12 research outputs found
Pumpjets in de binnenvaart
No full textBigger ships are replacing the small ships, also at the Amsterdam-Rijnkanaal. A direct consequence is the use of larger main propellers and increased installed engine power in order to realize acceptable ship speeds. To improve the maneuverability, the power of auxiliary bow and stern propulsion systems has increased as well. This results in higher flow velocities and thus more damage to bed protections at berthing places. Especially pump jet thrusters as a bow propulsion system may attack the bed protections more severely due to a vertical component of the flow field induced by the pump jet which is directed towards the bed. The aim of this research is, in cooperation with Rijkswaterstaat, to develop an analytical model for the flow field induced by the pump jet thruster. Subsequently, the required dimensions of a bed protection has been determined as well as an investigation on the possible scour effects in case of an unprotected bed of the Amsterdam-Rijnkanaal. In order to meet this goal, an inventory of the bow propulsion systems in inland vessels has been made by conducting an inquiry. Subsequently, the different propulsion systems have been compared qualitatively. Since existing formulas are based on the circular free jet, this system is also treated in the comparison. In addition, a water jet (hydro jets can be distinguished in low-powered and high-powered jets), often used as propulsion system by ferries, has been taken into account due to the strong analogy with the circular free jet. As a result, both the ratio of decrease of axial velocities and diffusion of the jets in radial direction of a circular free jet strongly correspond to a high-powered water jet. However, the free propeller and transverse tunnel thrusters are considered to have a faster decrease of axial velocities and a faster diffusion of the flow field. The applied power and the induced turbulence seem to be the main reasons for the flow field characteristics. An essential part of this research is the derivation of an analytical model for the pump jet thruster induced flow field. The principle is based on the free propeller theory. In the case of a pump jet, part of the contraction takes place inside the unit. Furthermore, the flow field has been subdivided in three parts: initial outflow velocity, axial flow velocity and the flow velocity distribution in the region of the established flow. The coefficients in the model have been empirically determined using a simulation with a CFD model. This model has been compared to flow fields induced by different other propulsion systems. It results in a similar axial flow velocity decrease as a low-powered water jet. However, the pump jet diverges faster and with a greater angle than any other jet. The derived model has been used to investigate the stone stability at the toe of a sheet pile wall. Firstly, the flow velocities at the bed have been evaluated by looking at berthed ships in different conditions (fully loaded, partly loaded and unloaded). Secondly, a stability analysis of the bed material has been executed by using a method presented by Deltares. However, in order to protect the bed against the high flow velocities, large stone diameters are required. An alternative is allowing scour holes to occur, but the length of the sheet piling should be extended in order to maintain stability of the entire quay wall. The predicted maximum scour depths caused by a pump jet are in the same range of measured scour depths at the Amsterdam-Rijnkanaal. This means that scour holes may cause instability problems of the existing sheet pile walls.Hydraulic EngineeringCivil Engineering and Geoscience
NewProfiler
No full textA report about the development of NewProfiler, a behavioral target market system that we developed for NewNomads. The report describes the various stages of development of the software, the problems we encountered during the development and our solutions to these problems.Electrical Engineering, Mathematics and Computer Scienc
Comparison of ovarian cycles of Hungarian riverine fish species representing different spawning strategies
No full textInvestigations on the ovarian cycle of fish species that inhabit Hungarian rivers are necessitated by both environmental and economic reasons. The objective of our research was to explore new fundamental knowledge concerning the ovarian cycle of the white bream (Blicca bjoerkna, Linnaeus, 1758), barbel (Barbus barbus, Linnaeus, 1758), orfe (Leuciscus idus, Linnaeus, 1758) and nase (Chondrostoma nasus, Linnaeus, 1758). Histological investigation of ovaries and determination of proportions of oocytes in different stages of development is an appropriate method for the description of spawning characteristics of these species. Our results show that the GSI value for all four investigated species starts to increase at the end of summer and reaches its maximum before spawning. In the barbel and white bream, the presence of oocytes in the stage of cortical alveoli and the heterogeneous size of oocytes in the stage of vitellogenesis in the pre-spawning period indicate that barbel and white bream are multiple spawners. In contrast, in the orfe and nase, the absence of oocytes in the stage of cortical alveoli and the homogeneous size of cells in the stage of vitellogenesis indicate that orfe and nase are single spawners
Integrated Coastal Planning and Protection at Cijin, Kaohsiung
No full textChanges in coastal environment are the balancing process of nature. However, most of the constructions on the coast affect the environment, cause erosion and further impair people\ue2s right of access to the water due to lacking in understanding the coastal changes. In the past decade, the author of this dissertation has worked on coastal protection and restoration for Kaohsiung, including Cijin coastal restoration and Sizihwan landscape improvement etc., and provided new thoughts for the domestic planners dealing with coastal environment.
