Parametric resonance of axially functionally graded pipes conveying pulsating fluid

Based on the generalized Hamilton's principle,the nonlinear governing equation of an axially functionally graded(AFG)pipe is established.The non-trivial equilibrium configuration is superposed by the modal functions of a simply supported beam.Via the direct multi-scale method,the response and stability boundary to the pulsating fluid velocity are solved analytically and verified by the differential quadrature element method(DQEM).The influence of Young's modulus gradient on the parametric resonance is investigated in the subcritical and supercritical regions.In general,the pipe in the supercritical region is more sensitive to the pulsating excitation.The nonlinearity changes from hard to soft,and the non-trivial equilibrium configuration introduces more frequency components to the vibration.Besides,the increasing Young's modulus gradient improves the critical pulsating flow velocity of the parametric resonance,and further enhances the stability of the system.In addition,when the temperature increases along the axial direction,reducing the gradient parameter can enhance the response asymmetry.This work further complements the theoretical analysis of pipes conveying pulsating fluid.

Nonlinear dynamics of a circular curved cantilevered pipe conveying pulsating fluid based on the geometrically exact model

Due to the novel applications of flexible pipes conveying fluid in the field of soft robotics and biomedicine,the investigations on the mechanical responses of the pipes have attracted considerable attention.The fluid-structure interaction(FSI)between the pipe with a curved shape and the time-varying internal fluid flow brings a great challenge to the revelation of the dynamical behaviors of flexible pipes,especially when the pipe is highly flexible and usually undergoes large deformations.In this work,the geometrically exact model(GEM)for a curved cantilevered pipe conveying pulsating fluid is developed based on the extended Hamilton's principle.The stability of the curved pipe with three different subtended angles is examined with the consideration of steady fluid flow.Specific attention is concentrated on the large-deformation resonance of circular pipes conveying pulsating fluid,which is often encountered in practical engineering.By constructing bifurcation diagrams,oscillating shapes,phase portraits,time traces,and Poincarémaps,the dynamic responses of the curved pipe under various system parameters are revealed.The mean flow velocity of the pulsating fluid is chosen to be either subcritical or supercritical.The numerical results show that the curved pipe conveying pulsating fluid can exhibit rich dynamical behaviors,including periodic and quasi-periodic motions.It is also found that the preferred instability type of a cantilevered curved pipe conveying steady fluid is mainly in the flutter of the second mode.For a moderate value of the mass ratio,however,a third-mode flutter may occur,which is quite different from that of a straight pipe system.

Research of Algorithm for Judgement of Joint Elongation of Conveyer Belt

By analyzing the feature of the joint image of the conveyer belt with steel ropes, a quick judgement algorithm based on the gradient search for the joint ’s elongation is put forward. And at the same time its experiment result is also given in this paper.

A X-ray Non-destructive Testing System for Mine Conveyer Belt

A system making use of X--ray projection image to make non--destructive testing of mine conveyer belt has been developed. In the system, an one--dimensional photoelectric diode array is used to receive the X--ray projection image signals and convert them into electric signals. The principle of signal conversion is introduced and the prototype of this system is presented in this paper.

Airtight negative pressure dust-control technology and application of transpersite in the coal conveyer belt system

Presented a new coal dust control program that was airtight negative pressure dust-control technology at the transpersite,combining with analysis with the movement of air currents and numerical simulation of gas-solid flow at the transpersite,and proved the mechanism of precipitation and proliferation for coal dust-controlt in theory.The technol- ogy has made good economic results at the Heidaigou Clean Plant,not only dust concen- tration control within 10 mg/m^3 to the work site,but also substantial energy savings and cost savings.

A New Joint Elongation Detection Algorithm of the Conveyer Belt

There is a considerable interest in the image processing method of the joint of the conveyer belt with steel ropes.This paper presents a significant development of the joint's elongation judgment based on template matching and statistics which provides more accurate local information compared to the algorithms in the references,and shows a reliable,real-time performance.

Principles of X-Ray Non-Destructive Testing for Steel Wire Ropes in Conveyer Belt

The principles of X-ray Non-destructive testing (NDT) for steel wire ropes buried in conveyer belt is described in the paper. The mathematical model for calculating the effective cross section of wire ropes has been developed. The test data on steel wire rope samples of various types are presented,which have been compared with the National Standard. And this calculation model for the effective cross section is very important to the prediction system for transverse failure of conveyer belt.

NOVEL REALIZATION OF FIRST-ORDER ALL-PASS NETWORKS USING CURRENT CONVEYER

Two novel networks for realizing first-order all-pass transfer functions are intro-duced. The networks use a current conveyer, a buffer and only three passive elements, and theyexhibit a high input impedance.

