Target detection for low angle radar based on multi-frequency order-statistics

For radar targets flying at low altitude, multiple pathways produce fade or enhancement relative to the level that would be expected in a free-space environment. In this paper, a new detec- tion method based on a wide-ranging multi-frequency radar for low angle targets is proposed. Sequential transmitting multiple pulses with different frequencies are first applied to decorrelate the cohe- rence of the direct and reflected echoes. After receiving all echoes, the multi-frequency samples are arranged in a sort descending ac- cording to the amplitude. Some high amplitude echoes in the same range cell are accumulated to improve the signal-to-noise ratio and the optimal number of high amplitude echoes is analyzed and given by experiments. Finally, simulation results are presented to verify the effectiveness of the method.

Bubble acoustical scattering cross section under multi-frequency acoustic excitation

The acoustical scattering cross section is usually employed to evaluate the scattering ability of the bubbles when they are excited by the incident acoustic waves. This parameter is strongly related to many important applications of performance prediction for search sonar or underwater telemetry, acoustical oceanography, acoustic cavitation, volcanology, and medical and industrial ultrasound. In the present paper, both the analytical and numerical analysis results of the acoustical scattering cross section of a single bubble under multi-frequency excitation are obtained. The nonlinear characteristics（e.g.,harmonics, subharmonics, and ultraharmonics） of the scattering cross section curve under multi-frequency excitation are investigated compared with single-frequency excitation. The influence of several paramount parameters（e.g., bubble equilibrium radius, acoustic pressure amplitude, and acoustic frequencies） in the multi-frequency system on the predictions of scattering cross section is discussed. It is shown that the combination resonances become significant in the multi-frequency system when the acoustic power is big enough, and the acoustical scattering cross section is promoted significantly within a much broader range of bubble sizes and acoustic frequencies due to the generation of more resonances.

Delamination Damage Detection in Laminated Composite by LDR-Based Multi-frequency Method

Local defected resonance(LDR)is a recently-developed non-destructive testing method,which identifies damage by detecting the vibrational response of the structural surface under the wideband ultrasonic excitation. The concept of LDR is studied and applied for damage imaging of delamination in composite laminates. Aiming at the problem of poor anti-noise ability and inaccurate damage identification in traditional detection process,an LDR-based multi-frequency method is proposed. Experimental results show that the proposed method can realize the localization and imaging of delamination damage in composite materials.

Test particle simulations of resonant interactions between energetic electrons and discrete, multi-frequency artificial whistler waves in the plasmasphere

Modulated high frequency （HF） heating of the ionosphere provides a feasible means of artificially generating ex- tremely low frequency （ELF）/very low frequency （VLF） whistler waves, which can leak into the inner magnetosphere and contribute to resonant interactions with high energy electrons. Combining the ray tracing method and test particle simulations, we evaluate the effects of energetic electron resonant scattering driven by the discrete, multi-frequency arti- ficially generated ELF/VLF waves. The simulation results indicate a stochastic behavior of electrons and a linear profile of pitch angle and kinetic energy variations averaged over all test electrons. These features are similar to those associated with single-frequency waves. The computed local diffusion coefficients show that, although the momentum diffusion of relativistic electrons due to artificial ELF/VLF whistlers with a nominal amplitude of ~ 1 pT is minor, the pitch angle scattering can be notably efficient at low pitch angles near the loss cone, which supports the feasibility of artificial triggering of multi-frequency ELF/VLF whistler waves for the removal of high energy electrons from the magnetosphere. We also investigate the dependences of diffusion coefficients on the frequency interval （△f） of the discrete, multi-frequency waves. We find that there is a threshold value of Af for which the net diffusion coefficient of multi-frequency whistlers is inversely proportional to △f （proportional to the frequency components Nw） when △f is below the threshold value but it remains unchanged with increasing Af when △f is larger than the threshold value. This is explained as being due to the fact that the resonant scattering effect of broadband waves is the sum of the effects of each frequency in the ＇effective frequency band＇. Our results suggest that the modulation frequency of HF heating of the ionosphere can be appropriately selected with reasonable frequency intervals so that better performance of controlled precipitation of high energy electrons in the plasmasphere by artificial ELF/VLF whistler waves can be achieved.

