Static Part Research Articles

How to use a Generic Model to Improve Part Quality and Testability

One big challenge in aeronautics is the combination of lightweight structures and a high degree of flight safety. Highly optimized structures and extensive quality assurance within NDT methods is one possibility to address this objective. The needs of NDT in respect of testability are often not considered during the design process of a structure or a part. This can lead to high inspection costs or even the need to redesign the part. The idea of this Generic Model would be to address this issue by highlighting the requirements of NDT allowing part optimization regarding these requirements in the early design process. This article presents the two parts of this Generic Model. The static part will be describing the test situation while the functional part will show the interaction of the static elements. Beginning with a single characteristic comparison, the example will show how to evaluate the testability of a complete part within the various aspects of NDT. An example of design considerations for a carbon fiber-reinforced plastic component is presented to demonstrate the application of the Generic Model. It will be seen how an automated evaluation is possible, and based on this idea a software tool could be developed. Two examples of design considerations for a carbon fiber-reinforced plastic component is presented to demonstrate the application of the Generic Model. The goal of implementing this Generic Model will be to improve part design, reduce iterations in the design process and increase the testability of NDT.

P218] Effect of flattening filter mounting surface position in Monte Carlo model of linear accelerators

Purpose Monte Carlo (MC) is considered as the gold standard for dose calculations of complex radiotherapy and the accuracy is mainly restricted by the statistical uncertainty. However, accurate MC simulations of radiation transport rely on a detailed description of the linear accelerator. The linac head is modelled in the specific MC code by using a geometrical description provided by the vendor. Interpreting the vendor provided drawings is, however, sometimes subject to uncertainties and vendors are not always willing to answer detail oriented questions. The position of the flattening filter (FF) mounting surface could be one such example. This study aimed at investigating the potential impact of an error in modelling the linac FF mounting surface. Methods Vendor-provided drawings of a modern linac head were interpreted and the 6 MV FF mounting surface was determined to have three possible positions. The positional uncertainty was in the distance from the linac target at which the mounting surface was placed. Discussions with the vendor and local engineers revealed one main candidate to be the correct choice, but nevertheless with doubt. The linac was therefore modelled in the BEAMnrc/EGSnrc user code with the three different geometries. Simulations of the radiation transport through the entire upper static part of the linac head were conducted and beam specific parameters were extracted and compared at a distance of 80 cm from the target. Results Interpreting the vendor provided drawings in three different ways revealed a maximum difference in the 6 MV FF mounting surface position of 1.6 mm from the most likely option. Analysis of the beam energy fluence (function of energy and off-axis position) at 80 cm distance from target revealed small differences (⩽1%). The beam was therefore considered to be independent of the mounting surface position within the distance variations investigated. Conclusions This study demonstrates that MC simulations are only marginally effected by various interpretations of the linac FF mounting surface position if positional differences are as low as 1.6 mm. Nonetheless, thorough and critical study of vendor provided drawings is necessary in order to conduct accurate MC simulations for radiotherapy purposes.

Equation-by-equation estimation of multivariate periodic electricity price volatility

Electricity prices are characterised by strong autoregressive persistence, periodicity (e.g. intraday, day-of-the week and month-of-the-year effects), large spikes or jumps, GARCH and – as evidenced by recent findings – periodic volatility. We propose a multivariate model of volatility that decomposes volatility multiplicatively into a non-stationary (e.g. periodic) part and a stationary part with log-GARCH dynamics. Since the model belongs to the log-GARCH class, the model is robust to spikes or jumps, allows for a rich variety of volatility dynamics without restrictive positivity constraints, can be estimated equation-by-equation by means of standard methods even in the presence of feedback, and allows for Dynamic Conditional Correlations (DCCs) that can – optionally – be estimated subsequent to the volatilities. We use the model to study the hourly day-ahead system prices at Nord Pool, and find extensive evidence of periodic volatility and volatility feedback. We also find that volatility is characterised by (positive) leverage in one third of the hours, and that a DCC model provides a better fit of the conditional correlations than a Constant Conditional Correlation (CCC) model.

