• Bulletin of the Korean Chemical Society
• /
• v.23 no.11
• /
• pp.1595-1603
• /
• 2002

In this paper we have presented the results of diffusion behavior of model systems for eight liquid n-alkanes ($C_{12}$-$C_{44}$) in a canonical (NVT) ensemble at several temperatures using molecular dynamics simulations. For these n-alkanes of small chain length n, the chains are clearly <$R_{ee}^2$>/6<$R_g^2$>>1 and non-Gaussian. This result implies that the liquid n-alkanes over the whole temperatures considered are far away from the Rouse regime, though the ratio becomes close to the unity as n increases. Calculated self-diffusion constants $D_{self}$ are comparable with experimental results and the Arrhenius plot of self-diffusion constants versus inverse temperature shows a different temperature dependence of diffusion on the chain length. The global rotational motion of n-alkanes is examined by characterizing the orientation relaxation of the end-to-end vector and it is found that the ratio ${\tau}1/{\tau}2$ is less than 3, the value expected for a isotropically diffusive rotational process. The friction constants ${\xi}$of the whole molecules of n-alkanes are calculated directly from the force auto-correlation (FAC) functions and compared with the monomeric friction constants ${\xi}_D$ extracted from $D_{self}$. Both the friction constants give a correct qualitative trends: decrease with increasing temperature and increase with increasing chain length. The friction constant calculated from the FAC's decreases very slowly with increasing temperature, while the monomeric friction constant varies rapidly with temperature. By considering the orientation relaxation of local vectors and diffusion of each site, it is found that rotational and translational diffusions of the ends are faster than those of the center.

• Journal of IKEEE
• /
• v.11 no.4
• /
• pp.205-212
• /
• 2007

The ubiquitous sensor network consists of micro sensors with wireless communication capabilities. Compared to wired communication, wireless communication is more subject to eavesdropping as well as data variation and manipulation. Accordingly, there must be efforts to secure the information delivered over the sensor network. Providing security to the sensor network, however, requires additional energy consumption, which is an important issue since energy transformation is difficult to implement in a sensor network. This paper proposes a routing mechanism based on the energy-efficient cluster that features security functions capable of safely processing the data acquired from the sensor network. The proposed algorithm reduces energy consumption by fixing the clusters formed at the initial stage and using the pre-distribution scheme so that the cluster and node keys generated and exchanged at the initial stage are not re-generated or re-exchanged. Simulation experiments confirmed that the proposed approach reduces energy consumption compared to implementing security measures to the conventional cluster-based routing mechanism.

• Journal of IKEEE
• /
• v.17 no.3
• /
• pp.324-331
• /
• 2013

In this paper, we implemented memristor emulator circuit on Printed Circuit Board (PCB) and observed the inherent pinched hysteresis characteristic of memristors by measuring the emulator circuit on PCB. The memristor emulator circuit implemented on PCB is composed of simple discrete devices not using any complicated circuit blocks thus we can integrate the memristor emulator circuits in very small layout area on Silicon substrate. The programmable gain amplifier is designed using the proposed memristor emulator circuit and verified that the amplifier's voltage gain can be controlled by programming memristance of the emulator circuit by circuit simulation. Threshold switching is also realized in the proposed emulator circuit thus memristance can remain unchanged when the input voltage applied to the emulator circuit is lower than VREF. The memristor emulator circuit and the programmable gain amplifier using the proposed circuit can be useful in teaching the device operation, functions, characteristics, and applications of memristors to students when thet cannot access to device and fabrication technologies of real memristors.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.12 no.6
• /
• pp.105-109
• /
• 2012

This paper proposed a method which enabled the designing and implementation of a serious game based on AVR microcontroller on a virtual serial port before making the actual circuit by performing simulation, and which made it possible to develop a serious game. The implemented serious game implemented a mole game which can be enjoyed by one person, a love game with which a male gamer and a female gamer can play, and a marathon game in which a gamer can run the marathon while listening to cheerful music and looking at a region he/she wants to visit. The development of a microcontroller device that provides those functions showed that not only does the device make it possible to develop games more easily and conveniently through the implementation of a game using virtual serial communications with a board designed by an ISIS simulator, but also it reduces trials and errors during game development.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.14 no.3
• /
• pp.7-12
• /
• 2014

The data forwarding transmission is an important function of the relay in cooperative communication in wireless communication systems. However, additional relay cause the waste of power consumption and cost. Therefore, in this paper, we consider how to use the user mobile devices in stead of relays to deal with this problem. In this paper, we proposed the protocol that divide each relay into two states of idle and non-idle. The receiver has two functions of base station and user mobile device. In this case, it is possible that no additional cost, and improve the spectral efficiency and network capacity. We verified BER performance for the proposed protocol over Rayleigh fading through Monte-Carlo simulation.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.46 no.3
• /
• pp.10-19
• /
• 2009

