As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding...As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding scenarios.This paper discusses interferogram modeling and phase distortion cor-rection techniques for spaceborne DASH interferometers.The modeling of phase distortion interferograms with and without Doppler shift for limb observation was conducted,and the effectiveness of the analytical expression was verified through numerical simulation.The simulation results indicate that errors propagate layer by layer while using the onion-peeling inversion algorithm to handle phase-distorted interferograms.In contrast,the phase distortion correction algorithm can achieve effective correction.This phase correction method can be successfully applied to correct phase distortions in the interferograms of the spaceborne DASH interferometer,providing a feasible solution to enhance its measurement accuracy.展开更多
The conversion of CO_(2)to dimethyl carbonate(DMC)offers a promising route for CO_(2)utilization.In this study,four CeO2 catalysts with distinct nanostructures were synthesized via a template-free hydrothermal method ...The conversion of CO_(2)to dimethyl carbonate(DMC)offers a promising route for CO_(2)utilization.In this study,four CeO2 catalysts with distinct nanostructures were synthesized via a template-free hydrothermal method by systematically varying the types and concentrations of precipitants as well as the hydrothermal reaction conditions,and they were employed for DMC synthesis from CO_(2)and methanol.The atomic arrangements of CeO_(2)varied significantly with its morphology,leading to differences in lattice distortion,which directly influenced the concentration of oxygen vacancies.Notably,the CeO_(2)nanospheres,which exhibited the highest lattice distortion and oxygen vacancy concentration,achieved a DMC yield(11.12 mmol/g)48 times greater than that of the nanocubes(0.23 mmol/g).The results indicated that oxygen vacancies played a pivotal role in the catalytic process by facilitating the adsorption and activation of CO_(2)to form bidentate carbonates,as well as activating methanol to generate methoxy species.These processes collectively promoted the formation of the key intermediate(*CH3OCOO).This study proposes a strategy to enhance the oxygen vacancy concentration by increasing lattice distortion,providing valuable insights for designing high-performance CeO_(2)catalysts for DMC synthesis.展开更多
In this research,the effect of the sintering and cooling process on geometry distortion and mechanical properties of PTFE/Al reactive material is investigated.Six particularly selected sintering temperatures,three dif...In this research,the effect of the sintering and cooling process on geometry distortion and mechanical properties of PTFE/Al reactive material is investigated.Six particularly selected sintering temperatures,three different cooling modes(annealing cooling,normalizing cooling and rapid cooling),three different initial cooling temperature s,as well as six different final cooling temperatures were designed to compare the effects of sintering temperature,cooling rate,initial cooling temperature and final cooling temperature on the properties of reactive materials.Geometry distortion was quantitatively analyzed by a statistic on the dimensional changes of the specimens and microscopic morphology.A mechanical response properties transition from brittle to ductile was found and analyzed.By combining the thermodynamic properties of PTFE and unsteady heat conduction theory,mechanisms of cooling induced morphology change,temperature induced distortion and strength decrease were obtained.The results showed that the cooling rate has the most significant effect on the morphology transformation,while initial cooling temperature has more significant effect on the dimensional distortion than final cooling temperature.As to the mechanical properties transition from brittle to plastic,a more prominent effect of initial cooling temperature than cooling rate and final temperature was revealed.展开更多
A new method named rotating extrusion was developed to mitigate residual distortion of thin-plate weldments. The basic principle and characteristic of rotating extrusion as well as an efficient rotating extrusion devi...A new method named rotating extrusion was developed to mitigate residual distortion of thin-plate weldments. The basic principle and characteristic of rotating extrusion as well as an efficient rotating extrusion device were introduced. Systematic trials were conducted to investigate the influence of several technological parameters including the distance between the extrusion tool and welding torch, the pressure acting on weldment, the dimension of the extrusion tool and its rotational speed on distortion control effect. Experimental results show that, as for 2A12T4 aluminum alloy weldment with 2 mm in thickness, 150 mm in width and 350 mm in length, when appropriate technological parameters are adopted, rotating extrusion can reduce its buckling deflection to below 3% of the original value. Implementing rotating extrusion during welding with an extrusion tool more than 100 mm away from the welding torch may achieve better distortion mitigation effect.展开更多
The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method(FEM) based Sysweld software and ...The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method(FEM) based Sysweld software and verified experimentally. The FEM analyses consisted of thermal and mechanical analyses.Thermal analysis was validated with experimental transient temperature measurements. In the mechanical analysis, three different weld sequences and directions were considered to understand the mechanism of out-of-plane distortion in the tube to pipe T-joints. It was learnt that the welding direction plays a major role in minimizing the out-of-plane distortion. Further, during circumferential fillet welding of the tube to pipe component, the out-of-plane distortion generated in the x direction was primarily influenced by heat input due to the start and stop points, whereas the distortion in the z direction was influenced by time lag and welding direction. The FEM predicted distortion was compared with experimental measurements and the mechanism of out-of-plane distortion was confirmed.展开更多
