벤튜리관 형상에 따른 배기가스 재순환 유동 특성에 관한 연구

하지수,심성훈,김대연 한국가스학회 2019 한국가스학회지 Vol.23 No.1

자동차 엔진이나 소각로 등의 연소기기에서 질소산화물을 저감하기 위한 여러 가지 방법 중에 배기가스 재순환방법이 널리 쓰이고 있다. 본 연구에서는 고온의 배기가스를 재순환 유입하기 위해 벤튜리 튜브를 사용할 경우에상온의 공기 노즐 출구 위치를 변화하여 고온의 배기가스를 재순환 유입하는 최적 위치를 도출하기 위해 전산 열유체해석을 통해 살펴보았다. 또한 상온의 공기 노즐 출구에 원뿔을 설치한 경우에 대한 배기가스 재순환 유입량 특성을 고찰하였다. 공기 노즐 출구 위치를 배기가스 재순환 유입 출구의 시작위치(z=0)에서 끝 위치(z=0.6m)로 변화하였을 때 유선과 온도 분포 변화를 관찰하였으며 배기가스 재순환 유입량비와 혼합가스 출구의 평균온도로 정량적으로 비교하였다. 본 연구를 통하여 상온의 공기 노즐 출구 위치는 z=0.15m(1/4L)에서 재순환 유입량과 출구에서의평균온도가 가장 최대가 되는 것을 알 수 있었다. 또한 공기 노즐 출구에 원뿔을 설치하면 공기 노즐 출구의 속도가증가하여 배기가스 재순환 유입량이 약 2배 증가하고 혼합가스 출구 온도도 116℃ 증가하는 것을 알 수 있었다.

미국 패션디자인에 나타난 기능주의

하지수 한국의류학회 2002 한국의류학회지 Vol.26 No.9,10

This research focuses on functionalism in American fashion designs which have become the center of public attention in recent. First, documentary studies about how functionalism, which originated in Europe in the beginning of the 20th century, has been developed throughout the 20th century were preceded. Second, content analysis was done for the articles, including the word 'function', 'utility' and 'practical' in the New York Times and American Vogue from January 1990 to January 2001. As a result, functionalism in 1990s has been developed in different ways from the mechanical, organic, and moral analogies of functionalism in the beginning of 20th century. It doesn't belong to an analogy but has the fused characteristics of those three analogies. It can be classified into techno functionalism influenced by new technology, pure functionalism related to minimalism, sports casual functionalism for those who are crazy about the speed and sports and enjoy the freedom and comfort, and symbolic functionalism which stresses Zen style. More casual manners of formal wear are distinct elements in functionalist fashion design in 1990s. It leads to strong expressions of sports casual functionalism, which plays a great role in sportswear industry of American fashion design. The American fashion designers who were mentioned often in the articles were Donna Karan, Calvin Klein, Ralph Lauren and Tommy Hilfiger. As well as their works have common formative features based on functionalism, each of them shows his/ her own strong color. All of these designers make American fashion design, which can be defined as casual wear or sportswear, vary popular worldwide based on the developed American functionalism. Functionalism considering practical and conceptional functions will continue in coming century and techno functionalism and sports casual functionalism in future fashion designs will be expressed more strongly with new technology and casual trends of life style.

열처리가 천마의 Gastrodin과 Gastrodigenin 및 라디칼 소거능에 미치는 영향

하지수,황경아,황인국 한국식품영양학회 2023 韓國食品營養學會誌 Vol.36 No.6

This study evaluated the effects of heat treatment on gastrodin and gastrodigenin content, and antioxidant activities, in Gastrodia elata Blume. Gastrodin and gastrodigenin content was analyzed post-method validation, and antioxidant activity evaluation, including assessing total polyphenol content, DPPH, and ABTS radical scavenging activities, was done. The validation of the analysis method demonstrated excellent linearity. The limits of quantification of gastrodin and gastrodigenin were 2.89 and 3.47 μg/mL, respectively. Moreover, the results of intra- and inter-day precision analysis demonstrated relative standard deviation values, within 5%. The recovery rates for gastrodin and gastrodigenin were 97.22~98.85 and 97.99~99.91%, respectively, indicating good accuracy. Under different heat treatment conditions, gastrodin and gastrodigenin content significantly increased (p<0.05), ranging from 91.15 to 310.27 and 559.66 to 830.02 mg/100 g DW, respectively. Additionally, the total polyphenol content exhibited a significant (p<0.05) increasing trend, ranging from 1,444 to 1,798 mg/100 g DW, as the temperature and time of heat treatment increased. The DPPH and ABTS radical scavenging abilities demonstrated an increasing trend at 120℃ during heat treatment. These research findings are expected to enhance our understanding of the changes in gastrodin and gastrodigenin content, and antioxidant effects in Gastrodia elata Blume during heat treatment.

