Interfacing heterogeneous PDM systems using the PLM Services

A PDM (Product Data Management) system allows improved management of the engineering process through better control of engineering data, engineering activities, engineering changes and product configurations. There are different commercial PDM systems and each company uses a PDM that supports the company’s needs. To collaborate with parts’ suppliers, companies frequently need to interface their PDM systems with those of their suppliers. There are two ways of interface: direct translation between PDM systems and translation based on a standard format. In this study two different PDM systems are interfaced based on the PLM Services standard of OMG (www.omg.org), which is itself based on Web Services. The PLM Services enables the data exchange via the Internet. The main objective of implementation is to use the PLM Services standard for PDM data exchange via Internet.     

Multi-objective Genetic Algorithms for grouping problems

Linear Linkage Encoding (LLE) is a convenient representational scheme for Genetic Algorithms (GAs). LLE can be used when a GA is applied to a grouping problem and this representation does not suffer from the redundancy problem that exists in classical encoding schemes. LLE has been mainly used in data clustering. One-point crossover has been utilized in these applications. In fact, the standard recombination operators are not suitable to be used with LLE. These operators can easily disturb the building blocks and cannot fully exploit the power of the representation. In this study, a new crossover operator is introduced for LLE. The operator which is named as group-crossover is tested on the data clustering problem and a very significant performance increase is obtained compared to classical one-point and uniform crossover operations. Graph coloring is the second domain where the proposed framework is tested. This is a challenging combinatorial optimization problem for search methods and no significant success has been obtained on the problem with pure GA. The experimental results denote that GAs powered with LLE can provide satisfactory outcomes in this domain, too.     

Monolithic Perovskite/Silicon Tandems with >28% Efficiency: Role of Silicon-Surface Texture on Perovskite Properties

Textured silicon wafers used in silicon solar cell manufacturing offer superior light trapping, which is a critical enabler for high-performance photovoltaics. A similar optical benefit can be obtained in monolithic perovskite/silicon tandem solar cells, enhancing the current output of the silicon bottom cell. Yet, such complex silicon surfaces may affect the structural and optoelectronic properties of the overlying perovskite films. Here, through extensive characterization based on optical and microstructural spectroscopy, it is found that the main effect of such substrate morphology lies in an altering of the photoluminescence response of the perovskite, which is associated with thickness variations of the perovskite, rather than lattice strain or compositional changes. With this understanding, the design of high-performance perovskite/silicon tandems is rationalized, yielding certified power conversion efficiencies of >28%.     

Measuring the efficiency of customer satisfaction and loyalty for mobile phone brands with DEA

The concept of customer satisfaction and loyalty (CS&L) has attracted much attention in recent years. A key motivation for the fast growing emphasis on CS&L can be attributed to the fact that higher customer satisfaction and loyalty can lead to stronger competitive position resulting in larger market share and profitability. Using a data envelopment analysis (DEA) approach, in this study we analyzed and compared CS&L efficiency for mobile phone brands in an emerging telecommunication market, Turkey. The constructs of European Customer Satisfaction Index (ECSI) model are treated and used as input and output indicators of our DEA model. Drawing on the perceptual responses of 251 mobile phone users, the DEA models reveal that from the top six mobile phone brands in Turkey, Nokia features as the most efficient brand followed by LG and Sonny Ericsson in terms of CS&L efficiency, while Motorola, Samsung and Panasonic rank as the least efficient brands.     

