Vilnius Gediminas Technical University
Vilniaus Gedimino Technikos Universitetas: VGTU Talpykla / Vilnius Gediminas Technical University: VGTU RepositoryNot a member yet
4122 research outputs found
Sort by
Thermodynamic model of wind driven turbine ventilator
No full textDisertacijoje taikant eksperimentinius tyrimus ir sisteminės analizės metodus tiriami vėjo energiją naudojantys stoginiai turbininiai ventiliatoriai, jų veikimas, efektyvumas, funkcionalumas. Tiriamos galimybės padidinti vėjo energijos panaudojimo efektyvumą vėdinimui, esant stochastiniam vėjo kitimui metų cikle. Disertacijos tikslas – parengti eksperimentiškai nustatomomis mechaninėmis ir aerodinaminėmis charakteristikomis paremtą turbininio ventiliatoriaus teorinį veikimo modelį.
Darbe sprendžiami šie pagrindiniai uždaviniai: pirmasis – parengti ir įvykdyti eksperimentinių tyrimų programą, kuria struktūrizuojami STV veikimo režimai į atskirus srautinius procesus; antrasis – kiekybiškai ir kokybiškai palyginti skirtingų tokio tipo įrenginių eksperimentines charakteristikas; trečiasis – pasiūlyti turbininio ventiliatoriaus konstrukciją ir tekėjimo procesus jame atspindinčią struktūrinio suskaidymo koncepciją; ketvirtasis – parengti turbininio ventiliatoriaus veikimo termodinaminį modelį; penktasis – įvertinti galimybes padidinti vėjo energijos panaudojimo efektyvumą turbininiuose ventiliatoriuose.
Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai.
Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, mokslinis darbo naujumas, ginamieji teiginiai, pristatomos disertacijos tema paskelbtos autoriaus publikacijos ir pranešimai konferencijose bei disertacijos struktūra.
Pirmajame skyriuje pateikiama vėjo energiją naudojančių natūralaus vėdinimo sistemų tyrimų apžvalga. Atliktos apžvalgos pagrindu suformuluoti tyrimo uždaviniai leidžiantys pasiekti tyrimo tikslą.
Antrajame skyriuje pristatoma turbininių ventiliatorių eksperimentinių tyrimų programa, metodika bei šių tyrimų rezultatai.
Trečiajame skyriuje pateiktas turbininio ventiliatoriaus veikimo termodinaminis modelis, kuris suformuotas eksperimentinių tyrimų pagrindu. Taip pat pateiktas teorinis turbininių ventiliatorių funkcionalumo padidinimo vertinimas, kuomet įrenginys gali akumuliuoti perteklinę vėjo energiją.Daktaro disertacij
Mažojo palydovo šilumos perdavimo optimizavimas gradientiniu metodu
No full textDue to high demand for performance and cost effectiveness, CubeSats are becoming more technically advanced. This implies increased power consumption for higher performance, which in turn increases the internal heat dissipation. As a result, power-intensive components can quickly overheat due to insufficient heat dissipation, thus limiting the maximum allowable electrical power. Due to the small volume and limited resources, the implementation of active thermal control techniques to increase power on smaller spacecrafts is technically complex and not always possible. Heat transfer depends not only on the parameters of the orbit, power consumption, but also on the structure of the spacecraft itself. As a result, the design of the spacecraft can be optimized so that the internal heat generation could be maximised. In the scope of this thesis a gradient-based method to perform spacecraft structural and mission optimization was developed in order to maximize the allowable heat dissipation of subsystems. The method proposed in this thesis can automatically compute analytic partial and total derivatives of steady state heat-transfer equations with respect to design variables by just using the data of geometrical mathematical model and thermal mathematical model. A pre-processor was developed to