Electron transport in E x B devices

A Hall thruster, an E × B device used for in-space propulsion, utilizes an axial electric field to electrostatically accelerate plasma propellant from the spacecraft. The axial electric field is created by positively biasing the anode so that the positivelycharged ions may be accelerated (repelled) from the thruster, which produces thrust. However, plasma electrons are much smaller than ions and may be accelerated much more quickly toward the anode; if electrons were not impeded, a short circuit due to the electron flow would eliminate the thrust mechanism. Therefore, a magnetic field serves to magnetize plasma electrons internal to the thruster and confines them in gyro-orbits within the discharge channel. Without outside factors electrons would be confined indefinitely; however, electron-neutral collisions provide a mechanism to free electrons from their orbits allowing electrons to cross the magnetic field toward the anode, where this process is described by classical transport theory. To make matters worse, cross-field electron transport has been observed to be 100-1000 times that predicted by classical collisional theory, providing an efficiency loss mechanism and an obstacle for modeling and simulations in Hall thrusters. The main difficulty in studying electron transport in Hall thrusters is the coupling that exists between the plasma and the fields, where the plasma creates and yet is influenced by the electric field. A device has been constructed at MTU’s Isp Lab, the Hall Electron Mobility Gage, which was designed specifically to study electron transport in E × B devices, where the coupling between the plasma and electric field was virtually eliminated. In this device the two most cited contributors to electron transport in Hall thrusters, fluctuation-induced transport, and wall effects, were absent. Removing the dielectric walls and plasma fluctuations, while maintaining the field environment in vacuum, has allowed the study of electron dynamics in Hall thruster fields where the electrons behave as test particles in prescribed fields, greatly simplifying the environment. Therefore, it was possible to observe any effects on transport not linked to the cited mechanisms, and it was possible to observe trends of the enhanced mobility with control parameters of electric and magnetic fields and neutral density– parameters that are not independently variable in a Hall thruster. The result of the investigation was the observation of electron transport that was ~ 20-100 times the classical prediction. The cross-field electron transport in the Mobility Gage was generally lower than that found in a Hall thruster so these findings do not negate the possibility of fluctuations and/or wall collisions contributing to transport in a Hall thruster. However, this research led to the observation of enhanced cross-field transport that had not been previously isolated in Hall thruster fields, which is not reliant on momentum-transfer collisions, wall collisions or fluctuations

The electrorheology of suspensions consisting of Na-Fluorohectorite synthetic clay particles in silicon oil

Under application of an electric field greater than a triggering electric field $E_c \sim 0.4$ kV/mm, suspensions obtained by dispersing particles of the synthetic clay fluoro-hectorite in a silicon oil, aggregate into chain- and/or column-like structures parallel to the applied electric field. This micro-structuring results in a transition in the suspensions' rheological behavior, from a Newtonian-like behavior to a shear-thinning rheology with a significant yield stress. This behavior is studied as a function of particle volume fraction and strength of the applied electric field, $E$. The steady shear flow curves are observed to scale onto a master curve with respect to $E$, in a manner similar to what was recently found for suspensions of laponite clay [42]. In the case of Na-fluorohectorite, the corresponding dynamic yield stress is demonstrated to scale with respect to $E$ as a power law with an exponent $\alpha \sim 1.93$, while the static yield stress inferred from constant shear stress tests exhibits a similar behavior with $\alpha \sim 1.58$. The suspensions are also studied in the framework of thixotropic fluids: the bifurcation in the rheology behavior when letting the system flow and evolve under a constant applied shear stress is characterized, and a bifurcation yield stress, estimated as the applied shear stress at which viscosity bifurcation occurs, is measured to scale as $E^\alpha$ with $\alpha \sim 0.5$ to 0.6. All measured yield stresses increase with the particle fraction $\Phi$ of the suspension. For the static yield stress, a scaling law $\Phi^\beta$, with $\beta = 0.54$, is found. The results are found to be reasonably consistent with each other. Their similarities with-, and discrepancies to- results obtained on laponite-oil suspensions are discussed

Session B2- Building a fishway for Lake Sturgeon: Successful testing of a prototype upstream fishway on the Menomine River in Northern Wisconsin

Historically, lake sturgeon (Acipenser fulvescens) were abundant in Lake Michigan with free and unobstructed access to the feeding and spawning areas within its many tributaries. Construction and operation of hydroelectric dams has impeded this access. One method for re-establishing this lost connection is to create an artificial pathway such as a fish passage facility. To help answer some basic questions, such as will sturgeon use a fishway, we constructed a prototype fish passage structure below a hydroelectric dam on the Menominee River in northern Wisconsin. This hydroelectric facility is located near Amberg, Wisconsin and owned by We Energies. The structure was designed with a ramp to a 1.07 meters per second (mps). The structure was equipped with a Passive Integrated Transponder tag (PIT tag) reader antenna and underwater video cameras equipped with infrared lights. All monitoring equipment were installed and activated before the start of the 2009 spring spawning season 9mid-April) and removed following the 2010 autumn migration (mid-October). PIT tag records indicated that 86 tagged lake surgeon used the passage structure in 2009 and 112 in 2010, with many sturgeon going through the structure multiple times. Video data verified these results and also indicated that these sturgeon moved through the structure rather quickly (mean = 3 sec in camera view). Extrapolated to the whole sturgeon population, nearly 20% of the spawning population went through the prototype fishway in 2009 and 24% in 2010. For both years of the study, larger sturgeon were observed during the spring spawning season versus the remainder of the year, 25.4 centimeters longer on average. In 2010, the structure was fitted with a V-trap (45.7 cm gap width with 0.46 mps constant water velocity) to test whether these fish can be trapped in an elevator hopper. Those results indicate both small and large sturgeon (as small as 49.5 cm and as large as 142.2cm, respectively) will pass through a 45.7 cm wide V-trap opening without hesitation. Video and PIT tag results indicated that sturgeon can be successfully attracted to and passed through a prototype upstream fish passage facilities currently planned for lake sturgeon in the Midwest

