A new marker design for a robust marker tracking system against occlusions

Marker systems are a widely used optical tracking method that does not support occlusions. Thus, this paper proposes a new marker design to overcome the problem of marker occlusions. It is highly adaptable, because it can be used by any marker tracking system that uses its central area to codify the digital identification. Our proposal takes advantage of an untapped frame to place some textures that will be tracked during marker occlusion. In addition, these textures are customizable, which lets users make their own designs. Two tracking methods are combined to offer a robust tracking, updating the six degrees of freedom of the camera in real time. The first one is a fast technique based on temporal coherence, whereas the second one is a robust technique based on appearance, which is used as a recovery mode. Copyright © 2012 John Wiley & Sons, Ltd.     

A large haptic device for aircraft engine maintainability

The virtual reality for maintainability (Revima) VR system supports maintainability simulation in aeronautics. Within this project we have developed and integrated a haptic device, the large haptic interface for aeronautic maintainability (LHIfAM). We use this device to track hand movements and provide force feedback within the large geometric models that describe aircraft engines. The user movements are the same as those that occur when testing physical mock-ups. An integrated haptic device and VR system for testing aircraft engines reduces development costs and avoids the necessity of physical mock-ups formaintainability.     

Low Prostate Concentration of Lycopene Is Associated with Development of Prostate Cancer in Patients with High-Grade Prostatic Intraepithelial Neoplasia

Prostate cancer (PC) is a frequent male malignancy and represents the second most diagnosed cancer in men. Since pre-cancerous lesions, i.e., the high-grade prostatic intraepithelial neoplasia (HGPIN), can be detected years before progression to PC, early diagnosis and chemoprevention are targeted strategies to reduce PC rates. Animal studies have shown that lycopene, a carotenoid contained in tomatoes, is a promising candidate for the chemoprevention of PC. However, its efficacy in humans remains controversial. The present study aimed to investigate the relevance of plasma and prostate concentration of lycopene after a lycopene-enriched diet in patients diagnosed with HGPIN. Thirty-two patients diagnosed with HGPIN were administered a lycopene-enriched diet (20–25 mg/day of lycopene; through 30 g/day of triple concentrated tomato paste) for 6 months. A 6-month follow-up prostate biopsy assessed progression to PC. Patients were classified into three groups according to the histopathological features of the 6-month follow-up biopsy results: prostatitis; HGPIN and PC. PSA and plasma lycopene levels were measured before and after the dietary lycopene supplementation. Prostatic lycopene concentration was only assessed after the supplementation diet. Only prostatic lycopene concentration showed significant differences between the three groups (p = 0.03). Prostatic lycopene concentration below a 1 ng/mg threshold was associated with PC at 6-month follow-up biopsy (p = 0.003). We observed no overall benefits from a 6-month lycopene supplementation, as the rate of HGPIN progression to PC in our population (9/32, 28%) was similar to rates reported in the literature. Baseline PSA levels also showed no significant changes after a lycopene-enriched diet. Our findings point to prostatic lycopene concentration as a promising biomarker of PC. Further prospective longitudinal studies are needed to assess the prognostic role of prostatic lycopene in PC.     

1990-1996: the experience of the La Fe Lung Transplant Group (Valencia)

Objective to review the experience of the lung transplantation unit at Hospital La Fe (Valencia). Between February 1990 and March 1996 we performed 40 lung transplants. The following causes were most common: cystic fibrosis (9 cases), emphysema (8), pulmonary fibrosis (8) and bronchiectasis (7). Types of intervention were 27 double lung transplants (25 sequential and 9 blocked), 9 single lung transplants, and 4 heart-lung transplants. We then reviewed the 36 single and double lung transplants. The main exclusion criteria were age over 65 years, malignant disease, kidney or liver disease, severe or non reversible central nervous system disease, and drug addiction. Prior surgery, mechanical ventilation and the presence of Aspergillus were considered lower-order contraindications. Mean patient age was 37.7 years (14-59). Six patients were colonized by Aspergillus before transplantation. Five had undergone earlier surgery and two were mechanically ventilated before the transplant. The most common complication was respiratory infection, which was present in 6 of the 7 patients who died. Other complications in order of frequency were dehiscence and/or bronchial stenosis, corticoid myopathy and postoperative bleeding. The actuarial survival rate of single and double lung transplants was 67.85 after 3 years, and 87.5% in patients with cystic fibrosis. Lung transplantation is a well-established procedure that is gradually being extended to treat more conditions. The main obstacle is the scarcity of donors. The main challenge at present is bronchiolitis obliterans.     

