Combined spatial frequency spectroscopy analysis with visible resonance Raman for optical biopsy of human brain metastases of lung cancers

The purpose of this study is to examine optical spatial frequency spectroscopy analysis(SFSA)combined with visible resonance Raman(VRR)spectroscopic method,for thefirst time,to discriminate human brain metastases of lung cancers adenocarcinoma(ADC)and squamous cell carcinoma(SCC)from normal tissues.A total of 31 label-free micrographic images of three type of brain tissues were obtained using a confocal micro-Raman spectroscopic system.VRR spectra of the corresponding samples were synchronously collected using excitation wavelength of 532 nm from the same sites of the tissues.Using SFSA method,the difference in the randomness of spatial frequency structures in the micrograph images was analyzed using Gaussian functionfitting.The standard deviations,calculated from the spatial frequencies of the micrograph images were then analyzed using support vector machine(SVM)classifier.The key VRR biomolecularfingerprints of carotenoids,tryptophan,amide II,lipids and proteins(methylene/methyl groups)were also analyzed using SVM classifier.All three types of brain tissues were identified with high accuracy in the two approaches with high correlation.The results show that SFSA–VRR can potentially be a dual-modal method to provide new criteria for identifying the three types of human brain tissues,which are on-site,real-time and label-free and may improve the accuracy of brain biopsy.

Modal Frequency Prediction of Chladni Patterns Using Machine Learning

The introduction of machine learning (ML) in the research domain is a new era technique. The machine learning algorithm is developed for frequency predication of patterns that are formed on the Chladni plate and focused on the application of machine learning algorithms in image processing. In the Chladni plate, nodes and antinodes are demonstrated at various excited frequencies. Sand on the plate creates specific patterns when it is excited by vibrations from a mechanical oscillator. In the experimental setup, a rectangular aluminum plate of 16 cm x 16 cm and 0.61 mm thickness was placed over the mechanical oscillator, which was driven by a sine wave signal generator. 14 Chladni patterns are obtained on a Chladni plate and validation is done with modal analysis in Ansys. For machine learning, a large number of data sets are required, as captured around 200 photos of each modal frequency and around 3000 photos with a camera of all 14 Chladni patterns for supervised learning. The current model is written in Python language and model has one convolution layer. The main modules used in this are Tensor Flow Keras, NumPy, CV2 and Maxpooling. The fed reference data is taken for 14 frequencies between 330 Hz to 3910 Hz. In the model, all the images are converted to grayscale and canny edge detected. All patterns of frequencies have an almost 80% - 99% correlation with test sample experimental data. This approach is to form a directory of Chladni patterns for future reference purpose in real-life application. A machine learning algorithm can predict the resonant frequency based on the patterns formed on the Chladni plate.

On the Downshift of Wave Frequency for Bragg Resonance

For surface gravity waves propagating over a horizontal bottom that consists of a patch of sinusoidal ripples,strong wave reflection occurs under the Bragg resonance condition.The critical wave frequency,at which the peak reflection coefficient is obtained,has been observed in both physical experiments and direct numerical simulations to be downshifted from the well-known theoretical prediction.It has long been speculated that the downshift may be attributed to higher-order rippled bottom and free-surface boundary effects,but the intrinsic mechanism remains unclear.By a regular perturbation analysis,we derive the theoretical solution of frequency downshift due to third-order nonlinear effects of both bottom and free-surface boundaries.It is found that the bottom nonlinearity plays the dominant role in frequency downshift while the free-surface nonlinearity actually causes frequency upshift.The frequency downshift/upshift has a quadratic dependence in the bottom/free-surface steepness.Polychromatic bottom leads to a larger frequency downshift relative to the monochromatic bottom.In addition,direct numerical simulations based on the high-order spectral method are conducted to validate the present theory.The theoretical solution of frequency downshift compares well with the numerical simulations and available experimental data.

AN IMPEDANCE ANALYSIS FOR CRACK DETECTION IN THE TIMOSHENKO BEAM BASED ON THE ANTI-RESONANCE TECHNIQUE

An alternative technique for crack detection in a Timoshenko beam based on the first anti-resonant frequency is presented in this paper. Unlike the natural frequency, the anti-resonant frequency is a local parameter rather than a global parameter of structures, thus the proposed technique can be used to locate the structural defects. An impedance analysis of a cracked beam stimulated by a harmonic force based on the Timoshenko beam formulation is investigated. In order to characterize the local discontinuity due to cracks, a rotational spring model based on fracture mechanics is proposed to model the crack. Subsequently, the proposed method is verified by a numerical example of a simply-supported beam with a crack. The effect of the crack size on the anti-resonant frequency is investigated. The position of the crack of the simply-supported beam is also determined by the anti-resonance technique. The proposed technique is further applied to the ＂contaminated＂ anti-resonant frequency to detect crack damage, which is obtained by adding 1-3% noise to the calculated data. It is found that the proposed technique is effective and free from the environment noise. Finally, an experimental study is performed, which further verifies the validity of the proposed crack identification technique.

