2.3–21 GHz broadband and high linearity distributed low noise amplifier

This paper focuses on the design of a 2.3–21 GHz Distributed Low Noise Amplifier (LNA) with low noise figure (NF), high gain (S₂₁), and high linearity (IIP3) for broadband applications. This distributed amplifier (DA) includes S/C/X/Ku/K-band, which makes it very suitable for heterodyne receivers. The proposed DA uses a 0.18 μm GaAs pHEMT process (OMMIC ED02AH) in cascade architecture with lines adaptation and equalization of phase velocity techniques, to absorb their parasitic capacitances into the gate and drain transmission lines in order to achieve wide bandwidth and to enhance gain and linearity. The proposed broadband DA achieved an excellent gain in the flatness of 13.5 ± 0.2 dB, a low noise figure of 3.44 ± 1.12 dB, and a small group delay variation of ±19.721 ps over the range of 2.3–21 GHz. The input and output reflection coefficients S₁₁ and S₂₂ are less than −10 dB. The input compression point (P_1dB) and input third-order intercept point (IIP3) are −1.5 dBm and 11.5 dBm, respectively at 13 GHz. The dissipated power is 282 mW and the core layout size is 2.2 × 0.8 mm².     

致密砂岩油藏能量补充方式评价及优化

针对致密砂岩油藏大规模体积压裂开发后能量补充困难的问题,利用自主设计制作的大型人造三维岩心物理模型和物理模拟实验舱,开展致密砂岩油藏能量补充方式优化研究。实验结果表明:致密砂岩油藏压裂开发过程中,地层能量损耗严重,采取注水或注气的方式可有效进行能量补充;地层中裂缝规模越大,越有利于原油渗流,后续补充能量的传播范围越广,有助于进一步提高原油采收率;从提高驱油效率和扩大波及系数方面优选吞吐渗吸介质,CO₂均优于活性水,CO₂吞吐开发在矿场试验中取得了显著的增油效果,因此,CO₂吞吐作为一种有效的能量补充方式在致密油开发中展现了良好的应用前景。该文分析了致密砂岩储层水平井压裂开发的渗流规律,优选出致密砂岩储层大规模压裂开发后最佳渗吸介质,可为致密砂岩油藏开发设计提供重要的理论依据。     

建筑结构控制爆破拆除的力学分析与应用

应用运动学、动力学理论建立建(构)筑物控爆坍落过程的力学模型,进而研究在非定常约束条件下坍落结构的力学特征。首次提出了采用延时起爆技术时,非自由质点系及其广义坐标应是建立在每一段位上的瞬间虚位移。在此基础上,分析求解运动过程中时控单元的质点自由度,为精确选定爆破部位及时序提供了设计理论和计算依据。同时,结合振动理论,将控爆时差、结构载荷分布调制为振动系统,形成坍落结构梁板单元的强迫振动,充分实现在运动中进一步解体、破碎其自身结构,并形成具有明显缓冲效果的下落过程。应用实践结果证明力学分析是正确的,为工程结构爆破拆除计算机辅助设计及动态模拟技术的有效应用奠定了基础。     

基于FLAC3D的破碎围岩巷道支护效果分析

为了解破碎围岩分别采用锚杆支护、锚喷支护以及锚喷+锚索耦合三种支护方式下的支护效果,进而为破碎围岩巷道选择合理的支护方式提供参考。通过借助FLAC^3D软件建立数值模型,分析不同支护条件下的破碎围岩巷道位移量、应力分布以及塑性区的时空演化特征。结果表明,采用锚喷+锚索耦合支护时,可以较好的控制巷道围岩的位移量、减小应力集中效应、缩小塑性区的影响范围。     

基于VMD和BSA-KELM的高陡边坡位移预测模型研究

边坡位移的时间序列曲线存在复杂的非线性特性,传统的预测模型精度不足以满足预测要求。为此提出了基于变分模态分解的鸟群优化-核极限学习机的预测模型,并用于河北省某水泥厂的边坡位移预测。该方法首先采用VMD把边坡位移序列分解为一系列的有限带宽的子序列,再对各子序列分别采用相空间重构并用核极限学习机预测,采用鸟群算法优化相空间重构的嵌入维度和KELM中惩罚系数和核参数三个数值,以取得最优预测模型。最后将各个子序列预测值叠加,得到边坡位移的最终预测值。结果表明：和KELM、BSA-KELM、EEMD-BSA-KELM模型相比,基于VMD的BSA-KELM预测精度更高,为边坡位移的预测提供一种有效的方法。     

