Open Access Publications

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Open access publications by faculty, postdocs, and graduate students in the Department of Civil and Environmental Engineering.

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A Bacillus velezensis strain shows antimicrobial activity against soilborne and foliar fungi and oomycetes
(Frontiers in Fungal Biology, 2024-02-23) Wockenfuss, Anna; Chan, Kevin; Cooper, Jessica G.; Chaya, Timothy; Mauriello, Megan A.; Yannarell, Sarah M.; Maresca, Julia A.; Donofrio, Nicole M.
Biological control uses naturally occurring antagonists such as bacteria or fungi for environmentally friendly control of plant pathogens. Bacillus spp. have been used for biocontrol of numerous plant and insect pests and are well-known to synthesize a variety of bioactive secondary metabolites. We hypothesized that bacteria isolated from agricultural soil would be effective antagonists of soilborne fungal pathogens. Here, we show that the Delaware soil isolate Bacillus velezensis strain S4 has in vitro activity against soilborne and foliar plant pathogenic fungi, including two with a large host range, and one oomycete. Further, this strain shows putative protease and cellulase activity, consistent with our prior finding that the genome of this organism is highly enriched in antifungal and antimicrobial biosynthetic gene clusters. We demonstrate that this bacterium causes changes to the fungal and oomycete hyphae at the inhibition zone, with some of the hyphae forming bubble-like structures and irregular branching. We tested strain S4 against Magnaporthe oryzae spores, which typically form germ tubes and penetration structures called appressoria, on the surface of the leaf. Our results suggest that after 12 hours of incubation with the bacterium, fungal spores form germ tubes, but instead of producing appressoria, they appear to form rounded, bubble-like structures. Future work will investigate whether a single antifungal molecule induces all these effects, or if they are the result of a combination of bacterially produced antimicrobials.
A Hyperelastic Bounding Surface Plasticity Model for Unsaturated Granular Soils
(Geosciences, 2024-05-30) Kadivar, Mehdi; Manahiloh, Kalehiwot Nega; Kaliakin, Victor N.
In this paper, a state-dependent, bounding surface plasticity model that simulates the behavior of unsaturated granular soils is presented. An unsaturated, soil mechanics-compatible elastoplastic response is adopted in which no part of the response occurs in a purely elastic fashion. To create an appropriate hydro-mechanical coupling, a newer generation stress framework, consisting of the Bishop-type effective stress and a second stress variable, is used in conjunction with a soil-water characteristic curve function. Details regarding the model development, parameter estimation, and assessment of the model’s predictive capabilities are outlined. With a single set of parameter values, the model realistically simulates the main features that characterize the shear and volumetric behavior of unsaturated granular soils over a wide range of matric suction, density, and net confining pressure.
Abiotic reduction of 3-nitro-1,2,4-triazol-5-one (NTO) and other munitions constituents by wood-derived biochar through its rechargeable electron storage capacity
(Environmental Science: Processes and Impacts, 2022-01-17) Xin, Danhui; Girón, Julián; Fuller, Mark E.; Chiu, Pei C.
The environmental fate of 3-nitro-1,2,4-triazol-5-one (NTO) and other insensitive munitions constituents (MCs) is of significant concern due to their high water solubility and mobility relative to legacy MCs. Plant-based biochars have been shown to possess a considerable electron storage capacity (ESC), which enables them to undergo reversible electron transfer reactions. We hypothesized biochar can act as a rechargeable electron donor to effect abiotic reduction of MCs repeatedly through its ESC. To test this hypothesis, MC reduction experiments were performed using wood-derived biochars that were oxidized with dissolved oxygen or reduced with dithionite. Removal of aqueous NTO, an anion at circumneutral pH, by oxidized biochar was minimal and occurred through reversible adsorption. In contrast, NTO removal by reduced biochar was much more pronounced and occurred predominantly through reduction, with concomitant formation of 3-amino-1,2,4-triazol-5-one (ATO). Mass balance and electron recovery with ferricyanide further showed that (1) the amount of NTO reduced to ATO was relatively constant (85–100 μmol per gram of biochar) at pH 6–10; (2) the fraction of biochar ESC reactive toward NTO was ca. 30% of that toward ferricyanide; (3) the NTO-reactive fraction of the ESC was regenerable over multiple redox cycles. We also evaluated biochar transformation of other MCs, including nitroguanidine (NQ), 2,4-dinitroanisole (DNAN), and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). While mass and electron balances could not be established due to sorption, DNAN and RDX reduction by reduced biochar was confirmed via detection of multiple reduction products. In contrast, NQ was not reduced under any of the conditions tested. This study is the first demonstration of organic contaminant degradation through biochar's rechargeable ESC. Our results indicate biochar is a regenerable electron storage medium and sorbent that can remove MCs from water through concurrent reduction and sorption, and is thus potentially useful for pollution control and remediation at military facilities.