Coupled vibrations and frequency shift of compound system consisting of quartz crystal resonator in thickness-shear motions and micro-beam array immersed in liquid

The dynamic characteristics of a quartz crystal resonator（QCR） in thicknessshear modes（TSM） with the upper surface covered by an array of micro-beams immersed in liquid are studied. The liquid is assumed to be inviscid and incompressible for simplicity. Dynamic equations of the coupled system are established. The added mass effect of liquid on micro-beams is discussed in detail. Characteristics of frequency shift are clarified for different liquid depths. Modal analysis shows that a drag effect of liquid has resulted in the change of phase of interaction（surface shear force）, thus changing the system resonant frequency. The obtained results are useful in resonator design and applications.

Analytical Solution of Vibration Analysis on Fixed-Free Single-Walled Carbon Nanotube-Based Mass Sensor

Fixed-free single-walled carbon nanotubes (SWCNTs) have attracted a lot of interest in recent years due to their suitability for a wide range of applications, such as field emission and vacuum microelectronic devices, nanosensors, and nanoactuators. Based on a cantilever beam-bending model with a rigid mass at the free end and mode analysis, an analytical solution is developed in the present study to deal with the resonant frequency and mode shapes of a SWCNT- based mass sensor. The resonant frequency shift and mode shape of the fixed-free SWCNTs caused by the addition of a nanoscale particle to the beam tip are examined in order to explore the suitability of SWCNTs as a mass detector device. The simulation results reveal that the volume of the added particle has little effect on the first resonant frequency. In contrast, the second resonant frequency decreases with increasing the volume of the added particle. Furthermore, the resonant frequency shift of the first mode is very obvious for the amount of added mass, and the second resonant frequency decreases rapidly with increasing volume of added particle. Therefore, the first and second resonant frequencies can be used in the measurement of the mass of added particle and its volume, respectively.

Numerical analysis of the molten pool vibration mode for arc-ultrasonic keyhole plasma arc welding

With considering the characteristics of keyhole plasma arc welding （K-PAW）, the resonant frequency between arc and molten pool was solved in the frequency range 15 000 Hz to 72 000 Hz by,finite element modal analysis, ClAM steel fiat butt arc-ultrasonic PAW test was carried out to evaluate the effect arc-ultrasonic frequency on weld structures. Experimental result confirmed that arc-ultrasonic with resonant frequencies treatment are more eJficient than non-resonant frequencies treatment in terms of grain size reduction and structure homogenization. But resonant frequency treatment has little effect on breaking up dendritic structures further and forming equiaxed structures at the lower part the weld.

Power Analysis for Piezoelectric Energy Harvester

Piezoelectric energy harvesting technology is used to design battery less microelectronic devices such as wireless sensor nodes. This paper investigates the necessary conditions to enhance the extracted AC electrical power from exciting vibrations energy using piezoelectric materials. The effect of tip masses and their mounting positions are investigated to enhance the system performance. The optimal resistive load is estimated to maximize the power output. Different capacitive loads are tested to store the output energy. The experimental results validated the theoretical analysis and highlighted remarks in the paper.

结构动力学应用中若干基本概念的研究

结构动力特性被广泛应用于结构振动控制、结构可靠性设计和健康监测,由此涉及到一些动力学基本概念的理解问题尚待深入探讨。采用一简支梁横向振动算例以及分别通过模态位移法和模态加速度法对多自由度系统的响应振幅进行分析计算,探讨结构位移响应与第一阶固有频率的关系、结构各阶位移模态的贡献与模态应变能的关系。基于模态正交性,通过分析多自由度振动系统的位移响应,论述了系统共振的必要条件,即在保证系统振动频率(某阶固有频率)等于激励频率的同时,其位移响应还应呈现出相应模态的形态;实现多自由度系统纯模态共振,可用于精确识别结构的模态参数。

双振头超声固结振动装置设计及实验

为了提高传统超声固结振动装置的输出振幅,达到金属箔材稳定固结的要求,提出了一种单侧双换能器结构的双振头超声固结振动装置。基于谐振系统设计理论完成了尺寸参数设计,对该装置进行模态分析及优化,得到最佳纵振频率为20 247 Hz;基于等效四端网络法对双振头超声固结振动装置进行建模仿真,最大输出振幅能达到36μm;最后,制作实验样机进行振幅测试实验,探究输出振幅与激励电压之间的关系。实验结果表明:输出振幅与激励电压线性相关,该装置的最大输出振幅为34.4μm,与仿真结果的误差率小于5%。验证了结构的合理性,有效提高了装置的输出振幅,促进了超声固结技术在相关领域的应用。

