Transducers utilizing single crystal piezoelectrics as the active elements have been shown to exhibit broader operating bands, higher response levels, and higher power efficiency than transducers using piezoceramics while also reducing the size and mass of the transducer (Moffett et al., J. Acoust. Soc. Am., 2007). The key to these high performance characteristics is the piezocrystal's inherent high electromechanical coupling coefficient. One potential application is to replace multiple narrowband piezoceramic transducers with a single broadband piezocrystal transducer which reduces the system's weight and size. This is very important for the new generation of smaller and power efficient unmanned underwater vehicles (UUVs). A third application is for use in very broadband communication networks. The work presented here focuses specifically on the design, modeling, and construction of Tonpilz transducers using piezoelectrics as the active material. The modeling includes lumped element and finite element analysis to approximate the performance of these transducers. These models serve as the main structure of an overall iterative design process. The objective of this research is to compare the performance characteristics of a piezocrystal and a piezoceramic Tonpilz transducer and to validate the models by comparing the model predictions with experimental results. / text

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Transducers whose outputs are characterized as a charge require signal conditioning to convert the charge produced to a voltage or current for use in instrumentation systems. Blast gauges, in particular, require processing which preserves the transient nature of the data and very fast risetimes, which would otherwise be degraded by long cable runs and parasitic capacitances. A charge amplifier which amplifies and converts a charge to a low-impedance voltage suitable for driving coaxial lines is described, along with theory of operation. Charge amplifiers of the type described are relatively unaffected by temperature and power supply variations, and occupy less than two square inches of printed circuit board space per channel.

Background: Ultrasound is safe and painless, produces pictures of the inside of the body using sound waves (not use ionizing radiation), thus there is no radiation exposure to the patient. The thyroid gland is among the most commonly imaged glands using ultrasound due to the limitation of clinical examination. The Radiographers' skills in ultrasound differ according to the country and the basic formations. And throught this study we want to emphasize about the role of radiographer. Aim: The porpuse of this study is determine the volume and morphological characteristics of normal thyroid order to get reference values for young adults. Material and Method: We selected 204 students consist of male and female from Danang University of Medical Technology And Pharmacy were studied. Mean age of our subjects was 22 (range 18-25) all of them were healthy and with normal thyroid gland status. Descriptive statistics and analytic statistic was used. Results: In our study, the thyroid volume between female and male is different. The total thyroid volume significantly correlated with individual’s height, weight, body surface area and body mass index. The mean of total thyroid volume was 7.44 ± 2.09ml (range 3.51-14.57). The thyroid volume was best correlated with height (r = 0.44; p = 0.0001). Conclusion: Knowledge about the size of the thyroid gland is important in following the thyroid diseases and the examination of the gland. The radiographer's role is very important in determining the volume of thyroid.Radiographer is an important member of the diagnostic health care team.

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Many of the undesirable side effects that occur during orthodontic treatment can be attributed directly to a lack of understanding of the physics involved in a given adjustment of an orthodontic appliance. A large number of variables in orthodontic treatment are not within our control, such as growth and tissue response to appliances. However, the force placed on the tooth should be a controllable variable (1), and careful study of the physics underlying our clinical application, can help in reducing those undesirable side effects. If researchers and clinicians can quantify the force systems applied to the teeth, they can better understand clinical and histologic responses. Orthodontic force systems used in everyday orthodontic mechanics are considered indeterminate force systems, in other words, there are too many unknowns to determine the different components of these force systems. Until recently, much of the literature was restricted to experimental two-dimensional analyses of the biomechanical aspects of orthodontic force systems, and computer modeling of three-dimensional analyses. Very little evidence exists in the literature regarding three dimensional experimental measurement and analysis of orthodontic force systems (2). Force system measurements were made on one or two tooth models, however in order for us to understand the orthodontic force systems we need to simultaneously, measure in 3D, the forces being applied on every tooth in the dental arch. With the very recent technological advances in force/torque sensors technology, data acquisition and data representation, it became possible to measure those forces and reveal the force systems we are applying to the dentition. The purpose of this PhD research study is the design and construction of an experimental device that is capable of revealing the details of the force systems used in modern day orthodontic mechano-therapy of continuous arch technique. / Orthodontics

