Hiroshi Ishikawa

109 papers A* 5A 1B 4C 22Misc 3Journal 25Unranked 46

Year	Rank	Type	Title / Venue / Authors
2025	J	`jnl`	Research and Development of Test Automation Maturity Model Building and Assessment Methods for E2E Testing. Softw. Daiju Kato, Ayane Mogi, Hiroshi Ishikawa, Yasufumi Takama
2024	—	`book`	Hypothesis Generation and Interpretation - Design Principles and Patterns for Big Data Applications Hiroshi Ishikawa
2024	J	`jnl`	Quality Control Methods Using Quality Characteristics in Development and Operations. Digit. Daiju Kato, Hiroshi Ishikawa
2023	C	`conf`	Time-Series Estimation of the Best Time to View Seasonal Organisms Using Geotagged Tweets and Co-occurring Words. MEDES Yusuke Takamori, Junya Sato, Ryoga Sato, Asahi Iha, Masaki Endo, Kenji Terada, Shigeyoshi Ohno, Hiroshi Ishikawa
2022	J	`jnl`	Estimating deflation representing people spreading in stream data and estimating a specific position. Int. J. Intell. Inf. Database Syst. Takuma Toyoshima, Masaki Endo, Takuo Kikuchi, Shigeyoshi Ohno, Hiroshi Ishikawa
2022	J	`jnl`	Estimating the Best Time to View Cherry Blossoms Using Time-Series Forecasting Method. Mach. Learn. Knowl. Extr. Tomonari Horikawa, Munenori Takahashi, Masaki Endo, Shigeyoshi Ohno, Masaharu Hirota, Hiroshi Ishikawa
2022	J	`jnl`	Performance Evaluation of High Availability Database Systems Using Low-latency I/O Devices. J. Inf. Process. Shinji Fujiwara, Riro Senda, Isamu Kaneko, Hiroshi Ishikawa
2022	C	`conf`	Quality Classification for Testing Work in DevOps. MEDES Daiju Kato, Ayumu Shimizu, Hiroshi Ishikawa
2022	J	`jnl`	Spot extraction and analysis using an automatic detection method of tourist spots using SNS. Int. J. Intell. Inf. Database Syst. Munenori Takahashi, Masaki Endo, Shigeyoshi Ohno, Masaharu Hirota, Hiroshi Ishikawa
2021	C	`conf`	Attractive Area Detection of Telemetry corresponding to Command. MEDES Yukio Yamamoto, Hiroshi Ishikawa
2021	C	`conf`	Numerical estimation of new COVID-19 positive cases using time series analysis by machine learning. MEDES Yusuke Takamori, Riku Watanabe, Daiju Kato, Masaki Endo, Hiroshi Ishikawa
2021	J	`jnl`	Social Big Data: Case Studies. Trans. Large Scale Data Knowl. Centered Syst. Hiroshi Ishikawa, Yasushi Miyata
2021	J	`jnl`	Social Big Data: Concepts and Theory. Trans. Large Scale Data Knowl. Centered Syst. Hiroshi Ishikawa, Yukio Yamamoto
2020	—	`conf`	A Method for Ranking Tourist Attractions based on Geo-tagged Photographs and Image Quality Assessment. WIMS Jhih-Yu Lin, Shu-Mei Wen, Masaharu Hirota, Tetsuya Araki, Hiroshi Ishikawa
2020	—	`conf`	Automatic detection method of tourist spots using SNS. WIMS Munenori Takahashi, Masaki Endo, Shigeyoshi Ohno, Masaharu Hirota, Hiroshi Ishikawa
2020	—	`conf`	Concept Drift Detection on Data Stream for Revising DBSCAN Cluster. WIMS Yasushi Miyata, Hiroshi Ishikawa
2020	—	`conf`	Coverage Analysis Method Using Quality Characteristics. IWESQ@APSEC Daiju Kato, Hiroshi Ishikawa
2020	—	`conf`	Data Management in Japanese Planetary Explorations for Big Data Era. WIMS Yukio Yamamoto, Hiroshi Ishikawa
2020	—	`conf`	Estimating Deflation Representing People Spreading in Stream Data. WIMS Takuma Toyoshima, Masaki Endo, Takuo Kikuchi, Shigeyoshi Ohno, Hiroshi Ishikawa
