bluuebunny/crossref_metadata_2025 huggingface dataset:
Review of cascade refrigeration systems for vaccine storage
Authors: Kasi Parthiban , Cheralathan M
Published: October 2021

Various models are already developed to achieve the refrigerating effect. Each refrigeration system has its own set of benefits and drawbacks, as well as a unique application. The vapor compression refrigeration system and the sorption refrigeration system are the two most prominent refrigeration technologies that may be utilized for a variety of purposes. In the medical profession, cascade refrigeration will be established in the storage of blood banks, plasma, vaccines, bone banks, biological fluids storage, etc. Storing heat-sensitive vaccines at the right temperature is crucial yet often difficult by the availability of ultralow temperature cold storage. This paper has reviewed that the different types of cascade refrigeration systems for a better refrigerating effect on vaccine storage.
Effect of bifurcation in phase change material by heat transfer tube in a horizontal solar thermal energy storage
Authors: Sarma Ishani , Bhimesh S , Senthil Ramalingam
Published: October 2021

A horizontal thermal storage that uses a phase change material (PCM) for energy reposition undergoes melting at the base and corners due to minimal natural convection. A storage container is split into two halves using a rectangular duct, which improves convection currents and facilitates heat transfer with a low melting time. The results emphasize the duct design in determining PCM melting. The fluid is held at a constant temperature of 50-60 °C at a flow rate of 5 kg/min. Conventional tube and duct designs are investigated. Thus, PCM melting increases up to 30% with enhanced melting rate. Comparing conventional fluid tube, rectangular duct is beneficial to improve the melting rate through reducing PCM size in the container.
Performance, combustion and emission characteristics of a diesel engine fuelled with biofuel and oxygenated additives
Authors: Shukla Apoorv , Mishra Aman , Paneerselvam S , Mathanraj V
Published: October 2021

The entire world has been seeing a continuous surge in the number of automobiles globally. This has further lead to a severe increase in the consumption of fossil fuels such as diesel, petrol, natural gas, etc. Biofuel can serve as a viable alternative to conventional fossil fuel made from renewable resources, such as edible as well as non-edible vegetable oils. This paper focuses on various studies related to the performance, combustion and emission characteristics of a diesel engine fuelled with Simarouba oil as the bio fuel and Isobutanol as the oxygenated additives. The experiments were carried out on a 4 - stroke, single cylinder diesel engine by varying load. Extensive research work is being done in this field using a variety of biofuels. Bio fuels are nothing but the fuels that are obtained from plants to be used in Internal Combustion engines which in turn have the added advantage of lower emissions to that of conventional diesel and gasoline. Simarouba oil blends had been used in direct injection compressed ignition engine as an alternate fuel that has similar properties of diesel.
Analysis of vapor compression refrigeration system employing tetrafluroethane and difluroethane as refrigerants
Authors: Goyal Kunal , Nanditta R V , Teja Potteli Dharma , Malarmannan S , Manikandaraja G
Published: October 2021

The axiomatic effects of ozone layer depletion have caused additional damage in the last few decades. The accretion in greenhouse gases has transformed to take cardinal steps immediately. The concoct blend of 1,1,1,2 Tetrafluroethane (R134a) and 1,1, Difluroethane (R152) a was tested in a vapour compression refrigeration system as these are non-toxic, eco-friendly, non-flammable and non-corrosive. Experimental performance analysis of vapor compression refrigeration system using R134a and blends of R152a and R134a is done for different dimensions of expansion valves. Various parameters like coefficient of performance (COP), refrigerating effect and compressor work were analyzed. Refrigeration effect and compressor work of R134a was higher than R152a. COP value was reliable for 60/40 ratio of R152a and R134a and maximum COP was achieved with the blend of 90/10 ratio in the first expansive coil. These aberrant results could be overcome by amalgamation of R134a and R152a as the discharge temperature of R152a is effectively controlled by blending.
Experimental investigation of performance of shell and coil heat exchanger in waste heat recovery systems in CI engine
Authors: Nanditta R V , Gowtham R , Udayakumar P , Manikandaraja G
Published: October 2021

This study analyses heat transfer coefficients in a shell and tube heat exchanger and the effectiveness of reduced temperature of exhaust gases in shell and helically coiled tube heat exchanger. This facilitates low installation cost, high performance and improved safety. The experimental setup consists of a shell with a coaxial outer tubular, end plates attached to the inner walls and a spiral coil through which water flows. These end plates encompass a shell cavity in tubular shape. This facilitates the inlet and outlet intended for exhaust gas. The coil is wounded in such a way that the axis of shell fit the inner and outer walls with limited radial clearance. Due to axial spacing of coils from one another, a spiral path is generated in the interior shell cavity which provide amenities for water flow. This path creates, helps in reducing the temperature of exhaust gas.
Study of heat generation and dissipation mechanism for an exciter shaft and its impact
Authors: Santhana Krishnan R , Nayani Sudha Sindhuja
Published: October 2021

