bluuebunny/crossref_metadata_2025 huggingface dataset:
Planktivores as trophic drivers of global coral reef fish diversity patterns
Authors: Siqueira Alexandre C. , Morais Renato A. , Bellwood David R. , Cowman Peter F.
Published: February 2021

Significance

For decades, marine biogeographers have been intrigued by the origins of the Indo-Australian Archipelago (IAA) biodiversity hotspot. Yet one important ecological factor remained unexplored: the trophic status of species across the diversity gradient. Here we show how trophic identity crucially underpins coral reef fish diversity patterns via a disproportional concentration of plankton-feeding species in the IAA. This planktivore hotspot, however, vanishes abruptly away from the IAA. Over the recent geological past, planktivorous reef fishes successfully partitioned constant resources promoted by unique oceanographic conditions in the IAA while likely undergoing disproportional extinctions in peripheral regions. This intriguing case of ecological success intertwined with differential extinctions offers key insights into the origins of biodiversity gradients.
Aqueous production of secondary organic aerosol from fossil-fuel emissions in winter Beijing haze
Authors: Wang Junfeng , Ye Jianhuai , Zhang Qi , Zhao Jian , Wu Yangzhou , Li Jingyi , Liu Dantong , Li Weijun , Zhang Yange , Wu Cheng , Xie Conghui , Qin Yiming , Lei Yali , Huang Xiangpeng , Guo Jianping , Liu Pengfei , Fu Pingqing , Li Yongjie , Lee Hyun Chul , Choi Hyoungwoo , Zhang Jie , Liao Hong , Chen Mindong , Sun Yele , Ge Xinlei , Martin Scot T. , Jacob Daniel J.
Published: February 2021

Significance

Secondary organic aerosol (SOA) from fossil-fuel combustion is a major component of Beijing winter haze pollution but its formation mechanisms are unclear. It is generally assumed to originate from atmospheric oxidation of volatile organic compounds (VOCs). However, we show here that fast aqueous-phase oxidation of directly emitted primary organic aerosol (POA) takes place at high relative humidity in Beijing winter haze and can explain the observed SOA. This could explain why SOA has decreased in response to POA emission controls even as VOC emissions have stayed flat. The mechanism may involve ring-breaking oxidation and functionalization of polycyclic aromatic hydrocarbons.
Reliability and sensitivity of the Notio Konect to quantify coefficient of drag area in elite track cyclists
Authors: Kordi Mehdi , Galis Gert , van Erp Teun , Terra Wouter
Published: February 2021

Elite level cycling events are performed at speeds in excess of 50 km/h. At these speeds, over 90% of the resistance forces come from aerodynamic resistance (CDA). Recently bicycle‐mounted pitot tubes, such as the Notio Konect (NK) have become more commercially available making CDA easier to measure. Its reliability and sensitivity would be useful for riders and coaches to be able to understand what constitutes as a change in CDA. Accordingly, the aim of this study was to establish the intra‐ and inter‐effort reliability and sensitivity of the CDA measures of the NK. Seven elite level track riders were used in this study which was broken into two parts: (1) Reliability and (2) Sensitivity. For both parts of the experiment, riders performed identical efforts, riding at ∼50 km/h for six laps of a 250 m indoor velodrome. For reliability, the riders performed six efforts without any changes in position or resistance. For sensitivity, they performed the efforts with a rod with discs of a known diameters attached at each end to vary the CDA by a known amount. For the reliability assessment, low coefficient of variation of intra – (0.47%) and inter‐effort (0.9%) reliability were measured. With regards to sensitivity, the smallest changes in resistance (from 5 – 6 cm, i.e. 1.2% or 0.002 m2) was identified by the NK. The data in this experiment suggests that the NK is a highly reliable in measuring CDA can detect changes up to at least 1.2% in an indoor velodrome using elite level track riders.

Highlights

The Notio Konect showed high levels of inter‐ and intra‐effort reliability.

The Notio Konect could detect a change as small as 1.2% in aerodynamic drag.

The findings suggest that the Notio Konect is suitable for detecting small changes in aerodynamic drag in a velodrome setting.
Agreement of bioelectrical resistance, reactance, and phase angle values from supine and standing bioimpedance analyzers
Authors: Dellinger Jacob R , Johnson Baylor A , Benavides Marqui L , Moore M Lane , Stratton Matthew T , Harty Patrick S , Siedler Madelin R , Tinsley Grant M
Published: February 2021

