1.Introduction The strength-ductility trade-offdilemma has long been a per-sistent challenge in Al matrix composites(AMCs)[1,2].This is-sue primarily arises from the agglomeration of reinforcements at the grain bounda...1.Introduction The strength-ductility trade-offdilemma has long been a per-sistent challenge in Al matrix composites(AMCs)[1,2].This is-sue primarily arises from the agglomeration of reinforcements at the grain boundaries(GBs),which restricts local plastic flow dur-ing the plastic deformation and leads to stress concentration[3,4].Recently,the development of concepts aimed at achieving hetero-geneous grain has emerged as a promising approach for enhanc-ing comprehensive mechanical properties[5,6].展开更多
Aspect-oriented sentiment analysis is a meticulous sentiment analysis task that aims to analyse the sentiment polarity of specific aspects. Most of the current research builds graph convolutional networks based on dep...Aspect-oriented sentiment analysis is a meticulous sentiment analysis task that aims to analyse the sentiment polarity of specific aspects. Most of the current research builds graph convolutional networks based on dependent syntactic trees, which improves the classification performance of the models to some extent. However, the technical limitations of dependent syntactic trees can introduce considerable noise into the model. Meanwhile, it is difficult for a single graph convolutional network to aggregate both semantic and syntactic structural information of nodes, which affects the final sentence classification. To cope with the above problems, this paper proposes a bi-channel graph convolutional network model. The model introduces a phrase structure tree and transforms it into a hierarchical phrase matrix. The adjacency matrix of the dependent syntactic tree and the hierarchical phrase matrix are combined as the initial matrix of the graph convolutional network to enhance the syntactic information. The semantic information feature representations of the sentences are obtained by the graph convolutional network with a multi-head attention mechanism and fused to achieve complementary learning of dual-channel features. Experimental results show that the model performs well and improves the accuracy of sentiment classification on three public benchmark datasets, namely Rest14, Lap14 and Twitter.展开更多
This paper is a continuation of our last paper [1] which describes the theory of Virt-BLP model. Based on Virt-BLP model,this paper implements a mandatory access control(MAC) framework applicable to multi-level securi...This paper is a continuation of our last paper [1] which describes the theory of Virt-BLP model. Based on Virt-BLP model,this paper implements a mandatory access control(MAC) framework applicable to multi-level security(MLS) in Xen. The Virt-BLP model is the theoretical basis of this MAC framework,and this MAC framework is the implementation of Virt-BLP model. Our last paper focuses on Virt-BLP model,while this paper concentrates on the design and implementation of MAC framework. For there is no MAC framework applicable to MLS in virtual machine system at present,our MAC framework fills the blank by applying Virt-BLP model to Xen,which is better than current researches to guarantee the security of communication between virtual machines(VMs) . The experimental results show that our MAC framework is effective to manage the communication between VMs.展开更多
To overcome the shortcomings of 1 D and 2 D Otsu’s thresholding techniques, the 3 D Otsu method has been developed.Among all Otsu’s methods, 3 D Otsu technique provides the best threshold values for the multi-level ...To overcome the shortcomings of 1 D and 2 D Otsu’s thresholding techniques, the 3 D Otsu method has been developed.Among all Otsu’s methods, 3 D Otsu technique provides the best threshold values for the multi-level thresholding processes. In this paper, to improve the quality of segmented images, a simple and effective multilevel thresholding method is introduced. The proposed approach focuses on preserving edge detail by computing the 3 D Otsu along the fusion phenomena. The advantages of the presented scheme include higher quality outcomes, better preservation of tiny details and boundaries and reduced execution time with rising threshold levels. The fusion approach depends upon the differences between pixel intensity values within a small local space of an image;it aims to improve localized information after the thresholding process. The fusion of images based on local contrast can improve image segmentation performance by minimizing the loss of local contrast, loss of details and gray-level distributions. Results show that the proposed method yields more promising segmentation results when compared to conventional1 D Otsu, 2 D Otsu and 3 D Otsu methods, as evident from the objective and subjective evaluations.展开更多
In this paper, we focus on the design of irregular QC-LDPC code based multi-level coded modulation(MLCM) scheme by jointly optimizing the component code rate and the degree distribution of the irregular QC-LDPC compon...In this paper, we focus on the design of irregular QC-LDPC code based multi-level coded modulation(MLCM) scheme by jointly optimizing the component code rate and the degree distribution of the irregular QC-LDPC component code. Firstly, the sub-channel capacities of MLCM systems is analyzed and discussed, based on which the optimal component code rate can be obtained. Secondly, an extrinsic information transfer chart based two-stage searching algorithm is proposed to find the good irregular QC-LDPC code ensembles with optimal component code rates for their corresponding sub-channels. Finally, by constructing the irregular QC-LDPC component codes from the designed ensembles with the aim of possibly enlarging the girth and reducing the number of the shortest cycles, the designed irregular QC-LDPC code based 16QAM and 64QAM MLCM systems can achieve 0.4 dB and 1.2 dB net coding gain, respectively, compared with the recently proposed regular QC-LDPC code based 16QAM and 64QAM MLCM systems.展开更多
