scholarly journals Improving the engine power of a catalytic Janus-sphere micromotor by roughening its surface

2017 ◽  
Author(s):  
Brooke W. Longbottom ◽  
Stefan Bon
Keyword(s):  
Surface Area ◽  
Large Deformations ◽  
Experimental Studies ◽  
Model System ◽  
Catalytic Layer ◽  
Irregular Surface ◽  
Catalytic Surface ◽  
Surface Deformations ◽  
Propulsive Mechanism ◽  
Engine Power

<div> <div> <div> <p>Microspheres with catalytic caps have become a popular model system for studying self- propelled colloids. Existing experimental studies involve predominantly “smooth” particle surfaces. In this study we determine the effect of irregular surface deformations on the propulsive mechanism with a particular focus on speed. The particle surfaces were deformed prior to depositing a catalytic layer which resulted in the formation of nanoscopic pillars of catalyst. These features were shown to boost speed (~2×) when the underlying surface deformations are small (nanoscale), whilst large deformations afforded little difference despite a substantial apparent catalytic surface area. Colloids with deformed surfaces were more likely to display a mixture of rotational and translational propulsion than their “smooth” counterparts. </p> </div> </div> </div>

scholarly journals Improving the engine power of a catalytic Janus-sphere micromotor by roughening its surface

2017 ◽  
Author(s):  
Brooke W. Longbottom ◽  
Stefan Bon
Keyword(s):  
Surface Area ◽  
Large Deformations ◽  
Experimental Studies ◽  
Model System ◽  
Catalytic Layer ◽  
Irregular Surface ◽  
Catalytic Surface ◽  
Surface Deformations ◽  
Propulsive Mechanism ◽  
Engine Power

<div> <div> <div> <p>Microspheres with catalytic caps have become a popular model system for studying self- propelled colloids. Existing experimental studies involve predominantly “smooth” particle surfaces. In this study we determine the effect of irregular surface deformations on the propulsive mechanism with a particular focus on speed. The particle surfaces were deformed prior to depositing a catalytic layer which resulted in the formation of nanoscopic pillars of catalyst. These features were shown to boost speed (~2×) when the underlying surface deformations are small (nanoscale), whilst large deformations afforded little difference despite a substantial apparent catalytic surface area. Colloids with deformed surfaces were more likely to display a mixture of rotational and translational propulsion than their “smooth” counterparts. </p> </div> </div> </div>

scholarly journals Flow mechanisms in axial turbine rim sealing

2018 ◽  
Vol 233 (23-24) ◽  
pp. 7637-7657 ◽  
Author(s):  
John W Chew ◽  
Feng Gao ◽  
Donato M Palermo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Experimental Studies ◽  
Power Cycle ◽  
Sealing Performance ◽  
Flow Interactions ◽  
Flow Mechanisms ◽  
Flow Effects ◽  
Main Engine ◽  
Engine Power

This paper presents a review of research on turbine rim sealing with emphasis placed on the underlying flow physics and modelling capability. Rim seal flows play a crucial role in controlling engine disc temperatures but represent a loss from the main engine power cycle and are associated with spoiling losses in the turbine. Elementary models that rely on empirical validation and are currently used in design do not account for some of the known flow mechanisms, and prediction of sealing performance with computational fluid dynamics has proved challenging. Computational fluid dynamics and experimental studies have indicated important unsteady flow effects that explain some of the differences identified in comparing predicted and measure sealing effectiveness. This review reveals some consistency of investigations across a range of configurations, with inertial waves in the rotating flow apparently interacting with other flow mechanisms which include vane, blade and seal flow interactions; disc pumping and cavity flows; shear layer and other instabilities; and turbulent mixing.

