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A geometrical method for assessing stochastic processes in plasma turbulence is investigated in this study. The thermodynamic length methodology allows using a Riemannian metric on the phase space; thus, distances between thermodynamic states can be computed. It constitutes a geometric methodology to understand stochastic processes involved in, e.g., order–disorder transitions, where a sudden increase in distance is expected. We consider gyrokinetic simulations of ion-temperature-gradient (ITG)-mode-driven turbulence in the core region of the stellarator W7-X with realistic quasi-isodynamic topologies. In gyrokinetic plasma turbulence simulations, avalanches, e.g., of heat and particles, are often found, and in this work, a novel method for detection is investigated. This new method combines the singular spectrum analysis algorithm with a hierarchical clustering method such that the time series is decomposed into two parts: useful physical information and noise. The informative component of the time series is used for the calculation of the Hurst exponent, the information length, and the dynamic time. Based on these measures, the physical properties of the time series are revealed.

Thermal runaway is a major concern for lithium-ion batteries in electric vehicles. A manufacturing fault or unusual operating conditions may lead to this event. Starting from a single battery cell, more cells may be triggered into thermal runaway, and the battery pack may be destroyed. To prevent this from happening, safety solutions need to be evaluated. Physical testing is an effective, yet costly, method to assessing battery safety performance. As such, the potential of a numerical tool, which can cut costs and reduce product development times, is investigated in terms of capturing a battery module’s tolerance to a single cell failure. A 3D-FE model of a battery module was built, using a commercial software, to study thermal runaway propagation. The model assumes that when the cell jelly roll reaches a critical value, thermal runaway occurs. This approach was considered to study the module’s tolerance to a single cell failure, which was in reasonable agreement with what had been observed in full-scale experiments. In addition, quantitative sensitivity study on the i) model input parameters, ii) model space, and iii) time resolutions on the computed start time instant and time duration of thermal runaway were performed. The critical temperature was found to have the greatest influence on thermal runaway propagation. The specific heat capacity of jelly roll was found to significantly impact the thermal runaway time duration. The multi-physics model for battery thermal propagation is promising and worth to be applied with care for designing safer batteries in combination with physical testing.

Purpose The purpose of this paper is to propose a simplified representation of the fire load in computational fluid dynamics (CFD) to represent the effect of large-scale travelling fire and to highlight the relevance of such an approach whilst coupling the CFD results with finite element method (FEM) to evaluate related steel temperatures, comparing the numerical outcomes with experimental measurements. Design/methodology/approach This paper presents the setup of the CFD simulations (FDS software), its corresponding assumptions and the calibration via two natural fire tests whilst focusing on gas temperatures and on steel temperatures measured on a central column. For the latter, two methods are presented: one based on EN 1993-1-2 and another linking CFD and FEM (SAFIR® software). Findings This paper suggests that such an approach can allow for an acceptable representation of the travelling fire both in terms of fire spread and steel temperatures. The inevitable limitations inherent to the simplifications made during the CFD simulations are also discussed. Regarding steel temperatures, the two methods lead to quite similar results, but with the ones obtained via CFD–FEM coupling are closer to those measured. Originality/value This work has revealed that the proposed simplified representation of the fire load appears to be appropriate to evaluate the temperature of steel structural elements within reasonable limits on computational time, making it potentially desirable for practical applications. This paper also presents the first comparisons of FDS–SAFIR® coupling with experimental results, highlighting promising outcomes.

Nine participants, representing eight different Swedish fire consultancy firms participated in a Round Robin study where two different cases were simulated with the Fire Dynamics Simulator. The first case included a large open warehouse where the activation of a sprinkler system was to be studied. In the second case time to critical conditions in a theatre was to be calculated. The participants were given clear instructions on the building layout and heat release rate for the two cases. Still, the results demonstrate a significant variation in time to sprinkler system activation (range of 110 seconds) and available safe escape time (range of 60 seconds), between the participants. It is important to emphasise that some degree of variation is unavoidable, as engineers can model things differently without the modelling solution necessarily being incorrect. Even though it is hard to isolate and specific cause of the variation, some of the variation seen in this study is related to modelling choices that are questionable and consequently problematic for the reliability of the fire safety design.

