yusuke1997/dblp-id-title huggingface dataset:
UAIC at SemEval-2019 Task 3: Extracting Much from Little
MIND at SemEval-2023 Task 11: From Uncertain Predictions to Subjective Disagreement
TueFact at SemEval 2019 Task 8: Fact checking in community question answering forums: context matters
QASSIT: A Pretopological Framework for the Automatic Construction of Lexical Taxonomies from Raw Texts
NITS_Legal at SemEval-2023 Task 6: Rhetorical Roles Prediction of Indian Legal Documents via Sentence Sequence Labeling Approach
ANDI at SemEval-2021 Task 1: Predicting complexity in context using distributional models, behavioural norms, and lexical resources
KSU KDD: Word Sense Induction by Clustering in Topic Space
NTNU: Domain Semi-Independent Short Message Sentiment Classification
HYU at SemEval-2022 Task 2: Effective Idiomaticity Detection with Consideration at Different Levels of Contextualization
Robust Controller Synthesis Is Convex for Systems without Control Channel Uncertainties
Constrained Reduced Order H∞ Synthesis with Optimal Filter Tuning Using Particle Swarm Optimization
Piezo-Actuated Vibration Attenuation of the Parallel Robot Par2
Design of Platoon Velocity Based on Multi-Criteria Optimization
A Pragmatic Approach to Robust Gain Scheduling
Descriptor-Type Robust Kalman Filter and Neural Adaptive Speed Estimation Scheme for Sensorless Control of Induction Motor Drive Systems
Robust and Resilient Finite-Time Control of a Class of Continuous-Time Nonlinear Systems
Robust and Efficient Algorithms for L ∞ -Norm Computation for Descriptor Systems
Direct Design of a Polynomial Model Predictive Controller
A Modified Homotopy Method for Nevanlinna-Pick Interpolation with Degree Constraint
Robust Model Predictive Control Design of Switched Systems
Multiple Model Adaptive Control Using Dual Youla-Kucera Factorisation
Low Order Controller Design for Continuous Fluidized Bed Spray Granulation with Internal Product Classification by Robust Control Methods
Linear Receding Horizon Control with Probabilistic System Parameters
Disturbance Rejection Design for a Bank-To-Turn Missile Using Decoupling Quantitative Feedback Theory
Network-Based Control under Round-Robin Scheduling and Quantization
Robust Parametric Fault Estimation in a Hopper System
Robust Analysis of Networked Control Systems with Time-Varying Delays
Metric on the Factorizations Factor-Classes As the Measure of Robustness
Stabilization of Diffusion Equations under Sampled-Data Spatially Averaged Measurements
Ship Trajectory Tracking in Harbour Area by Using Autonomous Tugboats
Stabilization of TITO Systems Over Parallel SNR-Constrained AWN Channels
Delay-Dependent Stability of Reset Control Systems with Anticipative Reset Conditions
Guaranteed Peaks of Spacing Errors in an Experimental Vehicle String
Reduced Order H-Infinity Controller Synthesis for Flexible Structures Control
Discretized Model-Reference Feedback and Robust Stabilization on Integer Grid Coordinates
When Is a Set of LMIs a Sufficient Condition for Stability?
