A new CMOS quaternary D flip-flop is implemented employing a multiple-valuedclock. PSpice simulation shows that the proposed flip-flop has correct operation. Compared withtraditional multiple-valued flip-flops, the pr...A new CMOS quaternary D flip-flop is implemented employing a multiple-valuedclock. PSpice simulation shows that the proposed flip-flop has correct operation. Compared withtraditional multiple-valued flip-flops, the proposed multiple-valued CMOS flip-flop is characterizedby improved storage capacity, flexible logic structure and reduced power dissipation.展开更多
Owing to the presence of a low-energy,long-lived nuclear isomeric state,^(229)Th is an ideal candidate for developing the next generation clock—the nuclear clock—holding great promise for both applied and fundamenta...Owing to the presence of a low-energy,long-lived nuclear isomeric state,^(229)Th is an ideal candidate for developing the next generation clock—the nuclear clock—holding great promise for both applied and fundamental physics.The^(229)Th ionic nuclear optical clock has garnered considerable attention,attributed to its high precision with a relative uncertainty of≤1.5×10^(-19)and the potential for common-mode noise cancellation via self-comparison between the nuclear transition and the electronic transition of thorium ions.In this article,we focus on Th^(n+)ions(n=1,2,3)and present a comprehensive review of the current progress in the development of ionic nuclear clocks,covering essential steps such as ion generation,trapping,and cooling.Furthermore,we discuss the realization of a closed-loop clock cycle,addressing key aspects including stable isomer excitation and efficient isomer deexcitation.展开更多
We report the SrII optical lattice clock at the National Time Service Center(NTSC).In this system,a blackbody radiation shield with movable lattice mitigates blackbody radiation shifts through active temperature contr...We report the SrII optical lattice clock at the National Time Service Center(NTSC).In this system,a blackbody radiation shield with movable lattice mitigates blackbody radiation shifts through active temperature control.A shallow optical lattice with minimal tunneling minimizes AC Stark shifts.Phase-locked counter-propagating lattice beams and conductive vacuum viewports further reduce systematic uncertainties and a novel initial-state preparation method simplifies the system.Clock transition spectra achieve a linewidth of 2.5 Hz with a 400 ms clock pulse,and self-comparison stability reaches 5.1×10^(-16)at 1 s.These advancements give this clock the potential to be a critical platform for realizing outstanding systematic uncertainties in the future.展开更多
Satellite clock bias(SCB)prediction is essential for enhancing the accuracy and reliability of real-time precise point positioning(RT-PPP)in Global Navigation Satellite Systems(GNSS).To address the nonlinearity,non-st...Satellite clock bias(SCB)prediction is essential for enhancing the accuracy and reliability of real-time precise point positioning(RT-PPP)in Global Navigation Satellite Systems(GNSS).To address the nonlinearity,non-stationarity,and short-term interruptions of SCB data under complex environments,this paper proposes an enhanced SCB prediction model combining Temporal Convolutional Networks(TCN)and Transformers.Experimental results indicate that,in a 24-h prediction task,the proposed model reduces root mean square error(RMSE)and range error(RE)by 95.6%,86.0%,and 61.3%,and93.7%,86.3%,and 58.8%,respectively,compared with LSTM,Transformer,and CNN-BiGRU-Attention models,while improving computational efficiency by 48.6%over the Transformer.Moreover,although the clock bias products generated by the proposed method result in slightly higher static PPP positioning errors than the International GNSS Service(IGS)rapid clock products,the error differences are generally at the millimeter level,demonstrating the feasibility of using predicted clock bias products to replace rapid clock products in the short term.This method addresses the PPP positioning issue during short-term network service interruptions from the perspective of time series prediction and provides potential solutions for engineering applications such as landslide,earthquake,and subsidence monitoring.展开更多
The isomeric transition of thorium-229(^(229)Th),as the only known laser-accessible nuclear transition,offers the possibility for the development of a new generation of optical clocks.Solid-state nuclear optical clock...The isomeric transition of thorium-229(^(229)Th),as the only known laser-accessible nuclear transition,offers the possibility for the development of a new generation of optical clocks.Solid-state nuclear optical clock based on^(229)Th-doped crystals or thin films has attracted much attention due to its potential advantages in high stability,miniaturization,and robustness.This paper reviews the research progress of solid-state nuclear optical clock materials,analyzes the preparation,defects,and properties of the candidate solid material systems for^(229)Th,explores the influence of the local crystal environment on the nuclear transition,focuses on introducing the latest research results of crystal materials such as Th-doped CaF_(2)and LiSrAlF_(6),and looks forward to the future development direction of this field.It could provide a reference for the material selection and optimization of solid-state nuclear optical clocks.展开更多