Several attempts have been made in the past to develop a European harmonized testing and assessment method for façades before the European commission decided to publish a call for tender on the topic. A project consortium from five countries (Sweden, UK, France, Germany and Hungary) applied to the call for tender and was contracted to develop a European approach to assess the fire performance of façades. 24 sub-contractors and 14 stakeholder entities were part of the project. The objective of the European project was to address a request from the Standing Committee of Construction (SCC) to provide EC Member States regulators with a means to regulate the fire performance of façade systems based on a European approach agreed by SCC. The initial stages of this project were focused on establishing a register of the regulatory requirements in all Member States in relation to the fire performance of façade systems, and to identify those Member States who have regulatory requirements for the fire performance façade systems which go beyond the current EN 13501 (reaction to fire and fire resistance) classification systems and to collate the details of these additional requirements. After having confirmed the regulatory needs a testing and classification methodology based on BS 8414 and DIN 4102-20 was developed to address the identified key performance and classification characteristics. This paper is a short overview of results the two-year development work, which Final Report published by the European Commission in 2018. © 2020 The Authors. Fire and Materials published by John Wiley & Sons Ltd.

The present paper investigates a travelling fire scenario in an elongated structure (Length 18 m × width 6 m × height 3 m) with a controlled fire source of six trays filled with diesel (width 4 m × length 0.5 m). The fire spread is controlled manually by initiating fires consecutively in the pools. Fire dynamics simulator (FDS) is used to a-priori investigate variations in geometry, material data and fire load, whereas simulations using the final design and measured heat release rates (HRR) were performed after the test. The input to the model beside fire source and geometry are thermal material data. The FDS simulations were used to determine the appropriate size of the downstands (2 m from the ceiling in the final design) on the side to create a sufficiently one-dimensional fire spread. The post-test simulations indicate that although there are a lot of variations not included in the model similar results were obtained as in the test.

UID/FIS/00068/2019 The EURAMET EMPIR project “16NRM05 - Ion gauge” aims to develop an ionisation vacuum gauge suitable as a reference vacuum standard. In such a gauge the electron trajectories and their kinetic energy inside the ionisation volume should be well defined and stable. In the search for a suitable design, a series of simulations on different ionisation gauge concepts that have the potential to meet stringent stability requirements have been carried out. Different software packages were used for this purpose. This paper focuses on the design aspects and the performance of the different ionisation gauge concepts that have been investigated by simulation. Parameters such as ionisation gauge sensitivity, ion collection efficiency and electron transmission efficiency, have been determined as a function of emission current, pressure and electron source alignment. publishersversion published

Fires in open large-floor plan spaces do not always reach a post-flashover fire state and recently, the “travelling fire” terminology has been used to define fires burning locally and moving across entire floor plates over a period of time [1]. Several studies have been presented about the behavior of a structure when it is subjected to this fire scenario [2-5]. Due to their limited number, fire tests are not enough to cover all possible configurations encountered in practice, but this limitation can potentially be overcome with help of CFD. In the frame of the European RFCS TRAFIR project, a simplified representation of the fire load was developed to calibrate an FDS model representing large scale travelling fire tests. The numerical and experimental results have been compared in terms of gas and steel temperatures (the radiative intensities and gas temperatures calculated by FDS have been used by SAFIR® to calculate the temperatures in a steel column). The approach provides acceptable representations of fire spread and steel temperatures within reasonable computational demands.

A new more insulated and faster responding plate thermometer (PT) is introduced, which has been developed for measurements particularly in air at ambient temperature. It is a cheaper and more pract ...

The impact of different passive protective measures against external vertical fire spread was investigated using the numerical tool Fire Dynamics Simulator (FDS). The numerical study was divided into a validation study and a comparative analysis. The validation study was performed to evaluate FDS as a calculation tool for modelling external vertical fire spread and was conducted using experimental results from a large-scale fire test done on a SP FIRE 105 test rig at SP, Sweden. It was concluded that FDS 6.2.0 could reproduce the experimental results with a reasonable level of detail. In the comparative analysis, the impact on the external fire from a smaller apartment was studied in FDS with different configurations of horizontal projections and spandrels in the building exterior. Also, the effects of an upper and lower facade set-back configuration were studied. The results show that facade solutions based on a horizontal projection or an upper facade set-back configuration result in comparable or better protection compared with a defined spandrel height. The results also show that a spandrel height of at least 1.2 m can be replaced by a 60-cm-deep horizontal projection, given that the balcony is wider than the underlying opening. (Less)

