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We propose to use a super-structured waveplate (called an S-waveplate) for vectorial optical vortex filtering, and experimentally demonstrate the radial Hilbert transform and selective edge enhancement. Based on the Jones calculus of polarization states and Fourier analysis, we calculate and analyze the point spread function of an optical 4-f system including an S-waveplate filter having the vectorial vortex of topological charge 1 (TC = 1). Numerical simulations and optical experiments demonstrate that a vectorial optical vortex filter can be used to implement selective edge enhancement with an analyzer before the output plane. The edge enhancement can be obtained even when the center of the filter is off-axis or the illuminating light is non-monochromatic.

Device-to-device (D2D) communication underlaying cellular networks brings significant benefits to resource utilization, improving user's throughput and extending battery life of user equipments. However, the allocation of radio resources and power to D2D communication needs elaborate coordination, as D2D communication causes interference to cellular networks. In this paper, we propose a novel joint radio resource and power allocation scheme to improve the performance of the system in the uplink period. Energy efficiency is considered as our optimization objective since devices are handheld equipments with limited battery life. We formulate the the allocation problem as a reverse iterative combinatorial auction game. In the auction, radio resources occupied by cellular users are considered as bidders competing for D2D packages and their corresponding transmit power. We propose an algorithm to solve the allocation problem as an auction game. We also perform numerical simulations to prove the efficacy of the proposed algorithm.

Low duty cycled sleep scheduling can largely prolong the lifetime of a wireless sensor network (WSN). However, it also brings big challenge to the design of efficient routing protocols. Inappropriate selection of routes can largely offset the efficiency of a sleep scheduling mechanism. This paper aims to provide a simple but efficient forwarding discipline for packet routing in a low duty cycled WSN wherein each node chooses its wakeup slot in a pseudo-random manner. In such a duty-cycled WSN, a big problem is how a node can make a forwarding decision in order to obtain an acceptable end-to-end (E2E) delivery latency as well as high energy efficiency. In this paper, we design a multipath routing protocol that combines gradient information and predictable link delay to make the forwarding decision. Simulation results show that the designed protocol can obtain high performance in terms of delivery latency and energy efficiency compared with existing work.

SUMMARY Introduction of mobile sinks into a wireless sensor network can largely improve the network performance. However, sink mobility can cause unexpected changes of network topology, which may bring excessive protocol overhead for route maintenance and may offset the benefit from using mobile sinks. In this paper, we propose an efficient data-driven routing protocol (DDRP) to address this problem. The design objective is to effectively reduce the protocol overhead for data gathering in wireless sensor networks with mobile sinks. DDRP exploits the broadcast feature of wireless medium for route learning. Specifically, each data packet carries an additional option recording the known distance from the sender of the packet to target mobile sink. The overhearing of transmission of such a data packet will gratuitously provide each listener a route to a mobile sink. Continuous such route-learning among nodes will provide fresh route information to more and more nodes in the network. When no route to mobile sink is known, random walk routing simply is adopted for data packet forwarding. Simulation results show that DDRP can achieve much lower protocol overhead and longer network lifetime as compared with existing work while preserving high packet delivery ratio. Copyright © 2012 John Wiley & Sons, Ltd.

The increasing popularity of smart mobile devices and their more and more powerful sensing ability make it possible to capture rich contextual information and personal context-aware preferences of mobile users by user context logs in devices. By leveraging such information, many context-aware services can be provided for mobile users such as personalized context-aware recommendation. However, to the best knowledge of ours, how to mine user context logs for personalized context-aware recommendation is still under-explored. A critical challenge of this problem is that individual user's historical context logs may be too few to mine their context-aware preferences. To this end, in this paper we propose to mine common context-aware preferences from many users' context logs through topic models and represent each user's personal context-aware preferences as a distribution of the mined common context-aware preferences. The experiments on a real-world data set contains 443 mobile users' historical context data and activity records clearly show the approach is effective and outperform baselines in terms of personalized context-aware recommendation.

In a wireless sensor network with mobile sinks, the maintenance of efficient data delivery structure often brings a large amount of control overhead, which may offset the benefit of introducing mobile sinks. In this paper, we propose a multi-stage data routing protocol (called MLRP) to address this problem. To reduce the protocol overhead, MLRP integrates layered Voronoi scoping and dynamic anchor selection. Such design is expected to greatly reduce the diffusion scope of sink movement updates and thus reduce the frequency at which the data delivery structure is refreshed. Simulation results show that MLRP can effectively reduce the protocol overhead while ensuring high packet delivery ratio as compared with existing work.

