1.
Fredenberg, Erik, 1979-
(author)
Spectral Mammography with X-Ray Optics and a Photon-Counting Detector
2009
Doctoral thesis (other academic/artistic) abstract
Early detection is vital to successfully treating breast cancer, and mammography screening is the most efficient and wide-spread method to reach this goal. Imaging low-contrast targets, while minimizing the radiation exposure to a large population is, however, a major challenge. Optimizing the image quality per unit radiation dose is therefore essential. In this thesis, two optimization schemes with respect to x-ray photon energy have been investigated: filtering the incident spectrum with refractive x-ray optics (spectral shaping), and utilizing the transmitted spectrum with energy-resolved photon-counting detectors (spectral imaging). Two types of x-ray lenses were experimentally characterized, and modeled using ray tracing, field propagation, and geometrical optics. Spectral shaping reduced dose approximately 20% compared to an absorption-filtered reference system with the same signal-to-noise ratio, scan time, and spatial resolution. In addition, a focusing pre-object collimator based on the same type of optics reduced divergence of the radiation and improved photon economy by about 50%. A photon-counting silicon detector was investigated in terms of energy resolution and its feasibility for spectral imaging. Contrast-enhanced tumor imaging with a system based on the detector was characterized and optimized with a model that took anatomical noise into account. Improvement in an ideal-observer detectability index by a factor of 2 to 8 over that obtained by conventional absorption imaging was found for different levels of anatomical noise and breast density. Increased conspicuity was confirmed by experiment. Further, the model was extended to include imaging of unenhanced lesions. Detectability of microcalcifications increased no more than a few percent, whereas the ability to detect large tumors might improve on the order of 50% despite the low attenuation difference between glandular and cancerous tissue. It is clear that inclusion of anatomical noise and imaging task in spectral optimization may yield completely different results than an analysis based solely on quantum noise.
2.
Stigwall, Johan, 1977, et al.
(author)
Photonic GHz to THz tunable signal generation by chirped-pulse mixing
2006
In: 2006 European ISIS Workshop, Emerging Optical Broadband Technologies, Boppard am Rhein, Germany, May 29 - June 1, 2006.
Conference paper (peer-reviewed) abstract
Frequency-tunable generation of pulsed tones in the millimeter to sub-millimeter range was demonstrated by mixing of two chromatically dispersing femtosecond laser pulses split up in time by an adjustable differential group delay (DGD) and a polarizer. The signal frequency was set by adjusting the amount of DGD and the amount of dispersion, and was here tuned from below 1 GHz to 0.9 THz. Time-domain measurements were conducted using a sampling oscilloscope for the lower frequencies and an auto-correlator for the higher frequencies. Near 100% modulation depth was obtained, and the signal phase was very stable, being locked to the pulses from the femtosecond laser. The line-width of the mm-wave waveform was found to be transform-limited if the signal chirp induced by higher order dispersion was compensated for. Suggested applications for this system are for instance THz spectroscopy, characterization of high performance photo-diodes and real-time dispersion measurements.
3.
Liu, Yang, et al.
(author)
A Study Towards Enhanced Reliability Performance of Remote Control and Monitoring Application Over Commercial Wireless Communication Networks
2006
In: 2006 International Conference on Wireless Communications, Networking and Mobile Computing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1424405173 - 1424405173 ; , s. 1-4
Conference paper (peer-reviewed) abstract
Remote control and monitoring systems provide many useful operating advantages in industrial automation and demand highly reliable and secure communication means. Their widespread use is, however, limited because of the high cost of current communications in use making them economically infeasible. Hence, there is a need to develop new low cost communication and control concepts by making such solutions economically feasible. In this paper, we present a scheme for implementing reliable wireless communication links for application of remote control and monitoring system based on current available commercial wireless communication networks, e.g. GPRS/EDGE/UMTS. The reliability enhancement over wireless networks has been proposed and its performance has been studied. This paper examines the proposed solution by means of both analytical and numerical evaluation, and has shown that the demanded reliability performance can be met by using only commercial wireless communication networks.
4.
5.
Siebert, Peter W.
