T-Y TUBE MODEL OF HUMAN ASCENDINGAORTIC INPUT IMPEDANCE

This paper proposed a T- Y tube model to simulate foe input impedance of arterial system. It improves and extends the asymmetric T-tube model which was firstproposed by O' Rourke[1] and developed laier by Liu et al.[2]. Based on foe asymmetricT-tube model. a T-Y tube model was proposed by adding branching tubes whichrepresem the iliac arteries.All the tubes are considered to be uniform,viscoelasticlongitudinally tethered cylindrical tubes.The upper tube terminates with a windkesselmodel, while the terminal arterioles of the lowr tube are expressed as a resistance.After proper eraluation of the parameters.the impedance of the arterial system iscalculated under normal physiological and hypertensive condition.The model canpredict impedance in good agreement with the experimentally obtained data no matterin normal physiological condition or in pathological condition In comparison with theasymmeric T-tube model,T- Y tube model is closer to anatomy structure of the human arlerial system and at the sametime much simpler than the extremely complex multiplebranching tube model Therefore it will be a valuable model in studying the influencesof various parameters on aorta impedance and ventricular-vascular coupling.

Double Multiple Streamtube Model and Numerical Analysis of Vertical Axis Wind Turbine

The present paper contributes to the modeling of unsteady flow analysis of vertical axis wind turbine (VAWT). Double multiple streamtube (DSMT) model was applied for the performance prediction of straight bladed fixed pitch VAWT using NACA0018 airfoil at low wind speed. A moving mesh technique was used to investigate two-dimensional unsteady flow around the same VAWT model with NACA0018 airfoil modified to be flexible at 150 from the main blade axis of the turbine at the trailing edge located about 70 % of the blade chord length using fluent solving Reynolds average Navier-strokes equation. The results obtained from DMST model and the simulation results were then compared. The result shows that the CFD simulation with airfoil modified has shown better performance at low tip speed ratios for the modeled turbine.

Conceptual Modeling of Contaminated Solute Transport Based on Stream Tube Model

In this study, we performed a conceptual modeling on solute transport based on theoretical stream tube model (STM) with various travel time distributions assuming a pure convective flow through each tube in order to investigate how the lengths and distributions of solute travel time through STM affect the breakthrough curves at the end mixing surface. The conceptual modeling revealed that 1) the shape of breakthrough curve (BTC) at the mixing surface was determined by not only input travel time distributions but also solute injection mode such as sampling time and pulse lengths;2) the increase of pulse length resulted in the linear increase of the first time moment (mean travel time) and quadratic increase of the second time moment (variance of travel time) leading to more spreading of solute, however, the second time moment was not affected by travel time distributions and 3) for a given input distributions the increase in travel distance resulted in more dispersion with the quadratic increase of travel time variance. This indicates that stream tube model obeying strictly pure convective flow follows the concept of convective-lognormal transport (CLT) model regardless the input travel time distributions.

Wind Tunnel Validation of Double Multiple Streamtube Model for Vertical Axis Wind Turbine

The performance and annual energy output have to be predicted to maximize the economic benefits from a wind turbine. Mathematically predicting the performance of Darrieus type lift based turbines are challenging due to the inconsistent angle of attack, blade wake interaction and local induced velocities giving rise to complex flow physics. A reliable and validated mathematical model is therefore essential to optimize the various design parameters prior to manufacture. The objective of the current study is to evaluate widely employed aerodynamic models based on their prediction accuracy, limitations, and computational requirements. Double multiple stream tube models have been discussed in detail and the predictions are experimentally validated through the wind tunnel test of three-bladed H-Darrieus rotor in terms of torque and power coefficient. The possible sources for the deviation between the predicted and measured values have been discussed and concluded with potential solutions.

Study of heavy-light hadrons within a flux tube model

A classic mass loaded flux tube model and the diquark picture are employed to explore both mesons and baryons. The spectrum of Λc＋ baryons and Ds mesons is systematically obtained. The spin-orbit interaction in Ds was simplified as an L·S coupling. The spin-orbit interaction in Λc was simplified as a Jl ·Jc coupling. The predicted masses are consistent with the latest experiments.

