Volume 19 – Issue 2

In the present paper, we find a surface family possessing the natural lift of a given timelike curve as a geodesic in Minkowski 3-space. We express necessary and sufficient conditions for the given curve such that its natural lift is a geodesic on any member of the surface family. Finally, we illustrate the method with some examples.

We establish a generalization of Ptolemy’s theorem and we also deduce Ptolemy’s inequality and its strengthened version from this generalization.

In this paper, the D – Pencil surface is studied in Minkowski 3-space. By using Darboux Frame in Minkowski space, we give the necessary and sufficient condition for a pencil surface. Then, we obtain general conditions of each other different G1 , G2 , G3 developable ruled surface with the line of curvature of the pencil surface. Finally, we construct the corresponding surfaces which possessing some representative curves as lines of curvature

This study deals with the generalized linear Volterra-type functional integro-differential equations with mixed delays. A combination between matrix-collocation method and Morgan-Voyce polynomials is developed to solve these type equations. In addition, an error analysis technique is given to improve the obtained solutions. Numerical examples are performed to confirm the efficiency and validity of the method. The comparisons are made in tables and figures. The discussions show that the method is fast and precise.

The notion of ideal convergence in 2–normed spaces was defined and studied by Gürdal [1] for single real sequences. After Gürdal work Saeed Sarabadan and Sorayya Talebi [2] defined and studied the notion of ideal convergence in 2–normed spaces for double sequences. The space of all double sequences of σ–bounded variation has been defined and studied by Vakeel [3]. In this present article we are working on to connect the above two studies and define some new spaces double sequences of σ–bounded variation in 2–normed spaces using the moduli F= (f_ij) and some others operators as well. Further, we study basic topological and algebraic properties and prove some inclusion relations on these spaces.

This paper is devoted to generate new numerical solutions of the generalized equal width wave (GEW) equation with Subdomain finite element method based on quartic B-splines over finite elements. Accuracy and efficiency of the proposed method is demonstrated by employing propagation of single solitary wave. L2 and L error norms are used to measure differences between the analytical and numerical solutions and also, three invariants I1; I2 and I3 have been calculated to determine the conservation properties of the presented algorithm. Fourier stability analysis of the linearized scheme shows that it is unconditionally stable. Numerical experiments prove the correctness and durableness of the method which can be further used for solving such problems.

In this paper, we implemented an improved tanh function Method for some exact solutions of (3+1)-dimensional Shallow water wave equation and (2+1)-dimensional fifth-order nonlinear equation.

The purpose of this study is to develop a Bezier spline in Minkowski 3 space called by the Timelike Bezier spline. In this paper firstly, we investigate the Frenet frame, curvatures and derivative formulations at the starting and end points of the Timelike Bezier Spline. Moreover, we obtain the derivative formulas of the Bishop frame and the curvatures according to the Bishop frame at starting and end points of the Timelike Bezier spline in Minkowski 3-space. Consequently we give some examples for this concept.

In this paper, we have introduced a new kind of variational inequality and offered its solution by proposing generalized weakly relaxed  -pseudomonotonicity and generalized weakly relaxed  -semi-pseudomonotonicity of set-valued map. The KKM theorem has been instrumental in proving the existence results. We also present the solvability of our proposed problem with weakly relaxed  -semi-pseudomonotone set-valued maps in arbitrary Banach spaces using Kakutani-Fan-Glicksberg fixed point theorem.

The object of this work is to contribute to the development of bicomplex numbers. For this purpose, in this study we firstly introduced bicomplex numbers with coefficients from complex Fibonacci sequence. And then, using Babadag’s work [1], we examined the dual form of the newly defined numbers. Moreover, we gave some fundamental identities such as Cassini and Catalan identities provided by the elements in defined sequence

The number of students enrolled in the technological studies has seen a downward trend in recent years, with significant decreases in the field of natural resource and environmental protection specialization. This paper uses the theory of Markov chains to forecast the number of students enrolled in pre-university education, upper secoundary, by groups of studies and profile. Knowing future trends allow an appropriate educational strategy based on reality and the requirements of the labor market.

