204 research outputs found
A design methodology for low-cost, high-performance capacitive sensors
No full textElectrical Engineering, Mathematics and Computer Scienc
An Integrated Knowledge Based Engineering Mechatronics Modeling Approach to Support the Design of Unstable and Unmanned Aircraft
No full textThe commercial transport aircraft industry is currently developing new “more electric aircraft” (MEA) designs in which various conventional mechanical, hydraulic and pneumatic power systems are replaced with electrically-based power systems. Their objective is to improve the overall flight performance by reducing the aircraft weight and by a lower overall energy requirement for the systems. The vision for the future is to ultimately replace all systems with electrical systems and even to replace a part of the fuel used as primary source of energy for the propulsion system by an electrical power supply and thereby to achieve either a hybrid electric aircraft (HEA) or even all electric aircraft (AEA) if permitted by future developments in battery technology. In recent years, many small scale electric aircraft were developed to demonstrate the AEA concept. It has been determined that although the MEA, HEA and AEA concepts reduce the overall complexity of the aircraft, it significantly increases the complexity of electrical and electronic systems (E/E systems) and their integration into the aircraft, introducing a new challenge for the aircraft design industry. Two specific categories of aircraft, currently in operation, face the same challenge. These categories are; (1) unmanned aerial vehicles (UAVs), which by nature have more electrical and electronic systems (E/E systems) on-board and require an automatic flight control system due to the absence of a pilot and (2) aircraft which are inherently unstable and therefore require automatic flight control systems for stabilization. These two aircraft categories can be classified as typical mechatronic products. E/E systems have a significant impact on the overall flight performance, directly determine the flying qualities of aircraft, and are critical for safety. Thus, these systems should be developed synchronously with the other traditional engineering domains such as aerodynamics, structures and propulsion. However, several challenges need to be overcome before this can be achieved effectively. Three specific challenges are identified and addressed in the current research study: \u95 The development of high fidelity multiphysics simulation models for analysis and development of the E/E systems is a complex, time consuming and multidisciplinary task that requires a large amount of manual work from simulation experts; \u95 The design of consistent automatic flight control systems for use throughout the entire flight envelope and for all aircraft weight and c.g. combinations is labor intensive and requires the availability of high fidelity multiphysics simulation models in the early design phases; \u95 The development of control software components is prone to errors due to inconsistencies between the description of the top level physical configuration, the control architecture and the associated software components. Traditional aircraft design methods which are largely dominated by the mechanical engineering domains are not suitable to synchronously design complex integrated E/E systems. Moreover, the conventional design process, which is sequential to a large extent, cannot support concurrent engineering requirements. Therefore, novel methods and tools to support the development of the E/E systems on-board aircraft are needed. The overall objective of this research study is to reduce the development time of aircraft with a high level of integrated E/E systems by automating the design process of the flight control systems, by creating more consistent control software through the entire design envelope. Besides a reduction in development time this will also improve the quality of the final (mechatronic) product. The three challenges described above will be tackled in particular. The novel methods and tools are based on the knowledge based engineering (KBE) approach. The KBE approach is highly suitable because it cannot only automate non-creative, repetitive design tasks done for example by simulation experts but also support for multidisciplinary design, analysis and optimization (MDAO). Compared to other existing KBE systems, the proposed system integrates the flight control system design with the physical design in three specific areas. First, in order to ensure a consistent design representation, the concept of a multiphysics information model (MIM) is proposed in order to integrate the design knowledge present from multiple engineering domains. The proposed MIM (a KBE system) defines objects with attributes to represent various aspects of physical entities (e.g., mass, inertia, geometry, material properties). Moreover, it uses functions to capture non-physical information, such as the control architecture, relevant test maneuvers, simulation procedures, etc. The problem of system coupling and interactions between disciplines