Search results for "pursuit"

Hits ?▲	Authors	Title	Venue	Year	Link	Author keywords
89	Tom Diethe, Zakria Hussain	Kernel Polytope Faces Pursuit.	ECML/PKDD (1)	2009	DBLP DOI BibTeX RDF	Polytope Faces Pursuit, Orthogonal Matching Pursuit, Pseudo-dimension, Sample Compression Bounds, Regression, Kernel methods
72	Jan L. Souman, Ignace Th. C. Hooge, Alexander H. Wertheim	Frame of reference transformations in motion perception during smooth pursuit eye movements.	J. Comput. Neurosci.	2006	DBLP DOI BibTeX RDF	smooth pursuit eye movements, efference copy, eye movement signal, frame of reference, motion perception
69	Raheleh Mohammadi, Ali Mahlooji Far	Resolution Improvement of Scanning Acoustic Microscopy Using Sparse Signal Representation.	J. Signal Process. Syst.	2009	DBLP DOI BibTeX RDF	Orthogonal matching pursuit, Resolution improvement, Scanning acoustic microscopy, Sparse signal representation, Stagewise orthogonal matching pursuit
63	Yingchun Chen, Huan Qi, Shan-Shan Wang	Multi-agent Pursuit-Evasion Algorithm Based on Contract Net Interaction Protocol.	ICNC (3)	2005	DBLP DOI BibTeX RDF
63	Henning U. Voss, Bruce D. McCandliss, Jamshid Ghajar, Minah Suh	A quantitative synchronization model for smooth pursuit target tracking.	Biol. Cybern.	2007	DBLP DOI BibTeX RDF	Smooth pursuit, Synchronization, Dynamical modeling
63	Sen Jia, Yuntao Qian	Improved Stone's Complexity Pursuit for Hyperspectral Imagery Unmixing.	ICPR (4)	2006	DBLP DOI BibTeX RDF	complexity pursuit, hyperspectral imagery unmixing, independent component analysis
63	Dirk Thierens	An adaptive pursuit strategy for allocating operator probabilities.	GECCO	2005	DBLP DOI BibTeX RDF	adaptive operator allocation, adaptive pursuit, non-stationary operator probabilities, multi-armed bandit, non-stationary environment
63	F. Bergeaud, Stéphane Mallat	Matching pursuit of images.	ICIP	1995	DBLP DOI BibTeX RDF	texture components, edge components, 2D Gabor oriented wavelets, phase discontinuity, amplitude discontinuity, matching pursuit algorithm, local image properties, local decomposition, matching pursuit decomposition, localization, wavelet transforms, image reconstruction, image analysis, image representation, image representation, scale, orientation, image texture, adaptive algorithm, image features, fast algorithm, adaptive signal processing, Gabor functions, textured regions
57	Stefan Kunis, Holger Rauhut	Random Sampling of Sparse Trigonometric Polynomials, II. Orthogonal Matching Pursuit versus Basis Pursuit.	Found. Comput. Math.	2008	DBLP DOI BibTeX RDF	Mathematics Subject Classification (2000) 94A20, 15A52, 90C25, 90C05, 42A05
54	Ze-Su Cai, Li-ning Sun, Hai-Bo Gao	A novel hierarchical decomposition for multi-player pursuit evasion differential game with superior evaders.	GEC Summit	2009	DBLP DOI BibTeX RDF	multi-player, pursuit evasion, coalition formation, hierarchical decomposition, differential game
54	Ze-Su Cai, Li-Ning Sun, Hai-Bo Gao, Pu-Cheng Zhou, Songhao Piao, Qing-Cheng Huang	Multi-robot Cooperative Pursuit Based on Task Bundle Auctions.	ICIRA (1)	2008	DBLP DOI BibTeX RDF	Pursuit-Evasion game, Auction Mechanism, Case-based Reasoning, Multi-robot system
54	Jianning Zhang, Lifeng Sun, Yuzhuo Zhong	A Novel Video Coding Framework by Perceptual Representation and Macroblock-Based Matching Pursuit Algorithm.	MMM (1)	2007	DBLP DOI BibTeX RDF	Hybrid Video Coding, Visual Perceptual, Filter-based Decompose, Video Representation, Matching Pursuit
