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Löfqvist, Torbjörn
Publications (10 of 37) Show all publications
Pamidi, T. R., Johansson, Ö. & Löfqvist, T. (2018). Comparison of Different Concepts of UltrasoundReactors Using Numerical Simulations. In: : . Paper presented at 16th Meeting of the European Society of Sonochemistry.
Open this publication in new window or tab >>Comparison of Different Concepts of UltrasoundReactors Using Numerical Simulations
2018 (English)Conference paper, Poster (with or without abstract) (Other (popular science, discussion, etc.))
Abstract [en]

Sonochemical reactors are used for process intensification based on efficientenergy transfer due to ultrasound in order to cause transient cavitation in the medium.Ultrasonic reactors are extensively used for numerous applications due to their differentfeatures. The process of ultrasound cavitation can be defined as generation, growth andviolent collapse of microbubbles under ultrasonic irradiation which can release a highamount of energy in a small volume. The released energy causes a sudden increase intemperature and pressure which thereby can lead to extensive process intensification. Thepresent work deals with the evaluation of two different configurations of ultrasound reactorsusing both numerical modeling and experimental verification. The evaluation is based onprediction of the pressure distribution, verified by foil tests and with calorimetric method.The two reactors were developed to be used for the treatment of cellulose fibers to improveenergy efficiency in the fibrillation process. The goal is to optimize cavitation intensityand minimize the coupling loss factors. The development and evaluation of these two reactorconcepts aim to improve the design methodology for a scalable flow through reactor conceptwith high yield and energy efficiency

National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Acoustics
Identifiers
urn:nbn:se:ltu:diva-73782 (URN)
Conference
16th Meeting of the European Society of Sonochemistry
Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-04-29
Johansson, Ö., Pamidi, T. R. & Löfqvist, T. (2017). Design of a high-intensity ultrasound reactor. In: : . Paper presented at 2017 IEEE International Ultrasonics Symposium (IUS),Washington, DC, 6-9 Sept. 2017. Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE)
Open this publication in new window or tab >>Design of a high-intensity ultrasound reactor
2017 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Design, and optimization of ultrasonic reactors are important objectives in sonochemical processing. The recent expansion of the use of ultrasonic reactors in various research areas all faces the problem of scaling up from laboratory results to industrial purposes. A traditional ultrasonic reactor usually has several issues, such as low effectiveness as well as complex and unstable system performance, which all are unfavorable for efficient sonochemical processing. This study addresses these issues and investigates a new flow type ultrasonic reactor designed to generate transient cavitation as the main source for ultrasound. Some important factors like pressure, material, flow and geometry are considered in the design. Numerical optimization as well as experimental investigations are performed to reach an optimized, energy-efficient and controlled ultrasound cavitation reactor. Results from numerical modeling are used for acoustic optimization of the reactor, which is driven with three transducers mounted radially in the reactor wall with 120° spacing. The final reactor is excited with dual frequencies a total of 9 sonotrodes. The reactor is intended to be used in studies of pre-treatment of cellulose fibers aiming at developing an alternative, energy efficient fibrillation process and for ultrasound leaching of minerals.

Place, publisher, year, edition, pages
Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2017
National Category
Fluid Mechanics and Acoustics Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Acoustics; Industrial Electronics
Identifiers
urn:nbn:se:ltu:diva-66534 (URN)10.1109/ULTSYM.2017.8092948 (DOI)978-1-5386-3383-0 (ISBN)
Conference
2017 IEEE International Ultrasonics Symposium (IUS),Washington, DC, 6-9 Sept. 2017
Available from: 2017-11-09 Created: 2017-11-09 Last updated: 2017-11-24Bibliographically approved
Johansson, Ö., Pamidi, T. R. & Löfqvist, T. (2017). Design of a high-intensity ultrasound reactor. In: IEEE International Ultrasonics Symposium, IUS: . Paper presented at 2017 IEEE International Ultrasonics Symposium (IUS), Washington, DC, 6-9 Sept. 2017. Piscataway, NJ: IEEE Computer Society, Article ID 8091660.
Open this publication in new window or tab >>Design of a high-intensity ultrasound reactor
2017 (English)In: IEEE International Ultrasonics Symposium, IUS, Piscataway, NJ: IEEE Computer Society, 2017, article id 8091660Conference paper, Published paper (Refereed)
Abstract [en]

