• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.47-52
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• 2011

Directional couplers based on plasmonic waveguides with nano-scale three channels are designed by utilizing mode coupling effect as well as rib-guiding structure. Longitudinal modal transmission-line theory(L-MTLT) is used for simulating the light propagation and optimizing the design parameters. The designed plasmonic coupler operating as power splitter has nano-scale size of about 200~250 nm width. In order to achieve the desired power splitting ratio, the refractive index of guiding modes is evaluated along the width variation of center channel. Finally, a power splitter based on triple rib directional coupler, which ensures maximum power transfer from one outermost guide to the other outermost guide, is designed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.5-13
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• 2017

Noise complaints among neighbors in apartment building are mainly caused by floor impact noise that is structure born noise due to occupant induced floor vibration. To control this noise problems many researchers have investigated floor systems and finishing materials. Light-weight impact noise affects by finishing materials, but heavy-weight impact noise induced by heel impacts during normal walking or jumping of children is concerned with structural system and floor vibration. To figure out the characteristics of floor impact noise and transmission of floor vibration due to human activities, vibration tests were conducted in apartment buildings. Impact hammer, heel drop and walking activities were loaded at center of upstairs living room, and accelerations of slabs for both upstairs and downstairs and sound pressure levels for downstairs were measured. The acceleration ratio of transmitted floor vibration to downstairs and human induced vibration in upstairs was between 0.5 and 1.0 according to slab size, wall, and load type. And floor impact noise occurred in the range of natural frequency of slab.

• Journal of Communications and Networks
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• v.18 no.6
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• pp.926-937
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• 2016

In this paper, we study the feasibility of receiver diversity for application to downlink cellular networks, where low-energy devices are equipped with information decoding and energy harvesting receivers for simultaneous wireless information and power transfer. We compare several options that are based on selection combining and maximum ratio combining, which provide different implementation complexities. By capitalizing on the Frechet inequality, we shed light on the advantages and limitations of each scheme as a function of the transmission rate and harvested power that need to be fulfilled at the low-energy devices. Our analysis shows that no scheme outperforms the others for every system setup. It suggests, on the other hand, that the low-energy devices need to operate in an adaptive fashion, by choosing the receiver diversity scheme as a function of the imposed requirements. With the aid of stochastic geometry, we introduce mathematical frameworks for system-level analysis. We show that they constitute an important tool for system-level optimization and, in particular, for identifying the diversity scheme that optimizes wireless information and power transmission as a function of a sensible set of parameters. Monte Carlo simulations are used to validate our findings and to illustrate the trade-off that emerge in cellular networks with simultaneous wireless information and power transfer.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.3
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• pp.1136-1151
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• 2018

This paper proposes a new hybrid scheme to decrease the high peak to average power ratio (PAPR) of optical orthogonal frequency division multiplexing (OFDM) signals in visible light communication (VLC) systems. The PAPR causes nonlinear signal distortions and high power requirements for the VLC transmitter (light emitting diode, LED). The proposed method is applicable for both direct current-biased optical OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM (ACO-OFDM). In the proposed scheme, the PTS method is firstly modified to fit both optical OFDM approaches transmission and then combined with signal clipping method for further PAPR reduction and bit error rate (BER) improvement of the VLC system. The performance of hybrid scheme has been evaluated and compared with the original OFDM based VLC system, conventional PTS and clipping methods. The results show that the hybrid scheme outperforms other methods in terms of both the PAPR reduction and BER performance.

• Korean Journal of Optics and Photonics
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• v.22 no.3
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• pp.122-128
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• 2011

The AWG-filtering effect was investigated on a bidirectional 100-GHz-channel-spacing WDM-PON link using spectrum-sliced and RSOA-amplified light sources for downstream signals and a wavelength reuse technique for upstream signals. Signal performances of three different filtering AWGs, including Gaussian, trapezoidal, and rectangular types, were compared on link transmission with fiber nonlinear effects. As an extinction ratio of a downstream signal varied, the effect for both directional signals was analyzed and optimized. It was found that there was an optimal pass bandwidth of an AWG for the balance between relative intensity noise decrement and cross phase modulation noise increment as the bandwidth got wider.

