Sequential Calculation Research Articles

Fuzzy Analytical Hierarchy Process for Embedded Risk Reduction in Selecting the Right Planning Decision

The aim of this work is to provide an efficient selection technique as a part of planning process to guide the decision makers to decide the preferences of one supplier over another for purchasing lab instruments in education domain. Fuzzy Analytical Hierarchy Process has used as a multi-criteria decision process, as an industrial engineering tool with certain emphasis on the qualitative aspects required to the decision makers. While the concept of degree of possibility for each criterion is used to reach its relative weights, a specific methodology created to reach the final objective decision of supplier selection. A questionnaire form was developed and distributed to five universities located in Baghdad province with a total number of 100 questionnaires. The response was very adequate. Three main criteria are adopted- supplier, instruments and service performance grade. Moreover, there are sixteen sub-criteria for evaluating three potential suppliers. The final decision is reached with almost risk-free as it relates to the qualitative aspects of experts. The conclusion reached is that local supplier has a large priority weight. Microsoft Excel is used to achieve the sequential calculations for Fuzzy AHP.

Sequential Power Flow Calculation of AC/DC Hybrid System Considering Converter Station Loss and Its Capacity Constraints

In the power flow calculation of AC/DC hybrid distribution network, the loss and capacity of the converter station have a great influence on the power flow calculation, and the AC/DC alternately solves the power flow, which has the disadvantage of poor convergence performance. In this paper, the power flow model of AC/DC hybrid distribution network with VSC is established. The loss mechanism of the converter station is analyzed and the capacity limit of the converter station is fully considered. The sequential power flow algorithm with VSC AC-DC hybrid distribution network is proposed. Its convergence performance is improved. In the improved 33-node AC/DC hybrid power distribution network with multiple types of DG, the correctness, effectiveness and algorithm fastness of the algorithm are verified.

Structural analysis of gas turbine blades made of Mo-Si-B under transient thermo-mechanical loads

Experimental investigations of turbine blade materials under real operating conditions are very demanding. Therefore, the thermal and mechanical analysis should be carried out based on the finite element method. The purpose of the present analysis is to estimate the stress-strain condition of a turbine blade model by performing two sequential calculations: thermal analysis and structural mechanics analysis. In this study, two molybdenum-based alloys Mo–17.5Si–8B and Mo–9Si–8B are compared to the state-of-the-art nickel-based superalloy CMSX-4 as a blade material during turbine start-up and shut-down processes. The time-dependent thermo-mechanical stresses are taken into account, so that the influence of temperature gradient on stress-strain behavior of the blade could be represented.

Life cycle inventories of the commonly used materials for lithium-ion batteries in China

With the fast growing of the electric vehicle (EV) market and soaring production of the EV lithium-ion batteries (LiBs) in China, more and more life cycle assessment (LCA) studies has been focused on their impacts towards resources, energy and environment in recent years. As the indispensable background data, the life cycle inventories (LCIs) of the cradle-to-gate stage of the commonly used materials for the production of LiBs play an important role in the related LCA studies, since their accuracy and reliability can affect the results and conclusions greatly. However, LCIs of the LiB materials produced in China are in scarcity nowadays, which has become an obstacle for the further understanding of the eco-performances of EVs and LiBs. In this study, a general unit-process model was established firstly, and then a variety of foreground data were collected from the representative manufacturers of LiB materials in China. With a sequential calculation procedure carried out step by step, the targeted LCIs of the materials were obtained, along with the corresponding 95% confidential intervals through Monte-Carlo simulations. According to the inventories analysis, it was found that among the materials studied, the polyethylene separator made by wet drawing process, lithium hexafluorophosphate, carbon nanotubes, lithium nickel manganese cobalt oxide and nickel cobalt aluminum are with relatively higher primary energy demands and greenhouse gas emissions in their cradle-to-gate stage. Besides, among the cathode materials studied, lithium iron phosphate consumes the lowest non renewable mineral resources. In addition, through a comparison with GREET, we found that the energy consumptions and greenhouse gas emissions of the LiB materials in this study are significantly higher than that drawn from GREET. This will lead to 62–91% more greenhouse gas emissions from materials made in China than those in the United States in order to produce LiB cells of the same capacity. However, it was also found the discrepancies may be stemmed from many difference in the processes of modeling and data acquisition between this study and the supportive studies for GREET.