Objective To prepare a noisome formulation of Semen Strychni alkaloids extract with high encapsulation efficiency. Method S. Strychni alkaloids were encapsulated into niosomes by pH gradient loading method. The factors influencing on the encapsulation efficiency were investigated, and formulation and preparation process of niosomes were optimised and validated. Result When the drug to lipid weight ratio was under 1: 10, pH gradient in buffer solution of citric acid at 50 degrees C was more than 4.0, the niosomes (mean diameter 179.2 nm and Zeta potential -25.41 mV) were formed with encapsulation efficiency of over 86.9%. Conclusion The pH gradient loading method was reliable for preparing niosomes of Semen Strychni alkaloids extract.

In this paper, we propose a data-driven routing protocol (called DDRP) for wireless sensor networks with mobile sinks (mWSNs). The design objective of DDRP is to effectively reduce the protocol overhead for data gathering in such networks. DDRP exploits the broadcast feature of wireless transmissions for sensor nodes for (gratuitous) route learning. To achieve this goal, each data packet carries an additional option recording the known distance from the sender of the packet to the destined mobile sink. The overhearing of such a data packet will gratuitously provide listeners a route to mobile sink. This is the so-called data-driven nature of DDRP. Continuous such route-learning among neighboring nodes will provide route information for more and more sensor nodes in the network. We present the detailed design of the DDRP protocol. Simulation results show that DDRP has much lower protocol overhead as compared with existing work while ensuring high packet delivery ratio.

A fundamental problem that a peer-to-peer (P2P) live streaming system faces is how to support flash crowds effectively. A flash crowd occurs when a burst of join requests arrive at a system. When a flash crowd occurs, the sudden arrival of numerous peers may starve the upload capacity of a P2P system, and degrade the quality of service. By theoretical analysis and simulations, we find that a system has limited capacity to handle a flash crowd: It can recover to a new stable state when the size of flash crowd is small or moderate, but collapse when the flash crowd is excessively large. The capacity of a system is independent of initial state of the system while relevant to stable peers' departure rate, which suggests this capacity is an essential property of a P2P live streaming system. In addition, we prove that a P2P live streaming system with admission control has excellent capacity to handle flash crowds: It can recover from flash crowds of excessively large size and a startup peer's waiting time scales logarithmically with the size of flash crowds. Our theoretical model and simulation results provide a promising framework to understand the capacity of a P2P live streaming system for handling flash crowds.

OBJECTIVE To study the preparation of cantharidin entrapped non-ionic surfactant vesicle (noisome)and evaluate its quality. METHOD The niosome loaded with cantharidin was prepared using injection method by non-ionic surfactants as the carrier. An centrifugation separation method and HPLC analysis method of the cantharidin were established to detect the entrapment efficiency. The optimum preparation technology was established by a orthogonal experiment. The morphology, and particle size were studied to evaluate the preparation. RESULT The average size of niosomes were (209. 8 +/- 0.5) nm. The entrapment efficiency of the CTD-NS was (27.5% +/- 2.0%) and Zeta potential was (41.5 +/- 0.65) mV. CONCLUSION The preparation of cantharidin noisome by TweenA and SpanB is practicable and successful. These experiments can be the basement of developing targeting drug delivery system.

Wireless sensor networks with mobile sinks (mWSN) have attracted a lot of attention recently. In an mWSN, each mobile sink can move freely and unpredictably. In this paper, we design two efficient data gathering protocols for mWSNs. The first protocol (called AVRP) adopts Voronoi scoping plus dynamic anchor selection to handle the sink mobility issue. In the second protocol (called TRAIL), the trail of mobile sink is used for guiding packet forwarding as sinks move in the network. In TRAIL, to forward a data packet, integration of trail-based forwarding and random walk is used. Specifically, when no fresh trail of any sink is known, random walk is used; once a sensor on a fresh sink trail is reached, data packet will be forwarded along the trail. TRAIL is simple to implement and has small protocol overhead. Simulation results show the designed protocols have high performance and further AVRP is suitable for mWSNs with heavy traffic while TRAIL is suitable for mWSNs with light traffic.

This chapter contains sections titled: Introduction Concepts and Major Challenges Broadcasting Mechanisms Multicasting Mechanisms Geocasting Mechanisms Summary and Future Directions Acknowledgments References

Efficient and reliable communications is a critical issue in wireless networks with lossy links. In this paper, we propose a neighbor-assisted coding aware opportunistic retransmission mechanism to increase the network throughput. The key idea behind our design is as follows. If a node fails to receive a packet due to link loss, its neighboring node(s) receiving the packet can assist the retransmission of the packet, possibly encoded with other packet(s) via localized network coding, if such retransmission is expected to be beneficial. This can effectively reduce the total number of packet retransmissions at the MAC layer. Simulation results show that our proposed mechanism can significantly increase the network throughput as compared with existing work.

