bluuebunny/crossref_metadata_2025 huggingface dataset:
Selection of High Entropy Alloy for Solid Solution Using Multi-Criteria Decision Making Tool
Authors: Soni Vinay Kumar , Sanyal Shubhashis , Sinha Sudip Kumar
Published: August 2019

High entropy alloys (HEA’s) have found a very special place in aerospace industries due to their property of forming solid solution. In past literatures on high entropy alloys, it is established that parameters like atomic size difference (), topological parameter (Ω) and electro-negativity difference (∆) plays a vital role in deciding whether solid solution will be formed or not. Therefore, the present study deals with the selection of optimal high entropy composition based on the three parameters δ, Ω and with the help of TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution). Ranking is done for 38 HEA different compositions such that the first rank represents the HEA which is most likely to form solid solution. The study reveals that TOPSIS method can be successfully implemented to predict the formation of solid solution in HEA’s.
Numerical Modelling of Nanocomposites Using GA and FD Techniques
Authors: Kosti Siddhartha , KUNDU JITENDER
Published: August 2019

Use of nanocomposites is increasing rapidly due to their enhanced thermal and structural properties. In the present work, the numerical modelling of nanocomposites is conducted with the help of the (GA) genetic algorithm and (FD) finite difference techniques to find out a set of nanocomposites with best thermal and structural properties. The genetic algorithm is utilized to find out the best set of nanocomposites on the basis of thermal and structural properties while the finite difference technique is utilized to solve the heat conduction equation. Different nanocomposites considered in the present work are Al-B4C, Al-SiC and Al-Al2O3. The weight percentage of these nanocomposites is varied to see its effect on the nanocomposites properties. In the end, the solidification curve for all the nanocomposites is plotted and analysed. Result reveals that GA helps in identifying the best set of nanocomposites while FD technique helps in predicting the solidification curve accurately. Increment in the wt. % of nanocomposites makes the solidification curve steeper.
Microstructure Characterization in Dissimilar TIG Welds of Inconel Alloy 718 and High Strength Tensile Steel
Authors: Anuradha M. , Das Vemulapalli Chittaranjan , Venkateswarlu D. , Cheepu Muralimohan
Published: August 2019

Nickel based super alloy Inconel 718 is widely used in aerospace and power generation industries. The dissimilar joining of high strength tensile steel to Inconel 718 was joined using TIG welding. The welding current and travel speed parameters were varied to identify the suitable welding conditions for achieving highest joint strength. Microstructural characterization of the weldments were evaluated by using optical, scanning electron microscope and energy dispersive spectroscopy analysis. The fracture surfaces of the tensile tested joints were investigated under scanning electron microscope to reveal the mode of fracture and its influence on the performance of the joints. Microhardness and tensile tests were conducted to evaluate mechanical properties of the joints. The microstructure evolution revealed that the formation of precipitates at the fusion boundary between the weld zone and Inconel 718 alloy. The hardness of the fusion boundary area id higher than the base metal and fusion zone on Inconel 718 side, whereas the highest hardness obtained in heat affected zone on high tensile strength steel. The strength of the joints were failed in the weld zone along the deposition of the filler metal, which strength is similar to the joint strength. The elemental line scan analysis confirmed the formation of Nb and Ti rich precipitates in weld zone and along the fusion boundary of Inconel alloy.
Finite Element Analysis and Mechanical Behavior of 316L Stainless Steel Processed by Room Temperature Rolling
Authors: Singh Rahul , Yadav Surya Deo , Malviya Nikhil , Goel Sunkulp , Jayaganthan R. , Kumar Abhishek
Published: August 2019

The present work deals with plastic deformation of 316L austenitic stainless steel (ASS) using room temperature rolling process. After solution treatment (annealing) as-received 316L ASS has been rolled for up to 90% of thickness reduction. To investigate the effect of processing on mechanical properties microstructural study, tensile and hardness tests have been conducted. The ultimate tensile strength has been improved from 767 MPa (before deformation) to 1420 MPa (after 90% deformation), and hardness value has been increased from 208 VHN (before deformation) to 449 VHN (after 90% reduction). Magnetic measurements and XRD characterization have been performed to confirm the formation of martensitic phase. Finite element analysis have also been simulated employing DEFORM-3D software to get the insight about deformation behavior. Keywords: Room temperature rolling, Finite Element Analysis, Mechanical properties, Austenitic stainless steel.
Influence of Lung Channel Design Bipolar Plate on Performance of PEMFC Using Computational Fluid Dynamic Analysis
Authors: Badduri Srinivasa Reddy , Srinivasulu G. Naga , Rao S. Srinivasa
Published: August 2019

A 3-D computational model was developed to examine the proton exchange membrane fuel cell (PEMFC) performance using Lung channel design bipolar plate. The model was developed using ANSYS FLUENT-15.0 software and simulations were carried out at 100 % humidity conditions. The parameters such as pressure distribution, hydrogen and oxygen concentrations and proton conductivity were briefly presented. The simulation results of Lung channel are presented in the form of polarization curves. The results of a Lung channel compare with the conventional flow channel and observed that the Lung channel gives a less pressure drop, uniform distribution of reactants and high cell voltage at a particular current density. From the observation from the polarization data, the Lung channel performance was 17% higher than triple serpentine flow channel. Keywords: Humidity conditions, Simulation, Lung channel, Polarization curves, Current density.
Optimization of Process Parameters Using Surface Response Methodology for Laser Welding of Titanium Alloy
Authors: Cheepu Muralimohan , Venkateswarlu D. , Rao P. Nageswara , Kumaran S. Senthil , Srinivasan Narayanan
Published: August 2019

