A Novel Single-Feed Circular Microstrip Antenna With Reconfigurable Polarization Capability

A single-feed circular microstrip antenna with reconfigurable polarization capability is proposed. This antenna has a simple structure, which consists of a radiating circular patch, five switches (PIN diode), three matching stubs, and a 50 microstrip feed line. It can be switched between 4 different states: two states (low-frequency and high-frequency) for linear polarization (LP), one state for left hand circular polarization (LHCP) and one for right hand circular polarization (RHCP) by controlling the bias voltage of two PIN diodes. At the same time, three switchable matching stubs are used for matching every polarization state. Simulation results and experimental results show that the proposed antenna demonstrates a low cross polarization level, good impedance bandwidth, and a very good axial ratio in the circularly polarized states.     

An efficient job management of computing service using integrated idle VM resources for high-performance computing based on OpenStack

In recent years, various studies on OpenStack-based high-performance computing have been conducted. OpenStack combines off-the-shelf physical computing devices and creates a resource pool of logical computing. The configuration of the logical computing resource pool provides computing infrastructure according to the user’s request and can be applied to the infrastructure as a service (laaS), which is a cloud computing service model. The OpenStack-based cloud computing can provide various computing services for users using a virtual machine (VM). However, intensive computing service requests from a large number of users during large-scale computing jobs may delay the job execution. Moreover, idle VM resources may occur and computing resources are wasted if users do not employ the cloud computing resources. To resolve the computing job delay and waste of computing resources, a variety of studies are required including computing task allocation, job scheduling, utilization of idle VM resource, and improvements in overall job’s execution speed according to the increase in computing service requests. Thus, this paper proposes an efficient job management of computing service (EJM-CS) by which idle VM resources are utilized in OpenStack and user’s computing services are processed in a distributed manner. EJM-CS logically integrates idle VM resources, which have different performances, for computing services. EJM-CS improves resource wastes by utilizing idle VM resources. EJM-CS takes multiple computing services rather than single computing service into consideration. EJM-CS determines the job execution order considering workloads and waiting time according to job priority of computing service requester and computing service type, thereby providing improved performance of overall job execution when computing service requests increase.

     

Structural and Dielectric Properties of PLZT Ceramics Modified with Lanthanide Ions

Lanthanide-modified lead lanthanum zirconate titanate (PLZT) ceramics were prepared through a hydroxide co-precipitation method, and the effects of the lanthanide ions on the structural and dielectric properties of the PLZT ceramics were investigated. The substitution site of the lanthanide ions was found to change from the A site to the B site with decreased lanthanide ionic radius by comparing theoretically calculated and experimentally measured unit-cell volumes and densities. The variation of structural and dielectric properties in the lanthanide-modified PLZT series was highly correlated to the change of substitution site, leading to the compositional change of the unit cell. Raman spectra showed that the B-site local structures were affected by the substitution type.     

SHSec: SDN based Secure Smart Home Network Architecture for Internet of Things

Mobile Networks and Applications - To address the challenges of flexible device utilization, heterogeneous device interoperability, and security enhancement in smart homes, this paper proposes a...     

RETRACTED ARTICLE: Simulator considering modeling and performance evaluation for high-performance computing of collaborative-based mobile cloud infrastructure

In recent years, as IT technology has progressed, mobile devices have been created that enable various manual tasks to be automated and portable. A variety of mobile devices has computing, storage, and Internet capabilities and can handle many tasks. When miniaturized mobile devices perform tasks that require a large amount of computing resources due to limited computing and storage, there is a delay in operation and a non-operation state. Therefore, collaborative-based mobile cloud infrastructure (MCI) research is being conducted to provide computing services composed of mobile devices. Computation off-loading studies have been conducted for MCI’s high-performance computing, but it is difficult to build various mobile infrastructures and verify algorithm performance. In addition, performance verification is performed in a predetermined MCI environment or is carried out through small-scale test equipment. This causes waste of time, cost, and manpower for constructing the environment. Various studies have been conducted for this purpose, but there is a difficulty in performance verification and analysis since only the results are displayed or outputted in text form. In this paper, we propose a mobile cloud infrastructure simulator (MCIS) for computing off-loading, resource management, mobile deployment, and mobile information for MCI. MCIS enables user tasks, resource allocation methods, and various mobile device performance settings. In addition, visualization of the operating state makes it easy to analyze the performance of the user, and it is possible to grasp the problems that occur during operation.

