• 전자공학회논문지CI
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• 제47권2호
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• pp.39-47
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• 2010

무선 센서 네트워크는 배터리 방전, 사물에 의한 간섭이나 센서 노드의 고장 등으로 인하여 통신이 불가능한 상황이 빈번하게 발생된다. Directed Diffusion이 데이터 중심 라우팅 알고리즘으로서 각광받고 있지만, 이러한 통신 에러에 대한 대처는 미흡하다. 본 논문에서는 Directed Diffusion 기반의 신뢰성 향상을 위한 라우팅 알고리즘을 제안한다. 제안 알고리즘은 교차계층 기법을 이용하여 무선 네트워크의 상황을 인지하고 에러 상황을 판단하여 링크 품질과 노드 통신 가능여부 정보를 경로 설정 알고리즘에 적용함으로써 에러 발생이 빈번한 네트워크에서 신뢰성 있는 데이터 전송 기법을 제시하였다. 제안 알고리즘은 다양한 에러율과 노드수를 갖는 시뮬레이션에서 전송률과 데이터 비율 측면에서 매우 우수한 성능을 보였다.

• 전기전자학회논문지
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• 제23권4호
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• pp.1328-1336
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• 2019

안전하고 최적의 배터리 성능을 유지하기 위해 정확한 충전상태(SOC) 추정 기술이 필수적이다. 본 논문에서는 기존의 전류적산 방법이 가지고 있는 문제를 해결하기 위해 시간 종속성을 가지는 인공지능 기반의 LSTM을 이용한 SOC 추정 방법을 적용하였다. 훈련과 검증에 필요한 데이터는 전기적 실험을 통해 일정 크기로 방전된 전류, 전압, 온도를 수집하였고 학습을 위한 입력데이터의 질을 향상시키기 위해 데이터 전처리를 수행하였다. 또한, LSTM 모델의 구조 및 하이퍼파라미터 설정에 따른 학습 능력과 SOC 추정 성능을 비교하였다. 학습한 모델은 UDDS 프로파일을 통해 검증하였으며, RMSE 0.82%, MAX 2.54%의 추정 정확도를 달성하였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제16권5호
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• pp.82-89
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• 2011

Understanding snowmelt movement to the watershed is crucial for both climate change and hydrological studies because the snowmelt is a significant component of groundwater and surface runoff in temperature area. In this work, a new energy balance budget algorithm has been developed for melting snow from a snowpack at the Central Sierra Snow Laboratory (CSSL) in California, US. Using two sets of experiments, artificial rain-on-snow experiments and observations of diel variations, carried out in the winter of 2002 and 2003, we investigate how to calculate the amount of snowmelt from the snowpack using radiation energy and air temperature. To address the effect of air temperature, we calculate the integrated daily solar radiation energy input, and the integrated discharge of snowmelt under the snowpack and the energy required to generate such an amount of meltwater. The difference between the two is the excess (or deficit) energy input and we compare this energy to the average daily temperature. The resulting empirical relationship is used to calculate the instantaneous snowmelt rate in the model used by Lee et al. (2008a; 2010), in addition to the net-short radiation. If for a given 10 minute interval, the energy obtained by the melt calculation is negative, then no melt is generated. The input energy from the sun is considered to be used to increase the temperature of the snowpack. Positive energy is used for melting snow for the 10-minute interval. Using this energy budget algorithm, we optimize the intrinsic permeability of the snowpack for the two sets of experiments using one-dimensional water percolation model, which are $52.5{\times}10^{-10}m^2$ and $75{\times}10^{-10}m^2$ for the artificial rain-on-snow experiments and observations of diel variation, respectively.

• Asian Pacific Journal of Cancer Prevention
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• 제17권sup3호
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• pp.93-99
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• 2016

Completeness is an important indicator of data quality in cancer registry programs. This study aimed to estimate the completeness of registered cases in a population based cancer registry program implemented in five provinces of Iran. Capture-recapture methods were used to estimate the number of cases that may have been missed and to estimate rates of completeness for different categories of age, year, and sex. The data used for this study were obtained from three sources: 1) National Pathology Database; 2) National Hospital Discharge Database; and 3) National Death Registry Database. The three sources were linked and duplicates were identified based on first name, last name, father's names, and date of birth, ICD code, and case's residency address using Microsoft Excel. Removing duplicates, the three sources reported a total of 35,643 cases from March 2008 to March 2011. Running many different multivariate models of capture-recapture and controlling for source dependencies revealed an overall under-reporting of 49% in all five registries combined. The estimated completeness differed based on age, sex, and year. The overall completeness was higher for males than females (71.2% for males and 59.9% for females). Younger age had lower rates of completeness compared to older age (38.1% for <40 years, 55.4% for 40-60 years, and 76.7 for >60 years). The results of this study indicated a moderate to severe (depending on the age, sex and year) degree of completeness in the population based cancer registration of Iran.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.243-243
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• 2015

