bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Studies of Rib Waveguide Material for Quantum Communication Application
Authors: Yusof Roshidah , Ali Norshamsuri , Kolenderski Piotr , Slowik Karolina , Ahmad Hambali N. A. M.
Published: August 2019

Recently, the needs to achieve a very high traffic capacity and superfast quantum computing led to advancement in optical waveguide technology. The selection of material with a high refractive index and transparent within the telecommunication wavelength range are crucially needed to achieve these. In this paper, the performance of two promising quantum materials, Silicon on Insulator (SOI) and Lithium Niobate on Insulator (LNOI) rib waveguide were studied. The mode analysis was conducted by using a finite element method to observe the confinement electromagnetic wave across rib waveguide. Apart from the variation of a material index, the width and height of core were optimized to achieve single mode propagation at the wavelength of 1550 nm. Based on the simulation work, it is shown that both material structures were able to produce single mode propagation with SOI showing higher confinement compared to the LNOI rib waveguide structure. LNOI structure was able to provide wide range of propagation signal wavelength.
Warpage optimisation using virgin and recycled polycarbonates: a case study of front panel housing
Authors: Aisyah Miza Ahmad Tamizi Nur , Zamree Abd Rahim Shayfull , Hidayah Mohamad Huzaim Nurul , Roslan Norshahira
Published: August 2019

Plastic product are commonly produced using an injection molding process. A large amount of product can produce within a very short time. One of the defect that often being encountered in the production is warpage. By determine the appropriate parameter setting by using optimisation method, the quality of the moulded part can be improve. The warpage can be minimise but difficult to eliminate. The part can be smaller than the actual size cause by the warpage. Due to this defect will cause the plastic part difficult to be assembled. Considering the increasing application of these thermoplastic materials, the use of recycled polymers has increased too. Environmental issues, the subsequent tendency to save resources and the high costs of polymers have made the recycling an inevitable option. This study provides a scientific knowledge that will be useful to plastic manufacturing industries in injection moulding process especially by using virgin and recycle material. The parameter that being significant from the studied that been review were mostly melt temperature, packing time, cooling time and packing pressure.
Optimization of Shrinkage and Strength of the Molded Part Produced using LDPE (Virgin and Recycled) material: A Review
Authors: Roslan Norshahira , Zamree Abd Rahim Shayfull , Hidayah Mohamad Nurul , Huzaim  , Aisyah Miza Ahmad Tamizi Nur
Published: August 2019

The injection molding process is seen to be one of a versatile and important manufacturing process. This is due to its ability in producing product with complicated design and producing part in large quantity. The advantages of this process had caused an active research on its quality improvement and process. This paper reviews the part quality issues happened in the processes. Along with the reviews of the parameters which affects the defects occurrences. Besides that, recycled plastic application in injection molding process was also reviewed. At the end, it is seen that as compared to other thermoplastic materials, LDPE is least popular and discussed as a subject of research. This paper organizes past research studies in few categories firstly the defects occurrences in plastic injection molding, followed by application of recycled material in molding plastic part, application of optimization method in injection molding, next the application of LDPE material in molding plastic part. Lastly, this paper ends with a brief summary and future work.
A Brief Conceptual View on Classification Using Support Vector Machine
Authors: Fatin Liyana Mohd Rosely Nur , Mohd Zain Azlan , Yusoff Yusliza , Yusup NorFadzlan
Published: August 2019

Classifier is an important element for a classification process to classify features or samples of a dataset successfully. The existence of classifier is important, especially involved multiple class dataset with huge number of features or samples. Support Vector Machine (SVM) classifier catches more attention over other classifiers as it is widely used in various fields. Therefore, this paper aims to give a brief conceptual view of SVM in classification. The important elements and principle of SVM are also described. Along with that an appropriate evaluation and validation for SVM performance are also included. As a result, SVM concept in solving real world classification problem is identified for future reference.
A Review on Simulation and Modelling for Patient Flow in Emergency Department
Authors: Hamza Nidal , Abdul Majid Mazlina , Adam Khalid , Akma Abu Bakar Noor
Published: August 2019

At the moment, most of the hospitals are more interested in patient satisfaction because this has been identified as a main issue of quality of service indexes. In most of the Asian countries’ the type of registration system being operated in the healthcare systems are a sort of mixed-mode. Specifically, there are scheduled patients, as well as patients who just walk in and register. Unfortunately, this type of registration structure could increase the patient waiting period even in emergency cases. Interestingly, various methodologies have been explored in order to shorten this undesirable waiting time. This paper focuses on exploration of the characteristics and significance of existing models and simulation techniques from the literature. The combination of agent-based modelling (ABM), DES and integration of DES and ABS technique has been chosen as the solution to modelling patient emergency waiting time in the emergency department realistically. The proactive and independent characteristics of agents in both approaches will contribute to the good representation of patient emergency waiting time in the especially in the emergency department.
AI for Heart Rate Measurements for Sport Performance: A review
Authors: Zarith Rahmah Syed Ahmad Sharifah , Yusoff Yusliza , Mohd Zain Azlan , Samsudin Ruhaidah , Effiyana Ghazali Nurzal
Published: August 2019

