Multiresolution hierarchy co-clustering for semantic segmentation in sequences with small variations

This paper presents a co-clustering technique that, given a collection of images and their hierarchies, clusters nodes from these hierarchies to obtain a coherent multiresolution representation of the image collection. We formalize the co-clustering as a Quadratic Semi-Assignment Problem and solve it with a linear programming relaxation approach that makes effective use of information from hierarchies. Initially, we address the problem of generating an optimal, coherent partition per image and, afterwards, we extend this method to a multiresolution framework. Finally, we particularize this framework to an iterative multiresolution video segmentation algorithm in sequences with small variations. We evaluate the algorithm on the Video Occlusion/Object Boundary Detection Dataset, showing that it produces state-of-the-art results in these scenarios.Comment: International Conference on Computer Vision (ICCV) 201

Static loads on the lower back for two modalities of the isometric smith squat

Introduction: The squat is one of the most effective exercises in athletic training. However, there is a scarcity of research that reports the muscular and joint loads in the lumbar region incurred when performing the high bar and the low bar isometric squat modalities in a Smith machine. Therefore, this study aims to determine the muscle force of the lower back extensors, and the compressive (Rc) and shear (Rs) forces at the lumbosacral joint for the one repetition maximum (1RM) high bar and low bar isometric parallel-depth Smith squats. Methods: Eight healthy male well-trained 400-m sprinters participated in the study. The athletes performed the two modalities of the isometric squat on a 7° backward-inclined Smith machine using a mean ± SD 1RM external resistance of 100.3 ± 7.2 kg. During the squat, the participants paused for 2-3 s at the bottom of the squat, corresponding to a position in which the thighs are parallel to the ground. This was, therefore, considered a static position for the calculation of isometric muscle forces and joint loads using static mechanical analysis. Moment arms, and joint and segmental angles were calculated from video images of the squatting performance. Internal forces were computed using a geometrical model of the trunk and lower limb. Results: Spinal extensor muscular forces and lumbo-sacral joint forces were higher when using the low bar technique; with the exception of Rs which was approximately equal. The mean Rc were 10.2 body weights (BW) or 8,014 N (high bar) and 11.1 BW or 8,729 N (low bar). Discussion: The low bar technique yields higher Rc and may therefore be avoided in the rehabilitation of spinal injuries. Increased bone mineral density and well-developed trunk musculature due to long term squat training can provide protection against passive spinal tissue failure. Therefore, the Rc found for the 1RM isometric parallel-depth Smith squat do not appear excessive for healthy well-trained athletes. The presence of Rs at the lumbo-sacral joint in both squat modalities suggests potential for damage to the intervertebral disc. The findings provide an in-depth understanding of the two squat modalities in isometric conditions for the prevention of lower back injury and the design of rehabilitation programs

Optimization of the ionization time of an atom with tailored laser pulses: a theoretical study

How fast can a laser pulse ionize an atom? We address this question by considering pulses that carry a fixed time-integrated energy per-area, and finding those that achieve the double requirement of maximizing the ionization that they induce, while having the shortest duration. We formulate this double-objective quantum optimal control problem by making use of the Pareto approach to multi-objetive optimization, and the differential evolution genetic algorithm. The goal is to find out how much a precise time-profiling of ultra-fast, large-bandwidth pulses may speed up the ionization process with respect to simple-shape pulses. We work on a simple one-dimensional model of hydrogen-like atoms (the P\"oschl-Teller potential), that allows to tune the number of bound states that play a role in the ionization dynamics. We show how the detailed shape of the pulse accelerates the ionization process, and how the presence or absence of bound states influences the velocity of the process

Static loads on the knee and ankle for two modalities of the isometric smith squat

Introduction: The back squat is a popular strength training exercise that recruits approximately 75% of the muscular system. However, knowledge of muscular and joint loads incurred when performing two variations of the back squat, namely the high bar and the low bar isometric parallel-depth Smith squat, is limited. Therefore this study aims to determine the lower limb muscle forces and the compressive and shear joint forces at the knee and ankle incurred in these two subtle variations of the one repetition maximum (1RM) isometric Smith squat. Method: Eight healthy male 400-m sprinters participated in the study. The participants performed the two modalities of the squat using a 7° backward-inclined Smith machine. The bottom of the squat corresponded to a position in which the thighs are parallel to the ground. The mean ± SD 1RM external load for the eight participants was 100.3 ± 7.2 kg. During the squat, the participants paused for 2-3 s at the bottom of the squat. This was, therefore, considered a static position for the calculation of isometric muscle forces and joint loads using static mechanical analysis. Moment arms, and joint and segmental angles were calculated from video images of the squat obtained at 25 Hz. Internal forces were computed using a geometrical model of the lower limb. Results: Quadriceps muscle and knee joint forces were higher in the high bar squat; where, the mean patellofemoral joint reaction force was 3.7 body weights (BW). The ankle extensor muscle and ankle joint forces were larger in the low bar squat; whereby, the mean compressive force at the ankle joint was 3.0 BW. Discussion: The high bar squatting modality may be avoided in the rehabilitation of ACL injury. Conversely, the low bar technique may be discouraged in conditions of ankle joint instability, strained Achilles tendon, and damaged gastrocnemius and soleus muscles. The findings of the static biomechanical evaluation provide an in-depth understanding of the musculoskeletal loads associated with the two squat modalities in isometric conditions and offer a foundation for the dynamic modelling of the high bar and low bar Smith squat. Further, the knowledge gained can be used for the prevention of injury in strength training and in the design of rehabilitation programs that control muscle recruitment and joint loads

