Rapid Polymer/Gas Solution Formation for Continuous Production of Microcellular Plastics

1996 ◽  
Vol 118 (4) ◽  
pp. 639-645 ◽  
Author(s):  
C. B. Park ◽  
N. P. Suh
Keyword(s):  
Rapid Heating ◽  
Continuous Production ◽  
Batch Process ◽  
Bubble Nucleation ◽  
Cycle Times ◽  
Solution Formation ◽  
Microcellular Plastics ◽  
Diffusion Phenomena ◽  
Order Of Magnitude ◽  
Time Required

An extrusion system that can create a polymer/gas solution rapidly for continuous processing of microcellular plastics is presented. Microcellular plastics are characterized by cell densities greater than 109 cells/cm3 and fully grown cells smaller than 10 μm. Previously these microcellular structures have been produced in a batch process by saturating a polymeric material with an inert gas under high pressure followed by inducing a rapid drop in the gas solubility. The diffusion phenomena encountered in this batch processing is typically slow, resulting in long cycle times. In order to produce microcellular plastics at industrial production rates, a means for the rapid solution formation is developed. The processing time required for completing the solution formation in the system was estimated from experimental data and the dispersive mixing theory based on an order-of-magnitude analysis. A means for promoting high bubble nucleation rates in the gas-saturated polymer via rapid heating is also discussed. The feasibility of the continuous production of microcellular plastics by the rapid polymer/gas solution formation and rapid heating was demonstrated through experiments. The paper includes not only a brief treatment of the basic science of the polymer/gas systems, but also the development of an industrially viable technology that fully utilizes the unique properties of microcellular plastics.

scholarly journals Statistical Uncertainty of DNS in Geometries without Homogeneous Directions

2021 ◽  
Vol 11 (4) ◽  
pp. 1399
Author(s):  
Jure Oder ◽  
Cédric Flageul ◽  
Iztok Tiselj
Keyword(s):  
Channel Flow ◽  
A Priori ◽  
Time Integration ◽  
Navier Stokes ◽  
Statistical Uncertainty ◽  
Time Step ◽  
Order Of Magnitude ◽  
Averaging Time ◽  
The Individual ◽  
Time Required

In this paper, we present uncertainties of statistical quantities of direct numerical simulations (DNS) with small numerical errors. The uncertainties are analysed for channel flow and a flow separation case in a confined backward facing step (BFS) geometry. The infinite channel flow case has two homogeneous directions and this is usually exploited to speed-up the convergence of the results. As we show, such a procedure reduces statistical uncertainties of the results by up to an order of magnitude. This effect is strongest in the near wall regions. In the case of flow over a confined BFS, there are no such directions and thus very long integration times are required. The individual statistical quantities converge with the square root of time integration so, in order to improve the uncertainty by a factor of two, the simulation has to be prolonged by a factor of four. We provide an estimator that can be used to evaluate a priori the DNS relative statistical uncertainties from results obtained with a Reynolds Averaged Navier Stokes simulation. In the DNS, the estimator can be used to predict the averaging time and with it the simulation time required to achieve a certain relative statistical uncertainty of results. For accurate evaluation of averages and their uncertainties, it is not required to use every time step of the DNS. We observe that statistical uncertainty of the results is uninfluenced by reducing the number of samples to the point where the period between two consecutive samples measured in Courant–Friedrichss–Levy (CFL) condition units is below one. Nevertheless, crossing this limit, the estimates of uncertainties start to exhibit significant growth.

scholarly journals Time scale of the largest imaginable magnetic storm

2013 ◽  
Vol 20 (1) ◽  
pp. 19-23 ◽  
Author(s):  
V. M. Vasyliūnas
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Storm ◽  
Energy Content ◽  
Horizontal Magnetic Field ◽  
Order Of Magnitude ◽  
Magnetosphere Plasma ◽  
Time Required ◽  
Parameter Values ◽  
Magnetic Field Perturbation

