Luminescence is defi ned broadly as the generation of light in excess of that radiated thermally. Man’s fascination with luminescence stems from when an otherwise invisible power is converted into visible light. The commercial importance of luminescence is ubiquitous, being manifest in lamps, displays, X-ray machines, etc.
Materials that generate luminescence are called phosphors. Commercial phosphors are mostly inorganic compounds prepared as powders (with grain sizes usually in the order of 2-20 µm) or thin films. The phosphor materials contain one or more impurity ions or activators (A), typically present in 0.01-100 mol % concentrations. The actual emission is generated on these activator ions.
Luminescence Science and Display Material, Ronda C., Srivastava A., The Electrochemical Society Interface, Spring 2006, Page: 55)
Direct Driven Press
In a direct driven press configuration. All rollers are driven independently by a
direct-drive rotary motor, without the need for gears or gearboxes. When the load is directly coupled, the settling time is no longer limited by the transmission, so the servo loop gain can be increased. This provides the necessary servo stiffness to achieve excellent speed regulation and phase control between the anilox, plate, and central impression cylinders. Press speeds using direct-drive technology can be increased in many applications because the accuracy of the mechanical transmission system is often the limiting factor.
Switching to direct-drive further improves press throughput by reducing setup and maintenance time. A typical flexo press servo system equipped with gearboxes requires periodic tuning
adjustments of the antibacklash control system to compensate for gear wear. DDR systems, on the other hand, since they are directly coupled to the load, require no periodic tuning. There is complete elimination of backlash and the need for antibacklash controls. Years later, the tuning settings are typically the same as the day the machine was installed. With a direct-drive press, the parts count on a typical Bill of Material (BOM) is reduced by up to 10 parts per color print deck.
(Direct Drive Technology - Improving Flexo Printing Quality and Throughput, England T., Flexo August 2009, page: 50 - 54)
Active Fillers
Filler materials are classified into two categories. Active and non - active fillers. Active fillers are composed of chemically active materials or compounds that convert readily and permanently from one composition to another when subjected to sufficient energy initiate reaction. For the purposes of this discussion, the active filters to be considered are often composed of active elements, such as titanium, aluminium, hafnium, zirconium, vanadium, and niobium, and the energy applied to initiate the conversion is heat. Brazing with active filler materials is a relatively simple method and is generally preferred over brazing with inactive fillers.
(Implantable Neural Prostheses 2: Techniques and Engineering Approaches, Zhou D., Greenbaum E., Page: 37)
Inactive Fillers
Inactive filler materials often require prior metallization of the ceramic substrate to provide for enough wetting, so an interface (usually reactive) is formed. Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), or mechanical metallization can be used to deposit metallic films such as molybdenum, manganese, tungsten, or their combination onto ceramic surfaces prior to brazing. This additional metallization step can complicate the brazing process and makes quality control of the joint more difficult.
(Implantable Neural Prostheses 2: Techniques and Engineering Approaches, Zhou D., Greenbaum E., Page: 37)
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