Effect of flow stress—strain relation on forming limit of 5754O aluminum alloy

A modified Swift type flow stress—strain relation was presented in order to describe the uniaxial tension test curve reasonably. The FLD-strain （forming limit diagram made up of limit strain） of 5754O aluminum alloy sheet was calculated based on the two flow stress—strain relations using Yld2000-2d yield function. By comparing the theoretical and experimental results, it is found that the calculated FLD-strain based on the modified Swift flow stress—strain relation can reasonably describe the experimental results. However, though the common Voce flow stress—strain relation can describe the deformation behavior during homogenous deformation phase accurately, the FLD-strain calculated based on it is obviously lower than the experimental result. It is concluded that the higher the hardening rate of sheet metal is, the higher the forming limit is. A method for determining the reasonable flow stress—strain relation is recommended for describing the material behavior during inhomogenous phase and the forming limit of sheet metal.

Using Fuzzy Relations and GIS Method to Evaluate Debris Flow Hazard

The study area, located in the southeast of Tibet along the Sichuan-Tibet highway, is a part of Palongzangbu River basin where mountain hazards take place frequently. On the ground of field surveying, historical data and previous research, a total of 31 debris flow gullies are identified in the study area and 5 factors are chosen as main parameters for evaluating the hazard of debris flows in this study. Spatial analyst functions of geographic information system （GIS） are utilized to produce debris flow inventory and parameter maps. All data are built into a spatial database for evaluating debris flow hazard. Integrated with GIS techniques,the fuzzy relation method is used to calculate the strength of relationship between debris flow inventory and parameters of the database. With this methodology,a hazard map of debris flows is produced. According to this map,6.6% of the study area is classified as very high hazard, 7.3% as high hazard,8.4% as moderate hazard,32. 1% as low hazard and 45.6% as very low hazard or non-hazard areas. After validating the results, this methodology is ultimately confirmed to be available.

The Relationship between Flow Experience in Leisure and Life Satisfaction in Undergraduates

Objective:To understand the current situation of undergraduates’flow experience in leisure and life satisfaction,and to explore the relationship between the two.Methods:A stratified random sampling method was used to select 781 undergraduates(377 males and 410 females)from 7 colleges and universities in Guangdong Province.They were investigated using the Flow Experience in Leisure Questionnaire(FELQ)and the Youth Life Satisfaction Scale(YLSS).Results:The total scores of FELQ and YLSS of the students in this group are(161.73±19.81)and(174.45±26.50).FELQ’s unity of knowledge and action,challenge and skill balance,concentration,grade ranking,family economic status are positively related to YLSS’life satisfaction(β=.227,.115,.098,.158,.082,P<.05);“Like to sleep during leisure”is negatively correlated with life satisfaction of YLSS(β=-.097,P<.05);FELQ’s unity of knowledge and action,concentration,grade ranking and family economic status are positively related to YLSS’s self-satisfaction(β=.286,.126,.194,.096,P<.01);“Like to sleep during leisure”is negatively correlated with YLSS’s self-satisfaction(β=-.091,P<.01);FELQ’s unity of knowledge and action,challenge and skill balance,father’s occupation,“like self-study in leisure”are positively related to YLSS’environmental satisfaction(β=.198,.131,.075,.073,P<.05);“Like to sleep during leisure”,gender and YLSS environment satisfaction negatively correlated(β=-.094,-.091,P<.01).Conclusion:Flow experience in leisure,types of leisure activities,gender,grade ranking and family factors(family economic status and father’s occupation)may be related factors for the development of college students’life satisfaction.

Comparison between Diastolic Subendocardial Tissue Pressures Measured Directly or Calculated from Pressure-Flow Relations

Changes in intramyocardial tissue pressure modulate the relationship between coronary pressure and flow during the cardiac cycle. The present study compared the relation between measured and calculated diastolic subendocardial tissue pressure and coronary pressure at zero flow in anesthetized dogs after modulation of either coronary sinus (i.e. Fogarty catheter) or left ventricular intracavity (i.e. volume loading) pressure. Experiments were conducted in anesthetized, instrumented dogs;coronary pressure flow relations were constructed during pharmacologic vasodilatation and intramyocardial tissue pressure was measured using micromanometer pressure sensors. Elevated coronary sinus pressures did not affect subendocardial pressure-flow relations signifying that diastolic tissue pressure within this layer is the effective coronary back pressure. Higher left ventricular intracavity pressure did not affect either diastolic subendocardial tissue pressure or pressure flow relations within this layer. Results show a direct linear relation (y = 1.106x - 0.652;r2 = 0.59. P = 0.001) between measured and calculated diastolic subendocardial tissue pressure and coronary pressure at zero-flow over a wide range of pressures after either LV systemic or coronary sinus pressure modulation. Knowledge of back pressure in the subendocardium is useful for the evaluation of efficacy of cardiac interventions on myocardial perfusion particularly at the level of the microcirculation.