Abstract. The depression of the horizontal magnetic field at Earth's equator for the largest imaginable magnetic storm has been estimated (Vasyliūnas, 2011a) as −Dst ~ 2500 nT, from the assumption that the total pressure in the magnetosphere (plasma plus magnetic field perturbation) is limited, in order of magnitude, by the minimum pressure of Earth's dipole field at the location of each flux tube. The obvious related question is how long it would take the solar wind to supply the energy content of this largest storm. The maximum rate of energy input from the solar wind to the magnetosphere can be evaluated on the basis either of magnetotail stress balance or of polar cap potential saturation, giving an estimate of the time required to build up the largest storm, which (for solar-wind and magnetospheric parameter values typical of observed superstorms) is roughly between ~2 and ~6 h.

scholarly journals AUTOMATED SYSTEM FOR CONTINUOUS MICROALGAE CULTIVATION IN PHOTOBIOREACTORS

2017 ◽  
Vol 16 (2) ◽  
pp. 03
Author(s):  
D. A. L. D’Agostin ◽  
G. M. Domene ◽  
A. S. Oliveira ◽  
M. J. C. Bonfim ◽  
A. B. Mariano
Keyword(s):  
Continuous Production ◽  
Batch Process ◽  
Automated System ◽  
Control Mode ◽  
Raspberry Pi ◽  
Percentage Error ◽  
Monitoring And Control ◽  
Microalgae Cultivation ◽  
Batch Mode ◽  
Continuous Regime

The objective of this work was to design a automate system for microalgae cultivation on a continuous modes in laboratory scale and allow its remote monitoring and control. For this, a sensor were developed is able to measure biomass concentration. The concentration sensor used the principle of light scattering, that is, by measuring the turbidity of the culture medium by the use of a set of phototransistor and green led. It presented an mean absolute percentage error of 8.46% during the experiment. A pH, temperature and light sensor were also installed. The control of all the sensors was accomplished by means of an microcontroller. For remote control and monitoring of the controller, a database was designed and implemented on a Raspberry Pi connected to the network. The graphics and data collected are available on an HTML page that allows changes in the control mode of the photobioreactor, for example by changing the dilution rates. The controller was able to operate the photobioreactor in batch mode, as well as to maintain the culture operating in continuous regime. The continuous production of microalgae biomass in a continuous regime showed productivity 74.5% higher than the traditional batch process and 28.2% higher than semicontinuous cultivation.

WIRELINE FORMATION-TESTER PERFORMANCE ON THE NORTH WEST SHELF

1975 ◽  
Vol 15 (1) ◽  
pp. 127
Author(s):  
M. D. Agostini
Keyword(s):  
Single Point ◽  
Test Method ◽  
Reservoir Rock ◽  
Relative Reduction ◽  
Well Testing ◽  
North West ◽  
Drill Stem ◽  
The North ◽  
Order Of Magnitude ◽  
Time Required

The formation-interval-tester was introduced to the North West Shelf in December, 1970 Originally it was used as a first-look test method, with drill stem testing retained as the standard evaluation technique in all potential reservoir sections. Systematic use of this technique in parallel with drill-stem testing has allowed the accumulation of a significant volume of comparative data. This has provided a unique opportunity to examine the validity of wireline-testing as an alternative to the more traditional method of reservoir evaluation.The wireline-tester has been found to be a reliable indicator of movable hydrocarbons in reservoir rock, after experience allowed the development of regional interpretation limits. Such variables as gas:oil ratios and oil gravities are determined within acceptable limits of accuracy. Formation pressure determinations are consistent' and are thought to be more reliable than those derived from drill-stem-testing. With the data available it is normally possible to calculate the indicated formation permeability. This however being a single point determination the result is of questionable value. Experience has shown that "order of magnitude" agreement is normally achieved between wireline-tester permeabilities and those determined from drill-stem-testing in the same interval.The reduction in cost resulting from the application of this technique is particularly significant. Savings may be related directly to the relative reduction in rig time required by this operation compared with that required for drill-stem-testing. As the cost of offshore operations increases rapidly the resultant savings will grow in significance.Also of concern in all well-testing operations is the risk to which the rig and personnel are subjected. On floating offshore rigs the flowing well condition required by drill-stem-testing requires the acceptance of certain associated risks. Wireline testing is by comparison a risk-free operation.The recognition of the inherent limits of this approach to well testing is important if satisfactory results are to be achieved. Where the required reservoir parameters are those that can be satisfactorily determined with the wireline tester it offers a real alternative to the more traditional evaluation techniques.

