Search results for "competition"

Hits ?▲	Authors	Title	Venue	Year	Link
9	Max Barth, Daniel Dietsch, Matthias Heizmann, Marie-Christine Jakobs	Ultimate TestGen: Test-Case Generation with Automata-based Software Model Checking (Competition Contribution).	FASE	2024	DBLP DOI BibTeX RDF
9	Hans Gersbach, Matthew O. Jackson, Philippe Muller, Oriol Tejada	Electoral competition with costly policy changes: A dynamic perspective.	J. Econ. Theory	2023	DBLP DOI BibTeX RDF
9	Kai-Hao Yang, Alexander Zentefis	Regulating oligopolistic competition.	J. Econ. Theory	2023	DBLP DOI BibTeX RDF
9	Daniel Andrei, Bruce Ian Carlin	Schumpeterian competition in a Lucas economy.	J. Econ. Theory	2023	DBLP DOI BibTeX RDF
9	Chen Lyu	Information design for selling search goods and the effect of competition.	J. Econ. Theory	2023	DBLP DOI BibTeX RDF
9	Federico Vaccari	Competition in costly talk.	J. Econ. Theory	2023	DBLP DOI BibTeX RDF
9	Dimitri J. Papageorgiou, Stuart M. Harwood, Francisco Trespalacios	Pooling problems under perfect and imperfect competition.	Comput. Chem. Eng.	2023	DBLP DOI BibTeX RDF
9	Muhammad Ali Al-Radhawi, Domitilla Del Vecchio, Eduardo D. Sontag	Identifying Competition Phenotypes in Synthetic Biochemical Circuits.	IEEE Control. Syst. Lett.	2023	DBLP DOI BibTeX RDF
9	Chen Chen 0101, Sudipto Dasgupta, Thanh D. Huynh, Ying Xia	Product Market Competition and Corporate Relocations: Evidence from the Supply Chain.	Manag. Sci.	2023	DBLP DOI BibTeX RDF
9	Jean-Etienne de Bettignies, Hua Fang Liu, David T. Robinson, Bulat Gainullin	Competition and Innovation in Markets for Technology.	Manag. Sci.	2023	DBLP DOI BibTeX RDF
9	Danmo Lin	Accelerability vs. Scalability: R&D Investment Under Financial Constraints and Competition.	Manag. Sci.	2023	DBLP DOI BibTeX RDF
9	Helena Fornwagner, Monika Pompeo, Nina Serdarevic	Choosing Competition on Behalf of Someone Else.	Manag. Sci.	2023	DBLP DOI BibTeX RDF
9	Maxime C. Cohen, Alexandre Jacquillat, Juan Camilo Serpa, Michael Benborhoum	Managing Airfares Under Competition: Insights from a Field Experiment.	Manag. Sci.	2023	DBLP DOI BibTeX RDF
9	Silke J. Forbes, Renáta Kosová	Does Competition Benefit Complements? Evidence from Airlines and Hotels.	Manag. Sci.	2023	DBLP DOI BibTeX RDF
9	Odilon Câmara, Nan Jia, Joseph Raffiee	Reputation, Competition, and Lies in Labor Market Recommendations.	Manag. Sci.	2023	DBLP DOI BibTeX RDF
9	Stephanie F. Cheng, Christine Cuny, Hao Xue	Disclosure and Competition for Capital.	Manag. Sci.	2023	DBLP DOI BibTeX RDF
9	Yixin (Iris) Wang, Jun Li 0049, Ravi Anupindi	Manufacturing and Regulatory Barriers to Generic Drug Competition: A Structural Model Approach.	Manag. Sci.	2023	DBLP DOI BibTeX RDF
9	Xin Zhang, Wei Thoo Yue, Yugang Yu, Xiong Zhang 0001	How to monetize data: An economic analysis of data monetization strategies under competition.	Decis. Support Syst.	2023	DBLP DOI BibTeX RDF
9	Bingxin Chen, Lifei Kuang, Wei He	Cheerleading athlete's action safety in sports competition based on Kohonen neural network.	Neural Comput. Appl.	2023	DBLP DOI BibTeX RDF
9	Yinggan Tang, Fei Zhou	An improved imperialist competition algorithm with adaptive differential mutation assimilation strategy for function optimization.	Expert Syst. Appl.	2023	DBLP DOI BibTeX RDF
