Experimental investigations on dynamic in-plane compressive behavior of a plain weave composite were performed using the split Hopkinson pressure bar. A quantitative criterion for calculating the constant strain rate ...Experimental investigations on dynamic in-plane compressive behavior of a plain weave composite were performed using the split Hopkinson pressure bar. A quantitative criterion for calculating the constant strain rate of composites was established. Then the upper limit of strain rate, restricted by stress equilibrium and constant loading rate, was rationally estimated and confirmed by tests. Within the achievable range of 0.001/s-895/s, it was found that the strength increased first and subsequently decreased as the strain rate increased. This feature was also reflected by the turning point(579/s) of the bilinear model for strength prediction. The transition in failure mechanism, from local opening damage to completely splitting destruction, was mainly responsible for such strain rate effects. And three major failure modes were summarized under microscopic observations: fiber fracture, inter-fiber fracture, and interface delamination. Finally, by introducing a nonlinear damage variable, a simplified ZWT model was developed to characterize the dynamic mechanical response. Excellent agreement was shown between the experimental and simulated results.展开更多
Poisson’s ratio changes during the tensile stress of technical fabric samples due to the anisotropy of technical fabrics.This paper examines the effects of the type of weave and the anisotropic characteristics of the...Poisson’s ratio changes during the tensile stress of technical fabric samples due to the anisotropy of technical fabrics.This paper examines the effects of the type of weave and the anisotropic characteristics of the technical fabric on maximum tensile force,corresponding elongation,work-to-maximum force,elasticity modulus,and Poisson’s ratio when axial tensile forces are applied to samples cut at various angles in the direction of the weft yarns of the technical fabric.In the lab,3 cotton fabric samples of constant warp and weft density with different structural weave types(plain weave,twill weave,atlas weave)were subjected to the tensile force until they broke at the following angles:0°,15°,30°,45°,60°,75°,90°.Based on the different measured values of technical fabric stretching in the longitudinal direction and lateral narrowing,Poisson’s ratio is calculated.The Poisson’s ratio was calculated up to a relative elongation of the fabric of 8%,as the buckling of the fabric occurs according to this elongation value.According to the results presented in this paper,the type of weave of the fabric,the direction of tensile force,and the relative narrowing of the technical fabrics all play important roles in the Poisson’s ratio value.The Poisson’s ratio curve of a technical fabric under tensile stress(i.e.elongation)is primarily determined by its behaviour in the opposite direction of the elongation.The change in the value of the Poisson’s ratio is represented by a graph that first increases nonlinearly and then decreases after reaching its maximum value.展开更多
In this paper, we investigate the method of computer simulation for derivative weave by adopting the way of weave differentiation with mathematical function. And on that base, we explore the way for dealing with compo...In this paper, we investigate the method of computer simulation for derivative weave by adopting the way of weave differentiation with mathematical function. And on that base, we explore the way for dealing with composed weave. It is purposed for building a simple and efficient way of computer simulation for weave.展开更多
The existing research of the woven fabric self-lubricating liner mainly focus on the tribological performance improvements and the service life raised by changing different fiber type combinations, adding additive mod...The existing research of the woven fabric self-lubricating liner mainly focus on the tribological performance improvements and the service life raised by changing different fiber type combinations, adding additive modification, and performing fiber surface modification. As fabric composites, the weave structures play an important role in the mechanical and tribological performances of the liners. However, hardly any literature is available on the friction and wear behavior of such composites with different weave structures. In this paper, three weave structures (plain, twill 1/3 and satin 8/5) of hybrid Kevlar/PTFE fabric composites are selected and pin-on-flat linear reciprocating wear studies are done on a CETR tester under different pressures and different frequencies. The relationship between the tensile strength and the wear performance are studied. The morphologies of the worn surfaces under the typical test conditions are analyzed by means of scanning electron microscopy (SEM). The analysis results show that at 10 MPa, satin 8/5 performs the best in friction-reduction and antiwear performance, and plain is the worst. At 30 MPa, however, the antiwear performance is reversed and satin 8/5 does not even complete the 2 h wear test at 16 Hz. There is no clear evidence proving that the tensile strength has an influence on the wear performance. So the different tribological performance of the three weave structures of fabric composites may be attributed to the different PTFE proportions in the fabric surface and the different wear mechanisms. The fabric composites are divided into three regions: the lubrication region, the reinforced region and the bonding region. The major mechanisms are fatigue wear and the shear effects of the friction force in the lubrication region. In the reinforced region fiber-matrix de-bonding and fiber breakage are involved. The proposed research proposes a regional wear model and further indicates the wear process and the wear mechanism of fabric composites.展开更多