Adhesion Characterization and Enhancement between Polyimide-Silica Composite and Nodulated Copper for Applications in Next-Generation Microelectronics
(ACS Applied Materials & Interfaces, 2024-01-17) Doshi, Sagar M.; Barry, Alexander; Schneider, Alexander; Parambil, Nithin; Mulzer, Catherine; Yahyazadehfar, Mobin; Samadi-Dooki, Aref; Foltz, Benjamin; Warrington, Keith; Wessel, Richard; Zhang, Lei; Simone, Christopher; Blackman, Gregory S.; Lamontia, Mark A.; Gillespie, John W. Jr.
As the need for high-speed electronics continues to rise rapidly, printed wiring board (PWB) requirements become ever-more demanding. A typical PWB is fabricated by bonding dielectric films such as polyimide to electrically conductive copper foil such as rolled annealed (RA) copper and is expected to become thinner, flexible, durable, and compatible with high-frequency 5G performance. Polyimide films inherently feature a higher coefficient of thermal expansion (CTE) than copper foils; this mismatch causes residual thermal stresses. To attenuate the mismatch, silica nanoparticles may be used to reduce the CTE of PI. A nodulated copper surface can be used to enhance the Cu/PI adhesion by additional bonding mechanisms that could include a type of mechanical bonding, which is a focus of this study. In this investigation, a 90° peel test was used to measure the peel strength in copper/polyimide/copper laminates containing nodulated copper and polyimide reinforced with 0, 20, and 40 wt % silica nanoparticles. The influence of silica nanoparticles on the peel strength was quantitatively evaluated. Laminates incorporating polyimide films lacking silica nanoparticles had a ∼3.75× higher peel strength compared with laminates reinforced with 40% silica. Their failure surfaces were analyzed by using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy to identify the mode of failure and to understand bonding mechanisms. The key bonding mechanism, mechanical interlocking, was achieved when the polyimide surrounded or engulfed the copper nodules when the laminate was created. Post-testing failure surface analysis revealed the presence of copper on the polyimide side and polyimide on the copper side, indicating mixed mode failure. An analytical model was developed to determine the impact of applied pressure, temperature, and time on the polyimide penetration and mechanical interlocking around the copper nodules. The model was validated by measuring the peel strength on another set of specimens fabricated using increased temperature and pressure that showed a 3× increase in peel strength compared to lower temperature/pressure processing conditions. This enhanced adhesion resulted from the lower polymer material viscosity at higher temperatures, which fosters deeper and more complete penetration around the copper nodules during processing at higher pressures for longer durations. The methodology of combining peel testing, viscosity and CTE measurement, SEM/EDX, surface chemical analysis, and penetration depth calculation developed herein enables the calculation of the desired processing parameters to enhance functionality and improve adhesion.
Aggregated Zero-Knowledge Proof and Blockchain-Empowered Authentication for Autonomous Truck Platooning
(IEEE Transactions on Intelligent Transportation Systems, 2023-05-10) Li, Wanxin; Meese, Collin; Guo, Hao; Nejad, Mark
Platooning technologies enable trucks to drive cooperatively and automatically, providing benefits including less fuel consumption, greater road capacity, and safety. To establish trust during dynamic platooning formation, ensure vehicular data integrity, and guard platoons against potential attackers in mixed fleet environments, verifying any given vehicle’s identity information before granting it access to join a platoon is pivotal. Besides, due to privacy concerns, truck owners may be reluctant to disclose private vehicular information, which can reveal their business data to untrusted third parties. To address these issues, this is the first study to propose an aggregated zero-knowledge proof and blockchain-empowered system for privacy-preserving identity verification in truck platooning. We provide the correctness proof and the security analysis of our proposed authentication scheme, highlighting its increased security and fast performance. The platooning formation procedure is re-designed to seamlessly incorporate the proposed authentication scheme, including the 1st catch-up and cooperative driving steps. The blockchain performs the role of verifier within the authentication scheme and stores platooning records on its digital ledger to guarantee data immutability and integrity. In addition, the proposed programmable access control policies enable truck companies to define who is allowed to access their platoon records. We implement the proposed system and perform extensive experiments on the Hyperledger platform. The results show that the blockchain can provide low latency and high throughput, the aggregated approach can offer a constant verification time of 500 milliseconds regardless of the number of proofs, and the platooning formation only takes seconds under different strategies. The experimental results demonstrate the feasibility of our design for use in real-world truck platooning.
