Surface acoustic waves (SAWs) have a large number of applications and the majority of them are in the sensor and actuator fields targeted to satisfy market needs. Recently, researchers have focused on optimizing and improving device functions, sensitivity, power consumption, etc. However, SAW actuators and sensors still cannot replace their conventional counterparts in some mechanical and biomedical areas, such as actuators for liquid pumping under microfluidic channels and sensors for real-time cell culture monitoring. The two objectives of this dissertation are to explore the potential of piezoelectric materials and surface acoustic waves for research on actuators and sensors in the mechanical pump and biosensor areas. Manipulation of liquids in microfluidic channels is important for many mechanical, chemical and biomedical applications. In this dissertation, we first introduced a novel integrated surface acoustic wave based pump for liquid delivery and precise manipulation within a microchannel. The device employed a hydrophobic surface coating (Cytop) in the device design to decrease the friction force and increase the bonding. Contrary to previous surface acoustic wave based pumps which were mostly based on the filling and sucking process, we demonstrated long distance media delivery (up to 8mm) and a high pumping velocity, which increased the device’s application space and mass production potential. Additionally, the device design didn’t need precise layers of water and glass between substrate and channel, which simplified the design significantly. In this study, we conducted extensive parametric studies to quantify the effects of the liquid volume pumped, microchannel size, and input applied power as well as the existence of hydrophobic surface coating on the pumping velocity and pump performance. Our results indicated that the pumping velocity for a constant liquid volume with the same applied input power could be increased by over 130% (2.31 mm/min vs 0.99 mm/min) by employing a hydrophobic surface coating (Cytop) in a thinner microchannel (250 µm vs 500 µm) design. This device could be used in circulation, dosing, metering and drug delivery applications which necessitated small-scale precise liquid control and delivery. This dissertation also introduced a novel SAW-based sensor designed and employed for detecting changes in cell concentration. Before conducting cell concentration experiments, preliminary experiments were conducted on weight concentration differentiation of microfluidic particles based on a polydimethylsiloxane (PDMS) channel and surface acoustic wave resonator design. The results confirmed that our device exerted an ultra-stable status to detect liquid properties by monitoring continuous fluids. An improved design was carried out by depositing a 200 nm ZnO layer on top of the lithium tantalate substrate surface increased the sensitivity and enabled cell concentration detection in a microfluidic system. Comprehensive studies on cell viability were carried out to investigate the effect of shear horizontal (SH) SAWs on both a cancerous (A549 lung adenocarcinoma) and a non-cancerous (RAW264.7 macrophage) cell line. Two pairs of resonators consisting of interdigital transducers (IDTs) and reflecting fingers were used to quantify mass loading by the cells in suspension media as well as within a 3-dimensional cell culture model. In order to predict the characteristics and optimize the design of the SH-SAW biosensor, a 3D COMSOL model was built to simulate the mass loading response of the cell suspensions. These results were compared to experimental data generated by pipetting cell concentrations of 3.125K, 6.25K 12.5K, 25K and 50K cells per 100µL into the PDMS well and measuring to obtain the relative frequency shift from the two oscillatory circuit systems (one of which functioned as a control). Frequency shift measurements were also collected from A549 cells cultured on a 3D nanofiber scaffold produced by electrospinning to evaluate the device’s ability to detect changes in cell density as the cells proliferated in culture over the course of eight days. The device’s ability to detect changes in cell density over time in a 3D model along with its biocompatibility reveal great potential for this device to be incorporated into 3D in vitro cancer research applications.

No description available.

Thesis (doctoral)--Lund University, 1992. / Added t.p. with thesis statement inserted. Booklet of related papers inserted.

Thesis (doctoral)--Lund University, 1992. / Added t.p. with thesis statement inserted. Booklet of related papers inserted.

