bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study on Effect of Steel Tube in Axial Behavior of CFST Stubs
Authors: Jayaprakash Narayana S. , Manvi Rao Kolan
Published: December 2020

Concrete filled steel tubular (CFST) columns are becoming popular due to its advantages from both steel and concrete in resisting loads. CFST members are made up of steel hollow section of rectangular or circular sections filled with plain or reinforced concrete. CFST columns can be used effectively in high raised structures and in bridges. The reduced cross sections of columns can be achieved by the composite action of steel and concrete. The steel tube provides confinement to the concrete and helps to improve load carrying capacity. The concrete core offers higher resistance to axial compression. The inward buckling of steel tube will be avoided due to concrete and the out buckling resistance may be improved due to higher stiffness of the column due to higher gross moment inertia with combined effect of steel and concrete. This experimental work made an attempt to understand the effect of thickness of steel tube in behavior of CFST stubs.

In the present experimental study, a total of 24 cylindrical concrete filled steel tube specimens were prepared to evaluate the uniaxial compressive behavior and to understand the effect of thickness and aspect ratio (h/D) on the compressive strength. Two different thickness of steel tubes 3 mm and 5 mm and four aspect ratios (h/D) 1, 2, 3 and 4 are considered in the present study. M30 grade of concrete is used. From this study, as the aspect ratio increases the buckling loads decreases. The decrement is up to 37% in aspect ratio 4 when compared to aspect ratio1.
Influence of Waste Brick Powder on Properties of Masonry Mortar and its Impact on the Masonry Strength
Authors: Murthi P , Poongodi K , Kottiswaran N
Published: December 2020

The rapid urban development leads the exponential growth of construction and demolition waste in India. The handling and disposal strategies of building debris are not properly developed and create more threats to environment. Brick and concrete materials are the main wastes generated during demolition. As an alternate measures of recycling the brick waste, it is proposed reusing the waste brick powder particles in to the development of masonry mortar. The waste brick powder is used as cement replacement material and four different level of replacement was considered in this investigation as 5%, 10%, 15% and 20%. The strength of masonry mortar with three ratios (1:4, 1:6 and 1:8)at 7 days, 28 days and 90 days were determined. Further, the impact of innovative masonry mortar on masonry prism strength and bond strength were determined. The results obtained from this investigation had concluded that the cement can be replaced 12% to 15% by brick powder without affecting the compressive strength and shear bond strength performance of brick masonry.
An Experimental Investigation on Concrete by Partial Replacement of Cement by Fly Ash and Fine Aggregate by Quarry Dust
Authors: Damodhara Reddy B , Aruna Jyothy S , Kiran Kumar N , Hemanth kumar K
Published: December 2020

The concrete is a composite construction material. The necessary ingredients like cement, Natural Sand, Gravel and potable Water are important components of concrete. The issue of environmental degradation and expensive nature of the river sand makes us to switch on to the alternative sources. One such material having strength and durability is quarry dust which is a by-product from quarries which is causing lot of environmental issues. In this present study the replacement of the fine aggregate is done with quarry dust and cement with fly ash. Replacements of cement are partially done with Fly Ash at 0%, 5%, 10%, 15%, 20% and 25%. The experimental work primarily concentrates with compressive strength, split tensile strength and sturdiness properties of M40 grade of concrete at completely different ages i.e., 7 days, 28 days, 56 days and 90 days. The Split tensile strength and sturdiness checks like Acid attack and Chloride penetration test for 28 day were done. The Test results were promising when cement was partially replaced by 10% of Fly ash for all the days.
Zinc in the body and somatic health of industrial workers
Authors: Slepchenko G , Moiseeva E , Khlusov I
Published: December 2020

30% of industrial workers have a chronic (at least 3-4 months) zinc deficiency as a vital trace element necessary for the functioning of a significant amount of metalloproteins. The cause of zinc deficiency may be copper intoxication noted earlier, which together is important for the development of structural pathology of internal organs.
Ecologically safe device technologies of road covering with the using technogenic materials
Authors: Potapova S O , Shepelev I I , Eskova E N , Bochkov N N , Nemerov A M
Published: December 2020

The influence of nepheline sludge on the soil of a roadside strip when used in the device of road coverings is studied. Chemical analysis of soil samples taken from the roadside strip of a highway constructed using a base made of nepheline sludge was performed. It is shown that the change in the content of calcium-the main element of the sludge at a distance from 5 to 100 m from the road did not exceed its value in the background sample, and the content of exchangeable aluminum in the soil of the analyzed areas was at a very low level-less than 0.5 mg/kg and practically did not affect its content in the soil at all sampling points from 0 to 150 m from the road. Based on the conducted ecotoxicity studies using single-and dicotyledonous plants, the possibility of using nepheline sludge as a component of road covering in the form of a nepheline-crushed stone mixture has been established and the absence of toxicity in the analyzed soil samples at various distances from the roadside strip has been proved.
Research of the process of vegetable oil extracting under the influence of a high frequency wave field
Authors: Yu Ovsyannikov V , Berestovoy A A , Lobacheva N N , Toroptsev V V , Trunov S A
Published: December 2020

