Physics

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2D-Euler Deconvolution and Forward Modeling of Gravity Data of Homa-Hills Geothermal Prospect, Kenya
(2014) Odek, A.; Otieno, A. B.; Githiri, Jg
In order to fully assess the potential of Homa Hills Geothermal prospect, the heat source which is one of the main features of a geothermal system had to be located based on its perturbation on the gravity field. Ground gravity survey was conducted in an area covering about 76 km2 and the data processed to remove all other effects which are not of geological interest. Qualitative interpretation was attempted and cross sections drawn across the anomalous areas on the complete Bouguer anomaly map. Quantitative interpretation attempted involved both Euler Deconvolution and 2‐D Forward modelling. The parameters obtained from Euler Deconvolution were used as the start up parameters for 2‐D Forward modeling. Well clustered Euler solutions were obtained at a shallow depth of approximately 200‐750 m which is consistent with the modeled shallow dike like intrusive probably of carbonatite origin.
2D-Euler Deconvolution and Forward Modeling of Gravity Data of Homa-Hills Geothermal Prospect, Kenya
(2013) Odek, O. 1; Otieno, A.B. 1; Ambusso, W.J. 1; Githiri, J. G 2
In order to fully assess the potential of Homa Hills Geothermal prospect, the heat source which is one of the main features of a geothermal system had to be located based on its perturbation on the gravity field. Ground gravity survey was conducted in an area covering about 76 km2 and the data processed to remove all other effects which are not of geological interest. Qualitative interpretation was attempted and cross sections drawn across the anomalous areas on the complete Bougu er anomaly map. Quantitative interpretation attempted involved both Euler Deconvolution and 2 ‐D Forward modelling. The parameters obtained from Euler Deconvolution were used as the start up parameters for 2 ‐D Forward modeling. Well clustered Euler solutions were obtained at a shallow depth of approximately 200‐750 m which is consistent with the modeled shallow dike like intrusive probably of carbonatite origin
Ab initio Investigation of the Structural and Electronic Properties of Alkaline Earth Metal - TiO2 Natural Polymorphs
(Hindawi Advances in Materials Science and Engineering, 2022) Mbae, J.K.; Muthui, Z.W.
Titanium (IV) oxide (TiO2) has gained much attention due to its application in technologies such as optoelectronics, electronics, sensors, photocatalysts, and sustainable energy generation. However, its optical absorption falls in the ultraviolet part of the electromagnetic spectrum, resulting in a low absorption ratio of solar light. In addition, rapid electron-hole recombination limits its photocatalytic activity. To extend the application range of TiO2, the structural and chemical properties can be modified by adding various dopants to tune its electronic structure for applications within a wider range of the solar energy spectrum and ideally extend towards the visible region, which forms the dominant part of the solar energy spectrum. In this study, the structural and electronic properties of three polymorphs of TiO2 have been studied using density functional theory (DFT) as implemented in the Quantum ESPRESSO simulation package. )e exchange-correlation potential has been treated with the generalised gradient approximation (GGA). Cationic substitution with non-toxic alkaline earth metal dopants Mg and Ca has been carried out with the aim of modifying the electronic structure of the polymorphs of TiO2. On 1–4% Mg and Ca cationic substitution, there is a slight expansion of the optimal unit cell volume and modulation of the band gap energy by raising the valence band maximum to higher energies. In addition, dopant inter and intra-band states are observed.
