bluuebunny/crossref_metadata_2025 huggingface dataset:
Groundwater pumping impacts on real stream networks: testing the performance of simple management tools
Authors: Zipper Samuel , Dallemagne Tom , Gleeson Tom , Boerman Thomas , Hartmann Andreas
Published: July 2018

Quantifying reductions in streamflow due to groundwater pumping (‘streamflow depletion’) is essential for conjunctive management of groundwater and surface water resources. Analytical models are widely used to estimate streamflow depletion but include potentially problematic assumptions such as simplified stream-aquifer geometry and rely on largely untested depletion apportionment equations to distribute depletion from a well among different stream reaches. Here, we use archetypal numerical models to evaluate the sensitivity of five depletion apportionment equations to stream networks with varying drainage densities, topographic relief, and groundwater recharge rates; and statistically evaluate the sources of error for each equation. We introduce a new depletion apportionment equation called web squared which considers stream network geometry, and find that it performs the best under most conditions tested. For all depletion apportionment equations, performance decreases with increases in drainage density, relief, or recharge rates, and all equations struggle to estimate depletion in short stream reaches. Poorly performing apportionment equations tend to underestimate streamflow depletion relative to numerical model results, leading to a negative bias and underpredicted variability, while error in the best performing apportionment equations tends to be due to imperfect correlation. From a management perspective, apportionment equations with error due to bias and variability are preferable as they correctly identify which reaches will be affected and can be statistically corrected. Overall, these results indicate that the web squared method introduced here, which explicitly considers stream geometry, performs the best over a range of real-world conditions, and will be most accurate in flatter and drier environments.
Methyl, ethyl, and propyl nitrates: global distribution and impacts on reactive nitrogen in remote marine environments
Authors: Fisher Jenny , Atlas Elliot , Barletta Barbara , Meinardi Simone , Blake Don , Thompson Chelsea , Ryerson Thomas , Peischl Jeff , Tzompa-Sosa Zitely , Murray Lee
Published: July 2018

Alkyl nitrates (RONO2) are important components of tropospheric reactive nitrogen that serve as reservoirs for nitrogen oxides (NOx ≡ NO + NO2). Here we implement a new simulation of atmospheric methyl, ethyl, and propyl nitrate chemistry in a global chemical transport model (GEOS‐Chem). We show that the model can reproduce the spatial and seasonal variability seen in a 20‐year ensemble of airborne observations. Methyl nitrate accounts for 17 Gg N globally, with maxima over the tropical Pacific and Southern Ocean. Propyl nitrate is enhanced in continental boundary layers, but its global impact (6 Gg N) is limited by a short lifetime (8 days, versus 26 days for methyl nitrate and 14 days for ethyl nitrate) that inhibits long‐range transport. Ethyl nitrate has the smallest impact of the three species (4 Gg N). We find that methyl nitrate is the dominant form of reactive nitrogen (NOy) in the Southern Ocean marine boundary layer, where its addition to the model corrects a large NOy underestimate in austral winter relative to recent aircraft data. RONO2 serve as a small net NOx source to the marine troposphere, except in the northern mid‐latitudes where the continental outflow is enriched in precursors that promote NOx loss via RONO2 formation. Recent growth in NOx emissions from East Asia has enhanced the role of RONO2 as a source of NOx to the remote free troposphere. This relationship implies projected future NOx emissions growth across the southern hemisphere may further enhance the importance of RONO2 as a NOx reservoir.
Stratigraphic modeling of the Western Taiwan foreland basin: sediment flux from a growing mountain range and tectonic implications
Authors: Nagel Stefan , Granjeon Didier , Willett Sean , Lin Andrew , Castelltort Sébastien
Published: July 2018

Sediment flux signals in foreland basins preserve a record oftectonics, sea level and climate through erosion and sedimentation.However, longitudinal sediment transport often occurs in foreland basin,thus removing part of the orogenic material flux from foreland basins.Here we use mass balance calculation and stratigraphic simulations ofsediment fluxes for the Taiwan orogen to provide a quantified order ofmagnitude estimate of how much orogenic material may bypass a forelandbasin. Our results indicate a significant, potentially more than 50%,mismatch between sediment volume currently preserved in the basin and theamount of material eroded from the orogen since the onset of collision inTaiwan. This supports previous paleogeographic work suggesting thatlongitudinal sediment transport in the paleo-Taiwan Strait served as abypass conduit important for the establishment of a steady state orogen.We identify candidate submarine topography in the South China Sea thatmay preserve Taiwans missing erosional mass.
Uncertainty in sea level rise projections due to the dependence between contributors
Authors: Le Bars Dewi
Published: July 2018

