Vilnius Gediminas Technical University
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Numerical investigation of the effect of bone tissue pathology on human spine stability
Get PDFŠioje disertacijoje nagrinėjamos slankstelių, paveiktų kaulinio audinio patologijos, savybės ir jų poveikis stuburo stabilumo praradimui. Pagrindinis tyrimo objektas – žmogaus juosmens dalies fragmentas, sudarytas iš trijų slankstelių, tarpusavyje sujungtų tarpslanksteliniais diskais. Disertacijos tikslas – taikant baigtinių elementų metodą ištirti slankstelių kaulinio audinio patologijos įtaką izoliuoto slankstelio ir stuburo fragmento stabilumui.
Darbo tikslui pasiekti, analizuojant pažeistų osteoporoze slankstelių elgseną, sprendžiami tris uždaviniai. Pirmas uždavinys – suformuluoti stuburo struktūrinio stabilumo baigtinių elementų modelį. Antras uždavinys suformuluotas siekiant nustatyti stuburo juosmens dalies slankstelio lūžio prognozės veiksnius. Trečias uždavinys – ištirti juosmens dalies kaulinio audinio patologijos įtaką stuburo globalaus stabilumo praradimui.
Disertaciją sudaro įvadas, keturi skyriai, bendrosios išvados, naudotos literatūros, autoriaus publikacijų disertacijos tema sąrašai, santrauka anglų kalba ir 3 priedai.
Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, pristatomas tyrimų objektas, formuluojamas darbo tikslas ir uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai. Pirmasis skyrius skirtas literatūros analizei.
Antrajame skyriuje pasiūlytas žmogaus stuburo geometriškai netiesinis tampriosios analizės BEM modelis. Šio modelio slankstelio kortikalinis apvalkalas modeliuojamas kaip plonasienis kevalas, o trabekulinis audinys – kaip erdvinis trimatis kūnas.
Trečiajame skyriuje pateikiama stuburo juosmens dalies L3 slankstelio paveikto kaulinio audinio patologijos stabilumo analizė. Nustatyta, kad nestabilumą sukelia lokalusis kortikalinio kaulo klupumas, atsirandantis dėl kortikalinio kaulo suplonėjimo ir ryšių tarp dviejų terpių degradacijos. Taip pat duotos išvados apie veiksnius veikiančius slankstelių laikomąją galią, ir slankstelių lūžio prognozės pagerinimo rekomendacijos.
Ketvirtajame skyriuje pateikiama žmogaus stuburo juosmens dalies L2–L4 stabilumo analizė. Nustatyta, kad dėl kaulinio audinio patologijos susidaranti papildoma slankstelių deformacija sukelia šlyties jėgas dėl kurių įvyksta globalusis stuburo stabilumo praradimas. Duotos išvados apie kaulinio audinio patologias veikiančius slankstelių kortikalinio kaulo stabilumą ir stuburo bendrą stabilumą.
Disertacijos tema paskelbtos keturios publikacijos: trys – mokslo žurnaluose,
įtrauktuose į Clarivate Analytics Web of Science sąrašą, viena – kituose žurnaluose. Disertacijos tema perskaityti septyni pranešimai Lietuvos bei kitų šalių konferencijose ir seminaruose.Disertacij
Energy efficiency improvement in modernization of public buildings using sustainable design methods
Get PDFEuropos Sąjunga (ES) užsibrėžė ilgalaikį tikslą iki 2050 m. sumažinti šiltnamio efektą sukeliančių dujų išmetimą 80–95 % ES energijos strateginiame dokumente (Energy Roadmap 2050) reikalaujama daugiau dėmesio skirti pastatų energijos vartojimo efektyvumui skatinti, nes Europoje pastatų suvartojimo energija siekia net 40 % visos suvartojamos energijos. Tuo tarpu Direktyvoje 2010/31/ES (Directive 2010) numatyta, jog statomų naujų pastatų nuo 2020 m. gruodžio 31 d. suvartojama energija turi siekti nulines sąnaudas. Ne išimtis yra ir seni visuomeniniai pastatai, kuriuos reikia modernizuoti dėl jų nusidėvėjimo ir neefektyvaus energijos vartojimo.