基于PCNN图像融合的ECT多相流测量系统设计

针对ECT在多相流测量过程中存在的成像质量不高、精度低、稳定性差等问题,提出并实现了基于PCNN图像融合的ECT多相流测量系统。系统采用模块化设计,主要包括阵列电极传感器模块、电容采集电路模块、上位机成像软件模块。文中设计改进的网络模型,将Tikhonov和Landweber算法的成像结果作为输入进行双通道融合成像,改善了传统算法存在的伪影、模糊的现象。实验结果表明:应用尼龙棒模拟气固两相流对系统进行测试,系统对于微小电容的测量具有良好的稳定性和准确性,通过系统的成像结果可以准确地分辨管道内不同介质的位置,其中对于流型的预测成功率为100%,相含率的测量误差在1%以内。

miR-223-3p与ECT2表达在食管鳞状细胞癌组织中的相关性及与其预后的关系

目的探讨miR-223-3p与ECT2表达在食管鳞状细胞癌中的相关性及与其预后的关系。方法纳入85例食管鳞状细胞癌的石蜡包埋食管鳞状细胞癌组织、相应的正常食管黏膜组织。实时荧光定量PCR检测miR-223-3p与ECT2 mRNA水平,Pearson相关系数分析miR-223-3p与ECT2 mRNA表达水平的相关性。Kaplan-Meier生存分析和Cox比例风险模型分析miR-223-3p、ECT2表达对食管鳞状细胞癌预后的影响。结果ECT2高表达食管鳞状细胞癌患者46例,ECT2低表达食管鳞状细胞癌患者39例。ECT2 mRNA表达水平食管鳞状细胞癌组织高于正常食管黏膜组织,miR-223-3p表达水平食管鳞状细胞癌组织低于正常食管黏膜组织。ECT2表达水平与肿瘤大小、分化程度、TNM分期、血管侵犯相关。miR-223-3p表达水平与肿瘤大小、分化程度、TNM分期、血管侵犯相关。此外,食管鳞状细胞癌中miR-223-3p与ECT2 mRNA表达存在相关性(ρ=-0.5223,P<0.0001),miR-223-3p与ECT2蛋白表达存在相关性(χ^(2)=21.56,P<0.0001)。Kaplan-Meier生存分析显示:TNM分期、淋巴结转移、神经侵犯、miR-223-3p表达水平、ECT2表达水平对食管鳞状细胞癌患者的总生存期有影响。Cox比例风险模型发现TNM分期、淋巴结转移、神经侵犯、miR-223-3p表达水平、ECT2表达水平对总生存期有影响。结论miR-223-3p与ECT2的表达水平在食管鳞状细胞癌中存在相关性。TNM分期、淋巴结转移、神经侵犯、miR-223-3p表达水平、ECT2表达水平可作为ESCC的独立预后因素。

Science Letters:Multi-frequency proportional-resonant (MFPR) current controller for PWM VSC under unbalanced supply conditions

This letter presents a multi-frequency proportional-resonant （MFPR） current controller developed for PWM voltage source converter （VSC） under the unbalanced supply voltage conditions. The delta operator is used in place of the shift operator for the implementation of MFPR by using a low-cost fixed-point DSE The experimental results with an alternative control strategy validated the feasibility of the proposed MFPR current controller for the PWM VSC during voltage unbalance.

Research on nonlinear characteristics of strata collapse because of the multi-frequency mining

Based on the complexity of mine stratum and coupling of the multi-frequency for the damage of mine stratum,using the method of on-site inspection and mathematical statistics,the regulation and nonlinear characteristics of strata collapse in mine stratum's multi-frequency mining were put forward and systemically studied.Study result shows that the influence of multi-frequency mining in mine stratum has the feature of multi-frequency incontinuity,multi-characteristic and multi-type nonlinear collapse,strata collapse activa- tion turned worse,presenting an accumulation effect of multi-frequency mining for the strata damage.With the example of multi-frequency mining in the mine,the real characte- ristics of strata collapse by multi-frequency mining and nonlinear characteristics of accu- mulative response damage were analyzed.Research achievements about the surface re- cover and controlling of strata collapse by the multi-frequency mining have instruction meaning.

