• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.186-188
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• 2014

In recent years, domestic as well as LTE wireless network of Wi-Fi and most used. In addition, mobile-intensive services that used mainly in our society makes it easier, SNS, application (APP), and file downloads. As such, the amount of data requested, while living at the time of mobile users will want to be safe from the earliest. And the wireless network communications mortality (3G, 4G (LTE), LTE-A) and Wi-Fi (802.11 n-2.4 G H z z H a c-5, 802.11 G), and users are mainly used in the death 4G (LTE), communication Wi-Fi, 802.11 n-2.4 GHz are used most frequently. As above, use the wireless network in order to safely and quickly developed the technology of the Li-Fi. Li-Fi light (visible light) technology to communicate with, and Wi-Fi (802.11 n-2.4 G z H) 100 times faster, LTE-A 66 times faster. However, the current Li-Fi to commercialise the big issue exists. In this paper, there are a lot of existing problems in the commercialization of Li-Fi being used in Wi-Fi, and a comparative analysis.

• Archives of Craniofacial Surgery
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• v.18 no.1
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• pp.30-36
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• 2017

Background: Nasal fractures have a tendency of resulting in structural or functional complications, and the results can vary according to the type of nasal bone fracture. The aim of this study was to evaluate the objective postoperative results according to the type of nasal bone fractures. Methods: We reviewed 313 patients who had a closed reduction of nasal bone fracture. The classification of nasal bone fracture by Stranc and Robertson was used to characterize the fracture type: frontal impact group type I (FI), frontal impact group type II (FII), lateral impact group type I (LI), lateral impact group type II (LII), and comminuted fracture group (C). For each patient, we tried to use the same axial image section of computed tomographic (CT) scans before and immediately after operation. Postoperative outcomes were classified into 4 grades: excellent (E), good (G), fair (F), and poor (P). We also analyzed postoperative complications by fracture type. Results: Regarding the postoperative CT images, 189 subjects showed E results, 99 subjects showed G, 18 subjects showed F, and 7 subjects showed P reduction. The rate of operation results graded as E by each fracture type was 66.67% in FI, 52.0% in FII, 64.21% in LI, 62.79% in LII, and 21.74% in C. Complications of FI (7.14%), LII (13.95%), and C (13.04%) groups occurred more than in the FII (4.00%) and LI (4.21%) groups. Conclusion: It seems that the operation result by fracture type was better in the FI, LI, and LII type than the FII and C type; after one month, however, LII type showed more complications than other types. The septal fracture can be thought to affect early reduction results in nasal bone fractures.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.65-67
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• 2021

This thesis is to proposer a new algorithm for a position measurement system using a trilateration method through visible light communication(VLC), by light emitting diode(LED). The length from each LED to the sensor is derived, and location information is found using trilateration method based on the derived length. Unlike th existing positioning system using visible light communication, the proposed positioning system is simpler and more cost effective because it does not require communication between the transmitter and the receiver.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.5
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• pp.1339-1355
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• 2023

Localization is a hot research spot for many areas, especially in the mobile robot field. Due to the weak signal of the global positioning system (GPS), the alternative schemes in an indoor environment include wireless signal transmitting and receiving solutions, laser rangefinder to build a map followed by a re-localization stage and visual positioning methods, etc. Among all wireless signal positioning techniques, Wi-Fi is the most common one. Wi-Fi access points are installed in most indoor areas of human activities, and smart devices equipped with Wi-Fi modules can be seen everywhere. However, the localization of a mobile robot using a Wi-Fi scheme usually lacks orientation information. Besides, the distance error is large because of indoor signal interference. Another research direction that mainly refers to laser sensors is to actively detect the environment and achieve positioning. An occupancy grid map is built by using the simultaneous localization and mapping (SLAM) method when the mobile robot enters the indoor environment for the first time. When the robot enters the environment again, it can localize itself according to the known map. Nevertheless, this scheme only works effectively based on the prerequisite that those areas have salient geometrical features. If the areas have similar scanning structures, such as a long corridor or similar rooms, the traditional methods always fail. To address the weakness of the above two methods, this work proposes a coarse-to-fine paradigm and an improved localization algorithm that utilizes Wi-Fi to assist the robot localization in a geometrically similar environment. Firstly, a grid map is built by using laser SLAM. Secondly, a fingerprint database is built in the offline phase. Then, the RSSI values are achieved in the localization stage to get a coarse localization. Finally, an improved particle filter method based on the Wi-Fi signal values is proposed to realize a fine localization. Experimental results show that our approach is effective and robust for both global localization and the kidnapped robot problem. The localization success rate reaches 97.33%, while the traditional method always fails.