External Perturbation Estimation Based on Super-Twisting Algorithm for Attitude Control of UAVs
Discrete-Time Modeling and Robust Analysis of a Buck Converter
On Implementing On-Line Designed Controller for Smooth Interconnection in the Behavioral Framework
Switching Control Consistency Analysis for Discrete-Time Switched Linear Systems
Lazy Global Feedbacks for Quantized Nonlinear Event Systems
Observer Design with Disturbance Rejection by Acceleration Feedforward
Design of Accommodation Process Applied to the Thrust Reverser of Aircraft Nacelle
Digital L1 Controller Based on Linear Matrix Inequality (LMI) for Line-Of-Sight Stabilization
A Simple Unified Formula for Discrete and Continuous-Time H-Infinity "All-Solutions" Controllers
Tube Reference Model Based Direct Adaptive Control
Sensitivity-Based State and Parameter Estimation for Fuel Cell Systems
Exact Solutions to a Two-Block $l_{1}$ Optimal Control Problem
Model Based Control of Wind Turbines: Look-Ahead Approach
H ∞ Robust Control Design for Teleoperation Systems
Guidance and Control for Spacecraft Autonomous Chasing and Close Proximity Maneuvers
Robust Stability of Periodic Systems with Memory: New Formulations, Analysis and Design Results
Measures and LMI for Space Launcher Robust Control Validation
Fixed-Structure H_2 Controller Design: An LMI Solution
A Numerical Procedure to Compute Stabilizing State Feedback Gains for Linear Time-Varying Periodic Systems
Increasing Energy Harvesting in Regenerative Suspension Systems Via Multiobjective H_inf Control
Reduced Order Controllers for Inertial Line of Sight Stabilization
Robust Model Predictive Control of a Nonlinear System with Known Scheduling Variable and Uncertain Gain
Delay-Dependent Feedforward Control of Uncertain Neutral Time-Delay Systems Via Dynamic IQCs
Robust Cooperative Visual SLAM with Textures Plating
Sampled - Data Control of Switched Affine Systems: A Continuous-Time Approach
A Study on the State Set Invariance for a Class of Discrete-Time Linear Control Systems
H_{infty}$/$H_2$ Model Reduction through Dilated Linear Matrix Inequalities
On the Design of Hybrid Robust Output Regulation for the METIS Cold Chopper
Feedforward Linearization and Disturbance Rejection of Mechanical Systems Using Acceleration Measurements
A Robust Kalman Conjecture for First-Order Plants
A New Approach to Design a Simple Structure µ Synthesis Controller: Application to an Uncertain DC Motor
Satisfaction of Temporal Logic by Control Systems and Finite Abstractions
Robust Safety Margin Assessment and Constrained Worst-Case Analysis of a Launcher Vehicle
Fault-Tolerant Servo Systems against Actuator Failures
Gain-Scheduled Two-Loop Autopilot for an Aircraft
Decentralized Robust Control of Linear Uncertain Systems
New Criteria of Reachable Set Estimation for Time Delay Systems Subject to Polytopic Uncertainties
Even Degree Polynomials with Roots on the Unit Circle and Segments of Schur Polynomials
Robust Stability and l 2 -gain Analysis of Linear Didcrete-Time Switched Systems with Dwell Time
Robust Passivity Preserving Parametric Model Order Reduction Using Matrix Interpolation
A Note on Discretization of Sparce Linear Systems
Continuous-Time Adaptive Lqg/ltr Control
Robust Synchronization of Nonlinear Agents Over Directed Communication Graph
Closed-Form Feedback Controllers for Set-Point and Trajectory Tracking for the Nonlinear Model of Quadrotor Helicopters
Upper and Lower Bounds of Frequency Interval Gramians for a Class of Perturbed Linear Systems
Output Regulation for General Infinite-Dimensional Exosystems
Frequency Determination in Control Applications: Excitation Based Approach
Approximate Robust Optimal Control of Periodic Systems with Invariants and High-Index Differential Algebraic Systems
Robust Nonlinear Control Design with Application to a Marine Cooling System
Decentralized Control of Uncertain Systems Via Adaptive Sliding and Overlapping Decomposition
Algebraic Conditions of Generalized Modal Control
Robust Anti-Windup Synthesis for Directionality Compensation
Optimal Solutions to Robust Stabilization Problem for a Class of Systems with Parametric Uncertainty
An Iterative Procedure for Multidimensional Realization by LFT Techniques
Gain-Scheduled Observers Using Inexact Scheduling Parameters