Design, and optimization of ultrasonic reactors are important objectives in sonochemical processing. The recent expansion of the use of ultrasonic reactors in various research areas all faces the problem of scaling up from laboratory results to industrial purposes. A traditional ultrasonic reactor usually has several issues, such as low effectiveness as well as complex and unstable system performance, which all are unfavorable for efficient sonochemical processing. This study addresses these issues and investigates a new flow type ultrasonic reactor designed to generate transient cavitation as the main source for ultrasound. Some important factors like pressure, material, flow and geometry are considered in the design. Numerical optimization as well as experimental investigations are performed to reach an optimized, energy-efficient and controlled ultrasound cavitation reactor. Results from numerical modeling are used for acoustic optimization of the reactor, which is driven with three transducers mounted radially in the reactor wall with 120° spacing. The final reactor is excited with dual frequencies a total of 9 sonotrodes. The reactor is intended to be used in studies of pre-treatment of cellulose fibers aiming at developing an alternative, energy efficient fibrillation process and for ultrasound leaching of minerals

Place, publisher, year, edition, pages
Piscataway, NJ: IEEE Computer Society, 2017
Series
IEEE International Ultrasonics Symposium, E-ISSN 1948-5719
National Category
Fluid Mechanics and Acoustics Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Acoustics; Industrial Electronics
Identifiers
urn:nbn:se:ltu:diva-66533 (URN)10.1109/ULTSYM.2017.8091660 (DOI)000416948400055 ()2-s2.0-85039413569 (Scopus ID)978-1-5386-3383-0 (ISBN)
Conference
2017 IEEE International Ultrasonics Symposium (IUS), Washington, DC, 6-9 Sept. 2017
Available from: 2017-11-09 Created: 2017-11-09 Last updated: 2018-01-16Bibliographically approved
Johansson, Ö., Löfqvist, T. & Pamidi, T. R. (2017). Design of high-intensity ultrasound reactor. In: IEEE International Ultrasonics Symposium, IUS: . Paper presented at 2017 IEEE International Ultrasonics Symposium (IUS), Washington, DC, 6-9 Sept. 2017. Piscataway, NJ: IEEE Computer Society, Article ID 8092948.
Open this publication in new window or tab >>Design of high-intensity ultrasound reactor
2017 (English)In: IEEE International Ultrasonics Symposium, IUS, Piscataway, NJ: IEEE Computer Society, 2017, article id 8092948Conference paper, Published paper (Refereed)
Abstract [en]

Design and optmiziation of ultrasonic reactors are important objectives in sonochemical processing. The recent expansion of the use of ultrasonic reactors in various research projects all faces the problem of scaling up laboratory results for industrial use. A traditional ultrasonic reactor usually has several issues, such as low effectiveness and complex and unstable system performance, which all are unfavorable for efficient sonochemical processing. This study adresses these issues and investigates a new flow type ultrasonic reactor designed to generate transient cavitation as the main source for ultrasound for sonochemical processing. This study proposes the principle of the flow type ultrasonic reactor design to generate transient cavitation. The objective of this work is to design an ultrasonic reactor with a new geometry. The idea is to improve process efficiency based on resonance enhanced ultrasound controlled cavitation

Place, publisher, year, edition, pages
Piscataway, NJ: IEEE Computer Society, 2017
Series
IEEE International Ultrasonics Symposium, ISSN 1948-5719
National Category
Fluid Mechanics and Acoustics Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Acoustics; Industrial Electronics
Identifiers
urn:nbn:se:ltu:diva-67244 (URN)10.1109/ULTSYM.2017.8092948 (DOI)000416948403005 ()2-s2.0-85039437533 (Scopus ID)978-1-5386-3383-0 (ISBN)
Conference
2017 IEEE International Ultrasonics Symposium (IUS), Washington, DC, 6-9 Sept. 2017
Available from: 2018-01-11 Created: 2018-01-11 Last updated: 2018-01-16Bibliographically approved
Hamfelt, J., Gustafsson, J., van Deventer, J., Löfqvist, T., Häggström, F. & Delsing, J. (2016). A passive Barkhausen noise sensor for low-power applications (ed.). In: (Ed.), 2016 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) Proceedings: . Paper presented at International Instrumentation and Measurement Technology Conference : 23/05/2016 - 26/05/2016 (pp. 280-284). Piscataway, NJ: IEEE Communications Society, Article ID 7520374.
Open this publication in new window or tab >>A passive Barkhausen noise sensor for low-power applications
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2016 (English)In: 2016 IEEE International Instrumentation and Measurement Technology Conference (I2MTC) Proceedings, Piscataway, NJ: IEEE Communications Society, 2016, p. 280-284, article id 7520374Conference paper, Published paper (Refereed)
Abstract [en]

