Experimental evaluation on well pattern adaptability of ultra-low permeability reservoir using sandstone flat model

As for ultra-low permeability reservoir,the adaptability of common nine-spot well pattern is studied through large-scale flat models made by micro-fractured natural sandstone outcrops.Combined with non-linear porous flow characteristics,the concept of dimensionless pressure sweep efficiency and deliverability index are put forward to evaluate the physical models' well pattern adaptability.Through experiments,the models' pressure distribution is measured and on which basis,the pressure gradient fields are drawn and the porous flow regions of these models are divided into dead oil region,non-linear porous flow region,and quasi-linear porous flow region with the help of twin-core non-linear porous flow curve.The results indicate that rectangular well pattern in fracture reservoirs has the best adaptability,while the worst is inverted nine-spot equilateral well pattern.With the increase of drawdown pressure,dead oil region decreases,pressure sweep efficiency and deliverability index increase; meantime,the deliverability index of rectangular well pattern has much more rational increase.Under the same drawdown pressure,the rectangular well pattern has the largest pressure sweep efficiency.

Flatness predictive model based on T-S cloud reasoning network implemented by DSP

The accuracy of present flatness predictive method is limited and it just belongs to software simulation. In order to improve it, a novel flatness predictive model via T-S cloud reasoning network implemented by digital signal processor(DSP) is proposed. First, the combination of genetic algorithm(GA) and simulated annealing algorithm(SAA) is put forward, called GA-SA algorithm, which can make full use of the global search ability of GA and local search ability of SA. Later, based on T-S cloud reasoning neural network, flatness predictive model is designed in DSP. And it is applied to 900 HC reversible cold rolling mill. Experimental results demonstrate that the flatness predictive model via T-S cloud reasoning network can run on the hardware DSP TMS320 F2812 with high accuracy and robustness by using GA-SA algorithm to optimize the model parameter.

Flashover Characteristics of Flat Plate Model Under DC Voltage in Wind-sand Condition

The influence of sand dust on discharge of external insulation has caused widespread concern.At present,the research results show wind-sand electricity has a remarkable effect on the discharge characteristics of insulator and has little influence on the discharge characteristics of air gap.The flashover of insulator strings occurs along the insulator surface and air gaps,and the sand dust deposited on the insulator surface may affect the flashover characteristics of insulator strings.This paper studies the flashover characteristics of flat plate model under DC voltage in wind-sand condition.The experimental results show that under positive polarity voltage,the flashover voltage of the flat plate model has a maximum value,while under negative polarity voltage,the flashover voltage of the flat plate model has a minimum value with a certain degree of sand dust deposition.The wind or sand in sand-dust weather has an important effect on the flashover characteristics of the flat plate model.In certain variation range of electric charge,electric charge of sand dust has little effect on the flashover voltage of flat plate model under DC voltage.The deposition of sand has significant influence on the flashover process of flat plate model,which is related to the deposition density and moisture content of sand particle.

The electronic structure of Nb＿3Al/Nb＿3Sn, a new test case for flat/steep band model of superconductivity

In this work, we choose Nb3Al/Nb3Sn as a new test case for flat/steep band model of superconductivity. Based on the density functional theory in the generalized gradient approximation, the electronic structure of Nb3Al/ Nb3Sn has been studied. The obtained results agree well with those of the earlier studies and show clearly fiat bands around the Fermi level. The steep bands as characterized in this work locate around the M point in the first Brillouin zone. The obtained results reveal that Nb3Al/Nb3Sn fits more to the ＂Flat/steep＂ band model than to the van-Hove singularity scenario. The fiat/steep band condition for superconductivity implies a different thermodynamic behavior of superconductors other than that predicted from the conventional BCS theory. This observation sets up an indicator for selecting a suitable superconductor when its large-scale industrial use is needed, for example, in superconducting maglev system or ITER project.

Itinerant Topological Magnons in SU (2) Symmetric Topological Hubbard Models with Nearly Flat Electronic Bands

We show that a suitable combination of flat-band ferromagnetism,geometry and nontrivial electronic band topology can give rise to itinerant topological magnons.An SU(2) symmetric topological Hubbard model with nearly flat electronic bands,on a Kagome lattice,is considered as the prototype.This model exhibits ferromagnetic order when the lowest electronic band is half-filled.Using the numerical exact diagonalization method with a projection onto this nearly flat band,we can obtain the magnonic spectra.In the flat-band limit,the spectra exhibit distinct dispersions with Dirac points,similar to those of free electrons with isotropic hoppings,or a local spin magnet with pure ferromagnetic Heisenberg exchanges on the same geometry.Significantly,the non-flatness of the electronic band may induce a topological gap at the Dirac points,leading to a magnonic band with a nonzero Chern number.More intriguingly,this magnonic Chern number changes its sign when the topological index of the electronic band is reversed,suggesting that the nontrivial topology of the magnonic band is related to its underlying electronic band.Our work suggests interesting directions for the further exploration of,and searches for,itinerant topological magnons.