Increasing sport performance in athletic has been a major task for coaches around the world. The ability to improve athletes’ performance benefits not only the coaches but to the athletes themselves. Heart rate analysis for sport performance has been investigated for many years. Heart rate plays an important role to measure the athletes’ ability to perform in sports of their choices. The heart rate information will not only aid in training the athletes according to personal abilities but it will also assist in monitoring athletes’ health by reducing the chances of cardiovascular mortality risk. This paper briefly outlines the potential of Artificial Intelligence (AI) in learning information contain in human heart rate measurement for improving the athlete’s sports performance.
The Comparison of Semantic Suffix Tree Clustering and Suffix Tree Clustering Algorithm Influence on the Accuracy Rate of an Indonesian Question Answering System
Authors: Isnurthina Dininta , Ihsan Jambak Muhammad , Yusliani Novi
Published: August 2019

This research analyses the comparison between Semantic Suffix Tree Clustering (SSTC) algorithm and Suffix Tree Clustering (STC) algorithm in clustering documents on Indonesian Question Answering System. The fundamental difference between the two algorithms is that SSTC considers the meaning of the words to generate clusters and readable labels rather than relying only on string matching like STC. As such, SSTC is able to return a more specific and accurate clusters, and has potential to increase the accuracy rate of a question answering system. However, contrary to the hypothesis, comparison results shows that the accuracy rate of Indonesian Question Answering System after the documents is clustered by SSTC is lower than by STC. The accuracy rate degradation occurred in almost every question category, except Definition category. In average, the accuracy rate obtained by Indonesian Question Answering System with SSTC is only 23.31%, while Indonesian Question Answering System with STC is able to obtain 83% accuracy rate. This significant difference indicates that Semantic Suffix Tree Clustering algorithm is not suitable in the context of document clustering on Indonesian Question Answering System.
Indoor Air Quality (IAQ) Sensing Device Prototype: Software-Hardware Architecture and Performance
Authors: Nor Azhar A , Rahmah M , Roslina AH , Fauziah Z
Published: August 2019

In a green environment, air quality is among the prominent aspects to be considered to prevent pollution and in turn maintain safe air. Sick Building Syndrome (SBS) and Building Related Illness (BRI) are the problems that must be encountered by building occupants. Existing devices are quite expensive, and more attention is needed on monitoring air quality. Therefore, this paper discusses a software-hardware architecture proposal to overcome the existing IAQ data retrieval performance problem. The objective of this work is to analyse the most recent IAQ sensing device developed by the researcher, to evaluate the performance attribute, and to implement the software-hardware architecture based on the Performance-Driven Software Architecture Refactoring (PDSAR) method. In order to assess the overall performance of the architecture proposed, the prototype of the Indoor Air Quality (IAQ) sensing device was developed. The testing was performed during a period of six months. The results demonstrate that the average performance for 540 readings is 76.67%. This shows that the architecture can be accepted as a generic IAQ sensing device development structure. The device act as an alternative, cheaper and safer device which can be employed by all building owners in the future.
Influence of Network Speed on Structured Query Language (SQL) Database Data Transmission Performance in an Internet of Things (IoT) Sensing Device on Single Board Computers (SBC)
Authors: Nor Azhar A , Nur Ayuni Hasna S , Roslina AH , Fauziah Z , Rahmah M
Published: August 2019

One of the crucial elements in an Internet of Things (IoT) environment is a database. IoT performance will be at stake if the wrong database is adopted. In this research, three Structured Query Language (SQL) databases were tested against multiple network speeds in an IoT device. Single board computers (SBC) were used as a media of testing instead of an ordinary computer. A controlled wireless sensor network (WSN) was developed with several uniform constants and variable network speeds. A new data transmission rate equation also was proposed and tested. From the result, it was found that not all SQL databases can cater IoT devices. Some of them showed that performance decreased along with network speed. The correlation, between 0.90 and 0.96, proved the strong influence between the research subjects. In addition, file-type database is the best option available for SQL-wise IoT storage.
WM-LEACH - An Improved Network Lifetime LEACH Protocol for Wireless Sensor Networks
Authors: Mahmuddin M. , Alabadleh W. A. , Kamarudin L. M.
Published: August 2019

Ad hoc network is divided into subcategories in which wireless sensor network (WSN) is one of them, which include several small devices known as sensor nodes (SNs) connected to base stations (BSs). The network lifetime is one of the most vital features as a trustworthy transmission. The low energy adaptive clustering hierarchy (LEACH) is one of the prominent protocols for deploying in the WSN that depends upon a procedure of clustering. Nevertheless, as cluster heads (CHs) share information with a BS openly irrespective of their interior distance, a maximum energy is utilized if the distance between them is too long, which alternatively minimizes the lifetime of the network. To cope with these challenges, various extensions of the LEACH protocol have been designed that send data in two ways, i.e., either in a single hop or multi hop. However, most of these extensions bring extra computational complexity for CHs due to the usage of residual energies. This study proposes an adaptive routing multi-hop LEACH (WM-LEACH) that would minimize the utilization of energy and augment the entire lifetime of the WSN. This rationale of the WM-LEACH is examined in the MATLAB simulator and the obtained outcomes are associated with other routing protocols in terms of network lifetime.
The Effect of Different Crumb Rubber Loading on the Properties of Fly Ash-Based Geopolymer Concrete
Authors: Azrem Azmi Ahmad , Mustafa Al Bakri Abdullah Mohd , Mohd Ruzaidi Ghazali Che , Ahmad Romisuhani , Musa Luqman , Sheau Rou Low
Published: August 2019

