• Journal of Power Electronics
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• v.16 no.5
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• pp.1894-1903
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• 2016

In general, electrolytic capacitors are used to reduce power pulsations on PV-panels. However, this can reduce the reliability of the PV AC-module system, because electrolytic capacitors have a shorter lifetime than PV-panels. In addition, PV-panels generate irregular power and inject it into the grid because the output power of a PV-panel depends on the surrounding conditions such as irradiation and temperature. To solve these problems, a grid-connected photovoltaic (PV) AC-module with active power decoupling and energy storage is proposed. A parallel bi-directional converter is connected to the AC module to reduce the output power pulsations of PV-panels. Thus, the electrolytic capacitor can be replaced with a film capacitor. In addition, the irregular output power due to the surrounding conditions can be regulated by using a parallel energy storage circuit. To maintain the discontinuous conduction mode at low irradiation, the frequency control method is adopted. The design method of the proposed converter and the operation principles are introduced. An experimental prototype rated at 125W was built to verify the performance of the proposed converter.

• Journal of Power Electronics
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• v.16 no.2
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• pp.610-620
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• 2016

The compound active clamp zero voltage soft switching (CACZVS) three-phase power factor correction (PFC) converter has many advantages, such as high efficiency, high power factor, bi-directional energy flow, and soft switching of all the switches. Triple closed-loop PI controllers are used for the three-phase power factor correction converter. The control objectives of the converter include a fast transient response, high accuracy, and unity power factor. There are six parameters of the controllers that need to be tuned in order to obtain multi-objective optimization. However, six of the parameters are mutually dependent for the objectives. This is beyond the scope of the traditional experience based PI parameters tuning method. In this paper, an improved chaotic particle swarm optimization (CPSO) method has been proposed to optimize the controller parameters. In the proposed method, multi-dimensional chaotic sequences generated by spatiotemporal chaos map are used as initial particles to get a better initial distribution and to avoid local minimums. Pareto optimal solutions are also used to avoid the weight selection difficulty of the multi-objectives. Simulation and experiment results show the effectiveness and superiority of the proposed method.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.05a
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• pp.419-422
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• 2019

The recent increase in single-person households and family income has led to an increase in the number of pet owners. However, due to the owners' difficulty to communicate with them for 24 hours, pets, and especially dogs, tend to display unwanted behavior that can be harmful to themselves and their environment when left alone. Therefore, detecting those behaviors when the owner is absent is necessary to suppress them and prevent any damage. In this paper, we propose a camera-based system that detects a set of normal and unwanted behaviors using deep learning algorithms to monitor dogs when left alone at home. The frames collected from the camera are arranged into sequences of RGB frames and their corresponding optical flow sequences, and then features are extracted from each data flow using pre-trained VGG-16 models. The extracted features from each sequence are concatenated and input to a bi-directional LSTM network that classifies the dog action into one of the targeted classes. The experimental results show that our method achieves a good performance exceeding 0.9 in precision, recall and f-1 score.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.05a
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• pp.615-617
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• 2023

In recent years, the growing popularity of dogs due to the benefits they bring their owners has contributed to the increase of the number of dogs raised. For owners, it is their responsibility to ensure their dogs' health and safety. However, it is challenging for them to continuously monitor their dogs' activities, which are important to understand and guarantee their wellbeing. In this work, we introduce a camera-based monitoring system to help owners automatically monitor their dogs' activities. The system receives sequences of RGB images and uses YOLOv7 to detect the dog presence, and then applies post-processing to perform dog-centered image cropping on each input sequence. The optical flow is extracted from each sequence, and both sequences of RGB and flow are input to a two-stream EfficientNet to extract their respective features. Finally, the features are concatenated, and a bi-directional LSTM is utilized to retrieve temporal features and recognize the activity. The experiments prove that our system achieves a good performance with the F-1 score exceeding 0.90 for all activities and reaching 0.963 on average.

• Journal of Broadcast Engineering
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• v.13 no.6
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• pp.817-827
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• 2008

The terrestrial-digital multimedia broadcasting(T-DMB) is now provided for the public service and the number of receivers reaches 15 million at the present of August 2008. The service of T-DMB itself has been succeeded in the presence. It is however remained as a supplementary role of stationed TV. It is necessary to find an additional business model as a new media to acquire surplus escaping from the deficit of the present T-DMB service. In the present paper, data service of T-DMB is proposed as candidate of such solution. Especially, TTI(Traffic and Travel Information) service is proposed as a killer application using TPEG(Transport Protocol Experts Group). At present, TPEG has not been so popular in the sense of various user satisfaction. Thus the variety of service including bi-directional service using DMB2.0 as in the sphere of Web2.0 is necessary for the service providers. In the paper, the restriction of TPEG-POI(Point of Interest) application service using the conventional mobile communication infrastructure is indicated. To overcome such restriction, TPEG-UCM(User Created Message) application service model using individual bi-directional media which is initiated and interacting by the users is proposed. In the experiment, the application program shows the usability of the proposed method so that the implementation results show its operability.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.89-94
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• 2012

