Kwan-Woong Kim

An Enhanced Broadcasting Algorithm in Wireless Ad-hoc Networks

In a multi-hop wireless ad hoc network, broadcasting is an elementary operation to support many applications. Broadcasting by flooding may cause serious redundancy, contention, and collision in the network, which is referred to as the broadcast storm problem. Many broadcasting schemes are proposed to give better performance than simple flooding in wireless ad hoc network. How to decide whether rebroadcast or not also poses a dilemma between reachability and efficiency under different host densities. In this paper, we propose enhanced broadcasting schemes, which can reduce rebroadcast packets without loss of reachability. Simulation results show that proposed schemes can offer better reachability as well as efficiency as compared to other previous schemes.

Dual Role of Cyanidin-3-glucoside on the Differentiation of Bone Cells:

Cyanidin-3-glucoside (C3G) is one of the major components of anthocyanin, a water-soluble phytochemical. Recent studies demonstrated the chemopreventive and chemotherapeutic activities of C3G in various conditions, including cancer, although the precise effects of C3G on osteoclast and osteoblast differentiation remain unclear. Here, we investigated the role of C3G in the differentiation of bone-associated cells and its underlying mechanism. C3G inhibited receptor activator of nuclear factor kappa-B ligand (RANKL)–mediated osteoclast differentiation and formation in a dose-dependent manner and downregulated the expression of osteoclast differentiation marker genes. Pretreatment with C3G considerably reduced the induction of extracellular signal–regulated kinase, c-Jun N-terminal kinase, and p38 mitogen-activated kinases activation by RANKL in osteoclast precursor cells. Furthermore, C3G dramatically inhibited the expression of c-Fos and nuclear factor of activated T-cells, cytoplasmic 1, which are important transcription factors for osteoclast differentiation and activation. The formation of osteoclasts in coculture of bone marrow cells and calvaria-derived osteoblasts was also inhibited by C3G treatment, although the expression of macrophage colony-stimulating factor and RANKL (master factors for osteoclast differentiation and formation) and osteoprotegerin (a decoy receptor for RANKL) on osteoblasts was unaffected. The inhibitory effect of C3G on osteoclastogenesis is therefore targeted specifically to osteoclasts but not osteoblasts. Moreover, analysis of the expression levels of osteoblast differentiation marker genes and alizarin red staining showed that osteoblast differentiation and matrix formation increased after C3G treatment. Taken together, these results strongly suggest that C3G has a dual role in bone metabolism, as an effective inhibitor of osteoclast differentiation but also as an activator of osteoblast differentiation. Therefore, C3G may be used as a potent preventive or therapeutic agent for bone-related diseases, such as osteoporosis, rheumatoid arthritis, and periodontitis.

In vitro metabolism of the new insecticide flupyrazofos by rat liver microsomes

1. The in vitro metabolism of the new insecticide flupyrazofos was studied using rat liver microsomes. Two metabolites were produced and identified as O,O-diethyl O-(1-phenyl-3-trifluoromethyl-5-pyrazoyl) phosphoric acid ester (flupyrazofos oxon) and 1-phenyl-3-trifluoromethyl-5-hydroxypyrazole (PTMHP) based on UV and mass spectral analysis. 2. Cytochrome P450 oxidatively converted flupyrazofos to flupyrazofos oxon, a major metabolite and phenobarbital-induced microsomes increased this desulphuration by 8-fold. 3. Flupyrazofos oxon was converted to PTMHP with a half-life of 47.8 min by chemical hydrolysis and this conversion also proceeded non-enzymatically under our microsomal incubation conditions.

LRCA: enhanced energy-aware routing protocol in MANETs

Mobile Ad hoc Networks (MANETs) is power constrained since mobile nodes operate with limited battery energy. So battery life is also important research issue in the routing protocol design. During packet transmission over multi-hop nodes, if a node failed, it should be caused link failure and source node will perform route recovery. It results that increases time of route recovery and packet loss rate. The objective of this study is to reduce route failure caused by dead nodes which consume all the battery life. We propose a new routing protocol based on AODV which provides an ability of changing routes to neighbor nodes before some of intermediate nodes be shutting down. From extensive simulations, results show that possibility of cut-offs and time-delay caused by packet-loss have been decreased and also improve overall performance by comparison with original AODV.