This study aims at viability study the effects of addition of crumb rubber loading in fly ash-based geopolymer concrete for its properties. Crumb rubber is the recycled rubber from automotive scrap tires which can reduce scrap into uniform granules shapes that can absorb stress that reduces the reflective cracking because of its elastic properties. Geopolymer concrete includes an alternate material i.e Fly ash in replacement of cement, as a binding material. Mortar cubes of size 50mm x 50mm x 50mm were casted and curing at room temperature. X-Ray Fluorescence (XRF) and Scanning Electron Microscopy (SEM) were used to analyze the chemical composition of fly ash and the microstructure of the concrete. Moreover, compressive strength, water absorption capacity, and density of concrete are interrelated. Compression test, water absorption capacity test and density test were performed in hardened state, for different proportions of replacing the aggregate with crumb rubber i.e. 5%, 10%, 15%, 20%. Compressive strength test was performed at 7, 14 and 28 days. Results were obtained and compared. Decrease in strength was observed at 7, 14 and 28 days.
Pull-Out Strength of Hooked Steel Fiber Reinforced Geopolymer Concrete
Authors: Ahmad Faris Meor , Mustafa Al Bakri Abdullah Mohd , Nizar Ismail Khairul , Aida Mohd Mortar Nurul , Firdaus Abu Hashim Mohammad , Hadi Abdul
Published: August 2019

Pull-out strength of fly ash steel fiber reinforced geopolymer concrete was studied. Fly ash steel fiber reinforced geopolymer concrete was produced by mixing of Class F fly ash which taken from Manjung power station, Lumut, Perak, Malaysia with alkaline activator which are combination of sodium hydroxide and sodium silicate. Steel wool fiber were added into the geopolymer concrete as reinforcement with different weight percentage vary from 0 % - 5 %. Chemical compositions of Malaysian fly ash was first analyzed by using X-ray fluorescence. All geopolymer concrete samples with inclusion of hooked steel fiber with different volume percentage which are 0 %, 0.5 %, 1.0 %, 1.5 %, and 2.0 % were tested in terms of microstructure, flexural strength, flexural toughness, and pull-out strength. Microstructure of steel fiber reinforced geopolymer concrete shows a good degree of bonding between geopolymer binder and hooked steel fibers. Flexural strength of samples increased with the addition of hooked steel fibers until at 3 % and will slightly decrease when amount of fibers addition over than 3 %. Meanwhile, addition of hooked steel fibers shows significantly improvement to the toughness of samples. However, there is no improvement of toughness with addition of fibers over than 3 %. Pull-out strength of samples shows an excellent result where maximum result of 505 N can be achieved that indicates a good degree of bonding between geopolymer matrix and fibers.
The Effect of Geopolymer Ceramic Additions to The Wettability and Shear strength of Sn-Ag-Cu (SAC) Solder: A Preliminary Study
Authors: Syahirah Mohamad Zaimi Nur , Arif Anuar Mohd Salleh Mohd , Mustafa Al Bakri Abdullah Mohd , Mostapha Marliza , Ahmad Romisuhani
Published: August 2019

The effect of geopolymer ceramics addition into Sn-3.0Ag-0.5Cu (SAC305) lead free solder was successfully investigated. The lead-free solder SAC305 with the addition of geopolymer ceramics was fabricated by using powder metallurgy microwave-sintering method in order to form a composite solder. The composite solder was analyzed based on wettability and shear strength. The wettability of SAC 305 solder was greatly enhanced with the decreasing in its contact angle. Then, the geopolymer ceramic addition enhanced the shear strength of SAC 305 solder.
Effects of Thermal Resistance to Fly Ash-Based Lightweight Geopolymer
Authors: Mastura Wan Ibrahim Wan , Mustafa Al Bakri Abdullah Mohd , Ahmad Romisuhani , Naveed Amir , Mohd Ruzaidi Ghazali Che , Ibrahim Masdiyana
Published: August 2019

Geopolymers are inorganic polymeric materials and cementations materials that replace the Ordinary Portland Cement. This study aimed to determine the effect of thermal resistance of fly ash based lightweight geopolymer and to investigate the physical, mechanical and microstructure properties of lightweight geopolymer at different thermal resistance. Considering the fire endurance assessment of geopolymers, the evolution of geopolymer during thermal exposure is of interest. This paper presents a comparative study of the characteristic of unfoamed (control sample) and lightweight geopolymers after exposure to elevated temperatures which is 200 °C, 400 °C, 600 °C and 800 °C. Lightweight geopolymers were prepared by adding foaming agent which is polyoxyethylene alkyether sulphate with geopolymer paste. Fly ash, alkaline activator and foam were mixed to produce a homogeneous mixture, which was placed into a cube 50 mm x 50 mm x 50 mm mould and cured at 80 °C for 24 hours. The compressive strength, density, chemical composition, microstructure and functional group analyses were studied. Unfoamed geopolymer exhibit higher compressive strength at 47.04 MPa compared to the highest strength of lightweight geopolymer which is 33.26 MPa at 200 °C. However, the lightweight geopolymer produced low density in range 1200 kg/m3 to 1500 kg/m3 compared to the density of unfoamed is 1813.79 kg/m3.
A Review of Carbonate Minerals as an Additive to Geopolymer Materials
Authors: Syauqi Sauffi Ahmad , Mastura Wan Ibrahim Wan , Mustafa Al Bakri Abdulla Mohd , Ahmad Romisuhani , Ahmad Zaidi Fakhryna , Victor Sandu Andrei , Subaer
Published: August 2019