Laser beam welding input conditions are greatly influence the quality of the welded joints and they have significant role on the controlling of their strength and metallurgical properties. The metallurgical properties and weld bead geometry and mechanical properties of the joints determine the quality of the joints. In this study, the fusion zone width, penetration, width of the heat affected zone and strength of the titanium alloy welds were investigated using laser welding process. The surface response methodology design is carried out for the experimental design by the development of regression equations. Analysis of variance (ANOVA) was used to check the validity of the model. In order to identify the significant parameters, student’s test is conducted. The obtained results from response surface methodology were compared with the experimental results and validated.
Influence of Temperature on Impact Sensitivity of Matchhead Composition while in Contact with Different Process Materials
Authors: Sivapirakasham S.P. , Phanindra K. Harisivasri , Surianarayanan Mahadevan , Balasubramanian K.R.
Published: August 2019

This research work aims to understand the influence of temperature (upto 80°C) on the impact sensitivity of matchhead composition with various process contact materials (Steel, aluminium, brass) and to find out the critical temperature for process safety. The BAM fall hammer was modified with a heating element for the measurement of impact sensitivity. The Limiting Impact Energy (LIE) at ambient temperature condition with steel surface on the top and bottom was found to be 3.73J. The lowest critical temperature was found to be 60.14°C for the matchhead composition when it is in contact with steel, which was used as the contact material for both top and bottom.
Effect of Back Pressure on the Consolidation Behaviour of Titanium Sponge Particles Processed by ECAP
Authors: Gudimetla Kondaiah , Mohanlal Smedha , Sankuru Anil Babu , Kumar S. Ramesh , Venkatachalam Perumal , Ravisankar Balasubramanian
Published: August 2019

Titanium is a hard metal with good mechanical properties, corrosion resistant and biocompatibility which makes it have a wide range of applications (biomedical and aerospace). Severe plastic deformation (SPD) is employed to produce Ultrafine Grained (UFG) structures. UFG structures have better mechanical properties due to their compaction. Equal Channel Angular Pressing (ECAP) is adapted to produce a UFG structure in Titanium. In this process, titanium sponge powder is filled in the aluminium shell by intermediate tapping to fill the volume of the shell. The shell is then closed with an Al cap and ECAP is done with continuous back pressure at 300°C. The test specimen has undergone four passes in route BC at different back pressure (50, 100 and 150 MPa) where titanium is consolidated without any crack. Titanium showed decreased grain size and porosity with increasing backpressure. In particular, it is seen that the sample ECAPed by 100 MPa backpressure showed a relative density of about 98% with a hardness of 37 HRC. It is seen that ECAP is more economical and the product obtained by the ECAP process has better properties.
Challenges and Opportunities in ECH of Gears
Authors: RAJ ATUL , Misra J.P.
Published: August 2019

Electrochemical honing (ECH) is an encouraging technique of gear finishing because of its micro-removal characteristic. In ECH, material removes by combined effect of anodic dissolution and mechanical abrasion. It is a hybrid micro-finishing process. ECH is a productive technique of gear finishing with high accuracy and long tool life. However, the lack of comprehensive research and complex setup design prevents it from being commercialized. This paper discusses the emphatic features of electrochemical honing of gears; its prospective features and capabilities. A comparative study is executed to explore the improvement in process capability and advantages of it. The shortcomings of the process are also discussed. Some guidelines are also mentioned for future research. It helps research community to mature this process further.
Effect of Mechanical Properties and Corrosion Behaviour of Martensitic Stainless Steel 410 1.6mm Butt Welded by Plasma Arc Welding
Authors: Sree Arravind M. , Kumar S. Ramesh , Kumaran S. Senthil , Venkateswarlu D.
Published: August 2019

Plasma Arc Welding (PAW) is one of the important arc welding processes used in electronics, medical, automotive and aerospace industries due its high accuracy and ability of welding any hard materials which is more tolerant to joint misalignment than Laser Beam Welding (LBW) at a lower cost. Thickness of 1.6mm plates were used to obtain full penetration and a strong joint with a very narrow Heat Affected Zone. The present study deals with the effect of mechanical and corrosion resistance properties of butt welded 1.6 mm thick martensitic stainless steel-similar (SS410 and SS410) joints made by plasma arc welding technique. Similar butt Welded joints were analyzed by using mechanical (Bend test, Erichsen cup test, Tensile test) characterization methods. Their corresponding corrosion resistance properties were also investigated by potentiodynamic polarization corrosion testing technique. The tensile strength was found to be 341 MPa for similar SS410 weld. During tensile test the failure occurred on the base metal on both similar joints Keywords: SS304; SS410; PAW; Butt weld; Erichsen Cup Test; Microstructure.
Analysis of Dimensional Accuracy (Over Cut) and Surface Quality (Roughness) in Electrical Discharge Machining of Inconel-718 Alloy
Authors: Kumar Rakesh , Pandey Anand , Sharma Pooja
Published: August 2019