involved are taken into account by the proposed KBE system in a knowledge acquisition process. Next, depending on the requirements, the proposed KBE system extracts necessary knowledge from the MIM which is needed for the development of a multiphysics simulation model, which is composed of a physical plant, flight control systems including the embedded control software and simulation configurations. By capturing the expertise of simulation experts, the proposed KBE system is able to automatically instantiate the multiphysics simulation models. This multiphysics simulation model can be used to evaluate the flight control systems in operation practice throughout the flight envelope, for example when performing maneuvers. Altogether, the MIM enables rapid development of high fidelity multiphysics simulation models for analysis and development of the flight control systems. Second, in order to evaluate the inherent flying qualities of unstable aircraft in a simulation environment, an automatic flight control system is required. For this purpose, model based inversion control is applied. This method has the advantage that tuning is not required. The techniques, processes and knowledge required to develop a model based control system based on the (nonlinear) multiphysics simulation model are captured by the KBE system. Model based inversion control has its disadvantages when implemented on real-life aircraft. For the final design solution developed by the framework, which will enter the detailed design phase and which will ultimately be produced, other control methods and architectures can be developed, more appropriate for a real-life situation. Such a control system will only have to be tuned and developed once in contrast to the thousands of designs evaluated in an MDO framework. This application of model based inversion control is considered new. Third, in order to avoid errors in the embedded control software as a result of manual programming activities, the dependencies of parameters in the software on physical parameters of an evolving design and the high complexity (thousands of lines of code), control software components of flight control systems should ideally be developed in an automated fashion. The proposed KBE system has the ability to generate consistent control software components. The system extracts the variable definitions and values from physical configurations and control architecture from the information model to specify the variables in the software components. In addition, the system divides software components into basic elements and writes them into strings, which can, in principle, be any computer language. When the top level configuration and control architecture changes, the proposed KBE system can operate the basic elements in specific order and automatically create new software components by capturing the expertise from software engineers. Summarizing, because both the geometry model and multiphysics simulation model including flight control system are obtained from one source, the MIM links the physical modeling and control system design with the development of software components with respect to data and topology structure. A multirotor UAV configuration is used as test case to demonstrate the novel methods and tools described above. This is an inherently unstable configuration with a wide range of applications. A computational framework is developed which enables the conceptual/preliminary design and optimization of this typical mechatronic product. The proposed KBE system automatically creates thirty thousand designs of multirotor UAVs with different topologies and then evaluates each solution by automatically simulating five test maneuvers and by checking twenty-two constraints. Results show that the proposed KBE system can automatically generate multiphysics simulation models to support the multidisciplinary analyses not restricted to the mechanical domain but also applicable for evaluation of flight control systems and other domains. Even though different design solutions can have a highly different topology, automatic flight control systems based on the model inversion control method are created automatically for each design solution, enabling the evaluation of the inherent flying qualities of the unstable aircraft configuration. Furthermore, within the framework, design processes are automatically completed from the initial definition of top-level aircraft requirements, to the design and optimization, and finally down to selecting feasible solutions. The approach demonstrated leads to: a reduction in manual work, improved quality of the final solution, and consistent control system and software components. Key to the MIM concept is that it focuses on capturing the intrinsic properties of physical systems by the KBE approach and a specific format of representation is avoided. Although the current research study focuses on the software of the flight control systems in particular, the concept of the MIM can in principle be applied to design the complete E/E system, including hardware components, as well as other multiphysics systems.Aerospace EngineeringAerospace Engineerin
