Abstract: A method and ballast for driving a high intensity discharge (HID) lamp include generating a very high frequency driving signal for the HID lamp, generating a low frequency modulating signal, amplitude modulating the driving signal with the modulating signal at a predetermined low initial modulation level, measuring a lamp voltage across the HID lamp, determining a standard deviation of the lamp voltage, comparing the standard deviation with a predetermined minimum level, if the standard deviation is above the predetermined minimum level, incrementally increasing the modulation level and repeating the amplitude modulating step, the measuring step, the determining step and the comparing step, and if the standard deviation is below the predetermined minimum level, maintaining the amplitude modulation at the determined level.

Abstract: A method and device for arc straightening in an HID lamp, the method comprising the steps of: determining and selecting a frequency signal or a frequency sweep signal that produces arc straightening for an HID lamp; and exciting an arc straightening acoustic mode in conjunction with a carrier frequency signal. In a preferred embodiment, the exciting step comprises amplitude modulating the carrier frequency signal with either the frequency signal or the frequency sweep signal which corresponds to the power frequencies for arc straightening. In a further embodiment, the exciting step comprises summing the carrier frequency signal with a second frequency signal or second frequency sweep signal to obtain a difference power frequency or power frequencies which excite an arc straightening acoustic mode.

Abstract: An apparatus and method for obtaining short-term color stability in an HID lamp, the apparatus comprising in a first embodiment a high intensity discharge lamp with a discharge vessel and electrodes; with a filling within the discharge vessel containing a metal halide dose of at least 20 mg/cc, where volume is defined as the volume of the main cylindrical section of the discharge vessel. In a preferred embodiment, the filling within the discharge vessel contains Hg of at least 20 mg/cc, where volume is defined as the volume of the main cylindrical section of the discharge vessel. In a yet further aspect, the resulting color temperature is stabilized independent of the shape and frequency of the current and voltage waveforms that drive the HID lamp.

Abstract: A method and structure for substantially overcome vertical segregation in HID lamps, the method comprising the steps of: determining and selecting a frequency sweep signal to produce arc straightening and a fixed frequency signal for exciting a second longitudinal acoustic mode; and exciting in conjunction with a carrier frequency an arc straightening acoustic mode together with a second longitudinal acoustic mode excitation. In a preferred embodiment, the exciting step comprises amplitude modulating the carrier frequency signal with a sum of the frequency sweep signal and the fixed frequency signal.

Abstract: A method for matching an acoustic load and an acoustic driver in a resonant acoustic system, and the acoustic system so formed. The load and driver may be independently designed. The invention provides, inter alia, a matching volume positioned between the acoustic driver and load that is substantially greater than a stroke volume of the driver. The matching volume is sized such that, in combination with the moving mass, the characteristic stiffness of the acoustic driver and the characteristic load impedance, a resulting pressure wave produces an operating resonant frequency substantially equal to the preferred operating frequency of the load. Alternatively, or in addition thereto, a stroke volume of the acoustic driver can be adjusted.

Abstract: Power source systems implementing methods for reducing vertical segregation (color mixing) in a long and thin high intensity discharge lamp are disclosed. Each system provides a current frequency signal to the lamp that excites an azimuthal acoustic and longitudinal acoustic combination mode of the lamp whereby color mixing within the lamp can be achieved. Each system further adjusts the current frequency signal as needed to stabilize color mixing within the lamp.

Abstract: A railway short span trestle is designed for quick erection at an installation site by assembly of a minimum number of parts. Those parts include a pair of spaced apart girders and whatever number of modular floor assemblies are required to span the length of those girders. Each floor assembly may be preassembled in the shop to include crossbeams for connection to the girders, a ballast floor plate which interconnects the crossbeams, and the bent curb plates which contain and support the ballast for a railway track. The invention is further directed to a method of constructing a railway short span trestle including tho preassembly of the modular floor assemblies and final connection of those floor assemblies to a pair of girders to provide a unitary trestle ready for placement onto a substructure.

Abstract: A protective helmet having an internal integral layer of reflective material and the method of constructing the same is disclosed. A first layer of catalyzed clear gel coat is sprayed under pressure into a helmet mold and allowed to dry. A second fog layer of clear gel coat is sprayed over the first layer to form a tacky surface upon which small double sided reflective chips can be sprinkled and brushed flat. The second gel coat is then dried thoroughly. A third backing layer of clear gel coat containing metal flakes is then sprayed over the second layer and completely dried. A layer of saturated fiber-glass mat is applied over the third layer to seal in the reflective chips and to eliminate any air pockets. Layers of fiberglass cloth are then applied over the mat and the fiberglass is completely dried. The helmet is popped from the mold, sanded and finished.