The interrelationship of pathogenicity between urinary tract infections and chronic kidney disease is an incompletely debated issue. In chronic kidney disease, a variety of quite different substances (uremic toxins, betaine, amino acids, creatinine, urea, glucose) influence the microbial environment by biochemical changes. The study was performed in one year period on a group of 105 patients admitted in a Nephrology Department, with urinary tract infection in the presence or absence of CKD. In the group with UTI and CKD, predominated females in the postmenopausal period, especially in CKD stages with higher severity. Analyzing the recurrent UTIs and deaths we have found the presence of advanced age, female gender, pre-existing kidney disease, diabetes mellitus, hemodialysis and a large number of multi-resistant urinary microbial strains. The use of mathematical relationships allowed us to make some correlations between CKD evolution with or without UTI. However, having a small group of patients over one year period with less few subgroups of demographic, causal, comorbidity and biological factors, risk factors for reinfection or death has sometimes made it impossible to interpret mathematically the data obtained from the retrospective observational study.

Bisphosphonates are medicines used to inhibit osteoclastic activity in a number of bone diseases (Paget’s disease, osteoporosis, hypercalcemia, primary and secondary hyperparathyroidism, bone metastases). Following in vitro release studies, crystalline hydroxyapatite (HA) was found to be a stable phase in contact with the release medium, and alendronate (AL) bound to HA by the synthesis process was slowly released from the metallic component (titanium) into the release medium for 10 days. Hydroxyapatite after implantation produces chemical species that support the adhesion of the implant to the surrounding tissue forming a functional connective structure. Thus synthesis of the HA-AL composite can be considered as a viable solution for the inclusion of bisphosphonate on the surface of metallic prosthetic components used in orthopedics.

. In this paper, we found three mathematical models that show the shear shear speed dependence on the shear stress. Experimental data for one type of coconut oil were used to calculate the accuracy the proposed models. Equation constants were determined by exponential beast curves obtained at different shear rates using the program Origin 6.0. The correlation coefficients thus obtained varied between 0.9595 and 0.9999.

Supramolecular chemistry, one of the topical fields of contemporary chemistry, deals sometimes with subtle interactions, sophisticated molecules, and huge molecular aggregates. Furthermore, many terms such as molecular self-assembly, mechanically-interlocked molecular architectures, container-molecule, and cryptand, may sound abstract and sometimes discouraging. The purpose of this paper is to show how a chemistry teacher can scrutinize supramolecular chemistry in terms of everyday chemistry. Four directions which can help to a better understanding of this domain are identified and analyzed. Simple synthetic procedures for most of the supramolecular receptors, the occurrence of supramolecular chemistry in Nature, the connection between supramolecular chemistry and life itself (self-assembly of nucleic acid bases) are useful examples for emphasizing the versatility of this domain. Last, but not least, the presence of supramolecular chemistry in food, drugs, drinks, tobacco-based products, homecare products, cosmetics, are relevant examples of how this concept is present in everyday life

Amide compounds have an important role in various human activity domains. The aim of the paper is to determine the structural descriptors that influence the antimicrobial activity of the studied amide derivatives. With the help of the structure-activity correlation method and molecular docking, we have identified the atoms in the molecule that have a greater contribution to the formation of the antimicrobial activity. In the case of the studied molecules, the nitrogen atoms in the azole nucleus are highlighted, the results being supported also by the 2D diagrams of the applied docking method.

Various plastic materials are used in candies packaging and most of them have inorganic pigments used in inks and plastics that can contaminate the food. Heavy metals, such as copper and chromium can pose health problems. Aim of the study was to determine the levels of Cu and Cr from different samples of candies and also from candy packages using standard addition method and flame atomic absorption spectrometry. The determination of the total metals concentration in the investigated samples was done after sample mineralization step, using two methods of digestion: the acid digestion method and the dry ash method. The calibration curves were obtained using solutions prepared by diluting stock solutions with deionized water to the desired concentrations. The recovery studies were carried out in triplicate for replicates of spiked samples. Results were satisfactory, with recoveries between 98 and 101% indicating the high accuracy of the method. The smaller concentrations of metals were observed in candy packages than in candies. The average highest level of Cu was recorded in apple candies. To appraise the health risk associated with heavy metal contamination of the studied products, estimated daily intake of metals (EDIM) was calculated. Data generated during the study was processed by means of various statistical tests, such as t test and the One-Way ANOVA. Results show that the mean concentration for all the elements was significantly different (α= 0.05) for all samples. The concentrations of Cu and Cr in candies and their packaging do not exceed the permissible limits.

