Applied Physics

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Applied Physics

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Seismic hazard assessment in Eastern and Southern Africa.
(ANNALI DI GEOFISICA,, 1999-12) Midzi, Vunganai; Hlatywayo, Dumisani J.; Chapola, Lostina S.; Kebede, Fekadu; Atakan, Kuvvet; Lombe, Daniel K.; Turyomurugyendo, Gadi; Tugume, Fred Alex
Seismic hazard assessment for the Eastern and Southern Africa region was done using the probabilistic approach. Seismic hazard maps for 10% exceedance in 50 years, 10% exceedance in 100 years, as well as for 50 and 100 years return periods were prepared using the FRISK88M software. The area involved covers a wide region bounded by latitudes 400 S-25°N and longitudes 100E and 55°E. Input parameters for the computations were obtained using the recent earthquake catalogue compiled by Turyomurugyendo. The catalogue which covers the time period 627-1994, contains earthquakes within the area bounded by 400 S-25°N and 100 E-55°E, with homogeneous magnitudes (M). Since a Poisson model of earthquake occurrence is assumed, dependent events were cleaned from the catalogue. Attenuation relations for the Eastern and Southern Africa region based on the strong motion data are virtually non-existent. However, attempts have been made recently by Jonathan 'and Twesigomwe to establish an average attenuation relation for the region. These relations were used in the computations. Possible uncertainties in the attenuation relations were accounted for using the logic-tree formalism. The results are presented in seismic hazard maps in terms of Peak Ground Acceleration (PGA) for the mean and the 85th percentile. The distribution ofPGA values indicate relatively high hazard along the EastAfrican rift system. In the northern segments of the rift system, they exceed 250 gals for 10% probability of exceedence in 50 years.
In vitro monitoring of rabbit anterior cruciate ligament damage by acoustic emission.
(Medical Engineering Physics, 2000-06) Azangwe, Godfrey
Anterior cruciate ligament (ACL) rupture is a major clinical problem leading to instability and degeneration of the knee joint. The problem is compounded by the limited ability of the ACL to heal when ruptured. The existing knowledge regarding the way the ACL ruptures is limited, and this investigation is an attempt to understand the nature of the ruptures using the rabbit as a model. A total of 16 rabbit tibia–ACL–femur complexes were stretched in tension to complete rupture. Four specimens were stretched to failure at a displacement rate of 0.5 mm/min and 12 specimens at 10 mm/min. Acoustic emission (AE) transducers were placed on both the tibia and the femur, and stress wave signals generated during the tensile test were recorded. Fibre fractures produced the highest amplitude signals with a relatively longer rise time. Other failure modes such as matrix failure and debonding produced lower amplitude signals with shorter rise times. We also noted that few events were recorded during the initial period of tensile loading (the elastic phase). The activity then increased significantly after maximum load was reached. The location information provided by the acoustic emission system was consistent with the final site of rupture. We have shown that AE can be used to characterise ligament damage, with fibre pull-outs and fibre fracture producing the highest signal amplitudes.
On a New 4-Vector Cosmological Field Theory.
(arXiv, 2005-05-05) Nyambuya, G. G.
The original Dirac Equation is modified in the simplest imaginable and most trivial manner to include a universal 4-Vector Cosmological Field term in the space and time dimensions. This cosmological field leads to a modified Dirac Equation capable of explaining why the Universe appears to be made up chiefly of matter. It is seen that this 4-Vector Cosmological Field is actually a particle field and this particle field can possibly be identified with the darkmatter and darkenergy field. Further, this 4-Vector Cosmological Field is seen to give spacetime the desired quantum mechanical properties of randomness. Furthermore, it is seen that in the emergent Universe, the position coordinates of a particle in space – contrary to the widely accepted belief that the position of a particle in space has no physical significance, we see that that opposite is true – namely that the position of a particle has physical significance. We further note that the 4-Vector Cosmological Field modification to the Dirac Equation leads us to a vacuum model redolent but differrent from that of Quantum Electrodynamics (QED). This new vacuum model is without virtual particles but darkparticles. We dare to make the suggestion that these darkparticles may possibly explain the current mystery of what really is darkmatter and darkenergy.
Optics education in a developing country.
(Society of Photo-optical Instrumentation Engineers, 2005-10-24) Jonathan, Enock.