Affected by recent coastal development and environmental changes in Kaohsiung, Cijin coast has suffered serious erosion. Besides, drowning accidence often occurs caused by rip currents. In order to preserve this beautiful beach with a time-honored history, Kaohsiung City Government commenced the \ue2Cijin Coastline Protection Project\ue2 in 2009, the first domestic coastal restoration project employing offshore submerged breakwaters. The project was successfully completed in July 2013. In this study, numerical tools (GENESIS, MIKE 21) and hydraulic model tests were adopted to investigate littoral drift issue, formulate beach stabilization policy, and evaluate the effects of beach nourishment. The results showed that predominant direction is northward during the prevailing wave season. At Cihou Mountain, wave deflects offshore, and deposits sediment into the navigation channel at the end of southern breakwater for the Kaohsiung First Harbor. Therefore, the best beach stabilization scheme for Cijin coast is to apply offshore submerged breakwaters (or with offshore breakwaters) cooperating with beach nourishment. In this way, the erosion at Cijin can be mitigated, as well as the speed of rip currents, and the safety of all beach users can be insured. As to the evaluation of beach nourishment, the results indicated that it was necessary to integrate the project with beach nourishment, otherwise the native beach sediment in the gap between the submerged break waters would be transported in their lee, thus causing adverse effect to the beach.
Upon the completion of the Cijin Coast Protection Project, the overall coastal environment, including submerged breakwaters, offshore breakwaters, the bathing beach, the coastal landscape trail, and the sea-lookout platform all together expand the recreational space from the land to the seaside by connecting with the existing coastal park. It has also enhanced the opportunities for the tourism industry and accelerated the development of service industry in Cijin area. The work described in this report not only initiates a domestic pioneer project of coastal protection, but also serves as an indicator of significance
Large eddy simulations of bubbly flows and breaking waves with smoothed particle hydrodynamics
No full textFor turbulent bubbly flows, multi-phase simulations resolving both the liquid and bubbles are prohibitively expensive in the context of different natural phenomena. One example is breaking waves, where bubbles strongly influence wave impact loads, acoustic emissions and atmospheric-ocean transfer, but detailed simulations in all but the simplest settings are infeasible. An alternative approach is to resolve only large scales, and model small-scale bubbles adopting sub-resolution closures. Here, we introduce a large eddy simulation smoothed particle hydrodynamics (SPH) scheme for simulations of bubbly flows. The continuous liquid phase is resolved with a semi-implicit isothermally compressible SPH framework. This is coupled with a discrete Lagrangian bubble model. Bubbles and liquid interact via exchanges of volume and momentum, through turbulent closures, bubble breakup and entrainment, and free-surface interaction models. By representing bubbles as individual particles, they can be tracked over their lifetimes, allowing closure models for sub-resolution fluctuations, bubble deformation, breakup and free-surface interaction in integral form, accounting for the finite time scales over which these events occur. We investigate two flows: bubble plumes and breaking waves, and find close quantitative agreement with published experimental and numerical data. In particular, for plunging breaking waves, our framework accurately predicts the Hinze scale, bubble size distribution, and growth rate of the entrained bubble population. This is the first coupling of an SPH framework with a discrete bubble model, with potential for cost-effective simulations of wave-structure interactions and more accurate predictions of wave impact loads. © The Author(s), 2023. Published by Cambridge University Press
Brand Search.
No full textConsumers frequently buy the products they find most easily. This has forced manufacturers and retailers to invest in package design, shelf layouts, and expensive advertising campaigns to facilitate findability of their products. Surprisingly, there is no research in marketing that investigates how consumers localize products, which we call brand search. This dissertation investigates the brand search process and develops a statistical model that describes the eye movements of consumers while they are searching for a specific product. The proposed model uncovers the search strategies of consumers and suggests which marketing tools manufacturers and retailers may use to influence this process.
An autonomous, in situ light-dark bottle device for determining community respiration and net community production
No full textAuthor Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography-Methods 16 (2018): 323-338, doi:10.1002/lom3.10247.We describe a new, autonomous, incubation-based instrument that is deployed in situ to
determine rates of gross community respiration and net community production in marine and aquatic
ecosystems. During deployments at a coastal pier and in the open ocean, the PHORCYS
(PHOtosynthesis and Respiration Comparison-Yielding System) captured dissolved oxygen fluxes
over hourly timescales that were missed by traditional methods. The instrument uses fluorescence-quenching optodes fitted into separate light and dark chambers; these are opened and closed with
piston-like actuators, allowing the instrument to make multiple, independent rate estimates in the
course of each deployment. Consistent with other studies in which methods purporting to measure
the same metabolic processes have yielded divergent results, respiration rate estimates from the
PHORCYS were systematically higher than those calculated for the same waters using a traditional
two-point Winkler titration technique. However, PHORCYS estimates of gross respiration agreed
generally with separate incubations in bottles fitted with optode sensor spots. An Appendix describes
a new method for estimating uncertainties in metabolic rates calculated from continuous dissolved
oxygen data. Multiple successful, unattended deployments of the PHORCYS represent a small step
toward fully autonomous observations of community metabolism. Yet the persistence of unexplained
disagreements among aquatic metabolic rate estimates — such as those we observed between rates
calculated with the PHORCYS and two existing, widely-accepted bottle-based methods — suggests
that a new community intercalibration effort is warranted to address lingering sources of error in
these critical measurements.This research was supported by the U.S.
