A digital electro-hydraulic 4-port differential pressure control valve with a novel principle and structure is presented. The valve is designed by applying the regulating pressure technique of a capillary damping tube...A digital electro-hydraulic 4-port differential pressure control valve with a novel principle and structure is presented. The valve is designed by applying the regulating pressure technique of a capillary damping tube and also making full use of double freedom of the spool motion. Thevalve can implement digitizing interface easily. The theoretical analysis and experimental resultsshow that the valve is not only very simple in structure and convenient in use, but also has manygood properties, such as fast response, no-null-shift, etc.展开更多
Protecting occupants or payloads in crashes and blasts is of utmost importance in both moving and immobile structures.One way of achieving this is by using a sacrificial energy absorber.Composite tubes have been studi...Protecting occupants or payloads in crashes and blasts is of utmost importance in both moving and immobile structures.One way of achieving this is by using a sacrificial energy absorber.Composite tubes have been studied as potential energy absorbers due to their ability to fail progressively under axial compression.In this study,the energy absorption capability of these tubes is enhanced by adding hollow glass particles to the matrix.Drop-weight tests are performed on composite tubes,and a digital image correlation(DIC)-based technique is used to capture their load-displacement behaviour.This eliminates the use of electronic data acquisition systems,load cells,and accelerometers.The load-displacement curves of the tubes are obtained from the DIC-based technique and examined to understand their crushing behaviour.Although the mean crush load shows a drop,an increase in crush length is noticed.The specific energy absorbed by the tubes improves with an increase in GMB volume fraction.The addition of 0.1,0.2,0.3 and 0.4 vol fractions of GMB results in the specific energy absorption increasing by6.6%,14.7%,24%and 36.6%,respectively,compared to neat glass fibre-epoxy tubes.Visual examination of the tubes and comparison with tubes subject to quasi-static compression is also performed.展开更多
Electro-hydraulic screw down servo system（HSDS） is widely used in seamless tube rolling mill in western companies.But in Chinese companies,mechanical screw down system（MSDS） is popularly equipped and has a serious...Electro-hydraulic screw down servo system（HSDS） is widely used in seamless tube rolling mill in western companies.But in Chinese companies,mechanical screw down system（MSDS） is popularly equipped and has a serious disadvantage that the roller would often be locked when it is overloaded.For the purpose of designing the first set of domestic twin-roller,four-cylinder and six-framework electro-hydraulic HSDS of seamless tube rolling mill,an experiment system that can simulate the process of seamless tube rolling is constructed.A digital simulation model of the experiment system is built with AMESim software and validated by comparing the simulation results with experiment results.The sudden load response of the screw piston position is studied with the built model and the experiment system.To improve the HSDS＇s positioning accuracy with large load,a hybrid control scheme of combining load disturbance feedforward compensation（LDFC） method based on servo valve＇s pressure-stroke feature and anti-saturation integral control（ASIC） is proposed.Both results of simulation and experiment indicate that the transient response time of the single-roller HSDS with the proposed scheme decreases from 0.65 s to less than 0.2 s without static error.To improve the system dynamic stiffness and production qualified rate,a flow rate feedforward compensation（FFC） control strategy based on oil compressibility to dynamic position error is proposed.This FFC strategy is validated with experiments in which the transient error caused by sudden load is reduced to less than 25% of that without FFC.By extending the simulation model to HSDS of a twin-roller,four-cylinder rolling mill,analyzing the mill deformation,and applying the LDFC,ASIC and FFC to the HSDS,the dynamic performance and positioning accuracy of compensated multi-roller HSDS at biting moment are predicted.The research results provide a theoretical and experimental basis for the design of HSDS of seamless steel tube rolling mill.展开更多
