Calculation of the Hardness Space Distribution in the As Quenched Condition of a Medium Hardening Tool Steel

The calculation of the hardness profile is a powerful tool for the selection of the right steel for a given purpose. Computer programs INC-PHATRAN and INDUCTER-B were formerly developed by the authors for the calculation of hardness profiles after heat treatment processes of low alloy and carbon steels. The first one simulates quenching as well as through hardening operations, and the second one models electromagnetic induction heat treatments processes. These codes make use of the SAE Standard 3406 in order to obtain the hardness profile, with enhanced regression coefficients recently obtained by the authors. The present work broadens the field of application of this method, allowing to apply it for low hardenability tool steels such as the ASTM O1 Tool Steel. The method used for the calculation of the hardness profile is here summarized, and an example of application is described, which shows good correspondence between the calculated and measured values.

Solution of a Green's function for a saturated porous medium in a half-space subjected to a torsional force

Based on the solutions of the Green＇s function for a saturated porous medium obtained by the authors, and using transformation of axisymmetric coordinates, Sommerfeld integrals and superposition of the influence field on a free surface, the authors have obtained displacement solutions of a saturated porous medium subjected to a torsional force in a half-space. The relationship curves of the displacement solutions and various parameters （permeability, frequency, etc.） under action of a unit of torque are also given in this paper. The results are consistent with previous Reissner＇s solutions, where a two-phase medium decays to a single-phase medium. The solution is useful in solving relevant dynamic problems of a two- phase saturated medium in engineering.

Green's function of multi-layered poroelastic half-space for models of ground vibration due to railway traffic

This study proposes a Green＇s function, an essential representation of water-saturated ground under moving excitation, to simulate ground borne vibration from trains. First, general solutions to the governing equations of poroelastic medium are derived by means of integral transform. Secondly, the transmission and reflection matrix approach is used to formulate the relationship between displacement and stress of the stratified ground, which results in the matrix of the Green＇s function. Then the Green＇s function is combined into a train-track-ground model, and is verified by typical examples and a field test. Additional simulations show that the computed ground vibration attenuates faster in the immediate vicinity of the track than in the surrounding area. The wavelength of wheel-rail unevenness has a notable effect on computed displacement and pore pressure. The variation of vibration intensity with the depth of ground is significantly influenced by the layering of the strata soil. When the train speed is equal to the velocity of the Rayleigh wave, the Mach cone appears in the simulated wave field. The proposed Green＇s function is an appropriate representation for a layered ground with shallow ground water table, and will be helpful to understand the dynamic responses of the ground to complicated moving excitation.

5D World-Universe Model Space-Time-Energy

5D Space-Time-Energy World-Universe Model is a unified model of the World built around the concept of Medium, composed of massive particles (protons, electrons, photons, neutrinos, and dark matter particles). The Model provides a mathematical framework that enables precise calculation of medium-bound physical parameters: Hubble’s parameter, intergalactic plasma parameters, temperature of microwave background radiation and the rest mass of photons. This paper aligns the World-Universe Model (WUM) with the theoretical framework developed by Prof. P. S. Wesson, albeit assigning a new physical meaning to the fifth coordinate. In the World-Universe Model, the fifth dimension is associated with the total energy of the Medium of the World, and the gravitomagnetic parameter of the Medium serves as the dimension-transposing parameter.

In-plane dynamic Green's functions for inclined and uniformly distributed loads in a multi-layered transversely isotropic half-space

The dynamic stiffness method combined with the Fourier transform is utilized to derive the in-plane Green’s functions for inclined and uniformly distributed loads in a multi-layered transversely isotropic（TI）half-space.The loaded layer is fixed to obtain solutions restricted in it and the corresponding reactions forces,which are then applied to the total system with the opposite sign.By adding solutions restricted in the loaded layer to solutions from the reaction forces,the global solutions in the wavenumber domain are obtained,and the dynamic Green’s functions in the space domain are recovered by the inverse Fourier transform.The presented formulations can be reduced to the isotropic case developed by Wolf（1985）,and are further verified by comparisons with existing solutions in a uniform isotropic as well as a layered TI halfspace subjected to horizontally distributed loads which are special cases of the more general problem addressed.The deduced Green’s functions,in conjunction with boundary element methods,will lead to significant advances in the investigation of a variety of wave scattering,wave radiation and soil-structure interaction problems in a layered TI site.Selected numerical results are given to investigate the influence of material anisotropy,frequency of excitation,inclination angle and layered on the responses of displacement and stress,and some conclusions are drawn.