Experimental and theoretical elucidation of catalytic pathways in TiO2-initiated prebiotic polymerization.

The tendency of glycine to form polymer chains on a rutile(110) surface under wet/dry conditions (dry-wet cycles at high temperature) is studied through a conjunction of surface sensitive experimental techniques and sequential periodic multilevel calculations that mimics the experimental procedures with models of decreasing complexity and increasing accuracy. X-ray photoemission spectroscopy (XPS) and thermal desorption spectroscopy (TDS) experimentally confirmed that the dry-wet cycles lead to Gly polymerization on the oxide support. This was supported by all the theoretical characterizations. First, classical reactive molecular dynamics (MD) simulations based on the ReaxFF approach were used to reproduce the adsorption of the experimental glycine solution droplets sprayed onto an oxide support and to identify the most probable arrangement of the molecules that triggered the polymerization mechanisms. Then, quantum chemistry density functional tight binding (DF-TB) MDs and static density functional theory (DFT) calculations were carried out to further explore favorable configurations and to evaluate the energy barriers of the most promising reaction pathways for the peptide bond-formation reactions. The results confirmed the fundamental role played by the substrate to thermodynamically and kinetically favor the process and disclosed its main function as an immobilizing agent: the molecules accommodated in the surface channels close to each other were the ones starting the key events of the dimerization process and the most favorable mechanism was the one where a water molecule acted as a proton exchange mediator in the condensation process.

Application of the Laplace transform to non-rectilinear momentary problems

The cross presentation of the Laplace transform method and the finite variance method to one-dimensional nonaligned momentary heat conduction problems is considered. The calculation is discretized in the interplanetary area by the finite difference method. The nodal heats are at that point changed by the use of the Laplace transform method. The changed heats are reversed mathematically to get the outcomes in the corporeal measures. This report depicts that the current technique does not need to achieve a time-pacing method. Therefore the outcomes at whatever time can be calculated in the time area deprived of any sequential calculations. The current outcomes are likened in tables with those achieved by the straight variational technique and other means. However, it is observed that their outcomes are in right agreement with per capita other. It can be established that the current cross technique is consistent and efficient. Furthermore, two diverse linearization methods for the nonaligned peripheral state are examined. Keywords : Laplace transform, finite change method, non-rectilinear momentary problems DOI : 10.7176/ISDE/10-1-04

High-Accuracy SINS/LDV Integration for Long-Distance Land Navigation

Since the conventional strapdown inertial navigation system (SINS)- and odometer (OD)-integrated navigation has certain limitations, such as suffering from scale factor variation and being affected by wheel slipping and skidding, we present a high-accuracy integrated navigation system that uses both the SINS and laser Doppler velocimeter (LDV) for land vehicles to overcome these problems. We took the lever-arm residual and boresight errors into consideration and formed a complete 21-state Kalman filter to accomplish integrated navigation and precise sensor-to-sensor calibration. The observability analysis of the SINS/LDV system provides valuable insights into the conditions under which the states can be estimated. In addition, the summed measurement model and sequential Kalman filter calculation are deduced to make full use of the nonholonomic constraints (NHC) and LDV measurements. Finally, a long-distance experiment (230 km) with a navigation-grade IMU demonstrated that positioning accuracies of better than 0.02% of the distance travelled can be achieved in both the horizontal and vertical directions.

