In the multilevel thresholding segmentation of the image, the classification number is always given by the supervisor. To solve this problem, a fast multilevel thresholding algorithm considering both the threshold val...In the multilevel thresholding segmentation of the image, the classification number is always given by the supervisor. To solve this problem, a fast multilevel thresholding algorithm considering both the threshold value and the classification number is proposed based on the maximum entropy, and the self-adaptive criterion of the classification number is given. The algorithm can obtain thresholds and automatically decide the classification number. Experimental results show that the algorithm is effective.展开更多
This study aims to investigate the mechanical response and acoustic emission(AE)characteristic of pre-flawed sandstone under both monotonic and multilevel constant-amplitude cyclic loads.Specifically,we explored how c...This study aims to investigate the mechanical response and acoustic emission(AE)characteristic of pre-flawed sandstone under both monotonic and multilevel constant-amplitude cyclic loads.Specifically,we explored how coplanar flaw angle and load type impact the strength and deformation behavior and microscopic damage mechanism.Results indicated that being fluctuated before rising with increasing fissure angle under monotonic loading,the peak strength of the specimen first increased slowly and then steeply under cyclic loading.The effect of multilevel cyclic loading on the mechanical parameters was more significant.For a single fatigue stage,the specimen underwent greater deformation in early cycles,which subsequently stabilized.Similar variation pattern was also reflected by AE count/energy/b-value.Crack behaviors were dominated by the fissure angle and load type and medium-scale crack accounted for 74.83%–86.44%of total crack.Compared with monotonic loading,crack distribution of specimen under cyclic loading was more complicated.Meanwhile,a simple model was proposed to describe the damage evolution of sandstone under cyclic loading.Finally,SEM images revealed that the microstructures at the fracture were mainly composed of intergranular fracture,and percentage of transgranular fracture jumped under cyclic loading due to the rapid release of elastic energy caused by high loading rate.展开更多
For nuclear measurements,it is necessary to obtain accurate information from nuclear pulses,which should be obtained by first shaping the pulses outputted by the detectors.However,commonly used pulse-shaping algorithm...For nuclear measurements,it is necessary to obtain accurate information from nuclear pulses,which should be obtained by first shaping the pulses outputted by the detectors.However,commonly used pulse-shaping algorithms have certain problems.For example,certain pulse-shaping algorithms have long dead-times in high-counting-rate environments or are difficult to achieve in digital systems.Gaussian signals are widely used in analog nuclear instruments owing to their symmetry and completeness.A Gaussian signal is usually implemented by using a multilevel S–K filter in series or in parallel.It is difficult to construct a real-time digital Gaussian filter for the complex Gaussian filtering algorithm.Based on the multilevel cascade convolution,a pulse-shaping algorithm for double exponential signals is proposed in this study,which,in addition to double exponential signals,allows more complex output signal models to be used in the new algorithm.The proposed algorithm can be used in high-counting-rate environments and has been implemented in an FPGA with fewer multipliers than those required in other traditional Gaussian pulse-shaping algorithms.The offline processing results indicated that the average peak base width of the output-shaped pulses obtained using the proposed algorithm was reduced compared with that obtained using the traditional Gaussian pulse-shaping algorithm.Experimental results also demonstrated that signal-to-noise ratios and energy resolutions were improved,particularly for pulses with a low energy.The energy resolution was improved by 0.1–0.2%while improving the counting rate.展开更多
As a result of the interplay between advances in computer hardware, software, and algorithm, we are now in a new era of large-scale reservoir simulation, which focuses on accurate flow description, fine reservoir char...As a result of the interplay between advances in computer hardware, software, and algorithm, we are now in a new era of large-scale reservoir simulation, which focuses on accurate flow description, fine reservoir characterization, efficient nonlinear/linear solvers, and parallel implementation. In this paper, we discuss a multilevel preconditioner in a new-generation simulator and its implementation on multicore computers. This preconditioner relies on the method of subspace corrections to solve large-scale linear systems arising from fully implicit methods in reservoir simulations. We investigate the parallel efficiency and robustness of the proposed method by applying it to million-cell benchmark problems.展开更多
Objective：To investigate a novel surgical method for multilevel cervical spondylotic myelopathy （CSM）. Methods： Totally 21 patients with multilevel CSM undergoing a novel surgical procedure from April 2001 to Janu...Objective：To investigate a novel surgical method for multilevel cervical spondylotic myelopathy （CSM）. Methods： Totally 21 patients with multilevel CSM undergoing a novel surgical procedure from April 2001 to January 2004 were analyzed retrospectively. All patients experienced anterior cervical decompression surgery in subsection, autograft fusion and internal fixation. Preoperative, immediate postoperative and follow-up image data, X-rays and semi-quantitative Japanese orthopaedics association （JOA） scores were used to evaluate the restoration of lordosis （Cobb＇s angle）, intervertebral heights, the stability of the cervical spine and the improvement of neurological impairment. Results： Preoperative symptoms were markedly alleviated or disappeared in most of the patients. According to the JOA scores, the ratio of improvement in neurological function was 72. 2%, including excellent in 9 cases （42.9%）, good in 7 cases （33.3%）, fair in 3 cases （14.3%） and poor in 2 cases （9.5%）. Immediate postoperative X-rays showed obvious improvements in lordosis and in the intervertebral height of the cervical spine （P〈0. 01）. There is no evidence of instrument failure during the mean follow-up period of 14. 2 months （9-24 months, P〉0. 01）. Conclusion：Anterior cervical decompression in subsection, autograft fusion and internal fixation is a rational effective method for the surgical treatment of multilevel CSM.展开更多