Compactor is a heavy-duty machinery that uses compaction to reduce the size of waste materials or biomass or compaction of load. A bearing is a machine element that restricts relative motion to only the desired motion, and decreases friction between moving parts. It is an essential component in a compactor and is used for supporting the exciter shaft. Compaction is achieved by vibration of roller drum, which in turn is achieved by means of generated at the exciter shaft with an eccentric mass. During this process of generation of forced excitation, heat is generated at shaft to bearing interface. The current heat generation and dissipation paths for the bearing on the exciter shaft of the compactor were studied and calculated. Suggestions for heat dissipation optimization are provided. Various optimization methods were devised for heat dissipation to improve the wear as well as efficiency of the bearing and further testing is required for implementation of same.
Software designed to digitize transitional characteristics when conducting bioimpedance studies on a biological object
Authors: Tomakova R A , Tomakov V I , Korsynskiy N A , Egorov I S
Published: October 2021

The essence of the article is to develop a method for the formation of descriptors intended for neural networking classifiers of medical risks based on the analysis of transition processes in the biomaterial in the in vivo experiment.

The essence of the proposed method is to form the test effects of the probing current on the anatomical areas with anomalous electrical conductivity and obtaining the amplitude-phase-frequency characteristics of the impedance of the biomaterial to which the test effect was carried out. The coordinates of the Cowla’s graphic were used as descriptors. Cowla’s graphic was obtained on the basis of the conversion of Carson counts of the transition process in a quadrupole, the element of which is the impedance of the studied biomaterial. A sequence of unipolar rectangular pulses was supplied to the inlet of the quadrupole.

It is shown that the linear model of the biomaterial impedance allows you to obtain descriptors based on its amplitude-phase-frequency characteristics, taking into account the dissipative properties of the biomaterial. The receipt of the Cowla’s graphic model with its dissipative properties, allows you to build medical risk classifiers for socially significant diseases.
On the efficiency of power transformers with «star-zig-zag with zero» winding connection scheme in rural electricity networks supplying household consumers
Authors: Hanin Yu I , Rodionova O V , Panchishkin A P , Zaichkina M A , Shakhbazova Ya E
Published: October 2021

The dependencies of the loss coefficient on the value of reverse- and zero-sequence current unbalance coefficients are obtained, allowing estimating the energy efficiency of power transformers operation at different unbalance characteristics. The electricity losses were calculated from these dependencies and from data obtained from instrumental measurements at rural substations supplying household consumers. It was obtained that the power transformer with «the star-zigzag with zero» scheme is 6 times more energy efficient than the power transformer with «the star–star with zero» scheme. However, with small values of the currents asymmetry (for five cases studied), the power transformer with «the star-zigzag with zero» scheme has overestimated power losses.
Classification of maintenance techniques and diagnosing failures methods
Authors: Nawfal Mustafa Mohanad
Published: October 2021

Equipment components essentially the parts responsible for power transmission and bearings will expose to multiple types of stresses, including external stresses coming from the nature of the working and internal stresses resulting from movement between the moving parts or thermal industrial processes. These stresses lead to damage or defect, which adversely affect the current or future performance of these systems. To ensure the reliability of the machine or structure has to establish a continuous condition monitoring system that can detect the abnormal condition state early. This paper will cover the monitoring techniques used to observe the mechanical conditioning of the vital components(such as bearings, shafts, gearboxes, etc.) In an ultra-low frequency rotating machinery in industrial applications including hydroelectric generator, steel mills, paper mills, water sewage plants, cement kilns, and wind turbines.
The search for R&D partners based on patent data
Authors: Borodin N , Korobkin D , Bezruchenko A , Fomenkov S
Published: October 2021

Nowadays, companies still rely heavily on expert knowledge when selecting research and development partners (R&D, R&D). In this paper, it is proposed to identify and select potential technology partners based on the analysis of the USPTO patent array using the Problem & Solution model. The process of identifying R&D partners will be based on the similarity of solutions to technological problems. This paper shows the development of software for extracting the semantic SAO structures from USPTO patent documents, which are used to form the Problem and Solution structures, and selecting potential technology partners based on them. The theoretical significance of the study lies in the developed algorithms for parsing patents; extracting SAO using semantic text analysis; formation of Problem-Solution structures based on SAO data; identifying R&D partners based on similarities in solutions to technological problems.
Cucumber cultivation technology using tunnel covers
Authors: Ovchinnikov A S , Borodychev V V , Akulinina M A , Krutoyarov A A
Published: October 2021

