Chord length sampling correction analysis for dispersion fuel in Monte Carlo simulation

Dispersion fuels,knowned for their excellent safety performance,are widely used in advanced reactors,such as hightemperature gas-cooled reactors.Compared with deterministic methods,the Monte Carlo method has more advantages in the geometric modeling of stochastic media.The explicit modeling method has high computational accuracy and high computational cost.The chord length sampling(CLS)method can improve computational efficiency by sampling the chord length during neutron transport using the matrix chord length?s probability density function.This study shows that the excluded-volume effect in realistic stochastic media can introduce certain deviations into the CLS.A chord length correction approach is proposed to obtain the chord length correction factor by developing the Particle code based on equivalent transmission probability.Through numerical analysis against reference solutions from explicit modeling in the RMC code,it was demonstrated that CLS with the proposed correction method provides good accuracy for addressing the excludedvolume effect in realistic infinite stochastic media.

Comparison study on measurement of rail weld joint between inertial reference method and multi-point chord reference method

Purpose – Straightness measurement of rail weld joint is of essential importance to railway maintenance. Dueto the lack of efficient measurement equipment, there has been limited in-depth research on rail weld joint with a5-m wavelength range, leaving a significant knowledge gap in this field.Design/methodology/approach – In this study, the authors used the well-established inertial referencemethod (IR-method), and the state-of-the-art multi-point chord reference method (MCR-method). Two methodshave been applied in different types of rail straightness measurement trollies, respectively. These instrumentswere tested in a high-speed rail section within a certain region of China. The test results were ultimatelyvalidated through using traditional straightedge and feeler gauge methods as reference data to evaluate the railweld joint straightness within the 5-m wavelength range.Findings – The research reveals that IR-method and MCR-method produce reasonably similar measurementresults for wavelengths below 1 m. However, MCR-method outperforms IR-method in terms of accuracy forwavelengths exceeding 3 m. Furthermore, it was observed that IR-method, while operating at a slower speed,carries the risk of derailing and is incapable of detecting rail weld joints and low joints within the track.Originality/value – The research compare two methods’ measurement effects in a longer wavelength rangeand demonstrate the superiority of MCR-method.

Seismic performance of recycled concrete-filled square steel tube columns

An experimental study on the seismic performance of recycled concrete-filled square steel tube （RCFST） columns is carried out. Six specimens were designed and tested under constant axial compression and cyclic lateral loading. Two parameters, replacement percentage of recycled coarse aggregate （RCA） and axial compression level, were considered in the test. Based on the experimental data, the hysteretic loops, skeleton curves, ductility, energy dissipation capacity and stiffness degradation of RCFST columns were analyzed. The test results indicate that the failure modes of RCFST columns are the local buckling of the steel tube at the bottom of the columns, and the hysteretic loops are full and their shapes are similar to normal CFST columns. Furthermore, the ductility coefficient of all specimens are close to 3.0, and the equivalent viscous damping coefficient corresponding to the ultimate lateral load ranges from 0.323 to 0.360, which demonstrates that RCFST columns exhibit remarkable seismic performance.

Axial Bearing Capacity of Short FRP Confined Concrete-filled Steel Tubular Columns

The bearing capacity of FRP confined concrete-filled steel tubular （FRP-CFST） columns under axial compression was investigated. This new type of composite column is a concrete-filled steel tube （CFST） confined with fiber-reinforced polymer （FRP） wraps. Totally 11 short column specimens were tested to failure under axial compression. The influences of the type and quantity of FRP, the thickness of steel tube and the concrete strength were studied. It was found that the bearing capacity of short FRP-CFST column was much higher than that of comparable CFST column. Furthermore, the formulas for calculating the bearing capacity of the FRP-CFST columns are proposed. The analytical calculated results agree well with the experimental results.

Effect of contact thermal resistance on temperature distributions of concrete-filled steel tubes in fire

To predicate the temperature distribution of concrete-filled steel tubes(CFSTs) being exposure to fire,a finite element analysis model was developed using a finite element package,ANSYS.A suggested value of contact thermal resistance was therefore proposed with the supporting of massive numbers of collected test data.Parametric analysis was conducted subsequently towards the cross-sectional temperature distribution of CFST columns in four-side fire,in which the exposure time,width of the cross section,steel ratio were taken into account with considering contact thermal resistance.It was found that contact thermal resistance has little effect on the overall temperature regulation with the exposure time,the width of cross-section or the change of steel ratio.However,great temperature dropping at the concrete adjacent to the contact interface,and gentle temperature increase at steel tube,exist if considering contact thermal resistance.The results of the study are expected to provide theoretical basis for the fire resistance behavior and design of the CFST columns being exposure to fire.

