Vegetable oil is one of the most widely available renewable sources of energy that can be used to meet the world’s demands. Many vegetable oils also have the advantage of containing little to no detectable amounts of nitrogen. Recently, research studies have revealed that when two liquids with different vapor pressure values are formed into droplet-like emulsions, a micro-explosion effect can happen under specific environmental conditions. Understanding the micro-explosion phenomena can help increase the efficiency of bio-emulsion combustion as well as reduce pollution levels. Many researchers have conducted experiments to find the optimal condition that induces microexplosion effects. Microexplosion is also associated with the formation of shock waves characteristic of explosions at larger scales. However, little is known about how emulsion composition and droplet size affect the micro-explosion process. Through this research, methanol-in-vegetable oil emulsion has been studied from the microexplosion point of view using custom made electric furnace equipment with a high speed camera system and an acoustic sensor system. The main goal of this study is to understand the effect of emulsion compositions, chamber temperatures, and droplet sizes on the characteristics of microexplosion. First, an n-hexadecane-in-water emulsion was prepared to validate the performance of the custom-made experimental apparatus using previous published data. Methanol-in-canola oil emulsions with different compositions were also prepared and used to compare the micro-explosion phenomena with water as a volatile compound. Microexplosion events of the blended fuels were captured using a high speed camera and an acoustic sensor. The wave signals generated by the microexplosion were analyzed after converting the signals using a Fast Fourier Transform coded in Matlab. One of the major findings of this research work was that higher temperatures and higher concentrations of high vapor pressure fluids such as methanol and water in emulsions causes a high probability of microexplosion event due to the sudden expansion of the emulsified fluid. Also, the effect of size on microexplosion was evident in the greater probability of explosion. Methanol-in-canola oil emulsion with 15 % methanol with droplets size of 200 m placed in a furnace chamber heated to 980 ˚C showed optimal microexplosion behavior based on the formation of fine droplets. Also, smaller droplets produced higher frequencies, which could be used to detect microexplosion without high speed imaging. When large droplets microexploded, lower frequencies were detected in all the blends.

In this study, we have successfully developed an acoustic modulation microscopy that is based on a laser scanning confocal microscopy and operates in the range of a few tens of kilohertz. The induced submicron oscillation is detected through the combination of differential confocal microscopy and lock-in circuit. In this way, the mechanical properties, such as elasticity and stiffness, can be mapped in a two-dimensional way rapidly.

In the present thesis, diamond-like carbon thin films were deposited on Si(100) and LiNbO3 substrates by a planar capacitor plasma-enhence-chemical-vapor-deposition system. The reaction gases were C2H2,CH4,O2 and mixed with Ar (95¢M) and H2(5¢M).The influence of the growth of the thin film from different substrates and three different source gases flow ratios have been studied. The bi-layers structure of SAW(Surface Acoustic Wave) device was then fabricated. The interdigital transducers (IDTs) were fabricated on the bi-layers structure. The conditions of the DLC thin film of the bi-layers structure was varied in order to discuss its effects on SAW devices. In addition to Raman analyses, SEM and AFM have been employed to characterize the DLC thin film quality. From the experimental results of Raman spectrum analysis reveals that the DLC film has wide and flat spectrum region at wavelength of 1585~1600cm-1 of G-band and 1390cm-1 of D-band .It indicates that the DLC film contains much graphite sp2 bonds and a small part of amorphous DLC sp3 bonds. The optimal deposition conditions of the DLC film have been found for the reaction gas of C2H2 and Ar, from which the insertion loss of the SAW filter shows the quality better than from the others. SEM and AFM analyses shows that the roughness of the DLC film is below 10 nm and the faces of the DLC films are flat to be made into devices.

