The objective of this paper is to evaluate the reliability of a system in its different states (absence of failures, partial failure and total failure) and to propose actions to improve this reliability by an approach...The objective of this paper is to evaluate the reliability of a system in its different states (absence of failures, partial failure and total failure) and to propose actions to improve this reliability by an approach based on Monte Carlo simulation. It consists of a probabilistic evaluation based on Markov Chains. In order to achieve this goal, the functionalities of Markov Chains and Monte Carlo simulation steps are deployed. The application is made on a production system. .展开更多
Magnesium alloys have been widely studied as materials for temporary implants,but their use has been limited by their corrosion rate.Recently,coatings have been proven to provide an effective barrier.Though only littl...Magnesium alloys have been widely studied as materials for temporary implants,but their use has been limited by their corrosion rate.Recently,coatings have been proven to provide an effective barrier.Though only little explored in the field,Atomic Layer Deposition(ALD)stands out as a coating technology due to the outstanding film conformality and density achievable.Here,we provide first insights into the corrosion behavior and the induced biological response of 100 nm thick ALD TiO_(2),HfO_(2)and ZrO_(2)coatings on AZ31 alloy by means of potentiodynamic polarization curves,electrochemical impedance spectroscopy(EIS),hydrogen evolution and MTS colorimetric assay with L929 cells.All three coatings improve the corrosion behavior and cytotoxicity of the alloy.Particularly,HfO_(2)coatings were characterized by the highest corrosion resistance and cell viability,slightly higher than those of ZrO_(2)coatings.TiO_(2)was characterized by the lowest corrosion improvements and,though generally considered a biocompatible coating,was found to not meet the demands for cellular applications(it was characterized by grade 3 cytotoxicity after 5 days of culture).These results reveal a strong link between biocompatibility and corrosion resistance and entail the need of taking the latter into consideration in the choice of a biocompatible coating to protect degradable Mg-based alloys.展开更多
The paper reported a comparative study of the methods of extraction of <span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;&qu...The paper reported a comparative study of the methods of extraction of <span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">vegetable fibres encountered in the literature;three main ones was chose, namely: combing, retting with pre-treatment of the bagasse in salt and distilled water,</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">and Chemical extraction at three concentration levels of soda (2N, 1N, 0.1N) </span><span style="font-family:Verdana;">with pre-treatment of bagasse with salt water and distilled water. After extracting the fibres using these methods, it appeared that the natural methods (retting and combing) have a higher yield of around 70% compared to the</span><span style="font-family:Verdana;"> chemical method which has a low yield of around 40%. The fibres obtained by the chemical extraction method (1N-BPD) had the best characteristics</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.</span></span></span>展开更多
The lack of synergy between infrastructure financing mechanisms and mechanisms for combating climate change does not favor the definition of sustainable infrastructure in Cameroon. The definition of a sustainable infr...The lack of synergy between infrastructure financing mechanisms and mechanisms for combating climate change does not favor the definition of sustainable infrastructure in Cameroon. The definition of a sustainable infrastructure could meet the requirements of these mechanisms, thanks to the control of Greenhouse Gas (GHG) emissions during its installation, in relation to a predefined value. However, the promotion of efforts to reduce emissions from new infrastructures is not subject to a local market. This situation is a limit in the implementation of the policies defined in the Nationally Determined Contribution (NDC). This article proposes a framework for promoting reduction efforts for a national carbon market, in favor of hydroelectric infrastructures. Thanks to the Life Cycle Assessment (LCA) environmental assessment tool, we are going to determine the carbon quota for a specific power. The study carried out on the hydroelectric power station of Mekin (HydroMekin) leads us to a reduction effort of 68.2% compared to the threshold defined at 14.057 gCO<sub>2eq</sub>/kWh<sub>e</sub>. The framework, developed, contributes to defining the environmental parameters in the decarbonation strategy during the implementation of new hydroelectric infrastructures and the market carbon design elements special to the construction phase of these infrastructures.展开更多
The objective of this study is to determine the thermal characteristics of bricks produced from clay soils in Chad using the asymmetric plane method. Indeed, in Sahelian countries like Chad, temperature variations are...The objective of this study is to determine the thermal characteristics of bricks produced from clay soils in Chad using the asymmetric plane method. Indeed, in Sahelian countries like Chad, temperature variations are excessive. The study of the thermal behavior of a recyclable local material with low environmental impact could not only improve thermal comfort in homes, but also help mitigate the effects of climate change. It is in this context that this study is envisaged. Before carrying out these measurements, we first produced different formulations of soil blocks 0%, 1% 1.5%, 2% and 2.5% by mass of rice husks (1.25 mm sieve refusal). Brick specimens of dimensions 10 cm × 10 cm × 1 cm were developed at 0 day, 7 days and 14 days of maturation of the formulated pastes. After, those bricks were submitted after drying to the measurements of various thermal parameters: in particular the conductivity, the effusivity, the volumetric capacity and the diffusivity. The obtained results show that the addition of rice husks to clay soils improves conductivity by 13% to 49%, effusivity by 19% to 24%, volumetric capacity by 23% to 27%, and diffusivity by 47% to 58% for the Moundou soils, depending on the maturation period. For the N’Djamena soil, these thermal characteristics are improved from 11% to 38%, from 11% to 13%, from 40% to 47% and from 39% to 40% respectively.展开更多
