Multi-objective Optimization of Aerodynamic Blade Shapes for Quadcopter System to Enhance Hovering Thrust and Power Consumption Efficiency

윤재현,임기훈,박상인,도재혁 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.3

This study focuses on maximizing hovering thrust and minimizing the power consumption of a quad-copter system at the same time by conducting multi-dimensional optimization of aerodynamic blade shapes. This work examines geometrical design variables for blades that influence thrusts, and the lift and drag (L&D) forces are calculated based on shape changes using computational fluid dynamics (CFD). Based on both L&D forces obtained from CFD, surrogate models are generated using the response surface method (RSM). The non-dominated sorting genetic algorithm (NSGA-II) is employed to acquire optimal blade shapes. Seven alternative shape combinations are obtained from the optimal combination obtained by the NSGA-II, each with a different L and D force value. These blades are printed engines via additive manufacturing, and a thrust test is conducted to measure power consumption using a voltmeter. As a result, it was possible to derive optimal blade shape combinations that can be chosen according to the flight conditions, and one can see that the predicted flight (i.e., an operating motor of a rotor blade) time by the analytical equation to identify battery specs is a good agreement with the actual battery consumption time measured via the thrust test.

음향시뮬레이션을 이용한 대형 실내체육관의 건축음향성능 개선에 관한 연구

윤재현,김재수,Yun, Jae-Hyun,Kim, Jae-Soo 한국주거학회 2008 한국주거학회 논문집 Vol.19 No.4

In this study, an analysis is carried out on the acoustic design for an indoor gymnasium scheduled to be built at Buan County, Chonbuk Province. By way of background, the study examines the case of a large-scale indoor gymnasium that has been constructed in the local area of Hangan-myeon. There are many examples whereby this gymnasium could be used not only as a sporting facility for the residents, but also as a multipurpose space for public performances such as leisure activities, lectures, assembling activities, theatre and concerts etc. In order to maximize the functional utilization of such an indoor gymnasium, it is important to simultaneously verify the acoustic capabilities of the space in terms of Definition of both Voice and Music. However, as a large-scaled athletic facility, the building was designed with a high ceiling-height to accommodate its functional characteristics. The space forms a Sound Focus whereby the sound is concentrated at a specific part, and because the vibration of sound is too loud due to its broad volume, acoustic defects arise such as a significant number of Echoes. Using this gymnasium as a precedent, this study proposes an acoustic design based on the drawings of the indoor gymnasium that is scheduled to be built at B County, Chonbuk Province. The gymnasium is equipped with an optimized acoustic condition passing through the Acoustic Simulation Phase. From the results of an Acoustic Simulation, we can design an indoor gymnasium that is equipped with a considerably satisfying and improved acoustic performance compared with the building before it was reformed. It is also considered that the use of such materials can fundamentally reduce construction costs and can improve acoustic performance, at the planning and design stages for similar sporting facilities in the future.

OTT 서비스 플랫폼 특성이 이용 만족을 통해 구독 유지 의도에 미치는 영향: 지각된 진단성의 조절효과를 중심으로

윤재현,김한구 한국산업경영학회 2022 경영연구 Vol.37 No.-

In the recent trend of various media appearing due to the development of the media environment, the growth of the OTT service market is remarkable as users' demand to watch desired content increases without restrictions on time and space. Therefore, this study aims to comprehensively analyze the factors affecting the intention to continue a OTT service subscription and expand the flow of user behavior research on OTT services. In this study, we analyzed the structural relationships between use satisfaction and intention to continue a subscription with OTT service platform characteristics (ubiquity, continuity, recommendation, choice possibility) as leading variables, and confirmed the moderating effect of perceived diagnosticity in the effect of use satisfaction on intention to continue a subscription. The main results are as follows. First, ubiquity, continuity, recommendation and choice possibility had positive (+) effect on use satisfaction. Second, use satisfaction had a positive (+) on intention to continue a subscription, and the effect of use satisfaction on intention to continue a subscription was moderated by perceived diagnosticity. This study is meaningful in that it comprehensively confirmed the effect on the behavior of existing subscribers by considering not only the OTT service platform characteristics but also psychological factor of users. In addition, the findings can provide practical guidelines for establishing effective platform management strategies for companies that providing OTT services. 최근 미디어 환경의 발달로 다양한 미디어들이 등장하는 추세에서, 시공간의 제약 없이 원하는 콘텐츠들을시청하려는 이용자들의 요구가 증가함에 따라 OTT 서비스 시장의 성장세가 두드러지고 있다. 이에 본 연구는OTT 서비스 구독 유지 의도에 영향을 미치는 요인들을 종합적으로 분석하고, OTT 서비스에 대한 이용자들의행동 연구에 대한 흐름을 확장하고자 한다. 본 연구에서는 OTT 서비스 플랫폼 특성(편재성, 연속성, 추천성, 선택 가능성)을 선행 변수로 하여 이용만족, 구독 유지 의도 간의 구조적 관계를 살펴보았으며, 이용 만족이 구독 유지 의도에 미치는 영향에서지각된 진단성의 조절 효과도 확인하였다. 주요 결과는 다음과 같다. 먼저, 편재성, 연속성, 추천성, 선택 가능성은 이용 만족에 정(+)의 영향을 미쳤다. 둘째, 이용 만족은 구독 유지 의도에 정(+)의 영향을 미치는 것으로나타났으며, 이용 만족이 구독 유지 의도에 미치는 영향은 지각된 진단성에 의해 조절되는 것으로 나타났다. 본 연구는 OTT 서비스 플랫폼 특성뿐만 아니라 이용자의 심리적 요인까지 함께 고려하여 기존 구독자들의행동에 미치는 영향을 종합적으로 확인했다는 점에서 의의가 있다. 또한, 본 연구의 결과는 OTT 서비스를제공하는 기업에게 효과적인 플랫폼 관리 전략을 수립할 수 있는 실무적인 지침을 제공하고자 한다.