The linearity of the traveling-wave tube is a very important characteristic for a modern communication system. To improve the linearity of the traveling-wave tube at no expense of the saturated output power and overal...The linearity of the traveling-wave tube is a very important characteristic for a modern communication system. To improve the linearity of the traveling-wave tube at no expense of the saturated output power and overall efficiency, a modified pitch profile combined with a small adjustment of operating parameters is proposed. The optimal design of the helix circuit is evaluated theoretically by a large signal analysis, and the experimental test is also carried out to make a comparison of performance between the novel and original designed traveling-wave tubes. The experiments show that the saturated output powers and efficiencies of these two tubes are close to each other, while the linearity of the traveling-wave tube is obviously improved. The total phase shift and AM/PM conversion at saturation of the novel tube, averaged over the operating band, are only 30.6°/d B and 2.5°/d B, respectively, which are 20.1°/d B and 1.6°/d B lower than those of the original tube, respectively. Moreover, the third-order intermodulation of the novel tube is up to 2.2 d Bc lower than that of the original tube.展开更多
目的探讨麻醉专业住院医师规范化培训医师使用数字压力表进行气管导管气囊充气触感训练的培训效果。方法选择2021年6—9月滨州医学院附属医院的麻醉专业住院医师规范化培训(简称“住培”)医师44名,按照随机数字表法,分为试验组和对照组...目的探讨麻醉专业住院医师规范化培训医师使用数字压力表进行气管导管气囊充气触感训练的培训效果。方法选择2021年6—9月滨州医学院附属医院的麻醉专业住院医师规范化培训(简称“住培”)医师44名,按照随机数字表法,分为试验组和对照组,每组22名。试验组住培医师在数字压力表指导下进行正确压力范围内的气管导管气囊充气,对照组住培医师使用传统的主观触感法进行气囊充气。两组住培医师均采用主观触感法进行气囊充气,使用数字压力表测量两组住培医师的气囊充气压力情况。分析测试阶段的两组气囊压力情况、两组患者术后咽痛的发生率及住培医师对此次培训的满意度。结果两组患者的美国麻醉医师协会健康状况分级(American Society of Anesthesiologists,ASA)及机械通气时间比较无统计学差异(P<0.05)。在试验组患者气囊压力低于对照组患者气囊压力,差异有统计学意义(P<0.05);试验组患者术后咽痛发生率低于对照组,差异有统计学意义(P<0.05)。试验组住培医师对此次培训的满意度更高,差异有统计学意义(P<0.05)。结论使用数字压力表训练麻醉专业住培医师气囊充气的触感,培养正确气囊压力范围内的主观感觉,减少麻醉相关并发症,有利于提高培训质量和教学满意度。展开更多
文摘A digital electro-hydraulic 4-port differential pressure control valve with a novel principle and structure is presented. The valve is designed by applying the regulating pressure technique of a capillary damping tube and also making full use of double freedom of the spool motion. Thevalve can implement digitizing interface easily. The theoretical analysis and experimental resultsshow that the valve is not only very simple in structure and convenient in use, but also has manygood properties, such as fast response, no-null-shift, etc.
基金supported by the Department of Science and Technology(DST,India)through the Indo-Russian collaborative project scheme。
文摘Protecting occupants or payloads in crashes and blasts is of utmost importance in both moving and immobile structures.One way of achieving this is by using a sacrificial energy absorber.Composite tubes have been studied as potential energy absorbers due to their ability to fail progressively under axial compression.In this study,the energy absorption capability of these tubes is enhanced by adding hollow glass particles to the matrix.Drop-weight tests are performed on composite tubes,and a digital image correlation(DIC)-based technique is used to capture their load-displacement behaviour.This eliminates the use of electronic data acquisition systems,load cells,and accelerometers.The load-displacement curves of the tubes are obtained from the DIC-based technique and examined to understand their crushing behaviour.Although the mean crush load shows a drop,an increase in crush length is noticed.The specific energy absorbed by the tubes improves with an increase in GMB volume fraction.The addition of 0.1,0.2,0.3 and 0.4 vol fractions of GMB results in the specific energy absorption increasing by6.6%,14.7%,24%and 36.6%,respectively,compared to neat glass fibre-epoxy tubes.Visual examination of the tubes and comparison with tubes subject to quasi-static compression is also performed.