A Dynamic Queue Management for Network Coding in Mobile Ad-hoc Network

Network Coding (NC) is a new paradigm for network communication. In network coding, intermediate nodes create new packets by algebraically combining ingress packets and send it to its neighbor node by broadcast manner. NC has rapidly emerged as a major research area in information theory due to its wide applicability to communication through real networks. Network coding is expected to improve throughput and channel efficiency in the wireless multi-hop network. Many researches have been carried out to employ network coding to wireless ad-hoc network. In this paper, we proposed a dynamic queue management to improve coding opportunistic to enhance efficiency of NC. In our design, intermediate nodes are buffering incoming packets to encode queue. We expect that the proposed algorithm shall improve encoding rate of network coded packet and also reduce end to end latency. From the simulation, the proposed algorithm achieved better performance in terms of coding gain and packet delivery rate than static queue management scheme.

LBG-Based Non-fuzzy Inference System for Nonlinear Process

We introduce a non-fuzzy inference system based on Linde-Buzo-Gray (LBG) Algorithm to construct model for nonlinear process. In grid partition, the generation of fuzzy rules has the problem that the number of fuzzy rules exponentially increases. To solve this problem, we generate the subspaces using the scatter partition of input space. The rules of non-fuzzy inference systems are generated by partitioning the input space in the scatter form using LBG algorithm. The consequence part of the rules is represented in the form of polynomial functions. The data widely used in nonlinear process is used to evaluate the performance of the proposed model.

Optimization of Non-fuzzy Neural Networks Based on Crisp Rules in Scatter Partition

We introduce a design of non-fuzzy neural networks that have crisp rules in scatter partition. To generate the crisp rules and construct the networks, we use hard c-means clustering algorithm. The partitioned local spaces indicate the crisp rules of the proposed networks. The consequence part of the rule is represented by polynomial functions. The coefficients of the polynomial functions are learned using back-propagation algorithm. In order to optimize the parameters of the proposed networks we use particle swarm optimization techniques. The proposed networks are evaluated with the example for nonlinear process.

An Enhanced Network Coding Scheme for Mobile Ad-hoc Network

Generally, in network coding, relay nodes mix the content of different packets to a single coded packet and broadcast the coded packet on the wireless medium. Network coding is expected to improve throughput and channel efficiency in the wireless multi-hop network. Prior researches have been carried out to employ network coding to wireless ad-hoc network. In this paper, we proposed an enhanced practical network coding scheme for wireless ad-hoc network. In our design, intermediate nodes identify one-hop bidirectional flows for network coding decision. It could make decoding failure probability to zero at neighbor nodes. We expect that the proposed algorithm shall improve decoding success rate of network coded packet. From the simulation, the proposed network coding scheme achieved better performance in terms of coding gain and packet delivery rate than traditional network coding scheme.

A Performance Enhancement for Ubiquitous Indoor Networking Using VLC-LED Driving Module

This study aims to use LED, a representative runner in electric energy reduction as Green IT technology in the field of lighting and suggest visible communication for using ubiquitous Indoor networking system. As LED is excellent in its efficiency, the aim has to use such LED to access ubiquitous environment, a network that can be used remotely at any time anywhere and determine the possibility of its application into various applications that promote users’ convenience. The communication performance by implementing a communication system for lighting in order to send a text message has been tested in ubiquitous environment within ~2.5m, 0.45V, 5% error rate, data rate Kbps and within disturbance light. We could confirm that the implementation of LED communication was possible in ubiquitous environment within ~2.25m, data rate ~Kbps, and 3% error rate, or more was weak or none where data transmission is seamlessly done indoors.

A Performance Evaluation on the Broadcasting Scheme for Mobile Ad-Hoc Networks

The broadcasting in the multi-hop sensor networks is a basic operation that supports many applications such as route search and setting up addresses. The broadcasting using flooding causes problems which can be mentioned as broadcasting storm such as redundancy, contention, collision. A variety of broadcasting techniques using wireless sensor networks have been proposed to achieve superior performance rather than simple flooding technique. The proposed broadcasting algorithms in wireless networks can be classified into six subcategories: flooding technique, probabilistic technique, counter-based scheme, distance-based technique, location-based techniques, and neighbor knowledge-based technique. This study analyzes simple flooding technique, probabilistic technique, counter-based scheme, distance-based technique, and neighbor knowledge-based technique, and compares the performance and efficiency of each technique through network simulation.