Steady flow and dynamic viscoelastic properties of branched polyethylene

The presentation of viscoelastic properties of molten high polymers in a complex plane makes three characteristic rheologic parameters appear. These are examined for a series of commercial samples of low density polyethylene. For instance, it enables products to be recognized which are very similar as far as the melt index is concerned but have different molecular weight distribution, different long chain branching index and consequently different processing properties.     

Diet as a risk factor for cardiovascular disease in residents of the metropolitan area, San Jose, Costa Rica]

The purpose of this study was to define the dietary pattern of fatty acids, cholesterol, fiber and sucrose in a random sample of 51 families of San José, Costa Rica. Food intake was estimated by using the one-day food weighing method. For food composition values, a single table was created using data taken from others. The results indicated that the level of macronutrient diet composition was in accordance with the United States National Cholesterol Education Program Recommendations. Nevertheless, total dietary fiber (20.3 g/d) intake was below the level suggested by the guidelines, and the percentage of calories from sucrose (12.6%) was above those recommendations. In conclusion, the low P/S ratio, low dietary fiber and high percentage of calories from sucrose in the diet of this urban population group of San José, has several atherogenic features representing one of the important risk factors associated with cardiovascular disease.     

Fruits and vegetables consumption among Costa Rican adolescents

Scientific evidence indicates that lower levels of fruit and vegetables consumption are associated with an increased risk of developing cancer and cardiovascular disease. Therefore, an increase of these foods' consumption may substantially improve public health. The purpose of this study was to examine the consumption of fruits and vegetables in 214 urban and rural adolescents in relation to the 5-A-DAY recommendation. Mean daily servings of fruits (1.7 servings) were not far from the minimum recommendation of 2 daily fruit servings. This mean decreased to 1.21 servings when banana was not counted. Mean vegetable intake (1.1 servings, including legumes) was well below the minimum recommendation of 3 vegetable servings per day. Urban adolescents and females consumed significantly (p = 0.000) fewer fruits and vegetables servings than did rural youngsters and males. However when pulses were not counted the mean daily servings of vegetables were higher in urban adolescents (p = 0.029). Only 16 from 214 adolescents (6%) consumed five or more servings of fruits and vegetables per day. This proportion decreased dramatically to 2% (p = 0.000) when pulses and banana were not counted. Examination of the factors associated with low intake of fruit and vegetables could be beneficial to develop effective interventions targeted to increase their consumption among adolescents.     

Fundamental solutions for transient heat transfer by conduction and convection in an unbounded, half-space, slab and layered media in the frequency domain

Analytical Green's functions in the frequency domain are presented for the three-dimensional diffusion equation in an unbounded, half-space, slab and layered media. These proposed expressions take into account the conduction and convection phenomena, assuming that the system is subjected to spatially sinusoidal harmonic heat line sources and do not require any type of discretization of the space domain. The application of time and spatial Fourier transforms along the two horizontal directions allows the solution of the three-dimensional time convection-diffusion equation for a heat point source to be obtained as a summation of one-dimensional responses. The problem is recast in the time domain by means of inverse Fourier transforms using complex frequencies in order to avoid aliasing phenomenon. Further, no restriction is placed on the source time dependence, since the static response is obtained by limiting the frequency to zero and the high frequency contribution to the response is small.

The proposed functions have been verified against analytical time domain solutions, known for the case of an unbounded medium, and the Boundary Element Method solutions for the case of the half-space, slab and layered media.     

Structural and longitudinal analysis of the knowledge base on spin-off research

Following the dynamism in spin-off research, in this study we conduct a structural and longitudinal bibliometric analysis of a sample of 812 articles on spin-offs published in 234 journals included in the ISI Web of Knowledge over a period of three decades. The analyses do not seek to establish a new conceptualization but rather to reveal the intellectual structure of the field and how it has evolved, and the profile of the knowledge network established in the three perspectives: corporate, academic and entrepreneurial spin-offs. The diversity involved in the three streams of spin-off research signals substantial differences. Theoretically, transaction costs, agency and the resource-based view have remained a foundation of spin-off research, albeit that research has been driven more by the phenomena than by developing the theory. The more traditional focus on corporate spin-offs was followed by emphasis on academic spin-offs and more recently on entrepreneurial spin-offs. This shift has been accompanied by a more business/management theoretical orientation, replacing a more financial and taxation-based perspective underlying corporate spin-offs. This study systematizes the existing stock of knowledge and raises avenues for additional inquiry.     

