bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistic mathematics – instrument for solving some problems in maintenance activities in the shipyards
Authors: Manea E , Zăgan R , Militaru E 
Published: September 2020

Abstract
The organizational performance plays a fundamental role in the context of the increasing market competition, so that the chance of survival in this competition is considerably favorable for those organizations that very quickly discover and minimize their vulnerabilities and, moreover, implement management performance tools, which facilitates the detection, explanation and resolution of the various shortcomings of the management activities, the main objective being the competitiveness increasing. In the most general way, the study of maintenance involves the calculation of certain numerical indicators that aim to determine the reliability level: the probability of uninterrupted operation over a period of time; probability of success (functioning); the probability of failure (failure). Probability theory and mathematical statistics are applied in the field of engineering sciences where there are conditions of risk and uncertainty and where it is necessary to make some rigorously argued decisions. The probability theory studies random events, that is, those experiences that, repeated several times, occur each time differently, the result being not possible to be anticipated. The random variable, if a series of measurements is made, it is a notion that gives information about the value number of the measured size, as well as the frequency of occurrence of a numerical value in a row. This paper aims to illustrate, by means of justifying examples, the opportunity to use probability theory in solving complex problems from the maritime vessels shipyard maintance and repairing activity, conditioned by uncertainty, risk and variability. By the examples presented and considered to be illustrative, the authors of this paper consider that a mathematical model based on the theory of probabilistic calculations could provide a solution for satisfying the need to predict how efficiently the time required for carrying out the maintenance work of the ships in the drydock and / or on the berth in a shipyard, as part of the maintenance program required by the classification societies.
Energy and exergy analysis of a VCRS working with R600a within a thermodynamic analysis
Authors: Memet F 
Published: September 2020

Abstract
The most significant concerns related to vapour compression refrigeration systems (VCRS) refer to environmental behaviour and energy efficiency. The present study is taking into consideration the refrigerant R600a due to its very good thermodynamic properties and environmental position. On the other hand, the maximum performance of such a system will be identified by the help of the laws of thermodynamics. This is due to the fact that the analysis based exclusively on the energy analysis will not reveal where the performance of the system is degraded and how intense. After the formulation of the specific mathematical background, within the analysis have been varied the evaporation temperature in the range (–22, –8) ° C. Exergy losses in the main components of VCRS were assessed; the energy and exergy efficiencies of VCRS – as well. Resulted that the system is working at its highest efficiency for the highest evaporation temperature considered: for te = –8°C, the energy efficiency is 2,7 while the exergy efficiency is 55%. The most inefficient component part was found to be the compressor, while the most efficient is the evaporator. Such an analysis is very useful when aiming the design, the optimization and performance assessment of VCRS.
Modelling of the energy transfer during scrap melting in microwave furnace
Authors: Mitrică D , Șerban B A , Olaru M , Burada M , Dumitrescu D , Bănică C. I. 
Published: September 2020

Abstract
Efficient recovery and processing of metal waste is a priority for today’s economy. Several technologies are dealing with the recovery of metals through furnace melting but the extraction efficiencies are rather low. The paper studies the influence of heat transfer, produced by the action of microwaves, on the melting of metal waste batch. Correlation equations of the heat flux transmitted through the crucibles inside the oven were calculated by means of MATLAB modeling. Specific dimensions for the furnace enclosure were used in the paper. The simulation results were than compared to the experimental findings, to verify the model. The experimental stage consisted in the melting of aluminum and copper waste in the microwave installation, at laboratory level, and at the optimized parameters of the system.
Analyse of dynamic operation mode for drilling machine equipped with drill for pits digging
Authors: Muscă (Anghelache) G. D. , Potîrniche M. A. , Căpățână G. F. 
Published: September 2020

Abstract
The working part of drilling machine is the drill. It is the one that performs soil dislocation, crushing, evacuation and depositing around the pit. Drilling machines with a drill operate according to dry rotating drilling method, where dislocation and evacuation of drilled soil are performed by the drill. To perform this, the drill is subject in the same time to rotation and vertical push-down. Milling cutter type equipment for pits digging was 3D generated in Mechanical Desktop. Cutter model was introduced in Algor medium and automatically digitized by this. After digitization, the user introduces in Algor the supporting set and loading set for all situations. The user has only available the possibility to refine the digitization within the entire model and not only in areas of interest (as it is mostly wanted). Two real situations were considered and analysed wherein the work equipment during digging process can be found: front stress on the cutter teeth performing material cutting and front stress on cutter teeth and body that go inside material and perform centring. In both situations, supporting has tried to follow real situations wherein work equipment components subject to analysis can be found. In both loading situations, it is noticed that the operating part is not at risk to crush under stress. It is also noticed that displacements of the knots belonging to analysed structures do not have greater values in either situations.
An Analysis of The Drawing with Aluminum Brazed Sheets
Authors: Olaru I 
Published: September 2020