Author Correction: Mg3Al2Si3O12 jeffbenite inclusion in super-deep diamonds is thermodynamically stable at very shallow Earth’s depths (Scientific Reports, (2023), 13, 1, (83), 10.1038/s41598-022-27290-9)
No full textThe Acknowledgments section in the original version of this Article was incomplete. “F.N. thanks the ERC Starting Grant n. 307322.” now reads: “F.N. thanks the ERC Starting Grant n. 307322. D.B. warmly acknowledges financial support by the Italian MIUR PRIN2017 (Project Number 2017KY5ZX8).” The original Article has been corrected
Different roles for TGF-β and VEGF in the pathogenesis of the cardinal features of diabetic nephropathy
No full textHemodynamic stress in concert with metabolic pathways that are activated by hyperglycemia, glycated proteins, and oxidative stress induce a host of growth factors in the kidney. The fibrogenic cytokine transforming growth factor-beta (TGF-β), through its Smad3 signaling pathway, is the etiologic agent of renal hypertrophy and the accumulation of mesangial extracellular matrix components in diabetes. Neutralizing anti-TGF-β antibodies, antisense TGF-β1 oligodeoxynucleotides or knocking off the Smad3 gene prevent and-or reverse the hypertrophic and profibrotic effects of the diabetic state in mice. However, there is limited evidence to support a role for TGF-β in the development of albuminuria. Podocyte-derived vascular endothelial growth factor (VEGF), a permeability and angiogenic factor whose expression is also increased in animal models of diabetic kidney disease, appears to act in a novel autocrine signaling mode to induce the podocytopathy of diabetes, especially the genesis of albuminuria. Future strategies for therapy of diabetic nephropathy may therefore need to involve interception of both the TGF-β and the VEGF signaling pathways to counter the matrix accumulation and to improve the albuminuria. Interception of the renin-angiotensin system may achieve this goal but other novel strategies will need to be developed that would be more efficacious. However, a note of caution should be raised not to lower the heightened activities of these two signaling pathways much below normal levels because a basal activity for each is essential for the optimal homeostasis of glomerular cells. © 2008.Agarwal R, 2002, AM J KIDNEY DIS, V39, P486, DOI 10.1053-ajkd.2002.31392; Chen S, 2004, DIABETES, V53, P2939, DOI 10.2337-diabetes.53.11.2939; Chen S, 2003, BIOCHEM BIOPH RES CO, V300, P16, DOI 10.1016-S0006-291X(02)02708-0; Chen SD, 2005, NEPHROL DIAL TRANSPL, V20, P1320, DOI 10.1093-ndt-gfh837; De Vriese A, 2001, J AM SOC NEPHROL, V12, P993; Ewens KG, 2005, DIABETES, V54, P3305, DOI 10.2337-diabetes.54.11.3305; Flyvbjerg A, 2002, DIABETES, V51, P3090, DOI 10.2337-diabetes.51.10.3090; HAN DC, 2000, AM J PHYSIOL, V278, pF629; Han DC, 1999, J AM SOC NEPHROL, V10, P1891; Hoffman BB, 1998, KIDNEY INT, V54, P1107, DOI 10.1046-j.1523-1755.1998.00119.x; Hong SW, 2001, AM J PATHOL, V158, P1653; Iglesias-de la Cruz MC, 2002, KIDNEY INT, V62, P901, DOI 10.1046-j.1523-1755.2002.00528.x; Isono M, 2002, BIOCHEM BIOPH RES CO, V296, P1356, DOI 10.1016-S0006-291X(02)02084-3; Isono M, 2000, AM J PHYSIOL-RENAL, V278, pF830; Kelly DJ, 2001, J AM SOC NEPHROL, V12, P2098; Lindenmeyer MT, 2007, J AM SOC NEPHROL, V18, P1765, DOI 10.1681-ASN.2006121304; Mogyorosi A, 2000, NEPHRON, V86, P234, DOI 10.1159-000045766; Mogyorosi A, 1999, NEPHROL DIAL TRANSPL, V14, P2827, DOI 10.1093-ndt-14.12.2827; ROCCO MV, 1992, KIDNEY INT, V41, P107, DOI 10.1038-ki.1992.14; Schiffer M, 2004, J BIOL CHEM, V279, P37004, DOI 10.1074-jbc.M403534200; Sharma K, 1996, DIABETES, V45, P522, DOI 10.2337-diabetes.45.4.522; SHARMA K, 1994, AM J PHYSIOL, V267, pF1001; SHARMA K, 1995, DIABETES, V44, P1139, DOI 10.2337-diabetes.44.10.1139; Sharma K, 1999, AM J KIDNEY DIS, V34, P818, DOI 10.1016-S0272-6386(99)70037-5; Sharma K, 1997, DIABETES, V46, P854, DOI 10.2337-diabetes.46.5.854; Sung SH, 2006, J AM SOC NEPHROL, V17, P3093, DOI 10.1681-ASN.2006010064; Tsuchida K, 2003, KIDNEY INT, V63, P2000, DOI 10.1046-j.1523-1755.2003.00009.x; Wang A, 2007, AM J PHYSIOL-RENAL, V293, pF1657, DOI 10.1152-ajprenal.00274.2007; WOLF G, 1992, KIDNEY INT, V42, P647, DOI 10.1038-ki.1992.330; Wolf G, 2005, DIABETES, V54, P1626, DOI 10.2337-diabetes.54.6.1626; YAMAMOTO T, 1993, P NATL ACAD SCI USA, V90, P1814, DOI 10.1073-pnas.90.5.1814; ZHU Y, 2000, J AM SOC NEPHROL, V11, pA3460; ZIYADEH FN, 1990, AM J PHYSIOL, V259, pF704; Ziyadeh Fuad N, 2008, Curr Diabetes Rev, V4, P39, DOI 10.2174-157339908783502370; Ziyadeh FN, 2000, P NATL ACAD SCI USA, V97, P8015, DOI 10.1073-pnas.120055097; Ziyadeh FN, 1998, KIDNEY INT, V53, P631, DOI 10.1046-j.1523-1755.1998.00815.x48474
Kademuren: Haalbaarheidsonderzoek naar een Camilla caisson voor grote kerende hoogtes
