• 로봇학회논문지
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• 제9권3호
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• pp.154-159
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• 2014

The Global Positioning System (GPS) is widely used to aid the navigation of aerial vehicles. However, the GPS cannot be used indoors, so alternative navigation methods are needed to be developed for micro aerial vehicles (MAVs) flying in GPS-denied environments. In this paper, a real-time three-dimensional (3-D) indoor navigation system and closed-loop control of a quad-rotor aerial vehicle equipped with an inertial measurement unit (IMU) and a low-cost light detection and ranging (LIDAR) is presented. In order to estimate the pose of the vehicle equipped with the two-dimensional LIDAR, an octree-based grid map and Monte-Carlo Localization (MCL) are adopted. The navigation results using the MCL are then evaluated by making a comparison with a motion capture system. Finally, the results are used for closed-loop control in order to validate its positioning accuracy during procedures for stable hovering and waypoint-following.

• 센서학회지
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• 제30권6호
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• pp.364-368
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• 2021

We developed a highly efficient organic photovoltaic (OPV) cell with a poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)]:[6,6]-phenyl-C71-butyric acid methyl ester active layer for harvesting lower-intensity indoor light energy to power various self-powered sensor systems that require power in the microwatt range. In order to achieve higher power conversion efficiency (PCE), we first optimized the thickness of the active layer of the OPV cell through optical simulations. Next, we fabricated an OPV cell with optimized active layer thickness. The device exhibited a PCE of 12.23%, open circuit voltage of 0.66 V, short-circuit current density of 97.7 ㎂/cm², and fill factor of 60.53%. Furthermore, the device showed a maximum power density of 45 ㎼/cm², which is suitable for powering a low-power (microwatt range) sensor system.

• 로봇학회논문지
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• 제18권4호
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• pp.487-495
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• 2023

This paper presents a method for autonomous exploration of indoor environments using a 2-dimensional Light Detection And Ranging (LiDAR) scanner. The proposed frontier-based exploration method considers navigability from the current robot position to extracted frontier targets. An approach to constructing the point cloud grid map that accurately reflects the occupancy probability of glass obstacles is proposed, enabling identification of safe frontier grids on the safety grid map calculated from the point cloud grid map. Navigability, indicating whether the robot can successfully navigate to each frontier target, is calculated by applying the skeletonization-informed rapidly exploring random tree algorithm to the safety grid map. While conventional exploration approaches have focused on frontier detection and target position/direction decision, the proposed method discusses a safe navigation approach for the overall exploration process until the completion of mapping. Real-world experiments have been conducted to verify that the proposed method leads the robot to avoid glass obstacles and safely navigate the entire environment, constructing the point cloud map and calculating the navigability with low computing time deviation.

• 한국통신학회논문지
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• 제36권9B호
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• pp.1108-1116
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• 2011

실내 가시광 무선 통신 기술은 반도체인 LED (Light Emitted Diode)의 발광 특성을 제어하여 디지털 신호를 송신하며, PD (Photo Diode)를 이용하여 광 신호를 송수신하는 차세대 무선 통신 기술이다. 이러한 가시광 무선통신에서 LED는 실내 조명기기로써의 역할 뿐 아니라 우선 통신 시스템의 송신기의 역할도 수행한다. 가시광 무선 통신 시스템은 그 특성 상 통신 영역이 빛의 도달하는 범위로 한정되며, 빛의 광량에 따라 통신 채널 품질이 결정된다. 이에 본 논문에서의 복수의 LED로 구성된 LED 패널의 위치 변화와 LED 발광 각도 변화가 통신 채널 품질에 미치는 영향을 분석하고자 한다. 이를 위한 모의실험을 수행하였고, 그 결과 LED 패널의 위치 및 LED 발광 각도가 조도 및 SNR 변화에 상당한 영향을 끼친다는 사실을 입증하였다.