Based on the heat diffusion equation of multilevel interconnects, a novel analytical thermal model for multilevel nano-scale interconnects considering the via effect is presented, which can compute quickly the tempera...Based on the heat diffusion equation of multilevel interconnects, a novel analytical thermal model for multilevel nano-scale interconnects considering the via effect is presented, which can compute quickly the temperature of multilevel interconnects, with substrate temperature given. Based on the proposed model and the 65 nm complementary metal oxide semiconductor （CMOS） process parameter, the temperature of nano-scale interconnects is computed. The computed results show that the via effect has a great effect on local interconnects, but the reduction of thermal conductivity has little effect on local interconnects. With the reduction of thermal conductivity or the increase of current density, however, the temperature of global interconnects rises greatly, which can result in a great deterioration in their performance. The proposed model can be applied to computer aided design （CAD） of very large-scale integrated circuits （VLSIs） in nano-scale technologies.展开更多
The advantages of read-only storage is the predominance of optical recording relative to magnetic and other rewritable methods. Multilevel （ML） read-only technology has been a trend to improve the data capacity and ...The advantages of read-only storage is the predominance of optical recording relative to magnetic and other rewritable methods. Multilevel （ML） read-only technology has been a trend to improve the data capacity and transfer rate. Based on the principle and coding method of ML, this paper demonstrates some ML read-only recording methods, of which a new ML read-only recording is developed. This recording method integrates amplitude modulation achieved by the reaction mechanism of physics and chemistry of photoresist with the run-length-limited technology. The discs can be achieved using standard photoresist mastering and replication techniques with great compatibility to conventional binary read-only discs.展开更多
With the implementation of new-generation launch vehicles,space stations,lunar and deep space exploration,etc.,the development of spacecraft structures will face new challenges. In order to reduce the spacecraft weigh...With the implementation of new-generation launch vehicles,space stations,lunar and deep space exploration,etc.,the development of spacecraft structures will face new challenges. In order to reduce the spacecraft weight and increase the payload,composite material structures will be widely used. It is difficult to evaluate the strength and life of composite materials due to their complex mechanism and various phenomena in damage and failure.Meanwhile,the structures of composite materials used in spacecrafts will bear complex loads,including the coupling loads of tension,pressure,bending,shear,and torsion. Static loads,thermal loads,and vibration loads may occur at the same time,which asks for verification requirements to ensure the structure safety. Therefore,it is necessary to carry out a systematic multi-level experimental study. In this paper,the building block approach (BBA) is used to investigate the multilevel composite material structures for spacecrafts. The advanced measurement technology is adopted based on digital image correlation (DIC) and piezoelectric and optical fiber sensors to measure the composite material structure deformation. The virtual experiment technology is applied to provide sufficient and reliable data for the evaluation of the composite material structures of spacecrafts.展开更多
Polymer injectivity is an important factor for evaluating the project economics of chemical flood,which is highly related to the polymer viscosity.Because the flow rate varies rapidly near injectors and significantly ...Polymer injectivity is an important factor for evaluating the project economics of chemical flood,which is highly related to the polymer viscosity.Because the flow rate varies rapidly near injectors and significantly changes the polymer viscosity due to the non-Newtonian rheological behavior,the polymer viscosity near the wellbore is difficult to estimate accurately with the practical gridblock size in reservoir simulation.To reduce the impact of polymer rheology upon chemical EOR simulations,we used an efficient multilevel local grid refinement（LGR）method that provides a higher resolution of the flows in the near-wellbore region.An efficient numerical scheme was proposed to accurately solve the pressure equation and concentration equations on the multilevel grid for both homogeneous and heterogeneous reservoir cases.The block list and connections of the multilevel grid are generated via an efficient and extensible algorithm.Field case simulation results indicate that the proposed LGR is consistent with the analytical injectivity model and achieves the closest results to the full grid refinement,which considerably improves the accuracy of solutions compared with the original grid.In addition,the method was validated by comparing it with the LGR module of CMG_STARS.Besides polymer injectivity calculations,the LGR method is applicable for other problems in need of near-wellbore treatment,such as fractures near wells.展开更多