The principle of a CAD method of converting the pre-designed figures in image form into complex dobby weaves with the appearances similar to the original figures is mainly introduced in this paper. A few designed weav...The principle of a CAD method of converting the pre-designed figures in image form into complex dobby weaves with the appearances similar to the original figures is mainly introduced in this paper. A few designed weaves by the created CAD system are also given as examples of the practical application in the area of complex dobby weave designing.展开更多
Quantitative research on the heat affected zone ( HAZ) o f weave bead welding ( WBW) joint fo r Invar alloy is carried out in this paper. Based on the morphology and related data analysis of the weld se...Quantitative research on the heat affected zone ( HAZ) o f weave bead welding ( WBW) joint fo r Invar alloy is carried out in this paper. Based on the morphology and related data analysis of the weld seam, the width difference o f each layer and the forming mechanism are analyzed. Results show that the bottom layer ( Layer 1 ) has the widest HAZ and the smallest fluctuation, which reaches 1 200 |jLm. HAZ width o f layer 2 to 5 is relatively narrower which is basically below 600 jjim, while the amplitude fluctuation is greater. The main reason lies in the welding path. The long straight welding without weave causes the base metal near the groove fully melts which causes by the long straight welding without weave, while welding with weave leads to the uneven and inadequate melting of metal near groove.展开更多
The craft of auxiliary dobby shaft is one of methods used in the traditional figured woven textiles and especially brocade in China.Based on the principle of auxiliary dobby shaft,a new method of weave design was prop...The craft of auxiliary dobby shaft is one of methods used in the traditional figured woven textiles and especially brocade in China.Based on the principle of auxiliary dobby shaft,a new method of weave design was proposed.The relevant arrangement of warp and weave design were discussed.It is shown that this method can be applied on one electronic jacquard loom with single warp beam for new product development and production.And this effect will open up a new way to reproduce traditional fabrics in order to protect and develop Chinese traditional culture.展开更多
Owing to the diversity of consumer’s demand, the traditional Sichuan brocade products have to be innovated in order to survive in a competitive environment. Since the construction of traditional Sichuan brocade was c...Owing to the diversity of consumer’s demand, the traditional Sichuan brocade products have to be innovated in order to survive in a competitive environment. Since the construction of traditional Sichuan brocade was composed of basic-weave, the surface of the fabric shows a regular interweaving planar texture and is difficult to represent a three-dimensional effect. Inspired by embroidery handcraft, this paper attempts to achieve the embroidery-like effect on the fabric through the jacquard process. Based on the multi-backed structure of traditional Sichuan brocade, we adopted the zoned-combination design mode and added extra free-floats interlacing weave in the area where we want to show the embroidered effect and arranged the interlacing points by referring to the feature of the pattern. As a result, designed Sichuan brocades by this method are capable of displaying embroidered effect with high realism and three-dimensionality. This approach improves the artistic effect of the traditional Sichuan brocade and provides a technical reference for further texture design of jacquard fabrics.展开更多
'Dawn sees saturated reds;the town’s heavy with blooms.'We,more than 90 experts and scholars from home and abroad,attended The Academic Seminar on the Land of Abundance and the Silk Road held by the Associati...'Dawn sees saturated reds;the town’s heavy with blooms.'We,more than 90 experts and scholars from home and abroad,attended The Academic Seminar on the Land of Abundance and the Silk Road held by the Association of Chinese Historians,the Guangming Daily Press,the Society for Chinese Archaeology,the Chinese Society on Ancient Capitals,the School of Archaeology and Museology of Peking University,and Sichuan Academy of展开更多