Numerical Tidal Current Modeling Using Fine Boundary-Fitted Grids for Tidal Flats

Fine grids with small spacing in boundary-fitted coordinates are normally used to treat the computation of fluid dynamics for estuarine areas and tidal flats. However, the adoption of Cartesian components of velocity vectors in this kind of non-orthogonal coordinates will definitely result in a difficulty in solving implicitly the transformed momentum equations, and also complicate the wet-dry point judgement used for flood areas. To solve this problem, equations in terms of generalized contravariant velocity vectors in curvilinear coordinates are derived in the present study, by virtue of which, an Alternative-Direction-Implicit numerical scheme in non-orthogonal grids would then be easily obtained, and wet-dry point judgement would as well be largely simplified. A comparison is made between the explicit scheme and implicit scheme, showing that the present model is accurate and numerically stable for computations of fluid dynamics for estuarine areas and tidal flats.

Melia’s R_h= ct Model Is by No Means Flat

With the support of numerous arguments, it has been shown that Melia’s claim that his cosmological Rh = ct model is flat and infinite is erroneous. In contrast, the model is positively curved, closed and, therefore, finite. With respect to results of Melia’s model, it is identical to our Subluminal Model.

米字型靠尺遍历离散点云检测隧道初支平整度

研究目的:为便捷、快速地开展隧道初支平整度检测,基于三维激光扫描的离散点云数据,提出运用米字型靠尺模拟人工检测的初支平整度全局检测方法,并对主要实现过程中的隧道设计轮廓嵌入、点云数据展开、米字型靠尺遍历、测站平整度计算、网格平整度评价等技术进行说明。研究结论:(1)本文方法直接基于离散点云进行模拟人工检测,不需要构建拟合曲面,能保持特征点云的位置不失真;(2)基于投影展开后的点云成果数据,可以从纵、横、斜向同步进行平整度检测,相比人工只能从纵向检测,该方法检测覆盖更全面,更贴近工程实际;(3)在桑园隧道应用本文方法进行初支平整度检测,检测结果的精度可以媲美人工检测,验证了本文方法的有效性,可为铁路隧道施工中的初支平整度质量检测提供实践参考。

缓倾层状岩体各向异性力学性能与破裂特征研究

为研究缓倾层状岩体结构特性对其各向异性力学性能和破裂演化特征的影响,本文考虑不同结构面间距、强度、倾角等结构特征参数及模型尺寸效应,开展缓倾层状砂泥岩多因素影响试验研究.基于颗粒流方法建立缓倾层状岩体数值力学模型,通过室内试验标定了层状砂泥岩参数,并验证了所建立模型的有效性.通过颗粒流数值力学试验,创新性地研究层状岩体结构面的裂纹发育速率,进而揭示缓倾层状砂泥岩强度各向异性及破裂演化特征,确立其力学特性与结构面间距、强度、倾角三个结构特性之间的关系.研究结论:(1)引入的平节理模型(FJM)与光滑节理模型(SJM)建立的离散元力学模型,能表征缓倾层状岩体强度各向异性力学特性与破裂演化过程;(2)缓倾层状岩体切线模量与强度,随层间距和层间强度的增大而增大,随结构面倾角的增大而减小,破裂特征受结构面的影响逐渐增大,基于单组结构面理论计算结构面发生剪切破坏的临界角度为24.5°;(3)结构面裂纹的发育速度,随结构面间距的增大而减小、随结构面倾角的减小而减小,随结构面强度的变化不明显.本文研究结果为缓倾层岩体隧道的力学行为与围岩稳定性研究提供了参考.