Разработка энергоэффективной индукционной системы для ремонтно-восстановительных технологий дисков газотурбинных двигателей

Актуальность работы обусловлена экономической необходимостью повышения надежности и ресурса работы деталей и узлов газотурбинных двигателей, широко применяемых в качестве привода газоперекачивающих агрегатов в нефтегазовой отрасли. Диски и колеса турбин и компрессоров относятся к наиболее ответственным элементам газотурбинных двигателей, испытывающим в процессе работы критические нагрузки. Существенное влияние на выносливость этих деталей оказывает качество поверхностного слоя. Для увеличения ресурса работы деталей используются различные методы поверхностного упрочнения. Одним из методов повышения качества поверхностного слоя является термопластическое упрочнение, включающее две стадии: нагрев до заданной температуры и последующее спрейерное охлаждение. Данное исследование посвящено решению задачи применения эффективного экологически чистого способа локального нагрева обрабатываемых поверхностей диска в процессе термопластического упрочнения. Цель работы: создание математических моделей электромагнитных и тепловых процессов при индукционном нагреве изделий сложной геометрической формы с учетом нелинейной зависимости электро и теплофизических характеристик нагреваемого металла изделия от температуры для расчета конструктивных параметров системы индукционного нагрева, а также режимных параметров - мощности и времени нагрева. Методы. Для решения взаимосвязанной электротепловой задачи использовались методы теории электромагнитного поля и теплопроводности, методы математического моделирования. Численное моделирование проводилось с помощью метода конечных элементов в современных инженерных пакетах. Результаты. Разработан комплекс электромагнитных и тепловых моделей процесса индукционного нагрева изделий сложной формы, ориентированный на решение задач проектирования и автоматического управления специализированными нагревательными установками для ремонтных технологий роторов газотурбинных двигателей; предложен алгоритм определения конструктивных и режимных параметров индукционной системы, включающий последовательный расчет электромагнитных и тепловых полей с учетом их взаимного влияния и наличия ограничений на предельно допустимые температуры.

Simulation of Complex Electric Power Systems

Iron birds of power facilities allow solving various functional tasks. The interaction with the hardware of these simulation benches relies on the computer model of an electric power system (EPS). This article considers the main aspects of computer-aided simulation of complex electric power systems. The dynamic mode calculation is presented as a sequential calculation of static modes at each sampling interval. The developed mathematical model of the system consists of mathematical models of its elements and a model of their interaction. The models of the elements are differential equation systems in the (d, q) frame of reference. The algorithms for calculating dynamic and static modes actively use the T-list and allow performing these computations in an optimal manner. The developed software has an expandable and flexible graphical shell. Java programming allows doing without integrative modules for full-scale and half-sized models and ensures high performance and the fulfillment of the cross-platformity requirement. The module for mathematically simulating electric power systems can be used not only as part of subsystems for testing gas turbine power plants, but also for other functional tasks of half-sized sectional simulation of electric power systems.

Linear assignment problem in the design of freeform refractive optical elements generating prescribed irradiance distributions.

We consider the problem of calculating the eikonal function defined on a certain curved surface from the condition of generating a prescribed irradiance distribution on a target surface. We show that the calculation of the "ray mapping" corresponding to the eikonal function is reduced to the solution of a linear assignment problem (LAP). We propose an iterative algorithm for calculating a refractive optical surface from the condition of generating a prescribed near-field irradiance distribution in a non-paraxial case. The algorithm is based on sequential calculation of eikonal functions defined on curved surfaces using the LAP-based approach. The proposed algorithm is applied to the calculation of refractive optical elements generating uniform irradiance distributions in a rectangular region and in a region in the form of the letters "IPSI" in the case of a circular incident beam. The presented ray-tracing simulations of the designed optical elements demonstrate high efficiency of the proposed iterative algorithm.

