Comparison study of harmonic imaging （HI） and fundamental imaging （FI） in fetal echocardiography

Objectives: To directly compare the quality of harmonic imaging (HI) and fundamental imaging (FI) in fetal echocardiography and to determine any differences in image quality between the two modalities. Methods: Fetal echocardiograms were performed with the use of FI and HI in 58 fetuses, image quality and visualization of left and right atria, left and right ventricles, mitral and tricuspid valves, aortic and pulmonary valves, left and right ventricular outflow tracts were evaluated and compared between FI and HI. Results: Mean HI scores were higher than mean FI scores (2.73±0.43 vs 2.16±0.69, P <0.001)for all the cardiovascular structures evaluated. Compared with FI, HI improved the image quality and visualization of fetal cardiac structures in subjects with both good (2.73±0.43 vs 2.88±0.32, P <0.001) and suboptimal (1.65±0.41 vs 2.58±0.47, P <0.001) echocardiographic windows. The interobserver correlation coefficient for the grading scores was 0.74 ( P <0.001). Conclusions: harmonic imaging enhances and improves the image quality of fetal echocardiography; and has important potential role in cardiac imaging in the fetus.

Evaluation of quantitative contrast harmonic imaging to assess malignancy of liver tumors:A prospective controlled two-center study

AIM: To establish the extent to which contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics facilitates the detection of hepatic tumors. METHODS: One hundred patients with histologically confirmed malignant or benign hepatic tumor (maximum size 5 cm) were analyzed. Contrast-enhanced ultrasound (bolus injection 2.5 mL SonoVue) was carried out with intermittent breath-holding technique using a multifrequency transducer (2.5-4 MHz). Native vascularization was analyzed with power Doppler. The contrast-enhanced dynamic ultrasound investigation was carried out with contrast harmonic imaging in true detection mode during the arterial,portal venous and late phases. Mechanical index was set at 0.15. Perfusion analysis was performed by post-processing of the raw data time intensity curve (TIC) analysis. The cut-off of the gray value differences between tumor and normal liver tissue was established using Receiver Operating Characteristic (ROC) analysis 64-line multi-slice computed tomography served as reference method in all cases. Magnetic resonance tomography was used additionally in 19 cases. RESULTS: One hundred patients with 59 malignant (43 colon,5 breast,2 endocrine metastases,7 hepatocellular carcinomas and 2 kidney cancers) and 41 benign (15 hemangiomas,7 focal nodular hyperplasias,5 complicated cysts,2 abscesses and 12 circumscribed fatty changes) tumors were included. The late venous phase proved to be the most sensitive for classification of the tumor type. Fifty-eight of the 59 malignant tumors were classified as true positive,and one as false negative. This resulted in a sensitivity of 98.3%. Of the 41 benign tumors,37 were classified as true negative and 4 as false negative,which corresponds to a specificity of 90.2%. Altogether,95.0% of the diagnoses were classified as correct on the basis of the histological classification. No investigator-dependency (P = 0.23) was noted. CONCLUSION: The results show the possibility of accurate prediction of malignancy of hepatic tumors with a positive prognostic value of 93.5% using advanced contrast-enhanced ultrasound. Contrast enhancement with SonoVue in combination with quantitative evaluation of contrast-medium dynamics is a valuable tool to discriminate hepatic tumors.

Theory of higher harmonics imaging in tapping-mode atomic force microscopy

The periodic impact force induced by tip-sample contact in a tapping mode atomic force microscope （AFM） gives rise to the non-harmonic response of a micro-cantilever. These non-harmonic signals contain the full characteristics of tip-sample interaction. A complete theoretical model describing the dynamical behaviour of tip-sample system was developed in this paper. An analytic formula was introduced to describe the relationship between time-varying tip-sample impact force and tip motion. The theoretical analysis and numerical results both show that the timevarying tip-sample impact force can be reconstructed by recording tip motion. This allows for the reconstruction of the characteristics of the tip-sample force, like contact time and maximum contact force. It can also explain the ability of AFM higher harmonics imaging in mapping stiffness and surface energy variations.

