Search results for: Yoshio Okamoto

Items from 1 to 20 out of 153 results

article

Preparation of cellulose derivative bearing bulky 4‐(2‐benzothienyl)phenylcarbamate substituents as chiral stationary phase for enantioseparation

Fan Wang, Yuqing Wang, Yixuan Min, Junqing Li, more

Chirality > 34 > 5 > 701 - 710

A novel cellulose derivative bearing bulky 4‐(2‐benzothienyl)phenylcarbamate substituents (Cel‐1) was readily synthesized by carbamoylation followed by Suzuki–Miyaura coupling reaction. The corresponding coated‐type chiral stationary phase (CSP) was prepared on basis of the derivative, and its chiral recognition ability was then evaluated by high‐performance liquid chromatography (HPLC). The chiral...

article

Synthesis of poly(phenylacetylene)s containing chiral phenylethyl carbamate residues as coated‐type CSPs with high solvent tolerability

Yanli Zhou, Ruiqi Zhu, Chunhong Zhang, Xudong Liu, more

Chirality > 32 > 5 > 547 - 555

Two novel helical poly(phenylacetylene) derivatives containing chiral phenylethyl carbamate residues in the end of each side chain (PPA‐S and PPA‐R) were synthesized by polymerization of the corresponding phenylacetylene monomers using Rh(nbd)BPh₄ as a catalyst in DMF. The enantioseparation properties of the polymers were evaluated as coated‐type chiral stationary phases (CSPs) for high‐performance...

article

Minimum-Cost b-Edge Dominating Sets on Trees

Takehiro Ito, Naonori Kakimura, Naoyuki Kamiyama, Yusuke Kobayashi, more

Algorithmica > 2019 > 81 > 1 > 343-366

In this paper, we consider the minimum-cost b-edge dominating set problem. This is a generalization of the edge dominating set problem, but the computational complexity for trees is an astonishing open problem. We make steps toward the resolution of this open problem in the following three directions. (1) We give the first combinatorial polynomial-time algorithm for paths. Prior to our work, the polynomial-time...

article

Reconfiguration of maximum-weight b-matchings in a graph

Takehiro Ito, Naonori Kakimura, Naoyuki Kamiyama, Yusuke Kobayashi, more

Journal of Combinatorial Optimization > 2019 > 37 > 2 > 454-464

Consider a graph such that each vertex has a nonnegative integer capacity and each edge has a positive integer weight. Then, a b-matching in the graph is a multi-set of edges (represented by an integer vector on edges) such that the total number of edges incident to each vertex is at most the capacity of the vertex. In this paper, we study a reconfiguration variant for maximum-weight b-matchings:...

article

Immobilization of helical poly(phenylacetylene)s having l-phenylalanine ethyl ester pendants onto silica gel as chiral stationary phases for HPLC

Yanli Zhou, Chunhong Zhang, Qianqian Geng, Lijia Liu, more

Polymer > 2017 > 131 > C > 17-24

Novel one-handed helical copoly(phenylacetylene)s bearing a small amount of 3-(triethoxysilyl)propyl residues (CPAs 1–4) were synthesized, and efficiently chemically immobilized onto silica gel by the intermolecular polycondensation of the triethoxysilyl groups. Their chiral recognition abilities were evaluated as immobilized-type chiral stationary phases (CSPs) for high performance liquid chromatography...

article

Efficient stabilization of cooperative matching games

Takehiro Ito, Naonori Kakimura, Naoyuki Kamiyama, Yusuke Kobayashi, more

Theoretical Computer Science > 2017 > 677 > C > 69-82

Cooperative matching games have drawn much interest partly because of the connection with bargaining solutions in the networking environment. However, it is not always guaranteed that a network under investigation gives rise to a stable bargaining outcome. To address this issue, we consider a modification process, called stabilization, that yields a network with stable outcomes, where the modification...

article

Computing the $$L_1$$ L 1 Geodesic Diameter and Center of a Polygonal Domain

Sang Won Bae, Matias Korman, Joseph S. B. Mitchell, Yoshio Okamoto, more

Discrete & Computational Geometry > 2017 > 57 > 3 > 674-701

For a polygonal domain with h holes and a total of n vertices, we present algorithms that compute the $$L_1$$ L 1 geodesic diameter in $$O(n^2+h^4)$$ O ( n 2 + h 4 ) time and the $$L_1$$ L 1 geodesic center in $$O((n^4+n^2 h^4)\alpha (n))$$ O ( ( n 4 + n 2 h 4 ) α ( n ) ) time, respectively, where $$\alpha (\cdot )$$ α ( · ) denotes...