Objective. Bioimpedance devices are commonly used to assess health parameters and track changes in body composition. However, the cross-sectional agreement between different devices has not been conclusively established. Thus, the objective of this investigation was to examine the agreement between raw bioelectrical variables (resistance, reactance, and phase angle at the 50 kHz frequency) obtained from three bioimpedance analyzers. Approach. Healthy male (n = 76, mean ± SD; 33.8 ± 14.5 years; 83.9 ± 15.1 kg; 179.4 ± 6.9 cm) and female (n = 103, mean ± SD; 33.4 ± 15.9 years; 65.6 ± 12.1 kg; 164.9 ± 6.4 cm) participants completed assessments using three bioimpedance devices: supine bioimpedance spectroscopy (BIS), supine single-frequency bioelectrical impedance analysis (SFBIA), and standing multi-frequency bioelectrical impedance analysis (MFBIA). Differences in raw bioelectrical variables between the devices were quantified via one-way analysis of variance for the total sample and for each sex. Equivalence testing was used to determine equivalence between methods. Main results. Significant differences in all bioelectrical variables were observed between the three devices when examining the total sample and males only. The devices appeared to exhibit slightly better agreement when analyzing female participants only. Equivalence testing using the total sample as well as males and females separately revealed that resistance and phase angle were equivalent between the supine devices (BIS, SFBIA), but not with the standing analyzer (MFBIA). Significance. The present study demonstrated disagreement between different bioimpedance analyzers for quantifying raw bioelectrical variables, with the poorest agreement between devices that employed different body positions during testing. These results suggest that researchers and clinicians should employ device-specific reference values to classify participants based on raw bioelectrical variables, such as phase angle. If reference values are needed but are unavailable for a particular bioimpedance analyzer, the set of reference values produced using the most similar analyzer and reference population should be selected.
State-independent quantum contextuality with projectors of nonunit rank
Authors: Xu Zhen-Peng , Yu Xiao-Dong , Kleinmann Matthias
Published: February 2021

Virtually all of the analysis of quantum contextuality is restricted to the case where events are represented by rank-one projectors. This restriction is arbitrary and not motivated by physical considerations. We show here that loosening the rank constraint opens a new realm of quantum contextuality and we demonstrate that state-independent contextuality (SIC) can even require projectors of nonunit rank. This enables the possibility of SIC with less than 13 projectors, which is the established minimum for the case of rank one. We prove that for any rank, at least 9 projectors are required. Furthermore, in an exhaustive numerical search we find that 13 projectors are also minimal for the cases where all projectors are uniformly of rank two or uniformly of rank three.
Separability of evolving W state in a noise environment
Authors: Men Qian-Tong , Jiang Li-Zhen , Chen Xiao-Yu
Published: February 2021

Entanglement is an important resource for quantum information processing. We provide a new entanglement witness to detect the entanglement of an evolving W state. Our results show that the new entanglement witness matches the evolving W state better than other witnesses or methods. The new witness significantly improves the performance of entanglement detection for some three-qubit states.
Effect of β-galactosidase immobilization on properties of chitosan/xanthan and xanthan/chitosan multilayers
Authors: Viraneva A , Grigorov A , Iliev I , Yovcheva T
Published: February 2021

Polyelectrolyte multilayers (PEMs) deposited on non lyophilized and lyophilized polylactic acid (PDLA) substrates were investigated. The substrates were charged in a corona discharge. The charging of the substrates was carried out by means of a conventional corona triode system consisting of a corona electrode (needle), a grounded plate electrode and a grid placed between them. Positive or negative 5 kV voltage was applied to the corona electrode and 1 kV voltage of the same polarity as that of the needle - to the grid. The dependences of the normalized surface potential on the storage time for positively and negatively charged non lyophilized and lyophilized PDLA substrates were studied. The results obtained show that the values of the normalized surface potential of non lyophilized substrates decay faster than those of the lyophilized ones. For multilayer build-up layer-by-layer (LbL) deposition technique was used. The first built-up layer always possesses an electric charge opposite to that of the substrate. PEMs with different number of layers (4 or 8 layers) were obtained. In the polyelectrolyte multilayers obtained the enzyme β-galactosidase were immobilized. The enzyme activity of each multilayer configuration was measured. The experimental results show that, in case of enzyme immobilization in multilayer films with 8 layers the efficiency of immobilization is considerably better compared to ones with 4 polyelectrolyte layers.
Photo-electrical response of nanocomposites from single-walled carbon nanotubes incorporated in tris(keto-hydrozone) discotic mesogen
Authors: Hadjichristov G B , Exner G K , Marinov Y G , Vlakhov T E
Published: February 2021

We report an experimental study on photo-electrical response of new nanocomposites produced from discotic mesogen LTTH-6 (possessing columnar liquid-crystalline phase) and single-walled carbon nanotubes (SWCNTs) with diameter ∼ 1.5 nm. The SWCNTs were incorporated in LTTH-6 at concentration of 1 wt.%. Thin layers of SWCNTs/LTTH-6 nanocomposites were formed with a thickness of 3 μm. The light-induced change in electrical conductivity of these layers was ascertained at room temperature by current-voltage measurements, upon illumination with a low-intensity (∼ 1 mW/cm2) continuous visible light. The effect of photoresponsivity of the glassy-like columnar phase of SWCNTs/LTTH-6 manifests the potential of such nanocomposites to be functional materials for applications in molecular electronics, sensorics and mechatronics.
Influence of sucrose on the phase behaviour of phospholipid model systems
Authors: Slavkova Z , Drinova N , Chamati H , Genova J
Published: February 2021

