On the basis of the survey of underground noise in Jinggezhuang and Donghuantuo mines, Kailuan Group, noise radiation intensity, noise propagation properties and noise frequency-spectrum characteristics of underground...On the basis of the survey of underground noise in Jinggezhuang and Donghuantuo mines, Kailuan Group, noise radiation intensity, noise propagation properties and noise frequency-spectrum characteristics of underground equipment were studied at different work conditions. The result indicates that the noise source intensity surpasses the noise limit requirement of 85 dBA completely. Nearly 70% noise sources exceed the noise limit of 90 dBA, and some are over 100 dBA. Noise attenua- tion in semi-free field environment on the ground is significantly different from underground far-field environment of noise source in coal mines. Noise of these regions, where staffs are long and highly concentrated, exceeds 85 dBA, the basic noise limit. The noise frequency-spectrum presents the wideband characteristics. Especially in the main frequency of the language communication 500, 1 000 and 2 000 Hz, the octave band of noise performs obviously.展开更多
Micro arc oxidation(MAO) and electrophoretic deposition(EPD) process are employed to fabricate a dense coating on magnesium alloy to protect it from corrosion in engineering application. The EPD film changes the dampi...Micro arc oxidation(MAO) and electrophoretic deposition(EPD) process are employed to fabricate a dense coating on magnesium alloy to protect it from corrosion in engineering application. The EPD film changes the damping characteristic of magnesium alloy, and both the MAO and EPD process change the bending stiffness of samples being treated. Damping loss factor(DLF) test and sound transmission experiments were carried out for AZ31 B magnesium alloy with coating fabricated by MAO and EPD processes. The results indicate that DLF is improved in frequency range from 0-850 Hz. Bending stiffness of the samples is improved with MAO and EPD treatment. As a result, the sound transmission loss(LST) is improved in the stiffness control stage of the sound transmission verse frequency curve. To the samples by electrophoresis process, the LST is improved in frequency range from 2500-3200 Hz, because the damping loss factor is improved with EPD process. The results are useful for the surface treatment to enhance the damping loss factor, LST and widespread application of magnesium alloy while improving the corrosion resistance.展开更多
AZ31B magnesium alloy was subjected to friction stir welding with various welding parameters. The equivalent Young's moduli of the friction stir welded samples and the base material were obtained by the three-poin...AZ31B magnesium alloy was subjected to friction stir welding with various welding parameters. The equivalent Young's moduli of the friction stir welded samples and the base material were obtained by the three-point method, and their transverse rigidities were obtained as well. Furthermore, the sound transmission characteristics of those samples were experimentally studied by four-microphone impedance tube method. The experimental results indicate that the transverse rigidities of the friction stir welded samples were only 79%, 83% and 92% of those of the base material, respectively. The sound transmission losses of the processed samples were also lower, which was largely due to the reduction of transverse rigidities induced by the decrease of equivalent Young's moduli.展开更多
Modern public buildings, such as multiplex cinemas and theaters, along with application of state of the art sound effects bring high acoustic insulation demands. Cinemas are often a part of building complexes such as ...Modern public buildings, such as multiplex cinemas and theaters, along with application of state of the art sound effects bring high acoustic insulation demands. Cinemas are often a part of building complexes such as shopping malls with subjects that produce serious level of noise and vibrations. Apart to regular use of polyurethane in thermal insulation purposes, it is widely used in field of acoustic insulation. Usage of polyurethane foam pads, with specific dynamic characteristics, as a base for structure supports gives a wide range of possibilities in controlling the amount of structural noise and vibrations transferred to the structure. Structure itself and acoustical pads becomes an integral system that behaves together and need to be analyzed as a whole in extensive design. Dynamic characteristics of acoustic pads depend on stress level and in same time they represent elastic supports to the structure and therefore analyzes and design is an iterative process. In other way, introduce of non-conventional material in bearing structure brings some issues, such as transfer of shear forces, that has to be governed by proper structural detailing. There are several possibilities of application in bearing structures, such as above and below steel structure. This paper gives an overall view on polyurethane as material, construction and design principles and example of usage of acoustic pads in steel structure of＂Ster＂ cineplex in Belgrade.展开更多
Drilling fluid is a common flushing medium used in pile foundation, geological drilling and petroleum drilling. Study on ultrasonic propagation properties in drilling fluid is of vital importance, not only for develop...Drilling fluid is a common flushing medium used in pile foundation, geological drilling and petroleum drilling. Study on ultrasonic propagation properties in drilling fluid is of vital importance, not only for developing equipments to non-contact measuring concrete casting level for bored pile, but also for developing equip- ments considering drilling fluid as signal channel. The existence of clay particles makes the ultrasonic propagation and attenuation in drilling fluid much different from pure water. In order to know the relation among ultrasound frequency, slun-y density and depth, a series of laboratory experiments about ultrasound propagation in water-based bentonite slurry were finished. Wavelet method was adopted to process the gained original waves of ultrasonic propagation in slurry, so we knew the velocity and attenuation coefficient of ultrasound propagated in different drilling fluids with different density. The first group experiments shows that with density of drilling fluid increase, ultrasonic velocity will decrease but attenuation coefficient will increase if ultrasonic frequency keep constant. The second group experiments shows that the power of ultrasound will intensify in small bore hole, the attenuation coefficient is much smaller than theoretical value.展开更多
基金Supported by the National Natural Science Foundation of China （50974061） the Natural Science Foundation of Hebei Province （E2009001420）
文摘On the basis of the survey of underground noise in Jinggezhuang and Donghuantuo mines, Kailuan Group, noise radiation intensity, noise propagation properties and noise frequency-spectrum characteristics of underground equipment were studied at different work conditions. The result indicates that the noise source intensity surpasses the noise limit requirement of 85 dBA completely. Nearly 70% noise sources exceed the noise limit of 90 dBA, and some are over 100 dBA. Noise attenua- tion in semi-free field environment on the ground is significantly different from underground far-field environment of noise source in coal mines. Noise of these regions, where staffs are long and highly concentrated, exceeds 85 dBA, the basic noise limit. The noise frequency-spectrum presents the wideband characteristics. Especially in the main frequency of the language communication 500, 1 000 and 2 000 Hz, the octave band of noise performs obviously.
