Elena Stoian - Academia.edu (original) (raw)

Papers by Elena Stoian

Agronomy

The main objective of this article is the analysis of crop rotation applied to three crop farms o... more The main objective of this article is the analysis of crop rotation applied to three crop farms of different sizes in Romania. The period under study is before the implementation of the “Environmentally beneficial practices applicable to arable land” eco-scheme, included in the National Strategic Plan of Romania, 2023–2027, in the section on direct payments related to subsidies. The analysed crop farms have different areas, as follows: Farm A—64.97 ha, Farm B—615.50 ha and Farm C—2881.33 ha. This research aims to highlight the agro-environmental conditions specific to each farm that are required to be met by 2023. The data analysis highlights the fact that farms under 100 ha, such as Farm A, must apply the conditions of the eco-scheme as follows: 3.25 ha with non-productive elements, including uncultivated land; 6.50 ha cultivated with crops from the Leguminosae family, 16.25 ha cultivated with cereals, 19.49 ha cultivated with corn, 12.99 ha cultivated with sunflowers, 3.25 ha cult...

Sustainability

The study analyzes the awareness of the effects of climate change on agriculture and the measures... more The study analyzes the awareness of the effects of climate change on agriculture and the measures that should be implemented in this regard from the farmer’s perspective, taking into account the financial and promotional measures supported by the European Union for farmers. Thus, the study tracks the level of openness of farmers to implementing the measures that European policy makers will take in the coming period. Taking into account the fact that agriculture plays a particularly important economic role, due to the share of agricultural products in Romania’s total exports, particularly in plant production, a quantitative survey was carried out among Romanian farmers, using a questionnaire as an instrument, with a total of 407 respondents. The farmers interviewed undoubtedly recognize that the problems they face are caused by the effects of climate change and are willing to adapt, seek and implement the necessary solutions. The most problematic climatic phenomenon identified by far...

In this paper we have analysed the determinants of the students’ leisure time, based on 198 respo... more In this paper we have analysed the determinants of the students’ leisure time, based on 198 respondents of an questionnaire. The students are at the bachelor level in the Faculty MIEADR, USAMV Bucharest. The questions have reffered to the conditions in which students used to spend their leisure time. The performed analysis consisted in several steps. First, we made a descriptive analysis of the variables, by doing the frequences tables; then, there were performed correlation tables and the crosstabulation between pairs of variables. In order to verify the level of the statistical significance among the variables, it was also performed a chi-square statistical test. As general requirement, we have chosen to emphasise the results by pointing out the influence of the gender and place of residence variables for the respondents. From the findings of this paper, we have concluded that students of our faculty have different approaches, divided by place of residence regarding the holidays s...

The paper presents an analysis on market elements that can influence the decision to cultivate ra... more The paper presents an analysis on market elements that can influence the decision to cultivate rapeseed. We have studied the market features as estimators on market supply-demand ratio (the annual production, imports and exports of rapeseed) and the area under rapeseed production as concrete estimator on decision to cultivate. Inter-conditionality analysis between estimators of market and the estimators of decision to cultivate, made for a time interval of 12 years (2002-2013) emphasized that, in the Romanian market of rape, one of the significant factors influencing the decision to growth (taken in the previous year at seeding) is the value of exports of rape in the harvest year. It also revealed that in recent years, it has generated a system of specialized farms in rapeseed production associated to the international market requirements. It also highlighted the fact that domestic market of rapeseed (understood as internal consumption) does not influence the decision to cultivate r...

The paper adresses an approach on indicators from the public database FADN (Farm Accountancy Data... more The paper adresses an approach on indicators from the public database FADN (Farm Accountancy Data Network), at farm level selected from Romania. The study focused on analyzing the data series in 2012 (the latest year reported in the FADN) and the second part of the study was supported by the report on the last six years (2007-2012) and four of the eight regions. The data comes from public database FADN and the methodology consisted of a descriptive analysis of the data and presenting them as graphic and tabular form. The results recorded consisted of highlighting the differences between regions and survey findings have highlighted a decrease in interest and rental costs and also in investment levels, compared to 2012; in the same conditions, the total production and cash flow increased.

