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Search Results: 1 - 10 of 175 matches for " Ilmu Byun "
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Cooperative Hybrid ARQ Protocols: Unified Frameworks for Protocol Analysis
Ilmu Byun,Kwang Soon Kim
Mathematics , 2008,
Abstract: Cooperative hybrid-ARQ (HARQ) protocols, which can exploit the spatial and temporal diversities, have been widely studied. The efficiency of cooperative HARQ protocols is higher than that of cooperative protocols, because retransmissions are only performed when necessary. We classify cooperative HARQ protocols as three decode-and-forward based HARQ (DF-HARQ) protocols and two amplified-and-forward based (AF-HARQ) protocols. To compare these protocols and obtain the optimum parameters, two unified frameworks are developed for protocol analysis. Using the frameworks, we can evaluate and compare the maximum throughput and outage probabilities according to the SNR, the relay location, and the delay constraint for the protocols.
A Tool Support for Design and Validation of Communication Protocol using State Transition Diagrams and Patterns
YoungJoon Byun
Journal of Software , 2007, DOI: 10.4304/jsw.2.3.56-63
Abstract: In this paper, we introduce a software tool to assist design and validation of a communication protocol specified in state transition diagrams and patterns. When protocol developers start development of a new system, they tend to describe the developing system with several highlevel description elements such as communicating blocks, communication paths, messages, and finite state machines. Then, they want to validate the correctness of their design as early as possible to find out any faults in the design. In this paper, we propose a software tool with which protocol developers can specify structural architectures and behavioral main operations of a protocol system through the graphical user interface. Then, the tool generates PROMELA code from the design specification to make it possible for the developers to validate the specification using the SPIN model checker. Meanwhile, we can specify a protocol system with more high-level abstraction using a pattern, a combination of several basic elements of the protocol. A pattern is a software reuse mechanism to apply a well-known solution of a recurring problem to the similar software developments repeatedly. In the paper, we also propose the usage of patterns in our tool. Using the pattern support, it will be possible for the tool to provide automatic pattern selection, instantiation, and composition. As results of this tool, protocol developers can describe a communication protocol more efficiently and reduce the development cost. Furthermore, they can have the confidence for the specification at the early stage of software development.
On the charged boson gas model as a theory of high Tc superconductivity
Yanghyun Byun
Physics , 2014,
Abstract: We construct a model of unconventional superconductors. The model is based on a hypothesis which assumes a short-lived bound state of electrons with a finite size and, moreover, in the free space. The hypothesis is a far-fetched one which is stated only qualitatively and in a minimal way. It still leads us to a condition under which the electron pairs may accumulate in one mobile state. The state turns out to be 'apparently' the highest of the occupied electron states. Therefore we call this condensation of electron pairs an 'apparent Fermi surface'. Since a charged boson gas is theoretically known to be a type 2 superconductor our model is also expected to be also such. In addition the transition temperature of our model is expected to be closely related to the Bose-Einstein condensation, similarly with the real high Tc superconductors. In particular in our model both a superconductor with a Fermi surface and the other without one are natural. There are also other theoretical works which have shown, not exploiting any specific binding mechanism, that tightly bound electrons may explain certain aspects of high Tc superconductors. To test our model we propose two types of experiments: a low energy electron-electron scattering and a photoemission on high Tc superconductors.
An exotic proposal on Cooper pairing in high-$T_c$ supercondutors
Yanghyun Byun
Physics , 2013,
Abstract: We propose that a Cooper pair in a high-$T_c$ superconductor might be in fact a bound system $\rm eex\bar x$ of two electrons, a particle $\rm x$ and its antiparticle. We assume $\rm eex\bar x$ is more massive than two free electrons. We observe that $\rm eex\bar x$ should be stable in a solid if it is in a low enough state in the solid. A solid which admits such a low state for $\rm eex\bar x$ has some properties which seem closely related to the behavior of HTS materials. The interaction of the $\rm x$-particle which binds the four particles into $\rm eex\bar x$ has been discussed. We also discuss the scale of the mass excess of $\rm eex\bar x$ relative to two free electrons. An experiment designed to detect a bound system of two electrons with a mass excess has been proposed.
Horizontal Displacement Of Curves In Bundle SO(n) -> SO_0(1,N) -> H^n
Taechang Byun
Mathematics , 2010,
Abstract: The Riemannian submersion $ \pi : \text{SO}_0(1,n) \to \mathbb{H}^n $ is a principal bundle and its fiber at $ \pi (e) $ is the imbedding of $\text{SO}(n)$ into $ \text{SO}_0(1,n) $, where $e$ is the identity of both $\text{SO}_0(1,n)$ and $\text{SO}(n)$. In this study, we associate a curve, starting from the identity, in $\text{SO}(n)$ to a given surface with boundary, diffeomorphic to the closed disk $D^2$, in $ \mathbb{H}^n $ such that the starting point and the ending point of the curve agree with those of the horizontal lifting of the boundary curve of the given surface with boundary, respectively, and that the length of the curve is as same as the area of the given surface with boundary.
