bluuebunny/crossref_metadata_2025 huggingface dataset:
A dynamic meshing technique for analysis of nonlinear sloshing in liquid tanks
Authors: Al-Zughaibi A I , Hussein E Q , Rashid F L
Published: March 2021

Fluid sloshing in tanks is a form of liquid surface motion that occurs when an external excitation is applied to a partially filled container. It is an important phenomenon, as the ensuing hydrodynamic pressure on the wall of the tank may cause the structure to fatigue and thus may destroy the tank. This work aimed to study the effects of baffles at different positions in a tank subject to sudden acceleration as part of countering such damage. An ANSYS Fluent model for three different fill levels of tank was used for transient analysis in 2D, while a multiphase model was used to track the free surface of the liquid based on Volume of Fluid (VOF) and a dynamic meshing technique was used to simulate the excitation sources via a User Defined Function (UDF) code in the C++ environment. The numerical simulation showed that the baffles significantly reduced the fluid flow in the partially filled tank, consequently influencing the sloshing pressure acting on the wall of the tank; this reduced the magnitude of sloshing in the tank by 30% and lowered the impact pressure by 21% at maximum, an important design outcome. As the level of fill increased, the pressure also increased, though the baffles limited this variation, leading to low sloshing. In general, the value of pressure inside the tank decreased with increases in the value of excitation frequency in all cases. Validation of the results is conducted by comparing the simulation data with experimental results, and good agreement between them was found, confirming the effectiveness and accuracy of the applied method.
Investigation of an integrated solar thermochemical plant for hydrogen production using high-temperature molten salt
Authors: Sadeghi S , Ghandehariun S
Published: March 2021

One of the most promising methods for producing hydrogen is the use of a water splitting process utilising the copper-chlorine (Cu-Cl) thermochemical cycle. The Cu-Cl cycle uses heat and electricity to produce hydrogen and oxygen from the decomposition of water molecules. In this paper, a new solar-powered integrated system is proposed which utilises (LiNaK)2CO3 high-temperature carbonate molten salt as both a heat transfer fluid and a thermal energy storage medium to provide the required heat for the Cu-Cl cycle reactors and heat exchangers. The system is integrated with a supercritical regenerative steam Rankine cycle (SRC) which produces the required electricity for the electrolyser unit. Thermodynamic and economic analyses were conducted to evaluate the proposed system in terms of hydrogen production cost and system performance. For the base case, the integrated system was found to be capable of producing 823.71 kg/h of hydrogen. The system is optimised for two objective parameters, overall system thermal efficiency and the levelized cost of hydrogen. The results of optimisation analysis indicated that, for the optimal Pareto solution, the overall system thermal efficiency and levelized cost of hydrogen were 29.17%, and $7.58/kg of H2, respectively.
Energy and exergy analyses of a solar magnesium-chlorine thermochemical plant for methane production
Authors: Teymouri M , Aieneh K , Sadeghi S , Ghandehariun S
Published: March 2021

Solar power as the most available type of renewable energy can be used as a clean driving source in the thermal systems. One of the ways to overcome the intermittency problem of solar energy is to convert it into a chemical that can be used whenever it is required. Hydrogen is a good candidate for using it as a fuel. Thermochemical methods for the production of hydrogen are considered as promising candidates. magnesium-chlorine (Mg-Cl) thermochemical cycle is one of the water-splitting cycles that can be used to produce hydrogen. Due to the problems related to storing hydrogen, it is more convenient if we convert it into another chemical like methane. A novel integrated system has been proposed in this study for the production of methane through the Mg-Cl thermochemical cycle. For the base case, hydrogen can be produced with a mass flow rate of 188.32 kg/h. Energy and exergy efficiencies of the Mg-Cl cycle are calculated as 26.25% and 59.88%, respectively. If the produced hydrogen is converted into methane, the methane production capacity of the plant would be 352.98 kg/h. Our results indicated that the energy and exergy efficiencies of the overall system are 7.04% and 60.28%, respectively.
Structural and DC-electrical properties of novel PMMA-PVA nanocomposites reinforced with graphene nanosheets
Authors: Kadhim M Abdul , Al-Bermany E
Published: March 2021

Polymer-graphene nanocomposites offer interesting opportunities to enhance the properties of polymer nanocomposites. In this study, new nanocomposites with polymethyl methacrylate and polyvinyl alcohol were successfully fabricated for the first time with various loading ratios of graphene oxide nanosheets (GO), with dimethylformamide-co-distilled water used as the developing solution. Fourier-transform infrared spectroscopy (FTIR), optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and DC electrical conductivity tests were conducted to investigate the structure and DC electrical properties of the resulting PMMA-PVA/GO nanocomposites. The OM and SEM images recorded a fine homogenous matrix and good distribution of GO in the nanocomposites, while the FTIR spectra displayed functional groups of all polymers and GO in the nanocomposites, with strong interfacial interaction between GO nanosheets and polymers, as confirmed by shifts in the XRD spectra of the PMMA. The results for conductivity in the DC electrical systems showed improvement after the addition of GO. The value of DC conductivity for PMMA-PVA/GO nanocomposites was 7.86 × 10-15 per ohm-cm at a GO ratio of 0.09%, while an increase in GO loading ratio to 0.27% caused an increase in conductivity to 4.53 × 10-9 per ohm-cm. The values of the activation energy of the nanocomposites were - 6.8%, -24.8%, and -66.91% eV for 0.09%, 0.18%, and 0.27% GO, respectively. These results suggest that such inclusions could allow for the development of better and wider applications for nanocomposites, including solar cells, electrical devices, IR-windows, microwave absorption panels, and sensors.
New Design of Single Band Elliptical Microstrip Antenna for Satellite Communication
Authors: Thaher Raad H , Jassim Hasanain M
Published: March 2021