Analytical Approach for Modeling Axisymmetric Levee Underseepage
(American Society of Civil Engineers., 2014) Benjasupattananan, Sittinan; Meehan, Christopher L.; Meehan, Christopher L., Benjasupattananan, Sittinan; Meehan, Christopher L. (orcid.org/0000-0002-9721-6275); Benjasupattananan, Sittinan
A variety of real-world levee underseepage problems can best be modeled using an axisymmetric analysis approach. In current practice, axisymmetric levee underseepage analyses are performed using numerical modeling approaches, such as the FEM. In contrast, levee underseepage analyses of planar cross sections are often analyzed using a blanket theory analytical approach, which is quicker and more convenient than numerical modeling. To address this problem, this paper provides a derivation of a series of closed-form blanket theory analytical equations that can be used to perform an axisymmetric levee underseepage analysis. This derivation begins from the governing equation of semiconfined uid ow beneath a levee in a shallow semiconfined aquifer. The equations that result from this derivation can be used to calculate the total head in the pervious foundation layer and the seepage quantity that passes through the levee foundation over time. Different equations are presented for different seepage directions relative to the axis of rotation and different model boundary conditions. A typical example problem is used to compare results from the axisymmetric analytical equations that are derived with those from axisymmetric finite-element analyses. For this example problem, the analytical equations yield results that are equal to or more conservative than those from the finite-element analysis, where conservative results correspond to greater seepage under the levee and higher heads at the levee toe.
Annulus Void Fill Material for Rehabilitated Sliplined Culverts
(The University of Akron, 2023-03) Patnaik, Anil; Alzlfawi, Abdullah; Das, Shagata
Sliplining is a method used by transportation agencies to rehabilitate deteriorated culverts. In recent years, ODOT discovered a number of sliplined culverts that did not have their annulus void spaces completely filled. Such culverts experience distortion and settlement as well as reduced structural capacity. Field inspections of several sliplined culverts in Ohio in this study confirmed that the lack of complete annulus void filling is a prevalent problem. Filler grout properties, particularly poor flow characteristics, would prevent the grout from completely filling annulus voids. This led to the investigation of grout properties that are most important to achieve good flow and fillability. New mixture proportions of a controlled low-strength material (CLSM) and cellular grout C40 were developed based on extensive laboratory testing. These improved grouts were also mixed in a batching plant at a larger scale and were pumped over a 200-ft length at an upslope of 2.5% to determine the suitability of these grouts in practical applications. Grouting of the annulus voids of 20-foot-long sections was verified using a 36-inch liner pipe sliplined within a 48-inch host pipe. A suggested basis for changes to the relevant ODOT specifications in SS 837 is recommended.
Application of New Lubricant and Modifier Formulations for the Reduction of Wheel Squeal Noise Under Freight and Passenger Service
(American Railway Engineering Association, 1999-09) Zarembski, Allan M.; Chiddick, Kelvin S.
Wheel sequel noise on curved track is a serious problem in residential areas where the tracks are near or adjacent to homes and residences. This was the case in a Southern California community that was adjacent to a Southern Pacific Railroad mainline that carried both freight and passenger traffic. The specific wheel squeal problem was associated with the negotiation of the moderate curved track by the mix of traffic at a range of speeds and operating conditions. While significant noise levels were recorded by all of the traffic, to include commuter and inter-urban passenger traffic, the highest levels of noise were recorded by intermodal freight equipment, both trailer and container carrying. These n0ise levels were of significant magnitude and resulted in numerous complaints as well a'$ follow up lawsuits from the residents. In order to address this noise problem, the dynamics of the wheel/rail interaction mechanism was examined and a two part solution applied. The solution consisted of using a low coefficient of friction modifiers on the gage face of the high rail of the curve(s) in conjunction with a high positive coefficient of friction modifiers on the top of the rail head on both the high and low rails. In this configuration, lateral slip of the wheel tread across the rail head was significantly reduced, together with the more traditional flanging effects 011 the gage face of the high rail. The result was a significant reduction in the level of noise generated by all of the traffic types. In order to achieve this dual application at specific locations on the rail head, a high rail vehicle mounted application system was developed and utilized. The hi-rail based system allowed for a uniform and accurate application of the friction modifiers onto the rail. However, the friction modifiers deteriorated with time and traffic (as a function of the number of axle passes), and as such had to be reapplied on a regular and ongoing basis. This paper describes the development and application of this combination of friction modifiers to the high noise curve(s) as well as the determination of the rate of degradation of the friction modifiers under traffic. The testing of the Friction Modifiers (Lubricants) performance led to the development of a well defined friction modifier effectiveness degradation curve which served as the basis for an ongoing program of friction modifiers aimed at keeping the level of noise below a defined threshold. In addition, the need for a "reasonably long" interval between friction modifier applications led to the development of an extended life version of the friction modifiers that made them appropriate for use in an ongoing maintenance application.