A comparison between full-scale façade fire tests where SP Fire 105 and BS 8414–1 were used regarding repeatability and the use of modelling to discern changes in the set-ups is presented. Two test series according to BS 8414 – 1 were repeated outside using the same façade systems on two different days whereas for the SP Fire 105 a set of common façade systems in Sweden were tested indoors. In particular, the results show that the wind around the test set-up may have a significant impact on the tests and that the heat exposure to the façade surface will depend on the thickness of the test specimen where an increased temperature in front of the façade, and a decreased temperature on the façade 2.1 m above the fire room, is observed experimentally. The heat exposure to the test specimen varies to a more limited extent when an uncontrollable free burning fire source is used (in this study heptane and wood respectively) and that this variation increases when wind is present.

In this paper a comparative simulation study on three large scale façade testing methods, namely the SP Fire 105, BS 8414 – 1 and the ISO 13785 – 2 methods, is presented. Generally good correspondence between simulations and experimental data has been found, provided that thermal properties of the façade material and heat release rates are known however the correspondence seems to deviate in close proximity of the fire source. Furthermore, a statistical ensemble for evaluating the effects stemming from uncertainty in input data is used. Here, it was found using a statistical ensemble the variability in input data could be assessed and that the variability was smaller in the ISO 13785 – 2 compared to the BS 8414 – 1 method. The heat release rates (HRR) used in the simulations were adopted from measurements except for the ISO method where the information in the standard was used to approximate the HRR. Furthermore, a quantitative similarity between the HRR in the ISO method and the British method was found.

In this paper, fractional factorial design (FFD) and deterministic sampling (DS) are applied to a finite element (FE) model of a fire resistance test of a loaded steel beam, to investigate how uncertainties are propagated through the FE model. The sought quantity was the time when the deflection of the beam exceeded 225 mm. The FFD method was used as a model reduction technique which reduced the number of uncertain parameters from 5 to 3. The DS method was compared to a reference Monte Carlo (MC) method of 1000 simulations from all 5 uncertain parameters, which was the minimum number of simulations in order for the statistical moments to converge. The combined FFD and DS method successfully computed the propagation of the mean and standard deviation in the model, compared to the MC method. Given the uncertainties in the FE model, the fractional factorial design reduced the number of simulations required in the DS method by 82%. The combined method of FFD and DS reduced the number of required simulations by 96% compared to the MC method. The DS method did not capture the tails of the probability distribution and is therefore not a suitable candidate for probabilistic evaluation of the time of failure at the edges of the domain of possible failure times. Future research could very well be on improving the tails in DS. However, the DS method provides a conservative 95% coverage interval of 6 min for the time to failure of the steel beam.

The impact of adiabatic electrons on drift-wave turbulence, modelled by the Hasegawa-Wakatani equations, is studied using information length. Information length is a novel theoretical method for measuring distances between statistical states represented by different probability distribution functions (PDFs) along the path of a system. Specifically, the time-dependent PDFs of turbulent fluctuations for a given adiabatic index $A$ is computed. The changes in fluctuation statistics are then quantified in time by using information length. The numerical results provide time traces exhibiting intermittent plasma dynamics, and such behaviour is identified by a rapid change in the information length. The effects of $A$ are discussed., Comment: 23 pages submitted to Physics of Plasmas. arXiv admin note: text overlap with arXiv:1706.02849

Microtearing mode (MTM) real frequency, growth rate, magnetic fluctuation amplitude, and resulting electron thermal transport are studied in systematic NSTX scans of relevant plasma parameters. The dependency of the MTM real frequency and growth rate on plasma parameters, suitable for low and high collision NSTX discharges, is obtained by using the reduced MTM transport model [T. Rafiq et al., Phys. Plasmas 23, 062507 (2016)]. The plasma parameter dependencies are compared and found to be consistent with the results obtained from MTM using the gyrokinetic GYRO code. The scaling trend of collision frequency and plasma beta is found to be consistent with the global energy confinement trend observed in the NSTX experiment. The strength of the magnetic fluctuation is found to be consistent with the gyrokinetic estimate. In earlier studies, it was found that the version of the multi-mode (MM) anomalous transport model, which did not contain the effect of MTMs, provided an appropriate description of the electron temperature profiles in standard tokamak discharges and not in spherical tokamaks. When the MM model, which involves transport associated with MTMs, is incorporated in the TRANSP code and is used in the study of electron thermal transport in NSTX discharges, it is observed that the agreement with the experimental electron temperature profile is substantially improved.