THERMAL CONSOLIDATION OF LAYERED POROUS HALF-SPACE TO VARIABLE THERMAL LOADING

An analytical method was derived for the thermal consolidation of layered, saturated porous half-space to variable thermal loading with time. In the coupled governing equations of linear thermoelastic media, the influences of thermo-osmosis effect and thermal filtration effect were introduced. Solutions in Laplace transform space were first obtained and then numerically inverted. The responses of a double-layered porous space subjected to exponential decaying thermal loading were studied. The influences of the differences between the properties of the two layers （e.g., the coefficient of thermal consolidation, elastic modulus） on thermal consolidation were discussed. The studies show that the coupling effects of displacement and stress fields on temperature field can be completely neglected, however, the the thermal responses. effect has an obvious influence on

Analytical solutions for dynamic pressures of coupling fluid-solid-porous medium due to P wave incidence

Wave reflection and refraction in layered media is a topic closely related to seismology,acoustics,geophysics and earthquake engineering.Analytical solutions for wave reflection and refraction coefficients in multi-layered media subjected to P wave incidence from the elastic half-space are derived in terms of displacement potentials.The system is composed of ideal fluid,porous medium,and underlying elastic solid.By numerical examples,the effects of porous medium and the incident wave angle on the dynamic pressures of ideal fluid are analyzed.The results show that the existence of the porous medium,especially in the partially saturated case,may significantly affect the dynamic pressures of the overlying fluid.

Optimal transmissions for space-time coded OFDM UWB systems

The emerging ultra-wideband (UWB) system offers a great potential for the design of high-speed short-range communications.Compared with great progress at physical layer,the corresponding medium access control (MAC) layer designs are naturally placed on the schedules.We focus on the optimal power load scheme,which is an integral part of the MAC layer protocol design,for UWB space-time coded (STC) orthogonal frequency-division multiplexing (OFDM) transmissions.Assumed the transmitter has perfect or partial channel stage information (CSI).Based on the optimization criteria of maximizing capacity,three kinds of power load schemes were presented with different tradeoff among performance,complexity and feedback bandwidth overhead.The proposed schemes are verified and compared under the channel prototype proposed by IEEE 802.15.3a Task Group.

基于空间三维非均匀SISO阵列雷达的介质目标快速成像算法

近年来,随着高精度定位系统的迅猛发展,基于手持式毫米波雷达的阵列成像技术在无损检测和医疗成像等涉及介质内部结构成像的领域中引起了广泛关注.与常见的二维(Two-Dimensional,2D)平面单发单收(SingleInput-Single-Output,SISO)阵列不同的是,基于手持式毫米波雷达的阵列,其阵元通常非均匀分布于三维(Three-Dimensional,3D)空间中,导致现有的基于平面SISO阵列的对介质目标内部结构进行快速成像重构的算法无法适用.为此,本文提出了一种适用于空间3D非均匀SISO阵列雷达的半空间介质目标快速成像算法.该算法将空间3D非均匀SISO阵列的每一个阵元扩展为一个的虚拟阵列,然后将所有虚拟阵列的回波数据变换至波数域后进行相干累加,最后通过3D逆傅里叶变换(Inverse Fourie Transform,IFT)实现快速成像.数值仿真和实验测量表明,与同样适用于该场景的改进后向投影(Improved Backward Projection,IBP)算法相比,在本文给定的成像参数条件下,所提算法可以在保证成像质量的同时,将成像时间缩短94%以上.