In this paper, a UHF cavity-backed spiral antenna for partial discharge diagnosis is proposed. The proposed antenna consists of two-arm Archimedean spiral, a cavity, and a balun for feeding. The spiral antenna is designed for 0.3-1.5 GHz operating frequency. Two spiral arms of the proposed antenna are fed by a microstrip tapered-balun. In order to enhance the gain, the cavity is located in the back side of the spiral pattern. The proposed antenna is designed and simulated using CST Microwave Studio. The designed antenna is also fabricated and tested to validate performance. The measured radiation patterns are directional to the +z-axis and measured peak gain is 9.92 dBi.

• Journal of IKEEE
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• v.24 no.2
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• pp.536-542
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• 2020

This paper presents a nature-inspired wideband sprout-leaf shaped antenna with end-fire radiation pattern. A sprout-leaf shape angled-radiator was designed for wide beamwidth radiation patterns for motion detection sensors. An extended and truncated ground plane was used as a reflector for end-fire radiation patterns. To feed the balanced radiator, a broadband microstrip (MS) to coplanar stripline (CPS) balun was utilized with excellent amplitude and phase balance. The proposed antenna demonstrates wide frequency bandwidth from 8.5 to 14.5 GHz with wide beamwidth and the radiation efficiency of 90%. The measured gain is from 4 to 5 dBi and front-to-back ratio was 10 to 20 dB. It has been shown that the proposed antenna can be used for imaging sensors, phased array systems, and radars that require a wide bandwidth and a directional radiation pattern.

• Journal of Advanced Navigation Technology
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• v.15 no.4
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• pp.549-555
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• 2011

In this paper, inverted triangle structural planar monopole antenna with Edge for UWB Communication (3.1 ~ 10.6 GHz) is presented. The antenna have broadband property structurally through inverted triangle structural planar monopole which have edge. Monopole and ground of proposed antenna exist on coplanar plane, and excite as CPW. It used FR4 dielectric substrate of ${\epsilon}_r=4.4$, and the size is $20{\times}20{\times}1.6mm$. Return loss is more than - 10dB in 3.1 ~ 10.1 GHz (7.0 GHz). Radiation pattern is about the same that of dipole antenna at all frequency. At measured result, max gain is 8.44 dBi at E - plane.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2223-2231
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• 2015

In this paper, we propose a built-in antenna for wireless USB dongle which has a modified structure from the existing planar monopole antenna. The proposed antenna implemented a dual-band characteristic by inserting Strip1, Strip2, Strip3 into the monopole structure combined with 'n' shape and feeded 50-Ω using coaxial cable. The antenna is designed on an FR-4 substrate of which the dielectric constant is 4.6, and its overall size is 10 mm × 50 mm × 1mm. Based on the measurement results of the return loss, it was confirmed to satisfy the dual band resonance characteristics of 740 MHz (2.3 ~ 2.7 GHz) and 1,200 MHz (5.15 ~ 5.825 GHz) by -10 dB. In addition, we obtain the omni-directional radiation pattern measurements in the operating frequency bands, and the maximum gain of the proposed antenna has 2.26~3.81 dBi in the 2.4 GHz band and 2.21~5.79 dBi. in the 5.5 GHz band, respectively.

• Journal of the Korea Knowledge Information Technology Society
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• v.12 no.4
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• pp.539-550
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• 2017

In this paper, we designed, fabricated and tested an UHF band cylindrical dipole array antenna. In the proposed antenna, cylindrical dipoles were vertically arranged in four stages. A parallel structure feeding circuit was installed inside the cylindrical dipole and mounted so as to be broadband matching. The feeding circuit was installed at the center of the cylindrical dipole to optimize the gain flatness characteristic of the azimuth direction omnidirectional radiation pattern. Minimizing the difference between the signals branched from the feeding circuit and realizing the symmetry of the radiation pattern. The required specifications are more than 11.2% bandwidth in UHF band, above 6dBi antenna gain, standing wave ratio of 2:1 or less, less than ${\pm}1dB$ gain flatness in azimuth radiation pattern, more than 13 degrees in elevation radiation pattern of 3dB beamwidth. We confirmed the possibility of implementation through M&S and verified the result of M&S through production and testing. The test results are 11.2% bandwidth in the UHF band, 6.30 to 8.31 dBi gain, 1.53:1 standing wave ratio or less, within ${\pm}0.2dB$ gain flatness in the azimuth radiation pattern, elevation radiation pattern of 3dB beam width was 15.62 to 15.84 degrees. The test result meets all requirements specifications.