The electronic structure of NdFe 10 M 2(M=Ti, V, Cr, Mn, Mo, W) compounds were obtained by the linear muffin tin orbit(LMTO) method, and the micro magnetic properties were examined through the total density of ...The electronic structure of NdFe 10 M 2(M=Ti, V, Cr, Mn, Mo, W) compounds were obtained by the linear muffin tin orbit(LMTO) method, and the micro magnetic properties were examined through the total density of state(TDOS) and the local density of state(DOS). The results suggest that there are two mechanisms which compete with each other and are responsible for variations in magnetic moments of NdFe 10 M 2 with intertitial N(or C) atoms, and the volume expansion leads to the enhancement of Fe Fe exchange interaction at 8i and 8f site, with the result that the magnetic moments at both sites increase. Meanwhile, the magnetic moments at 8j site decrease owing to the hybridization between 3d(Fe) and 2p(N or C) orbits.展开更多
A single-photon detector based on an InGaAs avalanche photodiode has been developed for use at telecom wavelengths. A suitable delay and sampling gate modulation circuit are used to prevent positive and negative trans...A single-photon detector based on an InGaAs avalanche photodiode has been developed for use at telecom wavelengths. A suitable delay and sampling gate modulation circuit are used to prevent positive and negative transient pulses from influencing the detection of true photon induced avalanches. A monostable trigger circuit eliminates the influence of avalanche peak jitter, and a dead time modulation feedback control circuit decreases the afterpulsing. From performance tests we lind that at the optimum operation point, the quantum efficiency is 12% and the dark count rate 1.5 × 10^-6 ns^-1, with a detection rate of 500 kHz.展开更多
In this paper, we have developed an algorithm based on singular value decomposition （SVD） for matrix. And the novel SVD algorithm with normalized period of cardiac cycles is presented. The results from real magnetoc...In this paper, we have developed an algorithm based on singular value decomposition （SVD） for matrix. And the novel SVD algorithm with normalized period of cardiac cycles is presented. The results from real magnetocardiography （MCG） data processing show that the new algorithm is better than the standard one not only in suppressing noises, but also in providing high-fidelity MCG signals.展开更多
We present a new least-mean-square algorithm of adaptive filtering to improve the signal to noise ratio for magneto-cardiography data collected with high-temperature SQUID-based magnetometers. By frequently adjusting ...We present a new least-mean-square algorithm of adaptive filtering to improve the signal to noise ratio for magneto-cardiography data collected with high-temperature SQUID-based magnetometers. By frequently adjusting the adaptive parameter a go systematic optimum values in the course of the programmed procedure, the convergence is accelerated with a highest speed and the minimum steady-state error is obtained simultaneously. This algorithm may be applied to eliminate other non-steady relevant noises as well.展开更多
The solvent peak in the intermolecular multiple-quantum coherence spectra can be suppressed by either applying pulse field gradients or spinning sample along the magic angle direction （φ = 54.7）. However, these two...The solvent peak in the intermolecular multiple-quantum coherence spectra can be suppressed by either applying pulse field gradients or spinning sample along the magic angle direction （φ = 54.7）. However, these two methods also suppress the signals of the solute. We design two pulse sequences with only z-axis gradients to suppress the solvent peak without reducing the intensity of solute signals. Compared to the former pulse sequence, the latter pulse sequence is insensitive to the imperfection of pulse flip angles. When the flip angles of the second pulse sequence are purposely deviated 1/10 from the optimal values, the solvent peak is still weak. Theoretical expressions, experimental observations and computer simulations demonstrate that the two methods can be used to effectively suppress solvent peak in intermolecular multiple-quantum coherence spectra.展开更多
An economical magnetocardiogram （MCG） system is built in our laboratory. It mainly consists of a MCG data acquisition stage equipped with two high-To superconducting quantum interference device （SQUID） magnetomete...An economical magnetocardiogram （MCG） system is built in our laboratory. It mainly consists of a MCG data acquisition stage equipped with two high-To superconducting quantum interference device （SQUID） magnetometers, a data processing stage with digital filtering and a one-layer μ-metal magnetically shielded room in conjunction with a high-Tc SQUID based active compensation. Experimental results show that a noise level of pico-tesla in MCG profiles, which is necessary for clinical applications, may be achieved with the system. Moreover, stable and convenient operations of the system are demonstrated with simulating MCG measurements.展开更多
文摘The electronic structure of NdFe 10 M 2(M=Ti, V, Cr, Mn, Mo, W) compounds were obtained by the linear muffin tin orbit(LMTO) method, and the micro magnetic properties were examined through the total density of state(TDOS) and the local density of state(DOS). The results suggest that there are two mechanisms which compete with each other and are responsible for variations in magnetic moments of NdFe 10 M 2 with intertitial N(or C) atoms, and the volume expansion leads to the enhancement of Fe Fe exchange interaction at 8i and 8f site, with the result that the magnetic moments at both sites increase. Meanwhile, the magnetic moments at 8j site decrease owing to the hybridization between 3d(Fe) and 2p(N or C) orbits.