Cement composites with expanded graphite as resistance heating elements

2020 ◽  
Vol 54 (25) ◽  
pp. 3821-3831
Author(s):  
Maksymilian Frąc ◽  
Waldemar Pichór ◽  
Paulina Szołdra
Keyword(s):  
Cement Mortar ◽  
Rapid Heating ◽  
Expanded Graphite ◽  
Electrical Current ◽  
Maximum Temperature ◽  
Cement Composites ◽  
Resistance Heating ◽  
Self Heating ◽  
Time Required ◽  
Heating Test

The following paper presents the results of research on cement composites with expanded graphite as resistance heating elements. Samples of cement mortar were prepared with expanded graphite obtained from intercalated graphite by means of rapid heating at 1000℃. Monotonic and cyclic self-heating tests of cement composites with differing contents of expanded graphite were conducted. In the monotonic self-heating test, the electrical current and the surface temperature of the cement composites with expanded graphite were measured at temperatures 23℃ and –10℃ in order to evaluate their capacity to generate heat. The maximum temperature of composites, the time required to raise the temperature by 10℃, and the power density were determined. Five cycles were applied in the cyclic self-heating test to investigate heat-dependent mechanical properties. The results of the research revealed that cement composites with expanded graphite exhibited promising properties for application as resistance heating elements.

Experimental Study on Bubble Nucleation in the Oscillating Pressure Field

1978 ◽  
Vol 100 (3) ◽  
pp. 460-465 ◽  
Author(s):  
K. Hijikata ◽  
Y. Mori ◽  
T. Nagatani
Keyword(s):  
Carbon Dioxide ◽  
Characteristic Time ◽  
Pressure Field ◽  
Pressure Oscillation ◽  
Oscillation Period ◽  
Bubble Nucleation ◽  
Dissolved Carbon ◽  
Dissolved Carbon Dioxide ◽  
Order Of Magnitude ◽  
Superheat Limit

In bubble nucleation under the oscillating pressure field, when the oscillation period τ is of the same order of magnitude as the characteristic time τn of bubble nucleation, it is expected that the distribution of radius of bubble embryo in liquid will be largely affected by the pressure oscillation and the degree of superheat limit may change. In order to clarify this point, superheat limits of homogeneous nucleation under the oscillating pressure field generated by ultrasonic oscillators are measured for propane with and without dissolved carbon dioxide by the floating droplet method. From the experimental results it is found that when τ > τn the measured superheat limit agrees with that calculated by the conventional theory where the quasi-steady state is assumed, but the bubble nucleation occurs at temperature lower than that preducted by the theory when τ nearly equals τn. It is also found that the characteristic time of bubble nucleation is changed by the amount of dissolved carbon dioxide.

scholarly journals Comparison Between Single-Aperture and Multi-Aperture Approaches to Computer Correction of Images

2020 ◽  
Vol 237 ◽  
pp. 06003
Author(s):  
Vadim Dudorov ◽  
Anna Eremina
Keyword(s):  
Numerical Simulation ◽  
Exposure Time ◽  
Image Synthesis ◽  
Short Exposure ◽  
Small Scale ◽  
Short Exposure Time ◽  
Observation Systems ◽  
Order Of Magnitude ◽  
Single Aperture ◽  
Time Required

