Belief propagation list(BPL) decoding for polar codes has attracted more attention due to its inherent parallel nature. However, a large gap still exists with CRC-aided SCL(CA-SCL) decoding.In this work, an improved s...Belief propagation list(BPL) decoding for polar codes has attracted more attention due to its inherent parallel nature. However, a large gap still exists with CRC-aided SCL(CA-SCL) decoding.In this work, an improved segmented belief propagation list decoding based on bit flipping(SBPL-BF) is proposed. On the one hand, the proposed algorithm makes use of the cooperative characteristic in BPL decoding such that the codeword is decoded in different BP decoders. Based on this characteristic, the unreliable bits for flipping could be split into multiple subblocks and could be flipped in different decoders simultaneously. On the other hand, a more flexible and effective processing strategy for the priori information of the unfrozen bits that do not need to be flipped is designed to improve the decoding convergence. In addition, this is the first proposal in BPL decoding which jointly optimizes the bit flipping of the information bits and the code bits. In particular, for bit flipping of the code bits, a H-matrix aided bit-flipping algorithm is designed to enhance the accuracy in identifying erroneous code bits. The simulation results show that the proposed algorithm significantly improves the errorcorrection performance of BPL decoding for medium and long codes. It is more than 0.25 d B better than the state-of-the-art BPL decoding at a block error rate(BLER) of 10^(-5), and outperforms CA-SCL decoding in the low signal-to-noise(SNR) region for(1024, 0.5)polar codes.展开更多
As a typical transportation tool in the intelligent manufacturing system,Automatic Guided Vehicle(AGV)plays an indispensable role in the automatic production process of the workshop.Therefore,integrating AGV resources...As a typical transportation tool in the intelligent manufacturing system,Automatic Guided Vehicle(AGV)plays an indispensable role in the automatic production process of the workshop.Therefore,integrating AGV resources into production scheduling has become a research hotspot.For the scheduling problem of the flexible job shop adopting segmented AGV,a dual-resource scheduling optimization mathematical model of machine tools and AGVs is established by minimizing the maximum completion time as the objective function,and an improved genetic algorithmis designed to solve the problem in this study.The algorithmdesigns a two-layer codingmethod based on process coding and machine tool coding and embeds the task allocation of AGV into the decoding process to realize the real dual resource integrated scheduling.When initializing the population,three strategies are designed to ensure the diversity of the population.In order to improve the local search ability and the quality of the solution of the genetic algorithm,three neighborhood structures are designed for variable neighborhood search.The superiority of the improved genetic algorithmand the influence of the location and number of transfer stations on scheduling results are verified in two cases.展开更多
In this study,organic geochemical and petrological analyses were conducted on 111 shale samples from a well to understand the retention,intraformational migration and segmented accumulation(shale oil enrichment in dif...In this study,organic geochemical and petrological analyses were conducted on 111 shale samples from a well to understand the retention,intraformational migration and segmented accumulation(shale oil enrichment in different intervals is unconnected)features of shale oil within the organic-rich shale in the Qingshankou Formation of the Gulong Sag.Our study shows that retained petroleum characteristics in the investigated succession are mainly influenced by three factors:organic richness,intraformational migration and segmented accumulation.Organic matter richness primarily controls the amount of retained petroleum,especially the‘live’component indicated by the S_(2)value rather than the total organic carbon(TOC)figure alone.The negative expulsion efficiencies determined by mass-balance calculations of hydrocarbons reveal that petroleum from adjacent organic-rich intervals migrates into the interval of about 2386-2408 m,which is characterized by high free hydrocarbon(S_(1)),OSI and saturated hydrocarbons content,along with a greater difference inδ^(13)C values between polar compounds(including resins and asphaltenes)and saturated hydrocarbons.The depth-dependent heterogeneity of carbon isotope ratios(δ^(13)C)of mud methane gas,δ^(13)C of extracts gross composition(SARA),δ^(13)C of kerogen and SARA content of extracts suggest that the studied succession can be subdivided into four intervals.The shale oil sealing enrichment character in each interval is further corroborated by the distinctδ^(13)C values of mud methane gas in different intervals.Due to the migration of petroleum into the 2386-2408 m interval,the S_(1),OSI and saturated hydrocarbons content of the interval show higher relative values.The maturity of organic matter in the 2471-2500 m interval is at the highest with the smaller size molecular components of the retained petroleum.Thus,favorable‘sweet spots’may be found in the 2386-2408 m interval and the 2471-2500 m interval,according to the experiment results in this study.展开更多
Pinhole corrosion is difficult to discover through conventional ultrasonic guided waves inspection,particularly for micro-sized pinholes less than 1 mm in diameter.This study proposes a new micro-sized pinhole inspect...Pinhole corrosion is difficult to discover through conventional ultrasonic guided waves inspection,particularly for micro-sized pinholes less than 1 mm in diameter.This study proposes a new micro-sized pinhole inspection method based on segmented time reversal(STR)and high-order modes cluster(HOMC)Lamb waves.First,the principle of defect echo enhancement using STR is introduced.Conventional and STR inspection experiments were conducted on aluminum plates with a thickness of 3 mm and defects with different diameters and depths.The parameters of the segment window are discussed in detail.The results indicate that the proposed method had an amplitude four times larger than of conventional ultrasonic guided waves inspection method for pinhole defect detection and could detect micro-sized pinhole defects as small as 0.5 mm in diameter and 0.5 mm in depth.Moreover,the segment window location and width(5-10 times width of the conventional excitation signal)did not affect the detection sensitivity.The combination of low-power and STR is more conducive to detection in different environments,indicating the robustness of the proposed method.Compared with conventional ultrasonic guided wave inspection methods,the proposed method can detect much smaller defect echoes usually obscured by noise that are difficult to detect with a lower excitation power and thus this study would be a good reference for pinhole defect detection.展开更多
