Ikechukwu Okafor - Academia.edu (original) (raw)

Papers by Ikechukwu Okafor

As a result of enormous uncertainties and high cost of materials employed in the design and formu... more As a result of enormous uncertainties and high cost of materials employed in the design and formulation of drilling fluids used drilling operations in the oil and gas industry, it is important to select the most appropriate drilling materials to increase drilling efficiency, while reducing the total cost of drilling through import substitution, especially with locally available materials. In this paper, an experiment was conducted to test and investigate the suitability of Yam Peel and Groundnut Shell as loss circulation materials. The selected lost circulation material was washed, purified, dried, and crushed, thereafter the materials were characterized using the FTIR and SEM. Different mud samples were prepared using the locally sourced materials and Carboxymethyl Cellulose (CMC), tested for its rheological properties, and thereafter compared to ascertain the suitability of the mud prepared with the locally sourced lost circulation material drilling, in line with established API standard. Results obtained shows viable comparison between the locally sourced loss circulation material and its imported lost circulation material.

Journal of Social and Political Sciences, Jun 30, 2021

Acknowledged as a policy target for the government of Nigeria, healthcare provision represents an... more Acknowledged as a policy target for the government of Nigeria, healthcare provision represents an important preoccupation for the government. As with other public policies, the achievement of policy goals in Nigeria is usually encumbered by numerous factors of implementation across various sectors. In the health sector, factors such as inadequate physical infrastructure, shortage of healthcare personnel, limited medical supplies etc. have hindered the implementation of several health policies. National Health Insurance Scheme (NHIS) is one of such policies and this study examined the effects of shortage of healthcare personnel on the implementation of NHIS policy in FCT, Abuja. Specifically, the study evaluated the opinions of health workers as well as enrollees of NHIS in four purposively chosen Area Councils of the six Area Councils in FCT. This study adopted a survey research design with Rensis Likert's five-point scale questionnaire instrument administered to both categories of respondents. The data were analyzed using the Statistical Package for Social Sciences (SPSS Version 25) and the T-tested statistical tool was used to test the hypothesis. The study found out that shortage of health personnel is a major barrier to the effective implementation of NHIS in the FCT, Abuja. Consequently, the study recommends that there should be massive recruitment of qualified healthcare personnel; training and retraining of healthcare workers; and timely and adequate remuneration for the healthcare workers in FCT, Abuja.

Journal of Visualization, Feb 16, 2018

The jet-vortex interaction is observed in settings ranging from aeronautics to physiology. In aer... more The jet-vortex interaction is observed in settings ranging from aeronautics to physiology. In aeronautics, it presents as a parallel interaction of the jet exhaust and aircraft wing-tip vortex, and in the diseased state of the heart called aortic regurgitation, the interaction between blood flows is characterized by a non-parallel interaction. While there is substantial research into the mechanisms of the parallel interaction, there is comparatively limited scientific material focused on the non-parallel interaction. The objective of this study was to characterize three distinct orientations (30°, 60°and 90°) of the non-parallel jet-vortex interaction in a simplified flow loop. The ratio of the jet Reynolds number to the vortex ring Reynolds number was used to define four levels of jet strength. Flow visualization and particle image velocimetry were used to qualitatively and quantitatively describe how the flow structures interacted, and the energy dissipation rate of each condition was calculated. It was determined that as the relative jet strength increases, the vortex ring dissipates more rapidly and the energy dissipation rate increases. This information provides a basis for the understanding of a vortex ring's interaction with an impinging jet. When the angle between the jet and vortex ring flows is perpendicular, the energy dissipation rate decreased from 6.1 W at the highest jet strength to 0.3 W at the lowest jet strength, while at an angle of 30°the energy dissipation rate decreased from 51.8 to 10.3 W. This finding contradicts the expected result, which potentiates further studies of various non-parallel arrangements.

Circulation, Nov 14, 2017

Introduction: Transcatheter aortic valve replacement (TAVR) leaflet thrombosis has been increasin... more Introduction: Transcatheter aortic valve replacement (TAVR) leaflet thrombosis has been increasingly reported with raised clinical awareness. Based on published literature occurrence rates appear l...

