• Nonlinear Functional Analysis and Applications
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• v.27 no.3
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• pp.553-568
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• 2022

In this paper, we introduce and study two different iterative hybrid projection algorithms for solving a fixed point problem of nonexpansive mappings. The first algorithm is generated by the combination of the inertial method and the hybrid projection method. On the other hand, the second algorithm is constructed by the convex combination of three updated vectors and the hybrid projection method. The strong convergence of the two proposed algorithms are proved under very mild assumptions on the scalar control. For illustrating the advantages of these two newly invented algorithms, we created some numerical results to compare various numerical performances of our algorithms with the algorithm proposed by Dong and Lu [11].

• Communications of the Korean Mathematical Society
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• v.39 no.3
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• pp.739-756
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• 2024

The ordinary mean curvature vector field 𝗛 on a submanifold M of a space form is said to be proper if it satisfies equality Δ𝗛 = a𝗛 for a constant real number a. It is proven that every hypersurface of an Riemannian space form with proper mean curvature vector field has constant mean curvature. In this manuscript, we study the Lorentzian hypersurfaces with proper second mean curvature vector field of four dimensional Lorentzian space forms. We show that the scalar curvature of such a hypersurface has to be constant. In addition, as a classification result, we show that each Lorentzian hypersurface of a Lorentzian 4-space form with proper second mean curvature vector field is C-biharmonic, C-1-type or C-null-2-type. Also, we prove that every 𝗛₂-proper Lorentzian hypersurface with constant ordinary mean curvature in a Lorentz 4-space form is 1-minimal.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.449-452
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• 2007

The present study numerically investigate the effects of the Syngas chemical kinetics on the basic flame properties and the structure of the Syngas diffusion flames. In order to realistically represent the turbulence-chemistry interact ion and the spatial inhomogeneity of scalar dissipation rate. the Eulerian Particle Flamelet Model(EPFM) with multiple flamelets has been applied to simulate the combustion processes and NOx formation in the syngas turbulent nonpremixed flames. Due to the ability for interactively describing the transient behaviors of local flame structures with CFD solver, the EPFM model can effectively account for the detailed mechanisms of NOx format ion including thermal NO path, prompt and nitrous NOx format ion, and reburning process by hydrocarbon radical without any ad-hoc procedure. validation cases include the Syngas turbulent nonpremixed jet and swirling flames. Based on numerical results, the detailed discussion has been made for the sensitivity of the Syngas chemical kinetics as well as the precise structure and NOx formation characteristics of the turbulent Syngas nonpremixed flames.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.4
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• pp.363-367
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• 2011

In this paper, friction coefficients between ices and model ship were studied in order to predict the resistance of ice. The friction coefficient is a dimensionless scalar value which describes the ratio of the force of friction between two bodies and the force pressing them together. The coefficient of friction depends on the materials, roughness on surface, lubrication, etc. We tested and analyzed the friction coefficient for the development of the test methodology. The friction coefficient for ice model test is very dominant to predict the ship performance, so every ice tank uses their own painting technique. In this study, the friction coefficient with changing the moving speed of ice was studies by using a flat plates which were made by the MOERI's paining technique and the basic research for the developing the paining methodology in the MOERI ice model basin was carried out.

• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.675-691
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• 2017

Jets in cross flow are of fundamental industrial importance and play an important role in validating turbulence models. Two jet configurations related to thermal fatigue phenomena are investigated: ${\bullet}$ T-junction of circular tubes where a heated jet discharges into a cold main flow and ${\bullet}$ Rectangular jet marked by a scalar discharging into a main flow in a rectangular channel. The T-junction configuration is a classical test case for thermal fatigue phenomena. The Vattenfall T-junction experiment was already subject of an OECD/NEA benchmark. A LES modelling and calculation strategy is developed and validated on this data. The rectangular-jet configuration is important for basic physical understanding and modelling and has been analyzed experimentally at CEA. The experimental work was focused on turbulent mixing between a slightly heated rectangular jet which is injected perpendicularly into the cold main flow of a rectangular channel. These experiments are analyzed for the first time with LES. The overall results show a good agreement between the experimental data and the CFD calculation. Mean values of velocity and temperature are well captured by both RANS calculation and LES. The range of critical frequencies and their amplitudes, however, are only captured by LES.

