Correlation power analysis(CPA)combined with genetic algorithms(GA)now achieves greater attack efficiency and can recover all subkeys simultaneously.However,two issues in GA-based CPA still need to be addressed:key de...Correlation power analysis(CPA)combined with genetic algorithms(GA)now achieves greater attack efficiency and can recover all subkeys simultaneously.However,two issues in GA-based CPA still need to be addressed:key degeneration and slow evolution within populations.These challenges significantly hinder key recovery efforts.This paper proposes a screening correlation power analysis framework combined with a genetic algorithm,named SFGA-CPA,to address these issues.SFGA-CPA introduces three operations designed to exploit CPA characteris-tics:propagative operation,constrained crossover,and constrained mutation.Firstly,the propagative operation accelerates population evolution by maximizing the number of correct bytes in each individual.Secondly,the constrained crossover and mutation operations effectively address key degeneration by preventing the compromise of correct bytes.Finally,an intelligent search method is proposed to identify optimal parameters,further improving attack efficiency.Experiments were conducted on both simulated environments and real power traces collected from the SAKURA-G platform.In the case of simulation,SFGA-CPA reduces the number of traces by 27.3%and 60%compared to CPA based on multiple screening methods(MS-CPA)and CPA based on simple GA method(SGA-CPA)when the success rate reaches 90%.Moreover,real experimental results on the SAKURA-G platform demonstrate that our approach outperforms other methods.展开更多
Differential Power Analysis (DPA) is an effective attack method to break the crypto chips and it has been considered to be a threat to security of information system. With analyzing the prin-ciple of resisting DPA,an ...Differential Power Analysis (DPA) is an effective attack method to break the crypto chips and it has been considered to be a threat to security of information system. With analyzing the prin-ciple of resisting DPA,an available countermeasure based on randomization is proposed in this paper. Time delay is inserted in the operation process and random number is precharged to the circuit during the delay time,the normal schedule is disturbed and the power is randomized. Following this meth-odology,a general DPA resistance random precharge architecture is proposed and DES algorithm following this architecture is implemented. This countermeasure is testified to be efficient to resist DPA.展开更多
The security of Internet of Things(IoT)is a challenging task for researchers due to plethora of IoT networks.Side Channel Attacks(SCA)are one of the major concerns.The prime objective of SCA is to acquire the informat...The security of Internet of Things(IoT)is a challenging task for researchers due to plethora of IoT networks.Side Channel Attacks(SCA)are one of the major concerns.The prime objective of SCA is to acquire the information by observing the power consumption,electromagnetic(EM)field,timing analysis,and acoustics of the device.Later,the attackers perform statistical functions to recover the key.Advanced Encryption Standard(AES)algorithm has proved to be a good security solution for constrained IoT devices.This paper implements a simulation model which is used to modify theAES algorithm using logicalmasking properties.This invariant of the AES algorithm hides the array of bits during substitution byte transformation of AES.This model is used against SCAand particularly Power Analysis Attacks(PAAs).Simulation model is designed on MATLAB simulator.Results will give better solution by hiding power profiles of the IoT devices against PAAs.In future,the lightweight AES algorithm with false key mechanisms and power reduction techniques such as wave dynamic differential logic(WDDL)will be used to safeguard IoT devices against side channel attacks by using Arduino and field programmable gate array(FPGA).展开更多
Stream ciphers based on linear feedback shift register(LFSR)are suitable for constrained environments,such as satellite communications,radio frequency identification devices tag,sensor networks and Internet of Things,...Stream ciphers based on linear feedback shift register(LFSR)are suitable for constrained environments,such as satellite communications,radio frequency identification devices tag,sensor networks and Internet of Things,due to its simple hardware structures,high speed encryption and lower power consumption.LFSR,as a cryptographic primitive,has been used to generate a maximum period sequence.Because the switching of the status bits is regular,the power consumption of the LFSR is correlated in a linear way.As a result,the power consumption characteristics of stream cipher based on LFSR are vulnerable to leaking initialization vectors under the power attacks.In this paper,a new design of LFSR against power attacks is proposed.The power consumption characteristics of LFSR can be masked by using an additional LFSR and confused by adding a new filter Boolean function and a flip-flop.The design method has been implemented easily by circuits in this new design in comparison with the others.展开更多
