Current research in broken rotor bar （BRB） fault detection in induction motors is primarily focused on a high-frequency resolution analysis of the stator current. Compared with a discrete Fourier transformation, the...Current research in broken rotor bar （BRB） fault detection in induction motors is primarily focused on a high-frequency resolution analysis of the stator current. Compared with a discrete Fourier transformation, the parametric spectrum estimation technique has a higher frequency accuracy and resolution. However, the existing detection methods based on parametric spectrum estima- tion cannot realize online detection, owing to the large computational cost. To improve the efficiency of BRB fault detection, a new detection method based on the min-norm algorithm and least square estimation is proposed in this paper. First, the stator current is filtered using a band-pass filter and divided into short overlapped data windows. The min-norm algorithm is then applied to determine the fre- quencies of the fundamental and fault characteristic com- ponents with each overlapped data window. Next, based on the frequency values obtained, a model of the fault current signal is constructed. Subsequently, a linear least squares problem solved through singular value decomposition is designed to estimate the amplitudes and phases of the related components. Finally, the proposed method is applied to a simulated current and an actual motor, the results of which indicate that, not only parametric spectrum estimation technique.展开更多
In spectrum analysis of induction motor current, the characteristic components of broken rotor bars（BRB） fault are often submerged by the fundamental component. Although many detection methods have been proposed for...In spectrum analysis of induction motor current, the characteristic components of broken rotor bars（BRB） fault are often submerged by the fundamental component. Although many detection methods have been proposed for this problem, the frequency resolution and accuracy are not high enough so that the reliability of BRB fault detection is a ected. Thus, a new multiple signal classification（MUSIC） algorithm based on particle swarm intelligence search is developed. Since spectrum peak search in MUSIC is a multimodal optimization problem, an improved bare?bones particle swarm optimization algorithm（IBPSO） is proposed first. In the IBPSO, a modified strategy of subpopulation determination is introduced into BPSO for realizing multimodal search. And then, the new MUSIC algorithm, called IBPSO?based MUSIC, is proposed by replacing the fixed?step traversal search with IBPSO. Meanwhile, a simulation signal is used to test the e ectiveness of the proposed algorithm. The simulation results show that its frequency precision reaches 10-5, and the computational cost is only comparable to that of traditional MUSIC with 0.1 search step. Finally, the IBPSO?based MUSIC is applied in BRB fault detection of an induction motor, and the e ectiveness and superiority are proved again. The proposed research provides a modified MUSIC algorithm which has su cient frequency precision to detect BRB fault in induction motors.展开更多
Stem cell-based therapy raises hopes for a better approach to promoting tissue repair and functional recovery.However,transplanted stem cells show a high death percentage,creating challenges to successful transplantat...Stem cell-based therapy raises hopes for a better approach to promoting tissue repair and functional recovery.However,transplanted stem cells show a high death percentage,creating challenges to successful transplantation and prognosis.Thus,it is necessary to investigate the mechanisms underlying stem cell death,such as apoptotic cascade activation,excessive autophagy,inflammatory response,reactive oxygen species,excitotoxicity,and ischemia/hypoxia.Targeting the molecular pathways involved may be an efficient strategy to enhance stem cell viability and maximize transplantation success.Notably,a more complex network of cell death receives more attention than one crucial pathway in determining stem cell fate,highlighting the challenges in exploring mechanisms and therapeutic targets.In this review,we focus on programmed cell death in transplanted stem cells.We also discuss some promising strategies and challenges in promoting survival for further study.展开更多
Density functional theory （DFT） calculations are reported for the structures of neutral and zwitterionic glycine-（CHaOH）n where n=1-6. Initial geometries of the clusters of neutral and zwitterionic glycine with 1-...Density functional theory （DFT） calculations are reported for the structures of neutral and zwitterionic glycine-（CHaOH）n where n=1-6. Initial geometries of the clusters of neutral and zwitterionic glycine with 1-6 methanol molecules are fully optimized at B3LYP/6-31＋G^＊ level of theory. The lowest energy configurations are located and their hydrogen bond structures are analyzed. Theoretical prediction reveals that the methanols prefer to locate near the carboxylic acid group for the small clusters （n_〈3） with the neutral form while the configurations with the methanols bridging the acid and the amino group are favorite in the zwitterionic form clusters. When the number of the methanol molecules in the clusters reaches five and six, the two forms tend to be isoenergetic.展开更多
