检索结果-南通市图书馆

Influence of Fresh Water on Microbubble Generation in an Airlift Column Applied to Aquaculture: Extraction Capacity

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Applied Sciences 2022年第11期12卷 1809-1823页

作者： Djimako Bongo Nekoulnang Djetounako Clarisse Edith Kadjangaba salif gaye Jean-Yves Champagne Higher Normal School of Technology of Sarh Sarh Chad Paleontology Department National Research Center for Development of N’djamena N’djamena Chad Faculty of Sciences and Techniques University of Doba Doba Chad LME Materials and Energetics Laboratory University Institute of Technology Thiès Senegal Laboratory of Fluid Mechanics and Acoustics INSA-Lyon Lyon France

Bubble flows consist a liquid phase and a gaseous phase dispersed as bubbles. They occur in nature and in many industrial applications, such as oil transportation in pipelines and steam generators for power generation. Due to large difference in density between gas and liquid, the flottability force causes bubbles to rise, which in turn can generate overall motion and agitation in liquid. This use of gravity as a flow driver, which is specific to disperse phase systems, is used in process engineering (bubble columns and gasosiphon) to sparingly promote mixing and exchange between gas and liquid. In many applications, bubbles are used to agitate a liquid in order to promote mixing and transfers. This work is devoted to study of hydrodynamics of a bubble column. Experimentally, we have determined properties fluctuations of velocities inside the aquarium of rising homogeneous bubbles for different bubble sizes and vacuum rates. The interfacial area between gas and liquid phase is a crucial factor for mass transfer in bubble columns. The molecular exchange between a given volume of gas and water can be enhanced by formation of smaller bubbles, leading to a larger gas-liquid interface. This work presents the various physical phenomena that apply to bubbles, as well as associated dimensionless numbers. A state art of Micro-Bubble Generators (MBG) is then presented, presenting systems using various phenomena such as cavitation, electrolysis, or shear.

关键词： Vacuum Airlift Column MIBC Casein Turbidity Surfactant Coalescence

Approach Thermal Habitat Assessment in N’Djamena in Chad

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Engineering and Technology 2016年第1期4卷 82-102页

作者： Ahmat Charfadine Mahamat Barka Abakar Mahamat Tahir Mohagir Ahmed Mohammed Pr. salif gaye Laboratory of Renewable Energy and Materials Premises of the University of N’Djamena N’Djamena Chad Laboratory of Materials Mechanics and Hydraulics of the University of Thies Thies Senegal

For the earth material construction is the most used one in Chad, the object of this work is the assessment of the thermal quality of earthen adobe mixed with straw. Different simulation software analyzes the CoDyBa which is conducted to determine the behavior of this material compared to living comfort thanks to the Fanger model, which is a method of approach to thermal comfort standpoint. The study focused on two configurations on the formation of the walls of a room. The first of these configurations led to the definition of a first cell constructed earthen adobe named Batter roofing sheet aluminum and a second cell built in blocks named Batbet which had the same geometric characteristics (thickness, dimensions and side openings) and covered in the same manner as the ground cell. The different comfort indices PMV and PPD values of these two configurations of habitat were identified and were used to determine their thermal comfort rating.

关键词： Habitat Assessment Habitat Suitability Building Monitoring Climate Change Thermal Habitat Orientation Solar

Improving the Stability of the Inflatable Soil of Diamniadio by Using Typha Australis in Order to Value It in Partitioning Wall

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Building Construction and Planning Research 2020年第4期8卷 273-284页

作者： Ahmadou Diop Macodou Thiam Mamadou Babacar Ndiaye Oumar Diallo Harouna Mamadou Bal salif gaye Laboratory of Materials and Energetics (LME) University Institute of Technology (IUT) Thiès Senegal

The construction industry in Senegal is experiencing an upsurge in the development of residential housing units and administrative buildings within the new Diamniadio municipality, an area located just about 35 km from the capital city of Dakar. Laboratory oedometer or expansive-index tests, however, show poor density and compromised shear strength in the soil samples within the area -posing serious construction problems due to significant volume changes (swellings) that occur when subjected to moisture, thus, bringing into question the structural performance integrity of the soil, and the financial implications of substitute soil types used to compensate for its poor tensile strength. By way, the companies collect the soil of this location (Diamniadio) and throw it to make pile or micro-pile (pious) for their structures. This article demonstrates how we can value the soil of Diamniadio and the Typha Australis in residential building with a reasonable cost. Typha Australis is a plant generally luxuriant within the northern and central belts of Senegal but also known for its negative ecological impacts on the agricultural production of rice. The valorisation of the soil of Diamniadio will pass by the ability to increase its stability or to decrease its shrinkage/swelling rate. When we achieve it, the soil associate with Typha Australis will be used for small bricks which can be useful for partition wall and so the soil will not be ever thrown as a non-useful material. Tests results of soil specimens extracted from the site show a shrinkage rate of 29.19% with estimated cracking depths of 3.5 cm. But by adding gradually Typha Australis, the shrinkage rate will pass from 29.19% to 5.13% with the material treats with 10% by mass of Typha Australis. Moreover, the crackings in the cylindrical specimen disappear. That shows the increase of the stability;thus the composition will be used for building bricks. However, the densities will also be affected by the presence of Ty