“Agriculture for Life, Life for Agriculture” Conference Proceedings, 2018

The changes from Tax Code foresee that societies with fiscal value under one milion euro (to 500.... more The changes from Tax Code foresee that societies with fiscal value under one milion euro (to 500.000 euro till 31.12.2017) to be included in the micro-enterprises category and according to this provision owes to the state budget a 1% tax from fiscal value to 16% corporate tax. The paper presents benchmarking of this new fiscal measure applying above some retail and cash&cary societies from Romania to taxing profit in case this measure would be applied to all tipes of companies analysis based on a set of indicators (Absolute abnormality, growth index, turnover dynamics etc). The conclusions following the paper are: increase revenue collected to the state budget and simplifying the methods of determination to this tax but general apply to this measure could lead to infringement, encouraging layoffs, increasing unemployment, discouragement of investments, the impossibility of companies to recover in situations of crisis, discourage entry on market of new envestors, encouraging tax evas...

Scientific Bulletin of Valahia University - Materials and Mechanics

An important category of widely used steels is chromium alloy improvement steels (STAS 9382/4-89)... more An important category of widely used steels is chromium alloy improvement steels (STAS 9382/4-89) intended for the execution of shafts, axles, cams, sprockets and sprockets subjected to operation at important demands. The properties of these steels are determined both by the chemical composition and by the way of plastic elaboration and deformation, but also by the way in which the structural transformations to the thermal treatments of tempering and recovery result. The properties of a certain steel are largely determined by the granulation size of the secondary structure, which in turn is dependent on the size of the austenitic granulation, respectively the hereditary granulation. At a given steel mark, the mode of heating (slow or fast) at the austenitization temperature is decisive regarding the dimensions of the austenitic grain respectively of the nature of the secondary granulation and of the operating properties. Studies and research were conducted on steels with an average ...

Scientific Bulletin of Valahia University - Materials and Mechanics

In this part of the paper, we will study the behavior of PUR polyurethane at different mechanical... more In this part of the paper, we will study the behavior of PUR polyurethane at different mechanical and thermal stresses, stresses for which this material behaves very well. It is known that this material behaves well as a protective material against shocks, so it is used as protection against mechanical elements. PUR behaves excellently at uneven static stresses and dynamic stresses. That is why it is used in the construction of the rollers of medium weight mobile devices or rollers that have cam functionality, strongly required for static and dynamic contact. PUR has very good thermal properties, it is used as a thermal insulator when it is in the form of high-density polyurethane foam (PUR / PIR).

Energies

This paper presents an analysis of the literature that studies the possibility of sewage sludge b... more This paper presents an analysis of the literature that studies the possibility of sewage sludge being used in the cement industry to reduce carbon dioxide emissions from cement production and thus solve the problem of disposing of sewage sludge so that it is no longer stored, avoiding soil pollution with heavy metals, and reducing pressure on the environment. The ash of sewage sludge is a good pozzolanic material, because when it is finely ground, it can be used as a partial substitute for Portland cement. This reduces waste storage costs. Sewage sludge ash was mixed with cement, and it was analyzed to determine whether the paste obtained could be used as a raw material in the cement industry. The presented results are on the hydration characteristics of the sewage sludge ash, the compressive strength of the cement determined after different days, the workability of the cement, and the porosity of the cement paste and the ash.

Scientific Bulletin of Valahia University - Materials and Mechanics

The use of guide ways in apparatus, devices and machines construction is frequent that the aspect... more The use of guide ways in apparatus, devices and machines construction is frequent that the aspects concerning their accuracy and durability are elements defining technical performances. The paper proposes a mathematical model for calculating the wear of torques with sliding motion. The proposed model makes it possible to establish a link between wear and tear and the accuracy of the movement of the moving part during operation. The model can be applied in the design phase for a known geometry and operating conditions.

Journal of Science and Arts, 2020

The guides of the machine tools, brakes, clutches there is the possibility of the intermittent mo... more The guides of the machine tools, brakes, clutches there is the possibility of the intermittent movement of stick-slip. This opens in the case of frictional couples with sliding motion, due to the low sliding speeds. Intermittent slip introduces vibrational phenomena and influences the uniformity of movement and the state of the surface of the couples due to their use. In this respect, the concerns related to the study of this phenomenon represent an interest in the machine building industry. The paper aims to achieve an original theoretical model for calculating the static and kinetic friction coefficients and its experimental verification on a stick-slip stand. The proposed theoretical model establishes the calculation relations of the static and kinetic friction coefficient and the connection between them taking into account the surface processing method. The originality of the approach is that the model is considered friction between the conical penetrator (steel material) and a ...

