• International journal of advanced smart convergence
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• v.12 no.2
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• pp.47-55
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• 2023

The automotive industry is undergoing a paradigm shift due to the convergence of IT and rapid digital transformation. Various components, including embedded structures and systems with complex architectures that incorporate IC semiconductors, are being integrated and modularized. As a result, there has been a significant increase in vehicle defects, raising expectations for the quality of automotive parts. As more and more data is being accumulated, there is an active effort to go beyond traditional reliability analysis methods and apply machine learning models based on the accumulated big data. However, there are still not many cases where machine learning is used in product development to identify factors of defects in performance and durability of products and incorporate feedback into the design to improve product quality. In this paper, we applied a prediction algorithm to the defects of automotive door devices equipped with automatic responsive sensors, which are commonly installed in recent electric and hydrogen vehicles. To do so, we selected test items, built a measurement emulation system for data acquisition, and conducted comparative evaluations by applying different machine learning algorithms to the measured data. The results in terms of R² score were as follows: Ordinary multiple regression 0.96, Ridge regression 0.95, Lasso regression 0.89, Elastic regression 0.91.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.07a
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• pp.261-262
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• 2020

현대에 흔히 쓰이는 도어락은 안전과 보안등의 목적과 편리함을 목적에 두고 있다. 실제로 그전에 쓰던 열쇠보다 더 편리하고 분실염려도 없고 복제키 등으로 인한 사건, 사고로 인한 범죄율이 줄어들었다. 도어락은 사용자가 손으로 직접 비밀번호를 입력하여 잠금을 해제하는 방식이고 이 과정에서 도어락에 지문이나 표시가 남으며 비밀번호가 주위에 쉽게 노출될 수 있다. 본 논문은 위의 문제를 해결하기 위해 아두이노로 라즈베리파이와 앱을 무선 통신하여 '원격 제어가 가능한 스마트 도어락'을 고안했다. 아두이노 와이파이 모듈을 통해 스마트폰으로 도어락을 원격으로 제어할 수 있으며 라즈베리파이 카메라 모듈과 초음파 센서를 통해 도어락에 접근하는 사람을 감지하고 확인할 수 있다. 이 기능으로 범죄를 예방할 수 있으며 자녀들의 귀가 여부도 확인할 수 있고 문을 열어줘야 할 상황에 비밀번호 노출없이 문을 열어줄 수 있다.

• Smart Structures and Systems
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• v.34 no.1
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• pp.41-50
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• 2024

The accurate measurement of temperature in the ground source heat pump system is crucial for assessing the thermal response of the system and validating the numerical model for parametric study, which is necessary for the thermal performance evaluation of the geothermal energy system. Conventional temperature sensors have some disadvantages such as they are difficult to install, and their position can be shifted during the backfill process of the ground heat exchanger. In this study, Fiber Bragg Grating (FBG) sensors were used to measure the temperature change of a recently developed ground heat exchanger (Coil Column Unit, CCU). FBG sensors were first calibrated in a thermal chamber alongside a correlation sensor (RTD sensor). The calibrated sensors were then mounted on the pipe surface at each spiral of the CCU to measure how temperature changes during the in-door mockup thermal response test. Finally, the measurement results of the FBG sensors were verified with a finite element coded program. The results indicated that the temperature difference between the numerical analysis and the experiment was less than 1%, which is significantly lower than that of the previous study using the RTD sensors. Therefore, it is feasible to apply FBG sensors for temperature measurement during the operation of the TRT of the geothermal energy system.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.6
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• pp.643-656
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• 2019

The development of hot social networking services, including the Internet, has transformed rental car services into IT-based car-sharing services. The car-sharing service is a service that allows people to rent cars online without having to face-to-face. It has become the preffered service among young people who are accustomed to drinking and eating alone. Users can use their smartphones to book their types of cars and hours of rent, and then go to a nearby designated parking lot to use their reserved cars. You can open a designated car door with a smart phone and drive. It is a very convenient service to pay for the distance you drive. However, the car-sharing service already in use in business has the following problems: underage who do not have a driver's license may drive a car borrowed by an acquaintance, the status of a license registered at the time of join membership with a car-sharing company may change to a suspension or cancellation of a license while renting and driving, or even a drunk person may rent a car and drive. In this paper, the method to solve these problems has been studied and proposed. The proposed method is to reduce the cost of investment by a car-sharing service provider and to minimize user inconvenience. And, it was compared and analyzed with the existing method. For the method to be used efficiently, the active operation of the car-sharing company and the government's policies will have to be supported.

• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.328-335
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• 2014

Numerical prediction methods were applied to investigate the turbulent air currents and air-conditioning efficiency in an underground subway station, and the results compared to experimental data. The Shin-gumho Station($8^{th}$ floor underground and 43.6m in depth) in Seoul was selected for the analysis. The entire station was covered for simulation and the ventilation mode was ordinary. The ventilation diffusers were modeled as 95 square shapes of $0.6m{\times}0.6m$ in the lobby and as 222 square shapes in the platform. Cooling air of $47,316m^3/h$ was supplied and the returned air of $33,980m^3/h$ is exhausted in the lobby and the cooling air of $33,968m^3/h$ is supplied and the returned air of $76,190m^3/h$ was exhausted in the platform which is the same as the experimental data. The cases of the screen-door-closed and open were respectively investigated. A total of 7.5million grids were generated and the whole domain divided into 22 blocks for MPI efficiency of calculation. Large eddy simulation (LES) was applied to solve the momentum and energy equation.

• Journal of the Korea Convergence Society
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• v.8 no.11
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• pp.37-42
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• 2017

Over the next decade, there are estimated to be 250 billion IoT devices in the future, and a variety of new services and device markets are expected to be created via a new network connection. However, it is difficult to accommodate various sensors and IoT devices, such as product and installation environments, for existing IP/SIP/IMS cameras and video door phone. Additionally, recently, sensors and actuators that can accommodate IoT technology and standards are continually updated. In addition, this paper has developed an SIP/IMS intelligent gateway to flexibly accommodate IoT related equipments and to interface with ZigBee/Z-Wave/NFC endpoints in addition to the gateway basic functions. This intelligent gateway will contribute to the development of the IMS system to replace the VoIP system with the IMS equipment due to the growth of the IMS market.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.5
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• pp.487-495
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• 2012

In this paper, a Smart Home Service Robot, McBot II, which performs mess-cleanup function etc. in house, is designed much more optimally than other service robots. It is newly developed in much more practical system than McBot I which we had developed two years ago. One characteristic attribute of mobile platforms equipped with a set of dependent wheels is their omni- directionality and the ability to realize complex translational and rotational trajectories for agile navigation in door. An accurate coordination of steering angle and spinning rate of each wheel is necessary for a consistent motion. This paper develops trajectory controller of 3-wheels omni-directional mobile robot using fuzzy azimuth estimator. A specialized anthropomorphic robot manipulator which can be attached to the housemaid robot McBot II, is developed in this paper. This built-in type manipulator consists of both arms with 4 DOF (Degree of Freedom) each and both hands with 3 DOF each. The robotic arm is optimally designed to satisfy both the minimum mechanical size and the maximum workspace. Minimum mass and length are required for the built-in cooperated-arms system. But that makes the workspace so small. This paper proposes optimal design method to overcome the problem by using neck joint to move the arms horizontally forward/backward and waist joint to move them vertically up/down. The robotic hand, which has two fingers and a thumb, is also optimally designed in task-based concept. Finally, the good performance of the developed McBot II is confirmed through live tests of the mess-cleanup task.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.1
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• pp.30-36
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• 2016

Recently, digital doorlock systems have been employing biometric recognition and smartphone as personal authentification means. The performance of a digital doorlock system is determined by the two conflicting indices such as security and convenience. This paper proposes and implements one grip based doorpull shaped doorlock systems using fingerprint and touch sensor grip pattern. The proposed system sequentially performs fingerprint recognition and grip pattern identification when a user grips the doorpull in order to open the door. This method so called 'One Grip' is considered to enhance security while maintaining users' convenience. We expect the proposed method can solve the phone missing problem encountered in developing smart doorlock systems based on smartphones.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1307-1312
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• 2015

The recent adoption of Bluetooth LE technology in smart phones triggered commercial interest in RSSI-based positioning technology. Estimation error in RSSI measurement due to the antenna pattern, multipath fading, environmental noise has to be considered for designing beacon systems. The paper proposes an analysis method and beacon planning rules for a small and isolated indoor service area, based on probabilistic model of RSSI estimation error. As an practically important guide, the beacons have to be installed at the boundary of the service area to minimize the maximum position error, whereas the beacons have to be evenly distributed in the service space to minimize the average estimation error.

• Journal of the Korea Society of Computer and Information
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• v.25 no.2
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• pp.113-122
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• 2020

In this paper, we propose the terminal authentication system using blockchain and TOTP(Time-based One-time Password Algorithm) to sustain a continuous authentication between user device and service device. And we experiment this system by using door-lock as a terminal of IoT(Internet of Things). In the future, we can apply this result to several devices of IoT for convenience and security. Although IoT devices frequently used everyday require convenience and security at the same time, it is difficult for IoT devices having features of the low-capacity and light-weight to apply the existing authentication technology requiring a high amount of computation. Blockchain technology having security and integrity have been used as a storage platform, but its authentication cannot be performed when the terminal cannot access any network. We show the method to solve this problem using Blockchain and TOPT.