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Open access

M. Maltisovs, K. Krumins, A. Ozols and D. Pikulins

Abstract

Nowadays liquid crystal display (LCD) is an integral part of humans’ everyday life. High demand for new and innovative LCD products force LCD industry to develop and implement new types of LCDs. Bistable smectic-A (SmA) LCD is one of the most promising devices for smart glass applications due to long-term bistability, low haze at clear state, low transmittance at scatter state and low power consumption.

The study describes the most relevant conclusions obtained from frequency response testing and electric current measurements of bistable SmA LCD samples. Bistable LCDs have two states: opaque (light scattering state) and focal conic (transparent state). Switching between clear and scatter states and vice versa is a frequency dependant process. The conducted research on bistable SmA LC frequency response provides important knowledge about operation principles of the smart glass devices.

Open access

A. Prohorenko and P. Dumenko

Abstract

Nowadays global engine construction gets significant progress at a technological level, but specified manufacturers do not release any information about the composition, the structure of the algorithms and the software used by their equipment. It is possible to obtain information only fragmentary and, for example, the description of the electronic control unit algorithm is completely missing. This is a barrier for small companies to improve and adjust existing engines for specific purposes. The present paper describes and develops algorithm synthesis for an electronic diesel engine regulator. Mathe-matical modelling of the automatic control system has been carried out within the framework of the research. The results of the research have demonstrated the efficiency and sustainability of automatic electronic control system using the proposed algorithm.

Open access

N. Remez, A. Dychko, S. Kraychuk, N. Ostapchuk, L. Yevtieieva and V. Bronitskiy

Abstract

The present paper provides numerical simulation of interaction of wave processes in the system “soil massif – underground pipeline” in explosion of charge on the surface of ground. Construction is considered in the framework of nonlinear theory of shells of Tymoshenko type. Soil is modelled by a solid porous multicomponent visco-plastic medium. The study establishes patterns of changes in stress-strain state of system depending on depth of pipeline laying and its diameter.

Open access

Duraisamy Velmurugan, Masilamany Santha Alphin and Benedict Jain AR Tony

Abstract

Background: Implant thread profile plays a vital role in magnitude and distribution of contact stresses at the implant-bone interface. The main goal of this study was to evaluate the biomechanical effects of four distinct thread profiles of a dental implant in the mandibular premolar region.

Methods: The dental implant represented the biocompatible Zirconia material and the bone block was modelled as transversely isotropic and elastic material. Three-dimensional finite element simulations were conducted for four distinct thread profiles of a dental implant at 50%, 75%, and 100% osseointegration. An axial static load of 500 N was applied on the abutment surface to estimate the stresses acting within the bones surrounding the implant.

Results: Regions of stress concentration were seen mostly along the mesiodistal direction compared to that in the buccolingual direction. The cortical bone close to the cervical region of the implant and the cortical bone next to the first thread of the implant experienced peak stress concentration. Increasing the degree of osseointegration resulted in increased von-Mises stresses on the implant-cortical transition region, the implant-cancellous transition region, the cortical bone, and the cancellous bone.

Conclusion: The results show that the application of distinct thread profiles at different degrees of osseointegration had significant effect on the stresses distribution contours in the surrounding bony structure. Comparing all four thread profiles, a dental implant with V-thread profile induced lower values of von-Mises stresses and shear stresses on the implant-cortical transition region, implant-cancellous transition region, cortical bone, and cancellous bone.

Open access

Baljeet Singh and Ritu Sindhu

Abstract

In this paper, the governing equations of a linear, homogeneous and transversely isotropic rotating micropolar piezoelectric medium are solved for surface wave solutions. The appropriate solutions satisfying the radiation conditions are obtained in a half-space. These solutions are applied to suitable boundary conditions at the free surface of the half-space. A frequency equation for Rayleigh wave is obtained for both charge free and electrically shorted cases. Using iteration method, the non-dimensional wave speed of Rayleigh wave is computed for relevant material constants modelling the medium. The effects of rotation, piezoelectricity, frequency and material parameters are observed graphically on the propagation speed.

Open access

Dominik Kern, Ignacio Romero, Sergio Conde Martín and Juan Carlos García-Orden

Abstract

Structure-preserving integrators are in the focus of ongoing research because of their distinguished features of robustness and long time stability. In particular, their formulation for coupled problems that include dissipative mechanisms is still an active topic. Conservative formulations, such as the thermo-elastic case without heat conduction, fit well into a variational framework and have been solved with variational integrators, whereas the inclusions of viscosity and heat conduction are still under investigation. To encompass viscous forces and the classical heat transfer (Fourier’s law), an extension of Hamilton’s principle is required. In this contribution we derive variational integrators for thermo-viscoelastic systems with classical heat transfer. Their results are compared for two discrete model problems vs. energy-entropy-momentum methods.