In this paper we present a synthesis method for obtaining hydroxyapatite nanopowders by chemical ... more In this paper we present a synthesis method for obtaining hydroxyapatite nanopowders by chemical precipitation. As the starting reagents, analytical grade Ca(OH)2, H3PO4 and NH4OH were used. The proposed method led to obtaining a hydroxyapatite with a high degree of crystallinity and purity. The synthesized samples were characterized by X-ray diffraction (XRD), Fourier transformed-infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques.

Journal of Science and Arts, 2021

Thermoplastic polymeric materials used in the case of friction couplings with sliding movement su... more Thermoplastic polymeric materials used in the case of friction couplings with sliding movement such as guides, bearings, linear bearings, must have good tribological properties related to friction and wear. Indication of these characteristics is a convenient means for faster characterization of the tribological behavior of any pair of materials when operating conditions are changed.The paper presents a comparative study of the friction characteristics for two thermoplastic polymeric materials (Relamid B-10-FC and Turcit B Slydway) that slide on a metal surface in dry or oil-lubricated environments.The evolution of the coefficient of friction for a non-compliant and a conforming contact under different operating and lubrication conditions was analyzed. The experimental research was done on a stand of pin on disk tribological tests illustrating graphically the evolution of the coefficient of friction with the load, speed and time for different surface roughness. The values of the norm...

Scientific Bulletin of Valahia University - Materials and Mechanics, 2018

The paper presents the study of internal defects resulting from the continuous casting of steels.... more The paper presents the study of internal defects resulting from the continuous casting of steels. The 50 samples were taken from a total of 20 continuously cast bits of different steel grades. The investigation of the causes of internal defects, shown on the analyzed samples, started from the assumption that the secondary metallurgy was performed correctly. The following internal defects have been evident: internal cracks (axial cracks, section cracks), central porosity and marginal punctuation impurities.

Materiale Plastice, 2019

Lately, PP-R pipes have become increasingly popular in terms of drinking water installations and ... more Lately, PP-R pipes have become increasingly popular in terms of drinking water installations and heating. Comparated to the classic pipes from copper or steel, pipes from propylene are much easier to use, they have obvious qualities and they are marketed at a much lower price. The study aims a comparative analysis of the physical-mechanical properties of the four most common types of pipes from propylene, which are currently found in commerce : simple without insertion(PP-R), with insert of composite fiber (PP-R-CF), with insert of basalt fiber (PP-R-BF) and with insert of aluminium (PP-R-AIF). Experimental research showed that from the point of view of thermal expansion, the best behavior is from the pipes from propylene without any insert and the value of the thermal expansion coefficient for the reinforcement pipe with basaltic fiber is very small. After these attempts at tensile, it resulted that all four samples which were analyzed from the point of view of the tensile strength...

Scientific Bulletin of Valahia University - Materials and Mechanics, 2019

The paper shows data related to coexistence of various binding systems, which could be present du... more The paper shows data related to coexistence of various binding systems, which could be present during the hardening of special concretes. It is taken into account the Ultra Low Aluminous Cement Concretes additivated with different materials (phosphates and mineral ultra dispersed powders - Condensed Silica Fume, Hydrated Alumina etc). In correlation to the pH-value, these substances can favour the forming of new binding systems besides the hydraulic binder (which is not important in this case). The new system is the coagulation binding form. The coagulation binding system has a very important role in the advanced compactness and in the increasing mechanical strengths of concrete structures.

Materiale Plastice, 2019

The character of the original paper is to provide electromagnetic radiation absorbing material th... more The character of the original paper is to provide electromagnetic radiation absorbing material that attenuation characteristics of the electromagnetic field very good, as compared to the absorbent materials studied to date. This paper presents results of research on processing, characterization and behavior of composite materials based on silicone rubber used for electromagnetic shielding. In this work silicone rubbers is reinforced with magnetic fillers (iron silicon). The obtaining of composite materials was with the aid of a doctor blade technique. Doctor blade technique is a coating technique widely used for producing thin films on large area surfaces. The samples were processed in the laboratory using a plated nettling (PN), that was impregnated with a silicone rubber based composite containing powder of iron silicon (SI). Were achieved measurements of the both parts of the materials obtaining. These have shown an electromagnetic shielding effectiveness the order of 3.35-41.62 ...

