The purpose of this study is to develop a new approach for Morphology Dependent Resonances (MDR) in dielectric microsphere based on Whispering Gallery Mode (WGM). Polarized electromagnetic wavCarlos Silva; Doseo Park, Egidio (Ed) Marotta, PhD; and Leroy (Skip) Fletcher, PhD Texas A&M University es, Transverse Electric (TE) and Transverse Magnetic (TM), are considered to analyze MDR. New asymptotic solutions have been developed based on TE & TM waves. The resonance conditions are characterized both theoretically and experimentally for dielectric microsphere. The newly developed approach is significantly less complicated than existing approaches based on quantum mechanics which are presented in the literatures. The theoretical results are validated by experimental data obtained via this study and from the literatures. The comparison of results is found to be very encouraging. This study could potentially be used for designing optical sensors based on WGM.

In this study, a heat exchanger with a suction line of steel tube was developed and applied as an evaporator of a refrigeration circuit. The flow-induced effects inside the evaporator were studied. The main area of interest was the transient and steady state noise due to the refrigerant flow. Temperature, pressure and acoustic measurements were made on the refrigerating system. One-third octave band analysis was performed in a range of 200-500Hz frequency bands. The relationship between the sound pressure level and the frequency for transient and steady state periods was developed. Also, the relation between the temperatures at specific locations and the noise level was established. The noise level at steady state was found to be lower compared to the transient period as expected.

The purpose of this paper is to explore the exact analytical solution to a single-degree-of- freedom oscillator whose spring force is a third order polynomial. The simple oscillator model has numerous applications not only in Newtonian mechanics, but also in quantum physics, atmospheric science, and phase transformation problems. The constant coefficients in the spring force are not restricted to a small number. Depending on the coefficients of the spring force, the spring can act as a hard and soft spring, resulting in periodic, diverging, and asymptotic solutions. In the past, only the periodic solution has been extensively investigated and used as an example to demonstrate the exact solution. This is perhaps so because a soft spring that results in a diverging solution may be no use in mechanics. In this paper, the full range of possible solution will be demonstrated. In addition, the physical significance of such solution is discussed.

Required external loads in friction stir welding (FSW) process are one of the most important parameters should be considered in appropriate machine selection and power transmission design. A distinctive amount of pressure, torque and transverse force should be applied for a typical FSW process to acquire a flawless weld. Here the attempt is to investigate the effect of process parameters variations on the drag, lifts and moment coefficients applied to the cylindrical-featured tool pin and shoulder during friction stir welding of 6061-T6 aluminum alloy with 6.3 mm in thickness. Flow of the plasticized material has been numerically modeled in Fluent- a CFD simulation environment- in order to calculate the fields of strain-rate, non-Newtonian viscosity, temperature, Reynolds number and drag, lifts and moment coefficients for different rotational and transverse velocities of the FSW tool. Temperature at specified locations was used to verify the model. Computational results are showing promising advances in predicting weld nugget region and understanding the effect of process parameters on the forces and toque applied to FSW tool.

Various systems, such as such as mechanical, electrical, pneumatic, hydraulic, and thermal systems, can be simplified and represented by 1st order and 2nd order systems. The study of the time response and frequency response of dynamic systems is a very important aspect of any attempt to design a system.

In this paper, a series of multifunctional Matlab Graphical User Interfaces (GUIs) have been developed to model and simulate the dynamic responses of 1st and 2nd order systems. The users are allowed to control the parameters of both system parameters and input forcing functions. System parameters are mass, damping coefficient, and spring constant in a 2nd order system, or resistance and capacitance in a 1st order system. Generally used forcing functions, such as sinusoid, step, ramp, and impulse inputs, are available to choose. The GUIs report both time response and frequency response of the system.

The visual interfaces present results in a way that the users can immediately identify the effects of changing system parameters and input functions. The developed models can be used extensively in the research of system dynamics and engineering vibrations.

Ionic wind is an electrohydrodymamic (EHD) effect that uses electrodes charged by high-voltage direct current to accelerate fluid particles without moving parts. Potential applications of ionic wind include maintaining a flame in space, maneuvering lighter-than-air vehicles, cooling electronics, drying runoff from hydromining, and reducing drag. The purpose of this paper is to present experimental results regarding the effectiveness of electrohydrodymamic drag reduction on a circular cylinder. The drag reduction is produced by a wire-plate electrode imbedded in the surface of the cylinder. The EHD drag reducing device consists of a positively charged emitting electrode with high curvature and a grounded collecting electrode with low curvature. This wire-plate electrode imparts energy to the fluid flowing around the cylinder. We hypothesize that this energy can delay boundary layer separation and reduce drag. Preliminary pressure distribution and drag data suggest that ionic wind does in fact reduce pressure drag on the cylinder for flow at low Reynolds numbers. At higher Reynolds numbers, the energy imparted to the flow by the electrostatic precipitator becomes negligible.

Heat transfer and fluid flow in a heterogeneous porous medium induced by buoyancy from a buried heated pipe has been examined in this study. Hele-Shaw cells with different gap widths were constructed to simulate a porous medium with distinct permeablities. The flow visualization experiment was set up to investigate how a step change in the permeability of the backfill would affect the flow patterns from a heated pipe. Both permeable and impermeable top surfaces with different buoyancy strengths were considered in this experiment. Using time-elapsed photographs, it revealed that the flow fields for permeable and impermeable top boundaries displayed distinct characteristics. The flow fields predicted by numerical work were in good agreement with those observed in the experiment. The presence of recirculating cell in the more permeable layer was confirmed, and the flow patterns closely resembled the actual flow field.

