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.

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.

Secret Error-Correcting Network Coding against Eavesdropping and Pollution Attacks

2012 ◽  
Vol 457-458 ◽  
pp. 1499-1507 ◽  
Author(s):  
Si Guang Chen ◽  
Meng Wu ◽  
Wei Feng Lu
Keyword(s):  
Network Coding ◽  
Necessary Condition ◽  
Information Theoretic ◽  
Transmitted Information ◽  
Information Theoretic Security ◽  
Secret Communication ◽  
Pollution Attacks ◽  
Rank Metric Codes ◽  
Shared Secret ◽  
And Performance

In this work we consider the problem of designing a secret error-correcting network coding scheme against an adversary that can re-select the tapping links in different time slot and inject z erroneous packets into network. We first derive a necessary condition for keeping the transmitted information secret from the adversary, while the network is only subject to the eavesdropping attack. We then design an error-correcting scheme by combining the rank-metric codes with shared secret model, which can decode the transmitted information correctly provided a sufficiently large q. With that, a secret error-correcting network coding is proposed by combining this error-correcting scheme with secret communication. We show that under the requirement of communication can achieve a rate of packets. Moreover, it ensures that the communicated information is reliable and information-theoretic security from the adversary. In particular, the requirement of packet length is not as large as the required in [12]. Finally, the security and performance analyses illustrate the characteristics of our scheme.

scholarly journals Sustainability of social economy organizations (SEOs): An analysis of the conditions for surviving and thriving

2021 ◽  
Author(s):  
Daewook Kim ◽  
Wonhyuk Cho ◽  
Barbara Allen
Keyword(s):  
Social Economy ◽  
Necessary Condition ◽  
Causal Process ◽  
Study Approach ◽  
Collaborative Networking ◽  
Social Economy Organizations ◽  
And Performance ◽  
Business Competitiveness

Social economy organizations (SEOs), designed to do good for society, have been attracting significant attention as an alternative to purely profit-driven businesses. However, the sustainability of these hybrid organizations has been questioned due to the challenges in meeting the dual bottom-lines of financial performance and social purpose. This article takes a causal-process tracing (CPT) case study approach and analyzes eight SEOs to investigate the common characteristics of sustainable SEOs. The results of the analysis show that effective leadership is a sufficient (but not necessary) condition for the survival of SEOs, while leadership is a necessary (but not sufficient) condition for SEOs’ thriving. Business competitiveness is found to be necessary for SEOs’ long-term success and performance over time. Collaborative networking is a contributory condition for SEOs thriving but not a necessary condition for their survival.

scholarly journals A Review of CFD Modelling and Performance Metrics for Osmotic Membrane Processes

Membranes ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 285
Author(s):  
Kang Yang Toh ◽  
Yong Yeow Liang ◽  
Woei Jye Lau ◽  
Gustavo A. Fimbres Weihs
Keyword(s):  
Performance Metrics ◽  
Forward Osmosis ◽  
Cfd Modelling ◽  
Membrane Processes ◽  
Pressure Retarded Osmosis ◽  
Multi Scale ◽  
Scale Modelling ◽  
Computational Fluid Dynamics Cfd ◽  
And Performance ◽  
Module Performance

Simulation via Computational Fluid Dynamics (CFD) offers a convenient way for visualising hydrodynamics and mass transport in spacer-filled membrane channels, facilitating further developments in spiral wound membrane (SWM) modules for desalination processes. This paper provides a review on the use of CFD modelling for the development of novel spacers used in the SWM modules for three types of osmotic membrane processes: reverse osmosis (RO), forward osmosis (FO) and pressure retarded osmosis (PRO). Currently, the modelling of mass transfer and fouling for complex spacer geometries is still limited. Compared with RO, CFD modelling for PRO is very rare owing to the relative infancy of this osmotically driven membrane process. Despite the rising popularity of multi-scale modelling of osmotic membrane processes, CFD can only be used for predicting process performance in the absence of fouling. This paper also reviews the most common metrics used for evaluating membrane module performance at the small and large scales.

scholarly journals The state of water in muscle and blood and the osmotic behaviour of muscle

1930 ◽  
Vol 106 (746) ◽  
pp. 477-505 ◽  
Keyword(s):  
Osmotic Pressure ◽  
Vapour Pressure ◽  
Free Water ◽  
Preceding Paper ◽  
The State ◽  
Initial Weight ◽  
Normal Manner ◽  
State Of Water ◽  
Osmotic Behaviour

In the course of the investigation described in the preceding paper by Hill and Kupalov it became necessary to determine the amount of “free” water in muscle, i.e. , the weight of water per gramme of muscle which is capable of dissolving in a normal manner (with the normal depression of vapour pressure) substances added to it. For many years, chiefly on the evidence of the experiments of Overton (1902), it has been commonly supposed that a large proportion of the water of muscle exists in some “bound” form, incapable of taking part in the osmotic changes which occur when the tissue is immersed in hypoor hyper-tonic solutions. From the fact that a muscle swells to much less than twice its initial weight when immersed in a solution of half the initial osmotic pressure Overton concluded “dass nicht das gesammte im Muskel befindliche Wasser in der Form eines Lösungsmittels enthalten sein kann.” I have confirmed Overton’s experiments (see below) but believe that a very different explanation of them is necessary.

scholarly journals Gas Turbine Compressor Operating Environment and Material Evaluation

1989 ◽  
Author(s):  
R. W. Haskell
Keyword(s):  
Gas Turbine ◽  
Material Selection ◽  
Necessary Condition ◽  
Base Materials ◽  
Material Evaluation ◽  
Filtration System ◽  
And Performance ◽  
A Site ◽  
Gas Turbine Compressor ◽  
Selection Of