Dynamical study of light scalar mesons below 1GeV in a flux-tube model

The light scalar mesons below 1GeV configured as tetraquark systems are studied in the framework of the flux-tube model. Comparative studies indicate that a multi-body confinement,instead of the additive two-body confinement, should be used in a multiquark system.The σ and κ mesons could be well accommodated in the diquark-antidiquark tetraquark picture, and could be colour-confinement resonances. The a0（980） and fo（980） mesons are not described as KK molecular states and ns diquark-antidiquark states.However, the mass of the first radial excited state of the diquark-antidiquark state, nn is 1019 MeV,is close to the experimental data of the fo （980）.

Application of Tube-Packaged FBG Strain Sensor in Vibration Experi ment of Submarine Pipeline Model

Optical fiber sensors have received increasing attention in the fields of aeronautic and civil engineering for their superior ability to stand explosion, immunity to electromagnetic interference and high accuracy, especially fit for measureroent applications in harsh environment. In this study, a novel FBG （fiber Bragg grating） strain sensor, which is packaged in a 1.2 mm stainless steel tube with epoxy resin, is developed. Experiments are conducted on the universal material testing machine to calibrate its strain transferring characteristics. The sensor has the advantages of small size, high precision and flexible use, and exhibits promising potentials. Five tube-packaged strain FBG sensors have been applied to the vibration experiment of a submarine pipeline model. The strain measttred with the FBG sensor agrees well with that measttred with the electric resistance strain sensor.

MODELING OF CONTROLLED THERMO-MECHANICAL PROCESSING OF TUBES FOR ENHANCED MANUFACTURING AND PERFORMANCE

An integrated mathematical model to simulate seamless tube rolling processes has been developed at The Timken Company. The model is capable of simulating the thermal, deformation and microstructure evolution in the piercing, elongating and reducing/sizing and the austenite decomposition in the mill annealing and cooling operations. Finite difference schemes are employed to model cooling, reducing/sizing and stretch reducing, and finite-element schemes are employed to simulate piercing and elongating. The model predicts the thermal history, deformation, rolling load, torque, recrystallization and grain growth in hot tube rolling, austenite decomposition in cooling or annealing, and the final structure-properties. In this paper mathematical models which are employed to describe the thermal, deformation and microstructure evolution along with the modeling results are presented. The developed 'tube rolling mill in the computer' provides a powerful tool for engineers for product and process development, process control, process optimization and quality control.

High-Quality Three-Dimensional Computed Tomography Angiography of Abdominal Viscera with Small Focal Spot, Low Tube Voltage, and Iterative Model Reconstruction Technique

Purpose: To evaluate the quality of three-dimensional (3D) CT angiography images of the abdominal viscera with small focal spot, low tube voltage, and iterative model reconstruction technique (IMR). Materials and Methods: Seven patients with suspected disease of the pancreatobiliary system had undergone CT with high-quality CTA protocol in the present study. There were 5 men and 2 women, ranging in age from 52 to 80 years (mean: 64 years). Results: Depiction of abdominal small artery, small portal vein was possible in all cases. In two cases that we were able to compare, it was superior to standard CTA in small vascular depiction in CTA made clearly in high quality protocol. Conclusions: Although the use of small focal spot, low tube voltage, and IMR can produce higher-quality images of abdominal vessels than standard CTA, this improvement is not significant at elevated radiation doses.

Thermogravimetric characteristics and different kinetic models for medical waste composition containing polyvinyl chloride-transfusion tube

Thermogravimetric study of medical transfusion tube(MTT) waste containing polyvinyl chloride(PVC) was carried out using the thermogravimetric analyser(TGA) with N2, at different heating rates of 5, 10, 20, 30, 50 °C/min. The purpose is to obtain pyrolysis characteristics and kinetic parameters of medical waste. The experimental results indicate that the pyrolysis behavior of the MTT sample is in agreement with its main ingredient of PVC, appearing two stair stepping stages. The influence of the additives in MTT on pyrolysis behavior was also revealed, which could improve MTT pyrolysis at lower temperature in the first stage, and cause obvious unsmoothness and asymmetry of the second DTG peak. Four n-order kinetic models of Coats-Redfern, Ozawa, Kissinger and Freeman-carroll were used to get the kinetic parameters. Furthermore, a novel "two-step four-reaction model" was established to simulate the whole continuous process. The different methods and the kinetic parameters thus obtained were discussed and compared with each other in literatures. The reasons of deviation among kinetic values were tried to be elucidated. The new established model could more satisfactorily describe the pyrolysis process of MTT, being more mechanistic and conveniently serving for the engineering.