温州某公轨共建高架车站结构设计

为了解决城市廊道资源的紧张和公共交通发展需求的矛盾,出现了轨道交通和快速路的共建型式,即公轨共建的复合型交通模式,以温州市域铁路S2线一期工程的人民路站为例,研究公轨共建高架车站的结构设计要点。首先,为降低浅层气体对桩基的承载力及沉降影响,对遇到局部浅层气体发育的基础设计提供了合理的解决方案。然后针对公轨共建一体化车站分别进行了多遇和罕遇地震作用分析,研究表明构件及整体指标满足规范要求。最后针对工程的一些关键技术,如快速路桥面体系的选型、超长结构温度应力的控制措施、轨道梁挠度及应力的控制、快速路桥面振动对车站的影响等进行了分析,并给出了具体的解决方案和指导意见。     

Control of viscous fingering and mixing in miscible displacements with time-dependent rates

In miscible displacements encountered in enhanced oil recovery processes, the unfavorable viscosity contrast between injected solvent and oil usually leads to viscous fingering (VF), a hydrodynamic instability which may result in a lower sweep efficiency and oil recovery. This phenomenon can be observed in a wide range of flows in subsurface porous media. This study examined a simple cyclic time-dependent displacement rate and its effects on the onset and longer development of VF. It is found that such varying displacement rate can either stabilize or destabilize VF, depending on the cycle period, amplitude, and displacement scenarios. The most important mechanism is that such time-dependent rate can effectively change the competition between convection (destabilizing effect) and dispersion (stabilizing effect). This is different from the widely used constant injection rate where the flow instability is actually determined by the Peclet number and mobility contrast for a given scenario. This study therefore provided a new aspect to control VF, either enhance or reduce, with low additional costs. It is therefore both scientifically and practically important for a wide range of flows in subsurface porous media. © 2017 American Institute of Chemical Engineers AIChE J, 65: 360–371, 2019     

核磁共振方法研究油水过渡带驱替特征

目前,利用常规手段难以对低含油饱和度油水过渡带进行开采,利用气驱及化学驱方式开采仍具有开发潜力,但对于不同类型的油水过渡带,其开发机理不明确。开展4组天然岩心驱替实验,利用核磁共振技术研究不同类型油水过渡带中剩余油的启动机理和主要分布状态,在此基础上研究油水过渡带的开发特征。实验结果表明,气驱开发方式更适用于低渗岩心;化学驱的乳化及降低表面张力作用对小孔隙中剩余油有较好的动用程度,提高采收率效果显著。     

Evaluation of Robustness of the Biosurfactant Derived from Balanites aegyptiaca (L.) Del.

Balanites aegyptiaca (L.) Del. is a widely distributed xerophytic multipurpose tree. The mesocarp of the fruit of B. aegyptiaca has detergent properties due to the presence of saponins. The stability potential of this biosurfactant at varying pH, temperature, and salinity has not been explored so far. In the present study, the relative surface tensions of five different concentrations of the biosurfactant were studied at different temperatures, salinity, and under pH conditions. This study reveals that this biosurfactant retains its activity over a wide range of pH (3–11) and at high salinity (7% NaCl). It is a thermostable cationic surfactant; surfactant activity was recorded even at 100 °C with the lowest relative surface tension of 0.47. High oil displacement (18.00 mm) was observed when studied with petrol. This biosurfactant was found to have a high emulsification index (E₂₄) of 70% with mustard oil. These results indicate that biosurfactant derived from B. aegyptiaca may find use in a wide range of sectors such as textile, food, cosmetics, oil recovery, and healthcare under a wide range of physical and chemical conditions. It offers an efficient, economically viable, and plant-derived alternative to synthetic detergents and adds a way to maintain a sustainable environment.