To prepare silymarin nanosuspension and lyophilized power for enhancing the dissilution of poorly soluble drugs.The precipitation technique was adapted to produce the silymarin nanosuspensions respectivly applying Tween 80, SDS and Poloxamer188 as stabilizers. The lyophilized formula contained 5% mannitol as cryoprotectant. Particle size, Polydispersity index and Zeta potential were detected by Mastersizer nano ZS (Malvern England). Morphological character was observed with Transmission Electron Microscopy. The product's structure was performed with X-ray diffractometer.The silymarin nanosuspension was successfully prepared, in which the drug particle size was about 100-300 nm,and the particles had ball-like shape and good dispersive properties.This study provided potential for the neotype dosage form development of the Chinese Traditional Medicine.

Localized network coding is a promising technique to improve the throughput of wireless multihop networks with multiple concurrent unicast sessions. However, most existing mechanisms in this field perform network coding without considering the maximization of joint coding gain among neighboring nodes. In this paper, we study how to improve network performance by maximizing the area-centric coding gains in wireless networks. To achieve this goal, we design an efficient coding-aware transmission scheduling mechanism. Simulation results show that our mechanism can remarkably improve the network throughput as compared with existing mechanisms.

In this paper, we design a destination-driven on-demand multicast routing protocol for wireless ad hoc networks. The design objective is to improve the multicast forwarding efficiency. To achieve this goal, the path to reach a multicast destination is biased towards those paths passing through another multicast destination. If multiple such choices are available, the one leading to the least extra cost is selected. Our protocol embeds this destination-driven feature into the on-demand multicast structure building process of an existing multicast protocol ODMRP. Detailed protocol design descriptions are provided. Simulation results show that our protocol can greatly improve the forwarding efficiency as compared with ODMRP. Moreover, our destination-driven design can also work well with other existing multicast routing protocols for wireless ad hoc networks.

Sink's vicinity is a hotspot area in a wireless sensor network, and has a significant impact on the normal operation and network performance of the entire network. A hybrid MAC protocol makes use of the advantages of both CSMA/CA and TDMA protocols and adaptively switches between the two protocols based on dynamic traffic load, and can thus improve the network performance within the sink's vicinity. In this paper, we study MAC for the sink's vicinity in a WSN. We develop performance models for CSMA/CA and TDMA systems and compare their performance under both non-saturation and saturation conditions based on the developed performance models. Through simulation results, we verify that the accuracy and correctness of the performance models. Moreover, the analytical results based on the performance models can be used as a guide for determining the optimal load point for protocol switch and designing an optimal hybrid MAC protocol for the sink's vicinity.

Opportunistic routing and network coding have been considered as effective strategies for improving the throughput of wireless mesh networks (WMN). However, most existing work studied opportunistic routing and network coding separately. This has largely limited the ability of the above strategies from effectively improving the network performance. To achieve improved network throughput, in this paper, we propose a coding-aware opportunistic routing mechanism for WMNs. The design goal is achieved by effectively integrating the above two strategies such that decision on each packet forwarding is made with the awareness of potential coding opportunities. Simulation results show that our proposed mechanism can remarkably improve the network throughput.

Location-based routing has been a critical and efficient routing strategy in large wireless sensor networks (WSN) with mobile sinks. However, the performance of location-based routing highly depends on how position information of mobile sinks are managed and updated. This is typically the task of location service. In this paper, we present the design of a hierarchical location service for WSNs with mobile sinks. The main design objective is to greatly reduce the communication overhead for providing location service while maintaining high routing performance. Detailed simulation results are used to verify the high performance of our designed location service.

Topology control plays a critical role in the design of wireless ad hoc and sensor networks. It can assign reduced transmit powers to nodes so as to create reduced topologies with certain desired properties. In this paper, we design an energy-efficient localized topology control algorithm. The design objective is to prolong the operational time of networks resulted by the implementation of localized topology controlling at nodes in network. For this purpose, our designed algorithm introduces the strategy of energy criticality avoidance in assigning nodal transmit powers as well as in selecting energy-efficient routes for packet deliveries. Simulation results demonstrate the high performance of our designed algorithm in prolonging the network lifetime as compared with related work.

In this work, we design a destination-initiated protocol, which aims at building source-rooted shortest path tree (SPT) in a hop-by-hop manner for providing scalable multicast. The designed protocol can support group applications with dynamic membership well. Performance analysis and simulation results show that the destination-initiated characteristic can significantly reduce the computation, storage and communication overhead associated with SPT constructions.

