钍基熔盐堆(Thorium Molten Salt Reactor,TMSR)是一种第四代反应堆。当反应堆运行时,中子探测环境温度可达550℃以上,因此,中子探测器的应用会受到极大的限制。裂变室(fission chamber)是中子探测器中最重要的类型之一,对高温裂变室(hi...钍基熔盐堆(Thorium Molten Salt Reactor,TMSR)是一种第四代反应堆。当反应堆运行时,中子探测环境温度可达550℃以上,因此,中子探测器的应用会受到极大的限制。裂变室(fission chamber)是中子探测器中最重要的类型之一,对高温裂变室(high temperature fission chamber,HTFC)的研究有助于TMSR测量方案的制定和对中子探测器应用的研究。为此,利用西安脉冲堆和便携式加热器,在17.1~550℃的温度范围内对Photonis的裂变室(型号:CFUE32)进行了实验测量。实验获得了不同温度下,探测器的计数率—电压曲线和脉冲幅度谱。实验结果表明,当温度在450℃以上时,探测器性能有明显的衰退。展开更多
This paper presents an LC VCO with auto-amplitude control （AAC）, in which pMOS FETs are used,and the varactors are directly connected to ground to widen the linear range of Kvco. The AAC circuitry adds little noise ...This paper presents an LC VCO with auto-amplitude control （AAC）, in which pMOS FETs are used,and the varactors are directly connected to ground to widen the linear range of Kvco. The AAC circuitry adds little noise to the VCO but provides it with robust performance over a wide temperature and carrier frequency range.The VCO is fabricated in a chartered 50GHz 0.35μm SiGe BiCMOS process. The measurements show that it has - 127. 27dBc/Hz phase noise at 1MHz offset and a linear gain of 32.4MHz/V between 990MHz and 1.14GHz.The whole circuit draws 6. 6mA current from 5V supply.展开更多
Converters with pulse width modulation are used for connections between the direct current （DC） and alternating current （AC） networks, e.g., in uninterrupted power supply systems, AC electromotor drives, for power...Converters with pulse width modulation are used for connections between the direct current （DC） and alternating current （AC） networks, e.g., in uninterrupted power supply systems, AC electromotor drives, for powering induction furnaces, in audio technique. Spectrum of signals sampled by pulse amplitude modulation and output voltage spectrum of the converter with pulse width modulation have similar properties. Spectrum of signals sampled by pulse amplitude modulation contains a harmonic of frequency equal to the frequency of the modulating signal and the harmonics of frequencies equal to the sum of frequency of the modulating signal and multiples of the sampling frequency. The output voltage spectrum of the converter with bipolar pulse width modulation contains harmonic of frequency equal to the frequency of the modulating signal and harmonics of frequencies equal to sum of the frequency of the modulating signal and multiples of the frequency of the carrier signal. It also contains harmonics of frequencies equal to the sum of the multiples of the frequency of the modulating signal and the multiples of the carrier signal. The comparison analysis was carried out for the harmonics of the output voltage of the converter with bipolar pulse width modulation in time domain. The dependency of the amplitudes and frequency spectrum on the wave forms of the carrier signal and modulating signal was shown. Similarity of the output voltage spectrum of the converter and signal spectrum sampled by the pulse width modulation was also shown. Key words： Output voltage converter with bipolar pulse width modulation, spectral analysis, Fourier series, carrier signal, reference signal.展开更多
High performance piezoelectric ceramics with high Curie temperatures(TC) are the bottle necks of relevant high temperature devices. In this study, the electrical performance and microstructure of Li and Mn codoped Aur...High performance piezoelectric ceramics with high Curie temperatures(TC) are the bottle necks of relevant high temperature devices. In this study, the electrical performance and microstructure of Li and Mn codoped Aurivillius-type composite ceramics with a composition Ca_(0.99-x_Bi_(6.99+x)(Li Mn)_(0.01) Nb Ti_5O_(24)(x = 0–0.8) were systematically investigated. The results indicated that uniform intergrowth structure with a lattice similar to that of the end member CBT could be formed at a low x value(x < 0.4). Phase separation occurred when more A-site Ca^(2+) ions were replaced by Bi^(3+) ions. Nevertheless, all composite samples showed d_(33) values about 2 to 3 times of that of the constituent phase Ca Bi_4Ti_4O_(15) and Bi_3 Ti NbO_9 with still a high depolarization temperature. The performance of the samples was found to be related to the density and larger lattice distortion along the polarization a axis. The results also demonstrated that formation of the compound system was an effective way in improving the performance of Aurivillius-type high TC piezoelectric ceramics.展开更多
