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Mixing Characteristics of Kerosene-Lox in a Swirl Injector at 100 bar
Heo, Junyoung,Kang, Jeongseok,Sung, Hong-Gye The Society for Aerospace System Engineering 2016 International Journal of Aerospace System Engineer Vol.3 No.1
The The turbulent mixing characteristics of Kerosene-LOx in a coaxial swirl injector 100 bar have been numerically investigated. Turbulent model is based on large eddy simulation with real-fluid transport and thermodynamics. The effects of equation of state (EOS), chamber pressure are evaluated in a point of the mixing efficiency and pressure fluctuations. The dominant frequency is same as the hairpin vortex shedding frequency generated by film wave at the LOx post.
Stock Price Prediction Based on Financial Statements Using SVM
Junyoung Heo,Jin Yong Yang 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.2
The support vector machine (SVM) is a fast, and reliable machine learning mechanism. In this paper, we evaluated the stock price predictability of SVM, which is a kind of fundamental analysis that predicts the stock price from corporate intrinsic value. Corporate financial statements are used as input into SVM. Based on the results, we predicted the rise or drop of the stock. In addition, we evaluated how long a given financial statement can be used to predict a stock’s price. Compared to the experts forecast, the results of SVM show good predictability. However, as times goes on, the predictability begins to drop. These predictions based on financial statements are excellent, but after a short period, the dissonance between financial statements and stock price can be offset by reasonable investors. These results support the efficient market hypothesis.
Junyoung Heo,Jiman Hong,Yookun Cho IEEE 2009 IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS - Vol.5 No.1
<P>Wireless industrial sensor networks are wireless sensor networks which have been adapted to industrial applications. Most techniques for wireless sensor networks can be applied to wireless industrial sensor networks. However, for industrial applications of wireless industrial sensor networks, new requirements such as real-time, reliable delivery need to be considered. In this paper, we propose EARQ, which is a novel routing protocol for wireless industrial sensor networks. It provides real-time, reliable delivery of a packet, while considering energy awareness. In EARQ, a node estimates the energy cost, delay and reliability of a path to the sink node, based only on information from neighboring nodes. Then, it calculates the probability of selecting a path, using the estimates. When packet forwarding is required, it randomly selects the next node. A path with lower energy cost is likely to be selected, because the probability is inversely proportional to the energy cost to the sink node. To achieve real-time delivery, only paths that may deliver a packet in time are selected. To achieve reliability, it may send a redundant packet via an alternate path, but only if it is a source of a packet. Experimental results show that EARQ is suitable for industrial applications, due to its capability for energy efficient, real-time, reliable communications.</P>
Navigation and Localization of Mobile Robot Based on Vision and Sensor Network Using Fuzzy Rules
Junyoung Heo,Sanghyuk Son,Kijoo Lee,Jaeyeon Lee,Won Chang Lee 한국멀티미디어학회 2008 한국멀티미디어학회 국제학술대회 Vol.2008 No.-
Algorithms of path planning and obstacle avoidance are essential to autonomous mobile robots that are working in unknown environments in the real time. This paper presents a new navigation algorithm of an autonomous mobile robot with vision, IR sensors and Zigbee sensor network using fuzzy rules. Temporary targets are set up by distance variation method and then the algorithms of trajectory planning, obstacle avoidance and localization are designed using fuzzy rules. An autonomous mobile robot with single vision and IR sensors, Zigbee sensor network is built up for experiments. We also show that the proposed algorithms are working well in complex unknown environments.
ON THE RATIO OF BIOMASS TO TOTAL CARRYING CAPACITY IN HIGH DIMENSIONS
Heo, Junyoung,Kim, Yeonho Korean Mathematical Society 2021 대한수학회지 Vol.58 No.5
This paper is concerned with a reaction-diffusion logistic model. In [17], Lou observed that a heterogeneous environment with diffusion makes the total biomass greater than the total carrying capacity. Regarding the ratio of biomass to carrying capacity, Ni [10] raised a conjecture that the ratio has a upper bound depending only on the spatial dimension. For the one-dimensional case, Bai, He, and Li [1] proved that the optimal upper bound is 3. Recently, Inoue and Kuto [13] showed that the supremum of the ratio is infinity when the domain is a multi-dimensional ball. In this paper, we generalized the result of [13] to an arbitrary smooth bounded domain in ℝ<sup>n</sup>, n ≥ 2. We use the sub-solution and super-solution method. The idea of the proof is essentially the same as the proof of [13] but we have improved the construction of sub-solutions. This is the complete answer to the conjecture of Ni.
