha ASR systems.展开更多
This paper develops a coupled dynamics model for a linear induction motor （LIM） vehicle and a subway track to investigate the influence of polygonal wheels of the vehicle on the dynamic behavior of the system. In th...This paper develops a coupled dynamics model for a linear induction motor （LIM） vehicle and a subway track to investigate the influence of polygonal wheels of the vehicle on the dynamic behavior of the system. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom. A Timoshenko beam is used to model the rails which are discretely supported by sleepers. The sleepers are modeled as rigid bodies with their vertical, lateral, and rolling motions being considered. In order to simulate the vehicle running along the track, a moving sleeper support model is introduced to simulate the excitation by the discrete sleeper supporters, in which the sleepers are assumed to move backward at a constant speed that is the same as the train speed. The Hertzian contact theory and the Shen– Hedrick–Elkins’ model are utilized to deal with the normal dynamic forces and the tangential forces between wheels and rails, respectively. In order to better characterize the linear metro system （LMS）, Euler beam theory based on modal superposition method is used to model LIM and RP. The vertical electric magnetic force and the lateral restoring force between the LIM and RP are also taken into consideration. The former has gap-varying nonlinear characteristics, whilst the latter is considered as a constant restoring force of 1 kN. The numerical analysis considers the effect of the excitation due to polygonal wheels on the dynamic behavior of the system at different wear stages, in which the used data regarding the polygonal wear on the wheel tread are directly measured at the subway site.展开更多
As the two most important indexes of bearing raceway, surface roughness and roundness have significant influence on bearing noise. Some researchers have carried out studies in this field, however, reason and extent of...As the two most important indexes of bearing raceway, surface roughness and roundness have significant influence on bearing noise. Some researchers have carried out studies in this field, however, reason and extent of the influence of raceway surface geometric characteristics on bearing running noise are not perfectly clear up to now. In this paper, the raceway of 6309 type bearing＇s inner and outer ring is machined by floating abrasive polishing adopting soft abrasive pad. Surface roughness parameters, arithmetical mean deviation of the profile Ra, the point height of irregularities Rz, maximum height of the profile Rmax and roundness fof raceways, are measured before and after machining, and the change rules of the measured results are studied. The study results show that the floating abrasive polishing can reduce the surface geometric errors of bearing raceway evidently. The roundness error is reduced by 25%, Rm^x value is reduced by 35.5%, Rz value is reduced by 22% and Ra value is reduced by 5%. By analyzing the change of the geometrical parameters and the shape difference of the raceway before and after machining, it is found that the floating abrasive polishing method can affect the roundness error mainly by modifying the local deviation of the raceway＇s surface profile. Bearings with different raceway surface geometrical parameter value are assembled and the running noise is tested. The test results show that Ra has a little, Rmax and Rz have a measurable, and the roundness error has a significant influence on the running noise. From the viewpoint of controlling bearings＇ running noise, raceway roundness error should be strictly controlled, and for the surface roughness parameters, R,n^x and Rz should be mainly controlled. This paper proposes an effective method to obtain the low noise bearing by machining the raceway with floating abrasive polishing after super finishing.展开更多
The quality of coke affects the performance of the blast furnace, factors affecting coke quality include coal properties, coal charge granulometry and carbonization conditions. The coke properties in elude the size an...The quality of coke affects the performance of the blast furnace, factors affecting coke quality include coal properties, coal charge granulometry and carbonization conditions. The coke properties in elude the size analysis, cold strength (Micum Indices-M4(). MI0) and hot strength (Coke Reactivity Index-CRI, Coke Strength after Reaction-CSR) properties and structural properties such as coke structure and texture. Structural properties comprise the porosity, pore-cell wall thickness and pore sizes, while textures consist of the carbon forms in the coke. In present work, advanced method such as image analysis method was used to interpret coke microstructure. Conventional methods such as determination of coke porosity by measurement of real and apparent density and mercury porosimetry have a number of limitations. Coke size, magnification, number of image frames captured, process of pellet preparations and coke properties such as M4(), M|0, CRI and CSR (low, medium and high values) were taken as variables for experimental purposes. The coke structure parameters such as porosity, length, perimeter, breadth, roundness, pore-wall thickness and pore size distribution of the pores were determined by image analysis method. This method provided average porosity in addition to pore-wall thickness and pore-size distribution. The pore wall thickness measuremenl by image analysis method provided significant correlations with M40, CRI and CSR values. This explained the usability of image analysis for coke structure measurement.展开更多