Inconel-718 is a nickel based super alloy (difficult-to-cut material) used in aerospace industry. Analysis of machining performances viz. Over Cut (OC) & Surface Roughness (SR) for Inconel-718 through rotary Cu-pin tool electrode have been carried out. Peak current (Ip), pulse-on time (Ton), tool rotation (Nt) & hole depth (h) were used as input factors in Electrical Discharge Drilling (EDD) of Inconel-718 work-piece. Effect of input parameters on performance characteristics like OC & SR were found by Taguchi’s L9 (34) orthogonal array. It is reveals that Ip & h are most affecting factors that affects OC & SR. The Scanning Electron Microscope image was used to measure diameter of hole on work-piece after machining.
Effects of Wire-EDM Machining Variables on Surface Roughness of D2 Steel Material
Authors: Rudrapati Ramesh , Rathod Lakhan
Published: August 2019

Newly developed D2 steel is widely used for various advanced engineering applications. Machining of D2 steel to obtain desired quality responses has immense importance for the effective utilization of these materials for advanced industrial applications like aerospace, marine, automobile, etc. Wire electrical discharge machining (WEDM) is used to machine difficult to machine materials and to produce sophisticated features with better dimensional accuracy. Obtaining the fine surface roughness in WEDM has highly depends on correct selection of process parameters. In the present work, experimental investigation was planned to study the effects of WEDM input parameters on surface roughness (Ra) of D2 steel. Experimental runs were conducted by using L16 orthogonal array of Taguchi method. The analysis of variance was employed to determine the influences of process parameters on Ra. Response surface methodology (RSM) and cuckoo search optimization (CSO) algorithm had been used to model and optimize the surface roughness. From the study, it was found that Ra value had improved as compared to initial experimental runs.
Analysis and Optimization of Wire EDM Process of Titanium by Using GRA Methodology
Authors: Sahoo Sarat Kumar , Bara A. , Sahu A.K. , Mahapatra S.S. , Kiran D.S. , Teja G.S. , Teja E.S. , Reddy S.P.
Published: August 2019

In this research work, an efficient optimization technique, grey relational analysis (GRA) has been used to for optimization of wire electrical discharge machining process of Titanium (grade 2) by considering multiple output parameters. This technique combines Taguchi’s orthogonal array with grey relational analysis for the design of the experiment. The central focus of this research is to achieve improved Kerf width, surface roughness and cutting speed. GRA method is implemented to decide the best input parameter that optimizes the output parameters. This study has been conducted by applying Taguchi’s L9 orthogonal array. Each experiment has been conducted in altered conditions of input variables. For the optimization of multiple criteria, GRA is suggested as a suitable technique for the optimization of complex interrelationships between multi-performance characteristics. By analysis of variance (ANOVA) it is found that the percentage of contribution of peak current on overall performance is maximum i.e.73.1%.
Formability Analyses on Single Point Incremental Sheet Forming Process on Aluminum 1050
Authors: Desalegn Dawit , Ramulu P. Janaki , Hailu Dagmawi , Kumaran S. Senthil , Velmurugan P. , Venkateswarlu D.
Published: August 2019

In recent years, there is a lot of demand on metal forming processes in which sheet metal forming process has lots of applications in the automotive and aerospace industries. In sheet metal forming operations, incremental forming is an emerging technology in which, single point incremental forming (SPIF) process is die-less in incremental forming process and providing a competitive alternative to economical and effective in fabricating low volume products. The objective of this work is to analyze the forming analysis on truncated pyramid product by avoiding cracking and maintaining the optimum forming conditions. The formability is analyzed by using ABAQUS software and simulation, different process parameters were varied such as sheet thickness, tool diameter, step depth, spindle rotational speed on aluminum AA1050 alloy. From the simulation results, stress stain and stain distribution were evaluated on the deformed sheet. The product produced is truncated pyramid dimension having square base of side and fillet at corner.
Evaluation of Microstructure and Mechanical Properties for Friction Stir Welding of Aluminium HE-30 Plates
Authors: Revelly Ajay Kumar , Rajkumar B. , Swapna V.
Published: August 2019

The main aim of the present topic is friction stir welding (FSW) of Aluminium HE-30, which shows that improved microstructures, strong weld and with less of defects. In the other hand, an attempt was made to correlate the welding parameters and mechanical properties. In the present investigation four rotational speeds of 1000 rpm, 1200 rpm, 1400 rpm and 1600 rpm with travelling speed of 30 mm/min. and tool geometry (straight cylindrical) was chosen. It was observed that the tool rotational speed is a sensitive parameter to decide the ultimate tensile strength and yield strength of the present material. Similarly, the hardness of Al plates is improved at the weld zone. Hence, it is suggested that to consider a parameter such as welding tool rotational speed, travelling speed and materials in selecting the welding methods of sound joints, because it influences the microstructure and mechanical properties in various applications. In the present study, non-destructive tests are also confirmed the defective nature of the weld zone of Al plates.
Tribological and Morphological Evaluation of Ni-P and Ni-P/D Coatings
Authors: Ramakrishnan Bijoy , Venkat Kiran K. Uday , Rangari Pranit , Prajapati Anuj , Firdouz Zuveria , Jugunta Tathwika , Kumar B. Uday , Srivastav Ajeet , Sunil B. Ratna , Dumpala Ravikumar
Published: August 2019

