bluuebunny/crossref_metadata_2025 huggingface dataset:
A PROMETHEE based multi criteria decision making analysis for selection of optimum site location for wind energy project
Authors: Manoj Vasupalli , Swathi Aakula , Rao Vemireddi Tejeswara
Published: January 2021

This paper presents a PROMETHEE (Preference Ranking Organization Method for Enrichment Evaluation) method based on AHP (Analytical Hierarchy Process) is applied to the selection of optimum site location for Wind energy projects. Our case study tried to find out the selection of best site for the wind energy project in India. For this study authors have chosen six wind energy projects which are located across in India. Wind power, Hub height, Distance, Cost, CO2, Wind speed and Blade height are the seven criteria had taken for the selection of best location. AHP is integrated with PROMETHEE to meet the objective of this study. Firstly, the weights of each criterion are to determine using Analytical Hierarchy. These weights will be used in PROMETHEE II method to select the best project. A case study is performed to exhibit the application of the methods was conducted to evaluate six types of wind power projects. The AHP-PROMETHEE II result showed that the Muppandal wind farm, Kanyakumari is the best wind power project among the six projects.
Finite Element Method (FEM) based Design and Simulation of Practical Transformer with Nano-Crystalline Core Using ANSYS
Authors: Kaur Sarpreet , Kaur Damanjeet
Published: January 2021

Transformer is the main apparatus of the power system for both transmission and distribution of electrical energy. It is the important component of electrical engineering because of its high efficiency and helps in step up and step down the voltage, impedance matching and circuit isolation. Team of designers, engineers and building owners struggled for high-performance in order to maximize the transformer efficiencies. Design and selection of material to construct a transformer core is a significant process. The purpose of this study is to model and simulate a practical 12.5MVA, 66/11kV, three phase power transformer with Nano-crystalline materials like FINEMET and VITROPERM using ANSYS. The study also put some light on the usage of these materials for core as they shows reduced losses in transformer.
Design and Static Analysis of Mono Composite Leaf Spring Made of Various Types of Composite Materials Using Finite Element Method
Authors: Singh Vishesh , Rastogi Vikas
Published: January 2021

In this study design and static analysis of mono composite leaf spring are performed in comparison to the existing structural steel leaf spring. The basic idea behind this work is to replace the existing structural steel leaf spring with composite materials. In this work, three different kinds of composite materials are taken such as laminated Carbon/Epoxy, Boron/Aluminum, and Carbon/Epoxy (Non-Laminated) with the same thickness, width, and load-carrying capacity. The main investigation of the study is to reduce the weight of existing structural steel leaf spring while upholding its strength. This study seeks to address, improving load-carrying capacity, and designing less stressed and lightweight mono composite leaf spring. In this study, 60% fiber volume fraction and 40% matrix volume fraction are taken. In present work total deflection and equivalent von-misses stresses induced in the different kinds of mono composite leaf spring are compared with total deflection and equivalent von-misses stresses of conventional structural steel leaf spring. For analysis purposes, Ansys workbench 19.2 is used and for modeling of composite leaf spring, NX 10 (Unigraphics) is used. Finally, from the static analysis results, it has been observed that the newly designed composite leaf spring made of Carbon/Epoxy (Non-Laminated) has better performance than the existing conventional structural steel leaf spring.
Design and Stability analysis of CNTFET based SRAM cell
Authors: Devi Meenakshi , Madhu Charu , Garg Nidhi , Singh Sarvjit , Singh Preeti
Published: January 2021

Carbon Nanotube Field Effect Transistor (CNTFET) has proved to be very beneficial for VLSI circuit designs in the nano scale range due to its amazing properties than MOSFETs. As we reduce the gate length of the device to below 45nm, we see a lot of changes in its parameters such as stability of the cell reduces, power consumption and delay increases which are different from the traditional MOSFETs. This becomes a serious issue when we try to take traditional MOSFETs scale down from this technology node. The main aim of this paper is to design CNTFET 6T SRAM memory cell which consumes less power and is highly stable at 32nm technology node. The Stanford model files have proved to be very good for the CNTFET devices, which simulates on 32 nm technology nodes in HSPICE tool. The results shown in this paper clearly indicate that the stability enhances by approx. 27.55% of the CNTFET SRAM cell with 37.44% improvement in the power consumption. Explicit analysis of the results shows that CNTFET based 6T SRAM cell has improved power consumption, less delay and high stability with improved read & write noise margin than conventional 6T SRAM cell.
Complex variable solution for mode-III quadratically varying PS model in piezoelectric media
Authors: Singh Sandeep , Sharma Kuldeep
Published: January 2021

