X-band inverse class-F GaN internally-matched power amplifier

An X-band inverse class-F power amplifier is realized by a 1-mm Al Ga N/Ga N high electron mobility transistor（HEMT）.The intrinsic and parasitic components inside the transistor,especially output capacitor Cds,influence the harmonic impedance heavily at the X-band,so compensation design is used for meeting the harmonic condition of inverse class-F on the current source plane.Experiment results show that,in the continuous-wave mode,the power amplifier achieves 61.7% power added efficiency（PAE）,which is 16.3% higher than the class-AB power amplifier realized by the same kind of HEMT.To the best of our knowledge,this is the first inverse class-F Ga N internally-matched power amplifier,and the PAE is quite high at the X-band.

Study on the amplitude inversion of internal waves at Wenchang area of the South China Sea

The field experiment is conducted from April 16, 2005 to July 20, 2005 at Wenchang area east of Hainan Island （19~35＇N, l12~E） of China. Internal wave packets are observed frequently with thermistor chains during the experiment. Meanwhile, internal waves are also detected from a synthetic aperture radar （SAR） image on June 19, 2005 and several other moderate-resolution imaging spectroradiometer （MODIS） images near a mooring position. The distance between the positive and negative peaks induced by the internal wave can be obtained from satellite images. Combined with remote sensing images and in situ data, a new method to inverse the amplitude of the internal wave is proposed based on a corrected nonlinear Schr6dinger （NLS） equation. Two relationships are given between the peak-to-peak distance and the characteristic wavelength of the internal wave for different nonlinear and dispersion coefficients. Based on the satellite images, the amplitude inversion of the internal waves are carried out with the NLS equation as well as the KdV equation. The calculated amplitudes of the NLS equation are close to the observation amplitude which promise the NLS equation a reliable method.

FE Simulation for Internal Inversion of Aluminium Alloy Tube

A double-walled tubular component can be formed from a metal tube under axial compression by inversion. Numerical simulation and experimental investigation show that die radius is the predominant factor affecting the deformation process. For the given dimensions of 3A21 aluminium alloy tube, the feasible die radius varies between 2-4mm. The deformation process predicted by the finite element simulation agrees with the experiment results well.

Internal Multiple Prediction Based on Imaging Profile Prediction and Kirchhoff Demigration

This paper introduces an internal multiple prediction method based on imaging profile prediction and Kirchhoff demigration.First,based on an inputted prestack time migration profile,the method predicts the prestack time migration profile that only includes internal multiples by inverse scattering series method.Second,the method uses velocity-weighted Kirchhoff demigration to create shot gathers that contains only internal multiples.Internal multiple prediction based on the prestack time migration profile effectively reduces the computational cost of multiple predictions,and the internal-multiple shot gathers created by Kirchhoff demigration remarkably reduces the complexity of the practical problem.Internal multiple elimination can be conducted through the combined adaptive multiple subtraction based on event tracing.Synthetic and field data tests show that the method effectively predicts internal multiples and possesses considerable potential in field data processing,particularly in areas where internal multiples develop seriously.

Observation of Internal Tides in the Qiongzhou Strait by Coastal Acoustic Tomography

In this study,power spectral density and inverse analyses were performed to obtain the frequency characteristics and spatial distribution of temperature in the Qiongzhou Strait using reciprocal sound transmission data obtained in a coastal acoustic tomo-graphy experiment conducted in 2013.The results reveal three dominant types of internal tides(diurnal,semidiurnal,and terdiurnal).Spectral analysis of the range-average temperature deviation along the northern and southern transmission paths shows that along the northern path,the energy of the diurnal internal tides was significantly larger than that of the semidiurnal tides.The semidiurnal internal tides,in contrast,were more pronounced along the southern path.A terdiurnal spectrum with an energy level equivalent to that of the semidiurnal internal tide was discernable for both the northern and southern paths.These three types of internal tides can also be recognized in the time variation of the zonal-average temperature deviation.The diurnal internal tides were strengthened along the northern coast,implying their westward propagation and the existence of coastally trapped effects.The other two types of internal tides,which have smaller wavelengths than the diurnal internal tides,were less resolved over the entire tomographic domain due to the insufficient resolution of the inversion.The data quality was verified to be satisfactory by error estimation.