Discretization and fitting of nominal data for autonomous robots

This paper presents methodologies to discretize nominal robot paths extracted from 3-D CAD drawings. Behind robot path discretization is the ability to have a robot adjusting the traversed paths so that the contact between robot tool and work-piece is properly maintained. In addition, a hybrid force/motion control system based on Fuzzy-PI control is proposed to adjust robot paths with external sensory feedback. All these capabilities allow to facilitate the robot programming process and to increase the robot’s autonomy.     

Improving the efficiency of inductive logic programming systems

Inductive logic programming (ILP) is a sub‐field of machine learning that provides an excellent framework for multi‐relational data mining applications. The advantages of ILP have been successfully demonstrated in complex and relevant industrial and scientific problems. However, to produce valuable models, ILP systems often require long running times and large amounts of memory. In this paper we address fundamental issues that have direct impact on the efficiency of ILP systems. Namely, we discuss how improvements in the indexing mechanisms of an underlying logic programming system benefit ILP performance. Furthermore, we propose novel data structures to reduce memory requirements and we suggest a new lazy evaluation technique to search the hypothesis space more efficiently. These proposals have been implemented in the April ILP system and evaluated using several well‐known data sets. The results observed show significant improvements in running time without compromising the accuracy of the models generated. Indeed, the combined techniques achieve several order of magnitudes speedup in some data sets. Moreover, memory requirements are reduced in nearly half of the data sets. Copyright © 2008 John Wiley & Sons, Ltd.     

Parallel ILP for distributed-memory architectures

The growth of machine-generated relational databases, both in the sciences and in industry, is rapidly outpacing our ability to extract useful information from them by manual means. This has brought into focus machine learning techniques like Inductive Logic Programming (ILP) that are able to extract human-comprehensible models for complex relational data. The price to pay is that ILP techniques are not efficient: they can be seen as performing a form of discrete optimisation, which is known to be computationally hard; and the complexity is usually some super-linear function of the number of examples. While little can be done to alter the theoretical bounds on the worst-case complexity of ILP systems, some practical gains may follow from the use of multiple processors. In this paper we survey the state-of-the-art on parallel ILP. We implement several parallel algorithms and study their performance using some standard benchmarks. The principal findings of interest are these: (1) of the techniques investigated, one that simply constructs models in parallel on each processor using a subset of data and then combines the models into a single one, yields the best results; and (2) sequential (approximate) ILP algorithms based on randomized searches have lower execution times than (exact) parallel algorithms, without sacrificing the quality of the solutions found. This is an extended version of the paper entitled Strategies to Parallelize ILP Systems, published in the Proceedings of the 15th International Conference on Inductive Logic Programming (ILP 2005), vol. 3625 of LNAI, pp. 136–153, Springer-Verlag.     

Scalable Unified Transform Architecture for Advanced Video Coding Embedded Systems

A novel high throughput and scalable unified architecture for the computation of the transform operations in video codecs for advanced standards is presented in this paper. This structure can be used as a hardware accelerator in modern embedded systems to efficiently compute all the two-dimensional 4 × 4 and 2 × 2 transforms of the H.264/AVC standard. Moreover, its highly flexible design and hardware efficiency allows it to be easily scaled in terms of performance and hardware cost to meet the specific requirements of any given video coding application. Experimental results obtained using a Xilinx Virtex-5 FPGA demonstrated the superior performance and hardware efficiency levels provided by the proposed structure, which presents a throughput per unit of area relatively higher than other similar recently published designs targeting the H.264/AVC standard. Such results also showed that, when integrated in a multi-core embedded system, this architecture provides speedup factors of about 120× concerning pure software implementations of the transform algorithms, therefore allowing the computation, in real-time, of all the above mentioned transforms for Ultra High Definition Video (UHDV) sequences (4,320 × 7,680 @ 30 fps).     

Fast topology estimation for image mosaicing using adaptive information thresholding

Over the past decade, several image mosaicing methods have been proposed in robotic mapping and remote sensing applications. Owing to rapid developments in obtaining optical data from areas beyond human reach, there is a high demand from different science fields for creating large-area image mosaics, often using images as the only source of information. One of the most important steps in the mosaicing process is motion estimation between overlapping images to obtain the topology, i.e., the spatial relationships between images.In this paper, we propose a generic framework for feature-based image mosaicing capable of obtaining the topology with a reduced number of matching attempts and of getting the best possible trajectory estimation. Innovative aspects include the use of a fast image similarity criterion combined with a Minimum Spanning Tree (MST) solution, to obtain a tentative topology and information theory principles to decide when to update trajectory estimation. Unlike previous approaches for large-area mosaicing, our framework is able to naturally deal with the cases where time-consecutive images cannot be matched successfully, such as completely unordered sets. This characteristic also makes our approach robust to sensor failure. The performance of the method is illustrated with experimental results obtained from different challenging underwater image sequences.