Complex variable technique and extended Stroh formalism approach are applied to develop the closed-form solutions for mode-III quadratically varying polarization saturation (PS) model in an infinite piezoelectric media. A semipermeable centre crack problem is considered for study under the influence of out of plane far-field mechanical loading and in-plane electrical displacement loading. Similar to PS model, the electrical yielding zones or saturated zones are considered just infront of the crack-tips in the form of a strip. But in place of constant PS condition imposed on yielding zones, the quadratically varying PS condition is considered for study. Mathematically, this problem reduces into simultaneous non-homogeneous Riemann-Hilbert problems which are solved by finding the solutions of involved singular integrals. Hence, some standard fracture parameters are derived in explicit forms such as saturated zone lengths, crack sliding displacement, crack potential drop and local stress intensity factor. Also, the comparative studies for quadratically varying PS model and PS model are presented graphically.
Design and Implementation of an Asymmetric Cascaded H-bridge Fifteen Level Inverter with Minimum Number of Switches for Smart Grid Applications
Authors: Gaur Parul , Verma Yajvender Pal , Singh Preeti
Published: January 2021

Multilevel inverters are nowadays getting more and more attention in the industrial world due to the attractive features offered by the multilevel inverters. However, usage of more semiconductor switches in the higher levels of these inverters poses a restriction to its wider applications in the industries. Therefore, a novel fifteen level inverter of cascaded H-bridge topology is being designed and implemented, that incorporates the minimum number of switches, thus confirms the reduction in size, minimum switching losses and further reduction in overall cost of the multilevel inverter. The foremost concern of the suggested work is to improve the efficiency and quality of the desired voltage waveform of the multilevel inverter using the effective controlling strategies keeping harmonics at a lower level. The control methods are applied to the fifteen level inverter for further improvement in the voltage regulation and thereby lead to the better efficiency, reliability and economic improvement. The performance assessment of the implemented fifteen level inverter has been done in respect of the total harmonic distortion and switching losses and is compared with the other existing topologies. The implemented inverter is well suited for drive, renewable energy and smart grid applications.
Influence of ammonium hydrogen carbonate molar ratio on structural and morphological properties of Y2O3nanoparticles
Authors: Kumar Sushil , Tripathi Harshit , Bhardwaj Sumit , Sharma J D , Batra Uma
Published: January 2021

The co-precipitation synthesis is considered as one of the greatest wet chemical route to produce nanoparticles because of its yield and control over synthesis parameters. In this manuscript, Yttria (Y2O3) nanoparticles (YNPs) have been synthesized through direct titration precipitation process using ammonium hydrogen carbonate (AHC) as precipitant to metal ion molar ratio (M3+) in acidic medium condition. The molar ratio [R= (NH4HCO3)/(M3+)] varies from 0.35 M to 0.55 M with constant metal ion (M3+=0.1M) concentration. The influence of R-value on crystallographic structure, particle size, surface morphology of YNPs are comprehensively studied. Rietveld refined parameters confirm the formation of pure cubic yttria phase in calcined powders. The FTIR results confirm the presence of Y-O-Y and Y-O bands. The influence of R-value on the development of morphological aspects was observed using field emission scanning electron microscopy which shows pseudo spherical morphology with a particle size range of 24.63±5.6 nm to 31.46±5.1 nm. TGA/DSC results confirm the complete transformation of intermediate yttrium compounds to pure cubic Y2O3single phase at a temperature of 780°C.
Study of pure and Ag-doped TiO2 nanoparticles for photocatalytic degradation of methylene blue
Authors: Singh Arshdeep , Kumar Sandeep
Published: January 2021

Titanium dioxide (TiO2) is one of the most basic materials in our daily life that has wide applications as a whitening agent and an excellent photocatalyst material. Other noticeable applications include dye-sensitized solar cells, sunscreen and UV blocking pigments, cosmetics, paint, paper, food additive and flavor enhancer. Metal doping enhances the photocatalytic activity of nanoparticles. Therefore, we have prepared pure and Ag-doped TiO2 nanoparticles using Ti-(IV)-isopropoxide as precursor. The resulting materials were characterized by x-ray diffraction (XRD) and UV-Visible spectroscopy. The XRD results showed the different structural phases and crystallite size of the nanoparticles. The band gap of the photocatalysts decreased by subsequent addition of the dopant. Further, the photocatalytic degradation of methylene blue (MB) was carried out for both pure and Ag doped TiO2 nanoparticles under sunlight upto 90 minutes. The degradation of MB dye was observed to be directly related to the radiation time.
Comparative Study of Gold Nanoparticles Synthesized via Wet Chemical and Green Chemistry approach
Authors: Rattan Sonal , Leal Anjali , Sharma Mamta , Kumar Suresh , Goswamy J K
Published: January 2021

Gold nanoparticles (Au NPs) undergo a huge research exposure owing to their extraordinary properties and potential applications. Herein, we report a comparative study between Au NPs synthesized via wet chemical method (reduction using sodium citrate) and green chemistry (reduction using vigna radiata (green grams)). The prepared Au NPs were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray Spectroscopy (EDS). UV-Visible spectrum of Au nanoparticles showed a peak around 534 nm in both the cases. Zeta Potential (ZP) values were 3.62 mV and -2.80 mV of Au nanoparticles prepared via wet chemical method and green chemistry approach respectively.
Structural studies of zirconia and yttria doped zirconia for analysing it phase stabilization criteria
Authors: Kumar Ankit , Kumar Pravin , Dhaliwal A S
Published: January 2021

