bluuebunny/crossref_metadata_2025_split huggingface dataset:
Silicon and aluminium leaching kinetics from acidic gold mine tailings
Authors: Falayi T , Mashifana T , Ntuli F 
Published: October 2019

Abstract
Si and Al were leached from gold mine tailings (GMT) in order to determine if the GMT could be used as precursors for the synthesis of geopolymers. Possible synthesis of geopolymers from GMT would help reduce their potential pollution effects through heavy metal immobilisations. The effect of type of alkali (NaOH/KOH), alkali concentration, temperature, milling and calcination of GMT and solid liquid ratio (S/L) on the leaching of Si and Al was investigated. The optimum conditions were 10 M KOH, S/L of 0.5% m/v and a leaching temperature of 95°C. The leaching obeyed the shrinking core model with the surface chemical reaction being the controlling step. The leaching of Si was linked to the Al leaching since the Si/Al ratio of the leachate was around 2 irrespective of leaching conditions. KOH yielded more Si and Al. as compared to NaOH, with 54.7 and 26.7 Si and Al leached respectively from as received GMT. Calcination at 900°C resulted in 18% and 22 % increase in Si and Al yield respectively for KOH based leaching. The successful leaching of Si and Al from GMT using KOH provides opportunities for the geopolymerisation of GMT thereby allowing the minimisation of their pollution effects.
Durability of desilicated fly ash lime composites
Authors: Falayi T , Sithole N.T , Okonta F 
Published: October 2019

Abstract
Remediation of residual fly ash from coal fired electric power plants is beneficial to the environment. The chemical, physical, geotechnical and radiological properties of desilicated fly ash (DFA) were investigated. The DFA: lime ratio of 70:30 composite was found to have an average UCS of 8.8 MPa showing 19.5% water absorption after a 24 h soak with a corresponding 23.5% reduction in UCS. The composite was found to meet the minimum UCS requirements after 8 wet and dry cycles but with failure at 10 cycles. The composite was found not to be resistant to acid attack at pH 2 and hence could not be used in the vicinity where landfill leachate may come into contact with the composite. The composite had relative stability against acid rain and normal rain. The composite met the minimum requirement of ASTM C34-13, and thus provide an opportunity for high volume utilization of the residual ash for construction of load bearing walls.
Reuse of pulverized fired clay brick wastes as cement substitute in mortar for sustainable construction
Authors: Olofinnade Oluwarotimi , Ede Anthony , Ndambuki Julius , Omole David , Francis Precious , Chigere Cynthia , Oyeyemi Kehinde 
Published: October 2019

Abstract
Recently, there has been an increase on the use of waste materials for development of new materials for construction. This is due to the need for sustainable development which emphasizes on waste reduction, reduction of greenhouse gases (GHG), greener clean environment and conservation of raw resources. This study examines the appropriateness of clay brick waste in powder form as a suitable material for partial substitute of cement in mortar. The clay bricks were obtained as generated waste materials from a brick producing factory in Lagos metropolis and then subjected to grinding. Tests which include; specific gravity, particle size distribution, x-ray fluorescence and scanning electron microscopy were carried out on the pulverized clay brick material (CBP). Further, it is used to partially replace cement in mortar at replacement percentage of 0, 5, 10, 20, 25, 30, 40 and 50% using a mix ratio of 1: 2.75 at 0.45 water-cement ratio. Compressive strength and strength activity index tests were carried out on the cube specimens after days of curing. The obtained results clearly indicate that the pulverized clay brick is an amorphous material and contains similar chemical oxide compounds of a pozzolana. Furthermore, it was observed that the compressive strength of the mortar was further improve at an optimum value of 20% cement replacement with clay brick powder compared to the control mortar. Therefore it implies that generated clay brick wastes can be pulverized and used as pozzolanic admixture in mortar production instead of discriminate dumping in landfill.
Oil Well Cement for high temperature-A review
Authors: Munjal Pankaj , Hau Kong Kian , Prabhakar Abhinav , Arthur Cheng Chuen Hon 
Published: October 2019

Abstract
Oil well cement (OWC) are widely used in oil industry both in exploration and in production of oil and gas. The purpose of OWC is to seal the annular space between metal casing and walls of a borehole. OWC has other application such as grouting and repair of offshore structure, and in cementing of other wells likes as water, waste disposal, geothermal, injection or storage. There are numerous problems such as high temperature and high pressure in the downhole condition of oil well. OWC slurry undergoes a reduction in strength (strength retrogression) with time when exposed to high temperature and high pressure. This paper reviews the OWC and its classifications, hydration process at ambient and higher temperature. Moreover, this study provides a comprehensive insight on anti-strength retrogression additives, which can potentially be use with OWC at high temperature and pressure.
Utilization of fly ash: basic oxygen furnace slag as a raw material in geopolymerization
Authors: Mashifana T , Sithole N 
Published: October 2019

