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An investigation showing the performance of compact long period grating (LPG) pairs under demanding experimental conditions, making comparisons with the use of single LPGs for the simultaneous measurement of strain and temperature is presented. In this work, a LPG pair (LPGP) sensor comprising two weak (2.5 dB each) LPGs, 13 mm apart, was compared against the performance of two single LPG sensors (LPG1 & LPG2) with coupling strengths of 2.5 dB and 12.5 dB, respectively. All the LPG sensors used were subjected to extreme conditions arising from the fabrication, by choosing a high amplitude mask period with short physical length LPGs, and the high temperature annealing processes. In addition, a low resolution detection instrument was used to capture the spectra under study. Results have shown that the LPGP is 40 times better than the first single LPG used (LPG1) and three times better than the second LPG (LPG2). Using the error analysis methodology of Brady et al., the temperature and strain errors due to the uncertainty of the wavelength measurement for each of the LPG1, LPG2, and LPGP were compared with the typical performance of various fibre Bragg grating (FBG)-based sensor schemes under similar testing conditions. It was found that LPGPs offer the best performance especially when using low resolution detection instrumentation. 相似文献
3.
The provision of online public goods: Examining social structure in an electronic network of practice 总被引:3,自引:0,他引:3
Electronic networks of practice are computer-mediated social spaces where individuals working on similar problems self-organize to help each other and share knowledge, advice, and perspectives about their occupational practice or common interests. These interactions occur through message postings to produce an on-line public good of knowledge, where all participants in the network can then access this knowledge, regardless of their active participation in the network. Using theories and concepts of collective action and public goods, five hypotheses are developed regarding the structural and social characteristics that support the online provision and maintenance of knowledge in an electronic network of practice. Using social network analysis, we examine the structure of message contributions that produce and sustain the public good. We then combine the results from network analysis with survey results to examine the underlying pattern of exchange, the role of the critical mass, the quality of the ties sustaining participation, the heterogeneity of resources and interests of participants, and changes in membership that impact the structural characteristics of the network. Our results suggest that the electronic network of practice chosen for this study is sustained through generalized exchange, is supported by a critical mass of active members, and that members develop strong ties with the community as a whole rather than develop interpersonal relationships. Knowledge contribution is significantly related to an individual's tenure in the occupation, expertise, availability of local resources and a desire to enhance one's reputation, and those in the critical mass are primarily responsible for creating and sustaining the public good of knowledge. Finally, we find that this structure of generalized exchange is stable over time although there is a high proportion of member churn in the network. 相似文献
4.
Samer Yahya M. Moghavvemi Haider A.F. Mohamed 《Simulation Modelling Practice and Theory》2011,19(1):406-422
A new method for inverse kinematics for hyper-redundant manipulators is proposed in this paper to plan the path of the end-effector. The basic idea is that for a given smooth path consisting of points close enough to each other; computing the inverse kinematics for these points is carried out geometrically using the proposed method. In this method, the angles between the adjacent links are set to be the same, which makes lining up of two or more joint axes impossible; therefore, avoiding singularities. The manipulability index has been used to show how far the manipulator from the singularity configuration is. The determination of the workspace of the manipulator using the proposed method has been presented in this paper. The simulation results have been carried out on a planar and a three dimensional manipulators. The effectiveness of the proposed method is clearly demonstrated by comparing its result with results calculated by the well-known method of measuring manipulability which is used for singularity avoidance for the last two decades. 相似文献
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Samer Aouad Cedric Gennequin Mary Mrad Haingomalala Lucette Tidahy Jane Estephane Antoine Aboukaïs Edmond Abi‐Aad 《国际能源研究杂志》2016,40(9):1287-1292
The wet impregnation method was used to prepare different ruthenium promoted Ce–Al catalysts. These catalysts were used in the steam reforming of methanol reaction (SRM). The effects of the reaction temperature (200–400 C) and the catalyst composition were studied for optimization reasons. The steam to methanol molar ratio was kept constant (S/M = 2). The promotion of cerium/aluminum oxides with Ru enhanced their catalytic activity. The catalytic test results showed that the Ru/Ce combination was the most beneficial. The synergy between Ru and cerium oxide led to the formation of active sites with excellent redox properties. For high active phase content, the 5 RuCe catalyst exhibited the highest hydrogen production amount with no CO formation. This catalyst was kept under stream for 5 days at 400 C, and no significant deactivation was observed. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
7.
