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Number of results: 79
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Abstract

In this paper, explain the preparation of CaTiO3 ceramics synthesized by the solid-state reaction method. Calcium carbonate and titanium dioxide were high energy mixed in stoichiometric amounts, and the obtained mixture was calcined at different temperatures (800, 900, 1000 and 1300ºC) for 2 h. The obtained samples were characterized by measurement of particle size, Energy Dispersive X-Ray (EDX) Analysis; differential thermal analysis, X-ray diffraction and SEM images. XRD patterns indicated that CaTiO3 ceramics with the structure of perovskite is obtained from calcined powders at 1,300°C for 2 h. SEM images show the formation of a very fine and homogeneous morphology. The measured values of electrical resistivity were within the typical range of insulating materials and approach values corresponding to insulating ceramics.
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Abstract

Al and Nb-doped Li7La3Zr2O12 (LLZO) and W-doped LLZO lithium ion conducting electrolyte samples were prepared and their H2O stability was investigated. The LLZO samples were exposed to 50% humidified air for 48 h. After H2O exposure, a cubic to tetragonal transformation occurred and acquired SEM images exhibited the presence of reaction phases at the grain boundaries of Al and Nb-LLZO. As a result, the lithium ion conductivity significantly decreased after H2O exposure. On the contrary, W-LLZO showed good stability against H2O. Although the cubic to tetragonal transformation was also observed in H2O-exposed W-LLZO, the decrease in lithium ion conductivity was found to be modest. No morphological changes of the W-LLZO samples were confirmed in the H2O-exposed W-LLZO samples.
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Abstract

The paper presents a thermomechanical computational solid mechanics analysis (CSM) of a pipe "double omega", used in the steam superheaters in circulating fluidized bed (CFB) boilers. The complex cross-section shape of the "double omega" tubes requires more precise analysis in order to prevent from failure as a result of the excessive temperature and thermal stresses. The results have been obtained using the finite volume method for transient state of superheater. The calculation was carried out for the section of pipe made of low-alloy steel.
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Abstract

The focus of research works on cavitation has changed since the 1960s; the behaviour of a single bubble is no more the area of interest for most scientists. Its place was taken by the cavitating flow considered as a whole. Many numerical models of cavitating flows came into being within the space of the last fifty years. They can be divided into two groups: multifluid and homogeneous (i.e., single-fluid) models. The group of homogenous models contains two subgroups: models based on transport equation and pressure based models. Several works tried to order particular approaches and presented short reviews of selected studies. However, these classifications are too rough to be treated as sufficiently accurate. The aim of this paper is to present the development paths of numerical investigations of cavitating flows with the use of homogeneous approach in order of publication year and with relatively detailed description. Each of the presented model is accompanied by examples of the application area. This review focuses not only on the list of the most significant existing models to predict sheet and cloud cavitation, but also on presenting their advantages and disadvantages. Moreover, it shows the reasons which inspired present authors to look for new ways of more accurate numerical predictions and dimensions of cavitation. The article includes also the division of source terms of presented models based on the transport equation with the use of standardized symbols.
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Abstract

In the paper, a method for determination of the near-critical region boundary is proposed. The boundary is evaluated with respect to variations of specific heat capacity along isobars. It is assumed that the value of specific heat capacity inside the near-critical region exceeds by more than 50% the practically constant value typical for fluids under normal conditions. It appears that large variations of heat capacity are also present for high-pressure subcritical states sufficiently close to the critical point. Therefore, such defined near-critical region is located not only in supercritical fluid domain but also extends into subcritical fluid. As an example, the boundaries of the near-critical region were evaluated for water, carbon dioxide and R143a.
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Abstract

Mechanical properties of the pipeline samples that had been cut in annular and axial directions were investigated. The methodology of modeling and calculation of the real stress-strain state was described. The stable state during in the deformation process was defined. The results of the experimental researches were used as a test variant during examination of pipe strength.
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Abstract

We study the autocovariance structure of a general Markov switching second-order stationary VARMA model.Then we give stable finite order VARMA(p*, q*) representations for those M-state Markov switching VARMA(p, q) processes where the observables are uncorrelated with the regime variables. This allows us to obtain sharper bounds for p* and q* with respect to the ones existing in literature. Our results provide new insights into stochastic properties and facilitate statistical inference about the orders of MS-VARMA models and the underlying number of hidden states.
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Abstract

The aim of these studies was to obtain single phase cubic modification of Li7La3Zr2O12 by mechanical milling and annealing of La(OH)3, Li2CO3 and ZrO2 powder mixture. Fritsch P5 planetary ball mill, Rigaku MiniFlex II X-ray diffractometer, Setaram TG-DSC 1500 analyser and FEI Titan 80-300 transmission electron microscope were used for sample preparation and investigations. The applied milling and annealing parameters allowed to obtain the significant contribution of c-Li7La3Zr2O12 in the sample structure, reaching 90%. Thermal measurements revealed more complex reactions requiring further studies.
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Abstract