• The Transactions of the Korea Information Processing Society
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• v.5 no.1
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• pp.202-214
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• 1998

Exploitation of instruction-level parallelism(ILP) is an effective mechanism for improving the performance of modern super-scalar and VLIW processors. Various software techniques can be applied to increase ILP. Among these techniques, predicated execution is the one that increases the degree of ILP by allowing instructions from different basic blocks to be converted to a single basic block by removing branch instructions. In this paper, a global predicate-sensitive scheduling algorithm is proposed to improve the performance for ILP processors that support predicated execution. In order to examine the performance of proposed algorithm, a C compiler and a simulator are developed. By simulating various benchmark programs with the compiler and the simulator, the performance results of this algorithm are measured and the effectiveness of the algorithm is verified. As a result of measure performance with I, 2, 4 issue execution, this study was confirmed average performance by 20% or more.

• Journal of the Korean Magnetic Resonance Society
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• v.12 no.1
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• pp.14-25
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• 2008

To investigate the 3-bond connectivity of human brain metabolites by scalar coupling interaction through 2D-correlation spectroscopy (COSY) techniques using high field NMR spectroscopy. All NMR experiments were performed at 298K on Unity Inova 500 or 600 (Varian Inc.) equipped with a triple resonance probe head with z-shield gradient. Human brain metabolites were prepared with 10% $D_2O$. Two dimensional 2D COSY spectra were acquired with 4096 complex data points in $t_2$ and 128 or 256 increments in $t_1$ dimension. The spectral width was 9615.4 Hz and solvent suppression was achieved using presaturation using low power irradiation of the water resonance during 2s of relaxation delay. NMR data were processed using VNMRJ (Varian Instrument) software and all the chemical shifts were referenced to the methyl resonance of N-acetyl aspartate (NAA) peak at 2.0 ppm. Total 10 metabolites such as N-acetyl aspartate (NAA), creatine (Cr), choline (Cho), glutamine (Gln), glutamate (Glu), myo-inositol (Ins), lactate (Lac), taurine (Tau), ${\gamma}$-aminobutyricacid (GABA), alanine (Ala) were included for major target metabolites. Symmetrical 2D-COSY spectra were successfully acquired. Total 14 COSY cross peaks were observed even though there were parallel/orthogonal noisy peaks induced by water suppression. Except for Cr, all of human brain metabolites produced COSY cross peaks. The spectra of NAA methyl proton at 2.02 ppm and Glu methylene proton ($CH_2(3)$) at 2.11 ppm and Gln methylene proton ($CH_2(3)$) at 2.14 ppm were overlapped in the similar resonance frequency between 2.00 ppm and 2.15 ppm. The present study demonstrated that in vitro 2D-COSY represented the 3-bond connectivity of human brain metabolites by scalar coupling interaction. This study could aid in better understanding the interactions between human brain metabolites in vivo 2D-COSY study. Also it would be helpful to determine the molecular stereochemistry in vivo by using two-dimensional MR spectroscopy.

• Investigative Magnetic Resonance Imaging
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• v.12 no.1
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• pp.8-19
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• 2008

