Metropolitan Library Problems of the Los Angeles Area

published or submitted for publicatio

Proceedings of a Workshop on Polar Stratospheric Clouds: Their Role in Atmospheric Processes

The potential role of polar stratospheric clouds in atmospheric processes was assessed. The observations of polar stratospheric clouds with the Nimbus 7 SAM II satellite experiment were reviewed and a preliminary analysis of their formation, impact on other remote sensing experiments, and potential impact on climate were presented. The potential effect of polar stratospheric clouds on climate, radiation balance, atmospheric dynamics, stratospheric chemistry and water vapor budget, and cloud microphysics was assessed. Conclusions and recommendations, a synopsis of materials and complementary material to support those conclusions and recommendations are presented

Identifying Common Patterns and Unusual Dependencies in Faults, Failures and Fixes for Large-scale Safety-critical Software

As software evolves, becoming a more integral part of complex systems, modern society becomes more reliant on the proper functioning of such systems. However, the field of software quality assurance lacks detailed empirical studies from which best practices can be determined. The fundamental factors that contribute to software quality are faults, failures and fixes, and although some studies have considered specific aspects of each, comprehensive studies have been quite rare. Thus, the fact that we establish the cause-effect relationship between the fault(s) that caused individual failures, as well as the link to the fixes made to prevent the failures from (re)occurring appears to be a unique characteristic of our work. In particular, we analyze fault types, verification activities, severity levels, investigation effort, artifacts fixed, components fixed, and the effort required to implement fixes for a large industrial case study. The analysis includes descriptive statistics, statistical inference through formal hypothesis testing, and data mining. Some of the most interesting empirical results include (1) Contrary to popular belief, later life-cycle faults dominate as causes of failures. Furthermore, over 50% of high priority failures (e.g., post-release failures and safety-critical failures) were caused by coding faults. (2) 15% of failures led to fixes spread across multiple components and the spread was largely affected by the software architecture. (3) The amount of effort spent fixing faults associated with each failure was not uniformly distributed across failures; fixes with a greater spread across components and artifacts, required more effort. Overall, the work indicates that fault prevention and elimination efforts focused on later life cycle faults is essential as coding faults were the dominating cause of safety-critical failures and post-release failures. Further, statistical correlation and/or traditional data mining techniques show potential for assessment and prediction of the locations of fixes and the associated effort. By providing quantitative results and including statistical hypothesis testing, which is not yet a standard practice in software engineering, our work enriches the empirical knowledge needed to improve the state-of-the-art and practice in software quality assurance

Empirical analysis of software reliability

This thesis presents an empirical study of architecture-based software reliability based on large real case studies. It undoubtedly demonstrates the value of using open source software to empirically study software reliability. The major goal is to empirically analyze the applicability, adequacy and accuracy of architecture-based software reliability models. In both our studies we found evidence that the number of failures due to faults in more than one component is not insignificant. Consequently, existing models that make such simplifying assumptions must be improved to account for this phenomenon. This thesis\u27 contributions include developing automatic methods for efficient extraction of necessary data from the available repositories, and using this data to test how and when architecture-based software reliability models work. We study their limitations and ways to improve them. Our results show the importance of knowledge gained from the interaction between theoretical and empirical research

Ensemble model output statistics for wind vectors

A bivariate ensemble model output statistics (EMOS) technique for the postprocessing of ensemble forecasts of two-dimensional wind vectors is proposed, where the postprocessed probabilistic forecast takes the form of a bivariate normal probability density function. The postprocessed means and variances of the wind vector components are linearly bias-corrected versions of the ensemble means and ensemble variances, respectively, and the conditional correlation between the wind components is represented by a trigonometric function of the ensemble mean wind direction. In a case study on 48-hour forecasts of wind vectors over the North American Pacific Northwest with the University of Washington Mesoscale Ensemble, the bivariate EMOS density forecasts were calibrated and sharp, and showed considerable improvement over the raw ensemble and reference forecasts, including ensemble copula coupling

