检索结果-南通市图书馆

Optimization of Ceramic Paste Viscosity Use for the Elaboration of Tubular Membrane Support by Extrusion and Its Application

引用

Journal of Materials Science and Chemical Engineering 2020年第3期8卷 1-22页

作者： Celestine Asobo Yanu joseph marie sieliechi Martin Benoit Ngassoum National School of Agro-Industrial Sciences Department of Applied Chemistry University of Ngaoundéré Ngaoundéré Cameroon

The objective of this work was to determine the optimum size and amount of raw materials which influence the viscosity of ceramic paste using the experimental design for the production of tubular support by the extrusion technique and its application in microfiltration. The Box Behnken design was used to optimize the viscosity of the ceramic paste. ANOVA was used to model the system represented by independent parameters and dependent output response and to optimize the system by estimating the statistical parameters. A three-factor and three-level design was used generating thus 15 experiments. The independent factors were the amount of porogen, size of porogen and amount of binder and dependent factor the viscosity of the ceramic paste. The minimum (−1), intermediate (0) and maximum (+1) level of the amount of porogen, size of porogen and amount of binder used were 20 g, 30 g and 40 g, 50 μm, 100 μm and 150 μm, and 2 g, 3.5 g and 5 g respectively. The statistical analyses showed that the values of the answers would adapt to a second degree polynomial model. The R-square value obtained was greater than 95%, the Biais factor was equal to the unit and the Absolute Average Deviation (AAD) equal to the zero thus validating the model. The optimal size of raw material was found to be 100 μm for an amount of clay of 66 g, amount of porogen of 30 g and amount of binder of 4 g. The optimum viscosity of the ceramic paste was found to be 26.7 Pa∙s which is close to the viscosity of the clay paste only found to be 28.5 Pa∙s, thus good for shaping by the extrusion technique. The ceramic paste showed a pseudo-plastic behavior. The tubular porous support was sintered at 950°C and the dimensions, such as outer and inner diameters and length of the tube were 4 cm, 2 cm, and 19 cm, respectively. The sintered membrane possesses a porosity of 43.5%, water permeability of 244.9 L/h∙m2 bar, an average pore size of 2.4 μm and mechanical strength of 9.2 MPa with ver

关键词： Optimization Tubular Support Extrusion Viscosity of Paste Microfiltration

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Elaboration of Ceramic Pot Filter from Kaolinite (Cameroon Clay) for the Elimination of Suspended Particles from Domestic Drinking Water

引用

Journal of Modern Physics 2023年第8期14卷 43-60页

作者： Celestine Asobo Yanu Ngiongboung Nguiamba joseph marie sieliechi Martin Benoit Ngassoum Faculty of Science Department of Chemistry University of Buea Buea Cameroon National School of Agro-Industrial Sciences Department of Applied Chemistry University of Ngaoundere Ngaoundere Cameroon

The objective of this work was to elaborate ceramic water filters from Kaolinite (Cameroon) clay for the elimination of suspended particles from domestic drinking water. In Sub-Sahara Africa and in Cameroon in particular health issues have been linked to the consummation of domestic tap water of high turbidity values both in the rural and urban areas. In order to remedy these problems, ceramic water pot filters have been elaborated in a pilot scale unit with aim of putting in place a unit production. The chemical composition, the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analyses of the raw materials (clay and rice husks) was determined. The crystal phases and scanning electron microscope of Wack clay was also determined. The ceramic pot filter membranes were fabricated from the formulations 70/20/10 of clay/porogen/chamotte respectively with the particle size of the raw material less than or equal to 500 μm. The formulated ceramic pot filters were then sintered at 900˚C in a furnace. These ceramic pot filters were characterized by determining their porosity, withdrawal percentages, water permeability, mechanical and chemical resistance. The study of the efficiency consisted in evaluating the retention rate and permeate flux with respect to time (days) with synthetic water suspensions of turbidity 100 NTU and particle size of 2 μm. The ceramic pot filters were made aiming at studying the efficiency after physical defouling of filters. Physical defouling consisted in brushing the inner surface of the ceramic pot filters with water and drying them at ambient temperature after being used for 11 days and reusing them under the same initial conditions. The produced ceramic pot filter had a volume of 4 L, an average porosity of 36.15%, shrinkage in mass or withdrawal percentage of 18.23%, a water permeability of 59.6 × 103 L∙h−2∙m−2, mechanical resistance of 6.8 MPa and corrosion resistance of

