Film-stalk spaced dual mulching is a new type of cultivation measure that is increasingly highlighted in semi-arid areas in China.Despite its potential,there is limited understanding of how different mulching material...Film-stalk spaced dual mulching is a new type of cultivation measure that is increasingly highlighted in semi-arid areas in China.Despite its potential,there is limited understanding of how different mulching materials affect both soil quality and crop yield in these areas.To address this gap,we conducted a two-year(2020-2021)field experiment in central China to explore the yield-enhancing mechanisms and assess the impact of various mulching materials on soil and corn yield.The experiment comprised six treatments,i.e.,plastic film-whole stalk spaced mulching in fall(PSF),plastic film-whole stalk spaced mulching in spring(PSS),black and silver plastic film-whole stalk spaced mulching in spring(BPSS),biodegradable film-whole stalk spaced mulching in spring(BSS),liquid film-whole stalk spaced mulching in spring(LSS),and non-mulching cultivation(CK).Results revealed that BPSS demonstrated the most significant yield increase,surpassing CK by a notable 10.0%and other mulching treatments by 2.4%-5.9%.The efficacy of BPSS lied in its provision of favorable hydrothermal conditions for corn cultivation,particularly during hot season.Its cooling effect facilitated the establishment of optimal temperature conditions relative to transparent mulching,leading to higher root growth indices(e.g.,length and surface area),as well as higher leaf photosynthetic rate and dry matter accumulation per plant.Additionally,BPSS maintained higher average soil moisture content within 0-100 cm depth compared with biodegradable mulching and liquid mulching.As a result,BPSS increased activities of urease,catalase,and alkaline phosphatase,as well as the diversity and abundance of soil bacteria and fungi in the rhizosphere zone of corn,facilitating nutrient accessibility by the plant.These findings suggest that selecting appropriate mulching materials is crucial for optimizing corn production in drought-prone areas,highlighting the potential of BPSS cultivation.展开更多
Three different kinds of PELE(the penetrator with lateral efficiency) were launched by ballistic artillery to impact the multi-layer spaced metal target plates.The lmpact velocities of the projectiles were measured by...Three different kinds of PELE(the penetrator with lateral efficiency) were launched by ballistic artillery to impact the multi-layer spaced metal target plates.The lmpact velocities of the projectiles were measured by the velocity measuring system.The damage degree and process of each laye r of target plate impacted by the three kinds of projectiles were analyzed.The experimental results show that all the three kinds of projectiles have the effect of expanding holes on the multi-layer spaced metal target plates.For the normal structure PELE(without layered) with tungsten alloy jacket and the radial layered PELE with tungsten alloy jacket,the diameters of holes on the seco nd layer of plates are 3.36 times and 3.76 times of the diameter of the projectile,re spectively.For radial layered PELE with W/Zr-based amorphous composite jacket,due to the large number of tungsten wires dispersed after the impact,the diameter of the holes on the four-layer spaced plates can reach 2.4 times,3.04 times,5.36 times and 2.68 times of the diameter of the projectile.Besides,the normal structure PELE with tungsten alloy jacket and the radial layered PELE whit tungsten alloy jacket formed a large number of fragments impact marks on the third target plate.Although the number of fragments penetrating the third target plate is not as large as that of the normal structure PELE,the area of dispersion of fragments impact craters on the third target plate is larger by the radial layered PELE.The radial layered PELE with W/Zr-based amorphous composite jacket released a lot of heat energy due to the impact of the matrix material,and formed a large area of ablation marks on the last three target plates.展开更多
With the continuous growth of air traffic flow, some airports in China or other countries begin to construct Closely Spaced Parallel Runways(CSPR) to meet the capacity requirement of civil aviation. In this paper, the...With the continuous growth of air traffic flow, some airports in China or other countries begin to construct Closely Spaced Parallel Runways(CSPR) to meet the capacity requirement of civil aviation. In this paper, the simulation and calculation method of flight trajectory is developed,as well as the collision risk calculation method and wake vortex encounter risk calculation method.New methods for departure and go-around procedures are proposed to achieve approximate segregated parallel operation in an attempt to obtain approximately the same results on closely spaced parallel runways as on widely spaced parallel runways. By comparing with the independent parallel departure and segregated parallel operation in ICAO Doc. 9643, it is found that the lateral separation between aircraft in this proposal is not less than the separations in the other two cases. Based on the simulation calculation of flight trajectories under different conditions, the probabilities of collision conflict and encountering wake vortex are lower than those in current operation plan.The proposed plan has no special requirements in pilot operation, control command procedures,airport facilities, or meteorological observation and prediction, so it is convenient to promote and implement at the airports with closely spaced parallel runways.展开更多
