GIS and Hydrological Model Based Hydropower Potential Assessments of Temcha Watershed

Hydropower is one of the major and sustainable energy production centers across the world.  Energy production has several challenges and uncertainty to alleviate poverty in our country.  The main aim of this study was selecteding the hydropower potentials of Temcha watershed with integrated approaches of using GIS and hydrological models (SWAT).  For the hydropower potential selection, it was used weather (metrological), hydrological and geospatial data.  The result shows that a high discharge amount with a corresponding head has been identified in the upper course of the river and its associated values 300m3/year.  In the middle course of the river, the power potential would be 126 MWmw/year.  Generally, the overall hydropower potentials of Temcha watershed were 2500 MWmw/year. Keywords :- hydropower, SWAT , GIS, Temcha watershed DOI: 10.7176/JETP/10-5-02 Publication date:September 30th 202

Hydro-Metrological Drought Assessments along the Blue Nile River Basin in East Gojjam Zone

The Upper Blue Nile basin is less-explored in drought studies as compared to other river basins in Ethiopia and a shortage of particular basin drought monitoring system. The area founds in along a Blue Nile basin faced a recurrent drought conditions in several years ago. The main objectives of this study to investigate droughts along a Blue Nile basin in the east Gojjam zone. To evaluate the drought duration, severity, occurrence and risks it was used different indices. The results shows a hydrological drought was occurring in a frequent condition in partial areas of Shebel Berenta, Goncha siso enese and Enarg enawuga woreda.  Based on 12-month time-scale, the total number of drought events were identified in the area, using Reconnaissance drought index (RDI) during the period of analysis (1995–1996) and its values 100% drought and its ranges were highly sever. Considering the drought events in the stream flow drought index (SDI) the values indicates drought severity was existed in the year 1984/1985 and 1989/1990. Inaddation standard precipitation index (SPI) also indicates a severe drought in 1984/1985, 1990/1991 and 1991/1992 and its values was -1.5. Generally the hydrological, metrological and agricultural drought where existed in the year (1984-2012) within the study area. Keywords: RDI, Drought, SDI, SPI, NDVI DOI: 10.7176/CER/12-9-04 Publication date:September 30th 202

Estimation of standard molar entropy of cement hydrates and clinker minerals

It is not straightforward to experimentally measure the standard molar entropy of cement hydrates or clinker minerals. This is further compounded by the controversies surrounding the entropy values reported in established thermodynamic datasets for cements. The purpose of this study is to assess the reliability of standard entropies compiled in those datasets. To this end, a simple but robust method is used in which the standard entropy of an inorganic solid is correlated to its formula unit volume via a linear equation. The results of this analysis show that the standard entropies and/or molar volumes (and in cases solubility products) of the following phases deserve closer scrutiny: meta-ettringite phases; magnesium/aluminium layered double hydroxide solid solutions; almost all iron-bearing monosulfate and hydrogarnet phases; and several calcium silicate hydrate solid solution end-members. In addition, this study reports the provisional estimates for the standard entropies of minerals ternesite and ye'elimite

Cytotoxic stilbenes and canthinone alkaloids from Brucea antidysenterica (Simaroubaceae)

Phytochemical study of the root and bark of Brucea antidysenterica J. F. Mill. (Simaroubaceae) afforded three new compounds including a stilbene glycoside bruceanoside A (1), and two canthinone alkaloids bruceacanthinones A (3) and B (4), as well as ten known secondary metabolites, rhaponticin (2), 1,11-dimethoxycanthin-6-one (5), canthin-6-one (6), 1-methoxycanthin-6-one (7), 2-methoxycanthin-6-one (8), 2-hydroxy-1,11-dimethoxycanthin-6-one (9), β-carboline-1-propionic acid (10), cleomiscosin C (11), cleomiscosin A (12) and hydnocarpin (13). The structures of all the compounds were determined using spectrometric and spectroscopic methods including 1D and 2D NMR, and HRSEIMS. The identity of the known compounds was further confirmed by comparison of their data with those reported in the literature. The root and bark methanolic extracts, the dichloromethane and ethyl acetate soluble fractions, as well as the isolated compounds (3–13), were assessed for their cytotoxicity against the cancer cell lines A-549, MCF-7 and PC-3. The results suggested that compounds in the extracts might possess a synergic action in their cytotoxicity

Thermodynamic modelling of alkali-activated slag cements

This paper presents a thermodynamic modelling analysis of alkali-activated slag-based cements, which are high performance and potentially low-CO2 binders relative to Portland cement. The thermodynamic database used here contains a calcium (alkali) aluminosilicate hydrate ideal solid solution model (CNASH_ss), alkali carbonate and zeolite phases, and an ideal solid solution model for a hydrotalcite-like Mg-Al layered double hydroxide phase. Simulated phase diagrams for NaOH- and Na2SiO3-activated slag-based cements demonstrate the high stability of zeolites and other solid phases in these materials. Thermodynamic modelling provides a good description of the chemical compositions and types of phases formed in Na2SiO3-activated slag cements over the most relevant bulk chemical composition range for these cements, and the simulated volumetric properties of the cement paste are consistent with previously measured and estimated values. Experimentally determined and simulated solid phase assemblages for Na2CO3-activated slag cements were also found to be in good agreement. These results can be used to design the chemistry of alkali-activated slag-based cements, to further promote the uptake of this technology and valorisation of metallurgical slags

