Low frequency vibrations induced by underground railways have attracted increasing attention in recent years. To obtain the characteristics of low frequency vibrations and the low frequency performance of a floating s...Low frequency vibrations induced by underground railways have attracted increasing attention in recent years. To obtain the characteristics of low frequency vibrations and the low frequency performance of a floating slab track (FST), low frequency vibration tests on an FST in an underground laboratory at Beijing Jiaotong University were carried out. The FST and an unbalanced shaker SBZ30 for dynamic simulation were designed for use in low frequency vibration experiments. Vibration measurements were performed on the bogie of the unbalanced shaker, the rail, the slab, the tunnel invert, the tunnel wall, the tunnel apex, and on the ground surface at distances varying from 0 to 80 m from the track. Measurements were also made on several floors of an adjacent building. Detailed results of low frequency vibration tests were reported. The attenuation of low frequency vibrations with the distance from the track was presented, as well as the responses of different floors of the building. The experimental results could be regarded as a reference for developing methods to control low frequency vibrations and for adopting countermeasures.展开更多
目的考察Fe_(3)O_(4)纳米颗粒在低频振动磁场(low-frequency vibrating magnetic field,VMF)驱动下通过磁场机械力杀伤肿瘤细胞的效果。方法通过共沉淀法合成一种磁性强、具有不规则形貌的立方相Fe_(3)O_(4)纳米颗粒。将其置于本课题组...目的考察Fe_(3)O_(4)纳米颗粒在低频振动磁场(low-frequency vibrating magnetic field,VMF)驱动下通过磁场机械力杀伤肿瘤细胞的效果。方法通过共沉淀法合成一种磁性强、具有不规则形貌的立方相Fe_(3)O_(4)纳米颗粒。将其置于本课题组自制的VMF中,研究其介导的磁场机械力对肿瘤细胞的杀伤效果。结果单纯施加VMF对细胞活力无影响;加入Fe_(3)O_(4)纳米颗粒后,细胞活力随VMF处理时间和Fe_(3)O_(4)纳米颗粒浓度的增加而降低,受损细胞释放的乳酸脱氢酶也随磁场处理时间延长而增加。结论不规则形貌Fe_(3)O_(4)纳米颗粒在VMF下可将机械力转移到肿瘤细胞,破坏细胞结构,导致细胞死亡;所采用的VMF装置结构简单、使用安全、操作方便。所采用的磁性粒子及其杀伤肿瘤细胞的方法,有临床转化潜力。展开更多
A continuum based model is presented which identifies a favorable set of operational conditions whereby an effective and efficient electromagnetically induced vibratory motion can proceed within an induction system.Sp...A continuum based model is presented which identifies a favorable set of operational conditions whereby an effective and efficient electromagnetically induced vibratory motion can proceed within an induction system.Specifically, an analytical assessment is presented for the electromagnetic field and the electromagnetically induced acoustic field, with parametric factors incorporated into the model to permit a normal modes solution for the acoustic field which here is sensitive to the compliance of both the molten metal and the wall,as well as electromagnetic properties of the metal.A parametric analysis is presented which identifies the importance of matching the mechanical impedances of the melt-wall configuration so that the generation of acoustic energy within the melt system can be more effectively utilized.Relatively straight-forward calculations,presented for the acoustic field,may provide a more computationally efficient means for implementing process simulation studies for these systems.展开更多
The motion of an inductively heated fluid volume of cylindrical shape is assessed based on time dependent oscillatory components of the Lorentz force.The applications considered include vibratory motion in a channel i...The motion of an inductively heated fluid volume of cylindrical shape is assessed based on time dependent oscillatory components of the Lorentz force.The applications considered include vibratory motion in a channel induction furnace and vibratory motion in an electromagnetically excited direct chill casting.The governing equations for the resulting magnetoacoustic problem are presented with the acoustic field solutions expressed in terms of normal modes. Closed form expressions are developed for the velocity,pressure and phase relationships between the excitation and the response.Calculations are prescribed for the pressure in both the channel furnace and the direct chill casting,with the calculational results from the casting application suggesting that,roughly,a two-fold increase in the effective peak acoustic pressure can be achieved by superimposing on the AC electromagnetic field a DC magnetic field of strength sufficient to match the peak alternating magnetic field.A procedure is also outlined for developing field descriptions of the velocity and pressure which can be effected in a MATLAB environ.展开更多