9	Hongjun Peng, Wenting Sun, Tao Pang	Optimal Strategies for A Dual-Channel Farming Supply Chain with Horizontal Competition and Cooperation.	Asia Pac. J. Oper. Res.	2023	DBLP DOI BibTeX RDF
9	Fengying Hu, Zhenglong Zhou	Information services and omnichannel retailing strategy choices of e-commerce platforms with supplier competition.	Electron. Commer. Res.	2023	DBLP DOI BibTeX RDF
9	Shugang Li 0001, Xiaoru Ji, Beiyan Zhang, Ying Liu, Hanyu Lu, Zhaoxu Yu	Modeling and evolution analysis of patent competition strategy system of AI enterprises.	J. Intell. Fuzzy Syst.	2023	DBLP DOI BibTeX RDF
9	Jiaguo Liu, Huida Zhao, Yibing Lyu, Xiaohang Yue	The provision strategy of blockchain service under the supply chain with downstream competition.	Ann. Oper. Res.	2023	DBLP DOI BibTeX RDF
9	Yuguang Song, Jia Liu, Wen Zhang, Jian Li	Blockchain's role in e-commerce sellers' decision-making on information disclosure under competition.	Ann. Oper. Res.	2023	DBLP DOI BibTeX RDF
9	Hui Lei 0003, Jingru Wang, Honglin Yang, Hong Wan	The impact of ex-post information sharing on a two-echelon supply chain with horizontal competition and capacity constraint.	Ann. Oper. Res.	2023	DBLP DOI BibTeX RDF
9	Yi Tao, Xiaofan Lai, Shaorui Zhou	Information sharing in a transparent supply chain with transportation disruptions and supplier competition.	Ann. Oper. Res.	2023	DBLP DOI BibTeX RDF
9	Guoqi Chai, Yufeng Zheng, Lingting Lei, Zongqi Yao, Mengyu Chen, Xiaoli Zhang	A novel solution for extracting individual tree crown parameters in high-density plantation considering inter-tree growth competition using terrestrial close-range scanning and photogrammetry technology.	Comput. Electron. Agric.	2023	DBLP DOI BibTeX RDF
9	Yinying Kong, Niangqiu Huang, Haodong Deng, Junwen Feng, Xingyi Liang, Weisi Lv, Jingyi Liu	Text classification in fair competition law violations using deep learning.	Frontiers Appl. Math. Stat.	2023	DBLP DOI BibTeX RDF
9	Tongshui Xia, Yuyan Wang, Lingxue Lv, Liang Shen, T. C. E. Cheng	Financing decisions of low-carbon supply Chain under Chain-to-Chain competition.	Int. J. Prod. Res.	2023	DBLP DOI BibTeX RDF
9	Chong Huang, Shaofu Du, Bill Wang, Wenzhi Tang	Accelerate or hinder it? Manufacturer transformation under competition and carbon emission trading.	Int. J. Prod. Res.	2023	DBLP DOI BibTeX RDF
9	Li Hu, Shaofu Du, Lei Wang, Wenzhi Tang	Differentiated premium membership mechanism in platform competition.	Int. J. Prod. Res.	2023	DBLP DOI BibTeX RDF
9	Ting Zhang, Peimiao Li, Ningning Wang	Multi-period price competition of blockchain-technology-supported and traditional platforms under network effect.	Int. J. Prod. Res.	2023	DBLP DOI BibTeX RDF
9	Adetunji David Ajimakin, V. Susheela Devi	The Competing Genes Evolutionary Algorithm: Avoiding Genetic Drift Through Competition, Local Search, and Majority Voting.	IEEE Trans. Evol. Comput.	2023	DBLP DOI BibTeX RDF
9	Carlos Fernando Joventino, Raphael de Abreu Alves e Silva, Jonathas H. M. Pereira, Jean Mimar Santa Cruz Yabarrena, André Schneider de Oliveira	A Sim-to-real Practical Approach to Teach Robotics into K-12: A Case Study of Simulators, Educational and DIY Robotics in Competition-based Learning.	J. Intell. Robotic Syst.	2023	DBLP DOI BibTeX RDF