In Malaysia, several geopolymer materials were mainly from fly ashes, kaolin, metakaolin, and boiler ash which were mainly used to prosper sustainable development especially in the building and construction sector. Geopolymers can be classified as inorganic materials that were formed with the reaction between alminosilicate materials and alkaline solutions. This reaction causing a crystalline compounds mixture to form that toughen to become a novel compound through a process called geopolymerization process. These geopolymer materials have many admirable advantages, including high strength, small shrinkage, decent thermal resistance and good chemical resistance. Although they were used as a stand-alone material with great properties, combination with another material might be another way to improve their properties. A few studies had shown that the geopolymer material can achieve better properties with the addition of moderate amount of calcium-containing material to a geopolymer. The addition of carbonate materials can have insignificant effect on the geopolymer configuration and properties. Thus, this paper review the usage of carbonate materials for example Dolomite (CaMg(CO3)2) and Calcite (CaCO3) as an addition into these geopolymer material.
Solderability of Sn-0.7Cu-0.05Ni-xZn Solder Ball on Sn-0.7Cu and Sn-0.7Cu-0.05Ni Solder Coating
Authors: Ramli M. I. I. , Mohd Salleh M. A. A.
Published: August 2019

In this study, the solderability of the Sn-0.7Cu-0.05NixZn solder ball on solder coating were investigated by using Gen3 wetting balance test machine. By using wetting balance test in globule mode, the solderability of solder ball was determined by the maximum force and wetting time. The result of a good solderability is generally referred to short wetting time and high wetting force. It was found that by increasing amount of Zn in Sn-0.7Cu-0.05Ni solder ball, the maximum force was decrease and wetting time was increase. This result indicates that by increasing amount of Zn in Sn-0.7Cu-0.05Ni solder ball, it will decrease the solderability of solder ball to the solder coating.
Influence of Expandable Graphite and Aluminium Hydroxide on Mechanical Properties of Polyurethane Foam
Authors: Rozyanty A.R. , Mofeed D.M.S. , Firuz Z , Amini M.H.M.
Published: August 2019

In this research, the influence of expendable graphite (EG) and aluminium hydroxide (ATH) on mechanical properties of polyurethane composite were investigated. Polyurethane foam was prepared by using oil palm based polyurethane with ratio 1:1.1 and mechanical properties was evaluated by compression test. Results shows that the addition of expendable graphite and aluminium hydroxide into polyurethane had improved the compression strength compared to polyurethane composite without additif. SEM micrograph shows the present of expendable graphite in the polyurethane cell wall which help to improve the mechanical properties. Especially, the compression strength at 10% EG/2% ATH loading sharply inproved by 66% over polyurethane foam.
Mesoporous Structure of Doped and Undoped PEG on Ag/TiO2 Thin Film
Authors: Abdul Razak Kamrosni , Suriyani Che Halin Dewi , Azani Azliza , Mustafa Al Bakri Abdullah Mohd , Arif Anuar Mohd Salleh Mohd , Mahmed Norsuria , Mahyiddin Ramli Muhammad , Sepeai Suhaila
Published: August 2019

In this reaserch, photocatalyst silver titanium dioxide was doped and modified by Polyethylene Glycol (PEG). The purpose of the present study was to analyse the synthesized Ag/TiO2 thin film doped and undoped PEG. Ag/TiO2 thin films on silicon wafer have been prepared by sol–gel spin coating. The samples were characterized by Grazing Incidence X-ray diffraction (GIXRD), Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscope (AFM). The doped and undoped PEG Ag/TiO2 thin films showed a mesoporous TiO2 matrix which includes TiO2 crystallites of 10-20 nm in size and small Ag nanoparticles (white spots) with various sizes ranging from 10 to 30 nm. However, doped PEG Ag/TiO2 thin film showed the Ag nanoparticles became agglomerates but still remained roughly uniform on the surface.
Characteristics and Heating Values of Pellets Made from Raw and Charred Rice Residues-Rubber Tree Twigs Mixture
Authors: Yit Leng Lee , Haruna Ahmed Osumanu , Abdul Wahid Samsuri , Abdul Razak Norawanis , Nadzirah Zulkeple Nurul , Izzati Ismail Ras , Makhtar Nurlailina
Published: August 2019

