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Analysis of a cellular automaton model for car traffic with a junction
Han, Yo-Sub,Ko, Sang-Ki Elsevier 2012 Theoretical computer science Vol.450 No.-
<P><B>Abstract</B></P><P>We propose a cellular automaton model that simulates traffic flow with a junction. We consider the form-one-lane rule and the merge-lane rule that decide which car moves ahead when two cars in two different lanes are in front of a junction. We simulate the proposed cellular automaton model for both rules, and generate fundamental diagrams and car distribution examples. Then, we analyze experimental results and demonstrate that the proposed model reflects the real world traffic flow with a junction according to the considered rules.</P>
Obtaining shorter regular expressions from finite-state automata
Han, Yo-Sub,Wood, Derick Elsevier 2007 Theoretical computer science Vol.370 No.1-3
<P><B>Abstract</B></P><P>We consider the use of state elimination to construct shorter regular expressions from finite-state automata (FAs). Although state elimination is an intuitive method for computing regular expressions from FAs, the resulting regular expressions are often very long and complicated. We examine the minimization of FAs to obtain shorter expressions first. Then, we introduce vertical chopping based on bridge states and horizontal chopping based on the structural properties of given FAs. We prove that we should not eliminate bridge states until we eliminate all non-bridge states to obtain shorter regular expressions. In addition, we suggest heuristics for state elimination that leads to shorter regular expressions based on vertical chopping and horizontal chopping.</P>
Alignment distance of regular tree languages
Han, Yo-Sub,Ko, Sang-Ki Elsevier 2019 Theoretical computer science Vol.787 No.-
<P><B>Abstract</B></P> <P>We consider the tree alignment distance problem between a tree and a regular tree language. The tree alignment distance is an alternative of the tree edit-distance, in which we construct an optimal alignment between two trees and compute its cost instead of directly computing the minimum-cost of tree edits. The alignment distance is crucial for understanding the structural similarity between trees.</P> <P>We, in particular, consider the following problem: given a tree <I>t</I> and a tree automaton recognizing a regular tree language <I>L</I>, find the most similar tree from <I>L</I> with respect to <I>t</I> under the tree alignment metric. Regular tree languages are commonly used in practice such as XML schema or bioinformatics. We propose an O ( m n ) time algorithm for computing the (ordered) alignment distance between <I>t</I> and <I>L</I> when the maximum degree of <I>t</I> and trees in <I>L</I> is bounded by a constant, and O ( m <SUP> n 2 </SUP> ) time algorithm when the maximum degree of trees in <I>L</I> is not bounded, where <I>m</I> is the size of <I>t</I> and <I>n</I> is the size of a finite tree automaton for <I>L</I>. We also study the case where a tree is not necessarily ordered, and show that the time complexity remains O ( m n ) if the maximum degree is bounded and MAX SNP-hard otherwise.</P>
Nondeterministic seedless oritatami systems and hardness of testing their equivalence
Han, Yo-Sub,Kim, Hwee,Ota, Makoto,Seki, Shinnosuke Springer-Verlag 2018 Natural Computing Vol.17 No.1
<P>The oritatami system (OS) is a model of computation by cotranscriptional folding, being inspired by the recent experimental success of RNA origami to self-assemble an RNA tile cotranscriptionally. The OSs implemented so far, including the binary counter and Turing machine simulator, are deterministic, that is, uniquely fold into one conformation, while nondeterminism is intrinsic in biomolecular folding. We introduce nondeterminism to the OS and propose a nondeterministic OS (NOS) that chooses an assignment of Boolean values nondeterministically and evaluates a logical formula on the assignment. This NOS is seedless in the sense that it does not require any initial conformation like the RNA origami. The NOS enables proving the coNP-hardness of deciding, given two NOSs, if there exists no conformation that one of them folds but the other does not.</P>
Ruleset optimization on isomorphic oritatami systems
Han, Yo-Sub,Kim, Hwee Elsevier 2019 Theoretical computer science Vol.785 No.-
<P><B>Abstract</B></P> <P>We study an optimization problem of a computational folding model, proving its hardness and proposing heuristic algorithms. RNA cotranscriptional folding refers to the phenomenon in which an RNA transcript folds upon itself while being synthesized out of a gene. An oritatami model (OM) is a computational model of this phenomenon that lets its sequence of beads (abstract molecules) fold cotranscriptionally by the interactions between beads, according to its ruleset. We study the problem of reducing the ruleset size, while keeping the terminal conformations geometrically the same. We first prove the hardness of finding the smallest ruleset, and then suggest two approaches that reduce the ruleset size efficiently.</P>
고강도 황동 , 알루미늄 청동 및 인청동합금의 용탕단조 조직과 기계적 성질에 관한 연구
한요섭(Yo Sub Han),이호인(Ho In Lee) 한국주조공학회 1999 한국주조공학회지 Vol.19 No.6
The microstructures and mechanical properties of high strength yellow brass, Al bronze and Sn bronze alloys fabricated by gravity die casting and squeeze casting were investigated. A rapid cooling of casting was enhanced by pressure applied during solidification of Cu alloys, the cooling rate of casting was more great for high strength yellow brass alloy than other Cu alloys. Grain size and phases of the squeeze cast products become refined to 1/2 level compared to gravity die castings. Squeeze cast Al bronze and high strength yellow brass has about 10-20% higher yield and tensile strength and slighter decreased or nearly same elongation, compared to gravity die cast ones. Sn bronze has nearly same strength and hardness, but shows increased in elongation, compared to gravity die cast ones. (Received November 1, 1999)
AlSi7Mg 알루미늄 합금의 초정 구형화에 대한 주조조건의 영향
한요섭 ( Yo Sub Han ),이호인 ( Ho In Lee ),이재철 ( Jae Chul Lee ) 한국주조공학회 2003 한국주조공학회지 Vol.23 No.1
N/A Semisolid forming requires alloys with non-dendritic microstructure of the thixotropy. Recently, low pouring temperture method without stirring, i.e. liquidus casting has been found out new fabrication method of the semisolid metals. Effects of melt superheat and mold conditions on the globulization of primary Al of AlSi_7Mg alloy were investigated in gravity casting process without stirring. The microstructures of primary Al as function of melt superheat and mold temperature show globular, rosette and dendritic shapes. The conditions for globular microstructure of primary Al were low melt superheat < 35 K and low mold temperature < 500 K. The thermal conditions for globular microstructure of primary Al were undercooled melt at early solidification stages and slow cooling < 0.6 K/s. It was found that the initial microstructure was maintained throughout the solidification and the globules of primary Al can be obtained by high nucleation of fine and spherical nuclei due to enhanced undercooling of melt.