CHAOS IN THE SOFTENING DUFFING SYSTEM UNDER MULTI-FREQUENCY PERIODIC FORCES

The chaotic dynamics of the softening-spring Duffing system with multi-frequency external periodic forces is studied. It is found that the mechanism for chaos is the transverse heteroclinic tori. The Poincaré map, the stable and the unstable manifolds of the system under two incommensurate periodic forces were set up on a two-dimensional torus. Utilizing a global perturbation technique of Melnikov the criterion for the transverse interaction of the stable and the unstable manifolds was given. The system under more but finite incommensurate periodic forces was also studied. The (Melnikov's) global perturbation technique was therefore generalized to higher dimensional systems. The region in parameter space where chaotic dynamics may occur was given. It was also demonstrated that increasing the number of forcing frequencies will increase the area in parameter space where chaotic behavior can occur.

HARMONIC, SUBHARMONIC, SUPERHARMONIC, SIMULTANEOUS SUB/SUPER HARMONIC AND COMBINATION RESONANCES OF SELF-EXCITED TWO COUPLED SECOND ORDER SYSTEMS TO MULTI-FREQUENCY EXCITATION

Harmonic, subharmonic, superharmonic, simultaneous sub/super harmonic, and combination resonances of the additive type of self-excited two coupled-second order systems to multi-frequency excitation are investigated. The theoretical results are obtained by the multiple-scales method. The steady state amplitudes for each resonance are plotted, showing the influence of the different parameters. Analysis for each figure is given. Approximate solution corresponding to each type of resonance is determined. Stability analyses are carried out for each case.

Positioning Precision Analysis of GNSS Multi-frequency Carrier Phase Combinations

GPS positioning precision is affected by various error sources, and traditional combinations of GPS carrier phase observations have their own limitations such as the wide-lane, the narrow-lane and the ionospheric-free combinations. To obtain the optimal positioning precision, a new linear combination method is addressed through the variance-covariance （VCV） of the GPS multi-frequency carrier phase combination equations, and the impact of the positioning precision is analyzed with the changing of the observation errors deduced by the law of error propagation. For the high precision positioning with only one carrier phase combination, the optimal combination method is deduced and further validated by an example of a baseline resolution with 60 km length. The result indicates that this method is the simplest, and the positioning precision is the best. Therefore, it is useful for long baseline quick positioning for different precision requirements in various distances.

通过卷积神经网络分析ECT成像和临床检验数据评估糖尿病视网膜病变和糖尿病肾病之间的相关性

目的从影像学和临床检验数据综合评估2型糖尿病患者(T2DM)中糖尿病肾病(DN)和糖尿病视网膜病变(DR)的相关性。方法选取2021年3月至2022年12月就诊于资阳市第一人民医院的T2DM患者600例,所有患者均行眼底照相和荧光素眼底血管造影检查,收集患者年龄、性别、T2DM持续时间、心血管疾病、脑血管疾病、高血压、吸烟史、饮酒史、体重指数、收缩压和舒张压等临床数据。测量空腹血糖、甘油三酯、总胆固醇、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇、糖化血红蛋白、24 h尿白蛋白、尿白蛋白/肌酐、血肌酐和血尿素氮水平。采用Logistic回归分析与DR相关的危险因素。根据眼底图片进行DR分期,采用卷积神经网络(CNN)算法作为图像分析方法,通过ECT成像技术和临床检验数据评估DR和DN之间的相关性。结果采用CNN算法进行分析,无明显DR、轻度非增生型DR(NPDR)、中度NPDR、重度NPDR和增生型DR(PDR)组患者的DR和DN病变面积率均高于采用传统算法(TCM)的结果。随着DR的加重,患者血肌酐、血尿素氮、24 h尿白蛋白和尿白蛋白/肌酐均逐渐升高,无明显DR、轻度NPDR、中度NPDR、重度NPDR和PDR组患者的DN发生率分别为1.67%、8.83%、16.16%、22.16%和30.83%。Logistic回归分析结果显示,T2DM持续时间、吸烟史、糖化血红蛋白、总胆固醇、甘油三酯、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇、24 h尿白蛋白、血肌酐、血尿素氮、尿白蛋白/肌酐、肾小球滤过率是DR的独立危险因素。肾动态ECT成像分析结果表明,随着DR的加重,肾血流灌注逐渐减少,从而导致肾过滤功能下降。结论在T2DM患者中,CNN算法早期应用于DR和DN图像的分析,将有助于提高DR和DN病变面积诊断准确性,随着DR病变的加重,DN的严重程度逐渐增加。

DOA estimation based on multi-frequency joint sparse Bayesian learning for passive radar