2020	J	`jnl`	Less-Known Tourist Attraction Discovery Based on Geo-Tagged Photographs. Mach. Learn. Knowl. Extr. Jhih-Yu Lin, Shu-Mei Wen, Masaharu Hirota, Tetsuya Araki, Hiroshi Ishikawa
2020	—	`ed.`	Transactions on Large-Scale Data- and Knowledge-Centered Systems XLV - Special Issue on Data Management and Knowledge Extraction in Digital Ecosystems Trans. Large-Scale Data- and Knowledge-Centered Systems Abdelkader Hameurlain, A Min Tjoa, Richard Chbeir, Yannis Manolopoulos, Hiroshi Ishikawa, Sergio Ilarri, Apostolos Papadopoulos
2019	C	`conf`	Applications of Generalized Difference Method for Hypothesis Generation to Social Big Data in Concept and Real Spaces. MEDES Hiroshi Ishikawa, Daiju Kato, Masaki Endo, Masaharu Hirota
2019	J	`jnl`	Crystalizing Effect of Simulated Annealing on Boltzmann Machine. J. Adv. Comput. Intell. Intell. Informatics Hiroki Shibata, Hiroshi Ishikawa, Yasufumi Takama
2019	C	`conf`	Detection of Car Abnormal Vibration using Machine Learning. ISM Wataru Hashimoto, Masaharu Hirota, Tetsuya Araki, Yukio Yamamoto, Masashi Egi, Morihiro Hirate, Masao Maura, Hiroshi Ishikawa
2019	C	`conf`	Generating Distributed Representation of User Movement for Extracting Detour Spots. MEDES Masaharu Hirota, Tetsuya Oda, Masaki Endo, Hiroshi Ishikawa
2019	C	`conf`	Measurement-Based Cost Calculation Method Focusing on CPU Architecture for Database Query Optimization. MEDES Tsuyoshi Tanaka, Hiroshi Ishikawa
2019	—	`conf`	Test Management Based on Quality Characteristics (short paper). IWESQ@APSEC Daiju Kato, Ayako Okuyama, Hiroshi Ishikawa
2019	C	`conf`	Tourism application with CNN-Based Classification specialized for cultural information. iiWAS Takuma Hirotsu, Masaharu Hirota, Tetsuya Araki, Masaki Endo, Hiroshi Ishikawa
2018	C	`conf`	Accelerating analysis of frequently gathered data with continuous density based clustering. MEDES Yasushi Miyata, Hiroshi Ishikawa
2018	J	`jnl`	Analyzing Potential of Personal Values-Based User Modeling for Long Tail Item Recommendation. J. Adv. Comput. Intell. Intell. Informatics Yasufumi Takama, Yu-Sheng Chen, Ryori Misawa, Hiroshi Ishikawa
2018	C	`conf`	Consideration on crystalizing simulated annealing for boltzmann machine. MEDES Hiroki Shibata, Hiroshi Ishikawa, Yasufumi Takama
2018	—	`conf`	Evaluation on Applicability of Measurement-Based Join Cost Calculation Method Using Different Generation CPUs. iThings/GreenCom/CPSCom/SmartData Tsuyoshi Tanaka, Hiroshi Ishikawa
2018	C	`conf`	Generalized difference method for generating integrated hypotheses in social big data. MEDES Hiroshi Ishikawa, Daiju Kato, Masaki Endo, Masaharu Hirota
2018	—	`conf`	Personal Values-based User Modeling from Browsing History of Reviews. IUI Workshops Yasufumi Takama, Suzuto Shimizu, Hiroshi Ishikawa
2018	C	`conf`	Predicting user gender on social media sites using geographical information. MEDES Rio Miura, Masaharu Hirota, Daiju Kato, Tetsuya Araki, Masaki Endo, Hiroshi Ishikawa
2018	C	`ed.`	Proceedings of the 10th International Conference on Management of Digital EcoSystems, MEDES 2018, Tokyo, Japan, September 25-28, 2018 MEDES Richard Chbeir, Hiroshi Ishikawa, Kazutoshi Sumiya, Kenji Hatano, Mario Koeppen