One of the important issues in the system identification and the spectrum analysis is the frequency resolution, i.e., the capability of distinguishing between two or more closely spaced frequency components. In the mo...One of the important issues in the system identification and the spectrum analysis is the frequency resolution, i.e., the capability of distinguishing between two or more closely spaced frequency components. In the modal identification by the empirical mode decomposition （EMD） method, because of the separating capability of the method, it is still a challenge to consistently and reliably identify the parameters of structures of which modes are not well separated. A new method is introduced to generate the intrin- sic mode functions （IMFs） through the filtering algorithm based on the wavelet packet decomposition （GIFWPD）. In this paper, it is demonstrated that the CIFWPD method alone has a good capability of separating close modes, even under the severe condition beyond the critical frequency ratio limit which makes it impossible to separate two closely spaced harmonics by the EMD method. However, the GIFWPD-only based method is impelled to use a very fine sampling frequency with consequent prohibitive computational costs. Therefore, in order to decrease the computational load by reducing the amount of samples and improve the effectiveness of separation by increasing the frequency ratio, the present paper uses a combination of the complex envelope displacement analysis （CEDA） and the GIFWPD method. For the validation, two examples from the previous works are taken to show the results obtained by the GIFWPD-only based method and by combining the CEDA with the GIFWPD method.展开更多
Several fractionally spaced equalizers(FSE) which could be used in 60 GHz systems are presented in this paper. For 60 GHz systems, low-power equalization algorithms are favorable. We focus on FSE in both time domain(T...Several fractionally spaced equalizers(FSE) which could be used in 60 GHz systems are presented in this paper. For 60 GHz systems, low-power equalization algorithms are favorable. We focus on FSE in both time domain(TD) and frequency domain(FD) in order to meet different complexity requirements of 60 GHz systems. Compared with symbol spaced equalizer(SSE), FSE can relax the requirement of sampling synchronization hardware significantly. Extensive simulation results show that our equalization algorithms not only eliminate ISI efficiently, but are also robust to timing synchronization errors.展开更多
When T/2 Fractionally Spaced blind Equalization Algorithm based Constant Modulus Algorithm (T/2-FSE- CMA) is employed for equalizing higher order Quadrature Amplitude Modulation signals (QAM), it has disadvantages of ...When T/2 Fractionally Spaced blind Equalization Algorithm based Constant Modulus Algorithm (T/2-FSE- CMA) is employed for equalizing higher order Quadrature Amplitude Modulation signals (QAM), it has disadvantages of low convergence speed and large Mean Square Error (MSE). For overcoming these disadvantages, a Modified T/2 Fractionally Spaced blind Equalization algorithm based on Coordinate Transformation and CMA (T/2-FSE-MCTCMA) was proposed by analyzing the character of 16QAM signal constellations. In the proposed algorithm, real and imaginary parts of input signal of T/2 fractionally spaced blind equalizer are equalized, respectively, and output signals of equalizer are transformed to the same unit circle by coordinate transformation method, a new error function is defined after making coordinate transformation and used to adjust weight vector of T/2 fractionally spaced blind equalizer. The proposed algorithm can overcome large misjudgments of T/2 fractionally spaced blind equalization algorithm for equalizing multi-modulus higher order QAM. Simulation results with underwater acoustic channel models demonstrate that the proposed T/2-FSE-MCTCMA algorithm outperforms T/2 Fractionally Spaced blind Equalization algorithm bas-ed on Coordinate Transformation and CMA (T/2-FSE-CTCMA) and the T/2-FSE-CMA in convergence rate and MSE.展开更多
