• Nonlinear Functional Analysis and Applications
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• 제28권3호
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• pp.831-850
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• 2023

Our long-standing Metatheorem in Ordered Fixed Point Theory is applied to some well-known order theoretic fixed point theorems. In the first half of this article, we introduce extended versions of the Zermelo fixed point theorem, Zorn's lemma, and the Caristi fixed point theorem based on the Brøndsted-Jachymski principle and our 2023 Metatheorem. We show some of their applications to other fixed point theorems or theorems on the existence of maximal elements in partially ordered sets. In the second half, we collect and improve order theoretic fixed point theorems in the collection of Howard-Rubin in 1991 and others. In fact, we improve or extend several ordering principles or fixed point theorems due to Brézis-Browder, Brøndsted, Knaster-Tarski, Tarski-Kantorovitch, Turinici, Granas-Horvath, Jachymski, and others.

• 한국정밀공학회지
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• 제11권1호
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• pp.166-176
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• 1994

The problem of reducing the vibration level of elastic plates driven by multiple random point forces is analyzed in this study. First, the analytical solution for the vibration level of finite thin plates with four simply supported edges under the action of multiple random point force is derived. By assuming the plates to be lightly damped, an approximate solution for the vibration level of the plate is obtained. A numerical study is carried out to determine an optimal spacing distance between the multiple point forces in order to produce a relative minimum in the plate's vibration level. The optimal spacing distance is shown to depend on the given excitation band. The effects of wave cancellation in the near field of the multiple point forces are discussed by using the equivalence of certain stationary random responses and deterministic pulse responese.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제8권7호
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• pp.289-302
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• 2019

시계열의 구조 변화란, 전체 시계열 자료를 구성하는 기간에서 관측치들의 분포가 상대적으로 안정적이다가, 특정 시점에서 분포 특성의 급격한 변화를 보이는 것을 의미한다. 비정상(non-stationary) 장기 시계열 안에서도, 단기적인 추세의 변화가 일시적인 것인지, 아니면 구조적으로 변한 것인지를 적시에 판단하는 것은 중요하다. 이는 시계열 추세의 변화를 상시 감지하여, 변화에 맞는 적정한 대응을 할 필요가 있기 때문이다. 본 연구에서는 단위근 검정법을 기반으로 한 검정 결과를 시각화함으로써, 의사결정자가 시계열의 구조 변화를 손쉽게 파악할 수 있는 방안을 제시하였다. 특히 시계열을 분할한 후 검정하는 방법을 통해, 장기 시계열일 때에도 단기 구조 변화를 파악할 수 있도록 하였다.

• 대한수학회보
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• 제36권4호
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• pp.637-647
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• 1999

In this paper, we consider a free boundary problem with Pushchino dynamics satisfying the Dirichlet boundary condition. We shall the stationary solutions ($v^{*}(x),s^{*}$) exist and the Hopf bifurcation occurs at a critical point when s $\in$ (1/3,1).

• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2000년도 하계종합학술대회논문집
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• pp.121-124
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• 2000

적응 학습 알고리즘으로 가중치를 변화시키는 단층 신경망의 출력부에 Ramp 임계 함수를 적용하여 입력이 zero-mean Gaussian random vector인 경우 가중치의 stationary point를 구하고, 적응 학습 알고리즘을 유도한다.

• 설비공학논문집
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• 제19권12호
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• pp.850-856
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• 2007

In a supercooled or capsule type ice storage system, aqueous solution (or water) may have trouble with non-uniform dissolution though the system contributes to the simplicity of system and ecological improvement. The non-uniform dissolution increases the instability of the system because it may cause an ice blockage in pipe or cooling part. In order to observe the supercooled state, a cooling experiment was performed with pressurization to an ethylene glycol(EG) 3 mass% solution in stationary state. Also, the effect of the pressurization from 101 to 505 kPa to the dissolution of supercooled aqueous solution was measured with the dissolution time of the supercooled aqueous solution at a fixed cooling rate of brine. At results, the dissolution of supercooled point decreased as the pressure of the aqueous solution in the vessel increased. Moreover, the dissolution point increased as the heat flux for cooling increased.