2018	C	`conf`	Scale-free dynamics of human behavior in personal computer operations. MEDES Masashi Egi, Hiroshi Ishikawa
2018	—	`conf`	Utilization of Information Interpolation using Geotagged Tweets. IUI Workshops Masaki Endo, Masaharu Hirota, Hiroshi Ishikawa
2018	—	`conf`	Where Is the Memorable Travel Destinations? SocInfo (2) Miho Toyoshima, Masaharu Hirota, Daiju Kato, Tetsuya Araki, Hiroshi Ishikawa
2017	C	`conf`	Analyzing Relationship of Words Using Biased LexRank from Geotagged Tweets. MEDES Takahito Tsuchida, Daiju Kato, Masaki Endo, Masaharu Hirota, Tetsuya Araki, Hiroshi Ishikawa
2017	C	`conf`	Analyzing Travel Behavior Using Multi-label Classification From Twitter. MEDES Kazuki Takahashi, Daiju Kato, Masaki Endo, Tetsuya Araki, Masaharu Hirota, Hiroshi Ishikawa
2017	—	`conf`	Introduction of Sparkline as Snippet to Context Search Engine Result Page. TAAI Yasufumi Takama, Koichi Yamaguchi, Lieu-Hen Chen, Hiroshi Ishikawa
2017	—	`conf`	Multilingualization of Restaurant Menu by Analogical Description. CEA@IJCAI Kensuke Nobumoto, Daiju Kato, Masaki Endo, Masaharu Hirota, Hiroshi Ishikawa
2017	J	`jnl`	Walking Route Recommender for Supporting a Walk as Health Promotion. IEICE Trans. Inf. Syst. Yasufumi Takama, Wataru Sasaki, Takafumi Okumura, Chi-Chih Yu, Lieu-Hen Chen, Hiroshi Ishikawa
2016	J	`jnl`	Application of search engine focusing on trend-related queries to market of data. Intell. Decis. Technol. Shogo Kori, Koichi Yamaguchi, Yanjun Zhu, Satoru Takiguchi, Yu Kato, Hiroshi Ishikawa, Yasufumi Takama
2016	J	`jnl`	Design of Context Search Engine Based on Analysis of User's Search Intentions. J. Adv. Comput. Intell. Intell. Informatics Yasufumi Takama, Yanjun Zhu, Shogo Kori, Koichi Yamaguchi, Lieu-Hen Chen, Hiroshi Ishikawa
2016	—	`conf`	How to Find Accessible Free Wi-Fi at Tourist Spots in Japan. SocInfo (1) Keisuke Mitomi, Masaki Endo, Masaharu Hirota, Shohei Yokoyama, Yoshiyuki Shoji, Hiroshi Ishikawa
2016	—	`conf`	Inferring Tourist Behavior and Purposes of a Twitter User. PRICAI Workshops Yuya Nozawa, Masaki Endo, Yo Ehara, Masaharu Hirota, Shohei Yokoyama, Hiroshi Ishikawa
2016	—	`conf`	Visualizing High-Risk Paths using Geo-tagged Social Data for Disaster Mitigation. LBSN@SIGSPATIAL/GIS Masaki Kanno, Yo Ehara, Masaharu Hirota, Shohei Yokoyama, Hiroshi Ishikawa
2015	—	`conf`	Disease Event Detection based on Deep Modality Analysis. ACL (Student Research Workshop) Yoshiaki Kitagawa, Mamoru Komachi, Eiji Aramaki, Naoaki Okazaki, Hiroshi Ishikawa
2015	—	`conf`	EBSCAN: An Entanglement-based Algorithm for Discovering Dense Regions in Large Geo-social Data Streams with Noise. LBSN@SIGSPATIAL/GIS Shohei Yokoyama, Ágnes Bogárdi-Mészöly, Hiroshi Ishikawa
2015	—	`conf`	Improving Chinese Grammatical Error Correction with Corpus Augmentation and Hierarchical Phrase-based Statistical Machine Translation. NLP-TEA@ACL/IJCNLP Yinchen Zhao, Mamoru Komachi, Hiroshi Ishikawa
2015	B	`conf`	NFC-based Tangible User Interface for Information Curation and Its Application to Analogy Game. KES Yasufumi Takama, Tomohiro Ito, Hiroshi Ishikawa
2015	—	`conf`	Visualizing Shooting Spots using Geo-tagged Photographs from Social Media Sites. EGC Masaharu Hirota, Masaki Endo, Shohei Yokoyama, Hiroshi Ishikawa