三种石英晶体谐振器频率测试方法对比分析研究

测试石英晶体谐振器频率的传统方法有间接计算法、信号源起振法和网络分析仪法,三种方法各有大的缺陷。根据石英晶体谐振器频率的特点,提出三种新的测试方法:示波器测试法、频率计测试法和频谱仪测试法。这三种方法在基本测试原理、设备配置要求、测试精度和适用环境等方面存在差异。对三种方法的优缺点进行了详细比较,并针对不同应用条件提出了选用建议:如果只单纯测量石英晶体谐振器频率,选用频谱仪测试法;如果需要测量频率的同时还需要知道频率的特性等内容,宜选用频率计测试法;示波器测试法则可用在对石英晶体谐振器频率定性的粗测。此外,还根据各自的优势探讨了仪器协作测试的可能性。

面向电磁水声换能器的高静低动型悬架动力学研究

针对目前线性悬架无法兼顾电磁水声换能器降低谐振频率与承载较大静水压力的难题,设计引入了高静低动型悬架装置,并分析其对换能器声辐射性能的影响。建立了系统动力学模型和动态特性微分方程组,仿真分析了引入非线性刚度前后换能器系统声源级及谐振频率的变化。研究了输入电压对不同系统谐振频率的影响,探究了不同高静低动系统之间的差异。通过锤击试验测得引入高静低动刚度前后悬架的固有频率和加速度导纳。研究结果表明:相较于原线性悬架,高静低动型悬架在承受相同负载时具备更低的固有频率,低频段内具有更高的加速度。在电磁换能器中引入具有高静低动刚度特性的悬架装置可以获得比原系统更低的谐振频率,使低频区域内的声源级得到提升。

Residue Based Open-Loop Modal Analysis Method for Detecting LFMR of PMSG-WFs Penetrated Power Systems

This paper proposes a residue based open-loop modal analysis method to detect low frequency modal resonance(LFMR),including asymmetric low frequency modal attraction(ALFMA)and asymmetric low frequency modal repulsion(ALFMR),of permanent magnetic synchronous generator based wind farms(PMSG-WFs)penetrated power systems.The formation of ALFMA and ALFMR caused by two open-loop low frequency oscillation(LFO)modes moving close and apart is analyzed in detail.Via predicting the trajectories of closed-loop LFO modes based on calculation of residue of open-loop LFO modes,both ALFMA and ALFMR can be detected.The proposed method can select LFO modes which move to the right half complex plane as control parameters vary.Simulation studies are carried out on a three-machine power system and a four-machine 11-bus power system to verify the properties of the proposed method.

基于自适应步长的电力系统谐波谐振快速分析方法

随着电力系统的快速发展,其规模越来越大、节点数量越来越多,频率扫描法和模态分析法作为目前应用最为广泛的两种谐波谐振分析方法,计算效率亟须提升。在传统方法的基础上,文中分别提出基于自适应步长的频率扫描法和基于自适应步长的模态分析法。首先,通过设置相应判据自适应改变扫描步长,使扫描区间能够快速到达谐振频率点附近,大幅减少了计算量;然后,在谐振频率点附近使用二次插值法确定谐振频率,保证了谐振频率计算精度;最后,以IEEE 14节点、IEEE 39节点和IEEE 118节点系统为例进行分析。结果表明,与传统方法相比,所提两种方法在保证谐振频率精度的同时可大幅提高运算速度,验证了所提方法的准确性和高效性。

大型核桃树振动响应特性与落果试验研究

为确定大型核桃树的振动响应特性,探究大型果树机械化摇振采收方法,以南疆大型核桃树为研究对象,利用ANSYS进行有限元分析获取各分枝振动响应特性;应用自主研发摇振收获设备进行扫频试验及落果试验研究,对各主枝进行共振频率检测,通过各分枝上的传感器获取的频率-加速度幅值曲线,确定曲线峰值对应的共振频率;最后,进行摇振落果试验,对比各主枝在不同共振频率下的落果情况。结果表明:大型果树同一主枝及其上侧枝共振频率相同,各主枝共振频率在22~26 Hz之间;同一主枝上的各检测点加速度响应曲线整体呈现先增加后减小的趋势,距离激振位置越远,加速度响应幅值越大;在共振条件下收获,能够获得更高的落果率。为此,提出一种基于大型核桃树主枝共振频率的摇振采收方法,通过获取主枝处的共振频率,以各主枝共振频率进行多次摇振收获作业,实现共振条件下以较低激振能量获得最大振动响应收获,可有效提高收获效率和采净率。研究结果可为大型果树摇振采收方法提供理论基础。