One of the key issues in QoS provisioning in high-speed networks is how to determine a feasible route that satisfies the given QOS requirements while efficiently utilizing network resources. In this paper, we study the NP-complete problem of path selection subject to multiple constraints and propose a heuristic solution, which essentially divides an entire QoS-path into at most two "superedges" that is connected by a "relay node". A superedge is defined as a connected segment of the path on which all routers use the same routing metric for packet forwarding. The node connecting the two superedges is called relay node. This property makes the heuristic be able to support stateless forwarding, i.e., no flow-specific state information is required to maintained at intermediated nodes on a QoS routing protocol. Its computational complexity is deduced to be 0(m|V/sup 2/|), where m, a very small integer, is the number of the concerned QoS metrics and |V| is the number of nodes in network. Simulation results show that the heuristic can achieve near optimal performance.

The multicast forwarding state scalability issue is one of the critical issues that delay the deployment of IP multicast in the global Internet. With traditional protocols, each router is required to maintain a forwarding entry locally for each group whose distribution tree passes through the router itself. Consequently, the number of forwarding entries at routers increases linearly with the number of concurrent ongoing multicast sessions. This can pose the forwarding state scalability issue when the number of multicast sessions is very large. The paper addresses this scalability issue in providing efficient delay-constrained multicasting in IP networks. We propose a scalable multicast routing heuristic. Its computational complexity is deduced to be O(m|V|/sup 2/), where m is the size of the multicast group and |V| is the size of the network. In particular, if the heuristic is executed online, its computational complexity can be further reduced to O(m/sup 2/). This property makes the heuristic scale well with the number of concurrent sessions since multicasting subject to a delay constraint is typically executed on a per-session basis. Simulation results show that the proposed heuristic can achieve high performance in reducing the forwarding state at routers and in utilizing network resources efficiently.

IP multicast suffers from the forwarding state scalability issue when the number of simultaneously on-going multicast sessions is very large, since traditional multicast routing protocols require each router to maintain a forwarding entry for each multicast session whose distribution tree passes through the router. We introduce the idea of recursive unicast into the existing MOSPF (multicast extension to open shortest path first) routing protocol to improve its scalability. Simulation results show that the designed protocol can significantly reduce multicast forwarding state and computational overhead at routers without hurting the per-destination shortest path characteristic of a resulting tree.

This paper proposes a multi-initiation mechanism for dynamic path restoration to handle single-link failures in GMPLS-based WDM networks. This mechanism allows multiple network nodes on the primary path of a disrupted connection to participate in the restoration of the disrupted connection. Each of the nodes respectively initiates a restoration process upon the detection or notification of a link failure. In each of the processes, the initiating node attempts to dynamically establish a backup path for the disrupted connection. The destination node acts as a coordinator among multiple restoration processes. The purpose is to reduce the path restoration time so that a backup path can be provisioned more quickly for each disrupted connection that traverses a failed link. Based on this mechanism, a path restoration protocol is then presented and the performance of the protocol is evaluated through simulation experiments in terms of path restoration time and path restoration probability.

This paper presents the design of a position-aided on demand routing (PAR) protocol. The objective is to effectively reduce the communication overhead associated with path discovery and maintenance with the assistance of position information. For this purpose, PAR employs a novel restricted directional flooding mechanism. This mechanism creates an ellipse-forwarding zone, across which control messages are propagated for route discovery. Moreover, PAR uses location-guided expanding ring search, which works by searching successively larger areas for paths. This searching strategy can effectively prevent unnecessary network-wide flooding. In terms of location tracking, we design a method of recursive passive listening at intermediate nodes for end-to-end location tracking. This method enables the source to effectively keep track of the up-to-date location of its communication partner at little control overhead. Simulation results demonstrate that the PAR protocol can significantly reduce the communication overhead associated with path discovery, compared with related work.

We extend an existing multicast routing protocol, multicast extension to OSPF (MOSPF), to achieve tunnel multicasting. The extension is as follows. Tunneling is introduced for supporting tunnel multicasting, which aims at reducing the protocol overhead associated with MOSPF. Simulation results show that the extension can reduce protocol overhead significantly without affecting the per-destination shortest path characteristics of a resulting tree or introducing any extra control overhead.