BACKGROUND Hepatobiliary scintigraphy(HBS)is a useful diagnostic imaging technique that uses radiotracers to evaluate the function of the gallbladder(GB)and biliary system.In segmented GB,some HBS images reveal a disc...BACKGROUND Hepatobiliary scintigraphy(HBS)is a useful diagnostic imaging technique that uses radiotracers to evaluate the function of the gallbladder(GB)and biliary system.In segmented GB,some HBS images reveal a discordant GB boundary as compared to anatomical images.AIM To evaluate the characteristics of HBS in segmented GB and determine the clinical relevance according to HBS characteristics.METHODS A total of 268 patients with chronic cholecystitis,gallstones,or biliary colic symptoms who underwent HBS between 2011 and 2020 were enrolled.Segmented GB was defined as segmental luminal narrowing of the GB body on computed tomography(CT)or magnetic resonance(MR)images,and HBS was examined 1 mo before or after CT or MR.Segmented GB was classified into 3 types based on the filling and emptying patterns of the proximal and distal segments according to the characteristics of HBS images,and GB ejection fraction(GBEF)was identified:Type 1 was defined as a normal filling and emptying pattern;Type 2 was defined as an emptying defect on the distal segment;and Type 3 was defined as a filling defect in the distal segment.RESULTS Segmented GB accounted for 63 cases(23.5%),including 36 patients(57.1%)with Type 1,18 patients(28.6%)with Type 2,and 9 patients(14.3%)with Type 3 emptying pattern.Thus,approximately 43%of HBS images showed a discordant pattern as compared to anatomical imaging of segmented GB.Although there were no significant differences in clinical symptoms,rate of cholecystectomy,or pathological findings based on the type,most gallstones occurred in the distal segment.Reported GBEF was 62.50%±24.79%for Type 1,75.89%±17.21%for Type 2,and 88.56%±7.20%for Type 3.Type 1 showed no difference in reported GBEF compared to the non-segmented GB group(62.50%±24.79%vs 67.40%±21.78%).In contrast,the reported GBEF was higher in Types 2 and 3 with defective emptying and filling when compared to Type 1(80.11%±15.70%vs 62.57%±24.79%;P=0.001).CONCLUSION In segmented GB,discordance in the filling patterns detected by HBS and anatomical imaging could lead to misinterpretation of GBEF.For this reason,clinicians should be cautious when interpreting HBS results in patients with segmented GB.展开更多
AIM:To evaluate the accuracy of eight different intraocular lens(IOL)power calculation formulas for a segmented multifocal IOL.METHODS:A total of 53 eyes of 41 adult cataract patients who underwent phacoemulsification...AIM:To evaluate the accuracy of eight different intraocular lens(IOL)power calculation formulas for a segmented multifocal IOL.METHODS:A total of 53 eyes of 41 adult cataract patients who underwent phacoemulsification and implantation with the SBL-3 segmented multifocal IOL between January 1,2017 and January 31,2019 were included in this retrospective study.Preoperative biometry measurements were obtained using an IOL Master.Manifest refraction was performed at least 4 wk postoperatively.Accuracy of the eight formulas[Barrett Universal II,Emmetropia Verifying Optical(EVO),Haigis,Hill-RBF 2.0,Hoffer Q,Holladay 1,Kane,and SRK/T]was analyzed.RESULTS:Using current lens constants,all formulas exhibited errors of slight myopic shift in refractive prediction.The Barrett Universal II formula had a significantly lower median absolute error(MedAE)than did Holladay 1(P=0.02),Kane(P=0.001)and Hill-RBF 2.0(P<0.001)formulas.The Haigis formula had a lower MedAE value than did the Hill-RBF 2.0 formula(P=0.005).Differences in MedAE values among SRK/T,EVO and Hoffer Q formulas were not significant.After optimizing lens constants,the MedAE values of all formulas were reduced;significant changes were noted for EVO(P=0.022),Haigis(P=0.048);Hill-RBF 2.0(P=0.014),Holladay 1(P=0.045)and Kane(P=0.022)formulas.All formulas performed equally well after optimization of lens constants(P=0.203).CONCLUSION:All eight formulas tend to result in a myopic shift when using current lens constants.Optimized lens constants improve the accuracy of these formulas among adult Chinese patients.展开更多
This paper proposes a desirable method to detect different kinds of low probability of intercept (LPI) radar signals, targeted at the main intra-pulse modulation method of LPI radar signals including the signals of li...This paper proposes a desirable method to detect different kinds of low probability of intercept (LPI) radar signals, targeted at the main intra-pulse modulation method of LPI radar signals including the signals of linear frequency modulation, phase code, and frequency code. Firstly, it improves the coherent integration of LPI radar signals by adding the periodicity of the ambiguity function. Then, it develops a frequency domain detection method based on fast Fourier transform (FFT) and segmented autocorrelation function to detect signals without features of linear frequency modulation by virtue of the distribution characteristics of noise signals in the frequency domain. Finally, this paper gives a verification of the performance of the method for different signal-to-noise ratios by conducting simulation experiments, and compares the method with existing ones. Additionally, this method is characterized by the straightforward calculation and high real-time performance, which is conducive to better detecting all kinds of LPI radar signals.展开更多
Hybrid Excited Flux Switching Machines(HEFSMs)unique feature of high torque density(T_(den))of Permanent Magnet(PM)machines and flux regulation capability of wound field excitation machines.Due to aforesaid unique fea...Hybrid Excited Flux Switching Machines(HEFSMs)unique feature of high torque density(T_(den))of Permanent Magnet(PM)machines and flux regulation capability of wound field excitation machines.Due to aforesaid unique features,stator active HEFSMs are preferred for EV/HEV applications.In this paper a new Segmented PM Consequent Pole HE-FSM(SPMCPHEFSM)with flux bridge is proposed for EV/HEV.The developed SPMCPHEFSM exhibits improved flux modulation and flux regulation capability at reduced PM usage(suppressed PM volume by 46.52%and PM cost by 46.48%)and eliminating stator leakage flux.First,SPMCPHEFSM is geometric optimized(GO)for investigating influence of leading design with key performance indicators such as flux linkage(Ф_(pp)),average torque(T_(avg)),cogging torque(T_(cog)),T_(den),average power(P_(avg))and power density(P_(den))and then proceeded optimized model to structure modification for optimal stator design and position of field excitation coils(FEC).Comprehensive performance analysis reveals that the developed SPMCPHEFSM show improvedФ_(pp)maximum up to 9.11%,improved T_(avg)maximum up to 23.63%,truncate T_(cog)up to 18.9%whereas T_(den)and P_(den)are boost up to 23.55%and 89.72%respectively.展开更多