This paper describes an empirical study aiming at identifying the main differences between different logistic regression models and collision data aggregation methods that are commonly applied in road safety literatur...This paper describes an empirical study aiming at identifying the main differences between different logistic regression models and collision data aggregation methods that are commonly applied in road safety literature for modeling collision severity. In particular, the research compares three popular multilevel logistic models （i.e., sequential binary logit models, ordered logit models, and multinomial logit models） as well as three data aggregation methods （i.e., occupant based, vehicle based, and collision based）. Six years of collision data （2001-2006） from 31 highway routes from across the province of Ontario, Canada were used for this analysis. It was found that a multilevel multinomial logit model has the best fit to the data than the other two models while the results obtained from occupant-based data are more reliable than those from vehicle- and collision-based data. More importantly, while generally consistent in terms of factors that were found to be significant between different models and data aggregation methods, the effect size of each factor differ sub- stantially, which could have significant implications forevaluating the effects of different safety-related policies and countermeasures.展开更多
In this paper, the self-compliance bipolar resistive switching characteristic of an HfO-based memory device with Ag/HfO/Au structure for multilevel storage is investigated. By applying a positive voltage, the dual-ste...In this paper, the self-compliance bipolar resistive switching characteristic of an HfO-based memory device with Ag/HfO/Au structure for multilevel storage is investigated. By applying a positive voltage, the dual-step set processes corresponding to three stable resistance states are observed in the device. The multilevel switching characteristics can still be observed after 48 hours. In addition, the resistance values of all the three states show negligible degradation over 104 s,which may be useful for the applications in nonvolatile multilevel storage.展开更多
Based on the multilevel interconnections temperature distribution model and the RLC interconnection delay model of the integrate circuit, this paper proposes a multilevel nano-scale interconnection RLC delay model wit...Based on the multilevel interconnections temperature distribution model and the RLC interconnection delay model of the integrate circuit, this paper proposes a multilevel nano-scale interconnection RLC delay model with the method of numerical analysis, the proposed analytical model has summed up the influence of the configuration of multilevel interconnections, the via heat transfer and self-heating effect on the interconnection delay, which is closer to the actual situation. Delay simulation results show that the proposed model has high precision within 5% errors for global interconnections based on the 65 nm CMOS interconnection and material parameter, which can be applied in nanometer CMOS system chip computer-aided design.展开更多
The recording density of multilevel photochromic memory is limited by the signal-to-noise ratio （SNR） of the readout signal. In this paper, shot noise and material noise are investigated through theoretical analysis...The recording density of multilevel photochromic memory is limited by the signal-to-noise ratio （SNR） of the readout signal. In this paper, shot noise and material noise are investigated through theoretical analysis of SNR. When the bandwidth of a system is less than 1MHz, the material noise takes a prominent position; when the bandwidth of the system is more than 10MHz, the shot noise becomes dominant. The thickness of recording layer can be optimized to maximize the SNR and reduce the influence of the bandwidth of the system on SNR.展开更多
With CMOS technologies approaching the scaling ceiling, novel memory technologies have thrived in recent years, among which the memristor is a rather promising candidate for future resistive memory （RRAM）. Memristor...With CMOS technologies approaching the scaling ceiling, novel memory technologies have thrived in recent years, among which the memristor is a rather promising candidate for future resistive memory （RRAM）. Memristor＇s potential to store multiple bits of information as different resistance levels allows its application in multilevel cell （MCL） tech- nology, which can significantly increase the memory capacity. However, most existing memristor models are built for binary or continuous memristance switching. In this paper, we propose the simulation program with integrated circuits emphasis （SPICE） modeling of charge-controlled and flux-controlled memristors with multilevel resistance states based on the memristance versus state map. In our model, the memristance switches abruptly between neighboring resistance states. The proposed model allows users to easily set the number of the resistance levels as parameters, and provides the predictability of resistance switching time if the input current/voltage waveform is given. The functionality of our models has been validated in HSPICE. The models can be used in multilevel RRAM modeling as well as in artificial neural network simulations.展开更多
The tail bits of intermediate resistance states（IRSs） achieved in the SET process（IRSS） and the RESET process（IRSR） of conductive-bridge random-access memory were investigated. Two types of tail bits were observ...The tail bits of intermediate resistance states（IRSs） achieved in the SET process（IRSS） and the RESET process（IRSR） of conductive-bridge random-access memory were investigated. Two types of tail bits were observed, depending on the filament morphology after the SET/RESET operation.（i） Tail bits resulting from lateral diffusion of Cu ions introduced an abrupt increase of device resistance from IRS to ultrahigh-resistance state, which mainly happened in IRSS.（ii） Tail bits induced by the vertical diffusion of Cu ions showed a gradual shift of resistance toward lower value. Statistical results show that more than 95% of tail bits are generated in IRSS. To achieve a reliable IRS for multilevel cell（MLC） operation, it is desirable to program the IRS in RESET operation. The mechanism of tail bit generation that is disclosed here provides a clear guideline for the data retention optimization of MLC resistive random-access memory cells.展开更多