54	Yuehai Wang, Mengmeng Zhang	Multiple Moving Prey Pursuit Algorithm Based on the Changeable Alliance.	SNPD (1)	2007	DBLP DOI BibTeX RDF	Changeable Alliance, Multiple Moving Preys Cooperative Pursuit, Pursuit and Evasion Games
52	Jian-Liang Lin, Wen-Liang Hwang, Soo-Chang Pei	Video compression based on orthonormal matching pursuits.	ISCAS	2006	DBLP DOI BibTeX RDF
46	Jonathan Annas, Jing Xiao 0001	Intelligent pursuit & evasion in an unknown environment.	IROS	2009	DBLP DOI BibTeX RDF
46	Richard R. Brooks, Jing-En Pang, Christopher Griffin 0001	Game and Information Theory Analysis of Electronic Countermeasures in Pursuit-Evasion Games.	IEEE Trans. Syst. Man Cybern. Part A	2008	DBLP DOI BibTeX RDF
46	Liying Yang 0002, Jianda Han, Chendong Wu, Yiyong Nie	A solution of mixed integer linear programming for obstacle-avoided pursuit problem.	IJCNN	2008	DBLP DOI BibTeX RDF
46	Patrick S. Huggins, Steven W. Zucker	Greedy Basis Pursuit.	IEEE Trans. Signal Process.	2007	DBLP DOI BibTeX RDF
46	Tobias Rohatsch, Gerhard Pöppel, Heinrich Werner	Robuste Indizes für Projection Pursuit.	Inform. Forsch. Entwickl.	2002	DBLP DOI BibTeX RDF	automatische Datenanalyse, Mustererkennung, Projection Pursuit
46	Chengjun Liu, Harry Wechsler	Evolutionary Pursuit and Its Application to Face Recognition.	IEEE Trans. Pattern Anal. Mach. Intell.	2000	DBLP DOI BibTeX RDF	Evolutionary pursuit, optimal basis, Fisher Linear Discriminant (FLD), genetic algorithms, face recognition, Principal Component Analysis (PCA)
45	Georgios I. Papadimitriou	Hierarchical Discretized Pursuit Nonlinear Learning Automata with Rapid Convergence and High Accuracy.	IEEE Trans. Knowl. Data Eng.	1994	DBLP DOI BibTeX RDF	rapid convergence, absorbing multiaction learning automaton, discretized pursuit nonlinear learning automata, stationary stochastic environment, pursuit learning, nonlinear output function, epsilon-optimal learning, positioning algorithm, convergence, unsupervised learning, finite automata, nonlinear systems, hierarchical systems, hierarchical tree
44	Thomas Blumensath, Michael E. Davies 0001	Gradient Pursuits.	IEEE Trans. Signal Process.	2008	DBLP DOI BibTeX RDF
43	Li Jie, James J. Clark	Game Design Guided by Visual Attention.	ICEC	2007	DBLP DOI BibTeX RDF	eye pursuit, game design, visual attention, eye fixation
43	Héctor Rotstein, Ehud Rivlin	Optimal servoing for active foveated vision.	CVPR	1996	DBLP DOI BibTeX RDF	servomechanisms, active foveated vision, active vision system, foveal window, foveated vision, smooth pursuit, performance, computer vision, active vision, saccade
43	Jingyu Yang 0002, YiGang Peng, Wenli Xu, Qionghai Dai	Ways to sparse representation: An overview.	Sci. China Ser. F Inf. Sci.	2009	DBLP DOI BibTeX RDF	redundant dictionary, redundant transform, iterative shrinkage, sparse representation, matching pursuit, nonlinear approximation, basis pursuit
39	Alireza Shoa, Shahram Shirani	Optimization of Matching Pursuit Encoder Based on Analytical Approximation of Matching Pursuit Distortion.	ICME	2006	DBLP DOI BibTeX RDF
37	Esra Kadioglu Urtis, Nikolaos Papanikolopoulos	Multi-robot pursuit with visibility constraints.	ISCIS	2009	DBLP DOI BibTeX RDF