Travelling waves and light-front approach in relativistic electrodynamics

We briefly report on a recent proposal (Fiore in J Phys A Math Theor 51:085203, 2018) for simplifying the equations of motion of charged particles in an electromagnetic (EM) field $F^{\mu\nu}$ that is the sum of a plane travelling wave $F_t^{\mu\nu}(ct\!-\!z)$ and a static part $F_s^{\mu\nu}(x,y,z)$; it adopts the light-like coordinate $\xi=ct\!-\!z$ instead of time $t$ as an independent variable. We illustrate it in a few cases of extreme acceleration, first of an isolated particle, then of electrons in a plasma in plane hydrodynamic conditions: the Lorentz-Maxwell \& continuity PDEs can be simplified or sometimes even completely reduced to a family of decoupled systems of ordinary ones; this occurs e.g. with the impact of the travelling wave on a vacuum-plasma interface (what may produce plasma waves or the slingshot effect).

Recursive identification of multiple-input single-output fractional-order Hammerstein model with time delay

This paper deals with identification of the continuous-time Hammerstein systems with time delay using Genetic Algorithm (GA) combined with the Recursive Least-Squares (RLS) method. This model consists of the Radial Basis Function Neural Network (RBFNN) as its nonlinear static part and fractional order transfer function as its dynamic linear part. The fractional orders are identified by GA with an innovative strategy called Modified Genetic Algorithm (MGA). The main innovative idea is the selection and transferring the best characteristics or properties to the next generation. On the other hand, the centers and widths and the weighting parameters of the RBFNN and the transfer function coefficients of the linear dynamic part are updated by the RLS method. Simulation results are applied to illustrate the proposed method accuracy.

Design Study of a 10-kW Fully Superconducting Synchronous Generator

In this paper, a 10-kW/150-r/min fully superconducting synchronous generator was designed and sent for manufacturing, which installs high temperature superconducting coils in both the stator and the rotor. It has a basic structure of eight poles and nine slots. The concentrated winding was adopted, and there are 16 field coils and 18 armature coils wound by using 5-mmwide YBa 2 Cu 3 O 7-δ (YBCO) tapes. The total tape consumption is around 2.0 km. Iron cores assembled by silicon-steel sheets will be installed in both the stator and the rotor. The peak gap field of 0.87 T can be achieved with a 42-A excitation current in field coils. The armature electric loading can reach 400 A/cm at the rated output. The present machine is designed to be cooled by using liquid nitrogen. The cryogenic structure can be divided into two parts: the conduction-cooled rotating part for field coils, and the immersion-cooled static part for armature coils. Both parts share the same vacuum chamber. A novel thermal insulated torque coupling will be installed to link the cold rotor and the warm shaft. The ac loss of armature coils was studied by H-formulation and it is within a reasonable range.

A comprehensive decoupling active disturbance rejection control for a gas flow facility

Based on the linear active disturbance rejection control (LADRC), a comprehensive decoupling controller for gas flow facilities is presented to guarantee stability and a fast response during the process of gas flowmeter performance tests. First, a mathematical model is developed to describe the pressure-flow coupling system. Then, a step response method is applied to identify parameters of this model. To realize the effective decoupling control, the static coupling part is introduced into the LADRC design. The overall effect of the dynamic coupling part among two channels, the internal uncertainties and the external disturbance, are treated as total disturbance, which is estimated using the extended state observer and cancelled out by the control law. After estimating and cancelling, the pressure-flow coupling system can be transformed into two single input single output subsystems with the form of cascade integrators. Then two proportional differential controllers are applied to control the two simplified subsystems. Simulation and experimental results show that the proposed algorithm has a shorter settling time, a more effective decoupling effect and a greater capability of disturbance rejecting and stronger performance robustness in gas flow facility than conventional proportional–integral–derivative algorithms.

Characteristic Analysis of an HTS Flux-Switching Synchronous Generator With NI-Type HTS Field Coils

This paper presents the characteristics analysis of the flux-switching synchronous generator (FSG) applying no-insulation (NI)-type high-temperature superconducting (HTS) field coils. The HTS FSG can be cost effective, since the field coils and armature windings are both installed in the stator, while the rotor is only made of iron core with tooth. Along with low cost, since HTS field coils in the FSGs are located in the stationary part of the generator, FSG can be a solution for the design complexities of the excitation and cooling systems for HTS field coils. In addition, several studies on HTS coils without turn-to-turn insulation (NI) have been reported for HTS field coils for applying in electrical rotating machines. The NI-type winding technique enhances the stability of the HTS field coil since the overcurrent is automatically bypassed through the contacts between winding turns. Nevertheless, there is still an issue about whether the NI-type HTS field coil can be applied to the electrical rotating machines. In this study, we fabricated and tested an NI-type HTS field coil. In addition, a 600-kW HTS FSG was designed using a fundamental design process and the characteristics analysis of the generator was performed based on the test results of the fabricated NI-type field coil. The results show that the HTS FSG having NI-type HTS field coils is able to operate normally under normal operating conditions. However, the field current charging problem issue has been revealed through this study. Therefore, further research will need to improve the problem.