In this work, the target of zirconia with 2-inch diameter is prepared from the powder form having a particle size 5 µm by giving 4 tonnes of pressure in the hydraulic press. The prepared target is sintered at 1000-degree Celsius for 10 hrs. Yttria-stabilized zirconia target is also obtained in a similar process. The structural properties of both targets are investigated using Ɵ-2Ɵ geometry of X-ray diffractometer system. The changes in structure are studied in doped and undoped zirconia. The structural findings are showing the transformation of phase with doping. These studies help to understand the structural properties of zirconia with and without doping for technological application.
Optical and Electrical characterization of Silver nanowire -reduced graphene oxide hybrid thin film on PET for transparent electronics
Authors: Kaur Manpreet , Twinkle  , Sharma Rahul , Anjali  , Harjot  , Mustafa Gh , Kumar Suresh , Goswamy J.K.
Published: January 2021

Graphene is an excellent nanoscale allotrope of carbon in which carbon atoms are bonded through sp2 hybridization. Graphene itself or its thin film exhibits excellent transparency to visible light. Silver nanowires are also being used for making transparent electrodes. Herein, we prepared a thin film of reduced graphene oxide and silver nanowires on flexible PET (polyethylene terephthalate) substrate. Characterization of graphene oxide/reduced graphene oxide has been carried out through X-ray diffractometry, FTIR (Fourier transformed infrared spectroscopy). Ultraviolet-visible spectroscopy and I-V measurements demonstrated high conductivity and transmittance of the above prepared film.
Fabrication and Characterization of Gaseous Detector for the identification of High Energy Particles.
Authors: Babbar J. , Bansal S. , Beri S.B. , Bhatnagar V. , Chauhan S. , Gupta R. , Kaur A. , Kaur H. , Kumar S. , Kumari P. , Meena M. , Singh J.B. , Virdi A.K.
Published: January 2021

There is a vast range of gases which get ionized, produce electron-ion pairs, on the passage of high energy charged particles. Such gases are extensively used in experiments such as LHC, Belle-II, RHIC, DAFNE, etc which produce high energy particles. Panjab University established a detector assembly and characterization laboratory dedicated to gaseous detectors such as Resistive Plate Chamber (RPC) and Gas Electron Multiplier (GEM) for the LHC experiment. Here, we present the recent work on the fabrication and characterizations of the GEM detector at Panjab University.
Mathematical Modeling of Elastic Plastic Transitional Stresses in CNT-GS based Hybrid Nanocomposite Thin Walled Spherical Pressure Vessels
Authors: Shahi Shivdev , Singh Satya Bir , Kumar Pushwinder
Published: January 2021

In this paper, an analytical solution is being provided for calculation of elastic plastic transitional stresses in Hybrid Nanocomposite made of Carbon Nano Tubes (CNT) and Graphene Sheets (GS) modeled in the form of thin walled Spherical shells, subjected to radial compression at the internal surface. The results are compared with a general use Carbon Nano Tubes based nanocomposite. The transition function given by Seth is being used to obtain the pressure at which the initial yielding takes place. The trends for radial and circumferential transitional stresses are obtained using the elastic stiffness constants obtained from young’s moduli, shear moduli and poisson’s ratios of the materials at the initial yielding and fully plastic state. The expressions for principal stresses are derived from the transition function considering the material anisotropy.
Comparative analysis of hydromagnetic stability of rotating nanofluid layer in two different boundaries with local thermal non-equilibrium effect
Authors: Ahuja J
Published: January 2021

Present article investigates the hydromagnetic stability of a rotating nanofluid layer with in two configurations of nanoparticles: (a) top heavy nanoparticle configuration and (b) zero nanoparticle flux across the boundaries. The fluid and particle phases are supposed to be thermally non-equilibrium. Thermally non-equilibrium phases of the system added three more parameters: Nield number, ratio of thermal capacities of fluid and particles and ratio of thermal diffusivity of fluid and particles in the conservation equations for nanofluid convection. Influence of these parameters along with other parameters is analysed using the method of superposition of basic modes and interpreted graphically using the software Mathematica. Taylor number and Chandrasekhar number make the system more stable while the thermally non-equilibrium phases make the system unstable in both the configuration of nanoparticles. Also, thermal instability of nanofluids is compared with in two configurations of nanoparticles: top heavy and zero nanoparticle flux configuration and a better conclusion is drawn.
Effect of anisotropy on creep of rotating functionally graded disc with varying thickness
Authors: Bose Tania , Chamoli Neeraj , Rattan Minto , Gupta Kunjan
Published: January 2021

