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Search Results: 1 - 10 of 27941 matches for " Dong Hwang "
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Renal cell carcionoma with synchronous metastases to the bladder and lung  [PDF]
Won Seok Jang, In Sang Hwang, Eu Chang Hwang, Seung Il Jung, Dong Deuk Kwon, Chan Choi
Case Reports in Clinical Medicine (CRCM) , 2013, DOI: 10.4236/crcm.2013.22026

Renal cell carcinoma can metastasize to virtually any organ, yet synchronous metastasis to the bladder is extremely rare. A 77-year-old woman presented with gross hematuria. Abdominal and chest computed tomography showed a bilateral renal masses, bladder dome mass, and multiple lung metastasis. Transurethral resection of the bladder tumor and sonography guided renal biopsy were performed. Both pathology diagnoses were clear cell renal cell carcinoma. Targeted therapy using pazopanib was administered to the patient without surgical resection of primary tumors and metastatic lung lesions. Herein, we report the synchronous metastasis of renal cell carcinoma to the bladder and lung.

Mathematical Modeling of the Actual Infiltration Process for the Preparation of C/C Composites  [PDF]
Gui Yung Chung, Dong Geun Hwang, Sung Soo Hong
Engineering (ENG) , 2012, DOI: 10.4236/eng.2012.412A117

The mathematical modeling for the preparation of C/C composites from propane by F-CVI (Forced-flow Chemical Vapor Infiltration) was studied. The modeling for the actual processes including overturning the preform in the middle of the deposition process was carried out. Effects of the interval and the number of overturning processes on the time changes of porosity distribution were observed. The actual deposition process could be continued longer by overturning the preform. Furthermore, the total amount of deposition increased twice when several times of overturning were applied. It was confirmed that a low concentration and a slow reaction rate are necessary for a uniform infiltration even when the preform is overturned in the middle of the process.

The Gromov width from Hamiltonian circle actions
Taekgyu Hwang,Dong Youp Suh
Mathematics , 2013,
Abstract: Let $(M, \omega)$ be a closed monotone symplectic manifold with a semifree Hamiltonian circle action with isolated maximum. We compute the Gromov width of $M$ using moment map.
A Method of Experimentally Probing Transeverse Momentum Dependent Distributions
Hwang, Dae Sung;Kim, Dong Soo
High Energy Physics - Phenomenology , 2007, DOI: 10.1016/j.physletb.2008.01.033
Abstract: We calculate the double spin asymmetry A_LL(x, y, z, P_hT) of pi^0 production with the spectator model and the model based on the factorization ansatz. We also calculate the double spin asymmetry for the integration over the range of (x,y,z) for the setups of the experiments of COMPASS, HERMES, and JLab. We find that the results are characteristically dependent on the model used. Therefore, we suggest that the measurements of the double spin asymmetry provides a method of experimentally probing the transeverse momentum dependent distributions.
Experimental Study on the Mechanical Properties of FRP Bars by Hybridizing with Steel Wires  [PDF]
Ji-Hyun Hwang, Dong-Woo Seo, Ki-Tae Park, Young-Jun You
Engineering (ENG) , 2014, DOI: 10.4236/eng.2014.67039

Many studies on fiber reinforced polymer composite bars, as a substitute for reinforcing bars, have been conducted to solve corrosion of steel in reinforced concrete structures since 1960s’. However, FRP Bars have a lower elastic modulus than steel rebar as a structural component of concrete structures. Material properties with brittleness fracture and low elastic modulus can be improved by combining cheaper steel than carbon or aramid fibers. In this study, prototypes of FRP Bars with inserted steel wires (i.e., “FRP Hybrid Bars”) were developed and their tensile performance was compared depending on the proportion and diameter of steel. The FRP Hybrid Bars were made by dividing them into D13 and D16 according to the diameter and proportion of inserted wires: GFRPs were combined with wires having different diameters of 0.5 mm, 1.0 mm, and 2.0 mm in the proportion of 10%, 30%, 50%, and 70%, respectively. As a result of tensile tests, the elastic modulus of FRP Hybrid Bars were improved as 20% - 190% in comparison with the fully GFRP Bars.

