• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.2
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• pp.323-335
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• 2015

Mobile healthcare is a fusion of information technology and biotechnology and is a new type of health management service to keep people's health at anytime and anywhere without regard to time and space. The WBAN(Wireless Body Area Network) technology that collects bio signals and the data analysis and monitoring technology using mobile devices are essential for serving mobile healthcare. WBAN consisting of users with mobile devices meet another WBAN during movement, WBANs transmit data to the other media. Because of WBAN conflict, several nodes transmit data in same time slot so a collision will occur, resulting in the data transmission being failed and need more energy for re-transmission. In this thesis, we proposed a MAC protocol for WBAN with mobility to solve these problems. First, we proposed a superframe structure for WBAN. The proposed superframe consists of a TDMA(Time Division Muliple Access) based contention access phase with which a node can transmit data in its own time slot and a contention phase using CSMA/CA algorithm. Second, we proposed a network merging algorithm for conflicting WBAN based on the proposed MAC protocol. When a WBAN with mobility conflicts with other WBAN, data frame collision is reduced through network reestablishment. Simulations are performed using a Castalia based on the OMNeT++ network simulation framework to estimate the performance of the proposed superframe and algorithms. We estimated the performance of WBAN based on the proposed MAC protocol by comparing the performance of the WBAN based on IEEE 802.15.6. Performance evaluation results show that the packet transmission success rate and energy efficiency are improved by reducing the probability of collision using the proposed MAC protocol.

• 한국지형공간정보학회:학술대회논문집
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• 2002.03a
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• pp.150-155
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• 2002

SAR 시스템은 능동적 센서로 마이크로파라 불리우는 전자기파를 직접 지상에 보내고 돌아오는 신호의 위상과 진폭을 이용하여 영상으로 나타내는 간섭성 시스템이다. 이러한 영상의 특성으로 인해 날씨나 태양의 유 무에 상관없이 영상을 취득할 수 있는 장점이 있다. 또한, 최근에는 기존의 다중분광 위성영상과의 SAR 영상의 Data Fusion을 통해 지상의 새로운 정성적 정보를 취득하려는 시도 등 나날이 그 활용성이 증대되고 있는 상황이다. 그러나 SAR 영상의 광범위한 활용을 위해서는 먼저 영상의 지형보정이 선행되어야 한다. 따라서 본 연구에서는 SAR 영상의 활용을 위해서 선행되어야 할 지형보정의 알고리즘을 컴포넌트 기반의 프로그램으로 구현하고 대상연구지역에 대한 적용을 통해 그 활용성과 가능성을 보여주고자 한다. 연구대상지역은 ERS-1, ERS-2 SAR로 촬영된 대전광역시와 그 주변지역으로 해당 SAR 영상에 대하여 엄밀지형보정 알고리즘과 경사거리 영상을 지상거리 영상으로 변환하는 알고리즘을 개발하여 적용하였다. 실험결과 공칭해상도 30m의 ERS 영상에 대하여 39.7m(X방향으로 24.5m, Y방향으로 31.3m)의 수평오차를 나타내었으며 경사거리 영상의 지상거리 영상으로의 변환도 원활하게 수행됨을 알 수 있었다. 마지막으로 본 연구를 통해 연구된 모든 알고리즘은 컴포넌트 기반으로 설계하고 구현되어 향후 국내 SAR 처리기술 개발에 있어서 공유할 수 있도록 하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.9
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• pp.2037-2051
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• 2012

Cognitive radio (CR) is envisioned as a promising paradigm of exploiting intelligence for enhancing efficiency of underutilized spectrum bands. In CR, the main concern is to reliably sense the presence of primary users (PUs) to attain protection against harmful interference caused by potential spectrum access of secondary users (SUs). In this paper, evolutionary algorithms, namely, particle swarm optimization (PSO) and genetic algorithm (GA) are proposed to minimize the total sensing decision error at the common soft data fusion (SDF) centre of a structurally-centralized cognitive radio network (CRN). Using these techniques, evolutionary operations are invoked to optimize the weighting coefficients applied on the sensing measurement components received from multiple cooperative SUs. The proposed methods are compared with each other as well as with other conventional deterministic algorithms such as maximal ratio combining (MRC) and equal gain combining (EGC). Computer simulations confirm the superiority of the PSO-based scheme over the GA-based and other conventional MRC and EGC schemes in terms of detection performance. In addition, the PSO-based scheme also shows promising convergence performance as compared to the GA-based scheme. This makes PSO an adequate solution to meet real-time requirements.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.3
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• pp.275-284
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• 2012

This paper proposes an attitude and direction control of a single wheel balanced robot. A unicycle robot is controlled by two independent control laws: the mobile inverted pendulum control method for pitch axis and the reaction wheel pendulum control method for roll axis. It is assumed that both roll dynamics and pitch dynamics are decoupled. Therefore the roll and pitch dynamics are obtained independently considering the interaction as disturbances to each other. Each control law is implemented by a controller separately. The unicycle robot has two DC motors to drive the disk for roll and to drive the wheel for pitch. Since there is no force to change the yaw direction, the present paper proposes a method for changing the yaw direction. The angle data are obtained by a fusion of a gyro sensor and an accelerometer. Experimental results show the performance of the controller and verify the effectiveness of the proposed control algorithm.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1780-1787
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• 2014

