PMN-PT弛豫型铁电材料的凝固组织与相结构

采用熔融法制备了PMN－32PT弛豫型铁电晶粒，研究了自由凝固条件下PMN－32PT晶体的生长形貌、组织形态、相结构和择优生长方向。结果表明，自由凝固条件下，从熔体中生长出的PMN－32PT晶体一般呈现三棱柱和八面体两种形态；PMN－32PT晶体的择优生长方向为＜211＞晶向；凝固过程中熔剂不足会引起组分中MgO的优先树枝状结晶；生长速度对PMN－32PT晶体的完整性有较大影响，生长速度过快会导致熔剂夹杂。     

Intermetallic phase formation and evolution during homogenization and solution in Al-Zn-Mg-Cu alloys

The effects of major alloy element contents of Zn, Mg, Cu in Al-Zn-Mg-Cu alloys on the formation and evolution of intermetallic phases during casting, homogenization and solution treatment have been investigated through using X-ray diffraction, scanning electron microscopy and differential scanning calorimetry. Experimental results showed that a relatively higher Zn content with lower Mg and Cu contents was beneficial to the formation of MgZn₂ phase instead of the Al₂CuMg phase, which resulted in the unicity of the intermetallics in the Al matrix, and that the MgZn₂ phase was easier for diffusion and dissolution during homogenization and solution than the Al₂CuMg phase. Additionally, the results of the first-principles calculations gave support for explaining the experimental phenomena. A larger absolute value of formation enthalpy and a smaller value of binding energy of the MgZn₂ phase, as compared with the Al₂CuMg phase, give it priority to precipitate during casting and make it easier to re-dissolve during homogenization and solution treatment. What’s more, higher elastic constants with severe anisotropy of Young’s modulus make undissolved blocks of Al₂CuMg phase act as crack initiation, which degrade the performance of the materials.     

煤层断层构造演化应力场分布特征数值模拟研究

采用有限元数值模拟软件ADINA,模拟了一次构造作用下煤层断层构造的形成过程以及煤层断层形成后受现代构造应力场作用下煤层的破坏情况及地应力的分布规律.模拟结果表明,一次构造作用下煤层断层构造的形成过程中,在接近断层面的下盘煤层底部和接近断层面的上盘顶部,煤体容易遭到破坏;断层构造形成后在不同的铅直应力和水平应力组合情况下,正逆断层的下盘断层面附近区域均存在应力集中现象,逆断层的应力场方向主要由最大应力的方向决定,而正断层仅在水平应力与铅直应力比较接近时,应力场方向主要由铅直应力决定.     

An improved modeling of precipitation phase and snow in the Lancang River Basin in Southwest China

Precipitation phase(e.g., rainfall and snowfall) and snow(e.g., snowpack and snowmelt runoff) in high-mountain regions may largely affect runoff generation, which is critical to water supply, hydropower generation, agricultural irrigation, and ecosystems downstream. Accurately modeling precipitation phase and snow is therefore fundamental to developing a better understanding of hydrological processes for high-mountain regions and their lower reaches. The Lancang River(LR, or the Upper Mekong River)in China, among the most important transboundary rivers originating from the Tibetan Plateau, features active dam construction and complex water resources allocation of various stakeholders in Southeast Asian countries under climate change. This study aims to improve precipitation phase and snow modeling for the LR basin with a hydrological model and multisource remotely sensed data. Results show that joint use of the Moderate Resolution Imaging Spectroradiometer(MODIS) land surface temperature product with high spatial resolution(1 km×1 km) and an air temperature product can more precisely distinguish precipitation phase than air and wet-bulb temperature products in the LR basin. Snowfall and snowmelt were found to be controlled primarily by rainfall and snowfall temperature thresholds in snow modeling. The rainfall and snowfall temperature thresholds derived from the hydrological model through calibration with remotely sensed snowpack at basin scales were considerably lower than those derived from in situ observations. Rainfall and snowfall temperature thresholds derived from in situ observations could lead to the overestimation of snowmelt runoff due mostly to the lack of representation of point-based measurements at basin scales. This study serves as a basis for better modeling and predicting snow for the LR basin and potentially other similar basins globally.     

利用耦合腔中的原子一步实现非传统几何相位门

利用囚禁在耦合腔中的三能级原子一步实现了两比特非传统几何相位门.在门操作期间,原子态不演化,而腔模在相空间中沿着一个闭合路径移动,从而获得一个高保真的非传统几何相位门.此方案不需要额外的单量子比特操作,一步完成几何相位门的构建,极大地简化了实验步骤;同时大失谐条件有效地抑制了原子自发辐射,使得方案更具有鲁棒性.数值模拟表明,此方案可以实现高保真度的相位门.     