Leakage power analysis(LPA) attacks aim at finding the secret key of a cryptographic device from measurements of its static(leakage) power. This novel power analysis attacks take advantage of the dependence of the lea...Leakage power analysis(LPA) attacks aim at finding the secret key of a cryptographic device from measurements of its static(leakage) power. This novel power analysis attacks take advantage of the dependence of the leakage power of complementary metal oxide semiconductor(CMOS) integrated circuits on the data they process. This paper proposes symmetric dual-rail logic(SDRL), a standard cell LPA attack countermeasure that theoretically resists the LPA attacks. The technique combines standard building blocks to make new compound standard cells, which are close to constant leakage power consumption. Experiment results show SDRL is a promising approach to implement an LPA-resistant crypto processor.展开更多
The security of CPU smart cards, which are widely used throughout China, is currently being threatened by side-channel analysis. Typical countermeasures to side-channel analysis involve adding noise and filtering the ...The security of CPU smart cards, which are widely used throughout China, is currently being threatened by side-channel analysis. Typical countermeasures to side-channel analysis involve adding noise and filtering the power consumption signal. In this paper, we integrate appropriate preprocessing methods with an improved attack strategy to generate a key recovery solution to the shortcomings of these countermeasures. Our proposed attack strategy improves the attack result by combining information leaked from two adjacent clock cycles. Using our laboratory-based power analysis system, we verified the proposed key recovery solution by performing a successful correlation power analysis on a Triple Data Encryption Standard (3DES) hardware module in a real-life 32-bit CPU smart card. All 112 key bits of the 3DES were recovered with about 80 000 power traces.展开更多
In stepped wedge cluster randomised trials(SW-CRTs),clusters of subjects are randomly assigned to sequences,where they receive a specific order of treatments.Compared to conventional cluster randomised studies,one uni...In stepped wedge cluster randomised trials(SW-CRTs),clusters of subjects are randomly assigned to sequences,where they receive a specific order of treatments.Compared to conventional cluster randomised studies,one unique feature of SW-CRTs is that all clusters start from control and gradually transition to intervention according to the randomly assigned sequences.This feature mitigates the ethical concern of withholding an effective treatment and reduces the logistic burden of implementing the intervention at multiple clusters simultaneously.This feature,however,presents challenges that need to be addressed in experimental design and data analysis,i.e.,missing data due to prolonged follow-up and complicated correlation structures that involve between-subject and longitudinal correlations.In this study,based on the generalised estimating equation(GEE)approach,we present a closed-form sample size formula for SW-CRTs with a binary outcome,which offers great flexibility to account for unbalanced randomisation,missing data,and arbitrary correlation structures.We also present a correction approach to address the issue of under-estimated variance by GEE estimator when the sample size is small.Simulation studies and application to a real clinical trial are presented.展开更多
With the structure of two air gaps and two rotors, the electromagnetic continuously variable transmission(EMCVT) is a novel power-split continuously variable transmission(CVT). There are two kinds of power flowing...With the structure of two air gaps and two rotors, the electromagnetic continuously variable transmission(EMCVT) is a novel power-split continuously variable transmission(CVT). There are two kinds of power flowing through the EMCVT, one is mechanical power and the other is electric power. In the mean time, there are three power ports in the EMCVT, one is the outer rotor named mechanical power port and the other two are the inner rotor and the stator named electric power ports. The mechanical power port is connected to the driving wheels through the final gear and the electric ports are connected to the batteries through the transducers. The two kinds of power are coupled on the outer rotor of the EMCVT. The EMCVT can be equipped on the conventional vehicle being regarded as the CVT and it also can be equipped on the hybrid electric vehicle(HEV) as the multi-energy sources assembly. The power flows of these two kinds of applications are analysed. The back electromotive force(EMF) equations are illatively studied and so the dynamic mathematic model is theorized. In order to certify the feasibility of the above theories, three simulations are carried out in allusion to the above two kinds of mentioned applications of the EMCVT and a five speed automatic transmission(AT) vehicle. The simulation results illustrate that the efficiency of the EMCVT vehicles is higher than that of the AT vehicle owed to the optimized operation area of the engine. Hence the fuel consumption of the EMCVT vehicles is knock-down.展开更多