An elliptical microstrip antenna with a special slot pattern on the patch was designed covering a bandwidth of 9.8701 GHz to 10.535 GHz, with gain of 3.1 dBi to 3.49 dBi with a voltage standing wave (VSWR) of less than two and reflection coefficient (S 11) of -63.4 dB. Computer simulation technology (CST) was used to obtain simulation results, while a vector network analyser (VNA) was used to obtain practical results. The proposed antenna is intended for radiolocation and satellite communications, with dimensions of (19 × 23 × 1.6)mm
3, making it smaller than most UWB antennas, manufactured on a substrate with a relative dielectric constant (εr) of 4.3 and loss tangent (tan δ) of 0.025. Reasonable agreement was found between the practical and simulation results.
Optimal PID Controller based on Convex Optimisation and Particle Swarm Techniques
Authors: Makki O T , Mohammad L S
Published: March 2021

This paper discusses the design and implementation of multiple optimisation algorithms for tuning a PID controller. A metaheuristic algorithm known as particle swarm optimisation (PSO) is used together with convex optimisation techniques, and the validity of the proposed algorithm is examined by comparing its performance with the performance of the classic PSO-PID and the well-known Ziegler–Nichols PID (ZN-PID). To obtain useful comparisons, a non-linear system, the air levitation system (AL), was utilised, controlled using a PID with three tuning strategies: the modified particle swarm technique (M-PSO-PID), the classic particle swarm (C-PSO-PID), and the Ziegler-Nichols method. The performance of the controllers was monitored through a cost function, the Integral Absolute Error (IAE). A disturbance was also imposed on the AL system to test the performance and the robustness of the algorithm under different conditions. The proposed algorithm is designed to determine and set the parameters for the M-PSO-PID controller utilising stabilising regions Kp, Ki, and Kd which form a convex problem. The PSO technique is then used to search for the optimal values inside the convex area. The simulation results for the control system show that the M-PSO-PID offered good closed-loop performance with advantages over other algorithms with regard to the system settling time and rise time. The results thus indicate the supremacy of the proposed algorithm.
Design and Implementation of a Smart Meter for Load Management
Authors: Hadi Abdul-Razzak Shehab , Mahdi Mohammed Chessab , Jassem Abed Al-Abass Muhseen , Sahib Ali
Published: March 2021

In this work, a method is outlined to convert a conventional electro-mechanical meter into a digital power meter as part of an Automated Meter Reading (AMR) system using a simple and cost-effective technique. A conventional electro-mechanical meter was converted to emit digitised pulses with the addition of an optical encoder, allowing automatic transmission of meter reading data and detection of meter tampering. In testing the proposed AMR system, the meter readings as read from the LCD were found to offer an accurate representation of the total power consumed. Further improvements suggested to enhance the functions of the AMR system, including load management and pre-payment. The proposed meter offers substantial savings for electric utility companies as well as enabling users to take advantage of fully automated meter readings.
Design and Implementation of a Zigbee, Bluetooth, and GSM-Based Smart Meter Smart Grid
Authors: Alubodi A O A , Al-Mashhadani I B N , Mahdi Dr S S
Published: March 2021

The first step in upgrading the billing and metering systems available in Iraq in most areas supplied by IMOELC (the Iraqi Ministry of Electricity) is the development and application of smart meter systems. These systems are based on two-way communication between consumers and suppliers, and the smart meter approach is thus more reliable than even digital meters with regard to billing and tamper prevention, as well as allowing the government to monitor electricity consumption in an enhanced and organised way based on the information obtained from data centres. To facilitate this data exchange, a new meter was proposed and tested in real-time in a few houses in Karbala, with the measured voltage, current, and power factors for energy multiplied every second and summed to determine energy consumption before being stored on the SD (Secure Digital) card in a backup text file in case of shutdown. The readings collected from the tested region were send to a Data Concentrator Unit (DCU) using three communication methods (Bluetooth, XBee and GSM). The data was then transferred from the DCU to the server via GSM, as GSM offers the lowest interference and fault occurrence, making it most suitable for long-distance transfers. Bills were generated based on the readings over time, with the division by time shown on the bill to urge users to rationalise their energy use at certain times during the day. The final error in current reading was less than 8% and the error in voltage reading was less than 0.64%.
Design and Implementation of a Remotely Controlled Two-Wheel Self-Balancing Robot
Authors: Aldhalemi A A , Chlaihawi A A , Al-Ghanimi A
Published: March 2021

