Current Abstracts

Railway noise can negatively affect both people’s health and the value of their real estate. Various noise mitigation measures can be used on the railways. One of them is a noise barrier. Under certain conditions, low-noise barriers can be used to mitigate noise along the rails. Such barriers are installed closer to the railway track than regular noise barriers, which mitigate the noise generated by the wheel-rail interaction. In some cases, the gauge at which structures at railway tracks can be installed is limited; thus, this research was carried out to determine which parameters of low noise barriers were most effective dependent on the distance of the track. The aim of the research was to determine which parameters the low noise barrier would be effective at a longer distance from the railway track compared to existing practice. A railway track noise simulation (existing situation without a noise barrier and with a 3.5 m height noise barrier located 4.0 m from the railway track) was developed. The insertion loss of noise barriers was carried out using the Computer Aided Noise Abatement (CadnaA) software. Numerical noise level simulation was done at a distance of 7.5 m and 45 m from the axis of the railway tracks and various speeds of rolling stock from 50 to 250 km/h. The noise level and insertion loss were calculated at different heights from the top of the railway track (1.5 m, 3.5 m, and 5.5 m). It was established that the speed of the rolling stock had almost no influence on the insertion loss of the noise barrier. Therefore, all additional barriers were simulated at the same rolling stock speed of 250 km/h.

This study is carried out in order to review the deformation properties, strength, applications and suitability of polyurethane resin as a ground improvement method applied for bridge abutment construction. Since it is applied in the ground, awareness on polyurethane degradation needs to be emphasised. Deformation properties were determined for resin injections before and after degradation. The degradation of samples was studied by exposure to gasoline, diesel, oil, NaCl salt solutions with different concentrations (59, 193 and 301 kg/m3) and a mixture of fungi. After the degradation tests, compressibility tests were also performed. The use of resin as a ground improvement method has several advantages over conventional methods. The information presented enables road and bridges engineers and construction professionals to make competent decisions about implementing this innovative technique in the projects.

The architecture of secondary school buildings implemented according to typified and customised design projects in Soviet Lithuania has been analysed as a manifestation of certain timeframe conditions and possibilities. The research has revealed architects’ creativity, represented values, and ideas under the conditions of a strictly regulated and standardised state construction industry. The influences of changing educational paradigms, building construction regulations, and the political and cultural context on the architectural results of a certain typological group have been taken into account. The research results are relevant for a more detailed understanding of the development peculiarities of the Soviet era, as well as the rearrangement of schooling spaces by adapting them to contemporary needs. The research is focused on the period starting from 1955, when a shift was made to industrialised and standardised architecture, up to 1990 when Lithuania regained its independence.

Vadovaujantis vadybos ir ekonomikos teorijomis grindžiamas į vertės kūrimą orientuoto valstybinio jūrų uosto valdymo poreikis, išskiriami pagrindiniai teoriniai efektyvaus valdymo elementai, atsižvelgiant į valstybinio jūrų uostų veiklos tyrimo kompleksiškumo pobūdį, formuojama veiklos vertinimo metodika, integruojanti pridėtinės vertės, mikro- ir makroekonominius, gyvenimo kokybės rodiklius. Teorinės prielaidos pagrindžiamos Estijos, Latvijos ir Lietuvos valstybinių jūrų uostų veiklos, šių valstybių gyvenimo kokybės analizės rezultatais.

The results of research on the impact of adding a hydrogen-containing gas obtained by water electrolysis to the air charge of a gasoline engine on the combustion process, the indicator values of the work process, fuel-consumption efficiency and environmental performance of the engine are provided in the paper. The indicator tests of the work process of the engine have been carried out and the key data on the indicator values of the work process of a gasoline engine have been calculated on the base of the obtained indicator-diagrams. It was found that adding a hydrogen-containing gas caused shortening of all phases of combustion and an improvement of the indicator values of the engine. If a hydrogen-containing gas is added to the air charge of a gasoline engine, fuel-consumption efficiency as well as its energy and environmental performance are improved.