МОДЕЛИРОВАНИЕ МНОГОКАНАЛЬНЫХ СИСТЕМ МАССОВОГО ОБСЛУЖИВАНИЯ КАК КОМПОНЕНТОВ СОЦИОТЕХНИЧЕСКИХ СИСТЕМ

For a multichannel queuing system, in which all calls have individual characteristics of arrival and maintenance in accordance with their characteristics in the required socio-technical system and switching from one call to another are performed in accordance with a specified switching function determined by the resolution policy adopted in the socio-technical system of conflict situations, recurrence relations have been obtained for the queue lengths, for the list of free instrument changes, for the list of call numbers waiting for service, and for a number of other characteristics at successive call termination services. The procedure of sequential calculation of all specified characteristics of the system is described taking into account their internal interrelation. In accordance with this procedure, in a strictly defined sequence, eleven characteristics of the system are calculated on the basis of recurrence relations. To increase the efficiency of the process of practical implementation of the modeling procedure, it is proposed to replace the initial distribution functions of random variables by their approximate values, which are mixtures of gamma distributions whose values can be calculated significantly faster than the values of the initial distributions. The problem of finding a set of exponential distributions for a given simulated distribution function is formalized, the mixture of which approximates the distribution function with a given accuracy.

Convergence Studies on Nonlinear Coarse-Mesh Finite Difference Accelerations for Neutron Transport Analysis

Application of partial current–based coarse-mesh finite difference (pCMFD) acceleration to a one-node scheme is devised for stability enhancement of the parallel neutron transport calculation algorithm. Conventional one-node coarse-mesh finite difference (CMFD) allows parallel algorithms to be more tractable than two-node CMFD, but it has an inherent stability issue for some problems. In order to overcome this issue, pCMFD is modified to be fitted into the one-node scheme and is tested for both sequential and parallel calculations. The superior stability of the one-node pCMFD is shown by comparing results from analytic and numerical approaches. To investigate the convergence behavior of the acceleration methods in an analytic way, Fourier analysis is applied to an infinite homogeneous slab reactor configuration with the monoenergetic neutron flux assumption, and the spectral radius is calculated as a convergence factor. This paper carefully describes the process of the Fourier analysis on the parallel algorithm for neutron transport and compares it to that of the conventional sequential algorithm.

On Some Properties of Semi-rings

The main objective of this paper is to prove a theorem according to which a method of successive elimination of unknowns in the solution of systems of linear equations in the semi-rings with iteration gives the really smallest solution of the system. The proof is based on the graph interpretation of the system and establishes a relationship between the method of sequential elimination of unknowns and the method for calculating a cost matrix of a labeled oriented graph using the method of sequential calculation of cost matrices following the paths of increasing ranks. Along with that, and in terms of preparing for the proof of the main theorem, we consider the following important properties of the closed semi-rings and semi-rings with iteration.We prove the properties of an infinite sum (a supremum of the sequence in natural ordering of an idempotent semi-ring). In particular, the proof of the continuity of the addition operation is much simpler than in the known issues, which is the basis for the well-known algorithm for solving a linear equation in a semi-ring with iteration.Next, we prove a theorem on the closeness of semi-rings with iteration with respect to solutions of the systems of linear equations. We also give a detailed proof of the theorem of the cost matrix of an oriented graph labeled above a semi-ring as an iteration of the matrix of arc labels.The concept of an automaton over a semi-ring is introduced, which, unlike the usual labeled oriented graph, has a distinguished "final" vertex with a zero out-degree.All of the foregoing provides a basis for the proof of the main theorem, in which the concept of an automaton over a semi-ring plays the main role.The article's results are scientifically and methodologically valuable. The proposed proof of the main theorem allows us to relate two alternative methods for calculating the cost matrix of a labeled oriented graph, and the proposed proofs of already known statements can be useful in presenting the elements of the theory of semi-rings that plays an important role in mathematical studies of students majoring in software technologies and theoretical computer science.

