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Search Results: 1 - 10 of 119377 matches for " Ron T. Chaoka "
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Regionalization of Rainfall Intensity-Duration-Frequency (IDF) Curves in Botswana  [PDF]
Berhanu F. Alemaw, Ron T. Chaoka
Journal of Water Resource and Protection (JWARP) , 2016, DOI: 10.4236/jwarp.2016.812088
Abstract: A regional analysis of design storms, defined as the expected rainfall intensity for given storm duration and return period, is conducted to determine storm Rainfall Intensity-Duration-Frequency (IDF) relationships. The ultimate purpose was to determine IDF curves for homogeneous regions identified in Botswana. Three homogeneous regions were identified based on topographic and rainfall characteristics which were constructed with the K-Means Clustering algorithm. Using the mean annual rainfall and the 24 hr annual maximum rainfall as an indicator of rainfall intensity for each homogeneous region, IDF curves and maps of rainfall intensities of 1 to 24 hr and above durations were produced. The Gamma and Lognormal probability distribution functions were able to provide estimates of rainfall depths for low and medium return periods (up to 100 years) in any location in each homogeneous region of Botswana.
Regional Design Storm and Flood Modelling—Risk Implications in Ungauged Catchments  [PDF]
Berhanu F. Alemaw, Ron T. Chaoka
Journal of Water Resource and Protection (JWARP) , 2016, DOI: 10.4236/jwarp.2016.813093
Abstract: Most planned developments in a catchment for control of excess water using a culvert, bridge or dam spillway are located at a site in a stream where there are no discharge measurements. Even though, for gauged catchments a number of established flood frequency models and rainfall-runoff models do exist, for ungauged catchments mostly regional flood frequency and event-based rainfall-runoff models are used, which depend on regional parameters. In this paper, a regional approach for design floods is presented and risk implication for design of drainage structures assessed. A case study in light of the above has been considered at four ungauged sites in the Limpopo Drainage Basin in north-eastern Botswana.
Investigating the causes of water-well failure in the Gaotlhobogwe wellfield in southeast Botswana
Ron T Chaoka, Berhanu F Alemaw, Loago Molwalelfhe, Oteng M Moreomongwe
Journal of Applied Sciences and Environmental Management , 2006,
Abstract: In the management of groundwater resources, identifying determinants of borehole failure is useful in planning borehole and wellfield remedial measures as well identifying appropriate water treatment mechanisms if deteriorating water quality prevails as a result of decline of borehole yield and water level. A continually declining well yield in the Gaotlhobogwe wellfield, in south eastern Botswana, triggered this investigation. The determinants of groundwater level decline, which reaches about 80% in the wellfield were identified and their contribution assessed through multivariate analysis. Even though there is a 50% of decline in the specific capacity of pumping wells within 8 years period from 1995- 2003, another 30% of the decline was found to be attributed to chemical determinants, namely as Mn, Mg, Fe NO3, HCO3, CO3 and SO4. The potential physical determinants are found to be pH, Ec and TDS. The geological and hydro-geological evidence of the possible causes of groundwater decline and the identified determinants is discussed in relation to borehole construction and completion guidelines for contractors and drillers. Journal of Applied Sciences and Environmental Management Vol. 10 (3) 2006: 59-65
Management of Water Supply Reservoirs under Uncertainties in Arid and Urbanized Environments  [PDF]
B. F. Alemaw, E. O. Keaitse, T. R. Chaoka
Journal of Water Resource and Protection (JWARP) , 2016, DOI: 10.4236/jwarp.2016.811080
Abstract: Simulation and evaluation study of the three Water Supply Reservoirs in the Notwane Catchment was undertaken using a hybrid modelling approach linking the reservoir simulation model (HEC-ResSim) model and a reservoir reliability analysis (RRA) model. It was used to understand the management challenges and operation aspects facing the recent failure and declining water supply from three reservoirs in Gaborone and the surrounding areas, a typical arid and urbanized environment where current and future water supply reliability is challenged by both climate and anthropologic factors. The model was analysed for a calibration period of ten years (1993-2002), and verification period of eight years (2003-2010) and then simulation period of 40 years (2011-2050). The simulation period up to the year 2050 was considered to include the year 2035, which is the planning horizon of the National Water Master Plan. The model calibration and verification results are satisfactorily accepted for the fit of the daily water levels. The values of R2 and the Nash-Sutcliffe model efficiency criteria for the calibration period, are 0.81/60%, 0.62/27% and 0.54/39% for the Bokaa dam, Gaborone dam and Nnywane dam, respectively. Various scenarios were considered to determine the plausible sources of uncertainty and challenge for operation and management of the water supply reservoirs considering: population and urbanization, sedimentation, seepage, climate change, operational aspects, among others. From the RRA model, it was found that Gaborone dam, which is the largest of the three dams has lower resilience, lower reliability and higher vulnerability associated with increasing population pressures, urbanisation and climatic factors. Climate change, sedimentation, seepage, operational rules, contributing to the operation and management of the dams could have accelerated the drying up of the reservoirs and the prevailing water supply situation, which might continue to be the future possible challenges of water supply in the area.
