Freewriting Article and Handout

An article describing a free writing activity and the instructor\u27s intentions. The activity is located at the end of the article and is intended to help students think more broadly about narrowly-focused research topics

Photovoltage Bleaching in Bulk Heterojunction Solar Cells through Occupation of the Charge Transfer State

We observe a strong peak in the capacitive photocurrent of a MDMO-PPV / PCBM bulk heterojunction solar cell for excitation below the absorbance threshold energy. Illumination at the peak energy blocks charge capture at other wavelengths, and causes the photovoltage to drop dramatically. These results suggest that the new peak is due to a charge transfer state, which provides a pathway for charge separation and photocurrent generation in the solar cell.Comment: submitted to Physical Review Letter

5 Years of User Research: Mary Idema Pew Library Learning & Information Commons, Grand Valley State University Libraries

The Mary Idema Pew Library Learning and Information Commons at Grand Valley State University opened in 2013. Ongoing user research has been conducted to learn how students use the building and to identify design successes and opportunities for improvement. This document synthesizes insights gained through five years of post-occupancy user research

Spin-dependent Quantum Interference in Single-Wall Carbon Nanotubes with Ferromagnetic Contacts

We report the experimental observation of spin-induced magnetoresistance in single-wall carbon nanotubes contacted with high-transparency ferromagnetic electrodes. In the linear regime the spin-induced magnetoresistance oscillates with gate voltage in quantitative agreement with calculations based on a Landauer-Buttiker model for independent electrons. Consistent with this interpretation, we find evidence for bias-induced oscillation in the spin-induced magnetoresistance signal on the scale of the level spacing in the nanotube. At higher bias, the spin-induced magnetoresistance disappears because of a sharp decrease in the effective spin-polarization injected from the ferromagnetic electrodes.Comment: Replaced with published versio

Wireless Sensor Network for Electric Transmission Line Monitoring

Generally, federal agencies tasked to oversee power grid reliability are dependent on data from grid infrastructure owners and operators in order to obtain a basic level of situational awareness. Since there are many owners and operators involved in the day-to-day functioning of the power grid, the task of accessing, aggregating and analyzing grid information from these sources is not a trivial one. Seemingly basic tasks such as synchronizing data timestamps between many different data providers and sources can be difficult as evidenced during the post-event analysis of the August 2003 blackout. In this project we investigate the efficacy and cost effectiveness of deploying a network of wireless power line monitoring devices as a method of independently monitoring key parts of the power grid as a complement to the data which is currently available to federal agencies from grid system operators. Such a network is modeled on proprietary power line monitoring technologies and networks invented, developed and deployed by Genscape, a Louisville, Kentucky based real-time energy information provider. Genscape measures transmission line power flow using measurements of electromagnetic fields under overhead high voltage transmission power lines in the United States and Europe. Opportunities for optimization of the commercial power line monitoring technology were investigated in this project to enable lower power consumption, lower cost and improvements to measurement methodologies. These optimizations were performed in order to better enable the use of wireless transmission line monitors in large network deployments (perhaps covering several thousand power lines) for federal situational awareness needs. Power consumption and cost reduction were addressed by developing a power line monitor using a low power, low cost wireless telemetry platform known as the ''Mote''. Motes were first developed as smart sensor nodes in wireless mesh networking applications. On such a platform, it has been demonstrated in this project that wireless monitoring units can effectively deliver real-time transmission line power flow information for less than $500 per monitor. The data delivered by such a monitor has during the course of the project been integrated with a national grid situational awareness visualization platform developed by Oak Ridge National Laboratory. Novel vibration energy scavenging methods based on piezoelectric cantilevers were also developed as a proposed method to power such monitors, with a goal of further cost reduction and large-scale deployment. Scavenging methods developed during the project resulted in 50% greater power output than conventional cantilever-based vibrational energy scavenging devices typically used to power smart sensor nodes. Lastly, enhanced and new methods for electromagnetic field sensing using multi-axis magnetometers and infrared reflectometry were investigated for potential monitoring applications in situations with a high density of power lines or high levels of background 60 Hz noise in order to isolate power lines of interest from other power lines in close proximity. The goal of this project was to investigate and demonstrate the feasibility of using small form factor, highly optimized, low cost, low power, non-contact, wireless electric transmission line monitors for delivery of real-time, independent power line monitoring for the US power grid. The project was divided into three main types of activity as follows; (1) Research into expanding the range of applications for non-contact power line monitoring to enable large scale low cost sensor network deployments (Tasks 1, 2); (2) Optimization of individual sensor hardware components to reduce size, cost and power consumption and testing in a pilot field study (Tasks 3,5); and (3) Demonstration of the feasibility of using the data from the network of power line monitors via a range of custom developed alerting and data visualization applications to deliver real-time information to federal agencies and others tasked with grid reliability (Tasks 6,8)

