Comparison of common dredging equipment air emissions

The purpose of this study is to provide a procedure to include emissions to the atmosphere resulting from the combustion of diesel fuel during dredging operations into the decision-making process of dredging equipment selection. The proposed procedure is demonstrated for typical dredging methods and data from the Illinois Waterway as performed by the U.S. Army Corps of Engineers, Rock Island District. The equipment included in this study is a 16-inch cutterhead pipeline dredge and a mechanical bucket dredge used during the 2005 dredging season on the Illinois Waterway. Considerable effort has been put forth to identify and reduce environmental impacts from dredging operations. Though environmental impacts of dredging have been studied no efforts have been applied to the evaluation of air emissions from comparable types of dredging equipment, as in this study. By identifying the type of dredging equipment with the lowest air emissions, when cost, site conditions, and equipment availability are comparable, adverse environmental impacts can be minimized without compromising the dredging project. A total of 48 scenarios were developed by varying the dredged material quantity, transport distance, and production rates. This produced an “envelope” of results applicable to a broad range of site conditions. Total diesel fuel consumed was calculated using standard cost estimating practices as defined in the U.S. Army Corps of Engineers Construction Equipment Ownership and Operating Expense Schedule (USACE, 2005). The diesel fuel usage was estimated for all equipment used to mobilize and/or operate each dredging crew for every scenario. A Limited Life Cycle Assessment (LCA) was used to estimate the air emissions from two comparable dredging operations utilizing SimaPro LCA software. An Environmental Impact Single Score (EISS) was the SimaPro output selected for comparison with the cost per CY of dredging, potential production rates, and transport distances to identify possible decision points. The total dredging time was estimated for each dredging crew and scenario. An average hourly cost for both dredging crews was calculated based on Rock Island District 2005 dredging season records (Graham 2007/08). The results from this study confirm commonly used rules of thumb in the dredging industry by indicating that mechanical bucket dredges are better suited for long transport distances and have lower air emissions and cost per CY for smaller quantities of dredged material. In addition, the results show that a cutterhead pipeline dredge would be preferable for moderate and large volumes of dredged material when no additional booster pumps are required. Finally, the results indicate that production rates can be a significant factor when evaluating the air emissions from comparable dredging equipment

New civil engineering program criteria: The rest of the story

The American Society of Civil Engineers (ASCE) organized the Civil Engineering Program Criteria Task Committee in October 2012 whose charge is to determine if the current ABET Civil Engineering Program Criteria (CEPC) should be changed to reflect one or more of the 24 outcomes of the second edition of the Civil Engineering Body of Knowledge published in 2008. After two years of work, a proposed CEPC has been approved by the relevant ASCE committees and forwarded to ABET for approval and incorporation into accreditation criteria. A paper chronicling the committee’s efforts through a review of the literature, the committee’s methodology and process, and the key issues that emerged was presented at the 2014 ASEE Annual Conference in Indianapolis. This paper updates that effort by presenting the resulting proposed criteria, the changes generated by constituency feedback, progress on the Commentary, the existing gap between the proposed accreditation criteria and the current body of knowledge, and the future work of the committee

Singlet and triplet bipolarons on the triangular lattice

We study the Coulomb-Fr\"ohlich model on a triangular lattice, looking in particular at states with angular momentum. We examine a simplified model of crab bipolarons with angular momentum by projecting onto the low energy subspace of the Coulomb-Fr\"ohlich model with large phonon frequency. Such a projection is consistent with large long-range electron-phonon coupling and large repulsive Hubbard $U$. Significant differences are found between the band structure of singlet and triplet states: The triplet state (which has a flat band) is found to be significantly heavier than the singlet state (which has mass similar to the polaron). We test whether the heavier triplet states persist to lower electron-phonon coupling using continuous time quantum Monte Carlo (QMC) simulation. The triplet state is both heavier and larger, demonstrating that the heavier mass is due to quantum interference effects on the motion. We also find that retardation effects reduce the differences between singlet and triplet states, since they reintroduce second order terms in the hopping into the inverse effective mass.Comment: Proceedings of SNS 200

Arginine side chain interactions and the role of arginine as a gating charge carrier in voltage sensitive ion channels

Gating charges in voltage-sensing domains (VSD) of voltage-sensitive ion channels and enzymes are carried on arginine side chains rather than lysine. This arginine preference may result from the unique hydration properties of the side chain guanidinium group which facilitates its movement through a hydrophobic plug that seals the center of the VSD, as suggested by molecular dynamics simulations. To test for side chain interactions implicit in this model we inspected interactions of the side chains of arginine and lysine with each of the 19 non-glycine amino acids in proteins in the protein data bank. The arginine guanidinium interacts with non-polar aromatic and aliphatic side chains above and below the guanidinium plane while hydrogen bonding with polar side chains is restricted to in-plane positions. In contrast, non-polar side chains interact largely with the aliphatic part of the lysine side chain. The hydration properties of arginine and lysine are strongly reflected in their respective interactions with non-polar and polar side chains as observed in protein structures and in molecular dynamics simulations, and likely underlie the preference for arginine as a mobile charge carrier in VSD

Investigating uptake of N2O in agricultural soils using a high-precision dynamic chamber method

