Potential theory method for 3D crack and contact problemsof multi-field coupled media： A survey

This paper presents an overview of the recent progress of potential theory method in the analysis of mixed boundary value problems mainly stemming from three-dimensional crack or contact problems of multi-field coupled media. This method was used to derive a series of exact three dimensional solutions which should be of great theoretical significance because most of them usually cannot be derived by other methods such as the transform method and the trial-and-error method. Further, many solutions are obtained in terms of elementary functions that enable us to treat more complicated problems easily. It is pointed out here that the method is usually only applicable to media characterizing transverse isotropy, from which, however, the results for the isotropic case can be readily obtained.

Wave field in two-phase media by the convolutional differentiator method

This paper applies the convolutional differentiator method, based on generalized Forsyte orthogonal polynomial （CFPD）, to simulate the seismic wave propagation in two-phase media. From the numerical results we can see that three types of waves, fast P-waves, S-waves and slow P-waves, can be observed in the seismic wave field. The experiments on anisotropic models demonstrate that the wavefront is elliptic instead of circular and S-wave splitting occurs in anisotropic two-phase media. The research has confirmed that the rules of elastic wave propagation in fluid-saturated porous media are controlled by Biot＇s theory. Experiment on a layered fault model shows the wavefield generated by the interface and the fault very well, indicating the effectiveness of CFPD method on the wavefield modeling for real layered media in the Earth. This research has potential applications to the investigation of Earth＇s deep structure and oil/gas exploration.

An eigen theory of static electromagnetic field for anisotropic media

Static electromagnetic fields are studied based on standard spaces of the physical presentation, and the modal equations of static electromagnetic fields for anisotropic media are derived. By introducing a new set of first-order potential functions, several novel theoretical results are obtained. It is found that, for isotropic media, electric or magnetic potentials are scalar; while for anisotropic media, they are vectors. Magnitude and direction of the vector potentials are related to the anisotropic subspaces. Based on these results, we discuss the laws of static electromagnetic fields for anisotropic media.

Simulation of thermal field induced by concave spherical transducer in multi-layer media

High intensity focused ultrasound(HIFU)therapy is an effective method in clinical treatment of tumors,in order to explore the bio-heat conduction mechanism of in multi-layer media by concave spherical transducer,temperature field induced by this kind of transducer in multi-layer media will be simulated through solving Pennes equation with finite difference method,and the influence of initial sound pressure,absorption coefficient,and thickness of different layers of biological tissue as well as thermal conductivity parameter on sound focus and temperature distribution will be analyzed,respectively.The results show that the temperature in focus area increases faster while the initial sound pressure and thermal conductivity increase.The absorption coefficient is smaller,the ultrasound intensity in the focus area is bigger,and the size of the focus area is increasing.When the thicknesses of different layers of tissue change,the focus position changes slightly,but the sound intensity of the focus area will change obviously.The temperature in focus area will rise quickly before reaching a threshold,and then the temperature will keep in the threshold range.

The Kinematics and Field Equations for Porous Media

With a porous medium regarded as an immiscible mixture of multiphase and each phase as a miscible mixture of multi constituent, a systematical research on the kinematics and field equations for porous media is carried out from the point of view of mixture theory. It is shown that the motion of each phase is the mathematical average of the motions of all constituents in the phase, and that the motion of porous media may be described as the motion of the skeleton and the relative motion of each phase with respect to the skeleton. The influence of mass exchange between different constituents in each phase and the influence of mass exchange of same constituent between different phases in porous media are considered in field equations which are self consistent in theory. All the field equations in the references are special cases of the equations proposed in this paper.

场域理论视角下高校网络舆情治理的防范困境与实践进路

作为意识形态工作的前沿阵地,高校肩负着培育时代新人的重大使命,是国内外各种社会思潮交锋和与西方敌对势力争夺青年一代的重要场所。在场域理论视角下,针对网络舆情治理面临的场域壁垒下的治理角色转化、资本制约下的治理权力更迭和惯习固化下的治理手段改变等危机风险,高校需在初始传播阶段建立健全舆情监测机制,构建动因性应对机制;在爆发扩散阶段强化精准研判控制局势,构建资源性保障机制;在逐渐消退阶段加强社会各界沟通协作,构建进路性导引机制。

