This study was conducted to reveal what Memrise, an online vocabulary study tool, can offer to upper-intermediate EFL learners compared to traditional vocabulary exercises in L2 vocabulary learning. Two groups of upper-intermediate learners (N=80) were randomly assigned to the experimental group and the control group and were given the Vocabulary Knowledge Scale, VKS for short, as the pre-test and post-test. The participants in both groups were exposed to the target vocabulary items in the same reading text. While those in the experimental group created list of target vocabulary items collaboratively in Memrise and then studied the sets individually, the learners in the control group did traditional vocabulary exercises. The results of the post-tests indicated that there was a significant difference between the control group and the experimental group in favor of the experimental group. The researchers discuss possible pedagogical implications of this significant finding for EFL vocabulary instruction.

The surface roughness of the end product is a very important indicator of laser cutting quality. The paper reports a comparison of surface roughness during CO2 laser cutting of tungsten alloy plate using oxygen as assist gas, based on control charts made by statistical process control (SPC) approach. Dependent variable is surface roughness, while independent variables are laser power and cutting speed. The control chart used within this paper is a variation of the ichart of experimental data samples, where using evaluation of moving range of the two consecutive values, in order to estimate value of standard error by average moving range and Hartley's constant d2. Applying the criteria often used in the SPC methods for the assessment of "out of control" situations, it may be inferred that the observed differences in surface roughness during CO2 laser cutting could be used to advice on the more appropriate laser power and cutting speed for the laser cutting quality. Keyword: laser cutting process; statistical process control; control chart; surface roughness; tungsten alloy This Publication has to be referred as: Begic-Hajdarevic, D[erzija]; Pasic, M[ugdim]; Vucijak, B[ranko] & Cekic, A[hmet] (2016). Statistical Process Control of Surface Roughness during CO2 Laser Cutting using Oxygen as Assist Gas, Proceedings of the 26th DAAAM International Symposium, pp.0247-0255, B. Katalinic (Ed.), Published by DAAAM International, ISBN 978-3-902734-07-5, ISSN 1726-9679, Vienna, Austria DOI:10.2507/26th.daaam.proceedings.034

The cut quality is of great importance during the laser cutting process. The quality of laser cut mainly depends on an appropriate selection of process parameters. In this paper, the effect of process parameters was analysed on the laser cut quality of an uncommon alloy, the tungsten alloy (W ≈ 92.5 % and the remainder Fe and Ni) sheet with thickness of 1 mm. This alloy has a wide application in different industrial areas, e.g. in medical applications, the automobile sectors, and the aircraft industry. This paper introduces a developed back-propagation artificial neural network (BP- ANN) model for the analysis and prediction of cut quality during the CO2 laser cutting process. In the presented study, three input process parameters were considered such as laser power, cutting speed and assist gas type, and two output parameters such as kerf width and average surface roughness. Amongst the 42 experimental results, 34 data sets were chosen for training the network, whilst the remaining 8 results were used as test data. The average prediction error was found to be 5.5 % for kerf width and 9.5 % for surface roughness. The results of the predicted kerf width and surface roughness by the BP-ANN model were compared with experimental data. Based on the results of the study, it was shown that the proposed artificial neural network model could be a useful tool for analysing and predicting surface roughness and kerf width during CO2 laser cutting processes.

This paper defines mathematical models during laser cutting that describe effects of certain processing regime parameters on values for surface roughness Ra and for width of heat affected zone HAZ. Cutting of high-alloyed steel 1.4864 (X13CrNiSi35-16), with thickness of s = 3 mm and 1.4541 (X6CrNiTi18-10), with thickness of s = 4 mm was performed by laser cutting using O2 and N2 as the assistance gas. For the definition of appropriate mathematical models, multiple linear regression analysis is used, with four independent variables that were varied at five levels. Following most influential cutting parameters were varied: cutting speed (V), assist gas pressure (p), focus position (fs) and stand-off (Nd). It is possible to sufficiently describe the effects of process parameters, with defined models in reliable way, on product quality and also to determine the best parameters of laser cutting of investigated high-alloyed steels.

This paper defines mathematical models of value changes for surface roughness (Ra, μm) and heat affected zone width (HAZ, mm) during high-alloyed steel 1.4828 laser cutting using oxygen as an assistance gas. For the definition of appropriate mathematical models, multiple linear regression analysis is used, with four independent variables that were varied at five levels. Following parameters are varied: cutting speed (V), assist gas pressure (p), focus position (fs) and stand-off (Nd). In comparison between the model and the experimental results, it can be concluded that the effects of specified parameters on cut quality, productivity and thus the legitimacy of this technology for cutting high-alloyed steels are well described by the obtained mathematical models. © 2015 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of DAAAM International Vienna.

A quality constructive solution can be considered one that ensures the proper functioning and reliability of the product with the least possible cost. Therefore, it is the main goal of every designer to obtain the required girder capacity with minimal material expense in the cross section design of a full plate girder. This ensures an optimal material participation in the overall price of the finished structure already in the initial stage of design. This paper presents the I-profile shape cross-section optimization at the overhead crane main girder, where the metal sheets stability calculation to buckling is made according to BAS/JUS U.E7.121/1986. The mathematical model is solved using the nonlinear programming method SUMT (sequential unconstrained minimization technique) where from the goal function with constraints, with introduction of the penalty function, a new function

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. © 2014 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of DAAAM International Vienna.