T<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">he present work examined the influence on thermal properties of...T<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">he present work examined the influence on thermal properties of the incorporation of banana pseudo-trunkfibres in a cementitious matrix morta</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">r that can be used as rendering or masonry block. The banana pseudo-trunkfibres are extracted, cut and characterized. Then the mortars are made with different proportions of fibres and characterized in order to identify the parameters influencing the characteristics of the material, both in the fresh and hardened state. The physical, mechanical and thermal tests carried out have shown an increase in the porosity and water absorption of the mortar with a decrease in the density, thus making the mortar lighter. It was also noted a decrease in the mortar’s flexural and compressive strengths as a function of the percentage of fibres;nevertheless, the values remain within an acceptable range</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.</span></span></span>展开更多
The present work deals with reducing greenhouse gas emissions through improving the life span of wooden power electric poles of Eucalyptus saligna. Indeed, in Sub-Saharan African countries, Cameroon in particular, mos...The present work deals with reducing greenhouse gas emissions through improving the life span of wooden power electric poles of Eucalyptus saligna. Indeed, in Sub-Saharan African countries, Cameroon in particular, most of the power line networks are made of wooden supports and according to the Cameroon energy distribution company, wooden poles represent 32% of the causes of death linked to the state of the network. The company’s 2019 annual report indicates that 40,000 wooden poles were in critical condition and should be replaced. A significant number of mechanical failures affecting these supports have been observed. For example, on the HVA/LV power line “D17 Nko- abang” in Yaoundé in Cameroon, less than three years old, 10 (ten) cases of poles falling and/or breaking, due to their mechanical loading, were observed over a period of fewer than nine months, causing an average service stoppage for more than 11 hours and affecting an average of 3280 customers. These incidents lead to questions about how the supports are dimensioned and what load capacities they are designed to support. The aim of this work is, therefore, to suggest a method of dimensioning wooden poles hence reducing green- house gas emissions due to the deforestation by reducing the number of woo- den poles at risk to be replaced on Cameroon’s electricity distribution network. And more specifically, to reduce the number of mechanical failures affecting the wooden supports observed by analyzing the current wooden supports with their loads and to make proposals for improving the actual dimensioning me- thods. From the study carried out, it appears that 449 out of 845 supports, i.e., 53% needed to be replaced or monitored because they support the nominal forces ranging from 85% to 150% of their admissible limit and proposals have been made to improve their dimensioning.展开更多
Droplet microfluidic techniques have shown promising outcome to study single cells at high throughput.However,their adoption in laboratories studying“-omics”sciences is still irrelevant due to the complex and multid...Droplet microfluidic techniques have shown promising outcome to study single cells at high throughput.However,their adoption in laboratories studying“-omics”sciences is still irrelevant due to the complex and multidisciplinary nature of the field.To facilitate their use,here we provide engineering details and organized protocols for integrating three droplet-based microfluidic technologies into the metagenomic pipeline to enable functional screening of bioproducts at high throughput.First,a device encapsulating single cells in droplets at a rate of~250 Hz is described considering droplet size and cell growth.Then,we expand on previously reported fluorescence-activated droplet sorting systems to integrate the use of 4 independent fluorescence-exciting lasers(i.e.,405,488,561,and 637 nm)in a single platform to make it compatible with different fluorescence-emitting biosensors.For this sorter,both hardware and software are provided and optimized for effortlessly sorting droplets at 60 Hz.Then,a passive droplet merger is also integrated into our pipeline to enable adding new reagents to already-made droplets at a rate of 200 Hz.Finally,we provide an optimized recipe for manufacturing these chips using silicon dry-etching tools.Because of the overall integration and the technical details presented here,our approach allows biologists to quickly use microfluidic technologies and achieve both single-cell resolution and high-throughput capability(>50,000 cells/day)for mining and bioprospecting metagenomic data.展开更多
文摘The objective of this paper is to evaluate the reliability of a system in its different states (absence of failures, partial failure and total failure) and to propose actions to improve this reliability by an approach based on Monte Carlo simulation. It consists of a probabilistic evaluation based on Markov Chains. In order to achieve this goal, the functionalities of Markov Chains and Monte Carlo simulation steps are deployed. The application is made on a production system. .