2015	—	`conf`	Walking Route Recommendation System for Taking a Walk as Health Promotion. WI-IAT (1) Yasufumi Takama, Wataru Sasaki, Takafumi Okumura, Chi-Chih Yu, Lieu-Hen Chen, Hiroshi Ishikawa
2015	—	`conf`	Who caught a cold ? - Identifying the subject of a symptom. ACL (1) Shin Kanouchi, Mamoru Komachi, Naoaki Okazaki, Eiji Aramaki, Hiroshi Ishikawa
2014	—	`conf`	An image estimation method by header information in JPEG 2000 codestreams and its application to image identification. APCCAS Katsuma Takimoto, Toshiyuki Dobashi, Hiroshi Ishikawa, Hitoshi Kiya
2014	—	`conf`	Can geo-tags on flickr draw coastlines? SIGSPATIAL/GIS Masaki Omori, Masaharu Hirota, Hiroshi Ishikawa, Shohei Yokoyama
2014	—	`conf`	Detecting Relations of Hotspots using Geo-tagged Photographs in Social Media Sites. GeoRich@SIGMOD Masaharu Hirota, Motohiro Shirai, Hiroshi Ishikawa, Shohei Yokoyama
2014	C	`conf`	Extracting a Chinese Learner Corpus from the Web: Grammatical Error Correction for Learning Chinese as a Foreign Language with Statistical Machine Translation. ICCE Yinchen Zhao, Mamoru Komachi, Hiroshi Ishikawa
2014	—	`conf`	Introduction of Search Engine Focusing on Trend-Related Queries to Market of Data. ICDM Workshops Yanjun Zhu, Yasufumi Takama, Yu Kato, Shogo Kori, Hiroshi Ishikawa
2014	Misc	`conf`	Proposal of time series data retrieval with user feedback. GrC Chengzhu Yin, Hiroshi Ishikawa, Yasufumi Takama
2014	C	`conf`	Towards Better Land Cover Classification Using Geo-tagged Photographs. ISM Hirotaka Oba, Masaharu Hirota, Richard Chbeir, Hiroshi Ishikawa, Shohei Yokoyama
2013	—	`conf`	A method of Area of Interest and Shooting Spot Detection using Geo-tagged Photographs. COMP@SIGSPATIAL Motohiro Shirai, Masaharu Hirota, Hiroshi Ishikawa, Shohei Yokoyama
2013	—	`conf`	SOM-Based Visualization for Classifying Large-Scale Sensing Data of Moonquakes. 3PGCIC Yasumichi Goto, Ryuhei Yamada, Yukio Yamamoto, Shohei Yokoyama, Hiroshi Ishikawa
2012	J	`jnl`	A Robust Clustering Method for Missing Metadata in Image Search Results. Inf. Media Technol. Masaharu Hirota, Naoki Fukuta, Shohei Yokoyama, Hiroshi Ishikawa
2012	J	`jnl`	A Robust Clustering Method for Missing Metadata in Image Search Results. J. Inf. Process. Masaharu Hirota, Naoki Fukuta, Shohei Yokoyama, Hiroshi Ishikawa
2012	—	`conf`	Algorithms to Improve Tag Clouds. ICETET Ágnes Bogárdi-Mészöly, András Rövid, Hiroshi Ishikawa
2012	—	`conf`	Discovering multiple HotSpots using geo-tagged photographs. SIGSPATIAL/GIS Motohiro Shirai, Masaharu Hirota, Shohei Yokoyama, Naoki Fukuta, Hiroshi Ishikawa
2011	B	`conf`	Parallel Distributed Rendering of HTML5 Canvas Elements. ICWE Shohei Yokoyama, Hiroshi Ishikawa
2010	—	`ch.`	Constraint-Based Clustering of Image Search Results Using Photo Metadata and Low-Level Image Features. Computer and Information Science Masaharu Hirota, Shohei Yokoyama, Naoki Fukuta, Hiroshi Ishikawa
2010	—	`conf`	Proposal of Spatiotemporal Data Extraction and Visualization System Based on Wikipedia for Application to Earth Science. ACIS-ICIS Akihiro Okamoto, Shohei Yokoyama, Naoki Fukuta, Hiroshi Ishikawa