基金Project supported by the National Natural Science Foundation of China (No. 51008017)the Fundamental Research Funds for the Central Universities of China (Nos. 2009JBM074 and 2009JBM075)
文摘Low frequency vibrations induced by underground railways have attracted increasing attention in recent years. To obtain the characteristics of low frequency vibrations and the low frequency performance of a floating slab track (FST), low frequency vibration tests on an FST in an underground laboratory at Beijing Jiaotong University were carried out. The FST and an unbalanced shaker SBZ30 for dynamic simulation were designed for use in low frequency vibration experiments. Vibration measurements were performed on the bogie of the unbalanced shaker, the rail, the slab, the tunnel invert, the tunnel wall, the tunnel apex, and on the ground surface at distances varying from 0 to 80 m from the track. Measurements were also made on several floors of an adjacent building. Detailed results of low frequency vibration tests were reported. The attenuation of low frequency vibrations with the distance from the track was presented, as well as the responses of different floors of the building. The experimental results could be regarded as a reference for developing methods to control low frequency vibrations and for adopting countermeasures.
文摘目的考察Fe_(3)O_(4)纳米颗粒在低频振动磁场(low-frequency vibrating magnetic field,VMF)驱动下通过磁场机械力杀伤肿瘤细胞的效果。方法通过共沉淀法合成一种磁性强、具有不规则形貌的立方相Fe_(3)O_(4)纳米颗粒。将其置于本课题组自制的VMF中,研究其介导的磁场机械力对肿瘤细胞的杀伤效果。结果单纯施加VMF对细胞活力无影响;加入Fe_(3)O_(4)纳米颗粒后,细胞活力随VMF处理时间和Fe_(3)O_(4)纳米颗粒浓度的增加而降低,受损细胞释放的乳酸脱氢酶也随磁场处理时间延长而增加。结论不规则形貌Fe_(3)O_(4)纳米颗粒在VMF下可将机械力转移到肿瘤细胞,破坏细胞结构,导致细胞死亡;所采用的VMF装置结构简单、使用安全、操作方便。所采用的磁性粒子及其杀伤肿瘤细胞的方法,有临床转化潜力。
文摘A continuum based model is presented which identifies a favorable set of operational conditions whereby an effective and efficient electromagnetically induced vibratory motion can proceed within an induction system.Specifically, an analytical assessment is presented for the electromagnetic field and the electromagnetically induced acoustic field, with parametric factors incorporated into the model to permit a normal modes solution for the acoustic field which here is sensitive to the compliance of both the molten metal and the wall,as well as electromagnetic properties of the metal.A parametric analysis is presented which identifies the importance of matching the mechanical impedances of the melt-wall configuration so that the generation of acoustic energy within the melt system can be more effectively utilized.Relatively straight-forward calculations,presented for the acoustic field,may provide a more computationally efficient means for implementing process simulation studies for these systems.
基金the Center for International Programs at the University of Dayton for support that facilitated collaborative aspects of this study
文摘The motion of an inductively heated fluid volume of cylindrical shape is assessed based on time dependent oscillatory components of the Lorentz force.The applications considered include vibratory motion in a channel induction furnace and vibratory motion in an electromagnetically excited direct chill casting.The governing equations for the resulting magnetoacoustic problem are presented with the acoustic field solutions expressed in terms of normal modes. Closed form expressions are developed for the velocity,pressure and phase relationships between the excitation and the response.Calculations are prescribed for the pressure in both the channel furnace and the direct chill casting,with the calculational results from the casting application suggesting that,roughly,a two-fold increase in the effective peak acoustic pressure can be achieved by superimposing on the AC electromagnetic field a DC magnetic field of strength sufficient to match the peak alternating magnetic field.A procedure is also outlined for developing field descriptions of the velocity and pressure which can be effected in a MATLAB environ.