Taking the raceway roundness error into account,mechanical characteristics of cross roller bearings(CRBs)were investigated.A static analysis model of CRBs considering the raceway roundness error was established.Based ...Taking the raceway roundness error into account,mechanical characteristics of cross roller bearings(CRBs)were investigated.A static analysis model of CRBs considering the raceway roundness error was established.Based on this model,the rotational accuracy and load distribution of CRBs under constraints of geometry and external loads were derived.The fatigue life of CRBs with roundness error was calculated by applying Palmgren-Miner linear cumulative damage theory.The influence of inner and outer raceway roundness error on the performance of the CRBs,such as rotational accuracy,load distribution,and fatigue life,was studied through the analysis of examples.The results indicate that the influence of roundness error on the rotating inner raceway is more significant than that of roundness error on the nonrotating outer raceway.The roundness error on the rotating inner raceway always degrades the performance of CRBs.However,a proper roundness error on the nonrotating outer raceway can reduce the loads acting on the rollers and thus improve the fatigue life of CRBs.The effect of the roundness error amplitude on the bearing performance is ordinal,whereas the effect of the roundness order on the bearing performance is not in order.展开更多
There have been interests to link different cuttings/cavings to various wellbore failure types during drilling. This concept is essential when caliper and image logs are not available. Identification ofwellbore failur...There have been interests to link different cuttings/cavings to various wellbore failure types during drilling. This concept is essential when caliper and image logs are not available. Identification ofwellbore failure during drilling gives more chance of immediate actions before wireline logging program. In this paper, an approach was presented based on the image processing of ditch cuttings. This approach uses the sphericity and roundness of cuttings as input data to classify caving types and subsequently deter- mine the dominant failure type. Likewise, common definitions of cavings were discussed initially before a new criterion is suggested. This quantitative criterion was examined by observations from caliper and acoustic image logs as well. The proposed approach and criterion were implemented on ditch cuttings taken from a well in Western Australia. Results indicate that the primary failure is shear failure （breakout） due to high levels of angular cavings. However, another failure due to the fluid invasion into pre-existing fractures was also recorded by blocky cavings.展开更多
基金Supported by the 2023 Central Government Finance Subsidy Project for Liaoning Fisheries,the Key Research Project of Liaoning Provincial Department of Education in 2022(No.LJKZZ20220091)the National Natural Science Foundation of China(No.31872609)+1 种基金the Innovation Support Program for High-level Talents of Dalian City(No.2019RD12)the earmarked fund for CARS-49。
文摘To improve the self-cleaning ability of aquaculture tank and the efficiency of circulating water,physical and numerical experiments were conducted on the influence of inlet structure on sewage discharge in a rounded square aquaculture tank with a single inlet.Based on the physical model of the tank,analysis of how inlet structure adjustment affects sewage discharge efficiency and flow field characteristics was conducted to provide suitable flow field conditions for sinkable solid particle discharge.In addition,an internal flow field simulation was conducted using the RNG k-εturbulence model in hydraulic drive mode.Then a solid-fluid multiphase model was created to investigate how the inlet structure affects sewage collection in the rounded square aquaculture tank with single inlet and outlet.The finding revealed that the impact of inlet structure is considerably affecting sewage collection.The conditions of C/B=0.07-0.11(the ratio of horizontal distance between the center of the inlet pipe and the tank wall(C)to length of the tank(B))andα=25°(αis the angle between the direction of the jet and the tangential direction of the arc angle)resulted in optimal sewage collection,which is similar to the flow field experiment in the rounded square aquaculture tank with single inlet and outlet.An excellent correlation was revealed between sewage collection and fluid circulation stability in the aquaculture tank.The present study provided a reference for design and optimization of circulating aquaculture tanks in aquaculture industry.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21573159 and 21621004)
文摘The collective motion of rounded squares with different comer-roundness ζ is studied by molecular dynamlcs （MD） simulation in this work. Three types of translational collective motion pattern are observed, including＇, gliding, hopping and a mixture of gliding and hopping. Quantitatively, the dynamics of each observed ordered phase is characterized by both mean square displacement and van Hove functions for both translation and rotation. The effect of corner-roundness on the dynamics is further studied by comparing the dynamics of the rhombic crystal phases folmed by different comer-.rounded particles at a same surface fraction. The results show that as ζ increases from 0.286 to 0.667, the translational collective motion of particles changes from a gliding-dominant pattern to a hopping-dominant patte;n, whereas the rotational motion pattern is hopping-like and does not change in its type, but the rotational hopping becomes much more frequent as increases （i.e., as particles become more rounded）. A simple geometrical model is proposed to explain the trend of gliding motion observed in MD simulations.
