伪火花放电开关的实验研究

设计了典型参数下的伪火花放电开关,进行了空气介质下的放电实验研究.测量了伪火花开关耐受电压与气压关系曲线,确定了产生伪火花放电的气压范围.研究表明,当间隙距离和孔径均为3mm时,开关的伪火花放电气压范围为4～29Pa.实验发现,在伪火花放电和普通辉光放电之间存在一气压阈值,在本文实验条件下,该点的气压为29Pa,此时开关放电电压为2kV.测得了单间隙伪火花开关耐受电压的上限值(40kV),并对此现象进行了理论分析.计算了开关的放电电流密度和电流上升陡度,当导通电流为93kA时,其电流密度大于1 7×104A/cm2,电流上升陡度大于7 8×1010A/s,反峰系数为90%.最后,分析了伪火花开关的设计要点与性能影响因素.

Design and Verification for Dual⁃mode CDFS and High⁃Load Compressor with a Large Flow Regulation Range

This paper presents the design and verification of the dual-mode core driven fan stage(CDFS)and high-load compressor with a large flow regulation range.In view of the characteristics of large flow regulation range of the two modes and high average stage load coefficient,this paper investigates the design technology of the dual-mode high-efficiency compressor with a large flow regulation range and high-load compressor with an average stage load coefficient of 0.504.Building upon this research,the design of the dual-mode CDFS and four-stage compressor is completed,and three-dimensional numerical simulation of the two modes is carried out.Finally,performance experiment is conducted to verify the result of three-dimensional numerical simulation.The experiment results show that the compressor performance is improved for the whole working conditions by using the new design method,which realizes the complete fusion design of the CDFS and high-pressure compressor(HPC).The matching mechanism of stage characteristics of single and double bypass modes and the variation rule of different adjustment angles on performance are studied comprehensively.Furthermore,it effectively reduces the length and weight of compressor,and breaks through the key technologies such as high-load compressor with the average load factor of 0.504.These findings provide valuable data and a methodological foundation for the development of the next generation aeroengine.

Ileocecal valve dysfunction in small intestinal bacterial overgrowth: A pilot study

AIM: To explore whether patients with a defective ileocecal valve (ICV)/cecal distension reflex have small intestinal bacterial overgrowth. METHODS: Using a colonoscope, under conscious sedation, the ICV was intubated and the colonoscope was placed within the terminal ileum (TI). A manometry catheter with 4 pressure channels, spaced 1 cm apart, was passed through the biopsy channel of the colonoscope into the TI. The colonoscope was slowly withdrawn from the TI while the manometry catheter was advanced. The catheter was placed across the ICV so that at least one pressure port was within the TI, ICV and the cecum respectively. Pressures were continuously measured during air insufflation into the cecum, under direct endoscopic visualization, in 19 volunteers. Air was insufflated to a maximum of 40 mmHg to prevent barotrauma. All subjects underwent lactulose breath testing one month after the colonoscopy. The results of the breath tests were compared with the results of the pressures within the ICV during air insufflation. RESULTS: Nineteen subjects underwent colonoscopy with measurements of the ICV pressures after intubation of the ICV with a colonoscope. Initial baseline readings showed no statistical difference in the pressures of the TI and ICV, between subjects with positive lactulose breath tests and normal lactulose breath tests. The average peak ICV pressure during air insufflation into the cecum in subjects with normal lactu-lose breath tests was significantly higher than cecal pressures during air insufflation (49.33 ± 7.99 mmHg vs 16.40 ± 2.14 mmHg, P = 0.0011). The average percentage difference of the area under the pressure curve of the ICV from the cecum during air insufflations in subjects with normal lactulose breath tests was significantly higher (280.72% ± 43.29% vs 100% ± 0%, P = 0.0006). The average peak ICV pressure during air insufflation into the cecum in subjects with positive lactulose breath tests was not significantly different than cecal pressures during air insufflation 21.23 ± 3.52 mmHg vs 16.10 ± 3.39 mmHg. The average percentage difference of the area under the pressure curve of the ICV from the cecum during air insufflation was not significantly different 101.08% ± 7.96% vs 100% ± 0%. The total symptom score for subjects with normal lactulose breath tests and subjects with positive lactu-lose breath tests was not statistically different (13.30 ± 4.09 vs 24.14 ± 6.58). The ICV peak pressures during air insufflations were significantly higher in subjects with normal lactulose breath tests than in subjects with positive lactulose breath tests (P = 0.005). The average percent difference of the area under the pressure curve in the ICV from cecum was significantly higher in subjects with normal lactulose breath tests than in subjects with positive lactulose breath tests (P = 0.0012). Individuals with positive lactulose breath tests demonstrated symptom scores which were significantly higher for the following symptoms: not able to finish normal sized meal, feeling excessively full after meals, loss of appetite and bloating. CONCLUSION: Compared to normal, subjects with a positive lactulose breath test have a defective ICV cecal distension reflex. These subjects also more commonly have higher symptom scores.

Solubilities of Nizatidine in Methanol+Water, Ethanol+Water and i-Propanol+Water from 273.15 to 303.15 K

The solubilities of nizatidine in methanol + water, ethanol + water and i-propanol + water mixtures were determined in the temperature range from 273.15 K to 303.15 K at atmospheric pressure by a static analytical method. The general single model was used to correlate the experimental data, which fits the data very well.

Determination of Paclitaxel Solubility in Carbon Dioxide Using Quartz Crystal Microbalance

A quartz crystal microbalance （QCM） is used to determine the phase equilibrium of paclitaxel-carbon dioxide system in the pressure range of 0-11 MPa and at temperatures of 35 °C,40 °C and 45 °C.The experimental results indicated that gaseous CO2 could be absorbed poorly into paclitaxel.The swelling of paclitaxel film in CO2 was observed before paclitaxel dissolved into supercritical carbon dioxide （ScCO2） with the increase of pressure.It was found that ScCO2 was not a good solvent for paclitaxel.The mole fraction of paclitaxel in ScCO2 was in the range of （4.5×10-9）-（7.8×10-9） under all our experimental conditions.Therefore,a much higher pressure than the CO2 supercritical point and/or a cosolvent must be used in any processes wherever paclitaxel dissolution in ScCO2 is required.

MILD Combustion for Hydrogen and Syngas at Elevated Pressures

As gas recirculation constitutes a fundamental condition for the realization of MILD combustion, it is necessary to determine gas recirculation ratio before designing MILD combustor. MILD combustion model with gas recirculation was used in this simulation work to evaluate the effect of fuel type and pressure on threshold gas recirculation ratio of MILD mode. Ignition delay time is also an important design parameter for gas turbine combustor, this parameter is kinetically studied to analyze the effect of pressure on MILD mixture ignition. Threshold gas recirculation ratio of hydrogen MILD combustion changes slightly and is nearly equal to that of 10 MJ/Nm3syngas in the pressure range of 1-19 atm, under the conditions of 298 K fresh reactant temperature and 1373 K exhaust gas temperature, indicating that MILD regime is fuel flexible. Ignition delay calculation results show that pressure has a negative effect on ignition delay time of 10 MJ/Nm3syngas MILD mixture, because OH mole fraction in MILD mixture drops down as pressure increases, resulting in the delay of the oxidation process.