1.5 Harmonic Imaging Sonography with microbubble contrast agent improves characterization of hepatocellular carcinoma

AIM： TO investigate the usefulness of 1.5 Harmonic Imaging Sonography with the use of the contrast agent Levovist for the diagnosis of hepatocellular carcinoma （HCC） and for the evaluation of therapeutic response. METHODS： Phantom experiments were performed to compare the contrast effects of 2^rd harmonic imaging and 1.5 Harmonic Imaging Sonography. 1.5 Harmonic Imaging Sonography was employed to examine 36 patients with HCC （42 nodules） before and after the treatment and to compare against the findings obtained using other diagnostic imaging modaUties. RESULTS： In 1.5 Harmonic Imaging Sonography, the tumor vessels of HCCs were clearly identified during the early phase, and late-phase images clearly demonstrated the differences in contrast enhancement between the tumor and surrounding hepatic parenchyma. Blood flow within the tumor was detected in 36 nodules （85.7%） during the early phase and in all 42 nodules （100%） during the late phase using 1.5 Harmonic Imaging Sonography, in 38 nodules （90.5%） using contrast-enhanced CT, in 34 nodules （81.0%） using digital subtraction angiography （DSA）, and in 42 nodules （100%） using US CO2angiography. Following transcatheter arterial embolization, 1.5 Harmonic Imaging Sonography detected blood flow and contrast enhancement within the tumors that were judged to contain viable tissue in 20 of 42 nodules （47.6%）. However, 6 of these 20 cases were not judged in contrastenhanced CT. 1.5 Harmonic Imaging Sonography was compared with the US CO2 angiography findings as the gold standard, and the sensitivity and specificity of these images for discerning viable and nonviable HCC after transcatheter arterial embolization were 100% and 100%,respectively. CONCLUSION： 1.5 Harmonic Imaging Sonography permits the vascular structures of HCCs to be identified and blood flow within the tumor to be clearly demonstrated. Furthermore, 1.5 Harmonic Imaging Sonography is potentially useful for evaluating the therapeutic effects of transcatheter arterial embolization on HCC. 2005 The WJG Press and Elsevier Inc. All rights reserved

Lock-in-Amplifier Model for Analyzing the Behavior of Signal Harmonics in Magnetic Particle Imaging

The purpose of this study was to present a lock-in-amplifier model for analyzing the behavior of signal harmonics in magnetic particle imaging (MPI) and some simulation results based on this model. In the lock-in-amplifier model, the signal induced by magnetic nanoparticles (MNPs) in a receiving coil was multiplied with a reference signal, and was then fed through a low-pass filter to extract the DC component of the signal (output signal). The MPI signal was defined as the mean of the absolute value of the output signal. The magnetization and particle size distribution of MNPs were assumed to obey the Langevin theory of paramagnetism and a log-normal distribution, respectively, and the strength of the selection magnetic field (SMF) in MPI was assumed to be given by the product of the gradient strength of the SMF and the distance from the field-free region (x). In addition, Gaussian noise was added to the signal induced by MNPs using normally-distributed random numbers. The relationships between the MPI signal and x were calculated for the odd- and even-numbered harmonics and were investigated for various time constants of the low-pass filter used in the lock-in amplifier and particle sizes and their distributions of MNPs. We found that the behavior of the MPI signal largely depended on the time constant of the low-pass filter and the particle size of MNPs. This lock-in-amplifier model will be useful for better understanding, optimizing, and developing MPI, and for designing MNPs appropriate for MPI.

IMAGING OF EEG BY SPHERICAL HARMONIC ANALYSIS

A new three dimensional imaging method for electroencephalogram(EEG) is suggested. It consists of the solution of an inward spherical harmonic continuation. The principle of the new method is introduced in Section II, then a few numerical simulation tests are shown and the feasibility of the new method is confirmed by the simulation results.

Cascading Enhancement of Reflected Optical Third-Harmonic Imaging in Bio-Tissues

A new nonlinear optical third\|harmonic imaging technology in reflected fashion in bio\|tissues by using cascading effect, a process whereby the second\|order effects combine to contribute to a third\|order nonlinear process, has been analyzed. The performance of the reflected optical third harmonic imaging enhanced by cascading effect in bio\|tissues is analyzed with the semi\|classical theory. The microscopic understanding of the enhancement of cascaded optical third\|harmonic imaging in reflected manner in bio\|tissues has been discussed.Some i deas for further enhancement is given.

IMAGING OF EEG BY SPHERICAL HARMONIC ANALYSIS

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Basic physical, acoustic properties, and in vitro ultrasound imaging enhancement of the lipid-coated microbubbles

Aim To research on a stable microbubble with good acoustic properties and excellent imaging enhancing effect, and to make it to be a promising agent for the enhancement of ultrasound imaging in the ultrasound diagnosis of cardiovascular system diseases. Methods The morphology, size and zeta potential of lipid-coated microbubbles （LCM）, the acoustic properties of backscatter, and the second harmonic scatter of LCM were determined. Furthermore, the relationship between the concentrations and the amplitude values of the second harmonic was investigated by testing the intensities of the second harmonic at different concentrations. The imaging effect of LCM was also studied in vitro. Results The mean diameter of LCM was 3.38 μm with 95% of the bubbles under 5 μm. The scatter signal generated by microbubbles was observed under different concentrations in the bistatic modes while the position of transmitting transducer and receiving transducer was orthogonal. The intensity of the second harmonic scatter fell with the decrease of microbubble concentration. The increase rate of the second harmonic amplitude values generated by the microbubbles versus that by physiological saline was linear with the natural logarithm of bubble concentrations. The LCM could enhance the ultrasound image of thrombus. Conclusion The LCM exhibited good physical state and acoustic properties, which could increase the imaging quality.

