Suppression of transient phenomena in hybrid Raman/EDF amplifier

Transient phenomena of hybrid Raman/erbium-doped fiber amplifier (EDFA) upon optical channel add-drop are investigated. The transient responses of surviving channels are resulted from the combined dynamics of Raman amplifier and EDFA. It is shown that the suggested method employing fast gain control of EDFA only can effectively suppress the transient variation of output power. The transient-suppressing hybrid Raman/EDFA is proven to be enough for wavelength-division-multiplexing networks including reconfigurable optical add-drop multiplexer and/or transparent optical cross-connect, if the optical switching speed is carefully chosen.     

Inverse halftoning algorithm using edge-based lookup table approach

The inverse halftoning algorithm is used to reconstruct a gray image from an input halftone image. Based on the recently published lookup table (LUT) technique, this paper presents a novel edge-based LUT method for inverse halftoning which improves the quality of the reconstructed gray image. The proposed method first uses the LUT-based inverse halftoning method as a preprocessing step to transform the given halftone image to a base gray image, and then the edges are extracted and classified from the base gray image. According to these classified edges, a novel edge-based LUT is built up to reconstruct the gray image. Based on a set of 30 real training images with both low- and high-frequency contents, experimental results demonstrated that the proposed method achieves a better image quality when compared to the currently published two methods, by Chang et al. and Mes$80e and Vaidyanathan.     

Exfoliation of graphite

The exfoliation of graphite is a phase transition involving the vaporization of the intercalate in the graphite. Exfoliated graphite is an expanded graphite with a low density. This paper reviews the process of the exfoliation of graphite and the exfoliated graphite material. It surveys the applications of exfoliated graphite, covers both reversible and irreversible exfoliation and reviews the methods and mechanism of exfoliation. Other topics include the structure and properties of exfoliated graphite, graphite foils, exfoliated carbon fibres and composites.     

The Effect of Magnesium Stearate Admixing in Different Types of Laboratory and Industrial Mixers on Tablet Crushing Strength

It is generally known that hydrophobic lubricants such as magnesium stearate can have a strong negative effect on the binding properties of directly compressible filler-binders. It was found that the decrease in binding forces is not only dependent on the tablet ingredients and the lubricant concentration used, but especially on the mixing time and mixing procedure. Most studies were performed, however with small laboratory scale mixers. In order to evaluate the effect of magnesium stearate admixing in different types of laboratory-scale and industrial mixers, the decrease in crushing strength was measured for a test formulation during mixing with the lubricant in different mixers. The formula used consisted of 90% a-lactose monohydrate 100 mesh, 9.5% microcrystalline cellulose and 0.5% magnesium stearate. The mixers used were two laboratory scale mixers: a 2 litre Turbula mixer and a 13 litre cubic mixer and five production scale mixers: a 45 litre drum mixer, 90 litre, 200 litre and 900 litre planetary mixers and a 1.000 litre V-shaped mixer, respectively. For the test formulation used, it was found that the effect of lubricant admixing on tablet crushing strength was strongly dependent on type, size and rotation speed of the mixer used.

When operated at the same rotation speed, the decrease in crushing strength was much faster for the large industrial mixers than for the small laboratory mixers. These differences were explained by differences in shear forces during the mixing process and the efficiency of the mixing procedure.

For the industrial mixers the decrease of the tablet crushing strength as an effect of lubricant admixing was mainly determined by the rotation speed and only to a small extent by the type and size of the apparatus. Moreover no effect of load could be observed between the mutual industrial mixers used.

For a prediction of the effect of lubricant admixing on tablet crushing strength in large mixers, efficient laboratory mixers, operating at high rotation speeds can be used. For this purpose a 2 litre Turbula mixer is a valuable tool in preformulation work.     

A study on fretting fatigue life for the Inconel alloy 600 at high temperature

Fatigue tests of the Inconel 600, a type of nickel-chromium based heat resistant alloy used for steam generator tubes in nuclear power plants, were carried out. Temperature increase to 320 °C did not change the fatigue strength much, but the fretting condition caused a significant reduction in the fatigue strength. The reduction at 10⁷ cycles was about 70% for both of room and the high temperatures. An apparatus to realize the fretting condition has been developed and instrumented to measure the normal and friction forces. The bridge type of contact pad was fabricated of SUS 409 stainless steel. Fracture surfaces and wear scars were observed by electron microscope and the profiles of wear scar were measured by non-contact 3D-profiler.     

Channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories

The channel width dependence of hot electron injection program/hot hole erase cycling behavior in silicon-oxide-nitride-oxide-silicon (SONOS) memories is investigated. While the trapped charge profile-dependent overerasure is observed in 10-μm-wide device, it is suppressed in 0.22-μm-wide device. Both the overerasure suppression and gradual positive threshold voltage shift in narrow device are explained as an elevated hot hole injection efficiency followed by more pronounced redistribution of the hole profile in the channel-center and the suppression of the lateral migration of injected holes in the channel-edge, by combining the measured endurance characteristics and TCAD simulation results. Main physical mechanisms are three-dimensional distribution of the electric field by gate/drain voltage, increasing interface states, and their trapped charge with cycling in the channel-edge.     

Spectral precoding for rectangularly pulsed OFDM

Spectrally precoded orthogonal frequency-division multiplexing (OFDM) is a promising rectangularly pulsed OFDM signaling format which can provide very small power spectral sidelobes, while allowing for efficient implementation by fast Fourier transform and guard interval insertion. In this paper, general constraints on spectral precoding are developed for OFDM signals with zero padding (ZP-OFDM) or cyclic prefix (CP-OFDM) to warrant the desirable spectral property that the power spectral sidelobes decay asymptotically as f^?2K?2, where K is a preassigned positive integer. In accordance with the constraints, block partitioning is adopted to construct a general signaling format to facilitate the precoder design of the spectrally precoded CP-OFDM that can provide fast decaying sidelobes. New correlative and orthogonal precoders are also devised so that the desirable spectral property of fast sidelobe decaying is achieved with spectrally precoded ZP-OFDM and CP-OFDM signals.     

A comparison of LII analysis results from numerical model and experiment at elevated surrounding pressures

With environmental concerns over emitted particulate matters(PM) from combustion systems, various researches have been conducted on reduction and measurement techniques of particulate matters. The LII analysis results from numerical models and experiments in an ethylene/air laminar diffusion flame at elevated pressure up to 2.0 MPa with laser fluence 0.07 J/cm², detection wavelength 400 nm were compared to validate a modified LII numerical model. The lifetime of the LII signal decreased as the elevated pressure increased, so that LII decay time also decreased in both results. In the aspect of heat transfer mechanism, it becomes earlier that dominant conduction starts. This shows that the results matched well under the pressure conditions. It is concluded that the LII numerical model could be applied to decide particle size in TIRE-LII at the high-pressure condition.     

Piezoresistivity in continuous carbon fiber polymer-matrix and cement-matrix composites

Piezoresistivity was observed in continuous unidirectional carbonfiber cement-matrix and polymer-matrix composites. The fiber volumefraction was 2.6–7.4% and 58% for cement-matrix andpolymer-matrix composites respectively. The DC electrical resistancein the fiber direction increased upon tension in the fiber directionfor the cement-matrix composite, due to fiber-matrix interfacedegradation, but decreased upon tension for the polymer-matrixcomposite due to increase in the degree of fiber alignment.