Sea level rises at an accelerating pace threatening coastal communities all over the world. In this context sea level projections are key tools to help risk mitigation and adaptation. Sea level projections are often made using models of the main contributors to sea level rise (e.g. thermal expansion, glaciers, ice sheets...). To obtain the total sea level these contributions are added, therefore the uncertainty of total sea level depends on the correlation between the uncertainties of the contributors. This fact is important to understand the differences in the uncertainty of sea level projections from different methods. Using two process-based models to project sea level for the 21st century, we show how to model the correlation structure and its time dependence. In these models the correlation primarily arises from uncertainty of future global mean surface temperature that correlates with almost all contributors. Assuming that sea level contributors are independent of each other, an assumption made in many sea level projections, underestimates the uncertainty in sea level projections. As a result, high-end low probability events that are important for decision making are underestimated. The uncertainty in the strength of the dependence between contributors is also explored. New dependence relation between the uncertainty of dynamical processes, and surface mass balance in glaciers and ice sheets are introduced in our model. Total sea level uncertainty is found to be as sensitive to the dependence between contributors as to uncertainty in individual contributors like thermal expansion and Greenland ice sheet.
Leaf trait acclimation amplifies simulated climate warming in response to elevated carbon dioxide
Authors: Kovenock Marlies , Swann Abigail
Published: July 2018

Vegetation modifies Earth’s climate by controlling the fluxes of energy, carbon, and water. Of critical importance is a better understanding of how vegetation responses to climate change will feedback on climate. Observations show that plant traits respond to elevated carbon dioxide concentrations. These plant trait acclimations can alter leaf area and thus productivity and surface energy fluxes. Yet, the climate impacts of plant structural trait acclimations remain to be tested and quantified. Here we show that one leaf trait acclimation in response to elevated carbon dioxide – a one third increase in leaf mass per area – significantly impacts climate and carbon cycling in Earth system model experiments. Global net primary productivity decreases (-5.8 PgC/yr, 95% confidence interval, CI95% -5.5 to -6.0), representing a decreased carbon dioxide sink of similar magnitude to current annual fossil fuel emissions (8 PgC/yr). Additional anomalous terrestrial warming (+0.3°C globally, CI95% 0.2 to 0.4), especially of the northern extratropics (+0.4°C, CI95% 0.2 to 0.5), results from reduced evapotranspiration and enhanced absorption of solar radiation at the surface. Leaf trait acclimation drives declines in productivity and evapotranspiration by reducing leaf area growth in response to elevated carbon dioxide, as a one third increase in leaf mass per area raises the cost of building leaf area and productivity fails to fully compensate. Our results suggest that plant trait acclimations, such as changing leaf mass per area, should be considered in climate projections and provide additional motivation for ecological and physiological experiments that determine plant responses to environment.
Aggradational lobe fringes: the influence of subtle intrabasinal seabed topography on sediment gravity flow processes and lobe stacking patterns
Authors: Spychala Yvonne , Hodgson David , Stevenson Christopher , Flint Stephen
Published: July 2018

Seabed topography is ubiquitous across basin-floor environments, and influences sediment gravity flows and sediment dispersal patterns. The impact of steep (several degrees) confining slopes on sedimentary facies and depositional architecture has been widely documented. However, the influence of gentle (fraction of a degree) confining slopes is less well-documented, largely due to outcrop limitations. Here, exceptional outcrop and research borehole data from Unit A of the Permian Laingsburg Formation, South Africa, provide the means to examine the influence of subtle lateral confinement on flow behaviour and lobe stacking patterns. The dataset describes the detailed architecture of subunits A.1 to A.6, a succession of stacked lobe complexes, over a palinspastically restored 22 km across-strike transect. Facies distributions, stacking patterns, thickness and palaeoflow trends indicate the presence of a south-east facing low angle (fraction of a degree) lateral intrabasinal slope. Interaction between stratified turbidity currents with a thin basal sand-prone part and a thick mud-prone part and the confining slope results in facies transition from thick-bedded sandstones to thin-bedded heterolithic lobe fringe-type deposits. Slope angle dictates the distance over which the facies transition occurs (hundreds of metres to kilometres). These deposits are stacked vertically over tens of metres in successive lobe complexes to form an aggradational succession of lobe fringes. Extensive slides and debrites are present at the base of lobe complexes, and are associated with steeper restored slope gradients. The persistent facies transition across multiple lobe complexes, and the mass flow deposits, suggests that the intrabasinal slope was dynamic and was never healed by deposition during Unit A times. This study demonstrates the significant influence that even subtle basin-floor topography has on flow behaviour and depositional architecture of submarine lobe complexes. In addition, we present a new aggradational lobe fringe facies associations and recognition criteria for subtle confinement in less well-exposed and subsurface basin fills.
The 11 October 2010 Novaya Zemlya Earthquake: Implications for Velocity Models and Regional Event Location
Authors: Gibbons Steven , Antonovskaya Galina , Asming Vladimir , Konechnaya Yana , Kremenetskaya Lene , Kværna Tormod , Schweitzer Johannes , Vaganova Natalia
Published: July 2018