Bulletin of the American Physical Society, Nov 24, 2013

exercise tolerance is used to delineate asymptomatic patients during the clinical diagnosis of di... more exercise tolerance is used to delineate asymptomatic patients during the clinical diagnosis of diastolic left heart failure. Examining the effects of varying heart rate on intra-ventricular filling can provide a physical understanding of the specific flow characteristics that are impacted during exercise. In this study, diastolic filling was investigated with an anatomical left ventricle (LV) physical model under normal heart rate of 70 bpm, and varying exercise conditions of 100 bpm and 120 bpm. The LV model was incorporated into a flow loop and tuned for physiological inflow rates and outflow pressures. 2D PIV measurements were conducted along 3 parallel longitudinal planes. The systemic pressure was maintained the same across all test conditions. The E/A ratio was maintained within 1.0-1.2 across all heart rates. The strength of the mitral vortex ring formed during E-wave, as well as the peak incoming jet velocity, decreased with increasing heart rate. During peak flow of the A-wave, the vortex ring propagated farther into the LV for 120 bpm as compared to 70 bpm. The results point to the heightened role of the atrial kick for optimal LV filling during exercise conditions.

Springer eBooks, 2018

Experimental measurement technologies have been critical to advancing scientific knowledge and to... more Experimental measurement technologies have been critical to advancing scientific knowledge and to the development of prosthetic heart valve devices. A myriad of innovative measurement technologies has been successfully utilized within in vivo, ex vivo, and in vitro models. Within these models, these technologies have been used to evaluate the function of native heart valves, models of heart valve disease, and prosthetic devices. These evaluations have focused on quantifying heart valve geometry, dynamics, tissue deformation, transvalvular flow, and valve and device mechanics. Knowledge gained from these studies has advanced reconstructive surgical techniques, implanted device function, and next generation devices. Understanding the application and relative advantages of these measurement technologies is important not only for scientific research but also in quantifying device function per international standards and regulatory guidance.

Journal of Cardiovascular Magnetic Resonance, Jun 26, 2015

Background: The development of clinically applicable fluid-structure interaction (FSI) models of ... more Background: The development of clinically applicable fluid-structure interaction (FSI) models of the left heart is inherently challenging when using in vivo cardiovascular magnetic resonance (CMR) data for validation, due to the lack of a well-controlled system where detailed measurements of the ventricular wall motion and flow field are available a priori. The purpose of this study was to (a) develop a clinically relevant, CMR-compatible left heart physical model; and (b) compare the left ventricular (LV) volume reconstructions and hemodynamic data obtained using CMR to laboratory-based experimental modalities. Methods: The LV was constructed from optically clear flexible silicone rubber. The geometry was based off a healthy patient's LV geometry during peak systole. The LV phantom was attached to a left heart simulator consisting of an aorta, atrium, and systemic resistance and compliance elements. Experiments were conducted for heart rate of 70 bpm. Wall motion measurements were obtained using high speed stereo-photogrammetry (SP) and cine-CMR, while flow field measurements were obtained using digital particle image velocimetry (DPIV) and phase-contrast magnetic resonance (PC-CMR). Results: The model reproduced physiologically accurate hemodynamics (aortic pressure = 120/80 mmHg; cardiac output = 3.5 L/min). DPIV and PC-CMR results of the center plane flow within the ventricle matched, both qualitatively and quantitatively, with flow from the atrium into the LV having a velocity of about 1.15 m/s for both modalities. The normalized LV volume through the cardiac cycle computed from CMR data matched closely to that from SP. The mean difference between CMR and SP was 5.5 ± 3.7 %. Conclusions: The model presented here can thus be used for the purposes of: (a) acquiring CMR data for validation of FSI simulations, (b) determining accuracy of cine-CMR reconstruction methods, and (c) conducting investigations of the effects of altering anatomical variables on LV function under normal and disease conditions.

Asian Journal of Probability and Statistics, Mar 26, 2022

This paper proposed a generalized estimator of population mean in the presence of correlated and ... more This paper proposed a generalized estimator of population mean in the presence of correlated and uncorrelated measurement errors under simple random strategy. Some known estimators belong to this class of proposed estimator. Under the large sample approximation, the properties of the proposed estimator namely bias and mean squared error were obtained. Theoretical comparison was carried out on the members of the proposed class of estimators when measurement errors are correlated and when they are uncorrelated and the necessary conditions under which the proposed estimator at its optimum value is expected to be more efficient than the existing estimators of finite population mean were obtained. It was observed that correlated and uncorrelated measurement errors inflate the bias and mean squared error of the proposed estimator. The paper concluded that the proposed estimator is more efficient than usual unbiased estimator and some members of the class of proposed estimator.