Scientific Bulletin of Valahia University - Materials and Mechanics, 2018

The aim of the paper was to develop a device (“pin-on-disc” type) for the measurement of friction... more The aim of the paper was to develop a device (“pin-on-disc” type) for the measurement of friction in plane friction couplings with sliding movement. On tribometric device (made in our laboratory) we can measure the friction force, friction coefficient and wear, for different loading conditions, speeds, time and material coupling. For the measurement of the frictional force as well as of the coefficients of friction, mainly the method with a resistive tensiometric transducer is used. With a DataQ DI 245 data acquisition board it is possible to record up to 2 kHz frequencies in the range of -10 ÷ +10 mV with a resolution of 13 bits. To test the functionality of the device, a preliminary test was carried out for a steel pin- on- cast iron disc, for different values of the normal pushing force. The device was calibrated and the measurement results were recorded and processed on the computer.

Scientific Bulletin of Valahia University - Materials and Mechanics, 2016

Following the sliding motion between two surfaces a heat release occures which leads to a changin... more Following the sliding motion between two surfaces a heat release occures which leads to a changing of the mechanical properties of the surfaces in contact. Amongst the factors that influence the heat release one may name the loading, the velocity, the surface topography, the surface material, the lubrication and last but not the least, the environment.The present paper proposes a computation model to determine the temperature in the working of a coupling to which the mechanical characteristics of the materials are not affected by changes which, at their turn, lead to undesired effects.

Proceeding of 10th Wseas International Conference on Electronics Hardware Wireless and Optical Communications and 10th Wseas International Conference on Signal Processing Robotics and Automation and 3rd Wseas International Conference on Nanotechnology and 2nd Wseas International Conference on Pla..., Feb 20, 2011

Agronomy

The main objective of this article is the analysis of crop rotation applied to three crop farms o... more The main objective of this article is the analysis of crop rotation applied to three crop farms of different sizes in Romania. The period under study is before the implementation of the “Environmentally beneficial practices applicable to arable land” eco-scheme, included in the National Strategic Plan of Romania, 2023–2027, in the section on direct payments related to subsidies. The analysed crop farms have different areas, as follows: Farm A—64.97 ha, Farm B—615.50 ha and Farm C—2881.33 ha. This research aims to highlight the agro-environmental conditions specific to each farm that are required to be met by 2023. The data analysis highlights the fact that farms under 100 ha, such as Farm A, must apply the conditions of the eco-scheme as follows: 3.25 ha with non-productive elements, including uncultivated land; 6.50 ha cultivated with crops from the Leguminosae family, 16.25 ha cultivated with cereals, 19.49 ha cultivated with corn, 12.99 ha cultivated with sunflowers, 3.25 ha cult...

Sustainability

The study analyzes the awareness of the effects of climate change on agriculture and the measures... more The study analyzes the awareness of the effects of climate change on agriculture and the measures that should be implemented in this regard from the farmer’s perspective, taking into account the financial and promotional measures supported by the European Union for farmers. Thus, the study tracks the level of openness of farmers to implementing the measures that European policy makers will take in the coming period. Taking into account the fact that agriculture plays a particularly important economic role, due to the share of agricultural products in Romania’s total exports, particularly in plant production, a quantitative survey was carried out among Romanian farmers, using a questionnaire as an instrument, with a total of 407 respondents. The farmers interviewed undoubtedly recognize that the problems they face are caused by the effects of climate change and are willing to adapt, seek and implement the necessary solutions. The most problematic climatic phenomenon identified by far...

