Using risk to inform overtopping protection decisions

Presented at the Protections 2016: 2nd international seminar on dam protection against overtopping: concrete dams, embankment dams, levees, tailings dams held on 7th-9th September, 2016, at Colorado State University in Fort Collins, Colorado, USA. The increasing demand for dam and levee safety and flood protection has motivated new research and advancements and a greater need for cost-effective measures in overtopping protection as a solution for overtopping concerns at levees and dams. This seminar will bring together leading experts from practice, research, development, and implementation for two days of knowledge exchange followed by a technical tour of the Colorado State University Hydraulic Laboratory with overtopping flume and wave simulator. This seminar will focus on: Critical issues related to levees and dams; New developments and advanced tools; Overtopping protection systems; System design and performance; Applications and innovative solutions; Case histories of overtopping events; Physical modeling techniques and recent studies; and Numerical modeling methods.Includes bibliographical references.The decision to implement overtopping protection as a dam safety modification alternative can be difficult. The decision involves a conscious decision to allow a dam to overtop for floods above a threshold flood. If a large flood occurs that initiates dam overtopping, there is no turning back, and the dam and the overtopping protection must be able to resist the overtopping flows. The chance of intervention being successful for a dam that is already overtopping, should erosion initiate, would be very unlikely. There is more of a comfort level among many dam engineers in providing conventional solutions to a dam overtopping issue. These traditional measures include raising the dam crest to provide additional surcharge space to store a portion of the flood inflows or providing additional spillway capacity to more closely match the peak flood inflows. There is often the perception among experienced dam engineers that these traditional measures provide a safer solution and pose less risk than an overtopping solution. This paper will present scenarios that demonstrate that in some cases, overtopping protection may be just as safe or the safer alternative, by exposing the downstream population to equal or less risk of dam failure during a large flood event. These scenarios will consist of an embankment dam where a replacement gated spillway alternative will be compared to overtopping protection and a concrete dam where raising of the dam will be compared to providing overtopping protection for the dam foundation

Managing Dam Safety Risks Related to Hydraulic Structures

The Bureau of Reclamation’s Dam Safety Program manages risk for over 300 high and significant hazard dams.When risk estimates for potential failure modes indicate increasing justification to take action to reduce risk, dam safety recommendations are typically made. The dam safety recommendations can focus on collecting additional data/performing studies to better quantify risk or on initiating corrective actions to address well defined risks. Dam safety recommendations within Reclamation’s inventory address a number of different issues, such as those related to internal erosion, flood overtopping of dams and seismic stability of dams. Dam safety recommendations related to hydraulic structure potential failure modes also represent a significant portion of the recommendations withinReclamation’s inventory. This paper will focus on the methodology used to estimate risks for hydraulic structure potential failure modes and will summarize the relative contribution of the risk posed by hydraulic structures to the overall risk within Reclamation’s inventory of dams. Potential failure modes related to hydraulic structures include overtopping of chute walls, stagnation pressure failure of spillway chute slabs, cavitation damage of concrete flow surfaces leading to loss of concrete lining, structural failure of spillway gates and erosion of the foundation and scour and head cutting in the downstream channel or dam/spillway foundations. The paper also includes examples of dam safety modifications related to hydraulic structure potential failure modes

A measure of centrality based on the spectrum of the Laplacian

We introduce a family of new centralities, the k-spectral centralities. k-Spectral centrality is a measurement of importance with respect to the deformation of the graph Laplacian associated with the graph. Due to this connection, k-spectral centralities have various interpretations in terms of spectrally determined information. We explore this centrality in the context of several examples. While for sparse unweighted networks 1-spectral centrality behaves similarly to other standard centralities, for dense weighted networks they show different properties. In summary, the k-spectral centralities provide a novel and useful measurement of relevance (for single network elements as well as whole subnetworks) distinct from other known measures.Comment: 12 pages, 6 figures, 2 table

Asymptotic behavior of the number of Eulerian orientations of graphs

We consider the class of simple graphs with large algebraic connectivity (the second-smallest eigenvalue of the Laplacian matrix). For this class of graphs we determine the asymptotic behavior of the number of Eulerian orientations. In addition, we establish some new properties of the Laplacian matrix, as well as an estimate of a conditionality of matrices with the asymptotic diagonal predominanceComment: arXiv admin note: text overlap with arXiv:1104.304

Finding community structure in very large networks

The discovery and analysis of community structure in networks is a topic of considerable recent interest within the physics community, but most methods proposed so far are unsuitable for very large networks because of their computational cost. Here we present a hierarchical agglomeration algorithm for detecting community structure which is faster than many competing algorithms: its running time on a network with n vertices and m edges is O(m d log n) where d is the depth of the dendrogram describing the community structure. Many real-world networks are sparse and hierarchical, with m ~ n and d ~ log n, in which case our algorithm runs in essentially linear time, O(n log^2 n). As an example of the application of this algorithm we use it to analyze a network of items for sale on the web-site of a large online retailer, items in the network being linked if they are frequently purchased by the same buyer. The network has more than 400,000 vertices and 2 million edges. We show that our algorithm can extract meaningful communities from this network, revealing large-scale patterns present in the purchasing habits of customers

