Vilnius Gediminas Technical University
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Socio-economic model of community resilience to shocks
No full textGausėjančių ekologinių, socialinių ir ekonominių sukrėtimų akivaizdoje šalims ir regionams tampa itin aktualu stiprinti gebėjimą efektyviai prisitaikyti prie įvykių, sukeliančių socioekonominę žalą. Mokslinė užduotis, kurią siekiama spręsti disertacijoje, – kaip užtikrinti atsparumą sukrėtimams vietos lygmeniu, efektyviai paskirstant ribotus išteklius. Šiuo tikslu moksliniame darbe yra pristatomas teoriškai pagrįstas ir empiriškai patikrintas originalus bendruomenių atsparumo sukrėtimams socioekonominis modelis, pritaikytas ekonomikos srities uždaviniams – ribotiems ištekliams paskirstyti, recesijos prevencijai, socioekonominei regionų plėtrai – spręsti.
Moksliniame darbe išplėtojama ir papildoma Norris et al. (2008) pasiūlyta bendruomenių atsparumo (ang. community resilience) koncepcija, suformuojama orginali socioekonominio atsparumo vertinimo duomenų matrica, sujungianti statines dedamąsias (sistemas) su dinaminiais požymiais (gebėjimais). Sukurtas socioekonominis bendruomenių atsparumo sukrėtimams modelis, patikrintas pasitelkiant kiekybinius ir kokybinius empirinius tyrimus. Remiantis BRIC (angl. Baseline Resilience Indicators for Communities) metodu (Cutter et al., 2010), apskaičiuotas Lietuvos savivaldybių socioekonominio atsparumo sukrėtimams indeksas. Pritaikius daugiakriterį analitinės hierarchijos proceso (AHP) metodą, išbandyta sprendimo priėmimo priemonė, leidžianti susieti kiekybinių rodiklių pagrindu formuojamą atsparumo indeksą su savivaldybių plėtros poreikiu ir pasirinkti geriausias atsparumo stiprinimo alternatyvas.Daktaro disertacij
Assessing the Barriers and Risks to Private Sector Participation in Infrastructure Construction Projects in Developing Countries of Middle East
No full textIn developing countries, governments are often unable to implement urban infrastructure construction projects (UICPs) on their own, mainly due to budget and financial resource limitations. The participation of the private sector, through public–private partnerships (PPPs), has been considered as an alternative effective method for increasing the efficiency and productivity of urban infrastructure development. However, in many developing countries such as those situated in the Middle East, attracting private sector investments for UICPs uncovers profound challenges that have not ever been comprehensively accounted for and prioritized. To fill this knowledge gap, this study seeks to determine and prioritize the major barriers and risks faced by governments and urban managers in attracting private sector investments through the PPP schemes launched by developing countries in the Middle East. Based on a Delphi study conducted in Iran as an example, the opinions of 60 UICPs experts in both the public and private sectors were collected and analyzed. Results show that technical and organizational barriers and risks were perceived as the most important to private sector participation, followed by economic and financial barriers and risks, and then political and legal barriers and risks.This article belongs to the Special Issue Sustainability and Risks in Construction Managemen
A component method for cold-formed steel beam-to-column bolted gusset plate joints
No full textCold-formed steel elements are being used more frequently on construction sites because of the good strength-to-cost ratio. Researches on such structures show that, in most cases, the behaviour of the constitutive joints is semi-rigid. However, insufficient studies are published examining the properties of these joints. This paper presents a study of cold-formed steel bolted gusset plate connections based on the component method approach. The component method considers any joint as a set of individual basic components. In this procedure, the joints are analysed using mechanical models that are able to simulate moment – rotation M – φ relationship. In this paper the joint is analysed as made of three springs: beam bolt group, column bolt group and gusset plate. A “three springs” mechanical model and a technique to calculate joint stiffness is presented. The results predicted through the proposed mechanical model are validated through comparisons to experimental and finite element results
Moment Resisting Connection with Curved Endplates: Behaviour Study