Creep study of rotating functionally graded (FGM) disc reinforced with non-linear SiC
p
with varying thickness has been analyzed using Hills yield criterion. The disc comprises of matrix of pure aluminium embedded with silicon carbide particles (SiC
p
). The analysis of stresses and strains as a result of disc rotation have been calculated. Stresses and strain rates are significantly affected by varying reinforcement gradient in the disc. The FGM disc having varying thickness along the radius shows lowest strain rates for anisotropy constant G/F and H/F less than 1 which further reduces with increase in particle gradient. Thus, better design of turbine discs can be obtained by selecting appropriate material anisotropy and optimum disc profile.
Performance Analysis on Effect of Variation in Oxide Material of Double Gate Tunnel Field Effect Transistor
Authors: Bhatia Rajeev , Gill S.S.
Published: January 2021

In this paper structure of Double Gate Tunnel Field Effect Transistor work to increase the efficiency of the device performance of Tunnel Field Effect Transistors making it one of the potential candidates for small scale devices. The essential point of this research work is to consider the performance analysis of the structure. This work is accomplished with the assistance of tool Cogenda TCAD version 1.9.2. The designing of the device, simulation and correlation of results have been gotten on this tool. The section gives the stream of Research Methodology and clarifies the footsteps for Design and Simulation of Double Gate Tunnel Field Effect Transistor.
Investigation of Surface Roughness and Tool wear during turning of Titanium Alloy Grade 5 (Ti-6Al-4V) by using coated carbide tool and optimization of process parameters
Authors: Kumar Ajay , Sehrawat Gaurav
Published: January 2021

The paper presents an experimental investigation to analyze the effects of process parameters on the surface roughness & tool wear in dry machining of Ti-6Al-4V. The process variable used are tool noise radius, feed rate & cutting speed to study their effect on surface roughness and tool wear using coated carbide as cutting tool. The surface roughness of the specimen has been measured with the help stylus-type Profilometer, Surfcom Flex 50A. The tool wear of cutting inserts is analysis by SEM analysis. The results show that the feed rate and nose radius are the significant variable for surface roughness. Surface roughness increases considerably with the increase in feed rate & tool wear and as the nose radius of cutting tool increases, the value of tool wear decreases. The process parameters are optimized for surface roughness.
Formulation of the butt joints of aluminum composite using friction stir welding and study of their mechanical properties
Authors: Chauhan Abhishek , Kumar Sanjeev
Published: January 2021

In this study, experiments were performed on the vertical milling machine to formulate butt joints of aluminum matrix composites (AMCs) having 5 vol% SiC as particulate using friction stir welding technique. Joints prepared were tested to find their mechanical properties using different testing methods. The butt joints were formed from the plates of Al-SiC composite plates. Alloy steel tool hardened at a temperature of 850°C was used to obtain welded joints. Three different pin shapes were used to do welding at three different tool rotations ranging from 600-1200 rpm based upon pilot experimentation. Tensile tests were done on the universal testing machine to find yield strength and ultimate strength. Hardness of the welded joint is also calculated using the vickers hardness test. The joints prepared using non tapered pin shape had better tensile properties as compared to other pin shapes. Good mechanical properties were obtained at 1200 rpm tool rotation. The hardness of the welded joint also got improved when welded at 1200 rpm using non tapered pin shape. The microstructure results also verified that refinement of grains takes place at higher tool rotations which improved mechanical properties.
The Comprehensive Review on machining of Inconel 718 superalloy
Authors: Shard Abhinav , Deepshikha  , Gupta Vishal , Garg M P
Published: January 2021

Inconel 718 is nickel based alloy, difficult to machine and precipitate which having tremendous mechanical properties. It has outstanding features like high shear strength, low thermal conductivity, potential to sustain its strength and hardness at prominent temperature. It plays a crucial role in various manufacturing applications for instance aircraft, defence, aviation and gas turbines. Numerous efforts have been to produce to the workability of Inconel 718 indifferent operating conditions; different tool electrodes and tool geometry. The main objectives which are focused in this review study are drilling, milling and turning. Finally, a brief idea of non-traditional cutting fluid over traditional cutting fluid is also discussed.
Electrochemical discharge machining process, variants and hybridization: A review
Authors: Saini Gaurav , Kumar Amresh , Mohal Sachin , Kumar Rajender , Chauhan Abhishek
Published: January 2021

Electrochemical discharge machining has been proven to fabricate micro holes, micro-channels and three dimensional shapes on difficult to machine non conductive materials very efficiently. Researchers have proposed some modification in the basic configuration of the ECDM process to increase the efficiency. These modifications results in the development of ECDM variants. Further improvement in the process researchers hybridized the ECDM process. In this review article different areas of electrochemical discharge machining has been focused, which includes sparking phenomena, variants and recent hybridization. Furthermore, the article provides the knowledge to understand the research potential of an ECDM process.
Evaluation and Analysis of Different Spectrum Slicing Techniques in Free Space Optical Systems
Authors: Jindal Jitesh , Kumar Arvind , Kumar Raj
Published: January 2021

