Ontologies in the context of product lifecycle management: state of the art literature review

The use of ontologies in the context of product lifecycle management (PLM) is gaining importance and popularity, while at the same time it generates a lot of controversy in discussions within scientific and engineering communities. Yet, what is ontology? What challenges have been addressed so far? What role does ontology play? Do we really need ontology? These are the core questions this paper seeks to address. We propose to conduct a comprehensive study of the concept of Ontology firstly in its domain of origin, Philosophy, and secondly in information science. Based on the understanding of this concept and an in-depth analysis of the state of the art, seven key roles of ontology are defined. These roles serve as a framework describing the general state of research on the use of ontologies in the context of PLM.     

Performance Analysis of Multiuser DS-CDMA in MIMO Systems Over Rayleigh Fading Channels

The performance of space-time transmit diversity is examined in a multiuser direct-sequence code-division multiple-access (DS-CDMA) system over fast- and slow-fading channels. The underlying space-time system employs transmit antennas and receive antennas at the mobile user and receiver base station, respectively. We consider the performance of the space-time multiuser system when using the linear decorrelator detector to combat the effect of multiuser interference. In our analysis, we derive a closed-form expression for the probability of bit error for both fast- and slow-fading channels. These theoretical results are shown to be very accurate when compared to system simulations. Both simulations and theoretical results prove that, regardless of the system load, the full diversity order of for fast-fading channels and for slow-fading channels is always maintained, and only a signal-to-noise ratio (SNR) loss is incurred. This SNR loss is proved to be a function of only the number of users (i.e., level of interference) and independent of the number of transmit and/or receive antennas. Using our theoretical results, we show that the loss in SNR from the single-user bound can be well approximated by , where represents the level of multiuser interference.     

Assessment of solar and wind energy as motive for potential hydrogen production of Algeria country; development a methodology for uses hydrogen-based fuel cells

This study is based on method of storing the part of renewable energy in the hydrogen form for using in a fuel cell at the absence of solar radiation due to overcast day or in the night. In addition, the system advantage don't need a batteries compared with other systems. The present work is compared energy potential of the wind and solar with the results of hydrogen production and to address the various obstacles to study and evaluation. This work is assessment the renewable resources in various sites of Algeria, especially in Adrar area which is one regions of the high solar energy in the world, where the radiation rates exceed more than $2300kWh/m^2$ per year, the area is also characterized by high wind power. In fact, by these two energy sources (solar and wind) that it characterized by Adrar, it's interesting to combine electrical producing energy and hydrogen production. The studies indicate that there are the meteorological factors related to the nature of site (irradiation, temperature and wind speed) are linked to the generation of electricity by renewable energy. The results obtained showing that the hydrogen production related to the solar radiation values, where southern of Algeria has more hydrogen potential compared with the northern. The simulation results show that the energy supplied by a photovoltaic module type UDTS 50 can supply energy for ten electrolyzer cells which are connected in series with this module.     

An interactive multi-objective algorithm for decentralized decision making in product design

To remain competitive and gain new shares of the market, industries must develop their products quickly while meeting the multiple customer requirements. To reduce product development time, the design step is often accomplished by several working groups working in parallel. These working groups are often decentralized and are supervised by a director. This paper focuses on solving a multi-objective problem in a setting that is called a “decentralized environment.” Collaborative optimization is a strategy used for solving problems in a decentralized environment. This strategy divides a problem into subproblems in order to give more autonomy to working groups, thus facilitating work in parallel. In this paper, collaborative optimization is paired with an interactive algorithm to solve multi-objective problems in a decentralized environment. It can be easily adjusted within the structure of a development process in a given industry and allows collaboration between the director and his/her working groups. The algorithm captures the director’s and the working groups’ preferences and generates several Pareto-optimal solutions. The algorithm was tested on a two-bar structure problem. The results obtained match those published in the literature.     

Energy-Aware Georouting with Guaranteed Delivery in Wireless Sensor Networks with Obstacles

We propose, end-to-end (EtE), a novel EtE localized routing protocol for wireless sensor networks that is energy-efficient and guarantees delivery. To forward a packet, a node s in graph G computes the cost of the energy weighted shortest path (SP) between s and each of its neighbors in the forward direction towards the destination which minimizes the ratio of the cost of the SP to the progress (reduction in distance towards the destination). It then sends the message to the first node on the SP from s to x: say node x′. Node x′ restarts the same greedy routing process until the destination is reached or an obstacle is encountered and the routing fails. To recover from the latter scenario, local minima trap, our algorithm invokes an energy-aware Face routing that guarantees delivery. Our work is the first to optimize energy consumption of Face routing. It works as follows. First, it builds a connected dominating set from graph G, second it computes its Gabriel graph to obtain the planar graph G′. Face routing is invoked and applied to G′ only to determine which edges to follow in the recovery process. On each edge, greedy routing is applied. This two-phase (greedy–Face) EtE routing process reiterates until the final destination is reached. Simulation results show that EtE outperforms several existing geographical routing on energy consumption metric and delivery rate. Moreover, we prove that the computed path length and the total energy of the path are constant factors of the optimal for dense networks.