The 1950-1998 warm ENSO events and regional implications to river flow variability in Southern Africa
BF Alemaw, TR Chaoka
Water SA , 2006,
Abstract: The variability of annual river runoff and its possible association with the 1950-1998 seasonal El Ni o/Southern Oscillation (ENSO) is investigated in 502 rivers gauged in 9 countries of the Southern African region. We found some evidence of possible links between available surface water resources in terms of mean annual runoff and warm ENSO events. This was revealed by the existence of strong and nearly-strong positive linear correlation between annual discharges and the warm seasonal ENSO indices explained by the sea level pressure (SLP) data. Of the 502 rivers we considered, 150 rivers exhibit strong positive correlation between the December to February quarter ENSO indices and the annual runoff – with 25% of the variance in annual runoff being accounted for by the warm ENSO events. A relatively weaker positive correlation also occurred in 174 rivers we considered. The strong positive correlation occurs in parts of Zambia, Namibia, Mozambique and the lowveld in South Africa. In these parts of Southern Africa, there is evidence of a general decline in annual runoff after the mid-1970s compared to the period before it. These revelations are explored and are found to be partly explained by the high frequency of drought-related warm ENSO phenomena that occurred during the same period. Water SA Vol.32 (4) 2006: pp.459-463
Balancing Robustness against the Dangers of Multiple Attractors in a Hopfield-Type Model of Biological Attractors
Ron C. Anafi,Jason H. T. Bates
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0014413
Abstract: Many chronic human diseases are of unclear origin, and persist long beyond any known insult or instigating factor. These diseases may represent a structurally normal biologic network that has become trapped within the basin of an abnormal attractor.
Unimodal primary sensory cortices are directly connected by long-range horizontal projections in the rat sensory cortex
Jimmy Stehberg,Phat T. Dang,Ron Frostig
Frontiers in Neuroanatomy , 2014, DOI: 10.3389/fnana.2014.00093
Abstract: Research based on functional imaging and neuronal recordings in the barrel cortex subdivision of primary somatosensory cortex (SI) of the adult rat has revealed novel aspects of structure-function relationships in this cortex. Specifically, it has demonstrated that single whisker stimulation evokes subthreshold neuronal activity that spreads symmetrically within gray matter from the appropriate barrel area, crosses cytoarchitectural borders of SI and reaches deeply into other unimodal primary cortices such as primary auditory (AI) and primary visual (VI). It was further demonstrated that this spread is supported by a spatially matching underlying diffuse network of border-crossing, long-range projections that could also reach deeply into AI and VI. Here we seek to determine whether such a network of border-crossing, long-range projections is unique to barrel cortex or characterizes also other primary, unimodal sensory cortices and therefore could directly connect them. Using anterograde (BDA) and retrograde (CTb) tract-tracing techniques, we demonstrate that such diffuse horizontal networks directly and mutually connect VI, AI and SI. These findings suggest that diffuse, border-crossing axonal projections connecting directly primary cortices are an important organizational motif common to all major primary sensory cortices in the rat. Potential implications of these findings for topics including cortical structure-function relationships, multisensory integration, functional imaging and cortical parcellation are discussed.
