Gain studies of 1.3-μm dilute nitride HELLISH-VCSOA for optical communications

The hot electron light emitting and lasing in semiconductor heterostructure-vertical-cavity semiconductor optical amplifier (HELLISH-VCSOA) device is based on Ga_0.35In_0.65 N_0.02As_0.08/GaAs material for operation in the 1.3-μm window of the optical communications. The device has undoped distributed Bragg reflectors (DBRs). Therefore, problems such as those associated with refractive index contrast and current injection, which are common with doped DBRs in conventional VCSOAs, are avoided. The gain versus applied electric field curves are measured at different wavelengths using a tunable laser as the source signal. The highest gain is obtained for the 1.3-μm wavelength when an electric field in excess of 2 kV/cm is applied along the layers of the device.     

Controlling single-molecule conductance through lateral coupling of π orbitals

In recent years, various single-molecule electronic components have been demonstrated. However, it remains difficult to predict accurately the conductance of a single molecule and to control the lateral coupling between the π orbitals of the molecule and the orbitals of the electrodes attached to it. This lateral coupling is well known to cause broadening and shifting of the energy levels of the molecule; this, in turn, is expected to greatly modify the conductance of an electrode-molecule-electrode junction. Here, we demonstrate a new method, based on lateral coupling, to mechanically and reversibly control the conductance of a single-molecule junction by mechanically modulating the angle between a single pentaphenylene molecule bridged between two metal electrodes. Changing the angle of the molecule from a highly tilted state to an orientation nearly perpendicular to the electrodes changes the conductance by an order of magnitude, which is in qualitative agreement with theoretical models of molecular π-orbital coupling to a metal electrode. The lateral coupling is also directly measured by applying a fast mechanical perturbation in the horizontal plane, thus ruling out changes in the contact geometry or molecular conformation as the source for the conductance change.     

Tetragonal-cubic phase boundary in nanocrystalline ZrO2-Y2O3 solid solutions synthesized by gel-combustion

By means of synchrotron X-ray powder diffraction (SXPD) and Raman spectroscopy, we have detected, in a series of nanocrystalline and compositionally homogeneous ZrO₂-Y₂O₃ solid solutions, the presence at room temperature of three different phases depending on Y₂O₃ content, namely two tetragonal forms and the cubic phase. The studied materials, with average crystallite sizes within the range 7-10 nm, were synthesized by a nitrate-citrate gel-combustion process. The crystal structure of these phases was also investigated by SXPD. The results presented here indicate that the studied nanocrystalline ZrO₂-Y₂O₃ solid solutions exhibit the same phases reported in the literature for compositionally homogeneous materials containing larger (micro)crystals. The compositional boundaries between both tetragonal forms and between tetragonal and cubic phases were also determined.     

Fuzzy Online Auto-Tuning for an Industrial PID Controller

This paper presents a fuzzy tuning system for real-time industrial PID （proportional-integral-derivative） controllers. The algorithm set the proportional gain, integral time and derivative time of a classical PID structure according to the set point, error and error derivative of the process, respectively. The tuning of the PID controller is based on a fuzzy inference machine. The set of rules of the fuzzy inference machine was obtained by experts engineering. The system is tested in an austempering process but can be applied in any industrial plant. Besides, an analysis between the response of the process with a PID controller and the system of fuzzy auto-tuning for P1D proposed was made.     

A formal framework to test soft and hard deadlines in timed systems

This paper introduces a formal framework to specify and test systems presenting both soft and hard deadlines. While hard deadlines must always be met on time, soft deadlines can be sometimes met in a different time, usually greater, from the specified one. It is this characteristic (to formally definetextitsometimes) that produces several reasonable alternatives to define appropriate implementation relations, that is, relations to decide whether an implementation is correct with respect to a specification. In addition to introducing these relations, the paper also presents a formal testing framework to test implementations and provides an algorithm to derive sound and complete test suites with respect to the implementation relations previously defined. That is, an implementation conforms to a specification if and only if the implementation successfully passes all the tests belonging to the suite derived from the specification. Copyright © 2011 John Wiley & Sons, Ltd.     

TLM simulation of electromagnetic wave propagation in anisotropic moving media

A transmission line matrix (TLM) model suitable to simulate the propagation of waves in moving anisotropic continuous media is presented. As is well known, an electromagnetic wave propagating in a general medium, moving with respect to its source, experiences a drag by the own medium, which involves a wave velocity dependent on the direction of propagation. In this work, we present a first approach for the case of uniform movement of an anisotropic dielectric medium with respect to an electromagnetic source. Although the technique allows for quantitative results, special attention is devoted to the simulation of wave fronts, distorted elliptical fronts, because a particular kind of ‘anisotropy’ appears, even in an isotropic medium. Copyright © 2005 John Wiley & Sons, Ltd.     

