GENERIC Integrators: Structure Preserving Time Integration for Thermodynamic Systems

Science.gov (United States)

Öttinger, Hans Christian

2018-04-01

Thermodynamically admissible evolution equations for non-equilibrium systems are known to possess a distinct mathematical structure. Within the GENERIC (general equation for the non-equilibrium reversible-irreversible coupling) framework of non-equilibrium thermodynamics, which is based on continuous time evolution, we investigate the possibility of preserving all the structural elements in time-discretized equations. Our approach, which follows Moser's [1] construction of symplectic integrators for Hamiltonian systems, is illustrated for the damped harmonic oscillator. Alternative approaches are sketched.

Improving Ambient Wind Environments of a Cross-flow Wind Turbine near a Structure by using an Inlet Guide Structure and a Flow Deflector

Institute of Scientific and Technical Information of China (English)

Tadakazu TANINO; Shinichiro NAKAO; Genki UEBAYASHI

2005-01-01

A cross-flow wind turbine near a structure was tested for the performance. The results showed that the performance of a cross-flow wind turbine near a structure was up to 30% higher than the one without a structure.In addition, we tried to get higher performance of a cross-flow wind turbine by using an Inlet Guide Structure and a Flow Deflector. An Inlet Guide Structure was placed on the edge of a structure and a Flow Deflector was set near a cross-flow wind turbine and can improve ambient wind environments of the wind turbine, the maximum power coefficients were about 15 to 40% higher and the tip speed ratio range showing the high power coefficient was wide and the positive gradients were steep apparently.

Optimal Structural Reliability of Offshore Wind Turbines

DEFF Research Database (Denmark)

Sørensen, John Dalsgaard; Tarp-Johansen, N.J.

2005-01-01

The main failure modes of modern large wind turbines are fatigue failure of wings, hub, shaft and main tower, local buckling of main tower, and failure of the foundation. This paper considers reliability-based optimal design of wind turbines. Compared to onshore wind turbines and building...... structures, humans spent little time in the vicinity of offshore wind turbines and the probability of human injury during storm conditions is small. Further environmental pollution will also in general be small in case of failure. One could therefore argue that the reliability level of offshore wind turbines...... can be lower than for onshore wind turbines and other civil engineering structures and can be assessed by reliability-based cost-optimization. Specifically this paper considers the main tower and foundation. Both fatigue and ultimate strength failure modes are included. Different formulations...

Financial structures for wind farms

International Nuclear Information System (INIS)

Johns, J.H.

1994-01-01

This paper provides a summary of the structures used to finance wind farms. It takes into account the impact of the 3rd tranche of the NFFO and provides an evaluation of cash returns using Ernst and Young's wind energy model. Suggestions for further developments in financing include the use of specialist financial instruments and tax planning techniques. (author)

Thermodynamically self-consistent integral equations and the structure of liquid metals

International Nuclear Information System (INIS)

Pastore, G.; Kahl, G.

1987-01-01

We discuss the application of the new thermodynamically self-consistent integral equations for the determination of the structural properties of liquid metals. We present a detailed comparison of the structure (S(q) and g(r)) for models of liquid alkali metals as obtained from two thermodynamically self-consistent integral equations and some published exact computer simulation results; the range of states extends from the triple point to the expanded metal. The theories which only impose thermodynamic self-consistency without any fitting of external data show an excellent agreement with the simulation results, thus demonstrating that this new type of integral equation is definitely superior to the conventional ones (hypernetted chain, Percus-Yevick, mean spherical approximation, etc). (author)

Molecular dynamics of the structure and thermodynamics of dusty ...

African Journals Online (AJOL)

The static structure and thermodynamic properties of two-dimensional dusty plasma are analyzed for some typical values of coupling and screening parameters using classical molecular dynamics. Radial distribution function and static structure factor are computed. The radial distribution functions display the typical ...

Structural Reliability Analysis of Wind Turbines: A Review

Directory of Open Access Journals (Sweden)

Zhiyu Jiang

2017-12-01

Full Text Available The paper presents a detailed review of the state-of-the-art research activities on structural reliability analysis of wind turbines between the 1990s and 2017. We describe the reliability methods including the first- and second-order reliability methods and the simulation reliability methods and show the procedure for and application areas of structural reliability analysis of wind turbines. Further, we critically review the various structural reliability studies on rotor blades, bottom-fixed support structures, floating systems and mechanical and electrical components. Finally, future applications of structural reliability methods to wind turbine designs are discussed.

Perspective: Structural fluctuation of protein and Anfinsen's thermodynamic hypothesis

Science.gov (United States)

Hirata, Fumio; Sugita, Masatake; Yoshida, Masasuke; Akasaka, Kazuyuki

2018-01-01

The thermodynamics hypothesis, casually referred to as "Anfinsen's dogma," is described theoretically in terms of a concept of the structural fluctuation of protein or the first moment (average structure) and the second moment (variance and covariance) of the structural distribution. The new theoretical concept views the unfolding and refolding processes of protein as a shift of the structural distribution induced by a thermodynamic perturbation, with the variance-covariance matrix varying. Based on the theoretical concept, a method to characterize the mechanism of folding (or unfolding) is proposed. The transition state, if any, between two stable states is interpreted as a gap in the distribution, which is created due to an extensive reorganization of hydrogen bonds among back-bone atoms of protein and with water molecules in the course of conformational change. Further perspective to applying the theory to the computer-aided drug design, and to the material science, is briefly discussed.

Thermodynamic analysis of energy conversion and transfer in hybrid system consisting of wind turbine and advanced adiabatic compressed air energy storage

International Nuclear Information System (INIS)

Zhang, Yuan; Yang, Ke; Li, Xuemei; Xu, Jianzhong

2014-01-01

A simulation model consisting of wind speed, wind turbine and AA-CAES (advanced adiabatic compressed air energy storage) system is developed in this paper, and thermodynamic analysis on energy conversion and transfer in hybrid system is carried out. The impacts of stable wind speed and unstable wind speed on the hybrid system are analyzed and compared from the viewpoint of energy conversion and system efficiency. Besides, energy conversion relationship between wind turbine and AA-CAES system is investigated on the basis of process analysis. The results show that there are several different forms of energy in hybrid system, which have distinct conversion relationship. As to wind turbine, power coefficient determines wind energy utilization efficiency, and in AA-CAES system, it is compressor efficiency that mainly affects energy conversion efficiencies of other components. The strength and fluctuation of wind speed have a direct impact on energy conversion efficiencies of components of hybrid system, and within proper wind speed scope, the maximum of system efficiency could be expected. - Highlights: • A hybrid system consisting of wind, wind turbine and AA-CAES system is established. • Energy conversion in hybrid system with stable and unstable wind speed is analyzed. • Maximum efficiency of hybrid system can be reached within proper wind speed scope. • Thermal energy change in hybrid system is more sensitive to wind speed change. • Compressor efficiency can affect other efficiencies in AA-CAES system

Thermodynamics and the structure of quantum theory

International Nuclear Information System (INIS)

Krumm, Marius; Müller, Markus P; Barnum, Howard; Barrett, Jonathan

2017-01-01

Despite its enormous empirical success, the formalism of quantum theory still raises fundamental questions: why is nature described in terms of complex Hilbert spaces, and what modifications of it could we reasonably expect to find in some regimes of physics? Here we address these questions by studying how compatibility with thermodynamics constrains the structure of quantum theory. We employ two postulates that any probabilistic theory with reasonable thermodynamic behaviour should arguably satisfy. In the framework of generalised probabilistic theories, we show that these postulates already imply important aspects of quantum theory, like self-duality and analogues of projective measurements, subspaces and eigenvalues. However, they may still admit a class of theories beyond quantum mechanics. Using a thought experiment by von Neumann, we show that these theories admit a consistent thermodynamic notion of entropy, and prove that the second law holds for projective measurements and mixing procedures. Furthermore, we study additional entropy-like quantities based on measurement probabilities and convex decomposition probabilities, and uncover a relation between one of these quantities and Sorkin’s notion of higher-order interference. (paper)

Concise chemical thermodynamics

CERN Document Server

Peters, APH

2010-01-01

EnergyThe Realm of ThermodynamicsEnergy BookkeepingNature's Driving ForcesSetting the Scene: Basic IdeasSystem and SurroundingsFunctions of StateMechanical Work and Expanding GasesThe Absolute Temperature Scale Forms of Energy and Their Interconversion Forms of Renewable Energy Solar Energy Wind Energy Hydroelectric Power Geothermal Energy Biomass Energy References ProblemsThe First Law of Thermodynamics Statement of the First Law Reversible Expansion of an Ideal GasConstant-Volume ProcessesConstant-Pressure ProcessesA New Function: EnthalpyRelationship between ?H and ?UUses and Conventions of

Fatigue strength ofcomposite wind turbine blade structures

DEFF Research Database (Denmark)

Ardila, Oscar Gerardo Castro

Wind turbines are normally designed to withstand 20-30 years of life. During this period, the blades, which are the main rotating structures of a wind turbine, are subjected to high fluctuating load conditions as a result of a combination of gravity, inertia, and aeroelastic forces. For this reason......, fatigue is one of the foremost concerns during the design of these structures. However, current standard fatigue methods used for designing wind turbine blades seem not to be completely appropriate for these structures because they are still based on methods developed for metals and not for composite...... materials from which the blades are made. In this sense, the aim of this work is to develop more accurate and reliable fatigue-life prediction models for composite wind turbine blades. In this project, two types of fatigue models are implemented: fatigue-life models and damage mechanics models. In the first...

Discerning Thermodynamic Basis of Self-Organization in Critical Zone Structure and Function

Science.gov (United States)

Richardson, M.; Kumar, P.

2017-12-01

Self-organization characterizes the spontaneous emergence of order. Self-organization in the Critical Zone, the region of Earth's skin from below the groundwater table to the top of the vegetation canopy, involves the interaction of biotic and abiotic processes occurring through a hierarchy of temporal and spatial scales. The self-organization is sustained through input of energy and material in an open system framework, and the resulting formations are called dissipative structures. Why do these local states of organization form and how are they thermodynamically favorable? We hypothesize that structure formation is linked to energy conversion and matter throughput rates across driving gradients. Furthermore, we predict that structures in the Critical Zone evolve based on local availability of nutrients, water, and energy. By considering ecosystems as open thermodynamic systems, we model and study the throughput signatures on short times scales to determine origins and characteristics of ecosystem structure. This diagnostic approach allows us to use fluxes of matter and energy to understand the thermodynamic drivers of the system. By classifying the fluxes and dynamics in a system, we can identify patterns to determine the thermodynamic drivers for organized states. Additionally, studying the partitioning of nutrients, water, and energy throughout ecosystems through dissipative structures will help identify reasons for structure shapes and how these shapes impact major Critical Zone functions.

Predicting structural properties of fluids by thermodynamic extrapolation

Science.gov (United States)

Mahynski, Nathan A.; Jiao, Sally; Hatch, Harold W.; Blanco, Marco A.; Shen, Vincent K.

2018-05-01

We describe a methodology for extrapolating the structural properties of multicomponent fluids from one thermodynamic state to another. These properties generally include features of a system that may be computed from an individual configuration such as radial distribution functions, cluster size distributions, or a polymer's radius of gyration. This approach is based on the principle of using fluctuations in a system's extensive thermodynamic variables, such as energy, to construct an appropriate Taylor series expansion for these structural properties in terms of intensive conjugate variables, such as temperature. Thus, one may extrapolate these properties from one state to another when the series is truncated to some finite order. We demonstrate this extrapolation for simple and coarse-grained fluids in both the canonical and grand canonical ensembles, in terms of both temperatures and the chemical potentials of different components. The results show that this method is able to reasonably approximate structural properties of such fluids over a broad range of conditions. Consequently, this methodology may be employed to increase the computational efficiency of molecular simulations used to measure the structural properties of certain fluid systems, especially those used in high-throughput or data-driven investigations.

Simulation of Cu-Mg metallic glass: Thermodynamics and structure

DEFF Research Database (Denmark)

Bailey, Nicholas; Schiøtz, Jakob; Jacobsen, Karsten Wedel

2004-01-01

We have obtained effective medium theory interatomic potential parameters suitable for studying Cu-Mg metallic glasses. We present thermodynamic and structural results from simulations of such glasses over a range of compositions. We have produced low-temperature configurations by cooling from...... the melt at as slow a rate as practical, using constant temperature and pressure molecular dynamics. During the cooling process we have carried out thermodynamic analyses based on the temperature dependence of the enthalpy and its derivative, the specific heat, from which the glass transition temperature...

Database on wind characteristics - Structure and philosophy

Energy Technology Data Exchange (ETDEWEB)

Larsen, G.C.; Hansen, K.S.

2001-11-01

The main objective of IEA R and D Wind Annex XVII - Database on Wind Characteristics - is to provide wind energy planners and designers, as well as the international wind engineering community in general, with easy access to quality controlled measured wind field time series observed in a wide range of environments. The project partners are Sweden, Norway, U.S.A., The Netherlands, Japan and Denmark, with Denmark as the Operating Agent. The reporting of IEA R and D Annex XVII falls in three separate parts. Part one deals with the overall structure and philosophy behind the database, part two accounts in details for the available data in the established database bank and part three is the Users Manual describing the various ways to access and analyse the data. The present report constitutes the first part of the Annex XVII reporting, and it contains a detailed description of the database structure, the data quality control procedures, the selected indexing of the data and the hardware system. (au)

Filament winding technique, experiment and simulation analysis on tubular structure

Science.gov (United States)

Quanjin, Ma; Rejab, M. R. M.; Kaige, Jiang; Idris, M. S.; Harith, M. N.

2018-04-01

Filament winding process has emerged as one of the potential composite fabrication processes with lower costs. Filament wound products involve classic axisymmetric parts (pipes, rings, driveshafts, high-pressure vessels and storage tanks), non-axisymmetric parts (prismatic nonround sections and pipe fittings). Based on the 3-axis filament winding machine has been designed with the inexpensive control system, it is completely necessary to make a relative comparison between experiment and simulation on tubular structure. In this technical paper, the aim of this paper is to perform a dry winding experiment using the 3-axis filament winding machine and simulate winding process on the tubular structure using CADWIND software with 30°, 45°, 60° winding angle. The main result indicates that the 3-axis filament winding machine can produce tubular structure with high winding pattern performance with different winding angle. This developed 3-axis winding machine still has weakness compared to CAWIND software simulation results with high axes winding machine about winding pattern, turnaround impact, process error, thickness, friction impact etc. In conclusion, the 3-axis filament winding machine improvements and recommendations come up with its comparison results, which can intuitively understand its limitations and characteristics.

Structural Reliability Aspects in Design of Wind Turbines

DEFF Research Database (Denmark)

Sørensen, John Dalsgaard

2007-01-01

Reliability assessment, optimal design and optimal operation and maintenance of wind turbines are an area of significant interest for the fast growing wind turbine industry for sustainable production of energy. Offshore wind turbines in wind farms give special problems due to wake effects inside...... the farm. Reliability analysis and optimization of wind turbines require that the special conditions for wind turbine operation are taken into account. Control of the blades implies load reductions for large wind speeds and parking for high wind speeds. In this paper basic structural failure modes for wind...... turbines are described. Further, aspects are presented related to reliability-based optimization of wind turbines, assessment of optimal reliability level and operation and maintenance....

A GLANCE AT OFFSHORE WIND TURBINE FOUNDATION STRUCTURES

Directory of Open Access Journals (Sweden)

Jianhua Zhang

2016-06-01

Full Text Available Energy poverty and climate change are crucial issues we face in our societies. Offshore wind energy has been a reliable solution to both of these problems - solving our growing energy problems while reducing CO2 emission. Innovative foundation design is one of the setbacks faced by this industry. Designing and constructing a cost effective offshore wind farm is greatly hampered by technical and infrastructural challenges, especially in foundation structures. This paper provides a detailed overview of issues related to this problem, with the aim of eliminating the frequent misunderstandings which can arise among engineers and investors working in the offshore wind energy sector. It begins by investigating the latest data and recommendations regarding the design and deployment of various kinds of offshore wind turbine (OWT foundations. It provides a framework which enables us to study the different OWT foundations, including prototypes and their limitations. Various structural failure modes are highlighted and corrosion measures are presented. Moreover, various removal methods of support structures are put forward. Finally, this paper presents the setbacks preventing the spread of offshore wind energy and the future works for offshore wind energy applications.

Thermodynamical properties and thermoelastic coupling of complex macroscopic structure

International Nuclear Information System (INIS)

Fabbri, M.; Sacripanti, A.

1996-11-01

Gross qualitative/quantitative analysis about thermodynamical properties and thermoelastic coupling (or elastocaloric effect) of complex macroscopic structure (running shoes) is performed by infrared camera. The experimental results showed the achievability of a n industrial research project

Grid faults' impact on wind turbine structural loads

Energy Technology Data Exchange (ETDEWEB)

Hansen, A.D.; Cutululis, N.A.; Soerensen, P.; Larsen, T.J. [Risoe National Lab., DTU, Wind Energy Dept. (Denmark); Iov, F.

2007-11-15

The objective of this work is to illustrate the impact of the grid faults on the wind turbine structural loads. Grid faults are typically in detailed power system simulation tools, which by applying simplified mechanical models, are not able to provide a throughout insight on the structural loads caused by sudden disturbances on the grid. On the other hand, structural loads of the wind turbine are typically assessed in advanced aeroelastic computer codes, which by applying simplified electrical models do not provide detailed electrical insight. This paper presents a simulation strategy, where the focus is on how to access a proper combination of two complementary simulation tools, such as the advanced aeroelastic computer code HAWC2 and the detailed power system simulation tool DIgSILENT, in order to provide a whole overview of both the structural and the electrical behaviour of the wind turbine during grid faults. The effect of a grid fault on the wind turbine flexible structure is assessed for a typical fixed speed wind turbine, equipped with an induction generator. (au)

Thermodynamics and structure of liquid alkali metals from the charged-hard-sphere reference fluid

International Nuclear Information System (INIS)

Lai, S.K.; Akinlade, O.; Tosi, M.P.

1989-12-01

The evaluation of thermodynamic properties of liquid alkali metals is re-examined in the approach based on the Gibbs-Bogoliubov inequality and using the fluid of charged hard spheres in the mean spherical approximation as reference system, with a view to achieving consistency with the liquid structure factor. The perturbative variational calculation of the Helmholtz free energy is based on an ab initio and highly reliable nonlocal pseudopotential. Only limited improvement is found in the calculated thermodynamic functions, even when full advantage is taken of the two variational parameters inherent in this approach. The role of thermodynamic self-consistency between the equations of state of the reference fluid derived from the routes of the internal energy and of the virial theorem is then discussed, using previous results by Hoye and Stell. An approximate evaluation of the corresponding contribution to the free energy of liquid alkali metals yields appreciable improvements in both the thermodynamic functions and the liquid structure factor. It thus appears that an accurate treatment of thermodynamic self-consistency in the charged-hard-sphere system may help to resolve some of the difficulties that are commonly met in the evaluation of thermodynamic and structural properties of liquid metals. (author). 55 refs, 4 figs, 4 tabs

Wind/seismic comparison for upgrading existing structures

International Nuclear Information System (INIS)

Giller, R.A.

1989-01-01

This paper depicts the analysis procedures and methods used to evaluate three existing building structures for extreme wind loads. The three structures involved in this evaluation are located at the US Department of Energy's Hanford Site near Richland, Washington. This site is characterized by open flat grassland with few surrounding obstructions and has extreme winds in lieu of tornados as a design basis accident condition. This group of buildings represents a variety of construction types, including a concrete stack, a concrete load-bearing wall structure, and a rigid steel-frame building. The three structures included in this group have recently been evaluated for response to the design basis earthquake that included non-linear time history effects. The resulting loads and stresses from the wind analyses were compared to the loads and stresses resulting from seismic analyses. This approach eliminated the need to prepare additional capacity calculations that were already contained in the seismic evaluations

Solar wind structure out of the ecliptic plane over solar cycles

Science.gov (United States)

Sokol, J. M.; Bzowski, M.; Tokumaru, M.

2017-12-01

Sun constantly emits a stream of plasma known as solar wind. Ground-based observations of the solar wind speed through the interplanetary scintillations (IPS) of radio flux from distant point sources and in-situ measurements by Ulysses mission revealed that the solar wind flow has different characteristics depending on the latitude. This latitudinal structure evolves with the cycle of solar activity. The knowledge on the evolution of solar wind structure is important for understanding the interaction between the interstellar medium surrounding the Sun and the solar wind, which is responsible for creation of the heliosphere. The solar wind structure must be taken into account in interpretation of most of the observations of heliospheric energetic neutral atoms, interstellar neutral atoms, pickup ions, and heliospheric backscatter glow. The information on the solar wind structure is not any longer available from direct measurements after the termination of Ulysses mission and the only source of the solar wind out of the ecliptic plane is the IPS observations. However, the solar wind structure obtained from this method contains inevitable gaps in the time- and heliolatitude coverage. Sokół et al 2015 used the solar wind speed data out of the ecliptic plane retrieved from the IPS observations performed by Institute for Space-Earth Environmental Research (Nagoya University, Japan) and developed a methodology to construct a model of evolution of solar wind speed and density from 1985 to 2013 that fills the data gaps. In this paper we will present a refined model of the solar wind speed and density structure as a function of heliographic latitude updated by the most recent data from IPS observations. And we will discuss methods of extrapolation of the solar wind structure out of the ecliptic plane for the past solar cycles, when the data were not available, as well as forecasting for few years upward.

On the application of thermodynamics of corrosion for service life design of concrete structures

DEFF Research Database (Denmark)

Küter, Andre; Geiker, Mette Rica; Møller, Per

2010-01-01

There are unexploited possibilities in the application of thermodynamics of corrosion for service life design (SLD) of concrete structures. Thermodynamics provides means for insightful descriptions of corrosion mechanisms and of corrosion protection mechanisms. Strategies for corrosion protection...... of the application of thermodynamics for SLD and gives examples of two applications: description of corrosion processes and design of countermeasures. Emphasis is set on chloride induced corrosion....... can be based on thermodynamically consistent corrosion mechanisms and evaluation of existing and design of new countermeasures can be performed using thermodynamics. Similarly, materials concepts for embedded electrodes can be designed using thermodynamics. The present paper provides a brief outline...

Thermodynamics and structure of liquid metals from a consistent optimized random phase approximation

International Nuclear Information System (INIS)

Akinlade, O.; Badirkhan, Z.; Pastore, G.

2000-05-01

We study thermodynamics and structural properties of several liquid metals to assess the validity of the generalized non-local model potential (GNMP) of Li et. al. [J.Phys. F16,309 (1986)]. By using a new thermodynamically consistent version of the optimized random phase approximation (ORPA), especially adapted to continuous reference potentials, we improve our previous results obtained within the variational approach based on the Gibbs - Bogoliubov inequality. Hinging on the unified and very accurate evaluation of structure factors and thermodynamic quantities provided by the ORPA, we find that the GNMP yields satisfactory results for the alkali metals, however, those for the polyvalent metals point to a substantial inadequacy of the GNMP for high valence systems. (author)

Thermodynamic analysis on an anisotropically superhydrophobic surface with a hierarchical structure

Energy Technology Data Exchange (ETDEWEB)

Zhao, Jieliang [Division of Intelligent and Biomechanical Systems, State Key Laboratory of Tribology, Tsinghua University, Room 3407, Building 9003, 100084 Beijing (China); Su, Zhengliang [Division of Intelligent and Biomechanical Systems, State Key Laboratory of Tribology, Tsinghua University, Room 3407, Building 9003, 100084 Beijing (China); Department of Automotive Engineering, Tsinghua University, Beijing 100084 (China); Yan, Shaoze, E-mail: yansz@mail.tsinghua.edu.cn [Division of Intelligent and Biomechanical Systems, State Key Laboratory of Tribology, Tsinghua University, Room 3407, Building 9003, 100084 Beijing (China)

2015-12-01

Graphical abstract: - Highlights: • We model the superhydrophobic surface with anisotropic and hierarchical structure. • Anisotropic wetting only shows in noncomposite state (not in composite state). • Transition from noncomposite to composite state on dual-scale structure is hard. • Droplets tend to roll in the particular direction. • Droplets tend to stably remain in one preferred thermodynamic state. - Abstract: Superhydrophobic surfaces, which refer to the surfaces with contact angle higher than 150° and hysteresis less than 10°, have been reported in various studies. However, studies on the superhydrophobicity of anisotropic, hierarchical surfaces are limited and the corresponding thermodynamic mechanisms could not be explained thoroughly. Here we propose a simplified surface model of anisotropic patterned surface with dual scale roughness. Based on the thermodynamic method, we calculate the equilibrium contact angle (ECA) and the contact angle hysteresis (CAH) on the given surface. We show here that the hierarchical structure has much better anisotropic wetting properties than the single-scale one, and the results shed light on the potential application in controllable micro-/nano-fluidic systems. Our studies can be potentially applied for the fabrication of anisotropically superhydrophobic surfaces.

Thermodynamic analysis on an anisotropically superhydrophobic surface with a hierarchical structure

International Nuclear Information System (INIS)

Zhao, Jieliang; Su, Zhengliang; Yan, Shaoze

2015-01-01

Graphical abstract: - Highlights: • We model the superhydrophobic surface with anisotropic and hierarchical structure. • Anisotropic wetting only shows in noncomposite state (not in composite state). • Transition from noncomposite to composite state on dual-scale structure is hard. • Droplets tend to roll in the particular direction. • Droplets tend to stably remain in one preferred thermodynamic state. - Abstract: Superhydrophobic surfaces, which refer to the surfaces with contact angle higher than 150° and hysteresis less than 10°, have been reported in various studies. However, studies on the superhydrophobicity of anisotropic, hierarchical surfaces are limited and the corresponding thermodynamic mechanisms could not be explained thoroughly. Here we propose a simplified surface model of anisotropic patterned surface with dual scale roughness. Based on the thermodynamic method, we calculate the equilibrium contact angle (ECA) and the contact angle hysteresis (CAH) on the given surface. We show here that the hierarchical structure has much better anisotropic wetting properties than the single-scale one, and the results shed light on the potential application in controllable micro-/nano-fluidic systems. Our studies can be potentially applied for the fabrication of anisotropically superhydrophobic surfaces.

Floating wind generators offshore wind farm: Implications for structural loads and control actions

International Nuclear Information System (INIS)

Garcia, E.; Morant F, Quiles E.; Correcher, A.

2009-01-01

This paper describes the work currently carried out in the design of floating wind generators and their involvement in the future development of power generation in marine farms in depths exceeding 20 m. We discuss the main issues to be taken into account in the design of floating platforms, including the involvement of structural loads they bear. Also from a standpoint of control engineering are discussed strategies to reduce structural loads such a system to ensure adequate durability and therefore ensuring their economic viability. Finally, the abstract modeling tools for floating wind turbines that can be used in both structural design and the design of appropriate control algorithms

Thermodynamic structure of the marine atmosphere over the region ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

course of observations the ship moved from an open ... Marine boundary layer; thermodynamic structure; saturation point; Bay of Bengal Monsoon Experiment; .... when the low-pressure area is close to the ship the pressure is low and as the system moves away, the .... over oceanic regions to characterize the differences.

Damage tolerance and structural monitoring for wind turbine blades.

Science.gov (United States)

McGugan, M; Pereira, G; Sørensen, B F; Toftegaard, H; Branner, K

2015-02-28

The paper proposes a methodology for reliable design and maintenance of wind turbine rotor blades using a condition monitoring approach and a damage tolerance index coupling the material and structure. By improving the understanding of material properties that control damage propagation it will be possible to combine damage tolerant structural design, monitoring systems, inspection techniques and modelling to manage the life cycle of the structures. This will allow an efficient operation of the wind turbine in terms of load alleviation, limited maintenance and repair leading to a more effective exploitation of offshore wind. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Structural Reliability of Wind Turbine Blades

DEFF Research Database (Denmark)

Dimitrov, Nikolay Krasimirov

turbine blades. The main purpose is to draw a clear picture of how reliability-based design of wind turbines can be done in practice. The objectives of the thesis are to create methodologies for efficient reliability assessment of composite materials and composite wind turbine blades, and to map...... the uncertainties in the processes, materials and external conditions that have an effect on the health of a composite structure. The study considers all stages in a reliability analysis, from defining models of structural components to obtaining the reliability index and calibration of partial safety factors...... by developing new models and standards or carrying out tests The following aspects are covered in detail: ⋅ The probabilistic aspects of ultimate strength of composite laminates are addressed. Laminated plates are considered as a general structural reliability system where each layer in a laminate is a separate...

Wind load modeling for topology optimization of continuum structures

NARCIS (Netherlands)

Zakhama, R.; Abdalla, M.M.; Gürdal, Z.; Smaoui, H.

2010-01-01

Topology optimization of two and three dimensional structures subject to dead and wind loading is considered. The wind loading is introduced into the formulation by using standard expressions for the drag force, and a strategy is devised so that wind pressure is ignored where there is no surface

Solar wind structure suggested by bimodal correlations of solar wind speed and density between the spacecraft SOHO and Wind

Science.gov (United States)

Ogilvie, K. W.; Coplan, M. A.; Roberts, D. A.; Ipavich, F.

2007-08-01

We calculate the cross-spacecraft maximum lagged-cross-correlation coefficients for 2-hour intervals of solar wind speed and density measurements made by the plasma instruments on the Solar and Heliospheric Observatory (SOHO) and Wind spacecraft over the period from 1996, the minimum of solar cycle 23, through the end of 2005. During this period, SOHO was located at L1, about 200 R E upstream from the Earth, while Wind spent most of the time in the interplanetary medium at distances of more than 100 R E from the Earth. Yearly histograms of the maximum, time-lagged correlation coefficients for both the speed and density are bimodal in shape, suggesting the existence of two distinct solar wind regimes. The larger correlation coefficients we suggest are due to structured solar wind, including discontinuities and shocks, while the smaller are likely due to Alfvénic turbulence. While further work will be required to firmly establish the physical nature of the two populations, the results of the analysis are consistent with a solar wind that consists of turbulence from quiet regions of the Sun interspersed with highly filamentary structures largely convected from regions in the inner solar corona. The bimodal appearance of the distributions is less evident in the solar wind speed than in the density correlations, consistent with the observation that the filamentary structures are convected with nearly constant speed by the time they reach 1 AU. We also find that at solar minimum the fits for the density correlations have smaller high-correlation components than at solar maximum. We interpret this as due to the presence of more relatively uniform Alfvénic regions at solar minimum than at solar maximum.

Modular structure of wind turbine models in IEC 61400-27-1

DEFF Research Database (Denmark)

Sørensen, Poul Ejnar; Andresen, Bjørn; Fortmann, Jens

2013-01-01

This paper presents the modular structure of wind turbine models to be published in a new standard IEC 61400-27 for “Electrical simulation models for wind power generation”. The purpose of this standardization work is to define generic simulation models for wind turbines (Part 1) and wind power...... plants (Part 2), which are intended for short-term power system stability analyses. Part 1 has passed the first committee draft stage, whereas Part 2 is in an early stage of development. Initially, the paper describes the interfaces between wind turbine, wind power plant and grid models, and then gives...... a more detailed description of the modular structure of the types of wind turbines that are included in Part 1....

Adaptive inflatable structures for protecting wind turbines against ship collisions

Energy Technology Data Exchange (ETDEWEB)

Graczykowski, C.; Heinonen, J.

2006-09-15

Collisions of small ships are one of main dangers for the offshore wind turbines. Using inflatable structures surrounding the tower on the water level is a possibility of effective protection. Modelling of such structures is based on interaction between solid wall and fluid enclosed inside. Inflatable structures can be adapted to various impact schemes by adjusting initial pressure and controlling release of compressed air by opening piezo-valves. Simulations of ship collision with 2D model of wind turbine tower protected by pneumatic structure are presented in the report. Numerical analysis is performed using ABAQUS/Standard and ABAQUS/Explicit. Performed feasibility study proves that inflatable structures can protect wind turbine tower and ship against serious damages. (orig.)

An Integrated Structural Strength Analysis Method for Spar Type Floating Wind Turbine

Institute of Scientific and Technical Information of China (English)

胡志强; 刘毅; 王晋

2016-01-01

An integrated structural strength analysis method for a Spar type floating wind turbine is proposed in this paper, and technical issues related to turbine structure modeling and stress combination are also addressed. The NREL-5MW “Hywind” Spar type wind turbine is adopted as study object. Time-domain dynamic coupled simulations are performed by a fully-coupled aero-hydro-servo-elastic tool, FAST, on the purpose of obtaining the dynamic characteristics of the floating wind turbine, and determining parameters for design load cases of finite element calculation. Then design load cases are identified, and finite element analyses are performed for these design load cases. The structural stresses due to wave-induced loads and wind-induced loads are calculated, and then combined to assess the structural strength of the floating wind turbine. The feasibility of the proposed structural strength analysis method for floating wind turbines is then validated.

Colliding Stellar Winds Structure and X-ray Emission

Science.gov (United States)

Pittard, J. M.; Dawson, B.

2018-04-01

We investigate the structure and X-ray emission from the colliding stellar winds in massive star binaries. We find that the opening angle of the contact discontinuity (CD) is overestimated by several formulae in the literature at very small values of the wind momentum ratio, η. We find also that the shocks in the primary (dominant) and secondary winds flare by ≈20° compared to the CD, and that the entire secondary wind is shocked when η ≲ 0.02. Analytical expressions for the opening angles of the shocks, and the fraction of each wind that is shocked, are provided. We find that the X-ray luminosity Lx∝η, and that the spectrum softens slightly as η decreases.

IDENTIFICATION OF WIND LOAD APPLIED TO THREE-DIMENSIONAL STRUCTURES BY VIRTUE OF ITS SIMULATION IN THE WIND TUNNEL

Directory of Open Access Journals (Sweden)

Doroshenko Sergey Aleksandrovich

2012-10-01

Full Text Available The authors discuss wind loads applied to a set of two buildings. The wind load is simulated with the help of the wind tunnel. In the Russian Federation, special attention is driven to the aerodynamics of high-rise buildings and structures. According to the Russian norms, identification of aerodynamic coefficients for high-rise buildings, as well as the influence of adjacent buildings and structures, is performed on the basis of models of structures exposed to wind impacts simulated in the wind tunnel. This article deals with the results of the wind tunnel test of buildings. The simulation was carried out with the involvement of a model of two twenty-three storied buildings. The experiment was held in a wind tunnel of the closed type at in the Institute of Mechanics of Moscow State University. Data were compared at the zero speed before and after the experiment. LabView software was used to process the output data. Graphs and tables were developed in the Microsoft Excel package. GoogleSketchUp software was used as a visualization tool. The three-dimensional flow formed in the wind tunnel can't be adequately described by solving the two-dimensional problem. The aerodynamic experiment technique is used to analyze the results for eighteen angles of the wind attack.

Course 12: Proteins: Structural, Thermodynamic and Kinetic Aspects

Science.gov (United States)

Finkelstein, A. V.

1 Introduction 2 Overview of protein architectures and discussion of physical background of their natural selection 2.1 Protein structures 2.2 Physical selection of protein structures 3 Thermodynamic aspects of protein folding 3.1 Reversible denaturation of protein structures 3.2 What do denatured proteins look like? 3.3 Why denaturation of a globular protein is the first-order phase transition 3.4 "Gap" in energy spectrum: The main characteristic that distinguishes protein chains from random polymers 4 Kinetic aspects of protein folding 4.1 Protein folding in vivo 4.2 Protein folding in vitro (in the test-tube) 4.3 Theory of protein folding rates and solution of the Levinthal paradox

Advancing viral RNA structure prediction: measuring the thermodynamics of pyrimidine-rich internal loops.

Science.gov (United States)

Phan, Andy; Mailey, Katherine; Saeki, Jessica; Gu, Xiaobo; Schroeder, Susan J

2017-05-01

Accurate thermodynamic parameters improve RNA structure predictions and thus accelerate understanding of RNA function and the identification of RNA drug binding sites. Many viral RNA structures, such as internal ribosome entry sites, have internal loops and bulges that are potential drug target sites. Current models used to predict internal loops are biased toward small, symmetric purine loops, and thus poorly predict asymmetric, pyrimidine-rich loops with >6 nucleotides (nt) that occur frequently in viral RNA. This article presents new thermodynamic data for 40 pyrimidine loops, many of which can form UU or protonated CC base pairs. Uracil and protonated cytosine base pairs stabilize asymmetric internal loops. Accurate prediction rules are presented that account for all thermodynamic measurements of RNA asymmetric internal loops. New loop initiation terms for loops with >6 nt are presented that do not follow previous assumptions that increasing asymmetry destabilizes loops. Since the last 2004 update, 126 new loops with asymmetry or sizes greater than 2 × 2 have been measured. These new measurements significantly deepen and diversify the thermodynamic database for RNA. These results will help better predict internal loops that are larger, pyrimidine-rich, and occur within viral structures such as internal ribosome entry sites. © 2017 Phan et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

Thermodynamic Upper Bound on Broadband Light Coupling with Photonic Structures

KAUST Repository

Yu, Zongfu; Raman, Aaswath; Fan, Shanhui

2012-01-01

to an upper bound dictated by the second law of thermodynamics. Such bound limits how efficient light can be coupled to any photonic structure. As one example of application, we use this upper bound to derive the limit of light absorption in broadband solar

The offshore trend: Structural changes in the wind power sector

International Nuclear Information System (INIS)

Markard, Jochen; Petersen, Regula

2009-01-01

In recent years, the wind power sector has begun to move offshore, i.e. to use space and good wind speeds on the open sea for large scale electricity generation. Offshore wind power, however, is not just technologically challenging but also a capital intensive and risky business that requires particular financial and organizational resources not all potential investors might have. We therefore address the question, what impact offshore wind power may have on ownership and organizational structures in the wind power sector. We compare on- and offshore wind park ownership in Denmark, the UK and Germany. The analysis shows that offshore wind power in all three countries is dominated by large firms, many of which are from the electricity sector. In Denmark and the UK, also investors from the gas and oil industry play an important role in the offshore wind business. This development represents a major shift for countries such as Germany and Denmark, in which the wind power sector has grown and matured on the basis of investments by individuals, farmers, cooperatives and independent project developers. The structural changes by which offshore wind power is accompanied have consequences for turbine manufacturers, project developers, investors, associations and policy makers in the field.

Transverse Resonant Vibration of Non-Bearing Structures Caused by Wind

Science.gov (United States)

Jendzelovsky, Norbert; Antal, Roland

2017-10-01

Nowadays, there are increasing use of very thin, subtle and light structures in the field of building constructions. We can find such a structures as part of roofs or design facades. By using these lamellas like, non-bearing structures as a part of architectural design of buildings, it is necessary to consider wind effects on these structures. Subtle structures of this type are prone to vibration in the transverse direction of the wind flow. The fact that the vibration occurs depends on wind parameters (wind velocity, direction of an air flow) and it also depends on the properties of lamella (shape, length, mass, natural frequency, support type). The principal idea of this article is to show susceptibility of lamellae-like structures to transverse resonant vibration caused by the phenomenon called Von Karman effect. Comparison of susceptibility to transverse resonance vibration was analysed on the different shapes of lamellas loaded by different wind speed. Analysis was based on usage of empirically derived equations. Von Karman effect arise from wind flow past an object. Turbulence in the form of vortices are formed at the object and shed into the flowing stream intermittently. The potential problem is that this turbulence can induce vibrations into the lamella itself. In terms of this vibration problem, two frequencies are interesting. Von Karman shedding frequency is the frequency at which the vortices are formed and shed at the object. The vortex-shedding frequency increases with the velocity of the wind flow and decreases with the size of the object. Natural frequency of the object depends on the construction of the lamella itself. Parameters of lamella as a shape, mass, length, elasticity modulus of material and support types are directly involved in the calculation of natural frequency. Worst case scenario in the term of transverse resonant vibration occurs when the natural frequency of lamella is equal to the vortex-shedding frequency. In this case

Structural Dynamic Behavior of Wind Turbines

Science.gov (United States)

Thresher, Robert W.; Mirandy, Louis P.; Carne, Thomas G.; Lobitz, Donald W.; James, George H. III

2009-01-01

The structural dynamicist s areas of responsibility require interaction with most other members of the wind turbine project team. These responsibilities are to predict structural loads and deflections that will occur over the lifetime of the machine, ensure favorable dynamic responses through appropriate design and operational procedures, evaluate potential design improvements for their impact on dynamic loads and stability, and correlate load and control test data with design predictions. Load prediction has been a major concern in wind turbine designs to date, and it is perhaps the single most important task faced by the structural dynamics engineer. However, even if we were able to predict all loads perfectly, this in itself would not lead to an economic system. Reduction of dynamic loads, not merely a "design to loads" policy, is required to achieve a cost-effective design. The two processes of load prediction and structural design are highly interactive: loads and deflections must be known before designers and stress analysts can perform structural sizing, which in turn influences the loads through changes in stiffness and mass. Structural design identifies "hot spots" (local areas of high stress) that would benefit most from dynamic load alleviation. Convergence of this cycle leads to a turbine structure that is neither under-designed (which may result in structural failure), nor over-designed (which will lead to excessive weight and cost).

A statistical-thermodynamic model for ordering phenomena in thin film intermetallic structures

International Nuclear Information System (INIS)

Semenova, Olga; Krachler, Regina

2008-01-01

Ordering phenomena in bcc (110) binary thin film intermetallics are studied by a statistical-thermodynamic model. The system is modeled by an Ising approach that includes only nearest-neighbor chemical interactions and is solved in a mean-field approximation. Vacancies and anti-structure atoms are considered on both sublattices. The model describes long-range ordering and simultaneously short-range ordering in the thin film. It is applied to NiAl thin films with B2 structure. Vacancy concentrations, thermodynamic activity profiles and the virtual critical temperature of order-disorder as a function of film composition and thickness are presented. The results point to an important role of vacancies in near-stoichiometric and Ni-rich NiAl thin films

The thermal structure of a wind-driven Reynolds ridge

Energy Technology Data Exchange (ETDEWEB)

Phongikaroon, Supathorn; Peter Judd, K.; Smith, Geoffrey B.; Handler, Robert A. [Remote Sensing Division, Naval Research Laboratory, 20375, Washington, DC (United States)

2004-08-01

In this study, we investigate the nature of a Reynolds ridge formed by wind shear. We have simultaneously imaged the water surface, with a deposit of a monolayer of the surfactant, oleyl alcohol, subject to different wind shears, by using a high-resolution infrared (IR) detector and a high-speed (HS) digital camera. The results reveal that the regions around the wind-driven Reynolds ridge, which have subtle manifestations in visual imagery, possess surprisingly complex hydrodynamical and thermal structures when observed in the infrared. The IR measurements reveal a warm, clean region upstream of the ridge, which is composed of the so called fishscale structures observed in earlier investigations. The region downstream of the ridge is composed of colder fluid which forms two counter-rotating cells. A region of intermediate temperature, which we call the mixing (wake) region, forms immediately downstream of the ridge near the channel centerline. By measuring the velocity of the advected fishscales, we have determined a surface drift speed of about 2% of the wind speed. The spanwise length-scale of the structures has also been used to estimate the wind shear. In addition, a comparison of IR and visual imagery shows that the thermal field is a very sensitive indicator of the exact position of the ridge itself. (orig.)

Structural and thermodynamic analysis of modified nucleosides in self-assembled DNA cross-tiles.

Science.gov (United States)

Hakker, Lauren; Marchi, Alexandria N; Harris, Kimberly A; LaBean, Thomas H; Agris, Paul F

2014-01-01

DNA Holliday junctions are important natural strand-exchange structures that form during homologous recombination. Immobile four-arm junctions, analogs to Holliday junctions, have been designed to self-assemble into cross-tile structures by maximizing Watson-Crick base pairing and fixed crossover points. The cross-tiles, self-assembled from base pair recognition between designed single-stranded DNAs, form higher order lattice structures through cohesion of self-associating sticky ends. These cross-tiles have 16 unpaired nucleosides in the central loop at the junction of the four duplex stems. The importance of the centralized unpaired nucleosides to the structure's thermodynamic stability and self-assembly is unknown. Cross-tile DNA nanostructures were designed and constructed from nine single-stranded DNAs with four shell strands, four arms, and a central loop containing 16 unpaired bases. The 16 unpaired bases were either 2'-deoxyribothymidines, 2'-O-methylribouridines, or abasic 1',2'-dideoxyribonucleosides. Thermodynamic profiles and structural base-stacking contributions were assessed using UV absorption spectroscopy during thermal denaturation and circular dichroism spectroscopy, respectively, and the resulting structures were observed by atomic force microscopy. There were surprisingly significant changes in the thermodynamic and structural properties of lattice formation as a result of altering only the 16 unpaired, centralized nucleosides. The 16 unpaired 2'-O-methyluridines were stabilizing and produced uniform tubular structures. In contrast, the abasic nucleosides were destabilizing producing a mixture of structures. These results strongly indicate the importance of a small number of centrally located unpaired nucleosides within the structures. Since minor modifications lead to palpable changes in lattice formation, DNA cross-tiles present an easily manipulated structure convenient for applications in biomedical and biosensing devices.

System Identification of Wind Turbines for Structural Health Monitoring

DEFF Research Database (Denmark)

Perisic, Nevena

Structural health monitoring is a multi-disciplinary engineering field that should allow the actual wind turbine maintenance programmes to evolve to the next level, hence increasing safety and reliability and decreasing turbines downtime. The main idea is to have a sensing system on the structure...... cases are considered, two practical problems from the wind industry are studied, i.e. monitoring of the gearbox shaft torque and the tower root bending moments. The second part of the thesis is focused on the influence of friction on the health of the wind turbine and on the nonlinear identification...... that monitors the system responses and notifies the operator when damages or degradations have been detected. However, some of the response signals that contain important information about the health of the wind turbine components cannot be directly measured, or measuring them is highly complex and costly...

Thermodynamic assessment of a wind turbine based combined cycle

International Nuclear Information System (INIS)

Rabbani, M.; Dincer, I.; Naterer, G.F.

2012-01-01

Combined cycles use the exhaust gases released from a Gas Turbine (GT). Approximately 30–40% of the turbine shaft work is typically used to drive the Compressor. The present study analyzes a system that couples a Wind Turbine (WT) with a combined cycle. It demonstrates how a WT can be used to supply power to the Compressor in the GT cycle and pump fluid through a reheat Rankine cycle, in order to increase the overall power output. Three different configurations are discussed, namely high penetration, low penetration and wind power addition. In the case of a low electricity demand and high penetration configuration, extra wind power is used to compress air which can then be used in the low penetration configuration. During a high load demand, all the wind power is used to drive the pump and compressor and if required additional compressed air is supplied by a storage unit. The analysis shows that increasing the combustion temperature reduces the critical velocity and mass flow rate. Increases in wind speed reduce both energy and exergy efficiency of the overall system. -- Highlights: ► This study analyzes a system that couples a wind turbine with a combined power generation cycle. ► Surplus wind power is used to compress air, which is then stored and used at a later time. ► Increasing the pressure ratio will reduce the work ratio between the Rankine and Brayton cycles. ► A higher combustion temperature will increase the net work output, as well as the system energy and exergy efficiencies.

Inverse load calculation procedure for offshore wind turbines and application to a 5-MW wind turbine support structure: Inverse load calculation procedure for offshore wind turbines

Energy Technology Data Exchange (ETDEWEB)

Pahn, T. [Pahn Ingenieure, Am Seegraben 17b 03051 Cottbus Germany; Rolfes, R. [Institut f?r Statik und Dynamik, Leibniz Universit?t Hannover, Appelstra?e 9A 30167 Hannover Germany; Jonkman, J. [National Renewable Energy Laboratory, 15013 Denver West Parkway Golden Colorado 80401 USA

2017-02-20

A significant number of wind turbines installed today have reached their designed service life of 20 years, and the number will rise continuously. Most of these turbines promise a more economical performance if they operate for more than 20 years. To assess a continued operation, we have to analyze the load-bearing capacity of the support structure with respect to site-specific conditions. Such an analysis requires the comparison of the loads used for the design of the support structure with the actual loads experienced. This publication presents the application of a so-called inverse load calculation to a 5-MW wind turbine support structure. The inverse load calculation determines external loads derived from a mechanical description of the support structure and from measured structural responses. Using numerical simulations with the software fast, we investigated the influence of wind-turbine-specific effects such as the wind turbine control or the dynamic interaction between the loads and the support structure to the presented inverse load calculation procedure. fast is used to study the inverse calculation of simultaneously acting wind and wave loads, which has not been carried out until now. Furthermore, the application of the inverse load calculation procedure to a real 5-MW wind turbine support structure is demonstrated. In terms of this practical application, setting up the mechanical system for the support structure using measurement data is discussed. The paper presents results for defined load cases and assesses the accuracy of the inversely derived dynamic loads for both the simulations and the practical application.