This paper proposes a passive Barkhausen noise sensor design suitable for low power applications. The sensor uses a permanent magnet and the relative motion between itself and a measured specimen instead of the conventional method that uses a fixed sensor and an alternating magnetic field. Since this novel design is passive, the sensor is well suited for low power applications and could potentially be used in e.g. A condition monitoring system integrated into a rolling element bearing. Proof of concept testing has been performed showing that the proposed sensor produces similar results as conventional Barkhausen noise sensors when applied to specimens being cyclically loaded until failure in a rotating bending rig. The results imply that material fatigue detection using the Barkhausen noise can be performed with the proposed sensor at a fraction of the energy cost compared to a conventional sensor. This warrants future research into the development of the proposed sensor, its advantages, disadvantages, and functionality

Place, publisher, year, edition, pages
Piscataway, NJ: IEEE Communications Society, 2016
Series
I E E E Instrumentation and Measurement Technology Conference. Proceedings, ISSN 1091-5281
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Industrial Electronics
Identifiers
urn:nbn:se:ltu:diva-27126 (URN)10.1109/I2MTC.2016.7520374 (DOI)000382523600050 ()2-s2.0-84980398147 (Scopus ID)07898908-71e1-408f-9457-00c2f43688d4 (Local ID)9781467392204 (ISBN)07898908-71e1-408f-9457-00c2f43688d4 (Archive number)07898908-71e1-408f-9457-00c2f43688d4 (OAI)
Conference
International Instrumentation and Measurement Technology Conference : 23/05/2016 - 26/05/2016
Note

Validerad; 2016; Nivå 1; 2016-10-11 (andbra)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-09-06Bibliographically approved
Delsing, J., van Deventer, J., Eliasson, J., Johansson, J., Löfqvist, T. & Sandin, F. (2016). Concepts and Architecture for a Thumb-Sized Smart IoT Ultrasound Measurement System. In: IEEE Ultrasonic Symposium 2016: . Paper presented at IEEE Ultrasonic Symposium, Tours, France, 18-21 Sep 2016. Piscataway, NJ: IEEE conference proceedings
Open this publication in new window or tab >>Concepts and Architecture for a Thumb-Sized Smart IoT Ultrasound Measurement System
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2016 (English)In: IEEE Ultrasonic Symposium 2016, Piscataway, NJ: IEEE conference proceedings, 2016Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents the technology concepts for a “thumb”-sized self-contained ultrasonic IoT measurement sys- tem. An overall architecture is proposed, and key elements are discussed with solutions using existing technology, thus arguing that realization is possible with the current technology.

Such an ultrasonic IoT measurement system is constrained by its size and available energy, although it requires at least decent computational and communication resources. Because streaming data from such a device is not advisable from an energy viewpoint, there is a need for resource efficient (energy, memory and computational power) data analysis.

An architecture with the following parts as well as some implementation details and performance data are proposed here:

  • Energy supply, battery and super capacitor

  • Transducer excitation achieving almost zero electrical losses

  • Event detection sensor interface

  • Data aggregation using sparse approximation and learned

    feature dictionaries, adapted to resource constrained em-

    bedded systems

  • IoT communication protocols and implementations enabling

    event -based communication and System of Systems integra- tion capabilities

    The optimization of system level performance requires each subsystem to be optimized for the specific measurement situation taking into account the subsystem interdependencies. This can be performed using a combined electrical and acoustical model of the system. Here, the model allowing electronic and acoustic co-simulation using SPICE is an important tool bridging the electronic and acoustic domains. 

