scholarly journals Effects of self-induction in an Iron cylinder when traversed by alternating currents

1908 ◽  
Vol 80 (539) ◽  
pp. 369-378
Keyword(s):  
Magnetic Induction ◽  
Alternating Current ◽  
Initial Position ◽  
Rate Of Change ◽  
Direction Parallel ◽  
Zero Current ◽  
In Series ◽  
Continuous Current ◽  
Different Depths ◽  
Flow Through

In a previous paper the effects of self-induction in an iron cylinder were studied when a continuous current flowing through the cylinder in a direction parallel with its axis of figure was suddenly reversed and again maintained steady. In the experiments reported in the present paper the currents in the cylinder were made to alternate in the following manner. A continuous current dynamo, capable of giving currents up to 2000 amperes or more, was weakly excited and its brushes were short-circuited by the cylinder to be experimented upon in series with the shunt of a moving-coil ampere meter. The brushes were moved round the commutator by aid of a worm and worm-wheel from the position of maximum to that of zero current. The field was then reversed and the brushes moved back to their initial position. By continuing these operations an alternating current was caused to flow through the cylinder, and its periodic time was controlled by the speed at which the brushes were moved. The worm axle was uniformly rotated by hand at a speed determined by the operator listening to a seconds clock. Simultaneously readings were taken at known epochs on ( a ) each of three dead-beat galvanometers connected to exploring coils threaded through holes in the mass of the cylinder for the purpose of obtaining the E. M. F. 's at different depths due to the rate of change of the magnetic induction, and on ( b ) the moving-coil ampere-meter.

Comparison of Aerobic and Anoxic-Aerobic Digestion of Waste Activated Sludge

1985 ◽  
Vol 17 (8) ◽  
pp. 1475-1478 ◽  
Author(s):  
A P. C. Warner ◽  
G. A. Ekama ◽  
G v. R. Marais
Keyword(s):  
Experimental Data ◽  
Activated Sludge ◽  
Waste Activated Sludge ◽  
Activated Sludge Process ◽  
Cycle Times ◽  
Waste Sludge ◽  
Volatile Solids ◽  
In Series ◽  
Flow Through ◽  
Theoretical Simulations

The laboratory scale experimental investigation comprised a 6 day sludge age activated sludge process, the waste sludge of which was fed to a number of digesters operated as follows: single reactor flow through digesters at 4 or 6 days sludge age, under aerobic and anoxic-aerobic conditions (with 1,5 and 4 h cycle times) and 3-in-series flow through aerobic digesters each at 4 days sludge age; all digesters were fed draw-and-fill wise once per day. The general kinetic model for the aerobic activated sludge process set out by Dold et al., (1980) and extended to the anoxic-aerobic process by van Haandel et al., (1981) simulated accurately all the experimental data (Figs 1 to 4) without the need for adjusting the kinetic constants. Both theoretical simulations and experimental data indicate that (i) the rate of volatile solids destruction is not affected by the incorporation of anoxic cycles and (ii) the specific denitrification rate is independent of sludge age and is K4T = 0,046(l,029)(T-20) mgNO3-N/(mg active VSS. d) i.e. about 2/3 of that in the secondary anoxic of the single sludge activated sludge stystem. An important consequence of (i) and (ii) above is that denitrification can be integrated easily in the steady state digester model of Marais and Ekama (1976) and used for design (Warner et al., 1983).

Poly Silk Peptide Film PH Sensor Based on Zero Current Potentiometry

2012 ◽  
Vol 450-451 ◽  
pp. 554-556
Author(s):  
Ming Ming Ma ◽  
Zhi Tong ◽  
Yong Wen
Keyword(s):  
Graphite Electrode ◽  
Ph Sensor ◽  
Reference Electrode ◽  
Pencil Graphite Electrode ◽  
Solution Ph ◽  
Counter Electrodes ◽  
System A ◽  
Zero Current ◽  
In Series ◽  
Silk Peptide

A poly silk peptide film pH sensor has been developed using zero current potentiometry system. A poly silk peptide film coated pencil graphite electrode is connected in series between the working and counter electrodes of a potentiostat, and immersed in solution together with a reference electrode. When the solution pH varies, the resulting zero current potentiometry is linear with the values of the solution pH in the range of 1.81 to 11.58. This pH sensor shows high stability, accuracy, selectivity and reproduction.