A minimum distortion direction prediction-based novel fast half-pixel motion vector search algorithm is proposed, which can reduce considerably the computation load of half-pixel search. Based on the single valley cha...A minimum distortion direction prediction-based novel fast half-pixel motion vector search algorithm is proposed, which can reduce considerably the computation load of half-pixel search. Based on the single valley characteristic of half-pixel error matching function inside search grid, the minimum distortion direction is predicted with the help of comparative results of sum of absolute difference(SAD) values of four integer-pixel points around integer-pixel motion vector. The experimental results reveal that, to all kinds of video sequences, the proposed algorithm can obtain almost the same video quality as that of the half-pixel full search algorithm with a decrease of computation cost by more than 66%.展开更多
For the ultimate strength model test evaluation of large ship structures, the distortion model with non-uniform ratio between the main size and the plate thickness size is usually adopted. It is the key to carry out s...For the ultimate strength model test evaluation of large ship structures, the distortion model with non-uniform ratio between the main size and the plate thickness size is usually adopted. It is the key to carry out scale model test to establish a distortion model similar to the real ship structure under combined load. A similarity criterion for ship distortion model under the combined action of bending moment and surface pressure was proposed, and the scale effect for the criterion was verified by a se ries of numerical analysis and model tests. The results show that the similarity criterion for ship distor tion model under combined loads has a certain scale effect. For the model tests of ship cabin struc tures, it is suggested that the scale range between the plate thickness scale and the main dimension scale should be controlled within 2:1, which can be used as a reference for distortion model design and ultimate strength test of large-scale ship structures.展开更多
To reduce the negative impact of the power amplifier(PA)nonlinear distortion caused by the orthogonal frequency division multiplexing(OFDM)waveform with high peak-to-average power ratio(PAPR)in integrated radar and co...To reduce the negative impact of the power amplifier(PA)nonlinear distortion caused by the orthogonal frequency division multiplexing(OFDM)waveform with high peak-to-average power ratio(PAPR)in integrated radar and communication(RadCom)systems is studied,the channel estimation in passive sensing scenarios.Adaptive channel estimation methods are proposed based on different pilot patterns,considering nonlinear distortion and channel sparsity.The proposed methods achieve sparse channel results by manipulating the least squares(LS)frequency-domain channel estimation results to preserve the most significant taps.The decision-aided method is used to optimize the sparse channel results to reduce the effect of nonlinear distortion.Numerical results show that the channel estimation performance of the proposed methods is better than that of the conventional methods under different pilot patterns.In addition,the bit error rate performance in communication and passive radar detection performance show that the proposed methods have good comprehensive performance.展开更多
Multi-level inverters(MLIs)have become popular in different applications such as industrial power control systems and distributed generations.There are different forms of MLIs.The cascaded MLIs(CMLIs)have some special...Multi-level inverters(MLIs)have become popular in different applications such as industrial power control systems and distributed generations.There are different forms of MLIs.The cascaded MLIs(CMLIs)have some special advantages among them such as more different output voltage levels using the same number of components and higher power quality.In this paper,a 27-level inverter switching algorithm considering total harmonic distortion(THD)minimization is investigated.Switching angles of the inverter switches are achieved by minimizing a THD-based objective function.In order to minimize the THD-based objective function,the hyper-spherical search(HSS)algorithm,as a novel optimization algorithm,is improved and the results of improved HSS(IHSS)are compared with HSS algorithm and other five evolutionary algorithms to show the advantages of IHSS algorithm.展开更多
The ingots of Pr0.15TbxDy0.85-xFe2 （x=0.10-0.85） series compounds with a single phase were prepared -by a arc melting method. The X-ray diffraction patterns were measured using a Philips X’pert MPD X-ray diffractom...The ingots of Pr0.15TbxDy0.85-xFe2 （x=0.10-0.85） series compounds with a single phase were prepared -by a arc melting method. The X-ray diffraction patterns were measured using a Philips X’pert MPD X-ray diffractometer with a non-ambient sample stage at different temperatures, the magnetostrictive distortion in (Pr0.15TbxDy0.85-xFe2) polycrystals was investigated by X-ray diffraction patterns and the magnetostriction coefficient λ111 was calculated. The results show -when the temperature is raised above the spin reorientation temperature region, a splitting appears in the reflection （440）; the λ111 increase with the increasing of Tb content for (Pr0.15TbxDy0.85-xFe2) polycrystals and the full width at half maximum （FWHM） of the reflection （440） increases gradually with the increasing of Tb content. Moreover, as the FWHM of the reflection （440） decreases gradually with the increasing of temperature, the λ111 decreases slightly with the increasing of temperature at the temperature region of 223-373K for Pr0.15Tb0.3Dy0.55Fe2 alloy.展开更多
