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Search Results: 1 - 10 of 358973 matches for " D. N. Faka "
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Establishment of IDF-curves for precipitation in the tropical area of Central Africa - comparison of techniques and results
B. Mohymont,G. R. Demarée,D. N. Faka
Natural Hazards and Earth System Sciences (NHESS) & Discussions (NHESSD) , 2004,
Abstract: The establishment of Intensity-Duration-Frequency (IDF) curves for precipitation remains a powerful tool in the risk analysis of natural hazards. Indeed the IDF-curves allow for the estimation of the return period of an observed rainfall event or conversely of the rainfall amount corresponding to a given return period for different aggregation times. There is a high need for IDF-curves in the tropical region of Central Africa but unfortunately the adequate long-term data sets are frequently not available. The present paper assesses IDF-curves for precipitation for three stations in Central Africa. More physically based models for the IDF-curves are proposed. The methodology used here has been advanced by Koutsoyiannis et al. (1998) and an inter-station and inter-technique comparison is being carried out. The IDF-curves for tropical Central Africa are an interesting tool to be used in sewer system design to combat the frequently occurring inundations in semi-urbanized and urbanized areas of the Kinshasa megapolis.
Assessment of the Direct Sun-Light on Rural Road Network through Solar Radiation Analysis Using GIS  [PDF]
Christos Chalkias, Antigoni Faka, Kleomenis Kalogeropoulos
Open Journal of Applied Sciences (OJAppS) , 2013, DOI: 10.4236/ojapps.2013.32030
Abstract:
The movement of vehicles on the roads, during summer, can sometimes hide risks involved in direct sunlight. In places where the relief is complicated, road network usually consists of a road complexity. This complexity in conjunction with the motion of a vehicle on a road and the position of the sun at the same time may result in the loss of vision in some sections of the road. This paper describes a GIS-based methodology of the spatiotemporal analysis of this phenomenon. Thus, for a given study area, in this case ofMilos Island,Greece, the geometry of the road network, the terrain morphology and the solar radiation (in specific time intervals during summer) have been analyzed. The result of this procedure is a map illustrating the sections of the road where direct sunlight includes a serious amount of risk for the drivers. Applying this methodology for long periods of time may lead to prevention policies adoption related to accidents of direct exposure to sunlight. Moreover, this methodology could be an additional module in car navigation systems.
Between the Barrio and the City: Pathways of Work among Scavenging Families  [PDF]
Débora Gorbán
Open Journal of Social Sciences (JSS) , 2014, DOI: 10.4236/jss.2014.24024
Abstract: In this article, I will reconstruct, through brief stories, some of the traits that characterize the way of life of families in the El Salvador neighborhood, in Buenos Aires, Argentina, go scavenging everyday in Buenos Aires city. These stories will not only tell us who they are and how they arrived at the El Salvador neighborhood, from where, and in what manner they began to salir con la carreta, but will also permit us to move closer to the day-to-day existence of these families in relationship to their life in the barrio and the activities they engage in, thereby giving us a fuller understanding of family dynamics. In the research that originated this paper, I followed an ethnographical perspective to study and analyze the way of life of those families living from the recyclable waste they recollect in Buenos Aires city.