电磁学中的格林函数

文章回顾了电磁学中的格林函数理论与格林函数方法。首先,引入标量波动方程对应的格林函数,并与信号系统中的冲击响应函数作类比。其次,引入矢量波动方程对应的并矢格林函数,包括均匀和非均匀介质中的格林函数,并探讨其与电磁理论中的互易定理、等效原理之间的联系。最后,介绍了考虑介质的运动效应和电磁场的量子效应下的格林函数理论。此外,文章也探讨了电磁格林函数在无线通信、电磁兼容等工程领域的应用。

CO_(2)快速吞吐提高页岩油采收率现场试验

页岩油注CO_(2)吞吐提高采收率技术处于探索阶段,目前面临着CO_(2)与页岩储层及流体相互作用机制不明确、数值模拟技术不成熟、缺乏规模注采及低成本回收工艺等技术难题。为探索页岩油注CO_(2)提高采收率主控机理,以苏北盆地溱潼凹陷古近系阜宁组二段页岩油为对象开展了超临界CO_(2)水岩反应实验,分析了高温高压条件下页岩矿物溶蚀作用及其对孔隙度和渗透率的影响,并通过注CO_(2)恒质膨胀实验、最小混相压力测试评价了地层超压条件下注CO_(2)后原油高压物性变化特征,并在此基础上开展考虑多因素数值模拟研究优化了设计注入参数,最终通过矿场试验验证了技术可行性。研究结果表明:(1) CO_(2)水岩反应以碳酸质矿物溶蚀占主导,长英质矿物部分溶解,生成中大孔隙;(2)在地层原油中注入适量的CO_(2),显著萃取了原油中间烃组分,原油黏度从5.151 mPa·s下降到1.250 mPa·s,且CO_(2)首先萃取轻烃组分,随生产时间增加萃取组分逐渐变为重烃;(3)基于人工压裂与天然缝网混合介质组分数模模型,优化设计单井吞吐注气量1.7×10~4 t,注气速度500~600 t/d,焖井时间50 d;(4)低压侧加热的页岩油CO_(2)吞吐地面工艺,可依据CO_(2)注入地面工艺多参数数据模型,实现精准控温,避免注入管线冻堵及井下油管和套管材料低温脆断问题;(5)产出气CO_(2)浓度高于80%时,采用气相回收直注工艺,实现产出气回收成本降至104元/t。结论认为,CO_(2)快速吞吐有效提高了页岩油采收率,形成的机理认识和技术系列可为页岩油注CO_(2)吞吐开发提供参考和借鉴。

基于COMSOL的纸浆模塑干燥模拟及验证

目的研究采用COMSOL Multiphysics模拟纸浆模塑干燥效率及厚度变化的可行性。方法基于多孔介质理论,应用有限元仿真软件COMSOL Multiphysics建立纸浆模塑干基含水率随时间变化的热湿、水分流动、非等温流动多物理场耦合模型,考虑干燥中含湿多孔介质的湿空气热对流及多孔基体的热传导,模拟在热板加热条件下纸浆模塑的干燥效率和厚度的变化,并与实验结果进行比较。结果模型内域探针所得模拟结果与实验结果具有良好的一致性,在干燥后期厚度预测误差范围为0.4%~7.7%,干燥效率预测差异值最低为4.3%。结论采用COMSOL Multiphysics模拟纸浆模塑干燥过程可行。

新媒体在卫生健康领域的应用与展望

新媒体主要指基于数字技术、网络技术及其他现代信息技术和通信技术的,具有互动性、融合性的媒介形态和平台。健康信息指与人们健康生活相关的信息。目前,通过新媒体传播健康信息并对人群进行科普或干预的方式越来越普遍。文章介绍了国内外新媒体在卫生健康领域的应用与研究现况,并对新媒体的优势、存在的问题与改进的办法进行分析。