INTERNATIONAL JOURNAL OF MANAGEMENT, SOCIAL SCIENCES, PEACE AND CONFLICT STUDIES, Dec 17, 2020

Health policies are an integrated approach towards achieving desired targets. Every nation desiro... more Health policies are an integrated approach towards achieving desired targets. Every nation desirous of healthy citizenry articulates critical approach towards addressing healthcare issues for her citizens over a determinable period of time. Like other policies, successful implementation of health policies are preconditioned by the provision of implementation factors as well as enabling environment. Healthcare infrastructure is one of the critical criteria for successful implementation of healthcare policies. In Nigeria, empirical findings have indicted poor health infrastructure as the bane of health of health policy failure. This study sought to join the debate by investigating the extent to which healthcare infrastructure has enabled/disabled the implementation of National Health Insurance Scheme (NHIS) which is an offshoot of the National Health Policy in Nigeria. The study which is a survey research was anchored on Andersen's Health Behaviour Theory and employed the instrument of questionnaire to elicit data from Health workers and NHIS enrollees in nine health institutions spread across four Area Councils in Abuja, namely, AMAC, Gwagwalada, Kuje and Kwali. The data was analysed using Statistical Package for Social Science (SPSS). The study observed the existence of inadequate health infrastructure like hospital bed space inhibits effective utilization of health facilities by enrollees and also that electricity supply to the health facilities are epileptic thereby leading to poor service delivery by health workers to enrollees. It concludes that the problem of poor health infrastructure affects the effective implementation of NHIS and that the issues of health infrastructure are very critical to the effective implementation of NHIS in FCT and Nigeria in general. The paper recommends among others, state of emergency should be declared on health infrastructure; that statutory provisions should be made to consolidate the provision of health infrastructure; A stronger collaboration between the government and Civil Society Organization and indigenous research establishments; and finally special attention to be paid to the power sector in Nigeria.

Bulletin of the American Physical Society, Nov 24, 2013

The natural geometry of the mitral orifice is D-shaped. However, most current designs of prosthet... more The natural geometry of the mitral orifice is D-shaped. However, most current designs of prosthetic valves employ O-shaped orifice geometry. The goal of this study was to compare the effect of geometrical modification between the D and O orifice on the intra-ventricular fluid dynamics during diastolic filling. The different mitral orifice geometries were incorporated into an in vitro left heart simulator consisting of a flexible-walled anatomical left ventricle (LV) physical model enclosed in an acrylic housing. Physiological flow rates and pressures were obtained via tuning systemic resistance and compliance elements in the flow loop. A programmable piston pump was used to generate the LV model wall motion. 2D Particle image velocimetry measurements were conducted along multiple longitudinal planes perpendicular to the annulus plane. During peak diastole, the incoming jet width at the LV central plane was smaller for the D-orifice than that of the O-orifice. Further, the core of the vortex ring in the D-orifice was reduced in size compared to that of the O-orifice. The spatiotemporal spreading of the inflow jet as well as the propagation of the vortex ring will be discussed.