The influences of the low-emissive graphite segmented electrode t)laeed near the channel exit on the discharge characteristics of a Hall thruster are studied using the particle- in-cell method. A two-dimensional phys...The influences of the low-emissive graphite segmented electrode t)laeed near the channel exit on the discharge characteristics of a Hall thruster are studied using the particle- in-cell method. A two-dimensional physical model is established according to the Hall thruster discharge channel configuration. The effects of electrode length on the potential, ion density, electron temperature, ionization rate and discharge current are investigated. It is found that, with tile increasing of the segmented electrode length, the equipotential lines bend towards the channel exit. and approximately parallel to the wall at the channel surface, the radial velocity and radial flow of ions are increased, and the electron temperature is also enhanced. Due to the conductive characteristic of electrodes, the radial electric field and the axial electron conductivity near the wall are enhanced, and the probability of the electron-atom ionization is reduced, which leads to the degradation of the ionization rate in the discharge channel. However, the interaction between electrons and the wall enhances the near wall conductivity, therefore the discharge current grows along with the segmented electrode length, and the performance of the thruster is also affected.展开更多
This paper introduces a four-dimensional (4D) segmented disc dynamo which possesses coexisting hidden attractors with one stable equilibrium or a line equilibrium when parameters vary. In addition, by choosing an ap...This paper introduces a four-dimensional (4D) segmented disc dynamo which possesses coexisting hidden attractors with one stable equilibrium or a line equilibrium when parameters vary. In addition, by choosing an appropriate bifurcation parameter, the paper proves that Hopf bifurcation and pitchfork bifurcation occur in the system. The ultimate bound is also estimated. Some numerical investigations are also exploited to demonstrate and visualize the corresponding theoretical results.展开更多
Direct current plasma torches have been applied to generate unique sources of thermal energy in many industrial applications. Nevertheless, the successful ignition of a plasma torch is the key process to generate the ...Direct current plasma torches have been applied to generate unique sources of thermal energy in many industrial applications. Nevertheless, the successful ignition of a plasma torch is the key process to generate the unique source (plasma jet). However, there has been tittle study on the underlying mechanism of this key process. A thorough understanding of the ignition process of a plasma torch will be helpful for optimizing the design of the plasma torch structure and selection of the ignition parameters to prolong the service life of the ignition module. Thus, in this paper, the ignition process of a segmented plasma torch (SPT) is theoretically and experimentally modeled and analyzed. Corresponding electrical models of different stages of the ignition process axe set up and used to derive the electrical parameters, e.g. the variations of the arc voltage and arc current between the cathode and anode. In addition, the experiments with different ignition parameters on a home-made SPT have been conducted. At the same time, the variations of the arc voltage and arc current have been measured, and used to verify the ones derived in theory and to determine the optimal ignition parameters for a particular SPT.展开更多
Due to double salient structure,Flux Switching Machines(FSMs)are preferred for brushless AC high speed applications.Permanent Magnet(PM)FSMs(PM-FSMs)are suited applicants where high torque density(Tden)and power densi...Due to double salient structure,Flux Switching Machines(FSMs)are preferred for brushless AC high speed applications.Permanent Magnet(PM)FSMs(PM-FSMs)are suited applicants where high torque density(Tden)and power density(Pden)are the utmost requisite.However conventional PM-FSMs utilizes excessive rare earth PM volume VPM,higher cogging torque Tcog,high torque ripples(Trip)and comparatively lower(Tden)and Pden due to flux leakage.To overcome the aforesaid demerits,a new high(Tden)Segmented PM Consequent Pole(CP)FSM(SPMCPFSM)with flux bridge and barrier is proposed which successfully reduces VPM by 46.52%and PM cost by 46.48%.Moreover,Multi-Objective Optimization(MOO)examines electromagnetic performance due to variation in geometric parameters for global optimum parameters with key metric such as flux linkage(Φpp),flux harmonics(ΦTHD)average torque(Tavg),Tcog,Trip,Tden,average power(Pavg)and Pden.Analysis reveals that MOO improveΦpp by 22.68%,boost Tavg by 11.41%,enhanced Pavg by 4.55%and increased Tden and Pden by 11.41%.Detailed electromagnetic performance comparison with existing state of the art shows that proposed SPMCPFSM offer Tavg maximum up to 88.8%,truncate Trip up to 24.8%,suppress Tcog up to 22.74%,and results 2.45 times Tden and Pden.展开更多
Monodispersed microsized copper oxalate particles were prepared in a segmented continuous flow tube reactor, and the effect of the main parameters such as organic additive agent, initial copper ions concentration, res...Monodispersed microsized copper oxalate particles were prepared in a segmented continuous flow tube reactor, and the effect of the main parameters such as organic additive agent, initial copper ions concentration, residence time, and segmented media on the final products were investigated experimentally. The obtained copper oxalate microsized particles were disc-like in the presence of citrate ligand,which was the shape inducer for the precipitated copper oxalate. Thermodynamic equilibrium diagrams of the Cu(Ⅱ)-oxalate-H_2O,Cu(Ⅱ)-oxalate-citrate-H_2O, and Cu(Ⅱ)-oxalate-EDTA-H_2O solution systems were drawn to estimate the possible copper species under the experimental conditions and to explain the formation mechanisms of copper oxalate particles in the segmented fluidic reactor. Both theoretical and experimental results indicated that the presence of chelating reagents such as citrate and EDTA had distinct effect on the evolution of particle shape. Air and kerosene were tested as media for the fluidic flow segmentation, and the latter was verified to better promote the growth of copper oxalate particles. The present study provides an easy method to prepare monodispersed copper oxalate microsized particles in a continuous scaling-up way, which can be utilized to prepare the precursor material for conductive inks.展开更多
In order to research segmented diverters for aircraft lightning protection, a transient 2 D multiphysics model based on magnetohydrodynamics theory is proposed to predict the location of the arc plasma discharge and l...In order to research segmented diverters for aircraft lightning protection, a transient 2 D multiphysics model based on magnetohydrodynamics theory is proposed to predict the location of the arc plasma discharge and lightning channel, and to simulate the electrothermal behavior.Based on numerical calculation and preliminary analysis, factors that affect the breakdown voltage of the segmented diverter are discussed. The results show that the voltage increase rate of the voltage source, the width of the air gap between metal segments and the geometry of these segments influence the breakdown voltage of the strip. High-voltage tests of the segmented diverter are performed to reveal air breakdown of the strip and redirect the lightning current.Experimental and numerical results are compared to verify the correctness of the numerical model. The ionization of the air gap between metal segments and the breakdown voltage of the strip calculated by the model are qualitatively consistent with experimental results. The breakdown voltage of the segmented diverter is far lower than the lightning voltage. When a lightning strike occurs, the segmented diverter can be quickly ionized to form a plasma channel which can guide the lightning current well.展开更多