Characterizing the seismicity of Novaya Zemlya and the surrounding Arctic seas requires accurate event‐location estimates. Low‐magnitude events in this region are currently observed only by a small number of stations in the European Arctic, with a large azimuthal gap, making the accuracy of regional velocity models all the more important. Regional travel‐time calibration is difficult given the scarcity of sufficiently well‐constrained events. On 11 October 2010, a magnitude 4.5 event occurred close to the northern tip of Novaya Zemlya. This event is significant in that it is the first event in this region to have been recorded both on the relatively recent regional networks and arrays, and also teleseismically with good azimuthal coverage. We examine how well we can constrain the location and origin time using only teleseismic phases. Using only first teleseismic P arrivals, we constrain the epicenter to approximately 76.25° N and 64.75° E but with no depth resolution. Clear depth phases, notably on stations in the southern United States, indicate a depth between 9 and 15 km. This independent hypocenter and origin time estimate allow evaluation of regional phase travel‐time prediction using different models. The predicted Sn travel time appears to cause the greatest variability in regional location estimates. The 3D Regional Seismic Travel Times models provide excellent Pn travel‐time estimates for Barents Sea paths but may slightly overestimate Sn travel times from this source region. A modified regional 1D velocity model is defined, which best predicts Pn and Sn observations at multiple stations up to 15°. The significance of the regional travel‐time models for estimating location is demonstrated for a low‐magnitude event on or close to the northern island of Novaya Zemlya in March 2014, recorded with a satisfactory signal‐to‐noise ratio at only four stations.
Decreasing cloud cover drives the recent mass loss on the Greenland Ice Sheet
Authors: Hofer Stefan , Tedstone Andrew , Fettweis Xavier , Bamber Jonathan
Published: July 2018

The Greenland Ice Sheet (GrIS) has been losing mass at an accelerating rate since the mid-1990s. This has been due to both increased ice discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface mass balance since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud cover enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud cover decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud cover, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud cover is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface mass loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation.
A comparison of GPS, VLBI and model estimates of ocean tide loading displacements
Authors: Thomas Ian , King Matt , Clarke Peter
Published: July 2018

In recent years, Ocean Tide Loading Displacements (OTLD) have been measured using the Global Positioning System (GPS) and Very Long Baseline Interferometry (VLBI). This study assesses the accuracy of GPS measurements of OTLD by comparison with VLBI measurements and estimates derived from numerical ocean tide models. A daily precise point positioning (PPP) analysis was carried out on ~11 years of GPS data for each of 25 sites that have previous OTLD estimates based on data from co-located VLBI sites. Ambiguities were fixed to integer values where possible. The resulting daily estimates of OTLD, at eight principal diurnal and semi-diurnal tidal frequencies, were combined to give GPS measurements of OTLD at each site. The three-dimensional GPS and VLBI measurements of OTLD were compared with estimates computed (by convolution with Green’s functions) from five modern ocean tide models (CSR4.0, FES2004, GOT00.2, NAO99b,TPXO6.2). The GPS / model agreement is shown to be similar to the VLBI / model agreement. In the important radial direction, the GPS / model misfit is shown to be smaller than the VLBI / model misfit for seven of the eight tidal constituents; the exception being the K2 constituent. Fixing of GPS carrier phase ambiguities to integer values resulted in marginal improvement to the GPS / model agreement. Statistically, it is shown there is no significance to the difference between the fit of the GPS and VLBI measurements of OTLD to modelled values. Equally, differences in fit of either the complete set of GPS or VLBI estimates to the five sets of model derived values cannot be identified with statistical significance. It is thus concluded that, overall, we cannot distinguish between GPS and VLBI measurements of OTLD, and that at the global scale, present ocean tide models are accurate to within the current measurement noise of these techniques.
Three-dimensional variations in Love and Rayleigh wave azimuthal anisotropy for the upper 800 km of the mantle
Authors: Yuan Kaiqing , Beghein Caroline
Published: July 2018

