Measurement Of Flux Distribution Research Articles

Flow and sediment processes in a cutoff meander of the Danube Delta during episodic flooding

This article analyzes the water and suspended solid fluxes through a straightened meander of the southern branch of the Danube Delta (the St. George branch) during episodic flooding. The Mahmudia study site corresponds to a vast natural meander which was cut off in 1984–1988 by an artificial canal opened to shipping. The meander correction accelerated fluxes through the artificial canal and dramatically enhanced deposition in the former meander. After his formation, the cutoff meander acted as sediment storage locations, essentially removing channel and point bar sediments from the active sediment budget of the main channel. Increases in slope and stream power in reaches upstream and downstream have also occurred, but to a lesser degree. During the one-hundred-year recurrent flood in April 2006, bathymetry, flow velocity and discharge data were acquired across several sections of both natural and artificial channels with an acoustic Doppler current profiler (aDcp Workhorse Sentinel 600 kHz, Teledyne RDI) in order to investigate the distribution of the flow and sediment and his impact on sedimentation in a channelized reach and its adjacent cutoff. The contrasting hydro-sedimentary processes at work in both channels and bifurcation/confluence nodal points are analyzed from the measured flux distribution, morphological profiles and velocity and concentration patterns. In the cutoff, a diminishing of the intensity of the flow velocity (c. 50%) and of the SSC was observed correlated with the aggradation of the river bed. In the bifurcation/confluence nodal points and in the artificial canal were observed the most intensive hydrodynamic activity (high flow velocity, SSC concentration, degradation of the river bad). Both the event-scale and long-term morphological trends of the alluvial system are discussed analyzing the boundary shear stress and SSC variability. Excess boundary shear stress in the sub-reaches directly affected by cutoffs resulted in scour that increased downstream bed material load. These high sediment loads play a key role in driving morphological adjustments towards equilibrium in the cutoff channel. The approach followed in this paper combines detailed episodic in-situ aDcp measurements and robust numerical 1D modeling in order to provide a practical comprehension of the relevant morphodynamical processes. The 1D model reproduces robustly the continuity of hydrodynamical variables along the streamwise axes of the two-channel network. The simulated are used in the paper for highlighting reach-scale morphological processes, at both event and long-term scales.

Finite-Element Modeling and Measurements of Flux and Eddy Current Distribution in Toroidal Cores Wound From Electrical Steel

Despite the apparent relative simplicity of the wound toroidal geometry, numerical modeling techniques are very difficult to implement due to the inherent large mesh size required to model a laminated core or spiral geometry. Recent advancements in computing capabilities have made the simulation and the study of such devices more feasible. Finite-element modeling of toroidal cores wound from grain-oriented electrical steel was conducted to accurately represent their magnetic circuits in order to calculate the internal magnetic flux distribution, its interaction with core geometry, and to be able to predict the associated magnetic losses. The general flux distribution trends agree with measured results from identical cores. The interlaminar flux and the associated induced planar eddy currents were also calculated. The measurements were performed using a series of search coils enclosing every five turns. In each case, the core was magnetized at 50 and 400 Hz under controlled sinusoidal flux density up to 1.5 T.

Slope Measurements of Parabolic Dish Concentrators Using Color-Coded Targets

A new fast and highly accurate method for measuring the slope errors of parabolic dish concentrators has been developed. This method uses a flat target with colored stripes placed close to the focal plane of the concentrator and a digital camera located at an observation point on the optical axis at some distance from it. A specially developed image analysis algorithm detects the different colors of the images of the reflection of the target in the concentrator and assigns them their known position on the color target. This information, along with the geometry of the measurement setup and the theoretical parabolic shape of the concentrator, is used to calculate the normal vectors of the concentrator surface. From these normal vectors, the radial and tangential slopes can be calculated and compared to the design values of the concentrator. The resulting slope errors not only give the total concentrator error for general characterization of the dish but also indicate systematic errors from fabrication and installation with a high spatial resolution. In order to verify the quality of the results obtained, a ray-tracing code was developed that calculates the flux distribution on planes perpendicular to the optical axis. Measured slope errors of a 8.5m dish concentrator are presented and the calculated flux distributions are compared to measured flux distributions. The comparison shows excellent agreement in the flux distribution on the absorber plane. This verifies the promising potential of this fast and highly precise new method for measuring imperfections in dish concentrator shape.