chapter

Linear-Time Counting Algorithms for Independent Sets in Chordal Graphs

Yoshio Okamoto, Takeaki Uno, Ryuhei Uehara

Lecture Notes in Computer Science > Graph-Theoretic Concepts in Computer Science > Regular Papers > 433-444

We study some counting and enumeration problems for chordal graphs, especially concerning independent sets. We first provide the following efficient algorithms for a chordal graph: (1) a linear-time algorithm for counting the number of independent sets; (2) a linear-time algorithm for counting the number of maximum independent sets; (3) a polynomial-time algorithm for counting the number of independent...

article

Synthesis and chiral recognition of amylose derivatives bearing regioselective phenylcarbamate substituents at 2,6- and 3-positions for high-performance liquid chromatography

Jun Shen, Geng Li, Zhongzheng Yang, Yoshio Okamoto

Journal of Chromatography A > 2016 > 1467 > C > 199-205

Eighteen novel amylose derivatives bearing different phenylcarbamate substituents at 2,6- and 3-positions of a glucose ring were synthesized through the regioselective protection at 2- and 6-positions using a bulky trialkylsilyl chloride. Their chiral recognition abilities were then evaluated as the chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) after coating them...

chapter

The Traveling Salesman Problem with Few Inner Points

Vladimir G. Deineko, Michael Hoffmann, Yoshio Okamoto, Gerhard J. Woeginger

Lecture Notes in Computer Science > Computing and Combinatorics > Data Structures and Algorithms II > 268-277

We study the traveling salesman problem (TSP) in the 2-dimensional Euclidean plane. The problem is NP-hard in general, but trivial if the points are in convex position. In this paper, we investigate the influence of the number of inner points (i.e., points in the interior of the convex hull) on the computational complexity of the problem. We give two simple algorithms for this problem. The first one...

chapter

Minimum and Maximum against k Lies

Michael Hoffmann, Jiří Matoušek, Yoshio Okamoto, Philipp Zumstein

Lecture Notes in Computer Science > Algorithm Theory - SWAT 2010 > 139-149

A neat 1972 result of Pohl asserts that ⌈3n/2 ⌉− 2 comparisons are sufficient, and also necessary in the worst case, for finding both the minimum and the maximum of an n-element totally ordered set. The set is accessed via an oracle for pairwise comparisons. More recently, the problem has been studied in the context of the Rényi–Ulam liar games, where the oracle may give up to k false answers. For...

chapter

Moving Vertices to Make Drawings Plane

Xavier Goaoc, Jan Kratochvíl, Yoshio Okamoto, Chan-Su Shin, more

Lecture Notes in Computer Science > Graph Drawing > Papers > 101-112

In John Tantalo’s on-line game Planarity the player is given a non-plane straight-line drawing of a planar graph. The aim is to make the drawing plane as quickly as possible by moving vertices. In this paper we investigate the related problem MinMovedVertices which asks for the minimum number of vertex moves. First, we show that MinMovedVertices is NP-hard and hard to approximate. Second, we establish...

chapter

The Minimum Weight Triangulation Problem with Few Inner Points

Michael Hoffmann, Yoshio Okamoto

Lecture Notes in Computer Science > Parameterized and Exact Computation > 200-212

We propose to look at the computational complexity of 2-dimensional geometric optimization problems on a finite point set with respect to the number of inner points (that is, points in the interior of the convex hull). As a case study, we consider the minimum weight triangulation problem. Finding a minimum weight triangulation for a set of n points in the plane is not known to be NP-hard nor solvable...

chapter

Drawing (Complete) Binary Tanglegrams

Kevin Buchin, Maike Buchin, Jaroslaw Byrka, Martin Nöllenburg, more

Lecture Notes in Computer Science > Graph Drawing > Papers > 324-335

A binary tanglegram is a pair 〈S,T〉 of binary trees whose leaf sets are in one-to-one correspondence; matching leaves are connected by inter-tree edges. For applications, for example in phylogenetics, it is essential that both trees are drawn without edge crossings and that the inter-tree edges have as few crossings as possible. It is known that finding a drawing with the minimum number of crossings...

chapter

Matroid Representation of Clique Complexes

Kenji Kashiwabara, Yoshio Okamoto, Takeaki Uno

Lecture Notes in Computer Science > Computing and Combinatorics > Graph Theory/Algorithms II > 192-201

In this paper, we approach the quality of a greedy algorithm for the maximum weighted clique problem from the viewpoint of matroid theory. More precisely, we consider the clique complex of a graph (the collection of all cliques of the graph) and investigate the minimum number k such that the clique complex of a given graph can be represented as the intersection of k matroids. This number k can be...