An optics laboratory plays a critical role in optics education. A major challenge for optics educators in Africa is the shortage or non-availability of laboratory teaching equipment. Optics teaching equipment is beyond the budget of most universities in the developing world such as the new National University of Science and Technology in Zimbabwe. The paper details a successful strategy - local fabrication/assembling of optics laboratory teaching aids - adopted by the Applied Physics Department at Zimbabwe's National University of Science and Technology. Students and technical staff under the guidance of an academic member of staff do equipment fabrication and assembling. The paper describes some of the project-type set-ups for performing experiments on (1) laser light scattering and impurity determination; (2) industrial imaging inspection (3) light transmission and reflection and (4) refractive index measurement
Unified Field Theory – Part II of Paper I: Gravitational, Electromagnetic, Weak & the Strong Force.
(C. Roy Keys Inc, 2008) Nyambuya, G. G.
New Curved Spacetime Dirac Equation-On the Anomalous Gyromagnetic Ratio.
(Springer Science+Business Media, LLC, 2008-07) Nyambuya, G. G.
I propose three new curved spacetime versions of the Dirac Equation. These equations have been developed mainly to try and account in a natural way for the observed anomalous gyromagnetic ratio of Fermions. The derived equations suggest that particles including the Electron which is thought to be a point particle do have a finite spatial size which is the reason for the observed anomalous gyromagnetic ratio. A serendipitous result of the theory, is that, two of the equation exhibits an asymmetry in their positive and negative energy solutions the first suggestion of which is clear that a solution to the problem as to why the Electron and Muon – despite their acute similarities - exhibit an asymmetry in their mass is possible. The Mourn is often thought as an Electron in a higher energy state. Another of the consequences of three equations emanating from the asymmetric serendipity of the energy solutions of two of these equations, is that, an explanation as to why Leptons exhibit a three stage mass hierarchy is possible.
The Twin Paradox Revisited and Reformulated-On the Possibility of Detecting Absolute Motion
(arXiv, 2008-09-06) Nyambuya, G. G.; Ngobeni, M.D.
The famous twin paradox of the Special Theory of Relativity by Einstein (1905) is revisited and revised. This paradox is not a paradox in the true sense of a paradox but a reflection of a misunderstanding of the problem and the Principle of Relativity. The currently accepted solution to this takes into account the accelerations and deceleration of the traveling twin thus introducing an asymmetry that solves the paradox. We argue here that, with the acceleration and deceleration neglected, the problem is asymmetric hence leading to the same conclusion that the traveling twin will age less than the stay at home. We introduce a symmetric twin paradox whose solution can not be found within the currently accepted provinces of the STR if one adopts the currently accepted philosophy of the STR namely that it is impossible for an inertial observer to determine their state of motion. To resolve this, we present (in our modest view) a simple and convincing argument that leads us to conclude that it must be possible for an inertial observer to determine their own state of motion. With this, we are able to solve the symmetric twin paradox. The fact that it is possible for an inertial observer to determine their state of motion – brings us back to the long rejected idea of an all pervading and permeating medium – the Aether, namely the Lorentz luminiferous Aether. An experiment capable of validating or invalidating this claim is suggested.
On the Origins of the Stellar Initial Mass Function: Azimuthally Symmetric Theory of Gravitation (III)
(2009) Nyambuya, G. G.
In this reading, a new theoreticalmodel of star and cluster formation is posited. Thismodel seeks to set a mathematical framework to understand the origins of the stellar Initial Mass Function and within this framework, explain star and cluster formation from a unified perspective by tieing together into a single garment three important observational facts: (1) that the most massive stars of most observed clusters of stars are preferentially found in their centers; (2) Larson’s 1982 empirical observation that the maximum stellar mass is related to the total mass of the parent cloud; (3) that clump masses in giant molecular clouds exhibit a power mass spectrum law akin to that found in star clusters and this behavior is also true for molecular clouds as well. Key to this model is the way the cloud fragments to form cores from which the new stars are born. We show that the recently proposed azimuthally symmetric theory of gravitation has two scale of fragmentation where one is the scale that leads to cloud collapse and the other is the scale on which the cloud fragments. The collapse and fragmentation takes place simultaneously. If the proposed model is anything to go by, then, one can safely posit that the slope of the IMF can be explained from two things: the star formation rate of the cores from which these stars form and the density index describing the density profile. Additionally and more importantly, if the present is anything to by, then, fragmentation of molecular clouds is posited as being a result of them possessing some spin angular momentum.
Dirac Equation for General Spin Particles Including Bosons
(National University of Science & Technology, 2009) Nyambuya, G. G.