Assessing Iron Complexation by Dissolved Organic Matter Using Mediated Electrochemical Oxidation
(ACS Earth and Space Chemistry, 2024-08-14) Hudson, Jeffrey M.; Luther, George W., III; Chin, Yu-Ping
FeII is an abundant reductant in the environment that participates in numerous biogeochemical cycles and pollutant attenuation. FeII in aquatic environments can exist as a complex with dissolved organic matter (DOM), where organic ligands in DOM can modulate iron’s redox potential (EH) and henceforth reactivity as a reductant. Previous studies have assessed the reactivity of FeII-complexes using probe compounds, although these compounds are limited in their ability to profile FeII oxidation across multiple thermodynamic conditions (i.e., both pH and EH) and fail to validate the EH of Fe(II)-complexes via their direct measurement. This study elucidated the redox potentials of FeII-DOM complexes via mediated electrochemical oxidation (MEO) and assessed the extent of FeII oxidation at two different applied EH and pH regimes. Furthermore, we used a Nernstian-based model calibrated with a training set between known iron-ligand thermodynamic stability constants and their respective measured potentials to indirectly determine the stability constants of both FeII and FeIII-DOM complexes as a function of EH and pH. This work highlights the versatility of MEO as an electrochemical technique and is the first to assess stability constants of Fe-complexes with aquatic DOM isolates. We also discuss linkages between speciation modeling and redox reactivity of FeII.
Backed-Up, Saturated, and Stagnant: Effect of Milldams on Upstream Riparian Groundwater Hydrologic and Mixing Regimes
(Water Resources Research, 2022-09-28) Sherman, Melissa; Hripto, Johanna; Peck, Erin K.; Gold, Arthur J.; Peipoch, Marc; Imhoff, Paul; Inamdar, Shreeram
How milldams alter riparian hydrologic and groundwater mixing regimes is not well understood. Understanding the effects of milldams and their legacies on riparian hydrology is key to assessing riparian pollution buffering potential and for making appropriate watershed management decisions. We examined the spatiotemporal effects of milldams on groundwater gradients, flow directions, and mixing regime for two dammed sites on Chiques Creek, Pennsylvania (2.4 m tall milldam), and Christina River, Delaware (4 m tall dam), USA. Riparian groundwater levels were recorded every 30 min for multiple wells and transects. Groundwater mixing regime was characterized using 30-min specific conductance data and selected chemical tracers measured monthly for about 2 years. Three distinct regimes were identified for riparian groundwaters—wet, dry, and storm. Riparian groundwater gradients above the dam were low but were typically from the riparian zone to the stream. These flow directions were reversed (stream to riparian) during dry periods due to riparian evapotranspiration losses and during peak stream flows. Longitudinal (parallel to the stream) riparian flow gradients and directions also varied across the hydrologic regimes. Groundwater mixing varied spatially and temporally between storms and seasons. Near-stream groundwater was poorly flushed or mixed during storms whereas that in the adjacent swales revealed greater mixing. This differential groundwater behavior was attributed to milldam legacies that include: berm and swale topography that influenced the routing of surface waters, varying riparian legacy sediment depths and hydraulic conductivities, evapotranspiration losses from riparian vegetation, and runoff input from adjoining roads. Key Points: - Milldams raise riparian groundwater levels, decrease hydraulic gradients, and cause reversals in groundwater flow - Milldam legacies contribute to reduced groundwater mixing in near-stream sediments - Altered groundwater regimes due to milldams could affect riparian water quality processes Plain Language Summary: Riparian zones can buffer streams from upland nitrogen pollution and are thus considered as important water quality management practices. How the presence of milldams affects groundwater flow paths and their buffering capacity is not known. This study showed that milldams back up stream water above dams, reduce the groundwater gradients from the upland to the stream, and also result in their reversal during summer dry conditions and floods. Milldams reduced the mixing of groundwaters for near-stream sediments. This response was attributed to the topographic and sediment conditions associated with the milldams.