Fatigue properties of Reactive Powder Concrete （RPC） under axial compression of single-stage and multi-level amplitude in cycles were studied. The tests reveal the fatigue life, the strain and residual life of the R...Fatigue properties of Reactive Powder Concrete （RPC） under axial compression of single-stage and multi-level amplitude in cycles were studied. The tests reveal the fatigue life, the strain and residual life of the RPC samples. Through the analysis of the test results under cyclic loads of single amplitude, the S-N curve of RPC and the evolution rule of macro-damage of RPC were presented, which can be divided into latency stage, stable development stage and instability development stage according to the evolution pattern of the fatigue crack. Accordingly, the development of longitudinal deformation presents the similar three-stage-model, and the proportion of each stage is 15%, 75%, and 10%. According to test results, the fatigue strength reduction factor is 0.564. We brought forward an empirical formula to predict the life of RPC via total longitudinal strain and got the evolving rule for the residual strength of the RPC. The analysis of the test results under cyclic loads of multi-level amplitude shows that the strain under this loading pattern experiences three stages. The characteristic value for the residual strain was obtained. The irreversible damage and non-linear evolution of RPC was described by the development of the residual plastic strain.展开更多
Partitioning is a fundamental problem with applications to many areas including data mining, parellel processing and Very-large-scale integration （VLSI） design. An effective multi-level algorithm for bisecting graph...Partitioning is a fundamental problem with applications to many areas including data mining, parellel processing and Very-large-scale integration （VLSI） design. An effective multi-level algorithm for bisecting graph is proposed. During its coarsening phase, an improved matching approach based on the global information of the graph core is developed with its guidance function. During the refinement phase, the vertex gain is exploited as ant＇s heuristic information and a positive feedback method based on pheromone trails is used to find the global approximate bipartitioning. It is implemented with American National Standards Institute （ANSI） C and compared to MeTiS. The experimental evaluation shows that it performs well and produces encouraging solutions on 18 different graphs benchmarks.展开更多
The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection （DPD） method in the signal waveform modulation multi-level （SWML） re...The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection （DPD） method in the signal waveform modulation multi-level （SWML） read-only disc. To solve this problem, this paper proposes a new tracking error detection method using amplitude difference. Based on the diffraction theory, the amplitude difference is proportional to the tracking error and is feasible to be used for obtaining the off-track information. The experimental system of the amplitude difference detection method is developed. The experimental results show that the tracking error signal derived from the new method has better performance in uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc.展开更多
As the differences of sensor＇s precision and some random factors are difficult to control,the actual measurement signals are far from the target signals that affect the reliability and precision of rotating machinery...As the differences of sensor＇s precision and some random factors are difficult to control,the actual measurement signals are far from the target signals that affect the reliability and precision of rotating machinery fault diagnosis.The traditional signal processing methods,such as classical inference and weighted averaging algorithm usually lack dynamic adaptability that is easy for trends to cause the faults to be misjudged or left out.To enhance the measuring veracity and precision of vibration signal in rotary machine multi-sensor vibration signal fault diagnosis,a novel data level fusion approach is presented on the basis of correlation function analysis to fast determine the weighted value of multi-sensor vibration signals.The approach doesn＇t require knowing the prior information about sensors,and the weighted value of sensors can be confirmed depending on the correlation measure of real-time data tested in the data level fusion process.It gives greater weighted value to the greater correlation measure of sensor signals,and vice versa.The approach can effectively suppress large errors and even can still fuse data in the case of sensor failures because it takes full advantage of sensor＇s own-information to determine the weighted value.Moreover,it has good performance of anti-jamming due to the correlation measures between noise and effective signals are usually small.Through the simulation of typical signal collected from multi-sensors,the comparative analysis of dynamic adaptability and fault tolerance between the proposed approach and traditional weighted averaging approach is taken.Finally,the rotor dynamics and integrated fault simulator is taken as an example to verify the feasibility and advantages of the proposed approach,it is shown that the multi-sensor data level fusion based on correlation function weighted approach is better than the traditional weighted average approach with respect to fusion precision and dynamic adaptability.Meantime,the approach is adaptable and easy to use,can be applied to other areas of vibration measurement.展开更多