Research in a laboratory press equipped with an ultrasonic vibrator was performed to study the nature of a high frequency wave field influence on the process of vegetable oil extracting from safflower seeds. The initial moisture content of safflower seeds, the rotational speed of the press screw, the frequency and amplitude of ultrasonic vibrations have the greatest influence on the oil yield and the cake residual oil content. The analysis of the dependences obtained showed that the parameters of the safflower seed pressing process, the values of which could be varied during the experiments, affect the oil yield identically, namely, with an increase in the rotational speed of the press screw, the oil yield decreases and, consequently, the cake oil content increases. It was found out that moisture content raising increases the oil yield and reduces the residual oil content. Moreover, the most rational value of moisture content in terms of absolutely dry matter is 8.7…11.2%. It was revealed that an increase in the pressure given to the product in the press occurs with a decrease in the effective viscosity inside the surface layer of the mass being pressed due to ultrasonic vibrations imposition. The following parameters should be focused on as rational parameters for safflower seeds pressing providing the minimum residual oil content in the cake: the ultrasonic waves frequency is 22…28 kHz, the amplitude is more than 40 • 10−3 m and the pressure value in the press is from 12…13 MPa. These values obviously depend directly on the grain behavior and its movement in the press during exposure to high-frequency ultrasonic vibrations.
Mathematical model of wedge-shaped sliding support with low melting metal coated guide for partially filled working gap
Authors: Mukutadze M A , Opatskikh A N , Morozova A V , Zadorozhnaya N S
Published: December 2020

The reported study presents an asymptotic series solution to a system of differential equations in powers of a small parameter K depending on melting and a mechanical energy dissipation rate. Further, a self-similar solution has been found, as a consequence, a profile of velocities, pressure, principal operational characteristics, load capability, and friction force have been determined for a partially grease-filled working gap.
Tribological tests of frictional carbon/carbon composite in braking mode
Authors: Alisin V V
Published: December 2020

The article discusses the issues of friction and wear testing of a carbon-carbon composite of tribological purpose. The experiments were performed on a bench, the work of which is based on the absorption of kinetic energy of rotating masses with materials intended for use in brake devices. The friction coefficient and wear rate of the friction carbon composite in braking mode are investigated. Ring samples are divided into 6 sectors, in each of which, after testing, the parameters of the roughness of the friction surfaces and wear during one braking are determined. The value of linear wear was determined as the average value over 6 sectors for rotating and stationary samples. Changes in the structure of friction surfaces are investigated. Metrological support of the experiments was carried out by statistical processing of the results. The errors in measuring the coefficient of friction and wear rate are determined. High resistance to energy absorption and thermal shock of the studied frictional material is established, which open up the prospects for the mass use of C/C in transport brake devices.
Assessment of the technical and technological condition of the transport complex
Authors: Gubin A V , Pavlova A V , Kosolapov Yu V , Morkovkin D E , Lineva E S , Gibadullin A A
Published: December 2020

The presented study is devoted to the assessment of the technical and technological state of the transport complex. The work analyzed indicators reflecting the share of fixed assets of the transport complex as part of national fixed assets and the degree of depreciation of production capacities of the transport industry. The analyzed indicators reflect that about a quarter of all fixed assets are related to the transport complex, and the volume of depreciated fixed assets exceeds 50%, while production capacities are updated to increase fixed assets, and not to ensure a qualitative or quantitative upgrade. The study proposed a model for ensuring the qualitative development of the transport complex, which contains measures to update existing fixed assets and new principles for the management and development of the transport complex.
Evaluation of friction behaviour on human finger skin considering precision grip task
Authors: Cârlescu V , Oprişan C M , Ianuş G , Olaru D N
Published: December 2020

Human hands perform daily different tasks and the fingers skin comes in contact with many surfaces and objects. Grip task of objects can be performed by using different combination of the fingers. Precision grip task is influenced by several factors which decide the grip force of the individuals performing the task. This study aims to evaluate in vivo the coefficient of friction (COF) between a steel cylinder and the skin of fingers’ phalanges from both hands for three healthy subjects. The experiments were realized in a reciprocating-sliding contact with normal loads of 1 N and 2 N and sliding speed of 1 mm/s. Also, indentation tests were realized in order to determine the skin deformation of the fingers phalanges under normal loads. The indentation results show that distal phalanges (fingertip) play a significant role in deciding the grip force. The friction tests reveal that the coefficient of friction varies between 0.3 and 1.1 along the fingers phalanges according to the age, gender and skin structure of the test subjects. The distal phalanges of index and middle fingers showed the highest value of the coefficient of friction in the case of the subjects that mainly use the right hand. These aspects can be considered in developing devices for grip and sensing tasks applications.
SR EN ISO 20623 - A standard for tribological evaluation of lubricants that may bust innovation
Authors: Deleanu L , Georgescu C , Ionescu T F , Guglea D , Isacescu D
Published: December 2020