chapter

Fair Cost Allocations under Conflicts — A Game-Theoretic Point of View —

Yoshio Okamoto

Lecture Notes in Computer Science > Algorithms and Computation > 10A Game Theory and Randomized Algorithm > 686-695

We study the cost allocation problem when the players are involved in a conflict situation. More formally, we consider a minimum coloring game, introduced by Deng, Ibaraki & Nagamochi, and provide algorithms for the core, the τ-value, the nucleolus and the Shapley value on some classes of graphs. The investigation gives several insights to the relationship of algorithm theory with cooperative...

chapter

Querying Two Boundary Points for Shortest Paths in a Polygonal Domain

Sang Won Bae, Yoshio Okamoto

Lecture Notes in Computer Science > Algorithms and Computation > 1054-1063

We consider a variant of two-point Euclidean shortest path query problem: given a polygonal domain, build a data structure for two-point shortest path query, provided that query points always lie on the boundary of the domain. As a main result, we show that a logarithmic-time query for shortest paths between boundary points can be performed using $\tilde{O}(n^5)$ preprocessing time and $\tilde{O}(n^5)$...

chapter

Core Stability of Minimum Coloring Games

Thomas Bietenhader, Yoshio Okamoto

Lecture Notes in Computer Science > Graph-Theoretic Concepts in Computer Science > Graph Classes and NP Hardness > 389-401

In cooperative game theory, a characterization of games with stable cores is known as one of the most notorious open problems. We study this problem for a special case of the minimum coloring games, introduced by Deng, Ibaraki & Nagamochi, which arises from a cost allocation problem when the players are involved in conflict. In this paper, we show that the minimum coloring game on a perfect graph...

chapter

Greedy Edge-Disjoint Paths in Complete Graphs

Paz Carmi, Thomas Erlebach, Yoshio Okamoto

Lecture Notes in Computer Science > Graph-Theoretic Concepts in Computer Science > Regular Papers > 143-155

The maximum edge-disjoint paths problem (MEDP) is one of the most classical NP-hard problems. We study the approximation ratio of a simple and practical approximation algorithm, the shortest-path-first greedy algorithm (SGA), for MEDP in complete graphs. Previously, it was known that this ratio is at most 54. Adapting results by Kolman and Scheideler [Proceedings of SODA, 2002, pp. 184–193], we show...

chapter

On Listing, Sampling, and Counting the Chordal Graphs with Edge Constraints

Shuji Kijima, Masashi Kiyomi, Yoshio Okamoto, Takeaki Uno

Lecture Notes in Computer Science > Computing and Combinatorics > Graph Theory and Algorithms > 458-467

We discuss the problems to list, sample, and count the chordal graphs with edge constraints. The objects we look at are chordal graphs sandwiched by a given pair of graphs where we assume at least one of the input pair is chordal. The setting is a natural generalization of chordal completions and deletions. For the listing problem, we give an efficient algorithm running in polynomial time per output...

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CHIRAL STATIONARY PHASE (16)
HPLC (14)
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Search results for: Yoshio Okamoto

Preparation of cellulose derivative bearing bulky 4‐(2‐benzothienyl)phenylcarbamate substituents as chiral stationary phase for enantioseparation

Synthesis of poly(phenylacetylene)s containing chiral phenylethyl carbamate residues as coated‐type CSPs with high solvent tolerability

Minimum-Cost b-Edge Dominating Sets on Trees

Reconfiguration of maximum-weight b-matchings in a graph

Immobilization of helical poly(phenylacetylene)s having l-phenylalanine ethyl ester pendants onto silica gel as chiral stationary phases for HPLC

Efficient stabilization of cooperative matching games

Computing the $$L_1$$ L 1 Geodesic Diameter and Center of a Polygonal Domain

Linear-Time Counting Algorithms for Independent Sets in Chordal Graphs

Synthesis and chiral recognition of amylose derivatives bearing regioselective phenylcarbamate substituents at 2,6- and 3-positions for high-performance liquid chromatography

The Traveling Salesman Problem with Few Inner Points

Minimum and Maximum against k Lies

Moving Vertices to Make Drawings Plane

The Minimum Weight Triangulation Problem with Few Inner Points

Drawing (Complete) Binary Tanglegrams

Matroid Representation of Clique Complexes

Fair Cost Allocations under Conflicts — A Game-Theoretic Point of View —

Querying Two Boundary Points for Shortest Paths in a Polygonal Domain

Core Stability of Minimum Coloring Games

Greedy Edge-Disjoint Paths in Complete Graphs

On Listing, Sampling, and Counting the Chordal Graphs with Edge Constraints

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