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Measurement-Based Achievable Throughput Estimation in IEEE 802.11a WLANs
Hayoung Yoon,JongWon Kim IEEE 2007 IEEE communications letters Vol.11 No.9
<P>Knowledge of dynamically changing achievable throughput is important in the design of an adaptive QoS-provisioning system over WLANs. In this letter, we introduce a novel measurement-based throughput estimation scheme and its practical realization for IEEE 802.11a WLAN environment. By utilizing traffic statistics measurements at the wireless AP (access point) in a timely manner, the proposed scheme estimates idle (i.e., remaining) channel time and converts it into available min/max throughput guidelines. Prototype realization in a Linux-based testbed verifies that the proposed scheme can estimate the available throughput with precision.</P>
Yoon, Hayoung,Lee, Ji Sung,Min, Ji Hyun,Wu, JunHua,Kim, Young Keun Springer 2013 Nanoscale research letters Vol.8 No.1
<P>We report the synthesis and characterization of ferrite nanocrystals which exhibit high crystallinity and narrow size distributions. The three types of samples including Zn ferrite, Mn ferrite, and Mn-Zn ferrite were prepared via a non-aqueous nanoemulsion method. The structural, chemical, and magnetic properties of the nanocrystals are analyzed by transmission electron microscopy, X-ray diffraction, X-ray fluorescence, and physical property measurement system. The characterization indicates that the three types of ferrite nanocrystals were successfully produced, which show well-behaved magnetic properties, ferrimagnetism at 5 K and superparamagnetism at 300 K, respectively. In addition, the magnetization value of the ferrites increases with the increasing concentration of Mn.</P>
윤혜원 ( Hyewon Yoon ),임하영 ( Hayoung Lim ),정혜원 ( Hyewon Jeong ),윤용익 ( Yong Ik Yoon ) 한국정보처리학회 2015 한국정보처리학회 학술대회논문집 Vol.22 No.1
2015 년 현재 정보통신기술(ICT)중 사물인터넷(IoT : Internet of Things)이 화두에 오르고 있다. 언제 어디서나 통신으로 연결만 되어 있으면 스마트폰으로 주변에 있는 사물들의 제어가 가능하다. 또, 주목 받고 있는 기술로서 근거 리 통신기능(NFC : Near Field Communication)이 IoT 와 결합해 우리 주변을 편리하게 해주고 있다. NFC 발달과 함께, 본 연구에서는 NFC 를 통해 메뉴를 공유하고 종업원 없이도 주방으로 Order 를 보낼 수 있는 제어기능이 탑재된 어플리케이션을 기획한다. 여러 명의 Order 를 한 사람의 스마트폰으로 NFC 를 이용한 기술인 P2P 기능을 이용해 모아준다. 그 후, 한 데 모은 주문내역을 대표 한 사람이 주방으로 Order 를 보내는 기능과 두 번 이상의 방문을 하게 될 경우 그 동안의 주문내역 히스토리를 분석해서 주문에 대한 피드백을 제공함으로써 편리하게 사용 할 수 있도록 연구하고자 한다.
( Hayoung Choi ),( Yun Su Sim ),( Tae Rim Shin ),( Dong-gyu Kim ),( Dong Won Park ),( Tai Sun Park ),( Ji-yong Moon ),( Sang-heon Kim ),( Tae-hyung Kim ),( Jang Won Sohn ),( Ho Joo Yoon ),( Hyun Lee ) 대한결핵 및 호흡기학회 2019 대한결핵 및 호흡기학회 추계학술대회 초록집 Vol.127 No.-
Background: The characteristics of bronchiectasis and its clinical implications in patients with previous pulmonary tuberculosis have not been well elucidated using a nationally representative database. Methods: We compared respiratory symptoms, comorbidities, lung function, quality of life, and socioeconomic status in post-tuberculosis subjects with bronchiectasis versus those without bronchiectasis participating in the Korean National Health and Nutritional Examination Survey 2007-2009. Results: The prevalence of bronchiectasis was 2.6% (n = 35) in the 1,352 subjects with previous pulmonary tuberculosis. Bronchiectasis subjects showed lower body mass index (BMI) (21.9 vs. 23.4 kg/m2, P = 0.002) and higher asthma rate (26.8% vs. 4.5%, P < 0.001) compared with those without bronchiectasis. There were no significant intergroup differences in age, lung function, respiratory symptoms, family income, and education. However, compared with subjects without bronchiectasis, bronchiectasis subjects showed lower EuroQoL five dimensions (EQ-5D) index (0.86 vs. 0.93, P = 0.010), which denotes the poor quality of life. Among EQ-5D components, there was a significant difference in the anxiety/depression component (38.5 vs. 12.1, P = 0.002) between two groups. Bronchiectasis subjects were associated with lower EQ-5D index (difference = 0.077, 95% confidence interval: 0.002-0.151), as compared with those without bronchiectasis, using multivariable linear regression with adjustment for demographic characteristics, BMI, education, and family income. Conclusion: The prevalence of bronchiectasis was 2.6% in the subjects with previous pulmonary tuberculosis. Post-tuberculosis subjects with bronchiectasis had higher asthma rate and reduced quality of life than those without bronchiectasis.
