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Kangho Lee,Tae-Hak Lee,Chang-Soo Ahn,Young-Sik Kim,Juseop Lee THE INSTITUTE OF ELECTRICAL ENGINEERS 2015 IEEE Microwave and Wireless Components Letters Vol. No.
<P>This letter proposes a new design method for a bandstop filter with two stopbands. Contrary to a conventional method, the presented method allows for achieving two stopbands without increasing the number of the couplings between resonators and the transmission line connecting the input and output ports. In addition, a filter designed using the presented method can not only have different center frequencies but also have different bandwidths by adjusting the resonant frequencies of the resonators. For verification of the proposed approach a dual-stopband filter using four tunable substrate-integrated waveguide resonators has been designed and measured.</P>
K-Band Substrate-Integrated Waveguide Resonator Filter With Suppressed Higher-Order Mode
Boyoung Lee,Tae-Hak Lee,Kangho Lee,Man-Seok Uhm,Juseop Lee THE INSTITUTE OF ELECTRICAL ENGINEERS 2015 IEEE Microwave and Wireless Components Letters Vol. No.
<P>In this letter, we present a design method for K-band substrate-integrated waveguide (SIW) resonator filters utilizing TM<SUB>02</SUB> mode. More importantly, a methodology for suppressing an unwanted higher-order mode ( TM<SUB>11</SUB>) close to the passband is demonstrated. It is shown that suppressing the unwanted mode give rise to the improved stopband performance. In addition, the resonator used in this filter design has capability of adjusting the resonant frequency, and this allows for compensating the fabrication error. Verification of the presented design method has been carried out by fabricating and measuring the filter.</P>
Frequency-Tunable Low- $Q$ Lumped-Element Resonator Bandstop Filter With High Attenuation
Lee, Tae-Hak,Kim, Byungguk,Lee, Kangho,Chappell, William J.,Lee, Juseop Professional Technical Group on Microwace Theory a 2016 IEEE Transactions on Microwave Theory and Techniqu Vol. No.
<P>This paper presents a new lumped-element absorptive bandstop filter topology. It exhibits infinite attenuation at the center frequency and no reflection regardless of the quality factor (Q-factor) of the resonators. The new topology exhibits the absorptive characteristic with extremely low-Q resonators, whereas an absorptive bandstop filter topology in the literature cannot be used for such resonators. This superiority of the new filter topology is verified by comparing it with the topology in the literature. The filter designed using the new topology can change its center frequency by tuning only the capacitor values of the resonators. A 1.6:1 frequency tuning range maintaining the absorptive characteristic has been obtained by measurement.</P>
Lee, Juseop,Kim, Byungguk,Lee, Kangho,Chappell, William J. Cambridge University Press 2015 International Journal of Microwave and Wireless Te Vol.7 No.6
<P>In this paper, we show a second-order (four-resonator) absorptive bandstop filter circuit topology which gives a larger bandwidth compared to a first-order topology. Due to the absorptive characteristic, it creates a large attenuation at the center frequency using low-Q resonators. Since low-Q resonators can be used in generating a large attenuation, small-size resonators can be employed in bandstop filter design. Analytic design equations are provided so that a higher-order absorptive bandstop filter can be designed analytically. It is also shown that the second-order filter topology exhibits a better frequency selectivity having a same bandwidth. The proposed filter topology has been applied to a design of a miniaturized low-temperature co-fired ceramic bandstop filter with low-Q resonators. The Q-factor of the lumped-element resonators has been chosen to be 5 for demonstration.</P>
Omnichannel Reaction to the COVID-19 Outbreak: Evidence from a Retailing Company
Lee, KangHo,Lee, Dongwon 한국지능정보시스템학회 2022 한국지능정보시스템학회 학술대회논문집 Vol.2022 No.6
The outbreak of the COVID-19 devastated many sectors of businesses around the world. This study investigates the impact of the COVID-19 pandemic on omnichannel sales, along with moderating effects of competition between nearby same brand stores and commercial vs. residential districts. We examine this by utilizing the channel (i.e., offline and online) sales data from a South Korea’s retailing company. The results indicate that a significant proportion of offline sales spilled over to online sales although social distancing issued in South Korea is less stringent than complete lockdowns. In addition, we find evidence that the number of nearby same brand stores further accelerates sales loss from the pandemic in the offline channel. In contrast, the overall pattern in the online channel remains unchanged. Under the COVID-19 situation, we find online channel more stable than offline channel in terms of moderating effect of nearby same brand competition.
