In this paper a novel method to generate high-precision and continuously adjustable digital time-delay by utilizing the linear phase of a FIR filter is presented. The generated time-delay can be continuously changed b...In this paper a novel method to generate high-precision and continuously adjustable digital time-delay by utilizing the linear phase of a FIR filter is presented. The generated time-delay can be continuously changed by adjusting the filter weights. The time-delay is pre cise and valid for wide-band, while the computational load is low. The proposed approach can find applications in wide-band digital beamforming, adaptive delay estimation, temporal analy sis of reflected waveform, etc.. In the paper, the basic principle, design steps and simulation re sults are given. Also shown are some typical practical applications.展开更多
In this paper, a new partial transmit sequence（PTS）scheme with low computational complexity is proposed for the problems of high computational complexity in the conventional PTS method. By analyzing the relationship...In this paper, a new partial transmit sequence（PTS）scheme with low computational complexity is proposed for the problems of high computational complexity in the conventional PTS method. By analyzing the relationship of candidate sequences in the PTS method under the interleaved partition method, it has been discovered that some candidate sequences generated by phase factor sequences have the same peak average power ratio（PAPR）. Hence, phase factor sequences can be optimized to reduce their searching times. Then, the computational process of generating candidate sequences can be simplified by improving the utilization of data and minimizing the calculations of complex multiplication. The performance analysis shows that, compared with the conventional PTS scheme, the proposed approach significantly decreases the computational complexity and has no loss of PAPR performance.展开更多
For future wireless communication systems,Power Domain Non-Orthogonal Multiple Access(PD-NOMA)using an advanced receiver has been considered as a promising radio access technology candidate.Power allocation plays an i...For future wireless communication systems,Power Domain Non-Orthogonal Multiple Access(PD-NOMA)using an advanced receiver has been considered as a promising radio access technology candidate.Power allocation plays an important role in the PD-NOMA system because it considerably affects the total throughput and Geometric Mean User Throughput(GMUT)performance.However,most existing studies have not completely accounted for the computational complexity of the power allocation process when the User Terminals(UTs)move in a slow fading channel environment.To resolve such problems,a power allocation method is proposed to considerably reduce the search space of a Full Search Power(FSP)allocation algorithm.The initial power reallocation coefficients will be set to start with former optimal values by the proposed Lemma before searching for optimal power reallocation coefficients based on total throughput performance.Step size and correction granularity will be adjusted within a much narrower power search range while invalid power combinations may be reasonably discarded during the search process.The simulation results show that the proposed power reallocation scheme can greatly reduce computational complexity while the total throughput and GMUT performance loss are not greater than 1.5%compared with the FSP algorithm.展开更多
Lung cancer, the leading cause of cancer deaths worldwide and in China, has a 19.7% five-year survival rate due to terminal-stage diagnosis^([1-3]).Although low-dose computed tomography(CT) screening can reduce mortal...Lung cancer, the leading cause of cancer deaths worldwide and in China, has a 19.7% five-year survival rate due to terminal-stage diagnosis^([1-3]).Although low-dose computed tomography(CT) screening can reduce mortality, high false positive rates can create economic and psychological burdens.展开更多
A new selected mapping(SLM)scheme based on constellation rotation is proposed to reduce the peak-to-average power ratio(PAPR)of orthogonal frequency division multiplexing(OFDM)signals.Its core idea is to generate abun...A new selected mapping(SLM)scheme based on constellation rotation is proposed to reduce the peak-to-average power ratio(PAPR)of orthogonal frequency division multiplexing(OFDM)signals.Its core idea is to generate abundant candidate signals by rotating different sub-signals of the original frequency signal with different angles.This new signal generation method can simplify the calculation process of candidate time signals into the linear addition of some intermediate signals,which are generated by the inverse fast Fourier transform(IFFT)operation of the original frequency signal.This feature can effectively reduce the computational complexity of candidate signal generation process.And compared to the traditional SLM scheme,the number of complex multiplication and complex addition of new scheme can separately be decreased by about 99.99% and 91.7% with some specific parameters.Moreover,with the help of the constellation detection mechanism at the receiver,there is no need to carry any side information at the transmitter.The simulation results show that,with the same channel transmission performance,the PAPR reduction performance of new scheme can approach or even exceed the upper bound of the traditional SLM scheme,which uses all the vectors in Hadamard matrix as the phase sequences.展开更多