This article focuses on the influence of sucrose on the properties of SOPC (1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine) lipid systems. Differential scanning calorimetry is used to investigate the phase behaviour of the lipid system in the presence of sucrose. This method is appropriate and widely used to study the phase transitions parameters for organic compounds, in particular, lipids and the influence of various admixtures on these properties. Research results reveal that sucrose affects both, mechanical and physico-chemical characteristics of lipid systems. There are tangible differences in the bending elasticity moduli and enthalpies of the phase transitions due the addition of sucrose.
Modelling of multiple-hollow-cathode-discharge laser
Authors: Yordanova D , Temelkov K , Mihailova D , Dijk J van
Published: February 2021

A laser tube configuration for metal vapour lasers with hollow cathode sputtering is theoretically studied. The construction consists of a main hollow cathode and a few hollow cathode holes. Optimal conditions for laser oscillation are realised inside the main cathode, while the current density in the side hollow cathodes is higher and the discharges that occur in the hollow cathode holes can be used as additional sources of metal atoms produced by sputtering. To study the processes in the discharge and the unique capabilities of the construction the PLASIMO modelling platform is used.
An Optical Excitation Study of Pure and Ru-doped Bi12SiO20 Crystals with Graphene Coating
Authors: Rafailov P M , Marinova V , Todorov R , Boyadjiev S
Published: February 2021

CVD-grown graphene was transferred onto polished crystal plates of pristine and Ru-doped bismuth silicate (Bi12SiO20:Ru), which are well known inorganic materials possessing very high carrier mobility and photo conductivity. The heterostructures obtained were investigated by optical absorption and Raman spectroscopy. We examine the influence of photoinduced phenomena in the crystal substrate on the graphene layer with possible implications for optical doping of graphene trough photo-induced space-charge field.
Electric properties of new composite materials based on RGO, nanosized ZnO and Cu nanoparticles
Authors: Martinov B , Slavov S , Staneva A , Dimitrov D , Mateeva J
Published: February 2021

Graphene nanostructures combine properties that make them an attractive material for various technical applications. The objective of this study is to obtain a series composites based on Reduced graphene oxide (RGO), nano-sized ZnO and Cu nanoparticles. RGO is synthesized by a modified Hammer’s method and chemical reduction after sonication. ZnO nanoparticles are obtained by the Sol-Gel method. The composites’ phases and structures are characterized by XRD, SEM, TEM, and EDX analysis. It is shown that ZnO is monophasic with a particle size of 48 nm. A series of composite materials based on RGO, ZnO and Cu nanoparticles is obtained by ultrasonic treatment. Electrical and dielectric properties are measured by Impedance analyser and RLC bridge. For comparison, the conductivity for 100% RGO is 309.513 S/m and for 100 % Cu nanosized is 0.0056 S/m. Therefore, it should be initially concluded that increasing the RGO in the mixture will increase the conductivity, and increasing nanosized Cu will decrease it. The presence of cluster regions in the composites with different conductivity is found: 1) nano grains of conductive copper which are partially or completely surrounded by 2) low-conductivity shells of copper oxide and a minimal number of RGO sheets. The present work shows promising results for future research for the creation of new composite materials with controlled shape and size of copper oxide - RGO clusters. Dielectric measurements for RGO/ZnO composites are made in range from 5 mass% to 100 mass% content of RGO, the composites show variable conductivity. For lower concentration of RGO, selected samples are dielectrics.
Synthesis and characterization of nanosized ZnTiO3doped with reduced graphene oxide (RGO)
Authors: Martinov B L , Staneva A D , Vlakhov T E , Slavov S , Dimitrov D , Marinov Y G , Hadjichristov G B
Published: February 2021

Composite materials based on nanosized zinc titanate (ZnTiO3) doped with reduced graphene oxide (RGO) were obtained by means of ultrasonically assisted precipitation. In these composites, the concentration of RGO nanopartiles was varied from 1 wt.% to 20 wt.%. The ZnTiO3ceramic was produced by sol-gel method. RGO was prepared by a modified Hammers method and subsequent chemical reduction with sodium borohydride. Structural and phase characterization of the fabricated composites was performed by XRD, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). It was identified that for all of the studied samples of the RGO/ZnTiO3series, the two phases are uniformly distributed over the observed areas, which proves the formation of homogeneous nanocomposite materials. The electrical properties of the series of RGO/ZnTiO3samples were characterized by complex electrochemical impedance spectroscopy (EIS) in the frequency range from 0.1 Hz to 1 MHz. The results obtained by EIS for the electrical conductance of RGO-doped ZnTiO3as a function of the concentration of RGO nanoparticles were correlated with the data from structural studies.
Influence of the molecular weight and concentration of PVP on the polyol synthesized silver nanoparticles
Authors: Atanasova A , Hristova-Vasileva T , Todorov R
Published: February 2021

