Error enhancement in geomagnetic models derived from scalar data

Models of the main geomagnetic field are generally represented by a scalar potential gamma expanded in a finite number of spherical harmonics. Very accurate observations of F were used, but indications exist that the accuracy of models derived from them is considerably lower. One problem is that F does not always characterize gamma uniquely. It is not clear whether such ambiguity can be encountered in deriving gamma from F in geomagnetic surveys, but there exists a connection, due to the fact that the counterexamples of Backus are related to the dipole field, while the geomagnetic field is dominated by its dipole component. If the models are recovered with a finite error (i.e. they cannot completely fit the data and consequently have a small spurious component), this connection allows the error in certain sequences of harmonic terms in gamma to be enhanced without unduly large effects on the fit of F to the model

A scanning tunneling microscope control system with potentiometric capability

Includes bibliographical references.This report starts by describing the background research and work that had already been done on the UCT scanning tunneling microscope (STM). This system is being developed in the Department of Electrical Engineering at UCT. It goes on to describe the continuation of the research work that was done for this dissertation on the STM at UCT. The work was originally started by Dr. Tapson for his PhD (1994). and continued by the author for his MTech degree in ) 997 and 1998. The work was temporary discontinued from May 2000 till August 2002 to enable the author to work as a contract engineer at the Institute of Physics in Basel, Switzerland to learn more about the construction of probe microscopes. The new work evolved around the need to implement scanning tunneling potentiometry (STP) capability in the new STM. This capability should give the end-user the capability of looking at the sub-surface structure of any material on a sub-micron scale. The basic STP function must be implemented in two dimensions in the plane of the specimen. The STM tip is then used as a highly localized voltmeter to sense what the potential distribution is at that point on the surface. The potential information that is obtained is then used to plot two images of the potential distribution over the surface in the X and Y directions. The topographic information is obtained in the usual way from the STM scan. This method gives three collocated imagesas the result and a better understanding of the surface structure is obtained in this way. The penetration depth of the potential scan can be varied by adjusting the frequency of the applied AC signal in the X and Y directions. This use of the skin effect should allow the end user to obtain slices of the surface at various penetration levels of the specimen. These slices will give a picture of what happens from the surface up to a certain penetration depth. The interpretation of these images could be very difficult because the skin effect does not stop at a defined penetration depth. Only the 3 dB point is defined, which means that sub surface structures below the 3 dB point will also have an influence on the obtained image. During the course of the research new hardware and scanning software was implemented to enable the error-free acquisition of new data. This entailed splitting the existing XY controller into three separate parts namely a Communications interface, and two STP measurement boards. This was suggested as one of the conclusions of the MTech thesis results. The PC software stayed the same but for a change in the array size, that holds theacquired data. This was again changed after the work experience in Basel and is explained in chapter 6

Fluorescence and phosphorescence of photomultiplier window materials under electron irradiation

The fluorescence and phosphorescence of photomultiplier window materials under electron irradiation were investigated using a Sr-90/Y-90 beta emitter as the electron source. Spectral emission curves of UV grade, optical grade, and electron-irradiated samples of MGF2 and LiF, CaF2, BaF2, sapphire, fused silica, and UV transmitting glasses were obtained over the spectral range of 200 nm to 650 nm. Fluorescence yields, expressed as the number of counts in a solid angle of 2 pi steradian per 1MeV of incident electron energy deposited, were determined on these materials utilizing photomultiplier tubes with cesium telluride, bialkali, and trialkali (S-20) photocathodes, respectively

Photonuclear interactions of ultrahigh energy cosmic rays and their astrophysical consequences

