http://41.89.164.27:8080/xmlui/handle/123456789/260 2026-04-07T23:33:47Z http://41.89.164.27:8080/xmlui/handle/123456789/2494 The Comparison between Inquiry-Based and Traditional Learning Approaches on the Student Performance in Physics in Kesses Sub- County, Kenya Kimiru, Kinyanjui Godfrey; . Samikwo, Dinah C.; Choge, Dismas Physics is one of the science subjects offered in the Kenyan secondary school curriculum. Despite attracting few learners over a long period of time, its performance has been poor as indicated in the Kenya National Examinations Council (KNEC) reports. This study aimed at investigating performance comparison between learners taught using the Inquiry-Based Learning (IBL) approach and those taught using Traditional Learning (TL) approaches in Secondary schools within Kesses Sub- County in Uasin Gishu County. The objective of the study was to compare the performance of students taught Physics using the IBL approach and those taught using TL approaches. The study was based on Experiential Learning theory by Carl Rogers (1969). The IBL approach for this study was an exploratory learning approach, which involves learners performing experiments and sharing results. The target population was 1,009 Form Three Physics students from 47 schools. Stratified random sampling, simple random sampling and purposive sampling were used in this study. Stratified random sampling was used to divide schools into three strata according to their categories. From each stratum, random sampling was used to select schools from the categories; extra county, County and Subcounty schools. The sample size comprised of 282 physics students from sampled schools. A quasi-experimental design was employed where sampled students were divided into control and experimental groups. Pre-tests and post tests were then administered and tests results were analyzed. Collected data was analyzed using softwares which were, SPSS version 25 and the Microsoft Excel 2021 version application programs. The findings showed that performance of learners taught Physics using IBL approach was greater than that of those taught using traditional approaches. The results of the study are expected to be instrumental to curriculum developers at the Kenya Institute of Curriculum Development (KICD) in designing a Physics curriculum that promotes the IBL approach in delivering instructions. The results will also help school administrators and teachers of Physics in coming up with policies that promote use of IBL approach. 2025-09-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2410 Wavelength reuse in passive optical network for polarization based environmental sensing Cherutoi, Henry C.; et. al... We propose and experimentally demonstrate a cost-effective technique of optical sensor that utilizes the reused wavelength in the customer’s premises. This has been achieved by utilizing the saturated EDFA to suppress the extinction ratio of the incoming optical signal hence erasing the downstream data allowing for channel reuse. A 1550nm distributed feedback (DFB) laser is directly modulated with a 10 Gbit/s NRZ data signal and used to characterize the erasing functionality of EDFA. The performance evaluation is done for different input power into the EDFA. The EDFA is shown to reduce the extinction ratio of the incoming signal from 6.48 dB to 0.81dB when the input powers of -7.3 dBm and 1.1 dBm were respectively used, therefore facilitating the direct reuse of the downstream carrier. The vibrational sensor was demonstrated at 85 MHz and the signal was fully recovered. These results indicated the ability of the sensor to detect a change in the environment, therefore giving an early warning signal. The optical fiber sensor system proved to be a reliable and cheaper alternative for environmental monitoring utilizing re-used wavelength. 2024-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2323 Parameters of Magic-Angle Twisted Bilayer Graphene (MATBG) Superconductors Kiboi, Dismas Chenge; Kapil, Mohan Khanna In general, a superconducting state is described by three critical parameters, such as, critical transition temperature (Tc), critical magnetic field (Hc), and critical current density (Jc) or density of states at the Fermi surface of the superconductor. In the case of Magic-angle-twisted-bilayer-graphene (MATBG), the angle of twist ( )  kT = Constant between the two layers of graphene is another important parameter since the variation in  changes the value of Tc, and by virtue of the relation between Tc and EF (Fermi energy),  of states ( ) D E F E F the value of F E changes. Change in F E can result in the change in density , and thus it can affect the current density. Hence in MATBG, the magic angle( )  of twist between the graphene layers becomes an essential parameter along with the three parameters ( c T H c , and c J , ) that influence superconductivity in such materials, and the parameters are calculated for MATBG. 