Computer Assisted Navigation in Knee Arthroplasty

Computer assisted surgery (CAS) was used to improve the positioning of implants during total knee arthroplasty (TKA). Most studies have reported that computer assisted navigation reduced the outliers of alignment and component malpositioning. However, additional sophisticated studies are necessary to determine if the improvement of alignment will improve long-term clinical results and increase the survival rate of the implant. Knowledge of CAS-TKA technology and understanding the advantages and limitations of navigation are crucial to the successful application of the CAS technique in TKA. In this article, we review the components of navigation, classification of the system, surgical method, potential error, clinical results, advantages, and disadvantages

A laser-based triggering system for remote actuation of tractor-mounted instrumentation

Instrumented tractors equipped with data acquisition systems developed in the last 10 years allow measurement of many vehicle and implement operational parameters. However, some systems lack the capability to initiate and terminate data acquisition precisely at predetermined points as the tractor is operated through the field. Results of previous experiments have indicated that measurement errors associated with manually actuating the data acquisition instrumentation can be considerable. Thus, a laser-based triggering device was developed to allow automatic remote actuation, both initiation and termination of data acquisition, of a tractor-mounted instrumentation system as a test vehicle was operated back and forth over a field plot, typically 60 m in length. The triggering device consists of three subsystems: a laser emitting unit, a laser receiving unit, and an interfacing unit. Two 5-mW helium-neon lasers are used to provide precise reference lines for the system. A photodiode in the laser receiver is used as the sensing element. An optical filter included in the receiver package eliminates much of the influence of sunlight. Two alternative triggering prototypes were designed. In the final system, laser light is continuously detected at the laser receiving unit. When the moving vehicle interrupts the laser beam, a radio transmitter in the laser receiving unit is actuated. Signals generated by the transmitter are used to excite a radio receiver designed to be mounted on the instrumented vehicle. The radio iii receiver then initiates or terminates, as appropriate, the data acquisition process. Laboratory tests indicate that the triggering system was able to repeatedly time events with a precision of 0.01 second

Asynchronous Ultrasonic Trilateration for Indoor Positioning of Mobile Phones

Spatial awareness is fast becoming the key feature on today‟s mobile devices. While accurate outdoor navigation has been widely available for some time through Global Positioning Systems (GPS), accurate indoor positioning is still largely an unsolved problem. One major reason for this is that GPS and other Global Navigation Satellite Systems (GNSS) systems offer accuracy of a scale far different to that required for effective indoor navigation. Indoor positioning is also hindered by poor GPS signal quality, a major issue when developing dedicated indoor locationing systems. In addition, many indoor systems use specialized hardware to calculate accurate device position, as readily available wireless protocols have so far not delivered sufficient levels of accuracy. This research aims to investigate how the mobile phone‟s innate ability to produce sound (notably ultrasound) can be utilised to deliver more accurate indoor positioning than current methods. Experimental work covers limitations of mobile phone speakers in regard to generation of high frequencies, propagation patternsof ultrasound and their impact on maximum range, and asynchronous trilateration. This is followed by accuracy and reliability tests of an ultrasound positioning system prototype.This thesis proposes a new method of positioning a mobile phone indoors with accuracy substantially better than other contemporary positioning systems available on off-theshelf mobile devices. Given that smartphones can be programmed to correctly estimate direction, this research outlines a potentially significant advance towards a practical platform for indoor Location Based Services. Also a novel asynchronous trilateration algorithm is proposed that eliminates the need for synchronisation between the mobile device and the positioning infrastructure

Doppler Radar Techniques for Distinct Respiratory Pattern Recognition and Subject Identification.

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017