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Dynamic Analysis for the Global Performance of An SPM-Feeder-Cage System Under Waves and Currents

China Ocean engineering 2015年第3期29卷 415-430页

作者： Cristian CIFUENTES M.H.KIM Ocean Engineering Program Department of Civil Engineering Texas A&M University College Station

In the present study, the dynamic response of a coupled SPM-feeder-cage system under irregular waves and shear currents is analyzed. A numerical model is developed by using the commercial software Orca Flex. Hydrodynamics coefficients of the vessel are calculated by using a 3D diffraction/radiation panel program. First- and second-order wave forces are included in the calculations. Morison equation is used to compute the drag force on line elements representing the net. Drag coefficients are determined at every time step in the simulation considering the relative normal velocity between the structural elements and the fluid flow. The dynamic response of the coupled system is analyzed for various environments and net materials. The results of the study show the effects of solidity ratio of the net and vertical positions of the cage on the overall dynamic response of the system, confirming the viability of this type of configuration for future development of offshore aquaculture in deep waters.

关键词： offshore aquaculture SPM(single point mooring) feeder vessel connecting lines operational/survival environment drag force equivalent net cage grouping net modeling line tensions solidity ratio

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GPU Implementation of a Gas-Phase Chemistry Solver in the CMAQ Chemical Transport Model

ACS ES&T air

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ACS ES&T air 2025年第2期2卷 226-235页

作者： Duncan Quevedo Khanh Do George Delic José Rodríguez-Borbón Bryan M Wong Cesunica E Ivey Department of Civil and Environmental Engineering University of California Berkeley California 94720 United States. Department of Chemical and Environmental Engineering University of California Riverside California 92557 United States. Center for Environmental Research and Technology Riverside California 92507 United States. Hiperism Consulting LLC Chapel Hill North Carolina 27514 United States. Department of Chemistry Department of Physics & Astronomy and Material Science & Engineering Program University of California Riverside California 92557 United States.

The Community Multiscale Air Quality (CMAQ) model simulates atmospheric phenomena, including advection, diffusion, gas-phase chemistry, aerosol physics and chemistry, and cloud processes. Gas-phase chemistry is often a major computational bottleneck due to its representation as large systems of coupled nonlinear stiff differential equations. We leverage the parallel computational performance of graphics processing unit (GPU) hardware to accelerate the numerical integration of these systems in CMAQ's CHEM module. Our implementation, dubbed CMAQ-CUDA, in reference to its use in the Compute Unified Device Architecture (CUDA) general purpose GPU (GPGPU) computing solution, migrates CMAQ's Rosenbrock solver from Fortran to CUDA Fortran. CMAQ-CUDA accelerates the Rosenbrock solver such that simulations using the chemical mechanisms RACM2, CB6R5, and SAPRC07 require only 51%, 50%, or 35% as much time, respectively, as CMAQv5.4 to complete a chemistry time step. Our results demonstrate that CMAQ is amenable to GPU acceleration and highlight a novel Rosenbrock solver implementation for reducing the computational burden imposed by the CHEM module.

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Spatio-temporal characterization of nonlinear forcing and response in turbulent channel flow

arXiv

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arXiv 2025年

作者： Huang, Yuting Toedtli, Simon S. Chini, Gregory P. McKeon, Beverley J. Mechanical and Civil Engineering California Institute of Technology PasadenaCA91125 United States National Center for Atmospheric Research BoulderCO80301 United States Program in Integrated Applied Mathematics Department of Mechanical Engineering University of New Hampshire DurhamNH03824 United States Department of Mechanical Engineering Center for Turbulence Research Stanford University StanfordCA94305 United States

The quadratic convection term in the incompressible Navier-Stokes equations is considered as a nonlinear forcing to the linear resolvent operator, and it is studied in the Fourier domain through the analysis of interactions between triadically compatible wavenumber-frequency triplets. A framework to quantify the triadic contributions to the forcing and response by each pair of triplets is developed and applied to data from direct numerical simulations of a turbulent channel at Reι ≈ 550. The linear resolvent operator is incorporated to provide the missing link from energy transfer between modes to the effect on the spectral turbulent kinetic energy. The coefficients highlight the importance of interactions involving large-scale structures, providing a natural connection to the modeling assumptions in quasi-linear (QL) and generalized quasi-linear (GQL) analyses. Specifically, it is revealed that the QL and GQL reductions efficiently capture important triadic interactions in the flow, especially when including of a small number of wavenumbers into the GQL large-scale base flow. Additionally, spatio-temporal analyses of the triadic contributions to a single mode representative of the near-wall cycle demonstrate the spatio-temporal nature of the triadic interactions and the effect of the resolvent operator, which selectively amplifies certain forcing profiles. The tools presented are expected to be useful for improving modeling of the nonlinearity, especially in QL, GQL, and resolvent analyses, and understanding the amplitude modulation mechanism relating large-scale fluctuations to the modulation of near-wall structures. © 2025, CC BY.