Attribute reduction is an important process in rough set theory.Finding minimum attribute reduction has been proven to help the user-oriented make better knowledge discovery in some cases.In this paper,an efficient mi...Attribute reduction is an important process in rough set theory.Finding minimum attribute reduction has been proven to help the user-oriented make better knowledge discovery in some cases.In this paper,an efficient minimum attribute reduction algorithm is proposed based on the multilevel evolutionary tree with self-adaptive subpopulations.A model of multilevel evolutionary tree with self-adaptive subpopulations is constructed,and interacting attribute sets are better decomposed into subsets by the self-adaptive mechanism of elitist populations.Moreover it can self-adapt the subpopulation sizes according to the historical performance record so that interacting attribute decision variables are captured into the same grouped subpopulation,which will be extended to better performance in both quality of solution and competitive computation complexity for minimum attribute reduction.The conducted experiments show the proposed algorithm is better on both efficiency and accuracy of minimum attribute reduction than some representative algorithms.Finally the proposed algorithm is applied to magnetic resonance image(MRI)segmentation,and its stronger applicability is further demonstrated by the effective and robust segmentation results.展开更多
The multilevel characteristic basis function method(MLCBFM)with the adaptive cross approximation(ACA)algorithm for accelerated solution of electrically large scattering problems is studied in this paper.In the convent...The multilevel characteristic basis function method(MLCBFM)with the adaptive cross approximation(ACA)algorithm for accelerated solution of electrically large scattering problems is studied in this paper.In the conventional MLCBFM based on Foldy-Lax multiple scattering equations,the improvement is only made in the generation of characteristic basis functions(CBFs).However,it does not provide a change in impedance matrix filling and reducing matrix calculation procedure,which is time-consuming.In reality,all the impedance and reduced matrix of each level of the MLCBFM have low-rank property and can be calculated efficiently.Therefore,ACA is used for the efficient generation of two-level CBFs and the fast calculation of reduced matrix in this study.Numerical results are given to demonstrate the accuracy and efficiency of the method.展开更多
XML＇s increasing popularity highlights the security demand for XML documents. A mandatory access control model for XML document is presented on the basis of investigation of the function dependency of XML documents a...XML＇s increasing popularity highlights the security demand for XML documents. A mandatory access control model for XML document is presented on the basis of investigation of the function dependency of XML documents and discussion of the integrity properties of multilevel XML document. Then, the algorithms for decomposition/recovery multilevel XML document into/from single level document are given, and the manipulation rules for typical operations of XQuery and XUpdate： QUERY, INSERT, UPDATE, and REMOVE, are elaborated. The multilevel XML document access model can meet the requirement of sensitive information processing application.展开更多
Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability...Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability and operation speed is one of key factors to restrain the development of phase-change memory.Here,N-doped Ge_(2)Sb_(2)Te_(5)-based optoelectronic hybrid memory is proposed to simultaneously implement high thermal stability and ultrafast operation speed.The picosecond laser is adopted to write/erase information based on reversible phase transition characteristics whereas the resistance is detected to perform information readout.Results show that when N content is 27.4 at.%,N-doped Ge_(2)Sb_(2)Te_(5)film possesses high ten-year data retention temperature of 175℃and low resistance drift coefficient of 0.00024 at 85℃,0.00170 at 120℃,and 0.00249 at 150℃,respectively,owing to the formation of Ge–N,Sb–N,and Te–N bonds.The SET/RESET operation speeds of the film reach 520 ps/13 ps.In parallel,the reversible switching cycle of the corresponding device is realized with the resistance ratio of three orders of magnitude.Four-level reversible resistance states induced by various crystallization degrees are also obtained together with low resistance drift coefficients.Therefore,the N-doped Ge_(2)Sb_(2)Te_(5)thin film is a promising phase-change material for ultrafast multilevel optoelectronic hybrid storage.展开更多
Four different states of Si15Sb85 and Ge2Sb2Te5 phase change memory thin films are obtained by crystallization degree modulation through laser initialization at different powers or annealing at different temperatures....Four different states of Si15Sb85 and Ge2Sb2Te5 phase change memory thin films are obtained by crystallization degree modulation through laser initialization at different powers or annealing at different temperatures. The polarization characteristics of these two four-level phase change recording media are analyzed systematically. A simple and effective readout scheme is then proposed, and the readout signal is numerically simulated. The results show that a high-contrast polarization readout can be obtained in an extensive wavelength range for the four-level phase change recording media using common phase change materials. This study will help in-depth understanding of the physical mechanisms and provide technical approaches to multilevel phase change recording.展开更多
文摘In the multilevel thresholding segmentation of the image, the classification number is always given by the supervisor. To solve this problem, a fast multilevel thresholding algorithm considering both the threshold value and the classification number is proposed based on the maximum entropy, and the self-adaptive criterion of the classification number is given. The algorithm can obtain thresholds and automatically decide the classification number. Experimental results show that the algorithm is effective.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.42077231 and 51574156).