Adsorption of Lead (II) Ions from Aqueous Solutions Using Mangroves Roots (Rhizophora Mucronata) Charcoal-Carbon Nanotubes Nanocomposite
(Journal of Multidisciplinary Engineering Science and Technology (JMEST), 2021) Ngugi, Fidelis; Mwangi, Joel; Njagi, Eric; Ombaka, Ochieng
Providing clean and affordable water to meet human needs is a grand challenge of the 21st century. Worldwide, water supply struggles to keep up with the fast growing demand, which is exacerbated by population growth, global climate change, and water quality deterioration. Nanotechnology holds great potential in advancing water treatment to improve water treatment efficiency. In this study, Mangrove Roots Charcoal and Carbon Nanotubes (MRCCNTs) nanocomposite was synthesized and utilized as a novel adsorbent for the removal of lead ions from aqueous solutions. The efficacy of MRC-CNT nanocomposites was investigated in batch mode which involved the effects of pH, temperature, concentration of the lead ions, adsorbent mass and contact time on adsorbates removal. Characterization of the adsorbent was carried out by Scanning Electron Microscopy (SEM) to observe the morphology of the adsorbent and surface area analysis and Energy Dispersive X-ray spectroscopy (EDX) to determine the elemental composition of the adsorbent. Adsorption isotherm models and adsorption kinetic studies were used for data analysis. It was observed that the removal efficiency of Pb (II) ions depended on pH of solution and the maximum efficiency was noticed at pH 7 with adsorption capacity of 3.629 mg/g which was calculated by the Freundlich isotherm model. Kinetic studies were well suited and found in good agreement with pseudo-second order. The results indicated that MRC-CNT nanocomposites would be a promising adsorbent for adsorption of Pb (II) ions from aqueous solutions.
Adsorption of rhodamine b from aqueous solution using mangroves (Rhizophora mucronata) carbon nanotubes nanocomposites
(www.allsubjectjournal.com, 2021) Ngugi, Fidelis; Mwangi, Joel; Njagi, Eric; Ombaka, Ochieng
The use of dyes has increased dramatically and uncontrollably in last few decades. Different types of dyes are frequently employed in plastics, paper, cosmetics, leather, and textile industries for coloring purposes. These dyes are released in water as effluents, which are of low Biological Oxygen Demand (BOD) and high Chemical Oxygen Demand (COD). Some of these dyes also are toxic and carcinogenic in nature. This study report on the synthesis of Mangroves Roots-Carbon Nanotubes (MRC-CNT) nanocomposite as an adsorbent for efficient removal of Rhodamine B (Rh. B) dye from aqueous solution. Effect of contact time, initial concentration of dye, pH, and shaking speed on adsorption behavior were systematically investigated. The data obtained were fitted into Langmuir, Freundlich, Dubinin-Rudishkevich (D-R), and Temkin adsorption isotherm models for evaluation of adsorption parameters. The results indicated that MRC-CNT nanocomposite would be a promising adsorbent for adsorption of Rh. B from aqueous solutions.
Analysis of Volatility of Real Exchange Rate and Exports in Kenya using the Garch Model: 2005:2012
(2015) Mohammed, Mustapha Wasseja *; Mwenda, Samwel N. 1; Musundi, Sammy W., 2; Njoroge, Elizabeth 2
Abstract The real exchange rate has proven to be an important factor in international trade because it is expected that exports respond to real exchange rate movements with respect to the characteristics of the importing and exporting countries. Exchange rate volatility increases uncertainty of profits on contracts denominated in foreign currency and subsequently dampens trade and economic growth. This study investigated how real exchange rate volatility affected exports of key Kenyan commodities to the European Union and United Kingdom, namely; tea, coffee and horticulture to the European Union. The presence of exchange rate volatility was determined using the GARCH model. A Bounds testing and Autoregressive Distributed Lag model was used to establish the presence of a long run relationship between exchange rate volatility and commodity exports. Findings revealed that exchange rate volatility affected tea exports to the UK and horticulture exports to the European Union. Foreign income played an important role in explaining tea and coffee exports to the UK and EU respectively. (PDF) ANALYSIS OF THE VOLATILITY OF REAL EXCHANGE RATE AND EXPORTS IN KENYA USING THE GARCH MODEL: 2005-2012.. Available from: https://www.researchgate.net/publication/298212379_ANALYSIS_OF_THE_VOLATILITY_OF_REAL_EXCHANGE_RATE_AND_EXPORTS_IN_KENYA_USING_THE_GARCH_MODEL_2005-2012 [accessed Dec 04 2019].
. Application of banach space ideal properties in image transmission over wireless network
(2014-03) Musundi, S. Wabomba,; Ombaka, C. Ochieng,; Njogu, S. Muriuki,; Muthengi, Fredrick M.
