Nonlinear Registration of Brain Magnetic Resonance Images with Cross Constraints of Intensity and Structure

Many deep learning-based registration methods rely on a single-stream encoder-decoder network for computing deformation fields between 3D volumes.However,these methods often lack constraint information and overlook semantic consistency,limiting their performance.To address these issues,we present a novel approach for medical image registration called theDual-VoxelMorph,featuring a dual-channel cross-constraint network.This innovative network utilizes both intensity and segmentation images,which share identical semantic information and feature representations.Two encoder-decoder structures calculate deformation fields for intensity and segmentation images,as generated by the dual-channel cross-constraint network.This design facilitates bidirectional communication between grayscale and segmentation information,enabling the model to better learn the corresponding grayscale and segmentation details of the same anatomical structures.To ensure semantic and directional consistency,we introduce constraints and apply the cosine similarity function to enhance semantic consistency.Evaluation on four public datasets demonstrates superior performance compared to the baselinemethod,achieving Dice scores of 79.9%,64.5%,69.9%,and 63.5%for OASIS-1,OASIS-3,LPBA40,and ADNI,respectively.

Optimization of Crosswalk Width Based on Bi-Directional Pedestrian Crossing Time at Signalized Intersections

The effects of the interactions between bi-directional pedestrians on the crossing time and the crosswalk width are studied. Firstly,the crossing process of bi-directional pedestrians is analyzed.The total crosswalk time is divided into a discharge time and a crossing time. The interactions between bi-directional pedestrians are quantified with the drag force theory. Then,a model is developed to study the crossing time based on the kinetic energy theory and momentum theory. Subsequently,the related parameters of the proposed model are calibrated with observed information. The relationships among crosswalk width,signal time,pedestrian volume and level of service are simulated with the proposed model. The results are verified and compared with other models. The proposed model has an absolute value of relative error of 9. 38%,which is smaller than that of the Alhajyaseen model（ 15. 26%） and Highway Capacity Manual（ HCM） model（ 12. 42%）. Finally,suggested crosswalk widths at different conditions are successfully estimated with the proposed crossing time model.

ANALYSIS OF COUPLING INFLUENCES OF LABYRINTH SEAL PARAMETERS ON CROSS COUPLED STIFFNESS AND DIRECT DAMPING COEFFICIENT

Labyrinth seal can cause steam-exciting, the structural and operating parameters of labyrinth seal have effect on stability of rotor-system. For investigating the coupling influences of the structure and operating parameters of labyrinth seals on dynamic coefficients, a model of calculating dynamic coefficients of labyrinth seals is presented using a two control volume model. The coupling influences of parameters on cross-coupled stiffness and direct damping of labyrinth seal are discussed. In the conclusion, a reference of preventing steam-exciting vibration and optimum determination of design parameters of labyrinth seals are provided.

Research on no Dig Directional Drilling Pipeline Laying Technique —The reseach on directional drilling tool

The directional crossing drilling works were applied in the West East gas pipeline (WEGTP) project. The main researchs on the directional crossing drilling include:(1)to analyze the forces applied on the drilling tool and the failure mechanism in order to obtain the proper configuration of the drilling tool and solve the failure prevention;(2)to analyze the existing mud, to propose a viable mud composition;(3)in respect of mud mixing and environmental protection, to develop a quick cycloning mud hydration and recycling device;(4)to develop a interface picture software for direction controlling measured parameter to improve directional drilling accuracy; (5) to develop an electronic search software incorporating large amount of construction specifications and mud compositions, used for construction. In this paper the first one of the above mentioned points is introduced, including existing problems with directional drilling, optimization of the drilling tool, analysis of drill collar fracture failure, research on stress scattering structure of drilling tool thread and thread sticking prevention measures, etc.

