油田输水管道不停输清洗

针对输水管道的生产需要和管道内部结垢情况,结合所取管道内垢样溶垢试验,采用不停输化学清洗技术。清洗后,输水压力下降、流量显著提高。在清洗过程中,加入防塌减速剂和硫化氢抑制剂,在清洗除垢的同时,很好地解决了大量污垢脱落堵塞管道及产生硫化氢气体带来的安全问题。     

滦河流域干湿变化及大尺度气候因子影响

利用经验正交函数、小波变换等方法,基于标准化降水指数分析滦河流域1957-2016年的干湿变化趋势,研究流域干湿变化典型场的时空和周期特征,并通过对比大尺度气候因子对不同典型场的影响差异,讨论滦河流域干湿变化的气候成因.结果 表明:滦河流域干湿条件在1989年发生突变,干旱有加剧趋势且在研究时段内年际干旱事件频发;流域...     

中国深水油气田工程勘察的阶段划分初探

深水油气田资源区地质环境与工程地质条件复杂,潜在及可能诱发的地质灾害类型多且危害严重,工程勘察的技术含量高、施工难度大、周期长、费用高。科学规划工程勘察阶段和各阶段任务,对实施具体深水油气田工程勘察有事半功倍的作用。通过分析深水油气田资源区的地质环境和工程地质条件的复杂性,以及勘察内容与技术手段的适用性等,阐述深水油气田工程勘察科学规划和分阶段实施的必要性,以及参照相关领域工程勘察的阶段划分,提出深水油气田开发工程勘察的阶段划分概念,给出了分阶段实施方案和流程。     

三参数小波变换瞬时属性分析及应用

针对薄层反射地震信号含有快速变化的振幅和频率分量的特点,研究了新的分析小波——三参数小波,并基于三参数小波变换提出了在相空间计算地震瞬时属性的方法.三参数小波有3个可调参数,对信号做小波分析时有很高的自由度,能够很好地匹配地震子波或给定的有效信号,三参数小波与BMSW小波或其他小波相比具有更好的时域局部化性质.实际应用...     

Ferroelectric behavior in bismuth ferrite thin films of different thickness

The ferroelectric behavior of BiFeO(3) thin films is modified by changing the film thicknesses, where the BiFeO(3) thin films with different thicknesses were grown on SrRuO(3)/Pt/TiO(2)/SiO(2)/Si(100) substrates by radio frequency sputtering. The mixture of (110) and (111) orientations is induced for all BiFeO(3) thin films regardless of their thicknesses, together with the columnar structure and the dense microstructure. Their dielectric behavior is almost independent of the film thickness where all thin films have a low dielectric loss. A giant remanent polarization of 2P(r) ≈ 156.6-188.8 μC/cm(2) is induced for the BiFeO(3) thin films in the thickness range of 190-600 nm. As a result, it is an effective way to improve the ferroelectric behavior of the BiFeO(3) thin film by tailoring the film thickness.     

苏通大桥外部变形监测体系设计

桥梁外部变形监测是运营期桥梁检查和检验的重要内容之一,可以与结构监测相互补充、相互验证,为确保桥梁的安全提供充足的技术支持.该文从讨论桥梁变形监测的重要性出发,就苏通大桥运营期变形监测体系进行详细设计.首先根据目前桥梁变形监测的现状提出了建立苏通大桥外部变形监测体系的目标;其次在充分分析苏通大桥结构组成、桥型等基础上确...     

寒冷地区汽机房自平衡通风采暖方案数值模拟

火力发电厂汽轮机房内部存在很多高温散热设备以及走向复杂的热力管道,导致大量余热聚集在机房顶部.对于此类特殊的高大空间建筑,以往研究重点多放在夏季通风状态下的余热排除,少有将此余热回收用于冬季采暖技术的研究.为研究冬季自平衡采暖方案在寒冷地区发电厂汽机房的可行性,采用CFD模拟技术进行分析.按实际汽机房空间结构建立几何模型,并在此基础上采用结构化网格进行划分,完成数值计算.对比分析汽机房冬季采暖的两种预置方案,并结合模拟结果提出采用射流口代替风机直接射流的优化方案.模拟结果表明:自平衡采暖方式能满足寒冷地区汽机房冬季供暖需求,减少汽机房内部散热器的布置;综合考虑节能与采暖效果,选用方案二的通风量;采用射流口的气流组织优于直接射流,在改善工作层平台处气流组织的同时使速度场分布更加均匀,达到较好的采暖效果.模拟结果从余热利用角度为寒冷地区高大厂房的采暖方案设计提供有益的参考.     

Multilevel Structure Engineered Lead-Free Piezoceramics Enabling Breakthrough in Energy Harvesting Performance for Bioelectronics

The prevalence of wearable/implantable medical electronics together with the rapid development of the Internet of Medicine Things call for the advancement of biocompatible, reliable, and high-efficiency energy harvesters. However, most current harvesters are based on toxic lead-based piezoelectric materials, raising biological safety concerns. What hinders the application of lead-free piezoelectric energy harvesters (PEHs) is the low power output, where the key challenge lies in obtaining a high piezoelectric voltage constant (g₃₃) and harvesting figure of merit (d₃₃ × g₃₃). Here, micron pores are introduced into phased boundary engineered high-performance (K, Na)NbO₃-based ceramic matrix, resulting in the state-of-the-art g₃₃ and the highest d₃₃ × g₃₃ values of 57.3 × 10⁻³ Vm N⁻¹ and 20887 × 10⁻¹⁵ m² N⁻¹ in lead-free piezoceramics, respectively. Concomitantly, ultrahigh energy harvesting performances are obtained in porous ceramic PEHs, with output voltage and power density of 200 V and 11.6 mW cm⁻² under instantaneous force impact and an average charging rate of 14.1 µW under high-frequency (1 MHz) ultrasound excitation, far outperforming previously reported PEHs. Porous ceramic PEHs are further developed into wearable and bio-implantable devices for human motion sensing and percutaneous ultrasound power transmission, opening avenues for the design of next-generation eco-friendly WIMEs.     

Enhanced ferroelectricity of CaBi2Nb2O9-based high-temperature piezoceramics by pseudo-tetragonal distortion

(LiBi)-doped CaBi₂Nb₂O₉ (CBN) ceramics were synthesized by the conventional solid-state sintering method. The effects of (LiBi) additives on the crystalline structure were explored by Rietveld refinements. The results showed that pseudo-tetragonal distortion was induced by (LiBi) additives when x ≥ 0.35. This structural distortion increased the spontaneous polarization along a-axis and decreased the quits spontaneous polarization along b-axis, which was beneficial to the polarization switching, thus promoting the ferroelectricity and decreasing the coercive field (E_C) of CBN based ceramics. The Ca_0.60(Li_0.5Bi_0.5)_0.40Bi₂Nb₂O₉ (CBNLB-40) ceramics possess the optimum ferroelectric property with 2P_r of 10 μC/cm² and a coercive field (E_C) lower than 100 kV/cm. Moreover, it exhibits a good ferroelectric fatigue-free property within 10⁷ switched cycles. This work may provide a new method to promote the performance of Aurivillius ferroelectric-based non-volatile memory devices.