The tribological characteristics of Electroless Ni-P and Ni-P/D (diamond) coatings were studied and analysed against AISI 52100 steel ball under dry reciprocating sliding conditions. Low and High Phosphorus Ni-P alloy coatings were deposited on steel substrate by Electroless deposition technique. Diamond particles were successfully reinforced into Ni-P matrix to produce Ni-P/D composite coatings. All coatings were subjected to heat treatment at 400°. The micro-hardness, surface features and elemental composition of the coatings was analysed. The surface morphology of Ni-P and Ni-P/D coatings is detailed. Presence of dia mond particles in Ni-P matrix was confirmed by EDS analysis. Dry sliding wear tests showed a significant enhancement in wear resistance of Ni-P/D composite coatings compared to Ni-P coatings. Experimental results indicate that combined effect of diamond particles reinforcement and heat treatment play a crucial role in modifying the surface characteristics and tribological performance of the Ni-P coatings.
Investigation of the Impact of Cutting Parameters on Surface Integrity in the End Milling of Inconel 625
Authors: Rajguru Ramesh , Vasudevan Hari
Published: August 2019

Nickel based super alloys, such as Inconel 625 is amongst the most difficult to machine, due to its low thermal conductivity and high strength at higher temperature. Although, they are used in aerospace exhaust systems and other applications, the strain hardening that results during the machining operation, which adversely affects surface integrity of machined surface of such materials especially in extensive applications, is a cause for concern. In this context, this study was carried out, involving the milling operation, using solid carbide tools coated with TiAlSiN, under specifically developed conditions for dry machining of the difficult to cut materials. The cutting parameters were 4 in number, namely radial rake angle, feed per tooth, cutting speed and radial depth of cut and the response parameters included surface integrity characteristics, such as residual stresses, surface roughness and micro-hardness. Based on the experimental analyses, it was found that the micro-hardness of machined surface was higher. Micro hardness of sub surface decreases with the depth (50,100,150,250μm) due to a reduction in the work hardening of the Inconel 625, underneath the surface layer. The residual stresses were analyzed using main effect plot, and it was seen that the residual stresses were significantly influenced by the radial rake angle, followed by feed per tooth.
Optimization of Injection Moulding Process Parameters for Manufacturing Plastic Components (PBT) Using Taguchi Method (TM)
Authors: Khavekar Rajendra , Vasudevan Hari , Vimal Gosar
Published: August 2019

In this Paper, the application of Taguchi Method (TM) on the process parameters of Injection Moulding of Polybutylene Terephthalate (PBT) is presented. The influence of process parameters, such as Injection Pressure, Suckback Pressure, Injection Time, Cooling Time, Zone 1 Temperature & Zone 2 Temperature (Barrel Temperatures) on Dark Spots and Short Shots (defects) were investigated using the Orthogonal Array L16 of Taguchi Method for 6 factors at 2 levels each with the response being percent defectives. It was found that Injection Pressure, Injection Time & Zone 1 Temperature had a major effect on the response. After the application of Taguchi Method, the rejection rate dropped down to 5.84% from 11.33%, which is a 48.45% reduction.
Mechanical and Abrasive Wear Behaviour of Waste Silk Fiber Reinforced Epoxy Biocomposites Using Taguchi Method
Authors: Darshan S.M. , Suresha Bheemappa
Published: August 2019

The aim of this research article is to study the static mechanical properties and abrasive wear behavior of epoxy biocomposites reinforced with different weight percentage of waste silk fibers. The effect of parameters such as velocity (A), load (B), fiber loading (C) and abrading distance (D) on abrasive wear has been considered using Taguchi's L25 orthogonal array. The objective is to examine parameters which significantly affect the abrasive wear of biocomposites. The addition of silk fiber has resulted in improved flexural properties of the epoxy matrix. The results of ANOVA indicated that the parameter which played a significant role was abrading distance followed by fiber loading, load and sliding velocity.
Application of Machine Learning Techniques for Multi Objective Optimization of Response Variables in Wire Cut Electro Discharge Machining Operation
Authors: Shukla Sidharth Kumar , Priyadarshini Amrita
Published: August 2019

Wire Cut Electrical Discharge Machining (WEDM) is a non-conventional thermal machining process which is capable of accurately machine alloys having high hardness or part having complex shapes that are very difficult to be machined by the conventional machining processes. The WEDM finds applications in automobiles, aero–space, medical instruments, tool and die industries, etc. The input parameters considered for WEDM are pulse on time, pulse off time, flushing pressure, servo voltage, wire feed rate and wire tension. Performance of WEDM is mainly assessed by output variables such as, material removal rate (MRR), kerf width (Kw) and surface roughness (Ra) of the work piece being machined. Looking at the need of a suitable optimization model, the present work explores the feasibility of machine learning concepts to predict optimum surface roughness and kerf width simultaneously by making use of experimental data available in the literature for machining of Hastelloy C– 276 using WEDM. In most of the literatures, single objective optimization has been carried out for predicting optimum cutting parameters for WEDM. Hence, the present work presents a methodology that makes use of a machine learning algorithm namely, gradient descent method as an optimization technique to optimize both surface roughness and kerf width simultaneously (multi objective optimization) and compare the results with the existing literatures. It was observed that the input parameters such as pulse on time, pulse off time, and peak current have significant effect on both surface roughness and kerf width. The gradient descent method was successfully used for predicting the optimum values of response variables.
Optimization of Welding Process Parameters in Novel Friction Stir Welding of Polyamide 66 Joints
Authors: Nandhini R. , Kumar R. Dinesh , Muthukumaran S. , Kumaran S.
Published: August 2019