A scheduling model of closely spaced parallel runways for arrival aircraft was proposed,with multi-objections of the minimum flight delay cost,the maximum airport capacity,the minimum workload of air traffic controlle...A scheduling model of closely spaced parallel runways for arrival aircraft was proposed,with multi-objections of the minimum flight delay cost,the maximum airport capacity,the minimum workload of air traffic controller and the maximum fairness of airlines′scheduling.The time interval between two runways and changes of aircraft landing order were taken as the constraints.Genetic algorithm was used to solve the model,and the model constrained unit delay cost of the aircraft with multiple flight tasks to reduce its delay influence range.Each objective function value or the fitness of particle unsatisfied the constrain condition would be punished.Finally,one domestic airport hub was introduced to verify the algorithm and the model.The results showed that the genetic algorithm presented strong convergence and timeliness for solving constraint multi-objective aircraft landing problem on closely spaced parallel runways,and the optimization results were better than that of actual scheduling.展开更多
An increasing number of engineering accidents have shown that the failure of a tunnel can propagate to a neighbouring tunnel.However,due to the complex interaction between the failed tunnel structure and the soil medi...An increasing number of engineering accidents have shown that the failure of a tunnel can propagate to a neighbouring tunnel.However,due to the complex interaction between the failed tunnel structure and the soil medium,the mechanism by which the failure is propagated between two closely spaced tunnels remains unclear.In this study,the coupled EulerianLagrangian(CEL)modelling technique was adopted to investigate the influence of a failed tunnel(FT)on an adjacent tunnel,which was termed an“influenced tunnel”(IT).The safety of the IT was analysed in detail under different circumstances,such as different failure positions of the FT,different failure degrees of the FT,and different spatial relationships between the two tunnels.The simulation results indicated that the most adverse case may occur when the two tunnels are arranged as offsets and the IT is the upper tunnel.Under this circumstance,significant shear deformation may occur in IT because IT is located at the shear band of the FT.展开更多
A new quantitative concept is introduced in this paper, which may be used to facilitate the measurement of the controllability of a subspace similar to subspace controllability degree. Then the concrete form of the su...A new quantitative concept is introduced in this paper, which may be used to facilitate the measurement of the controllability of a subspace similar to subspace controllability degree. Then the concrete form of the subspace controllability degree of a flexible structure is derived, and the errors of subspace controllability degree and dynamical response caused by the substitution of a repeated mode subspace for a closely spaced mode subspace are discussed. All the results show that this substitution is rational under some conditions.展开更多
An orthogonal wavelet transform fractionally spaced blind equalization algorithm based on the optimization of genetic algorithm(WTFSE-GA) is proposed in viewof the lowconvergence rate,large steady-state mean square er...An orthogonal wavelet transform fractionally spaced blind equalization algorithm based on the optimization of genetic algorithm(WTFSE-GA) is proposed in viewof the lowconvergence rate,large steady-state mean square error and local convergence of traditional constant modulus blind equalization algorithm(CMA).The proposed algorithm can reduce the signal autocorrelation through the orthogonal wavelet transform of input signal of fractionally spaced blind equalizer,and decrease the possibility of CMA local convergence by using the global random search characteristics of genetic algorithm to optimize the equalizer weight vector.The proposed algorithm has the faster convergence rate and smaller mean square error compared with FSE and WT-FSE.The efficiency of the proposed algorithm is proved by computer simulation of underwater acoustic channels.展开更多
To establish the algorithm of SAT-TMD system with the wavelet transform(WT),the modal mass participation ratio is proposed to distinguish if the high-rising structure has the characteristic of closely distributed freq...To establish the algorithm of SAT-TMD system with the wavelet transform(WT),the modal mass participation ratio is proposed to distinguish if the high-rising structure has the characteristic of closely distributed frequencies.A time varying analytical model of high-rising structure such as TV-tower with the SAT-TMD is developed.The proposed new idea is to use WT to identify the dominant frequency of structural response in a segment time,and track its variation as a function of time to retune the SAT-TMD.The effectiveness of SAT-TMD is investigated and it is more robust to change in building stiffness and damping than that of the TMD with a fixed frequency corresponding to a fixed mode frequency of the building.It is proved that SAT-TMD is particularly effective in reducing the response even when the building stiffness is changed by ±15%;whereas the TMD loses its effectiveness under such building stiffness variations.展开更多