The Banach space operator ideals and nuclear maps have a large class of morphisms which behave as if they were part of a compact closed category, that is, they allow one to transfer variables between the domain and the codomain. We use the concept of nuclearity in functional analysis to establish application aspect of Banach space ideal properties in the transmission of image over wireless network based on the embedded system.
APPLICATION OF DESIRABILITY FUNCTION FOR OPTIMIZATION OF MULTIPLE RESPONSES OF WATERMELON USING ORGANIC MANURE
(2018) Muriithi, D.K.
Field experiment was conducted at horticultural research and teaching farm of Chuka University to evaluate the responses of watermelon to organic manure using Central Composite Design (CCD) to formulate optimal organic manure that maximizes growth and yield of watermelon. The objective was to optimize the multiple responses of watermelon to organic manure using desirability function. A 5-level-3-factor central composite design was employed where optimization required 20 experimental runs. The parameters assessed were vine length, number of branches per plant and fruit weight of watermelon. A statistical model of the second-order that best fits the data was used to achieve the objective. Desirability function approach for simultaneous optimization of several response variables was adopted in this study. The findings revealed that the process was well optimized, because the indices were very close or equal to the condition great value of one. The study found that the optimal values of watermelon responses are 93.73 t/ha of fruit weight at maturity, 9 branches/plant and vine length of 225.43 cm at 8 weeks. Based on the findings of the present study, it was recommended that farmers in the study area apply 17.64 t/ha, 11.17 t/ha and 18.05 t/ha of poultry, goat and cow manure, respectively, for increased growth and yield of watermelon. Further research may be commissioned with CCD, Box–Behnken and Doehlert design approach to plan the experiments for growth and yield of watermelon with an overall objective of optimizing the responses (such as number of fruits per plant and number of leaves per plant) of watermelon to organic manure (poultry manure, goat manure, rabbit manure and donkey manure). The study exemplified that the development of statistical models for crop production can be useful for predicting and understanding the effects of experimental factors.
Automation of pressure and temperature measurements in vacuum deposition systems
(2013-08) Tuwei, A. K.; Kirimi, P. M.; Njogu, S. M.
This paper describes a simple automated instrumentation and measurement system that is designed to offer a more reliable and fast method of measuring temperature and pressure, in thin film deposition systems. The designed computer based measuring system was based on thermocouple type K temperature sensor, MP20C-01-F2 pressure sensor, parallel port for interfacing and LabVIEW driver for accessing data. The system was able to measure ultaneously when implemented in Edward Auto 306 Magnetron Sputtering System and stored these values in a computer memory, hence retrieved at operator’s will. It had a temperature and a temperature error of ± 0.2 %. However, the designed system recorded varied pressure errors. In higher vacuum, pressure range of 1.0 x10-2 to 1.0 mbar, the mbar, the error of 0.5 % was observed. These errors were within acceptable range and therefore, the system is viable to be used in thin film deposition systems to automate the measurement of process parameters: temperature and pressure to achieve high quality thin films.
Calorific Value and Moisture Content Of Selected Solid Wastes at Chuka University
(IJRP.ORG., 2020-04-02) Kanogo Thuo, Daniel; Kamweru Kuria, Paul
Solid waste, which typically consists of metals, plastics, glasses, paper, wood, and organics, is generated and accumulated due to human day to day activities. The waste often leads to ecological pollution unless an appropriate solid waste management system is applied. Remarkably, solid waste can be channeled into a very useful form to generate energy leading to the reduction of the use of fossils fuels which are rapidly becoming limited, reduction of wastes in dumping sites and also be an additional source of energy. For such ventures though, the amount of energy that can be recovered from burning solid waste needs to be determined. In this work, solid waste samples were collected, classified, sundried, powdered and sieved using a sieve of size 500µm. The percentage moisture content of fruits waste, animal dung, and yard trimming & vegetables were found to be 33, 48, and 55 % respectively. The fruits waste had the highest calorific value of 104,130.91J/g, followed by the animal dung with 95,804.13 J/g and the least was yard trimming and vegetables with 95,100.39 J/g. The average specific energy content is 98345.14 J/g.