Free space optical communication systems are competent in the context of supporting high data rate, license free operation, absence of Electromagnetic interference (EMI), cost effective operation etc. Wavelength division multiplexed systems (WDM) provide high capacity but at the cost of multiple number of laser sources which inturn increase the overall cost of the system. Spectrum slicing is emerged as an optimal method to reduce the cost of the multi channel systems and also increase the performance. In this work, different spectrum slicing techniques such as Light emitting diodes (LEDs), Arrayed waveguide grating (AWG), Highly nonlinear fiber (HNLF), and Semiconductor optical amplifier (SOA) are used and compared in terms of Q factor and BER at 5 Gbps. It is perceived that SOA provide best performance followed by HNLF and LED is least performing.
Comparative Study of Optimization of Plate Fin Heat Exchanger and Pressure Vessel Design using mTLBO Algorithm
Authors: Pendse A S , Kamble A G
Published: January 2021

Teaching Learning Based Optimization (TLBO) algorithm has been proved beneficial in many engineering applications. This algorithm is free from any algorithm specific parameters and can be adapted to all types of design problems. However, there are some drawbacks like convergence to local optimal solution, large computational time and slow convergence rate for complex functions. Some modifications were introduced to overcome these drawbacks in modified Teaching Learning Based Optimization (mTLBO) algorithm. In this paper mTLBO has been applied to optimize plate fin heat exchanger and pressure vessel design. The performance of mTLBO algorithm was compared with original algorithm and other population based techniques such as Particle Swarm Optimization, Generic Algorithm and Artificial Bee Colony. It was found that mTLBO gives the least value of entropy generation units that is 7.22% less than the value obtained using TLBO. Also cost of pressure vessel design using mTLBO is 3.2% lower than that of TLBO design.
Rayleigh waves propagation in orthotropic solids with two temperature in context of thermoelasticity
Authors: Singh Mandeep , Kumari Sangeeta , Sonu
Published: January 2021

The main objective of this paper is to study Rayleigh wave propagation in homogeneous orthotropic half space with two temperature in reference to Three Phase Lag(TPL) model of thermoelasticity. The surface wave solutions are obtained for governing equations of Rayleigh wave. The relevant boundary condition satisfy the solutions and corresponding frequency equation is derived for the Rayleigh wave in orthotropic half-space. A simulation study is conduced for numerical discussion and the results are demonstrated graphically for phase velocity and attenuation coefficient with respect to frequency in the context of Green-Nagdhi, Lord-Shulman and three phase lag models of thermoelasticity.
Probing thermoelectric properties of high potential Ca3PbO: An Ab Initio Study
Authors: Kaur Tavneet , Sinha M. M.
Published: January 2021

The fascinating electron transport properties of anti-perovskites have gathered incredible research consideration. In the search for novel thermoelectric materials, a Density Functional Theory (DFT) based computational assessment of electron transport properties of Ca3PbO has been made based on the grounds of Boltzmann transport theory. The variation of transport properties specifically Seeback coefficient (S), electrical conductivity (σ), electronic thermal conductivity (κe) and power factor (PF) versus chemical potential (µ) have been plotted at 300 K, 600 K and 800 K. The present study proposes Ca3PbO to be an excellent n-type high temperature thermoelectric material. The optimized values of equilibrium structural parameters have been determined. The current analysis tends to stimulate experimental work towards designing and improving thermoelectric performance of Ca3PbO for realistic applications.
Influence of Heat Source on Thermal Behaviour of Solid Cylinder.
Authors: Shinde A K , Navlekar A A , Ghadle K P
Published: January 2021

The present manuscript deals with determination of influence of internal heat source on thermal behaviour of a long solid cylinder. A direct, steady state, nonhomogeneous boundary value problem with internal heat generation is formulated to analyse heat transfer and thermal stresses. The cylindrical surface heat source situated in annular region of long cylinder results in internal heat generation. Finite Hankel transform, Goodier’s thermoelastic displacement potential and Michell function are adopted to obtain the analytical solution. The outcomes are represented in the form of infinite series comprising Bessel’s functions. By considering a mathematical model for steel plate, outcomes are verified numerically. Some numerical results for the temperature distribution, displacement components, and the associated stresses are shown in figures drawn using Matlab software.
Negative effect of zinc compounds on hydration kinetics of ordinary Portland cement
Authors: Matejka L , Siler P , Novotny R , Svec J , Masilko J , Soukal F
Published: January 2021

Metals and metal containing compounds have significant effect on cement hydration mechanism and kinetics. The recycling of waste materials leads to increase of content of metals in various industrial products and visibly affects properties of the Portland cement. One of the metals that has been known to drastically increase the setting time is zinc. Zinc forms various hydroxyl species with calcium cations. Pore solution thus has lowered concentration of calcium which suppresses formation of portlandite. Due to insufficient concentration of calcium the formation of CSH gel and further hydration of clinker grains is inhibited The aim of this study is to quantify the negative effects of zinc at different concentrations at ambient temperature at 20°C. Isoperibolic calorimetry was used to measure the negative effects of zinc on hydration kinetics of ordinary Portland cement. Zinc was added to the cement in the form of two soluble salts Zn(NO3)2 hydrate, ZnCl2 and a poorly soluble compound ZnO. The concentration of zinc added was chosen between 0.1 and 1 wt. % of clinker. Significant retardation of cement hydration with increasing zinc content was proven.
Characterization of fillers made of natural stones as a cement substitute
Authors: Musil L , Cibulka T , Vodicka J , Chylik R
Published: January 2021

The article deals with the classification of fillers according to the type and method of rock processing and their use as a partial cement replacement in the concrete mixture. The aim is to better classify fillers by their origin, maximise their usability and design a concrete mixture with effective use of filler as a cement replacement.

