scholarly journals Computational simulation of flocculent sedimentation based on experimental results

2012 ◽  
Vol 65 (6) ◽  
pp. 1007-1013 ◽  
Author(s):  
Mafeni S. Ramatsoma ◽  
Evans M. N. Chirwa
Keyword(s):  
Empirical Model ◽  
Mechanistic Model ◽  
Computational Simulation ◽  
Data Sets ◽  
Random Errors ◽  
Wide Range ◽  
Model Predictions ◽  
Sedimentation Basins ◽  
Semi Empirical ◽  
Better Than

Computerised interpolation algorithms as well as the empirical model for analysing the flocculent settling data were developed. A mechanistic semi-empirical model developed from fundamental physical principles of a falling particle in a viscous fluid was tested against actual flocculation column data. The accuracy of the mechanistic model was evaluated using the sum of the squared errors between the interpolated values (real values) and the model predictions. Its fitting capabilities were compared with Özer's model using nine flocculent data sets of which four were obtained from literature and the rest were actual data from the performed experiments. The developed model consistently simulated the flocculation behaviour of particles in settling columns better than Özer's model in eight of the nine data sets considered. It is recommended that the model's performance be further compared with other models like the Rule based and San's model. The errors due to the use of interpolated values when determining the performance of the empirical models need to be investigated. Furthermore, a three-way rather than two-way interpolation should now be achievable using the interpolation algorithm developed in this study thereby reducing the effects of interpolation bias. The above work opens the way to full automation of design of flocculation sedimentation basins and other gravitational particle separation systems which at present are designed manually and are susceptible to a wide range of human and random errors.

Study on Precision Polishing of a Mini Roller Mold

2010 ◽  
Vol 126-128 ◽  
pp. 551-556
Author(s):  
Choung Lii Chao ◽  
Ying Ching Hsiao ◽  
Wen Chen Chou ◽  
Chia Wei Kuo ◽  
Wen Lang Lai ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Material Removal Rate ◽  
Surface Finish ◽  
Empirical Model ◽  
Material Removal ◽  
Removal Rate ◽  
Surface Condition ◽  
Microscopic Analysis ◽  
Semi Empirical ◽  
Better Than

This research aimed to design and develop a polishing system for precision polishing mini roller mold to nanometer surface finish. An experimental polishing system was built in the present study to polish nickel plated specimens with various polishing compounds. The polished specimens were subsequently examined by Alfa-step, OM and SEM for surface finish, morphology and microscopic analysis respectively. The obtained surface condition and material removal rate were correlated to the polishing parameters such as spindle speed, abrasive concentration, and abrasive grit size for the improvement of the polishing effect. Mini-rollers of 5mm in diameter, 50mm in length were successfully polished to a surface roughness better than 2nm Ra in several hours without damaging the roundness and cylindricalness using abrasive of 0.3μm, 10,000rpm polishing speed and 0.5mm gap distance between polisher and the specimen. A semi-empirical model of polishing was also developed in the study for predicting the materials removal rate.

scholarly journals A semi-empirical model for streamwise vortex intensification

2019 ◽  
Vol 233 (12) ◽  
pp. 4396-4409
Author(s):  
Grant McLelland ◽  
David MacManus ◽  
Chris Sheaf
Keyword(s):  
Empirical Model ◽  
Vortex Core ◽  
Axial Strain ◽  
Empirical Relationship ◽  
Tangential Velocity ◽  
Streamwise Vortex ◽  
Stereoscopic Particle Image Velocimetry ◽  
Wide Range ◽  
Semi Empirical ◽  
Vortex Intensification

Vortex intensification plays an important role in a wide range of flows of engineering interest. One scenario of interest is when a streamwise vortex passes through the contracting streamtube of an aircraft intake. There is, however, limited experimental data of flows of this type to reveal the dominant flow physics and to guide the development of vortex models. To this end, the evolution of wing-tip vortices inside a range of streamtube contractions has been measured using stereoscopic particle image velocimetry. A semi-empirical model has been applied to provide new insight on the role of vorticity diffusion during the intensification process. The analysis demonstrates that for mild flow contractions, vorticity diffusion has a negligible influence due to the low rates of diffusion in the vortex flow prior to intensification and the short convective times associated with the streamtube contraction. As the contraction levels increase, there is a substantial increase in the rates of diffusion which is driven by the greater levels of vorticity in the vortex core. A new semi-empirical relationship, as a function of the local streamtube contraction levels and vortex Reynolds number, has been developed. The model comprises a simple correction to vortex filament theory and provides a significant improvement in the estimation of vortex characteristics in contracting flows. For the range of contractions investigated, errors in the estimation of vortex core radius, peak tangential velocity and vorticity are reduced by an order of magnitude. The model can be applied to estimate the change in vortex characteristics for a range of flows with intense axial strain, such as contracting intake streamtubes and swirling flows in turbomachinery.