Shortest path tree (SPT) is the most widely-used multicast tree type due to its simplicity and low per-destination cost. An SPT is constructed by the union of the shortest paths from the source node to each destination. However, SPT does not consider overall network resource utilization. We propose a destination-driven shortest path tree algorithm, which aims to construct a low-cost SPT by considering link sharing between different destinations. The computational complexity of the presented algorithm is O(|E|log|V|), where |E| and |V| are the number of edges and nodes in a network respectively. Simulation results are used to demonstrate the high performance of the proposed algorithm.

QoS routing has generally been addressed in the context of reservation-based network services (e.g. ATM, IntServ), which require explicit (out of band) signaling of reservation requests and maintenance of per-flow state information. It has been recognized that the processing of per-flow state information poses scalability problems, especially at core routers. To remedy this situation, in this paper we introduce an approach for stateless QoS routing in IP networks that assumes no support for signaling or reservation from the network. Simple heuristics are proposed to identify a low-cost delay-constrained path. These heuristics essentially divide the end-to-end path into at most two "superedges" that are connected by a "relay node". Routers that lie on the same superedge use either the cost metric or the delay metric (but not both) to forward the packet. Simulations are presented to evaluate the cost performance of the proposed approach.

In this paper, we propose a fast multicast routing heuristic, called DCMA, for delay-sensitive applications. The running complexity of DCMA is O(m log m+|V|), where m is the size of the multicast group and |V| is the number of nodes in the network. We first present a unicast version of DCMA, called SDCR, which is used to setup an end-to-end, cost effective delay-constrained path between two nodes. SDCR can always find a delay-constrained path if one exists. Its running complexity is O(|V|). SDCR is used in constructing DCMA, which is guaranteed to be loop free. Simulation results are used to demonstrate the high performance and cost effectiveness of the proposed heuristic.

We provide an example to illustrate the worst case message complexity of two of heuristics (R. Sriram, G. Manimaran, C.Siva Ram Murthy, Preferred link based delay-constrained least cost routing in wide area networks, Computer Communiations, 21(1998), 1655-1669) is exponential which was not stated by the authors.

This article proposes a destination-driven on-demand multicast routing protocol (D-ODMRP) to improve the multicast forwarding efficiency in mobile ad hoc networks (MANETs). In D-ODMRP, the path from the multicast source to a multicast destination tends to use those paths passing through another multicast destination. If such multiple paths are available, the one leading to the least extra cost is preferred. This destination-driven strategy is introduced into the on-demand construction process of a multicast forwarding structure in a popular multicast protocol ODMRP. Simulation results show that D-ODMRP can significantly improve the forwarding efficiency as compared with ODMRP. Moreover, the destination-driven strategy can also be introduced into other existing multicast routing protocols for MANETs.

Location-based routing has been considered as an efficient routing paradigm for wireless sensor networks (WSNs). The performance of location-based routing highly depends on the way the position information of mobile sinks are updated and managed, which is the typical function of location service. Frequent location updating can improve the location accuracy at the expense of additional communication overhead. In this study, the authors propose a scalable location service for supporting efficient location-based routing in WSNs with mobile sinks. The proposed location service enables each sensor node to locate its closest (mobile) sink with low overhead. Analytical and simulation results show that it can significantly reduce the communication overhead for providing location service while maintaining high routing performance.

In this article, we propose an asynchronous cooperative transmission mechanism for Mobile ad hoc Networks (MANETs). The proposed cooperative transmission mechanism employs distributed Unitary Space-Frequency Coded-Orthogonal Frequency Division Multiplexing (USFC-OFDM), which does not require any channel estimation and has a lower decoding complexity, and therefore can provide better reliability and robustness when mobile nodes move fast. Moreover, it can achieve a larger diversity gain and multiplexing gain, and can thus combat fast time-varying and frequency-selective channel fading, and tolerate imperfect synchronisation among mobile nodes. To support USFC-OFDM, a Time Division Multiple Access-based Cooperative Medium Access Control protocol and an on-demand Cooperative Dynamic Source Routing protocol are also proposed. Through simulation results, we show that the proposed USFC-OFDM-based cooperative transmission mechanism can significantly improve the network performance in terms of packet delivery ratio and bit error rate in highly dynamic mobile environments.

QoS routing has been a critical issue for providing QoS in high-speed networks. The authors present the design of a fast routing algorithm for selecting the shortest path connecting a pair of nodes subject to a bandwidth constraint. The algorithm works by combining the strategies of informed search and backwards routing. Its worst-case computational complexity is deduced to be O(∣E∣lg∣V∣), where ∣E∣ and ∣V∣ represent the number of links and nodes in the network, respectively. Simulation results indicate, however, that the designed algorithm can greatly reduce the average-case running time in computing such constrained shortest paths as compared with existing work.