基金Project supported by the National Natural Science Foundation of China (No.50479038)
文摘The mutual relationships of three effective factors, the diameter D/d （d is the diameter of exit） of obstructed plate, exit densimetric Froude number and the distance Hid of the plate from jet orifice for obstructed buoyant jet in static ambient, are analyzed to explain normal and abnormal rounded flowing （reverberated and bifurcated flowing）. The critical Froude numbers for obstructed buoyant jets with H/d=2, 4, 6, 8 which distinguished normal and abnormal flowing pattern are obtained. Normal rounded flowing is found only for a plate under a special value of H/d. A fitted formula of critical Froude numbers with H/d and D/d is presented to distinguish rounded flowing types. The occurring of reverberated or bifurcated flowing in abnormal rounded flow is analyzed. Based on the results of obstructed buoyant jets with D/d=1, normal rounded flowing occurred only for all conditions and axial dilution behind the plate under different H/D is obtained.
文摘Preface Throughout history,women have played an essential role in shaping human civilization and have made immense contributions to social progress.But the paths towards gender equality and women's well-rounded development across the world have been long and arduous.Since its founding in 1921,the Communist Party of China(CPC)has remained committed to women's liberation and development and gender equality.
文摘BACKGROUND Colorectal cancer(CRC)is the second leading cause of cancer-related deaths worldwide with an alarming rise in early-onset CRC(eoCRC)over the past several decades.Unlike late-onset CRC,the drivers behind eoCRC remain less clear.While certain risk factors such as obesity and smoking have demonstrated a relatively strong association with eoCRC in the literature,some studies have challenged these associations,emphasizing the need for additional studies.METHODS This cross-sectional study used de-identified data from the National Health and Nutrition Examination Survey(1999-2023),including 30321 United States adults aged 18 to 49 years.Participants with missing key variables were excluded.Standardized protocols were used to collect demographic,lifestyle,anthropo-metric[body mass index(BMI),body roundness index(BRI),waist circumference(WC)],and self-reported CRC data.Logistic regression and propensity score matching assessed associations between obesity-related parameters and eoCRC.Statistical analyses were performed in R and Stata,with P<0.05 defined as significant.RESULTS Of 30321 participants,48 received a diagnosis of eoCRC.Patients with eoCRC were older(mean age 39.96 years vs 34.36 years;P<0.001)and had higher WC and BRI.None of the eoCRC patients were heavy drinkers(P=0.006).Unadjusted models demonstrated significant associations of eoCRC with BRI quartiles,as well as BMI-defined obesity,WC,and smoking.In unadjusted models,BRI remained the strongest independent predictor;those in the highest BRI quartiles had over 10-fold greater odds of eoCRC.In fully adjusted models,BRI remained significant,but BMI-and waist-based obesity were not.CONCLUSION BRI is a stronger predictor of eoCRC risk compared to other obesity indices and is a superior tool for identifying young individuals at higher risk of CRC.
基金The second author is supported by National Natural Science Foundation of China （Grant No. 10871036）
文摘Observations of sampling are often subject to rounding, but are modeled as though they were unrounded. This paper examines the impact of rounding errors on parameter estimation with multi-layer ranked set sampling. It shows that the rounding errors seriously distort the behavior of covariance matrix estimate, and lead to inconsistent estimation. Taking this into account, we present a new approach to implement the estimation for this model, and further establish the strong consistency and asymptotic normality of the proposed estimators. Simulation experiments show that our estimates based on rounded multi-layer ranked set sampling are always more efficient than those based on rounded simple random sampling.
文摘提出了一种基于混沌遗传算法的计算圆度误差的新方法.它利用混沌优化方法的遍历性和随机性,通过混沌扰动操作可克服传统遗传算法中的早熟问题,确保算法的全局收敛性.该方法满足最小条件原理,其计算结果的精确度非常高,理论上可以获得全局最优解.实例计算表明,这种算法简单明确,具有精度高、收敛速度快、易于计算机程序实现和推广应用等特点.
