26 research outputs found
Feasibility and Favourability Study Upend/Tilt-over Mechanism of Pioneering Spirit’s Jacket Lift System
No full textAllseas Group S.A. is a leading offshore contractor in the field of pipeline installation, heavy lifting and subsea construction. One of Allseas’ vessels is Pioneering Spirit. The main activities of Pioneering Spirit can be subdivided into pipeline installation, topside installation/removal and jacket installation/removal. The equipment of the first two activities has been successfully put into operation. The equipment to install and remove jackets (Jacket Lift System (JLS)) is currently under development. The mechanism to upend/tilt-over the Jacket Lift System is the subject of this graduation project. The design challenge of Pioneering Spirit’s Jacket Lift System is to install or remove a jacket with a height of at least 70 meters and a mass of up to 20 000 mt (in air) in a single lift/operation. In this thesis project, an additional design solution has been investigated and developed. The objective was to investigate the feasibility and favourability of various principles and concepts to upend/tilt-over a jacket using Pioneering Spirit. Key topics in the development of the design solution were the controllability of the operation, the compatibility of the system in the current appearance of Pioneering Spirit’s, the complexity of the operation and the investments costs to construct, operate and maintain the system. The design solution found in this graduation project consists of a tilting system that rotates over the stern of Pioneering Spirit. The system is driven by a pushing system installed on the reinforced transverse frames on the aftdeck of Pioneering Spirit. The system must be movable to relocate the centre of gravity before upending or after tilting-over of the system. The system is controlled by two winch systems, one attached to the tip of the tilting lift beams (Derrick Hoist system, consisting of 10 winches) and the other to the upper pivot point of the pushing system (Upend/Tilt-over Mechanism, consisting of 8 winches). The system can be controlled in both rotational directions using the two winch systems. The tilting lift beams and pushing system are connected by means of a roller/slider connection. The maximum forces, stability and controllability of the system were checked with a coarse dynamic mathematical model. The natural frequency of the system with and without jacket appeared to be in the same frequency range as the excitation response spectra. This was solved by stiffening the system by increasing the effective diameter of the winch systems and by applying pre-tension. Subsequently, the system appeared to be possibly instable during the first/last 18 degrees of the tilting operation. This was solved by applying an auxiliary construction during the first/last 30 degrees of the tilting process. The maximum response amplitude of the system was calculated by means of a calculation of the maximum excitation in the frequency domain (regular waves) and for time series (irregular waves) for the positions in which the Jacket Lift System can be positioned and all incoming wave directions. The maximum response amplitude of the system occurs in beam waves when the system is positioned vertically. Although the maximum response amplitude of the system is small, mainly because of the stiffness, the maximum forces in the system are exorbitantly large. To give an indication, the maximum tension in the Derrick Hoist System is 4125 mt. At a certain moment in the tilting procedure, the entire mass of the Jacket Lift System (15 000 mt) and Jacket (20 000 mt) is applied to the pivot points at the stern of Pioneering Spirit. In general, the static forces deliver the greatest contribution to the total force. The maximum loads are considered feasible, although strengthening measures must be taken.Offshore and Dredging Engineerin
Design, fabrication and validation of an ankle-foot orthosis simulator system to optimize mechanical characteristics of AFOs for humans with impaired locomotion
No full textThe muscles around the ankle (calf and dorsal flexors) are essential for performing activities in daily life, like walking. Neurological and muscular pathologies, such as stroke, cerebral palsy, spinal cord injury, muscle atrophy and post-polio syndrome, affect the ability of voluntary muscle control and/or muscle strength of such muscles. This severely impairs the gait function of many people worldwide. An ankle-foot orthosis (AFO) or ankle brace, which is an assistive device that provides support to the ankle and foot, are in many cases a solution. Therefore, patients are fitted with an AFO to promote a functional gait pattern. To optimize the resulting gait pattern, the mechanical characteristics of the AFO should be matched to the specific malfunctioning muscles of a patient. This especially holds for the stiffness of the AFO. Generally, the AFO should be stiff enough to support the ankle's function, but also compliant enough to not restrict voluntary motion.The optimal stiffness of an AFO for a patient can vary a lot, as the severity of the pathology differs and hence, the consequences, ranging from spastic to paralyzed muscles. It was found that issuing a sub-optimal AFO in the longer term may contribute to deterioration of physical function and gait. Thus, finding the optimal AFO joint stiffness for this group of patients and improving the speed of doing so, is an important clinical treatment goal.Currently, this is achieved by a trial-and-error method consisting of fitting the patient with several orthoses. This method is time consuming and can possibly result in a sub-optimal AFO prescription. Ideally a human-in-the-loop setup is developed to find the AFO characteristics during tests using an AFO simulator. The corresponding AFO can then be fabricated and fitted to that specific patient. Hence, increasing the speed and quality of providing an AFO to a patient. However, current solutions are too expensive.This assignment aims to create a proof of principle of a simplified, affordable, human-in-the-loop solution to vary the AFO stiffness, that enables clinicians to tune the AFO stiffness to a specific patient. This report describes the process of designing a lightweight AFO simulator with a continuously variable stiffness mechanism (VSM) and a predetermined torque-angle curve. The resulting design combines two key elements: A leaf spring of varying stiffness by changing the active length, and a cam part the serves as the transmission between the leaf spring and the AFO mockup. The design was fabricated and then validated with a dedicated AFO stiffness tester (BRUCE) based on manual deflection of the ankle-foot orthosis.It was shown that the predicted plantarflexion stiffness range closely resembled the measured stiffness values. However, the measured dorsiflexion stiffness range was roughly two times smaller than predicted.Concluding, the designed AFO simulator can change its stiffness, while being compact and lightweight. The potential of the design has been shown. Now it can be developed further into a fully functional AFO simulator system that can be worn by patients in a clinical gait laboratory setting.Mechanical Engineering | Biomechanical Design - BioRobotic
Can transgenic maize affect soil microbial communities?