t. Pure and Manganese doped Sodium Hexa-titanates (Na2Ti6-xMnxO13 where x = 0.0, 0.04, 0.08, 0.12) were synthesized using solid state reaction method. X-ray diffraction pattern reveals single phase and exhibit monoclinic structure of pure and doped samples. Morphologies of all synthesized materials have been studied using SEM. Photocatalytic behaviour of these samples have also been studied and found that on increasing the exposure time the suspension of methlyne blue graduadually decreases under the UV-exposure and finally beacmes almost colorless after ceratin time.

In the selection of special alloys, account must be taken of their particular physico-mechanical properties such as breaking strength and plasticity much higher than the resistance of conventional alloys and last but not least relative corrosion resistance, especially if these alloys are used in the aeronautical industry. This paper presents the results of electron microscopy research on a sample taken from an aluminum 2024 (AU4G1) used for the aeronautical industry.

Within many years microelectronics developed based on p-n junctions made of germanium or silicon, namely on homojunctions (BJT). In this case the main technological difficulty was to control the level of doping concentrations. Semiconductor structures were obtained by the variation of type and concentration of the doping impurities. A new phase of the evolution of the semiconductor devices is the manufacturing and large scale using of heterojunctions. Heterojunction is the contact of two semiconductors, different according to the chemical composition, existing in a single crystal. Within this contact not only the energetic areas structure varies, but also the effective body of the carriers, their mobility and other parameters. The possibility of variation of these parameters allows the manufacture of unique devices that have record performance. Heterojunction bipolar transistors (HBT) have the following benefits: static gain in current, high cutting frequency, high speed of conversion, low temperature running. The aim of my study is transit time study through the base in case of drift transistors

The present study is carried out to examine the effect of chemical reaction on unsteady flow of a viscous, incompressible and electrically conducting fluid past an impulsively started vertical cylinder with variable temperature and mass diffusion in the presence of transversely applied uniform magnetic field. The temperature and concentration level near the surface increase linearly with time. The governing equations of nondimensional form of flow model have been solved numerically using Crank-Nicolson implicit finite difference method. The velocity profile is discussed with the help of graphs drawn for different parameters like thermal Grashof number, mass Grashof number, Prandtl number, chemical reaction parameter, the magnetic field parameter, Schmidt number and time. The numerical values obtained for skin-friction, Nusselt number and Sherwood number have been tabulated. We found that the values obtained for velocity, concentration and temperature are in concurrence with the actual flow of the fluid.

The distribution of electric microfields influences many elementary processes in plasma as well as governs a number of its optic properties. It is well known that the Holtsmark distribution was first used for plasma microfields. Because the stars are consisting of plasmas, the Holtsmark distribution may give valuable information to the astrophysicists. With this spirit in mind, we have proposed an analytical expression for the calculation of Holtsmark distribution. The obtained results show that our approximation is in good agreement with literature data. The proposed method can be easily applied in plasma physical and astrophysical studies.

This paper proposes a control strategy, on each direction, based only on brain impulses of a mobile robot with tracks. In this respect it is used a neural headset able to read user’s brain impulses. The system is composed of: tanks chassis, 12V DC motor equipped with drivers, Bluetooth module HC-05, microcontroller Arduino mega 2560, RGB LEDs and neural headset Neurosky mind wave mobile. The added value of the paper consists in building a board using Arduino Mega 2560 for controlling the mobile robot. It integrates hardware devices for the command of 12V motor through driver motor, four RGB LEDs indicating the direction enabled. It receives data from Neurosky neural headset, through Bluetooth module.