文摘This study aims to investigate the mechanical response and acoustic emission(AE)characteristic of pre-flawed sandstone under both monotonic and multilevel constant-amplitude cyclic loads.Specifically,we explored how coplanar flaw angle and load type impact the strength and deformation behavior and microscopic damage mechanism.Results indicated that being fluctuated before rising with increasing fissure angle under monotonic loading,the peak strength of the specimen first increased slowly and then steeply under cyclic loading.The effect of multilevel cyclic loading on the mechanical parameters was more significant.For a single fatigue stage,the specimen underwent greater deformation in early cycles,which subsequently stabilized.Similar variation pattern was also reflected by AE count/energy/b-value.Crack behaviors were dominated by the fissure angle and load type and medium-scale crack accounted for 74.83%–86.44%of total crack.Compared with monotonic loading,crack distribution of specimen under cyclic loading was more complicated.Meanwhile,a simple model was proposed to describe the damage evolution of sandstone under cyclic loading.Finally,SEM images revealed that the microstructures at the fracture were mainly composed of intergranular fracture,and percentage of transgranular fracture jumped under cyclic loading due to the rapid release of elastic energy caused by high loading rate.
基金supported by the National Natural Science Foundation of China(Nos.11975060,12005026,and 12075038)the Science and Technology Project in Sichuan Province(No.2021JDRC0028).
文摘For nuclear measurements,it is necessary to obtain accurate information from nuclear pulses,which should be obtained by first shaping the pulses outputted by the detectors.However,commonly used pulse-shaping algorithms have certain problems.For example,certain pulse-shaping algorithms have long dead-times in high-counting-rate environments or are difficult to achieve in digital systems.Gaussian signals are widely used in analog nuclear instruments owing to their symmetry and completeness.A Gaussian signal is usually implemented by using a multilevel S–K filter in series or in parallel.It is difficult to construct a real-time digital Gaussian filter for the complex Gaussian filtering algorithm.Based on the multilevel cascade convolution,a pulse-shaping algorithm for double exponential signals is proposed in this study,which,in addition to double exponential signals,allows more complex output signal models to be used in the new algorithm.The proposed algorithm can be used in high-counting-rate environments and has been implemented in an FPGA with fewer multipliers than those required in other traditional Gaussian pulse-shaping algorithms.The offline processing results indicated that the average peak base width of the output-shaped pulses obtained using the proposed algorithm was reduced compared with that obtained using the traditional Gaussian pulse-shaping algorithm.Experimental results also demonstrated that signal-to-noise ratios and energy resolutions were improved,particularly for pulses with a low energy.The energy resolution was improved by 0.1–0.2%while improving the counting rate.
基金support through PetroChina New-generation Reservoir Simulation Software (2011A-1010)the Program of Research on Continental Sedimentary Oil Reservoir Simulation (z121100004912001)+7 种基金founded by Beijing Municipal Science & Technology Commission and PetroChina Joint Research Funding12HT1050002654partially supported by the NSFC Grant 11201398Hunan Provincial Natural Science Foundation of China Grant 14JJ2063Specialized Research Fund for the Doctoral Program of Higher Education of China Grant 20124301110003partially supported by the Dean’s Startup Fund, Academy of Mathematics and System Sciences and the State High Tech Development Plan of China (863 Program 2012AA01A309partially supported by NSFC Grant 91130002Program for Changjiang Scholars and Innovative Research Team in University of China Grant IRT1179the Scientific Research Fund of the Hunan Provincial Education Department of China Grant 12A138
文摘As a result of the interplay between advances in computer hardware, software, and algorithm, we are now in a new era of large-scale reservoir simulation, which focuses on accurate flow description, fine reservoir characterization, efficient nonlinear/linear solvers, and parallel implementation. In this paper, we discuss a multilevel preconditioner in a new-generation simulator and its implementation on multicore computers. This preconditioner relies on the method of subspace corrections to solve large-scale linear systems arising from fully implicit methods in reservoir simulations. We investigate the parallel efficiency and robustness of the proposed method by applying it to million-cell benchmark problems.