Obtaining early cucumber production in the Volgograd region sharp-continental climate with frequent early spring frosts is possible only with using tunnel covers. A distinctive feature of the considered technology is cucumber cultivation using tunnel covers with insulated zone organization by making cracks in the soil with filling them with straw. This provides the comfortable conditions creation for the plants preservation when there is a sharp drop in air and soil temperature in spring and a possible return of spring frosts. Maintaining soil moisture in the 0,5 m layer at the level of 90% of the lowest moisture capacity by drip irrigation allowed to obtain a cucumber yield at the level of 85,9 t/ha, which is 7,8 t/ha more than in the basic option.
Restricted Boltzmann machine based on a Fermi sea
Authors: Lyakhova Ya S , Polyakov E A , Rubtsov A N
Published: October 2021

In recent years, there has been an intensive research on how to exploit the quantum laws of nature in the machine learning. Models have been put forward which employ spins, photons, and cold atoms. In this work we study the possibility of using the lattice fermions to learn the classical data. We propose an alternative to the quantum Boltzmann machine, the so-called spin-fermion machine (SFM), in which the spins represent the degrees of freedom of the observable data (to be learned), and the fermions represent the correlations between the data. The coupling is linear in spins and quadratic in fermions. The fermions are allowed to tunnel between the lattice sites. The training of SFM can be efficiently implemented since there are closed expressions for the log-likelihood gradient. We find that SFM is more powerful than the classical restricted Boltzmann machine with the same number of physical degrees of freedom. The reason is that SFM has additional freedom due to the rotation of the Fermi sea. We show examples for several data sets.
Thermodynamics of

TT¯

perturbations of some single particle field theories
Authors: LeClair André
Published: October 2021

We study the thermodynamic Bethe ansatz (TBA) equations for pure

T

T

¯

perturbations of some simple integrable quantum field theories with a single bosonic or fermionic particle, in particular the massive sinh-Gordon model and its ultraviolet (UV) limit which is a deformation of the conformally invariant free massless boson. Whereas the TBA equations for

T

T

¯

deformations of massive theories are in principle known, the TBA equations we propose for the deformations of conformal field theories are relatively new and require a special factorization in rapidity variables of the CDD factor for the scattering of the massless particles. The latter TBA equations can be solved exactly and reproduce the known results for the ground state energy on a cylinder of circumference R which were previously obtained using different methods based for instance on the Burgers differential equation. Special attention is paid to the c-theorem in this context which is discussed in some detail. For positive infra-red central charge c
IR, for flows consistent with the c-theorem the ground state energy develops a (previously known) square-root singularity toward the UV, which strongly suggests the theories are UV incomplete in these physically important cases. We suggest that the singularity indicates a tachyonic vacuum instability. Other cases with c
IR < 0 do not have this singularity are interpreted as being UV complete with c
UV = 0. We extend our results to a continuously variable c
IR by introducing a chemical potential and suggest this as a possible toy model for the

T

T

¯

perturbed Liouville theory.
Complexity-like properties and parameter asymptotics of

Lq

-norms of Laguerre and Gegenbauer polynomials
Authors: Dehesa Jesús S , Sobrino Nahual
Published: October 2021

The main monotonic statistical complexity-like measures of the Rakhmanov’s probability density associated to the hypergeometric orthogonal polynomials (HOPs) in a real continuous variable, each of them quantifying two configurational facets of spreading, are examined in this work beyond the Cramér–Rao one. The Fisher–Shannon and LMC López-Ruiz–Mancini–Calvet (LMC) complexity measures, which have two entropic components, are analytically expressed in terms of the degree and the orthogonality weight-function’s parameter(s) of the polynomials. The degree and parameter asymptotics of these two-fold spreading measures are shown for the parameter-dependent families of HOPs of Laguerre and Gegenbauer types. This is done by using the asymptotics of the Rényi and Shannon entropies, which are closely connected to the

L

q

-norms of these polynomials, when the weight-function’s parameter tends toward infinity. The degree and parameter asymptotics of these Laguerre and Gegenbauer algebraic norms control the radial and angular charge and momentum distributions of numerous relevant multidimensional physical systems with a spherically-symmetric quantum-mechanical potential in the high-energy (Rydberg) and high-dimensional (quasi-classical) states, respectively. This is because the corresponding states’ wavefunctions are expressed by means of the Laguerre and Gegenbauer polynomials in both position and momentum spaces.
To the theory and practice of creating modern roller machines
Authors: Abdukarimov A , Madaminov S
Published: October 2021