Nonlinear system identification of fractional Wiener models

The Wiener model is a case of block-oriented model, which is suitable for modeling a large class of nonlinear systems. It consists of the cascade of two parts, where a linear dynamic part is followed by a static nonlinear part. On the other hand, fractional order models have gained increasing interest over the last decades due to their better representation of some physical phenomena. In this paper, the fractional Wiener system identification is aimed. The polynomial nonlinear fractional state space equations are used to describe the nonlinear model. Thus, the extension of an output error method (Levenberg Marquard algorithm) is developed to estimate the fractional Wiener system. The efficiency of the identification method is evaluated and confirmed by simulation examples.

Методика перераспределения функционирующих виртуальных машин по серверам в дата-центре

The need for centralized processing and storage of data is growing every year. Data centers of still greater capacity and computing power are put into operation for this purpose. To reduce their expenses the owners of data centers pay special attention to optimizing the energy consumed by the data center infrastructure. An approach for improving the data center’s overall energy efficiency through redistributing its load with subsequently shutting down the idle servers is considered. A mechanism governing the migration of virtual machines for optimizing power consumption by the servers is outlined. The existing methods used to redistribute virtual machines either perform a full search which is impossible in the case of real dimensions or disregard the power consumption criterion. A procedure is proposed that excludes the need to perform a full search and places focus on improving the efficiency according to the criterion of total energy consumption by the data center servers due to redistribution of the operating virtual machines among the data center servers. The proposed method is based on a heuristic procedure of selecting the destination servers and consists of a static part, which collects information about the available resources, and a dynamic part in which the virtual machines are distributed among the servers depending on the initial data and the preset limiting parameters. A model example demonstrating the operability of the method is given which outlines the steps in applying the method and shows how the destination servers are selected for migrations.

Travelling waves and a fruitful ‘time’ reparametrization in relativistic electrodynamics

We simplify the nonlinear equations of motion of charged particles in an external electromagnetic field that is the sum of a plane travelling wave and a static part : by adopting the light-like coordinate instead of time t as an independent variable in the Action, Lagrangian and Hamiltonian, and deriving the new Euler–Lagrange and Hamilton equations accordingly, we make the unknown disappear from the argument of . We first study and solve the single particle equations in a few significant cases of extreme accelerations. In particular, we obtain a rigorous formulation of a Lawson–Woodward-type (no-final-acceleration) theorem and a compact derivation of cyclotron autoresonance, beside new solutions in the presence of uniform . We then extend our method to plasmas in hydrodynamic conditions, and apply it to plane problems: the system of (Lorentz–Maxwell + continuity) partial differential equations may be partially solved or sometimes even completely reduced to a family of decoupled systems of ordinary ones; this occurs e.g. with the impact of the travelling wave on a vacuum-plasma interface (what may produce the slingshot effect).Our method can be seen as an application of the light-front approach. Since Fourier analysis plays no role in our general framework, the method can be applied to all kinds of travelling waves, ranging from almost monochromatic to so-called ‘impulses’, which contain few, one or even no complete cycles.

NEST – una plataforma para acelerar la innovación en edificios

La calidad en la innovación dentro del sector de la construcción debe ser rápidamente adaptada para cumplir con los inmediatos desafíos relacionados con la mejora de las edificaciones actuales. NEST es una plataforma de investigación y transferencia tecnológica flexible y abierta a universidades e industrias donde nuevas soluciones pueden ser implementadas y validadas en un entorno real. NEST consiste en una estructura fija con una serie módulos individuales que son utilizados como oficinas o apartamentos donde poder vivir y trabajar. Además, cada uno de estos módulos actúa a modo de laboratorio donde se investigan diferentes aspectos como el uso de madera como material de construcción o la fabricación digital y donde, continuamente, se lleva a cabo el desarrollo de materiales innovadores, así como su evaluación. NEST es un edificio modular cuyas unidades están individualmente conectadas por medio de redes comunes de suministro de energía y gestión y tratamiento de aguas. Cuando finalizan los estudios asociados a un módulo y los nuevos productos han sido optimizados, éste es desinstalado y remplazado por una nueva unidad de cara a abordar nuevos retos e investigaciones.

