William Lama - Academia.edu (original) (raw)
I have a physics PhD. I worked at Xerox as a scientist and lab manager retiring in 2002.
less
Related Authors
Homi Bhabha National Institute (HBNI, BARC, MUMBAI)
Uploads
Papers by William Lama
Journal of Electrostatics, 1977
ABSTRACT Overall, the meteoric rise in the size of this conference in the last two years is an in... more ABSTRACT Overall, the meteoric rise in the size of this conference in the last two years is an indication of the importance of electrostatics in many practical applications. It is unfortunate that the subject of electrostics has been comparatively neglected by the scientific, academic and industrial communities for many years. This conference is helping to stimulate interest and fill that void.
The question whether it is possible to account for spontaneous emission of electromagnetic radiat... more The question whether it is possible to account for spontaneous emission of electromagnetic radiation from atoms without quantum electrodynamics has lately been the subject of further discussion.[1–5] In a recent article Nesbet[5] has considered an approach to the problem that differs substantially from the neoclassical approach of Jaynes and his co-workers.[1–3] In this theory the electromagnetic field is expressed explicitly in terms of its sources, which are quantized, and it obeys the algebra of the sources, while the concept of the free boson field is discarded altogether. Although he has referred to it as ‘semi-quantized radiation theory’, the theory is actually a fully quantized one, in the sense that no c-number currents or fields appear. When the rate of energy flow into the far electromagnetic field written in normal order is equated to the rate of energy loss of a two-level atom, Nesbet’s theory apparently leads to exponential decay of the atomic energy.[5,6]
The theory and measurement of optical spectra impact a wide range of scientific fields including ... more The theory and measurement of optical spectra impact a wide range of scientific fields including spectroscopy and astrophysics. Under certain conditions, the spectral lines from sources and from scattering media can be shifted and spread or narrowed relative to their natural wavelengths and linewidths. These spectral modifications have been predicted from optical coherence theory by Wolf (Phys Rev Lett 56, p1370, 1986) and others and demonstrated in a host of experiments. The underlying physical mechanism involves correlations among the components of the radiating medium. The correlations may be understood at the microscopic level as due to interactions between the atoms induced by their radiation fields. However, the main features of this effect may be understood from a purely classical theory employing macroscopic optical correlation functions. We will present a high level, hopefully intuitive, overview of this theory. We will show that, under reasonable physical conditions, the p...
ABSTRACT A hybrid halftone cell selection method enables selection of gray levels in halftone pri... more ABSTRACT A hybrid halftone cell selection method enables selection of gray levels in halftone printing algorithms to minimize the effects of noise resulting in nonuniformities, such as, for example, halftone banding. The method requires selection of hybrid halftone cells possessing structures wherein the total number of gray pixels are limited. The number of gray pixels having any given intermediate reflectance level in any halftone cell is also limited. The cell selection method thus reduces the number of TRC gray steps to some minimum required number by eliminating the most noise sensitive cells (i.e. those cells having the highest percentage of gray level pixels). The intermediate reflectance values of the gray pixels in the selected cells are then selected to produce uniform gray steps and reduce variability in the TRC.
ABSTRACT A multi-beam laser ROS print system is described which is adapted to minimize banding in... more ABSTRACT A multi-beam laser ROS print system is described which is adapted to minimize banding in output prints. Multiple beams from a laser source are separated by a distance which causes the beam to scan consecutive lines in a non-consecutive scan; e.g., according to a particular beam interlacing sequence. It has been found that as a general proposition, banding decreases with increasing interlacing orders and, furhter, that once a print system error frequency, or another frequency of interest has been identified, there are a number of interlacing orders, each an optimum value, which can be introduced to reduce banding which would ordinarily result from the particular frequency error.
Journal of Electrostatics, 1977
ABSTRACT Overall, the meteoric rise in the size of this conference in the last two years is an in... more ABSTRACT Overall, the meteoric rise in the size of this conference in the last two years is an indication of the importance of electrostatics in many practical applications. It is unfortunate that the subject of electrostics has been comparatively neglected by the scientific, academic and industrial communities for many years. This conference is helping to stimulate interest and fill that void.
The question whether it is possible to account for spontaneous emission of electromagnetic radiat... more The question whether it is possible to account for spontaneous emission of electromagnetic radiation from atoms without quantum electrodynamics has lately been the subject of further discussion.[1–5] In a recent article Nesbet[5] has considered an approach to the problem that differs substantially from the neoclassical approach of Jaynes and his co-workers.[1–3] In this theory the electromagnetic field is expressed explicitly in terms of its sources, which are quantized, and it obeys the algebra of the sources, while the concept of the free boson field is discarded altogether. Although he has referred to it as ‘semi-quantized radiation theory’, the theory is actually a fully quantized one, in the sense that no c-number currents or fields appear. When the rate of energy flow into the far electromagnetic field written in normal order is equated to the rate of energy loss of a two-level atom, Nesbet’s theory apparently leads to exponential decay of the atomic energy.[5,6]
The theory and measurement of optical spectra impact a wide range of scientific fields including ... more The theory and measurement of optical spectra impact a wide range of scientific fields including spectroscopy and astrophysics. Under certain conditions, the spectral lines from sources and from scattering media can be shifted and spread or narrowed relative to their natural wavelengths and linewidths. These spectral modifications have been predicted from optical coherence theory by Wolf (Phys Rev Lett 56, p1370, 1986) and others and demonstrated in a host of experiments. The underlying physical mechanism involves correlations among the components of the radiating medium. The correlations may be understood at the microscopic level as due to interactions between the atoms induced by their radiation fields. However, the main features of this effect may be understood from a purely classical theory employing macroscopic optical correlation functions. We will present a high level, hopefully intuitive, overview of this theory. We will show that, under reasonable physical conditions, the p...
ABSTRACT A hybrid halftone cell selection method enables selection of gray levels in halftone pri... more ABSTRACT A hybrid halftone cell selection method enables selection of gray levels in halftone printing algorithms to minimize the effects of noise resulting in nonuniformities, such as, for example, halftone banding. The method requires selection of hybrid halftone cells possessing structures wherein the total number of gray pixels are limited. The number of gray pixels having any given intermediate reflectance level in any halftone cell is also limited. The cell selection method thus reduces the number of TRC gray steps to some minimum required number by eliminating the most noise sensitive cells (i.e. those cells having the highest percentage of gray level pixels). The intermediate reflectance values of the gray pixels in the selected cells are then selected to produce uniform gray steps and reduce variability in the TRC.
ABSTRACT A multi-beam laser ROS print system is described which is adapted to minimize banding in... more ABSTRACT A multi-beam laser ROS print system is described which is adapted to minimize banding in output prints. Multiple beams from a laser source are separated by a distance which causes the beam to scan consecutive lines in a non-consecutive scan; e.g., according to a particular beam interlacing sequence. It has been found that as a general proposition, banding decreases with increasing interlacing orders and, furhter, that once a print system error frequency, or another frequency of interest has been identified, there are a number of interlacing orders, each an optimum value, which can be introduced to reduce banding which would ordinarily result from the particular frequency error.