检索结果-南通市图书馆

Numerical Study of the Vibrations of Beams with Variable Stiffness under Impulsive or Harmonic Loading

World Journal of Engineering and Technology 2024年第2期12卷 401-425页

作者： moussa Sali Fabien Kenmogne Jean Bertin Nkibeu Abdou Njifenjou Laboratory of Materials Mechanics and Civil Engineering National Higher Polytechnic School of Maroua University of Maroua Maroua Cameroon Department of Civil Engineering Advanced Teachers Training College of the Technical Education University of Douala Douala Cameroon Laboratory Engineering Civil and Mechanics National Advanced School of Engineering University of Yaound&#233 1 Yaound&#233 Cameroon Laboratory of Energy Materials Modeling and Method (E3M) National Advanced School of Engineering University of Douala Douala Cameroon Laboratory of Mathematical Engineering and Information Systems National Advanced School of Engineering University of Yaound&#233 1 Yaound&#233 Cameroon

The behavior of beams with variable stiffness subjected to the action of variable loadings (impulse or harmonic) is analyzed in this paper using the successive approximation method. This successive approximation method is a technique for numerical integration of partial differential equations involving both the space and time, with well-known initial conditions on time and boundary conditions on the space. This technique, although having been applied to beams with constant stiffness, is new for the case of beams with variable stiffness, and it aims to use a quadratic parabola (in time) to approximate the solutions of the differential equations of dynamics. The spatial part is studied using the successive approximation method of the partial differential equations obtained, in order to transform them into a system of time-dependent ordinary differential equations. Thus, the integration algorithm using this technique is established and applied to examples of beams with variable stiffness, under variable loading, and with the different cases of supports chosen in the literature. We have thus calculated the cases of beams with constant or variable rigidity with articulated or embedded supports, subjected to the action of an instantaneous impulse and harmonic loads distributed over its entire length. In order to justify the robustness of the successive approximation method considered in this work, an example of an articulated beam with constant stiffness subjected to a distributed harmonic load was calculated analytically, and the results obtained compared to those found numerically for various steps (spatial h and temporal τ ¯ ) of calculus, and the difference between the values obtained by the two methods was small. For example for ( h=1/8 , τ ¯ =1/ 64 ), the difference between these values is 17%.

关键词： Successive Approximations Method Direct Integration Differential Equations Beams of Variable Stiffness Quadratic Parabola Impulse and Harmonic Loads

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

Influence of Anthropogenic Activities on Surface Water Resources—Case of the Sub-Prefecture of Kamsar-Boké

引用

Journal of Geoscience and Environment Protection 2024年第8期12卷 168-179页

作者： Konate Daouda Kone Tidiani Kamano Saa moussa Diallo Mamadou Oury Higher Institute of Veterinary Sciences and Medicine of Dalaba Dalaba Guinea Jean Lorougnon Guede-Daloa-RCI University Daloa Ivory Coast

Living fishery resources, although rich and important for human populations, are subject to strong anthropization, thus causing a change in the environmental parameters of aquatic ecosystems. These multiple combined pressures: chemical, hydro-morphological, thermal or trophic, affect and disrupt the functioning of aquatic organisms. The objective of this study was to assess the main human pressures influencing the surface water resources of the Kamsar sub-prefecture, in order to propose mitigation measures. The following methodological approach was adopted: 1) Survey of managers and analysis records;2) Survey of stakeholders;3) Assessment of the effect of human activities on surface water resources;4) Data processing;5) Corrective measures. The survey farmers working near aquatic environments, revealed a low use of chemical substances, in particular 3 to 11 kg of fertilizer and 0 to 3 boxes of herbicide on fields of 40 m2 to 2 ha. Some physico-chemical parameters have been determined: Temperature (28.5˚C, 23.7˚C, 22.8˚C, 21.3˚C, 21.6˚C), Salinity (26.9‰, 21.9‰, 21.5‰, 15‰, 15.3‰) and Turbidity (21.3 UTN, 19.3 UTN, 17.8 UTN, 16.7 UTN, 17 UTN). These values show a fluctuation in the environmental parameters of aquatic ecosystems, which constitutes an obstacle to the development and survival of the resources.