Seismic Behavior of Diaphragm-Through Connections of Concrete-Filled Square Steel Tubular Columns and H-Shaped Steel Beams

Based on the introductions of a type of diaphragm-through connection between concrete-filled square steel tubular columns (CFSSTCs) and H-shaped steel beams,a finite element model of the connection is developed and used to investigate the seismic behavior of the connection.The results of the finite element model are validated by a set of cyclic loading tests.The cyclic loading tests and the finite element analyses indicate that the failure mode of the suggested connections is plastic hinge at the beam with inelastic rotation angle exceeding 0.04 rad.The suggested connections have sufficient strength,plastic deformation and energy dissipation capacity to be used in composite moment frames as beam-to-column rigid connections.

Influence of Axial Load Ratio on Shear Behavior of Through-Diaphragm Connections of Concrete-Filled Square Steel Tubular Columns

Nonlinear finite element analysis and parametric studies were carried out to study the influence of axial load ratio on the shear behavior of the through-diaphragm connections of concrete-filled square steel tubular columns. The analysis reveals that smaller axial load ratio can improve the shear bearing capacity and ductility while larger axial load ratio will decrease the shear behavior of the through-diaphragm connections. The parametric studies indicate that the axial load ratio should be limited to less than 0.4 and its influence should be considered in the analysis and design of such connections.

Reliability analysis of circular concrete-filled steel tube with material and geometrical nonlinearity

Most of the previous research on concrete-filled steel tube is restricted to a deterministic approach. To gain clear insight into the random properties of circular concrete-filled steel tube, reliability analysis is carried out in the present study. To obtain the Structural nonlinear response and ultimate resistance capacity, material and geometrical nonlinear analysis of circular concrete-filled steel tube is performed with a three-dimensional degenerated beam ele- ment. Then we investigate the reliability of concrete-filled steel tube using the first-order reliability method combined with nonlinear finite element analysis. The influences of such parameters as material strength, slenderness, initial geo- metrical imperfection, etc. on the reliability of circular concrete-filled steel tube column are studied. It can be con- cluded that inevitable random fluctuation of those parameters has significant influence on structural reliability, and that stochastic or reliability methods can provide a more rational and subjective evaluation on the safety of CFT structures than a deterministic approach.

Prediction of Axial Capacity of Concrete-Filled Square Steel Tubes Using Neural Networks

The application of artificial neural network to predict the ultimate bearing capacity of CFST （ concrete-filled square steel tubes） short columns under axial loading is explored. Input parameters consiste of concrete compressive strength, yield strength of steel tube, confinement index, sectional dimension and width-to-thickness ratio. The ultimate bearing capacity is the only output parameter. A multilayer feedforward neural network is used to describe the nonlinear relationships between the input and output variables. Fifty-five experimental data of CFST short columns under axial loading are used to train and test the neural network. A comparison between the neural network model and three parameter models shows that the neural network model possesses good accuracy and could be a practical method for predicting the ultimate strength of axially loaded CFST short columns.

Ductility and Ultimate Capacity of Concrete-Filled Lattice Rectangular Steel Tube Columns

A kind of concrete-filled lattice rectangular steel tube(CFLRST)column was put forward.The numerical simulation was modeled to analyze the mechanical characteristic of CFLRST column.By comparing the load-deformation curves from the test results,the rationality and reliability of the finite element model has been confirmed,moreover,the change of the section stiffness and stress in the forcing process and the ultimate bearing capacity of the column were analyzed.Based on the model,the comparison of ultimate bearing capacity and ductility between CFLRST column and reinforced concrete(RC)column were also analyzed.The results of the finite element analysis show that the loading process of CFLRST column consists of elastic stage,yield stage and failure stage.The failure modes are mainly strength failure and failure of elastoplastic instability.CFLRST column has higher bearing capacities in comparison with reinforced concrete columns with the same steel ratio.In addition,the stiffness degeneration of CFLRST column is slower than RC column and CFLRST column has good ductility.

Experiments on two-phase flow in hydraulic jump on pebbled rough bed:Part 1–Turbulence properties and particle chord time and length

This study reported and discussed turbulence characteristics,such as turbulence intensity,correlation time scales,and advective length scales.The characteristic air–water time scale,including the particle chord time and length and their probability density functions(PDFs),was investigated.The results demonstrated that turbulence intensity was relatively greater on a rough bed in the roller length,whereas further downstream,the decay rate was higher.In addition,the relationship between turbulence intensity and dimensionless bubble count rate reflected an increase in turbulence intensity associated with the number of entrained particles.Triple decomposition analysis(TDA)was performed to determine the contributions of slow and fast turbulent components.The TDA results indicated that,regardless of bed type and inflow conditions,the sum of the band-pass(T'_(u))and high-pass(T″_(u))filtered turbulence intensities was equal to the turbulence intensity of the raw signal data(T_(u)).T″_(u) highlighted a higher turbulence intensity and larger vorticities on the rough bed for an identical inflow Froude number.Additional TDA results were presented in terms of the interfacial velocity,auto-and cross-correlation time scales,and longitudinal advection length scale,with the effects of low-and high-frequency signal components on each highlighted parameter.The analysis of the air chord time indicated an increase in the proportion of small bubbles moving downstream.The second part of this research focused on the basic properties of particle grouping and clustering.

