start-ver=1.4 cd-journal=joma no-vol=84 cd-vols= no-issue=3 article-no= start-page=755 end-page=781 dt-received= dt-revised= dt-accepted= dt-pub-year=2022 dt-pub=20220430 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=A novel update rule of HALS algorithm for nonnegative matrix factorization and Zangwill’s global convergence en-subtitle= kn-subtitle= en-abstract= kn-abstract=Nonnegative Matrix Factorization (NMF) has attracted a great deal of attention as an effective technique for dimensionality reduction of large-scale nonnegative data. Given a nonnegative matrix, NMF aims to obtain two low-rank nonnegative factor matrices by solving a constrained optimization problem. The Hierarchical Alternating Least Squares (HALS) algorithm is a well-known and widely-used iterative method for solving such optimization problems. However, the original update rule used in the HALS algorithm is not well defined. In this paper, we propose a novel well-defined update rule of the HALS algorithm, and prove its global convergence in the sense of Zangwill. Unlike conventional globally-convergent update rules, the proposed one allows variables to take the value of zero and hence can obtain sparse factor matrices. We also present two stopping conditions that guarantee the finite termination of the HALS algorithm. The practical usefulness of the proposed update rule is shown through experiments using real-world datasets. en-copyright= kn-copyright= en-aut-name=SanoTakehiro en-aut-sei=Sano en-aut-mei=Takehiro kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MigitaTsuyoshi en-aut-sei=Migita en-aut-mei=Tsuyoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TakahashiNorikazu en-aut-sei=Takahashi en-aut-mei=Norikazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=2 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= affil-num=3 en-affil=Graduate School of Natural Science and Technology, Okayama University kn-affil= en-keyword=Nonnegative matrix factorization kn-keyword=Nonnegative matrix factorization en-keyword=Hierarchical alternating least squares algorithm kn-keyword=Hierarchical alternating least squares algorithm en-keyword=Global convergence kn-keyword=Global convergence END start-ver=1.4 cd-journal=joma no-vol=10 cd-vols= no-issue=4 article-no= start-page=cnac033 end-page= dt-received= dt-revised= dt-accepted= dt-pub-year=2022 dt-pub=2022629 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=An algorithm for updating betweenness centrality scores of all vertices in a graph upon deletion of a single edge en-subtitle= kn-subtitle= en-abstract= kn-abstract=Betweenness centrality (BC) is a measure of the importance of a vertex in a graph, which is defined using the number of the shortest paths passing through the vertex. Brandes proposed an efficient algorithm for computing the BC scores of all vertices in a graph, which accumulates pair dependencies while traversing single-source shortest paths. Although this algorithm works well on static graphs, its direct application to dynamic graphs takes a huge amount of computation time because the BC scores must be computed from scratch every time the structure of graph changes. Therefore, various algorithms for updating the BC scores of all vertices have been developed so far. In this article, we propose a novel algorithm for updating the BC scores of all vertices in a graph upon deletion of a single edge. We also show the validity and efficiency of the proposed algorithm through theoretical analysis and experiments using various graphs obtained from synthetic and real networks. en-copyright= kn-copyright= en-aut-name=SatotaniYoshiki en-aut-sei=Satotani en-aut-mei=Yoshiki kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=MigitaTsuyoshi en-aut-sei=Migita en-aut-mei=Tsuyoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=TakahashiNorikazu en-aut-sei=Takahashi en-aut-mei=Norikazu kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= affil-num=1 en-affil=Graduate School of Natural Science and Technology, Okayama University , 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan kn-affil= affil-num=2 en-affil=Graduate School of Natural Science and Technology, Okayama University , 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan kn-affil= affil-num=3 en-affil=Graduate School of Natural Science and Technology, Okayama University , 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan kn-affil= END start-ver=1.4 cd-journal=joma no-vol=3 cd-vols= no-issue= article-no= start-page=1155 end-page=1160 dt-received= dt-revised= dt-accepted= dt-pub-year=2006 dt-pub=20068 dt-online= en-article= kn-article= en-subject= kn-subject= en-title= kn-title=A Real-life Test of Face Recognition System for Dialogue Interface Robot in Ubiquitous Environments en-subtitle= kn-subtitle= en-abstract= kn-abstract=

This paper discusses a face recognition system for a dialogue interface robot that really works in ubiquitous environments and reports an experimental result of real-life test in a ubiquitous environment. While a central module of the face recognition system is composed of the decomposed eigenface method, the system also includes a special face detection module and the face registration module. Since face recognition should work on images captured by a camera equipped on the interface robot, all the methods are tuned for the interface robot. The face detection and recognition modules accomplish robust face detection and recognition when one of the registered users is talking to the robot. Some interesting results are reported with careful analysis of a sufficient real-life experiment.

en-copyright= kn-copyright= en-aut-name=SakaueFumihiko en-aut-sei=Sakaue en-aut-mei=Fumihiko kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=1 ORCID= en-aut-name=KobayashiMakoto en-aut-sei=Kobayashi en-aut-mei=Makoto kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=2 ORCID= en-aut-name=MigitaTsuyoshi en-aut-sei=Migita en-aut-mei=Tsuyoshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=3 ORCID= en-aut-name=ShakunagaTakeshi en-aut-sei=Shakunaga en-aut-mei=Takeshi kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=4 ORCID= en-aut-name=SatakeJunji en-aut-sei=Satake en-aut-mei=Junji kn-aut-name= kn-aut-sei= kn-aut-mei= aut-affil-num=5 ORCID= affil-num=1 en-affil= kn-affil=Nagoya Institute of Technology affil-num=2 en-affil= kn-affil=Okayama University affil-num=3 en-affil= kn-affil=Okayama University affil-num=4 en-affil= kn-affil=Okayama University affil-num=5 en-affil= kn-affil=National Institute of Information and Communications Technology END