The article describes the areas of application of roller machines, trends in the development of their designs, research work on the modernization and creation of new roller machines. Special attention given to the roller machines with a variable center distance of the working shafts. The descriptions of the gear-lever differential transmission mechanisms created by authors are given. In particular, the correct applications of the created mechanisms in roller machines of six types are shown; they are 1. One of the working shafts has the ability to rotate around its own axis, and the second working shaft, in addition to rotation around its own axis, moves relative to the first working shaft along the line, passing through the center of the axes of rotation of both working shafts; 2. Both working shafts have the ability to rotate around their own axes and move symmetrically along a line passing through the same axes of rotation relative to each other; 3. One of the working shafts has the ability to rotate around its own axis, and the second working shaft, in addition to rotation around its own axis, moves relative to the first working shaft along an arc with a certain radius of curvature; 4. Both working shafts can rotate around their own axes and move symmetrically relative to each other along an arc with some symmetrical centers of rotation; 5. One of the working shafts has the ability to rotate around its own axis, and the second working shaft, in addition to rotation around its own axis, moves relative to the first working shaft along a complex trajectory; 6. Both working shafts can rotate around their own axes and move symmetrically relative to each other along a complex trajectory.
Analysis of Carbon Fibers Treatment Technology to Obtain Composites Materials with Metal and Non-Metal Matrix
Authors: Caliman R
Published: October 2021

When designing any composite material, the compatibility between the component elements must be considered, a compatibility that can be seen from a physical and chemical point of view. Chemical compatibility refers to the existence or development to a small extent of reactions between components. Thus, at high temperatures, the diffusion processes intensify, and fragile compounds can form, which cancel the direct connection between the components, resulting in a significant decrease in the mechanical strength of the composite material. A successful process of manufacturing carbon fiber-reinforced composites requires that the fiber to be protected, usually with a coating, during their manufacture and use. The paper aims to analyze the process of Chemical Vapor Deposition (CVD) which is a successful process of manufacturing carbon fiber reinforced composites. They require that the fiber be protected with a coating during their manufacture and use.
Aspects regarding 3d modelling and finite element analysis of a crusher bucket
Authors: Căpățână G F , Potîrniche M A
Published: October 2021

The highest consumption of solid materials, especially rocks extracted from quarries, has the construction materials industry. These materials can be used either in natural form (gravel, sand), or after a reduced processing (marble, large stone, for foundations), or after a complex processing (lime, plaster, cement, sandstone, clay). The crusher buckets are used to grind materials in order to reach optimal or convenient sizes of processed materials in order to carry out a good technological process. The study of the shredding processes and of the equipment related to these processes is done in order to reduce the energy consumption necessary to reduce the dimensions of the raw materials to dimensions necessary for further processing. This study is of particular importance due to the fact that the shredding operation is energy intensive. This paper presents aspects regarding the geometric modelling of a crusher bucket and the finite element analysis of the bucket housing. All the components of the bucket were modelled in the Inventor software and then assembled to obtain the assembly. The modelling was based on an example of a crusher bucket taken from the literature. Finite element analysis was performed to highlight the eigenmodes of the crusher bucket in order to estimate the eigenfrequencies range of this equipment.
Computational fluid dynamics simulations for composite rocket propellant optimization
Authors: Dîrloman F-M , Matache L-C , Rotariu T , Țigănescu T-V , Zvîncu D , Ungureanu M-I , Iorga O
Published: October 2021

When designing a rocket engine configuration, both in terms of propellant grain, combustion chamber and nozzle geometry, one of the most convenient approach is using Computational Fluid Dynamics (CFD) Simulation. Numerical simulation is an alternative method of scientific investigation, which substitutes large number of experiments that often imply high financial burden and are also dangerous for the personnel involved. The numerical approach is often more useful than consecrated experimental method because it provides complete data that cannot be directly observed or measured, or it is difficult to highlight by other means. In this study we focused on applying CFD simulation to composite rocket propellants in a rocket engine with convergent-divergent nozzle configuration using Ansys Fluent Software. An ammonium nitrate (AN) based composite rocket propellant having four components was analyzed: oxidizer, metallic fuel, binder and catalyst agent. Explo5®, a thermochemical software, was also used to calculate the equilibrium compositions of the combustion products in the combustion chamber. It turned out that the results obtained on the basis of the simulation are consistent with those of the experimental testing. The data collected so far will be used to optimize the grain configuration of the composite rocket propellant.
Study of the functional parameters of the freshwater generation system, as an integral part of the waste heat recovery system for a tanker ship
Authors: Faităr C , Stan L-C , Buzbuchi N , Baciu M
Published: October 2021

A ship needs fuel for both travel and on-board operations. In the most general case, the fuel is converted on board the ship into energy in the form required for its end use: mechanical power for propulsion, electrical power for auxiliary board systems and thermal power for thermal needs. In this paper, I propose to deal with both elements of theoretical calculation and real elements of the operation of the freshwater generation system from the main engine of the ship. I chose to treat this system because it is the main subassembly of the residual heat recovery system from the main engine through cooling water. In the theoretical calculation, The results of the paper will be focus on calculation of the geometric and functional parameters of the fresh water generator. In the final part of the chapter, I will refer to the real parameters of the freshwater generation system where I will draw operation diagrams to highlight as concretely as possible the operation of this system on board the ship.
XPS, SEM, AFM, and Nano-Indentation characterization for powder recycling within additive manufacturing process
Authors: Gorji N E , O’Connor R , Brabazon D
Published: October 2021

