Tobias Dahl - Academia.edu (original) (raw)
Papers by Tobias Dahl
Food Quality and Preference, 2008
In this paper we propose some new plots for three-way analysis of sensory data. One of the plots ... more In this paper we propose some new plots for three-way analysis of sensory data. One of the plots is called ''Manhattan plot" and offers an alternative way of presenting explained variances, while the ''Hiding plot" provides information about how the different axes in the consensus space are related to the original measurements. Correlation loadings plots exhibit correlations between the common scores acquired from the consensus matrix and the variables in the original multi-way data. For the computation of the consensus matrices we propose a new tool that bridges Generalised Canonical Analysis and Tucker-1 by defining intermediate combinations of the two. This is accomplished by altering a parameter in a more general model that covers these two methods. Three-way sensory profiling data from cheese are used as input for this general model to compute consensus matrices at different values for the parameter. External validation is pointed out as a useful tool for indicating which of the two statistical methods is most appropriate for computing a consensus matrix representing all assessors.
2011 IEEE International Ultrasonics Symposium, 2011
ABSTRACT A novel Twisted Acoustic Lens (TAL) design to spread the radiated acoustic energy of a f... more ABSTRACT A novel Twisted Acoustic Lens (TAL) design to spread the radiated acoustic energy of a flat transducer is proposed. The lens is comprised of many perforations deployed uniformly, with trajectories that are circular helices of different radii. We have fabricated and characterized a disc-shaped TAL of thickness 7 mm and twist angle of 45° and demonstrated that the energy radiated by a directive ultrasonic transducer can be significantly dispersed. It is possible to almost triple the -6 dB directivity of a circular transducer of 20 mm of diameter at frequencies between 60 kHz and 80 kHz. The proposed lens design has great potential in certain ultrasonic touchless applications in which a commercially available ultrasonic transducer needs to be turned into field-of-view maximizing acoustic component while maintaining a flat front end.
... Procrustes methods have also found useful applications in another completely different branch... more ... Procrustes methods have also found useful applications in another completely different branch of statistics, namely statistical shape analysis (see [Dryden & Mardia, 1997] , [Goodall, 1991] , [Kendall, 1984] and [Kendall, 1989] ). ...
2012 IEEE International Ultrasonics Symposium, 2012
ABSTRACT In the present paper we explore transducer housing designs for high-resolution ultrasoni... more ABSTRACT In the present paper we explore transducer housing designs for high-resolution ultrasonic gesture tracking systems (UGTS) in future portable devices. We show characterization results of two design concepts based on the use of diffractive properties of ultrasound in order to maximize the sensing volume useful for touchless interaction. The designs are described in detail, a validation prototype was constructed and evaluated both using simulations and measurements. In doing so, we develop some simple yet relevant numerica models for the diffractive slits. The proposed design ideas have the potential to be implemented in future UGTS while maintaining sufficiently low friction in the industrial design process, sufficiently low cost and high performance in the user experience.
IEEE International Conference on Acoustics Speech and Signal Processing, 2002
Identification of the channel matrix is of main concern in wireless MIMO (Multiple Input Multiple... more Identification of the channel matrix is of main concern in wireless MIMO (Multiple Input Multiple Output) systems. Here, we present an SVDbased approach for blind identification of the main independent parallel channels. The right and left singular vectors are estimated directly (no channel matrix estimation is necessary) and continuously updated during normal transmission. The approach is related to the iterative Power Method [8], as well as the time reversal approach ([4]).
Ultrasonics, 2014
Airborne ultrasound is a rapidly developing subfield within human-computer interaction (HCI). Tou... more Airborne ultrasound is a rapidly developing subfield within human-computer interaction (HCI). Touchless ultrasonic interfaces and pen tracking systems are part of recent trends in HCI and are gaining industry momentum. This paper aims to provide the background and overview necessary to understand the capabilities of ultrasound and its potential future in human-computer interaction. The latest developments on the ultrasound transducer side are presented, focusing on capacitive micro-machined ultrasonic transducers, or CMUTs. Their introduction is an important step toward providing real, low-cost multi-sensor array and beam-forming options. We also provide a unified mathematical framework for understanding and analyzing algorithms used for ultrasound detection and tracking for some of the most relevant applications.
IEEE Transactions on Signal Processing, 2004
Identification of the channel matrix is of main concern in wireless multiple input multiple outpu... more Identification of the channel matrix is of main concern in wireless multiple input multiple output (MIMO) systems. To maximize the SNR, the best way to utilize a MIMO system is to communicate on the top singular vectors of the channel matrix. Here, we present a new approach for direct blind identification of the main independent singular modes, without estimating the channel matrix itself. The right and left singular vectors with maximum corresponding singular values are determined using payload data and are continuously updated while at the same time being used for communication. The feasibility of the approach is demonstrated by simulating the performance over a noisy, fading time-varying channel. Mathematically, the technique is related to the iterative numerical Power method for finding eigenvalues of a matrix as well as the "time reversal mirror" technique developed within acoustics.