The article compares the fillers that originated from natural stone. The research is focused primarily on the granite filler, as it is not currently explored in detail. As the results of existing research differ, tests of the filler and its effect on the compressive strength of cement composites were performed, for better characterization of the effect of filler pozzolanic activity. The results of the tests are compared with each other, and the probable causes of differences in the individual research results are described.
Effects of elevated temperature on the behaviour of concrete beams reinforced with fiber reinforced polymers
Authors: Prokeš J , Rozsypalová I , Girgle F , Daněk P , Štěpánek P
Published: January 2021

Fiber reinforced polymer (FRP) rebars have increasing popularity in the construction industry all around the world although steel rebars are widely used for reinforcing of the concrete so far. FRP bars, which have higher tensile strength compared to steel rebars with the same nominal diameter under normal conditions, are composed of resin matrix and fibers. In this paper, the load-bearing capacity of FRP reinforced concrete after elevated temperature exposition are present. The results are compared with concrete sample with steel reinforcement. Commercially produced glass FRP (GFRP) and carbon FRP (CFRP) rebars with sand coatings surface treatments were implemented in concrete beam and subjected to four-point bending load. The residual flexural strength of reinforced concrete after heating to 1000°C was obtained and evaluated and compared to results of non-heated elements. The results indicate that fire resistance of FRP reinforced beams can reach at least 60 minutes according the standard ČSN EN 13501-2.
Comparison of structure and properties of gypsum mortars with different types of aggregates
Authors: Dolezelova M , Krejsova J , Scheinherrova L , Vimmrova A
Published: January 2021

Gypsum is one of the most environmentally friendly building materials and therefore its importance increases nowadays. Since the gypsum is mostly used in the form of the paste, the influence of aggregates on properties of gypsum mortars is not investigated very often. The article deals with the structure and properties of gypsum mortars with two different aggregates (silica sand and basalt). It was found, that even if the chemical composition and shape of particles of both aggregates differs significantly, the structure and properties of gypsum mortars with both types of aggregates are similar and the properties of the gypsum composite depends more on the aggregate granulometry and the quality of its surface. The aggregate with rougher surface of particles has more distinct interfacial transition zone, higher porosity and higher compressive strength.
HPC cement materials prepared by mixing under reduced pressure
Authors: Vojtisek J , Novotny R , Bartonickova E , Hruby P , Marko M , Janca M
Published: January 2021

This article deals with HPC (High Performance composite) materials whose main advantages are increased mechanical properties, durability and stability. The limiting parameter for such materials is the presence of air bubbles that cannot be removed just by the compacting. Mixing of cement mixtures under reduced pressure can be used to reduce porosity and eliminate the presence of air bubbles. Moreover, it is associated by the improvement of the mechanical properties. The influence of preparation of HPC by mixing under the atmospheric pressure and by mixing under reduced pressure to parameters like mechanical properties, porosity, microstructure was studied in this paper. The porosity of the samples was analysed in a cross-section using an optical method. The effect of the reduced pressure on the resulting strength of the samples was observed.
The influence of alkaline activator on immobilization of metals in alkali-activated blast furnace slag
Authors: Bystrianska E , Koplik J
Published: January 2021

In this work the influence of alkaline activator on immobilization of lead and copper in alkali-activated blast furnace slag was investigated. A total of five alkali activators were used; sodium waterglass, potassium waterglass, sodium hydroxide, potassium hydroxide and sodium carbonate. The leaching test according to ČSN EN 12457°-4 was used to evaluate the level of immobilization of heavy metals, the leached solutions were analyzed by ICP-OES. For a better understanding of immobilization process, the selected samples were characterized by analytical methods (SEM, XPS). It was found that the degree of immobilization of Pb2+ and Cu2+ in AAS was very high regardless of the type of alkaline activator used. The high degree of immobilization is caused by formation of insoluble or poorly soluble lead and copper compounds in an alkaline environment while the insoluble compounds have been confirmed by SEM and XPS.
Study of calcium-silicate composite lightened by waste expanded perlite
Authors: Sebestova P , Cerny V , Drochytka R
Published: January 2021