• KIEAE Journal
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• 제17권3호
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• pp.5-13
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• 2017

Purpose: Various studies have been performed to address the issue of increased energy use by buildings. In particular, research on complex envelopes that combines diverse envelope element techniques is currently in progress in the building sector. The present study aimed to develop an awning system using a light shelf, and to verify its validity through performance evaluation. Method: In the present study, a testbed was established for the performance evaluation of the awning system using a light shelf, and the uniformity ratio and lighting energy consumption were compared and analyzed relative to those with no awning and light shelf installation (Case 1), awning installation (Case 2), and light shelf installation (Case 3). Result: 1) In the present study, an awning system using a light shelf (Case 4) where an opening is made on the awning screen and natural light can be introduced through the light shelf located at the bottom was developed. 2) The optimum standard for Case 4 obtained through the performance evaluation was a 0.6m lighting length and a 2m extension length at a light shelf angle of $30^{\circ}$. 3) Case 4 with the optimum standard had a 5.5% lower uniformity ratio than Case 2, but had a higher uniformity ratio than Case 1 and Case 3. 4) Case 4 with the optimum standard showed 13.3%, 44.6%, and 0%~8.7% lighting energy reductions compared to Case 1, Case 2, and Case 3, respectively. 5) Based on the above results, Case 4 suggested in the present study was found to be effective for indoor light environment improvement and lighting energy reduction.

• 한국통신학회논문지
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• 제37B권9호
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• pp.787-794
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• 2012

가시광 무선 통신 기술은 LED와 PD를 이용한 차세대 무선 통신 기술로서, LOS 통신 채널 확보의 용이성과 저렴한 인프라 구축 비용의 장점을 토대로 실내 측위 시스템 개발에 활발한 연구가 진행되고 있다. 하지만 기존 가시광 무선 통신 기반 측위 시스템은 복잡한 측위 계산 및 별도의 센서 설치에 따른 구축 비용이 증가하는 문제가 발생하였다. 이에 본 논문에서는 실내 가시광 무선 통신 환경에 TDoA 측위 기법을 적용하여 별도의 장치 없이 측위 시스템 구축이 가능한 VLC-TDoA 시스템을 제안한다. 또한 측위 시스템 운용에 필요한 LED 패널 제어 절차 및 단말기의 파일럿 신호 인식 방법을 제안한다. 이와 더불어 모의실험을 토대로 VLC-TDoA 측위 시스템의 측위 가능성 및 파일럿 신호 인식 방법에 따른 측위 오차를 분석하였다.

• 산업진흥연구
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• 제5권2호
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• pp.1-7
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• 2020

본 연구는 실내 또는 실외를 조명으로 밝게 비추는 조명등에 관한 기술로서, 보다 상세하게 설명하면 외관을 구성하는 케이스에 사방으로 투시창을 만들고, 사방 투시창에 얇은 패널(panel) 형태로 가공된 옥돌을 부착하여 조명등을 구성함으로써, 옥돌을 통해 은은한 불빛이 실내 또는 실외로 조사(照射)되므로, 사용자에게 아늑함과 따스함을 제공하고, 실내 또는 실외의 인테리어 효과를 높이는 한편 원적외선과 음이온을 발산하며, 은은한 꽃향기를 방출하는 옥돌을 이용한 조명등에 관한 기술이다. 본 연구개발의 제품의 특징은 외관을 구성하는 케이스에 사방으로 투시창이 형성되고, 사방 투시창에 얇은 패널(panel) 형태로 가공된 옥돌을 부착하여 조명등이 구성되며, 스피커를 통해 사용자에게 유익한 음악, 불경, 성경, 시조 등의 음향을 발생시키는 옥돌을 이용한 조명등을 연구했다는데 의미가 있다.

• 한국조경학회지
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• 제26권3호
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• pp.258-266
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• 1998