In the present work the synthesis of silver nanoparticles by the polyol method is investigated. The self-seeding polyol process was chosen from the number of variations of this method. In this approach AgNO3 was used as a precursor, poly (N-vinylpyrrolidone) (PVP) as capping agent and ethylene glycol as solvent and reducing agent. We investigated the influence of the molecular weight of PVP on the microstructure of the particles considering a polymer with molecular weight Mw = 58 and 360 K by changing the molar ratio of PVP/AgNO3 for both polymers. The molar ratios were varied from 0.5 to 2.5. The as prepared nanoparticles were characterized by microscopic and structural methods. The shape and the size distribution were characterized by Transmission Electron Microscopy. The crystal structure of the nanoparticles was studied by X-ray Diffraction and Selected Area Electron Diffraction. Due to their plasmonic properties, the silver nanoparticles find application for improvement of the efficiently of the solar cells, substrates for surface-enhanced Raman and florescence spectroscopies. All these applications require the frequencies of the localized surface plasmon resonance (LSPR) to appear at an exact position. Therefore we indicated the wavelength of the LSPR of the as prepared nanoparticles trough the absorbance spectra. A variation between 380 and 470 nm was observed.
Magnetic phase transitions in Ba0.5Sr1.5Zn2Fe11.92Al0.08O22 hexaferrites
Authors: Georgieva B , Kolev S , Krezhov K , Ghelev Ch , Kovacheva D , Tran L-M , Babij M , Zaleski A , Vertruyen B , Closset R , Koutzarova T
Published: February 2021

We report studies on the effect of substituting the magnetic Fe3+ cations with nonmagnetic Al3+ cations in Y-type hexaferrite Ba0.5Sr1.5Zn2Fe11.92Al0.08O22 powders on their magnetic properties and especially on the magnetic phase transitions responsible for observing the magnetoelectric effect. In this research, the Y-type hexaferrite powders were synthesized by citric acid sol-gel auto-combustion. After the auto-combustion process, the precursor powders were annealed at 1170 °C in air to obtain the Y-type hexaferrite materials. The effects of Al substitution on the structural, microstructural properties and phase content were investigated in detail using X-ray powder diffraction and scanning electron microscopy. Hysteresis measurements were performed by a physical-property-measurement-system (PPMS) (Quantum Design) at 4.2 K and at room temperature. Dc-magnetic measurements of the temperature dependence of the magnetization at magnetic fields of 50 Oe, 100 Oe and 500 Oe were used to determine the effect of applying a magnetic field on the temperature of magnetic-phase transitions. We demonstrated that the helical spin state can be modified further by varying the magnetic field.
Optimization of AlN films grown by atomic layer deposition
Authors: Beshkova M , Blagoev B S , Mehandzhiev V , Yakimova R , Avramova I , Terziyska P , Kovacheva D , Strijkova V
Published: February 2021

AlN thin films (∼25 nm) have been grown with a Beneq TFS-200 ALD reactor on Si (111) substrates. TMA (trimethylaluminum) and NH3 were used as precursors. The substrate temperatures were 330°C, ALD cycles 550. In order to study the stoichiometry of AlN film the TMA and NH3 doses (pulses) were varied from 60 to 180 ms and from 60 to 90 ms, respectively. X-ray diffraction (XRD) data showed that the AlN films have amorphous structure. Chemical composition and bonding states were investigated by X-ray photoelectron spectroscopy (XPS). High resolution Al 2p and N 1s spectra confirmed the presence of AlN with peaks located at 73.6 and 396.8eV, respectively for all layers. Furthermore, the atomic concentration of constituent elements has been calculated from the high-resolution XPS scan. The results revealed the Al/N ratio is close to the stoichiometric value (1:1) only for AlN film grown at TMA and NH3 doses/pulses of 180 and 90 ms, respectively. AFM analysis showed that RMS roughness value for AlN films grown at TMA: NH3 pulse ratio 2:1 is about 1 nm. The results are promising in view of further studies of AlN films for SAW device application
Properties of ZnSe nanocrystalline thin films prepared by thermal evaporation
Authors: Dzhurkov V , Levi Z , Nesheva D , Hristova-Vasileva T , Terziyska P
Published: February 2021

ZnSe thin films with thickness of 30 nm and 50 nm were prepared on Corning 7059 glass substrates at room temperature by applying periodically interrupted physical vapour deposition of ZnSe and various deposition rates. All as-deposited films were annealed at 200°C and some of them were further annealed at 400°C. Results from spectroscopic ellipsometry have shown that the porosity of the films which is important for the ethanol sensitivity decreases with increasing deposition rate and annealing temperature. The porosity changes caused by annealing of the films at 400°C are accompanied with thickness decrease.
Efficiency study of aeroelastic energy harvester via analytical approach
Authors: Sarbinowski F , Labudzkiand R Talar R
Published: February 2021

In the paper we examined the impact of structure parameters of aeroelastic energy harvester on the efficiency it provides. Study of system was preceded by deriving dimensionless analytical equations describing the power generated by the device. For this purpose, the Harmonic Balance Method method was used while adopting a simplifying assumption about the sinusoidal motion of the device. By analysing the obtained solutions, the characteristic quantities of system has been defined. By further calculations, impact of device parameters on operational flow velocity range was studied.
Chaotic evolutionary algorithms for dynamic instability enhancement
Authors: Sarbinowski F , Labudzki R , Talar R
Published: February 2021