With 3D orthogonal and pseudo-orthogonal weaves, woven sructures with lengthwise and widthwise changing cross section on one side or both sides of the structure can be constructed. The weave formation and the looming ...With 3D orthogonal and pseudo-orthogonal weaves, woven sructures with lengthwise and widthwise changing cross section on one side or both sides of the structure can be constructed. The weave formation and the looming draft creation are discussed in this paper which can be used as references to manufacture woven preforms with changing cross sections.展开更多
Cotton fabrics with different weaves are designed and the influence of weave on wrinkle recovery property and tensile property is analyzed. Weave type plays a prominent part in determining fabric wrinkle recovery prop...Cotton fabrics with different weaves are designed and the influence of weave on wrinkle recovery property and tensile property is analyzed. Weave type plays a prominent part in determining fabric wrinkle recovery property and tensile property. Weave factor C is in direct relation to wrinkle recovery angle and in inverse relation to tensile property. This trend also exists after resin treatment. 3/1 left-twill fabric shows good wrinkle recovery angle and lest tensile loss after resin treatment.展开更多
In the light of the mapping between[0,1]matrixes of fab-ric weaves,we establish in this paper a mathematical modelfor fabric weave design- One type of non- associative al-gebra composed of 7 basic transformations in a...In the light of the mapping between[0,1]matrixes of fab-ric weaves,we establish in this paper a mathematical modelfor fabric weave design- One type of non- associative al-gebra composed of 7 basic transformations in a 2- elementfield.In view of practice,we expand the generative set ofmapping of this matematical model to cover the generaltransformation methods in traditional weave design.Takingthe algorethm of" Kronecker product" as an example,wefurthermore illustrate applied potentialities of the generativeset of mapping in the CAD of fabic weaves.展开更多
TMAS,Textile Machinery Association of Sweden,has established a local office in the 7th district of Ho Chi Minh City.Heading the office is Mr.Tran Phuoc Thanh,Business Development Representative for TMAS in Vietnam.Mr....TMAS,Textile Machinery Association of Sweden,has established a local office in the 7th district of Ho Chi Minh City.Heading the office is Mr.Tran Phuoc Thanh,Business Development Representative for TMAS in Vietnam.Mr.Tran comes with experience from the展开更多
As one of the three backbone con- sumptions (apparel, home-textile, tech- textile or industrial applications), non- woven textile industry performed well in 2005, but problems still remain. An official from the State ...As one of the three backbone con- sumptions (apparel, home-textile, tech- textile or industrial applications), non- woven textile industry performed well in 2005, but problems still remain. An official from the State Development and Reform Commission - China’s top planner, mapped out economic blue- prints for this fast-growing sector in 2006.展开更多
Ceramic matrix composites(CMCs) are one of the most promising materials in the field of gas turbines,with superior weight and thermal properties. Its surface morphology is different from the traditional casting airfoi...Ceramic matrix composites(CMCs) are one of the most promising materials in the field of gas turbines,with superior weight and thermal properties. Its surface morphology is different from the traditional casting airfoil components, which mainly comes from different weaving methods and different braided tow thickness. However, few people have studied the influence of surface morphology of ceramic matrix composites(CMCs) on the development of boundary layer and the resulting flow loss. In this paper, Tex Gen is used to generate different surface morphology structures of ceramic matrix composites(CMCs), and the surface flow characteristics of corresponding CMCs plates are numerically studied. It is found that the slope of the displacement thickness of the woven surface first increases and then decreases in the whole transition interval. Thicker braided tow thickness and denser braiding method will induce earlier flow transition phenomenon and produce greater flow loss;The flow loss on the surface of CMCs plate is mainly composed of the vortex loss in the pit and the boundary layer loss outside the pit, and the boundary layer loss is dominant. The weaving methods has a greater influence on the flow state and flow loss of the boundary layer.展开更多
Novel micromechanical curved beam models were presented for predicting the ten- sile and shear moduli of triaxial weave fabric (TWF) composites by considering the interactions between the triaxial yarns of 0° a...Novel micromechanical curved beam models were presented for predicting the ten- sile and shear moduli of triaxial weave fabric (TWF) composites by considering the interactions between the triaxial yarns of 0° and ±60° The triaxial yarns in micromechanieal representative unit cell (RUC) were idealized as curved beams with a path depicted using the sinusoidal shape functions, and the tensile and shear moduli of TWF composites were derived by means of the strain energy approach founded on micromechanics. In order to validate the new models, the predictions were compared with the experimental data from literature. It was shown that the predictions from the new model agree well with the experimental results. Using these models, the tensile and shear properties of TWF composites could be predicted based only on the properties of basic woven fabric.展开更多
