Cuixian Chen

Generalized multi-ethnic face age-estimation

Age estimation from digital pictures of the face is a very promising research field that is now receiving wide attention. As with any good research problem, face age-estimation is wrought with many challenging interactions that cannot easily be separated out. In general, aging patterns are well understood for all humans, however, these patterns become confounded by intrinsic factors of genetics, gender differences, and ethnic deviations and, equally as important, extrinsic factors of the environment and behavior choices (i.e. sun exposure, drugs, cigarettes, etc). This novel work focuses on the development of a generalized multi-ethnic age-estimation technique — the first of its kind. In addition to the novelty of this approach, the systems overall performance measure (MAE) is “on par” with algorithms that are tuned for a specific ethnic group. Further, the proposed system performance proves to be far more stable across age than the best published results.

Face age estimation using model selection

Face age estimation is a difficult problem due to the dynamics of facial aging and its complex interactions owing to genetics and behavior factors. In this work we develop a robust age estimation system tuned by model selection that outperforms all prior systems on the FG-NET face database. We study various model selection methods systematically to determine the best selection methods among Least Angle Regression (LAR), Principle Component Analysis (PCA), and Locality Preserving Projections (LPP) for age estimation. Our performance analysis on PAL and FG-NET databases suggest that age estimation with LAR or LPP outperforms the full feature model. Furthermore, this work develops a novel operator named “graph age preserving” (GAP) to build a neighborhood graph for LPP for age estimation.

Gender classification from infants to seniors

Many believe that gender classification is a solved problem, however, gender classification for children is a very difficult problem that has not been adequately addressed by the research community. In this work we demonstrate this fact and present a system that performs gender classification on children that outperforms humans. Motivated by the significant improvement in model selection for age estimation [5], we investigate a robust gender classification system via model selection and evaluate the systems using leave-one-person-out cross-validation and 5-fold cross-validation schemes on FG-NET database. Furthermore, this work develops a novel operator, graph gender preserving, to build a neighborhood graph for locality preserving projection for gender classification.

Facial feature fusion and model selection for age estimation

Automatic face age estimation is challenging due to its complexity owing to genetic difference, behavior and environmental factors, the dynamics of facial aging between different individuals, etc. In this work we propose to fuse the global facial feature extracted from Active Appearance Model (AAM) and the local facial features extracted from Local Binary Pattern (LBP), as the representation of faces. Furthermore, we introduce an advanced age estimation system combining feature fusion and model selection schemes such as Least Angle Regression (LAR) and sequential approaches. Due to the fact that different facial feature representations may come with various types of measurement scales, we compare multiple normalization schemes for both facial features. We demonstrate that the feature fusion with model selection can achieve significant improvement in age estimation over single feature representation alone. Our experiment on multi-ethnicity UIUC-PAL database suggests that age estimation with feature fusion and model selection outperforms the single feature, or the full feature model.

Gender classification via global-local features fusion

Computer vision based gender classification is an interesting and challenging research topic in visual surveillance and human-computer interaction systems. In this paper, based on the results of psychophysics and neurophysiology studies that both local and global information is crucial for the image perception, we present an effective global-local features fusion (GLFF) method for gender classification. First, the global features are extracted based on active appearance models (AAM) and the local features are extracted by LBP operator. Second, the global features and local features are fused by sequent selection for gender classification. Third, gender is predicted based on the selected features via support vector machines (SVM). The experimental results show that the proposed local-global information combination scheme could significantly improve the gender classification accuracy obtained by either local or global features, leading to promising performance.

Learning gabor features for facial age estimation

In this work we aim to study rigorously the facial age estimation in a multiethnic environment with 39 possible combination of four feature normalization methods, two simple feature fusion methods, two feature selection methods, and three face representation methods as Gabor, AAM and LBP. First, Gabor feature is extracted as facial representation for age estimation. Inspired by [3], we further fuse the global Active Appearance Model (AAM) and the local Gabor features as the representation of faces. Combining with feature selection schemes such as Least Angle Regression (LAR) and sequential selection, an advanced age estimation system is proposed on the fused features. Systematic comparative of 39 experiments demonstrate that (1) As a single facial representation, Gabor features surprisedly outperform LBP features or even AAM features. (2) With global/local feature fusion scheme, fused Gabor and AAM or fused LBP and AAM features can achieve significant improvement in age estimation over single feature representation alone.

Ensemble of global and local features for face age estimation

Automatic face age estimation is a challenging task due to its complexity owing to genetic difference, behavior and environmental factors, and also the dynamics of facial aging between different individuals. In this paper, we propose a feature fusion method to estimate the face age via SVR, which ensembles global feature from Active Appearance Model (AAM) and the local feature from Gabor wavelet transformation. Our experimental results on UIUC-PAL database show that our proposed method works well.

Bayesian model-averaged benchmark dose analysis via reparameterized quantal-response models.

An important objective in biomedical and environmental risk assessment is estimation of minimum exposure levels that induce a pre-specified adverse response in a target population. The exposure points in such settings are typically referred to as benchmark doses (BMDs). Parametric Bayesian estimation for finding BMDs has grown in popularity, and a large variety of candidate dose-response models is available for applying these methods. Each model can possess potentially different parametric interpretation(s), however. We present reparameterized dose-response models that allow for explicit use of prior information on the target parameter of interest, the BMD. We also enhance our Bayesian estimation technique for BMD analysis by applying Bayesian model averaging to produce point estimates and (lower) credible bounds, overcoming associated questions of model adequacy when multimodel uncertainty is present. An example from carcinogenicity testing illustrates the calculations.

Variance estimation of the Buckley–James estimator under discrete assumptions

The Buckley–James estimator (BJE) is a widely recognized approach in dealing with right-censored linear regression models. There have been a lot of discussions in the literature on the estimation of the BJE as well as its asymptotic distribution. So far, no simulation has been done to directly estimate the asymptotic variance of the BJE. Kong and Yu [Asymptotic distributions of the Buckley–James estimator under nonstandard conditions, Statist. Sinica 17 (2007), pp. 341–360] studied the asymptotic distribution under discontinuous assumptions. Based on their methodology, we recalculate and correct some missing terms in the expression of the asymptotic variance in Theorem 2 of their work. We propose an estimator of the standard deviation of the BJE by using plug-in estimators. The estimator is shown to be consistent. The performance of the estimator is accessed through simulation studies under discrete underline distributions. We further extend our studies to several continuous underline distributions through simulation. The estimator is also applied to a real medical data set. The simulation results suggest that our estimation is a good approximation to the true standard deviation with reference to the empirical standard deviation.

Eyebrow shape analysis by using a modified functional curve procrustes distance

To tackle the problem of automatic recognition of human eyebrow, a novel approach for shape analysis based on frontal face images is proposed in this paper. First, eyebrow curves are acquired by fitting cubic splines based on landmark points. Next, we propose to use a modified functional curve procrustes distance to measure the similarities among the cubic splines, and finally a multidimensional scaling method is adopted to evaluate the effectiveness of the distance. This work extends previous work in analyzing the eyebrow for both human and machine recognition by providing a framework based on shape contours. Further this work demonstrates the effectiveness of eyebrow shape for discrimination when teamed with the appropriate metric distance.