Drilling through shale formation can be challenging and sometimes results in wellbore instability... more Drilling through shale formation can be challenging and sometimes results in wellbore instability problems due to the reaction between hydrophilic shale and drilling fluids. The typical low permeability of shale, the presence of ions and charged surface of the constituent clay are factors which makes the problem of wellbore instability very complex despite efforts dedicated to the study by researchers. The study of wellbore stability in shale is quite important because 75% of all formation drilled worldwide are shale formations and 90% of all wellbore instability problems occur in shale formations costing the industry more than $1 billion USD/year (Chenevert, 2002; Zeynali, 2012); the lost time due to this challenge also account for over 40% of all drilling related non-productive time (Zhang et al, 2009) and these instabilities are responsible for 10-20% of the total drilling cost. A solution through this challenge is critical to the sustenance of the investment made by operating companies in the oil and gas industry. This will drastically reduce drilling cost, completion and workover cost as well as the accompanying downtime involved. It will also improve the net present value of operating company in the industry. Basically wellbore instability occurs when the mechanical stress induced by drilling into the formation exceeds the formation rock strength. Chemical interactions between the drilling mud and the in-situ shale affect the in-situ stress state of the formation hence the stability of the formation. Geo-mechanical models have been designed to tackle mechanical wellbore instability in the Niger Delta the challenge therefore is a chemical solution to the wellbore instability problems of the region. Oil-based muds have been known to overcome wellbore stability problems, but disposal challenges and environmental concerns have led to infrequent use. The challenge therefore is to formulate an environmentally friendly drilling mud having the inhibitive properties to tackle the wellbore instability challenges. This paper presents a review of studies carried out to characterize the mineralogy of shales and the salinity distribution of formation water in the Niger Delta depobelts with a view of designing a &amp;amp;quot;balanced-activity&amp;amp;quot; drilling fluid to help stabilize the formation during drilling. Results obtained from the reviewed researches showed that shale mineralogy characterization and formation water salinity distribution is critical in designing a balanced-activity drilling mud that can effectively tackle the problems of wellbore instability.

Drilling fluid are complex fluids consisting of several additives. These additives are added to e... more Drilling fluid are complex fluids consisting of several additives. These additives are added to enhance and control the rheological properties (such as viscosity, gel strength and yield point) of the mud. These properties are controlled for effective drilling of a well. This research work is focused on determining the rheological behavior of drilling mud using industry-based polymer and Irvingia Gabonensis (ogbono) as viscosifiers. Water based muds were formulated from the aforementioned locally sourced viscosifier and that of the conventional used viscosifier (Carboxylmetyl cellulose, CMC). Laboratory tests were carried out on the different muds formulated and their rheological properties (such as yield stress, shear stress, plastic viscosity and shear rate) are evaluated. The concentration of the viscosifiers were varied. The expected outcome of the research work aims at lowering the total drilling cost by reducing the importation of foreign polymer which promotes the development of local content in the oil and gas industry. The research compares the rheology of mud samples and the effect of varying the concentration (2g, 4g, 6g, 8g, and 10g) of both CMC and Ogbono and determining the changes in their rheological properties. The total volume of each mud sample is equivalent to 350ml which represent one barrel (42gal) in the lab. From the result, at concentration of 2g, the ogbono mud has a better rheology than the CMC mud, but at a concentration above 2g, CMC mud shows a better rheology than ogbono mud, that is, as the concentration of CMC is increased, the rheological properties of the mud increased while as the concentration of ogbono is increased the rheological properties decreased. The viscosity of the drilling fluid produced from the ogbono were lower than that of CMC, it could be used together with another local product such as cassava starch, offor or to further improve the rheology and then be a substitute to the conventional viscosifiers.

A reservoir non-damaging Nano treated aqueous-based drilling fluid was proposed. The study was ca... more A reservoir non-damaging Nano treated aqueous-based drilling fluid was proposed. The study was carried out to obtain a drilling ﬂuid with rheological properties able to keep cuttings in suspension for transport to the surface, minimize ﬁltration and ﬂuid loss. These rheological properties were also predicted using Artificial Neural Network (ANN) due to limitations of existing flow models in predicting Nano-based mud systems. Diﬀerent concentrations of the Nanoparticles were added to these suspensions of water to act as filtration loss materials. A total number of 160 data were used to train the ANN which consists of both the input data and output data acquired from the experiment. The study shows good agreement between experimental data and the artificial neural network prediction of plastic viscosity (PV) and yield point (YP), for multiwall carbon nanotubes (MWCNT) formulated muds. The addition of different concentrations of MWCNT (0.5 – 3 g) as rheology modifier-additive was put to test in a field applicable aqueous mud system. The developed neural network has a Mean Absolute Deviation (MAD) of 0.61529, MSE of 0.57174, Root Mean Square Error (RMSE) of 0.75614 and Mean Absolute Percentage Error (MAPE) of 1.92331 for the predicted plastic viscosity and yield point which are all indicative of good levels of accuracy. It is important to explore the reservoir impairment mechanisms so as to improve and optimize the reservoir performance during the production of hydrocarbons. Having satisfied all the conditions, permeability was determined using Darcy's equation. A reduction in permeability within the range of 12 – 16 mD was recorded for the Nano treated water-based mud system.

