• Journal of Broadcast Engineering
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• v.13 no.5
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• pp.636-650
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• 2008

DTV has a great advantage as compared to Analog TV in picture quality under low reception field strength. Various high quality tuners have been developed to result in much smaller Noise Figure of the receivers and many trials for receiving DTV signal through indoor antenna. In this paper, results of intensive field tests on the indoor reception of DTV are presented. Tests were carried out around Seoul-Gyeonggi Metropolitan area. Commercial directional and omni-directional antennas and 5th generation receiver were used for reception availability tests. The effects of heights, locations, and types of the house as well as the distance to the transmitter on the reception performances are analyzed. Our test results will be applied to improve the indoor reception environment of DTV.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.3
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• pp.113-120
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• 2017

In recent years, indoor localization has been researched for the improvement of its localization accuracy capability in Wi-Fi environment. The fingerprint and RF propagation models has been the main approach in determining indoor positioning. With the use of fingerprint, a low-cost, versatile localization system can be achieved without the use of external hardware. However, only a few research have been made on virtual access points (VAPs) among indoor localization models. In this paper, the idea of indoor localization system using fingerprint with the addition of VAP in Wi-Fi environment is discussed. The idea is to virtually add APs in the existing indoor Wi-Fi system, this would mean additional virtually APs in the network. The experiments of the proposed algorithm shows the positive results when 2VAPs are used compared with only APs. A combination of 3APs and 2VAPs in the 3rd case had the lowest average error of 3.99 among its 4 scenarios.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4B
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• pp.300-308
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• 2012

Many indoor location tracking technologies have been proposed. Generally indoor location tracking using TOA signal is used, there is a weak point that it's difficult to track the location due to obstacles like a refraction, reflection and dispersion of radio wave. In this paper, we apply ETOA(Estimated-TOA) algorithm in NLOS(Non-Line-Of-Sight) environment to solve above problem. In NLOS environment, TOA value between Beacon and Mobile node is predicted by ETOA algorithm and the tracking of indoor location is also possible to identify using two NLOS beacons of three beacons by this algorithm. We show that the proposed algorithm is accurate location tracking is accomplished using the applying the proposed algorithm to indoor moving robot and the inertia sensor of robot and Kalman filter algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.1
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• pp.131-140
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• 2013

Due to the limitations of the existing indoor positioning system depending on the radio wave, at present, it is required to introduce a new method in order to improve the accuracy in indoor environment. Recently, bio-inspired technology has become the future core technology. Thus, this study examined the accurate positioning method applying the abilities that animals with homing instinct measure their position by searching geomagnetic field with the use of their biomagnets. In order to confirm the applicability of geomagnetic field, a new source for indoor positioning, this study separated the constituent materials and building structure and designed the structures that can carry the actual magnetic field sensor and the data collection module. Subsequently, this study investigated the applicability of geomagnetic field as a positioning source by establishing the positioning system of Fingerprint method. In performance evaluation of the positioning system, the geomagnetic strength-based positioning system was similar to or approximately 20 percent higher than the wireless LAN-based positioning system in the buildings with the existing wireless LAN. Thus, in the environment without infrastructure for indoor positioning, the geomagnetic, an independent earth resource, can make it possible to realize the indoor positioning.

• Journal of the Korean Geotechnical Society
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• v.36 no.5
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• pp.25-34
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• 2020

Studies on nondestructive evaluation methods using electromagnetic waves have been commonly conducted to evaluate necking defects in bored piles. However, the propagation of electromagnetic waves are affected by water contents of surrounding materials. This study aims to investigate a suitability of electromagnetic waves for evaluating necking defects in bored piles embedded in sandy soils through laboratory experiments. Laboratory experiments are performed with a model pile having a necking defect. The diameter and length of model pile are 600 mm and 1 m, respectively, and the model pile is embedded in sandy soils with different water contents of 10%, 20%, and 30%. For the propagation of electromagnetic waves, a transmission line is configured in reinforcement cage using an electrical wire. The generation and detection of electromagnetic waves are conducted using a time domain reflectometer. Experimental results show that the peak amplitude of electromagnetic waves reflected at the necking defect decreases with an increase in the water content in sandy soils. In addition, the velocity of electromagnetic waves reflected from the toe of the model pile decreases win an increase in the water content. However, estimated locations of the necking defects are almost the same to that of the actual location of the necking defect. This study demonstrates that electromagnetic waves may be an effective method for evaluating necking defects in bored piles embedded in sandy soils

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.1
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• pp.15-20
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• 2020