文摘Objective：To investigate a novel surgical method for multilevel cervical spondylotic myelopathy （CSM）. Methods： Totally 21 patients with multilevel CSM undergoing a novel surgical procedure from April 2001 to January 2004 were analyzed retrospectively. All patients experienced anterior cervical decompression surgery in subsection, autograft fusion and internal fixation. Preoperative, immediate postoperative and follow-up image data, X-rays and semi-quantitative Japanese orthopaedics association （JOA） scores were used to evaluate the restoration of lordosis （Cobb＇s angle）, intervertebral heights, the stability of the cervical spine and the improvement of neurological impairment. Results： Preoperative symptoms were markedly alleviated or disappeared in most of the patients. According to the JOA scores, the ratio of improvement in neurological function was 72. 2%, including excellent in 9 cases （42.9%）, good in 7 cases （33.3%）, fair in 3 cases （14.3%） and poor in 2 cases （9.5%）. Immediate postoperative X-rays showed obvious improvements in lordosis and in the intervertebral height of the cervical spine （P〈0. 01）. There is no evidence of instrument failure during the mean follow-up period of 14. 2 months （9-24 months, P〉0. 01）. Conclusion：Anterior cervical decompression in subsection, autograft fusion and internal fixation is a rational effective method for the surgical treatment of multilevel CSM.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60676009 and 60725415)the National High Technology Research and Development Program of China (Grant Nos 2009AA01Z258 and 2009AA01Z260)
文摘Based on the heat diffusion equation of multilevel interconnects, a novel analytical thermal model for multilevel nano-scale interconnects considering the via effect is presented, which can compute quickly the temperature of multilevel interconnects, with substrate temperature given. Based on the proposed model and the 65 nm complementary metal oxide semiconductor （CMOS） process parameter, the temperature of nano-scale interconnects is computed. The computed results show that the via effect has a great effect on local interconnects, but the reduction of thermal conductivity has little effect on local interconnects. With the reduction of thermal conductivity or the increase of current density, however, the temperature of global interconnects rises greatly, which can result in a great deterioration in their performance. The proposed model can be applied to computer aided design （CAD） of very large-scale integrated circuits （VLSIs） in nano-scale technologies.
基金Project supported by the National Natural Science Foundation of China （Grant No 60577035）.
文摘The advantages of read-only storage is the predominance of optical recording relative to magnetic and other rewritable methods. Multilevel （ML） read-only technology has been a trend to improve the data capacity and transfer rate. Based on the principle and coding method of ML, this paper demonstrates some ML read-only recording methods, of which a new ML read-only recording is developed. This recording method integrates amplitude modulation achieved by the reaction mechanism of physics and chemistry of photoresist with the run-length-limited technology. The discs can be achieved using standard photoresist mastering and replication techniques with great compatibility to conventional binary read-only discs.
文摘With the implementation of new-generation launch vehicles,space stations,lunar and deep space exploration,etc.,the development of spacecraft structures will face new challenges. In order to reduce the spacecraft weight and increase the payload,composite material structures will be widely used. It is difficult to evaluate the strength and life of composite materials due to their complex mechanism and various phenomena in damage and failure.Meanwhile,the structures of composite materials used in spacecrafts will bear complex loads,including the coupling loads of tension,pressure,bending,shear,and torsion. Static loads,thermal loads,and vibration loads may occur at the same time,which asks for verification requirements to ensure the structure safety. Therefore,it is necessary to carry out a systematic multi-level experimental study. In this paper,the building block approach (BBA) is used to investigate the multilevel composite material structures for spacecrafts. The advanced measurement technology is adopted based on digital image correlation (DIC) and piezoelectric and optical fiber sensors to measure the composite material structure deformation. The virtual experiment technology is applied to provide sufficient and reliable data for the evaluation of the composite material structures of spacecrafts.
文摘Polymer injectivity is an important factor for evaluating the project economics of chemical flood,which is highly related to the polymer viscosity.Because the flow rate varies rapidly near injectors and significantly changes the polymer viscosity due to the non-Newtonian rheological behavior,the polymer viscosity near the wellbore is difficult to estimate accurately with the practical gridblock size in reservoir simulation.To reduce the impact of polymer rheology upon chemical EOR simulations,we used an efficient multilevel local grid refinement（LGR）method that provides a higher resolution of the flows in the near-wellbore region.An efficient numerical scheme was proposed to accurately solve the pressure equation and concentration equations on the multilevel grid for both homogeneous and heterogeneous reservoir cases.The block list and connections of the multilevel grid are generated via an efficient and extensible algorithm.Field case simulation results indicate that the proposed LGR is consistent with the analytical injectivity model and achieves the closest results to the full grid refinement,which considerably improves the accuracy of solutions compared with the original grid.In addition,the method was validated by comparing it with the LGR module of CMG_STARS.Besides polymer injectivity calculations,the LGR method is applicable for other problems in need of near-wellbore treatment,such as fractures near wells.