COMPARISON OF TWO ELLIPTICAL MOTION RUNNING MACHINES AND TREADMILL RUNNING

INTRODUCTION: One of the major problems associated with rehabilitation from impact- associated running injuries is maintaining cardiovascular fitness. Recently, elliptical motion exercise machines have been developed in an attempt to simulate running while minimizing impact forces. These machines have been shown to maintain cardiovascular fitness. However, they have not yet been shown to truly simulate the running motion. The purpose of this study was to provide a quantitative comparison of two elliptical motion exercise machines (C1 and C2) and treadmill running (C3). METHODS: Both of the elliptical motion machines fixed stride length, although one allowed a greater stride length (C1). Eight subjects were tested in each of three submaximal exercise conditions during a 15 minute bout. Subjects performed at a stride frequency that resulted in a heart rate of 65% of their age-predicted maximum heart rate. Five 60 Hz digital cameras were used to collect lower extremity kinematic data. Pre-amplified surface electrodes measured the muscle activity of seven lower extremity muscles. Impact forces were assessed using a 1.7g PCB accelerometer placed on the distal medial aspect of the tibia. Both the accelerometer and EMG data were collected concurrently on a microcomputer sampling at 600 Hz. Lower extremity joint and segment parameters, onset and offset of muscles during stride, peak impact force and time to peak impact force were calculated. An analysis of variance was used to compare the measured parameters between each machine condition and to identify whether the duration of the exercise bout had an effect. RESULTS: There were no significant differences in stride duration with controlled stride frequency. The results of the analysis of the kinematic data showed that the majority of the differences between the machines and treadmill running occurred at the ankle and knee joints. At the ankle and knee joints, the touchdown angle was greater for the two machines (C1 and C2) than for treadmill running (ankle: 11.97 o and 22.14 o versus 2.23o; knee: 34.94 o and 33.89 o versus 12.05 o). At the ankle joint, the maximum plantar flexion angle was greatest in treadmill running, while there were no significant differences in any knee angles subsequent to touchdown. There were no differences in any of the hip angles at any time in the stride. Impact values on the two machines were 30% of those measured during treadmill running, and the time of occurrence of the impact was substantially longer into the stride. The results of the EMG data showed that the duration of muscle activity throughout the stride was different in the triceps surae, rectus femoris and vastus lateralis. In each case, the duration of the stride in which these muscles were active was least in treadmill running. CONCLUSIONS: In conclusion, while there are a few differences between the elliptical machines and running, it appears that the machines could be considered representative of running with distinctly less impact. Thus, these machines could be used as rehabilitation tools for runners recovering from impact-related injuries

How much is '5-a-day'? A qualitative investigation into consumer understanding of fruit and vegetable intake guidelines.

BACKGROUND: Despite the known health benefits of fruit and vegetables (FV), population intakes remain low. One potential contributing factor may be a lack of understanding surrounding recommended intakes. The present study aimed to explore the understanding of FV intake guidelines among a sample of low FV consumers. METHODS: Six semi-structured focus groups were held with low FV consumers (n = 28, age range 19-55 years). Focus groups were recorded digitally, transcribed verbatim and analysed thematically using nvivo (QSR International, Melbourne, Australia) to manage the coded data. Participants also completed a short questionnaire assessing knowledge on FV intake guidelines. Descriptive statistics were used to analyse responses. RESULTS: The discussions highlighted that, although participants were aware of FV intake guidelines, they lacked clarity with regard to the meaning of the '5-a-day' message, including what foods are included in the guideline, as well as what constitutes a portion of FV. There was also a sense of confusion surrounding the concept of achieving variety with regard to FV intake. The sample highlighted a lack of previous education on FV portion sizes and put forward suggestions for improving knowledge, including increased information on food packaging and through health campaigns. Questionnaire findings were generally congruent with the qualitative findings, showing high awareness of the '5-a-day' message but a lack of knowledge surrounding FV portion sizes. CONCLUSIONS: Future public health campaigns should consider how best to address the gaps in knowledge identified in the present study, and incorporate evaluations that will allow the impact of future initiatives on knowledge, and ultimately behaviour, to be investigated

Infectivity of an Infectious Clone of Banana Streak CA Virus in A-Genome Bananas (Musa acuminata ssp.)

We have characterized the complete genome sequence of an Australian isolate of banana streak CA virus (BSCAV). A greater-than-full-length, cloned copy of the virus genome was assembled and agroinoculated into five tissue-cultured plants of nine different Musa acuminata banana accessions. BSCAV was highly infectious in all nine accessions. All five inoculated plants from eight accessions developed symptoms by 28 weeks post-inoculation, while all five plants of M. acuminata AA subsp. zebrina remained symptomless. Symptoms were mild in six accessions but were severe in Khae Phrae (M. acuminata subsp. siamea) and the East African Highland banana accession Igisahira Gisanzwe. This is the first full-length BSCAV genome sequence reported from Australia and the first report of the infectivity of an infectious clone of banana streak virus