Darbo tikslas – sukurti senų visuomeninių pastatų modernizavimo sistemos optimizavimo modelį, siekiant padidinti pastatų vartojamos energijos efektyvumą.
Disertaciją sudaro: įvadas, trys skyriai, bendrosios išvados, literatūros ir šaltinių sąrašas, autorės mokslinių publikacijų disertacijos tema sąrašas ir keturi priedai.
Įvade aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas ir uždaviniai, nurodomas mokslinis darbo naujumas, ginamieji teiginiai. Įvado pabaigoje pateikti autorės pranešimai konferencijose ir publikacijos, disertacijos struktūra.
Pirmajame skyriuje analizuojamos mokslinės literatūros šaltiniuose nurodomos senų visuomeninių pastatų problemos ir galimi modernizacijos sprendimo būdai. Pateikta pastatų energijos naudojimo didinimo priemonių analizė, pastatų atnaujinimo būdai ir galimybės bei BIM technologijos eiga ir jos pritaikymą atliekant pastatų modernizaciją.
Antrajame skyriuje pateikiamas modernizacijos modelis visuomeninių pastatų rekonstrukcijai atlikti. Pateikta baziniai pastatų analizės metodai taikant tokias naujas technologijas: fotogrammetrinio modelio sudarymas, klasifikatoriaus pritaikymas BIM aplinkoje, Optimizavimo modelio algoritmas.
Trečiajame skyriuje patikrinta sukurta metodika bei visuomeninių pastatų modernizavimo technologijos daugiakriteris modelis pritaikant BIM. Optimizavimo modelio algoritmas pritaikytas Radviliškio manevrinio dispečerinio posto (Bokšto g. 13) pastatui modernizuoti atliekant projektavimo darbus. Įvertinti gauti rezultatai ir pateiktos išvados.Disertacij
Deformation Analysis of Reinforced Beams Made of Lightweight Aggregate Concrete
No full textIn the present trend of constructing taller and longer structures, the application of lightweight aggregate concrete is becoming an increasingly important advanced solution in the modern construction industry. In engineering practice, the analysis of lightweight concrete elements is performed using the same algorithms that are applied for normal concrete elements. As an alternative to traditional engineering methods, nonlinear numerical algorithms based on constitutive material models may be used. The paper presents a comparative analysis of curvature calculations for flexural lightweight concrete elements, incorporating analytical code methods EN 1992-1 and ACI 318-19, as well as a numerical analysis using the constitutive model of cracked tensile lightweight concrete recently proposed by the authors. To evaluate the adequacy of the theoretical predictions, experimental data of 51 lightweight concrete beams of five different programs reported in the literature were collected. A comparison of theoretical and experimental results showed that the most accurate predictions are obtained using numerical analysis and the constitutive model proposed by the authors. In the future, the latter algorithm can be used as a reliable tool for improving the design standard methods or numerical modeling of lightweight concrete elements subjected to short-term loading.This article belongs to the Special Issue Advances in Lightweight Aggregate ConcreteThe study was performed within the project No. 09.3.3-LMT-K-712-01-0145 that has received funding from European Social Fund under grant agreement with the Research Council of Lithuania (LMTLT)
The Influence of Different Loads on the Footbridge Dynamic Parameters
No full textBringing together the experience and knowledge of engineers allowed building modern footbridges as very slender structures. This in turn has led to structural vibration problems, which is a direct consequence of slender structures. In some footbridges, this problem occurs when natural construction frequencies are close to excitation frequencies. This requires a design methodology, which would ensure user safety and convenience of use of the footbridge in operation. Considering the aforementioned dynamic response, the analysis of the finite element model of a footbridge was conducted focusing on critical acceleration and deformation meanings. The model was based on the footbridge prototype located in Vilnius, Lithuania. Two different loading methods were developed to investigate the dynamic effects caused by people crossing a footbridge. The comparison of experimental and finite element model (FEM) results revealed that the footbridge in operation is within the limit values of comfort requirements in terms of its vibrations.This article belongs to the Special Issue Symmetry in Mechanical Engineering ⅡThe second author has received funding from European Social Fund under grant agreement with the Research Council of Lithuania (LMTLT) for the project No 09.3.3-LMT-K-712-01-0145
Indoor Navigation Systems for Visually Impaired Persons: Mapping the Features of Existing Technologies to User Needs