This research included the design and implementation of a real-time remotely controlled Two-Wheel Self-Balancing Robot (TWSBR). The aim was to build a low cost TWSBR that could be remotely navigated using Bluetooth wireless technology. Experimentally, the TWSBR consists of two parts: the hardware device and the software algorithm. Bluetooth protocols were used to facilitate communication between a smartphone device and a gyroscope sensor. As the dynamic structure of the robot is inherently unstable, self-stabilisation represents a major challenge, and a robust control algorithm was thus required for this task. A Proportional-Integral-Derivative (PID) was employed to achieve this in real-time with the help of an 8-bit microcontroller. The feedback signal was fed to the PID controller through the gyroscope sensor with the aim of maintaining TWSBR stability and balance based on adjusting its longitudinal angle in response to the gyroscope feedback signal. A prototype robot was then built to validate the proposed algorithm.
Biosensor Based on Photonic Crystal Fibre with Mode Coupling of a Dual-Core
Authors: Naife Riyadh Mwad , Abbas AbdulSattar K.
Published: March 2021

In recent years, photonic biosensors have attracted increasing attention due to the enormous range of applications in many fields to which they may be put, including medical diagnostics, environment monitoring, organic chemical detection, temperature sensing, and work with magnetic fields. In this work, photonic crystal fibre (PCF) was utilised as a biosensor using a Finite Element Method (FEM). Several important optical sensor properties such as the field distribution profiles, the real part of the effective refractive index and the relative sensitivity of the proposed PCF structure are affected by mode coupling between the fundamental mode and the second order super mode of the inner and outer cores, respectively. These properties were thus those studied by applying FEM. The proposed biosensor can thus be used for bio-sensing, as the holes in the PCF are filled with analytes. Relatively high sensitivity can thus be obtained using appropriate design by selecting design parameters such as the radius of holes in the cladding region and pitch distance, or distance between the centres of neighbouring holes, appropriately. The results from this work show that the electric field distribution is affected by mode coupling between the outer and inner modes; the effects of mode coupling of the PCF on the relative sensitivity were also determined.
Design and Analysis of a Novel Artificial Ankle-Foot Joint Mechanism
Authors: Kokz Samer A , Alher Murtadha A , Ajibori Hakim S Sultan , Muhsin J.Jweeg
Published: March 2021

Globally, more than one million limbs are amputated annually. Theoretical and experimental studies thus been undertaken in many countries to develop prosthetics to help alleviate the suffering of people with amputated limbs. This study aimed to design and simulate an artificial ankle joint to mimic huma walking on sloped surfaces efficiently. The new design also attempts to mimic the shape, the size and the range of angle motion of the human ankle joint while simultaneously reducing the cost and weight of the prototype prosthetic ankle unit and increasing durability and responsiveness. The weight of the individual user is the main factor controlling the engagement and disengagement of the artificial ankle joint during the gait cycle, and the new design for the artificial ankle joint was prepared and tested using CATIA and ANSYS software. The suggested model was shown to be effective and reliable and able to adapt to multiple different surfaces. It also achieved high flexibility under various weights of users.
A Finite Element Simulation of Nano Effects on Stress Distribution in a Below Knee Prosthetic
Authors: Jweeg Muhsin J. , Hamzah H. A. , Al-Waily Muhannad , Al-Shammari Mohsin Abdullah
Published: March 2021

In the authors’ previous work, various mechanical properties such as modulus of elasticity, strength, creep, impact and fatigue behaviours for different laminates composites with and without different Nano-material additions and reinforcements with different types of fibres were tested experimentally. The four best lamination types and suitable Nano-material percentages were used in this work to develop a numerical investigation of a below knee prosthesis, facilitating the investigation of the effect of different Nano-material types and weight fractions on the stress and deformation in below-knee socket prosthetic structures manufactured from composite laminated materials with various reinforcement fibres. Numerical analysis using the finite element method was adopted to estimate the Von Mises stresses and deformation behaviours for the below-knee prosthetic structures, with the mechanical properties of the relevant composite materials taken from previous published work. The comparison of different Nano-material types and weight fractions suggested that the best Nano-material was SiO2 at a weight fraction of about 2% for the sample 2Perlon+2Kevlar+1Perlon+2Carbon+1Perlon+2Kevlar+2Perlon, where the stress for the socket was reduced by about 40%, with a reduction in the deformation of about 38%.
Movement of polymers in an asymmetric nano-channel under various parameters
Authors: Taghavi Firoozeh , Bianco Valentino , Malgaretti Paolo , Nikoofard Narges
Published: March 2021