Breakthrough and significance of technology on internal multiple recognition and suppression: A case study of Ordovician Dengying Formation in Central Sichuan Basin, SW China

Aimed at the serious mismatch between the synthetic seismogram and the real data of the Sinian Dengying Formation and the Lower Cambrian Qiongzhusi Formation in the GS1 well area, Sichuan Basin, four aspects of internal multiples identification and suppression were studied. Firstly, a forward modeling method of internal multiple based on reflectivity method was developed. Through eight means such as post-stack and pre-stack forward modeling of internal multiple, and combined with VSP data, it was demonstrated that well-seismic mismatching in this area is mainly caused by the internal multiples. Secondly, the simulation results of internal multiple forward modeling using the stripping method combined with the internal multiple periodicity analysis showed that four groups of overburden layers with velocity inversion were the main sources of the internal multiples. Thirdly, by identifying internal multiples accurately and using suppression technology based on pattern recognition, an effective and replicable suppression scheme suitable for these formations was established, overcoming the difficulty of the small speed difference between internal multiple and primary reflection wave which makes the current methods ineffective. Fourthly, an evaluation index of internal multiple intensity was proposed, and the internal multiple intensity distribution diagram of the fourth member of Dengying Formation(Deng-4 Member) in Gaoshiti-Moxi area was compiled. This scheme greatly improved the well-seismic match, and the strata sedimentary features are clearer on the new seismic profiles with higher lateral resolution, with which smaller faults and geological anomalies can be identified and a series of the bead reflections in the Dengying Formation are first discovered. The coincidence rate of reservoir prediction based on seismic waveform classification was increased from 60% to 90%, and that of hydrocarbon detection based on dual phase medium theory was increased from 70% to 100%.

Start-up current adaptive control for sensorless high-speed brushless DC motors based on inverse system method and internal mode controller

The start-up current control of the high-speed brushless DC（HS-BLDC） motor is a challenging research topic. To effectively control the start-up current of the sensorless HS-BLDC motor, an adaptive control method is proposed based on the adaptive neural network（ANN）inverse system and the two degrees of freedom（2-DOF） internal model controller（IMC）. The HS-BLDC motor is identified by the online least squares support vector machine（OLS-SVM） algorithm to regulate the ANN inverse controller parameters in real time. A pseudo linear system is developed by introducing the constructed real-time inverse system into the original HS-BLDC motor system. Based on the characteristics of the pseudo linear system, an extra closed-loop feedback control strategy based on the 2-DOF IMC is proposed to improve the transient response performance and enhance the stability of the control system. The simulation and experimental results show that the proposed control method is effective and perfect start-up current tracking performance is achieved.

深埋软土盾构输水隧洞管片内力反演分析

依托滇中引水工程盾构隧洞监测试验环,于掘进方向进口和出口埋设两排混凝土应变计,同时埋设钢筋计作为对照组,对试验环的内力分布情况进行了现场试验监测。依据所获取的大量现场监测数据,分析了监测试验环混凝土应变与钢筋应变的误差、反演管片内力及其变化规律和内力安全性。结果表明,钢筋应变大于等于混凝土应变,受盾构机盾尾作用面的影响,进口处的钢筋应变与混凝土应变误差明显小于出口处;拱顶和拱底受较小正弯矩的作用,两侧受负弯矩作用,轴力值表现出持续的增长趋势且F块轴力明显大于其余块管片,F型管片部位整体性较差,是受力薄弱点,应尽量避免将F块布置到拱肩处;内力均在1.3的安全系数包络图内,表明该环结构适用于此处地质条件。

利用舰船内部磁场的反演建模方法

积分方程法被广泛应用于舰船磁场反演建模当中,但模型要求有足够多的测量点用于获取舰船在特定深度的磁场。针对积分方程法利用近场磁场建模时精度较差的问题,提出一种增加约束方程的改进措施,并分别开展了薄钢板模型和三维舰船模型磁场数值仿真。采用有限元方法对舰船内部测量点进行初始化选择,基于舰船内部磁场测量值构建了反演模型,采用奇异值分解法求解磁源参数并预测船外空间磁场,舰船外部空间磁场预测结果的均方根误差小于12%。舰船舱段模型磁场推算实验表明,由舱段内部磁场预测外部磁场的均方根误差约为13%,证明了所提出方法的有效性,可以改善传统反演模型的不稳定和精度不足的问题,研究结果可为舰船闭环消磁的算法设计提供思路。

一种新的内翻管理论模型及其耐撞性研究

圆管圆角模具内翻作为金属薄壁管的一种变形模式有着良好的吸能特性.现有关于内翻模式的理论模型均假设变形区曲率恒定且很少有关于翻转全过程翻转力的研究.通过试验测试和有限元模拟对6063铝管的内翻过程进行了研究,并结合外翻模式变形特点详细探讨了内翻模式的变形特点.根据试验和有限元结果提出了一种新的描述内翻模式的理论模型,该理论模型在同时考虑了变形区曲率变化和管壁增厚的基础上,对内翻全过程的翻转力也进行了预测,进而可以得到内翻模式总吸能和比吸能的理论结果.通过与前人理论结果和试验结果的对比得到,文章理论结果更吻合试验和有限元结果.最后,根据验证后的理论模型对内翻模式的耐撞性进行了分析讨论,结果表明:存在最优模具半径使得内翻稳态力、总吸能和比吸能最小;增大圆管壁厚可显著提高内翻模式吸能特性;增大圆管半径能提高内翻稳态力和总吸能,但会降低比吸能.新的内翻理论模型为描述内翻变形模式和内翻管作为吸能元件提供了理论依据.