开孔泡沫金属传热和流动特性

近年来开孔泡沫金属运用于散热设备逐渐成为研究的热点。由于开孔泡沫金属结构复杂无序,数值模拟时大都将其结构进行化简,目前已有种类繁多的简化模型,然而适用于其传热与流动特性模拟研究的简化模型尚不明确;另外,适用于散热领域的泡沫金属结构参数有待详细研究。为此,建立开孔泡沫金属的5种简化三维模型,并进行传热和流动特性的对比研究,认为Gibson-Ashby模型更能准确描述实际开孔泡沫金属的传热和流动性能。在此基础上,采用Gibson-Ashby模型对开孔泡沫金属的关键结构参数进行传热和流动综合性能分析,发现孔隙率90%、孔密度30PPI开孔泡沫金属翅片的综合性能j/f^(1/3)(j为换热因子,f为阻力因子)最优;将孔隙率90%、孔密度30PPI开孔泡沫金属翅片与平直翅片进行对比,发现开孔泡沫金属翅片换热效果是平直翅片的2倍以上,综合性能也优于平直翅片。所得研究成果可为开孔泡沫金属在换热领域的应用和设计提供参考。

民用飞机高平尾侧向载荷传递结构有限元建模及仿真分析

民用飞机高平尾结构的平尾置于垂尾上方,平尾与垂尾都承受侧向载荷。为研究平尾的侧向载荷如何传到垂尾,提出一套关于高平尾侧向载荷传递结构的优化设计、有限元建模、仿真分析(涉及linear gap接触设置)的完整方法。该方法已成功应用于某型号民用飞机的研制,可推广到类似飞机结构的设计中。

基于模型试验的风力机基底应力分布特征及平面度修正

为有效掌握风荷载作用下风力发电机地基的复杂应力分布,提出关于基底应力平面分布假定的修正方法。以相似法则为理论基础,建立山区风力发电机地基缩尺物理模型试验系统,模拟不同平均风速和脉动风时间步长时的水平风荷载,测试不同风荷载下的基底静压力和动压力,研究应力的分布模式、变化规律,提出基底应力的平面度修正方法。研究结果表明:风速越大,基底静压力越大;而当风速一定时,基底各点的压力差异随着时间步长增加而加大,因此,低频脉动风更容易威胁地基稳定性;在不同工况下,动压力仅为静压力的1/20~1/12,故可采用拟静力法对风力机基底应力进行计算;若按常用的建筑规范基底应力计算方法,会低估基底应力差异,结果偏于不安全,而进行平面度修正后,应力修正值与实测值更加接近,这证明了利用平面度修正的合理性,也意味着基础设计埋深可更大,这为山区风力机的地基基础安全设计提供了新思路。

高功率微波频率对PIN限幅器的影响分析

通过TCAD器件建模,建立了PIN二极管的电热耦合模型,搭建PIN限幅器HPM耦合仿真电路以进行高功率微波效应仿真。仿真得到了不同频率下PIN限幅器瞬态电压响应以及PIN二极管内部电场、载流子、结温分布。仿真结果表明,在HPM耦合电压作用下,PIN限幅器平顶泄漏负向电压随频率增大而降低,PIN限幅器平顶泄漏正向电压随频率增大而降低。PIN二极管内部PIN限幅器的限幅能力随微波频率增加先增强后减弱。HPM频率较低时PIN二极管内部晶格温度积累集中于I层界面处,随着频率升高,晶格温度积累集中于I层中间位置,因此频率变化会造成PIN限幅器的HPM毁伤敏感位置变化。

FLAT网络在发酵过程建模中的应用

本文使用FLAT网络对一种工业规模的连续发酵过程进行了辨识 .发酵过程作为一种复杂的生化反应 ,它比一般的非线性系统更加复杂 ,FLAT网络用于发酵过程的辨识 ,可以得到较高的辨识精度 ,而且辨识速度快。

基于适宜性和生态网络的沿海滩涂农渔业利用空间优化

对沿海滩涂区域农渔业国土利用空间进行布局优化,是推进我国“蓝色粮仓”建设和促进滩涂资源可持续利用的重要途径。本研究以黄河三角洲南部滩涂围垦地区为例,基于遥感和GIS技术揭示了研究区1995—2020年滩涂主要农业种植和海水养殖等农渔业空间利用格局演变特征,并将生态适宜性评价、生态网络构建与土地利用变化模型相结合,模拟预测2035年不同发展情景下滩涂农渔业主要土地利用变化格局,并提出空间布局优化调整建议。结果表明:研究期间滩涂农业种植与海水养殖利用总面积呈现先增后减的趋势,由1995年的924.62 km^(2)增长至2004年的1224.96 km^(2),2004年后规模开始缩减,2020年缩减至1129.38 km^(2);水田和养殖池塘空间分布格局变化较为明显,旱地空间聚集度增加,海域开放式养殖向远离海岸方向逐渐扩张,滩涂区域主要农渔业利用空间分布呈现明显的陆海梯度分异特征;滩涂农业种植和海水养殖现状分布的生态适宜性较好,但是农业种植未来增长空间受限,滩涂池塘养殖和开放式养殖仍有一定空间发展潜力。严格的湿地生态保护措施限制了滩涂农渔业利用空间的增长;在遵循生态保护优先的前提下,农渔业发展情景下滩涂农业种植与海水养殖土地利用规模会有明显增加,但需要重点关注未利用土地的合理开发、滩涂陆海生态连通性的提升和高效生态种养模式的应用推广。研究结果可以为黄河三角洲滩涂农垦区农渔业高质量发展提供决策支持。