We present a new mantle model (YB14SHani) of azimuthal anisotropy for horizontally polarized shear waves (SH) in parallel with our previously published vertically polarized shear wave (SV) anisotropy model (YB13SVani). YB14SHani was obtained from higher mode Love wave phase velocity maps with sensitivity to anisotropy down to ~1200 km depth. SH anisotropy is present down to the mantle transition zone (MTZ) with an average amplitude of ~2% in the upper 250 km and ~1% in the MTZ, consistent with YB13SVani. Changes in SV and SH anisotropy were found at the top of the MTZ where olivine transforms into wadsleyite, which might indicate that MTZ anisotropy is due to the lattice-preferred orientation of anisotropic material. Beneath oceanic plates, SV fast axes become subparallel to the absolute plate motion (APM) at a depth that marks the location of a thermally controlled lithosphere-asthenosphere boundary (LAB). In contrast, SH anisotropy does not systematically depend on ocean age. Moreover, while upper mantle SV anisotropy is anomalously high in the middle of the Pacific, as seen in radial anisotropy models, SH anisotropy amplitude remains close to the average for other oceans. Based on the depth at which SV fast axes and the APM direction begin to align, we also found that the average thickness of cratonic roots is ~ 250 km, consistent with Yuan and Romanowicz (2010) for North America. Here we add new constraints on the nature of the cratonic LAB and show that it is characterized by changes in both SV and SH anisotropy.
Normal fault growth in layered basaltic rocks: the role of strain rate in fault evolution
Authors: Bubeck Alodie , Walker Richard , Imber Jonathan , MacLeod Chris
Published: July 2018

Conceptual models for the evolution of dilatant faults in volcanic rift settings involve a step-wise growth pattern, involving upward propagation of subsurface faults, surface monocline formation, which are breached by subvertical, open faults. Immature, discontinuous normal faults are considered representative of the early stages of mature, linked faults that accommodate extensional strains. We consider the evolution of surface-breaching normal faults using a comparison of the distribution and geometry of normal faults from two volcanic rift zones: the Koaʻe fault system, Hawaiʻi, and the Krafla fissure swarm, NE Iceland. Field mapping highlights similarities to current predicted geometries, but also prominent differences that are not reconciled by current models. Variable deformation styles record magma supply changes within the rift zones, which drive local strain rate gradients. Building on existing studies, we present a conceptual model of fault growth that accounts for spatial and temporal changes in strain rate within the deforming regions. We propose that faults in separate rift systems may not advance through the same stages of evolution and that faults within individual rift systems can show differing growth patterns. Variations in surface strains may be indicative of subsurface magmatic system changes, with important implications for our understanding of volcano-tectonic coupling.
Development and validation of a meshless 3D material point method for simulating the micro-milling process
Authors: Leroch Sabine , Eder Stefan J , Ganzenmüller Georg , Murillo Jose Luis Sandoval , Ripoll Manel Rodriguez
Published: July 2018

A meshless Generalized Interpolation Material Point Method for simulating the micro-milling process was developed. This method has several advantages over well-established approaches (such as finite elements) when it comes to large plastic strains and deformations, since it inherently does not suffer from tensileinstability problems. The feasibility of the developed material point model for simulating micro-milling is verified against finite element simulations and experimental data. The model is able to successfully predict experimentally measured cutting forces and determine chip temperatures in agreement with conventional finite element simulations. After having verified the approach, the model was applied to perform extensive numerical 3D simulations of the micro-milling process. The goal is to evaluate the response of the micro-milling cutting forces as function of the hardening behavior of the micro-milled material. The meshless 3D simulations reveal a dependency of tool force slopes (with respect to the uncut chip thickness) on the hard-ening parameters. Based on these findings, a new approach is outlined to determine hardening parametersdirectly from two micro-milling experiments with distinct, sufficiently large uncut chip thicknesses.
Is sulfide stress cracking an anodic or a cathodic process?
Authors: Iannuzzi Mariano
Published: July 2018

Is sulfide stress cracking an anodic or a cathodic process? Does hydrogen play a role or is SSC controlled by anodic dissolution?
Influence of Crosslinking on the Mechanical Behavior of 3D Printed Alginate Scaffolds: Experimental and Numerical Approaches
Authors: Naghieh Saman , Karamooz-Ravari Mohammad Reza , Sarker Md , Karki Eva , Chen Xiongbiao
Published: July 2018

Tissue scaffolds fabricated by three-dimensional (3D) bioprinting are attracting considerableattention for tissue engineering applications. Because the mechanical properties of hydrogelscaffolds should match the damaged tissue, changing various parameters during 3D bioprintinghas been studied to manipulate the mechanical behavior of the resulting scaffolds. Crosslinkingscaffolds using a cation solution (such as CaCl2) is also important for regulating the mechanicalproperties, but has not been well documented in the literature. Here, the effect of variedcrosslinking agent volume and crosslinking time on the mechanical behavior of 3D bioplottedalginate scaffolds was evaulated using both experimental and numerical methods. Compressiontests were used to measure the elastic modulus of each scaffold, then a finite element model wasdeveloped and a power model used to predict scaffold mechanical behavior. Results showed thatcrosslinking time and volume of crosslinker both play a decisive role in modulating the mechanicalproperties of 3D bioplotted scaffolds. Because mechanical properties of scaffolds can affect cellresponse, the findings of this study can be implemented to modulate the elastic modulus ofscaffolds according to the intended application.
Perancangan Sistem Informasi Pendataan Penelitian Dosen Di Lingkungan Kopertis Wilayah II Palembang
Authors: Sutedi Sutedi
Published: July 2018

