1,696 research outputs found
Solving Dynamic Multi-objective Optimization Problems Using Incremental Support Vector Machine
The main feature of the Dynamic Multi-objective Optimization Problems (DMOPs)
is that optimization objective functions will change with times or
environments. One of the promising approaches for solving the DMOPs is reusing
the obtained Pareto optimal set (POS) to train prediction models via machine
learning approaches. In this paper, we train an Incremental Support Vector
Machine (ISVM) classifier with the past POS, and then the solutions of the DMOP
we want to solve at the next moment are filtered through the trained ISVM
classifier. A high-quality initial population will be generated by the ISVM
classifier, and a variety of different types of population-based dynamic
multi-objective optimization algorithms can benefit from the population. To
verify this idea, we incorporate the proposed approach into three evolutionary
algorithms, the multi-objective particle swarm optimization(MOPSO),
Nondominated Sorting Genetic Algorithm II (NSGA-II), and the Regularity
Model-based multi-objective estimation of distribution algorithm(RE-MEDA). We
employ experiments to test these algorithms, and experimental results show the
effectiveness.Comment: 6 page
Regularity Model for Noisy Multiobjective Optimization
Regularity models have been used in dealing with noise-free multiobjective optimization problems. This paper studies the behavior of a regularity model in noisy environments and argues that it is very suitable for noisy multiobjective optimization. We propose to embed the regularity model in an existing multiobjective evolutionary algorithm for tackling noises. The proposed algorithm works well in terms of both convergence and diversity. In our experimental studies, we have compared several state-of-the-art of algorithms with our proposed algorithm on benchmark problems with different levels of noises. The experimental results showed the effectiveness of the regularity model on noisy problems, but a degenerated performance on some noisy-free problems
Vector Autoregressive Evolution for Dynamic Multi-Objective Optimisation
Dynamic multi-objective optimisation (DMO) handles optimisation problems with
multiple (often conflicting) objectives in varying environments. Such problems
pose various challenges to evolutionary algorithms, which have popularly been
used to solve complex optimisation problems, due to their dynamic nature and
resource restrictions in changing environments. This paper proposes vector
autoregressive evolution (VARE) consisting of vector autoregression (VAR) and
environment-aware hypermutation to address environmental changes in DMO. VARE
builds a VAR model that considers mutual relationship between decision
variables to effectively predict the moving solutions in dynamic environments.
Additionally, VARE introduces EAH to address the blindness of existing
hypermutation strategies in increasing population diversity in dynamic
scenarios where predictive approaches are unsuitable. A seamless integration of
VAR and EAH in an environment-adaptive manner makes VARE effective to handle a
wide range of dynamic environments and competitive with several popular DMO
algorithms, as demonstrated in extensive experimental studies. Specially, the
proposed algorithm is computationally 50 times faster than two widely-used
algorithms (i.e., TrDMOEA and MOEA/D-SVR) while producing significantly better
results
Comparison of serious inhaler technique errors made by device-naĂŻve patients using three different dry powder inhalers: a randomised, crossover, open-label study
Background: Serious inhaler technique errors can impair drug delivery to the lungs. This randomised, crossover, open-label study evaluated the proportion of patients making predefined serious errors with Pulmojet compared with Diskus and Turbohaler dry powder inhalers. Methods: Patients ≥18 years old with asthma and/or COPD who were current users of an inhaler but naïve to the study devices were assigned to inhaler technique assessment on Pulmojet and either Diskus or Turbohaler in a randomised order. Patients inhaled through empty devices after reading the patient information leaflet. If serious errors potentially affecting dose delivery were recorded, they repeated the inhalations after watching a training video. Inhaler technique was assessed by a trained nurse observer and an electronic inhalation profile recorder. Results: Baseline patient characteristics were similar between randomisation arms for the Pulmojet-Diskus (n = 277) and Pulmojet-Turbohaler (n = 144) comparisons. Non-inferiority in the proportions of patients recording no nurse-observed serious errors was demonstrated for both Pulmojet versus Diskus, and Pulmojet versus Turbohaler; therefore, superiority was tested. Patients were significantly less likely to make ≥1 nurse-observed serious errors using Pulmojet compared with Diskus (odds ratio, 0.31; 95 % CI, 0.19–0.51) or Pulmojet compared with Turbohaler (0.23; 0.12–0.44) after reading the patient information leaflet with additional video instruction, if required. Conclusions These results suggest Pulmojet is easier to learn to use correctly than the Turbohaler or Diskus for current inhaler users switching to a new dry powder inhaler
Optimizing Logistic Regression Coefficients for Discrimination and Calibration Using Estimation of Distribution Algorithms.
Logistic regression is a simple and efficient supervised learning algorithm for estimating the probability of an outcome or class variable. In spite of its simplicity, logistic regression has shown very good performance in a range of fields. It is widely accepted in a range of fields because its results are easy to interpret. Fitting the logistic regression model usually involves using the principle of maximum likelihood. The Newton–Raphson algorithm is the most common numerical approach for obtaining the coefficients maximizing the likelihood of the data. This work presents a novel approach for fitting the logistic regression model based on estimation of distribution algorithms (EDAs), a tool for evolutionary computation. EDAs are suitable not only for maximizing the likelihood, but also for maximizing the area under the receiver operating characteristic curve (AUC). Thus, we tackle the logistic regression problem from a double perspective: likelihood-based to calibrate the model and AUC-based to discriminate between the different classes. Under these two objectives of calibration and discrimination, the Pareto front can be obtained in our EDA framework. These fronts are compared with those yielded by a multiobjective EDA recently introduced in the literature
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