In this paper a joint timing and frequency synchronization method based on Fractional Fourier Transform (FIFT) is proposed for Orthogonal Frequency-Division Multiplexing (OFDM) system. The combination of two chirp...In this paper a joint timing and frequency synchronization method based on Fractional Fourier Transform (FIFT) is proposed for Orthogonal Frequency-Division Multiplexing (OFDM) system. The combination of two chirp signals with opposite chirp rates are used as the training signal, the received training signal with timing and frequency offset is transformed by FrFT and the two peaks representing two chirps in FrFT domain are detected, then the position coordinates of the two peaks are precisely corrected and substituted into an equation group to calculate timing and frequency offset simultaneously. This method only needs one FrFT calculation to implement synchronization, the computational complexity is equal to that of FFT and less than that of correlation or maximum likelihood calculation of existing methods, and estimation range of frequency offset is Large, greater than half the signal bandwidth, while the simulation results show that even at low SNR it can accurately estimate timing and frequency offset and the estimation error is less than that of existing methods.展开更多
Fault detection of an induction motor was carried out using the information of the stator current. After synchronizing the actual data, Fourier and wavelet transformations were adopted in order to obtain the sideband ...Fault detection of an induction motor was carried out using the information of the stator current. After synchronizing the actual data, Fourier and wavelet transformations were adopted in order to obtain the sideband or detail value characteristics under healthy and various faulty operating conditions. The most reliable phase current among the three phase currents was selected using an approach that employs the fuzzy entropy measure. Data were trained with a neural network system, and the fault detection algorithm was verified using the unknown data. Results of the proposed approach based on Fourier and wavelet transformations indicate that the faults can be properly classified into six categories. The training error is 5.3×10-7, and the average test error is 0.103.展开更多
Recently, an interest in a hybrid system combining only the merits of the conventional wheel-rail system and Maglev propulsion system is growing as an alternative to high-speed maglev train. This hybrid-type system is...Recently, an interest in a hybrid system combining only the merits of the conventional wheel-rail system and Maglev propulsion system is growing as an alternative to high-speed maglev train. This hybrid-type system is based on wheel-rail method, but it enables to overcome the speed limitation by adhesion because it is operated through a non-contact method using a linear motor as a propulsion system and reduce the overall construction costs by its compatibility with the conventional railway systems. Therefore, a comparative analysis on electromagnetic characteristics according to the structural combinations on the stator-mover of LSM (linear synchronous motor) for VHST (very high speed train) maintaining the conventional wheel-rail method is conducted, and the structure of coreless superconducting LSM suitable for 600 km/h VHST is finally proposed in this paper.展开更多
In 1778, Abbe Guinot, a priest native of Lorraine and professor in the seminary of Toul, published in Nancy the two volumes of his philosophical lectures, whose subtitle is "On Logic." This concerns a general philos...In 1778, Abbe Guinot, a priest native of Lorraine and professor in the seminary of Toul, published in Nancy the two volumes of his philosophical lectures, whose subtitle is "On Logic." This concerns a general philosophy of knowledge and a critic of philosophical systems. Guinot is interested in science and natural discoveries. He describes the organization of institutional science and appreciates the progress of sciences but he makes a distinction between scientific progress and philosophers' sophisms that he criticizes. In order to favor science and avoid philosophical errors, logic is essential in students' training. According to Guinot, logic allows us to extend our intellectual abilities, upliR our ideas, help our thought processes, and mature our reflection. However, this logic refers to the great book of nature written in mathematical language. Guinot thinks that scientific experiment is of the highest importance for accuracy of mind. This logic lecture is inspired by Aristotle but above all by Port-Royal Logic. It gives a place to Locke empiricism and it favors development of sciences. Abbe Guinot was a chaplain in the cathedral of Nancy; he emigrated in 1791. He came back in France during the Consulate and he died a few time later.展开更多