Based on forward modeling of detachment fold, this study presents a method to analyze multi-level detachment structures and identify the authenticity of deep-seated anticlines using time-domain seismic section. The st...Based on forward modeling of detachment fold, this study presents a method to analyze multi-level detachment structures and identify the authenticity of deep-seated anticlines using time-domain seismic section. The steps include the conversion of the time-migrated seismic image into depth domain image using a constant velocity field, structural interpretation of the depth seismic image, measurement of each structural relief area and each height above reference level, plotting of area-height relationship chart with piecewise fitting etc. The area-depth correlation can help the division of structural sequences, the definition of detachment levels, the calculation of the tectonic shortening, and the identification of deep-seated structure. The segment area-height relationship is a feature of multi-level detachment structures, while little or no linear correlation between area and height is an indicator of non-deformation or pseudo-anticline. Regardless of the uncertainty of area-height relationship, the segment slopes will correspond to the differential shortenings of multi-level detachments, the intersection between adjacent segments will give the height of detachment surface above reference level and then help define the detachment level in original time-domain seismic section. This method can make use of time-domain seismic data to determine the geologic structure of complicated structure areas and assess risks of deep exploration targets. It has achieved good results in southern Junggar and eastern Sichuan areas.展开更多
To implement a quantificational evaluation for mechanical kinematic scheme more effectively,a multi-level and multi-objective evaluation model is presented using neural network and fuzzy theory. Firstly,the structure ...To implement a quantificational evaluation for mechanical kinematic scheme more effectively,a multi-level and multi-objective evaluation model is presented using neural network and fuzzy theory. Firstly,the structure of evaluation model is constructed according to evaluation indicator system. Then evaluation samples are generated and provided to train this model. Thus it can reflect the relation between attributive value and evaluation result,as well as the weight of evaluation indicator. Once evaluation indicators of each candidate are fuzzily quantified and fed into the trained network model,the corresponding evaluation result is outputted and the best alternative can be selected. Under this model,expert knowledge can be effectively acquired and expressed,and the quantificational evaluation can be implemented for kinematic scheme with multi-level evaluation indicator system. Several key problems on this model are discussed and an illustration has demonstrated that this model is feasible and can be regarded as a new idea for solving kinematic scheme evaluation.展开更多
One process based on phase inversion of fillers in microstructures for the fabrication of multi-level three-dimensional(3-D) microstructures is described using SU-8, a kind of epoxy photoresist, as the model construct...One process based on phase inversion of fillers in microstructures for the fabrication of multi-level three-dimensional(3-D) microstructures is described using SU-8, a kind of epoxy photoresist, as the model constructing materials. This process is depicted by use of the routine photolithography technique to construct the top layer of 3-D microstructures on the bottom layer of 3-D microstructures layer by layer. This process makes it possible to fabricate multi-level 3-D microstructures with connectors at desired locations, and to seal long span microstructures(e.g. very shallow channels with depth less than 50 μm and width more than 300 μm) without blockage. In addition, this process can provide a sealing layer by the solidification of a liquid polymer layer, which can be as strong as the bulk constructing materials for microstructures due to a complete contact and cross-linking between the sealing layer and the patterned layers. The hydrodynamic testing indicates that this kind of sealing and interconnection can endure a static pressure of more than 10 MPa overnight and a hydrodynamic pressure drop of about 5.3 MPa for more than 8 hours by pumping the tetrahydrofuran solution through a 60 μm wide micro-channels.展开更多
The time-dependence bilinear mixed-regression deformation model and time-dependence bilinear dynamic system deformation model are established for deformation observation series. According to the multi- level recursive...The time-dependence bilinear mixed-regression deformation model and time-dependence bilinear dynamic system deformation model are established for deformation observation series. According to the multi- level recursive method, the time-dependence parameters are first traced and predicted, and then the dynamic system states. Due to the method considering time-dependence of deformation and having stronger adaptability to time-dependence system, it can improve forecast’s precision. It is very effective for data processing of nonlinear dynamic deformation monitoring to make multi-step forecasting.展开更多
Under saturation dosage of all kinds of SP, the free water amount was examined by centrifuge. The distribution of solution and flocculation microstructures in fresh cement paste was observed in three- dimensional spac...Under saturation dosage of all kinds of SP, the free water amount was examined by centrifuge. The distribution of solution and flocculation microstructures in fresh cement paste was observed in three- dimensional space by confocal laser scanning microscope（CLSM）. Results indicate that SP can increase the free water amount by destroying the flocculated cement particle structure and different free water amount is released by different kinds of SP. The changes of the size of flocculation structures and the dispersion of solution were obviously detected with confocal laser scanning microscope： the size of flocculation structures was smaller and more dispersed in fresh cement paste with polycarboxylate superplasticizer, but the size of flocculation structures was bigger and cannot be dispersed uniformly in fresh cement paste with others SP. The multi- level flocculation structures theoretical model of fresh cement paste was then set up. The theory indicates that different kinds of SP with different dispersion strength will open the flocculation structures at different levels, which in turn present different water reducing rate.展开更多