The Jumonji C domain-containing(JmjC)histone demethylases(JMJs)are involved in various aspects of plant development and responses to environmental changes.AtJMJs have been extensively studied in Arabidopsis for their ...The Jumonji C domain-containing(JmjC)histone demethylases(JMJs)are involved in various aspects of plant development and responses to environmental changes.AtJMJs have been extensively studied in Arabidopsis for their roles in regulating flowering time,while their functions and molecular mechanisms in regulating flowering time in rice remain underexplored.Here,we demonstrate that the JmjC domain-only group member OsJMJ712 regulates heading date in rice.OsJMJ712 exhibits H3K36me3 demethylase activity at Ehd1 and RFT1 and represses the expression of Ehd1,Hd3a,and RFT1.Furthermore,loss of function of OsJMJ712 disrupts the circadian clock,and OsLHY directly binds to the promoter of OsJMJ712 to suppress its expression.These findings uncover that OsJMJ712 integrates histone demethylation and the circadian clock to fine-tune photoperiodic flowering in rice,providing new insights into the epigenetic control of photoperiodic flowering in crops.展开更多
Clock synchronization has important applications in multi-agent collaboration(such as drone light shows,intelligent transportation systems,and game AI),group decision-making,and emergency rescue operations.Synchroniza...Clock synchronization has important applications in multi-agent collaboration(such as drone light shows,intelligent transportation systems,and game AI),group decision-making,and emergency rescue operations.Synchronization method based on pulse-coupled oscillators(PCOs)provides an effective solution for clock synchronization in wireless networks.However,the existing clock synchronization algorithms in multi-agent ad hoc networks are difficult to meet the requirements of high precision and high stability of synchronization clock in group cooperation.Hence,this paper constructs a network model,named DAUNet(unsupervised neural network based on dual attention),to enhance clock synchronization accuracy in multi-agent wireless ad hoc networks.Specifically,we design an unsupervised distributed neural network framework as the backbone,building upon classical PCO-based synchronization methods.This framework resolves issues such as prolonged time synchronization message exchange between nodes,difficulties in centralized node coordination,and challenges in distributed training.Furthermore,we introduce a dual-attention mechanism as the core module of DAUNet.By integrating a Multi-Head Attention module and a Gated Attention module,the model significantly improves information extraction capabilities while reducing computational complexity,effectively mitigating synchronization inaccuracies and instability in multi-agent ad hoc networks.To evaluate the effectiveness of the proposed model,comparative experiments and ablation studies were conducted against classical methods and existing deep learning models.The research results show that,compared with the deep learning networks based on DASA and LSTM,DAUNet can reduce the mean normalized phase difference(NPD)by 1 to 2 orders of magnitude.Compared with the attention models based on additive attention and self-attention mechanisms,the performance of DAUNet has improved by more than ten times.This study demonstrates DAUNet’s potential in advancing multi-agent ad hoc networking technologies.展开更多
Aiming at the problems that the clock bias prediction model of the Wavelet Neural Network(WNN)is greatly affected by the selection of network parameters,and the Particle Swarm Optimization Wavelet Neural Network is pr...Aiming at the problems that the clock bias prediction model of the Wavelet Neural Network(WNN)is greatly affected by the selection of network parameters,and the Particle Swarm Optimization Wavelet Neural Network is prone to fall into local optima and has insufficient convergence efficiency in clock bias prediction,a short-term clock bias prediction model for BDS-3 based on the Rime Optimization Algorithm(RIME)-optimized Wavelet Neural Network is proposed.Firstly,the specific steps of the WNN model based on the RIME optimization algorithm in clock bias prediction are elaborated in detail.Then,the stability characteristics and training efficiency of the RIME optimization algorithm during the optimization stage are analyzed to determine the population size that suits the characteristics of clock bias data.Finally,using the BDS-3 clock bias data provided by the Wuhan University Data Center,shortterm clock bias prediction experiments with durations of 1 h,3 h,and 6 h are carried out.The experimental results show that in the 6h prediction,the average prediction accuracy of the RIME-WNN model is better than 0.1 ns,which is 93.92%,88.35%,and 48.11%higher than that of the Quadratic Polynomial model,the Grey Model(GM(1,1)),and the PSO-WNN model,respectively.In addition,when the RIMEWNN model predicts different types of Beidou satellites,the maximum difference in the Root Mean Square Error(RMSE)is relatively smaller,which fully demonstrates that the model has a wide and good accuracy adaptability when predicting various types of Beidou satellites.展开更多