Structural Dynamic Analysis of Semi-Submersible Floating Vertical Axis Wind Turbines

Directory of Open Access Journals (Sweden)

Jeremiah Ishie

2016-12-01

Full Text Available The strong and stable wind at offshore locations and the increasing demand for energy have made the application of wind turbines in deeper water surge. A novel concept of a 5 MW baseline Floating Vertical Axis Wind Turbine (FVAWT and a 5 MW optimised FVAWT with the DeepWind Darrieus rotor and the optimised DeepWind Darrieus rotor, respectively, were studied extensively. The structural responses, fatigue damages, platform global motions and mooring line dynamics of the FVAWTs were investigated comprehensively during normal operating conditions under steady wind and turbulent wind conditions, using a coupled non-linear aero-hydro-servo-elastic code (the Simo-Riflex-DMS code which was developed by Wang et al. for modeling FVAWTs. This coupled code incorporates the models for the turbulent wind field, aerodynamics, hydrodynamics, structural dynamics, and generator controller. The simulation is performed in a fully coupled manner in time domain. The comparison of responses under different wind conditions were used to demonstrate the effect of turbulence on both FVAWTs dynamic responses. The turbulent wind condition has the advantage of reducing the 2P effects. Furthermore, comparative studies of the FVAWTs responses were undertaken to explore the advantages of adopting the optimised 5 MW DeepWind Darrieus rotor over the baseline model. The results identified the 5 MW optimised FVAWT to having: lower Fore-Aft (FA but higher lower Side-Side (SS bending moments of structural components; lower motions amplitude; lower short-term fatigue equivalent loads and a further reduced 2P effects.

Thermodynamic and structural properties in complexing media

International Nuclear Information System (INIS)

Di Giandomenico, M.V.

2007-10-01

Protactinium is experiencing a renewal of interest in the frame of long-term energy production. Modelling the behaviour of this element in the geosphere requires thermodynamic and structural data relevant to environmental conditions. Now deep clayey formation are considered for the disposal of radioactive waste and high values of natural sulphate contents have been determined in pore water in equilibrium with clay surface. Because of its tendency to polymerisation, hydrolysis and sorption on all solid supports, the equilibria constants relative to monomer species were determined at tracer scale (ca. 10 - 12 M) with 233 Pa. The complexation constants of Pa(V) and sulphate ions were calculated starting from a systematic study of the apparent distribution coefficient D in the system TTA/Toluene/H 2 O/Na 2 SO 4 /HClO 4 /NaClO 4 and as a function of ionic strength, temperature, free sulphate, protons and chelatant concentration. First of all, the interaction between free species H + , SO 4 - , Na + leads to the formation of HSO 4 - and NaSO 4 - , for which concentrations depend upon the related thermodynamic constants. For this purpose a computer code was developed in order to determine all free species concentration. This iterative code takes into account the influence of temperature and ionic strength (SIT modelling) on thermodynamic constants. The direct measure of Pa(V) in the organic and aqueous phase by g-spectrometry had conducted to estimate the apparent distribution coefficient D as function of free sulphate ions. Complexation constants have been determined after a mathematical treatment of D. The extrapolation of these constants at zero ionic strength have been realized by SIT modelling at different temperatures. Besides, enthalpy and entropy values were calculated. Parallelly, the structural study of Pa(V) was performed using 231 Pa. XANES and EXAFS spectra show unambiguously the absence of the trans di-oxo bond that characterizes the other early actinide

Development of a Fast Fluid-Structure Coupling Technique for Wind Turbine Computations

DEFF Research Database (Denmark)

Sessarego, Matias; Ramos García, Néstor; Shen, Wen Zhong

2015-01-01

Fluid-structure interaction simulations are routinely used in the wind energy industry to evaluate the aerodynamic and structural dynamic performance of wind turbines. Most aero-elastic codes in modern times implement a blade element momentum technique to model the rotor aerodynamics and a modal......, multi-body, or finite-element approach to model the turbine structural dynamics. The present paper describes a novel fluid-structure coupling technique which combines a threedimensional viscous-inviscid solver for horizontal-axis wind-turbine aerodynamics, called MIRAS, and the structural dynamics model...... used in the aero-elastic code FLEX5. The new code, MIRASFLEX, in general shows good agreement with the standard aero-elastic codes FLEX5 and FAST for various test cases. The structural model in MIRAS-FLEX acts to reduce the aerodynamic load computed by MIRAS, particularly near the tip and at high wind...

The analysis of dynamic characteristics and wind-induced displacement response of space Beam String Structure

Directory of Open Access Journals (Sweden)

Chen Yong Jian

2018-01-01

Full Text Available The Beam String Structure structural system, also called BSS, has the advantages of lighter dead weight and greater flexibility. The wind load is the main design control factor. The dynamic characteristics and wind-induced displacement response of BSS are studied by the finite element method. The roof structure of the stadium roof of the Fuzhou Olympic Sports Center is the engineering background. 1The numerical model was built by ANSYS, by shape finding, determine the initial stress state of structural members such as external cables; 2From the analysis of dynamic characteristics, the main mode of vibration is the vibration of cables; 3The wind speed spectrum of MATLAB generation structure is obtained by AR method, the structural response of the structure under static wind load and fluctuating wind load is calculated. From the analysis result, considering the equivalent static wind load of BSS , the design of adverse wind is not safe, and the fluctuating wind load should be taken into account.

Thermodynamics and kinetics of RNA tertiary structure formation in the junctionless hairpin ribozyme.

Science.gov (United States)

White, Neil A; Hoogstraten, Charles G

2017-09-01

The hairpin ribozyme consists of two RNA internal loops that interact to form the catalytically active structure. This docking transition is a rare example of intermolecular formation of RNA tertiary structure without coupling to helix annealing. We have used temperature-dependent surface plasmon resonance (SPR) to characterize the thermodynamics and kinetics of RNA tertiary structure formation for the junctionless form of the ribozyme, in which loops A and B reside on separate molecules. We find docking to be strongly enthalpy-driven and to be accompanied by substantial activation barriers for association and dissociation, consistent with the structural reorganization of both internal loops upon complex formation. Comparisons with the parallel analysis of a ribozyme variant carrying a 2'-O-methyl modification at the self-cleavage site and with published data in other systems reveal a surprising diversity of thermodynamic signatures, emphasizing the delicate balance of contributions to the free energy of formation of RNA tertiary structure. Copyright © 2017 Elsevier B.V. All rights reserved.

Using Structured Examples and Prompting Reflective Questions to Correct Misconceptions about Thermodynamic Concepts

Science.gov (United States)

Olakanmi, E. O.; Doyoyo, M.

2014-01-01

This paper explores the effectiveness of using "structured examples in concert with prompting reflective questions" to address misconceptions held by mechanical engineering students about thermodynamic principles by employing pre-test and post-test design, a structured questionnaire, lecture room observation, and participants'…

Simulation of Cu-Mg metallic glass: Thermodynamics and structure

International Nuclear Information System (INIS)

Bailey, Nicholas P.; Schioetz, Jakob; Jacobsen, Karsten W.

2004-01-01

We have obtained effective medium theory interatomic potential parameters suitable for studying Cu-Mg metallic glasses. We present thermodynamic and structural results from simulations of such glasses over a range of compositions. We have produced low-temperature configurations by cooling from the melt at as slow a rate as practical, using constant temperature and pressure molecular dynamics. During the cooling process we have carried out thermodynamic analyses based on the temperature dependence of the enthalpy and its derivative, the specific heat, from which the glass transition temperature may be determined. We have also carried out structural analyses using the radial distribution function (RDF) and common neighbor analysis (CNA). Our analysis suggests that the splitting of the second peak, commonly associated with metallic glasses, in fact, has little to do with the glass transition itself, but is simply a consequence of the narrowing of peaks associated with structural features present in the liquid state. In fact, the splitting temperature for the Cu-Cu RDF is well above T g . The CNA also highlights a strong similarity between the structure of the intermetallic alloys and the amorphous alloys of similar composition. We have also investigated the diffusivity in the supercooled regime. Its temperature dependence indicates fragile-liquid behavior, typical of binary metallic glasses. On the other hand, the relatively low specific-heat jump of around 1.5k B /atom indicates apparent strong-liquid behavior, but this can be explained by the width of the transition due to the high cooling rates

Formation and thermodynamic stability of (polymer + porphyrin) supramolecular structures in aqueous solutions

International Nuclear Information System (INIS)

Costa, Viviana C.P. da; Hwang, Barrington J.; Eggen, Spencer E.; Wallace, Megan J.; Annunziata, Onofrio

2014-01-01

Highlights: • Thermodynamic stability of a (polymer + porphyrin) supramolecular structure was characterized. • Isothermal titration calorimetry provided two ways to determine reaction enthalpies. • Exothermic (polymer + porphyrin) binding competes with porphyrin self-association. • (Polymer + porphyrin) binding is entropically favored with respect to porphyrin self-association. • Spectral shifts show importance of porphyrin central hydrogens in polymer binding. - Abstract: Optical properties of porphyrins can be tuned through (polymer + porphyrin) (host + guest) binding in solution. This gives rise to the formation of supramolecular structures. In this paper, the formation, thermodynamic stability and spectroscopic properties of (polymer + porphyrin) supramolecular structures and their competition with porphyrin self-association were investigated by both isothermal titration calorimetry (ITC) and absorption spectroscopy. Specifically, reaction enthalpies and equilibrium constants were measured for meso-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) self-association and TPPS binding to the polymer poly(vinylpyrrolidone) (PVP, 40 kg/mol) in aqueous solutions at pH 7 and three different temperatures (12, 25 and 37 °C). ITC, compared to spectroscopic techniques, provides two independent means to determine reaction enthalpies: direct measurements and Van’t Hoff plot. This was used as a criterion to assess that (1) self-association of TPPS is limited to the formation of dimers and (2) TPPS binds to PVP in its monomeric state only. The formation of TPPS dimers and (PVP + TPPS) supramolecular structures are both enthalpically driven. However, (polymer + porphyrin) binding was found to be entropically favored compared to dimerization. Furthermore, the reaction enthalpies of these two processes significantly depend on temperature. This behavior was attributed to hydrophobic interactions. Finally, the limiting absorption spectra of monomeric, dimeric and polymer

Observations of neutral winds, wind shears, and wave structure during a sporadic-E/QP event

Directory of Open Access Journals (Sweden)

M. F. Larsen

2005-10-01

Full Text Available The second Sporadic E Experiment over Kyushu (SEEK-2 was carried out on 3 August 2002, during an active sporadic-E event that also showed quasi-periodic (QP echoes. Two rockets were launched into the event from Kagoshima Space Center in southern Japan 15 min apart. Both carried a suite of instruments, but the second rocket also released a trimethyl aluminum (TMA trail to measure the neutral winds and turbulence structure. In a number of earlier measurements in similar conditions, large winds and shears that were either unstable or close to instability were observed in the altitude range where the ionization layer occurred. The SEEK-2 wind measurements showed similar vertical structure, but unlike earlier experiments, there was a significant difference between the up-leg and down-leg wind profiles. In addition, wave or billow-like fluctuations were evident in the up-leg portion of the trail, while the lower portion of the down-leg trail was found to have extremely strong turbulence that led to a rapid break-up of the trail. The large east-west gradient in the winds and the strong turbulence have not been observed before. The wind profiles and shears, as well as the qualitative characteristics of the strong turbulence are presented, along with a discussion of the implications of the dynamical features. Keywords. Ionosphere (Mid-latitude ionosphere; Ionospheric irregularities; Electric field and currents

Extended thermodynamics

CERN Document Server

Müller, Ingo

1993-01-01

Physicists firmly believe that the differential equations of nature should be hyperbolic so as to exclude action at a distance; yet the equations of irreversible thermodynamics - those of Navier-Stokes and Fourier - are parabolic. This incompatibility between the expectation of physicists and the classical laws of thermodynamics has prompted the formulation of extended thermodynamics. After describing the motifs and early evolution of this new branch of irreversible thermodynamics, the authors apply the theory to mon-atomic gases, mixtures of gases, relativistic gases, and "gases" of phonons and photons. The discussion brings into perspective the various phenomena called second sound, such as heat propagation, propagation of shear stress and concentration, and the second sound in liquid helium. The formal mathematical structure of extended thermodynamics is exposed and the theory is shown to be fully compatible with the kinetic theory of gases. The study closes with the testing of extended thermodynamics thro...

Grid faults' impact on wind turbine structural loads

DEFF Research Database (Denmark)

Hansen, Anca Daniela; Cutululis, Nicolaos Antonio; Iov, F.

2007-01-01

The objective of this work is to illustrate the impact of the grid faults on the wind turbine structural loads. Grid faults are typically simulated in detailed power system simulation tools, which by applying simplified mechanical models, are not able to provide a throughout insight...... on the structural loads caused by sudden disturbances on the grid. On the other hand, structural loads of the wind turbine are typically assessed in advanced aerolastic computer codes, which by applying simplified electrical models do not provide detailed electrical insight. This paper presents a simulation...... strategy, where the focus is on how to access a proper combination of two complimentary simulations tools, such as the advanced aeroelastic computer code HAWC2 and the detailed power system simulation tool DIgSILENT, in order to provide a whole overview of both the structural and the electrical behaviour...

Dynamic Analysis of Wind Turbines Including Soil-Structure Interaction

DEFF Research Database (Denmark)

Harte, M.; Basu, B.; Nielsen, Søren R.K.

2012-01-01

This paper investigates the along-wind forced vibration response of an onshore wind turbine. The study includes the dynamic interaction effects between the foundation and the underlying soil, as softer soils can influence the dynamic response of wind turbines. A Multi-Degree-of-Freedom (MDOF......) horizontal axes onshore wind turbine model is developed for dynamic analysis using an Euler–Lagrangian approach. The model is comprised of a rotor blade system, a nacelle and a flexible tower connected to a foundation system using a substructuring approach. The rotor blade system consists of three rotating...... for displacement of the turbine system are obtained and the modal frequencies of the combined turbine-foundation system are estimated. Simulations are presented for the MDOF turbine structure subjected to wind loading for different soil stiffness conditions. Steady state and turbulent wind loading, developed using...

Thermodynamics, maximum power, and the dynamics of preferential river flow structures at the continental scale

Directory of Open Access Journals (Sweden)

A. Kleidon

2013-01-01

Full Text Available The organization of drainage basins shows some reproducible phenomena, as exemplified by self-similar fractal river network structures and typical scaling laws, and these have been related to energetic optimization principles, such as minimization of stream power, minimum energy expenditure or maximum "access". Here we describe the organization and dynamics of drainage systems using thermodynamics, focusing on the generation, dissipation and transfer of free energy associated with river flow and sediment transport. We argue that the organization of drainage basins reflects the fundamental tendency of natural systems to deplete driving gradients as fast as possible through the maximization of free energy generation, thereby accelerating the dynamics of the system. This effectively results in the maximization of sediment export to deplete topographic gradients as fast as possible and potentially involves large-scale feedbacks to continental uplift. We illustrate this thermodynamic description with a set of three highly simplified models related to water and sediment flow and describe the mechanisms and feedbacks involved in the evolution and dynamics of the associated structures. We close by discussing how this thermodynamic perspective is consistent with previous approaches and the implications that such a thermodynamic description has for the understanding and prediction of sub-grid scale organization of drainage systems and preferential flow structures in general.

A New Structure Based on Cascaded Multilevel Converter for Variable Speed Wind Turbine

DEFF Research Database (Denmark)

Deng, Fujin; Chen, Zhe

2010-01-01

An alternative structure for variable speed wind turbine, using multiple permanent magnet synchronous generators (PMSGs) drive-train configuration and cascaded multilevel converter is proposed in this paper. This study presents a power electronic solution for the wind turbine. A transformer......-less cascaded multilevel converter interface based on PMSGs is developed to synthesize a desired high ac sinusoidal output voltage. The benefits of high power and high ac voltage make this structure possible to be applied in the wind power generation. In addition, the bulky transformer could be omitted....... A simulation model of 10 MW variable speed wind turbine based on PMSGs developed in PSCAD/EMTDC is presented. The dynamic performance of grid-connected wind turbine is analyzed. Simulation results shows that the proposed structure may be attractive in wind power generation....

Damage Analysis and Evaluation of Light Steel Structures Exposed to Wind Hazards

Directory of Open Access Journals (Sweden)

Na Yang

2017-03-01

Full Text Available Compared to hot-rolled steel structures, cold-formed steel structures are susceptible to extreme winds because of the light weight of the building and its components. Many modern cold-formed steel structures have sustained significant structural damage ranging from loss of cladding to complete collapse in recent cyclones. This article first provides some real damage cases for light steel structures induced by the high winds. After that, the paper reviews research on the damage analysis and evaluation of light steel structures caused by strong winds, which include connection failure, fatigue failure, purlin buckling, and primary frame component instability problems. Moreover, this review will mention some applications of structure damage assessment methods in this area, such as vulnerability analysis and performance-based theory, etc.

The Influence of Content Organization on Student's Cognitive Structure in Thermodynamics.

Science.gov (United States)

Moreira, Marco A.; Santos, Carlos A.

1981-01-01

Two approaches to the content of thermodynamics were used in an introductory college physics course: traditional organization and organization based on Ausubel's learning theory. The influence of these organizations on engineering student's (N=58) cognitive structure was investigated using a word association test analyzed through hierarchical…

Damage tolerance and structural monitoring for wind turbine blades

DEFF Research Database (Denmark)

McGugan, Malcolm; Pereira, Gilmar Ferreira; Sørensen, Bent F.

2015-01-01

The paper proposes a methodology for reliable design and maintenance of wind turbine rotor blades using a condition monitoring approach and a damage tolerance index coupling the material and structure. By improving the understanding of material properties that control damage propagation it will b......The paper proposes a methodology for reliable design and maintenance of wind turbine rotor blades using a condition monitoring approach and a damage tolerance index coupling the material and structure. By improving the understanding of material properties that control damage propagation...

Lightweight structure design for wind energy by integrating nanostructured materials

International Nuclear Information System (INIS)

Li, Ying; Lu, Jian

2014-01-01

Highlights: • Integrate high-strength nano-materials into lightweight design. • Lightweight design scheme for wind turbine tower application. • Expand the bending formulae for tapered tubular structures with varying thickness. • We rewrite the Secant Formula for a tapered beam under eccentric compression. - Abstract: Wind power develops very fast nowadays with high expectation. Although at the mean time, the use of taller towers, however, smacks head-on into the issue of transportability. The engineering base and computational tools have to be developed to match machine size and volume. Consequently the research on the light weight structures of tower is carrying out in the main countries which are actively developing wind energy. This paper reports a new design scheme of light weight structure for wind turbine tower. This design scheme is based on the integration of the nanostructured materials produced by the Surface Mechanical Attrition Treatment (SMAT) process. The objective of this study is to accomplish the weight reduction by optimizing the wall thickness of the tapered tubular structure. The basic methods include the identification of the critical zones and the distribution of the high strength materials according to different necessities. The equivalent strength or stiffness design method and the high strength material properties after SMAT process are combined together. Bending and buckling are two main kinds of static loads concerned in consideration. The study results reveal that there is still enough margin for weight reduction in the traditional wind turbine tower design

Verification of the Wind Response of a Stack Structure

Directory of Open Access Journals (Sweden)

D. Makovička

2003-01-01

Full Text Available This paper deals with verification analysis of the wind response of a power plant stack structure. Over a period two weeks the actual history of the dynamic response of the structure, and the direction and intensity of the actual wind load was measured, reported and processed with the use of a computer. The resulting data was used to verify the design stage data of the structure, with the natural frequencies and modes assumed by the design and with the dominant effect of other sources on the site. In conclusion the standard requirements are compared with the actual results of measurements and their expansion to the design load.

Community investment in wind farms: funding structure effects in wind energy infrastructure development.

Science.gov (United States)

Beery, Joshua A; Day, Jennifer E

2015-03-03

Wind energy development is an increasingly popular form of renewable energy infrastructure in rural areas. Communities generally perceive socioeconomic benefits accrue and that community funding structures are preferable to corporate structures, yet lack supporting quantitative data to inform energy policy. This study uses the Everpower wind development, to be located in Midwestern Ohio, as a hypothetical modeling environment to identify and examine socioeconomic impact trends arising from corporate, community and diversified funding structures. Analysis of five National Renewable Energy Laboratory Jobs and Economic Development Impact models incorporating local economic data and review of relevant literature were conducted. The findings suggest that community and diversified funding structures exhibit 40-100% higher socioeconomic impact levels than corporate structures. Prioritization of funding sources and retention of federal tax incentives were identified as key elements. The incorporation of local shares was found to mitigate the negative effects of foreign private equity, local debt financing increased economic output and opportunities for private equity investment were identified. The results provide the groundwork for energy policies focused to maximize socioeconomic impacts while creating opportunities for inclusive economic participation and improved social acceptance levels fundamental to the deployment of renewable energy technology.

Organogels thermodynamics, structure, solvent role, and properties

CERN Document Server

Guenet, Jean-Michel

2016-01-01

This book provides a physics-oriented introduction to organogels with a comparison to polymer thermoreversible gels whenever relevant. The past decade has seen the development of a wide variety of newly-synthesized molecules that can spontaneously self-assemble or crystallize from their organic or aqueous solutions to produce fibrillar networks, namely organogels, with potential applications in organic electronics, light harvesting, bio-imaging, non-linear optics, and the like. This compact volume presents a detailed outlook of these novel molecular systems with special emphasis upon their thermodynamics, morphology, molecular structure, and rheology. The definition of these complex systems is also tackled, as well as the role of the solvent. The text features numerous temperature-phase diagrams for a variety of organogels as well as illustrations of their structures at the microscopic, mesoscopic and macroscopic level. A review of some potential applications is provided including hybrid functional materials ...

Molecular structure and thermodynamic predictions to create highly sensitive microRNA biosensors

International Nuclear Information System (INIS)

Larkey, Nicholas E.; Brucks, Corinne N.; Lansing, Shan S.; Le, Sophia D.; Smith, Natasha M.; Tran, Victoria; Zhang, Lulu; Burrows, Sean M.

2016-01-01

Many studies have established microRNAs (miRNAs) as post-transcriptional regulators in a variety of intracellular molecular processes. Abnormal changes in miRNA have been associated with several diseases. However, these changes are sometimes subtle and occur at nanomolar levels or lower. Several biosensing hurdles for in situ cellular/tissue analysis of miRNA limit detection of small amounts of miRNA. Of these limitations the most challenging are selectivity and sensor degradation creating high background signals and false signals. Recently we developed a reporter+probe biosensor for let-7a that showed potential to mitigate false signal from sensor degradation. Here we designed reporter+probe biosensors for miR-26a-2-3p and miR-27a-5p to better understand the effect of thermodynamics and molecular structures of the biosensor constituents on the analytical performance. Signal changes from interactions between Cy3 and Cy5 on the reporters were used to understand structural aspects of the reporter designs. Theoretical thermodynamic values, single stranded conformations, hetero- and homodimerization structures, and equilibrium concentrations of the reporters and probes were used to interpret the experimental observations. Studies of the sensitivity and selectivity revealed 5–9 nM detection limits in the presence and absence of interfering off-analyte miRNAs. These studies will aid in determining how to rationally design reporter+probe biosensors to overcome hurdles associated with highly sensitive miRNA biosensing. - Highlights: • Challenges facing highly sensitive miRNA biosensor designs are addressed. • Thermodynamic and molecular structure design metrics for reporter+probe biosensors are proposed. • The influence of ideal and non-ideal reporter hairpin structures on reporter+probe formation and signal change are discussed. • 5–9 nM limits of detection were observed with no interference from off-analytes.

Molecular structure and thermodynamic predictions to create highly sensitive microRNA biosensors

Energy Technology Data Exchange (ETDEWEB)

Larkey, Nicholas E.; Brucks, Corinne N.; Lansing, Shan S.; Le, Sophia D.; Smith, Natasha M.; Tran, Victoria; Zhang, Lulu; Burrows, Sean M., E-mail: sean.burrows@oregonstate.edu

2016-02-25

Many studies have established microRNAs (miRNAs) as post-transcriptional regulators in a variety of intracellular molecular processes. Abnormal changes in miRNA have been associated with several diseases. However, these changes are sometimes subtle and occur at nanomolar levels or lower. Several biosensing hurdles for in situ cellular/tissue analysis of miRNA limit detection of small amounts of miRNA. Of these limitations the most challenging are selectivity and sensor degradation creating high background signals and false signals. Recently we developed a reporter+probe biosensor for let-7a that showed potential to mitigate false signal from sensor degradation. Here we designed reporter+probe biosensors for miR-26a-2-3p and miR-27a-5p to better understand the effect of thermodynamics and molecular structures of the biosensor constituents on the analytical performance. Signal changes from interactions between Cy3 and Cy5 on the reporters were used to understand structural aspects of the reporter designs. Theoretical thermodynamic values, single stranded conformations, hetero- and homodimerization structures, and equilibrium concentrations of the reporters and probes were used to interpret the experimental observations. Studies of the sensitivity and selectivity revealed 5–9 nM detection limits in the presence and absence of interfering off-analyte miRNAs. These studies will aid in determining how to rationally design reporter+probe biosensors to overcome hurdles associated with highly sensitive miRNA biosensing. - Highlights: • Challenges facing highly sensitive miRNA biosensor designs are addressed. • Thermodynamic and molecular structure design metrics for reporter+probe biosensors are proposed. • The influence of ideal and non-ideal reporter hairpin structures on reporter+probe formation and signal change are discussed. • 5–9 nM limits of detection were observed with no interference from off-analytes.

Turbulence and turbulence-generated structural loading in wind turbine clusters

DEFF Research Database (Denmark)

Frandsen, Sten Tronæs

2007-01-01

of the model is that it became part of the Danish standard for wind turbine design DS 472 (2001) in August 2001 and it is part of the corresponding international standard, IEC61400-1 (2005). Also, extreme loading under normal operation for wake conditions and the efficiency of very large wind farms......Turbulence - in terms of standard deviation of wind speed fluctuations - and other flow characteristics are different in the interior of wind farms relative to the free flow and action must be taken to ensure sufficient structural sustainability of the wind turbines exposed to “wind farm flow......”. The standard deviation of wind speed fluctuations is a known key parameter for both extreme- and fatigue loading, and it is argued and found to be justified that a model for change in turbulence intensity alone may account for increased fatigue loading in wind farms. Changes in scale of turbulence...

Structural Analysis of Basalt Fiber Reinforced Plastic Wind Turbine Blade

Directory of Open Access Journals (Sweden)

Mengal Ali Nawaz

2014-07-01

Full Text Available In this study, Basalt fiber reinforced plastic (BFRP wind turbine blade was analyzed and compared with Glass fiber reinforced plastic blade (GFRP. Finite element analysis (FEA of blade was carried out using ANSYS. Data for FEA was obtained by using rule of mixture. The shell element in ANSYS was used to simulate the wind turbine blade and to conduct its strength analysis. The structural analysis and comparison of blade deformations proved that BFRP wind turbine blade has better strength compared to GFRP wind turbine blade.

Thermodynamic Upper Bound on Broadband Light Coupling with Photonic Structures

KAUST Repository

Yu, Zongfu

2012-10-01

The coupling between free space radiation and optical media critically influences the performance of optical devices. We show that, for any given photonic structure, the sum of the external coupling rates for all its optical modes are subject to an upper bound dictated by the second law of thermodynamics. Such bound limits how efficient light can be coupled to any photonic structure. As one example of application, we use this upper bound to derive the limit of light absorption in broadband solar absorbers. © 2012 American Physical Society.

Aspects of structural health and condition monitoring of offshore wind turbines.

Science.gov (United States)

Antoniadou, I; Dervilis, N; Papatheou, E; Maguire, A E; Worden, K

2015-02-28

Wind power has expanded significantly over the past years, although reliability of wind turbine systems, especially of offshore wind turbines, has been many times unsatisfactory in the past. Wind turbine failures are equivalent to crucial financial losses. Therefore, creating and applying strategies that improve the reliability of their components is important for a successful implementation of such systems. Structural health monitoring (SHM) addresses these problems through the monitoring of parameters indicative of the state of the structure examined. Condition monitoring (CM), on the other hand, can be seen as a specialized area of the SHM community that aims at damage detection of, particularly, rotating machinery. The paper is divided into two parts: in the first part, advanced signal processing and machine learning methods are discussed for SHM and CM on wind turbine gearbox and blade damage detection examples. In the second part, an initial exploration of supervisor control and data acquisition systems data of an offshore wind farm is presented, and data-driven approaches are proposed for detecting abnormal behaviour of wind turbines. It is shown that the advanced signal processing methods discussed are effective and that it is important to adopt these SHM strategies in the wind energy sector.

Aspects of structural health and condition monitoring of offshore wind turbines

Science.gov (United States)

Antoniadou, I.; Dervilis, N.; Papatheou, E.; Maguire, A. E.; Worden, K.

2015-01-01

Wind power has expanded significantly over the past years, although reliability of wind turbine systems, especially of offshore wind turbines, has been many times unsatisfactory in the past. Wind turbine failures are equivalent to crucial financial losses. Therefore, creating and applying strategies that improve the reliability of their components is important for a successful implementation of such systems. Structural health monitoring (SHM) addresses these problems through the monitoring of parameters indicative of the state of the structure examined. Condition monitoring (CM), on the other hand, can be seen as a specialized area of the SHM community that aims at damage detection of, particularly, rotating machinery. The paper is divided into two parts: in the first part, advanced signal processing and machine learning methods are discussed for SHM and CM on wind turbine gearbox and blade damage detection examples. In the second part, an initial exploration of supervisor control and data acquisition systems data of an offshore wind farm is presented, and data-driven approaches are proposed for detecting abnormal behaviour of wind turbines. It is shown that the advanced signal processing methods discussed are effective and that it is important to adopt these SHM strategies in the wind energy sector. PMID:25583864

Structural and Thermodynamic Properties of Amyloid-β Peptides: Impact of Fragment Size

Science.gov (United States)

Kitahara, T.; Wise-Scira, O.; Coskuner, O.

2010-10-01

Alzheimer's disease is a progressive neurodegenerative disease whose physiological characteristics include the accumulation of amyloid-containing deposits in the brain and consequent synapse and neuron loss. Unfortunately, most widely used drugs for the treatment can palliate the outer symptoms but cannot cure the disease itself. Hence, developing a new drug that can cure it. Most recently, the ``early aggregation and monomer'' hypothesis has become popular and a few drugs have been developed based on this hypothesis. Detailed understanding of the amyloid-β peptide structure can better help us to determine more effective treatment strategies; indeed, the structure of Amyloid has been studied extensively employing experimental and theoretical tools. Nevertheless, those studies have employed different fragment sizes of Amyloid and characterized its conformational nature in different media. Thus, the structural properties might be different from each other and provide a reason for the existing debates in the literature. Here, we performed all-atom MD simulations and present the structural and thermodynamic properties of Aβ1-16, Aβ1-28, and Aβ1-42 in the gas phase and in aqueous solution. Our studies show that the overall structures, secondary structures, and the calculated thermodynamic properties change with increasing peptide size. In addition, we find that the structural properties of those peptides are different from each other in the gas phase and in aqueous solution.

Thermodynamic heuristics with case-based reasoning: combined insights for RNA pseudoknot secondary structure.

Science.gov (United States)

Al-Khatib, Ra'ed M; Rashid, Nur'Aini Abdul; Abdullah, Rosni

2011-08-01

The secondary structure of RNA pseudoknots has been extensively inferred and scrutinized by computational approaches. Experimental methods for determining RNA structure are time consuming and tedious; therefore, predictive computational approaches are required. Predicting the most accurate and energy-stable pseudoknot RNA secondary structure has been proven to be an NP-hard problem. In this paper, a new RNA folding approach, termed MSeeker, is presented; it includes KnotSeeker (a heuristic method) and Mfold (a thermodynamic algorithm). The global optimization of this thermodynamic heuristic approach was further enhanced by using a case-based reasoning technique as a local optimization method. MSeeker is a proposed algorithm for predicting RNA pseudoknot structure from individual sequences, especially long ones. This research demonstrates that MSeeker improves the sensitivity and specificity of existing RNA pseudoknot structure predictions. The performance and structural results from this proposed method were evaluated against seven other state-of-the-art pseudoknot prediction methods. The MSeeker method had better sensitivity than the DotKnot, FlexStem, HotKnots, pknotsRG, ILM, NUPACK and pknotsRE methods, with 79% of the predicted pseudoknot base-pairs being correct.

Turbulence and turbulence-generated structural loading in wind turbine clusters

Energy Technology Data Exchange (ETDEWEB)

Frandsen, Sten

2007-01-15

Turbulence, in terms of standard deviation of wind speed fluctuations, and other flow characteristics are different in the interior of wind farms relative to the free flow and action must be taken to ensure sufficient structural sustainability of the wind turbines exposed to 'wind farm flow'. The standard deviation of wind speed fluctuations is a known key parameter for both extreme- and fatigue loading, and it is argued and found to be justified that a model for change in turbulence intensity alone may account for increased fatigue loading in wind farms. Changes in scale of turbulence and horizontal flow-shear also influence the dynamic response and thus fatigue loading. However, these parameters are typically negatively or positively correlated with the standard deviation of wind speed fluctuations, which therefore can, if need be, represent these other variables. Thus, models for spatially averaged turbulence intensity inside the wind farm and direct-wake turbulence intensity are being devised and a method to combine the different load situations is proposed. The combination of the load cases implies a weighting method involving the slope of the considered material's Woehler curve. In the context, this is novel and necessary to avoid excessive safety for fatigue estimation of the structure's steel components, and non-conservatism for fibreglass components. The proposed model offers significant reductions in computational efforts in the design process. The status for the implementation of the model is that it became part of the Danish standard for wind turbine design DS 472 (2001) in August 2001 and it is part of the corresponding international standard, IEC61400-1 (2005). Also, extreme loading under normal operation for wake conditions and the efficiency of very large wind farms are discussed. (au)

Objective estimation of tropical cyclone innercore surface wind structure using infrared satellite images

Science.gov (United States)

Zhang, Changjiang; Dai, Lijie; Ma, Leiming; Qian, Jinfang; Yang, Bo

2017-10-01

An objective technique is presented for estimating tropical cyclone (TC) innercore two-dimensional (2-D) surface wind field structure using infrared satellite imagery and machine learning. For a TC with eye, the eye contour is first segmented by a geodesic active contour model, based on which the eye circumference is obtained as the TC eye size. A mathematical model is then established between the eye size and the radius of maximum wind obtained from the past official TC report to derive the 2-D surface wind field within the TC eye. Meanwhile, the composite information about the latitude of TC center, surface maximum wind speed, TC age, and critical wind radii of 34- and 50-kt winds can be combined to build another mathematical model for deriving the innercore wind structure. After that, least squares support vector machine (LSSVM), radial basis function neural network (RBFNN), and linear regression are introduced, respectively, in the two mathematical models, which are then tested with sensitivity experiments on real TC cases. Verification shows that the innercore 2-D surface wind field structure estimated by LSSVM is better than that of RBFNN and linear regression.

Modal Analysis on Fluid-Structure Interaction of MW-Level Vertical Axis Wind Turbine Tower

Directory of Open Access Journals (Sweden)

Tan Jiqiu

2014-05-01

Full Text Available In order to avoid resonance problem of MW-level vertical axis wind turbine induced by wind, a flow field model of the MW-level vertical axis wind turbine is established by using the fluid flow control equations, calculate flow’s velocity and pressure of the MW-level vertical axis wind turbine and load onto tower’s before and after surface, study the Modal analysis of fluid-structure interaction of MW-level vertical axis wind turbine tower. The results show that fluid-structure interaction field of MW- level vertical axis wind turbine tower has little effect on the modal vibration mode, but has a great effect on its natural frequency and the maximum deformation, and the influence will decrease with increasing of modal order; MW-level vertical axis wind turbine tower needs to be raised the stiffness and strength, its structure also needs to be optimized; In the case of satisfy the intensity, the larger the ratio of the tower height and wind turbines diameter, the more soft the MW-level vertical axis wind turbine tower, the lower its frequency.

Electronic band structure, optical, dynamical and thermodynamic properties of cesium chloride (CsCl from first-principles

Directory of Open Access Journals (Sweden)

Bingol Suat

2015-01-01

Full Text Available The geometric structural optimization, electronic band structure, total density of states for valence electrons, density of states for phonons, optical, dynamical, and thermodynamical features of cesium chloride have been investigated by linearized augmented plane wave method using the density functional theory under the generalized gradient approximation. Ground state properties of cesium chloride are studied. The calculated ground state properties are consistent with experimental results. Calculated band structure indicates that the cesium chloride structure has an indirect band gap value of 5.46 eV and is an insulator. From the obtained phonon spectra, the cesium chloride structure is dynamically stable along the various directions in the Brillouin zone. Temperature dependent thermodynamic properties are studied using the harmonic approximation model.

Damage Analysis and Evaluation of Light Steel Structures Exposed to Wind Hazards

OpenAIRE

Na Yang; Fan Bai

2017-01-01

Compared to hot-rolled steel structures, cold-formed steel structures are susceptible to extreme winds because of the light weight of the building and its components. Many modern cold-formed steel structures have sustained significant structural damage ranging from loss of cladding to complete collapse in recent cyclones. This article first provides some real damage cases for light steel structures induced by the high winds. After that, the paper reviews research on the damage analysis and e...

Natural Frequency and Damping Estimation of an Offshore Wind Turbine Structure

DEFF Research Database (Denmark)

Damgaard, Mads; Andersen, Jacob K. F.; Ibsen, Lars Bo

2012-01-01

During the last years, offshore wind turbines have increased significantly in size with larger rotors and more powerful generators. The costs are kept as low as possible by reducing the overall weight, which leads to very slender and flexible structures. An improper design may cause resonance due...... of an offshore wind turbine located in the North Sea. Simple Fourier Transformation and least square fitting to the vibration decay of ten “rotor stop” tests make it possible to evaluate the dynamic properties of the wind turbine structure. Based on the traditionally p-y curve method (Winkler type approach...

Combined Structural Optimization and Aeroelastic Analysis of a Vertical Axis Wind Turbine

DEFF Research Database (Denmark)

Roscher, Björn; Ferreira, Carlos Simao; Bernhammer, Lars O.

2015-01-01

Floating offshore wind energy poses challenges on the turbine design. A possible solution is vertical axis wind turbines, which are possibly easier to scale-up and require less components (lower maintenance) and a smaller floating structure than horizontal axis wind turbines. This paper presents...... a structural optimization and aeroelastic analysis of an optimized Troposkein vertical axis wind turbine to minimize the relation between the rotor mass and the swept area. The aeroelastic behavior of the different designs has been analyzed using a modified version of the HAWC2 code with the Actuator Cylinder...... model to compute the aerodynamics of the vertical axis wind turbine. The combined shape and topology optimization of a vertical axis wind turbine show a minimum mass to area ratio of 1.82 kg/m2 for blades with varying blade sections from a NACA 0040 at the attachment points to a NACA 0015...

Structural, Mechanical and Thermodynamic Properties under Pressure Effect of Rubidium Telluride: First Principle Calculations

Directory of Open Access Journals (Sweden)

Bidai K.

2017-06-01

Full Text Available First-principles density functional theory calculations have been performed to investigate the structural, elastic and thermodynamic properties of rubidium telluride in cubic anti-fluorite (anti-CaF2-type structure. The calculated ground-state properties of Rb2Te compound such as equilibrium lattice parameter and bulk moduli are investigated by generalized gradient approximation (GGA-PBE that are based on the optimization of total energy. The elastic constants, Young’s and shear modulus, Poisson ratio, have also been calculated. Our results are in reasonable agreement with the available theoretical and experimental data. The pressure dependence of elastic constant and thermodynamic quantities under high pressure are also calculated and discussed.

Wake structure of a single vertical axis wind turbine

International Nuclear Information System (INIS)

Posa, Antonio; Parker, Colin M.; Leftwich, Megan C.; Balaras, Elias

2016-01-01

Highlights: • The wake structure of an isolated Vertical Axis Wind Turbine is studied by both Particle Imaging Velocimetry and Large Eddy Simulation. • The wake structure is investigated for two values of tip speed ratio, TSR_1=1.35 and TSR_2=2.21. • A displacement of the momentum deficit towards the windward side is verified in the wake. • Higher turbulence and coherence is observed on the leeward side of the wake, due to the upwind stall of the blades. • Coherence in the wake core, associated to the downwind stall, decays quickly downstream. - Abstract: The wake structure behind a vertical axis wind turbine (VAWT) is both measured in a wind tunnel using particle imaging velocimetry (PIV) and computed with large-eddy simulation (LES). Geometric and dynamic conditions are closely matched to typical applications of VAWTs (Re_D ∼ 1.8 × 10"5). The experiments and computations were highly coordinated with continuous two-way feedback to produce the most insightful results. Good qualitative agreement is seen between the computational and experimental results. The dependence of the wake structure on the tip speed ratio, TSR, is investigated, showing higher asymmetry and larger vortices at the lower rotational speed, due to stronger dynamic stall phenomena. Instantaneous, ensemble-averaged and phase-averaged fields are discussed, as well as the dynamics of coherent structures in the rotor region and downstream wake.

Modal Analysis on Fluid-Structure Interaction of MW-Level Vertical Axis Wind Turbine Tower

OpenAIRE

Tan Jiqiu; Zhong Dingqing; Wang Qiong

2014-01-01

In order to avoid resonance problem of MW-level vertical axis wind turbine induced by wind, a flow field model of the MW-level vertical axis wind turbine is established by using the fluid flow control equations, calculate flow’s velocity and pressure of the MW-level vertical axis wind turbine and load onto tower’s before and after surface, study the Modal analysis of fluid-structure interaction of MW-level vertical axis wind turbine tower. The results show that fluid-structure interaction fie...

Coherent application of a contact structure to formulate Classical Non-Equilibrium Thermodynamics

NARCIS (Netherlands)

Knobbe, E; Roekaerts, D.J.E.M.

2017-01-01

This contribution presents an outline of a new mathematical formulation for
Classical Non-Equilibrium Thermodynamics (CNET) based on a contact
structure in differential geometry. First a non-equilibrium state space is introduced as the third key element besides the first and second law of

Insight into the microscopic structure of an AdS black hole from a thermodynamical phase transition.

Science.gov (United States)

Wei, Shao-Wen; Liu, Yu-Xiao

2015-09-11

Comparing with an ordinary thermodynamic system, we investigate the possible microscopic structure of a charged anti-de Sitter black hole completely from the thermodynamic viewpoint. The number density of the black hole molecules is introduced to measure the microscopic degrees of freedom of the black hole. We found that the number density suffers a sudden change accompanied by a latent heat when the black hole system crosses the small-large black hole coexistence curve, while when the system passes the critical point, it encounters a second-order phase transition with a vanishing latent heat due to the continuous change of the number density. Moreover, the thermodynamic scalar curvature suggests that there is a weak attractive interaction between two black hole molecules. These phenomena might cast new insight into the underlying microscopic structure of a charged anti-de Sitter black hole.

FADING CORONAL STRUCTURE AND THE ONSET OF TURBULENCE IN THE YOUNG SOLAR WIND

Energy Technology Data Exchange (ETDEWEB)

DeForest, C. E. [Southwest Research Institute, 1050 Walnut Street, Boulder, CO (United States); Matthaeus, W. H. [Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States); Viall, N. M. [NASA/Goddard Space Flight Center, Mail Code 671, Greenbelt, MD 20771 (United States); Cranmer, S. R. [University of Colorado, Duane E226, Boulder, CO 80305 (United States)

2016-09-10

Above the top of the solar corona, the young, slow solar wind transitions from low- β , magnetically structured flow dominated by radial structures to high- β , less structured flow dominated by hydrodynamics. This transition, long inferred via theory, is readily apparent in the sky region close to 10° from the Sun in processed, background-subtracted solar wind images. We present image sequences collected by the inner Heliospheric Imager instrument on board the Solar-Terrestrial Relations Observatory ( STEREO /HI1) in 2008 December, covering apparent distances from approximately 4° to 24° from the center of the Sun and spanning this transition in the large-scale morphology of the wind. We describe the observation and novel techniques to extract evolving image structure from the images, and we use those data and techniques to present and quantify the clear textural shift in the apparent structure of the corona and solar wind in this altitude range. We demonstrate that the change in apparent texture is due both to anomalous fading of the radial striae that characterize the corona and to anomalous relative brightening of locally dense puffs of solar wind that we term “flocculae.” We show that these phenomena are inconsistent with smooth radial flow, but consistent with the onset of hydrodynamic or magnetohydrodynamic instabilities leading to a turbulent cascade in the young solar wind.

Fading Coronal Structure and the Onset of Turbulence in the Young Solar Wind

Science.gov (United States)

DeForest, C. E.; Matthaeus, W. H.; Viall, N. M.; Cranmer, S. R.

2016-01-01

Above the top of the solar corona, the young, slow solar wind transitions from low-beta, magnetically structured flow dominated by radial structures to high-beta, less structured flow dominated by hydrodynamics. This transition, long inferred via theory, is readily apparent in the sky region close to 10deg from the Sun in processed, background-subtracted solar wind images. We present image sequences collected by the inner Heliospheric Imager instrument on board the Solar-Terrestrial Relations Observatory (STEREO/HI1) in 2008 December, covering apparent distances from approximately 4deg to 24deg from the center of the Sun and spanning this transition in the large-scale morphology of the wind. We describe the observation and novel techniques to extract evolving image structure from the images, and we use those data and techniques to present and quantify the clear textural shift in the apparent structure of the corona and solar wind in this altitude range. We demonstrate that the change in apparent texture is due both to anomalous fading of the radial striae that characterize the corona and to anomalous relative brightening of locally dense puffs of solar wind that we term "flocculae." We show that these phenomena are inconsistent with smooth radial flow, but consistent with the onset of hydrodynamic or magnetohydrodynamic instabilities leading to a turbulent cascade in the young solar wind.

Three-dimensional structure of wind turbine wakes as measured by scanning lidar

Science.gov (United States)

Bodini, Nicola; Zardi, Dino; Lundquist, Julie K.

2017-08-01

The lower wind speeds and increased turbulence that are characteristic of turbine wakes have considerable consequences on large wind farms: turbines located downwind generate less power and experience increased turbulent loads. The structures of wakes and their downwind impacts are sensitive to wind speed and atmospheric variability. Wake characterization can provide important insights for turbine layout optimization in view of decreasing the cost of wind energy. The CWEX-13 field campaign, which took place between June and September 2013 in a wind farm in Iowa, was designed to explore the interaction of multiple wakes in a range of atmospheric stability conditions. Based on lidar wind measurements, we extend, present, and apply a quantitative algorithm to assess wake parameters such as the velocity deficits, the size of the wake boundaries, and the location of the wake centerlines. We focus on wakes from a row of four turbines at the leading edge of the wind farm to explore variations between wakes from the edge of the row (outer wakes) and those from turbines in the center of the row (inner wakes). Using multiple horizontal scans at different elevations, a three-dimensional structure of wakes from the row of turbines can be created. Wakes erode very quickly during unstable conditions and can in fact be detected primarily in stable conditions in the conditions measured here. During stable conditions, important differences emerge between the wakes of inner turbines and the wakes of outer turbines. Further, the strong wind veer associated with stable conditions results in a stretching of the wake structures, and this stretching manifests differently for inner and outer wakes. These insights can be incorporated into low-order wake models for wind farm layout optimization or for wind power forecasting.

Role of thermodynamic, kinetic and structural factors in the recrystallization behavior of amorphous erythromycin salts

Energy Technology Data Exchange (ETDEWEB)

Nanakwani, Kapil; Modi, Sameer R.; Kumar, Lokesh; Bansal, Arvind K., E-mail: akbansal@niper.ac.in

2014-04-01

Graphical abstract: - Highlights: • Crystallization kinetics of amorphous erythromycin salts was assessed. • Contribution of thermodynamic, kinetic and structural factors was evaluated. • Role of counterions on physical stability of amorphous salts was investigated. • Implications of the study: In rationalizing stabilization approach for amorphous form. - Abstract: Amorphous form has become an important drug delivery strategy for poorly water soluble drugs. However, amorphous form has inherent physical instability due to its tendency to recrystallize to stable crystalline form. In the present study, amorphous forms of erythromycin free base (ED) and its salts namely, stearate (ES), phosphate (EP) and thiocyanate (ET) were generated by in situ melt quenching and evaluated for their crystallization tendency. Salts were characterized for kinetic, thermodynamic and structural factors to understand crystallization behavior. Kinetics of crystallization followed the order as ES > EP > ET > ED. Fragility and molecular mobility does not completely explain these findings. However, configurational entropy (S{sub conf}), indicative of entropic barrier to crystallization, followed the order as ET > EP > ES > ED. Lower crystallization tendency of ED can be explained by its lower thermodynamic driving force for crystallization (H{sub conf}). This correlated well with different structural parameters for the counter ions.

Field investigation of a wake structure downwind of a VANT (Vertical-Axis Wind Turbine) in a wind farm array

Science.gov (United States)

Liu, H. T.; Buck, J. W.; Germain, A. C.; Hinchee, M. E.; Solt, T. S.; Leroy, G. M.; Srnsky, R. A.