9	Gabriele Roggi, Salvatore Meraglia, Marco Lovera	Leonardo Drone Contest Autonomous Drone Competition: Overview, Results, and Lessons Learned from Politecnico di Milano Team.	J. Intell. Robotic Syst.	2023	DBLP DOI BibTeX RDF
9	Lovro Markovic, Frano Petric, Antun Ivanovic, Jurica Goricanec, Marko Car, Matko Orsag, Stjepan Bogdan	Towards A Standardized Aerial Platform: ICUAS'22 Firefighting Competition.	J. Intell. Robotic Syst.	2023	DBLP DOI BibTeX RDF
9	Xueli Zhang, Defeng Yang, Can Li	Search engine marketing for different competition modes - Interfirm and intrafirm.	RAIRO Oper. Res.	2023	DBLP DOI BibTeX RDF
9	Junchang Li, Jiantong Zhang, Hongzhen Song	Bilateral "pricing" for consultation companies' competition considering customers' switching behavior.	RAIRO Oper. Res.	2023	DBLP DOI BibTeX RDF
9	Jianchang Fan, Nana Wan, Zhun Li, Hong Fu	Quality and price competition in a duopoly under product liability and traceability.	RAIRO Oper. Res.	2023	DBLP DOI BibTeX RDF
9	Seyed Parsa Parvasi, Ata Allah Taleizadeh, Leopoldo Eduardo Cárdenas-Barrón	Retail price competition of domestic and international companies: A bi-level game theoretical optimization approach.	RAIRO Oper. Res.	2023	DBLP DOI BibTeX RDF
9	Yael Perlman	What type of contract should e-tailers offer sellers when facing internal competition.	Central Eur. J. Oper. Res.	2023	DBLP DOI BibTeX RDF
9	Jason L. Harman, Jaelle Scheuerman	Simple rules outperform machine learning for personnel selection: insights from the 3rd annual SIOP machine learning competition.	Discov. Artif. Intell.	2023	DBLP DOI BibTeX RDF
9	Ali Asghar Talebi, Hossein Rashmanlou, Seyed Hossein Sadati	Interval-valued Intuitionistic Fuzzy Competition Graph.	J. Multiple Valued Log. Soft Comput.	2023	DBLP BibTeX RDF
9	Dong-Lin Chen, Min Fu, Meng-Di Yao, Lei Wang	Two-level cooperation and competition strategies of government and technology service platforms: considering government subsidies.	Kybernetes	2023	DBLP DOI BibTeX RDF
9	Jing Yu, Zonghui Song, Chi Zhou	Self-supporting or third-party? The optimal delivery strategy selection decision for e-tailers under competition.	Kybernetes	2023	DBLP DOI BibTeX RDF
9	Yilu Liu, Jing Liu 0006, Kai Wu 0003	Cost-effective competition on social networks: A multi-objective optimization perspective.	Inf. Sci.	2023	DBLP DOI BibTeX RDF
9	Sheng Qi, Rui Wang 0017, Tao Zhang 0033, Nan-Jiang Dong 0001	Cooperative coevolutionary competition swarm optimizer with perturbation for high-dimensional multi-objective optimization.	Inf. Sci.	2023	DBLP DOI BibTeX RDF
9	Decui Liang, Weiyi Duan	Large-scale three-way group consensus decision considering individual competition behavior in social networks.	Inf. Sci.	2023	DBLP DOI BibTeX RDF
9	Geoff Sutcliffe, Martin Desharnais	The 11th IJCAR automated theorem proving system competition - CASC-J11.	AI Commun.	2023	DBLP DOI BibTeX RDF
9	Youwei Yang, Daiyong Wu, Chuansheng Shen, Jian Gao, Fengping Lu	Impacts of fear effect and nonlocal competition on a diffusive prey-predator model with delay.	J. Appl. Math. Comput.	2023	DBLP DOI BibTeX RDF
9	Suparna Dash, Subhas Khajanchi	Dynamics of intraguild predation with intraspecies competition.	J. Appl. Math. Comput.	2023	DBLP DOI BibTeX RDF
9	Kento Suemitsu, Isao Nambu	Effects of Data Including Visual Presentation and Rest Time on Classification of Motor Imagery of Using Brain-Computer Interface Competition Datasets.	IEEE Access	2023	DBLP DOI BibTeX RDF