In this study, the characteristics and heating values of raw pellet (RP) and charred pellet (CP) made from rice residues-rubber tree twigs mixture were compared. The carbonization process to produce the charred plant residues was conducted in a locally fabricated stainless steel kiln. Both the RP and CP were evaluated for their heating values, pellet durability, carbon and inorganic ash content. The CP had higher heating value and carbon content than the RP. However, the ash content of CP was higher. The results indicate that the pellet made from the charred rice residues-rubber tree twigs mixture could be a suitable source of renewable fuel.
Sustainable Extraction of Micronutrient of Food Waste by Thermal Treatment under Elevating Temperature
Authors: Kamaruddin M.A. , Azman Z.N. , Ahmad N.F. , Hanif M.H.
Published: August 2019

Food waste management by biological treatment is widely used due to the eco-friendly and more attractive than physical and chemical treatment. However, the use of biological treatment takes longer time for the food waste to degrade. To overcome this problem the pretreatment of food waste is proposed. The aim of this study is to determine the characteristic of food waste when subject to pretreatment, to determine the effect of thermal pretreatment on chemical compositions of food waste, and to determine the relationship between the effect of temperature and time on food waste carbon to nitrogen ratio, pH and micronutrient by using statistical analysis. The water bath method was carried out in this experiment. The parameter measured were Carbon to Nitrogen ratio (C;N), pH and micronutrient with the effect of temperature and time. The result of the food waste before treatment and after pretreatment was compare. The laboratory results showed that the chemical composition of the food waste was affected by the thermal pretreatment of water bath method for C:N and pH which in the range 11.18 to 25.94 and 5.32 to 5.72 respectively. The statistical analysis indicates that the interaction effect between retention time and temperature was not significant for pH, Fe, Cu and Mn except for C:N (F = 4.394, P = 0.003). Overall, the thermal pretreatment applied on the food waste revealed that temperature below 100 °C did not suitable to use as a pretreatment before the biological treatment, in order to expedite the degradation process. Instead, high temperature which above 100°C and long heating duration are beneficial for the release and reduction of organic compounds.
Synthesis Of Epoxidized Oleic Acid- Based Palm Oil by Peracid Mechanism
Authors: Jumain Jalil Mohd , Farhan Mohd Yamin Aliff , Saufi Md Zaini Mohd , Azahar Mohd Ariff Mohd , Hua Chang Siu , Morad Norhashimah , Hadi Abdul
Published: August 2019

Commercial epoxides available in the market are mainly petroleum and animal based which are non-environmental friendly and often non-halal. Oleic acid (C18:1) derived from palm kernel oil contains the unsaturation double bond (C=C) in its long alkyl chain makes it an attractive fatty acid for the production of eco-friendly epoxide. The epoxidation of oleic acid was carried out by using in situ generated performic acid (HCOOOH) to produce epoxidized oleic acid. Performic acid was formed by mixing formic acid (as oxygen carrier) and hydrogen peroxide (as oxygen donor). The results indicated that optimum conditions occurred at moderate agitation speed 300 rpm and by using 30% hydrogren peroxide. Sulfuric acid was found to be the most efficient catalyst. It was found that a maximum relative conversion to oxirane (RCO) achieved was 87.61 % at optimal condition.
Optimization of Acid Orange II Degradation using Fe3-xMnxO4 Catalyst in UV assisted Fenton-like reaction
Authors: Edwin Elsabba , Aida Zubir Nor , Khairul Azam Selamat Mohamad , Alrozi Rasyidah , Nasuha Norhaslinda , Imam Maarof Hawaiah
Published: August 2019

In this work, detailed investigation on the optimization of acid orange II (AOII) degradation using Fe3-xMnxO4 catalyst in UV assisted Fenton-like reaction was performed. The Central Composite Design (CCD) based on Response Surface Methodology (RSM) with four independent operational parameters (catalyst dosage, oxidant concentration, pH and UV irradiation) and one response (percentage of AOII removal) was applied for statistical and optimization analysis. The maximum AOII removal (~100%) was found at optimal conditions of 0.4 g/L catalyst dosage, 35 mM oxidant concentration, pH 2.6 and 3 x 9W UVC. Interestingly, validation of these optimal conditions was confirmed by the experimental findings of having less than 2% absolute deviation. Such findings confer that the derived empirical quadratic model was in good agreement with the experimental findings.
Hydrothermal reaction products of brick recyclates
Authors: Palovcik J , Opravil T , Soukal F , Masilko J
Published: August 2019

This paper deals with possibilities of the brick-grind-dust application as a precursor for hydrothermal synthesis. Currently, this brick dust is partially reused in brick masonry or buried to the landfill site. The basic idea of this paper was to examine possibilities of the reaction of phases in brick dust with lime under hydrothermal conditions. The aim of the work was to find out an optimal ratio between lime and brick dust for maximal production of tobermorite. Physical and chemical properties of the brick-grind-dust were studied, and then a series of samples in autoclaves were prepared. The maximum amount of tobermorite after 24 hours of reaction was found in samples with addition of 25% lime. Phase composition of raw material and products of hydrothermal synthesis were analysed by powder X-ray diffraction analysis and differential thermal analysis. Structure of prepared samples was observed by scanning electron microscope.
Influence of curing temperature on the mechanical properties of high-performance concrete
Authors: Fladr J , Broukalova I
Published: August 2019