This paper presents the opportunities offered for research by using the four ball machine and the procedures included in SR ISO 20623:2018. There are presented results of research studies that are started from the procedures and parameters included in standard, but also wear and friction parameters that derived from recording friction and wear scar dimensions and texture parameters.
Experimental assessment of permeability variation with the compression of soft reticulated foams
Authors: Enescu C. , Turtoi P. , Cicone T. , Istrate C.V.
Published: December 2020

The resistance to flow of imbibed fluids in soft porous structures subjected to compression can be a solution for impact attenuation. The mechanism, named ex-poro-hydrodynamic (XPHD) lubrication, is based on permeability variation with porosity, which, at its turn, depends on the compression degree of the porous structure. A literature survey revealed scarce information regarding the permeability of compressed reticulated foams or 3D fiber-based structures, used in XPHD applications. Moreover, the permeability depends on the fluid and its velocity. This paper presents experimental data of the permeability of glycerine for an in-plane, axisymmetric flow through a porous material subjected to various degrees of compression. The experiments were done on an in-house made radial permeameter with pressure differentials up to 6 bars. The experimental data was compared with the predicted results, using the well-known Kozeny-Carman equation and related formulations.
Light_Sport_Aircraft, wing design elements and resistance calculus for a new 3D model applied for flaps control
Authors: Ghiţescu I-M , Ghiţescu M , Borza P N , Stroe I
Published: December 2020

The aim of the paper is analyze of a new linkages used in Light_Sport_Aircraft control, flaps control, on bases of the aerodynamics, structural modelling of linkages with Multibody System method (MBS) and resistance calculus of wing. In virtual prototyping of the aircraft, these linkages have to be modelled by a minimum number of bodies (MBS min). In this paper is described one concrete mechanical flaps control. This will be the bases for virtual modelling and prototyping of these subsystems as parts of the whole product (airplane).
Simulation of high-pressure pump behaviour after running in urban regime
Authors: Iordache R C , Bujoreanu C , Petrea N D , Ianuş G
Published: December 2020

The wear of the high-pressure pump is directly proportional with the engine operating mode of the vehicle. Due to the urban areas congestion, the engine assembly components can be affected and they can lose their reliability. The engine operation can be described as a cyclical model, reaching all the operating points: idle, cranking, maximum torque and maximum power. Thus, the discontinuous operation (proportional with car engine cycles) of the high pressure pump can create different types of wear for its components. Our paper presents an experimental test that simulates the behaviour of the pump after the operation of the vehicle in urban regime with a cyclical type in a course of 10.000 km. It aims to achieve the most important engine operating points. In order to do this, an electronic control unit is installed on the test machine, which has the role of controlling the electronic pump valve. All data (pressure, speed, temperature) are recorded in real time and stored in the memory unit of the test machine. The obtained data are analyzed and the pump is disassembled. Wear is observed on the main components (roller, shoe and driveshaft), but this does not lead to pump malfunction. After this analysis, the main components of the tested pump are compared with new components in order to evaluate the wear level.
Experimental investigation of the limits of fluid squeeze out from an imbibed porous material
Authors: Turtoi P , Lupu G , Cicone T , Apostol D
Published: December 2020

The resistance to flow of a liquid squeezed out of a soft, porous structure subjected to compression generates a high load capacity and represents the mechanism on which the XPHD lubrication is based. The process is dependent on permeability which, in turn, depends on porosity, variable during compression. This study investigates experimentally the effect of compression on the porosity of open-cell polyurethane foams. An experimental device is used to compress a disc made of a porous material imbibed with glycerine and the volume of the remaining fluid is measured. Two reticulated foams with the same internal structure but with different initial porosities were selected for the study. The results are consistent and show a good correlation when compared with theoretical predictions. It is shown that the deformation of the solid fraction closes pores before squeezing out all the fluid. A residual porosity and a threshold strain when the pores are closed are put in evidence.
The dimensional accuracy of plastic parts made by the fused filament fabrication
Authors: Boca M A , Sover A , Slătineanu L
Published: December 2020

