Learning with Augmented Features for Heterogeneous Domain Adaptation

We propose a new learning method for heterogeneous domain adaptation (HDA), in which the data from the source domain and the target domain are represented by heterogeneous features with different dimensions. Using two different projection matrices, we first transform the data from two domains into a common subspace in order to measure the similarity between the data from two domains. We then propose two new feature mapping functions to augment the transformed data with their original features and zeros. The existing learning methods (e.g., SVM and SVR) can be readily incorporated with our newly proposed augmented feature representations to effectively utilize the data from both domains for HDA. Using the hinge loss function in SVM as an example, we introduce the detailed objective function in our method called Heterogeneous Feature Augmentation (HFA) for a linear case and also describe its kernelization in order to efficiently cope with the data with very high dimensions. Moreover, we also develop an alternating optimization algorithm to effectively solve the nontrivial optimization problem in our HFA method. Comprehensive experiments on two benchmark datasets clearly demonstrate that HFA outperforms the existing HDA methods.Comment: ICML201

MiniMax Entropy Network: Learning Category-Invariant Features for Domain Adaptation

How to effectively learn from unlabeled data from the target domain is crucial for domain adaptation, as it helps reduce the large performance gap due to domain shift or distribution change. In this paper, we propose an easy-to-implement method dubbed MiniMax Entropy Networks (MMEN) based on adversarial learning. Unlike most existing approaches which employ a generator to deal with domain difference, MMEN focuses on learning the categorical information from unlabeled target samples with the help of labeled source samples. Specifically, we set an unfair multi-class classifier named categorical discriminator, which classifies source samples accurately but be confused about the categories of target samples. The generator learns a common subspace that aligns the unlabeled samples based on the target pseudo-labels. For MMEN, we also provide theoretical explanations to show that the learning of feature alignment reduces domain mismatch at the category level. Experimental results on various benchmark datasets demonstrate the effectiveness of our method over existing state-of-the-art baselines.Comment: 8 pages, 6 figure

Electronic structure of self-assembled InAs/InP quantum dots: A Comparison with self-assembled InAs/GaAs quantum dots

We investigate the electronic structure of the InAs/InP quantum dots using an atomistic pseudopotential method and compare them to those of the InAs/GaAs QDs. We show that even though the InAs/InP and InAs/GaAs dots have the same dot material, their electronic structure differ significantly in certain aspects, especially for holes: (i) The hole levels have a much larger energy spacing in the InAs/InP dots than in the InAs/GaAs dots of corresponding size. (ii) Furthermore, in contrast with the InAs/GaAs dots, where the sizeable hole $p$, $d$ intra-shell level splitting smashes the energy level shell structure, the InAs/InP QDs have a well defined energy level shell structure with small $p$, $d$ level splitting, for holes. (iii) The fundamental exciton energies of the InAs/InP dots are calculated to be around 0.8 eV ($\sim$ 1.55 $\mu$m), about 200 meV lower than those of typical InAs/GaAs QDs, mainly due to the smaller lattice mismatch in the InAs/InP dots. (iii) The widths of the exciton $P$ shell and $D$ shell are much narrower in the InAs/InP dots than in the InAs/GaAs dots. (iv) The InAs/GaAs and InAs/InP dots have a reversed light polarization anisotropy along the [100] and [1$\bar{1}$0] directions

Electronic properties and 4f→ 5d transitions in Ce-doped Lu2SiO5: a theoretical investigation

This is an electronic version of an article published in Journal of Materials Chemistry. Ning, L., Lin, L., Li, L., Wu, C., Duan, C., Zhang, Y. and Luis Seijo. "Electronic properties and 4f 5d transitions in Ce-doped Lu2SiO5: a theoretical investigation". Journal of Materials Chemistry 22 (2012): 13723-1373

Theoretical study on structural properties and 4f 5d transitions of locally charge-compensated Ce3+ in CaF2

Reprinted with permission from Ning, L., Wu, C.,Li, L., Lin,L., Duan, C., Zhang, Y. and Luis Seijo. "Theoretical study on structural properties and 4f 5d transitions of locally charge-compensated Ce3+ in CaF2". The Journal of Physical Chemistry C 116.34 (2012): 18419-18426.The structural properties and 4f → 5d transitions of Ce3+ in CaF2, with local charge compensation by an interstitial fluoride (Fi ′) or an oxygen substitution for fluoride (OF′), have been studied using the density functional theory (DFT) within the supercell model and the wave function-based embedded cluster calculations, respectively. The DFT results indicate that the incorporation of locally charge-compensated Ce3+ in CaF2 induces an anisotropic distortion of the structure around the dopant site. On the basis of the DFToptimized structures, the Ce-centered embedded clusters are constructed, on which the wave function-based CASSCF/CASPT2/ RASSI−SO calculations at the spin−orbit level are performed to obtain the Ce3+ 4f1 and 5d1 level energies. The calculated 4f−5d transition energies and relative intensities are in good agreement with available experimental results. From the present calculations, we conclude that the 5d1 level missing in the low-temperature absorption spectrum of the tetragonal Ce center with Fi ′ compensation is the second-lowest one, and the absorption at this level is overshadowed by an adjacent cluster band usually assigned to Ce clusters and thus was not observed in experiments. We also assign the two closely spaced absorption lines around 3118.5 Å observed in experiments to the lowest two quasi-degenerated 4f → 5d transitions of the monoclinic center with Fi ′ compensation rather than those of the trigonal center as proposed earlier. Finally, we analyze the structural and electronic reasons for the large reduction (∼2000 cm−1 ) of the lowest 4f → 5d transition energy from a Fi ′ to a nearest-neighbor OF′ compensation, in terms of the changes in the centroid energy difference and crystal- field splittingThis work was supported by the NSFC (Grants 11174005, 11074315, 90922022, and 10804001) and the Program for Innovative Research Teams in Anhui Normal University of China. L.S. acknowledges support from MEC-Spain (Grant MAT2011-24586