Place, publisher, year, edition, pages
Piscataway, NJ: IEEE conference proceedings, 2016
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Industrial Electronics
Identifiers
urn:nbn:se:ltu:diva-59677 (URN)10.1109/ULTSYM.2016.7728708 (DOI)978-1-4799-8182-3 (ISBN)978-1-4673-9897-8 (ISBN)
Conference
IEEE Ultrasonic Symposium, Tours, France, 18-21 Sep 2016
Projects
Arrowhead
Available from: 2016-10-12 Created: 2016-10-12 Last updated: 2018-06-11Bibliographically approved
Aitomäki, Y., Berglund, L., Noël, M., Linder, T., Löfqvist, T. & Oksman, K. (2016). Light scattering in cellulose nanofibre suspensions: Model and experiments (ed.). In: (Ed.), (Ed.), Computers in Chemistry Proceeding from ACS National Meeting San Diego: Proceeding from ACS National Meeting San Diego. Paper presented at American Chemical Society (ACS) National Meeting & Exposition : 13/03/2016 - 17/03/2016 (pp. 122). : American Chemical Society (ACS), Article ID CELL 235.
Open this publication in new window or tab >>Light scattering in cellulose nanofibre suspensions: Model and experiments
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2016 (English)In: Computers in Chemistry Proceeding from ACS National Meeting San Diego: Proceeding from ACS National Meeting San Diego, American Chemical Society (ACS), 2016, p. 122-, article id CELL 235Conference paper, Meeting abstract (Other academic)
Abstract [en]

Here light scattering theory is used to assess the size distribution in a suspension of cellulose as it is fibrillated from micro-scaled to nano-scaled fibres. A model based on Monte carlo simulations of the scattering of photons by different sizes of cellulose fibres was used to predict the UV-IF spectrum of the suspensions. Bleached cellulose hardwood pulp was tested and compared to the visually transparent tempo-oxidised hardwood cellulose nanofibres (CNF) suspension. The theoretical results show that different diameter size classes exhibit very different scattering patterns. These classes could be identified in the experimental results and used to establish the size class dominating the suspension. A comparison to AFM/microscope size distribution was made and the results indicated that using the UV-IF light scattering spectrum maybe more reliable that size distribution measurement using AFM and microscopy on dried CNF samples. The UV-IF spectrum measurement combined with the theoretical prediction can be used even at this initial stage of development of this model to assess the degree of fibrillation when processing CNF.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
National Category
Bio Materials Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Wood and Bionanocomposites; Industrial Electronics
Identifiers
urn:nbn:se:ltu:diva-27433 (URN)0e1f8cb1-032d-4e71-956c-b2aca7925036 (Local ID)0e1f8cb1-032d-4e71-956c-b2aca7925036 (Archive number)0e1f8cb1-032d-4e71-956c-b2aca7925036 (OAI)
Conference
American Chemical Society (ACS) National Meeting & Exposition : 13/03/2016 - 17/03/2016
Note
Godkänd; 2016; 20160418 (aitomaki)Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2017-11-25Bibliographically approved
Nordlund, M., Bhandary, S., Sanyal, B., Almqvist, N., Löfqvist, T. & Grennberg, H. (2016). Side-selective self-assembly of graphene and FLG on piezoelectric PVDF from suspension (ed.). Paper presented at . Journal of Physics D: Applied Physics, 49(7), Article ID 07LT01.
Open this publication in new window or tab >>Side-selective self-assembly of graphene and FLG on piezoelectric PVDF from suspension
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2016 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 49, no 7, article id 07LT01Article in journal (Refereed) Published
Abstract [en]

The deposition of few-layer graphene by self-assembly from suspension onto a piezoelectric polymer substrate is presented. The graphene self-assembles with negligible overlap between flakes, and with high selectivity for one of the faces of the substrate, an observation which is discussed and rationalized. A computational study on a model system further confirms the theory and supports the experimental results. The highest obtained degree of surface coverage was estimated to 77%