Fused filament fabrication (FFF) process has gained considerable public interest in the last years and due to its numerous advantages, a study that identifies and explains the influence of used plastic materials on the accuracy of the parts achieved by FFF could be considered as necessary. The present study contains a brief introduction in the additive manufacturing basic notions, technologies, and equipments. In a similarly manner the 3D scanning process is also synthetically presented. The main focus is on studying the accuracy of test parts obtained in laboratory conditions using the most used 5 polymer materials (PLA, ABS, PP, PA and PET). The experiments were conducted using software and equipment dedicated to 3D printing for FFF-technology and optical scanning. Results sustained by graphs, tables and images showed that the ABS type material provided the best results concerning the linear dimensional accuracy along the X and Y axes. For the circular and linear dimensions accuracy along the Z-axis, the lowest deviations in comparison with the nominal dimensions were found in the case of the test part made of PLA. The experiments also proved that the materials that had a higher proportion of the studied points included in the tolerance zone were the PLA and the PET.
A hands-on approach to demonstrating active noise cancelling
Authors: Coandă P , Avram M , Comeagă D
Published: December 2020

As noise pollution has become an increasingly major factor in the quality of urban life, noise cancelling methods started to be a relevant option for everyday life. Starting from the first active noise cancelling headphones build for aircraft industry in order to facilitate communication between pilots, in the last decade, active noise cancelling products have become more and more relevant. Factories, military and lately, civil usage of active noise cancelling technology transformed this industry and made it widely available. The purpose of this paper is to demonstrate a practical way of active noise cancelling using LabVIEW. Two sound waves are guided through a cylindrical conduit and at a given position, by modifying the phase and amplitudes between the two signals, an amplitude close to zero is expected.
Bearing fault diagnosis using the Kolmogorov-Smirnov test on frequency features extracted using the Goertzel algorithm
Authors: Cordoneanu Daniel
Published: December 2020

Fault diagnosis has been a field of interest during the last period, especially for predictive maintenance, given the advances in artificial intelligence and the available state of the art algorithms for machine learning, in a great number of libraries. In the industrial sector, fault diagnosis plays a very important role in order to avoid as much as possible downtime. Usually, rotating motors are involved in the actuation of the machines used in industry; therefore, bearings are an important part of the kinematic chain. The faults of the defective bearings can be detected within the frequency spectrum, at particular frequencies, which can be mathematically computed on the geometrical bases. Moreover, the use of the Goertzel algorithm allows the extraction of the specific features for these frequencies and their harmonics. The paper proposes a new approach of these features use for creating an initial data distribution, in order to be compared with future acquired data by use of the Kolmogorov-Smirnov test, as a good-fitness test for the new data.
Torsion frequency response function of a train driving wheelset
Authors: Gheţi M A , Mazilu T
Published: December 2020

The driven wheelset is used in traction rail vehicles (locomotives, electric trains, trams, etc.) to support part of the weight of the vehicle and to drive and brake the vehicle. The wheelset consists of the axle on which two wheels and the drive gear are mounted. The torsion vibrations of the driven wheelset may be induced by the variation of the adhesion force at the level of the contact between the wheels and the track but may also result from electromechanical interactions between the electric traction motor and the motor axle. In this paper, a mechanical model of the driven wheelset consisting of a circular shaft free at both ends and three rigid discs representing the two wheels and the drive gear is considered. The modal analysis method is used to solve vibrational motion equations in steady state harmonic behavior. The frequency response function of the system and the impact of the positioning of the drive gear on the wheelset shall be highlighted. For the verification of the proposed mechanical model, the numerical results are compared with the results obtained by experimental determinations carried out on a laboratory stand.
Hydraulic pitch control including virtual instruments
Authors: Pelin R I , Tiţa I
Published: December 2020

The main objective of this research work is to analyse and develop elements of a controller for hydraulic system used for pitch control of a horizontal axis wind turbine. Simulation of a hydraulic system is necessary in order to discover weak points before starting the design of the system. Some elements of the system may remain virtual elements and instruments as LabVIEW offers the possibility. These elements may be analysed and developed before the experimental model is realised and finally used, as they are, as a part of the experimental equipment. For some purposes it is possible to develop specific elements using the built-in blocks.
A comparative analysis between some dynamic models for the vehicle suspension system
Authors: Alexandru C
Published: December 2020

This article deals a comparative analysis between several representative dynamic models for the suspension system of the motor vehicles, namely quarter-vehicle, half-vehicle and full-vehicle models. The dynamic model of the suspension system contains the guiding linkages of the front and rear wheels/axle, by case, along with the elastic and dissipative suspension elements (helical springs, shock absorbers/dampers, buffers limiting the expansion & compression suspension travel, bushings, tires). The dynamic analysis (simulation) of the considered models was carried out with the help of virtual prototyping software solution ADAMS (currently developed by MSC Software Corporation), by considering the dynamic with shock regime, which consists in the sudden release of the car to fall on the ground from a given height. This is one of the standard tests in automotive industry for evaluating the comfort performance of the vehicles.
Theoretical aspects on internal cylindrical gears with small tooth number difference
Authors: Doroftei I , Crivoi O
Published: December 2020

