Zeta Potential of Aggregate and Dynamic Modulus of HMA Estimation Using Aggregate Silica Content

The mineralogical composition of an aggregate influences its adhesion with bitumen and therefore its dynamic modulus. However, few studies have been conducted on this aspect. One of the most used properties to describe the impact of aggregate on the adhesiveness phenomena is the zeta potential. In this study, the first mineralogical and chemical properties were considered through the percentage of silica in the rock source of aggregates and the electric aggregate particles charge zeta. Dynamic modulus values used for regression process are determined from complex modulus test on nine asphalt concretes mix designed with aggregate types (basalt of Diack, quartzite of Bakel and Limestone of Bandia). The results showed that aggregate with high percentage of silica have higher zeta potential than aggregate with low percentage of silica. The development of a zeta potential predictive model showed a strong sensitivity to silica. The results of the complex modulus tests showed that Hot Mixture Asphalt (HMA) mixed with aggregate containing high silica contents gave better results than those mixed with aggregates containing low percentage of silica. The dynamic modulus predictive models of HMA developed shows that it is the properties of bitumen that influence more. However, the effect of silica although low, is very marked at low temperatures and high frequencies.

Impact of Non-Compliance of Exposure Classes in Reinforced Concrete Structures

From the National Agency for the Organization and Construction of Infrastructures (ANOCI) program to the Emerging Senegal Plan (PSE), construction in Senegal has improved considerably. However, deficiencies remain in the specification of materials used mainly in hydraulic concrete. They are generally related to the specification of aggregates for alkali reactivity and the choice of exposure classes specified in NF EN 206-1. The purpose of this article is to study the incidence of non-compliance with exposure classes in reinforced concrete structures. To carry out this study, surveys were carried out at several sites (districts) in Dakar (Cité Avion, Touba Ouakam, Cité Asecna, Cité Batrain, Cité Comico, Cité Assemblée and Terme Sud) in order to collect information on the formulation and implementation methods used. The comparison of the various readings carried out made it possible to deduce conclusions and to give recommendations when using standard NF EN 206-1.

Flood Forecasting and Warning System: A Survey of Models and Their Applications in West Africa

Flood events occurrences and frequencies in the world are of immense worry for the stability of the economy and life safety. Africa continent is the third continent the most negatively affected by the flood events after Asia and Europe. Eastern Africa is the most hit in Africa. However, Africa continent is at the early stage in term of flood forecasting models development and implementation. Very few hydrological models for flood forecasting are available and implemented in Africa for the flood mitigation. And for the majority of the cases, they need to be improved because of the time evolution. Flash flood in Bamako (Mali) has been putting both human life and the economy in jeopardy. Studying this phenomenon, as to propose applicable solutions for its alleviation in Bamako is a great concern. Therefore, it is of upmost importance to know the existing scientific works related to this situation in Mali and elsewhere. The main aim was to point out the various solutions implemented by various local and international institutions, in order to fight against the flood events. Two types of methods are used for the flood events adaptation: the structural and non-structural methods. The structural methods are essentially based on the implementation of the structures like the dams, dykes, levees, etc. The problem of these methods is that they may reduce the volume of water that will inundate the area but are not efficient for the prediction of the coming floods and cannot alert the population with any lead time in advance. The non-structural methods are the one allowing to perform the prediction with acceptable lead time. They used the hydrological rainfall-runoff models and are the widely methods used for the flood adaptation. This review is more accentuated on the various types non-structural methods and their application in African countries in general and West African countries in particular with their strengths and weaknesses. Hydrologiska Byråns Vattenbalansavdelning (HBV), Hydrologic Engineer Center Hydrologic Model System (HEC-HMS) and Soil and Water Assessment Tool (SWAT) are the hydrological models that are the most widely used in West Africa for the purpose of flood forecasting. The easily way of calibration and the weak number of input data make these models appropriate for the West Africa region where the data are scarce and often with bad quality. These models when implemented and applied, can predict the coming floods, allow the population to adapt and mitigate the flood events and reduce considerably the impacts of floods especially in terms of loss of life.

Exploring willingness-to-pay for the restoration and maintenance of reserved forests in the Greater Accra Region of Ghana

In recent years, debates on the alarming rate of forest depletion emanating from growth in urban settlement and changed urban land-use patterns have gained prominence across the globe. The present study adopts a demandside management approach to investigate household’s willingness-to-pay for the restoration and maintenance of protected forest reserves in three municipalities in Ghana. Using survey data of 733 households from the Greater Accra Region of Ghana, we model the demand for forest restoration and maintenance, respectively, by means of the contingent valuation technique. As part of the findings, the study shows evidence that a household is willing to pay Gh￠50.99($8.67) and Gh￠31.12($5.29) per annum to restore and maintain the protected forests,respectively. These amounts constitute less than one percent of the average household income per month.Consequently, critical validity tests are conducted to validate the robustness of the results. This study provides willingness-to-pay estimates for forest and forest resources, and its associated determinants. These estimates seek to bridge the information gap and inform policy decisions toward the overarching aim of ensuring sustainable forest management in Ghana.

