• ETRI Journal
• /
• v.34 no.1
• /
• pp.24-34
• /
• 2012

In this paper, the directional carrier sense multiple access/collision avoidance (CSMA/CA) protocol in the immediate acknowledgement mode for IEEE 802.15.3c is analyzed under saturation environments. For the analysis, a sensing region and an exclusive region with a directional antenna are computed probabilistically and a Markov chain model in which the features of IEEE 802.15.3c and the effects of using directional antennas are incorporated is analyzed. An algorithm to find the maximal number of concurrently transmittable frames is proposed. The system throughput and the average transmission delay are obtained in closed forms. The numerical results show the impact of directional antennas on the CSMA/CA media access control (MAC) protocol. For instance, the throughput with a small beamwidth of antenna is more than ten times larger than that for an omnidirectional antenna. The overall analysis is verified by a simulation. The obtained results will be helpful in developing an MAC protocol for enhancing the performance of mmWave wireless personal area networks.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.2503-2508
• /
• 2005

In this paper, we propose a new discrete-time predictive current controller for a PMSM(Permanent Magnet Synchronous Motor). The main objectives of the current controllers are to ensure that the measured stator currents tract the command values accurately and to shorten the transient interval as much as possible, in order to obtain high-performance of ac drive system. The conventional predictive current controller is hard to implement in full digital current controller since a finite calculation time causes a delay between the current sensing time and the time that it takes to apply the voltage to motor. A new control strategy in this paper is seen the scheme that gets the fast adaptation of transient current change, the fast transient response tracking. Moreover, the validity of the proposed method is demonstrated by numerical simulations and the simulation results will present the improvements of predictive controller and accuracy of the current controller.

• Smart Structures and Systems
• /
• v.15 no.6
• /
• pp.1601-1623
• /
• 2015

Electroactive polymers have attracted considerable attention in recent years due to their sensing and actuating properties which make them a material of choice for a wide range of applications including sensors, biomimetic robots, and biomedical micro devices. This paper presents an effective modeling strategy for nonlinear large deformation (small strains and moderate rotations) dynamic analysis of polymer actuators. Considering that the complicated electro-chemo-mechanical dynamics of these actuators is a drawback for their application in functional devices, establishing a mathematical model which can effectively predict the actuator's dynamic behavior can be of paramount importance. To effectively predict the actuator's dynamic behavior, a comprehensive mathematical model is proposed correlating the input voltage and the output bending displacement of polymer actuators. The proposed model, which is based on the rigid finite element (RFE) method, consists of two parts, namely electrical and mechanical models. The former is comprised of a ladder network of discrete resistive-capacitive components similar to the network used to model transmission lines, while the latter describes the actuator as a system of rigid links connected by spring-damping elements (sdes). Both electrical and mechanical components are validated through experimental results.

• Journal of Information Technology Applications and Management
• /
• v.18 no.3
• /
• pp.31-39
• /
• 2011

The weakening of the traditional cultures is becoming more evident from the final quarter of the last century, a period of time where the world starts to look like a "small village" in all means. A substantial cause of cultural deterioration shows to be the growing use of information and communication technologies widening the views, mentalities, and perspectives of people. Today the adolescent groups frequently owning, utilizing and consequently being charmed by the electronic equipment such like computers, internet and cellular phones have developed a unique tradition/practice in sensing and meaning life triggering larger generation gap and fading of established cultures. The main focusing of the paper is on the correlation between computer and internet use and life satisfaction, level of hope, personal development assessments and expectations of the adolescent groups in Turkey. Interpretation of the survey findings indicates that this group grading highest in use of that shows to be the happiest, most hopeful and optimistic ones among other groups. Methodologically, the study is based on data analysis and a review of recent key literature. For more dependable results a further study comparing similar tendencies of the similar groups of other nationalities is recommended.

• Journal of Power Electronics
• /
• v.17 no.1
• /
• pp.212-221
• /
• 2017

Permanent-Magnet Synchronous Generators (PMSGs) are used widely in Wind Power Generation Systems (WPGSs), and the Vienna rectifier was recently proposed to be used as the generator-side converter to rectify the AC output voltage in PMSG-based WPGS. Compared to conventional six-switch two-level PWM (2L-PWM) converters, the Vienna rectifier has several advantages, such as higher efficiency, improved total harmonic distortion, etc. The motivation behind this paper is to verify the performance of direct-driven PMSG wind turbine system based-Vienna rectifier by using a simulated direct-driven PMSG WPGS. In addition, for the purpose of reducing the reactive power loss of PMSGs, this paper proposes an induced voltage sensing scheme which can make the stator current maintain accurate synchronization with the induced voltage. Meanwhile, considering the Neutral-Point Voltage (NPV) variation in the DC-side of the Vienna rectifier, a NPV balancing control strategy is added to the control system. In addition, both the effectiveness of the proposed method and the performance of the direct-driven PMSG based-Vienna rectifier are verified by simulation and experimental results.