The article presents issues related to the application of a moving horizon estimator for state variables reconstruction in an advanced control structure of a drive system with an elastic joint. Firstly, a short review of the commonly used methods for state estimation in presented. Then, a description of a state controller structure follows. The design methodology based on the poles-placement method is briefly described. Next, the mathematical algorithm of MHE is presented and some crucial features of MHE are analysed. Then, selected simulation and experimental results are shown and described. The investigation shows, among others, the influence of window length on the quality of state variables estimation.
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Abstract

This paper presents the improved methodology for the direct calculation of steady-state periodic solutions for electromagnetic devices, as described by nonlinear differential equations, in the time domain. A novel differential operator is developed for periodic functions and the iterative algorithm determining periodic steady-state solutions in a selected set of time instants is identified. Its application to steady-state analysis is verified by an elementary example. The modified algorithm reduces the complexity of steady-state analysis, particularly for electromagnetic devices described by high-dimensional nonlinear differential equations.
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Abstract

The paper proposes a study of molecular interactions using the planetary model of the atomic structure. The description refers to transfer of the interactions by electrons bonded with an atom in a planetary system. In molecules we refer to analysis of electrons that remain unpaired during the formation of chemical compounds. The planetary electronic state of molecular interactions is defined by considering the action arm for interatomic forces. Then the interaction torque is defined. The problem is studied in a collection of atoms forming a nanoparticle and then analysis is carried on in the entire volume of the nanocomposite, which is defined as a set of the nanoparticles in a field of matrix-nanofiller interactions. As a result, new mechanical, magnetic, and optical properties of the nanocomposite arise and are described herein. The atomic-scale phenomena are described by both classical and quantum mechanics and are then transferred to the nanoparticle scale by applying statistical mechanics. The quantum solutions for the optically active electrons form the basis for the optical properties of the nanocomposite using forced gyrobirefringence and Maxwell equations. The results of the theoretical analysis are confirmed by experiment using an electron paramagnetic resonance spectrometer.
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Abstract

The European standards, developed extensively over last 30 years, are driven by the need for continuous evolution and their Authors’ pursuit of better EU-wide quality in civil engineering – combining safety, economy, and sustainable development. The adoption of theory of reliability as the basis for design has played a major role in shaping current geotechnical practice. However, it requires from practitioners a greater understanding of underlying uncertainties. Furthermore, a number of alternative approaches, not generally used in structural design, are also allowed, as some situations in geotechnical engineering require an individual approach. Moreover, the current trends in geoengineering increase the importance of risk assessment and management. The paper presents general philosophy guiding the geotechnical design and pointing to some of the ideas introduced by Eurocode 7 and its requirements, in relation to preexisting practice of geotechnical design in civil engineering.
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Abstract

This study presents cause-effect dependencies between inputs and outputs of business transitions that are software objects designed for processing information-decision state variables in integrated enterprise process control (EntPC) systems. Business transitions are elementary components of controlling units in enterprise processes that have been defined as self-controlling, generalized business processes, which may serve not only as business processes but also as business systems or their roles. Business events, which have zero durations by definition, are interpreted as executions of business actions that are main operations of business transitions. Any ordered set of business actions, performed in the controlling unit of a given enterprise process and attributed to the same discrete-time instant, is referred to as ‘the information-decision process’. The i-d processes may be substituted by managerial business processes, performed on the lower organizational level, where durations of activity executions are greater than zero, but discrete-time periods are considerably shorter. In such a case, procedures of business actions are performed by corresponding activities of managerial processes, but on the level of business transitions the durations of their executions are imperceptible, and many different business events may occur at the same discrete-time instant. It has been demonstrated in the paper how to control business actions to ensure that a given i-d state variable may not change more than once at a given instant. Furthermore, the rules of designing the i-d process structures, which prevent random changes of transitory states, have been presented.
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Abstract

This paper investigates state estimation of linear time-invariant systems where the sensors and controllers are geographically separated and connected over limited capacity, additive white Gaussian noise (AWGN) communication channels. Such channels are viewed as dropout (erasure) channels. In particular, we consider the case with limited data rates, present a necessary and sufficient condition on the data rate for mean square observability over an AWGN channel. The system is mean square observable if the data rate of the channel is larger than the lower bound given. It is shown in our results that there exist the inherent tradeoffs among the limited data rate, dropout probability, and observability. An illustrative example is given to demonstrate the effectiveness of the proposed scheme.
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Abstract

