Daniel Weihs | Technion Israel Institute of Technology (original) (raw)

Papers by Daniel Weihs

Progress in IS, 2018

This chapter discusses the problems arising from the development of more and more capable and ind... more This chapter discusses the problems arising from the development of more and more capable and independent thinking machines, so-called “autosomes”. With this development, even the top level of knowledge workers in business are challenged, and it is not clear how things will play out. Adding autosomes to all levels of work will clearly make work-streams more efficient, but as machines start making decisions, the criteria for good and bad decisions, as well as loyalty (to the firm to the stakeholders, to mankind) may lead to unexpected results.

Pied kingfishers (Ceryle rudis) capture fish by plunge diving from hovering that may last several... more Pied kingfishers (Ceryle rudis) capture fish by plunge diving from hovering that may last several minutes. Hovering is the most energy-consuming mode of flight and depends on active wing flapping and facing headwind. The power for hovering is mass dependent increasing as the cube of the size, while aerodynamic forces increase only quadratically with size. Consequently, birds above a certain body mass can hover only with headwind and for very short durations. Hummingbirds are referred to as the only birds capable of hovering without wind (sustained hovering) due to their small size (ca. 2-20 gr), high wing-beat frequency and unique anatomy.We studied the hovering characteristics of pied kingfishers in relation to wind and sun orientation, in 139 hovers. Furthermore, plunge diving necessitates the coping with the visual effects of light at the air/water interface. The kingfishers oriented their body axis towards the wind more than towards the sun. Hovering in little or no wind was com...

The swimming behavior of larval northern anchovy, Engraulis mordax, in the first few days after h... more The swimming behavior of larval northern anchovy, Engraulis mordax, in the first few days after hatching is different from the intermittent beat-and-glide mode used by older larvae and later stage fish. It is shown mathematically that the bursts of continuous swimming typical of these yolk-sac larvae is the more efficient form oflocomotion at this stage, because of their small size. This advantage changes as the larva grows out of the size range in which water viscosity is the dominant factor (small Reynolds number). When the larva reaches a length of5 mm, typical Reynolds numbers are such that intermittent swimming gradually becomes the more economical mode, and this mode is dominant when the larvae reach 15 mm. These analytical results compare well with observed behavioral changes.

... Sunday–Tuesday, November 19–21, 2006; Tampa Bay, Florida. ... Session BM: Aerodynamics. 11:00... more ... Sunday–Tuesday, November 19–21, 2006; Tampa Bay, Florida. ... Session BM: Aerodynamics. 11:00 AM–12:44 PM, Sunday, November 19, 2006. Tampa Marriott Waterside Hotel and Marina Room: Meeting Room 10 Chair: Jamey Jacob, Oklahoma State University Abstract ID ...

Journal of Experimental Biology

Journal of Experimental Biology

The hunting flight of the kestrel (Falco tinnunculus) consists of short bouts of flight at wind s... more The hunting flight of the kestrel (Falco tinnunculus) consists of short bouts of flight at wind speed against the wind with the eyes in a fixed position relative to the ground, and of short flights from one such position to the next.

Journal of Experimental Biology

A theoretical model describes how an intermittent swimming style can be energetically advantageou... more A theoretical model describes how an intermittent swimming style can be energetically advantageous over continuous swimming at high average velocities. Kinematic data are collected from high-speed cine pictures of free swimming cod and saithe at high velocities in a burst-and-coast style. These data suggest that fish make use of the advantages shown by choosing initial and final burst velocities close to predicted optimal values. The limiting role of rapid glycogen depletion in fast white anaerobic muscle fibres is discussed.

The diurnal cycle of metabolic rate (MR, J/g.h, based on Vo2 and Vco2) was measured in 14 Griffon... more The diurnal cycle of metabolic rate (MR, J/g.h, based on Vo2 and Vco2) was measured in 14 Griffon Vultures (Gypsfulvus), two Hooded Vultures (Necrosyrtes monachus) and one White-backed Vulture (Gyps africanus) at different ambient temperatures (-7 to +34 °C).