With the rise of the Internet of Things(IoT),various devices in life and industry are closely linked.Because of its high payload,stable error correction capability,and convenience in reading and writing,Quick Response...With the rise of the Internet of Things(IoT),various devices in life and industry are closely linked.Because of its high payload,stable error correction capability,and convenience in reading and writing,Quick Response(QR)code has been widely researched in IoT.However,the security of privacy data in IoT is also a very important issue.At the same time,because IoT is developing towards low-power devices in order to be applied to more fields,the technology protecting the security of private needs to have the characteristics of low computational complexity.Visual Secret Sharing(VSS),with its features of safety and low computational cost,can fully meet the requirements of communication security in IoT.Therefore,a VSS scheme with QR code(VSS-QR)was proposed and has been applied to some extent.In VSS-QR,the secret is shared into a series of shares.These shares are usually common QR codes,which cannot cause the attention of the attacker.However,if there is dishonesty among participants,the secret cannot be recovered,which will lead to VSS-QR cannot be widely used due to its inadequate security.In this paper,we propose a visual secret sharing scheme with authentication based on QR code(VSSA-QR).Both the reconstructed secret QR code and shares can be verified whether they are forged by attackers.The above-mentioned operations conveniently are performed on low-power QR scanning devices.Not only does the proposed scheme prevent some dishonest participants or attackers from cheating,but also prevent all participants from conspiring.In addition,the payload is the QR code itself,which is higher than other schemes.Theoretical analysis and experiments prove that the proposed scheme is effective.展开更多
Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design. With the motivation to design high performance and clean combustor, computational fluid dynamics ...Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design. With the motivation to design high performance and clean combustor, computational fluid dynamics （CFD） is utilized as the powerful design approach. In this paper, Reynolds averaged Navier-Stokes （RANS） equations of reactive two-phase flow in an experimental low emission combustor is performed. The numerical approach uses an implicit compressible gas solver together with a Lagrangian liquid-phase tracking method and the extended coherent flamelet model for turbulence-combustion interaction. The NOx formation is modeled by the concept of post-processing, which resolves the NOx transport equation with the assumption of frozen temperature distribution. Both turbulence-combustion interaction model and NOx formation model are firstly evaluated by the comparison of experimental data published in open literature of a lean direct injection （LDI） combustor. The test rig studied in this paper is called low emission stirred swirl （LESS） combustor, which is a two-stage model combustor, fueled with liquid kerosene （RP-3） and designed by Beihang University （BUAA）. The main stage of LESS combustor employs the principle of lean prevaporized and premixed （LPP） concept to reduce pollutant, and the pilot stage depends on a diffusion flame for flame stabili-zation. Detailed numerical results including species distribution, turbulence performance and burning performance are qualita-tively and quantitatively evaluated. Numerical prediction of NOx emission shows a good agreement with test data at both idle condition and full power condition of LESS combustor. Preliminary results of the flame structure are shown in this paper. The flame stabilization mechanism and NOx reduction effort are also discussed with in-depth analysis.展开更多
Lung cancer(LC)is still one of the most frequent cancers with a high related mortality.Their prognosis is directly proportional to the stage at the time of diagnosis.Seventy percent are currently diagnosed in advanced...Lung cancer(LC)is still one of the most frequent cancers with a high related mortality.Their prognosis is directly proportional to the stage at the time of diagnosis.Seventy percent are currently diagnosed in advanced or locally advanced stage(higher than stage III),making a cure unlikely for the majority of patients.Developments in LC treatment are significant however they do not seem to be enough to reverse the current situation,at least,in a short period of time.Despite recent advances in treatment,primary prevention and early diagnosis appear to be the key to reduce the incidence and mortality of this disease.Many countries have developed LC screening programs based on the results of clinical trials published in recent years.The aim of this paper is to review the latest results of the NEderlands Leuvens Longkanker Screenings Onderzoek and compare them with the findings of the National Lung Screening Trial.We address the question whether it is necessary to continue discussing the evidence regarding LC screening.In both trials,there is a clear impact on LC mortality but,with a modest reduction in over all mortality.Undoubtedly,the benefit of screening can be expected to grow as low-dose computed tomographys are performed over longer periods of time.展开更多
文摘In this paper a novel method to generate high-precision and continuously adjustable digital time-delay by utilizing the linear phase of a FIR filter is presented. The generated time-delay can be continuously changed by adjusting the filter weights. The time-delay is pre cise and valid for wide-band, while the computational load is low. The proposed approach can find applications in wide-band digital beamforming, adaptive delay estimation, temporal analy sis of reflected waveform, etc.. In the paper, the basic principle, design steps and simulation re sults are given. Also shown are some typical practical applications.
