• Smart Structures and Systems
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• 제24권4호
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• pp.435-446
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• 2019

The existing piezoelectric spherical transducers with fixed prescribed dynamic characteristics limit their application in scenarios with multi-frequency or frequency variation requirement. To address this issue, this work proposes an improved design of piezoelectric spherical transducers using the resistance tuning method. Two piezoceramic shells are the functional elements with one for actuation and the other for tuning through the variation of load resistance. The theoretical model of the proposed design is given based on our previous work. The effects of the resistance, the middle surface radius and the thickness of the epoxy adhesive layer on the dynamic characteristics of the transducer are explored by numerical analysis. The numerical results show that the multi-frequency characteristics of the transducer can be obtained by tuning the resistance, and its electromechanical coupling coefficient can be optimized by a matching resistance. The proposed design and derived theoretical solution are validated by comparing with the literature given special examples as well as an experimental study. The present study demonstrates the feasibility of using the proposed design to realize the multi-frequency characteristics, which is helpful to improve the performance of piezoelectric spherical transducers used in underwater acoustic detection, hydrophones, and the spherical smart aggregate (SSA) used in civil structural health monitoring, enhancing their operation at the multiple working frequencies to meet different application requirements.

• 한국초전도ㆍ저온공학회논문지
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• 제24권2호
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• pp.27-38
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• 2022

Urban air mobility (UAM) has recently attracted lots of attention as a solution to urban centralization and global warming. Electric vertical take-off and landing (eVTOL) is a concept that emerges as one of the promising and clean technologies for UAM. There are two difficult challenges for eVTOL aircraft to solve. One is how to improve the weight efficiency of aircraft, and the other is how to complete long-range missions for UAM's flight scenarios. To approach these challenges, we propose a consolidated concept design of battery-fuel cell hybrid tiltrotor aircraft with a liquid hydrogen (LH₂) fuel tank. The efficiency of a battery-fuel cell hybrid powertrain system on the designed eVTOL aircraft is compared to that of a battery-only powertrain system. This paper shows how much payload can increase and the flight scenario can be improved by hybridizing the battery and fuel cell and presenting a detailed concept of a cryogenic storage tank for LH₂.

• International Journal of Computer Science & Network Security
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• 제24권4호
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• pp.107-112
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• 2024

Plant leaf diseases and destructive insects are major challenges that affect the agriculture production of the country. Accurate and fast prediction of leaf diseases in crops could help to build-up a suitable treatment technique while considerably reducing the economic and crop losses. In this paper, Convolutional Neural Network based model is proposed to detect leaf diseases of a plant in an efficient manner. Convolutional Neural Network (CNN) is the key technique in Deep learning mainly used for object identification. This model includes an image classifier which is built using machine learning concepts. Tensor Flow runs in the backend and Python programming is used in this model. Previous methods are based on various image processing techniques which are implemented in MATLAB. These methods lack the flexibility of providing good level of accuracy. The proposed system can effectively identify different types of diseases with its ability to deal with complex scenarios from a plant's area. Predictor model is used to precise the disease and showcase the accurate problem which helps in enhancing the noble employment of the farmers. Experimental results indicate that an accuracy of around 93% can be achieved using this model on a prepared Data Set.

• 융합보안논문지
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• 제24권1호
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• pp.77-82
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• 2024

최근 연구를 통해 다양한 물체 탐지 및 분류 모델은 전반적으로 크게 성능 향상이 이루워졌지만, 물체가 부분적으로 노출된 상황에서의 물체 탐지 및 분류에 대한 연구는 미흡한 실정이다. 특히, 군사 분야에서 무인전투체계가 물체를 탐지하고 분류하는 데 사용되는 경우, 군사적 상황에서 물체는 일반적으로 부분적으로 가려진 상태나 위장된 상태일 가능성이 높다. 본 연구에서는 부분적으로 가려진 물체의 분류 성능을 향상시키는 방법을 제안한다. 이 방법은 물체 이미지 상에 특정 부분을 주변 환경을 고려하여 가리는 부분을 추가하여 은·엄폐 및 위장된 물체에 대한 분류 성능을 개선시켰다. 실험결과로 제안 방법을 적용하였을 때 은·엄폐 및 위장된 물체에 대해서 기존 방법에 비해 물체 분류 향상이 있음을 볼 수가 있었다.