Analysis of weighted networks

The connections in many networks are not merely binary entities, either present or not, but have associated weights that record their strengths relative to one another. Recent studies of networks have, by and large, steered clear of such weighted networks, which are often perceived as being harder to analyze than their unweighted counterparts. Here we point out that weighted networks can in many cases be analyzed using a simple mapping from a weighted network to an unweighted multigraph, allowing us to apply standard techniques for unweighted graphs to weighted ones as well. We give a number of examples of the method, including an algorithm for detecting community structure in weighted networks and a new and simple proof of the max-flow/min-cut theorem.Comment: 9 pages, 3 figure

A Cosmic Ray Measurement Facility for ATLAS Muon Chambers

Monitored Drift Tube (MDT) chambers will constitute the large majority of precision detectors in the Muon Spectrometer of the ATLAS experiment at the Large Hadron Collider at CERN. For commissioning and calibration of MDT chambers, a Cosmic Ray Measurement Facility is in operation at Munich University. The objectives of this facility are to test the chambers and on-chamber electronics, to map the positions of the anode wires within the chambers with the precision needed for standalone muon momentum measurement in ATLAS, and to gain experience in the operation of the chambers and on-line calibration procedures. Until the start of muon chamber installation in ATLAS, 88 chambers built at the Max Planck Institute for Physics in Munich have to be commissioned and calibrated. With a data taking period of one day individual wire positions can be measured with an accuracy of 8.3 micrometers in the chamber plane and 27 micrometers in the direction perpendicular to that plane.Comment: 14+1 pages, 11 figures, contributed paper to the EPS2003 conference, Aache

Line graphs, link partitions, and overlapping communities.

Accepted versio

Reliable, Semi-Automated Wound Healing Rate Determination in Muscle

In the field of Regenerative and Sport Medicine, there is great interest in the development and validation of compounds and devices with the potential to accelerate wound healing and muscle regeneration. In vitro, this effect can be evaluated in a scratch test model, in which a pipette removes a line of cells from a confluent monolayer of cells with high regenerative capacity and the time to close this injury measured. PURPOSE: To develop a reliable, dynamic, and quantitative process with a shorter duty cycle and semi-automatic operation for the determination of wound healing rate, as compared to fully manual operation. METHODS: C2C12 murine myoblasts were cultured to confluence under standard conditions. A 200 µL pipette tip was used to make a scratch across each well, and 0 and 0.5mM of pro-myogenic Si-ions were added to the media. A Keyence BZX-710 microscope was used to capture images every 183 seconds over 36 hours at 10x magnification with 0.7 pixels/μm and 4 µm pitch. An enclosed cell culture stage contained a cell incubator system keeping cells at 37°C with a 5% CO2 humidified air. For the manual operation, one image was randomly selected from the automated images every 12hr. ImageJ Macro WH_NJ was used to quantify the percent area of the field (scratched) of interest without cells and was normalized as needed per experimental conditions. RESULTS: The manual and automatic slopes for the 0 and 0.5mM Si-ion treatments were -4.87E-06, -4.84E-06, -6.01E-06, and -5.98E-06, respectively, for the full 0-36hr. There was a high degree of correlation between the manual and semi-automatic rates for both the 0 and 0.5mM Si-ions, at r=.84 and .98, respectively. There were no statistically significant differences between healing rates (i.e., closure times) for the automatic or manual 0 or 0.5mM Si-ions, or within either method, following a two-tailed student’s t-test with alpha level of p\u3c.05. Within 12hr periods, the semi-automatic method provided greater detail for the healing rate, such as the faster initial rate seen in 0.5mM Si-ion, not discernible in 12-hour increments for the manual method. CONCLUSION: These data support the functionality of our new methodology described here. The descriptive and inferential statistics shown here demonstrate agreement between the two analyses, while the semi-automated method presented additional dynamics and kinetics information beyond the manual method in early-test behavior that could not be measured manually. Further development in this area will focus on continuing to shorten duty cycles for higher fidelity and the quantitative analysis of dynamic behaviors. Potential clinical-translational applications of our new method are to screen libraries of compounds with putative muscle regeneration capacity using human muscle cells. We also plan to test basal differences in muscle cells from biopsies of sedentary and active individuals, as well as healthy individuals vs. those with various metabolic and musculoskeletal and cardiovascular disorders, and aging sarcopenia. Our new methodology coupled with these translational studies will help advance new compounds and devices with early promise for the field of Regenerative and Sport Medicine into the pre-clinical animal phases of validation