Separation is an important process in various fields in science and technology, and nano-structures are now being widely used to improve the resolution and speed of separation processes. Continuous separation occurs when the components of a mixture separate at different locations in a device; this makes it possible to inject a new sample into the device at any time during an on-going separation process. Continuous separation of nano-particles in a nano-channel composed of consecutive cones has been shown previously, while this study investigates whether a nano-channel can perform continuous separation of polymers such that polymers of different lengths are separated at the two sides of the channel. For this purpose, the motion of a charged polymer in an asymmetric nano-channel under constant and alternating applied electric fields was studied theoretically and by applying computer simulations. Theoretical formalism was used to determine the situation under which the channel could perform continuous separation, with computer simulations used to check the theoretical results. The effect of different channel parameters on the performance of the nano-channel, as a device for continuous separation, was thus determined.
Human Gait Cycle Classification Improvements Using Median and Root Mean Square Filters Based on EMG Signals
Authors: Ghalyan M F , Alher M A , Jweeg M J
Published: March 2021

Human walking is an important and intuitive operation in daily life, but it is different for people missing this ability. Recognizing human gait cycle portions during walking is very useful for understanding the biomechanics of the muscles, pre-disease’s diagnosis, and designing lower limb prosthetics. The normal gait cycle is divided into stance and swing phases. In this work, benchmarking of several classification techniques is performed, based on electromyography (EMG) data collected from seven lower limb muscles, with the gait cycle phase used as a target vector to label the EMG data. The dataset is split into a training set used to build a statistical model using a specified classification technique, and a test set for purpose of testing a pre-generated statistical model. EMG signals are unfortunately normally corrupted with noise, which drastically reduces their classification performance. A median filter and root mean square (RMS) filter were thus applied to the raw EMG signals, and the performance of the classification techniques calculated in all cases for the raw EMG, EMG with median filter, and EMG with RMS filters for comparison purposes. The use of filters offered good enhancement in the classification process. The median filtered EMG signal performed best and gave higher accuracy than the raw EMG and RMS filtered EMG signals due to the technique’s efficacy in removing outliers. This work also offers a simple explanation of each classifier algorithm used, and a graphical feature selection was also applied to all seven muscles of interest to identify the muscle with the most influence on the gait cycle. The Rectus Femoris muscle shows the best activity separation between swing and stance phases, working mainly during the swing phase; this higher activity during the swing phase thus caused it to be identified as the muscle with the most influence over the normal gait cycle.
Electrochemical treatment enhancment with dissolved air floatation to minimise organic pollutants of leachate in the press stations in Baghdad
Authors: Mahdi Ruqaya S , Asrar A Hassan , Jaafar Mahdi Sh
Published: March 2021

Leachate is a complex solution of contaminants produced from municipal waste compacting stations, being primarily comprised of household waste. In this research, leachate was treated in an electrochemical batch process with a dissolved air floatation system using aluminium as the anode with cathode electrodes. Conditions such as pH, current density (i), contact time, and air flowrate were varied and tested to determine their effects on the removal efficiency in terms of Chemical Oxygen Demand (COD), Oil, and Turbidity (Turb.). Under the best conditions, the removal efficiencies for oil, COD, and turbidity were 78.7%, 77.5%, and 98.6%, respectively, suggesting that this method can be considered an efficient and effctive treatment for leachate.
Evaluation of transport processes in a catalytic reforming reactor with high performance nanocatalysts
Authors: Sukkar Khalid A.
Published: March 2021

Catalytic reforming reactors are the most important multiphase reactors in petroleum refineries producing high octane gasoline. The reforming process usually generates an unstable operation combined with catalyst activity loss due to the high levels of interaction between the heat transfer and mass transfer processes in the reactor and the specifications of the catalyst. In this investigation, n-heptane reforming reactions were investigated by preparing three types of nanocatalysts (Pt/HY, Pt-Ge/HY, and Pt-Re/HY). The reforming reactions were investigated at 440, 460, 480, 500, and 520 °C under atmospheric pressure in a reactor of dimensions 2 cm (inner diameter) by 30 cm (height) manufactured from stainless steel. The H2/n-heptane was selected to operate at a value of 2 with WHSV=2, and the effects of heat and mass transfer processes on the catalyst and reactor performance were thus evaluated. The results indicated that the Pt-Gr/HY catalyst showed the highest activity, selectivity, and stability at a reaction temperature of 480 °C. It was also noted that the heating rate and diffusional processes were severely affected by reaction selectivity during formation of the desired products as well as by the hydrodynamic parameters of the reactor. The activity of the prepared nanocatalysts demonstrated the sequence Pt-Ge/HY> Pt-Re/HY> Pt/HY, and the prepared nanocatalysts were able to offer high performance under controlled transport processes in terms of producing high-quality gasoline.
Predicting Drilling Rate of Penetration Using Artificial Neural Networks
Authors: Mahdi Doaa Saleh
Published: March 2021