关键词： Influence Anthropogenic Activities Water Resources

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

Physical and Thermo-Mechanical Properties of Composite Materials Based on Raw Earth and Crushed Palm Leaf Fibers (Borassus aethiopum)

引用

Materials Sciences and Applications 2024年第9期15卷 358-377页

作者： Mouhamadou Nabi Kane Mapathe Ndiaye Pape moussa Touré Adama Dione University College of Architecture of Dakar (CUAD) UFR SI University of Thies This Senegal Laboratory of Mechanics and Modeling UFR SI University of This This Senegal Laboratoire dEnergtique Applique (LEA) Cheikh Anta Diop University Dakar Senegal Institut of Earth Sciences (IST) Universit Cheikh Anta Diop (UCAD) Dakar Senegal

The objective of this study is to seek solutions to reduce the impact of buildings on climate change and to promote the use of local bio-sourced or geo-sourced materials for sustainable construction. Different samples of raw earth from 3 sites were taken in the commune of Mlomp. Geotechnical tests showed that the raw earth samples from sites 2 and 3 have more clay fraction while site 1 contains more sand. The fact of integrating fibers from crushed palm leaves (Borassus aethiopum) (2%, 4% and 6%) into the 3 raw earth samples reduced the mechanical resistance to compression and traction of the 3 raw earths. The experimental results of thermal tests on samples of earth mixtures with crushed Palma leaf fibers show a decrease in thermal conductivity as well as thermal effusivity as the percentages increase (2%, 4% and 6%) of fibers in raw earth for the 3 sites. This shows that this renewable composite material can help improve the thermal insulation of building envelopes.

关键词： Raw Earth Palma Leaf Fibers Ecological Composite Materials Physical Thermo-Mechanical Thermal Conductivity Thermal Effusivity

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

Mapping Climate Services for Disaster Risk Management: A Systematic Review and Research Gaps from a Policy Process Perspective

引用

American Journal of Climate Change 2024年第2期13卷 314-360页

作者： Aboubacar Issaka Ousman Gaoh Wolfram Laube Georges Abbevi Abbey moussa Waongo West African Science Service Centre on Climate Change and Adapted Land Use (WASCAL) Accra Ghana Department of Geography-DRP-Climate Change and Disaster Risk Management University of Lom Lom Togo Department of Political and Cultural Change Centre for Development Research (ZEF) University of Bonn Bonn Germany Department of Agricultural Economics and Agribusiness Management School of Agriculture University of Lom Lom Togo Department of Training and Research Regional Centre for West Africa and the Sahel (AGRHYMET) Niamey Niger

Climate services (CS) are crucial for mitigating and managing the impacts and risks associated with climate-induced disasters. While evidence over the past decade underscores their effectiveness across various domains, particularly agriculture, to maximize their potential, it is crucial to identify emerging priority areas and existing research gaps for future research agendas. As a contribution to this effort, this paper employs the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology to review the state-of-the-art in the field of climate services for disaster risk management. A comprehensive search across five literature databases combined with a snowball search method using ResearchRabbit was conducted and yielded 242 peer-reviewed articles, book sections, and reports over 2013-2023 after the screening process. The analysis revealed flood, drought, and food insecurity as major climate-related disasters addressed in the reviewed literature. Major climate services addressed included early warning systems, (sub)seasonal forecasts and impact-based warnings. Grounded in the policy processes’ theoretical perspective, the main focus identified and discussed three prevailing policy-oriented priority areas: 1) development of climate services, 2) use-adoption-uptake, and 3) evaluation of climate services. In response to the limitations of the prevalent supply-driven and top-down approach to climate services promotion, co-production emerges as a cross-cutting critical aspect of the identified priority areas. Despite the extensive research in the field, more attention is needed, particularly pronounced in the science-policy interface perspective, which in practice bridges scientific knowledge and policy decisions for effective policy processes. This perspective offers a valuable analytical lens as an entry point for further investigation. Hence, future research agendas would generate insightful evidence by scrutinizing this critical aspect g

关键词： Climate Services Disaster Risk Management Policy Process Science-Policy Interface Institutional Analysis

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

Microbiological and Physico-Chemical Analysis of the Waters of the “Mamouwol” Stream in the Urban District of Mamou (Republic of Guinea)

引用

Journal of Water Resource and Protection 2024年第8期16卷 559-568页

作者： Mamadou Lamarana Souare Mamadou Madaniou Sow Saran Camara Adama moussa Sakho Technical Department of Laboratory Superior Institute of Technology Mamou Republic of Guinea Study and Research Center in the Environment (CERE) Gamal Abdel Nasser University of Conakry Republic of Guinea

