Imaging performance evaluation in depth-of-interaction PET with a new method of sinogram generation:A Monte Carlo simulation study

In conventional PET systems,the parallax error degrades image resolution and causes image distortion.To remedy this,a PET ring diameter has to be much larger than the required size of field of view(FOV),and therefore the cost goes up.Measurement of depth-of-interaction(DOI)information is effective to reduce the parallax error and improve the image quality.This study is aimed at developing a practical method to incorporate DOI information in PET sinogram generation and image reconstruction processes and evaluate its efficacy through Monte Carlo simulation.An animal PET system with 30-mm long LSO crystals and 2-mm DOI measurement accuracy was simulated and list-mode PET data were collected.A sinogram generation method was proposed to bin each coincidence event to the correct LOR location according to both incident crystal indices and DOI positions of the two annihilation photons.The sinograms were reconstructed with an iterative OSMAPEM(ordered subset maximum a posteriori expectation maximization)algorithm.Two phantoms(a rod source phantom and a Derenzo phantom)were simulated,and the benefits of DOI were investigated in terms of reconstructed source diameter(FWHM)and source positioning accuracy.The results demonstrate that the proposed method works well to incorporate DOI information in data processing,which not only overcomes the image distortion problem but also significantly improves image resolution and resolution uniformity and results in satisfactory image quality.

Development of a compact DOI-TOF detector module for high-performance PET systems

To increase spatial resolution and signal-to-noise ratio in PET imaging,we present in this paper the design and performance evaluation of a PET detector module combining both depth-of-interaction(DOI) and time-offlight(TOF) capabilities.The detector module consists of a staggered dual-layer LYSO block with2 mm × 2 mm × 7 mm crystals.MR-compatible SiPM sensors(MicroFJ-30035-TSV,SensL) are assembled into an 8× 8 array.SiPM signals from both fast and slow outputs are read out by a 128-channel ASIC chip.To test its performance,a flood histogram is acquired with a ^(22)Na point source on top of the detector,and the energy resolution and the coincidence resolving time(CRT) value for each individual crystal are measured.The flood histogram shows excellent crystal separation in both layers.The average energy resolution at 511 keV is 14.0 and 12.7%at the bottom and top layers,respectively.The average CRT of a single crystal is 635 and 565 ps at the bottom and top layers,respectively.In conclusion,the compact DOI-TOF PET detector module is of excellent crystal identification capability,good energy resolution and reasonable time resolution and has promising application prospective in clinical TOF PET,PET/MRI,and brain PET systems.

THE INTERACTIONS BETWEEN WAVE-CURRENTS AND OFFSHORE STRUCTURES WITH CONSIDERATION OF FLUID VISCOSITY

Study of the how held around the large scale offshore structures under the action of waves and viscous currents is of primary importance for the scouring estimation and protection in the vicinity of the structures. But very little has been known in its mechanism when the viscous effects is taken into consideration. As a part of the efforts to tackle the problem, a numerical model is presented for the simulation of the how held around a fixed vertical truncated circular cylinder subjected to waves and viscous currents based on the depth-averaged Reynolds equations and depth-averaged k-epsilon turbulence model. Finite difference method with a suitable iteration defect correct method and an artificial open boundary condition are adopted in the numerical process. Numerical results presented relate to the interactions of a pure incident viscous current with Reynolds number Re = 10(5), a pure incident regular sinusoidal wave, and the coexisting of viscous current and wave with a circular cylinder, respectively. Flow fields associated with the hydrodynamic coefficients of the fixed cylinder, as well as corresponding free surface profiles and wave amplitudes, are discussed. The present method is found to be relatively straightforward, computationally effective and numerically stable for treating the problem of interactions among waves, viscous currents and bodies.

知识建构社区交互行为对观点深度影响的研究

知识建构理论注重学习者主动提出观点,通过各种交互行为让学生提出的观点走向更深的层次。文章对18节知识建构课堂交互行为进行了分析,探究不同交互行为对观点深度的影响。研究发现,知识建构社区中交互行为对观点深度的作用主要表现在教师的言语行为和学生的言语行为两个方面,其中教师语言行为对观点深度的作用要大于学生语言行为的影响,由此可见知识建构社区走向深入教师的言语行为引导非常重要。

利用RGB-Depth相机的机械模型建模

从真实机械模型出发,提出了一种利用RGB-Depth相机重建机械模型的方法。该方法流程如下:首先,利用RGB-Depth相机捕获真实的机械模型,获取机械模型的RGB图像和深度数据,注册出模型的粗糙点云数据;其次,用户通过简单的交互,快速将点云分割成多个部分;再次,利用机械模型构造基元简单、规整性好、复用性高的特点,从零件数据库中选取合适的基元,匹配分割的子部分;最后,通过模型部件之间位置关系的优化,重建出多零件机械模型的网格数据。实验结果表明,这种建模方法可以为机械模型重建出具有良好几何特性且符合机械模型构成规则的网格数据,为机械模型的建模技术提供一种新的选择。