基金supported by National Natural Science Foundation of China(Grant No.50575156)Open Fund of the State Key Laboratory of Fluid Power Transmission and Control of Zhejiang University,China(Grant No.GZKF-2008006)
文摘Electro-hydraulic screw down servo system（HSDS） is widely used in seamless tube rolling mill in western companies.But in Chinese companies,mechanical screw down system（MSDS） is popularly equipped and has a serious disadvantage that the roller would often be locked when it is overloaded.For the purpose of designing the first set of domestic twin-roller,four-cylinder and six-framework electro-hydraulic HSDS of seamless tube rolling mill,an experiment system that can simulate the process of seamless tube rolling is constructed.A digital simulation model of the experiment system is built with AMESim software and validated by comparing the simulation results with experiment results.The sudden load response of the screw piston position is studied with the built model and the experiment system.To improve the HSDS＇s positioning accuracy with large load,a hybrid control scheme of combining load disturbance feedforward compensation（LDFC） method based on servo valve＇s pressure-stroke feature and anti-saturation integral control（ASIC） is proposed.Both results of simulation and experiment indicate that the transient response time of the single-roller HSDS with the proposed scheme decreases from 0.65 s to less than 0.2 s without static error.To improve the system dynamic stiffness and production qualified rate,a flow rate feedforward compensation（FFC） control strategy based on oil compressibility to dynamic position error is proposed.This FFC strategy is validated with experiments in which the transient error caused by sudden load is reduced to less than 25% of that without FFC.By extending the simulation model to HSDS of a twin-roller,four-cylinder rolling mill,analyzing the mill deformation,and applying the LDFC,ASIC and FFC to the HSDS,the dynamic performance and positioning accuracy of compensated multi-roller HSDS at biting moment are predicted.The research results provide a theoretical and experimental basis for the design of HSDS of seamless steel tube rolling mill.
基金Project supported by the National Natural Science Foundation of China(Grant No.61401430)
文摘The linearity of the traveling-wave tube is a very important characteristic for a modern communication system. To improve the linearity of the traveling-wave tube at no expense of the saturated output power and overall efficiency, a modified pitch profile combined with a small adjustment of operating parameters is proposed. The optimal design of the helix circuit is evaluated theoretically by a large signal analysis, and the experimental test is also carried out to make a comparison of performance between the novel and original designed traveling-wave tubes. The experiments show that the saturated output powers and efficiencies of these two tubes are close to each other, while the linearity of the traveling-wave tube is obviously improved. The total phase shift and AM/PM conversion at saturation of the novel tube, averaged over the operating band, are only 30.6°/d B and 2.5°/d B, respectively, which are 20.1°/d B and 1.6°/d B lower than those of the original tube, respectively. Moreover, the third-order intermodulation of the novel tube is up to 2.2 d Bc lower than that of the original tube.
文摘目的探讨麻醉专业住院医师规范化培训医师使用数字压力表进行气管导管气囊充气触感训练的培训效果。方法选择2021年6—9月滨州医学院附属医院的麻醉专业住院医师规范化培训(简称“住培”)医师44名,按照随机数字表法,分为试验组和对照组,每组22名。试验组住培医师在数字压力表指导下进行正确压力范围内的气管导管气囊充气,对照组住培医师使用传统的主观触感法进行气囊充气。两组住培医师均采用主观触感法进行气囊充气,使用数字压力表测量两组住培医师的气囊充气压力情况。分析测试阶段的两组气囊压力情况、两组患者术后咽痛的发生率及住培医师对此次培训的满意度。结果两组患者的美国麻醉医师协会健康状况分级(American Society of Anesthesiologists,ASA)及机械通气时间比较无统计学差异(P<0.05)。在试验组患者气囊压力低于对照组患者气囊压力,差异有统计学意义(P<0.05);试验组患者术后咽痛发生率低于对照组,差异有统计学意义(P<0.05)。试验组住培医师对此次培训的满意度更高,差异有统计学意义(P<0.05)。结论使用数字压力表训练麻醉专业住培医师气囊充气的触感,培养正确气囊压力范围内的主观感觉,减少麻醉相关并发症,有利于提高培训质量和教学满意度。