文摘钍基熔盐堆(Thorium Molten Salt Reactor,TMSR)是一种第四代反应堆。当反应堆运行时,中子探测环境温度可达550℃以上,因此,中子探测器的应用会受到极大的限制。裂变室(fission chamber)是中子探测器中最重要的类型之一,对高温裂变室(high temperature fission chamber,HTFC)的研究有助于TMSR测量方案的制定和对中子探测器应用的研究。为此,利用西安脉冲堆和便携式加热器,在17.1~550℃的温度范围内对Photonis的裂变室(型号:CFUE32)进行了实验测量。实验获得了不同温度下,探测器的计数率—电压曲线和脉冲幅度谱。实验结果表明,当温度在450℃以上时,探测器性能有明显的衰退。
文摘This paper presents an LC VCO with auto-amplitude control （AAC）, in which pMOS FETs are used,and the varactors are directly connected to ground to widen the linear range of Kvco. The AAC circuitry adds little noise to the VCO but provides it with robust performance over a wide temperature and carrier frequency range.The VCO is fabricated in a chartered 50GHz 0.35μm SiGe BiCMOS process. The measurements show that it has - 127. 27dBc/Hz phase noise at 1MHz offset and a linear gain of 32.4MHz/V between 990MHz and 1.14GHz.The whole circuit draws 6. 6mA current from 5V supply.
文摘Converters with pulse width modulation are used for connections between the direct current （DC） and alternating current （AC） networks, e.g., in uninterrupted power supply systems, AC electromotor drives, for powering induction furnaces, in audio technique. Spectrum of signals sampled by pulse amplitude modulation and output voltage spectrum of the converter with pulse width modulation have similar properties. Spectrum of signals sampled by pulse amplitude modulation contains a harmonic of frequency equal to the frequency of the modulating signal and the harmonics of frequencies equal to the sum of frequency of the modulating signal and multiples of the sampling frequency. The output voltage spectrum of the converter with bipolar pulse width modulation contains harmonic of frequency equal to the frequency of the modulating signal and harmonics of frequencies equal to sum of the frequency of the modulating signal and multiples of the frequency of the carrier signal. It also contains harmonics of frequencies equal to the sum of the multiples of the frequency of the modulating signal and the multiples of the carrier signal. The comparison analysis was carried out for the harmonics of the output voltage of the converter with bipolar pulse width modulation in time domain. The dependency of the amplitudes and frequency spectrum on the wave forms of the carrier signal and modulating signal was shown. Similarity of the output voltage spectrum of the converter and signal spectrum sampled by the pulse width modulation was also shown. Key words： Output voltage converter with bipolar pulse width modulation, spectral analysis, Fourier series, carrier signal, reference signal.
基金supported by the National Natural Science Foundation of China(Grant Nos.51302015&11574346)the National Basic Research Program of China(“973”Project)(Grant No.2013CB632900)+1 种基金the Overseas Talent Foundation of Beijing Academy of Science and Technology(Grant No.OTP-2013-001)the Open Foundation of the State Key Laboratory of New Ceramics and Fine Processing of Tsinghua University
文摘High performance piezoelectric ceramics with high Curie temperatures(TC) are the bottle necks of relevant high temperature devices. In this study, the electrical performance and microstructure of Li and Mn codoped Aurivillius-type composite ceramics with a composition Ca_(0.99-x_Bi_(6.99+x)(Li Mn)_(0.01) Nb Ti_5O_(24)(x = 0–0.8) were systematically investigated. The results indicated that uniform intergrowth structure with a lattice similar to that of the end member CBT could be formed at a low x value(x < 0.4). Phase separation occurred when more A-site Ca^(2+) ions were replaced by Bi^(3+) ions. Nevertheless, all composite samples showed d_(33) values about 2 to 3 times of that of the constituent phase Ca Bi_4Ti_4O_(15) and Bi_3 Ti NbO_9 with still a high depolarization temperature. The performance of the samples was found to be related to the density and larger lattice distortion along the polarization a axis. The results also demonstrated that formation of the compound system was an effective way in improving the performance of Aurivillius-type high TC piezoelectric ceramics.