关键词： Ceramic Pot Filter Retention Rate Flux Defouling Formulation Production Cost

来源：

维普期刊数据库

维普期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Identification of an Appropriate Formulation for Domestic Water Ceramic Filters from Soukamna Clay(Cameroon)

引用

Journal of Metallic Material Research 2021年第1期4卷 12-18页

作者： Ngiongboung Nguiamba Celestine Asobo Yanu Placide Desire Belibi Belibi joseph marie sieliechi Martin Benoit Ngassoum National School of Agro-Industrial Sciences Department of Applied ChemistryUniversity of NgaoundereNgaoundereCameroon

This paper deals with the formulation of ceramic filters having the porosity adapted to domestic potable water *** filters were made from clays and rice husk obtained from the Far North region of Cameroon(Logone Valley).Nine formulations were investigated to choose those that might have the porosity standing between 35 and 50%(the ideal porosity adapted for water treatment).The nine formulations investigated were as follows:clay:rice husk mixture weight ratio 0.7:0.3;0.8:0.2 and 0.9:0.1 with the particle size of 100:100 *** sintering temperatures of 900℃,950℃ and 1000℃ were applied for each of the *** results showed that only filters with weight ratio 0.7:0.3 sintered at 900℃,950℃ and 1000℃ had porosity between 35 and 50% with values of 39.41±0.96;40.15±1.59;40.14±1.31 *** strength,permeability and iron leaching behavior were investigated for these three *** formulation 0.7:0.3 with sintering temperature of 1000℃ had the higher permeability and was the more stable for iron leaching so it is the more adapted for water treatment in terms of flow rate and iron leaching behavior,pore size distribution showed that these filters were macroporous and designed for microfiltration with average pore diameter of 0.46μm.

关键词： Ceramic filter Porosity Permeability Iron leaching Soukamna

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Physico-Chemical Characterization and Stability Study in Acidic and Basic Solution of Ceramic Filters from Mouka’s Clay (Cameroon)

引用

Journal of Materials Science and Chemical Engineering 2019年第11期7卷 42-53页

作者： Ngiongboung Nguiamba Placide Désirée Belibi Belibi joseph marie sieliechi Martin Benoî t Ngassoum University of Ngaoundéré Department of Applied Chemistry University of Ngaoundéré Ngaoundéré Cameroon

This paper deals with the characterisation and study of physico-chemical stability of ceramic filters from clays and rice husk obtained from the far north region of Cameroon (Logone Valley) and their application in potable water treatment. Clays from Mouka were characterized by FTIR analysis. The results showed that the filter formulated with a mixture containing 80% clay and 20% rice husk of 100 μm in size each gave the lowest filter shrinkage rate;these formulated filters were chosen for the remaining work. Leaching tests showed that with filters at a sintering temperature of 830°C the leaching was not observed under neutral (pH 6.8) and acidic (pH 5) conditions as compared to 950°C and 1000°C where the leaching was observed. In basic (pH 9) condition, all the filters obtained released ions. Leaching tests revealed that the conductivity of the leachate for the filters sintered at 830°C was lower than those sintered at 950°C and 1000°C. Meanwhile, conductivity decreases with increasing sintering temperature (temperature up to 830°C) due to the fact that ceramization starts as from 850°C that leads to an amorphous state that favours chemical stability, the leaching ions were Fe2+, Ca2+, Mg2+ and Al3+. The ceramic filters sintered at 950°C were applied to the filtration of water and the performance in terms of turbidity reduction was 95% and the flow rate after 50 minutes was 100 × 10−3 L/h.

关键词： Ceramic Filter Chemical Stability Clay Filtration Lixiviation Test

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Physico-Chemical Study of the Adsorption of Carotenoids from Carrots on Raw and Modified Kaolinites

引用

Advances in Chemical Engineering and Science 2023年第2期13卷 132-148页

作者： Orléans Ngomo Etienne Dongo joseph sieliechi Department of Organic Chemistry Faculty of Sciences University of Yaoundé I Yaounde Cameroon Department of Applied Chemistry The National School of Agro-Industrial Sciences University of Ngaoundere Ngaoundere Cameroon

This study focuses on the adsorption at temperatures below 70℃, of carotenoids from carrots on clay materials such as kaolinite in the raw state, activated with a 0.5 M HCl solution or treated with a sodium solution of Al+. The kinetic study of carotenoid adsorption shows that equilibrium is reached after 30 minutes and the temperature has little influence on carotenoid adsorption. On the other hand, the quantities adsorbed at equilibrium increase with the initial concentration of carotenoids. The kinetic model that best describes the experimental data is that of the pseudo-second order, adsorption is made in two time. For the carotenoid adsorption isotherms, the best correlation is obtained with the Freundlich model. The low values of the Freundlich constants indicate that the adsorption is probably of a physical type. This conclusion is confirmed by the effective desorption of carotenoids observed during desorption experiments.

