Michael B. Histand

Fluid density and concentration measurement using noninvasive in situ ultrasonic resonance interferometry

A method of noninvasively measuring the density of fluids contained within pipes, cans, tanks, and bottles has been developed. The container-fluid system is interrogated using an ultrasonic transducer. A second transducer is used to observe transmitted energy as the input frequency is swept through an appropriate range determined by the geometry. Resonance peaks are observed in the transmitted energy. The periodicity of the resonant peaks is determined by analyzing the response data using a fast Fourier transform. The technique is tested using known NaCl concentration standards within a stainless steel pipe. The concentration of unknown NaCl solutions is measured in situ with an accuracy of +or-0.15 M over a range of 0.4 to 3.4 M corresponding to an accuracy of +or-0.02 specific gravity (SG) units over a range of 1.000 to 1.134 SG units.<<ETX>>

The resolution of the ultrasound pulsed Doppler for blood velocity measurements

Abstract Pulsed ultrasound Doppler velocity meters (PUDVM) permit noninvasive blood velocity measurements. The emitted ultrasound beam characteristics primarily determine the resolution of the instrument when recording velocity profiles. The sample volume, the small region over which velocity information data are detected, was found to be > 2·3 mm3 depending on the transducer disk dia., distance in front of the disk, sampling time increment, and pulse length. The shape of the sample volume approximates a cylinder in the near field and a frustrum of a cone in the far field. The end surfaces of the sample volume were affected by the emitted pulse shape. Ultrasonic beam cross-sections were found to be smaller than predicted by theory due to the finite threshold levels of the PUDVM. The variation of the sample volume with range was illustrated by steady laminar flow velocity profile measurements in rigid tubes. The accuracy of velocity measurements was within 5 per cent with slightly larger deviations occurring near the walls due to the finite sample volume.

Inverse effect of chronically elevated blood flow on atherogenesis in miniature swine

The effect of chronically elevated blood flow on the development of atherosclerosis in miniature swine was studied. Fistulas connecting the right external iliac artery and vein were surgically created in four swine, while three were not fistulated. Pulsed Doppler velocity detection cuffs placed around the abdominal aorta and both iliac arteries of all pigs permitted chronic measurements of blood velocity, blood velocity distributions, and blood flow. All swine were fed an atherogenic diet consisting of 20% beef tallow, 3% cholesterol, and 5% cholic acid for 6 months. This diet elevated the serum cholesterol to values exceeding 500 mg/100 ml. Creation of the arteriovenous fistula (AVF) markedly elevated blood velocity and flow in the abdominal aorta and in the shunted iliac artery. In the shunted animals the aortic blood flow was 42.1 +/- 2.0 ml/sec compared with 17.3 +/- 1.4 ml/sec in the unshunted swine. The velocity distribution pattern across the vessel was also indicative of an elevated wall shear stress. After 6 months, the animals were killed and the arterial vessels examined macroscopically and microscopically for the presence of atherosclerotic lesions. In the shunted pigs, 17 +/- 15% of the lumenal surface was occupied by sudanophilic lesions, whereas 80 +/- 8% of the surface was covered by lesions in the unshunted (control) pigs. From these studies, it is apparent that mechanical factors related to blood flow rates can influence the development of atherosclerotic lesions in swine.

Integrating mechatronics into a mechanical engineering curriculum

We present what we believe is a more manageable approach to enhancing a mechatronics-based mechanical engineering program-a stepwise method to restructure a traditional mechanical engineering curriculum with a mechatronics theme. The result can be a curriculum with contemporary emphasis, enhanced content, and improved sequencing and coupling of traditional topics including modeling and analysis, computing, electrical circuits and machines, measurements and instrumentation, control theory, and design. Mechatronics provides a natural focus for this restructuring and creates an opportunity to better connect and utilize interesting exercises and design experiences throughout the curriculum. The proposed restructuring method consists of four evolutionary steps that allow manageable incremental changes that can be reasonably coordinated with faculty and laboratory development.

Mechatronics at Colorado State University

Abstract An innovative four-credit junior-level semester course is described, which combines measurement theory, instrumentation, analog and digital electronics, sensors and actuators, and computer control topics with a laboratory experience. The course, entitled Mechatronics and Measurement Systems, is a core course for mechanical engineering students at Colorado State University which has evolved over the last 12 years. In the future it will be offered as a joint course for mechanical and electrical engineering students. Topics covered by the paper include: • • course objective, description, and current syllabus • • laboratory exercises designed to complement and supplement the lecture material • • term projects used in previous years including a 3-D surface laser digitizer, a cylindrical robot with optical tracking capabilities, and an acoustic mapping system • • textbook and laboratory manuals developed to support the course: “Mechatronics and Measurement Systems”, “Mechatronics and Measurement Systems Laboratory Exersices” , and “Mechatronics and Measurement Systems Examination and Homework Manual” , all by M. Histand and D. Alciatore. This course is an integral part of our recently reorganized curriculum which emphasizes engineering design in each year of study. Mechatronics and Measurement Systems is the focal experience that students have in making the transition from the fundamentals of engineering to the application of those principles in “real world” engineering design problems.

Nontraumatic Measurement of Aortic Blood Velocity Fields, Flow, and Wall Properties

Previously, in formation on aortic velocity fields in dogs has been obtained using heated film probes, which require complicated surgical procedures. The pulsed ultrasound Doppler velocity meter allows such measurements to be made nontraumatically, from a probe inserted into the esophagus. The same probe can also be used in ultrasonic echo measurements of arterial wall motion. For accurate blood velocity measurements using ultrasound, the angle between the sound beam and the flow axis must be precisely known, and this angle is determined using a triangulation procedure. Descending aorta blood velocity measurements in normal Beagles indicate an increase in peak forward velocity with increasing distance from the heart. A unique flow Dattern has also been detected which results in a higher peak shear rate at the dorsal wall. Calculations of the pressure-strain elastic modulus from aortic wall motion shows a definite increase in arterial stiffness with increasing distance from the heart.

A Mechanical and Histological Comparison of Bone Healing Using Titanium Bone Plates with Porous Surfaced Titanium Screws versus Smooth Surfaced Titanium Screws

The comparison of bone healing between porous surfaced versus smooth surfaced titanium screws, used in the stabilization of a canine fracture gap model, is discussed. Mechanical and histological parameters indicate that there are advantages to using porous surfaced screws to maintain bone/plate friction over a prolonged period, when subjected to dynamic loading.

Measurement of Hemodynamics in Atherogenic Swine Using Ultrasound

Local blood velocity patterns in the abdominal aorta and iliac arteries of conscious miniature swine were studied with a pulsed ultrasonic Doppler velocity meter (PUDVM). An arteriovenous shunt between the right iliac artery and vein was surgically produced in Group 1. Grout) I was subsequently fed a 2% cholestrol based atherogenic diet for a period of 6 months. Group II was also fed the diet but had no AV shunt, and Group III received a normal diet and had no AV shunt. The swine with the AV shunt developed significantly less atherogenic plaques throughout the arterial system compared with Group II. Group I had a markedly higher blood flow in the abdominal aorta and shunted vessels in comparison to similar vessels for Groups II and III. Coincident with the higher blood flow in Group I. was a higher mean shear stress at the walls of the abdominal aorta and iliac (shunt).