Vilnius Gediminas Technical University
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Technologies for sustainable circular business: using crushing device for used tires
No full textTechnological entrepreneurship plays increasing role in our path towards sustainble economy. Tires, stored in landfills, pose a risk to human health and environment. There may be long and dangerous fires, combustion process produces pollution, extremely dangerous to human health and environment. Therefore, in order to reduce the surplus of tires in landfills, this work investigates the dependence of tyre tread crushed machine output on the usage of the saws with different technical characteristics as well as the dependence of the machine output on the feed rate and the crushed cutting angle. The temperature dependence on the crushed cutting angle and feed is investigated. The particle sizes obtained during tyre tread crushed are also analysed. The study showed that the maximum machine output is 502 g/min, and as much as 62% of the resulting particle sizes are up to 0.63 mm, which is the most suitable size for the use as an adsorbent for oil products. It was established that the increase of the crushed cutting angle leads to the increase of the temperature of the circular saw by 26%
Mokslų klasifikacija, hierarchija ir subordinacija scholastinėje mokslo teorijoje
No full textStraipsnyje nagrinėjamos vienos svarbiausių scholastinės mokslo teorijos temų: mokslų klasifikacija, hierarchija
ir subordinacija. Straipsnio autorius susitelkia ties šių scholastinių procedūrų teorinėmis ištakomis
ir kriterijais. Prieinama prie išvados, kad scholastinėje mokslo teorijoje perimtas aristotelinis mokslų skirstymas
į teorinius ir praktinius, tačiau kūrybiniai mokslai neteko savarankiškos mokslų srities statuso. Kita
vertus, pastebima, kad ne visi scholastai praktiniams mokslams priskyrė tikrojo mokslo statusą. Mokslų
hierarchijos rėmuose išskirti du vienų mokslų pirmumo kitų mokslų atžvilgiu atvejai: a) pagal pačią mokslų
prigimtį; b) žmogiškojo pažinimo požiūriu. Galiausiai fiksuoti du mokslų subordinacijos, arba pavaldumo,
atvejai: a) pagal mokslų prielaidas; b) pagal tiriamus objektus
Evaluation of the spur gear condition using extended frequency range
No full textThe paper focuses on working out an algorithm for spur gear condition monitoring, based on the results of numerical simulation.
The nonlinear mathematical model has been used for investigation of the dynamic parameters of the cylindrical spur gear
with defective teeth. Backlash between gear teeth, backlash in bearings, time-varying mesh stiffness, and variations of the centre
distance have been evaluated in the model. Diagnostic parameters suitable for determining the condition of the gears under investigation
have been established. Frequency intervals mostly affected by changes in diagnostic parameters under damage have
been found. An algorithm for diagnostics based on mathematical modelling, vibro-acoustic, and acoustic emission methods, and
wavelet transform has been worked out
Single stage microinverter based on two-switch DC-DC flyback converter
No full textThe single stage photovoltaic microinverter based on couple of two-switch DC-DC flyback converters has been suggested. The results of simulation and experimental investigation for the case when photovoltaic microinverter operates in off-grid and grid-tied modes are presented. The proposed single stage microinverter is characterized by simple design and high efficiency
Exergy efficiency of a ventilation heat recovery exchanger at a variable reference temperature
No full textThe purpose of this paper is to develop the appli-cation of exergy analysis for assessing the performance of building mechanical systems. When exergy analysis is ap-plied to thermal processes in HVAC systems, this method faces the conditions when variable reference temperature is placed below, above and across the operating temperatures of working fluids. Using the derivative status parameter from enthalpy and entropy, the methodology for calculating the exergy efficiency for HVAC equipment is proposed. The capabilities of this method are demonstrated in the case study of exergy analysis of a ventilation heat recovery ex-changer. Thermodynamically justified numerical values of the universal and functional exergy efficiencies for variable reference temperatures are shown.