International Journal of Ecology, 2014

Journal of biology, 2004

Drafting in cetaceans is defined as the transfer of forces between individuals without actual phy... more Drafting in cetaceans is defined as the transfer of forces between individuals without actual physical contact between them. This behavior has long been surmised to explain how young dolphin calves keep up with their rapidly moving mothers. It has recently been observed that a significant number of calves become permanently separated from their mothers during chases by tuna vessels. A study of the hydrodynamics of drafting, initiated in the hope of understanding the mechanisms causing the separation of mothers and calves during fishing-related activities, is reported here. Quantitative results are shown for the forces and moments around a pair of unequally sized dolphin-like slender bodies. These include two major effects. First, the so-called Bernoulli suction, which stems from the fact that the local pressure drops in areas of high speed, results in an attractive force between mother and calf. Second is the displacement effect, in which the motion of the mother causes the water in...

The Journal of experimental biology, 2001

Swimming movements in boxfishes were much more complex and varied than classical descriptions ind... more Swimming movements in boxfishes were much more complex and varied than classical descriptions indicated. At low to moderate rectilinear swimming speeds (<5 TL s(-1), where TL is total body length), they were entirely median- and paired-fin swimmers, apparently using their caudal fins for steering. The pectoral and median paired fins generate both the thrust needed for forward motion and the continuously varied, interacting forces required for the maintenance of rectilinearity. It was only at higher swimming speeds (above 5 TL s(-1)), when burst-and-coast swimming was used, that they became primarily body and caudal-fin swimmers. Despite their unwieldy appearance and often asynchronous fin beats, boxfish swam in a stable manner. Swimming boxfish used three gaits. Fin-beat asymmetry and a relatively non-linear swimming trajectory characterized the first gait (0--1 TL s(-1)). The beginning of the second gait (1--3 TL s(-1)) was characterized by varying fin-beat frequencies and ampli...

The Journal of experimental biology, 1982

A theoretical model describes how an intermittent swimming style can be energetically advantageou... more A theoretical model describes how an intermittent swimming style can be energetically advantageous over continuous swimming at high average velocities. Kinematic data are collected from high-speed ciné pictures of free swimming cod and saithe at high velocities in a burst-and-coast style. These data suggest that fish make use of the advantages shown by choosing initial and final burst velocities close to predicted optimal values. The limiting role of rapid glycogen depletion in fast white anaerobic muscle fibres is discussed.

Progress in IS, 2018

This chapter discusses the problems arising from the development of more and more capable and ind... more This chapter discusses the problems arising from the development of more and more capable and independent thinking machines, so-called “autosomes”. With this development, even the top level of knowledge workers in business are challenged, and it is not clear how things will play out. Adding autosomes to all levels of work will clearly make work-streams more efficient, but as machines start making decisions, the criteria for good and bad decisions, as well as loyalty (to the firm to the stakeholders, to mankind) may lead to unexpected results.

Pied kingfishers (Ceryle rudis) capture fish by plunge diving from hovering that may last several... more Pied kingfishers (Ceryle rudis) capture fish by plunge diving from hovering that may last several minutes. Hovering is the most energy-consuming mode of flight and depends on active wing flapping and facing headwind. The power for hovering is mass dependent increasing as the cube of the size, while aerodynamic forces increase only quadratically with size. Consequently, birds above a certain body mass can hover only with headwind and for very short durations. Hummingbirds are referred to as the only birds capable of hovering without wind (sustained hovering) due to their small size (ca. 2-20 gr), high wing-beat frequency and unique anatomy.We studied the hovering characteristics of pied kingfishers in relation to wind and sun orientation, in 139 hovers. Furthermore, plunge diving necessitates the coping with the visual effects of light at the air/water interface. The kingfishers oriented their body axis towards the wind more than towards the sun. Hovering in little or no wind was com...

The swimming behavior of larval northern anchovy, Engraulis mordax, in the first few days after h... more The swimming behavior of larval northern anchovy, Engraulis mordax, in the first few days after hatching is different from the intermittent beat-and-glide mode used by older larvae and later stage fish. It is shown mathematically that the bursts of continuous swimming typical of these yolk-sac larvae is the more efficient form oflocomotion at this stage, because of their small size. This advantage changes as the larva grows out of the size range in which water viscosity is the dominant factor (small Reynolds number). When the larva reaches a length of5 mm, typical Reynolds numbers are such that intermittent swimming gradually becomes the more economical mode, and this mode is dominant when the larvae reach 15 mm. These analytical results compare well with observed behavioral changes.