한국 스트리트 패션에서 도덕성과 관련한 미의식 변화에 관한 연구

하지수 韓國衣類學會 2005 한국의류학회지 Vol.29 No.2

Relationship between Androgen Deprivation Therapy and Normal-Tension Glaucoma in Patients with Prostate Cancer: A Nationwide Cohort Study

하지수,이혜선,박주영,전진형,김도경,김민,황호식,김태효,안현규,조강수 연세대학교의과대학 2022 Yonsei medical journal Vol.63 No.10

Purpose: This study assessed the relationship between newly developed normal-tension glaucoma (NTG) and androgen depri vation therapy (ADT) in patients with prostate cancer. Materials and Methods: A retrospective population-based cohort study was performed. During the period between 2008 and 2017, a total of 218203 prostate cancer patients were identified in a nationwide claims database in the Republic of Korea. The final analysis included 170874 patients (42909 in the ADT group, 127965 in the control group) after applying the inclusion and exclusion criteria. The incidences of NTG according to ADT duration were compared with controls. Exact matching was conducted to adjust comorbidities between cohorts. Cox proportional hazard regression models were performed after controlling for latent confound ing factors, and adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the incidence of NTG according to ADT were obtained. Results: In the matched cohort, the ADT group was associated with a significantly reduced risk of NTG in multivariable analysis compared to the control group. The risk of NTG decreased in patients who underwent ADT for less than 2 years (HR=0.824; 95% CI, 0.682–0.995; p=0.0440) and in those using ADT over 2 years (HR=0.796; 95% CI, 0.678–0.934; p=0.0051), compared to the controls. Conclusion: Medical castrations for patients with prostate cancer results in a lower incidence of newly diagnosed NTG compared to no ADT. These findings suggest that testosterone may be involved in the pathogenesis of NTG.

양쪽 출구가 트인 배기가스 재순환 버너의 냉간 유동 특성에 관한 연구

하지수 한국가스학회 2018 한국가스학회지 Vol.22 No.3

Thermal NOx is generated in a high temperature environment in a combustion facilities. Exhaustgas recirculation method is widely used among various methods for reducing nitrogen oxides in combustiondevices. In the present study, the computational fluid dynamic analysis was accomplished to elucidate the coldflow characteristics in the flue gas recirculation burner with both outlets opening. Because the reciculationpipes is installed toward the tangential direction, the swirling flow is formulated in the burner and the phenomenonof the reverse flow creation is detected at the center area of circular burner. We are confirmed that this isthe similar trend with the burner with one side outlet closed. From the present study, it was seen that the recirculatedinflow from both recirculated burner outlets increased by about 5% compared to the burner with one sideoutlet opening. At the outlet located at the exhaust gas recirculation pipe inlet(gas exit 1), the inlet flow wasformed in the entire region. At the opposite outlet(gas exit 2), the total flow was discharged, but the center partof the burner was observed to have a reverse flow. The flow rate at the gas exit 2 was 3 ~ 5 times larger thanthe flow rate at the gas exit 1.

