... on the future of ultrasonics chaired by L. Bjorno.In this forum, five panelists gave their view ... NDT (R. E. Green); (5) underwater ultrasonics (L.Bjorno).In these Proceedings I encounter a surprising number ...
Tópico(s): Music Technology and Sound Studies
1989 - Acoustical Society of America | The Journal of the Acoustical Society of America
Torunn Forberg, Eli Bjørnø Sjulstad, Ingrid Bakke, Yngvar Ôlsen, Atsushi Hagiwara, Yoshitaka Sakakura, Ôlav Vadstein,
The vertebrate gut is host to large communities of bacteria, and one of the beneficial contributions of this commensal gut microbiota is the increased nutritional gain from feed components that the host cannot degrade on its own. Fish larvae of similar age and under the same rearing conditions often diverge with regards to growth. The underlying reasons for this could be differences in genetic background, feeding behavior or digestive capacity. Both feeding behavior and digestion can be influenced ...
Tópico(s): Aquaculture disease management and microbiota
2016 - Nature Portfolio | Scientific Reports
A brief review of the basic principles of fluid mechanics needed for development of linear and nonlinear ultrasonic concepts will be given. The fundamental equations of nonlinear ultrasonics will be derived and their physical properties explained. It will be shown how an originally monochromatic finite-amplitude ultrasonic wave, due to nonlinear effects, will distort during its propagation in time and space to form higher harmonics to its fundamental frequency. The concepts of shock formation will ...
Tópico(s): Ultrasound Imaging and Elastography
2010 - Elsevier BV | Physics Procedia
Nonlinear ultrasound forms an integrated discipline of nonlinear acoustics founded in 1755. A short outline of the state-of-the-art in nonlinear ultrasound in 1960 forms the introduction to this paper. Some of the most important contributions to the development in the theoretical, analytical and numerical basis of nonlinear ultrasound and in experimental investigations of nonlinear ultrasonic processes published during the period of 1960 through 2000 are discussed and their successes and failures ...
Tópico(s): Advanced Thermodynamics and Statistical Mechanics
2002 - Elsevier BV | Ultrasonics
Head flapping has often been considered to be deleterious for obtaining a tonpilz transducer with broadband, high power performance. In the present work, broadband, high power tonpilz transducers have been designed using the finite element (FE) method. Optimized vibrational modes including the flapping mode of the head are effectively used to achieve the broadband performance. The behavior of the transducer in its longitudinal piston mode and in its flapping mode is analysed for in-air and in-water ...
Tópico(s): Underwater Vehicles and Communication Systems
1997 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control
C. Bjerrum-Niese, L. Bjørnø, Marc Pinto, B. Quellec,
The paper discusses the development of a simulation tool to model high data-rate acoustic communication in shallow water. The simulation tool is able to generate synthetic time series of signals received at a transducer array after transmission across a shallow-water communication channel. The simulation tool is suitable for testing advanced signal processing techniques for message recovery. A channel model has been developed based on the physical aspects of the acoustic channel. Special emphasis ...
Tópico(s): Speech and Audio Processing
1996 - Institute of Electrical and Electronics Engineers | IEEE Journal of Oceanic Engineering
In-band full-duplex (IBFD) underwater acoustic (UWA) communication can significantly improve the throughput of UWA communication networks. In this paper, we focus on the self-interference (SI) channel modeling which is essential for SI cancellation in an IBFD modem. The SI consists of direct self-loop interference (SLI) and self multi-path interference (SMI) due to reflections from water surface and bottom. Therefore, we first propose a simplified finite element model for SLI in an IBFD UWA modem. Then ...
Tópico(s): Energy Harvesting in Wireless Networks
1991 - Elsevier BV | Ultrasonics
CT imaging is widely used in medical science over the last decades. The process of CT image reconstruction depends on many physical measurements such as radiation dose, software/hardware. Due to statistical uncertainty in all physical measurements in Computed Tomography, the inevitable noise is introduced in CT images. Therefore, edge-preserving denoising methods are required to enhance the quality of CT images. However, there is a tradeoff between noise reduction and the preservation of actual ...
Tópico(s): Image and Signal Denoising Methods
1988 - Elsevier BV | Ultrasonics
P.C. Pederson, Peter A. Lewin, L. Bjørnø,
Time-delay spectrometry (TDS) can conveniently be used for calibration and performance evaluation of piezoelectric electroacoustic transducers. The main emphasis of the work reported here is an experimental evaluation of the TDS technique. The TDS concept is introduced through a theoretical analysis. The experimental evaluation is carried out using specially designed measurement methods and instrumentation which uses a spectrum analyzer as the central analog signal processing unit. The optimal performance ...
Tópico(s): Underwater Acoustics Research
1988 - Institute of Electrical and Electronics Engineers | IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control
... Underwater Acoustics and Signal Processing, edited by Leif Bjorno (Reidel, Dordrecht, The Netherlands, 1981), pp. 87–91]. ...