Multi-style Chord Music Generation Based on Artificial Neural Network

With the continuous development of deep learning and artificial neural networks(ANNs), algorithmic composition has gradually become a hot research field. In order to solve the music-style problem in generating chord music, a multi-style chord music generation(MSCMG) network is proposed based on the previous ANN for creation. A music-style extraction module and a style extractor are added by the network on the original basis;the music-style extraction module divides the entire music content into two parts, namely the music-style information Mstyleand the music content information Mcontent. The style extractor removes the music-style information entangled in the music content information. The similarity of music generated by different models is compared in this paper. It is also evaluated whether the model can learn music composition rules from the database. Through experiments, it is found that the model proposed in this paper can generate music works in the expected style. Compared with the long short term memory(LSTM) network, the MSCMG network has a certain improvement in the performance of music styles.

Chord Company PowerARAY&PowerARAY Professional电源降噪产品

英国Chord Company推出了两款最新产品,PowerARAY和PowerARAY Professional。新推出的PowerARAY和PowerARAY Professional是Chord Company新一代降低及吸收噪音设备系列的最新成员。类似于先前大受好评的GroundARAY降噪棒(银手指),PowerARAY可以插在未使用的主电源插座上G&WTW-DB1000K(墙上或电源拖板),这些插座位置相邻与用在音响设备供电的插座。

北美黄杉和云杉-松木-冷杉平行弦木桁架承载性能比较

【目的】对比不同腹杆角度下北美黄杉和云杉-松木-冷杉(SPF)华伦式平行弦木桁架的承载性能,探究腹杆角度和结构用材对华伦式平行弦木桁架承载性能的影响规律,为平行弦木桁架结构设计提供理论依据。【方法】以承载力和稳定性为验算指标,利用Smsolver结构力学求解器对平行弦木桁架各杆件的内力变化及其变形情况进行定量分析,得到平行弦木桁架腹杆角度的上、下临界角度和最优腹杆角度;采用ABAQUS有限元软件对3种腹杆角度的北美黄杉和SPF平行弦木桁架进行有限元模型分析与验证,获得不同基材平行弦木桁架在不同腹杆角度情况下的内力变化规律,判断其可能的破坏形式和受力机理;以SPF和北美黄杉为基材分别制作3种腹杆角度的平行弦木桁架,进行抗弯承载性能静力试验,探究平行弦木桁架的极限荷载、应力分布及主要破坏形式,并与有限元模拟结果进行对比,验证平行弦木桁架有限元模型分析的准确性和适用性。【结果】1)华伦式平行弦木桁架的最优腹杆角度为47°,下临界角度为34°,上临界角度为60°;2)北美黄杉平行弦木桁架的极限荷载范围为26.53~40.83 kN,跨中挠度范围为30.57~31.01 mm,SPF平行弦木桁架的极限荷载范围为23.48~34.16 kN,跨中挠度范围为31.85~32.05 mm;3)腹杆角度34°、47°、60°的北美黄杉和SPF平行弦木桁架极限荷载分别为26.53和23.48 kN、35.10和30.06 kN、40.83和34.16 kN,对应跨中挠度分别为31.85和31.01 mm、30.72和32.05 mm、30.57和31.97 mm;4)北美黄杉平行弦木桁架的破坏形式主要表现为靠近桁架支座处的腹杆出现裂纹以及桁架端部或荷载施加点处齿板拔出,SPF平行弦木桁架的破坏形式主要表现为桁架端部和荷载施加点处齿板拔出;5)ABAQUS有限元模拟和试验验证发现,2种平行弦木桁架跨中处弦杆轴力最大,往两边逐次递减,桁架跨中处腹杆轴力最小,往两边逐次递增,且弦杆轴力大于腹杆。【结论】北美黄杉平行弦木桁架承载性能优于SPF平行弦木桁架;平行弦木桁架的承载性能随腹杆角度增加而增加;2种平行弦木桁架的薄弱点均为桁架端部和荷载施加点处的齿板连接节点;ABAQUS有限元模型能有效反映出平行弦木桁架受力分布和整体结构变形趋势。