We investigate the effect of decay-induced interference on photon correlation in a nearly equispaced three-level driven ladder atom.It is found that the combination of destructive interference and two-photon resonance...We investigate the effect of decay-induced interference on photon correlation in a nearly equispaced three-level driven ladder atom.It is found that the combination of destructive interference and two-photon resonance are responsible for the occurrence of nonclassical correlations.In addition,the bunching or antibunching behavior of the two emission processes can be controlled by the relative phase of the two applied fields attributed to the phase control spontaneous emission enhancement or cancellation.展开更多
Thin films of Zn1-xCuxSe （x= 0.00, 0.05, 0.10, 0.15, 0.20） were grown on glass substrates by closed space sublimation technique. The deposited films were annealed at 200 ~C and 400 ~C in air for 1 h. The annealed sa...Thin films of Zn1-xCuxSe （x= 0.00, 0.05, 0.10, 0.15, 0.20） were grown on glass substrates by closed space sublimation technique. The deposited films were annealed at 200 ~C and 400 ~C in air for 1 h. The annealed samples have been investigated through Rutherford backscattering spectroscopy （RBS）, X-ray diffraction （XRD）, spectroscopic ellipsometer, spectrophotometer and Raman spectroscopy. Through RBS, the composition of the films was calculated and compared with the initial concentration. Structural characteriza- tion including crystal structure, crystal orientation, lattice parameter, grain size, strain and dislocation density were carried out using XRD data. From XRD spectra it was revealed that the as-deposited and annealed films were polycrystalline in nature with zinc-blende structure. However, the crystallinity and the grain size were improved with the increase of annealing temperature. According to Raman spectroscopy, it was observed that as deposited and annealed samples have the same characteristic vibrational modes of ZnSe at low and high frequency optical phonon modes while another mode was observed for 400 ℃ annealed samples at 745 cm-1. Spectroscopic ellipsometer has been used to found annealing effect on the optical properties of ZnSe. The band gap energy has been determined using transmission spectra. It was found that the band gap energy of the film increased with the increase of annealing temperature.展开更多
Constructing surface-enhanced Raman scattering(SERS)substrates is a recognized and effective approach for amplifying Raman signals.However,the simultaneous acquisition of nanostructured substrates with high enhancemen...Constructing surface-enhanced Raman scattering(SERS)substrates is a recognized and effective approach for amplifying Raman signals.However,the simultaneous acquisition of nanostructured substrates with high enhancement factors and repeatability poses challenges due to cost and technological limitations.Here,we developed nanometer-spaced metal gratings(NSMGs)with high sensitivity and uniformity for SERS applications by combining nanoimprint techniques with a flexible polydimethylsiloxane(PDMS)substrate.The grating spacing of NSMGs could be adjusted by capitalizing on the stretchability of PDMS,resulting in the acquisition of SERS gratings with different nano-sized gaps(minimum~22 nm)under a single imprinting mold with wide spacing.Importantly,the hotspots on the substrate can be flexibly tailored by the spacing adjustment,leading to the further enhancement of SERS signal,maximum up to nine-fold.Besides,the target molecule could be easily squeezed into the metal gaps with a strong localized electromagnetic field through active stretching and releasing of the substrate,which can further amplify the SERS signal.The high sensitivity and versatility of NSMGs were further proved by the label-free detection of rhodamine 6G(R6G)and adenine at nanomolar level.The proposed NSMG substrate is cost-effective and can be mass-produced,which has great potential for SERS applications.展开更多
背景:新型生物材料不仅提供必要的机械支撑,还能促进细胞增殖和分化、诱导骨再生,从而改善治疗效果,为骨再生技术的发展提供了新的视角和方法。目的:通过文献计量学方法可视化分析生物材料在骨再生领域的研究状况及发展前景。方法:在Web...背景:新型生物材料不仅提供必要的机械支撑,还能促进细胞增殖和分化、诱导骨再生,从而改善治疗效果,为骨再生技术的发展提供了新的视角和方法。目的:通过文献计量学方法可视化分析生物材料在骨再生领域的研究状况及发展前景。方法:在Web of Science核心数据库中,精选了数据库建库至2024-09-24关于骨再生和生物材料领域最具影响力的文献500篇,运用VOSviewer和CiteSpace两款工具进行深入的计量学可视化分析,以揭示该领域的研究趋势和核心文献结果与结论:在所选的500篇文献中,中国和美国在发表论文数量和被引用率方面均占据领先地位,而常江是发文最多的作者,发表文章最多的期刊为Acta Biomaterialia。骨再生和材料学是一个跨学科的研究范畴,涵盖了材料科学、生物医学工程、细胞生物学、分子生物学等多个学科领域。骨修复材料的研究正从传统的生物惰性材料向生物活性材料转变,这些材料不仅提供机械支撑,还能促进细胞增殖和分化,诱导骨再生。合成骨修复材料因丰富的来源、可调节的物理化学特性以及较低的免疫排斥和疾病传播风险,正逐渐替代传统材料,成为临床骨移植手术的首选。研究者们正在不断改进这些材料的生物相容性、仿生特性、骨传导性和骨诱导性,使其更接近天然骨,前沿主要集中在生物活性陶瓷、3D打印、水凝胶、壳聚糖、羟基磷灰石等材料。新型材料在骨再生领域中的作用至关重要,随着材料科学技术的不断进步,这些新型材料在骨再生领域的应用前景非常广阔,有望为骨缺损治疗提供更为有效和个性化的治疗方案。展开更多
随着全球供应链的日益复杂化和不确定性增加,提升供应链韧性成为我国面临的重要挑战。本文基于Web of Science数据库和知网数据库,结合可视化分析方法,对2013—2024年国内外供应链韧性领域相关文献进行对比分析,研究结果表明:(1)国内研...随着全球供应链的日益复杂化和不确定性增加,提升供应链韧性成为我国面临的重要挑战。本文基于Web of Science数据库和知网数据库,结合可视化分析方法,对2013—2024年国内外供应链韧性领域相关文献进行对比分析,研究结果表明:(1)国内研究起步晚于国外,且发文量少于国外。国外整体合作密切程度强于国内,国内、国外均未形成核心作者群。(2)国内相关研究主要集中在技术创新对供应链韧性的影响、供应链韧性战略以及供应链韧性评价等方面;国外相关研究主要集中在供应链韧性内涵、供应链韧性作用机制、供应链韧性评估模型等方面。(3)国内研究演进脉络分为两个阶段,国外研究演进脉络分为三个阶段。(4)在研究前沿方面,国内现阶段聚焦数字化方面,反映了产业升级需求;国外现阶段侧重于数字化与地缘政治方面。展开更多
基金financially supported by the Projects of National Key Research and Development Program of China(2021YFD1901101-5)the Special Major Research and Development Project of Shanxi Province(202101140601026-5)the Earmarked Fund for Modern Agro-industry Technology Research System(2023CYJSTX01-11).