In this paper we have analysed the determinants of the students’ leisure time, based on 198 respo... more In this paper we have analysed the determinants of the students’ leisure time, based on 198 respondents of an questionnaire. The students are at the bachelor level in the Faculty MIEADR, USAMV Bucharest. The questions have reffered to the conditions in which students used to spend their leisure time. The performed analysis consisted in several steps. First, we made a descriptive analysis of the variables, by doing the frequences tables; then, there were performed correlation tables and the crosstabulation between pairs of variables. In order to verify the level of the statistical significance among the variables, it was also performed a chi-square statistical test. As general requirement, we have chosen to emphasise the results by pointing out the influence of the gender and place of residence variables for the respondents. From the findings of this paper, we have concluded that students of our faculty have different approaches, divided by place of residence regarding the holidays s...

The paper presents an analysis on market elements that can influence the decision to cultivate ra... more The paper presents an analysis on market elements that can influence the decision to cultivate rapeseed. We have studied the market features as estimators on market supply-demand ratio (the annual production, imports and exports of rapeseed) and the area under rapeseed production as concrete estimator on decision to cultivate. Inter-conditionality analysis between estimators of market and the estimators of decision to cultivate, made for a time interval of 12 years (2002-2013) emphasized that, in the Romanian market of rape, one of the significant factors influencing the decision to growth (taken in the previous year at seeding) is the value of exports of rape in the harvest year. It also revealed that in recent years, it has generated a system of specialized farms in rapeseed production associated to the international market requirements. It also highlighted the fact that domestic market of rapeseed (understood as internal consumption) does not influence the decision to cultivate r...

The paper adresses an approach on indicators from the public database FADN (Farm Accountancy Data... more The paper adresses an approach on indicators from the public database FADN (Farm Accountancy Data Network), at farm level selected from Romania. The study focused on analyzing the data series in 2012 (the latest year reported in the FADN) and the second part of the study was supported by the report on the last six years (2007-2012) and four of the eight regions. The data comes from public database FADN and the methodology consisted of a descriptive analysis of the data and presenting them as graphic and tabular form. The results recorded consisted of highlighting the differences between regions and survey findings have highlighted a decrease in interest and rental costs and also in investment levels, compared to 2012; in the same conditions, the total production and cash flow increased.

“Agriculture for Life, Life for Agriculture” Conference Proceedings, 2018

The changes from Tax Code foresee that societies with fiscal value under one milion euro (to 500.... more The changes from Tax Code foresee that societies with fiscal value under one milion euro (to 500.000 euro till 31.12.2017) to be included in the micro-enterprises category and according to this provision owes to the state budget a 1% tax from fiscal value to 16% corporate tax. The paper presents benchmarking of this new fiscal measure applying above some retail and cash&cary societies from Romania to taxing profit in case this measure would be applied to all tipes of companies analysis based on a set of indicators (Absolute abnormality, growth index, turnover dynamics etc). The conclusions following the paper are: increase revenue collected to the state budget and simplifying the methods of determination to this tax but general apply to this measure could lead to infringement, encouraging layoffs, increasing unemployment, discouragement of investments, the impossibility of companies to recover in situations of crisis, discourage entry on market of new envestors, encouraging tax evas...

Scientific Bulletin of Valahia University - Materials and Mechanics

An important category of widely used steels is chromium alloy improvement steels (STAS 9382/4-89)... more An important category of widely used steels is chromium alloy improvement steels (STAS 9382/4-89) intended for the execution of shafts, axles, cams, sprockets and sprockets subjected to operation at important demands. The properties of these steels are determined both by the chemical composition and by the way of plastic elaboration and deformation, but also by the way in which the structural transformations to the thermal treatments of tempering and recovery result. The properties of a certain steel are largely determined by the granulation size of the secondary structure, which in turn is dependent on the size of the austenitic granulation, respectively the hereditary granulation. At a given steel mark, the mode of heating (slow or fast) at the austenitization temperature is decisive regarding the dimensions of the austenitic grain respectively of the nature of the secondary granulation and of the operating properties. Studies and research were conducted on steels with an average ...

Scientific Bulletin of Valahia University - Materials and Mechanics

In this part of the paper, we will study the behavior of PUR polyurethane at different mechanical... more In this part of the paper, we will study the behavior of PUR polyurethane at different mechanical and thermal stresses, stresses for which this material behaves very well. It is known that this material behaves well as a protective material against shocks, so it is used as protection against mechanical elements. PUR behaves excellently at uneven static stresses and dynamic stresses. That is why it is used in the construction of the rollers of medium weight mobile devices or rollers that have cam functionality, strongly required for static and dynamic contact. PUR has very good thermal properties, it is used as a thermal insulator when it is in the form of high-density polyurethane foam (PUR / PIR).

