• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38B no.5
• /
• pp.315-327
• /
• 2013

Wireless Body Area Network (WBAN) is a network around a human body within 3~5m which consists of medical or non-medical device. WBAN has to satisfy many kinds of demands such as low-power, a variety of data rate and a data priority. Especially, it is hard for the nodes for monitoring vital signs to replace battery. Thus energy and channel efficiency is important because the battery power is limited. In this thesis, a novel algorithm for reducing the energy consumption is proposed. The proposed algorithm adjusts transmission period according to traffic. by means of determining transmission period by amount of data, the node can reduce energy consumption. Energy detection is performed in order to guarantee data priority before attempting to transmit. In case of failing to transmit, it is proposed that energy consumption is reduced through avoiding collision by changing priority. The comparison result shows that the proposed algorithm reduces power consumption and increasing maximum channel efficiency by avoiding collision.

• Nuclear Engineering and Technology
• /
• v.44 no.5
• /
• pp.507-522
• /
• 2012

When decommissioning a nuclear power plant, it is difficult to make an appropriate plan to ensure sufficient space for temporary placement and conveyance operations of dismantling targets. This paper describes a system to support temporary placement and conveyance operations using augmented reality (AR). The system employs a laser range scanner to measure the three-dimensional (3D) information of the environment and a dismantling target to produce 3D surface polygon models. Then, the operator simulates temporary placement and conveyance operations using the system by manipulating the obtained 3D model of the dismantling target in the work field. Referring to the obtained 3D model of the environment, a possible collision between the dismantling target and the environment is detectable. Using AR, the collision position is presented intuitively. After field workers evaluated this system, the authors concluded that the system is feasible and acceptable to verify whether spaces for passage and temporary storage are sufficient for temporary placement and conveyance operations. For practical use in the future, some new functions must be added to improve the system. For example, it must be possible for multiple workers to use the system simultaneously by sharing the view of dismantling work.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.11
• /
• pp.25-32
• /
• 2007

In this paper, we propose the Group Separation Algorithm for RFID Tag Anti-Collision. We study the RFID Tag anti-collision technique of ALOHA and the anti-collision algorithm of binary search. The existing technique is several problems; the transmitted data rate included of data, the recognition time and energy efficiency. For distinction of all tags, the Group Separation algorithm identify each Tag_ID bit#s sum of bit #1#. In other words, Group Separation algorithm had standard of selection by collision table, the algorithm can reduce unnecessary number of search even than the exisiting algorithm. The Group Separation algorithm had performance test that criterions were reader#s number of repetition and number of transmitted bits for understanding tag. We showed the good performance of Group Separation algorithm better than exisiting algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.4
• /
• pp.1-9
• /
• 2007

in this paper, we propose the Adaptive Decision Algorithm for RFID Tag Anti-Collision. We study the RFID Tag anti-collision technique of ALOHA and the anti-collision algorithm of binary search. The existing technique is several problems; the transmitted data rate included of data, the recognition time and energy efficiency. For distinction of all tags, the Adaptive Decision algorithm identify smaller one ,each Tag_ID bit's sum of bit '1'. In other words, Adaptive Decision algorithm had standard of selection by actively, the algorithm can reduce unnecessary number of search even than the exisiting algorithm. The Adaptive Decision algorithm had performance test that criterions were reader's number of repetition and number of transmitted bits for understanding tag. We showed the good performance of Adaptive Decision algorithm better than exisiting algorithm.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.10 no.11
• /
• pp.1225-1230
• /
• 2015

MAC protocol for WBAN performs CSMA/CA(:Carrier Sense Multiple Access with Collision Avoidance)algorithm that handles traffic which occurs in emergency with top priority in order to deal with variable data of sensor node for medicine. Emergency message that node sends undergoes collision and delay of transmission by retransmission of emergency message and waste of energy by retransmission. This paper suggests algorithm that minimizes loss of frame caused by collision and applies different backoff parameters by setting order of priority between MAC instruction frame and data frame in CSMA/CA algorithm case which applies order of priority queuing to improve aforementioned problem. According to performance evaluation, it has been found that using suggested MAC protocol showed lower collision probability, higher packet transmission processing ratio and lower packet loss compared with using IEEE 802.15.6.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.36 no.2
• /
• pp.113-120
• /
• 2023