Instability Modes of Two-Phase Flows in a Mixing-Layer Microdevice

2001 ◽  
Author(s):  
Tak For Yu ◽  
Sylvanus Yuk Kwan Lee ◽  
Yitshak Zohar ◽  
Man Wong
Keyword(s):  
Gas Flow ◽  
Mixing Layer ◽  
Fluid Flows ◽  
Two Phase Flows ◽  
Two Phase ◽  
Pressure Distributions ◽  
Instability Modes ◽  
In Series ◽  
Mass Flow Rates ◽  
Flow Through

Abstract Extensive development of biomedical and chemical analytic microdevices involves microscale fluid flows. Merging of fluid streams is expected to be a key feature in such devices. An integrated microsystem consisting of merging microchannels and distributed pressure microsensors has been designed and characterized to study this phenomenon on a microscale. The two narrow, uniform and identical channels merged smoothly into a wide, straight and uniform channel downstream of a splitter plate. All of the devices were fabricated using standard micromachining techniques. Mass flow rates and pressure distributions were measured for single-phase gas flow in order to characterize the device. The experimental results indicated that the flow developed when both inlets were connected together to the gas source could be modeled as gas flow through a straight and uniform microchannel. The flow through a single branch while the other was blocked, however, could be modeled as gas flow through a pair of microchannels in series. Flow visualizations of two-phase flows have been conducted when driving liquid and gas through the inlet channels. Several instability modes of the gas/liquid interface have been observed as a function of the pressure difference between the two streams at the merging location.

Inertia-Driven Controlled Passive Actuation

2015 ◽  
Author(s):  
Douwe Dresscher ◽  
Theo J. A. de Vries ◽  
Stefano Stramigioli
Keyword(s):  
Energy Flow ◽  
Legged Locomotion ◽  
Continuously Variable Transmission ◽  
The State ◽  
Rate Of Change ◽  
Storage Element ◽  
Abstraction Layer ◽  
Variable Transmission ◽  
Alternative Means ◽  
Flow Through

A serious problem with using electrical actuators in legged locomotion is the significant energy loss. For this reason, we propose and analyse an alternative means of actuation: Controlled Passive Actuation. Controlled Passive Actuation aims at reducing the energy flow through electric actuators by actuating with a combination of an energy storage element and a Continuously Variable Transmission. In this work, we present a method where we apply a Continuously Variable Transmission with a storage element in the form of a mass to change the state of another mass (“the load”). An abstraction layer is created to abstract the inertia-driven Controlled Passive Actuation to a source of effort, a force actuator. On this abstracted system, feedback control can be applied to achieve control goals such as path tracking. With simulations and experiments, we show that inertia-driven Controlled Passive Actuation can be used to control the state of an (inertial) load. The experimental results show that the performance of the system is affected by the internal dynamics and limited rate of change of the transmission ratio of the Continuously Variable Transmission.

scholarly journals SIZE EFFECT ON THE PERMEABILITY AND SHEAR INDUCED FLOW ANISOTROPY OF FRACTAL ROCK FRACTURES

Fractals ◽  
2018 ◽  
Vol 26 (02) ◽  
pp. 1840001 ◽  
Author(s):  
NA HUANG ◽  
YUJING JIANG ◽  
RICHENG LIU ◽  
YUXUAN XIA
Keyword(s):  
Fluid Flow ◽  
Stable State ◽  
Simulation Method ◽  
Shear Direction ◽  
Direction Parallel ◽  
Flow Channels ◽  
Fracture Size ◽  
Flow Through ◽  
Model Size ◽  
Induced Flow