Oil well drilling processes are generally high-cost operations; however, these costs can be reduced by optimising drilling operations. In particular, it is vital to optimise the drilling rate of penetration during oil well drilling operations. Many parameters affect drilling penetration rate, and these have complex relationships with each other. The accurate prediction of the drilling rate of penetration has particular importance in the optimisation of all drilling parameters and the reduction of drilling costs. In this paper, a neural network model is developed to predict the rate of penetration for an Iraqi oil field as a function of well depth, drilling fluid inflow, bit rotation speed (RPM), weight on bit (WOB), standpipe pressure, and bit size. The data on which the network was trained was collected from one drilled oil well, and 3,939 data points were used to develop the new model. These were randomly divided into two parts, with 70% used for training and 30% used for testing. The results showed that the resulting neural network model offers high accuracy for predicting the drilling rate of penetration. The statistical analysis showed that the developed neural network model predicted the rate of penetration very high accuracy (correlation coefficient of 0.983 and average absolute error of just 7.78%). The new model can also be used to determine the optimum drilling parameters to obtain a desired rate of penetration.
An approach for applying managed pressure drilling techniques to troublesome formations in an oil well in southern Iraq
Authors: Dhayea Batool Abdullah , Almahdawi Faleh H. M.
Published: March 2021

Many southern Iraqi oil field formations, such as Dammam and Hartha, are characterised as loose formations, making overbalanced drilling difficult due to increased frequency and volume of mud losses. Managed pressure drilling techniques (MPD) may thus be applied. This process uses conventional hydrostatic column pressure and annular friction pressure in addition to the surface back pressure to generate a constant bottomhole pressure (CBHP) to drill such formations, which enables the use of the lowest mud weight (closest to pore pressure) and back pressure treatment utilising a choke manifold during the drilling process to maintain an equivalent circulating density (ECD) slightly greater than the pore pressure, reducing the risk of mud loss, and the concomitant stuck pipes and non-productive time (NPT), thus enhancing drilling efficiency. In this paper, Wellflo software was utilized to model multi-phase flow in wells to examine the use of aerated mud used at different injection rates for gas and liquid to identify the best injection rate for drilling operations without losses. Several cases were examined using various mud weights and surface back pressure of the assumed injection rates, to choose the appropriate mud weight and the surface back pressure ranges. The highest pore pressure gradient expected in such holes is 0.465 psi/ft, and consequently, the minimum required mud weight was 8.95 ppg, in order to ensure control and avoid loss; however, due to back pressure and friction pressure in the annular region, this weight leads to problems in some formations. A mud weight of 8.8 ppg was therefore chosen as the closest feasible weight to pore pressure, with back pressures of 200 and 250 psi. A gas injection rate of 1,200 gpm was selected as the best injection rate for various liquid rates (581, 631, 681,731, and 781 gpm). The use of aerated mud at 8.8 ppg mud weight increased the penetration rate, offering a more efficient cutting transportation ratio (CTR) and allowing more control over wellbore instability and formation damage, as well as limiting mud losses.
Estimation of Bourgoyne and Young Model Coefficients to Predict Optimum Drilling Rates and Bit Weights using Genetic Algorithms – a case study of the Faihaa Oil Field in Iraq
Authors: Khaleel AbdulKareem A , Adnan Mohammed S , Alhamd Salem J
Published: March 2021

Drilling optimization requires maximizing rate of penetration (ROP) by controlling parameters such as bit weight (WOB) and rotary speed (N) to reduce drilling time and cost and to mitigate hole problems. The Bourgoyne and Young model was selected to study the effects of all parameters concerned with oil well drilling (depth, pore pressure, equivalent circulating density, bit weight, rotary speed, bit tooth dullness and jet impact force) based on actual bit records for a well in Faihaa oil field. A multiple regression analysis technique and genetic algorithm procedure were employed to analyze the field data, with the results used to develop a general equation relating rate of penetration to all variables. All the constants of the model were thus determined, and the optimized bit weight calculated for different depths of well to achieve the optimum penetration rate.
Role model of model-based systems engineering application
Authors: Gräßler Iris , Wiechel Dominik , Pottebaum Jens
Published: March 2021

The transition to model-based systems engineering (MBSE) is essential to meet the demands of increasing system complexity, productivity, quality and shorter design cycles. Necessary perspectives, associated roles and competencies for the application of MBSE are not sufficiently defined. The paper at hand presents a role model for the practical application of MBSE based on three major steps: (1) identification, (2) categorization and (3) association of stakeholders, which implement and apply MBSE within an enterprise. The use of the role model is demonstrated and evaluated in a test case based on personas within a fictional scenario which illustrates the implementation of MBSE. The roles, which are adapted to today’s conditions, serve as a practical guide comprising all basic conditions that have to be considered when applying MBSE. Practitioners can easily tailor the illustrated results to their own use case.
Investigations on the Micro-Pitting and Wear Behavior of Nitrided Internal Gears
Authors: Geitner M , Zornek B , Hoja S , Tobie T , Stahl K
Published: March 2021