No full textThis article provides a behaviour analysis of moment resisting joints with curved endplates. This is a new type of connection that can be used for joining steel beams to the circular hollow section (CHS) columns by means of bolts. Some researchers apply the Eurocode model without considering the differences in calculation schemes and assumptions, such as by using the general model of an equivalent T-stub in tension. Consequently, many of the existing behaviour studies are somewhat misleading, thus there is a need for further research. Apart from the absence of analytical methods that are devoted to predicting the initial stiffness and strength of the curved T-stub, other technical difficulties were encountered, such as gaps between the endplate and the column, as well as the initial pre-loading force of the bolts. In the previous studies, endplates were manufactured by rolling flat plates to the precise curvature which resulted in firm contact. In contrast, in this study, endplates were manufactured from a standard CHS tube, which led to significant initial gaps. Meanwhile, in terms of preloading force, it was found that it affected the moment resistance of the joint. This paper discusses problems associated with ongoing researches and presents experimental tests of the two connections. The obtained results were further used in the parametric finite element analysis (FEA) to determine the effect of the gaps and preloading force of the bolts on the moment resistance and initial rotational stiffness of the joint. The results indicate that the behaviour of curved plated connections is exceedingly complex and that the preloading force is the key factor, therefore, it should be controlled.This article belongs to the Special Issue Advanced Construction Systems and Techniques for Composite Steel-Concrete Bridges and Building
Research of crystalline silicon modules under action of dynamic loads
No full textEksploatuojami saulės moduliai yra veikiami įvairių aplinkos veiksnių, tokių kaip vėjas, sniegas ir kruša. Ypač pastarasis veiksnys – kruša – padaro didelę žalą saulės moduliams, nes krintantys krušos ledukai gali įskelti kristalinio silicio plokšteles (saulės elementus). Pažeistos, įskeltos saulės modulio silicio plokštelės gali nutraukti elektros kontaktą tarp plokščių ir taip sumažinti saulės modulio generuojamą elektros galią. Saulės modulių atsparumas mechaniniam poveikiui prailgina jų naudojimo laiką ir užtikrina stabilesnį elektros energijos tiekimą.
Darbe sprendžiami keli pagrindiniai uždaviniai: atliekami krušos poveikio saulės moduliams tyrimai, naudojant naują krušos imitavimo stendą, taip pat atliekama konstrukcijos jautrumo analizė. Pirmasis uždavinys suformuluotas atlikus literatūros apžvalgą. Nustatyta, kad atliekant krušos poveikio tyrimus naudojama tik viena technologija, kurioje imamas suslėgtasis oras ir ledo rutuliukai. Antrasis siejamas su pirmojo uždavinio spendimu. Remiantis gautais tyrimo duomenimis, sumodeliuota krušos poveikio imitacija, kuria remiantis nustatyta, kokią įtaką skirtingi modulio sluoksnių storiai gali daryti saulės elementams po krušos rutuliuko kontakto.
Disertaciją sudaro įvadas, trys skyriai ir bendrosios išvados.
Įvadiniame skyriuje nagrinėjamas problemos aktualumas, formuluojamas darbo tikslas bei uždaviniai, aprašomas mokslinis darbo naujumas, pristatomi autoriaus pranešimai ir publikacijos, sudaryta disertacijos struktūra.
Pirmasis skyrius skirtas literatūros apžvalgai. Jame apžvelgta saulės modulių struktūra, pagrindiniai pažeidimai ir krušos poveikio saulės moduliams atlikti tyrimai. Aptariama krušos poveikio saulės moduliams įtaka, suformuluojami disertacijos darbo tikslas ir uždaviniai.
Antrajame skyriuje aprašyti teoriniai saulės modulių modalinės analizės ir krušos poveikio saulės moduliams tyrimai. Nustatytos ir aptartos saulės modulių virpesių formos bei jų dažniai. Aprašytas skaitmeninis dvimatis krušos poveikio saulės moduliams imitavimas, kurio metu apskai-čiuojami įtempiai, atsiradę saulės modulių konstrukcijose po ledo rutuliuko smūgio.
Trečiajame skyriuje aprašyti eksperimentiniai saulės modulių modalinės analizės, krušos poveikio saulės moduliams tyrimai ir saulės modulių konstrukcijų jautrumo analizės. Aprašytos tyrimų metodikos, tyrimų įranga ir pateikti tyrimų duomenys. Nustatyta ir aptarta krušos poveikio įtaka nelankstiems ir lankstiems saulės moduliams. Palyginti saulių modulių teorinių ir eksperimentinių modalinių analizių rezultatai. Aprašyta, kokią įtaką nelankstaus ir lankstaus monokristalinio saulės modulio sluoksnių storiai daro silicio plokštelėse atsirandantiems įtempiams po krušos rutuliuko smūgio.Daktaro disertacij
Katalizatorių su aktyviu padengimu azoto oksidams šalinti iš dujų tyrimai ir įrenginio kūrimas
No full textThe dissertation deals with nitrogen oxides (NOx) removal from gas by using the selective catalytic reduction approach. The research object covers supported catalysts with the active coating made of transition metal oxides for removing NOx from gas. The purpose of the dissertation is to develop novel supported catalysts with the active coating, possessing high NOx conversion efficiency and chemical stability at low temperatures. The dissertation approaches several tasks. Task 1 is related to a theoretical investigation of the fluidized bed catalyst for the reduction of NOx. Tasks 2 and 3 are aimed at the creation of a laboratory setup as well as preparing catalysts using various carriers, active components, and methods, with the following investigation of NOx removal efficiency of the prepared catalysts. Task 4 focuses on a detailed investigation of the physicochemical properties of the prepared catalysts. Task 5 faces numerical simulation of the NOx catalytic reduction efficiency using the fixed bed supported catalyst. The final Task 6 is related to engineering solutions aimed at the creation of the apparatus for NOx removal from flue gas using the supported catalysts investigated.