interface the open-source optimization framework OpenMDAO with the thermal model outputs obtained in ESATAN-TMS – the main software tool for spacecraft thermal control design in European Space Agency. It was found that simulation results abtained with Open-MDAO agree well with those of Esatan-TMS. The worst case absolute and relative errors for a CubeSat model with solar arrays are below 2 ◦C and 1.2%, respectively. The cause of the error is mainly attributed to external reflections, which, for the sake of computational efficiency, are not accounted for in the OpenMDAO model. Finally, SLSQP algorithm was used to solve the multidisciplinary optimization problem of the interplanetary CubeSat mission, consisting of power and thermal disciplines. A 265% improvement of maximum radio transmitter power was achieved by optimizing 859 thermal, power and attitude design variables with 17 temperature and power constraints. The solution was obtained within less than 3 hours on Intel Core i5-5300U processor. The results also showed that a coupled multidisciplinary modeled that accounted for the dependency of solar cell efficiency on temperature achieved superior results than the uncoupled model, with 7% improvements.Doctoral dissertatio
Numerical and experimental investigations of aerosol solid particle interaction in acoustic field
No full textDisertacijoje nagrinėjami aerozolio ultrasmulkių (0,1–10 μm) kietųjų dalelių aglomeracijos efektyvumo akustiniame lauke metodai. Pagrindinis tyrimo objektas – ultrasmulkių kietųjų dalelių akustinės aglomeracijos, veikiant harmoninei stovinčiai bangai. Disertacijos tikslas – harmoninio akustinio lauko dėsningumų ir aglomeraciją lemiančių parametrų skaitinis ir eksperimentinis tyrimas, siekiant pagerinti ultrasmulkiųjų kietųjų dalelių aglomeraciją. Norint pasiekti išsikeltą tikslą, darbe sprendžiami keli pagrindiniai uždaviniai. Pirmasis skirtas sudaryti skaitinio eksperimento modelį ultrasmulkiųjų kietųjų dalelių aglomeracijai tirti, apimant DEM modelio pritaikymą ultrasmulkiųjų kietųjų dalelių aglomeracijai tirti, veikiant harmoninei stovinčiai bangai ir skaitiškai ištirti akustinio sužadinimo, gravitacinio lauko ir paribio sluoksnio poveikius kietųjų dalelių aglomeracijai. Antrasis uždavinys skirtas atlikti automobilio išmetamųjų dujų kietųjų dalelių aglomeracijos fizinį eksperimentą, apimanti eksperimentinio įrenginio ir eksperimento metodikos sukūrimą, taip pat sukurto eksperimentinio įrenginio tinkamumo ultrasmulkiųjų dalelių aglomeracijai vertinti.
Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai, santrauka anglų kalba ir 4 priedai.
Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas ir uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai. Įvado pabaigoje pristatomos disertacijos tema autoriaus paskelbtos publikacijos ir pranešimai konferencijose bei disertacijos struktūra. Pirmame skyriuje apžvelgiama literatūra, išanalizuota aerozolio kietųjų dalelių įtaka žmogaus sveikatai, jų susidarymo šaltiniai, pagrindinės kietųjų dalelių charakteristikos, akustinės aglomeracijos mechanizmai, apžvelgtos akustinės aglomeracijos analizinės, skaitinės ir eksperimentinės tyrimų metodikos. Skyriaus pabaigoje formuluojamos išvados ir tikslinami disertacijos uždaviniai. Antrajame skyriuje pateikti teoriniai tyrimai, įvertinantys gravitacijos lauko ir akustinės toliveikos poveikį kietųjų dalelių akustinei aglomeracijai bei kokią įtaką daro paribio sluoksnis dalelių suartėjimui akustiniame lauke. Trečiajame skyriuje pateikti sukurtos akustinės kameros eksperimentiniai tyrimai, analizuojant dyzelinio automobilio išmetamųjų teršalų dalelių sklaidos į aplinką mažinimą pagal sukurtą tyrimų metodiką.