A model is presented for predicting the cell-to-cell propagation of a thermal runaway/fire in a lithium-ion battery cell to neighboring cells by simulating the temperature development in neighboring cells. The modelling work comprises of two major steps; setting up a model of the cells including the thermal properties of the cells, and then validating the model through experiments where the boundary conditions in the validation test must be determined carefully. The model is developed to allow a fast evaluation of several different preventive means of thermal insulation, it is not modelling the pack and cells to a great detail. Still the experimental validation indicates that the model is good enough to fulfil its purpose of the model. A feasibility study using the model is conducted assessing two different types of fire walls between battery modules of 10 cells. The results show that there is a substantial risk for a cascading of thermal events in a battery pack, although cooling systems and fire walls may mitigate these risks.

The~numerical solutions to a non-linear Fractional Fokker--Planck (FFP) equation are studied estimating the generalized diffusion coefficients. The~aim is to model anomalous diffusion using an FFP description with fractional velocity derivatives and Langevin dynamics where L\'{e}vy fluctuations are introduced to model the effect of non-local transport due to fractional diffusion in velocity space. Distribution functions are found using numerical means for varying degrees of fractionality of the stable L\'{e}vy distribution as solutions to the FFP equation. The~statistical properties of the distribution functions are assessed by a generalized normalized expectation measure and entropy and modified transport coefficient. The~transport coefficient significantly increases with decreasing fractality which is corroborated by analysis of experimental data., Comment: 20 pages 7 figures

The work presented here is a review of current developments in modelling anomalous diffusion using a Fokker-Planck description with fractional velocity derivatives and Langevin dynamics where Levy fluctuations are introduced to model the effect of non-local transport due to fractional diffusion in velocity space. Distribution functions are found using numerical means for varying degree of fractionality of the stable Levy distribution as solutions to the Fokker-Planck equation and is compared to results from Langevin simulations. The statistical properties of the distribution functions are assessed by a generalized normalized expectation measure and entropy in terms of Tsallis statistical mechanics.

Resistive drift wave turbulence is a multipurpose paradigm that can be used to understand transport at the edge of fusion devices. The Hasegawa-Wakatani model captures the essential physics of drift turbulence while retaining the simplicity needed to gain a qualitative understanding of this process. We provide a theoretical interpretation of numerically generated probability density functions (PDFs) of intermittent events in Hasegawa-Wakatani turbulence with enforced equipartition of energy in large scale zonal flows and small scale drift turbulence. We find that for a wide range of adiabatic index values the stochastic component representing the small scale turbulent eddies of the flow, obtained from the ARIMA model, exhibits super-diffusive statistics, consistent with intermittent transport. The PDFs of large events (above one standard deviation) are well approximated by the Laplace distribution, while small events often exhibit a Gaussian character. Furthermore there exist a strong influence of zonal flows for example, via shearing and then viscous dissipation maintaining a sub-diffusive character of the fluxes.

As a natural material, the response of timber structures under normal conditions and to fire is subject to wide variability. Deterministic models therefore struggle to reflect the reality of the response of timber since small variations in input influence the output significantly. However it is relatively straightforward to quantify uncertainties in model inputs in order to determine the uncertainties in the model response by employing uncertainty quantification (UQ) techniques. UQ of structural response to fire traditionally employs Monte Carlo techniques (Eamon and Jensen 2013) which are computationally expensive for a large number of variables. Deterministic Sampling (DS) (Hessling 2013) is a relatively new efficient alternative method for UQ. DS assumes that a continuous probability density function can be replaced by an ensemble of discrete deterministic samples if the two representations have the same statistical moments. DS has been demonstrated applied to, e.g. CFD simulations (Anderson et al. 2016). This paper applies DS techniques to study glued-laminated (glulam) timber in fire. Results are compared with random sampling techniques to show the validity of this method in this application.