Effect of surface morphology on screen printed solar cells
Hayoung Park,Joon Sung Lee,Soonwoo Kwon,Sewang Yoon,김동환 한국물리학회 2010 Current Applied Physics Vol.10 No.1
Surface texturing is well known as one of the major paths to improving the efficiency of silicon solar cells by increasing the short circuit current through effective photon trapping. However, the effects of the pyramids created after surface texturing on the other properties remain obscure. In this work, we studied the effect of the surface morphologies on the formation of both the emitter layer and metal electrode using the screen printing method, which is a cost-effective method of fabricating silicon solar cells. Various textured surfaces, such as with large, small, sharp or smooth pyramids, were investigated in comparison with a flat surface. The contact resistance was measured from a TLM patterned cell by I-V measurement under dark conditions and SEM, TEM and UV-vis spectrophotometer were used to evaluate the surfaces.
Deep learning framework for bovine iris segmentation
Heemoon Yoon,Mira Park,Hayoung Lee,Jisoon An,이태현,이상희 한국축산학회 2024 한국축산학회지 Vol.66 No.1
Iris segmentation is an initial step for identifying the biometrics of animals when establishing a traceability system for livestock. In this study, we propose a deep learning framework for pixel-wise segmentation of bovine iris with a minimized use of annotation labels utilizing the BovineAAEyes80 public dataset. The proposed image segmentation framework encompasses data collection, data preparation, data augmentation selection, training of 15 deep neural network (DNN) models with varying encoder backbones and segmentation decoder DNNs, and evaluation of the models using multiple metrics and graphical segmentation results. This framework aims to provide comprehensive and in-depth information on each model’s training and testing outcomes to optimize bovine iris segmentation performance. In the experiment, U-Net with a VGG16 backbone was identified as the optimal combination of encoder and decoder models for the dataset, achieving an accuracy and dice coefficient score of 99.50% and 98.35%, respectively. Notably, the selected model accurately segmented even corrupted images without proper annotation data. This study contributes to the advancement of iris segmentation and the establishment of a reliable DNN training framework.
첨가제가 나트륨 이온 전지용 고분자전구체 기반 하드카본 음극 표면에 형성되는 고체 전해질 내부상 특성에 미치는 영향
김하영(Hayoung Kim),윤승욱(Seung Uk Yoon),박수봉(Subong Park),진형준(Hyoung-Joon Jin) 한국고분자학회 2020 폴리머 Vol.44 No.1
고분자 전구체(polymeric precursor) 기반의 하드카본(hard carbon)은 난층 구조(turbostractic structure)와 난층 구조들 사이의 기공으로 이루어져 있기 때문에 나트륨 이온 배터리의 음극소재로써 약 300mA h g<SUP>-1</SUP>의 높은 용량을 나타낸다. 하지만, 불안정하게 형성된 고체 전해질 내부상(solid electrolyte interphase, SEI)의 영향으로 인해, 하드카본은 제한된 수명특성을 가진다. 이러한 문제를 개선하기 위해 적절한 첨가제를 찾는 연구가 진행되고 있다. 본 연구에서는 첨가제 fluoroethylene carbonate(FEC) 및 succinic anhydride(SA)가 하드카본의 수명특성에 미치는 영향을 관찰하고 원인을 조사하였다. 그 결과, 첨가제에 의한 필름 저항 증가로 인해 하드카본의 수명 특성이 저하되었다. FEC를 첨가한 전해질에서의 높은 필름 저항은 3.34 eV의 비교적 높은 배리어 에너지를 갖는 sodium fluoride 성분이 도입된 SEI 층 형성에 기인하였다. 반면, SA를 첨가한 전해질에서의 높은 필름 저항은 두껍게 형성된 SEI 층 형성에 기인한 것으로 두 첨가제의 필름 저항 증가 원인이 상이하였다. Polymeric precursor-based hard carbon with a disordered turbostratic structure has a high capacity of approximately 300 mA h g<SUP>-1</SUP> as an anode material for a sodium-ion battery. However, hard carbon has a limited cycle performance owing to the formation of unstable solid electrolyte interphase (SEI). To improve the cycle performance, several studies are underway to find suitable additives. In this study, the effects of fluorocarbon carbonate (FEC) and succinic anhydride (SA) on the life characteristics of hard carbon were investigated and the reasons were examined. All additives negatively affected the cycle performance because they increase film resistance. The high film resistance in the electrolyte with FEC was due to the formation of the SEI layer with the introduction of the sodium fluoride component with a relatively high barrier energy of 3.34 eV. On the other hand, the high film resistance in the electrolyte with SA was due to the formation of a thick formed SEI layer, and the reason of the increase in film resistance of the two additives was different.