Water is essential to life and to the sustainable socio-economic development of a nation, It is therefore interesting to have a better knowledge of the quality of this water. The aim was to determine the degree of microbiological and physico-chemical pollution of the water of the “Mamouwol” river in the town of Mamou. To do this, we chose four (4) sampling sites spread throughout the town of Mamou. During the month of March (2024), 4 water samples were analyzed to monitor the water quality of this river. The average values of the flora analyzed show that these water are heavily contaminated with bacteria indicative of fecal and metal pollution. This study showed that sites: Mam4;Mam2 and Mam1 contain the highest loads, with Total Coliform counts ranging from 1534 CFU/100 ml to 2100 CFU/100 ml, the number of faecal coliforms varies between 526 and 1240 CFU/100 ml, and that of faecal streptococci between 526 and 841 CFU/100 ml. Metal content, BOD5 and COD all comply with the laboratory’s analysis criteria, although they vary from point to point.

关键词： Pollution Water Watercourses Waterborne Diseases Microbiological Analysis

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

Trends of Land Use and Land Cover Change in the Savannah Ecological of the Protected Area Reserve Partielle de Dosso, Niger

引用

Natural Resources 2024年第3期15卷 61-68页

作者： Amadou Issoufou Abdourhimou moussa Boubacar Habou Rabiou Soumana Idrissa Mahamane Ali Faculté des Sciences Agronomiques Université de Diffa Diffa Niger Institut National de la Recherche Agronomique du Niger Niamey Niger Faculté des Sciences et Techniques Université Abdou Moumouni de Niamey Niamey Niger

Information on the dynamics of savannah is important to a country's plan to overcome the problems of uncontrolled development and environmental hazards. Taking the reserve partielle de Dosso, Niger as the case study area, this paper analyzed the long-term land use land cover change from 2002 to 2022. Satellite images were processed by using Google Earth Engine (GEE). Therefore, four major land cover classes were identified based on spectral characteristics of Land sat, namely, built-up, vegetation, cropland, bare land and water. The result revealed that barren and built-up areas increased at the expense of vegetation and water. From the four major land use land cover the large area is covered by vegetation which comprises about 192963.5 hectares followed by cropland and water consisting of 32506.43 and 1596.4 hectares respectively. The built-up area gained substantial area (most) during the study period. The reduction in some of the land cover/uses underlines the dangerous trend of the pressure poised by population growth and the changing functionality. Land cover change is influenced by a variety of societal factors operating on several spatial and temporal levels. The area estimates and spatial distributions of the LULC classes produced from the current study will assist local authorities, managers, and other stakeholders in decision-making and planning regarding forest land cover and uses.

关键词： Land Use/Cover Change Detection Classification Dosso

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 Analysis of Soils Used for Pineapple Cultivation in the Sub-Prefectures of Maferinyah and Friguiagbé (Prefectures of Forécariah and Kindia) Republic of Guinea

引用

Journal of Agricultural Chemistry and Environment 2024年第3期13卷 251-262页

作者： Sâa Gerard Tolno Saran Camara Amadou Sylla Adama moussa Sakho Lounceny Traore Department of Laboratory Techniques Higher Institute of Technology Mamou Republic of Guinea Environmental Studies and Research Centre Conakry Republic of Guinea Department of Chemical Engineering Gamal Abdel Nasser University of Conakry Conakry Republic of Guinea

Over the years, pineapple production in the Republic of Guinea has become less competitive in the West African sub-region, with a world ranking of 144th. It is therefore only natural to review certain parameters in order to improve this ranking. To do this, certain physico-chemical parameters of soil samples from Friguiagbé and Maferinyah (in the Kindia and Forécariah prefectures) were taken and analysed using the following techniques: Pipette de Robinson, Anne, Bray II, Kapen HICDVITZ, Mc. Lead (1982). The analytical results show that the soils at Friguiagbé in Kindia and Maferinyah in Forécariah are acidic, with pH values of 4.4 and 4.7 (fields I and II) and 4.8 and 4.7 (fields I and II) respectively. The soils have a silty-sandy texture. This study could therefore serve as a guide for the Ministry of Agriculture of the Republic of Guinea.

