scholarly journals Difference of two norms-regularizations for Q-Lasso

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Abdellatif Moudafi
Keyword(s):  
Computational Effort ◽  
Gradient Algorithm ◽  
Signal Recovery ◽  
Cardinality Constraint ◽  
Linear Measurements ◽  
Dc Algorithm ◽  
Difference Of Convex Functions ◽  
Convergence Results ◽  
The Difference ◽  
New Algorithms

The focus of this paper is in Q-Lasso introduced in Alghamdi et al. (2013) which extended the Lasso by Tibshirani (1996). The closed convex subset Q belonging in a Euclidean m-space, for m∈IN, is the set of errors when linear measurements are taken to recover a signal/image via the Lasso. Based on a recent work by Wang (2013), we are interested in two new penalty methods for Q-Lasso relying on two types of difference of convex functions (DC for short) programming where the DC objective functions are the difference of l1 and lσq norms and the difference of l1 and lr norms with r>1. By means of a generalized q-term shrinkage operator upon the special structure of lσq norm, we design a proximal gradient algorithm for handling the DC l1−lσq model. Then, based on the majorization scheme, we develop a majorized penalty algorithm for the DC l1−lr model. The convergence results of our new algorithms are presented as well. We would like to emphasize that extensive simulation results in the case Q={b} show that these two new algorithms offer improved signal recovery performance and require reduced computational effort relative to state-of-the-art l1 and lp (p∈(0,1)) models, see Wang (2013). We also devise two DC Algorithms on the spirit of a paper where exact DC representation of the cardinality constraint is investigated and which also used the largest-q norm of lσq and presented numerical results that show the efficiency of our DC Algorithm in comparison with other methods using other penalty terms in the context of quadratic programing, see Jun-ya et al. (2017).

Nonsubmodular Constrained Profit Maximization in Attribute Networks

2021 ◽  
Author(s):  
Liman Du ◽  
Wenguo Yang ◽  
Suixiang Gao
Keyword(s):  
Profit Maximization ◽  
Logistic Function ◽  
Influence Maximization ◽  
Maximization Problem ◽  
Cardinality Constraint ◽  
Three Phase ◽  
Marginal Increment ◽  
The Difference ◽  
Classical Influence ◽  
Influence Maximization Problem

The number of social individuals who interact with their friends through social networks is increasing, leading to an undeniable fact that word-of-mouth marketing has become one of the useful ways to promote sale of products. The Constrained Profit Maximization in Attribute network (CPMA) problem, as an extension of the classical influence maximization problem, is the main focus of this paper. We propose the profit maximization in attribute network problem under a cardinality constraint which is closer to the actual situation. The profit spread metric of CPMA calculates the total benefit and cost generated by all the active nodes. Different from the classical Influence Maximization problem, the influence strength should be recalculated according to the emotional tendency and classification label of nodes in attribute networks. The profit spread metric is no longer monotone and submodular in general. Given that the profit spread metric can be expressed as the difference between two submodular functions and admits a DS decomposition, a three-phase algorithm named as Marginal increment and Community-based Prune and Search(MCPS) Algorithm frame is proposed which is based on Louvain algorithm and logistic function. Due to the method of marginal increment, MPCS algorithm can compute profit spread more directly and accurately. Experiments demonstrate the effectiveness of MCPS algorithm.

The Relative Growth of Parts in Palaemon Carcinus

1930 ◽  
Vol 7 (2) ◽  
pp. 165-174
Author(s):  
M. A. TAZELAAR
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Linear Measurements ◽  
Relative Growth ◽  
Male And Female ◽  
Relative Growth Rates ◽  
Rate Of Growth ◽  
The Difference ◽  
Rates Of Growth

Linear measurements of certain appendages and the carapace of P. carcinus were made and plotted in various ways. The following conclusions were drawn: 1. The cheliped shows heterogonic growth in both male and female, but more markedly in the male, the values of k being: male 1.8 and female 1.48 2. The pereiopods in both male and female are slightly heterogonic. The relative growth rates are graded from p3 to p5, that of p3 being slightly greater than that of p5 3. Of the ordinary pereiopods the rate of growth of p1 is the smallest in the male, but the largest in the female. 4. The difference between the rates of growth of p1 and p3 in male and female is greatest where the rate of growth in the heterogonic organ, the cheliped, is most excessive in the male. 5. The growth of the 3rd maxilliped is slightly negatively heterogonic, the value of k in the male being 0.93 and in the female 0.95. Hence there seems to be a correlation between the marked heterogony in the cheliped on the growth rate of neighbouring appendages. In those immediately posterior to the cheliped the growth rate is increased and in those anterior decreased.