Abstract
The aim of this project was to develop a basic oxygen furnace slag (BOFS) and fly ash (FA) based geopolymer. The developed geopolymer were required to have strength to withstand hydraulic load. In respect to BOFS and FA, there are two main ways in which they can be handled following the best practices of conserving the environment. The two are disposal and utilisation, the disposal thereof is a problem because it increases the amount of FA annually since they are not consumed completely yearly. Results also showed that wastes beneficiate FA and BOFS can be utilised for other applications and this will reduce these wastes in the landfills. The development of the geopolymer to investigate the optimum conditions to enhance strength has resulted in a 20 % FA mass blend ratio, 9 M concentration of sodium hydroxide, 20 % liquids solid-liquid ratio and 80 °C curing temperature. The addition of hydrogen peroxide to the geopolymer increased the porosity of the geopolymer.
Applications of UAS-obtained thermal images for vegetation coverage ratio monitoring of mudstone areas
Authors: Chen Chien-Yuan , Lin Chai-Li 
Published: October 2019

Abstract
Soil vegetation coverage is a crucial factor for those wishing to protect naked slopes. Thermal imaging enables monitoring of the changes in infrared temperature of a slope surface and calculating the vegetation coverage ratio (VCR). The VCR is an efficient method for determining infrared temperature changes in different slope lands, which include regions exposed to sunlight, vegetation areas, and shaded areas. The thermal images capture the infrared temperature distribution, boundary of vegetation of temperature, and barren vegetation areas. The VCR can be subsequently calculated. In this study, thermal images were obtained using an unmanned aircraft system (UAS) according to airline planning, frame size of an image, and overlapping of lateral and front images for taking pictures. Moreover, 3D images can compare the VCR by calculating the aggregation of the study area and vegetation area. A satisfactory agreement was obtained between the infrared temperature obtained through thermal imaging and the VCR. Thermal imaging can thus be used to monitor changes in the VCR of mudstone. Moreover, a 3D topographic map was created using the UAS-obtained images to overlap with the thermal images.
Research on Wire-Broken Monitoring of Bridge cable based on Acoustic Emission technique
Authors: Zhu Zhiqin , Wang Dawei , Liu Chen , Wang Bingjian 
Published: October 2019

Abstract
Acoustic emission signals generated by broken prestressed steel strand of cable can transmit up to 29.5 meters without maintaining significant attenuation of the amplitude. Therefore, the installation of a few acoustic emission sensors can comprehensively monitor the damage of the entire prestressed steel strand. Thereby, the detection of unknown defects is realized, and the structural health status can be quantitatively and quantitatively evaluated. In this paper, the acoustic emission technology is used to monitor the damage and fracture of prestressed steel strand under over tension. The acoustic emission technology is used to test the broken wires of cable of a concrete-filled steel tubular arch bridge. The correlation of the broken wires test results of the bridge is qualitatively analysed, including the stress state of the cable, the location of the measuring points and whether there is a PVC sheath at the measuring points. Therefore, a safe, reliable and efficient method is sought to monitor the damage status of the in-service cable-supported bridge.
Exploration of key commercial space design indicators
Authors: Lin Mu-Fa , Perng Yeng-Horng 
Published: October 2019

Abstract
The designs of commercial spaces change with time. This study explored competitive factors that affect commercial space development by using the Delphic hierarchy process with the aim of enhancing the overall performance of commercial spaces in a highly competitive retail market. The findings provide key factors that can be used by shopping center operators when selecting commercial space designers. Competitiveness indices were proposed by referring to the literature and conducting interviews with industry experts, scholars, and practitioners. Subsequently, hierarchy structures and indices were established, and relative weights were allocated to each dimension and index. Finally, the evaluation data were calculated and consistency tests were conducted. This study adopted 18 performance indicators to demonstrate the validity of the overall competitiveness indicators, which were verified as possessing high validity.
Effective use of a helicopter with a Bambi bucket firefighting system in Bulgaria
Authors: Seyzinski D T , Georgiev I , Panayotov H P , Penchev S I 
Published: October 2019

Abstract
The present paper studies the effectiveness of the use of the Mi-17 helicopter with a Bambi bucket firefighting system in operations against mountain and forest fires in the Republic of Bulgaria. It makes an analysis of the conditions under which it is used, on the basis of numerous publications about theoretical and experimental studies, including ones aimed at increasing the efficiency of using helicopters with other external hanging firefighting systems. The preparation and conduct of flying experiments with a Bambi bucket system have been made. They take into account the specifics of this system, the characteristics of the firefighting methods used in the Republic of Bulgaria, and the of country specific external factors. On the basis of the results of these studies, and by taking into consideration the flight safety requirements, recommendations have been made to improve the effectiveness of using a Bambi bucket firefighting system in Bulgaria.
Optimal three-loop cascade PI-P-PI controller for electro-hydraulic power steering system
Authors: Kralev Jordan , Mitov Alexander , Slavov Tsonyo , Angelov Ilcho 
Published: October 2019

