• Journal of Korean Society of Forest Science
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• v.110 no.1
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• pp.72-81
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• 2021

We developed smartphone application and web application server to acquire and effectively manage tree measurement information. Smartphone applications can measure tree height, diameter at breast height (DBH), azimuth, altitude, slope, and positional coordinates using augmented reality (Google AR core) and motion sensors. The web application server effectively manages and stores measurement information. To evaluate the accuracy of information acquired using a smartphone, 90 Korean pine trees (Pinus koraiensis) were randomly selected from a natural mixed forest, with a total of 90 representative trees randomly collected from a natural mixed forest. Then, height and DBH were measured using a Haglof Vertex Laser Hypsometer and caliper. Comparisons of the results indicated significant results at the 95% level and a very high average correlation of 0.972 for both tree height and DBH. In terms of DBH, the average errors were 0.6745 cm and 1.0139 cm for artificial coniferous and natural mixed forests, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.5
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• pp.459-465
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• 2022

This paper reports a method to use a wireless sensor network deployed in the field to real-time monitor soil moisture, warning when the moisture level reaches a specific value, and wirelessly controlling an additional device (LED or water supply system, etc.). In addition, we report all processes related to wireless irrigation system, including field deployment of sensors, real-time monitoring using a smartphone, data calibration, and control of additional devices deployed in the field by smartphone. A commercially available open-source Internet of Things (IoT) platform, NodeMCU, was used, which was combined with a 9V battery, LED and soil humidity sensor to be integrated into a portable prototype. The IoT-based soil humidity sensor prototype deployed in the field was installed next to a tree for on-site demonstration for the measurement of soil humidity in real-time for about 30 hours, and the measured data was successfully transmitted to a smartphone via Wifi. The measurement data were automatically transmitted via e-mail in the form of a text file, stored on the web, followed by analyses and calibrations. The user can check the humidity of the soil real-time through a personal smartphone. When the humidity of a soil reached a specific value, an additional device, an LED device, placed in the field was successfully controlled through the smartphone. This LED can be easily replaced by other electronic devices such as water supplies, which can also be controlled by smartphones. These results show that farmers can not only monitor the condition of the field real-time through a sensor monitoring system manufactured simply at a low cost but also control additional devices such as irrigation facilities from a distance, thereby reducing unnecessary energy consumption and helping improve agricultural productivity.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.11
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• pp.411-418
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• 2016

Context-aware application has a lot of power consumption because it creates context by using a number of smartphone's sensors. Furthermore, only few kinds of researches have been conducted that provide information for the evaluation result of power consumption in the aspect of applications. In addition, evaluation of power consumption do not consider user's usage pattern or provide only total amount of power consumption, and inform developers power consumption of sensors undistinguishable. It makes developers hard to develop a power consumption-considered application. If developers could get information for power consumption of context-aware application in detail, a development of power-considered context-aware applications would be possible. Consequently, this paper proposes a BMT(Bench Mark Test) model which is able to inform developers useful evaluation criteria and result about power consumption of smartphone's components and sensors with usage pattern considered.

• KIISE Transactions on Computing Practices
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• v.23 no.3
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• pp.148-155
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• 2017

In this paper, we develop a new system to estimate the step count for a smartphone user. The system analyzes data obtained from the accelerometer, magnetic sensor, and gyroscope of an android smartphone to extract pattern information of human steps. We conduct an experiment and evaluation to confirm that the proposed system successfully estimates the number of steps with 96% accuracy when hand-held and 95.5% accuracy when in-pocket. In addition, we found that detection errors were caused by human motions such as touching the screen, shaking the device up and down, sitting up and sitting down, and waving the phone around.

• Journal of Sensor Science and Technology
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• v.27 no.1
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• pp.6-12
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• 2018

In this paper, a 32-variable pulse position modulation (32-VPPM) scheme is proposed to support a red-green-blue light-emitting-diode (RGB-LED)-based optical camera communication (OCC) system. Our proposed modulation scheme is designed to enhance the OCC data transmission rate, which is targeted for the wearable biomedical data monitoring system. The OCC technology has been utilized as an alternative solution to the radio frequency (RF) wireless system for long-term self-healthcare monitoring. Different biomedical signals, such as electrocardiograms, photoplethysmograms, and respiration signals are being monitored and transmitted wirelessly from the wearable biomedical device to the smartphone receiver. A common 30 frames per second (fps) smartphone camera with a CMOS image sensor is used to record a transmitted optical signal. Moreover, the overall proposed system architecture, modulation scheme, and data demodulation are discussed in this paper. The experimental result shows that the proposed system is able to achieve > 9 kbps using only a common smartphone camera receiver.

