柚皮果胶的提取方法比较及其粘流性能研究

比较了从江永柚皮中提取果胶的不同方法。研究了柚皮果胶溶液的粘流性能,测定了果胶的特性粘度并由此计算出果胶的分子量。结果表明:盐酸逆流萃取法为从柚皮中提取果胶的较好方法,果胶溶液的粘流活化能约为17.14kJ/mol(依赖于果胶浓度大小),采用逆流萃取法提取的果胶特性粘度为4.492ml/g,果胶分子量为7.17×104。

Relationship between rheological manufacturing process and optical performance of optical fiber coupler

Through theoretical analysis and experiments, the viscoelastic mechanical model of optical fiber coupler in the process of fused biconical taper was established, and the numerical analysis in non-uniform temperature field was made. The results show that the rheological parameters, such as drawing speed and fused temperature, have a tremendous influence on stress distribution and performance of optical fiber coupler, especially the influence of fused temperature. The change of fused temperature by 5℃ can lead to the change of the maximum stress by 30% and stress difference by 20% in the same cross section. The change of temperature gradient by 3% can result in the change of stress difference by 90%. In the present condition of rheological technology, rheological defects such as crystallizations and microcracks are easy to generate in the optical fiber coupler.

Mechanism of Downcutting Erosion of Debris Flow over a Movable Bed

The phenomenon of debris flow is intermediate between mass movement and solid transport. Flows can be sudden, severe and destructive. Understanding debris flow erosion processes is the key to providing geomorphic explanations, but progress has been limited because the physical-mechanical properties, movement laws and erosion characteristics are different from those of sediment-laden flow. Using infinite slope theory, this research examines the process and mechanism of downcutting erosion over a moveable bed in a viscous debris flow gully. It focuses specifically on the scour depth and the critical slope for viscous debris flow,and formulas for both calculations are presented.Both scour depth and the critical conditions of downcutting erosion are related to debris flow properties(sand volume concentration and flow depth) and gully properties(longitudinal slope,viscous and internal friction angle of gully materials,and coefficient of kinetic friction). In addition, a series of flume experiments was carried out to characterize the scouring process of debris flows with different properties. The calculated values agreed well with the experimental data. These theoretical formulas are reasonable, and using infinite slope theory to analyze down cutting erosion from viscous debris flow is feasible.

Thick Domain Walls in Lyra Geometry with Bulk Viscosity

In this paper, we evaluate the general solutions for plane-symmetric thick domain walls in Lyra geometry in presence of bulk viscous fluid. Expressions for the energy density and pressure of domain walls are derived in both cases of uniform and time varying displacement field β. Some physical consequences of the models are also given. Finally, the geodesic equations and acceleration of the test particle are discussed.

Numerical simulation of effect of bionic V-riblet non-smooth surface on tire anti-hydroplaning

Inspired by the idea that bionic non-smooth surfaces(BNSS) can reduce fluid adhesion and resistance, and the effect of bionic V-riblet non-smooth structure arranged in tire tread pattern grooves surface on anti-hydroplaning performance was investigated by using computational fluid dynamics(CFD). The physical model of the object(model of V-riblet surface distribution, hydroplaning model) and SST k-ω turbulence model were established for numerical analysis of tire hydroplaning. With the help of a orthogonal table L16(45), the parameters of V-riblet structure design compared to the smooth structure were analyzed, and obtained the priority level of the experimental factors as well as the best combination within the scope of the experiment. The simulation results show that V-riblet structure can reduce water flow resistance by disturbing the eddy movement in boundary layers. Then, the preferred type of V-riblet non-smooth structure was arranged on the bottom of tire grooves for hydroplaning performance analysis. The results show that bionic V-riblet non-smooth structure can effectively increase hydroplaning velocity and improve tire anti-hydroplaning performance. Bionic design of tire tread pattern grooves is a good way to promote anti-hydroplaning performance without increasing additional groove space, so that tire grip performance and roll noise are avoided due to grooves space enlargement.

Coupled effect of viscosity enhancing admixtures and superplasticizers on rheological behavior of cement paste

The coupled effect of viscosity enhancing admixtures(VEA)and superplasticizer(SP)on the rheological behavior of cement paste was investigated in this work.Two types of VEAs,including hydroxypropyl methylcellulose(HPMC)and Welan gum,and two types of SPs,i.e.polycarboxylate(PCA)and polynaphthalenesulfonate(PNS)were used as admixtures for cement paste.Rheological curves of cement paste and simulated pore solution containing VEA and SP were tested.Simulated pore solution test results show that molecules of different SPs may generate different effects on the viscosity of VEA solutions.Hershel-Bulkley(H-B)model was used to fit rheological curve of cement paste.Strong interaction between PNS and HPMC was observed in this work.