Abstract
This paper analyzes drawing of aluminum sheets joined by brazing. Drawing is the transformation of a plan workpiece into the drawn part or workpiece, transformation with decreasing of depth corresponding transverse dimensions. The brazing process is based on the difference by the melting points of the base materials and filler metal. During the brazing process, the aluminum sheets to be assembled are heated to a temperature between the melting temperatures of the two alloys, this process tends to modify the geometry and the microstructure of the brazed sheets. In various industries such as automotive, aerospace, electronics, machine building industry etc., aluminum alloys can be used to replace the steel parts of carcasses (car body). Brazed sheets are widely used in the manufacture of heat exchangers by using an aluminum alloy. These sheets have different thicknesses and are generally made by hot rolling. Aluminum in natural form is very soft and ductile, slightly used due to its mechanical properties. The brazing process is based on the difference in the melting points of the base materials and filler metal. During the brazing process, the sheets to be assembled are heated at a temperature between the melting temperatures of the alloy, this process tends to modify the geometry and the microstructure of the brazed sheets.
Effect of laser cladding parameters on structure properties of cobalt-based coatings
Authors: Poloczek T , Kotarska A 
Published: September 2020

Abstract
The article presents results of microstructure, microhardness and geometry tests of cobalt-based alloys deposited on low-alloy steel by a laser cladding process. As a deposited material MetcoClad 6 powder was used. Powder is characterized by a spherical shape of particles obtained in inert gas-atomization process with a size of -106 +45 µm suited to a variety of hardfacing processes. The experiments were carried out using a disk laser Yb:YAG TruDisk 3302, with a wavelength of 1.03um equipped with a disc powder feeder. The laser cladding process was carried out at various parameters of cladding speed, beam power and powder feed rate in order to obtain layers with low dilution, low porosity and good coating uniformity. Macroscopic studies were performed using a metallographic microscope light stereoscopic Olympus SZX9. Vickers microhardness tests were provided on the cross-section of layers on Wilson Wolpert 401 MVD device.
Creative Simulation Environment for Automation Control
Authors: Pomazan V M , Sintea S R 
Published: September 2020

Abstract
Modern automation control design requires new technologies to develop, test and transfer technology from design to real world. One important step in automation design is testing automation algorithms in a simulated environment appropriate by real world. Our scope is to help designers to create a simulated environment for testing automation control. We created an interface and programming tool which help designers to simulate industrial installation and can connect with automation control equipment, using real electrical signals. Our base equipment is an industrial input/output controller, which connects with the computer. On the computer, is defined and runs a simulation environment, using a software tool. This environment communicates with the real world via an input/output controller. Design engineers can create their own simulation environment, using high level programming language (C++.Net, VB.Net or C#.Net) and can connect their software with external controller, using the proposed tool or a set of objects, from the library that might be added to it. This tool is useful for the creation of a simulation environment for industrial installation or subsection of a plant.
Usage of Coloured Petri Nets for the Performance Evaluation of the Metallographic Samples Analysis Automated Systems
Authors: Pop A , Blaga F S , Ursu M P , Vesselenyi T , Bungău C 
Published: September 2020

Abstract
This paper presents the results that we attained about modeling and simulation of the metallographic samples preparation and analysis automated systems, made of two subsystems. The first subsystem polishes the samples and assesses the surface state by means of a microscope. In the second subsystem the samples are reagent attacked, washed, dried and analyzed by the electronic microscope. The evaluation of the system performance and the identification of possible bottlenecks was made by means of coloured Petri nets modeling and simulation. The CPN Tools software was used to make the model. Three coloured Petri nets models were developed. The first version assumes the analysis of the system operation by means of coloured Petri nets with simple colours, and such a simple colour was assigned to each entity of the subsystem: samples to be analyzed, robots, storage devices, microscopes etc. For a better observation of the analyzed sample path within the system, the second model version was designed, with complex colours assigned to the marks. The third version considers the time factor. The models with timed coloured Petri nets allow the system performance evaluation considering the number of analyzed samples in a given time interval. This paper presents the first and the third model, as the last one includes the second model.
Experimental study of thermal behavior of heated Natural Composite Materials
Authors: Qasim M S , Fadhel A A , Mohammed H R 
Published: September 2020