Characterization and classification of clay minerals for potential applications in Rugi Ward, Kenya
(2016) Ombaka, Ochieng
The applications of various clayey minerals are related to their structural, physical and chemical characteristics. The physical and chemical properties of the clayey minerals dictate their utilization in the process industries and beneficiation required before usage. The study aimed at establishing the potentiality of clayey minerals from the study area, and the possibility of exploring and exploiting them in order to spur industrial development and promote economic self reliance of Kenya as a nation. The plasticity, particle size, surface area, chemical and mineralogy composition, morphological, thermal analysis and other physical properties were studied using various techniques. The clay samples composed of albite (5-16.7%), kaolinite (11.4-36.2%), microcline (15.2-35.3%), quartz (24.3-68.1%), hornblende (7.6% in samples from Ngamwa only), and other mineral impurities in small amounts. Ngamwa clayey materials consist of high impurities of chemical oxides such as TiO2, MnO, MgO and Fe2O3. Generally, quartz and iron were the major impurities present in the samples from the concerned sites. The findings shows that clayey minerals from the study area can be exploited for commercial production of ceramic products after beneficiation using low cost and environmental friendly techniques in order to reduce the levels of iron, quartz, and other impurities to acceptable levels.
A Comparative study of the transmission parameters of the sound of mosquito predators and EMR”
(2012) Mang’are, P. A. 1; Maweu, O. M. 2; Ndiritu, F. G. 3; Vulule, J. M. 3
The wide bandwidth EMR ultrasound, exploited in mosquito repellency, yielded only 20 % effectiveness. Due to this wide bandwidth, ultrasound from Amolops tormotus and Coleura afra, mosquito predators, was investigated. The sound was recorded, filtered and anaysed by Avisoft software; transmission parameters determined and compared with those of EMR. Spectrogram analysis showed harmonics, FM and CF components. The fundamental frequency of A. tormotus and C. afra sound was 5.371 kHz and 6.836 kHz respectively. The bandwidth of unfiltered sound of A. tormotus and C. afra was 10.98 kHz and 17.71 kHz respectively. The maximum peak amplitude of unfiltered sound of A. tormotus and C. afra was 135.19 dB SPL and 134.97 dB SPL; maximum acoustic energy was 19.57 Pa2s and 35.80 Pa2s respectively. Maximum acoustic energy of A. tormotus and C. afra sound was 10.843 Pa2s and 14.857 Pa2s recorded in 35-60 kHz and 10-34 kHz ranges respectively. Optimum acoustic parameters included 58.5 kHz peak frequency, 12.32-10.84 Pa2s acoustic energy, 19.40-19.85 kHz bandwidth, 55.13-55.48 kHz and 34.66-44.26 kHz as mean maximum and minimum frequency respectively, 134.08-134.28 dB SPL peak amplitude and 132.06-133.27 dB SPL minimum peak amplitude; bandwidth significantly narrowed from EMR. These parameters are critical in realizing effective EMR.
Concentration of Inorganic Contaminants in Shallow Borehole Water in Chuka Sub-County, Kenya
(Journal of Chemical, Biological and Physical Sciences, 2020-11-24) M. Rugendo, Edith; C. Njagi, Eric; Ombaka, Ochieng
Groundwater from shallow aquifers is an important source of portable water in Chuka Sub-County. However, most shallow boreholes in Chuka Sub-County are undocumented and susceptible to contamination by both geogenic and anthropogenic activities. This study was conducted to evaluate the quality of shallow boreholes water in Chuka Sub-County. Samples were collected from twenty boreholes in Chuka Sub County during the dry and wet seasons. The temperature, pH and conductivity were determined in situ using a meter. The concentration of cations was determined using ICP-MS. The concentrations of anions were determined using standard APHA analytical methods. The temperatures and conductivities of borehole waters were within the limits set by KEBS and WHO. The pH of water in most boreholes during the wet season was within the limits set by KEBS and WHO for portable water. However, borehole water at Karandini (T15) was highly acidic (pH of 3.95) during the wet season. During the dry season, borehole waters were slightly acidic (4.42 - 6.44) except for the borehole at Ndagani market (T11), whose water was alkaline (pH = 8.75). The concentrations of trace and toxic cations and anions (NO3 - , SO4 2- , Cl and PO4 3- ) were within the limits set by KEBS and WHO. However, the concentration of nitrate in several boreholes during the dry season was within the range that cause chronic health effects. Groundwater from most boreholes in Chuka Sub-County is generally safe for domestic uses but require regular monitoring for quality.