1988-09-01

The effects of upwind turbine wakes on the performance of a FloWind 17-m vertical-axis wind turbine (VAWT) were investigated through a series of field experiments conducted at the FloWind wind farm on Cameron Ridge, Tehachapi, California. From the field measurements, we derived the velocity and power/energy deficits under various turbine on/off configurations. Much information was provided to characterize the structure of VAWT wakes and to assess their effects on the performance of downwind turbines. A method to estimate the energy deficit was developed based on the measured power deficit and the wind speed distributions. This method may be adopted for other turbine types and sites. Recommendations are made for optimizing wind farm design and operations, as well as for wind energy management.

Probabilistic Calibration of Fatigue Design Factors for Offshore Wind Turbine Support Structures

DEFF Research Database (Denmark)

Ramirez, José Rangel; Sørensen, John Dalsgaard

2010-01-01

for the considered offshore wind turbines in such a way that the specific uncertainties for the fatigue life are accounted in a rational manner. Similar approaches have been used for offshore oil & gas sub-structures, but the required reliability level for offshore wind turbines is generally lower and the fatigue......This paper describes a reliability-based approach to determine fatigue design factors (FDF) for offshore wind turbine support structures made of steel. The FDF values are calibrated to a specific reliability level and linked to a specific inspection and maintenance (I&M) strategy used...

Wind-Induced Fatigue Analysis of High-Rise Steel Structures Using Equivalent Structural Stress Method

Directory of Open Access Journals (Sweden)

Zhao Fang

2017-01-01

Full Text Available Welded beam-to-column connections of high-rise steel structures are susceptive to fatigue damage under wind loading. However, most fatigue assessments in the field of civil engineering are mainly based on nominal stress or hot spot stress theories, which has the disadvantage of dependence on the meshing styles and massive curves selected. To address this problem, in this paper, the equivalent structural stress method with advantages of mesh-insensitive quality and capability of unifying different stress-life curves (S-N curves into one is introduced to the wind-induced fatigue assessment of a large-scale complicated high-rise steel structure. The multi-scale finite element model is established and the corresponding wind loading is simulated. Fatigue life assessments using equivalent structural stress method, hot spot stress method and nominal stress method are performed, and the results are verified and comparisons are made. The mesh-insensitive quality is also verified. The results show that the lateral weld toe of the butt weld connecting the beam flange plate and the column is the location where fatigue damage most likely happens. Nominal stress method considers fatigue assessment of welds in a more global way by averaging all the stress on the weld section while in equivalent structural stress method and hot spot method local stress concentration can be taken into account more precisely.

Active vibration-based structural health monitoring system for wind turbine blade: Demonstration on an operating Vestas V27 wind turbine

DEFF Research Database (Denmark)

Tcherniak, Dmitri; Mølgaard, Lasse Lohilahti

2017-01-01

enough to be able to propagate the entire blade length. This article demonstrates the system on a Vestas V27 wind turbine. One blade of the wind turbine was equipped with the system, and a 3.5-month monitoring campaign was conducted while the turbine was operating normally. During the campaign, a defect......—a trailing-edge opening—was artificially introduced into the blade and its size was gradually increased from the original 15 to 45 cm. Using a semi-supervised learning algorithm, the system was able to detect even the smallest amount of damage while the wind turbine was operating under different weather......This study presents a structural health monitoring system that is able to detect structural defects of wind turbine blade such as cracks, leading/trailing-edge opening, or delamination. It is shown that even small defects of at least 15 cm size can be detected remotely without stopping the wind...

Spatial-temporal analysis of coherent offshore wind field structures measured by scanning Doppler-lidar

Science.gov (United States)

Valldecabres, L.; Friedrichs, W.; von Bremen, L.; Kühn, M.

2016-09-01

An analysis of the spatial and temporal power fluctuations of a simplified wind farm model is conducted on four offshore wind fields data sets, two from lidar measurements and two from LES under unstable and neutral atmospheric conditions. The integral length scales of the horizontal wind speed computed in the streamwise and the cross-stream direction revealed the elongation of the structures in the direction of the mean flow. To analyse the effect of the structures on the power output of a wind turbine, the aggregated equivalent power of two wind turbines with different turbine spacing in the streamwise and cross-stream direction is analysed at different time scales under 10 minutes. The fact of considering the summation of the power of two wind turbines smooths out the fluctuations of the power output of a single wind turbine. This effect, which is stronger with increasing spacing between turbines, can be seen in the aggregation of the power of two wind turbines in the streamwise direction. Due to the anti-correlation of the coherent structures in the cross-stream direction, this smoothing effect is stronger when the aggregated power is computed with two wind turbines aligned orthogonally to the mean flow direction.

Generalization of Gibbs Entropy and Thermodynamic Relation

OpenAIRE

Park, Jun Chul

2010-01-01

In this paper, we extend Gibbs's approach of quasi-equilibrium thermodynamic processes, and calculate the microscopic expression of entropy for general non-equilibrium thermodynamic processes. Also, we analyze the formal structure of thermodynamic relation in non-equilibrium thermodynamic processes.

Statistical properties of thermodynamically predicted RNA secondary structures in viral genomes

Science.gov (United States)

Spanò, M.; Lillo, F.; Miccichè, S.; Mantegna, R. N.

2008-10-01

By performing a comprehensive study on 1832 segments of 1212 complete genomes of viruses, we show that in viral genomes the hairpin structures of thermodynamically predicted RNA secondary structures are more abundant than expected under a simple random null hypothesis. The detected hairpin structures of RNA secondary structures are present both in coding and in noncoding regions for the four groups of viruses categorized as dsDNA, dsRNA, ssDNA and ssRNA. For all groups, hairpin structures of RNA secondary structures are detected more frequently than expected for a random null hypothesis in noncoding rather than in coding regions. However, potential RNA secondary structures are also present in coding regions of dsDNA group. In fact, we detect evolutionary conserved RNA secondary structures in conserved coding and noncoding regions of a large set of complete genomes of dsDNA herpesviruses.

Wind induced fatigue of slender light weight structures in structural dynamics

NARCIS (Netherlands)

Staalduinen, P.C. van; Courage, W.M.G.

1996-01-01

The paper presents a simplified analytical method for calculating the stress ranges in light weight slender structures due to wind loading. The background and assumptions of the method have been explained as well as the derivation of the relevant formula. The application of the simplified method on

Wind energy

International Nuclear Information System (INIS)

Portilla S, L.A.

1995-01-01

The wind energy or eolic energy is a consequence of solar energy, the one which is absorbed by the atmosphere and is transformed into energy of movement of large bulks of air. In this process the atmosphere acts as the filter to the solar radiation and demotes the ultraviolet beams that result fatal to life in the Earth. The ionosphere is the most external cap and this is ionized by means of absorption process of ultraviolet radiation arising to the Sun. The atmosphere also acts as a trap to the infrared radiation, it that results from the continual process of energetic degradation. In this way, the interaction between Earth - Atmospheres, is behaved as a great greenhouse, maintaining the constant temperatures, including in the dark nights. Processes as the natural convection (that occur by the thermodynamic phenomenon), equatorial calmness, trade winds and against trade winds and global distribution of the air currents are described. The other hand, techniques as the transformation of the wind into energy and its parameters also are shown

Study of thermodynamic and structural properties of a flexible homopolymer chain using advanced Monte Carlo methods

Directory of Open Access Journals (Sweden)

Hammou Amine Bouziane

2013-03-01

Full Text Available We study the thermodynamic and structural properties of a flexible homopolymer chain using both multi canonical Monte Carlo method and Wang-Landau method. In this work, we focus on the coil-globule transition. Starting from a completely random chain, we have obtained a globule for different sizes of the chain. The implementation of these advanced Monte Carlo methods allowed us to obtain a flat histogram in energy space and calculate various thermodynamic quantities such as the density of states, the free energy and the specific heat. Structural quantities such as the radius of gyration where also calculated.

[Relationships between microscope structure and thermodynamic properties

International Nuclear Information System (INIS)

Wu, R.S.; Lee, L.L.; Cochran, D.

1990-01-01

This paper exhibits on the molecular level, the relationships between the microscopic structure and thermodynamic properties of dilute supercritical solutions by application of the integral equation theories for molecular distribution functions. To solve the integral equations, the authors use Baxter's Wiener-Hopf factorization of the Ornstein-Zernike equations and then apply this method to binary Lennard-Jones mixtures. A number of closure relations have been used: such as the Percus-Yevick (PY), the reference hypernetted chain (RHNC), the hybrid mean spherical approximation (HMSA), and the reference interaction-site (RISM) methods. The authors examine the microstructures of several important classes of supercritical mixtures, including the usual attractive-type and the less known repulsive-type solutions. The clustering of solvent molecules for solvent-solute structures in the attractive mixtures and, correspondingly, the solvent cavitation in the repulsive mixtures are clearly demonstrated. These are shown to be responsible for the large negative growth of the solute partial molar volumes in the attractive case and the positive growth in the repulsive case

Quantum Thermodynamics at Strong Coupling: Operator Thermodynamic Functions and Relations

Directory of Open Access Journals (Sweden)

Jen-Tsung Hsiang

2018-05-01

Full Text Available Identifying or constructing a fine-grained microscopic theory that will emerge under specific conditions to a known macroscopic theory is always a formidable challenge. Thermodynamics is perhaps one of the most powerful theories and best understood examples of emergence in physical sciences, which can be used for understanding the characteristics and mechanisms of emergent processes, both in terms of emergent structures and the emergent laws governing the effective or collective variables. Viewing quantum mechanics as an emergent theory requires a better understanding of all this. In this work we aim at a very modest goal, not quantum mechanics as thermodynamics, not yet, but the thermodynamics of quantum systems, or quantum thermodynamics. We will show why even with this minimal demand, there are many new issues which need be addressed and new rules formulated. The thermodynamics of small quantum many-body systems strongly coupled to a heat bath at low temperatures with non-Markovian behavior contains elements, such as quantum coherence, correlations, entanglement and fluctuations, that are not well recognized in traditional thermodynamics, built on large systems vanishingly weakly coupled to a non-dynamical reservoir. For quantum thermodynamics at strong coupling, one needs to reexamine the meaning of the thermodynamic functions, the viability of the thermodynamic relations and the validity of the thermodynamic laws anew. After a brief motivation, this paper starts with a short overview of the quantum formulation based on Gelin & Thoss and Seifert. We then provide a quantum formulation of Jarzynski’s two representations. We show how to construct the operator thermodynamic potentials, the expectation values of which provide the familiar thermodynamic variables. Constructing the operator thermodynamic functions and verifying or modifying their relations is a necessary first step in the establishment of a viable thermodynamics theory for

Three-dimensional density and compressible magnetic structure in solar wind turbulence

Science.gov (United States)

Roberts, Owen W.; Narita, Yasuhito; Escoubet, C.-Philippe

2018-03-01

The three-dimensional structure of both compressible and incompressible components of turbulence is investigated at proton characteristic scales in the solar wind. Measurements of the three-dimensional structure are typically difficult, since the majority of measurements are performed by a single spacecraft. However, the Cluster mission consisting of four spacecraft in a tetrahedral formation allows for a fully three-dimensional investigation of turbulence. Incompressible turbulence is investigated by using the three vector components of the magnetic field. Meanwhile compressible turbulence is investigated by considering the magnitude of the magnetic field as a proxy for the compressible fluctuations and electron density data deduced from spacecraft potential. Application of the multi-point signal resonator technique to intervals of fast and slow wind shows that both compressible and incompressible turbulence are anisotropic with respect to the mean magnetic field direction P⟂ ≫ P∥ and are sensitive to the value of the plasma beta (β; ratio of thermal to magnetic pressure) and the wind type. Moreover, the incompressible fluctuations of the fast and slow solar wind are revealed to be different with enhancements along the background magnetic field direction present in the fast wind intervals. The differences in the fast and slow wind and the implications for the presence of different wave modes in the plasma are discussed.

Applicability of special quasi-random structure models in thermodynamic calculations using semi-empirical Debye–Grüneisen theory

International Nuclear Information System (INIS)

Kim, Jiwoong

2015-01-01

In theoretical calculations, expressing the random distribution of atoms in a certain crystal structure is still challenging. The special quasi-random structure (SQS) model is effective for depicting such random distributions. The SQS model has not been applied to semi-empirical thermodynamic calculations; however, Debye–Grüneisen theory (DGT), a semi-empirical method, was used here for that purpose. The model reliability was obtained by comparing supercell models of various sizes. The results for chemical bonds, pair correlation, and elastic properties demonstrated the reliability of the SQS models. Thermodynamic calculations using density functional perturbation theory (DFPT) and DGT assessed the applicability of the SQS models. DGT and DFPT led to similar variations of the mixing and formation energies. This study provides guidelines for theoretical assessments to obtain the reliable SQS models and to calculate the thermodynamic properties of numerous materials with a random atomic distribution. - Highlights: • Various material properties are used to examine reliability of special quasi-random structures. • SQS models are applied to thermodynamic calculations by semi-empirical methods. • Basic calculation guidelines for materials with random atomic distribution are given.

The structure and strength of public attitudes towards wind farm development

Science.gov (United States)

Bidwell, David Charles

A growing social science literature seeks to understand why, despite broad public support for wind energy, proposals for specific projects are often met with strong local opposition. This gap between general and specific attitudes is viewed as a significant obstacle to the deployment of wind energy technologies. This dissertation applies theoretical perspectives and methodological tools from social psychology to provide insights on the structure and strength of attitudes towards the potential development of commercial wind farm in three coastal areas of Michigan. A survey of attitudes was completed by 375 residents in these communities and structural equation modeling was used to explore the relationship among variables. The analysis found that attitudes towards wind farm development are shaped by anticipated economic benefits to the community, but expectations of economic benefit are driven by personal values. Social psychology has long recognized that all attitudes are not created equal. Weak attitudes are fleeting and prone to change, while strong attitudes are stable over time and resistant to change. There are two fundamental paths to strong attitudes: repeated experience with an attitude object or the application of deeply held principles or values to that object. Structural equation models were also used to understand the strength of attitudes among the survey respondents. Both the anticipated effects of wind farm development and personal values were found to influence the strength of attitudes towards wind farms. However, while expectations that wind farm development will have positive effects on the economy bolster two measures of attitude strength (collective identity and importance), these expectations are associated with a decline in a third measure (confidence). A follow-up survey asking identical questions was completed by completed by 187 respondents to the initial survey. Linear regressions models were used to determine the effects of attitude

Random lock-in intervals for tubular structural elements subject to simulated natural wind

DEFF Research Database (Denmark)

Christensen, Claus F.; Ditlevsen, Ove Dalager

1999-01-01

The paper reports on wind tunnel experiments with an elastically suspended circular cylinder vibrating under the excitation of natural wind of high turbulence degree. The natural wind turbulence was simulated bysuperposing the low frequency part of the natural wind turbulence on the background high...... structural elements subject to thenatural wind. The engineering relevance of the investigation is supported by comparing with the unrealistic highlyconservative rules of wind induced fatique commonly given in codes of practice. The stochastic lock-in model aswell as the related fatigue calculation procedure...

First Principles Prediction of Structure, Structure Selectivity, and Thermodynamic Stability under Realistic Conditions

Energy Technology Data Exchange (ETDEWEB)

Ceder, Gerbrand [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Materials and Engineering

2018-01-28

Novel materials are often the enabler for new energy technologies. In ab-initio computational materials science, method are developed to predict the behavior of materials starting from the laws of physics, so that properties can be predicted before compounds have to be synthesized and tested. As such, a virtual materials laboratory can be constructed, saving time and money. The objectives of this program were to develop first-principles theory to predict the structure and thermodynamic stability of materials. Since its inception the program focused on the development of the cluster expansion to deal with the increased complexity of complex oxides. This research led to the incorporation of vibrational degrees of freedom in ab-initio thermodynamics, developed methods for multi-component cluster expansions, included the explicit configurational degrees of freedom of localized electrons, developed the formalism for stability in aqueous environments, and culminated in the first ever approach to produce exact ground state predictions of the cluster expansion. Many of these methods have been disseminated to the larger theory community through the Materials Project, pymatgen software, or individual codes. We summarize three of the main accomplishments.

Model of the thermodynamic properties and structure of the non-stoichiometric plutonium and cerium oxides

International Nuclear Information System (INIS)

Manes, L.; Mari, C.; Ray, I.

1979-01-01

The tetrahedral defect consisting of one oxygen vacancy bonded to two reduced cations - is an important concept, which, as shown in the present work, can explain both the thermodynamic properties and the structures of the phases of the PuO 2 -x and CeO 2 -x systems. Based on this concept a statistical thermodynamic model has been developed and this model is described along with some preliminary calculations. A relatively good agreement with experimental thermodynamic data was obtained in this calculation. Using the exclusion principle, defect complexes each containing one tetrahedral defect are derived and it is shown that a systematic packing of these gives a good description both of the non-stoichiometric and the ordered phases observed for these oxide systems. (orig.) [de

Wind Loads on Ships and Offshore Structures Estimated by CFD

DEFF Research Database (Denmark)

Aage, Christian; Hvid, S.L.; Hughes, P.H.

1997-01-01

Wind loads on ships and offshore structures could until recently be determined only by model tests, or by statistical methods based on model tests. By the development of Computational Fluid Dynamics or CFD there is now a realistic computational alternative available. In this paper, wind loads...... on a seagoing ferry and on a semisubmersible offshore platform have been estimated by CFD. The results have been compared with wind tunnel model tests and, for the ferry, a few full-scale measurements, and good agreement is obtained. The CFD method offers the possibility of a computational estimate of scale...... effects related to wind tunnel model testing. An example of such an estimate on the ferry is discussed. Due to the time involved in generating the computational mesh and in computing the solution, the CFD method is not at the moment economically competitive to routine wind tunnel model testing....

Towards uncovering the structure of power fluctuations of wind farms.

Science.gov (United States)

Liu, Huiwen; Jin, Yaqing; Tobin, Nicolas; Chamorro, Leonardo P

2017-12-01

The structure of the turbulence-driven power fluctuations in a wind farm is fundamentally described from basic concepts. A derived tuning-free model, supported with experiments, reveals the underlying spectral content of the power fluctuations of a wind farm. It contains two power-law trends and oscillations in the relatively low- and high-frequency ranges. The former is mostly due to the turbulent interaction between the flow and the turbine properties, whereas the latter is due to the advection between turbine pairs. The spectral wind-farm scale power fluctuations Φ_{P} exhibit a power-law decay proportional to f^{-5/3-2} in the region corresponding to the turbulence inertial subrange and at relatively large scales, Φ_{P}∼f^{-2}. Due to the advection and turbulent diffusion of large-scale structures, a spectral oscillation exists with the product of a sinusoidal behavior and an exponential decay in the frequency domain.

Contact symmetries and Hamiltonian thermodynamics

International Nuclear Information System (INIS)

Bravetti, A.; Lopez-Monsalvo, C.S.; Nettel, F.

2015-01-01

It has been shown that contact geometry is the proper framework underlying classical thermodynamics and that thermodynamic fluctuations are captured by an additional metric structure related to Fisher’s Information Matrix. In this work we analyse several unaddressed aspects about the application of contact and metric geometry to thermodynamics. We consider here the Thermodynamic Phase Space and start by investigating the role of gauge transformations and Legendre symmetries for metric contact manifolds and their significance in thermodynamics. Then we present a novel mathematical characterization of first order phase transitions as equilibrium processes on the Thermodynamic Phase Space for which the Legendre symmetry is broken. Moreover, we use contact Hamiltonian dynamics to represent thermodynamic processes in a way that resembles the classical Hamiltonian formulation of conservative mechanics and we show that the relevant Hamiltonian coincides with the irreversible entropy production along thermodynamic processes. Therefore, we use such property to give a geometric definition of thermodynamically admissible fluctuations according to the Second Law of thermodynamics. Finally, we show that the length of a curve describing a thermodynamic process measures its entropy production

Structural health monitoring of wind turbine blades

Science.gov (United States)

Rumsey, Mark A.; Paquette, Joshua A.

2008-03-01

As electric utility wind turbines increase in size, and correspondingly, increase in initial capital investment cost, there is an increasing need to monitor the health of the structure. Acquiring an early indication of structural or mechanical problems allows operators to better plan for maintenance, possibly operate the machine in a de-rated condition rather than taking the unit off-line, or in the case of an emergency, shut the machine down to avoid further damage. This paper describes several promising structural health monitoring (SHM) techniques that were recently exercised during a fatigue test of a 9 meter glass-epoxy and carbon-epoxy wind turbine blade. The SHM systems were implemented by teams from NASA Kennedy Space Center, Purdue University and Virginia Tech. A commercial off-the-shelf acoustic emission (AE) NDT system gathered blade AE data throughout the test. At a fatigue load cycle rate around 1.2 Hertz, and after more than 4,000,000 fatigue cycles, the blade was diagnostically and visibly failing at the out-board blade spar-cap termination point at 4.5 meters. For safety reasons, the test was stopped just before the blade completely failed. This paper provides an overview of the SHM and NDT system setups and some current test results.

Structural Optimization of an Innovative 10 MW Wind Turbine Nacelle

DEFF Research Database (Denmark)

Dabrowski, Dariusz; Natarajan, Anand; Stehouwer, Ewoud

2015-01-01

For large wind turbine configurations of 10 MW and higher capacities, direct-drives present a more compact solution over conventional geared drivetrains. Further, if the generator is placed in front of the wind turbine rotor, a compact “king-pin” drive is designed, that allows the generator...... to be directly coupled to the hub. In presented study, the structural re-design of the innovative 10 MW nacelle was made using extreme loads obtained from a 10 MW reference wind turbine. On the basis of extreme loads the ultimate stresses on critical nacelle components were determined to ensure integrity...

Noncanonical structures and their thermodynamics of DNA and RNA under molecular crowding: beyond the Watson-Crick double helix.

Science.gov (United States)

Sugimoto, Naoki

2014-01-01

How does molecular crowding affect the stability of nucleic acid structures inside cells? Water is the major solvent component in living cells, and the properties of water in the highly crowded media inside cells differ from that in buffered solution. As it is difficult to measure the thermodynamic behavior of nucleic acids in cells directly and quantitatively, we recently developed a cell-mimicking system using cosolutes as crowding reagents. The influences of molecular crowding on the structures and thermodynamics of various nucleic acid sequences have been reported. In this chapter, we discuss how the structures and thermodynamic properties of nucleic acids differ under various conditions such as highly crowded environments, compartment environments, and in the presence of ionic liquids, and the major determinants of the crowding effects on nucleic acids are discussed. The effects of molecular crowding on the activities of ribozymes and riboswitches on noncanonical structures of DNA- and RNA-like quadruplexes that play important roles in transcription and translation are also described. © 2014 Elsevier Inc. All rights reserved.

Electronic structure, thermodynamic properties and hydrogenation of LaPtIn and CePtIn compounds by ab-initio methods

International Nuclear Information System (INIS)

Jezierski, Andrzej; Szytuła, Andrzej

2016-01-01

The electronic structures and thermodynamic properties of LaPtIn and CePtIn are studied by means of ab-initio full-relativistic full-potential local orbital basis (FPLO) method within densities functional (DFT) methodologies. We have also examined the influence of hydrogen on the electronic structure and stability of CePtInH and LaPtInH systems. The positions of the hydrogen atoms have been found from the minimum of the total energy. Our calculations have shown that band structure and topology of the Fermi surfaces changed significantly during the hydrogenation. The thermodynamic properties (bulk modulus, Debye temperatures, constant pressure heat capacity) calculated in quasi-harmonic Debye-Grüneisen model are in a good agreement with the experimental data. We have applied different methods of the calculation of the equation of states (EOS) (Murnaghan, Birch-Murnaghan, Poirier–Tarantola, Vinet). The thermodynamic properties are presented for the pressure 0< P<9 GPa and the temperature range 0< T<300 K. - Highlights: • Full relativistic band structure of LaPtIn and CePtIn. • Fermi surface of LaPtIn, LaPtInH, CePtIn, CePtInH. • Effect of hydrogenation on the electronic structure of LaPtIn and CePtIn. • Thermodynamic properties in the quasi-harmonic Debye-Grüneisen model.

Structured, Gain-Scheduled Control of Wind Turbines

DEFF Research Database (Denmark)

Adegas, Fabiano Daher

2013-01-01

Improvements in cost-effectiveness and reliability of wind turbines is a constant in the industry. This requires new knowledge and systematic methods for analyzing and designing the interaction of structural dynamics, aerodynamics, and controllers. This thesis presents novel methods and theoretical....... Robustness and fault-tolerance capabilities are also important properties, which should be considered in the design process. Novel gain-scheduling and robust control methods that adapt to variations in the operational conditions of the wind turbine are proposed under the linear parameter-varying (LPV...... intuitive and physical specifications for vibration control, such as minimum damping and decay rate of aeroelastic modes. Moreover, the number of weighting functions and consequently the order of the final controller is reduced. Inspired by this application, theoretical control developments are presented...

Interfacial structures - Thermodynamical and experimental studies of the interfacial mass transfer

International Nuclear Information System (INIS)

Morel, Jean-Emile

1972-01-01

In the first section, we put forward hypotheses concerning the structure of the interfacial regions between two immiscible liquid phases. It appears that the longitudinal structure is comparable with that of a crystallized solid and that the transversal structure is nearest of that of a liquid. In the second section, we present a thermodynamical treatment of the irreversible phenomena in the interfacial region. The equation of evolution of a system consisting of two immiscible liquid phases are deduced. The third part allows an experimental verification of the theoretical relations. We also make clear, in certain cases, the appearance of a great 'interfacial resistance' which slows down the interfacial mass transfer. (author) [fr

Soil structure interaction in offshore wind turbine collisions

DEFF Research Database (Denmark)

Samsonovs, Artjoms; Giuliani, Luisa; Zania, Varvara

2014-01-01

Vessel impact is one of the load cases which should be accounted for in the design of an offshore wind turbine (OWT) according to design codes, but little guidance or information is given on the employed methodology. This study focuses on the evaluation of the distress induced in a wind turbine...... after a ship collision, thus providing an insight on the consequences of a collision event and on the main aspects to be considered when designing for this load case. In particular, the role of the foundation soil properties (site conditions) on the response of the structural system is investigated....... Dynamic finite element analyses have been performed taking into account the geometric and material nonlinearity of the tower, and the effects of soil structure interaction (SSI) have been studied in two representative collision scenarios of a service vessel with the turbine: a moderate energy impact...

Stochastic model for joint wave and wind loads on offshore structures

DEFF Research Database (Denmark)

Ditlevsen, Ove Dalager

2002-01-01

_s,T_z)$ from the North Sea a well fitting joint distribution of $(H_s,T_z)$ is obtained as a so-called Nataf model. Since the wave field is wind driven, there is a correlation between the time averaged wind velocity pressure $Q$ and the characteristic wave height in the stationary situation. Using the Poisson...... process model to concentrate on those load events that are of importance for the evaluation of the safety of the structure, that is, events with $Q$ larger than some threshold $q_0$, available information about the wind velocity pressure distributionin high wind situations can be used to formulate a Nataf...

Solar wind plasma structure near a 'HELIOS-Perihelion'

International Nuclear Information System (INIS)

Kikuchi, H.

1979-01-01

The purpose of this paper is to introduce a couple of preliminary but important results obtained from HELIOS observation concerning solar wind plasma structure near a ''HELIOS-Perihelion'' among the data analyses in progress, partly in relation to laboratory plasma. Idealized profiles of the bulk velocity, density and temperature of solar wind near 0.3 AU as deduced from HELIOS A data and correlated K-coronal contours were obtained. During 1974 - 1976, the sun was in the period of declining cycle, and the coronal holes expanded to lower latitudes from northern and southern holes. There is general tendency that the northern coronal hole is somewhat larger than the southern coronal hole. In regards to solar wind velocity, there are two fast stream regions with velocity as high as 800 Km/sec. An electron spectrum measured near a HELIOS-Perihelion (0.3 AU) approximately in the solar direction is shown. Three regions can be distinguished in velocity distribution. The density contours of solar wind electrons in velocity space exhibit a narrow beam of electrons in the magnetic field direction close to the plane of observation. (Kato, T.)

Structural, elastic, mechanical and thermodynamic properties of Terbium oxide: First-principles investigations

Directory of Open Access Journals (Sweden)

Samah Al-Qaisi

Full Text Available First-principles investigations of the Terbium oxide TbO are performed on structural, elastic, mechanical and thermodynamic properties. The investigations are accomplished by employing full potential augmented plane wave FP-LAPW method framed within density functional theory DFT as implemented in the WIEN2k package. The exchange-correlation energy functional, a part of the total energy functional, is treated through Perdew Burke Ernzerhof scheme of the Generalized Gradient Approximation PBEGGA. The calculations of the ground state structural parameters, like lattice constants a0, bulk moduli B and their pressure derivative B′ values, are done for the rock-salt RS, zinc-blende ZB, cesium chloride CsCl, wurtzite WZ and nickel arsenide NiAs polymorphs of the TbO compound. The elastic constants (C11, C12, C13, C33, and C44 and mechanical properties (Young’s modulus Y, Shear modulus S, Poisson’s ratio σ, Anisotropic ratio A and compressibility β, were also calculated to comprehend its potential for valuable applications. From our calculations, the RS phase of TbO compound was found strongest one mechanically amongst the studied cubic structures whereas from hexagonal phases, the NiAs type structure was found stronger than WZ phase of the TbO. To analyze the ductility of the different structures of the TbO, Pugh’s rule (B/SH and Cauchy pressure (C12–C44 approaches are used. It was found that ZB, CsCl and WZ type structures of the TbO were of ductile nature with the obvious dominance of the ionic bonding while RS and NiAs structures exhibited brittle nature with the covalent bonding dominance. Moreover, Debye temperature was calculated for both cubic and hexagonal structures of TbO in question by averaging the computed sound velocities. Keywords: DFT, TbO, Elastic properties, Thermodynamic properties

On the Value of Structural Health Monitoring Information for the Operation of Wind Parks

DEFF Research Database (Denmark)

Thöns, Sebastian; Faber, Michael H.; Val, Dimitri V.

2017-01-01

wind turbine systems and its components is developed accounting for the wind park functionality, i.e. power production, its operation and its cascading damage and failure scenarios. This system model facilitates to quantify the expected benefits and risks throughout the service life accounting......In the present paper, an approach for the quantification of the Value of Structural Health Monitoring (SHM) Information building upon a framework for infrastructure system utility and decision analysis is developed and applied to the operation of wind parks. The quantification of the value of SHM...... facilitates a benefit and risk informed assessment and optimization of SHM strategies and encompasses models for the infrastructure functionality, the structural constituent and system risks and its management as well as the performance of SHM strategies. A wind park system model incorporating the structural...

Influence of thermodynamically unfavorable secondary structures on DNA hybridization kinetics

Science.gov (United States)

Hata, Hiroaki; Kitajima, Tetsuro

2018-01-01

Abstract Nucleic acid secondary structure plays an important role in nucleic acid–nucleic acid recognition/hybridization processes, and is also a vital consideration in DNA nanotechnology. Although the influence of stable secondary structures on hybridization kinetics has been characterized, unstable secondary structures, which show positive ΔG° with self-folding, can also form, and their effects have not been systematically investigated. Such thermodynamically unfavorable secondary structures should not be ignored in DNA hybridization kinetics, especially under isothermal conditions. Here, we report that positive ΔG° secondary structures can change the hybridization rate by two-orders of magnitude, despite the fact that their hybridization obeyed second-order reaction kinetics. The temperature dependence of hybridization rates showed non-Arrhenius behavior; thus, their hybridization is considered to be nucleation limited. We derived a model describing how ΔG° positive secondary structures affect hybridization kinetics in stopped-flow experiments with 47 pairs of oligonucleotides. The calculated hybridization rates, which were based on the model, quantitatively agreed with the experimental rate constant. PMID:29220504

Active structural control of a floating wind turbine with a stroke-limited hybrid mass damper

Science.gov (United States)

Hu, Yaqi; He, Erming

2017-12-01

Floating wind turbines are subjected to more severe structural loads than fixed-bottom wind turbines due to additional degrees of freedom (DOFs) of their floating foundations. It's a promising way of using active structural control method to improve the structural responses of floating wind turbines. This paper investigates an active vibration control strategy for a barge-type floating wind turbine by setting a stroke-limited hybrid mass damper (HMD) in the turbine's nacelle. Firstly, a contact nonlinear modeling method for the floating wind turbine with clearance between the HMD and the stroke limiters is presented based on Euler-Lagrange's equations and an active control model of the whole system is established. The structural parameters are validated for the active control model and an equivalent load coefficient method is presented for identifying the wind and wave disturbances. Then, a state-feedback linear quadratic regulator (LQR) controller is designed to reduce vibration and loads of the wind turbine, and two optimization methods are combined to optimize the weighting coefficients when considering the stroke of the HMD and the active control power consumption as constraints. Finally, the designed controllers are implemented in high fidelity simulations under five typical wind and wave conditions. The results show that active HMD control strategy is shown to be achievable and the designed controllers could further reduce more vibration and loads of the wind turbine under the constraints of stroke limitation and power consumption. "V"-shaped distribution of the TMD suppression effect is inconsistent with the Weibull distribution in practical offshore floating wind farms, and the active HMD control could overcome this shortcoming of the passive TMD.

A thermodynamical analysis of the π and K meson valence structure functions

International Nuclear Information System (INIS)

Angelini, C.; Pazzi, R.

1982-01-01

The π and K meson valance structure functions are analysed in the framework of a thermodynamical model already applied to the nucleon. We obtain a simple expression which reproduces quite well the data for chi > 0.3. The effective temperatures are found to be of the order of 20 MeV for the pion and 65 MeV for the kaon. (orig.)

Molecular thermodynamics of nonideal fluids

CERN Document Server

Lee, Lloyd L

2013-01-01

Molecular Thermodynamics of Nonideal Fluids serves as an introductory presentation for engineers to the concepts and principles behind and the advances in molecular thermodynamics of nonideal fluids. The book covers related topics such as the laws of thermodynamics; entropy; its ensembles; the different properties of the ideal gas; and the structure of liquids. Also covered in the book are topics such as integral equation theories; theories for polar fluids; solution thermodynamics; and molecular dynamics. The text is recommended for engineers who would like to be familiarized with the concept

Large fog collectors: New strategies for collection efficiency and structural response to wind pressure

Science.gov (United States)

Holmes, Robert; Rivera, Juan de Dios; de la Jara, Emilio

2015-01-01

Most studies of large fog collectors (LFC) have focused on the collection efficiency, the amount of water collected, or economic and social aspects, but have not addressed the effects of strong winds on the system. Wind pressure is directly related to fog water collection efficiency but on the other hand may cause serious damage on the structure of LFCs. This study focuses in the effects of wind pressure on the components of the LFC as an integral system, and the ways to face strong winds with no significant damage. For this purpose we analysed cases of mechanical failure of LFCs both in our experimental station at Peña Blanca in Chile and elsewhere. The effects of wind pressure can be described as a sequence of physical processes, starting with the mesh deformation as a way of adapting to the induced stresses. For a big enough pressure, local stress concentrations generate a progressive rupture of the mesh. In cases where the mesh is sufficiently strong the wind force causes the partial or total collapse of the structure. Usually the weakest part is the mesh, especially close to where it is attached to the structure. The way the mesh is attached to the frame or cable of the structure is particularly important since it can induce significant stress concentrations. Mesh failure before the structure failure may be considered as a mechanical fuse, since it is cheaper to repair. However, more practical mechanical fuses can be conceived. In relation to structural performance and water collection efficiency, we propose a new design strategy that considers a three-dimensional spatial display of the collection screen, oblique incidence angle of wind on mesh and small mesh area between the supporting frame. The proposed design strategies consider both the wind pressure on mesh and structure and the collection efficiency as an integral solution for the LFC. These new design strategies are the final output of this research. Applying these strategies a multi-funnel LFC is

First principal studya of structural, electronic and thermodynamic properties of KTaO3-perovskite.

Directory of Open Access Journals (Sweden)

Hiadsi S.

2013-03-01

Full Text Available The results of first-principles theoretical study of structural, elastic, electronic and thermodynamic properties of KTaO3 compound, have been performed using the full-potential linear augmented plane-wave method plus local orbitals (FP-APW+lo as implemented in the Wien2k code. The exchange-correlation energy, is treated in generalized gradient approximation (GGA using the Perdew–Burke–Ernzerhof (PBE96 and PBEsol, Perdew 2008 parameterization. Also we have used the Engel-Vosko GGA optimizes the corresponding potential for band structure calculations. The calculated equilibrium parameter is in good agreement with other works. The elastic constants were calculated by using the Mehl method. The electronic band structure of this compound has been calculated using the Angel-Vosko (EV generalized gradient approximation (GGA for the exchange correlation potential. We deduced that KTaO3-perovskite exhibit an indirect from R to Γ point. To complete the fundamental characterization of KTaO3 material we have analyzed the thermodynamic properties using the quasi-harmonic Debye model.

Lawn Structured Triboelectric Nanogenerators for Scavenging Sweeping Wind Energy on Rooftops.

Science.gov (United States)

Zhang, Lei; Zhang, Binbin; Chen, Jun; Jin, Long; Deng, Weili; Tang, Junfeng; Zhang, Haitao; Pan, Hong; Zhu, Minhao; Yang, Weiqing; Wang, Zhong Lin

2016-02-24

A novel triboelectric nanogenerator (TENG) is designed, based on flexible and transparent vertical-strip arrays, for environmental wind-energy harvesting. Given the low cost, simple structure, and wide applicability, the TENGs present a green alternative to traditional methods used for large-scale wind-energy harvesting. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural experiment of wind turbine blades; Fushayo blade no zairyo rikigakuteki jikken kenkyu

Energy Technology Data Exchange (ETDEWEB)

Seki, K; Shimizu, Y; Kuroyanagi, H [Tokai University, Tokyo (Japan)

1997-11-25

Aluminum, GFRP and composite of aluminum coated with carbon as structural materials for wind turbine blades were bending-tested, to improve blade bending stiffness, understand stress conditions at each position, and clarify structural dynamic strength by the bending-failure test. It is possible to estimate stress conditions at each position from the test results of displacement and strain at each load. The test results with GFRP are well explained qualitatively by the boundary theory, known as a theory for composite materials. The test gives reasonable material strength data, useful for designing wind turbines of high functions and safety. The results of the blade bending-failure test are in good agreement with the calculated structural blade strength. It is also found that GFRP is a good material of high structural strength for wind turbines. 8 refs., 6 tabs.

Design of Large Wind Turbines using Fluid-Structure Coupling Technique

DEFF Research Database (Denmark)

Sessarego, Matias

Aerodynamic and structural dynamic performance analysis of modern wind turbines are routinely carried out in the wind energy field using computational tools known as aero-elastic codes. Most aero-elastic codes use the blade element momentum (BEM) technique to model the rotor aerodynamics......-dimensional viscous-inviscid interactive method, MIRAS, with the dynamics model used in the aero-elastic code FLEX5. Following the development of MIRAS-FLEX, a surrogate optimization methodology using MIRAS alone has been developed for the aerodynamic design of wind-turbine rotors. Designing a rotor using...... a computationally expensive MIRAS instead of an inexpensive BEM code represents a challenge, which is resolved by using the proposed surrogate-based approach. The approach is unique because most aerodynamic wind-turbine rotor design codes use the more common and inexpensive BEM technique. As a verification case...

Investigation Of Failure Mechanisms In A Wind Turbine Blade Root Sub-Structure

DEFF Research Database (Denmark)

Bender, Jens Jakob; Hallett, S.R.; Lindgaard, Esben

2017-01-01

and realistic results at the fraction of the cost of a full-scale test. Therefore, this work focuses on testing of sub-structures from the root end of wind turbine blades at the transition from the thick root laminate to the thinner main laminate. Some wind turbine blade manufacturers include pre-cured tapered...... beams in the root to reduce the time required to place the large quantity of material in the mould and to decrease manufacturing defects in these elements. However, this entails the risk of introducing other manufacturing defects during the Vacuum Assisted Resin Transfer Moulding process such as resin...... pockets and fibre wrinkles. Through this work it is sought to determine the effect that these manufacturing defects can have on the strength properties of the sub-structure. The sub-structures used in this work are cut out from actual wind turbine blades, meaning that the manufacturing defects...

Wind Turbine Model and Observer in Takagi-Sugeno Model Structure

International Nuclear Information System (INIS)

Georg, Sören; Müller, Matthias; Schulte, Horst

2014-01-01

Based on a reduced-order, dynamic nonlinear wind turbine model in Takagi- Sugeno (TS) model structure, a TS state observer is designed as a disturbance observer to estimate the unknown effective wind speed. The TS observer model is an exact representation of the underlying nonlinear model, obtained by means of the sector-nonlinearity approach. The observer gain matrices are obtained by means of a linear matrix inequality (LMI) design approach for optimal fuzzy control, where weighting matrices for the individual system states and outputs are included. The observer is tested in simulations with the aero-elastic code FAST for the NREL 5 MW reference turbine, where it shows a stable behaviour in turbulent wind simulations

3D WindScanner lidar measurements of wind and turbulence around wind turbines, buildings and bridges

Science.gov (United States)

Mikkelsen, T.; Sjöholm, M.; Angelou, N.; Mann, J.

2017-12-01

WindScanner is a distributed research infrastructure developed at DTU with the participation of a number of European countries. The research infrastructure consists of a mobile technically advanced facility for remote measurement of wind and turbulence in 3D. The WindScanners provide coordinated measurements of the entire wind and turbulence fields, of all three wind components scanned in 3D space. Although primarily developed for research related to on- and offshore wind turbines and wind farms, the facility is also well suited for scanning turbulent wind fields around buildings, bridges, aviation structures and of flow in urban environments. The mobile WindScanner facility enables 3D scanning of wind and turbulence fields in full scale within the atmospheric boundary layer at ranges from 10 meters to 5 (10) kilometers. Measurements of turbulent coherent structures are applied for investigation of flow pattern and dynamical loads from turbines, building structures and bridges and in relation to optimization of the location of, for example, wind farms and suspension bridges. This paper presents our achievements to date and reviews briefly the state-of-the-art of the WindScanner measurement technology with examples of uses for wind engineering applications.

A numerical study on the mechanism and optimization of wind-break structures for indirect air-cooling towers

International Nuclear Information System (INIS)

Gu, Hongfang; Wang, Haijun; Gu, Yuqian; Yao, Jianan

2016-01-01

Highlights: • Numerical study on the optimization of windbreak structure for IDAC was conducted. • Windbreak wall is the most effective structure but is affected by wind direction. • The louver is next best and it can be flexibly adjusted at the windy conditions. • An optimal louver opening was obtained for achieving a good cooling performance. - Abstract: The heat transfer performance of indirect air-cooling (IDAC) towers in large power stations is sensitive to the ambient wind velocity. To ensure the economic and reliable operation of units under windy conditions, it is important to conduct research on the optimization of different wind-break structures. This paper uses computational fluid dynamics method (CFD) to simulate the heat transfer performance of a 1000 MW IDAC tower power stations with four different wind-break structures namely, cross walls, wind-break walls, cross line-screen, and louvers. The research results show that the order of the effective heat transfer improvement of four wind-break structures is the wind-break, cross wall, line-screen and louvers. The wind-break wall is the most optimal structure, but its performance is strictly influenced by the direction and velocity of the wind, and the cross walls and cross line-screen structure have similar limitation in the practice operation. The louver is installed in each sector, and it is the next best option for increasing the heat transfer performance. It can be flexibly adjusted based on the wind direction and velocity. With the decrease in the louver opening, k, there is a decrease in the heat transfer rate of the windward sectors, and a significant increase in the heat transfer rate of the leeward sectors. Thus the total heat transfer rate of the IDAC tower can be improved tremendously. Based on the analysis of heat transfer and air flow mechanisms, there is an optimal opening, k, which achieves the largest heat transfer performance in an IDAC tower at each wind velocity. This study

Structure and thermodynamic properties of molten strontium chloride

International Nuclear Information System (INIS)

Pastore, G.; Ballone, P.; Tosi, M.P.; Trieste Univ.

1985-05-01

Self-consistent calculations of pair distribution functions and thermodynamic properties are presented for a pair-potentials model of molten strontium chloride. The calculations extend to a strongly asymmetric ionic liquid an earlier assessment of bridge diagrams in a modified hypernetted chain approach to the liquid structure of alkali halides. Good agreement is found with computer simulation data obtained by de Leeuw with the same set of pair potentials, showing that the present approach incorporates genuine general features of liquid structure theory for multicomponent liquids with strong relative ordering of the component species. It is further shown that the strong correlations between the divalent cations, both in the model and in real molten strontium chloride, can be approximately reproduced on the basis of a simple one-component-plasma model, provided that dielectric screening is allowed for in the real liquid. This allows us to tentatively attribute the significant level of disagreement between a pair potentials model of this liquid and the neutron diffraction data of McGreevy and Mitchell to many-body distortions of the electronic shells of the ions. (author)

Thermodynamics of Accelerating Black Holes.

Science.gov (United States)

Appels, Michael; Gregory, Ruth; Kubizňák, David

2016-09-23

We address a long-standing problem of describing the thermodynamics of an accelerating black hole. We derive a standard first law of black hole thermodynamics, with the usual identification of entropy proportional to the area of the event horizon-even though the event horizon contains a conical singularity. This result not only extends the applicability of black hole thermodynamics to realms previously not anticipated, it also opens a possibility for studying novel properties of an important class of exact radiative solutions of Einstein equations describing accelerated objects. We discuss the thermodynamic volume, stability, and phase structure of these black holes.

Near-wake flow structure downwind of a wind turbine in a turbulent boundary layer

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wei; Markfort, Corey D. [University of Minnesota, Saint Anthony Falls Laboratory, Department of Civil Engineering, Minneapolis, MN (United States); Porte-Agel, Fernando [Ecole Polytechnique Federale de Lausanne (EPFL), ENAC-IIE-WIRE, Wind Engineering and Renewable Energy Laboratory (WIRE), Lausanne (Switzerland)

2012-05-15

Wind turbines operate in the surface layer of the atmospheric boundary layer, where they are subjected to strong wind shear and relatively high turbulence levels. These incoming boundary layer flow characteristics are expected to affect the structure of wind turbine wakes. The near-wake region is characterized by a complex coupled vortex system (including helicoidal tip vortices), unsteadiness and strong turbulence heterogeneity. Limited information about the spatial distribution of turbulence in the near wake, the vortex behavior and their influence on the downwind development of the far wake hinders our capability to predict wind turbine power production and fatigue loads in wind farms. This calls for a better understanding of the spatial distribution of the 3D flow and coherent turbulence structures in the near wake. Systematic wind-tunnel experiments were designed and carried out to characterize the structure of the near-wake flow downwind of a model wind turbine placed in a neutral boundary layer flow. A horizontal-axis, three-blade wind turbine model, with a rotor diameter of 13 cm and the hub height at 10.5 cm, occupied the lowest one-third of the boundary layer. High-resolution particle image velocimetry (PIV) was used to measure velocities in multiple vertical stream-wise planes (x-z) and vertical span-wise planes (y-z). In particular, we identified localized regions of strong vorticity and swirling strength, which are the signature of helicoidal tip vortices. These vortices are most pronounced at the top-tip level and persist up to a distance of two to three rotor diameters downwind. The measurements also reveal strong flow rotation and a highly non-axisymmetric distribution of the mean flow and turbulence structure in the near wake. The results provide new insight into the physical mechanisms that govern the development of the near wake of a wind turbine immersed in a neutral boundary layer. They also serve as important data for the development and

Response of the dynamic and thermodynamic structure of the stratosphere to the solar cycle in the boreal winter

Science.gov (United States)

Shi, Chunhua; Gao, Yannan; Cai, Juan; Guo, Dong; Lu, Yan

2018-04-01

The response of the dynamic and thermodynamic structure of the stratosphere to the solar cycle in the boreal winter is investigated based on measurements of the solar cycle by the Spectral Irradiance Monitor onboard the SORCE satellite, monthly ERA-Interim Reanalysis data from the European Center for Medium-Range Weather Forecasts, the radiative transfer scheme of the Beijing Climate Center (BCC-RAD) and a multiple linear regression model. The results show that during periods of strong solar activity, the solar shortwave heating anomaly from the climatology in the tropical upper stratosphere triggers a local warm anomaly and strong westerly winds in mid-latitudes, which strengthens the upward propagation of planetary wave 1 but prevents that of wave 2. The enhanced westerly jet makes a slight adjustment to the propagation path of wave 1, but prevents wave 2 from propagating upward, decreases the dissipation of wave 2 in the extratropical upper stratosphere and hence weakens the Brewer-Dobson circulation. The adiabatic heating term in relation to the Brewer-Dobson circulation shows anomalous warming in the tropical lower stratosphere and anomalous cooling in the mid-latitude upper stratosphere.

Thermodynamic properties and static structure factor for a Yukawa fluid in the mean spherical approximation.