The size and shape of the effective test area are crucial to consider when short-crested waves are created by segmented wavemakers. The range of the effective test area of short-crested waves simulated by two-sided se...The size and shape of the effective test area are crucial to consider when short-crested waves are created by segmented wavemakers. The range of the effective test area of short-crested waves simulated by two-sided segmented wavemakers is analyzed in this paper. The experimental investigation on the wave field distribution of short-crested waves generated by two-sided segmented wavemakers is conducted by using an array of wave gauges. Wave spectra and directional spreading function are analyzed and the results show that when the main direction is at a certain angle with the normal line of wave generators, the wave field of 3D short-crested waves generated by two-sided segmented wavemakers has good spatial uniformity within the model test area. The effective test area can provide good wave environments for seakeeping model tests of various ocean engineering structures in the deep ocean engineering basin.展开更多
A novel class of segmented copolymers, dimethyldiphenylpolysiloxane/poly (oxytetramethylene)-polyurea (PSPEU), was synthesized from α , ω-bis (γ-aminopropyl) dimethyldiphenylpolysiloxane (APMPS), which was prepared...A novel class of segmented copolymers, dimethyldiphenylpolysiloxane/poly (oxytetramethylene)-polyurea (PSPEU), was synthesized from α , ω-bis (γ-aminopropyl) dimethyldiphenylpolysiloxane (APMPS), which was prepared by means of basic ring-opening copolymerization of octamethylcyclotetrasiloxane, hexaphenylcyclotrisiloxane and 1, 3-bis (γ-aminopropyl) tetramethyl disiloxane. The relationships between the diphenylsiloxy contents and the properties of APMPS, including refractive index, glass transition temperature, solubility parameter as well as thermal stability, were investigated; meanwhile, the thermal stability, dynamic mechanical properties, mechanical properiesas well as the antithrombogenicity in vitro of the PSPEU were also revealed.展开更多
The thermally stimulated shape memory behavior of ethylene oxide-butylene terephthalate (EOBT) segmented copolymers with different soft segment molecular weight and hard segment content was investigated. The deformati...The thermally stimulated shape memory behavior of ethylene oxide-butylene terephthalate (EOBT) segmented copolymers with different soft segment molecular weight and hard segment content was investigated. The deformation recovery ratio R-f of the EOBT samples increases with the soft segment molecular weight and the hard segment weight content, while the average overall deformation recovery speed V-r increases with the hard segment content. The temperature of maximum deformation recovery speed (T-M) is determined by the melting temperature of the soft segment crystals and the stability of the crystallized hard segment domains.展开更多
Passive dynamic walking has been developed as a possible explanation for the efficiency of the human gait. This paper presents a passive dynamic walking model with segmented feet, which makes the bipedal walking gait ...Passive dynamic walking has been developed as a possible explanation for the efficiency of the human gait. This paper presents a passive dynamic walking model with segmented feet, which makes the bipedal walking gait more close to natural human-like gait. The proposed model extends the simplest walking model with the addition of fiat feet and torsional spring based compliance on ankle joints and toe joints, to achieve stable walking on a slope driven by gravity. The push-off phase includes foot rotations around the toe joint and around the toe tip, which shows a great resemblance to human normal walking. This paper investigates the effects of the segmented foot structure on bipedal walking in simulations. The model achieves satisfactory walking results on even or uneven slopes.展开更多
In order to explore the correlation between the adjacent segments of a long term EEG, an improved principal component analysis(PCA) method based on mutual information algorithm is proposed. A one-dimension EEG time se...In order to explore the correlation between the adjacent segments of a long term EEG, an improved principal component analysis(PCA) method based on mutual information algorithm is proposed. A one-dimension EEG time series is divided equally into many segments, so that each segment can be regarded as an independent variables and multi-segmented EEG can be expressed as a data matrix. Then, we substitute mutual information matrix for covariance matrix in PCA and conduct the relevance analysis of segmented EEG. The experimental results show that the contribution rate of first principal component(FPC) of segmented EEG is more larger than others, which can effectively reflect the difference of epileptic EEG and normal EEG with the change of segment number. In addition, the evolution of FPC conduce to identify the time-segment locations of abnormal dynamic processes of brain activities,these conclusions are helpful for the clinical analysis of EEG.展开更多
Aiming at the problems of demagnetization effect of electromagnetic buffer(EMB)caused by high velocity under intensive impact load and the difficulty and error of machining composite thin-walled long tube,a segmented ...Aiming at the problems of demagnetization effect of electromagnetic buffer(EMB)caused by high velocity under intensive impact load and the difficulty and error of machining composite thin-walled long tube,a segmented EMB is proposed.The inner tube and air-gap are divided into initial segments and the traversing segments.Through theoretical analysis,impact test and simulation,it can be found that the RRF curve has two peaks.Firstly,in order to reduce the resultant resistance force(RRF)peaks,the sensitivity analysis based on optimal Latin hypercube design(OLHD)and polynomial regression was performed.The results show that the smallest contribution ratio to the dynamic response is the seventh and ninth segments of the inner tube,which are less than 1%.Then,fully considering the uncertain factors,important parameters are selected for uncertain optimization after sensitivity analysis.The interval order and interval probability degree methods are used to establish interval uncertain optimization model of the RRF considering robustness.The model was solved using an interval nested optimization method based on radial basis function(RBF)neural network.Finally,the Pareto front is obtained and numerical simulation is performed to verify the optimal value.It indicates that the two kinds of RRF peak is obviously reduced,and the optimization object and strategy are effective.展开更多
基金funded by the Key Project of NSFC-Guangdong Province Joint Program(Grant No.U2001204)the National Natural Science Foundation of China(Grant Nos.61873290 and 61972431)+1 种基金the Science and Technology Program of Guangzhou,China(Grant No.202002030470)the Funding Project of Featured Major of Guangzhou Xinhua University(2021TZ002).