Pyrrolidine,a five membered heterocyclic molecule,is widely existing in organism.Herein,infrared spectra of pyrrolidine monomer in neutral and cationic states were obtained by vacuum ultraviolet ionization,infrared ph...Pyrrolidine,a five membered heterocyclic molecule,is widely existing in organism.Herein,infrared spectra of pyrrolidine monomer in neutral and cationic states were obtained by vacuum ultraviolet ionization,infrared photodissociation and time of flight mass spectrometry.Both in neutral and cationic states,it is found that their CH stretching vibration bands are red shifted.In the IR spectrum of neutral pyrrolidine,because the electric dipole moment of NH is small,we have not observed the NH stretching vibration bands.However,the NH stretching vibration band of pyrrolidine is greatly enhanced after ionization,and this band red-shifts compared with the previous experiment.The red shifts of CH stretching vibrations in neutral and cationic states are caused by the negative and positive hyperconjugation,respectively.The enhancement and red shift of the NH stretching band are owing to the ejection of the electrons on the N atom after ionization.Through the calculations,it is found that the acidity of the CH bond is a little stronger than that of NH bond.These kinds of studies would be helpful to understand the intrinsic properties of biomolecules in neutral and cationic states,and to provide reference for the further study of living organic macromolecules.展开更多
A new direct ultrasonic treatment(DUT) setup with the ultrasonic horn placed in the horizontal direction was developed and used in the preparation of semi-solid Sn-62 Bi slurry. The influence of DUT temperature on mic...A new direct ultrasonic treatment(DUT) setup with the ultrasonic horn placed in the horizontal direction was developed and used in the preparation of semi-solid Sn-62 Bi slurry. The influence of DUT temperature on microstructure and properties of Sn-62 Bi alloy were studied. The test results of XRD showed that the semi-solid Sn-62 Bi alloy obtained by the DUT process exhibits pronounced preferential orientation of Bi(2 0 2), Bi(-1 1 1), Bi(-2 0 1), Sn(1 1 0) and Sn(2 2 0) planes. Compared to the conventional liquid casting Sn-62 Bi alloy without DUT, it was discovered that the primary Bi blocks of semi-solid Sn-62 Bi alloy prepared with the DUT process distribute more homogeneously and are smaller. With the treatment by ultrasonic vibration in the semi-solid state for 120 s, the higher the primary Bi phase fraction in the slurry, the smaller the size of primary semi-solid Bi blocks formed after solidification. The average side length of the primary Bi blocks was from 30 μm to 80 μm. The elongation of Sn-62 Bi alloy treated by DUT for 120 s at 145 °C is 43.21%, reflecting a distinctly improvement by 129.10%, as compared to the conventional liquid casting Sn-62 Bi alloy without DUT. This indicates that DUT process could improve dramatically the ductility of Sn-62 Bi alloys content. The microstructure evolution mechanism of semi-solid Sn-62 Bi alloy slurry was also analyzed.展开更多
The radiation damage of biomolecules, in particular with aliphatic compound, has been extensively studied. Morpholine is a typical six-membered aliphatic heterocyclic compound. In the present work, photoionization and...The radiation damage of biomolecules, in particular with aliphatic compound, has been extensively studied. Morpholine is a typical six-membered aliphatic heterocyclic compound. In the present work, photoionization and dissociation of the morpholine monomer and subsequent fragmentations have been investigated by synchrotron vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The vertical ionization energy of morpholine monomer is 8.37±0.05 eV, which agrees reasonably well with a theoretical value 8.41 eV of morpholine. Experimentally observed fragmentation of morpholine (m/z=87 amu) gives rise to m/z=86 amu, m/z=57 amu, and m/z=29 amu. Based on experimental and theoretical results, it is found that the m/z=86 amu is produced by losing H atom, the m/z=57 amu is formed by the elimination of CH2O with a ring-opening process, the m/z=29 amu is generated by further dissociation of the fragment m/z=57 amu (C3H7N)+ by the elimination of C2H4. This finding would provide valuable insight into the photo-damage of aliphatic compounds, which may be related to living cells and other biological system.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.51607180)
文摘Current research in broken rotor bar （BRB） fault detection in induction motors is primarily focused on a high-frequency resolution analysis of the stator current. Compared with a discrete Fourier transformation, the parametric spectrum estimation technique has a higher frequency accuracy and resolution. However, the existing detection methods based on parametric spectrum estima- tion cannot realize online detection, owing to the large computational cost. To improve the efficiency of BRB fault detection, a new detection method based on the min-norm algorithm and least square estimation is proposed in this paper. First, the stator current is filtered using a band-pass filter and divided into short overlapped data windows. The min-norm algorithm is then applied to determine the fre- quencies of the fundamental and fault characteristic com- ponents with each overlapped data window. Next, based on the frequency values obtained, a model of the fault current signal is constructed. Subsequently, a linear least squares problem solved through singular value decomposition is designed to estimate the amplitudes and phases of the related components. Finally, the proposed method is applied to a simulated current and an actual motor, the results of which indicate that, not only parametric spectrum estimation technique.