Abstract The traditional fault inspection of the motorcar engine cannot detect the noise and sound signal resulted from the abnormalities of some mechanical parts. For instance, the cylinder misfires; the looseness of the fan belt is irregular; the valve clearance is out of order¡K. and so on. When the fault message cannot be delivered by the ECU of the computer, the skilled senior engineers are required at this moment to make the experiential judgments. In the present society, due to the development of information, the computer technology makes progress by leaps and bounds. If we can make use of the monitoring method by the Acoustic signal instrument, build up a set of complete and efficient fault diagnosis system through the computer software and apply speedy and accurate way to assist the repairmen in relocating the causes for such faults, the accuracy of inspection can be greatly enhanced with a huge help in the preventive maintenance work. In that case, the fault conditions of the engine can be validated precisely and effectively, so the overhaul efficiency of the engine can be upgraded to a large extent. In this article, the procedures of sound signal recording will be brought forward by linking the digital camera with such a recording equipment as the high-precision microphone to make records of the fault sounds made when the engine runs. It uses the frequency analyzer to conduct the sampling and combine the computer software to further process and analyze the same. Finally the character parameters will be obtained. By applying the mathematical exercise of ¡§Back-Propagation Neural Network¡¨ to undertake the training and detection of the sounds for the purpose of identifying the kinds of the faults. It replaces the errors caused from the experiential judgments made by the expert senior engineers. In terms of the training and maintenance ability of the newly recruited technical repairmen, their capability for exact and reasonable recognition of the fault types is substantially promoted. Keywords¡GAcoustic Signal¡ABack Propagation Neural Network

Carbonate reservoirs are usually diffcult to map and identify in seismic sections due to their complex structure, lithology and diagenetic frabrics. The Midland Basin, located in the Permian Basin of West Texas, is an excellent example of these complex carbonate structures. In order to obtain a better characterization and imaging of the carbonate buildups, an acoustic impedance inversion is proposed here. The resolution of the acoustic impedance is the same as the input seismic data, which is greatly improved with the addition of the low frequency content extracted from well data. From the broadband volume, high resolution maps of acoustic impedance distributions were obtained, and therefore the locations of carbonate buildups were easily determined. A correlation between acoustic impedance and porosity extracted from well data shows that areas with high acoustic impedance were correlated with low porosity values, whereas high porosities were located in areas of low acoustic impedance. Theoretical analyses were performed using the time-average equation and the Gassmann equation. These theoretical models helped to understand how porosity distributions affect acoustic impedance. Both equations predicted a decrease in acoustic impedance as porosity increases. Inversion results showed that average porosity values are 5% [plus or minus] 5%, typical for densely cemented rocks. Previous studies done in the study area indicate that grains are moderately to well-sorted. This suggests that time-average approximation will overestimate porosity values and the Gassmann approach better predicts the measured data. A comparison between measured data and the Gassmann equation suggests that rocks with low porosities (less than 5%) tend to have high acoustic impedance values. On the other hand, rocks with higher porosities (5% to 10%) have lower acoustic impedance values. The inversion performed on well data also shows that the fluid bulk modulus for currently producing wells is lower than in non-productive wells, (wells with low production rates for brine and hydrocarbons), which is consistent with pore fluids containing a larger concentration of oil. The acoustic impedance inversion was demonstrated to be a robust technique for mapping complex structures and estimating porosities as well. However, it is not capable of differentiating different types of carbonate buildups and their origin.

To characterize low-pressure, brittle deformation in porous, granular rock, notchcut cylinders (30 mm neck diameter) of Berea Sandstone were extended in a triaxial apparatus from 10 to 160 MPa confining pressure at strain rates of 10-4 s-1 and 10-5 s-1. Acoustic emission counts were monitored when extending samples at a slow strain rate. Stress at fracture is characterized by the least compressive principal stress, ??3, and maximum compressive principal stress, ??1 (??1 = Pc). A change in strength dependence on pressure at Pc = 50 MPa corresponds to a change from pure macroscopic extension fracture to mixed-mode opening and shear fracture, and likely reflects the increase in mean stress that suppresses the propagation of extension fractures and the interaction between closely-spaced stepped cracks. Within the extension fracture regime (Pc < 50 MPa), ??3 at failure becomes slightly more tensile with an increase in Pc. At Pc > 50 MPa, ??3 at failure becomes more compressive with an increase in Pc and follows Coulomb behavior; however, the angle between the fracture surface and ??1 increases continuously with Pc. Fracture surfaces characteristic of the extension to shear fracture transition appear as linked, stepped extension fractures; the length of extensional segments decreases with increasing pressure. The onset of acoustic emissions and inelastic strain at fracture occurs at earlier points in the strain history with pressure, consistent with the Griffith prediction of the beginning of fracture growth.