Stochastic resonance in a gain-noise model of a single-mode laser driven by pump noise and quantum noise with cross-correlation between real and imaginary parts under direct signal modulation

Stochastic resonance （SR） is studied in a gain-noise model of a single-mode laser driven by a coloured pump noise and a quantum noise with cross-correlation between real and imaginary parts under a direct signal modulation. By using a linear approximation method, we find that the SR appears during the variation of signal-to-noise ratio （SNR） separately with the pump noise self-correlation time τ, the noise correlation coefficient between the real part and the imaginary part of the quantum noise λq, the attenuation coefficient γ＇ and the deterministic steady-state intensity I0. In addition, it is found that the SR can be characterized not only by the dependence of SNR on the noise variables of and λq, but also by the dependence of SNR on the laser system variables of γ and I0. Thus our investigation extends the characteristic quantity of SR proposed before.

2023年对外直接投资回顾与2024年展望

2023年,全球跨境直接投资总体起色不大,其中绿地投资增速下滑,跨境并购交易依旧疲软。与之相较,我国对外直接投资发展稳中向好,特别是绿地投资动力强劲。预计2024年,全球跨境直接投资将依然疲弱,但我国对外投资仍有较强动力。对此,建议相关政府部门以服务国内大循环为最终目的,引导跨境产业链合理有序布局,提升对外投资便利化水平;同时,鼓励企业创新对外投资方式,强化企业风险防范应对能力。

一种长基线被动传感器数据关联方法

为了提高测向交叉定位系统多目标环境下的去鬼点性能,提出了一种长基线被动传感器数据关联方法.首先利用被动传感器量测的视线矢量信息进行交叉定位并计算定位误差协方差矩阵,然后基于两个定位点构造了一个卡方分布的检验统计量,将多目标条件下的去鬼点问题转换为假设检验问题.为了分析该方法的性能,定义了真实目标的正确关联概率和鬼点目标的错误关联概率,并在使用两部和三部被动雷达的情况下分别与倾斜角方法进行了仿真对比.仿真结果表明所提出的方法在使用三部被动雷达或多目标与被动雷达共面时关联性能更好.

跨模态语义时空动态交互情感分析研究

针对传统情感分析中存在的模态间交互性差、时空特征融合度低的问题,建立了一种跨模态的语义时空动态交互网络。通过引入双向长短期记忆网络挖掘各模态的时间序列特征,加入自注意力机制强化模态内特征的权重赋值,将自动筛选出的特征矩阵送入图卷积神经网络进行语义交互。然后以时间戳为基础进行特征聚合,计算聚合层的相关系数,获得融合后的联合特征,实现跨模态空间交互,最终完成情感极性的分类与预测。使用公开数据集对所提出的模型进行评估验证,实验结果表明,多模态时间序列提取和跨模态语义空间交互机制可以实现模态内和模态间特征的全动态融合,有效地提升了情感分类的准确率和F1值,在CMU-MOSEI数据集上分别提高了1.7%~13.5%和2.1%~14.0%,表现出良好的健壮性和先进性。

基于SODIX方法的叶片前缘噪声指向性及降噪实验研究

以NACA 65(12)–10独立基准叶片为对象,使用线性传声器阵列和SODIX(SOurce DIrectivity modeling in the cross-spectral matriX)方法对基准叶片前缘噪声指向性分布特征及波浪前缘对叶片前缘噪声的影响进行了实验研究。开发了SODIX数据处理程序并进行了数值仿真验证,结果表明:不同指向角下计算结果的最大误差不超过0.26 dB。在半消声室内,利用由31个传声器组成的非均匀分布优化阵列,对NACA 65(12)–10独立基准叶片和仿生学叶片的前缘噪声开展了参数化声学实验。结果表明:在40°~142°指向角测量范围内,基准叶片前缘噪声指向性符合典型偶极子声源特征,峰值在130°指向角附近;随着频率升高,基准叶片前缘噪声指向性产生了显著的“波瓣”现象,频率越高,“波瓣”越多。进一步研究表明:不同波长和幅值的前缘构型都可以有效降低指向角测量范围内的前缘噪声;与波浪前缘的波长相比,波浪前缘的幅值对前缘噪声的影响更为显著,特别是在90°~120°指向角范围内,A30W20叶型的降噪量可达7.71 dB。