In plasma turbulence theory, due to the complexity of the system with many non-linearly interacting waves, the dynamics of the phases is often disregarded and the so-called random-phase approximation (RPA) is used assuming the existence of a Chirikov-like criterion for the onset of wave stochasticity. The dynamical amplitudes are represented as complex numbers, $\psi = \psi_r + i\psi_i = ae^{i\theta}$, with the amplitudes slowly varying whereas the phases are rapidly varying and, in particular, distributed uniformly over the interval $[0;2\pi)$. However, one could expect that the phase dynamics can play a role in the self-organisation and the formation of coherent structures. In the same manner it is also expected that the RPA falls short to take coherent interaction between phases into account. In this work therefore, we studied the role of phase dynamics and the coupling of phases between different modes on the characteristic time evolution of the turbulent. We assume a simple turbulent system where the so-called stochastic oscillator model can be employed. The idea of interpreting turbulence by stochastic oscillators. The stochastic oscillator models can be derived from radical simplifications of the nonlinear terms in the Navier-Stokes or Gyro-Kinetic equations. In this particular case we adopt the basic equation for the stochastic oscillator model with passive advection and random forcing from Ref., Comment: Proceedings of the 43rd EPS Conference on Plasma Physics, July 4-8, Leuven, Belgium 2016

Collective synchronous motion of the phases is introduced in a model for the stochastic passive advection-diffusion of a scalar with external forcing. The model for the phase coupling dynamics follows the well known Kuramoto model paradigm of limit-cycle oscillators. The natural frequencies in the Kuramoto model are assumed to obey a given scale dependence through a dispersion relation of the drift-wave form $-\beta\frac{k}{1+k^2}$, where $\beta$ is a constant representing the typical strength of the gradient. The present aim is to study the importance of collective phase dynamics on the characteristic time evolution of the fluctuation energy and the formation of coherent structures. Our results show that the assumption of a fully stochastic phase state of turbulence is more relevant for high values of $\beta$, where we find that the energy spectrum follows a $k^{-7/2}$ scaling. Whereas for lower $\beta$ there is a significant difference between a-synchronised and synchronised phase states, and one could expect the formation of coherent modulations in the latter case., Comment: Accepted for publication in Physics of Plasmas

In this paper a comparison between test and modelling results are performed for two large-scale façade fire testing methods, namely SP Fire 105 and BS 8414-1. In order to be able to compare tests and modelling the uncertainties have to be quantified both in the test and the modelling. Here we present a methodology based on deterministic sampling to quantify uncertainties in the modelling input. We find, in general good agreement between the models and the test results. Moreover, temperatures estimated by plate thermometers is indicated to be less sensitive to small variations in model input and is thus suitable for these kind of comparisons. References: SP FIRE 105, Method for Fire Testing of Façade Materials, , Dnr 171-79-360 Department of Fire Technology, Swedish National Testing and Research Institute; (2002) Fire Performance of External Cladding Systems - Part 1: Test Method for Non-loadbearing External Cladding Systems Applied to the Face of the Building; White, N., Delichatsios, M., (2014) Fire Hazards of Exterior Wall Assemblies Containing Combustable Components, , National Fire Protection Association (NFPA) Fire Protection Research Foundation Report; Yokoi, S., (1960) Study on the Prevention of Fire-spread Caused by Hot Upward Current, , Japanese Ministry of Construction, Building Research Institute Report; Ödeen, K., Nordström, A., (1967) Fire and Smoke Spread Along Facades and in Ventilation Ducts (in Swedish), , Arbetshandling 12:1967 från Byggforskningen, Statens Provningsanstalt (SP Technical Research Institute of Sweden); Ondrus, J., Pettersson, O., (1986) Fire Hazards of Façades with Externally Applied Additional Thermal Insulation, , LUTVDG/(TVBB-3025); Anderson, J., Boström, L., Jansson, R., Milovanović, B., Fire dynamics in façade fire tests: Measurement, modelling and repeatability (2015) Applications in Structural Fire Engineering, , 15-16 October; Anderson, J., Jansson, R., Façade fire tests - Measurements and modeling (2013) MATEC Web of Conferences, 9, p. 02003; Anderson, J., Jansson, R., Fire dynamics in Façade fire tests: Measurement and modeling (2013) Proceedings of Interflam 2013, p. 93. , Royal Holloway College, University of London UK; Jansson, R., Anderson, J., Experimental and numerical investigation of fire dynamics in a façade test rig (2012) Proceedings of Fire Computer Modeling, p. 247. , Santander, Spain, 18-19th October; McGrattan, K., McDermott, R., Hostikka, S., Floyd, J., (2015) Fire Dynamics Simulator (Version 6) - User's Guide, , NIST Special Publication 1019; (2002) Guide for the Verification and Validation of Computational Fluid Dynamics Simulations, , (AIAA G-077-1998); (2014) A Primer for NAFEMS QSS, , NAFEMS; Hessling, J.P., Deterministic sampling of propagating model covariance (2013) SIAM/ASA J. Uncertainty Quantification, 1, pp. 297-318; Hermansson, K., (2015) Quality Assurance and the Simulation of Fires - A Practical Application for Automated Validation of User-generated Input Data for FDS, , Thesis Report 5501 Lund University; Babrauskas, V., Facade fire tests: Towards an international test standard (1996) Fire Technology, 32, pp. 219-230