2009	J	`jnl`	Guest Editors' Introduction: Multimedia Metadata and Semantic Management. IEEE Multim. Richard Chbeir, Harald Kosch, Frédéric Andrès, Hiroshi Ishikawa
2007	—	`conf`	Incrementally-Updatable Stream Processors for XPath Queries based on Merging Automata via Ordered Hash-keys. DEXA Workshops Hajime Takekawa, Hiroshi Ishikawa
2006	J	`jnl`	Galois' Lattices as a Classification Technique for Image Retrieval. Inf. Media Technol. Erwan Loisant, José Martinez, Hiroshi Ishikawa, Kaoru Katayama
2006	J	`jnl`	Multi-vector feature space based on pseudo-Euclidean space and oblique basis. Multim. Tools Appl. Yasuo Yamane, Tadashi Hoshiai, Hiroshi Tsuda, Manabu Ohta, Kaoru Katayama, Hiroshi Ishikawa
2005	Misc	`conf`	An Access Control Method Based on the Prefix Labeling Scheme for XML Repositories. ADC Shohei Yokoyama, Manabu Ohta, Kaoru Katayama, Hiroshi Ishikawa
2005	—	`conf`	Building a Navigation Structure from a Fuzzy Relationship for Image Retrieval. ICDE Workshops Erwan Loisant, José Martinez, Hiroshi Ishikawa, Manabu Ohta, Kaoru Katayama
2005	—	`conf`	On Mining XML Structures Based on Statistics. KES (1) Hiroshi Ishikawa, Shohei Yokoyama, Manabu Ohta, Kaoru Katayama
2005	J	`jnl`	Semantic Image Retrieval based on Ontology and Relevance Model - A Preliminary Study. J. Digit. Inf. Manag. Ernest Weke Maina, Manabu Ohta, Kaoru Katayama, Hiroshi Ishikawa
2004	B	`conf`	A Peer-to-Peer Approach to Parallel Association Rule Mining. KES Hiroshi Ishikawa, Yasuo Shioya, Takeshi Omi, Manabu Ohta, Kaoru Katayama
2004	—	`conf`	Multi-Vector Feature Space Based on Pseudo-Euclidean Space and Oblique Basis for Similarity Searches of Images. CVDB Yasuo Yamane, Tadashi Hoshiai, Hiroshi Tsuda, Kaoru Katayama, Manabu Ohta, Hiroshi Ishikawa
2004	—	`conf`	Overlapping Clustering Methods for a Japanese Meta Search Engine. Databases and Applications Manabu Ohta, Hirokazu Narita, Kaoru Katayama, Hiroshi Ishikawa
2003	B	`conf`	Active Knowledge Mining for Intelligent Web Page Management. KES Hiroshi Ishikawa, Manabu Ohta, Shohei Yokoyama, Takuya Watanabe, Kaoru Katayama
2002	C	`conf`	An Intelligent Web Recommendation System: A Web Usage Mining Approach. ISMIS Hiroshi Ishikawa, Toshiyuki Nakajima, Tokuyo Mizuhara, Shohei Yokoyama, Junya Nakayama, Manabu Ohta, Kaoru Katayama
2002	—	`conf`	On the Effectiveness of Web Usage Mining for Page Recommendation and Restructuring. Web, Web-Services, and Database Systems Hiroshi Ishikawa, Manabu Ohta, Shohei Yokoyama, Junya Nakayama, Kaoru Katayama
2002	J	`jnl`	Web usage mining approaches to page recommendation and restructuring. Intell. Syst. Account. Finance Manag. Hiroshi Ishikawa, Manabu Ohta, Shohei Yokoyama, Junya Nakayama, Kaoru Katayama
2001	C	`conf`	A Decentralized XML Database Approach to Electronic Commerce. ISADS Hiroshi Ishikawa, Manabu Ohta
2001	—	`conf`	An Active Web-based Distributed Database System for E-Commerce. WebDyn@ICDT Hiroshi Ishikawa, Manabu Ohta
2001	—	`conf`	Document Warehousing: A Document-Intensive Application of A Multimedia Database. RIDE-DM Hiroshi Ishikawa, Manabu Ohta, Koki Kato
2001	—	`conf`	On Business Modeling, Distributed Processing, and Data Compression for E-Commerce. IMSA Hiroshi Ishikawa, Shohei Yokoyama, Seiji Isshiki, Manabu Ohta