文摘Film-stalk spaced dual mulching is a new type of cultivation measure that is increasingly highlighted in semi-arid areas in China.Despite its potential,there is limited understanding of how different mulching materials affect both soil quality and crop yield in these areas.To address this gap,we conducted a two-year(2020-2021)field experiment in central China to explore the yield-enhancing mechanisms and assess the impact of various mulching materials on soil and corn yield.The experiment comprised six treatments,i.e.,plastic film-whole stalk spaced mulching in fall(PSF),plastic film-whole stalk spaced mulching in spring(PSS),black and silver plastic film-whole stalk spaced mulching in spring(BPSS),biodegradable film-whole stalk spaced mulching in spring(BSS),liquid film-whole stalk spaced mulching in spring(LSS),and non-mulching cultivation(CK).Results revealed that BPSS demonstrated the most significant yield increase,surpassing CK by a notable 10.0%and other mulching treatments by 2.4%-5.9%.The efficacy of BPSS lied in its provision of favorable hydrothermal conditions for corn cultivation,particularly during hot season.Its cooling effect facilitated the establishment of optimal temperature conditions relative to transparent mulching,leading to higher root growth indices(e.g.,length and surface area),as well as higher leaf photosynthetic rate and dry matter accumulation per plant.Additionally,BPSS maintained higher average soil moisture content within 0-100 cm depth compared with biodegradable mulching and liquid mulching.As a result,BPSS increased activities of urease,catalase,and alkaline phosphatase,as well as the diversity and abundance of soil bacteria and fungi in the rhizosphere zone of corn,facilitating nutrient accessibility by the plant.These findings suggest that selecting appropriate mulching materials is crucial for optimizing corn production in drought-prone areas,highlighting the potential of BPSS cultivation.
基金supported by National Natural Science Foundation of China(Grant No.11802141)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX18_0465)。
文摘Three different kinds of PELE(the penetrator with lateral efficiency) were launched by ballistic artillery to impact the multi-layer spaced metal target plates.The lmpact velocities of the projectiles were measured by the velocity measuring system.The damage degree and process of each laye r of target plate impacted by the three kinds of projectiles were analyzed.The experimental results show that all the three kinds of projectiles have the effect of expanding holes on the multi-layer spaced metal target plates.For the normal structure PELE(without layered) with tungsten alloy jacket and the radial layered PELE with tungsten alloy jacket,the diameters of holes on the seco nd layer of plates are 3.36 times and 3.76 times of the diameter of the projectile,re spectively.For radial layered PELE with W/Zr-based amorphous composite jacket,due to the large number of tungsten wires dispersed after the impact,the diameter of the holes on the four-layer spaced plates can reach 2.4 times,3.04 times,5.36 times and 2.68 times of the diameter of the projectile.Besides,the normal structure PELE with tungsten alloy jacket and the radial layered PELE whit tungsten alloy jacket formed a large number of fragments impact marks on the third target plate.Although the number of fragments penetrating the third target plate is not as large as that of the normal structure PELE,the area of dispersion of fragments impact craters on the third target plate is larger by the radial layered PELE.The radial layered PELE with W/Zr-based amorphous composite jacket released a lot of heat energy due to the impact of the matrix material,and formed a large area of ablation marks on the last three target plates.
