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
Sea environment influence on hydrotechnical concrete durability
Get PDFDisertacijoje išanalizuotos Baltijos jūros aplinkoje esančių konstrukcijų hidro- techninio betono naudojimo sąlygos, Baltijos jūros vandens bei užšaldymo ir atšildymo ciklų ir chloridų difuzijos veikiamo betono irimo priežastys. Eksperi- mentiniais tyrimais nustatyta mineralinių priedų (aukštakrosnių šlako, klinties, akmens anglies deginimo pelenų, SiO2 mikrodulkių) įtaka hidrotechninio betono savybėms bei tvarumui veikiant Baltijos jūros vandens cheminės sudėties tirpa- lais bei užšaldymo ir atšildymo ciklais. Ištirtos ir įvertintos Baltijos jūros aplin- kos sąlygos Klaipėdos uosto akvatorijoje ir jų poveikis naudojamam hidrotech- niniam betonui su skirtingais cementais, mineraliniais priedais ir stambiaisiais užpildais. Atlikus įvairių veiksnių (sorbcijos ir desorbcijos, chloridų difuzijos, užšaldymo ir atšildymo ciklų) poveikio hidrotechnikos statinių betonui analizę, sudaryta hidrotechninio betono ilgaamžiškumo bandymo metodika.
Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, naudotos literatūros ir disertacijos autorės publikacijų sąrašai.
Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas ir uždaviniai, aprašoma tyrimų metodika ir jos metodologija, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai. Įvado pabaigoje pristatomos disertacijos tema autorės paskelbtos publikacijos ir pranešimai konferencijose, seminaruose bei disertacijos struktūra.
Pirmasis skyrius skirtas literatūros analizei. Atliktoje literatūros analizėje aprašytos jūros uosto statinių betoninių ir gelžbetoninių konstrukcijų naudojimo sąlygos, hidrotechninio betono irimo procesai dėl cikliško užšaldymo ir atšildymo bei druskų poveikio, jūros vandens įtaka betono koroziniams procesams, mineralinių priedų įtaka hidrotechninio betono ilgaamžiškumui bei chloridų difuzijos procesai hidrotechniniame betone.
Antrajame skyriuje aprašytos tyrimams naudotos medžiagos ir jų savybės, betono mišinių sudėtys, taikyti tyrimų metodai ir naudota įranga, bandinių paruošimo, kietinimo ir tyrimų metodikos.
Trečiajame disertacijos skyriuje pateikti atliktų tyrimų rezultatai: Baltijos jūros aplinkoje eksploatuotų konstrukcijų pažaidų analizė ir ilgą laiką naudoto betono stiprumo charakteristikos ir druskų kiekis jame, aktyviųjų mineralinių priedų poveikis hidrotechninio betono savybėms, jo sorbcinėms charak- teristikoms, chloridų difuzijai ir ilgaamžiškumui.
Iš gautų rezultatų suformuluotos bendrosios išvados ir parengta betono atsparumo Baltijos jūros aplinkos poveikiui bandymo metodika
Factors influencing a bank’s competitive ability: the case of Lithuania and Latvia
No full textResearch background: A commercial bank’s competitive ability is of great importance as it plays a vital role in ensuring a bank’s success; hence, it is necessary to identify the factors that contribute to the development of competitive advantage of commercial banks and to shift competitive ability to a higher level. The competiveness of banks is assessed from customers’ perspective, highlighting the main factors that influence them in choosing a particular bank. Purpose of the article: The paper aims to assess the determinants influencing bank’s competitive ability from customers’ perspective by indicating the level of their influence. The following objectives are set: to distinguish the determinants influencing commercial bank’s competitive ability, to prepare a methodology for the assessment of factors, to evaluate the importance of the factors using expert evaluation method based on fuzzy analytic hierarchy process. Methods: A questionnaire was prepared for the experts in order to collect the data; fuzzy analytic hierarchy process was implemented for processing the data. Findings & Value added: The research was conducted in Latvia and Lithuania at the be-ginning of 2017. The results showed that the most important factor for bank’s competitive ability in both — Lithuania and Latvia — is customers’ trust. Reliability of the bank (both in Latvia and Lithuania) and the privileges of loyal customers (only in Latvia) have gained experts’ attention as well. The proposed model of bank’s competitive ability allows to evaluate the level of bank’s competitiveness effectively, which would help the bank to plan its activities successfully and attract new customers in order to take the leading position in the market
Quantitative assessment of the dynamics of the economic development of socioeconomic systems based on the MDD method
No full textMultiple criteria selection of design solutions for single-family houses
Get PDFDisertacijoje nagrinėjami vienbučių namų architektūrinių-konstrukcinių sprendinių (konstrukcinių elementų ir tvarių medžiagų, vidinių laiptų formų ir įvairių garažo padėčių) parinkimo ir vertinimo modeliai, grindžiami daugiakriteriais sprendimų priėmimo metodais. Literatūros analizė atskleidė, kad šiuo metu tvarumas yra vienas svarbiausių klausimų, į kuriuos reikia atsižvelgti projektuojant ir statant namą. Vis labiau įsitikinama, kad reikia sukurti priemonių siekiant integruoti tvarumo kriterijus į pastatų projektavimo ir statybos procesą, be to, atsiranda vis didesnis žinių, kaip suderinti tvarumą su vienbučių namų statyba, poreikis. Šiame darbe siekiama susieti dvi mokslines sritis sprendžiant vienbučių namų architektūrinių-konstrukcinių sprendinių parinkimo klausimus.
Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, naudotos literatūros ir autorės publikacijų disertacijos tema sąrašai.
Įvadiniame skyriuje aptariamos problemos, aprašomi tiriamieji objektai, formuluojamas darbo tikslas ir uždaviniai, iškeliamas mokslinis darbo naujumas, ginamieji teiginiai. Įvado pabaigoje pateikiamos disertacijos tema autorės paskelbtos publikacijos ir pranešimai konferencijose.
Pirmajame skyriuje pateikiama tvaraus gyvenamojo būsto sprendinių analizė ir nagrinėjamas komforto, erdvinių zonų, vienbučių namų elementų formų bei medžiagų parinkimas gyvenamajam namui statyti. Apžvelgiamos MCDM (daugiakriterių sprendimų priėmimo metodų, angl. Multiple Criteria Decision Making) panaudojimo galimybės statybos srities uždaviniams spręsti. Skyriaus pabaigoje formuluojamos išvados ir pateikiami disertacijos uždaviniai.
Antrajame skyriuje apžvelgiami namo konstrukcinių elementų (laiptų) formų grafiniai kūrimo metodai. Aprašomi daugiakriteriai vertinimo metodai, kuriais įvertinami disertacijoje suformuluoti uždaviniai.
Trečiajame skyriuje pateiktas trijų praktinių suformuluotų uždavinių sprendimas, taikant pasiūlytus MCDM metodus: pirmuoju ieškoma geriausia garažo padėtis vienbučio namo atžvilgiu; antruoju – vertinamas vienbučių namų konstrukcinių elementų ir tvarių medžiagų parinkimas; trečiuoju – pagrindžiamas ergonomiškų laiptų formų parinkimas
Automated method for fractographic analysis of shape and size of dimples on fracture surface of high-strength titanium alloys
No full textAn automated method for analyzing the shape and size of dimples of ductile tearing formed
during static and impact fracture of titanium alloys VT23 and VT23M is proposed. The method is
based on the analysis of the image topology. The method contains the operations of smoothing the
initial fractographic image; its convolution with a filter to identify the topological ridges; thresholding
with subsequent skeletonization to identify boundaries between dimples; clustering to isolate
the connected areas that represent the sought objects—dimples. For each dimple, the following
quantitative characteristics were calculated: area, coefficient of roundness and visual depth in units of
image intensity. The surface of ductile tearing was studied by analyzing the peculiarities of parameter
distribution of the found dimples. The proposed method is applied to fractograms of fracture surfaces
of titanium alloys VT23 and VT23M
Experimental study on spine segment fixation technique
No full textThe paper presents a study on instrumented evaluation
of the single spinal segment fixation techniques. In
vitro tests have been completed with 6 porcine spinal samples.
Two different methods of rigidly fixed segment of the
lumbar spine were tested and compared with control
group/unfixed spinal units (CO). One fixation technique
was obtained using screws and straight rods (FSR), another
- screws and bent rods simulating the anatomy of the spine
(FBR). Experimental data contains deformation data under
experimental test loading limitations. Obtained results
showed no significant difference between fixation techniques
FSR and FBR in any case of loading parameters.