Restrained distortional buckling is an important buckling mode of steel-concrete composite box beams(SCCBB)under the hogging moment.Rotational and lateral deformation restraints of the bottom plate by the webs are ess...Restrained distortional buckling is an important buckling mode of steel-concrete composite box beams(SCCBB)under the hogging moment.Rotational and lateral deformation restraints of the bottom plate by the webs are essential factors affecting SCCBB distortional buckling.Based on the stationary potential energy principle,the analytical expressions for the rotational restraint stiffness(RRS)of the web upper edge as well as the RRS and the lateral restraint stiffness(LRS)of the bottom plate were derived.Also,the SCCBB critical moment formula under the hogging moment was derived.Using twenty specimens,the theoretical calculation method is compared with the finite-element method.Results indicate that the theoretical calculation method can effectively and accurately reflect the restraint effect of the studs,top steel flange,and other factors on the bottom plate.Both the RRS and the LRS have a nonlinear coupling relationship with the external loads and the RRS of the web’s upper edge.Under the hogging moment,the RRS of the web upper edge has a certain influence on the SCCBB distortional buckling critical moment.With increasing RRS of the web upper edge,the SCCBB critical moment increases at first and then tends to be stable.展开更多
Background:Segregation distortion(SD)is a common phenomenon among stable or segregating populations,and the principle behind it still puzzles many researchers.The F2:3 progenies developed from the wild cotton species ...Background:Segregation distortion(SD)is a common phenomenon among stable or segregating populations,and the principle behind it still puzzles many researchers.The F2:3 progenies developed from the wild cotton species of the D genomes were used to investigate the possible plant transcription factors within the segregation distortion regions(SDRs).A consensus map was developed between two maps from the four D genomes,map A derived from F2:3 progenies of Gossypium klotzschianum and G.davidsonii while Map B from G.thurberi and G.trilobum F2:3 generations.In each map,188 individual plants were used.Results:The consensus linkage map had 1492 markers across the 13 linkage groups with a map size of 1467.445 cM and an average marker distance of 1.0370 cM.Chromosome D502 had the highest percentage of SD with 58.6%,followed by Chromosome D507 with 47.9%.Six thousand and thirty-eight genes were mined within the SDRs on chromosome D502 and D507 of the consensus map.Within chromosome D502 and D507,2308 and 3730 genes were mined,respectively,and were found to belong to 1117 gourp out of which 622 groups were common across the two chromosomes.Moreover,genes within the top 9 groups related to plant resistance genes(R genes),whereas 188 genes encoding protein kinase domain(PF00069)comprised the largest group.Further analysis of the dominant gene group revealed that 287 miRNAs were found to target various genes,such as the gra-miR398,gramiR5207,miR164a,miR164b,miR164c among others,which have been found to target top-ranked stress-responsive transcription factors such as NAC genes.Moreover,some of the stress-responsive cis-regulatory elements were also detected.Furthermore,RNA profiling of the genes from the dominant family showed that higher numbers of genes were highly upregulated under salt and osmotic stress conditions,and also they were highly expressed at different stages of fiber development.Conclusion:The results indicated the critical role of the SDRs in the evolution of the key regulatory genes in plants.展开更多
The influence of the distorted plane of the active phased array antenna on the electromagnetic performance is of great significance to the research on and development of the high-performance antennas. On the bent and ...The influence of the distorted plane of the active phased array antenna on the electromagnetic performance is of great significance to the research on and development of the high-performance antennas. On the bent and bowl-shape distortion, the model is established of the relationship between the electromagnetic performance and the position error of the radiated elements. The method is presented of analyzing the far-field pattern of the distorted rectangular active phased array antenna. The analysis results of a planar phased array antenna with different distortions grades prove the validity of the model. Therefore, by the method, the antenna designers may set the reasonable requirement on the structural tolerance in manufacturing antenna.展开更多
The high precision assemblies with considerable radial interference should be accompanied by heating and cooling processes.However,the mechanical properties of metals are greatly affected by thermal operations.So,for ...The high precision assemblies with considerable radial interference should be accompanied by heating and cooling processes.However,the mechanical properties of metals are greatly affected by thermal operations.So,for evaluating the stress distribution and distortion of teeth profiles in a gear/shaft assembly,a transient thermal analysis is necessary for finding the change in mechanical properties.The friction on the contact surface is another important parameter in interaction of the gear with the shaft.Evaluating the gear stress and deformation fields for several modes of heat transfer and friction coefficients showed that the maximum radial or tangential stresses on contact surface of the joint may have more than 8%increase by increasing friction coefficient;while the intensity of heat transfer at cooling stage has lower effect on stress distribution.展开更多