关键词： Navier Stokes equations

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Increasing risk of oppressive heatwaves over India in the future warming

arXiv

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arXiv 2025年

作者： Sudharsan, Naveen Singh, Jitendra Ghosh, Subimal Karmakar, Subhankar Environmental Science and Engineering Department Indian Institute of Technology Maharashtra Bombay India Department of Environmental Systems Science ETH Zürich Zürich Switzerland Department of Civil Engineering Indian Institute of Technology Maharashtra Bombay India Interdisciplinary Program in Climate Studies Indian Institute of Technology Maharashtra Bombay India Centre for Urban Science & Engineering Indian Institute of Technology Maharashtra Bombay India

The frequency of heatwave events has been increasing with climate change across the globe, causing devastating impacts on human and natural systems. Particularly, the co-occurrence of high temperature with high humidity has the potential of worse impacts on human health than extreme temperature alone. We use observations to examine the characteristics of extreme (high temperature and low humidity) and oppressive (high temperature and high humidity) heatwaves and their impacts on human mortality. We also use climate model simulations to understand the likelihood of heatwaves under varied warming conditions in future climates. We find an increasing trend in the number of days of extreme and oppressive heatwaves, with surprisingly a higher rate of increase in oppressive heatwaves. We also observe a higher correlation between oppressive heatwaves and historical heat-stress-related human deaths than extreme heatwaves, indicating more substantial impacts of oppressive heatwaves on the human population than extreme heatwaves. Further, our results show a five-fold increase in the number of days of oppressive heatwaves under 1.5°warming in both mid (2035-2065) and end (2070- 2100) of the 21st century, relative to the historical period (1975 to 2005) whereas the number of extreme heatwave days remains relatively constant in mid and end of this century. Remarkably, 2°warming results in an eight-fold and almost two-fold increase in the number of days of oppressive heatwaves by the end of the century relative to the historical period and 1.5°warming conditions. These results suggest that limiting the mean global warming to 1.5°can reduce the likelihood of oppressive and extreme heatwaves by 44% and 25% by the end of the century relative to the 2°warming world. Moreover, the remarkable increase in oppressive heatwave days highlights the elevated risk of heatwaves over densely populated countries and indicates an imminent need for adaptation measures. © 2025, CC BY.

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Review of mayflies (Insecta Ephemeroptera) as a bioindicator of heavy metals and microplastics in freshwater

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Science of the Total Environment 2025年 958卷 178057页

作者： Benhadji, Nadhira Kurniawan, Setyo Budi Imron, Muhammad Fauzul Institute of Technology and Life Sciences—National Research Institute Falenty Hrabska Avenue 3 Raszyn05-090 Poland Department of Chemical and Process Engineering Faculty of Engineering and Built Environment Universiti Kebangsaan Malaysia Selangor UKM Bangi43600 Malaysia Study Program of Environmental Engineering Department of Biology Faculty of Science and Technology Universitas Airlangga Campus C UNAIR Jalan Mulyorejo Surabaya60115 Indonesia Department of Water Management Faculty of Civil Engineering and Geosciences Delft University of Technology Stevinweg 1 CN Delft2628 Netherlands