Conjecture of banach space operator ideals in nuclear spaces
(2013-06) Wabomba, Musundi S.; Ombaka, C. Ochieng; Njogu, S. Muriuki; Muthengi, Fredrick; Mugambi, Dennis; Aywa, Shem O.
We apply the notion of Banach space operator ideals in nuclear spaces through topological vector spaces. The motivation for this study came from attempts to generalize the structure of nuclear spaces as a result of nuclear maps from functional analysis context. The compact closed structure associated with the category of relations results to nuclear ideals. Basic properties of Banach space operator ideals in relation to the structure of nuclear spaces will be demonstrated. We therefore establish a close correspondence between Banach space operator ideals and nuclear ideals through topological vector spaces.
Correlation Between Electromagnetic Wave Equation And Einstein Theory Of Relativity In Derivation Of Schrödinger Equation And Hilbert Space Operators
(Journal of Multidisciplinary Engineering Science Studies (JMESS), 2020-03) Mbatha M., Elizabeth; Musundi W., Sammy; Kamweru K., Paul
Operators in Hilbert space have properties which are useful in the study of mathematical abstract areas such as approximation theory, Banach Fixed point theory, the spectral theory as well as Quantum Mechanics. Schrödinger equation is a fundamental entity with many applications in Quantum Mechanics. This equation was initially derived by applying the knowledge of electromagnetic wave function and Einstein theory of relativity. Later, it was derived by applying the knowledge of Newtonian mechanics. It was also derived by extending the wave equation for classical fields to photons and simplified using approximations consistent with generalized non-zero rest mass. However, from the existing literature no study has been done on deriving Schrödinger equation using properties of Hilbert space operators. In this study, Hilbert space operators that include unitary operators, self adjoint operators and compact operators, norms of linear operators, Hilbert Schmidt operator, normal operators together with Lebesque Integral, Neumann Integral and spectrum are used in place of the existing concepts of electromagnetic wave function, Einstein theory of relativity and approximation consistent with generalized non zero mass to derive the Schrödinger equation. The derivation of Schrödinger equation and its application using Hilbert space operators enhances a better understanding of the concept of Schrödinger equation. The results of this work can further find use in quantum mechanics as well as in mathematical operator theory.
Correspondence of Fixed-Point Theorem in 𝑻𝟐, 𝑻𝟑 − 𝑺𝑷𝑨𝑪�
(Asian Research Journal of Mathematic, 2024-09-19) Amos Koros a , Musundi Sammy Wabomba a* and Mark Okongo
Fixed-point theory (FPT) has lot of applications not only in the field of mathematics but also in various other disciplines. Fixed Point Theorem presents that if 𝑇: 𝑋 → 𝑋 is a contraction mapping on a complete metric space (𝑋, 𝑑) then there exists a unique fixed point in 𝑋. FPT is also essential in game theory, in this case Brower Fixed Point has an application in game theory specifically in non-cooperative games and existence of Equilibrium. In particular, a game is a set of actions done by the participants defined by a set of rules. This is commonly described using mathematical concepts, which offers a concrete model to describe a variety of situations. On the other hand, the separation axioms 𝑇𝑖 , 𝑖 = 0,1,2,3,4 are vital properties that describes the topological spaces 𝑇0 , 𝑇1 , 𝑇2, 𝑇3 and 𝑇4 . It is noted that a 𝑇3 − 𝑠𝑝𝑎𝑐𝑒 is a generalized version of 𝑇2-space and since various results on application of fixed point theory in game theory on an arbitrary locally convex 𝑇2 − space has been established, in this study we sort to extend this concept to the general 𝑇3 − 𝑠𝑝𝑎𝑐𝑒. The utilization of a symmetric property of Hausdorff space established that if two continuous commutative mappings are defined on a 𝑇3 − 𝑠𝑝𝑎𝑐𝑒, then the two maps achieves unique fixed points.