Recent advances in atomic optical clocks based on electronic transitions have achieved frequency uncertainties at the10^(-19)level,enabling wide applications in testing variations of physical constants,exploring dark ...Recent advances in atomic optical clocks based on electronic transitions have achieved frequency uncertainties at the10^(-19)level,enabling wide applications in testing variations of physical constants,exploring dark matter signatures,and enhancing precision metrology for position,navigation,and timing systems.To pursue higher-precision optical clocks,the development of nuclear optical clocks has emerged,with the^(229)Th system distinguished by its unique low-lying isomeric state at~8.4 eV and a natural linewidth of approximately 100μHz,promising uncertainties below 10^(-19).The intrinsic insensitivity of nuclear transitions to external perturbations and their subatomic-scale spatial confinement provide significant advantages over electronic transitions in mitigating environmental shifts.Recent experimental breakthroughs include the excitation of the nuclear clock transition in solid-state^(229)Th-doped crystals with spectral resolution at the k Hz level.However,critical challenges persist,particularly in implementing effective laser excitation schemes(e.g.,via the electronic bridge mechanism)and closed-loop quantum control in trapped ion systems.Addressing these requires comprehensive understanding of complex many-body interactions in^(229)Th,encompassing electronic structure,nuclear deformation,hyperfine and field shift,and solid-state environmental coupling.This review synthesizes recent advancements in(i)the characterization of nuclear and atomic structures of the^(229)Th nuclear clock,and(ii)precise evaluation and mitigation of external perturbations affecting the clock transitions.The analysis provides a solid theoretical and experimental foundation for optimizing^(229)Th-based nuclear clock performance.展开更多
The single fault and multiple fault detections for multiple-valued logic circuits are studied in this paper. Firstly, it is shown that the cardinality of optimal single fault test set for fanout-free m-valued circuits...The single fault and multiple fault detections for multiple-valued logic circuits are studied in this paper. Firstly, it is shown that the cardinality of optimal single fault test set for fanout-free m-valued circuits with n primary inputs is not more than n + 1, for linear tree circuits is two, and for multiplication modulo circuits is two if n is an odd number or if n is an even number and m ＞ 3, where the optimal test set of a circuit has minimal number of test vectors. Secondly,it is indicated that the cardinality of optimal multiple fault test set for linear tree circuits with n primary inputs is 1 + [n/(m - 1)], for multiplication modulo circuits is n+ 1, for fanout-free circuits that consist of 2-input linear tree circuits and 2-input multiplication modulo circuits is not greater than n+ 1, where [x] denotes the smallest integer greater than or equal to x. Finally,the single fault location approaches of linear tree circuits and multiplication modulo circuits are presented, and all faults in the two types of circuits can be located by using a test set with n + 1 vectors.展开更多
There are many kinds of special relationships between multiple-valued logical func-tions and their variables, and they are difficult to be judged from their expressions. In thispaper, some sufficient and necessary con...There are many kinds of special relationships between multiple-valued logical func-tions and their variables, and they are difficult to be judged from their expressions. In thispaper, some sufficient and necessary conditions of the independence and statistical independenceof multiple-valued logical functions on their variables are given. Some conditions of algebraicindependence of multiple-valued logical functions on some of their variables and the way to de-generate a function to the greatest extent are proposed, and some applications of these resultsare indicated. All the results are studied by using Chrestenson spectral techniques.展开更多
A new AB^2 operation in Galois Field GF(24)is presented and its systolic realization based on multiple-valued logic(MVL)is proposed.The systolic structure of the operation employs multiple-valued current mode(MVCM)by ...A new AB^2 operation in Galois Field GF(24)is presented and its systolic realization based on multiple-valued logic(MVL)is proposed.The systolic structure of the operation employs multiple-valued current mode(MVCM)by using dynamic source-coupled logic(SCL)to reduce the transistor and wire counts,and the initial delay.The performance is evaluated by HSPICE simulation with 0.18.μm CMOS technology.A comparison is conducted between our proposed implementation and those reported in the literature.The transistor counts,the wire counts and the initial delay in our MVL design show savings of about 23%,45%,and 72%,in comparison with the corresponding binary CMOS implementation.The systolic architecture proposed is simple,regular,and modular,well suited for very large scale integration(VLSI)implementation.The combination of MVCM circuits and relevant algorithms based on MVL seems to be a potential solution for high performance arithmetic operations in GF(2^k).展开更多