2001	Misc	`conf`	Querying web distributed databases for XML-based E-businesses: requirement analysis, design, and implementation. ADC Hiroshi Ishikawa, Manabu Ohta
2001	—	`conf`	Xanadu: XML- and Active-Database-Unified Approach to Distributed E-Commerce. DEXA Workshop Hiroshi Ishikawa, Shohei Yokoyama, Seiji Isshiki, Manabu Ohta
1999	A*	`conf`	Document Warehousing Based on a Multimedia Database System. ICDE Hiroshi Ishikawa, Kazumi Kubota, Yasuo Noguchi, Koki Kato, Miyuki Ono, Naomi Yoshizawa, Yasuhiko Kanemasa
1999	—	`conf`	The Design of a Query Language for XML Data. DEXA Workshop Hiroshi Ishikawa, Kazumi Kubota, Yasuhiko Kanemasa, Yasuo Noguchi
1998	—	`conf`	A Document Warehouse: A Multimedia Database Approach. DEXA Workshop Hiroshi Ishikawa, Kazumi Kubota, Yasuo Noguchi, Koki Kato, Miyuki Ono, Naomi Yoshizawa, Akiko Kanaya
1998	A*	`conf`	An Extended Object-Oriented Database Approach to Networked Multimedia Applications. ICDE Hiroshi Ishikawa, Koki Kato, Miyuki Ono, Naomi Yoshizawa, Kazumi Kubota, Akiko Kanaya
1998	—	`conf`	XQL: A Query Language for XML Data. QL Hiroshi Ishikawa, Kazumi Kubota, Yasuhiko Kanemasa
1997	—	`conf`	An Extended Object-Oriented Approach to a Multimedia Database System for Networked Applications. DEXA Workshop Hiroshi Ishikawa, Koki Kato, Miyuki Ono, Naomi Yoshizawa, Kazumi Kubota, Akiko Kanaya
1996	A*	`conf`	A Next Generation Industry Multimedia Database System. ICDE Hiroshi Ishikawa, Koki Kato, Miyuki Ono, Naomi Yoshikawa, Kazumi Kubota, Akiko Kondo
1996	J	`jnl`	An Object-Oriented Database System Jasmine: Implementation, Application, and Extension. IEEE Trans. Knowl. Data Eng. Hiroshi Ishikawa, Yasuo Yamane, Yoshio Izumida, Nobuaki Kawato
1995	C	`conf`	An autonomous decentralized database system based on scripts and active objects. ISADS Hiroshi Ishikawa, Kazumi Kubota
1995	J	`jnl`	The Design and Implementation of an Interoperable Database System Based on Scripts and Active Objects. IEICE Trans. Inf. Syst. Hiroshi Ishikawa, Kazumi Kubota, Koki Kato
1993	A*	`conf`	An Active Object-Oriented Database: A Multi-Paradigm Approach to Constraint Management. VLDB Hiroshi Ishikawa, Kazumi Kubota
1993	J	`jnl`	The Model, Language, and Implementation of an Object-Oriented Multimedia Knowledge Base Management System. ACM Trans. Database Syst. Hiroshi Ishikawa, Fumio Suzuki, Fumihiko Kozakura, Akifumi Makinouchi, Mika Miyagishima, Yoshio Izumida, Masaaki Aoshima, Yasuo Yamane
1992	—	`conf`	An Object-Oriented Database System and its View Mechanism for Schema Integration. Future Databases Hiroshi Ishikawa, Yoshio Izumida, Nobuaki Kawato, Tatsuya Hayashi
1987	J	`jnl`	KID: Designing A Knowledge-Based Natural Language Interface. IEEE Expert Hiroshi Ishikawa, Yoshio Izumida, Toshiaki Yoshino, Tadashi Hoshiai, Akifumi Makinouchi
1986	A*	`conf`	A Knowledge-Based Approach to Design a Portable Natural Language Interface to Database Systems. ICDE Hiroshi Ishikawa, Yoshio Izumida, Toshiaki Yoshino, Tadashi Hoshiai, Akifumi Makinouchi
1985	A	`conf`	A Natural Language Interface Using A World Model. EACL Yoshio Izumida, Hiroshi Ishikawa, Toshiaki Yoshino, Tadashi Hoshiai, Akifumi Makinouchi