1,244 research outputs found
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Energy recovery from wastewater treatment plants in the United States: A case study of the energy-water nexus
No full textAshlynn Stillwell is with UT Austin, David Hoppock is with Duke University, and Michael Webber is with UT Austin.This manuscript uses data from the U.S. Environmental Protection Agency to analyze the potential for energy recovery from wastewater treatment plants via anaerobic digestion with biogas utilization and biosolids incineration with electricity generation. These energy recovery strategies could help offset the electricity consumption of the wastewater sector and represent possible areas for sustainable energy policy implementation. We estimate that anaerobic digestion could save 628 to 4,940 million kWh annually in the United States. In Texas, anaerobic digestion could save 40.2 to 460 million kWh annually and biosolids incineration could save 51.9 to 1,030 million kWh annually.Mechanical Engineerin
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Ammonia monitoring near 1.5µm with diode-laser absorption sensors
No full textWhen this research was performed, all the authors were with the
High Temperature Gasdynamics Laboratory, Department of Mechanical
Engineering, Stanford University. M. E. Webber is now
with Pranalytica, Inc. D. S. Baer is now with Informed Diagnostics.We investigated ammonia spectroscopy near 1.5 µm to select transitions appropriate for trace ammonia
detection in air-quality and combustion emissions-monitoring applications using diode lasers. Six ammonia
features were selected for these trace-gas detection applications based on their transition
strengths and isolation from interfering species. The strengths, positions, and lower-state energies for
the lines in each of these features were measured and compared with values published in the literature.
Ammonia slip was measured in the exhaust above an atmospheric pressure premixed ethylene–air
burner to demonstrate the feasibility of the in situ diode-laser sensor.Mechanical Engineerin
The rise of Chinese cyber warriors: towards a theoretical model of online hacktivism
No full textChina is frequently reported as the source of many transnational cyber-attacks. Yet, there have been very few studies on the people behind such attacks. In this paper, we have studied some of the reasons behind the rise of a specific form of hacking: hacktivism emanating from China. Using various criminological theories, as well as political and sociological approaches, a novel theoretical framework behind Chinese hacktivism is proposed in this paper. This is supported by an empirical analysis that was carried out on the membership growth patterns of online Chinese hacktivist forums and the observed patterns are used to support the proposed framework.</p
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Measurements of NH3 and CO2 with distributed-feedback diode lasers near 2.0 µm in bioreactor vent gases
No full textWhen this research was performed, M. E. Webber, J. B. Jeffries and R. K. Hanson were with the
High Temperature Gasdynamics Laboratory, Department of Mechanical
Engineering, Stanford University. M. E. Webber is now with Pranalytica, Inc.
When this research was performed, R. Claps, F. V. Englich, and
F. K. Tittel were with the Laser Science Group, Rice Quantum
Institute, Department of Electrical and Computer Engineering,
Rice University. R. Claps is now
with Radiant Photonics, Inc.Measurements of NH3 and CO2 were made in bioreactor vent gases with distributed-feedback diode-laser
sensors operating near 2 um. Calculated spectra of NH3 and CO2 were used to determine the optimum
transitions for interrogating with an absorption sensor. For ammonia, a strong and isolated absorption
transition at 5016.977 cm-1 was selected for trace gas monitoring. For CO2, an isolated transition at
5007.787 cm-1 was selected to measure widely varying concentrations [500 parts per million (ppm) to
10%], with sufficient signal for low mole fractions and without being optically thick for high mole
fractions. Using direct absorption and a 36-m total path-length multipass flow-through cell, we achieved
a minimum detectivity of 0.25 ppm forNH3 and 40 ppm for CO2. We report on the quasi-continuous field
measurements of NH3 and CO2 concentration in bioreactor vent gases that were recorded at NASA
Johnson Space Center with a portable and automated sensor system over a 45-h data collection window.Mechanical Engineerin
Hacktivism: a theoretical and empirical exploration of China’s cyber warriors
No full textChina is frequently reported as the source of many politically motivated cyber-attacks. Yet, there have been very few studies on the people behind such attacks, also known as hacktivists. In this paper, we have taken a step back and studied some of the reasons behind the rise of freelance hacktivism emanating from China. Using various criminological theories, as well as political and sociological approaches, we propose a novel theoretical framework behind Chinese hacktivism. Furthermore, we present an empirical analysis on the membership growth patterns of online Chinese hacktivist forums and use the observed patterns to support our proposed framework
Drifting on and off-line: humanising the cyber criminal
No full textTechnological change represents one of the clearest areas in which criminology has had to work hard to keep-up. In this chapter Webber and Yip provide a cutting edge analysis of a particular kind of cybercrime, carding, and use online forums as a means of investigating the mechanisms and culture of hackers working in this illicit economy. Using this data they develop ideas taken from criminological theory to suggest that hackers operate within disorganised fields in which association with others allows hackers to learn how to operate effectively. In contrast to the sterility of much web crime analysis the authors use their data to highlight some of the more complex aspects of hacker identity and the conflicts that sometimes emerge around the relative morality of their actions
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In situ combustion measurements of CO2 by use of a distributed-feedback diode-laser sensor near 2.0µm
No full textM. E. Webber, S. Kim, S. T. Sanders,
D. S. Baer, and R. K. Hanson are with the High Temperature
Gasdynamics Laboratory, Department of Mechanical Engineering,
Stanford University. Ikeda is