No full textHet afstudeerwerk betreft het uitwerken van een patent van de Ballast Nedam Groep. Het patent heeft betrekking op een caisson gebruikt als kademuur. Het afstudeerwerk is geheel volbracht binnen de Ballast Nedam Groep, in een tijdsbestek van 9 maanden, 1 september 1985 tot 30 mei 1986. Het patent omvat een caisson als kadeconstructie. De Caisson is genaamd Camilla caisson. Kenmerkend hieraan, is de naar achteren hellende achterwand en bijbehorende uitsparing in de bodemplaat. In het eerste deel van het afstudeerwerk is de veronderstelde optredende reductie van de horizontale grondkracht op de schuine achterwand van de caisson in gebruiksfase onderzocht. Dit is gebeurt met en semi-plastisch, interactief, eindige elementen methode programma. Deze studie is uitgevoerd bij de sectie Geotechniek. In het tweede deel van het afstuderen is een ontwerpproces doorlopen. Er is een inventarisatie gemaakt van mogelijke soorten kadeconstructies. Van deze kadeconstructies is een eerste selectie gemaakt. In een volgende fase is van de overgebleven kadeconstructies een ontwerpberekening gemaakt. Aan de hand van de hieruit voortkomende afmetingen voor de constructie is een prijscalculatie opgesteld. Hierna zijn de uitwendige afmetingen van de Camilla caisson voor een kerende hoogte van 30 meter, geoptimaliseerd. Met de hieruit voort gekomen resultaten, zijn de mogelijke uitvoeringswijze van de caisson bekeken. De studie eindigt met een vergelijking tussen een traditioneel caisson en het Camilla caisson.Hydraulic EngineeringCivil Engineering and Geoscience
Characterization of Brazed Joints on Threaded X52 Steel Pipe Connections
No full textMaterials Science & EngineelingMechanical, Maritime and Materials Engineerin
Trillingen van betonnen voetgangersbruggen / Vibrations of concrete footbridges
No full textNowadays more and more slender concrete footbridges are designed. Footbridges are designed thinner to increase esthetic value, as well as incorporate sustainability and to reduce building costs, with a consequence that the eigenfrequency of the bridge can drop so low that it may fall into a range of frequencies that is susceptible to vibrations caused by human beings who move along the bridge. When the eigenfrequency of the bridge is nearly the same as the stepfrequency of a person who moves along the deck this may lead to large displacements of the bridge. In this report the consideration of comfort of short-length concrete footbridges is investigated and checked whether this forms a decisive criteria for the determination of the slenderness of the bridge. Requirements of strength and usage are not taken into account. In order to prevent discomfort of users there are demands for comfort compiled for footbridges. The guidelines being compared in this report are: \u95 Expired standard since April 2012: ‘NEN 6723: Guidelines Concrete – Bridges – Constructive Demands and Designmethods’ \u95 National Attachment Eurocode The Netherlands: ‘EUR 23984 EN – Design of Lightweight Footbridges for Human Induced Vibrations’ o Single Degree of Freedom Method (SDOFM) o Response Spectra Method (RSM) \u95 National Attachment Eurocode France: ‘SETRA Guide – Footbridges – Assessment of Vibrational Behaviour of Footbridges Under Pedestrian Loading’ \u95 United States Guideline: ‘AASHTO – LRFD Guide Specifications for the Design of Pedestrian Bridges’ In this comparison it is found that the design calculations according to NEN 6723 and AASHTO are based upon the relation between the eigenfrequency- and a minimum prescribed weight of the bridge, in which the NEN 6723 is based on the concrete material while the AASHTO is independent of the material being used. The requirement for comfort in standard NEN 6723 must be used when the eigenfrequency of the footbridge is below 5 Hz. Besides the rule mentioned, there must also be a load taken into consideration of 1.5 kN, which is not allowed to cause a deformation of 0.25 mm of the deck. Contrary to the AASHTO which additionally requires that the eigenfrequency of the system is at least 3 Hz. The Eurocode proposes to check comfort when the eigenfrequency of the system is below 5 Hz. Where allowable bridge deck acceleration limits are the basis for design criteria, and the calculation method is independent of the material being used. In this report only the vertical direction is considered, because the other directions do not lead to low frequencies that may cause discomfort. The National Attachment of The Netherlands recommends EUR 23984 EN guideline that determines the occurring bridge deck acceleration based upon the amount of pedestrians and also so-called joggers (running persons) present on the deck. The design calculations in EUR 23984 EN are the SDOFM and the RSM, where the SDOFM takes both pedestrians and joggers into account, while the RSM only takes pedestrians into account. The SDOFM is based upon the usage of a mass-spring system and states comfort has to be checked when one of the eigenfrequencies falls into the critical range, which is between 1.25 Hz and 4.6 Hz. In contrary, the RSM calculates the occurring acceleration with an empirical formula in case one of the eigenfrequencies is below 5 Hz (as prescribed in the Eurocode). The guideline SETRA was released earlier than the EUR 23984 EN and also uses the SDOFM. Comfort has to be checked when one of the eigenfrequencies falls in between 1 Hz and 5 Hz, in which case only pedestrians are being taken into account. No