Science.gov (United States)

Montes-Perez, J; Cruz-Vera, A; Herrera, J N

2011-12-01

This work presents the full analytic expressions for the thermodynamic properties and the static structure factor for a hard sphere plus 1-Yukawa fluid within the mean spherical approximation. To obtain these properties of the fluid type Yukawa analytically it was necessary to solve an equation of fourth order for the scaling parameter on a large scale. The physical root of this equation was determined by imposing physical conditions. The results of this work are obtained from seminal papers of Blum and Høye. We show that is not necessary the use the series expansion to solve the equation for the scaling parameter. We applied our theoretical result to find the thermodynamic and the static structure factor for krypton. Our results are in good agreement with those obtained in an experimental form or by simulation using the Monte Carlo method.

Diode rectifier bridge-based structure for DFIG-based wind turbine

DEFF Research Database (Denmark)

Zhu, Rongwu; Chen, Zhe; Wu, Xiaojie

2015-01-01

This paper proposes a new structure for the doubly-fed induction generator (DFIG)-based wind turbine. The proposed structure consists of a DFIG controlled by a partial rated power converter in the rotor side, a three-phase diode rectifier bridge (DRB) connected to the stator, and a DC/AC full rated...

Structure-thermodynamics-antioxidant activity relationships of selected natural phenolic acids and derivatives: an experimental and theoretical evaluation.

Science.gov (United States)

Chen, Yuzhen; Xiao, Huizhi; Zheng, Jie; Liang, Guizhao

2015-01-01

Phenolic acids and derivatives have potential biological functions, however, little is known about the structure-activity relationships and the underlying action mechanisms of these phenolic acids to date. Herein we investigate the structure-thermodynamics-antioxidant relationships of 20 natural phenolic acids and derivatives using DPPH• scavenging assay, density functional theory calculations at the B3LYP/6-311++G(d,p) levels of theory, and quantitative structure-activity relationship (QSAR) modeling. Three main working mechanisms (HAT, SETPT and SPLET) are explored in four micro-environments (gas-phase, benzene, water and ethanol). Computed thermodynamics parameters (BDE, IP, PDE, PA and ETE) are compared with the experimental radical scavenging activities against DPPH•. Available theoretical and experimental investigations have demonstrated that the extended delocalization and intra-molecular hydrogen bonds are the two main contributions to the stability of the radicals. The C = O or C = C in COOH, COOR, C = CCOOH and C = CCOOR groups, and orthodiphenolic functionalities are shown to favorably stabilize the specific radical species to enhance the radical scavenging activities, while the presence of the single OH in the ortho position of the COOH group disfavors the activities. HAT is the thermodynamically preferred mechanism in the gas phase and benzene, whereas SPLET in water and ethanol. Furthermore, our QSAR models robustly represent the structure-activity relationships of these explored compounds in polar media.

Probabilistic Design of Wind Turbine Structures: Design Studies and Sensitivities to Model Parameters

DEFF Research Database (Denmark)

NJOMO WANDJI, Wilfried

: decrease of conservatism level, improvement of design procedures, and development of innovative structural systems that suit well for large wind turbines. The increasing size of the structure introduces new problems that were not present for small structures. These problems include: (i) the preparation...... substructures. In addition to being aggressive, conditions for offshore environments and the associated models are highly uncertain. Appropriate statistical methodologies should be used in order to design robust structures, which are structures whose engineering performance is not significantly affected....... These research areas are differentially implemented through tasks on various wind turbine structures (shaft, jacket, semi-floater, monopile, and grouted joint). In particular the following research questions are answered: How are extreme and fatigue loads on a given structure influenced by the design of other...

Modeling the Thermosphere as a Driven-Dissipative Thermodynamic System

Science.gov (United States)

2013-03-01

8 Figure 2: Illustration of the geocentric solar magnetospheric coordinate system............15 Figure 3: Diagram of the...to test new methods of modeling the thermospheric environment. Thermosphere as a Driven-Dissipative Thermodynamic System One approach for modeling... approach uses empirical coupling and relaxation constants to model the 4 input of energy to the thermosphere from the solar wind during

Statistical Evaluation of the Identified Structural Parameters of an idling Offshore Wind Turbine

International Nuclear Information System (INIS)

Kramers, Hendrik C.; Van der Valk, Paul L.C.; Van Wingerden, Jan-Willem

2016-01-01

With the increased need for renewable energy, new offshore wind farms are being developed at an unprecedented scale. However, as the costs of offshore wind energy are still too high, design optimization and new innovations are required for lowering its cost. The design of modern day offshore wind turbines relies on numerical models for estimating ultimate and fatigue loads of the turbines. The dynamic behavior and the resulting structural loading of the turbines is determined for a large part by its structural properties, such as the natural frequencies and damping ratios. Hence, it is important to obtain accurate estimates of these modal properties. For this purpose stochastic subspace identification (SSI), in combination with clustering and statistical evaluation methods, is used to obtain the variance of the identified modal properties of an installed 3.6MW offshore wind turbine in idling conditions. It is found that one is able to obtain confidence intervals for the means of eigenfrequencies and damping ratios of the fore-aft and side-side modes of the wind turbine. (paper)

Effect of soil-foundation-structure interaction on the seismic response of wind turbines

Directory of Open Access Journals (Sweden)

Sam Austin

2017-09-01

Full Text Available Soil-foundation-structure interaction can affect the seismic response of wind turbines. This paper studies the effects of soil-foundation-structure interaction on the seismic response of 65 kW, 1 MW, and 2 MW horizontal-axis wind turbines with truncated cone steel towers. Four types of foundations with frequency-based design were analyzed, including spread foundation, mono pile, pile group with cap, and anchored spread foundation. Soil is modeled both implicitly (subgrade reaction modulus and explicitly. The finite element model developed using the ANSYS program was first validated using experimental data. Numerical models are then analyzed in both frequency and time domains using the Block Lanczos and generalized HHT-α formulations. Recommendations were given to simplify the soil-foundation-structure interaction analysis of wind turbines subjected to seismic loading.

THz limb sounder (TLS) for lower thermospheric wind, oxygen density, and temperature

Science.gov (United States)

Wu, Dong L.; Yee, Jeng-Hwa; Schlecht, Erich; Mehdi, Imran; Siles, Jose; Drouin, Brian J.

2016-07-01

Neutral winds are one of the most critical measurements in the lower thermosphere and E region ionosphere (LTEI) for understanding complex electrodynamic processes and ion-neutral interactions. We are developing a high-sensitivity, low-power, noncryogenic 2.06 THz Schottky receiver to measure wind profiles at 100-140 km. The new technique, THz limb sounder (TLS), aims to measure LTEI winds by resolving the wind-induced Doppler shift of 2.06 THz atomic oxygen (OI) emissions. As a transition between fine structure levels in the ground electronic state, the OI emission is in local thermodynamic equilibrium (LTE) at altitudes up to 350 km. This LTE property, together with day-and-night capability and small line-of-sight gradient, makes the OI limb sounding a very attractive technique for neutral wind observations. In addition to the wind measurement, TLS can also retrieve [OI] density and neutral temperature in the LTEI region. TLS leverages rapid advances in THz receiver technologies including subharmonically pumped (SHP) mixers and Schottky-diode-based power multipliers. Current SHP Schottky receivers have produced good sensitivity for THz frequencies at ambient environment temperatures (120-150 K), which are achievable through passively cooling in spaceflight. As an emerging technique, TLS can fill the critical data gaps in the LTEI neutral wind observations to enable detailed studies on the coupling and dynamo processes between charged and neutral molecules.

Dynamic Analysis of A 5-MW Tripod Offshare Wind Turbine by Considering Fluid-Structure Interaction

Institute of Scientific and Technical Information of China (English)

ZHANG Li-wei; LI Xin

2017-01-01

Fixed of fshore wind turbines usually have large underwater supporting structures. The fluid influences the dynamic characteristics of the structure system. The dynamic model of a 5-MW tripod of fshore wind turbine considering the pile–soil system and fluid structure interaction (FSI) is established, and the structural modes in air and in water are obtained by use of ANSYS. By comparing low-order natural frequencies and mode shapes, the influence of sea water on the free vibration characteristics of of fshore wind turbine is analyzed. On basis of the above work, seismic responses under excitation by El-Centro waves are calculated by the time-history analysis method. The results reveal that the dynamic responses such as the lateral displacement of the foundation and the section bending moment of the tubular piles increase substantially under the influence of the added-mass and hydrodynamic pressure of sea water. The method and conclusions presented in this paper can provide a theoretical reference for structure design and analysis of of fshore wind turbines fixed in deep seawater.

Dynamic analysis of a 5-MW tripod offshore wind turbine by considering fluid-structure interaction

Science.gov (United States)

Zhang, Li-wei; Li, Xin

2017-10-01

Fixed offshore wind turbines usually have large underwater supporting structures. The fluid influences the dynamic characteristics of the structure system. The dynamic model of a 5-MW tripod offshore wind turbine considering the pile-soil system and fluid structure interaction (FSI) is established, and the structural modes in air and in water are obtained by use of ANSYS. By comparing low-order natural frequencies and mode shapes, the influence of sea water on the free vibration characteristics of offshore wind turbine is analyzed. On basis of the above work, seismic responses under excitation by El-Centro waves are calculated by the time-history analysis method. The results reveal that the dynamic responses such as the lateral displacement of the foundation and the section bending moment of the tubular piles increase substantially under the influence of the added-mass and hydrodynamic pressure of sea water. The method and conclusions presented in this paper can provide a theoretical reference for structure design and analysis of offshore wind turbines fixed in deep seawater.

On the vertical structure of wind gusts

DEFF Research Database (Denmark)

Suomi, I.; Gryning, Sven-Erik; Floors, Rogier Ralph

2015-01-01

The increasing size of wind turbines, their height and the area swept by their blades have revised the need for understanding the vertical structure of wind gusts. Information is needed for the whole profile. In this study, we analyzed turbulence measurements from a 100m high meteorological mast...... and the turbulence intensity, of which the turbulence intensity was found to dominate over the peak factor in determining the effects of stability and height above the surface on the gust factor. The peak factor only explained 15% or less of the vertical decrease of the gust factor, but determined the effect of gust...... duration on the gust factor. The statistical method to estimate the peak factor did not reproduce the observed vertical decrease in near-neutral and stable conditions and near-constant situation in unstable conditions. Despite this inconsistency, the theoretical method provides estimates for the peak...

Contact Geometry of Mesoscopic Thermodynamics and Dynamics

Directory of Open Access Journals (Sweden)

Miroslav Grmela

2014-03-01

Full Text Available The time evolution during which macroscopic systems reach thermodynamic equilibrium states proceeds as a continuous sequence of contact structure preserving transformations maximizing the entropy. This viewpoint of mesoscopic thermodynamics and dynamics provides a unified setting for the classical equilibrium and nonequilibrium thermodynamics, kinetic theory, and statistical mechanics. One of the illustrations presented in the paper is a new version of extended nonequilibrium thermodynamics with fluxes as extra state variables.

Conceptual Design of a Floating Support Structure and Mooring System for a Vertical Axis Wind Turbine

DEFF Research Database (Denmark)

Berthelsen, Petter Andreas; Fylling, Ivar; Vita, Luca

2012-01-01

This paper deals with the conceptual design of a floating support structure and mooring system for a 5MW vertical axis offshore wind turbine. The work is carried out as part of the DeepWind project, where the main objective is to investigate the feasibility of a floating vertical axis offshore wind...... turbine. The DeepWind concept consists of a Darrieus rotor mounted on a spar buoy support structure. The conceptual design is carried out in an iterative process, involving the different subcomponents. The present work is part of the first design iteration and the objective is to find a feasible floating...... support structure and mooring system for the DeepWind concept. The conceptual design is formulated as an optimization problem: Starting with an initial configuration, the optimization procedure tries to find a cheaper solution while satisfying a set of design requirements. This approach utilizes available...

Modified Adaptive Control for Region 3 Operation in the Presence of Wind Turbine Structural Modes

Science.gov (United States)

Frost, Susan Alane; Balas, Mark J.; Wright, Alan D.

2010-01-01

Many challenges exist for the operation of wind turbines in an efficient manner that is reliable and avoids component fatigue and failure. Turbines operate in highly turbulent environments resulting in aerodynamic loads that can easily excite turbine structural modes, possibly causing component fatigue and failure. Wind turbine manufacturers are highly motivated to reduce component fatigue and failure that can lead to loss of revenue due to turbine down time and maintenance costs. The trend in wind turbine design is toward larger, more flexible turbines that are ideally suited to adaptive control methods due to the complexity and expense required to create accurate models of their dynamic characteristics. In this paper, we design an adaptive collective pitch controller for a high-fidelity simulation of a utility-scale, variable-speed horizontal axis wind turbine operating in Region 3. The objective of the adaptive pitch controller is to regulate generator speed, accommodate wind gusts, and reduce the excitation of structural modes in the wind turbine. The control objective is accomplished by collectively pitching the turbine blades. The adaptive collective pitch controller for Region 3 was compared in simulations with a baseline classical Proportional Integrator (PI) collective pitch controller. The adaptive controller will demonstrate the ability to regulate generator speed in Region 3, while accommodating gusts, and reducing the excitation of certain structural modes in the wind turbine.

Observations of peculiar sporadic sodium structures and their relation with wind variations

Science.gov (United States)

Sridharan, S.; Prasanth, P. Vishnu; Kumar, Y. Bhavani; Ramkumar, Geetha; Sathishkumar, S.; Raghunath, K.

2009-04-01

Resonance lidar observations of sodium density in the upper mesosphere region over Gadanki (13.5°N, 79.2°E) rarely show complex structures with rapid enhancements of sodium density, completely different from normal sporadic sodium structures. The hourly averaged meteor radar zonal winds over Trivandrum (8.5°N, 76.5°E) show an eastward shear with altitude during the nights, when these events are formed. As suggested by Kane et al. [2001. Joint observations of sodium enhancements and field-aligned ionospheric irregularities. Geophysical Research Letters 28, 1375-1378], our observations show that the complex structures may be formed due to Kelvin-Helmholtz instability, which can occur in the region of strong wind shear.

Structural monitoring and smart control of a wind turbine

DEFF Research Database (Denmark)

Caterino, Nicola; Trinchillo, Francesco; Georgakis, Christos T.

2014-01-01

The remarkable growth in height of wind turbines in the last years - for a higher production of electricity - makes the issues of monitoring and control of such challenging engineering works pressing than ever. The research herein proposed is addressed to monitor the structural demand imposed to ...

Mapping 3D plasma structure in the solar wind with the L1 constellation: joint observations from Wind, ACE, DSCOVR, and SoHO

Science.gov (United States)

Stevens, M. L.; Kasper, J. C.; Case, A. W.; Korreck, K. E.; Szabo, A.; Biesecker, D. A.; Prchlik, J.

2017-12-01

At this moment in time, four observatories with similar instrumentation- Wind, ACE, DSCOVR, and SoHO- are stationed directly upstream of the Earth and making continuous observations. They are separated by drift-time baselines of seconds to minutes, timescales on which MHD instabilities in the solar wind are known to grow and evolve, and spatial baselines of tens to 200 earth radii, length scales relevant to the Earth's magnetosphere. By comparing measurements of matched solar wind structures from the four vantage points, the form of structures and associated dynamics on these scales is illuminated. Our targets include shocks and MHD discontinuities, stream fronts, locii of reconnection and exhaust flow boundary layers, plasmoids, and solitary structures born of nonlinear instability. We use the tetrahedral quality factors and other conventions adopted for Cluster to identify periods where the WADS constellation is suitably non-degenerate and arranged in such a way as to enable specific types of spatial, temporal, or spatiotemporal inferences. We present here an overview of the geometries accessible to the L1 constellation and timing-based and plasma-based observations of solar wind structures from 2016-17. We discuss the unique potential of the constellation approach for space physics and space weather forecasting at 1 AU.

Electronic, elastic, thermodynamic properties and structure disorder of γ-AlON solid solution from ab initio calculations

International Nuclear Information System (INIS)

Wang, Yuezhong; Lu, Tiecheng; Zhang, Rongshi; Jiang, Shengli; Qi, Jianqi; Wang, Ying; Chen, Qingyun; Miao, Naihua; He, Duanwei

2013-01-01

Highlights: ► We reassess the chemical bonding character of γ-AlON which shows strong ionicity. ► γ-AlON single-crystals exhibit highly elastic anisotropy. ► The thermodynamic properties are investigated in a wider temperature/pressure range. ► γ-AlON is an O/N partially disordered structure. - Abstract: Spinel aluminium oxynitride (γ-AlON), as a kind of transparent ceramic material expectable, is studied using the ab initio density functional method, in terms of electronic, elastic, thermodynamic properties and structure disorder. The results show that γ-AlON exhibits strong ionicity, as quantitatively expressed by (Al O 2.43+ ) 15 (Al T 2.41+ ) 8 (O 1.64- ) 27 (N 2.27- ) 5 from our reassessment of the ionic character. We summarize and speculate that the considered oxynitride single-crystals exhibit highly elastic anisotropy. The interpretation of the thermodynamic properties of γ-AlON according to quasi-harmonic Debye model confirm the available experiments and are extended to a wider temperature/pressure range. This material holds high elastic strength under extreme environments, where dB/dT absolute value is less than 0.03 GPa/K, independent of the pressure. Finally, we study the O/N structure disorder character of γ-AlON solid solution by investigating nine possible crystal structures. It is found that γ-AlON should be partially disordered, and in fact, the O/N ordering has a significant effect on the properties.

Quark–hadron phase structure, thermodynamics, and magnetization of QCD matter

Science.gov (United States)

Nasser Tawfik, Abdel; Magied Diab, Abdel; Hussein, M. T.

2018-05-01

The SU(3) Polyakov linear-sigma model (PLSM) is systematically implemented to characterize the quark-hadron phase structure and to determine various thermodynamic quantities and the magnetization of quantum chromodynamic (QCD) matter. Using mean-field approximation, the dependence of the chiral order parameter on a finite magnetic field is also calculated. Under a wide range of temperatures and magnetic field strengths, various thermodynamic quantities including trace anomaly, speed of sound squared, entropy density, and specific heat are presented, and some magnetic properties are described as well. Where available these results are compared to recent lattice QCD calculations. The temperature dependence of these quantities confirms our previous finding that the transition temperature is reduced with the increase in the magnetic field strength, i.e. QCD matter is characterized by an inverse magnetic catalysis. Furthermore, the temperature dependence of the magnetization showing that QCD matter has paramagnetic properties slightly below and far above the pseudo-critical temperature is confirmed as well. The excellent agreement with recent lattice calculations proves that our QCD-like approach (PLSM) seems to possess the correct degrees of freedom in both the hadronic and partonic phases and describes well the dynamics deriving confined hadrons to deconfined quark-gluon plasma.

Damping Wind and Wave Loads on a Floating Wind Turbine

DEFF Research Database (Denmark)

Christiansen, Søren; Bak, Thomas; Knudsen, Torben

2013-01-01

Offshore wind energy capitalizes on the higher and less turbulent wind speeds at sea. To enable deployment of wind turbines in deep-water locations, structures are being explored, where wind turbines are placed on a floating platform. This combined structure presents a new control problem, due......, and we show the influence that both wind speed, wave frequencies and misalignment between wind and waves have on the system dynamics. A new control model is derived that extends standard turbine models to include the hydrodynamics, additional platform degrees of freedom, the platform mooring system...

3D WindScanner lidar measurements of wind and turbulence around wind turbines, buildings and bridges

DEFF Research Database (Denmark)

Mikkelsen, Torben Krogh; Sjöholm, Mikael; Angelou, Nikolas

2017-01-01

WindScanner is a distributed research infrastructure developed at DTU with the participation of a number of European countries. The research infrastructure consists of a mobile technically advanced facility for remote measurement of wind and turbulence in 3D. The WindScanners provide coordinated...... structures and of flow in urban environments. The mobile WindScanner facility enables 3D scanning of wind and turbulence fields in full scale within the atmospheric boundary layer at ranges from 10 meters to 5 (10) kilometers. Measurements of turbulent coherent structures are applied for investigation...

A novel structure of transmission line pulse transformer with mutually coupled windings.

Science.gov (United States)

Yu, Binxiong; Su, Jiancang; Li, Rui; Zhao, Liang; Zhang, Xibo; Wang, Junjie

2014-03-01

A novel structure of transmission line transformer (TLT) with mutually coupled windings is described in this paper. All transmission lines except the first stage of the transformer are wound on a common ferrite core for the TLT with this structure. A referral method was introduced to analyze the TLT with this structure, and an analytic expression of the step response was derived. It is shown that a TLT with this structure has a significantly slower droop rate than a TLT with other winding structures and the number of ferrite cores needed is largely reduced. A four-stage TLT with this structure was developed, whose input and output impedance were 4.2 Ω and 67.7 Ω, respectively. A frequency response test of the TLT was carried out. The test results showed that pulse response time of the TLT is several nanoseconds. The TLT described in this paper has the potential to be used as a rectangle pulse transformer with very fast response time.

Application of microwave radiometer and wind profiler data in the estimation of wind gust associated with intense convective weather

International Nuclear Information System (INIS)

Chan, P W; Wong, K H

2008-01-01

Estimates of the wind gusts associated with intense convective weather could be obtained using empirical relationships such as GUSTEX based on radiosonde measurements. However, such data are only available a couple of times a day and may not reflect the rapidly changing atmospheric condition in spring and summer times. The feasibility of combining the thermodynamic profiles from a ground-based microwave radiometer and wind profiles given by radar wind profilers in the continuous estimation of wind gusts is studied in this paper. Based on the results of a 4-month trial of a microwave radiometer in Hong Kong in 2004, the estimated and the actual gusts are reasonably well correlated. It is also found that the wind gusts so estimated provide better indications of the strength of squalls compared with those based on radiosonde measurements and with a lead time of about one hour

Thermodynamic metrics and optimal paths.

Science.gov (United States)

Sivak, David A; Crooks, Gavin E

2012-05-11

A fundamental problem in modern thermodynamics is how a molecular-scale machine performs useful work, while operating away from thermal equilibrium without excessive dissipation. To this end, we derive a friction tensor that induces a Riemannian manifold on the space of thermodynamic states. Within the linear-response regime, this metric structure controls the dissipation of finite-time transformations, and bestows optimal protocols with many useful properties. We discuss the connection to the existing thermodynamic length formalism, and demonstrate the utility of this metric by solving for optimal control parameter protocols in a simple nonequilibrium model.

Cost-efficient foundation structures for large offshore wind farms

International Nuclear Information System (INIS)

Birch, C.; Gormsen, C.; Lyngesen, S.; Rasmussen, J. L.; Juhl, H.

1997-01-01

This paper presents the results of the development of a cost-efficient foundation for large (1.5 MW) offshore wind farms at water depth of 5 to 11 m. Previously, medium sized wind turbines (500 kW) in Denmark have been installed offshore at water depths of approximately 5 m on concrete gravity foundations. The installation of larger turbines at greater depth does, however, hold great promise in terms of wind environment and environmental considerations. The costs of a traditional gravity foundation at these increased water depths is expected to be prohibitive, and the aim of the project has been to reduce the foundations costs in general. This paper describes the theoretical basis for the geotechnical and structural design of three alternative concepts and presents an optimised layout of each based on a research and development project. The basis has been a wind farm consisting of 100 turbines. The R and D project has been undertaken by the consulting engineers Nellemann, Nielsen and Rauschenberger A/S (Gravity foundation), LICengineering A/S (Mono pile) and Ramboell (Tripod) in co-operation with the Danish utility engineering companies Elkraft and Elsamprojekt A/S. The project was partly financed by the participants and by the Danish Energy Agency through their 1996 Energy Research Programme (EFP-96). (au) 18 refs

The vitreous state thermodynamics, structure, rheology, and crystallization

CERN Document Server

Gutzow, Ivan S

2013-01-01

This book summarizes the experimental evidence and modern classical and theoretical approaches in understanding the vitreous state, from structural problems, over equilibrium and non-equilibrium thermodynamics, to statistical physics. Glasses, and especially silicate glasses, are only the best known representatives of this particular physical state of matter. Other typical representatives include organic polymer glasses, and many other easily vitrifying organic and inorganic substances, technically important materials, amidst them vitreous water and vitrified aqueous solutions, and also many metallic alloy systems. Some of these systems only form glasses under particular conditions, e.g. through ultra-rapid cooling. This book describes the properties and the formation of both every-day technical glasses and especially of such more exotic forms of vitreous matter. It is a unique source of knowledge and new ideas for materials scientists, engineers and researchers working on condensed matter. The new edition e...

Stochastic and information-thermodynamic structures of population dynamics in a fluctuating environment

Science.gov (United States)

Kobayashi, Tetsuya J.; Sughiyama, Yuki

2017-07-01

Adaptation in a fluctuating environment is a process of fueling environmental information to gain fitness. Living systems have gradually developed strategies for adaptation from random and passive diversification of the phenotype to more proactive decision making, in which environmental information is sensed and exploited more actively and effectively. Understanding the fundamental relation between fitness and information is therefore crucial to clarify the limits and universal properties of adaptation. In this work, we elucidate the underlying stochastic and information-thermodynamic structure in this process, by deriving causal fluctuation relations (FRs) of fitness and information. Combined with a duality between phenotypic and environmental dynamics, the FRs reveal the limit of fitness gain, the relation of time reversibility with the achievability of the limit, and the possibility and condition for gaining excess fitness due to environmental fluctuation. The loss of fitness due to causal constraints and the limited capacity of real organisms is shown to be the difference between time-forward and time-backward path probabilities of phenotypic and environmental dynamics. Furthermore, the FRs generalize the concept of the evolutionary stable state (ESS) for fluctuating environment by giving the probability that the optimal strategy on average can be invaded by a suboptimal one owing to rare environmental fluctuation. These results clarify the information-thermodynamic structures in adaptation and evolution.

Wind tower service lift

Science.gov (United States)

Oliphant, David; Quilter, Jared; Andersen, Todd; Conroy, Thomas

2011-09-13

An apparatus used for maintaining a wind tower structure wherein the wind tower structure may have a plurality of legs and may be configured to support a wind turbine above the ground in a better position to interface with winds. The lift structure may be configured for carrying objects and have a guide system and drive system for mechanically communicating with a primary cable, rail or other first elongate member attached to the wind tower structure. The drive system and guide system may transmit forces that move the lift relative to the cable and thereby relative to the wind tower structure. A control interface may be included for controlling the amount and direction of the power into the guide system and drive system thereby causing the guide system and drive system to move the lift relative to said first elongate member such that said lift moves relative to said wind tower structure.

Dynamics, thermodynamics and structure of liquids and supercritical fluids: crossover at the Frenkel line

Science.gov (United States)

Fomin, Yu D.; Ryzhov, V. N.; Tsiok, E. N.; Proctor, J. E.; Prescher, C.; Prakapenka, V. B.; Trachenko, K.; Brazhkin, V. V.

2018-04-01

We review recent work aimed at understanding dynamical and thermodynamic properties of liquids and supercritical fluids. The focus of our discussion is on solid-like transverse collective modes, whose evolution in the supercritical fluids enables one to discuss the main properties of the Frenkel line separating rigid liquid-like and non-rigid gas-like supercritical states. We subsequently present recent experimental evidence of the Frenkel line showing that structural and dynamical crossovers are seen at a pressure and temperature corresponding to the line as predicted by theory and modelling. Finally, we link dynamical and thermodynamic properties of liquids and supercritical fluids by the new calculation of liquid energy governed by the evolution of solid-like transverse modes. The disappearance of those modes at high temperature results in the observed decrease of heat capacity.

Vfold: a web server for RNA structure and folding thermodynamics prediction.

Science.gov (United States)

Xu, Xiaojun; Zhao, Peinan; Chen, Shi-Jie

2014-01-01

The ever increasing discovery of non-coding RNAs leads to unprecedented demand for the accurate modeling of RNA folding, including the predictions of two-dimensional (base pair) and three-dimensional all-atom structures and folding stabilities. Accurate modeling of RNA structure and stability has far-reaching impact on our understanding of RNA functions in human health and our ability to design RNA-based therapeutic strategies. The Vfold server offers a web interface to predict (a) RNA two-dimensional structure from the nucleotide sequence, (b) three-dimensional structure from the two-dimensional structure and the sequence, and (c) folding thermodynamics (heat capacity melting curve) from the sequence. To predict the two-dimensional structure (base pairs), the server generates an ensemble of structures, including loop structures with the different intra-loop mismatches, and evaluates the free energies using the experimental parameters for the base stacks and the loop entropy parameters given by a coarse-grained RNA folding model (the Vfold model) for the loops. To predict the three-dimensional structure, the server assembles the motif scaffolds using structure templates extracted from the known PDB structures and refines the structure using all-atom energy minimization. The Vfold-based web server provides a user friendly tool for the prediction of RNA structure and stability. The web server and the source codes are freely accessible for public use at "http://rna.physics.missouri.edu".

Structural, electronic, elastic, and thermodynamic properties of CaSi, Ca2Si, and CaSi2 phases from first-principles calculations

Science.gov (United States)

Li, X. D.; Li, K.; Wei, C. H.; Han, W. D.; Zhou, N. G.

2018-06-01

The structural, electronic, elastic, and thermodynamic properties of CaSi, Ca2Si, and CaSi2 are systematically investigated by using first-principles calculations method based on density functional theory (DFT). The calculated formation enthalpies and cohesive energies show that CaSi2 possesses the greatest structural stability and CaSi has the strongest alloying ability. The structural stability of the three phases is compared according to electronic structures. Further analysis on electronic structures indicates that the bonding of these phases exhibits the combinations of metallic, covalent, and ionic bonds. The elastic constants are calculated, and the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and anisotropy factor of polycrystalline materials are deduced. Additionally, the thermodynamic properties were theoretically predicted and discussed.

Optimised and balanced structural and system reliability of offshore wind turbines. An account

Energy Technology Data Exchange (ETDEWEB)

Tarp-Johansen, N.J.; Kozine, I. (Risoe National Lab., DTU, Roskilde, (DK)); Rademarkers, L. (Netherlands Energy Research Foundation (NL)); Dalsgaard Soerensen, J. (Aalborg Univ. (DK)) Ronold, K. (Det Norske Veritas (DK))

2005-04-15

This report gives the results of the research project 'Optimised and Uniform Safety and Reliability of Offshore Wind Turbines (an account)'. The main subject of the project has been the account of the state-of-the art of knowledge about, and/or attempts to, harmonisation of the structural reliability of wind turbines, on the one hand, and the reliability of the wind turbine's control/safety system, on the other hand. Within the project some research pointing ahead has also been conducted. (au)

Electronic, elastic, thermodynamic properties and structure disorder of {gamma}-AlON solid solution from ab initio calculations

Energy Technology Data Exchange (ETDEWEB)

Wang, Yuezhong, E-mail: wyzphysics@163.com [Department of Physics and Key Laboratory for Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Tianjin Jinhang Institute of Technical Physics, Tianjin 300192 (China); Lu, Tiecheng, E-mail: lutiecheng@scu.edu.cn [Department of Physics and Key Laboratory for Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); International Center for Material Physics, Chinese Academy of Sciences, Shenyang 110015 (China); Zhang, Rongshi [Tianjin Jinhang Institute of Technical Physics, Tianjin 300192 (China); Jiang, Shengli; Qi, Jianqi; Wang, Ying [Department of Physics and Key Laboratory for Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Chen, Qingyun [Department of Physics and Key Laboratory for Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); National Defense Key Discipline Laboratory of Nuclear Waste and Environmental Safety, Southwest University of Science and Technology, Mianyang 621010 (China); Miao, Naihua [Physique Theorique des Materiaux, Universite de Liege, Sart Tilman B-4000 (Belgium); He, Duanwei [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610064 (China)

2013-01-25

Highlights: Black-Right-Pointing-Pointer We reassess the chemical bonding character of {gamma}-AlON which shows strong ionicity. Black-Right-Pointing-Pointer {gamma}-AlON single-crystals exhibit highly elastic anisotropy. Black-Right-Pointing-Pointer The thermodynamic properties are investigated in a wider temperature/pressure range. Black-Right-Pointing-Pointer {gamma}-AlON is an O/N partially disordered structure. - Abstract: Spinel aluminium oxynitride ({gamma}-AlON), as a kind of transparent ceramic material expectable, is studied using the ab initio density functional method, in terms of electronic, elastic, thermodynamic properties and structure disorder. The results show that {gamma}-AlON exhibits strong ionicity, as quantitatively expressed by (Al{sub O}{sup 2.43+}){sub 15}(Al{sub T}{sup 2.41+}){sub 8}(O{sup 1.64-}){sub 27}(N{sup 2.27-}){sub 5} from our reassessment of the ionic character. We summarize and speculate that the considered oxynitride single-crystals exhibit highly elastic anisotropy. The interpretation of the thermodynamic properties of {gamma}-AlON according to quasi-harmonic Debye model confirm the available experiments and are extended to a wider temperature/pressure range. This material holds high elastic strength under extreme environments, where dB/dT absolute value is less than 0.03 GPa/K, independent of the pressure. Finally, we study the O/N structure disorder character of {gamma}-AlON solid solution by investigating nine possible crystal structures. It is found that {gamma}-AlON should be partially disordered, and in fact, the O/N ordering has a significant effect on the properties.

One-Way Fluid-Structure Interaction Simulation of an Offshore Wind Turbine

Directory of Open Access Journals (Sweden)

Zhi-Kui Wang

2014-07-01

Full Text Available The Fluid-Structure Interaction (FSI has gained great interest of scholars recently, meanwhile, extensive studies have been conducted by the virtue of numerical methods which have been implemented on wind turbine models. The blades of a wind turbine have been gained a deep insight into the FSI analyses, however, few studies have been conducted on the tower and nacelle, which are key components of the wind turbine, using this method. We performed the one-way FSI analysis on a 2-MW offshore wind turbine, using the Finite Volume Method (FVM with ANSYS CFX solver and the RNG k-ε turbulence model, to achieve a comprehensive cognition of it. The grid convergence was studied and verified in this study, and the torque value is chosen to determine the optimal case. The superior case, which was chosen to conduct the FSI analysis, with a relative error is only 2.15%, thus, the accuracy of results is credible.

Implications of Stably Stratified Atmospheric Boundary Layer Turbulence on the Near-Wake Structure of Wind Turbines

Directory of Open Access Journals (Sweden)

Kiran Bhaganagar

2014-09-01

Full Text Available Turbulence structure in the wake behind a full-scale horizontal-axis wind turbine under the influence of real-time atmospheric inflow conditions has been investigated using actuator-line-model based large-eddy-simulations. Precursor atmospheric boundary layer (ABL simulations have been performed to obtain mean and turbulence states of the atmosphere under stable stratification subjected to two different cooling rates. Wind turbine simulations have revealed that, in addition to wind shear and ABL turbulence, height-varying wind angle and low-level jets are ABL metrics that influence the structure of the turbine wake. Increasing stability results in shallower boundary layers with stronger wind shear, steeper vertical wind angle gradients, lower turbulence, and suppressed vertical motions. A turbulent mixing layer forms downstream of the wind turbines, the strength and size of which decreases with increasing stability. Height dependent wind angle and turbulence are the ABL metrics influencing the lateral wake expansion. Further, ABL metrics strongly impact the evolution of tip and root vortices formed behind the rotor. Two factors play an important role in wake meandering: tip vortex merging due to the mutual inductance form of instability and the corresponding instability of the turbulent mixing layer.

Design and Manufacturing of Composite Tower Structure for Wind Turbine Equipment

Science.gov (United States)

Park, Hyunbum

2018-02-01

This study proposes the composite tower design process for large wind turbine equipment. In this work, structural design of tower and analysis using finite element method was performed. After structural design, prototype blade manufacturing and test was performed. The used material is a glass fiber and epoxy resin composite. And also, sand was used in the middle part. The optimized structural design and analysis was performed. The parameter for optimized structural design is weight reduction and safety of structure. Finally, structure of tower will be confirmed by structural test.

Structure and thermodynamics of core-softened models for alcohols

International Nuclear Information System (INIS)

Munaò, Gianmarco; Urbic, Tomaz

2015-01-01

The phase behavior and the fluid structure of coarse-grain models for alcohols are studied by means of reference interaction site model (RISM) theory and Monte Carlo simulations. Specifically, we model ethanol and 1-propanol as linear rigid chains constituted by three (trimers) and four (tetramers) partially fused spheres, respectively. Thermodynamic properties of these models are examined in the RISM context, by employing closed formulæ for the calculation of free energy and pressure. Gas-liquid coexistence curves for trimers and tetramers are reported and compared with already existing data for a dimer model of methanol. Critical temperatures slightly increase with the number of CH 2 groups in the chain, while critical pressures and densities decrease. Such a behavior qualitatively reproduces the trend observed in experiments on methanol, ethanol, and 1-propanol and suggests that our coarse-grain models, despite their simplicity, can reproduce the essential features of the phase behavior of such alcohols. The fluid structure of these models is investigated by computing radial distribution function g ij (r) and static structure factor S ij (k); the latter shows the presence of a low−k peak at intermediate-high packing fractions and low temperatures, suggesting the presence of aggregates for both trimers and tetramers

Increased Surface Wind Speeds Follow Diminishing Arctic Sea Ice

Science.gov (United States)

Mioduszewski, J.; Vavrus, S. J.; Wang, M.; Holland, M. M.; Landrum, L.

2017-12-01

Projections of Arctic sea ice through the end of the 21st century indicate the likelihood of a strong reduction in ice area and thickness in all seasons, leading to a substantial thermodynamic influence on the overlying atmosphere. This is likely to have an effect on winds over the Arctic Basin, due to changes in atmospheric stability and/or baroclinicity. Prior research on future Arctic wind changes is limited and has focused mainly on the practical impacts on wave heights in certain seasons. Here we attempt to identify patterns and likely mechanisms responsible for surface wind changes in all seasons across the Arctic, particularly those associated with sea ice loss in the marginal ice zone. Sea level pressure, near-surface (10 m) and upper-air (850 hPa) wind speeds, and lower-level dynamic and thermodynamic variables from the Community Earth System Model Large Ensemble Project (CESM-LE) were analyzed for the periods 1971-2000 and 2071-2100 to facilitate comparison between a present-day and future climate. Mean near-surface wind speeds over the Arctic Ocean are projected to increase by late century in all seasons but especially during autumn and winter, when they strengthen by up to 50% locally. The most extreme wind speeds in the 90th percentile change even more, increasing in frequency by over 100%. The strengthened winds are closely linked to decreasing lower-tropospheric stability resulting from the loss of sea ice cover and consequent surface warming (locally over 20 ºC warmer in autumn and winter). A muted pattern of these future changes is simulated in CESM-LE historical runs from 1920-2005. The enhanced winds near the surface are mostly collocated with weaker winds above the boundary layer during autumn and winter, implying more vigorous vertical mixing and a drawdown of high-momentum air.The implications of stronger future winds include increased coastal hazards and the potential for a positive feedback with sea ice by generating higher winds and

Linking landscape structure and rainfall runoff behaviour in a thermodynamic optimality context

Science.gov (United States)

Zehe, Erwin; Ehret, Uwe; Blume, Theresa; Kleidon, Axel; Scherer, Ulrike; Westhoff, Martijn

2015-04-01

gradients, and thus a faster relaxation back towards local thermodynamic equilibrium. Thermodynamic optimality principles allow for a priory optimization of the resistance field at a given gradient, not in the sense how they exactly look like but in the sense how they function with respect to export and dissipation of free energy associated with rainfall runoff processes. Based on this framework we explored the possibility of independent predictions of rainfall runoff, in the sense that the a-priory optimum model structures should match independent observations. We found that spatially organized patterns of soils and macropores observed in two distinctly different landscapes are in close accordance with thermodynamic optima expressed either by minimized relaxation times towards local thermodynamic equilibrium in cohesive soils or as steady state in the potential energy of soil water in non-cohesive soils. Predicted rainfall runoff based on the two optimized model structures was in both catchments in acceptable accordance with independent discharge observations. However, the nature of these optima suggests there might be two distinctly different thermodynamically optimal regimes of rainfall runoff behaviour. In the capillary- or c--regime, free energy dynamics of soil water is dominated by changes in its capillary binding energy, which is the case for cohesive soils. Soil wetting during rainfall in the c-regime implies pushing the system back towards LTE, especially after long dry spells. Dead ended macropores (roots, worm burrows which end in the soil matrix) act as dissipative wetting structures by enlarging water flows against steep gradients in soil water potential after long dry spells. This implies accelerated depletion of these gradients and faster relaxation back towards LTE during rainfall runoff. In the c-regime several optimum macropore densities with respect to maximization of net reduction of free energy exist. This is because the governing equation is a second

The Thermodynamic Structure of Arctic Coastal Fog Occurring During the Melt Season over East Greenland

Science.gov (United States)

Gilson, Gaëlle F.; Jiskoot, Hester; Cassano, John J.; Gultepe, Ismail; James, Timothy D.

2018-05-01

An automated method to classify Arctic fog into distinct thermodynamic profiles using historic in-situ surface and upper-air observations is presented. This classification is applied to low-resolution Integrated Global Radiosonde Archive (IGRA) soundings and high-resolution Arctic Summer Cloud Ocean Study (ASCOS) soundings in low- and high-Arctic coastal and pack-ice environments. Results allow investigation of fog macrophysical properties and processes in coastal East Greenland during melt seasons 1980-2012. Integrated with fog observations from three synoptic weather stations, 422 IGRA soundings are classified into six fog thermodynamic types based on surface saturation ratio, type of temperature inversion, fog-top height relative to inversion-base height and stability using the virtual potential temperature gradient. Between 65-80% of fog observations occur with a low-level inversion, and statically neutral or unstable surface layers occur frequently. Thermodynamic classification is sensitive to the assigned dew-point depression threshold, but categorization is robust. Despite differences in the vertical resolution of radiosonde observations, IGRA and ASCOS soundings yield the same six fog classes, with fog-class distribution varying with latitude and environmental conditions. High-Arctic fog frequently resides within an elevated inversion layer, whereas low-Arctic fog is more often restricted to the mixed layer. Using supplementary time-lapse images, ASCOS microwave radiometer retrievals and airmass back-trajectories, we hypothesize that the thermodynamic classes represent different stages of advection fog formation, development, and dissipation, including stratus-base lowering and fog lifting. This automated extraction of thermodynamic boundary-layer and inversion structure can be applied to radiosonde observations worldwide to better evaluate fog conditions that affect transportation and lead to improvements in numerical models.

The structure of rotational discontinuities. [in solar wind

Science.gov (United States)

Neugebauer, M.

1989-01-01

This study examines the structures of a set of rotational discontinuities detected in the solar wind by the ISEE-3 spacecraft. It is found that the complexity of the structure increases as the angle theta between the propagation vector k and the magnetic field decreases. For rotational discontinuities that propagate at a large angle to the field with an ion (left-hand) sense of rotation, the magnetic hodograms tend to be flattened, in agreement with prior numerical simulations. When theta is large, angular 'overshoots' are often observed at one or both ends of the discontinuity. When the propagation is nearly parallel to the field (when theta is small), many different types of structure are seen, ranging from straight lines, to S-shaped curves, to complex, disorganized shapes.

Thermodynamic matchers for the construction of the cuckoo RNA family.

Science.gov (United States)

Reinkensmeier, Jan; Giegerich, Robert

2015-01-01

RNA family models describe classes of functionally related, non-coding RNAs based on sequence and structure conservation. The most important method for modeling RNA families is the use of covariance models, which are stochastic models that serve in the discovery of yet unknown, homologous RNAs. However, the performance of covariance models in finding remote homologs is poor for RNA families with high sequence conservation, while for families with high structure but low sequence conservation, these models are difficult to built in the first place. A complementary approach to RNA family modeling involves the use of thermodynamic matchers. Thermodynamic matchers are RNA folding programs, based on the established thermodynamic model, but tailored to a specific structural motif. As thermodynamic matchers focus on structure and folding energy, they unfold their potential in discovering homologs, when high structure conservation is paired with low sequence conservation. In contrast to covariance models, construction of thermodynamic matchers does not require an input alignment, but requires human design decisions and experimentation, and hence, model construction is more laborious. Here we report a case study on an RNA family that was constructed by means of thermodynamic matchers. It starts from a set of known but structurally different members of the same RNA family. The consensus secondary structure of this family consists of 2 to 4 adjacent hairpins. Each hairpin loop carries the same motif, CCUCCUCCC, while the stems show high variability in their nucleotide content. The present study describes (1) a novel approach for the integration of the structurally varying family into a single RNA family model by means of the thermodynamic matcher methodology, and (2) provides the results of homology searches that were conducted with this model in a wide spectrum of bacterial species.

Kinetic, Thermodynamic and Structural Studies of Native and N-Bromosuccinimide-Modified Mushroom Tyrosinase

Directory of Open Access Journals (Sweden)

Saeed Emami

2016-10-01

Full Text Available Background Mushroom tyrosinase (MT as a metalloenzyme is a good model for mechanistic studies of melanogenesis. To recognize the mechanism of MT action, it is important to investigate its inhibition, activation, mutation, and modification properties. Objectives In this study, the chemical modification of MT tryptophan residues was carried out by using N-bromosuccinimide (NBS and then, the activity, stability, and structure of the native and modified enzymes were compared. Methods Chemical modification of MT tryptophan residues was accomplished by enzyme incubation with different concentrations of NBS. The relative activity of native and modified MT was investigated through catecholase enzyme reaction in presence of dihydroxyphenylalanine (L-Dopa as substrate. Thermodynamic parameters including standard Gibbs free energy change (∆G25°C and Melting temperature (Tm were obtained from thermal denaturation of the native and modified enzymes. The circular dichroism and intrinsic fluorescence techniques were used to study secondary and tertiary structure of MT, respectively. All experiments were conducted in 2015 in biophysical laboratory of Qazvin University of Medical Sciences and Islamic Azad University, Science and Research Branch, Tehran. Results The relative activity reduced from 100% for native enzyme to 10%, 7.9%, and 6.4% for modified MT with different NBS of concentrations 2, 10, and 20 mM, respectively. Thermal instability of modified enzyme was confirmed by decreased Tm and ∆G25°C values after modification. In accordance with kinetic and thermodynamic results, the lower stability of modified MT was observed from the changes occurred on its secondary and tertiary structures. Conclusions Chemical modification of tryptophan residues with NBS reduces the activity and stability of MT simultaneously with its structural change. Thus, this study emphasizes the crucial role of tryptophan residues in the structure-function relationship of MT

Field measurement of wind pressure and wind-induced vibration of large-span spatial cable-truss system under strong wind or typhoon

Directory of Open Access Journals (Sweden)

ZHANG Zhihong

2013-10-01

Full Text Available In order to ensure wind-resistance safety of large-span pre-stressed flexible system in southeast coast area of China,and to prepare something for revising of current codes of practice or technical standards,the present paper conducts field measurement of wind pressure and wind-induced vibration of a practical and typical large-span spatial cable-truss system-lunar stadium in Yueqing city.Wind loading and wind effects on full-scale structure under strong wind or typhoon in real architectural environment can be obtained directly and effectively.Field measurement is the best way to investigate the wind loading property,wind effects,and wind-structure interactions of large-span flexible system.Measured data will be highly valuable for scientific research and practical design.On the other hand,it also provides the basis of wind-resistance safety design of this kind of tension structures.If any creative development,it would dramatically improve the research level of large-span pre-stressed flexible system in our country.

Design and calibration of a semi-active control logic to mitigate structural vibrations in wind turbines

DEFF Research Database (Denmark)

Caterino, Nicola; Georgakis, Christos T.; Spizzuoco, Mariacristina

2016-01-01

The design of a semi-active (SA) control system addressed to mitigate wind induced structural demand to high wind turbine towers is discussed herein. Actually, the remarkable growth in height of wind turbines in the last decades, for a higher production of electricity, makes this issue pressing....../20 scale model of a real, one hundred meters tall wind turbine has been assumed as case study for shaking table tests. A special control algorithm has been purposely designed to drive MR dampers. Starting from the results of preliminary laboratory tests, a finite element model of such structure has been...... calibrated so as to develop several numerical simulations addressed to calibrate the controller, i.e., to achieve as much as possible different, even conflicting, structural goals. The results are definitely encouraging, since the best configuration of the controller leaded to about 80% of reduction of base...

Thermodynamic and structural models compared with the initial dissolution rates of SON glass samples

International Nuclear Information System (INIS)

Tovena, I.; Advocat, T.; Ghaleb, D.; Vernaz, E.

1993-01-01

The experimentally determined initial dissolution rate R 0 of nuclear glass was correlated with thermodynamic parameters and structural parameters. The initial corrosion rates of six ''R7T7'' glass samples measured at 100 deg C in a Soxhlet device were correlated with the glass free hydration energy and the glass formation enthalpy. These correlations were then tested with a group of 26 SON glasses selected for their wide diversity of compositions. The thermodynamic models provided a satisfactory approximation of the initial dissolution rate determined under Soxhlet conditions for SON glass samples that include up to 15 wt% of boron and some alumina. Conversely, these models are inaccurate if the boron concentration exceeds 15 wt% and the glass contains no alumina. Possible correlations between R 0 and structural parameters, such as the boron coordination number and the number of nonbridging oxygen atoms, were also investigated. The authors show that R 0 varies inversely with the number of 4-coordinate boron atoms; conversely, the results do not substantiate published reports of a correlation between R 0 and the number of nonbridging oxygen atoms. (authors). 13 refs., 2 figs., 4 tabs

Vacancy formation energies in close-packed crystals correlated with melting temperature via thermodynamics and liquid structure

International Nuclear Information System (INIS)

Rashid, R.I.M.A.; March, N.H.