Monte-Carlo Method of Calculating Weakly Coupled Systems Using the PRIZMA-DSP Code

A Monte Carlo method implemented in the PRIZMA-DSP code to calculate multiplying systems, including weakly coupled systems, is described. In the code, the basis of the method is a sequential calculation of a prescribed chain of active generations, which is described by, first and foremost, the dominant ratio of the system. The fission points of the running generation serve as a source for constructing neutron trajectories, new fission points arising on a trajectory are transmitted unchanged to calculate the next generation, and so on. In the calculation of the active generation, Keff and made-to-order linear-fractional functions are evaluated. In order for the distribution to become established, a passive calculation with prescribed chain length is made before the active calculation. In addition, after the calculation of each generation the operation of random mixing of the entire set of fission points and their distribution over the nuclei is performed in order to obtain a uniform distribution. At the start of the calculation, a special rejection procedure performs a pre-set number of preliminary computational iterations so that an arbitrary zeroth distribution over all nuclei goes to a distribution obtained via a characteristic function.

ESTIMATION OF TOPOGRAPHIC DEFECTS DIMENSIONS OF SEMICONDUCTOR SILICON STRUCTURES

The effect of non-flatness of semiconductor wafers on characteristics of manufactured devices is shown through defocusing of an image of a topological layout of a structure being formed and through reduction of resolution at photolithographic processing. For quality control of non-flatness the Makyoh method is widely used. However, it does not allow obtaining quantitative characteristics of observed defects, which essentially restricts its application. The objective of this work has been developing of a calculation method for dimensions of topographic defects of wafers having semiconductor structures formed on them, which has allowed determining acceptability criteria for wafers, depending on defects dimensions and conducting their timely penalization.A calculation method under development is based on deduction of relationships linking distortion of image elements to curvature of local sections of a semiconductor wafer that has formed structures. These structures have been considered to be image finite elements and within this range the curvature radius has been assumed to be constant. Sequential calculation of deviation of element ends from ideal plane based on determining their curvature radius has allowed obtaining geometry of a target surface in a set range of elements. Conditions of image formation and requirements to structures have been determined.Analytical expressions relating a deviation value of elements of a light-to-dark image with surface geometry have been obtained. This allows conducting effective quantitative control of observed topographic defects both under production and research conditions. Examples of calculation of topographic defects of semiconductor silicon wafers have been provided. Comparison of the obtained results with the data obtained by conventional methods has shown their complete conformity.

Parallel simulations for a 2D x/z two-phase flow fluid-solid particle model

The importance of the two-phase flow model relies upon the correct simulation of specific problems in which the passive tracer model fails; however, the mathematical and numerical models need to be improved in order to reproduce fluid-solid particle interactions of greater complexity. Such is the case with regard to simulating erosion patterns suffered upon horizontal granular beds by means of a vertical water jet as shown here. Moreover, sequential platforms have proven to be insufficient in providing the required computational power needed to obtain fast and detailed simulations. In this paper, a fully parallel algorithm for a two-dimensional x/z two-phase Eulerian approach is presented and applied for the numerical solution of the erosion of sediment beds. The parallelization is designed by a row and column block domain decomposition technique using a distributed memory platform with Message Passing Interface (MPI). Arising from the numerical method, a Poisson problem for the pressure is solved at each time step. The discretization results in a non-symmetric variable-coefficient linear system which is solved using several parallel Successive Over-Relaxation (SOR) algorithms, including partitioning and coloring methods. The specification of the optimal relaxation parameter to achieve efficiency is found numerically. Results show that SOR methods achieve faster convergence rates and the simulation time achieves an order similar to that required for the typical, widely-used Bi-Conjugate Gradient Stabilized (Bi-CGSTAB) method. The performances of the algorithms are evaluated in terms of speedup and efficiency. The results indicate that the parallel code significantly improves the results of the sequential calculation in general.