The effectiveness of the reconstruction of images formed by single- and multi-aperture systems and distorted by an atmospheric turbulence is analyzed in this work. Based on numerical simulation, we show that the use of multi-aperture observation systems for the computer correction of atmospheric distortions under anisoplanar conditions can significantly reduce the exposure time. Main distortions are well corrected during image synthesis for a short exposure time, which corresponds to a “frozen” turbulence. The time required for the correction of residual small-scale distortions is an order of magnitude shorter than in the case of synthesis of long-exposure images with the use of traditional single-aperture observation systems.

scholarly journals Design, Optimization and Validation of Conformal Cooling Technique for Additively Manufactured Mold Insert

2021 ◽  
Vol 2070 (1) ◽  
pp. 012225
Author(s):  
G.Dongre Ganesh ◽  
S.Chaitanya Sarang ◽  
M.Jonnalagadda Sai
Keyword(s):  
Injection Molding ◽  
Mold Insert ◽  
Cooling Time ◽  
Cyclic Process ◽  
Conformal Cooling ◽  
Cooling Circuit ◽  
Cycle Times ◽  
Cooling Channels ◽  
Conventional Cooling ◽  
Time Required

Abstract Injection molding is a cyclic process comprising of cooling phase as the largest part of this cycle. Providing efficient cooling in lesser cycle times is of significant importance in the molding industry. Conformal cooling is a proven technique for reduction in cycle times for injection molding. In this study, we have replaced a conventional cooling circuit with an optimized conformal cooling circuit in an injection molding tool (mold). The required heat transfer rate, coolant flow rate and diameter of channel was analytically calculated. Hybrid Laser powder bed fusion technique was used to manufacture this mold tool with conformal channels. The material used for manufacturing mold was maraging steel (M300). Thermal efficiency of the conformal channels was experimentally calculated using thermal imaging. Autodesk MoldFlow software was used to simulate and predict the cooling time required using conformal cooling channels. The results showed a decrease in cooling time and increase in cooling efficiency with the help of conformal cooling in additively manufactured mold insert.

scholarly journals Survey of 8 UAV Set-Covering Algorithms for Terrain Photogrammetry

2020 ◽  
Vol 12 (14) ◽  
pp. 2285 ◽  
Author(s):  
Joshua E. Hammond ◽  
Cory A. Vernon ◽  
Trent J. Okeson ◽  
Benjamin J. Barrett ◽  
Samuel Arce ◽  
...  
Keyword(s):  
Linear Programming ◽  
Pareto Front ◽  
Computational Cost ◽  
Set Covering ◽  
Greedy Heuristics ◽  
Order Of Magnitude ◽  
Covering Algorithms ◽  
Time Required ◽  
Grid Independence

Remote sensing with unmanned aerial vehicles (UAVs) facilitates photogrammetry for environmental and infrastructural monitoring. Models are created with less computational cost by reducing the number of photos required. Optimal camera locations for reducing the number of photos needed for structure-from-motion (SfM) are determined through eight mathematical set-covering algorithms as constrained by solve time. The algorithms examined are: traditional greedy, reverse greedy, carousel greedy (CG), linear programming, particle swarm optimization, simulated annealing, genetic, and ant colony optimization. Coverage and solve time are investigated for these algorithms. CG is the best method for choosing optimal camera locations as it balances number of photos required and time required to calculate camera positions as shown through an analysis similar to a Pareto Front. CG obtains a statistically significant 3.2 fewer cameras per modeled area than base greedy algorithm while requiring just one additional order of magnitude of solve time. For comparison, linear programming is capable of fewer cameras than base greedy but takes at least three orders of magnitude longer to solve. A grid independence study serves as a sensitivity analysis of the CG algorithms α (iteration number) and β (percentage to be recalculated) parameters that adjust traditional greedy heuristics, and a case study at the Rock Canyon collection dike in Provo, UT, USA, compares the results of all eight algorithms and the uniqueness (in terms of percentage comparisons based on location/angle metadata and qualitative visual comparison) of each selected set. Though this specific study uses SfM, the principles could apply to other instruments such as multi-spectral cameras or aerial LiDAR.

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