The Validity of Approximate Boundary Conditions for Natural Convection With Thermal Radiation in Open Cavities

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Om Singh ◽  
Shireesh B. Kedare ◽  
Suneet Singh
Keyword(s):  
Natural Convection ◽  
Boundary Conditions ◽  
Significant Loss ◽  
Computational Effort ◽  
Computational Domain ◽  
Maximum Difference ◽  
Open Cavities ◽  
Shallow Cavities ◽  
Approximate Boundary Conditions ◽  
The Difference

Abstract The use of approximate boundary conditions at the opening of the cavities leads to restriction of the computational domain and, hence, the reduction in computational effort. However, the accuracy of the restricted domain approach (RDA) had been evaluated only for the natural convection inside open cavities and that too only for one aspect ratio (AR). The validity of the approach had not been evaluated for inclined, as well as, shallow cavities. This study focuses on the analysis of the accuracy of RDA against extended domain approach (EDA) in open cavities of different ARs, at different inclinations and different Rayleigh numbers (Ra). The results show that the difference between the approaches is only significant in very shallow cavities (AR is defined as the height of the hot wall divided by the depth of the cavity) at low Ra. For Ra higher than  106 and an AR greater than 0.2, the maximum difference between the two approaches is around 5% and hence RDA can be recommended in these ranges, resulting in increased computational efficiency without significant loss in the accuracy. Moreover, the maximum difference in the results for the two methods is for intermediate inclinations. Even there, an increase in the difference is more pronounced at lower Ra. Furthermore, distribution of the exit velocity and temperature at the opening as well as the distribution of the Nusselt number at the hot wall is compared for RDA and EDA to explain the behavior of error at different ARs and inclinations.

Online Learning Based on Online DCA and Application to Online Classification

2020 ◽  
Vol 32 (4) ◽  
pp. 759-793 ◽  
Author(s):  
Hoai An Le Thi ◽  
Vinh Thanh Ho
Keyword(s):  
Online Learning ◽  
State Of The Art ◽  
Classification Algorithms ◽  
Data Sets ◽  
Prediction Problem ◽  
Dc Algorithm ◽  
Difference Of Convex Functions ◽  
Online Classification ◽  
Learning Techniques ◽  
Difference Of Convex

We investigate an approach based on DC (Difference of Convex functions) programming and DCA (DC Algorithm) for online learning techniques. The prediction problem of an online learner can be formulated as a DC program for which online DCA is applied. We propose the two so-called complete/approximate versions of online DCA scheme and prove their logarithmic/sublinear regrets. Six online DCA-based algorithms are developed for online binary linear classification. Numerical experiments on a variety of benchmark classification data sets show the efficiency of our proposed algorithms in comparison with the state-of-the-art online classification algorithms.

A Methodology for Blast Furnace Hearth Inner Profile Analysis

2007 ◽  
Vol 129 (12) ◽  
pp. 1729-1731 ◽  
Author(s):  
Yu Zhang ◽  
Rohit Deshpande ◽  
D. Huang ◽  
Pinakin Chaubal ◽  
Chenn Q. Zhou
Keyword(s):  
Heat Transfer ◽  
Blast Furnace ◽  
Profile Analysis ◽  
Furnace Hearth ◽  
Temperature Distributions ◽  
Blast Furnace Hearth ◽  
Computational Fluid Dynamics Cfd ◽  
The Difference ◽  
New Algorithms ◽  
Face Temperature

The wear of a blast furnace hearth and the hearth inner profile are highly dependent on the liquid iron flow pattern, refractory temperatures, and temperature distributions at the hot face. In this paper, the detailed methodology is presented along with the examples of hearth inner profile predictions. A new methodology along with new algorithms is proposed to calculate the hearth erosion and its inner profile. The methodology is to estimate the hearth primary inner profile based on 1D heat transfer and to compute the hot-face temperature using the 3D CFD hearth model according to the 1D preestimated and reestimated profiles. After the hot-face temperatures are converged, the hot-face positions are refined by a new algorithm, which is based on the difference between the calculated and measured results, for the 3D computational fluid dynamics (CFD) hearth model further computations, until the calculated temperatures well agree with those measured by the thermocouples.

