Volume 15 – Issue 2

In the present paper, we find a surface family possessing the natural lift of a given curve as a common asymptotic curve. We express necessary and sufficient conditions for the given curve such that its natural lift is an asymptotic curve on any member of the surface family. We present important results for ruled surfaces. Finally, we illustrate the method with some examples.

In this study,some interesting results about the original timelike curve were obtained depending on the assumption that the natural lift curves should be the integral curve of the geodesic spray on the tangent bundle T(S^3_1 ) and T(H^3_0)

In the process of devising better and better sieves for generation of prime numbers, the efforts gradually lead to the classical Sieve of Eratosthenes. The main theme of Sieve of Eratosthenes is that while deciding primality of a positive integer, it is altogether unnecessary to test composite numbers for divisibility. This along with additional property that even numbers other than 2 are never prime, generates refined versions of all; standing on the top of as many as 15 earlier sieves

The aim of this paper is to describe an efficient numerical method for solving system of two-point boundary value problems subject to the Dirichelet boundary conditions. We present the construction of Numerov type method by assuming extra continuity condition on the solution. The order of the propose method is quadratic. This propose method is suitable for solving an obstacle problems. We have considered an obstacle problem and solved by the propose method to illustrate the efficiency and the accuracy. Results are compared with the other methods.

In this paper, we derive certain relations between the integral of the incomplete generalized beta function and the complete version, which will also hold for the standard beta function. These results lead to relations for the generalized beta function and hence the standard beta functions. In particular, it is showed that the difference between the function with first variable shifted by any integer and that of the function with the first variable shifted by one is the same as the corresponding difference for the second variable.

This article is a collection of a few interesting applications on finite groups and morphisms of groups, applications which already have been given to undergraduate’s international and national contests, some of them using only basic ideas of modern and abstract algebra. Students studying algebra in school will obviously go further, as will those who are interested in one or more of the applications. The aim of this paper is to sustain students studying algebra and improve their ability to handle abstract ideas.

The superalloy Hastelloy G30 (trademark of Haynes International, Inc.) is an alloy with a high proportion of nickel, characterized by a high corrosion resistance in environments containing extra oxidizing acids. The alloy consists essentially of 43% of nickel with a proportion of chromium which varies from 28 to 31.5% and from 13 to 17% for iron. Its matrix is austenitic and its structure is face-centered cubic. The objective of this work is to treat the alloy G30 thermally at 4 different temperatures 700 °C, 800 °C, 900 °C and 1000 °C for 3 hours. Indeed, we followed the progression of structural and mechanical properties. The micro structural evolution influence slightly on the mechanical properties of the alloy G30: hardness of the alloys treated at 700 °C and 800 °C is equal to 46 HRF and that of the alloys treated at 900 °C and 1000 °C is 46.25 HRF. The images obtained by optical microscopy revealed the presence of carbides at the joints and inside the grains .The X-ray diffraction spectra obtained after the isothermal treatments showed the presence of peaks of the precipitates and the peaks of the austenite phase.

Grapes and grape products are important sources of fiber, nutrients and minerals to the human body. For example, zinc and copper are two elements that are found in all parts of grapes (seeds, pulp, skins). In optimal concentrations, they are beneficial. If, however, it exceeds the daily dose of zinc (overdose), can occur several adverse reactions in the stomach (heartburn, nausea), tiredness, weakness. Copper overdose can lead to poor absorption of other essential minerals for the body (iron, calcium, magnesium, etc.). The aim of this study is to analyze the level of Zn and Cu in Vitis Vinifera L. grapes fruits and soil from the Murfatlar city, Constanta, Romania. These elements were quantified by flame atomic absorption spectrometry (FAAS) after the chemical mineralization of the samples with nitric acid and hydrogen peroxide in a Digesdahl device. It can be noticed that the values of cooper and zinc concentrations from both kind of samples (grapes and soil) were lower than the recommendable maximum limit of these metals in fruits respectively soil.

Distillation is one of many processes that can be used for water purification. This process consists in heating water directly by the solar radiation in a closed enclosure covered with glazing. The produced vapor, which condenses on the colder glazing and slightly inclined, east collects in gutters. The principle is very simple, reliable and does not require any maintenance. But its output is relatively weak, 4 to 6 liters/day. In this research we have developed a new design of a greenhouse solar distiller with parabolic trough in order to increase the performance of the distiller and subsequently obtaining a important distillate flow.

For the analyze of communication we need to study the main parameters that describe the vocal sounds from the point of view of information content transfer efficiency. In this paper we analyze the physical quality of the “on-air” information transfer, according to the audio streaming parameters and from the particular phonetical nature of the human factor. Applying this statistical analyze we aim to identify and recording the correlation level of the acoustical parameters with the vocal ones and the impact which the presence of this cross-correlation can have on the communication structures improvement.