The coordinates and orientation of a total station can be determined by using common points, i.e. pointssurveyed both by total station and RTK (Real Time Kinematics) GPS. In this paper we use a trial anderror method to analyse how the number and distribution of common points affects the precision of thetotal station establishment. It was found that a reasonable number of common points is 10 – 30, and thatthese should be distributed around the total station on a half circle. The radius of the half circle doesnot significantly affect precision of horizontal and vertical positions; it affects only orientationprecision. Therefore we suggest locating most of the common points close to the total station and a fewof them at longer distance.

The role of the phase dynamics in turbulence is investigated. As a demonstration of the importance of the phase dynamics, a simplified system is used, namely the one-dimensional Burgers equation, which is evolved numerically. The system is forced via a known external force, with two components that are added into the evolution equations of the amplitudes and the phase of the Fourier modes, separately. In this way, we are able to control the impact of the force on the dynamics of the phases. In the absence of the direct forcing in the phase equation, it is observed that the phases are not stochastic as assumed in the Random Phase Approximation (RPA) models, and in contrast, the non-linear couplings result in intermittent locking of the phases to ± π/2. The impact of the force, applied purely on the phases, is to increase the occurrence of the phase locking events in which the phases of the modes in a wide k range are now locked to ± π/2, leading to a change in the dynamics of both phases and amplitudes, with a significant localization of the real space flow structures.

PurposeThe ever present need for the miniaturization of electronic assemblies has driven the size of passive components to as small as the 01005 package size. However, the packaging standards for these components are still under development. The purpose of this work is to report results from experiments designed to establish optimum process parameters, pad sizes and component clearances for the surface mounting of 01005 passive components.Design/methodology/approachThe experiments were designed using MODDE, an experimental design software tool, and were carried out with both 01005 capacitors and resistors. All the assembled components were examined under microscope and judged according to industrial workmanship standards.FindingsIt was found that a viable solder paste printing process for the assembly of 01005 components can be achieved with a 75 μm thick stencil. Type 5 solder paste achieved a similar printing performance to type 4. Under the experimental conditions used, the optimum pad dimensions for the 01005 capacitors were 210 μm length, 220 μm width, 160 μm separation and for the resistors were 190 μm length, 220 μm width, 160 μm separation. The smallest component clearance to reliably avoid bridging was found to be 100 μm. A high placement force of 3.5 N was found to cause cracking of 01005 resistors.Originality/valueFrom this work, a surface mount process for 01005 passive components is established and it is concluded that electronics packaging density can be increased through the assembly of these small components. In the near future, the widespread use of them will definitely facilitate a further reduction in the size of electronic assemblies, especially in handheld and portable devices.

Presented is a comparison between full-scale façade tests where SP Fire 105 and BS 8414-1 were used regarding repeatability and the use of modelling to discern changes in the set-ups. Results show that the air movements around the test set-up (the wind) may have a significant impact on the tests and that the heat exposure to the façade surface will among other depend on the thickness of the test specimen. Also demonstrated was that good results could be obtained by modelling of the façade fire tests giving us the opportunity to use these methods to determine the effect of a change in the experimental setup.

A theoretical interpretation of numerically generated probability density functions (PDFs) of intermittent plasma transport events in unforced zonal flows is provided within the Charney-Hasegawa-Mima (CHM) model. The governing equation is solved numerically with various prescribed density gradients that are designed to produce different configurations of parallel and anti-parallel streams. Long-lasting vortices form whose flow is governed by the zonal streams. It is found that the numerically generated PDFs can be matched with analytical predictions of PDFs based on the instanton method by removing the autocorrelations from the time series. In many instances the statistics generated by the CHM dynamics relaxes to Gaussian distributions for both the electrostatic and vorticity perturbations, whereas in areas with strong nonlinear interactions it is found that the PDFs are exponentially distributed., Comment: Accepted for publication in Physics of Plasmas