Electrical Characteristics of Molybdenum Disulfide Flakes Produced by Liquid Exfoliation
Lee, Kangho,Kim, Hye‐,Young,Lotya, Mustafa,Coleman, Jonathan N.,Kim, Gyu‐,Tae,Duesberg, Georg S. WILEY‐VCH Verlag 2011 Advanced Materials Vol.23 No.36
<P><B>Semiconducting 2D MoS<SUB>2</SUB> flakes produced by liquid phase exfoliation</B> are contacted with metal electrodes, which are defined by electron beam lithography. Electrical analysis of the metal–semiconductor–metal structures reveals high mobilities for individual MoS<SUB>2</SUB> flakes. Thus, scalable liquid‐phase exfoliation of layered semiconductor compounds can yield novel materials with potential uses in future electronic devices.</P>
Exposure assessment of workers in printed electronics workplace
Lee, Ji Hyun,Sohn, Eun Kyung,Ahn, Jin Soo,Ahn, Kangho,Kim, Keun Soo,Lee, Jong Hwan,Lee, Taik Min,Yu, Il Je Informa Healthcare USA, Inc. 2013 Inhalation toxicology Vol.25 No.8
<P>Printed electronics uses converging technologies, such as printing, fine mechanics, nanotechnology, electronics and other new technologies. Consequently, printed electronics raises additional health and safety concerns to those experienced in the traditional printing industry. This study investigated two printed electronics workplaces based on a walk-through survey and personal and area sampling. All the printed electronics operations were conducted in a cleanroom. No indication of exposure to excess silver nanoparticles or carbon nanotubes (CNTs) was found. While the organic solvents were lower than current occupational exposure limits, there was a lack of engineering controls, such as local exhaust ventilation, correct enclosure and duct connections. There was also an insufficient quantity of personal protective equipment, and some organic solvents not described in the safety data sheets (SDSs) were detected in the air samples. Plus, the cleaning work, a major emissions operation, was not conducted within a hood, and the cleaning waste was not properly disposed of. Therefore, the present exposure assessment results from two printed electronics workplaces suggest that the printed electronics industry needs to take note of the occupational safety and health risks and hazards already established by the traditional printing industry, along with new risks and hazards originating from converging technologies such as nanotechnology.</P>
( Kangho Lee ),( Dongyeon Ryu ),( Hohyun Kim ),( Chang Ho Jeon ),( Jae Hun Kim ),( Chan Yong Park ),( Seok Ran Yeom ) 대한외상학회 2022 大韓外傷學會誌 Vol.35 No.1
Purpose: The scoring system for traumatic liver injury (SSTLI) was developed in 2015 to predict mortality in patients with polytraumatic liver injury. This study aimed to validate the SSTLI as a prognostic factor in patients with polytrauma and liver injury through a generalized estimating equation analysis. Methods: The medical records of 521 patients with traumatic liver injury from January 2015 to December 2019 were reviewed. The primary outcome variable was in-hospital mortality. All the risk factors were analyzed using multivariate logistic regression analysis. The SSTLI has five clinical measures (age, Injury Severity Score, serum total bilirubin level, prothrombin time, and creatinine level) chosen based on their predictive power. Each measure is scored as 0-1 (age and Injury Severity Score) or 0-3 (serum total bilirubin level, prothrombin time, and creatinine level). The SSTLI score corresponds to the total points for each item (0-11 points). Results: The areas under the curve of the SSTLI to predict mortality on post-traumatic days 0, 1, 3, and 5 were 0.736, 0.783, 0.830, and 0.824, respectively. A very good to excellent positive correlation was observed between the probability of mortality and the SSTLI score (γ=0.997, P<0.001). A value of 5 points was used as the threshold to distinguish low-risk (<5) from high-risk (≥5) patients. Multivariate analysis using the generalized estimating equation in the logistic regression model indicated that the SSTLI score was an independent predictor of mortality (odds ratio, 1.027; 95% confidence interval, 1.018-1.036; P<0.001). Conclusions: The SSTLI was verified to predict mortality in patients with polytrauma and liver injury. A score of ≥5 on the SSTLI indicated a high-risk of post-traumatic mortality.