Enhancement of a subcritical experimental facility via MCNP simulations

At the University of Cincinnati Nuclear and Radiological Engineering Program, a once moth-balled vintage subcritical reactor facility was reassembled to provide a practical laboratory experience for students in nuclear science. The relative simplicity and accessibility of this facility are some of its most desirable features. Recent work had led to supplementing the experimental aspects of this facility with a three-dimensional, full detail, MCNP model of this reactor. This article emphasizes the latest validations of this simulation model against the most recently available laboratory measurements of neutron flux distributions and subcritical neutron multiplication factors, while illustrating a unique feature of this facility which enables experimentalists to carry out step by step measurements, and the corresponding simulations, while the core is being loaded and unloaded. Furthermore, additional simulations are herein included to evaluate the impact of different moderator and reflector arrangements upon core reactivity, including a few combinations of heavy water and/or beryllium, primarily as a venue for researchers to begin studying potential upgrades or changes to the current design.

Identification of Genome-Scale Metabolic Network Models Using Experimentally Measured Flux Profiles

Genome-scale metabolic network models can be reconstructed for well-characterized organisms using genomic annotation and literature information. However, there are many instances in which model predictions of metabolic fluxes are not entirely consistent with experimental data, indicating that the reactions in the model do not match the active reactions in the in vivo system. We introduce a method for determining the active reactions in a genome-scale metabolic network based on a limited number of experimentally measured fluxes. This method, called optimal metabolic network identification (OMNI), allows efficient identification of the set of reactions that results in the best agreement between in silico predicted and experimentally measured flux distributions. We applied the method to intracellular flux data for evolved Escherichia coli mutant strains with lower than predicted growth rates in order to identify reactions that act as flux bottlenecks in these strains. The expression of the genes corresponding to these bottleneck reactions was often found to be downregulated in the evolved strains relative to the wild-type strain. We also demonstrate the ability of the OMNI method to diagnose problems in E. coli strains engineered for metabolite overproduction that have not reached their predicted production potential. The OMNI method applied to flux data for evolved strains can be used to provide insights into mechanisms that limit the ability of microbial strains to evolve towards their predicted optimal growth phenotypes. When applied to industrial production strains, the OMNI method can also be used to suggest metabolic engineering strategies to improve byproduct secretion. In addition to these applications, the method should prove to be useful in general for reconstructing metabolic networks of ill-characterized microbial organisms based on limited amounts of experimental data.

Interpretation of metabolic flux maps by limitation potentials and constrained limitation sensitivities

Two new concepts, "Limitation Potential" and "Constraint Limitation Sensitivity" are introduced that use definitions derived from metabolic flux analysis (MFA) and metabolic network analysis (MNA). They are applied to interpret a measured flux distribution in the context of all possible flux distributions and thus combine MFA with MNA. The proposed measures are used to quantify and compare the influence of intracellular fluxes on the production yield. The methods are purely based on the stoichiometry of the network and constraints that are given from irreversible fluxes. In contrast to metabolic control analysis (MCA), within this approach no information about the kinetic mechanisms are needed. A limitation potential (LP) is defined as the reduction of the reachable (theoretical) maximum by a measured flux. Measured fluxes that strongly narrow the reachable maximum are assumed to be limiting as the network has no ability to counterbalance the restriction due to the observed flux. In a second step, the sensitivity of the reduced maximum is regarded. This measure provides information about the necessitated changes to reach higher yields. The methods are applied to interpret the capabilities of a network based on measured fluxes for a L-phenylalanine producer. The strain was examined by a series of experiments and three flux maps of the production phase are analyzed. It can be shown that the reachable yield is drastically reduced by the measured efflux into the TCA cycle, while the oxidative pentose-phosphate pathway only plays a secondary role on the reachable maximum.

