Numerical Study of Flow Features Around Submerged Circular and Square Piles at Flat and Scoured Beds Using OpenFOAM

Elucidating the flow features around piles in local scouring processes is crucial for studies of local scouring mechanisms and scour depth estimates.This study details the flow turbulence characteristics of two submerged piles that are determined by solving the Navier-Stokes equations with the improved delayed detached eddy simulation model.This model is verified by comparing experimental and numerical results for hydrodynamic parameters with the literature for both square-crossing piles(SCPs)and circular-crossing piles(CCPs).Original topographies of flat and scoured beds(i.e.,the initial and equilibrium scouring stages)are based on experimental results obtained by the authors in the present paper.SCP and CCP flow features in the scouring process are discussed.The results indicate that during the scouring process,the time-averaged drag coefficient and root mean square(rms)of the lift coefficient increase linearly in the CCP test,while the rms of the lift coefficient in the SCP test decreases linearly.Moreover,the minimum pressure coefficient is always located in the upstream corners in the SCP case but moves from 72.5°to 79.5°when the scour hole is completely developed in the CCP case.Downward flow behind the pile,which is generated by separated boundary layers above the top face of the pile,can reach the sand bed and turn the separated shear layers into patches of small vortices in the near-wake regions.Thus,the high shear stress zones are mainly at the scour edges under scoured-bed conditions.

Experimental observation of Fermi-level flat band in novel kagome metal CeNi_(5)

Kagome materials are a class of material with a lattice structure composed of corner-sharing triangles that produce various exotic electronic phenomena,such as Dirac fermions,van Hove singularities,and flat bands.However,most of the known kagome materials have a flat band detached from the Fermi energy,which limits the investigation of the emergent flat band physics.In this work,by combining soft x-ray angle-resolved photoemission spectroscopy(ARPES)and the first-principles calculations,the electronic structure is investigated of a novel kagome metal CeNi_(5) with a clear dispersion along the kz direction and a Fermi level flat band in theΓ–K–M–Γplane.Besides,resonant ARPES experimental results indicate that the valence state of Ce ions is close to 4^(+),which is consistent with the transport measurement result.Our results demonstrate the unique electronic properties of CeNi_(5) as a new kagome metal and provide an ideal platform for exploring the flat band physics and the interactions between different types of flat bands by tuning the valence state of Ce ions.

Layered kagome compound Na_(2)Ni_(3)S_(4)with topological flat band

We report structural and electronic properties of Na_(2)Ni_(3)S_(4),a quasi-two-dimensional compound composed of alternating layers of[Ni_(3)S_(4)]^(2-)and Na^(+).The compound features a remarkable Ni-based kagome lattice with a square planar configuration of four surrounding S atoms for each Ni atom.Magnetization and electrical measurements reveal a weak paramagnetic insulator with a gap of about 0.5 eV.Our band structure calculation highlights a set of topological flat bands of the kagome lattice derived from the rotated dxz-orbital with C_(3)+T symmetry in the presence of crystal-field splitting.

Observation of flat-band localized state in a one-dimensional diamond momentum lattice of ultracold atoms

We investigated the one-dimensional diamond ladder in the momentum lattice platform. By inducing multiple twoand four-photon Bragg scatterings among specific momentum states, we achieved a flat band system based on the diamond model, precisely controlling the coupling strength and phase between individual lattice sites. Utilizing two lattice sites couplings, we generated a compact localized state associated with the flat band, which remained localized throughout the entire time evolution. We successfully realized the continuous shift of flat bands by adjusting the corresponding nearest neighbor hopping strength, enabling us to observe the complete localization process. This opens avenues for further exploration of more complex properties within flat-band systems, including investigating the robustness of flat-band localized states in disordered flat-band systems and exploring many-body localization in interacting flat-band systems.

Laser-induced breakdown spectroscopy as a method for millimeter-scale inspection of surface flatness

A non-contact method for millimeter-scale inspection of material surface flatness via Laser-Induced Breakdown Spectroscopy(LIBS)is investigated experimentally.The experiment is performed using a planished surface of an alloy steel sample to simulate its various flatness,ranging from 0 to 4.4 mm,by adjusting the laser focal plane to the surface distance with a step length of 0.2 mm.It is found that LIBS measurements are successful in inspecting the flatness differences among these simulated cases,implying that the method investigated here is feasible.It is also found that,for achieving the inspection of surface flatness within such a wide range,when univariate analysis is applied,a piecewise calibration model must be constructed.This is due to the complex dependence of plasma formation conditions on the surface flatness,which inevitably complicates the inspection procedure.To solve the problem,a multivariate analysis with the help of Back-Propagation Neural Network(BPNN)algorithms is applied to further construct the calibration model.By detailed analysis of the model performance,we demonstrate that a unified calibration model can be well established based on BPNN algorithms for unambiguous millimeter-scale range inspection of surface flatness with a resolution of about 0.2 mm.