The friction stir welding of polyamide 66 with a specially modified tool is studied. A variation of the conventional friction stir welding is investigated by incorporating a friction plate for the purpose of heating the polymer in the course of welding process through the tool shoulder. This in turn, improves the efficiency of the weld. The association of the welding process parameters and the weld performance has been investigated by the grey relational analysis with multi response characteristics like weld tensile strength, percent elongation and hardness. Macrostructure of the weld joint cross section has been explored by Stereo microscope. The maximum weld tensile strength of 63 MPa and a Shore hardness of 60 D at the weld nugget are obtained. The hardness profiles of the welded samples have been analyzed in this investigation.
Effect of Welding Speed on the Microstructure and Corrosion Properties of Weld and Heat Affected Zones in GTA Welded AA2014 Alloy
Authors: Shankar M.P. , Sokkalingam R. , Kosuri Bhavani , Sivaprasad Katakam , Muthupandi V.
Published: August 2019

The microstructure and corrosion properties of weld fusion zone and the heat affected zones of gas tungsten arc (GTA) welded AA2014 alloy, welded at varying speeds of 1.5mm/s, 2.5 mm/s and 3.5 mm/s were examined for gaining knowledge on the effect of welding speed on corrosion behavior at localized regions of the weldment. The macrostructure and microstructure of the welds were evaluated with optical microscope. The corrosion properties were examined with potentiodynamic polarization in aqueous 3.5% NaCl solution. The GTA welding has resulted in grain refinement fusion zone and dispersion of coarse Al2Cu phases within the grains and along the grain boundaries of heat affected zones. With increase in welding speed the grain size of AA2014 at the fusion zone reduces significantly and also the corrosion resistance of the fusion zone and heat affected zone could decrease as it shows higher negative corrosion potential.
Investigation on Machining of Hybrid Metal Matrix Composite
Authors: Bodukuri Anil Kumar , Eswaraiah Kesha , Pradeep V.
Published: August 2019

Hybrid metal matrix composites (HMMC) are advanced materials which are not simply depicting in improvement of mechanical properties but also on characteristics of machinability for thorny shapes to machine. Electric discharge machining (EDM) shows a potential technique for machining hybrid metal matrix composites. An investigation is done on hybrid metal matrix composite for response parameters like MRR, TWR by conducting a range of experiments with choosing typical process parameters such as peak current, tool lift, pulse-on time and pulse-off time.
Study on Effect of Tool Overhang on Machining Characteristics of Al 7075-T6 in Orthogonal Turning Process
Authors: Venkat Kiran K. Uday , Rodge Chetan , Dhurve Rameshwar , Jain Romil , Dumpala Ravikumar
Published: August 2019

In the present experimental study, the effect of turning tool overhang on the chip morphology and vibrations during orthogonal turning has been investigated. Orthogonal cutting (turning) setup was developed to ensure the cutting process happens in a 2-dimesional plane. Orthogonal cutting was realized by turning a circular tube with geometry of 33.88 mm external diameter and 3.5 mm wall thickness (7075-T6 Alloy). High speed steel (HSS) rod with a square cross-section (1⁄2 x 1⁄2 square inch) was used to fabricate the orthogonal turning tool with a geometry of 15 ̊ back rake angle and 9 ̊ clearance angle. The cutting experiments were conducted for different tool overhang lengths (2cm, 3cm, 4cm, 5cm & 6cm) by keeping constant cutting speed (25 m/min) and feed (0.15mm/rev). The vibrational characteristics were measured using accelerometer and Ni-DAQ card. The morphology and microstructure of the chips collected during cutting were studied under optical microscope using metallographic procedures. It was found that for increasing overhang length of cutting tool the chips serrations was found increasing. The frequency of cutting tool and amplitude of vibration was found increasing with increasing tool overhang length.
The Influence of Gas Tungsten Arc Welding Parameters on Mechanical and Microstructure Properties of the TC4 Titanium Alloy
Authors: Cheepu Muralimohan , Venkateswarlu D. , Rao P. Nageswara , Kumaran S. Senthil , Srinivasan Narayanan
Published: August 2019

In the present study, TC4 titanium alloy was gas tungsten arc welded to evaluate the mechanical and metallurgical properties of the welds. The welds were carried out at different welding conditions such as welding speed and current to identify their effect on microstructural changes and strength of the welds. The results of bead geometry measurements suggests that the fusion zone width and depth was greatly varying with the welding speed and current. It is also observed that the fusion zone microstructure and heat affected zones are greatly controlled by welding conditions. Therefore the mechanical properties of the welds were improved with the changes in welding conditions and are correlated with the metallurgical features of the welds. The optimal welding conditions were analysed using Box-Behnken design and analysis of variance technique for identifying strength of the welds and better bead geometry parameters.
Microstructural and Corrosion Studies by Immersion in 3.5% NaCl Solution on Aged Mg-9Al-1Zn-XCa Alloy
Authors: Manivannan S. , Narenthiran B. , Sivanantham A. , Babu S.P. Kumaresh
Published: August 2019