Abstract
An experimental investigation was carried out for the thermal behavior of horizontal heated natural composite material plates; (polyester resin mixed with seed dates, or egg shells, or and feathers) with different volume fraction (10%, 20%, and 30%). Natural composite materials are heated with different heat flux (1078W/m2, 928W/m2, 750W/m2, 608W/m2 and 457W/m2). Experimental test rig is used to measure the temperature distribution upper surface of composite materials. Also the thermal properties (thermal conductivity, specific heat, and thermal diffusivity) of natural composite materials are studied. The results show that the maximum value of temperature occurs at the mid- point of the all types of natural composite material plate when the volume fraction equal to 30% and the heat flux equal to 1078 W/m2. Results show that the thermal conductivity for seed dates composite material, the specific heat for feathers composite material and the thermal diffusivity for seed dates composite material are higher value when the volume fraction equal to 30%.
Design and Model of a Prosthesis for Hand
Authors: Radu (Frenţ) C , Roşu M M , Iliescu M 
Published: September 2020

Abstract
This paper presents research results on a prosthesis for human hand, focused on the need to be light weight and user friendly, with relatively low costs and enabling people have almost normal life. The idea to have a customized hand prosthesis, whose dimensios and aspect look as much as possible to that of the real hand pointed to the reverse engineering technique. The authors’ concept of prosthesis for hand is that of three phalanges finger and, mainly, two rotational motions for each of the fingers. Considering the 3D model of the hand prosthesis, with phalanges lengths and joints, there has been done kinematic analysis so that trajectories of fingers were determined and plotted. For the research presentd by this paper, are evidenced the 3D models and stages of rapid prototyping fused deposition models (FDM) of the index finger phalanges. Motion control has been modelled using fuzzy logic. The studied motion is that of getting closer to an object in order to take / grip it. Further development of the research will be focused on: all mechanical components detailed design; complete desgin of the command and control system for the mechatronic parts; prototyping; test and validation of the prosthesis prototype.
Assessment of occupational noise exposure in tyre manufacturing
Authors: Roșca (Ciocan) I , Dascălu L C , Solomon G 
Published: September 2020

Abstract
According to the legislation in force the employer has a responsibility to evaluate and to measure the noise levels to which workers are exposed, paying special attention: level, type and duration of noise. Noise risk assessment is critical to protecting workers from the risks that threaten their health and safety from noise exposure. The noise risk assessment identifies the workers exposed to the risk generated by the noise and determines their level of noise exposure to ensure that the maximum noise exposure limit is not exceeded. When the worker exposure is exceeded, the noise becomes a risk for safety and health, because high noise levels cause hearing loss and this is irreversible. Also, stress from time spent at a high noise level was associated with increased workplace accident rates. This paper presents a technical method for measuring noise exposure in working environment using homogeneous noise exposure groups. The measuring process requires observation and analysis of all noise exposure conditions so that the quality of the measurements can be controlled. The uncertainty of the results is also taken into account. More than half of the workers were investigated during the research (over 900 workers), covering all the production workplaces. The results of the measurements obtained according to this method provided useful informations in order to define the main priorities regarding noise control measures.
Analysis of flow in fluidized bed of particles
Authors: Sabau A 
Published: September 2020

Abstract
The paper presents a study of the flow in a fluidized bed. The analysis is based on measurements made on an experimental stand and computer simulations. Free software packages have been used for simulations. Simulation is done used the most common model for this kind of problem. The first type of model is the Eulerian-Eulerian type and have as their first approximation, the assimilation of the solid phase with a continuous environment. The second category of models is Eulerian-Lagrangean type, they treat the fluid phase as continuous and the solid phase as individual particles or groups of particles “parcels” with similar characteristics. The results of the simulations were compared with the measurements performed on an experimental stand. The experimental stand is composed of a glass column with a diameter of 75mm and a height of 500mm and allows the study of flow in a fluidized bed containing spherical glass beads of 250–500μm in diameter. The results of the simulation were in good agreement whit measured data and in accordance whit the result presented in other specialized studies.
Thrust force evaluation for a ROV (Remont Operating Vehicle) propeller
Authors: Sabau A 
Published: September 2020

