Articles: Department of Computing and Information Technology
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Item A Link Fabrication Attack Mitigation Approach (LiFAMA) for Software Defined Networks(MDPI, 2022-05) Katongole, Joseph; Odongo, Steven Eyobu; Kasyoka, Philemon; Oyana, Tonny J.n software defined networks (SDNs), the controller is a critical resource, yet it is a potential target for attacks as well. The conventional OpenFlow Discovery Protocol (OFPD) used in building the topological view for the controller has vulnerabilities that easily allow attackers to poison the network topology by creating fabricated links with malicious effects. OFDP makes use of the link layer discovery protocol (LLDP) to discover existing links. However, the LLDP is not efficient at fabricated link detection. Existing approaches to mitigating this problem have mostly been passive approaches that depend on observing unexpected behaviour. Examples of such behaviour include link latency and packet patterns to trigger attack alerts. The problem with the existing solutions is that their implementations cause longer link discovery time. This implies that a dense SDN would suffer from huge delays in the link discovery process. In this study, we propose a link fabrication attack (LFA) mitigation approach (LiFAMA), which is an active mitigation approach and one that minimises the link discovery time. The approach uses LLDP packet authentication together with keyed-hashbased message authentication code (HMAC) and a link verification database (PostgreSQL) that stores records of all known and verified links in the network. This approach was implemented in an emulated SDN environment using Mininet and a Python-based open-source OpenFlow (POX) controller. The results show that the approach detects fabricated links in an SDN in real time and helps mitigate them. Additionally, the link discovery time of LiFAMA out-competes that of an existing LFA mitigation approach.Item The hybrid Cramer-Rao bound of direction finding by a uniform circular array of isotropic sensors that suffer stochastic dislocations(Acoustical Society of America, 2017-11-15) Zakayo, N. Morris; Wong, Kainam Thomas; Kitavi, Dominic M.; Tsair-Chuan, LinConsider azimuth-elevation direction finding by a uniform circular array of isotropic sensors. In the real world, the sensors may dislocate from their nominal positions. These dislocations could be modeled as random variables having an a priori known distribution. This paper investigates how the dislocations would affect azimuth-elevation direction finding by deriving the corresponding hybrid Cramer-Rao bounds. Maximum a posteriori estimators are derived and Monte Carlo simulations are conducted to validate the derived hybrid Cramer-Rao boundsItem Hybrid Cramer-Rao bound for near-field source localization using a spatially spread acoustic vector sensor(Acoustical Society of America, 2019-03) Zakayo, Ndiku Morris; Yuting, HanThis presentation characterizes the source-localization precision obtainable via "received signal strength indication" (RSSI) based on data from a tri-axial velocity sensor and a spatially separated pressure sensor. That scheme was proposed originally by Y. I. Wu and K. T. Wong in January 2012 in the IEEE Transactions on Aerospace and Electronic Systems. That source-localization scheme depends on the acoustic propagation path-loss exponent, which is typically not precisely known a priori but could be modeled stochastically. That exponent may also differ in value for the propagation path to the tri-axial velocity sensor and for the propagation path to the pressure sensor. This presentation accounts for these two practical considerations in characterizing the scheme's source-localization precision, through the metric of the "hybrid Cramer-Rao bound" (HCRB), the correctness of which is here validated by Monte Carlo simulations of the corresponding "maximum a posteriori" (MAP) estimator.Item A Centrosymmetric Array Comprising a Horizontal Uniform Circular Subarray and a Vertical Uniform Linear Subarray—Its Design in Reference to Its Direction-Finding Cramér–Rao Bound.(IEEE, 2021-06) Lin, Yang; Wong, Kainam Thomas; Zakayo, Ndiku MorrisAzimuthal centrosymmetry in an array grid is typically associated with arrays that are circular, concentric, cylindrical, spherical, or hemispherical. However, a recently proposed alternative combines an azimuthal circular array with a linear vertical array. For this elegantly simple new array grid's use in the direction-of-arrival estimation, this article advances array-design insights to meet a given estimation-precision threshold, by examining the tradeoff between the azimuth-angle Cramér-Rao bound vis-a-vis the polar-angle Cramér-Rao bound in a proposed two-step design procedure.Item On the Performance of L- and V-Shaped Arrays of Cardioid Microphones for Direction Finding(IEEE, 2021-01-15) Nnonyelu, Chibuzo Joseph; Zakayo, Ndiku Morris; Chinaza, Alice MadukweThe L-shaped and V-shaped arrays of first-order cardioid microphones for direction finding are presented in this paper. A comparative study of the direction of arrival estimation performance of the arrays was carried out by analytically deriving, in