文摘Belief propagation list(BPL) decoding for polar codes has attracted more attention due to its inherent parallel nature. However, a large gap still exists with CRC-aided SCL(CA-SCL) decoding.In this work, an improved segmented belief propagation list decoding based on bit flipping(SBPL-BF) is proposed. On the one hand, the proposed algorithm makes use of the cooperative characteristic in BPL decoding such that the codeword is decoded in different BP decoders. Based on this characteristic, the unreliable bits for flipping could be split into multiple subblocks and could be flipped in different decoders simultaneously. On the other hand, a more flexible and effective processing strategy for the priori information of the unfrozen bits that do not need to be flipped is designed to improve the decoding convergence. In addition, this is the first proposal in BPL decoding which jointly optimizes the bit flipping of the information bits and the code bits. In particular, for bit flipping of the code bits, a H-matrix aided bit-flipping algorithm is designed to enhance the accuracy in identifying erroneous code bits. The simulation results show that the proposed algorithm significantly improves the errorcorrection performance of BPL decoding for medium and long codes. It is more than 0.25 d B better than the state-of-the-art BPL decoding at a block error rate(BLER) of 10^(-5), and outperforms CA-SCL decoding in the low signal-to-noise(SNR) region for(1024, 0.5)polar codes.
文摘As a typical transportation tool in the intelligent manufacturing system,Automatic Guided Vehicle(AGV)plays an indispensable role in the automatic production process of the workshop.Therefore,integrating AGV resources into production scheduling has become a research hotspot.For the scheduling problem of the flexible job shop adopting segmented AGV,a dual-resource scheduling optimization mathematical model of machine tools and AGVs is established by minimizing the maximum completion time as the objective function,and an improved genetic algorithmis designed to solve the problem in this study.The algorithmdesigns a two-layer codingmethod based on process coding and machine tool coding and embeds the task allocation of AGV into the decoding process to realize the real dual resource integrated scheduling.When initializing the population,three strategies are designed to ensure the diversity of the population.In order to improve the local search ability and the quality of the solution of the genetic algorithm,three neighborhood structures are designed for variable neighborhood search.The superiority of the improved genetic algorithmand the influence of the location and number of transfer stations on scheduling results are verified in two cases.
基金the support from the Scientific Research Project from RIPED(2021ycq01)the Scientific Research and Technological Development Project of CNPC(2021DJ0107)the Basic Research and Strategic Reserve Technology Research Project of CNPC(2020D-5008-01)。
文摘In this study,organic geochemical and petrological analyses were conducted on 111 shale samples from a well to understand the retention,intraformational migration and segmented accumulation(shale oil enrichment in different intervals is unconnected)features of shale oil within the organic-rich shale in the Qingshankou Formation of the Gulong Sag.Our study shows that retained petroleum characteristics in the investigated succession are mainly influenced by three factors:organic richness,intraformational migration and segmented accumulation.Organic matter richness primarily controls the amount of retained petroleum,especially the‘live’component indicated by the S_(2)value rather than the total organic carbon(TOC)figure alone.The negative expulsion efficiencies determined by mass-balance calculations of hydrocarbons reveal that petroleum from adjacent organic-rich intervals migrates into the interval of about 2386-2408 m,which is characterized by high free hydrocarbon(S_(1)),OSI and saturated hydrocarbons content,along with a greater difference inδ^(13)C values between polar compounds(including resins and asphaltenes)and saturated hydrocarbons.The depth-dependent heterogeneity of carbon isotope ratios(δ^(13)C)of mud methane gas,δ^(13)C of extracts gross composition(SARA),δ^(13)C of kerogen and SARA content of extracts suggest that the studied succession can be subdivided into four intervals.The shale oil sealing enrichment character in each interval is further corroborated by the distinctδ^(13)C values of mud methane gas in different intervals.Due to the migration of petroleum into the 2386-2408 m interval,the S_(1),OSI and saturated hydrocarbons content of the interval show higher relative values.The maturity of organic matter in the 2471-2500 m interval is at the highest with the smaller size molecular components of the retained petroleum.Thus,favorable‘sweet spots’may be found in the 2386-2408 m interval and the 2471-2500 m interval,according to the experiment results in this study.