Disertacijos tema išspausdintos keturios mokslinės publikacijos: trys – mokslo žurnaluose, įtrauktuose į Clarivate Analytics Web of Science sąrašą, viena – recenzuojamame mokslo žurnale, referuojamame kitose tarptautinėse duomenų bazėse. Disertacijos tema perskaityti aštuoni pranešimai Lietuvos bei kitų šalių konferencijose ir seminaruose.Daktaro disertacij
Human Emotion Recognition: Review of Sensors and Methods
No full textAutomated emotion recognition (AEE) is an important issue in various fields of activities which use human emotional reactions as a signal for marketing, technical equipment, or human–robot interaction. This paper analyzes scientific research and technical papers for sensor use analysis, among various methods implemented or researched. This paper covers a few classes of sensors, using contactless methods as well as contact and skin-penetrating electrodes for human emotion detection and the measurement of their intensity. The results of the analysis performed in this paper present applicable methods for each type of emotion and their intensity and propose their classification. The classification of emotion sensors is presented to reveal area of application and expected outcomes from each method, as well as their limitations. This paper should be relevant for researchers using human emotion evaluation and analysis, when there is a need to choose a proper method for their purposes or to find alternative decisions. Based on the analyzed human emotion recognition sensors and methods, we developed some practical applications for humanizing the Internet of Things (IoT) and affective computing systems.This article belongs to the Section Biomedical SensorsThis project has received funding from European Regional Development Fund (project No 01.2.2-LMT-K-718-01-0073) under grant agreement with the Research Council of Lithuania (LMTLT)
Customized ViNeRS Method for Video Neuro-Advertising of Green Housing
No full textThe implementation of advertising for green housing usually involves consideration of individual differences among potential buyers, their desires for residential unit features as well as location impacts on a selected property. Much more rarely, there is consideration of the arousal and valence, affective behavior, emotional, and physiological states of possible buyers of green housing (AVABEPS) while they review the advertising. Yet, no integrated consideration of all these factors has been undertaken to date. The objective of this study was to consider, in an integrated manner, the AVABEPS, individual differences, and location impacts on property and desired residential unit features. During this research, the applications for the above data involved neuromarketing and multicriteria examination of video advertisements for diverse client segments by applying neuro decision tables. All of this can be performed by employing the method for planning and analyzing and by multiple criteria and customized video neuro-advertising green-housing variants (hereafter abbreviated as the ViNeRS Method), which the authors of this article have developed and present herein. The developed ViNeRS Method permits a compilation of as many as millions of alternative advertising variants. During the time of the ViNeRS project, we accumulated more than 350 million depersonalized AVABEPS data. The strong and average correlations determined in this research (over 35,000) and data examination by IBM SPSS tool support demonstrate the need to use AVABEPS in neuromarketing and neuro decision tables. The obtained dependencies constituted the basis for calculating and graphically submitting the ViNeRS circumplex model of affect, which the authors of this article developed. This model is similar to Russell’s well-known earlier circumplex model of affect. Real case studies with their related contextual conditions presented in this manuscript show a practical application of the ViNeRS Method.This article belongs to the Special Issue Trends in Sustainable Buildings and InfrastructureThis project has received funding from European Regional Development Fund (project No
01.2.2-LMT-K-718-01-0073) under grant agreement with the Research Council of Lithuania (LMTLT). The sponsor
had no involvement in the study design, the collection, analysis and interpretation of data, or the preparation of
the article
Probing Nanoelectroporation and Resealing of the Cell Membrane by the Entry of Ca2+ and Ba2+ Ions
No full textThe principal bioeffect of the nanosecond pulsed electric field (nsPEF) is a lasting cell membrane permeabilization, which is often attributed to the formation of nanometer-sized pores. Such pores may be too small for detection by the uptake of fluorescent dyes. We tested if Ca2+, Cd2+, Zn2+, and Ba2+ ions can be used as nanoporation markers. Time-lapse imaging was performed in CHO, BPAE, and HEK cells loaded with Fluo-4, Calbryte, or Fluo-8 dyes. Ca2+ and Ba2+ did not change fluorescence in intact cells, whereas their entry after nsPEF increased fluorescence within 7 kV/cm for the formation of larger pores that admitted YO-PRO-1, TO-PRO-3, or propidium dye into the cells. Ba2+ entry caused a gradual emission rise, which reached a stable level in 2 min or, with more intense nsPEF, kept rising steadily for at least 30 min. Ca2+ entry could elicit calcium-induced calcium release (CICR) followed by Ca2+ removal from the cytosol, which markedly affected the time course, polarity, amplitude, and the dose-dependence of fluorescence change. Both Ca2+ and Ba2+ proved as sensitive nanoporation markers, with Ba2+ being more reliable for monitoring membrane damage and resealing.This article belongs to the Section Molecular BiophysicsThe study was supported by a 2015 AFOSR MURI grant A9550-15-1-0517 (to A.G.P.), by a scholarship
from the China Scholarship Council (to W.B.), and by a grant S-MIP-19-13 from the Research Council of Lithuania
(to V.N.)
