Influence of measurement noise and laser arrangement on measurement uncertainty of laser tracker multilateration in machine tool volumetric verification

This paper aims to present different techniques and factors that affect the measurement accuracy of a commercial laser tracker responsible for capturing checkpoints used in machine tool volumetric verification. This study was conducted to uncover various sources of error affecting the measurement uncertainty of the laser tracker, additional sources of error that further contributed to the uncertainty, and the factors influencing these techniques. We also define several noise reduction techniques for the measurements.The improvement in the accuracy of captured points focuses on a multilateration technique and its various resolution methods both analytically and geometrically. Similarly, we present trilateration and least squares techniques that can be used for laser tracker self-calibration, which is an essential parameter in multilateration.This paper presents the influence of the spatial distribution of laser trackers (LTs) in measurement noise reduction by multilateration, which produces an improvement in volumetric error machine tool reduction. A study of the spatial angle between LTs, the distance and the visibility of the point to be measured are presented using a synthetic test. All of these factors limit the scope of multilateration. Similarly, a comparison of self-calibration techniques using the least squares and trilateration methods with which to determine the relative position of the laser tracker employees is presented. We also present the influence of the relationship between the radial and angular measurement noise self-calibration processes as it relates to the volumetric error reduction achieved by the machine tool with multilateration. All studies were performed using synthetic tests generated using a synthetic data parametric generator.     

Cracking behavior of FRC slabs with traditional reinforcement

The combination of fibers with traditional reinforcement may be a very interesting design solution to achieve more durable and economical structures. This paper deals with the analysis of the aforementioned solution through the study at serviceability and ultimate limit states. For this purpose, a total of eighteen concrete slabs were produced (3 × 1 × 0.2 m) with different reinforcement configurations, types of fibers (steel and plastic) and the fiber dosage used (0.25 and 0.50%). These slabs were tested under the configuration of a four point bending test. The results of this experimental campaign were used in the study of the cracking and deflection of the various types of concrete, tackling the analysis from several points of view.     

Dynamic Routing and Wavelength Assignment in Optical Networks by Means of Genetic Algorithms

We propose a novel genetic algorithm for solving the dynamic routing and wavelength assignment (DRWA) problem in wavelength-routed optical networks. The algorithm not only obtains low call blocking probability, but it also employs a very short computation time. Moreover, it is capable of providing fairness among connections, that is, to offer approximately the same quality of service (in terms of blocking probability) for all source-destination node pairs. Since requirements on optical network availability are highly severe, we also propose an extension of the algorithm to provide fault-tolerance capability at the optical layer. It is achieved by means of protection, where each optical connection request is provided with a pair of lightpaths (a primary and a backup lightpath). Again, the genetic algorithm proves to be highly efficient, in this case, at performing routing and wavelength assignment of pairs of lightpaths.     

Experimental assessment of in-operation spectrum defragmentation

Dynamic operation of flexgrid networks might cause optical spectrum to be divided into fragments, which makes it difficult finding contiguous spectrum of the required width for incoming connection requests, leading thus to an increased blocking probability. To alleviate to some extent that spectrum fragmentation, the central frequency of already established connections can be shifted to create wider contiguous spectrum fragments to be allocated to incoming connections; this procedure is called spectrum defragmentation. In this paper, we propose using the so called applications based network operations (ABNO) architecture, currently under standardization in the IETF, to deal with the defragmentation use case while the network is in operation. A workflow involving several elements in the ABNO architecture is proposed and experimentally assessed in a distributed test bed connecting facilities in three major European cities.     