Adaptive filtration of radio source movement parameters with complex use of sensor network data based on TDOA and RSS methods

The optimal and quasi-optimal adaptive algorithms for filtration of parameters of radio source movement with different kinds of maneuvers have been synthesized on the basis of mathematical tools of discrete-time mixed Markov processes. These algorithms involve the complex use of sensor network data obtained on the basis of the TDOA and RSS methods. The devices implementing the above algorithms are multichannel and belong to the class of devices with feedbacks between channels. The presence of feedbacks between channels is stipulated by the Markov property of discrete component describing types of radio source movement. In the quasi-optimal adaptive algorithm, the processing of measurement values coming from sensors of the sensor network is performed by using the sequential calculation procedure. At the same time, this algorithm ensures polygaussian approximation of a posteriori probability density of the estimated vector of parameters of radio source movement. The analysis of quasi-optimal algorithm is carried out by employing the computer-aided statistical simulation using an example of estimating the movement parameters of UAV performing different kinds of maneuvers and sending out radio waves.

Modeling non-Fickian pollutant mixing in open channel flows using two-dimensional particle dispersion model

The non-Fickian particle dispersion model was developed in this study to model two-dimensional pollutant mixing in open channel flows. The proposed model represents shear dispersion using step-by-step arithmetic calculations, which consist of horizontal transport and vertical mixing steps, instead of using Fick's law. In the sequential calculations, the model directly applied the effect of vertical variations of both longitudinal and transverse velocities, whereas the Fickian dispersion model incorporates the effect of shear flow in the dispersion coefficients. Furthermore, in order to avoid the numerical diffusion errors induced by the grid tracking method of previously developed non-Fickian dispersion models, this model adopted the particle tracking technique to trace each particle. The simulation results in the straight channel show that the proposed model reproduced the anomalous mixing, which shows a non-linear increase of variance with time and large skewness coefficient in the initial period. However, in the Taylor period, the variance and skewness of the concentration curves approached the Fickian mixing. The simulation results in the meandering channel reveal that the proposed model adequately reproduced the skewed concentration–time curves of the experimental results whereas the Fickian dispersion model, CTM-2D, generated symmetrical curves. Further comparison between the simulation results and the tracer test results conducted in the Hongcheon River shows that the proposed model properly demonstrated the two-dimensional mixing without adopting Fick's law.

Influence of the initial cooling rate from γ′ supersolvus temperatures on microstructure and phase compositions in a nickel superalloy

Different cooling paths from a supersolvus temperature have been applied to FGH96, a polycrystalline nickel base superalloy for turbine disc applications, in order to simulate the different microstructures that exist through the thickness of a disc following an industrial heat treatment. Secondary and tertiary γ′ precipitate size distributions and morphology have been analysed and compared for the different heat treatments using SEM and atom probe tomography (APT). Detailed compositional data for both γ′ precipitate and γ matrix are presented, and compared to equilibrium compositions calculated by Thermo-Calc. For the heat-treatments studied, the secondary γ′ composition indicates a shell of differing composition to that towards the precipitate core. From sequential equilibria compositional calculations, it is suggested that the ‘shell’ forms at a lower temperature than the precipitate core. The fine tertiary precipitates do not show the core-shell compositional differences on continuous cooling. W peaks are noted at the γ/γ′ interfacial region, which is of significance for retarding coarsening. A γ′ depletion zone surrounds the secondary precipitates, within which the γ matrix composition differs significantly to the γ far-field values, Finally, a precipitate nucleation and growth mechanistic model is suggested based on the experimental data and Thermo-Calc calculations.

Direct Resonant Control Strategy for Torque Ripple Mitigation of DFIG Connected to DC Link through Diode Rectifier on Stator

This paper presents a torque ripple mitigation method for the doubly-fed Induction generator (DFIG) connected to the dc link through a diode rectifier on the stator winding. A resonant regulator based on torque compensator is directly added to the conventional rotor current control loop, and the sequential separations and calculations of rotor harmonic current references can be avoided. Then, a novel stator flux orientation method is achieved by indirectly controlling the q -axis stator flux linkage to be zero without calculating the stator flux linkage angle. The stator frequency is controlled by regulating the stator flux without calculating the stator frequency. Based on a mathematical model of the DFIG control system, the effects on system stability using the resonant controller, analysis of the steady-state error, and the dynamic performance are discussed. Finally, the proposed control method is validated by the experiment results.