As part of the research focused on high-performance concrete (HPC) at our workplace, the impact of temperature curing on compression strength of HPC has been investigated. Four sets of samples (100 x 100 x 100 mm cubes, 30 samples in each set) were produced with the same mix design. Each set was cured with a different temperature: 20°C (reference samples), 50°C and 80°C (high and very high temperature curing) and 10°C (simulation of concreting in winter conditions). The curing was always carried out in a water bath with a given temperature during the whole time of maturing of the samples. Samples were tested in 1, 3, 7, 14 and 28 days of age. In each time step, three cubes were tested for compression strength and three cubes for tensile splitting strength. The results of the primary research are the time records of the increase of both strengths.
Utilization of basalt fabrics as reinforcement for alkali-activated blast furnace slag systems
Authors: Hruby P , Kalina L , Masilko J , Kimm M , Gries T
Published: August 2019

Alkali-activated materials based on the alkali-activated blast furnace slag (AABFS) seem to be a suitable alternative construction material due to the environmental and economic aspects. More widespread application potential could be supported by the utilization of fabric reinforcement into the matrix to form AABFS composite with improved mechanical properties. The basalt fibres or fabrics (BFs) represent a reinforcing material suitable for the AABFS due to its favourable price/properties ratio. However, the question of fibres stability under the alkaline conditions should be taken into account. The effect of BFs implementation in one or more layers into various types of matrices to the mechanical properties was studied with the regard to the compressive and flexural strengths. The used matrices were based on the alkali-activation of the BFS with various activators. The fabric/matrix adhesion same as the transition zone properties were studied using the SEM analysis and pull-out tests. Indication of appreciable improvement of mechanical properties utilizing one layer of BFs for some of the mixtures activated using sodium water glass and sodium carbonate was found out.
Application of carbon black in conductive fly ash geopolymer mortars
Authors: Mizerová C , Kusák I , Rovnaník P
Published: August 2019

Materials with enhanced electrical properties are widely studied concerning their future application in smart or self-sensing constructions. Carbon black is known as one of the inexpensive multipurpose admixtures used in polymeric materials. This study is focused on the application of carbon black in fly ash geopolymer mortar to enhance its conductivity and other electrical properties. Geopolymer samples were prepared with the carbon black content from 0.5 to 4.0% to evaluate their performance in selected electrical properties (conductivity, resistance, capacitance). Further investigations included its influence on the mechanical properties (compressive and flexural strength) and microstructure of the binder (mercury intrusion porosimetry, SEM). Despite the considerable improvement in conductivity, the amount of conductive filler over 2% was also associated with increased porosity and reduced compressive strengths.
Stabilization of the ammonia in SNCR fly ash - the influence of tannins presence on the preparation of an autoclaved aerated concrete
Authors: Galvankova L , Ledl M , Beranova D , Opravil T
Published: August 2019

Due to the legislative regulations on NOxemissions, a selective non-catalytic reduction (SNCR) technology had been introduced to a coal combustion process in power plants. The valuable by-product, fly ash, contains ammonia in the form of soluble salts, e.g. NH4HSO4and (NH4)2SO4. After mixing SNCR fly ash with cement, thanks to the rise of pH, the toxic ammonia releases and contaminates the working area, so the presence of these salts is undesirable in an autoclaved aerated concrete (AAC) manufacturing process. A possible solution is the conversion of soluble ammonium salts to an insoluble form. Tannins are a class of polyphenolic biomolecules, which react with the ammonium ions to form insoluble compounds. The AAC samples were mixed using SNCR fly ash and two different ammonium binding additives - pure tannic acid and the cost-effective animal food supplement containing chestnut tannins. The influence of additives on the hydration process of the starting mixture was studied by isoperibolic calorimetry. The results suggest that the cost-effective source of tannins retards the hydration. The presence of insoluble compounds was studied by the infrared spectroscopy.
Improving the dispersion of silica fume in cement pastes and mortars
Authors: Janca M , Siler P , Opravil T , Kotrla J
Published: August 2019

There are many possibilities how to improve concrete properties such as compressive strength, flexural strength, durability, and others. The change in the composition of ordinary Portland concrete (OPC) is one possible way. This change may result in the formation of concrete with added properties known as high-performance concrete (HPC). Traditional methods used to receive high-performance concrete design and manufacture emphasize the removal of coarse aggregates. This is achieved by using the specially sorted fine aggregates at relatively low doses along with super-plasticizers and silica fume. Problem with fine reactive aggregates is their agglomeration which causes reduction of the reactive surface. This work is focused on evaluation of the ultrasound technology for the dispersion of silica fume. For comparison, different cement mixtures were prepared to study the effects of the treatment of silica fume prior to its use in HPC applications.
Effects of shrinkage-reducing admixtures on autogenous shrinkage in alkali-activated materials
Authors: Kotrla J , Soukal F , Bilek V , Alexa M
Published: August 2019

This paper deals with possible solutions of chemical and autogenous shrinkage of alkali-activated blast furnace slag (AAS). Shrinkage is the main reason why AAS is not used in practice. One of the solutions how to reduce the shrinkage is the utilization of special chemical admixtures. In concrete technology, the use of chemical compounds based on hydrocarbon alcohols is well known, however the efficiency in AAS is still very poorly elucidated. Therefore, isopropanol was used in this study. The main aim of the work was to recognize and study the relations between chemical processes in the early stages of hydration. The effect of isopropanol on alkali activation was determined by calorimetric measurements and compared with the initial and final setting time of binder. It was found out that the presence of isopropanol additive had only insignificant effect on the setting time. On the other hand, the results indicated that an increasing amount of isopropanol deaccelerates the hydration process which was represented by smaller amount of primary CSH gel formation and delayed time of secondary binder phase formation.
Mechanical activation of two different types of fly ash and their effect on alkali activation.
Authors: Marcin M , Sisol M , Brezani I , Behunova D
Published: August 2019