No full textThe aim of the experiment was to determine if temporal variations of belowground activity reflect the influence of the Cry1Ab protein from transgenic maize on soil bacteria and, hence, on a regulatory change of the microbial community (ability to metabolize sources belonging to different chemical guilds) and/or a change in numerical abundance of their cells. Litter placement is known for its strong influence on the soil decomposer communities. The effects of the addition of crop residues on respiration and catabolic activities of the bacterial community were examined in microcosm experiments. Four cultivars of Zea mays L. of two different isolines (each one including the conventional crop and its Bacillus thuringiensis cultivar) and one control of bulk soil were included in the experimental design. The growth models suggest a dichotomy between soils amended with either conventional or transgenic maize residues. The Cry1Ab protein appeared to influence the composition of the microbial community. The highly enhanced soil respiration observed during the first 72 h after the addition of Bt-maize residues can be interpreted as being related to the presence of the transgenic crop residues. This result was confirmed by agar plate counting, as the averages of the colony-forming units of soils in conventional treatments were about one-third of those treated with transgenic straw. Furthermore, the addition of Bt-maize appeared to induce increased microbial consumption of carbohydrates in BIOLOG EcoPlates. Three weeks after the addition of maize residues to the soils, no differences between the consumption rate of specific chemical guilds by bacteria in soils amended with transgenic maize and bacteria in soils amended with conventional maize were detectable. Reaped crop residues, comparable to post-harvest maize straw (a common practice in current agriculture), rapidly influence the soil bacterial cells at a functional level. Overall, these data support the existence of short Bt-induced ecological shifts in the microbial communities of croplands' soils
Effects of sulfamethoxazole on soil microbial communities after adding substrate.
No full textThe effect of the antibiotic sulfamethoxazole (SMX) on soil bacteria was studied using two methods (leucine incorporation and Biolog plates) of estimating pollution-induced community tolerance (PICT). SMX was added to an agricultural soil in a microcosm setup. The addition of different substrates (manure and alfalfa), and a non-amended soil, were also studied over 5 weeks. PICT measurements were validated by comparison with other measurements. Community structure was assessed using phospholipid fatty acid (PLFA) analysis and community-level physiological profiling (CLPP), and bacterial growth was estimated using leucine incorporation. Increased PICT was found at SMX concentrations of 20 and 500 mg SMX kg(-1) soil in samples containing manure and alfalfa, and at 500 mg SMX kg(-1) soil in non-amended soil (only concentration tested) using leucine incorporation. No effect was seen at 1 mg SMX kg(-1) soil. It was not necessary to add any substrate to increase the microbial activity in order to detect the effects of a bacteriostatic toxicant such as SMX when using measures based on bacterial growth. Direct inhibition of bacterial growth 2 days after SMX addition was correlated to PICT. No major changes in PICT due to SMX addition were found when using Biolog plates. However, there was a tendency towards increased PICT at the higher SMX concentrations in the manure-amended soil. Thus, different methods of detecting PICT have different sensitivities in detecting the toxic effects of SMX The effects of substrate amendment were reflected by changes in the microbial community, estimated using both PLEA and CLPP SMX was found to have a clear effect at the two highest levels of SMX in the manure- and alfalfa-amended soils, with an increase in fungal and a decrease in bacterial PLFAs. Little difference in the PLFA composition was found in the non-amended soil. CLPP was only affected at the highest SMX concentration. Although different variables showed different sensitivities to the effects of SMX, the results were consistent with an initial decrease in bacterial growth rates of sensitive species, which eventually transformed into more tolerant species, altering the community composition. (C) 2009 Elsevier Ltd. All rights reserved
Leaders Needed: Experimental Evidence from Rural Producer Organizations in Senegal
No full textMost decisions are taken in group contexts where one persons behavior is affected by others. We explore drivers of coordination in Rural Producer Organizations (RPOs) of groundnut farmers in Senegal. We conduct a randomized controlled trial motivated by a theoretical model, where we varied the number and type of individuals invited to a training on collective commercialization. We use this variation to identify effects on subsequent commercialization behavior of members who did not attend the training. Our results suggest that non-trained individuals are likely to sell more through the group if a sufficient number of group leaders attended the training. KEYWORDS: Coordination, Leadership, Farmer Groups, Strategic Uncertainty, Collective Marketing, Field Experiments, Developmen
Dissipative particle dynamic simulation and experimental assessment of the impacts of humic substances on aqueous aggregation and dispersion of engineered nanoparticles.