• Korean Journal of Computational Design and Engineering
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• v.19 no.3
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• pp.272-280
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• 2014

Most of the car navigation systems pzrovide 2D or 3D virtual map-based driving guidance. One of the important issues is how to reduce cognitive burden to the driver who should interpret the abstracted information to real world driving information. Recently, an augmented reality (AR)-based navigation is considered as a new way to reduce cognitive workload by superimposing guidance information into the real world scene captured by the camera. In particular, head-up display (HUD) is popular to implement AR navigation. However, HUD is too expensive to be set up in most cars so that the HUD-based AR navigation is currently unrealistic for navigational assistance. Meanwhile, smartphones with advanced computing capability and various sensors are popularized and also provide navigational assistance. This paper presents a research on cognitive effect and responsiveness of an AR navigation by a comparative study with a conventional virtual map-based navigation on the same smartphone. This paper experimented both quantitative and qualitative studies to compare cognitive workload and responsiveness, respectively. The number of eye gazing at the navigation system is used to measure the cognitive effect. In addition, questionnaires are used for qualitative analysis of the responsiveness.

• Journal of Korea Multimedia Society
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• v.20 no.8
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• pp.1421-1429
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• 2017

Human activity recognition has been studied using various sensors and algorithms. Human activity recognition can be divided into sensor based and vision based on the method. In this paper, we proposed an activity recognition system using acceleration sensor and gyroscope sensor in smartphone among sensor based methods. We used Deep Belief Network (DBN), which is one of the most popular deep learning methods, to improve an accuracy of human activity recognition. DBN uses the entire input set as a common input. However, because of the characteristics of different time window depending on the type of human activity, the RBMs, which is a component of DBN, are configured hierarchically by combining them from different time windows. As a result of applying to real data, The proposed human activity recognition system showed stable precision.

• Proceedings of the Korea Contents Association Conference
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• 2015.05a
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• pp.13-14
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• 2015

In the past few decades, many catastrophic natural disasters have occurred not only in Japan and Korea, but also in other countries in the world, forcing people to live in unfamiliar houses for middle or long range evacuation periods. Residents staying in temporary houses exhibit insomnia, resulting in severe fatigue. In order to investigate sleeping state of residents, measuring vital signals has been performed at examination room of a hospital. To avoid the restriction of residents' movement, we propose to use smartphone and/or wearable devices with various high performance sensors like measuring heart beat rate. We clarify the availability and usefulness of those devices as support for analyzing daily sleeping state of residents.

• IEMEK Journal of Embedded Systems and Applications
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• v.5 no.4
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• pp.195-205
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• 2010

The popularity of Smartphones makes new fields of applications based on location based service easily feasible with a new user interface called augmented reality (AR). It presents a particularly powerful user interface to context-aware computing environments. AR on Smartphones integrates virtual information into a person's physical environment by overlaying information on an image taken through Smartphone's camera and motion sensors. Mobile augmented reality systems provide this service without constraining the individual's whereabouts to a specially equipped area. This work presents an overview of handheld augmented reality focusing on applications with introducing the basic issues of them. For this purpose, an example system, Studierstube ES (embedded system), is cited, which introduces the most significant problems and various methods of solving them through the experience of converting existing PC-based AR system into handheld AR.

• Proceedings of the Korean Society of Computer Information Conference
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• 2012.01a
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• pp.177-178
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• 2012

최근의 게임 시장에서 체감형 게임은 홈 엔터테인먼트의 중심이 되어가고 있으며 그만큼 큰 인기를 끌며 발전하고 있다. 본 논문에서는 스마트폰 모션 센서를 실제 게임에 적용하기 위한 동작 인식 방법과 적용방법을 제안한다. 본 논문에서는 모션 센서를 이용하여 테니스 게임에 사용되는 모션들을 인식하고 적용시킨다. 실험의 결과 스마트폰 모션 센서를 적용시켜 게임에 이용하는 데에 사용자가 충분한 만족도를 보였다.