We demonstrate (show) that the Dirac equation – which is universally assumed to represent only spin 1/2 particles; can be ma- nipulated using legal mathematical operations – starting from the Dirac equation – so that it describes any general spin particle. If our approach is acceptable and is what Nature employs, then, as currently obtaining, one will not need a unique and separate equation to describe particles of different spins, but only one equation is what is needed – the Gen- eral Spin Dirac Equation. This approach is more economic and very much in the spirit of unification – i.e., the tie-ing together into a single unified garment – a number of phenomenon (or facets of physical and natural reality) using a single principle, which, in the present case is the bunching together into one theory (equation), all spin particles into the General Spin Dirac Equation.
Azimuthally SymmetricTheory of Gravitation (I) On the Perihelion Precession of Planetary Orbits
(arXiv, 2009-12-15) Nyambuya, G. G.
From a purely none-general relativistic standpoint,we solve the empty space Poisson equation(∇2Φ=0) for an azimuthally symmetric setting, i.e., for a spinning gravitational system like the Sun. We seek the general solution of the formΦ = Φ(r,θ). This general solution is constrained such that in the zeroth order approximation it reduces to Newton’swell known inverse square law of gravitation. For this general solution, it is seen that it has implications on the orbits of test bodies in the gravitational ﬁeld of this spinning body. We show that to second order approximation,this azimuthally symmetric gravitational ﬁeld is capable of explaining at least two things (1) the observed perihelion shift of solar planets (2) that the mean Earth-Sun distance must be increasing–this resonates with the observations of two independent groups of astronomers(Krasinsky&Brumberg 2004; Standish 2005) who have measured that the mean Earth-Sun distance must be increasing at a rate of about7.0±0.2m/cy (Standish 2005) to 15.0±0.3m/cy (Krasinsky&Brumberg 2004).In-principle,we are able to explain this result as a consequence of loss of orbit alangular momentum–this loss of orbit alangular momentum is a direct prediction of the theory.Further,we show that the theory is able to explain at a satisfactory level the observed secular increase Earth Year (1.70±0.05ms/yr; Miuraet al. 2009). Furthermore, we show that the theory makes a signiﬁcant and testable prediction to the effect that the period of the solar spin must be decreasing at a rate of at least8.00±2.00s/cy.
Lepton Generation Problem Some Properties and Implications of the Curved Space Time Dirac Equation ( Curved Spacetime Dirac Equation II).
(arXiv, 2010-01-22) Nyambuya, G. G.
Where three new Curved Spacetime Dirac Equations have been derived mainly to try and account in a natural way for the observed anomalous gyromagnetic ratio of fermions and the suggestions is that particles including the Electron, which is thought to be a point particle, do have a finite spatial size and this is one of the reasons for the observed anomalous gyromagnetic ratio. Combining the idea in Nyambuya (2008) which lead to the derivation of the three new Curved Spacetime Dirac Equations, and the proposed Unified Field Theory (Nyambuya 2007), a total of 12 equations each with 16 sub-components are generated thus leading to a total of 192 equations for the Curved Spacetime Dirac Equation. Some symmetries of these equations are investigated, i.e., the Lorentz symmetry, charge conjugation symmetry (C), time reversal symmetry (T), Space reversal (P) and a combination of the C, P&T-symmetries. It is shown that these equations are Lorentz invariant, obey C-symmetry and that some violate T and P-symmetry while others do not and that they all obey PT-symmetry. These symmetries show (or modestly said – seem to suggest) that anti-particles have positive mass and energy but a negative rest-mass and the opposite sign in electronic charge. Through the inspection of these symmetries, a suggestion is (here) made to the effect that the rest-mass of a particle must be related to the electronic charge of that particle thus leading us to a possible resolution of whether or not Neutrinos do have a none-zero rest-mass. Additionally, we demonstrate that these equations have the potency to explain naturally the observed lepton generation phenomena.
On the Radiation Problem of High Mass Stars.
(arXiv, 2010-03-10) Nyambuya, G. G.
