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In this work, single crystals of TlIn${}_{1-x}$Ga${}_x$Se₂ solid solutions were grown by the methods of zone recrystallization, technologies for the manufacture of strain gauges based on them were developed and the tensoresistive properties of these phases were studied, the coefficient of strain sensitivity was determined by the static method depending on the temperature, the magnitude of mechanical deformation and optical illumination. Revealing that the single crystals have a high strain sensitivity coefficient, by the variation of the composition, quantity of mechanical deformation and the optical illumination, it is possible to control the phase coefficients investigated tensosensitivity.

Various kinds of orthosis have been designed for paraplegic subjects to stand and walk. They have been designed based on this assumption that most of the loads applied on the orthosis (OR) and body complex is transmitted by OR. In this study, it was aimed to determine the role of OR to transmit the loads by use of strain gauge system. Three spinal cord injury subjects, with lesion between T12 and L1, were recruited in this study. A motion analysis system with a Kistler force plate was used to collect the kinetic and kinematic parameters. Moreover, the loads applied on the OR were determined by use of strain gauges attached on the lateral bar of OR. The pattern of the loads applied on the complex, OR and body, differed from that of OR. Nearly 43% of adduction moment was transmitted by OR. In contrast the role of OR to transmit the flexing/extending moments and vertical force is negligible. The results of strain gauge and motion analysis systems differed completely from each other's. As the strain gauge show the absolute values of the loads applied on OR, it is recommended using its result in order to design an OR for paraplegic subjects.

Sensors for the measurement of mechanical deformation are frequently used in industrial measurements. The sensors are realized using different technologies. The sensors of the type strain gauge is utilized for the measurement of change in length of geometrical dimensions. The strain gauge is realized on a thin cantilever structure. Piezoresistive strain gauge is realized by implanting resistive layers into substrate or with sputtered thin film resistance layer. Another type of the strain gauge is being developed for temperatures higher than 300°C. Simulation using CoventorWare program is used for verification of mechanical properties and temperature distribution in cantilever structures. At realized structures of cantilever with strain gauges, there have been measured basic parameters, as dependence of electric parameters of strain gauges on mechanical deformation, temperature dependence at different mechanical load, temperature stability of output parameters, temperature dependence of pn junctions in the structure. The piezoresistive coefficients, coefficients of deformation sensitivity, linearity, hysteresis, temperature coefficients of resistance, etc have been calculated from measured data. Wheatstone bridge with piezoresistors is used as transducer of mechanical deformation to electric parameters in the form of resistance change. The measured charateristics show very good linearity, small hysteresis and very good sensitivity.

In Singapore, ground settlement is one of the major problems in build-up area in housing and industrial estates. Large amount of ground settlements are due to presence of thick layer of soft peaty and/or clayey soil underneath the service road and car park area. In addition, settlement due to thick layer of peaty and/or clayey soil will continue for a long time after the construction of service road and cark park. In build-up area, conventional ground improvement methods such as jet grouting, dynamic compaction, vibro-compaction, pre-loading with vertical drains etc may not be suitable to solve such settlement problems due to space constraint and huge equipment required for treatment. Therefore, in present research, a new technique is developed in which micropile supported geotextile is used on top of sub-grade of service road to limit the settlement.

In this technique, micropiles with pile caps were installed at an interval of ~ 4 m c/c along two sides of road. The capping beam was constructed linking the pile caps. The geotextile was laid on top of compacted subgrade and fixed on capping beam at two ends to mobilize the tension membranes effect. Layer of sand and graded stone were laid on top of geotextile and compacted before interlocking paving blocks were laid to the required road level.

To evaluate the performance of this technique, several sections of geotextile were instrumented and installed along the service road. For instrumentation of geotextile, the strain gauges and TPCs were used to measure stain and total vertical pressure during and after installation of geotextile. In addition to this, settlement markers were used to measure the settlement of road during vehicle movement on it. It was found that both the strain gauges and TPCs readings responded accordingly to the compactor load and vehicle load acting on the layer. The results obtained from strain gauges showed that maximum base value of strain developed during vehicle movement was about 12% which is well within the allowable strain of geotextile. The maximum base value of total vertical stress from TPCs was found to be about 70 kPa which is low enough for this compacted soil subgrade. Apart from above results, the settlements obtained from settlement marker were found to be lower than allowable settlement of 2 mm/month and the settlement was also stabilized after 20,000 passes of vehicles. Thus, it can be concluded that micropiles supported geotextile sheet is effective in solving settlement problems for service road, car-park etc in build-up area.