Among the many safety hazards facing chainsaw operators, the phenomenon known as kickback is the most dangerous. Kickback occurs when the chain at the tip of the chainsaw is caused to stop abruptly, and transfers the energy of the cutting chain to motion of the saw. The saw will rotate backward toward the operator rapidly. The limited amount of published research on the topic of chainsaw kickback was conducted to develop standardized testing for consumer chainsaws. Modern chainsaws are equipped with safety measures such as low-kickback cutting chains and hand-guard braking mechanisms. These mechanisms have greatly improved the safety of chainsaws, but their inherent mechanical simplicity leaves room for improvement. The current work presents the research that analyzed the possible methods for detecting kickback electronically. Phase 1 of this work utilized a set of two accelerometers and a single gyroscope to determine if it is possible to distinguish a kickback event from normal cutting operations. A method for applying weighting coefficients to the three sensor readings, then summing the three signal values was optimized to obtain the greatest margin between kickback and normal cutting. The result of this study was that kickback is most easily identified by using only a gyroscope and setting a threshold. Phase 2 focused on detecting kickback as early as possible. Three methods were attempted: Signal Differentiation, a Simplified Bag of Words method, and applying a Support Vector Machine with selective undersampling and a stack of classifier vectors. Signal differentiation, while detecting the kickback events earlier, also suffered from many false positives. The Bag of Words method was unsuccessful in creating results different than the threshold method from Phase 1. The Support Vector Machine classification was able to detect kickback an average of 19.4 ms before the simple threshold method with no occurrence of either false positives or false negatives. This method is the most reliable and provides the greatest likelihood of detecting kickback early. / Graduation Date: 2013

Thesis (M.A.)--University of Tennessee, Knoxville, 2003. / Title from title page screen (viewed Mar. 29, 2004). Thesis advisor: Walter E. Klippel. Document formatted into pages (ix, 135 p. : ill. (some col.)). Vita. Includes bibliographical references (p. 115-127).

The SAWS is interested in demonstrating the economic and social benefits of the products or services it provides to the public, industries and other organisations. It is also important for the organisation to carry out ongoing performance assessment of public and commercial weather services to ensure that these services are efficient and effectively meeting the public's and customer's needs and contribute to longer term commercial and societal objectives. Some other National Weather Services has developed "Service Charters" which detail their pledge of performance to the user communities, specifically, customers and the general public. These service charters provide a brief overview of the services provided, a commitment of performance against specific targets and a commitments to consult and identify a means by which the customers and the public may register their concern. As a result the service charters has become an important component of the Weather Services branding measurement strategy. The acceptance of the SAWS products or services by the public and other weather users depends on a number of factors. Scientific accuracy is just one of those factors. Also the health of the SAWS depends on the perceptions from full spectrum of weather users ranging from individual citizens, media, aviation, ... Ill marine, industry, government departments, construction companies, and insurance. These perceptions include those about requirements, accessibility, availability, accuracy, timelines, utility, comprehension, sufficient and packaging. The objective is to ultimately measure performance from the user perspective and identify user's needs. It is also to measure the acceptance of the services provided from such dimensions as expectations, understanding, importance, satisfaction, and utility. This study has been framed within the hypothesis that the SAWS brand associations are not strong, not favourable and not unique to create a positive brand. It has come critical to assess the level of customer awareness and familiarity with the SAWS brand so as to improve the dissemination mechanisms of the weather forecast information. Based on a literature review, two types of brand association are identified. One is product association including functional attribute association and non-functional attribute association. The other is organisational association including corporate ability association and corporate social responsibility association. It has been found that, the greater the number of the core brand association, the higher the brand equity. The feedback received on the questionnaire and interviews directed at awareness and familiarity with the SAWS brand indicated that, a need exists to educate the public and potential customers about the products and services of the SAWS. Of paramount important is the improvement of the SAWS dissemination mechanisms and partnerships with other scientific research organisations. This will enable the SAWS to reach a wide range of the public and weather users and to safeguard property and life of all South Africans. / Thesis (MBA)-University of KwaZulu-Natal, Durban, 2005.

Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains xi, 238 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 231-238).