with the Center for Instrumental Analysis, Department of Mechanical
Engineering, Kobe University.High-resolution absorption measurements of CO2 were made in a heated static cell and in the combustion
region above a flat-flame burner for the development of an in situ CO2 combustion diagnostic based on
a distributed-feedback diode laser operating near 2.0 um. Calculated absorption spectra of high temperature
H2O and CO2 were used to find candidate transitions for CO2 detection, and the R(50)
transition at 1.997 um (the v1 + 2v2 + v3 band) was selected on the basis of its line strength and its
isolation from interfering high-temperature water absorption. Measurements of spectroscopic parameters
such as the line strength, the self-broadening coefficient, and the line position were made for the
R(50) transition, and an improved value for the line strength is reported. The combustion-product
populations of CO2 in the combustion region above a flat-flame burner were determined in situ to verify
the measured spectroscopic parameters and to demonstrate the feasibility of the diode-laser sensor.Mechanical Engineerin
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The water intensity of the transitional hydrogen economy
No full textThe water intensity of the transitional hydrogen economy is analyzed by quantifying the direct
and indirect water requirements to annually manufacture 60 billion kg of hydrogen partly by
thermoelectrically powered electrolysis. It is determined that up to 143 billion gallons of water
would be directly consumed as a feedstock, with a total consumption including evaporation of
cooling water at power plants of 0.5–1.7 trillion gallons annually. Total water withdrawals for
thermoelectric cooling (most of which is not consumed) are expected to increase by 27–97%
from 195 000 million gallons/day today, depending primarily on the aggregate efficiency of
electrolyzers that will be in place and the portion of hydrogen that is produced by
thermoelectrically powered electrolysis. On a per unit basis, thermoelectric power generation
for electrolysis will on average withdraw approximately 1100 gallons of cooling water and will
consume 27 gallons of water as a feedstock and coolant for every kilogram of hydrogen that is
produced using an electrolyzer that has an efficiency of 75%. Given that water withdrawals
have remained steady for decades, this increase in water use represents a significant potential
impact of the hydrogen economy on a critical resource, and is consequently relevant to water
resource planners. Thus, if minimizing the impact of water resources is a priority and
electrolysis becomes a widespread method of hydrogen production, hydrogen production would
need to be from hydrogen production pathways that do not use much water (such as wind or
solar), or effective water-free cooling methods (e.g. air cooling) will need to be developed and
widely deployed.Mechanical Engineerin
The Energy-Water Nexus: An Analysis and Comparison of Various Configurations Integrating Desalination with Renewable Power
No full textThis investigation studies desalination powered by wind and solar energy, including a study of a configuration using PVT solar panels. First, a water treatment was developed to estimate the power requirement for brackish groundwater reverse-osmosis (BWRO) desalination. Next, an energy model was designed to (1) size a wind farm based on this power requirement and (2) size a solar farm to preheat water before reverse osmosis treatment. Finally, an integrated model was developed that combines results from the water treatment and energy models. The integrated model optimizes performances of the proposed facility to maximize daily operational profits. Results indicate that integrated facility can reduce grid-purchased electricity costs by 88% during summer months and 89% during winter when compared to a stand-alone desalination plant. Additionally, the model suggests that the integrated configuration can generate 252 during winter from sales of wind- and solar-generated electricity to supplement revenue from water production. These results indicate that an integrated facility combining desalination, wind power, and solar power can potentially reduce reliance on grid-purchased electricity and advance the use of renewable power
Air quality impacts of plug-in hybrid electric vehicles in Texas: Evaluating three battery charging scenarios
No full textTammy Thompson is with Massachusetts Institute of Technology, Carey King is with UT Austin, David Allen is with UT Austin, and Michael Webber is with UT AustinThe air quality impacts of replacing approximately 20% of the gasoline-powered light duty vehicle
miles traveled (VMT) with electric VMT by the year 2018 were examined for four major cities in
Texas: Dallas/Ft Worth, Houston, Austin, and San Antonio. Plug-in hybrid electric vehicle (PHEV)
charging was assumed to occur on the electric grid controlled by the Electricity Reliability Council of
Texas (ERCOT), and three charging scenarios were examined: nighttime charging, charging to
maximize battery life, and charging to maximize driver convenience. A subset of electricity generating
units (EGUs) in Texas that were found to contribute the majority of the electricity generation needed to
charge PHEVs at the times of day associated with each scenario was modeled using a regional
photochemical model (CAMx). The net impacts of the PHEVs on the emissions of precursors to the
formation of ozone included an increase in NOx emissions from EGUs during times of day when the
vehicle is charging, and a decrease in NOx from mobile emissions. The changes in maximum daily 8 h
ozone concentrations and average exposure potential at twelve air quality monitors in Texas were
predicted on the basis of these changes in NOx emissions. For all scenarios, at all monitors, the impact
of changes in vehicular emissions, rather than EGU emissions, dominated the ozone impact. In general,
PHEVs lead to an increase in ozone during nighttime hours (due to decreased scavenging from both
vehicles and EGU stacks) and a decrease in ozone during daytime hours. A few monitors showed a
larger increase in ozone for the convenience charging scenario versus the other two scenarios.
Additionally, cumulative ozone exposure results indicate that nighttime charging is most likely to
reduce a measure of ozone exposure potential versus the other two scenarios.Mechanical Engineerin
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