과팽창 초음속제트의 방향 제어를 위한 유체역학적 제어의 동특성 연구
허준영(Junyoung Heo),유광희(Kwanghee Yoo),조민경,성홍계(Hong-Gye Sung),이열(Yeol Lee),전영진(Youngjin Jeon),조승환(Seunghwan Cho) 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.5
기계적 제어장치를 사용하지 않으면서도 추력방향 제어가 가능한 유체역학적 추력편향제어(Fluidic Thrust Vector Control; FTVC)기법에 대한 연구 논문이다. 2차 유동은 주 유동 흐름과 같은 방향으로 분사하였고, 선행연구를 통해 정상(steady)상태의 수치해석 결과는 실험과 비교·검증하였다. 이를 바탕으로 비정상(unsteady) 수치해석을 수행하였고, 위아래로 제트가 편향이 될 때에 소요되는 시간과 벽면에서의 압력 분포 등을 조사하여 추력벡터의 동특성을 연구하였다. The purpose of this research is to investigate the dynamic characteristics of fluidic thrust vector control using the co-flow injection. In previous research, both numerical and experimental approaches for steady state were conducted to investigate operation-parameters and detail flow structure of the fluidic thrust vector control system. Based upon the previous results, numerical unsteady calculation was conducted to analyze the dynamic characteristics of jet up- and down-ward vectoring so that the transition time and the pressure distribution along the wall, and so on were investigated.
가변 추력용 핀틀 노즐의 동적 특성에 관한 수치적 연구
허준영(Junyoung Heo),정기연(Kiyeon Jeong),성홍계(Hong-Gye Sung) 한국추진공학회 2013 한국추진공학회 학술대회논문집 Vol.2013 No.5
핀틀의 형상과 작동조건에 따른 성능변화와 유동박리특성을 비교하였다. 비정상상태 이동격자 수치해석기법을 이용하여 시간에 따른 핀틀의 위치변화를 고려하였으며, 핀틀의 작동조건에 따른 추력과 연소실 압력변화의 경향성과 박리부근에 대한 분석을 수행하였다. 핀틀의 이동속도는 각각 0.1 m/s, 1.0 m/s이며 작동시퀀스는 핀틀이 노즐 목에 머무르지 않는 경우(case 1), 0.5초 머무를 경우(case 2)를 고려하였다. The pintle nozzle performance and flow separation characteristics are analyzed to the pintle shape and operation conditions. A unsteady numerical technique with moving grid system is applied to take account the pintle movement and flow separation characteristics are estimated to the operation conditions. Pintle speed is 0.1m/s and 1.0m/s respectively. The operation sequences are 1; the pintle moves toward the nozzle throat and instantly turns back and 2; stops at the nozzle throat for 0.5sec.
초임계 정상 화염편 모델을 이용한 케로신/기체산소 동축 전단분사기의 끝단 두께에 따른 혼합 및 연소 특성
허준영(Junyoung Heo),강정석(Jeongseok Kang),성홍계(Hong-Gye Sung) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12
고압 환경에서 작동하는 케로신/기체산소 전단 동축 분사기의 끝단 두께가 혼합 및 연소 특성에 미치는 영향을 수치적으로 연구하였다. 난류모델은 LES를 기반으로 하였고, 실기체 상태량을 계산하기위해 RK-PR 상태 방정식을 적용하였다. 초임계 화염구조해석을 위하여 초임계 물성치 식을 적용하였으며, 케로신/기체산소 화염구조해석을 통해 실기체 정상 화염편 모델(steady flamelet model)에 적용하였다. 끝단 두께에 따른 비반응/반응계산의 혼합면에 발생되는 와류발생과 연소 특성을 비교하였다. 끝단 두께가 두꺼워짐에 따라 와류가 끝단면 길이보다 작게 형성이 되며 이로 인하여 불균일한 온도분포가 형성되었다. 하지만 scalar dissipation rate의 분포경향과 크기는 유사하였다. The effect of the splitter thickness of a kerosene/gaseous oxygen shear-coaxial injector under supercritical condition is numerically investigated in order to analyze the mixing and combustion characteristics. Turbulent numerical model is based on large eddy simulation with Redlich-Kwong-Peng-Robinson equation of state to calculate real-fluid properties. A combustion model is applied to the real-fluid steady flamelet model which is based on kerosene/gaseous oxygen flame structure results. The vortex generation and combustion characteristics on the mixing layer are compared the reacting with non-reacting result according to the tip thickness. As the tip thickness increases, the temperature distribution is in non-uniform due to the vortex size. However, a tendency of the scalar dissipation rate is similar to each other.