The dissertation consists of the introduction, 3 chapters, general conclusions, recommendations, references, and the list of scientific publications by the author on the topic of the dissertation. The introduction discusses the research problem, the relevance of the dissertation, the object of the research, formulates the aim and tasks, describes the research methodology, scientific novelty of the dissertation, defended statements and the practical value of the research findings. At the end of the introduction, the author’s publications on the topic of the dissertation and the structure of the dissertation are provided.
An overview of the main anthropogenic sources of NOx and their impact on the environment and human health, the application of the selective catalytic method for NOx removal from gas, and analysis of different catalysts available is presented in the 1st chapter. The second chapter includes methodologies applied for preparation and investigation of the catalysts. The third chapter covers the results and discussion of theoretical, experimental research and simulation, as well as engineering solutions.
5 articles focusing on the subject of the dissertation have been published in the scientific journals included in the Clarivate Analytics Web of Science database. 2 patents of the Republic of Lithuania have been granted, and 2 European patent applications have been submitted to the European patent office. 8 presentations on the subject of the dissertation have been presented in the conferences at both the national and international level.Doctoral dissertatio
Oxidative Effects during Irreversible Electroporation of Melanoma Cells—In Vitro Study
No full textIrreversible electroporation (IRE) is today used as an alternative to surgery for the excision of cancer lesions. This study aimed to investigate the oxidative and cytotoxic effects the cells undergo during irreversible electroporation using IRE protocols. To do so, we used IRE-inducing pulsed electric fields (PEFs) (eight pulses of 0.1 ms duration and 2–4 kV/cm intensity) and compared their effects to those of PEFs of intensities below the electroporation threshold (eight pulses, 0.1 ms, 0.2–0.4 kV/cm) and the PEFs involving elongated pulses (eight pulses, 10 ms, 0.2–0.4 kV/cm). Next, to follow the morphology of the melanoma cell membranes after treatment with the PEFs, we analyzed the permeability and integrity of their membranes and analyzed the radical oxygen species (ROS) bursts and the membrane lipids’ oxidation. Our data showed that IRE-induced high cytotoxic effect is associated both with irreversible cell membrane disruption and ROS-associated oxidation, which is occurrent also in the low electric field range. It was shown that the viability of melanoma cells characterized by similar ROS content and lipid membrane oxidation after PEF treatment depends on the integrity of the membrane system. Namely, when the effects of the PEF on the membrane are reversible, aside from the high level of ROS and membrane oxidation, the cell does not undergo cell death.This article belongs to the Special Issue Novel Physical and Chemical Methods for Facilitated Drug DeliveryThis research was financially supported by the Ministry of Health Subsidy according to
number STM.D260.20.142 from the IT Simple system of Wroclaw Medical University and partially by
Statutory Subsidy Funds of the Department of Molecular and Cellular Biology no. SUB.D260.20.009.
The publication was supported by FAST II (WCA) programme no. GMIN.D260.20.010
Two-Color Infrared Sensor on the PbTe: In p-n Junction
Full text linkA lead telluride sensor was fabricated on the base of a p-n PbTe junction created on a PbTe single crystal grown by the Czochralski technique, followed by the diffusion of an indium donor impurity into a crystal. The capacitance-voltage and current-voltage characteristics of the sensor were measured over the temperature range from 80 K to 150 K. A prototype of a high-temperature mid-IR sensor, a PbTe diode, with a cut-off wavelength of 4 μm, operating at temperatures up to 150 K, was demonstrated for the first time. The advantage of the sensor is that its operating temperature is high enough to be reached by a solid-state thermoelectric cooler. The sensor showed a specific detectivity value of 1010 cm Hz1/2/W at a temperature of 150 K and a wavelength of 4.2 μm. The possibility to sense pulses of long-IR radiation by means of the PbTe diode was also demonstrated over the 100–180 K temperature range. For the first time, a two-photon absorption-caused photovoltaic effect was observed in PbTe at a wavelength of 9.5 μm at 150 K.This article belongs to the Section Optical Sensor