Abstract Laser beam machining (LBM) is one of the most widely used thermal energy based non-contact type advance machining process which can be applied for almost whole range of materials. This paper defines mathematical models for surface roughness prediction (Ra, μm) and width of heat affected zone (HAZ, mm) during laser cutting of alloy steels 1.4571 and 1.4828 with nitrogen as assist gas. For defining appropriate mathematical models multiple regression analysis is used with four independent variables. Following parameters are varied: cutting speed, focus position, nitrogen assist gas pressure and stand-off. Obtained mathematical models describe dependence of Ra and HAZ from varied process parameters.

Abstract The aim of this study is to determine the effect of teaching English vocabulary to 5th graders through music on their achievement in vocabulary, attitudes towards English course and retention of new words. While the students in the experimental group (n=28) were taught new vocabulary in the English syllabus through songs composed by the researchers, the students in the control group (n=28) were taught new vocabulary using the methods in the current English education program. The study was implemented for 12 weeks. At the end of the study, English Vocabulary Test developed by Koksal (2012) and attitude scale towards English course were administrated. A month later English Vocabulary Test was given to the students again as a retention test and data obtained were statistically analyzed. The experimental group in which music was utilized outscored the students in the control group both on the English Vocabulary test and English Vocabulary Retention test and also on the attitude scale.

Original scientific paper Machining system VBS was constructed and built at the Faculty of Mechanical Engineering in Sarajevo, for investigations of the phenomena in high speed milling. Since the requests for high speeds and accelerations of the main spindles and the transmitters for the feed motions require specific design and mechatronic solutions, this paper presents the selection of optimal design variety of components integrated in machining system VBS. The investigation of the effect of the cutting parameters on the cutting forces during high speed face milling (range of cutting speed from 750 m/min to 3000 m/min) was conducted on the machining system VBS. Investigations were carried out on hardened alloy steel EN 10083-3 (41Cr4). The results show that cutting force FR decreases by increasing cutting speed. Also the investigations show that the feed per tooth has significant effect upon the values of cutting forces. This paper further presents the mathematical model for calculating cutting force in high speed cutting. Experimental results are compared with calculation results.

Transmissive quarterwave retardation plates have been successfully fabricated recently using birefringent thin films (~3 μm thick) obtained by oblique-incidence deposition of metal oxides on glass slides.1 The desired retardance is acquired in one-way transmission through the film at normal incidence and the effect of (incoherent) multiple-beam interference was apparently negligible. In this paper light interference in a birefringent thin film deposited on a reflecting (typically metallic) substrate for normally incident coherent illumination is considered. The object is to design birefringent mirrors that function as quarterwave and halfwave retarders in normal-incidence reflection. For a given substrate at a given wavelength, the constraint on the birefringence, average refractive index, and thickness of the film so that quarterwave or halfwave retardation is attained at normal incidence is determined. A 2-D Newton-Raphson method is utilized to find all possible solutions. The sensitivity of a given design (i.e., the deviation from exact quarterwave or halfwave retardation) is calculated for given perturbations of the film parameters.