In this paper, an efficient optical watermark method using multiple phase wrapping and real-valued decoding key is proposed. In the embedding process, two zero-padded original images placed in two quadrants on input plane are multiplied with two statistically independent random phase patterns and are Fourier transformed, respectively. Two encoded images are obtained by taking the real-valued data from these Fourier transformed images. And then two phase-encoded patterns, used as a hidden image and a decoding key, are generated by the use of multiple phase wrapping from each of the encoded images. A transmitted image is made from the linear superposition of the weighted hidden images and a cover image. In reconstruction process, the mirror reconstructed images can be obtained at all quadrants by the inverse-Fourier transform of the product of the transmitted image and the decoding key. Computer simulation and optical experiment are demonstrated in order to confirm the proposed method.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.12
• /
• pp.9-16
• /
• 2011

Most of the current mobility management protocols such as MIPv4/6 and its variants standardized by the IETF do not support global seamless handover. This is because they require comprehensive changes of the existing network infrastructure. In this article, we propose a simple mobility management protocol (SMMP) which can support global seamless handover between homogeneous or heterogeneous wireless networks. The idea is that the SMMP employs separate location management function as done in SIP to support global user and service mobility. In addition, the bidirectional tunnels are dynamically constructed to support seamless IP mobility by extending the IEEE 802.21 MIH standards. The detailed architecture and functions of the SMMP have been designed. Finally, the simulation results, using NS-2, show that the proposed SMMP outperforms the existing MIPv6 and HMIPv6 in terms of handover latency, packet loss, pear signal noise ratio (PSNR).

• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.6
• /
• pp.35-47
• /
• 2003

Seismic ground motion can vary significantly over distances comparable to the length of a majority of highway bridges on multiple supports. This paper presents results of fragility analysis of two actual highway bridges under ground motion with spatial variation. Ground motion time histories are artificially generated with different amplitudes, phases, as well as frequency contents at different support locations. Monte Carlo simulation is performed to study dynamic responses of the bridges under these ground motions. The effect of spatial variation on the seismic response is systematically examined and the resulting fragility curves are compared with those under identical support ground motion. This study shows that ductility demands for the bridge columns can be underestimated if the bridge is analyzed using identical support ground motions rather than differential support ground motions. Fragility curves are developed as functions of different measures of ground motion intensity including peak ground acceleration(PGA), peak ground velocity(PGV), spectral acceleration(SA), spectral velocity(SV) and spectral intensity(SI). This study represents a first attempt to develop fragility curves under spatially varying ground motion and provides information useful for improvement of the current seismic design codes so as to account for the effects of spatial variation in the seismic design of long-span bridges.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.10 no.3
• /
• pp.127-141
• /
• 2014

A Vehicle Tracking System consists of GPS tracking device which fits into the vehicle and captures the GPS location information at regular intervals to a central GIS server, and GIS tracking server providing three major responsibilities: receiving data from the GPS tracking unit, securely storing it, and serving this information on demand of the user. GPS based tracking systems supporting a multi-session processing among RMA, RM, and RCP can make a quick response to various services including other vehicle information between RSU and OBU on demand of the user. In this paper we design RSU lower layers and RCP applications in OBU for a multisession processing simulation and test message processing transactions among RMA-RM and RM-RCP. Furthermore, we implement the additional functions of handling access commands simultaneously on multiple service resources which are appropriate for the experimental testing conditions. In order to make a multi-session processing test, it reads 30 resource data,0002/0001 ~ 0002/0030, in total and then occurs 30 session data transmissions simultaneously. We insert a sequence number field into a special header of dummy data as a corresponding response to check that the messages are received correctly. Thus, we find that GIS service system with a multi-session processing is able to provide additional 30 services in a same speed of screen presentation loading while identifying the number of session processing of Web GIS service, the number of OBU service, and the speed of screen presentation loading by comparing a single session and a multi-session of GIS service system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1995.04a
• /
• pp.196-201
• /
• 1995

The broadband and discrete sources of sound in small cooling fans of propeller type and centrifugal type were investigated to understand the turbulent vortex structures from many bladed fans using ANSI test plenum for small air-moving devices (AMDs). The noise measurement method uses the plenum as a test apparatus to determine the acoustic source spectral density function at each operating conditions similar to real engineering applications based on acoustic similarity laws. The characteristics of fans including the head rise vs. volumetric flow rate performance were measured using a performance test facility. The sound power spectrum is decomposed into two non-dimensional functions: an acoustic source spectral distribution function F(St,.phi.) and an acoustic system response function G(He,.phi.) where St, He, and .phi. are the Strouhal number, the Helmholtz number, and the volumetric flow rate coefficient, respectively. The autospectra of radiated noise measurements for the fan operating at several volumetric flow rates,.phi., are analyzed using acoustical similarity. The rotating stall in the small propeller fan with a bell-mouth guided is mainly due to a leading edge separation. It creates a blockage in the passage and the reduction in the flow rate. The sound power levels with respect to the rotational speeds were measured to reveal the mechanisms of stall and/or surge for different loading conditions and geometries, for example, fans installed with a impinging plate. Lee and Meecham (1993) studied the effect of the large-scale motions like impinging normally on a flat plate using Large-Eddy Simulation(LES) and Lighthill's analogy.[ASME Winter Annual Meeting 1993, 93-WA/NCA-22]. The dipole and quadrupole sources in the fans tested are shown closely related to the vortex structures involved using cross-correlations of the hot-wire and microphone signals.