Robust estimators incorporating voltage and current phasors from PMUs

EASL-Vol. 2 (2019), Issue 1, pp. 48–59 Open Access Full-Text PDF
Farhan Ammar Ahmad, Ibrahim Omar Habiballah
Abstract: State Estimation is the backbone of modern electric power system and is used by almost all Energy Management Systems (EMS) in the world to ensure the real-time monitoring and secure operation of a power system. Phasor Measurement Unit (PMU) is most popular meter in today’s electrical power industry because of its high refresh rates and measurement accuracy. Meanwhile, state estimation with only PMUs is not practical because of the very high initial installation cost. Consequently, the use of PMU meters along with conventional Supervisory Control and Data Acquisition (SCADA) meters can improve the performance of the state estimation. In this paper, phasor measurements (voltage and current phasors) are incorporated in two robust estimators: Weighted Least Absolute Value (WLAV) and Least Measurement Rejected (LMR). Further, we have investigated the importance of locating PMUs to save cost and improve the performance of state estimation. The performance of these two estimators after incorporating voltage and current phasors is investigated in terms of estimation accuracy of state variables and computational efficiency in the presence of different bad-data scenarios on IEEE-30 and IEEE-118 bus systems.
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A method to compute the determinant of square matrices of order five and six

OMS-Vol. 3 (2019), Issue 1, pp. 84–93 Open Access Full-Text PDF
Armend Salihu
Abstract: In this paper we present a new method to compute the determinants of square matrices of order 5 and 6. To prove the main results we have combined the Farhadian’s Duplex Fraction method and Salihu’s method to reduce the order of determinants to second order. Hence, this paper gives the possibility to develop a general method to compute the determinants of higher order.
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Box-Behnken design of quadratic model for Gas Metal Arc Welding (GMAW) and optimization analysis on desirability function

EASL-Vol. 2 (2019), Issue 1, pp. 38–47 Open Access Full-Text PDF
Kashif Nazir, Anwar Khalil Sheikh, Muhammad Asad Ahmad
Abstract: Gas Metal Arc Welding (GMAW) is one of those welding processes which is increasingly being used in many varieties of fabrication and manufacturing industries due to high production rate and ease of work such as fewer fumes/smoke and less time chipping slag. Important parameters which affect GMAW process are amperage, arc length, wire feed speed, welding speed and welding voltage. In this paper, we have focused and studied important controllable factor’s effects on depth of penetration, deposition efficiency, bead width and bead reinforcement to find best weld during welding in mobile or outdoor welding shop in stress and overloaded conditions by Box-Behnken design of quadratic model for GMAW process and optimization analysis on desirability function. Quality of welds is defined as “the level of perfection that welds exhibit pertaining to the entire volume of weldment as well as to the profile of weld surface appearance”. With reference to quality weld definition as defined above, the study is performed to find out the best welding condition whereas best weld is the weld with deposition efficiency value as larger the best, depth of penetration value with “larger the best”, bead width value “nominal the best”, discontinuities number per weld’s count value “smaller the best”. Productivity in term of quality is defined as an optimum blend of parameters which inevitably develop minimum or no defect then the process will result in high productivity. For given certain material and similar welding circumstances, our analysis has found the most optimal factor’s values for the similar condition of field data. This study will contribute welding research work in terms of points as described, firstly to enhance the knowledge of welding process and analysis by utilizing DOE along with desirability function, secondly ability to provide narrow window of weld process parameter to produce the quality weld and thirdly to study the GMAW process for mobile welding shop in the toughest condition such as the windy and dusty environment.
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Small convective motions of a visco-elastic fluid filling completely a container when the fluid is heated from below

OMA-Vol. 3 (2019), Issue 1, pp. 30–41 Open Access Full-Text PDF
Hilal Essaouini, Pierre Capodanno
Abstract: In this paper, we study the small oscillations of a visco-elastic fluid that is heated from below and fills completely a rigid container, restricting to the more simple Oldroyd model. We obtain the operatorial equations of the problem by using the Boussinesq hypothesis. We show the existence of the spectrum, prove the stability of the system if the kinematic coefficient of viscosity and the coefficient of temperature conductivity are sufficiently large and the existence of a set of positive real eigenvalues having a point of the real axis as point of accumulation. Then, we prove that the problem can be reduced to the study of a Krein-Langer pencil and obtain new results concerning the spectrum. Finally, we obtain an existence and unicity theorem of the solution of the associated evolution problem by means of the semigroups theory.
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On further results of hex derived networks

