scholarly journals Mathematical modeling of high-precision surfaces finishing in elastic plates with surface-active matters

2016 ◽  
Vol 1 (10) ◽  
pp. 26-32
Author(s):  
Владимир Богуцкий ◽  
Vladimir Bogutskiy ◽  
С. Братан ◽  
S. Bratan ◽  
А. Колесов ◽  
...  
Keyword(s):  
High Precision ◽  
Material Removal ◽  
Elastic Plates ◽  
Stochastic Nature ◽  
Manufacturing Operations ◽  
Current State ◽  
Operations Control ◽  
Surface Active ◽  
The Impact ◽  
A Current

At present a significant problem at the production of high-precision machinery and devices is the ensuring of stability of quality specified parameters and increase of working productivity. The simultaneous achievement of these values may be obtained only at the expense of the destination of optimum modes and methods of manufacturing operations control for that there were necessary adequate mathematical models. The existing engineering processes are formed on determined procedures without taking into account a stochastic nature of a process and the interference of chemical and mechanical phenomena in the area of working. In the paper the mechanism of allowance removal at finishing with abrasive pastes having in their composition as fillers the surface-active matters as a factor defining the effectiveness of a finishing procedure is investigated. A process mathematical model is developed allowing the computation of material removal at any time at different algorithms of modes changes including parameters of a contact area, a current state of a surface layer in a blank. A model formed taking into account the process of passivation, machine cutting, takes into account a stochastic character of a process and allows estimating differentially the impact of separate factors upon material removal.

Magnetorheological (MR) Jet Finishing Technology

2004 ◽  
Author(s):  
William I. Kordonski ◽  
Aric B. Shorey ◽  
Marc Tricard
Keyword(s):  
High Precision ◽  
Material Removal ◽  
High Speed ◽  
Axial Magnetic Field ◽  
Fundamental Property ◽  
Cfd Modeling ◽  
Surface Shear Stress ◽  
Round Jet ◽  
Mr Polishing Fluid ◽  
The Impact

Conformal (or freeform) and steep concave optics are important classes of optics that are difficult to finish using conventional techniques due to mechanical interferences and steep local slopes. One suitable way to polish these classes of optics is by using a jet of abrasive/fluid mixture. In doing so, the energy required for polishing may be supplied by the radial spread of a liquid jet, which impinges a surface to be polished. Such fluid flow may generate sufficient surface shear stress to provide material removal in the regime of chemical mechanical polishing. Once translated into a polishing technique, this unique tool may resolve a challenging problem of finishing steep concave surfaces and cavities. A fundamental property of a fluid jet is that it begins to lose its coherence as the jet exits a nozzle. This is due to a combination of abruptly imposed longitudinal and lateral pressure gradients, surface tension forces, and aerodynamic disturbance. This results in instability of the flow over the impact zone and consequently polishing spot instability. To be utilized in deterministic high precision finishing of remote objects, a stable, relatively high-speed, low viscosity fluid jet, which remains collimated and coherent before it impinges the surface to be polished, is required. A method of jet stabilization has been proposed, developed and demonstrated whereby the round jet of magnetorheological fluid is magnetized by an axial magnetic field when it flows out of the nozzle. It has been experimentally shown that a magnetically stabilized round jet of MR polishing fluid generates a reproducible material removal function (polishing spot) at a distance of several tens of centimeters from the nozzle. In doing so, the interferometrically derived distribution of material removal for an axisymmetric MR Jet, which impinges normal to a plane glass surface, coincides well with the radial distribution of rate of work calculated using computational fluid dynamics (CFD) modeling. Polishing results support the assertion that the MR Jet finishing process may produce high precision surfaces on glasses and single crystals. The technology is most attractive for the finishing of complex shapes like freeform optics, steep concaves and cavities.