closed-form, and comparing the Cramér-Rao bounds of an incident signal's direction-of-arrival (DoA) azimuth and polar angles for these arrays. The maximum-likelihood estimator is used to verify the correctness of derived bounds. This investigation reveals that for direction finding, the L-shaped array of cardioid microphones would generally outperform the V-shaped array of cardioid microphones in more sub-regions of the DoA polar-azimuth angle space. However, in regions where the V-shaped array of cardioid microphones outperforms the L-shaped array of cardioid microphone, the variance ratios are usually higher in favor of the V-shaped array.Item Three-dimensional dislocations in a uniform linear array's isotropic sensors-Direction finding's hybrid Cramér-Rao bound(Acoustical Society of America, 2020-05) Ndiku, Morris, Zakayo; Wong, Kainam Thomas; Wu, Yue IvanThe linear array’sone-dimensional spatial geometry is simple but suffices forunivariate direction finding, i.e., isadequate for the estimation of an incident source’s direction-of-arrival relative to the linear array axis. However, thisnominalone-dimensional ideality could be often physically compromised in the real world, as the constituentsensors may dislocatethree-dimensionally from their nominal positions. For example, a towed array is subject toocean-surface waves and to oceanic currents [Tichavsky and Wong (2004). IEEE Trans. Sign. Process.52(1),36–47]. This paper analyzes how a nominally linear array’sone-dimensional direction-finding accuracy would bedegraded by thethree-dimensional random dislocation of the constituent sensors. This analysis derives the hybridCram er-Rao bound (HCRB) of the arrival-angle estimate in a closed form expressed in terms of the sensors’ disloca-tion statistics. Surprisingly, the sensors’ dislocation could improve and not necessarily degrade the HCRB, depend-ing on the dislocation variances but also on the incident source’s arrival angle and the signal-to-noise power ratioItem Comparing the “Rim” Versus the “Filled” Rectangular Array Grids—Their Direction-Finding Cramér-Rao Bounds(IEEE, 2018) Zakayo, Ndiku Morris; Wong, Kainam ThomasA rectangular array of sensors is often used in direction finding, due to the geometric regularity in its spatial rectangular grid. The sensor positions may be confined to the rectangle's perimeter (as in a “rim” array), or may span over the rectangle's entire interior as well (as in a “filled” array). This paper compares these two array grids by their precision in direction finding, by pioneering Cramér-Rao bound expressions for both array grids above, in closed forms and explicitly in terms of the array parameters.Item Acoustical Direction Finding using a Bayesian Regularized Multilayer Perceptron Artificial Neural Networks on a Tri-Axial Velocity Sensor(IJMEC, 2020-01) Nnonyelu, Chibuzo Joseph; Zakayo, Ndiku MorrisA two-dimensional direction-of-arrival estimation scheme based on Bayesian-regularized (BR) Multilayer Perceptron (MLP) artificial neural network (ANN) is developed around a unit acoustic vector sensor (AVS). The AVS basically consists of three collocated and orthogonally oriented velocity sensors, hence, senses acoustic waves in the three Cartesian directions while offering portability in size and simplicity in its array manifold. It is shown that the Bayesian regularized Multilayered Perceptron neural network performs well in terms of estimation’s root-mean-square error even when tested with data of different signal-to-noise ratio (SNR) after training. This is useful as it accounts for unexpected changes of received data SNR during field operation. The proposed system is ideal for applications in mobile systems such as robots for search-and-rescue operations or soldiers in the battle field to estimate the source of a sniper fire.Item Rules-of-thumb to design a uniform spherical array for direction finding—Its Cramér– Rao bounds' nonlinear dependence on the number of sensors(Acoustical Society of America, 2019-02) Ndiku, Morris, Z; Wong, Kainam, T; Nnonyelu, Joseph,CABSTRACT This paper discovers rules-of-thumb on how the estimation precision for an incident source's azimuth-polar direction-of-arrival (ϕ,θ) depends on the number (L) of identical isotropic sensors spaced uniformly on an open sphere of radius R. This estimation's corresponding Cramér–Rao bounds (CRB) are found to follow these elegantly simple approximations, useful for array design: (i) For the azimuth arrival angle: 2π(R/λ)(σs/σn) √ 2LMCRB(ϕ) sin(θ)≈(Le1/14)−1+ √ 3 → L→∞ √ 3 , ∀(ϕ,θ); and (ii) for the polar arrival angle: 2π(R/λ)(σs/σn) √ 2LMCRB(θ) ≈ √ 3 −(Le6/7)−1 → L→∞ √ 3 , ∀(ϕ,θ). Here, M denotes the number of snapshots, λ refers to the incident signal's wavelength, and (σs/σn)2 symbolizes the signal-to-noise power ratio.Item Gender-specific determinants of Zai technology use intensity for improved soil water management in the drylands of Upper Eastern Kenya(Elsevier Ltd., 2021-06-01) Ndeke, Amos ,M; Ngetich, Felix; Mugwe, Jayne ,N; Mogaka, Hezron; Kiboi, Milka; Nyabuga, George; Mucheru-Muna, Monicah; Sijali, IsayaDegraded landscapes and soil water stress are long-standing problems to smallholder agriculture in the drylands. Despite