Experimental Study on the Viscoelastic Behaviors of Debris Flow Slurry

The rheological properties of most liquid in nature are between liquids and solids, including both elastic changes and viscosity changes, that is socalled ＂viscoelastic＂. Dynamic oscillatory test was used to quantitatively study the distinct viscoelastic behaviors of debris flow slurry in the shear stress conditions for the first time in this study. The debris flow slurry samples were from Jiangjiagou Ravine, Yunnan Province, China. The experimental results were found that at the low and middle stages of shearing, when the angular velocity 09〈72.46 s-1, the loss modulus （G was greater than the storage modulus （G3, i.e. G＂〉G＇. At the late stage of shearing, when the angular velocity co-72.46 s-x, the storage modulus was greater than or equal to the loss G = G, tan -〈 1 （where phase-shift modulus, i.e. ＇ 〉 ＂ angle 5=G＂,/G3, and the debris flow slurry was in a gel state. Therefore, the progress of this experimental study further reveals the mechanism of hyperconcentrated debris flows with a high velocity on low-gradient ravines.

Effects of Moisture on Rheological Properties of PAV Aged Asphalt Binders

For the most coastal areas where the air is very humid,study on the effect of humidity on the performance of asphalt has its practical significance.However,limited research has been done to investigate the effect of humidity on rheological properties of asphalt.In this study,asphalt binders were aged in the pressure aging vessel(PAV)under different conditions of moisture and aging time.Then Dynamic Shear Rheometer(DSR)and Bending Beam Rheometer(BBR)measurements were conducted to obtain the parameters relating to the complex modulus,phase angle,failure temperature,and creep stiffness.It was found that the low temperature performance decreased as evidenced by the results of the creep stiffness.While there were no significant differences among conditioned binders based on complex modulus G*and phase angleδ,it was found that theδvalue increased when the humidity increased from 0% to 80% ,and then theδvalue decreased when the humidity increased to 100% .In addition,the results of the failure temperature indicated that the humidity of 80% would be a critical point for the high temperature performance of the asphalt binders.

Bond Property Test of Reinforced Concrete with All Soaking and Impressed Current Method Corrosion

In order to research the bond properties between corroded reinforcement bars and concrete,reinforcement bars with different diameters and different types and concrete with different strength levels were treated specially with all soaking and impressed current method,and the bond properties were measured with the pull-out test.The comparative analysis of the bond properties of corroded reinforcement bars was carried out.The results showed that the types of reinforcement bars and concrete had great influence on the bond strength.The corrosion and volume expansion of reinforcement bars made concrete in tensile condition,which tended to produce cracks in parallel reinforced direction.The typical bond failure of plain reinforcement bars was pull-out,while the typical bond failure of ribbed reinforcement bars was split.The bond strength between corroded reinforcement bars and concrete increased with the increase of concrete strength.The bond strength of plain and ribbed reinforcement bars showed a decreasing trend after the first increase with the increase of the extent of corrosion.Through the test,the coefficients of the bond strength of plain and ribbed reinforcement bars were given,respectively.

Analysis of heat transfer performance for turbulent viscoelastic fluid-based nanofluid using field synergy principle

In this paper,the field synergy principle is firstly performed on the viscoelastic fluid-based nanofluid and other relevant fluid in channel at turbulent flow state to scrutinize their heat transfer performance based on our direct numerical simulation database.The cosine values of intersection angle between velocity vector and temperature gradient vector are calculated for different simulated cases with varying nanoparticle volume fraction,nanoparticle diameter,Reynolds number and Weissenberg number.It is found that the filed synergy effect is enhanced when the nanoparticle volume fraction is increased,nanoparticle diameter is decreased and Weissenberg number is decreased,i.e.the heat transfer is also enhanced.However,the filed synergy effect is weakened with the increase of Reynolds number which may be the possible reason for the power function relationship in empirical correlation of heat transfer between heat transfer performance and Reynolds number with the constant power exponent lower than 1.Finally,it is also observed that the field synergy principle can be used to analyze the heat transfer process of viscoelastic fluid-based nanofluid at the turbulent flow state even if some negative cosine values of intersection angle exist in the flow field.