2023-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2322 ELECTRON-HOLE SUPERCONDUCTIVITY IN BI-LAYER GRAPHENE SUPERCONDUCTORS Chenge, Kiboi D.; et. al... Superconductivity has been discovered in many different types of materials, such as metals, metallic alloys, doped semiconductors, cuprate oxides, heavy fermion superconductors, and so on; and now recently bi-layer and trilayer graphene superconductors. What is common among all these superconductors is that the super-current is due to the frictionless flow of pairs of charge carriers, called Cooper pairs, and the charge carriers can be electrons, holes in pairs, or electron-hole pairs. In this manuscript, the role of electron-hole pairs in determining the superconductivity in bi-layer graphene superconductors is studied theoretically. It is based on the spontaneous inter-layer phase coherence in a bi-layer quantum Hall system studied using graphene layers. The phase coherence state is assumed to be a gas of super-fluid electron-hole pairs whose components (electrons and holes) belong to two different layers which are one above the other and are separated by a dielectric of a very small thickness (d), and the value of d, should be such that the state of phase coherence is not disturbed. For such a superconductor, specific heat (Cv), entropy (S), and transition temperature (Tc) have been calculated and compared with values known so far 2023-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2175 ANFIS-Controlled Boost and Bidirectional Buck-Boost DC-DC Converters for Solar PV, Fuel Cell, and BESS-Based Microgrid Application Aeggegn, Dessalegn Bitew; et. al... DC-DC converters are essential for integrating distributed energy resources into microgrid (MG) systems. Tese converters are designed to incorporate intermittent renewable energy sources such as solar photovoltaic (PV) panels, fuel cells (FCs), and battery energy storage systems (BESSs) into the grid. However, conventional DC-DC converters have limitations including lower ef- fciency, voltage ripple, insufcient voltage regulation, and compatibility issues. Tis article presents boost and bidirectional buck- boost converters for direct current microgrid (DCMG) applications, employing an adaptive neuro-fuzzy inference system (ANFIS) for control. Tese proposed converter confgurations adeptly manage wide input voltage fuctuations from intermittent sources, consistently supplying power to the DC bus at 500 V and 120 V for boost and buck operations, respectively, with an efciency of 98.8%. Te output voltage result shows that the ANFIS-based boost converter has 10% overshoot as compared to 41% and 50% overshoot in proportional integral (PI) and fuzzy logic controller (FLC), respectively. In both buck and boost modes, the converters’ voltage gain is infuenced by duty ratio adjustments only, not sensitive to dynamic input voltage and fexible manipulation of the output voltage for BESS charging. Moreover, the designed converters accommodate load variations within the MG. To assess the converters’ ability to regulate output voltage efectively, PI, FLC, and ANFIS controllers are implemented and compared. And the ANFIS controller demonstrates superior performance, ofering faster response times and enhanced stability. Evaluations are conducted through simulations in the MATLAB/Simulink environment. 2024-07-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2100 Coherent High-Speed Signal Transmission in Passive Optical Networks Cherutoi, Henry; Waswa, David; Choge, Dismas A comparative study of digital M-ary Quadrature Amplitude Modulation (16-QAM) and QPSK modulationformats for high-speed transmission is presented. Based on VPI optical simulation software. This paper builds a high-bit rate dual polarization (DP) QPSK and16-QAM modulation formats coherent optical transmission system for Passive Optical Networks (PON). Higher-order modulation formats could be used to provide huge data capacity, extended coverage, and long-reach connections. Channel impairments are mitigated by using digital signal processing (DSP) for dispersion compensation, carrier frequency recovery, and carrier phase estimation. The performance of our system is analysed on Bit Error Rate (BER=1e-9), the threshold for a communication system. For a 32-Splitter PON configuration operating with 16-QAM modulation format, a data rate of 80 Gb/s per ONU is achieved after 24km using standard single mode fibre (SSMF). The results indicate that the proposed schemes are a promising solution for coherent high-speed transmission in PONs. 2023-11-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/2086 Mechanical and Elastic Properties of Selected 211 MAX Phases: A Density Functional Theory Study ARUSEI, Geoffrey; et al. MAX Phases are a class of ternary materials that have continued to play a greater role in the field of materials science due to their unique properties that bridge the gap between metals and ceramics which have uses in a wide range of applications. However, in spite of these progress, there are still a lot of open questions and properties that needs to be understood. The Mechanical and elastic properties of (Nine) MAX phase materials, namely, Ti2AlC, Ti2AlN, Ti2GaC, Ti2GaN, Ti2PbC, Ti2CdC, Ti2SiC, Ti2GeC and Ti2SnC have been investigated using the density functional theory within the generalized gradient approximations as expressed in Quantum Espresso and VASP codes. The values of elastic anisotropy, Young’s modulus, Poisson ratio and shear modulus revealed that the compounds were indeed stable and ductile. Out of all the nine MAX Phase materials, Ti2PbC and Ti2CdC are more stable than the other considered compounds. The findings of this study suggest that the nine MAX phases are potential candidates in various industrial applications requiring hard materials. 