文摘Magnesium alloys have been widely studied as materials for temporary implants,but their use has been limited by their corrosion rate.Recently,coatings have been proven to provide an effective barrier.Though only little explored in the field,Atomic Layer Deposition(ALD)stands out as a coating technology due to the outstanding film conformality and density achievable.Here,we provide first insights into the corrosion behavior and the induced biological response of 100 nm thick ALD TiO_(2),HfO_(2)and ZrO_(2)coatings on AZ31 alloy by means of potentiodynamic polarization curves,electrochemical impedance spectroscopy(EIS),hydrogen evolution and MTS colorimetric assay with L929 cells.All three coatings improve the corrosion behavior and cytotoxicity of the alloy.Particularly,HfO_(2)coatings were characterized by the highest corrosion resistance and cell viability,slightly higher than those of ZrO_(2)coatings.TiO_(2)was characterized by the lowest corrosion improvements and,though generally considered a biocompatible coating,was found to not meet the demands for cellular applications(it was characterized by grade 3 cytotoxicity after 5 days of culture).These results reveal a strong link between biocompatibility and corrosion resistance and entail the need of taking the latter into consideration in the choice of a biocompatible coating to protect degradable Mg-based alloys.
文摘The paper reported a comparative study of the methods of extraction of <span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">vegetable fibres encountered in the literature;three main ones was chose, namely: combing, retting with pre-treatment of the bagasse in salt and distilled water,</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">and Chemical extraction at three concentration levels of soda (2N, 1N, 0.1N) </span><span style="font-family:Verdana;">with pre-treatment of bagasse with salt water and distilled water. After extracting the fibres using these methods, it appeared that the natural methods (retting and combing) have a higher yield of around 70% compared to the</span><span style="font-family:Verdana;"> chemical method which has a low yield of around 40%. The fibres obtained by the chemical extraction method (1N-BPD) had the best characteristics</span></span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.</span></span></span>
文摘The lack of synergy between infrastructure financing mechanisms and mechanisms for combating climate change does not favor the definition of sustainable infrastructure in Cameroon. The definition of a sustainable infrastructure could meet the requirements of these mechanisms, thanks to the control of Greenhouse Gas (GHG) emissions during its installation, in relation to a predefined value. However, the promotion of efforts to reduce emissions from new infrastructures is not subject to a local market. This situation is a limit in the implementation of the policies defined in the Nationally Determined Contribution (NDC). This article proposes a framework for promoting reduction efforts for a national carbon market, in favor of hydroelectric infrastructures. Thanks to the Life Cycle Assessment (LCA) environmental assessment tool, we are going to determine the carbon quota for a specific power. The study carried out on the hydroelectric power station of Mekin (HydroMekin) leads us to a reduction effort of 68.2% compared to the threshold defined at 14.057 gCO<sub>2eq</sub>/kWh<sub>e</sub>. The framework, developed, contributes to defining the environmental parameters in the decarbonation strategy during the implementation of new hydroelectric infrastructures and the market carbon design elements special to the construction phase of these infrastructures.