Crystal Structures of Half-Sandwich Ru(II) Complexes, [(η6-p- Cymene)(3-chloro-6-(1H-pyrazol-1-yl)pyridazine)Ru(X)]BF4, (X = Cl, Br, I)
(MDPI, 2022) Mambanda, A.; Ongoma, P.; Gichumbi, J.; Omondi, R. O.; Hunter, L. A.; Kanyora, A. K.
Herein, we report the synthesis and single-crystal X-ray structures of three (η6-p-cymene)Ru(II) tetrafluoroborate salts, viz., [(η6-p-cymene)(3-chloro-6-(1H-pyrazol-1-yl)pyridazine)Ru(X)]BF4, (X = Cl, Br, I), Ru1-3. They were prepared by the reactions of [(η6-p-cymene)Ru(µ-X)(X)]2, (X = Cl, Br, I) with two-mole equivalents of 3-chloro-6-(1H-pyrazol-1-yl)pyridazine, under inert conditions at ambient temperatures, and subsequently precipitated by the addition of excess BF4− ions. Orange crystalline precipitates were obtained in good yields, from which the respective single crystals for X-ray diffrac- tion analysis were recrystallized by slow evaporation from their methanolic/diethyl ether solutions. The Ru(II) complexes were characterized by various spectroscopic techniques and chemical meth- ods, which included FTIR, 1H/13C NMR, UV-visible absorption, mass spectrometry, and elemental analysis. The molecular structures were solved by single-crystal X-ray crystal diffraction analysis. The complexes crystallized in the monoclinic crystal system in the P21/c (Ru1-2) and P21/n (Ru3) space groups. Density Functionals Theoretical (DFT) calculations were performed in methanol to gain an understanding of the electronic and structural properties of the complexes. Trends in the data metrics were established, and selected data were compared with the diffraction data. The electrophilicity indices of Ru1-3 follow the order Ru3 > Ru2 > Ru1, and the trend is in line with their anticipated order of reactivity towards nucleophiles.
Density functional study of structural and electronic properties of Ca and Mg doped TiO2
(Journal of Environmental Sustainability Advancement Research, 2022) Mbae, J. K.; Muthui, Z. W.
The scarcity of affordable and environment-friendly sources of energy has led to emergence of photocatalysis to mitigate this problem. This is especially so if the photo catalysts are active in as much a wide region of the solar energy spectrum as possible. Environment-friendly, non-toxic and economical photocatalysts would find application in water treatment, providing another solution to the problem of clean water for domestic use. Of many materials available for photocatalysis is Titanium (IV) oxide (TiO2). It possesses many merits such as low cost, high photocatalytic activity, non-toxicity and high availability. However, drawbacks that limit its application include its optical absorption that falls in the ultraviolet part of the electromagnetic spectrum and rapid electron-hole recombination, which limits its photoquantum efficiency. To extend the optical absorption to a wider region of the solar energy spectrum, various dopants have been added to the oxide. In this study, the effect of doping rutile TiO2 with alkaline earth metals Ca and Mg is investigated using the Density Functional Theory (DFT) method as implemented in the Quantum ESPRESSO simulation package, treating the exchange correlation potential with the Generalised Gradient Approximation. The optimized cell parameters for pure rutile crystal system are 𝑎 = 𝑏 = 4.603Å 𝑐 = 2.992Å, with a volume of 63.393 (Å)3 . On doping there is a slight expansion of the crystal structure and its volume slightly increases by 8.753 (Å) 3 and 28.816 (Å) 3 with Mg and Ca doping respectively. The calculated band gap of undoped rutile is 1.8 eV. Mg and Ca doping raises the valence band edge by 0.2 eV in both Ca and Mg doped rutile. Dopant inter band and intra band states are observed that would be useful in mitigating against charge recombination hence enhancing the efficiency of the photocatalysts. Isolated O 2p states are observed in the Projected Density of States (PDOS) of the doped systems which are normally attributed to enhanced optical absorption of photocatalysts in the visible region. Alkaline earth metal doping of TiO2 rutile modifies the structural and electronic properties of rutile TiO2 in a manner that would make it a more efficient photocatalyst. Co-doping with the alkaline metal dopants could be attempted to investigate the combined effect
Determination of Hall Effect Parameters of Gallium Arsenide and Gallium Manganese Arsenide by Van Der Pauw Geometry
(2012) Kemei, S.K*; Kirui, M.S.K.,; Ndiritu, F.G.,; Odhiambo, P.M.,; Ngumbu, R.G.,; Amollo, T.A .