No full textCurrently, several outdoor navigation and orientation electronic traveling aid (ETA) solutions for visually impaired (VI) people are commercially available or in active development. This paper’s survey of blind experts has shown that after outdoor navigation, the second most important ETA feature for VI persons is indoor navigation and orientation (in public institutions, supermarkets, office buildings, homes, etc.). VI persons need ETA for orientation and navigation in unfamiliar indoor environments with embedded features for the detection and recognition of obstacles (not only on the ground but also at head level) and desired destinations such as rooms, staircases, and elevators. The development of such indoor navigation systems, which do not have Global Positioning System (GPS) locational references, is challenging and requires an overview and evaluation of existing systems with different navigation technologies. This paper presents an evaluation and comparison of state-of-the-art indoor navigation solutions, and the research implications provide a summary of the critical observations, some insights, and directions for further developments. The paper maps VI needs in relation to research and development (R&D) trends using the evaluation criteria deemed most important by blind experts.This article belongs to the Section Physical SensorsThis project has received funding from the European Regional Development Fund (project No 01.2.2-LMT-K-718-01-0060) under grant agreement with the Research Council of Lithuania (LMTLT)
Essential Safety Factors for the Transport of Dangerous Goods by Road: A Case Study of Lithuania
No full textDangerous goods accidents occur infrequently, but the consequences are extremely large and cause many losses. The transport of hazardous substances itself is time consuming and requires a great deal of responsibility compared to a simple load. The safe transport of dangerous goods depends on a large number of factors. The purpose of this article is to examine the conditions of carriage of dangerous goods and to evaluate the factors affecting the carriage of these goods by road transport. This is done by analyzing the scientific literature and statistics and conducting a qualitative survey. The study identified three group factors that have the greatest impact on the safe transport of dangerous goods by road. The survey results were processed using the Kendall ratings correlation method, and the compatibility of the expert sample was studied using the matching factor. The study, using the medium-range transformation weights (ARTIW) method, identified the main factors of normalized subjective weights that influence the safe transport of dangerous goods. The outcomes of the research presented in the paper show that the main factors of Group I have the greatest impact on the likelihood of an accident during dangerous goods transportation by road transport; they include incorrect loading of cargo, driver fatigue, vehicle condition, and weather and road surface conditions. The most important technical/technological factors of Group II are correct loading or unloading of the cargo, tightness of the vehicle semi-trailer/container/tank, and the technical condition of the vehicle. The most important organizational factors in Group III are the risks associated with the carriage of goods, the choice of route, and communication with the emergency services. In the following stages of research, the main factors of the three groups identified should be used to develop models to make the transport of dangerous goods safer.This article belongs to the Section Sustainable Transportatio
Experimental Research on the Behavior of the Rail Seat Section of Different Types of Prestressed Concrete Sleepers
No full textNowadays, prestressed concrete sleepers are the most common type of sleepers. In different countries all over the world prestressed concrete sleepers are designed with different shapes, with different types of prestressed reinforcement and arrangements in cross-section. Additionally, different manufacturing methods and techniques are used for prestressed concrete sleepers. These railway members are stiff, durable and can withstand heavy loads. Despite that, damaged or deteriorated prestressed concrete sleepers appear on railway tracks even before the end of their service life. Therefore, there is a need for better understanding of the behavior of different types of prestressed concrete sleepers to optimize their design. The rail seat section of the sleeper is the most affected part of sleeper. Therefore, analysis of experimental results of bearing capacity, cracking, and deformation of the rail seat section of sleeper under static and dynamic loads are provided in this article. Furthermore, different types, diameters, and anchoring methods of prestressed reinforcement were analyzed in this article. Additionally, comparison of experimental results of different types of prestressed concrete sleepers is discussed.This article belongs to the Section Construction and Building Material