波导谐振环微带阵列多裂纹检测传感器设计

针对飞行器机翼的大面积壁板等金属结构的多形态裂纹分布难以同时检测、检测精度低等问题,设计了一种互补开口波导谐振环微带阵列多裂纹检测传感器。该传感器群阵列中不同尺寸的互补开口波导谐振环微带传感器能够检测直裂纹、针孔、星型3种裂纹的特征参数。实验结果表明,传感器对3种裂纹的参数变化的最大检测灵敏度达到了150 MHz/mm,传感器可检测出的最小直裂纹尺寸为10 mm×1 mm×0.1 mm。该传感器结合了互补开口谐振环辐射能力强、易于表面共形和基片集成波导低损耗、品质因数高、尺寸小的特性,能够实现对金属材料上多形态裂纹的同时检测,具有灵敏度高、检测范围大等优点。

离散方法对覆冰输电线主共振的影响分析

为对比分析覆冰输电线主共振响应的两种不同离散方法,对固有频率和激励频率接近情况下的覆冰输电线做影响分析,本文主要采取位移响应曲线以及幅频响应曲线分析导线的舞动特征及主共振响应.基于哈密顿原理推导输电导线舞动控制偏微分方程,在面内方向施加谐波荷载以定义主共振,基于三阶模态分别采取直接使用Galerkin方法转换偏微分方程为常微分方程;以及先将动张力平均分配在长度范围内离散后再采用Galerkin离散转换成常微分方程的方法;应用多尺度法求解幅频响应曲线,研究第二种离散方法下调谐参数与激励幅值对覆冰输电线主共振响应的影响以及气动荷载对幅频响应曲线的影响.结果表明,不同的离散方法会影响导线的舞动特征与主共振响应,调谐参数与激励幅值也会对导线的主共振造成影响,第二种离散方法的舞动幅值和相位明显大于第一种离散方法.

基于多能量场景谐振域构建的风机控制器参数优化方案

文中提出了一种基于谐振域(RA)的风机控制器参数优化方案,用于刻画在多能量场景下风机与多机系统的模式谐振,并通过优化风机的控制器参数降低潜在的模式谐振风险。首先,建立计及能量场景变化的系统小信号模型。其次,提出确定复平面上可能发生模式谐振区域的RA概念。然后,设计衡量谐振强度以及谐振对模式振荡阻尼影响的谐振强度指标(RSI)。为了避免潜在的模式谐振风险,基于RA和RSI对风机控制器参数进行优化。通过IEEE 39节点模型,验证了所提优化方案可在多能量场景下捕捉模式谐振发生区域,并通过风机控制器参数优化有效避免系统潜在的模式谐振。

芳纶纸蜂窝材料超声波振动切割刀的设计研究

采用传统的铣削方式对芳纶纸蜂窝材料加工时,芳纶纸蜂窝材料会产生蜂窝坍塌、撕裂和纤维拉毛等质量问题,而采用超声波振动切割方式加工蜂窝材料时,可以避免传统铣削加工中出现的问题。文中首先对芳纶纸蜂窝材料超声振动切割刀进行总体结构设计,使用ANSYS有限元软件进行模态分析和谐响应分析,并根据分析结果优化超声波振动切割刀振子结构,确定其谐振频率,并分析其振动特性;然后对超声波振动切割刀样机进行阻抗测试和振幅测试,验证芳纶纸蜂窝材料超声波振动切割刀设计的合理性及可行性;最后观察芳纶纸蜂窝材料切割表面形貌,发现随着振幅的增大,样件切割表面成形更加完好,验证了超声波振动切割加工蜂窝材料能够提高芳纶纸蜂窝材料的加工质量。

折叠特征的低频Helmholtz共振器的数值计算与实验研究

Helmholtz共振器可有效抑制共振频率处噪声。提出一种具备折叠特征的Helmholtz共振器。基于有限元分析,计算共振器在100至800 Hz频带内传输损失曲线,并根据传递函数法进行实验,验证数值计算的准确性。结果表明,在等体积条件下,具备折叠特征Helmholtz共振器有效频率更低,且在共振频率处传递损失达35 dB。使用响应面法对该共振器结构参数进行相关性分析,并获取结构参数对声学特征的影响。研究表明具备折叠特征的Helmholtz共振器能够有效降低共振频率,在低频降噪控制工程领域中具有广阔应用前景。