This paper presents a novel sideslip angle estimator based on the pseudo-multi-sensor fusion method. The kinematics-based and dynamics-based sideslip angle estimators are designed for sideslip angle estimation. Also, considering the influence of ill-conditioned matrix and model uncertainty, a novel sideslip angle estimator is proposed based on the wheel speed coupling relationship using a modified recursive least squares algorithm. In order to integrate the advantages of above three sideslip angle estimators, drawing lessons from the multisensory information fusion technology, a novel thinking of sideslip angle estimator design is presented through information fusion of pseudo-multi-sensors. Simulations and experiments were carried out, and effectiveness of the proposed estimation method was verified.
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Abstract

The aim of this contribution is to derive a general matrix formula for the net period premium paid in more than one state. In order to avoid “overpayment” which implies higher premiums we give a formula for replacement of lump sum benefit into annuity benefits paid in more than one state. The obtained result is useful for example to more advanced models of dread disease insurances allowing period premiums paid by both healthy and ill person (e.g. not terminally yet). As an application, we supply analysis of dread disease insurances against the risk of lung cancer based on the actual data for the Lower Silesian Voivodship in Poland.
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Abstract

In this paper a semi-structural econometric model is implemented in order to estimate the natural rates of interest in two large economies of the Euro Area: Germany an Italy. The estimates suggest that after the financial crisis of 2007–2008 a decrease of the growth rate of potential output and the corresponding natural rate of interest was greater in Italy than in Germany which could have had important implications for the effectiveness of a common monetary policy. Unlike in other studies, it is found that the monetary policy stance was less expansionary in Italy as compared to Germany for the whole after-crisis period.
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Abstract

Both the growing number of dispersed generation plants and storage systems and the new roles and functions on the demand side (e.g. demand side management) are making the operation (monitoring and control) of electrical grids more complex, especially in distribution. This paper demonstrates how to integrate phasor measurements so that state estimation in a distribution grid profits optimally from the high accuracy of PMUs. Different measurement configurations consisting of conventional and synchronous mea- surement units, each with different fault tolerances for the quality of the calculated system state achieved, are analyzed and compared. Weighted least squares (WLS) algorithms for conventional, linear and hybrid state estimation provide the mathematical method used in this paper. A case study of an 18-bus test grid with real measured PMU data from a 110 kV distribution grid demonstrates the improving of the system’s state variable’s quality by using synchrophasors. The increased requirements, which are the prerequisite for the use of PMUs in the distribution grid, are identified by extensively analyzing the inaccuracy of measurement and subsequently employed to weight the measured quantities.
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Abstract

This paper presents an adaptive particle swarm optimization (APSO) based LQR controller for optimal tuning of state feedback controller gains for a class of under actuated system (Inverted pendulum). Normally, the weights of LQR controller are chosen based on trial and error approach to obtain the optimum controller gains, but it is often cumbersome and tedious to tune the controller gains via trial and error method. To address this problem, an intelligent approach employing adaptive PSO (APSO) for optimum tuning of LQR is proposed. In this approach, an adaptive inertia weight factor (AIWF), which adjusts the inertia weight according to the success rate of the particles, is employed to not only speed up the search process but also to increase the accuracy of the algorithm towards obtaining the optimum controller gain. The performance of the proposed approach is tested on a bench mark inverted pendulum system, and the experimental results of APSO are compared with that of the conventional PSO and GA. Experimental results prove that the proposed algorithm remarkably improves the convergence speed and precision of PSO in obtaining the robust trajectory tracking of inverted pendulum.
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Abstract

An approach to power system state estimation using a particle filter has been proposed in the paper. Two problems have been taken into account during research, namely bad measurements data and a network structure modification with rapid changes of the state variables. For each case the modification of the algorithm has been proposed. It has also been observed that anti-zero bias modification has a very positive influence on the obtained results (few orders of magnitude, in comparison to the standard particle filter), and additional calculations are quite symbolic. In the second problem, used modification also improved estimation quality of the state variables. The obtained results have been compared to the extended Kalman filter method.
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Abstract

In light of contemporary circumstances, on the 30th anniversary of the Nicaragua judgment it is worth revisiting and considering again certain legal problems decided by – and raised by – the ICJ judgment. This article addresses the importance of the judgment in terms of international legal regulations on the use of force. First and foremost, the article examines the concept of armed attack based on the “gravity” criterion elaborated by the Court and the exercise of the right of self-defence. Moreover, the relationship between customary international law and treaty law, as well as forcible counter-measures and military actions against non-State actors are also discussed in the article. It is argued that the “gravity” criterion used by the ICJ seems controversial and, consequently, may limit the right of self-defence. On the other hand, however, the judgment established a strong barrier to the realization of individual political interests by militarily powerful States. This is the Nicaragua judgment’s long-lasting legacy. In this sense the judgment has stood the test of time.
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