37	Shaunak Dattaprasad Bopardikar, Francesco Bullo, João Pedro Hespanha	On Discrete-Time Pursuit-Evasion Games With Sensing Limitations.	IEEE Trans. Robotics	2008	DBLP DOI BibTeX RDF
37	Alireza Shoa, Shahram Shirani	Progressive Coding of a Gaussian Source Using Matching Pursuit.	IEEE Trans. Signal Process.	2008	DBLP DOI BibTeX RDF
37	Alireza Shoa, Shahram Shirani	Adaptive Rate-Distortion Optimal In-Loop Quantization for Matching Pursuit.	IEEE Trans. Image Process.	2008	DBLP DOI BibTeX RDF
37	Tae-Hyoung Kim, Shinji Hara	Stabilization of multi-agent dynamical systems for cyclic pursuit behavior.	CDC	2008	DBLP DOI BibTeX RDF
37	Santhosh Kodipaka, Arunava Banerjee, Baba C. Vemuri	Large margin pursuit for a Conic Section classifier.	CVPR	2008	DBLP DOI BibTeX RDF
37	Xiao Zhang, Lin Liang, Xiaoou Tang, Heung-Yeung Shum	L1 regularized projection pursuit for additive model learning.	CVPR	2008	DBLP DOI BibTeX RDF
37	Xiong-Liang Wang, Chun-Ling Wang, Zhengming Wang	Super-resolution Processing of SAR Images by Match Pursuit Method Based on Fourier Dictionary.	CGIV	2007	DBLP DOI BibTeX RDF
37	Hui Li 0025, Richard Heusdens, Michael Muskulus, Lex Wolters	Analysis and Synthesis of Pseudo-Periodic Job Arrivals in Grids: A Matching Pursuit Approach.	CCGRID	2007	DBLP DOI BibTeX RDF
37	Yufeng Zhang 0002, Le Wang, Yali Gao, Jianhua Chen 0001, Xinling Shi	Automatic De-noising of Doppler Ultrasound Signals Using Matching Pursuit Method.	ICA	2006	DBLP DOI BibTeX RDF
37	Adel Rahmoune, Pierre Vandergheynst, Pascal Frossard	The M-term pursuit for image representation and progressive compression.	ICIP (1)	2005	DBLP DOI BibTeX RDF
37	Ichiro Fukumoto	A Computer Diagnosing System of Dementia Using Smooth Pursuit Oculogyration.	MICCAI (1)	2002	DBLP DOI BibTeX RDF
37	P. Jonathon Phillips	Matching pursuit filters applied to face identification.	IEEE Trans. Image Process.	1998	DBLP DOI BibTeX RDF
37	Amith Singhee, Pamela Castalino	Pareto sampling: choosing the right weights by derivative pursuit.	DAC	2010	DBLP DOI BibTeX RDF	derivative pursuit, multi-objective optimization, tradeoff, Pareto
37	François Malgouyres, Tieyong Zeng	A Predual Proximal Point Algorithm Solving a Non Negative Basis Pursuit Denoising Model.	Int. J. Comput. Vis.	2009	DBLP DOI BibTeX RDF	Proximal point algorithm, ell1 minimization, Algorithm, Sparse representation, Basis Pursuit
37	Monica Fira, Liviu Goras	Biomedical signal compression based on basis pursuit.	ICHIT	2009	DBLP DOI BibTeX RDF	compression, electroencephalography, basis pursuit
37	Joc Cing Tay, Cheun Hou Tng, Chee Siong Chan	Environmental effects on the coevolution of pursuit and evasion strategies.	Genet. Program. Evolvable Mach.	2008	DBLP DOI BibTeX RDF	Pursuit and evasion, Chemical Genetic Programming, Competitive coevolution, Game of tag
37	Alfredo Jiménez, Álvaro Herrero 0001, Emilio Corchado	Country and Political Risk Analysis of Spanish Multinational Enterprises Using Exploratory Projection Pursuit.	IDEAL	2008	DBLP DOI BibTeX RDF	multinational firm, country and political risk, foreign direct investment, exploratory projection pursuit, unsupervised learning
37	Sedigheh Ghofrani, Desmond C. McLernon	Comparison of the Cross Deleted Wigner Representation and the Matching Pursuit Distribution (Via Adaptive Signal Decomposition).	ICISP	2008	DBLP DOI BibTeX RDF	Wigner-Ville distribution, cross deleted Wigner representation, Gabor expansion, matching pursuit