Despite of some drawbacks, internal-external gear pairs with small tooth number difference have some advantages, especially when they are used in planetary or differentially gear mechanisms, as high transmission ratio and high torque at small size. In order to study the limits of these gears, regarding the minimum number of teeth of internal gear, the minimum tooth difference of the gear pair, the center distance, the addendum modification coefficients, the influence of the different geometric parameters on interference phenomena, an algorithm was designed that allowed to do that. In this paper, some numerical results based on a study on the theoretical aspects on such internal-external gear pairs will be reported.
An elastic model for tooth contact analysis of spur gears using FEM simulation
Authors: Radu M C , Dourado N , Coltun I G , Andrei G
Published: December 2020

Gears are a class of machine parts very often used in the most diverse industries due to their many advantages. In addition to the many benefits they provide, gears also have some disadvantages related to the noise and vibrations they can introduce into the system they are part of. The operating drawback which may occur is closely related to the geometry of contact and manufacturing and assembling errors. Investigation of the contact error effect on the operating condition should be first carried out through simulation approach. Gear efficiency can be investigated through the tooth contact analysis (TCA) method and stress analysis. The main target of TCA is to set up the contact path and to determine the transmission error function caused by clearance, gear misalignments or backlash. Generally, TCA is performed considering the elastic behaviour, which frequently implies to get data for different contact positions for full meshing analysis. Nevertheless, TCA outcome delivers noteworthy data about kinematic errors, contact ellipses and the estimation of the instantaneous contact point of the meshing gears. A numerical tool was developed in this work to obtain the contact path in spur gears, which allowed to compute the displacements, stress and strain fields in the contact regions. Furthermore, an analysis of the influence of manufacturing and assembling errors on the contact path and mesh quality was performed. Such an approach may provide an optimal design solution for spur gears.
On the kinematic modelling of an accurate tracking system to be implemented into solar-thermal collectors
Authors: Saulescu R , Jaliu C , Ciobanu D
Published: December 2020

One of the possibilities for increasing the energy performance of a parabolic trough-type solar thermal collector is by its diurnal orientation. The paper presents the kinematics of a tracking system with linkages, having as a starting point a patent proposal elaborated by the authors. The tracking system consists of a monoaxial mechanism, driven by three linear actuators, designed for the accurate orientation on large angular strokes of concentrated solar thermal collectors. The tracking system has two linear actuators in a triangular arrangement, articulated at the fixed ends, with the role of achieving the orientation accuracy and favourable transmission angles, and a third actuator aimed to allow a fine increase of the angular stroke of the collector under controlled conditions. The first steps in the kinematic modelling are to determine the orientation stroke of the collector and the transmission angles required in the static modelling by considering the third actuator as fixed and the strokes of the other two actuators as independent of each other. The aim of this modelling is to allow the subsequent optimization of an orientation program for a parabolic trough solar collector that takes into account the geometrical, kinematic, static and operating requirements. The simulation results allow drawing conclusions that are useful to the designers and developers in the field for dimensioning the collector tracking system under correct functioning conditions.
Comparative analysis of two wind turbines with counter-rotating vs. fixed-stator electric generator
Authors: Saulescu R , Neagoe M , Cretescu N
Published: December 2020

The paper presents a comparative study of two wind turbines with counter-rotating versus classical electric generator (with fixed stator). The wind turbines include a speed increaser that can operate with one or two counter-rotating outputs. The analytical modelling of the operating point of the wind turbines is firstly developed, based on the transmitting functions of the speed increaser and the mechanical characteristics of the wind rotor and the electric generator. The operating point is simulated, using the grapho-analytical method by reducing the mechanical characteristic of the wind rotor at the shaft of the electric generator rotor. This study highlights the advantage of higher efficiency for systems with parallel flow of the mechanical power as used in the wind turbines with counter-rotating electric generator.
Step of the vertical walls for warpage compensation on plastic housings
Authors: Pal S G , Goanţă V , Bistriceanu D P
Published: December 2020

All plastic parts suffer deformations during cooling of the material after the injection process. The effect is called warpage. This problem is known by all mechanical design engineers and in development, each engineer tries to compensate this warpage using different design solutions. In this article we are analyzing one important solution for warpage compensation and we will present our results and the optimization steps that led us to the results. The solution is a step for a vertical wall of the housings. For this step we analyzed different dimensions and combinations to provide the best solution.
Dynamic behaviour of a car trailer
Authors: Stanciu M D , Năstac S M , Dobrescu D
Published: December 2020

The most common causes of accidents involving trailer are poor environmental conditions, materials from which trailers are built, inappropriate assembly processes (incorrectly made welds, choosing screws or placing them so that they cannot withstand loads etc.), the inadequacy of the vehicle's speed to the runway quality, the detachment of the trailer from the towing hitch attached to the vehicle, lack of verification of the condition of the trailer (worn tires, the absence of the braking system, damaged of the resistance elements), the resonance of the trailer or the lack of attention of the drivers in traffic. The paper presents the experimental researches performed on a real trailer with one axle attached to a vehicle and driven on a road with and without obstacles. So, the influence of uncontrolled disturbing dynamic effects was analyzed based on acceleration signals recorded during test.
Non-convex layup optimization of the composite laminates with fast and robust FEA model and modified SPEA-II
Authors: Şerban Alexandru , Barsanescu Paul-Doru
Published: December 2020