基金supported by MTO in part through the Highway Infrastructure and Innovations Funding Program(HIIFP)
文摘This paper describes an empirical study aiming at identifying the main differences between different logistic regression models and collision data aggregation methods that are commonly applied in road safety literature for modeling collision severity. In particular, the research compares three popular multilevel logistic models （i.e., sequential binary logit models, ordered logit models, and multinomial logit models） as well as three data aggregation methods （i.e., occupant based, vehicle based, and collision based）. Six years of collision data （2001-2006） from 31 highway routes from across the province of Ontario, Canada were used for this analysis. It was found that a multilevel multinomial logit model has the best fit to the data than the other two models while the results obtained from occupant-based data are more reliable than those from vehicle- and collision-based data. More importantly, while generally consistent in terms of factors that were found to be significant between different models and data aggregation methods, the effect size of each factor differ sub- stantially, which could have significant implications forevaluating the effects of different safety-related policies and countermeasures.
基金supported by the National Natural Science Foundation of China(Grant Nos.61664001,61574070,and 61306148)the Application Research and Development Plan of Gansu Academy of Sciences,China(Grant Nos.2015JK-11 and 2015JK-01)
文摘In this paper, the self-compliance bipolar resistive switching characteristic of an HfO-based memory device with Ag/HfO/Au structure for multilevel storage is investigated. By applying a positive voltage, the dual-step set processes corresponding to three stable resistance states are observed in the device. The multilevel switching characteristics can still be observed after 48 hours. In addition, the resistance values of all the three states show negligible degradation over 104 s,which may be useful for the applications in nonvolatile multilevel storage.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60971066 and 60725415)the National High-Tech Program of China (Grant Nos. 2009AA01Z258 and 2009AA01Z260)National Key Laboratory Foundation of China(Grant No. ZHD200904)
文摘Based on the multilevel interconnections temperature distribution model and the RLC interconnection delay model of the integrate circuit, this paper proposes a multilevel nano-scale interconnection RLC delay model with the method of numerical analysis, the proposed analytical model has summed up the influence of the configuration of multilevel interconnections, the via heat transfer and self-heating effect on the interconnection delay, which is closer to the actual situation. Delay simulation results show that the proposed model has high precision within 5% errors for global interconnections based on the 65 nm CMOS interconnection and material parameter, which can be applied in nanometer CMOS system chip computer-aided design.
基金Project supported by the State Key Development Program For Basic Research of China （Grant No 19990330） and the National Natural Science Foundation of China （Grant No 60577035）.
文摘The recording density of multilevel photochromic memory is limited by the signal-to-noise ratio （SNR） of the readout signal. In this paper, shot noise and material noise are investigated through theoretical analysis of SNR. When the bandwidth of a system is less than 1MHz, the material noise takes a prominent position; when the bandwidth of the system is more than 10MHz, the shot noise becomes dominant. The thickness of recording layer can be optimized to maximize the SNR and reduce the influence of the bandwidth of the system on SNR.
基金Project supported by the Science Fund for Creative Research Groups of the National Natural Science Foundation of China (GrantNo. 60921062)the National Natural Science Foundation of China (Grant No. 61003075)
文摘With CMOS technologies approaching the scaling ceiling, novel memory technologies have thrived in recent years, among which the memristor is a rather promising candidate for future resistive memory （RRAM）. Memristor＇s potential to store multiple bits of information as different resistance levels allows its application in multilevel cell （MCL） tech- nology, which can significantly increase the memory capacity. However, most existing memristor models are built for binary or continuous memristance switching. In this paper, we propose the simulation program with integrated circuits emphasis （SPICE） modeling of charge-controlled and flux-controlled memristors with multilevel resistance states based on the memristance versus state map. In our model, the memristance switches abruptly between neighboring resistance states. The proposed model allows users to easily set the number of the resistance levels as parameters, and provides the predictability of resistance switching time if the input current/voltage waveform is given. The functionality of our models has been validated in HSPICE. The models can be used in multilevel RRAM modeling as well as in artificial neural network simulations.
基金Project supported by the Ministry of Science and Technology of China(Grant Nos.2016YFA0203800,2016YFA0201803,and 2018YFB0407502)the National Natural Science Foundation of China(Grant Nos.61522408,61334007,and 61521064)+1 种基金Beijing Municipal Science&Technology Commission Program,China(Grant No.Z161100000216153)Huawei Data Center Technology Laboratory
文摘The tail bits of intermediate resistance states（IRSs） achieved in the SET process（IRSS） and the RESET process（IRSR） of conductive-bridge random-access memory were investigated. Two types of tail bits were observed, depending on the filament morphology after the SET/RESET operation.（i） Tail bits resulting from lateral diffusion of Cu ions introduced an abrupt increase of device resistance from IRS to ultrahigh-resistance state, which mainly happened in IRSS.（ii） Tail bits induced by the vertical diffusion of Cu ions showed a gradual shift of resistance toward lower value. Statistical results show that more than 95% of tail bits are generated in IRSS. To achieve a reliable IRS for multilevel cell（MLC） operation, it is desirable to program the IRS in RESET operation. The mechanism of tail bit generation that is disclosed here provides a clear guideline for the data retention optimization of MLC resistive random-access memory cells.