The properties of lightweight geopolymer materials (GM) based on refractory technogenic aluminosilicate wastes were studied. The effect of the ratio of the oxides SiO2 and Al2O3 in the compositions of GM on the physical and mechanical properties of GM was investigated. It was found that SiO2/Al2O(3) reduction in the GM composition results in higher density and strength and lower water absorption of the samples after a keeping period. After firing at temperatures 800 and 1000A degrees C the strength of the samples becomes all the higher the lower the ratio SiO2/Al2O3 in the composition. The heat resistance of the samples comprises four thermal cycles for high and more than seven cycles low ratio SiO2/Al2O3.

In this paper, a recently proposed global Lipschitz optimization algorithm Pareto-Lipschitzian Optimization with Reduced-set ( PLOR) is further developed, investigated and applied to truss optimization problems. Partition patterns of the PLOR algorithm are similar to those of DIviding RECT angles (DIRECT), which was widely applied to different real-life problems. However here a set of all Lipschitz constants is reduced to just two: the maximal and the minimal ones. In such a way the PLOR approach is independent of any user-defined parameters and balances equally local and global search during the optimization process. An expanded list of other well-known DIRECT-type algorithms is used in investigation and experimental comparison using the standard test problems and truss optimization problems. The experimental investigation shows that the PLOR algorithm gives very competitive results to other DIRECT-type algorithms using standard test problems and performs pretty well on real truss optimization problems.

In the waste management hierarchy, the least preferable option is waste disposal. Nonetheless, disposal is an integral part of any waste management system. In a landfill, during waste degradation processes leachate is formed that can potentially cause clogging of bottom drainage layers. To ensure stability of landfill construction, the physical properties of its components have to be controlled. In a landfill, waste presents the largest structural element and often controls both the stability and integrity of the lining system. The hydrology of precipitation, evaporation, runoff and the hydraulic performance of the capping and liner materials are important controls of the moisture content. It is important to understand the hydrology of a landfill site as it affects sustainability of landfill leachate management system. The water balance also depends on waste characteristics and waste particle size distribution. Waste characteristics are closely related to the waste composition in a landfill. The aim of the study is to determine the hydraulic permeability in a landfill depending on the particle size distribution of municipal solid waste disposed. Samples were taken from a landfill operating for five years. The samples were sorted to obtain fractions with differing particle sizes. The largest fraction of the waste was within the size-range of 20–100mm. The permeability test was conducted using the column test. The paper presents the results of the test indicating higher permeability with larger waste particle size.

Due to the rising demand for high comfort standards and efficient energy use, heat pumps and solar technologies have drawn a great deal of attention as means through which significant energy reductions can be achieved. During the last decade, a number of investigations have been conducted on the design and modelling of different heat pump systems. This paper examines the performance of a solar assisted air source heat pump (ASHP) system for cold climate. The study compares the operation of a stand-alone ASHP against the solar assisted ASHP. The experimental measurements are used to test the performance of the ASHP system in different operating conditions. In addition, using TRNSYS (Transient Systems Simulation) software, simulation models were developed. The simulations using TRNSYS are compared to experimental data. Validation results for system modes of operation are included which demonstrate good conformity between model and experimental performance.

Accuracy of laser optical beam steering strongly depends on dynamic characteristics of the positioning mechanism of the mirror. Novel design of the beam steering mirror with an integrated piezoelectric active kinematic pair is introduced in the paper. Rotation mechanism of the mirror has a simple design and allows achieving nano-scale resolution. Rotation of the mirror is achieved by exciting harmonic vibrations in the special clamping mechanism. Plate type piezoelectric transducer is used to generate vibrations. Two different electrode patterns and excitation schemes of the actuator are analyzed. Numerical modelling was performed to confirm operating principle of the rotation mechanism. Experimental prototype of the piezoelectric mirror was made and corresponding measurements were performed. Results of numerical and experimental studies are discussed.