It is important for lecturers to improve the quantity and quality of their research. Tosupport this, Kopertis Wilayah II oftenly provides some grants for the lecturers to improvetheir research. With more research carried out, good data information system oflecturers’ research is needed. Making use of information technology can be a solution tofulfill the need of information related to the lecturers’ research as well as to check thelecturers’ research data to minimize the plagiarism practices and the problems ofredundancies in lecturers title of research.
Moving Towards an Improved Liquefaction Hazard Framework: Lessons Resulting From the 2010-2011 Canterbury, New Zealand, Earthquake Sequence
Authors: Maurer Brett
Published: July 2018

The 2010-2011 Canterbury, New Zealand,Earthquake Sequence (CES) resulted in a liquefaction dataset of unprecedented size and quality, presenting a truly unique opportunity to assess and improve the efficacy of liquefaction-analyticsin the field. Towards this end, the study presented herein develops and analyzes a database of 10,000 high-quality liquefaction case histories resulting from the CES. The objectives of these analyses are varied, but underlying each is the desire to more accurately assess liquefaction hazard for civil infrastructure (i.e., to predict both the occurrence and damage-potential of soil liquefaction). Major contributions from this work include, but are not limited to: (1) the Liquefaction Potential Index (LPI), the state-of-practice framework for assessing liquefaction hazard, is shown to produce erroneous predictions for a significant percentage of the assessed case histories; (2) the cause of poor predictions is rigorously investigated and specific shortcomings of the LPI framework are identified; (3) based on the limitations identified, and using insights from historical data, a revised liquefaction hazard framework is developed; and (4) the revised framework is shown to assess liquefaction hazard more efficiently relative to both LPI and a competing alternative framework newly proposed in the literature. Ultimately, significant room for improvement remains with respect to accurate assessment of liquefaction hazard. The findings presented in this dissertation thus form the basis for future development of a further-improved framework. Moreover, a methodology is proposed by which improvements can be measured in a standardized and objective manner.
A Type–II Fuzzy Entropy Based Multi-Level Image Thresholding Using Adaptive Plant Propagation Algorithm
Authors: Nag Sayan
Published: July 2018

One of the most straightforward, direct and efficient approaches to Image Segmentation isImage Thresholding. Multi-level Image Thresholding is an essential viewpoint in many image processing andPattern Recognition based real-time applications which can effectively and efficiently classify the pixels intovarious groups denoting multiple regions in an Image. Thresholding based Image Segmentation using fuzzyentropy combined with intelligent optimization approaches are commonly used direct methods to properlyidentify the thresholds so that they can be used to segment an Image accurately. In this paper a novel approachfor multi-level image thresholding is proposed using Type II Fuzzy sets combined with Adaptive PlantPropagation Algorithm (APPA). Obtaining the optimal thresholds for an image by maximizing the entropy isextremely tedious and time consuming with increase in the number of thresholds. Hence, Adaptive PlantPropagation Algorithm (APPA), a memetic algorithm based on plant intelligence, is used for fast and efficientselection of optimal thresholds. This fact is reasonably justified by comparing the accuracy of the outcomes andcomputational time consumed by other modern state-of-the-art algorithms such as Particle SwarmOptimization (PSO), Gravitational Search Algorithm (GSA) and Genetic Algorithm (GA).
Current challenges and frontiers for the EHD simulation of journal bearings: a review
Authors: Allmaier Hannes
Published: July 2018

In this manuscript the authors discuss the current state of the art in the EHD-simulation of journal bearings in automotive applications like the internal combustion engine.
Desktop Load/Deflection Measurement
Authors: Berg Devin R.
Published: July 2018

In order to achieve a low-cost solution for the collection of load/deflection data, a simple device based upon a balance like mechanism and two variable measurements was designed and tested. The device uses a linear variable differential transformer and a potentiometer to determine the load applied to the test specimen and the extension that the specimen exhibits under such a load. Test samples of known characteristics were used in order to provide a basis for gaging the performance of the device against well-established measurement systems. It was found that the slope of the load/deflection curve obtained with this device was within 10 % of the accepted data. This performance is considered reasonable for a device of this nature and several areas for improvement are discussed.
Simulation-based study of the energy requirements linked to the temperature control of micro-algae culture in outdoor photobioreactors.
Authors: CAPPAI Lorenzo , d’Avray Marie-Amélie de Ville , Mdere Ounayda , Linnekoski Juha , Verdú Eduardo Rodríguez , Fernández Eloy Chápuli
Published: July 2018