The article aim is to analyze the influence of mechanical activation of a fly ash, with different proportion of mechanically activated and not mechanically activated material on alkali activation. The paper describes fly ash based geopolymers and their mechanical properties. Fly ashes were mixed in four different ratios with mechanically activated fly ash. Activation solution was constant in all specimens. Compressive and flexural strengths of the hardened product were tested after 7 and 28 days of the storage in laboratory conditions and samples were cured after activation in hot air chamber for 6 hours in 80°C temperature. The results show how mechanical activation of materials affects their strengths with highest amount achieved was 44 MPa.
Properties of the composite with recycled concrete manufactured by modified technology
Authors: Trtik T , Seps K , Chylik R , Fladr J , Pavlu T
Published: August 2019

The article describes basic mechanical, physical and durability characteristics of concrete with recycled aggregate. Recycled concrete aggregates from AZS s.r.o. are made using newly modified technology and properties for use in concrete have been tested. In this part of the research the compressive strength, tensile strength, modulus, freeze and thaw resistance are tested. The basic aim was to test two mixtures with fifty percent substitution of the coarse component of natural aggregate by recycled one (the standard EN 206 does not already allow this) and to prove that such a quantity of recycled aggregate can be used for concrete constructions. The properties were tested on 150 mm cubes and beams 100 x 100 x 400 mm after 28 days.
The products of a high temperature reaction of fly ash with lime and soda
Authors: Beranova D , Galvankova L , Masilko J , Ptacek P
Published: August 2019

A composition of coal combustion fly ash depends on a coal composition and conditions of a combustion process. The main components are SiO2 and Al2O3. An amount of Al2O3 in coal combustion fly ash is relatively high, about 30–40%, and for this reason, the fly ash could be potentially used as a raw material source for alumina production. There are several ways to get alumina. The fly ash could be acid leached or sintered with a suitable additive. One of the possible sintering processes is lime-soda sinter process. The article deals with products of lime-soda sinter process of the fly ash produced from brown coal in Czech thermal power plant. The phase composition of sintered material was determined by X-ray diffraction analysis (XRD). The presence of sodium aluminate and dicalcium silicate was confirmed.
The determination of measurement errors in impedance spectroscopy
Authors: Lunak M , Kusak I , Chobola Z
Published: August 2019

The paper deals with the methodology, quantification and comparison of measurement deviations for two types of the ceramic shard. The ceramic material has better polarization properties than concrete material. For impedance measurement the ceramic shard is more appropriate. The IS method diagnostics based on processing of measured data which aims evaluating the absolute error and the relative error (deviation) of the loss factor values. Results show the spectrum parts which are useful in the lower frequency range only. When Agilent 33220A and Agilent 54645A are used to carry out the IS, the most important factor from the viewpoint of the tgδ(f) determination accuracy is the accuracy of the phase shift between the excitation signal and that at the measured system output. Other factors are the measurement accuracy of the electric capacity and resistance of the oscilloscope input channel.
Examples of testing methods focussed on evaluation of corrosion influence on steel structures
Authors: Sperl M , Gajdos L
Published: August 2019

The paper presents methodologies and results of two case studies dealing with corrosion damage in steels. Specifically, it is concerned with corrosion fatigue and stress corrosion cracking. Description is given of preparing test specimens, special devices and loading frames that have been used to obtain significant experimental results. These are referred to influence of three different chemical solutions on the fatigue life of specimens taken from L485MB steel crude oil pipeline IKL. In the second part of the paper negative effects of stress corrosion cracking on the fracture toughness of structural steel CSN411353 were investigated and main results of this investigation are presented.
Analysis of cutting forces and surface quality during face milling of a magnesium alloy
Authors: Chirita B , Grigoras C , Tampu C , Herghelegiu E
Published: August 2019

This paper presents an experimental study carried out in order to assess the effects of the cutting parameters (cutting speed, feed and depth of cut) and also of cooling conditions on the cutting force and the surface quality during high speed face milling of a magnesium alloy. With its high ratio of strength to weight, good machinability and overall physico – mechanical properties magnesium has attracted a large interest upon itself, especially in fields such as automotive, aeronautics, electronics or biomaterials. On the other hand, there has been lately an increased interest for cooling techniques that are more environmentally friendly, which is why in this study two cooling systems were used: dry machining and minimum quantity lubrication (MQL). The tests have been organised according to design of experiment technique. By using the response surface methodology (RSM), a central composite experimental matrix was designed. Statistical analysis (ANOVA) has allowed to create mathematical models of the cutting force and surface roughness and to analyse the effects of the effects of the input parameters on these outcomes. It was thus revealed that the depth of cut and the feed, and the interactions feed – depth of cut and feed direction – cooling, respectively, have the most significant influence on the main cutting force, whereas when it comes to the surface roughness, the most significant factors were the feed, the feed direction and the interaction between feed direction and cooling type.
Some considerations on the welding heat flow
Authors: Cohal V
Published: August 2019