In vitro lipolytic effect of leptin on mouse adipocytes: evidence for a possible autocrine/paracrine role of leptin

The present study has examined the effects of the adipocyte-derived hormone, leptin, on lipolysis in fat cells of different types of mice. Exposure to leptin (1.25.10(-6) M to 1.25.10(-12) M) increased (P < 0.01) the lipolytic activity of fat cells obtained from lean mice. A greater stimulation was observed when adipocytes from ob/ob mice were examined. Throughout the concentrations tested, the leptin-induced lipolysis observed in fat cells of lean animals was smaller than that obtained in ob/ob mice. The maximal lipolytic effect in obese animals was observed with 10(-8) M of OB protein. The lipolytic activity following the addition of 1.25.10(-10) M to 1.25.10(-6) M was significantly increased (P < 0.01) in ob/ob mice compared to lean animals. Adipocytes from ob/ob mice responded in a dose-dependent manner to the OB protein, while the leptin-induced lipolysis observed in lean animals was dose-independent. In contrast to lean and ob/ob mice, leptin did not stimulate lipolysis in adipocytes from db/db mice, which have a mutation in the leptin receptor gene. These in vitro studies suggest an autocrine/paracrine action of leptin on white fat cells and envisages the involvement of the OB protein, not only in centrally mediated pathways, but also in physiological functions which take place peripherally.     

Reaggregation and binding of cell wall proteins from Candida albicans to structural polysaccharides

Urea or hot sodium dodecyl sulphate extracted a significant amount of the same proteins from the matrix of the cell wall of the yeast form and mycelial cells of Candida albicans. Gel filtration analysis of the urea-extracted proteins revealed that they occurred in the form of large complexes which were unaffected by up to 8 M urea. Among them, proteins en route to becoming covalently associated within the wall scaffold were identified by their reaction with specific antibodies. When urea was removed by dialysis, some of these proteins specifically reassociated into large aggregates which bound strongly with ConA, whereas others remained soluble in smaller associated products. The ability of some of these proteins to bind to the insoluble wall polysaccharides was also assessed. No self-assembling proteins were able to bind to glucans and/or chitin. Specificity of the binding to polysaccharides made of beta-bound glucosyl or N-acetylglucosaminyl residues was determined by the competitive effect of several disaccharides. Whereas laminaribiose and diacetylchitobiose were strong inhibitors of protein binding to both glucan and chitin, lactose, maltose and sucrose were ineffective.     

Intentions and behaviors of risky drug consumption in users at the rehabilitation centers in Valencia]

Several criteria have been used for differentiating hepatic cavernous hemangioma from other tumors at magnetic resonance imaging (MRI). Included are signal intensity and lobulation of the tumor. We counted the frequency of presence of lobulation of liver hemangiomas on T2-weighted images (T2WI), and measured the signal-intensity ratio (SIR) on T1-weighted images (T1WI) and on T2WI with a 0.9 mm x 0.9 mm pixel size using a 0.5 T magnetic resonance system. Eighty-three cavernous hemangiomas in 44 patients and 67 malignant tumors in 44 patients were retrospectively studied. Seventy-five of the cavernous hemangiomas (90%) exhibited lobules of various sizes, and four of the malignant tumors (6%) exhibited lobulations. The cavernous hemangiomas had a significantly higher SIR than the malignant tumors on T2WI: 3.0 +/- 0.7 and 1.9 +/- 0.8 (p < 0.001), respectively. The presence of lobulation together with a high SIR was a useful measure for differentiating cavernous hemangiomas from other liver tumors.     

Influence of environmental temperatures on the concrete compressive strength: Simulation of hot and cold weather conditions

The objective of this work is to study the influence of mixing hour on the properties of concrete, such as workability and compressive strength, under hot and cold weather conditions, with a view to industrial application. The variable focused on was the concrete mixing hour, and five different mixing hours were used for each type of weather condition. Three batches of concrete were prepared for each mixing hour, and the compressive strength of 15 cylindrical concrete specimens was measured after 7 and 28 days. In addition, the hydration kinetics of each batch of concrete was studied on the basis of the climatic conditions and the mixing hour. The results for compressive strength show that the concrete's best mechanical performance occurred when there was the least difference between ambient temperature and concrete temperature, that is, during the later hours of the day in hot weather conditions.