Powder recycling and reducing the waste metallic powder is EU’s key provision in waste framework directive (2008/98/EC). The aim of this investigation is to analyse the correlation between the surface and morphology properties of (virgin and recycled) powders and the microstructure and mechanical properties of the 3D printed parts (made of three powders). Two biomedical Tibia implants have been 3D printed from virgin and 3-5 times recycled powders of stainless steel 316L. For this, the surface composition and microstructure of the powders has been characterized and correlated to the nanoindentation measurements carrier out on these implants. X-ray surface spectroscopy (XPS) has been used to analyse the oxidation level on the powder’s surface revealing less than 10% more oxygen on the surface of recycled powders. SEM analysis shows less than 5 μm difference in powder size distribution even though the shape and circularity of the recycled powders seem to be affected under several reusing cycles. The size of the powder particles does not show much difference but satellites and binding between the powders increased in recycled powder. The hardness and effective modulus of the parts from recycled powders are significantly smaller than the virgin-made implants, which could be due to higher porosity present in the recycled powder or due to oxygen increment on recycled powder. The surface roughness (AFM analysis) has slightly increased on part made of recycled powders. However, the overall morphology shows little difference between the two parts.
Dynamic Lean 4.0 Cyber-Physical System for Polymeric Products Manufacturing in Industry 4.0
Authors: Ionel D-S , Gh Opran C
Published: October 2021

In the polymer products industry, the adoption of the intelligent production system offers solutions to increase automation and reduce the complexity of manufacturing processes. Simultaneously with the emergence and development of the Industry 4.0 concept and techniques, numerous approaches have appeared in order to implement Lean principles and tools at the intelligent production system level, with the main purpose of increasing efficiency and eliminating waste. Lean 4.0 architectures rely on the physical and digital resources of Industry 4.0, which can be active (directly involved in the production processes of the product) and passive (which have a supporting role). The implementation of Lean 4.0 principles is based on Lean 4.0 tools, defined at cybernetic level, and on the corresponding physical assets, which intervene in the management of the production flow. The objective of this paperwork is to present the realization and implementation framework of the cyber-physical system Lean 4.0 at the manufacturing cell level into an Industry 4.0 production system.
Development of machine steering with use of PLC as introduction to 4.0 Industry
Authors: Lysek K , Gwiazda A , Herbuś K
Published: October 2021

Article was written in order to make an attempt at developing a simple steering system for numerically controlled machines, with use of virtual modelling environment and an actual driver together with HMI panel. It was made as a response to demand of centralized system for steering a smart factory containing many machines. In the article, creation of a simple single machine steering system was described, which can be upscaled to the entire production hall. Used steering in this case is setting of position in an absolute system, in which only 3 variables X, Y and Z are known, and the operator can perform a correction of location and speed. Obviously, in real conditions these values will be set by a different program - like a post processor generating G-code. Usage of one data communication server can allow integration of devices within one production, and this allow creation of a smart factory suitable for 4.0 industry. In order to obtain such communication, an OPC server was used. Furthermore, the process of creating and connecting machines or programs to it was briefly presented.
Comments regarding the use of Monte Carlo method in the analysis of maritime ship maintenance works
Authors: Manea M G , Zăgan R , Manea E
Published: October 2021

Elaboration of a mathematical structure, together with a list of correspondences between the mathematical symbols and the objects of the concrete situation considered, led to what is called the mathematical model. The Monte Carlo simulation method is increasingly applied to the analysis of stochastic problems or in conditions of risk, when the same direction of action can have several consequences, the probabilities of which can be estimated. The Monte Carlo simulation can be used to analyze the flow of processes involved in the maintenance works of a ship in a shipyard, because it represents a system characterized by both input and output variables that can interact and therefore the same course of action may have several consequences. Thus, the execution of a certain type of maintenance work on the ship may lead to an increase or decrease in the volume of work initially estimated depending on: class society inspections, limiting the budget for works due to the crisis on the maritime transport market, labor force resources of the shipyard (limited in certain periods with peak load). Consequently, a stochastic model is outlined in which randomness is present, and the states of the variables are not described by unique values, but rather by probability distributions. The paper highlights, through concrete examples, some applications of the Monte Carlo method for the analysis of maintenance works performed for seagoing vessels.
Research on advances in roller bearing manufacturing
Authors: Mehmet I , Dogan G , Chitariu D F , Dumitraș C , Negoescu F
Published: October 2021