Food Quality and Preference, 2004
... Procrustes methods have also found useful applications in another completely different branch... more ... Procrustes methods have also found useful applications in another completely different branch of statistics, namely statistical shape analysis (see [Dryden & Mardia, 1997] , [Goodall, 1991] , [Kendall, 1984] and [Kendall, 1989] ). ...
Food Quality and Preference, 2009
In this paper we discuss methods for detecting outlying assessors in descriptive sensory analysis... more In this paper we discuss methods for detecting outlying assessors in descriptive sensory analysis. A new method is proposed which is based on fuzzy clustering with the use of the noise cluster method. The technique ends up with a plot which can be used to provide information about which assessors that are different from the rest and also to suggest reasons why the assessors are different. The method is based on data compression by the use of either Tucker-1 or Tucker-2 for multi-block data. The technique is used on a dataset based on an oxidation experiment of cheese. There are 9 trained and 3 untrained assessors in the panel.
Food Quality and Preference, 2008
In this paper we propose some new plots for three-way analysis of sensory data. One of the plots ... more In this paper we propose some new plots for three-way analysis of sensory data. One of the plots is called ''Manhattan plot" and offers an alternative way of presenting explained variances, while the ''Hiding plot" provides information about how the different axes in the consensus space are related to the original measurements. Correlation loadings plots exhibit correlations between the common scores acquired from the consensus matrix and the variables in the original multi-way data. For the computation of the consensus matrices we propose a new tool that bridges Generalised Canonical Analysis and Tucker-1 by defining intermediate combinations of the two. This is accomplished by altering a parameter in a more general model that covers these two methods. Three-way sensory profiling data from cheese are used as input for this general model to compute consensus matrices at different values for the parameter. External validation is pointed out as a useful tool for indicating which of the two statistical methods is most appropriate for computing a consensus matrix representing all assessors.
A new method is proposed for blindly estimating the top singular modes in a reciprocal MIMO Outpu... more A new method is proposed for blindly estimating the top singular modes in a reciprocal MIMO Output) channel, while at the same time using these modes for multi-stream communication without the need for training data. The uplink and downlink parties obtain the relevant singular modes from the received data blocks as the eigenvectors/eigenvalues of the spatial empirical correlation matrices. The only requirement is that the separate data streams are statistically uncorrelated. The approach relies on a key and simple "need to know" observation about MIMO transmission :
Food Quality and Preference, 2008
In this paper we propose some new plots for three-way analysis of sensory data. One of the plots ... more In this paper we propose some new plots for three-way analysis of sensory data. One of the plots is called ''Manhattan plot" and offers an alternative way of presenting explained variances, while the ''Hiding plot" provides information about how the different axes in the consensus space are related to the original measurements. Correlation loadings plots exhibit correlations between the common scores acquired from the consensus matrix and the variables in the original multi-way data. For the computation of the consensus matrices we propose a new tool that bridges Generalised Canonical Analysis and Tucker-1 by defining intermediate combinations of the two. This is accomplished by altering a parameter in a more general model that covers these two methods. Three-way sensory profiling data from cheese are used as input for this general model to compute consensus matrices at different values for the parameter. External validation is pointed out as a useful tool for indicating which of the two statistical methods is most appropriate for computing a consensus matrix representing all assessors.
2011 IEEE International Ultrasonics Symposium, 2011
ABSTRACT A novel Twisted Acoustic Lens (TAL) design to spread the radiated acoustic energy of a f... more ABSTRACT A novel Twisted Acoustic Lens (TAL) design to spread the radiated acoustic energy of a flat transducer is proposed. The lens is comprised of many perforations deployed uniformly, with trajectories that are circular helices of different radii. We have fabricated and characterized a disc-shaped TAL of thickness 7 mm and twist angle of 45° and demonstrated that the energy radiated by a directive ultrasonic transducer can be significantly dispersed. It is possible to almost triple the -6 dB directivity of a circular transducer of 20 mm of diameter at frequencies between 60 kHz and 80 kHz. The proposed lens design has great potential in certain ultrasonic touchless applications in which a commercially available ultrasonic transducer needs to be turned into field-of-view maximizing acoustic component while maintaining a flat front end.
... Procrustes methods have also found useful applications in another completely different branch... more ... Procrustes methods have also found useful applications in another completely different branch of statistics, namely statistical shape analysis (see [Dryden & Mardia, 1997] , [Goodall, 1991] , [Kendall, 1984] and [Kendall, 1989] ). ...