Magnetic radiation phenomena appear inevitably in the magnetic-resonance wireless power transfer (MR-WPT) system, and regarding this problem the magnetic-shielding scheme is applied to improve the electromagnetic pe...Magnetic radiation phenomena appear inevitably in the magnetic-resonance wireless power transfer (MR-WPT) system, and regarding this problem the magnetic-shielding scheme is applied to improve the electromagnetic performance in engineering. In this study, the shielding effectiveness of a two-coil MR-WPT system for different material shields is analyzed in theory using Moser's formula and Schelkunoff's formula. On this basis a candidate magnetic-shielding scheme with a double-layer structure is determined, which has better shielding effectiveness and coils coupling coefficient. Finally, some finite element simulation results validate the correctness of the theoretical analysis, and the shielding effectiveness with the double-layer shield in maximum is 30?dB larger than the one with the single-layer case.展开更多
Power supply and demand inJanuary-September, 2007Since 2007, the national economy developed continu-ously, showing a situation of rapid growth, more optimizedstructure, increased efficiency and improvement of people...Power supply and demand inJanuary-September, 2007Since 2007, the national economy developed continu-ously, showing a situation of rapid growth, more optimizedstructure, increased efficiency and improvement of people'slivelihood. In the first three quarters, GDP achieved 16.6043trillion Yuan, and its year-on-year growth rate was 11.5%;展开更多
At the beginning of 2008, the Central, East and South China suffered a rare snow and ice disaster. After the disaster, power generation and power grid enterprises faced a big problem of power coal supply.
In the first half of 2007, the power industry in Shandongprovince continued to maintain a rapid growth momentum.The gross electricity consumption amounted to 121.25 TWh,14.4% higher over that in the same period of las...In the first half of 2007, the power industry in Shandongprovince continued to maintain a rapid growth momentum.The gross electricity consumption amounted to 121.25 TWh,14.4% higher over that in the same period of last year. The totalinstalled capacity reached 53.29 GW. It was expected that bythe end of 2007, the gross electricity consumption in Shan-dong would reach 260 TWh, increasing by 14.4% on ayear-on-year basis; the maximum load would reach 40.展开更多
Introduction With ever-increasing of power sources, the capabilityof power supply was further enforced in 2007. This met thestrong demand of national economy development. Restruc-turing of power sources was deepening,...Introduction With ever-increasing of power sources, the capabilityof power supply was further enforced in 2007. This met thestrong demand of national economy development. Restruc-turing of power sources was deepening, of which "substi-tuting large power units for small ones" started well, theinstalled capacity of wind power was doubled and obviousresults were achieved in the energy-conservation and pollu-展开更多
In this paper,we propose two new attack algorithms on RSA implementations with CRT(Chinese remainder theorem).To improve the attack efficiency considerably,a clustering collision power attack on RSA with CRT is introd...In this paper,we propose two new attack algorithms on RSA implementations with CRT(Chinese remainder theorem).To improve the attack efficiency considerably,a clustering collision power attack on RSA with CRT is introduced via chosen-message pairs.This attack method is that the key parameters dp and dq are segmented by byte,and the modular multiplication collisions are identified by k-means clustering.The exponents dp and dq were recovered by 12 power traces of six groups of the specific message pairs,and the exponent d was obtained.We also propose a second order clustering collision power analysis attack against RSA implementation with CRT,which applies double blinding exponentiation.To reduce noise and artificial participation,we analyze the power points of interest by preprocessing and k-means clustering with horizontal correlation collisions.Thus,we recovered approximately 91%of the secret exponents manipulated with a single power curve on RSA-CRT with countermeasures of double blinding methods.展开更多
The accuracy of the velocity field will be affected by the noise model and common mode errors through GPS time series analysis.In order to analyze the influence of these two factors on the accuracy of the velocity fie...The accuracy of the velocity field will be affected by the noise model and common mode errors through GPS time series analysis.In order to analyze the influence of these two factors on the accuracy of the velocity field,two kinds of data are used,including the three-year observation from 20 permanent GPS stations with high spatial correlation in the Everest,which is about 650 km from north to south and 1068 km from east to west,and three-year 80 ascending images and 141 descending images from sentinel-1A,which are processed by GAMIT/GLOBK software and Small Baseline Subset-Interferometric Synthetic Aperture Radar method(SBAS-InSAR),respectively.The vertical