The experimatal alloys were aged at different temperatures of 180°C, 200°C, 220°C, and 240º C with calcium addition levels of (X=0.5, 1, 1.5, 2%) on Mg-6Al-1Zn-XCa alloy were investigated in 3.5% NaCl solution. All the experimatal alloys were immersed in 3.5% NaCl solutions and the resulted surface were analyzed to study the corrosion behaviour and its surface topography by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersed spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The result shows that corrosion attack occurred predominantly on ß phase and α phase exhibit relatively minor corrosion. In addition to that the increased aging temperature coarsens the intermetallic as well as α- Mg grains, which shows adverse effect to corrosion resistances and the best result were obtained at composition of 0.5wt.% Ca aged at 200°C.
Investigation of Engine–Airframe Vibration Due to Main Rotor Hub Loads Using a Substructuring Framework
Authors: Sidle Stacy , Sridharan Ananth , Chopra Inderjit , Feshler Matt , Kull Peter
Published: August 2019

This paper presents a methodology to analyze the coupled structural dynamic response of an elastic airframe and engines of a helicopter in response to main rotor hub loads. Transfer functions of individual components (airframe, engine, mount struts, and torque tube) are coupled together
using a substructuring approach to obtain consistent coupled solutions of the entire system. Using this approach, a twin-engine, four-bladed helicopter is analyzed using NASTRAN-based models of the airframe and engines. This efficient substructuring approach is validated against the fully
coupled NASTRAN model using forced response studies. Characteristics of the mount properties, i.e., the torque tube stiffness, and aft mount stiffness and damping are systematically varied to study their effect on the engine vibration response. The fore and aft mount element properties for
minimizing the 8P engine response are identified without increasing 4P response. A compromise between 4P and 8P response is also identified from parametric studies of rear mount properties, using just three parameters to represent the design space. Using the substructuring approach presented
here, future studies can be performed to rapidly match airframe characteristics with available engines at approximately 1000 times the speed of running a detailed finite element model (millions of degrees of freedom), without any reduction in accuracy.
An unusual case of Lyme borreliosis: can we miss it?
Authors: Gerqari Antigona Begolli , Ferizi Mybera , Halimi Sadije , Ponosheci Albina , Berisha Arjeta Zogaj , Gerqari Idriz
Published: August 2019

Lyme borreliosis is an infective disease that is usually transmitted to humans via biting by bacteria-infected Ixodes tick. The disease is multisystemic and the affected organs are the skin (Erythema migrans), nervous system, eyes, heart and joints. Borrelia burgdorferi is the bacterium that causes borreliosis and the hosts are rodents of the genus Apodemus. In the Balkan region, Ixodes ricinus is the most representative vector. A bite from an infected insect is the most common mode of transmitting Borrelia; however, transplacental transmission has also been documented. Pathogenesis of the disease consists of both direct and indirect mechanisms of immunological reactions which result in the production of IgM antibodies to Borrelia in the first 3-6 weeks, and production of IgG class after 6 weeks. Many skin diseases and skin symptoms mimicking Lyme borreliosis, such as dermatomycosis, erysipelas, and undefined hyperpigmentation must be elaborated and considered for borreliosis, as skin symptoms of borreliosis can imitate many of them.
Dal venire al mondo al venire alla tecnica. Il rovesciamento bioetico di Peter Sloterdijk
Authors: Della Torre Cecilia
Published: August 2019

L’origine dell’uomo è sempre stata identificata con la generazione umana: nell’epoca attuale, però, con l’introduzione delle nuove tecnologie, la riproduzione sta assumendo connotati sempre diversi, tali da comportare una vera e propria riformulazione della prospettiva antropologica legata all’ambito del “natale”. Attraverso l’analisi del pensiero di Peter Sloterdijk, si intende mostrare il ribaltamento del modello di riferimento, che invece di porre l’uomo come figlio, mira a renderlo alla stregua di un prodotto tecnico. L’indagine si sofferma specialmente sulle trasformazioni sloterdijkiane del lessico legato all’ambito della generazione con l’intento di mettere in luce come, pur utilizzando gli stessi termini madre-figlio, il loro significato ne risulti completamente stravolto. L’intento è quello di analizzare e valutare la rivoluzione antropologica di Sloterdijk, per mostrare le contraddizioni teoriche del cambio di paradigma da lui proposto.
Employees’ perceived effectiveness of the performance management system at a North-West provincial government department
Authors: Modipane Pheagane I. , Botha Petrus A. , Blom Tonja
Published: August 2019

Orientation: The implementation of the performance management system (PMS) within a specific North-West provincial government department appears to be ineffective.Research purpose: To measure employees’ perceived effectiveness of the PMS.Motivation for the study: Employees’ experiences of employee PMSs may be different from that which it intends. The motivation for this study was to quantify employees’ perceptions of PMS effectiveness.Research approach/design and method: The researchers used a quantitative research approach and collected data using self-administered e-mail questionnaires on a total population of 247 employees at a North-West provincial government department.Main findings: Utilising two measurement constructs, namely, performance management accuracy and fairness, the study revealed that employees perceived the PMS as effective. However, some deficiencies were identified. The major shortcomings related to the lack of coaching provided and manager’s non-compliance with procedural, distributive and procedural justice principles. The overall mean score of the perceived accuracy was slightly above the midpoint of the range, indicating that employees perceived PMS as accurate, and were generally satisfied with the implementation of the system. However, employees perceived the PMS as unfair.Practical/managerial implications: A perception of effective and accurate PMS does not translate into perceptions of fairness. When employees feel unfairly treated during the appraisal system, morale and performance are likely to be adversely affected. Coaching and/or training related to PMS remains imperative.Contribution/value-add: This study contributes to the body of knowledge by quantifying the perceptions of employees regarding the factors that determine the effectiveness of PMS, namely, accuracy and fairness. It contributes towards the theory and practice regarding employees’ perceived effectiveness of the PMS.
Recovery of Left Ventricular Twist and Left Ventricular Untwist Rate in Patients with ST-segment Elevation Acute Myocardial Infarction
Authors: Hristova Krasimira
Published: August 2019

Background:

Left ventricular (LV) functional recovery and morphological remodeling after acute myocardial infarction (AMI) followed by reperfusion remain incompletely understood. The aim of the study was to describe the recovery of LV twist (LVT) and LV untwist rate (LVUR) upon revascularization after AMI using two-dimensional (2D) speckle tracking.