Nitriding processes can significantly increase the load carrying capacity of gears, compared e.g. to through hardened gears. Nitrided gears are generally characterized by a thin and hard compound layer on the surface and an adjacent diffusion layer that extends deeper into the material. Structure and properties of the compound layer significantly determine especially the tribologically dominated load carrying capacity characteristics of the tooth flank surface such as micro-pitting and wear. Previous investigations on nitrided gears were mainly focused on fatigue limits for the surface durability against pitting and tooth root bending strength. Furthermore, mostly external nitrided gears were investigated. Results of systematic investigations on the wear and micro-pitting behavior of nitrided internal gears are scarcely available. Based on the investigations in the research project FVA 482 IV, experimental test results confirm that nitrided internal gears in the material pairing “case hardened/nitrided” provide a significantly better performance regarding wear compared to through hardened or case hardened internal gears. Furthermore, it was shown that nitriding can have a positive influence on the micro-pitting behavior. A detailed analysis of the microstructure shows that the properties of the compound layer are primarily responsible for both, the micro-pitting and wear behavior.
Investigations on the rolling bearing cage dynamics with regard to different operating conditions and cage properties
Authors: Schwarz S. , Grillenberger H. , Tremmel S. , Wartzack S.
Published: March 2021

The dynamic behavior of a cage can have a significant influence on the performance and the noise of a rolling bearing. In case of an unstable or high-frequency cage movement, vibrations are transmitted to the adjacent machine elements and the environment, which can influence the operating behavior of the whole system. In addition, a loud noise can often be perceived, which is referred to in the literature as cage rattling or squealing. In this paper, characteristics of different cage movements are investigated using multibody simulations and experimental investigations. For this purpose, essential properties of the fundamentally observable cage movement types “stable”, “unstable” and “circling” are presented. The calculated cage dynamics and the type of cage motion are used to show dependencies between the operating conditions and the resulting cage movement such as inner ring rotational speed, bearing load or cage characteristics such as pocket clearance. Based on the simulations, interactions between the input parameters can also be determined. The results are used to identify operation-critical conditions and cage properties that lead to high cage dynamics. Finally, a comparison between the results of the multibody calculations and optical measurements is made. The optical measurements are performed using high-speed cameras. Reference markers fixed on the cage and digital image correlation allow the evaluation of the kinematics as well as the deformation of the cage. These results are compared with the simulation data to ensure a high quality of dynamics simulation.
Damage Diagnosis of Cardan Shafts in Mobile Mining Machines using Vibration Analysis
Authors: Golafshan Reza , Dascaliuc Catalin , Jacobs Georg , Roth David , Berroth Joerg , Neumann Stephan
Published: March 2021

The ability of prediction of machine condition may become even more crucial in mobile mining machines considering their instantly-varying conditions. The field of early damage diagnosis for mobile machinery is gaining increasing attention in modern and predictive maintenance strategies. In general, vibration-based machine condition monitoring methods offer the possibility to detect and localize the damages in mechanical systems at their early stages. In vibration monitoring, the vibration signals are captured via accelerometers, and are processed in the time and frequency domains in signal processing packages to extract diagnostic information. However, in real-world mobile applications, vibration analysis alone may not reveal the diagnostic information due to extreme transient and nonstationary operating conditions. In this regard, additional metadata available on the machine’s CAN bus system, can improve the reliability of vibration analysis for mobile applications. The current study aims to investigate the usage of metadata as additional information to the vibration analysis on cardan shaft of a test wheel loader in field conditions. Two various damage types, namely, misalignment and bearing clearance, both on cardan shaft, are investigated in some detail. The experimental results show how vibration analysis together with metadata processing can identify the state of the machine even in harsh operating conditions.
Design and manufacturing of a cylinder head by laser powder bed fusion
Authors: Willkomm J , Kuhlbach K , Merget D , Wagner M , Reich S , Ziegler S , Schleifenbaum J H
Published: March 2021

Nowadays the reduction of fuel consumption is the most important challenge for engine development. Laser Powder Bed Fusion (LPBF) as an additive manufacturing process with its implied design freedom makes it possible to reduce combustion emissions, increase engine efficiency and respond specifically to customer requirements. In this work, the outstanding degree of freedom of LPBF is exploited for a new design concept for a cylinder head of an engine in automotive industry in order to address further reduction of fuel consumption through improved cooling performance. Within the given installation space and under consideration of the existing mounting and connection positions, the design concept was developed, subsequently manufactured and reworked. In order to develop a design that meets the LPBF requirements, both the potential of the LPBF using the geometric degrees of freedom as effectively as possible and the limitations are considered. The opposing design drivers between exploitation of potentials and limitations in LPBF are achieved by an iterative design process supported by an own developed design tool. With the new design concept, a reduction of the metal temperature in the cylinder head of approx. 25 K is achieved, verified by simulation.
Influence of Basic Airfoil Layout on Aerodynamic Characteristics of Forward-swept Wing
Authors: Jun-yi Zhang , Xin-bing Su , Wen Jiang , Xi-wei Zhao
Published: March 2021

