scholarly journals Variations of graphene nanotube membrane support layer in outlet flux of PAFO system

2020 ◽  
Vol 11 (30) ◽  
pp. 99-124
Author(s):  
Leila Javarani ◽  
Mohammad Malakootian ◽  
Amir Hessam Hassani ◽  
Amir Hossein Javid
Keyword(s):  
Osmotic Pressure ◽  
Theoretical Modeling ◽  
Hydraulic Pressure ◽  
High Flux ◽  
Practical Application ◽  
Membrane Synthesis ◽  
Matlab Software ◽  
Backing Layer ◽  
Efficiency Determination

The PAFO system is a solution in the desalination of seawater using a hydraulic pressure of 5 bar, which competes with the FO system (direct osmosis). The project includes four stages of pilot construction, entrainment detection, graphene nanotube membrane synthesis and, finally, efficiency determination and outflow modeling of the PAFO system. High Flux is the most important parameter of the system test for practical application. According to the results, the highest flow of current (120 l / m2.hr) was calculated at the osmotic pressure of 55, indicating a 50% increase in the flow of water with KOH fertilizer as entrainment solution and membrane of low thickness backing layer. Outflow values were calculated using theoretical modeling (MATLAB software). The results show the consistency of the outflow with the flow of the proposed chi model.

scholarly journals Metastable State of Water and Performance of Osmotically Driven Membrane Processes

Membranes ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 43 ◽  
Author(s):  
Haifeng Zhang ◽  
Jie Wang ◽  
Ken Rainwater ◽  
Lianfa Song
Keyword(s):  
Osmotic Pressure ◽  
Metastable State ◽  
Necessary Condition ◽  
Hydraulic Pressure ◽  
Membrane Thickness ◽  
Semipermeable Membranes ◽  
Membrane Processes ◽  
State Of Water ◽  
Fundamental Reason ◽  
And Performance

Semipermeable membranes play critical roles in many natural and engineering systems. The osmotic pressure is found experimentally much less effective than the hydraulic pressure to drive water through the membrane, which is commonly attributed to the internal concentration polarization (ICP) in the porous layer of the membrane. In this study, it has been shown that a necessary condition for the osmotic pressure to be effective is water continuity across the entire membrane thickness under negative pressure, i.e., the water inside the membrane remains in a metastable state. However, the metastable state of water cannot be maintained indefinitely, and cavitation will undoubtedly occur in the osmotically driven processes. Collapse of the water metastable state was suggested for the first time to be a more important and fundamental reason for the low water fluxes in the osmotically driven membrane processes.

Flows of Electrolytes Through Charged Hydrated Biological Tissue

1994 ◽  
Vol 47 (6S) ◽  
pp. S277-S281 ◽  
Author(s):  
W. M. Lai ◽  
W. Gu ◽  
V. C. Mow
Keyword(s):  
Osmotic Pressure ◽  
Pressure Difference ◽  
Finite Thickness ◽  
Concentration Field ◽  
Ion Concentration ◽  
Solid Matrix ◽  
Hydraulic Pressure ◽  
Neutral Salt ◽  
Apparent Permeability ◽  
Osmotic Pressure Difference

In this paper, analyses of the flows of water and electrolytes through charged hydrated biologic tissues (e.g., articular cartilage) are presented. These analyses are based on the triphasic mechano-electrochemical theory developed by Lai and coworkers (1991). The problems analyzed are 1-D steady permeation flows generated by a hydraulic pressure difference and/or by an osmotic pressure difference across a finite thickness layer of the tissue. The theory allows for the complete determination of the ion concentration field, the matrix strain field as well as the ion and water velocity field inside the tissue during the steady permeation. For flows generated by a hydraulic pressure difference, the frictional drag induces a compaction of the solid matrix causing the fixed charge density (FCD) to increase and the neutral salt concentration to decrease in the downstream direction. Further, while both ions move downstream, but relative to the solvent (water), the anions (Cl−) move with the flow while the cations (Na+) move against the flow. The theory also predicts a well-known experimental finding that the apparent permeability decreases nonlinearly with FCD. For flows generated by an osmotic pressure difference, first, fluid flow varies with the FCD in a nonlinear and non-monotonic manner. Second, there exists a critical FCD below which negative osmosis takes place.