Tópico(s): Water Systems and Optimization
1988 - Acoustical Society of America | The Journal of the Acoustical Society of America
Tópico(s): Social and Educational Sciences
1988 - Society of Media Researchers In Denmark | MedieKultur Journal of media and communication research
Eva Spaun, Kurt Bjørnø Klünder,
In spite of the very common occurrence of vaginal candidiasis in pregnant women (1), the uterus is seldom affected. There are few reports in the literature of intra‐uterine infection. the present paper presents a case of pla‐cental and fetal candidiasis in association with the presence of an intra‐uterine contraceptive device (IUD).
Tópico(s): Reproductive Health and Contraception
1986 - Informa | Acta Obstetricia Et Gynecologica Scandinavica
This review presents the state-of-the-art in applications of the second order acoustic non-linearity parameter, B/A, for the characterization of biological media. The close relationship between B/A and the molecular structure of certain liquids, as well as the influence of the inhomogeneous nature of biological materials on B/A, are discussed. The finite amplitude and the thermodynamic methods are presented, and their advantages, disadvantages and accuracy of data produced are discussed. A new and ...
Tópico(s): Ultrasound Imaging and Elastography
1986 - Elsevier BV | Ultrasonics
Speech separation algorithms are faced with a difficult task of producing high degree of separation without containing unwanted artifacts. The time–frequency (T–F) masking technique applies a real-valued (or binary) mask on top of the signal’s spectrum to filter out unwanted components. The practical difficulty lies in the mask estimation. Often, using efficient masks engineered for separation performance leads to presence of unwanted musical noise artifacts in the separated signal. This lowers the ...
Tópico(s): Structural Health Monitoring Techniques
1985 - Elsevier BV | Ultrasonics
Bjarne Rud, Kurt Bjørnø Klünder,
Abstract. With the aim of being able to advise women concerning a recommended interval between spontaneous abortion and a new pregnancy, the course of 91 pregnancies following spontaneous abortion was studied. Nineteen women conceived within the first 12 weeks. There were no abortions, and 18 pregnancies proceeded normally. Thirty women conceived between 12 and 26 weeks, 29 pregnancies proceeded normally, and none aborted. Forty‐two women conceived later than 26 weeks after the abortion. Seven pregnancies ...
Tópico(s): Ectopic Pregnancy Diagnosis and Management
1985 - Informa | Acta Obstetricia Et Gynecologica Scandinavica
This paper addresses the detection of weak astronomical signals that are contaminated by strong frequency-hopping (FH) interferers and suffer from missing samples. The problem is considered in the time–frequency domain and we successively suppress artifacts due to missing samples, estimate and remove FH interferers, and detect the weak astronomical signals. More specifically, we first suppress the artifacts due to missing samples by developing a waveform-adaptive time–frequency kernel. The instantaneous ...
Tópico(s): Ultrasonics and Acoustic Wave Propagation
1983 - Elsevier BV | Ultrasonics
In this paper, we propose complete radiation boundary conditions (CRBCs) for solutions of the convected Helmholtz equation with a uniform mean flow in a waveguide. We first study CRBCs for the Helmholtz equation in a waveguide. Noting that the convected Helmholtz equation is associated with the Helmholtz equation via the Prandtl–Glauert transformation, CRBCs for the convected Helmholtz equation is derived from CRBCs for the Helmholtz equation. We analyse well-posedness and convergence of approximate ...
Tópico(s): Electromagnetic Simulation and Numerical Methods
1983 - Elsevier BV | Ultrasonics
Whilst heating is an important mechanism for in vivo irradiation it can be eliminated in the nonabsorbing medium of in vitro cell suspension. (Love & Kremkau, 1980). Also the use of short pulses and the absence of plane strong reflectors minimise standing wave effects. Even when present their damaging effects are apparently mediated by cavitational activity.In vitro mechanisms of interaction which have been clearly identified involve gas bubble activation, where radiation pressure forces attract cells ...
Tópico(s): Ultrasound and Cavitation Phenomena
1981 - Elsevier BV | Ultrasonics
The formation of the coarse columnar crystal structure of Ti-6Al-4V alloy in the process of additive manufacturing greatly reduces the mechanical performance of the additive manufactured parts, which hinders the applications of additive manufacturing techniques in the engineering fields. In order to refine the microstructure of the materials using the high intensity ultrasonic via the acoustic cavitation and acoustic flow effect in the process of metal solidification, an ultrasonic vibration technique ...
Tópico(s): Ultrasound and Cavitation Phenomena
1980 - Elsevier BV | Ultrasonics
Kurt Bjørnø Klünder, Bjarne Rud, Jørgen F. Hansen,
The possible relationship between football playing and osteoarthritis in the hip and knee joints has been examined. the results of clinical and radiographic examinations of 57 retired football players and a corresponding control group were compared. Osteoarthritis of the hip joint was found to occur significantly more often in the football players than in the controls. Such a relationship could not be found regarding the knee joint.