Leveraging User Experience Expertise for Engaging and Sustainable Social Media

This presentation discusses an evolution of our staffing model that revived our library’s Twitter account, beginning with creating a sustainable workflow to allow for more engaging content by leveraging the expertise and creativity of front line user experience staff. We’ll discuss the entire evolution from having a single librarian generating content to this team-based approach, discuss missteps, and share the positive outcomes. Lastly, we’ll discuss meaningful assessment to ensure the identifying and transmitting of key messages frequently and effectively, and sustainable expansion into new social media platforms

Anaerobic granular sludge : characterization, and factors affecting its functioning

Many UASB reactors are designed in such a fashion that the presence of granular sludge is necessary for a proper purification process. For achieving an optimum wastewater purification with such reactors, knowledge of the factors that determine the growth, retention and disintegration of anaerobic granular sludge is essential. The present research focused on gaining more insight in the factors determining the growth and quality of anaerobic granular sludge.For determining the total available pore volume and the pore diameter distribution of granular sludge, a method based on size exclusion chromatography has been developed. For most types of sludge, the available pore volume varies between 40% and 80%, granules with a lower porosity probably contain layers that are impermeable to substrate. Small granules were found to have a considerably higher porosity and a higher maximum methanogenic activity than larger granules from the same sludge sample.In applying higher sludge loads, the average granule diameter increases. A decrease in sludge load or changes in substrate composition result in a weakening of sludge granules, probably due to a lack of substrate for the bacteria in the centre of the granules. In view of the stability of methanogenic granular sludge, this should be attributed to the dying off of the acidifying population inside the sludge granules.The process in UASB reactors is strongly influenced by the composition and degree of pre- acidification of the wastewater. It was found that non-acidified gelatine can be treated in an one- phase UASB reactor without difficulties up to a sludge load of 1.2 gCOD.(gVSS.d) -1. However, sucrose-containing wastewater can be treated only at a sludge load below 0.5 gCOD.(gVSS.d) -1. At higher sludge loading rates nonacidified sucrose in the reactor influent can cause problems with regard to sludge retention. However, too much pre-acidification of wastewater can also cause problems. Acidogenic bacteria suspended in the influent may cause very serious flotation of granular sludge.In treating sulphate-containing wastewater, sulphate-reducing bacteria (SRB) and methane- producing bacteria (MPB) will compete for substrate. It is often assumed that MPB can maintain in high-rate anaerobic reactors because of the poor ability of SRB to attach themselves compared to MPB. However, the present study shows that sulphate-reducing bacteria are capable to maintain in granular sludge. They were even found to be able to attach themselves: on pumice stone as carrier material, purely sulphidogenic aggregates were formed.A negative effect of a deficiency in phosphate on the methanogenic activity of granular sludge was found to be fully reversible in the presence of phosphate. The phosphorus content of granular sludge from the laboratory reactors fed with gelatine varied between 6 mgP.gVSS -1for sludge from reactors fed with influent that contained almost no phosphate and 10.5 mgP.gVSS -1for sludge from reactors with a sufficient supply of phosphate. Deficiency in phosphate was found to be easily demonstrable: an increase in methanogenic activity after phosphate dosage and/or a rapid uptake of phosphate are clear indications of a deficiency in phosphate in granular sludge

A New Transport Regime in the Quantum Hall Effect

This paper describes an experimental identification and characterization of a new low temperature transport regime near the quantum Hall-to-insulator transition. In this regime, a wide range of transport data are compactly described by a simple phenomenological form which, on the one hand, is inconsistent with either quantum Hall or insulating behavior and, on the other hand, is also clearly at odds with a quantum-critical, or scaling, description. We are unable to determine whether this new regime represents a clearly defined state or is a consequence of finite temperature and sample-size measurements.Comment: Revtex, 3 pages, 2 figure

Gated Spin Transport through an Individual Single Wall Carbon Nanotube

Hysteretic switching in the magnetoresistance of short-channel, ferromagnetically contacted individual single wall carbon nanotubes is observed, providing strong evidence for nanotube spin transport. By varying the voltage on a capacitively coupled gate, the magnetoresistance can be reproducibly modified between +10% and -15%. The results are explained in terms of wave vector matching of the spin polarized electron states at the ferromagnetic / nanotube interfaces.Comment: 14 pages, 5 figure