1988-08-01

In earlier work, the vacancy formation energy E v in close-packed crystals, in units of the thermal energy k B T m at the melting temperature T m , has been connected with compressibility and specific heats, plus terms dependent on the liquid structure at T m . Here, this connection has been examined quantitatively for (a) the insulating condensed rare gases Ne, Ar and Kr, and (b) a variety of close-packed metals. For case (a), E v /k B T m can be calculated directly from thermodynamic data to obtain agreement with experiment for Ar and Kr, though not for Ne. A 'residual' contribution is estimated for Ar and Kr from diffraction and computer experiments on the density dependence of the liquid pair correlation function and is shown to be very small. Agreement is less impressive for case (b) for the eight close-packed metals for which all data required is known, the thermodynamic formula giving an average value E v /k B T m =7.8+-1.1 whereas experiment yields 9.4+-1.8. However, for the body-centred cubic alkalis the thermodynamic average value of 4.5+-0.5 is much lower than the experimental value 11.5+-2.0 consistent with the known role of ionic relaxation round the vacancy in such open structures. (author). 16 refs, 2 tabs

Structural investigation of composite wind turbine blade considering various load cases and fatigue life

International Nuclear Information System (INIS)

Kong, C.; Bang, J.; Sugiyama, Y.

2005-01-01

This study proposes a structural design for developing a medium scale composite wind turbine blade made of E-glass/epoxy for a 750 kW class horizontal axis wind turbine system. The design loads were determined from various load cases specified at the IEC61400-1 international specification and GL regulations for the wind energy conversion system. A specific composite structure configuration, which can effectively endure various loads such as aerodynamic loads and loads due to accumulation of ice, hygro-thermal and mechanical loads, was proposed. To evaluate the proposed composite wind turbine blade, structural analysis was performed by using the finite element method. Parametric studies were carried out to determine an acceptable blade structural design, and the most dominant design parameters were confirmed. In this study, the proposed blade structure was confirmed to be safe and stable under various load conditions, including the extreme load conditions. Moreover, the blade adapted a new blade root joint with insert bolts, and its safety was verified at design loads including fatigue loads. The fatigue life of a blade that has to endure for more than 20 years was estimated by using the well-known S-N linear damage theory, the service load spectrum, and the Spera's empirical equations. With the results obtained from all the structural design and analysis, prototype composite blades were manufactured. A specific construction process including the lay-up molding method was applied to manufacturing blades. Full-scale static structural test was performed with the simulated aerodynamic loads. From the experimental results, it was found that the designed blade had structural integrity. In addition, the measured results of deflections, strains, mass, and radial center of gravity agreed well with the analytical results. The prototype blade was successfully certified by an international certification institute, GL (Germanisher Lloyd) in Germany

Structural design of the Sandia 34-M Vertical Axis Wind Turbine

Science.gov (United States)

Berg, D. E.

Sandia National Laboratories, as the lead DOE laboratory for Vertical Axis Wind Turbine (VAWT) development, is currently designing a 34-meter diameter Darrieus-type VAWT. This turbine will be a research test bed which provides a focus for advancing technology and validating design and fabrication techniques in a size range suitable for utility use. Structural data from this machine will allow structural modeling to be refined and verified for a turbine on which the gravity effects and stochastic wind loading are significant. Performance data from it will allow aerodynamic modeling to be refined and verified. The design effort incorporates Sandia's state-of-the-art analysis tools in the design of a complete machine. The analytic tools used in this design are discussed and the conceptual design procedure is described.

Structural Reliability Methods for Wind Power Converter System Component Reliability Assessment

DEFF Research Database (Denmark)

Kostandyan, Erik; Sørensen, John Dalsgaard

2012-01-01

Wind power converter systems are essential subsystems in both off-shore and on-shore wind turbines. It is the main interface between generator and grid connection. This system is affected by numerous stresses where the main contributors might be defined as vibration and temperature loadings....... The temperature variations induce time-varying stresses and thereby fatigue loads. A probabilistic model is used to model fatigue failure for an electrical component in the power converter system. This model is based on a linear damage accumulation and physics of failure approaches, where a failure criterion...... is defined by the threshold model. The attention is focused on crack propagation in solder joints of electrical components due to the temperature loadings. Structural Reliability approaches are used to incorporate model, physical and statistical uncertainties. Reliability estimation by means of structural...

Real-time monitoring and structural control of a wind turbine using a rocking system

DEFF Research Database (Denmark)

Caterino, Nicola; Spizzuoco, Mariacristina; Georgakis, Christos T.

2016-01-01

The design of a semi-active (SA) control system to mitigate wind induced structural demand to high wind turbine towers is discussed herein. A variable restraint at the base, able to modify in real time its mechanical properties according to the instantaneous response of the tower, is proposed...

Thermodynamic analysis of elastic-plastic deformation

International Nuclear Information System (INIS)

Lubarda, V.

1981-01-01

The complete set of constitutive equations which fully describes the behaviour of material in elastic-plastic deformation is derived on the basis of thermodynamic analysis of the deformation process. The analysis is done after the matrix decomposition of the deformation gradient is introduced into the structure of thermodynamics with internal state variables. The free energy function, is decomposed. Derive the expressions for the stress response, entropy and heat flux, and establish the evolution equation. Finally, we establish the thermodynamic restrictions of the deformation process. (Author) [pt

A comparative analysis of business structures suitable for farmer-owned wind power projects in the United States

International Nuclear Information System (INIS)

Bolinger, Mark; Wiser, Ryan

2006-01-01

For years, farmers in the United States have looked with envy on their European counterparts' ability to profitably farm the wind through ownership of distributed, utility-scale wind projects. Only within the past few years, however, has farmer- or community-owned wind power development become a reality in the United States. The primary hurdle to this type of development in the United States has been devising and implementing suitable business and legal structures that enable such projects to take advantage of tax-based federal incentives for wind power. This article discusses the limitations of such incentives in supporting farmer- or community-owned wind projects, describes four ownership structures that potentially overcome such limitations, and finally conducts comparative financial analysis on those four structures, using as an example a hypothetical 1.5 MW farmer-owned project located in the state of Oregon. We find that material differences in the competitiveness of each structure do exist, but that choosing the best structure for a given project will largely depend on the conditions at hand; e.g., the ability of the farmer(s) to utilize tax credits, preference for individual versus 'cooperative' ownership, and the state and utility service territory in which the project will be located

Unbalanced voltage faults: the impact on structural loads of doubly fed asynchronous generator wind turbines

DEFF Research Database (Denmark)

Barahona Garzón, Braulio; Cutululis, Nicolaos Antonio; Hansen, Anca Daniela

2014-01-01

This paper investigates the impact that unbalanced voltage faults have on wind turbine structural loads. In such cases, electromagnetic torque oscillations occur at two times the supply voltage frequency. The objectives of this work are to quantify wind turbine structural loads induced...... by unbalanced voltage faults relative to those during normal operation; and to evaluate the potential for reducing structural loads with the control of the generator. The method applied is integrated dynamic analysis. Namely, dynamic analysis with models that consider the most important aeroelastic, electrical...

Thermodynamics of ionic processes in solutions

International Nuclear Information System (INIS)

Krestov, G.A.

1984-01-01

The present nitions about the mechanism of solvation of atomic-molecular particles and the structure of electrolyte and non electrolyte solutions are given. From common positions a wide range of interrelated problems (general and thermodynamic characteristic of ions, thermodynamic characteristic of ion solvation and various ionic reactions in solutions, structural changes of the solvent in the above processes etc...) is considered. The latest scientific data including those on the effect on the thermodynamio properties of low temperatures, various impurities (air, water), large ions, peculiarities of the structure of solvent molecules reflected. Considerable attention is given to new conceptions definitions, structural notions as well as theoretical and experimental methods of obtaining quantitative characteristics of ion solvation

Thermodynamic geometry and phase transitions of AdS braneworld black holes

Energy Technology Data Exchange (ETDEWEB)

Chaturvedi, Pankaj, E-mail: cpankaj@iitk.ac.in; Sengupta, Gautam, E-mail: sengupta@iitk.ac.in

2017-02-10

The thermodynamics and phase transitions of charged RN–AdS and rotating Kerr–AdS black holes in a generalized Randall–Sundrum braneworld are investigated in the framework of thermodynamic geometry. A detailed analysis of the thermodynamics, stability and phase structures in the canonical and the grand canonical ensembles for these AdS braneworld black holes are described. The thermodynamic curvatures for both these AdS braneworld black holes are computed and studied as a function of the thermodynamic variables. Through this analysis we illustrate an interesting dependence of the phase structures on the braneworld parameter for these black holes.

An Introduction to Operational Modal Identification of Offshore Wind Turbine Structures

DEFF Research Database (Denmark)

Damgaard, Mads

excitation originating from the rotating rotor and broadband excitation from air turbulence is present, which sets limitations on the applicability of operational modal analysis to wind turbine structures. The technical memorandum contains an introduction to the theory within experimental modal analysis and......The present technical memorandum “An Introduction to Operational Modal Identification of Offshore Wind Turbine Structures” is prepared in connection with an ongoing Ph.D study at Aalborg University. The memorandum is intended for use in the civil engineering field and may serve as an inspiration...

Fluid-structure interaction modeling of wind turbines: simulating the full machine

Science.gov (United States)

Hsu, Ming-Chen; Bazilevs, Yuri

2012-12-01

In this paper we present our aerodynamics and fluid-structure interaction (FSI) computational techniques that enable dynamic, fully coupled, 3D FSI simulation of wind turbines at full scale, and in the presence of the nacelle and tower (i.e., simulation of the "full machine"). For the interaction of wind and flexible blades we employ a nonmatching interface discretization approach, where the aerodynamics is computed using a low-order finite-element-based ALE-VMS technique, while the rotor blades are modeled as thin composite shells discretized using NURBS-based isogeometric analysis (IGA). We find that coupling FEM and IGA in this manner gives a good combination of efficiency, accuracy, and flexibility of the computational procedures for wind turbine FSI. The interaction between the rotor and tower is handled using a non-overlapping sliding-interface approach, where both moving- and stationary-domain formulations of aerodynamics are employed. At the fluid-structure and sliding interfaces, the kinematic and traction continuity is enforced weakly, which is a key ingredient of the proposed numerical methodology. We present several simulations of a three-blade 5~MW wind turbine, with and without the tower. We find that, in the case of no tower, the presence of the sliding interface has no effect on the prediction of aerodynamic loads on the rotor. From this we conclude that weak enforcement of the kinematics gives just as accurate results as the strong enforcement, and thus enables the simulation of rotor-tower interaction (as well as other applications involving mechanical components in relative motion). We also find that the blade passing the tower produces a 10-12 % drop (per blade) in the aerodynamic torque. We feel this finding may be important when it comes to the fatigue-life analysis and prediction for wind turbine blades.

Thermodynamic properties and atomic structure of Ca-based liquid alloys

Science.gov (United States)

Poizeau, Sophie

To identify the most promising positive electrodes for Ca-based liquid metal batteries, the thermodynamic properties of diverse Ca-based liquid alloys were investigated. The thermodynamic properties of Ca-Sb alloys were determined by emf measurements. It was found that Sb as positive electrode would provide the highest voltage for Ca-based liquid metal batteries (1 V). The price of such a battery would be competitive for the grid-scale energy storage market. The impact of Pb, a natural impurity of Sb, was predicted successfully and confirmed via electrochemical measurements. It was shown that the impact on the open circuit voltage would be minor. Indeed, the interaction between Ca and Sb was demonstrated to be much stronger than between Ca and Pb using thermodynamic modeling, which explains why the partial thermodynamic properties of Ca would not vary much with the addition of Pb to Sb. However, the usage of the positive electrode would be reduced, which would limit the interest of a Pb-Sb positive electrode. Throughout this work, the molecular interaction volume model (MIVM) was used for the first time for alloys with thermodynamic properties showing strong negative deviation from ideality. This model showed that systems such as Ca-Sb have strong short-range order: Ca is most stable when its first nearest neighbors are Sb. This is consistent with what the more traditional thermodynamic model, the regular association model, would predict. The advantages of the MIVM are the absence of assumption regarding the composition of an associate, and the reduced number of fitting parameters (2 instead of 5). Based on the parameters derived from the thermodynamic modeling using the MIVM, a new potential of mixing for liquid alloys was defined to compare the strength of interaction in different Ca-based alloys. Comparing this trend with the strength of interaction in the solid state of these systems (assessed by the energy of formation of the intermetallics), the systems with

Design and Analysis of Wind Turbine Rotors Using Hinged Structures and Rods

Science.gov (United States)

Lu, Hongya; Zeng, Pan; Lei, Liping

2018-03-01

Light weight and high stiffness are key design factors in ensuring cost effectiveness and reliability of wind turbines, especially for the inboard region of the rotor blades. In this study, several novel designs were developed to improve the mechanical performance of the rotor. Experiments were performed on an isolated blade incorporating the new features of a hinged structure and rods. The results validated the effectiveness of these features at alleviating the root-bending moment of the blade under varying wind loads and enhancing the stiffness of the blade. A numerical investigation was carried out to further examine the bending moment distribution, shear and axial force, and rod tension of these novel rotor designs under uniform loads. Longitudinal geometrical variations of the blade were considered in the model. Results showed that two designs realized a favorable bending moment distribution and improved the modal frequencies of the edgewise modes: bisymmetrical rods on a single-hinged structure and interveined symmetrical rods on a cantilevered structure. However, these designs have different deformation mechanisms. In addition, the first group of edgewise modal frequencies of these two designs were improved compared with the traditional rotor design. Their potential values in the application to the design of a lightweight, high-stiffness, and reliable wind turbine rotor were discussed.

Fundamentals for remote structural health monitoring of wind turbine blades - a preproject. Annex A. Cost-benefit for embedded sensors in large wind turbine blades

OpenAIRE

Hansen, L.G.; Lading, Lars

2002-01-01

This report contains the results of a cost-benefit analysis for the use of embed-ded sensors for damage detection in large wind turbine blades - structural health monitoring - (in connection with remote surveillance) of large wind turbine placedoff-shore. The total operating costs of a three-bladed 2MW turbine placed offshore either without sensors or with sensors are compared. The price of a structural health monitoring system of a price of 100 000 DKK (per tur-bine) results in a break-event...

Statistical thermodynamics

International Nuclear Information System (INIS)

Hwang, Jeong Ui; Jang, Jong Jae; Jee, Jong Gi

1987-01-01

The contents of this book are thermodynamics on the law of thermodynamics, classical thermodynamics and molecule thermodynamics, basics of molecule thermodynamics, molecule and assembly partition function, molecule partition function, classical molecule partition function, thermodynamics function for ideal assembly in fixed system, thermodynamics function for ideal assembly in running system, Maxwell-Boltzmann's law of distribution, chemical equilibrium like calculation of equilibrium constant and theory of absolute reaction rate.

Student Oriented Approaches in the Teaching of Thermodynamics at Universities--Developing an Effective Course Structure

Science.gov (United States)

Partanen, Lauri

2016-01-01

The aim of this study was to apply current pedagogical research in order to develop an effective course and exercise structure for a physical chemistry thermodynamics course intended for second or third year university students of chemistry. A mixed-method approach was used to measure the impact the changes had on student learning. In its final…

Large eddy simulation study of the kinetic energy entrainment by energetic turbulent flow structures in large wind farms

Science.gov (United States)

VerHulst, Claire; Meneveau, Charles

2014-02-01

In this study, we address the question of how kinetic energy is entrained into large wind turbine arrays and, in particular, how large-scale flow structures contribute to such entrainment. Previous research has shown this entrainment to be an important limiting factor in the performance of very large arrays where the flow becomes fully developed and there is a balance between the forcing of the atmospheric boundary layer and the resistance of the wind turbines. Given the high Reynolds numbers and domain sizes on the order of kilometers, we rely on wall-modeled large eddy simulation (LES) to simulate turbulent flow within the wind farm. Three-dimensional proper orthogonal decomposition (POD) analysis is then used to identify the most energetic flow structures present in the LES data. We quantify the contribution of each POD mode to the kinetic energy entrainment and its dependence on the layout of the wind turbine array. The primary large-scale structures are found to be streamwise, counter-rotating vortices located above the height of the wind turbines. While the flow is periodic, the geometry is not invariant to all horizontal translations due to the presence of the wind turbines and thus POD modes need not be Fourier modes. Differences of the obtained modes with Fourier modes are documented. Some of the modes are responsible for a large fraction of the kinetic energy flux to the wind turbine region. Surprisingly, more flow structures (POD modes) are needed to capture at least 40% of the turbulent kinetic energy, for which the POD analysis is optimal, than are needed to capture at least 40% of the kinetic energy flux to the turbines. For comparison, we consider the cases of aligned and staggered wind turbine arrays in a neutral atmospheric boundary layer as well as a reference case without wind turbines. While the general characteristics of the flow structures are robust, the net kinetic energy entrainment to the turbines depends on the presence and relative

Thermodynamics and Structure of Actinide(IV) Complexes with Nitrilotriacetic Acid

Energy Technology Data Exchange (ETDEWEB)

Bonin, L.; Guillaumont, D.; Jeanson, A.; Den Auwer, C.; Moisy, Ph. [CEA Marcoule, DEN, DRCP, SCPS, F-30207 Bagnols Sur Ceze (France); Grigoriev, M. [RAS, AN Frumkin Inst Phys Chem and Electrochem, Moscow 119991 (Russian Federation); Berthet, J.C. [CEA Saclay, DSM, IRAMIS, URA 331, Serv Chim Mol, CNRS, F-91191 Gif Sur Yvette (France); Hennig, C.; Scheinost, A. [Forschungszentrum Dresden Rossendorf, Inst Radiochem, D-01314 Dresden (Germany)

2009-05-15

Nitrilotriacetic acid, commonly known as NITA (N(CH{sub 2}CO{sub 2}H){sub 3}), can be considered a representative of the polyamino-carboxylic family. The results presented in this paper describe the thermodynamical complexation and structural investigation of An(IV) complexes with NTA in aqueous solution. In the first part, the stability constants of the An(IV) complexes (An = Pu, Np, U, and Th) have been determined by spectrophotometry. In the second part, the coordination spheres of the actinide cation in these complexes have been described using extended X-ray absorption fine structure spectroscopy and compared to the solid-state structure of (Hpy){sub 2}[U(NTA){sub 2}].H{sub 2}O. These data are further compared to quantum chemical calculations, and their evolution across the actinide series is discussed. In particular, an interpretation of the role of the nitrogen atom in the coordination mode is proposed. These results are considered to be model behavior of polyamino-carboxylic ligands such as diethylenetriamine pentaacetic acid, which is nowadays the best candidate for a chelating agent in the framework of actinide decorporation for the human body. (authors)

Introduction to physics mechanics, hydrodynamics thermodynamics

CERN Document Server

Frauenfelder, P

2013-01-01

Introduction of Physics: Mechanics , Hydrodynamics, Thermodynamics covers the principles of matter and its motion through space and time, as well as the related concepts of energy and force. This book is composed of eleven chapters, and begins with an introduction to the basic principles of mechanics, hydrodynamics, and thermodynamics. The subsequent chapters deal with the statics of rigid bodies and the dynamics of particles and rigid bodies. These topics are followed by discussions on elasticity, mechanics of fluids, the basic concept of thermodynamic, kinetic theory, and crystal structure o

Accuracy of an efficient framework for structural analysis of wind turbine blades

DEFF Research Database (Denmark)

Blasques, José Pedro Albergaria Amaral; Bitsche, Robert D.; Fedorov, Vladimir

2016-01-01

-section analysis tool is able to capture the effects stemming from material anisotropy and inhomogeneity for sections of arbitrary geometry. The proposed framework is very efficient and therefore ideally suited for integration within wind turbine aeroelastic design and analysis tools. A number of benchmark......This paper presents a novel framework for the structural design and analysis of wind turbine blades and establishes its accuracy. The framework is based on a beam model composed of two parts—a 2D finite element-based cross-section analysis tool and a 3D beam finite element model. The cross...... examples are presented comparing the results from the proposed beam model to 3D shell and solid finite element models. The examples considered include a square prismatic beam, an entire wind turbine rotor blade and a detailed wind turbine blade cross section. Phenomena at both the blade length scale...

Wind structure during mid-latitude storms and its application in Wind Energy

DEFF Research Database (Denmark)

Larsén, Xiaoli Guo; Du, Jianting; Bolanos, Rodolfo

2015-01-01

in Denmark. The extreme wind and wave conditions in the coastal area for wind energy application are important but have rarely been studied in the literature. Our experiments are done to the Danish coasts where the mid-latitude depression systems are causes of the extreme wind and wave conditions....... The numerical modeling is done through an atmosphere-wave coupled system, where the atmospheric model is the Weather Research and Forecasting (WRF) model and the wave model is the Simulating WAves Nearshore (SWAN) model. Measurements from offshore stations, Horns Rev and the FINO platform, as well as satellite...... and the modeling will be presented. Here the “key” is referring both to the application of wind energy and the wind-wave coupling system. The various parameterization of the interface parameter for the atmospheric and wave modeling, the roughness length, has been examined. Data analysis reveals the importance...

Energy effects on the structure and thermodynamic properties of nanoconfined fluids (a density functional theory study).

Science.gov (United States)

Keshavarzi, Ezat; Kamalvand, Mohammad

2009-04-23

The structure and properties of fluids confined in nanopores may show a dramatic departure from macroscopic bulk fluids. The main reason for this difference lies in the influence of system walls. In addition to the entropic wall effect, system walls can significantly change the energy of the confined fluid compared to macroscopic bulk fluids. The energy effect of the walls on a nanoconfined fluid appears in two forms. The first effect is the cutting off of the intermolecular interactions by the walls, which appears for example in the integrals for calculation of the thermodynamic properties. The second wall effect involves the wall-molecule interactions. In such confined fluids, the introduction of wall forces and the competition between fluid-wall and fluid-fluid forces could lead to interesting thermodynamic properties, including new kinds of phase transitions not observed in the macroscopic fluid systems. In this article, we use the perturbative fundamental measure density functional theory to study energy effects on the structure and properties of a hard core two-Yukawa fluid confined in a nanoslit. Our results show the changes undergone by the structure and phase transition of the nanoconfined fluids as a result of energy effects.

Solar wind and coronal structure near sunspot minimum - Pioneer and SMM observations from 1985-1987

Science.gov (United States)

Mihalov, J. D.; Barnes, A.; Hundhausen, A. J.; Smith, E. J.

1990-01-01

Changes in solar wind speed and magnetic polarity observed at the Pioneer spacecraft are discussed here in terms of the changing magnetic geometry implied by SMM coronagraph observations over the period 1985-1987. The pattern of recurrent solar wind streams, the long-term average speed, and the sector polarity of the interplanetary magnetic field all changed in a manner suggesting both a temporal variation, and a changing dependence on heliographic latitude. Coronal observations during this epoch show a systematic variation in coronal structure and the magnetic structure imposed on the expanding solar wind. These observations suggest interpretation of the solar wind speed variations in terms of the familiar model where the speed increases with distance from a nearly flat interplanetary current sheet, and where this current sheet becomes aligned with the solar equatorial plane as sunspot minimum approaches, but deviates rapidly from that orientation after minimum.

Structural Load Alleviation Applied to Next Generation Aircraft and Wind Turbines

Science.gov (United States)

Frost, Susan

2011-01-01

Reducing the environmental impact of aviation is a goal of the Subsonic Fixed Wing Project under the Fundamental Aeronautics Program of NASAs Aeronautics Research Mission Directorate. Environmental impact of aviation is being addressed by novel aircraft configurations and materials that reduce aircraft weight and increase aerodynamic efficiency. NASA is developing tools to address the challenges of increased airframe flexibility created by wings constructed with reduced structural material and novel light-weight materials. This talk will present a framework and demonstration of a flight control system using optimal control allocation with structural load feedback and constraints to achieve safe aircraft operation. As wind turbines age, they become susceptible to many forms of blade degradation. Results will be presented on work in progress that uses adaptive contingency control for load mitigation in a wind turbine simulation with blade damage progression modeled.

Heliospheric pick-up ions influencing thermodynamics and dynamics of the distant solar wind

Directory of Open Access Journals (Sweden)

H. J. Fahr

2002-01-01

Full Text Available Neutral interstellar H-atoms penetrate into the inner heliosphere and upon the event of ionization are converted into pick-up ions (PUIs. The magnetized solar wind flow incorporates these ions into the plasma bulk and enforces their co-motion. By nonlinear interactions with wind-entrained Alfvén waves, these ions are then processed in the comoving velocity space. The complete pick-up process is connected with forces acting back to the original solar wind ion flow, thereby decelerating and heating the solar wind plasma. As we show here, the resulting deceleration cannot be treated as a pure loading effect, but requires adequate consideration of the action of the pressure of PUI-scattered waves operating by the PUI pressure gradient. Hereby, it is important to take into proper account the stochastic acceleration which PUIs suffer from at their convection out of the inner heliosphere by quasi-linear interactions with MHD turbulences. Only then can the presently reported VOYAGER observations of solar wind decelerations and heatings in the outer heliosphere be understood in view of the most likely values of interstellar gas parameters, such as an H-atom density of 0.12 cm-3 . Solar wind protons (SWPs appear to be globally heated in their motion to larger solar distances. Ascribing the needed heat transfer to the action of suprathermal PUIs, which drive MHD waves that are partly absorbed by SWPs, in order to establish the observed SWP polytropy, we can obtain a quantitative expression for the solar wind proton pressure as a function of solar distance. This expression clearly shows the change from an adiabatic to a quasi-polytropic SWP behaviour with a decreasing polytropic index at increasing distances. This also allows one to calculate the average percentage of initial pick-up energy fed into the thermal proton energy. In a first order evaluation of this expression, we can estimate that about 10% of the initial PUI injection energy is eventually

Wind energy systems

Science.gov (United States)

Stewart, H. J.

1978-01-01

A discussion on wind energy systems involved with the DOE wind energy program is presented. Some of the problems associated with wind energy systems are discussed. The cost, efficiency, and structural design of wind energy systems are analyzed.

Surface adsorption of lattice HP proteins: Thermodynamics and structural transitions using Wang-Landau sampling

International Nuclear Information System (INIS)

Li Yingwai; Landau, David P; Wüst, Thomas

2012-01-01

Wang-Landau sampling has been applied to investigate the thermodynamics and structural properties of a lattice hydrophobic-polar heteropolymer (the HP protein model) interacting with an attractive substrate. For simplicity, we consider a short HP sequence consisting of only 36 monomers interacting with a substrate which attracts all monomers in the sequence. The conformational “phase transitions” have been identified by a canonical analysis of the specific heat and suitable structural observables. Three major “transitions”, namely, adsorption, hydrophobic core formation and “flattening” of adsorbed structures, are observed. Depending on the surface attractive strength relative to the intra-protein attraction among the H monomers, these processes take place in different sequences upon cooling.

Periodic Density Structures and the Origin of the Slow Solar Wind

Science.gov (United States)

Viall-Kepko, Nicholeen M.; Vourlidas, Angelos

2015-01-01

The source of the slow solar wind has challenged scientists for years. Periodic density structures (PDSs), observed regularly in the solar wind at 1 AU (Astronomical Unit), can be used to address this challenge. These structures have length scales of hundreds to several thousands of megameters and frequencies of tens to hundreds of minutes. Two lines of evidence indicate that PDSs are formed in the solar corona as part of the slow solar wind release and/or acceleration processes. The first is corresponding changes in compositional data in situ, and the second is PDSs observed in the inner Heliospheric Imaging data on board the Solar Terrestrial Relations Observatory (STEREO)/Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) suite. The periodic nature of these density structures is both a useful identifier as well as an important physical constraint on their origin. In this paper, we present the results of tracking periodic structures identified in the inner Heliospheric Imager in SECCHI back in time through the corresponding outer coronagraph (COR2) images. We demonstrate that the PDSs are formed around or below 2.5 solar radii-the inner edge of the COR2 field of view. We compute the occurrence rates of PDSs in 10 days of COR2 images both as a function of their periodicity and location in the solar corona, and we find that this set of PDSs occurs preferentially with a periodicity of approximately 90 minutes and occurs near streamers. Lastly, we show that their acceleration and expansion through COR2 is self-similar, thus their frequency is constant at distances beyond 2.5 solar radii.

Forest structure and light regimes following moderate wind storms: implications for multi-cohort management.

Science.gov (United States)

Hanson, Jacob J; Lorimer, Craig G

2007-07-01

Moderate-severity disturbances appear to be common throughout much of North America, but they have received relatively little detailed study compared to catastrophic disturbances and small gap dynamics. In this study, we examined the immediate impact of moderate-intensity wind storms on stand structure, opening sizes, and light regimes in three hemlock-hardwood forests of northeastern Wisconsin. These were compared to three stands managed by single-tree and group selection, the predominant forest management system for northern hardwoods in the region. Wind storms removed an average of 41% of the stand basal area, compared to 27% removed by uneven-aged harvests, but both disturbances removed trees from a wide range of size classes. The removal of nearly half of the large trees by wind in two old-growth stands caused partial retrogression to mature forest structure, which has been hypothesized to be a major disturbance pathway in the region. Wind storms resulted in residual stand conditions that were much more heterogeneous than in managed stands. Gap sizes ranged from less than 10 m2 up to 5000 m2 in wind-disturbed stands, whereas the largest opening observed in managed stands was only 200 m2. Wind-disturbed stands had, on average, double the available solar radiation at the forest floor compared to managed stands. Solar radiation levels were also more heterogeneous in wind-disturbed stands, with six times more variability at small scales (0.1225 ha) and 15 times more variability at the whole-stand level. Modification of uneven-aged management regimes to include occasional harvests of variable intensity and spatial pattern may help avoid the decline in species diversity that tends to occur after many decades of conventional uneven-aged management. At the same time, a multi-cohort system with these properties would retain a high degree of average crown cover, promote structural heterogeneity typical of old-growth forests, and maintain dominance by late

Noise pollution from wind turbine gears loudness of structural noise sources related to gears

International Nuclear Information System (INIS)

Crone, A.

1995-04-01

The purpose of the project has been to develop a method for determination of the structure-borne noise source strength of the gearbox in a typical modern Danish wind turbine construction, with special reference to the tonal noise emission form the turbines. Through study and evaluation of eight potential methods, a simple method has ben formulated. The method is based on measurements of the free vibration velocity level on the gearbox in a load test bed. The relation between this source strength measure and the gearbox related noise from wind turbines has been documented by measurements made during the project together with earlier measurements. The method is intended as a tool for the wind turbine manufacturer, for control of the gearbox related noise from the wind turbines, due to structure-borne noise from the gearbox. It may be used for preparation of specifications to the gearbox manufacturer on test procedure and acceptable source strength levels. Also, it may be used for evaluation of the transmission and radiation of gearbox related noise, for example in order to uncover weaknesses in a prototype turbine. Suggestions for adaptation and evolution of the method has been given, thereby improving the strength of the method for the individual wind turbine manufacturer. (au) 19 refs

The importance of including dynamic soil-structure interaction into wind turbine simulation codes

DEFF Research Database (Denmark)

Damgaard, Mads; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo

2014-01-01

A rigorous numerical model, describing a wind turbine structure and subsoil, may contain thousands of degrees of freedom, making the approach computationally inefficient for fast time domain analysis. In order to meet the requirements of real-time calculations, the dynamic impedance of the founda......A rigorous numerical model, describing a wind turbine structure and subsoil, may contain thousands of degrees of freedom, making the approach computationally inefficient for fast time domain analysis. In order to meet the requirements of real-time calculations, the dynamic impedance...... of the foundation from a rigorous analysis can be formulated into a so-called lumped-parameter model consisting of a few springs, dashpots and point masses which are easily implemented into aeroelastic codes. In this paper, the quality of consistent lumped-parameter models of rigid surface footings and mono piles...... is examined. The optimal order of the models is determined and implemented into the aeroelastic code HAWC2, where the dynamic response of a 5.0 MW wind turbine is evaluated. In contrast to the fore-aft vibrations, the inclusion of soil-structure interaction is shown to be critical for the side-side vibrations...

Breaking wave impact forces on truss support structures for offshore wind turbines

Science.gov (United States)

Cieślikiewicz, Witold; Gudmestad, Ove T.; Podrażka, Olga

2014-05-01

Due to depletion of the conventional energy sources, wind energy is becoming more popular these days. Wind energy is being produced mostly from onshore farms, but there is a clear tendency to transfer wind farms to the sea. The foundations of offshore wind turbines may be truss structures and might be located in shallow water, where are subjected to highly varying hydrodynamic loads, particularly from plunging breaking waves. There are models for impact forces prediction on monopiles. Typically the total wave force on slender pile from breaking waves is a superposition of slowly varying quasi-static force, calculated from the Morison equation and additional dynamical, short duration force due to the impact of the breaker front or breaker tongue. There is not much research done on the truss structures of wind turbines and there are still uncertainties on slamming wave forces, due to plunging breaking waves on those structures. Within the WaveSlam (Wave slamming forces on truss structures in shallow water) project the large scale tests were carried out in 2013 at the Large Wave Flume in Forschungszentrum Küste (FZK) in Hannover, Germany. The following institutions participated in this initiative: the University of Stavanger and the Norwegian University of Science and Technology (project management), University of Gdańsk, Poland, Hamburg University of Technology and the University of Rostock, Germany and Reinertsen AS, Norway. This work was supported by the EU 7th Framework Programme through the grant to the budget of the Integrating Activity HYDRALAB IV. The main aim of the experiment was to investigate the wave slamming forces on truss structures, development of new and improvement of existing methods to calculate forces from the plunging breakers. The majority of the measurements were carried out for regular waves with specified frequencies and wave heights as well as for the irregular waves based on JONSWAP spectrum. The truss structure was equipped with both

Comparison and application of wind retrieval algorithms for small unmanned aerial systems

Science.gov (United States)

Bonin, T. A.; Chilson, P. B.; Zielke, B. S.; Klein, P. M.; Leeman, J. R.

2013-07-01

Recently, there has been an increase in use of Unmanned Aerial Systems (UASs) as platforms for conducting fundamental and applied research in the lower atmosphere due to their relatively low cost and ability to collect samples with high spatial and temporal resolution. Concurrent with this development comes the need for accurate instrumentation and measurement methods suitable for small meteorological UASs. Moreover, the instrumentation to be integrated into such platforms must be small and lightweight. Whereas thermodynamic variables can be easily measured using well-aspirated sensors onboard, it is much more challenging to accurately measure the wind with a UAS. Several algorithms have been developed that incorporate GPS observations as a means of estimating the horizontal wind vector, with each algorithm exhibiting its own particular strengths and weaknesses. In the present study, the performance of three such GPS-based wind-retrieval algorithms has been investigated and compared with wind estimates from rawinsonde and sodar observations. Each of the algorithms considered agreed well with the wind measurements from sounding and sodar data. Through the integration of UAS-retrieved profiles of thermodynamic and kinematic parameters, one can investigate the static and dynamic stability of the atmosphere and relate them to the state of the boundary layer across a variety of times and locations, which might be difficult to access using conventional instrumentation.

Development and comparisons of wind retrieval algorithms for small unmanned aerial systems

Science.gov (United States)

Bonin, T. A.; Chilson, P. B.; Zielke, B. S.; Klein, P. M.; Leeman, J. R.

2012-12-01

Recently, there has been an increase in use of Unmanned Aerial Systems (UASs) as platforms for conducting fundamental and applied research in the lower atmosphere due to their relatively low cost and ability to collect samples with high spatial and temporal resolution. Concurrent with this development comes the need for accurate instrumentation and measurement methods suitable for small meteorological UASs. Moreover, the instrumentation to be integrated into such platforms must be small and lightweight. Whereas thermodynamic variables can be easily measured using well aspirated sensors onboard, it is much more challenging to accurately measure the wind with a UAS. Several algorithms have been developed that incorporate GPS observations as a means of estimating the horizontal wind vector, with each algorithm exhibiting its own particular strengths and weaknesses. In the present study, the performance of three such GPS-based wind-retrieval algorithms has been investigated and compared with wind estimates from rawinsonde and sodar observations. Each of the algorithms considered agreed well with the wind measurements from sounding and sodar data. Through the integration of UAS-retrieved profiles of thermodynamic and kinematic parameters, one can investigate the static and dynamic stability of the atmosphere and relate them to the state of the boundary layer across a variety of times and locations, which might be difficult to access using conventional instrumentation.

Strength Analysis of a Large-Size Supporting Structure for an Offshore Wind Turbine

Directory of Open Access Journals (Sweden)

Niklas Karol

2017-04-01

Full Text Available The offshore wind power industry is the branch of electric energy production from renewable sources which is most intensively developed in EU countries. At present, there is a tendency to install larger-power wind turbines at larger distances from the seashore, on relatively deep waters. Consequently, technological solutions for new supporting structures intended for deeper water regions are undergoing rapid development now. Various design types are proposed and analysed, starting from gravitational supports (GBS, through monopiles and 3D frame structures (jackets, tripods, and ending with floating and submerged supports anchored to the seabed by flexible connectors, including TLP type solutions.

Reactive-site hydrolyzed Cucurbita maxima trypsin inhibitor-V: function, thermodynamic stability, and NMR solution structure.

Science.gov (United States)

Cai, M; Gong, Y; Prakash, O; Krishnamoorthi, R

1995-09-26

Reactive-site (Lys44-Asp45 peptide bond) hydrolyzed Cucurbita maxima trypsin inhibitor-V (CMTI-V*) was prepared and characterized: In comparison to the intact form, CMTI-V* exhibited markedly reduced inhibitory properties and binding affinities toward trypsin and human blood coagulation factor XIIa. The equilibrium constant of trypsin-catalyzed hydrolysis, Khyd, defined as [CMTI-V*]/[CMTI-V], was measured to be approximately 9.4 at 25 degrees C (delta G degrees = -1.3 kcal.mol-1). From the temperature dependence of delta G degrees, the following thermodynamic parameters were estimated: delta H degrees = 1.6 kcal.mol-1 and delta S degrees = 9.8 eu. In order to understand the functional and thermodynamic differences between the two forms, the three-dimensional solution structure of CMTI-V* was determined by a combined approach of NMR, distance geometry, and simulated annealing methods. Thus, following sequence-specific and stereospecific resonance assignments, including those of beta-, gamma-, delta-, and epsilon-hydrogens and valine methyl hydrogens, 809 interhydrogen distances and 123 dihedral angle constraints were determined, resulting in the computation and energy-minimization of 20 structures for CMTI-V*. The average root mean squared deviation in position for equivalent atoms between the 20 individual structures and the mean structure obtained by averaging their coordinates is 0.67 +/- 0.15 A for the main chain atoms and 1.19 +/- 0.23 A for all the non-hydrogen atoms of residues 5-40 and residues 48-67.(ABSTRACT TRUNCATED AT 250 WORDS)

Wind Power Today: 1998 Wind Energy Program Highlights

Energy Technology Data Exchange (ETDEWEB)

Tromly, K.

1999-06-17

The US Department of Energy's Office of Energy Efficiency and Renewable Energy manages the Federal Wind Energy Program. The mission of the program is to help the US wind industry to complete the research, testing, and field verification needed to fully develop advanced wind technologies that will lead the world in cost-effectiveness and reliability. This publication, printed annually, provides a summary of significant achievements in wind energy made during the previous calendar year. Articles include wind energy in the Midwest, an Alaskan wind energy project, the US certification program, structural testing, and the federal program in review.

Boron-substitution and defects in B2-type AlNi compound: Site-preference and influence on structural, thermodynamic and electronic properties

Energy Technology Data Exchange (ETDEWEB)

Capaz, Rodrigo B. [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21941-972 (Brazil); ElMassalami, M., E-mail: massalam@if.ufrj.br [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21941-972 (Brazil); Terrazos, L.A. [Centro de Educação e Saúde, Universidade Federal de Campina Grande, Cuité, PB 58175-000 (Brazil); Elhadi, M. [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21941-972 (Brazil); Takeya, H. [National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, 305-0047 (Japan); Ghivelder, L. [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21941-972 (Brazil)

2016-06-05

Using a combination of theoretical (first-principles total-energy and electronic structure calculations) as well as experimental (structural, thermodynamics) techniques, we systematically investigated the influence of B incorporation on the structural, electronic and thermodynamic properties of a series of technologically-important B-containing AlNi matrix. Special attention was paid to calculating the energy cost of placing B at various sites within the cubic unit cell. The most energetically favorable defects were identified to be, depending on initial stoichiometry, substitutional B at Al site (B{sub Al}), Ni vacancy (V{sub Ni}), or Ni antisite (Ni{sub Al}). We show that the induced variation in the lattice parameters can be correlated with the type and concentration of the involved defects: e.g. the surge of V{sub Ni} defects leads to a stronger lattice-parameter reduction, that of Ni{sub Al} ones to a relatively weaker reduction while that of B{sub Al} defects to a much weaker influence. Both electronic band structure calculations as well as thermodynamics measurements indicate that the 3d bands of Ni are fully occupied and magnetically unpolarized and that the resulting N(E{sub F}) is very small: all studied compounds are normal conductors with no trace of superconductivity or magnetic polarization.

Understanding Mn-Based Intercalation Cathodes from Thermodynamics and Kinetics

Directory of Open Access Journals (Sweden)

Yin Xie

2017-07-01

Full Text Available A series of Mn-based intercalation compounds have been applied as the cathode materials of Li-ion batteries, such as LiMn2O4, LiNi1−x−yCoxMnyO2, etc. With open structures, intercalation compounds exhibit a wide variety of thermodynamic and kinetic properties depending on their crystal structures, host chemistries, etc. Understanding these materials from thermodynamic and kinetic points of view can facilitate the exploration of cathodes with better electrochemical performances. This article reviews the current available thermodynamic and kinetic knowledge on Mn-based intercalation compounds, including the thermal stability, structural intrinsic features, involved redox couples, phase transformations as well as the electrical and ionic conductivity.

Ice accretion modeling for wind turbine rotor blades

Energy Technology Data Exchange (ETDEWEB)

Chocron, D.; Brahimi, T.; Paraschivoiu, I.; Bombardier, J.A. [Ecole Polytechnique de Montreal (Canada)

1997-12-31

The increasing application of wind energy in northern climates implies operation of wind turbines under severe atmospheric icing conditions. Such conditions are well known in the Scandinavian countries, Canada and most of Eastern European countries. An extensive study to develop a procedure for the prediction of ice accretion on wind turbines rotor blades appears to be essential for the safe and economic operation of wind turbines in these cold regions. The objective of the present paper is to develop a computer code capable of simulating the shape and amount of ice which may accumulate on horizontal axis wind turbine blades when operating in icing conditions. The resulting code is capable to predict and simulate the formation of ice in rime and glaze conditions, calculate the flow field and particle trajectories and to perform thermodynamic analysis. It also gives the possibility of studying the effect of different parameters that influence ice formation such as temperature, liquid water content, droplet diameter and accretion time. The analysis has been conducted on different typical airfoils as well as on NASA/DOE Mod-0 wind turbine. Results showed that ice accretion on wind turbines may reduce the power output by more than 20%.

Probabilistic analysis of wind-induced vibration mitigation of structures by fluid viscous dampers

Science.gov (United States)

Chen, Jianbing; Zeng, Xiaoshu; Peng, Yongbo

2017-11-01

The high-rise buildings usually suffer from excessively large wind-induced vibrations, and thus vibration control systems might be necessary. Fluid viscous dampers (FVDs) with nonlinear power law against velocity are widely employed. With the transition of design method from traditional frequency domain approaches to more refined direct time domain approaches, the difficulty of time integration of these systems occurs sometimes. In the present paper, firstly the underlying reason of the difficulty is revealed by identifying that the equations of motion of high-rise buildings installed with FVDs are sometimes stiff differential equations. Thus, an approach effective for stiff differential systems, i.e., the backward difference formula (BDF), is then introduced, and verified to be effective for the equation of motion of wind-induced vibration controlled systems. Comparative studies are performed among some methods, including the Newmark method, KR-alpha method, energy-based linearization method and the statistical linearization method. Based on the above results, a 20-story steel frame structure is taken as a practical example. Particularly, the randomness of structural parameters and of wind loading input is emphasized. The extreme values of the responses are examined, showing the effectiveness of the proposed approach, and also necessitating the refined probabilistic analysis in the design of wind-induced vibration mitigation systems.

ON THE LAUNCHING AND STRUCTURE OF RADIATIVELY DRIVEN WINDS IN WOLF–RAYET STARS

Energy Technology Data Exchange (ETDEWEB)

Ro, Stephen; Matzner, Christopher D., E-mail: ro@astro.utoronto.ca [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada)

2016-04-20

Hydrostatic models of Wolf–Rayet (WR) stars typically contain low-density outer envelopes that inflate the stellar radii by a factor of several and are capped by a denser shell of gas. Inflated envelopes and density inversions are hallmarks of envelopes that become super-Eddington as they cross the iron-group opacity peak, but these features disappear when mass loss is sufficiently rapid. We re-examine the structures of steady, spherically symmetric wind solutions that cross a sonic point at high optical depth, identifying the physical mechanism through which the outflow affects the stellar structure, and provide an improved analytical estimate for the critical mass-loss rate above which extended structures are erased. Weak-flow solutions below this limit resemble hydrostatic stars even in supersonic zones; however, we infer that these fail to successfully launch optically thick winds. WR envelopes will therefore likely correspond to the strong, compact solutions. We also find that wind solutions with negligible gas pressure are stably stratified at and below the sonic point. This implies that convection is not the source of variability in WR stars, as has been suggested; however, acoustic instabilities provide an alternative explanation. Our solutions are limited to high optical depths by our neglect of Doppler enhancements to the opacity, and do not account for acoustic instabilities at high Eddington factors; yet, they do provide useful insights into WR stellar structures.

[Thermodynamics of the origin of life, evolution and aging].

Science.gov (United States)

Gladyshev, G P

2014-01-01

Briefly discusses the history of the search of thermodynamic approach to explain the origin of life, evolution and aging of living beings. The origin of life is the result of requirement by the quasi-equilibrium hierarchical thermodynamics, in particular, the supramolecular thermodynamics. The evolution and aging of living beings is accompanied with changes of chemical and supramolecular compositions of living bodies, as well as with changes in the composition and structure of all hierarchies of the living world. The thermodynamic principle of substance stability predicts the existence of a single genetic code in our universe. The thermodynamic theory optimizes physiology and medicine and recommends antiaging diets and medicines. Hierarchical thermodynamics forms the design diversity of culture and art. The thermodynamic theory of origin of life, evolution and aging is the development of Clausius-Gibbs thermodynamics. Hierarchical thermodynamics is the mirror of Darwin-Wallace's-theory.

Grid inhomogeneous solvation theory: hydration structure and thermodynamics of the miniature receptor cucurbit[7]uril.

Science.gov (United States)

Nguyen, Crystal N; Young, Tom Kurtzman; Gilson, Michael K

2012-07-28

The displacement of perturbed water upon binding is believed to play a critical role in the thermodynamics of biomolecular recognition, but it is nontrivial to unambiguously define and answer questions about this process. We address this issue by introducing grid inhomogeneous solvation theory (GIST), which discretizes the equations of inhomogeneous solvation theory (IST) onto a three-dimensional grid situated in the region of interest around a solute molecule or complex. Snapshots from explicit solvent simulations are used to estimate localized solvation entropies, energies, and free energies associated with the grid boxes, or voxels, and properly summing these thermodynamic quantities over voxels yields information about hydration thermodynamics. GIST thus provides a smoothly varying representation of water properties as a function of position, rather than focusing on hydration sites where solvent is present at high density. It therefore accounts for full or partial displacement of water from sites that are highly occupied by water, as well as for partly occupied and water-depleted regions around the solute. GIST can also provide a well-defined estimate of the solvation free energy and therefore enables a rigorous end-states analysis of binding. For example, one may not only use a first GIST calculation to project the thermodynamic consequences of displacing water from the surface of a receptor by a ligand, but also account, in a second GIST calculation, for the thermodynamics of subsequent solvent reorganization around the bound complex. In the present study, a first GIST analysis of the molecular host cucurbit[7]uril is found to yield a rich picture of hydration structure and thermodynamics in and around this miniature receptor. One of the most striking results is the observation of a toroidal region of high water density at the center of the host's nonpolar cavity. Despite its high density, the water in this toroidal region is disfavored energetically and

Reliability assessment of Wind turbines

DEFF Research Database (Denmark)

Sørensen, John Dalsgaard

2015-01-01

Wind turbines can be considered as structures that are in between civil engineering structures and machines since they consist of structural components and many electrical and machine components together with a control system. Further, a wind turbine is not a one-of-a-kind structure...... but manufactured in series production based on many component tests, some prototype tests and zeroseries wind turbines. These characteristics influence the reliability assessment where focus in this paper is on the structural components. Levelized Cost Of Energy is very important for wind energy, especially when...... comparing to other energy sources. Therefore much focus is on cost reductions and improved reliability both for offshore and onshore wind turbines. The wind turbine components should be designed to have sufficient reliability level with respect to both extreme and fatigue loads but also not be too costly...