关键词： Buildings Clay Cracking Fine Particle Shrinkage Rate Stabilization Typha Australis Valorisation

Thermomechanical Characterization of Three Soils of Abeche in Chad

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Civil Engineering 2024年第3期14卷 348-362页

作者： Mahamat Saleh Abdel-Khadir Abdallah Dadi Mahamat Abderahman Adoum Oumar Mahamoud Youssouf Khayal salif gaye Energy and Materials Research Laboratory (LREM-INSTA) National Higher Institute of Science and Technology of Abch Abch Chad Faculty of Physics University of NDjamena NDjamena Chad Laboratory of Energy Electricity and Economic Materials (LM3E) Iba Der Thiam University of This This Senegal

The study carried out concerns the valorization of agricultural waste for the development of biosourced materials that can be used as insulation in homes. This article is devoted to the influence of gum arabic on the mechanical and thermal properties of clay soils in the town of Abéché. The mechanical tests were carried out using the CBR press equipped with two devices (bending device and compression device). Thermal property such as thermal conductivity was determined by the hot wire method and thermal resistance was derived by calculation. Thus, the tests were carried out on test pieces made from a mixture of clay and gum arabic in solution. The experimental program includes seven formulations (0%, 2%, 4%, 6%, 8%, 10% and 12%). The results obtained showed that the best flexural and compressive strengths are obtained by using gum arabic with a rate of 8% and a maximum stress of 4.3 MPa. In addition, the thermal results also showed that the thermal conductivity decreases when the percentage of gum arabic increases, which makes it possible to increase the thermal resistance, thus confirming the capacity of gum arabic to provide thermal insulation.

关键词： Soils Mechanical Characterization Thermal Characterization Thermal Conductivity Thermal Resistance

Thermophysical Characterization of Typha’s Concrete for Its Integration into Construction

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Building Construction and Planning Research 2021年第1期9卷 56-65页

作者： Ababacar Sadikh Diaw Harouna Mamadou Bal Oumar Diallo Mamadou Babacar Ndiaye Mamadou Wade salif gaye Laboratory of Materials and Energetics (LME) University Institute of Technology (IUT) Thies Senegal Laboratory of Sciences and Technology of Water and Environment (LaSTEE) Polytechnic School of Thies Thies Senegal

Energy consumption in the building sector is constantly increasing and represents more than 44% in the residential and tertiary sectors in many countries [1]. Thus, the building represents a real possibility of energy saving and is the subject of several studies particularly in actual context of experimentation with materials based on plant fibers (hemp, flax, millet wastage, etc.). These biobased materials such as typha have shown real interest in the buildings construction due to their light and porous nature. It’s in this context that we were interested in typha australis mixed with classic aggregates (cement, sand, gravel 3/8) to make typha’s concrete. On this concrete, we carried out experimental measurements in order to better understand its contributions in the building. The interesting results obtained show that typha australis, which is an invasive and harmful grass, can be valued and integrated among local building materials in the form of typha’s concrete in order to improve the energy efficiency of buildings.

关键词： Typha Australis Bio-Based Materials Thermal Conductivity Thermal Diffusivity Energy Efficiency Asymmetric Hot Plane

Improvement of the Microalgae Harvest by the “Foaming-Scumming” Function of an Airlift Column

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Fluid Dynamics 2019年第1期9卷 63-71页

作者： Djimako Bongo Nekoulnag Clarice Jean-Mari Mbailao Mbaiguinam Alexis Mouangue Naminina Jean-Yves Champagne salif gaye National Institute of Science and Technology of Abeché Abeché Chad Faculty of Exact and Applied Sciences University of N’Djamena N’Djamena Chad Laboratory of Fluid Mechanics and Acoustics INSA-Lyon Lyon France LME Materials and Energetics Laboratory University Institute of Technology Thiès Senegal

The aim of this research work is to valorize the microalgae grown-up in an Airlift column. The system of fluid circulation and mass transfer is based on the principle of interaction between gas bubbles and a liquid. Thus, this study focuses on the phenomenon of the determination of the vacuum rate, the size and the speed of the bubbles including the optimization of microalgae development within the culture process. In addition, this study tries to understand the close relationship between these phenomena, its environment and the microalgae cell. These studies were conducted on the operation of an Airlift column in aquaculture, mainly in freshwater [1]. However, other researchers [2] are interested in studying saline water. In conclusion, a series of experiments were carried out in order to evaluate the profitability of the Microflotation technique, as a method of separation and concentration in microalgae. These results are very interesting since they reveal that the efficiency of the column, for the foaming-skimming function, is greater by working with less significant air injections, which lead to a reduction in energy cost.