关键词： Kaolinite Carrots Antioxidant Cosmetic Adsorption

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Redistribution and magnitude of stresses around horse shoe and circular excavations opened in anisotropic rock

引用

International Journal of Mining Science and Technology 2015年第4期25卷 615-621页

作者： Mambou Ngueyep Luc Leroy Ndop joseph Ndjaka Jean-marie Bienvenu Laboratory of Material Sciences Department of Physics Faculty of Sciences University of Yaoundé 1 Department of Mine Mineral Processing and Environment School of Geology and Mining Engineering University of Ngaoundéré Douala Institute of Technology

In this paper numerical analysis of underground structures, taking account the transverse isotropy system of rocks, was done using CAST 3M code by varying the shape of excavation and the coefficient of earth pressure k. Numerical results reveal that the anisotropy behavior, the shape of hole and the coefficient of earth pressure k have significant influence to the mining induced stress field and rock deformations which directly control the stability of underground excavation design. The magnitude of horizontal stress obtained for the horse shoe shape excavation(25.2 MPa for k = 1; 52.7 MPa for k = 2)is lower than the magnitude obtained for circular hole(26.4 MPa for k = 1; 59.5 MPa for k = 2).Therefore, we have concluded that the horse shoe shape offers the best stability and the best design for engineer. The anisotropy system presented by rock mass can also influence the redistribution of stresses around hole opened. Numerical results have revealed that the magnitude of redistribution of horizontal stresses obtained for transverse isotropic rock(12.1 MPa for k = 0.5; 25.2 MPa for k = 1 and52.7 MPa for k = 2) is less than those obtained in the case of isotropic rock(27.6 MPa for k = 1;48.6 MPa for k = 2 and 90.81 MPa for k = 2). The more the rock has the anisotropic behavior, the more the mass of rock around the tunnel is stable.

关键词： Horse shoe excavation Stress Strain Transverse isotropy Finite element

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Artificial intelligence in colonoscopy

引用

World Journal of Gastroenterology 2021年第29期27卷 4802-4817页

作者： Joel joseph Ella marie LePage Catherine Phillips Cheney Rishi Pawa Department of Internal Medicine Wake Forest Baptist Medical CenterWinston SalemNC 27157United States Department of Internal Medicine Wake Forest School of MedicineWinston SalemNC 27157United States Department of Internal Medicine Section of Gastroenterology and HepatologyWake Forest Baptist Medical CenterWinston-SalemNC 27157United States

Colorectal cancer remains a leading cause of morbidity and mortality in the United *** in artificial intelligence(AI),specifically computer aided detection and computer-aided diagnosis offer promising methods of increasing adenoma detection rates with the goal of removing more pre-cancerous ***,these methods also may allow for smaller non-cancerous lesions to be diagnosed in vivo and left in place,decreasing the risks that come with unnecessary *** review will provide an overview of current advances in the use of AI in colonoscopy to aid in polyp detection and characterization as well as areas of developing research.

关键词： Colonoscopy Artificial intelligence Computer-aided detection Detection Characterization Computer-aided diagnosis

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Benchmarks of 3D Laplace Equation Solvers in a Cubic Configuration for Streamer Simulation

引用

Plasma Science and Technology 2016年第5期18卷 538-543页

作者： joseph-marie PLEWA Olivier DUCASSE Philippe DESSANTE Carolyn JACOBS Olivier EICHWALD Nicolas RENON Mohammed YOUSFI Universite de Toulouse UPS INPT LAPLACE (Laboratoire Plasma et Conversion d'Energie) Toulouse Cedex 9 F-31062 France Group of Electrical Engineering-Paris (GeePs) UMR 8507 CNRS CentraleSupelec Universite Paris-Sud-UPMC 11 rue Joliot-Curie Plateau de Moulon 91192 Gif-sur-Yvette Cedex F-91192 France CALMIP Universite de Toulouse-CNRS-INPT-INSA-UPS UMS 3667 France CNRS LAPLACE Toulouse F-31062 France

The aim of this paper is to test a developed SOR R＆B method using the Chebyshev accelerator algorithm to solve the Laplace equation in a cubic 3D configuration. Comparisons are made in terms of precision and computing time with other elliptic equation solvers proposed in the open source LIS library. The first results, obtained by using a single core on a HPC, show that the developed SOR R＆B method is efficient when the spectral radius needed for the Chebyshev acceleration is carefully pre-estimated. Preliminary results obtained with a parallelized code using the MPI library are also discussed when the calculation is distributed over one hundred cores.

