Large increase of Curie temperature in (110)-oriented La0.7Sr0.3MnO3 films

From the perspectives of scientific researches and practical applications, it is desirable to explore high operating temperature ferromagnetic films. The effect of biaxial strain on magnetic properties of (110)-oriented La_0.7Sr_0.3MnO₃ films was studied. High quality La_0.7Sr_0.3MnO₃ films were grown on (110)-oriented perovskite single crystal substrates using pulsed laser deposition, varying substrate-induced misfit strains from ??2.27–0.75%. A remarkable enhancement of Curie temperature has been achieved for (110)-oriented La_0.7Sr_0.3MnO₃ films clamped with small misfit strains (i.e., grown on LAST (110)). The enhanced Curie temperature of (110)-oriented La_0.7Sr_0.3MnO₃ films could be attributed to the misfit strain between the films and the underlying substrates and may have technological implication for applications at high temperature environments.     

湿式摩擦副滑摩过程温度场分析及实验验证

湿式摩擦副滑摩过程温度场与应力场相互耦合作用,温度场分布受到多种因素影响,其中压力、旋转速度、润滑流量作为湿式摩擦副工作参数对其温度场的影响尤为显著。在理论分析基础上,采用有限元数值模拟分析与实验研究相结合的方法,对摩擦界面温度场时空分布特性进行研究,同时研究界面温度场在摩擦副工作压力、相对转速和润滑流量作用下的变化规律。研究表明:在对偶钢片和摩擦片近外径侧更易出现高温和应力集中区,且对偶钢片相对于摩擦片更易出现温度和应力分布不均匀情况;温度场中高温集中区与应力场中应力集中区相对应,最大温度随着压力增加、相对转速增大、润滑流量减少而显著上升,该结果得到试验结果的验证。     

关于信息化测绘时代工程测量发展的思考

如今我国信息化技术全面发展，尤其对于工程测量工作领域来讲，不管是在工程建设和管理方面都产生不小的支撑引导效用。由此，笔者具体结合如今工程建设信息化测绘核心任何以及设备布置细节，进行结构整体安全管理周期和周边地理空间信息技术发展能效整理解析，试图将工程测量最新发展机遇和技术挑战问题处理完全。希望能够借此为日后一定时期范围内相关工程测量规划主体提供合理指导性建议内容，最终为我国各类工程事业可持续发展前景绽放奠定深刻适应基础。     

基于振动实测的非均质地层钻头失效分析与对策

四川盆地作为国内页岩气开发的重点区域,通过近几年的不断攻关和实践,机械钻速得到了提高,但由于受地层复杂、可钻性差、非均质性强等地质因素的影响,导致井下钻柱系统不良振动剧烈,容易出现钻头损坏严重、钻速较低等问题,严重影响了钻井时效。为了解决上述难题,以该盆地涪陵工区上二叠统龙潭组—中二叠统茅口组为例,采用井下振动高频测量工具的实测手段,测量了钻头—钻柱系统的动态振动加速度参数,结合地层的岩性和矿物组分分析,研究钻头失效原因与对策,并开展了现场试验。研究结果表明:①在非均质地层中钻进的钻头—钻柱系统产生了大于40 m/s~2的高幅值瞬时冲击振动,高幅值的瞬时冲击是导致钻头先期失效的主要原因;②提出了抑制高幅值的瞬时冲击振动采用"减振+增压"工具组合和避免井下工具共振的钻井参数;③采用钻井新参数的试验井比邻井的高幅值瞬时振动降低了17%,单只钻头进尺增加24%,钻头工作环境得到了较大的改善,钻头使用数量减少。结论认为,该研究成果能够有效地改善钻头—钻柱系统的振动状态,有利于达成延长钻头使用寿命的目标。     