The term calcium-silicate composite can be recalled several basic building materials. The most common representatives are lime-silicate bricks and autoclaved aerated concrete. It is any material based on the reaction of lime and siliceous raw material. In this paper, attention is paid to composites based on autoclaved aerated concrete production technology. Possibilities of lightening the composite utilizing waste expanded perlite as a secondary raw material were investigated without the use of aluminium powder, which is commonly used in aerated concrete technology. Replacements of 10%, 30%, 50%, and 100% waste expanded perlite for sand were used. Based on physico-mechanical properties, and with the assessment of the microstructure, it has been found that up to 50% of the replacement of waste expanded perlite results in a lightening of the composite while increasing the compressive strength.
Utilization of flue dust arising from metakaolin production for alkali-activated materials preparation
Authors: Kubatova D , Nespor B , Kukletova I , Cechmanek R
Published: January 2021

This paper assesses the feasibility of using flue dust, which is a residue from metakaolin manufacturing in a rotary kiln as a raw material for production of alkali-activated materials. This material contains besides metakaolin also residues of clays, and mullite. Metakaolin and blast furnace slag were used as initial materials. Flue dust was used for the replacement of initial materials up to 100%. Mortars were prepared for the determination of compressive strength by adding sand at the weight ratio of 1:1. As an alkaline activator was used potassium water glass and s/w ratio was 1.25. The prepared samples were tested for physical-mechanical properties after 28, 56, 90 and 180 days. Setting time and leaching characteristic were also evaluated.
Energy-active roof system – design, development and testing
Authors: Bibora P , Cechmanek R , Leber P , Vlach L
Published: January 2021

The aim of the research is a development of a new energy effective roof system, fulfilling a function of a roof covering as well as solar active element, reducing energy performance of buildings. There were designed and tested energy active roof elements, consisted of glass-fibre-reinforced-concrete carrier with integrated photovoltaic and heat-exchange layer, which ensures cooling of photovoltaic elements as well as enables a transfer of excessive thermal energy into a storage tank for a later use. The effort of project solvers is to achieve entirely new economic efficient using solar energy by means of energy active roof covering. Current research and tests proved, that there is a possibility to create such a system using present materials and technological solutions. However, for the successful realization it is necessary to solve further technological aspects, namely mutual connection of the roof elements and prove load-bearing capacity and fire resistance of the designed system.
Mitigation possibilities of concrete pavement degradation
Authors: Grosek J , Zavrel T , Stryk J
Published: January 2021

Monolithic as well as precast Portland Cement Concrete pavement have shown a gradual increase in quantity and severity of defects and failures in recent years. Especially, the radical increase in the auto-destructive deterioration of the concrete structure, which is most often described as the expansion reaction, is alarming. The consequences may lead to extreme reduction of the lifetime of concrete on loaded or unloaded surface courses. The main causes are due to the combined effect of environmental effects (climate, chemical pollution), drainage of roads and the behaviour of the existing cement binders, provided that we do not reflect the modification of pavement structure layers. Only the impact of climate effects can be effectively reduced on the existing roads. The paper presents a summary of results obtained from the current portfolio of secondary concrete protection products. The testing was performed in terms of resistance to water infiltration and durability against the common effects of freeze/thaw and salt. The results show a dependence or independence according to the material basis when exposed to secondary protection products. Oils, silicate emulsions and a group with other material bases, so called other products, behave quite differently.
Testing methods of various materials for development of cement composites with low electrical resistance
Authors: Melichar J , Cerny V , Drochytka R , Steffan P , Dohnalek P
Published: January 2021

Our entire planet is filled by communication routes, and as a result of the evolving information technologies, their numbers will continue to grow in the future. Demand for their reliability and hence the importance of protecting related technologies from all kinds of interference is increasing as well. Therefore, it is necessary to develop new materials in order to protect these routes against negative influences of the environment such as the atmospheric discharge. The main aim of the research is to develop and verify the properties of the cement composite that can be applied in systems of protection of building structures against lightning strike and overvoltage. The first step in the development of this material was the selection of suitable feedstocks, which by their presence in the newly developed material will increase its electrical conductivity respectively reduce its electrical impedance. For this purpose, a spectrum of potential raw materials with a high content of metals and organic carbon was chosen. By means of a suitably selected set of laboratory methods which consisted of determination of specific surface, impedance and total organic carbon content (TOC), materials with the most suitable properties were selected and their parameters determined also in a cement matrix. In order to realize this goal specimens with each conducive material as filler were created with incorporated copper electrodes. Impedance has been significantly reduced compared to the reference samples. The lowest values in the tens of ohms were obtained from samples containing carbon grit 0.5–4.0. This fact proves that the tested fillers can be used in order to produce electrically conductive cement composites.
Chemical stability of innovative grouts for cast basalt elements
Authors: Zlebek T , Hodul J , Meszarosova L , Drochytka R
Published: January 2021