The overall combustion efficiency of a grate fired furnace in an industrial boiler depends on the mixing of the secondary air with the off-bed gases. Previous research has established residence time of the undergrate air in the boiler as a critical parameter that affects the combustion. This paper discusses the state of the art of techniques used in industrial boilers to improve the residence time: ecotubes and ecojets. Ecojet is a relatively newer technique over the ecotube system that distributes the secondary air more evenly and effectively. The main objective of this paper is to increase the flow residence time of the undergrate air b replacing the ecotube air system with the ecojets. This paper presents the cold flow simulation results using Fluent and discusses the mechanism of the residence time increase. The optimum location of the ecojets and the injection angle were identified for a typical 36MW boiler and a 20% increase in residence time was attained.

Carbon/carbon (C/C) composites are the top preference for the high performance friction applications due to their ability to retain their excellent thermal and mechanical properties at elevated temperatures. Thus, significant surface heating and the ability to control the heat dissipation from the friction surface considerably contributes to improved frictional performance. The aim of this research is to explore the effects of final heat treatment temperature (HTT) on the microstructure of C/C composites and determine the relations between the microstructure and thermal properties. The microstructure of C/C composites was studied by light microscopy. Laser flash thermal diffusivity (LFTD) technique was employed to measure each principal direction thermal diffusivity from room temperature to 1300°C. The results reveled that the fiber orientation, crystallite size and orientation of the 002 basal planes with respect to reinforcing the fiber, and matrix play a crucial role in determining the thermal properties.

The primary objective of this paper is to develop quasi-steady heat transfer models of typical Friction Stir Welding (FSE) configurations available in literature using Fluent. It is assumed that mechanical dissipation heating is responsible for most of the heating that produces the weld. Corresponding infinite length models were developed and the resulting temperature distributions were found to replicate the benchmark cases. In addition, the quasi-steady nature of the problem was investigated by studying temperatures close to the tool surface, for a particular configuration with a finite domain, while placing the tool at arbitrary locations along the joining line of the weld. It is shown that the variation in temperatures is very insignificant and thus the assumption of heat transfer being quasi-steady from the tool point of view is justified.

A comprehensive experiment has been set up to monitor events and conditions of pin and shoulder arising in friction stir butt welding (FSW) of AISI 1018 steel to 6061-T6 aluminum alloy. Acoustic emission (AE) was chosen as a process monitoring tool due to its capability in monitoring movement of distinct events that have their own sources in the material itself (inherent in FSW). The signal processing results demonstrate a unique pattern for the events that suddenly change the AE wave propagation in specimens. In addition, significant fluctuations in burst-type AE signal frequency ranges are observed due to process condition variations. Tests has been further conducted to capture the natural frequency of the setup and it is shown that the major obtained frequency range pertains to the continuous AE signal with frequency equal to resonant frequency of the setup. Cumulatively this procedure is capable to identify: 1) process initiation and termination; (2) the pin-workpiece contact (particularly crucial when having contact with faying surface of steel); (3) contact between shoulder and workpiece; (4) change of the tool traverse direction; and (5) tool pin breakage.

Three-dimensional electronic packages provide several advantages including shorter interconnects and faster signal processing. Plasmas are used to generate ions which are accelerated to very high energies to etch through-silicon-vias (TSV), needed for 3D packages. The topology of the TSV is dependent on the plasma parameters; thus characterization of the plasma as a function of the operating parameters is important. In this study, we used optical emission spectroscopy to monitor the excited state densities of fluorine atoms in a deep reactive ion etching system. Emission data were collected from 350nm to 1000nm using a CCD system. Results indicate a population inversion, but this result is consistent with other data in the literature. We suspect the cause for this finding is the low pressure, and thus low collision frequencies, in conjunction with an upper state pumping mechanism due either to the applied power or a nearly resonant transition with one of the other plasma species.

The effect of dimple shape and dimple orientation on the heat transfer coefficient of a heatsink was studied both numerical and experimentally. The study was performed for the channel flow between fins of a microelectronic-cooling-heatsink under laminar flow regime (Re=500, 1000) and with several heat loads. Numerical studies were performed using Fluent 6.2.16 to analyze optimum dimple shape and orientation; then an experimental study was conducted for flat and circular-dimple plates for comparison purposes. Numerical results indicated that oval dimples with their 'long' axis oriented perpendicular to the direction of the flow offered the best temperature improvement, hence the Nusselt number increased for the heatsink. Experimental work confirmed these results with a wall-averaged temperature reduction ranging from 0.6 to 3 K depending on heat load and Reynolds number. Pressure losses due to the dimple patterning were also briefly explored in this work.

More and more people have been using portable telecommunication devices, such as mobile phones, personal digital assistances, laptop PCs, etc. It is not uncommon for those portable electronic products to be accidentally dropped onto the ground. The impacts and shocks thus can lead to the failure of electronic electronic packages and the malfunction of the products.

In this paper, the block diagram based SIMULINK analysis is introduced for the dynamic response of portable systems with various configurations. SIMULINK is an interactive, block diagram based tool for modeling and analyzing dynamic systems, and it is tightly coupled with MATLAB and supported by blocksets and extensions. Using such a tool, the relationship between input and output can be obtained and visualized easily as a function of system parameters. The dynamic responses to the different input impact profiles are compared and discussed in detail as well. Finally, an engineering guideline is proposed for the preliminary selection of the geometries and materials of PCBs.