Evaluation of the seismic behavior of reinforced concrete structures with flat slab-column gravity frame and shear walls through nonlinear analysis methods

This paper presents an investigation of the seismic behavior of reinforced concrete(RC)structures in which shear walls are the main lateral load-resisting elements and the participation of flat slab floor systems is not considered in the seismic design procedure.In this regard,the behavior of six prototype structures(with different heights and plan layouts)is investigated through nonlinear static and time history analyses,implemented in the OpenSees platform.The results of the analyses are presented in terms of the behavior of the slab-column connections and their mode of failure at different loading stages.Moreover,the global response of the buildings is discussed in terms of some parameters,such as lateral overstrength due to the gravity flat slab-column frames.According to the nonlinear static analyses,in structures in which the slab-column connections were designed only for gravity loads,the slab-column connections exhibited a punching mode of failure even in the early stages of loading.However,the punching failure was eliminated in structures in which a minimum transverse reinforcement recommended in ACI 318(2019)was provided in the slabs at joint regions.Furthermore,despite neglecting the contribution of gravity flat slab-column frames in the lateral load resistance of the structures,a relatively significant overstrength was imposed on the structures by the gravity frames.

A More Accurate Determination of the Magnitude of Cosmic Inflation in the Big Bang Model

According to our hypothesis, at the very beginning of the Big Bang, a hyperenergetic spherical wave was created. We described its characteristics in our previous work, and the present work is based on them. Logically, we saw that in cosmic inflation the frequency of such a wave would decrease sharply. Based on the temperature that prevailed immediately after inflation according to the hot Big Bang model, we determined a measure of the size of the inflation in this model, in accordance with our hypothesis.

Thermodynamic Analysis and Optimization of Flat Plate Solar Collector Using TiO_(2)/Water Nanofluid

To research solar energy's efficiency and environmental benefits,the thermal efficiency,exergy,and entropy of solar collectors were calculated.The experiment involved two glass-topped collectors,fluid transfer tubes,and aluminum heat-absorbing plates.Glass wool insulation minimized heat loss.A 0.5% TiO_(2)/Water nanofluid was created using a mechanical and ultrasonic stirrer.Results showed that solar radiation increased thermal efficiency until midday,reaching 48.48% for water and 51.23% for the nanofluid.With increasing mass flow rates from 0.0045 kg/s to 0.02 kg/s,thermal efficiency improved from 16.26% to 47.37% for water and from 20.65% to 48.76% for the nanofluid.Filtered water provided 380 W and 395 W of energy in March and April,while the nanofluid increased it to 395 W and 415 W during these months.Mass flow generated energy,and the Reynolds number raised entropy.The noon exergy efficiency for nanofluids was 50%-55%,compared to 30% for water.At noon,the broken exergy measured 877.53 W for the nanofluid and 880.12 W for water.In Kirkuk,Iraq,the 0.5% TiO_(2)/Water nanofluid outperformed water in solar collectors.

Changes of coastline and tidal flat and its implication for ecological protection under human activities: Take China’s Bohai Bay as an example

The change processes and trends of shoreline and tidal flat forced by human activities are essential issues for the sustainability of coastal area,which is also of great significance for understanding coastal ecological environment changes and even global changes.Based on field measurements,combined with Linear Regression(LR)model and Inverse Distance Weighing(IDW)method,this paper presents detailed analysis on the change history and trend of the shoreline and tidal flat in Bohai Bay.The shoreline faces a high erosion chance under the action of natural factors,while the tidal flat faces a different erosion and deposition patterns in Bohai Bay due to the impact of human activities.The implication of change rule for ecological protection and recovery is also discussed.Measures should be taken to protect the coastal ecological environment.The models used in this paper show a high correlation coefficient between observed and modeling data,which means that this method can be used to predict the changing trend of shoreline and tidal flat.The research results of present study can provide scientific supports for future coastal protection and management.

How the Flat Space Cosmology Model Correlates the Recombination CMB Temperature of 3000 K with a Redshift of 1100

This paper shows how the Flat Space Cosmology model correlates the recom-bination epoch CMB temperature of 3000 K with a cosmological redshift of 1100. This proof is given in support of the recent publication that the Tatum and Seshavatharam Hubble temperature formulae can be derived using the Stephan-Boltzmann dispersion law. Thus, as explained herein, the era of high precision Planck scale quantum cosmology has arrived.

Product Development of High Strength and Toughness Spring Flat Steel

With the continuous development of mechanical industry,higher requirements are put forward for the comprehensive properties of spring steel.The chemical composition and production process of spring flat steel are designed to meet the requirements of high strength and high toughness of spring flat steel,through the test,the product surface quality and internal quality all meet the national standards,the performance indicators to meet user requirements.