Numerical Modelling of Performance of R22 and R290 in Adiabatic Capillary Tubes Considering Metastable Two-Phase Region ——Theoretical Model Description and Validation

A homogeneous theoretical model is developed to predict the performance of R22 and R290 in adiabatic capillary tubes. The model is based on conservation equations of mass, momentum and energy. Metastable both liquid and two-phase flow regions are considered in the model. In metastable two-phase region, superheated liquid is introduced into the metastable mixture viscosity and two methods are presented to evaluate it. The model is validated by comparing the predicted pressure and temperature profile and mass flow rate with several investigators′ experimental data of R22 and one of its alternatives R290 reported in literature. All of the predicted mass flow rates are within ±800 of measured values. Comparisons are also made between the present model and other investigators′ models or sizing correlation. The model can be used for design or simulation calculation of adiabatic capillary tubes.

Modeling and Analysis of Transitional Tube with Constant Sectional Area along Derivative Central Route

Firstly, sample square-circular transition tube along straight central route was modeled on CATIA software. The parameters are as follows： let the tube length is L, and the constant cross section area is S, and S = πR^2 = a2, in which R stands for the circle radius on one end, and a the square side length on the other end; set up the coordinate system with OX axis on the central route in which the origin O is on centroid of the square end and assume the cross section size at x as the square shaped with all four comers filleted in radius r which is proportional to x, that is, the linear slope of r is R/L, thus, both values r and square side length ax can be attained on the constant cross section area assumption. Secondly, some sample polygonal-circular transition tubes along straight, circular and helical central route were implemented similarly. Thirdly, numerical analysis of stress and displacement of these tubes were carried out on MSC/PATRAN software which are important to the distribution of turbulent flow and the layout of these transitional tube structures.

基于正交切削逆识别井下管柱的Johnson-Cook本构模型

在有限元仿真金属切削过程中,本构模型是仿真的基础,目前井下生产管柱J55油管材料的本构模型参数尚不明确,为此,提出一种基于正交切削理论逆识别油管材料Johnson-Cook(J-C)本构模型参数的方法。首先,通过准静态拉伸试验得到油管材料的应力-应变曲线,根据曲线拟合确定J55油管的初始屈服强度A、应变硬化系数B和应变硬化因子n;其次,通过正交切削试验获得切削力以及进给力,根据正交切削试验和平行剪切区模型,计算正交切削过程主剪切区中的流动应力、应变、应变率以及切削温度,并将这些参数与计算出的A、B、n代入J-C模型中,得到多组应变率敏感性参数C以及热软化效应参数m,从而确定其约束范围;第三,采用自适应权重粒子群算法在约束范围中搜索出参数C和m的最优值,进而确定J55油管材料本构模型参数;最后,使用逆识别法得出的J-C本构模型进行有限元仿真,将仿真结果与试验结果进行了对比。研究结果表明:与试验相比,有限元仿真的切削力和进给力最大相对误差分别为14.4%和13.64%,有限元仿真模拟温度与实际测量温度的最大相对误差为10.57%,仿真模型和实际切削过程在切屑形态上表现出了一致规律,验证了逆识别方法可行性和本构模型的可靠性。

反复荷载下圆钢管型钢再生混凝土组合柱恢复力模型研究

为建立圆钢管型钢再生混凝土组合柱的恢复力模型,对11根圆钢管型钢再生混凝土组合柱试件进行了低周反复荷载试验研究,考虑了再生骨料取代率、配钢率及钢管径厚比等不同设计参数的影响,分析了组合柱的地震破坏形态及滞回性能。基于组合柱的力学特征及曲线形状,提出了圆钢管型钢再生混凝土组合柱骨架曲线的三折线参数模型,采用理论推导与数据拟合的方法确定了组合柱骨架曲线的模型参数。在此基础上,给出了组合柱的滞回规则和卸载规律,构建了组合柱的恢复力模型,计算滞回曲线与试验滞回曲线吻合良好,表明该恢复力模型较好地反映了反复荷载下组合柱的受力特征点及滞回性能,可为此类组合柱的推广提供技术参考。