In general the manufacturing of bearing require strict technological step that are performed on highly specialized equipments that require timely adjustments at batch changes. The process of forging and heat treatment stages consume the most amount of energy but the most expensive stage is the grinding operation. An alternative to grinding and honing processes is hybrid machining by combined hard turning and rolling process. One main development directions of all major roller bearing manufacturers is improving durability of bearings by reducing the roughness by inducing high residual stresses in the surface layers of bearing rings and improving the profile of roller for reduced contact stress. Rolling can induce higher surface stresses and reduce roughness with benefits to the durability of the bearings. The present paper presents and analysis of the technological route for bearing ring and bearing roller and focuses on the research direction on the advances in manufacturing / machining methods for bearing rings and rollers.
Exergy and energy analysis of a vapour compression refrigeration system for the investigation of a new refrigerant to be used on board the ships
Authors: Memet F
Published: October 2021

This paper investigates the comparison between single stage vapour compression refrigeration cycles working with R134a - a traditional refrigerant for marine applications, and R435A - a new refrigerant having Dimethyleter (DME) 80% and R152a 20%. Since R134a shows a high GWP (Global Warming Potential), in the next future this refrigerant will be a subject for replacement. The new refrigerant taken into discussion here, R435A, shows a much lower GWP (3 compared with 1300 of R134a). The study allows the investigation of the performance of the cycles working with these two refrigerants, within a thermodynamic analysis, based on both first and second laws of thermodynamics. This kind of research is a strong tool used in design, optimisation and performance assessment of refrigeration systems. In the present paper are analysed the influence of evaporation temperatures on first and second law efficiencies and on exergy losses in the system. The results are obtained when this temperature varies in the range (248÷278) K. These results reveal the fact that R435A is a viable solution for R134a replacement, since average COP for R435A is about 35% higher than for R134a, the average exergy loss is around 40% smaller and the average exergy efficiency is approximately 35% higher.
NRM30 as a possible substitute for R22 in marine vapour compression refrigeration systems
Authors: Memet F
Published: October 2021

The purpose of this paper is to investigate the possibility of using NRM30 in order to replace R22, in existing plants on board the ships. NRM30 is a refrigerant mixture of R134a/R1270/RE170 (55/37.5/7.5 by mass percentage). This approach is based on the better environmental behaviour of NRM30. The comparison between R22 and NMR30 has been developed on the basis of Coefficient of Performance (COP), temperature at compressor exit, power consumption per ton of refrigeration and volumetric refrigeration capacity variations, when evaporation temperature and condensation temperature increase. The above mentioned are calculated when the evaporation temperature varies in the range (-2, +10)° C and the condensation temperature varies in the range (40, 50)° C. The results reveal that COP increases with the increase of the evaporation temperature and the decrease of the condensation temperature- for both refrigerants. Although the ecological refrigerant (NRM30) shows an average COP value lower than the one of R22 (about 30% lower), NRM30 ensures an ecological operation of the plant and lower temperatures at compressor exit- which it is benefic for the long life of this machine. For the considered temperature ranges, the plant operates in efficient conditions for the higher value of the evaporation temperature (+10°C) and for the lowest value of the condensation temperature (40°C). For this conditions, it is seen that the vapours temperatures at the compressor exit are lowest, being ensured also the safe operation of the compressor.
Experimental Modal Analysis of Violin Bodies with Different Structural Patterns of Resonance Spruce
Authors: Mihalcica M , Stanciu M D , Gliga V G , Campean M , Dinulică F , Nastac S M
Published: October 2021

The paper aims to highlight the modal response of violin bodies made of four quality classes of resonant wood, following the anatomical structure of the wood. The four categories of musical instruments, made at the S.C. Gliga Instrumente Muzicale S.A., were excited by an impact hammer type B&K 8204 and its response was captured by an accelerometer type B&K 4517-002 (Brüel & Kjær, Denmark, Nærum). The received signals were transmitted through a conditioning device to a Dynamic Signal Acquisition System (DAQ) - NI USB-9233 (National Instruments, USA, Austin), connected to a laptop. The obtained signals were in the form of the natural frequencies and the damping factor. The results highlighted the nonlinear and inhomogeneous behavior of violins with different structural patterns, proving that their vibrations depend on many factors.
Aspect related to 3D modelling and finite elements study of the lifting platform
Authors: Muscă(Anghelache) G D , Potîrniche M A , Căpățană G F
Published: October 2021