Dirichlet Averages, Fractional Integral Operators and Solution of Euler-Darboux Equation on Hölder Spaces  [PDF]
D. N. Vyas
Applied Mathematics (AM) , 2016, DOI: 10.4236/am.2016.714129
Abstract: In the present paper, we discuss the solution of Euler-Darboux equation in terms of Dirichlet averages of boundary conditions on H?lder space and weighted H?lder spaces of continuous functions using Riemann-Liouville fractional integral operators. Moreover, the results are interpreted in alternative form.
Third Order Current Mode Universal Filter Using Only Op.amp. and OTAs  [PDF]
G. N. Shinde, D. D. Mulajkar
Circuits and Systems (CS) , 2010, DOI: 10.4236/cs.2010.12011
Abstract: A novel current mode active-only universal filter using four dual current output Operational Transconductance Amplifiers (OTAs) and three Operational Amplifiers (OAs) is presented. The circuit can realize low pass and high pass filter characteristics by choosing the suitable current output branches. The filter performance factors natural frequency (ω0), bandwidth , quality factor Q and transconductance gain gm are electronically tunable. The proposed circuit has very low sensitivities with respect to circuit active elements. From sensitivity analysis, it has been clearly shown that the proposed circuit has very low sensitivities with respect to the circuit active elements. The gain roll-off of high pass and low pass configuration is 18 dB/oc- tave. The proposed circuit facilitates integrability, programmability and ease of implementation.
Effects of LiF on the Structure and Electrical Properties of (Na0.52K0.435Li0.045)Nb0.87Sb0.08Ta0.05O3 Lead-Free Piezoelectric Ceramics Sintered at Low Temperatures  [PDF]
P. D. Gio, N. D. Phong
Journal of Materials Science and Chemical Engineering (MSCE) , 2015, DOI: 10.4236/msce.2015.311003
Abstract: The (Na0.52K0.435 Li0.045)Nb0.87Sb0.08Ta0.05O3 (KNNLST) + x wt% LiF piezoelectric ceramics, where x = 0, 2, 4, and 6, have been fabricated successfully by the conventional solid-state reaction method. The effect of LiF on the sintering temperature, the structure and electrical properties of KNNLST ceramics was systematically studied. The LiF addition significantly reduced the sintering temperature of the ceramics from 1100℃ to 930℃. Experimental results showed that with the doping of LiF, all the ceramic samples could be well sintered and exhibit a dense, pure perovskite structure. With increasing LiF content, the tetragonal-orthorhombic transition point (TO-T) and the Curie temperature (Tc) of the ceramics shifted to the lower and higher temperatures, respectively. The specimens containing 4 wt% LiF sintered at 930℃ showed the good electrical properties: the density of 4.26 g/cm3; the electromechanical coupling factor, kp = 0.27 and kt = 0.40; the dielectric constant, ε = 744; the piezoelectric constant (d31) of 41 pC/N.
Characterization of the Organic Matter in the Formations with Juniperus phoenicea, and Pinus halepensis in the Matorrals of the Mostaganémois Littoral  [PDF]
N. Lahouel, N. Benabadji, D. Benmansour
Open Journal of Ecology (OJE) , 2014, DOI: 10.4236/oje.2014.45024
Abstract:


In the present work, we were able to verify the utility of splitting the organic matter that seems to be indispensable, especially when it comes to the soil humus which is very little polymerized and containing a large proportion of non-decomposed organic matter. This study even if it remains unfinished, it provides some useful information. Moreover, this work reflects the fundamental influence exerted by the organic matter as a soil and as a driving force of its dynamics. Humus factor in the vocation of a soil can promote or remove some plant species. The statistic analysis shows that the humification of the organic matter is faster on calcareous sandstone substrate (Calabrien) as on Tithonique Substrate with advanced cretaceous which can be explained by the very high rate of humic acids as the calcareous sandstone substrate. At the level of plant development, the organic matter provided by the mixed stands (Eucalyptus, Pinus halepensis, Juniperus phoenicea) with an undergrowth which is formed by (Retama monosperma,calycotome spinosa,Pistachia lentiscus, Phylaria latifolia, Lavandula stoecka) has a very god humification with a predominance of humic acids that indicate the acceleration of the development of clay-humic complexes and a permanent wealth of energy reserves.



Analytical Signal and Reduction to Pole Interpretation of Total Magnetic Field Data at Eppawala Phosphate Deposit  [PDF]
N. D. Subasinghe, W. K. D. G. D. R. Charles, S. N. De Silva
Journal of Geoscience and Environment Protection (GEP) , 2014, DOI: 10.4236/gep.2014.23023
Abstract:

A magnetic survey was carried out to find out the possibilities of demarcating a phosphate deposit from the surrounding country rocks. It is a well-established fact that the magnetic mapping can be utilised to investigate the subsurface objects, materials or different rock types based on their magnetic properties. Those rocks with ferro-magnetic minerals such as magnetite generate magnetic anomalies which in turn help to investigate the subsurface occurrence of mineral deposits. An economic phosphate deposit in Sri Lanka, known as Eppawala Phosphate deposit was selected for this study. The deposit was formed as an accumulation of secondary products of an apatite-rich carbonatite. Due to weathering of iron-rich carbonatite, magnetite and its derivatives are intimately bound with the said deposit. Therefore, the magnetic signature of the phosphate body is different to that of the surrounding country rocks. Despite some studies on different aspects of the deposit, subsurface extents of the ore body are so far not adequately studied. Therefore, this study was conducted to identify the boundaries of the phosphate body. The study was carried over an area of 12 km2 5 km north from the current mining site and survey was conducted. GSM-19 Overhouser system with integrated GPS was used to collect field data. Magnetic anomalies were plotted using a predefined grid. The maximum positive and negative anomalies encountered in the survey area are 690 nT and 829 nT respectively. This study showed that magnetite is not distributed evenly in the area and the deposit extended along the north south direction. Further, processing of analytical signal using the anomalies showed that the carbonatite occurs as a continuous body trending in North South direction. Low magnetic latitudes magnetic data interpretation is difficult because the vector nature of the magnetic field. Therefore, “reduction to pole” concept and “analytical signal concept” were used for the data analysis. Reduction to pole map and analytical signal map are comparatively similar and the change of declination value has no significant effect on the map of reduction to pole.

Paediatric gallstones and laparoscopic cholecystectomy  [PDF]
D. G. Samuel, N. N. Naguib, A. Y. Izzidien
Health (Health) , 2010, DOI: 10.4236/health.2010.21011
Abstract: Introduction: Gall stones disease is a rare oc-currence in paediatric patients and the diagno-sis is often overlooked. Patients often present with non-specific symptoms of abdominal pain and the classic features of gallstones are some-times absent [1]. The aim of our study is to in-crease the awareness of cholecystitis and acute pancreatitis being a possible occurrence in the paediatric age group and should therefore be in the differential diagnosis of acute abdominal pain in children. We undertook a retrospective analy- sis of all the paediatric patients recorded as hav- ing had a laparoscopic Cholecystectomy per-formed at Prince Charles Hospital. 8 paediatric patients underwent Laparoscopic cholecysteco- my between 2000 and 2008 consisting of 5 fe-male patients and 3 male patients. The average age of the cohort was 14.1 years [12-16]. Pre- morbid obesity was a feature in 4 patients and all patients reported high fat diet. Abdominal Ul- trasound used to assess all 8 patients who pre- sented with acute abdomen showed gallstones to be present in all. 7 patients underwent an ele- ctive procedure 3-6 months after the initial di-agnosis was made and 1 patient had laparosco- pic Cholecystectomy within 72 hours of initial presentation. 1 patient was found to have an in- herited haematological disorder and 2 of the pa- tients were sisters with a family history of gall- stone disease. 2 patients presented with acute pancreatitis. Gallstone related cholecystitis is a rare occurrence amongst paediatric patients and is often overlooked as a differential diagnosis. We report 8 patients over an 8 year period. Con- clusion: It is important that clinicians include cholecystitis and biliary colic in the differential diagnosis of patients presenting with acute ab-domen in childhood not explained by other di-agnoses. Laparoscopic Cholecystectomy is the treatment of choice and has minimal complica-tions.
The New Data on Stratigraphy of the Riphean Stratotype in the Southern Urals, Russia  [PDF]
V. N. Puchkov, A. A. Krasnobaev, N. D. Sergeeva
Journal of Geoscience and Environment Protection (GEP) , 2014, DOI: 10.4236/gep.2014.23015
Abstract:

A recent series of U-Pb age determinations of zircons (SHRIMP, IDTIMS) from volcanic flows of several levels permitted to refine stratigraphy of the Riphean of Bashkirian megaanticlinorium (Urals, Russia), and provide a better correlation of this straton with the International and Chinese scales of the Proterozoic.

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