Beyond the Wedge: Impact of Tidal Streams on Salinization of Groundwater in a Coastal Aquifer Stressed by Pumping and Sea-Level Rise
(Water Resources Research, 2024-09-27) Hingst, M. C.; Housego, R. M.; He, C.; Minsley, B. J.; Ball, L. B.; Michael, H. A.
Saltwater intrusion (SWI) is a well-studied phenomenon that threatens the freshwater supplies of coastal communities around the world. The development and advancement of numerical models has led to improved assessment of the risk of salinization. However, these studies often fail to include the impact of surface waters as potential sources of aquifer salinity and how they may impact SWI. Based on field-collected data, we developed a regional, variable-density groundwater model using SEAWAT for east Dover, Delaware. In this location, major users of groundwater from the surficial aquifer are the City of Dover and irrigation for agriculture. Our model includes salinized marshland and tidal streams, along with irrigation and municipal pumping wells. Model scenarios were run for 100 years and included changes in pumping rates and sea-level rise (SLR). We examined how these drivers of SWI affect the extent and location of salinization in the surficial aquifer by evaluating differences in chloride concentration near surface waters and the subsurface freshwater-saltwater interface. We found the presence of the marsh inverts the typical freshwater-saltwater wedge interface and that the edge of the interface did not migrate farther inland. Additionally, we found that tidal streams are the dominant pathways of SWI at our site with salinization from streams being exacerbated by SLR. Our results also show that spatial distribution of pumping affects both the magnitude and extent of salinization, with an increase in concentrated pumping leading to more intensive salinization than a more widely distributed increase of the same total pumping volume. Key Points - Presence of a saltmarsh inverts the freshwater-saltwater interface in our study location - Tidal streams contribute substantially to salinization of inland groundwater - Concentrated pumping led to more intensive salinization than widespread pumping
Biochar and zero-valent iron sand filtration simultaneously removes contaminants of emerging concern and Escherichia coli from wastewater effluent
(Biochar, 2023-07-19) Zhu, Linyan; Chattopadhyay, Suhana; Akanbi, Oluwasegun Elijah; Lobo, Steven; Panthi, Suraj; Malayil, Leena; Craddock, Hillary A.; Allard, Sarah M.; Sharma, Manan; Kniel, Kalmia E.; Mongodin, Emmanuel F.; Chiu, Pei C.; Sapkota, Amir; Sapkota, Amy R.
Advanced treated municipal wastewater is an important alternative water source for agricultural irrigation. However, the possible persistence of chemical and microbiological contaminants in these waters raise potential safety concerns with regard to reusing treated wastewater for food crop irrigation. Two low-cost and environmentally-friendly filter media, biochar (BC) and zero-valent iron (ZVI), have attracted great interest in terms of treating reused water. Here, we evaluated the efficacy of BC-, nanosilver-amended biochar- (Ag-BC) and ZVI-sand filters, in reducing contaminants of emerging concern (CECs), Escherichia coli (E. coli) and total bacterial diversity from wastewater effluent. Six experiments were conducted with control quartz sand and sand columns containing BC, Ag-BC, ZVI, BC with ZVI, or Ag-BC with ZVI. After filtration, Ag-BC, ZVI, BC with ZVI and Ag-BC with ZVI demonstrated more than 90% (> 1 log) removal of E. coli from wastewater samples, while BC, Ag-BC, BC with ZVI and Ag-BC with ZVI also demonstrated efficient removal of tested CECs. Lower bacterial diversity was also observed after filtration; however, differences were marginally significant. In addition, significantly (p < 0.05) higher bacterial diversity was observed in wastewater samples collected during warmer versus colder months. Leaching of silver ions occurred from Ag-BC columns; however, this was prevented through the addition of ZVI. In conclusion, our data suggest that the BC with ZVI and Ag-BC with ZVI sand filters, which demonstrated more than 99% removal of both CECs and E. coli without silver ion release, may be effective, low-cost options for decentralized treatment of reused wastewater. Graphical Abstract available at: https://doi.org/10.1007/s42773-023-00240-y Highlights - The efficacy of BC, Ag-BC, and ZVI sand filtration, and their combinations, in removing contaminants from reused water was evaluated. - Ag-BC, ZVI, BC with ZVI and Ag-BC with ZVI demonstrated > 90% removal of E. coli. - BC, Ag-BC, BC with ZVI and Ag-BC with ZVI demonstrated efficient removal of selected contaminants of emerging concern.