• Journal of the Korean Ceramic Society
• /
• v.47 no.1
• /
• pp.92-96
• /
• 2010

Based on the differential electrode equilibria approach, potentiometric YSZ sensors with semiconducting oxide electrodes for CO detection are developed. To improve the selectivity, sensitivity and response-time of the sensor, our strategy includes (a) selection of an oxide with a semiconducting response to CO, (b) addition of other semiconducting materials, (c) addition of a catalyst (Pd), (d) utilization of combined p- and n-type electrodes in one sensor configuration, and (e) optimization of operating temperatures. Excellent sensing performance is obtained by a novel device structure incorporating $La_2CuO_4$ electrodes on one side and $TiO_2$-based electrodes on opposite substrate faces with Pt contacts. The resulting response produces additive effects for the individual $La_2CuO_4$ and $TiO_2$-based electrodes voltages, thereby realizing an even higher CO sensitivity. The device also is highly selective to CO versus NO with minor sensitivity for NO concentration, compared to a notably large CO sensitivity.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.16 no.1
• /
• pp.72-78
• /
• 2006

It is essential for robot to have the sensing and communication abilities in the swarm robot system. In general, as the number of robot goes on increasing, the limitation of communication capacity and information overflow occur in global communication system. Therefore a local communication is more effective than global one. In this paper, we propose the novel method for determining the optimal communication radius through the analyzing of the information propagation based on local communication. And we also propose a method of cooperative strategies and group behavior of swarm robot based on artificial immune system.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.16 no.1
• /
• pp.8-17
• /
• 2006

It is essential for robot to have the sensing and communication abilities in the swarm robot system. In general, as the number of robot goes on increasing, the limitation of communication capacity and information overflow occur in global communication system. Therefore a local communication is more effective than global one. In this paper, we analyze information propagation mechanism based on local communication. To find an optimal communication radius, we propose several methods with different conditions. Also, to avoid chaotic behavior which occurs when a robot obtains and loses information, we will suggest the stable condition of information propagation.

• Fisheries and Aquatic Sciences
• /
• v.12 no.4
• /
• pp.265-275
• /
• 2009

G Protein-coupled receptors (GPCRs) mediating wide ranges of physiological responses is one of the most attractive targets for drug development. Rhodopsin, a dim-light photoreceptor, has been extensively used as a model system for structural and functional study of GPCRs. Fish have rhodopsin finely-tuned to their habitats where the intensity and the wavelength of lights are changed depending on its water-depth. To study the detailed molecular characteristics of GPCR architecture and to understand the fishery light-sensing system, genes encoding rod opsins were isolated from fishes living under different photic environments. Full-length rod opsin genes were obtained by combination of PCR amplification and DNA walking strategy of genomic DNA isolated from olive flounder, P. olivaceus, Japanese eel, A. japonica, and Common carp C. carpio. Deduced amino acid sequences showed a typical feature of rod opsins including the sites for Schiffs base formation (Lys296) and its counter ion (Glu113), disulfide formation (Cys110 and Cys187), and palmitoylation (Cys322 and Cys323) although Cys322 is replaced by Phe in Japanese eel. Comparison of opsins by amino acid sequence alignment indicated the closest similarity between P. olivaceus and H. hippoglossus (94%), A. japonica and A. anguilla (98%), and C. carpio and C. auratus (95%), respectively.

• Journal of Electrical Engineering and Technology
• /
• v.11 no.3
• /
• pp.733-740
• /
• 2016

To achieve bipedal walking in real human environments, a bipedal robot should be capable of modifiable walking both on uneven terrain with different heights and on flat terrain. In this paper, a novel walking pattern generator based on a 3-D linear inverted pendulum model (LIPM) is proposed to achieve this objective. By adopting a zero moment point (ZMP) variation scheme in real time, it is possible to change the center-of-mass (COM) position and the velocity of the 3-D LIPM throughout the single support phase. Consequently, the proposed method offers the ability to generate a modifiable pattern for walking on uneven terrain without the necessity for any extra footsteps to adjust the COM motion. In addition, a control strategy for bipedal walking on uneven terrain with unknown height is developed. The torques and ground reaction force are measured through force-sensing resisters (FSRs) on each foot and the foot of the robot is modeled as three virtual spring-damper models for the disturbance compensation. The methods for generating the foot and vertical COM of 3-D LIPM trajectories are proposed to achieve modifiable bipedal walking on uneven terrain without any information regarding the height of the terrain. The effectiveness of the proposed method is confirmed through dynamic simulations.