2023-10-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/1605 Ab initio insights into Graphene-Zirconium disulfide/diselenide heterostructure as electrode material for alkali-ion batteries King’ori, Gladys W.; et. al... In the search for an energy storage medium with higher electronic conductivity, rate performance and moderate volume expansion, van der Waals heterostructures are a promising alternative. Herein, the potential of graphene (Gr) and Zirconium dichalcogenide (ZrX2, X = S, Se) van der Waals heterostructures for applications as battery electrodes is explored using density functional theory (DFT) calculations. Through intercalating alkali ions (Li and K) between the Gr and ZrX2, we obtain low energy activation barriers, indicating that Gr-ZrX2 van der Waals heterostructures can be candidates for high rate performance electrode application. DFT calculations also indicate that the Gr-ZrX2 heterostructure formation is energetically favoured with better volume expansion as compared to bilayer Gr and ZrX2. The calculated open circuit voltage (OCV) for K intercalation was 0.66 V (Gr-ZrSe2) and 0.77 V (Gr-ZrS2), hence suitable for anodic application in Potassium-ion batteries (KIB). The calculated OCV for Li interaction was 2.83 V (Gr-ZrSe2) and 2.95 V (Gr-ZrS2) hence suitable for cathodic applications 2021-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/1433 Landau Criteria of Superfluidity of Two Component Mixture of Bosons Namwetako, Jophine S.; et. al... Using the quasi-particle energy of a mixture of two-component gas of bosons which is assumed to be in a superfluid state, the Landau criterion for superfluidity has been applied to obtain the magnitude of the Landau’s critical velocity (Vc) below which the superfluid state can exist as stable state. Different combinations of bosons have been used to calculate Vc. It is found that, the magnitude of Vc increases with scattering length (a) and its magnitude is less than the velocity of sound (Vs) in superfluid liquid Helium (Vs=238m/s), and it varies roughly between 10.95m/s to 15.12m/s. The value of Landau critical velocity for superfluid Helium is of the order of 50m/s to 60m/s depending on the type of inter particle interaction assumed between the Helium atoms 2020-01-01T00:00:00Z http://41.89.164.27:8080/xmlui/handle/123456789/1420 Assessing the Potential of Using Satellite Data on Radiation in the Analysis of Earth’s Climate System to Complement the Scarce Radiation Data Measured from the Ground Stations Onyaga, Collins Ochieng; Wanyonyi, Samson W.; Stern, Roger High quality solar radiation data is required for the appropriate monitoring and analysis of the Earth’s climate system as well as efficient planning and operation of solar energy systems. However, well maintained radiation measurements are rare in many regions of the world. Therefore, satellite-derived radiation estimates are an alternative to these scarce solar radiation measurements from the weather stations. Satellite estimates of solar radiation have an advantage over solar radiation measurements from weather stations because of their high spatial and temporal resolutions. These satellite radiation estimates at approximately 5-6 Km resolution derived from geostationary Meteosat satellites are available through the EUMETSAT Satellite Application Facilities (SAFs). CM-SAF (SAF on Climate Monitoring) provides consistent dataset of hourly, daily and monthly solar radiation from 1983 to 2013. In this study, we examined the potential of using satellite estimates of solar radiation to fill in the data gaps in records from the weather stations as well as the areas where radiation data is not available. The analysis carried out showed that the satellite data had fewer missing values than the ground data, and that they are both similar in distribution. The average correlation between the two data sets was found to be 0.71 for both monthly and daily analysis. However, the month of September showed a very low correlation of 0.21. Mean percentage error, mean bias error and mean absolute deviation were found to be 2.46, 18.84, 50.32 and 3.08, 559.87, 1135.93 for daily and monthly analysis, respectively. The solar radiation distribution in Dodoma was found to follow Weibull distribution throughout the year. 2018-01-01T00:00:00Z