In order to get a deep understanding of composite failure mechanisms, the new advanced signal processing methodologies are established for the analysis of the large number of acoustic emission (AE) data obtained from ...In order to get a deep understanding of composite failure mechanisms, the new advanced signal processing methodologies are established for the analysis of the large number of acoustic emission (AE) data obtained from the quasi-static tension test of carbon fiber twill weave composite. For this purpose, AE signals have been collected and post-processed for tension test, and are analyzed with three signal processing methods: Empirical Mode Decomposition (EMD), Hilbert-Huang Transform (HHT) and modified energy entropy algorithm. AE signals can be decomposed into a set of Intrinsic Mode Functions (IMF) components, results from this study reveal that the peak frequency of IMF components based on Fast Fourier Transform (FFT) corresponds to different damage mechanisms of composite. HHT of AE signals can clearly express the frequency distribution of IMF component in time-scale in different damage stages, and can calculate accurate instantaneous frequency for damage modes recognition. The energy entropy based on EMD is introduced to act as a new relevant descriptor of composite damage modes in order to improve the characterization and the discrimination of the damage mechanisms.展开更多
LAST May, as a special correspondent, I went to Guizhou Province with several experts from the State Education Commission. In order to investigate Guizhou’s whole educational situation, we had to be divided into thre...LAST May, as a special correspondent, I went to Guizhou Province with several experts from the State Education Commission. In order to investigate Guizhou’s whole educational situation, we had to be divided into three groups. Without hesitation, I chose Sandu County, partly because it is展开更多
基金the National Science and Technology Major Project(Grant No.2017-VII-0011-0106)Natural Science Foundation of Heilongjiang Province(Grant No.ZD2019A001).
文摘Experimental investigations on dynamic in-plane compressive behavior of a plain weave composite were performed using the split Hopkinson pressure bar. A quantitative criterion for calculating the constant strain rate of composites was established. Then the upper limit of strain rate, restricted by stress equilibrium and constant loading rate, was rationally estimated and confirmed by tests. Within the achievable range of 0.001/s-895/s, it was found that the strength increased first and subsequently decreased as the strain rate increased. This feature was also reflected by the turning point(579/s) of the bilinear model for strength prediction. The transition in failure mechanism, from local opening damage to completely splitting destruction, was mainly responsible for such strain rate effects. And three major failure modes were summarized under microscopic observations: fiber fracture, inter-fiber fracture, and interface delamination. Finally, by introducing a nonlinear damage variable, a simplified ZWT model was developed to characterize the dynamic mechanical response. Excellent agreement was shown between the experimental and simulated results.
文摘Poisson’s ratio changes during the tensile stress of technical fabric samples due to the anisotropy of technical fabrics.This paper examines the effects of the type of weave and the anisotropic characteristics of the technical fabric on maximum tensile force,corresponding elongation,work-to-maximum force,elasticity modulus,and Poisson’s ratio when axial tensile forces are applied to samples cut at various angles in the direction of the weft yarns of the technical fabric.In the lab,3 cotton fabric samples of constant warp and weft density with different structural weave types(plain weave,twill weave,atlas weave)were subjected to the tensile force until they broke at the following angles:0°,15°,30°,45°,60°,75°,90°.Based on the different measured values of technical fabric stretching in the longitudinal direction and lateral narrowing,Poisson’s ratio is calculated.The Poisson’s ratio was calculated up to a relative elongation of the fabric of 8%,as the buckling of the fabric occurs according to this elongation value.According to the results presented in this paper,the type of weave of the fabric,the direction of tensile force,and the relative narrowing of the technical fabrics all play important roles in the Poisson’s ratio value.The Poisson’s ratio curve of a technical fabric under tensile stress(i.e.elongation)is primarily determined by its behaviour in the opposite direction of the elongation.The change in the value of the Poisson’s ratio is represented by a graph that first increases nonlinearly and then decreases after reaching its maximum value.
文摘In this paper, we investigate the method of computer simulation for derivative weave by adopting the way of weave differentiation with mathematical function. And on that base, we explore the way for dealing with composed weave. It is purposed for building a simple and efficient way of computer simulation for weave.
