WiSEGATE: Wireless Sensor Network Gateway framework for internet of things

With internet of things vision, computing systems get the ubiquity of real world. Wireless Sensor Network (WSN) technology plays a critical role for the construction of this paradigm. Hence, WSN technology should be adapted to support interoperability with the commodity internet entities. Since technological background of WSN and IP networks do not fit each other, this effort is not a straightforward process. In this paper, we introduce WiSEGATE which addresses end-to-end reliable interconnection problem between multiple internet entities and sensor nodes. WiSEGATE is a prototype of a new web server which supports three tier service scheme with a data acquisition mechanism of WSN to access the physical data in particular locations in the real world. In WiSEGATE, an interconnection gateway handles operations required for the interoperability. Since this gateway maintains reliable TCP/IP connections of the interconnected entities, the resource constraint sensor nodes on WSN do not require a TCP/IP stack for handling end-to-end connections. A lightweight service layer is implemented on a sensor node for operations required by the interconnection. The strength and novelty of the model lies in the fact that this lightweight service layer relieves extra memory usage for end-to-end connection management. For determining limits of the proposed model, firstly, we examined the steps for request/response mechanism and modeled the gateway as a queueing system. By doing this, we derive a definition of the request traffic. For proof of concept, we performed comprehensive tests in simulation and real testbed environments for WLAN connection. WiSEGATE can achieve reasonable response times up to 80 simultaneous connections from remote entities to WSN when WLAN PER is less than 0.2.     

Geometrically Non-Linear Analysis of Adhesively Bonded Double Containment Corner Joints

In cases where adhesively bonded joints may experience large displacements and rotations whilst the strains remain small, although all joint members behave elastically the small strain-small displacement (SSSD) theory cannot correctly predict the stresses and deformations in the adhesive joint members. Previous studies have shown that the small strain-large displacement theory considering the non-linear effects of the large displacements in the stresses and deformations has to be used in the analysis of adhesively bonded joints. In this study, the geometrical non-linear analysis of an adhesively bonded double containment corner joint was carried out using the incremental finite element method based on the small strain-large displacement (SSLD) theory. The objective of the study was to determine the effects of the large displacements on the adhesive and adherend stresses of the corner joint. Therefore, the corner joint was analysed for two different loading conditions; a compressive applied load, P_x, at the free end of the horizontal plate and one normal to the plane of the horizontal plate, P_y. The plates, support and adhesive layer were assumed to have elastic properties. In practice, the adhesive accumulations, called spew fillets, arising around the adhesive free ends were taken into account in the analysis since their presence results in a considerable decrease in the peak stresses around the free ends of the adhesive. The SSLD and SSSD analyses showed that the stress concentrations occurred around the free end of the adhesive, thus at the adherend (slot) corners inside the right vertical and the lower horizontal adhesive fillets, and inside the left vertical and the upper horizontal adhesive fillets for the loading conditions P_x and P_y, respectively. In addition, the plate regions around the adherend (slot) free ends along the outer fibres of the vertical and horizontal plates undergo very high stress concentrations. The SSLD analysis predicted a non-linear effect in the displacement and stress variations at the critical adhesive and plate locations, whereas the SSSD analysis showed their variations were lower and proportional to the applied incremental load. This non-linear effect became more evident for the loading condition P_x, whereas both analyses predicted very close displacement and stress variations in the adhesive fillets and in the horizontal plate for the loading condition P_y. As a result, the geometrical non-linear behaviour of the corner joint is strictly dependent on the loading condition and the large displacements affect the stress and deformation states in the joint members, and result in higher stresses than those predicted by the SSSD theory.     

Effects of aging on latex film formation from polystrene particles: A photon transmission study

Aging due to the storage time on latex film formation was studied using the photon transmission method. The UV visible technique was used to monitor the evolution of transparency during film formation from two different polystyrene (PS) particles produced by using two different steric stabilizers, i.e., polyvinyl alcohol and polyvinyl pyrrolidone. The latex films were prepared from PS particles at room temperature before and after aging and annealed at elevated temperatures in various time intervals above glass transition (T_g). The increase in the transmitted photon intensity I_tr was attributed to the increase in the number of disappeared particle–particle interfaces. Relative decrease in transparency and delay in film formation were observed in the aged latex films compared to the nonaged ones. The Prager–Tirrell model was employed to interpret the increase in crossing density at the junction surface. The back and forth activation energies (ΔE) were measured and found to be dependent on aging for a diffusing polymer chain across the junction surface. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2014–2021, 2001     

Interactions between milk proteins and polyphenols: Binding mechanisms,related changes,and the future trends in the dairy industry

The biological activity and techno-functional properties of phenolic compounds have gained great importance due to the epidemiologically-proved health benefits. Use of polyphenols as fortification agents for functional food production and nanotechnological approaches using natural vehicles for polyphenol delivery have been recently discussed. In this respect, milk proteins and dairy products represent unique characteristics for polyphenol studies. The conflicting results on the functionality of polyphenols interacting with milk proteins either in model systems or in complex dairy matrices reveal the need for future studies.     