A massive star is defined to be one with a mass greater than 8 - 10M . Central to the on-going debate on how these objects [massive stars] come into being is the so-called Radiation Problem. For nearly forty years now, it has been argued that the radiation field emanating from massive stars is high enough to cause a global reversal of direct radial in-fall of material onto the nascent star. We argue that only in the case of a non-spinning isolated star does the gravitational field of the nascent star overcome the radiation field. An isolated non-spinning star is a non-spinning star without any circumstellar material around it, the gravitational field beyond its surface is described exactly by Newton’s inverse square law. The fact that massive stars should have their gravitational field being much stronger than their radiation field is drawn from the analysis of an isolated massive star, where in this case the gravitational field is much stronger than the radiation field. This conclusion is erroneously extended to the case of massive stars enshrouded in gas & dust. We find that, for the case of a non-spinning gravitating body where we take into consideration the circumstellar material, that at 8 - 10M , the radiation field will not reverse the radial in-fall of matter but a stalemate between the radiation and gravitational field will be achieved – i.e., in-fall is halted but not reversed. This picture is very different from the common picture that is projected and accepted in the popular literature that at 8 - 10M , all the circumstellar material – from the surface of the star, right up to the edge of the core; is expected to be swept away by the radiation field. We argue that massive stars should be able to come into being if the molecular core from which they form exhibit some rotation because a rotating core exhibits an ASGF which causes there to be an equatorial accretion disk and along this equatorial disk, the radiation field can not be much stronger than the gravitational field hence this equatorial accretion disk becomes the channel via which the nascent massive star accretes all of its material.
Are Flyby Anomalies an ASTG Phenomenon? (ASTGII)
(arXiv, 2010-05-10) Nyambuya, G. G.
This reading expounds with expediency on the recently proposed Azimuthally Symmetric Theory of Gravitation(ASTG) set-up earlier. At its inspection,it was demonstrated that the ASTG is capable (among others solar anomalies) of explaining the precession of the perihelion of solar planets. In the present, we show that the ASTG is capable of explaining the puzzling observation of ﬂyby anomalies, i.e. the anomalous asymptotic speed increases of the osculating hyperbolic speed excess. It is shown that these ﬂyby anomalies occur naturally in the ASTG. We derive the empirical formula proposed by Andersonet al. in 2008,which up to now has no physical or foundational basis except that experience suggest it. If the ASTG model is correct,then for the ﬁrst time the Andersonet al.formula is given a physical meaning.
The longitudinally excited continuous wave CO2 laser
(LAP LAMBERT Academic Publishing, 2010-10) Baricholo, Peter
Bipolar Outﬂows as a Repulsive Gravitational Phenomenon –Azimuthally SymmetricTheory of Gravitation (II)
(arXiv, 2010-10-18) Nyambuya, G. G.
This reading is part in a series on the Azimuthally Symmetric Theory of Gravitation (ASTG) set-out in Nyambuya (2010a). This theory is built on Laplace- Poisson’s well known equation and it has been shown therein (Nyambuya 2010a) that the ASTG is capable of explaining – from a purely classical physics standpoint; the precession of the perihelion of solar planets as being a consequence of the azimuthal symmetry emerging from the spin of the Sun. This symmetry has and must have an influence on the emergent gravitational field. We show herein that the emergent equations from the ASTG – under some critical conditions determined by the spin – do possess repulsive gravitational fields in the polar regions of the gravitating body in question. This places the ASTG on an interesting pedal to infer the origins of outflows as a repulsive gravitational phenomena. Outflows are an ubiquitous phenomena found in star forming systems and their true origins is a question yet to be settled. Given the current thinking on their origins, the direction that the present reading takes is nothing short of an asymptotic break from conventional wisdom; at the very least, it is a complete paradigm shift as gravitation is not at all associated; let alone considered to have anything to do with the out-pour of matter but is thought to be an all-attractive force that tries only to squash matter together into a single point. Additionally, we show that the emergent Azimuthally Symmetric Gravitational Field from the ASTG strongly suggests a solution to the supposed Radiation Problem that is thought to be faced by massive stars in their process of formation. That is, at 8 - 10M , radiation from the nascent star is expected to halt the accretion of matter onto the nascent star. We show that in-falling material will fall onto the equatorial disk and from there, this material will be channelled onto the forming star via the equatorial plane thus accretion of mass continues well past the curtain value of 8-10M albeit via the disk. Along the equatorial plane, the net force (with the radiation force included) on any material there-on right up-till the surface of the star, is directed toward the forming star, hence accretion of mass by the nascent star is un-hampered.
Dielectric barrier discharge CO2 TEA laser operated at frequencies up to 400 Hz
(SA Institute of Physics, 2011) Baricholo, Peter; Stehmann, Timo; Rohwer, Erich G.; Collier, M.; Hlatywayo, Dumisani J.; Von Bergmann, Hubertus M.