Mesoscopic modeling of structural and thermodynamic properties of fluids confined by rough surfaces.

Science.gov (United States)

Terrón-Mejía, Ketzasmin A; López-Rendón, Roberto; Gama Goicochea, Armando

2015-10-21

The interfacial and structural properties of fluids confined by surfaces of different geometries are studied at the mesoscopic scale using dissipative particle dynamics simulations in the grand canonical ensemble. The structure of the surfaces is modeled by a simple function, which allows us to simulate readily different types of surfaces through the choice of three parameters only. The fluids we have modeled are confined either by two smooth surfaces or by symmetrically and asymmetrically structured walls. We calculate structural and thermodynamic properties such as the density, temperature and pressure profiles, as well as the interfacial tension profiles for each case and find that a structural order-disorder phase transition occurs as the degree of surface roughness increases. However, the magnitude of the interfacial tension is insensitive to the structuring of the surfaces and depends solely on the magnitude of the solid-fluid interaction. These results are important for modern nanotechnology applications, such as in the enhanced recovery of oil, and in the design of porous materials with specifically tailored properties.

Investigating fundamental properties of wind turbine wake structure using particle image velocimetry

Energy Technology Data Exchange (ETDEWEB)

Whale, J. [Univ. of Edinburgh, Dept. of Mechanical Engineering, Edinburgh (United Kingdom)

1997-08-01

Low Reynolds number flow visualization tests are often used for showing the flow pattern changes associated with changes in lift-coefficients at a higher Reynolds number. In wind turbine studies, analysis of measured wake structures at small scale may reveal fundamental properties of the wake which will offer wake modellers a more complete understanding of rotor flows. Measurements are presented from experiments on a model wind turbine rig conducted in a water channel. The laser-optics technique of Particle Image Velocimetry (PIV) is used to make simultaneous multi-point measurements of the wake flow behind small-scale rotors. Analysis of the PIV data shows trends in velocity and vorticity structure in the wake. Study of the flow close to the rotor plane reveals information on stalled flow and blade performance. (au)

NWTC Researchers Field-Test Advanced Control Turbine Systems to Increase Performance, Decrease Structural Loading of Wind Turbines and Plants

Energy Technology Data Exchange (ETDEWEB)

2015-08-01

Researchers at the National Renewable Energy Laboratory's (NREL's) National Wind Technology Center (NWTC) are studying component controls, including new advanced actuators and sensors, for both conventional turbines as well as wind plants. This research will help develop innovative control strategies that reduce aerodynamic structural loads and improve performance. Structural loads can cause damage that increase maintenance costs and shorten the life of a turbine or wind plant.

On Teaching Thermodynamics

Science.gov (United States)

Debbasch, F.

2011-01-01

The logical structure of classical thermodynamics is presented in a modern, geometrical manner. The first and second law receive clear, operatively oriented statements and the Gibbs free energy extremum principle is fully discussed. Applications relevant to chemistry, such as phase transitions, dilute solutions theory and, in particular, the law…

Soft matter in hard confinement: phase transition thermodynamics, structure, texture, diffusion and flow in nanoporous media

Science.gov (United States)

Huber, Patrick

2015-03-01

Spatial confinement in nanoporous media affects the structure, thermodynamics and mobility of molecular soft matter often markedly. This article reviews thermodynamic equilibrium phenomena, such as physisorption, capillary condensation, crystallisation, self-diffusion, and structural phase transitions as well as selected aspects of the emerging field of spatially confined, non-equilibrium physics, i.e. the rheology of liquids, capillarity-driven flow phenomena, and imbibition front broadening in nanoporous materials. The observations in the nanoscale systems are related to the corresponding bulk phenomenologies. The complexity of the confined molecular species is varied from simple building blocks, like noble gas atoms, normal alkanes and alcohols to liquid crystals, polymers, ionic liquids, proteins and water. Mostly, experiments with mesoporous solids of alumina, gold, carbon, silica, and silicon with pore diameters ranging from a few up to 50 nm are presented. The observed peculiarities of nanopore-confined condensed matter are also discussed with regard to applications. A particular emphasis is put on texture formation upon crystallisation in nanoporous media, a topic both of high fundamental interest and of increasing nanotechnological importance, e.g. for the synthesis of organic/inorganic hybrid materials by melt infiltration, the usage of nanoporous solids in crystal nucleation or in template-assisted electrochemical deposition of nano structures.

Structural damage identification in wind turbine blades using piezoelectric active sensing with ultrasonic validation

Energy Technology Data Exchange (ETDEWEB)

Claytor, Thomas N [Los Alamos National Laboratory; Ammerman, Curtt N [Los Alamos National Laboratory; Park, Gyu Hae [Los Alamos National Laboratory; Farinholt, Kevin M [Los Alamos National Laboratory; Farrar, Charles R [Los Alamos National Laboratory; Atterbury, Marie K [Los Alamos National Laboratory

2010-01-01

This paper gives a brief overview of a new project at LANL in structural damage identification for wind turbines. This project makes use of modeling capabilities and sensing technology to understand realistic blade loading on large turbine blades, with the goal of developing the technology needed to automatically detect early damage. Several structural health monitoring (SHM) techniques using piezoelectric active materials are being investigated for the development of wireless, low power sensors that interrogate sections of the wind turbine blade using Lamb wave propagation data, frequency response functions (FRFs), and time-series analysis methods. The modeling and sensor research will be compared with extensive experimental testing, including wind tunnel experiments, load and fatigue tests, and ultrasonic scans - on small- to mid-scale turbine blades. Furthermore, this study will investigate the effect of local damage on the global response of the blade by monitoring low-frequency response changes.

Thermodynamics and Structural Evolution during a Reversible Vesicle-Micelle Transition of a Vitamin-Derived Bolaamphiphile Induced by Sodium Cholate.

Science.gov (United States)

Tian, Jun-Nan; Ge, Bing-Qiang; Shen, Yun-Feng; He, Yu-Xuan; Chen, Zhong-Xiu

2016-03-09

Interaction of endogenous sodium cholate (SC) with dietary amphiphiles would induce structural evolution of the self-assembled aggregates, which inevitably affects the hydrolysis of fat in the gut. Current work mainly focused on the interaction of bile salts with classical double-layered phospholipid vesicles. In this paper, the thermodynamics and structural evolution during the interaction of SC with novel unilamellar vesicles formed from vitamin-derived zwitterionic bolaamphiphile (DDO) were characterized. It was revealed that an increased temperature and the presence of NaCl resulted in narrowed micelle-vesicle coexistence and enlarged the vesicle region. The coexistence of micelles and vesicles mainly came from the interaction of monomeric SC with DDO vesicles, whereas micellar SC contributed to the total solubilization of DDO vesicles. This research may enrich the thermodynamic mechanism behind the structure transition of the microaggregates formed by amphiphiles in the gut. It will also contribute to the design of food formulation and drug delivery system.

A Comparison on the Dynamics of a Floating Vertical Axis Wind Turbine on Three Different Floating Support Structures

OpenAIRE

Borg, Michael; Collu, Maurizio

2014-01-01

To increase the competitiveness of offshore wind energy in the global energy market, it is necessary to identify optimal offshore wind turbine configurations to deliver the lowest cost of energy. For deep waters where floating wind turbines are the feasible support structure option, the vertical axis wind turbine concept might prove to be one of these optimal configurations. This paper carries out a preliminary investigation into the dynamics of a vertical axis wind turbine coupled with three...

Influence of the control system on wind turbine loads during power production in extreme turbulence: Structural reliability

DEFF Research Database (Denmark)

Abdallah, Imad; Natarajan, Anand; Sørensen, John Dalsgaard

2016-01-01

structural reliability are assessed when the extreme turbulence model is uncertain. The structural reliability is assessed for the wind turbine when three configurations of an industrial grade load alleviation control system of increasing complexity and performance are used. The load alleviation features......The wind energy industry is continuously researching better computational models of wind inflow and turbulence to predict extreme loading (the nature of randomness) and their corresponding probability of occurrence. Sophisticated load alleviation control systems are increasingly being designed...... and deployed to specifically reduce the adverse effects of extreme load events resulting in lighter structures. The main objective herein is to show that despite large uncertainty in the extreme turbulence models, advanced load alleviation control systems yield both a reduction in magnitude and scatter...

Magnetic and thermodynamic properties of Ising model with borophene structure in a longitudinal magnetic field

Science.gov (United States)

Shi, Kaile; Jiang, Wei; Guo, Anbang; Wang, Kai; Wu, Chuang

2018-06-01

The magnetic and thermodynamic properties of borophene structure have been studied for the first time by Monte Carlo simulation. Two-dimensional borophene structure consisting of seven hexagonal B36 units is described by Ising model. Each B36 basic unit includes three benzene-like with spin-3/2. The general formula for the borophene structure is given. The numerical results of the magnetization, the magnetic susceptibility, the internal energy and the specific heat are studied with various parameters. The possibility to test the predicted magnetism in experiment are illustrated, for instance, the maximum on the magnetization curve. The multiple hysteresis loops and the magnetization plateaus are sensitive to the ferromagnetic or ferrimagnetic exchange coupling in borophene structure. The results show the borophene structure could have applications in spintronics, which deserves further studies in experiments.

Wind of opportunity

International Nuclear Information System (INIS)

Jamieson, Peter

1999-01-01

This article traces the move towards the offshore exploitation of wind energy in Europe, and presents information on existing offshore wind energy projects and proposed wind turbine prototypes for offshore operation. The building of the first major offshore wind project at Vindeby, the use of rock socketed monopile foundations for pile drilling and erection of the wind turbines from a mobile jack-up barge, the costs of wind turbines, the fatigue loads on the support structures due to the wind loading, and the offshore wind market in the UK and Europe are discussed. (UK)

Anisotropy and temperature dependence of structural, thermodynamic, and elastic properties of crystalline cellulose Iβ: a first-principles investigation

Science.gov (United States)

ShunLi Shang; Louis G. Hector Jr.; Paul Saxe; Zi-Kui Liu; Robert J. Moon; Pablo D. Zavattieri

2014-01-01

Anisotropy and temperature dependence of structural, thermodynamic and elastic properties of crystalline cellulose Iβ were computed with first-principles density functional theory (DFT) and a semi-empirical correction for van der Waals interactions. Specifically, we report the computed temperature variation (up to 500...

Monte Carlo thermodynamic and structural properties of the TIP4P water model: dependence on the computational conditions

Directory of Open Access Journals (Sweden)

João Manuel Marques Cordeiro

1998-11-01

Full Text Available Classical Monte Carlo simulations were carried out on the NPT ensemble at 25°C and 1 atm, aiming to investigate the ability of the TIP4P water model [Jorgensen, Chandrasekhar, Madura, Impey and Klein; J. Chem. Phys., 79 (1983 926] to reproduce the newest structural picture of liquid water. The results were compared with recent neutron diffraction data [Soper; Bruni and Ricci; J. Chem. Phys., 106 (1997 247]. The influence of the computational conditions on the thermodynamic and structural results obtained with this model was also analyzed. The findings were compared with the original ones from Jorgensen et al [above-cited reference plus Mol. Phys., 56 (1985 1381]. It is notice that the thermodynamic results are dependent on the boundary conditions used, whereas the usual radial distribution functions g(O/O(r and g(O/H(r do not depend on them.

Thermodynamics

CERN Document Server

Fermi, Enrico

1956-01-01

Indisputably, this is a modern classic of science. Based on a course of lectures delivered by the author at Columbia University, the text is elementary in treatment and remarkable for its clarity and organization. Although it is assumed that the reader is familiar with the fundamental facts of thermometry and calorimetry, no advanced mathematics beyond calculus is assumed.Partial contents: thermodynamic systems, the first law of thermodynamics (application, adiabatic transformations), the second law of thermodynamics (Carnot cycle, absolute thermodynamic temperature, thermal engines), the entr

Diurnal evolution of wind structure and data availability measured by the DOE prototype radar system

Science.gov (United States)

Hirth, Brian D.; Schroeder, John L.; Guynes, Jerry G.

2017-11-01

A new Doppler radar prototype has been developed and deployed at Texas Tech University with a focus on enhancing the technologies’ capability to contribute to wind plant relevant complex flow measurements. In particular, improvements in data availability, total data coverage, and autonomous operation were targeted to enable contributions to a wider range of wind energy applications. Doppler radar offers rapid scan speeds, extended maximum range and excellent along-beam range resolution allowing for the simultaneous measurement of various wind phenomena ranging from regional and wind plant scales to inflow and wake flow assessment for an individual turbine. Data examples and performance improvements relative to a previous edition of the technology are presented, including insights into the influence of diurnal atmospheric stability evolution of wind structure and system performance.

Binding thermodynamics discriminates fragments from druglike compounds: a thermodynamic description of fragment-based drug discovery.

Science.gov (United States)

Williams, Glyn; Ferenczy, György G; Ulander, Johan; Keserű, György M

2017-04-01

Small is beautiful - reducing the size and complexity of chemical starting points for drug design allows better sampling of chemical space, reveals the most energetically important interactions within protein-binding sites and can lead to improvements in the physicochemical properties of the final drug. The impact of fragment-based drug discovery (FBDD) on recent drug discovery projects and our improved knowledge of the structural and thermodynamic details of ligand binding has prompted us to explore the relationships between ligand-binding thermodynamics and FBDD. Information on binding thermodynamics can give insights into the contributions to protein-ligand interactions and could therefore be used to prioritise compounds with a high degree of specificity in forming key interactions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermodynamic Studies for Drug Design and Screening

Science.gov (United States)

Garbett, Nichola C.; Chaires, Jonathan B.

2012-01-01

Introduction A key part of drug design and development is the optimization of molecular interactions between an engineered drug candidate and its binding target. Thermodynamic characterization provides information about the balance of energetic forces driving binding interactions and is essential for understanding and optimizing molecular interactions. Areas covered This review discusses the information that can be obtained from thermodynamic measurements and how this can be applied to the drug development process. Current approaches for the measurement and optimization of thermodynamic parameters are presented, specifically higher throughput and calorimetric methods. Relevant literature for this review was identified in part by bibliographic searches for the period 2004 – 2011 using the Science Citation Index and PUBMED and the keywords listed below. Expert opinion The most effective drug design and development platform comes from an integrated process utilizing all available information from structural, thermodynamic and biological studies. Continuing evolution in our understanding of the energetic basis of molecular interactions and advances in thermodynamic methods for widespread application are essential to realize the goal of thermodynamically-driven drug design. Comprehensive thermodynamic evaluation is vital early in the drug development process to speed drug development towards an optimal energetic interaction profile while retaining good pharmacological properties. Practical thermodynamic approaches, such as enthalpic optimization, thermodynamic optimization plots and the enthalpic efficiency index, have now matured to provide proven utility in design process. Improved throughput in calorimetric methods remains essential for even greater integration of thermodynamics into drug design. PMID:22458502

Thermodynamic studies for drug design and screening.

Science.gov (United States)

Garbett, Nichola C; Chaires, Jonathan B

2012-04-01

A key part of drug design and development is the optimization of molecular interactions between an engineered drug candidate and its binding target. Thermodynamic characterization provides information about the balance of energetic forces driving binding interactions and is essential for understanding and optimizing molecular interactions. This review discusses the information that can be obtained from thermodynamic measurements and how this can be applied to the drug development process. Current approaches for the measurement and optimization of thermodynamic parameters are presented, specifically higher throughput and calorimetric methods. Relevant literature for this review was identified in part by bibliographic searches for the period 2004 - 2011 using the Science Citation Index and PUBMED and the keywords listed below. The most effective drug design and development platform comes from an integrated process utilizing all available information from structural, thermodynamic and biological studies. Continuing evolution in our understanding of the energetic basis of molecular interactions and advances in thermodynamic methods for widespread application are essential to realize the goal of thermodynamically driven drug design. Comprehensive thermodynamic evaluation is vital early in the drug development process to speed drug development toward an optimal energetic interaction profile while retaining good pharmacological properties. Practical thermodynamic approaches, such as enthalpic optimization, thermodynamic optimization plots and the enthalpic efficiency index, have now matured to provide proven utility in the design process. Improved throughput in calorimetric methods remains essential for even greater integration of thermodynamics into drug design. © 2012 Informa UK, Ltd.

Wind Turbine Converter Control Interaction with Complex Wind Farm Systems

DEFF Research Database (Denmark)

Kocewiak, Lukasz Hubert; Hjerrild, Jesper; Bak, Claus Leth

2013-01-01

. The same wind turbine converter control strategy is evaluated in two different wind farms. It is emphasised that the grid-side converter controller should be characterised by sufficient harmonic/noise rejection and adjusted depending on wind farms to which it is connected. Various stability indices......This study presents wind turbine converter stability analysis of wind farms in frequency domain. The interaction between the wind turbine control system and the wind farm structure in wind farms is deeply investigated. Two wind farms (i.e. Horns Rev II and Karnice) are taken into consideration...... in this study. It is shown that wind farm components, such as long high-voltage alternating current cables and park transformers, can introduce significant low-frequency series resonances seen from the wind turbine terminals that can affect wind turbine control system operation and overall wind farm stability...

Structural health monitoring tools for late and end of life management of offshore wind turbines

DEFF Research Database (Denmark)

McGugan, Malcolm; McKirdy, Scott

2016-01-01

The late and end of life stages in an offshore wind turbines (OWT) life cycle have unique features that must be considered. The initial focus on risks associated with start-up issues due to design, manufacturing or process elements gives way to a stable period of operation and maintenance...... margins and the predominance of low redundancy structures, accurate structural health monitoring can play a strong role in safe management and enable increased operating time at end of life and decommissioning. Late life operations of offshore wind farms can pose significant challenges, balancing...

Nonequilibrium thermodynamics of nucleation

NARCIS (Netherlands)

Schweizer, M.; Sagis, L.M.C.

2014-01-01

We present a novel approach to nucleation processes based on the GENERIC framework (general equation for the nonequilibrium reversible-irreversible coupling). Solely based on the GENERIC structure of time-evolution equations and thermodynamic consistency arguments of exchange processes between a

Structural health and prognostics management for offshore wind turbines :

Energy Technology Data Exchange (ETDEWEB)

Myrent, Noah J.; Kusnick, Joshua F.; Barrett, Natalie C.; Adams, Douglas E.; Griffith, Daniel

2013-04-01

Operations and maintenance costs for offshore wind plants are significantly higher than the current costs for land-based (onshore) wind plants. One way to reduce these costs would be to implement a structural health and prognostic management (SHPM) system as part of a condition based maintenance paradigm with smart load management and utilize a state-based cost model to assess the economics associated with use of the SHPM system. To facilitate the development of such a system a multi-scale modeling approach developed in prior work is used to identify how the underlying physics of the system are affected by the presence of damage and faults, and how these changes manifest themselves in the operational response of a full turbine. This methodology was used to investigate two case studies: (1) the effects of rotor imbalance due to pitch error (aerodynamic imbalance) and mass imbalance and (2) disbond of the shear web; both on a 5-MW offshore wind turbine in the present report. Based on simulations of damage in the turbine model, the operational measurements that demonstrated the highest sensitivity to the damage/faults were the blade tip accelerations and local pitching moments for both imbalance and shear web disbond. The initial cost model provided a great deal of insight into the estimated savings in operations and maintenance costs due to the implementation of an effective SHPM system. The integration of the health monitoring information and O&M cost versus damage/fault severity information provides the initial steps to identify processes to reduce operations and maintenance costs for an offshore wind farm while increasing turbine availability, revenue, and overall profit.

Thermodynamic analysis of a novel hybrid wind-solar-compressed air energy storage system

International Nuclear Information System (INIS)

Ji, Wei; Zhou, Yuan; Sun, Yu; Zhang, Wu; An, Baolin; Wang, Junjie

2017-01-01

Highlights: • We present a novel hybrid wind-solar-compressed air energy storage system. • Wind and solar power are transformed into stable electric energy and hot water. • The system output electric power is 8053 kWh with an exergy efficiency of 65.4%. • Parametric sensitivity analysis is presented to optimize system performance. - Abstract: Wind and solar power have embraced a strong development in recent years due to the energy crisis in China. However, owing to their nature of fluctuation and intermittency, some power grid management problems can be caused. Therefore a novel hybrid wind-solar-compressed air energy storage (WS-CAES) system was proposed to solve the problems. The WS-CAES system can store unstable wind and solar power for a stable output of electric energy and hot water. Also, combined with organic Rankin cycle (ORC), the cascade utilization of energy with different qualities was achieved in the WS-CAES system. Aiming to obtain the optimum performance, the analysis of energy, exergy and parametric sensitivity were all conducted for this system. Furthermore, exergy destruction ratio of each component in the WS-CAES system was presented. The results show that the electric energy storage efficiency, round trip efficiency and exergy efficiency can reach 87.7%, 61.2% and 65.4%, respectively. Meanwhile, the parameters analysis demonstrates that the increase of ambient temperature has a negative effect on the system performance, while the increase of turbine inlet temperature has a positive effect. However, when the air turbine inlet pressure varies, there is a tradeoff between the system performance and the energy storage density.

Thermodynamic forces in coarse-grained simulations

Science.gov (United States)

Noid, William

Atomically detailed molecular dynamics simulations have profoundly advanced our understanding of the structure and interactions in soft condensed phases. Nevertheless, despite dramatic advances in the methodology and resources for simulating atomically detailed models, low-resolution coarse-grained (CG) models play a central and rapidly growing role in science. CG models not only empower researchers to investigate phenomena beyond the scope of atomically detailed simulations, but also to precisely tailor models for specific phenomena. However, in contrast to atomically detailed simulations, which evolve on a potential energy surface, CG simulations should evolve on a free energy surface. Therefore, the forces in CG models should reflect the thermodynamic information that has been eliminated from the CG configuration space. As a consequence of these thermodynamic forces, CG models often demonstrate limited transferability and, moreover, rarely provide an accurate description of both structural and thermodynamic properties. In this talk, I will present a framework that clarifies the origin and impact of these thermodynamic forces. Additionally, I will present computational methods for quantifying these forces and incorporating their effects into CG MD simulations. As time allows, I will demonstrate applications of this framework for liquids, polymers, and interfaces. We gratefully acknowledge the support of the National Science Foundation via CHE 1565631.

Structural, electronic, magnetic and thermodynamic properties of Ni1-xTixO alloys an ab initio calculation and Monte Carlo study

Science.gov (United States)

Klaa, K.; Labidi, S.; Masrour, R.; Jabar, A.; Labidi, M.; Amara, A.; Drici, A.; Hlil, E. K.; Ellouze, M.

2018-06-01

Structural, electronic, magnetic and thermodynamic main features for Ni1-xTixO ternary alloys in rock-salt structure with Ti content in the range ? were studied using the full potential Linearized augmented plane wave (FP-LAPW) method within density functional theory. The exchange-correlation potential was calculated by the generalized gradient approximation. The analysis of the electronic density of states curves allowed the computation of the magnetic moments which are considered to lie along (010) axes. The thermodynamic stability of this alloy was investigated by calculating the excess enthalpy of mixing ? as well as the phase diagram. In addition, the Monte Carlo simulations have been exploited to calculate the transition temperature and magnetic coercive field in the alloy.

Radar micro-Doppler of wind turbines : Simulation and analysis using rotating linear wire structures

NARCIS (Netherlands)

Krasnov, O.A.; Yarovoy, A.

2015-01-01

A simple electromagnetic model of wind-turbine's main structural elements as the linear wired structures is developed to simulate the temporal patterns of observed radar return Doppler spectra (micro-Doppler). Using the model, the micro-Doppler for different combinations of the turbines rotation

The design of models for cryogenic wind tunnels. [mechanical properties and loads

Science.gov (United States)

Gillespie, V. P.

1977-01-01

Factors to be considered in the design and fabrication of models for cryogenic wind tunnels include high model loads imposed by the high operating pressures, the mechanical and thermodynamic properties of materials in low temperature environments, and the combination of aerodynamic loads with the thermal environment. Candidate materials are being investigated to establish criteria for cryogenic wind tunnel models and their installation. Data acquired from these tests will be provided to users of the National Transonic Facility.

Statistical thermodynamics

International Nuclear Information System (INIS)

Lim, Gyeong Hui

2008-03-01

This book consists of 15 chapters, which are basic conception and meaning of statistical thermodynamics, Maxwell-Boltzmann's statistics, ensemble, thermodynamics function and fluctuation, statistical dynamics with independent particle system, ideal molecular system, chemical equilibrium and chemical reaction rate in ideal gas mixture, classical statistical thermodynamics, ideal lattice model, lattice statistics and nonideal lattice model, imperfect gas theory on liquid, theory on solution, statistical thermodynamics of interface, statistical thermodynamics of a high molecule system and quantum statistics

Thermodynamic and Quantum Thermodynamic Analyses of Brownian Movement

OpenAIRE

Gyftopoulos, Elias P.

2006-01-01

Thermodynamic and quantum thermodynamic analyses of Brownian movement of a solvent and a colloid passing through neutral thermodynamic equilibrium states only. It is shown that Brownian motors and E. coli do not represent Brownian movement.

Thermodynamic properties of Al-Mn, Al-Cu, and Al-Fe-Cu melts and their relations to liquid and quasicrystal structure

International Nuclear Information System (INIS)

Zaitsev, A I; Zaitseva, N E; Shimko, R Yu; Arutyunyan, N A; Dunaev, S F; Kraposhin, V S; Lam, Ha Thanh

2008-01-01

Thermodynamic properties of molten Al-Mn, Al-Cu and Al-Fe-Cu alloys in a wide temperature range of 1123-1878 K and the whole range of concentrations have been studied using the integral effusion method and Knudsen mass spectrometry. Thermodynamic functions of melts were described by the associated solution model. The possibility of icosahedral quasicrystal (i-QC) precipitation from liquid Al-Mn and Al-Cu-Fe alloys was found to be a consequence of the existence in liquid associates (clusters). A geometric model is suggested for the structure of associates in liquid

Structure and thermodynamic properties of molten alkali chlorides

International Nuclear Information System (INIS)

Ballone, P.; Pastore, G.; Tosi, M.P.; Trieste Univ.

1984-03-01

Self-consistent calculations of partial pair distribution functions and thermodynamic properties are presented for molten alkali chlorides in a non-polarizable-ion model. The theory starts from the hypernetted chain approximation and analyzes the role of bridge diagrams both for a two-component ionic plasma on a neutralizing background and for a binary ionic liquid of cations and anions. A simple account of excluded-volume effects suffices for a good description of the pair distribution functions in the two-component plasma, in analogy with earlier work on one-component fluids. The interplay of Coulomb attractions and repulsions in the molten salt requires, on the other hand, the inclusion of (i) excluded-volume effects for the various ion pairs as in a mixture of hard spheres with non-additive radii and (ii) medium-range Coulomb effects reflected mainly in the like-ion correlations. All these effects are included approximately in an empirical evaluation of the bridge functions, with numerical results which compare very well with computer simulation data. A detailed discussion of the results against experimental structural data is then given in the case of molten sodium chloride. (author)

Fundamentals for remote structural health monitoring of wind turbine blades - a preproject. Annex A. Cost-benefit for embedded sensors in large wind turbine blades

DEFF Research Database (Denmark)

Hansen, L.G.; Lading, Lars

2002-01-01

-bladed 2MW turbine placed offshore either without sensors or with sensors are compared. The price of a structural health monitoring system of a price of 100 000 DKK (per tur-bine) results in a break-eventime of about 3 years. For a price of 300 000 DKK the break-even time is about 8 years. However......This report contains the results of a cost-benefit analysis for the use of embed-ded sensors for damage detection in large wind turbine blades - structural health monitoring - (in connection with remote surveillance) of large wind turbine placedoff-shore. The total operating costs of a three......, the cost/benefit analysis has large uncertainties....

Structural Considerations of a 20MW Multi-Rotor Wind Energy System

International Nuclear Information System (INIS)

Jamieson, P; Branney, M

2014-01-01

The drive to upscale offshore wind turbines relates especially to possiblereductions in O and M and electrical interconnection costs per MW of installed capacity.Even with best current technologies, designs with rated capacity above about 3 MW are less cost effective exfactory per rated MW(turbine system costs) than smaller machines.Very large offshore wind turbines are thereforejustifiedprimarily by overall offshore project economics. Furthermore, continuing progress in materials and structures has been essential to avoid severe penalties in the power/mass ratio of large multi-MW machines.The multi-rotor concept employs many small rotors to maximise energy capture area withminimum systemvolume. Previous work has indicated that this can enablea very large reduction in the total weight and cost of rotors and drive trains compared to an equivalent large single rotor system.Thus the multi rotor concept may enable rated capacities of 20 MW or more at a single maintenancesite. Establishing the cost benefit of a multi rotor system requires examination of solutions for the support structure and yawing, ensuring aerodynamic losses from rotor interaction are not significant and that overall logistics, with much increased part count (more reliable components) and less consequence of single failuresare favourable. This paper addresses the viability of a support structure in respect of structural concept and likely weight as one necessary step in exploring the potential of the multi rotor concept

Structural Considerations of a 20MW Multi-Rotor Wind Energy System

Science.gov (United States)

Jamieson, P.; Branney, M.

2014-12-01

The drive to upscale offshore wind turbines relates especially to possiblereductions in O&M and electrical interconnection costs per MW of installed capacity.Even with best current technologies, designs with rated capacity above about 3 MW are less cost effective exfactory per rated MW(turbine system costs) than smaller machines.Very large offshore wind turbines are thereforejustifiedprimarily by overall offshore project economics. Furthermore, continuing progress in materials and structures has been essential to avoid severe penalties in the power/mass ratio of large multi-MW machines.The multi-rotor concept employs many small rotors to maximise energy capture area withminimum systemvolume. Previous work has indicated that this can enablea very large reduction in the total weight and cost of rotors and drive trains compared to an equivalent large single rotor system.Thus the multi rotor concept may enable rated capacities of 20 MW or more at a single maintenancesite. Establishing the cost benefit of a multi rotor system requires examination of solutions for the support structure and yawing, ensuring aerodynamic losses from rotor interaction are not significant and that overall logistics, with much increased part count (more reliable components) and less consequence of single failuresare favourable. This paper addresses the viability of a support structure in respect of structural concept and likely weight as one necessary step in exploring the potential of the multi rotor concept.

First principles thermodynamics of alloys

International Nuclear Information System (INIS)

Ducastelle, F.

1993-01-01

We present a brief report on the methods of solid state physics (electronic structure, statistical thermodynamics) that allow us to discuss the phase stability of alloys and to determine their phase diagrams. (orig.)

An extended structure-function model and its application to the analysis of solar wind intermittency properties

Directory of Open Access Journals (Sweden)

C.-Y. Tu

Full Text Available An extended structure-function model is developed by including the new effect in the p-model of Meneveau and Sreenivasan which shows that the averaged energy cascade rate changes with scale, a situation which has been found to prevail in non-fully-developed turbulence in the inner solar wind. This model is useful for the small-scale fluctuations in the inner heliosphere, where the turbulence is not fully developed and cannot be explained quantitatively by any of the previous intermittency turbulence models. With two model parameters, the intrinsic index of the energy spectrum α, and the fragmentation fraction P₁, the model can fit, for the first time, all the observed scaling exponents of the structure functions, which are calculated for time lags ranging from 81 s to 0.7 h from the Helios solar wind data. From the cases we studied we cannot establish for P₁ either a clear radial evolution trend, or a solar-wind-speed or stream-structure dependence or a systematic anisotropy for both the flow velocity and magnetic field component fluctuations. Generally, P₁ has values between 0.7 and 0.8. However, in some cases in low-speed wind P₁ has somewhat higher values for the magnetic components, especially for the radial component. In high-speed wind, the inferred intrinsic spectral indices α of the velocity and magnetic field components are about equal, while the experimental spectral indices derived from the observed power spectra differ. The magnetic index is somewhat larger than the index of the velocity spectrum. For magnetic fluctuations in both high- and low-speed winds, the intrinsic exponent α has values which are near 1.5, while the observed spectral exponent has much higher values. In the solar wind with considerable density fluctuations near the interplanetary current sheet near 1 AU, it is found that P₁ has a comparatively high value of 0

Basic Thermodynamics

International Nuclear Information System (INIS)

Duthil, P

2014-01-01

The goal of this paper is to present a general thermodynamic basis that is useable in the context of superconductivity and particle accelerators. The first part recalls the purpose of thermodynamics and summarizes its important concepts. Some applications, from cryogenics to magnetic systems, are covered. In the context of basic thermodynamics, only thermodynamic equilibrium is considered

Basic Thermodynamics

Energy Technology Data Exchange (ETDEWEB)

Duthil, P [Orsay, IPN (France)

2014-07-01

The goal of this paper is to present a general thermodynamic basis that is useable in the context of superconductivity and particle accelerators. The first part recalls the purpose of thermodynamics and summarizes its important concepts. Some applications, from cryogenics to magnetic systems, are covered. In the context of basic thermodynamics, only thermodynamic equilibrium is considered.

Wind Turbine Test. Wind Matic WM 17S

DEFF Research Database (Denmark)

Friis Pedersen, Troels

The report describes standard measurements performed on a Wind-Matic WM 17S, 75 kW wind turbine. The measurements carried out and reported here comprises the power output, system efficiency, energy production, transmission efficiency, rotor power, rotor efficiency, air-brakes efficiency, structural...

Experimental thermodynamics experimental thermodynamics of non-reacting fluids

CERN Document Server

Neindre, B Le

2013-01-01

Experimental Thermodynamics, Volume II: Experimental Thermodynamics of Non-reacting Fluids focuses on experimental methods and procedures in the study of thermophysical properties of fluids. The selection first offers information on methods used in measuring thermodynamic properties and tests, including physical quantities and symbols for physical quantities, thermodynamic definitions, and definition of activities and related quantities. The text also describes reference materials for thermometric fixed points, temperature measurement under pressures, and pressure measurements. The publicatio

Thermodynamics of micellization from heat-capacity measurements.

Science.gov (United States)

Šarac, Bojan; Bešter-Rogač, Marija; Lah, Jurij

2014-06-23

Differential scanning calorimetry (DSC), the most important technique for studying the thermodynamics of structural transitions of biological macromolecules, is seldom used in quantitative thermodynamic studies of surfactant micellization/demicellization. The reason for this could be ascribed to an insufficient understanding of the temperature dependence of the heat capacity of surfactant solutions (DSC data) in terms of thermodynamics, which leads to problems with the design of experiments and interpretation of the output signals. We address these issues by careful design of DSC experiments performed with solutions of ionic and nonionic surfactants at various surfactant concentrations, and individual and global mass-action model analysis of the obtained DSC data. Our approach leads to reliable thermodynamic parameters of micellization for all types of surfactants, comparable with those obtained by using isothermal titration calorimetry (ITC). In summary, we demonstrate that DSC can be successfully used as an independent method to obtain temperature-dependent thermodynamic parameters for micellization. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A thermodynamic definition of protein domains.

Science.gov (United States)

Porter, Lauren L; Rose, George D

2012-06-12

Protein domains are conspicuous structural units in globular proteins, and their identification has been a topic of intense biochemical interest dating back to the earliest crystal structures. Numerous disparate domain identification algorithms have been proposed, all involving some combination of visual intuition and/or structure-based decomposition. Instead, we present a rigorous, thermodynamically-based approach that redefines domains as cooperative chain segments. In greater detail, most small proteins fold with high cooperativity, meaning that the equilibrium population is dominated by completely folded and completely unfolded molecules, with a negligible subpopulation of partially folded intermediates. Here, we redefine structural domains in thermodynamic terms as cooperative folding units, based on m-values, which measure the cooperativity of a protein or its substructures. In our analysis, a domain is equated to a contiguous segment of the folded protein whose m-value is largely unaffected when that segment is excised from its parent structure. Defined in this way, a domain is a self-contained cooperative unit; i.e., its cooperativity depends primarily upon intrasegment interactions, not intersegment interactions. Implementing this concept computationally, the domains in a large representative set of proteins were identified; all exhibit consistency with experimental findings. Specifically, our domain divisions correspond to the experimentally determined equilibrium folding intermediates in a set of nine proteins. The approach was also proofed against a representative set of 71 additional proteins, again with confirmatory results. Our reframed interpretation of a protein domain transforms an indeterminate structural phenomenon into a quantifiable molecular property grounded in solution thermodynamics.

Floating wind turbine system

Science.gov (United States)

Viterna, Larry A. (Inventor)

2009-01-01

A floating wind turbine system with a tower structure that includes at least one stability arm extending therefrom and that is anchored to the sea floor with a rotatable position retention device that facilitates deep water installations. Variable buoyancy for the wind turbine system is provided by buoyancy chambers that are integral to the tower itself as well as the stability arm. Pumps are included for adjusting the buoyancy as an aid in system transport, installation, repair and removal. The wind turbine rotor is located downwind of the tower structure to allow the wind turbine to follow the wind direction without an active yaw drive system. The support tower and stability arm structure is designed to balance tension in the tether with buoyancy, gravity and wind forces in such a way that the top of the support tower leans downwind, providing a large clearance between the support tower and the rotor blade tips. This large clearance facilitates the use of articulated rotor hubs to reduced damaging structural dynamic loads. Major components of the turbine can be assembled at the shore and transported to an offshore installation site.

Application of a Thermodynamic Concept for the Analysis of Structural Degradation of Soap Thickened Lubricating Greases

Directory of Open Access Journals (Sweden)

Erik Kuhn

2018-01-01

Full Text Available Lubricating greases are special lubricants with a wide range of application. The tribologically stressed grease is used as tribological system and finally modeled as an open thermodynamic system. This study investigated the phenomenon of self-optimization and applied to the process of shearing a grease. The conditions for self-optimization and the consequences of created dissipative structures are investigated according to the interpreted literature.

Solar wind and coronal structure near sunspot minimum: Pioneer and SMM observations from 1985-1987

International Nuclear Information System (INIS)

Mihalov, J.D.; Barnes, A.; Hundhausen, A.J.; Smith, E.J.

1990-01-01

The solar wind speeds observed in the outer heliosphere (20 to 40 AU heliocentric distance, approximately) by Pioneers 10 an 11, and at a heliocentric distance of 0.7 AU by the Pioneer Venus spacecraft, reveal a complex set of changes in the years near the recent sunspot minimum, 1985-1987. The pattern of recurrent solar wind streams, the long-term average speed, and the sector polarity of the interplanetary magnetic field all changed in a manner suggesting both a temporal variation, and a changing dependence on heliographic latitude. Coronal observations made from the Solar Maximum Mission spacecraft during the same epoch show a systematic variation in coronal structure and (by implication) the magnetic structure imposed on the expanding solar wind. These observations suggest interpretation of the solar wind speed variations in terms of the familiar model where the speed increases with distance from a nearly flat interplanetary current sheet (or with heliomagnetic latitude), and where this current sheet becomes aligned with the solar equatorial plane as sunspot minimum approaches, but deviates rapidly from that orientation after minimum. The authors confirm here that this basic organization of the solar wind speed persists in the outer heliosphere with an orientation of the neutral sheet consistent with that inferred at a heliocentric distance of a few solar radii, from the coronal observations

Development of Wind Operated Passive Evaporative Cooling Structures for Storage of Tomatoes

Directory of Open Access Journals (Sweden)

M. O. Sunmonu

2016-08-01

Full Text Available A Wind operated passive evaporative cooler was developed. Two cooling chambers were made with clay container (cylindrical and square shapes. These two containers were separately inserted inside bigger clay pot inter- spaced with clay soil of 7 cm (to form pot-in-pot and wall-in wall with the outside structure wrapped with jute sack. The soil and the jute sacks were wetted with salt solution. Five blades were constructed inside the cooling chambers with aluminium material which were connected with a shaft to a vane located on a wooden cover outside the cooling chamber. The vanes (made of aluminium were to be powered by the wind which in turn rotates the blades inside the cooling chamber. The total volume of 40500cm3 and storage capacity of 31500cm3 were recorded for the square structures while total volume of 31792.5cm3 and storage capacity of 24727.5cm3 were recorded for the cylindrical structures. During the test period, the average temperatures of 27.07oC, 27.09oC and 33.6oC were obtained for the pot-in-pot (cylindrical, wall-in-wall (square and the ambient respectively. The average relative humidity of 92.27%, 91.99% and 69.41% were obtained for the pot-in-pot (cylindrical, wall-in-wall (square and the ambient respectively. The average minimum and maximum wind speed recorded for the month of October was 2.5m/s and 2.6m/s respectively

Chemical thermodynamics. An introduction

Energy Technology Data Exchange (ETDEWEB)

Keszei, Ernoe [Budapest Univ. (Hungary). Dept. of Physical Chemistry

2012-07-01

Eminently suitable as a required textbook comprising complete material for or an undergraduate chemistry major course in chemical thermodynamics. Clearly explains details of formal derivations that students can easily follow and so master applied mathematical operations. Offers problems and solutions at the end of each chapter for self-test and self- or group study. This course-derived undergraduate textbook provides a concise explanation of the key concepts and calculations of chemical thermodynamics. Instead of the usual 'classical' introduction, this text adopts a straightforward postulatory approach that introduces thermodynamic potentials such as entropy and energy more directly and transparently. Structured around several features to assist students' understanding, Chemical Thermodynamics: - Develops applications and methods for the ready treatment of equilibria on a sound quantitative basis. - Requires minimal background in calculus to understand the text and presents formal derivations to the student in a detailed but understandable way. - Offers end-of-chapter problems (and answers) for self-testing and review and reinforcement, of use for self- or group study. This book is suitable as essential reading for courses in a bachelor and master chemistry program and is also valuable as a reference or textbook for students of physics, biochemistry and materials science.

Theoretical investigation of the structural stabilities, optoelectronic properties and thermodynamic characteristics of GaPxSb1-x ternary alloys

Science.gov (United States)

Oumelaz, F.; Nemiri, O.; Boumaza, A.; Ghemid, S.; Meradji, H.; Bin Omran, S.; El Haj Hassan, F.; Rai, D. P.; Khenata, R.

2018-06-01

In this theoretical study, we have investigated the structural, phase transition, electronic, thermodynamic and optical properties of GaPxSb1-x ternary alloys. Our calculations are performed with the WIEN2k code based on density functional theory using the full-potential linearized augmented plane wave method. For the electron exchange-correlation potential, a generalized gradient approximation within Wu-Cohen scheme is considered. The recently developed Tran-Blaha modified Becke-Johnson potential has also been used to improve the underestimated band gap. The structural properties, including the lattice constants, the bulk moduli and their pressure derivatives are in very good agreement with the available experimental data and theoretical results. Several structural phase transitions were studied here to establish the stable structure and to predict the phase transition under hydrostatic pressure. The computed transition pressure (Pt) of the material of our interest from the zinc blende (B3) to the rock salt (B1) phase has been determined and found to agree well with the experimental and theoretical data. The calculated band structure shows that GaSb binary compound and the ternary alloys are direct band gap semiconductors. Optical parameters such as the dielectric constants and the refractive indices are calculated and analyzed. The thermodynamic results are also interpreted and analyzed.

A new paradigm for intensity modification of tropical cyclones: thermodynamic impact of vertical wind shear on the inflow layer

Directory of Open Access Journals (Sweden)

M. Riemer

2010-04-01

Full Text Available An important roadblock to improved intensity forecasts for tropical cyclones (TCs is our incomplete understanding of the interaction of a TC with the environmental flow. In this paper we re-visit the canonical problem of a TC in vertical wind shear on an f-plane. A suite of numerical experiments is performed with intense TCs in moderate to strong vertical shear. We employ a set of simplified model physics – a simple bulk aerodynamic boundary layer scheme and "warm rain" microphysics – to foster better understanding of the dynamics and thermodynamics that govern the modification of TC intensity. In all experiments the TC is resilient to shear but significant differences in the intensity evolution occur.

The ventilation of the TC core with dry environmental air at mid-levels and the dilution of the upper-level warm core are two prevailing hypotheses for the adverse effect of vertical shear on storm intensity. Here we propose an alternative and arguably more effective mechanism how cooler and drier (lower θ_e air – "anti-fuel" for the TC power machine – can enter the core region of the TC. Strong and persistent, shear-induced downdrafts flux low θ_e air into the boundary layer from above, significantly depressing the θ_e values in the storm's inflow layer. Air with lower θ_e values enters the eyewall updrafts, considerably reducing eyewall θ_e values in the azimuthal mean. When viewed from the perspective of an idealised Carnot-cycle heat engine a decrease of storm intensity can thus be expected. Although the Carnot cycle model is – if at all – only valid for stationary and axisymmetric TCs, a close association of the downward transport of low θ_e into the boundary layer and the intensity evolution offers further evidence in support of our hypothesis.

The downdrafts that flush the boundary layer with low

Conditioning and Robustness of RNA Boltzmann Sampling under Thermodynamic Parameter Perturbations.

Science.gov (United States)

Rogers, Emily; Murrugarra, David; Heitsch, Christine

2017-07-25

Understanding how RNA secondary structure prediction methods depend on the underlying nearest-neighbor thermodynamic model remains a fundamental challenge in the field. Minimum free energy (MFE) predictions are known to be "ill conditioned" in that small changes to the thermodynamic model can result in significantly different optimal structures. Hence, the best practice is now to sample from the Boltzmann distribution, which generates a set of suboptimal structures. Although the structural signal of this Boltzmann sample is known to be robust to stochastic noise, the conditioning and robustness under thermodynamic perturbations have yet to be addressed. We present here a mathematically rigorous model for conditioning inspired by numerical analysis, and also a biologically inspired definition for robustness under thermodynamic perturbation. We demonstrate the strong correlation between conditioning and robustness and use its tight relationship to define quantitative thresholds for well versus ill conditioning. These resulting thresholds demonstrate that the majority of the sequences are at least sample robust, which verifies the assumption of sampling's improved conditioning over the MFE prediction. Furthermore, because we find no correlation between conditioning and MFE accuracy, the presence of both well- and ill-conditioned sequences indicates the continued need for both thermodynamic model refinements and alternate RNA structure prediction methods beyond the physics-based ones. Copyright © 2017. Published by Elsevier Inc.

Structure and thermodynamic properties of molten rubidium chloride

International Nuclear Information System (INIS)

Ballone, P.; Pastore, G.; Tosi, M.P.; Trieste Univ.

1984-02-01

Self-consistent calculations of partial pair distribution functions and thermodynamic properties are presented for molten RbCl in a non-polarizable-ion model and compared with computer simulation data. The theory, which is quantitatively very successful, hinges on an empirical evaluation of bridge diagrams including both excluded-volume effects and long-range Coulomb effects. (author)

Improved ADRC for a Maglev planar motor with a concentric winding structure

NARCIS (Netherlands)

Kou, Baoquan; Xing, Feng; Zhang, Chaoning; Zhang, L.; Zhou, Yiheng; Wang, Tiecheng

2016-01-01

In the semiconductor industry, positioning accuracy and acceleration are critical parameters. To improve the acceleration speed of a motor, this paper proposes the moving-coil maglev planar motor with a concentric winding structure. The coordinate system has been built for the multiple degrees of

Structural and thermodynamic basis of a frontometaphyseal dysplasia mutation in filamin A.

Science.gov (United States)

Ithychanda, Sujay S; Dou, Kevin; Robertson, Stephen P; Qin, Jun

2017-05-19

Filamin-mediated linkages between transmembrane receptors (TR) and the actin cytoskeleton are crucial for regulating many cytoskeleton-dependent cellular processes such as cell shape change and migration. A major TR binding site in the immunoglobulin repeat 21 (Ig21) of filamin is masked by the adjacent repeat Ig20, resulting in autoinhibition. The TR binding to this site triggers the relief of Ig20 and protein kinase A (PKA)-mediated phosphorylation of Ser-2152, thereby dynamically regulating the TR-actin linkages. A P2204L mutation in Ig20 reportedly cause frontometaphyseal dysplasia, a skeletal disorder with unknown pathogenesis. We show here that the P2204L mutation impairs a hydrophobic core of Ig20, generating a conformationally fluctuating molten globule-like state. Consequently, unlike in WT filamin, where PKA-mediated Ser-2152 phosphorylation is ligand-dependent, the P2204L mutant is readily accessible to PKA, promoting ligand-independent phosphorylation on Ser-2152. Strong TR peptide ligands from platelet GP1bα and G-protein-coupled receptor MAS effectively bound Ig21 by displacing Ig20 from autoinhibited WT filamin, but surprisingly, the capacity of these ligands to bind the P2204L mutant was much reduced despite the mutation-induced destabilization of the Ig20 structure that supposedly weakens the autoinhibition. Thermodynamic analysis indicated that compared with WT filamin, the conformationally fluctuating state of the Ig20 mutant makes Ig21 enthalpically favorable to bind ligand but with substantial entropic penalty, resulting in total higher free energy and reduced ligand affinity. Overall, our results reveal an unusual structural and thermodynamic basis for the P2204L-induced dysfunction of filamin and frontometaphyseal dysplasia disease. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Full-scale investigation of wind-induced vibrations of mast-arm traffic signal structures.