基金National Natural Science Foundation of China(Grant No.62071433)National Key R&D Program of China(Grant No.2022YFC3005002)。
文摘Pinhole corrosion is difficult to discover through conventional ultrasonic guided waves inspection,particularly for micro-sized pinholes less than 1 mm in diameter.This study proposes a new micro-sized pinhole inspection method based on segmented time reversal(STR)and high-order modes cluster(HOMC)Lamb waves.First,the principle of defect echo enhancement using STR is introduced.Conventional and STR inspection experiments were conducted on aluminum plates with a thickness of 3 mm and defects with different diameters and depths.The parameters of the segment window are discussed in detail.The results indicate that the proposed method had an amplitude four times larger than of conventional ultrasonic guided waves inspection method for pinhole defect detection and could detect micro-sized pinhole defects as small as 0.5 mm in diameter and 0.5 mm in depth.Moreover,the segment window location and width(5-10 times width of the conventional excitation signal)did not affect the detection sensitivity.The combination of low-power and STR is more conducive to detection in different environments,indicating the robustness of the proposed method.Compared with conventional ultrasonic guided wave inspection methods,the proposed method can detect much smaller defect echoes usually obscured by noise that are difficult to detect with a lower excitation power and thus this study would be a good reference for pinhole defect detection.
基金reviewed and approved by the Jeonbuk National University Hospital Institutional Review Board,No.2021-07-005.
文摘BACKGROUND Hepatobiliary scintigraphy(HBS)is a useful diagnostic imaging technique that uses radiotracers to evaluate the function of the gallbladder(GB)and biliary system.In segmented GB,some HBS images reveal a discordant GB boundary as compared to anatomical images.AIM To evaluate the characteristics of HBS in segmented GB and determine the clinical relevance according to HBS characteristics.METHODS A total of 268 patients with chronic cholecystitis,gallstones,or biliary colic symptoms who underwent HBS between 2011 and 2020 were enrolled.Segmented GB was defined as segmental luminal narrowing of the GB body on computed tomography(CT)or magnetic resonance(MR)images,and HBS was examined 1 mo before or after CT or MR.Segmented GB was classified into 3 types based on the filling and emptying patterns of the proximal and distal segments according to the characteristics of HBS images,and GB ejection fraction(GBEF)was identified:Type 1 was defined as a normal filling and emptying pattern;Type 2 was defined as an emptying defect on the distal segment;and Type 3 was defined as a filling defect in the distal segment.RESULTS Segmented GB accounted for 63 cases(23.5%),including 36 patients(57.1%)with Type 1,18 patients(28.6%)with Type 2,and 9 patients(14.3%)with Type 3 emptying pattern.Thus,approximately 43%of HBS images showed a discordant pattern as compared to anatomical imaging of segmented GB.Although there were no significant differences in clinical symptoms,rate of cholecystectomy,or pathological findings based on the type,most gallstones occurred in the distal segment.Reported GBEF was 62.50%±24.79%for Type 1,75.89%±17.21%for Type 2,and 88.56%±7.20%for Type 3.Type 1 showed no difference in reported GBEF compared to the non-segmented GB group(62.50%±24.79%vs 67.40%±21.78%).In contrast,the reported GBEF was higher in Types 2 and 3 with defective emptying and filling when compared to Type 1(80.11%±15.70%vs 62.57%±24.79%;P=0.001).CONCLUSION In segmented GB,discordance in the filling patterns detected by HBS and anatomical imaging could lead to misinterpretation of GBEF.For this reason,clinicians should be cautious when interpreting HBS results in patients with segmented GB.
基金Supported by National Key Research and Development Program of China(No.2017YFC1104600)National Natural Science Foundation of China(No.81770909)。
文摘AIM:To evaluate the accuracy of eight different intraocular lens(IOL)power calculation formulas for a segmented multifocal IOL.METHODS:A total of 53 eyes of 41 adult cataract patients who underwent phacoemulsification and implantation with the SBL-3 segmented multifocal IOL between January 1,2017 and January 31,2019 were included in this retrospective study.Preoperative biometry measurements were obtained using an IOL Master.Manifest refraction was performed at least 4 wk postoperatively.Accuracy of the eight formulas[Barrett Universal II,Emmetropia Verifying Optical(EVO),Haigis,Hill-RBF 2.0,Hoffer Q,Holladay 1,Kane,and SRK/T]was analyzed.RESULTS:Using current lens constants,all formulas exhibited errors of slight myopic shift in refractive prediction.The Barrett Universal II formula had a significantly lower median absolute error(MedAE)than did Holladay 1(P=0.02),Kane(P=0.001)and Hill-RBF 2.0(P<0.001)formulas.The Haigis formula had a lower MedAE value than did the Hill-RBF 2.0 formula(P=0.005).Differences in MedAE values among SRK/T,EVO and Hoffer Q formulas were not significant.After optimizing lens constants,the MedAE values of all formulas were reduced;significant changes were noted for EVO(P=0.022),Haigis(P=0.048);Hill-RBF 2.0(P=0.014),Holladay 1(P=0.045)and Kane(P=0.022)formulas.All formulas performed equally well after optimization of lens constants(P=0.203).CONCLUSION:All eight formulas tend to result in a myopic shift when using current lens constants.Optimized lens constants improve the accuracy of these formulas among adult Chinese patients.
基金supported by the National Natural Science Foundation of China(61571462)Weapons and Equipment Exploration Research Project(7131464)
文摘This paper proposes a desirable method to detect different kinds of low probability of intercept (LPI) radar signals, targeted at the main intra-pulse modulation method of LPI radar signals including the signals of linear frequency modulation, phase code, and frequency code. Firstly, it improves the coherent integration of LPI radar signals by adding the periodicity of the ambiguity function. Then, it develops a frequency domain detection method based on fast Fourier transform (FFT) and segmented autocorrelation function to detect signals without features of linear frequency modulation by virtue of the distribution characteristics of noise signals in the frequency domain. Finally, this paper gives a verification of the performance of the method for different signal-to-noise ratios by conducting simulation experiments, and compares the method with existing ones. Additionally, this method is characterized by the straightforward calculation and high real-time performance, which is conducive to better detecting all kinds of LPI radar signals.
