Output-only modal identification by in-operation modal appropriation for use with enhanced frequency domain decomposition method

Journal of Mechanical Science and Technology - Output-only modal identification or operational modal analysis (OMA) has gained increasing popularity in many fields of engineering. In the context of...     

Swarm intelligence routing approach in networked robots

Robot swarm combined with wireless communication has been a key driving force in recent few years and has currently expanded to wireless multihop networks, which include ad hoc radio networks, sensor networks, wireless mesh networks, etc. The aim of this paper is to propose an approach which introduces a polynomial time approximation path navigation algorithm and constructs dynamic state-dependent navigation policies. The proposed algorithm uses an inductive approach based on trial/error paradigm combined with swarm adaptive approaches to optimize simultaneously two criteria: cumulative cost path and end-to-end delay path. The approach samples, estimates, and builds the model of pertinent aspects of the environment. It uses a model that combines both a stochastic planned prenavigation for the exploration phase and a deterministic approach for the backward phase. To show the robustness and performances of the proposed approach, simulation scenario is built through the specification of the interested network topology and involved network traffic between robots. For this, this approach has been compared to traditional optimal path routing policy.     

An integrated optimisation for the weight,the structural performance and the cost of composite structures

An integrated optimisation methodology is proposed to optimise the manufacturing cost as well as the structural performance and the weight of composite laminated plates manufactured by the resin transfer moulding (RTM) process. In the present approach, the fibre type, the number of fabrics, the layer stacking sequence and the fibre volume fraction are optimised to minimise the structural weight and the material cost of composite structure under the stiffness constraint and the mould filling time constraint which is a part of process cycle time. With the results obtained, it is investigated how the weight and the material cost are traded-off. The optimisation methodology suggests a guide to cost-effective material selection in the preliminary conceptual design stage.     

Effect of the tank geometry on the storage and destocking of hydrogen on metal hydride (LaNi5H2)

The present numerical study aimed at studying the solid-statehydrogen storage and destocking in the LanthanumNickel (LaNi₅H₂) in a concentric triple-tube heat exchanger. Moreover, the influence of the thermal-reactor geometry for the storage and destocking hydrogen have been examined by changing the diameters of the heat exchanger. The performance of LanthanumNickel was compared with those of the hydride (MmNi₄.₆Fe₀.₄) and activated carbon. The flowing parameters: kinetics of hydrogen absorption/desorption, chemical reactions, enthalpy of fusion, equilibrium pressure, hydrogen concentration and the storage capacity were considered for calculating the terms of mass and energy equations. The hydride thermal and mass behaviour was integrated in the CFD Fluent with software (C++). A good agreement between the presented model and the literature experimental results was obtained. Additionally, the mentioned above parameters have shown a significant impact on the geometry of the reactor.     

Screening of four vascular aquatic plants for uptake of monosodium methanearsonate (MSMA)

The post-emergent herbicide, MSMA, is used extensively for weed control in non-edible crops and for chemical mowing along roadside rights-of-way. Herbicide may gain access to adjacent water bodies by accidental application or by runoff from sprayed plots. This study utilized floating and rooted plant species in hydroponic solution to monitor the uptake of trace levels of the herbicide from an aqueous concentration of 24 μg/ml. Plant species evaluated included Eichhornia crassipes, Alternanthera philoxeroides, Hydrophila lacustris and Lemna minor. Plants were analyzed for total arsenic over the 6 weeks of study using the silver diethyldithiocarbamate (SDDC) procedure. Bioaccumulation ratios were then determined for each plant species.     

The joint use of IHS transform and redundant wavelet decomposition for fusing multispectral and panchromatic images

Intensity hue saturation (IHS) and wavelet decomposition are two distinct fusion methods used for enhancing the spatial resolution of multispectral images by exploiting a high-resolution panchromatic image. In this paper, a combination of the IHS transform and redundant wavelet decomposition is proposed as a general method for fusing multisensor images. The principle consists of transforming low-resolution multispectral images into IHS independent components. The low-resolution intensity component is fused with the high-resolution panchromatic image in the redundant wavelet domain through an appropriate model. Subsequently, the high-resolution intensity produced is substituted to the low-resolution intensity. High spatial resolution multispectral images are then obtained through an inverse IHS transformation. SPOT images are used to illustrate the superiority of this approach over the IHS fuser in terms of preservation of spectral properties.     

String Matching Over Compressed Text on Handheld Devices Using Tagged Sub-Optimal Code (TSC)

This paper presents Tagged Sub-optimal code (TSC), a new coding technique to speed up string matching over compressed databases on personal digital assistants (PDA). TSC is a variable-length sub-optimal code that supports minimal prefix property. It always determines its codeword boundary without traversing a tree or lookup table. TSC technique may be beneficial in many types of applications: speeding up string matching over compressed text, and speeding decoding process. This paper also presents two algorithms for string matching over compressed text using TSC (SCTT) and the Byte Pair Encoding (BPE) technique (SCTB). indent Several experiments were conducted to compare the performance of TSC, Byte Pair Encoding (BPE), and Huffman code. Several PDA databases with different record sizes were used: the well-known Calgary dataset and a set of small-sized PDA databases. Experimental results show that SCTT is almost twice as fast as the Huffman-based algorithm. SCTT has also the same performance in search time as the search in uncompressed databases and is faster than the SCTB algorithm. For frequently updated PDA databases such as phone books, to-do list, and memos, SCTT is the recommended method regardless of the size of the average record length, since the time required to compress the updated records using BPE poses significant delays compared to TSC.Abdeghani Bellaachia is an associate professor at the Computer Science Department, George Washington University. He received his Diploma of Engineering from Mohammadia School of Engineering in Rabat, Morocco, in 1983, the MS and Doctoral of Science degrees from the George Washington University in 1992. He was the chief architect of the Arabization of the Palm-OS platform. His research interests include data mining, multi-lingual information retrieval systems, cross-language retrieval systems, database management systems, bio-informatics, design and analysis of algorithms, handheld computing, and parallel processing.Iehab AL Rassan works for Ministry of higher education in Saudi Arabia, director of information technology department. He received his B.A. in Computer Information Systems from King Faisal University. He then received his M.S. in Computer Science from Fairleigh Dickinson University and his Doctor of Science in Computer Science from the George Washington University. His research interests include coding theories, information retrieval, string-matching algorithms, data compression, and handheld computing.