Combined Effect of Calcium Oxide and Sonication to Reduce Foodborne Pathogens on Fresh Produce

윤재현,배영민,정규석,허성기,이선영 한국식품과학회 2013 Food Science and Biotechnology Vol.22 No.1

This study was conducted to investigate the antibacterial activity of calcium oxide (CaO), sonication,and their combination against foodborne pathogens on several fresh produce. The results showed that combined treatment inhibited Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium on fresh produce. However, the effectiveness of treatments for reducing populations of foodborne pathogens varied depending on the types and condition of the fresh produce. This study demonstrated that the antibacterial potency of CaO and its application with sonication could be one of alternatives for controlling foodborne pathogens on fresh produce.

Effects of varying concentrations of sodium chloride and acidic conditions on the behavior of Vibrio parahaemolyticus and Vibrio vulnificus cold-starved in artificial sea water microcosms

윤재현,배영민,이선영 한국식품과학회 2017 Food Science and Biotechnology Vol.26 No.3

There has been limited information available on the behavior of Vibrio parahaemolyticus and Vibrio vulnificus as a function of higher levels of NaCl in combination with acidic pH. In the present study, bacterial suspensions were transferred into artificial seawater (pH 4–7) microcosms containing 0.75% NaCl and supplemented with 5, 10, and 30% NaCl, respectively. Each of V. parahaemolyticus and V. vulnificus was inoculated in these microcosms and fermented seafood, and then stored at 4 C until the microbial populations reached below the detectable levels on agar plates (thiosulphate-citrate-bile salts-sucrose agar and tryptic soy agar amended with 3% NaCl). Consequently, V. parahaemolyticus ATCC 27969, V. parahaemolyticus ATCC 33844, and V. vulnificus ATCC 33815 rapidly reached the viable-but-nonculturable (VBNC) state with increasing levels (B30%) of NaCl at 4 C. Within seven days, these pathogens in seafood appeared to enter the VBNC state at 4 C, as shown by the fluorescence microscopic assay.

Optimization of resuscitation-promoting broths for the revival of Vibrio parahaemolyticus from a viable but nonculturable state

윤재현,배영민,조수영,문성권,오세욱,이선영 한국식품과학회 2021 Food Science and Biotechnology Vol.30 No.1

This study was conducted to examine the effectof formulated resuscitation-promoting broths on the revivalof viable but nonculturable Vibrio parahaemolyticusinduced by cold and starvation stresses. Vibrio parahaemolyticuswas incubated in artificial sea water at 4 Cfor more than 8 months until this bacterium becameundetectable, while retaining its intact cell count of morethan 105 CFU/field over time. On day 250, V. parahaemolyticuswas collected and enriched in tryptic soybroth supplemented with 3% NaCl, 10,000 U/mg catalase,2% sodium pyruvate, 20 mM MgSO4, 5 mM EDTA, and acell-free supernatant taken from V. parahaemolyticusATCC 17802 in the stationary phase (pH 8). V. parahaemolyticusreturned partially to a culturable state with amaximal cell density of 7.91 log CFU/mL in this formulatedmedium following 7 days of enrichment at 25 C. Incontrast, no V. parahaemolyticus was resuscitated whenenriched in alkaline peptone water and tryptic soy broth.