关键词： Vacuum Column Microalgae Vacuum Rate Bubble Size Bubble Speed

Thermophysical Characterization of Local Materials from a Locality in Chad for Use in Eco-Building

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Civil Engineering 2024年第3期14卷 486-497页

作者： Abderahman Adoum Oumar Malloum Soultan Abdallah Dadi Togdjim Jonas Mahamat Saleh Abdel-Khadir Mahamoud Youssouf Khayal salif gaye Laboratoire de Recherche en Energtique et Matriaux (LREM) de lINSTA Institut National Suprieur des Sciences et Techniques dAbch Abch Chad Ecole Doctorale Science Technique et Environnement Universit de NDjamena NDjamena Tchad Laboratoire CABET (Construction Alternative Basse Energie au Tchad) NDjamena Chad Laboratoire de Matriaux dnergtique dlectricit et dconomie (LM3E) Universit Iba Der Thiam de This This Sngal

With the aim of enhancing the value of local building materials, the subject of this paper is a thermophysical study of natural Chadian clay from the eastern region of Chad, “Abeche”. Samples were taken from a brickwork in Abeche from a depth of 1 m, then using a clay brick-making press, 4 × 5 × 8 cm3 clay test tubes were made with 2%, 4%, 6% and 8% cow dung, and a 100% clay sample was used as a control. These samples underwent thermophysical characterization using the hot-wire method with a hot-plane option, yielding results that could improve thermophysical performance. The thermal conductivity of the test sample is in the order of 0.715 to 0.420 W/m. K, at 8% for cow dung, so the addition of cow dung as a percentage in the clay matrix enabled us to obtain various satisfactory thermal parameters.

关键词： Soils Characterization Thermophysical Local Building

Incidence and Factors Associated with the Switch to the Second Line Antiretroviral Treatment at the Ambulatory Treatment Center (CTA) in Dakar

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Health 2016年第14期8卷 1566-1575页

作者： Ndeye Fatou Ngom-Gueye Gilbert Batista Abdoul Aziz Ndiaye Assane Diouf KA. Daye Alioune Badara Tall Awa Diouf Kine Ndiaye Makhtar Ndiaga Diop Mountaga Dia Cheikh Tacko Diop Awa gaye Cheikh Tidiane Ndour Moussa Seydi Lamine Gueye Bernard Marcel Diop Papa salif Sow Ambulatory Treatment Center Fann University Teaching Hospital Dakar Senegal Department of Community Health Alioune Diop University Bambey Senegal Department of Infectious Diseases Fann University Teaching Hospital Dakar Senegal

Introduction: Over the past years, efforts have been made to expand access to antiretroviral combinations (cART) in low-income countries. However, major concerns are noted with drug resistance emergence, as treatment failure result and need to introduce a second line treatment, more expensive and difficult to implement. The objective was to study the incidence of switch to second line, reasons for switch and risk factors using a cohort of people living with HIV in an Ambulatory Treatment Center in Dakar. Methodology: This was a cohort study of people living with HIV under cART from January 2004 to December 2013. Naive patients monitored for at least six months, regardless of their profile and regimen with baseline CD4 counts Results: The median age of the 827 patients included was 44 [IQR = 18 - 78]. The switch to second-line treatment was observed in 72 patients (8.7%) after an average of 38.5 months of follow-up. The overall incidence rate of switch to second line of antiretroviral treatment was 1.59 per 100 persons-years. Most of changes in first-line treatment were motivated by virological failures (n = 60, 83.3%) under treatment with AZT/3TC/NVP (n = 25, 34.7%) or AZT/3TC/EFV21 (29.2%). 9.7% of switch occurred after immunological failure, 1.4% after clinical failure, 4.2% after severe toxicity and 1.4% was not documented. Predictive factors identifying failures at the end of the multivariate analysis were age Conclusions: In total, CTA identified a low incidence rate of treatment failure of the first line of treatment. Associated risk factors were age 3 and high viral load at treatment initiation.

关键词： Incidence Associated Factors Switch to 2nd Line cART CTA Dakar