结合神经文本生成的FLAT模型的中文电子病历命名实体识别

随着医疗信息化的发展,电子病历命名实体识别受到了广泛关注。电子病历中包含大量的专业词汇,而专业词汇的切分错误会使命名实体识别效果不佳。FLAT模型在引入词边界信息时能有效避免分词错误信息的传播,提高命名实体识别效果,但FALT模型依赖于高质量的词典信息。针对这一问题,提出了结合神经文本生成的FLAT模型,使用神经文本生成方法生成大量新病历文本,通过提出的评分函数筛选通顺的文本训练词向量作为FLAT模型的词典信息。实验表明:结合神经文本生成的FLAT模型在CCKS2017数据集上取得了95.32%的F1分数,比BiLSTM CRF模型提高了1.16%,比BERT CRF模型提高了0.89%;在CCKS2019数据集上取得了85.87%的F1分数,比BiLSTM CRF模型提高了5.19%,比BERT CRF模型提高了1.34%。

基于深度学习的腕关节DR成像质控模型的研究与应用

目的基于深度学习的方法建立腕关节直接数字平板X线成像系统(DR)自动质控模型生成系统,并对质控性能进行初步研究。方法采用人工智能深度学习的方法建立腕关节正位和侧位DR图像质控系统模型,回顾性收集重庆大学附属中心医院临床怀疑腕关节病变的1315张图像,按6︰4的比例划分训练集和验证集。在MobileNet V2分类模型和Global Universal U-Net(GU2Net)关键点检测模型上进行训练,然后分别使用模型准确率、精准度、召回率和曲线下面积(AUC),以及平均径向误差(MRE)和成功检出率(SDR)进行评估。结果根据验证数据集的实验所得到的伪影分类模型在伪影识别方面具有较高的性能,AUC=0.9701,95%可信区间(95%CI)0.9700~0.9703,其准确率、精准度、召回率分别为0.93、0.88和0.97。正位和侧位影像中关键点检测模型的MRE也在合理水平,分别达到(0.7944±3.2535)mm和(3.8134±7.4087)mm。距离10.0 mm下正位和侧位关键点检测模型的SDR分别为99.64%、92.51%。结论基于深度卷积神经网络开发的全自动腕关节DR质控系统模型,能够对腕关节正位和侧位片自动生成图像质量控制报告,且效果较好。

Black Hole Complementarity in Terms of the Outsider and Insider Perspectives

A complementarity hypothesis concerning outsider and insider perspectives of a gargantuan black hole is proposed. The two thought experiments presented herein are followed by a brief discussion of a new interpretation of black hole interior “space-and-time-reversal”. Specifically, it is proposed that the “singularity” space of the black hole interior is time-like and the expansion time of the black hole interior is space-like. The resemblance of this new insider interpretation to our own expanding and redshifting big bang universe is compelling.

Shrinkage and trajectory of the flat jet with inclination angle

The performance of the flat jet with an inclination angle was investigated bya water model. A mathematical model for the shrinkage and the trajectory of the flat jet with aninclination angle was derived theoretically and verified by experimental data of the water model.The experimental results indicate that the inclination angle (alpha) has no influence on theshrinkage of the flat jet, the shrinkage of the flat jet along the width direction decreases withthe increasing of the initial velocity at the exit (u_0) and the initial thickness of the flat jet(t_0). Enough bigger initial exit velocity (u_0) and initial thickness can suppress the shrinkage ofthe flat jet along the width direction and keep the flat jet stabilized. In addition, thetrajectory of the flat jet with an inclination angle is parabolic and must be taking intoconsideration when to determine the striking distance.

A Solution to the Cosmological Constant Problem Using the Holographic Principle (A Brief Note)

This paper integrates a quantum conception of the Planck epoch early universe with FSC model formulae and the holographic principle, to offer a reasonable explanation and solution of the cosmological constant problem. Such a solution does not appear to be achievable in cosmological models which do not integrate black hole formulae with quantum formulae such as the Stephan-Boltzmann law. As demonstrated herein, assuming a constant value of Lambda over the great span of cosmic time appears to have been a mistake. It appears that Einstein’s assumption of a constant, in terms of vacuum energy density, was not only a mistake for a statically-balanced universe, but also a mistake for a dynamically-expanding universe.