In this paper, delay diffusion for exhibition hall and conference room was measured and analyzed in the indoor environment of the building. Scenarios for the indoor environment of the two buildings were written. also, the system configuration and measurement methods were conducted under the same conditions. The measurement conditions were set to 3 GHz and 6 GHz of center frequencies and analysis band selected 2 GHz. The measurement system consisted of vector network analyzer, power amplifier, omni-directional transmit and receive antenna, and transmission line. According to the indoor environment scenario of the two buildings, the location of the receiving antenna was divided into three zones based on the location of the transmitting antenna and this was measured at 1 m intervals according to 18 locations. The power delay profiles, RMS delay spread, and K-factor results of two buildings were compared and analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.7
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• pp.775-782
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• 2016

In this paper, we presented the paper-based reconfigurable frequency selective surface(FSS) for transmitting or blocking the wireless LAN signal in indoor environments. The proposed reconfigurable FSS are designed on coated paper using a printing of conductive ink and conductive adhesive for PIN diode, which provides ON/OFF of the reconfigurable FSS for passing or blocking the 5GHz signal. The reconfigurable FSS attached on the wall can pass or block the incident wireless signal as the received signal strength in indoor. To provide the validity of the proposed FSS, we fabricated the reconfigurable FSS on the paper and confirmed the very similar results between simulations and measurements. From the measured results of the proposed spectrum control system, we know that the proposed reconfigurable FSS can block about 20dB at 5.745GHz~5.805GHz.

• Journal of Internet of Things and Convergence
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• v.2 no.4
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• pp.35-39
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• 2016

This paper is about IoT(Internet of Things)-based indoor localization scheme. GPS and WiFi are widely used to estimate the location of things. However, GPS has drawback of poor reception and radio disturbance in doors. To estimate the location in WiFi-based method, the user collects the information by scanning nearby WiFi(s) and transferring the information to WiFi database server. This is a fingerprint method with disadvantage of having an additional DB server. IoT is the internetworking of things, and this is on rapid rise. I propose the IoT-based indoor localization scheme. Under the proposed method, a device internetworking with another device with its own location information like GPS coordinate can estimate its own location through RSSI. With more devices localizing its own, the localization accuracy goes high. The proposed method allows the user to estimate the location without GPS and WiFi DB server.

• Journal of the Society of Disaster Information
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• v.17 no.3
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• pp.465-486
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• 2021

Purpose: Since most disaster information systems are centered on non-disabled people, the reality is that there is a lack of disaster information delivery systems for the vulnerable, such as the disabled, the elderly, and children, who are relatively vulnerable to disasters. The purpose of the service is to improve the safety of the disabled and the elderly by eliminating blind spots of informatization and establishing customized disaster information services to respond to disasters through IoT-based integrated control technology. Method: The model at the core of this study is the disaster alert propagation model and evacuation support model, and it shall be developed by reflecting the behavioral characteristics of the disabled and the elderly in the event of a disaster. The disaster alert propagation model spreads disaster situations collected using IoT technology, and the evacuation support model uses geomagnetic field-based measuring technology to identify the user's indoor location and help the disabled and the elderly evacuate safely. Results: Demonstration model demonstration resulted in an efficient qualitative evaluation of indoor location accuracy, such as the suitability of evacuation route guidance and satisfaction of services from the user's perspective. Conclusion: Disaster information and evacuation support services were established for the safety vulnerable groups of mobile app for model verification. The disaster situation was demonstrated through experts in the related fields and the disabled by limiting it to the fire situation. It was evaluated as "satisfaction" in the adequacy of disaster information delivery and evacuation support, and its functional satisfaction and user UI were evaluated as "normal" due to the nature of the pilot model. Through this, the disaster information and evacuation support services presented in this study were evaluated to support the safety vulnerable groups to a faster disaster evacuation without missing the golden time of disaster evacuation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1B
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• pp.53-57
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• 2012

This study presents a numerical model that is capable of simulating the evolution of mining pit in a stream. The numerical model is based on the quasi-steady assumption that the flow is steady with time-dependent morphological change. This hypothesis is valid due to the fact that the stream morphology changes over a long period compared with the time of flow change. Before applications, numerical experiments are carried out with two total load formulas such as Engelund and Hansen's (1967) and Ackers and White's (1973). It is found that the use of Engelund and Hansen's formula reproduces evolution of mining pit best compared with simulated profiles in Parker (2004). Then, the model is applied to two laboratory experiments in the literature. In general, the numerical model simulates properly the evolution of mining pit in laboratory open-channels. However, it is found that the model does not reproduce head-cutting, propagating upstream, and under-estimates the wave of the bed, propagating downstream, after finishing the re-fill of the mining pit.