Numerical calculation is made for a transistor inverter which is suitable for discharge lamp ballast. The inverter is composed of a power transistor, two inductors, two capacitors, a diode and a trigger unit which drives the power transistor.
Power delivered to the load, distortion of the output waveform and peak voltage across the power transistor are calculated. Following results are obtained where f₀=1/2π√L₂C₂, R₀=√L₂/C₂ and R_L is lamp resistance (lamp voltage divided by lamp current).
(1) Drive frequency f must be equal to or higher than f₀.
(2) The power depends strongly on f/f₀ and R_L/R₀, and weakly on L₁/L₂ and C₁/C₂.
(3) With small value of R_L/R₀(≅0.1), the output waveform is almost sinusnoidol. Increasing R_L/R₀ results large distortion in the output waveform.
(4) Peak voltage on the power transistor depeds on L₁/L₂ and /C₂, and weakly on f/f₀ and R_L/R₀.
These results are useful for designing the discharge lamp ballast and a procedure to determine the values of L₁, L₂, C₁ and C₂ is described.

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This research relates to the harmonic characteristics of the continuous dimmer circuit for the incandescent lamp. The research has been conducted in the following sequence.
When the firing angles caused by the TRIAC are varied on the main voltage of the input terminal, Fourier series are developed on the voltage and current of a distorted wave at each element of the continuos dimmer circuit. And with the Fourier expansion, each harmonic character at each element of the continuous dimmer circuit is theoretically obtained, and the experiment is performed to demonstrate it.
(1) From the voltage and current of a distorted wave at each element of the continuous dimmer circuit, the vector diagram is obtained for the harmonic of each firing angle, and their characteristics are clarified.
(2) From the voltage and current of a distorted wave at each element of the continuous dimmer circuit, the impedance (i. e., its resistance and reactance component) is obtained for the harmonic of each firing angle, and their characteristics are clarified.
(3) From the voltage and current of a distorted wave at each element of the continuous dimmer circuit, the equivalent circuit is obtained for each harmonic, and their characteristics are clarifvied.
(4) From the voltage and current of a distorted wave at each element of the continuous dimmer circuit, the effective power and reactive power are obtained for the harmonic of each firing angle, and the effective power, reactive power, apparent power, and distorted power at each element are obtained and their characteristics are clarified.
(5) The research is made to improve the power factor in the power circuit by using condensers for the harmonic of each firing angle.

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The absolute spectral reflectance in 0/d condition (ρ (λ)) of Several white diffusers have been measured by third Taylor's method, using the integrating sphere of usual spectrophotometer and the relative spectral radiance factor in 0/45° condition (B₄₅ (λ)) of same samples are also measured by simple goniometric method. The wavelength region of measurements are 210-2, 500 nm in ρ (λ), and 280-760 nm in B45 (λ). The samples of these measurements are the pressed BaSO₄, LiF, flowers of sulfur and the sintered Al₂O₃ plate. The results of ρ (λ) and B₄₅ (λ) are compared respectively for same sample. The reflectance change with the passage of time is also measured for some samples. The results are as follows;
(1) ρ (λ) on the pressed BaSO₄ is over 90% in the wavelength region of 320-1, 800 nm, but that goes down in the regionshorter 300 nm and that has remarkable dips in the region longer than 1, 800 nm.
(2) ρ (λ) on the pressed LiF is same as that on BaSO₄ in visible (VIS) region and is somewhat higher than that on BaSO₄ in ultraviolet (UV) and infrared (IR) region.
(3) ρ (λ) on the sintered Al₂O₃ is same as that on BaSO₄ in VIS region and is higher than that on BaSO₄ in IR region, but goes down suddenly in UV region.
(4) ρ (λ) on the pressed flowers of sulfur is almost constant in the wavelength region of 700-2, 200 nm, but goes down in the wavelength region shorter than 600 nm.
(5) On the pressed BaSO₄ and LiF, the relative value of ρ (λ) is consistent with the B₄₅ (λ) in the wavelength region of 320-760 nm.
(6) On the pressed BaSO₄ and LiF, the difference of ρ (λ) on samples which are made from same lot and the change of ρ (λ) with the passage of time are very small through the measurement period (about half a year).

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This paper describes several types of filters for visual display terminals (VDT) that are currently available, and discusses their effectiveness.
For a limited comparison of the effectiveness of several filters and filter types, the effects of 42 filters on different types of VDT screen were measured.
The results indicate that most filters are more effective in reducing diffuse reflections than in reducing specular reflections. Especially, for the matte-finish or multi-coating screen, none of the filters resulted in a significant improvement in reducing specular reflections. The use of VDT filters, therefore, should be considered with caution.

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