• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.5
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• pp.1075-1084
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• 2024

Efforts to expand the installation of devices that assist visually impaired individuals in their mobility are ongoing, but there are significantly fewer devices installed indoors compared to outdoors, causing considerable inconvenience for indoor navigation. Therefore, this paper aims to address these issues by applying the results of machine learning using YOLO(You Only Look Once) to a Raspberry Pi and by researching techniques to reduce errors through the trilateration method of UWB(Ultra-Wideband) sensors, applying it with a Kalman filter. The research results implemented an object recognition algorithm with a comprehensive accuracy of 91.7% using YOLO technology. Based on this object recognition, the direction (left, right, or front) was determined using the distance difference between two ultrasonic sensors set at an angle difference of 15 degrees. A distance of up to 1.5m was accepted through an infrared sensor to output a warning message according to the distance. The distance between the user's tag and the fixed three anchors was measured indoors through a UWB sensor, and the user's location was also measured indoors by linking the distance value with the three-side positioning technique.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.823-826
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• 2008

This paper will show how to design home network management system in the wired/wireless environment using graphical language LabVIEW, J2ME and to apply the design to monitoring and remote controling for the information devices at home. This paper also provides with efficiency of device control and current status check according to the circumstances of administrators by constructing the wire/wirelessly integrated administration system. It means the administrators can access to central administration server and acquire the control right through web being able to operate the system with flexibility and can access to the server without computer whenever, wherever they need to control and administrate it through this wired/wireless unit easily.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.115-128
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• 2010

Recently the use heat sink material grows where the polymer filled with thermal conductive fillers effectively dissipates heat generated from electronic components. Therefore the management of heat is directly related to the lifetime of electronic devices. For the purpose of improving thermal conductivity of composites, fillers with excellent thermaly conductive behavior are commonly used. Polymer composites filled with thermally conductive particles have advantages due to their processibility, cheap price, and durability to the corrosion. This paper aims to review the thermal interface materials and their model equations for predicting the thermal conductivity of polymer composites, and to introduce the commercial thermal conductive fillers and their applications.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.11
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• pp.1005-1013
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• 2005

The use of river water as a heat source of a heat pump has the advantage in the performance compared to the use of atmospheric air because the temperature variation of river water over the year is relatively small. In this study, the performance of the heat pump system using river water as a heat source was numerically investigated. A simulation model for the 2-stage compression heat pump system was developed with each component model composed of compressors, heat exchangers, a flash tank and electronic expansion devices. The peformance of the heat pump system using river water was improved by $50\%$ compared to that using atmospheric air in winter conditions.

• Journal of Magnetics
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• v.7 no.3
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• pp.80-93
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• 2002

The role of magnetic anisotropy of the antiferromagnetic layer on the magnetization process of exchange coupled polycrystalline ferromagnetidantiferromagnetic bilayers is discussed. In order to elucidate the magnetic torque response of Ni-Fe/Mn-Ir bilayers, the single spin ensemble model is newly introduced, taking into account the two-dimensionally random distribution of the magnetic anisotropy axes of the antiferromagnetic grains. The mechanism of the reversible inducement of the exchange anisotropy along desirable directions by field cooling procedure is successfully explained with the new model. Unidirectional anisotropy constant, J$k$, of polycrystalline Ni-Fe/Mn-Ir and Co-Fe/Mn-Ir bilayers is investigated as functions of the chemical composition of both the ferromagnetic layer and the antiferromagnetic layer. The effects of microstructure and surface modification of the antiferromagnetic layer on JK are also discussed. As a notable result, an extra large value of J$k$, which exceeds 0.5 erg/cm$^2$, is obtained for $Co_{70}Fe_{30}Mn_{75}Ir_{25}$ bilayer with the ultra-thin (50${\AA}$∼100${\AA}$) Mn-Ir layer. The exchange anisotropy of $Co_{70}Fe_{30}$ 40 ${\AA}/Mn_{75}Ir_{25}$ 100 ${\AA}$ bilayer is stable for thermal annealing up to $400{^{\circ}C}$, which is sufficiently high for the application of spin valve magnetoresistive devices.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.582-588
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• 2012