(author)
Cooling Structure for EMC Shielded High Frequency Electronics
2006
In: IEEE transactions on components and packaging technologies (Print). - 1521-3331 .- 1557-9972. ; 29:1, s. 155-163
Journal article (peer-reviewed) abstract
Cooling of electronics is normally achieved using air passing through apertures in the enclosure; as a result the shielding effectiveness of the shielded enclosure is reduced. In this paper, the design of a new cooling structure and its evaluation in a wind tunnel is presented.The developed design presented here is a double heat sink in extruded aluminum. Into one side of the heat sink, the printed circuit boards (PCBs) are inserted and enclosed by a complementary shielding surface. The other side of the heat sink is cooled by forced ventilation. The heat transport between these parts is completely inside the same body, without any heat flow interruptions. Tests carried out on a prototype have shown that the performance of the cooling structure is satisfactory for electronic cooling. An additional electromagnetic compatibility (EMC)-test has also elucidated the satisfactory shielding effectiveness of the structure.The cooling structure is scaleable and can accommodate for both future smaller printed circuit boards (PCBs) and those of today. The entire enclosure is furthermore based on near-standard items, which allows it to be inexpensive in high volume production.
6.
Siebert, Peter W.
(author)
New Solutions for High Frequency Electronic Packaging
2003
In: 2003 IEEE International Symposium on Electromagnetic Compatibility (EMC), Vols 1 and 2, Symposium Record. - 0780377796 ; , s. 954-957
Conference paper (peer-reviewed) abstract
A new concept for shielded enclosures of electronics is presented in this paper. An inexpensive doubled heatsink in extruded aluminum forms the base of the enclosure. The electronics are inserted into one part and is enclosed by a complementary shielding surface. The outer heatsink is cooled by forced ventilation. As openings are made redundant, seams between the parts of the enclosure are the only path for significant electromagnetic emissions.
7.
Seoane Martinez, Fernando, 1976
(author)
Electrical Bioimpedance Cerebral Monitoring: Fundamental Steps towards Clinical Application
2007
Doctoral thesis (other academic/artistic) abstract
Neurologically related injuries cause a similar number of deaths as cancer, and brain damage is the second commonest cause of death in the world and probably the leading cause of permanent disability. The devastating effects of most cases of brain damage could be avoided if it were detected and medical treatment initiated in time. The passive electrical properties of biological tissue have been investigated for almost a century and electrical bioimpedance studies in neurology have been performed for more than 50 years. Even considering the extensive efforts dedicated to investigating potential applications of electrical bioimpedance for brain monitoring, especially in the last 20 years, and the specifically acute need for such non-invasive and efficient diagnosis support tools, Electrical Bioimpedance technology has not made the expected breakthrough into clinical application yet. In order to reach this stage in the age of evidence-based medicine, the first essential step is to demonstrate the biophysical basis of the method under study. The present research work confirms that the cell swelling accompanying the hypoxic/ischemic injury mechanism modifies the electrical properties of brain tissue, and shows that by measuring the complex electrical bioimpedance it is possible to detect the changes resulting from brain damage. For the development of a successful monitoring method, after the vital biophysical validation it is critical to have available the proper electrical bioimpedance technology and to implement an efficient protocol of use. Electronic instrumentation is needed for broadband spectroscopy measurements of complex electrical bioimpedance; the selection of the electrode setup is crucial to obtain clinically relevant measurements, and the proper biosignal analysis and processing is the core of the diagnosis support system. This work has focused on all these aspects since they are fundamental for providing the solid medico-technological background necessary to enable the clinical usage of Electrical Bioimpedance for cerebral monitoring.
8.
Haasl, Sjoerd, et al.
(author)
Hybrid mounted micromachined aluminium hot-wire for near-wall turbulence measurements
2002
In: FIFTEENTH IEEE INTERNATIONAL CONFERENCE ON MICRO ELECTRO MECHANICAL SYSTEMS. - : IEEE. - 0780371852 ; , s. 336-339
Conference paper (peer-reviewed) abstract
We present the first micromachined metal hot-wire anemometer sensor for use in near-wall turbulence measurements. To measure close to the surface without the circuitry interfering with the flow, a novel hybrid assembly of the sensor has been developed. We present the design, fabrication and characteristics of this sensor.
9.
Nybacka, Mikael, et al.
(author)
Project: CASTT - Centre for Automotive Systems Technologies and Testing
2007
Other publication (pop. science, debate, etc.) abstract
Through the Centre for Automotive Systems Technologies and Testing, Luleå University of Technology aims to first of all support automotive winter testing in Northern Sweden. This means to support the local automotive test entrepreneurs and through them their customers: the car manufacturers and their suppliers. To succeed in this task, the center relies on the university's areas of leading research and most importantly on the cooperation between those areas.
10.
Banik, Biddut Kumar, 1978, et al.