Purpose : To investigate the 3-bond and spatial connectivity of human brain metabolites by scalar coupling and dipolar nuclear Overhauser effect/enhancement (NOE) interaction through 2D- correlation spectroscopy (COSY) and 2D- NOE spectroscopy (NOESY) techniques. Materials and Methods : All 2D experiments were performed on Bruker Avance 500 (11.8 T) with the zshield gradient triple resonance cryoprobe at 298 K. Human brain metabolites were prepared with 10% $D_2O$. Two-dimensional spectra with 2048 data points contains 320 free induction decay (FID) averaging. Repetition delay was 2 sec. The Top Spin 2.0 software was used for post-processing. Total 7 metabolites such as N-acetyl aspartate (NAA), creatine (Cr), choline (Cho), lutamine (Gln), glutamate (Glu), myo-inositol (Ins), and lactate (Lac) were included for major target metabolites. Results : Symmetrical 2D-COSY and 2D-NOESY pectra were successfully acquired: COSY cross peaks were observed in the only 1.0-4.5 ppm, however, NOESY cross peaks were observed in the 1.0-4.5 ppm and 7.9 ppm. From the result of the 2-D COSY data, cross peaks between the methyl protons ($CH_3$(3)) at 1.33 ppm and methine proton (CH(2)) at 4.11 ppm were observed in Lac. Cross peaks between the methylene protons (CH2(3,$H{\alpha}$)) at 2.50ppm and methylene protons ($CH_2$,(3,$H_B$)) at 2.70 ppm were observed in NAA. Cross peaks between the methine proton (CH(5)) at 3.27 ppm and the methine proton (CH(4,6)) at 3.59 ppm, between the methine proton (CH(1,3)) at 3.53 ppm and methine proton (CH(4,6)) at 3.59 ppm, and between the methine proton (CH(1,3)) at 3.53 ppm and methine proton (CH(2)) at 4.05 ppm were observed in Ins. From the result of 2-D NOESY data, cross peaks between the NH proton at 8.00 ppm and methyl protons ($CH_3$) were observed in NAA. Cross peaks between the methyl protons ($CH_3$(3)) at 1.33 ppm and methine proton (CH(2)) at 4.11 ppm were observed in Lac. Cross peaks between the methyl protons (CH3) at 3.03 ppm and methylene protons (CH2) at 3.93 ppm were observed in Cr. Cross peaks between the methylene protons ($CH_2$(3)) at 2.11 ppm and methylene protons ($CH_2$(4)) at 2.35 ppm, and between the methylene protons($CH_2$ (3)) at 2.11 ppm and methine proton (CH(2)) at 3.76 ppm were observed in Glu. Cross peaks between the methylene protons (CH2 (3)) at 2.14 ppm and methine proton (CH(2)) at 3.79 ppm were observed in Gln. Cross peaks between the methine proton (CH(5)) at 3.27 ppm and the methine proton (CH(4,6)) at 3.59 ppm, and between the methine proton (CH(1,3)) at 3.53 ppm and methine proton (CH(2)) at 4.05 ppm were observed in Ins. Conclusion : The present study demonstrated that in vitro 2D-COSY and NOESY represented the 3-bond and spatial connectivity of human brain metabolites by scalar coupling and dipolar NOE interaction. This study could aid in better understanding the interactions between human brain metabolites in vivo 2DCOSY study.

• Journal of the Korea Computer Graphics Society
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• v.4 no.1
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• pp.79-88
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• 1998

Till now there are several rendering models for water and simulating other fluids and their dynamics. Especially in order to generate a curved surface of flexible objects such as liquid and snow, the implicit metaball formulation is widely used in favor of its simplicity and flexibility. This paper proposes one excellent method for generating water droplets, which would be deformed in gravitation field. In previous works, a water droplet was simply represented by approximated curved surfaces of a symmetric metaball. Thus the final result of the rendered water droplet was far from a realistic droplet, because they do not consider the gravitational effect in droplets. We propose a new metaball model for rendering water droplets placed on an arbitrary surface considering the gravitation and friction between droplet and plate. Our new metaball model uses a new vector field isosurface function to control the basic scalar metaball with respect to the norm of gravitational force. In several experiments, we could render a photo-realistic water droplets with natural-looking shadows by applying ray-tracing.

• Journal of the Korean Mathematical Society
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• v.48 no.4
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• pp.669-689
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• 2011

The notion of quasi-Einstein manifolds arose during the study of exact solutions of the Einstein field equations as well as during considerations of quasi-umbilical hypersurfaces. For instance, the Robertson-Walker spacetimes are quasi-Einstein manifolds. The object of the present paper is to study Lorentzian quasi-Einstein manifolds. Some basic geometric properties of such a manifold are obtained. The applications of Lorentzian quasi-Einstein manifolds to the general relativity and cosmology are investigated. Theories of gravitational collapse and models of Supernova explosions [5] are based on a relativistic fluid model for the star. In the theories of galaxy formation, relativistic fluid models have been used in order to describe the evolution of perturbations of the baryon and radiation components of the cosmic medium [32]. Theories of the structure and stability of neutron stars assume that the medium can be treated as a relativistic perfectly conducting magneto fluid. Theories of relativistic stars (which would be models for supermassive stars) are also based on relativistic fluid models. The problem of accretion onto a neutron star or a black hole is usually set in the framework of relativistic fluid models. Among others it is shown that a quasi-Einstein spacetime represents perfect fluid spacetime model in cosmology and consequently such a spacetime determines the final phase in the evolution of the universe. Finally the existence of such manifolds is ensured by several examples constructed from various well known geometric structures.