National Science Foundation (awards OCE-1155438 to B.A.S.V.M., J.R.V., and R.G.K., and OCE-
1059884 to B.A.S.V.M.), the Woods Hole Oceanographic Institution through a Cecil and Ida Green
Foundation Innovative Technology Award and an Interdisciplinary Science Award, and a U.S.
Environmental Protection Agency (EPA) STAR Graduate Fellowship to J.R.C. under Fellowship
Assistance Agreement no. FP-91744301-0
The molecular products and biogeochemical significance of lipid photooxidation in West Antarctic surface waters
No full textAuthor Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 232 (2018): 244-264, doi:10.1016/j.gca.2018.04.030.The seasonal depletion of stratospheric ozone over the Southern Hemisphere allows abnormally
high doses of ultraviolet radiation (UVR) to reach surface waters of the West Antarctic Peninsula (WAP)
in the austral spring, creating a natural laboratory for the study of lipid photooxidation in the shallow
mixed layer of the marginal ice zone. The photooxidation of lipids under such conditions has been
identified as a significant source of stress to microorganisms, and short-chain fatty acids altered by
photochemical processes have been found in both marine aerosols and sinking marine particle material.
However, the biogeochemical impact of lipid photooxidation has not been quantitatively compared at
ecosystem scale to the many other biological and abiotic processes that can transform particulate organic
matter in the surface ocean. We combined results from field experiments with diverse environmental data,
including high-resolution, accurate-mass HPLC-ESI-MS analysis of lipid extracts and in situ
measurements of ultraviolet irradiance, to address several unresolved questions about lipid photooxidation
in the marine environment. In our experiments, we used liposomes — nonliving, cell-like aggregations of
lipids — to examine the photolability of various moieties of the intact polar diacylglycerol (IP-DAG)
phosphatidylcholine (PC), a structural component of membranes in a broad range of microorganisms. We
observed significant rates of photooxidation only when the molecule contained the polyunsaturated fatty
acid (PUFA) docosahexaenoic acid (DHA). As the DHA-containing lipid was oxidized, we observed the
steady ingrowth of a diversity of oxylipins and oxidized IP-DAG; our results suggest both the intact IPDAG
the degradation products were amenable to heterotrophic assimilation. To complement our
experiments, we used an enhanced version of a new lipidomics discovery software package to identify the
lipids in water column samples and in several diatom isolates. The galactolipid digalactosyldiacylglycerol
(DGDG), the sulfolipid sulfoquinovosyldiacylglycerol (SQDG) and the phospholipids PC and
phosphatidylglycerol (PG) accounted for the majority of IP-DAG in the water column particulate (≥ 0.2
μm) size fraction; between 3.4 and 5.3 % of the IP-DAG contained fatty acids that were both highly
polyunsaturated (i.e., each containing ≥ 5 double bonds). Using a broadband apparent quantum yield (AQY) that accounted for direct and Type I (i.e., radical-mediated) photooxidation of PUFA-containing
IP-DAG, we estimated that 0.7 ± 0.2 μmol IP-DAG m-2 d-1 (0.5 ± 0.1 mg C m-2 d-1) were oxidized by
photochemical processes in the mixed layer. This rate represented 4.4 % (range, 3-21 %) of the mean
bacterial production rate measured in the same waters immediately following the retreat of the sea ice.
Because our liposome experiments were not designed to account for oxidation by Type II photosensitized
processes that often dominate in marine phytodetritus, our rate estimates may represent a sizeable
underestimate of the true rate of lipid photooxidation in the water column. While production of such
diverse oxidized lipids and oxylipins has been previously observed in terrestrial plants and mammals in
response to biological stressors such as disease, we show here that a similar suite of molecules can be
produced via an abiotic process in the environment and that the effect can be commensurate in magnitude
with other ecosystem-scale biogeochemical processes.J.R.C. acknowledges support
from a U.S. Environmental Protection Agency (EPA) STAR Graduate Fellowship (Fellowship
Assistance agreement FP-91744301-0). This work was also supported by U.S. National
Science Foundation awards OCE-1059884 and PLR-1543328 to B.A.S.V.M., NSF award PLR-
1341479 to A. M., the Gordon and Betty Moore Foundation through grant GBMF3301 to B.A.S.V.M.,
and a WHOI Ocean Ventures Fund award to J.R.C
A multimodal dataset for authoring and editing multimedia content: The MAMEM project
No full textWe present a dataset that combines multimodal biosignals and eye tracking information gathered under a human-computer interaction framework. The dataset was developed in the vein of the MAMEM project that aims to endow people with motor disabilities with the ability to edit and author multimedia content through mental commands and gaze activity. The dataset includes EEG, eye-tracking, and physiological (GSR and Heart rate) signals collected from 34 individuals (18 able-bodied and 16 motor-impaired). Data were collected during the interaction with specifically designed interface for web browsing and multimedia content manipulation and during imaginary movement tasks. The presented dataset will contribute towards the development and evaluation of modern human-computer interaction systems that would foster the integration of people with severe motor impairments back into society
Discernment of relevation in the Gospel of Matthew
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