基金supported by the National Natural Science Foundation of China(6167309361370152)the Science and Technology Project of Shenyang(F16-205-1-01)
文摘In this paper, a new partial transmit sequence（PTS）scheme with low computational complexity is proposed for the problems of high computational complexity in the conventional PTS method. By analyzing the relationship of candidate sequences in the PTS method under the interleaved partition method, it has been discovered that some candidate sequences generated by phase factor sequences have the same peak average power ratio（PAPR）. Hence, phase factor sequences can be optimized to reduce their searching times. Then, the computational process of generating candidate sequences can be simplified by improving the utilization of data and minimizing the calculations of complex multiplication. The performance analysis shows that, compared with the conventional PTS scheme, the proposed approach significantly decreases the computational complexity and has no loss of PAPR performance.
基金supported in part by the Science and Technology Research Program of the National Science Foundation of China(61671096)Chongqing Research Program of Basic Science and Frontier Technology(cstc2017jcyjBX0005)+1 种基金Chongqing Municipal Education Commission(KJQN201800642)Doctoral Student Training Program(BYJS2016009).
文摘For future wireless communication systems,Power Domain Non-Orthogonal Multiple Access(PD-NOMA)using an advanced receiver has been considered as a promising radio access technology candidate.Power allocation plays an important role in the PD-NOMA system because it considerably affects the total throughput and Geometric Mean User Throughput(GMUT)performance.However,most existing studies have not completely accounted for the computational complexity of the power allocation process when the User Terminals(UTs)move in a slow fading channel environment.To resolve such problems,a power allocation method is proposed to considerably reduce the search space of a Full Search Power(FSP)allocation algorithm.The initial power reallocation coefficients will be set to start with former optimal values by the proposed Lemma before searching for optimal power reallocation coefficients based on total throughput performance.Step size and correction granularity will be adjusted within a much narrower power search range while invalid power combinations may be reasonably discarded during the search process.The simulation results show that the proposed power reallocation scheme can greatly reduce computational complexity while the total throughput and GMUT performance loss are not greater than 1.5%compared with the FSP algorithm.
基金supported by the National Natural Science Foundation of China(grant numbers 82204127 and 72204172)。
文摘Lung cancer, the leading cause of cancer deaths worldwide and in China, has a 19.7% five-year survival rate due to terminal-stage diagnosis^([1-3]).Although low-dose computed tomography(CT) screening can reduce mortality, high false positive rates can create economic and psychological burdens.
文摘A new selected mapping(SLM)scheme based on constellation rotation is proposed to reduce the peak-to-average power ratio(PAPR)of orthogonal frequency division multiplexing(OFDM)signals.Its core idea is to generate abundant candidate signals by rotating different sub-signals of the original frequency signal with different angles.This new signal generation method can simplify the calculation process of candidate time signals into the linear addition of some intermediate signals,which are generated by the inverse fast Fourier transform(IFFT)operation of the original frequency signal.This feature can effectively reduce the computational complexity of candidate signal generation process.And compared to the traditional SLM scheme,the number of complex multiplication and complex addition of new scheme can separately be decreased by about 99.99% and 91.7% with some specific parameters.Moreover,with the help of the constellation detection mechanism at the receiver,there is no need to carry any side information at the transmitter.The simulation results show that,with the same channel transmission performance,the PAPR reduction performance of new scheme can approach or even exceed the upper bound of the traditional SLM scheme,which uses all the vectors in Hadamard matrix as the phase sequences.