Energies

This paper presents an analysis of the literature that studies the possibility of sewage sludge b... more This paper presents an analysis of the literature that studies the possibility of sewage sludge being used in the cement industry to reduce carbon dioxide emissions from cement production and thus solve the problem of disposing of sewage sludge so that it is no longer stored, avoiding soil pollution with heavy metals, and reducing pressure on the environment. The ash of sewage sludge is a good pozzolanic material, because when it is finely ground, it can be used as a partial substitute for Portland cement. This reduces waste storage costs. Sewage sludge ash was mixed with cement, and it was analyzed to determine whether the paste obtained could be used as a raw material in the cement industry. The presented results are on the hydration characteristics of the sewage sludge ash, the compressive strength of the cement determined after different days, the workability of the cement, and the porosity of the cement paste and the ash.

Scientific Bulletin of Valahia University - Materials and Mechanics

The use of guide ways in apparatus, devices and machines construction is frequent that the aspect... more The use of guide ways in apparatus, devices and machines construction is frequent that the aspects concerning their accuracy and durability are elements defining technical performances. The paper proposes a mathematical model for calculating the wear of torques with sliding motion. The proposed model makes it possible to establish a link between wear and tear and the accuracy of the movement of the moving part during operation. The model can be applied in the design phase for a known geometry and operating conditions.

Journal of Science and Arts, 2020

The guides of the machine tools, brakes, clutches there is the possibility of the intermittent mo... more The guides of the machine tools, brakes, clutches there is the possibility of the intermittent movement of stick-slip. This opens in the case of frictional couples with sliding motion, due to the low sliding speeds. Intermittent slip introduces vibrational phenomena and influences the uniformity of movement and the state of the surface of the couples due to their use. In this respect, the concerns related to the study of this phenomenon represent an interest in the machine building industry. The paper aims to achieve an original theoretical model for calculating the static and kinetic friction coefficients and its experimental verification on a stick-slip stand. The proposed theoretical model establishes the calculation relations of the static and kinetic friction coefficient and the connection between them taking into account the surface processing method. The originality of the approach is that the model is considered friction between the conical penetrator (steel material) and a ...

In this paper we present a synthesis method for obtaining hydroxyapatite nanopowders by chemical ... more In this paper we present a synthesis method for obtaining hydroxyapatite nanopowders by chemical precipitation. As the starting reagents, analytical grade Ca(OH)2, H3PO4 and NH4OH were used. The proposed method led to obtaining a hydroxyapatite with a high degree of crystallinity and purity. The synthesized samples were characterized by X-ray diffraction (XRD), Fourier transformed-infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques.

Journal of Science and Arts, 2021

Thermoplastic polymeric materials used in the case of friction couplings with sliding movement su... more Thermoplastic polymeric materials used in the case of friction couplings with sliding movement such as guides, bearings, linear bearings, must have good tribological properties related to friction and wear. Indication of these characteristics is a convenient means for faster characterization of the tribological behavior of any pair of materials when operating conditions are changed.The paper presents a comparative study of the friction characteristics for two thermoplastic polymeric materials (Relamid B-10-FC and Turcit B Slydway) that slide on a metal surface in dry or oil-lubricated environments.The evolution of the coefficient of friction for a non-compliant and a conforming contact under different operating and lubrication conditions was analyzed. The experimental research was done on a stand of pin on disk tribological tests illustrating graphically the evolution of the coefficient of friction with the load, speed and time for different surface roughness. The values of the norm...

Scientific Bulletin of Valahia University - Materials and Mechanics, 2018

The paper presents the study of internal defects resulting from the continuous casting of steels.... more The paper presents the study of internal defects resulting from the continuous casting of steels. The 50 samples were taken from a total of 20 continuously cast bits of different steel grades. The investigation of the causes of internal defects, shown on the analyzed samples, started from the assumption that the secondary metallurgy was performed correctly. The following internal defects have been evident: internal cracks (axial cracks, section cracks), central porosity and marginal punctuation impurities.