Low-flow simulation and forecasting is one of the emerging issues in hydrology due to the increasing demand of water in dry periods. Even though low-flow simulation and forecasting remains a difficult issue for hydrologists better simulation and earlier prediction of low flows are crucial for efficient water management. The UN has never stated that South Korea is in a water shortage. However, a recent study by MOLIT indicates that Korea will probably lack water by 4.3 billion m3 in 2020 due to several factors, including land cover and climate change impacts. The two main situations that generate low-flow events are an extended dry period (summer low-flow) and an extended period of low temperature (winter low-flow). This situation demands the hydrologists to concentrate more on low-flow hydrology. Korea's annual average precipitation is about 127.6 billion m3 where runoff into rivers and losses accounts 57% and 43% respectively and from 57% runoff discharge to the ocean is accounts 31% and total water use is about 26%. So, saving 6% of the runoff will solve the water shortage problem mentioned above. The main objective of this study is to present the hydrological modelling approach for low-flow simulation and forecasting using a model that have a capacity to represent the real hydrological behavior of the catchment and to address the water management of summer as well as winter low-flow. Two lumped hydrological models (GR4J and CAT) will be applied to calibrate and simulate the streamflow. The models will be applied to Seolmacheon catchment using daily streamflow data at Jeonjeokbigyo station, and the Nash-Sutcliffe efficiencies will be calculated to check the model performance. The expected result will be summarized in a different ways so as to provide decision makers with the probabilistic forecasts and the associated risks of low flows. Finally, the results will be presented and the capacity of the models to provide useful information for efficient water management practice will be discussed.

• 한국분말재료학회지
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• 제28권6호
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• pp.470-477
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• 2021

Energy storage systems should address issues such as power fluctuations and rapid charge-discharge; to meet this requirement, CoFe₂O₄ (CFO) spinel nanoparticles with a suitable electrical conductivity and various redox states are synthesized and used as electrode materials for supercapacitors. In particular, CFO electrodes combined with carbon nanofibers (CNFs) can provide long-term cycling stability by fabricating binder-free three-dimensional electrodes. In this study, CFO-decorated CNFs are prepared by electrospinning and a low-cost hydrothermal method. The effects of heat treatment, such as the activation of CNFs (ACNFs) and calcination of CFO-decorated CNFs (C-CFO/ACNFs), are investigated. The C-CFO/ACNF electrode exhibits a high specific capacitance of 142.9 F/g at a scan rate of 5 mV/s and superior rate capability of 77.6% capacitance retention at a high scan rate of 500 mV/s. This electrode also achieves the lowest charge transfer resistance of 0.0063 Ω and excellent cycling stability (93.5% retention after 5,000 cycles) because of the improved ion conductivity by pathway formation and structural stability. The results of our work are expected to open a new route for manufacturing hybrid capacitor electrodes containing the C-CFO/ACNF electrode that can be easily prepared with a low-cost and simple process with enhanced electrochemical performance.

• Journal of Electrochemical Science and Technology
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• 제14권1호
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• pp.75-84
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• 2023

The accumulation of spent carbide (YG8), not only pollutes the environment but also causes waste of tungsten, cobalt and other rare metal resources. To better address this issue, we proposed a combined electrochemical separation process of low-temperature aqueous solution and high-temperature molten salt for tungsten and cobalt. H₂WO₄ was obtained from spent carbide in an aqueous solution, and we calcined it to obtain WO₃, which was used as a raw material to obtain tungsten by using molten salt electrodeposition. The influence of the current efficiency and the electrochemical behavior of the discharge precipitation of W(VI) were also studied. The calcination results showed that the morphology of WO₃ was regular and there were no other impurities. The maximum current efficiency of 82.91% was achieved in a series of electrodeposition experiments. According to XRD and SEM analysis, the recovered product was high purity tungsten, which belongs to the simple cubic crystal system. In the W(VI) reduction mechanism experiments, the electrochemical process of W(VI) in NaCl-Na₂WO₄-WO₃ molten salt was investigated using linear scanning voltammetry (LSV) and chronoamperometry in a three-electrode system. The LSV showed that W(VI) was reduced at the cathode in two steps and the electrode reaction was controlled by diffusion. The fitting results of chronoamperometry showed that the nucleation mechanism of W(VI) was an instantaneous nucleation mode, and the diffusion coefficient was 7.379×10^-10 cm²·s^-1.