deformation rate is solved by time series analysis through a self-made adaptive algorithm.In the analysis,the linear change rate,period,half period coefficient,and residual sequence of all stations are solved by using James L.Davis periodic model.The noise type of residual sequence is analyzed by the power spectrum model.The spatio-temporal correlated noise,Common Mode Error(CME),is extracted by the Principal Component Analysis(PCA)and Karhunen-Loeve(KLE)methods.The results show that noises can be best described by“flicker noise+white noise”model.After the removal of CME,the R^(2) estimates of all stations are above 0.8,with RMS value of velocity field decreasing from 1.428 mm/yr to 1.062 mm/yr and 1.063 mm/yr to 0.815 mm/yr,in N and E directions,respectively,indicating that the influence of CME can't be ignored in the extraction of the high-precision velocity field in the Nepal and Everest region.展开更多
The TiN, TiAlN, and TiAlSiN coatings were prepared on YT14 cutting tool surface with CAIP(cathode arc ion plating), the surface morphologies and phases were analyzed with FESEM(field emission scanning electron micr...The TiN, TiAlN, and TiAlSiN coatings were prepared on YT14 cutting tool surface with CAIP(cathode arc ion plating), the surface morphologies and phases were analyzed with FESEM(field emission scanning electron microscopy), and XRD(X-ray diffraction), respectively, and the coating parameters such as 3D surface micro-topography, grain size, surface height, hierarchy, profile height, and power spectral density, etc, were measured with AFM(atomic force microscope). The results show that the phases of TiN, TiAlN, and TiAlSiN coatings are TiN, TiN+TiAlN, TiN+Si_3N_4+TiAlN, respectively, while the surface roughness Sa of TiN, TiAlN, and TiAlSiN coatings is 75.3, 98.9, and 42.1 nm, respectively, and the roughness depth Sk is 209, 389, and 54 nm, respectively, the sequence of average grain sizes is TiAlN〉TiN〉TiAlSiN. The surface bearing index Sbi of TiN, TiAlN, and TiAlSiN coatings is 0.884, 1.01, and 0.37, respectively, and the sequence of surface bearing capability is TiAlN〉TiN〉TiAlSiN. At the lower wavelength(102-103 nm), the power spectral densities have a certain correlation, and the sequence of TiN〉TiAlN〉TiAlSiN, while the correlation is low at the higher wavelength(〉103 nm).展开更多
Nonlinear mode evolution for relativistic electrons in dense plasmas is analyzed in a three-dimensional fluid approach. Similar to the results previously obtained in particle-in-cell simulations, it is found that obli...Nonlinear mode evolution for relativistic electrons in dense plasmas is analyzed in a three-dimensional fluid approach. Similar to the results previously obtained in particle-in-cell simulations, it is found that oblique modes dominate two-stream and filamentation modes in the linear stage. On the other hand a power spectrum analysis shows the nonlinear development of the high wavenumber modes.展开更多
Purpose: Heart rate variability (HRV) is acknowledged as a useful tool to estimate autonomic function. Fast Fourier transform (FFT) and autoregressive model (AR) are used for power spectral analysis of HRV. However, t...Purpose: Heart rate variability (HRV) is acknowledged as a useful tool to estimate autonomic function. Fast Fourier transform (FFT) and autoregressive model (AR) are used for power spectral analysis of HRV. However, there is little evidence of agreement between FFT and AR in relation to HRV following food intake in females. In the present study, we applied both FFT and AR after food intake during the follicular and luteal phases, and compared raw low-frequency (LF) and high- frequency (HF) powers, and LF/HF ratio obtained with the two power-spectral analytical methods. Methods: All subjects participated in two sessions: follicular phase session and luteal phase session. In each session, R-R intervals were continuously recorded before and after meals, and power spectral analysis of heart rate variability was performed. We analyzed low-frequency power (LF: 0.04 - 0.15 Hz) and high-frequency power (HF: 0.15 - 0.40 Hz) by using FFT and AR. LF and HF power were computed for each 30 sec, 1 min, 2.5 min, and 5 min of the 5-min R-R data before meal intake and at 20, 40, 60 and 80 min after meal intake. The LF/HF ratio was calculated as an index of sympathovagal balance. Results: In the present study, after 30 sec and 1 min of segment analysis, there was little interchangeability between AR and FFT in LF, HF, and LF/HF ratio in both follicular and luteal phases. In 2.5 min or 5 min of segment analysis, there was interchangeability between FFT and AR in LF and HF, but not in the LF/HF ratio in both follicular and luteal phases. Additionally, FFT underestimated HRV compared with AR, and the extent of underestimation increased with increasing AR value. Conclusion: FFT underestimated HRV compared with AR, and FFT correlated poorly with AR when the analysis segment was shortened.展开更多
基金supported by the Hunan Provincial Natrual Science Foundation of China(2022JJ30103)“the 14th Five-Year”Key Disciplines and Application Oriented Special Disciplines of Hunan Province(Xiangjiaotong[2022],351)the Science and Technology Innovation Program of Hunan Province(2016TP1020).