(author)
Catadioptric Dielectric Lens for Imaging Applications
2008
In: Proceedings of 33rd International Conference on Infrared, Millimeter, and Terahertz Waves. - 9781424421190 ; , s. 1 - 2
Conference paper (peer-reviewed) abstract
The design and characterization results of a novel catadioptric dielectric lens are presented. Although being electrically small, the lens provides a focus in the close vicinity which makes it suitable to be used in microwave and terahertz systems. Several lenses of different dielectric materials and dimensions have been fabricated. A simple backscattering measurement method has been implemented in order to determine the focusing property of the lens.
11.
Chiragwandi, Zackary, 1968, et al.
(author)
Properties of a bio-photovoltaic nano-device
2008
In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:48, s. 18717-18721
Journal article (peer-reviewed) abstract
Properties of an on-chip photovoltaic nanodevice are demonstrated. The dyes comprise green florescent proteins(GFP). Dependence of recently reported zero external potential bias (ZEPB) photocurrent (I) on temperature,power, and wavelength (λ) is shown. Correlation between UV-vis spectrum of the GFP and the ZEPB I(λ)of the device is reported. The temperature dependence suggests the ZEPB photocurrent to reflect a liquidcrystal type ordering where the current declines monotonically with increasing temperature. The influence ofan external bias on the photocurrent is demonstrated. The resulting light-induced current is analyzed in termsof resistive and quantum mechanical contributions.
12.
Bollen, Math, et al.
(author)
Classification of Underlying Causes of Power Quality Disturbances: Deterministic versus Statistical Methods
2007
In: Eurasip Journal on Applied Signal Processing. - : Springer Science and Business Media LLC. - 1110-8657 .- 1687-0433. ; 2007, s. 17 pages (Article ID 79747)-
Journal article (peer-reviewed) abstract
This paper presents the two main types of classification methods for power quality disturbances based on underlying causes: deterministic classification, giving an expert system as an example, and statistical classification, with support vector machines as an example. An expert system is suitable when one has limited amount of data and sufficient power system expert knowledge, however its application requires a set of threshold values. Statistical methods are suitable when large amount of data is available for training. Two important issues to guarantee the effectiveness of a classifier, data segmentation and featureextraction, are discussed. Segmentation of a sequence of data recording is pre-processing to partition the datainto segments each representing a duration containing either an event or transition between two events. Extraction of features is applied to each segment individually. Some useful features and their effectiveness are then discussed. Some experimental results are included for demonstrating theeffectiveness of both systems. Finally, conclusions are given together with the discussion of some future research directions.
13.
14.
Mamontov, Eugen, 1955, et al.
(author)
Asymptotic trajectory matching in self-navigation of autonomous manless interceptors: Nonsearch method and a formulation of the functional optimization of the stability of random systems
2006
In: Proc. 5th MATHMOD Vienna Conf., 8-10 February, 2006 (Vienna Univ. of Technol., Vienna, Austria). - 3901608303 ; 2
Conference paper (peer-reviewed) abstract
In the field of self-navigation autonomous manless robots there is a noticeable interest to the robot-based target-interception problem. The interceptor trajectory is usually determined by search-based optimization algorithms. In contrast to this, the present work treats the interception as asymptotic trajectory matching and introduces a nonsearch method for the interceptor trajectory. This method is substantially simpler than the well-known proportional navigation and requires very limited computing resources. The latter feature makes the proposed method especially suitable to the interceptors based on embedded onboard computers and civil applications. An example of the latter discussed in the work is the protection of the infrastructure components against intended or unintended attacks. In a general case when parameters of the interceptor are random, the new method leads to a formulation of a new problem in stochastic optimization, namely the functional optimization of (the so-called targetal) stability of the interceptor trajectory. Certain aspects of a practical implementation of the new systems are analyzed. The work proposes the basic physical principle and schemes for innovative sensors which can make the interceptors truly autonomous, in particular, fully GPS-free. A list of the fundamental and applied topics for future research is also suggested.
15.
16.
Nilsson, Björn, et al.
(author)
Selecting back off algorithm in active RFID CSMA/CA based medium-access protocols
2008
In: International Symposium on Industrial Embedded Systems, 2008. SIES 2008. - Piscataway, N.J. : IEEE Press. - 9781424419944 ; , s. 265-270, s. 265-270
Conference paper (peer-reviewed) abstract
Active radio frequency identification (A-RFID) is a technology where the tags (transponders) carry an on board energy source for powering the radio, processor circuits, and sensors. Besides offering longer working distance between RFID-reader and tag than passive RFID, this also enables the tags to do sensor measurements, calculations and storage even when no RFID-reader is in the vicinity of the tags. In this paper we study the effect on tag energy cost and read out delay incurred by some typical back-off algorithms (constant, linear, and exponential) used in a contention based CSMA/CA (carrier sense multiple access/collision avoidance) protocol for A-RFID communication.