Unification and Harmonization in True Color Image City Map

True color image city map is a sort of new-style map which combines the high resolution image and map symbols and shows both advantages in visualization. At the same time, the map unification and harmonization should be taken into account dur-ing the design process, since some visual conflicts appear when map symbols overlaid on the true color image. The objective of this research is to explore the rules in the process of true color image city map design based on chromatic and aesthetic knowledge. At the end, taking the Image Atlas of Guangzhou as an example, image color adjustment, road network presentation, and symbol de-signing issues will be discussed in the application.

Design optimization of 3.9GHz fundamental power coupler for the SHINE project

The third harmonic superconducting cryomodule is being designed for the Shanghai High repetition rate XFEL and Extreme light facility(SHINE)project,which is under construction.In contrast to the European X-ray Free Electron Laser(E-XFEL)project,the 3.9 GHz cryomodules in the SHINE project will operate in the continuous wave regime with higher radio frequency average power for both cavities and couplers.We propose a 3.9 GHz fundamental power coupler with an adjustable antenna length,for satisfying the SHINE project requirements.Here,we describe the 3.9 GHz fundamental power coupler's design considerations and power requirements for various operating modes of the SHINE Linac.We also present the results of the radio frequency simulation and optimization,including the studies on multipacting and thermal analysis of the proposed 3.9 GHz coupler.

Two-Colour Effect on the Ionization and Harmonic Generation of One-Dimensional He^(+)

Using the one-demensional ion mode,We theoretically investigate the dynamics ionization process and the high-order harmonic generation of the He^(+)subject to different kinds of two-colour laser pulse with the same fundamental frequency but various harmonic frequencies.It is found that from the results calculated by numerically solving the time-dependent Schrödinger equation,the two-colour laser pulse with the fundamental frequency and harmonic frequency enables the power spectrum of high-order harmonic generation to increase by a few orders of magnitude and the yield of He^(+)to enhance significantly when the harmonic frequency of laser pulse is close to the energy interval between the ground state and the first excited state of He^(+);even the harmonic field added into the pulse is much weaker than the fundamental one.

基于曲率驱动的p-harmonic模型图像修复算法

在p-harmonic模型的基础上,引入曲率诱导项,提出一种新的图像修复模型,建立了与之对应的扩散方程,利用有限差分法对所建立的扩散方程进行数值求解,给出该修补模型的离散格式和具体的算法步骤,得到修复的图像。实验结果表明:该算法能提高修复的速度,并且具有较好的修补效果。

Harmonic Minimization in Seven Level Cascaded Multilevel Inverter Using Selective Harmonic Elimination PWM Techniques

This paper concentrates on enhancing the productivity of the multilevel inverter and nature of yield voltage waveform. Seven level lessened switches topology has been actualized with just seven switches. Essential Switching plan and Selective Harmonics Elimination were executed to diminish the Total Harmonics Distortion (THD) esteem. Selective Harmonics Elimination Stepped Waveform (SHESW) strategy is executed to dispense with the lower order harmonics. Fundamental switching plan is utilized to control the switches in the inverter. The proposed topology is reasonable for any number of levels. The harmonic lessening is accomplished by selecting fitting switching angles. It indicates would like to decrease starting expense and unpredictability consequently it is able for modern applications. In this paper, third and fifth level harmonics have been disposed of. Simulation work is done utilizing the MATLAB/Simulink programming results have been displayed to accept the hypothesis.

Transverse Velocity Field Measurements in High-resolution Solar Images Based on Deep Learning

To address the problem of the low accuracy of transverse velocity field measurements for small targets in highresolution solar images,we proposed a novel velocity field measurement method for high-resolution solar images based on PWCNet.This method transforms the transverse velocity field measurements into an optical flow field prediction problem.We evaluated the performance of the proposed method using the Hαand TiO data sets obtained from New Vacuum Solar Telescope observations.The experimental results show that our method effectively predicts the optical flow of small targets in images compared with several typical machine-and deeplearning methods.On the Hαdata set,the proposed method improves the image structure similarity from 0.9182 to0.9587 and reduces the mean of residuals from 24.9931 to 15.2818;on the TiO data set,the proposed method improves the image structure similarity from 0.9289 to 0.9628 and reduces the mean of residuals from 25.9908 to17.0194.The optical flow predicted using the proposed method can provide accurate data for the atmospheric motion information of solar images.The code implementing the proposed method is available on https://github.com/lygmsy123/transverse-velocity-field-measurement.