In this paper, we present a distributed multi-level cache system based on cloud storage, which is aimed at the low access efficiency of small spatio-temporal data files in information service system of Smart City. Tak...In this paper, we present a distributed multi-level cache system based on cloud storage, which is aimed at the low access efficiency of small spatio-temporal data files in information service system of Smart City. Taking classification attribute of small spatio-temporal data files in Smart City as the basis of cache content selection, the cache system adopts different cache pool management strategies in different levels of cache. The results of experiment in prototype system indicate that multi-level cache in this paper effectively increases the access bandwidth of small spatio-temporal files in Smart City and greatly improves service quality of multiple concurrent access in system.展开更多
Objective To evaluate the effect of the aluminum hydroxide （Al-OH） adjuvant on the 2009 pandemic influenza A/H1N1 （pH1N1） vaccine. Methods In a multicenter, double-blind, randomized, placebo-controlled trial, part...Objective To evaluate the effect of the aluminum hydroxide （Al-OH） adjuvant on the 2009 pandemic influenza A/H1N1 （pH1N1） vaccine. Methods In a multicenter, double-blind, randomized, placebo-controlled trial, participants received two doses of split-virion formulation containing 15 ug hemagglutinin antigen, with or without aluminum hydroxide （N-OH）. We classified the participants into six age categories （〉61 years, 41-60 years, 19-40 years, 13-18 years, 8-12 years, and 3-7 years） and obtained four blood samples from each participant on days 0, 21, 35, and 42 following the first dose of immunization. We assessed vaccine immunogenicity by measuring the geometric mean titer （GMT） of hemagglutination inhibiting antibody. We used a two-level model to evaluate the fixed effect of aluminum Al-OH and other factors, accounting for repeated measures. Results The predictions of repeated measurement on GMTs of formulations with or without Al-OH, were 80.35 and 112.72, respectively. Al-OH significantly reduced immunogenicity after controlling for time post immunization, age-group and gender. Conclusion The Al-OH adjuvant does not increase but actually reduces the immunogenicity of the split-virion pH1N1 vaccine.展开更多
By converting an optimal control problem for nonlinear systems to a Hamiltonian system,a symplecitc-preserving method is proposed.The state and costate variables are approximated by the Lagrange polynomial.The state v...By converting an optimal control problem for nonlinear systems to a Hamiltonian system,a symplecitc-preserving method is proposed.The state and costate variables are approximated by the Lagrange polynomial.The state variables at two ends of the time interval are taken as independent variables.Based on the dual variable principle,nonlinear optimal control problems are replaced with nonlinear equations.Furthermore,in the implementation of the symplectic algorithm,based on the 2N algorithm,a multilevel method is proposed.When the time grid is refined from low level to high level,the initial state and costate variables of the nonlinear equations can be obtained from the Lagrange interpolation at the low level grid to improve efficiency.Numerical simulations show the precision and the efficiency of the proposed algorithm in this paper.展开更多
A novel read channel for signal waveform modulation multi-level disc is presented in this paper. This read channel employs timing recovery system and partial response maximum likelihood detector. Compared to the previ...A novel read channel for signal waveform modulation multi-level disc is presented in this paper. This read channel employs timing recovery system and partial response maximum likelihood detector. Compared to the previous read channel composed of level detection and run-length detection, the present read channel shows superiority in capacity increase and robust performance. Especially, relying on the partial response maximum likelihood detection, lower bit error rate can be obtained.展开更多
This paper presents a new topology to connect high voltage direct current(HVDC) offshore wind farm into the grid.The offshore part consists of five units,each unit contains permanent magnet synchronous generator(PMSG)...This paper presents a new topology to connect high voltage direct current(HVDC) offshore wind farm into the grid.The offshore part consists of five units,each unit contains permanent magnet synchronous generator(PMSG) connected to three-phase/three-phase matrix converter to control the generator speed by using a maximum power point tracking(MPPT) control.The offshore platform consists of a three-phase medium frequency transformer(MFT) and a modular multi-level converter(MMC).The primary of each phase of the transformer connected to one phase from each unit.The secondary of the transformer connected to MMC to get HVDC.The HVDC cable will be used to transfer power from the offshore side to the on-shore side.Five-level MMC is used in the onshore side to control the DC voltage and to connect the offshore wind farm into the grid by converting the HVDC to high voltage alternative current(HVAC).展开更多
基金support by the National Natural Science Foundation of China(Grant Nos.U23A20546 and 52271010)the Chinese National Natural Science Fund for Distinguished Young Scholars(Grant No.52025015)the Natural Science Foundation of Tianjin City(No.21JCZDJC00510).