scholarly journals Modeling and Optimization of Membrane Process for Salinity Gradient Energy Production

Separations ◽  
2021 ◽  
Vol 8 (5) ◽  
pp. 64
Author(s):  
Lianfa Song
Keyword(s):  
Osmotic Pressure ◽  
Energy Production ◽  
Salinity Gradient ◽  
Water Flux ◽  
Hydraulic Pressure ◽  
Semipermeable Membranes ◽  
Pressure Retarded Osmosis ◽  
Higher Power ◽  
Gradient Energy ◽  
Breakeven Point

When hydraulic pressure was added on the feed side of the membrane in the otherwise conventional pressure retarded osmosis (PRO) process, the production rate of the salinity gradient energy could be significantly increased by manipulating the hydraulic pressures on both sides of the membrane. With hydraulic pressure added on the feed side of the membrane, much higher water flux could be obtained than that under the osmotic pressure of the same value. The osmotic pressure of the draw solution, instead of drawing water through the membrane, was mainly reserved to increase the hydraulic pressure of the permeate. In this way, orders of magnitude higher power density than that in the conventional PRO can be obtained with the same salinity gradient. At the optimal conditions, it was demonstrated that the energy production rates that were much higher than the economical breakeven point could be obtained from the pair of seawater and freshwater with the currently available semipermeable membranes.

Research of the Reasons of Frost Destruction of Road Concrete

2020 ◽  
Vol 864 ◽  
pp. 175-179
Author(s):  
Serhij Tolmachov
Keyword(s):  
Sodium Chloride ◽  
Osmotic Pressure ◽  
Linear Thermal Expansion ◽  
Simultaneous Action ◽  
Hydraulic Pressure ◽  
Freezing And Thawing ◽  
Sodium Chloride Solutions ◽  
Concrete Failure ◽  
Initial Stage ◽  
The Difference

The article analyzes the causes of the destruction of road concrete in the winter. The basic theories of concrete failure during freezing are presented. Hypothesis of R. Collins according to which the destruction occurs as a result of the pressure of ice, which is formed when water freezes onto the pore walls. The hydraulic pressure hypothesis of T. Powers, according to which the main cause of concrete destruction during cyclic freezing and thawing, is the hydraulic pressure that creates water in the pores and capillaries of concrete under the action of ice. The hypothesis of thermal destruction of concrete due to the difference in the coefficients of linear thermal expansion of its components. In winter, sodium chloride (NaCl) solutions are most often used to combat ice on the surface of road surfaces. Therefore, an important consequence of this may be osmotic pressure. To calculate the osmotic pressure, the Vant-Hoff formula for true solutions was used. The maximum values of the osmotic pressure were determined at temperatures of 255...293 K. The critical concentrations of sodium chloride solutions at which concrete was destroyed were calculated. It was established that at the initial stage of freezing-thawing of concrete with the simultaneous action of an aqueous NaCl solution, the structure of concrete is densified and its strength is increased.

Progress In The Practical Application Of Automated Image Analysis To Tem Negatives

1977 ◽  
Vol 35 ◽  
pp. 214-217
Author(s):  
F. A. Heckman ◽  
E. Redman ◽  
J.E. Connolly
Keyword(s):  
Image Analysis ◽  
Image Quality ◽  
Exposure Time ◽  
Image Contrast ◽  
Automated Image Analysis ◽  
Practical Application ◽  
Factors Affecting ◽  
High Image Quality ◽  
Qualitative Evidence ◽  
Comprehensive Study

In our initial publication on this subject1) we reported results demonstrating that contrast is the most important factor in producing the high image quality required for reliable image analysis. We also listed the factors which enhance contrast in order of the experimentally determined magnitude of their effect. The two most powerful factors affecting image contrast attainable with sheet film are beam intensity and KV. At that time we had only qualitative evidence for the ranking of enhancing factors. Later we carried out the densitometric measurements which led to the results outlined below.Meaningful evaluations of the cause-effect relationships among the considerable number of variables in preparing EM negatives depend on doing things in a systematic way, varying only one parameter at a time. Unless otherwise noted, we adhered to the following procedure evolved during our comprehensive study:Philips EM-300; 30μ objective aperature; magnification 7000- 12000X, exposure time 1 second, anti-contamination device operating.