Gallium Arsenide (GaAs) has been used widely in electronic industry to make diodes and transistors. As a semiconductor, it can be doped up with impurities with magnetic properties such as manganese to increase its electron conductivity. The storage capacity of the electronic devices made of gallium manganese arsenide (Ga1-xMnxAs) and the proportion of manganese atoms is worth studying. Here, GaAs was doped at different manganese levels, x, and the charge carrier concentrations at varied applied magnetic fields was investigated using Van der Pauw configuration. The tests were conducted at room temperature of 230C with magnetic field, 0.9 ≤ B ≤ 3.6mT and direct current of 1.19A. All the samples were studied for their hall voltage VH, carrier mobility µ, hall resistivity ρH and charge carrier concentration for different values of x. It was determined for Ga1-xMnxAs, 10% ≤ x ≤ 20% range, has maximum hall resistivity at B≈ 1.9 mT. For x=10%, 44.0 . ρ H ≈ Ω m ; x=20%, 79.0 . ρ H ≈ Ω m and for x=1%, the applied magnetic field has no effect on hall resistivity at initial states until B≈1.7mT. Beyond this point, magnetic field increases linearly with the hall resistivity to a maximum of 72.0 . ρ H ≈ Ω m . Maximum hall resistivity for x=50% was 2596.0 . ρ H ≈ Ω m at B mT ≈ 0.9 . For 0 20% ≤ ≤ x , carrier mobility µ , was of order of 7 2 1 1 10 m V s − − − while for x = 50% , µ was of order 9 2 1 1 10 m V s − − − . It was found out that the most probable doping percentage of GaAs with Mn dopants is approximately 20% and 10% as they show a hysteric response to an applied magnetic field. It suggests a good doping level of GaAs for making of volatile memory chips.
Determination of optical band gap and heat dissipation of Ga1-xMnxAs with Light in UV-VIS-IR Region using OSA SPECTRO 320”,
(International Knowledge Sharing Platform, 2012) Kemei, S. K* .,; Kirui, M.S.K.,; Ndiritu, F.G.,; Ngumbu, R.G.,; Odhiambo, P.M.,; Amollo, T.A.
Heat generated by silicon-based transistors due to high energy photo irradiation interferes with the electronic conductivity of transistors in the ICs. There is need to search for an alternative semiconductor material for making diodes and transistors with little or no heat dissipation. Dilute magnetic semiconductor such as Gallium Arsenide (GaAs) has demonstrated to be a better candidate to substitute silicon in electronic technology. UV-VIS-IR light was illuminated on the Ga1-xMnxAs samples of thickness 500nm−1000nm of varied doping levels during the study. Reflectance and transmittance spectra were determined using OSA SPECTRO 320 with light obtained from sodium lamp (240V, 100 W) with irradiance of 33.4807 W/m2 . The maximum absorbance within the UV-VIS-IR range was, A≤ 83.82% at λ≈200nm and minimum absorbance was, A≥0.96% at λ≈300nm with Ga1-xMnxAs, x=20% having the highest absorbance value and Ga1- xMnxAs, x=1%, the least absorbance. For Ga1-xMnxAs; x=0, x=10%, x=1% and x=20%; maximum absorbance occurred at UV region while for x=50%, maximum absorbance was observed at λ≈707nm. The results show that GaAs generate most heat due to its wide optical energy gap of 1.43eV while for x=1% dissipates little heat because of its small optical energy gap of 0.36eV.

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