文摘Hybrid Excited Flux Switching Machines(HEFSMs)unique feature of high torque density(T_(den))of Permanent Magnet(PM)machines and flux regulation capability of wound field excitation machines.Due to aforesaid unique features,stator active HEFSMs are preferred for EV/HEV applications.In this paper a new Segmented PM Consequent Pole HE-FSM(SPMCPHEFSM)with flux bridge is proposed for EV/HEV.The developed SPMCPHEFSM exhibits improved flux modulation and flux regulation capability at reduced PM usage(suppressed PM volume by 46.52%and PM cost by 46.48%)and eliminating stator leakage flux.First,SPMCPHEFSM is geometric optimized(GO)for investigating influence of leading design with key performance indicators such as flux linkage(Ф_(pp)),average torque(T_(avg)),cogging torque(T_(cog)),T_(den),average power(P_(avg))and power density(P_(den))and then proceeded optimized model to structure modification for optimal stator design and position of field excitation coils(FEC).Comprehensive performance analysis reveals that the developed SPMCPHEFSM show improvedФ_(pp)maximum up to 9.11%,improved T_(avg)maximum up to 23.63%,truncate T_(cog)up to 18.9%whereas T_(den)and P_(den)are boost up to 23.55%and 89.72%respectively.
基金supported by National Natural Science Foundation of China(Nos.11375039 and 11275034)the Key Project of Science and Technology of Liaoning Province,China(No.2011224007)the Fundamental Research Funds for the Central Universities,China(No.3132014328)
文摘The influences of the low-emissive graphite segmented electrode t)laeed near the channel exit on the discharge characteristics of a Hall thruster are studied using the particle- in-cell method. A two-dimensional physical model is established according to the Hall thruster discharge channel configuration. The effects of electrode length on the potential, ion density, electron temperature, ionization rate and discharge current are investigated. It is found that, with tile increasing of the segmented electrode length, the equipotential lines bend towards the channel exit. and approximately parallel to the wall at the channel surface, the radial velocity and radial flow of ions are increased, and the electron temperature is also enhanced. Due to the conductive characteristic of electrodes, the radial electric field and the axial electron conductivity near the wall are enhanced, and the probability of the electron-atom ionization is reduced, which leads to the degradation of the ionization rate in the discharge channel. However, the interaction between electrons and the wall enhances the near wall conductivity, therefore the discharge current grows along with the segmented electrode length, and the performance of the thruster is also affected.
基金supported by the National Natural Science Foundation of China(Grant No.11671149)
文摘This paper introduces a four-dimensional (4D) segmented disc dynamo which possesses coexisting hidden attractors with one stable equilibrium or a line equilibrium when parameters vary. In addition, by choosing an appropriate bifurcation parameter, the paper proves that Hopf bifurcation and pitchfork bifurcation occur in the system. The ultimate bound is also estimated. Some numerical investigations are also exploited to demonstrate and visualize the corresponding theoretical results.
基金the support of National Natural Science Foundation of China (No. 51405315)the Talents Introduction Project of Sichuan University (No. yj2012043)
文摘Direct current plasma torches have been applied to generate unique sources of thermal energy in many industrial applications. Nevertheless, the successful ignition of a plasma torch is the key process to generate the unique source (plasma jet). However, there has been tittle study on the underlying mechanism of this key process. A thorough understanding of the ignition process of a plasma torch will be helpful for optimizing the design of the plasma torch structure and selection of the ignition parameters to prolong the service life of the ignition module. Thus, in this paper, the ignition process of a segmented plasma torch (SPT) is theoretically and experimentally modeled and analyzed. Corresponding electrical models of different stages of the ignition process axe set up and used to derive the electrical parameters, e.g. the variations of the arc voltage and arc current between the cathode and anode. In addition, the experiments with different ignition parameters on a home-made SPT have been conducted. At the same time, the variations of the arc voltage and arc current have been measured, and used to verify the ones derived in theory and to determine the optimal ignition parameters for a particular SPT.
文摘Due to double salient structure,Flux Switching Machines(FSMs)are preferred for brushless AC high speed applications.Permanent Magnet(PM)FSMs(PM-FSMs)are suited applicants where high torque density(Tden)and power density(Pden)are the utmost requisite.However conventional PM-FSMs utilizes excessive rare earth PM volume VPM,higher cogging torque Tcog,high torque ripples(Trip)and comparatively lower(Tden)and Pden due to flux leakage.To overcome the aforesaid demerits,a new high(Tden)Segmented PM Consequent Pole(CP)FSM(SPMCPFSM)with flux bridge and barrier is proposed which successfully reduces VPM by 46.52%and PM cost by 46.48%.Moreover,Multi-Objective Optimization(MOO)examines electromagnetic performance due to variation in geometric parameters for global optimum parameters with key metric such as flux linkage(Φpp),flux harmonics(ΦTHD)average torque(Tavg),Tcog,Trip,Tden,average power(Pavg)and Pden.Analysis reveals that MOO improveΦpp by 22.68%,boost Tavg by 11.41%,enhanced Pavg by 4.55%and increased Tden and Pden by 11.41%.Detailed electromagnetic performance comparison with existing state of the art shows that proposed SPMCPFSM offer Tavg maximum up to 88.8%,truncate Trip up to 24.8%,suppress Tcog up to 22.74%,and results 2.45 times Tden and Pden.
文摘Monodispersed microsized copper oxalate particles were prepared in a segmented continuous flow tube reactor, and the effect of the main parameters such as organic additive agent, initial copper ions concentration, residence time, and segmented media on the final products were investigated experimentally. The obtained copper oxalate microsized particles were disc-like in the presence of citrate ligand,which was the shape inducer for the precipitated copper oxalate. Thermodynamic equilibrium diagrams of the Cu(Ⅱ)-oxalate-H_2O,Cu(Ⅱ)-oxalate-citrate-H_2O, and Cu(Ⅱ)-oxalate-EDTA-H_2O solution systems were drawn to estimate the possible copper species under the experimental conditions and to explain the formation mechanisms of copper oxalate particles in the segmented fluidic reactor. Both theoretical and experimental results indicated that the presence of chelating reagents such as citrate and EDTA had distinct effect on the evolution of particle shape. Air and kerosene were tested as media for the fluidic flow segmentation, and the latter was verified to better promote the growth of copper oxalate particles. The present study provides an easy method to prepare monodispersed copper oxalate microsized particles in a continuous scaling-up way, which can be utilized to prepare the precursor material for conductive inks.