基于现场测试的复合地层盾构隧道荷载反演分析

[目的]当隧道穿越横向复合地层时,荷载模式尚不明确,最终内力设计值往往与实际值存在偏差,因此有必要研究上软下硬复合地层中,地铁盾构隧道管片与土体的相互作用关系。[方法]以深圳地铁13号线留仙洞站—百旺港大站盾构穿越混合花岗岩区段为例,分析主体结构的内力情况,根据管片内力稳定后的现场实测值,选取待反演参数,定义优化目标函数。采用QPSO(量子粒子群)算法优化荷载参数,反演分析上软下硬地层中荷载的合理参数取值和具体受荷情况。[结果及结论]相比于TB 10003—2016《铁路隧道设计规范》中的取值,通过QPSO算法反演计算得到的荷载参数更适用于上软下硬地层,所计算出的内力分布形式较为接近实际情况,验证了所提分析方法的可行性与合理性。针对上软下硬的复合地层,隧道上覆荷载可取塌落拱高度计算,下层硬岩段侧压力系数应对地勘值进行适当放大。

西部陆海新通道综合运输效率及资源分配研究

西部陆海新通道是连接中国西部和东南亚国家的贸易走廊,对该地区的交通、贸易和经济都有重要的影响。运用SBM-DDF模型和GML指数对西部陆海新通道沿线省份2017—2021年的综合运输效率进行测算,然后运用基于前沿变化的逆DEA模型对2025年发展规划目标进行合理的资源分配,最后结合综合运输效率和资源分配情况进行相关性分析。结果表明:2017—2021年,宁夏、广东、陕西、海南的综合运输效率较高,而云南、新疆、四川的效率较低;在2025年目标规划中,广东、海南几乎不需要增加投入就可以达到效率前沿,而对于其他省份则需要减小相应的投入,这在云南、广西、四川、重庆等地尤为明显;通过对综合运输效率和发展规划的研究可以看出,综合运输效率较高的省份,更容易达到效率前沿,但综合运输效率较低的省份则需要通过减小相应投入才能达到效率前沿。

大尺寸CH_(3)NH_(3)PbBr_(3)晶体生长和光电性能表征

卤化物钙钛矿材料作为一种新型的半导体材料,具有材料廉价和光电转换性能优异的优点,基于该材料的各类光电器件已经开始逐步应用。虽然多晶薄膜仍然是主要的研究方向,但其具有形态无序、杂质较多的缺点,而单晶具有无晶界、低缺陷的特点,因此基于大尺寸单晶的研究开始被广泛关注。本文设计了一套内外反控温循环过滤生长装置,采用逆温结晶和籽晶相结合的方法制备了直径大于60 mm的CH_(3)NH_(3)PbBr_(3)单晶,对晶体样品进行了物相、微观形貌、光学和电学性能的研究。该晶体属于立方晶系,空间群为Pm3m;紫外-可见吸收光谱显示吸收截止边约为576 nm,荧光发射谱峰值552 nm;摇摆曲线显示晶体(100)晶面半峰全宽为91.42″。切割抛光后的晶片光响应灵敏,开关比为2.4×10^(3)。

波动方程压制多次波的技术方法

多次波问题是海洋地震勘探中最突出的问题之一 ,如何有效地压制多次波是解决问题的关键。多次波数据处理的压制方法和技术分为运动学的滤波方法和动力学的波动方程方法两大类。波动方程方法由于几乎不需要先验信息和具有较好的压制效果 ,已经成为多次波压制方法和技术发展的主要趋势。文章首先对波动方程方法进行了较全面的综述 ;然后 ,对波动方程方法中的反馈迭代反演方法做了深入的讨论 ;最后 ,通过理论模型的正反演计算 ,验证了运用波动方程反馈迭代反演法不需要知道震源函数、地下岩层结构和岩性等先验信息。此方法适用于压制多种类型的多次波 ,具有优异的振幅保真性等独特的优点。