关键词： numerical methods for elliptic equations high performance computing 3Dstreamer simulation SOR IDR BiCGSTAB

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Vertical accuracy evaluation of freely available latest high-resolution(30 m)global digital elevation models over Cameroon(Central Africa)with GPS/leveling ground control points.

引用

International Journal of Digital Earth 2019年第5期12卷 500-524页

作者： Loudi Yap Ludovic Houetchak Kande Robert Nouayou joseph Kamguia Nasser Abdou Ngouh marie Brigitte Makuate Research Laboratory in Geodesy National Institute of CartographyYaound3Cameroon Department of Physics Faculty of SciencesUniversity of Yaoundé1YaoundéCameroon

Digital Elevation Models(DEMs)contain topographic relief data that are vital for many geoscience *** study relies on the vertical accuracy of publicly available latest high-resolution(30 m)global DEMs over *** models are(1)the ALOS World 3D-30 m(AW3D30),(2)the Shuttle Radar Topography Mission 1 Arc-Second CBand Global DEM(SRTM 1)and(3)the Advanced Spaceborne Thermal Emission and Reflection Global DEM Version 2(ASTER GDEM 2).After matching their coordinate systems and datums,the horizontal positional accuracy evaluation was carried out and it shows that geolocation errors significantly influence the vertical accuracy of global *** this,the three models are compared among them,in order to access random and systematic effects in the elevation data each of them ***,heights from 555 GPS/leveling points distributed all over Cameroon are compared to each DEM,for their vertical accuracy *** and robust statistical measures,normality test,outlier detection and removal were used to describe the vertical quality of the *** test of the normality rejected the hypothesis of normal distribution for all tested global *** vertical accuracies obtained for the three models after georeferencing and gross error removal in terms of Root Mean Square(RMS)and Normalized Median Absolute Deviation(NMAD)are:AW3D30(13.06 m and 7.75 m),SRTM 1(13.25 m and 7.41 m)and ASTER GDEM 2(18.87 m and 13.30 m).Other accuracy measures(MED,68.3% quantile,95% quantile)supply some evidence of the good quality of AW3D30 over ***,the effect of land cover and slope on DEM vertical accuracy was also *** models have proved to be worse in the areas dominated by forests and shrubs *** 1 and AW3D30 are more resilient to the effects of the scattering objects respectively in forests and cultivated *** dependency of DEMs accuracy on the terrain roughness is *** all slope intervals,AW3D30 is performing

关键词： DEM AW3D30 SRTM 1 ASTER GDEM 2 Cameroon GPS/leveling orthometric heights vertical accuracy

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Modeling and numerical analysis of granite rock specimen under mechanical loading and fire

引用

Journal of Rock Mechanics and Geotechnical Engineering 2015年第1期7卷 101-108页

作者： Luc Leroy Ngueyep. Mambou joseph Ndop Jean-marie Bienvenu Ndjaka Laboratory of Sciences Material Department of Physics Faculty of Science University of Yaounde Yaounde Cameroon Department of Mine Mineral Processing and Environment School of Geology and Mining Engineering University of Ngaoundere Meiganga Cameroon Douala Institute of Technology Douala Cameroon

The effect of ISO 834 fire on the mechanical properties of granite rock specimen submitted to uniaxial loading is numerically investigated. Based on Newton＇s second law, the rate-equation model of granite rock specimen under mechanical load and fire is established. The effect of heat treatment on the me- chanical performance of granite is analyzed at the center and the ends of specimen. At the free end of granite rock specimen, it is shown that from 20 ~C to 500 ~C, the internal stress and internal strain are weak; whereas above 500 ~C, they start to increase rapidly, announcing the imminent collapse. At the center of specimen, the analysis of the internal stress and internal strain reveals that the fire reduces the mechanical performance of granite significantly. Moreover, it is found that after 3 min of exposure to fire, the mechanical energy necessary to fragment the granite can be reduced up to 80%.

关键词： Granite rock specimenHigh temperatureInternal stressInternal strainISO 834 fire

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：