IOSR Journal of Environmental Science, Toxicology and Food Technology, 2013

A detailed lithostratigraphic study of the Campanian-Maastrichtian formations (Early basal Campan... more A detailed lithostratigraphic study of the Campanian-Maastrichtian formations (Early basal Campanian to Maastrichtian) from a borehole and wells in the Anambra Basin has been undertaken. The lithofacies of the Nsukka Formation comprises shales, sandy clay and sands. The formation was encountered at several wells in the Anambra Basin. The Elf Nigeria Ltd well numbers 447/1/AAR-1, 7/4/AO-1 and 447/6/NM-1 penetrated the entire Campanian-Maastrichtian sequences of the formations. A lectostratotype has been proposed from the lithological differences between the Mamu and Nsukka Formations for the proper definition of the stratigraphic unit. This is to satisfy the code of accepted stratigraphic practice which states that stratotype should be proposed for established formations. It will also help to reduce the general assumption on similarities in the stratigraphic nomenclature of some lithofacies in the Mamu and Nsukka Formations.

European Journal of Human Resource Management Studies, Feb 4, 2022

This research examined graduates' unemployment reduction in Abuja, using the NYSC's Skill Acquisi... more This research examined graduates' unemployment reduction in Abuja, using the NYSC's Skill Acquisition and Entrepreneurship Development (SAED) Programme as a case in point. The study adopted a descriptive approach, and anchored on the Oxenfeldt's refugee effects theory which states that unemployment drives youth to self-employment. The study revealed that SAED programme has contributed to 35% business employment for those who completed the post-camp training. Findings also show that corps members participate in the in-camp training. However, there seems to be a very sharp decline in participation between the in-camp and post camp segments of the programme as very few participates in the post-camp exercise where the main skill acquisition training is expected to take place. The reduction in number in the post-camp training is occasioned by some challenges ranging from unconducive training/seminar venues, attitude of trainers, inadequate time etc. which leads to loss of interest in the programme. This is coupled with the fact that the post camp training attracts payment, and the NYSC is not actually involved in the negotiation of the terms of engagement of the corps members with the trainers in the post-camp training. More still, training centres do not exist in all the areas especially in the remote ones. It is against this backdrop that the study recommends that for effective and efficient skill acquisition and participation of corps members both in the in-camp and post-camp training exercise, adequate sensitization, conducive training environment, quality lectures/trainings, availability of skill acquisition centres, accessibility to credit facilities, and that NYSC should be involved in negotiation and monitoring of skill acquisition training programmes in the post-camp exercises among others.

<jats:title>Abstract</jats:title> <jats:p>Globally, there are two types of petr... more <jats:title>Abstract</jats:title> <jats:p>Globally, there are two types of petroleum fiscal system; the concessionary and the contractual petroleum fiscal system. The main differences between the two types of petroleum fiscal system is the ownership of the resources and some distinct fiscal terms. The contractual petroleum fiscal system specifies a cost recovery option and profit oil split unlike the concessionary petroleum fiscal system that allows the contractor to recoup his capital before payment of tax. This tends to increase the risk associated with the host government revenue as investment in the production of hydrocarbon is filled with uncertainties. There is a need to redesign the concessionary petroleum fiscal to enable it reduce the risk associated with the host government revenue by making the host government to earn revenue early from petroleum investment. This research therefore evaluated a hybrid petroleum fiscal system for investment in the exploration and production of hydrocarbon. The concessionary petroleum fiscal system was adjusted to include a cost recovery option. Petroleum economic model for investment in a typical onshore oil field was built using spreadsheet modelling technique with the fiscal terms in the hybrid petroleum fiscal system embedded in it. The cost recovery option and oil price in the model were varied between 0-100% and 20−20-20−100 per barrel. The NCF, IRR and payout period of the investment were determined. It was observed that the lower the cost recovery option, the higher the host government revenue. From the profitability analysis of the investment in the hybrid petroleum fiscal system, it was observed that when the price of oil was 100/bbl,theNCFofthehostgovernmentwas100/bbl, the NCF of the host government was 100/bbl,theNCFofthehostgovernmentwas9146 and $8426.3 for 0% and 80% cost recovery option. The lower the cost recovery option, the higher the payout period and the lower the internal rate of return. Though lower cost recovery increased the host government revenue more but it may make the hybrid petroleum fiscal system unattractive for investment in periods of low oil price. Hence a higher cost recovery option was recommended for the use of this type of petroleum fiscal system.</jats:p>