The effect of model size on fluid flow through fractal rough fractures under shearing is investigated using a numerical simulation method. The shear behavior of rough fractures with self-affine properties was described using the analytical model, and the aperture fields with sizes varying from 25 to 200[Formula: see text]mm were extracted under shear displacements up to 20[Formula: see text]mm. Fluid flow through fractures in the directions both parallel and perpendicular to the shear directions was simulated by solving the Reynolds equation using a finite element code. The results show that fluid flow tends to converge into a few main flow channels as shear displacement increases, while the shapes of flow channels change significantly as the fracture size increases. As the model size increases, the permeability in the directions both parallel and perpendicular to the shear direction changes significantly first and then tends to move to a stable state. The size effects on the permeability in the direction parallel to the shear direction are more obvious than that in the direction perpendicular to the shear direction, due to the formation of contact ridges and connected channels perpendicular to the shear direction. The variances of the ratio between permeability in both directions become smaller as the model size increases and then this ratio tends to maintain constant after a certain size, with the value mainly ranging from 1.0 to 3.0.

scholarly journals Properties, processes and regimes of soil solutions and surface waters

2020 ◽  
Vol 175 ◽  
pp. 12022
Author(s):  
Guriyat Podvolotskaya ◽  
Sergey Belopukhov ◽  
Vitaly Savich ◽  
Andrey Sorokin ◽  
Nikolay Tyutrin
Keyword(s):  
Biological Activity ◽  
Surface Water ◽  
Surface Waters ◽  
Pair Correlation ◽  
Rate Of Change ◽  
Water Soluble ◽  
Soil Solutions ◽  
Different Depths ◽  
Different Soils

Soil solutions and the surface waters are characterized by properties, processes and regimes. Soil solutions of different soils and their surface water have different biological activity and change the activity of dissolved stimulants and inhibitors. The object of the study are soil solutions of the main types of soils obtained in the model experiments with the ratio of soils: water equal to 1:1 and 1: 2, soil solutions and surface water in the flooding of soils with water for 1 week – 3 months. The research method consisted in the assessment of pH, Eh, activity of K, NO3, NH4, Ca, Mg by conventional methods, assessment of concentrations of water-soluble compounds extracted from soils by ionite membranes, in the assessment of biological activity of solutions using biotests. The following is suggested for additional evaluation: the using of cation and anion membranes, determination of interrelation between the properties of waters, equation of pair correlation and multiply regression. The informative value of the gradient of surface water concentrations at different distances from the floor of the reservoir, at different depths of the overwatered soils is shown. The mobility of Ca, Mg, Fe, Mn in soils and the content of their water-soluble forms depends on both pH and Eh, whose influence on the content of water-soluble forms of the considered cations shows the effects of synergy and antagonism. The rate of change in the composition of soil solutions during soil flooding depends on a combination of soil properties, temperature, and duration of flooding. Soil solutions of different soils and their surface waters have differentrates.

scholarly journals The ignition of gases by condenser discharge sparks

1914 ◽  
Vol 91 (623) ◽  
pp. 17-22 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
High Temperature ◽  
Low Frequency ◽  
Spark Ignition ◽  
Alternating Current ◽  
Characteristic Type ◽  
Current Break ◽  
Continuous Current ◽  
Parabolic Form

