3,362 research outputs found
Review of Magnetic Shark Deterrents: Hypothetical Mechanisms and Evidence for Selectivity
Several papers published since 2006 describe effects of magnetic fields on
elasmobranchs and assess their utility in reducing negative interactions
between sharks and humans, including bycatch reduction. Most of these repeat a
single untested hypothesis regarding physical mechanisms by which elasmobranchs
detect magnetic fields and also neglect careful consideration of
magnetoreception in teleosts. Several species of teleosts are known to have
magnetoreception based in biogenic magnetite, and direct magnetic field
detection also has support in several species of elasmobranchs. The overly
narrow focus of earlier papers on the unsupported hypothesis that
magnetoreception in elasmobranchs is based in the ampullae of Lorenzini creates
the impression that all teleosts will be insensitive to magnetic deterrents.
However, magnetite based magnetoreception has been demonstrated in several
teleosts, and is supported in others. Furthermore, electroreception is present
in many teleost species; therefore, the possibility of induction based indirect
magnetoreception should be considered. Finally, experiments reported as
demonstrating insensitivity in teleost species to magnetic deterrents suffer
from inadequate design and sample sizes to reject the hypothesis of magnetic
detection in any given species. Since adoption of deterrent hook technologies
depends on both deterrent effects in sharks and the absence of effects in
target teleosts, the hypothesis of detection in teleost species must be
independently tested with adequate sample sizes.Comment: 11 page
Experimental Tests of the Proportionality of Aerodynamic Drag to Air Density for Supersonic Projectiles
Pure theory recognizes the dependence of supersonic drag coefficients on both
Mach number and Reynolds number, which includes an implicit dependence of drag
coefficient on air density. However, many modern approaches to computing
trajectories for artillery and small arms treat drag coefficients as a function
of Mach number and assume no dependence on Reynolds number. If drag force is
strictly proportional to air density for supersonic projectiles (as suggested
by applied theory), the drag coefficient should be independent of air density
over a range of Mach numbers. Experimental data to directly support this are
not widely available for supersonic projectiles. The experiment determined drag
on a 2.59 g projectile from M1.2 to M2.9 using optical chronographs to measure
initial and final velocities over a separation of 91.44 m. The free flight
determination of drag coefficients was performed at two significantly different
atmospheric densities (0.93 kg/m3 and 1.15 kg/m3 ). This experiment supported
direct proportionality of aerodynamic drag to air density from M1.2 to M2.9
within the experimental error of 1%-2%
A method for testing bullets at reduced velocity
Reconstruction of shooting events occasionally requires testing of bullets at
velocities significantly below the typical muzzle velocity of cartridge arms.
Trajectory, drag, and terminal performance depend strongly on velocity, and
realistic results require accurately reconstructing the velocity. A method is
presented for testing bullets at reduced velocities by loading the bullet into
a sabot and firing from a muzzle loading rifle with a suitably reduced powder
charge. Powder charges can be safely reduced to any desirable level when
shooting saboted bullets from a muzzleloader; in contrast, cartridge arms can
only be safely operated within a narrow window of powder charges/muzzle
velocities. This technique is applicable to a wide range of both pistol and
rifle bullets at velocities from 700 ft/s to 2000 ft/s
Apparent measurement errors in "Development of biomechanical response corridors of the thorax to blunt ballistic impacts"
"Development of biomechanical response corridors of the thorax to blunt
ballistic impacts" (Bir, C., Viano, D., King, A., 2004, Journal of Biomechanics
37, 73-79.) contains apparent measurement errors. Areas under several force vs.
time (Fig. 2) and force vs. deflection curves (Fig.4) differ significantly from
the momentum and kinetic energy changes, respectively. These differences
violate Newton's second law and the work-energy theorem
An Acoustic Method for Determining Ballistic Coefficients
This paper presents a method for using a PC soundcard, microphone and a
chronograph to determine bullet BC with an accuracy of 6%. This is useful when
a second chronograph is unavailable or when the projectile accuracy is
insufficient to use a far chronograph.Comment: Related to forensic science (shooting event reconstruction
The Truth About Ballistic Coefficients
The ballistic coefficient of a bullet describes how it slows in flight due to
air resistance. This article presents experimental determinations of ballistic
coefficients showing that the majority of bullets tested have their previously
published ballistic coefficients exaggerated from 5-25% by the bullet
manufacturers. These exaggerated ballistic coefficients lead to inaccurate
predictions of long range bullet drop, retained energy and wind drift.Comment: related to forensic science (shooting event reconstructions
Acoustic measurement of potato cannon velocity
This article describes measurement of potato cannon velocity with a digitized
microphone signal. A microphone is attached to the potato cannon muzzle and a
potato is fired at an aluminum target about 10 m away. The potato's flight time
can be determined from the acoustic waveform by subtracting the time in the
barrel and time for sound to return from the target. The potato velocity is
simply the flight distance divided by the flight time.Comment: 3 page
Impossible? Publication Quality Research with the Weakest 10% of Incoming Freshmen
Undergraduate research is widely regarded as a high impact practice. However,
usually only the highest achieving students are rewarded with undergraduate
research opportunities. This paper reports on the successful implementation of
a student research program offering the weakest 10% of incoming freshmen
opportunities to conduct original research in one of several science or
engineering disciplines with the possibility of publication if the research and
report meet a suitable standard, defined as earning an A on the final research
project report in the introductory math course. The opportunity has been
offered now for two years to incoming cadets at the United States Air Force
Academy who are placed in Basic Math. The cadets placed in this course score in
the bottom 5% of incoming cadets on the math placement exam. During the second
semester of their freshman year, cadets enrolled in Calculus 1 are also offered
a similar research opportunity. About 10% of cadets are enrolled in this course
each Spring, the 5% who began in Basic Math and matriculate to Calculus 1 and
the 5% who failed Calculus 1 in their first attempt. During the first four
semesters, the program has yielded 22 cadet papers which have been published or
are currently under review and expected to be published. This represents
approximately 38% of the projects in the program, because the majority of the
projects do not earn As and are not suitable for publication. Over 80% of the
cadet co-authors on the publication quality papers are minorities, women,
and/or intercollegiate athletes.Comment: 12 page
Ballistic pressure wave contributions to rapid incapacitation in the Strasbourg goat tests
This article presents empirical models for the relationship between peak
ballistic pressure wave magnitude and incapacitation times in the Strasbourg
goat test data. Using a model with the expected limiting behavior at large and
small pressure wave magnitudes, the average incapacitation times are highly
correlated (R = 0.91) with peak pressure wave magnitude. The cumulative
incapacitation probability as a function of time reveals both fast (t < 5 s)
and slow (t > 5 s) incapacitation mechanisms. The fast incapacitation mechanism
can be accurately modeled as a function of peak pressure wave magnitude. The
slow incapacitation mechanism is presumably due to blood loss via damaged
vascular tissue.Comment: Related to traumatic brain injur
The Ballistic Pressure Wave Theory of Handgun Bullet Incapacitation
This paper presents a summary of seven distinct chains of evidence, which,
taken together, provide compelling support for the theory that a ballistic
pressure wave radiating outward from the penetrating projectile can contribute
to wounding and incapacitating effects of handgun bullets. These chains of
evidence include the fluid percussion model of traumatic brain injury,
observations of remote ballistic pressure wave injury in animal models,
observations of rapid incapacitation highly correlated with pressure magnitude
in animal models, epidemiological data from human shootings showing that the
probability of incapacitation increases with peak pressure magnitude, case
studies in humans showing remote pressure wave damage in the brain and spinal
cord, and observations of blast waves causing remote brain injury.Comment: eight page
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