• Structural Engineering and Mechanics
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• v.69 no.6
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• pp.699-712
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• 2019

A cable-stayed bridge (CSB) is one of the most complicated structures, especially when subjected to earthquakes and taking into consideration the effect of soil-structure-interaction (SSI). A CSB of a 500 m mid-span was modeled by the SAP2000 software and was subjected to four different earthquakes. To mitigate the harmful effect of the vibration generated from each earthquake, four mitigation schemes were used and compared with the non-mitigation model to determine the effectiveness of each scheme, when applying on the SSI or fixed CSB models. For earthquake mitigation, tuned mass damper (TMD) systems and spring dampers with different placements were used to help reduce the seismic response of the CBS model. The pylons, the mid-span of the deck and the pylon-deck connections are the best TMDs and spring dampers placements to achieve an effective reduction of the earthquake response on such bridges.

• Journal of IKEEE
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• v.23 no.2
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• pp.735-738
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• 2019

Recently, orthogonal non-orthogonal multiple access (O NOMA) with polar on-off keying (POOK) has been proposed to mitigate the severe effect of the superposition. However, it is observed that the performance of the O NOMA strong channel user is better than that of the perfect successive interference cancellation (SIC), i.e., the performance of a single user transmission with binary phase shift keying (BPSK). Can the performance of the BPSK modulation be better that that of itself? It is not normal. It should be clearly understood theoretically, with the ultimate bound, i.e., the channel capacity. This paper proves that the channel capacity of the O NOMA strong channel user is non-zero with zero power allocation. Thus, it is shown that the interference is transformed effectively into the meaningful signal.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1182-1192
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• 2019

In order to improve the conversion efficiency and mitigate the EMI problem of conventional hard-switching inverters, a new soft-switching DC-AC inverter with a compact structure and a low modulation complexity is proposed in this paper. In the proposed structure, resonant inductors are connected in series for the arm branches, and resonant capacitors are connected in parallel for the neutral point branches. With the help of resonant components, the proposed structure achieves zero-current switching on the arm branches and zero-voltage switching on the neutral point branches. When compared with state-of-art soft-switching topologies, the proposed topology does not need auxiliary switches. Moreover, the commutation algorithm to realize soft-switching can be easily implemented. In this paper, the principle of the resonant operation of the proposed soft-switching converter is presented and its performance is verified through simulation studies. The feasibility of the proposed inverter is evaluated experimentally with a 2.4-kW prototype.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.4
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• pp.395-403
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• 2019

The excessive need of power is creating an unbalance situation in power sector, where solar energy is one of the best solutions among other energy sources to mitigate this demand. It is globally accepted because of its flexibility and long life compared to others. A lot research is going on to enhance the energy efficiency by introducing photovoltaic (PV) power generation technology, but still irradiation of PV power is the major problem. In this manuscript, we have designed PV module using single diode methodology and also the solar conversion efficiency was boosted with maximum power point tracking (MPPT) by using perturb and observe (P&O) algorithm. The simulation was done for $1000W/m^2$ and $800W/m^2$ at solar irradiance in cell temperature of 25C and 40C degree levels in PSIM tool.

• Journal of the Korea Society of Computer and Information
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• v.24 no.3
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• pp.151-157
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• 2019

In this paper, we present a prototype system for controlling IoT home appliances via voice-based commands. A voice command has been widely deployed as one of unobtrusive user interfaces for applications in a variety of IoT domains. However, interoperability between diverse IoT systems is limited by several dominant companies providing voice assistants like Amazon Alexa or Google Now due to their proprietary systems. A global IoT standard, oneM2M has been proposed to mitigate the lack of interoperability between IoT systems. In this paper, we deployed oneM2M-based platforms for a voice record device like a wrist band and LED control device like a home appliance. We developed all the components for recording voices and controlling IoT devices, and demonstrate the feasibility of our proposed method based on oneM2M platforms and Google STT (Speech-to-Text) API for controlling home appliances by showing a user scenario for turning the LED device on and off via voice commands.

• International Journal of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.60-68
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• 2019

In this paper, we propose the adaptive beamforming algorithm for the MIMO (Multi-Input Multi-Out)-OFDMA(Orthogonal Frequency Division Multiplexing Access)system to improve the performance. The performance of MIMO-OFDMA systems is greatly decreased in the wireless channel environment with multiusers, because the received signals are much distorted by a cochannel interference (CCI) during the space-time decoding. The proposed approach can track the DOA of each signal from the multiple antennas of the desired user without being greatly dependent on the impinging angle. And beams are directed toward the multiple transmitters of the desired user while null beams are directed toward interference directions. Therefore, we can can effectively cancel CCI and mitigate the impairment of delay spread while preserving the STC(space time code) diversity. BER performance improvement is investigated through computer simulation by applying the proposed approach to MIMO-OFDMA system in a multipath fading channel with CCI.

• ETRI Journal
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• v.40 no.6
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• pp.726-735
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• 2018

Femtocells are good examples of the ultimate networking technology, offering enhanced indoor coverage and higher data rate. However, the dense deployment of femto base stations (FBSs) and the exploitation of subcarrier reuse between macrocell base stations and FBSs result in significant co-tier and cross-tier interference, thus degrading system performance. Therefore, appropriate resource allocations are required to mitigate the interference. This paper proposes a discrete bacterial foraging optimization (DBFO) algorithm to find the optimal resource allocation in two-tier networks. The simulation results showed that DBFO outperforms the random-resource allocation and discrete particle swarm optimization (DPSO) considering the small number of steps taken by particles and bacteria.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.323-325
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• 2014

SNOMED CT is a standard clinical terminology which is to efficiently record, manage and utilize clinical records during clinical processes. However, huge expressive power of SNOMED CT makes it difficult to select appropriate terms during short consultation hours. In addition, true meaning of a written record using the terminology may be misunderstood or even distorted since one clinical meaning could be expressed in a variety of ways. This paper analyzes such known problems in a database point of view, and presents effective selection methods of similar terminologies to mitigate the problem.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.195-196
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• 2016

In the maritime mobile radiocommunication service, AIS(Automatic Identification System) devices are most widely using for the exchange of ship's navigational information. The AIS time slot usage increases due to increasing number of ships installed with AIS, and thus the reception rate of AIS data decrease. In order to mitigate this problem, international organizations recommend a sectorised receiving technique using directional antenna. This paper analyzed the sectorised receiving effectiveness of AIS data using Yaga antenna.

• Journal of Information Processing Systems
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• v.15 no.4
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• pp.717-723
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• 2019

Smart systems and services aim to facilitate growing urban populations and their prospects of virtual-real social behaviors, gig economies, factory automation, knowledge-based workforce, integrated societies, modern living, among many more. To satisfy these objectives, smart systems and services must comprises of a complex set of features such as security, ease of use and user friendliness, manageability, scalability, adaptivity, intelligent behavior, and personalization. Recently, artificial intelligence (AI) is realized as a data-driven technology to provide an efficient knowledge representation, semantic modeling, and can support a cognitive behavior aspect of the system. In this paper, an integration of AI with the smart systems and services is presented to mitigate the existing challenges. Several novel researches work in terms of frameworks, architectures, paradigms, and algorithms are discussed to provide possible solutions against the existing challenges in the AI-based smart systems and services. Such novel research works involve efficient shape image retrieval, speech signal processing, dynamic thermal rating, advanced persistent threat tactics, user authentication, and so on.