文摘Correlation power analysis(CPA)combined with genetic algorithms(GA)now achieves greater attack efficiency and can recover all subkeys simultaneously.However,two issues in GA-based CPA still need to be addressed:key degeneration and slow evolution within populations.These challenges significantly hinder key recovery efforts.This paper proposes a screening correlation power analysis framework combined with a genetic algorithm,named SFGA-CPA,to address these issues.SFGA-CPA introduces three operations designed to exploit CPA characteris-tics:propagative operation,constrained crossover,and constrained mutation.Firstly,the propagative operation accelerates population evolution by maximizing the number of correct bytes in each individual.Secondly,the constrained crossover and mutation operations effectively address key degeneration by preventing the compromise of correct bytes.Finally,an intelligent search method is proposed to identify optimal parameters,further improving attack efficiency.Experiments were conducted on both simulated environments and real power traces collected from the SAKURA-G platform.In the case of simulation,SFGA-CPA reduces the number of traces by 27.3%and 60%compared to CPA based on multiple screening methods(MS-CPA)and CPA based on simple GA method(SGA-CPA)when the success rate reaches 90%.Moreover,real experimental results on the SAKURA-G platform demonstrate that our approach outperforms other methods.
文摘Differential Power Analysis (DPA) is an effective attack method to break the crypto chips and it has been considered to be a threat to security of information system. With analyzing the prin-ciple of resisting DPA,an available countermeasure based on randomization is proposed in this paper. Time delay is inserted in the operation process and random number is precharged to the circuit during the delay time,the normal schedule is disturbed and the power is randomized. Following this meth-odology,a general DPA resistance random precharge architecture is proposed and DES algorithm following this architecture is implemented. This countermeasure is testified to be efficient to resist DPA.
文摘The security of Internet of Things(IoT)is a challenging task for researchers due to plethora of IoT networks.Side Channel Attacks(SCA)are one of the major concerns.The prime objective of SCA is to acquire the information by observing the power consumption,electromagnetic(EM)field,timing analysis,and acoustics of the device.Later,the attackers perform statistical functions to recover the key.Advanced Encryption Standard(AES)algorithm has proved to be a good security solution for constrained IoT devices.This paper implements a simulation model which is used to modify theAES algorithm using logicalmasking properties.This invariant of the AES algorithm hides the array of bits during substitution byte transformation of AES.This model is used against SCAand particularly Power Analysis Attacks(PAAs).Simulation model is designed on MATLAB simulator.Results will give better solution by hiding power profiles of the IoT devices against PAAs.In future,the lightweight AES algorithm with false key mechanisms and power reduction techniques such as wave dynamic differential logic(WDDL)will be used to safeguard IoT devices against side channel attacks by using Arduino and field programmable gate array(FPGA).
文摘Stream ciphers based on linear feedback shift register(LFSR)are suitable for constrained environments,such as satellite communications,radio frequency identification devices tag,sensor networks and Internet of Things,due to its simple hardware structures,high speed encryption and lower power consumption.LFSR,as a cryptographic primitive,has been used to generate a maximum period sequence.Because the switching of the status bits is regular,the power consumption of the LFSR is correlated in a linear way.As a result,the power consumption characteristics of stream cipher based on LFSR are vulnerable to leaking initialization vectors under the power attacks.In this paper,a new design of LFSR against power attacks is proposed.The power consumption characteristics of LFSR can be masked by using an additional LFSR and confused by adding a new filter Boolean function and a flip-flop.The design method has been implemented easily by circuits in this new design in comparison with the others.