The biggest design challenge regarding composite laminates is the selection of a stacking sequence such that the cost and/or weigth of the laminate to be minimized subject to constraints like failure criteria. The layup optimization of the composite laminates involves a very complex multidimensional solution space which is usually non-exhaustively explored using heuristic computational methods like genetic/evolutionary algorithms. To ensure the convergence of the prefered method it is necessary to evaluate a lot of layup configurations during the optimization process which involves that the evaluation of a single configuration should be fast enough to keep the overall optimization time to an acceptable level. On the other hand the mechanical behaviour of the composite laminates is very complex and it is analyzed with expensive computational tools such as finite element analysis. In this paper we propose a computational efficient framework which combines a very fast and robust Matlab-based FEA model with a non-convex evolutionary algorithm (strength pareto evolutionary algorithm II). We speed up the convergence by modifying the standard algorithm to generate new potentially pareto-optimal individuals. Also, a detalied numerical example is presented in order to highligth the steep computational time improvement between our method and a convex genetic algorithm.
Dynamics study of an automobile equipped with a hybrid powertrain system compared with the classic one
Authors: Burciu S M
Published: December 2020

Cars with hybrid powertrain substantially reduce the fuel consumption and the environmental pollution, especially at medium and low speeds, because they uses mostly electrical propulsion. The paper presents the mathematical calculation for working regimes of a car with parallel hybrid powertrain system, mathematical model which permits calculation of the propulsion power and torque, as well as the power and mechanical couple at the electrical generator. Dynamics performances for a car with a parallel hybrid powertrain system are presented and compared with the dynamics performances of the same car equipped only with same gasoline internal combustion engine and without hybrid system. From the point of view of performances, hybrid-powered cars can achieve higher accelerations and traction forces than classic cars during autonomy of electric system, due to the propulsion with this system.
Experimental investigations of an automotive diesel engine fuelled with natural gas in dual fuel mode
Authors: Rotaru S , Pana C , Negurescu N , Cernat Al , Fuiorescu D , Nutu Cr N
Published: December 2020

The compressed natural gas (CNG) is a viable alternative fuel for diesel engine use due to its good combustion properties and low carbon content. The general objective of the research is CNG use at the automotive diesel engine for improving of the energetic performance and decrease of the emissions level. By achieving these specific objectives, the paper brings an important contribution to solving pollution problems in large urban areas for diesel engines, the solution can be easily implemented on diesel engines in running, even on the old design which can be converted to fit the current rules of pollution. All investigations were conducted at engine operating regime of 55% load and 2000 rev/min. Following the analysis of all recorded data the proper quantity of CNG will be determined in order to have lower emissions level and better energetic performances. The specific energetic consumption is expected to decrease with more than 40%; at the highest substitution ratio the maximum in-cylinder pressure reaches values superior with more than 10% and the maximum pressure rise rate with over 20%; CO2 emission reaches 10% lower level. The CNG use at automotive diesel engine leads to the improvement of combustion process and engine energetic performance.
Study case regarding the measurement of an intake gallery airflow
Authors: Stoica M , Cretu C , Cucu L
Published: December 2020

This paper is a scientific approach designed to highlight the importance and relevance of developing and optimizing intake galleries for cars and high-performance vehicles. It is of major importance to get a low fuel consumption and a lower pollution index. It is desirable to get cleaner, recyclable products. Several individual tests, such as computer simulations and prototype testing are being implemented to produce a new product, thus gaining valuable insight into the characteristics of the new product. Also, a major challenge for engineers is the cost and time of getting assemblies and subassemblies done. That is why we are continuously looking for faster production methods in step with technology.
A mathematical model of an adiabatic helical capillary tube used for R1234yf and R600a refrigerants
Authors: Hmood K S , Pop H , Apostol V , Al Douri J , Al Qaisy S J , Badescu V
Published: December 2020

This paper presents a mathematical model to simulate the effect of the coiling diameter, subcooling degree and internal diameter on the characteristics flow of the refrigerants R1234yf and R600a, flowing through an adiabatic helical capillary tube. The homogeneous flow model was developed in the two-phase region based on the fundamentals of conservation of mass, momentum and fluid energy in the capillary tube. To validate this model, a comparison with numerical data on helical capillary tubes obtained by previous investigators has been made. It was reported that the coiling diameter, the inner diameter and inlet temperature of the capillary tube significantly influence on the pressure drop and quality and temperature distribution of the refrigerants R1234yf and R600a flowing inside the adiabatic helical tube. To validate this model, a comparison with numerical data on helical capillary tubes obtained by previous investigators has been made. Finally, the outcomes obtained from the present model exhibit satisfactory agreement with the available numerical data of helical capillary tubes.
CFD analysis of a round shaped air cushion vehicle with flexible skirt segments at 90° and different air clearance height
Authors: Pavăl M S , Popescu A , Zahariea D
Published: December 2020