Success factors in global project management : A study of practices in organizational support and the effects on cost and schedule

Author's accepted version (postprint).This is an Accepted Manuscript of an article published by Emerald Group Publishing Limited in International Journal of Managing Projects in Business on 5 June 2019.Available online: https://www.emerald.com/insight/content/doi/10.1108/IJMPB-09-2018-0182/full/htmlThe purpose of this paper is to identify and complete the existing lack of quantitative data at the crossroads between organizational support (OS) practices and project management success in global projects (GPs) and discuss implication of the results in perspective of the theory–practice gap.Success factors in global project management: A study of practices in organizational support and the effects on cost and scheduleacceptedVersio

Intercalation-enhanced electric polarization and chain formation of nano-layered particles

Microscopy observations show that suspensions of synthetic and natural nano-layered smectite clay particles submitted to a strong external electric field undergo a fast and extended structuring. This structuring results from the interaction between induced electric dipoles, and is only possible for particles with suitable polarization properties. Smectite clay colloids are observed to be particularly suitable, in contrast to similar suspensions of a non-swelling clay. Synchrotron X-ray scattering experiments provide the orientation distributions for the particles. These distributions are understood in terms of competing (i) homogenizing entropy and (ii) interaction between the particles and the local electric field; they show that clay particles polarize along their silica sheet. Furthermore, a change in the platelet separation inside nano-layered particles occurs under application of the electric field, indicating that intercalated ions and water molecules play a role in their electric polarization. The resulting induced dipole is structurally attached to the particle, and this causes particles to reorient and interact, resulting in the observed macroscopic structuring. The macroscopic properties of these electro-rheological smectite suspensions may be tuned by controlling the nature and quantity of the intercalated species, at the nanoscale.Comment: 7 pages, 5 figure

Cosmic-ray detector with interdigitated-finger pixels for two-dimensional position information from a single wafer side

This paper describes a type of cosmic ray detector for isotopic and energy detection of energetic nuclei which derives both dimensions of position information from one side of the detector. This simplifies the required readout electronics, since only one precision amplifier connected to the other side is required for an accurate detection of the energy loss. Two dimensional readout is enabled by the use of pixels consisting of closely spaced interdigitated electrodes alternately connected to row and column lines. Spreading of the charge produced by the cosmic ray results in the charge being collected by more than one electrode producing both a row and column signal on one side of the detector. The design, fabrication, and characterization of the interdigitated-pixel detector is discussed

Ets homologous factor (EHF) has critical roles in epithelial dysfunction in airway disease

The airway epithelium forms a barrier between the internal and external environments. Epithelial dysfunction is critical in the pathology of many respiratory diseases, including cystic fibrosis. Ets homologous factor (EHF) is a key member of the transcription factor network that regulates gene expression in the airway epithelium in response to endogenous and exogenous stimuli. EHF , which has altered expression in inflammatory states, maps to the 5' end of an intergenic region on Chr11p13 that is implicated as a modifier of cystic fibrosis airway disease. Here we determine the functions of EHF in primary human bronchial epithelial (HBE) cells and relevant airway cell lines. Using EHF ChIP followed by deep sequencing (ChIP-seq) and RNA sequencing after EHF depletion, we show that EHF targets in HBE cells are enriched for genes involved in inflammation and wound repair. Furthermore, changes in gene expression impact cell phenotype because EHF depletion alters epithelial secretion of a neutrophil chemokine and slows wound closure in HBE cells. EHF activates expression of the SAM pointed domain-containing ETS transcription factor, which contributes to goblet cell hyperplasia. Our data reveal a critical role for EHF in regulating epithelial function in lung disease

Biologiske ressurser i området som er aktuelt som trasé for kraftkabler fra Norge til kontinentet

Rapporten er utarbeidet på oppdrag fra Statkraft Engineering, i anledning planleggingen av linjenett for overføring av elektrisk kraft fra Norge til kontinentet. Utredningen er en del av arbeidet med å vurdere konsekvensene for marine biologiske ressurser ved overføring av elektrisk kraft i monopol likestrømskabel. Rapporten er en sammenstillelse av kunnskap om biologiske ressurser i området som er aktuellt for elektrodeanlegg og kabel. Det er gitt en beskrivelse samt kartmessig framstilling av utbredelse av viktige fiskebestander i området, samt migasjon av fisk gjennom det aktuelle området