基于时空编码数字超表面的雷达散射截面积缩减及波达角估计方法

传统的波达角(DOA)估计方法的实现通常基于相控阵天线系统,而其高昂的硬件成本限制该技术在不同领域的应用和推广,此外相控阵天线普遍不具备隐身性能,其在工作频段内雷达散射截面积(RCS)普遍较高。为解决上述问题,该文在时空编码(STC)理论的基础上提出了一种基于超表面同时实现RCS缩减和DOA估计的方法,并利用一款毫米波超表面对算法进行了验证。实验结果表明,该方法实现的波达角估计误差在1°以内,同时RCS缩减大于10 dB,为DOA估计和RCS缩减功能的集成提供了全新的思路,具有高性能、低成本等特点。

Effect of Magnetic Field Configuration on Stray-Crystal Formation with Different Platform Sizes during Directional Solidification of Single-Crystal Superalloy

The magnetic field is an effective means to control the solidification structure and the defects of metal and semiconductor crystals.This work investigates the effects of Cusp magnetic field(CMF)and longitudinal magnetic field(LMF)on the stray-crystal formation in the platform regions during the directional solidification of single-crystal superalloy with the different cross section sizes.The application of CMF reduces the formation of platform stray-crystal,while LMF increases its generation.As the platform size increases,the stray-crystal ratio increases regardless of whether the magnetic fields are applied or not,the effectiveness of CMF increases,while that of LMF decreases.The reason that the effects of CMF and LMF on the platform stray-crystal formation could be attributed to the change of flow structure from the distribution characteristics of the thermoelectric magnetic force and the magnetic damping force near the liquid-solid interface.

融合停车线方向的端到端停车位检测网络

智能汽车自动泊车功能的基本要求之一是能够快速准确地检测出未被占用的停车位。针对这一问题,设计了一种融合停车线方向与全局特征的端到端可训练的停车位检测网络。首先提取出车位关键点的坐标以及关键点对应停车线的方向,并从图像全局特征中使用关键点的坐标提取出局部特征。将关键点信息、局部特征、全局特征使用交叉注意力机制融合,利用入口线鉴别器推断出关键点的停车位构成关系。根据关键点的停车位构成关系以及停车线方向,裁剪出停车位的区域图像并送入定制的车位占用分类网络进行分类,得到车位的占用信息。本文提出的方法在公共基准数据集PS2.0上进行了实验,其中该方法对矩形停车位的检测精度为99.65%,对倾斜停车位的检测精度为99.04%,在单块GPU上能够达到80 fps的检测速率。经验证,所提出的方法可以实时高精度的检测停车位位置、方向以及占用情况。

改进MUSIC算法的超声波测风方法研究

针对传统超声波测风装置测风精度不高、抗噪声能力弱,提出了一种改进多重信号分类(multiple signal classification,MUSIC)算法的超声波测风方法。采用一种弧形6阵元超声波传感器阵列的测风结构,推导其阵列流型;在此基础上,添加小波阈值降噪算法提高信号信噪比,降低噪声信号协方差矩阵的秩;再使用PHAT加权广义互相关时延估计算法以提高时延估计的准确性,同时根据时延关系对传统MUSIC算法矢量矩阵进行改进;最后通过MUSIC算法实现对风速风向的测量。理论分析与仿真结果表明:改进后的MUSIC算法具有较好的抗噪性能和较高的风参数测量精度,测量风速绝对误差达到0.15 m/s,风向绝对误差达到2°,可以应用于对风参数要求较高的场景。

远场环境下基于方向角的测向交叉定位技术研究

针对远场条件下小孔径阵列被动定位在强干扰下精度差的问题,提出基于方向角的测向交叉定位算法。分析侧向交叉定位方法的工作机理,构建改进的目标定位几何模型和数值模型;利用构建的模型建立目标估计预测方程,并对非线性预测方程进行线性化处理,将预测方程在参考点处按泰勒级数展开,获得修正方程;通过迭代过程的优化控制获得目标的无偏渐近估计,实现目标精确定位;对所提算法的主要误差来源进行分析,研究不同误差项对目标定位精度的影响。仿真实验表明,提出的算法能有效的对目标进行定位,在方向角误差和背景噪声较大时定位精度明显高于传统定位算法,具有更优的定位性能。