Materiale Plastice, 2019

Lately, PP-R pipes have become increasingly popular in terms of drinking water installations and ... more Lately, PP-R pipes have become increasingly popular in terms of drinking water installations and heating. Comparated to the classic pipes from copper or steel, pipes from propylene are much easier to use, they have obvious qualities and they are marketed at a much lower price. The study aims a comparative analysis of the physical-mechanical properties of the four most common types of pipes from propylene, which are currently found in commerce : simple without insertion(PP-R), with insert of composite fiber (PP-R-CF), with insert of basalt fiber (PP-R-BF) and with insert of aluminium (PP-R-AIF). Experimental research showed that from the point of view of thermal expansion, the best behavior is from the pipes from propylene without any insert and the value of the thermal expansion coefficient for the reinforcement pipe with basaltic fiber is very small. After these attempts at tensile, it resulted that all four samples which were analyzed from the point of view of the tensile strength...

Scientific Bulletin of Valahia University - Materials and Mechanics, 2019

The paper shows data related to coexistence of various binding systems, which could be present du... more The paper shows data related to coexistence of various binding systems, which could be present during the hardening of special concretes. It is taken into account the Ultra Low Aluminous Cement Concretes additivated with different materials (phosphates and mineral ultra dispersed powders - Condensed Silica Fume, Hydrated Alumina etc). In correlation to the pH-value, these substances can favour the forming of new binding systems besides the hydraulic binder (which is not important in this case). The new system is the coagulation binding form. The coagulation binding system has a very important role in the advanced compactness and in the increasing mechanical strengths of concrete structures.

Materiale Plastice, 2019

The character of the original paper is to provide electromagnetic radiation absorbing material th... more The character of the original paper is to provide electromagnetic radiation absorbing material that attenuation characteristics of the electromagnetic field very good, as compared to the absorbent materials studied to date. This paper presents results of research on processing, characterization and behavior of composite materials based on silicone rubber used for electromagnetic shielding. In this work silicone rubbers is reinforced with magnetic fillers (iron silicon). The obtaining of composite materials was with the aid of a doctor blade technique. Doctor blade technique is a coating technique widely used for producing thin films on large area surfaces. The samples were processed in the laboratory using a plated nettling (PN), that was impregnated with a silicone rubber based composite containing powder of iron silicon (SI). Were achieved measurements of the both parts of the materials obtaining. These have shown an electromagnetic shielding effectiveness the order of 3.35-41.62 ...

Scientific Bulletin of Valahia University - Materials and Mechanics, 2018

The aim of the paper was to develop a device (“pin-on-disc” type) for the measurement of friction... more The aim of the paper was to develop a device (“pin-on-disc” type) for the measurement of friction in plane friction couplings with sliding movement. On tribometric device (made in our laboratory) we can measure the friction force, friction coefficient and wear, for different loading conditions, speeds, time and material coupling. For the measurement of the frictional force as well as of the coefficients of friction, mainly the method with a resistive tensiometric transducer is used. With a DataQ DI 245 data acquisition board it is possible to record up to 2 kHz frequencies in the range of -10 ÷ +10 mV with a resolution of 13 bits. To test the functionality of the device, a preliminary test was carried out for a steel pin- on- cast iron disc, for different values of the normal pushing force. The device was calibrated and the measurement results were recorded and processed on the computer.

Scientific Bulletin of Valahia University - Materials and Mechanics, 2016

Following the sliding motion between two surfaces a heat release occures which leads to a changin... more Following the sliding motion between two surfaces a heat release occures which leads to a changing of the mechanical properties of the surfaces in contact. Amongst the factors that influence the heat release one may name the loading, the velocity, the surface topography, the surface material, the lubrication and last but not the least, the environment.The present paper proposes a computation model to determine the temperature in the working of a coupling to which the mechanical characteristics of the materials are not affected by changes which, at their turn, lead to undesired effects.

Proceeding of 10th Wseas International Conference on Electronics Hardware Wireless and Optical Communications and 10th Wseas International Conference on Signal Processing Robotics and Automation and 3rd Wseas International Conference on Nanotechnology and 2nd Wseas International Conference on Pla..., Feb 20, 2011