Probabilistic Robust Approach for Discrete Multi-Objective Control of Track-Following Servo Systems in Hard Disk Drives
PIDrobust Toolbox - Performance Tuning for PID Controlled Time Delay Systems with Parameter Uncertainties
All Controllers for an LPV Robust Control Problem
Optimization of Stable Periodic Attractors for Nonlinear Dynamic Systems
Maximizing the Stability Region in the Parameter Space for a Nonlinear Control System
Improved Vertex Control for a Ball and Plate System
Design of Robust Fault Detection Filters for Linear Descriptor Systems Using Sliding-Mode Observers
Robust Observer-Based Fault Detection and Isolation in the Standard Control Problem Framework
Robust Utilization of Wind Turbine Flexibility for Grid Stabilization
Reconstruction of Sensor Faults for a Class of Uncertain Nonlinear Systems Using Adaptive Sliding Mode Observers
Fixed Structure Flight Control Design of an Over-Actuated Aircraft in the Presence of Actuators with Different Dynamic Performance
Stable Weighted Multiple Model Adaptive Control with Improved Convergence Rate
A Toolkit for Efficient Computation of Sensitivities in Approximate Robust Optimal Control Problems
A Stochastic Model to Account for System Uncertainties Applied to an Optimal Harvesting Problem
PWM Modeling for Attitude Control of a Launcher During Ballistic Phase and Comparative Stability Analysis
Modified Internal Model Control Anti-Windup : Some New Insights and Interpretations
A New Smooth Parameter Projection High Order Tuner for Robust Adaptive Control
Origins of Robust Control: Early History and Future Speculations
Disturbance Decoupling with Quadratic Stability for Polytopic Uncertain Switched Linear Systems
H_inf Subsystem Pairwise Distributed Control of Uncertain Linear Systems
Tolerance of Aircraft Longitudinal Control to the Loss of Scheduling Information : Toward a Performance Oriented Approach
Singular $mathcal{L}_2$-Optimization Problem and Fixed Poles for Sampled-Data Systems with Delays
Robust Stability Analysis of Nonlinear Switched Systems with Filippov Solutions
Fault Tolerant Adaptive Sliding Mode Controller for Wind Turbine Power Maximisation
Simultaneous Improvement of Time and Frequency Performance
Design of Robust Synthetic Genetic Oscillators Based on RSGA
Design of Adaptive Robust State Observers with Simpler Structure for a Class of Uncertain Time-Delay Systems
Quasi-Analytical Describing Function for the Karnopp Friction Model
A Robust Cascade Sliding Mode Control for a Hybrid Piezo-Hydraulic Actuator in Camless Internal Combustion Engines
Flexible Closed-Loop Iterative Learning Control for Industrial Batch Processes with State Delay and Time-Varying Uncertainties
Design of an LPV-Based Integrated Control for Driver Assistance Systems
An Observer Based State Feedback LFT LPV Controller for an Industrial Manipulator
Robust Compensation of Discrete-Time Plant Using 2-Periodic Controller
Observer Synthesis for Uncertain Nonlinear Systems. Application to Waste-Water Treatment Plants
Predictive Control of Fractional Order Systems
Evaluating Regions of Attraction of LTI Systems with Saturation in IQS Framework
An Adaptive Sliding Mode Observer for Nonlinear Systems Subject to Mismatched Uncertainties
Estimation of Biases in Gyro Drifts by Means of L 1 -Norm Approximation
Stability Analysis of Closed Loops of Non-Linear Systems and LPV Controllers Designed Using Approximated Quasi-LPV Systems
Design of Integrated Vehicle Control Using Driver Models
A LPV/Hinf Global Chassis Controller for Performances Improvement Involving Braking, Suspension and Steering Systems
Robust Load Disturbance Torque Estimation for a DC Motor Drive System
Fully Probabilistic Adaptive Control with Arbitrary Density Functions of Forward Models and Inverse Controllers
Frozen-Time and Time-Varying Robust Stability Certificates for the Coupled Pitch/yaw Motion of an Axial-Symmetric Launch Vehicle
Robust Mean Field Games with Application to Production of an Exhaustible Resource
LQG/LTR Design for the Concentration Process: Use in the Enological Industry
Robust Networked Output Feedback Predictive Controller Design
Worst Case Analysis of a Launcher Vehicle Using Surrogate Models
State Feedback Control for a Class of Polynomial Nonlinear Discrete-Time Systems with Norm-Bounded Uncertainties: An Integrator Approach
