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991.
滑块与轨面阻尼对实验结果的影响 总被引:3,自引:0,他引:3
在气垫导轨实验装置的使用过程中,实验误差,大致从以下四个方面引起:(1)导轨变形;(2)计时、计速装置的光电转换系统的影响;(3)滑块在运动中受各种阻尼;(4)气源供气量、气压不适或不稳定.在本文中主要探讨滑块与滑面阻尼对实验结果的影响做一定量的分析. 相似文献
992.
Determinations of plasma density and decay time in the hollow cathode discharge by microwave transmission 下载免费PDF全文
The microwave (MW) transmission method is employed to measure both the plasma density and the plasma decay time in the hollow cathode discharge (HCD) in argon at low pressure. The plasma density in DC-driven or pulsed HCD is on the order of 1012 cm-3, which can block the X-band MW effectively. In the case of pulsed HCD, the MW transmittance shows the same waveform as the pulsed current during the rising edge if the driving frequency is low, but with a longer delay during the falling edge. The MW transmittance reaches a constant low level when the driving frequency is high enough. The plasma decay time in the HCD system is measured to be about 100 μs around a pressure of 120 Pa. The ambipolar diffusion is considered to be the major mechanism in the decay process. 相似文献
993.
Effects of density profile and multi-species target on laser-heated thermal-pressure-driven shock wave acceleration 下载免费PDF全文
The shock wave acceleration of ions driven by laser-heated thermal pressure is studied through one-dimensional particle-in-cell simulation and analysis. The generation of high-energy mono-energetic protons in recent experiments (D. Haberberger et al., 2012 Nat. Phys. 8 95) is attributed to the use of exponentially decaying density profile of the plasma target. It does not only keep the shock velocity stable but also suppresses the normal target normal sheath acceleration. The effects of target composition are also examined, where a similar collective velocity of all ion species is demonstrated. The results also give some reference to future experiments of producing energetic heavy ions. 相似文献
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996.
电容去离子(CDI)技术是一种新型的海水淡化技术,因其具有环境友好、操作简单和能耗低等优势而受到广大研究者的关注。在CDI技术中,电吸附的性能与装置的构型有着密切的联系。本文综述了目前常见的几种CDI装置,包括膜电容去离子(MCDI)、流动电极电容去离子(FCDI)、杂化电极电容去离子(HCDI)、反式电极电容去离子(i-CDI)以及脱盐电池(DB),对这几种装置的发展历程和装置构型进行介绍,最后,对CDI的装置构型在未来的研究发展方向进行了展望,以期为CDI装置在电脱盐领域的研究和应用提供参考。 相似文献
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998.
Kerosene is an ideal endothermic hydrocarbon. Its pyrolysis plays a significant role in the thermal protection for high-speed aircraft. Before it reacts, kerosene experiences thermal decomposition in the heat exchanger and produces cracked products. Thus, to use cracked kerosene instead of pure kerosene, knowledge of their ignition properties is needed. In this study, ignition delay times of cracked kerosene/air and kerosene/air were measured in a heated shock tube at temperatures of 657–1333 K, an equivalence ratio of 1.0, and pressures of 1.01 × 105–10.10 × 105 Pa. Ignition delay time was defined as the time interval between the arrival of the reflected shock and the occurrence of the steepest rise of excited-state CH species (CH*) emission at the sidewall measurement location. Pure helium was used as the driver gas for high-temperature measurements in which test times needed to be shorter than 1.5 ms, and tailored mixtures of He/Ar were used when test times could reach up to 15 ms. Arrhenius-type formulas for the relationship between ignition delay time and ignition conditions (temperature and pressure) were obtained by correlating the measured high-temperature data of both fuels. The results reveal that the ignition delay times of both fuels are close, and an increase in the pressure or temperature causes a decrease in the ignition delay time in the high-temperature region (> 1000 K). Both fuels exhibit similar high-temperature ignition delay properties, because they have close pressure exponents (cracked kerosene: τign∝P-0.85; kerosene:τign∝P-0.83) and global activation energies (cracked kerosene: Ea = 143.37 kJ·mol-1; kerosene: Ea = 144.29 kJ·mol-1). However, in the low-temperature region (< 1000 K), ignition delay characteristics are quite different. For cracked kerosene/air, while the decrease in the temperature still results in an increase in the ignition delay time, the negative temperature coefficient (NTC) of ignition delay does not occur, and the low-temperature ignition data still can be correlated by an Arrhenius-type formula with a much smaller global activation energy compared to that at high temperatures. However, for kerosene/air, this NTC phenomenon was observed, and the Arrhenius-type formula fails to correlate its low-temperature ignition data. At temperatures ranging from 830 to 1000 K, the cracked kerosene ignites faster than the kerosene; at temperatures below 830 K, kerosene ignition delay times become much shorter than those of cracked kerosene. Surrogates for cracked kerosene and kerosene are proposed based on the H/C ratio and average molecular weight in order to simulate ignition delay times for cracked kerosene/air and kerosene/air. The simulation results are in fairly good agreement with current experimental data for the two fuels at high temperatures (> 1000 K). However, in the low-temperature NTC region, the results are in very good agreement with kerosene ignition delay data but disagree with cracked kerosene ignition delay data. The comparison between experimental data and model predictions indicates that refinement of the reaction mechanisms for cracked kerosene and kerosene is needed. These test results are helpful to understand ignition properties of cracked kerosene in developing regenerative cooling technology for high-speed aircraft. 相似文献
1000.
本研究以镍离子为模板离子,水杨醛缩乙二胺席夫碱为功能单体,乙二醇二甲基丙烯酸酯为交联剂,以烷基化硅胶为载体,通过表面印迹法在微波条件下制备了镍离子印迹聚合物(IIP)。用傅里叶红外光谱(FITR)和扫描电子显微镜(SEM)对离子印迹聚合物进行了表征。通过研究吸附过程中pH值、温度和初始浓度等因素对IIP吸附性能的影响,确定最佳吸附条件为:pH=8,温度为30℃,吸附时间为40 min,浓度为30 mg·L~(-1)。结果表明,Langmuir等温线可以较好地描述IIP吸附过程,最大吸附量为24.23 mg·g~(-1),与饱和吸附量24.97mg·g~(-1)基本相符,符合准二级动力学模型。此外,对IIP进行了镍离子的选择吸附性能研究,其选择性系数远大于1,表明该聚合物有良好的选择性吸附性能。 相似文献