Vilnius Gediminas Technical University
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4122 research outputs found
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Assessment and research of river restoration processes in regulated streams of Southeastern Lithuania
No full textThe article deals with the auto-naturalization problems of regulated streams in Lithuania. Research on such streams overgrown with woody vegetation was conducted in the Neris River basin in the Baltic Highlands. We chose to investigate the most urbanized rough terrain area of southeastern Lithuania. The regulated streams found in this area include stretches with a relatively high reserve of hydraulic conductivity. Therefore, with reference to the Water Framework Directive for improving the ecological situation, we assessed the possibilities of promoting the naturalization process. The average density of woody vegetation on the investigated slopes of regulated streams is T = 1.26±0.20 items m-2. The slopes with northeastern exposure point to the average density of woody vegetation counting TNE = 0.91 items m-2, which is 2.42 times more than that observed on the slopes with eastern exposure and 2.30 times more than those with southern exposure (TS = 0.39 items m-2). Under the presence of the recent density of woody vegetation, hydraulic measurements established Manning’s roughness coefficient that varied from 0.030 to 0.094. The conducted simulation indicates that the studied stretches of regulated streams lose a margin of hydraulic conductivity when Manning’s roughness coefficient reaches a threshold of 0.060-0.080. Planning the naturalization of regulated streams is first offered in the stretches of higher slopes (S0>0.003), where the maintenance of the adequate roughness of the bed may assist in designing the overgrowth of both slopes with woody vegetation
Dynamic research of carriage system of the angle measuring comparator
No full textWith modern equipment it is possible to implement calibration during dynamic regime, when the location of raster elements of measured object is detected during the motion of movable components of measurement equipment. During this process it is acting external as well as internal sources of vibration. In this work the object of investigation is originally developed angle measurement comparator. The main aim of this research is to determine the dynamic characteristics of multibody mechanical systems of the angle comparator carriage on which optical system is attached to it and to compare the experiment with the results obtained by theoretical calculations
Theoretical evaluation of the influence of the thermodynamic processes on the selection of shock absorbers for sports cars
No full textIn the paper a theoretical analysis of the monotube and twin-tube shock absorbers' suitability for sports cars, based on the thermodynamic processes occuring in them, is done. Investigation is carried out by modelling the transfer of heat, which forms in the shock absorbers of different constructions, to the atmosphere and the distribution of temperature in their bodies under different conditions. The thermodynamic processes thet happen in the shock absorbers are presented by dependency graphs according to the linear heat flux density and the heat transfer to the atmosphere coefficient. In the article theoretically and by experiments the way the thermodynamic processes change the shock absorbers' oil viscosity's and density's characteristics and the damping force is also analysed
Kalman filter for hybrid tracking technique in augmented reality
No full textAugmented reality started to emerge as a promising visualization technique that tracks real objects and adds virtual content into real world context using camera view. Many augmented reality solutions are based on computer vision techniques to identify and track objects. Problems that must be solved are image transformations, chaotic environment, lighting condition and occlusion from users’ or objects in the environment, which causes virtual content to disappear. This has a negative impact for augmented reality usability, therefore, object recognition and tracking in real-time becomes difficult and sometimes an impossible task. In this research orientationposition information acquisition using computer vision and sensor fusion techniques are analysed. Experiments are accomplished with predefined assumptions and simulated orientation-position information. Conditions for optimal orientation-position estimates are introduced. Research results are compared and supplementary properties are presented of a proposed hybrid tracking technique using Kalman filter
Sensitivity analysis in MADM methods: application of material selection
No full textMaterial evaluation studies are getting very strategic subject in design and engineering. Decision about effective modeling of material selection framework is always a concern for management of manufacturing and production. This study is involved with a new approach to select materials based on expert’s policy and multi attribute decision making theory due to some technical conflicting variables and quantity of materials. Weighting method SWARA for the first time is applied in material selection and then to prioritize candidate material list WASPAS and MOORA are employed. To verify material ranking outcomes, sensitivity analysis as putting new normalization tool for WASPAS and MOORA is performed. Two real material selection case studies are presented to configure and model effective structure of material selection database
Egzistencinio tikėjimo slėpinys Kierkegaard'o filosofijoje
