Search results

The air drawing model plays an important in spunbonding. The purpose of this paper is to study the influence of the density and the specific heat capacity of polymer melt at constant pressure changing with polymer temperature on the fiber diameter.

The air drawing model of the polypropylene polymer in a spunbonding process is presented and solved by introducing the numerical computation results of the air flow field of aerodynamic device.

The model prediction of the filament fiber diameter coincides well with the experimental data. The effects of the processing parameters on the filament fiber diameter are discussed. A lower polymer throughput rate, higher polymer melt temperature, higher primary air temperature, higher venturi gap, higher air suction speed, and higher quench pressure can all produce finer filament fiber.

The experimental results show that the agreement between the results and experimental data are very better, which verifies the reliability of these models. The results show great prospects for this research in the field of computer assisted design of spunbonding technology.

The polymer air-drawing model of spunbonding nonwovens has been established. The influence of the density and the specific heat capacity of polymer melt at constant pressure changing with polymer temperature on the fiber diameter have also been studied. The paper aims to discuss these issues.

TDMA method is used to solve the difference equations.

It can be concluded that a lower polymer throughput rate, a higher polymer melt initial temperature, a higher air initial temperature, and a higher air initial velocity can all produce finer fibers.

The results also reveal the great potential for this research in the computer-assisted design of spunbonding technology.

The purpose of this paper is to varify, the air drawing model and the air jet flow field model of dual slot shape die for a polymer in a melt blowing process were established, by the experimental results obtained with experimental equipment.

The air jet flow field model is solved by introducing the finite difference method. The air drawing model of polymers in the melt blowing process was studied with the help of the simulation results of the air jet flow field.

The higher air initial velocity and air initial temperature can all yield finer fibers and causes the fibers to be attenuated to a greater extent.

The predicted fiber diameter agrees well with the experimental result, which verifies the reliability of these models. At the same time, the results also reveal the great potential of this research for the computer-assisted design of melt blowing technology.

The purpose of this paper is to attempt to predict the fiber diameter of melt blowing nonwovens by means of physics model.

The effects of the processing parameters on the fiber diameter is studied using the established physics model.

The results show that the predicted and experimental values agree well, the physics model produces more accurate and stable predictions, which also indicates that the physics model is really an effective and available modeling method for predictors.

The results show the great potential of this research for computer assisted design of the melt blowing technology.

This paper aims to discuss the combination of electrospinning and melt blowing in theory, which may be a good way to produce nanofibers.

In this paper, the electrostatic field and the air flow field were numerical simulated and analyzed, the compound field of which was also discussed.

It is pointed out that the air flow angle will be a key factor to produce nanofibers in the compound process of electrospinning and melt blowing.

The combination of electrostatic force and air drawing force may be a good way to produce nanofibers when the material is high viscosity melt. Air jets with high temperature and high velocity will provide favorable conditions for attenuating the polymer jet. The flow angle of the air jets effect the whole attenuation force exerted to the polymer jet and should be selected properly.

The purpose of this paper is to establish three modeling methods (physical model, statistical model, and artificial neural network (ANN) model) and use it to predict the fiber diameter of spunbonding nonwovens from the process parameters.

The results show the physical model is based on the inherent physical principles, it can yield reasonably good prediction results and provide insight into the relationship between process parameters and fiber diameter.

By analyzing the results of the physical model, the effects of process parameters on fiber diameter can be predicted. The ANN model has good approximation capability and fast convergence rate, it can provide quantitative predictions of fiber diameter and yield more accurate and stable predictions than the statistical model.

The effects of process parameters on fiber diameter are also determined by the ANN model. Excellent agreement is obtained between these two modeling methods.

An aircraft landing gear bracing strut comprises two arms, pivoted to the aircraft and the landing gear, respectively, and also pivoted together about an axis lying outside the plane containing the pivotal axes of the two arms to the aircraft and landing gear when the latter is extended, wherein one of the arms constitutes the body of a fluid operated jack, of which the piston rod is coupled to the other arm through a connecting link. In FIG. 1, the wheel strut 1 is pivoted to an aircraft wing at C, and braced by a strut 3 breakable at D and pivoted to the wing at A and to the strut 1 at B. In FIG. 2, the strut 3 comprises two arms 4, 5 hinged on a pin 6. The arm 4 forms a cylinder in which works a piston 12, the rod 13 of which is universally jointed to a coupling rod 15 pivoted to the arm 5 at 16. The universal joint runs on a roller 17 in a guide 18 formed in the arm 4. Admission of fluid under pressure to port 21 and connexion of port 22 exhaust breaks and folds the strut, retracting the undercarriage, and vice versa. An abutment 19 on arm 5 abuts a strengthened portion 20 on arm 4 when the strut is extended. The cylinder is formed with members 23, and the piston with a sliding portion 24 as in Specification 527,225 to form a down‐lock. When the strut is fully opened, the piston actuates a member 26 to give an indication to the pilot. Specification 551,673 also is referred to.