the important roles of zai technology in restoring degraded landscapes and improving agricultural productivity, the technology is yet to be adopted to its fullest extent. This can be attributed to gender-linked disparities in agricultural technology utilization. The study, therefore, sought to determine gender-specific determinants of zai technology choice and use-intensity. A multistage sampling technique was employed in randomly selecting 133 female-headed households and 267 male-headed households in Tharaka South subcounty. Quantitative data were collected in a cross-sectional survey using an interviewer-administered questionnaire. Using sex-disaggregated data, Chi-square and t-test statistic were employed to test the statistical significance of dummy and mean value of continuous variables, respectively. Gender specific determinants of zai technology choice and use-intensity were determined using the Heckman-two-step econometric model. The results revealed that, more women farmers (44%) were using zai technology as compared to men (38%). Among women farmers, total cultivated land, access to animal-drawn farm implements, and group membership had an influence on zai technology choice. For men, total cultivated land, group membership and access to extension services positively influenced choice of zai technology. With regard to zai technology use-intensity, total land cultivated, livestock densities, group membership and frequency of trainings on soil and water management were important determinants among women farmers. For men, zai technology use-intensity was determined by total cultivated land and farmers’ perceptions on soil erosion. We recommend that, gender-sensitive farm-level policies oriented towards farmer socioeconomic profiles are important deliberations towards choice and intense application of soil and water conservation strategies such as the zai technology.Item Decomposition of Riemannian Curvature Tensor Field and Its Properties(Science Domain, 2018-11-22) Gicheru, James,G; Ngari, Cyrus, GDecomposition of recurrent curvature tensor fields of R-th order in Finsler manifolds has been studied by B. B. Sinha and G. Singh [1] in the publications del’ institute mathematique, nouvelleserie, tome 33 (47), 1983 pg 217-220. Also Surendra Pratap Singh [2] in Kyungpook Math. J. volume 15, number 2 December, 1975 studied decomposition of recurrent curvature tensor fields in generalised Finsler spaces. Sinha and Singh [3] studied decomposition of recurrent curvature tensor fields in a Finsler space. In this paper we study the Riemannian Curvature tensor with its properties its decomposition of the Riemannian curvature tensor and its properties. This raises important question: in Riemannian manifold , is it possible to decompose Riemannian curvature tensor of rank four, get another tensor of rank two and study its properties?Item Parameters And State Estimates Of Sex Based Covid-19 Model Using Kenya Data, Nonlinear Least Square And Interpolating Polynomials(International Journal of Scientific and Research Publications, 2021-05-05) Kitavi, Dominic, M; Ngari, Cyrus, G; Ngari, Paul, M; Muchangi, David, MCOVID-19 spread in Kenya has been growing at a very high rate in the recent past. According to the Kenya’s ministry of health, the confirmed COVID-19 infections as of 19th July 2020 was 13,353 with recorded 5,122 recoveries and 234 deaths. Based on quarantine data, there is media speculation about COVID-19 manifesting gender dimension, however, no studies have been carried out to establish the gender-based dimension in the community. This paper aimed at: formulating gender based Mathematical model, estimate gender-based disease burden in the community using quarantine data and using estimated parameters and states to predict dynamics of the disease in the quarantine centers. Mathematical compartment model was developed using characteristic and status of disease. Daily number of infectious and exposed in the community was estimated using interpolating polynomials. Nonlinear least square was used to fit observed data in the developed model. Prediction of the initial value problem was carried out using MATLAB inbuilt ode solver. Daily estimate of states in Figures 8 and 9 confirms that COVID-19 is also burdening more males in the community than females. Simulation using MATLAB indicated that the number of individuals who will remain constantly infected after disease induced deaths and recoveries ranges between (567 − 219) and (363 − 116) for males and females respectively. Future studies should focus on Mathematical model analysis and predictions of disease burden in the community.Item Simulation of a Deterministic Model of HIV Transmission between Two Closed Patches(Journal of Advances in Mathematics and Computer Science, 2020-09-08) Mirgichan, James Khobocha; Cyrus, Gitonga Ngari; Karanja, StephenNumerical simulation of a deterministic model of HIV transmission between major cities in Kenya is carried out. The model considered two closed patches connected by the commuter movements of truck drivers being the agents of HIV transmission. The transmission kernel being the function of distance between the patches is ignored. The numerical algorithms