     

Distributed scheduling algorithms for channel access in TDMA wireless mesh networks

In this paper, we have considered the distributed scheduling problem for channel access in TDMA wireless mesh networks. The problem is to assign time-slot(s) for nodes to access the channels, and it is guaranteed that nodes can communicate with all their one-hop neighbors in the assigned time-slot(s). And the objective is to minimize the cycle length, i.e., the total number of different time-slots in one scheduling cycle. In single-channel ad hoc networks, the best known result for this problem is proved to be K ² in arbitrary graphs (IEEE Trans Comput C-36(6):729–737, 1987) and 25K in unit disk graphs (IEEE/ACM Trans Netw pp 166–177, 1993) with K as the maximum node degree. There are multiple channels in wireless mesh networks, and different nodes can use different control channels to reduce congestion on the control channels. In this paper, we have considered two scheduling models for wireless mesh networks. The first model is that each node has two radios, and the scheduling is simultaneously done on the two radios. We have proved that the upper bound of the cycle length in arbitrary graphs can be 2K. The second model is that the time-slots are scheduled for the nodes regardless of the number of radios on them. In this case, we have proved that the upper bound can be (4K?2). We also have proposed greedy algorithms with different criterion. The basic idea of these algorithms is to organize the conflicting nodes by special criterion, such as node identification, node degree, the number of conflicting neighbors, etc. And a node cannot be assigned to a time-slot(s) until all neighbor nodes, which have higher criterion and might conflict with the current node, are assigned time-slot(s) already. All these algorithms are fully distributed and easy to realize. Simulations are also done to verify the performance of these algorithms.     

Adaptive resource management scheme for monitoring of CPS

In recent years, various studies based on cyber physical systems (CPS) that integrate networking, computation, and physical processes have been actively carried out in different industries, national defense, and daily living. To physically reflect the theoretical aspect of CPS, consideration of various features is necessary to more easily integrate and effectively manage real-world components and the cyber world. This study suggests an adaptive resource management scheme (ARMS) to reduce the loss of sensing information and increase the level of accurate data obtained in the controller manager (CM) among the CPS components. A CPS-based system consists of a number of nodes (sensors and actuators) used to observe or monitor specific areas. ARMS utilizes data about the location and remaining battery capacity of each node to reduce the loss of information due to the irregular lifespans and unexpected breakdowns of resources in the CPS, and to obtain accurate data. Once a broken sensor in the physical world is sensed in the cyber world, the CM searches the locations of adjacent alternative nodes within a user-defined range based on the location of the broken node. In this process, an adjacent node search (ANS) algorithm is run to decide on a node (senor or actuator) to replace the broken node, taking into account the remaining battery capacity of candidate nodes. ARMS provides the adaptive resource management function of CPS by sending information on the identity (ID) and destination of the selected node to the controller to move the node to the destination and control the move.     

An efficient strategy of nonuniform sensor deployment in cyber physical systems

In this paper, we study the sensor deployment pattern problem in cyber physical systems. When designing the sensor deployment pattern, the network lifetime maximization while covering the given area/targets and forwarding sensor data to a sink node is an important issue. In order to prolong the network lifetime by balancing energy depletion across all sensors, we propose a novel nonuniform sensor distribution strategy. Since sensors located closer to the sink are more involved in data forwarding, sensor densities in different areas should be varied according to the distance to the sink. Based on the nonuniform sensor distribution, we propose sensor deployment patterns to satisfy the coverage and connectivity requirements and prolong the network lifetime. A numerical computation is performed to validate and compare the effectiveness of the proposed deployment patterns.     

Dynamic stability of a cantilevered Timoshenko beam on partial elastic foundations subjected to a follower force

This paper presents the dynamic stability of a cantilevered Timoshenko beam with a concentrated mass, partially attached to elastic foundations, and subjected to a follower force. Governing equations are derived from the extended Hamilton’s principle, and FEM is applied to solve the discretized equation. The influence of some parameters such as the elastic foundation parameter, the positions of partial elastic foundations, shear deformations, the rotary inertia of the beam, and the mass and the rotary inertia of the concentrated mass on the critical flutter load is investigated. Finally, the optimal attachment ratio of partial elastic foundation that maximizes the critical flutter load is presented.