Optimal Filtering Scheme for Bilinear Discrete-Time Systems: A Linear Matrix Inequality Approach
7th IFAC Symposium on Robust Control Design, ROCOND 2012, Aalborg, Denmark, June 20-22, 2012
Blind Identification of Polynomial Matrix Fraction for Disturbance Rejection
Design of Modal Control Providing Guaranteed Stability Margin to Continuous Systems
Approximation Ineffectiveness of a Tour-Untangling Heuristic
"Almost Stable" Matchings in the Roommates Problem
Scenario Submodular Cover
Approximation and Online Algorithms - 8th International Workshop, WAOA 2010, Liverpool, UK, September 9-10, 2010. Revised Papers
Stackelberg Strategies and Collusion in Network Games with Splittable Flow
Improved Approximation Algorithm for Convex Recoloring of Trees
Improved (In-)Approximability Bounds for d-Scattered Set
An Improved Deterministic Algorithm for the Online Min-Sum Set Cover Problem
LP-Based Algorithms for Multistage Minimization Problems
Approximation and Online Algorithms, Second International Workshop, WAOA 2004, Bergen, Norway, September 14-16, 2004, Revised Selected Papers
Constant-Time Local Computation Algorithms
A Note on Semi-online Machine Covering
Minimum Linear Arrangement of Series-Parallel Graphs
Call Admission Problems on Grids with Advice (Extended Abstract)
Generalized Maximum Flows over Time
Online Removable Square Packing
Fast Parallel Algorithms for Submodular p-Superseparable Maximization
Simple Approximations for General Spanner Problems
Cooperation in Multiorganization Matching
The Primal-Dual Approach for Online Algorithms
Peak Shaving through Resource Buffering
Generalized Hypergraph Matching via Iterated Packing and Local Ratio
Online Packet Scheduling Under Adversarial Jamming
Online Dual Edge Coloring of Paths and Trees
SONET ADMs Minimization with Divisible Paths
Hardness of Dynamic Core and Truss Decompositions
Fair Coresets and Streaming Algorithms for Fair k-means
Improved Online Hypercube Packing
Online Colored Bin Packing
Online Coloring and a New Type of Adversary for Online Graph Problems
Distributed Algorithms for Matching in Hypergraphs
Black and White Bin Packing
Weighted Completion Time Minimization for Capacitated Parallel Machines
On Lagrangian Relaxation and Subset Selection Problems
On Fixed Cost k-Flow Problems
Experimental Analysis of Scheduling Algorithms for Aggregated Links
Online Algorithm for Parallel Job Scheduling and Strip Packing
Scheduling with an Orthogonal Resource Constraint
Open Block Scheduling in Optical Communication Networks
Scheduling AND/OR-Networks on Identical Parallel Machines
Low Recourse Arborescence Forests Under Uniformly Random Arcs
Concave Connection Cost Facility Location and the Star Inventory Routing Problem
On-line Search in Two-Dimensional Environment
Randomized Algorithms for Buffer Management with 2-Bounded Delay
Better Bounds for Minimizing SONET ADMs
On the Approximation Complexity Hierarchy
Approximation and Online Algorithms - 22nd International Workshop, WAOA 2024, Egham, UK, September 5-6, 2024, Proceedings
On the FirstFit Algorithm for Online Unit-Interval Coloring
Approximating the Quadratic Knapsack Problem on Special Graph Classes
Sublinear Graph Augmentation for Fast Query Implementation
Approximation and Online Algorithms - 20th International Workshop, WAOA 2022, Potsdam, Germany, September 8-9, 2022, Proceedings
A Better-Than-Greedy Algorithm for k -Set Multicover
Deterministic Online Optical Call Admission Revisited
Approximation and Online Algorithms - 19th International Workshop, WAOA 2021, Lisbon, Portugal, September 6-10, 2021, Revised Selected Papers
Covering the Edges of Bipartite Graphs Using K 2, 2 Graphs
Inapproximability Results for Graph Convexity Parameters
Approximation Algorithms for k-Connected Graph Factors
Linear Time Approximation for Dominating Sets and Independent Dominating Sets in Unit Disk Graphs
Online Scheduling of Bounded Length Jobs to Maximize Throughput
Scheduling Parallel Jobs with Linear Speedup
Degree-Constrained Graph Orientation: Maximum Satisfaction and Minimum Violation
Online Multi-Coloring with Advice
Improved Online Sorting
Buyer-Supplier Games: Optimization over the Core
Better Bounds for Incremental Medians