The circuit testable realizations of multiple-valued functions are studied in this letter. First of all,it is shown that one vector detects all skew faults in multiplication modulo circuits or in addi-tion modulo circ...The circuit testable realizations of multiple-valued functions are studied in this letter. First of all,it is shown that one vector detects all skew faults in multiplication modulo circuits or in addi-tion modulo circuits,and n+1 vectors detect all skew faults in the circuit realization of multiple-valued functions with n inputs. Secondly,min(max) bridging fault test sets with n+2 vectors are pre-sented for the circuit realizations of multiple-valued logic functions. Finally,a tree structure is used instead of cascade structure to reduce the delay in the circuit realization,it is shown that three vec-tors are sufficient to detect all single stuck-at faults in the tree structure realization of multiple-valued logic functions.展开更多
Objective To investigate the structural changes of rat thoracic aorta and changes in expression levels of Bmal1 and cyclins in thoracic aorta endothelial cells following heat stress.Methods Twenty male SD rats were ra...Objective To investigate the structural changes of rat thoracic aorta and changes in expression levels of Bmal1 and cyclins in thoracic aorta endothelial cells following heat stress.Methods Twenty male SD rats were randomized equally into control group and heat stress group.After exposure to 32℃for 2 weeks in the latter group,the rats were examined for histopathological changes and Bmal1 expression in the thoracic aorta using HE staining and immunohistochemistry.In the cell experiments,cultured rat thoracic aortic endothelial cells(RTAECs)were incubated at 40℃for 12 h with or without prior transfection with a Bmal1-specific small interfering RNA(si-Bmal1)or a negative sequence.In both rat thoracic aorta and RTAECs,the expressions of Bmal1,the cell cycle proteins CDK1,CDK4,CDK6,and cyclin B1,and apoptosis-related proteins Bax and Bcl-2 were detected using Western blotting.TUNEL staining was used to detect cell apoptosis in rat thoracic aorta,and the changes in cell cycle distribution and apoptosis in RTAECs were analyzed with flow cytometry.Results Compared with the control rats,the rats exposed to heat stress showed significantly increased blood pressures and lowered heart rate with elastic fiber disruption and increased expressions of Bmal1,cyclin B1 and CDK1 in the thoracic aorta(P<0.05).In cultured RTAECs,heat stress caused significant increase of Bmal1,cyclin B1 and CDK1 protein expression levels,which were obviously lowered in cells with prior si-Bmal1 transfection.Bmal1 knockdown also inhibited heat stress-induced increase of apoptosis in RTAECs as evidenced by decreased expression of Bax and increased expression of Bcl-2.Conclusion Heat stress upregulates Bmal1 expression and causes alterations in expressions of cyclins to trigger apoptosis of rat thoracic aorta endothelial cells,which can be partly alleviated by suppressing Bmal1 expression.展开更多
The circadian clock is a highly hierarchical network of endogenous pacemakers that primarily maintains and directs oscillations through transcriptional and translational feedback loops,which modulates an approximately...The circadian clock is a highly hierarchical network of endogenous pacemakers that primarily maintains and directs oscillations through transcriptional and translational feedback loops,which modulates an approximately 24-h cycle of endocrine and metabolic rhythms within cells and tissues.While circadian clocks regulate metabolic processes and related physiology,emerging evidence indicates that metabolism and circadian rhythm are intimately intertwined.In this review,we highlight the concept of metabolites,including lipids and other polar metabolites generated from intestinal microbial metabolism and nutrient intake,as time cues that drive changes in circadian rhythms,which in turn influence metabolism and aging.Furthermore,we discuss the roles of functional metabolites as circadian cues,paving a new direction on potential intervention targets of circadian disruption,pathological aging,as well as metabolic diseases that are clinically important.展开更多
We present analog clocks fitted to the Mars solar day.These clocks use the standard Earth-based second of the International System of Units(SI)as their operational unit of time,unlike current practice for Mars timekee...We present analog clocks fitted to the Mars solar day.These clocks use the standard Earth-based second of the International System of Units(SI)as their operational unit of time,unlike current practice for Mars timekeeping.We discuss the importance of preserving the SI second.On this basis,we identify the two analog clocks most suitable for public use by a future Mars population.These are a 20-hour clock with a hand motion similar to that of the standard Earth clock,and a 24-hour clock with a novel“Martian”hand motion which strikes the hour when all 3 hands converge onto that hour mark on the dial.Both clocks have Earth-day equivalents to assist learning.We also present a 24-hour“SpaceClock”,similar to the Martian clock but with no favored reference plane,hence equally readable from any viewing orientation.展开更多
文摘A new CMOS quaternary D flip-flop is implemented employing a multiple-valuedclock. PSpice simulation shows that the proposed flip-flop has correct operation. Compared withtraditional multiple-valued flip-flops, the proposed multiple-valued CMOS flip-flop is characterizedby improved storage capacity, flexible logic structure and reduced power dissipation.