At present time, the most used flexible skirt in construction of air cushion vehicles is the segmented one. Therefore, this study focuses on performing CFD analysis specific to the area of the segments of such a skirt. The proposed construction model has the outer diameter of flexible skirt segments of 1 meter, the segment thickness of 2 mm and the feed hole of 50 mm. A particular feature of proposed model is the circular ring shape of feed hole. Considering that segments height and air clearance height directly influence the performance of the air cushion, these two parameters were varied. Values ranged between 50 to 200 mm for flexible skirt segment height and from 10 to 50 mm for air clearance height. CFD analyses were performed in ANSYS Fluent program to determine velocity contours, pressure contours and streamlines. The main purpose of simulation was to determine lift force for all analysed configurations. The lift force variation was subsequently plotted according to air clearance height values through MATLAB program. Using Curve Fitting Toolbox application, it was concluded that the power type function with two terms best characterizes the analysed curves.
Case study regarding the use of three different fuels in a multi-stage hybrid rocket engine
Authors: Predoi S , Grigorean S , Dumitrascu G
Published: December 2020

Based on previous researches carried in the field on hybrid rocket engines, the authors propose the idea of three different fuel used in a multi-stage hybrid rocket engine. The aim of this paper is make a comparative analysis of rockets hybrid propulsion systems, considering a three stage hybrid rocket engine using one single type of fuel, and a three stage hybrid rocket engine using three different fuels for each stage. Numerical modelling is assuming a similar design mathematical model for both rockets. It is assumed that a concept like this, using different fuel types could lead to a reduction of pollutants and the improvement of combustion efficiency. For both design solution, the comparative analysis is using one imposed criteria, respectively the payload. The calculations are made in order to determine the required thrust force based on the required mass flows of fuel and oxidizer, and next, it is resulting the length and critical diameter of the flue gases nozzle. It is to be mentioned that the mathematical modelling is based on estimated values regarding combustion processes from different studies available in this research field. The numerical model can be used in loop cycle, to obtain a proper design of combustion system for each stage, and thus to get the performance of rocket engine.
Predicting vehicle waste heat recovery potential in road gradient driving cycle - A case study
Authors: Sandu V , Ungureanu V B , Leahu C , Mazilu A
Published: December 2020

A commercial vehicle was instrumented for assessing the engine operation modes on a mountain route in Romania, in a 70.4 km round trip with mean road gradients +4.2% and -4.5%. The real world test cycle was processed to find the distribution of the most frequent engine operation modes (time intervals versus n × n speed and load rankings) in order to extract a steady-state gradient road cycle. The direct injection turbocharged diesel engine has been tested on the dynamometric brake in the selected operation modes, investigating the energy recovery potential of the exhaust system. An exergy analysis has been performed by processing the variables of the exhaust gas flow rates for each operation mode (gas composition, pressure and temperature) which have been weighted with the time share of each mode in the driving cycle. The exergy exhaust potential has been evaluated by means of several indicators such as mean weighted exergy rate, weighted exergy to energy ratio and weighted exergy to fuel exergy ratio. By comparing the results to local urban and extra-urban cycles from previous works, it has been revealed that the gradient road cycle has a higher energy potential than the urban cycle, but a lower one than the extra-urban cycle.
HeartMate II thrombosis treated without explantation in the waiting period for heart transplantation: a case report
Authors: Villacorta Judith , Simeone Pierre , Theron Alexis , Guidon Catherine
Published: December 2020

Background

The HeartMate II (HMII) is a high speed, axial flow, rotary blood pump that restores systemic flow by draining blood from the left ventricular (LV) apex and ejecting into the aortic root. This LV assist device was previously used in patients with medically refractory advanced-stage heart failure, for both destination therapy and bridge to transplantation until the introduction of HeartMate III.

Case summary

We report herein a case of a 25-year-old patient with Interagency Registry for Mechanical Assisted circulatory 3 profile implanted with HMII device for an end-stage dilated cardiomyopathy, who experienced a pump thrombosis despite a well-conducted anticoagulant protocol. A thrombophilia with heterozygous mutation of factor II and V was diagnosed at that time. We chose to stop the device without explantation until heart transplantation.