When the swept angle of the wing varies, the parameters such as the aspect ratio of the forward-swept wing aircraft and the relative speed of the cross-section airfoil relative to the incoming flow will change, which will play a great influence on the aerodynamic characteristics of the wing. Based on this purpose, this paper explores the impact of the oblique angle of the basic airfoil on the aerodynamic performances of the forward-swept wing. Firstly, the wing models of the upright and oblique basic airfoil were established, meanwhile the one-equation Spalart-Allmaras turbulence model and CFD technique were used for numerical simulation calculation. The change law of the aerodynamic characteristics of the wing with the fundamental airfoil upright and tilted are compared and analyzed when the swept angle varies.
Utilization of Low-Potential Energy Through to the Use in Aircraft Fuel System
Authors: Badykov Renat R. , Panshin Roman A. , Tremkina Olga V. , Prokofieva Anastasia A.
Published: March 2021

The article discusses the possibility of improving the main characteristics (efficiency, specific thrust) of a gas turbine engine by using liquefied natural gas (LNG) as fuel. This possibility is considered on the example of using as fuel instead of aviation kerosene on PS-90A and NK-93 engines. The parameters of the engine were determined at various stages in the cruise flight mode when operating on kerosene and LNG. The parameters evaluating the fuel consumption of the engine are calculated and compared for both fuels. The performance characteristics for kerosene and LNG were evaluated in the system of the Tu-330 subsonic transport aircraft. Energy losses during storage of cryogenic fuel on board the aircraft are estimated.
Analysis of Sound Insulation Mechanism and Optimization Design of an Acoustic Coating Layer with Multi-section Cylindrical Cavities
Authors: Zhou J L , Meng X J , Huang Fu H D , Zhang J H , Su K , Tao W , Chen H Y
Published: March 2021

Introducing the insulation layer is an effective way to reduce sound radiation from underwater structures. Impedance mismatch properties between water and layer is closely related to sound insulation performance. Finite element method with COMSOL is used to calculate sound insulation loss in this paper. In order to investigate the insulation mechanisms of coating layer embedded with multi-section cylindrical cavities, the coating layer is approximated to a homogeneous layer with equivalent material properties. The results show that acoustic coating layer with multi-section cylindrical cavities, which causes a higher impendence mismatch has a better sound insulation performance than cylindrical cavity acoustic coating layer of the same cavity volume. The coating layer with optimized multi-section cylindrical cavities structure has obvious sound insulation advantages in the range of 200Hz to 4000Hz. Finally the theoretical analysis is verified by experiments.
Dynamic Modelling and Pendulation Laws of Cable Hoisting System
Authors: Tian Z X , Lin X X , Li J P , Hu P
Published: March 2021

The dynamic characteristics of the cable hoisting system (CHS) are studied by combining theoretical modelling and visual simulation. The dynamic model is derived using D’Alembert’s principle. It contains the effect of horizontal motion and lifting motion, and also takes into account the quality of the cable to improve the accuracy of model. The Runge-Kutta method is used to solve model numerically, and simulation is conducted within Adams environment to verify the dynamic model. Based on the dynamic model and numerical calculation, the effect of horizontal motion, lifting motion and system parameters on swing was studied. The results show that the dynamic model and numerical calculations are accurate; during the movement, the payload oscillation is mainly affected by the initial acceleration, sudden change of acceleration and lifting speed; the length of steel cable and the mass of hoisting payload determine the frequency of CHS, which does not affect the payload oscillation; the oscillation and frequency are affected by lifting laws; and the study of acceleration laws can be used to guide the design and control of CHS.
Application of Closed Magnetic Circuit Method for Evaluating the Stress Distribution along Depth Direction
Authors: Di Jingyu , He Cunfu , Liu Xiucheng , Lee Yung-Chun
Published: March 2021

Electromagnetic nondestructive evaluation method is feasible in assessing stress or residual stress levels in ferromagnetic structures, for there is a strong inherent correlation between the permeability and the stress. This study is based on the closed magnetic circuit method for testing stress distribution along depth. Firstly, a theory is proposed for describing the propagation of electromagnetic energy inside ferromagnetic materials. A layered model is established considering the electromagnetic field experienced different attenuation at different depths. And each layer is assumed to have the identical physical state. Then, multi-frequency eddy current method is proposed to testing the in-depth permeability variation and consequently the stress-depth profile. For simply using the convolution integral, a novel inversion algorithm is given to resolve the convolution integral. To apply the proposed method for testing the stress-depth profile, multi-frequency eddy current experiments are conducted through a four-point bending device; with the specimen material employed is 45# steel. Finally, map the experimental data fitting curve to the theoretical calculation curve, and hence can verify the proposed theory and the inversion algorithm.
Effects of Misalignment on the Sliding Rates of Parallel Line Gear Pair
Authors: Lin Yifan , Chen Yangzhi
Published: March 2021