This paper introduces a simulation method for the collision between roadblocks and vehicles using LS-DYNA. The need to evaluate the performance of anti-ram barriers to prepare for vehicle impact has increased since vehicle impact threats have been included as a design criterion for nuclear power plants. Anti-ram barriers are typically certified for their performance through collision experiments. However, because Koreas has no performance testing facilities for anti-ram barriers, their performance can only be verified through simulations. LS-DYNA is a specialized program for collision simulation. Various organizations, including NCAC, distributes numerical models that have been validated for their accuracy with collision tests. In this study, we constructed a finite element model of the most critical vehicle barrier module and simulated collision between roadblocks and vehicles. The calculated results were verified by applying the validation criteria for vehicle safety facility collision simulations of NCHRP 179.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2009.04a
• /
• pp.108-108
• /
• 2009

The main object of this research is to minimize the shock effects which frequently result in fatal damage in wind met mast on impact of barge. The collision between wind met mast and barge is generally a complex problem and it is often not practical to perform rigorous finite element analyses to include all effects and sequences during the collision. LS-dyna generally purpose explicit finite element code, which is a product of ANSYS software, is used to model and analyze the non-linear response of the met mast due to barge collision. A significant part of the collision energy is dissipated as strain energy and except for global deformation modes, the contribution from elastic straining can normally be neglected. On applying impact force of a barge to wind met mast, the maximum acceleration, internal energy and plastic strain were calculated for each load cases using the finite element method and then compare it, varying to the velocity of barge, with one varying to the thickness of rubber fender conditions. Hence, we restrict the present research mainly to the wind met mast and also parametric study has been carried out with various velocities of barge, thickness of wind met mast, thickness and Mooney-Rivlin coefficient of rubber fender with experimental data. The equation of motion of the wind met mast is derived under the assumption that it was ignored vertical movement effect of barge on sea water. Such an analyzing method which was developed so far, make it possible to determine the proper size and material properties of rubber fender and the optimal moving conditions of barge, and finally, application method can be suggested in designing process of rubber fender considering barge impact.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.7
• /
• pp.567-578
• /
• 2015

Single droplet-wall collision heat transfer characteristics on a heated plate above Leidenfrost temperature were experimentally investigated considering the effects of impact velocity. The collision characteristics of the droplet impinged on the heated wall and the changes in temperature distribution were simultaneously measured using synchronized high-speed video and infrared cameras. The surface heat flux distribution was obtained by solving the three-dimensional transient heat conduction equation for the heated substrate using the measured surface temperature data as the boundary condition for the collision surface. As the normal impact velocity increased, heat transfer effectiveness increased because of an increase in the maximum spreading diameter and a decrease in the vapor film thickness between the droplet and heated wall. For We < 30, droplets stably rebounded from a heated wall without breakup. However, the droplets broke up into small droplets for We > 30. The tendency of the heat transfer to increase with increasing impact velocity was degraded by the transition from the rebounding region to the breakup region; this was resulted from the reduction in the effective heat transfer area enlargement due to the breakup phenomenon.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.18 no.2
• /
• pp.217-226
• /
• 2018

Since the sides of a vehicle are designed asymmetrically unlike its front or rear, the degree of deformation of the car body greatly differs depending on the site of collision if a broadside collision takes place. When elastic deformation and plastic deformation occur in the car body occur due to a collision, the kinetic energy is absorbed into the body, and the momentum decreases. Generally, an analysis of traffic accidents analyzes the vehicle's behavior after a collision by the law of momentum conservation and corrects the error of the amount of energy absorption due to the deformation of the car body, applying a restitution coefficient. This study interpreted a finite element vehicle model applying the structure of the car body and the material properties of each part with LS-DYNA, analyzed the result and drew the restitution coefficient and the depth of penetration according to the contact area of the vehicle in a broadside collision between an SUV and a passenger car. When the finally calculated restitution coefficient and depth of penetration were applied to the examples of the actual traffic accidents, there was an effect on the improvement of the error in the result. It was found that when the initial input value, drawn using the finite element analysis model, it had a higher reliability of the interpretation than that of the existing analysis techniques.

• Transactions of the Korean hydrogen and new energy society
• /
• v.12 no.3
• /
• pp.191-199
• /
• 2001

In this paper molecular dynamics simulations have been carried out to investigate energy and momentum transfer of hydrogen ions impacted on the Ni (100) surface with $45^{\circ}$ and $90^{\circ}$ incident angles. The initial kinetic energies of the hydrogen ion were ranged from 100 eV to 1,600 eV to study the layer-by-layer energy variation as a dependence of incident energies and angles. At low incident energies, the scattering energy transfer is dominated by the normal motion of surface layers due to thermal vibrations and multiple collision effects. For higher incident energies, the scattering energy transfer in a normal direction is greater than that in a parallel direction. In the case of penetration, the amount of transferred energies do not affect much on Ni layers at low incident energy. It was found channeling effects through Ni layers with increasing incident energies.