Healthcare sector in Nigeria has performed so abysmally over the years. This owes partly to the i... more Healthcare sector in Nigeria has performed so abysmally over the years. This owes partly to the inability of the vast majority of the populace to access affordable healthcare services and the lack of comprehensive healthcare framework for the masses. This abysmal performance of the healthcare sector in Nigeria led to the introduction of National Health Insurance Scheme (NHIS) in 2005 with the hope of increasing the performance of the healthcare delivery system in the Country. The NHIS is saddled with the mandate of universal coverage of all citizens by the end of 2020. As part of strategies to pursue this mandate, the Scheme has designed various programmers targeting the various segments of the Nigerian economy. The Tertiary Institutions Social Health Insurance Programme (TISHIP) is one of such programmes designed for students in postsecondary institutions in Nigeria. Since TISHIP commenced in 2009, it is important to assess the level of patronage and awareness of the scheme among students of tertiary education institutions in Abuja, Nigeria as a proxy to gauge the extent of patronage of the scheme and derive suitable lessons that could be used in its expansion. Anchored on Systems Theory, this is cross-sectional, descriptive survey was carried out among students from

Day 1 Tue, August 11, 2020, 2020

This study attempts to show the effectiveness of using coconut fibre as a loss circulation materi... more This study attempts to show the effectiveness of using coconut fibre as a loss circulation material in drilling operation. The research incorporated a practical approach. Laboratory experiments was conducted to design drilling muds with the desired loss circulation materials. Their rheological properties and permeability plugging ability was ascertained and compared to determine the most effective loss circulation material blend. To formulate the loss circulation materials, the coconut fibre was processed and particle sizing distribution was conducted on the processed coconut fibre. The coconut fibre was separated into coarse sizes (3350, 2360, 1700 and 1180) and medium be sizes (850 and 425). The distinction between the formulated muds is the loss circulation material combination in them. The three drilling muds had medium-coarse coconut fibre ratio of 60:40, 40:60 and 30:70. The rheological properties of each drilling mud was determined to show suitability of use as a drilling flu...

IOP Conference Series: Earth and Environmental Science, 2021

The drilling fluids should exhibit shear thinning characteristics to have less resistance at high... more The drilling fluids should exhibit shear thinning characteristics to have less resistance at high shear rates. Nanoparticles can enhance the rheological properties of drilling fluids using different mechanisms. Nanomaterials are engineered materials with at least one dimension in the range of 1–100 nm. Carbon nanotubes were chosen in this study due to their unique physio-chemical properties, thus, a good candidate for smart oil based mud formulation. This study investigates the multifunctional ability of carbon nanotubes in oil based mud system and its impact on the drilling hydraulics. Application of carbon nanoparticles in literature have mostly been on water based mud systems and mostly at weight less than 2 g. Effect of carbon nanotubes on flow properties of oil based mud systems within the range of 1 to 3 g weight was analysed. The result shows that the carbon nanotubes improved the flow properties of the formulated oil based mud systems into an acceptable and desirable range r...

Journal of Social and Political Sciences, Jun 30, 2021

Journal of Visualization, Feb 16, 2018

Circulation, Nov 14, 2017

Bulletin of the American Physical Society, Nov 24, 2013

Springer eBooks, 2018

Journal of Cardiovascular Magnetic Resonance, Jun 26, 2015

Asian Journal of Probability and Statistics, Mar 26, 2022

INTERNATIONAL JOURNAL OF MANAGEMENT, SOCIAL SCIENCES, PEACE AND CONFLICT STUDIES, Dec 17, 2020

Bulletin of the American Physical Society, Nov 24, 2013

IOSR Journal of Environmental Science, Toxicology and Food Technology, 2013

European Journal of Human Resource Management Studies, Feb 4, 2022

Day 1 Tue, August 11, 2020, 2020

IOP Conference Series: Earth and Environmental Science, 2021