文摘1.Introduction The strength-ductility trade-offdilemma has long been a per-sistent challenge in Al matrix composites(AMCs)[1,2].This is-sue primarily arises from the agglomeration of reinforcements at the grain boundaries(GBs),which restricts local plastic flow dur-ing the plastic deformation and leads to stress concentration[3,4].Recently,the development of concepts aimed at achieving hetero-geneous grain has emerged as a promising approach for enhanc-ing comprehensive mechanical properties[5,6].
文摘Aspect-oriented sentiment analysis is a meticulous sentiment analysis task that aims to analyse the sentiment polarity of specific aspects. Most of the current research builds graph convolutional networks based on dependent syntactic trees, which improves the classification performance of the models to some extent. However, the technical limitations of dependent syntactic trees can introduce considerable noise into the model. Meanwhile, it is difficult for a single graph convolutional network to aggregate both semantic and syntactic structural information of nodes, which affects the final sentence classification. To cope with the above problems, this paper proposes a bi-channel graph convolutional network model. The model introduces a phrase structure tree and transforms it into a hierarchical phrase matrix. The adjacency matrix of the dependent syntactic tree and the hierarchical phrase matrix are combined as the initial matrix of the graph convolutional network to enhance the syntactic information. The semantic information feature representations of the sentences are obtained by the graph convolutional network with a multi-head attention mechanism and fused to achieve complementary learning of dual-channel features. Experimental results show that the model performs well and improves the accuracy of sentiment classification on three public benchmark datasets, namely Rest14, Lap14 and Twitter.
基金supported by National Key Basic Research and Development Plan (973 Plan) of China (No. 2007CB310900)National Natural Science Foundation of China (No. 90612018, 90715030 and 60970008)
文摘This paper is a continuation of our last paper [1] which describes the theory of Virt-BLP model. Based on Virt-BLP model,this paper implements a mandatory access control(MAC) framework applicable to multi-level security(MLS) in Xen. The Virt-BLP model is the theoretical basis of this MAC framework,and this MAC framework is the implementation of Virt-BLP model. Our last paper focuses on Virt-BLP model,while this paper concentrates on the design and implementation of MAC framework. For there is no MAC framework applicable to MLS in virtual machine system at present,our MAC framework fills the blank by applying Virt-BLP model to Xen,which is better than current researches to guarantee the security of communication between virtual machines(VMs) . The experimental results show that our MAC framework is effective to manage the communication between VMs.
文摘To overcome the shortcomings of 1 D and 2 D Otsu’s thresholding techniques, the 3 D Otsu method has been developed.Among all Otsu’s methods, 3 D Otsu technique provides the best threshold values for the multi-level thresholding processes. In this paper, to improve the quality of segmented images, a simple and effective multilevel thresholding method is introduced. The proposed approach focuses on preserving edge detail by computing the 3 D Otsu along the fusion phenomena. The advantages of the presented scheme include higher quality outcomes, better preservation of tiny details and boundaries and reduced execution time with rising threshold levels. The fusion approach depends upon the differences between pixel intensity values within a small local space of an image;it aims to improve localized information after the thresholding process. The fusion of images based on local contrast can improve image segmentation performance by minimizing the loss of local contrast, loss of details and gray-level distributions. Results show that the proposed method yields more promising segmentation results when compared to conventional1 D Otsu, 2 D Otsu and 3 D Otsu methods, as evident from the objective and subjective evaluations.