Correlation between Aerodynamic Noise and Velocity Fluctuation of Tip Leakage Flow of Axial Flow Fan

In the present paper the attention is focused on correlation between fan noise and velocity fluctuations of tip leakage vortex around rotor blade of a low pressure axial flow fan at the maximum pressure operating point. We measured time fluctuating velocity near the rotor tip around the rotor blades by using a hot-wire sensor from a relative flame of refer- ence fixed to the rotor blades. As the results, it is clear that the velocity fluctuation due to tip leakage vortex has weak periodicity and the hump portion appeared in its spectrum. If the flow rate was lower than the design condition, the tip leakage flow became to attach to the following blade and the sound pressure level at frequency of velocity fluctuation of this flow was increased. The correlation measurements between the velocity fluctuation of tip leakage flow and the aerodynamic noise were made using a rotating hot-wire sensor near the rotor tip in the rotating frame. The correlation between the velocity fluctuation due to tip leakage flow and acoustic pressure were increased due to generation of weak acoustic resonance at the maximum pressure operating point.

Non-Darcy flow in oil accumulation (oil displacing water) and relative permeability and oil saturation characteristics of low-permeability sandstones

Hydrocarbon resources in low-permeability sandstones are very abundant and are extensively distributed. Low-permeability reservoirs show several unique characteristics, including lack of a definite trap boundary or caprock, limited buoyancy effect, complex oil-gas-water distribution, without obvious oil-gas-water interfaces, and relatively low oil （gas） saturation. Based on the simulation experiments of oil accumulation in low-permeability sandstone （oil displacing water）, we study the migration and accumulation characteristics of non-Darcy oil flow, and discuss the values and influencing factors of relative permeability which is a key parameter characterizing oil migration and accumulation in low-permeability sandstone. The results indicate that： 1） Oil migration （oil displacing water） in low- permeability sandstone shows non-Darcy percolation characteristics, and there is a threshold pressure gradient during oil migration and accumulation, which has a good negative correlation with permeability and apparent fluidity; 2） With decrease of permeability and apparent fluidity and increase of fluid viscosity, the percolation curve is closer to the pressure gradient axis and the threshold pressure gradient increases. When the apparent fluidity is more than 1.0, the percolation curve shows modified Darcy flow characteristics, while when the apparent fluidity up＂ non-Darcy percolation curve; 3） Oil-water is less than 1.0, the percolation curve is a ＂concave- two-phase relative permeability is affected by core permeability, fluid viscosity, apparent fluidity, and injection drive force; 4） The oil saturation of low- permeability sandstone reservoirs is mostly within 35%-60%, and the oil saturation also has a good positive correlation with the permeability and apparent fluidity.

QUICK ASSESSMENT METHODOLOGY FOR RELIABILITY OF SOLDER JOINTS IN BALL GRID ARRAY (BGA) ASSEMBLY——PART Ⅰ: CREEP CONSTITUTIVE RELATION AND FATIGUE MODEL

In this study, a new unified creep constitutive relation and a mod- ified energy-based fatigue model have been established respectively to describe the creep flow and predict the fatigue life of Sn-Pb solders. It is found that the relation successfully elucidates the creep mechanism related to current constitutive relations. The model can be used to describe the temperature and frequency dependent low cycle fatigue behavior of the solder. The relation and the model are further employed in part Ⅱ to develop the numerical simulation approach for the long-term reliability assessment of the plastic ball grid array (BGA) assembly.

Relative permeability estimation of oil-water two-phase flow in shale reservoir

Oil-water two-phase flow is ubiquitous in shale strata due to the existence of connate water and the injection of fracturing fluid.In this work,we propose a relative permeability model based on a modified Hagen-Poiseuille(HP)equation and shale reconstruction algorithm.The proposed model can consider the nanoconfined effects(slip length and spatially varying viscosity),oil-water distribution,pore size distribution(PSD),total organic matter content(TOC),and micro-fracture.The results show that the increasing contact angles of organic matters(OM)and inorganic minerals(iOM)increase the relative permeability of both oil and water.As the viscosity ratio increases,the relative permeability of oil phase increases while that of water phase decreases,due to the different water-oil distribution.The effective permeability of both oil and water decreases with the increasing TOC.However,the relative permeability of water phase increases while that of oil phase decreases.The increasing number and decreasing deviation angle of micro-fracture increase the effective permeability of oil and water.However,microfracture has a minor effect on relative permeability.Our model can help understand oil-water twophase flow in shale reservoirs and provide parameter characterization for reservoir numerical simulation.