数字媒介时代中国儿童文学的游戏新质

游戏精神是儿童文学的核心审美要素,反映儿童本能心理需求。从纸媒时代到数字媒介时代,儿童文学的创作和传播形式发生巨大转向,其游戏形式与游戏场域发生根本性转换。数字图书实体能够与故事分离,成为阅读游戏的新主体,读者身体亦参与进阅读活动,作为精神游戏的阅读活动被加入实体游戏形式。非线性叙事和自由选择模式让数字图书阅读增加了建构个性化故事的游戏形式。与此同时,传统儿童文学阅读形成的“书与人”的私密阅读空间被打破,数字图书提供了群体交互空间,数字阅读表现出群体性活动特征和社交性活动转向。文本世界与现实世界的界限因数字技术变得模糊,图书元素可通过数字技术呈现于现实世界,现实世界的不确定性经由互动进入文本世界。游戏的结构特性和数字媒介表达形式、内在符号会深刻影响儿童认知和文化生成。数字儿童文学的游戏精神由“出世”的精神幻想转为“入世”的互动乐趣,表现出与数字媒介特性相符的狂欢性、主动性、社交性特征,以及由故事幻想转向世界幻想的新特质。

论抗战前后上海出版传媒业的结构转型

抗战前后是上海乃至中国出版传媒业发展的历史转折点,具体而言,上海媒介场域发生了从民营商业媒体主导向政治报刊主导的结构转型。随着20世纪20年代末30年代初新闻业危机的出现与解决,上海出版传媒业的发展方向从商业化重归政治化,这一发展意义重大、影响深远。上海出版传媒业的结构转型主要表现为从抗战以前的民营报刊主导,转变为抗战爆发后局部抗战时期的抗日报刊、孤岛时期的“洋旗报”和全面沦陷时期的日伪报刊等政治性报刊主导的过程;其成因包括政治社会环境的变化尤其是抗战爆发等外因,以及对新闻业发展新路径的探索等内因。文章以场域理论和媒介史为视角,从传媒的公共性、商品化和专业性等维度,探讨抗战前后上海出版传媒业结构转型的特征、成因及影响,旨在为上海抗战传媒史的研究开拓新的视野和提供新的启示。

新媒体视域下的江汉文化传播媒介形象研究

在新媒体环境下,以江汉文化为主题的传播媒介形象朝着可视化方向演变,并突显出即时性、交互性、社群化和个性化等特点。本论文通过探讨新媒体视域和江汉文化传播形象的构建,以及新媒体话语形象的重塑、加强江汉文化传播教育、挖掘文化资源和塑造文化品牌等手段,旨在重新塑造新媒体视域下的江汉文化传播媒介形象,为传承与发展江汉地区的优秀地域文化提供经验借鉴。

基于相场法的预制双裂隙岩体水力压裂扩展数值模拟研究

水力压裂裂隙扩展形态对于深部岩体油气开采和地热能开采具有重要意义。针对深部地层岩体水力压裂裂隙扩展问题,基于相场法理论、Biot多孔弹性介质力学理论和渗流力学理论建立了相场法应力−渗流耦合模型。该模型采用有限元方法对方程组进行离散化处理,运用牛顿迭代法(Newton-Raphson method,简称NR法)和分离式耦合方法求解方程组以提高计算精度。对比了该模型数值解与室内试验模拟结果和基于数值流形法(numerical manifold method,简称NMM)的数值解,并将数值解与理论解析解进行比较,验证了模型的可靠性。基于该模型,研究了地应力差、裂隙间距和注入流量等因素对垂直于最大主应力方向的双裂隙水力压裂裂隙扩展的影响规律。研究结果表明:随着地应力差的增大,裂隙扩展路径的偏转角度增大,扩展分支路径相应增多;较小的裂隙间距使裂隙更易贯通,且裂隙扩展的偏转程度和扩展长度均随着裂隙间距的增大而逐渐增大;较大的注入流量更有利于裂隙扩展长度和扩展速度的增加。通过探讨不同因素对裂隙扩展的影响,为深部岩体水力压裂优化复杂裂隙网络提供了理论依据。

社交媒体场域下容貌焦虑性别鸿沟的生成机理及补偿行为

伴随着社会经济转型与传播结构的变革,容貌焦虑已经成为当代青年共通的心理症候。观察抖音与微博平台中不同用户主体的容貌焦虑情绪表征,探究社交媒体场域下容貌焦虑情绪的性别差异及其生成机理。研究发现:凝视权力的争夺与个体媒介使用宽度差异,导致女性用户焦虑程度更深;社会规范对情绪表达的影响,导致女性用户的情绪表达行为比男性更活跃,表达形式更多元;性别回音室效应导致男女用户的焦虑面向不同,男性偏重整体,女性关注细节。主体在应对容貌焦虑情绪时,展现出主观能动性,会通过认知补偿、社会网络补偿、媒介补偿的方式缓解焦虑情绪。