某高校既有建筑室内人员相关VOCs目标污染物的实测分析

为研究高校既有建筑室内人群散发对室内VOCs的影响，对高校不同人群样本的教室及会议室两类典型人群密集房间，共82个人群样本对象进行了VOCs采样分析，得到不同实际场景下的人员相关的VOCs浓度水平，并对其潜在的影响因素进行分析。结果表明，共确认了29种与室内人员相关的高检出率且较高浓度值的物质，包括芳香族化合物9种，烷烯烃类9种，酮类和醛类8种，醇酯类以及卤化物3种，并得到主要VOCs物质的浓度水平和I/O比。对影响因素的统计分析表明，室内人员密度、季节和房间类型对不同VOCs物质存在显著性影响，其中季节性因素对目标VOCs污染物影响最为广泛，其次是房间类型与室内人员密度。该研究可为进一步了解人员密集室内VOCs污染现状及控制策略提供一定的科学参考。     

Assessment of local strain field in adhesive layer of an unsymmetrically repaired CFRP panel using digital image correlation

The present study focuses on experimental investigation of through the thickness displacement and strain field in thin adhesive layer in single sided (unsymmetrical) patch repaired CFRP (carbon fiber reinforced polymer) panel under tensile load. Digital image correlation (DIC) technique is employed to acquire the displacement and strain (longitudinal, peel and shear) field. Experimental determination of shear transfer length based on shear strain field obtained from DIC is introduced to estimate the optimum overlap length which is an essential parameter in patch design for the repair of CFRP structures. Further, DIC experiment with magnified optics is performed to get an insight into complex and localized strain field over thin adhesive layer especially at critical zones leading to damage initiation. The failure mechanism, load displacement behavior, damage initiation and propagation are closely monitored using DIC. The influence of patch edge tapering on strain distribution in adhesive layer is also investigated. The DIC successfully captures the global and localized strain field at critical zones over thin adhesive layer and further helps in monitoring the damage based on strain anomalies. Strains are found to have maximum magnitude at the patch overlap edge and the shear strain level in adhesive layer is higher than the peel strain. Normal tapering increases the peel strain and has negligible influence on shear strain level in adhesive layer. The recommended overlap length is found to be consistent with the recommendation in the literature. Whole field strain pattern and the overlap length obtained from experiment are further compared with the finite element analysis results and they appear to be in good coherence.     

Enhanced piezoelectric strain of BiFeO3–Ba(Zr0.02Ti0.98)O3 lead-free ceramics near the phase boundary

The xBiFeO₃-(1-x)Ba(Zr_0.02Ti_0.98)O₃ + 1.0 mol% MnO₂ (xBF-BZT) lead-free piezoelectric ceramics were prepared by conventional solid-state reaction method. The structure, dielectric, and piezoelectric properties were studied. X-ray diffraction (XRD) analysis showed that xBF-BZT ceramics exhibited pure perovskite structure with the coexistence of tetragonal and rhombohedral phases (0.66 ≤ x ≤ 0.74). The Curie temperature T_c, the dielectric constant ε_r (1 kHz), dielectric loss tanδ (1 kHz), piezoelectric constant d₃₃, coercive field E_c (80 kV/cm), and remnant polarization P_r (80 kV/cm) of 0.7BF-0.3BZT-Mn ceramics were 491°C, 633, 0.044, 165 pC/N, 35.6 kV/cm, and 22.6 μC/cm², respectively. The unipolar strain of 0.7BF-0.3BZT reached up to 0.20% under the electric field of 60 kV/cm, which is larger than that (0.15%) of BiFeO₃–BaTiO₃ ceramics. These results indicated that the xBF-BZT ceramics were promising candidates for high-temperature piezoelectric materials.     

硫化物预处理方法研究及测定中的质量保证

针对水和废水中硫离子的特点,设计制作了测定硫化物的酸化—吹气—吸收预处理装置,并验证了该装置对硫化物的回收效果,简化了原来的预处理方法。总结分光测定过程中注意的若干事项,确定了最佳实验条件,使该方法具有更准确、简便、快速的特点。     

光纤布拉格光栅的无源温度补偿

分析了通过施加应变补偿光纤布拉格光栅(FBG)中心波长随温度漂移的原理，给出了一种新型的无源温度补偿的方法和相应的实验结果。该方法采用了两种不同热膨胀系数的金属，对光栅先施加预应变。在0-60℃范围内，中心波长仅偏移了0．02nm。