Fiber optic sensing and performance evaluation of a water conveyance tunnel with composite linings under super-high internal pressures

For long-distance water conveyance shield tunnels in operation,the high internal water pressure may cause excessive deformation of composite linings,affecting their structural integrity and serviceability.However,the deformation and failure characteristics of lining structures under internal water pressure are not well investigated in the literature,particularly for three-layer composite linings.This study presents an in situ experimental investigation on the response of two types of composite linings(i.e.separated and combined lining structures)subjected to internal pressures,in which a fiber optic nerve system(FONS)equipped with distributed strain and displacement sensing nerves was employed to monitor the performance of the two composite linings during testing.The experimental results clearly show that the damage of the tunnel lining under different internal pressures was mainly located in the self-compaction concrete layer.The separated lining structure responded more aggressively to the variations in internal pressures than the combined one.Moreover,two evaluation indices,i.e.radial displacement and effective stiffness coefficient,are proposed for describing the changes in the structural bearing performance.The effective stiffness coefficients of the two types of lining structures were reduced by 39.4%and 29.5%,respectively.Considering the convenience of field monitoring,it is suggested that the average strains at different layers can be used as characteristic parameters for estimating the health conditions of lining structures in service.The analysis results provide a practical reference for the design and health evaluation of water conveyance shield tunnels with composite linings.

Nonlinear Dynamics of Viscoelastic Pipe Conveying Pulsating Fluid Subjected to Base Excitation

Based on the Euler-Bernoulli beam theory and Kelvin-Voigt model,a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established.The governing partial differential equation is transformed into a nonlinear system of fourth-order ordinary differential equations by using the generalized integral transform technique(GITT).The effects of the combined excitation of base motion and pulsating internal flow on the nonlinear dynamic behavior of the pipe are investigated using a bifurcation diagram,phase trajectory diagram,power spectrum diagram,time-domain diagram,and Poincare map.The results show that the base excitation amplitude and frequency significantly affect the dynamic behavior of the pipe system.Some new resonance phenomena can be observed,such as the period-1 motion under the base excitation or the pulsating internal flow alone becomes the multi-periodic motion,quasi-periodic motion or even chaotic motion due to the combined excitation action.

The Comparative Study of Chuangtse’s English Translations Under the Theory of Spirit Transmission and Meaning Conveyance

Cultural-loaded word is one of the most popular topics in translation studies.The theory of spirit transmission and meaning conveyance provides a new way for the translation of cultural-loaded word.Based on the A Happy Excursion,this paper makes a comparative analysis of the translation strategies of seven English versions.This study will reveal the similarities and differences between Chinese and foreign translators’translation strategies.

湿陷性黄土区输水隧洞盾构施工风险评估

为了提高针对湿陷性黄土区输水隧洞盾构法施工安全评估的可靠性,从人员管理、机械材料、施工技术、施工环境4个方面构建较为完善的施工安全风险评估指标体系;利用灰色-DEMATEL方法对中心度进行处理得到风险指标权重;以风险发生概率和风险损失程度两个维度为基础构建二维云评估模型,其中发生概率由主、客观方法相结合来确定,损失程度通过改进雷达图法从人员伤亡、经济损失、工期延误、功能缺陷和环境影响5个方面来综合确定。将该评估模型运用到引汉济渭工程X输水隧洞盾构法施工项目的安全评估中。结果表明:该项目施工风险评估等级为Ⅱ级,施工安全风险程度较小,评价结果符合工程实际,验证了该评估模型的可行性和有效性。研究成果可为湿陷性黄土区类似输水隧洞盾构法施工安全风险评估提供借鉴和参考。

长距离多支线有压输水系统起动水锤防护

为研究同时包含重力流输水管线与泵站加压提水管线的长距离多支线有压输水系统开启运行时的水锤问题,基于瞬变流分析的特征线法建立了输水系统过渡过程计算的数学模型,结合实际工程计算了输水系统开启运行时调节阀与水泵及其出口阀不同的开启时间与控制策略对水锤的影响,并在此基础上提出了空气阀联合阀门开启的水锤防护方案。结果表明:采取提水泵站滞后调节阀开启运行,且各提水泵站相继开启的策略可有效改善输水系统沿线的内水压力分布;采用空气阀联合阀门开启的水锤防护方案可在不影响输水系统反应速度的情况下以较小尺寸的空气阀达到较好的水锤防护效果。