Assessment of Progress towards Achieving Sustainable Development Goals of the “Agenda 2030” by Using the CoCoSo and the Shannon Entropy Methods: The Case of the EU Countries
No full textThe United Nations Member States adopted the “Agenda 2030” which contains 17 sustainable development goals (SDG) that involve a certain number of targets and indicators. Although the indicators are helpful in defining the position of the current country relative to the goals’ achievement, it is very complex to determine its position relative to other countries, because this requires an extensive analysis. Therefore, in this paper, the application of the multiple-criteria decision-making approach (MCDM) in defining the position of the EU (Europe Union) countries relative to the SDGs is proposed. The MCDM model is based on the Combined Compromise Solution (CoCoSo) and the Shannon Entropy methods. The final results highlight Sweden as the country that best implemented the set SD goals and has the best outputs relative to them, while Romania is in last place. The main reason for these kinds of results could be that the countries on the bottom of the list are relatively new EU members and have not been made to properly implement SDGs yet. The conclusion is that the obtained results are fully objective and rational, and that the applied model is applicable for performing this kind of analysis.This article belongs to the Special Issue Sustainability as a Multi-criteria Concept: New Developments and Application
The Modelling of Roof Installation Projects Using Decision Trees and the AHP Method
Get PDFIn this work, the process of roofing projects’ execution is considered. The proper analysis of this process is important to optimise the behaviour of a project’s participants and to perform risk evaluation. The main result of this work is methodology, which can be used to optimise a project owner’s decisions and potentially can be applied for risk control or integrated into expert systems. This methodology includes the application of a decision tree and AHP (analytic hierarchy process) method to perform the modelling for roof installation project selection. In the proposed approach, a decision tree describes the process with nodes representing the states of a project. The tree includes the decision on whether to sell the project results or not, which requires the estimation of the subjective opinion of the project owner. These subjective values are used in the decision tree leaves. We propose to perform this estimation with the AHP method and describe how to do it in this paper. A particular example was considered. The proposed methodology was applied to that case, and all details of the process and results are provided. Using the proposed methodology, the adapted version of a specific, current situation model of project participants’ behaviours can be formed, allowing one to make the most efficient decisions in the light of the existing constraints. The application of results can increase the investor protection and contribute to the general sustainability of investments.This article belongs to the Special Issue Sustainable Construction Engineering and Managemen
A New Hybrid MCDM Model for Personnel Selection Based on a Novel Grey PIPRECIA and Grey OCRA Methods
No full textPeople represent one of the most significant resources of an organization, and therefore, personnel selection is one of the problems that organizations have increasingly been facing. The criteria that influence the final decision are usually opposing, so the application of multiple-criteria decision-making methods (MCDM) represents a suitable way for the facilitation of the given process. Additionally, the decision environment is characterized by the vagueness and uncertainty and, because of that, it is very hard to express the criteria over the exact crisp numbers. To acknowledge the unpredictability and obscurity of the available information important for the selection of the optimal candidate, a hybrid grey MCDM model for personnel selection is proposed in this paper. As an extension of the PIPRECIA method, the novel Grey Pivot Pairwise Relative Criteria Importance Assessment—the PIPRECIA-G method—is proposed and used for the determination of criteria importance. The PIPRECIA-G method preserved the good features of the PIPRECIA, but its superiority is reflected in its ability to deal with input data that are vague and grey. For the final ranking of the considered alternative candidates, the OCRA-G method is used. Basing the decision process and candidate selection on the two grey extended MCDM methods contributes to the increase of the reliability and confidence in the performed selection.This article belongs to the Special Issue Multiple Criteria Decision Makin