Electrical Resistance Tomography of Conductive Thin Films

The Electrical Resistance Tomography (ERT) technique is applied to the measurement of sheet conductance maps of both uniform and patterned conductive thin films. Images of the sheet conductance spatial distribution, and local conductivity values are obtained. Test samples are tin oxide films on glass substrates, with electrical contacts on the sample boundary, some samples are deliberately patterned in order to induce null conductivity zones of known geometry while others contain higher conductivity inclusions. Four-terminal resistance measurements among the contacts are performed with a scanning setup. The ERT reconstruction is performed by a numerical algorithm based on the total variation regularization and the L-curve method. ERT correctly images the sheet conductance spatial distribution of the samples. The reconstructed conductance values are in good quantitative agreement with independent measurements performed with the van der Pauw and the four-point probe methods.Comment: IEEE Transactions on Instrumentation and Measuremen

Risk factors of conceiving a project to produce electrical energy

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A correlation noise spectrometer for flicker noise measurement in graphene samples

We present a high-resolution digital correlation spectrum analyzer for the measurement of low frequency resistance fluctuations in graphene samples. The system exploits the cross-correlation method to reject the amplifiers' noise. The graphene sample is excited with a low-noise DC current. The output voltage is fed to two two-stage low-noise amplifiers connected in parallel; the DC signal component is filtered by a high-pass filter with a cutoff frequency of 34 mHz. The amplified signals are digitized by a two-channel synchronous ADC board; the cross-periodogram, which rejects uncorrelated amplifiers' noise components, is computed in real time. As a practical example, we measured the noise cross-spectrum of graphene samples in the frequency range from 0.153 Hz to 10 kHz, both in two- and four-wire configurations, and for different bias currents. We report here the measurement setup, the data analysis and the error sources

Thermal emittance measurements of a cesium potassium antimonide photocathode

Thermal emittance measurements of a CsK2Sb photocathode at several laser wavelengths are presented. The emittance is obtained with a solenoid scan technique using a high voltage dc photoemission gun. The thermal emittance is 0.56+/-0.03 mm-mrad/mm(rms) at 532 nm wavelength. The results are compared with a simple photoemission model and found to be in a good agreement.Comment: APL 201

Design of deep geothermal wells

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Voices of cully: a case study of the living cully weatherization and home repair project 2.0

The Cully neighborhood is situated in the Northeast quadrant of Portland, Oregon. It is 2.75 square mile plot of land and home to roughly 13,000 people. In addition to being one of the most diverse neighborhoods in Portland, it is the most densely populated, with the smallest amount of parkland per capita. Over the last two decades, home value has increased 203% in Cully, compared to a 90% citywide increase. Amidst these development trends are stories of incredible resilience, resistance and activism from the affected community. My project is a case study of one anti-displacement initiative, which was developed and implemented by a multi-partner community-based organization: Living Cully. The Living Cully Weatherization and Home Repair Project 2.0 presents a unique example of one group’s ability to reinterpret sustainability – a common goal in an ostensibly “green” city – to include the strengthening of social cohesion and community health. The organization garnered support from energy conscious funders by developing a weatherization project that targeted majority low-income, minority homeowners. The goal was to lower residents’ bills, but what they found was that a majority of homes were in no condition to be weatherized, as they needed to first undergo critical repairs. Improving residents’ living conditions and the structural integrity of their homes effectively safeguarded them from being evicted and contributed to preventing the involuntary displacement of these vulnerable residents. By distributing surveys to and conducting one-year follow-up interviews with the clients of this project, I [1] evaluated the effectiveness of the project as an anti-displacement initiative to [2] gain a better understanding of the way gentrification is experienced inside of the home. Gentrification literature often focuses on identifying and defining broad economic and neighborhood-level processes underpinning gentrification. This diverts attention away from the home, where gentrification is perhaps most intimately experienced. Gentrification manifests radically differently depending on place, as well as the scale at which it is being addressed. Causes and solutions similarly vary. It is crucial for gentrification theorists and policy-makers alike to define gentrification in a way that encourages the development of place-specific solutions. Doing so requires listening to the voices of experience, the voices that are often dismissed. This project takes a first step toward analyzing the scalar impact of gentrification. I urge academics, community workers and policy-makers to move beyond a neighborhood-scale analysis and consider the ways in which gentrification impacts residents inside of their homes by highlighting the vast, complex interaction between gentrification related social, economic and physical restructurings

Cold electron beams from cryo-cooled, alkali antimonide photocathodes

In this letter we report on the generation of cold electron beams using a Cs3Sb photocathode grown by co-deposition of Sb and Cs. By cooling the photocathode to 90 K we demonstrate a significant reduction in the mean transverse energy validating the long standing speculation that the lattice temperature contribution limits the mean transverse energy or thermal emittance near the photoemission threshold, opening new frontiers in generating ultra-bright beams. At 90 K, we achieve a record low thermal emittance of 0.2 $\mu$m (rms) per mm of laser spot diameter from an ultrafast (sub-picosecond) photocathode with quantum efficiency greater than $7\times 10^{-5}$ using a visible laser wavelength of 690 nm