基金Project supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0920000)the National Natural Science Foundation of China(Grant No.12341401)。
文摘Owing to the presence of a low-energy,long-lived nuclear isomeric state,^(229)Th is an ideal candidate for developing the next generation clock—the nuclear clock—holding great promise for both applied and fundamental physics.The^(229)Th ionic nuclear optical clock has garnered considerable attention,attributed to its high precision with a relative uncertainty of≤1.5×10^(-19)and the potential for common-mode noise cancellation via self-comparison between the nuclear transition and the electronic transition of thorium ions.In this article,we focus on Th^(n+)ions(n=1,2,3)and present a comprehensive review of the current progress in the development of ionic nuclear clocks,covering essential steps such as ion generation,trapping,and cooling.Furthermore,we discuss the realization of a closed-loop clock cycle,addressing key aspects including stable isomer excitation and efficient isomer deexcitation.
基金supported by the Innovation Pro-gram for Quantum Science and Technology(Grant Nos.2021ZD0300900 and 2021ZD0300902)the Strate-gic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB35010202)the Operation and Maintenance of Major Scientific and Technological In-frastructure of the Chinese Academy of Sciences(Grant No.2024000014).
文摘We report the SrII optical lattice clock at the National Time Service Center(NTSC).In this system,a blackbody radiation shield with movable lattice mitigates blackbody radiation shifts through active temperature control.A shallow optical lattice with minimal tunneling minimizes AC Stark shifts.Phase-locked counter-propagating lattice beams and conductive vacuum viewports further reduce systematic uncertainties and a novel initial-state preparation method simplifies the system.Clock transition spectra achieve a linewidth of 2.5 Hz with a 400 ms clock pulse,and self-comparison stability reaches 5.1×10^(-16)at 1 s.These advancements give this clock the potential to be a critical platform for realizing outstanding systematic uncertainties in the future.
基金supported by the National Natural Science Foundation of China(42304050)Major Science and Technology Projects in Anhui Province,grant number(202103a05020026)+1 种基金Open Foundation of the Key Laboratory of Universities in Anhui Province for Prevention of Mine Geological Disasters(2022-MGDP-08)University Natural Science Research Project of Anhui Province(2023AH051190)。
文摘Satellite clock bias(SCB)prediction is essential for enhancing the accuracy and reliability of real-time precise point positioning(RT-PPP)in Global Navigation Satellite Systems(GNSS).To address the nonlinearity,non-stationarity,and short-term interruptions of SCB data under complex environments,this paper proposes an enhanced SCB prediction model combining Temporal Convolutional Networks(TCN)and Transformers.Experimental results indicate that,in a 24-h prediction task,the proposed model reduces root mean square error(RMSE)and range error(RE)by 95.6%,86.0%,and 61.3%,and93.7%,86.3%,and 58.8%,respectively,compared with LSTM,Transformer,and CNN-BiGRU-Attention models,while improving computational efficiency by 48.6%over the Transformer.Moreover,although the clock bias products generated by the proposed method result in slightly higher static PPP positioning errors than the International GNSS Service(IGS)rapid clock products,the error differences are generally at the millimeter level,demonstrating the feasibility of using predicted clock bias products to replace rapid clock products in the short term.This method addresses the PPP positioning issue during short-term network service interruptions from the perspective of time series prediction and provides potential solutions for engineering applications such as landslide,earthquake,and subsidence monitoring.