3D modeling of the lifting platform was done in Catia V5R20 software. This soft was chosen as it gives an integrated solution, besides facilities related to modelling with solids which are common to all representative applications this also offers modules intended for stylists this way allowing extension of computer use also on previous stages of constructive engineering. The truck undercarriage is of LT28 type from Volkswagen producer. For 3D modelling, a leaflet from producing company was used. To represent the assembly of lifting platform firstly we realized a 3D model of the vehicle, and thereafter we realized the model of the nacelle type system and the manner of fixing on undercarriage. The finite elements study of the lifting platform was done by using Autodesk Inventor and for starting we determined the initial conditions type of network and material used. The main boom structure is calculated to stand for all stresses the platform is subject to. The structure is so designed that it can be fixed on the vehicle undercarriage frame. As a result of study, its maximum allowable stresses, travels and safety factor can be noticed. The first finite elements study was done on joint area between lifting platform boom and machine undercarriage, initial conditions were set within the study as follows: material mechanical properties type of performed study, force loading. Further to static study, data related to stresses, deformations and safety factor resulted. Maximum allowable stress in the boom of lifting platform has very small values wherefrom results that this stands a force applied on the other end.
The effects of the bending moment upon the mobile element of CNC Machine Tools with great distance between slides
Authors: Petrea L , Stan Gh
Published: October 2021

CNC Machine Tools with kinematical feed chains with great distance between slides (gantry milling machines, cutting machines, carousel lathes etc.) are utilized extensively for machining large and heavy parts. In this type of machine, we can observe a specific phenomenon where the gravity center of the vertical actuated elements moves in the direction of the balancing force for the mobile elements, causing a bending moment to be induced in the mobile element (the mechanical coupling between the two kinematical feed chains). This effect leads to deformations and in worse case looking of the mobile element during movement, all of this has a detrimental effect on machining accuracy and efficiency. In this paper, using finite element analysis (FEA) several studies where preformed. A static analysis that calculates the stresses, displacements and strains. A modal analysis to determine the first six natural frequencies and modal deformed shapes. A harmonic response analysis to determine the response of the mobile element structure. This studies will highlight the week points of mobile element and will provide the machine tool builder with important information regarding the points that need to be address in order to improve the behavior of the mobile element during actuation.
Heat Transfer Augmentation of Laminar Flow in Horizontal Circular Nano-Composite Tube with Insert
Authors: Qasim M S , Abdulla F A , Nahla H D
Published: October 2021

A numerical investigation was carried out to predict the heat transfer behavior and friction factor in heated circular nano- composite tube with two cases: plain tube and inserted tube. Typical twisted tape (TTT) and triangular cut twisted tape (TCTT) were used as insert if twisted tape ratio equal 2 and thickness equal 1 mm. The composite material consist of polyester resin mixed with nano copper with different weight fraction 3%, 7%, 33%, 50% and 75%. The governing equations were solved by using commercial ANSYS Fluent package (2017) with the assistance of Solid Works and Gambit software program. The finite volume approach was used in solving the equations to predict the pressure flow, heat transfer and temperature distribution along the tube. Nano- composite material tube was heated under constant heat flux (1244W/m2). The water flow in the tube was laminar (297 < Re < 1670). The dimensions of circular tube were 800 mm length, 20 mm diameter and 1.5 mm thickness. Numerical results show that the heat transfers was augmented when (TTT or TCTT) was used as a swirl flow devices comparing with plain tube. The water temperature increases significantly at the center line of tube by 25% when TTT is used, while the friction losses increase in an undesirable rate of 155 %.Finally, it can be concluded that the nano-composite tube is efficient in heat transfer applications.
Concept development and prototypes for robotic systems in active assisted living
Authors: Todirițe I , Radu-Frenț C , Cotfas P-Al , Iliescu M
Published: October 2021

Active and Assistive Living, AAL, is a concept that attention have been focused on in the last decades. There are many young people with disabilities, such as visually impairment, missing limbs, AVC stroke problems. There are also many old people who have locomotion, eyesight and many other health problems that make their lives so very difficult. The authors of this paper present aspects of their research regarding new concepts, models and prototypes (virtual and 3D printed) of robotic systems intended to assist people with disabilities for an active and normal life. An innovative open source system for guidance of young people (but, also elderly ones) with eyesight problems has been developed. It is intended to be used indoors also outdoors, to provide audio guidance, haptic guidance, or both. Research aspects on a bionic prosthesis for the upper limb are evidenced. The focus is on a two fingers model that should be considered as the proof of concept. Innovative mechatronic system designed to help people, who can no longer stand and / or walk is further presented. A virtual platform concept aimed at the integration of all these devices, and similar others, to communicate by IoT is shown.
Novel method suitable for decreasing the roofing tile failures generated during rapid drying
Authors: Vasić M R , Rekecki R , Radojević Z
Published: October 2021