The Electrochemical Reduction of a Flexible Mn(II) Salen-Based Metal-Organic Framework

2021 ◽  
Author(s):  
Marcello B Solomon ◽  
Carol Hua ◽  
Bun Chan ◽  
Tamara L Church ◽  
Seth M Cohen ◽  
...  
Keyword(s):  
Electrochemical Reduction ◽  
Surface Area ◽  
Metal Organic Framework ◽  
Experimental Studies ◽  
Bet Surface Area ◽  
Salen Complex ◽  
Computational Calculations ◽  
Metal Organic ◽  
Organic Framework

A new metal-organic framework (MOF) containing a Mn(II) salen complex (BET surface area = 967±6 m2 g−1) undergoes a reversible crystalline-to-amorphous transformation. Experimental studies and computational calculations show that the...

scholarly journals Design-controlled synthesis of IrO2 sub-monolayers on Au nanoflowers: marrying plasmonic and electrocatalytic properties

Nanoscale ◽  
2020 ◽  
Vol 12 (23) ◽  
pp. 12281-12291 ◽  
Author(s):  
Isabel C. de Freitas ◽  
Luanna S. Parreira ◽  
Eduardo C. M. Barbosa ◽  
Barbara A. Novaes ◽  
Tong Mou ◽  
...  
Keyword(s):  
Surface Area ◽  
Light Harvesting ◽  
Controlled Synthesis ◽  
Catalytic Surface ◽  
Electrocatalytic Properties

Au–IrO2 nanostructures optimized for light harvesting with closely spaced plasmonic branches and catalytic surface area (ultra-thin IrO2 layers) were developed.

scholarly journals The gasoline vapors spread from “small” spills in an urban environment at low wind speeds

2020 ◽  
Vol 164 ◽  
pp. 01006
Author(s):  
Ruslan Khrestenko ◽  
Ekaterina Sokolova ◽  
Dmitrii Okulovsky ◽  
Valeri Azarov
Keyword(s):  
Wind Speed ◽  
Urban Environment ◽  
Surface Area ◽  
Experimental Studies ◽  
Calculated Data ◽  
Hazardous Substances ◽  
Ethyl Benzene ◽  
Atmospheric Air ◽  
Wind Speeds ◽  
Low Wind Speeds

It is noted that the urban environment is polluted by oil products; in particular, there is a large pollution of atmospheric air. It is indicated that one of the pollution sources is the “small” spills, which are characteristic of urban areas. Experimental studies have been carried out on the gasoline distribution in atmospheric air at “small” spills. A single experiment at a low wind speed is considered. Data were obtained on the dependence of gasoline concentration in atmospheric air on the distance from the spill, the height above the level of the spill and the time of the spill. The component composition was studied using chromatographic studies. It is indicated that the distribution of gasoline vapors in the atmosphere is influenced by the ambient temperature, wind speed, surface area of the spill, time from the moment of spilling and the distance above the level of the spill. The gasoline dispersion in atmospheric air was calculated with the software using experimental and calculated data on the surface area of the spill. It is indicated that at low wind speeds (up to 0.5 m/s) from “small” spills of gasoline (up to 3 liters), significant excesses of standards for the content of harmful substances in the atmospheric air can be observed. It was determined that during spilling there is an excess of maximum permissible concentrations of single, hazardous substances such as ethyl benzene, m-xylene and amyl alcohol in the air.

scholarly journals Bacteriophage Migration via Nematode Vectors: Host-Parasite-Consumer Interactions in Laboratory Microcosms

2006 ◽  
Vol 72 (3) ◽  
pp. 1974-1979 ◽  
Author(s):  
John J. Dennehy ◽  
Nicholas A. Friedenberg ◽  
Yul W. Yang ◽  
Paul E. Turner
Keyword(s):  
Experimental Studies ◽  
Virus Transmission ◽  
Growth Dynamics ◽  
Model System ◽  
Pathogen Transmission ◽  
Trophic Levels ◽  
Future Research ◽  
Evolution Of Virulence ◽  
Consumer Interactions ◽  
Host Parasite