Recent Progress In High-Resolution Shadowing For Biological Transmission Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 510-511 ◽  
Author(s):  
Heinz Gross ◽  
Katarina Krusche ◽  
Peter Tittmann
Keyword(s):  
Heavy Metal ◽  
High Resolution ◽  
Freeze Drying ◽  
Atmospheric Conditions ◽  
Vacuum Equipment ◽  
Transmission Electron ◽  
Gas Atmosphere ◽  
Gas Molecules ◽  
Residual Gas ◽  
Backing Layer

Freeze-drying followed by heavy metal shadowing is a long established and straight forward approach to routinely study the structure of dehydrated macromolecules. Very thin specimens such as isolated membranes or single macromolecules are directly adsorbed on C-coated grids. After rapid freezing the grids are transferred into a suitable vacuum equipment for freeze-drying and heavy metal shadowing.To improve the resolution power of shadowing films we introduced shadowing at very low specimen temperature (−250°C). To routinely do that without the danger of contamination we developed in collaboration with Balzers an UHV (p≤10-9 mbar) machine (BAF500K, Fig.2). It should be mentioned here that at −250°C the specimen surface acts as effective cryopump for practically all impinging residual gas molecules from the residual gas atmosphere.Common high resolution shadowing films (Pt/C, Ta/W) have to be protected from alterations due to air contact by a relatively thick C-backing layer, when transferred via atmospheric conditions into the TEM. Such an additional C-coat contributes disturbingly to the contrast at high resolution.

The role of ligands in electron transport in nanocrystal solids

Nanoscale ◽  
2020 ◽  
Vol 12 (45) ◽  
pp. 23028-23035
Author(s):  
Artem R. Khabibullin ◽  
Alexander L. Efros ◽  
Steven C. Erwin
Keyword(s):  
Electron Transport ◽  
Theoretical Modeling

Theoretical modeling of wavefunction overlap in nanocrystal solids elucidates the important role played by ligands in electron transport.

Fifth Edition: the New Standard

2000 ◽  
Vol 5 (6) ◽  
pp. 1-7
Author(s):  
Christopher R. Brigham ◽  
James B. Talmage ◽  
Leon H. Ensalada
Keyword(s):  
Musculoskeletal System ◽  
Medical Information ◽  
Objective Assessment ◽  
Scientific Data ◽  
Practical Application ◽  
Fourth Edition ◽  
Appropriate Use ◽  
Medical Evaluation ◽  
Single Set

Abstract The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fifth Edition, is available and includes numerous changes that will affect both evaluators who and systems that use the AMA Guides. The Fifth Edition is nearly twice the size of its predecessor (613 pages vs 339 pages) and contains three additional chapters (the musculoskeletal system now is split into three chapters and the cardiovascular system into two). Table 1 shows how chapters in the Fifth Edition were reorganized from the Fourth Edition. In addition, each of the chapters is presented in a consistent format, as shown in Table 2. This article and subsequent issues of The Guides Newsletter will examine these changes, and the present discussion focuses on major revisions, particularly those in the first two chapters. (See Table 3 for a summary of the revisions to the musculoskeletal and pain chapters.) Chapter 1, Philosophy, Purpose, and Appropriate Use of the AMA Guides, emphasizes objective assessment necessitating a medical evaluation. Most impairment percentages in the Fifth Edition are unchanged from the Fourth because the majority of ratings currently are accepted, there is limited scientific data to support changes, and ratings should not be changed arbitrarily. Chapter 2, Practical Application of the AMA Guides, describes how to use the AMA Guides for consistent and reliable acquisition, analysis, communication, and utilization of medical information through a single set of standards.

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