Multi-layered structure

The performance of the classifier has been verified using a number of practical applications, such as civil engineering [3], inspection of aerospace composite structures, ball bearings and aircraft multi-layer structures. Here we present shortly some results, focusing on detection of disbonds in adhesively joint multi-layer aerospace structures using Fokker Bond Tester resonance instrument, details can be found in [1]. 

Fokker Bond Tester. An ultrasonic inspection technique commonly used for aircraft structures is based on ultrasonic spectroscopy [2]. Commercially available instruments (bond testers) used for this test operate on the principle of mechanical resonance in a multi-layer structure. A piezoelectric probe shown in Figure 3b, excited by a variable frequency sine signal is placed on the surface of the inspected structure. A frequency spectrum in the range of some tens of kHz to several MHz is acquired by the instrument, see Figure 3a. 

A resonance in the layered stracture occurs when echoes between two boundaries travel back and forth due to differences in acoustic impedances at the boundaries. For multi-layer structures a number of resonances can be observed depending on their geometry and condition. For each particular defect-free structure and given transducer we obtain a characteristic resonance pattern, an ultrasonic signature, which can be used as a reference. 

We have presented a neural network based spectrum classifier (NSC) aimed at ultrasonic resonance spectroscopy. The ultrasonic spectroscopy and the NSC has been evaluated in many industrial applications, such as concrete inspection, testing of aerospace composite structures, ball bearings, and aircraft multi-layer structures. The latter application has been presented in some detail. 

The new instrument introduced for inspection of multi-layer structures from polymeric and composite metals and materials in air-space industry and this is acoustic flaw detector AD-64M. The principle of its operation based on impedance and free vibration methods with further spectral processing of the obtained signal. 

The values of these parameters in the polymer layers making up a multi-layer structure plays an important role in the operation of the device. 

The utility and importance of multi-layer device structures was demonstrated in the first report of oiganic molecular LEDs [7]. Since then, their use has been widespread in both organic molecular and polymer LEDs [45, 46], The details of the operating principles of many multi-layer structures continue to be investigated [47—49], The relative importance of charge carrier blocking versus improved carrier transport of the additional, non-luminescent layers is often unclear. The dramatic improvements in diode performance and, in many cases, device lifetime make a detailed understanding of multi-layer device physics essential. 

Recent work with multi-layer polymer LEDs has achieved impressive results and highlights the importance of multi-layer structures [46]. Single-layer, two-layer and three-layer devices were fabricated using a soluble PPV-based polymer as the luminescent layer. The external quantum efficiencies of the single-layer, two-layer, and three-layer devices were 0.08%, 0.55%, and 1%, respectively, with luminous efficiencies of about 0.5 hn/W, 3 lm/W, and 6 lm/W. These results clearly demonstrate improvement in the recombination current because of the increase in quantum efficiency. The corresponding increase in luminous efficiency demonstrates that the improvement in recombination efficiency was achieved without a significant increase in the operating bias. 

To reduce the permeation of specific compounds through plastic sheets, barriers are introduced in multi-layer structures. Each layer provides its own performance in terms of heat sealing, barrier properties, chemical resistance, stiffness, etc., and... 

CDs are 12 cm in diameter and 1.2 mm thick. They have a multi-layer structure as shown in Figure 4. 

The vent area ratio for a single layer structure is the vent area divided by the total area of the wall. The vent area ratio for a multi-layer structure is... 

Process by which the layers of a multi-layered structure separate. 

The multi-layer structure of cartons continues to be an environmental issue. However, much has been done to develop recyclable technology for drinks cartons. One output uses a chipboard-effect material of the type used to make furniture at the other end of the lifecycle is incineration with reclaimed heat. 

Our thanks also go to Dr. B. Wagner and I. Lisec of the Fraunhofer Institute fur Silizium-technologie for the fabrication of multi-layer structures by photo- and e-beam-lithography and for the anisotropic etching of silicon membranes. 

Photo-detector regions are formed in JP-A-1205476 by laser annealing a multi-layer structure of HgTe and CdTe. Radiation which has generated charge carriers between two detector elements will be absorbed in the multi-layer structure thereby reducing cross-talk. 

In summary, good barrier properties can only be achieved by optimizing all the factors affecting the metallization process. Under these conditions, metallized layer barrier properties will be excellent. Superior barrier properties may only be achieved by using multi-layer structures. Such ultra high barrier films, formed from metallized A1 sandwiched between two acrylate layers, were first reported in 2000 [13]. 

If we compare the data in Table 8.5 with the barrier requirements set in polymer electronics (Fig. 8.11), it is evident they cannot be met with metallized films, not even with ultra-high-barrier films, multi-layer structures from metal evaporation, and polymeric layers. For transparent barriers, as required for OLEDs, displays, organic solar cells, etc., evaporated oxide layers are even further from meeting the values required. 

Printing by laser ablation involves transfer of a digital image from a donor film on to a flexible receiver, with the electronics device being built by sequential transfer of separate solid layers. The architecture of these films is illustrated in Fig. 10.2. The donor film comprises a multi-layer structure on a flexible polymeric sub-... 

Multi-layer structure Increase Promote Retard... 

Fig. 11(a) shows the AFM image of an 11-layer mixed-stack CT film of octadecyl-TCNQ and (Me)2P scanned at room temperature with a scan area of 2x2 pm2 [29]. It can be seen from the image that the CT film consists of platelet microcrystal domains of a few micrometers in size in which a multi-layered structure with many steps is observed. An analysis of the cross-sectional profile revealed that the layered platelet microcrystal domains have a step of 3.3 nm thickness [29]. This is in good agreement with the d value measured by the X-ray diffraction method [28]. Therefore, it seemed that the X-ray diffraction peaks originate from the multi-layered structure inside the domains. Each layer in the domains apparently consists of biomolecular layers of octadecyl-TCNQ and (Me)2P because the layer thickness of 3.3 nm is larger than the molecular length (3.0nm) of octadecyl-TCNQ. The biomolecular layer structure also supports that the CT film is in a mixed-stack pattern. 

Figure 149 PL and EL spectra of the multi-layer structure shown in the inset. The principal maximum is characteristic of rubrene (Rb) doped in the thin (3nm) layer of Alq3 [10% Rb Alq3], Adapted from Ref. 565.

Nodax C4/C6 is said to be a natural fit for injection moulding and extrusion of sheet or film. The polymer has mechanical properties similar to a polyolefin and surface properties much like PET, including high receptivity to printing inks and dyes. Adhesion to LDPE and PP is good enough to avoid tie layers in multi-layer structures. Nodax s oxygen barrier property approaches that of EVOH. 

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