The algorithm principle is presented based on a geometry optimization of aeroelastic energy harvester. Efficiency of this class of devices highly depends on oscillation amplitude caused by dynamic instability of the system, which is related to its geometry. Optimization was performed using a genetic algorithm (GA) that processes data from CFD calculations. This algorithm generated a random population of twenty-arm geometrical figures. Each geometry was subjected to a numerical experiment during which its movement in a fluid-filled channel were simulated and resultant force acting on body was calculated. The calculations were repeated for angular orientation of the object varying from 0 to 180 degrees, at 5 degrees step, in order to obtain a complete characteristic of aerodynamical forces acting on body related to its angular orientation. For each of the obtained functions, satisfaction of Den Hartog’s criterion is examined, which is the basis for geometry evaluation. In order to accelerate the calculations, classical GA has been modified by substituting random crossover process by operation determined by chaotic process — in this case, a logistic map. The numerical calculations was carried by Method of Fundamental Solutions.
The behavior to cavitation erosion-corrosion of the CuZn39Pb3 brass structures, obtained by in-depth heat treatments
Authors: Lazar I , Bordeasu I , Pirvulescu L D , Hluscu M , Mitelea I , Ghera C
Published: February 2021

The paper highlights the behavior at the vibratory cavitation erosion of CuZn39Pb3 brass microstructures, as obtained by in-depth heat treatments. Two heat treatment cycles are analysed (hardening at 800ºC, followed by cooling in water, and hardening at 800ºC, with cooling in water, followed by tempering at 400ºC with cooling in air). The micro-hardness measurements show that the change in the microstructure, relative to the initial status of the material (semi-finished), determines higher values of the micro-hardness. The studies of the cavitation erosion, using the vibrating standard piezoelectric crystal assembly, available in the Cavitation Research Laboratory at the Polytechnic University from Timisoara, presented in the paper, shows significant increases in the surface resistance to the stress determined by the cavitation micro-jets, as compared to the initial state of the material (semi-finished).
Design features of comminution disc and their relation with CO2 emission in disc life cycle
Authors: Kruszelnicka W
Published: February 2021

The structure of the comminution discs has the greatest impact on the comminution process efficiency and energy consumption and on the product fragmentation degree. Manufacturing, use and utilization of machine components carries environmental burdens in the form of emissions and energy consumption. The purpose of the work was to analyze the impact of the design features of the comminution disc (the construction material, the number and diameter of disk holes) on the amount of CO2 emissions in their life cycle. The 3D model of discs was made in SolidWorks and then an analysis of CO2 emission was made in Solid Works on the basis of the LCA and CM method. Sustainability was performed as well. It was found that energy consumption and CO2 emissions were higher for the life cycle of steel discs than those made of HDPE. Emissions of carbon dioxide during the life cycle of the working disk decrease along with an increase in the diameter and the number of holes. Regression equations describing the relationship between the diameter, number of holes in the disc and the amount of CO2 emissions in the life cycle were obtained on the basis of multiple regression analysis.
Free oscillations of a dissipative oscillator with double quadratic nonlinearity
Authors: Ol’shanskii V P , Kharchenko S O , Кovalyshyn S Y , Kharchenko F M , Kovalyshyn O , Tomporowski A , Bałdowska-Witos P
Published: February 2021

Approximate formulas for calculating the amplitudes of free damped oscillations of the oscillator with a quadratic nonlinear elastic characteristic under the action of a resistance force that is proportional to the square of the velocity are derived by the energy balance method. Two variants of this method have been implemented. In the first, an approximate differential equation of the envelope graph of oscillations is composed and its analytical solution is constructed. As a result, for the calculation of amplitudes, iterative relations were obtained using the Lambert W function. The argument of this special function is positive for the hard power characteristic and negative for the soft one. Asymptotic approximations of the Lambert W function, which simplify the practical implementation of analytical solutions, are proposed, and the possibility of using known tables of this special function is indicated. In presenting the second variant of the energy balance method, the recurrent relation between the amplitudes of oscillations related to the analytical solution of the cubic equation is derived. Unlike the first option, it does not require iterations. It has been made a comparison of numerical results, which these methods of calculating the amplitudes lead to, and numerical computer integration of the differential equation of oscillations of the oscillator. Satisfactory consistency of the results obtained in different ways confirmed the suitability of the derived approximate formulas for engineering calculations. The main advantage of this method is that it does not involve the construction and use of an exact solution of the double nonlinear differential equation of motion of the oscillator. In addition to the direct problem, the inverse problem of determining the coefficient of quadratic resistance of the medium based on the results of measuring the amplitudes of free oscillations on the oscillogram is also analytically solved here. The obtained solution of the direct dynamics problem was used to check the accuracy of the coefficient identification.
A slightly different view of complexity
Authors: Malivuk Gak D , Rajilic Z , Stupar N
Published: February 2021

This paper presents a different approach to understanding the concept of complexity and its relation to various phenomena in the field of physics [1-6]. A unique definition of complexity does not yet exist. Complexity Cmp was calculated in three systems simulated in computational experiments. In the first simulation a body in free fall was observed while falling towards body of much greater mass. Second observed system was two bodies with different temperatures, and third system was crystals in crystallization chamber. Complexity increases when the temperatures of two bodies are equalized, when one body falls to another and the crystal grows from the solution. In crystal growth theory, there are also still some concerns about the growth of some types of crystals.
Conformity assessment of metal framing elements
Authors: Bajramovic E , Bajramovic E , Islamovic F
Published: February 2021