The sliding rates of parallel line gear pair (PLGP) are equal to zero and pure rolling meshing can be achieved under ideal condition. In this paper, effects of misalignment on the sliding rates of PLGP were studied. Firstly, the geometric model of PLGP was presented. Then the contact curves of PLGP with misalignment were obtained by the tooth contact analysis (TCA) method and the sliding rates were calculated. The calculation results of the example show that PLGP under ideal condition or with only axial deviation accomplishes transmission along the theoretical contact curves, the sliding rates are equal to zero, and pure rolling meshing can be achieved. For PLGP with centre distance deviation and parallelism misalignment, the sliding rates are not equal to zero and the form of relative motion between the meshing surfaces combines rolling and sliding. This investigation provides a theoretical basis for the further study of meshing efficiency and wear prediction of line gear pair under actual operating condition.
Bolt Load Calculation for Hybrid Joint Considering Friction and Nonlinear Stiffness under Combined Thermal and Mechanical Loads
Authors: He Tiren , Xu Jifeng , Zhu Kaige , Wang Haijun
Published: March 2021

An improved analytical method for calculating the bolt load distribution in single-lap or double-lap multi-bolt composite-metal joint structure considering material nonlinear behaviour and thermal stress is proposed in this paper. The analytical method is based on the stiffness method and the composite material mechanics. The bolt load ratios calculation results of a three-bolt joint structures by the improved method is compared with the results from finite element (FE) method and the relative error less than 7%. The great agreement verifies the accuracy of the analytical method. Besides, this improved has more considering factors and higher accuracy than traditional stiffness method and less calculating cost than FE method.
Engineering bioinks for 3D bioprinting
Authors: Decante Guy , Costa João B , Silva-Correia Joana , Collins Maurice N , Reis Rui L , Oliveira J Miguel
Published: March 2021

In recent years, three-dimensional (3D) bioprinting has attracted wide research interest in biomedical engineering and clinical applications. This technology allows for unparalleled architecture control, adaptability and repeatability that can overcome the limits of conventional biofabrication techniques. Along with the emergence of a variety of 3D bioprinting methods, bioinks have also come a long way. From their first developments to support bioprinting requirements, they are now engineered to specific injury sites requirements to mimic native tissue characteristics and to support biofunctionality. Current strategies involve the use of bioinks loaded with cells and biomolecules of interest, without altering their functions, to deliver in situ the elements required to enhance healing/regeneration. The current research and trends in bioink development for 3D bioprinting purposes is overviewed herein.
Ab-initio energetics of graphite and multilayer graphene: stability of Bernal versus rhombohedral stacking
Authors: Paul Nery Jean , Calandra Matteo , Mauri Francesco
Published: March 2021

There has been a lot of excitement around the observation of superconductivity in twisted bilayer graphene, associated to flat bands close to the Fermi level. Such correlated electronic states also occur in multilayer rhombohedral stacked graphene (RG), which has been receiving increasing attention in the last years. In both natural and artificial samples however, multilayer stacked Bernal graphene (BG) occurs more frequently, making it desirable to determine what is their relative stability and under which conditions RG might be favored. Here, we study the energetics of BG and RG in bulk and also multilayer stacked graphene using first-principles calculations. It is shown that the electronic temperature, not accounted for in previous studies, plays a crucial role in determining which phase is preferred. We also show that the low energy states at room temperature consist of BG, RG and mixed BG–RG systems with a particular type of interface. Energies of all stacking sequences (SSs) are calculated for N = 12 layers, and an Ising model is used to fit them, which can be used for larger N as well. In this way, the ordering of low energy SSs can be determined and analyzed in terms of a few parameters. Our work clarifies inconsistent results in the literature, and sets the basis to studying the effect of external factors on the stability of multilayer graphene systems in first principles calculations.
Effect of different operating conditions on the conversion efficiency of triple-junction solar cell
Authors: Kumar Durgesh , Dheer Dharmendra Kumar , Kumar Lawrence
Published: March 2021

In this work, a theoretical study based on the detailed balance limit has been carried out for the performance evaluation of series-connected triple-junction solar cell. The effect of different operating conditions on the conversion efficiency of the solar cell is evaluated by numerical modeling using MATLAB. The performance has been measured for three standard spectra (AM0, AM1.5D and AM1.5 G) and over a range of temperatures (273 K–523 K) under varying solar concentration. It has been observed that changes in operating conditions have a significant impact on conversion efficiency. The conversion efficiency is found to be highly sensitive to spectrum distribution. By selecting the appropriate bandgap combination as per the incident spectrum, conversion efficiency is improved significantly. The effect of temperature on the conversion efficiency is mitigated by increasing the ratio of solar concentration. The finding of the present study indicates that appropriate combination of bandgap and solar concentration can be an effective tool to improve the conversion efficiency. This study can further be extended for higher generation solar cells to evaluate their performance.
An explicit derivation of the time–information uncertainty relation in thermodynamics
Authors: Tanabe Katsuaki
Published: March 2021

A direct, explicit derivation of the recently discovered time–information uncertainty relation in thermodynamics [S. B. Nicholson et al (2020), Nat. Phys.
16, 1211] is presented.