基金the Software and Integrated CircuitIndustries Development Foundation of Shanghai(No.12Z116010001)
文摘Leakage power analysis(LPA) attacks aim at finding the secret key of a cryptographic device from measurements of its static(leakage) power. This novel power analysis attacks take advantage of the dependence of the leakage power of complementary metal oxide semiconductor(CMOS) integrated circuits on the data they process. This paper proposes symmetric dual-rail logic(SDRL), a standard cell LPA attack countermeasure that theoretically resists the LPA attacks. The technique combines standard building blocks to make new compound standard cells, which are close to constant leakage power consumption. Experiment results show SDRL is a promising approach to implement an LPA-resistant crypto processor.
基金supported by the Major Program“Core of Electronic DevicesHigh-End General Chips+1 种基金and Basis of Software Products”of the Ministry of Industry and Information Technology of China(No.2014ZX01032205)the Key Technologies Research and Development Program of the Twelfth Five-Year Plan of China(No.MMJJ201401009)
文摘The security of CPU smart cards, which are widely used throughout China, is currently being threatened by side-channel analysis. Typical countermeasures to side-channel analysis involve adding noise and filtering the power consumption signal. In this paper, we integrate appropriate preprocessing methods with an improved attack strategy to generate a key recovery solution to the shortcomings of these countermeasures. Our proposed attack strategy improves the attack result by combining information leaked from two adjacent clock cycles. Using our laboratory-based power analysis system, we verified the proposed key recovery solution by performing a successful correlation power analysis on a Triple Data Encryption Standard (3DES) hardware module in a real-life 32-bit CPU smart card. All 112 key bits of the 3DES were recovered with about 80 000 power traces.
基金supported by the Patient-Centered Outcomes Research Institute[ME-1609-36761].
文摘In stepped wedge cluster randomised trials(SW-CRTs),clusters of subjects are randomly assigned to sequences,where they receive a specific order of treatments.Compared to conventional cluster randomised studies,one unique feature of SW-CRTs is that all clusters start from control and gradually transition to intervention according to the randomly assigned sequences.This feature mitigates the ethical concern of withholding an effective treatment and reduces the logistic burden of implementing the intervention at multiple clusters simultaneously.This feature,however,presents challenges that need to be addressed in experimental design and data analysis,i.e.,missing data due to prolonged follow-up and complicated correlation structures that involve between-subject and longitudinal correlations.In this study,based on the generalised estimating equation(GEE)approach,we present a closed-form sample size formula for SW-CRTs with a binary outcome,which offers great flexibility to account for unbalanced randomisation,missing data,and arbitrary correlation structures.We also present a correction approach to address the issue of under-estimated variance by GEE estimator when the sample size is small.Simulation studies and application to a real clinical trial are presented.
基金supported by National Natural Science Foundation of China(No.50605020)Guangdong Provincial Science and Technology Project of China(No.2006A10501001).
文摘With the structure of two air gaps and two rotors, the electromagnetic continuously variable transmission(EMCVT) is a novel power-split continuously variable transmission(CVT). There are two kinds of power flowing through the EMCVT, one is mechanical power and the other is electric power. In the mean time, there are three power ports in the EMCVT, one is the outer rotor named mechanical power port and the other two are the inner rotor and the stator named electric power ports. The mechanical power port is connected to the driving wheels through the final gear and the electric ports are connected to the batteries through the transducers. The two kinds of power are coupled on the outer rotor of the EMCVT. The EMCVT can be equipped on the conventional vehicle being regarded as the CVT and it also can be equipped on the hybrid electric vehicle(HEV) as the multi-energy sources assembly. The power flows of these two kinds of applications are analysed. The back electromotive force(EMF) equations are illatively studied and so the dynamic mathematic model is theorized. In order to certify the feasibility of the above theories, three simulations are carried out in allusion to the above two kinds of mentioned applications of the EMCVT and a five speed automatic transmission(AT) vehicle. The simulation results illustrate that the efficiency of the EMCVT vehicles is higher than that of the AT vehicle owed to the optimized operation area of the engine. Hence the fuel consumption of the EMCVT vehicles is knock-down.