However, results indicated significant differences under
flexion tests after rigid fixation of the spine. Due to these
results, we can presume that flexion movement is the most
hazardous for developing adjacent segment disease
Influence of the piezoelectric ringing on the temperature of the beta barium borate crystal
No full textThe influence of the piezoelectric ringing on the temperature of the beta barium borate Pockels cell crystal has been investigated. The experimental setup for the investigations was developed. The measurements of the Pockels cell crystal contrast ratio and temperature dependences on the applied high voltage pulse frequency for 10 different 3 mm_3 mm_25 mm beta barium borate Pockels cell crystals were performed. The transients of the beta barium borate Pockels cell temperature were measured at various high voltage pulse frequencies. Two parameters were recorded: the contrast ratio and the crystal temperature. The frequencies, at which the temperature increase caused by the piezoelectric ringing occurs, were determined. It has been shown that the contrast ratio of the beta barium borate Pockels cell crystal does not depend on the temperature. Additionally, the investigation of the deuterated potassium dihydrogen phosphate Pockels cell crystal ringing phenomenon was performed. It has been shown that from the point of view of the contrast ratio temperature stability Pockels cells based on the beta barium borate crystals are more preferable
Iš anksto įtemptais bazalto pluošto strypais armuotų lenkiamųjų betoninių elementų elgsenos analizė
Get PDFIn general, prestressed concrete (PC) is by far one of the most economical concrete construction techniques, but at the same time, it requires specific knowledge of the properties and behavior of this material. Precompression of the concrete by transferred prestressed force flexural stiffness can be increased and the main issue – cracking might be eliminated, correspondingly. Based on the development progress PC is widely being utilized in the construction of the structures for transport and energy sectors (bridges, viaducts, gasholders, reactors, oil&gas tanks, etc.). It has been used in order to store potentially dangerous materials during operation and to resist dynamic effects. However, even in PC case cracking appears, and it is common that it causes corrosion of conventional reinforcement. Finally, it influences the maintenance of existing infrastructure.
Within this research, the author develops the particular subject of concrete – application of new composite material – basalt fiber reinforced polymer (BFRP) to be used for prestressed concrete structures considering subsequent loading stages (stretching at the bulkheads, prestress transfer to concrete, application of service load, etc.). In order to design PC structures, it is significant to estimate effective prestress force with respect to the time-dependent process of concrete and reinforcement. In accordance with design codes requirements, typical formulas from regular concrete structures (RC) are to be used for the estimate of serviceability conditions of flexural PC members. However, a complete review of prestress losses and serviceability shall be employed in order to avoid errors in the structural prognosis of the PC structures with non-conventional composite reinforcement.
Unlike other composites, experimental test work and calculation methods have yet to be developed for BFRP reinforcement in order to determine stress relaxation behavior. Currently, this phenomena is not fully documented in the literature. Based on this, the author approached an innovative stress relaxation test method to describe the effect of stress relaxation and its impact on the final value of the effective prestress force. Full-scale testing beams were tested in order to evaluate the impact of prestress level (degree) to the flexural stiffness of concrete beams internally prestressed with BFRP bars.
The dissertation is structured within the introduction, three main chapters, verification of the results, the lists of references and author’s publications on the subject of the dissertation.
The topic of the thesis has been discussed in 9 articles: 3 – in the journals with an Impact Factor, 5 – in scientific journals of other international databases and 1 in the conference proceedings referred by the Clarivate Analytics Web of Science
Concerning translation of Heidegger’s „Being and Time“
No full textThe article discusses some issues on the Lithuanian translation of Heidegger’s Being and Time by Tomas
Kačerauskas and reviewed by Mintautas Gutauskas. The article focuses on the translator’s and reviewer’s
disagreement concerning appropriate translation of the fragments related to the Greek sources of modern
technology. Its aim is not a critique of the translator’s version and an advocacy for the reviewer. The aim is
the manifestation of an incommensurability between the potential richness of possible translations and the
essential poverty of its real versio
Factors Influencing Individual Customers Trust in Internet Banking: Case of Baltic States
No full textThe investigation of trust in commercial banks needs to focus specifically on internet
banking, as it is the fastest growing banking service. The article explores factors influencing trust
in internet banking and estimates this impact in the Baltics states. The factors are as follows:
Provided information, e-banking system, the website of a bank, and a bank’s characteristics. Overall,
1013 respondents and 21 experts took part in the current study. The results of the respondents’
survey showed that the factor that is necessary for trust building in all the examined countries differs:
In Lithuania, information and the bank, in Latvia, the website, and in Estonia, the bank. According
to the experts, the most powerful factor in the trust-building process in Lithuania and Latvia is the
e-banking system while in Estonia, the website. The research has the following limitations: The online
survey of individual customers (however, internet banking relates to internet users, so this limitation
is not essential); the analysis of only the positively affecting criteria of the trust-building process; only
experts assessed the subfactors.This article belongs to the Special Issue CSR and Business Ethics for Sustainable Developmen