基于伪解析法的TTI介质纯qP波地震波场正演模拟

近年来,各向异性介质纯qP波正演模拟及逆时偏移成像技术受到广泛关注。常规拟声波方程存在伪横波干扰、受模型参数限制(ε≥δ)、传播不稳定和计算精度不高等因素影响,极大地限制了其应用。为此,本文将qP波拟微分方程变换到空间—波数域,并通过坐标变换,推导了时间域TTI介质二阶纯qP波波动方程;为提高计算精度,引入伪解析算法(pseudo analytical method, PAM),实现了基于伪解析法的TTI介质纯qP波地震波场正演模拟。数值模拟结果表明:(1)本文方法克服了拟声波方程的局限性,消除了伪横波干扰,不受模型参数限制且地震波场能稳定传播;(2)与其他方法相比,伪解析法能有效提高数值模拟精度;(3)简单及复杂模型测试验证了本文方法的正确性与适用性。

场域迁移与功能转向:中国民族民间舞蹈的“融媒体”传播探析

舞蹈传播的场域及功能适应着文化生态变迁与时代发展,融媒体时代的到来深刻影响着中国民族民间舞蹈传播的结构与功能。舞蹈传播作为传承舞蹈文化的重要途径,其传播场域历经了从自然衍生场域面向舞台演艺场域、教育教学场域的双向传播拓展,即原生态民间舞、舞台化民间舞和学院派民间舞三种传播场域。梳理中国民族民间舞蹈传播的场域类型及场域迁移中的功能转向,有助于把握融媒体时代下中国民族民间舞蹈传播的核心特征及高质量发展路径,以期更好地实现民族民间舞蹈文化的创造性转化和创新性发展。

社交媒介视域下用户原创内容评论区场域建设的路径

社交媒介视域下用户原创内容评论经历了早期的单向性新闻评论阶段、互联网背景下的新媒体评论阶段、网络媒介技术催生下的社交媒介评论阶段,进而推进了用户原创内容评论区场域的形成。用户原创内容评论区是平台、用户、评论区三者在运行中相互支持、相互促进、相互依存的必然结果,借由社交媒体平台支撑赋予用户主体角色、用户积极参与构建信息交互场景、原创内容与评论信息暴涨引发事件热议,用户原创内容评论区场域得以形成。把握社交媒介视域下用户原创内容评论区场域属性及主要特征,并围绕用户原创内容评论区场域主旨意向的表达、用户原创内容评论区场域围观参与的体验、用户原创内容评论区场域趋利欲望的实现三大维度,为推动用户原创内容评论区场域建设指明方向。

冷媒温度和渗流速度对富水砂层冻结温度场的影响规律研究

针对天津地区地铁隧道施工中存在富水砂层等复杂水文地质条件下的冻结问题,通过室内模型试验和数值模拟的结合,研究了冷媒温度和渗流速度对砂土冻结温度场、交圈时间和冻结壁发展的影响。研究结果表明:随着冷媒温度降低,冻结管附近的温度梯度越陡,冻结壁也变得更厚。渗流存在时,渗流水将冷量从上游带到下游,阻碍了冻结壁在上游方向的发展,同时在一定程度上推动了冻结壁在下游方向的发展,导致冻结壁厚度不均匀。最终,冻结壁的形状从静水时的圆形发展为心形。在实际工程中,采用注浆等手段减缓渗流速度,并降低冷媒温度,可缩短交圈时间,确保冻结进程顺利进行。

A Second-Order Eigen Theory for Static Electromagnetic Fields

The static electromagnetic fields are studied here based on the standard spaces of the physical presentation, and the modal equations of static electromagnetic fields for anisotropic media are deduced. By introducing a set of new potential functions of order 2, several novel theoretical results were obtained: The classical potential functions of order 1 can be expressed by the new potential functions of order 2, the electric or magnetic potentials are scalar for isotropic media, and vector for anisotropic media. The amplitude and direction of the vector potentials are related to the anisotropic subspaces. Based on these results, we discuss the laws of static electromagnetic fields for anisotropic media.