Biophysical flocculation reduces variability of cohesive sediment settling velocity
(Communications Earth & Environment, 2023-04-24) Ye, L.; Penaloza-Giraldo, J. A.; Manning, A. J.; Holyoke, J.; Hsu, T.-J.
Biophysical cohesion, introduced predominantly by Extracellular Polymeric Substances (EPS) during mineral flocculation in subaqueous environments, plays important role in morphodynamics, biogeochemical cycles and ecosystem processes. However, the mechanism of how EPS functioning with cohesive particles and affects settling behaviors remain poorly understood. We measure initial flocculation rate, floc size and settling velocity of mineral and artificial EPS (Xanthan gum) mixtures. Combining results from these and previous studies demonstrate coherent intensification of EPS-related flocculation compare with those of pure mineral and oil-mineral mixtures. Importantly, the presence of EPS fundamentally changes floc structure and reduces variability of settling velocity. Measured data shows that ratios of microfloc and macrofloc settling velocity for pure mineral flocs is 3.9 but greatly reduced to a lowest value of 1.6 due to biological EPS addition. The low variability of settling velocity due to EPS participation explains the seemingly inconsistent results previously observed between field and laboratory studies.
Bladder expandable robotic system and UV materials for rapid internal pipeline repair
(SAMPE Conference Proceedings 2023, 2023-04-18) Tierney, John J.; Vanarelli, Alex; Fuessel, Lukas; Abu-Obaid, Ahmad; Sauerbrunn, Steve; Das, Shagata; Deitzel, Joseph; Tatar, Jovan; Heider, Dirk; Shenton, Harry W. III; Kloxin, Christopher J.; Sung, Dae Han; Thostenson, Erik; Gillespie, John W. Jr.
This paper describes a novel composite placement process to fabricate stand-alone structural pipe within existing legacy pipelines—with no disruption in gas service. The process utilizes low-cost, UV-curable, glass fiber reinforced plastics (GFRP) for discrete preforms made from continuous fiber fabrics. These sections are designed to meet 50-year service life by addressing the unique loading conditions of the pipe repair allowing for the design customization of the preforms to accommodate the state of pipe corrosion, access points or other local features that may vary along the length of the pipe. The approach offers maximum design flexibility and customization while minimizing installation time and cost. The preforms are fabricated above ground using rapid automated manufacturing methods for quality control. The preforms are transported by a tethering system to the robot. The robot is comprised of a self-propelled dual inflation expandable bladder system that places, consolidates, and cures standard or custom composite sections along the entire pipe length in a continuous co-cure process. This system is designed to adapt to pipe features that include lateral tees, service connections, joints, gaps, and irregular cross sections. In addition, variable thickness composite sections can be placed along the pipe where exposed to high external loads under railroads, highways, airports or where soil erosion and movement occurs. This paper presents the robot design, assessment of UV curable resins, embedded sensing methods, and fabrication of pipe sections with this system.
Block-structured, equal-workload, multi-grid-nesting interface for the Boussinesq wave model FUNWAVE-TVD (Total Variation Diminishing)
(Geoscientific Model Development, 2022-07-18) Choi, Young-Kwang; Shi, Fengyan; Malej, Matt; Smith, Jane M.; Kirby, James T.; Grilli, Stephan T.
We describe the development of a block-structured, equal-CPU-load (central processing unit), multi-grid-nesting interface for the Boussinesq wave model FUNWAVE-TVD (Fully Nonlinear Boussinesq Wave Model with Total Variation Diminishing Solver). The new model framework does not interfere with the core solver, and thus the core program, FUNWAVE-TVD, is still a standalone model used for a single grid. The nesting interface manages the time sequencing and two-way nesting processes between the parent grid and child grid with grid refinement in a hierarchical manner. Workload balance in the MPI-based (message passing interface) parallelization is handled by an equal-load scheme. A strategy of shared array allocation is applied for data management that allows for a large number of nested grids without creating additional memory allocations. Four model tests are conducted to verify the nesting algorithm with assessments of model accuracy and the robustness in the application in modeling transoceanic tsunamis and coastal effects.
BNSF Tests Risk-Based Ultrasonic Detection
(Railway Track & Structures Magazine, 2001-02) Palese, J. W.; Zarembski, Allan M.; Patel, P. K.