基金funded by the National Natural Science Foundation of China (Nos. U1533116, U1633125)Project Foundation of Civil Aircraft for MIIT of China (No. MJ-2016-Y76)the Fundamental Research Funds for the Central Universities of CAUC of China (No. 3122017067)
文摘With the continuous growth of air traffic flow, some airports in China or other countries begin to construct Closely Spaced Parallel Runways(CSPR) to meet the capacity requirement of civil aviation. In this paper, the simulation and calculation method of flight trajectory is developed,as well as the collision risk calculation method and wake vortex encounter risk calculation method.New methods for departure and go-around procedures are proposed to achieve approximate segregated parallel operation in an attempt to obtain approximately the same results on closely spaced parallel runways as on widely spaced parallel runways. By comparing with the independent parallel departure and segregated parallel operation in ICAO Doc. 9643, it is found that the lateral separation between aircraft in this proposal is not less than the separations in the other two cases. Based on the simulation calculation of flight trajectories under different conditions, the probabilities of collision conflict and encountering wake vortex are lower than those in current operation plan.The proposed plan has no special requirements in pilot operation, control command procedures,airport facilities, or meteorological observation and prediction, so it is convenient to promote and implement at the airports with closely spaced parallel runways.
基金supported by the State Key Program of National Natural Science of China (No. 11232009)the Shanghai Leading Academic Discipline Project (No. S30106)
文摘One of the important issues in the system identification and the spectrum analysis is the frequency resolution, i.e., the capability of distinguishing between two or more closely spaced frequency components. In the modal identification by the empirical mode decomposition （EMD） method, because of the separating capability of the method, it is still a challenge to consistently and reliably identify the parameters of structures of which modes are not well separated. A new method is introduced to generate the intrin- sic mode functions （IMFs） through the filtering algorithm based on the wavelet packet decomposition （GIFWPD）. In this paper, it is demonstrated that the CIFWPD method alone has a good capability of separating close modes, even under the severe condition beyond the critical frequency ratio limit which makes it impossible to separate two closely spaced harmonics by the EMD method. However, the GIFWPD-only based method is impelled to use a very fine sampling frequency with consequent prohibitive computational costs. Therefore, in order to decrease the computational load by reducing the amount of samples and improve the effectiveness of separation by increasing the frequency ratio, the present paper uses a combination of the complex envelope displacement analysis （CEDA） and the GIFWPD method. For the validation, two examples from the previous works are taken to show the results obtained by the GIFWPD-only based method and by combining the CEDA with the GIFWPD method.
基金supported in part by the National High Technology Research and Development Program of China(863 Program)(No.2011AA010201)National Science and Technology Major Project(No.2013ZX03005010)+1 种基金the National Natural Science Foundation of China(NSFC)(No.61371103 and No.60902025)Key Science and Technology Program of Sichuan Province of China(No.2012FZ0119 and No.2012FZ0029)
文摘Several fractionally spaced equalizers(FSE) which could be used in 60 GHz systems are presented in this paper. For 60 GHz systems, low-power equalization algorithms are favorable. We focus on FSE in both time domain(TD) and frequency domain(FD) in order to meet different complexity requirements of 60 GHz systems. Compared with symbol spaced equalizer(SSE), FSE can relax the requirement of sampling synchronization hardware significantly. Extensive simulation results show that our equalization algorithms not only eliminate ISI efficiently, but are also robust to timing synchronization errors.
文摘When T/2 Fractionally Spaced blind Equalization Algorithm based Constant Modulus Algorithm (T/2-FSE- CMA) is employed for equalizing higher order Quadrature Amplitude Modulation signals (QAM), it has disadvantages of low convergence speed and large Mean Square Error (MSE). For overcoming these disadvantages, a Modified T/2 Fractionally Spaced blind Equalization algorithm based on Coordinate Transformation and CMA (T/2-FSE-MCTCMA) was proposed by analyzing the character of 16QAM signal constellations. In the proposed algorithm, real and imaginary parts of input signal of T/2 fractionally spaced blind equalizer are equalized, respectively, and output signals of equalizer are transformed to the same unit circle by coordinate transformation method, a new error function is defined after making coordinate transformation and used to adjust weight vector of T/2 fractionally spaced blind equalizer. The proposed algorithm can overcome large misjudgments of T/2 fractionally spaced blind equalization algorithm for equalizing multi-modulus higher order QAM. Simulation results with underwater acoustic channel models demonstrate that the proposed T/2-FSE-MCTCMA algorithm outperforms T/2 Fractionally Spaced blind Equalization algorithm bas-ed on Coordinate Transformation and CMA (T/2-FSE-CTCMA) and the T/2-FSE-CMA in convergence rate and MSE.
文摘A scheduling model of closely spaced parallel runways for arrival aircraft was proposed,with multi-objections of the minimum flight delay cost,the maximum airport capacity,the minimum workload of air traffic controller and the maximum fairness of airlines′scheduling.The time interval between two runways and changes of aircraft landing order were taken as the constraints.Genetic algorithm was used to solve the model,and the model constrained unit delay cost of the aircraft with multiple flight tasks to reduce its delay influence range.Each objective function value or the fitness of particle unsatisfied the constrain condition would be punished.Finally,one domestic airport hub was introduced to verify the algorithm and the model.The results showed that the genetic algorithm presented strong convergence and timeliness for solving constraint multi-objective aircraft landing problem on closely spaced parallel runways,and the optimization results were better than that of actual scheduling.