This paper considers multi-frequency passive radar and develops a multi-frequency joint direction of arrival(DOA)estimation algorithm to improve estimation accuracy and resolution.The developed algorithm exploits the sparsity of targets in the spatial domain.Specifically,we first extract the required frequency channel data and acquire the snapshot data through a series of preprocessing such as clutter suppression,coherent integration,beamforming,and constant false alarm rate(CFAR)detection.Then,based on the framework of sparse Bayesian learning,the target’s DOA is estimated by jointly extracting the multi-frequency data via evidence maximization.Simulation results show that the developed algorithm has better estimation accuracy and resolution than other existing multi-frequency DOA estimation algorithms,especially under the scenarios of low signalto-noise ratio(SNR)and small snapshots.Furthermore,the effectiveness is verified by the field experimental data of a multi-frequency FM-based passive radar.

玉米ECT家族成员的全基因组分析及非生物胁迫下的响应表达

ECT结构域蛋白家族作为一种重要的转录后调控因子,在调控m6A修饰中发挥重要功能,在植物正常生长发育和响应逆境胁迫时的基因表达调控中具有重要作用。为了研究ECT结构域蛋白家族在玉米(Zea mays L.)非生物胁迫下的生长发育与胁迫响应中的功能,本研究采用生物信息学方法鉴定到玉米ECT家族成员22个,并分析其序列和结构特征、染色体分布、启动子顺式作用元件、GO富集、蛋白质互作网络和系统发育进化关系,通过实时荧光定量PCR(qRT-PCR)分析了玉米ZmECTs在冷胁迫以及不同激素处理下的表达模式。结果表明,玉米ECT家族成员分布在10条染色体上,编码的蛋白质所含氨基酸残基数目为119~748 aa,相对分子量(MW)范围为13412.17~81823.70 Da,等电点(pI)范围为5.43~8.82,大部分蛋白定位在细胞核。在ZmECT家族中共鉴定到10个motif。顺式作用元件分析结果表明,ZmECT家族成员启动子包含多个与胁迫、激素和生长发育相关的响应元件。GO富集分析结果显示,ZmECT家族成员可能参与mRNA的剪接和维持RNA稳定性。蛋白质互作网络预测,ZmECT6是该家族蛋白的核心成员。系统进化树显示,ZmECT家族成员分为4组。qRT-PCR结果显示,经不同激素处理后,ZmECT家族成员表现出复杂的响应模式,部分ZmECT家族成员响应冷胁迫。本研究结果为玉米ECT基因后续的生物学功能解析及分子机制研究提供了参考。

On Multi-Frequency Channel Interference Alignment of 3 Channels and 4 Users

This paper explores the multi-frequency independent channel interference alignment(MFC-IA) system of 3 channels and4 users,and single data stream transmit,i.e.(3×3,1)~4 system.We derive the analytic solution for(3×3,1)~4 MFC-IA system.Based on the analytic solution,an optimization problem is proposed aim at the optimal IA solution.Then based on such a math model,we propose a simulated annealing(SA) algorithm to search optimal IA solution.The simulation results show that the simulated annealing IA algorithm has a better sum rate performance than iterative maximize signal to interference plus noise ratio(Max-SINR) algorithm.This result can be extended to single data stream multi-antenna IA system with 3 antennas and4 users.

曲妥珠单抗联合ECT化疗方案对晚期乳腺癌患者疗效、血清CA153、CEA及造血功能影响

目的 探讨曲妥珠单抗联合表柔比星(E)+环磷酰胺(C)+紫杉醇(T)化疗方案对晚期乳腺癌患者疗效、血清癌抗原153(CA153)、癌胚抗原(CEA)及造血功能的影响。方法 选择安徽阜南县人民医院2019年10月至2022年10月收治的60例晚期乳腺癌患者,按照随机数表法分为ECT组30例(接受表柔比星+环磷酰胺、多西他赛治疗)和联合组30例(ECT组基础上使用曲妥珠单抗),比较两组临床疗效、血清CA153、CEA、造血功能、不良反应。结果 联合组有效率高于ECT组(96.67%vs. 80.00%),差异有统计学意义(χ^(2)=4.043,P<0.05)。两组血清CA153、CEA均较治疗前降低,疗程结束时,联合组上述水平低于ECT组,差异有统计学意义(t=14.795、17.472,P<0.05)。两组血小板计数(PLT)、血红蛋白(Hb)、白细胞计数(WBC)均较治疗前降低,疗程结束时,两组上述指标及不良反应比较差异无统计学意义(t=1.052、1.751、1.676,P>0.05)。结论 相较于单一使用ECT化疗方案,ECT化疗方案联合曲妥珠单抗可以提高晚期乳腺癌患者临床疗效,降低血清CA153、CEA水平,且不会对患者造血功能造成影响。