双线大直径输水隧道建设对既有桥梁及桩基的影响分析

为准确分析双线大直径输水隧道下穿对既有桥梁结构的影响,构建桥梁-地层-桩基-盾构隧道高精度数值仿真模型,对桥梁桩基结构及盾构过程进行精细化模拟,结合基于智能算法的土层参数反演模型,获取更接近真实情况的土层参数,以提高数值模拟精度。结果表明:输水隧道盾构开挖引起的地表最大沉降量为15.01 mm,基于反演的地表变形计算结果与实际监测值的误差减少约70%;盾构隧道双线开挖会引起地表二次沉降变形,两条盾构隧道中间区域的地表二次沉降量最大,约占总沉降量的60%,最大二次沉降量为5.06 mm;隧道两侧的桩基受到影响较大,最大位移为10.03 mm,位于桩基顶部,而隧道开挖对桩基内应力分布影响较小,可以认为无影响。

大型副立井提升容器布置形式设计研究

结合某矿设计实例,对大型副立井提升容器布置形式的设计要点进行归纳总结,深入分析可行方案,从实用性、便利性和井筒直径等方面进行研究,得出了大型副立井最适用的提升容器布置形式,为其他矿井类似工程设计提供了经验,具有较高的参考价值。

离心泵变频调速在长距离输水工程中的应用与研究

介绍了南水北调大兴支线工程输水管道系统,特别是在处理水锤现象和保证安全输水方面的应对措施。对整个输水系统建立数学模型,阐述数学模型在供水系统瞬变流数值计算中的应用,对比离心泵启动及停止瞬态过程中工频与变频的变化对整个系统安全运行的影响,并提出了大兴支线输水工程过渡过程计算分析结果。通过建立合理的数学模型和设置边界条件,可有效解决供水系统瞬变流产生的问题,保证输水管道系统的安全稳定运行,为长距离输水工程设计及运行管理提供参考依据。

船闸单侧闸墙主廊道输水系统岔管水动力特性研究

船闸单侧闸墙主廊道输水系统具有结构简单、开挖量小、工程投资省等优点,在河谷狭窄、边坡陡峭等地形受限地区具有明显的技术优势,但工程应用难点之一在于如何保证廊道内断面流速的均匀性,避免出现严重的偏流、脱流现象。依托嘉陵江草街二线船闸工程,采用通用CFD软件FLUENT,对船闸单侧闸墙主廊道双阀门输水系统布置中的岔管水动力特性进行较为详细的研究,探讨岔管分岔角、墩头曲线形式以及外壁曲线形式对岔管水力特性的影响,提出外壁采用正弦曲线,内壁采用圆弧-直线-圆弧形曲线的单侧输水廊道阀门段岔管布置体形,可为类似工程设计提供参考。

长距离输水管道沿线穿洪沟防护设计研究

以新疆某长距离输水工程为例,针对管道沿线穿越不同的地质条件、不同宽度洪沟,在工程管线设计洪水重现期内洪水的防护进行分析。通过分析交通、明渠、埋地管道等常见的线性工程防护型式,确定工程建筑物布设型式;再根据穿越的山前倾斜砾质平原区、低山丘陵区、山前剥蚀准平原区三个地貌单元,对防护关键参数进行定量化分析;最后结合洪沟洪痕确定防护范围,为长距离输水管道沿线洪沟处防护设计提供参考。

长距离输水管道工程超大跨径托管桥方案比选研究

输水管道跨越沟渠、河道、山谷常采用桁架跨越、拱桥跨越、悬索跨越、斜拉索跨越等形式,但各种跨越形式均存在一定的问题。文章介绍准东供水工程长距离输水管道跨越渠道采用变截面连续钢箱梁桥,最大单跨跨径150m,为国内规模最大的同类型托管结构,其设计荷载为1.8m直径有压输水管,每延米水管及满管水重与3车道汽车满载相近。通过对悬索桥、拱桥、混凝土连续梁桥及变截面连续钢箱梁桥四种桥型从施工工期、经济性、抗震性能及抗风性能等多方面进行综合分析,最终选择了受冬期影响最小(施工期最短)且造价最低的80m+150m+80m变截面连续钢箱梁桥方案。输水管桥具有大跨径、窄桥面、风荷载大等特点,文中介绍的设计理念、计算方法、施工方案,可为类似工程提供借鉴。

基于“木郁达之”理论探析排便障碍型便秘的诊治思路

“木郁达之”理论首见于《黄帝内经》,通过追溯其理论源流发现:“木郁”是对肝脏生理功能失常的高度概括,即肝失疏泄。“达之”是一种治疗原则,目的在于使肝气条达、舒畅。排便障碍型便秘是临床常见病,肝失疏泄作为基本病机贯穿疾病始终,并常伴见脾虚湿阻、肺失宣降、肾阳不足等。临床辨治上以“达之”为治疗原则,针对肝脏自身病变灵活应用养血柔肝、疏肝理气、清肝泻火、温补肝阳,并视患者情况不同予以升阳除湿、肃降肺气、温补肾阳等。