Metal framing elements made of thin sheets in combination with gypsum board panels create the system widely used in construction, primarily for partition walls and suspended ceilings. The quality of the metal framing elements depends on the quality and metal sheet thickness from which they are made of, the geometric shape of the profile, the equipment used to produce them, etc. Before being placed on the market, all products used in construction and manufactured in production facilities must meet prescribed technical requirements and specifications. The paper will present the conformity assessment of metal framing elements in accordance with the European harmonized standard EN 14195:2014 and Regulation on Construction Products No. 305/2011. The Regulation defines the conditions for the marketing of construction products on the EU internal market, as well as methods and systems for evaluation to demonstrate the continuity of the characteristics of construction products.
Reduction of pollution by controlled disposal of hazardous pharmaceuticals
Authors: Ardelean E , Ordodi V , Ardelean M , Socalici A , Lemle K L
Published: February 2021

Human activities generate a series of waste increasingly more complex and difficult to manage (through the containment, inertization or destruction). Particular attention must be paid to hazardous waste with a high risk of environmental pollution but especially for infestation to the human generator.

In this context, we considered the possibility of integrated waste management resulted from the pharmaceutical industry, which is frequently mishandled and ends (reach) in the environment. This paper proposes a method for neutralizing some hazardous pharmaceutical waste, using electrochemical methods for inactivation, respectively an electrochemical reactor with asymmetric current densities. The results obtained in the laboratory for four of these substances leads to the generation of viable solutions that can be used in practice.
Impact of silicon carbide reinforcement on characteristics of aluminium metal matrix composite
Authors: Sharma Arun Kumar , Bhandari R , Pinca-Bretotean C
Published: February 2021

The consumption of composites has gradually raised in recent times and is incredibly likely to expand more in the future. Metal Matrix Composites (MMCs) provide an extensive range of benefits when compared with the common materials in certain conditions. Aluminum and its alloy-based composites in the current manufacturing scenario have a significant role to play in the advanced technological fields. Typically Aluminum Metal Matrix Composites (AlMMCs) used for its good strength, less density, excellent stiffness, lightweight, toughness, resistance to corrosion, fatigue, creep and wear relative to non-reinforced alloy. The AlMMCs, since their combination of the above-mentioned properties, are ideal suitable materials for many applications. Enhancement in these properties is accomplished by adequate customizing reinforcements in the base metal matrix. It is commonly used therefore in the aircraft, automobile, marine, leisure, telecommunications industries. In assessing the overall effectiveness of the composites there is a significant factor is reinforcement materials. The decision of a suitable type of reinforcement materials and volume are also important challenges within this paper the impact of different amounts of reinforcement has been studied. The silicon carbide (SiC) used as reinforcement material and Al6061used as Matrix material in AlMMCs are addressed. The effect of SiC on characteristics of AlMMCs explored in brief.
Physico-mechanical and tribological characteristics of composites used for brake pads
Authors: Pinca-Bretotean C , Craciun A L , Preda C , Sharma Arun Kumar
Published: February 2021

Brake pads are a crucial component of the braking system in an automotive vehicle. It is a primary factor in ensuring the normal driving of motor vehicles and the safety of passengers. Therefore, the research and study of the brake pads are extremely important. The materials which used in the manufacturing of brake pads should be environmentally friendly as harmful substances releases during operations by asbestos containing brake pads, which pollute the environment and thus harmful for human so becomes a primary reason of acceleration for research and development of new materials for brake pads. Composite materials have required excellent properties, so it is gaining an important position in this field. In this research, composite materials with coconut fibre are produced in the laboratory which can be used to produce brake pads for braking systems of the medium-performance small car. This research aims primarily towards producing the composite material which consists of the best proportion of organic fibre to have superior physical-mechanical and tribological characteristics. To achieve these goals, the following steps have been taken, the laboratory manufacturing of organic composite materials, technological analysis of the samples, improving the qualitative characteristics of friction materials, determination of the physical-mechanical and tribological characteristics of the materials according to the standards in force. This paper provides a detailed investigation on the characteristics of composite materials made with coconut fibre for brake pads.
A method of detecting the feature of cylindrical pin based on machine vision
Authors: He Y F , Tirian G O
Published: February 2021

As a common mechanic part, cylindrical pin is mainly used for positioning the parts in assembling process. Chamfer angle is an important feature of cylindrical pin, which guides the pin into the pin hole. Manual method is used by cylindrical pin manufacturer to detect the chamfer feature and so as to filter the defective products. But it is found that many problems including inevitable subjective error, high intensity of labor, and low detection efficiency exist during manual operation. A new method based on machine vision is proposed in this paper to detect the chamfer feature and size of cylindrical pin. Contour of cylindrical pin is obtained by camera, chamfer feature and size is then extracted through image analysis. Experiment result proves that the method is feasible.
Characterization of three phase solid state VAR compensation scheme in three phase pulse width modulation voltage source inverter
Authors: Josephine Mbunwe Muncho , Edwin Ezema Ejiofor , Augustine Ngwu Anene , Anghel Drugarin C V , Ajmal Mohammad Rehan , Ayaz Ahmad M
Published: February 2021