As the railroad industry continues its focus on increased safety, rail defects and resulting rail caused derailments, have become an important area of interest. Analysis of FRA statistics on reportable mainline derailments, attributed to rail defects, shows an overall industry increase in reported derailments per billion gross ton mile (BGTM) of 4% in the period 1997 to 1999 [1,2]. This trend is illustrated in Figure 1 together with the corresponding increase in the average cost of rail related derailments for that same time period of more than 40%. Examining the FRA derailment data further, Figure 2 shows the distribution of derailments by rail defect type along with the average cost of derailment for that defect type. This figure clearly shows that the most predominant cause of rail related derailments is the transverse defect or TD class of defects, with the Detail Fracture (DF) representing the second most common cause of rail related derailments. For the entire range of rail defects, the average derailment cost varied from $200,000 to $1,400,000 depending on defect type, with an overall average of the order of $400,000. Note, this is FRA reportable cost only, the actual cost of the derailment, which could include loss of lading, train delays, or train rerouting, can be double that amount. This increasing trend in rail related derailments suggests that there is a need for improved rail maintenance and/or inspection practices to prevent the occurrence of these defects or to find the defects before they cause these expensive derailments. These improvements can take several forms, to include more aggressive rail replacement or maintenance practices or improved rail testing equipment. However, the focus of this article is on a easier to implement approach, one that can be applied almost immediately with a relatively modest impact on a railroad’s maintenance of way budget, specifically the improvement in the scheduling of conventional rail test equipment. As rail accumulates tonnage, it tends to develop more internal fatigue defects, based on various factors such as metallurgy of the rail, traffic (to include such factors as axle loading and speed), track support conditions, etc. This behavior is illustrated in Figure 3. As defects occur more frequently, it becomes important to test more frequently in order to insure that internal defects can be located and replaced before they have the opportunity to propagate to failure, and possibly result in a derailment. Earlier studies have indicated that approximately 1.3 derailments occur per thousand defects (detected plus service), thus highlighting the importance of matching test frequency to the rate of defect occurrence [3]. Simplistic rail test scheduling approaches, such as those based on annual tonnage levels, which do not account for aging rails and corresponding increased defects, do not give the railroad the flexibility to adjust test frequency to the actual rail conditions encountered. Likewise, simplified “rules of thumb” for scheduling ultrasonic testing, while often accounting for such factors as age of rail (usually in cumulative MGT) annual traffic density, class of track, type of traffic, defect counts, etc., do not do so in a manner that is directly tied into the “risk” of a derailment occurring. Rather, it is necessary to have a risk based scheduling methodology which makes use of site specific and directly measurable performance parameters that, in turn, can be related to a defined level of risk. Such a methodology was developed by US Department of Transportation Center Volpe National Transportation Systems Center [4], and further enhanced by ZETA-TECH Associates, Inc. [5].
Burlington Northern's Assessment of the Economics of High Capacity/ Heavy Axle Load Cars
(American Railway Engineering Association, 1990-05) Zarembski, Allan M.; Newman, R. R.; Resor, R. R.
North American freight cars and trains have been growing heavier for many years. For the most part this has been a response to competitive pressures, the inflexible nature of train crew costs, and the changing mix of traffic. The shift in traffic towards bulk commodities and unit trains (grain, coal, ore, and aggregates) was one manifestation of this change in traffic mix and its consequent movement toward heavier cars. Figure I shows graphically the near doubling of average car capacity since 1929. This trend to heavier cars has been accompanied by considerable research into the costs and benefits of larger cars and heavier trains. In particular, the issue of increasing car size, and consequently increasing axle loads, has been the subject of much examination and discussion. There s also the related issue of increasing the loading of existing cars. This issue was raised in 1986 at the Third International Heavy Haul Railways Conference (I) attended by representatives of Burlington Northern's Research & Development Department. In the opening paper of the conference, representatives of Mt. Newman Mining Co. and BHP Melbourne Research Laboratories stated that heavier axle loads were not only technically feasible but were also economically feasible under the conditions as experienced, tested, and applied in Australian heavy haul operations. This paper emphasized that since existing ore cars were only loaded to about 75% capacity, axle loads could be further increased. Following the First International Heavy Haul Railways Conference in 1978, axle loads were increased by the Australians to 33 tonnes (36.3 tons) and this axle load was adopted as a system wide standard. The successful gain led to adoption of an additional axle load increase to 35 tonnes (38.5 tons). Even higher axle loads appeared economically justifiable; however, the 35 tonnes provided an additional margin of comfort below the 37 tonnes (40.7 tons) level at which the Australian road's studies indicated that major, cost-impacting bridge upgradings would be required. As illustrated in Figure 2, the main point of the Australian findings was that axle loads between 33 and 37 tonnes (36 and 41 tons) were expected to reduce total railway maintenance and replacement costs. Costs were reduced 1-4% by increasing axle loads from 36 to 40 tons but began increasing beyond that point. In many ways, BN's Northern Coal Route is similar to the Mt. Newman Railway. It is composed almost entirely of welded rail, the bulk of it being 132 1b. section. Locomotive-borne lubrication is used and profile grinding of the rail is carried out twice per year. The vast majority of the traffic on the line is unit coal traffic. However, since BN's Northern Coal route is not an isolated captive railway, maintenance standards for both track and structures may be less rigorous. Mixed traffic and bridges of varying age and capacity present problems not encountered by the Australian railways.