The modelling of a weld is not only related to the heat flow in the thermal part of the simulations. Addition of additive material and the simplification of thermal and mechanical behaviour should be considered. The basic idea is to replace a complex physical process with a much simpler one. This brings not only approximations, but also the need for calibration procedures to determine the heat flow. In the present paper we aim to model the relationship between welding temperature variation depending on the time and depth, and to model the relationship between stress and distance from the heat source (welding).
MAG welding of 960QL quenched and tempered steel
Authors: Gorka J , Kotarska A
Published: August 2019

The article presents research of the welding technology of S960QL quenched and tempered steel with the thickness of 10 mm. The main problem during welding heat-treated fine-grained steels is cold cracking. The aim of the research was to develop welding technology of tested steel to obtain high ductility and strength properties of the joint and to avoid the problem of crack formation after welding process. For the test the butt joint was welded. For this it was used MAG process in the flat position. Welding process was carried out based on preliminary tests and pre-prepared Welding Procedure Specification according to ISO 15609-1 standard. During welding the M21 mixture was used as the shielding gas. As the filler metal a solid wire G Mn4Ni2.5CrMo was used. The welded joint was tested in accordance with the ISO 15614 standard requirements. The research included non-destructive tests and destructive tests. The non-destructive tests included visual, magnetic particle and radiographic tests. The destructive tests included transverse tensile, root and face bend, impact, macroscopic, microscopic and hardness. Impact test was carried out in the temperature of - 20°C. Hardness measurements were made using the Vickers method and the load of 9.80 N. All of the tests ended with the positive result. The results of research show that tested welding technology and pre-heating temperature equal to 80°C allow to obtain a welded joint meeting the high quality requirements and the international standards requirements.
Scuffing analysis of roller-shoe mechanism after an aggressive test
Authors: Iordache C R , Ciornei F C , Bujoreanu C
Published: August 2019

The roller-shoe assembly is a known and efficient mechanism used for movement transmission in order to obtain mechanical energy. This mechanism is found in high pressure pumps and its role is to change the rotating motion in a translation one. During the running time, some wear types can be identified such as scuffing, corrosion, material removal. Scuffing is the main type of wear appearing in this mechanism. The aim of our paper is to analyse the behaviour of these two components (roller and shoe) over an aggravating test. The main defect is low clearance between components. The roller and shoe assembly is mounted in a diesel fuel pump for test. The test chosen for this experiment is Low Sommerfeld Number. It was stopped after 10% from time set. After visual analysis, it was observed the roller-shoe scuffing. The shoe was analysed and it was observed that the diamond like carbon (DLC) layer is non-conform. In the same pump, the affected components were replaced with new components to be convinced that the wear was caused by low clearance between them correlated to non-conform DLC layer. The test results confirm the reason of scuffing.
An analysis on some mechanical properties of AlMg10-SiCp ultralight metal composites
Authors: Rusu O , Rusu I
Published: August 2019

The paper presents some results on analysis of some mechanical properties of AlMg10-SiCp composite materials, namely hardness and behaviour at static compression. Hardness values clearly separated the range of cellular composite materials from the porous ones, the compression tests data showing that with the increase of porosity the energy absorbed by the composite materials rises, the cellular composites requiring a higher mechanical deformation work that the porous ones. The increase of the silicon carbide percentage causes the increase of mechanical deformation work and of the absorbed energy, which can be explained by the stabilizing role of the respective particles on the composite material cells walls. The investigated samples were obtained using two methods: a method based on melt bubbling with a reactive gas (M1) and a method based on using various salts powders particles, soluble in suitable solvents (M2). We chose AlMg10 alloy for the material base and silicon carbide reinforcement particles introduced in varying amounts in the base mass (5%, 10% and 15% SiC). First method leads us to cellular composites and the second one to porous composites.
Numerical study of the dynamic characteristics of a hybrid steel-concrete bridge
Authors: Scutaru M C , Taranu N , Comisu C C , Boaca G , Ungureanu D , Hudisteanu I
Published: August 2019

Due to the continuous development of the transportation sector and the industrial areas, the roads network has become complex nowadays. The administrators of these networks are thus responsible for maintaining it in proper conditions, using the limited budget available, insufficient for the many structures and problems identified across the network. Therefore, effective systems have been created and developed to prioritize the required works, and the benefits of their implementation have been ascertained from the early stages of the degradation development. One of these systems is the modern methodology for assessing the structural state of bridges, called Structural Health Monitoring (SHM), responsible for discovering and monitoring the degradation occurrence and development. In this paper, the authors present the numerical modelling and the dynamic analysis of a bridge with mixed steel-concrete structure. The bridge is located in Romania, ensuring the continuity of DN 28 road near Scheia. The bridge superstructure, 220.70 m in length, was fully modelled using the SAP2000 program, highlighting the specific behaviour of a continuous girder. The frequencies and deformations for the first four vibration modes were determined. The data will be used in a forthcoming experimental study and compared to those recorded in-situ, in order to determine the structural degradation.