Only few papers in which principles for decreasing the failures generated during semi and rapid drying of porous shrinking materials, for example roofing tiles, are reported. One of the main differences between the traditional and rapid drying regimes is related with the fact that during the heating step products are heated to the much higher temperatures during rapid drying. If the humidity inside the industrial drying tunnels or chambers is not controlled all the time in the prescribed range of 90 - 95 %, especially during the heating step of the rapid drying regime, crack failures will be developed. In order to inhibit the cracks generation during intensive drying the non-ionic surfactant Igepal CO-630 was added in the raw material during forming process. Various amounts of surfactant around the critical micelle concentration (CMC) were used. Five isothermal experiments were recorded, on laboratory extruded roofing tiles, for each surfactant concentration. Calculated effective diffusivity and material strength -moisture ratio (Deff-MR & MS-MR) curves were used to monitor the development of the cracks during drying and to determine the most suitable concentration of the surfactant. The explanation, how the interaction of the surfactants with clay helps the water molecules to easily move up to the surface was also reported. The application of surfactant in a recommended amount has significantly reduced the drying induced fractures in roofing tiles during its intensive drying and consequently the industrial scarp-rate was accordingly lowered.
Heat treatment of 3D printed polyethylene terephthalate glycol in a supporting powder bed
Authors: Zapciu A , Gh Amza C , Baciu F , Vasile M I
Published: October 2021

Material extrusion 3D printing is a fabrication process that produces layered polymer parts with complex geometry but with inferior mechanical properties compared to parts made with other methods such as injection molding. Post fabrication heat treatment is a valid post-processing method that reduces the internal thermal stresses and improves layer adhesion in 3D printed polymers, resulting in superior mechanical properties. This study investigates the mechanical changes produced in 3D printed PETG (polyethylene terephthalate glycol-modified) parts after heat treatment. A novel technique is used, where the parts are embedded into a bed of sodium chloride powder in order to prevent deformation during postprocessing. Fully filled 3D printed PETG parts with various geometries are tightly packed in a bed of powder. The parts are subjected to heat treatment at a temperature above the material’s glass transition temperature but below its melting temperature. Destructive and non-destructive testing performed on the treated 3D printed samples shows a substantial improvement of mechanical properties. Tensile strength testing reveals an increase of tensile strength by 40% for parts printed horizontally and by over 100% for parts printed vertically. Increased stiffness is also observed in treated parts. Compressive strength testing shows a strength increase of 43% after treatment. Dimensional measurements made prior to and after treatment show significantly reduced deformation when using the supporting powder method versus unsupported treatment. Scanning electron microscopy (SEM) analysis is used to assess internal structural changes in the polymer after post-processing. This analysis reveals changes in internal void shape and distribution, increased interlayer adhesion and increased interface area of deposited filaments, providing insight into the mechanisms that lead to the improved properties observed in destructive testing. The supporting powder heat treatment allows the fabrication of parts with complex geometry through material extrusion 3D printing while mitigating the inherent disadvantage of the fabrication process of producing parts with inferior mechanical properties.
Cold in-place recycling of aged and deteriorated asphalt and concrete pavements
Authors: Zghibarcea Ș , Ungureanu D , Țăranu N , Hoha D , Polcovnicu RA , Leizeriuc TA
Published: October 2021

This study focuses on implementing two distinct recycling methods, the reclaimed asphalt pavement and the reclaimed concrete material, on classical road pavements, by totally replacing the surface or base courses with ones made with recovered materials. The majority of the road networks in the eastern European countries were built between 1950 and 1980 and are, nowadays, aged and degraded. Within this frame, the cold in-place recycling methods were developed, which can be applied to both asphalt and concrete pavements. During the cold in-place recycling process, the reclaimed asphalt or concrete materials do not leave the construction site at all, but they are processed on the spot and reused immediately. Thus, the material is granulated to the desired depth, mixed with the binding agent and water and then repaved and compacted in a new layer. One of the most significant benefits of the cold in-place recycling process is that the material is simultaneously recycled and mixed with the binding agent, enabling the road pavement to be strengthened without the need to import expensive virgin aggregates. This work describes the manufacturing technology and the equipment train used to cold recycle aged and deteriorated asphalt and concrete pavements.
Analytical study of the melt pool distortion in the Laser Powder Bed Fusion Process caused by the angle of incidence of the laser and its effect on the surface finish of the part
Authors: Sendino S , Martinez S , Lamikiz A , Lartategui F , Gardon M , Gonzalez J J
Published: October 2021

One of the factors that most affects surface roughness is the angle of incidence of the laser with respect to the platform, which varies across the platform. However, to make the L-PBF process a competitive technology, several parts must be manufactured on the same platform, using maximum building volume. Nevertheless, due to this angle of incidence, even if identical parameters and geometries are used, the surface finish of the parts varies considerably depending on the positioning of the part on the platform. Throughout this work, the effect that this angle of incidence has on the surface of parts manufactured in the different positions of the platform is presented. For this purpose, first the angle of incidence on the whole platform was determined. Then, based on these results, the distortion of the melt pool was analyzed analytically, with the aim of relating the poor surface finish, seen by different technologies such as infinite focus microscope or SEM, with the distortion of the melt pool generated by the angle of incidence.