Science.gov (United States)

2014-08-01

Because of their inherent : fl : exibility and low damping ratios, cantilevered mast : - : arm : tra : ffi : c signal structures are suscepti : b : le to : wind : - : induced vibrations. : These vibrations : cause stru : ctural stresses and strains t...

The Thermodynamic Machinery of Life

CERN Document Server

Kurzynski, Michal

2006-01-01

Living organisms are open thermodynamic systems whose functional structure has developed and been kinetically frozen during the historical process of biological evolution. A thermodynamics of both nonequilibrium and complex systems is needed for their description. In this book, the foundations of such a thermodynamics are presented. Biological processes at the cellular level are considered as coupled chemical reactions and transport processes across internal and the cytoplasmic membrane. All these processes are catalyzed by specific enzymes hence the kinetics of enzymatic catalysis and its control are described here in detail. The coupling of several processes through a common enzyme is considered in the context of free energy or signal transduction. Special attention is paid to evidence for a rich stochastic internal dynamics of native proteins and its possible role in the control of enzyme activity and in the action of biological molecular machines.

Finite element structural study of the VGOT wind turbine

Energy Technology Data Exchange (ETDEWEB)

Otero, A.D. [University of Buenos Aires (Argentina). College of Engineering; Ponta, F.L. [University of Illinois, Urbana, IL (United States). Dept. of Theoretical and Applied Mechanics

2004-07-01

We analyse the implementation of the finite element method to simulate the structural behaviour of the blade-wagons of variable-geometry oval-trajectory (VGOT) Darrieus wind turbines. The key feature of a VGOT machine is that each blade, instead of rotating around a central vertical axis, slides over rails mounted on a wagon formed by a tubular reticulated structure supported by standard train bogies. The structure should be designed to absorb the efforts in the vertical and traverse directions of the railroad due to the aerodynamic loads, the weight of the components and the centrifugal acceleration along the curved tracks. We show some results for the tip deflection and the tip torsion of the blade, the frontal and lateral angle variations in the blade bottom and the Von Misses tensions of five sample beams, all of them in function of the trajectory-length parameter; and some examples of the deformed configuration of the reticulated structure. (author)

Surface thermodynamics

International Nuclear Information System (INIS)

Garcia-Moliner, F.

1975-01-01

Basic thermodynamics of a system consisting of two bulk phases with an interface. Solid surfaces: general. Discussion of experimental data on surface tension and related concepts. Adsorption thermodynamics in the Gibbsian scheme. Adsorption on inert solid adsorbents. Systems with electrical charges: chemistry and thermodynamics of imperfect crystals. Thermodynamics of charged surfaces. Simple models of charge transfer chemisorption. Adsorption heat and related concepts. Surface phase transitions

Black Hole Thermodynamics in an Undergraduate Thermodynamics Course.

Science.gov (United States)

Parker, Barry R.; McLeod, Robert J.

1980-01-01

An analogy, which has been drawn between black hole physics and thermodynamics, is mathematically broadened in this article. Equations similar to the standard partial differential relations of thermodynamics are found for black holes. The results can be used to supplement an undergraduate thermodynamics course. (Author/SK)

Thermodynamic tables to accompany Modern engineering thermodynamics

CERN Document Server

Balmer, Robert T

2011-01-01

This booklet is provided at no extra charge with new copies of Balmer's Modern Engineering Thermodynamics. It contains two appendices. Appendix C contains 40 thermodynamic tables, and Appendix D consists of 6 thermodynamic charts. These charts and tables are provided in a separate booklet to give instructors the flexibility of allowing students to bring the tables into exams. The booklet may be purchased separately if needed.

Thermodynamic Stability of Structure H Hydrates Based on the Molecular Properties of Large Guest Molecules

OpenAIRE

Tezuka, Kyoichi; Taguchi, Tatsuhiko; Alavi, Saman; Sum, Amadeu K.; Ohmura, Ryo

2012-01-01

This paper report analyses of thermodynamic stability of structure-H clathrate hydrates formed with methane and large guest molecules in terms of their gas phase molecular sizes and molar masses for the selection of a large guest molecule providing better hydrate stability. We investigated the correlation among the gas phase molecular sizes, the molar masses of large molecule guest substances, and the equilibrium pressures. The results suggest that there exists a molecular-size value for the ...

Wind Spires as an Alternative Energy Source

Energy Technology Data Exchange (ETDEWEB)

Majid Rashidi, Ph.D., P.E.

2012-10-30

This report discloses the design and development of an innovative wind tower system having an axisymmetric wind deflecting structure with a plurality of symmetrically mounted rooftop size wind turbines near the axisymmetric structure. The purpose of the wind deflecting structure is to increase the ambient wind speed that in turn results in an overall increase in the power capacity of the wind turbines. Two working prototypes were constructed and installed in the summer of 2009 and 2012 respectively. The system installed in the Summer of 2009 has a cylindrical wind deflecting structure, while the tower installed in 2012 has a spiral-shape wind deflecting structure. Each tower has 4 turbines, each rated at 1.65 KW Name-Plate-Rating. Before fabricating the full-size prototypes, computational fluid dynamic (CFD) analyses and scaled-down table-top models were used to predict the performance of the full-scale models. The performance results obtained from the full-size prototypes validated the results obtained from the computational models and those of the scaled-down models. The second prototype (spiral configuration) showed at a wind speed of 11 miles per hour (4.9 m/s) the power output of the system could reach 1,288 watt, when a typical turbine installation, with no wind deflecting structure, could produce only 200 watt by the same turbines at the same wind speed. At a wind speed of 18 miles per hour (8 m/sec), the spiral prototype produces 6,143 watt, while the power generated by the same turbines would be 1,412 watt in the absence of a wind deflecting structure under the same wind speed. Four US patents were allowed, and are in print, as the results of this project (US 7,540,706, US 7,679,209, US 7,845,904, and US 8,002,516).

Response of an ocean general circulation model to wind and ...

Indian Academy of Sciences (India)

The stretched-coordinate ocean general circulation model has been designed to study the observed variability due to wind and thermodynamic forcings. The model domain extends from 60°N to 60°S and cyclically continuous in the longitudinal direction. The horizontal resolution is 5° × 5° and 9 discrete vertical levels.

Wind loads and competition for light sculpt trees into self-similar structures.

Science.gov (United States)

Eloy, Christophe; Fournier, Meriem; Lacointe, André; Moulia, Bruno

2017-10-18

Trees are self-similar structures: their branch lengths and diameters vary allometrically within the tree architecture, with longer and thicker branches near the ground. These tree allometries are often attributed to optimisation of hydraulic sap transport and safety against elastic buckling. Here, we show that these allometries also emerge from a model that includes competition for light, wind biomechanics and no hydraulics. We have developed MECHATREE, a numerical model of trees growing and evolving on a virtual island. With this model, we identify the fittest growth strategy when trees compete for light and allocate their photosynthates to grow seeds, create new branches or reinforce existing ones in response to wind-induced loads. Strikingly, we find that selected trees species are self-similar and follow allometric scalings similar to those observed on dicots and conifers. This result suggests that resistance to wind and competition for light play an essential role in determining tree allometries.

Fragmentation increases wind disturbance impacts on forest structure and carbon stocks in a western Amazonian landscape.

Science.gov (United States)

Schwartz, Naomi B; Uriarte, María; DeFries, Ruth; Bedka, Kristopher M; Fernandes, Katia; Gutiérrez-Vélez, Victor; Pinedo-Vasquez, Miguel A

2017-09-01

Tropical second-growth forests could help mitigate climate change, but the degree to which their carbon potential is achieved will depend on exposure to disturbance. Wind disturbance is common in tropical forests, shaping structure, composition, and function, and influencing successional trajectories. However, little is known about the impacts of extreme winds on second-growth forests in fragmented landscapes, though these ecosystems are often located in mosaics of forest, pasture, cropland, and other land cover types. Indirect evidence suggests that fragmentation increases risk of wind damage in tropical forests, but no studies have found such impacts following severe storms. In this study, we ask whether fragmentation and forest type (old vs. second growth) were associated with variation in wind damage after a severe convective storm in a fragmented production landscape in western Amazonia. We applied linear spectral unmixing to Landsat 8 imagery from before and after the storm, and combined it with field observations of damage to map wind effects on forest structure and biomass. We also used Landsat 8 imagery to map land cover with the goals of identifying old- and second-growth forest and characterizing fragmentation. We used these data to assess variation in wind disturbance across 95,596 ha of forest, distributed over 6,110 patches. We find that fragmentation is significantly associated with wind damage, with damage severity higher at forest edges and in edgier, more isolated patches. Damage was also more severe in old-growth than in second-growth forests, but this effect was weaker than that of fragmentation. These results illustrate the importance of considering landscape context in planning tropical forest restoration and natural regeneration projects. Assessments of long-term carbon sequestration potential need to consider spatial variation in disturbance exposure. Where risk of extreme winds is high, minimizing fragmentation and isolation could increase

Smart Sensor System for Structural Condition Monitoring of Wind Turbines: 30 May 2002--30 April 2006

Energy Technology Data Exchange (ETDEWEB)

Schulz, M. J.; Sundaresan, M. J.

2006-08-01

This report describes the efforts of the University of Cincinnati, North Carolina A&T State University, and NREL to develop a structural neural system for structural health monitoring of wind turbine blades.

Optimization of offshore wind turbine support structures using analytical gradient-based method

OpenAIRE

Chew, Kok Hon; Tai, Kang; Ng, E.Y.K.; Muskulus, Michael

2015-01-01

Design optimization of the offshore wind turbine support structure is an expensive task; due to the highly-constrained, non-convex and non-linear nature of the design problem. This report presents an analytical gradient-based method to solve this problem in an efficient and effective way. The design sensitivities of the objective and constraint functions are evaluated analytically while the optimization of the structure is performed, subject to sizing, eigenfrequency, extreme load an...

Structural Load Analysis of a Wind Turbine under Pitch Actuator and Controller Faults

International Nuclear Information System (INIS)

Etemaddar, Mahmoud; Gao, Zhen; Moan, Torgeir

2014-01-01

In this paper, we investigate the characteristics of a wind turbine under blade pitch angle and shaft speed sensor faults as well as pitch actuator faults. A land-based NREL 5MW variable speed pitch reg- ulated wind turbine is considered as a reference. The conventional collective blade pitch angle controller strategy with independent pitch actuators control is used for load reduction. The wind turbine class is IEC-BII. The main purpose is to investigate the severity of end effects on structural loads and responses and consequently identify the high-risk components according to the type and amplitude of fault using a servo-aero-elastic simulation code, HAWC2. Both transient and steady state effects of faults are studied. Such information is useful for wind turbine fault detection and identification as well as system reliability analysis. Results show the effects of faults on wind turbine power output and responses. Pitch sensor faults mainly affects the vibration of shaft main bearing, while generator power and aerodynamic thrust are not changed significantly, due to independent pitch actuator control of three blades. Shaft speed sensor faults can seriously affect the generator power and aerodynamic thrust. Pitch actuator faults can result in fully pitching of the blade, and consequently rotor stops due to negative aerodynamic torque

Measurements of Coastal Winds and Temperature. Sensor Evaluation, Data Quality, and Wind Structures

Energy Technology Data Exchange (ETDEWEB)

Heggem, Tore

1997-12-31

The long Norwegian coastline has excellent sites for wind power production. This thesis contains a documentation of a measurement station for maritime meteorological data at the coast of Mid-Norway, and analysis of temperature and wind data. It discusses experience with different types of wind speed and wind direction sensors. Accurate air temperature measurements are essential to obtain information about the stability of the atmosphere, and a sensor based on separately calibrated thermistors is described. The quality of the calibrations and the measurements is discussed. A database built up from measurements from 1982 to 1995 has been available. The data acquisition systems and the programs used to read the data are described, as well as data control and gap-filling methods. Then basic statistics from the data like mean values and distributions are given. Quality control of the measurements with emphasis on shade effects from the masts and direction alignment is discussed. The concept of atmospheric stability is discussed. The temperature profile tends to change from unstable to slightly stable as maritime winds passes land. Temperature spectra based on two-year time series are presented. Finally, there is a discussion of long-term turbulence spectra calculated from 14 years of measurements. The lack of a gap in the one-hour region of the spectra is explained from the overweight of unstable atmospheric conditions in the dominating maritime wind. Examples of time series with regular 40-minute cycles, and corresponding effect spectra are given. The validity of local lapse rate as a criterion of atmospheric stability is discussed. 34 refs., 86 figs., 11 tabs.

Measurements of Coastal Winds and Temperature. Sensor Evaluation, Data Quality, and Wind Structures

Energy Technology Data Exchange (ETDEWEB)

Heggem, Tore

1998-12-31

The long Norwegian coastline has excellent sites for wind power production. This thesis contains a documentation of a measurement station for maritime meteorological data at the coast of Mid-Norway, and analysis of temperature and wind data. It discusses experience with different types of wind speed and wind direction sensors. Accurate air temperature measurements are essential to obtain information about the stability of the atmosphere, and a sensor based on separately calibrated thermistors is described. The quality of the calibrations and the measurements is discussed. A database built up from measurements from 1982 to 1995 has been available. The data acquisition systems and the programs used to read the data are described, as well as data control and gap-filling methods. Then basic statistics from the data like mean values and distributions are given. Quality control of the measurements with emphasis on shade effects from the masts and direction alignment is discussed. The concept of atmospheric stability is discussed. The temperature profile tends to change from unstable to slightly stable as maritime winds passes land. Temperature spectra based on two-year time series are presented. Finally, there is a discussion of long-term turbulence spectra calculated from 14 years of measurements. The lack of a gap in the one-hour region of the spectra is explained from the overweight of unstable atmospheric conditions in the dominating maritime wind. Examples of time series with regular 40-minute cycles, and corresponding effect spectra are given. The validity of local lapse rate as a criterion of atmospheric stability is discussed. 34 refs., 86 figs., 11 tabs.

Thermodynamic database for proteins: features and applications.

Science.gov (United States)

Gromiha, M Michael; Sarai, Akinori

2010-01-01

We have developed a thermodynamic database for proteins and mutants, ProTherm, which is a collection of a large number of thermodynamic data on protein stability along with the sequence and structure information, experimental methods and conditions, and literature information. This is a valuable resource for understanding/predicting the stability of proteins, and it can be accessible at http://www.gibk26.bse.kyutech.ac.jp/jouhou/Protherm/protherm.html . ProTherm has several features including various search, display, and sorting options and visualization tools. We have analyzed the data in ProTherm to examine the relationship among thermodynamics, structure, and function of proteins. We describe the progress on the development of methods for understanding/predicting protein stability, such as (i) relationship between the stability of protein mutants and amino acid properties, (ii) average assignment method, (iii) empirical energy functions, (iv) torsion, distance, and contact potentials, and (v) machine learning techniques. The list of online resources for predicting protein stability has also been provided.

RBI Optimization of Offshore Wind Turbines

DEFF Research Database (Denmark)

Ramírez, José G. Rangel; Sørensen, John Dalsgaard

2009-01-01

methods for oil & gas installations, a framework for optimal inspection and maintenance planning of offshore wind turbines is presented. Special aspects for offshore wind turbines considered are the fatigue loading characteristics where usually the wind loading are dominating the wave loading, wake......Wind turbines for electricity production have increased significantly the last years both in production capability and size. This development is expected to continue also in the coming years. Offshore wind turbines with an electricity production of 5-10 MW are planned. Typically, the wind turbine...... support structure is a steel structure consisting of a tower and a monopile, tripod or jacket type foundation. This paper considers aspects of inspection and maintenance planning of fatigue prone details in jacket and tripod type of wind turbine support structures. Based on risk-based inspection planning...

Progress in wind tunnel experimental techniques for wind turbine?

Institute of Scientific and Technical Information of China (English)

Jingping XIAO; Li CHEN; Qiang WANG; Qiao WANG

2016-01-01

Based on the unsteady aerodynamics experiment (UAE) phase VI and the model experiment in controlled conditions (MEXICO) projects and the related research carried out in China Aerodynamic Research and Development Center (CARDC), the recent progress in the wind tunnel experimental techniques for the wind turbine is sum-marized. Measurement techniques commonly used for di?erent types of wind tunnel ex-periments for wind turbine are reviewed. Important research achievements are discussed, such as the wind tunnel disturbance, the equivalence of the airfoil in?ow condition, the three-dimensional (3D) e?ect, the dynamic in?ow in?uence, the ?ow ?eld structure, and the vortex induction. The corresponding research at CARDC and some ideas on the large wind turbine are also introduced.

On the structural behaviour of variable-geometry oval-trajectory Darrieus wind turbines

Energy Technology Data Exchange (ETDEWEB)

Otero, A.D. [College of Engineering, University of Buenos Aires, Paseo Colon 850, Buenos Aires C1063ACV (Argentina); Ponta, F.L. [Department of Mechanical Engineering - Engineering Mechanics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 (United States)

2009-03-15

We developed a computational model based on a finite-element mixed formulation with quadratic isoparametric beam elements. We applied this model to the analysis of a blade-wagon: a novel structure characteristic of an innovative concept in wind-power called VGOT Darrieus turbine. We studied the structural behaviour of its main components: chassis, suspension and blade, using combinations of beam/bar elements in an appropriate assembling. We defined a set of parameters to characterize the structural behaviour which help to understand the contribution of the different components and assist the process of redesign. (author)

Thermodynamic and structural signatures of water-driven methane-methane attraction in coarse-grained mW water.

Science.gov (United States)

Song, Bin; Molinero, Valeria

2013-08-07

Hydrophobic interactions are responsible for water-driven processes such as protein folding and self-assembly of biomolecules. Microscopic theories and molecular simulations have been used to study association of a pair of methanes in water, the paradigmatic example of hydrophobic attraction, and determined that entropy is the driving force for the association of the methane pair, while the enthalpy disfavors it. An open question is to which extent coarse-grained water models can still produce correct thermodynamic and structural signatures of hydrophobic interaction. In this work, we investigate the hydrophobic interaction between a methane pair in water at temperatures from 260 to 340 K through molecular dynamics simulations with the coarse-grained monatomic water model mW. We find that the coarse-grained model correctly represents the free energy of association of the methane pair, the temperature dependence of free energy, and the positive change in entropy and enthalpy upon association. We investigate the relationship between thermodynamic signatures and structural order of water through the analysis of the spatial distribution of the density, energy, and tetrahedral order parameter Qt of water. The simulations reveal an enhancement of tetrahedral order in the region between the first and second hydration shells of the methane molecules. The increase in tetrahedral order, however, is far from what would be expected for a clathrate-like or ice-like shell around the solutes. This work shows that the mW water model reproduces the key signatures of hydrophobic interaction without long ranged electrostatics or the need to be re-parameterized for different thermodynamic states. These characteristics, and its hundred-fold increase in efficiency with respect to atomistic models, make mW a promising water model for studying water-driven hydrophobic processes in more complex systems.

Wind Farms: Modeling and Control

DEFF Research Database (Denmark)

Soleimanzadeh, Maryam

2012-01-01

is minimized. The controller is practically feasible. Yet, the results on load reduction in this approach are not very significant. In the second strategy, the wind farm control problem has been divided into below rated and above rated wind speed conditions. In the above rated wind speed pitch angle and power....... Distributed controller design commences with formulating the problem, where a structured matrix approach has been put in to practice. Afterwards, an H2 control problem is implemented to obtain the controller dynamics for a wind farm such that the structural loads on wind turbines are minimized.......The primary purpose of this work is to develop control algorithms for wind farms to optimize the power production and augment the lifetime of wind turbines in wind farms. In this regard, a dynamical model for wind farms was required to be the basis of the controller design. In the first stage...

Preliminary design of offshore wind turbine support structures : The importance of proper mode shape estimation

NARCIS (Netherlands)

Van der Male, P.

2013-01-01

Offshore wind turbines are highly exposed to timevarying loads. For support structures, estimation of the fatigue damage during the lifetime of the structure is an essential design aspect. This already applies for the preliminary design stage. In determining the dynamic amplification in the

Life as Thermodynamic Evidence of Algorithmic Structure in Natural Environments

Directory of Open Access Journals (Sweden)

David A. Rosenblueth

2012-11-01

Full Text Available In evolutionary biology, attention to the relationship between stochastic organisms and their stochastic environments has leaned towards the adaptability and learning capabilities of the organisms rather than toward the properties of the environment. This article is devoted to the algorithmic aspects of the environment and its interaction with living organisms. We ask whether one may use the fact of the existence of life to establish how far nature is removed from algorithmic randomness. The paper uses a novel approach to behavioral evolutionary questions, using tools drawn from information theory, algorithmic complexity and the thermodynamics of computation to support an intuitive assumption about the near optimal structure of a physical environment that would prove conducive to the evolution and survival of organisms, and sketches the potential of these tools, at present alien to biology, that could be used in the future to address different and deeper questions. We contribute to the discussion of the algorithmic structure of natural environments and provide statistical and computational arguments for the intuitive claim that living systems would not be able to survive in completely unpredictable environments, even if adaptable and equipped with storage and learning capabilities by natural selection (brain memory or DNA.

Ab initio thermodynamic model for magnesium carbonates and hydrates.

Science.gov (United States)

Chaka, Anne M; Felmy, Andrew R

2014-09-04

An ab initio thermodynamic framework for predicting properties of hydrated magnesium carbonate minerals has been developed using density-functional theory linked to macroscopic thermodynamics through the experimental chemical potentials for MgO, water, and CO2. Including semiempirical dispersion via the Grimme method and small corrections to the generalized gradient approximation of Perdew, Burke, and Ernzerhof for the heat of formation yields a model with quantitative agreement for the benchmark minerals brucite, magnesite, nesquehonite, and hydromagnesite. The model shows how small differences in experimental conditions determine whether nesquehonite, hydromagnesite, or magnesite is the result of laboratory synthesis from carbonation of brucite, and what transformations are expected to occur on geological time scales. Because of the reliance on parameter-free first-principles methods, the model is reliably extensible to experimental conditions not readily accessible to experiment and to any mineral composition for which the structure is known or can be hypothesized, including structures containing defects, substitutions, or transitional structures during solid state transformations induced by temperature changes or processes such as water, CO2, or O2 diffusion. Demonstrated applications of the ab initio thermodynamic framework include an independent means to evaluate differences in thermodynamic data for lansfordite, predicting the properties of Mg analogues of Ca-based hydrated carbonates monohydrocalcite and ikaite, which have not been observed in nature, and an estimation of the thermodynamics of barringtonite from the stoichiometry and a single experimental observation.

Co-operative intra-protein structural response due to protein-protein complexation revealed through thermodynamic quantification: study of MDM2-p53 binding.

Science.gov (United States)

Samanta, Sudipta; Mukherjee, Sanchita

2017-10-01

The p53 protein activation protects the organism from propagation of cells with damaged DNA having oncogenic mutations. In normal cells, activity of p53 is controlled by interaction with MDM2. The well understood p53-MDM2 interaction facilitates design of ligands that could potentially disrupt or prevent the complexation owing to its emergence as an important objective for cancer therapy. However, thermodynamic quantification of the p53-peptide induced structural changes of the MDM2-protein remains an area to be explored. This study attempts to understand the conformational free energy and entropy costs due to this complex formation from the histograms of dihedral angles generated from molecular dynamics simulations. Residue-specific quantification illustrates that, hydrophobic residues of the protein contribute maximum to the conformational thermodynamic changes. Thermodynamic quantification of structural changes of the protein unfold the fact that, p53 binding provides a source of inter-element cooperativity among the protein secondary structural elements, where the highest affected structural elements (α2 and α4) found at the binding site of the protein affects faraway structural elements (β1 and Loop1) of the protein. The communication perhaps involves water mediated hydrogen bonded network formation. Further, we infer that in inhibitory F19A mutation of P53, though Phe19 is important in the recognition process, it has less prominent contribution in the stability of the complex. Collectively, this study provides vivid microscopic understanding of the interaction within the protein complex along with exploring mutation sites, which will contribute further to engineer the protein function and binding affinity.

Co-operative intra-protein structural response due to protein-protein complexation revealed through thermodynamic quantification: study of MDM2-p53 binding

Science.gov (United States)

Samanta, Sudipta; Mukherjee, Sanchita

2017-10-01

The p53 protein activation protects the organism from propagation of cells with damaged DNA having oncogenic mutations. In normal cells, activity of p53 is controlled by interaction with MDM2. The well understood p53-MDM2 interaction facilitates design of ligands that could potentially disrupt or prevent the complexation owing to its emergence as an important objective for cancer therapy. However, thermodynamic quantification of the p53-peptide induced structural changes of the MDM2-protein remains an area to be explored. This study attempts to understand the conformational free energy and entropy costs due to this complex formation from the histograms of dihedral angles generated from molecular dynamics simulations. Residue-specific quantification illustrates that, hydrophobic residues of the protein contribute maximum to the conformational thermodynamic changes. Thermodynamic quantification of structural changes of the protein unfold the fact that, p53 binding provides a source of inter-element cooperativity among the protein secondary structural elements, where the highest affected structural elements (α2 and α4) found at the binding site of the protein affects faraway structural elements (β1 and Loop1) of the protein. The communication perhaps involves water mediated hydrogen bonded network formation. Further, we infer that in inhibitory F19A mutation of P53, though Phe19 is important in the recognition process, it has less prominent contribution in the stability of the complex. Collectively, this study provides vivid microscopic understanding of the interaction within the protein complex along with exploring mutation sites, which will contribute further to engineer the protein function and binding affinity.

Measuring and modelling of the wind on the scale of tall wind turbines

DEFF Research Database (Denmark)

Floors, Rogier Ralph

The air flow in the lower atmosphere on the spatial scale of the modern wind turbines is studied. Because wind turbines are nowadays often taller than 100 m, the validity of current analytical and numerical atmospheric models has to be evaluated and more knowledge about the structure of the atmos......The air flow in the lower atmosphere on the spatial scale of the modern wind turbines is studied. Because wind turbines are nowadays often taller than 100 m, the validity of current analytical and numerical atmospheric models has to be evaluated and more knowledge about the structure...

Thermodynamic and structural models compared with the initial dissolution rates of open-quotes SONclose quotes glass samples

International Nuclear Information System (INIS)

Tovena, I.; Advocat, T.; Ghaleb, D.; Vernaz, E.; Larche, F.

1994-01-01

The experimentally determined initial dissolution rate R 0 of nuclear glass was correlated with thermodynamic parameters and structural parameters. The initial corrosion rates of six open-quotes R7T7close quotes glass samples measured at 100 degrees C in a Soxhlet device were correlated with the glass free hydration energy and the glass formation enthalpy. These correlations were then tested with a group of 26 SON glasses selected for their wide diversity of compositions. The thermodynamic models provided a satisfactory approximation of the initial dissolution rate determined under Soxhlet conditions for SON glass samples that include up to 15 wt% of boron and some alumina. Conversely, these models are inaccurate if the boron concentration exceeds 15 wt% and the glass contains no alumina. Possible correlations between R 0 and structural parameters, such as the boron coordination number and the number of nonbridging oxygen atoms, were also investigated. The authors show that R 0 varies inversely with the number of 4-coordinate boron atoms; conversely, the results do not substantiate published reports of a correlation between R 0 and the number of nonbridging oxygen atoms

Correlation between sequence conservation and structural thermodynamics of microRNA precursors from human, mouse, and chicken genomes

Directory of Open Access Journals (Sweden)

Wang Shengqi

2010-10-01

Full Text Available Abstract Background Previous studies have shown that microRNA precursors (pre-miRNAs have considerably more stable secondary structures than other native RNAs (tRNA, rRNA, and mRNA and artificial RNA sequences. However, pre-miRNAs with ultra stable secondary structures have not been investigated. It is not known if there is a tendency in pre-miRNA sequences towards or against ultra stable structures? Furthermore, the relationship between the structural thermodynamic stability of pre-miRNA and their evolution remains unclear. Results We investigated the correlation between pre-miRNA sequence conservation and structural stability as measured by adjusted minimum folding free energies in pre-miRNAs isolated from human, mouse, and chicken. The analysis revealed that conserved and non-conserved pre-miRNA sequences had structures with similar average stabilities. However, the relatively ultra stable and unstable pre-miRNAs were more likely to be non-conserved than pre-miRNAs with moderate stability. Non-conserved pre-miRNAs had more G+C than A+U nucleotides, while conserved pre-miRNAs contained more A+U nucleotides. Notably, the U content of conserved pre-miRNAs was especially higher than that of non-conserved pre-miRNAs. Further investigations showed that conserved and non-conserved pre-miRNAs exhibited different structural element features, even though they had comparable levels of stability. Conclusions We proposed that there is a correlation between structural thermodynamic stability and sequence conservation for pre-miRNAs from human, mouse, and chicken genomes. Our analyses suggested that pre-miRNAs with relatively ultra stable or unstable structures were less favoured by natural selection than those with moderately stable structures. Comparison of nucleotide compositions between non-conserved and conserved pre-miRNAs indicated the importance of U nucleotides in the pre-miRNA evolutionary process. Several characteristic structural elements were

Structural and functional plasticity specific to musical training with wind instruments

Directory of Open Access Journals (Sweden)

Uk-Su eChoi

2015-10-01

Full Text Available Numerous neuroimaging studies have shown structural and functional changes resulting from musical training. Among these studies, changes in primary sensory areas are mostly related to motor functions. In this study, we looked for some similar functional and structural changes in other functional modalities, such as somatosensory function, by examining the effects of musical training with wind instruments. We found significant changes in two aspects of neuroplasticity, cortical thickness and resting-state neuronal networks. A group of subjects with several years of continuous musical training and who are currently playing in university wind ensembles showed differences in cortical thickness in lip- and tongue-related brain areas versus non-music playing subjects. Cortical thickness in lip-related brain areas was significantly thicker and that in tongue-related areas was significantly thinner in the music playing group compared with that in the non-music playing group. Association analysis of lip-related areas in the music playing group showed that the increase in cortical thickness was caused by musical training. In addition, seed-based correlation analysis showed differential activation in the precentral gyrus and supplementary motor areas between the music and non-music playing groups. These results suggest that high-intensity training with specific musical instruments could induce structural changes in related anatomical areas and could also generate a new functional neuronal network in the brain.

Probabilistic Fatigue Analysis of Jacket Support Structures for Offshore Wind Turbines Exemplified on Tubular Joints

OpenAIRE

Kelma, Sebastian; Schaumann, Peter

2015-01-01

The design of offshore wind turbines is usually based on the semi-probabilistic safety concept. Using probabilistic methods, the aim is to find an advanced structural design of OWTs in order to improve safety and reduce costs. The probabilistic design is exemplified on tubular joints of a jacket substructure. Loads and resistance are considered by their respective probability distributions. Time series of loads are generated by fully-coupled numerical simulation of the offshore wind turbine. ...

Design methods to assess the resistance of Offshore wind Turbine Structures impacted by a ship

OpenAIRE

Echeverry Jaramillo, Sara; Le Sourne, Hervé; Bela, Andreea; Pire, Timothée; Rigo, Philippe

2017-01-01

The dynamic modes of jacket, monopile and Floating offshore wind turbines (FOWT) after a collision event are presented. The authors have developed simplified analytical formulations based on plastic limit analysis to assess the resistance of an offshore wind turbine jacket impacted by a ship. For the case of collisions with monopile foundations and FOWT, the crushing behavior and structure dynamics are studied by means of finite element simulations. Numerical results for both monopile and flo...

Wind lens technology and its application to wind and water turbine and beyond

OpenAIRE

Ohya Yuji; Karasudani Takashi; Nagai Tomoyuki; Watanabe Koichi

2017-01-01

Wind lens is a new type of wind power system consisting of a simple brimmed ring structure that surrounds the rotor causing greater wind to pass through the turbine. As a consequence, the turbine's efficiency of capturing energy from the wind gets dramatically increased. A Wind lens turbine can generate 2–5 times the power of an existing wind turbine given at the same rotor diameter and incoming wind speed. This fluid dynamical effect is also effective in the water. We have developed 1–3 kW W...

Structures of PEP–PEO Block Copolymer Micelles: Effects of Changing Solvent and PEO Length and Comparison to a Thermodynamic Model

DEFF Research Database (Denmark)

Jensen, Grethe Vestergaard; Shi, Qing; Deen, G. Roshan

2012-01-01

Structures of poly(ethylene propylene)–poly(ethylene oxide) (PEP–PEO) block copolymer micelles were determined from small-angle X-ray scattering and static light scattering and compared to predictions from a thermodynamic model. Both the corona block length and the solvent water–ethanol ratio were...... changed, leading to a thorough test of this model. With increasing ethanol fraction, the PEP core–solvent interfacial tension decreases, and the solvent quality for PEO changes. The weight-average block masses were 5.0 kDa for PEP and 2.8–49 kDa for PEO. For the lowest PEO molar mass and samples in pure...... water (except for the highest PEO molar mass), the micelles were cylindrical; for other conditions they were spherical. The structural parameters can be reasonably well described by the thermodynamic model by Zhulina et al. [Macromolecules2005, 38 (12), 5330–5351]; however, they have a stronger...

Offshore wind energy developments

DEFF Research Database (Denmark)

Stolpe, Mathias; Buhl, Thomas; Sumer, B. Mutlu

2014-01-01

This chapter will give a brief overview of a few of the activities within offshore wind energy research, specifically 1) Support structure optimization, 2) Blade coatings for wind turbines; 3) Scour protection of foundations, 4) Offshore HVDC and 5) Offshore wind services....

Thermodynamic fingerprints of ligand binding to human telomeric G-quadruplexes

OpenAIRE

Bon?ina, Matja?; Podlipnik, ?rtomir; Piantanida, Ivo; Eilmes, Julita; Teulade-Fichou, Marie-Paule; Vesnaver, Gorazd; Lah, Jurij

2015-01-01

Thermodynamic studies of ligand binding to human telomere (ht) DNA quadruplexes, as a rule, neglect the involvement of various ht-DNA conformations in the binding process. Therefore, the thermodynamic driving forces and the mechanisms of ht-DNA G-quadruplex-ligand recognition remain poorly understood. In this work we characterize thermodynamically and structurally binding of netropsin (Net), dibenzotetraaza[14]annulene derivatives (DP77, DP78), cationic porphyrin (TMPyP4) and two bisquinolini...

Wind power takes off. A structural revolution; Vindkraften tar fart. En strukturell revolution

Energy Technology Data Exchange (ETDEWEB)

Staahl, Benjamin; Lilliecreutz, Johan

2009-03-15

is still important growth opportunities in the future. It is still a relatively open market - which also can have large impact on the management of the electricity market as a whole. Wind power has reached a 'Tipping point' and growth will continue to be very strong. A dominant design has been established where the majority of development can be carried out, which in itself is accelerating the development. The growing market attracts new entrants, for example from China. Wind power contributes to a structural overhaul of the electricity market. Expansion of wind power changes the conditions of the electricity market as a whole. Traditionally, wind power was owned and operated on a smaller scale by local actors. Although the power companies are now taking a more active role, wind power is still suitable for small scale electricity generation, modular expansion and power generation close to the consumer. It allows for partial or full self-sufficiency for forestry and agriculture enterprises, associations and individual citizens. They can also become net producers of electricity. This can mean a big change long-term electricity market as a whole, particularly as some other renewable energy sources share this characteristic

THERMODYNAMIC PARAMETERS OF LEAD SULFIDE CRYSTALS IN THE CUBIC PHASE

Directory of Open Access Journals (Sweden)

T. O. Parashchuk

2016-07-01

Full Text Available Geometric and thermodynamic parameters of cubic PbS crystals were obtained using the computer calculations of the thermodynamic parameters within density functional theory method DFT. Cluster models for the calculation based on the analysis of the crystal and electronic structure. Temperature dependence of energy ΔE and enthalpy ΔH, Gibbs free energy ΔG, heat capacity at constant pressure CP and constant volume CV, entropy ΔS were determined on the basis of ab initio calculations of the crystal structure of molecular clusters. Analytical expressions of temperature dependences of thermodynamic parameters which were approximated with quantum-chemical calculation points have been presented. Experimental results compared with theoretically calculated data.

Thermodynamic Presynthetic Considerations for Ring-Opening Polymerization.

Science.gov (United States)

Olsén, Peter; Odelius, Karin; Albertsson, Ann-Christine

2016-03-14

The need for polymers for high-end applications, coupled with the desire to mimic nature's macromolecular machinery fuels the development of innovative synthetic strategies every year. The recently acquired macromolecular-synthetic tools increase the precision and enable the synthesis of polymers with high control and low dispersity. However, regardless of the specificity, the polymerization behavior is highly dependent on the monomeric structure. This is particularly true for the ring-opening polymerization of lactones, in which the ring size and degree of substitution highly influence the polymer formation properties. In other words, there are two important factors to contemplate when considering the particular polymerization behavior of a specific monomer: catalytic specificity and thermodynamic equilibrium behavior. This perspective focuses on the latter and undertakes a holistic approach among the different lactones with regard to the equilibrium thermodynamic polymerization behavior and its relation to polymer synthesis. This is summarized in a monomeric overview diagram that acts as a presynthetic directional cursor for synthesizing highly specific macromolecules; the means by which monomer equilibrium conversion relates to starting temperature, concentration, ring size, degree of substitution, and its implications for polymerization behavior are discussed. These discussions emphasize the importance of considering not only the catalytic system but also the monomer size and structure relations to thermodynamic equilibrium behavior. The thermodynamic equilibrium behavior relation with a monomer structure offers an additional layer of complexity to our molecular toolbox and, if it is harnessed accordingly, enables a powerful route to both monomer formation and intentional macromolecular design.

Structural health and prognostics management for offshore wind turbines :

Energy Technology Data Exchange (ETDEWEB)

Griffith, Daniel; Resor, Brian Ray; White, Jonathan Randall; Paquette, Joshua A.; Yoder, Nathanael C.

2012-12-01

Operations and maintenance costs for offshore wind plants are expected to be significantly higher than the current costs for onshore plants. One way in which these costs may be able to be reduced is through the use of a structural health and prognostic management system as part of a condition based maintenance paradigm with smart load management. To facilitate the creation of such a system a multiscale modeling approach has been developed to identify how the underlying physics of the system are affected by the presence of damage and how these changes manifest themselves in the operational response of a full turbine. The developed methodology was used to investigate the effects of a candidate blade damage feature, a trailing edge disbond, on a 5-MW offshore wind turbine and the measurements that demonstrated the highest sensitivity to the damage were the local pitching moments around the disbond. The multiscale method demonstrated that these changes were caused by a local decrease in the blades torsional stiffness due to the disbond, which also resulted in changes in the blades local strain field. Full turbine simulations were also used to demonstrate that derating the turbine power by as little as 5% could extend the fatigue life of a blade by as much as a factor of 3. The integration of the health monitoring information, conceptual repair cost versus damage size information, and this load management methodology provides an initial roadmap for reducing operations and maintenance costs for offshore wind farms while increasing turbine availability and overall profit.

Deconstructing thermodynamic parameters of a coupled system from site-specific observables.

Science.gov (United States)

Chowdhury, Sandipan; Chanda, Baron

2010-11-02

Cooperative interactions mediate information transfer between structural domains of a protein molecule and are major determinants of protein function and modulation. The prevalent theories to understand the thermodynamic origins of cooperativity have been developed to reproduce the complex behavior of a global thermodynamic observable such as ligand binding or enzyme activity. However, in most cases the measurement of a single global observable cannot uniquely define all the terms that fully describe the energetics of the system. Here we establish a theoretical groundwork for analyzing protein thermodynamics using site-specific information. Our treatment involves extracting a site-specific parameter (defined as χ value) associated with a structural unit. We demonstrate that, under limiting conditions, the χ value is related to the direct interaction terms associated with the structural unit under observation and its intrinsic activation energy. We also introduce a site-specific interaction energy term (χ(diff)) that is a function of the direct interaction energy of that site with every other site in the system. When combined with site-directed mutagenesis and other molecular level perturbations, analyses of χ values of site-specific observables may provide valuable insights into protein thermodynamics and structure.

Thermodynamic properties of a quasi-harmonic model for ferroelectric transitions

International Nuclear Information System (INIS)

Mkam Tchouobiap, S E; Mashiyama, H

2011-01-01

Within a framework of a quasi-harmonic model for quantum particles in a local potential of the double Morse type and within the mean-field approximation for interactions between particles, we investigate the thermodynamic properties of ferroelectric materials. A quantum thermodynamic treatment gives analytic expressions for the internal energy, the entropy, the specific heat, and the static susceptibility. The calculated thermodynamic characteristics are studied as a function of temperature and energy barrier, where it is shown that at the proper choice of the theory parameters, particularly the energy barrier, the model system exhibits characteristic features of either second-order tricritical or first-order phase transitions. Our results indicate that the barrier energy seems to be an important criterion for the character of the structural phase transition. The influence of quantum fluctuations manifested on zero-point energy on the phase transition and thermodynamic properties is analyzed and discussed. This leads to several quantum effects, including the existence of a saturation regime at low temperatures, where the order parameter saturates giving thermodynamic saturation of the calculated thermodynamic quantities. It is found that both quantum effects and energy barrier magnitude have an important influence on the thermodynamic properties of the ferroelectric materials and on driving the phase transition at low temperatures. Also, the analytical parameters' effect on the transition temperature is discussed, which seems to give a general insight into the structural phase transition and its nature.

Numerical and Observational Investigations of Long-Lived Mcs-Induced Severe Surface Wind Events: the Derecho

Science.gov (United States)

Schmidt, Jerome Michael

This study addresses the production of sustained, straight-line, severe surface winds associated with mesoscale convective systems (MCSs) of extratropical origin otherwise known as derechos. The physical processes which govern the observed derecho characteristics are identified and their possible forcing mechanisms are determined. Detailed observations of two derechos are presented along with simulations using the Colorado State University Regional Atmospheric Modeling System (CSU-RAMS). The observations revealed a derecho environment characterized by strong vertical wind shear through the depth of the troposphere and large values of convective available potential energy (CAPE). The thermodynamic environment of the troposphere in each case had a distinct three-layer structure consisting of: (i) a surface-based stable layer of 1-to-2 km in depth, (ii) an elevated well -mixed layer of 2-4 km in depth, and (iii) an upper tropospheric layer of intermediate stability that extended to the tropopause. Two primary sets of simulations were performed to assess the impact of the observed environmental profiles on the derecho structure, propagation, and longevity. The first set consisted of nested-grid regional-scale simulations initialized from the standard NMC analyses on a domain having relatively coarse horizontal resolution (75 km). The second set of simulations consisted of two and three-dimensional experiments initialized in a horizontally homogeneous environment having a relatively fine horizontal resolution (2 km) and explicit microphysics. The results from these experiments indicate the importance of convectively -induced gravity waves on the MCS structure, propagation, longevity, and severe surface wind development. The sensitivity of the simulated convection and gravity waves to variations in the vertical wind shear and moisture profiles are described. Detailed Doppler radar analyses and 3-D simulations of a severe, bow echo squall line are presented which reveal

Correlation of thermodynamics and grain growth kinetics in nanocrystalline metals

International Nuclear Information System (INIS)

Song Xiaoyan; Zhang Jiuxing; Li Lingmei; Yang Keyong; Liu Guoquan

2006-01-01

We investigated the correlation of thermodynamics and grain growth kinetics of nanocrystalline metals both theoretically and experimentally. A model was developed to describe the thermodynamic properties of nanograin boundaries, which could give reliable predictions in the destabilization characteristics of nanograin structures and the slowing down of grain growth kinetics at a constant temperature. Both the temperature-varying and isothermal nanograin growth behaviors in pure nanocrystalline Co were studied to verify the thermodynamic predictions. The experimental results showing that discontinuous nanograin growth takes place at a certain temperature and grain growth rate decreases monotonically with time confirm our thermodynamics-based description of nanograin growth characteristics. Therefore, we propose a thermodynamic viewpoint to explain the deviation of grain growth kinetics in nanocrystalline metals from those of polycrystalline materials

Multiple tuned mass damper based vibration mitigation of offshore wind turbine considering soil-structure interaction

Science.gov (United States)

Hussan, Mosaruf; Sharmin, Faria; Kim, Dookie

2017-08-01

The dynamics of jacket supported offshore wind turbine (OWT) in earthquake environment is one of the progressing focuses in the renewable energy field. Soil-structure interaction (SSI) is a fundamental principle to analyze stability and safety of the structure. This study focuses on the performance of the multiple tuned mass damper (MTMD) in minimizing the dynamic responses of the structures objected to seismic loads combined with static wind and wave loads. Response surface methodology (RSM) has been applied to design the MTMD parameters. The analyses have been performed under two different boundary conditions: fixed base (without SSI) and flexible base (with SSI). Two vibration modes of the structure have been suppressed by multi-mode vibration control principle in both cases. The effectiveness of the MTMD in reducing the dynamic response of the structure is presented. The dynamic SSI plays an important role in the seismic behavior of the jacket supported OWT, especially resting on the soft soil deposit. Finally, it shows that excluding the SSI effect could be the reason of overestimating the MTMD performance.

Facilitating wind development: the importance of electric industry structure

Energy Technology Data Exchange (ETDEWEB)

Kirby, Brendan; Milligan, Michael

2008-04-15

ISOs and RTOs, with their day-ahead and real-time markets, large geographies to aggregate diverse wind resources, large loads to aggregate with wind, large generation pools that tap conventional-generator flexibility, and regional transmission planning efforts, offer the best environments for wind generation to develop. (author)

Stochastic thermodynamics

Science.gov (United States)

Eichhorn, Ralf; Aurell, Erik

2014-04-01

'Stochastic thermodynamics as a conceptual framework combines the stochastic energetics approach introduced a decade ago by Sekimoto [1] with the idea that entropy can consistently be assigned to a single fluctuating trajectory [2]'. This quote, taken from Udo Seifert's [3] 2008 review, nicely summarizes the basic ideas behind stochastic thermodynamics: for small systems, driven by external forces and in contact with a heat bath at a well-defined temperature, stochastic energetics [4] defines the exchanged work and heat along a single fluctuating trajectory and connects them to changes in the internal (system) energy by an energy balance analogous to the first law of thermodynamics. Additionally, providing a consistent definition of trajectory-wise entropy production gives rise to second-law-like relations and forms the basis for a 'stochastic thermodynamics' along individual fluctuating trajectories. In order to construct meaningful concepts of work, heat and entropy production for single trajectories, their definitions are based on the stochastic equations of motion modeling the physical system of interest. Because of this, they are valid even for systems that are prevented from equilibrating with the thermal environment by external driving forces (or other sources of non-equilibrium). In that way, the central notions of equilibrium thermodynamics, such as heat, work and entropy, are consistently extended to the non-equilibrium realm. In the (non-equilibrium) ensemble, the trajectory-wise quantities acquire distributions. General statements derived within stochastic thermodynamics typically refer to properties of these distributions, and are valid in the non-equilibrium regime even beyond the linear response. The extension of statistical mechanics and of exact thermodynamic statements to the non-equilibrium realm has been discussed from the early days of statistical mechanics more than 100 years ago. This debate culminated in the development of linear response

Hamiltonian and Thermodynamic Modeling of Quantum Turbulence

Science.gov (United States)

Grmela, Miroslav

2010-10-01

The state variables in the novel model introduced in this paper are the fields playing this role in the classical Landau-Tisza model and additional fields of mass, entropy (or temperature), superfluid velocity, and gradient of the superfluid velocity, all depending on the position vector and another tree dimensional vector labeling the scale, describing the small-scale structure developed in 4He superfluid experiencing turbulent motion. The fluxes of mass, momentum, energy, and entropy in the position space as well as the fluxes of energy and entropy in scales, appear in the time evolution equations as explicit functions of the state variables and of their conjugates. The fundamental thermodynamic relation relating the fields to their conjugates is left in this paper undetermined. The GENERIC structure of the equations serves two purposes: (i) it guarantees that solutions to the governing equations, independently of the choice of the fundamental thermodynamic relation, agree with the observed compatibility with thermodynamics, and (ii) it is used as a guide in the construction of the novel model.

Generation of electricity by wind power

Energy Technology Data Exchange (ETDEWEB)

Golding, E W

1976-01-01

Information on wind power is presented concerning the history of windmills; estimation of the energy obtainable from the wind; wind characteristics and distribution; wind power sites; wind surveys; wind flow over hills; measurement of wind velocity; wind structure and its determination; wind data and energy estimation; testing of wind driven ac generators; wind-driven machines; propeller type windmills; plants for isolated premises and small communities; economy of wind power generation; construction costs for large wind-driven generators; relationship of wind power to other power sources; research and development; and international cooperation.

Thermodynamic and structure-property study of liquid-vapor equilibrium for aroma compounds.

