Matrix-pattern-based computer algorithm for solving fuzzy relation equations

This paper proposes a new computer algorithm to solve the fuzzy relation equation P/spl ogr/Q=R, where /spl ogr/ denotes max-min composition or max-product composition. This algorithm operates systematically and graphically on a matrix pattern to get all the solutions of P. Furthermore, by using MATLAB software 6.0, the algorithm is implemented in a computer program attached in the appendix of this paper. Two examples are given to illustrate the effectiveness of the proposed algorithm.     

Passive gain-equalized wide-band erbium-doped fiber amplifier using samarium-doped fiber

A passive gain-equalization technique of erbium-doped fiber amplifier (EDFA) using a samarium-doped fiber to obtain wide-band flattened gain operation is reported. In the wavelength range from 1529-1559-nm, small inter-channel gain variations can be achieved. This simple technique is suitable for multiwavelength wide-band in-line-amplifier cascaded transmission applications.     

Determination of intraparticulate mass transfer coefficients via permeation measurements: theory and experimental validation

A mathematical model of mass transfer through a heterogeneous, multiphase barrier has been developed where the dispersed phase is capable of uptake of the diffusant according to a linear relationship. The model was used to describe the penetration of drugs through dispersions of permeable globules in media of known diffusional properties. Water-in-oil-in-water (W/O/W) multiple emulsions have been studied by this method. When used to analyze data obtained with a simple diffusion cell, the model allows the calculation of the mass transfer coefficient which characterizes the diffusional mass transfer across oil-water interfaces within the emulsions. The mass transfer coefficient is directly related to the drug release rate from the internal phases of multiple emulsions. Those cases where instantaneous equilibria are established or where impermeable globules are present can be treated as special limiting cases. Differential equations which express diffusant concentrations as functions of time, space, and dispersion system parameters have been solved by Laplace transformation without recourse to numerical methods. The values of the mass transfer coefficient are shown to reflect the physical characteristics of multiple emulsion systems.     

Surface modification and functionalization of electroactive polymer films via grafting of polyelectrolyte,polyampholyte and polymeric acids

Films of electroactive polymers, such as polyaniline (PAN) in its emeraldine base form, and poly(3-alkylthiophene), poly(3-hexylthiophene) (P6TH), poly(3-octylthiophene) (P8TH), and poly(3-dodecylthiophene) (P12TH) can be readily functionalized via thermal or near ultraviolet-light-induced surface graft copolymerization with monomers of polyelectrolyte, polyampholyte and polymeric acids. The monomers used in the present work include dimethyl sulphate quaternized dimethylamino-ethylmethacrylate (DMAEM·C₂H₆SO₄), 3-dimethyl(methacryloyloxyethyl)ammonium propane sulphonate (DMAPS), acrylic acid (AAc) and a sodium salt of styrene sulphonic acid (NaSS). The surface structures and compositions of the electroactive polymer films after functionalization via graft copolymerization were characterized by angle-resolved X-ray photoelectron spectroscopy. Graft copolymerization of poly(3-alkylthiophene) films, but not PAN films, with the hydrophilic monomers readily results in a stratified surface microstructure arising from the migration of the hydrophilic graft chains beneath a thin surface layer which is much richer in the substrate chains. On the other hand, graft copolymerization of PAN films with AAc and NaSS readily gives rise to a self-protonated (and thus conductive) surface structure.     

Crossing the planes at high speed. Signal integrity issues at splitground and power planes

This article discusses a specific design situation that represents quite a broad class of problems in the study of signal integrity. The article focuses on the effects on high-speed signals that need to cross split ground planes and split power planes that act as signal references or partial references. Such configurations are frequently needed in the layout of printed circuit boards (PCBs), multichip modules (MCMs), and even single-chip modules. Examples of split ground and power planes are discussed first. The conventional effective inductance model is described briefly, and an accurate and efficient transmission line model is then discussed in detail. Examples of modeling and design trade-offs are also presented     

Eight-channel bidirectional WDM add/drop multiplexer

The authors propose and demonstrate an eight-channel reconfigurable bidirectional wavelength division multiplexed (WDM) add-drop multiplexer in which all channels can be added/dropped independently in either direction. The performance of the bidirectional WDM add/drop multiplexer is experimentally studied for a data rate of 10 Gbit/s per channel, providing an overall capacity of 80 Gbit/s. It is found that the performance of the add/drop multiplexer is not degraded by a backward propagating signal     

Generalized impedance control of robot for assembly tasks requiringcompliant manipulation