17.
18.
Chilo, José, 1960-, et al.
(author)
A flexible electronic nose for odor discrimination using different methods of classification
2009
In: 2009 16th IEEE-NPSS Real Time Conference - Conference Record. - New York : IEEE. - 9781424444557 ; , s. 317-320, s. 317-320
Conference paper (peer-reviewed) abstract
Ovarian cancer is one of the leading causes of death from cancer in women. The lifetime risk is around 1.5%, which makes it the second most common gynecologic malignancy (the first one being breast cancer). To have a definitive diagnose, a surgical procedure is generally required and suspicious areas (samples) will be removed and sent for microscopic and other analysis. This paper describes the result of a pilot study in which an electronic nose is used to "smell" the aforementioned samples, analyze the multi-sensor signals and have a close to real-time answer on the detection of cancer. Besides being fast, the detection method is inexpensive and simple. Experimental analysis using real ovarian carcinoma samples shows that the use of proper algorithms for analysis of the multi-sensor data from the electronic nose yielded surprisingly good results with more than 77% classification rate. The electronic nose used in this pilot study was originally developed to be used as a "bomb dog" and can distinguish between e.g. TNT, Dynamex, Prillit. However, it was constructed to be a flexible multi-sensor device and the individual (16) sensors can easily be replaced/exchanged. This is suggestive for further investigations to obtain even better results with new, specific sensors. In another pilot experiment, headspace of an ovarian carcinoma sample and a control sample were analyzed using gas chromatography-mass spectrometry. Significant differences in chemical composition and compound levels were recorded, which would explain the different response obtained with the electronic nose.
19.
Avelin, Anders, et al.
(author)
Time based data reconciliation and decision support for a CFB boiler
2009
In: IFAC Proceedings Volumes (IFAC-PapersOnline), 2009. - Tampere : Tampere University Press. ; , s. 338-343
Conference paper (peer-reviewed) abstract
This paper covers a method for operator decision support, where physical simulation models are used to connect different physical variables to each other. By comparing energy and material balances for a larger process area inconsistencies in single process parts and sensor measurements can be detected, by following the development between single measurements and values predicted from the simulations. This information then can be used as input to e.g. a BN, Bayesian Network, for decision support. The application has been for a CFB boiler at Mälarenergi AB. The simulators have been made in Modelica respectively a more advanced model in APROS.
20.
Hallberg, Josef, et al.
(author)
Enriched media-experience of sport events
2004
In: Proceedings. - Los Alamitos, Calif : IEEE Communications Society. - 0769522580 ; , s. 2-9
Conference paper (peer-reviewed) abstract
This paper describes a system where Internet-enabled sensor technology was integrated into a context-aware platform to give viewers of sport events an enriched media experience. The system was developed as a proof of concept and was evaluated during real-life use at the Vasaloppet cross-country ski event. Using Bluetooth wireless ad-hoc networking and GPRS technology, sensor data was transmitted from contestants to the context-aware platform Alipes, which in turn presented the sport event viewer with a personalized, context-aware view. In this paper we discuss the system architecture and integration of components. The system was evaluated both from technical and user perspectives, where the evaluation results confirm our approach to be technically feasible and that the system provide an enriched media-experience for the majority of viewers.
21.
Buendia, Ruben, 1982, et al.
(author)
A Novel Approach for Removing the Hook Effect Artefact from Electrical Bioimpedance Spectroscopy Measurements
2009
In: Journal of Physics: Conference Series. - : Institute of Physics Publishing Ltd.. - 1742-6596.
Conference paper (peer-reviewed) abstract
Very often in Electrical Bioimpedance (EBI) spectroscopy measurements the presence of stray capacitances creates a measurement artefact commonly known as Hook Effect. Such an artefact creates a hook-alike deviation of the EBI data noticeable when representing the measurement on the impedance plane. Such Hook Effect is noticeable at high frequencies but it also causes a data deviation at lower measurement frequencies. In order to perform any accurate analysis of the EBI spectroscopy data, the influence of the Hook Effect must be removed. An established method to compensate the hook effect is the well known Td compensation, which consist on multiplying the obtained spectrum, Zmeas() by a complex exponential in the form of exp[jTd]. Such a method cannot correct entirely the Hook Effect since the hook-alike deviation occurs a broad frequency range in both magnitude and phase of the measured impedance, and by using a real value for Td. First, a real value only modifies the phase of the measured impedance and second, it can only correct the Hook Effect at a single frequency. In addition, the process to select a value for Td by an iterative process with the aim to obtain the best Cole fitting lacks solid scientific grounds. In this work the Td compensation method is revisited and a modified approach for correcting the Hook Effect that includes a novel method for selecting the correcting values is proposed. The initial validation results confirm that the proposed method entirely corrects the Hook Effect at all frequencies.