Open access

Karthick Raj Mani, Md Anisuzzaman Bhuiyan, Md. Shakilur Rahman and S. M. Azharur Islam

Abstract

True Beam medical linear accelerator is capable of delivering flattening filter free (FFF) and with flattening filter (WFF) photon beams. True Beam linear accelerator is equipped with five photon beam energies (6 FFF, 6 WFF, 10 FFF, 10 WFF and 15 WFF) as well as six electron beam energies (6 MeV, 9 MeV, 12 MeV, 15 MeV and 18 MeV). The maximum dose rate for the 6 WFF, 10 WFF and 15 WFF is 600 MU/min, whereas 6 FFF has a maximum dose rate of 1400 MU/min and 10 FFF with a maximum dose rate of 2400 MU/min. In this report we discussed the open beam dosimetric characteristics of True Beam medical linear accelerator with FFF and WFF beam. All the dosimetric data (i.e. depth dose, cross-line profiles, diagonal profiles, output factors, MLC transmission, etc.) for 6 MV, 6 FFF, 10 MV, 10 FFF and 15 MV were measured and compared with the published data of the True Beam. Multiple detectors were used in order to obtain a consistent dataset. The measured data has a good consistency with the reference golden beam data. The measured beam quality index for all the beams are in good agreement with the published data. The percentage depth dose at 10 cm depth of all the available photon beams was within the tolerance of the Varian acceptance specification. The dosimetric data shows consistent and comparable results with the published data of other True Beam linear accelerators. The dosimetric data provide us an appreciated perception and consistent among the published data and may be used for future references.

Open access

A.J. Janavičius and S. Turskienė

Abstract

The paper discusses the properties of the nonlinear thermodiffusion equation corresponding to the diffusion processes, which occur with a finite velocity. In the previous papers, A. J. Janavičius proposed the nonlinear diffusion equation with the diffusion coefficient directly proportional to the concentration of impurities. This equation provides a more exact description of the profiles of impurities in Si crystals. The heat transfer in gases carries a greater average kinetic energy based on nonlinear diffusion of gas molecules from hot regions to the coldest ones with a finite velocity by random Brownian motions. In this case, the heat transfer in gases can be described by using nonlinear thermodiffusion equation with heat transfer and thermodiffusion coefficients directly proportional to temperature T. The obtained approximate analytical solutions are successfully applied in defining temperature profiles and heat transfer coefficients in gases as well as providing opportunities for practical applications. It has been concluded that heat spreading in gases depends on temperature differences and pressure in gases.

Open access

R.V.M.S.S. Kiran Kumar and S.V.K. Varma

Abstract

The hydromagnetic nanofluid flow over a stretching sheet in a porous medium with variable wall thickness in the presence of Brownian motion and thermophoresis is investigated. The heat transfer characteristics with variable conductivity are explored by using Cattaneo-Christov heat flux model. The governing non-linear ordinary differential equations are solved by using boundary value problem default solver in MATLAB bvp4c package. The impact of various important flow parameters on velocity, temperature and nanoparticle concentration as well as the friction factor coefficient and the rate of heat and mass transfer coefficients are presented and discussed through graphs and tables. It is found that the fluid velocity is accelerated with an increase in wall thickness parameter for n > 1, while the reverse trend is observed for n < 1.

Open access

I. Smirnova, E. Lipenbergs and V. Bobrovs

Abstract

Since Regulation (EU) 2015/2120 of the European Parliament and of the Council came into force, Internet service providers have to fulfill various additional requirements in order to guarantee access to the open internet and provide transparent information to the end-users. Of the utmost importance is to ensure achievable, meaningful and comparable results of the internet quality indicators, particularly upload and download speed values. Regulation (EU) 2015/2120 stipulates that specific speeds should be indicated in the contracts: for fixed internet access service those are maximum, minimum, normally available and advertised speed and for mobile internet access service – estimated maximum and advertised speed. However, there are no common methods put in place to calculate required speed indicators that can lead to a large amount of noncomparable and unreviewable information and create difficulties for internet providers to describe quality indicators. Within the framework of the present research, a mathematical estimation algorithm has been elaborated and applied in order to ensure that required quality parameters are represented objectively and that they are intercomparable among different internet service providers. Unified calculation principle would foster end-user awareness of the meaning of quality indicators and also of the quality of received internet services. It would also facilitate the indication of the required information for internet service providers.