Uptake (or negative flux) of nitrous oxide (N2O)in agricultural soils is a controversial issue which has proved difficult to investigate in the past due to constraints such as instrumental precision and methodological uncertainties. Using a recently developed high-precision quantum cascade laser gas analyser combined with a closed dynamic chamber, a well-defined detection limit of 4 μg N2O-N m could be achieved for individual soil flux measurements. 1220 mea- surements of N2O flux were made from a variety of UK soils using this method, of which 115 indicated uptake by the soil (i.e. a negative flux in the micrometeorological sign convention). Only four of these apparently negative fluxes were greater than the detection limit of the method, which suggests that the vast majority of reported negative fluxes from such measurements are actually due to instrument noise. As such, we suggest that the bulk of negative N2O fluxes reported for agricultural fields are most likely due to limits in detection of a particular flux measurement methodology and not a result of microbiological activity consuming atmospheric N2O

Accreditation insights and the next body of knowledge

The American Society of Civil Engineers (ASCE) published the second edition of the Civil Engineering Body of Knowledge (BOK2) in 2008 expanding the knowledge, skills and attitudes required of future civil engineers. There were major changes to the BOK2 as the number of expected outcomes increased from 15 to 24 and the cognitive level of attainment was more precisely defined. A major implementation and enforcement mechanism for the BOK is the ABET accreditation criteria which includes both general criteria 3 and 5 and the discipline-specific program criteria. Of those, the program criteria are the easiest to change. In 2013, ASCE created the Civil Engineering Program Criteria Task Committee (CEPCTC) whose charge was to determine if the current CEPC should be changed to reflect an additional one or more of the 24 outcomes of BOK2. After two years of meetings, conference calls, draft criteria, constituency input, and associated revisions, a proposed change to the CEPC was approved by ASCE and submitted to ABET for approval. The CEPC was supplemented with an associated commentary. The proposed CEPC are currently going through the two-year ABET approval process and are expected to go into effect in September 2016. The results of the committee’s work were presented in papers at the 2014 and 2015 ASEE Annual Conferences in Indianapolis and Seattle.1,2 The Body of Knowledge is a living document that will continue to be updated and revised. ASCE has developed an eight year cycle of change that will make future iterations of the BOK and CEPC both systematic and predictable.3 As such, a Body of Knowledge Task Committee (BOKTC) is scheduled to be formed in October 2016. The BOKTC could recommend no revisions, minor revisions, or extensive revisions to BOK2. If substantive changes are recommended to BOK2, the master plan calls for the completion of the third edition of the Civil Engineering Body of Knowledge for the 21st Century (BOK3) before October 2018. Because the CEPC was created to be compatible with the BOK2 outcomes, the CEPCTC studied the BOK2 in depth. The BOK2 is an aspirational and visionary document which only partially accounts for the real-world constraints faced by engineering programs in terms of mandated maximum units in an undergraduate program and additional requirements imposed by a state government or a university. Conversely, the ABET accreditation criteria (general plus program) define the minimum requirements for a program to receive accreditation. There will naturally be a gap between those two standards. For the cycle of change to be successful, the insights and lessons learned from the development of the CEPC should be communicated with the BOKTC and vice versa. This paper attempts to do that. The paper will define the gap between (1) the BOK2 and (2) EAC/ABET accreditation criteria (general plus proposed CEPC) and make recommendations for closing the gap. During their work, the CEPCTC encountered issues with the BOK2 that suggest potential revisions for the BOK3. This paper is a mechanism for sharing CEPCTC insights, lessons learned, suggestions and recommendations with the rest of the academic and professional community

Bcc 4^4He as a Coherent Quantum Solid

In this work we investigate implications of the quantum nature of bcc $^{4}$% He. We show that it is a unique solid phase with both a lattice structure and an Off-Diagonal Long Range Order of coherently oscillating local electric dipole moments. These dipoles arise from the local motion of the atoms in the crystal potential well, and oscillate in synchrony to reduce the dipolar interaction energy. The dipolar ground-state is therefore found to be a coherent state with a well defined global phase and a three-component complex order parameter. The condensation energy of the dipoles in the bcc phase stabilizes it over the hcp phase at finite temperatures. We further show that there can be fermionic excitations of this ground-state and predict that they form an optical-like branch in the (110) direction. A comparison with 'super-solid' models is also discussed.Comment: 12 pages, 8 figure

Increasing Engagement in Materials Laboratory with Backward Design and Quadcopters

This paper describes a laboratory experiment that was designed to increase student engagement and enhance student development in a materials laboratory. The laboratory module described is part of a broader effort to enhance the mechanical engineering laboratory curriculum to incorporate modern pedagogical methods and to improve student outcomes using backward design. The new laboratory modules encourage students to work in small groups, develop team skills, and learn about basic measurement methods. The first module is a simple cantilever beam mounted with a strain gage. Students develop an understanding of the correlation between bending stress and strain. While doing so, they also determine a calibration factor for the beam in order to use the beam as a load cell to measure the weight of an object. For the second module, students are provided an instrumented beam with a known calibration factor and are asked to determine the amount of lift produced by a small quadcopter. To assess the effectiveness of the laboratory experiment, a student survey was designed and the experiments were observed by an education expert. The results indicate the new laboratory modules have been successful in increasing student engagement and meeting learning objectives

Anderson localization of polaron states

Using the vanishing of the typical polaron tunneling rate as an indicator of the breakdown of itinerancy, we study the localization of polaron states in a generic model for a disordered polaronic material. We find that extremely small disorder causes an Anderson localization of small polaron states. However, the ratio between the critical disorder strength needed to localize all states in the polaron band and the renormalized bandwidth is not necessarily smaller than for a bare electron.Comment: 4 pages, 3 figure