The delta-sigma converter is one of the high speed and resolution analog-to-digital modulators. Its implementation needs the low oversampling technique and the multi-bit D/A converter. The noise induced by the multi-b...The delta-sigma converter is one of the high speed and resolution analog-to-digital modulators. Its implementation needs the low oversampling technique and the multi-bit D/A converter. The noise induced by the multi-bit D/A converter becomes one of the key factors deteriorating the signal-to-noise rate of the delta-sigma A/D converter. A novel structure with signal unity transfunction, dynamic element matching(DEM) and noise-shaping is discussed. The method is investigated to design converter based on the proposed structure. The behavior simulation indicates that the structure and the design method are feasible.展开更多
A solution of the scattering problem of guided SH_wave by apartly debonded circular cylinder centered in a traction free plate has been set up. The plate is divided up into three regions with two imaginary planes perp...A solution of the scattering problem of guided SH_wave by apartly debonded circular cylinder centered in a traction free plate has been set up. The plate is divided up into three regions with two imaginary planes perpendicular to the plate walls. In the central region where the partly debonded cylindrical obstacle is posted, the wave field is expanded into the cylindrical wave modes and Chebyshev polynomials. In the other two exterior regions the fields are expanded into the plate wave modes. A system of fundamental equations to solve the problem is obtained according to the traction free boundary condition on the plate walls and the continuity condition of the traction and the displacement across the imaginary planes. The approximate numerical method termed mode_matching technique is used to construct a matrix equation to obtain curves showing the coefficient of reflection and transmission versus the ratio of the cylinder's radius to the plate's half_thickness and the angular width of the debonded region. A comparison of the numerical results between the welded interface condition and the debonded interface condition is made, and the results are discussed.展开更多
This paper mainly studies case representation based on fuzzy technology, the comparing framework of case properties and the method of similarity assessment. Firstly, this paper proposes the method of case representati...This paper mainly studies case representation based on fuzzy technology, the comparing framework of case properties and the method of similarity assessment. Firstly, this paper proposes the method of case representation based on fuzzy technology. Secondly, it discusses the comparing framework of case fuzzy properties. Thirdly, it presents the case representation framework composed of structure data and related properties and b＇ased on which it studies the method and step of gaining case similarity assessment through adjusting similarity value of a property. This paper proposes a similarity assessment method in comparing stage of CBR using fuzzy technology. This method not only simples the computing complexity of CBR in comparing stage but also resolves the difficulties of similarity assessment on different levels.展开更多
基金National Natural Science Foundation of China(50677014)Doctoral Special Found of Ministry of Education(20060532016)+2 种基金Natural Science Foundation of Hunan Province(06JJ2024)Program for New CenturyExcellent Talents in University(NCET-04-0767)Found of Hunan Education depart ment(05C141)
文摘The delta-sigma converter is one of the high speed and resolution analog-to-digital modulators. Its implementation needs the low oversampling technique and the multi-bit D/A converter. The noise induced by the multi-bit D/A converter becomes one of the key factors deteriorating the signal-to-noise rate of the delta-sigma A/D converter. A novel structure with signal unity transfunction, dynamic element matching(DEM) and noise-shaping is discussed. The method is investigated to design converter based on the proposed structure. The behavior simulation indicates that the structure and the design method are feasible.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 19774065) .
文摘A solution of the scattering problem of guided SH_wave by apartly debonded circular cylinder centered in a traction free plate has been set up. The plate is divided up into three regions with two imaginary planes perpendicular to the plate walls. In the central region where the partly debonded cylindrical obstacle is posted, the wave field is expanded into the cylindrical wave modes and Chebyshev polynomials. In the other two exterior regions the fields are expanded into the plate wave modes. A system of fundamental equations to solve the problem is obtained according to the traction free boundary condition on the plate walls and the continuity condition of the traction and the displacement across the imaginary planes. The approximate numerical method termed mode_matching technique is used to construct a matrix equation to obtain curves showing the coefficient of reflection and transmission versus the ratio of the cylinder's radius to the plate's half_thickness and the angular width of the debonded region. A comparison of the numerical results between the welded interface condition and the debonded interface condition is made, and the results are discussed.
文摘This paper mainly studies case representation based on fuzzy technology, the comparing framework of case properties and the method of similarity assessment. Firstly, this paper proposes the method of case representation based on fuzzy technology. Secondly, it discusses the comparing framework of case fuzzy properties. Thirdly, it presents the case representation framework composed of structure data and related properties and b＇ased on which it studies the method and step of gaining case similarity assessment through adjusting similarity value of a property. This paper proposes a similarity assessment method in comparing stage of CBR using fuzzy technology. This method not only simples the computing complexity of CBR in comparing stage but also resolves the difficulties of similarity assessment on different levels.