Science.gov (United States)

Tromelin, Anne; Andriot, Isabelle; Kopjar, Mirela; Guichard, Elisabeth

2010-04-14

Thermodynamic parameters (T, DeltaH degrees , DeltaS degrees , K) were collected from the literature and/or calculated for five esters, four ketones, two aldehydes, and three alcohols, pure compounds and compounds in aqueous solution. Examination of correlations between these parameters and the range values of DeltaH degrees and DeltaS degrees puts forward the key roles of enthalpy for vaporization of pure compounds and of entropy in liquid-vapor equilibrium of compounds in aqueous solution. A structure-property relationship (SPR) study was performed using molecular descriptors on aroma compounds to better understand their vaporization behavior. In addition to the role of polarity for vapor-liquid equilibrium of compounds in aqueous solution, the structure-property study points out the role of chain length and branching, illustrated by the correlation between the connectivity index CHI-V-1 and the difference between T and log K for vaporization of pure compounds and compounds in aqueous solution. Moreover, examination of the esters' enthalpy values allowed a probable conformation adopted by ethyl octanoate in aqueous solution to be proposed.

Financing renewables - wind energy

International Nuclear Information System (INIS)

Armstrong, J.

1998-01-01

This paper describes the status of the wind energy markets world-wide, in Europe and in the UK. It outlines the main methods of financing wind energy installations and discusses why different institutional structures have led to different markets in the UK and in Germany, with some concern about the state of the UK onshore industry. The paper looks ahead to the opening up of the potentially much larger offshore wind resource, concluding that in this area, existing UK development and financing structures are well suited. (Author)

Observations of the structure and evolution of surface and flight-level wind asymmetries in Hurricane Rita (2005)

Science.gov (United States)

Rogers, Robert; Uhlhorn, Eric

2008-11-01

Knowledge of the magnitude and distribution of surface winds, including the structure of azimuthal asymmetries in the wind field, are important factors for tropical cyclone forecasting. With its ability to remotely measure surface wind speeds, the stepped frequency microwave radiometer (SFMR) has assumed a prominent role for the operational tropical cyclone forecasting community. An example of this instrument's utility is presented here, where concurrent measurements of aircraft flight-level and SFMR surface winds are used to document the wind field evolution over three days in Hurricane Rita (2005). The amplitude and azimuthal location (phase) of the wavenumber-1 asymmetry in the storm-relative winds varied at both levels over time. The peak was found to the right of storm track at both levels on the first day. By the third day, the peak in flight-level storm-relative winds remained to the right of storm track, but it shifted to left of storm track at the surface, resulting in a 60-degree shift between the surface and flight-level and azimuthal variations in the ratio of surface to flight-level winds. The asymmetric differences between the surface and flight-level maximum wind radii also varied, indicating a vortex whose tilt was increasing.

Quality and Control of Water Vapor Winds

Science.gov (United States)

Jedlovec, Gary J.; Atkinson, Robert J.

1996-01-01

Water vapor imagery from the geostationary satellites such as GOES, Meteosat, and GMS provides synoptic views of dynamical events on a continual basis. Because the imagery represents a non-linear combination of mid- and upper-tropospheric thermodynamic parameters (three-dimensional variations in temperature and humidity), video loops of these image products provide enlightening views of regional flow fields, the movement of tropical and extratropical storm systems, the transfer of moisture between hemispheres and from the tropics to the mid- latitudes, and the dominance of high pressure systems over particular regions of the Earth. Despite the obvious larger scale features, the water vapor imagery contains significant image variability down to the single 8 km GOES pixel. These features can be quantitatively identified and tracked from one time to the next using various image processing techniques. Merrill et al. (1991), Hayden and Schmidt (1992), and Laurent (1993) have documented the operational procedures and capabilities of NOAA and ESOC to produce cloud and water vapor winds. These techniques employ standard correlation and template matching approaches to wind tracking and use qualitative and quantitative procedures to eliminate bad wind vectors from the wind data set. Techniques have also been developed to improve the quality of the operational winds though robust editing procedures (Hayden and Veldon 1991). These quality and control approaches have limitations, are often subjective, and constrain wind variability to be consistent with model derived wind fields. This paper describes research focused on the refinement of objective quality and control parameters for water vapor wind vector data sets. New quality and control measures are developed and employed to provide a more robust wind data set for climate analysis, data assimilation studies, as well as operational weather forecasting. The parameters are applicable to cloud-tracked winds as well with minor

A Laminar Model for the Magnetic Field Structure in Bow-Shock Pulsar Wind Nebulae

Science.gov (United States)

Bucciantini, N.

2018-05-01

Bow Shock Pulsar Wind Nebulae are a class of non-thermal sources, that form when the wind of a pulsar moving at supersonic speed interacts with the ambient medium, either the ISM or in a few cases the cold ejecta of the parent supernova. These systems have attracted attention in recent years, because they allow us to investigate the properties of the pulsar wind in a different environment from that of canonical Pulsar Wind Nebulae in Supernova Remnants. However, due to the complexity of the interaction, a full-fledged multidimensional analysis is still laking. We present here a simplified approach, based on Lagrangian tracers, to model the magnetic field structure in these systems, and use it to compute the magnetic field geometry, for various configurations in terms of relative orientation of the magnetic axis, pulsar speed and observer direction. Based on our solutions we have computed a set of radio emission maps, including polarization, to investigate the variety of possible appearances, and how the observed emission pattern can be used to constrain the orientation of the system, and the possible presence of turbulence.

Calculation and design of steel bearing structure for wind turbine

Directory of Open Access Journals (Sweden)

Bešević Miroslav

2014-01-01

Full Text Available Wind represents directed movement of the air and is caused by differences in atmospheric pressure which are caused by uneven heating of air masses. Global and local winds can be distinguished. Global winds have high altitude, while local winds occur in the ground layer of the atmosphere. Given that the global wings have high altitude they cannot be used as propellant for wind generators, but they should be known for their effects on the winds in the lower atmosphere. Modern wind turbines are made with a horizontal axle that has a system for the swiveling axis in the horizontal plane for tracking wind direction changes. They can have different number of blades, but for larger forces three blades are commonly used because they provide the greatest efficiency. Rotor diameter of these turbines depends on the strength and it ranges from 30 m for the power of 300 kW to 115 m for the power of 5 MW. Wind turbines are mounted on vertical steel tower which can be high even more than 100 m. Depending on the diameter of the turbine rotor, column is usually built as steel conical and less often as a steel-frame. This study includes analysis and design of steel tower for wind generator made by manufacturer Vestas, type V112 3MW HH 119 (power 3.2 MW for the construction of wind farm 'Kovačica'.

Solvation Structure and Thermodynamic Mapping (SSTMap): An Open-Source, Flexible Package for the Analysis of Water in Molecular Dynamics Trajectories.

Science.gov (United States)

Haider, Kamran; Cruz, Anthony; Ramsey, Steven; Gilson, Michael K; Kurtzman, Tom

2018-01-09

We have developed SSTMap, a software package for mapping structural and thermodynamic water properties in molecular dynamics trajectories. The package introduces automated analysis and mapping of local measures of frustration and enhancement of water structure. The thermodynamic calculations are based on Inhomogeneous Fluid Solvation Theory (IST), which is implemented using both site-based and grid-based approaches. The package also extends the applicability of solvation analysis calculations to multiple molecular dynamics (MD) simulation programs by using existing cross-platform tools for parsing MD parameter and trajectory files. SSTMap is implemented in Python and contains both command-line tools and a Python module to facilitate flexibility in setting up calculations and for automated generation of large data sets involving analysis of multiple solutes. Output is generated in formats compatible with popular Python data science packages. This tool will be used by the molecular modeling community for computational analysis of water in problems of biophysical interest such as ligand binding and protein function.

On the electronic, structural, and thermodynamic properties of Au supported on α-Fe{sub 2}O{sub 3} surfaces and their interaction with CO

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Manh-Thuong, E-mail: manhth.nguyen@gmail.com; Gebauer, Ralph [The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste (Italy); Farnesi Camellone, Matteo, E-mail: mfarnesi@sissa.it [CNR-IOM DEMOCRITOS, Istituto Officina dei Materiali, Consiglio Nazionale delle Ricerche and SISSA Scuola Internazionale di Studi Superiori Avanzati, Via Bonomea 265, I-34136 Trieste (Italy)

2015-07-21

Extensive first principles calculations are carried out to investigate Au monomers and dimers supported on α-Fe{sub 2}O{sub 3}(0001) surfaces in terms of structure optimizations, electronic structure analyses, and ab initio thermodynamics calculations of surface phase diagrams. All computations rely on density functional theory in the generalized gradient approximation (Perdew-Burke-Ernzerhof (PBE)) and account for on-site Coulomb interactions via inclusion of a Hubbard correction (PBE+U). The relative stability of Au monomers/dimers on the stoichiometric termination of α-Fe{sub 2}O{sub 3}(0001) decorated with various vacancies (multiple oxygen vacancies, iron vacancy, and mixed iron-oxygen vacancies) has been computed as a function of the oxygen chemical potential. The charge rearrangement induced by Au at the oxide contact is analyzed in detail and discussed. On one hand, ab initio thermodynamics predicts that under O-rich conditions, structures obtained by replacing a surface Fe atom with a Au atom are thermodynamically stable over a wide range of temperatures. On the other hand, the complex of a CO molecule on a Au atom substituting surface Fe atoms is thermodynamically stable only in a much more narrow range of values of the O chemical potential under O-rich conditions. In the case of a Au dimer, under O-rich conditions, supported Au atoms at an O-Fe di-vacancy are more stable. However, upon CO adsorption, the complex of a CO molecule and 2 Au atoms located at a single Fe vacancy is more favorable.

Fisher Information, Entropy, and the Second and Third Laws of Thermodynamics

Science.gov (United States)

We propose Fisher Information as a new calculable thermodynamic property that can be shown to follow the Second and the Third Laws of Thermodynamics. Fisher Information is, however, qualitatively different from entropy and potentially possessing a great deal more structure. Hence...

Effective Method for Determining Environmental Loads on Supporting Structures for Offshore Wind Turbines

Directory of Open Access Journals (Sweden)

Dymarski Paweł

2016-01-01

Full Text Available This paper presents a description of an effective method for determining loads due to waves and current acting on the supporting structures of the offshore wind turbines. This method is dedicated to the structures consisting of the cylindrical or conical elements as well as (truncates pyramids of polygon with a large number of sides (8 or more. The presented computational method is based on the Morison equation, which was originally developed only for cylindrically shaped structures. The new algorithm shown here uses the coefficients of inertia and drag forces that were calculated for non-cylindrical shapes. The analysed structure consists of segments which are truncated pyramids on the basis of a hex decagon. The inertia coefficients, CM, and drag coefficients, CD, were determined using RANSE-CFD calculations. The CFD simulations were performed for a specific range of variation of the period, and for a certain range of amplitudes of the velocity. In addition, the analysis of influence of the surface roughness on the inertia and drag coefficients was performed. In the next step, the computations of sea wave, current and wind load on supporting structure for the fifty-year storm were carried out. The simulations were performed in the time domain and as a result the function of forces distribution along the construction elements was obtained. The most unfavourable distribution of forces will be used, to analyse the strength of the structure, as the design load.

Integrated analysis of wind turbines - The impact of power systems on wind turbine design

DEFF Research Database (Denmark)

Barahona Garzón, Braulio

Megawatt-size wind turbines nowadays operate in very complex environmental conditions, and increasingly demanding power system requirements. Pursuing a cost-effective and reliable wind turbine design is a multidisciplinary task. However nowadays, wind turbine design and research areas...... conditions that stem from disturbances in the power system. An integrated simulation environment, wind turbine models, and power system models are developed in order to take an integral perspective that considers the most important aeroelastic, structural, electrical, and control dynamics. Applications...... of the integrated simulation environment are presented. The analysis of an asynchronous machine, and numerical simulations of a fixedspeed wind turbine in the integrated simulation environment, demonstrate the effects on structural loads of including the generator rotor fluxes dynamics in aeroelastic studies. Power...

Aerodynamics of Wind Turbines

DEFF Research Database (Denmark)

Hansen, Martin Otto Laver

Aerodynamics of Wind Turbines is the established essential text for the fundamental solutions to efficient wind turbine design. Now in its second edition, it has been entirely updated and substantially extended to reflect advances in technology, research into rotor aerodynamics and the structural...... response of the wind turbine structure. Topics covered include increasing mass flow through the turbine, performance at low and high wind speeds, assessment of the extreme conditions under which the turbine will perform and the theory for calculating the lifetime of the turbine. The classical Blade Element...... Momentum method is also covered, as are eigenmodes and the dynamic behavior of a turbine. The new material includes a description of the effects of the dynamics and how this can be modeled in an aeroelastic code, which is widely used in the design and verification of modern wind turbines. Further...

Effect of secondary structure on the thermodynamics and kinetics of PNA hybridization to DNA hairpins

DEFF Research Database (Denmark)

Kushon, S A; Jordan, J P; Seifert, J L

2001-01-01

The binding of a series of PNA and DNA probes to a group of unusually stable DNA hairpins of the tetraloop motif has been observed using absorbance hypochromicity (ABS), circular dichroism (CD), and a colorimetric assay for PNA/DNA duplex detection. These results indicate that both stable PNA...... structures in both target and probe molecules are shown to depress the melting temperatures and free energies of the probe-target duplexes. Kinetic analysis of hybridization yields reaction rates that are up to 160-fold slower than hybridization between two unstructured strands. The thermodynamic and kinetic...

Strategic structure matrix: A framework for explaining the impact of superstructure organizations on the diffusion of wind energy infrastructure

International Nuclear Information System (INIS)

Tang, Amy; Taylor, John E.; Mahalingam, Ashwin

2013-01-01

Increasing the use of renewables in the global energy mix has become a top priority for policy makers. In this paper, we use a diffusion theory based approach to analyze the impact of government initiatives on the development of wind energy infrastructure focusing on the specific case of wind energy diffusion in India. We propose a new framework—the strategic structure matrix—as a way to characterize the strategic focus and analyze the effectiveness of different initiatives to increase wind power diffusion. We apply the matrix to explain the different pace and paths of wind energy growth observed in five Indian states: Tamil Nadu, Gujarat, Maharashtra, Andhra Pradesh, and Karnataka. Our findings suggest the importance of a comprehensive approach that includes multiple strategies across initiatives, local regulatory measures, and supply-side incentives. - Highlights: • A new framework—the Strategic Structure Matrix—is proposed. • It characterizes strategic initiatives designed to promote innovation diffusion. • The matrix was validated using case study data on wind power diffusion in India. • The matrix can help shape government policies to improve RET diffusion

Crystal structures and thermodynamics/kinetics of Zn(II) coordination polymers with helical chains

Energy Technology Data Exchange (ETDEWEB)

He, Tian [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an 710069 (China); Yue, Ke-Fen, E-mail: ykflyy@nwu.edu.cn [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an 710069 (China); Zhao, Yi-xing; Chen, San-Ping [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an 710069 (China); Zhou, Chun-sheng, E-mail: slzhoucs@126.com.cn [Shaanxi Key Laboratory of Comprehensive Utilization of Tailings Resources, College of Chemical Engineering and Modern Materials, Shangluo University, Shangluo 726000 (China); Yan, Ni [Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Xi’an 710069 (China)

2016-07-15

Solvothermal reactions of Zn(II) acetates and four V-shaped carboxylates ligands in the presence of 1,4-Bis(2-methyl-imidazol-1-yl)butane afforded four interesting Zn(II) coordination polymers with helical chains, namely, {[Zn(bib)(atibdc)]·2H_2O}{sub n} (1), {[Zn(bib)(atbip)]·H_2O}{sub n} (2), {[Zn(bib)(2,2′-tda)]}{sub n} (3) and {[Zn(bib)(5-tbipa)]·EtOH}{sub n} (4), (H{sub 2}atibdc=5-amino-2,4,6-triiodoisophthalic acid, H{sub 2}atbip=5-amino-2,4,6-tribromoisophthalic acid, 2,2′-H{sub 2}tad=2,2′-thiodiacetic acid, 5-H{sub 2}tbipa=5-tert-butyl-isophthalic acid). 1 reveals a 3D chiral framework with three kinds of helical chains along a, b and c axis. 2 shows a 2D step-type chiral framework with right-handed helical chains. 3 displays a wavelike 2D layer network possessing alternate left- and right-handed helical chains. 4 presents a four-connected 3D framework with zigzag and meso-helical chains. The different spacers and substituent group of carboxylic acid ligands may lead to the diverse network structures of 1–4. The fluorescent properties of complexes 1−4 were studied. In addition, the thermal decompositions properties of 1–4 were investigated by simultaneous TG/DTG–DSC technique. The apparent activation energy E and the pre-exponential factor (A) of skeleton collapse for the complexes 1–4 are calculated by the integral Kissinger's method and Ozawa–Doyle's method. The activation energy E (E{sub 1}=209.658 kJ·mol{sup −1}, E{sub 2}=250.037 kJ mol{sup −1}, E{sub 3}=225.300 kJ mol{sup −1}, E{sub 4}=186.529 kJ·mol{sup −1}) demonstrates that the reaction rate of the melting decomposition is slow. The thermodynamic parameters (ΔH{sup ‡}, ΔG{sup ‡} and ΔS{sup ‡}) at the peak temperatures of the DTG curves were also calculated. ΔG{sup ‡}>0 indicates that the skeleton collapse is not spontaneous. ΔH{sub d}>0 suggests that the skeleton collapse is endothermic, corresponding to the intense endothermic peak of the DSC

Structured Linear Parameter Varying Control of Wind Turbines

DEFF Research Database (Denmark)

Adegas, Fabiano Daher; Sloth, Christoffer; Stoustrup, Jakob

2012-01-01

High performance and reliability are required for wind turbines to be competitive within the energy market. To capture their nonlinear behavior, wind turbines are often modeled using parameter-varying models. In this chapter, a framework for modelling and controller design of wind turbines is pre...... in the controller synthesis are solved by an iterative LMI-based algorithm. The resulting controllers can also be easily implemented in practice due to low data storage and simple math operations. The performance of the LPV controllers is assessed by nonlinear simulations results....

Structural, electronic, and thermodynamic properties of curium dioxide: Density functional theory calculations

Science.gov (United States)

Hou, Ling; Li, Wei-Dong; Wang, Fangwei; Eriksson, Olle; Wang, Bao-Tian

2017-12-01

We present a systematic investigation of the structural, magnetic, electronic, mechanical, and thermodynamic properties of CmO2 with the local density approximation (LDA)+U and the generalized gradient approximation (GGA)+U approaches. The strong Coulomb repulsion and the spin-orbit coupling (SOC) effects on the lattice structures, electronic density of states, and band gaps are carefully studied, and compared with other A O2 (A =U , Np, Pu, and Am). The ferromagnetic configuration with half-metallic character is predicted to be energetically stable while a charge-transfer semiconductor is predicted for the antiferromagnetic configuration. The elastic constants and phonon spectra show that the fluorite structure is mechanically and dynamically stable. Based on the first-principles phonon density of states, the lattice vibrational energy is calculated using the quasiharmonic approximation. Then, the Gibbs free energy, thermal expansion coefficient, specific heat, and entropy are obtained and compared with experimental data. The mode Grüneisen parameters are presented to analyze the anharmonic properties. The Slack relation is applied to obtain the lattice thermal conductivity in temperature range of 300-1600 K. The phonon group velocities are also calculated to investigate the heat transfer. For all these properties, if available, we compare the results of CmO2 with other A O2 .

Structural design optimization of a morphing trailing edge flap for wind turbine blades

DEFF Research Database (Denmark)

Barlas, Athanasios; Lin, Yu-Huan; Aagaard Madsen, Helge

A flap actuation system, the Controllable Rubber Trailing Edge Flap (CRTEF), for distributed load control on a wind turbine blade had been developed in the period from 2006 to 2013 at DTU (http://www.induflap.dk/). The purpose of the presented work is to optimize the structural design of the flex......A flap actuation system, the Controllable Rubber Trailing Edge Flap (CRTEF), for distributed load control on a wind turbine blade had been developed in the period from 2006 to 2013 at DTU (http://www.induflap.dk/). The purpose of the presented work is to optimize the structural design...... of the flexible part of the CRTEF based on a realistic blade section geometry in order to meet the required objectives and constraints. The objectives include the deflection requirements and the energy efficiency, while the constraints include the bending stiffness of the structure, the local shape deformations......, critical material strength, and manufacturing limitations. A model with arches forming concave on the flap surface and enclosing the voids to be pressurized results in the bending movement of the flap when pressure is applied on the voids to straighten the arches. The model is designed using SolidWorks...

Rational extended thermodynamics

CERN Document Server

Müller, Ingo

1998-01-01

Ordinary thermodynamics provides reliable results when the thermodynamic fields are smooth, in the sense that there are no steep gradients and no rapid changes. In fluids and gases this is the domain of the equations of Navier-Stokes and Fourier. Extended thermodynamics becomes relevant for rapidly varying and strongly inhomogeneous processes. Thus the propagation of high­ frequency waves, and the shape of shock waves, and the regression of small-scale fluctuation are governed by extended thermodynamics. The field equations of ordinary thermodynamics are parabolic while extended thermodynamics is governed by hyperbolic systems. The main ingredients of extended thermodynamics are • field equations of balance type, • constitutive quantities depending on the present local state and • entropy as a concave function of the state variables. This set of assumptions leads to first order quasi-linear symmetric hyperbolic systems of field equations; it guarantees the well-posedness of initial value problems and f...

Thermodynamic and structural properties of ball-milled mixtures composed of nano-structural graphite and alkali(-earth) metal hydride

International Nuclear Information System (INIS)

Miyaoka, Hiroki; Ichikawa, Takayuki; Fujii, Hironobu

2007-01-01

Hydrogen desorption properties of mechanically milled materials composed of nano-structural hydrogenated-graphite (C nano H x ) and alkali(-earth) metal hydride (MH; M = Na, Mg and Ca) were investigated from the thermodynamic and structural points of view. The hydrogen desorption temperature for all the C nano H x and MH composites was obviously lower than that of the corresponding each hydride. In addition, the desorption of hydrocarbons from C nano H x was significantly suppressed by making composite of C nano H x with MH, even though C nano H x itself thermally desorbs a considerably large amount of hydrocarbons. These results indicate that an interaction exists between C nano H x and MH, and hydrogen in both the phases is destabilized by a close contact between polar C-H groups in C nano H x and the MH solid phase. Moreover, a new type of chemical bonding between the nano-structural carbon (C nano ) and the Li, Ca, or Mg metal atoms may be formed after hydrogen desorption. Thus, the above metal-C-H system would be recognized as a new family of H-storage materials

Classical and statistical thermodynamics

CERN Document Server

Rizk, Hanna A

2016-01-01

This is a text book of thermodynamics for the student who seeks thorough training in science or engineering. Systematic and thorough treatment of the fundamental principles rather than presenting the large mass of facts has been stressed. The book includes some of the historical and humanistic background of thermodynamics, but without affecting the continuity of the analytical treatment. For a clearer and more profound understanding of thermodynamics this book is highly recommended. In this respect, the author believes that a sound grounding in classical thermodynamics is an essential prerequisite for the understanding of statistical thermodynamics. Such a book comprising the two wide branches of thermodynamics is in fact unprecedented. Being a written work dealing systematically with the two main branches of thermodynamics, namely classical thermodynamics and statistical thermodynamics, together with some important indexes under only one cover, this treatise is so eminently useful.

3D printing meets computational astrophysics: deciphering the structure of η Carinae's inner colliding winds

Science.gov (United States)

Madura, T. I.; Clementel, N.; Gull, T. R.; Kruip, C. J. H.; Paardekooper, J.-P.

2015-06-01

We present the first 3D prints of output from a supercomputer simulation of a complex astrophysical system, the colliding stellar winds in the massive (≳120 M⊙), highly eccentric (e ˜ 0.9) binary star system η Carinae. We demonstrate the methodology used to incorporate 3D interactive figures into a PDF (Portable Document Format) journal publication and the benefits of using 3D visualization and 3D printing as tools to analyse data from multidimensional numerical simulations. Using a consumer-grade 3D printer (MakerBot Replicator 2X), we successfully printed 3D smoothed particle hydrodynamics simulations of η Carinae's inner (r ˜ 110 au) wind-wind collision interface at multiple orbital phases. The 3D prints and visualizations reveal important, previously unknown `finger-like' structures at orbital phases shortly after periastron (φ ˜ 1.045) that protrude radially outwards from the spiral wind-wind collision region. We speculate that these fingers are related to instabilities (e.g. thin-shell, Rayleigh-Taylor) that arise at the interface between the radiatively cooled layer of dense post-shock primary-star wind and the fast (3000 km s-1), adiabatic post-shock companion-star wind. The success of our work and easy identification of previously unrecognized physical features highlight the important role 3D printing and interactive graphics can play in the visualization and understanding of complex 3D time-dependent numerical simulations of astrophysical phenomena.

Structural modelling of composite beams with application to wind turbine rotor blades

DEFF Research Database (Denmark)

Couturier, Philippe

The ever changing structure and growing size of wind turbine blades put focus on the accuracy and flexibility of design tools. The present thesis is organized in four parts - all concerning the development of efficient computational methods for the structural modelling of composite beams which...... will support future growth in the rotor size.The first part presents a two-node beam element formulation, based on complementary elastic energy, valid for fully coupled beams with variable cross-section properties.The element stiffness matrix is derived by use of the six equilibrium states of the element...

Turbulent Structure Under Short Fetch Wind Waves

Science.gov (United States)

2015-12-01

maximum 200 words ) Momentum transfer from wind forcing into the ocean is complicated by the presence of surface waves. Wind momentum and energy are...1,520 m from the mouth of the river to the deployment site ). Map created in Google Earth, October 12, 2015, http://www.google.com/earth/. 33...Doppler processing electronics for each transducer uses 14 bit analog to digital converter to digitize the 1.2 MHz acoustic frequency from the four

Evaluation of different inertial control methods for variable-speed wind turbines simulated by fatigue, aerodynamic, structures and turbulence (FAST)

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiao; Gao, Wenzhong; Scholbrock, Andrew; Muljadi, Eduard; Gevorgian, Vahan; Wang, Jianhui; Yan, Weihang; Zhang, Huaguang

2017-10-18

To mitigate the degraded power system inertia and undesirable primary frequency response caused by large-scale wind power integration, the frequency support capabilities of variable-speed wind turbines is studied in this work. This is made possible by controlled inertial response, which is demonstrated on a research turbine - controls advanced research turbine, 3-bladed (CART3). Two distinct inertial control (IC) methods are analysed in terms of their impacts on the grids and the response of the turbine itself. The released kinetic energy in the IC methods are determined by the frequency measurement or shaped active power reference in the turbine speed-power plane. The wind turbine model is based on the high-fidelity turbine simulator fatigue, aerodynamic, structures and turbulence, which constitutes the aggregated wind power plant model with the simplified power converter model. The IC methods are implemented over the baseline CART3 controller, evaluated in the modified 9-bus and 14-bus testing power grids considering different wind speeds and different wind power penetration levels. The simulation results provide various insights on designing such kinds of ICs. The authors calculate the short-term dynamic equivalent loads and give a discussion about the turbine structural loadings related to the inertial response.

Evidence for a connection between photospheric and wind structure in HD 64760

Science.gov (United States)

Kaufer, A.; Prinja, R. K.; Stahl, O.

2002-02-01

structure which is maintained throughout the photosphere - wind transition zone (this work) out into the UV regime of the terminal velocity outflow. Based on observations collected at the European Southern Observatory at La Silla, Chile (Proposal ID 56.D-0235).

Condensation of long-term wave climates for the fatigue design of hydrodynamically sensitive offshore wind turbine support structures

DEFF Research Database (Denmark)

Passon, Patrik; Branner, Kim

2016-01-01

important for hydrodynamically sensitive structures since the applied met-ocean parameters have a non-linear influence on calculated fatigue design loads. The present article introduces a new wave lumping method for condensation of the wave climate. The novelty is predominantly based on refined equivalence......Cost-efficient and reliable fatigue designs of offshore wind turbine support structures require an adequate representation of the site-specific wind–wave joint distribution. Establishment of this wind–wave joint distribution for design load calculation purposes requires typically a correlation...... of the marginal wind and wave distribution. This is achieved by condensation of the site-specific wave climate in terms of wave period or wave height lumping, subsequently used as input for a correlation with the corresponding wind climate. The quality of this resulting wind–wave correlation is especially...

Structural optimization procedure of a composite wind turbine blade for reducing both material cost and blade weight

Science.gov (United States)

Hu, Weifei; Park, Dohyun; Choi, DongHoon

2013-12-01

A composite blade structure for a 2 MW horizontal axis wind turbine is optimally designed. Design requirements are simultaneously minimizing material cost and blade weight while satisfying the constraints on stress ratio, tip deflection, fatigue life and laminate layup requirements. The stress ratio and tip deflection under extreme gust loads and the fatigue life under a stochastic normal wind load are evaluated. A blade element wind load model is proposed to explain the wind pressure difference due to blade height change during rotor rotation. For fatigue life evaluation, the stress result of an implicit nonlinear dynamic analysis under a time-varying fluctuating wind is converted to the histograms of mean and amplitude of maximum stress ratio using the rainflow counting algorithm Miner's rule is employed to predict the fatigue life. After integrating and automating the whole analysis procedure an evolutionary algorithm is used to solve the discrete optimization problem.

Development of Self-Powered Wireless Structural Health Monitoring (SHM) for Wind Turbine Blades

Science.gov (United States)

Lim, Dong-Won

Wind turbine blade failure can lead to unexpected power interruptions. Monitoring wind turbine blades is important to ensure seamless electricity delivery from power generation to consumers. Structural health monitoring (SHM) enables early recognition of structural problems so that the safety and reliability of operation can be enhanced. This dissertation focuses on the development of a wireless SHM system for wind turbine blades. The sensor is comprised of a piezoelectric energy harvester (EH) and a telemetry unit. The sensor node is mounted on the blade surface. As the blade rotates, the blade flexes, and the energy harvester captures the strain energy on the blade surface. Once sufficient electricity is captured, a pulse is sent from the sensing node to a gateway. Then, a central monitoring algorithm processes a series of pulses received from all three blades. This wireless SHM, which uses commercially available components, can be retrofitted to existing turbines. The harvested energy for sensing can be estimated in terms of two factors: the available strain energy and conversion efficiency. The available strain energy was evaluated using the FAST (Fatigue, Aerodynamics, Structures, and Turbulence) simulator. The conversion efficiency was studied analytically and experimentally. An experimental set-up was designed to mimic the expected strain frequency and amplitude for rotor blades. From a series of experiments, the efficiency of a piezoelectric EH at a typical rotor speed (0.2 Hz) was approximately 0.5%. The power requirement for sending one measurement (280 muJ) can be achieved in 10 minutes. Designing a detection algorithm is challenging due to this low sampling rate. A new sensing approach-the timing of pulses from the transmitter-was introduced. This pulse timing, which is tied to the charging time, is indicative of the structural health. The SHM system exploits the inherent triple redundancy of the three blades. The timing data of the three blades are

Comparative Study on Uni- and Bi-Directional Fluid Structure Coupling of Wind Turbine Blades

Directory of Open Access Journals (Sweden)

Mesfin Belayneh Ageze

2017-09-01

Full Text Available The current trends of wind turbine blade designs are geared towards a longer and slender blade with high flexibility, exhibiting complex aeroelastic loadings and instability issues, including flutter; in this regard, fluid-structure interaction (FSI plays a significant role. The present article will conduct a comparative study between uni-directional and bi-directional fluid-structural coupling models for a horizontal axis wind turbine. A full-scale, geometric copy of the NREL 5MW blade with simplified material distribution is considered for simulation. Analytical formulations of the governing relations with appropriate approximation are highlighted, including turbulence model, i.e., Shear Stress Transport (SST k-ω. These analytical relations are implemented using Multiphysics package ANSYS employing Fluent module (Computational Fluid Dynamics (CFD-based solver for the fluid domain and Transient Structural module (Finite Element Analysis-based solver for the structural domain. ANSYS system coupling module also is configured to model the two fluid-structure coupling methods. The rated operational condition of the blade for a full cycle rotation is considered as a comparison domain. In the bi-directional coupling model, the structural deformation alters the angle of attack from the designed values, and by extension the flow pattern along the blade span; furthermore, the tip deflection keeps fluctuating whilst it tends to stabilize in the uni-directional coupling model.

[On the principle of substance stability and thermodynamic feedback in hierarchic systems of the bio-world].

Science.gov (United States)

Gladyshev, G P

2002-01-01

The creation of structural hierarchies in open natural biosystems within the framework of quasi-closed systems is investigated by the methods of hierarchic thermodynamics (thermostatics). During the evolution of natural open systems, every higher hierarchic level j appears as a consequence of thermodynamic self-organization (self-assembly) of the structures of the lower (j-1)-th level. Such a self-assembly proceeds as a result of stabilization of the j-th level. This is related to the Gibbs' (Helmholtz') specific function of formation of the structure of the j-th level tending to a minimum. As a result of action of the principle of substance (matter) stability, the structures of the j-th level are enriched with less stable structures of the (j-1)-th level in the course of evolution. This provides a thermodynamic feedback between the structures of the higher j-th level and lower (j-1)-th level, thus preventing full structural stabilization of the j-th level and causing "thermodynamic rejuvenation" of biosystems. The latter enhances "thermodynamic" deceleration of evolution and practically unlimited maintenance of life. Examples of quantitative correlations are provided that call for further application of the substance stability principle to living and nonliving hierarchic structures.

A density functional reactivity theory (DFRT) based approach to understand the effect of symmetry of fullerenes on the kinetic, thermodynamic and structural aspects of carbon NanoBuds

Energy Technology Data Exchange (ETDEWEB)

Sarmah, Amrit; Roy, Ram Kinkar, E-mail: rkroy2@rediffmail.com

2016-06-15

Highlights: • Kinetic and thermodynamic aspects of the interaction between fullerene (C{sub 32}) and SWCNT using CDASE scheme. • Role of symmetry of fullerenes as well as the site of covalent attachment to the SWCNT in the structural stability of the NanoBud structure. • Increase in the fullerene symmetry improves the relative stability of hybrid NanoBud structure. - Abstract: In the present study, we have rationalized the effect of variation in the symmetry of relatively smaller fullerene (C{sub 32}) on the mode of its interaction with semi-conducting Single-Walled Carbon Nanotubes (SWCNTs) in the process of formation of stable hybrid carbon NanoBuds. Thermodynamic and kinetic parameters, along with the charge transfer values associated with the interaction between fullerene and SWCNTs, have been evaluated using an un-conventional and computationally cost–effective method based on density functional reactivity theory (DFRT). In addition to this, conventional DFT based studies are also performed to substantiate the growth of NanoBud structures formed by the interaction between fullerene and SWCNTs. The findings of the present study suggest that the kinetic, thermodynamic and structural aspects of hybrid carbon NanoBuds are significantly influenced by both the symmetry of C{sub 32} fullerene and its site of covalent attachment to the SWCNT.

Wind Turbine Blade Design System - Aerodynamic and Structural Analysis

Science.gov (United States)

Dey, Soumitr

2011-12-01

The ever increasing need for energy and the depletion of non-renewable energy resources has led to more advancement in the "Green Energy" field, including wind energy. An improvement in performance of a Wind Turbine will enhance its economic viability, which can be achieved by better aerodynamic designs. In the present study, a design system that has been under development for gas turbine turbomachinery has been modified for designing wind turbine blades. This is a very different approach for wind turbine blade design, but will allow it to benefit from the features inherent in the geometry flexibility and broad design space of the presented system. It starts with key overall design parameters and a low-fidelity model that is used to create the initial geometry parameters. The low-fidelity system includes the axisymmetric solver with loss models, T-Axi (Turbomachinery-AXIsymmetric), MISES blade-to-blade solver and 2D wing analysis code XFLR5. The geometry parameters are used to define sections along the span of the blade and connected to the CAD model of the wind turbine blade through CAPRI (Computational Analysis PRogramming Interface), a CAD neutral API that facilitates the use of parametric geometry definition with CAD. Either the sections or the CAD geometry is then available for CFD and Finite Element Analysis. The GE 1.5sle MW wind turbine and NERL NASA Phase VI wind turbine have been used as test cases. Details of the design system application are described, and the resulting wind turbine geometry and conditions are compared to the published results of the GE and NREL wind turbines. A 2D wing analysis code XFLR5, is used for to compare results from 2D analysis to blade-to-blade analysis and the 3D CFD analysis. This kind of comparison concludes that, from hub to 25% of the span blade to blade effects or the cascade effect has to be considered, from 25% to 75%, the blade acts as a 2d wing and from 75% to the tip 3D and tip effects have to be taken into account

Reliability Assessment Of Wind Turbines

DEFF Research Database (Denmark)

Sørensen, John Dalsgaard

2014-01-01

Reduction of cost of energy for wind turbines are very important in order to make wind energy competitive compared to other energy sources. Therefore the turbine components should be designed to have sufficient reliability but also not be too costly (and safe). This paper presents models...... for uncertainty modeling and reliability assessment of especially the structural components such as tower, blades, substructure and foundation. But since the function of a wind turbine is highly dependent on many electrical and mechanical components as well as a control system also reliability aspects...... of these components are discussed and it is described how there reliability influences the reliability of the structural components. Two illustrative examples are presented considering uncertainty modeling, reliability assessment and calibration of partial safety factors for structural wind turbine components exposed...

Offshore code comparison collaboration continuation (OC4), phase I - Results of coupled simulations of an offshore wind turbine with jacket support structure

DEFF Research Database (Denmark)

Popko, Wojciech; Vorpahl, Fabian; Zuga, Adam

2012-01-01

In this paper, the exemplary results of the IEA Wind Task 30 "Offshore Code Comparison Collaboration Continuation" (OC4) Project - Phase I, focused on the coupled simulation of an offshore wind turbine (OWT) with a jacket support structure, are presented. The focus of this task has been the verif......In this paper, the exemplary results of the IEA Wind Task 30 "Offshore Code Comparison Collaboration Continuation" (OC4) Project - Phase I, focused on the coupled simulation of an offshore wind turbine (OWT) with a jacket support structure, are presented. The focus of this task has been...... the verification of OWT modeling codes through code-to-code comparisons. The discrepancies between the results are shown and the sources of the differences are discussed. The importance of the local dynamics of the structure is depicted in the simulation results. Furthermore, attention is given to aspects...

Structures and Intermittency in Small Scales Solar Wind Turbulence

International Nuclear Information System (INIS)

Sahraoui, Fouad; Goldstein, Melvyn

2010-01-01

Several observations in space plasmas have reported the presence of coherent structures at different plasma scales. Structure formation is believed to result from nonlinear interactions between the plasma modes, which depend strongly on their phase synchronization. Despite this important role of the phases in turbulence, very limited work has been devoted to study the phases as potential tracers of nonlinearities in comparison with the wealth of literature on power spectra of turbulence where phases are totally missed. The reason why the phases are seldom used is probably because they usually appear to be completely mixed (due to their dependence on an arbitrary time origin and to 2π periodicity). To handle the phases properly, a new method based on using surrogate data has been developed recently to detect coherent structures in magnetized plasmas [Sahraoui, PRE, 2008]. Here, we show new applications of the technique to study the nature (weak vs strong, self-similar vs intermittent) of the small scale turbulence in the solar wind using the Cluster observations.

Wind turbine structural dynamics - a review of the principles for modern power generation, onshore and offshore

Energy Technology Data Exchange (ETDEWEB)

Tempel, J. van der; Molenaar, D.-P.

2002-07-01

Wind turbines for electricity production have two seemingly opposing constraints; they need to be structural secure yet of low cost. To meet the first constraint, it would be an obvious choice to design a stiff structure of consequently large mass but this would drive up the cost. By reducing the mass a more cost effective turbine can be realized. However, such lightweight structures are by definition more flexible. To design a cost effective flexible system, thorough understanding of the dynamics is essential. This paper reviews the theoretical basics of the dynamic design options and applies these to realistic situations, including offshore machines under wave action. The wind energy converter and the support structure form an integrated dynamic system that must be developed in mutual interdependency and close co-operation. This paper provides a contribution to this integration process by extending the design approach initiated in the Opti-OW ECS study and the work of Kuhn. (author)

Thermodynamic model of natural, medieval and nuclear waste glass durability

International Nuclear Information System (INIS)

Jantzen, C.M.; Plodinec, M.J.

1983-01-01

A thermodynamic model of glass durability based on hydration of structural units has been applied to natural glass, medieval window glasses, and glasses containing nuclear waste. The relative durability predicted from the calculated thermodynamics correlates directly with the experimentally observed release of structural silicon in the leaching solution in short-term laboratory tests. By choosing natural glasses and ancient glasses whose long-term performance is known, and which bracket the durability of waste glasses, the long-term stability of nuclear waste glasses can be interpolated among these materials. The current Savannah River defense waste glass formulation is as durable as natural basalt from the Hanford Reservation (10 6 years old). The thermodynamic hydration energy is shown to be related to the bond energetics of the glass. 69 references, 2 figures, 1 table

Aerodynamics of wind turbines emerging topics

CERN Document Server

Amano, R S

2014-01-01

Focusing on Aerodynamics of Wind Turbines with topics ranging from Fundamental to Application of horizontal axis wind turbines, this book presents advanced topics including: Basic Theory for Wind turbine Blade Aerodynamics, Computational Methods, and Special Structural Reinforcement Technique for Wind Turbine Blades.

Generalization of first-principles thermodynamic model: Application to hexagonal close-packed ε-Fe3N

DEFF Research Database (Denmark)

Bakkedal, Morten B.; Shang, Shu- Li; Liu, Zi-Kui

2016-01-01

A complete first-principles thermodynamic model was developed and applied to hexagonal close-packed structure ε-Fe3N. The electronic structure was calculated using density functional theory and the quasiharmonic phonon approximation to determine macroscopic thermodynamic properties at finite...

Aeroelastic impact of above-rated wave-induced structural motions on the near-wake stability of a floating offshore wind turbine rotor

Science.gov (United States)

Rodriguez, Steven; Jaworski, Justin

2017-11-01

The impact of above-rated wave-induced motions on the stability of floating offshore wind turbine near-wakes is studied numerically. The rotor near-wake is generated using a lifting-line free vortex wake method, which is strongly coupled to a finite element solver for kinematically nonlinear blade deformations. A synthetic time series of relatively high-amplitude/high-frequency representative of above-rated conditions of the NREL 5MW referece wind turbine is imposed on the rotor structure. To evaluate the impact of these above-rated conditions, a linear stability analysis is first performed on the near wake generated by a fixed-tower wind turbine configuration at above-rated inflow conditions. The platform motion is then introduced via synthetic time series, and a stability analysis is performed on the wake generated by the floating offshore wind turbine at the same above-rated inflow conditions. The stability trends (disturbance modes versus the divergence rate of vortex structures) of the two analyses are compared to identify the impact that above-rated wave-induced structural motions have on the stability of the floating offshore wind turbine wake.

Wind Observatory 2017. Analysis of the wind power market, wind jobs and future of the wind industry in France

International Nuclear Information System (INIS)

2017-09-01

Two years after the enactment of the Energy Transition for Green Growth Act, wind power capacity continues to grow in France, exceeding 12 GWatt the end of 2016 and soon to account for 5% of France's electric power consumption. This vitality, which is set to continue in 2017, will help France achieve its objectives of an installed capacity of 15,000 MW in onshore wind by 2018 and 21,800 to 26,000 MW by 2023. The current pace will nevertheless have to be accelerated in order to reach the realistic objective of 26 GW by 2023 mentioned in the multi-annual energy plan (PPE). With 1,400 jobs created in one year and more than 3,300 over the last two years, the relevance of wind power as a driving force of sustainable job creation throughout the country is unequivocally confirmed: the increase in wind power capacity continues to contribute to the growth in employment in the country. Prepared in collaboration with the consulting firm BearingPoint, the 2017 edition of the Observatory aims to give the reader an overview of employment in the wind industry and the wind power market over the period under consideration. Any changes from the three previous editions are highlighted. It is based on a comprehensive census of all market participants on three themes: employment, the market and the future of wind power. The Observatory gives an accurate picture of how the wind energy industry is structured, thereby presenting a precise overview of the wind energy industry and all its components

design of a small scale wind generator for low wind speed areas

African Journals Online (AJOL)

USER

Most small scale level wind turbine generators are directly driven system, variable speed, and partially ... the best solutions for small-scale wind power plants. Low-speed multi-pole PM generators ..... Designs of the Same Magnet Structure for.

An analytical coarse-graining method which preserves the free energy, structural correlations, and thermodynamic state of polymer melts from the atomistic to the mesoscale.

Science.gov (United States)

McCarty, J; Clark, A J; Copperman, J; Guenza, M G

2014-05-28

Structural and thermodynamic consistency of coarse-graining models across multiple length scales is essential for the predictive role of multi-scale modeling and molecular dynamic simulations that use mesoscale descriptions. Our approach is a coarse-grained model based on integral equation theory, which can represent polymer chains at variable levels of chemical details. The model is analytical and depends on molecular and thermodynamic parameters of the system under study, as well as on the direct correlation function in the k → 0 limit, c0. A numerical solution to the PRISM integral equations is used to determine c0, by adjusting the value of the effective hard sphere diameter, dHS, to agree with the predicted equation of state. This single quantity parameterizes the coarse-grained potential, which is used to perform mesoscale simulations that are directly compared with atomistic-level simulations of the same system. We test our coarse-graining formalism by comparing structural correlations, isothermal compressibility, equation of state, Helmholtz and Gibbs free energies, and potential energy and entropy using both united atom and coarse-grained descriptions. We find quantitative agreement between the analytical formalism for the thermodynamic properties, and the results of Molecular Dynamics simulations, independent of the chosen level of representation. In the mesoscale description, the potential energy of the soft-particle interaction becomes a free energy in the coarse-grained coordinates which preserves the excess free energy from an ideal gas across all levels of description. The structural consistency between the united-atom and mesoscale descriptions means the relative entropy between descriptions has been minimized without any variational optimization parameters. The approach is general and applicable to any polymeric system in different thermodynamic conditions.

Thermodynamic theory of equilibrium fluctuations

International Nuclear Information System (INIS)

Mishin, Y.

2015-01-01

The postulational basis of classical thermodynamics has been expanded to incorporate equilibrium fluctuations. The main additional elements of the proposed thermodynamic theory are the concept of quasi-equilibrium states, a definition of non-equilibrium entropy, a fundamental equation of state in the entropy representation, and a fluctuation postulate describing the probability distribution of macroscopic parameters of an isolated system. Although these elements introduce a statistical component that does not exist in classical thermodynamics, the logical structure of the theory is different from that of statistical mechanics and represents an expanded version of thermodynamics. Based on this theory, we present a regular procedure for calculations of equilibrium fluctuations of extensive parameters, intensive parameters and densities in systems with any number of fluctuating parameters. The proposed fluctuation formalism is demonstrated by four applications: (1) derivation of the complete set of fluctuation relations for a simple fluid in three different ensembles; (2) fluctuations in finite-reservoir systems interpolating between the canonical and micro-canonical ensembles; (3) derivation of fluctuation relations for excess properties of grain boundaries in binary solid solutions, and (4) derivation of the grain boundary width distribution for pre-melted grain boundaries in alloys. The last two applications offer an efficient fluctuation-based approach to calculations of interface excess properties and extraction of the disjoining potential in pre-melted grain boundaries. Possible future extensions of the theory are outlined.

Participation of mechanical oscillations in thermodynamics of crystals with superlattice

International Nuclear Information System (INIS)

Jacjimovski K, S.; Mirjanicj Lj, D.; Shetrajchicj P, J.

2012-01-01

The superlattice, consisting of two periodically repeating films, is analyzed in proposal paper. Due to the structural deformations and small thickness, the acoustic phonons do not appear in these structures. The spontaneous appearance of phonons is possible in an ideal structure only. Therefore the thermodynamical analysis of phonon subsystems is the first step in investigations of superlattice properties. Internal energy as well as specific heat will be analyzed, too. Low-temperature behavior of these quantities will be compared to the corresponding quantities of bulk structures and of thin films. The general conclusion is that the main thermodynamic characteristics of superlattices are considerably lower than those of the bulk structure. Consequently, their superconductive characteristics are better than the superconductive characteristics of corresponding bulk structures. Generally considered, the application field of superlattices is wider than that of bulk structures and films. (Author)

Design of Offshore Wind Turbine Support Structures: Selected topics in the field of geotechnical engineering

DEFF Research Database (Denmark)

Bakmar, Christian LeBlanc

.D. thesis was to enable low-cost and low-risk support structures to be designed in order to improve the economic feasibility of future offshore wind farms. The research work was divided in the following four selected research topics in the field of geotechnical engineering, relating to the monopile......Breaking the dependence on fossil fuels offers many opportunities for strengthened competitiveness, technological development and progress. Offshore wind power is a domestic, sustainable and largely untapped energy resource that provides an alternative to fossil fuels, reduces carbon emissions......, and decreases the economic and supply risks associated with reliance on imported fuels. Today, the modern offshore wind turbine offers competitive production prices for renewable energy and is therefore a key technology in achieving the energy and climate goals of the future. The overall aim of this Ph...

Nonlinear Dynamics of Wind Turbine Wings

DEFF Research Database (Denmark)

Larsen, Jesper Winther

, large wind turbines become increasingly flexible and dynamically sensitive. This project focuses on the structural analysis of highly flexible wind turbine wings, and the aerodynamic loading of wind turbine wings under large changes in flow field due to elastic deformations and changing wind conditions....

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