Francesca Soglia Massimiliano Petracci Samer Mudalal Lucia Vannini Giorgia Gozzi Lucia Camprini Claudio Cavani 《International Journal of Food Science & Technology》2014,49(10):2184-2191
This study was aimed at evaluating the consequences of sodium chloride reduction by potassium chloride up to 50% on technological, sensorial and microbiological traits of marinated rabbit meat. In total, 226 rabbit loin meat samples were obtained and subjected to vacuum tumbling using solutions with different NaCl/KCl ratios. Replacing of sodium chloride up to 30% by potassium chloride did not change microbiological traits (total aerobic mesophilic and lactic acid bacteria maximum cell loads), sensorial acceptability (perceived saltiness and overall liking) and technological traits (pH, colour, texture, cooking loss and yield). Otherwise, reduction in sodium chloride to 50% significantly decreased perceived saltiness (4.15 vs. 4.73; P < 0.05) and reduced microbial shelf life by 1 day when compared to control, even if there was still no effect on technological traits. In conclusion, it is feasible imparting an added value for processed rabbit meat products by reduction in sodium content that could increase market interest. 相似文献
8.
Khaled Safi Samer Mohammed Inke Marie Albertsen Eric Delechelle Yacine Amirat Mohamad Khalil Jean-Michel Gracies Emilie Hutin 《Signal, Image and Video Processing》2017,11(6):1081-1088
The present study proposes a new approach for the assessment of the human balance control. This approach is based on the decomposition of the center of pressure displacement using empirical mode decomposition (EMD) that provides an effective time-frequency analysis of non-stationary signals. Twenty-eight healthy subjects performed quiet standing in four conditions—feet apart/together with respect to eyes open/closed—while recording the stabilometric signals in the anteroposterior (AP) and mediolateral (ML) directions. The EMD method decomposes each stabilometric signal into several subsignals called intrinsic mode functions (IMFs). Stabilogram-diffusion analysis technique is applied to generate the diffusion curve of each IMF signal. Each diffusion curve is modeled as a second-order system and provides representative features, such as the gain parameter. Analysis of the gain parameter shows the major effect of visual input and feet conditions on the strategy to control/stabilize the balance. Significant differences were found between young and elderly, and between women and men. In addition, the impact of feet position seems to be higher in ML direction than in AP direction. 相似文献
9.
Melt spun matrix fibers of toughened polypropylene copolymers modified by high energy electrons 下载免费PDF全文
Binary blends of polypropylene (PP) and ethylene‐octene copolymer (EOC) are prepared by continuous electron‐induced reactive processing at various mass ratios of the blend components and various doses without adding of any grafting agents. The influence of mass ratio and dose is investigated in order to get the optimum processing behavior of toughened PP as well as optimum properties of resulting fibers. It is found that toughened PP with a PP/EOC blend ratio of 97.5–2.5 mass % can be used advantageously as a matrix component for the process of online spinning of glass fiber/toughened PP hybrid yarns. Such hybrid yarns belong to one of the most advanced production methods for the manufacturing of fiber reinforced thermoplastic composites with an increased mechanical performance. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44011. 相似文献
10.
Samer El Oukaili Michael Schwan Stefan Federlein 《Electrical Engineering (Archiv fur Elektrotechnik)》2009,90(8):569-576
Liberalization has increased economic pressure on network operators, urging them to compromise between cost savings and supply
reliability. In this context, the detailed and quantitative evaluation of supply reliability is gaining ever more importance—especially
its application in comprehensive asset management methods. However, the large number of components especially in medium voltage
distribution networks leads to high computation times for such probabilistic reliability analyses. A recent research project
deals with investigations into a forecast of system supply reliability performance following a simplified methodology. Developing
different forecasting methods, also several aspects of significant importance for the calculation of supply reliability in
MV distribution systems in general were identified. Especially for electrical networks of a certain size, the overlapping
of independent single failures, as well as complex failures play an important role. This paper presents the background of
the reliability centered asset management approach as well as the general idea and different approaches to the forecasting
methods in theory briefly. Following, the application on two different example networks demonstrates the approaches and the
achieved results, and reveals also the relevance of overlapping and complex failures in these results. 相似文献