A dielectric barrier discharge CO2 TEA laser excited by a thyratron driven power supply has been developed and characterized. Laser output was observed at frequencies up to 25 Hz for an electrode separation of 10 mm with 1.8 mm suprasil glass covering the electrodes. At this gap separation, pulsed power output of about 9 W was detected for gas pressures between 100 and 400 mbar. The laser has a pulse duration was about 0.3 flS with a risetime of ~100 ns. Changing the electrode separation to 5 mm and using 1.4 mm suprasil glass dielectric increased the output power to 23 Wand enabled laser output to be observed at gas pressures up to 700 mbar and maximum pulse excitation frequencies of up to 400 Hz. The developed laser does not require water cooling since the system operates in burst pulse mode.
Spin-density-wave behaviour of the (Cr100-xAlx)95Mo5 alloy system
(SAIP, 2011) Muchono, Blessed; Prinsloo, A.R.E.; Sheppard, C.J; Alberts, H.L.; Strydom, A.M.
Electrical resistivity, Seebeck coefficient and specific heat measurements on a (Cr100-xAlx)95Mo5, 0 8.1 at.% Al alloy system are reported. The results indicate two possible quantum critical points in the magnetic phase diagram of this system. One is an incommensurate spin-density-wave – paramagnetic quantum critical point situated at 1.5 at.% Al and the other a paramagnetic – commensurate spin-density-wave critical point at 5 at.% Al. We forward experimental evidence that this system harbours two spin-density-wave related quantum critical points which presents an unusually rich case study for magnetic quantum criticality of the itinerant kind.
Magnetic behaviour of the Cr-Al alloy system around the triple point
(South African Institute of Physics, 2011) Sheppard, C.J; Prinsloo, A.R.E.; Alberts, H.L.; Strydom, A.M.; Muchono, Blessed
Electrical resistivity and specific heat measurements on a series of Cr1-xAlx (0 ≤ x ≤ 0.034) alloy single crystals are reported. The results indicate that the triple point, where the incommensurate and commensurate spin-density-wave phases coexist with the paramagnetic phase, is situated close to T = 0 K on the magnetic phase diagram.
Influence of gas discharge parameters on emissions from a dielectric barrier discharge excited argon excimer lamp.
(AOSIS Open Journals., 2011-11) Baricholo, Peter; Hlatywayo, Dumisani J.; Von Bergmann, Hubertus M.; Stehmann, Timo; Rohwer, Erich G.; Collier, M.
A dielectric barrier discharge excited neutral argon (Ar I) excimer lamp has been developed and characterised. The aim of this study was to develop an excimer lamp operating at atmospheric pressure that can replace mercury lamps and vacuum equipment used in the sterilisation of medical equipment and in the food industry. The effects of discharge gas pressure, flow rate, excitation frequency and pulse width on the intensity of the Ar I vacuum ultraviolet (VUV) emission at 126 nm and near infrared (NIR) lines at 750.4 nm and 811.5 nm have been investigated. These three lines were chosen as they represent emissions resulting from deexcitation of excimer states that emit energetic photons with an energy of 9.8 eV. We observed that the intensity of the VUV Ar2* excimer emission at 126 nm increased with increasing gas pressure, but decreased with increasing excitation pulse frequency and pulse width. In contrast, the intensities of the NIR lines decreased with increasing gas pressure and increased with increasing pulse frequency and pulse width. We have demonstrated that energetic VUV photons of 9.8 eV can be efficiently generated in a dielectric barrier discharge in Ar.
On a Theoretical Proof of the Weak Equivalence Principle from within the confines of Newtonian Gravitation.
(arXiv, 2011-11-17) Nyambuya, G. G.
The great Italian scientist and philosopher, Galileo Galilee, is reported to have stood at the learning tower of Pisa in Italy and famously dropped objects of different masses (and compositions), thereby demonstrating that the motion of matter in a gravitational field is independent of the body’s composition since these objects, despite their different masses (and compositions), their free-fall time was practically equal. By so doing, Galileo demolished a more than one and a half millennium of dogma that had been set forth by the Greek philosopher, Aristotle, namely that, in a gravitational field, heavier objects fall faster than lighter ones. Galileo’s conclusion is a posteriori justified current scientific dogma, we all accept this as a durable fact of experience. Gently and modestly, this reading appears to furnish this hypothesis. We unambiguously demonstrate beyond any shadow of doubt that Newtonian gravitation implies that gravitational and inertial mass are equal.

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