基于一种新型正弦幅值积分器的谐波检测方法

针对基于瞬时无功理论的ip-iq谐波检测法结构复杂、响应速度慢等问题,提出了一种采用改进正弦幅值积分器结构的谐波电流检测方法。首先,利用二阶广义积分器的输出滤波特性及正弦幅值积分器的极性选择特性,使其相结合构造出了一种滤波性能更强,同时具有频率及极性选择作用的新型积分器。然后,利用该积分器快速准确地提取基波正序分量,并有效应用于谐波检测环节中。当电网电压存在直流偏置问题时,该积分器所构造的锁相环也能准确锁定电网频率及相位信息。最后,理论分析及仿真实验结果表明:该方法无需进行瞬时对称分量分离,就可提取出电网电压及负载电流基波的正负序分量,计算量小,谐波检测更精确。

贴敷宏纤维复合材料片的飞机壁板振动响应预测

传统的有限元模型存在计算成本高、黑箱操作多、缺乏自主知识产权等问题。采用解析法研究基础谐波激励下贴敷宏纤维复合材料(MFC)片的飞机壁板振动响应的预测问题;基于经典层合板理论、机电耦合本构方程和能量法,建立基础谐波激励下MFC-壁板的解析模型;利用速度反馈法和模态叠加原理,实现对该激励条件下结构系统在主动控制前后振动响应的求解;结合文献和组建的振动测试系统获得的实验数据,对该解析模型及其预测结果进行详细验证。结果表明:相较于文献结果,模型等固有频率计算偏差最大不超过2%,模型预测获得的前两阶共振响应的最大误差不超过8.6%,均在误差允许的范围内。

输入电压波动下变模态宽增益谐振变换器研究

针对传统LLC谐振变换器在宽输入下开关损耗过大、增益范围较窄、难以保持输出稳定的问题,研究一种变模态宽增益谐振变换器。该变换器及其控制策略能够依据输入电压的大小,在全桥和半桥两种模态之间自由切换,有效拓宽电压增益范围。通过对变换器谐振腔结构的优化,进一步拓宽增益,减小能量循环、降低开关管损耗,同时能够在电流传输中引入三次谐波,降低损耗。利用基波近似法对电压增益进行推导,绘制增益曲线图,分析谐振参数对电压增益的影响,根据需求设计合适的参数,并运用变频控制,通过调节输入电压,使得变换器运行在不同模态,实现电压平稳输出。搭建一台55~220 V输入、30 V输出的300 W实验样机,实验结果证明了所提变换器控制策略的有效性。

混合级联H桥逆变器的新型SHEPWM功率均衡控制策略

对于直流侧电压比为1∶1∶2的混合级联H桥逆变器,传统的指定谐波消除脉宽调制法(SHEPWM)存在各单元间输出功率不均衡问题,因此,提出一种双层功率均衡调制策略。首先,通过对消谐方程组中的基波幅值方程表达式进行等效拆分,使2个低压H桥单元的输出电压基波幅值之和与高压H桥单元的输出电压基波幅值相等,实现了高低压H桥单元间的功率均衡,即外层功率均衡。其次,利用逻辑运算的方法对低压单元的初始驱动信号进行逻辑重组,实现2个低压单元间的功率均衡,即内层功率均衡;然后使用改进的实数型遗传算法(IRCGA-2)求出消谐方程组的解,消除指定的谐波,得到高质量的输出电压。最后,通过仿真和实验证明了调制策略的正确性与有效性。

新能源场站高比例接入下主流类型工频量距离保护比对

新能源场站高比例接入电网后,已有广泛应用的工频量距离保护判据存在无法准确识别电网故障的问题。文章着重从装置中保护判据与工频量提取算法入手,对比分析新能源场站高比例接入场景下不同类型距离保护算法的适应性。针对保护判据,对比分析了方向圆、多边形、比相式以及工频变化量距离保护各自的适应性,明确了能够较好适用于新能源场站高比例接入的距离保护判据。针对工频量提取算法,探究了不同类型新能源场站所提供短路电流中非周期谐波量的变化特性,进一步推导了受谐波量影响的傅里叶算法对工频量提取产生的计算误差,确定了影响工频量提取精度的关键谐波分量。