Boosted Electrocatalytic Glucose Oxidation Reaction on Noble-Metal-Free MoO_(3)-Decorated Carbon Nanotubes

Electrocatalytic glucose oxidation reaction(GOR)has attracted much attention owing to its crucial role in biofuel cell fabrication.Herein,we load MoO_(3)nanoparticles on carbon nanotubes(CNTs)and use a discharge process to prepare a noblemetal-free MC-60 catalyst containing MoO_(3),Mo_(2)C,and a Mo_(2)C–MoO_(3)interface.In the GOR,MC-60 shows activity as high as 745μA/(mmol/L cm^(2)),considerably higher than those of the Pt/CNT(270μA/(mmol/L cm^(2)))and Au/CNT catalysts(110μA/(mmol/L cm^(2))).In the GOR,the response minimum on MC-60 is as low as 8μmol/L,with a steady-state response time of only 3 s.Moreover,MC-60 has superior stability and anti-interference ability to impurities in the GOR.The better performance of MC-60 in the GOR is attributed to the abundant Mo sites bonding to C and O atoms at the MoO_(3)–Mo_(2)C interface.These Mo sites create active sites for promoting glucose adsorption and oxidation,enhancing MC-60 performance in the GOR.Thus,these results help to fabricate more effi cient noble-metal-free catalysts for the fabrication of glucose-based biofuel cells.

Vibration energy harvesting for low frequency using auto-tuning parametric rolling pendulum under exogenous multi-frequency excitations

An electromagnetic parametrically excited rolling pendulum energy harvester with self-tuning mechanisms subject to multi-frequency excitation is proposed and investigated in this paper.The system consists of two uncoupled rolling pendulum.The resonance frequency of each the rolling pendulum can be automatically tuned by adjusting its geometric parameters to access parametric resonance.This harvester can be used to harvest the energy at low frequency.A prototype is developed and evaluated.Its mathematical model is derived.A cam with rolling follower mechanism is employed to generate multi-frequency excitation.An experimental study is conducted to validate the proposed concept.The experimental results are confirmed by the numerical results.The harvester is successfully tuned when the angular velocity of the cam is changed from 1.149 to 1.236 Hz.

BIFURCATION IN A NONLINEAR DUFFING SYSTEM WITHMULTI-FREQUENCY EXTERNAL PERIODIC FORCES

By introducing nonlinear frequency, using Floquet theory and referring to the characteristics of the solution when it passes through the transition boundaries, all kinds of bifurcation modes and their transition boundaries of Duffing equation with two periodic excitations as well as the possible ways to chaos are studied in this paper.

Optimization of ultrasonic elastography by coded excitation and transmit-side multi-frequency compounding

To improve the quality of ultrasonic elastography, by taking the advantage of code excitation and frequency compounding, a transmitting-side multi-frequency with coded excitation for elastography （TFCCE） was proposed. TFCCE adopts the chirp signal excitation scheme and strikes a balance in the selection of sub-signal bandwidth, the bandwidth overlap and the number of sub-strain image based on theoretical derivation, so as to further improve the quality of elastic image. Experiments have proved that, compared with the other optimizing methods, the elastographyic signal-to-noise ratio（Re-SN） and contrast-to-noise ratio（Re-CN） are improved significantly with different echo signal-to-noise ratios （ReSN） and attenuation coefficients. When ReSN is 50 dB, compared with short pulse, Rc-SN and Re-CN obtained by TFCCE increase by 53% and 143%, respectively. Moreover, in a deeper investigation （85-95 mm）, the image has lower strain noise and clear details. When the attenuation coefficient is in the range of 0-1 dB/（cm.MHz）, Re-SN and Re-CN obtained by TFCCE can be kept in moderate ranges of 5〈Re-SN〈6.8 and 11.4〈Re-CN〈15.2, respectively. In particular, for higher tissue attenuation, the basic image quality cannot be ensured with short pulse excitation, while mediocre quality strain figure can be obtained by TFCCE. Therefore, the TFCCE technology can effectively improve the elastography quality and can be applied to ultrasonic clinical trials.