No full textComprehensive experimental quantification and mapping of the aggregation and dispersion state of engineered nanoparticles (NPs) in the presence of humic substances is a great challenge. Dissipative particle dynamic (DPD) simulation was adopted to investigate the aggregation and dispersion mechanisms of NPs in the presence of a humic substance analog. Twelve different types of NPs including 2 metal-based NPs, 7 metal oxide-based NPs, and 3 carbon-based NPs in pure water (pH 3.0) and algae medium (pH 8.0) in the presence of a humic substance analogy were selected for experimental verification of the DPD simulation results. In agreement with results obtained with dynamic light scattering and phase analysis light scattering techniques, the simulations demonstrated that the presence of humic substances reduced the aggregation extent of the NPs. The DPD simulations showed that the stability and dispersity of the NPs increased first, and then decreased with increasing concentrations of humic substances. Moreover, there existed a concentration of humic substances where the NPs became more stable and more dispersed, which was experimentally verified in the case of all the NPs in the pure water and in the algae medium. Furthermore, theory and simulation indicate that both hydrophobic and hydrogen interaction play an important role in controlling the formation of NP aggregates in the presence of humic substances. Electrostatic interaction and steric repulsion are the main mechanisms underlying the effects of humic substances on the aqueous dispersion stability of NPs. Environ Toxicol Chem 2018;9999:1-8. © 2017 SETAC
Importance of exposure dynamics of metal-based nano-ZnO, -Cu and -Pb governing the metabolic potential of soil bacterial communities.
No full textMetal-based engineered nanomaterials (ENMs) are known to affect bacterial processes and metabolic activities. While testing their negative effects on biological components, studies traditionally rely on initial exposure concentrations and thereby do not take into consideration the dynamic behavior of ENMs that ultimately determines exposure and toxicity (e.g. ion release). Moreover, functional responses of soil microbial communities to ENMs exposure can be caused by both the particulate forms and the ionic forms, yet their relative contributions remain poorly understood. Therefore, we investigated the dynamic changes of exposure concentrations of three different types of ENMs (nano-ZnO, -Cu and -Pb) and submicron particles (SMPs) in relation to their impact on the capacity of soil bacterial communities to utilize carbon substrates. The different ENMs were chosen to differ in dissolution potential. The dynamic exposures of ENMs were considered using a time weighted average (TWA) approach. The joint toxicity of the particulate forms and the ionic forms of ENMs was evaluated using a response addition model. Our results showed that the effect concentrations of spherical nano-ZnO, -Cu and SMPs, and Pb-based perovskites expressed as TWA were lower than expressed as initial concentrations. Both particulate forms and ionic forms of spherical 18nm, 43nm nano-ZnO and 50nm, 100nm nano-Cu contribute to the overall response at the EC50 levels. The particulate forms for 150nm, 200nm and 900nm ZnO SMPs and rod-shaped 78nm nano-Cu mainly affected the soil microbial metabolic potential, while the Cu ions released from spherical 25nm nano-Cu, 500nm Cu SMPs and Pb ions released from perovskites mainly described the effects to bacterial communities. Our results indicate that the dynamic exposure of ENMs and relative contributions of particles and ions require consideration in order to pursue a naturally realistic assessment of environmental risks of metal-based ENMs
Examples of Amended Soils at the Beginning of the Experiment
No full text<p>Some soil samples before entering the 1.0-L pots after the addition of crop residues (reaped maize straw, see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.0020128#pcbi-0020128-g001" target="_blank">Figure 1</a>B). Please note the slightly different colors.</p
Multivariate Analysis of the Soils Amended with Transgenic Maize
No full text<p>PRCs of the summarized metabolic fingerprints of the two <i>Bt</i>-maize straws (both Nobilis and Prelude as conventional isoline control level as horizontal <i>x</i>-axis) according to all BIOLOG EcoPlate carbon sources (<i>n</i> = 3 in duplicate). Day 3 is the most significant by time for all maize cultivars (SD = ± 0.242, <i>p</i> = 0.064, <i>F</i>-ratio = 2.66).</p