基金Supported by the State Key Basic Research Programme of China Grant No 2001CB309301, and the National Natural Science Foundation of China under Grant No 60578029.
文摘A single-photon detector based on an InGaAs avalanche photodiode has been developed for use at telecom wavelengths. A suitable delay and sampling gate modulation circuit are used to prevent positive and negative transient pulses from influencing the detection of true photon induced avalanches. A monostable trigger circuit eliminates the influence of avalanche peak jitter, and a dead time modulation feedback control circuit decreases the afterpulsing. From performance tests we lind that at the optimum operation point, the quantum efficiency is 12% and the dark count rate 1.5 × 10^-6 ns^-1, with a detection rate of 500 kHz.
文摘In this paper, we have developed an algorithm based on singular value decomposition （SVD） for matrix. And the novel SVD algorithm with normalized period of cardiac cycles is presented. The results from real magnetocardiography （MCG） data processing show that the new algorithm is better than the standard one not only in suppressing noises, but also in providing high-fidelity MCG signals.
文摘We present a new least-mean-square algorithm of adaptive filtering to improve the signal to noise ratio for magneto-cardiography data collected with high-temperature SQUID-based magnetometers. By frequently adjusting the adaptive parameter a go systematic optimum values in the course of the programmed procedure, the convergence is accelerated with a highest speed and the minimum steady-state error is obtained simultaneously. This algorithm may be applied to eliminate other non-steady relevant noises as well.
基金Supported by the National Natural Science Foundation of China under Grants Nos 20573084 and 10575085, and NCET of the Ministry of Education of China.
文摘The solvent peak in the intermolecular multiple-quantum coherence spectra can be suppressed by either applying pulse field gradients or spinning sample along the magic angle direction （φ = 54.7）. However, these two methods also suppress the signals of the solute. We design two pulse sequences with only z-axis gradients to suppress the solvent peak without reducing the intensity of solute signals. Compared to the former pulse sequence, the latter pulse sequence is insensitive to the imperfection of pulse flip angles. When the flip angles of the second pulse sequence are purposely deviated 1/10 from the optimal values, the solvent peak is still weak. Theoretical expressions, experimental observations and computer simulations demonstrate that the two methods can be used to effectively suppress solvent peak in intermolecular multiple-quantum coherence spectra.
文摘An economical magnetocardiogram （MCG） system is built in our laboratory. It mainly consists of a MCG data acquisition stage equipped with two high-To superconducting quantum interference device （SQUID） magnetometers, a data processing stage with digital filtering and a one-layer μ-metal magnetically shielded room in conjunction with a high-Tc SQUID based active compensation. Experimental results show that a noise level of pico-tesla in MCG profiles, which is necessary for clinical applications, may be achieved with the system. Moreover, stable and convenient operations of the system are demonstrated with simulating MCG measurements.