This work focuses on uncertainty analysis, that is, how the input data uncertainty affects the output data uncertainty in small but realistic product systems. The motivation for the study is to apply the Monte Carlo simulation for uncertainty estimation in life cycle inventory and environmental assessment of microelectronics applications. The present paper addresses the question whether there is an environmental advantage of using digital enhanced cordless telecommunications (DECT) phones instead of global system for mobile (GSM) phones in offices. This paper also addresses the environmental compatibility of electrochemical pattern replication (ECPR) compared to classical photolithography-based microscale metallization (CL) for pattern transfer. Both environmental assessments in This work consider electricity consumption and CO/sub 2/ emissions and the projects undertaken are two comparative studies of DECT phone/GSM phone and ECPR/CL, respectively. The research method used was probabilistic uncertainty modeling with a limited number of inventory parameters used in the MATLAB tool. For the DECT/GSM study the results reflects the longer DECT technical life which is an environmental advantage. For the electrochemical pattern replication (ECPR)/classical photolithography based microscale metallization (CL) study the results reflects the fewer number of process steps and the lower electricity consumption needed by the ECPR to reach the functional unit. The difference in results is large enough to be able to draw conclusions, as the processes, having the highest electricity consumption within the system boundaries have been determined. Based on an earlier work, a straightforward method to include uncertainty for input life cycle inventory data is used to quantify the influence of realistic errors for input data in two microelectronic applications. The conclusion is that the ECPR technology is more electricity efficient than CL in producing one layer of copper on a silicon wafer having a diameter of 20.32 cm. Furthermore, the longer technical life of a cordless DECT phone is reflected in an electricity/CO/sub 2/ comparison with a GSM phone, if office use is considered. Reasonable uncertainty intervals, used for the input life cycle inventory data for the studied DECT/GSM and ECPR/CL system, does affect the outcome of calculation of emission of CO/sub 2/, but not to the degree that conclusions are not valid. Different uncertainty intervals and probability distributions could apply for different types of data and the interrelated input data dependencies should be investigated. Today there exist very few life cycle inventory (LCI) data with the range of uncertainty for input and output elements. It must be emphasized that the upcoming LCI databases should have standard deviation characterized LCI data just as the Swiss ecoinvent LCI database. More inventory parameters and probability distributions characteristic for microsystems could be included and error analysis should be applied to future life inventory methodology, especially for future packaging concepts such as system-in-a-package and system-on-a-chip comparisons.

In this paper, we demonstrate the importance of the details of the equilibria on the stability of electron drift waves. A comparison of electrostatic electron drift waves in numerical and analytical tokamak equilibria is presented in fully three-dimensional circular and non-circular tokamaks. The numerical equilibria are obtained using the variational moments equilibrium code and the analytical equilibria used is the generalized ŝ-α model. An eigenvalue equation for the model is derived using the ballooning mode formalism and solved numerically using a standard shooting technique. The stability and the localization of the electron drift wave is found to be strongly dependent on the local shear of the magnetic field. Large values of the local shear are found to be stabilizing. A disagreement in the results is found between analytical and numerical equilibria at aspect ratios of typical tokamaks, suggesting that the latter approach should be used in the transport calculations. The effects of the local shaping of the magnetic surfaces are complicated and can be both stabilizing and destabilizing, depending on the details of the equilibria.

The stability of electromagnetic ion temperature gradient driven (ITG) modes is investigated using an advanced fluid model allowing for arbitrary elongation (κ) and finite beta effects and Shafranov shift. The ITG eigenvalue equation is solved numerically and the stability properties are discussed and compared in both the circular and noncircular geometry. It is found that elongation and finite beta effects reduce the growth rates and that the ITG mode is stabilized for large beta values as elongation is increased. Elongation increases the beta threshold of the ITG mode with larger growth rates as compared with circular geometry.

The influence of plasma geometry on the linear stability of electrostatic ion-temperature-gradient driven drift modes (ITG modes) is investigated. An advanced fluid model is used for the ions together with Boltzmann distributed electrons. The derived eigenvalue equation is solved numerically. A comparison is made between an H – 1NF [Fusion Technol. 17, 123 (1990)] like stellarator equilibrium, a numerical tokamak equilibrium and the analytical s - alpha equilibrium. The numerical and the analytical tokamak are found to be in good agreement in the low inverse aspect ratio limit. The growth rates of the tokamak and stellarator are comparable whereas the modulus of the real frequency is substantially larger in the stellarator. The threshold in Ln/LT for the stellarator is found to be somewhat larger. In addition, a stronger stabilization of the ITG mode growth is found for large L n / R in the stellarator case.