... Sunday–Tuesday, November 19–21, 2006; Tampa Bay, Florida. ... Session BM: Aerodynamics. 11:00... more ... Sunday–Tuesday, November 19–21, 2006; Tampa Bay, Florida. ... Session BM: Aerodynamics. 11:00 AM–12:44 PM, Sunday, November 19, 2006. Tampa Marriott Waterside Hotel and Marina Room: Meeting Room 10 Chair: Jamey Jacob, Oklahoma State University Abstract ID ...

Journal of Experimental Biology

Journal of Experimental Biology

The hunting flight of the kestrel (Falco tinnunculus) consists of short bouts of flight at wind s... more The hunting flight of the kestrel (Falco tinnunculus) consists of short bouts of flight at wind speed against the wind with the eyes in a fixed position relative to the ground, and of short flights from one such position to the next.

Journal of Experimental Biology

A theoretical model describes how an intermittent swimming style can be energetically advantageou... more A theoretical model describes how an intermittent swimming style can be energetically advantageous over continuous swimming at high average velocities. Kinematic data are collected from high-speed cine pictures of free swimming cod and saithe at high velocities in a burst-and-coast style. These data suggest that fish make use of the advantages shown by choosing initial and final burst velocities close to predicted optimal values. The limiting role of rapid glycogen depletion in fast white anaerobic muscle fibres is discussed.

The diurnal cycle of metabolic rate (MR, J/g.h, based on Vo2 and Vco2) was measured in 14 Griffon... more The diurnal cycle of metabolic rate (MR, J/g.h, based on Vo2 and Vco2) was measured in 14 Griffon Vultures (Gypsfulvus), two Hooded Vultures (Necrosyrtes monachus) and one White-backed Vulture (Gyps africanus) at different ambient temperatures (-7 to +34 °C).

International Journal of Ecology, 2014

Journal of biology, 2004

Drafting in cetaceans is defined as the transfer of forces between individuals without actual phy... more Drafting in cetaceans is defined as the transfer of forces between individuals without actual physical contact between them. This behavior has long been surmised to explain how young dolphin calves keep up with their rapidly moving mothers. It has recently been observed that a significant number of calves become permanently separated from their mothers during chases by tuna vessels. A study of the hydrodynamics of drafting, initiated in the hope of understanding the mechanisms causing the separation of mothers and calves during fishing-related activities, is reported here. Quantitative results are shown for the forces and moments around a pair of unequally sized dolphin-like slender bodies. These include two major effects. First, the so-called Bernoulli suction, which stems from the fact that the local pressure drops in areas of high speed, results in an attractive force between mother and calf. Second is the displacement effect, in which the motion of the mother causes the water in...

The Journal of experimental biology, 2001

Swimming movements in boxfishes were much more complex and varied than classical descriptions ind... more Swimming movements in boxfishes were much more complex and varied than classical descriptions indicated. At low to moderate rectilinear swimming speeds (<5 TL s(-1), where TL is total body length), they were entirely median- and paired-fin swimmers, apparently using their caudal fins for steering. The pectoral and median paired fins generate both the thrust needed for forward motion and the continuously varied, interacting forces required for the maintenance of rectilinearity. It was only at higher swimming speeds (above 5 TL s(-1)), when burst-and-coast swimming was used, that they became primarily body and caudal-fin swimmers. Despite their unwieldy appearance and often asynchronous fin beats, boxfish swam in a stable manner. Swimming boxfish used three gaits. Fin-beat asymmetry and a relatively non-linear swimming trajectory characterized the first gait (0--1 TL s(-1)). The beginning of the second gait (1--3 TL s(-1)) was characterized by varying fin-beat frequencies and ampli...

The Journal of experimental biology, 1982

A theoretical model describes how an intermittent swimming style can be energetically advantageou... more A theoretical model describes how an intermittent swimming style can be energetically advantageous over continuous swimming at high average velocities. Kinematic data are collected from high-speed ciné pictures of free swimming cod and saithe at high velocities in a burst-and-coast style. These data suggest that fish make use of the advantages shown by choosing initial and final burst velocities close to predicted optimal values. The limiting role of rapid glycogen depletion in fast white anaerobic muscle fibres is discussed.