Synthesis of Silicon and Fluorine Containing Block Copolymers

하지수,조성준,류두열 한국고분자학회 2017 한국고분자학회 학술대회 연구논문 초록집 Vol.42 No.1

통합 전자전에서 기계학습을 이용한 위협체 역추정 모델링

하지수,노상욱,박소령 한국차세대컴퓨팅학회 2015 한국차세대컴퓨팅학회 논문지 Vol.11 No.5

본 논문은 통합전자전 상황에서 전자정보 수집신호의 변수를 분석하여 전자파 신호를 발산하는 레이더 및 위협체계를 역변환으로 모델링하는 기법을 다루고자 한다. 전자전 수신기가 위협체로부터 수신한 변수 중 가장 중요한 속성을 1-rule 알고리즘을 통하여 파악하였으며, 베이지안 분류 알고리즘, 의사결정 트리 학습 알고리즘 및 인공 신경망알고리즘을 사용하여 위협체를 추정할 수 있는 프로토타입을 구축하였다. 다양한 통합전자전 상황에서 생성한 규칙을 기반으로 역변환 모델을 구축하고 새로운 데이터가 주어지면 모델링한 위협체로 분류한다. 실험에서 베이지안 분류 알고리즘, 의사결정 트리 학습 알고리즘 및 인공 신경망 알고리즘을 각각 적용하여 학습 곡선을 생성하였으며, 학습 곡선에서 최적의 성능을 나타내는 역변환 모델을 실험적으로 정립하였다. This paper proposes a method to model the reverse extrapolation of RF threats through the attributes representing RF threats in an integrated electronic warfare situation. Using 1-rule algorithm, the most important attribute figuring out the threat could be assured among the attributes which a receiver collected. And also, we build a prototype which estimates threats using three machine learning algorithms, i.e., naive Bayesian classifier, decision tree, and artificial neural network. In various integrated electronic warfare situations, we tested our reverse extrapolation model based on the outputs of machine learning algorithms, where new test data were given to identify a threat. We also generated learning curves for each algorithm, and experimentally decided their optimal reverse extrapolation models. To verify the prototype of our model compiled, we evaluated the accuracy of reverse extrapolation models and the resulting performance showed more than 99% of accuracy.

e-시대의 디자인과 ‘입는(wearable)' 경향

하지수 한국차세대컴퓨팅학회 2005 한국차세대컴퓨팅학회 논문지 Vol.1 No.1

코안다 노즐을 이용한 배기가스 재순환 장치의 형상에 따른 재순환 유동 특성에 관한 연구

하지수,심성훈,김대연 한국가스학회 2019 한국가스학회지 Vol.23 No.3

The purpose of the present study is to elucidate flue gas recirculation device for reduction of nitrogen oxides using coanda nozzle without adopting additional power driving fan in a waste incinerator. The characteristics of the exhaust gas recirculation flow rate and the average temperature change at the outlet of the mixed gas were investigated according to the change of air supply nozzle gap and the position of air supply nozzle. When the gap of the air supply nozzle was changed to 3.22, 4.03, and 4.84 mm, the largest recirculation flow ratio, which is the ratio of exhaust gas recirculation flow rate and air supply flow rate, was 2.227 for the case with 3.22 mm and its mean temperature at outlet was 594.8 ℃. When the position of the air supply nozzle changes to the front position, neck position, and expansion position of the coanda nozzle neck, the recirculation flow ratios at the forward position and the neck position were nearly almost the same value, 1.843, and 1.696 at the expansion position, their mean temperatures were 559.8 ℃ and 544.3 ℃, respectively. 본 연구는 폐기물 소각로에서 질소산화물 저감을 위해 고온의 배기가스를 연소로에서 재순환하여 연소용 공기와 혼합하여 배기가스 재순환을 이용한 방법에서 고온의 배기가스를 별도의 동력 팬이 없이 코안다 노즐을 이용한배기가스 재순환 장치에 관한 연구이다. 코안다 노즐에서 공기 공급 노즐 간극의 변화와 공기 공급 노즐의 위치에따른 배기가스 재순환 유량 특성과 혼합 가스의 출구에서 평균온도 변화를 살펴보았다. 공기 공급 노즐의 간극이3.22, 4.03, 4.84 mm로 변할 때 가장 좁은 3.22 mm일 때가 배기가스 재순환 유량과 공기 공급 유량의 비인 배기가스재순환 유량비가 2.227로 가장 재순환 유량이 크게 나타났고 혼합가스 평균 온도는 594.8 ℃로 나타났다. 공기 공급노즐의 위치가 코안다 노즐 목의 전방 위치, 목 위치, 확관 위치로 변할 때를 살펴보았으며 전방 위치와 목 위치일때는 재순환 유량비가 1.843으로 거의 같은 값이고 확관 위치에서는 1.696으로 나타났으며 평균 온도는 559.8 ℃와544.3 ℃로 나타났다.