Approximation Schemes for Packing Splittable Items with Cardinality Constraints
Deterministic Min-Cost Matching with Delays
Approximation Algorithms for Spreading Points
Bidding to the Top: VCG and Equilibria of Position-Based Auctions
On the Approximability of the Minimum Fundamental Cycle Basis Problem
Constant Factor Approximation for Tracking Paths and Fault Tolerant Feedback Vertex Set
Approximating Subset k-Connectivity Problems
On the max min vertex cover Problem
Throughput Maximization for Periodic Packet Routing on Trees and Grids
Optimization over Integers with Robustness in Cost and Few Constraints
Minimum Sum Multicoloring on the Edges of Trees: (Extended Abstract)
Energy-Efficient Algorithms for Non-preemptive Speed-Scaling
R-LINE: A Better Randomized 2-Server Algorithm on the Line
Scheduling with Machine Conflicts
Improved Approximation Algorithms for MAX NAE-SAT and MAX SAT
Approximating Frequent Items in Asynchronous Data Stream over a Sliding Window
An Experimental Study of the Misdirection Algorithm for Combinatorial Auctions
Approximating the Unweighted k -Set Cover Problem: Greedy Meets Local Search
Lower Bounds for Approximate (& Exact) k-Disjoint-Shortest-Paths
On the Smoothness of Paging Algorithms
Min-Sum 2-Paths Problems
Improved Approximation Algorithm for Fault-Tolerant Facility Placement
Full and Local Information in Distributed Decision Making
An Improved Algorithm for Online Rectangle Filling
The Shortest Separating Cycle Problem
Tight Approximation Bounds on a Simple Algorithm for Minimum Average Search Time in Trees
Graph Burning and Non-uniform k-centers for Small Treewidth
Minimum Sum Multicoloring on the Edges of Planar Graphs and Partial k-Trees
Greedy Is Optimal for Online Restricted Assignment and Smart Grid Scheduling for Unit Size Jobs
The Price of Fixed Assignments in Stochastic Extensible Bin Packing
FIFO and Randomized Competitive Packet Routing Games
An Improved Upper Bound for the Ring Loading Problem
Longest Wait First for Broadcast Scheduling [Extended Abstract]
Total Completion Time Scheduling Under Scenarios
Deterministic Algorithms for Rank Aggregation and Other Ranking and Clustering Problems
A Unifying Tool for Bounding the Quality of Non-cooperative Solutions in Weighted Congestion Games
An Improved Approximation Bound for Minimum Weight Dominating Set on Graphs of Bounded Arboricity
Caching Content under Digital Rights Management
Complexity of Fixed Order Routing
Online k -Server Routing Problems
Primal-Dual Algorithms for Precedence Constrained Covering Problems
Online Rectangle Filling
Improved Deterministic Strategy for the Canadian Traveller Problem Exploiting Small Max-(s, t)-Cuts
Low Dimensional Embeddings of Doubling Metrics
Approximation and Online Algorithms - 11th International Workshop, WAOA 2013, Sophia Antipolis, France, September 5-6, 2013, Revised Selected Papers
On Minimum-and Maximum-Weight Minimum Spanning Trees with Neighborhoods
Canadian Traveller Problem with Predictions
Parameterized Analysis of Paging and List Update Algorithms
Approximation Schemes Under Resource Augmentation for Knapsack and Packing Problems of Hyperspheres and Other Shapes
Hitting Sets when the Shallow Cell Complexity is Small
Bin Packing with Colocations
Lower Bounds for Smith's Rule in Stochastic Machine Scheduling
OnlineMin: A Fast Strongly Competitive Randomized Paging Algorithm
Approximating Maximum Cut with Limited Unbalance
Approximating Survivable Networks with Minimum Number of Steiner Points
Interval-Constrained Bipartite Matching over Time
The Power of Amortization on Scheduling with Explorable Uncertainty
Competitive Router Scheduling with Structured Data
On the Competitiveness of the Online Asymmetric and Euclidean Steiner Tree Problems
Improved Approximation Bounds for Edge Dominating Set in Dense Graphs
Optimal Online and Offline Algorithms for Robot-Assisted Restoration of Barrier Coverage
Improved Approximation Algorithms for Minimum Power Covering Problems
On the Minimum Load Coloring Problem
Online Ad Assignment with an Ad Exchange
Robust Online Algorithms for Certain Dynamic Packing Problems
Approximating Directed Buy-at-Bulk Network Design
Reoptimization of Weighted Graph and Covering Problems
The Power of Amortized Recourse for Online Graph Problems