基金Supported by the National Natural Science Foundation of China under Grant No 51377185
文摘Magnetic radiation phenomena appear inevitably in the magnetic-resonance wireless power transfer (MR-WPT) system, and regarding this problem the magnetic-shielding scheme is applied to improve the electromagnetic performance in engineering. In this study, the shielding effectiveness of a two-coil MR-WPT system for different material shields is analyzed in theory using Moser's formula and Schelkunoff's formula. On this basis a candidate magnetic-shielding scheme with a double-layer structure is determined, which has better shielding effectiveness and coils coupling coefficient. Finally, some finite element simulation results validate the correctness of the theoretical analysis, and the shielding effectiveness with the double-layer shield in maximum is 30?dB larger than the one with the single-layer case.
文摘Power supply and demand inJanuary-September, 2007Since 2007, the national economy developed continu-ously, showing a situation of rapid growth, more optimizedstructure, increased efficiency and improvement of people'slivelihood. In the first three quarters, GDP achieved 16.6043trillion Yuan, and its year-on-year growth rate was 11.5%;
文摘At the beginning of 2008, the Central, East and South China suffered a rare snow and ice disaster. After the disaster, power generation and power grid enterprises faced a big problem of power coal supply.
文摘In the first half of 2007, the power industry in Shandongprovince continued to maintain a rapid growth momentum.The gross electricity consumption amounted to 121.25 TWh,14.4% higher over that in the same period of last year. The totalinstalled capacity reached 53.29 GW. It was expected that bythe end of 2007, the gross electricity consumption in Shan-dong would reach 260 TWh, increasing by 14.4% on ayear-on-year basis; the maximum load would reach 40.
文摘Introduction With ever-increasing of power sources, the capabilityof power supply was further enforced in 2007. This met thestrong demand of national economy development. Restruc-turing of power sources was deepening, of which "substi-tuting large power units for small ones" started well, theinstalled capacity of wind power was doubled and obviousresults were achieved in the energy-conservation and pollu-
基金supported by the National Key R&D Program of China(No.2017YFB0802300)the Key Research and Development Project of Sichuan Province(No.2020YFG0307,No.2018TJPT0012)the Key Research and Development Project of Chengdu(No.2019-YF05-02028-GX).
文摘In this paper,we propose two new attack algorithms on RSA implementations with CRT(Chinese remainder theorem).To improve the attack efficiency considerably,a clustering collision power attack on RSA with CRT is introduced via chosen-message pairs.This attack method is that the key parameters dp and dq are segmented by byte,and the modular multiplication collisions are identified by k-means clustering.The exponents dp and dq were recovered by 12 power traces of six groups of the specific message pairs,and the exponent d was obtained.We also propose a second order clustering collision power analysis attack against RSA implementation with CRT,which applies double blinding exponentiation.To reduce noise and artificial participation,we analyze the power points of interest by preprocessing and k-means clustering with horizontal correlation collisions.Thus,we recovered approximately 91%of the secret exponents manipulated with a single power curve on RSA-CRT with countermeasures of double blinding methods.
基金This research was supported by national nature science foundation of china(gratnt Nos.41674015,41731071)Qinghai high score remote sensing data industrialization application fund project(94-Y40G14-9001-15/18).
文摘The accuracy of the velocity field will be affected by the noise model and common mode errors through GPS time series analysis.In order to analyze the influence of these two factors on the accuracy of the velocity field,two kinds of data are used,including the three-year observation from 20 permanent GPS stations with high spatial correlation in the Everest,which is about 650 km from north to south and 1068 km from east to west,and three-year 80 ascending images and 141 descending images from sentinel-1A,which are processed by GAMIT/GLOBK software and Small Baseline Subset-Interferometric Synthetic Aperture Radar method(SBAS-InSAR),respectively.The vertical deformation rate is solved by time series analysis through a self-made adaptive algorithm.In the analysis,the linear change rate,period,half period coefficient,and residual sequence of all stations are solved by using James L.Davis periodic model.The noise type of residual sequence is analyzed by the power spectrum model.The spatio-temporal correlated noise,Common Mode Error(CME),is extracted by the Principal Component Analysis(PCA)and Karhunen-Loeve(KLE)methods.The results show that noises can be best described by“flicker noise+white noise”model.After the removal of CME,the R^(2) estimates of all stations are above 0.8,with RMS value of velocity field decreasing from 1.428 mm/yr to 1.062 mm/yr and 1.063 mm/yr to 0.815 mm/yr,in N and E directions,respectively,indicating that the influence of CME can't be ignored in the extraction of the high-precision velocity field in the Nepal and Everest region.