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Magnetic studies of spin wave excitations in Co/Pt multilayers

The magnetization of Co(t_Co)/Pt(t_Pt) (4 t_Co10 , 7 t_Pt20 ) multilayers has been measured as a function of temperature. For Co/Pt multilayers with fixed cobalt layer thickness of 4 , the magnetization decreases faster with temperature as the platinum layers are made thicker. A simple theoretical model based on an anisotropic ferromagnetic system has been used to explain the temperature dependence of the magnetization and the approximate values for the in-plane exchange interaction J₀ and the interlayer coupling strength J₁ for various Co/Pt multilayers have been obtained.     

An Adaptive MMOE-PIC Detector for Asynchronous DS-CDMA Communications

We propose a modified linear parallel interference cancelation (PIC) structure using the adaptive minimum mean output-energy (MMOE) algorithm for direct-sequence code-division multiple-access (DS-CDMA) systems. The complexity of the proposed receiver structure is shown to be linear in the number of users and hence, lower complexity than the centralized minimum mean-squared error (MMSE) multiuser detector. It is demonstrated that the proposed receiver structure can significantly reduce the long training period required by the standard adaptive MMOE receiver in near-far environments. Both numerical and theoretical results show that the proposed receiver performs close to the optimum MMSE receiver whereas the conventional adaptive MMOE detector suffers from high BER’s due to the imperfect filter coefficients. Also our results show a three fold increase in the number of users when the MMOE-PIC is used relative to the conventional MMOE receiver. Furthermore, the transient behavior of the proposed MMOE-PIC receiver due to abrupt changes in the interference level is examined. It is shown that the proposed adaptive receiver offers much faster self recovery, with less signal-to-interference ratio (SIR) degradation, than the standard MMOE in sever near-far scenarios.     

Quality Improvement Partnerships with Industry Using Student Teams

The 1993 Quality Challenge is a cooperative partnership between Milliken and Company, the National Science Foundation and three North Carolina Universities. The project goal was to activate a multidisciplinary team of students, faculty, and industry representatives in a real-world quality improvement project. The 1993 project was an expanded follow-up to the 1992 University Challenge Project, also sponsored by Milliken. Based upon past experience, project coordinators broke the 1993 project into three components: Preparation, Identification, and Action. Preparation included a preliminary course held in the Spring to teach students fundamental Total Quality Management tools, team building skills and communication skills needed in industry. A team of students was selected from the course to participate in the summer Identification and Action phases of the project. The Identification phase included introduction to project goals, team process training, specialized team formation and project focus. The Action phase of the project included process capability studies, shade variation studies, root cause trials and a statistical design of experiment on shade variables. The project resulted in many recommendations to improve the process and reduce shade variation. The overall project methodology and approach can be applied to industries other than textile manufacturing. Educational benefits for all participants included: team building and teamwork experience, enhancement of effective communication skills, experience in design of experiments, engineering design and practice, greater self confidence, and industrial experience with real-world quality improvement opportunities.     

Crushing behaviour of composite hemispherical shells subjected to quasi-static axial compressive load

This paper examines the effects of composite constituents and geometry on the energy absorption capability of composite hemispherical shells. To examine the effects of matrix types on their energy absorption capability, glass fibre/epoxy and glass fibre/polyester hemispherical shells were fabricated. While glass fibre/epoxy and carbon fibre/epoxy hemispherical shells were fabricated to investigate the effect of fibre reinforcements. Effect of aspect ratio (R/t) was also examined and the results were presented. The results obtained showed that the energy absorption capability of the hemispherical shells significantly affected by the composite constituents as well as R/t ratio.     

Simulated annealing with auxiliary knowledge for process planning optimization in reconfigurable manufacturing

In this paper, three simulated annealing based algorithms that exploit auxiliary knowledge in different ways are devised and employed to handle a manufacturing process planning problem for reconfigurable manufacturing. These algorithms are configured based on a generic combination of the simulated annealing technique with; (a) heuristic knowledge, and (b) metaknowledge. Capabilities of the implemented algorithms are tested and their performances compared against a basic simulated annealing algorithm. Computational and optimization performances of the implemented algorithms are investigated and analyzed for two problem sizes. Each problem size consists of five different forms of a manufacturing process planning problem. The five forms are differentiated by five alternative objective functions. Experimental results show that the implemented simulated annealing algorithms are able to converge to good solutions in reasonable time. A computational analysis indicates that significant improvements towards a better optimal solution can be gained by implementing simulated annealing based algorithms that are supported by auxiliary knowledge.