A Numerical Study of Radial Basis Function Based Methods for Options Pricing under the One Dimension Jump-diffusion Model
Ron T. L. Chan,Simon Hubbert
Computer Science , 2010,
Abstract: The aim of this chapter is to show how option prices in jump-diffusion models can be computed using meshless methods based on Radial Basis Function (RBF) interpolation. The RBF technique is demonstrated by solving the partial integro-differential equation (PIDE) in one-dimension for the American put and the European vanilla call/put options on dividend-paying stocks in the Merton and Kou jump-diffusion models. The radial basis function we select is the Cubic Spline. We also propose a simple numerical algorithm for finding a finite computational range of an improper integral term in the PIDE so that the accuracy of approximation of the integral can be improved. Moreover, the solution functions of the PIDE are approximated explicitly by RBFs which have exact forms so we can easily compute the global integral by any kind of numerical quadrature. Finally, we will not only show numerically that our scheme is second order accurate in both spatial and time variables in a European case but also second order accurate in spatial variables and first order accurate in time variables in an American case.
From “Employer-Employee” to “Family of Choice”: The Development of the Relationship between Philippine Worker Immigrants and Elderly Care Recipients  [PDF]
Pnina Ron
Advances in Aging Research (AAR) , 2015, DOI: 10.4236/aar.2015.42007
Abstract: The current study adds to the pool of findings regarding experiences of female Philippine work immigrants employed in elderly caregiving in Israel, as they cope with their role as caregivers. Based on an analysis of the qualitative interviews with 27 Philippine women, three themes emerged. The first is the manner in which these caregivers perceive the treatment and care they give their elderly employers, taking into account the initial stage of the professional relationship, the various types of support, and the employer-employee interactions. The second theme deals with the manner in which these caregivers perceive their role once the relationship with the elderly care recipient is established and the employer’s needs and preferences become familiar; that is, once there is a clear caregiver-client relationship. The third theme deals with the manner in which the caregivers perceive their relationship with their elderly employers and with the employers’ family members, and the way they believe their employer and family perceive their role as caregivers. This stage of the relationship they define as “family of choice”. The combination of the three themes presents a comprehensive picture of positive change in terms of the caregivers perception of their role, and a shift in the manner in which they perceive their employers: from a “source of income” to “parent”.
The Relationship between Attachment Styles in Adulthood and Attitudes towards Filial Responsibility: A Comparison between Three Generations of Arabs and Jewish Women  [PDF]
Pnina Ron
Psychology (PSYCH) , 2016, DOI: 10.4236/psych.2016.76077

Background: Care giving for an elderly parent is a universal developmental task, and in all societies is one of the women tasks; its expectations are considered norms known as filial responsibility. The aim of the study is to examine the possibility of connections between the attitudes toward filial responsibility to elderly parents and the attachment style in adulthood and age (generation) among women. Methods: The research participants were 63 Jewish and Arab university students, their mothers (N = 62) and their grandmothers (N = 63). Research instruments consisted of a self- report questionnaire, which revealed background characteristics, and measured attitudes toward filial responsibility, style of adult attachment; self-esteem; sense of mastery and, family support. Results revealed ethnicity differences as well as between-generations differences regarding normative attitudes toward filial responsibility, which may indicate a changing taking place in the Arab society’s approach concerning these attitudes. An additional finding brought to light the cross-generational differences in the relationship between the attachment style in adulthood and the attitudes regarding filial responsibility. Conclusion: It seems that in attitudes towards filial responsibility, Arab society is still traditional in terms of its approach to the institutions of clan and family mostly among the elderly Arab Muslims. All of the modern changes most likely have an effect on adults’ sense of filial responsibility, on social norms, and on familial traditions.

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