Myeloid Lineage Ablation of Phlpp1 Regulates M-CSF Signaling and Tempers Bone Resorption in Female Mice

Prior work demonstrated that Phlpp1 deficiency alters trabecular bone mass and enhances M-CSF responsiveness, but the cell types and requirement of Phlpp1 for this effect were unclear. To understand the function of Phlpp1 within myeloid lineage cells, we crossed Phlpp1 floxed mice with mice harboring LysM-Cre. Micro-computed tomography of the distal femur of 12-week-old mice revealed a 30% increase in bone volume per total volume of Phlpp1 female conditional knockouts, but we did not observe significant changes within male Phlpp1 cKO_LysM mice. Bone histomorphmetry of the proximal tibia further revealed that Phlpp1 cKO_LysM females exhibited elevated osteoclast numbers, but conversely had reduced levels of serum markers of bone resorption as compared to littermate controls. Osteoblast number and serum markers of bone formation were unchanged. In vitro assays confirmed that Phlpp1 ablation enhanced osteoclast number and area, but limited bone resorption. Additionally, reconstitution with exogenous Phlpp1 suppressed osteoclast numbers. Dose response assays demonstrated that Phlpp1^−/− cells are more responsive to M-CSF, but reconstitution with Phlpp1 abrogated this effect. Furthermore, small molecule-mediated Phlpp inhibition enhanced osteoclast numbers and size. Enhanced phosphorylation of Phlpp substrates—including Akt, ERK1/2, and PKCζ—accompanied these observations. In contrast, actin cytoskeleton disruption occurred within Phlpp inhibitor treated osteoclasts. Moreover, Phlpp inhibition reduced resorption of cells cultured on bovine bone slices in vitro. Our results demonstrate that Phlpp1 deficiency within myeloid lineage cells enhances bone mass by limiting bone resorption while leaving osteoclast numbers intact; moreover, we show that Phlpp1 represses osteoclastogenesis and controls responses to M-CSF.     

Specification and testing of autonomous agents in e‐commerce systems

This paper presents a generic formal framework to specify and test autonomous e‐commerce agents. First, the formalism to represent the behaviour of agents is introduced. The corresponding machinery to define how implementations can be tested follows. Two testing approaches are considered. The first of them, which can be called active, is based on stimulating the implementation under test (IUT) with a test. The peculiarity is that tests will be defined as a special case of autonomous e‐commerce agent. The second approach, which can be called passive, consists of observing the behaviour of the tested agent in an environment containing other agents. As a case study the framework is applied to the e‐commerce system Kasbah. Copyright © 2005 John Wiley & Sons, Ltd.     

Comparison of machine learning algorithms for optimization and improvement of process quality in conventional metallic materials

This paper presents a particular problem dealing with the apparition of burr during the drilling process in the aeronautic industry. This burr cannot exceed a height limit of 127?μm as set out by the aeronautical guidelines and must be eliminated before riveting. If this is not performed, it can cause structural damage which would constitute a danger due to the lack of safety. Moreover, the industry needs to find an automated and optimised process in which the drilling and deburring can be carried out in real time, eliminating those other unnecessary tasks, in order to obtain high-quality pieces. The work presents the applicability of data mining and machine learning techniques so as to obtain a real time burr detection model. This model could be implanted in the computer numerical control of the machine allowing the whole process to be automated and optimised. These techniques can be applied to other types of processes.     

Use of solution crystallization analysis by laser light scattering for studying the solution crystallization of various Ziegler–Natta‐catalysed polypropylenes

Solution crystallization analysis by laser light scattering (SCALLS) involves the observation of the scattering of diode mercury laser lamp light after it passes through a polymer solution. An increase in turbidity occurs when the hot polymer solution is cooled and the polymer starts to crystallize out of solution. This causes a decrease in the amount of laser light that can pass through the solution and an increase in the amount of scattered light. The reverse of this process leads to the turbidity decreasing with an increase in temperature. According to this concept, it is possible to follow the solution crystallization of various polypropylenes under controlled cooling. In this study, SCALLS was able to differentiate between different isotactic and syndiotactic polypropylenes with similar chemical structures, but different tacticity and molecular weights. Furthermore, SCALLS provided good crystallization information that is similar to that from crystallization analysis fractionation and temperature rising elution fractionation. In addition, SCALLS can be used as a quantitative tool for the measurement of weight fractions during dissolution. © 2014 Society of Chemical Industry