Na-ion diffusion kinetics is a key factor that decided the charge/discharge rate of the electrode materials in Na-ion batteries.In this work,two extreme concentrations of NaMnO_(2) and Na_(2/3)Li_(1/6)Mn_(5/6)O_(2) ar...Na-ion diffusion kinetics is a key factor that decided the charge/discharge rate of the electrode materials in Na-ion batteries.In this work,two extreme concentrations of NaMnO_(2) and Na_(2/3)Li_(1/6)Mn_(5/6)O_(2) are considered,namely,the vacancy migration of Na ions in the fully intercalated and the migration of Na ions in the fully de-intercalated.The Na-vacancy and Na^(+)distribution in NaMnO_(2) migrated along oxygen dumbbell hop(ODH)and tetrahedral site hop(TSH),and the migration energy barriers were 0.374 and 0.296 eV,respectively.In NaLi_(1/6)Mn_(5/6)O_(2),the inhomogeneity of Li doping leads to the narrowing of the interlayer spacing by 0.9%and the increase of the energy barrier by 53.8%.On the other hand,due to the alleviation of Jahn-Teller effect of neighboring Mn,the bonding strength of Mn-O was enhanced,so that the energy barrier of path 2-3 in Mn-L1 and Mn-L2 was the lowest,which was 0.234 and 0.424 eV,respectively.In Na_(1/6)Li_(1/6)Mn_(5/6)O_(2),the migration energy barriers of Na-L2 and Na-L3 are 1.233 and 0.779 eV,respectively,because Li+migrates from the transition(TM)layer to the alkali metal(AM)layer with Na^(+)migration,which requires additional energy.展开更多
The paper considers application of artificial neural networks(ANNs)for fast numerical evaluation of a residual impactor velocity for a family of perforated PMMA(Polymethylmethacrylate)targets.The ANN models were train...The paper considers application of artificial neural networks(ANNs)for fast numerical evaluation of a residual impactor velocity for a family of perforated PMMA(Polymethylmethacrylate)targets.The ANN models were trained using sets of numerical results on impact of PMMA plates obtained via dynamic FEM coupled with incubation time fracture criterion.The developed approach makes it possible to evaluate the impact strength of a particular target configuration without complicated FEM calculations which require considerable computational resources.Moreover,it is shown that the ANN models are able to predict results for the configurations which cannot be processed using the developed FEM routine due to numerical instabilities and errors:the trained neural network uses information from successful computations to obtain results for the problematic cases.A simple static problem of a perforated plate deformation is discussed prior to the impact problem and preferable ANN architectures are presented for both problems.Some insight into the perforation pattern optimization using a genetic algorithm coupled with the ANN is also made and optimized perforation patterns which theoretically enhance the target impact strength are constructed.展开更多
This paper developed a statistical damage constitutive model for deep rock by considering the effects of external load and thermal treatment temperature based on the distortion energy.The model parameters were determi...This paper developed a statistical damage constitutive model for deep rock by considering the effects of external load and thermal treatment temperature based on the distortion energy.The model parameters were determined through the extremum features of stress−strain curve.Subsequently,the model predictions were compared with experimental results of marble samples.It is found that when the treatment temperature rises,the coupling damage evolution curve shows an S-shape and the slope of ascending branch gradually decreases during the coupling damage evolution process.At a constant temperature,confining pressure can suppress the expansion of micro-fractures.As the confining pressure increases the rock exhibits ductility characteristics,and the shape of coupling damage curve changes from an S-shape into a quasi-parabolic shape.This model can well characterize the influence of high temperature on the mechanical properties of deep rock and its brittleness-ductility transition characteristics under confining pressure.Also,it is suitable for sandstone and granite,especially in predicting the pre-peak stage and peak stress of stress−strain curve under the coupling action of confining pressure and high temperature.The relevant results can provide a reference for further research on the constitutive relationship of rock-like materials and their engineering applications.展开更多
Based on Hertz theory of elastic contact and the design theory of ball bearings, a new type of rolling coupling was designed. The two halves of the rolling coupling can be moved relatively by a small axial force when ...Based on Hertz theory of elastic contact and the design theory of ball bearings, a new type of rolling coupling was designed. The two halves of the rolling coupling can be moved relatively by a small axial force when a great moment is exerted on it. The rolling coupling was used to connect the principal axis and the decelerator of continuous extrusion machine and it can greatly decrease the harmful axial forces on the continuous machine. The engineering formulas for the contact stress and distance of apporach of the rolling elements were deduced and the method for designing the rolling couplings was proposed. The formulas for the forces exerted on the rolling element were verified by the experiment.展开更多
