• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.9 no.1
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• pp.179-187
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• 2019

With the recent development of small computing devices, IoT sensor network can be widely deployed and is now readily available with sensing, calculation and communi-cation functions at low cost. Sensor data management is a major component of the Internet of Things environment. The huge volume of data produced and transmitted from sensing devices can provide a lot of useful information but is often considered the next big data for businesses. New column-wise compression technology is mounted to the large data server because of its superior space efficiency. Since sensor nodes have narrow bandwidth and fault-prone wireless channels, sensor-based storage systems are subject to incomplete data services. In this study, we will bring forth a short overview through providing an analysis on IoT sensor networks, and will propose a new storage management scheme for IoT data. Our management scheme is based on RAID storage model using column-wise segmentation and compression to improve space efficiency without sacrificing I/O performance. We conclude that proposed storage control scheme outperforms the previous RAID control by computer performance simulation.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.3
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• pp.74-85
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• 2021

Global Navigation Satellite System (GNSS) receivers are intrinsically vulnerable to radio frequency jamming signals due to the fundamental property of radio navigation systems. A GNSS jamming monitoring system that is capable of jamming detection, classification and localization is essential for infrastructure for autonomous driving systems. For these 3 functionalities, a GNSS jamming monitoring network consisting of a multiple of low-cost GNSS receivers distributed in a certain area is needed, and the precise time synchronizaion between multiple independent GNSS receivers in the network is an essential element. This paper presents a precise time synchronization method based on the direct use of Time Difference of Arrival (TDOA) technique in signal domain. A block interpolation method is additionally incorporated into the method in order to maintain the precision of time synchronization even with the relatively low sampling rate of the received signals for computational efficiency. The feasibility of the proposed approach is verified in the numerical simualtions.

• Journal of Internet of Things and Convergence
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• v.8 no.2
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• pp.61-70
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• 2022

Connectivity and knowledge are the main keywords of the IoT. In this paper, I analyzed how the two civilizations, Christianity and Islam, were connected through Mughal paintings and what result they have brought in the spread of knowledge. For that, I analyzed literature as well as paintings of those days. In terms of theme matter, Western painting was used as a means of strengthening the royal authority of the Mughal Emperor. In terms of style, perspective and shading from the Western Paintings began to be used in Mughal painting. Later, Christian symbols and themes were linked to absolute power of kingship, and further utilized them to develop into the concept of kingship = spirituality = divinity, creating an original art style that was unprecedented in the history of world painting. By analyzing the two disparate cultures in terms of 'connectivity' and 'knowledge' of the Internet of Things, such research could serve as a platform for future humanities research on the Internet of Things.

• Journal of Korea Society of Industrial Information Systems
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• v.27 no.5
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• pp.145-156
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• 2022

In recent years, as there is growing concern with ESG (Environmental, Social, and Governance), the strategic direction of business management is changing from maximizing shareholders wealth to maximizing stakeholders value. ESG is reshaping a corporation's supply chain management strategies. The purpose of this study is to explore the ESG challenges in supply chain management. As a result of network text analysis and topic modeling analysis on 3226 news articles, 'Suppliers', 'Sustainability', 'Shared Growth' 'Carbon Neutral', 'Safety and Health', 'Responsible Business Alliance', 'Supply Chain Due Diligence Law' were identified as the main issue. Since ESG initiatives in the supply chain are not limited to the efforts of individual firms, future research should focus on figuring out what difficulties and challenges exist in the diffusion of ESG practices along multi-tiered supply chains, and how to overcome them.

• Journal of the Korea Society of Computer and Information
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• v.27 no.11
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• pp.81-87
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• 2022

In this paper, we propose diffraction-based sound control method to improve sound immersion in a virtual environment. The proposed technique can express the wave and flow of sound in a physical environment and a pattern similar to diffraction in real-time. Our approach determines whether there is an obstacle from the location of the sound source and then calculates the position of the new sound reflected and diffracted by the obstacle. Based on ray tracing, it determines whether or not it collides with an obstacle, and predicts the sound level of the agent behind the obstacle by using the vector reflected and refraction by the collision. In this process, the sound attenuation according to the distance/material is modeled by attenuating the size of the sound according to the number of reflected/refracted rays. As a result, the diffraction pattern expressed in the physics-based approach was expressed in real time, and it shows that the diffraction pattern also changes as the position of the obstacle is changed, thereby showing the result of naturally spreading the size of the sound. The proposed method restores the diffusion and diffraction characteristics of sound expressed in real life almost similarly.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.255-255
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• 2023