The reliability and performance of a gas turbine compressor is strongly dependent upon the environment in which it operates, the materials which are used, and the filtration system. Erosion and to a certain extent fouling can be controlled by the filtration system, but corrosion is largely controlled through site and material selection. The factors which determine the corrosivity of a site are humidity, the concentration of acid-forming gases, and the composition of particulates. The interrelationships of these factors are discussed with an aim of reducing their impact on compressor operation. A necessary condition for corrosion is the presence of moisture. The acidity of the moisture results from its interaction with the gases and particulates of the environment. The details of these interactions which are important to turbine operators are discussed. A considerable amount of corrosion testing of base materials and coatings has been performed and this is reviewed. A table is presented for selection of compressor materials based on the nature of the site environment and the type of compressor filtration.

scholarly journals Flux Optimization in Reverse Osmosis via the Solution-Diffusion Model

2019 ◽  
Vol 4 (5) ◽  
pp. 39-44
Author(s):  
Hisham A. Maddah
Keyword(s):  
Osmotic Pressure ◽  
Reverse Osmosis ◽  
Diffusion Model ◽  
Water Flux ◽  
Applied Pressure ◽  
Arabian Gulf ◽  
Water Sources ◽  
Operating Conditions ◽  
Membrane Thickness ◽  
Membrane Type

This paper suggests a new method of predicting flux values at reverse osmosis (RO) desalination plants.  The study is initiated by using the solution-diffusion model that is applied to the groundwater source at Abqaiq plant (500 RO plant) at Saudi Aramco, Dhahran, Saudi Arabia in order to calculate the osmotic pressure of the treated water for Shedgum/Abqaiq groundwater. For modelling purposes, the same technique is used to determine the osmotic pressure drops at the same plant configuration and operating conditions when using seawater sources such that of Arabian Gulf and the Red Sea waters. High rejection brackish water RO (BWRO) element Toray TM720D-400 with 8" is the RO membrane type that is used at Abqaiq plant. The calculated osmotic pressures of the three water sources, assuming that they are all treated at Abqaiq plant, are utilized to determine the appropriate flux values as well as membrane resistances of different BWRO Toray membranes. Values of numerous parameters such as water permeability constant, applied pressure, gas constant, water temperature, water molar volume and membrane thickness, water salinity/TDS are taken into account to develop our calculations through the solution-diffusion model. A comparison between low-pressure, standard and high-pressure BWRO Toray membranes performance have been established to select the ideal membrane type for the treatment of water from various sources at Abqaiq plant. The model results confirm an inverse relationship between the membrane thickness and the water flux rate. Also, a proportional linear relation between the overall water flux and the applied pressure across the membrane is identified. Higher flux rates and lower salinity indicate lower membrane resistance which yields to the higher water production. Modelled data predict that BWRO Toray TM720D-440 with 8" membrane is the optimal BWRO membrane choice for the three water sources at Abqaiq plant.

State and Performance of Water Retention Structures of Earthen Irrigation Dams in Northern Ghana

2018 ◽  
Vol 1 (1) ◽  
pp. 34-43
Author(s):  
T. A. Adongo ◽  
F. K. Abagale ◽  
G. Kranjac-Berisavljevic
Keyword(s):  
Field Observation ◽  
Water Retention ◽  
Structural Defects ◽  
Northern Ghana ◽  
Key Informants ◽  
Storage Reservoirs ◽  
State Of Water ◽  
Northern Regions ◽  
And Performance ◽  
Retention Structures

The study assessed performance and state of water retention infrastructure of eight (8) irrigation schemes in three (3) northern regions of Ghana. Data was collected using field observation and key informants’ interviews. The results indicated that the Tono and Bontanga earthen irrigation dams’ embankments had no structural defects whereas the embankments of Libga, Golinga, Karni, Vea, Doba and Sankana had some structural defects. Except Libga, all the spillways had no structural deficiencies and signs of risk of failure. All the reservoirs contained some amounts of sediments and weeds. The night storage reservoirs at Tono and Vea were weedy and silted up. The developed irrigable areas of Vea, Tono, Doba, Sankana and Karni schemes had average irrigation rates ranging from 12 - 76 % for the years 2010 - 2017. The water retention infrastructure of the irrigation schemes are recommended for maintenance and periodic repairs to ensure sustainable water retention and availability for crop irrigation.

ANXIETY IN PSYCHOLOGICAL RESEARCH (BASING ON THE MATERIALS OF THE LITERARY REVIEW)

2021 ◽  
Vol 68 (3) ◽  
Author(s):  
S.K. Kudaibergenova ◽  
Keyword(s):  
Professional Sports ◽  
Personal Characteristics ◽  
Law Enforcement Officers ◽  
Optimal Level ◽  
Psychological Research ◽  
Necessary Condition ◽  
Psychophysiological State ◽  
And Performance ◽  
The Relationship ◽  
Sports Activities

This article is devoted to a review of research on anxiety states in fundamental and applied writings. The issues of prevalence, etiological factors of anxiety, historical and modern perceptions about this emotional state are considered. Main symptoms and specificity of manifestations of various types of anxiety, as well as the influence of gender, age and personal characteristics of an individual on its manifestations are highlighted. The studies of anxiety reveal the relationship with the productivity and performance of professional / sports activities, communication and psychophysiological state of a person. Currently, anxiety is considered not only a negative emotional phenomenon, but also as a necessary condition for the normal functioning of the psyche at its optimal level. The ruminations of anxious experiences in the types of activities associated with special working conditions (athletes, law enforcement officers, defense officials) are revealed.

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