37	Damien Pellier, Humbert Fiorino	Coordinated exploration of unknown labyrinthine environments applied to the pursuit evasion problem.	AAMAS	2005	DBLP DOI BibTeX RDF	pursuit-evasion problem, coordination, multiagent systems, distributed robotics
37	Emilio Corchado, Donald MacDonald, Colin Fyfe	Maximum and Minimum Likelihood Hebbian Learning for Exploratory Projection Pursuit.	Data Min. Knowl. Discov.	2004	DBLP DOI BibTeX RDF	exploratory projection pursuit, artificial neural networks
37	Chung-Lin Huang, Shih-Hung Hsu	Road Sign Interpretation Using Matching Pursuit Method.	ICPR	2000	DBLP DOI BibTeX RDF	Matching pursuit filters, Template matching
35	Rémi Gribonval, Morten Nielsen 0002	Beyond sparsity: Recovering structured representations by l1{\ell}^1 minimization and greedy algorithms.	Adv. Comput. Math.	2008	DBLP DOI BibTeX RDF	Mathematics subject classification (2000) Primary 41A30, Secondary 65D16
35	Mads Græsbøll Christensen, Søren Holdt Jensen	On perceptual distortion minimization and nonlinear least-squares frequency estimation.	IEEE Trans. Speech Audio Process.	2006	DBLP DOI BibTeX RDF
35	Cheng-en Guo, Song Chun Zhu, Ying Nian Wu	Towards a Mathematical Theory of Primal Sketch and Sketchability.	ICCV	2003	DBLP DOI BibTeX RDF
35	Chunmei Wu, Jiansheng Wu	An Effective Hybrid GA-PP Strategy for Artificial Neural Network Ensemble and Its Application Stock Market Forecasting.	ISNN (2)	2009	DBLP DOI BibTeX RDF	Projection pursuit technology, Genetic algorithm, Artificial neural network, Logistic regress
35	Reda Alhajj, Mehmet Kaya	Multiagent Association Rules Mining in Cooperative Learning Systems.	ADMA	2005	DBLP DOI BibTeX RDF	pursuit domain, data mining, association rules, reinforcement learning, multiagent systems
35	William Dickinson, David Leon, Andy Podgurski	Pursuing failure: the distribution of program failures in a profile space.	ESEC / SIGSOFT FSE	2001	DBLP DOI BibTeX RDF	cluster filtering, failure-pursuit sampling, software testing, cluster analysis, adaptive sampling, multivariate data analysis, observation-based testing
35	Michael L. Littman	Review: Computer Language Games.	Computers and Games	2000	DBLP DOI BibTeX RDF	word meanings, word games, hangman, Boggle, crosswords, cryptics, Trivial Pursuit, puns
35	Tomas Uhlin, Peter Nordlund, Atsuto Maki, Jan-Olof Eklundh	Towards an Active Visual Observer.	ICCV	1995	DBLP DOI BibTeX RDF	active visual observer, binocular active vision system, environment interaction, figure-ground segmentation, partial real-time implementations, real-world situations, target occlusions, stationary targets, target motion, target disparity, overall robust behavior, pursuit, performance, real-time systems, computer vision, image segmentation, motion estimation, observers, attention, motion detection, active vision, stereo image processing, motor control, cues, ego-motion, moving target
33	Heino Mohrmann, Peter Thier	The influence of structured visual backgrounds on smooth-pursuit initiation, steady-state pursuit and smooth-pursuit termination.	Biol. Cybern.	1995	DBLP DOI BibTeX RDF
28	Xiong-Liang Wang, Jubo Zhu, Chun-Ling Wang, Dian-Nong Liang	Extended Basis Pursuit Model and Its Application in Image De-noising.	CGIV	2009	DBLP DOI BibTeX RDF