基金the National Natural Science Foundation of China(Nos.41630641 and 51808387)。
文摘An increasing number of engineering accidents have shown that the failure of a tunnel can propagate to a neighbouring tunnel.However,due to the complex interaction between the failed tunnel structure and the soil medium,the mechanism by which the failure is propagated between two closely spaced tunnels remains unclear.In this study,the coupled EulerianLagrangian(CEL)modelling technique was adopted to investigate the influence of a failed tunnel(FT)on an adjacent tunnel,which was termed an“influenced tunnel”(IT).The safety of the IT was analysed in detail under different circumstances,such as different failure positions of the FT,different failure degrees of the FT,and different spatial relationships between the two tunnels.The simulation results indicated that the most adverse case may occur when the two tunnels are arranged as offsets and the IT is the upper tunnel.Under this circumstance,significant shear deformation may occur in IT because IT is located at the shear band of the FT.
基金The project supported by the National Natural Science Foundation of Chinathe Doctoral Research Foundation of Chinese Ministry of Education.
文摘A new quantitative concept is introduced in this paper, which may be used to facilitate the measurement of the controllability of a subspace similar to subspace controllability degree. Then the concrete form of the subspace controllability degree of a flexible structure is derived, and the errors of subspace controllability degree and dynamical response caused by the substitution of a repeated mode subspace for a closely spaced mode subspace are discussed. All the results show that this substitution is rational under some conditions.
基金Sponsored by the Nature Science Foundation of Jiangsu(BK2009410)
文摘An orthogonal wavelet transform fractionally spaced blind equalization algorithm based on the optimization of genetic algorithm(WTFSE-GA) is proposed in viewof the lowconvergence rate,large steady-state mean square error and local convergence of traditional constant modulus blind equalization algorithm(CMA).The proposed algorithm can reduce the signal autocorrelation through the orthogonal wavelet transform of input signal of fractionally spaced blind equalizer,and decrease the possibility of CMA local convergence by using the global random search characteristics of genetic algorithm to optimize the equalizer weight vector.The proposed algorithm has the faster convergence rate and smaller mean square error compared with FSE and WT-FSE.The efficiency of the proposed algorithm is proved by computer simulation of underwater acoustic channels.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50478031)China Postdoctoral Science Foundation(Grant No.2006040240)
文摘To establish the algorithm of SAT-TMD system with the wavelet transform(WT),the modal mass participation ratio is proposed to distinguish if the high-rising structure has the characteristic of closely distributed frequencies.A time varying analytical model of high-rising structure such as TV-tower with the SAT-TMD is developed.The proposed new idea is to use WT to identify the dominant frequency of structural response in a segment time,and track its variation as a function of time to retune the SAT-TMD.The effectiveness of SAT-TMD is investigated and it is more robust to change in building stiffness and damping than that of the TMD with a fixed frequency corresponding to a fixed mode frequency of the building.It is proved that SAT-TMD is particularly effective in reducing the response even when the building stiffness is changed by ±15%;whereas the TMD loses its effectiveness under such building stiffness variations.
基金Supported by the National Natural Science Foundation of China under Grant No 11104163the Science Foundation of China Three Gorges University under Grant No KJ2011B019.
文摘We investigate the effect of decay-induced interference on photon correlation in a nearly equispaced three-level driven ladder atom.It is found that the combination of destructive interference and two-photon resonance are responsible for the occurrence of nonclassical correlations.In addition,the bunching or antibunching behavior of the two emission processes can be controlled by the relative phase of the two applied fields attributed to the phase control spontaneous emission enhancement or cancellation.
文摘Thin films of Zn1-xCuxSe （x= 0.00, 0.05, 0.10, 0.15, 0.20） were grown on glass substrates by closed space sublimation technique. The deposited films were annealed at 200 ~C and 400 ~C in air for 1 h. The annealed samples have been investigated through Rutherford backscattering spectroscopy （RBS）, X-ray diffraction （XRD）, spectroscopic ellipsometer, spectrophotometer and Raman spectroscopy. Through RBS, the composition of the films was calculated and compared with the initial concentration. Structural characteriza- tion including crystal structure, crystal orientation, lattice parameter, grain size, strain and dislocation density were carried out using XRD data. From XRD spectra it was revealed that the as-deposited and annealed films were polycrystalline in nature with zinc-blende structure. However, the crystallinity and the grain size were improved with the increase of annealing temperature. According to Raman spectroscopy, it was observed that as deposited and annealed samples have the same characteristic vibrational modes of ZnSe at low and high frequency optical phonon modes while another mode was observed for 400 ℃ annealed samples at 745 cm-1. Spectroscopic ellipsometer has been used to found annealing effect on the optical properties of ZnSe. The band gap energy has been determined using transmission spectra. It was found that the band gap energy of the film increased with the increase of annealing temperature.