9	Takuya Yoshihiro, Simo Hosio	Simulation-Based IoT Stream Data Pricing Incorporating Seller Competition and Buyer Demands.	IEEE Access	2023	DBLP DOI BibTeX RDF
9	Shuchih Ernest Chang, Ching Yu	Exploring Gamification for Live-Streaming Shopping - Influence of Reward, Competition, Presence and Immersion on Purchase Intention.	IEEE Access	2023	DBLP DOI BibTeX RDF
9	David Gallarta Sáenz, Javier Rico-Azagra, Montserrat Gil-Martínez	Learning Enhancement of Control Engineering: A Competition-Based Case.	IEEE Access	2023	DBLP DOI BibTeX RDF
9	Éric Piette, Dennis J. N. J. Soemers, Matthew Stephenson, Cameron Browne	The 2022 Ludii AI competition.	J. Int. Comput. Games Assoc.	2023	DBLP DOI BibTeX RDF
9	Yun Hui Lin, Qingyun Tian, Shaojun Liu	Service expansion for chained business facilities under congestion and market competition.	Comput. Oper. Res.	2023	DBLP DOI BibTeX RDF
9	Chengyi Liu, Yu Tao, Geng Chen, Song Xing, Kah Hou Teng	A novel user clustering and a low-complexity power allocation in multi-user and multi-cluster NOMA system via Stackelberg game competition.	Ad Hoc Networks	2023	DBLP DOI BibTeX RDF
9	Heeju Hwang, Soojeen Jang, Yanghon Chung, Hangyeol Seo	How do technological intensity and competition affect R&D persistence?: a new approach using cost asymmetry model.	Technol. Anal. Strateg. Manag.	2023	DBLP DOI BibTeX RDF
9	Pu-yan Nie, Chan Wang, Hong-xing Wen	Technology standard under Cournot competition.	Technol. Anal. Strateg. Manag.	2023	DBLP DOI BibTeX RDF
9	Haojia He, Xingzheng Ai, Ganfu Wang, Li Zhong	Manufacturer rebate strategy under chain to chain competition.	J. Oper. Res. Soc.	2023	DBLP DOI BibTeX RDF
9	Ning Li, Xue Qiao, Zheng Wang 0021	Joint markdown, ordering and freshness-keeping policy under demand competition between new and old products.	J. Oper. Res. Soc.	2023	DBLP DOI BibTeX RDF
9	Xiaoxue Ma, Liguang Chen, Weijie Wu, Yang Liu 0193, Weiliang Qiao, Laihao Ma	Comparative Analysis of Arctic-Related Strategies at the National Level: Competition and Collaboration.	Syst.	2023	DBLP DOI BibTeX RDF
9	Wanying Li, Zaijin You, Kaiyuan Lou, Zhaowei Wang 0008	Development of GPCN Model to Assess Domestic and International Competition Patterns of Coastal Container Ports in China.	Syst.	2023	DBLP DOI BibTeX RDF
9	Inga Ulnicane	Against the new space race: global AI competition and cooperation for people.	AI Soc.	2023	DBLP DOI BibTeX RDF
9	Crismary Ospina Gallego, Maria Nuria Lloret Romero, Valeria Herrero Ruiz	Present and past of competition versus sharing economy in the music live industry.	Int. J. Arts Technol.	2023	DBLP DOI BibTeX RDF
9	Chi Zhou 0001, He Li, Linlin Zhang, Yufei Ren	Optimal Recommendation Strategies for AI-Powered E-Commerce Platforms: A Study of Duopoly Manufacturers and Market Competition.	J. Theor. Appl. Electron. Commer. Res.	2023	DBLP DOI BibTeX RDF
9	Paramita Koley, Aurghya Maiti, Sourangshu Bhattacharya, Niloy Ganguly	Offsetting Unequal Competition Through RL-Assisted Incentive Schemes.	IEEE Trans. Comput. Soc. Syst.	2023	DBLP DOI BibTeX RDF
9	Zikai Yin, Tong Xu 0001, Ziwei Zhao, Aakas Zhiyuli, Xueying Li, Enhong Chen	Competition Analysis on Enterprise Ecosystems via Multiview Relational Hypergraph Embedding.	IEEE Trans. Comput. Soc. Syst.	2023	DBLP DOI BibTeX RDF