基金supported by Zhangjiang Laboratory(Grant No.ZJSP21A001D)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0920000)the National Natural Science Foundation of China(Grant Nos.12341402 and 12341403)。
文摘The isomeric transition of thorium-229(^(229)Th),as the only known laser-accessible nuclear transition,offers the possibility for the development of a new generation of optical clocks.Solid-state nuclear optical clock based on^(229)Th-doped crystals or thin films has attracted much attention due to its potential advantages in high stability,miniaturization,and robustness.This paper reviews the research progress of solid-state nuclear optical clock materials,analyzes the preparation,defects,and properties of the candidate solid material systems for^(229)Th,explores the influence of the local crystal environment on the nuclear transition,focuses on introducing the latest research results of crystal materials such as Th-doped CaF_(2)and LiSrAlF_(6),and looks forward to the future development direction of this field.It could provide a reference for the material selection and optimization of solid-state nuclear optical clocks.
基金funded by the Zhejiang Zhengjingyuan Pharmacy Chain Co.,Ltd.,China(Grant No.2025-KYY-516030-0001).
文摘The Jumonji C domain-containing(JmjC)histone demethylases(JMJs)are involved in various aspects of plant development and responses to environmental changes.AtJMJs have been extensively studied in Arabidopsis for their roles in regulating flowering time,while their functions and molecular mechanisms in regulating flowering time in rice remain underexplored.Here,we demonstrate that the JmjC domain-only group member OsJMJ712 regulates heading date in rice.OsJMJ712 exhibits H3K36me3 demethylase activity at Ehd1 and RFT1 and represses the expression of Ehd1,Hd3a,and RFT1.Furthermore,loss of function of OsJMJ712 disrupts the circadian clock,and OsLHY directly binds to the promoter of OsJMJ712 to suppress its expression.These findings uncover that OsJMJ712 integrates histone demethylation and the circadian clock to fine-tune photoperiodic flowering in rice,providing new insights into the epigenetic control of photoperiodic flowering in crops.
文摘Clock synchronization has important applications in multi-agent collaboration(such as drone light shows,intelligent transportation systems,and game AI),group decision-making,and emergency rescue operations.Synchronization method based on pulse-coupled oscillators(PCOs)provides an effective solution for clock synchronization in wireless networks.However,the existing clock synchronization algorithms in multi-agent ad hoc networks are difficult to meet the requirements of high precision and high stability of synchronization clock in group cooperation.Hence,this paper constructs a network model,named DAUNet(unsupervised neural network based on dual attention),to enhance clock synchronization accuracy in multi-agent wireless ad hoc networks.Specifically,we design an unsupervised distributed neural network framework as the backbone,building upon classical PCO-based synchronization methods.This framework resolves issues such as prolonged time synchronization message exchange between nodes,difficulties in centralized node coordination,and challenges in distributed training.Furthermore,we introduce a dual-attention mechanism as the core module of DAUNet.By integrating a Multi-Head Attention module and a Gated Attention module,the model significantly improves information extraction capabilities while reducing computational complexity,effectively mitigating synchronization inaccuracies and instability in multi-agent ad hoc networks.To evaluate the effectiveness of the proposed model,comparative experiments and ablation studies were conducted against classical methods and existing deep learning models.The research results show that,compared with the deep learning networks based on DASA and LSTM,DAUNet can reduce the mean normalized phase difference(NPD)by 1 to 2 orders of magnitude.Compared with the attention models based on additive attention and self-attention mechanisms,the performance of DAUNet has improved by more than ten times.This study demonstrates DAUNet’s potential in advancing multi-agent ad hoc networking technologies.