28	Wei Ding, Gangfeng Yan, Zhiyun Lin	Formations on two-layer pursuit systems.	ICRA	2009	DBLP DOI BibTeX RDF
28	Nikhil Karnad, Volkan Isler	Bearing-only pursuit.	ICRA	2008	DBLP DOI BibTeX RDF
28	Yu Su 0010, Shiguang Shan, Xilin Chen 0001, Wen Gao 0001	Classifiability-based Optimal Discriminatory Projection Pursuit.	CVPR	2008	DBLP DOI BibTeX RDF
28	Chunhui Li 0001, Zhifeng Yang, Gordon H. Huang, Yanpeng Cai	Genetic Projection Pursuit Interpolation Model for Social Renewability Assessment of Water Resources.	FSKD (5)	2008	DBLP DOI BibTeX RDF
28	Adrian Dumitrescu, Howi Kok, Ichiro Suzuki, Pawel Zylinski	Vision-Based Pursuit-Evasion in a Grid.	SWAT	2008	DBLP DOI BibTeX RDF
28	Gang Xu, Jie Gao	A new method of weak signal detection based on improved matching pursuit algorithm.	IJCNN	2008	DBLP DOI BibTeX RDF
28	Jian-Liang Lin, Wen-Liang Hwang, Soo-Chang Pei	Fast Matching Pursuit Video Coding by Combining Dictionary Approximation and Atom Extraction.	IEEE Trans. Circuits Syst. Video Technol.	2007	DBLP DOI BibTeX RDF
28	Joel A. Tropp, Anna C. Gilbert	Signal Recovery From Random Measurements Via Orthogonal Matching Pursuit.	IEEE Trans. Inf. Theory	2007	DBLP DOI BibTeX RDF
28	Lorenzo Peotta, Pierre Vandergheynst	Matching Pursuit With Block Incoherent Dictionaries.	IEEE Trans. Signal Process.	2007	DBLP DOI BibTeX RDF
28	Rayan Saab, Özgür Yilmaz, Martin J. McKeown, Rafeef Abugharbieh	Underdetermined Anechoic Blind Source Separation via ellq-Basis-Pursuit With q<<1.	IEEE Trans. Signal Process.	2007	DBLP DOI BibTeX RDF
28	Warren Cheung, William S. Evans	Pursuit-Evasion Voronoi Diagrams in ell_1.	ISVD	2007	DBLP DOI BibTeX RDF
28	Jianxin Pang, Rong Zhang, Lu Lu 0001, Zhengkai Liu	Quality Assessment for Image Coding Based on Matching Pursuit.	ICME	2007	DBLP DOI BibTeX RDF
28	M. Hosseinpour, M. N. Ranjbar, M. Mousavinejad	Speech Unit Selection Based on Matching Pursuit.	AICCSA	2007	DBLP DOI BibTeX RDF
28	Laurent Daudet	Sparse and structured decompositions of signals with the molecular matching pursuit.	IEEE Trans. Speech Audio Process.	2006	DBLP DOI BibTeX RDF
28	Beibei Wang 0005, Yao Wang 0001, Peng Yin 0002	A Two Pass H.264-Based Matching Pursuit Video Coder.	ICIP	2006	DBLP DOI BibTeX RDF
28	Qing Li 0065, Licheng Jiao, Shuyuan Yang	MRA Kernel Matching Pursuit Machine.	PRICAI	2006	DBLP DOI BibTeX RDF
28	Mark D. Plumbley	Recovery of Sparse Representations by Polytope Faces Pursuit.	ICA	2006	DBLP DOI BibTeX RDF
28	Shuiping Gou, Qing Li 0065, Xiangrong Zhang	A New Dictionary Learning Method for Kernel Matching Pursuit.	FSKD	2006	DBLP DOI BibTeX RDF
28	Qing Li 0065, Licheng Jiao, Shuiping Gou	Wavelet Kernel Matching Pursuit Machine.	Australian Conference on Artificial Intelligence	2006	DBLP DOI BibTeX RDF
28	Alireza Shoa, Shahram Shirani	Tree structure search for matching pursuit.	ICIP (3)	2005	DBLP DOI BibTeX RDF
28	Jian Ji, Zheng Tian 0001, Wei Lin 0006, Yanwei Ju	The SAR Image Compression with Projection Pursuit Neural Networks.	ISNN (2)	2005	DBLP DOI BibTeX RDF
28	Tian Zheng, Zi Jin, Fang He, Ling Wei	The Projection Pursuit Learning Network for Nonlinear Time Series Modeling and Forecasting.	ISNN (2)	2005	DBLP DOI BibTeX RDF
28	Peter Filzmoser, Sven Serneels, Christophe Croux, Pierre J. Van Espen	Robust Multivariate Methods: The Projection Pursuit Approach.	GfKl	2005	DBLP DOI BibTeX RDF
