• Journal of IKEEE
• /
• v.25 no.1
• /
• pp.32-36
• /
• 2021

This paper presents a novel collided tag signals's periodic characteristic based radio frequency identification (RFID) tag collision detection method for the ultra high frequency (UHF) RFID. The proposed method utilizes that periodicity of tag signals is maintained even under tag collision. In the proposed method, the correlation between received signal and reference edge signal is used. Simulation result shows that the detection performance using the proposed method is about 10 dB better than that of existing method. In addition, the detection performances with different magnitude difference, phase difference, delay, number of tags are analyzed.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.8
• /
• pp.32-42
• /
• 2022

Asymptotic tracking of a non-minimum phase nonlinear system has been a popular topic in control theory and application. In this paper, we propose a new control scheme to achieve asymptotic output tracking in anon-minimum phase nonlinear system for periodic trajectories through an iterative learning control with the stable inversion. The proposed design method is robust to parameter uncertainties and periodic external disturbances since it is based on iterative learning. The performance of the proposed algorithm was demonstrated through the simulation results using a typical non-minimum nonlinear system of an inverted pendulum on a cart.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2007.05a
• /
• pp.1291-1293
• /
• 2007

Due to dense deployment and innumerable amount of traffic flow in wireless sensor networks (WSNs), congestion becomes more common phenomenon from simple periodic traffic to unpredictable bursts of messages triggered by external events. Even for simple network topology and periodic traffic, congestion is a likely event due to dynamically time varying wireless channel condition and contention caused due to interference by concurrent transmissions. In this paper, we have proposed three mechanisms: upstream source count and buffer based rate control and snoop based MAC level ACK scheme to avoid congestion. The simulation results show that our proposed mechanism achieves around 80% delivery ratio even under bursty traffic condition

• Journal of Mechanical Science and Technology
• /
• v.17 no.4
• /
• pp.545-561
• /
• 2003

We use the first-passage-time formulation by Torquato, Kim and Cule ［J. Appl. Phys., Vol. 85, pp. 1560∼1571 (1999) ］, which makes use of the first-passage region in association with the diffusion tracer's Brownian movement, and develop a new efficient Brownian motion simulation method to compute the effective conductivity of digitized composite media. By using the new method, one can remarkably enhance the speed of the Brownian walkers sampling the medium and thus reduce the computation time. In the new method, we specifically choose the first-passage regions such that they coincide with two, four, or eight digitizing units according to the dimensionality of the composite medium and the local configurations around the Brownian walkers. We first obtain explicit solutions for the relevant first-passage-time equations in two-and three-dimensions. We then apply the new method to solve the illustrative benchmark problem of estimating the effective conductivities of the checkerboard-shaped composite media. for both periodic and random configurations. Simulation results show that the new method can reduce the computation time about by an order of magnitude.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.337-342
• /
• 2007

In this study, molecular dynamics simulation of nano imprint lithography in which patterned stamp is pressed onto amorphous polyethylene(PE) surface are performed to study the behaviour of polymer. Force fields including bond, angle, torsion, and Lennard Jones potential are used to describe the inter-molecular and intra-molecular force of PE molecules and stamp, substrate. Periodic boundary condition is used in horizontal direction and canonical NVT ensemble is used to control the system temperature. As the simulation results, the behaviour of polymer is investigated during the imprinting process. The mechanism of polymer deformation is studied by means of inspecting the surface shape, volume, density, atom distribution. Deformation of the polymer resist was found for various of the stamp geometry and the alignment state of the polymer molecules.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.2 s.257
• /
• pp.237-244
• /
• 2007

In order to obtain mechanical properties of CNT/Polymer nano-composites, molecular dynamics simulation is performed. Overall system was modeled as a flexible unit cell in which carbon nanotubes are embedded into a polyethylene matrix for N $\sigma$ T ensemble simulation. COMPASS force field was chosen to describe inter and intra molecular potential and bulk effect was achieved via periodic boundary conditions. In CNT-polymer interface, only Lennard-Jones non-bond potential was considered. Using Parrinello-Rahman fluctuation method, mechanical properties of orthotropic nano-composites under various temperatures were successfully obtained. Also, we investigated thermal behavior of the short CNT reinforced nanocomposites system with predicting glass transition temperature.

• Proceeding of EDISON Challenge
• /
• 2016.03a
• /
• pp.55-61
• /
• 2016

$A{\beta}_{40}$ peptides form oligomers that later aggregate into a plaque, which is deemed to be a leading cause of Alzheimer's Disease. Its non-crystalline morphology has limited an understanding of comprehensive structural study. In this research, computational biomolecular simulations were performed in the following order: solvent and ion addition in a box, energy minimization of protein, equilibration, and periodic boundary condition disaggregation of a monomer from fibril. The result founded the two-fold model is 25% more stable in the simulation environment, and the steric zippers held on most tightly until 220 ps of simulation. The study supports the previous findings that two-fold aggregate $A{\beta}_{40}$ is more stable at 310 K and discusses further how much contribution steric-zipper and hydrogen bonding are making.

• The Transactions of the Korea Information Processing Society
• /
• v.7 no.7
• /
• pp.2229-2237
• /
• 2000

This paper intends to improve the problems of the slack stealing algorithm scheduling for periodic tasks with fixed priority and aperiodic tasks which occur dynamically. The Slack stealing algorithm reduces unnecessary waiting time by making the service possible immediately when the slack stealing server gives suitable priority to aperiodic tasks according to the status of aperiodic tasks arrivals at runtime. But no performs the slack stealing, we must calculate execution time of periodic tasks till the point of random. And, execution time of periodic tasks is being repeatedly every hours while the slack algorithm is applied. We show time complexity hen is used as to O(n) if the nubmer of tasks which is applied to the calculation is n. In this appear, due to stored in tables slack times and the execution times of the scheduled periodic tasks, the complexity of aperiodic tasks which is occurring dynamically reduced to O(log n) and improves the responses times. We prove the algorithm proposed in this paper through the simulation.

• The Journal of the Korea Contents Association
• /
• v.7 no.1
• /
• pp.83-93
• /
• 2007

In this paper, we address a power-aware scheduling algorithm for a mixed real-time system which consists of periodic and sporadic tasks, each of which is characterized by its minimum period, worst-case execution requirement and deadline. We propose a dynamic voltage scaling algorithm called DVSMT(DVS for mixed tasks), which dynamically scales down the supplying voltage(and thus the frequency) using on-line distribution of the borrowed resources when jobs complete while still meeting their deadlines. With this scheme, we could reduce more energy consumption. As the proposed algorithm can be easily incorporated with RTOS(Real-Time Operating System), it is applicable for handhold devices and sensor network nodes that use a limited battery power. Simulation results show that DVSMT saves up 60% more than the existing algorithms both in the periodic-task and mixed-task systems.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.45 no.6
• /
• pp.18-26
• /
• 2008

In this paper, dynamic GTS scheduling method based on IEEE 802.15.4 is proposed for wireless control system considering reliability and real-time property. The proposed methods can guarantee a transmission of real-time periodic and sporadic data within the limited time frame in factory environment. The superframe of IEEE 802.15.4 is used for the dynamic transmission method of real-time mixed traffic (periodic data, sporadic data, and non real-time message). By separating CFP and CAP properly, the periodic, sporadic, and non real-time messages are transmitted effectively and guarantee real-time transmission within a deadline. The simulation results show the improvement of real-time performance of periodic and sporadic data at the same time.