数据场理论在互联网络拓扑建模中的应用

通过对数据场理论的研究以及互联网络拓扑研究现状的分析,将势函数引入到拓扑建模当中,尝试利用节点拓扑势作为依据衡量节点在网络中的重要性进行节点分类,并给出了一个体现互联网络层次性特征的拓扑生成算法.通过实验,证明了将数据场理论应用到拓扑建模研究中具有可行性.     

新筑冻土路堤温度场的变化过程

采用有限单元法，通过综合考虑各种边界条件及模拟路堤修筑的蓄热作用，对路堤修筑后温度场逐年变化过程进行了计算研究，得到了不同高度路基温度场年稳定变化的年限及逐年变化较大的年限、融土核存在及变化规律，指出浅层土温度分布的非对称性有冬季强、夏季弱的特点，通过最低和最高温度的比较发现，深层土温度变化滞后于表层土及气温约5个月。     

基于水沙床耦合的滩槽冲淤模拟与疏浚量计算

为了提高疏浚量的预报准确度,将平面二维水沙床耦合数值模型应用于长江下游东流水道的滩槽演变和疏浚量计算,成功复演了2010年大水作用下主要的滩槽冲淤特征,西港航槽内计算疏浚量与实测疏浚施工方量的误差较小. 分析影响疏浚量计算不确定性的主要因素. 结果表明,计算网格尺寸对计算疏浚量有较大的影响,当网格尺度约等于或小于实测地形数据间隔时,计算疏浚量较一致,否则网格给疏浚量计算带来较大的不确定性;进口泥沙体积分数对计算疏浚量的影响较大.     

In-situ observation and modeling approach to evolution of pore-fracture structure in coal

The characterisation of the pore-fracture structure(PFS) and its evolution in coal during mining are essential for preventing gas outbursts and improving gas extraction efficiency. In this study, the evolution of the PFS in coal samples under the condition of mining stress was directly captured in situ by combination of the mechanical testing system with high-precision visualisation nuclear magnetic resonance equipment. A fractional derivative model was established to describe the relationship b...     

塔里木盆地巴楚组层序地层及沉积演化

为了揭示塔里木盆地巴楚组层序地层样式和沉积演化规律,运用沉积学原理和层序地层学原理,通过对录井、测井和地震资料的分析,建立了巴楚组层序地层格架并对沉积演化规律进行了研究.结果表明:巴楚组发育了SQb1和SQb2两个层序,每个层序均可划分出海侵体系域(TST)和高位体系域(HST),各层序的地层分布范围逐层扩展超覆.沉积环境主要为浅海、临滨、前滨、后滨、滨岸沙丘及碳酸盐浅滩,从巴楚组沉积早期至晚期持续存在陆源碎屑与内源沉积物混积的沉积特征,总体具有由早期陆源碎屑沉积体系为主向晚期碳酸盐岩台地占优势的相带演化趋势.陆表海的古地貌和总体海侵的背景控制了巴楚组层序发育和沉积演化.     

QFP器件激光软钎焊温度场的建模与仿真

为了解决不同工艺参数组合下激光焊接 QFP器件后其器件的温度场分布问题,选取激光焊接有效功率、时间和光斑面积3个工艺参数,采用有限元软件 ANSYS,对特定 QFP 器件激光软钎焊温度场的分布进行模拟。仿真结果表明：激光焊接有效功率、光斑面积与焊点处的最高温度几乎为线性关系,焊接时间与焊点处的最高温度为正相关关系,且切线斜率逐渐减小;当焊接有效功率为1-4 W,焊接时间为1-2 s,光斑面积为0.03-0.11 mm2,封装体、印制板、焊点温度最高分别可达240、350、510℃。仿真结果为激光软钎焊工艺参数的预选提供参考,并为相关产品激光软钎焊的综合参数优化打下基础。     

GPU-accelerated phase field simulation of directional solidification

The phase field simulation has been actively studied as a powerful method to investigate the microstructural evolution during the solidification.However,it is a great challenge to perform the phase field simulation in large length and time scale.The developed graphics processing unit(GPU)calculation is used in the phase filed simulation,greatly accelerating the calculation efficiency.The results show that the computation with GPU is about 36 times faster than that with a single Central Processing Unit(CPU)core.It provides the feasibility of the GPU-accelerated phase field simulation on a desktop computer.The GPU-accelerated strategy will bring a new opportunity to the application of phase field simulation.     