The principle of a three phase solid state VAR compensation (SSVC) system that uses a three-phase pulse width-modulated (PWM) Voltage-Source Inverter (VSI) is presented and analyzed. The proposed SSVC system can compensate for leading and lagging displacement power factor and the PWM is used as a means of reducing the size of reactive components. The significant aspect of the presented VAR compensator is the adjustment of the angle difference between the static fundamental circuit output voltage and the utility supply voltage in order to optimize the alternating current (a.c.) power factor to a non-linear load. The SSVC system is analyzed under self-controlled DC bus voltage operating conditions. Other areas of investigation include the design of SSVC reactive components. The dynamic analysis is carried out in a d-q reference frame to verify the performance of the VAR compensator in terms of speed of response and stability. Analysis and stability plots generated confirm a high performance static VAR compensator. Finely, the findings of present research work were found within good agreement with some other workers.
Energy efficiency of wind power plants in various wind condition
Authors: Chioncel C P , Erdodi G , Tirian O G
Published: February 2021

The present paper determines the optimum energy operation area of an electric wind power system, under time varying wind speed conditions. The determinations of the optimal area, from the energy point of view, is done based on experimental values from the Romanian black sea cost, Dobrogea area. The optimum operation area is defined by the optimal mechanical velocity, ωOPTIM. For this, the dependence between the wind speed, v, and ωOPTIM are computed based on the current wind speed and the current mechanical velocity ω. Due to the high inertia of the wind turbine (WT), the generators speed is not able to follow the changes of the wind speed. Knowing the optimum value ωOPTIM, the solution is to determine the load at the permanent magnet synchronous generator (PMSG) in order that the mechanical speed should timely reach his optimum.
The power factor and the upper harmonics
Authors: Spunei E , Piroi I , Protea B , Piroi F
Published: February 2021

Upper harmonics that occur in electrical installations due to the use of semiconductor components increases the angle of phase difference between the voltage and the current of a phase. Following this, the power factor decreases, which necessitate, then, installations to compensate for it - to reduce or cancel the upper harmonics. In this work we present a case study on how upper harmonics influence the power factor. This work has been supported by Project CNFIS-FDI-2018-0282.
Power factor measuring device using microcontroller for single-phase consumers
Authors: Diniş C M , Popa G N , Iagăr A
Published: February 2021

The paper presents a device with microcontroller for measuring the power factor used for single-phase low voltage electrical consumers. Voltage and current are measured, and the paper presents two constructive variants of pulse circuits (TTL compatible) used to measure the phase-shift between current and voltage. In the first constructive variant, without galvanic separation, the voltage measurement is performed with a voltage divider connected in parallel with the consumer, and the current measurement is made by a shunt resistor connected in series with the consumer. In the second construction variant, with galvanic separation, the voltage is measured by a step-down voltage transformer, and the current is measured with a current transformer that has a load resistance. The signals coming from the voltage and current measuring equipment are limited by a group of diodes, then amplified-separated, and the resulting signals are connected to the input of a XOR TTL logic gate. The signal from the XOR TTL gate output has constant amplitude pulses and time durations proportional to the phase-shift value between current and voltage. The signal after the XOR TTL gate is applied to the digital input of a microcontroller development board that, also, has an LCD shield. The program used to calculate the power factor according to the pulse length (proportional with phase-shift value) is presented. Experiments are performed with RL consumers to measure the power factor and the obtained measurements are compared with those measured with a precision device (power quality analyser).
The importance of recovering precious metals from waste electrical and electronic equipment
Authors: Ardelean M , Ardelean E , Mihuţ G , Găianu O
Published: February 2021

The evolution of electronic equipment in recent decades is experiencing a remarkable development. Due to increasing of consumption and also a very fast replacement rate due mainly to obsolescence, the amount of resulting electrical and electronic waste (WEEE) is increasing.

The WEEE term includes all of electrical and electronic equipment starting from mobile phones, computers, video cameras to tv set, washing machines, refrigerators. In other words, all electrical and electronic equipment from a household, electronic equipment from automotive or industrial electronic components. Now in all worldwide it is estimated that WEEE represents about 5% of all municipal solid waste.

The recovery process can be taken into account only if the cost of recovery is much lower than the value of the precious metals recovered from this. Regarding to waste disposal restrictions and strict environmental regulations, are needed economically viable and environmentally friendly technologies.