Determination of polyphenolic constituents and biological activities of bark extracts from different Pinus species

BACKGROUND: The most common commercially available pine bark extract is Pycnogenol^®, a standardised extract of Pinus maritima, which has been reported to have cardiovascular benefits and enhance microcirculation. The present study was conducted to determine the chemical composition of four pine bark extracts, assess their biological activities and to compare the results with Pycnogenol^®. RESULTS: The Pinus species were analysed by LC and LC‐MS; extracts of P. brutia and P. nigra showed higher levels of phenolic constituents compared to P. sylvestris and P. pinea. In particular, P. brutia contained extremely high concentrations of taxifolin (18.5%). The highest radical scavenging activities were attained with P. pinea (88.6%), P. nigra (87.2%) and P. brutia (86.4%) bark extracts. Additionally, anticarcinogenic effects of the extracts and their kinetics were determined in four cell lines including human prostate (PC‐3, DU 145, LNCaP) and breast adenocarcinoma (MCF7) by the MTT assay. Cell viability was reduced to 40% by extracts of P. pinea, and P. sylvestris in PC‐3 cells showing a similar effect like the positive control, CPT‐11. CONCLUSION: Pinus species other than P. maritima definitively possess high biological activities, and therefore present a huge potential to be utilised in the food and the pharmaceutical industries. Copyright © 2009 Society of Chemical Industry     

First-Principles Calculations on Structure,Elastic and Thermodynamic Properties of Al2X （X=Sc,Y） under Pressure

To understand deeply the structural,elastic and thermodynamic characteristics of Al 2 X (X= Sc,Y) compounds in C15 type (space number 227) Cu 2 Mg structure,we have performed ab-initio density functional theory within the local density approximation (LDA) and the generalized gradient approximation (GGA).The thermodynamic properties of the considered structures are obtained through the quasi-harmonic Debye model.We have presented the results on the basic physical parameters,such as the lattice constant,bulk modulus,pressure derivative of bulk modulus,second-order elastic constants,Zener anisotropy factor,Poisson s ratio,Young s modulus,and isotropic shear modulus.In order to gain further information,the pressure-and temperature-dependent behaviour of the volume,bulk modulus,thermal expansion coefficient,heat capacity,entropy,Debye temperature and Gru¨neisen parameter were also evaluated over a pressure range of 0-20 GPa for Al 2 Sc and 0-17 GPa for Al 2 Y compound and a wide temperature range of 0-2000 K for both compounds.The obtained results were compared with the other reported values.     

The impact of data aggregation on the performance of wireless sensor networks

With the increasing need for different energy saving mechanisms in Wireless Sensor Networks (WSNs), data aggregation techniques for reducing the number of data transmissions by eliminating redundant information have been studied as a significant research problem. These studies have shown that data aggregation in WSNs may produce various trade‐offs among some network related performance metrics such as energy, latency, accuracy, fault‐tolerance and security. In this paper, we investigate the impact of data aggregation on these networking metrics by surveying the existing data aggregation protocols in WSNs. Our aim is twofold: First, providing a comprehensive summary and comparison of the existing data aggregation techniques with respect to different networking metrics. Second, pointing out both the possible future research issues and the need for collaboration between data management and networking research communities working on data aggregation in WSNs. Copyright © 2006 John Wiley & Sons, Ltd.     

A taxonomy and evaluation for developing 802.11‐based wireless mesh network testbeds

The definition of wireless mesh networks (WMNs) has been used in the literature to connote and epitomize the ideal, ubiquitous, pervasive, and autonomic networking technology. An increasing interest has been emerging on the development of 802.11‐based WMN testbeds to test the new ideas and approaches more realistically as opposed to relying solely on simulations. Although the developed testbeds have provided several insights to researchers for furthering the technology, there are still several issues that need to be addressed, particularly, with the approval of new standards, such as IEEE 802.11s, IEEE 802.11n, and IEEE 802.16, and upcoming protocols, such as IEEE 802.11ac, 802.11ad, 802.11ah, and 802.11af TV White Space efforts. In this paper, our goal is to provide a taxonomy and insightful guidelines for the creation of 802.11‐based WMN testbeds as well as to identify several features that future WMN testbeds should possess. Utilizing these features, we evaluate the existing WMN testbeds. Finally, in addition to the existing WMN testbed experiments conducted at several layers of the protocol stack, we provide a list of open future research issues that can benefit from experiments on WMN testbeds. Copyright © 2011 John Wiley & Sons, Ltd.     

Extended sliding frame R-Aloha: Medium access control (MAC) protocol for mobile networks

Proliferation of mobile communication devices necessitates a reliable and efficient medium access control (MAC) protocol. In this paper, A MAC protocol, called extended sliding frame reservation Aloha (ESFRA), based on sliding frame R-Aloha (SFRA) is proposed for network access technique. ESFRA is particularly designed to solve the mobile hidden station (MHS) problem in a mobile ad hoc network (MANET) by including relative locations of transmitting stations in the packet frame information header. The MHS problem is unique in mobile networks and occurs if a mobile station enters in a collision free zone of any ongoing communication and disturbs this communication with its transmission. In addition to the MHS problem, ESFRA simultaneously solves hidden station, exposed station, and neighborhood capture problems typically observed in wireless networks. A Markov model of ESFRA is developed and provided here to estimate throughput, delay and collision probabilities of the proposed protocol. The Markov modeling is extended to the analysis of SFRA and IEEE 802.11 to compare these competing MAC protocols with ESFRA. The analysis shows that ESFRA decreases frame transmission delay, increases throughput, and reduces collision probabilities compared to IEEE 802.11 and SFRA. ESFRA improves the network throughput 28 percent compared to that of IEEE 802.11, and 33 percent compared to that of SFRA. The improved performance is obtained at the expense of the synchronization compared to IEEE 802.11, but there is virtually no extra cost compared to SFRA.