双层错位DOI脑PET探测器晶体厚度组合优化设计

双层错位晶体阵列是正电子发射断层成像(PET)仪获取作用深度(DOI)信息的一种低成本且简便的方案。为获得晶体厚度最优组合方案,本文使用GATE软件进行蒙特卡罗仿真研究。模拟兼容核磁共振成像(MRI)的嵌入式脑PET,环内径345 mm,使用硅酸钇镥(LYSO)晶体,2层晶体总厚度20 mm,内层晶体从0 mm到10 mm共11种厚度(间隔1 mm);进行点源模拟实验,点源位于中心断层x轴上,偏移从x=0 cm到x=10 cm共6种情况(间隔2 cm)。计算中心点灵敏度;采用滤波反投影算法重建图像,评估径向空间分辨率。结果显示,双层晶体的设计相比于单层晶体灵敏度略有下降,但系统径向空间分辨率显著提高且其均匀性得到改善。随着内层晶体厚度的增大,视野平均径向空间分辨率先减小后增大,在内层晶体厚度为8 mm时达到最小。综上所述,所设计的双层错位DOI脑PET探测器晶体厚度最优组合方案为内层晶体厚度8 mm、外层晶体厚度12 mm。

Foraging Behavior,Direct Interference and Habitat Use in Three Species of Flamingos(Phoenicopterus Chilensis,Phoenicoparrus Andinus and Phoenicoparrus Jamesi) in Mar Chiquita Lagoon,Córdoba,Argentina

The Laguna Mar Chiquita,located northeast of the province of Córdoba in Argentina,is the only non-Andean place where three flamingo species regularly coexist in the southern part of South America.Two of these species,

Effects of monsoon onset vortex on heat budget in the mixed layer of the Bay of Bengal

We investigated the effects of monsoon onset vortex(MOV)on the mixed layer heat budget in the Bay of Bengal(BOB)in spring 2003 using the reanalysis datasets.The results suggest that the solar radiation flux penetrating the mixed layer and the existence of barrier layer are both able to modulate the effects of MOV on the evolution of sea surface temperature(SST)in the BOB.Prior to the formation of BOB MOV,the local SST raised quickly due to mass of solar radiation reaching the sea surface under the clear-sky condition.Meanwhile,since the mixed layer was shallow before the onset of the Asian summer monsoon(ASM),some solar radiation flux could penetrate to directly heat the deeper water,which partly offset the warming effect of shortwave radiation.On the other hand,the in-situ SST started to cool due to the upwelling of cold water when the MOV generated over the BOB,along with the rapidly increased surface wind speed and its resultant deeper mixed layer.As the MOV developed and moved northward,the SST tended to decrease remarkably because of the strong upward surface latent heat flux over the BOB ascribed to the wind-evaporation mechanism.However,the MOV-related precipitation brought more fresh water into the upper ocean to produce a thicker barrier layer,whose thermal barrier effect damped the cooling effect of entrainment upwelling on the decrease tendency of the BOB SST.In other words,the thermal barrier effect could slow down the decreasing trend of the BOB SST even after the onset of ASM,which facilitated the further enhancement of the MOV.

The Influence of Dust and Black Carbon on Clouds, in Africa

The aerosol can change the clouds properties;the clouds, however, affect the normal behavior of aerosol optical depth. Considerable effects arise while the interaction of aerosol and clouds unavoidably encounters the presence of greenhouse gases (GHGs) in atmosphere. This research discusses the influence of two selected aerosol types, on the clouds in Africa, over the selected sub-time series in the years 1980-2018. Sahara desert’s dust is mainly constituted by hematite minerals;which, in return, is mainly composed by the iron oxides, a powerful solar and infra-red radiation absorbing matter and thus a strong and direct radiative forcing agent. For that reason, together with the fact that it is windblown over the biggest region that surrounds the desert, dust is one of the strongly considered aerosol in this research. Besides, black carbon (BC), mostly from the anthropogenic biomass burning process in the mid latitude’s African savanna, is the second aerosol type selected for this research: it is one of the abundantly available aerosol types and it is one of the strongest atmospheric radiant energy absorbers. For sake of valid and trustworthy results, the data is collected from multiple satellite remote sensing tools and instruments, all targeting the aerosol-cloud interaction and effects. In this research, different measurements were carried out;those are the spatiotemporal averaged cloud cover, the aerosol (dust and BC) extinction optical thickness (AOT), the anomaly of aerosol optical depth (AAOD) as well as different scatter plots’ correlation analysis. For findings: the direct influence of hydrophilic BC on clouds formation in central African sub-region is experimentally demonstrated;the dust aerosol highly influences the North African sub-region’s cloud formation.

