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Investigation and Testing of Location Systems Using WiFi in Indoor Environments
Guenther Retscher,Esmond Mok 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.2 No.-
Many applications in the area of location-based services and personal navigation require nowadays the location determination of a user not only in outdoor environment but also indoor. To locate a person or object in a building, systems that use either infrared, ultrasonic or radio signals, and visible light for optical tracking have been developed. The use of WiFi for location determination has the advantage that no transmitters or receivers have to be installed in the building like in the case of infrared and ultrasonic based location systems. WiFi positioning technology adopts IEEE802.11x standard, by observing the radio signals from access points installed inside a building. These access points can be found nowadays in our daily environment, e.g. in many office buildings, public spaces and in urban areas. The principle of operation of location determination using WiFi signals is based on the measurement of the signal strengths to the surrounding available access points at a mobile terminal (e.g. PDA, notebook PC). An estimate of the location of the terminal is then obtained on the basis of these measurements and a signal propagation model inside the building. The signal propagation model can be obtained using simulations or with prior calibration measurements at known locations in an offline phase. The most common location determination approach is based on signal propagation patterns, namely WiFi fingerprinting. In this paper the underlying technology is briefly reviewed followed by an investigation of two WiFi positioning systems. Testing of the system is performed in two localization test beds, one at the Vienna University of Technology and the second at the Hong Kong Polytechnic University. First test showed that the trajectory of a moving user could be obtained with a standard deviation of about ± 3 m.
Guenther Retscher,Michael Thienelt 한국항해항만학회 2006 한국항해항만학회 학술대회논문집 Vol.1 No.-
In the work package “Integrated Positioning” of the research project NAVIO (Pedestrian Navigation Systems in Combined Indoor/Outdoor Environements) we are dealing with the navigation and guidance of visitors of our University. Thereby start points are public transport stops in the surroundings of the Vienna University of Technology and the user of the system should be guided to certain office rooms or persons. For the position determination of the user different location sensors are employed, i.e., for outdoor positioning GPS and dead reckoning sensors such as a digital compass and gyro for heading determination and accelerometers for the determination of the travelled distance as well as a barometric pressure sensor for altitude determination and for indoor areas location determination using WiFi fingerprinting. All sensors and positioning methods are combined and integrated using a Kalman filter approach. Then an optimal estimate of the current location of the user is obtained using the filter. To perform an adequate weighting of the sensors in the stochastic filter model, the sensor characteristics and their performance was investigated in several tests. The tests were performed in different environments either with free satellite visibility or in urban canyons as well as inside of buildings. The tests have shown that it is possible to determine the user’s location continuously with the required precision and that the selected sensors provide a good performance and high reliability. Selected tests results and our approach will be presented in the paper.
( Guenther C. Feigl ),( Daniel Staribacher ),( Gavin Britz ),( Dzmitry Kuzmin ) 대한뇌종양학회·대한신경종양학회·대한소아뇌종양학회 2024 Brain Tumor Research and Treatment Vol.12 No.2
Background Intracranial meningiomas, being a fairly common disease in the population, often require surgical treatment, which, in turn, can completely heal the patient. The localization of meningiomas often influences treatment even if they are asymptomatic. By modernizing approaches to surgical treatment, it is possible to minimize intra- and postoperative risks, while achieving complete removal of the tumor. One of these methods is minimally invasive neurosurgery, the development of which in recent years allows it to compete with standard surgical methods. The purpose of this study was the objectification of minimally invasive approaches, such as the calculation of the craniotomy area and the ratio of craniotomy area to the resected tumor volume. Methods The retrospective study consisted of a group of 54 consecutive patients who were operated on in our neurosurgery clinic specialized on minimally invasive neurosurgery. Preoperative planning was carried out using the Surgical Theater visualization platform. Using this system, the tumor volume and craniotomy surface area were calculated. During the analysis, the symptoms before and after the surgery, classification of tumors, postoperative complications, further treatment and follow-up results were assessed. Results Twelve (22.2%) patients were men and 42 (77.8%) were women. The mean age of the group was 64.2 years (median 67.5). The craniotomy area ranged from 202 to 2,108 mm2 (mean 631 mm<sup>2</sup>). Tumor volume ranged from 0.85 to 110.1 cm<sup>3</sup> (mean 21.6 cm<sup>3</sup>). The craniotomy size of minimally invasive approaches to the skull base was 3-5 times smaller than standard approaches. Skull base meningiomas accounted for 19 cases (35.2%), convexity meningiomas for 26 cases (48.1%), and falx and tentorium meningiomas for 9 cases (16.7%). Three complications were reported: postoperative hemorrhage, CSF leakage, and ophthalmoplegia. Relapse was detected in 2 patients with a mean follow-up of 26.3 months (median 20). Conclusion Minimally invasive approaches in the surgical treatment of intracranial meningiomas reduce the possibility of operating trauma by several times; they are safe and sufficient for complete removal of the tumor.
A MATHEMATICAL MODEL OF A POWER STEERING SYSTEM
장봉춘(B.C.Jang),이성철(S.C.Lee),D.A.Guenther(D.A.Guenther) 한국자동차공학회 1996 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1996 No.6_1
The focus of this research is to set up and describe the mathematical derivation of an automobile power-assisted rack and pinion steering system dynamics. The mathematical model of the power steering system dynamics with a 5 degree-of-freedom linear vehicle model will be used in the computer simulation and evaluated comparing with the experimental results. This model is flexible to accommodate different vehicles through simple parameter changes. The developed mathematical model will attempt to provide enhanced driver realism to a Systems Technology, Inc. driving SIMulator (STISIM).