Abstract
The present paper presents an optimally tuned proportional integral differential (PID) system which calculates the driving signal for the switching valves in order to achieve steering trajectory tracking. The designed cascade control algorithm consists of three PID controllers respectively for the spool valve position, for the effective flow rate and for the steering cylinder position. The stages of the cascade control algorithm synthesis are presented. The goals of control algorithm are to achieve fast transients with minimal overshot and steady state error. Controllers’ are tuned consequently by starting from the innermost loop based on an identified single-input multiple output (SIMO) model of the steering system by optimization algorithm with a quadratic cost. After one of the controllers is successfully tuned the model of the corresponding closed loop system is approximated and employed in the optimization procedure for the next control loop from the cascade system. The developed control algorithm is programmed into a specialized vehicle microcontroller and tested on a steering system test bench in the laboratory.
Study of the stresses in the front suspension components of a car passing over speed breakers
Authors: Georgiev Z A , Kunchev L P 
Published: October 2019

Abstract
To reduce the speed of vehicles before pedestrian crossings or as a warning for lowering the speed, vertical deflection devices or road profiles are placed transversely to the direction of travel. The type of profiles is different – speed bumps and humps with different height and length. Some of the profiles have the task of alerting the driver of changing conditions or potential danger - such are the rumble strips, while others aim to force the driving speed below 30 km/h. The amplitudes of the second profiles are considerably larger than those of the first and can cause significant stresses in the front suspension elements and its connections. The purpose of the study is to obtain information on the load on the front suspension components when passing over speed breakers.
Neural model of projecting flexural strength of cement concrete intended for airfield pavements
Authors: Linek Małgorzata 
Published: October 2019

Abstract
This work present to the mathematical model in the form of Artificial Neural Network (ANN), intended for projecting concrete flexural strength. Input data was classified according to the type of component material and its content in concrete mix (cement contents, coarse aggregate, fine aggregate, water and admixtures). In order to determine mathematical model, a multilayer, one-way perceptron network was used, recursion network with sigmoidal neurons. The model assumes that neurons are gathered in some layers (one input layer, hidden layers and one output layer). The conducted cross-section of the impact of variable parameters values (learning constant α and momentum values η) on the accuracy of representation of flexural strength was analyses. Assessment criterion was assumed as consideration the lowest mistake level and 100% compliance. According to the obtained results ANN was assumed to be the best representing network for constant value of momentum 0.3, learning constant of 0.04 and 9 neurons in a hidden layer. Very good coincidence of component models with experiment results was achieved. At testing stage, the coincidence was achieved at the level of 99.25%, in case of the assumed network structure. During model verification by means of experimental results, the average coincidence was 99.68%.
Rationalization of cross-sections of the composite reinforced concrete span structure of bridges with a monolithic reinforced concrete roadway slab
Authors: Vatulia G L , Lobiak O V , Deryzemlia S V , Verevicheva M A , Orel Ye F 
Published: October 2019

Abstract
The article presents the developed rationalization technique of composite steel reinforced concrete sections with steel open section beams based on the criterion of equal strength of the section elements that are extremely distant from the neutral line. Algorithms for search for geometric parameters of a composite section limited to a certain range of values are implemented to achieve the equal strength condition. The dimensions of the individual elements which are parts of the cross-section are obtained from the condition of the constant ratio of the distances from the neutral axis to the extreme concrete and steel fibers. The numerical methods were used for calculation of continuous three-span composite reinforce concrete bridge. The technique implements the steps of bridge construction, taking into account the contact yield of the composite section, the redistribution of forces between the elements, and the effect of elastic-plastic and rheological properties of materials. The generalized kinetic curve was utilized for evaluation of concrete creep together with the phenomenological equations for the development of deformations based on a colloid-chemical representation of the mechanism for long-term concrete deformation. The proposed methodology is implemented in the LIRA-SAPR software package based on the Building Information Model Technology (BIM) and the Finite Element Method (FEM).
Multicriterial synthesis of the control law for a semi-active spatial model of the vehicle suspension
Authors: Genov Julian 
Published: October 2019