• Archives of Plastic Surgery
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• v.37 no.4
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• pp.433-442
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• 2010

Purpose: Many authors reported about the posttraumatic nasal aesthetic complications. However, the studies for functional or intranasal complications are not enough yet. We identified relatively high prevalence of nasal obstruction and olfactory dysfunction in nasal synechiae, and the synechiae formation was a frequently occurred after the nasal bone reduction. And then, the aim of this study is to identify the usefulness of the treatment of intranasal synechiae. Methods: We reviewed the data from 10 patients with symptomatic intranasal synechiae from June 2007 to June 2009. We enforced evaluation with preoperative CT in all patients but postoperative CT within complicated patients. We studied 10 patients with intranasal synechiae who had persistence postoperative symptoms. We studied the patients who were operated by removal of synechiae and ancillary surgical treatments in the last two years. Results: In the previous report, the incidence of intranasal synechiae was 15% (n=62) and symptomatic synechiae was 16% (10/62). We classified the nasal bone fracture according to Stranc classification. In this paper, the incidence of treated intranasal synechiae was 13% (2/15) in Frontal Impact (FI) Type I, 11% (2/18) in FI Type II, 100% (2/2) in FI Type III, 0% (0/2) in Lateral Impact (LI) Type I, 25% (3/12) in LI Type II, and 33% (1/3) in LI Type III, respectively. After removal of synechiae, all patients improved nasal obstruction and little improved olfactory disturbance. Conclusion: Simple removal of synechiae by scissors improved postoperative symptoms and complications such as nasal obstruction and olfactory dysfunction. After removal of synechiae, all patients improved nasal obstruction, however, little improved anosmia. So, we thought that olfactory dysfunction may result in many intranasal factors. First of all, education of delicate procedure regarding this subject should be empathized accordingly.

• Spatial Information Research
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• v.23 no.3
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• pp.1-10
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• 2015

Due to recent improvement of various sensor technologies, indoor positioning becomes available. However, Indoor positioning technologies by Wi-Fi radio map and acceleration sensor and digital campus still have a certain level of errors and a number of researches have been done to increase the positioning accuracy of the indoor positioning. If we could provide a room level accuracy, indoor location based services with current indoor positioning methods such as Wi-Fi radio map and acceleration sensors would be possible. In this paper, we propose an indoor map matching method to provide a room level accuracy based on hidden markov model.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.667-669
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• 2003

IEEE 802.11 표준에 포함되어 있는 WEP 방식의 무선 랜 보안이 취약한 것으로 알려진 후 WEP을 대치할 새로운 표준이 802.1li 워킹그룹에 의하여 작성되고 있다. Wi-Fi는 중간단계로서 802.1li의 일부만을 구현하는 WPA 규격을 만들었다. 이 규격은 기존의 하드웨어를 그대로 사용하면서 소프트웨어와 펌웨어 갱신만으로 기존의 무선랜 취약점을 제거할 수 있게 한다. WPA규격을 준수하는 무선 랜 액세스포인트의 개발을 위하여 기존의 액세스포인트 디바이스 드라이버를 WPA를 지원하도록 수정하였으며, 사용자 인증 및 키 교환을 수행하는 소프트웨어를 설계 및 개발하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.149-156
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• 2014

Floor number determination has attracted considerable attention because many applications require accurate floor number information for providing better localization services in multistory buildings. This paper describes a Wi-Fi-based, low-complexity floor number determination method for multistory buildings. In our scheme, with the exception of floor ID and received signal strength of each WAP, detailed information on the wireless access point (WAP) coordinates is not needed. The multi-wall-floor model is used for the simulation and analysis. The simulation results show that the floor determination accuracy is nearly 100 given an adequate deployment density of WAPs on each floor. The results also show that the proposed method provides a good estimate of floor number even when only a few WAPs are implemented on each floor. Specifically, the proposed method can work under extreme conditions, i.e., where there are no WAPs on a floor.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.3
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• pp.155-161
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• 2015

Dike lines are important features for describing the detailed shapes of dikes and for detecting topographic changes on dike surfaces. Historically, dike lines have been generated using only the LiDAR data. This paper proposes a new methodology for selecting an appropriate dike line on various dike surfaces using the topographic LiDAR data and multispectral orthoimages taken in the Nakdong River basins. The fi rst baselines were generated from the given LiDAR data using the modified convex hull algorithm and smoothing spline function, and the second baselines were generated from the given orthoimages by the Canny operator. Next, one baseline was selected among the two baselines at 10m intervals by comparing their elevations, and the selected baseline at 10m interval was defined as the dike line segment. Finally, the selected dike line segments were connected to construct the 3D dike lines. The statistical results show that the dike lines generated using both the LiDAR data and multispectral orthoimages had the improved horizontal and vertical accuracies than the dike lines generated only using the LiDAR data on the various dike surfaces.

• TTA Journal
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• s.173
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• pp.106-109
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• 2017

LED 조명의 가시광에 데이터를 담아 보내는 가시광 통신(VLC) 기술 특허출원이 2009년 이후 가파르게 상승하고 있는 추세이다. 빛(Light)과 와이파이(Wi-Fi)를 합쳐 이른바 라이파이(Li-Fi, Light Fidelity)라고도 부르는 이 기술은 백만 분의 1초 간격으로 LED 조명을 켜고 끄는 것을 반복하여 데이터를 교환한다. 국내에서는 (주)유양디앤유가 2013년 이마트와 협력해 쇼핑 관련 VLC 기술을 적용한 시범 사업을 한 바 있다. (주)유양디앤유는 VLC 기술의 노하우를 바탕으로 미래 기술로 각광받고 있는 IoT를 접목해 사업을 다각화하고자 하였다. 이를 위해, 관련된 특허를 개발하고 국제 표준으로 제안하기 위해 TTA에 도움을 요청했다. TTA는 자문서비스와 함께 표준특허 인큐베이팅 사업을 연계하여 (주)유양디앤유를 지원하였다. 이를 통해 IoT를 접목한 VLC 무선 통신 국내 특허와 PCT 국제출원이 동시에 진행되는 성과를 거두었다.