逆散射级数法预测层间多次波的算法改进及其策略

波动方程预测层间多次波有两类算法.一是由Berkhout和Verschuur(1998)提出的基于CFP(共聚焦点)延拓的算法,另一是由Weglein(1997)等人提出的基于逆散射级数法的算法.ISS(逆散射级数)算法具有不依赖速度模型的优点,但是其计算成本很高.本文改进了Weglein提出的1-D预测公式,提高了计算效率.从理论方面。改进算法的计算速度提高了大约12倍.实际结果表明其计算速度更快,提高近80倍左右,主要原因在于后者的空间复杂度小.此外,由于时间-空间域比伪深度-波数域的层间多次波预测有更多的优点,本文推导了1.5-D时间-空间域ISS层间多次波预测算法,该算法有计算速度快、预测噪音小、适应观测系统能力强和不依赖地震子波等优点.在实际应用中,计算成本高是ISS预测层间多次波算法的主要障碍.因此,本文还讨论了预测层间多次波的策略.结合本文提出的改进算法和应用策略,能够在实际地震资料处理中较好地应用ISS预测层间多次波.

波动方程多次波压制技术的进展

多次波问题是海洋地震勘探中最突出的问题之一 ,如何有效地压制多次波是数据处理中的一个关键问题 .多次波压制技术分为两大类 :基于有效波和多次波之间差异的滤波方法和基于波动方程的多次波预测减去法 .针对有代表性的波动方程方法 -基于反馈模型的迭代反演多次波压制技术做了较深入的讨论 .目前在解决多次波问题时 ,基于波动理论的方法应得到重视 .

管材向内翻卷变形的力学分析

采用旋转壳体的薄膜理论,建立管材向内翻卷变形力学模型,对内翻变形的力学特征、变形特征、影响因素进行分析.实现内翻须满足的受力条件为:内翻力应小于传力区产生轴对称失稳变形的临界失稳力及镦粗变形的镦粗力;翻卷圆角半径对内翻力的影响明显,是主要的变形工艺参数,存在最佳翻卷圆角半径,它取决于管坯尺寸与摩擦条件,使内翻变形力最小,内翻变形过程非常稳定;内翻变形区管壁壁厚存在增厚效应,其变形程度越大,管壁增厚量增大,内翻力也增大.

基于逆系统方法的内模控制在吊车消摆运动中的应用

针对非线性、欠驱动的桥式吊车水平运动系统,先运用非线性逆系统方法将其转化为伪线性系统,然后按照线性系统理论设计内模控制器来控制吊车的水平定位.同时设计了一个角度反馈控制器来确保摆角迅速衰减.最后和常规PID、模糊控制做了比较.实验结果表明,本方案能保证定位无静差、摆角迅速衰减,同时具有良好的抗干扰能力和较强的鲁棒性,控制效果优于PID和模糊控制.*

电力装备内部状态反演重构研究框架与应用展望

电力装备内部状态准确评估是数字化电力装备的重要组成部分。针对电力装备内部状态反演重构问题,系统分析了电力装备外部检测信号面临的传播路径多样性、传播过程耦合性和非线性衰减问题,借鉴地球物理勘探和医学影像诊断领域的反演思想,提出电力装备内部状态反演重构的研究思路,并建立了包含感知层、通信层、模型层和应用层四个层次的研究框架。分析了三维空间数据获取与重构技术、多物理场多介质全耦合建模技术、多参数全波形反演技术以及反演重构应用适应性评估技术等关键技术的研究目的和实现方法。提出了变压器、气体绝缘开关设备(gas insulated switchgear,GIS)、电抗器等主要电力装备内部振动、热、应力等状态参量的重构方法,阐述了状态重构条件下的故障诊断与状态推演应用场景。最后分析了电力装备状态反演重构技术面临的挑战与发展趋势,为数字化电力装备的发展提供一种技术支撑。

水泥中Al和Fe的激光诱导击穿光谱测量分析

水泥中铝和铁含量是对水泥进行分类和质量监督的一个重要依据。通过采用激光诱导击穿光谱技术对水泥样品中的Al和Fe含量进行了定量分析。从光谱强度以及特征谱线信噪比出发,确定单脉冲能量为30 m J光谱积分延迟时间为1μs为最佳实验参数并以此为基础采用内标法去定量分析水泥样品中的Al和Fe。通过内标法建立的Al和Fe元素的定量分析曲线的线性度分别达到了0.998和0.997,同时通过循环反演的方式去检测定量分析的精度,得到铝和铁的最大测量相对偏差分别为2.32%和5.11%,平均相对偏差为1.34%和2.40%。实验结果表明:采用激光诱导击穿光谱去定量分析水泥样品中的Al和Fe在一定的误差范围内是可行的。