基金This work was supported in part by the Startup Foundation for Introducing Talent of Nanjing University of Information Science and Technology under Grant 2016r055in part by the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions.
文摘With the rise of the Internet of Things(IoT),various devices in life and industry are closely linked.Because of its high payload,stable error correction capability,and convenience in reading and writing,Quick Response(QR)code has been widely researched in IoT.However,the security of privacy data in IoT is also a very important issue.At the same time,because IoT is developing towards low-power devices in order to be applied to more fields,the technology protecting the security of private needs to have the characteristics of low computational complexity.Visual Secret Sharing(VSS),with its features of safety and low computational cost,can fully meet the requirements of communication security in IoT.Therefore,a VSS scheme with QR code(VSS-QR)was proposed and has been applied to some extent.In VSS-QR,the secret is shared into a series of shares.These shares are usually common QR codes,which cannot cause the attention of the attacker.However,if there is dishonesty among participants,the secret cannot be recovered,which will lead to VSS-QR cannot be widely used due to its inadequate security.In this paper,we propose a visual secret sharing scheme with authentication based on QR code(VSSA-QR).Both the reconstructed secret QR code and shares can be verified whether they are forged by attackers.The above-mentioned operations conveniently are performed on low-power QR scanning devices.Not only does the proposed scheme prevent some dishonest participants or attackers from cheating,but also prevent all participants from conspiring.In addition,the payload is the QR code itself,which is higher than other schemes.Theoretical analysis and experiments prove that the proposed scheme is effective.
文摘Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design. With the motivation to design high performance and clean combustor, computational fluid dynamics （CFD） is utilized as the powerful design approach. In this paper, Reynolds averaged Navier-Stokes （RANS） equations of reactive two-phase flow in an experimental low emission combustor is performed. The numerical approach uses an implicit compressible gas solver together with a Lagrangian liquid-phase tracking method and the extended coherent flamelet model for turbulence-combustion interaction. The NOx formation is modeled by the concept of post-processing, which resolves the NOx transport equation with the assumption of frozen temperature distribution. Both turbulence-combustion interaction model and NOx formation model are firstly evaluated by the comparison of experimental data published in open literature of a lean direct injection （LDI） combustor. The test rig studied in this paper is called low emission stirred swirl （LESS） combustor, which is a two-stage model combustor, fueled with liquid kerosene （RP-3） and designed by Beihang University （BUAA）. The main stage of LESS combustor employs the principle of lean prevaporized and premixed （LPP） concept to reduce pollutant, and the pilot stage depends on a diffusion flame for flame stabili-zation. Detailed numerical results including species distribution, turbulence performance and burning performance are qualita-tively and quantitatively evaluated. Numerical prediction of NOx emission shows a good agreement with test data at both idle condition and full power condition of LESS combustor. Preliminary results of the flame structure are shown in this paper. The flame stabilization mechanism and NOx reduction effort are also discussed with in-depth analysis.
文摘Lung cancer(LC)is still one of the most frequent cancers with a high related mortality.Their prognosis is directly proportional to the stage at the time of diagnosis.Seventy percent are currently diagnosed in advanced or locally advanced stage(higher than stage III),making a cure unlikely for the majority of patients.Developments in LC treatment are significant however they do not seem to be enough to reverse the current situation,at least,in a short period of time.Despite recent advances in treatment,primary prevention and early diagnosis appear to be the key to reduce the incidence and mortality of this disease.Many countries have developed LC screening programs based on the results of clinical trials published in recent years.The aim of this paper is to review the latest results of the NEderlands Leuvens Longkanker Screenings Onderzoek and compare them with the findings of the National Lung Screening Trial.We address the question whether it is necessary to continue discussing the evidence regarding LC screening.In both trials,there is a clear impact on LC mortality but,with a modest reduction in over all mortality.Undoubtedly,the benefit of screening can be expected to grow as low-dose computed tomographys are performed over longer periods of time.