are applied in the solution of a nonlinear firstorder differential equations. The algorithms are implemented with the aid of MATLAB solver which has an in- built mechanism of Runge Kutta method of fourth order. Numerical simulation indicated the population dynamics of the patches, effect of migration on female sex workers and model reproduction number. The findings of the study were that the migration of the truck drivers between two closed patches contributed significantly to the spread of HIV. In this regard, it was recommended that, stakeholders should target the truck driving population and towns along the transport corridors to mitigate the growing HIV infections and integrate the truck drivers in the national health strategyItem A Theoretical Model of Corruption Using Modified Lotka Volterra Model: A Perspective of Interactions between Staff and Students(Journal of Advances in Mathematics and Computer Science, 2020-08) Kawira, Mercy; Ngari, Cyrus Gitonga; Karanja, StephenCorruption is the misuse of power or resources for private gain. This undermines economic development, political stability, and government legitimacy, the society fabric, allocation of resources to sectors crucial for development, and encourages and perpetuates other illegal opportunities. Despite Mathematical modeling being a powerful tool in describing real life phenomena it still remains unexploited in the fight of corruption menace. This study uses Lotka Volterra, predator-prey equations to develop a model to describe corruption in institutions of higher learning, use the developed model to determine its equilibria, determine the condition for stability of the equilibria and finally carry out the simulation. The corrupt students and staff act as predators while their non-corrupt counterparts act as prey in the paper. Theory of ordinary differential equations was used to determine steady states and their stability. Mathematica was used for algebraic analysis and Matlab was used for numerical analysis and simulation. Analytical result suggested multiple steady state however numerical result confirmed that the model has four steady states. Numerical bifurcation analysis suggests the possibility of backward of corrupt staff when is about 39. Numerical simulation points to an increasing trend on corrupt staff and decrease trend on corrupt student. This study concludes that more focus should be put to staff than students in curbing the spread of corruption. Future study should strive to fit this model in real data.Item Identifying the Most Feasible Technologies for mHealth Maternal Mortality Interventions in Sub-Saharan Africa(SpringerLink, 2021-03-19) Mukami, Victoria, M; Millham, Richard; Puckree, Threethambal; Fong, Simon JamesmHealth is considered as an acceptable solution toward health-related challenges especially within maternal and neonatal health. This paper is a review of acceptable mHealth technologies and the impact on maternal and neonatal health. A focus is directed toward Sub-Saharan Africa where a review of mHealth technologies that work in the area is conducted. A randomized control trial utilizing text messages is reviewed to check on the reliability, and viability of the solution within the Kenyan context. Additional tools that are reviewed include open data kit, a data collection tool as well as Google Aggregate server, a data storage tool which are used to evaluate the viability of the ICT intervention. Key findings show that not only text messages are cost effective but also can be scaled for larger projects. A combination of text messages, open data kit, and Google aggregate provides for a feasible and reliable combination when running feasible control trials interventions. In conclusion, it is recommended that a customized developed system to be used instead of a commercial system especially when running large-size control trials which may require a more cost-effective solution.Item Socioeconomic Impact of Establishment of University of Embu on Small Scale Farmers in Nthambo Sub-Location, Kenya(Asian Journal of Probability and Statistics, 2018-11) Akelo, Gogo Jacqueline; Ngari, Cyrus GitongaThe University of Embu is one of the fast developing and recently chartered University in Kenya. It is located in Nthambo sub-location, which is an agricultural potential area. Universities establishment have considerable influence on the activities of community that stays around it. Despite the fact that several studies have been conducted on the socioeconomic impact of establishment of different Universities to the community they reside in, a research on the socioeconomic impact of establishment of University of Embu on small scale farmers in their agricultural activities have never been done. Given that the University of Embu has been established on the agricultural potential area, this study sought to investigate the impact of the establishment of University of Embu on agricultural resources and productivity, describe the community diversity and living standards of the community. Methodology used in this research was descriptive survey design and stratified random sampling technique obtaining a sample of 100 households which was proportionate to the