Methods:

We evaluated 88 subjects: 22 normal volunteers (mean age 31 ± 5 years), and 66 patients with AMI (mean age 65 ± 12 years), of which 40 had an inferior AMI and 26 an anterior one. All AMI patients had ST-segment elevation. Echocardiography was performed in all subjects. Patients were scanned within 36 h (baseline) after revascularization (percutaneous coronary intervention) and after 4 months (4 mFU). Apical and basal short-axis images were acquired (frame rate 67 ± 5 frames/s) and analyzed offline to extract the rotation (rate) curves. From these, maximal systolic LVT and peak LVUR were derived. Finally, the infarct size (IS) was estimated based on magnetic resonance imaging delayed enhancement and expressed as a percentage of the total LV volume.

Results:

At 36 h, LVT and LVUR were significantly reduced in both AMI groups when compared to normals. At 4 mFU, both AMI groups showed recovery in ejection fraction (EF) and reduction in IS (7.24 ± 10.07 vs. 20.13 ± 13.9, P < 0.0001 for inferior AMI and 13.13 ± 10.3 vs. 24.40 ± 15, P < 0.0001 for anterior AMI). LVT and LVUR increased significantly but remained below normal levels. Correlation of LVT and LVUR with IS was significant, but weak (r = 0.34 and r = 0.34, respectively). In addition, a fair correlation of LVT with EF (r = 0.64) and a weak correlation of LVUR with end-diastolic volume (r = 0.43) were found.

Conclusion:

LVT and LVUR are reduced in AMI patients early after reperfusion and recover incompletely upon follow-up. Interestingly, recovery of LVT characteristics as measured with this 2D speckle tracking-based method showed to be independent of infarct location or extent. LVT and LVUR might be good parameters to monitor the recovery of global LV function after treatment.
Myocardial Contrast Echocardiography – Use in Viability Assessment and Acute Myocardial Infarction
Authors: Pradhan Jiwan , Senior Roxy
Published: August 2019

Myocardial contrast echocardiography (MCE) is now guideline-directed tool to assess myocardial perfusion both at rest and during stress. Its prognostic value has been established in the scenario of stable and unstable coronary artery disease and heart failure through assessment of myocardial ischemia, myocardial viability, coronary flow reserve, and microvascular dysfunction. We will discuss the pathophysiologic basis of MCE and its role in myocardial viability assessment both in the setting of chronic ischemic left ventricular dysfunction and acute myocardial infarction.
Stress Echocardiography in Aortic Stenosis
Authors: Burkule Nitin
Published: August 2019

In apparently asymptomatic severe aortic stenosis (AS) group, stress echocardiography objectively identifies symptomatic, high-risk AS patients requiring early aortic valve replacement (AVR). The low-flow, low-gradient AS is well-characterized clinical entity with distinct diagnostic, management, and clinical outcome challenges. A comprehensive two-dimensional transthoracic echocardiography (2D echo) and Doppler and low-dose dobutamine stress echocardiography are of paramount importance for accurate diagnosis and timely decision of AVR. However, clinicians and imaging experts should be aware of the pitfalls and inaccuracies inherent in 2D echo/Doppler measurements and the effects of pathophysiological factors which impact the stroke volume and transvalvular gradient measurements. In appropriate clinical situations, clinicians should take additional help of cardiac computational tomography, cardiac magnetic resonance imaging, and biomarkers.
Multiple mixing and parabolic divergence in smooth area-preserving flows on higher genus surfaces
Authors: Kanigowski Adam , Kułaga-Przymus Joanna , Ulcigrai Corinna
Published: August 2019

We consider typical area-preserving flows on higher genus surfaces and prove that the flow restricted to mixing minimal components is mixing of all orders, thus answering affirmatively Rokhlin’s multiple mixing question in this context. The main tool is a variation of the Ratner property originally proved by Ratner for the horocycle flow, i.e. the
switchable
Ratner property introduced by Fayad and Kanigowski for special flows over rotations. This property, which is of independent interest, provides a quantitative description of the parabolic behavior of these flows and has implications for joining classification. The main result is formulated in the language of special flows over interval exchange transformations with asymmetric logarithmic singularities. We also prove a strengthening of one of Fayad and Kanigowski’s main results, by showing that Arnold’s flows are mixing of all orders for almost every location of the singularities.
Publicaciones periódicas y vida intelectual en Nicaragua: El Mentor nicaragüense de Frutos Chamorro (1841-1842)
Authors: Ayerdis Miguel
Published: August 2019

