Application of electronic techniques in the evaluation of picture quality.

Thesis (M.A.)--Boston UniversityA study was previously made by Dr. Duncan E. Macdonald and his group at the Optical Research Laboratory of Boston University. This study dealt with the determination of photographic image quality by edge analysis, where an edge here was defined as B greater than or equal to ten percent occurring between a successive trough and peak of a micro-densitometer trace across the photograph. ∆ B is defined as the brightness change across the edge and B is the minimum absolute brightness where this change took place. This thesis is a further study into the work done by Dr. Macdonald. The analysis of his data was done from direct measurements of the paper recorded micro-densitometer traces, but in this study it was proposed that the same or similar data could be recorded automatically using electronic equipment. This thesis presupposes no quantitative definition of an edge, but suggests that with further work a quantitative definition of an edge may be determined. An edge is simply defined as the boundary which separates a picture element from its surroundings on a photograph so that the object is discernible to the eye. We assume that the quality of the picture is a function of its edges and that the edge can be described by two variables; 1) the slope or rate of change of brightness across the edge, and 2) the relative brightness difference across the edge. The equipment used was designed to measure the magnitude of the relative slope, and count the number of slopes of given magnitude in a unidirectional scan across the photograph. Other equipment was designed to measure the magnitude of the reflectivity difference across the edge and count the number of occurences for a given magnitude per linescan. An edge is defined electronically as the change in reflectivity from black to white of a uni-directional scan between any two points where the derivative of this linescan waveform is zero. In this definition no notice is taken as to whether an observer can detect the edge. Five aerial photographs were used in this study graded by impartial observers. Three of the photos are aerial photographs of trees graded as (A) unus~ble, (B) just usuable, (C) excellent. The other two pictures are aerial photos of the Boston suburban area graded as (P) unusable and (G) excellent. These photographs were mounted on a rotating drum which can be adjusted so that any part of the drum can be scanned. The drum was illuminated from a suitable light source. The target is imaged on a pinhole through an optical system. Behind the pinhole is a photo-multiplier tube. The output of the photo-tube serves as the input to a D.C. amplifier. The output of the amplifier is then a voltage scan of a line on the target. To work with the derivative of this waveform the voltage function is then differentiated and level selected. All derivatives above the level selected are counted on an electronic counter. By varying the level selector from zero to maximum level all derivatives are counted and magnitudes recorded. To get the reflectivity difference across an edge a circuit is used which allows an output of the linescan signal to appear only when the derivative is positive. Thus the reflectivity difference across an edge appears relative to a common base line irrespective of what background reflectivity the edge occurred. This in turn was electronically level selected and counted in the same manner as was the derivative. The data consisted of between 1, 500 and 2, 000 counts for every curve drawn. This data was reworked and presented in graphical form, as shown in figures XVII through XX, as cumulative frequency of counts plotted against the magnitude of the relative derivative of the edge in one case and the magnitude of relative reflectivity across an edge in the other. These curves show quite clearly that a difference exists between the good and poor pictures. The excellent photos have slopes that are much greater than the just usuable or unusable pictures. The higher magnitude slopes seem to indicate the quality of the photograph, the lower value slopes being fairly uniform throughout. Similarly the higher reflectivity across an edge appears on the best quality photographs with commensurate degrading for poorer quality pictures. With the knowledge that the edge criterion chosen can lead to objective results for picture quality, it would be interesting to carry on this work in experimentally determining a definition for the threshold photographic edge. This threshold edge is defined as the minimum observable boundary permitting a picture element to be seen in a photograph by a human observer. This could be done by using a large sample from photo-interpreters and the apparatus already perfected for this thesis

Families Index for Pseudodifferential Operators on Manifolds with Boundary

An analytic index is defined for a family of cusp pseudodifferential operators, $P_b,$ on a fibration with fibres which are compact manifolds with boundaries, provided the family is elliptic and has invertible indicial family at the boundary. In fact there is always a perturbation $Q_b$ by a family of cusp operators of order $-\infty$ such that each $P_b+Q_b$ is invertible. Thus any elliptic family of symbols has a realization as an invertible family of cusp pseudodifferential operators, which is a form of the cobordism invariance of the index. A crucial role is played by the weak contractibility of the group of cusp smoothing operators on a compact manifold with non-trivial boundary and the associated exact sequence of classifying spaces of odd and even K-theory.Comment: 21 pages; corrected typos, changed the abstract, added a paragraph in the introductio

Index in K-theory for families of fibred cusp operators

A families index theorem in K-theory is given for the setting of Atiyah, Patodi and Singer of a family of Dirac operators with spectral boundary condition. This result is deduced from such a K-theory index theorem for the calculus of cusp, or more generally fibred cusp, pseudodifferential operators on the fibres (with boundary) of a fibration; a version of Poincare duality is also shown in this setting, identifying the stable Fredholm families with elements of a bivariant K-group.Comment: 64 pages, corrected typo

