Vilnius Gediminas Technical University
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Delay systems synthesis using multi-layer perceptron network
No full textThe aim of this paper is to accelerate development and investigation of the delay systems. The computational time for investigation of particular design of delay system may take from several minutes up to several days. To achieve the required constructional parameters of the system, the iterative calculations usually should be repeated many times. In this paper, an artificial neural network is proposed to be used as the universal approximator for solving mathematical problems of delay system investigation instead of usual analytical and numerical techniques. The application of a multi-layer perceptron is proposed for approximation of solution space with discrete estimates, which were initially received by application of numerical techniques. Different structures of the multi-layer perceptron were tested for approximation. The difference between delay systems synthesis, which was estimated using numerical techniques and trained multi-layer perceptron did not exceed 5% for any of the six design parameter values. The execution time for estimating single delay system was reduced from 240 s to 20 ms. Such fast estimation of design parameters enables performing delay system analysis and design in real time, preserving time for structure visualization in 3D or virtual reality environment
Geležinkelio kelias. Projektavimas, tiesimas, eksploatacija ir priežiūra
No full textVadovėlyje išsamiai išnagrinėti geležinkelio kelio projektavimo, tiesimo, eksploatacijos ir priežiūros klausimai, pateikiama informacija apie standartinės, plačiosios ir sugretintų vėžės pločių geležinkelio kelią. Aptarti ir apžvelgti greitųjų, sunkiųjų traukinių linijų geležinkelio kelio konstrukcijos ir bebalasčio kelio ypatumai. Nepamiršti ir aplinkosaugos, eismo saugumo, gaisrinės saugos reikalavimai bei darbų saugos ir sveikatos užtikrinimo klausimai. Pateiktas sąvokų aiškinamasis žodynas padeda vienodai ir teisingai suprasti vartojamus terminus, jų apibrėžtis, paskirtį ir vartojimo sritį.
Knyga skirta geležinkelių sistemos darbuotojams, kurių veikla susijusi su geležinkelio kelio projektavimu, tiesimu, priežiūra, eksploatacija ir remontu, bei siekiantiems kelti kvalifikaciją ir praplėsti žinias. Ji taip pat naudinga asmenims, kurie studijuoja su geležinkelio keliu susijusius kursus aukštosiose ar aukštesniosiose mokyklose
Long-term curing impact on properties, mineral composition and microstructure of hemp shive-cement composite
No full textFibre Hemp Shiv (FHS) is one of the most widely used bio-aggregates for the development of eco-friendly building materials. Research on composites with an FHS aggregate has usually been limited to short-term property analyses that depend on the type of binder. Such properties are determined after (7–90) days of curing. Most scientists have focused on researching composites with lime (L) based binders. This work focuses on composites with a cement (CEM) binder and FHS aggregate, and investigates the impact of long-term curing (for 1 year) on the physical properties (density, compressive strength and thermal conductivity) of composites with non-treated and mineralized FHS (mineralization is performed with aluminium sulphate (AS) and hydrated lime (L)). In order to determine the causes of the changes in properties during long-term curing, changes in the mineralogical composition are analysed. X-ray diffraction, differential thermal and thermogravimetric analyses as well as research on the microstructure of the composites are implemented. The lowest change in properties due to inhibition of hydration is determined for composites with a non-treated aggregate.