Thin Film bulk acoustic wave devices have the advantages of low loss, low temperature coefficient of the resonant frequency, and high power handling. These excellent characteristics are suitable for the applications on high frequency communication systems. In this study, thin film bulk acoustic wave filters using the ladder-type filter and stacked crystal filter configurations were investigated. Platinum was chosen as the top and bottom electrodes. To improve the platinum adhesion on SiNx/SiO2/Si substrates, a seeding layer of titanium is used. Highly c-axis oriented piezoelectric zinc oxide thin films were deposited by two-step deposition method under room temperature. As resonant area decreases, the band rejection of ladder-type filter will increase. Because the resonant area decreased, the distance between signal and ground will increase the results in an increased insertion loss. On the other hand, stacked crystal filters have larger band rejection and less 3dB bandwidth, which are suitable for the application of narrow band filters.

In this study, T-ladder type thin film bulk acoustic wave filters had been fabricated based on thin film bulk acoustic wave resonators. The titanium (Ti) seeding layer and platinum (Pt) for bottom electrode were deposited on silicon substrates by a dual-gun DC sputtering system. Field-emission scanning electron microscopy, atomic force microscopy and the four-point probe method showed that the Pt bottom electrode deposited on the Ti seeding layer exhibited favorable characteristics, such as a surface roughness of 0.69 nm and a sheet resistance of 2.27 £[/¡¼. The ZnO piezoelectric film was deposited using the two-step deposition method by RF magnetron sputtering. Field-emission scanning electron microscopy, atom force microscopy and X-ray diffraction revealed that ZnO piezoelectric film exhibited excellent characteristics, such as a the high preferred c-axis orientation and a rigidly precise surface structure with surface roughness of 7.37 nm. The wet etching process is adopted to fabricate cavity of device. The concentration of 30 wt% KOH and etching temperature of 100 ¢J had been indicated appropriate for etching processes. Finally, the top electrodes of the devices are varied to approach the performances of device applications. The results showed the highest coupling coefficient (kt2) of FBAR device can be obtained using platinum top electrode. The high coupling coefficient of FBAR device is appropriate for wide passband filter. The annealing processes had been used in order to improve the characteristics of piezoelectric films. The stress of ZnO film has been improved from -1.656 Gpa to 0.611 Gpa through the annealing process. At the annealing temperature of 400¢J, the ZnO piezoelectric film exhibited excellent characteristics, such as a large grain size with smooth surface. The quality factor of FBAR device using ZnO film with 400¢J annealing was better than that without annealing. The optimal conditions of fabrication processes are adopted to fabricate top electrode, bottom electrode and piezoelectric film. The T-ladder type FBAR band pass filter was constructed by FBAR resonators. The frequency response is measured using an HP8720 network analyzer and a CASCADE probe station. The 3-dB bandwidth, insertion loss and band rejection of the T-ladder type thin film bulk acoustic wave filter are 79MHz, -3.5 dB and 8.4dB at 2,379MHz, respectively.

The analysis and development of robust sensing platforms based on solidly-mounted ZnO bulk acoustic wave devices was proposed. The exploitation of acoustic energy trapping was investigated and demonstrated as a method to define active sensing areas on a substrate. In addition, a new "hybrid" acoustic mode experiencing acoustic energy trapping was studied theoretically and experimentally. This mode was used as an explanation of historical inconsistencies in observed thickness-shear mode velocities. Initial theoretical and experimental results suggest that this mode is a coupling of thickness-shear and longitudinal particle displacements and, as such, may offer more mechanical and/or structural information about a sample under test. Device development was taken another step further and multi-mode ZnO resonators operating in the thickness-shear, hybrid, and longitudinal modes were introduced. These devices were characterized with respect to sample viscosity and conductivity and preliminary results show that, with further development, the multi-mode resonators provide significantly more information about a sample than their single-mode counterparts. An alternative to resonator-based platforms was also presented in the form of bulk acoustic delay lines. Initial conceptual and simulation results show that these devices provide a different perspective of typical sensing modalities by using properly designed input pulses, device tuning, and examining overall input and output signal spectra.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 285-320). Available also in a digital version from Dissertation Abstracts.