The proposed method is distinguished by its uni-versality and can be applied on other HVAC equipment. Re-sults from this study could be useful for creating exergy op-timized design and developing efficient control of HVAC systems operating at variable reference temperatures
A model for shovel capital cost estimation, using a hybrid model of multivariate regression and neural networks
No full textCost estimation is an essential issue in feasibility studies in civil engineering. Many different
methods can be applied to modelling costs. These methods can be divided into several main groups:
(1) artificial intelligence, (2) statistical methods, and (3) analytical methods. In this paper, the
multivariate regression (MVR) method, which is one of the most popular linear models, and the
artificial neural network (ANN) method, which is widely applied to solving different prediction
problems with a high degree of accuracy, have been combined to provide a cost estimate model
for a shovel machine. This hybrid methodology is proposed, taking the advantages of MVR and
ANN models in linear and nonlinear modelling, respectively. In the proposed model, the unique
advantages of the MVR model in linear modelling are used first to recognize the existing linear
structure in data, and, then, the ANN for determining nonlinear patterns in preprocessed data
is applied. The results with three indices indicate that the proposed model is efficient and capable of
increasing the prediction accuracy
Asphalt wearing course optimization for road traffic noise reduction
No full textNowadays traffic noise and air pollution are as important as durability parameters, what leads to the need of more comprehensive approach when planning, designing, constructing and maintaining road pavements. Having in mind country differences in traffic volumes, climate conditions and financial capabilities it is not easy to transfer various solutions from country to country. Due to such peculiarities, large research study was initiated in Lithuania seeking to develop efficient and effective low noise pavement solution for specific regional climate conditions. This paper presents research of commonly used asphalt concrete (AC), stone mastic asphalt (SMA), porous asphalt (PA) and a concept of noise reducing asphalt mixtures. As part of this study large scale laboratory testing of acoustical and mechanical performance, durability and resilience to climate were performed. The paper also presents analysis of laboratory testing results which were positive and followed with the pilot implementation of developed asphalt mixtures for further research activities under real traffic and climate conditions
Comparison of Material Properties of Lightweight Concrete with Recycled Polyethylene and Expanded Clay Aggregates
Get PDFThe article discusses the possibility of using high and low density polyethylene waste as aggregate in lightweight concrete with high strength cement mortar. Research is dedicated to experimental investigation and comparison of material properties of concrete made of polyethylene waste and expanded clay aggregates. Hydration kinetics studies of concrete specimens with different aggregates are performed using measurements of ultrasonic pulse velocity. For the experimental investigation high and low density polyethylene plastic waste aggregates with low water absorption and hydrophobic surface were used. It is stated that concrete with low water absorption plastic waste aggregates after 7 days of curing showed significant decrease in strength growth rate. The specimens had a density of 1950 – 2050 kg/m3 with a compressive strength of at least 40 MPa. Using pre-wetted expanded clay aggregate with similar mix composition, concrete density was 1900 kg/m3 with a compressive strength up to 70.2 MPa. Although having similar mechanical properties as the waste plastic aggregate, pre-wetted expanded clay allows better cement hydration process, resulting in lower water absorption of lightweight concrete.12th international conference “Modern Building Materials, Structures and Techniques” (MBMST 2016)The authors gratefully acknowledge the financial support provided by the Research Council of Lithuania (Research
project No. MIP-093/2015). The authors also wish to thank JSC “Plasta” for providing recycled polyethylene
aggregates
Sklypo užstatymo erdvinio planavimo koncepcija taikant statinio informacinio modeliavimo technologiją
Get PDFDisertacijoje nagrinėjamos sklypo užstatymo erdvinio planavimo galimybės taikant statinio informacinio modeliavimo (angl. Building Information Modeling – BIM) technologiją. Tyrimo objektas yra sklypo užstatymo erdvinis planavimas skaitmeninėje BIM aplinkoje. Skaitmeninės statybos vystymas statybos sektoriuje šiuo metu yra prioritetinė veiklos kryptis visame pasaulyje. Siekiant sukurti kuo tikslesnį statinio informacinį modelį būtina žinoti bei kuo anksčiau įvertinti išsamią informaciją apie teritoriją, kurioje statinys planuojamas. Disertacijoje aprašytas sukurtas sklypo užstatymo erdvinio planavimo koncepcinis modelis. Naudojant modelį praktikoje būtų galima greitai keisti pagrindinius pastato parametrus (matmenis, erdvinę formą ir kt.) ir nedelsiant patikrinti suplanuoto pastato atitiktį teritorijų planavimo dokumentų reikalavimams. Tokiu būdu ilgai neužtrunkant galima būtų parinkti racionaliausią pastato pirminį modelį, kurio pagrindu būtų atliekamas detalus projektavimas.
Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai bei 9 priedai.
Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei 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.
Pirmajame skyriuje aptariama BIM samprata ir reikšmė statybos sektoriuje. Taip pat analizuojamas pastato planavimo etapas ir BIM panaudojimo galimybės jo metu, aptariama pastato planavimo etapo reikšmė ir rizika. Skyriaus pabaigoje suformuluojami disertacijos uždaviniai.
Antrajame skyriuje apibrėžiama sklypo užstatymo erdvinio planavimo samprata, nustatomi ir išskiriami sklypo užstatymo erdvinio planavimo elementai. Šiame skyriuje taip pat detaliai išanalizuoti reikalavimai pastato erdvinio modelio tūriniams sprendiniams ir privalomųjų sklypo dalių išskyrimui.
Trečiajame skyriuje analizuojami ir aprašomi pagrindiniai pastato tūrinio sprendinio komponentai, pristatomas sukurtas sklypo užstatymo erdvinio planavimo koncepcinis modelis ir algoritmas, skirti Lietuvos statybos sektoriui. Atlikti supaprastinto modelio empiriniai tyrimai.
Disertacijos tema paskelbti 6 straipsniai: du – mokslo žurnaluose, įtrauktuose į Thomson ISI sąrašą, du – kituose recenzuojamuose leidiniuose, vienas – recenzuojamoje tarptautinės konferencijos medžiagoje, vienas – Lietuvos konferencijų straipsnių rinkinyje. Disertacijos tema perskaityti 3 pranešimai mokslinėse konferencijose
On economic-technological optimization of high-voltage electric cables
No full textIn this paper, mathematical modelling of high voltage cables for power transmission line design is presented. The Finite Volume Method (FVM) is used to approximate the developed mathematical model (a system of nonlinear multi-physic differential equations) and OpenFOAM (Open source Field Operation And Manipulation) tool is used to implement the obtained parallel finite volume schemes. In order to optimize the design of power lines with respect to technological parameters, different cases of nonstationary load dynamics are investigated and the influence of system nonlinearity and external day, month and years periodical boundary conditions and the source function regimes are simulated. The main aim of this paper is to include into the mathematical model also economic requirements and to optimize sizes of cables with respect to both technologic and economic requirements. Numerical algorithms targeted to solve PDE-constrained optimization problems are developed. Results of computational experiments are presented