Optimum structure of CT probe and spectral components in 2-D magnetic field visualization based on the magnetic CT method

The precise measurement of two-dimensional and three-dimensional magnetic flux distribution is indispensable for the development of magnetic machinery and device. The magnetic computed tomography (CT) method is proposed to visualize magnetic flux distribution. In order to determine the optimum structure of the magnetic CT probe, an evaluation model is employed to simulate the reconstruction accuracy of magnetic flux distribution. The spectrum of a distribution of magnetic field has been discussed of the components. As a result, the numerical simulation shows the optimum design of the multi layer CT probe.

Flux and energy distribution of axial protons emitted from the hydrogen plasma focus

Experimental results and theoretical studies show that protons from the hydrogen plasma focus are emitted predominantly in the axial direction. In this work the results of the flux and energy distribution measurements of the axial protons using CR-39 detector are presented. The main purpose of the experiment is to test the suitability of a plasma focus device as a source for ( p , α ) nuclear reactions, especially Li 7 ( p , α ) He 4 and B 11 ( p , α ) 2 He 4 .

An investigation of an industrial coating environment with planar probe technology

A novel electrostatic probe method has been applied to the plasma characterization of an industrial magnetron-based ion plating plasma system. The probe consists of a small, 7-mm diameter, disk fitted with a guard ring and mounted near the substrate position. A negative DC self-bias is achieved on the probe surface relative to the plasma by application of a radio frequency (RF) burst across an in-line capacitor. Following the termination of the RF burst a current–voltage characteristic is obtained as the probe potential returns to a floating condition through the arrival of positive ions from the plasma. Use of capacitively coupled RF biasing permits operation of the probe in a deposition environment. The guard ring maintains sheath planarity at the probe surface and eliminates edge effects. Total positive ion flux and the energetic tail of the electron distribution function are determined from the probe's current–voltage characteristic. Results are reported for ion flux and electron energy distribution measurements in DC and pulsed DC plasmas in closed field unbalanced magnetron sputter ion plating (CFUBMSIP) industrial coating equipment. Argon and combined argon and reactive gas atmospheres at below 0.5 Pa were used. Measurements are correlated with the deposition system's configuration and deposition parameters, including magnetron and substrate voltages, bias currents, and pulsing conditions. Potential applications and limitations of the planar probe technique for routine process control in an industrial coating environment are discussed.

Dust measurements in the coma of comet 81P/Wild 2 by the Dust Flux Monitor Instrument.

We present measurements of the dust particle flux and mass distribution from the Stardust Dust Flux Monitor Instrument (DFMI) throughout the flyby of comet 81P/Wild 2. In the particle mass regime from 10(-14) to 10(-7) kilograms, the spacecraft encountered regions of intense swarms of particles, together with bursts of activity corresponding to clouds of particles only a few hundred meters across. This fine-scale structure can be explained by particle fragmentation. We estimate that 2800 +/- 500 particles of diameter 15 micrometers or larger impacted the aerogel collectors, the largest being approximately 6 x 10(-7) kilograms, which dominates the total collected mass.

The effects of a highly viscous liquid phase on vertically upward two-phase flow in a pipe

Water and glycerine solutions were used to produce nominal liquid viscosities of 1, 50, 200 and 550 mPa s. These liquids flowed concurrently with air to allow measurements of momentum flux, void fraction and pressure distributions to be made at mass fluxes consistent with an exit “homogeneous” Mach number of 0.4. The flow pattern in the pipe was, in the main, annular up-flow. The data are shown to be consistent with the annular flow model. However, entrained liquid fractions were estimated at conditions where they were unexpected and the interfacial friction factors were significantly different to those implied from low viscosity fluid correlations. A new correlation for the interfacial friction factor is proposed for the highly viscous dataset. Choking tests were carried out with air–liquid flows with liquid viscosities of 1 and 50 mPa s. These data showed that the annular model approach extends to cover these flow conditions. More traditional methods are shown not to represent the measured void fraction, frictional pressure drop or choking mass flow rates.