In-flight measurement of propeller noise on the fuselage of an airplane

In-flight measurements of propeller noise on the fuselage of an OV-10A aircraft were obtained using a horizontal and a vertical microphone array. A wide range of flight conditions were tested including changes in angle of attack, sideslip angle, power coefficient, helical tip Mach number and advance ratio, and propeller direction of rotation. Results show a dependence of the level and directivity of the tones on the angle of attack and on the sideslip angle with the propeller direction of rotation, which is similar to results obtained in wind tunnel tests with advanced propeller designs. The level of the tones at each microphone increases with increasing angle of attack for inboard-down propeller rotation and decreases for inboard-up rotation. The level also increases with increasing slideslip angle for both propeller directions of rotation. Increasing the power coefficient results in a slight increase in the level of the tones. A strong shock wave is generated by the propeller blades even at relatively low helical tip Mach numbers resulting in high harmonic levels. As the helical tip Mach number and the advance ratio are increased, the level of the higher harmonics increases much faster than the level of the blade passage frequency

Entry and Asymmetric Lobbying: Why Governments Pick Losers

Governments frequently intervene to support domestic industries, but a surprising amount of this support goes to ailing sectors. We explain this with a lobbying model that allows for entry and sunk costs. Specifically, policy is influenced by pressure groups that incur lobbying expenses to create rents. In expanding industry, entry tends to erode such rents, but in declining industries, sunk costs rule out entry as long as the rents are not too high. This asymmetric appropriablity of rents means losers lobby harder. Thus it is not that government policy picks losers, it is that losers pick government policy.

The Impact of Trade on Intraindustry Reallocation and Aggregate Industry Productivity: A Comment

Melitz (2003) demonstrates that greater trade openness raises industry productivity via a selection effect and via a production re-allocation effect. Our comment points out that the set-up assumed in the Melitz model displays a trade off between static and dynamic efficiency gains. That is, although freer trade improves industry productivity in a level sense, it harms it in a growth sense. To make this point as simply as possible, we introduce a slight modification to the model that endogenises the growth rate of industry productivity and we show that liberalisation slows growth.

Temperature dependence of core loss in cobalt substituted Ni-Zn-Cu ferrites

The temperature dependence of core loss in cobalt substituted Ni-Zn-Cu ferrites was investigated. Co2+ ions are known to lead to a compensation of the magneto-crystalline anisotropy in Ni-Zn ferrites, at a temperature depending on the cobalt content and the Ni/Zn ratio. We observed similar behaviour in Ni-Zn-Cu and it was found that the core loss goes through a minimum around this magneto-crystalline anisotropy compensation. Moreover, the anisotropy induced by the cobalt allowed a strong decrease of core loss, a ferrite having a core loss of 350 mW/cm3 at 80 ^\circ C was then developed (measured at 1.5 MHz and 25 mT). This result represents an improvement of a factor 4 compared to the state of art Ni-Zn ferrites

Temperature dependence of spin resonance in cobalt substituted NiZnCu ferrites

Cobalt substitutions were investigated in Ni0.4Zn0.4Cu0.2Fe2O4 ferrites, initial complex permeability was then measured from 1 MHz to 1 GHz. It appears that cobalt substitution led to a decrease in the permeability and an increase in the \mus\timesfr factor. As well, it gave to the permeability spectrum a sharp resonance character. We also observed a spin reorientation occurring at a temperature depending on the cobalt content. Study of the complex permeability versus temperature highlighted that the most resonant character was obtained at this temperature. This shows that cobalt contribution to second order magnetocrystalline anisotropy plays a leading role at this temperature

Complex Remanence vs. Simple Persistence: Are Hysteresis and Unit-Root Processes observationally equivalent?

The hysteresis terminology has mainly been used in two fields of economics, unemplyment and international trade, with a different meaning however, involving either linear autoregressive macro behaviour or non- linear heterogenous mico behaviour. There may nonetheless be observational equivalence between the 'persistence' characterising unit- root processes and the 'remanence' created by the aggregation of non- linear dynamics. Stochastic simulations are employed to analyse the properties of the output of an hysteretic system, subject to white noise and random walk inputs. Non-linear hysteretic systems are found to generate a sizeable proportion - two-thirds - of stationary output from stationary input, and to possibly generate an output cointegrated with the corresponding input. Such processes therefore appear significantly different from an integrated process. This stresses the specific relevance of a non-linear approach to hysteresis.hysteresis, non-linearity, aggregation, heterogeneity, experimental economics