Florentina Bunea

article

Experimental PIV and LIF characterization of a bubble column flow

Irina Murgan, Florentina Bunea, Gabriel Dan Ciocan

Flow Measurement and Instrumentation > 2017 > 54 > C > 224-235

Experimental 2D Particle Image Velocimetry (PIV) measurements, with uniform background lighting and Laser Induced Fluorescence (LIF) of the tracking particles, were performed in order to characterize the air-water biphasic flow and the 2D bubble column rising velocity in static water. Some applications require knowledge of the simultaneity of two-phase flow characteristics. The two phase flow air/water...

chapter

Aeration process influence over the operation of a small hydro turbine - generator unit

Diana Maria Bucur, Georgiana Dunca, Florentina Bunea, Constantin Calinoiu

2017 10th International Symposium on Advanced Topics in Electrical Engineering (ATEE) > 746 - 751

2017 10th International Symposium on Advanced Topics in Electrical Engineering (ATEE)

The environmental friendly concept is a worldwide necessity for the future of the hydropower development as a renewable energy source. For this purpose, aeration devices and techniques are tested and implemented in order to assess the preservation of the aquatic life. The present paper investigates the influence of the aeration process over the operation parameters of a full scale machine (hydro turbine...

chapter

Cavitation characterization using wide band signals in an acoustic active sensing system

Angela Digulescu, Cornel Ioana, Florentina Bunea, Adrian Nedelcu, more

OCEANS 2016 MTS/IEEE Monterey > 1 - 5

OCEANS 2016 MTS/IEEE Monterey

The paper presents a different approach based on an active acoustic system for the characterization of a vortex generating cavitation phenomenon. In the present work, the experiment was carried out in a reduced scale facility. The flow rate of the hydraulic system was varied and, when the flow became stable, the acoustic active system was started. The system is based on two ultrasonic transceivers...

article

A new type of linear magnetostrictive motor

Lucian Pîslaru-Dănescu, Alexandu M. Morega, Mihaela Morega, Florentina Bunea, more

Electrical Engineering > 2017 > 99 > 2 > 601-613

Magnetostrictive materials that may alter their shape significantly in response to external magnetic fields are used in unidirectional motion and force actuators and linear motors. In this study, we present a linear magnetostrictive motor (LMM) powered through a pulse width modulation (PWM) drive, whose core is a waveform controller of DRV101T type. Mathematical modeling and numerical simulations...

chapter

Aggregation and Sparsity Via ℓ₁ Penalized Least Squares

Florentina Bunea, Alexandre B. Tsybakov, Marten H. Wegkamp

Lecture Notes in Computer Science > Learning Theory > Online Aggregation > 379-391

This paper shows that near optimal rates of aggregation and adaptation to unknown sparsity can be simultaneously achieved via ℓ₁ penalized least squares in a nonparametric regression setting. The main tool is a novel oracle inequality on the sum between the empirical squared loss of the penalized least squares estimate and a term reflecting the sparsity of the unknown regression function.

chapter

Sparse Density Estimation with ℓ₁ Penalties

Florentina Bunea, Alexandre B. Tsybakov, Marten H. Wegkamp

Lecture Notes in Computer Science > Learning Theory > Dimensionality Reduction > 530-543

This paper studies oracle properties of ℓ₁-penalized estimators of a probability density. We show that the penalized least squares estimator satisfies sparsity oracle inequalities, i.e., bounds in terms of the number of non-zero components of the oracle vector. The results are valid even when the dimension of the model is (much) larger than the sample size. They are applied to estimation in sparse...

article

ENCAPP: elastic-net-based prognosis prediction and biomarker discovery for human cancers

Jishnu Das, Kaitlyn M Gayvert, Florentina Bunea, Marten H Wegkamp, more

BMC Genomics > 2015 > 16 > 1 > 1-13

Background With the explosion of genomic data over the last decade, there has been a tremendous amount of effort to understand the molecular basis of cancer using informatics approaches. However, this has proven to be extremely difficult primarily because of the varied etiology and vast genetic heterogeneity of different cancers and even within the same cancer. One particularly challenging problem...

chapter

Aeration solution of water used by hydraulic turbines to respect the environmental policies

Florentina Bunea, Diana Maria Bucur, Gabriel Dan Ciocan, Georgiana Dunca

2014 International Conference and Exposition on Electrical and Power Engineering (EPE) > 1015 - 1020

2014 International Conference and Exposition on Electrical and Power Engineering (EPE)

Preserving the quality of the water is a major concern from ecological, economical and sustainable development point of view, but also a condition when using water for renewable energy production. The European Water Policy defines a common regulation for sustainable and integrated management of water corps and requires that all impact factors to be considered. The environmental friendly concept represents...