A novel possibility of self-organized behaviour of stochastically driven oscillators is presented. It is shown that synchronization by L\'evy stable processes is significantly more efficient than that by oscillators with Gaussian statistics. The impact of outlier events from the tail of the distribution function was examined by artificially introducing a few additional oscillators with very strong coupling strengths and it is found that remarkably even one such rare and extreme event may govern the long term behaviour of the coupled system. In addition to the multiplicative noise component, we have investigated the impact of an external additive L\'evy distributed noise component on the synchronisation properties of the oscillators., Comment: Accepted in J. Phys. A: Math. Theor. (2017)

A novel methodology to analyze non-Gaussian probability distribution functions (PDFs) of intermittent turbulent transport in global full-f gyrokinetic simulations is presented. In this work, the Auto-Regressive Integrated Moving Average (ARIMA) model is applied to time series data of intermittent turbulent heat transport to separate noise and oscillatory trends, allowing for the extraction of non-Gaussian features of the PDFs. It was shown that non-Gaussian tails of the PDFs from first principles based gyrokinetic simulations agree with an analytical estimation based on a two fluid model., arXiv admin note: text overlap with arXiv:1008.3214

This paper demonstrates the possibility to predict a battery system's performance in a fire resistance test according to the new amendment of United Nations Regulation No. 100 “Uniform Provisions Concerning the Approval of Vehicles with Regard to Specific Requirements for the Electric Power Train” (R100) based on careful measurements of the physical properties of the casing material, as well as modeling of the battery modules and computer simulations. The methodology of the work consists of estimating the heat transfer coefficients by using a gasoline pool fire model in the computational fluid dynamics (CFD) software FireDynamicsSimulator (FDS), followed by finite-element (FE) calculations of the temperatures in the battery

The ion-temperature-gradient (ITG)-driven drift mode is studied in three-dimensional stellarator geometry using a two-fluid reactive model in the electrostatic limit. The model includes first-order FLR effect in the presence of parallel ion dynamics and using the Boltzmann distribution for the electrons. The resulting eigenvalue is solved numerically using the ballooning mode theory. The results are contrasted with the corresponding tokamak results with positive shear. In stellarators, the level of the maximum growth rate of the ITG mode is found to be smaller and the threshold (ηi2.2) is somewhat higher. The effects of small and large temperature ratios and density gradients are found to be stabilizing on electrostatic ITG modes in stellarators.

Resistive edge modes in a shifted noncircular tokamak geometry are investigated in the electrostatic limit. The reduced Braghinskii equations are used as a model for the electrons and an advanced fluid model for the ions. An eigenvalue problem is derived from these equations which is solved numerically. It is found that the resistive ballooning modes are stabilized by plasma elongation for peaked density profiles. In addition, it is found that the resistive ITG mode may be either stabilized or destabilized by elongation depending on the collision frequency.

In two recent papers [1, 2] the fire dynamics in a test rig for facade constructions according to the test method SP Brand 105 [3, 4] was investigated both experimentally and numerically. The experimental setup simulates a three-story apartment building (height 6.7 m, width 4 m and depth 1.6 m), with external wall-cladding and a “room fire” at the base. The numerical model was developed in the CFD program Fire Dynamics Simulator (FDS) [5] with analogous geometry and instrumentation. The general features of the fire test were well reproduced in the numerical model however temperatures close to the fire source could not be properly accounted for in the model. In this paper the bi-directional probe measurements are elaborated on and the test used in Ref. [1] is revisited using different heat release rates in the numerical model. The velocity of the hot gases along the facade was well reproduced by the simulations although some deviations were found.

The influence of plasma elongation and Shafranov shift on the stability of electrostatic ion-temperature-gradient driven modes (ηi-modes) is investigated. An advanced fluid model is used for the ions together with Boltzmann distributed electrons. The derived eigenvalue equation is solved both analytically, in the strong ballooning limit, and numerically. It is found that the effects of elongation change from stabilizing, for peaked density profiles, to destabilizing in the flat density regime. In addition, it is shown that the maximum growth rate is shifted towards shorter wavelengths as the elongation increases. The effects of shaping on tokamak stability are exemplified with data from a Joint European Torus (JET) high-performance mode discharge.