Newly developed tile grouts are intended mainly for environment with strong chemical loading. For this reason, chemical resistance was one of the key parameters observed. The grout for cast basalt tile was polymer based, in particular with epoxide binder and it utilized solidified hazardous wastes as fillers. It is well-known that epoxide binder has high resistance to solutions of inorganic substances. However, it is easily degraded by organic compounds. This was taken into consideration when assessed aggressive environments and their concentrations were selected. Examined substances were 60% solution of sulfuric acid, vapors of this acid (at concentration 96%) and 10% solution of acetic acid. After exposition to action of these aggressive substances, first of all the visual changes were assessed, i.e. change of color, formation of blisters, cracks, flaking or change of sheen. Then influence on microstructure, changes of bulk density and strengths of materials were observed.
Cooperation effect of indium and vanadium co-doped into bismuth-iron garnets on magnetic properties
Authors: Jiang Fan , Lan Jianghe , Wei Zhantao , You Bin , Li Jun , Li Yang , Shi Deli , Xiong Zhengwei , Zhang Pingchuan , Chen Jinsong
Published: January 2021

For achieving tunable saturation magnetization and line width, different cations were doped into the YIG-based garnets, which the standard molecular formula could be expressed as A3[Fe2−xMx](Fe3−yNy)O12. Most researchers have reported a single rule of one element doping (x or y) on its magnetic properties. However, the cooperation effect of x + y to the magnetic contribution was not clearly clarified. In this work, multi-doped bismuth-iron garnets {Bi0.84Ca2.16}[Fe2−xInx](Fe3−yVy)O12 (x = 0.72–0.14 and y = 1.24–1.38) with low saturation magnetizations (4πM
s = 200–600 Gs at 298 K) were prepared by a conventional fluxing agent method. The cooperation effect of In3+ and V5+ co-doped into bismuth-iron garnets (BIG) on their structures and magnetic properties were systematically investigated using XPS, TEM and VSM. It could be found that the total doped concentration (x + y) was decreasing regardless of the increasing V concentration (y) and decreasing In concentration (x). As-synthesized BIG presented a well single-crystal structure, and the lattice spacing was decreasing with the decrease of x + y in accompanying with the transition of dislocations from point defects to edge dislocations. Both linear increase of Curie temperature and 4πM
s with the decrease of x + y was revealed. The mechanism could be attributed that the doped non-magnetic ions could reduce the average nearest-neighbor coordination irons for oxygen ions and weaken the anti-ferromagnetic super-exchange interactions among the magnetic ions within the structure, namely dilution effect. By comparison, the total concentraions were higher than that of previous works, which the tailorable 4πM
s of ferrite was not reported. Here we revealed the controllable 4πM
s with higher total concentrations (x + y ≥ 1.52). These findings will be provided more opportunities for applications in microwave devices.
Stratification and optimal resampling for sequential Monte Carlo
Authors: Li Yichao , Wang Wenshuo , Deng Ke , Liu Jun S
Published: January 2021

Sequential Monte Carlo algorithms are widely accepted as powerful computational tools for making inference with dynamical systems. A key step in sequential Monte Carlo is resampling, which plays the role of steering the algorithm towards the future dynamics. Several strategies have been used in practice, including multinomial resampling, residual resampling, optimal resampling, stratified resampling and optimal transport resampling. In one-dimensional cases, we show that optimal transport resampling is equivalent to stratified resampling on the sorted particles, and both strategies minimize the resampling variance as well as the expected squared energy distance between the original and resampled empirical distributions. For general $d$-dimensional cases, we show that if the particles are first sorted using the Hilbert curve, the variance of stratified resampling is $O(m^{-(1+2/d)})$, an improvement over the best previously known rate of $O(m^{-(1+1/d)})$, where $m$ is the number of resampled particles. We show that this improved rate is optimal for ordered stratified resampling schemes, as conjectured in Gerber et al. (2019). We also present an almost-sure bound on the Wasserstein distance between the original and Hilbert-curve-resampled empirical distributions. In light of these results, we show that for dimension $d>1$ the mean square error of sequential quasi-Monte Carlo with $n$ particles can be $O(n^{-1-4/\{d(d+4)\}})$ if Hilbert curve resampling is used and a specific low-discrepancy set is chosen. To our knowledge, this is the first known convergence rate lower than $o(n^{-1})$.
Today in Light of Yesterday: An Exploration of Workers’ Childhood Memories in the Context of Child Protection Practice
Authors: St. Jean Sean A R , Rasmussen Brian , Gillespie Judy , Salhani Daniel
Published: January 2021

Child protection workers are routinely faced with emotionally intense work, both personally and vicariously through the traumatic narratives and experiences of parents and children. What remains largely unknown is how child protection workers’ own childhood memories might influence the manner in which they experience and are affected by those narratives. The aim of this explorative study was to use Interpretive Phenomenological Analysis as a research methodology to answer the research question, ‘In what ways do social workers experience, and make sense of, their own childhood memories in the context of their child protection practice?’ Semi-structured interviews were conducted with eight child protection workers, aiming to understand their personal and professional experiences with regard to this question. The study found a relationship between various forms of childhood adversity and the presence of negative present-day triggers when participants were faced with practice scenarios that bore similarity to those experiences. Implications with regard to child protection worker well-being, countertransference and risk decision-making are discussed.