Heavy metal and microplastic pollutions are prevalent in freshwater ecosystems, with many freshwater bodies being contaminated by one or both of these pollutants. Recent studies reported extreme detections of Cd, Pb and Zn, high concentrations of Cr, Pb and Cu and microplastics acting as vectors of pollutants, including heavy metals. Mayflies can serve as bioindicators of heavy metal contamination in freshwater ecosystems because changes in their community structure, physiology, and behaviour can reflect and help predict the concentrations of metals in these environments. This review discusses the ecological alterations induced by tissue metal concentration in mayflies and other macroinvertebrates. As sensitive taxa to heavy metal contamination, mayflies can reflect the impacts of this pollution through their ethology and relationship to the substrate, highlighting issues such as eutrophication, alterations in community structure, inhibitory effects and sediment toxicity. Mayflies are also highly affected by microplastic exposure, which leads to ingestion, bioaccumulation, biomagnification, habitat and community alteration, behavioural changes, physiology alteration and toxicity. Mayflies bioindication metrics for assessing the impact of heavy metals and microplastics include the examination of community alteration, functional feeding behaviour, molecular structure, dietary and toxicity impacts, bioaccumulation and biomagnification and biomarkers. Current challenges for the utilization of mayflies as bioindicators include temporal variations in sensitivity, lack of universally recognised protocols and need for standardised protocols for microplastic analysis. Additionally, the applicability of mayflies as bioindicators may vary across different ecosystems, emphasising the need for selecting suitable indicators that align with the unique characteristics of the ecosystem. © 2024 The Authors

关键词： Macroinvertebrates

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Upgradation of 2D applied element method (AEM) for soil-structure interaction (SSI)

Progress in Engineering Science

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Progress in engineering Science 2025年第2期2卷

作者： Hossain, Md Shakhawat Timsina, Kishor Gadagamma, Chaitanya Krishna Numada, Muneyoshi Kamal, ASM Maksud Meguro, Kimiro Department of Disaster Science and Climate Resilience University of Dhaka Dhaka Bangladesh Institute of Industrial Science the University of Tokyo Tokyo Japan Sustainable and Resilient Infrastructure Program Madan Bhandari University of Science and Technology Nepal Structural Engineering School of Engineering and Technology Asian Institute of Technology Thailand Department of Civil Engineering Chennai Institute of Technology India

The applied element method (AEM) can comprehensively analyze structural behavior from initial loading to complete collapse with simple material models. However, AEM research predominantly centers on structures, with limited exploration in the soil-structure interaction (SSI) context. Therefore, in this paper, essential upgrades have been integrated into AEM to analyze SSI effects. These upgrades include boundary conditions, damping, material models, and failure criteria. Boundary conditions, including Free-H (Horizontal) with viscous damping boundaries, are crucial to analyzing the SSI effect. Rayleigh damping is employed to capture the dynamic response of the structure-soil system. The choice of material model is pivotal;the Hardin-Drnevich (HD) model is used to characterize soil behavior. Mohr Column failure criteria are integrated to predict soil failure. After incorporating these improvements, a verification process is conducted, including verification for fixed-based structures, boundary conditions, soil site response analysis, and the SSI. The results of the verification process ensure the model's ability to analyze SSI effectively. © 2025 Elsevier B.V.

关键词： Applied element method (AEM) Soil-structure interaction (SSI)

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Optimizing dispersion of torrefied spent coffee grounds for enhanced biochar-EVA composite properties through sodium percarbonate-assisted treatment

引用

Journal of Industrial and engineering Chemistry 2025年

作者： Lee, Kuan-Ting Gabriela, Situmorang Chen, Wei-Hsin Rajendran, Saravanan Selvarajoo, Anurita Department of Chemical and Materials Engineering Tunghai University Taichung407 Taiwan International Master Degree Program on Energy Engineering National Cheng Kung University Tainan701 Taiwan Department of Aeronautics and Astronautics National Cheng Kung University Tainan701 Taiwan Research Center for Smart Sustainable Circular Economy Tunghai University Taichung407 Taiwan Department of Mechanical Engineering National Chin-Yi University of Technology Taichung411 Taiwan Instituto de Alta Investigación Universidad de Tarapacá Arica1000000 Chile Department of Civil Engineering Faculty of Science and Engineering University of Nottingham Malaysia

This study aims to optimize biochar by combining 10 % sodium percarbonate with 90 % spent coffee grounds and torrefying at 300 °C for 30 min. Biochar enhances black color dispersion in a composite when blending the optimal biochar and ethylene vinyl acetate. The maximum carbon content of the optimal biochar is 59.97 %, exhibiting similar dispersion, packing density, pore size, and contact angle to carbon black. The optimal biochar's specific surface area and total pore volume are 7.12 m2·g−1 and 0.0018 cm3·g−1, respectively, 2.9 times and 1.2 times that of untreated torrefied spent coffee grounds with SP treated. The mechanical properties of the composite, which is blended with 15 wt% of the optimal biochar to ethylene vinyl acetate through trade-off analysis, indicate a tensile strength and Young's modulus of 1.03 MPa and 9.69 MPa, respectively. As the amount of blended optimal biochar increases, the tensile strength decreases while Young's modulus increases. Compared with a composite blended with the same 15 wt% of carbon black, the tensile strength and Young's modulus are 0.77 MPa and 9.55 MPa, respectively. In conclusion, the optimal biochar is a potential alternative material that could replace carbon black. This finding aligns with the developmental direction of achieving negative carbon emissions, promoting a circular economy and valorizing waste. © 2025 The Korean Society of Industrial and engineering Chemistry