National Category
Other Physics Topics Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Experimental physics; Industrial Electronics
Identifiers
urn:nbn:se:ltu:diva-12657 (URN)10.1088/0022-3727/49/7/07LT01 (DOI)000369403700001 ()2-s2.0-84957599945 (Scopus ID)bd171426-9d23-4dac-a405-bf9941156e93 (Local ID)bd171426-9d23-4dac-a405-bf9941156e93 (Archive number)bd171426-9d23-4dac-a405-bf9941156e93 (OAI)
Note
Validerad; 2016; Nivå 2; 20160219 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Svanström, E., Linder, T. & Löfqvist, T. (2014). Analytical one-dimensional model for laser-induced ultrasound in planar optically absorbing layer (ed.). Paper presented at . Ultrasonics, 54(3), 888-893
Open this publication in new window or tab >>Analytical one-dimensional model for laser-induced ultrasound in planar optically absorbing layer
2014 (English)In: Ultrasonics, ISSN 0041-624X, E-ISSN 1874-9968, Vol. 54, no 3, p. 888-893Article in journal (Refereed) Published
Abstract [en]

Ultrasound generated by means of laser-based photoacoustic principles are in common use today and applications can be found both in biomedical diagnostics, non-destructive testing and materials characterisation. For certain measurement applications it could be beneficial to shape the generated ultrasound regarding spectral properties and temporal profile. To address this, we studied the generation and propagation of laser-induced ultrasound in a planar, layered structure. We derived an analytical expression for the induced pressure wave, including different physical and optical properties of each layer. A Laplace transform approach was employed in analytically solving the resulting set of photoacoustic wave equations. The results correspond to simulations and were compared to experimental results. To enable the comparison between recorded voltage from the experiments and the calculated pressure we employed a system identification procedure based on physical properties of the ultrasonic transducer to convert the calculated acoustic pressure to voltages. We found reasonable agreement between experimentally obtained voltages and the voltages determined from the calculated acoustic pressure, for the samples studied. The system identification procedure was found to be unstable, however, possibly from violations of material isotropy assumptions by film adhesives and coatings in the experiment. The presented analytical model can serve as a basis when addressing the inverse problem of shaping an acoustic pulse from absorption of a laser pulse in a planar layered structure of elastic materials.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Industrial Electronics
Identifiers
urn:nbn:se:ltu:diva-8569 (URN)10.1016/j.ultras.2013.10.019 (DOI)000329130100020 ()24262676 (PubMedID)2-s2.0-84891628340 (Scopus ID)715c2dcc-dc3e-4bdc-a8b2-de3e73ab0814 (Local ID)715c2dcc-dc3e-4bdc-a8b2-de3e73ab0814 (Archive number)715c2dcc-dc3e-4bdc-a8b2-de3e73ab0814 (OAI)
Note
Validerad; 2014; 20131029 (erisva)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Linder, T., Löfqvist, T., Wernersson, E. L. .. & Gren, P. (2014). Light scattering in fibrous media with different degrees of in-plane fiber alignment (ed.). Paper presented at . Optics Express, 22(14), 16829-16840
Open this publication in new window or tab >>Light scattering in fibrous media with different degrees of in-plane fiber alignment
2014 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, no 14, p. 16829-16840Article in journal (Refereed) Published
Abstract [en]

Fiber orientation is an important structural property in paper and other fibrous materials. In this study we explore the relation between light scattering and in-plane fiber orientation in paper sheets. Light diffusion from a focused light source is simulated using a Monte Carlo technique where parameters describing the paper micro-structure were determined from 3D x-ray computed tomography images. Measurements and simulations on both spatially resolved reflectance and transmittance light scattering patterns show an elliptical shape where the main axis is aligned towards the fiber orientation. Good qualitative agreement was found at low intensities and the results indicate that fiber orientation in thin fiber-based materials can be determined using spatially resolved reflectance or transmittance.

National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Applied Mechanics
Research subject
Industrial Electronics; Experimental Mechanics
Identifiers
urn:nbn:se:ltu:diva-11199 (URN)10.1364/OE.22.016829 (DOI)000340674700017 ()2-s2.0-84904306888 (Scopus ID)a1c78736-b76c-41bb-bc0b-95eeadf04dfa (Local ID)a1c78736-b76c-41bb-bc0b-95eeadf04dfa (Archive number)a1c78736-b76c-41bb-bc0b-95eeadf04dfa (OAI)
Note
Validerad; 2014; 20140627 (tomlin)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
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