In 2006 a Numerical Weather Prediction (NWP) model known as the Unified Model (UM) from the United Kingdom Meteorological Office (UK Met Office) was installed at the South African Weather Service (SAWS). Since then it has been used operationally at SAWS, replacing the Eta model that was previously used. The research documented in this dissertation was inspired by the need to verify the performance of the UM in simulating and predicting weather over South Africa. To achieve this aim, three model configurations of the UM were compared against each other and against observations. Verification of rainfall as well as minimum and maximum temperature for the year 2008 was therefore done to achieve this. 2008 is the first year since installation, where all the configurations of the UM used in the study are present. For rainfall verification the model was subjectively verified using the eyeball verification for the entire domain of South Africa, followed by objective verification of categorical forecasts for rainfall regions grouped according to standardized monthly rainfall totals obtained by cluster analysis and finally objective verification using continuous variables for selected stations over South Africa. Minimum and maximum temperatures were subjectively verified using the eyeball verification for the entire domain of South Africa, followed by objective verification of continuous variables for selected stations over South Africa, grouped according to different heights above mean sea level (AMSL). Both the subjective and objective verification of the three model configurations of the UM (for both rainfall as well as the minimum and maximum temperatures) suggests that 12km UM simulation with DA gives better and reliable results than the 12km and 15km UM simulations without DA. It was further shown that although there was no significant difference between the model outputs from the 12km and the 15km UM without DA, the 15km UM simulation without DA, proved to me more reliable and accurate than the 12km UM simulation without DA in simulating minimum and maximum temperatures over South Africa, on the other hand the 12km UM simulation without DA is more reliable and accurate than the 15km UM simulation without DA in simulating rainfall over South Africa. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Geography, Geoinformatics and Meteorology / unrestricted

Positive lightning flashes are known to be more intense and cause more damage than negative flashes, although positive flashes only occur about 10% of the time. This study expounds on cloud microphysical aspects of thunderstorms and investigates the occurrence, timing and location of ice particles within thunderstorms and correlates this to the occurrence of positive cloud-to-ground lightning events. Satellite data obtained from the Meteosat Second Generation (MSG) satellite, were used to: 1) depict Cloud Top Temperatures (CTT) by considering Infra Red (IR) radiation with a wave length of 10.8μm, 2) compare results from the CTT with the Brightness Temperature Difference (BTD) calculated by subtracting IR10.8μm from IR8.7μm, 3) after the cloud particle phase was determined from the abovementioned comparison, the sum of cloud-to-ground lightning strokes over a 1-hour period around the time of a reported lightning fatality was compared with cloud microphysical properties and then 4) these results were further compared with the lightning polarity obtained from the South African Weather Service (SAWS) Lightning Detection Network (LDN) data set. Four case studies were identified to investigate from the many available case study dates. These four cases occurred on 3 separate days namely: 1)22 November 2007, iii 2) 10 February 2009 and 3) 29 October 2009. There were two fatal events reported on 22 November 2007 and therefore two cases studies were compiled for this one date. On 10 February 2009 over 250 insurance damage claims were honoured but no fatality was reported. The three case studies mentioned above were classified as primary case studies. The 29 October 2009 case was classified as a secondary, more generalized case which was chosen in order to test whether the results gained from the first three cases were indeed noteworthy. Results gathered from two of the three primary case studies showed that the fatalities occurred when the most intense part of the thunderstorm was to the east of the location where the lightning struck the victims, although actual storm properties were not considered as being particularly severe. The lightning data for the primary case studies showed that the percentage of cloud-to-ground lightning was within 10% of the total number of strokes recorded for 22 November 2007, and above 10% for 10 February 2009. In the one secondary case study of 29 October 2009 the percentage of positive lightning was only between 2% and 4% of the total number of strokes recorded, which was significantly lower than in the three primary cases. A significant difference in cloud microphysics between the primary and secondary cases was the possible occurrence of super-cooled liquid water found in Cumulonimbus (CB) clouds in the secondary case. This could have been a determining factor for the difference in percentage of positive lightning between the primary and secondary case studies. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Geography, Geoinformatics and Meteorology / unrestricted