Results of detailed Monte Carlo calculations of the interaction histories of ultrahigh energy cosmic-ray nuclei with intergalactic radiation fields are presented. Estimates of these fields and empirical determinations of photonuclear cross sections are used, including multinuclear disintegrations for nuclei up to 56Fe. Intergalactic and galactic energy loss rates and nucleon loss rates for nuclei up to 56Fe are also given. Astrophysical implications are discussed in terms of expected features in the cosmic-ray spectrum between quintillion and sextillion eV for the universal and supercluster origin hypotheses. The results of these calculations indicate that ultrahigh energy cosmic rays cannot be universal in origin regardless of whether they are protons or nuclei. Both the supercluster and galactic origin hypotheses, however, are possible regardless of nuclear composition

Visualization Techniques in Space and Atmospheric Sciences

Unprecedented volumes of data will be generated by research programs that investigate the Earth as a system and the origin of the universe, which will in turn require analysis and interpretation that will lead to meaningful scientific insight. Providing a widely distributed research community with the ability to access, manipulate, analyze, and visualize these complex, multidimensional data sets depends on a wide range of computer science and technology topics. Data storage and compression, data base management, computational methods and algorithms, artificial intelligence, telecommunications, and high-resolution display are just a few of the topics addressed. A unifying theme throughout the papers with regards to advanced data handling and visualization is the need for interactivity, speed, user-friendliness, and extensibility

State work and the testing concours of citizenship

Anyone trying to be a citizen has to pass through a set of practices trying to be a state. This paper investigates some of the ways testing practices calibrate citizens, and in doing so, perform “the state.” The paper focuses on three forms of citizenship testing, which it considers exemplary forms of “state work,” and which all, in various ways, concern “migration.” First, the constitution of a “border crossing,” which requires an identity test configured by deceptibility. Second, the Dutch asylum process, in which “being gay” can, in certain cases, be reason for being granted asylum, but where “being gay” is also the outcome of an examination organized by suspicion. And third, the Dutch measurement of immigrants’ “integration,” which is comprised of a testing process in which such factishes as “being a member of society” and “being modern” surface. Citizenship is analyzed in this paper as accrued and (re)configured along a migration trajectory that takes shape as a testing concours, meaning that subjects become citizens along a trajectory of testing practices. In contributing both to work on states and citizenship, and to work on testing, this paper thus puts forward the concept of citizenship testing as state work, where “state work is the term for that kind of labor that most knows itself as comparison, equivalency, and exchange in the social realm” (Harney, 2002, pp. 10–11). Throughout the testing practices discussed here, comparison, equivalency, and exchange figure prominently as the practical achievements of crafting states and citizens

Head of State of Exception

During the escalation of the “German Autumn” in 1977 the Federal German government resorted to a specific form of crisis management that had been described as an undeclared state of exception. It was Federal chancellor Helmut Schmidt in the first place who oversaw the anti-terrorist measures in the situation room where the executive branch ruled for six weeks beyond any parliamentary control. This article examines the role that Helmut Schmidt had played for the creation of a “subjective state of exception” (Julius Hatschek) and how this could be seen as stemming from Schmidt’s earlier experiences and handling of crisis situations dating back to the 1960s. In this regard it has to be asked with Giorgio Agamben, if in the West German case, the state of exception had become the rule

Wastage amidst shortage: Strategies for the mitigation of standby electricity in residential sector in Nigeria

Abstract : Due to rising population and the increasing rate of urbanization, residential electricity usage accounts for a large chunk of Nigeria’s electricity consumption. However, little attention is paid to electricity conservation in the country. In response to this, several studies are been tailored to ensure a rapid reduction in energy consumption through various alternatives including energy efficient technologies given the current state of inadequate electricity supply in the country. On this note, this article discusses the significance of standby electricity in Nigeria. The electricity generation and consumption patterns were briefly discussed while the current electricity saving behaviour and practices among the urban dwellers were detailed with a case study analysed. Based on the case study, it was discovered that the mean standby load across the 30 households were estimated at 60 W ranging from 34-144 W. Also, standby consumption accounts for 13-44% of the annual electricity consumption across the households. Finally, the strategies for electricity saving and sustainable consumption, most especially the mitigation of standby electricity were highlighted