우리나라의 경우 집중호우와 돌발홍수로 인한 침수 발생에 대응하기 위해 유역 및 하천관리 사업, 각종 풍수해 예방사업 등을 추진하고 있으며, 관련 분야의 스마트기술 도입을 적극 추진하고 있다. 그러나, 2013년 노량진 상수도관 공사 현장 사고, 2019년 신월 빗물저류 배수시설 현장 사고 등과 같은 건설현장 침수 피해 사고가 지속적으로 발생하고 있다. 또한, 건설현장의 다양한 조건 및 시시각각 변화하는 상황에 따라 구조적 대책 및 대응방안을 수립하는 데 한계가 있으며 지금까지는 법, 제도에 기초한 대응 매뉴얼을 제작·배포하여 현장 근로자 교육을 실시하는 수준에서 진행되어 왔다. 본 연구에서는 건설현장의 자연재해, 특히 수재해에 대응하기 위해 보다 과학적인 방법을 통한 현장 침수 예경보 체계를 수립하였으며, 강우예측-침수예측-침수예경보 생산-현장 상황전파에 이르는 일련의 시스템을 개발하여 공사별, 규모별, 공정별 침수 대응 솔루션을 제공하고자 한다. 건설현장 침수예경보 시스템 개발의 주요 내용은 요소기술 개발이며, 간략하게 정리하면 다음과 같다. ① 강우 예측정보 생산: 현장에서 발생하는 집중호우를 고려하는 실시간 강우측정 자료와 연계한 초단기 강우예측 기술 개발, ② 침수 예측모델 개발: 현장의 시공간적 특성, 수재해 피해의 유형 등을 반영할 수 있는 침수피해 예측 모델 개발, ③ 침수예경보 의사결정 방법론 개발: 침수 피해 예경보를 위한 침수 위험단계 세분화 및 노모그래프 개발과 모델 적용(예측정확도 85% 이상), 이를 통합하여 건설현장 침수예경보 시스템 개발을 수행하게 된다. 연구에서 개발된 침수 예경보 통합 시스템은 향후 수재해로 인한 건설현장의 인명, 재산 피해 최소화에 기여할 것으로 기대된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.18-18
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• 2021

초음파 도플러 유속계(ADCP)는 초음파를 이용하여 하천의 유속 및 수심을 측정하는 장비로 기존의 지점식 유속계와는 다르게 수심방향 유속분포와 수심을 한번에 측정하게 되며, 보트를 이용하여 하천을 횡단하게 되면 기존의 유속-면적법을 이용하는 방식보다 간편하고 빠르게 한 단면의 유량을 측정할 수 있다. 이와 같은 이점으로 인해 국내뿐만 아니라 해외에서도 대하천에서부터 중·소규모의 하천까지 다양한 범위에서 유량을 측정하는 장비로서 사용되어지고 있다. ADCP의 측정 유량은 유량관측소에서 수위-유량관계식을 구축할 때 사용하고 있으며, 이렇게 제공되는 유량은 하천의 중·장기 계획 수립, 수공구조물의 설계 및 수문·수리분야의 연구에 활용되고 있다. 하지만 ADCP의 유량측정은 ADCP의 미측정 영역의 유량 추정, ADCP 잠김깊이의 정확도, 하안에서의 고정 측정시간 등 ADCP의 측정 과정이나, 유량 추정 방법에 따라 영향을 받게 되며. 이외에도 하천의 수심, 하상의 상태와 같은 측정 조건에 따라서도 정확도의 변화가 발생할 수 있다. 측정결과의 정확성을 향상시키고, 신뢰도가 높은 자료를 제공하기 위해서는 ADCP의 유량 측정결과에 대한 불확도를 발생시키는 요인들에 대한 분석과 이를 감소시킬 수 있는 방법을 찾는 것이 중요하다. 1993년 ISO, BIPM, IFCC 등 6개 기구에서는 측정불확도를 산정하기 위한 측정불확도 산정 지침서(GUM, Guide to the expression of Uncertainty of Measurement)를 제시하였다. GUM 표준안은 측정과정에서 발생하는 다양한 불확도 요인들을 불확도 전파법칙을 통해 전체 불확도를 산정하는 방식으로 WMO와 ISO의 유량 측정분야에서도 GUM 표준안을 측정불확도 산정 기준으로 공인하여 사용하고 있다(JCGM 100, 2008; ISO 25377, 2020). 이에 본 연구에서는 GUM 표준안을 이용하여 ADCP로 측정된 유량의 측정불확도를 산정하는 방법을 개발하고 각 요인들에 대한 실험 및 분석을 진행하였다. ADCP의 측정 정확도를 분석하기 위한 실험은 자연에 가까운 형상을 모의하고 있고, 소하천 규모를 갖고 있는 하천연구센터에서 수행하였으며, 요인들에 대한 분석 방법 및 총 불확도를 계산하는 방법에 대하여 제시하였다.