Arterial oxygen saturation ($SpO_2$) monitoring for newborns requires special attention in neonatal intensive care units (NICUs). Newborns have very low photo-plethysmogram (PPG) amplitudes and their body movements are difficult to contain. Hardware design and its associated signal processing algorithms should be robust enough so that faulty measurements can be avoided. In this study, improved designs were implemented to deal with low perfusion, motion artifact, and the influence of ambient light. Dynamic range was increased by using different LED intensities and a feedback system. To minimize the effects of motion artifact and to discard other unqualified data, four additional algorithms were used, which were based on dual-trace detection, continuity of DC level, morphology of PPG, and simultaneity check of $SpO_2$. Our $SpO_2$ system was tested with newborns with normal respiration in the NICU. Our system provided fast, real-time responses and 100% artifact detection was accomplished under 84% of $SpO_2$.

• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.4
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• pp.239-247
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• 2022

The existing studies on the localization in the GNSS (Global Navigation Satellite System) denied environment usually exploit low-cost MEMS IMU (Micro Electro Mechanical Systems Inertial Measurement Unit) sensors to replace the GNSS signals. However, the navigation system still requires GNSS signals for the normal environment. This paper presents an integrated GNSS/INS (Inertial Navigation System) navigation system which combines GNSS and multiple IMU sensors using extended Kalman filter in partially GNSS-denied environments. The position and velocity of the INS and GNSS are used as the inputs to the integrated navigation system. The Mahalanobis distance is used for novelty detection to detect the outlier of GNSS measurements. When the abnormality is detected in GNSS signals, GNSS data is excluded from the fusion process. The performance of the proposed method is evaluated using MATLAB/Simulink. The simulation results show that the proposed algorithm can achieve a higher degree of positioning accuracy in the partially GNSS-denied environment.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3485-3492
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• 2023

One of the major topic of tokamak research is the determination of the magnetic profile due to magnetic coil fields and plasma current by mean of data from magnetic probes. The most practical approach is to use the current filament method, which models the plasma column with multiple current carrying filaments and the total current of these filaments is equal to the plasma current. Determining the plasma boundary in Alvand-U tokamak is the main purpose of this paper. In order to determine the magnetic field profile and plasma boundary, information concerning the magnetic coils, their position, and current is required in the computing code. Then, the plasma shape is determined and finally the plasma boundary is extracted by the code. In the conducted research, we discuss how to determine the plasma boundary and the performance of the computing code for extraction of the plasma boundary. The developed algorithm shows to be effective by running it in the regular pc machine with characteristics of Intel (R) core (TM) i3-10100 CPU @3.60 GHz and 8.00 GB of RAM. Finally, we present results of a test run for computing code using a typical experimental pulse.

• Journal of Digital Contents Society
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• v.19 no.4
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• pp.701-709
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• 2018

Our research team implemented and operated the system by analyzing the membership information and identifying the different preferences for each group and providing the results of the recommendation based on accumulated membership information and activity log data to the individual. The utilization log was followed up. We analyzed how many people use recommended services and analyzed whether there are any factors other than the personalization service algorithm that affect the service utilization of the system with personalization. In addition, we propose recommendation methods based on behavioral changes when incentives are given through analyzing patterns of users' usage according to methods of recommending services and contents that are often used based on analysis contents.

• Journal of Internet Computing and Services
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• v.21 no.5
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• pp.109-118
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• 2020

Recently, people are spending a lot of time inside their homes because of various diseases. It is difficult to ask others for help in the case of a single-person household that is injured in the house or infected with a disease and needs help from others. In this study, an algorithm is proposed to detect emergency event, which are situations in which single-person households need help from others, such as injuries or disease infections, in their homes. It proposes vision pattern detection algorithms using home CCTVs, audio pattern detection algorithms using artificial intelligence speakers, activity pattern detection algorithms using acceleration sensors in smartphones, and dust pattern detection algorithms using air purifiers. However, if it is difficult to use due to security issues of home CCTVs, it proposes a fusion method combining audio, activity and dust pattern sensors. Each algorithm collected data through YouTube and experiments to measure accuracy.

• Journal of Welding and Joining
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• v.27 no.4
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• pp.54-59
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• 2009

In the process to manufacture for metallic structures, control of welding deformation is one of an important problems connected with reliability of the manufactured structures so that welding deformation should be measured and controlled with quickly and actively. Also, welding parameters which have as lot of effects on welding deformation such as arc voltage, welding current and welding speed can also be controlled. The objectives for this study were to develop a simple 2-D FEM to calculate not only the transient thermal histories but also the sizes of fusion and heat-affected zone (HAZ) in multi pass arc welds including the butt and fillet weld type with dissimilar thickness, and to concentrate on a developed model for the finding the parameters of Godak's moving heat source model based on a GA. The developed model includes a GA program using MATLB and GA toolbox, and a batch mode thermal model using ANSYS software. Not only the thermal model was verified by comparison with Goldak's work but also the developed model was validated with molten zone section experimental data.