• International Journal of Aeronautical and Space Sciences
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• 제9권1호
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• pp.111-120
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• 2008

A particle image velocimetry (PIV) technique was employed to investigate the effects of blowing jet on the flow characteristics over stationary and pitch-oscillating airfoils. The Reynolds number was $7.84{\times}10^5$ based on the chord length. It was found that for stationary airfoil cases, continuous and pulsating blowing jets successfully reduced separated wake region at high angles of attack. A comparison study of two different types of jet blowing indicated that pulsating jet is more effective than continuous jet for flow separation control. Pulsating leading-edge blowing postpones flow separation and increased stall angle of attack by $2^{\circ}{\sim}3^{\circ}$. For pitch-oscillating airfoil cases, the PIV results showed that blowing jet efficiently delays the separation onset point during pitch-up stroke, whereas it does not prevent flow separation during pitch-down stroke, even at angles of attack smaller than static ones.

• 대한인간공학회지
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• 제30권6호
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• pp.739-747
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• 2011

Objective: The present study evaluated information presentation methods applicable to a wearable Braille display in terms of performance and satisfaction measures. Background: A Braille display wearable at a finger can improve accessibility of information for the blind by presenting information in real time. Method: A Braille display with six pins operated by DC servomotors was developed to simulate four information presentation methods(active, stationary, simultaneous, and sequential methods). An evaluation experiment was conducted with 16 participants(8 normal and 8 blind participants) by using three objective measures(reaction time, RT, unit: sec; recognition time, CT, unit: sec; correct response percentage, CP) and two subjective measures(overall satisfaction, OS; perception easiness, PE) with a 7-point scale. Results: The average RTs and CTs of the active and stationary methods were significantly shorter than those of the simultaneous and sequential methods for the blind participants. Also, the average CPs, OSs, and PEs of the active and sequential methods were significantly higher than those of the stationary and simultaneous methods. Conclusion: The active and sequential methods were preferred to the other methods for the blind. Application: The performance characteristics identified in the present study for the four braille display methods can be utilized to develop an effective wearable Braille display system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권4호
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• pp.1975-1988
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• 2019

Short-term traffic flow prediction plays an important role in intelligent transportation systems (ITS) in areas such as transportation management, traffic control and guidance. For short-term traffic flow regression predictions, the main challenge stems from the non-stationary property of traffic flow data. In this paper, we design an ensemble cascading prediction framework based on extremely randomized trees (extra-trees) using a boosting technique called EET to predict the short-term traffic flow under non-stationary environments. Extra-trees is a tree-based ensemble method. It essentially consists of strongly randomizing both the attribute and cut-point choices while splitting a tree node. This mechanism reduces the variance of the model and is, therefore, more suitable for traffic flow regression prediction in non-stationary environments. Moreover, the extra-trees algorithm uses boosting ensemble technique averaging to improve the predictive accuracy and control overfitting. To the best of our knowledge, this is the first time that extra-trees have been used as fundamental building blocks in boosting committee machines. The proposed approach involves predicting 5 min in advance using real-time traffic flow data in the context of inherently considering temporal and spatial correlations. Experiments demonstrate that the proposed method achieves higher accuracy and lower variance and computational complexity when compared to the existing methods.

• Journal of Mechanical Science and Technology
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• 제16권5호
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• pp.583-590
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• 2002

When a mechanical structure is driven by stationary wide band random point forces, the resulting vibration depends upon the number, location, and joint statistical properties of the exciting forces. In this study, under the assumption of light damping, an approximate procedure for analyzing plates is briefly outlined. The effects of number, location and correlation of the force field on the vibration level are then investigated for various cases in which random point forces with band limited white noise are applied, and the optimal spacing between input forces that produces a relative minimum in the vibration response is predicted.