• Composites Research
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• v.37 no.1
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• pp.21-31
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• 2024

This review paper investigates the use of shockwave attenuating materials within composite structures to enhance personnel protection against blast-induced traumatic brain injury (bTBI). This paper also introduces experimental methodologies exploited in the generation and measurement of shockwaves to evaluate the performance of the shock dissipating composites. The generation of shockwaves is elucidated through diverse approaches such as high-energy explosives, shock tubes, lasers, and laser-flyer techniques. Evaluation of shockwave propagation and attenuation involves the utilization of cutting-edge techniques, including piezoelectric, interferometer, electromagnetic induction, and streak camera methods. This paper investigates phase-separated materials, including polyurea and ionic liquids, and provides insight into composite structures in the quest for shockwave pressure attenuation. By synthesizing and analyzing the findings from these experimental approaches, this review aims to contribute valuable insights to the advancement of protective measures against blast-induced traumatic brain injuries.

• The Journal of the Acoustical Society of Korea
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• v.25 no.7
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• pp.339-345
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• 2006

We suggest new 2D two-way Parabolic equation algorithm for multiple scattering. Our method is based on the successive performance of the single scattering approach. First. as the single scattering algorithm, the reflected and transmitted fields are calculated at the vertical interface of a range independent sector. Then. the reflected field is saved and the transmitted field Propagated to the next vertical interface with the split-step Pade method. After one step ends, the same Process is repeatedly performed with the change of the Propagation direction until the reflected field at the vertical interface is close to zero. Final incoming and outgoing fields are obtained as the sum of the wave fields obtained for each step. Our algorithm is relatively simple for the numerical implementation and requires less computational resources than the existing algorithm for multiple scattering

• Geophysics and Geophysical Exploration
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• v.9 no.3
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• pp.207-224
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• 2006

It has been widely known that the seismic piezo-cone penetration test (SCPTu) is one of the most useful techniques for investigating the geotechnical characteristics such as static and dynamic soil properties. As practical applications in Korea, SCPTu was carried out at two sites in Busan and four sites in Incheon, which are mainly composed of alluvial or marine soil deposits. From the SCPTu waveform data obtained from the testing sites, the first arrival times of shear waves and the corresponding time differences with depth were determined using the cross-over method, and the shear wave velocity $(V_S)$ profiles with depth were derived based on the refracted ray path method based on Snell's law. Comparing the determined $V_S$ profile with the cone tip resistance $(q_t)$ profile, both trends of profiles with depth were similar. For the application of the conventional CPTu to earthquake engineering practices, the correlations between $V_S$ and CPTu data were deduced based on the SCPTu results. For the empirical evaluation of $V_S$ for all soils together with clays and sands which are classified unambiguously in this study by the soil behavior type classification index $(I_C)$, the authors suggested the $V_S-CPTu$ data correlations expressed as a function of four parameters, $q_t,\;f_s,\;\sigma'_{v0}$ and $B_q$, determined by multiple statistical regression modeling. Despite the incompatible strain levels of the downhole seismic test during SCPTu and the conventional CPTu, it is shown that the $V_S-CPTu$ data correlations for all soils, clays and sands suggested in this study is applicable to the preliminary estimation of $V_S$ for the soil deposits at a part in Korea and is more reliable than the previous correlations proposed by other researchers.