The JPEG2000 image compression standard is the powerful encoder which can provide phenomenal rate-control performance. The post-compression rate-distortion(PCRD) algorithm in JPEG2000 is not efficient. It requires enc...The JPEG2000 image compression standard is the powerful encoder which can provide phenomenal rate-control performance. The post-compression rate-distortion(PCRD) algorithm in JPEG2000 is not efficient. It requires encoding all coding passes even though a large contribution of them will not be contained in the final code-stream. Tier-1 encoding in the JPEG2000 standard takes a significant amount of memory and coding time. In this work, a low-complexity rate distortion method for JPEG2000 is proposed. It is relied on a reverse order for the resolution levels and the coding passes. The proposed algorithm encodes only the coding passes contained in the final code-stream and it does not need any post compression rate control part. The computational complexity of proposed algorithm is negligible, making it suitable to compression and attaining a significant performance. Simulations results show that the proposed algorithm obtained the PSNR values are comparable with the optimal PCRD.展开更多
文摘As an advanced device for observing atmospheric winds,the spaceborne Doppler Asymmetric Spatial Heterodyne(DASH)interferometer also encounters challenges associated with phase distortion,par-ticularly in limb sounding scenarios.This paper discusses interferogram modeling and phase distortion cor-rection techniques for spaceborne DASH interferometers.The modeling of phase distortion interferograms with and without Doppler shift for limb observation was conducted,and the effectiveness of the analytical expression was verified through numerical simulation.The simulation results indicate that errors propagate layer by layer while using the onion-peeling inversion algorithm to handle phase-distorted interferograms.In contrast,the phase distortion correction algorithm can achieve effective correction.This phase correction method can be successfully applied to correct phase distortions in the interferograms of the spaceborne DASH interferometer,providing a feasible solution to enhance its measurement accuracy.
基金National Natural Science Foundation of China(22008166)Fundamental Research Program of Shanxi Province(202403021211029,201901D211047).
文摘The conversion of CO_(2)to dimethyl carbonate(DMC)offers a promising route for CO_(2)utilization.In this study,four CeO2 catalysts with distinct nanostructures were synthesized via a template-free hydrothermal method by systematically varying the types and concentrations of precipitants as well as the hydrothermal reaction conditions,and they were employed for DMC synthesis from CO_(2)and methanol.The atomic arrangements of CeO_(2)varied significantly with its morphology,leading to differences in lattice distortion,which directly influenced the concentration of oxygen vacancies.Notably,the CeO_(2)nanospheres,which exhibited the highest lattice distortion and oxygen vacancy concentration,achieved a DMC yield(11.12 mmol/g)48 times greater than that of the nanocubes(0.23 mmol/g).The results indicated that oxygen vacancies played a pivotal role in the catalytic process by facilitating the adsorption and activation of CO_(2)to form bidentate carbonates,as well as activating methanol to generate methoxy species.These processes collectively promoted the formation of the key intermediate(*CH3OCOO).This study proposes a strategy to enhance the oxygen vacancy concentration by increasing lattice distortion,providing valuable insights for designing high-performance CeO_(2)catalysts for DMC synthesis.
基金The authors are very grateful for the support received from the National Natural Science Foundation of China(No.11202030)State Key Laboratory of the State Key Laboratory of Explosion Science and Technology(QNKT19-03).
文摘In this research,the effect of the sintering and cooling process on geometry distortion and mechanical properties of PTFE/Al reactive material is investigated.Six particularly selected sintering temperatures,three different cooling modes(annealing cooling,normalizing cooling and rapid cooling),three different initial cooling temperature s,as well as six different final cooling temperatures were designed to compare the effects of sintering temperature,cooling rate,initial cooling temperature and final cooling temperature on the properties of reactive materials.Geometry distortion was quantitatively analyzed by a statistic on the dimensional changes of the specimens and microscopic morphology.A mechanical response properties transition from brittle to ductile was found and analyzed.By combining the thermodynamic properties of PTFE and unsteady heat conduction theory,mechanisms of cooling induced morphology change,temperature induced distortion and strength decrease were obtained.The results showed that the cooling rate has the most significant effect on the morphology transformation,while initial cooling temperature has more significant effect on the dimensional distortion than final cooling temperature.As to the mechanical properties transition from brittle to plastic,a more prominent effect of initial cooling temperature than cooling rate and final temperature was revealed.
基金Project(2007DFR70070) supported by Sino-Russia Intergovernmental Science and Technology Cooperation Program
文摘A new method named rotating extrusion was developed to mitigate residual distortion of thin-plate weldments. The basic principle and characteristic of rotating extrusion as well as an efficient rotating extrusion device were introduced. Systematic trials were conducted to investigate the influence of several technological parameters including the distance between the extrusion tool and welding torch, the pressure acting on weldment, the dimension of the extrusion tool and its rotational speed on distortion control effect. Experimental results show that, as for 2A12T4 aluminum alloy weldment with 2 mm in thickness, 150 mm in width and 350 mm in length, when appropriate technological parameters are adopted, rotating extrusion can reduce its buckling deflection to below 3% of the original value. Implementing rotating extrusion during welding with an extrusion tool more than 100 mm away from the welding torch may achieve better distortion mitigation effect.