基金supported by National Defense Foundation of China
文摘The existing research of the woven fabric self-lubricating liner mainly focus on the tribological performance improvements and the service life raised by changing different fiber type combinations, adding additive modification, and performing fiber surface modification. As fabric composites, the weave structures play an important role in the mechanical and tribological performances of the liners. However, hardly any literature is available on the friction and wear behavior of such composites with different weave structures. In this paper, three weave structures (plain, twill 1/3 and satin 8/5) of hybrid Kevlar/PTFE fabric composites are selected and pin-on-flat linear reciprocating wear studies are done on a CETR tester under different pressures and different frequencies. The relationship between the tensile strength and the wear performance are studied. The morphologies of the worn surfaces under the typical test conditions are analyzed by means of scanning electron microscopy (SEM). The analysis results show that at 10 MPa, satin 8/5 performs the best in friction-reduction and antiwear performance, and plain is the worst. At 30 MPa, however, the antiwear performance is reversed and satin 8/5 does not even complete the 2 h wear test at 16 Hz. There is no clear evidence proving that the tensile strength has an influence on the wear performance. So the different tribological performance of the three weave structures of fabric composites may be attributed to the different PTFE proportions in the fabric surface and the different wear mechanisms. The fabric composites are divided into three regions: the lubrication region, the reinforced region and the bonding region. The major mechanisms are fatigue wear and the shear effects of the friction force in the lubrication region. In the reinforced region fiber-matrix de-bonding and fiber breakage are involved. The proposed research proposes a regional wear model and further indicates the wear process and the wear mechanism of fabric composites.
文摘The principle of a CAD method of converting the pre-designed figures in image form into complex dobby weaves with the appearances similar to the original figures is mainly introduced in this paper. A few designed weaves by the created CAD system are also given as examples of the practical application in the area of complex dobby weave designing.
基金the financial support of the project from Shanghai Municipal Commission of Economy and Informatization (15XI-1-15)Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘Quantitative research on the heat affected zone ( HAZ) o f weave bead welding ( WBW) joint fo r Invar alloy is carried out in this paper. Based on the morphology and related data analysis of the weld seam, the width difference o f each layer and the forming mechanism are analyzed. Results show that the bottom layer ( Layer 1 ) has the widest HAZ and the smallest fluctuation, which reaches 1 200 |jLm. HAZ width o f layer 2 to 5 is relatively narrower which is basically below 600 jjim, while the amplitude fluctuation is greater. The main reason lies in the welding path. The long straight welding without weave causes the base metal near the groove fully melts which causes by the long straight welding without weave, while welding with weave leads to the uneven and inadequate melting of metal near groove.
文摘The craft of auxiliary dobby shaft is one of methods used in the traditional figured woven textiles and especially brocade in China.Based on the principle of auxiliary dobby shaft,a new method of weave design was proposed.The relevant arrangement of warp and weave design were discussed.It is shown that this method can be applied on one electronic jacquard loom with single warp beam for new product development and production.And this effect will open up a new way to reproduce traditional fabrics in order to protect and develop Chinese traditional culture.
文摘Owing to the diversity of consumer’s demand, the traditional Sichuan brocade products have to be innovated in order to survive in a competitive environment. Since the construction of traditional Sichuan brocade was composed of basic-weave, the surface of the fabric shows a regular interweaving planar texture and is difficult to represent a three-dimensional effect. Inspired by embroidery handcraft, this paper attempts to achieve the embroidery-like effect on the fabric through the jacquard process. Based on the multi-backed structure of traditional Sichuan brocade, we adopted the zoned-combination design mode and added extra free-floats interlacing weave in the area where we want to show the embroidered effect and arranged the interlacing points by referring to the feature of the pattern. As a result, designed Sichuan brocades by this method are capable of displaying embroidered effect with high realism and three-dimensionality. This approach improves the artistic effect of the traditional Sichuan brocade and provides a technical reference for further texture design of jacquard fabrics.
文摘'Dawn sees saturated reds;the town’s heavy with blooms.'We,more than 90 experts and scholars from home and abroad,attended The Academic Seminar on the Land of Abundance and the Silk Road held by the Association of Chinese Historians,the Guangming Daily Press,the Society for Chinese Archaeology,the Chinese Society on Ancient Capitals,the School of Archaeology and Museology of Peking University,and Sichuan Academy of
文摘With 3D orthogonal and pseudo-orthogonal weaves, woven sructures with lengthwise and widthwise changing cross section on one side or both sides of the structure can be constructed. The weave formation and the looming draft creation are discussed in this paper which can be used as references to manufacture woven preforms with changing cross sections.
文摘Cotton fabrics with different weaves are designed and the influence of weave on wrinkle recovery property and tensile property is analyzed. Weave type plays a prominent part in determining fabric wrinkle recovery property and tensile property. Weave factor C is in direct relation to wrinkle recovery angle and in inverse relation to tensile property. This trend also exists after resin treatment. 3/1 left-twill fabric shows good wrinkle recovery angle and lest tensile loss after resin treatment.