Ionic polymers are a recently discovered class of active materials that exhibit bidirectional electromechanical coupling. They are `soft' transducers that perform best when the mechanical deformation involves bending of the transducer. Ionic polymers are low voltage actuators -- they only require inputs on the order of 1V and cannot tolerate voltages above approximately 10V. The mechanisms responsible for the electromechanical coupling are not yet fully understood, and reports of the capabilities and limitations of ionic polymer transducers vary widely. In addition, suitable engineering models have not been developed. This document presents a dynamic model for ionic polymer transducers that is based on a pair of symmetric, linearly coupled equations with frequency dependent coefficients. The model is presented in the form of an equivalent circuit, employing an ideal transformer with a frequency dependent turns ratio to represent the electromechanical coupling. The circuit elements have clear physical interpretations, and expressions relating them to transducer dimensions and material properties are derived herein. The material parameters required for the model: modulus, density, electrical properties, and electromechanical coupling term are determined experimentally. The model is then validated by comparing simulated and experimental responses, and the agreement is good. Further validation is presented in the form of extensive experiments that confirm the predicted changes in transducer performance as transducer dimensions are varied. In addition, reciprocity between mechanical and electrical domains is demonstrated. This reciprocity is predicted by the model, and is a direct result of the symmetry in the equations on which the model is based. The capabilities of ionic polymer sensors and actuators, when used in the cantilevered bender configuration, are discussed and compared to piezoceramic and piezo polymer cantilevered benders. The energy density of all three actuators are within an order of magnitude of one another, with peak values of approximately 10J/m^3 and 4mJ/kg for ionic polymer actuators actuated with a 1.2V signal. Ionic polymer sensors compare favorably to piezoelectric sensors. Their charge sensitivity is approximately 320E-6C/m for a 0.2 x 5 x 17mm cantilevered bender, two orders of magnitude greater than a piezo polymer sensor with identical dimensions. This work is concluded with a demonstration of feedback control of a device powered by ionic polymer actuators. An ionic polymer sensor was used to provide the displacement feedback signal. This experiment is the first demonstration of feedback control using an ionic polymer sensor. Compensator design was performed using the model developed in the first chapter of this document, and experiments confirmed that implementation of the control scheme improved, in a narrow frequency range, the system's ability to track sinusoidal inputs. / Ph. D.

abstract: Microwave circuits are an essential part of technology in the modern day. Everything from cell phone communications, television and radio reception, medical imaging, and radar surveillance depend on microwave circuitry. Constant efforts are being made to introduce new methods of implementing more efficient microwave circuitry while maintaining well known fabrication methods. These improvements typically focus on lower loss, smaller size, and higher operating frequencies [1-6]. This thesis will focus on the specific application of a planar orthomode transducer (OMT) in Home Direct Broadcast (DBS) Systems used in residential satellite receivers. The need for low-loss circuitry becomes increasingly important in the realm of satellite reception, as the carrier to noise levels at the receiver can be as low as 10dB [7]. Interference and loss of signal integrity can occur very easily if the receiving network is not properly designed. This thesis will investigate the design of a planar transmission media that produces ultra-low losses when compared to more conventional planar transmission media. This design, which is called Double Sided Suspended Stripline (DSSL), utilizes air as its primary propagation medium. The design will be similar to standard suspended stripline in geometry, but has signal traces on the top and bottom of the substrate. The traces are connected using plated through-hole vias. This geometry is hugely beneficial because it virtually eliminates one of the major loss mechanisms in classical microwave structures: dielectric loss. This thesis will focus mainly on empirically derived equations and performance metrics obtained through rigorous simulation. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

Histotripsy is a nonthermal ultrasound therapy used to treat cancer noninvasively by tissue mechanical fractionation with cavitation bubble clouds. Histotripsy is conducted through focused ultrasound transducers, where the piezoceramic (PZT) plate or disc, which emits the ultrasound wave, is the fundamental unit of the transducer. For modular prototype histotripsy designs, these PZTs are housed in a 3D printed focused lens. However, 3D printing transducer components can be time consuming and expensive when scaling up manufacturing, and 3D printing is limited in material selection for transducer applications. This thesis investigates the use of a novel fabrication process for prototype focused ultrasound transducers, injection molding, with an in-house benchtop injection molding machine. Acoustic material properties for investigated injection molded materials, ABS, GPPS, 30% glass filled nylon, nylon 6/6, and nylon 101, are quantified experimentally. Single elements are constructed with injection molded lenses made from ABS, 30% glass-filled nylon, nylon 6/6, and nylon 101 on an in-house benchtop machine. Results show that injection molding is a novel feasible method for applications in focused ultrasound devices and the investigated plastics have favorable properties for developing prototype histotripsy transducers, comparable to 3D printed transducer housings. Future work aims to apply injection molding to various transducer designs and additional materials for focused ultrasound therapy devices. / Master of Science / Histotripsy is a cancer therapy that can noninvasively treat tumors without surgery. This is done through devices called focused ultrasound transducers which emit ultrasound waves to administer treatment to ablate tumors. These transducers are constructed using 3D printing methods, but this can be limiting when scaling up manufacturing or in material selection for transducer applications, therefore additional fabrication methods are needed. This thesis presents injection molding as a novel method for making transducer components with an in-house benchtop injection molding machine. Five plastic materials are investigated to determine ultrasound properties that would identify preferred transducer materials. Single element transducers are made from injection molded materials, tested, and compared with 3D printed single element transducers. Results of this thesis show that injection molding is a feasible manufacturing method capable of producing transducers for histotripsy, and researched materials have favorable properties for this application. In future research, additional injection molded materials should be investigated and multiple transducer designs created for injection molding fabrication. These injection molded transducers can be applied to histotripsy or applied to other focused ultrasound therapies.