Interaction between a Liquid Surface and an Impinging Gas Jet

The water-air and Wood’s metal-air systems are modeled by means of Computational Fluid Dynamics to study the interaction between a liquid surface and an impinging air jet under the near field blowing conditions. The effect of the air jet velocity, the height of the injection lance, and the density of the liquid on the depth of the formed cavity is numerically studied. The CFD results of the cavity depth are compared with results previously reported by other authors. The emergence of the splashing phenomenon is predicted in terms of the critical velocity for each liquid-air system. Besides, the blowing number indicates that the drop generation rate is not significant for jet velocities below the critical velocity, and therefore neither the splashing is significant.

原发性舌鳞癌MRI浸润深度与病理浸润深度的相关性研究

目的:探讨原发性舌鳞状细胞癌(tongue squamous cell carcinoma,TSCC)的术前磁共振浸润深度(MRI depth of invasion,MRI-DOI)与术后病理浸润深度(pathologic DOI,p-DOI)之间的相关性。方法:回顾性选取2015年1月至2018年12月上海交通大学医学院附属第九人民医院经病理证实的TSCC患者入组,测量p-DOI,分析p-DOI与患者临床病理参数及预后的关系,进一步回顾性测量MRI-DOI,研究MRI-DOI与p-DOI之间的相关性。结果:入组患者共52例,p-DOI为1~30 mm,平均值(8.5±5.5)mm;p-DOI>5 mm时,P-DOI与肿瘤大小(P=0.021)、肿瘤部位(P=0.047)显著相关;p-DOI≥10 mm时,p-DOI与颈部Ⅲ区淋巴结转移显著相关(P=0.010);p-DOI>7 mm时,与患者的5年生存率最密切相关(P=0.048)。MRI-DOI为3.1~19.9 mm,平均值为(10.3±4.3)mm;MRI-DOI≥10 mm时,与原发性舌鳞癌患者的不良预后密切相关(P=0.043)。MRI-DOI测量值总体略高于p-DOI,平均差值为1.94 mm,相关性较强(r=0.831,P<0.001)。结论:基于MRI的术前放射学DOI测量有助于估计TSCC的术后p-DOI,有助于术前预测肿瘤的侵袭深度,对原发性舌鳞癌外科手术方式的制定及预后评估具有重要的参考价值。

评价支架如何影响在线同伴互评交互质量?——基于SOLO分类理论的视角分析

学习者充足的交互是保证同伴互评有效性的重要途径。为解决当前在线同伴互评中缺乏对同伴之间深度交互的引导,导致学习者交互处于较浅层级等问题,以SOLO分类理论为指导,围绕5种不同的思维水平设计评价支架,以“现代教育技术”课程为例,采用准实验研究法,对评价活动产生的交互文本进行量化内容分析,以及对学习者的作品改进情况进行分析,探究评价支架对在线同伴互评交互质量的影响。研究发现:(1)评价支架能够显著提升学习者参与互评活动的交互结果质量;(2)评价支架促进学习者的交互深度由浅层级向更深层级转化;(3)学习者对评价支架持认可态度,评价支架作为一种评价工具,可以有效指导互评活动,促进学习者自身的课程学习。

深度报道中河南形象的立场表达——以转述语为对象

立场研究历经对言/作者主体性、交互主体性和话语主体性的关注,凝练了立场主体、立场客体和立场表达三个要素。以这三个要素为主要节点,可以建构包括主体定位、交互程度和索引指向为一级指标的系统,用以描述西方网络媒介涉豫深度报道中以转述语为载体的立场表达。这些报道主要依靠以公众为主体的转述语来确定自己的身份认同,使用占据绝对优势的扩展类非叙实转述词语来获取读者的承认,征用大量的描述性报道句来实现对涉豫事实的话语性改造。与河南形象相关的呈现、认同和承认都是在事实的基础上以话语为依归而动态交互的。

面向桌面交互场景的双目深度测量方法

基于视觉的虚拟现实交互方式在桌面书写应用场景中尚未有针对性的解决方案,书写交互中精细动作准确识别的实现,需要一种全新的高精度手笔联合三维识别技术,其中深度准确度是影响三维识别精度的重要因素。为此提出一种高精度双目深度测量方法,该方法针对书写交互采用了高分辨率、近距离的图像对作为输入,并在算法上提出全局与局部重要信息交叉融合的思想以提升速度与精度,减少计算成本。算法使用区域检测模块提取图像对中的手部和笔尖关键区域以重要程度分尺度输入;并且引入区域特征金字塔结构结合多尺度语义信息;同时利用视差级联模块缩小匹配范围,提高网络实时性。实验证明,提出的深度测量方法在手部和笔尖交互区域精度高,实时性好,能够有效辅助提高手笔联合三维识别精度以提供更好的虚拟书写交互体验,具有广泛的应用前景。

