Reflectometry for structural health monitoring

ManuscriptAging wiring and structural cables in buildings, aircraft and transportation systems, consumer products, industrial machinery, etc. are among the most significant potential causes of catastrophic failure and maintenance cost in these structures. Smart wire health monitoring can therefore have a substantial impact on the overall health monitoring of the system. Reflectometry is commonly used for locating faults on wire and cables. It can also be used for location of faults on structural cables, if they are electrically isolated. This chapter describes and compares several reflectometry methods -- time domain reflectometry (TDR), frequency domain reflectometry (FDR), mixed signal reflectometry (MSR), sequence time domain reflectometry (STDR), and spread spectrum time domain reflectometry (SSTDR) -- in terms of their accuracy, convenience, cost, size, and ease of use. Advantages and limitations of each method are outlined and evaluated for several types of aircraft cables, and the general equations that govern their performance are given. The impact of the fault location and size is also discussed

Faster than fourier -- ultra-efficient time-to-frequency domain conversions for FDTD

Journal ArticleTwo highly efficient methods of computing magnitude and phase from time-domain data are demonstrated. These methods, based on solution of linear equations, are found to be equally accurate and more efficient than Fourier transform methods (DIT and FFT) for limited numbers of Frequencies. These methods provide a significant savings in computation time and storage requirements for FDTD simulations which require a large number of time-to-frequency domain conversions. Although some FDTD researchers may have applied the method for single frequency simulations, it is not widely known or used. The multiple frequency extension of this method has not been used previously, to my knowledge

Calculation of electric fields and currents induced in a millimeter-resolution human model at 60 Hz using the FDTD method with a novel time-to-frequency-domain conversion

Journal ArticleThe finite-difference time-domain (FDTD) method has previously been used to calculate induced currents in anatomically based models of the human body at frequencies ranging from 20 to 915 MHz and resolutions down to 1.31 cm . Calculations at lower frequencies and higher resolutions have been precluded by the huge number of time steps which would be needed to run these simulations in the traditional way. This paper describes a new method used to overcome this problem and calculate the induced currents in a MRI-based 6-mm-resolution human model at 60 Hz. A new algorithm based on solving two equations with two unknowns is used for calculating magnitude and phase from the CW FDTD simulation. This allows magnitude and phase calculations to be made as soon as steady-state is reached, which is within a fraction of a cycle. For incident electric fields of 10 kV/m, local induced current densities above 16 mA/m2 have been calculated in the torso, with even higher values up to 65 mNmz for the legs. These are considerably higher than the 4 or even 10 mA/m2 that have been suggested in the safety guidelines

Teaching and learning combined (TLC)

Journal ArticleMost professors have to lean a LOT. Every day, it seems, there IS something that we need that we don't know. So what do you do to lean this new information? Perhaps you hit the Web or the library, find a tutorial, a textbook, or a paper, and give it a little reading time in between a 12:00 class and a 2:00 meeting. But you still don't quite "get it." No wonder, by the next day, most people only remember 10% of what they read. Of your precious hour, you received six useable minutes

Work in progress - Utahs engineering initiative

Journal ArticleAbstract - In response to a shortage of engineers in Utah an interdisciplinary team at the University of Utah developed an outreach program intended to increase the number of students recruited into the College of Engineering and who complete engineering degrees. An innovative mix of service learning, outreach, and peer mentoring comprises the program. Recruitment efforts include outreach, integration with teachers and public relations. In outreach, college students work with high school teachers and engineering faculty to prepare and present engineering-based teaching modules that meet requirements of the state core science curriculum. Education and public relations materials aimed at students, parents, teachers, and counselors also contribute to outreach. Retention efforts include academic advising, tutoring, peer mentoring, and service learning. Retention programs are based on college student retention research, and focus on engaging students both academically and socially. This paper reports on the first year of the initiative, including the creation of outreach teams and the development of high school teaching. We also discuss how participation in the outreach team impacted current students

Biomedical telemetry: today's opportunities and challenges

Journal ArticleBiomedical telemetry is used today to communication with cardiac devices, insulin pumps, and a few other implantable devices that are on the order of 1-2" in diameter. Future systems promise advanced communication with cardiac, optical, neurological and auditory devices that are on the order of a centimeter in dimension. Miniaturized antennas and inductive coupling systems provide the radio interface between air and the implantable device. New materials and methods allow miniaturized communication systems to be seamlessly integrated within the medical device itself. This paper describes recent advances in biotelemetry, the challenges faced today, and opportunities for the future

Electromagnetic absorption in the human head and neck for mobile telephones at 835 and 1900 MHz

Journal ArticleWe have used the finite-difference time-domain method and a new millimeter-resolution anatomically based model of the human to study electromagnetic energy coupled to the head due to mobile telephones at 835 and 1900 MHz. Assuming reduced dimensions characteristic of today's mobile telephones, we have obtained SAR distributions for two different lengths of monopole antennas of lengths λ / 4 and 3λ/8 for a model of the adult male and reduced-scale models of 10- and 5-year-old children and find that peak one-voxel and 1-g SAR's are larger for the smaller models of children, particularly at 835 MHz. Also, a larger in-depth penetration of absorbed energy for these smaller models is obtained. We have also studied the effect of using the widely disparate tissue properties reported in the literature and of using homogeneous instead of the anatomically realistic heterogeneous models on the SAR distributions. Homogeneous models are shown to grossly overestimate both the peak 1-voxel and 1-g SAR's. Last, we show that it is possible to use truncated one-half or one-third models of the human head with negligible errors in the calculated SAR distributions. This simplification will allow considerable savings in computer memory and computation times

13 crazy, notorious things to do in an EM class

Journal ArticleThe average attention span of an adult human is 12-20 minutes. Our lectures are 50-80 minutes. Attention Span Math reminds us to take a break now and then, and to bring the class back to life by bringing some life to the class. Many students learn things better if they can see and touch them, so this column is dedicated to them. Here are 13 physical, kinetic, visual (and fun) things to do to make your EM class notorious (and to wake up even the students in the back row)

Utah's engineers: a statewide initiative for growth

posterImagine finding a place where inventors gather to create their inventions. Envision getting a sneak peek at the latest technological innovations in engineering and computer science. Can you see yourself as an inventor? Join us on February 20 for Meet an Inventor Day sponsored by the students of Tau Beta Pi at the College of Engineering on the University of Utah campus. Invention is a daily activity for students and faculty in the College of Engineering. Come meet our inventors and see how we work together to build many of the necessities and conveniences of modern life. Students and faculty from Bio-, Chemical, Electrical, Civil, Computer, Mechanical, Materials Science Engineering, and Computer Science will give explanations and demonstrations of their latest inventions. Check-in begins at 9:00 and participants will choose four demonstrations from approximately 14 to visit. Half-hour demonstrations will begin promptly at 9:30 and end at Noon. Pizza will be provided after the last demonstrations. This event is geared for high school students and their parents, but all people interested in invention are welcome to attend

New IEEE AP-S education web site: course/lab notes, scholarships, K-12 outreach

Journal ArticleGreetings from the Snowy West! This month I am pleased to announce a new effort on the part of the IEEE Antennas and Propagation Society Education Committee to collect course and laboratory links relevant to the AP-S community, and compile them in a central location where they can be easily accessed