基金Supported by the National Natural Science Foundation of China(61139002,61171132)the Natural Science Foundation of Jiangsu Education Department(12KJB520013)+2 种基金the Fundamental Research Funds for the Central Universitiesthe Funding of Jiangsu Innovation Program for Graduate Education(CXZZ110219)the Open Project Program of State Key Lab for Novel Software Technology in Nanjing University(KFKT2012B28)
文摘Attribute reduction is an important process in rough set theory.Finding minimum attribute reduction has been proven to help the user-oriented make better knowledge discovery in some cases.In this paper,an efficient minimum attribute reduction algorithm is proposed based on the multilevel evolutionary tree with self-adaptive subpopulations.A model of multilevel evolutionary tree with self-adaptive subpopulations is constructed,and interacting attribute sets are better decomposed into subsets by the self-adaptive mechanism of elitist populations.Moreover it can self-adapt the subpopulation sizes according to the historical performance record so that interacting attribute decision variables are captured into the same grouped subpopulation,which will be extended to better performance in both quality of solution and competitive computation complexity for minimum attribute reduction.The conducted experiments show the proposed algorithm is better on both efficiency and accuracy of minimum attribute reduction than some representative algorithms.Finally the proposed algorithm is applied to magnetic resonance image(MRI)segmentation,and its stronger applicability is further demonstrated by the effective and robust segmentation results.
基金supported by the National Natural Science Foundation of China (No.61401003)the Specialized Research Fund for the Doctoral Program of Higher Education of China (No.20123401110006)the Natural Science Research Project of Anhui Education ( No. KJ2015A436)
文摘The multilevel characteristic basis function method(MLCBFM)with the adaptive cross approximation(ACA)algorithm for accelerated solution of electrically large scattering problems is studied in this paper.In the conventional MLCBFM based on Foldy-Lax multiple scattering equations,the improvement is only made in the generation of characteristic basis functions(CBFs).However,it does not provide a change in impedance matrix filling and reducing matrix calculation procedure,which is time-consuming.In reality,all the impedance and reduced matrix of each level of the MLCBFM have low-rank property and can be calculated efficiently.Therefore,ACA is used for the efficient generation of two-level CBFs and the fast calculation of reduced matrix in this study.Numerical results are given to demonstrate the accuracy and efficiency of the method.
基金The National Natural Science Foundationof China (No.60703048)Hubei Municipal Natural Science Foundation (No.2007ABA313)
文摘XML＇s increasing popularity highlights the security demand for XML documents. A mandatory access control model for XML document is presented on the basis of investigation of the function dependency of XML documents and discussion of the integrity properties of multilevel XML document. Then, the algorithms for decomposition/recovery multilevel XML document into/from single level document are given, and the manipulation rules for typical operations of XQuery and XUpdate： QUERY, INSERT, UPDATE, and REMOVE, are elaborated. The multilevel XML document access model can meet the requirement of sensitive information processing application.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62205231 and 22002102)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX223271)Jiangsu Key Laboratory for Environment Functional Materials。
文摘Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability and operation speed is one of key factors to restrain the development of phase-change memory.Here,N-doped Ge_(2)Sb_(2)Te_(5)-based optoelectronic hybrid memory is proposed to simultaneously implement high thermal stability and ultrafast operation speed.The picosecond laser is adopted to write/erase information based on reversible phase transition characteristics whereas the resistance is detected to perform information readout.Results show that when N content is 27.4 at.%,N-doped Ge_(2)Sb_(2)Te_(5)film possesses high ten-year data retention temperature of 175℃and low resistance drift coefficient of 0.00024 at 85℃,0.00170 at 120℃,and 0.00249 at 150℃,respectively,owing to the formation of Ge–N,Sb–N,and Te–N bonds.The SET/RESET operation speeds of the film reach 520 ps/13 ps.In parallel,the reversible switching cycle of the corresponding device is realized with the resistance ratio of three orders of magnitude.Four-level reversible resistance states induced by various crystallization degrees are also obtained together with low resistance drift coefficients.Therefore,the N-doped Ge_(2)Sb_(2)Te_(5)thin film is a promising phase-change material for ultrafast multilevel optoelectronic hybrid storage.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61178059 and 61137002)the Key Program of the Science and Technology Commission of Shanghai Municipality,China(Grant No.11jc1413300)
文摘Four different states of Si15Sb85 and Ge2Sb2Te5 phase change memory thin films are obtained by crystallization degree modulation through laser initialization at different powers or annealing at different temperatures. The polarization characteristics of these two four-level phase change recording media are analyzed systematically. A simple and effective readout scheme is then proposed, and the readout signal is numerically simulated. The results show that a high-contrast polarization readout can be obtained in an extensive wavelength range for the four-level phase change recording media using common phase change materials. This study will help in-depth understanding of the physical mechanisms and provide technical approaches to multilevel phase change recording.