scholarly journals Unsupervised water scene dehazing network using multiple scattering model

PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0253214
Author(s):  
Shunmin An ◽  
Xixia Huang ◽  
Linling Wang ◽  
Zhangjing Zheng ◽  
Le Wang
Keyword(s):  
Multiple Scattering ◽  
Loss Functions ◽  
Data Sets ◽  
Image Dehazing ◽  
Scattering Model ◽  
Unsupervised Neural Network ◽  
Wide Range ◽  
Dark Channel ◽  
Previous Image ◽  
Better Than

In water scenes, where hazy images are subject to multiple scattering and where ideal data sets are difficult to collect, many dehazing methods are not as effective as they could be. Therefore, an unsupervised water scene dehazing network using atmospheric multiple scattering model is proposed. Unlike previous image dehazing methods, our method uses the unsupervised neural network and the atmospheric multiple scattering model and solves the problem of difficult acquisition of ideal datasets and the effect of multiple scattering on the image. In our method, in order to embed the atmospheric multiple scattering model into the unsupervised dehazing network, the unsupervised dehazing network uses four branches to estimate the scene radiation layer, transmission map layer, blur kernel layer and atmospheric light layer, the hazy image is then synthesized from the four output layers, minimizing the input hazy image and the output hazy image, where the output scene radiation layer is the final dehazing image. In addition, we constructed unsupervised loss functions which applicable to image dehazing by prior knowledge, i.e., color attenuation energy loss and dark channel loss. The method has a wide range of applications, with haze being thick and variable in marine, river and lake scenes, the method can be used to assist ship vision for target detection or forward road recognition in hazy conditions. Through extensive experiments on synthetic and real-world images, the proposed method is able to recover the details, structure and texture of the water image better than five advanced dehazing methods.

scholarly journals Hedging and machine learning driven crude oil data analysis using a refined Barndorff–Nielsen and Shephard model

2021 ◽  
pp. 2150015
Author(s):  
Humayra Shoshi ◽  
Indranil SenGupta
Keyword(s):  
Crude Oil ◽  
Classification Problem ◽  
Commodity Markets ◽  
Data Sets ◽  
Refined Model ◽  
Hedging Strategy ◽  
Data Set ◽  
Wide Range ◽  
S Model ◽  
Better Than

In this paper, a refined Barndorff-Nielsen and Shephard (BN-S) model is implemented to find an optimal hedging strategy for commodity markets. The refinement of the BN-S model is obtained with various machine and deep learning algorithms. The refinement leads to the extraction of a deterministic parameter from the empirical data set. The problem is transformed to an appropriate classification problem with a couple of different approaches — the volatility approach and the duration approach. The analysis is implemented to the Bakken crude oil data and the aforementioned deterministic parameter is obtained for a wide range of data sets. With the implementation of this parameter in the refined model, the resulting model performs much better than the classical BN-S model.

Research on CO2 Corrosion Rate Prediction of Gathering Pipelines Considering the Effect of Oil

2015 ◽  
Vol 737 ◽  
pp. 788-793 ◽  
Author(s):  
Yuan Peng Cheng ◽  
Zi Li Li ◽  
Qian Qian Liu
Keyword(s):  
Corrosion Rate ◽  
Empirical Model ◽  
Prediction Models ◽  
Mechanistic Model ◽  
Experimental Studies ◽  
Research Directions ◽  
Rate Prediction ◽  
Semi Empirical ◽  
The Impact ◽  
Sweet Corrosion

Experimental studies show that under special conditions, oils in corrosion environment have some inhibiting effect on CO2corrosion behavior of gathering pipelines. Oil wetting and corrosion product film are the great difference in existent rate prediction models of sweet corrosion. The progress of CO2corrosion rate prediction including empirical model, semi-empirical model, mechanistic model and artificial neural networks model considering the impact of oil in recent years are introduced in detail, the present problems and further research directions are also discussed.

scholarly journals Performance of IMERG as a Function of Spatiotemporal Scale

2017 ◽  
Vol 18 (2) ◽  
pp. 307-319 ◽  
Author(s):  
Jackson Tan ◽  
Walter A. Petersen ◽  
Pierre-Emmanuel Kirstetter ◽  
Yudong Tian
Keyword(s):  
Climate Models ◽  
Random Errors ◽  
Spatial And Temporal Scales ◽  
Precipitation Characteristics ◽  
Wide Range ◽  
Weather And Climate ◽  
Precipitation Estimates ◽  
Precipitation Analysis ◽  
Rain Rates ◽  
Better Than