Outdoor microalgae photobioreactors are exposed to continuously variable weather conditions, causing permanent fluctuations of culture temperature that must be limited within a strain-dependent range. The optimization of photobioreactor performance requires to be able to predict the culture temperature evolution and related power requirements as a function of weather conditions as well as photobioreactor design. Based on this perspective, a thermal model for vertical tubular photobioreactors was proposed and validated using experimental data from industrial-scale photobioreactors. The model was then used to predict the annual amount of energy required to maintain the culture temperature within a desired range, for different reactor configurations and for several locations in the world. The use of weather databases is of major importance to choose the best location to build microalgae production facilities and to optimize influent geometrical and operating parameters, which can play wanted or unwanted roles depending on the meteorological conditions of the site.
A digital implementation of 2D Hindmarsh–Rose neuron
Authors: Kandalaft Nabeeh , Ahmadi Arash , Heidarpur Moslem
Published: July 2018

Different architectures and techniques havedeveloped in the neuromorphic field to mimic andinvestigate the activity of biological neural networks.This paper presents a set of piece-wise linear approximationsof a two-dimensional Hindmarsh–Rose neuronmodel for digital circuit implementation to achievehigher speeds and lower hardware costs in large-scaleimplementation of the biological neural networks. Theperformance of the model was evaluated with a timedomain signal error. Synthesis and hardware implementationon a field-programmable gate array, as aproof of concept, indicates that the proposed modelreproduces several neuronal behaviors similar to theoriginal model with higher performance and considerablylower implementation costs.
Heterogeneous Simulated Annealing Teams: An Optimizing Search Algorithm Inspired by Engineering Design Teams
Authors: McComb Christopher , Cagan Jonathan , Kotovsky Kenneth
Published: July 2018

Although insights uncovered by design cognition are often utilized to develop the methods used by human designers, using such insights to inform computational methodologies also has the potential to improve the performance of design algorithms. This paper uses insights from research on design cognition and design teams to inform a better simulated annealing search algorithm. Simulated annealing has already been established as a model of individual problem solving. This paper introduces the Heterogeneous Simulated Annealing Team (HSAT) algorithm, a multi-agent simulated annealing algorithm. Each agent controls an adaptive annealing schedule, allowing the team develop heterogeneous search strategies. Such diversity is a natural part of engineering design, and boosts performance in other multi-agent algorithms. Further, interaction between agents in HSAT is structured to mimic interaction between members of a design team. Performance is compared to several other simulated annealing algorithms, a random search algorithm, and a gradient-based algorithm. Compared to other algorithms, the team-based HSAT algorithm returns better average results with lower variance.
Research and Practice Group Methodology: A Case Study in Student Success
Authors: McComb Christopher , Tehrani Fariborz M
Published: July 2018

Experiential learning is a key component in engineering education. In civil engineering, this component is typically delivered through multiple projects. These projects may include term projects for individual courses, senior design projects, theses, or independent studies. The focus of these experiences may gradually shift from practice-oriented projects in undergraduate studies to research-oriented projects in graduate studies. Thus, learning objectives should always address both areas with a strong emphasis on common fields, such as applied research. Experiential learning has the capacity to include various program-level outcomes, such as technical knowledge, communication and teamwork. Development of a research and practice group facilitates these outcomes by creating an environment to share the learning experience. Such a group should replicate the working environment of civil engineers by incorporating multidisciplinary projects and diverse individuals, including cross-generational members. As a case study, this work examines a Research and Practice Group at California State University Fresno. This group consists of junior and senior undergraduates, graduate students, and former members who are participating as alumni. The major focus of research within the group is resilient and sustainable structural mechanics and design. This paper outlines the methodology that has been employed to ensure academic and professional success for members of the group. This methodology incorporates a recruitment process, meetings, consultation, mentorship, networking, and support. The level of student success achieved by the group is presented in terms of the achievements of the group’s members. This includes a discussion of completed projects, research funding, and group presentations. To further demonstrate the efficacy of the methodology, students in the research group are compared to the general body of engineering students at CSU Fresno though the results of a survey. This survey is analyzed using traditional methods, as well as Latent Semantic Analysis. Our results indicate that group members are better at embodying and communicating outcomes than the rest of the student body, and that the research and practice group provides an experience that allows students to internalize and take responsibility for their own goals.
Effects of a zeolite-selective catalytic reduction system on comprehensive emissions from a heavy-duty diesel engine
Authors: Liu Z. Gerald , Berg Devin R. , Schauer‡ James J.
Published: July 2018

The effects of a zeolite urea-selective catalytic reduction aftertreatment system on a comprehensive spectrum of chemical species from diesel engine emissions were investigated in the present study. Representative samples were collected with a newly developed source dilution sampling system after an aging process designed to simulate atmospheric dilution and cooling conditions. Samples were analyzed with established procedures and compared between the measurements taken from a baseline heavy-duty diesel engine and also from the same engine equipped with the exhaust aftertreatment system. The results have shown significant reductions for nitrogen oxides, carbon monoxide, total hydrocarbons, polycyclic aromatic hydrocarbons, and organic carbon emissions. Additionally, less significant yet notable reductions were observed for particulate matter mass and metals emissions. Although two ionic compounds, sulfate and nitrate, displayed increased emission levels, the production of new species was not observed with the addition of the zeolite urea-selective catalytic reduction system joined with a downstream oxidation catalyst.
Bone Pose Estimation in the Presence of Soft Tissue Artifact Using Triangular Cosserat Point Elements
Authors: Solav Dana , Rubin MB , Cereatti Andrea , Camomilla Valentina , Wolf Alon
Published: July 2018