基金the 2023 Liaoning Institute of Science and Technology Doctoral Program Launch Fund(2307B29),covering aspects such as data collection and publication of the paper。
文摘Aiming at the problems that the clock bias prediction model of the Wavelet Neural Network(WNN)is greatly affected by the selection of network parameters,and the Particle Swarm Optimization Wavelet Neural Network is prone to fall into local optima and has insufficient convergence efficiency in clock bias prediction,a short-term clock bias prediction model for BDS-3 based on the Rime Optimization Algorithm(RIME)-optimized Wavelet Neural Network is proposed.Firstly,the specific steps of the WNN model based on the RIME optimization algorithm in clock bias prediction are elaborated in detail.Then,the stability characteristics and training efficiency of the RIME optimization algorithm during the optimization stage are analyzed to determine the population size that suits the characteristics of clock bias data.Finally,using the BDS-3 clock bias data provided by the Wuhan University Data Center,shortterm clock bias prediction experiments with durations of 1 h,3 h,and 6 h are carried out.The experimental results show that in the 6h prediction,the average prediction accuracy of the RIME-WNN model is better than 0.1 ns,which is 93.92%,88.35%,and 48.11%higher than that of the Quadratic Polynomial model,the Grey Model(GM(1,1)),and the PSO-WNN model,respectively.In addition,when the RIMEWNN model predicts different types of Beidou satellites,the maximum difference in the Root Mean Square Error(RMSE)is relatively smaller,which fully demonstrates that the model has a wide and good accuracy adaptability when predicting various types of Beidou satellites.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB0920100 and XDB0920101)the National Natural Science Foundation of China(Grant Nos.12174402,12393821,12274417)the Chinese Academy of Sciences Project for Young Scientists in Basic Research(Grant No.YSBR-055)。
文摘Recent advances in atomic optical clocks based on electronic transitions have achieved frequency uncertainties at the10^(-19)level,enabling wide applications in testing variations of physical constants,exploring dark matter signatures,and enhancing precision metrology for position,navigation,and timing systems.To pursue higher-precision optical clocks,the development of nuclear optical clocks has emerged,with the^(229)Th system distinguished by its unique low-lying isomeric state at~8.4 eV and a natural linewidth of approximately 100μHz,promising uncertainties below 10^(-19).The intrinsic insensitivity of nuclear transitions to external perturbations and their subatomic-scale spatial confinement provide significant advantages over electronic transitions in mitigating environmental shifts.Recent experimental breakthroughs include the excitation of the nuclear clock transition in solid-state^(229)Th-doped crystals with spectral resolution at the k Hz level.However,critical challenges persist,particularly in implementing effective laser excitation schemes(e.g.,via the electronic bridge mechanism)and closed-loop quantum control in trapped ion systems.Addressing these requires comprehensive understanding of complex many-body interactions in^(229)Th,encompassing electronic structure,nuclear deformation,hyperfine and field shift,and solid-state environmental coupling.This review synthesizes recent advancements in(i)the characterization of nuclear and atomic structures of the^(229)Th nuclear clock,and(ii)precise evaluation and mitigation of external perturbations affecting the clock transitions.The analysis provides a solid theoretical and experimental foundation for optimizing^(229)Th-based nuclear clock performance.
基金Supported by the National Natural Science Foundation of China (No.60006002) Education Department of Guangdong Province of China (No. Z02019)
文摘The single fault and multiple fault detections for multiple-valued logic circuits are studied in this paper. Firstly, it is shown that the cardinality of optimal single fault test set for fanout-free m-valued circuits with n primary inputs is not more than n + 1, for linear tree circuits is two, and for multiplication modulo circuits is two if n is an odd number or if n is an even number and m ＞ 3, where the optimal test set of a circuit has minimal number of test vectors. Secondly,it is indicated that the cardinality of optimal multiple fault test set for linear tree circuits with n primary inputs is 1 + [n/(m - 1)], for multiplication modulo circuits is n+ 1, for fanout-free circuits that consist of 2-input linear tree circuits and 2-input multiplication modulo circuits is not greater than n+ 1, where [x] denotes the smallest integer greater than or equal to x. Finally,the single fault location approaches of linear tree circuits and multiplication modulo circuits are presented, and all faults in the two types of circuits can be located by using a test set with n + 1 vectors.
文摘There are many kinds of special relationships between multiple-valued logical func-tions and their variables, and they are difficult to be judged from their expressions. In thispaper, some sufficient and necessary conditions of the independence and statistical independenceof multiple-valued logical functions on their variables are given. Some conditions of algebraicindependence of multiple-valued logical functions on some of their variables and the way to de-generate a function to the greatest extent are proposed, and some applications of these resultsare indicated. All the results are studied by using Chrestenson spectral techniques.
基金National Natural Science Foundation of China(61801027)。
文摘A new AB^2 operation in Galois Field GF(24)is presented and its systolic realization based on multiple-valued logic(MVL)is proposed.The systolic structure of the operation employs multiple-valued current mode(MVCM)by using dynamic source-coupled logic(SCL)to reduce the transistor and wire counts,and the initial delay.The performance is evaluated by HSPICE simulation with 0.18.μm CMOS technology.A comparison is conducted between our proposed implementation and those reported in the literature.The transistor counts,the wire counts and the initial delay in our MVL design show savings of about 23%,45%,and 72%,in comparison with the corresponding binary CMOS implementation.The systolic architecture proposed is simple,regular,and modular,well suited for very large scale integration(VLSI)implementation.The combination of MVCM circuits and relevant algorithms based on MVL seems to be a potential solution for high performance arithmetic operations in GF(2^k).