Gamma irradiation resistance of early age Ba(OH)₂-Na₂SO₄-slag cementitious grouts

The gamma irradiation resistance of early age Ba(OH)₂-Na₂SO₄-slag cementitious grouts, formulated for the immobilisation of sulfate bearing nuclear waste, was assessed. The observable crystalline phases were not modified upon heating (50 °C) or upon gamma irradiation up to a total dose of 2.9 MGy over 256 h, but the compressive strengths of the irradiated samples increased significantly. ²⁷Al and ²⁹Si MAS NMR spectroscopy showed that the main binding phase, a calcium aluminosilicate hydrate (C-A-S-H) type gel, had a more ordered and polymerised structure upon heating and irradiation compared to that identified in reference samples. This is associated with a higher degree of reaction of the slag. Samples formulated with the waste simulant Na₂SO₄, but without Ba(OH)₂, became porous and cracked upon heating and irradiation, but still retained their compressive strength. The Ba(OH)₂-Na₂SO₄-slag grouts evaluated in this work withstand gamma irradiation without showing identifiable damage, and are thus a technically feasible solution for immobilisation of sulfate-bearing nuclear wastes

Composition-solubility-structure relationships in calcium (alkali) aluminosilicate hydrate (C-(N,K-)A-S-H)

The interplay between the solubility, structure and chemical composition of calcium (alkali) aluminosilicate hydrate (C-(N,K-)A-S-H) equilibrated at 50 °C is investigated in this paper. The tobermorite-like C-(N,K-)A-S-H products are more crystalline in the presence of alkalis, and generally have larger basal spacings at lower Ca/Si ratios. Both Na and K are incorporated into the interlayer space of the C-(N,K-)A-S-H phases, with more alkali uptake observed at higher alkali and lower Ca content. No relationship between Al and alkali uptake is identified at the Al concentrations investigated (Al/Si ≤ 0.1). More stable C-(N,K-)A-S-H is formed at higher alkali content, but this factor is only significant in some samples with Ca/Si ratios ≤1. Shorter chain lengths are formed at higher alkali and Ca content, and cross-linking between (alumino)silicate chains in the tobermorite-like structure is greatly promoted by increasing alkali and Al concentrations. The calculated solubility products do not depend greatly on the mean chain length in C-(N,K-)A-S-H at a constant Ca/(Al + Si) ratio, or the Al/Si ratio in C-(N,K-)A-S-H. These results are important for understanding the chemical stability of C-(N,K-)A-S-H, which is a key phase formed in the majority of cements and concretes used worldwide

Effect of temperature and aluminium on calcium (alumino)silicate hydrate chemistry under equilibrium conditions

There exists limited information regarding the effect of temperature on the structure and solubility of calcium aluminosilicate hydrate (C–A–S–H). Here, calcium (alumino)silicate hydrate (C–(A–)S–H) is synthesised at Ca/Si = 1, Al/Si ≤ 0.15 and equilibrated at 7–80 °C. These systems increase in phase-purity, long-range order, and degree of polymerisation of C–(A–)S–H chains at higher temperatures; the most highly polymerised, crystalline and cross-linked C–(A–)S–H product is formed at Al/Si = 0.1 and 80 °C. Solubility products for C–(A–)S–H were calculated via determination of the solid-phase compositions and measurements of the concentrations of dissolved species in contact with the solid products, and show that the solubilities of C–(A–)S–H change slightly, within the experimental uncertainty, as a function of Al/Si ratio and temperature between 7 °C and 80 °C. These results are important in the development of thermodynamic models for C–(A–)S–H to enable accurate thermodynamic modelling of cement-based materials

Solid-state nuclear magnetic resonance spectroscopy of cements

Cement is the ubiquitous material upon which modern civilisation is built, providing long-term strength, impermeability and durability for housing and infrastructure. The fundamental chemical interactions which control the structure and performance of cements have been the subject of intense research for decades, but the complex, crystallographically disordered nature of the key phases which form in hardened cements has raised difficulty in obtaining detailed information about local structure, reaction mechanisms and kinetics. Solid-state nuclear magnetic resonance (SS NMR)spectroscopy can resolve key atomic structural details within these materials and has emerged as a crucial tool in characterising cement structure and properties. This review provides a comprehensive overview of the application of multinuclear SS NMR spectroscopy to understand composition–structure–property relationships in cements. This includes anhydrous and hydrated phases in Portland cement, calcium aluminate cements, calcium sulfoaluminate cements, magnesia-based cements, alkali-activated and geopolymer cements and synthetic model systems. Advanced and multidimensional experiments probe 1 H, 13 C, 17 O, 19 F, 23 Na, 25 Mg, 27 Al, 29 Si, 31 P, 33 S, 35 Cl, 39 K and 43 Ca nuclei, to study atomic structure, phase evolution, nanostructural development, reaction mechanisms and kinetics. Thus, the mechanisms controlling the physical properties of cements can now be resolved and understood at an unprecedented and essential level of detail