基金Fundamental Research Funds for the Central Universities(Grant No.2017XKQY032)
文摘In spectrum analysis of induction motor current, the characteristic components of broken rotor bars（BRB） fault are often submerged by the fundamental component. Although many detection methods have been proposed for this problem, the frequency resolution and accuracy are not high enough so that the reliability of BRB fault detection is a ected. Thus, a new multiple signal classification（MUSIC） algorithm based on particle swarm intelligence search is developed. Since spectrum peak search in MUSIC is a multimodal optimization problem, an improved bare?bones particle swarm optimization algorithm（IBPSO） is proposed first. In the IBPSO, a modified strategy of subpopulation determination is introduced into BPSO for realizing multimodal search. And then, the new MUSIC algorithm, called IBPSO?based MUSIC, is proposed by replacing the fixed?step traversal search with IBPSO. Meanwhile, a simulation signal is used to test the e ectiveness of the proposed algorithm. The simulation results show that its frequency precision reaches 10-5, and the computational cost is only comparable to that of traditional MUSIC with 0.1 search step. Finally, the IBPSO?based MUSIC is applied in BRB fault detection of an induction motor, and the e ectiveness and superiority are proved again. The proposed research provides a modified MUSIC algorithm which has su cient frequency precision to detect BRB fault in induction motors.
基金Supported by the National Natural Science Foundation of China,No.81772134,No.81971891,and No.81571939.
文摘Stem cell-based therapy raises hopes for a better approach to promoting tissue repair and functional recovery.However,transplanted stem cells show a high death percentage,creating challenges to successful transplantation and prognosis.Thus,it is necessary to investigate the mechanisms underlying stem cell death,such as apoptotic cascade activation,excessive autophagy,inflammatory response,reactive oxygen species,excitotoxicity,and ischemia/hypoxia.Targeting the molecular pathways involved may be an efficient strategy to enhance stem cell viability and maximize transplantation success.Notably,a more complex network of cell death receives more attention than one crucial pathway in determining stem cell fate,highlighting the challenges in exploring mechanisms and therapeutic targets.In this review,we focus on programmed cell death in transplanted stem cells.We also discuss some promising strategies and challenges in promoting survival for further study.
基金VI. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （（No.20973067） and Guangdong-Natural Science Foundation （No.7005823）, the Scientific Research Foundation for the Returned Overseas Chinese scholars, the State Education Ministry and the Foundation for Introduction of Talents by the Universities in Guangdong Province. Initial computation contributed by Mr. Xiting Zhang is gratefully acknowledged.
文摘Density functional theory （DFT） calculations are reported for the structures of neutral and zwitterionic glycine-（CHaOH）n where n=1-6. Initial geometries of the clusters of neutral and zwitterionic glycine with 1-6 methanol molecules are fully optimized at B3LYP/6-31＋G^＊ level of theory. The lowest energy configurations are located and their hydrogen bond structures are analyzed. Theoretical prediction reveals that the methanols prefer to locate near the carboxylic acid group for the small clusters （n_〈3） with the neutral form while the configurations with the methanols bridging the acid and the amino group are favorite in the zwitterionic form clusters. When the number of the methanol molecules in the clusters reaches five and six, the two forms tend to be isoenergetic.
