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1

Numerical model of capacitance-related phenomena in semiconductor lasers based on partial differential equations

Wasiak Michał, Sarzała Robert P.

Opto-Electronics Review

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2024

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Vol. 32, No. 2

art. no. e150606

EN

This paper presents a model of the capacitance and electrical properties of semiconductor lasers biased with modulated voltage. The model is based on the finite-element method (FEM), which is widely used in computer modelling and is a natural generalisation of a wellknown constant-voltage FEM electrical model. In principle, the model can be applied to any kind of device where inductance can be neglected. Here, it is applied to simulate the complex impedance and other high-frequency electrical properties of a vertical-cavity surface-emitting laser. These properties are very important for the application of such lasers in optical data transfer systems. The results show that both the diameter of the top mesa and the surface area of the top electrical contact have a strong impact on the performance of the laser. This impact is analysed as a function of the modulation frequency.

2

Using FreeFEM open software for modelling the vibrations of piezoelectric devices

Moszyński Marek

Vibrations in Physical Systems

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2021

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Vol. 32, nr 1

art. no. 2021112

EN

Modelling vibrations of piezoelectric transducers has been a topic discussed in the literature for many decades. The first models - so-called one-dimensional - describe the vibrations only near operating frequency and near its harmonics. Attempts to introduce two-dimensional models were related to the possibility of one transducer working at several frequencies, including both thickness vibrations and those resulting from the transducer horizontal dimensions. In recent decades, thanks to the use of the finite element method and its derivatives, and the progress related to the increase in processor speed and memory availability, the implementation of models based on three-dimensional modelling is possible using software on personal computers. As the implementation of finite element method algorithms is characterized by high complexity, several professional software packages have been created on the commercial market, among which only a few implement the piezoelectric equations. In this context, this article presents how to use open source software along with developed programming language for intuitive definition of piezoelectric equations and its solution.

3

Diagnostics of the strength and stiffness of the loader carrier system structural elements in terms of thinning of walls by numerical methods

Orobey Viktor, Nemchuk Oleksii, Lymarenko Oleksandr, Piterska Varvara, Sherstiuk Olha, Romanov Oleksandr, Tkachuk Kateryna

Diagnostyka

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2021

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Vol. 22, No. 3

73--81

EN

Modern gantry cranes are an indispensable element of large industrial and transport enterprises. Port handling equipment is operated under conditions of complex spatial loading of varying intensity, as well as under conditions when the walls of structural elements are thinned in the crane carrier system. During the operation of handling equipment in ports, at construction sites, in machine-building industries, in addition to the external load, aggressive media act on the carrier system elements, which leads to various types of wear: corrosive, abrasive and mechanical. Monitoring of the state of handling equipment structures is a very important task of diagnosing the state of the material of elements of the carrier system of cranes and transporting machines. An important and urgent scientific and technical problem of taking into account the influence of aggressive environment on the stress-strain state of the metal structures of gantry cranes is considered. It is noted that during corrosion, a significant thinning of the walls of structural elements occurs. The safety of crane operation requires this factor to be taken into account. It is proposed to use modern numerical methods for this, i.e. the boundary element method (BEM) and the finite element method (FEM). The implementation of these methods is performed in the Matlab programming and modeling environment (BEM), and the FEM is used in the Ansys package. In accordance with the technologies of these methods, the design diagrams of the lower girders and the crane structure as a whole were formed. Exact models of strain of crane elements during transverse bending and constrained torsion are given. Calculations of the stressstrain state of the crane metal structures have been performed. On the basis of a preliminary field study, a numerical model is proposed for diagnosing the strength and stiffness characteristics of the carrier system of handling equipment using the BEM and FEM, which has never been used in the world. Conclusions are drawn about the influence of the thinning of the walls of metal structures on the values of normal and tangential stresses.

4

Porównanie efektywności iteracyjnej metody rozwiązań fundamentalnych i metody elementów skończonych w analizie zagadnień elektrostatyki

Pawłowski S., Plewako J., Grodzki P.

Przegląd Elektrotechniczny

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2017

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R. 93, nr 12

135--138

PL

(MES) na podstawie analizy rezultatów testów numerycznych przeprowadzonych na modelowym zagadnieniu elektrostatyki. Stwierdzono, że za pomocą IMRF można uzyskać rozwiązanie o danej dokładności w czasie wielokrotnie krótszym (nawet kilkadziesiąt razy) niż za pomocą MES.

EN

The article presents efficiency comparison of the iterative method of fundamental solutions (IMFS) and finite element method (FEM), based on the analysis of numerical tests results obtained for the model of electrostatics problem. It has been found, that applying the IMFS a solution of assumed accuracy could be obtained numerous times shorter (even several dozen times) than using the FEM.

5

Model numeryczny kończyny górnej człowieka i jego analiza w aspekcie upadków do przodu

Biesiacki A., Grzelczyk D., Mrozowski J., Awrajcewicz J.

Aktualne Problemy Biomechaniki

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2017

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z. 12

5--14

PL

Praca przedstawia model numeryczny kończyny górnej człowieka przydatny do analizy ryzyka złamania kości kończyny podczas upadku do przodu. W odróżnieniu od innych modeli spotykanych w literaturze, proponowany w tej pracy model uwzględnia wszystkie trzy główne kości kończyny górnej połączone powierzchniami stawowymi w stawie łokciowym i nadgarstkowym przy zastosowaniu kontaktu typu bonded jako jeden złożony układ biomechaniczny. Analizę dynamiczną przeprowadzono dla różnych konfiguracji kości przedramienia, wykorzystując dwa kryteria wytrzymałościowe do oceny potencjalnych miejsc złamań kości kończyny.

EN

The paper presents numerical model of the human upper extremity useful for the analysis of the upper extremity bones fracture risk during the falling process in a forward direction. Unlike previous models met in literature, the proposed in this paper model considers all three main upper extremity bones connected in the elbow and wrist joints by the bonded type contact as one complex biomechanical system. Transient analysis has been carried out for different forearm configurations by using two strength criteria to estimate possible sites of upper extremity bone fractures.

6

New Continuum Formulations for Modelling of Fiber Reinforced Composites

Zmindak M., Novák P., Melicher R.

Machine Dynamics Problems

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2006

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Vol. 30, No. 4

190-199

EN

The composites reinforced by rigid particles improve considerably many properties of matrix materials, they poses higher stiffness, strength, better wear resistance, superior electrical properties. The fibers are supposed to be much stiffer than the matrix and their diameter can be much smaller than their length. On the other side the number of the reinforcing particles can be very high and they can be not uniformly distributed over the structure. From material structure point view the particles present inclusions. For of such problems the methods like (finite element methods) FEM and BEM (boundary element methods) are not very efficient. Computational time for FEM is huge for an accurate solution of the mechanical fields. BEM using distributed forces, dislocations and dipoles along the fiber axis (the source points) enable to model these effects much more efficiently. The intensity of the source functions simulates the interaction of the fiber with the other subjects. Because of very close distance of the source points to the fiber boundary and the quasi-singular form of the integrals, the integration is performed analytically in the fiber direction. In this paper we will present two new methods for modelling composites reinforced by fibers: First proposed method is called here the method of continuous source functions (MCSF) which use continuously distributed dipoles as source functions. The second method is Boundary point method (BPM). In this method all internal fields will be approximated by the Trefftz functions (T-functions).