Bilingual Effects on Cognition in Children

2020 ◽  
Author(s):  
Ellen Bialystok
Keyword(s):  
Cognitive Development ◽  
20Th Century ◽  
Brain Function ◽  
Potential Role ◽  
Home Language ◽  
Cognitive Level ◽  
Heritage Languages ◽  
Current State ◽  
The Impact ◽  
A Current

Since the mid-20th century, there have been dramatic changes in our conception of how bilingualism affects children’s cognitive development, moving from one of certain negativity, to unlimited advantage, and finally resting in a current state defined largely by confusion because of the complexity in how bilingualism is defined. However, the question has great consequences, so it is important to evaluate the evidence to understand the impact. Such information determines how families make decisions about their home language, particularly regarding the maintenance of heritage languages; how schools offer programs based on alternative languages; how clinicians assess children for learning or other special needs; and how communities offer services to diverse members. By defining the concepts more precisely than has typically been the case, the complexity of the relation between bilingualism and cognition becomes clear. The evidence shows that bilingualism impacts cognitive level and brain function across the lifespan, but the nature and extent of those effects are modified by the type and degree of bilingualism and the nature of the task. Understanding the conditions under which various effects emerge is essential for interpreting the effects of bilingualism on children’s cognitive development and their potential role in education.

Magnetorheological Jet (MR JetTM) Finishing Technology

2005 ◽  
Vol 128 (1) ◽  
pp. 20-26 ◽  
Author(s):  
William I. Kordonski ◽  
Aric B. Shorey ◽  
Marc Tricard
Keyword(s):  
High Precision ◽  
Material Removal ◽  
High Speed ◽  
Axial Magnetic Field ◽  
Fundamental Property ◽  
Cfd Modeling ◽  
Surface Shear Stress ◽  
Round Jet ◽  
Mr Polishing Fluid ◽  
The Impact

Conformal (or freeform) and steep concave optics are important classes of optics that are difficult to finish using conventional techniques due to mechanical interferences and steep local slopes. One suitable way to polish these classes of optics is by using a jet of abrasive/fluid mixture. The energy required for polishing may be supplied by the radial spread of a liquid jet, which impinges a surface to be polished. Such fluid flow may generate sufficient surface shear stress to provide material removal in the regime of chemical mechanical polishing. Once translated into a polishing technique, this unique tool may resolve a challenging problem of finishing steep concave surfaces and cavities. A fundamental property of a fluid jet is that it begins to lose its coherence as the jet exits a nozzle. This is due to a combination of abruptly imposed longitudinal and lateral pressure gradients, surface tension forces, and aerodynamic disturbance. This results in instability of the flow over the impact zone and consequently polishing spot instability. To be utilized in deterministic high precision finishing of remote objects, a stable, relatively high-speed, low viscosity fluid jet, which remains collimated and coherent before it impinges the surface to be polished, is required. A method of jet stabilization has been proposed, developed, and demonstrated whereby the round jet of magnetorheological fluid is magnetized by an axial magnetic field when it flows out of the nozzle. It has been experimentally shown that a magnetically stabilized round jet of magnetorheological (MR) polishing fluid generates a reproducible material removal function (polishing spot) at a distance of several tens of centimeters from the nozzle. The interferometrically derived distribution of material removal for an axisymmetric MR Jet™ , which impinges normal to a plane glass surface, coincides well with the radial distribution of rate of work calculated using computational fluid dynamics (CFD) modeling. Polishing results support the assertion that the MR Jet finishing process may produce high precision surfaces on glass and single crystals. The technology is most attractive for the finishing of complex shapes like freeform optics, steep concaves, and cavities.

The Development of Agritourism in the Podkarpackie Voivodeship in the Light of International and National Conditions

2017 ◽  
Vol 13 ◽  
pp. 244-261
Author(s):  
Mariola Tracz ◽  
Małgorzata Bajgier-Kowalska ◽  
Radosław Uliszak
Keyword(s):  
Development Strategy ◽  
Current State ◽  
Central Statistical ◽  
Central Statistical Office ◽  
Tourism Resources ◽  
The One ◽  
The Impact ◽  
District Offices ◽  
Socio Economic Factors

Podkarpackie Voivodeship is one of the regions of Poland in which the number of agritourism entities is very high. Therefore tourism plays a significant role in its development strategy. The aim of the paper is to identify the current state of agritourism and the changes that have occurred in the region in the years 2000–2016. Specific objectives are to determine the distribution of agritourism farms and their offer, together with a comprehensive analysis of the environmental and socio-economic factors, as well as the impact of the Slovak-Ukrainian border. The report was developed on the statistical materials from the Polish Central Statistical Office, Podkarpackie Agricultural Advisory Centre in Boguchwała and data collected from municipalities and district offices that is published on their websites, as well as through interviews with 100 owners of agritourism farms in the Podkarpackie Voivodeship. The research has shown, on the one hand, the decline in the number of farms in the region and, on the other hand, the increase in the diversity of the tourist offer of these entities. Distribution of agritourism farms is closely linked to the attractiveness of natural environment and quality of secondary tourism resources. Traditional agritourism has not yet fully used its countryside, as well as cross-border advantages of its location.