22.
Shiu, Jin-Yu, 1978, et al.
(author)
Oxygen Ion Implantation Isolation Planar Process for AlGaN/GaN HEMTs
2007
In: IEEE Electron Device Letters. ; 28:6, s. 476-478
Journal article (peer-reviewed) abstract
A multienergy oxygen ion implantation process wasdemonstrated to be compatible with the processing of highpower microwave AlGaN/GaN high electron mobility transistors (HEMTs). HEMTs that are isolated by this process exhibited gate-lag- and drain-lag-free operation. A maximum output power density of 5.3 W/mm at Vgs = −4 V and Vds = 50 V and a maximum power added efficiency of 51.5% at Vgs = −4 V and Vds = 30 V at 3 GHz were demonstrated on HEMTs withoutfield plates on sapphire substrate. This isolation process results in planar HEMTs, circumventing potential problems with enhancedgate leakage due to the gate contacting the 2-D electron gas at themesa sidewall.
23.
Hemida, Hassan, 1972, et al.
(author)
LES study of the influence of the vortex generators on cooling of surface-mounted cubes
2007
In: 1st International Conference on Thermal Issues in Emerging Technologies, Theory and Applications, Proceedings - ThETA1, Cairo, Egypt, 3-6 January 2007. - 1424408970 ; , s. 55-62
Conference paper (peer-reviewed) abstract
The influence of vortex generators on the enhancement of heat transfer from a wall-mounted cube matrix was investigated by numerical simulation using finite-volume method. The momentum and convective heat transfer equations were discretized and solved using large-eddy simulation. The numerical simulation was performed on a fully developed turbulent flow over one cube mounted in the middle of a cube matrix. Constant heat flux was generated from the cubes. Periodic boundary conditions were applied in both the streamwise and the spanwise directions. In order to study the influence of vortex generator on the flow structures and heat transfer coefficient, the flow and the convective heat transfer equations were solved around two cube configurations: a smooth cube and a cube with vortex generator attached to its surface. The vortex generator used in this investigation is a simple rib attached to the top and the side walls of the cube close to the streamwise edge. The flow Reynolds number based on the bulk velocity and the height of the channel was 13000. Standard Smagorinsky subgrid-scale model was used to model the unresolved scales and heat fluxes. The LES results were compared with the experimental results and good agreement was obtained. Numerical flow visualization was used to provide a better insight into the flow structures and heat transfer coefficient around the cubes. The LES results showed that the flow in the boundary layer around the cube with vortex generator is more turbulent and unsteady than the flow around the smooth cube without the vortex generator. More turbulent structures are generated close to the surface of the cube resulting in a good mixing of heat and hence high heat transfer coefficient
24.
25.
Gu, Irene Yu-Hua, 1953, et al.
(author)
Intelligent Video Surveillance for Detecting Snow and Ice Coverage on Electrical Insulators of Power Transmission Lines
2009
In: Springer LNCS (for CAIP'09). ; 5702, s. 1179-1187
Conference paper (peer-reviewed) abstract
One of the problems for electrical power delivery throughpower lines in northern countries is when snow or ice accumulates on electrical insulators. This could lead to snow or ice-induced outages and voltage collapse, causing huge economic loss. This paper proposes a novel real-time intelligent surveillance and image analysis system for detecting and estimating the snow and ice coverage on electric insulators using images captured from an outdoor 420 kV power transmission line. In addition, the swing angle of insulators is estimated, as large swing angles due to wind cause short circuits. Hybrid techniques by combining histogram, edges, boundaries and cross correlations are employed for handling a broad range of scenarios caused by changing weather and lighting conditions. Experiments have been conducted on the captured images over several month periods. Results have shown that the proposed system has provided valuable estimation results. For image pixels related to snows on the insulator, the current system has yielded an averagedetection rate of 93% for good quality images, and 67.6% for images containing large amount of poor quality ones, and the corresponding average false alarm ranges from 9% to 18.1%. Further improvement may be achieved by using video-based analysis and improved camera settings.