文摘In the light of the mapping between[0,1]matrixes of fab-ric weaves,we establish in this paper a mathematical modelfor fabric weave design- One type of non- associative al-gebra composed of 7 basic transformations in a 2- elementfield.In view of practice,we expand the generative set ofmapping of this matematical model to cover the generaltransformation methods in traditional weave design.Takingthe algorethm of" Kronecker product" as an example,wefurthermore illustrate applied potentialities of the generativeset of mapping in the CAD of fabic weaves.
文摘TMAS,Textile Machinery Association of Sweden,has established a local office in the 7th district of Ho Chi Minh City.Heading the office is Mr.Tran Phuoc Thanh,Business Development Representative for TMAS in Vietnam.Mr.Tran comes with experience from the
文摘As one of the three backbone con- sumptions (apparel, home-textile, tech- textile or industrial applications), non- woven textile industry performed well in 2005, but problems still remain. An official from the State Development and Reform Commission - China’s top planner, mapped out economic blue- prints for this fast-growing sector in 2006.
基金National Science and Technology Major Project (Y2019-I-0018-0017)。
文摘Ceramic matrix composites(CMCs) are one of the most promising materials in the field of gas turbines,with superior weight and thermal properties. Its surface morphology is different from the traditional casting airfoil components, which mainly comes from different weaving methods and different braided tow thickness. However, few people have studied the influence of surface morphology of ceramic matrix composites(CMCs) on the development of boundary layer and the resulting flow loss. In this paper, Tex Gen is used to generate different surface morphology structures of ceramic matrix composites(CMCs), and the surface flow characteristics of corresponding CMCs plates are numerically studied. It is found that the slope of the displacement thickness of the woven surface first increases and then decreases in the whole transition interval. Thicker braided tow thickness and denser braiding method will induce earlier flow transition phenomenon and produce greater flow loss;The flow loss on the surface of CMCs plate is mainly composed of the vortex loss in the pit and the boundary layer loss outside the pit, and the boundary layer loss is dominant. The weaving methods has a greater influence on the flow state and flow loss of the boundary layer.
基金Project supported by the National Natural Science Foundation of China(Nos.51375033 and 51405006)
文摘Novel micromechanical curved beam models were presented for predicting the ten- sile and shear moduli of triaxial weave fabric (TWF) composites by considering the interactions between the triaxial yarns of 0° and ±60° The triaxial yarns in micromechanieal representative unit cell (RUC) were idealized as curved beams with a path depicted using the sinusoidal shape functions, and the tensile and shear moduli of TWF composites were derived by means of the strain energy approach founded on micromechanics. In order to validate the new models, the predictions were compared with the experimental data from literature. It was shown that the predictions from the new model agree well with the experimental results. Using these models, the tensile and shear properties of TWF composites could be predicted based only on the properties of basic woven fabric.
基金supported by the National Natural Science Foundation of China (Grand No.51275221)the Natural Science Foundation of Jiangsu Province, China (Grand No. BK2011261)
文摘In order to get a deep understanding of composite failure mechanisms, the new advanced signal processing methodologies are established for the analysis of the large number of acoustic emission (AE) data obtained from the quasi-static tension test of carbon fiber twill weave composite. For this purpose, AE signals have been collected and post-processed for tension test, and are analyzed with three signal processing methods: Empirical Mode Decomposition (EMD), Hilbert-Huang Transform (HHT) and modified energy entropy algorithm. AE signals can be decomposed into a set of Intrinsic Mode Functions (IMF) components, results from this study reveal that the peak frequency of IMF components based on Fast Fourier Transform (FFT) corresponds to different damage mechanisms of composite. HHT of AE signals can clearly express the frequency distribution of IMF component in time-scale in different damage stages, and can calculate accurate instantaneous frequency for damage modes recognition. The energy entropy based on EMD is introduced to act as a new relevant descriptor of composite damage modes in order to improve the characterization and the discrimination of the damage mechanisms.
文摘LAST May, as a special correspondent, I went to Guizhou Province with several experts from the State Education Commission. In order to investigate Guizhou’s whole educational situation, we had to be divided into three groups. Without hesitation, I chose Sandu County, partly because it is