chapter

On the vortex parameter estimation using wide band signals in active acoustic system

Angela Digulescu, Teodor Petrut, Ion Candel, Florentina Bunea, more

OCEANS 2014 - TAIPEI > 1 - 5

OCEANS 2014 - TAIPEI

This paper proposes a new method for detection of the vortex presence in fluid flow based on an active acoustic system. The experiment that validates the theory was done on a reduced scale facility using ultrasonic transceivers. The main objective was to highlight the effect of a cavitation vortex on an applied wide band signal. In order to accomplish that, the Recurrence Plot Analysis (RPA) was investigated...

article

The Group Square-Root Lasso: Theoretical Properties and Fast Algorithms

Florentina Bunea, Johannes Lederer, Yiyuan She

IEEE Transactions on Information Theory > 2014 > 60 > 2 > 1313 - 1325

We introduce and study the group square-root lasso (GSRL) method for estimation in high dimensional sparse regression models with group structure. The new estimator minimizes the square root of the residual sum of squares plus a penalty term proportional to the sum of the Euclidean norms of groups of the regression parameter vector. The net advantage of the method over the existing group lasso-type...

article

Adaptive inference for the mean of a Gaussian process in functional data

Florentina Bunea, Andrada E. Ivanescu, Marten H. Wegkamp

Journal of the Royal Statistical Society: Series B (Statistical Methodology) > 73 > 4 > 531 - 558

Summary. We propose and analyse fully data‐driven methods for inference about the mean function of a Gaussian process from a sample of independent trajectories of the process, observed at random time points and corrupted by additive random error. Our methods are based on thresholded least squares estimators relative to an approximating function basis. The variable threshold levels are determined...

article

Penalized least squares regression methods and applications to neuroimaging

Florentina Bunea, Yiyuan She, Hernando Ombao, Assawin Gongvatana, more

NeuroImage > 2011 > 55 > 4 > 1519-1527

The goals of this paper are to review the most popular methods of predictor selection in regression models, to explain why some fail when the number P of explanatory variables exceeds the number N of participants, and to discuss alternative statistical methods that can be employed in this case. We focus on penalized least squares methods in regression models, and discuss in detail two such methods...

article

Consistent variable selection in high dimensional regression via multiple testing

Florentina Bunea, Marten H. Wegkamp, Anna Auguste

Journal of Statistical Planning and Inference > 2006 > 136 > 12 > 4349-4364

This paper connects consistent variable selection with multiple hypotheses testing procedures in the linear regression model Y=Xβ+ɛ, where the dimension p of the parameter β is allowed to grow with the sample size n. We view the variable selection problem as one of estimating the index set I0⊆{1,…,p} of the non-zero components of β∈Rp. Estimation of I0 can be further reformulated in terms of testing...

article

Covariate selection for semiparametric hazard function regression models

Florentina Bunea, Ian W. McKeague

Journal of Multivariate Analysis > 2005 > 92 > 1 > 186-204

We study a flexible class of nonproportional hazard function regression models in which the influence of the covariates splits into the sum of a parametric part and a time-dependent nonparametric part. We develop a method of covariate selection for the parametric part by adjusting for the implicit fitting of the nonparametric part. Asymptotic consistency of the proposed covariate selection method...

INFONA - science communication portal

Search results for: Florentina Bunea

Experimental PIV and LIF characterization of a bubble column flow

Aeration process influence over the operation of a small hydro turbine - generator unit

Cavitation characterization using wide band signals in an acoustic active sensing system

A new type of linear magnetostrictive motor

Aggregation and Sparsity Via ℓ₁ Penalized Least Squares

Sparse Density Estimation with ℓ₁ Penalties

ENCAPP: elastic-net-based prognosis prediction and biomarker discovery for human cancers

Aeration solution of water used by hydraulic turbines to respect the environmental policies

On the vortex parameter estimation using wide band signals in active acoustic system

The Group Square-Root Lasso: Theoretical Properties and Fast Algorithms

Adaptive inference for the mean of a Gaussian process in functional data

Penalized least squares regression methods and applications to neuroimaging

Consistent variable selection in high dimensional regression via multiple testing

Covariate selection for semiparametric hazard function regression models

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