Discussion

Pump thrombosis with HMII is associated with a prohibitive risk of morbidity and mortality. Pump thrombosis is suspected when haemolysis or congestive heart failure occurs, also in cases of overconsumption of pump power (>10 W). Pump thrombosis treatment is challenging in the case of clotting factors mutation. Pump exchange could be ineffective, exposing the patient to the recurrence of thrombo-embolic events. Intravenous thrombolysis may be used for patients not candidates for redo procedures but could be unsuccessful and expose patients to high bleeding risk. Heart transplantation remains a reliable option. In our case, pump explantation was considered too hazardous by the heart team due to a prohibitive risk of redo surgery. Then, we decided to turn off the HMII pump after the introduction of continuous intravenous dobutamine support. The haemodynamic stability allowed us to wait for heart transplantation in favourable conditions.
A point dislocation in a layered, transversely isotropic and self-gravitating Earth. Part IV: exact asymptotic solutions of dislocation Love numbers for the special case of isotropy
Authors: Zhou J , Pan E , Bevis M
Published: December 2020

We derive exact asymptotic solutions for the static deformation due to a concentrated or point-like dislocation in a spherical, layered, elastic, isotropic and self-gravitating Earth. The exact asymptotic solutions are quite general and can provide the dislocation Love numbers on the Earth's surface, near the dislocation or ‘source’, and close to any layer interface or boundary. We also discuss the special case where both the source and field points are located on the Earth's surface. We compare our exact asymptotic solutions with previous results obtained from the analytical dual variable and position (DVP) method via curve fitting. Our comparison confirms that the analytical DVP results converge to the exact asymptotic solutions. These new exact asymptotic solutions are particularly helpful when evaluating slowly convergent series of Green's functions using a Kummer transformation, anywhere within the layered Earth, especially for field points located very close to the point dislocation or source.
Patronage and insanity: tolerance, reputation and mental disorder in the British navy 1740–1820
Authors: Beck Catherine
Published: December 2020

This article examines contradictory attitudes towards insanity in the navy and how mental disorder affected officers and seamen’s reputations and careers. It challenges assumptions that dangerous sea-service and the prioritization of ability meant that those who experienced disorder were considered inherently ‘unfit’, exposing the complexity of eighteenth-century ideas of merit and disability. Using medical and administrative records, it reconstructs treatment and service patterns which prove that insanity was not an irrevocable bar to employment. Medical ideas underpinned a policy of indifference towards derangement, fostering cultures of sympathy and tolerance in which personal connection and patronage operated predominantly as mechanisms of inclusion, rather than exclusion.
Horae Subsecivae, ‘that remarkable glossary of West Country words’ (Bodl. MS Eng. lang. d. 66)
Authors: Ruano-García Javier
Published: December 2020

This paper examines Horae Subsecivae (Bodl. MS Eng. lang. d. 66), an unprinted glossary of the late eighteenth century that was conceived as an addition to Franciscus Junius’s Etymologicum Anglicanum (1743). Although the manuscript drew the attention of some dialect lexicographers and antiquarians of the nineteenth century, it has remained largely ignored in recent times despite its important contribution to the dialect record of the West Country. In fact, it appears that no other compilation of the seventeenth and the eighteenth centuries was chiefly concerned with West Country words, most of which went unnoticed by the renowned contemporary glossaries of Francis Grose (1787) and William Humphrey Marshall (1789, 1796). My aim is to uncover Horae Subsecivae, describing its peculiarities and lexicographical method, whilst showing its significant impact on the history of West Country dialects and our knowledge of eighteenth-century lexical dialect variation more generally.
Foreign Fighters and Conflict-Related Sexual Violence
Authors: Doctor Austin C
Published: December 2020

Do foreign fighters increase the prevalence of rebel-inflicted sexual violence? Evidence from recent armed conflicts indicates that this may be the case. However, little is known regarding the generalizability and nature of this relationship. This article argues that foreign fighters present local insurgencies with both strategic benefits—i.e., a reduced dependency on local civilians for material support—and organizational challenges—i.e., threats to intra-group cohesion. In combination, these factors increase local rebel commanders’ willingness to institute policies and oversee practices of sexual violence. I test this theory with a mixed methods research design. In the first stage, I estimate a series of ordinal logistic regression models with a sample of 143 rebel groups active from 1989 to 2011. In the second stage, I investigate further with a case study of the Islamic State in Iraq and the Levant. Together, the results demonstrate that when foreign fighters are present in the rank and file, a rebel group is likely to perpetrate more prevalent levels of sexual violence. In addition to explaining group-level differences in rebel-inflicted sexual violence, this study demonstrates how local rebel commanders adjust their internal management strategies to the presence of foreign recruits.
Teaching: A Life Spent Learning
Authors: Hamilton Johanna
Published: December 2020

Beverly Clarke CITP MBCS, Computing at School (CAS) National Community Manager, shares her passion for lifelong learning, IT and community outreach with Johanna Hamilton AMBCS.
Who to Train and When
Authors: Melson Bernard
Published: December 2020

Bernard Melson FBCS, explores tactics and techniques that will enable leaders to map capability in their organisation and then deploy training to enhance those capabilities. The process will enable businesses to achieve maximum effectiveness and efficiency.