Tópico(s): Shoulder and Clavicle Injuries
1980 - Taylor & Francis | Acta Orthopaedica Scandinavica
Underwater explosions have found extensive application in technology, acoustics and physics. Most investigations using underwater explosions are performed as full-scale tests, this is mainly due to the widely held view that reliable measurements of pressure waves taken at a short range from the detonation of small amounts of chemical explosives are extremely difficult, if not impossible, to perform. On the basis of a number of tests where small amounts of explosives, ranging from 0.2 to 6 g were ...
Tópico(s): Combustion and Detonation Processes
1976 - Elsevier BV | Ultrasonics
Experiments and a simple theoretical analysis have been performed concerning the flow through circular (stenosis) and annular (catheter piece) lumen area reduction of rigid- and elastic-walled vessels. Both steady and pulsatile flow at various volumetric flow rates were investigated. A good agreement between the experimental and the analytical results has been found. A critical annular lumen area reduction exists on a par with the well-known critical stenosis. The strongest reduction in pressure and ...
Tópico(s): Cardiac Arrhythmias and Treatments
1976 - SAGE Publishing | Acta Radiologica Diagnosis
L. Gaete-Garretón, J.A. Gallego-Juárez, Enrique Riera,
This paper in memory of Leif Bjørnø deals with the non-linear acoustic problems linked to high-intensity ultrasonics, an area that he deeply cultivated. The generation, propagation and ... experimental work developed, partly on collaboration with Leif Bjørnø.
Tópico(s): Structural Health Monitoring Techniques
2017 - Acoustical Society of America | Proceedings of meetings on acoustics
Tópico(s): Underwater Acoustics Research
2003 - Pleiades Publishing | Acoustical Physics
A new PE model for solving three-dimensional, forward and backward sound propagation in a cylindrical coordinate system is presented. The model marches a wave field in the radial direction including the azimuthal diffraction effects, and solves for a backscattered field based on a three-dimensional, single scattering approach. A periodic sidewall boundary condition is applied for computations in a 360-degree sector, while an approximate sidewall boundary condition is used for calculation in a sector ...
Tópico(s): Ocean Waves and Remote Sensing
2000 - Acoustical Society of America | The Journal of the Acoustical Society of America
Natural laminar flow technology can significantly reduce aircraft aerodynamic drag and has excellent technical appeal for transport aircraft development with high aerodynamic efficiency. Accurately and efficiently predicting the laminar-to-turbulent transition and revealing the maintenance mechanism of laminar flow in a transport aircraft’s flight environment are significant for developing natural laminar flow wings. In this research, we carry out natural laminar flow flight experiments with different ...
Tópico(s): Vehicle Noise and Vibration Control
1985 - Elsevier BV | Ultrasonics
The volumetric flow rate and the pressure course through free and catheterized stenoses have been analysed experimentally. The influence of the following parameters has been considered: (a) the penetration depth of the catheter into stenoses of various geometrical shapes and various dimensions, (b) the length of the stenosis, (c) the size of the annular lumen area between the catheter and the stenosis wall, (d) the geometrical shape of the stenosis. Some previous attempts to derive a simple relation ...
Tópico(s): Renal and Vascular Pathologies
1977 - SAGE Publishing | Acta Radiologica Diagnosis
Peter D. Thorne, Shaobo Sun, Jingdong Zhang, Irina K. Bjørnø, Thierry Mazoyer,
Underwater acoustic studies of backscattering by submerged targets have generally focused on bodies with spherical and cylindrical symmetry. However, there are interests in scattering by objects which may be characterized by more angular features, with surfaces that tend to be composed of facets and edges. To investigate the scattering properties of such bodies, the backscattering by a number of elastic cubes, and irregularly shaped polyhedra, have been studied. Data were collected by measuring ...
Tópico(s): Geophysical Methods and Applications
1997 - Acoustical Society of America | The Journal of the Acoustical Society of America
Ben Toscher, Aksel Morris Bjørnø,
Entrepreneurship education in higher music education has grown rapidly, yet little is known about what music students think of entrepreneurship. Using a qualitative description approach guided by analytic rigor, we present results from a survey of 114 music students. Respondents most commonly define entrepreneurship as "self-employment" as introduced by McClelland, with a Schumpeterian theme of "innovation and disequilibrium" following behind. Fifty-two percent of respondents value entrepreneurial ...
Tópico(s): Cultural Industries and Urban Development
2019 - Routledge | The Journal of Arts Management Law and Society
An experimental and a theoretical investigation has been performed on some essential factors influencing the volumetric flow rate through and the static pressure in a catheterized, rigid-walled vessel model. These factors comprise: (a) the length of the catheter introduced into the vessel, (b) the catheter diameter, (c) the vessel diameter, (d) the dynamic viscosity of the liquid and (e) the mode of catheterization. Theoretical expressions for pressure and volumetric flow rates have been observed for ...
Tópico(s): Coronary Interventions and Diagnostics
1977 - SAGE Publishing | Acta Radiologica Diagnosis