To perform assembly tasks requiring compliant manipulation, the robot must follow a motion trajectory and exert an appropriate force profile while making compliant contact with a dynamic environment. For this purpose, a generalized impedance in the task space consisting of a second-order function relating the motion errors and interaction force errors is introduced such that the contact force can be commanded and controlled. With generalized impedance control, the robot can behave with a desired dynamic characteristic when it interacts with the environment. To ensure the success of the assembly, a strategy during task planning which takes into consideration the interrelation between motion and force trajectories as well as contact compliance is introduced. The generalized impedance control method is applied to the prismatic joint of a selective compliance assembly robot arm (SCARA) robot for inserting a printed circuit board (PCB) into an edge connector socket. Depending on the progress of the parts joining operation, various amount of interaction forces are generated which have to be accommodated. It is demonstrated that an assembly strategy which consists of a sequence of carefully planned target impedance can enable the task to be executed in a desirable manner. The effectiveness of this approach is illustrated through experiments by comparing the results with those obtained using a well-established position control scheme as well as the original impedance control method     

The behavior of small fatigue cracks at notches in corrosive environments

The behavior of small cracks growing out of the roots of blunt notches in compact type specimens of an austenitic steel was characterized under fatigue loading in wet H ₂ plus air environment. The growth rates of cracks in the size range of 0.125 mm to 0.75 mm were up to two orders of magnitude higher than the rates expected for conventional cracks at equal stress intensity range, K. It was also observed that the small cracks grew at these fast rates only in corrosive environments when the loading frequency was 0.02 Hz or less. At a frequency of 10 Hz, the behavior was in agreement with the trend predicted for conventional size cracks.The above observations are rationalized in terms of the breakdown of the concept of a single parameter representation of the crack tip stress and strain field by K or in terms of differences in crack tip environments between small and long cracks for the same bulk environment. A simple engineering model is proposed which adequately represents the observed small crack growth behavior.

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Résumé On a procédé à la caractérisation, sous charges de fatigue en atmosphère humide de H ₂ et d'air, de petites fissures se développant à partir des racines d'entailles arrondies dans des éprouvettes compactes.Les vitesses de croissance des fissures d'une taille allant de 0,125 à 0,750 mm se sont révélé être de deux ordres de grandeur plus grandes que les vitesses prévues dans le cas de fissures conventionnelle, soumises aux mêmes variations de l'intensité de contrainte K. On a également observé que de petites fissures croissaient à ces grandes vitesses seulement dans des atmosphères corrosives, lorsque la fréquence de sollicitation était de 0,02 Hz ou moins. A la fréquence de 10 Hz, le comportement observé s'est trouvé en accord avec les tendances prévues pour des fissures de taille conventionnelle.Les observations ci-dessus sont rationnalisées en un élargissement du concept de représentation monoparamétrique par le facteur K du champ de contraintes et de dilatation à l'extrémité de la fissure, ou en termes des différences rencontrées dans l'environnement local de l'extrémité d'une fissure, selon que celle-ci est longue ou courte, et ce dans un même environnement global.On propose un modèle simple utilisable en pratique, pour représenter de manière adéquate le comportement à la croissance observé pour des petites fissures.

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Metallurgy Department     

Preparation and properties of (BATB–ODPA) polyimide–clay nanocomposite materials

A series of polymer–clay nanocomposite (PCN) materials consisting of 1,4‐bis(4‐aminophenoxy)‐2‐tert‐butylbenzene–4,4′‐oxydiphthalic anhydride (BATB–ODPA) polyimide (PI) and layered montmorillonite (MMT) clay were successfully prepared by an in situ polymerization reaction through thermal imidization up to 300°C. The synthesized PCN materials were subsequently characterized by Fourier‐Transform infrared (FTIR) spectroscopy, wide‐angle powder X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of material composition on thermal stability, mechanical strength, molecular permeability and optical clarity of bulk PI and PCN materials in the form of membranes were studied by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), molecular permeability analysis (GPA) and ultraviolet‐visible (UV/VIS) transmission spectra, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1072–1079, 2004     

The Influence of Diphenyl Siloxane on Morphology and Physical Properties in the Poly(Imide Siloxane)(PIS) Copolymer

Various numbers of diphenyl-siloxane groups were incorporated in α,ω-bis(aminopropyl)polydimethylsiloxane (APPS) to prepare α,ω-bis(aminopropyl)-polydimethyldiphenylsiloxane (APPPS) oligomers of three different number-average molecular weights(Mn = 547,772,1210 g mol⁻¹).These APPPS oligomers were than used, together with 3,3′,4,4′-bezonphenone tetracarboxylic dianhydride (BTDA) and 2-2′-bis[4-(3-aminophenoxy)phenyl] sulfone (m-BAPS), to synthesize a series of APPPS containing poly(imide siloxane) (PIS) copolymers. Microstructural studies showed that at certain APPPS content, a critical microphase separation point existed, beyond which, microphase separation began to develop. This critical point of microphase separation was found to be affected by the Mn of the APPPS oligomers (8.0, 4.3 and 2.1 mol% for Mn of 547, 772 and 1,210 g mol⁻¹, respectively). Diphenyl-siloxane significantly improved compatibility between polyimide and polysiloxane segments. Physical studies showed that the introduction of diphenyl siloxane changed the thermal stabilities and mechanical properties of the PIS copolymers. These findings have potential applications for design purposes in engineering polymers.