En este ensayo se hace una aproximación a la vida cultural nicaragüense de la primera mitad del siglo XIX, en diálogo con E.B. Burns quien en Patriarcas y pueblos. El surgimiento de Nicaragua. 1798-1858, afirma que en la Nicaragua de esos primeros años de vida republicana, había una actividad intelectual digna de documentar. Sobre este aspecto, se estudia a uno de los personajes controversiales en la historia de este país, Fruto Chamorro, a partir  de su veta intelectual, principalmente en su faceta de periodista, al frente de El Mentor Nicaragüense (1841-1842). Otro aspecto que se integra al tema, es la labor de documentalista de Orlando Cuadra Downing, quien desde la Revista Conservadora del Pensamiento Centroamericano, divulgó documentos valiosos para la historia de Nicaragua.Por ello, este trabajo además de problematizar acerca de la cultura de Nicaragua en las primeras décadas del siglo XIX, hace una valoración al trabajo documental.
Costa Caribe de Nicaragua: autonomía, interculturalidad, ética y emancipación social
Authors: Álvarez Arzate María Dolores
Published: August 2019

El propósito de este ensayo es la puesta en perspectiva de la relevancia de la autonomía e interculturalidad en la resolución de problemas prácticos de la sociedad, sustentada en valores éticos humanistas, como instrumento emancipador. Nicaragua es un país que otorga reconocimiento jurídico sobre regiones geográficas compuestas por una diversidad de pueblos originarios: negros, mestizos y otras poblaciones migrantes menos numerosas. El marco jurídico, el sistema educativo, de salud tradicional ancestral y la sociedad en su conjunto, trabajan en la búsqueda del bien común, promoviendo la tolerancia, respeto, equidad, justicia e inclusión, en todos los ámbitos del desarrollo social, económico, político y cultural. El propósito es la construcción de ciudadanías autónomas e interculturales estableciendo y fortaleciendo espacios de diálogo, comunicación e interacción entre personas, comunidades y pueblos de diferentes culturas. La metodología es de tipo cualitativo y asume la Teoría Basada en Datos. En los resultados se abordan dos grandes aspectos, por un lado, el marco jurídico general y por otro, las experiencias de autonomía e interculturalidad.
Ladrones de inocencia: Análisis jurídico-doctrinal de la pederastia y el derecho penal nicaragüense
Authors: Pavón Alejandra
Published: August 2019

La pederastia se define como la acción u omisión no accidental, que priva al niño de sus derechos y su bienestar, amenazando y/o interfiriendo su desarrollo físico, psíquico, social y sexual cuyos autores pueden ser personas, instituciones o la propia sociedad. En la actualidad el fenómeno de pederastia presenta múltiples facetas que inciden de manera negativa sobre la sociedad nicaragüense, causando a su vez serias afectaciones en la psiquis y en su desarrollo comoindividuo en los menores. Uno de los propósitos que impulsaron realizar este ensayo, es problematizar a partir de la sistematización de la información relacionada al tema, e identificar patrones de comportamiento y acciones para su prevención oportuna. Un aspecto fundamental de la investigación, es la diferenciación que se debe hacer entre pederastia y pedofilia, para ello se hizo un breve análisis jurídico-doctrinal de la pederastia. Entre los aportes al tema, está el aprendizaje, la valoración y la acción que podría establecer la norma jurídica ante este tipo de conductas sexuales. En este sentido, se ha querido dar relevancia a las fuentes provenientes de especialistas en la materia y de instituciones encargadas de la protección de la niñez y adolescencia.
Dispositions for Inclusive Literacy: Fostering an Equitable and Empowering Education for Academically Diverse Learners
Authors: Valtierra Kristina M. , Siegel Lesley N.
Published: August 2019

This article offers teacher educators’ practical methods for, and shares findings from a study of, developing teachercandidate dispositions for inclusive literacy. Based on the extensive teacher disposition literature, the authors discernthat dispositions for inclusive literacy include the belief that all students have valid ways of being literate; the valueof inclusive literacy experiences for all students; and an attitude that all students should be participants in meaningfulliteracy experiences. Using a within-site case study approach, qualitative thematic analysis of three assignments usedin a literacy teaching methods course suggest that it is possible to shift narrow dispositions to broader and moreinclusive conceptualizations that support struggling readers and students with disabilities in the general educationclassroom. Conclusions suggest that dispositional development toward inclusive literacy can support teachercandidates’ implementation of inclusive literacy practices; thus, fostering an equitable and empowering education foracademically diverse learners.
What Do Teacher Candıdates Know About the Limits of the Sequences?
Authors: Tuna Abdulkadir , Biber Abdullah Cagri , Korkmaz Samet
Published: August 2019

candidates. Research is a case study in which qualitative methods are adopted. The first phase of the study wasconducted with a total of 45 teacher candidates taking the course of Analysis III. At this stage, the "Limit KnowledgeTest in Sequences", which was developed by the researchers to investigate the concept knowledge of the sequenceconcept, was used as a data collection tool. At this stage, "Limit Knowledge Test in Sequences", which wasdeveloped by researchers to investigate the limit concept knowledge in sequences of the teacher candidates, included2 open-ended problems were used as data collection tool. In the second phase of the research, individual interviewswere made with 8 teacher candidates selected from the sample to conduct in-depth research. Content analysis wasused to analyze the obtained data. As a result of the analysis of the data, significant shortcomings were found in theknowledge of the concept of the limit topic in the sequences of teacher candidates. It is seen that the candidates donot know the importance of the concept of "accumulation point", which is indispensable to convergence.