基金supported by National Natural Science Foundation of China(No.61571061)
文摘In this paper, we focus on the design of irregular QC-LDPC code based multi-level coded modulation(MLCM) scheme by jointly optimizing the component code rate and the degree distribution of the irregular QC-LDPC component code. Firstly, the sub-channel capacities of MLCM systems is analyzed and discussed, based on which the optimal component code rate can be obtained. Secondly, an extrinsic information transfer chart based two-stage searching algorithm is proposed to find the good irregular QC-LDPC code ensembles with optimal component code rates for their corresponding sub-channels. Finally, by constructing the irregular QC-LDPC component codes from the designed ensembles with the aim of possibly enlarging the girth and reducing the number of the shortest cycles, the designed irregular QC-LDPC code based 16QAM and 64QAM MLCM systems can achieve 0.4 dB and 1.2 dB net coding gain, respectively, compared with the recently proposed regular QC-LDPC code based 16QAM and 64QAM MLCM systems.
基金Funded by the National 863 Plan Foundation of China (No.2006AA03Z536)the National Natural Science Foundation of China (No.50778021)
文摘Fatigue properties of Reactive Powder Concrete （RPC） under axial compression of single-stage and multi-level amplitude in cycles were studied. The tests reveal the fatigue life, the strain and residual life of the RPC samples. Through the analysis of the test results under cyclic loads of single amplitude, the S-N curve of RPC and the evolution rule of macro-damage of RPC were presented, which can be divided into latency stage, stable development stage and instability development stage according to the evolution pattern of the fatigue crack. Accordingly, the development of longitudinal deformation presents the similar three-stage-model, and the proportion of each stage is 15%, 75%, and 10%. According to test results, the fatigue strength reduction factor is 0.564. We brought forward an empirical formula to predict the life of RPC via total longitudinal strain and got the evolving rule for the residual strength of the RPC. The analysis of the test results under cyclic loads of multi-level amplitude shows that the strain under this loading pattern experiences three stages. The characteristic value for the residual strain was obtained. The irreversible damage and non-linear evolution of RPC was described by the development of the residual plastic strain.
基金the International Cooperation Project of Ministry of Science and Technology of P. R. China (GrantNo.CB7-2-01)SEC E-Institute: Shanghai High Institutions Grid
文摘Partitioning is a fundamental problem with applications to many areas including data mining, parellel processing and Very-large-scale integration （VLSI） design. An effective multi-level algorithm for bisecting graph is proposed. During its coarsening phase, an improved matching approach based on the global information of the graph core is developed with its guidance function. During the refinement phase, the vertex gain is exploited as ant＇s heuristic information and a positive feedback method based on pheromone trails is used to find the global approximate bipartitioning. It is implemented with American National Standards Institute （ANSI） C and compared to MeTiS. The experimental evaluation shows that it performs well and produces encouraging solutions on 18 different graphs benchmarks.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60977005)
文摘The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection （DPD） method in the signal waveform modulation multi-level （SWML） read-only disc. To solve this problem, this paper proposes a new tracking error detection method using amplitude difference. Based on the diffraction theory, the amplitude difference is proportional to the tracking error and is feasible to be used for obtaining the off-track information. The experimental system of the amplitude difference detection method is developed. The experimental results show that the tracking error signal derived from the new method has better performance in uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc.
基金supported by National Hi-tech Research and Development Program of China (863 Program, Grant No. 2007AA04Z433)Hunan Provincial Natural Science Foundation of China (Grant No. 09JJ8005)Scientific Research Foundation of Graduate School of Beijing University of Chemical and Technology,China (Grant No. 10Me002)
文摘As the differences of sensor＇s precision and some random factors are difficult to control,the actual measurement signals are far from the target signals that affect the reliability and precision of rotating machinery fault diagnosis.The traditional signal processing methods,such as classical inference and weighted averaging algorithm usually lack dynamic adaptability that is easy for trends to cause the faults to be misjudged or left out.To enhance the measuring veracity and precision of vibration signal in rotary machine multi-sensor vibration signal fault diagnosis,a novel data level fusion approach is presented on the basis of correlation function analysis to fast determine the weighted value of multi-sensor vibration signals.The approach doesn＇t require knowing the prior information about sensors,and the weighted value of sensors can be confirmed depending on the correlation measure of real-time data tested in the data level fusion process.It gives greater weighted value to the greater correlation measure of sensor signals,and vice versa.The approach can effectively suppress large errors and even can still fuse data in the case of sensor failures because it takes full advantage of sensor＇s own-information to determine the weighted value.Moreover,it has good performance of anti-jamming due to the correlation measures between noise and effective signals are usually small.Through the simulation of typical signal collected from multi-sensors,the comparative analysis of dynamic adaptability and fault tolerance between the proposed approach and traditional weighted averaging approach is taken.Finally,the rotor dynamics and integrated fault simulator is taken as an example to verify the feasibility and advantages of the proposed approach,it is shown that the multi-sensor data level fusion based on correlation function weighted approach is better than the traditional weighted average approach with respect to fusion precision and dynamic adaptability.Meantime,the approach is adaptable and easy to use,can be applied to other areas of vibration measurement.
