Transient modeling of an adsorber using finned-tube heat exchanger

This paper presents a heat and mass transfer simulation of an adsorber, taking into consideration the geometry of the heat exchanger and the diffusion in the adsorbent medium. In this model, an increment in the direction of heating/cooling fluid containing one (or more) fin pitch was considered. In the domain of this increment, the distribution of the adsorbent temperature was evaluated in the radial and axial directions. The model is validated by experimental data of different adsorbents, volume flows and temperatures. All data were collected in an adsorber test-bench at Fraunhofer ISE. As a result it was found a coefficient of multiple determination of around 0.94 and an error of 20% during the transient. Finally, the model was run on typical operation for cooling application and compared with data from literature. A numerical energy balance was also evaluated. In summary, the results obtained by a independent group shows the same range of confidence of the model developed here, in terms of the tendency of the curves and even the absolute values.     

The influence of ECAP on the small punch creep of Al–4 vol.% Al<Subscript>4</Subscript>C<Subscript>3</Subscript> composite

The creep behaviour of a composite based on an aluminium matrix reinforced by 4 vol.% Al₄C₃ was studied at temperatures of 623 and 723 K by small punch testing with a constant force. The composite was tested in two different states: (i) as received by mechanical alloying with hot extrusion (HE) as the final operation and (ii) with equal channel angular pressing (ECAP) superimposed on the hot-extruded material. The ECAP does not improve the observed creep resistance. The reduction of force leading to the same deflection rate is not very significant. This points out that the ECAP process of the present composite, which produces substantial strengthening at lower temperatures, is not accompanied by pronounced weakening of creep resistance at elevated temperatures. The threshold force in the ECAP material is about 5 N weaker than in the HE material.     

Did MPOA achieve its objective?

Layer 3 switching is a subject vehemently discussed in the networking community. In addition to a number of manufacturer-specific approaches, multi-protocol over ATM (MPOA) and multiprotocol label switching (MPLS) are the most important examples of this technology. MPOA (Multi-Protocol Over ATM Specification v1.0, af-mpoa-0087.000, July 1997; Multi-Protocol Over ATM Specification v1.1, af-mpoa-0114.000, May 1999) was released in 1997 by the ATM Forum; MPLS (A Framework for Multiprotocol Label Switching, draft-ietf-mpls-framework-02.txt, 21 November 1997; Multiprotocol Label Switching Architecture, draft-ietf-mpls-arch-02.txt, July 1998) is a collection of IETF Internet drafts.This paper presents the concept of MPOA and reports on experiences resulting from the practical use of MPOA implementations from several manufacturers. The report also discusses the areas in which MPOA can be appropriately employed. Two years after the release of the MPOA standard, the time has come to critically discuss the original objective of MPOA, to examine the implementations of several manufacturers and to compare MPOA with other solutions and their objectives.     

An Introduction to High-resolution EELS in Transmission Electron Microscopy

The practical advantages of an electron monochromator for electron energy-loss spectroscopy (EELS) in transmission electron microscopy are described. Typical examples from materials and nanoparticle research demonstrate the use of EELS with high energy and spatial resolution. Recent instrumental developments are also reviewed with a discussion of how the technique could be used to study catalyst structures of the future.     

Speed Dependence,Takeoff and Stiction of a New Class of Gas Bearing Sliders

While searching for a less-speed-sensitive programmable air bearing slider, the author noted that the primary reason for the sluggish takeoff and large dependence of fly height on speed is the very common 10 mrad taper. This taper is found on many sliders in the railed, taper/flat class. A single, plane wedge bearing operating at a large bearing number and a pitch angle considerably below that which gives maximum lift does not suffer from such speed sensitivity. The “inlet throttled” condition of the bearing inlet fixes the mass flux into the bearing gap. Because a single pad of this type has poor pitch stability, the author placed two of these pads in a tandem configuration, and abandoned rails. The result defines a new air bearing class, called Tango, which has front and rear pads, each having inlet throttled leading edges. Some members of this class offer takeoff velocities equalling and even improving more-complex designs using subambient pressure. In addition, numerical and hardware experiments have verified the considerably reduced sensitivity of fly height to speed, a reduced sensitivity to crown distortion, and improved stiction. Disk designers benefit by not having to accept a longer takeoff run when the fly height decreases.     

High-temperature 434 Mhz surface acoustic wave devices based on GaPO4

Research into surface acoustic wave (SAW) devices began in the early 1970s and led to the development of high performance, small size, and high reproducibility devices. Much research has now been done on the application of such devices to consumer electronics, process monitoring, and communication systems. The use of novel materials, such as gallium phosphate (GaPO4), extends the operating temperature of the elements. SAW devices based on this material operating at 434 MHz and up 800 degrees C, can be used for passive wireless sensor applications. Interdigital transducer (IDT) devices with platinum/zirconium metallization and 1.4 microm finger-gap ratio of 1:1 have been fabricated using direct write e-beam lithography and a lift-off process. The performance and long-term stability of these devices has been studied, and the results are reported in this paper.     

Bridge-splitting of trans-[PtCl2(η2-CH2CH2)]2 by weak nucleophiles: Crystal and molecular structure of trans-[PtCl2(η2-CH2CH2)(MeCN)]

Bridge-splitting of trans-[PtCl₂(η²-CH₂CH₂)]₂, 1, by L in dichloromethane yields trans-[PtCl₂(η²-CH₂CH₂)(L)] (L = THF, 2, or MeCN, 3) with bridge-splitting equilibrium constants of 0.0289 ± 0.0007 and 3601 ± 215 mol^?1 dm³, respectively, as determined by UV/Vis measurements. The reaction of 3 in MeCN with Cl^? is essentially quantitative. The crystal structure of trans-[PtCl₂(η²-CH₂CH₂)(CH₃CN)] is reported.     

A Defect Localization Scheme for Cellular Nanocomputers

Computers with device feature sizes of a few nanometers—so-called nanocomputers—are expected within a few decades, but this expectation is accompanied by the realization that the boundary conditions of such systems differ substantially from those of current VLSI-based computers. Prominent among the concerns is the increased degree of permanent defects that will affect nanocomputers, such as defects caused by imperfections at the manufacturing stage, but also defects occurring later, possibly even during the use of these systems. New techniques to deal with defects are called for, but given the huge number of devices involved, such techniques may need to be self-contained: they need be applicable at local levels without outside control, even while computations continue to take place. This paper proposes an important element in such techniques, i.e. the localization of defects among a huge number of devices. It employs a cellular automaton-based architecture, and uses statistical techniques combined with randomly moving configurations in the cellular space to estimate defect locations.