In this paper,we point out that the Fourier series of a classical function∑^∞k=1 sin kx/k has the Gibbs phenomenon in the neighborhood of zero.Furthermore,we estimate the upper bound of its partial sum and get:sup ...In this paper,we point out that the Fourier series of a classical function∑^∞k=1 sin kx/k has the Gibbs phenomenon in the neighborhood of zero.Furthermore,we estimate the upper bound of its partial sum and get:sup n≥1||∑^n k=1sin kx/k||=∫^x 0sin x/x dx=1.85194, which is better than that in[1].展开更多
文摘In this paper a joint timing and frequency synchronization method based on Fractional Fourier Transform (FIFT) is proposed for Orthogonal Frequency-Division Multiplexing (OFDM) system. The combination of two chirp signals with opposite chirp rates are used as the training signal, the received training signal with timing and frequency offset is transformed by FrFT and the two peaks representing two chirps in FrFT domain are detected, then the position coordinates of the two peaks are precisely corrected and substituted into an equation group to calculate timing and frequency offset simultaneously. This method only needs one FrFT calculation to implement synchronization, the computational complexity is equal to that of FFT and less than that of correlation or maximum likelihood calculation of existing methods, and estimation range of frequency offset is Large, greater than half the signal bandwidth, while the simulation results show that even at low SNR it can accurately estimate timing and frequency offset and the estimation error is less than that of existing methods.
基金Project supported by the Second Stage of Brain Korea 21 Projects
文摘Fault detection of an induction motor was carried out using the information of the stator current. After synchronizing the actual data, Fourier and wavelet transformations were adopted in order to obtain the sideband or detail value characteristics under healthy and various faulty operating conditions. The most reliable phase current among the three phase currents was selected using an approach that employs the fuzzy entropy measure. Data were trained with a neural network system, and the fault detection algorithm was verified using the unknown data. Results of the proposed approach based on Fourier and wavelet transformations indicate that the faults can be properly classified into six categories. The training error is 5.3×10-7, and the average test error is 0.103.
文摘Recently, an interest in a hybrid system combining only the merits of the conventional wheel-rail system and Maglev propulsion system is growing as an alternative to high-speed maglev train. This hybrid-type system is based on wheel-rail method, but it enables to overcome the speed limitation by adhesion because it is operated through a non-contact method using a linear motor as a propulsion system and reduce the overall construction costs by its compatibility with the conventional railway systems. Therefore, a comparative analysis on electromagnetic characteristics according to the structural combinations on the stator-mover of LSM (linear synchronous motor) for VHST (very high speed train) maintaining the conventional wheel-rail method is conducted, and the structure of coreless superconducting LSM suitable for 600 km/h VHST is finally proposed in this paper.
文摘In 1778, Abbe Guinot, a priest native of Lorraine and professor in the seminary of Toul, published in Nancy the two volumes of his philosophical lectures, whose subtitle is "On Logic." This concerns a general philosophy of knowledge and a critic of philosophical systems. Guinot is interested in science and natural discoveries. He describes the organization of institutional science and appreciates the progress of sciences but he makes a distinction between scientific progress and philosophers' sophisms that he criticizes. In order to favor science and avoid philosophical errors, logic is essential in students' training. According to Guinot, logic allows us to extend our intellectual abilities, upliR our ideas, help our thought processes, and mature our reflection. However, this logic refers to the great book of nature written in mathematical language. Guinot thinks that scientific experiment is of the highest importance for accuracy of mind. This logic lecture is inspired by Aristotle but above all by Port-Royal Logic. It gives a place to Locke empiricism and it favors development of sciences. Abbe Guinot was a chaplain in the cathedral of Nancy; he emigrated in 1791. He came back in France during the Consulate and he died a few time later.
基金Foundation item: the Natural Science Foundation of Zhejiang Province (No. 102058).
文摘In this paper,we point out that the Fourier series of a classical function∑^∞k=1 sin kx/k has the Gibbs phenomenon in the neighborhood of zero.Furthermore,we estimate the upper bound of its partial sum and get:sup n≥1||∑^n k=1sin kx/k||=∫^x 0sin x/x dx=1.85194, which is better than that in[1].