A Generalization of Connes-Kreimer Hopf Algebra
Jungyoon Byun
Mathematics , 2005, DOI: 10.1063/1.1951591
Abstract: ``Bonsai'' Hopf algebras, introduced here, are generalizations of Connes-Kreimer Hopf algebras, which are motivated by Feynman diagrams and renormalization. We show that we can find operad structure on the set of bonsais. We introduce a new differential on these bonsai Hopf algebras, which is inspired by the tree differential. The cohomologies of these are computed here, and the relationship of this differential with the appending operation $*$ of Connes-Kreimer Hopf algebras is investigated.
Stability of nets of quadrics in $\mathbb{P}^5$ and associated discriminants
Sangho Byun
Mathematics , 2015,
Abstract: Let $S$ be a complete intersection surface defined by a net $\Lambda$ of quadrics in $\mathbb P^5$. In this paper we analyze GIT stability of nets of quadrics in $\mathbb P^5$ up to projective equivalence, and discuss some connections between a net of quadrics and the associated discriminant sextic curve. In particular, we prove that if $S$ is normal and the discriminant $\Delta(S)$ of $S$ is stable then $\Lambda$ is stable. And we prove that if $S$ has the reduced discriminant and $\Delta(S)$ is stable then $\Lambda$ is stable. Moreover, we prove that if $S$ has simple singularities then $\Delta(S)$ has simple singularities.
Area and holonomy of the principal $U(n)$ bundles over the dual of grassmannian manifolds
Taechang Byun
Mathematics , 2015,
Abstract: Consider the principal $U(n)$ bundles over the dual of Grassmann manifolds $U(n)\ra U(n,m)/U(m) \stackrel{\pi}\ra D_{n,m}$. Given a 2-dimensional subspace $\frakm' \subset \frakm $ $ \subset \mathfrak{u}(n,m), $ assume either $\frakm'$ is induced by $X,Y \in U_{m,n}(\bbc)$ with $X^{*}Y = \mu I_n$ for some $\mu \in \bbr$ or by $X,iX \in U_{m,n}(\bbc)$. Then $\frakm'$ gives rise to a complete totally geodesic surface $S$ in the base space. Furthermore, let $\gamma$ be a piecewise smooth, simple closed curve on $S$ parametrized by $0\leq t\leq 1$, and $\wt\gamma$ its horizontal lift on the bundle $U(n) \ra \pi^{-1}(S) \stackrel{\pi}{\rightarrow} S,$ which is immersed in $U(n) \ra U(n,m)/U(m) \stackrel{\pi}\ra D_{n,m} $. Then $$ \wt\gamma(1)= \wt\gamma(0) \cdot (e^{i \theta} I_n) \text{\hskip24pt or\hskip12pt} \wt\gamma(1)= \wt\gamma(0), $$ depending on whether $S$ is a complex submanifold or not, where $A(\gamma)$ is the area of the region on the surface $S$ surrounded by $\gamma$ and $\theta= 2 \cdot \tfrac{1}{n} A(\gamma).$
Biology inspires engineering
Reine Byun, Attila Becskei
Genome Biology , 2009, DOI: 10.1186/gb-2009-10-11-317
Abstract: Engineering has predominantly interacted with physics, while biology has played the second fiddle for a long time, even if biologically inspired contrivances, such as aircraft imitating bird flight, can be traced back as far as Classical Antiquity. A rapid intensification of the interplay between engineering and biology occurred in the second half of the 20th century, as evidenced by magnetic resonance imaging (MRI), the artificial heart pacemaker, and production of human recombinant insulin. The fifth annual meeting of Engineering Principles in Biology held recently in Hinxton, on the outskirts of Cambridge, presented engineering successes inspired by biology and explored the principles that have been extracted from the workings of living organisms to aid engineering, especially biomedical engineering. The most frequently recurring principles were optimal design, economy in design, and the harnessing of and coping with the variability inherent in biological systems.Robert Full (University of California, Berkeley, USA) opened the meeting with a discussion of his research in neuromechanical systems biology. By integrating disciplines encompassing biology, engineering and physics, he and his team have built models based on the locomotion of animals ranging from cockroaches to geckos. Stability analysis of these models revealed that mechanical features of the animals alone are sufficient to stabilize the moving body against perturbations due to destabilizing forces or the unevenness of the environment. Neuronal feedbacks are required only for complex locomotive actions. This research inspired the engineering of robots that can climb trees or overcome obstacles such as mud lakes by rotational paddling movements.The importance of inherent mechanics over control was echoed in the presentation by Raymond Goldstein (University of Cambridge, UK) who has studied the synchronous flagella-driven swimming of the colonial alga Volvox. Despite the lack of a nervous system, coordin
An inequality on solutions of heat equation
Byun Du-Won
Journal of Inequalities and Applications , 1998,
Abstract: Let be the solution of the initial value problem for the dimensional heat equation. Then, for any and for any , an inequality about and is obtained.
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