No full textŠis straipsnis skirtas egzistencinio mąstymo pirmtako Søreno Kierkegaard’o filosofijos religinių aspektų analizei. Čia keliamas ir įvairiais aspektais nagrinėjamas autentiško egzistencinio tikėjimo klausimas. Pirmoje straipsnio dalyje daugiausia dėmesio skiriama tikėjimo sampratai, jo etinei vertei ir poveikiui, kurį daro asmenybės gyvenimui ir vertybinėms nuostatoms. Racionalistinė Vakarų klasikinė metafizika, vienašališkai sureikšmindama racionalų protą ir objektyvumą, atsainiai žvelgia į pamatines individualios žmogaus egzistencijos problemas ir ignoruoja pamatines religinės pasaulio sampratos nuostatas. Kierkegaard’as skelbia, kad aukščiausia asmenybės dvasinio tobulėjimo pakopa yra religinė, kuri negali būti apibrėžiama abstrakčiomis formuluotėmis, bet išgyvenama ir patiriama individualiai, – tai gyvenimas tikėjimu Dievo akivaizdoje. Antroji straipsnio dalis skirta aptarti vidinį tikėjimo slėpinį siekiant išryškinti tikėjimo kaip vilties ir meilės vienovę. Gvildenamas glaudus tikėjimo santykis su paties individo autentiška egzistencija, jo pasirinkimu. Iš čia kyla esminė straipsnio išvada, kad tikėjimas yra svarbiausias žmogaus gyvenimo tikslas ir pašaukimas. Kierkegaard’o filosofijoje egzistencinis tikėjimas neatsiskleidžia kaip galutinė koncepcija, bet lieka paslaptis, kuri išgyvenama vidine patirtimi ir asmenišku apsisprendimu
Procesinio požiūrio taikymas veiklos gerinimui: ekspedijavimo jūrų transportu atvėjis
No full textProcesinio požiūrio taikymas yra populiariausių vadybos sistemų (ISO, EFQM, LEAN ir kt.) pagrindas. Naujoji ISO 9001:2015 redakcija (išleista 2015 rudenį) akcentuoja, kad tik tvarkingai procesus susitvarkiusios, juos valdančios, tobulinančios ir prižiūrinčios organizacijos gali pasiekti ilgalaikės sėkmės. Straipsnyje pateikiamas teorinio potencialo analizės rezultatas bei procesinio požiūrio taikymas Lietuvoje veikiančioje ekspedijavimo jūrų transportu paslaugas teikiančioje įmonėje. Atsižvelgiant į konkurencinį kontekstą bei konfidencialių duomenų publikavimą, įmonės pavadinimas straipsnyje nenurodomas
Triukšmo sukeliamo neigiamo poveikio mažinimo priemonių ekspertinis vertinimas
No full textTransporto srautų keliamas triukšmas skverbiasi į gyvenamąją ir darbinę aplinką, sukeliantis sveikatos sutrikimus ir problemas visuomenei. Triukšmo mažinimui yra teikiamas didelis dėmesys tiek iš Europos Sąjungos institucijų tiek vietinės valdžios. Naudojamos įvairios techninės priemonės šiai problemai spręsti. Šiame straipsnyje siekiama išaiškinti, kaip mokslininkų įvardijamos triukšmo mažinimo priemonės yra vertinamos ekspertų ir kaip moksliniuose šaltiniuose minimi elementai koreliuoja su praktika, kokių priemonių turima imtis pirmiausiai
ES struktūrinė parama: poveikis Lietuvos viešojo sektoriaus raidai
No full text2014-2020-ųjų metų ES struktūrinių fondų investicijų veiksmų programa ženkliai įtakoja viešojo sektoriaus raidą Lietuvoje. Pasikeitė finansavimo modeliai, programos, taip pat finansavimo intensyvumas. Galima pastebėti, jog Lietuvos ir užsienio autoriai skiria nepakankamai dėmesio vertinant struktūrinių fondų poveikį viešajam sektoriui. Pasigendama išsamesnės analizės, apimančios ilgesnį tiriamąjį laikotarpį, taip pat požiūrio į Lietuvos makroekonominių rodiklių dinamiką. Dėl Šios priežasties pasirinkta ES struktūrinių fondų poveikio Lietuvos viešajam sektoriaus raidai tema. Tyrimo apimtis - trejų metų laikotarpis. Straipsnyje taip pateikiamos Lietuvos ir užsienio autorių įžvalgos apie struktūrinės paramos konkurencingumą bei jos svarbą Europos Sąjungos šalių raidos kontekste. Aiškinamasi, kokios problemos yra sprendžiamos šios paramos pagalba. Pasitelkiant lyginamąją analizę yra aptariami konkretūs pastarojo penkmečio investicijų į Lietuvos viešąjį sektorių pavyzdžiai, šių dienų aktualijos, pateikiami pasiūlymai ir išvados, skirtos didinti ES struktūrinės paramos poveikį Lietuvos viešojo sektoriaus raidai
Development of self-organizing methods for radio spectrum sensing
Get PDFA problem of wide-band radio spectrum analysis in real time was solved and presented in the dissertation. The goal of the work was to develop a spectrum sensing method for primary user emission detection in radio spectrum by investigating new signal feature extraction and intelligent decision making techniques. A solution of this problem is important for application in cognitive radio systems, where radio spectrum is analyzed in real time.
In thesis there are reviewed currently suggested spectrum analysis methods, which are used for cognitive radio. The main purpose of these methods is to optimize spectrum description feature estimation in real-time systems and to select suitable classification threshold. For signal spectrum description analyzed methods used signal energy estimation, analyzed energy statistical difference in time and frequency. In addition, the review has shown that the wavelet transform can be used for signal pre-processing in spectrum sensors. For classification threshold selection in literature most common methods are based on statistical noise estimate and energy statistical change analysis. However, there are no suggested efficient methods, which let classification threshold to change adaptively, when RF environment changes.
It were suggested signal features estimation modifications, which let to increase the efficiency of algorithm implementation in embedded system, by decreasing the amount of required calculations and preserving the accuracy of spectrum analysis algorithms.
For primary signal processing it is suggested to use wavelet transform based features extraction, which are used for spectrum sensors and lets to increase accuracy of noisy signal detection. All primary user signal emissions were detected with lower than 1% false alarm ratio. In dissertation, there are suggested artificial neural network based methods, which let adaptively select classification threshold for the spectrum sensors. During experimental tests, there was achieved full signals emissions detection with false alarm ratio lower than 1%.
It was suggested self organizing map structure modification, which increases network self-training speed up to 32 times. This self-training speed is achieved due to additional inner weights, which are added in to self organizing map structure. In self-training stage network structure changes especially fast and when topology, which is suited for given task, is reached, in further self-training iterations it can be disordered. In order to avoid this over-training, self-training process monitoring algorithms must be used. There were suggested original methods for self-training process control, which let to avoid network over-training and decrease self-training iteration quantity