<p style='text-indent:20px;'>The paper surveys, classifies and investigates theoretically and numerically main classes of line search methods for unconstrained optimization. Quasi-Newton (QN) and conjugate gradient (CG) methods are considered as representative classes of effective numerical methods for solving large-scale unconstrained optimization problems. In this paper, we investigate, classify and compare main QN and CG methods to present a global overview of scientific advances in this field. Some of the most recent trends in this field are presented. A number of numerical experiments is performed with the aim to give an experimental and natural answer regarding the numerical one another comparison of different QN and CG methods.</p>

Tourism is one of the fastest growing branches of the Serbian economy in which much potential is recognized, but still largely underutilized. The level and manner of potential utilization is currently inadmissibly low, without any clear indicators which would point out a problem-solving progression plan. Business entities from the tourism sector are constantly exposed to unpredictable market changes and to the impact of the business environment in which the level of competition is constantly increasing. In addition to strengthening their own internal environment in order to prevent stagnation in following market trends, tourist organizations in Serbia pay great attention to the limiting factors that are imposed by the state administration and local self-government. For this reason, there is a lot of effort to ensure an unhindered business process and the possibility of obtaining assistance from the state of Serbia, or the cities in which tourist organizations operate. In order to ensure that Serbian tourism doesn't turn into a missed opportunity, systemic solutions are needed. The paper gives a modest contribution to tourism business in Serbia. The authors described the environmental factors in which business entities in the industry operate, as well as the ways in which the factors influence tourist demand. The paper puts emphasis on Tourist Organizations (TO) and as an example, it presents the case study of Tourist Organization of Vranje -city in Eastern Serbia. SWOT analysis points to the possibility of achieving better operations of this tourist organization indicating that such business practices could be applied to other tourist organizations in Serbia.

Natural phenolic compounds are significant component of the human diet, as they are present in fruits and vegetables, and they have very important biological activity in the living organisms. Because of their structure, they are subject of numerous oxidation processes, such as autoxidation, but are easily to oxidize in presence of various oxidizing agents and enzymes. Many authors have been investigating phenolic oxidation processes, and have successfully identified their pathways and a significant number of intermediates and products generated by these processes. Also, particular attention has been made to the effects of these processes on food quality and other biological processes in living organisms. Phenols are persistent pollutants of water systems from various agricultural activities and industrial wastewater discharges. It is known that the presence of phenolic compounds in water supplies and industrial effluents directly affects natural processes in the environment due to their toxicity and natural ability to decompose. This property, to easily oxidize and, as a result of it, to mineralize, is practically useful for the treatment of the wastewaters, so it is of global concern to manage the best technology to remove phenols and other organic pollutants, assisted with the oxidation processes. In the aspect of treatment of wastewaters polluted with phenols, we reviewed oxidative processes such as autoxidation, enzyme-catalyzed oxidation, photo-oxidation, electrochemical oxidation and oxidation by Fenton's reagent and, based on the literature data, we presented advantages and disadvantages of these processes compared to each other.