文摘The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method(FEM) based Sysweld software and verified experimentally. The FEM analyses consisted of thermal and mechanical analyses.Thermal analysis was validated with experimental transient temperature measurements. In the mechanical analysis, three different weld sequences and directions were considered to understand the mechanism of out-of-plane distortion in the tube to pipe T-joints. It was learnt that the welding direction plays a major role in minimizing the out-of-plane distortion. Further, during circumferential fillet welding of the tube to pipe component, the out-of-plane distortion generated in the x direction was primarily influenced by heat input due to the start and stop points, whereas the distortion in the z direction was influenced by time lag and welding direction. The FEM predicted distortion was compared with experimental measurements and the mechanism of out-of-plane distortion was confirmed.
文摘A minimum distortion direction prediction-based novel fast half-pixel motion vector search algorithm is proposed, which can reduce considerably the computation load of half-pixel search. Based on the single valley characteristic of half-pixel error matching function inside search grid, the minimum distortion direction is predicted with the help of comparative results of sum of absolute difference(SAD) values of four integer-pixel points around integer-pixel motion vector. The experimental results reveal that, to all kinds of video sequences, the proposed algorithm can obtain almost the same video quality as that of the half-pixel full search algorithm with a decrease of computation cost by more than 66%.
文摘For the ultimate strength model test evaluation of large ship structures, the distortion model with non-uniform ratio between the main size and the plate thickness size is usually adopted. It is the key to carry out scale model test to establish a distortion model similar to the real ship structure under combined load. A similarity criterion for ship distortion model under the combined action of bending moment and surface pressure was proposed, and the scale effect for the criterion was verified by a se ries of numerical analysis and model tests. The results show that the similarity criterion for ship distor tion model under combined loads has a certain scale effect. For the model tests of ship cabin struc tures, it is suggested that the scale range between the plate thickness scale and the main dimension scale should be controlled within 2:1, which can be used as a reference for distortion model design and ultimate strength test of large-scale ship structures.
基金supported by the National Natural Science Foundation of China(61931015,62071335,62250024)the Natural Science Foundation of Hubei Province of China(2021CFA002)+1 种基金the Fundamental Research Funds for the Central Universities of China(2042022dx0001)the Science and Technology Program of Shenzhen(JCYJ20170818112037398).
文摘To reduce the negative impact of the power amplifier(PA)nonlinear distortion caused by the orthogonal frequency division multiplexing(OFDM)waveform with high peak-to-average power ratio(PAPR)in integrated radar and communication(RadCom)systems is studied,the channel estimation in passive sensing scenarios.Adaptive channel estimation methods are proposed based on different pilot patterns,considering nonlinear distortion and channel sparsity.The proposed methods achieve sparse channel results by manipulating the least squares(LS)frequency-domain channel estimation results to preserve the most significant taps.The decision-aided method is used to optimize the sparse channel results to reduce the effect of nonlinear distortion.Numerical results show that the channel estimation performance of the proposed methods is better than that of the conventional methods under different pilot patterns.In addition,the bit error rate performance in communication and passive radar detection performance show that the proposed methods have good comprehensive performance.
文摘Multi-level inverters(MLIs)have become popular in different applications such as industrial power control systems and distributed generations.There are different forms of MLIs.The cascaded MLIs(CMLIs)have some special advantages among them such as more different output voltage levels using the same number of components and higher power quality.In this paper,a 27-level inverter switching algorithm considering total harmonic distortion(THD)minimization is investigated.Switching angles of the inverter switches are achieved by minimizing a THD-based objective function.In order to minimize the THD-based objective function,the hyper-spherical search(HSS)algorithm,as a novel optimization algorithm,is improved and the results of improved HSS(IHSS)are compared with HSS algorithm and other five evolutionary algorithms to show the advantages of IHSS algorithm.
基金Project(50271023) supported by the National Natural Science Foundation of China
文摘The ingots of Pr0.15TbxDy0.85-xFe2 （x=0.10-0.85） series compounds with a single phase were prepared -by a arc melting method. The X-ray diffraction patterns were measured using a Philips X’pert MPD X-ray diffractometer with a non-ambient sample stage at different temperatures, the magnetostrictive distortion in (Pr0.15TbxDy0.85-xFe2) polycrystals was investigated by X-ray diffraction patterns and the magnetostriction coefficient λ111 was calculated. The results show -when the temperature is raised above the spin reorientation temperature region, a splitting appears in the reflection （440）; the λ111 increase with the increasing of Tb content for (Pr0.15TbxDy0.85-xFe2) polycrystals and the full width at half maximum （FWHM） of the reflection （440） increases gradually with the increasing of Tb content. Moreover, as the FWHM of the reflection （440） decreases gradually with the increasing of temperature, the λ111 decreases slightly with the increasing of temperature at the temperature region of 223-373K for Pr0.15Tb0.3Dy0.55Fe2 alloy.