ABSTRACT Pathogens vectored by nematodes pose serious agricultural, economic, and health threats; however, little is known of the ecological and evolutionary aspects of pathogen transmission by nematodes. Here we describe a novel model system with two trophic levels, bacteriophages and nematodes, each of which competes for bacteria. We demonstrate for the first time that nematodes are capable of transmitting phages between spatially distinct patches of bacteria. This model system has considerable advantages, including the ease of maintenance and manipulation at the laboratory bench, the ability to observe many generations in short periods, and the capacity to freeze evolved strains for later comparison to their ancestors. More generally, experimental studies of complex multispecies interactions, host-pathogen coevolution, disease dynamics, and the evolution of virulence may benefit from this model system because current models (e.g., chickens, mosquitoes, and malaria parasites) are costly to maintain, are difficult to manipulate, and require considerable space. Our initial explorations centered on independently assessing the impacts of nematode, bacterium, and phage population densities on virus migration between host patches. Our results indicated that virus transmission increases with worm density and host bacterial abundance; however, transmission decreases with initial phage abundance, perhaps because viruses eliminate available hosts before migration can occur. We discuss the microbial growth dynamics that underlie these results, suggest mechanistic explanations for nematode transmission of phages, and propose intriguing possibilities for future research.

Scaling Issues of Micro Catalytic Reactors

2013 ◽  
Vol 284-287 ◽  
pp. 2137-2141
Author(s):  
Tzong Shyng Leu ◽  
Shun Yi Li
Keyword(s):  
Surface Area ◽  
Catalytic Reaction ◽  
Volume Ratio ◽  
Efficiency Improvement ◽  
Gas Temperature ◽  
Catalytic Reactors ◽  
Catalytic Surface ◽  
Reaction Efficiency ◽  
Operation Conditions

Micro catalytic combustors are studied experimentally. Microchannels, coated with Pt catalytic walls and columns were fabricated to investigate microscale catalytic reaction. This microscale reaction enhancement by Pt catalytic surface area is characterized by increasing outlet gas temperature with the increase of surface-to-volume ratio. It is found that the reaction efficiency improvement by Pt catalytic columns will extend the operation conditions especially for smaller microchannel size.

scholarly journals SIZING AND EXPERIMENTAL STUDY OF A SOLAR STILL FOR THE PRODUCTIVITY OF WATER DESALINATION IN SOUTH-WEST OF ALGERIA – BECHAR: التصميم والدراسة التجريبية لجهاز التقطير الشمسي لإنتاجية تحلية المياه في جنوب غرب الجزائر – بشار

2020 ◽  
Vol 4 (4) ◽  
Author(s):  
Abdelkarim Maamar Abdelkader, Bounegta Bachir Mohammed
Keyword(s):  
Drinking Water ◽  
Free Surface ◽  
Surface Area ◽  
Evaporation Rate ◽  
Salt Content ◽  
Experimental Studies ◽  
Water Desalination ◽  
Solar Still ◽  
Free Surface Area ◽  
The Third World

Algeria, like many countries belonging mostly to the Third World, has considerable water resources saline (salt content ranging between 1500 and 2000 ppm, exceeding the required standards for drinking water and therefore unfit for consumption). We must therefore think of making use these huge reserves interested in desalination techniques. The stain majored is therefore to achieve a distiller solar plan which meets these needs in drinking water. The absorber surface of the modified solar still is coated with black enamel paint and covered with copper chips. The evaporation rate of the water in the solar still is directly proportional to the exposure area of the water. Thus the productivity of the solar still increases with the free surface area of the water in the basin. The distillate yield was found to have improved considerably, especially when the water depth was high. The study also indicated some design features that would further enhance the improvement in output due to the modification made, the evaporation rate is proportional to the temperature of the free surface area of the water only. A general model based on heat transfer balances in each component of the system was developed to predict the mass of freshwater. The efficiency of this still was about 65% and can produce about 5.13 l/m2 per day, experimental studies and the outcomes are discussed in the article. We propose a new design of the cascading solar desalination still with obstacles and preheating of inlet water.

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