基金Funded by the Jiangsu Province Science and Technology Support Program(Industry)(No.BE2014818)
文摘The TiN, TiAlN, and TiAlSiN coatings were prepared on YT14 cutting tool surface with CAIP(cathode arc ion plating), the surface morphologies and phases were analyzed with FESEM(field emission scanning electron microscopy), and XRD(X-ray diffraction), respectively, and the coating parameters such as 3D surface micro-topography, grain size, surface height, hierarchy, profile height, and power spectral density, etc, were measured with AFM(atomic force microscope). The results show that the phases of TiN, TiAlN, and TiAlSiN coatings are TiN, TiN+TiAlN, TiN+Si_3N_4+TiAlN, respectively, while the surface roughness Sa of TiN, TiAlN, and TiAlSiN coatings is 75.3, 98.9, and 42.1 nm, respectively, and the roughness depth Sk is 209, 389, and 54 nm, respectively, the sequence of average grain sizes is TiAlN〉TiN〉TiAlSiN. The surface bearing index Sbi of TiN, TiAlN, and TiAlSiN coatings is 0.884, 1.01, and 0.37, respectively, and the sequence of surface bearing capability is TiAlN〉TiN〉TiAlSiN. At the lower wavelength(102-103 nm), the power spectral densities have a certain correlation, and the sequence of TiN〉TiAlN〉TiAlSiN, while the correlation is low at the higher wavelength(〉103 nm).
基金supported by National Natural Science Foundation of China(Nos.40731056,10778613,and 10575018)the National Basic Research Program of China(No.2008CB787103)
文摘Nonlinear mode evolution for relativistic electrons in dense plasmas is analyzed in a three-dimensional fluid approach. Similar to the results previously obtained in particle-in-cell simulations, it is found that oblique modes dominate two-stream and filamentation modes in the linear stage. On the other hand a power spectrum analysis shows the nonlinear development of the high wavenumber modes.
文摘Purpose: Heart rate variability (HRV) is acknowledged as a useful tool to estimate autonomic function. Fast Fourier transform (FFT) and autoregressive model (AR) are used for power spectral analysis of HRV. However, there is little evidence of agreement between FFT and AR in relation to HRV following food intake in females. In the present study, we applied both FFT and AR after food intake during the follicular and luteal phases, and compared raw low-frequency (LF) and high- frequency (HF) powers, and LF/HF ratio obtained with the two power-spectral analytical methods. Methods: All subjects participated in two sessions: follicular phase session and luteal phase session. In each session, R-R intervals were continuously recorded before and after meals, and power spectral analysis of heart rate variability was performed. We analyzed low-frequency power (LF: 0.04 - 0.15 Hz) and high-frequency power (HF: 0.15 - 0.40 Hz) by using FFT and AR. LF and HF power were computed for each 30 sec, 1 min, 2.5 min, and 5 min of the 5-min R-R data before meal intake and at 20, 40, 60 and 80 min after meal intake. The LF/HF ratio was calculated as an index of sympathovagal balance. Results: In the present study, after 30 sec and 1 min of segment analysis, there was little interchangeability between AR and FFT in LF, HF, and LF/HF ratio in both follicular and luteal phases. In 2.5 min or 5 min of segment analysis, there was interchangeability between FFT and AR in LF and HF, but not in the LF/HF ratio in both follicular and luteal phases. Additionally, FFT underestimated HRV compared with AR, and the extent of underestimation increased with increasing AR value. Conclusion: FFT underestimated HRV compared with AR, and FFT correlated poorly with AR when the analysis segment was shortened.