28	Alexei D. Miasnikov, Jayson E. Rome, Robert M. Haralick	A Hierarchical Projection Pursuit Clustering Algorithm.	ICPR (1)	2004	DBLP DOI BibTeX RDF
28	Seiichi Kawata, Kazuya Morohashi, Takeshi Tateyama	Some Emergences of Mobiligence in the Pursuit Game.	KES	2004	DBLP DOI BibTeX RDF
28	Stefan Mandl, Herbert Stoyan	Evolution of Agent Coordination in an Asynchronous Version of the Predator-Prey Pursuit Game.	MATES	2004	DBLP DOI BibTeX RDF
28	Ying Han, Colin Fyfe	Complexity Pursuit for Financial Prediction.	IDEAL	2002	DBLP DOI BibTeX RDF
28	Jacky Baltes, Yongjoo Park	Comparison of Several Machine Learning Techniques in Pursuit-Evasion Games.	RoboCup	2001	DBLP DOI BibTeX RDF
28	Yocheved Dotan, Nathan Intrator	Multimodality exploration by an unsupervised projection pursuit neural network.	IEEE Trans. Neural Networks	1998	DBLP DOI BibTeX RDF
28	Chengjun Liu, Harry Wechsler	Face Recognition Using Evolutionary Pursuit.	ECCV (2)	1998	DBLP DOI BibTeX RDF
28	Michael J. Horowitz, David L. Neuhoff	Image Coding By Perceptural Pursuit.	ICIP (3)	1997	DBLP DOI BibTeX RDF
28	David William Murray 0001, Kevin J. Bradshaw, Philip F. McLauchlan, Ian D. Reid 0001, Paul M. Sharkey	Driving saccade to pursuit using image motion.	Int. J. Comput. Vis.	1995	DBLP DOI BibTeX RDF
28	Malrey Lee, Ok-Bae Chang, Cheol-Jung Yoo, Yong-Sung Kim, Oubong Gwun	Behavior Evolution of Multiple Mobile Agents under Solving a Continuous Pursuit Problem Using Artificial Life Concept.	J. Intell. Robotic Syst.	2004	DBLP DOI BibTeX RDF	pursuit domain, multi-agent system, artificial neural network, artificial life
26	Li Jie, James J. Clark	Video game design using an eye-movement-dependent model of visual attention.	ACM Trans. Multim. Comput. Commun. Appl.	2008	DBLP DOI BibTeX RDF	HCI, eye tracking, Entertainment, video games, eye movements, visual attention
26	Fethi Belkhouche, Boumediene Belkhouche	Modeling and controlling a robotic convoy using guidance laws strategies.	IEEE Trans. Syst. Man Cybern. Part B	2005	DBLP DOI BibTeX RDF
26	Siwei Lyu	Infomax Boosting.	CVPR (1)	2005	DBLP DOI BibTeX RDF
26	Zeljko Obrenovic, Dusan Starcevic, Emil Jovanov	Toward Optimization of Multimodal User Interfaces for Tactical Audio Applications.	User Interfaces for All	2002	DBLP DOI BibTeX RDF
26	Martin Pauly, Klaus Kopecz, Reinhard Eckhorn	Gaze Control with Neural Networks: A Unified Approach for Saccades and Smooth Pursuits.	IWANN (1)	1999	DBLP DOI BibTeX RDF
26	Ngoc-Minh Lê	On Determining Optimal Strategies in Pursiut Games in the Plane.	ICALP	1995	DBLP DOI BibTeX RDF
26	Masumi Ishikawa, Kosuke Ueno	Hierarchical Architecture with Modular Network SOM and Modular Reinforcement Learning.	ICANN (1)	2009	DBLP DOI BibTeX RDF	Modular network SOM, modular reinforcement learning, pursuit-evasion game, hierarchical architecture
26	Marc Strickert, Petra Schneider, Jens Keilwagen, Thomas Villmann, Michael Biehl, Barbara Hammer	Discriminatory Data Mapping by Matrix-Based Supervised Learning Metrics.	ANNPR	2008	DBLP DOI BibTeX RDF	Supervised feature characterization, adaptive matrix metrics, attribute dependence modeling, LDA, projection pursuit
26	Jianwu Li, Xiaocheng Deng	Kernel Matching Reduction Algorithms for Classification.	RSKT	2008	DBLP DOI BibTeX RDF	Kernel matching reduction algorithms, Kernel matching pursuit, Support vector machines, Radial basis function neural networks