Measurements of heat flux distribution toward substrate by means of the LiNbO 3 interferometer, and electron density in a capacitively coupled rf discharge plasma

Measurement of temperature by the laser interferometry method with a LiNbO 3 substrate and determination of heat flux in capacitively coupled plasma (CCP) are described. This method is based on monitoring the variation on nature birefringence with temperature. The CCP is generated at 20 or 40 mm gap length, 100 mTorr argon gas pressure, and 250 cc/min gas flow with an rf input power of 100 W. The rf power is supplied to the lower electrodes through a L-type matching network containing a coupling capacitor and the upper electrode is grounded. The heat flux and electron density distribution possess the same peak characteristics around the maximal point of plasma density under the same experimental conditions. The average diffusion flux for electrons and ions can be calculated from the electron distribution and ambipolar diffusion coefficient. The axial and radial diffusion fluxes are 2.4 × 10 12 and 8.1 × 10 12 #/cm 2 s, respectively. Taking account of the electrode and side area, we find that the total axial flux is 10 times larger than the radial one.

Development of a New Large Flaming Ignition Source for Upholstered Seating and Mattress Tests. Part 1: Characterisation of Ignition Sources

Flaming ignition sources are used in standard tests to assess the ignitability of upholstery seating and mattress composites. These sources should preferably be equivalent to the ignition source occurring in real life situations. BS 5852 defines a total of seven ignition sources of which the No. 5 Crib is used for testing upholstered seating and mattresses designated for use in public premises. In this paper this ignition source is compared to two newspaper ignition sources of 20 grams and several other ignition sources. Extensive rate of heat release measurements in the cone calorimeter tests and heat flux distribution measurements towards the back and the base of an inert L-shaped test rig simulating the seating test rig are presented and discussed. Flaming ignition sources are used in standard tests to assess the ignitability of upholstery seating and mattress composites. These sources should preferably be equivalent to ignition sources occurring in real life situations. BS5852 defines a total of seven ignition sources of which the No. 5 Crib is used for testing upholstered seating and mattresses designated for use in public premises. This paper discusses different candidate ignition sources and compares them with the 20 gram newspaper ignition source required by the EC as part of the earlier draft Furniture Directive. Modified crib structures as well as multi-jet gas burners have been studied and the final selection of the ignition source was based on extensive tests on upholstery seating and mattress composites.

Critical evaluation and limitations of localized flux density measurements in electrical steels

Search coils and needle probes are existing experimental sensors that can measure flux distributions in electrical steels. This work investigates and evaluates the limitations of each method, proposes the use of a new modified needle probe method and gives reasons for its improved applicability and relative merits.

Estimating scalar sources, sinks, and fluxes in a forest canopy using Lagrangian, Eulerian, and hybrid inverse models

A new method was developed to estimate canopy sources and sinks from measured mean concentration profiles within the canopy (referred to as the “inverse” problem). The proposed method combined many of the practical advantages of the Lagrangian localized near‐field (LNF) theory and higher‐order Eulerian (EUL) closure principles. Particularly, this “hybrid” method successfully combined the essential conservation equations of closure modeling and the robustness of the regression source inversion developed for LNF theory. The proposed method along with LNF and EUL were tested using measurements from two field experiments collected in a pine forest and published measurements from a wind tunnel experiment. The field experiments were conducted to investigate the vertical distribution of the scalar fluxes within the canopy and the temporal patterns of the scalar fluxes above the canopy. This comparison constitutes the first “inverse method” comparison performed using the same data sets on all three models. For the wind tunnel data, all three models well reproduced the measured flux distribution. For the field experiments, all three models recovered the measured spatial and temporal flux distribution in an ensemble sense. The agreement between these three models is desirable to the inverse problem because it adds the necessary confidence in the computed flux distributions. However, the agreement among all three models with the field measurements, on a 30‐min time step, was less than satisfactory. Additionally, the divergence between models and measurements increased with departure from a near‐neutral atmospheric state. Despite fundamental differences in these model approximations, this similarity in model performance suggests that the source information recovered from a measured one‐dimensional mean concentration profile will not be further enhanced by a one‐dimensional steady state, planar homogeneous model of neutral flows.