Nanogrinding of SiC wafers with high flatness and low subsurface damage

Nanogrinding of SiC wafers with high flatness and low subsurface damage was proposed and nanogrinding experiments were carried out on an ultra precision grinding machine with fine diamond wheels. Experimental results show that nanogrinding can produce flatness less than 1.0μm and a surface roughness Ra of 0.42nm. It is found that nanogrinding is capable of producing much flatter SiC wafers with a lower damage than double side lapping and mechanical polishing in much less time and it can replace double side lapping and mechanical polishing and reduce the removal amount of chemical mechanical polishing.

Feasible Rate of Tidal Flat Reclamation——Jiangsu Mud Coast as a Case Study

Reclamation of tidal flat is one of the main ways to get a dynamic balance of the total amount of plowland. With the development of social economy and the increasing demand for plowland, the contradiction between tidal flat reclamation and environment protection becomes more and more outstanding. However, tidal flat reclamation should also follow the dynamic balance of total amount of tidal flat amount. The paper analyzed the history of reclamation and development of Jiangsu mud coast, and calculated the feasible rates of tidal flat reclamation on different stretches respectively, and pointed out that both the economic social benefits of reclamation and the natural erosion-accretion conditions of the coasts should be taken into consideration in deciding the intensity of tidal flat reclamation, so as to satisfy demands on both reclamation and protection of tidal flat resource.

The Submanifolds with Parallel Mean Curvature Vector in a Locally Symmetric and Conformally Flat Riemannian Manifold

In the present paper we obtain the following result: Theorem Let M^R be a compact submanifold with parallel mean curvature vector in a locally symmetric and conformally flat Riemannian manifold N^(n+p)(p>1). If then M^n lies in a totally geodesic submanifold N^(n+1).

SI-FLAT板形仪激振频率设定

SI-FLAT板形仪是国内宽带钢冷连轧机首次采用的非接触式工业用板形仪,但实际使用过程中发现,对于常轧规格的带钢,其激振频率设定始终为同一固定值,激振力仅随张应力的变化而变化,导致板形控制不稳定,激振频率的设置严重影响着板形检测的精度.本文在分析现场实际生产数据的基础上,提出了激振频率的设置应该遵循的两个基本原则,即振幅控制原则和检测间隔控制原则.为了对带钢振动进行固有频率和受迫振动振幅的分析和计算,采用大型有限元软件ANSYS12.0建立了带钢振动仿真模型,分析了带钢板形、宽度、厚度、张应力等因素所导致的带钢固有频率波动对带钢振幅的影响.研究发现,张应力和板形对带钢固有频率的影响较大.最后,基于振幅控制原则和检测间隔控制原则提出了可行性方案,即通过限制最小张应力,减小板形对测量结果的影响;同时为了控制最小检测间隔,便于对板形的在线控制,激振频率的大小应根据带钢速度进行调节设定.

FLAT-PRO深水合成基钻井液恒流变作用机理研究

目前,适应于深水、超深水作业的FLAT-PRO恒流变合成基钻井液体系由于其良好的恒流变特性、抗污染能力及储层保护性,已在中国南海成功应用近10井。但是近年来,所钻遇的地层越来越复杂,要求的温度范围和密度范围越来越高,这需要对合成基钻井液恒流变机理有更清楚的认识。文章旨在FLAT-PRO恒流变合成基钻井液体系的基础上,对体系恒流变机理进行研究。体系中的核心处理剂流型调节剂通过氢键作用插入有机土层间,扩大层间距并促进其片层在油中高度分散,温度越高,插入有机土层间的流型调节剂分子越多,补偿由于温度升高导致的粘度降低,从而形成具有温度响应的网架结构。

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。

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%。

Influence of Seawall Line Choice on Tide Lock Drainage in Tidal Flat Inning——Cangdongpian Inning Area on the west part of Tiaozini Sand as a case study

Most of the flood from the wide inner lowland plain discharges through tide locks on coast, and the influence of tidal flat inning projects on the tide lock drainage must be solved by seawall line choice. Taking the Cangdongpian inning area on the west side of Tiaozini Sand as a case study, the paper analyzed the compages and validity of ebb tide water to maintain the flood discharge creek below the tide lock for different projects of seawall line. Result indicates that a rational seawall line program has little influence on the flood discharge of lock during the mean tide or general spring tides, but has certain influences during a storm surge or an extreme spring tide in autumn. However it could be resolved by several times of artificial scour on the creek.

An Uncertainty Assessment Approach for Measuring Flatness Error in Close Way

It is necessary for precise measurement to estimate the uncertainty of measurement result. When measuring flatness error in close way by pitch, usually the uncertainty of measurement result is independently estimated according to pitch points. By analyzing a concrete example, this paper proposed that the uncertainty should be evaluated by the correlation calculating method. This approach greatly improved the deficiencies of the assessment method according to independent measurement and enhanced measurement precision. It provides a reference value for uncertainty assessment in leveling a flat.