joggers are considered because of the assumption that joggers will be present on the bridge for only a short amount of time, which does not lead to discomfort of other users, and the crossing time of a jogger is less than the time required to resonate the bridge. The guidelines mentioned above are applied to the case study Hoevebrug which is an existing bridge. The Hoevebrug is a clamped slab bridge constructed in concrete class B65. The results are summarized in the table below. *A table has to be made from the text below* Guideline Slenderness [-] Percentage [%] NEN 6723 1 op 44.2 100 EUR 23984 EN – SDOFM – Pedestrians 1 op 90.3 204.3 EUR 23984 EN – SDOFM – Pedestrians and Joggers 1 op 61.4 138.9 EUR 23984 EN – RSM 1 op 42.1 95.2 SETRA 1 op 84.2 190.5 AASHTO 1 op 70.2 158.8 Subsequently a separate study of parameters is conducted for short footbridges with the aid of the SDOFM of guideline EUR 23984 EN. The lengths considered vary between 10- and 30 meters. The influence and response of the bridge are considered with parameters of density, Young’s modulus, length, imposition, and height, where the quantity of pedestrians present on the deck is taken to be 0.5 persons/m2 as the Eurocode prescribes. It is found that the second harmonic of pedestrians (the EUR 23984 EN describes this as the stepfrequency between 2.3 Hz and 4.6 Hz) does not lead to discomfort because of the small load being excited by the pedestrian. So it can be stated the second harmonic of pedestrians is not a criteria for the determination of the height of the deck. Joggers however lead in all cases to extremely high values of acceleration of the deck, because the joggers may be assumed to be placed on the deck where the displacement is expected to be the largest. To check whether the response due to joggers can be reduced, a more detailed calculation is considered. The jogger is modeled as a moving harmonic load in time on a deck that is hinged on both sides. Next the differential equation of the continuous system is established and solved. Hereby creating a relation between stepfrequency, velocity, and load of the jogger. Allowing for a more accurate estimation of bridge response, multiple situations of joggers moving along the bridge as a group are then considered and in many cases show the response of the deck is not very similar to the result obtained from SDOFM. In the case of the calculation method of the moving harmonic, the response of the deck will only be significant when the stepfrequency almost equals the eigenfrequency of the system. The conclusion requires that joggers satisfy the condition that every jogger must run with the same frequency across the deck, as well as the interval between the joggers (if present) is equal to the period of the stepfrequency. Besides this the process of an occurring acceleration in vertical direction in case of a person moving along the bridge is ‘self-limiting’. This means that a person is not able to move along the bridge when the occurring acceleration in vertical direction is too large. Because the person stops moving there will no longer be a dynamic load excited any more so that the construction will damp out.Master: concrete structuresStructural EngineeringCivil Engineering and Geoscience
Diabetes mellitus: Is the presence of nephropathy important as a cardiovascular risk factor for cardioneral syndrome?
No full textDiabetes mellitus is a well established risk factor for cardiovascular diseases (CVD). In addition, a significant proportion of diabetic patients go on to develop nephropathy. Moreover, the presence of nephropathy further increases the risk of CVD in patients with all stages of diabetic nephropathy, including microalbuminuria, macroalbuminuria, and renal failure. The fibrogenic cytokine transforming growth factor beta (TGF-β) and the vascular endothelial growth factor (VEGF) are implicated in the development of cardinal features of diabetic nephropathy, namely, mesangial expansion and albuminuria, respectively. The pathogenesis of CVD in diabetes is multifactorial and can be affected by metabolic factors, such as oxidative stress, glycoxidation, procoagulant states, and inflammation. Furthermore, endothelial dysfunction may lead to simultaneous development and progression of renal and cardiac pathology in diabetes. The risk of microvascular complications can be reduced by intensive glycemic control, whereas cardiovascular benefit is less clear. Intensified intervention involving other vascular risk factors, such as hypertension and dyslipidemia, demonstrated benefits in terms of both macrovascular and microvascular complications. In addition, treatment with angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor antagonists is associated with a significant reduction in the risk for renal disease progression in diabetes, which parallels the reduced cardiovascular risk. Moreover, changes in microalbuminuria translate into parallel changes in renal and cardiovascular risk. 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Vascular endothelial growth factor and diabetic nephropathy
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