The gender gap in educational mismatch: evidence from the Dominican Republic

In this paper we test the existence of gender gaps in educational mismatch for a developing country (Dominican Republic), an interesting case study due to its recent policies of education promotion, which achieved an important increase in enrolment rates at all levels of schooling, particularly for women. We use recent microdata to distinguish between over and undereducation, finding asymmetric effects by gender, particularly harmful for women. Various matching techniques based on propensity score methods were implemented in order to evaluate the impact of the over and under education index on earnings.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

A Community-Driven Validation Service for Standard Medical Imaging Objects

Digital medical imaging laboratories contain many distinct types of equipment provided by different manufacturers. Interoperability is a critical issue and the DICOM protocol is a de facto standard in those environments. However, manufacturers' implementation of the standard may have non-conformities at several levels, which will hinder systems' integration. Moreover, medical staff may be responsible for data inconsistencies when entering data. Those situations severely affect the quality of healthcare services since they can disrupt system operations. The existence of software able to confirm data quality and compliance with the DICOM standard is important for programmers, IT staff and healthcare technicians. Although there are a few solutions that try to accomplish this goal, they are unable to deal with certain situations that require user input. Furthermore, these cases usually require the setup of a working environment, which makes the sharing of validation information more difficult. This article proposes and describes the development of a Web DICOM validation service for the community. This solution requires no configuration by the user, promotes validation results share-ability in the community and preserves patient data privacy since files are de-identified on the client side.Comment: Computer Standards & Interfaces, 201

Analysis of Mesostructure Unit Cells Comprised of Octet-truss Structures

A unit truss finite element analysis method allowing non-linear deformation is employed to analyze a unit cell comprised of n 3 octet-truss structures for their stiffness and displacement compared to their relative density under loading. Axial, bending, shearing, and torsion effects are included in the analysis for each strut in the octet-truss structure which is then related to the mesostructure level (unit cell). The versatility of additive manufacturing allows for the fabrication of these complex unit cell truss structures which can be used as building blocks for macro-scale geometries. The finite element calculations are compared to experimental results for samples manufactured on a Stereolithography Apparatus (SLA) out of a standard resin.Mechanical Engineerin

Speeding up the solution of the Bethe-Salpeter equation by a double-grid method and Wannier interpolation

The Bethe-Salpeter equation is a widely used approach to describe optical excitations in bulk semiconductors. It leads to spectra that are in very good agreement with experiment, but the price to pay for such accuracy is a very high computational burden. One of the main bottlenecks is the large number of k-points required to obtain converged spectra. In order to circumvent this problem we propose a strategy to solve the Bethe-Salpeter equation based on a double-grid technique coupled to a Wannier interpolation of the Kohn-Sham band structure. This strategy is then benchmarked for a particularly difficult case, the calculation of the absorption spectrum of GaAs, and for the well studied case of Si. The considerable gains observed in these cases fully validate our approach, and open the way for the application of the Bethe-Salpeter equation to large and complex systems.Comment: 5 pages, 3 figures. Accepted for Phys. Rev.

Efficient Detectors for MIMO-OFDM Systems under Spatial Correlation Antenna Arrays

This work analyzes the performance of the implementable detectors for multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) technique under specific and realistic operation system condi- tions, including antenna correlation and array configuration. Time-domain channel model has been used to evaluate the system performance under realistic communication channel and system scenarios, including different channel correlation, modulation order and antenna arrays configurations. A bunch of MIMO-OFDM detectors were analyzed for the purpose of achieve high performance combined with high capacity systems and manageable computational complexity. Numerical Monte-Carlo simulations (MCS) demonstrate the channel selectivity effect, while the impact of the number of antennas, adoption of linear against heuristic-based detection schemes, and the spatial correlation effect under linear and planar antenna arrays are analyzed in the MIMO-OFDM context.Comment: 26 pgs, 16 figures and 5 table