The paper presents the results of laboratory experiments on the recovery of precious metals, especially gold, present in various electrical and electronic components. WEEE used in the experiments was used from mobile phones, computer motherboards, computerized microprocessors and various types of gold-plated contacts.
Possibilities of 3D reconstruction of the vehicle collision scene in the photogrammetric environment Agisoft Metashape 1.6.2
Authors: Dascăl A , Popa M
Published: February 2021

Agisoft Metashape software is an advanced 3D modelling solution for a road accident scene. The re-creation of the accident scene through high quality professional content, allows the use of the result obtained by this photogrammetric method in the subsequent reconstruction of the dynamics of any road accident, having the advantage that the accident scene can be made and presented suggestively in 3D from different positions.
Half-hard cast-iron rolls: statistically research on the manufacturing technology for increase their quality and safety in exploitation
Authors: Kiss I , Alexa V , Cioată V G , Ratiu S
Published: February 2021

The regression analysis provides an opportunity to specify hypotheses concerning the quality assurance of cast-iron rolls, as well as explanatory factors in their manufacturing practice. When the analysis is correctly executed, having on base the statistically valid adjustment, this can produce quantitative effects on the quality assurance process. In the practice of the rolling rolls manufacturing by casting many variables interact with each other simultaneously (the iron properties, the casting equipment and they execution, the casting temperature, the cooling and solidification and so on). Multivariate research and visualization comes to the fore when the engineers have difficulties in comprehending many dimensions at one time, especially in the iron melting and alloying stages. In order to establish the optimal condition for hardness assurance in the cast-iron rolls manufacturing we proposed a statistical modelling study by using the multivariate regression. Our research propose to analyse the half-hard cast-iron rolls, an analysis defined by the statistically analyse of the cast rolls manufacturing technology, using the modelling phenomenon and the mathematical approach. The optimization model is based on industrial data, obtained from half-hard cast-iron rolls. Their analysis shall lead to the optimization pattern, through the prism of the multicomponent correlations, expressed by mathematical formulae.
Using SHERPA screening tool for design and assessment of local and regional air quality management
Authors: Popescu F , Vujic B , Cioabla A E , Marceta U , Dungan L I , Trif-Tordai G , Laza E A
Published: February 2021

As atmospheric pollution continue to be a significant issue on global level, but with a particular importance at European Union level, the air pollution reduction policies will continue to be enforced in the next decades. At EU level, especially on most developed countries, NO2 and Particulate Matter (fine and coarse fractions) remain an acute problem. To help decision factors to have a better view on entire EU region the SHERPA (Screening for High Emission Reduction Potentials on Air quality) was developed, a tool that was proven helpful in addressing source allocation, governance and the assessment of scenario impacts.
Manufacturing process management for cast iron brake blocks
Authors: Bucur F , Josan A , Socalici A , Gaianu O
Published: February 2021

In order to insure a proper management in cast iron foundries it is necessary to coordinate all the processes that are involved in manufacturing cast parts. The organisation management offers the necessary conditions for developing activities, with great emphasis on the activity of quality control. The paper presents the necessity of establishing a management strategy which can lead to the supervision of the entire manufacturing cycle of cast iron brake blocks for rolling stock. To this end, it is necessary to measure, monitor and analyze the results obtained in the industrial practice and to compare them with product standards.
Research on the influence of casting powders on the higher quality of continuous cast semi-finished parts
Authors: Radu M , Heput T , Ardelean E , Dascal A
Published: February 2021

Pursuant of the modernization of steel elaboration and casting technologies, at present over 90% of the liquid steel undergoes continuous casting. The quality of the cast parts is influenced by: the casting temperature and rate, the flow rate of the cooling water and the characteristics of the casting powders. The research under consideration was done on a low manganese alloy steel X60QS elaborated in an EBT-type, 100 ton oven and cast on a 5-strand MCT casting machine. The paper gives the results of the research on the variation of the carbon, manganese and sulphur content per cast product for each casting strand and for each rod of the strand. The research managed to establish the causes that lead to deviations from the required chemical content for these elements, as well as the possibilities of eradicating them. The results are applicable in research and in practice.
Technology of thin metal sheet cutting with fiber laser
Authors: Zgripcea L , Putan V , Ardelean M , Birtok Baneasa C
Published: February 2021

Laser cutting is a thermal cutting process where it is made use of the physical fact that laser light is absorbed in materials. The process is used for many materials in the manufacturing industry. Nowadays, the most suitable laser regarding range of materials, cutting speed, cutting quality is fiber laser. The article studies the correlation between cut quality and process parameters for thin plates, steel and aluminum. The laser machine used for experiments is a Continuous Wawe fiber laser with 1000W power source.
Structural analysis of a modulated load-bearing structure designed to investigate the interaction between soil and the working parts of agricultural machines
Authors: Cardei P , Constantin N , Sfiru R , Muraru V , Muraru S L
Published: February 2021

The article presents how to approach the structural analysis of a modulated load-bearing structure (MLBS) for researching the interaction between the soil and the working parts of agricultural machines. The special approach, in relation to the usual structures, is due to the fact that the supporting structure is a modulated, multifunctional one and, consequently, all the usual modular types of operation must be tested. The structure is analyzed in the hypothesis of the loads that maintain the demands of the materials used in the characteristic range of the linear elasticity, because the structure is expected to work in such conditions. The analyzed modulated structure is obtained by modular design for use in research, in several working variants. The authors also present the difficulties related to the transformations of CAD / CAM models into CAD / CAE models and opinions on the necessity of mixed analysis teams in addressing such problems.