关键词： Tensile strength

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BUILDUP FACTORS FOR POINT ISOTROPIC GAMMA RAY SOURCES IN INFINITE MEDIUM OF ORDINARY CONCRETE

引用

NUCLEAR engineering AND DESIGN 1967年第3期6卷 205-+页

作者： CHILTON, AB Civil Engineering Department and Nuclear Engineering Program University of Illinois Urbana Illinois USA

In order to provide more definitive values for buildup factors for point, isotropic gamma ray sources in an infinite medium of ordinary concrete, a Monte Carlo program has been undertaken to make such calculations. Previous approaches to this problem had been through the assumption of a Z eff for concrete and in interpolation in the existing Goldstein-Wilkins results for single elements. In addition to the approximate character of the old procedure, such calculations have been variable because different values of Z eff have been used by different workers. The specific method of Monte Carlo calculation is briefly described, with emphasis on the assumptions, approximations, and sources of data. The resulting data are estimated to have an uncertainty less than 5%. They are compared with results using the Z eff approach, and the asymptotic trends at very small and very large penetration distances are discussed.

关键词： Nuclear reactors

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ANALYSIS OF ACID-VOLATILE SULFIDE (AVS) AND SIMULTANEOUSLY EXTRACTED METALS (SEM) FOR THE ESTIMATION OF POTENTIAL TOXICITY IN AQUATIC SEDIMENTS

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ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 1993年第8期12卷 1441-1453页

作者： ALLEN, HE FU, GM DENG, BL Environmental Engineering Program Department of Civil Engineering University of Delaware Newark Delaware 19716

Acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) are operationally defined methods for the analysis of sulfide and associated metals in aquatic sediments. The SEM-to-AVS ratio has been useful in explaining the results of bioassay tests of metal toxicants. This paper describes apparatus that can be used in the evolution of sulfide from sediments and a method for the analysis of the evolved sulfide and the liberated metal. The method was studied with respect to gas flow rate, digestion time, and acid concentration. Liberated and trapped sulfide was determined by a colorimetric method of analysis. Using the apparatus and conditions described in this paper, the colorimetric method of analysis is capable of detecting AVS at concentrations normally encountered with a recovery of sulfide of at least 90%. High precision is possible if this apparatus is used. The limit of detection of the method is approximately 0.01 mumol/g dry sediment. We added 6 M HCl to produce a final concentration of approximately 1 M for the release of the AVS and SEM from unheated samples. We found that sulfide was not released from pyrite (FeS2) or copper sulfide (CuS) under these conditions. The liberation of copper from the two studied sediments indicates that copper was probably associated with another phase in these sediments. AVS is stable for several weeks in refrigerated or frozen samples.

关键词： ACID-VOLATILE SULFIDE SIMULTANEOUSLY EXTRACTED METALS SEDIMENT COPPER TOXICITY

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MEASUREMENT AND MODELING OF WESTERN WASHINGTON PRECIPITATION CHEMISTRY

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WATER AIR AND SOIL POLLUTION 1985年第1期26卷 71-84页

作者： VONG, RJ LARSON, TV COVERT, DS WAGGONER, AP Environmental Engineering and Science Program Department of Civil Engineering University of Washington Seattle USA

Precipitation was collected and chemically analyzed for a 1 yr period at four sites in western Washington. Spatial and seasonal variabilities in concentrations were identified with the highest concentrations nearest emission sources and in the summer. Multiple correlations among measured species revealed five groupings which were interpreted as the influences of seasalt, metals from a Cu smelter, an urban factor, soil, and acidic sulfate aerosol. A simple washout model predicted that the Cu smelter was the major contributor to a budget for rainwater sulfate. Measurement uncertainties were estimated for each analyte.

关键词： METEOROLOGY

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