Rescaled Pure Greedy Algorithm for Convex Optimization

In this thesis, we suggest a new algorithm for solving convex optimization problems in Banach spaces. This algorithm is based on a greedy strategy, and it could be viewed as a nonlinear conjugate gradient type method. We prove its convergent rates under a suitable behavior of the modulus of uniform smoothness of the objective function. We apply the proposed algorithm on several examples such as approximation in Hilbert spaces, solving linear systems, and others. We also perform several numerical tests in the case when the objective function is the opposite of the log-likelihood function under the Logistic Regression model. Our numerical results confirm the fast convergence rate of the proposed algorithm and its potential for solving real life problems

Clean Hydrocarbon Refrigerant Explosion Hazards

Explosion hazards are fire safety concerns resulting from the development of clean hydrocarbon refrigerants (environmental friendly flammable refrigerants) to reduce the emission of substances with high global warning potential. Several clean hydrocarbon refrigerants are flammable with propane. Explosion hazards due to flammable refrigerant leakage from refrigerators put inside a small cupboard may give a concentration higher than its lowest flammability. A small amount of ignition energy can ignite the flammable gas to give combustion. Limiting the pressure development in a small cupboard will result in deflagration, and then transition to detonation. Since the compositions of many of environmental friendly flammable refrigerants are not disclosed and odourless, it is very difficult to assess their hazard upon leakage. This study reveals that the hidden hazard of environmental friendly flammable refrigerants would lead to serious consequences using earlier experimental studies on explosion. This is a big problem taking time to solve. Indoor aerodynamics would affect the mixing between leaked refrigerant with air in the room. Appropriate ventilation should be provided to avoid keeping the heavier explosive gas at lower levels. Different ventilation modes with air inlets and outlets at high and low positions should be considered. Use of environmental friendly flammable refrigerants and the ways in protecting against possible explosion hazards for refrigerators commonly put in kitchen cupboards in small rooms, inter alia, economy-class hotel rooms, small apartments, or subdivided units in densely populated cities, such as Hong Kong have to be watched. At the moment, fire safety management must be enhanced to address the problem

A kernel-free L1 norm regularized ν-support vector machine model with application

With a view to overcoming a few shortcomings resulting from the kernel-based SVM models, these kernel-free support vector machine (SVM) models are newly promoted and researched. With the aim of deeply enhancing the classification accuracy of present kernel-free quadratic surface support vector machine (QSSVM) models while avoiding computational complexity, an emerging kernel-free ν-fuzzy reduced QSSVM with L1 norm regularization model is proposed. The model has well-developed sparsity to avoid computational complexity and overfitting and has been simplified as these standard linear models on condition that the data points are (nearly) linearly separable. Computational tests are implemented on several public benchmark datasets for the purpose of showing the better performance of the presented model compared with a few known binary classification models. Similarly, the numerical consequences support the more elevated training effectiveness of the presented model in comparison with those of other kernel-free SVM models. What`s more, the presented model is smoothly employed in lung cancer subtype diagnosis with good performance, by using the gene expression RNAseq-based lung cancer subtype (LUAD/LUSC) dataset in the TCGA database

A Novel Markov Model for Near-Term Railway Delay Prediction

Predicting the near-future delay with accuracy for trains is momentous for railway operations and passengers' traveling experience. This work aims to design prediction models for train delays based on Netherlands Railway data. We first develop a chi-square test to show that the delay evolution over stations follows a first-order Markov chain. We then propose a delay prediction model based on non-homogeneous Markov chains. To deal with the sparsity of the transition matrices of the Markov chains, we propose a novel matrix recovery approach that relies on Gaussian kernel density estimation. Our numerical tests show that this recovery approach outperforms other heuristic approaches in prediction accuracy. The Markov chain model we propose also shows to be better than other widely-used time series models with respect to both interpretability and prediction accuracy. Moreover, our proposed model does not require a complicated training process, which is capable of handling large-scale forecasting problems.Comment: 36 pages, 3 figures, 4 table

Total Synthesis and Structural Determination of the Dimeric Tetrahydroxanthone Ascherxanthone A

The first total synthesis of the dimeric tetrahydroxanthone ascherxanthone A has been accomplished. This synthetic strategy features (1) enantioselective intramolecular allylic C–H oxidation to construct a core chiral chromane, (2) intramolecular aldol reaction/dehydration to form the enone group, and (3) intermolecular Suzuki–Miyaura coupling to connect two monomeric tetrahydroxanthones. This synthetic work allowed us to determine the axial chirality of the 2,2′-biaryl C–C bond and the absolute configuration of the ascherxanthone A. This approach should facilitate the preparation of derivatives and structurally related natural products for medicinal studies

Pharmacokinetics and metabolism of olerciamide A from Portulaca oleracea L. in rats by UHPLC-UV and UHPLC-ESI-Q-TOF/MS

The aim of this study was to elucidate the pharmacokinetics of olerciamide A in rats after oral and intravenous administration of Portulaca oleracea L. extract by a simple and rapid ultra high-performance liquid chromatography method with bergapten as internal standard. The pharmacokinetic results indicated that olerciamide A was rapidly distributed with a time to peak concentration of 30min after oral administration and presented a low oral absolute bioavailability of 4.57%. The metabolism of olerciamide A in rats was also investigated using ultra-high-performance liquid chromatography electrospray coupled with quadrupole-time of flight mass spectrometry to elucidate the reason for the low absolute bioavailability of olerciamide A and seven metabolites of oleraciamide A were found in rat plasma and urine