1.It may be taken as an axiom of electrical ignition that the closer its conditions resemble those in the explosion wave front the more readily will it occur. These conditions are high temperature and pressure, and in the case of hydrocarbons combustion to carbon monoxide. They are also characteristic of condenser discharge sparks, for in the first place the surface of a platinum pole to which condenser discharge has been made becomes pitted to a remarkable extent, greater than when large currents are broken by separation of the poles. The sparks have therefore a high temperature. That they give rise to high gas pressure is clear from the intensity of the sound of a single spark discharge, and finally it will be shown that combustion to carbon monoxide rather than to carbon dioxide is peculiar in certain cases to ignition by capacity sparks. In addition to these the sparks are of very short duration, are oscillatory in character, and start with ionisation or breakdown of the gas between the poles. The belief that all visible sparks will ignite explosive mixtures no doubt arose from observations of the activity of condenser discharge in this respect, but while in certain cases, especially in the ignition of hydrogen, the least is in every case a well marked limit to their igniting power, and as the percentage of gas limits of inflammability are approached they require to be large. 2. The Paraffins—Ethane, Propane, and Butane .—The gases used in the present work were from the same stocks as those used for break-spark ignition. The results obtained from them are given in fig. 1. They have two interesting features; their minimum igniting current is the same in every case, in this resembling their ignition by continuous current break-sparks, but they have the parabolic form characteristic of alternating current break-spark ignition. Ethane has, however, a minimum at 7∙7 per cent., the point of combustion to carbon monoxide, the others, as before, midway between this and combustion to carbon dioxide. There is, however, on the higher side of the ethane and propane curves—the supply of butane gave out before this could be examined fully—a step or increase in difficulty of ignition corresponding to mixtures midway between four and five atoms of oxygen to one molecule of ethane, and between six and seven to one of propane. This point was thought to be some failure in the quality of the gas, but when it appeared in both, and to a still greater extent in methane, it was more fully examined. Condenser-spark ignition has therefore some of the features of both continuous and low frequency alternating current break-spark ignition, but it has a characteristic type of its own.

Diel and Annual Cycles of Net Plankton Photosynthesis in Lake Ontario

1973 ◽  
Vol 30 (12) ◽  
pp. 1779-1787 ◽  
Author(s):  
G. P. Harris
Keyword(s):  
Inverse Correlation ◽  
Lake Ontario ◽  
Rate Of Change ◽  
Annual Cycles ◽  
Light Regimes ◽  
Static Water ◽  
Different Depths ◽  
Diel Fluctuations ◽  
Photosynthesis And Respiration ◽  
Net Phytoplankton

Photosynthesis measurements on net plankton have been carried out for the period April, 1972 to January, 1973 in Lake Ontario. The rising and falling light regimes used on the net phytoplankton (> 64 μ) give marked photosynthetic hysteresis effects in winter and in spring for diatom-dominated populations. Diel fluctuations in photosynthesis and "sun" or "shade" adaptations showed a close interaction between the phytoplankton and the surface light intensity. Systematic seasonal changes have been recorded in the magnitude of the photosynthetic hysteresis effect, saturation light intensities, compensation points, maximum photosynthesis, and respiration rates. An inverse correlation has been found between net plankton mean maximum photosynthesis rates and the rate of change of water temperature. Also phytoplankton respiration rate is largely a function of temperature.The data have been unified to give a picture of daily photosynthesis patterns at different depths in a static water column. The data compare well with 14C moored bottle experiments. Predictive equations have been calculated for maximum photosynthesis rates at different times of the year.

Photospheric Flux Changes and the MHD Approximation

1984 ◽  
Vol 5 (4) ◽  
pp. 500-502 ◽  
Author(s):  
P. R. Wilson
Keyword(s):  
Magnetic Flux ◽  
Magnetic Induction ◽  
Closed Curve ◽  
Rate Of Change ◽  
Plasma Velocity ◽  
Magnetic Diffusivity

The rate of change of magnetic flux Ф contained within a closed curve C moving with the plasma velocity u, is given bywhere B is the magnetic induction and S is a surface bounded by the curve C. Using the hydromagnetic equation,where η is the magnetic diffusivity, this becomesIn many astrophysical contexts η is small and thus approximatelySince this implies that the flux within any moving closed curve does not change, the field is said to be ‘frozen into’ the plasma and moving with it.

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