基金Projects(U1934207,52078487,51778630) supported by the National Natural Science Foundations of ChinaProject(502501006) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2019RS3009) supported by the Hunan Innovative Provincial Construction Project,China。
文摘Restrained distortional buckling is an important buckling mode of steel-concrete composite box beams(SCCBB)under the hogging moment.Rotational and lateral deformation restraints of the bottom plate by the webs are essential factors affecting SCCBB distortional buckling.Based on the stationary potential energy principle,the analytical expressions for the rotational restraint stiffness(RRS)of the web upper edge as well as the RRS and the lateral restraint stiffness(LRS)of the bottom plate were derived.Also,the SCCBB critical moment formula under the hogging moment was derived.Using twenty specimens,the theoretical calculation method is compared with the finite-element method.Results indicate that the theoretical calculation method can effectively and accurately reflect the restraint effect of the studs,top steel flange,and other factors on the bottom plate.Both the RRS and the LRS have a nonlinear coupling relationship with the external loads and the RRS of the web’s upper edge.Under the hogging moment,the RRS of the web upper edge has a certain influence on the SCCBB distortional buckling critical moment.With increasing RRS of the web upper edge,the SCCBB critical moment increases at first and then tends to be stable.
基金This research program was financially sponsored by the National Key Research and Development Plan(2016YFD0100306)the National Natural Science Foundation of China(31671745,31530053).
文摘Background:Segregation distortion(SD)is a common phenomenon among stable or segregating populations,and the principle behind it still puzzles many researchers.The F2:3 progenies developed from the wild cotton species of the D genomes were used to investigate the possible plant transcription factors within the segregation distortion regions(SDRs).A consensus map was developed between two maps from the four D genomes,map A derived from F2:3 progenies of Gossypium klotzschianum and G.davidsonii while Map B from G.thurberi and G.trilobum F2:3 generations.In each map,188 individual plants were used.Results:The consensus linkage map had 1492 markers across the 13 linkage groups with a map size of 1467.445 cM and an average marker distance of 1.0370 cM.Chromosome D502 had the highest percentage of SD with 58.6%,followed by Chromosome D507 with 47.9%.Six thousand and thirty-eight genes were mined within the SDRs on chromosome D502 and D507 of the consensus map.Within chromosome D502 and D507,2308 and 3730 genes were mined,respectively,and were found to belong to 1117 gourp out of which 622 groups were common across the two chromosomes.Moreover,genes within the top 9 groups related to plant resistance genes(R genes),whereas 188 genes encoding protein kinase domain(PF00069)comprised the largest group.Further analysis of the dominant gene group revealed that 287 miRNAs were found to target various genes,such as the gra-miR398,gramiR5207,miR164a,miR164b,miR164c among others,which have been found to target top-ranked stress-responsive transcription factors such as NAC genes.Moreover,some of the stress-responsive cis-regulatory elements were also detected.Furthermore,RNA profiling of the genes from the dominant family showed that higher numbers of genes were highly upregulated under salt and osmotic stress conditions,and also they were highly expressed at different stages of fiber development.Conclusion:The results indicated the critical role of the SDRs in the evolution of the key regulatory genes in plants.
基金supported partly by the National Natural Science Foundation of China(50805111)the Natural Science Basic Research Plan in Shaanxi Province of China(SJ08E_203.)
文摘The influence of the distorted plane of the active phased array antenna on the electromagnetic performance is of great significance to the research on and development of the high-performance antennas. On the bent and bowl-shape distortion, the model is established of the relationship between the electromagnetic performance and the position error of the radiated elements. The method is presented of analyzing the far-field pattern of the distorted rectangular active phased array antenna. The analysis results of a planar phased array antenna with different distortions grades prove the validity of the model. Therefore, by the method, the antenna designers may set the reasonable requirement on the structural tolerance in manufacturing antenna.
文摘The high precision assemblies with considerable radial interference should be accompanied by heating and cooling processes.However,the mechanical properties of metals are greatly affected by thermal operations.So,for evaluating the stress distribution and distortion of teeth profiles in a gear/shaft assembly,a transient thermal analysis is necessary for finding the change in mechanical properties.The friction on the contact surface is another important parameter in interaction of the gear with the shaft.Evaluating the gear stress and deformation fields for several modes of heat transfer and friction coefficients showed that the maximum radial or tangential stresses on contact surface of the joint may have more than 8%increase by increasing friction coefficient;while the intensity of heat transfer at cooling stage has lower effect on stress distribution.