Accurate estimation of the position and orientation (pose) of a bone from a cluster of skin markers is limited mostly by the relative motion between the bone and the markers, which is known as the Soft Tissue Artifact (STA). This work presents a method, based on continuum mechanics, to describe the kinematics of a cluster affected by STA. The cluster is characterized by Triangular Cosserat Point Elements (TCPEs) defined by all combinations of three markers. The effects of the STA on the TCPEs are quantified using three parameters describing the strain in each TCPE and the relative rotation and translation between TCPEs. The method was evaluated using previously collected ex-vivo kinematic data. Femur pose was estimated from 12 skin markers on the thigh, while its reference pose was measured using bone pins. Analysis revealed that instantaneous subsets of TCPEs exist which estimate bone position and orientation more accurately than the Procrustes Superimposition applied to the cluster of all markers. It has been shown that some of these parameters correlate well with femur pose errors, which suggests that they can be used to select, at each instant, subsets of TCPEs leading an improved estimation of the underlying bone pose.
Optimizing Design Teams Based on Problem Properties: Computational Team Simulations and an Applied Empirical Test
Authors: McComb Christopher , Kotovsky Kenneth , Cagan Jonathan
Published: July 2018

The performance of a team with the right characteristics can exceed the mere sum of the constituent members’ individual efforts. However, a team having the wrong characteristics may perform more poorly than the sum of its individuals. Therefore, it is vital that teams are assembled and managed properly in order to maximize performance. This work examines how the properties of configuration design problems can be leveraged to select the best values for team characteristics (specifically team size and interaction frequency). A computational model of design teams which has been shown to effectively emulate human team behavior is employed to pinpoint optimized team characteristics for solving a variety of configuration design problems. These configuration design problems are characterized with respect to the local and global structure of the design space, the alignment between objectives, and the resources allotted for solving the problem. Regression analysis is then used to create equations for predicting optimized values for team characteristics based on problem properties. These equations achieve moderate to high accuracy, making it possible to design teams based on those problem properties. Further analysis reveals hypotheses about how the problem properties can influence a team’s search for solutions. This work also conducts a cognitive study on a different problem to test the predictive equations. For a configuration problem of moderate size, the model predicts that zero interaction between team members should lead to the best outcome. A cognitive study of human teams verifies this surprising prediction, offering partial validation of the predictive theory.
Torsional Dynamics Response of Shafts with Longitudinal and Circumferential Cracks
Authors: Nabian Mohsen , Nabian Mohammad Ali , Hashemi Hamid Nayeb
Published: July 2018

Turbo generators shafts are manufactured through the extrusion process. This results in formation of weak planes along the extrusion process. It has been observed that large longitudinal cracks often form in these shafts before any circumferential cracks when these shafts are subjected to cyclic torsion due to electrical line faults. The presence of these cracks could severely compromise the shaft resonance frequencies. Dynamic response of shafts with longitudinal and circumferential cracks is investigated. The longitudinal cracked section of the shaft section is modeled as a shaft with reduced torsional rigidity. The torsional rigidity is obtained as a function of the crack depth. It was found for various shaft diameters, torsional rigidity could be represented as a function of crack depth/ shaft radius only. The circumferential cracked section is modeled as a torsional spring. The torsional spring constant has been obtained using fracture mechanics. It was found the resonance frequency of the shaft may be little affected by the presence of longitudinal crack. The resonance frequencies of the shaft with the circumferential crack depend on the crack length and location. The effects of crack surface interactions for both longitudinal and circumferential cracks were also investigated.
Investigation of Biofuels from Microorganism Metabolism for Use as Anti-Knock Additives
Authors: Mack John Hunter , Rapp Vi H. , Broeckelmann Malte , Lee Taek Soon , Dibble Robert W.
Published: July 2018

This paper investigates the anti-knock properties of biofuels that can be produced from microorganism metabolic processes. The biofuels are rated using Research Octane Number (RON) and Blending Research Octane Number (BRON), which determine their potential as additives for fuel in spark ignition (SI) engines. Tests were conducted using a single-cylinder Cooperative Fuel Research (CFR) engine and performance of the biofuels was compared to primary reference fuels (PRFs). The investigated fuels include 3-methyl-2-buten-1-ol, 3-methyl-3-buten-1-ol, 2-methylpropan-1-ol (isobutanol), and limonene. Results show that 3-methyl-2-buten-1-ol, 3-methyl-3-buten-1-ol, and 2-methylpropan-1-ol (isobutanol) sufficiently improve the anti-knock properties of gasoline.
On Advantages of the Kelvin Mapping in Finite Element Implementations of Deformation Processes
Authors: Nagel Thomas , Moerman Kevin Mattheus
Published: July 2018