Mineralized aggregates are characterized by lower cement hydration capability over a long-term period. The change of properties after 1 year of curing depends on the AS/CEM ratio. For all 1-year cured composites, there is a reduction in the peak intensities of C2S, C3S and ettringite, whereas there is an increase in the peak intensities of calcite, (except for composition with the highest AS/CEM ratio – AS30L18), Calcium Silicate Hydrate (CSH) and portlandite (except for the non-mineralized composition). Lower ratios for AS/CEM (AS18L36 and AS21L42) and, respectively, higher L/CEM ratios in compositions lead to the formation of vaterite. In addition, the above-mentioned composition has the highest L/CEM ratio, which ensures that more hydrates participate in the carbonation process, thus leading to higher compressive strength, denser composite structure and higher thermal conductivity due to higher heat transfer by conduction
Experimental and numerical analysis of strain gradient in tensile concrete prisms reinforced with multiple bars
No full textThis work is a continuation of the ongoing research on deformation behavior of reinforced concrete elements under tension. The previous studies have revealed that deformation behaviors of elements reinforced with multiple bars and the traditional prismatic members reinforced with a center bar are essentially different. The latter layout, though typical of laboratory specimens, could not represent the norm of structures in real-life. Thus, a new test methodology to investigate the strain distribution in concrete prismatic members reinforced with multiple bars subjected to axial tension is devised. Prismatic concrete specimens with different reinforcement configurations were fabricated and tested using the proposed setup. Deformation behavior of the specimens is modeled with a tailor-designed bond modeling approach for rigorous finite element analysis. It is revealed that the average deformations of the concrete could be different from the prevailing approach of average deformations of the steel, and are dependent on the reinforcement configurations. Therefore, the efficiency of concrete in tension should be carefully taken into account for rational design of structural elements. The study endorses promising abilities of finite element technique as a versatile analysis tool whose full potential is to be revealed with the advent of computer hardware.The authors gratefully acknowledge the financial support provided
by the Research Council of Lithuania (Research Project S-MIP-17-
62). Dr Pui-Lam Ng wishes to express his gratitude for the support
provided by the European Commission under the Marie
Skłodowska-Curie Actions Fellowship (Project No. 751461)
Induction of Different Sensitization Patterns of MRSA to Antibiotics Using Electroporation
No full textTreatment of bacteria-associated infections is complicated and antibiotic treatment alone is often inadequate to overcome biofilm infections. Physical methods allow overcoming this problem and propose solutions that are non-dependent on drug resistance. In this work, we investigated the feasibility of pulsed electric fields for sensitization of MRSA to common antibiotics. We analyzed the efficacy of inactivation of methicillin-resistant Staphylococcus aureus in 5–20 kV/cm electric field separately and in combination with gentamicin, doxycycline, ciprofloxacin, sulfamethoxazole, and vancomycin. Combined treatment allowed using up to 1000-fold smaller concentrations of antibiotics to induce the same inactivation of S. aureus.This article belongs to the Collection Antibiotics & Superbugs: New Strategies to Combat Antimicrobial ResistanceThis research was funded by Research Council of Lithuania grant number LAT-02/2016
A Novel Rough WASPAS Approach for Supplier Selection in a Company Manufacturing PVC Carpentry Products
No full textThe decision-making process requires the prior definition and fulfillment of certain factors, especially when it comes to complex areas such as supply chain management. One of the most important items in the initial phase of the supply chain, which strongly influences its further flow, is to decide on the most favorable supplier. In this paper a selection of suppliers in a company producing polyvinyl chloride (PVC) carpentry was made based on the new approach developed in the field of multi-criteria decision making (MCDM). The relative values of the weight coefficients of the criteria are calculated using the rough analytical hierarchical process (AHP) method. The evaluation and ranking of suppliers is carried out using the new rough weighted aggregated sum product assessment (WASPAS) method. In order to determine the stability of the model and the ability to apply the developed rough WASPAS approach, the paper analyzes its sensitivity, which involves changing the value of the coefficient λ in the first part. The second part of the sensitivity analysis relates to the application of different multi-criteria decision-making methods in combination with rough numbers that have been developed in the very recent past. The model presented in the paper is solved by using the following methods: rough Simple Additive Weighting (SAW), rough Evaluation based on Distancefrom Average Solution (EDAS), rough MultiAttributive Border Approximation area Comparison (MABAC), rough Višekriterijumsko kompromisno rangiranje (VIKOR), rough MultiAttributiveIdeal-Real Comparative Analysis (MAIRCA) and rough Multi-objective optimization by ratio analysis plus the full multiplicative form (MULTIMOORA). In addition, in the third part of the sensitivity analysis, the Spearman correlation coefficient (SCC) of the ranks obtained was calculated which confirms the applicability of all the proposed approaches. The proposed rough model allows the evaluation of alternatives despite the imprecision and lack of quantitative information in the information-management processThis article belongs to the Special Issue Multiple-Criteria Decision-Making (MCDM) Techniques for Business Processes Information Managemen