Performance Evaluation of New Two Axes Tracking PV-Thermal Concentrator

The overall problem with PV （photovoltaic） systems is the high cost for the photovoltaic modules. This makes it interesting to concentrate irradiation on the PV-module, thereby reducing the PV area necessary for obtaining the same amount of output power. The tracking capability of two-axes tracking unit driving a new concentrating paraboloid for electric and heat production have been evaluated. The reflecting optics consisting of flat mirrors provides uniform illumination on the absorber which is a good indication for optimised electrical production due to series connection of solar cells. The calculated optical efficiency of the system indicates that about 80% of the incident beam radiation is transferred to the absorber. Simulations of generated electrical and thermal energy from the evaluated photovoltaic thermal （PV/T） collector show the potential of obtaining high total energy efficiency.

温室微气候环境与蒸散发模拟技术综述

通过温室作物生产,人工驯化植物已经彻底改变了世界各地的农业耕作制度。选择合适的温室技术和用户友好的蒸散量(ETc)模型可以优化作物水分利用。温室微气候环境具有近零风速和低辐射等特点,由于温室内高温和高湿,蒸腾作用较低。将温室微气候与适当的ETc模型相匹配可以优化作物水分利用效率,这是弥合各种先进ETc模型的应用与温室作物生产者之间距离的原因之一。更实用的温室ETc模型将会在更大的温室作物生产者群体中迅速传播,而ETc估算技术进步的可能性也将增加。温室系统对增加和实现粮食可持续生产的贡献必须通过改进现有温室管理模式来实现。粮农组织建议使用参考蒸散量(ET0)和作物系数(Kc)值的乘积来确定作物需水量的标准方法。该方法也可用于温室栽培系统,然而,关于温室条件下ET0或ETc测量方法研究还相当有限。在不同类型温室条件下,比较ET0或ETc模型性能的研究也很少。该综述强调了温室环境控制技术与ET0或ETc模型之间的联系,以及ET0或ETc测量中,现有知识和方法如何实际提高温室农业的可持续性。该综述旨在评估和总结目前可用的ET0或ETc估算模型,以及在各种类型温室中使用的ET0或ETc模型的准确性与适用性。

Irradiation Analysis for Maputo

In the present paper was investigated the influence of the surface geometry on the amount of solar radiation arriving on that surface. The total, beam and diffuse radiation incident onto a surface was simulated using WINSUN software, which is a simulation tool developed at Lund Technical University, Sweden. The irradiation analysis are made for Maputo, latitude 25°58＇ South, longitude 32°36＇ East, Mozambique. The climate date was derived from Meteonorm files. Such study has practical value since the output of solar systems is depending upon the amount of solar radiation reaching to the surface of the collector.

Unravelling the drivers of technological innovations in the Czech Republic: Do international technological linkages matter?

This study aims to investigate the main factors driving technological innovation within firms in the manufacturing and service sectors of the Czech Republic.We apply a binary logistic regression model to cross-sectional data from 502 firms,obtained from the World Bank Enterprise Survey.The results of our empirical investigation show that certain elements of the business environment,such as the tax rate,serve as significant obstacles to firms’product innovations.The results also confirm that international technological linkagesdmeasured by international quality certificates and foreign technology licensesdaffect technological innovations.Moreover,we found that internal R&D activities positively impact technological innovation across all sectors;contrarily,we found that process innovation in the manufacturing sector is positively influenced by foreign technology licenses and business association membership.Process innovations in the service sector are positively correlated with external R&D and financing from banking institutions.Finally,business association membership does not positively influence technological innovation in the service sector.Our findings have salient implications for firm managers,policymakers,and scholars aiming to explore and improve innovation outcomes in transitional economies.

Overview of modelling techniques for greenhouse microclimate environment and evapotranspiration

Domestication of plants by man through greenhouse crop production has revolutionized agricultural farming systems worldwide.Selecting the appropriate greenhouse technology together with the user-friendly evapotranspiration(ETc)model can optimize crop water use.The greenhouse microclimate environment has nearly zero wind speed and low radiation,hence low transpiration due to high temperature and humidity.Therefore,matching the greenhouse microclimate with the appropriate ETc model will certainly optimize crop water use efficiency since water is becoming a scarce resource globally,more so in the greenhouse environment.This is one of the main reasons why the gap between the dissemination of various advanced ETc models and the application by the greenhouse crop producers’community needs to be bridged.The likelihood or chances of rapidly disseminating and adopting advances in ETc estimating technology by a larger greenhouse crop producers community will increase if greenhouse ETc models become more user-friendly and available.The contribution of the greenhouse system to increased and sustainable food production must come through improved disseminating,adopting and use of existing greenhouse ETc models.FAO recommends a standard approach for the determination of crop water requirements utilizing the product of reference evapotranspiration(ET0)and crop coefficient(Kc)values.The FAO approach can also be used in greenhouse cultivation systems.However,studies connecting greenhouse technologies and methodologies for measuring ET0 or ETc in greenhouses are not available.There are also few studies undertaken that compared the performance of ET0 or ETc models under different categories of greenhouse conditions.In this review,a link between greenhouse technology and ET0 model or ETc model,and how existing knowledge and methodologies in ET0 or ETc measurements can actually enhance the sustainability of greenhouse farming have been highlighted.The categories of greenhouses,equipment commonly used,and the data collected for ET0 and ETc measurements have been established in the article.This review aimed to evaluate and summarize ET0 and ETc models currently available and being used in the various greenhouse categories.The accuracy assessment levels of the ET0 models about the category of the greenhouse microclimate environment were carried out.