基金supported by National Natural Science Foundation of China (No. 51475369)the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2018JM1001)
文摘In order to research segmented diverters for aircraft lightning protection, a transient 2 D multiphysics model based on magnetohydrodynamics theory is proposed to predict the location of the arc plasma discharge and lightning channel, and to simulate the electrothermal behavior.Based on numerical calculation and preliminary analysis, factors that affect the breakdown voltage of the segmented diverter are discussed. The results show that the voltage increase rate of the voltage source, the width of the air gap between metal segments and the geometry of these segments influence the breakdown voltage of the strip. High-voltage tests of the segmented diverter are performed to reveal air breakdown of the strip and redirect the lightning current.Experimental and numerical results are compared to verify the correctness of the numerical model. The ionization of the air gap between metal segments and the breakdown voltage of the strip calculated by the model are qualitatively consistent with experimental results. The breakdown voltage of the segmented diverter is far lower than the lightning voltage. When a lightning strike occurs, the segmented diverter can be quickly ionized to form a plasma channel which can guide the lightning current well.
基金financially supported by the National Natural Science Foundation of China(Grant No.51239007)
文摘The size and shape of the effective test area are crucial to consider when short-crested waves are created by segmented wavemakers. The range of the effective test area of short-crested waves simulated by two-sided segmented wavemakers is analyzed in this paper. The experimental investigation on the wave field distribution of short-crested waves generated by two-sided segmented wavemakers is conducted by using an array of wave gauges. Wave spectra and directional spreading function are analyzed and the results show that when the main direction is at a certain angle with the normal line of wave generators, the wave field of 3D short-crested waves generated by two-sided segmented wavemakers has good spatial uniformity within the model test area. The effective test area can provide good wave environments for seakeeping model tests of various ocean engineering structures in the deep ocean engineering basin.
文摘A novel class of segmented copolymers, dimethyldiphenylpolysiloxane/poly (oxytetramethylene)-polyurea (PSPEU), was synthesized from α , ω-bis (γ-aminopropyl) dimethyldiphenylpolysiloxane (APMPS), which was prepared by means of basic ring-opening copolymerization of octamethylcyclotetrasiloxane, hexaphenylcyclotrisiloxane and 1, 3-bis (γ-aminopropyl) tetramethyl disiloxane. The relationships between the diphenylsiloxy contents and the properties of APMPS, including refractive index, glass transition temperature, solubility parameter as well as thermal stability, were investigated; meanwhile, the thermal stability, dynamic mechanical properties, mechanical properiesas well as the antithrombogenicity in vitro of the PSPEU were also revealed.
文摘The thermally stimulated shape memory behavior of ethylene oxide-butylene terephthalate (EOBT) segmented copolymers with different soft segment molecular weight and hard segment content was investigated. The deformation recovery ratio R-f of the EOBT samples increases with the soft segment molecular weight and the hard segment weight content, while the average overall deformation recovery speed V-r increases with the hard segment content. The temperature of maximum deformation recovery speed (T-M) is determined by the melting temperature of the soft segment crystals and the stability of the crystallized hard segment domains.
基金supported by the National Natural Science Foundation of China (61005082, 61020106005)Doctoral Fund of Ministry of Education of China (20100001120005)+1 种基金PKU-Biomedical Engineering Join Seed Grant 2012the 985 Project of PekingUniversity (3J0865600)
文摘Passive dynamic walking has been developed as a possible explanation for the efficiency of the human gait. This paper presents a passive dynamic walking model with segmented feet, which makes the bipedal walking gait more close to natural human-like gait. The proposed model extends the simplest walking model with the addition of fiat feet and torsional spring based compliance on ankle joints and toe joints, to achieve stable walking on a slope driven by gravity. The push-off phase includes foot rotations around the toe joint and around the toe tip, which shows a great resemblance to human normal walking. This paper investigates the effects of the segmented foot structure on bipedal walking in simulations. The model achieves satisfactory walking results on even or uneven slopes.
基金Natural Science Foundatoin of Fujian Province of Chinagrant number:2010J01210,2012J01280
文摘In order to explore the correlation between the adjacent segments of a long term EEG, an improved principal component analysis(PCA) method based on mutual information algorithm is proposed. A one-dimension EEG time series is divided equally into many segments, so that each segment can be regarded as an independent variables and multi-segmented EEG can be expressed as a data matrix. Then, we substitute mutual information matrix for covariance matrix in PCA and conduct the relevance analysis of segmented EEG. The experimental results show that the contribution rate of first principal component(FPC) of segmented EEG is more larger than others, which can effectively reflect the difference of epileptic EEG and normal EEG with the change of segment number. In addition, the evolution of FPC conduce to identify the time-segment locations of abnormal dynamic processes of brain activities,these conclusions are helpful for the clinical analysis of EEG.
基金the National Natural Science Foundation of China(grant number 301070603)。
文摘Aiming at the problems of demagnetization effect of electromagnetic buffer(EMB)caused by high velocity under intensive impact load and the difficulty and error of machining composite thin-walled long tube,a segmented EMB is proposed.The inner tube and air-gap are divided into initial segments and the traversing segments.Through theoretical analysis,impact test and simulation,it can be found that the RRF curve has two peaks.Firstly,in order to reduce the resultant resistance force(RRF)peaks,the sensitivity analysis based on optimal Latin hypercube design(OLHD)and polynomial regression was performed.The results show that the smallest contribution ratio to the dynamic response is the seventh and ninth segments of the inner tube,which are less than 1%.Then,fully considering the uncertain factors,important parameters are selected for uncertain optimization after sensitivity analysis.The interval order and interval probability degree methods are used to establish interval uncertain optimization model of the RRF considering robustness.The model was solved using an interval nested optimization method based on radial basis function(RBF)neural network.Finally,the Pareto front is obtained and numerical simulation is performed to verify the optimal value.It indicates that the two kinds of RRF peak is obviously reduced,and the optimization object and strategy are effective.