Statybos modeliavimas ekonominio nuosmukio aplinkoje
No full textDaktaro disertacijos santrauka
Technologijos mokslai, statybos inžinerija (02T)Daktaro disertacijos santrauk
Statybinių medžiagų ir konstrukcijų akustinių savybių tyrimas ir panaudojimas triukšmui mažinti patalpose
No full textSummary of Doctoral Dissertation
Technological sciences, environmental engineering (04T)Daktaro disertacijos santrauk
Review of V2X–IoT Standards and Frameworks for ITS Applications
No full textThe intelligent transport system (ITS) has become one of the most globally researched topics with a lot of investment and development resources being dedicated into it due to its foreseen impact on the economic growth of the transport sector. Currently there are two main vehicle-to-everything (V2X) technologies, whose primary application is focused on ITS, backed up by the key players of various automotive, telecommunication and transport industries: dedicated short-range communications (DSRC) and cellular vehicle-to-everything (C-V2X), respectively based on IEEE 802.11p and 3GPP LTE/5G NR. While DSRC already has deployments, C-V2X is expected to see larger scale trails and deployments in 2020. In this work, the authors provide insight and review into two main V2X technologies, DSRC and C-V2X, their core parameters, shortcomings and limitations, and explore the need for integration of IoT-based technologies into modern ITS solutions. A comprehensive overview and analysis of currently commercially available V2X products, their sub-blocks and features is provided.This article belongs to the Special Issue Technologies and Applications of Communications in Road TransportThis research was funded by Research Council of Lithuania, grant number DOTSUT-235, No.
01.2.2-LMT-K-718-01-0054
The Usage of Alternative Materials to Optimize Bus Frame Structure
No full textThe strength and stiffness of the frame is one of the key indicators of vehicle structures. Insufficient stiffness causes vibration and noise, and is also less comfortable for both the passengers and the driver. Symmetry is required between the strength and comfort of the structural frame, which depends on vibration and noise. This article analyses the frame of the structure of a medium-sized passenger bus and its dynamic properties, when replacing materials of structural elements which do not affect the symmetry of the structure. The conducted theoretical and experimental modal analysis of the bus, allows for evaluating dynamic parameters and validating the theoretical model based on the experimental results. The optimization of the medium-sized passenger bus frame—by replacing the material of the ancillary frame elements with fiberglass—reveals that its dynamic characteristics change by up to 20%, comparing the values of the first three resonant frequencies with those of the steel structure. The obtained results show that replacing the material of ancillary frame elements with fiberglass, while maintaining the symmetrical arrangement of the elements in the structure, does not change the safety characteristics of the structure, reducing the mass of the frame by 11%, and shifting the coordinate of the centre of gravity vertically downwards, which is very important for stability, comfort and fuel consumption.This article belongs to the Special Issue Symmetry in Mechanical Engineering