The Impact of Bioconjugation on the Interfacial Activity of a Protein Biosurfactant

2018 ◽  
Author(s):  
Hossam H Tayeb ◽  
Marina Stienecker ◽  
Anton Middelberg ◽  
Frank Sainsbury
Keyword(s):  
Polyethylene Glycol ◽  
Colloidal Stability ◽  
Point Mutations ◽  
Pharmaceutical Formulations ◽  
Industrial Processes ◽  
Parent Molecule ◽  
Site Specific ◽  
Interfacial Activity ◽  
Surface Active ◽  
The Impact

Biosurfactants, are surface active molecules that can be produced by renewable, industrially scalable biologic processes. DAMP4, a designer biosurfactant, enables the modification of interfaces via genetic or chemical fusion to functional moieties. However, bioconjugation of addressable amines introduces heterogeneity that limits the precision of functionalization as well as the resolution of interfacial characterization. Here we designed DAMP4 variants with cysteine point mutations to allow for site-specific bioconjugation. The DAMP4 variants were shown to retain the structural stability and interfacial activity characteristic of the parent molecule, while permitting efficient and specific conjugation of polyethylene glycol (PEG). PEGylation results in a considerable reduction on the interfacial activity of both single and double mutants. Comparison of conjugates with one or two conjugation sites shows that both the number of conjugates as well as the mass of conjugated material impacts the interfacial activity of DAMP4. As a result, the ability of DAMP4 variants with multiple PEG conjugates to impart colloidal stability on peptide-stabilized emulsions is reduced. We suggest that this is due to constraints on the structure of amphiphilic helices at the interface. Specific and efficient bioconjugation permits the exploration and investigation of the interfacial properties of designer protein biosurfactants with molecular precision. Our findings should therefore inform the design and modification of biosurfactants for their increasing use in industrial processes, and nutritional and pharmaceutical formulations.

Self-leadership Training Review

2019 ◽  
Author(s):  
Andrew Sidwell ◽  
Michael Perry
Keyword(s):  
Leadership Training ◽  
Future Research ◽  
Training Methods ◽  
Current State ◽  
A Current

The purpose of this article was to examine the current state of self-leadership training. The authors analyzed all published, publicly available studies (in English) pertaining to self-leadership training methods, offering a current state of self-leadership training, and implications for future research.

Artificial Intelligence and Inequality in the Middle East

2020 ◽  
pp. 624-649 ◽  
Author(s):  
Nagla Rizk
Keyword(s):  
Artificial Intelligence ◽  
Human Resources ◽  
Young Population ◽  
Mena Region ◽  
Poor Countries ◽  
Current State ◽  
Resource Poor ◽  
Youth Entrepreneurship ◽  
The Arab Spring ◽  
The Impact

This chapter looks at the challenges, opportunities, and tensions facing the equitable development of artificial intelligence (AI) in the MENA region in the aftermath of the Arab Spring. While diverse in their natural and human resource endowments, countries of the region share a commonality in the predominance of a youthful population amid complex political and economic contexts. Rampant unemployment—especially among a growing young population—together with informality, gender, and digital inequalities, will likely shape the impact of AI technologies, especially in the region’s labor-abundant resource-poor countries. The chapter then analyzes issues related to data, legislative environment, infrastructure, and human resources as key inputs to AI technologies which in their current state may exacerbate existing inequalities. Ultimately, the promise for AI technologies for inclusion and helping mitigate inequalities lies in harnessing grounds-up youth entrepreneurship and innovation initiatives driven by data and AI, with a few hopeful signs coming from national policies.

scholarly journals Smoothing additive manufactured parts using ns-pulsed laser radiation