基金Supported by the China National Science and Technology Major Project(2016ZX 05003-001)
文摘Based on forward modeling of detachment fold, this study presents a method to analyze multi-level detachment structures and identify the authenticity of deep-seated anticlines using time-domain seismic section. The steps include the conversion of the time-migrated seismic image into depth domain image using a constant velocity field, structural interpretation of the depth seismic image, measurement of each structural relief area and each height above reference level, plotting of area-height relationship chart with piecewise fitting etc. The area-depth correlation can help the division of structural sequences, the definition of detachment levels, the calculation of the tectonic shortening, and the identification of deep-seated structure. The segment area-height relationship is a feature of multi-level detachment structures, while little or no linear correlation between area and height is an indicator of non-deformation or pseudo-anticline. Regardless of the uncertainty of area-height relationship, the segment slopes will correspond to the differential shortenings of multi-level detachments, the intersection between adjacent segments will give the height of detachment surface above reference level and then help define the detachment level in original time-domain seismic section. This method can make use of time-domain seismic data to determine the geologic structure of complicated structure areas and assess risks of deep exploration targets. It has achieved good results in southern Junggar and eastern Sichuan areas.
基金Supported by the Shanxi Natural Science Foundation under contract number 20041070 and Natural Science Foundation of north u-niversity of China .
文摘To implement a quantificational evaluation for mechanical kinematic scheme more effectively,a multi-level and multi-objective evaluation model is presented using neural network and fuzzy theory. Firstly,the structure of evaluation model is constructed according to evaluation indicator system. Then evaluation samples are generated and provided to train this model. Thus it can reflect the relation between attributive value and evaluation result,as well as the weight of evaluation indicator. Once evaluation indicators of each candidate are fuzzily quantified and fed into the trained network model,the corresponding evaluation result is outputted and the best alternative can be selected. Under this model,expert knowledge can be effectively acquired and expressed,and the quantificational evaluation can be implemented for kinematic scheme with multi-level evaluation indicator system. Several key problems on this model are discussed and an illustration has demonstrated that this model is feasible and can be regarded as a new idea for solving kinematic scheme evaluation.
基金financially supported by the National Science Foundation of China(No.50971010)New Teacher Foundation of Beihang University(211109)+1 种基金New Teacher Funds of Education Ministry of China(2008-00061025)SRF and SEM funds of Education Ministry of China
文摘One process based on phase inversion of fillers in microstructures for the fabrication of multi-level three-dimensional(3-D) microstructures is described using SU-8, a kind of epoxy photoresist, as the model constructing materials. This process is depicted by use of the routine photolithography technique to construct the top layer of 3-D microstructures on the bottom layer of 3-D microstructures layer by layer. This process makes it possible to fabricate multi-level 3-D microstructures with connectors at desired locations, and to seal long span microstructures(e.g. very shallow channels with depth less than 50 μm and width more than 300 μm) without blockage. In addition, this process can provide a sealing layer by the solidification of a liquid polymer layer, which can be as strong as the bulk constructing materials for microstructures due to a complete contact and cross-linking between the sealing layer and the patterned layers. The hydrodynamic testing indicates that this kind of sealing and interconnection can endure a static pressure of more than 10 MPa overnight and a hydrodynamic pressure drop of about 5.3 MPa for more than 8 hours by pumping the tetrahydrofuran solution through a 60 μm wide micro-channels.
文摘The time-dependence bilinear mixed-regression deformation model and time-dependence bilinear dynamic system deformation model are established for deformation observation series. According to the multi- level recursive method, the time-dependence parameters are first traced and predicted, and then the dynamic system states. Due to the method considering time-dependence of deformation and having stronger adaptability to time-dependence system, it can improve forecast’s precision. It is very effective for data processing of nonlinear dynamic deformation monitoring to make multi-step forecasting.
基金Funded by the National Natural Science Foundation of China(No.50872151)the Outstanding Innovative Talents Program of China University of Mining&Technology(Beijing)(No.00-800015Z637)
文摘Under saturation dosage of all kinds of SP, the free water amount was examined by centrifuge. The distribution of solution and flocculation microstructures in fresh cement paste was observed in three- dimensional space by confocal laser scanning microscope（CLSM）. Results indicate that SP can increase the free water amount by destroying the flocculated cement particle structure and different free water amount is released by different kinds of SP. The changes of the size of flocculation structures and the dispersion of solution were obviously detected with confocal laser scanning microscope： the size of flocculation structures was smaller and more dispersed in fresh cement paste with polycarboxylate superplasticizer, but the size of flocculation structures was bigger and cannot be dispersed uniformly in fresh cement paste with others SP. The multi- level flocculation structures theoretical model of fresh cement paste was then set up. The theory indicates that different kinds of SP with different dispersion strength will open the flocculation structures at different levels, which in turn present different water reducing rate.