Lipid oxidation inhibiting capacities of blackseed essential oil and rosemary extract

Lipid oxidation is the main deterioration process that occurs in vegetable oils containing lipid molecules with polyunsaturation. The aim of the present study was to investigate the possible effects of blackseed (Nigella sativa L.) essential oil (BEO) and rosemary (Rosmarinus officinalis L.) extract (RE) on stabilization of sunflower oil under accelerated storage conditions. RE was obtained by soxhlet extraction using methanol, whereas BEO was hydrodistilled from the blackseed extract obtained by extraction using petroleum ether (b.p. 40–60°C). The results indicate that both extracts stabilize sunflower oil to a certain extent, the extent being greater with RE than with BEO based on measurements of peroxide value, p‐anisidine value, amount of nonoxidized linoleic acid in saponified oil samples by HPLC‐DAD, concentration of conjugated diene hydroperoxide, and UV light absorption. The oil stabilizing effect of BEO against lipid oxidation, especially at concentrations of 0.06 and 0.1 g/100 g oil was found to increase as the temperature increased, according to principal component analysis results. Based on its strong lipid oxidation inhibiting capacity, RE can be used as a potential natural extract for stabilizing sunflower oil against oxidation. BEO, at carefully selected concentrations, can be suggested as an alternative supplement of plant origin for improving oil stabilization. Practical applications: Sunflower oil is a widely used vegetable oil for cooking and frying, and has a high linoleic acid content of about 40–70%. Here we show that sunflower oil can be stabilized by adding rosemary and blackseed extracts. The treatment can be useful especially in applications which require heating the oil to high temperatures.     

An improved metric for measuring multi-item multi-level schedule instability under rolling schedules

Disruptions in material plans due to unrealistic schedules and frequent plan revisions are common symptoms of a phenomenon generally referred to as nervousness or schedule instability in literature. A number of instability measures had been proposed so far. However, none of them deals with instability measurement comprehensively. An appropriate measurement should be able to reflect the degree of changes under rolling schedules, as well as a tool for analyzing the performance of planning systems and nervousness dampening procedures.The intent of this paper is to present a new metric for measuring multi-item multi-level schedule instability under rolling schedules and to compare it with the previous measures in literature. The new metric composed of linear combination of four sub-instability measures separates quantity and timing changes for both scheduled receipts (SRs) and planned orders (PORs). The new metric is tested by a detailed numerical example taken from literature, and results of simulation studies under various experimental factors are presented at the end of the study.     

Automatic knot adjustment using an artificial immune system for B-spline curve approximation

Reverse engineering transforms real parts into engineering concepts or models. First, sampled points are mapped from the object’s surface by using tools such as laser scanners or cameras. Then, the sampled points are fitted to a free-form surface or a standard shape by using one of the geometric modeling techniques. The curves on the surface have to be modeled before surface modeling. In order to obtain a good B-spline curve model from large data, the knots are usually respected as variables. A curve is then modeled as a continuous, nonlinear and multivariate optimization problem with many local optima. For this reason it is very difficult to reach a global optimum. In this paper, we convert the original problem into a discrete combinatorial optimization problem like in Yoshimoto et al. [F. Yoshimoto, M. Moriyama, T. Harada, Automatic knot placement by a genetic algorithm for data fitting with a spline, in: Proceedings of the International Conference on Shape Modeling and Applications, IEEE Computer Society Press, 1999, pp. 162-169] and Sarfraz et al. [M. Sarfraz, S.A. Raza, Capturing outline of fonts using genetic algorithm and splines, in: Fifth International Conference on Information Visualisation (IV’01), 2001, pp. 738-743]. Then, we suggest a new method that solves the converted problem by artificial immune systems. We think the candidates of the locations of knots as antibodies. We define the affinity measure benefit from Akaike’s Information Criterion (AIC). The proposed method determines the appropriate location of knots automatically and simultaneously. Furthermore, we do not need any subjective parameter or good population of initial location of knots for a good iterative search. Some examples are also given to demonstrate the efficiency and effectiveness of our method.     

