No description available.

No description available.

No description available.

No description available.

No description available.

This thesis describes a theoretical and experimental investigation into compressional wave ultrasonic probes for use in high resolution non-destructive testing. In the theoretical section, the pulse performance of the ultrasonic probe is analysed in detail. The response of the piezoelectric transducer is initially determined by direct time domain analysis of electrical equivalent circuits and specially devised computer programs are then used ito predict the performance of various probe constructions The effects of intermediate layers lying between the transducer and the backing and between the transducer and the job are included. In the experimental section, the design, construction and subsequent performance of high resolution probes is described. Both contact and immersion probes are included, the former having a resonant frequency of 5MHz, and the latter having resonant frequencies of 5MHz and 10MHz. Whilst the computer analysis does not extend to contact probes, agreement between predicted pulse shapes and those obtained experimentally is excellent in the case of immersion probes. In addition to pulse shapes, full details of such aspects as repeatability of probe performance, suppression of acoustic waves in the backing and experimentally observed beam-profiles are also given. Finally, the performance of a single immersion probe having a resonant frequency of 20MHz is described and some suggestions for further work are given.

A simple stand-alone Scanning Tunnelling Microscope has been designed and constructed with the aim of providing first stage toward an in-situ instrument for study of thin-film growth. It is functionally capable of STM operation (constant current, constant height, line test) and STS operation (I - V and dI/dv - V). This thesis describes mechanical design, electronic design, computer interfacing in hardware and software, and computer graphics, and presents the results of testing and some applications. The STM head mechanical design features a helical spring/diaphragm coarse approach assembly and a concentric tube scanner. An analysis of the control system indicates that an integrator and single-pole low-pass filter provides near optimal behaviour of the control loop and deals with mechanical resonance in a particularly satisfactory manner. A discussion of hardware/software tradeoff and analog/digital tradeoff leads to a stand-alone design based on a PC, giving good performance with maximum use of standard commercial components and relatively simple special-purpose interface. Commercial graphical software package UNIRAS PC-DOS is employed for image display and hardcopy output. Results show excellent repeatability and stability of STM operation, with atomic resolution.

Since the early days of software testing, automatic test generation has been suggested as a way of allowing tests to be created at a lower cost. However, industrially useful and applicable tools for automatic test generation are still scarce. As a consequence, the evidence regarding the applicability or feasibility of automatic test generation in industrial practice is limited. This is especially problematic if we consider the use of automatic test generation for industrial safety-critical control systems, such as are found in power plants, airplanes, or trains. In this thesis, we improve the current state of automatic test generation by developing a technique based on model-checking that works with IEC 61131-3 industrial control software. We show how automatic test generation for IEC 61131-3 programs, containing both functional and timing information, can be solved as a model checking problem for both code and mutation coverage criteria.  The developed technique has been implemented in the CompleteTest tool. To evaluate the potential application of our technique, we present several studies where the tool is applied to industrial control software. Results show that CompleteTest is viable for use in industrial practice; it is efficient in terms of the time required to generate tests that satisfy both code and mutation coverage and scales well for most of the industrial programs considered. However, our results also show that there are still challenges associated with the use of automatic test generation. In particular, we found that while automatically generated tests, based on code coverage, can exercise the logic of the software as well as tests written manually, and can do so in a fraction of the time, they do not show better fault detection compared to manually created tests. Specifically, it seems that manually created tests are able to detect more faults of certain types (i.e, logical replacement, negation insertion and timer replacement) than automatically generated tests. To tackle this issue, we propose an approach for improving fault detection by using mutation coverage as a test criterion. We implemented this approach in the CompleteTest tool and used it to evaluate automatic test generation based on mutation testing. While the resulting tests were more effective than automatic tests generated based on code coverage, in terms of fault detection, they still were not better than manually created tests. In summary, our results highlight the need for improving the goals used by automatic test generation tools. Specifically, fault detection scores could be increased by considering some new mutation operators as well as higher-order mutations. Our thesis suggests that automatically generated test suites are significantly less costly in terms of testing time than manually created test suites. One conclusion, strongly supported by the results of this thesis, is that automatic test generation is efficient but currently not quite as effective as manual testing. This is a significant progress that needs to be further studied; we need to consider the implications and the extent to which automatic test generation can be used in the development of reliable safety-critical systems.

The objective of the work reported in this paper is one of a two-fold nature. The first objective is to develop a disk-plate sensitivity test that is more rapid than that of existing methods. The second requisite is that the materials, techniques, interpretation, and reporting of results be the sane as those required for the disk-plate method described in the Difco Manual.

The purpose of this study was to examine (1) whether the Weigl-Goldstein-Scheerer Color Form Test and the Proverbs Test were able to discriminate between a sample of normal patients and a sample of schizophrenic patients, and (2) to determine if there was a significant correlation between these two instruments.