Development of enhanced selective media for detection of Vibrio parahaemolyticus in oysters

윤재현,배영민,송하나,이소율,문성권,오세욱,이선영 한국식품과학회 2021 Food Science and Biotechnology Vol.30 No.3

This study was undertaken to develop enhancedselective media for detection of Vibrio parahaemolyticus inoysters. Primarily, tryptic soy agar (TSA) was supplementedwith 4.5–5% NaCl, 0.1–0.5% oxgall, and/or 1–2%sodium citrate, and adjusted to pH 8–9. A total of 21 Vibriospp., 24 indicators, and 26 food-borne isolates werestreaked on the modified media, followed by 24 h ofincubation at 37 C. While all the indicators and isolatesfailed to grow on TSA containing 5% NaCl, 0.5% oxgall,and 2% sodium citrate (TSAOSS1; pH 9), V. parahaemolyticuswas culturable on this selective medium. Particularly, the ability of TSAOSS1 to quantify V. parahaemolyticusin oysters was superior to thiosulphate citratebile salts sucrose (TCBS) agar. V. parahaemolyticus distinctlyproduced its white-yellowish, round, and edgepointedcolony on TSAOSS1. TSAOSS1 with high selectivitypotentials over TCBS may be a promising alternative fordetection of V. parahaemolyticus in seafoods or naturalreservoirs.

Colonization of Listeria monocytogenes in potting soils as affected by bacterial community composition, storage temperature, and natural amendment

윤재현,김솔아,심원보,서동철,최송이,이선영,김세리 한국식품과학회 2021 Food Science and Biotechnology Vol.30 No.6

This study aimed to characterize the bacterialcommunity of commercial potting soils with or withoutListeria monocytogenes inoculation at 5–35 C using 16Smetagenomic sequencing and evaluate the effect of naturalamendments on the reduction L. monocytogenes in nonsterilepotting soils. An increase in the expected operationaltaxonomic units of each sample with or without L. monocytogenes was proportional to the increasing storagetemperatures after 5 days. Biodiversity was distinct amongall potting soils for Shannon and inverse Simpson indices,with the highest diversity being observed in a soil samplestored at 35 C for 5 days with L. monocytogenes. Anincrease in richness and diversity of soil bacterial communitystructure positively correlated with less survival ofthe invading L. monocytogenes. Particularly, garlic extractwas demonstrated as a promising soil-amendment substrate,reducing L. monocytogenes by C 4.50 log CFU/g inpotting soils stored at 35 C.

Evaluation of the microbiological quality of jacopevers and plaices in Korea, 2015-2016

윤재현,황진하,한아름,Yun-Sun Choi,현정은,이선영 한국식품과학회 2016 Food Science and Biotechnology Vol.25 No.6

In Southeast Asian countries, including Korea, China, and Japan, the considerable amounts of raw fish have been annually consumed in the manner of live fish fillets without minimally thermal processing, increasing the risks of causing food-borne diseases. This study investigated the occurrence of total aerobic bacteria (TAB), coliform, Vibrio parahaemolyticus, Salmonella enterica serovar spp., Listeria monocytogenes, and Staphylococcus aureus in jacopevers and plaices. Total 200 live fishes were collected from randomly selected restaurants located in Anseong-si, and then they were microbiologically monitored. TAB ranged from 3.09 to 3.21 Log10 CFU/g in jacopever and plaice. Coliform in the levels of 1.54 Log10 CFU/g were detected in samples. Out of 100 jacopevers, a single jacopever (1%) exhibited the prevalence of S. aureus in the edible part, though none of pathogenic bacteria were detected. These results will be useful for understanding the microbial prevalence in the domestic living jacopevers and plaices.

강화 PID 제어 시뮬레이션을 이용한 쿼드콥터 시스템의 제자리 비행 안정성에 관한 연구

윤재현,문현철,도재혁 대한기계학회 2022 大韓機械學會論文集A Vol.46 No.9

쿼드콥터 시스템의 안정한 비행 제어를 위한 최적 이득 값 적용은 반복적인 비행 실험이 필요로 하는 문제점이 있다. 본 연구에서는 쿼드콥터(quadcopter) 시스템의 제자리 비행(hovering) 안정성을 확보하기 위한 수학적 모델을 유도하여 Matlab Simulink 기반의 강화 PID 제어 시뮬레이터 설계를 수행하였다. 이를 기반으로 기체가 기울진 자세에서 제자리 비행을 위한 위치로 안정성 있게 신속히 회복할 수 있는 P, I, D 제어기 이득 값을 제어 시뮬레이션을 통해 획득하였다. 이를 통해 기체가 기울어진 상태에서 제자리 비행 위치로 회복되는 과정에서 오버슛(overshoot) 현상이 발생하지 않았으며, 기체가 제자리 비행상태에서도 안정된 상태를 유지하는 것을 확인할 수 있었다.