The Multi-Aspect Criterion in the PMADM Outline and Its Possible Application to Sustainability Assessment
No full textOver the past few centuries, the process of decision-making has become more complicated in different respects. Since the initial phase of Multiple Criteria Decision Making (MCDM) around fifty years ago, Multiple Attribute Decision Making (MADM) has continued developing over the years as a sub-concept of MCDM. Noticeably, the importance of the decision-making process is increasingly expanding to such an extent that it necessarily blends into the undeniable processes of MADM actual models. Novel methods with different perspectives have been introduced considering the dynamic MADM concepts of time and future in classical frameworks; however, they do not overcome challenges in practice. Recently, Prospective MADM (PMADM) as a specific approach has presented future-oriented models using already known approaches of MCDM, and it has innovative items which show barriers of classic model of MADM. However, PMADM practically needs more conceptual bases to illustrate and plan the future of real decision-making problems. The Multi-Aspect Criterion is a new concept in mapping the future of the PMADM outline. In this regard, two examples of sustainability will be analyzed, and different requirements and aspects associated with PMADM will be discussed in this study. This new approach can support the PMADM outline in more detail and deal with a decision-making structure that can be considered as novel to industry experts.This article belongs to the Collection Advanced Methodologies for Sustainability Assessment: Theory and Practic
Ranking and selecting the best performance appraisal method using the MULTIMOORA approach integrated Shannon’s entropy
No full textThe selection process of appropriate Performance Appraisal (PA) methods for organizations in today’s dynamic and agile environments along with its funding scales is a complex problem. Performance appraisal in modern organizations has become a part of the strategic approach toward integrating business policies and human resource activities. The existence of multiple criteria in the decision-making procedure makes finding the optimal PA method more challenging. The current study tackles a PA method assessment by applying a multiple criteria decision analysis method i.e., MULTIMOORA integrated Shannon’s entropy significance coefficient. A case study on the optimal PA method selection is analyzed by identifying the criteria and alternatives based on the literature and expert comments of the case-study employing two approaches, that is, MULTIMOORA and Entropy MULTIMOORA. The final rankings of the suggested methods are compared to TOPSIS and TOPSIS integrated Shannon’s entropy methods utilizing correlation coefficients of the final ranks. Eventually, by identifying the optimal PA approach i.e., 360-degree feedback, the selected optimal method employed in the case study and results are demonstrated and described with a comprehensive example.This article is distributed under the terms of the Creative Commons Attribution 4.0 International
License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium,
provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and
indicate if changes were made
Investigation of armature-rail interaction in linear electromagnetic launcher
Get PDFThe behavior of the electromagnetic (EM) launcher depends on the structure of the construction. The dynamics of the EM construction and the local effects of the EM forces are topical issue in exploring and designing EM launcher device. This paper is aimed to refine mechanical behavior of the open barrel design EM launcher structure due to EM force evaluated by EM analysis based on three different shapes of armatures. The 3D finite element EM model was generated and the J×B force density distribution in the rail volume was calculated. The results of EM model calculations were applied further as input for structural mechanics model. The results of the finite element EM and mechanical analysis of the armatures influence are presented.This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
Investigation into the properties of concrete modified with biomass combustion fly ash
No full textConcrete is the most widely used construction material obtained after the setting of the mix composed of coarse and fine aggregates, cement and water. The main properties of concrete are determined by the quality and characteristics of aggregates, W/C ratio, and the uniformity of mix compaction. Compressive strength is one of the key characteristics of concrete. Materials used: Portland cement CEM I 42.5 R, 0/4 fraction sand, 4/16 fraction gravel, biomass combustion fly ash, superplasticizer, and water. Seven batches of specimens were made with different biomass fly ash content: 0%, 5%, 10%, 15%, 20%, 25%, and 30% (replacing cement in the mix, %). The following properties of modified concretes were tested: compressive strength, water absorption, density, ultrasonic pulse velocity, porosity (open and closed), and predicted resistance to freezing and thawing cycles. Concrete, where 15% of cement is replaced with biomass combustion fly ash, has higher density (2360 kg/m3), compressive strength after 28 days (38.3 MPa), ultrasonic pulse velocity (4466 m/s), lower water absorption rate (3.72%) and higher closed porosity (2.54%). All these characteristics improve the freeze-thaw resistance of concrete. The tests revealed that concrete modified with 15% of biomass fly ash had better durability and freeze-thaw resistance characteristics and can be used in construction works. The obtained linear regression equations illustrate the relationships between the density, compressive strength after 28 days of curing, ultrasonic pulse velocity after 28 days of curing, and predicted freeze-thaw resistance of modified concrete