鄂尔多斯盆地中部上古生界沉积相演化

利用钻井资料和地质资料对鄂尔多斯盆地上古生界沉积相演化进行详细的研究,分析了本溪期 (海侵)、太原期(海侵扩大)、山西期(海退)、石盒子期(海陆交互)和石千峰期(陆缘湖泊)等5个时期的古 地理环境、岩石类型、沉积相类型和平面展布特征,得出这5个时期在盆地内构成了一个海侵海退旋回,形 成了从滨浅海相到海陆过渡的三角洲相、河流湖泊相陆源沉积。控制生成了三角洲相分流河道砂砾岩、水 下分流河道砂砾岩以及潮坪相砂坝等有利储集岩带,潮坪相发育的煤系地层为烃源岩,上石盒子组洪泛平 原形成泥质岩盖层。生油岩和储集岩叠置或互侧式组合关系,形成本区受砂体分布控制的岩性气藏。     

双光子Jaynes-Cummings模型中场熵的演化特性

研究了双光子Jaynes-Cummings模型中,在原子处于相干迭加态、场处于相干态时场熵的演化规律,进而给出了JCM模型中光场与原子耦合时,在共振条件下系统任意时刻的态势情况下场墒的演化特性.通过解析式和图表分析了初始光场平均光子数n和耦合常数g对场熵演化的影响,给出了教为确切的结论.     

Phase field modeling for dendritic morphology transition and micro-segregation in multi-component alloys

By using the phase field model for the solidification of multi-component alloys and coupling with real thermodynamic data, the dendritic morphology transition and the dendritic micro-segregation of Ni-Al-Nb ternary alloys are simulated in two cases, i.e., varying the alloy composition at a fixed under-cooling and varying the undercooling at a fixed alloy composition. The simulated results indicate that with the increase of the dimensionless undercooling U (U=ΔT/ΔT0, where ΔT is the undercooling and ΔT0 the temperature interval between the solidus and liquidus), the dendritic morphology transfers from dendritic to globular growth in both cases. As to the dendritic micro-segregation, both cases present a regularity of increasing at first and then decreasing.     

掘进工作面前方力学场动态耦合演化规律

以登槽煤矿为试验矿井,采用现场试验和数值模拟方法对掘进工作面前方力学场进行动态观测分析和模拟,获得了力学场的分布规律,揭示了不同力学场之间耦合演化控制机理。结果显示:分步匀速掘进的煤层巷道前方瓦斯压力呈现典型的三带特征,循环向前推移,瓦斯压力场对地应力场具有一致的动态耦合响应特征;卸压区瓦斯压力场响应滞后地应力场1~2 m,压力升高带和原始压力带基本一致;工作面前方的地应力峰值随工作面推进呈波浪式向前移动,且峰值应力逐渐增大至临界值;瓦斯压力分布受地应力大小、煤体结构和掘进速度影响。     

基于内力的卫星编队飞行动力学建模

基于内力的卫星编队飞行凭借良好的性能正日益受到重视,但由于该类编队的控制力对卫星间的相对位置和相对姿态均高度敏感,并且控制力和控制力矩之间存在耦合,给动力学建模带来了很大的挑战.首先,建立了六自由度的内力编队姿轨耦合动力学模型,该动力学模型利用了控制力和控制力矩的耦合效应,可以同时针对编队卫星的相对位置和相应姿态设计相应的控制律,从而实现编队的六自由度协同控制.最后,通过采用伪谱法求解编队构型的重构问题,对该动力学模型进行了验证.     

太原西山二叠系山西组沉积微相及其演化规律

在对太原西山地区山西组野外露头实地观测的基础上,通过采样分析、薄片镜下观测和粒度分析等手段,对太原西山地区二叠系山西组沉积微相发育特征及其演化规律进行研究。结果表明:太原西山地区二叠系山西组主要为河控三角洲沉积,可进一步划分为两个亚相和七个微相。伴随着研究区山西组沉积期海水总体由北西向南东退去,沉积环境从三角洲前缘过渡为三角洲平原沉积;沉积微相呈现出由分支河口沙坝微相→水下分支河道微相→水下天然堤→支流间湾微相→沼泽微相→陆上分支河道微相→陆上天然堤微相→沼泽微相的演化规律。     

龙门地热田温热水成因探讨

根据地面调查和勘探资料,作者系统地分析了龙门地热田的构造特点、温热水的分布及水化学特征,指出龙门地热田温热水的分布具有两个特点一是在地热田的南部主要受F1断层的控制呈线状分布;二是在地热田的北部由于F41断层与F1断层相交和滑动构造(HF3)的共同作用,呈面状分布.温热水的形成是热源、构造、盖层以及热储层等因素最佳配套的产物.地热田的南部,沿F1断层带是寻找温热水的主要场所;北部、北西部,F1断层带、F41断层带、滑动构造(HF3)分布区均是温热水赋存的有利地段.     

龙门地热田温热水成因探讨

根据地面调查和勘探资料,作者系统地分析了龙门地热田的构造特点、温热水的分布及水化学特征,指出龙门地热田温热水的分布具有两个特点:一是在地热田的南部主要受F1断层的控制呈线状分布;二是在地热田的北部由于F41断层与F1断层相交和滑动构造(HF3)的共同作用,呈面状分布.温热水的形成是热源、构造、盖层以及热储层等因素最佳配套的产物.地热田的南部,沿F1断层带是寻找温热水的主要场所;北部、北西部,F1断层带、F41断层带、滑动构造(HF3)分布区均是温热水赋存的有利地段.