• 중환자간호학회지
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• 제16권3호
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• pp.11-23
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• 2023

Purpose : This study investigates the experiences of patients in intensive care units (ICUs), and the factors influencing these experiences. Method : We used a cross-sectional survey design to analyze previously collected cohort data from 891 patients who spent over 24 hours in 19 ICUs across four university hospitals in Busan, South Korea between June 2019 and July 2020. Within a week of ICU discharge, participants completed the Korean version of the Intensive Care Experience Questionnaire, covering four areas: "awareness of surroundings," "frightening experiences," "satisfaction with care," and "recall of experiences." We used multiple linear regression to identify factors associated with the ICU experience. Results : Low income (𝛽 = -.08, p = .016), unplanned hospitalization (𝛽 = -.09, p = .006), sedation (𝛽 = -.16, p < .001), and delirium (𝛽 = -.15, p < .001) reduce patients' awareness of their surroundings. Frightening experiences are associated with being female (𝛽 = -.07, p = .027), experiencing delirium(𝛽= -.15, p<.001), and longer stays in the ICU (𝛽= -.14, p <.001). Using sedatives decreases satisfaction with care (𝛽 = -.08, p = .048). Living alone (𝛽 = -.08, p = .013) and using painkillers (𝛽 = -.08, p = .020) reduces recall of experiences. Conclusion : Negative ICU experiences are significantly associated with being female, living alone, lower income, unplanned admission, using sedatives and painkillers, delirium, and longer stays in the ICU. Thus, improving ICU experiences requires interventions that address modifiable factors, such as delirium, medication, and length of ICU stays.

• Composites Research
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• 제37권3호
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• pp.190-196
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• 2024

분리판은 바나듐 레독스 흐름전지(VRFB) 스택 내 셀의 전기적 통로 및 구조적 지지 역할 수행하는 매우 중요한 부품 중 하나이다. 흑연 소재는 전기 전도성이 뛰어나 분리판에 주로 사용되지만, 셀 스택에서 전극과 분리판 사이에 높은 계면 접촉 저항(ICR)이 발생하여 VRFB의 성능에 심각한 제한이 존재한다. 본 연구에서는 ICR의 한계를 해결할 수 있는 일체형 전극-분리판 조립체를 개발하는 것을 목표로 하였다. 일체형 조립체는 핫 프레스 방법을 활용하여 열가소성 및 열경화성 폴리머와 단일 탄소 펠트를 사용하여 제작하였다. 실험 결과, 일체형 조립체가 연속적인 전기 경로로 인해 감소된 전체 저항을 나타냄을 확인하였다. 또한, 충/방전 셀 테스트 결과에서 일체형 조립체는 향상된 셀 성능을 보여주었다. 따라서 개발된 일체형 전극-분리판 조립체는 기존의 분리판 및 전극 조립체를 대체할 수 있을 것으로 판단된다.

• 청정기술
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• 제30권3호
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• pp.267-275
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• 2024

Lithium-ion batteries (LIBs) have attracted significant attention as potential energy storage solutions due to their high energy density, minimal self-discharge, extended cycle life, and absence of memory effects. However, conventional LIBs use graphite as the anode material and as a result struggle to meet the increasing demand for higher energy density because of the low theoretical capacity of graphite. In order to enhance Li storage capacity and address the current limitations of LIBs, this study designed and analyzed SnO₂ nanoflakes/CNF, which is an advanced anode material with a unique hierarchical structure synthesized via a facile method involving incipient wetness followed by annealing. The in-situ formed SnO₂ nanoflakes improve the electrolyte accessibility and shorten the ion and electron transport pathways, thereby enhancing the reaction kinetics. Additionally, the CNF matrix enhances the electrical conductivity, accelerates electron transport, and mitigates volume changes. The integrated SnO₂ nanoflakes/CNF cell demonstrated outstanding cycling performance and excellent rate capability, achieving a notable reversible capacity of 636 mAh g^-1 after 100 cycles at 0.1 C. This study provides valuable insights into the design of high-efficiency anode materials for the advancement of high-performance LIBs.