基于Tube不变集的鲁棒模型预测控制

针对具有持续有界扰动的线性变参数系统,设计一种基于Tube不变集的鲁棒模型预测控制算法。离线算法结合系统多胞体模型参数变化的影响,构建系统的Tube不变集。在对应标称模型状态变量的多面体不变集算法基础上,得到系统的多面体状态允许不变集序列。在线算法通过强控制优化得到标称模型系统的控制量,以得到符合实际控制过程的系统控制量,给出本算法的详细步骤和系统稳定性证明。仿真结果验证了本算法的有效性,表明本算法将持续有界扰动对系统的影响限制在Tube不变集中,实现了系统的快速稳定控制。

负泊松比点阵结构填充薄壁管轴向压缩行为及吸能特性

薄壁填充结构具有轻量化、高比吸能的优点,被广泛应用于航空航天、汽车、轨道交通等工程领域。负泊松比结构在受到冲击时力学性能会逐渐增强,因此本文基于双箭头型负泊松比点阵提出一种新型薄壁填充管吸能结构,通过准静态压缩实验和有限元数值模拟方法研究了新型填充管在压缩载荷作用下的变形失效模式与力学响应。建立了平均碰撞力的理论预测模型,并通过有限元分析验证了模型可靠性,在此基础上研究了负泊松比点阵结构的细观设计参数对填充管抗压缩性能的影响规律。结果表明,填充管在压缩载荷作用下的失效模式为局部屈曲失效,相比于单一薄壁管与点阵结构,填充管具有更好的抗压缩性能;通过参数分析明确了通过增加胞元杆件壁厚和下支撑杆夹角,能显著提高填充管抗压缩性能,这将为后续负泊松比点阵填充结构的抗冲击优化设计提供重要参考。

黄土盾构下穿不同地下非连续管线的模型试验

针对城市盾构隧道施工下穿既有输气管线引起管线沉降与受力问题,以河南省某在建高速公路为工程背景,进行室内模型试验和有限元数值模拟.考虑不同非连续管线接头间距、接头刚度和管隧间距的影响,探讨管隧正交工况下,隧道开挖对非连续管线沉降、弯矩及管土接触应力的影响.研究结果表明:黄土盾构正交下穿管线存在沉降集中区,在该区范围内,管线接头与管段相对刚度比的大小对管线平均沉降增长速率影响较大,相对刚度比由1.30减小至0.21,非连续管线平均沉降增长速率增大1.5倍;相对刚度比相对大小对非连续管线沉降和弯矩起到决定性作用;通过定义非连续管线综合刚度比,揭示不同综合刚度比下非连续管线最大沉降变化规律和管线最大正负弯矩相对变化规律,其中综合刚度比与管线最大沉降服从3次多项式拟合函数,管线的最大正弯矩值随着最大负弯矩值的改变服从4次多项式拟合函数;管线的管土接触应力变化均呈现“双峰型”变化,管土接触峰值应力随着接头间距的增大而增大;数值模拟表明,管线最大沉降随着管隧间距增大而呈现折线型减小,该转折点出现在管隧间距与隧道开挖直径比为1处.

Mathematical Modelling of Operating Temperature Variations of Shell-and-Tube Heat Exchanger (10-E-01)

The technique of modeling operating temperature variations of shell-and-tube heat exchanger 10-E-01 of kerosene-crude oil streams of Port Harcourt refinery crude distillation unit is presented in this research. Appropriate first-order model equations were developed applying principles of energy balance. The differential equations developed for the process streams which exchanged heat was evaluated numerically to predict the temperature variations as a function of time. The relevant parameters associated with typical heat exchanger works were calculated using plant data of 10-E-02. The model strives to predict the final kerosene temperature from 488 to 353.6 K. While the crude oil streams temperature rose from 313 to 353.6 K. The developed model enables the operator to predict the final temperature at the kerosene hydro-treating unit and thereby prevent regular emergency shutdowns due to excessive temperature rise.