ODAM-Vol. 2 (2019), Issue 1, pp. 32–40 Open Access Full-Text PDF
Haidar Ali, Ammara Sajjad
Abstract: Topological indices are real numbers associated with molecular graphs of compounds that help to guess properties of compounds. Hex-Derived networks has an assortment of valuable applications in drug store, hardware, and systems administration. Imran et al. [1] computed the general Randić, first Zagreb, ABC, GA, ABC\(_{4}\), and GA\(_{5}\) indices for these hex-derived networks. In this article, we extend the work of [1] and compute some new topological indices of these networks.
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General Zagreb index of some cactus chains

ODAM-Vol. 2 (2019), Issue 1, pp. 24–31 Open Access Full-Text PDF
Nilanjan De
Abstract: The mathematical chemistry deals with applications of graph theory to study the physicochemical properties of molecules theoretically. A chemical graph is a simple graph where hydrogen depleted atoms are vertices and covalent bonds between them represent the edges. A topological index of a graph is a numeric quantity obtained from the graph mathematically. A cactus graph is a connected graph in which no edges lie in more than one cycle. In this study, we derive exact expressions of general Zagreb index of some cactus chains.
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K Banhatti and K hyper-Banhatti indices of nanotubes

EASL-Vol. 2 (2019), Issue 1, pp. 19–37 Open Access Full-Text PDF
Muhammad Shahzad Anjum, Muhammad Usman Safdar
Abstract: Nanomaterials are compound substances or materials that are produced and utilized at an exceptionally little scale. Nanomaterials are created to display novel attributes contrasted with a similar material without nanoscale highlights, for example, expanded quality, synthetic reactivity or conductivity. Topological indices are numbers related to molecular graphs that catch symmetry of molecular structures and give it a scientific dialect to foresee properties, such as: boiling points, viscosity, the radius of gyrations and so on. In this paper, we aim to compute topological indices of \(TUC_4[m,n]\), \(TUZC_6[m,n]\), \(TUAC_6[m,n]\), \(SC_5C_7[p,q]\), \(NPHX[p,q]\), \(VC_5C_7[p,q]\) and \(HC_5C_7[p,q]\) nanotubes. We computed first and second K Banhatti indices, first and second K hyper-Banhatti indices and harmonic Banhatti indices of understudy nanotubes. We also computed multiplicative version of these indices. Our results can be applied in physics, chemical, material, and pharmaceutical engineering.
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Unsteady Casson nanofluid squeezing flow between two parallel plates embedded in a porous medium under the influence of magnetic field

OMS-Vol. 3 (2019), Issue 1, pp. 59–73 Open Access Full-Text PDF
Gbeminiyi Sobamowo, Lawrence Jayesimi, David Oke, Ahmed Yinusa, Oluwatoyin Adedibu
Abstract: This paper investigates the squeezing flow of an electrically conducting magnetohydrodynamic Casson nanofluid between two parallel plates embedded in a porous medium using differential transformation and variation of parameter methods. The accuracies of the approximate analytical methods for the small and large values of squeezing and separation numbers are investigated and established. Good agreements are established between the results of the approximate analytical methods are compared with the results numerical method using fourth-fifth order Runge-KuttaFehlberg method. However, the results of variation of parameter methods show better agreement with the results of numerical method than the results of differential transformation method. Thereafter, the developed approximate analytical solutions are used to investigate the effects of pertinent flow parameters on the squeezing phenomena of the nanofluids between the two moving parallel plates. The results established that the squeezing number and magnetic field parameters decrease as the flow velocity increases when the plates were coming together. Also, the velocity of the nanofluids further decreases as the magnetic field parameter increases when the plates move apart. However, the velocity is found to be directly proportional to the nanoparticle concentration during the squeezing flow i.e. when the plates are coming together and an inverse variation between the velocity and nanoparticle concentration is recorded when the plates are moving apart. As increased physical insights into the flow phenomena are provided, it is hope that this study will enhance the understanding the phenomena of squeezing flow in various applications such as power transmission, polymer processing and hydraulic lifts.
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Review of isolation enhancement with the help of theory of characteristic modes

EASL-Vol. 2 (2019), Issue 1, pp. 12–18 Open Access Full-Text PDF
Farhan Ammar Ahmad
Abstract: Multiple-input-multiple-output (MIMO) antennas performance can be degraded due to the poor isolation between the MIMO antenna elements. In this paper, we present a review of the different isolation enhancement schemes available in the literature. Empirically the isolation between the antennas can be improved by placing the antenna as far as possible and it can be enhanced further by introducing different isolation enhancement schemes. Theory of characteristic modes (TCM) was recently proposed that has useful benefits. TCM is also used to enhance the isolation. Moreover, this papers focus on the different approaches of TCM, to enhance the isolation.
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