基金Projects(51602352,51974373,51874358,51772333,61533020) supported by the National Natural Science Foundation of ChinaProject(2019JZZY020123) supported by the Major Scientific and Technological Innovation Projects of Shandong Province,China。
文摘Na-ion diffusion kinetics is a key factor that decided the charge/discharge rate of the electrode materials in Na-ion batteries.In this work,two extreme concentrations of NaMnO_(2) and Na_(2/3)Li_(1/6)Mn_(5/6)O_(2) are considered,namely,the vacancy migration of Na ions in the fully intercalated and the migration of Na ions in the fully de-intercalated.The Na-vacancy and Na^(+)distribution in NaMnO_(2) migrated along oxygen dumbbell hop(ODH)and tetrahedral site hop(TSH),and the migration energy barriers were 0.374 and 0.296 eV,respectively.In NaLi_(1/6)Mn_(5/6)O_(2),the inhomogeneity of Li doping leads to the narrowing of the interlayer spacing by 0.9%and the increase of the energy barrier by 53.8%.On the other hand,due to the alleviation of Jahn-Teller effect of neighboring Mn,the bonding strength of Mn-O was enhanced,so that the energy barrier of path 2-3 in Mn-L1 and Mn-L2 was the lowest,which was 0.234 and 0.424 eV,respectively.In Na_(1/6)Li_(1/6)Mn_(5/6)O_(2),the migration energy barriers of Na-L2 and Na-L3 are 1.233 and 0.779 eV,respectively,because Li+migrates from the transition(TM)layer to the alkali metal(AM)layer with Na^(+)migration,which requires additional energy.
基金Russian Science Foundation[grant number 22-71-10019].
文摘The paper considers application of artificial neural networks(ANNs)for fast numerical evaluation of a residual impactor velocity for a family of perforated PMMA(Polymethylmethacrylate)targets.The ANN models were trained using sets of numerical results on impact of PMMA plates obtained via dynamic FEM coupled with incubation time fracture criterion.The developed approach makes it possible to evaluate the impact strength of a particular target configuration without complicated FEM calculations which require considerable computational resources.Moreover,it is shown that the ANN models are able to predict results for the configurations which cannot be processed using the developed FEM routine due to numerical instabilities and errors:the trained neural network uses information from successful computations to obtain results for the problematic cases.A simple static problem of a perforated plate deformation is discussed prior to the impact problem and preferable ANN architectures are presented for both problems.Some insight into the perforation pattern optimization using a genetic algorithm coupled with the ANN is also made and optimized perforation patterns which theoretically enhance the target impact strength are constructed.
基金Project(11272119)supported by the National Natural Science Foundation of China。
文摘This paper developed a statistical damage constitutive model for deep rock by considering the effects of external load and thermal treatment temperature based on the distortion energy.The model parameters were determined through the extremum features of stress−strain curve.Subsequently,the model predictions were compared with experimental results of marble samples.It is found that when the treatment temperature rises,the coupling damage evolution curve shows an S-shape and the slope of ascending branch gradually decreases during the coupling damage evolution process.At a constant temperature,confining pressure can suppress the expansion of micro-fractures.As the confining pressure increases the rock exhibits ductility characteristics,and the shape of coupling damage curve changes from an S-shape into a quasi-parabolic shape.This model can well characterize the influence of high temperature on the mechanical properties of deep rock and its brittleness-ductility transition characteristics under confining pressure.Also,it is suitable for sandstone and granite,especially in predicting the pre-peak stage and peak stress of stress−strain curve under the coupling action of confining pressure and high temperature.The relevant results can provide a reference for further research on the constitutive relationship of rock-like materials and their engineering applications.
文摘Based on Hertz theory of elastic contact and the design theory of ball bearings, a new type of rolling coupling was designed. The two halves of the rolling coupling can be moved relatively by a small axial force when a great moment is exerted on it. The rolling coupling was used to connect the principal axis and the decelerator of continuous extrusion machine and it can greatly decrease the harmful axial forces on the continuous machine. The engineering formulas for the contact stress and distance of apporach of the rolling elements were deduced and the method for designing the rolling couplings was proposed. The formulas for the forces exerted on the rolling element were verified by the experiment.
文摘The JPEG2000 image compression standard is the powerful encoder which can provide phenomenal rate-control performance. The post-compression rate-distortion(PCRD) algorithm in JPEG2000 is not efficient. It requires encoding all coding passes even though a large contribution of them will not be contained in the final code-stream. Tier-1 encoding in the JPEG2000 standard takes a significant amount of memory and coding time. In this work, a low-complexity rate distortion method for JPEG2000 is proposed. It is relied on a reverse order for the resolution levels and the coding passes. The proposed algorithm encodes only the coding passes contained in the final code-stream and it does not need any post compression rate control part. The computational complexity of proposed algorithm is negligible, making it suitable to compression and attaining a significant performance. Simulations results show that the proposed algorithm obtained the PSNR values are comparable with the optimal PCRD.