The Effect of the Relative Velocity on Traffic Flow

The optimal velocity model of traffc is extended to take the relative velocity into account. The traffcbehavior is investigated numerically and analytically with this model. It is shown that the car interaction with therelative velocity can effect the stability of the traffic flow and raise critical density. The jamming transition between thefreely moving and jamming phases is investigated with the linear stability analysis and nonlinear perturbation methods.The traffic jam is described by the kink solution of the modified Korteweg-de Vries equation. The theoretical result isin good agreement with the simulation.

Particle characteristics and rheological constitutive relations of high concentration red mud

Red mud has relatively small solid particles （d50= 13.02 μm） and will flow in paste form under high pressure during pipeline transport. Red mud belongs to a two-phase flow of materials with high viscosity and a high concentration of non-sedimentation, homogeneous solid-liquids. It is difficult to test its rheological properties under atmospheric pressure. Measurements such as rotational viscometry can not reflect the real state of the material when it is flowing in a pipe. Tested rheological parameters are somewhat higher than the actual values. In our investigation, grain shape, distinctive modality and grain size distribution of red mud were tested. Based on the principle of tube measurement, rheological experiments on red mud at different concentrations were carried out by using our independently developed tube-type pressure theology test facility, and obtained constitutive equations. We conclude that red mud behaves as non-Newtonian pseudo-plastic fluid in pipe flows. Its consistency and power-law indices vary considerably with different concentrations.

A traffic flow lattice model considering relative current influence and its numerical simulation

Based on Xue＇s lattice model, an extended lattice model is proposed by considering the relative current information about next-nearest-neighbour sites ahead. The linear stability condition of the presented model is obtained by employing the linear stability theory. The density wave is investigated analytically with the perturbation method. The results show that the occurrence of traffic jamming transitions can be described by the kink-antikink solution of the modified Korteweg-de Vries （mKdV） equation. The simulation results are in good agreement with the analytical results, showing that the stability of traffic flow can be enhanced when the relative current of next-nearest-neighbour sites ahead is considered.

High-precision nonisothermal transient wellbore drift flow model suitable for the full flow pattern domain and full dip range

A reliable multiphase flow simulator is an important tool to improve wellbore integrity and production decision-making.To develop a multiphase flow model with high adaptability and high accuracy,we first build a multiphase flow database with 3561 groups of data and developed a drift closure relationship with stable continuity and high adaptability.Second,a high-order numerical scheme with strong fault capture ability is constructed by effectively combining MUSCL technology,van Albada slope limiter and AUSMV numerical scheme.Finally,the energy equation is coupled into the AUSMV numerical scheme of the drift flow model in the form of finite difference.A transient non-isothermal wellbore multiphase flow model with wide applicability is formed by integrating the three technologies,and the effects of various factors on the calculation accuracy are studied.The accuracy of the simulator is verified by comparing the measurement results with the blowout experiment of a full-scale experimental well.

Rotation invariant constitutive relation for Reynolds stress structure parameter

A new Reynolds stress constitutive formula is constructed using the first- order statistics of turbulent fluctuations instead of the mean strain rate. It includes zero empirical coefficients. The formula is validated with the direct numerical simulation （DNS） data of turbulent channel flow at Reτ=180. The Reynolds stresses given by the proposed formula agree very well with the DNS results. The good agreement persists even after the multi-angle rotation of the coordinate system, indicating the rotation in- variance of the formula. The autocorrelation of the fluctuating velocity rather than the mean strain rate is close to the essence of the Reynolds stress.

RELATIVE ENTROPY AND COMPRESSIBLE POTENTIAL FLOW

Compressible （full） potential flow is expressed as an equivalent first-order system of conservation laws for density ρ and velocity v. Energy E is shown to be the only nontrivial entropy for that system in multiple space dimensions, and it is strictly convex in ρ, v if and only if ｜v｜ 〈 c. For motivation some simple variations on the relative entropy theme of Dafer- mos/DiPerna are given, for example that smooth regions of weak entropy solutions shrink at finite speed, and that smooth solutions force solutions of singular entropy-compatible per- turbations to converge to them. We conjecture that entropy weak solutions of compressible potential flow are unique, in contrast to the known counterexamples for the Euler equations.

THE EXPERIMENTAL STUDY OF STRESS-RELATED PATHOLOGICAL CHANGES IN CEREBRAL VENOUS BLOOD FLOW IN NEWBORN RATS ASSESSED BY DOCT

In experiments on newbom rats with stress related intracrani al hemorhage(ICH)using Doppler optical coberence tomognaphy(DOCT)we have shown that latent stage of ICH(4 h after stress)is characterized by decrease of venous blood outflow and the loss of sensitivity of sagittal vein to vasoconstrictor ffect of adrenaline.The incidence of ICH(24 h after stress)was accompanied by progressi on of early pathological changes in cerebral venous blood flow(CVBF)and development of venous insufficiency.Taking into consideration of this fact,we suggest that the suppression of CVBF related to the severity to the deleterious effect of stress on the brain hemodynamics in newborn rats.These facts allow us to conclude that the venous insufficiency with the loss of vasoconstrictor response to adrenaline is an informative and sensitive component of pattern of CVBF that can be important diagnostic criteria of risk of ICH development in newborns.