Parallel RRT-based path planning for selective disassembly planning

The planning of disassembly sequences requires the identification of the extraction trajectories of the different parts or assemblies. The failure to find these trajectories can make a planner fail to generate correct sequences or not evaluate potential solutions. In this paper, we analyze the disassembly path-planning problem, its relation to the general path-planning problem and the main differences between both of them, such as the lack of a target configuration. We present a modification of the rapid-growing random tree-based algorithm (RRT) that addresses these differences. RRTs are easily parallelized so we analyze two different parallelization methods using dual-core-based CPUs as well as the impact of the target selection probability of the algorithm in execution time. The method described is applied to several real-world and synthetic examples.     

Influence of multisensory feedback on haptic accessibility tasks

Environments of a certain nature, such as those related to maintenance tasks can benefited from haptic stimuli by performing accessibility simulation in a realistic manner. Accessibility is defined as the physical feasibility of accessing an element of a 3D model avoiding undesirable collisions. This paper studies the benefits that multisensory systems can provide in performing this kind of tasks. The research is specially focused on the improvements provided by auditory feedback to the user’s performance. We have carried out a user study where participants had to perform an accessibility task with the aid of different combinations of sensorial stimuli. A large haptic interface for aeronautic maintainability has been extended with real-time sound generation capabilities to study this issue. The results of these experiments show that auditory stimuli provide with useful cues to the users helping them to correct trajectories and hence improving their performance.     

A methodology for optimal voxel size computation in collision detection algorithms for virtual reality

Real-time Virtual Reality applications require accuracy but are also time dependent; therefore, in these environments, the time consumption is particularly important. For that reason, when facing the problem of Collision Detection for a Virtual Reality application, we firstly focus our attention on optimizing time performance for collisions among objects. Spatial Partitioning algorithms have been broadly used in Collision Detection. In particular, voxel-based methods are simple and quick, but finding the optimum voxel size is not trivial. We propose a methodology to easily determine the optimal voxel size for Collision Detection algorithms. Using an algorithm which represents volumetric objects with tetrahedra as an example, a performance cost function is defined in order to analytically bound the voxel size that gives the best computation times. This is made by inferring and estimating all the parameters involved. Thus, the cost function is delimited to depend only on geometric data. By doing so, it is possible to determine the optimal voxelization for any algorithm and scenario. Several solutions have been researched and compared. Experimental results with theoretical and real 3D models have validated the methodology. The reliability of our research has also been compared with traditional experimental solutions given by previous works.     

Junction assisted 3D pose retrieval of untextured 3D models in monocular images

This article presents a comprehensive framework for the recognition of untextured 3D models in a single image. The method proposed here is capable of recovering a 3D pose in a few hundred of milliseconds, which is a difficult challenge using this type of model.     

Approximation of Optimal Voxel Size for Collision Detection in Maintainability Simulations within Massive Virtual Environments

This paper describes a Collision Method for massive virtual environments composed of millions of triangles. It has been applied in the aeronautics industry for maintainability simulations using virtual aircraft engine mock‐ups. The method performs well and has a good interactive frame rate even when it is used for computing force feedback with haptic devices. Space sorting problems chiefly related to voxel techniques, such as memory requirements and optimal voxel size, have been solved. We use advanced memory structures and hashing techniques. To find the optimal voxel size, several analytical solutions have been proposed and compared. These solutions are based on the performance cost function of the algorithm used. Experiments have been undertaken to verify these analytical solutions.