基金the National Natural Science Foundation of China(No.U1732146,No.21273083)the Project under Scientific and Technological Planning Grant(No.201805010002)by Guangzhou City.
文摘Pyrrolidine,a five membered heterocyclic molecule,is widely existing in organism.Herein,infrared spectra of pyrrolidine monomer in neutral and cationic states were obtained by vacuum ultraviolet ionization,infrared photodissociation and time of flight mass spectrometry.Both in neutral and cationic states,it is found that their CH stretching vibration bands are red shifted.In the IR spectrum of neutral pyrrolidine,because the electric dipole moment of NH is small,we have not observed the NH stretching vibration bands.However,the NH stretching vibration band of pyrrolidine is greatly enhanced after ionization,and this band red-shifts compared with the previous experiment.The red shifts of CH stretching vibrations in neutral and cationic states are caused by the negative and positive hyperconjugation,respectively.The enhancement and red shift of the NH stretching band are owing to the ejection of the electrons on the N atom after ionization.Through the calculations,it is found that the acidity of the CH bond is a little stronger than that of NH bond.These kinds of studies would be helpful to understand the intrinsic properties of biomolecules in neutral and cationic states,and to provide reference for the further study of living organic macromolecules.
基金financially supported by the National Natural Science Foundation of China(Grant no.51104049)
文摘A new direct ultrasonic treatment(DUT) setup with the ultrasonic horn placed in the horizontal direction was developed and used in the preparation of semi-solid Sn-62 Bi slurry. The influence of DUT temperature on microstructure and properties of Sn-62 Bi alloy were studied. The test results of XRD showed that the semi-solid Sn-62 Bi alloy obtained by the DUT process exhibits pronounced preferential orientation of Bi(2 0 2), Bi(-1 1 1), Bi(-2 0 1), Sn(1 1 0) and Sn(2 2 0) planes. Compared to the conventional liquid casting Sn-62 Bi alloy without DUT, it was discovered that the primary Bi blocks of semi-solid Sn-62 Bi alloy prepared with the DUT process distribute more homogeneously and are smaller. With the treatment by ultrasonic vibration in the semi-solid state for 120 s, the higher the primary Bi phase fraction in the slurry, the smaller the size of primary semi-solid Bi blocks formed after solidification. The average side length of the primary Bi blocks was from 30 μm to 80 μm. The elongation of Sn-62 Bi alloy treated by DUT for 120 s at 145 °C is 43.21%, reflecting a distinctly improvement by 129.10%, as compared to the conventional liquid casting Sn-62 Bi alloy without DUT. This indicates that DUT process could improve dramatically the ductility of Sn-62 Bi alloys content. The microstructure evolution mechanism of semi-solid Sn-62 Bi alloy slurry was also analyzed.
基金supported by the National Natural Science Foundation of China (No.U1732146 and No.21273083)the Scientific and Technological Planning Project of Guangzhou City (No.201805010002)
文摘The radiation damage of biomolecules, in particular with aliphatic compound, has been extensively studied. Morpholine is a typical six-membered aliphatic heterocyclic compound. In the present work, photoionization and dissociation of the morpholine monomer and subsequent fragmentations have been investigated by synchrotron vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The vertical ionization energy of morpholine monomer is 8.37±0.05 eV, which agrees reasonably well with a theoretical value 8.41 eV of morpholine. Experimentally observed fragmentation of morpholine (m/z=87 amu) gives rise to m/z=86 amu, m/z=57 amu, and m/z=29 amu. Based on experimental and theoretical results, it is found that the m/z=86 amu is produced by losing H atom, the m/z=57 amu is formed by the elimination of CH2O with a ring-opening process, the m/z=29 amu is generated by further dissociation of the fragment m/z=57 amu (C3H7N)+ by the elimination of C2H4. This finding would provide valuable insight into the photo-damage of aliphatic compounds, which may be related to living cells and other biological system.