Geminga TeV晕周围星际介质的湍动特性

空间功率谱分析是研究星际介质湍动特性的常用方法。以此方法利用GALFA HI巡天数据分析Geminga附近一块中性氢云的湍动特性,其21 cm谱线积分亮温度图的空间功率谱符合幂律分布,谱指数为-4.0±0.1。与银河系内本地星际介质的功率谱(谱指数大于-3.0)相比,该云的功率谱较陡。分析陡谱的成因,排除了中性氢云在视线方向所取的速度宽度不足、云周围存在垂直于视线方向的有序磁场、能量传递过程中有损失等因素的影响。这个结果暗示Geminga周围可能存在一个区域,其内部湍动特性与银河系其他区域的湍动特性不同,进而导致了Geminga TeV晕中较低的扩散系数。

作为媒介的“红色地铁”:意识形态传播与公共空间争夺

“红色地铁”将红色文化融入地铁空间,成为主流意识形态大众化传播的重要渠道。“红色地铁”通过嵌入式“看见”、直陈式“劝服”以及流动式“捕捉”使主流意识形态进入公众日常生活,即通过空间嵌入将主流意识形态置于公众视觉审视的中心,通过空间修辞增强公众对主流意识形态的认同,通过空间延伸扩大主流意识形态的影响范围。然而地铁空间中消费主义的渗入对主流意识形态产生冲击,以传播消费主义为中心的商业广告与以传播主流意识形态为中心的“红色地铁”之间形成空间竞争,资产阶级意识形态不断通过空间渗透与社会主义意识形态进行空间争夺。为了维护社会主义意识形态的主导地位,应不断推进主流意识形态大众化传播的生活空间转向,使主流意识形态牢牢占据日常生活空间。

从技术到“材料”——互动城市空间初探

虚拟网络世界的入侵削减了城市物理空间中的具身(1)体验,20世纪中后期的思想家和艺术家们最先预感到“危机”,先锋建筑师也相继展开了实验,互动设计作为人与环境关系的新探索进入人们的视野。该文创新性提出将互动设计作为“材料”建构城市空间的观点,将当下最新的互动素材与城市空间结合,提炼出结构、界面、节点、媒介四个可以搭载互动行为的构成要素,初步建立互动城市空间体系。探索互动设计与城市空间塑造的关系,体现了一种技术城市化而非城市技术化的思想,以期实现高质量城市环境建设的人本回归。

圆月形独塔自锚式悬索桥总体设计

随着人们对展现城市地域特色的景观桥梁造型需求的不断增长,由于中等跨径自锚式悬索桥设计独特、极具艺术美感,备受选桥方案的青睐,成为城市地标。案例为圆月形独塔自锚式悬索桥,中等跨度;通过桥梁的方案造型,结构设计、计算分析等方面的简要介绍,为设计同类型的中等跨径自锚式悬桥提供经验借鉴。

基于改进的EAL边界条件的地震波场数值模拟

在地震波场数值模拟过程中,人工截断边界会产生数值反射而影响地震波场模拟的精度.应用PML(Perfectly Matched Layer)吸收边界条件是消除人工边界反射的有效手段,但是该方法计算量较大,实现较为复杂,且在某些各向异性介质中不稳定.EAL(Effective Absorbing Layer)边界条件是通过简化PML吸收边界条件的阻尼项推导出来的一种吸收边界条件.EAL的吸收项作用于波动方程的时间导数项,故EAL边界条件具有计算量小且利于并行实现的特点.应用EAL边界条件能够在保证全波形反演和逆时偏移精度的前提下,提升计算效率并降低内存消耗.本文对EAL边界条件进行两点改进:(1)引入减速阻尼项;(2)采用高斯型空间加权函数构建阻尼项.正演模拟结果表明,改进的EAL边界条件在不增加计算量和内存消耗的同时,有效提升了EAL边界条件的吸收效果且适用于复杂介质和各向异性介质.特别地,相比于PML吸收边界条件,EAL边界条件在各向异性模型中表现出良好的稳定性.