9	Lukas Jäger, Roberto de Souza Baptista, Chiara Basla, Patricia Capsi-Morales, Yong Kuk Kim, Shuro Nakajima, Cristina Piazza, Michael Sommerhalder, Luca Tonin, Giacomo Valle, Robert Riener, Roland Sigrist	How the CYBATHLON Competition Has Advanced Assistive Technologies.	Annu. Rev. Control. Robotics Auton. Syst.	2023	DBLP DOI BibTeX RDF
9	Yasong Li, Zheng Zhou, Chuang Sun 0001, Jun Peng, Asoke K. Nandi, Ruqiang Yan 0001	Life-cycle modeling driven by coupling competition degradation for remaining useful life prediction.	Reliab. Eng. Syst. Saf.	2023	DBLP DOI BibTeX RDF
9	Wenting Huang, Xiaofang Duan, Lijuan Qin, Junpyo Park	Fitness-based mobility enhances the maintenance of biodiversity in the spatial system of cyclic competition.	Appl. Math. Comput.	2023	DBLP DOI BibTeX RDF
9	Yulia Kareeva, Artem A. Sedakov, Mengke Zhen	Influence in social networks with stubborn agents: From competition to bargaining.	Appl. Math. Comput.	2023	DBLP DOI BibTeX RDF
9	Changwen Li, Bin Cao, Yong-Wu Zhou, T. C. Edwin Cheng	Pricing, coalition stability, and profit allocation in the pull assembly supply chains under competition.	OR Spectr.	2023	DBLP DOI BibTeX RDF
9	Yuan Xue, Jinli Xu, Yuting Ding	Spatiotemporal Dynamics of a Diffusive Immunosuppressive Infection Model with Nonlocal Competition and Crowley-Martin Functional Response.	Axioms	2023	DBLP DOI BibTeX RDF
9	Kaihong Zhao	Existence and Stability of a Nonlinear Distributed Delayed Periodic AG-Ecosystem with Competition on Time Scales.	Axioms	2023	DBLP DOI BibTeX RDF
9	Aurelien T. Mozipo, John M. Acken	Residual vulnerabilities to power side channel attacks of lightweight ciphers cryptography competition finalists.	IET Comput. Digit. Tech.	2023	DBLP DOI BibTeX RDF
9	Hao Shen 0001, Yinsheng Song, Jing Wang 0071, Ju H. Park 0001	$\mathcal {H}_{\infty }$ State Estimation for PDT-Switched Coupled Neural Networks Under Round-Robin Protocol: A Cooperation-Competition-Based Mechanism.	IEEE Trans. Netw. Sci. Eng.	2023	DBLP DOI BibTeX RDF
9	Dawei Zhao, Shudong Li, Zhen Wang 0004, Haipeng Peng	Cooperation and Competition Coupled Diffusion of Multi-Feature on Multiplex Networks and Its Control.	IEEE Trans. Netw. Sci. Eng.	2023	DBLP DOI BibTeX RDF
9	Yuliya Oparina, Andrei Savilov	Coherent Spontaneous Emission from Short Electron Bunches: Competition between Different Transverse Waveguide Modes.	Symmetry	2023	DBLP DOI BibTeX RDF
9	Yinghua Song, Xiaoyan Sang, Zhe Wang, Hongqian Xu	An Option Game Model of Supplier R&D Co-Competition under Uncertainty.	Symmetry	2023	DBLP DOI BibTeX RDF
9	Mahmoud H. DarAssi, Muhammad Altaf Khan, Fatmawati, Marei Saeed Alqarni	Analysis of the Competition System Using Parameterized Fractional Differential Equations: Application to Real Data.	Symmetry	2023	DBLP DOI BibTeX RDF
9	Danmei Chen	Upper Bounds of the Generalized Competition Indices of Symmetric Primitive Digraphs with d Loops.	Symmetry	2023	DBLP DOI BibTeX RDF
9	Takashi Minato, Ryuichiro Higashinaka, Kurima Sakai, Tomo Funayama, Hiromitsu Nishizaki, Takayuki Nagai	Design of a competition specifically for spoken dialogue with a humanoid robot.	Adv. Robotics	2023	DBLP DOI BibTeX RDF
9	Yoshiaki Mizuchi, Hiroki Yamada, Tetsunari Inamura	Evaluation of an online human-robot interaction competition platform based on virtual reality - case study in RCAP2021.	Adv. Robotics	2023	DBLP DOI BibTeX RDF