以效果为目标的激光机技术参数优化组合

探究了CO_(2)激光切削柞木时,激光切削工艺参数对其切削质量的影响,得出了最佳的技术参数组合。采用正交试验法,考察了光强、进给速度和镜头高三因素对缝宽、缝深的影响,分析其主效应与交互作用的试验数据变化规律。结果表明:影响激光切削的主要因素为镜头高,进给速度与光强之间的交互作用较为显著。在实际生产中,可根据所需的不同切削效果来确定最佳组合技术参数,如激光切削含水率约为6.5%的柞木,为得到缝深约3000μm,缝宽约200μm,可采用镜头高5 mm,进给速度40 mm/s和激光强度40%。

基于力学仿真分析的PCCP断丝预警及报警阈值评估方法

分析了钢丝的预应力作用机理和管道的破坏过程,提出了一种基于力学仿真分析的PCCP断丝预警与报警阈值评估方法。通过ABAQUS程序建立了PCCP有限元模型,模拟了包括铺设垫层、安装管道、分步回填在内的完整施工过程,计算了不同埋深、不同设计工作压力近百种工况下管道预应力钢丝、钢筒和管芯混凝土的应力状态,提出将管芯混凝土在水锤作用下起裂的最大允许断丝数作为爆管预警阈值,将管道埋地承载力极限状态的最大允许断丝数作为爆管报警阈值,并分析了不同工作内压和埋深条件下PCCP断丝预警与报警阈值之间的关系。

界面的再造:形塑社会的深度媒介化——以GPT-4和Sora等生成式大模型为例

随着生成式AI技术在近年来的飞速跃迁,人工智能正在颠覆性地改变传统的媒介生态,并推动社会的媒介化进程不断深入。为了深入探讨智能媒介在当下技术环境中呈现出的“形塑力”和社会意义,需要结合“媒介界面”的理论视角来深入分析。智能传播时代媒介界面的再造分为三个不同层次:人机交互界面、场景连接界面和产业协同界面。三个不同层次的界面指涉了社会深度媒介化过程中涵盖的新意涵,包括对“对主体自由度的拓展”“对认知边界的突破”以及“对产业生长模式的变革”。当前的智能技术集群所呈现出的形塑力表明,我们正处在“技术奇点”和媒介化进程发生转向的前端,社会进一步的媒介化仍需通用性技术的进一步普及和更多技术组合的落地。

WAVE-BODY INTERACTIONS FOR A SURFACE-PIERCING BODY IN WATER OF FINITE DEPTH

Nonlinear wave-body interactions for a stationary surface-piercing body in water of finite depth with fiat and sloping bottoms are simulated in a two-dimensional numerical wave tank, which is constructed mainly based on the spatially averaged Navier-Stokes equations with the k- ε model for simulating the turbulence. The equations are discretized based on the finite volume method and the scheme of the pressure implicit splitting of operators is employed to solve the Navier-Stokes equations. By using the force time histories, the mean and higher-harmonic force components are calculated. The computational results are shown to be in good agreement with experimental and numerical results of other researchers. Then, the horizontal force, the vertical force and the moment on the surface-piercing body under nonlinear regular waves with flat and sloping bottoms are obtained. The results indicate that the bottom topographies have a significant influence on the wave loads on the surface-piercing body.

线上线下融合式课堂互动助力思政课深度教学探析

深度教学是思政课教学实效性的重要保证。线上线下融合式课堂互动聚焦课堂教学主渠道,具有主体间性、开放生成性、互动高效性和协同学习等特征,是信息技术与教育教学深度融合的结果,也提供了以深度互动助力思政课深度教学的可能。线上线下融合式课堂互动助力思政课深度教学具有深厚的学理支持,是思政课教学的实践反思,也是扭转思政课混合式教学浅层化的重要路径。以线上线下融合式课堂互动助力思政课深度教学应准确把握教学目标与教学内容,打好深度互动基础;推动教材体系向教学体系转换,创设深度互动条件;从问题出发开展全员深度互动,开启深度教学过程;加强互动总结升华,落实思政课深度教学。

飞机智慧座舱发展技术研究

未来飞机座舱智慧化转型是必然趋势,研究飞机智慧座舱发展技术能够为未来飞机智慧座舱的设计提供参考支撑。本文探讨了智能与智慧的区别,提出了飞机智慧座舱的概念与设计内涵,总结出深度感知与沉浸式交互、类人的认知及开放性与个性化定制服务的智慧座舱功能设计要素;梳理了发展飞机智慧座舱亟需解决的五项关键技术:多维度深度信息感知与融合技术、先进信息显示技术、沉浸式自然交互技术、智能态势认知技术、多智能体自主适应技术。通过关键技术的分析对未来飞机智慧座舱的发展提出了新的思考。