Classical continuum mechanical theories operate on three-dimensionalEuclidian space using scalar, vector, and tensor-valued quantities usuallyup to the order of four. For their numerical treatment, it is commonpractice to transform the relations into a matrix-vector format. Thistransformation is usually performed using the so-called Voigt mapping. Thismapping does not preserve tensor character leaving significant room forerror as stress and strain quantities follow from different mappings andthus have to be treated differently in certain mathematical operations.Despite its conceptual and notational difficulties having been pointed out,the Voigt mapping remains the foundation of most current finite elementprogrammes. An alternative is the so-called Kelvin mapping which hasrecently gained recognition in studies of theoretical mechanics. Thisarticle is concerned with benefits of the Kelvin mapping in numericalmodelling tools such as finite element software. The decisive difference tothe Voigt mapping is that Kelvin’s method preserves tensor character, andthus the numerical matrix notation directly corresponds to the originaltensor notation. Further benefits in numerical implementations are thattensor norms are calculated identically without distinguishing stress orstrain-type quantities and tensor equations can be directly transformedinto matrix equations without additional considerations. The onlyimplementational changes are related to a scalar factor in certain finiteelement matrices and hence, harvesting the mentioned benefits comes at verylittle cost.
Open Research, Open Engineering, and the Role of the University in Society
Authors: Berg Devin R.
Published: July 2018

This is a white paper submitted as part of the joint NIH/NSF-funded event, "Imagining Tomorrow’s University: Rethinking scholarship, education, and institutions for an open, networked era", to be held March 8th and 9th in Rosemont, IL. In this paper I present my personal (not my employer's) thoughts and reflections on the role that open research can play in defining the purpose and activities of the university. I have made some specific recommendations on how I believe the public university can recommit and push the boundaries of its role as the creator and promoter of public knowledge. In doing so, serving a vital role to the continued economic, social, and technological development of society. I have also included some thoughts on how this applies specifically to my field of engineering and how a culture of openness and sharing within the engineering community can help drive societal development.
Deep Learning of Vortex Induced Vibrations
Authors: Raissi Maziar , Wang Zhicheng , Triantafyllou Michael S , Karniadakis George
Published: July 2018

Vortex induced vibrations of bluff bodies occur when the vortex shedding frequency is close to the natural frequency of the structure. Of interest is the prediction of the lift and drag forces on the structure given some limited and scattered information on the velocity field. This is an inverse problem that is not straightforward to solve using standard computational fluid dynamics (CFD) methods, especially since no information is provided for the pressure. An even greater challenge is to infer the lift and drag forces given some dye or smoke visualizations of the flow field. Here we employ deep neural networks that are extended to encode the incompressible Navier-Stokes equations coupled with the structure's dynamic motion equation. In the first case, given scattered data in space-time on the the velocity field and the structure's motion, we use four coupled deep neural networks to infer very accurately the structural parameters, the entire time-dependent pressure field (with no prior training data), and reconstruct the velocity vector field and the structure's dynamic motion. In the second case, given scattered data in space-time on a concentration field only, we use five coupled deep neural networks to infer very accurately the vector velocity field and all other quantities of interest as before. This new paradigm of inference in fluid mechanics for coupled multi-physics problems is part of our ongoing development of physics-informed learning machines, where the traditional CFD methodology is abandoned in favor of deep neural networks inference, circumventing the tyranny of elaborate mesh generation.
Malawi Power Transfer System
Authors: Bauer Jacob
Published: July 2018

This is a power transfer system created to help upgrade electrical power generation in Malawi.
Estimating the global warming emissions of the LCAXVII conference: connecting flights matter.
Authors: Astudillo Miguel Fernández
Published: July 2018

Conferences are an important element of scientific activity but also one of the major causes of environmental burden. In this conference report, we analyse the carbon footprint of the annual conference of the American Center for Life Cycle Assessment, as well as some of the potential ways to reduce it. The average emissions per participant are estimated to be 952 kg CO2eq, but with a large variability due to differences in travelled distance. Results indicate that studies should use distance-dependent flight emissions to increase the accuracy of the assessment. Connection flights are found to increase emissions up to 32 % compared with direct flights, due to the increased number of take-offs and landings. A method to calculate the ideal location is proposed, which can be used to identify unreasonably distant conference locations. Some of the measures taken to reduce the impact, such as meat-free menus, had a relatively minor contribution to emissions reductions, but could be important, as scientist advocating for the reduction of environmental burden should lead by example.