Abstract The Integrated Multisatellite Retrievals for GPM (IMERG), a global high-resolution gridded precipitation dataset, will enable a wide range of applications, ranging from studies on precipitation characteristics to applications in hydrology to evaluation of weather and climate models. These applications focus on different spatial and temporal scales and thus average the precipitation estimates to coarser resolutions. Such a modification of scale will impact the reliability of IMERG. In this study, the performance of the Final Run of IMERG is evaluated against ground-based measurements as a function of increasing spatial resolution (from 0.1° to 2.5°) and accumulation periods (from 0.5 to 24 h) over a region in the southeastern United States. For ground reference, a product derived from the Multi-Radar/Multi-Sensor suite, a radar- and gauge-based operational precipitation dataset, is used. The TRMM Multisatellite Precipitation Analysis (TMPA) is also included as a benchmark. In general, both IMERG and TMPA improve when scaled up to larger areas and longer time periods, with better identification of rain occurrences and consistent improvements in systematic and random errors of rain rates. Between the two satellite estimates, IMERG is slightly better than TMPA most of the time. These results will inform users on the reliability of IMERG over the scales relevant to their studies.

Research of the activity and viability of spermatozoa at different concentrations and proportions of diluents after incubation

2020 ◽  
pp. 88-95
Author(s):  
Svitlana Lobchenko ◽  
Tetiana Husar ◽  
Viktor Lobchenko
Keyword(s):  
Plasma Concentration ◽  
Incubation Time ◽  
Coefficient Of Variation ◽  
Incubation Medium ◽  
Wide Range ◽  
Series Of Experiments ◽  
The Subject ◽  
Boar Spermatozoa ◽  
Native Plasma ◽  
Better Than

The results of studies of the viability of spermatozoa with different incubation time at different concentrations and using different diluents are highlighted in the article. (Un) concentrated spermatozoa were diluented: 1) with their native plasma; 2) medium 199; 3) a mixture of equal volumes of plasma and medium 199. The experiment was designed to generate experimental samples with spermatozoa concentrations prepared according to the method, namely: 0.2; 0.1; 0.05; 0.025 billion / ml. The sperm was evaluated after 2, 4, 6 and 8 hours. The perspective of such a study is significant and makes it possible to research various aspects of the subject in a wide range. In this regard, a series of experiments were conducted in this area. The data obtained are statistically processed and allow us to highlight the results that relate to each stage of the study. In particular, in this article it was found out some regularities between the viability of sperm, the type of diluent and the rate of rarefaction, as evidenced by the data presented in the tables. As a result of sperm incubation, the viability of spermatozoa remains at least the highest trend when sperm are diluted to a concentration of 0.1 billion / ml, regardless of the type of diluent used. To maintain the viability of sperm using this concentration of medium 199 is not better than its native plasma, and its mixture with an equal volume of plasma through any length of time incubation of such sperm. Most often it is at this concentration of sperm that their viability is characterized by the lowest coefficient of variation, regardless of the type of diluent used, which may indicate the greatest stability of the result under these conditions. The viability of spermatozoa with a concentration of 0.1 billion / ml is statistically significantly reduced only after 6 or even 8 hours of incubation. If the sperm are incubated for only 2 hours, regardless of the type of diluent used, the sperm concentrations tested do not affect the viability of the sperm. Key words: boar, spermatozoa, sperm plasma, concentration, incubation, medium 199, activity, viability, rarefaction.

Effect of Contact Ratio on Spur Gear Dynamic Load With No Tooth Profile Modifications

1996 ◽  
Vol 118 (3) ◽  
pp. 439-443 ◽  
Author(s):  
Chuen-Huei Liou ◽  
Hsiang Hsi Lin ◽  
F. B. Oswald ◽  
D. P. Townsend
Keyword(s):  
Dynamic Load ◽  
Spur Gear ◽  
Tooth Size ◽  
Contact Ratio ◽  
Gear Dynamics ◽  
Wide Range ◽  
Gear Contact ◽  
Center Distance ◽  
Selection Of ◽  
Better Than

This paper presents a computer simulation showing how the gear contact ratio affects the dynamic load on a spur gear transmission. The contact ratio can be affected by the tooth addendum, the pressure angle, the tooth size (diametral pitch), and the center distance. The analysis presented in this paper was performed by using the NASA gear dynamics code DANST. In the analysis, the contact ratio was varied over the range 1.20 to 2.40 by changing the length of the tooth addendum. In order to simplify the analysis, other parameters related to contact ratio were held constant. The contact ratio was found to have a significant influence on gear dynamics. Over a wide range of operating speeds, a contact ratio close to 2.0 minimized dynamic load. For low-contact-ratio gears (contact ratio less than two), increasing the contact ratio reduced gear dynamic load. For high-contact-ratio gears (contact ratio equal to or greater than 2.0), the selection of contact ratio should take into consideration the intended operating speeds. In general, high-contact-ratio gears minimized dynamic load better than low-contact-ratio gears.

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