Abstract
The underwater vehicles operated remotely, known from the specialized literature under the name of ROV are common and are intensively used in the maritime industry. Depending on the area of use, ROV must satisfy numerous constructive and functional requirements, which are difficult to achieve in practice and the simulation is a challenging alternative. The big challenge is the simulation of the thrust force generated by the propeller. The present work aims to present such a simulation realized with the Ansys Fluid Dynamics software package. The simulation presented uses a 3D model of an asymmetrical propeller in the duct, having as reference the T100 propeller marketed by Blue Robotics. The fluid volume extracted after the model was made was separated into two domains one static and other rotating around the propeller, which was discretized using the default grid generator. The solution was obtained under stationary conditions using only the flow equations together with the standard k-ε model for turbulence modelling. The calculation was made for rotation speed values in the working domain. In the end, using the facilities of the program, the thrust force of the propeller was calculated. The obtained results were compared with the experimental measurements and critical analysis will be done.
Injection moulded composite bipolar plates for a portable hydrogen fuel cell charger
Authors: Serban D , Opran C Gh 
Published: September 2020

Abstract
Fuel cells are electrochemical devices that convert the chemical energy of a reactants directly into electricity and heat with high efficiency. Proton Exchange Membrane or Polymer Electrolyte Membrane (PEM) fuel cells are one of the most common type of fuel cells. In a convection PEM fuel cell, the oxygen from air is introduced to the cathode and hydrogen is introduced to anode. Between the anode and cathode electrodes is sandwiched the polymer electrolyte membrane. The hydrogen molecules break apart into protons and electrons due to the reaction helped by catalysts. The protons travel through the membrane to the cathode and electrons travel to an external circuit. At cathode side the protons, electrons and oxygen molecules combine to form water. Research work was directed to the study of hydrogen fuel cell power systems for portable applications. Last decade the industry developed portable power systems based on hydrogen fuel cell, mobile telephone chargers, vehicles energy supply. In this paper are presented the experiments with a hydrogen fuel cell stack in which were assembled resin filled graphite bipolar plates and then injection moulded polymeric conductive composite bipolar plates and results were compared concluding that injection moulded bipolar plates could represent an attractive alternative in building efficient fuel cell portable power systems.
Computer Simulation of Thermal Processing of Steel
Authors: Smoljan B , Iljkić D , Hajdek K , Sitek W 
Published: September 2020

AbstractThe review of the numerical modelling of casting and welding of steel workpieces was studied. The contemporary industry needs tools to optimize and control parameters of processes by considering the favourite chemical composition of steel. In recent time, very efficient tool for optimizing and controlling of the process parameters is numerical modelling of engineering processes. At casting and welding numerical modelling is focused on optimization of distribution of microstructure contents, mechanical and physical properties distribution and tolerated distortions and residual stresses. Mechanical properties and prevention of distortion and cracking can be accomplished by prediction and control of residual stresses and microstructure distribution. The numerical modelling of thermal processing of metals consists of the research of multi-scale processes and multi-physics processes, such as phase transformations, heat transfer and mechanics of materials, and research of numerical methods for computer interpretation of the problem. By means of the numerical modelling and computer simulation of thermal processing should calculate the transient temperature field, melting and solidification processes, as well as, to calculate distribution of mechanical and physical properties and microstructure composition. In this work, the numerical models of studied thermal processes are based on the finite volume method. Values of surface heat transfer coefficient, heat capacity and heat conductivity coefficient were obtained by the inversion method. The microstructures composition has been predicted by CCT diagrams and additionally improved by the kinetic equations. The mathematical model has accomplished to solve thermal processing of 3-D axially symmetric specimens.
An Analysis of Performance Factors Evaluation of Reusable/Returnable Packaging
Authors: Smoljan B , Hajdek K , Šarkanj B , Bogunović J 
Published: September 2020

Abstract
Development and application of reusable industrial packages, which can be used in assembly line has been investigated. The reusable industrial packages are often called reusable crates and totes or reusable/returnable packaging containers. The trend of development of reusable packaging systems has been facilitated by the plastics industry developing lightweight rugged crates and totes, which can be used in storages and manufacturing lines. Sizes range of these kind packages is from handled totes to pallet-load sized intermediate bulk containers for manufacturing.
Possibility that each component reaches the manufacture at the right time, in the right sequence, and in the appropriate version, referred as Just-In-Sequence was analysed. An automotive supply chain characteristics and scheme of component suppliers’ structure in Just-In-Sequence way was illustrated. Materials properties of reusable packaging was studied. The most important packaging performance factors are durability, flammability, sanitation and ergonomics of packaging, which affect the cost, and operations of a reusable packaging system. Since the importance of industrial reusable packaging is growing up, the new sophisticated test method for transport packages are needed by which vulnerabilities and exposures in the application of reusable industrial containers will be taken into account.