A New Method for Interpreting Nonstationary Running Correlations and Its Application to the ENSO‐EAWM Relationship

AbstractWe here propose a new statistical method to interpret nonstationary running correlations by decomposing them into a stationary part and a first‐order Taylor expansion approximation for the nonstationary part. Then, this method is applied to investigate the nonstationary behavior of the El Niño–Southern Oscillation (ENSO)‐East Asian winter monsoon (EAWM) relationship, which exhibits prominent multidecadal variations. It is demonstrated that the first‐order approximation of the nonstationary part can be expressed to a large extent by the impact of the nonlinear interaction between the Atlantic Multidecadal Oscillation (AMO) and ENSO (AMO*Niño3.4) on the EAWM. Therefore, the nonstationarity in the ENSO‐EAWM relationship comes predominantly from the impact of an AMO modulation on the ENSO‐EAWM teleconnection via this key nonlinear interaction. This general method can be applied to investigate nonstationary relationships that are often observed between various different climate phenomena.

Modelling of Halbach Array Based Targeting Part of a Magnetic Drug Delivery Device

A problem of optimal assembly from magnets modelling for steering of magnetic nanoparticles in a closed environment containing a stream of close-to-blood liquid is considered in this research. The targeting assembly from magnets is designed based on Halbach arrays and contains 18 permanent magnets forming a movable and a stationary block of the targeting part of a magnetic drug delivery device. The injected particles were diverted from their flow path near the vicinity of movable part of assembly from magnets while not aggregating thereat, but migrating to the target zone under the stationary part of the said assembly. Minimum magnetic force value was established for the injected particle path manipulation towards the target area. DOI: http://dx.doi.org/10.5755/j01.mech.23.6.19645

Characterization of Sphinx1 ASIC X-ray detector using photon counting and charge integration

Sphinx1 is a novel pixel architecture adapted for X-ray imaging, it detects radiation by photon counting and charge integration. In photon counting mode, each photon is compensated by one or more counter-charges typically consisting of 100 electrons (e-) each. The number of counter-charges required gives a measure of the incoming photon energy, thus allowing spectrometric detection. Pixels can also detect radiation by integrating the charges deposited by all incoming photons during one image frame and converting this analog value into a digital response with a 100 electrons least significant bit (LSB), based on the counter-charge concept. A proof of concept test chip measuring 5 mm × 5 mm, with 200 μm × 200 μm pixels has been produced and characterized. This paper provides details on the architecture and the counter-charge design; it also describes the two modes of operation: photon counting and charge integration. The first performance measurements for this test chip are presented. Noise was found to be ∼80 e-rms in photon counting mode with a power consumption of only 0.9 μW/pixel for the static analog part and 0.3 μW/pixel for the static digital part.

A computational study on the influence of the delayed yielding phenomenon in magnetorheological oils on the steady state vibration and forces transmitted between the rotor and its frame

The theoretical analyses and practical experience show that only the damping effect adaptable to the current operating conditions makes it possible to achieve optimum performance of damping devices inserted in the supports of rotating machines. This is offered by magnetorheological squeeze film dampers. The magnetorheological oils are liquids sensitive to magnetic induction. Their response to the change of a magnetic field is not instantaneous, but it is a process called the delayed yielding. The research was focused on enhancement of the mathematical model of the magnetorheological squeeze film damper by considering the delayed yielding phenomenon and on its application for the study of the influence of the delayed yielding on the force transmission between the rotor and its stationary part. The results of the computational simulations show that rising value of the delayed yielding time constant that characterizes the delayed yielding process reduces the damping effect and efficiency of the magnetorheological damping devices.

