• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.923-938
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• 2019

Surge motion of top-end platform induced by periodic wave makes marine flexible riser encounter equivalent sheared-oscillatory flow, under which the Vortex-induced Vibration (VIV) response will be more complicated than pure sheared flow or oscillatory flow cases. Based on a time domain force-decomposition model, the VIV response characteristics under sheared-oscillatory flows are investigated numerically in this paper. Firstly, the adopted numerical model is validated well against laboratory experiments under sheared flow and oscillatory flow. Then, 20 sheared-oscillatory flow cases with different oscillation periods and top maximum current velocities are designed and simulated. Under long and short oscillation period cases, the structural response presents several similar features owing to the instantaneous sheared flow profile at each moment, but it also has some different patterns because of the differently varying flow field. Finally, the effects and essential mechanism of oscillation period and top maximum current velocity on VIV response are discussed systematically.

• The Korean Journal of Food And Nutrition
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• v.31 no.6
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• pp.873-882
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• 2018

This research is about the quality characteristics of white bread mixed with varying ratios of Seomcho powder, such as 1%, 3%, 5%, and 7% (Spinacia oleracea L.). The pH level of dough decreased as more Seomcho powder (Spinacia oleracea L.) was added, and 7% addition recorded the lowest pH. The fermentation power of dough expansion decreased as the additional ratio increased in both the first and second proofing, and it was negatively correlated to the fermentation time factor. The moisture content of bread decreased as the addition ratio increased. The bread volume became smaller as the addition ratio increased, but it correlated negatively with its specific volume. The color of the crumb, the lightness and redness decreased in comparison to the control, but the yellowness increased. The total amino acid contents increased as the addition ratio increased, and glutamic acid was positively correlated to the additional ratio. The total free amino acids increased as the additional ratio increased, but cysteine levels were high at 5% and 7% additional ratio. The textural characteristics of the bread, springiness and cohesiveness were lower than the control, but gumminess, brittleness, and hardness were higher than the control. The adhesiveness was realized at 7% additional ratio.

• Wind and Structures
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• v.37 no.5
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• pp.361-373
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• 2023

Suspended monorail trains (SMTs) are sensitive to crosswinds, and instantaneous aerodynamic characteristics of two SMTs passing each other under crosswinds are particularly complicated. In this study, a pressure measurement test is carried out on stationary train-bridge models arranged in several critical positions. In addition, a validated moving CFD model is developed with the dynamic and sliding mesh method to explore the realistic train movement effects. The time-varying aerodynamic forces and surface pressure distribution on, as well as the flow field around running trains and bridges during trains passing each other, are computed in detail to illustrate the shielding effect of the upstream train. The results reveal that when two trains begin to pass each other, the side force coefficient of the downstream train reduces significantly to negative values due to the wind shielding effect of the upstream train. The moving model successfully captures that airflow is separated on the middle line of the head car for the suspended monorail train, and the surrounding bluff double-beams can significantly affect the flow structures around the train. The wind shielding effect of the upstream train on the downstream train will weaken as the relative yaw angle decreases.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.2
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• pp.26-32
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• 2006

This paper targets a direct and quantitative prediction of characteristics of unstable waves in a combustion chamber, which employs the governing equations derived in terms of amplification factors of flow variables. A freshly formulated nonlinear acoustic equation is obtained and the analysis of unsteady waves in a rocket engine is attempted. In the present formalism, perturbation method decomposes the variables into time-averaged part that can be obtained easily and accurately and time-varying part which is assumed to be harmonic. Excluding the use of conventional spatially sinusoidal eigenfunctions, a direct numerical solution of wave equation replaces the initial spatial distribution of standing waves and forms the nonlinear space-averaged terms. Amplification factor is also calculated independently by the time rate of changes of fluctuating variables, and is no longer an explicit function for compulsory representation. Employing only the numerical computation, major assumptions inevitably inherent, and in erroneous manner, in up to date analytical methods could be avoided. With two definitions of amplification factor, 1-D stable wave and 3-D unstable wave are examined, and clearly demonstrated the potentiality of a suggested theoretical-numerical method of combustion instability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.2
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• pp.49-58
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• 1990

A numerical procedure is developed to analyze the time-dependent deflections of prestressed concrete bridges constructed by the segmental cantilever method. The developed computer program accounts for the time-dependent properties of prestressed concrete materials due to the varying modulus of elasticity, creep and shrinkage of concrete and the stress relaxation of prestressing steel. It also accounts for the stiffness increase due to the presence of the steel reinforcements and the effects of the shear deformation of the prestressed concrete bridge girders. The program is applied to a multi-span continuous segmental prestressed concrete bridge to demonstrate its capabilities and to explore the behavior characteristics of the segmental bridges.

• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.436-445
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• 2013

The use of a demand response controller is necessary for electric devices to effectively respond to time varying price signals and to achieve the benefits of cost reduction. This paper describes a new formulation with the form of constrained optimization for designing an optimal demand response controller. It is demonstrated that constrained optimization is a better approach for the demand response controller, in terms of the ambiguity of device operation and the practicality of implementation of the optimal control law. This paper also proposes a design scheme to construct a demand response controller that is useful when a system controller is already adapted or optimized for the system. The design separates the demand response function from the original system control function while leaving the system control law unchanged. The proposed formulation is simulated and compared to the system with simple dynamics. The effects of the constraints, the system characteristics and the electricity price are examined further.

