Chemical sensor based on a novel capacitive microwave flexible transducer with polymer nanocomposite-carbon nanotube sensitive film

Microsystem Technologies - This study presents the results on the feasibility of a resonant planar chemical capacitive sensor in the microwave frequency range suitable for gas detection and...     

Aramid pulp treated with imidazolium ionic liquids as a filler in rigid polyurethane bio-foams

This article reports an aramid pulp (AP) treated with two ionic liquids (IL), namely 1-n-butyl-3-methylimidazolium chloride (C₄.Cl) and 1-carboxymethyl-3-methylimidazolium chloride (HO₂C), and its use as a filler in reinforced rigid polyurethane foams (RPUF). The RPUF were incorporated with the treated AP at three weight fractions (c.a. 0.1, 0.5, and 1.0 wt%) and were produced by the free rising method. The results showed that the studied IL promoted a better interaction between the AP and the RPUF system, which increased the overall reactivity, imparting a higher cell anisotropy. This also yielded a positive effect in mechanical properties and thermal stability of the RPUF. Compared to the neat RPUF, outstanding increases of approximately 50 and 20% were achieved in compressive modulus and strength, respectively. In all, the use of IL promoted increased compatibility between matrix and reinforcement, especially that HO₂C IL.     

Selecting linear algebra kernel composition using response time prediction

Numerical linear algebra libraries provide many kernels that can be composed to perform complex computations. For a given computation, there is typically a large number of functionally equivalent kernel compositions. Some of these compositions achieve better response times than others for particular data and when executed on a particular computer architecture. Previous research provides methods to enumerate (a subset of) these kernel compositions. In this work, we study the problem of determining the composition that yields the lowest response time. Our approach is based on a response time prediction for each candidate combination. While this prediction could in principle be obtained using analytical and/or empirical performance models, developing accurate such models is known to be challenging. Instead, we define a feature space that captures salient properties of kernel combinations and predict response time using supervised machine learning. We experiment with a standard set of machine learning algorithms and identify an effective algorithm for our kernel composition selection problem. Using this algorithm, our approach widely outperforms the strategy that would consist in always using the simplest kernel composition and is often close to the fastest kernel compositions among those evaluated. We quantify the potential benefit of our approach if it were to be implemented as part of an interactive computational tool. We find that although the potential benefit is substantial, a limiting factor is the kernel composition enumeration overhead. Copyright © 2014 John Wiley & Sons, Ltd.     

Calcium carbonate and ammonium polyphosphate flame retardant additives formulated to protect ethylene vinyl acetate copolymer against fire: Hydrated or carbonated calcium?

In this study, the effect of the chemical nature of different calcium (Ca)-based minerals as flame retardant additives in combination with ammonium polyphosphate (APP), in 1:1 proportions, on the flame retardancy behavior and performance of ethylene vinyl acetate copolymer was discussed. Combining APP with partly and completely hydrated calcium oxide led to superior flame-retardant function detected in mass loss calorimeter measurements with respect to the corresponding system containing carbonated calcium. This privileged character was attributed to the higher reactivity of hydrated Ca-based fillers toward APP in comparison with Ca carbonate, which induced the formation of an intumescent residue. The difference between reactivity potential of hydrated and dry Ca was demonstrated by the newly formed thermally stable species, and further evidenced by thermogravimetric analysis performed on APP/fillers blends. Moreover, the presence of more crystalline domains in the Ca/phosphorus-based compounds was evidenced by XRD analysis of the mass loss calorimeter test residues. The results of this work highlight the role of blend additive systems on the performance of flame retardancy of polymer materials.     

The implementation of the Hammurabi system: indexing and interprocess communication

Hammurabi is a software application designed to help the UNIX system administrator to evaluate better the consequences of the actions he/she carries out, in order to maintain the system and to make it change. In this paper, we describe the implementation of Hammurabi's inference engine. This engine is a multiactor Prolog-like engine. The actors have, on the one hand, the ability to spy the events occurring inside the whole machine (inside the engine, and inside the UNIX OS), and on the other hand, the ability to forbid or to freeze some events. This ability is used as a synchronization mechanism. In the first part of this paper, we describe the data representation. In its second part, we describe the implementation of the spying mechanism.     

Silicon Vibrating Wires at Low Temperatures

Nowadays microfabrication techniques originating from micro-electro nics enable to create mechanical objects of micron-size. The field of Micro-Electro-Mechanical devices (MEMs) is continuously expanding, with an amazingly broad range of applications at room temperature. Vibrating objects (torsional oscillators, vibrating wires) widely used at low temperatures to study quantum fluids, can be replaced advantageously by Silicon MEMs. In this letter we report on the study of Silicon vibrating wire devices. A goal-post structure covered with a metal layer is driven at resonance by the Laplace force acting on a current in a magnetic field, while the induced voltage arising from the cut magnetic flux allows to detect the motion. The characteristics of the resonance have been studied from 10 mK to 30 K, in vacuum and in ⁴He gas. In this article, we focus on the results obtained above 1.5 K, in vacuum and gas, and introduce some features observed at lower temperatures. The resonant properties can be quantitatively understood by means of simple models, from the linear regime to a highly non-linear response at strong drives. We demonstrate that the non-linearity is mostly due to the geometry of the vibrators. We also show that in our device the friction mechanisms originate in the metallic layers, and can be fully characterized. The interaction with ⁴He gas is fit to theory without adjustable parameters.      

Thermal modelling of the multi-stage heating system with variable boundary conditions in the wafer based precision glass moulding process

In the precision glass moulding process, the heat transfer and the resulting transient temperature distributions of the molten glass are of great importance because they significantly affect the productivity as well as the thermally induced residual stresses in the final product. Thermal modelling of the heating system in the glass moulding process considering detailed heating mechanisms therefore plays an important part in optimizing the heating system and the subsequent pressing stage in the lens manufacturing process.The current paper deals with three-dimensional transient thermal modelling of the multi-stage heating system in a wafer based glass moulding process. In order to investigate the importance of the radiation from the interior and surface of the glass, a simple finite volume code is developed to model one dimensional radiation–conduction heat transfer in the glass wafer for an extreme case with very high temperature difference considering temperature dependant thermal conductivity and heat capacity. Afterwards, by using three-dimensional FEM modelling along with a predefined experimental test, the equivalent glass–mould interface contact resistance is determined for two different pressures. Finally, the three-dimensional modelling of the multi-stage heating system in the wafer based glass moulding process is simulated with the FEM software ABAQUS for a particular industrial application for mobile phone camera lenses to obtain the temperature distribution in the glass wafer. In the numerical modelling, the interface boundary conditions for each heating stage are changed according to the determining heat transfer mechanism(s). Numerical results are compared with experimental data to show the validity of the numerical modelling. The obtained results show that the right thermal modelling is highly dependent on the proper choice of thermal boundary conditions in different stages according to the real physical phenomena behind the process.     

European research policy and bibliometric indicators, 1990�C2005

This paper describes and analyses the role played in the development of bibliometric indicators??and the use made of bibliometric indicators for policy purposes??by the European Commission??s Directorate-General Research in the period 1990?C2005.     

Equivalent network representation of boundary conditions involving generalized trial quantities

Virtual adjustable sources are introduced in equivalent network representation of boundary conditions. For this purpose, integral equations are to be solved simple application of analog Kirchoff’s and Ohm’s laws. These adjustable sources represent generalized trial quantities. In order to illustrate this proposed approach, equivalent network representation of lossy planar transmission lines with arbitrary metallization thickness is presented.