The purpose of this study is to respond to the Journal of Historical Research in Marketing special issue call for discussions that can assist advertising and marketing history researchers locate primary sources of interest to their research by describing the resources available through the online family history websites Ancestry.com and FindMyPast.com.

Brief histories of Ancestry and FindMyPast are presented, based on publicly available records and secondary sources. This paper explains the types of data researchers can access via Ancestry.com and FindMypast.com, the costs of access and then provides some examples of how these resources have been used in past research by marketing and advertising historians.

Family history websites such as Ancestry and FindMyPast can provide researchers with access to a wide variety of data sources, such as census and voting records; immigration records; city directories; birth, marriage and death records; military records; and almanacs and gazetteers, but at a cost. In some cases, paying for digital access to records is more convenient, timely and can cost less than travelling to access these same documents in physical form. Depending on the researcher’s geographical location and the country from which records are sought, this can add up to quite a cost savings. When using these sources, it is wise to determine which database contains more of the records you are searching for; Ancestry tends to have better US and Canadian resources, while FindMyPast covers the UK better.

Researchers interested in conducting advertising and marketing history research need access to primary data sources. Given restricted travel budgets and, indeed, restricted travel under COVID-19 conditions, gaining access to primary sources in digital form can allow researchers to continue their work. At any time, gaining access to digital records without having to travel can speed up the research process. Researchers new to the field, and those with many years of experience, can benefit from learning more about family history databases as primary data sources.

Reynolds number in small-size low-pressure turbines (LPT) can drop below 2.5 · 10⁴ at high altitude cruise, which in turn can lead to laminar boundary layer separation on the suction surface of the blades. The purpose of this paper is to investigate the potential of an alternate current (AC)-driven Single Dielectric Barrier Discharge Plasma Actuator (AC-SDBDPA) for boundary layer control on the suction side of a LPT blade, operating at a Reynolds number of 2 · 10⁴.

Experimental and numerical analyses were conducted. The experimental approach comprised the actuator testing over a curved plate with a shape designed to reproduce the suction surface of a LPT blade. A closed loop wind tunnel was employed. Sinusoidal voltage excitation was tested. Planar velocity measurements were performed by laser Doppler velocimetry (LDV) and particle image velocimetry (PIV). The device electrical power dissipation was also calculated. Computational fluid dynamics (CFD) simulations using OpenFOAM© were conducted, modelling the actuator effect as a body force calculated by the dual potential algebraic model. Unsteady RANS (Reynolds Averaged Navier-Stokes equations), also known as URANS approach, with the k-ε Lam-Bremhorst Low-Reynolds turbulence model was used.

The AC-SDBDPA operation brought to a reduction of the separation region; in particular, the boundary layer thickness and the negative velocity values decreased substantially. Moreover, the flow angle in both the main flow and in the boundary layer was reduced by the plasma control effect. The actuation brought to a reduction of the 17 per cent in the total pressure loss coefficient. The pressure coefficient and skin friction coefficient distributions indicated that under actuation the reattacnment point was displaced upstream, meaning that the flow separation was effectively controlled by the plasma actuation. Adopting slightly higher actuation parameters could bring to a full reattachment of the flow.

The work underlines the potentialities of an AC-SDBDPA to control separation in LPTs of aeroengines.

The present work sets a methodological framework, in which the validated procedure to obtain the body force model combined with CFD simulations can be used to study a configuration with multiple actuators allocated in array without requiring further experiments.

Having taken up our position on the above definition of this fundamental point, which closes the long‐standing discussion between upholders of the airscrew and those of the reaction system (just as in earlier days the distinction between impulse and work closed the classic discussion between the followers of Leibnitz and Descartes), we must now admit, without going into details, that this supposed attainment of equal efficiencies cannot be considered easy, if even possible, for the normal speeds of flight. It must also be admitted that a power unit, consisting of engine, compressor and jet, is at first sight a unit more complex, heavier and more bulky than the ordinary engine‐airscrew unit which has now been reduced to a high degree of simplicity and neatness. There is no doubt at all that in the sphere of the sub‐acoustic velocities the airscrew will reign supreme.