Causality between fluid motions and bathymetric features
(Journal of Fluid Mechanics, 2022-02-07) Hsu, Tian-Jian
Can morphodynamic problems be solved using a first-principles approach in multiphase fluid mechanics? This is the holy grail for many sediment transport researchers but has yet to be achieved in practice. Using a fully resolved direct numerical simulation for turbulent flow over a bed of spheres, the study of Scherer et al. (J. Fluid Mech., vol. 930, 2022, A11) investigates the onset of morphodynamics from a statistically flat bed. The study shows that the formation of streamwise-aligned sediment ridges is due to large-scale turbulent streaks in the logarithmic layer, which drives local sediment sweeps and bursts. The study provides a solid physical justification for introducing initial perturbations in other reduced-complexity models and opens up new perspectives for simulating sediment transport and morphodynamic problems using high-fidelity models.
Characterization of an Unconventional Rhodopsin from the Freshwater Actinobacterium Rhodoluna lacicola
(American Society for Microbiology., 2015-06-08) Keffer, J. L.; Hahn, M. W.; Maresca, Julia Anne; J.L. Keffer, M.W. Hahn, J.A. Maresca; Keffer, J. L.; Maresca, Julia Anne
Rhodopsin-encoding microorganisms are common in many environments. However, knowing that rhodopsin genes are present provides little insight into how the host cells utilize light. The genome of the freshwater actinobacterium, Rhodoluna lacicola encodes a rhodopsin of the uncharacterized actinorhodopsin family. We hypothesized that actinorhodopsin was a light-activated proton pump, and confirmed this by heterologously expressing R. lacicola actinorhodopsin in retinal-producing Escherichia coli. However, cultures of R. lacicola did not pump protons, even though actinorhodopsin mRNA and protein were both detected. Proton pumping in R. lacicola was induced by providing exogenous retinal, suggesting that the cells lacked the retinal cofactor. We used HPLC and oxidation of accessory pigments to confirm that R. lacicola does not synthesize retinal. These results suggest that in some organisms, the actinorhodopsin gene is constitutively expressed, but rhodopsin-based light capture may require cofactors obtained from the environment.
ChemisTree: A Novel, Interactive Chemistry Game to Teach Students about Electron Configuration
(Journal of Chemical Education, 2024-01-12) Goldman, Slade; Coscia, Katie A.; Genova, Lauren A.
Electron configuration provides insight into the chemical behaviors of elements and is an important concept for students to master in introductory chemistry. To better strengthen undergraduate students’ mastery of electron configurations of atoms and ions, we designed a novel, interactive chemistry game called ChemisTree that uses active-learning techniques (e.g., physically building electron configurations onto a game board, small group work, and whole class discussion) and incorporates the three rules for electrons filling orbitals (Aufbau principle, Pauli exclusion principle, and Hund’s rule), using LEGO tiles and plates to represent electrons and orbitals. Students watch an introductory video explaining the rules and components of the game prior to applying their knowledge of electron configuration by working in small groups to build the orbital diagrams of atoms and ions using the materials provided in their ChemisTree game kits. Student understanding is assessed using multiple-choice pre/post-test questions, scoring sheets with peer discussion, and self-reported postactivity evaluations. Students who played the game scored significantly higher in the post-test (62.7%) compared to the pre-test (51.2%), representing an 11.5% increase in average score. Here we provide details about the activity and present data suggesting that student understanding of electron configuration is improved.

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