9	Xindong Si, Zhen Wang 0008, Yingjie Fan 0003, Xia Huang, Hao Shen 0001	Sampled-Data-Based Bipartite Leader-Follower Synchronization of Cooperation-Competition Neural Networks via Interval-Scheduled Looped-Functions.	IEEE Trans. Circuits Syst. I Regul. Pap.	2023	DBLP DOI BibTeX RDF
9	Mengji Shi, Lei Shi 0012, Weihao Li, Boxian Lin	Bipartite Flocking Control for Multi-Agent Systems With Cooperation-Competition Interactions and Random Packet Dropouts.	IEEE Trans. Circuits Syst. II Express Briefs	2023	DBLP DOI BibTeX RDF
9	Bara Kim, Jeongsim Kim, Yan Su, Chia-Li Wang	Proofs of conjectures on the competition between observable and unobservable servers.	Queueing Syst. Theory Appl.	2023	DBLP DOI BibTeX RDF
9	Shuhua Chang, Haiteng Ma, Pengwen Hou, Li Cao	Who should adopt blockchain? The interplay between blockchain adoption and online channel under competition.	Electron. Commer. Res. Appl.	2023	DBLP DOI BibTeX RDF
9	Yuelin Shen	Price and advertising competition in an online marketplace: The tradeoff between quality and cost.	Electron. Commer. Res. Appl.	2023	DBLP DOI BibTeX RDF
9	Yingqian Zhang 0001, Laurens Bliek, Paulo da Costa 0001, Reza Refaei Afshar, Robbert Reijnen, Tom Catshoek, Daniël Vos, Sicco Verwer, Fynn Schmitt-Ulms, André Hottung, Tapan Shah 0001, Meinolf Sellmann, Kevin Tierney, Carl Perreault-Lafleur, Caroline Leboeuf, Federico Bobbio, Justine Pepin, Warley Almeida Silva, Ricardo Gama, Hugo L. Fernandes, Martin Zaefferer, Manuel López-Ibáñez 0001, Ekhine Irurozki	The first AI4TSP competition: Learning to solve stochastic routing problems.	Artif. Intell.	2023	DBLP DOI BibTeX RDF
9	Chao Ding, Wael Jabr, Hong Guo	Electoral Competition in the Age of Social Media: The Role of Social Media Influencers.	MIS Q.	2023	DBLP DOI BibTeX RDF
9	Kui Du, Hüseyin Tanriverdi	Does IT Enable Collusion or Competition: Examining the Effects of IT on Service Pricing in Multimarket Multihospital Systems.	MIS Q.	2023	DBLP DOI BibTeX RDF
9	Lei Shi 0012, Qingchen Liu, Jinliang Shao, Yuhua Cheng 0001, Wei Xing Zheng 0001	A Cooperation-Competition Evolutionary Dynamic Model Over Signed Networks.	IEEE Trans. Autom. Control.	2023	DBLP DOI BibTeX RDF
9	Jose Manuel Jurado-Castro, Salvador Vargas-Molina, Jose L. Gómez-Urquiza, Javier Benítez-Porres	Effectiveness of real-time classroom interactive competition on academic performance: a systematic review and meta-analysis.	PeerJ Comput. Sci.	2023	DBLP DOI BibTeX RDF
9	Hao Shen 0001, Xuelian Wang, Peiyong Duan, Jinde Cao, Jing Wang 0071	H∞ Bipartite Synchronization Control of Markov Jump Cooperation-Competition Networks With Reaction-Diffusions.	IEEE Trans. Cybern.	2023	DBLP DOI BibTeX RDF
9	Anna-Carina Kurth, Oliver Sawodny	Control of age-structured population dynamics with intraspecific competition in context of bioreactors.	Autom.	2023	DBLP DOI BibTeX RDF
9	Jiaming Fang, Lu Liu, Md Altab Hossin, Chao Wen, Guoen Xia	Market Competition as a Moderator of the Effect of Social Signals on Viewership in Video-Sharing Platforms.	Inf. Process. Manag.	2023	DBLP DOI BibTeX RDF
9	Liman Du, Wenguo Yang, Suixiang Gao	Competition-based generalized self-profit maximization in dual-attribute network.	Theor. Comput. Sci.	2023	DBLP DOI BibTeX RDF