In this paper, a highly miniaturized and performed UWB bandpass filter has been newly designed and implemented by embedding all the passive elements into a multi-layered PCB substrate with high dielectric $SrTiO_3$ composite film for 3.1 - 4.75 GHz compact UWB system applications. The high dielectric composite film was utilized to increase the capacitance densities and quality factors of capacitors embedded into the PCB. In order to reduce the size of the filter and avoid parasitic EM coupling between the embedded filter circuit elements, it was designed by using a $3^{rd}$ order Chebyshev circuit topology and a capacitive coupled transformation technology. Independent transmission zeros were also applied for improving the attenuation of the filter at the desired stopbands. The measured insertion and return losses in the passband were better than 1.68 and 12 dB, with a minimum value of 0.78 dB. The transmission zeros of the measured response were occurred at 2.2 and 5.15 GHz resulting in excellent suppressions of 31 and 20 dB at WLAN bands of 2.4 and 5.15 GHz, respectively. The size of the fabricated bandpass filter was $2.9{\times}2.8{\times}0.55(H)mm^3$.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.1
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• pp.55-64
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• 2013

The USB-IF has specified a Wireless USB (WUSB) protocol based on UWB for high speed wireless home networks and WPANs. In this paper, firstly, performance degradation due to the Private Distributed Reservation Protocol (DRP) conflict problem caused by devices' mobility is analyzed. And a novel relay transmission protocol combined with Private DRP conflict resolution is proposed to overcome the performance degradation at Private DRP conflicts. In order to give the loser device due to Private DRP conflicts another chance to maintain resources, the proposed relay transmission protocol executed at each device helps the loser device reserve another indirect link maintaining the required resources via a relay node.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1566-1570
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• 2013

In this paper, we analyzed the electric characteristics of the OLEDs device of which anode ITO has been treated with the oxygen plasma. We fabricated the basic three-layer structure (ITO / AF / $Alq_3$ / $Cs_2CO_3$ / Al) device, analyzed how the oxygen plasma treatments of the ITO surface affects to the electrical characteristics of OLEDs. We also produced a four-layer structure device (ITO / AF / TPD / $Alq_3$ / $Cs_2CO_3$ / Al) with the oxygen plasma treatment. From the comparative analysis to the devices, we confirmed following results. The three-layer structure OLEDs device with oxygen plasma treatment has better characteristics than the device without the treatments; maximum luminance, luminous efficiency, and external quantum efficiency are improved approximately 151 [%], 126 [%], and 175[%], respectively. Also, the electric characteristics of the four-layer structure device with oxygen plasma treatment are improved comparing to the characteristics of the three-layer structure device with oxygen plasma treatment; maximum luminance, luminous efficiency, and external quantum efficiency are improved approximately 144 [%], 115 [%], and 124[%], respectively.

• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.64-68
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• 2012

We have successfully demonstrated a bandgap alteration of transparent zinc oxide (ZnO) thin film with Mg dopant by using sol-gel spin coating technique. By increasing the dopant from 0 to 30 atomic percent (at.%), a decrement value in the cutoff is observed, where the absorption edge shifts continuously to the shorter wavelength side, towards 300 nm. This resulted in a significant bandgap increment from 3.28 to 3.57 eV. However, the transmittance of the thin film at 350-800 nm gradually downgraded, from 93 to 80 % which is most probably due to the grain size that becomes bigger, and it also affected the electrical properties. The decrement from 45 to 0.05 mA at +10 V was observed in the I-V characteristics, concluding the significant relationship; where higher optical bandgap materials will exhibit lower conductivity. These findings may be useful in optoelectronics devices.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.4
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• pp.570-574
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• 2014

This paper proposes a wireless digital endoscope with a ultra-wide-angle view. Two key components are implemented to demonstrate the feasibility of the proposed endoscope. First, a ultra-wide-angle lens module with the field of view of 144 degree and F-number of 2.2 is designed and manufactured. Second, a wireless module for a high-speed video transfer is implemented using a USB device server and wireless LAN router. The wireless module can directly transfer a streaming video to a computer with the resolution of 1920x1080, frame rate of 30 fps, and data rate of 53.3 Mbps without an internet connection. Since the wireless module supports two USB devices, two spots can be simultaneously observed using the proposed endoscope.