关键词： Soil Pineapple Crop Physico-Chemical Analysis

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

Spatio-Temporal Dynamics of Land Use Units in the Kadzel Sub-Catchment Basin in Diffa, Niger

引用

Journal of Geographic Information System 2024年第4期16卷 259-275页

作者： Karema Ary Madou Kaoulé moussa Mamoudou Boubacar Amadou Issoufou Abdorhimou Mahamane Ali Faculty of Agronomic Sciences University of Diffa Diffa Niger Faculty of Science and Technology Abdou Moumouni University of Niamey Niamey Niger

Environmental degradation linked to land occupation and use, such as climate change and anthropogenic activities, has led to the modification of the landscape units of the Kadzel sub-watershed. The objective of this study is to analyze the dynamics of land use units in the Kadzel area in Diffa between 1992 and 2022 and to propose a future scenario for sustainable environmental management. The approach used relies on remote sensing and geographic information systems to analyze the dynamics of land use units. Additionally, the Markov Cellular Automata (CA) model was used to predict future land use. The land cover maps were produced from a supervised classification by maximum likelihood based on the true and false color compositions of bands 4/3/2 (TM5), 3/2/1 (ETM+) and 7/5/4 (8 OLI). Ten occupation classes were discriminated. Between 1992 and 2022, there was a decrease in the areas of irrigated crops (4.91% and 2.88%), of shrubby tree steppes (14.31% and 9.48%), field-fallow complexes (22.23% and 10.52%), and degraded areas. Grassy steppes (25.76% and 13.32%). However, this reduction has been beneficial for wastelands, urban areas and bodies of water. Based on predictive modeling, it is predicted that by 2052, urban areas, fallow field complexes and bare soils will constitute the main types of housing units. The regressive trend in natural resources appears to continue into the future with current land use practices.

关键词： Occupation Dynamics Environmental Problems Population Growth Lake Chad and Kadzel Basin

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

Characteristics of Gold and Its Mineralization Style in the Boulon Djounga Eastern Perimeter of Liptako Mining Company (Central Southwestern Niger)

引用

Natural Resources 2024年第1期15卷 28-50页

作者： Gambo Ranaou Noura Kamayé Tourba Karimou Dia Hantchi Bouba Hassane moussa Konaté Department of Geology Faculty of Science and Techniques Abdou Moumouni University Niamey Niger Department of Geology Faculty of Science and Techniques Dan Dicko Dankoulodo University Maradi Niger

The Boulon Djounga eastern perimeter is part of the Tiawa operating permit of the Société des Mines du Liptako (SML), located in the central southwestern part of Liptako (Niger). In this study, we used field data, Reverse Circulation (RC) surveys and chemical analyzes of gold to determine the characteristics of gold and its mineralization style. The eastern perimeter of Boulon Djounga is represented by a succession of metabasalts and metasediments both intersected by intrusions of quartz and dolerite dykes, and covered by sandstone and clayey rocks. Gold is present in low contents (0.00 - 0.30 ppm) in the sedimentary cover and in medium (0.30 - 1.00 ppm) or high contents (1.00 - 4.534 ppm) in the metasediments, and in the gray quartz veins and locally in the volcanics. It exists in a disseminated state or in a concentrated state in the surrounding areas in the form of discrete grains associated with sulphurous minerals (pyrite: FeS2, chalcopyrite: CuFeS2 or arsenopyrite: FeAsS). The presence of gold in the quartz veins, and the NE-SW and NW-SE orientations of the ore bodies suggest that the eastern Boulon Djounga gold mineralization would be established during a late magmatic extensive phase.

关键词： Liptako Gold Mineralization Metasediments-Volcanics Quartz Veins Sulphurous Minerals Niger

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

Investigation of Anthropogenic Activities along the Mamouwol River in the Urban Commune of Mamou (Republic of Guinea)

引用

Journal of Environmental Science and Engineering(A) 2024年第1期13卷 15-22页

作者： Mamadou Lamarana Souaré Saran Camara Adama moussa Sakho Mamadou Madaniou Sow Laboratory Technique Higher Institute of Technology of MamouMamou 063Republic of Guinea IRLA-Guinea Laboratory Institute for Applied Language Research(IRLA)Conakry 2201Republic of Guinea

The monitoring of our watercourses for their preservation must be an imperative concern of the whole *** aim of this study is to describe the main causes of degradation and destruction of the natural resources of the Mamouwol River in the Mamou *** were collected using a survey method(questionnaire,interviews and observations).The study revealed that extensive agro-pastoral activities are the main socio-economic activity of the population,accounting for 78.5%-90%and 20.30%*** follows(1.2%).Related activities include handicrafts and petty trade;Other human activities:hunting(11%),charcoal burning(58%),brick making and firing(45.6%).Riverbanks and water resources in the vicinity of dwellings are damaged and polluted by socio-economic activities and the use of agricultural *** absence of industrial units on the path for the data collection.

关键词： Natural resources human activity degradation Mamouwol River Mamou.

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

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：