Approximation and Online Algorithms - 23rd International Workshop, WAOA 2025, Warsaw, Poland, September 18-19, 2025, Proceedings
Approximating Length-Restricted Means Under Dynamic Time Warping
On Minimizing the Maximum Flow Time in the Online Dial-a-Ride Problem
The Pledge Algorithm Reconsidered under Errors in Sensors and Motion
A Constant-Factor Approximation Algorithm for Red-Blue Set Cover with Unit Disks
Minimizing Maximum Flowtime of Jobs with Arbitrary Parallelizability
Approximating Fair k-Min-Sum-Radii in Euclidean Space
Approximation Schemes for Packing with Item Fragmentation
Finding Dense Subgraphs in G ( n , 1/2)
Approximation and Online Algorithms - 21st International Workshop, WAOA 2023, Amsterdam, The Netherlands, September 7-8, 2023, Proceedings
Improved Lower Bounds for Non-utilitarian Truthfulness
Buyback Problem with Discrete Concave Valuation Functions
Max-Min and 1-Bounded Space Algorithms for the Bin Packing Problem
On Approximating Restricted Cycle Covers
On Min-Max r -Gatherings
Online Unit Clustering in Higher Dimensions
A Lower Bound on Deterministic Online Algorithms for Scheduling on Related Machines without Preemption
On the Additive Constant of the k -Server Work Function Algorithm
The Routing Open Shop Problem: New Approximation Algorithms
Approximation with a Fixed Number of Solutions of Some Biobjective Maximization Problems
Covering Many or Few Points with Unit Disks
A Refined Analysis of Online Path Coloring in Trees
Bin Packing Games with Weight Decision: How to Get a Small Value for the Price of Anarchy
Terrain-Like Graphs: PTASs for Guarding Weakly-Visible Polygons and Terrains
Linear-Time Approximation Algorithms for Unit Disk Graphs
Strategic Contention Resolution in Multiple Channels
Buy-at-Bulk Facility Location on Trees
Counting Approximately-Shortest Paths in Directed Acyclic Graphs
k -Edge-Connectivity: Approximation and LP Relaxation
New Models and Algorithms for Throughput Maximization in Broadcast Scheduling - (Extended Abstract)
Off-line Admission Control for Advance Reservations in Star Networks
Minimizing Average Flow Time on Unrelated Machines
Densest k -Subgraph Approximation on Intersection Graphs
An O(\log \mathrmOPT) O ( log OPT ) -Approximation for Covering/Packing Minor Models of θ _r θ r
Online Tracking of the Dominance Relationship of Distributed Multi-dimensional Data
An Online Algorithm Optimally Self-tuning to Congestion for Power Management Problems
Max-Weight Integral Multicommodity Flow in Spiders and High-Capacity Trees
Incremental-Decremental Maximization
This Side Up!
Non-clairvoyant Weighted Flow Time Scheduling on Different Multi-processor Models
Online Packing of Rectangular Items into Square Bins
On Online Algorithms with Advice for the k-Server Problem
On the Online Unit Clustering Problem
Strategyproof Mechanisms for Additively Separable Hedonic Games and Fractional Hedonic Games
Price Fluctuations: To Buy or to Rent
Approximation Algorithms for Prize-Collecting Network Design Problems with General Connectivity Requirements
Approximation Algorithms for k-Scenario Matching
Approximate Distance Queries in Disk Graphs
The Online Multicommodity Connected Facility Location Problem
Online Knapsack Revisited
An Improved Approximation Algorithm for the Uniform Cost-Distance Steiner Tree Problem
Approximate Fair Cost Allocation in Metric Traveling Salesman Games
On Temporally Connected Graphs of Small Cost
Parameterized Approximation Algorithms for Hitting Set
Approximation Algorithms for Graph Search Problems with Imperfect Detection
Packet Routing: Complexity and Algorithms
Online Ranking for Tournament Graphs
A Constant-Factor Approximation Algorithm for Vertex Guarding a WV-Polygon
Scheduling with State-Dependent Machine Speed
Algorithms for Cost-Aware Scheduling
Better Algorithms for Online Bin Stretching
Scheduling to Minimize Average Completion Time Revisited: Deterministic On-Line Algorithms
The Survival of the Weakest in Networks
Improved Approximation Algorithms for Covering Pliable Set Families and Flexible Graph Connectivity
Approximating Largest Convex Hulls for Imprecise Points
Scheduling Parallel Jobs Online with Convex and Concave Parallelizability
Approximating the Sparsest k-Subgraph in Chordal Graphs
On the Maximum Edge Coloring Problem