C1q/TNF-Related Protein 1 promotes arterial endothelial barrier dysfunction under disturbed flow

Objective Atherosclerotic lesions preferentially occur at branch points of arterial trees where the blood flow is disturbed.Disturbed flow increases endothelial permeability,vascular barrier dysfunction,and finally the development of atherosclerosis.CTRP1,a member of C1q/TNF related protein(CTRP)family,is a novel secreted glycoprotein and its biological functions are largely undefined.

Impact pressure of debris flow on beam dam

The use of open-type check dams in mountainous areas has become common practice in order to mitigate the effects of debris flow and extend the service life of engineering structures.The beam dam,a common debris flow control system,has received less attention in research on the impact process of debris flow and check dams compared to solid check dams.Additionally,the estimation of impact pressure in debris flow primarily considers debris flow characteristics,without taking into account the influence of geometric characteristics of the transmission structure.To better understand the impact process of debris flow on beam dams,a series of small-scale debris flow impact tests were conducted in a model flume.Key parameters,including velocity,depth,and impact pressure,were measured.The results show that the maximum impact pressure of debris flow is affected by both the characteristics of the debris flow and the relative opening size of the beam dam.Due to flow and edge occlusion in the middle of the beam dam,the discharge of debris flow is enhanced,resulting in a longer impact process and higher maximum impact pressure.Based on these findings,a calculation model of the maximum impact pressure of debris flow at the midpoint of the middle beam is proposed,which can be used to estimate the impact of debris flow on the discharge part of the beam dam.

工作沉浸感在手术室护士工效学负荷与职业召唤间的中介作用

目的探讨工作沉浸感在手术室护士工效学负荷与职业召唤间的中介作用,为提高手术室护士职业召唤水平提供参考。方法采用便利抽样法选取218名手术室护士,采用一般资料调查表、护士工作沉浸感量表、手术室护士人体工效学评价问卷和职业召唤量表进行调查。结果218名手术室护士工效学负荷总分(50.47±9.84)分,职业召唤(38.78±5.59)分,工作沉浸感(129.37±11.19)分。手术室护士人体工效学负荷与职业召唤及工作沉浸感呈负相关(r_(1)=-0.645,r_(2)=-0.477,P<0.01),工作沉浸感与职业召唤呈正相关(r_(3)=0.517,P<0.01)。工作沉浸感在手术室护士工效学负荷与职业召唤间起部分中介作用,中介效应占总效应的20.2%。结论手术室护士职业召唤处于中等水平,护士工效学负荷既可以直接负向预测职业召唤,也可以通过降低护士的工作沉浸感间接影响职业召唤。提示医院管理者应关注手术室护士工效学负荷,采取相关措施降低其工效学负荷,提高护士工作沉浸感来提高职业召唤水平。

松花江干流造床水沙动力及河相关系的探究

在分析松花江干流河道特性的基础上,基于实测资料,探究了造床水沙动力条件和河相关系。结果表明,枯水期和涨水期水流的造床作用不甚明显,主汛期水流是主要造床动力,退水期水流也具有一定造床作用;通过对比河道特征流量和计算得到的造床流量,说明常年洪水的造床作用依然十分有限,只有3~5年一遇的较大洪水才会形成较为明显的造床作用;河道河床呈现宽浅型,主槽相对窄小,洪漫滩地宽阔,中游段主槽河相关系系数√B/H在2~5之间,上游段和下游段大多超过5;基于河床最小活动性假设,得到河相关系与流量及含沙量之间的关系式,采用造床流量针对主槽进行检验,公式相符性较好。

基于冲刷指数的雨水管渠冲刷淤积分析

流速、雷诺数、充满度等单因素指标虽然与雨水管渠的冲刷和淤积量有一定的关联,但是通过单因素指标不足以全面地判断雨水管道的冲刷和淤积。在起动流速和止动流速的基础上,提出了冲刷指数的概念。结合连续非恒定流不同工况下冲刷和淤积量模拟,计算了流速、雷诺数、充满度、冲刷指数4个因素与冲刷量的灰色关联度,其关联度大小依次为:冲刷指数>雷诺数>充满度>流速。根据不同工况的恒定流模型实验的结果,其关联度大小依次为:冲刷指数>>流速>雷诺数>充满度。可以认为,在恒定流与非恒定流工况下,冲刷量和冲刷指数有显著的强相关性,冲刷指数能代替具体的冲刷量计算实现对冲刷程度和趋势的合理判断。