Pre-Swirled Cooling Air Delivery System Performance

2005 ◽  
Author(s):  
J. W. Chew ◽  
F. Ciampoli ◽  
N. J. Hills ◽  
T. Scanlon
Keyword(s):  
System Performance ◽  
Computational Effort ◽  
Measured Data ◽  
Numerical Results ◽  
Simplified Model ◽  
Swirl Chamber ◽  
Aero Engine ◽  
The Difference ◽  
Cooling Air ◽  
Good Agreement

This paper reports results from numerical simulations of the flow in pre-swirl cooling air delivery systems. Two different systems have been investigated corresponding to experimental rigs for which measured data is available. The rigs are representative of aero-engine conditions. The difference in the performance of the two rigs has been addressed. The flow in the pre-swirl nozzles and in the pre-swirl chambers has been investigated separately. For the pre-swirl chamber a simplified model, in which the nozzle is replaced by a slot, has been used to reduce the computational effort required. Nevertheless numerical results are in good agreement with experimental measurements. It is shown that the difference in the geometry of the pre-swirl chambers is largely responsible for the difference in performance of the rigs. Numerical results have also been compared with predictions from a previously published simplified model. An adjustment of the empirical constants in the simple model has been proposed in order to improve the prediction of the moments in the pre-swirl chamber.

scholarly journals Properties and Iterative Methods for theQ-Lasso

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Maryam A. Alghamdi ◽  
Mohammad Ali Alghamdi ◽  
Naseer Shahzad ◽  
Hong-Kun Xu
Keyword(s):  
Iterative Methods ◽  
Convex Subset ◽  
Gradient Algorithm ◽  
Tuning Parameter ◽  
Linear Measurements ◽  
Tolerance Level ◽  
Basic Properties ◽  
Proximal Gradient Algorithm ◽  
Signal Image

We introduce theQ-lasso which generalizes the well-known lasso of Tibshirani (1996) withQa closed convex subset of a Euclideanm-space for some integerm≥1. This setQcan be interpreted as the set of errors within given tolerance level when linear measurements are taken to recover a signal/image via the lasso. Solutions of theQ-lasso depend on a tuning parameterγ. In this paper, we obtain basic properties of the solutions as a function ofγ. Because of ill posedness, we also applyl1-l2regularization to theQ-lasso. In addition, we discuss iterative methods for solving theQ-lasso which include the proximal-gradient algorithm and the projection-gradient algorithm.

scholarly journals Stomach Volume Evaluation on Fetal MRI and its use in Prenatal Identification of Esophageal Atresia

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Aditya Phadnis ◽  
Monica Forbes-Amrhein
Keyword(s):  
Esophageal Atresia ◽  
Fetal Mri ◽  
Third Trimester ◽  
Linear Measurements ◽  
Significant Difference ◽  
The Difference ◽  
Magnetic Resonance Imaging Mri ◽  
Stomach Volume ◽  
Post Hoc ◽  
One Way Anova

Swallowing of amniotic fluid alters the volume of the fetal stomach; therefore an abnormal fetal stomach size can be indicative of pathology. Previous studies have used linear measurements on ultrasound to approximate stomach sizes. Fetal magnetic resonance imaging (MRI) allows for volumetric measurement of the stomach. The objective of this study was to develop a library of normal fetal stomach volumes on MRI at each gestational age. We also sought to measure stomach volumes of fetuses with esophageal atresia and compare to normal volumes at similar gestation ages (GA).  A retrospective review of fetal MRIs from patients 20-38 weeks GA was conducted.  Exclusion criteria for the controls included any impairment that would impede swallowing or alter stomach sizes.  Patients with esophageal atresia were identified and postnatal records were reviewed to confirm the diagnosis. The stomach volume was measured on T2-weighted imaging using Phillips Intellispace software. The stomach volumes of the controls at each GA were compared using one-way ANOVA with Games-Howell Post-Hoc (p<0.05).  The stomach volume in esophageal atresia was compared to controls using a T-test (p<0.001).    185 control studies, 10 at each week of gestation, and 8 patients with esophageal atresia were included. For normal fetuses, there was a trend of increased stomach size and broadened standard deviation with increasing GA.  No significant difference was found between any two sequential weeks, however the difference in second and third trimester volumes was significant (p<0.001).   The patients with esophageal atresia had significantly smaller stomach volumes compared to control patients of the same GA range (p<0.001).   This pilot study established reference values for fetal stomach volume, which was found to increase with GA. The stomach volume is significantly smaller in patients with esophageal atresia.  Thus, esophageal atresia can be identified prenatally, allowing for delivery at an appropriate acuity NICU and early intervention.   

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