• Journal of Korean Society of Water and Wastewater
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• v.11 no.4
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• pp.126-132
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• 1997

Trihalomethanes (THMs) are formed during the chlorination of waters containing precusors compounds, most commonly humic substances, changes in pH, TOC, temperature, precusor source and concentration chlorine dosage, bromide level and reaction time directly influence trihalomethane formation potential (THMFP) and kinetics. A standard THMFP experiment was conducted for each water under the following conditions ; $20^{\circ}C$, pH 7.4, reaction time of 48hr, TOC 5.7mgC/L. A series of kinetic experiments was conducted for each water to provide THM formation under varying conditions of reaction time, pH, temperature and TOC, chlorine dosage. The resultant mutiple parameter powre function predicts a THM which allows direct calculation of THM, is $[THM]=0.00039(pH-2.81)[TOC][Cl_2]^{0.321}\;t^{0.266}\;T^{0.286}$ Characteristics of raw water in advanced drinking water treatment pilot plant were, TOC levels ran from 4.42~6.84mgC/L, pH 7.2~7.8, temperature $7.0{\sim}18.4^{\circ}C$, UV-254 absorbance $0.057{\sim}0.85cm^{-1}$, THM levels ranged from 0.031~0.049mgC/L.

• Korean Journal of Metals and Materials
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• v.50 no.7
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• pp.545-548
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• 2012

The optical and electronic properties of Indium Tin Oxide (ITO) thin films deposited on a RF-plasma treated glass substrate were investigated by X-Ray Photoelectron Spectroscopy (XPS), Ultra-violet Photoelectron Spectroscopy (UPS), Reflected Electron Energy Loss Spectroscopy (REELS). The modification of glass substrates was carried out by varying the time of the plasma surface treatment in an oxygen atmosphere. The focus of this research was to examine how the optical and electronic properties of ITO thin films change with the plasma treatment time. The surface energy increased since the carbon bonds were removed from the surface after the glass substrate received the surface treatment. The ITO thin films produced on the glass substrate with surface treatment showed that the high optical transmittance was approximately 85%. The measured band gap energy was as high as 3.23 eV when the plasma treatment time was 60 s and the work function after the treatment was increased by 0.5 eV in comparison to that before the treatment of 60 s. The ITO thin film exhibited an excellent sheet resistance of $2.79{\Omega}/{\Box}$. We found that the optical and electronic properties of ITO thin films can be improved by RF-plasma surface treatment.

• Asia-Pacific Journal of Business
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• v.14 no.1
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• pp.113-129
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• 2023

Purpose - The purpose of this study is to examine whether trading volume amplifies the extent to which lottery-type stocks are overpriced, and whether economic sentiment index explains time-variation in the magnitude of the volume amplification effect. Design/methodology/approach - We examine monthly returns on 5x5 monthly bivariate portfolios formed by lottery characteristics (measured by maximum daily return) and trading volume. In addition, we perform time-series regression tests to examine how the volume amplification effect changes in high and low economic sentiment periods, after controlling for Fama-French three factors. Findings - Our bivariate portfolio analysis shows that the overpricing of lottery-type stocks are mostly pronounced among high trading volume stocks. In contrast, for low trading volume stocks, overpricing of lottery-type stocks appears to vanish. Furthermore, the amplification effect of trading volume on overpricing of lottery-type stock is concentrated in high economic sentiment periods. Research implications or Originality - This study is the first attempt to examine whether trading volume drives lottery-type stocks' overpricing in the Korean stock market. Furthermore, our analysis unveils the time-varying nature of volume amplification effect. The results suggest that trading volume might play a important hidden role in asset pricing, opening a new line of researches in the future.

• International Journal of Computer Science & Network Security
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• v.24 no.2
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• pp.169-177
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• 2024

Interacting Spherical tank has maximum storage capacity is broadly utilized in industries because of its high storage capacity. This two tank level system has the nonlinear characteristics due to its varying surface area of cross section of tank. The challenging tasks in industries is to manage the flow rate of liquid. This proposed work plays a major role in controlling the liquid level in avoidance of time delay and error. Several researchers studied and investigated about reducing the nonlinearity problem and their approaches do not provide better result. Different types of controllers with various techniques are implemented by the proposed system. Intelligent Adaptive Neuro Fuzzy Inference System (ANFIS) based Sliding Mode Controller (SMC) with Fractional order PID controller is a novel technique which is developed for a liquid level control in a interacting spherical tank system to avoid the external disturbances perform better result in terms of rise time, settling time and overshoot reduction. The performance of the proposed system is obtained by analyzing the simulation result obtained from the controller. The simulation results are obtained with the help of FOMCON toolbox with MATLAB 2018. Finally, the performance of the conventional controller (FOPID, PID-SMC) and proposed ANFIS based SMC-FOPID controllers are compared and analyzed the performance indices.