population. Using SPSS software for cross-tabulation, the results indicated that: the rate of both livestock and crop production have been declining with supporting evidence of (60.2%) and (66%) of the households respectively, the community was diverse (87.2%) with majority being university students (68.1%), most of the small scale farmers had access to electricityconnection (78.1%), even though farming activity remains main economic activity of community within the area, it has been declining from (95.3%) to (53.2%), business activities have increased from (3.5%) to (41.5%), most of the households (54.3%) have constructed rental houses majorly to earn more money (70.2%). The researchers recommend that Embu County government should adopt a policy such that the communities surrounding University of Embu must develop, implement and enforce mechanisms for effective preservation of productive agricultural land (i.e. Urban growth boundaries, purchase of development rights, exclusive agricultural zoning among others).Item mHealth: ICT framework for mitigating the determinants of maternal and neonatal morality(IEEE, 2019) Mukami, Victoria M.; Millham, Richard; Puckree, ThreethambalMaternal and neonatal mortality is a great challenge towards the family unit within Sub-Saharan Africa. This paper is a review of frameworks that look at mitigating factors toward a reduction of maternal and neonatal deaths. A greater focus is placed on the mHealth frameworks that target maternal and neonatal health. Additionally, a framework is proposed that combines the mitigating frameworks toward maternal and neonatal mortality as well as the mHealth frameworks. A qualitative experimental study was conducted that was used to propose the framework. The study was conducted in two locations in Kenya and each location had both an interventional and control group. The study was focused on pregnant women and used an information dissemination system as the intervention. Several complications were observed during the study at both locations. In addition, there were three neonate mortalities at one of the locations, one of which may have been prevented had the woman been empowered. Key findings revealed that while SMS messages did not necessarily have an immense impact on the well-being of the mother, with the necessary information, a mother is able to promptly make certain informed decisions based on symptoms that occur that could prevent mortalities. In conclusion, a lengthy health worker strikes during the entire study impacted the study and as such a similar study conducted when local health workers are in session may display different results.Item Feasible E-Health Strategies to Reduce Maternal Mortality in Kenya(2020) Mukami, Victoria, M.Maternal mortality remains a persistent cause of death in Sub-Saharan Africa. Although e-health technologies are rapidly advancing, many technologies are infeasible given the infrastructure constraints and context of Sub-Saharan Africa. This paper proposes and implement a feasible e-health strategy, which involves the use of simple mobile phone technology and was designed to reduce maternal mortality and neonatal rates through information dissemination, among the nomadic people within a select part of Kenya. This strategy was developed, through an interactive pilot study, to determine the most feasible technique, which was found to be SMS messages, and most appropriate customized information depending on the patient's condition and period in pregnancy. A cross-sectional randomized e-health intervention was implemented in order to determine the effectiveness of the intervention. Due to exceptional circumstances, such as a prolonged health strike, this intervention had mixed results but shows promise of both feasibility and effectiveness.Item Internet of Things based Model for Identifying Pediatric Emergency Cases(2021-08) Musyoka, Faith Mueni; Muchori, Juliet Gathoni; Kamau, GabrielPediatric emergency cases need rapid systems that measure vital body parameters data, analyze and categorize emergency cases for precise action. Current systems use manual examination resulting in delayed medication, death, or other severe medical conditions.In this paper, we propose a Internet of Things (IoT) based model, created using Balena fin with Raspberry pi compute module. It is used for determining emergency cases, in pediatric section, specifically the triage section. It is later tested using hospital data that represents the vital parameters in pediatric. Our approach entails designing and setting up the hardware and software infrastructure, to accommodate data via Bluetooth protocol, and transmit it to the cloud server database via Message Queuing Telemetry Transport (MQTT). Later, we perform machine learning on the data by training a model and finally develop a Plotly Dash analytical application integrating the model for visualization near real-time.Findings show that emergency cases are detected using vital body parameters which include the body temperature, oxygen levels, heart rate and the age. The model indicates a 97% accuracy.In conclusion, children’s emergency cases are detected in time using IoT gadgets and machine learning classification.