卷曲温度对中碳钢组织及力学性能的影响

在中碳钢轧制变形过程中,卷曲温度对其显微组织和力学性能有较大影响。利用拉伸试验、维氏硬度测试、金相检验及扫描电镜分析等方法对不同卷曲温度下的中碳钢进行分析。结果表明:随着卷曲温度的降低,铁素体和珠光体分布更加均匀,珠光体片层间距减小,带状级别变小,材料的强度、韧性、硬度明显变大,塑性变差。

耦合深度学习的水丰水库入库径流中长期预测方法研究

少资料地区径流中长期预测关系发电厂中长期发电量的多寡,也对电厂短期经济运行有较强的指导作用。鸭绿江流域是东北地区重要的清洁能源基地,由于朝鲜控制了鸭绿江流域超过一半的面积,但其径流数据难以与中方共享,给鸭绿江流域径流中长期预测带来一定的阻碍。以鸭绿江流域水丰水库入库径流为研究对象,分别采用相空间重构模型(局域法、全局法)、LSTM模型、小波分析-LSTM模型、耦合相空间重构(局域法、全局法)和小波分析模型共6个模型方法对水丰水库旬、月及年尺度入库径流进行中长期径流预报工作,以平均绝对误差、平均绝对百分比误差与合格率对上述6个模型的预测结果进行精度评比。结果表明,年径流预报采用耦合相空间重构(全局法)和小波分析模型;月尺度径流预报中,1月预见期1-5月采用耦合相空间重构(局域法)和小波分析模型以及小波分析-LSTM模型效果较好,而6-12月耦合相空间重构(全局法)和小波分析模型具有明显优势;1年预见期中,小波分析-LSTM模型效果较好。旬尺度径流预测,1旬预见期采用小波分析-LSTM模型效果较好,3旬预见期采用小波分析-LSTM模型或耦合相空间重构(全局法)和小波分析模型,1年预见期中耦合相空间重构(全局法)和小波分析模型有明显优势。研究将为水丰水库及下游发电厂制定中长期调度计划提供支持。

生态价值视角下中小城市山水空间城市设计策略——以宣城市彩金湖片区为例

在“绿水青山就是金山银山”理念指引下,中小城市山水空间肩负着生态保护与经济发展的多重任务,强调在保护生态环境的同时,利用生态资源禀赋做大做强城市经济,构建可持续的生态价值实现路径。基于价值转化原理,提出中小城市山水空间生态价值的核算体系、计算方法与优化路径。并以宣城市彩金湖片区城市设计实践为例,在现状生态价值核算的基础上,分别从保护自然生态格局、保持现状生态价值、提升生态衍生价值、保障生态价值可持续性4个方面,对彩金湖片区山、城、水空间关系进行优化配置,从而实现生态价值最优化的空间布局和形态,探索中小城市人、城、境、业和谐统一的城市形态与发展范式。

中小户型住宅建筑设计存在的问题及设计方法探讨

探究中小户型住宅建筑设计存在的问题及适用的设计方法,对于提升中小户型住宅舒适度、建筑使用效率具有重要作用。本文分析中小户型住宅建筑设计中平面布局、住宅灵活性、空间整合性、环境互通性及内饰等方面存在的问题,并基于建筑设计中的问题提出有效的解决策略,旨在改善现阶段中小户型住宅建筑设计效果。

可调直角管接头高压密封设计

中重型商用车液压助力转向系统的介质压力很高,甚至能达到18 MPa,这对管接头的密封性提出了很高要求。在北汽福田公司,目前用于18 MPa介质压力下的管接头密封类型有3种,包括卡套式、铜平垫式、铜平垫硫化橡胶组合垫圈式,没有单纯橡胶密封的类型。鉴于此,整合文献成果,提出一种橡胶密封的设计方法,并将其与成熟的铜平垫式管接头密封方式相组合,形成了可调直角管接头高压密封产品设计方案。经过样品试验和批量验证,可知该设计方案的密封效果良好。

间隔介质对射流侵彻间隔靶影响的数值模拟

为了研究间隔介质对聚能射流侵彻间隔靶能力的影响,运用AUTODYN软件分别对射流侵彻水和空气介质间隔靶过程进行数值模拟。主要从侵彻过程中射流形态、间隔介质形态、射流头部速度三个方面出发,对模拟结果进行分析。首先与试验结果进行对比,验证了数值模拟分析的合理性和可靠性。然后通过分析数值模拟结果,得到射流头部速度随侵彻介质距离变化的拟合公式,并得出:射流头部速度在间隔靶水介质中衰减比空气介质中高17.6%,且金属射流速度愈低,相同距离水间隔介质对射流侵彻能力的衰减效果愈明显。