Numerical Study of Mixing Thermal Conductivity Models for Nanofluid Heat Transfer Enhancement

Researchers have paid attention to nanofluid applications, since nanofluids have revealed their potentials as working fluids in many thermal systems. Numerical studies of convective heat transfer in nanofluids can be based on considering them as single- and two-phase fluids. This work is focused on improving the single-phase nanofluid model performance, since the employment of this model requires less calculation time and it is less complicated due to utilizing the mixing thermal conductivity model, which combines static and dynamic parts used in the simulation domain alternately. The in-house numerical program has been developed to analyze the effects of the grid nodes, effective viscosity model, boundary-layer thickness, and of the mixing thermal conductivity model on the nanofluid heat transfer enhancement. CuO–water, Al2O3–water, and Cu–water nanofluids are chosen, and their laminar fully developed flows through a rectangular channel are considered. The influence of the effective viscosity model on the nanofluid heat transfer enhancement is estimated through the average differences between the numerical and experimental results for the nanofluids mentioned. The nanofluid heat transfer enhancement results show that the mixing thermal conductivity model consisting of the Maxwell model as the static part and the Yu and Choi model as the dynamic part, being applied to all three nanofluids, brings the numerical results closer to the experimental ones. The average differences between those results for CuO–water, Al2O3–water, and CuO–water nanofluid flows are 3.25, 2.74, and 3.02%, respectively. The mixing thermal conductivity model has been proved to increase the accuracy of the single-phase nanofluid simulation and to reveal its potentials in the single-phase nanofluid numerical studies.

On a ‘time’ reparametrization in relativistic electrodynamics with travelling waves

We briefly report on our method [23] of simplifying the equations of motion of charged particles in an electromagnetic (EM) field that is the sum of a plane travelling wave and a static part; it is based on changes of the dependent variables and the independent one (light-like coordinate ξ instead of time t). We sketch its application to a few cases of extreme laser-induced accelerations, both in vacuum and in plane problems at the vacuum-plasma interface, where we are able to reduce the system of the (Lorentz-Maxwell and continuity) partial differential equations into a family of decoupled systems of Hamilton equations in 1 dimension. Since Fourier analysis plays no role, the method can be applied to all kind of travelling waves, ranging from almost monochromatic to socalled “impulses”.

Optimal condition monitoring of wind turbines using intelligent image processing and internet of things

The aim is to suggest a control scheme for the wind mills which convert wind energy to electrical energy. The functioning of the governing scheme is characterised by incorporating it to a doubly fed induction generator (DFIG). The stationary part of the DFIG is unswervingly linked to the electric network. The rotating part is allied to this electric network all the way through a back-to-back AC-DC-AC PWM converter. Fuzzy logic is used to acquire features using decision making logic which as human-like flexibility. The FLC provides a crisp and smooth control action. The governing process of the converter on rotating part is comprehended by stationary magnetic flux to adjust the performance of the fuzzy logic controller (FLC). The FLC is opted to have an intelligent speed control. To enable a level direct current voltage and to guarantee a pure sine wave for the current in the grid side a Grid Side Converter (GSC) is used which is controlled using FLC. The accuracy of the FLC used for the control of DFIG has a quick vibrant retort with almost unsteady error value once evaluated with the scheme using conformist proportional integral (PI) controller. Image processing algorithms are used to track the blade sweep and angular velocity. The entire monitoring is implemented using ATmega processor and incorporated in cloud service for online monitoring.

Consumption and Wealth in the Long Run: An Integrated Unobserved Component Approach

The ratio of consumption to total household wealth (i.e., tangible assets plus unobserved human wealth) is commonly calculated from the estimation of a log-linear version of the household intertemporal budget constraint as a cointegrating relationship between consumption, assets and earnings (i.e., the variable cay). The evidence in favor of a stable cointegrating relationship between these variables in the US is weak however. This paper follows an alternative empirical approach using an unobserved component model applied to US data over the period 1951Q4-2016Q4. The regression of consumption on assets and earnings is augmented with an unobserved stochastic trend, i.e., an integrated component. The results strongly support the presence of such an unobserved component in the consumption equation. We provide evidence that this component is related to financial liberalization which, by relaxing liquidity constraints of consumers, has permanently increased the consumption-to-wealth ratio over the sample period. We calculate an alternative cay variable, i.e., the stationary part of the consumption-to-wealth ratio, and find that its predictive ability for future (excess) stock returns is comparable to that of the standard cay variable.