Overcast sky conditions can be classified into two groups. The one is a group of unstable and fluctuating overcast skies. The other is a group of stable overcast skies. As for the first group, it is almost impossible to derive a typical distribution pattern on a sky. As for the second group, however, it is possible to derive a typical radiance distribution pattern. The author found out that the radiance distribution pattern on a stable overcast sky can be characterized by an equation similar to but a little different from the equation for the luminance distribution on the CIE standard Overcast Sky. In a stable overcast sky, the radiance at the zenith is almost always greater than that of any other sky element.

View full abstract

In-vehicle navigation devices display road maps including place names to provide drivers with such information as their present location, the route to the destination, etc. The authors conduct tests (including both indoor tests and driving tests) to investigate how quickly observers can find the destination name when multiple place names are displayed simultaneously on the screen of the display device. Because the time required to read the information is related to the age of the observer and the number of place names, etc., the authors consider the age of observers and conduct the experiment by varying the number of place names over a range from 6 to 12 place names. Moreover, two types of tests are carried out: those in which the destination name is displayed and those in which it is not displayed. This is carried out in order to investigate how the time required to judge whether the destination name is displayed or not changes. Test results show, for example, that older people require a longer time to read the information than young or middleaged observers.

View full abstract

This paper presents a fluorescent lamp ballasting system using a neutral-point type inverter using MOS FETs one of authors has already shown as similar circuit that decrease the harmonic current of lighting circuit of the compact fluorescent lamp. This time, by the application of this method to the electronic ballast of the fluorescent lamp, the harmonic current was reduced by easier circuit structure than the previous circuit. We report on the crease of the harmonic current and characteristics of power factor and total efficiency.

View full abstract

Firefly luciferin (Ln) is an absorbing substance which showing a high quantum efficiency of the bioluminescence. Several proposals about the mechanism of the luminescence in this system have been explained by investigators. A dioxetane structure exists within the intermediate of Ln and plays an important role to occure the emission. In this report, we attempt to calculate the electronic structures of the dioxetane and to correlate the calculated results with the experimental observations as a first step to recognize the mechanism of the bioluminescence of Ln. Obtained results show that the 2p electrons of O and C are important as to the electronic excitations of the luminescence. The calculated excitation energy agrees with the observed value in spite of a simplified system.

View full abstract

This paper proposes a statistical method for modeling the voltage versus current characteristics of a fluorescent lamp. Parameters of the model are selected from various parameters by applying a maximum R ² improvement method to keep generality of the model. The voltage-current characteristic of the fluorescent lamp is expressed by an equivalent resistance as a function of instantaneous lamp power and its differential coefficient. Therefore, the fluorescent lamp is modeled without knowing physical constants such as the electron impact excitation cross sections of mercury atoms. The simplicity of the equivalent resistance of the fluorescent lamp reduces instability and the computation time required for an analysis of the lamp circuit. Numerical simulations under various conditions are performed using Electromagnetic Transient Program (EMTP). Results calculated for various applied voltages ranging from 50 Hz to 100 kHz agree well with experimental results. The proposed model is confirmed to be independent of voltage waveform and also to be applicable to various types of lighting circuits such as an inductive ballast and an electronic ballast. The stable characteristic of the proposed model opens a way of a computer aided design of a lighting equipment.

View full abstract

Effects of reflection properties of liquid-crystal displays (LCDs) on the reflected glare disturbances were investigated by subjective rating. We studied seven TFT-color LCDs and three CRT displays having different anti-reflection treatments. The specular reflection coefficients of these displays were measured for different source sizes. The disturbing reflections on these displays were subjectively rated to elucidate the relationship between the specular reflection coefficient and the reflected glare disturbance. The results indicated that the interrelation was most obvious (r²>0.9) for a 1-degree source between the specular reflection coefficient and the subjective rating of the glare disturbances from the overhead illuminations. Similarly the subjective ratings of reflected glare from a simulated window were estimated from the specular reflection coefficient for a 10-degree source size. These results have been incorporated into a model for predicting reflected glare disturbances.

View full abstract