基金Project(2011BAE22B05)supported by National Technology R&D Program in the 12th Five year Plan of ChinaProject(2011DFA50900)supported by the Canada-China-USA Collaborative Research&Development ProjectProject(51071121)supported by the National Natural Science Foundation of China
文摘Micro arc oxidation(MAO) and electrophoretic deposition(EPD) process are employed to fabricate a dense coating on magnesium alloy to protect it from corrosion in engineering application. The EPD film changes the damping characteristic of magnesium alloy, and both the MAO and EPD process change the bending stiffness of samples being treated. Damping loss factor(DLF) test and sound transmission experiments were carried out for AZ31 B magnesium alloy with coating fabricated by MAO and EPD processes. The results indicate that DLF is improved in frequency range from 0-850 Hz. Bending stiffness of the samples is improved with MAO and EPD treatment. As a result, the sound transmission loss(LST) is improved in the stiffness control stage of the sound transmission verse frequency curve. To the samples by electrophoresis process, the LST is improved in frequency range from 2500-3200 Hz, because the damping loss factor is improved with EPD process. The results are useful for the surface treatment to enhance the damping loss factor, LST and widespread application of magnesium alloy while improving the corrosion resistance.
基金Supported by the National Technology Research and Development Program in the 12th Five-Year Plan of China(No.2011BAE22B05)Canada-China-USA Collaborative Research and Development Project(No.2011DFA50900)
文摘AZ31B magnesium alloy was subjected to friction stir welding with various welding parameters. The equivalent Young's moduli of the friction stir welded samples and the base material were obtained by the three-point method, and their transverse rigidities were obtained as well. Furthermore, the sound transmission characteristics of those samples were experimentally studied by four-microphone impedance tube method. The experimental results indicate that the transverse rigidities of the friction stir welded samples were only 79%, 83% and 92% of those of the base material, respectively. The sound transmission losses of the processed samples were also lower, which was largely due to the reduction of transverse rigidities induced by the decrease of equivalent Young's moduli.
文摘Modern public buildings, such as multiplex cinemas and theaters, along with application of state of the art sound effects bring high acoustic insulation demands. Cinemas are often a part of building complexes such as shopping malls with subjects that produce serious level of noise and vibrations. Apart to regular use of polyurethane in thermal insulation purposes, it is widely used in field of acoustic insulation. Usage of polyurethane foam pads, with specific dynamic characteristics, as a base for structure supports gives a wide range of possibilities in controlling the amount of structural noise and vibrations transferred to the structure. Structure itself and acoustical pads becomes an integral system that behaves together and need to be analyzed as a whole in extensive design. Dynamic characteristics of acoustic pads depend on stress level and in same time they represent elastic supports to the structure and therefore analyzes and design is an iterative process. In other way, introduce of non-conventional material in bearing structure brings some issues, such as transfer of shear forces, that has to be governed by proper structural detailing. There are several possibilities of application in bearing structures, such as above and below steel structure. This paper gives an overall view on polyurethane as material, construction and design principles and example of usage of acoustic pads in steel structure of＂Ster＂ cineplex in Belgrade.
文摘Drilling fluid is a common flushing medium used in pile foundation, geological drilling and petroleum drilling. Study on ultrasonic propagation properties in drilling fluid is of vital importance, not only for developing equipments to non-contact measuring concrete casting level for bored pile, but also for developing equip- ments considering drilling fluid as signal channel. The existence of clay particles makes the ultrasonic propagation and attenuation in drilling fluid much different from pure water. In order to know the relation among ultrasound frequency, slun-y density and depth, a series of laboratory experiments about ultrasound propagation in water-based bentonite slurry were finished. Wavelet method was adopted to process the gained original waves of ultrasonic propagation in slurry, so we knew the velocity and attenuation coefficient of ultrasound propagated in different drilling fluids with different density. The first group experiments shows that with density of drilling fluid increase, ultrasonic velocity will decrease but attenuation coefficient will increase if ultrasonic frequency keep constant. The second group experiments shows that the power of ultrasound will intensify in small bore hole, the attenuation coefficient is much smaller than theoretical value.