基金Guangdong Introducing Innovative and Enterpreneurial Teams of“The Pearl River Talent Recruitment Program”(2019ZT08X340)Guangzhou Basic and Applied Basic Research Foundation(2023A04J2043)+1 种基金Basic and Applied Basic Research Foundation of Guangdong Province(2024A1515011728)National Natural Science Foundation of China(62275054,62175039)。
文摘Constructing surface-enhanced Raman scattering(SERS)substrates is a recognized and effective approach for amplifying Raman signals.However,the simultaneous acquisition of nanostructured substrates with high enhancement factors and repeatability poses challenges due to cost and technological limitations.Here,we developed nanometer-spaced metal gratings(NSMGs)with high sensitivity and uniformity for SERS applications by combining nanoimprint techniques with a flexible polydimethylsiloxane(PDMS)substrate.The grating spacing of NSMGs could be adjusted by capitalizing on the stretchability of PDMS,resulting in the acquisition of SERS gratings with different nano-sized gaps(minimum~22 nm)under a single imprinting mold with wide spacing.Importantly,the hotspots on the substrate can be flexibly tailored by the spacing adjustment,leading to the further enhancement of SERS signal,maximum up to nine-fold.Besides,the target molecule could be easily squeezed into the metal gaps with a strong localized electromagnetic field through active stretching and releasing of the substrate,which can further amplify the SERS signal.The high sensitivity and versatility of NSMGs were further proved by the label-free detection of rhodamine 6G(R6G)and adenine at nanomolar level.The proposed NSMG substrate is cost-effective and can be mass-produced,which has great potential for SERS applications.
文摘背景:新型生物材料不仅提供必要的机械支撑,还能促进细胞增殖和分化、诱导骨再生,从而改善治疗效果,为骨再生技术的发展提供了新的视角和方法。目的:通过文献计量学方法可视化分析生物材料在骨再生领域的研究状况及发展前景。方法:在Web of Science核心数据库中,精选了数据库建库至2024-09-24关于骨再生和生物材料领域最具影响力的文献500篇,运用VOSviewer和CiteSpace两款工具进行深入的计量学可视化分析,以揭示该领域的研究趋势和核心文献结果与结论:在所选的500篇文献中,中国和美国在发表论文数量和被引用率方面均占据领先地位,而常江是发文最多的作者,发表文章最多的期刊为Acta Biomaterialia。骨再生和材料学是一个跨学科的研究范畴,涵盖了材料科学、生物医学工程、细胞生物学、分子生物学等多个学科领域。骨修复材料的研究正从传统的生物惰性材料向生物活性材料转变,这些材料不仅提供机械支撑,还能促进细胞增殖和分化,诱导骨再生。合成骨修复材料因丰富的来源、可调节的物理化学特性以及较低的免疫排斥和疾病传播风险,正逐渐替代传统材料,成为临床骨移植手术的首选。研究者们正在不断改进这些材料的生物相容性、仿生特性、骨传导性和骨诱导性,使其更接近天然骨,前沿主要集中在生物活性陶瓷、3D打印、水凝胶、壳聚糖、羟基磷灰石等材料。新型材料在骨再生领域中的作用至关重要,随着材料科学技术的不断进步,这些新型材料在骨再生领域的应用前景非常广阔,有望为骨缺损治疗提供更为有效和个性化的治疗方案。
文摘随着全球供应链的日益复杂化和不确定性增加,提升供应链韧性成为我国面临的重要挑战。本文基于Web of Science数据库和知网数据库,结合可视化分析方法,对2013—2024年国内外供应链韧性领域相关文献进行对比分析,研究结果表明:(1)国内研究起步晚于国外,且发文量少于国外。国外整体合作密切程度强于国内,国内、国外均未形成核心作者群。(2)国内相关研究主要集中在技术创新对供应链韧性的影响、供应链韧性战略以及供应链韧性评价等方面;国外相关研究主要集中在供应链韧性内涵、供应链韧性作用机制、供应链韧性评估模型等方面。(3)国内研究演进脉络分为两个阶段,国外研究演进脉络分为三个阶段。(4)在研究前沿方面,国内现阶段聚焦数字化方面,反映了产业升级需求;国外现阶段侧重于数字化与地缘政治方面。