• 융합보안논문지
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• 제24권2호
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• pp.175-180
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• 2024

미래전의 양상은 첨단과학기술의 발전에 따라 다양한 유·무인 전투체계들이 전투를 수행하는 것으로 변화하고 있다. 미래의 무기체계들은 대량의 정보를 생성하고 송·수신하게 되며, 이에 따라 현재의 전술정보통신체계는 미래의 기반 통신체계로 운용하기에 제한된다. 또한 군단급 이상의 대규모 제대의 정보유통량을 분석하기 위해서는 전장에서 발생할 수 있는 다양한 상황들을 고려하여야 한다. 이에 본 논문에서는 Army TIGER 군단의 정보유통량을 분석하기 위해 지상망 단독 운용, 통합망 운용, 부하 분산, 장애 극복 시나리오 등 네 가지 시나리오를 기반으로 한 M&S 결과를 분석한다. 또한 지상·공중·우주망이 통합된 다계층 통합 전술통신망의 운용을 통해 네트워크의 신뢰성과 안정성을 향상할 수 있음을 제시한다.

• Journal of Dental Anesthesia and Pain Medicine
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• 제24권1호
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• pp.75-80
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• 2024

Dental sedation plays a pivotal role in alleviating patient anxiety during various procedures. Remimazolam, a benzodiazepine derivative, stands out for its distinctive attributes, particularly its rapid onset of sedation coupled with a brief duration, making it an invaluable option for dental applications. The patient was admitted for the extraction of impacted third molars via patient-controlled sedation and not only demonstrated stable vital signs but also expressed a high level of satisfaction with the procedure. An in-depth analysis of plasma remimazolam concentrations and changes in the Patient State Index revealed negative correlation patterns, highlighting the inherent potential of remimazolam in achieving effective sedation. This expanded research scope aims to provide a more nuanced understanding of the pharmacological responses to remimazolam in dental sedation scenarios. This case report offers valuable insights into the evolving landscape of dental sedation methodologies and paves the way for a more informed and evidence-based approach to the use of remimazolam in patient-controlled sedation.

• International Journal of Computer Science & Network Security
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• 제24권5호
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• pp.119-128
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• 2024

The moveable ad hoc networks are untrustworthy and susceptible to any intrusion because of their wireless interaction approach. Therefore the information from these networks can be stolen very easily just by introducing the attacker nodes in the system. The straight route extent is calculated with the help of hop count metric. For this purpose, routing protocols are planned. From a number of attacks, the wormhole attack is considered to be the hazardous one. This intrusion is commenced with the help of couple attacker nodes. These nodes make a channel by placing some sensor nodes between transmitter and receiver. The accessible system regards the wormhole intrusions in the absence of intermediary sensor nodes amid target. This mechanism is significant for the areas where the route distance amid transmitter and receiver is two hops merely. This mechanism is not suitable for those scenarios where multi hops are presented amid transmitter and receiver. In the projected study, a new technique is implemented for the recognition and separation of attacker sensor nodes from the network. The wormhole intrusions are triggered with the help of these attacker nodes in the network. The projected scheme is utilized in NS2 and it is depicted by the reproduction outcomes that the projected scheme shows better performance in comparison with existing approaches.