基于DEMATEL-ISM模型的装配式建筑施工质量控制体系的构建

装配式建筑是建筑业的未来发展趋势,其施工质量直接关乎人民群众的利益。为提高装配式建筑施工质量,从人员、材料、机械、方法和环境5个层面分析得到15个影响因素,构建装配式建筑施工质量评价指标体系,基于DEMATEL-ISM模型对各指标之间的因果关系进行分析。结果表明,管理人员水平是影响装配式建筑施工质量的主要因素,预制构件存储状况、施工器具误差、预制构件安装方案合理性、工程质量管理环境是影响装配式建筑施工质量的次要因素,根据分析结果为装配式建筑施工质量控制提供合理建议。

小型化超宽带3 dB定向耦合器设计

设计并实现了一个小型化超宽带3 dB定向耦合器,采用对称多节耦合带状线的形式,由一个十七阶耦合器和一个五阶耦合器交叉串联构成,并通过采用弯折线,缩减了整体尺寸,可实现13:1倍频程的工作带宽。测试结果表明,在0.2~2.65 GHz频率范围内,电压驻波比小于1.35,隔离度小于-17 dB,带内波动为-3.4±0.6 dB,能够实现90°相移。

混合三端直流输电系统受端交流故障穿越协调控制策略

以乌东德电站送电广东广西特高压多端柔性直流示范工程为研究对象,考虑混合三端柔性直流输电系统因受端不同位置交流故障所致的直流过电压,提出相应的故障穿越协调控制策略。在受端主站发生网侧交流瞬时故障的情形下,通过设计混合型模块化多电平电压源换流器全桥子模块自适应负投入策略,实现了利用子模块电容短时过电压储能的能力来快速补偿站间直流电压的上升;短暂时延后,送端电网换相换流器通过定量调整电流指令值策略来减小子模块的不平衡充电功率。在受端主站发生阀侧交流故障的情形下,优先利用输电健全极的功率转代裕度来消纳故障极的部分不平衡功率;同时,故障极从站跟随主站半压运行,相应的高低压阀组切换至定电流及定电压模式,最终实现抑制站间过电流及减小盈余功率。仿真结果表明,2种故障条件下,所提的协调控制策略均可较快实现故障期间的功率平衡,有效抑制仅配备稳态基本协调控制策略下系统所出现的直流过电压现象,同时也基本维持了送端的总体有功传输容量。

强干扰下基于三阶互累积量的FMCW雷达信号DOA估计算法

针对车载调频连续波雷达存在相互干扰的实际情况,本文提出了一种基于三阶互累积量的多目标波达方向超分辨估计方法.该方法利用同步采集的阵列信号并根据回波信号和干扰信号的非相关特性,构造三阶互累积量矩阵,随后根据子空间方法获得二维空间谱,实现距离和方位的联合估计.计算机仿真结果表明,本文所提方法能够在抑制强干扰影响的同时实现3°以内多目标识别,与现有超分辨法和重构法相比,具有更高的角度分辨率和估计精度.

市政工程热力管道非开挖定向穿越施工技术的运用分析

为降低市政工程热力管道施工周期以及对于周围环境和交通的影响,以某地区的整合供热工程为例,研究非开挖定向穿越施工技术在市政工程热力管道施工中的运用效果。结合施工范围内的地质条件情况,确定非开挖定向穿越施工工艺流程,首先在施工前对入土口和出土口两侧夯入隔离套管,其次选择施工设备,完成钻孔施工,在计算穿越管道所受的回拖力的情况下进行管道回拖施工,最后测试管道强度和气密性以确保结果满足规范要求。

市政工程热力管道非开挖定向穿越施工技术的应用分析

为解决管道施工质量问题,论文结合工程案例提出一种管道非开挖定向穿越施工技术,从基坑开挖、管道焊接、水平定向钻穿越施工等方面对该施工技术的应用进行研究,总结质量控制要点。