Abstract
This article explores the task for the multicriterial synthesis of the control-law from the type Linear Quadratic Regulator (LQR), for a semi-active vehicle suspension. It is consists of obtaining the optimal compromise between the requirements for sufficient ride comfort and vehicle stability on the road pavement. The relevant object-functions are defined. It is proposed an algorithm for a multicriterial hierarchical approach for identifying in the Pareto’s set of solutions, this solution that realizes the optimal compromise in the sense of John Nash’s sustained strategy from the antagonistic games theory. Based on this approach, a new algorithm for the synthesis of LQR is proposed, combined with a compensator, in which the weight matrices being the subject of optimization. This synthesis was applied for a spatial model of a semi-active suspension of a vehicle.
Economic aspects of using hydrogen in compression ignition engine operating on gas-diesel cycle
Authors: Dimitrov E , Pantchev S , Michaylov Ph , Peychev M 
Published: October 2019

Abstract
The article gives an overview of the economic aspects of a single-cylinder internal combustion engine dual fuel operation with diesel fuel and hydrogen. The engine operating costs are calculated. Two separate cases are investigated. The first case is at constant engine speed – 1500 rpm, constant engine power (1.5 kW) and variable hydrogen mass fraction in the total fuel mass (from 0 to 50%) and the second case is at constant engine speed – (1500 and 2000 rpm), constant hydrogen mass fraction in the total fuel mass (10%) and variable engine power (1 to 4 kW). The following parameters (as a function of the corresponding variable) are determined for both cases: expenses for hydrogen and diesel fuel (in €;/hour), price of the energy obtained at the engine crankshaft (in €;/kWh), expenses for the CO2 emissions emitted by the engine (in €;/hour). The weighted average of the fuel mixture price (in €;/kg) is also determined for the first case. The calculations are made using average fuel prices in Germany for April 2019. A predominant growth in the operating costs is observed as a function of the growing hydrogen mass fraction and increasing engine power. A significant reduction in the price of CO2 emissions at constant engine power and growing hydrogen mass fraction is observed due to the lower exhaust gas toxicity.
Vibroacoustic analysis of marine engine supplied with mixture of fuels
Authors: Wróbel Radosław , Andrych - Zalewska Monika , Tkaczyk Marcin , Fryda Szymon , Dimitrov Radostin 
Published: October 2019

Abstract
The main purpose of this paper is to obtain the differences in the vibrations of engine (Doosan MDT196TI) which was powered using two different fuel mixtures – liquefied natural gas with diesel pilot and diesel only. LNG and diesel oil differ in combustion temperature, density, and cetane number; the combustion process of various fuels proceeds differently, so it has an impact on the generated vibroacoustic vibrations (vibrations have a direct impact on the degree of machine degradation). In the research, the diagnostic system is based on piezoelectric accelerometers and Digital Signal Processing operations (windowing, Fast Fourier Transform). In the conclusions section the obtained results are analysed, indicating how the tested fuels have an effect on vibrations.
Comparative analysis of the results of theoretical and experimental studies of freight wagon Sdggmrss-twin
Authors: Stoilov V , Simić G , Purgić S , Milković D , Slavchev S , Radulović S , Maznichki V 
Published: October 2019

Abstract
This paper presents a comparative analysis based on the results from static strength calculation of wagon body, series Sdggmrss-twin, and on the results from the real wagon test. The verification of results from calculations and tests and their comparison was mandatory for client’s commissioning of the wagon by notified body. Calculations based on the finite elements method were carried out in the Department of Railway Engineering at Technical University of Sofia. Experimental studies on real wagon construction were conducted at the facilities of Bulgarian National Transport Research Institute by testing team from Laboratory of rail vehicles at University of Belgrade. It was found that the obtained static stress results are similar, which proves that the proposed models are appropriate and they can help to solve a wide range of issues, for example those related to lightweight design of railway vehicles.
Development of a repair technology for locomotive units on the basis of the theory of decision
Authors: Puzyr V , Datsun Y , Obozny O , Pyvo V 
Published: October 2019

Abstract
The operative condition of locomotives is maintained by the existing repair system; it consists of the following elements: strategy, organization and technology. This repair technology for units and aggregates is based on disassembling and elimination of defects, and it can be inappropriate. The actual technical condition of the nodes requires an individual approach in determining the volume and content of technological impact during the repair process. Therefore, the purpose of this work is to research the task of developing a repair technology for locomotive units, depending on their actual technical condition. As far as probability distribution functions of the operating condition of units are known, a repair technology is chosen under risky conditions. Therefore, the decision-finding problem is framed in the theory of decision terms. The analysis of the decision tree of the choice of repair technology for fuel injectors of a diesel locomotive demonstrated that at least four variants of technologies (strategies) were possible. Operational costs were taken as the evaluation criterion for the technological process. The pay-off matrix obtained does not have a saddle point; therefore, the problem of choice of the technology cannot be solved only strategically. It substantiates a need to use flexible, adaptive repair technologies which consider the actual technical state of each unit. For a known distribution of states for fuel injectors, the greatest gain with minimum risks is the repair technology of dismantling and reseating the worn-out parts. Application of the described approach at locomotive repair enterprises will allow for improvement of the quality of repair and reduction of costs.