• Korean Journal of Optics and Photonics
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• v.14 no.5
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• pp.498-503
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• 2003

We analyze the electro-optic polarization transmission characteristics of liquid crystal cells in the Poincare sphere representation. We determine fundamental conditions on maximizing of brightness and contrast ratio of liquid crystal display devices for polychromatic light by use of retardation films. For optimizing two colors, at least two properly designed retardation films are needed, and for three wavelengths, either it can be approximated to the two-color case or three retardation films are needed.

• Journal of the Optical Society of Korea
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• v.10 no.2
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• pp.63-66
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• 2006

In microband-induced fiber gratings, polarization properties and birefringence are investigated as a function of an applied line force. With the transmission curves associated with the maximum and minimum resonant wavelengths, the polarization-dependent behaviors are analyzed. By increasing the transverse line force, the resonance wavelength for an incident light polarized to the same direction of the force is blue-shifted as much as 0.69 nm/(N/cm) while that for the other polarization is insensitive. Using the resonant wavelength separation corresponding to the force variation, the transverse effective index change or modal birefringence variation is obtained. The ratio of modal birefringence versus applied line force is ${\Delta}B/{\Delta}f_x={\sim}8.38{\times}10^{-7}$.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.1
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• pp.63-72
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• 2003

A new 6-DOF parallel haptic device is proposed. Many existing haptic devices require large power due to having floating actuator and also have small workspaces. The proposed new mechanism can generate 6-DOF reflecting force. This device is relatively light by employing non-floating actuators and has large workspace. Kinematic analysis and kinematic optimal design is performed for this mechanism. Dexterous workspace, global isotropic index, and global maximum force transmission ratio are considered as kinematic design indices. To deal with such multi-criteria optimization problem. composite design index is employed. For the given operational specifications, actuator sizing for this mechanism is also carried out.

• Korean Journal of Agricultural and Forest Meteorology
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• v.1 no.2
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• pp.103-109
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• 1999

This study was carried out to investigate spectral characterisistics and chlorophyll contents of Pinus koraiensis needles in Gwangju-gun, Kyunggi-do. In spectrum analysis by each age, needle showed difference on 700∼1,100 nm(NIR : near infrared ray). Light reflexibility keeps constant between 1st year needle and 3rd year needle, current year needle's value was higher than others and that was higher for 400∼500 nm and 600∼700 nm at 550 nm. Transmission to needle's age showed the highest result in current year needle. It showed in order of current, 1st, 2nd and 3rd year needle at 550 nm and 750 nm. Especially, current year needles of Pinus koraiensis showed a tendency to change transmission coefficient in NIR. The result of transmission coefficient measurement by each position of slope showed in order of middle slope, upper slope and lower slope. But the gathered needle in middle slope made marked change at NIR. Chlorophyll a content of the upper slope's needles was higher than other 4 positions but a component ratio was lower. In needle of the oppressed tree, Chlorophyll a content was rather low than others. Chlorophyll a content by slope positions, the upper slope's needle showed a highest value(4.48 mg/g) and lower slope was lowest value(1.35 mg/g). Chlorophyll b content also showed a similar tendency to chlorophyll a and chlorophyll(a+b) contents.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.860-863
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• 2003

Pulse oximetry has gained wide spread clinical acceptance in the latter part of the 21st century. The principle of pulse oximetry is based on the red and infrared light absorption features and uses a light emitter with red and infrared LEDs that shines through a reasonably translucent site with good blood flow. There are two methods of sending light through the measuring site : transmission and reflectance. After the transmitted red and infrared signals pass through the measuring site and received at the photodetector, the red/infrared ratio is calculated. But, pulse of oximeters are so sensitive that they may detect pulses when pressure is too low to provide adequate tissue blood flow, that is, SpO2 may decrease due to O2 consumption by the finger of the pulsing but stagnant arterial blood at low pressure or with vasoconstriction. This project has the limitations of pulse oximetry. Therefore, this paper is focused on the resuction of motion artifact that caused by moving when someone measures with SpO2 system.