文摘The objective of this study is to determine the thermal characteristics of bricks produced from clay soils in Chad using the asymmetric plane method. Indeed, in Sahelian countries like Chad, temperature variations are excessive. The study of the thermal behavior of a recyclable local material with low environmental impact could not only improve thermal comfort in homes, but also help mitigate the effects of climate change. It is in this context that this study is envisaged. Before carrying out these measurements, we first produced different formulations of soil blocks 0%, 1% 1.5%, 2% and 2.5% by mass of rice husks (1.25 mm sieve refusal). Brick specimens of dimensions 10 cm × 10 cm × 1 cm were developed at 0 day, 7 days and 14 days of maturation of the formulated pastes. After, those bricks were submitted after drying to the measurements of various thermal parameters: in particular the conductivity, the effusivity, the volumetric capacity and the diffusivity. The obtained results show that the addition of rice husks to clay soils improves conductivity by 13% to 49%, effusivity by 19% to 24%, volumetric capacity by 23% to 27%, and diffusivity by 47% to 58% for the Moundou soils, depending on the maturation period. For the N’Djamena soil, these thermal characteristics are improved from 11% to 38%, from 11% to 13%, from 40% to 47% and from 39% to 40% respectively.
文摘T<span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">he present work examined the influence on thermal properties of the incorporation of banana pseudo-trunkfibres in a cementitious matrix morta</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">r that can be used as rendering or masonry block. The banana pseudo-trunkfibres are extracted, cut and characterized. Then the mortars are made with different proportions of fibres and characterized in order to identify the parameters influencing the characteristics of the material, both in the fresh and hardened state. The physical, mechanical and thermal tests carried out have shown an increase in the porosity and water absorption of the mortar with a decrease in the density, thus making the mortar lighter. It was also noted a decrease in the mortar’s flexural and compressive strengths as a function of the percentage of fibres;nevertheless, the values remain within an acceptable range</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">.</span></span></span>
文摘The present work deals with reducing greenhouse gas emissions through improving the life span of wooden power electric poles of Eucalyptus saligna. Indeed, in Sub-Saharan African countries, Cameroon in particular, most of the power line networks are made of wooden supports and according to the Cameroon energy distribution company, wooden poles represent 32% of the causes of death linked to the state of the network. The company’s 2019 annual report indicates that 40,000 wooden poles were in critical condition and should be replaced. A significant number of mechanical failures affecting these supports have been observed. For example, on the HVA/LV power line “D17 Nko- abang” in Yaoundé in Cameroon, less than three years old, 10 (ten) cases of poles falling and/or breaking, due to their mechanical loading, were observed over a period of fewer than nine months, causing an average service stoppage for more than 11 hours and affecting an average of 3280 customers. These incidents lead to questions about how the supports are dimensioned and what load capacities they are designed to support. The aim of this work is, therefore, to suggest a method of dimensioning wooden poles hence reducing green- house gas emissions due to the deforestation by reducing the number of woo- den poles at risk to be replaced on Cameroon’s electricity distribution network. And more specifically, to reduce the number of mechanical failures affecting the wooden supports observed by analyzing the current wooden supports with their loads and to make proposals for improving the actual dimensioning me- thods. From the study carried out, it appears that 449 out of 845 supports, i.e., 53% needed to be replaced or monitored because they support the nominal forces ranging from 85% to 150% of their admissible limit and proposals have been made to improve their dimensioning.
基金The work was supported by the grants from King Abdullah University of Science and Technology(KAUST),Saudi Arabia(Grant Nos.BAS/1/1059/01/01,URF/1/1976/03/01,URF/1/1976-17-01,URF/1/1976-20-01,and FCS/1/3326-01-01).
文摘Droplet microfluidic techniques have shown promising outcome to study single cells at high throughput.However,their adoption in laboratories studying“-omics”sciences is still irrelevant due to the complex and multidisciplinary nature of the field.To facilitate their use,here we provide engineering details and organized protocols for integrating three droplet-based microfluidic technologies into the metagenomic pipeline to enable functional screening of bioproducts at high throughput.First,a device encapsulating single cells in droplets at a rate of~250 Hz is described considering droplet size and cell growth.Then,we expand on previously reported fluorescence-activated droplet sorting systems to integrate the use of 4 independent fluorescence-exciting lasers(i.e.,405,488,561,and 637 nm)in a single platform to make it compatible with different fluorescence-emitting biosensors.For this sorter,both hardware and software are provided and optimized for effortlessly sorting droplets at 60 Hz.Then,a passive droplet merger is also integrated into our pipeline to enable adding new reagents to already-made droplets at a rate of 200 Hz.Finally,we provide an optimized recipe for manufacturing these chips using silicon dry-etching tools.Because of the overall integration and the technical details presented here,our approach allows biologists to quickly use microfluidic technologies and achieve both single-cell resolution and high-throughput capability(>50,000 cells/day)for mining and bioprospecting metagenomic data.