2021 ◽  
Author(s):  
Florian Kuisat ◽  
Fernando Lasagni ◽  
Andrés Fabián Lasagni
Keyword(s):  
Surface Roughness ◽  
Mechanical Performance ◽  
State Of The Art ◽  
Pulsed Laser ◽  
Industrial Applications ◽  
Laser Source ◽  
Pulsed Laser Radiation ◽  
Current State ◽  
The Impact

AbstractIt is well known that the surface topography of a part can affect its mechanical performance, which is typical in additive manufacturing. In this context, we report about the surface modification of additive manufactured components made of Titanium 64 (Ti64) and Scalmalloy®, using a pulsed laser, with the aim of reducing their surface roughness. In our experiments, a nanosecond-pulsed infrared laser source with variable pulse durations between 8 and 200 ns was applied. The impact of varying a large number of parameters on the surface quality of the smoothed areas was investigated. The results demonstrated a reduction of surface roughness Sa by more than 80% for Titanium 64 and by 65% for Scalmalloy® samples. This allows to extend the applicability of additive manufactured components beyond the current state of the art and break new ground for the application in various industrial applications such as in aerospace.

scholarly journals A Model-Based Tool for Assessing the Impact of Land Use Change Scenarios on Flood Risk in Small-Scale River Systems—Part 1: Pre-Processing of Scenario Based Flood Characteristics for the Current State of Land Use

Hydrology ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 102
Author(s):  
Frauke Kachholz ◽  
Jens Tränckner
Keyword(s):  
Land Use ◽  
River Flow ◽  
Land Use Changes ◽  
Small Rivers ◽  
Small Scale ◽  
Model Parameters ◽  
Ungauged Catchments ◽  
Model Based ◽  
Current State ◽  
The Impact

Land use changes influence the water balance and often increase surface runoff. The resulting impacts on river flow, water level, and flood should be identified beforehand in the phase of spatial planning. In two consecutive papers, we develop a model-based decision support system for quantifying the hydrological and stream hydraulic impacts of land use changes. Part 1 presents the semi-automatic set-up of physically based hydrological and hydraulic models on the basis of geodata analysis for the current state. Appropriate hydrological model parameters for ungauged catchments are derived by a transfer from a calibrated model. In the regarded lowland river basins, parameters of surface and groundwater inflow turned out to be particularly important. While the calibration delivers very good to good model results for flow (Evol =2.4%, R = 0.84, NSE = 0.84), the model performance is good to satisfactory (Evol = −9.6%, R = 0.88, NSE = 0.59) in a different river system parametrized with the transfer procedure. After transferring the concept to a larger area with various small rivers, the current state is analyzed by running simulations based on statistical rainfall scenarios. Results include watercourse section-specific capacities and excess volumes in case of flooding. The developed approach can relatively quickly generate physically reliable and spatially high-resolution results. Part 2 builds on the data generated in part 1 and presents the subsequent approach to assess hydrologic/hydrodynamic impacts of potential land use changes.

scholarly journals Neuroimaging at Term Equivalent Age: Is There Value for the Preterm Infant? A Narrative Summary

Children ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 227
Author(s):  
Rudaina Banihani ◽  
Judy Seesahai ◽  
Elizabeth Asztalos ◽  
Paige Terrien Church
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Preterm Infant ◽  
Resonance Imaging ◽  
Long Term Outcomes ◽  
Equivalent Age ◽  
Current State ◽  
Patterns Of Injury ◽  
The Impact

Advances in neuroimaging of the preterm infant have enhanced the ability to detect brain injury. This added information has been a blessing and a curse. Neuroimaging, particularly with magnetic resonance imaging, has provided greater insight into the patterns of injury and specific vulnerabilities. It has also provided a better understanding of the microscopic and functional impacts of subtle and significant injuries. While the ability to detect injury is important and irresistible, the evidence for how these injuries link to specific long-term outcomes is less clear. In addition, the impact on parents can be profound. This narrative summary will review the history and current state of brain imaging, focusing on magnetic resonance imaging in the preterm population and the current state of the evidence for how these patterns relate to long-term outcomes.

Sign in / Sign up

Export Citation Format

Share Document