基金Supported by the National Natural Science Foundation of China (No.60006002)the Education Department of Guangdong Province of China (No.02019).
文摘The circuit testable realizations of multiple-valued functions are studied in this letter. First of all,it is shown that one vector detects all skew faults in multiplication modulo circuits or in addi-tion modulo circuits,and n+1 vectors detect all skew faults in the circuit realization of multiple-valued functions with n inputs. Secondly,min(max) bridging fault test sets with n+2 vectors are pre-sented for the circuit realizations of multiple-valued logic functions. Finally,a tree structure is used instead of cascade structure to reduce the delay in the circuit realization,it is shown that three vec-tors are sufficient to detect all single stuck-at faults in the tree structure realization of multiple-valued logic functions.
文摘Objective To investigate the structural changes of rat thoracic aorta and changes in expression levels of Bmal1 and cyclins in thoracic aorta endothelial cells following heat stress.Methods Twenty male SD rats were randomized equally into control group and heat stress group.After exposure to 32℃for 2 weeks in the latter group,the rats were examined for histopathological changes and Bmal1 expression in the thoracic aorta using HE staining and immunohistochemistry.In the cell experiments,cultured rat thoracic aortic endothelial cells(RTAECs)were incubated at 40℃for 12 h with or without prior transfection with a Bmal1-specific small interfering RNA(si-Bmal1)or a negative sequence.In both rat thoracic aorta and RTAECs,the expressions of Bmal1,the cell cycle proteins CDK1,CDK4,CDK6,and cyclin B1,and apoptosis-related proteins Bax and Bcl-2 were detected using Western blotting.TUNEL staining was used to detect cell apoptosis in rat thoracic aorta,and the changes in cell cycle distribution and apoptosis in RTAECs were analyzed with flow cytometry.Results Compared with the control rats,the rats exposed to heat stress showed significantly increased blood pressures and lowered heart rate with elastic fiber disruption and increased expressions of Bmal1,cyclin B1 and CDK1 in the thoracic aorta(P<0.05).In cultured RTAECs,heat stress caused significant increase of Bmal1,cyclin B1 and CDK1 protein expression levels,which were obviously lowered in cells with prior si-Bmal1 transfection.Bmal1 knockdown also inhibited heat stress-induced increase of apoptosis in RTAECs as evidenced by decreased expression of Bax and increased expression of Bcl-2.Conclusion Heat stress upregulates Bmal1 expression and causes alterations in expressions of cyclins to trigger apoptosis of rat thoracic aorta endothelial cells,which can be partly alleviated by suppressing Bmal1 expression.
基金supported by grants from the Chinese Academy of Sciences(XDB39050800)the Major Project of Guangzhou National Laboratory(GZNL2024A03013)the National Natural Science Foundation of China(92357308 and 32321004)。
文摘The circadian clock is a highly hierarchical network of endogenous pacemakers that primarily maintains and directs oscillations through transcriptional and translational feedback loops,which modulates an approximately 24-h cycle of endocrine and metabolic rhythms within cells and tissues.While circadian clocks regulate metabolic processes and related physiology,emerging evidence indicates that metabolism and circadian rhythm are intimately intertwined.In this review,we highlight the concept of metabolites,including lipids and other polar metabolites generated from intestinal microbial metabolism and nutrient intake,as time cues that drive changes in circadian rhythms,which in turn influence metabolism and aging.Furthermore,we discuss the roles of functional metabolites as circadian cues,paving a new direction on potential intervention targets of circadian disruption,pathological aging,as well as metabolic diseases that are clinically important.
文摘We present analog clocks fitted to the Mars solar day.These clocks use the standard Earth-based second of the International System of Units(SI)as their operational unit of time,unlike current practice for Mars timekeeping.We discuss the importance of preserving the SI second.On this basis,we identify the two analog clocks most suitable for public use by a future Mars population.These are a 20-hour clock with a hand motion similar to that of the standard Earth clock,and a 24-hour clock with a novel“Martian”hand motion which strikes the hour when all 3 hands converge onto that hour mark on the dial.Both clocks have Earth-day equivalents to assist learning.We also present a 24-hour“SpaceClock”,similar to the Martian clock but with no favored reference plane,hence equally readable from any viewing orientation.