2012 IEEE International Ultrasonics Symposium, 2012
ABSTRACT In the present paper we explore transducer housing designs for high-resolution ultrasoni... more ABSTRACT In the present paper we explore transducer housing designs for high-resolution ultrasonic gesture tracking systems (UGTS) in future portable devices. We show characterization results of two design concepts based on the use of diffractive properties of ultrasound in order to maximize the sensing volume useful for touchless interaction. The designs are described in detail, a validation prototype was constructed and evaluated both using simulations and measurements. In doing so, we develop some simple yet relevant numerica models for the diffractive slits. The proposed design ideas have the potential to be implemented in future UGTS while maintaining sufficiently low friction in the industrial design process, sufficiently low cost and high performance in the user experience.
IEEE International Conference on Acoustics Speech and Signal Processing, 2002
Identification of the channel matrix is of main concern in wireless MIMO (Multiple Input Multiple... more Identification of the channel matrix is of main concern in wireless MIMO (Multiple Input Multiple Output) systems. Here, we present an SVDbased approach for blind identification of the main independent parallel channels. The right and left singular vectors are estimated directly (no channel matrix estimation is necessary) and continuously updated during normal transmission. The approach is related to the iterative Power Method [8], as well as the time reversal approach ([4]).
Ultrasonics, 2014
Airborne ultrasound is a rapidly developing subfield within human-computer interaction (HCI). Tou... more Airborne ultrasound is a rapidly developing subfield within human-computer interaction (HCI). Touchless ultrasonic interfaces and pen tracking systems are part of recent trends in HCI and are gaining industry momentum. This paper aims to provide the background and overview necessary to understand the capabilities of ultrasound and its potential future in human-computer interaction. The latest developments on the ultrasound transducer side are presented, focusing on capacitive micro-machined ultrasonic transducers, or CMUTs. Their introduction is an important step toward providing real, low-cost multi-sensor array and beam-forming options. We also provide a unified mathematical framework for understanding and analyzing algorithms used for ultrasound detection and tracking for some of the most relevant applications.
IEEE Transactions on Signal Processing, 2004
Identification of the channel matrix is of main concern in wireless multiple input multiple outpu... more Identification of the channel matrix is of main concern in wireless multiple input multiple output (MIMO) systems. To maximize the SNR, the best way to utilize a MIMO system is to communicate on the top singular vectors of the channel matrix. Here, we present a new approach for direct blind identification of the main independent singular modes, without estimating the channel matrix itself. The right and left singular vectors with maximum corresponding singular values are determined using payload data and are continuously updated while at the same time being used for communication. The feasibility of the approach is demonstrated by simulating the performance over a noisy, fading time-varying channel. Mathematically, the technique is related to the iterative numerical Power method for finding eigenvalues of a matrix as well as the "time reversal mirror" technique developed within acoustics.
Food Quality and Preference, 2004
... Procrustes methods have also found useful applications in another completely different branch... more ... Procrustes methods have also found useful applications in another completely different branch of statistics, namely statistical shape analysis (see [Dryden & Mardia, 1997] , [Goodall, 1991] , [Kendall, 1984] and [Kendall, 1989] ). ...
Food Quality and Preference, 2009
In this paper we discuss methods for detecting outlying assessors in descriptive sensory analysis... more In this paper we discuss methods for detecting outlying assessors in descriptive sensory analysis. A new method is proposed which is based on fuzzy clustering with the use of the noise cluster method. The technique ends up with a plot which can be used to provide information about which assessors that are different from the rest and also to suggest reasons why the assessors are different. The method is based on data compression by the use of either Tucker-1 or Tucker-2 for multi-block data. The technique is used on a dataset based on an oxidation experiment of cheese. There are 9 trained and 3 untrained assessors in the panel.
Food Quality and Preference, 2008
In this paper we propose some new plots for three-way analysis of sensory data. One of the plots ... more In this paper we propose some new plots for three-way analysis of sensory data. One of the plots is called ''Manhattan plot" and offers an alternative way of presenting explained variances, while the ''Hiding plot" provides information about how the different axes in the consensus space are related to the original measurements. Correlation loadings plots exhibit correlations between the common scores acquired from the consensus matrix and the variables in the original multi-way data. For the computation of the consensus matrices we propose a new tool that bridges Generalised Canonical Analysis and Tucker-1 by defining intermediate combinations of the two. This is accomplished by altering a parameter in a more general model that covers these two methods. Three-way sensory profiling data from cheese are used as input for this general model to compute consensus matrices at different values for the parameter. External validation is pointed out as a useful tool for indicating which of the two statistical methods is most appropriate for computing a consensus matrix representing all assessors.
A new method is proposed for blindly estimating the top singular modes in a reciprocal MIMO Outpu... more A new method is proposed for blindly estimating the top singular modes in a reciprocal MIMO Output) channel, while at the same time using these modes for multi-stream communication without the need for training data. The uplink and downlink parties obtain the relevant singular modes from the received data blocks as the eigenvectors/eigenvalues of the spatial empirical correlation matrices. The only requirement is that the separate data streams are statistically uncorrelated. The approach relies on a key and simple "need to know" observation about MIMO transmission :