Abstract：
A new method for calculating the roundness error based on chaos genetic algorithms is proposed. The system utilizes the ergodicity and randomness of chaos optimal method and by means of chaos stir operation, which can overcame the problem of premature convergence in traditional genetic algorithms and ensured an convergence of the algorithms. The method satisfies the principle of the least condition, the precision of calculating result is very high and can find .the global optimal solution. An actual calculated example showed that this method is simple and clear and it has features of high precision and fast convergent speed as well as using computer easily and popularizing application easily.
基金supported by the National Science and Technology Major Project of China (No. 2014ZX04002041)
文摘In this paper, an aeronautical thin-walled part with a complex geometry which has several sharp bends and curvatures in different directions was investigated. This kind of part is difficult to be manufactured only in one stage. Therefore, an innovative multi-stage active hydroforming process assisted by the rigid forming method was designed. In addition, an optimized blank geometry is obtained. In fact, the main focused point of this paper is to propose a new small radius rounded corner forming technique and analyze the mechanism. Two kinds of forming modes of changing a big rounded corner into a small one, which are related to different tangential positions of the die in the process of calibration, are analyzed theoretically. Meanwhile, the stress and strain states of the deformation region are compared. The relationships between the minimum relative radii of rounded corners I and II in the first stage and the hydraulic pressure are calculated by the bending theory. Finally, the influences of the tensile-bulging effect and the interface condition of the double-layer sheet on the forming quality of the specimen are investigated. The achieved results can make a foundation for utilizing the proposed method in forming of thin-walled parts with very small radii.
文摘Automatic speech recognition (ASR) is vital for very low-resource languages for mitigating the extinction trouble. Chaha is one of the low-resource languages, which suffers from the problem of resource insufficiency and some of its phonological, morphological, and orthographic features challenge the development and initiatives in the area of ASR. By considering these challenges, this study is the first endeavor, which analyzed the characteristics of the language, prepared speech corpus, and developed different ASR systems. A small 3-hour read speech corpus was prepared and transcribed. Different basic and rounded phone unit-based speech recognizers were explored using multilingual deep neural network (DNN) modeling methods. The experimental results demonstrated that all the basic phone and rounded phone unit-based multilingual models outperformed the corresponding unilingual models with the relative performance improvements of 5.47% to 19.87% and 5.74% to 16.77%, respectively. The rounded phone unit-based multilingual models outperformed the equivalent basic phone unit-based models with relative performance improvements of 0.95% to 4.98%. Overall, we discovered that multilingual DNN modeling methods are profoundly effective to develop Chaha speech recognizers. Both the basic and rounded phone acoustic units are convenient to build Chaha ASR system. However, the rounded phone unit-based models are superior in performance and faster in recognition speed over the corresponding basic phone unit-based models. Hence, the rounded phone units are the most suitable acoustic units to develop Chaha ASR systems.
文摘This paper develops a coupled dynamics model for a linear induction motor （LIM） vehicle and a subway track to investigate the influence of polygonal wheels of the vehicle on the dynamic behavior of the system. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom. A Timoshenko beam is used to model the rails which are discretely supported by sleepers. The sleepers are modeled as rigid bodies with their vertical, lateral, and rolling motions being considered. In order to simulate the vehicle running along the track, a moving sleeper support model is introduced to simulate the excitation by the discrete sleeper supporters, in which the sleepers are assumed to move backward at a constant speed that is the same as the train speed. The Hertzian contact theory and the Shen– Hedrick–Elkins’ model are utilized to deal with the normal dynamic forces and the tangential forces between wheels and rails, respectively. In order to better characterize the linear metro system （LMS）, Euler beam theory based on modal superposition method is used to model LIM and RP. The vertical electric magnetic force and the lateral restoring force between the LIM and RP are also taken into consideration. The former has gap-varying nonlinear characteristics, whilst the latter is considered as a constant restoring force of 1 kN. The numerical analysis considers the effect of the excitation due to polygonal wheels on the dynamic behavior of the system at different wear stages, in which the used data regarding the polygonal wear on the wheel tread are directly measured at the subway site.