The purpose of this study is to investigate the actual conditions, to find problems, and to present an improvement plan of interior landscape in the subway stationis. Moreoiver, it will presume the possibilties to develop the subway and ways to utilie underground space effectively. The results are summarized as follows A light intensity was recorded 0-100 Lux as the lowest light and 500 Lux below as the highest in 61 subway stations. An average temperature of 12 $^{\circ}C$and an air humidity of 38% were recorded over a 4 month period from January to April, but includes a drastic variaton between -8.5$^{\circ}C$ and 21.5$^{\circ}C$. Soil acidity of pH 7 below and soil moisture of 1-2 wet degree were apeared in subway stations mostly. Plant forms consisted of artificial flower & flower. Plant species were recorded at a total of 54 species and appeared in the order of Araucaria heteropylla, Ophiophogon jaburan, Aspidistra elatior cv. 'Asahi' and Hedera helix. Plant height was, for the most part, below 0.5m. Plant species that was fined of conditions were Palm, Camellia japonica, Araucaria heterophylla as a high plant, dracaena fragrans, dracaena deremensis cv. Wakneckii as a middle plant, and Ophiopogon jaburan, Hedra helix, ytomium falcatum, Aspidistra elatior cv. Asahi as a low plant. It used to water materials such as small pool, small cascade, water cycles and natural materials such as natural rock, small rock, sand, bark and animal materials such as squirrels, birds, goldfish as an object for plants in the subway stations. From these actual conditions, First of all, It must make up physical environments such as light, temperature humidity, soil for plant growth, and is important to chooce suitable indoor plants and draw up systematic management in the subway environments. Also, it change plants frequently and uses variable objects for subway stationi individuatism, Moreover, indoor plants with strong environmental adaptation abities such as shade tolerance, drought tolerance and cold tolerance need to develope variable species possibly. If these improvements occur, utilization and amenity of subway stationis will increase, according to the use of interior landscape.

• ALGAE
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• 제36권4호
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• pp.231-240
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• 2021

Saccharina sculpera is highly valued for human consumption and value-added products. However, natural resources of this kelp have decreased sharply and it is in danger of extinction. Resources recovery through cultivation is being trialed to enable the sustainable use of this species. In this study, the temperature range for survival and optimal growth of juvenile S. sculpera was identified and applied to field cultivation. This study investigated the survival and growth of juvenile S. sculpera under six temperatures (i.e., 5, 10, 15, 16, 18, and 20℃) and two light intensities (i.e., 20 and 40 µmol photons m^-2 s^-1) in an indoor culture experiment. In these experiments, the blade length decreased at 16℃ under the both light intensities. The thalli died at 20℃ and 20 µmol photons m^-2 s^-1, and at 18-20℃ and 40 µmol photons m^-2 s^-1. During the field cultivation, early growth of S. sculpera was highest at the 5 m depth and growth decreased as the water depth increased. When the initial rearing depth was maintained without adjustment throughout the cultivation period (from December to October), all the cultivated S. sculpera plants died during August and September. However, S. sculpera plants lowered from 5 to 15 m and grew to 90.8 ± 13.1 cm in July. The seawater temperature at 15 m depth was similar to the upper level of thermal tolerance demonstrated by juvenile S. sculpera in the indoor culture experiments (16℃ or lower). The plants were subsequently lowered to 25 m depth in August, which eventually led to their maturation in October. The present study confirmed that improved growth rates and a delay in biomass loss can be achieved by adjusting the depth at which the seaweeds are grown during the cultivation period. These results will contribute to the establishment of sustainable cultivation systems for S. sculpera.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권4호
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• pp.1502-1519
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• 2020

Recently, new devices have been developed for the Internet of Things concept. The devices commonly use RF (Radio Frequency) based wireless communication. With the increase in the number of devices, the space allocated for the radio frequency band in wireless communication fills rapidly. Visible Light Communication (VLC) is an alternative, secure and economical communication technology that uses light instead of radio frequencies. While Web of Things (WoT) is the adaptation of the experience and knowledge acquired from the web into the internet of things ecosystems. By combining these two technologies, the development of the Visible Light Communication for Web of Things (VLC4WoT) system, which can use VLC and WoT technologies, has been our motivation. In our study, microcontroller control circuit was created for VLC4WoT system. Control of the circuits over the internet was performed. VLC based receiver and transmitter units have been developed for wireless communication. Web based interface was created for control. The test apparatus consisting of four objects with four outputs and a transfer unit was carried out. In this test, communication was achieved successfully. It was presented in the study that VLC can be used in the web of things architecture. In the future, it is envisaged to use this system as a safe and economical system in indoor environments.