• 한국화재소방학회논문지
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• 제15권4호
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• pp.24-33
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• 2001

현재 전세계적으로 공장내(on-site)뿐만 아니라 공장외지역(off-site)에 대한 사고영향평가의 필요성이 대두되고 있으며, 공장외지역에 대한 영향평가 수행후 이에 대한 적절한 비상계획을 제출하도록 하고 있고, 국내에서도 종합적위험관리체계(IRMS : Integrated Risk Management System)를 PSM이나 SMS와 더불어 시행 준비중에 있다. 그러나 공장외지역에 대한 위험영향 평가시 가장 먼저 결정되어야 할 가상시나리오에 대한 기준이 체계적으로 마련되어 있지 않아 사용자나 분석자에 따라 평가결과가 다양하게 나오며, 또한 공정에서 발생할 수 있는 사고의 이상원을 정확하게 파악하지 못한다는 단점이 있다. 따라서 본 연구에서는 이러한 가상시나리오를 결정하는데 필요한 공정요소를 분석한 후, 분석결과에 따라 발생 가능하고, 먼저 고려되어야 할 시나리오를 산정할 수 있도록 전략을 제시하고자 한다. 분석된 공정요소들은 요소에 따른 가중치를 부여하여 위험등급을 결정한 후 등급에 따른 위험영향 평가를 수행하도록 한다. 분석의 결과는 가상시나리오의 신뢰성을 향상시킴으로써 위험영향평가가 과대평가되는 것을 방지하고, 공정의 설계나 비상계획의 수립시 효과적이고 적절한 대책마련을 유도할 수 있다.

• 한국환경과학회지
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• 제16권8호
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• pp.921-928
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• 2007

The objective of this work is the air quality modeling according to the scenarios of emission on complex terrain. The prognostic meteorological fields and air quality field over complex areas of Seoul, Korea are generated by the PSU/NCAR mesoscale model (MM5) and the Third Generation Community Multi-scale Air Quality Modeling System (Models - 3/CMAQ), respectively. The emission source was driven from the Clean Air Policy Support System of the Korea National institute of Environmental Research (CAPSS), which is a 1 km x 1 km grid in South Korea during 2003. In comparison of air quality fields, the simulated averaged $PM_{10},\;NO_2,\;and\;O_3$ concentration on complex terrain in control case were decreased as compared with base case. Particularly $PM_{10}$ revealed most substantial localized differences by $(18{\sim}24{\mu}g/m^3)$. The reduction rate of $PM_{10},\;NO_2,\;and\;O_3$ is respectively 18.88, 13.34 and 4.17%.

• 한국농공학회논문집
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• 제55권5호
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• pp.37-48
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• 2013

The objective of this study is to assess the impact of potential climate change on the hydrological components, especially on the streamflow, evapotranspiration and snowmelt, by using the Soil Water Assessment Tool (SWAT) for 17 Hanriver middle watersheds of South Korea. For future assessment, the SWAT model was calibrated in multiple sites using 4 years (2006-2009) and validated by using 2 years (2010-2011) daily observed data. For the model validation, the Nash-Sutcliffe model efficiency (NSE) for streamflow were 0.30-0.75. By applying the future scenarios predicted five future time periods Baseline (1992-2011), 2040s (2021-2040), 2060s (2041-2060), 2080s (2061-2080) and 2100s (2081-2100) to SWAT model, the 17 middle watersheds hydrological components of evapotranspiration, streamflow and snowmelt were evaluated. For the future precipitation and temperature of RCP 4.5 scenario increased 41.7 mm (2100s), $+3^{\circ}C$ conditions, the future streamflow showed +32.5 % (2040s), +24.8 % (2060s), +50.5 % (2080s) and +55.0 % (2100s). For the precipitation and temperature of RCP 8.5 scenario increased 63.9 mm (2100s), $+5.8^{\circ}C$ conditions, the future streamflow showed +35.5 % (2040s), +68.9 % (2060s), +58.0 % (2080s) and +63.6 % (2100s). To determine the impact on snowmelt for Hanriver middle watersheds, snowmelt parameters of SWAT model were determined through evaluating observed streamflow data during snowmelt periods (November-April). The results showed that average SMR (snowmelt / runoff) of 17 Hanriver middle watersheds was 62.0 % (Baseline). The annual average SMR were 42.0 % (2040s), 39.8 % (2060s), 29.4 % (2080s) and 27.9 % (2100s) by applying RCP 4.5 scenario. Also, the annual average SMR by applying RCP 8.5 scenario were 40.1 % (2040s), 29.4 % (2060s), 18.3 % (2080s) and 12.7 % (2100s).