基金Supported by National Natural Science Foundation of China(Grant No.51275062)Open Foundation of Tsinghua University State Key Laboratory of Tribology of China(Grant No.SKLTKF11B08)
文摘As the two most important indexes of bearing raceway, surface roughness and roundness have significant influence on bearing noise. Some researchers have carried out studies in this field, however, reason and extent of the influence of raceway surface geometric characteristics on bearing running noise are not perfectly clear up to now. In this paper, the raceway of 6309 type bearing＇s inner and outer ring is machined by floating abrasive polishing adopting soft abrasive pad. Surface roughness parameters, arithmetical mean deviation of the profile Ra, the point height of irregularities Rz, maximum height of the profile Rmax and roundness fof raceways, are measured before and after machining, and the change rules of the measured results are studied. The study results show that the floating abrasive polishing can reduce the surface geometric errors of bearing raceway evidently. The roundness error is reduced by 25%, Rm^x value is reduced by 35.5%, Rz value is reduced by 22% and Ra value is reduced by 5%. By analyzing the change of the geometrical parameters and the shape difference of the raceway before and after machining, it is found that the floating abrasive polishing method can affect the roundness error mainly by modifying the local deviation of the raceway＇s surface profile. Bearings with different raceway surface geometrical parameter value are assembled and the running noise is tested. The test results show that Ra has a little, Rmax and Rz have a measurable, and the roundness error has a significant influence on the running noise. From the viewpoint of controlling bearings＇ running noise, raceway roundness error should be strictly controlled, and for the surface roughness parameters, R,n^x and Rz should be mainly controlled. This paper proposes an effective method to obtain the low noise bearing by machining the raceway with floating abrasive polishing after super finishing.
文摘The quality of coke affects the performance of the blast furnace, factors affecting coke quality include coal properties, coal charge granulometry and carbonization conditions. The coke properties in elude the size analysis, cold strength (Micum Indices-M4(). MI0) and hot strength (Coke Reactivity Index-CRI, Coke Strength after Reaction-CSR) properties and structural properties such as coke structure and texture. Structural properties comprise the porosity, pore-cell wall thickness and pore sizes, while textures consist of the carbon forms in the coke. In present work, advanced method such as image analysis method was used to interpret coke microstructure. Conventional methods such as determination of coke porosity by measurement of real and apparent density and mercury porosimetry have a number of limitations. Coke size, magnification, number of image frames captured, process of pellet preparations and coke properties such as M4(), M|0, CRI and CSR (low, medium and high values) were taken as variables for experimental purposes. The coke structure parameters such as porosity, length, perimeter, breadth, roundness, pore-wall thickness and pore size distribution of the pores were determined by image analysis method. This method provided average porosity in addition to pore-wall thickness and pore-size distribution. The pore wall thickness measuremenl by image analysis method provided significant correlations with M40, CRI and CSR values. This explained the usability of image analysis for coke structure measurement.
基金Project(51775059)supported by the National Natural Science Foundation of ChinaProject(2017YFB1300700)supported by the National Key Research&Development Program of China。
文摘Taking the raceway roundness error into account,mechanical characteristics of cross roller bearings(CRBs)were investigated.A static analysis model of CRBs considering the raceway roundness error was established.Based on this model,the rotational accuracy and load distribution of CRBs under constraints of geometry and external loads were derived.The fatigue life of CRBs with roundness error was calculated by applying Palmgren-Miner linear cumulative damage theory.The influence of inner and outer raceway roundness error on the performance of the CRBs,such as rotational accuracy,load distribution,and fatigue life,was studied through the analysis of examples.The results indicate that the influence of roundness error on the rotating inner raceway is more significant than that of roundness error on the nonrotating outer raceway.The roundness error on the rotating inner raceway always degrades the performance of CRBs.However,a proper roundness error on the nonrotating outer raceway can reduce the loads acting on the rollers and thus improve the fatigue life of CRBs.The effect of the roundness error amplitude on the bearing performance is ordinal,whereas the effect of the roundness order on the bearing performance is not in order.
文摘There have been interests to link different cuttings/cavings to various wellbore failure types during drilling. This concept is essential when caliper and image logs are not available. Identification ofwellbore failure during drilling gives more chance of immediate actions before wireline logging program. In this paper, an approach was presented based on the image processing of ditch cuttings. This approach uses the sphericity and roundness of cuttings as input data to classify caving types and subsequently deter- mine the dominant failure type. Likewise, common definitions of cavings were discussed initially before a new criterion is suggested. This quantitative criterion was examined by observations from caliper and acoustic image logs as well. The proposed approach and criterion were implemented on ditch cuttings taken from a well in Western Australia. Results indicate that the primary failure is shear failure （breakout） due to high levels of angular cavings. However, another failure due to the fluid invasion into pre-existing fractures was also recorded by blocky cavings.