基金Supported by the Natural Science Foundation of Hubei Province(2012FFC034,2014CFC1100)
文摘In this paper, we present a distributed multi-level cache system based on cloud storage, which is aimed at the low access efficiency of small spatio-temporal data files in information service system of Smart City. Taking classification attribute of small spatio-temporal data files in Smart City as the basis of cache content selection, the cache system adopts different cache pool management strategies in different levels of cache. The results of experiment in prototype system indicate that multi-level cache in this paper effectively increases the access bandwidth of small spatio-temporal files in Smart City and greatly improves service quality of multiple concurrent access in system.
基金supported by the Infectious Disease Prevention and Control Major Research plan from the Ministry of Science and Technology of China-the Platform of Construction of Clinical Trial of Vaccine. (Project number 2009ZX0004-806)
文摘Objective To evaluate the effect of the aluminum hydroxide （Al-OH） adjuvant on the 2009 pandemic influenza A/H1N1 （pH1N1） vaccine. Methods In a multicenter, double-blind, randomized, placebo-controlled trial, participants received two doses of split-virion formulation containing 15 ug hemagglutinin antigen, with or without aluminum hydroxide （N-OH）. We classified the participants into six age categories （〉61 years, 41-60 years, 19-40 years, 13-18 years, 8-12 years, and 3-7 years） and obtained four blood samples from each participant on days 0, 21, 35, and 42 following the first dose of immunization. We assessed vaccine immunogenicity by measuring the geometric mean titer （GMT） of hemagglutination inhibiting antibody. We used a two-level model to evaluate the fixed effect of aluminum Al-OH and other factors, accounting for repeated measures. Results The predictions of repeated measurement on GMTs of formulations with or without Al-OH, were 80.35 and 112.72, respectively. Al-OH significantly reduced immunogenicity after controlling for time post immunization, age-group and gender. Conclusion The Al-OH adjuvant does not increase but actually reduces the immunogenicity of the split-virion pH1N1 vaccine.
基金supported by the National Natural Science Foundation of China(Nos.10632030,10902020,and 10721062)the Research Fund for the Doctoral Program of Higher Education of China(No.20070141067)+2 种基金the Doctoral Fund of Liaoning Province(No.20081091)the Key Laboratory Fund of Liaoning Province of China(No.2009S018)the Young Researcher Funds of Dalian University of Technology(No.SFDUT07002)
文摘By converting an optimal control problem for nonlinear systems to a Hamiltonian system,a symplecitc-preserving method is proposed.The state and costate variables are approximated by the Lagrange polynomial.The state variables at two ends of the time interval are taken as independent variables.Based on the dual variable principle,nonlinear optimal control problems are replaced with nonlinear equations.Furthermore,in the implementation of the symplectic algorithm,based on the 2N algorithm,a multilevel method is proposed.When the time grid is refined from low level to high level,the initial state and costate variables of the nonlinear equations can be obtained from the Lagrange interpolation at the low level grid to improve efficiency.Numerical simulations show the precision and the efficiency of the proposed algorithm in this paper.
文摘A novel read channel for signal waveform modulation multi-level disc is presented in this paper. This read channel employs timing recovery system and partial response maximum likelihood detector. Compared to the previous read channel composed of level detection and run-length detection, the present read channel shows superiority in capacity increase and robust performance. Especially, relying on the partial response maximum likelihood detection, lower bit error rate can be obtained.
文摘This paper presents a new topology to connect high voltage direct current(HVDC) offshore wind farm into the grid.The offshore part consists of five units,each unit contains permanent magnet synchronous generator(PMSG) connected to three-phase/three-phase matrix converter to control the generator speed by using a maximum power point tracking(MPPT) control.The offshore platform consists of a three-phase medium frequency transformer(MFT) and a modular multi-level converter(MMC).The primary of each phase of the transformer connected to one phase from each unit.The secondary of the transformer connected to MMC to get HVDC.The HVDC cable will be used to transfer power from the offshore side to the on-shore side.Five-level MMC is used in the onshore side to control the DC voltage and to connect the offshore wind farm into the grid by converting the HVDC to high voltage alternative current(HVAC).