Semifree Hamiltonian circle actions on 6-dimensional symplectic manifolds with non-isolated fixed point set
Yunhyung Cho,Taekgyu Hwang,Dong Youp Suh
Mathematics , 2010,
Abstract: Let $(M, \omega)$ be a 6-dimensional closed symplectic manifold with a symplectic $S^1$-action with $M^{S^1} \neq \emptyset$ and $\dim M^{S^1} \leq 2$. Assume that $\omega$ is integral with a generalized moment map $\mu$. We first prove that the action is Hamiltonian if and only if $b_2^+(M_{\red})=1$, where $M_{\red}$ is any reduced space with respect to $\mu$. It means that if the action is non-Hamiltonian, then $b_2^+(M_{\red}) \geq 2$. Secondly, we focus on the case when the action is semifree and Hamiltonian. We prove that if $M^{S^1}$ consists of surfaces, then the number $k$ of fixed surfaces with positive genera is at most four. In particular, if the extremal fixed surfaces are spheres, then $k$ is at most one. Finally, we prove that $k \neq 2$ and we construct some examples of 6-dimensional semifree Hamiltonian $S^1$-manifolds such that $M^{S^1}$ contains $k$ surfaces of positive genera for $k = 0$ and 4. Examples with $k=1$ and 3 were given in \cite{L2}.
Dynamics of false vacuum bubbles: beyond the thin shell approximation
Jakob Hansen,Dong-il Hwang,Dong-han Yeom
Physics , 2009, DOI: 10.1088/1126-6708/2009/11/016
Abstract: We numerically study the dynamics of false vacuum bubbles which are inside an almost flat background; we assumed spherical symmetry and the size of the bubble is smaller than the size of the background horizon. According to the thin shell approximation and the null energy condition, if the bubble is outside of a Schwarzschild black hole, unless we assume Farhi-Guth-Guven tunneling, expanding and inflating solutions are impossible. In this paper, we extend our method to beyond the thin shell approximation: we include the dynamics of fields and assume that the transition layer between a true vacuum and a false vacuum has non-zero thickness. If a shell has sufficiently low energy, as expected from the thin shell approximation, it collapses (Type 1). However, if the shell has sufficiently large energy, it tends to expand. Here, via the field dynamics, field values of inside of the shell slowly roll down to the true vacuum and hence the shell does not inflate (Type 2). If we add sufficient exotic matters to regularize the curvature near the shell, inflation may be possible without assuming Farhi-Guth-Guven tunneling. In this case, a wormhole is dynamically generated around the shell (Type 3). By tuning our simulation parameters, we could find transitions between Type 1 and Type 2, as well as between Type 2 and Type 3. Between Type 2 and Type 3, we could find another class of solutions (Type 4). Finally, we discuss the generation of a bubble universe and the violation of unitarity. We conclude that the existence of a certain combination of exotic matter fields violates unitarity.
Responses of the Brans-Dicke field due to gravitational collapses
Dong-il Hwang,Dong-han Yeom
Physics , 2010, DOI: 10.1088/0264-9381/27/20/205002
Abstract: We study responses of the Brans-Dicke field due to gravitational collapses of scalar field pulses using numerical simulations. Double-null formalism is employed to implement the numerical simulations. If we supply a scalar field pulse, it will asymptotically form a black hole via dynamical interactions of the Brans-Dicke field. Hence, we can observe the responses of the Brans-Dicke field by two different regions. First, we observe the late time behaviors after the gravitational collapse, which include formations of a singularity and an apparent horizon. Second, we observe the fully dynamical behaviors during the gravitational collapse and view the energy-momentum tensor components. For the late time behaviors, if the Brans-Dicke coupling is greater (or smaller) than -1.5, the Brans-Dicke field decreases (or increases) during the gravitational collapse. Since the Brans-Dicke field should be relaxed to the asymptotic value with the elapse of time, the final apparent horizon becomes time-like (or space-like). For the dynamical behaviors, we observed the energy-momentum tensors around $\omega$ ~ -1.5. If the Brans-Dicke coupling is greater than -1.5, the $T_{uu}$ component can be negative at the outside of the black hole. This can allow an instantaneous inflating region during the gravitational collapse. If the Brans-Dicke coupling is less than -1.5, the oscillation of the $T_{vv}$ component allows the apparent horizon to shrink. This allows a combination that violates weak cosmic censorship. Finally, we discuss the implications of the violation of the null energy condition and weak cosmic censorship.
The no-boundary measure in scalar-tensor gravity
Dong-il Hwang,Hanno Sahlmann,Dong-han Yeom
Physics , 2011, DOI: 10.1088/0264-9381/29/9/095005
Abstract: In this article, we study the no-boundary wave function in scalar-tensor gravity with various potentials for the non-minimally coupled scalar field. Our goal is to calculate probabilities for the scalar field - and hence the effective gravitational coupling and cosmological constant - to take specific values. Most calculations are done in the minisuperspace approximation, and we use a saddle point approximation for the Euclidean action, which is then evaluated numerically. We find that for potentials that have several minima, none of them is substantially preferred by the quantum mechanical probabilities. We argue that the same is true for the stable and the runaway solution in the case of a dilaton-type potential. Technically, this is due to the inclusion of quantum mechanical effects (fuzzy instantons). These results are in contrast to the often held view that vanishing gravitation or cosmological constants would be exponentially preferred in quantum cosmology, and they may be relevant to the cosmological constant problem and the dilaton stabilization problem.
Dynamical formation and evolution of (2+1)-dimensional charged black holes
Dong-il Hwang,Hongbin Kim,Dong-han Yeom
Physics , 2011, DOI: 10.1088/0264-9381/29/5/055003
Abstract: In this paper, we investigate the dynamical formation and evolution of 2 + 1-dimensional charged black holes. We numerically study dynamical collapses of charged matter fields in an anti de Sitter background and note the formation of black holes using the double-null formalism. Moreover, we include re-normalized energy-momentum tensors assuming the S-wave approximation to determine thermodynamical back-reactions to the internal structures. If there is no semi-classical effects, the amount of charge determines the causal structures. If the charge is sufficiently small, the causal structure has a space-like singularity. However, as the charge increases, an inner Cauchy horizon appears. If we have sufficient charge, we see a space-like outer horizon and a time-like inner horizon, and if we give excessive charge, black hole horizons disappear. We have some circumstantial evidences that weak cosmic censorship is still satisfied, even for such excessive charge cases. Also, we confirm that there is mass inflation along the inner horizon, although the properties are quite different from those of four-dimensional cases. Semi-classical back-reactions will not affect the outer horizon, but they will affect the inner horizon. Near the center, there is a place where negative energy is concentrated. Thus, charged black holes in three dimensions have two types of curvature singularities in general: via mass inflation and via a concentration of negative energy. Finally, we classify possible causal structures.
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