CCII-Based Grounded to Floating Immittance Converter and a Floating Inductance Simulator

A new circuit employing second-generation current conveyors (CCIIs), and unmatched resistors for converting a grounded immittance to the corresponding floating immittance with either positive or negative adjustable multiplier, is presented. Moreover, the proposed circuit can also realize a synthetic floating inductance employing a grounded capacitor depending on the passive element selection. Simulation results using 0.35 μ m TSMC CMOS technology parameters are given. Erkan Yuce was born in 1969 in Nigde, Turkey. He received the B.Sc. from Middle East Technical University and M.Sc. degrees from Pamukkale University in 1994 and 1998 respectively. He is a Ph.D. student at Bogazici University all in Electrical and Electronics Engineering. He is currently Research Assistant at the Electrical and Electronics Engineering Department of Bogazici University. His current research interests include analog circuits, active filters, synthetic inductors, and current-mode circuits. He is the author or co-author of about 10 papers published in scientific journals or conference proceedings. Oguzhan Cicekoglu was born in 1963 in Istanbul, Turkey. He received the B.Sc. and M.Sc. degrees from Bogazici University and the Ph.D. degree from Istanbul Technical University all in Electrical and Electronics Engineering in 1985, 1988 and 1996 respectively. He served as lecturer at the School of Advanced Vocational Studies Electronics Prog. of Bogazici University where he held various administrative positions between 1993 and 1999, and as part time lecturer at various institutions. He was with Biomedical Engineering Institute between 1999 and 2001. He is currently Associate Professor at the Electrical and Electronics Engineering Department of Bogazici University. His current research interests include analog circuits, active filters, analog signal processing applications and current-mode circuits. He is the author or co-author of about 150 papers published in scientific journals or conference proceedings. Oguzhan Cicekoglu is a member of the IEEE. Shahram Minaei received his B.Sc. degree in Electrical and Electronics Engineering from Iran University of Science and Technology in 1993. He received his M.Sc. and Ph.D. degrees in Electronics and Communication Engineering from Istanbul Technical University in 1997 and 2001, respectively. He is currently an Associate Professor at the Electronics and Communication Engineering Department of Dogus University in Istanbul, Turkey. He has more than 50 journal or conference papers in scientific review. He served as reviewer for a number of international journals and conferences. His current field of research concerns current-mode circuits and analog signal processing. Shahram Minaei is a member of the IEEE.     

A kinetic study of oxidation development in sunflower oil under microwave heating: Effect of natural antioxidants

The antioxidative effects of carnosic acid and sesamol on sunflower oil under temperature-controlled microwave heating were investigated as a function of time and temperature. The concentration of conjugated diene hydroperoxide and p-anisidine value were determined spectrophotometrically, as measures of oxidation, during microwave heating of sunflower oil with or without added antioxidants at 40 °C, 60 °C and 80 °C. The kinetics of hydroperoxide formation was examined on the basis of previously proposed mechanisms and found to be of the half-order with respect to the concentration of conjugated diene hydroperoxide. The amounts of added antioxidants remaining in sunflower oil after different microwave heating periods at different temperatures were determined by HPLC-DAD. The results were interpreted in terms of antioxidative effects of carnosic acid and sesamol. Carnosic acid was found to be a more effective antioxidant than sesamol for sunflower oil.     

Computer anxiety: A cross-cultural comparative study of Dutch and Turkish university students

The purpose of this study is to determine Dutch and Turkish university students’ computer anxiety levels and to find out whether their computer anxiety levels differ according to their culture, gender and computer experience (i.e., personal computer (PC) ownership, computer usage frequency, computer usage level). A total of 106 university students (30 Dutch female, 22 Dutch male, 26 Turkish female, 28 Turkish male) participated in this research. The data were collected through computer anxiety rating scale (CARS) validated by Heinssen et al. [Heinssen, R. K., Glass, C. R., & Knight, L. A. (1987). Assessing computer anxiety: Development and validation of the computer anxiety rating scale. Computers in Human Behavior, 3, 49–59]. The data were analyzed by t-test and one-way-analysis of variance (ANOVA). The results indicated that the Turkish students have significantly higher computer anxiety levels than the Dutch students. The students’ computer anxiety levels do not differ depending on gender. However, post-hoc analysis revealed that the Turkish female students have significantly higher computer anxiety levels than the Dutch female and Dutch male students. Also, results indicated that while the students’ computer experience increase their computer anxiety levels decrease significantly.