Rapid Estimation of Core-Power Ratio in Coupled-Core System by Rod Drop Method

To determine rapidly the core-power ratio in a coupled-core system, a method is proposed on the basis of the control rod drop experiment. A formula of an asymmetrical two-point version was derived to deduce the core-power ratio and subcriticalities of the individual cores. It requires only a familiar measurement technique and tools for the conventional rod drop experiment to apply this formula for the purpose of obtaining these quantities. The present method was applied to the rod drop data measured in coupled-core systems, where the core-power ratio sensitively depended on the rod patterns. The validity of the proposed method was experimentally demonstrated through the comparison between the measured core-power ratios obtained by the present method and that derived from the flux distribution measurement.

ＥＤＭアークプラズマ内温度分布の分光測定

This paper describes the measurement of temperature distribution and radiant flux distribution in the EDM arc plasma using the spectroscopic analysis. These distributions were obtained by the use of a lens which magnifies the image of the plasma and a mask which can limit the plasma region to be observed. The temperature distribution was computed from the radiant flux by the line pair method. This paper investigates first the influence of working conditions on the temperature distribution. Secondly, observing the radiant flux distribution in the plasma, the rate of evaporation of the electrode materials is estimated in order to understand the material removal mechanism. Thirdly, decrease in the plasma temperature during the discharge interval is measured in order to estimate the time required for the plasma to be deionized.

The design of the J-type neutron flux distribution measurement system

This paper introduces the design of a J-type aeroball system that the tube penetrates the lateral wall of reactor pressurized vessel (RPV), then immediately goes down to the vessel bottom and then goes up through the lower core support plate into the reactor core. Some experimental results related to gas flowing within a thin tube are presented in the paper, such as the gas friction drag coefficient on the ball’s way and etc. From theoretical and experimental viewpoints, the feasibility of the system is proved in pneumatic holding-up and β measurement aspects. In order to ensure an enough ratio of signal to noise, the maximum distance between two measuring points in water reactors is given. The paper gives out the measuring number per two-assemblies width N i =Int( n i /2+0.51), which is the accuracy relation between the number of fuel assembly and the minimum one of measuring point to only reconstruct 2D neutron flux distribution completely by the measured data.

Photogrammetry: An Available Surface Characterization Tool for Solar Concentrators, Part II: Assessment of Surfaces

In a previous paper, the results of photogrammetric measurements of a number of paraboloidal reflecting surfaces were presented. These results showed that photogrammetry can provide three-dimensional surface characterisations of such solar concentrators. The present paper describes the assessment of the quality of these surfaces as a derivation of the photogrammetrically produced surface coordinates. Statistical analysis of the z-coordinate distribution of errors indicates that these generally conform to a univariate Gaussian distribution, while the numerical assessment of the surface normal vectors on these surfaces indicates that the surface normal deviations appear to follow an approximately bivariate Gaussian distribution. Ray tracing of the measured surfaces to predict the expected flux distribution at the focal point of the 400 m2 dish show a close correlation with the videographically measured flux distribution at the focal point of the dish.

Magnetization in the mixed state of superconducting thin films

Magnetic measurements on type-II superconducting thin films subjected to a transverse external field can be explained by a model that takes demagnetizing effects into account. We carried out measurements of magnetic flux distribution on the film surface by means of a self made apparatus, based on two Hall probes and a differential transformer and we tested the validity of a recent model presented in the literature.