温度作用下大跨度斜拉桥长波不平顺限值研究

研究目的:为研究大跨度斜拉桥在温度作用下的变形及其引起的长波不平顺对列车运行的影响,以泉州湾跨海钢混结合梁斜拉桥为研究对象,在其主梁截面布置温度传感器以监测主梁温度变化,利用ANSYS软件分析实测温度作用下的斜拉桥主梁竖向变形,将温度变形与轨道不平顺叠加且基于弹性系统动力学总势能不变值原理建立考虑该长波不平顺的车桥耦合模型,以研究长波不平顺对列车动力响应的影响、弦测法对其进行评价的适配性,以及温度变形极限条件下的对应限值。研究结论:(1)温度监测系统共收集了1年的温度数据,将其分解为均匀温度和线性温差后,对应的温度变化范围分别为[5.82°C,37.51°C]和[2.36°C,29.94°C],主梁主跨跨中的最大竖向位移为28.6 mm,最小竖向位移为14.1 mm;(2)相比于未考虑温度作用,考虑了温度作用引起的长波不平顺的车桥耦合振动模型得到的列车轮重减载率、竖向加速度和竖向舒适度指标均有一定增大,竖向加速度增幅最为明显;(3)考虑了因列车运行引起的桥梁动态位移的影响后,60 m弦中点弦测法依然能够很好地体现列车振动响应,与车体竖向加速度响应相关性最好;(4)通过分析60 m弦的不平顺计算结果并进行验证,可知桥塔附近是双线行车时会车的危险位置;(5)在温度变形极限条件下列车的竖向加速度达到规范限值,对应的60 m弦矢度限值为7.22 mm;(6)本研究成果可为大跨度斜拉桥长波不平顺的评测方法选取及限值要求提供参考。

大跨径刚性悬链桁架桥不带加劲弦顶推施工技术

针对悬链形上加劲连续钢桁梁桥建造,提出不带加劲弦多点同步顶推施工技术,在边跨设置拼装平台,在中跨设置临时墩,分段拼装,顶推钢桁梁,最后吊装合龙加劲弦。在施工中,设置大临结构,以减小钢桁梁的悬臂长度,适应了钢桁梁拼装及顶推装置布置的要求;采用同步控制系统与纠偏装置,解决了多点同步顶推与钢桁梁线性控制的难题;通过有限元仿真分析,验证了顶推过程的可行性;采用落梁法,解决了钢桁主梁合龙及加劲弦合龙的难题。

高速铁路主跨320 m钢-混部分斜拉桥无砟轨道适应性研究

南玉高铁六景郁江特大桥设计将钢-混部分斜拉桥结构引入时速350 km高速铁路领域,而300 m级以上大跨度桥上无砟轨道的竖向变形极易超限,影响列车通过的安全性和舒适性,因此,系统研究在此大跨桥梁结构上铺设无砟轨道的适应性十分必要。通过建立有限元及动力学模型,分析不同组合工况下无砟轨道结构的变形特点及动力特性,运用60 m弦测法探究各工况下无砟轨道的线形变化规律,从而确定大跨度钢-混部分斜拉桥铺设无砟轨道的适应性,并对设计和施工提出合理化建议。主要结论如下:在各种不利组合荷载作用下,桥上无砟轨道结构强度满足规范要求,列车通过大桥的各项安全性与舒适性指标均满足规范要求;混凝土收缩徐变和斜拉索升降温是影响无砟轨道线形标准的两大主因,应在无砟轨道施工前确保足够的沉降观测期和收缩徐变释放期,并充分考虑拉索的保温设计;在温度组合荷载作用下,桥上无砟轨道的60 m弦测不平顺幅值为6.79 mm,满足高速铁路静态验收标准;但在叠加列车荷载和收缩徐变后,变形弦测值均出现Ⅱ级及以上超限,通过合理设置预拱度后可有效改善轨道平顺性标准。

Dual-Chord:一种更加有效的分布式哈希表

在基于分布式哈希表构造的对等网中,关键字的搜索效率一直是一个非常重要的指标.Chord提出在Chord环上构建结构化的分布式哈希表.Chord协议中查找的过程是单一的顺时针方向.Dual-Chord通过对路由表的扩展,使得系统的查找策略可以根据关键字在Chord环上位置离当前节点的远近来确定查找的方向,这样大大的提高了在对等网中的查找效率.同时,Dual-Chord综合考虑了网络延时对查找的影响.在设计中也根据节点间的网络延时来优化查找的性能.实验表明,在对等网中Dual-Chord协议定义的查找算法效率比Chord定义的查找算法要高.

RR-Chord:一个基于Chord的低开销快速查询P2P系统

针对结构化P2P系统高异质性和节点频繁加入或离开带来的系统性能问题,基于Chord设计了一个RR-Chord系统.该系统所有节点被分为路由节点和非路由节点.路由节点具有更多的资源和路由信息,并可根据自身能力的强弱调整其路由表的大小,所有的路由节点形成路由环,所有的路由信息在路由环上路由以提高系统的查询效率.设计的新的加入算法,进一步减少了节点频繁加入与离开造成的维护开销.理论分析和实验结果表明,RR-Chord具有较好的路由性能和非常低的维护开销.