arXiv subjects

Michael Courtney

Publications and source records attributed to Michael Courtney.

At least 37 records · Page 2Linked to original sources

arXiv2014

Is it Possible to Accurately Identify a Shooter's Face as Illuminated by the Muzzle Flash of a 22 LR Pistol?

The science of firearms muzzle flash has been dominated by three perspectives: 1) Does the muzzle flash reveal friendly positions to naked eye observers so as to draw fire from enemy combatants? 2) Can flash signatures be recognized by electronic surveillance with sufficient accuracy to identify source firearms? 3) Is the muzzle flash so bright as to diminish the night vision of friendly forces during a firefight? This paper addresses a fourth question: Does the muzzle flash of a specific cartridge provide sufficient duration and intensity of illumination with visible light to allow observers to positively identify a shooter's face? The experiment used two shooters firing a total of 20 shots from a 22 LR semi-automatic pistol. Shooters fired in randomized order, while eight observers (male US military veterans) attempted to identify the shooter for each trial shot. The firing range was mostly darkened with only enough ambient light to safely conduct firing tests at the direction of a range safety officer. There was not enough ambient light to identify the shooter's face. Observers correctly identified the shooter 54% of the time and failed to correctly identify the shooter 46% of the time. Observers were unanimous that there was no hint of any visible illumination on the shooter's face provided by the muzzle flash. In cases where the shooter was correctly identified, observers reported using visual cues such as the sillhouette of the shooters' hair and slight differences in arm positions when firing the pistol. Other people in the room (including the author) were in unanimous agreement that there was no illumination of the shooters' faces from discharge of a 22 LR pistol.

physics.pop-ph↗

arXiv2013

Seasonal Variations in Relative Weight of Lake Trout (Salvelinus namaycush), Kokanee Salmon (Oncorhynchus nerka), Rainbow Trout (Onocorhynchus mykiss), and Brown Trout (Salmo trutta) in Blue Mesa Reservoir, Colorado

Blue Mesa Reservoir is the largest body of water in Colorado and is located on the western slope of the Rocky Mountains at an elevation of 7520 feet. Blue Mesa Reservoir contains recreationally important populations of lake trout (Salvelinus namaycush), kokanee salmon (Oncorhynchus nerka), rainbow trout (Onocorhynchus mykiss), and brown trout (Salmo trutta). A management challenge in recent years has been the overpopulation of lake trout, which has led to a steep decline in abundance of kokanee salmon (a preferred food source) followed by a steep decline in body condition of the lake trout. Relative weight, Wr, is commonly used to assess body condition and prey availability of fish in a variety of ecosystems, but its seasonal variability has not been well documented in cold water species. Relative weight is 100 times the actual weight of a fish divided by expected weight (or standard weight) of that species at the measured total length. The present study uses multi-year, multi-season length and weight data provided by the Colorado Department of Parks and Wildlife to quantify seasonal variations in mean relative weight in these four species. It is found that lake trout consistently lose significant body condition between the spring and the fall of a given year, with a mean loss in relative weight of 11.7 +/- 2.4. In contrast, kokanee salmon tend to gain significant body condition between spring and fall with a mean gain in relative weight of 5.2 +/- 2.9. Rainbow trout tend to lose body condition between summer and fall with a mean loss of relative weight of 7.4 +/- 1.7. Brown trout tend to gain body condition between spring and fall with a mean gain of 5.6 +/- 1.8. These findings can be interpreted in terms of the feeding habits, forage availability, and metabolic activity of each species.

q-bio.PE↗

arXiv2013

Bullet Retarding Forces in Ballistic Gelatin by Analysis of High Speed Video

Though three distinct wounding mechanisms (permanent cavity, temporary cavity, and ballistic pressure wave) are described in the wound ballistics literature, they all have their physical origin in the retarding force between bullet and tissue as the bullet penetrates. If the bullet path is the same, larger retarding forces produce larger wounding effects and a greater probability of rapid incapacitation. By Newton's third law, the force of the bullet on the tissue is equal in magnitude and opposite in direction to the force of the tissue on the bullet. For bullets penetrating with constant mass, the retarding force on the bullet can be determined by frame by frame analysis of high speed video of the bullet penetrating a suitable tissue simulant such as calibrated 10% ballistic gelatin. Here the technique is demonstrated with 9mm NATO bullets, 32 cm long blocks of gelatin, and a high speed video camera operating at 20,000 frames per second. It is found that different 9mm NATO bullets have a wide variety of potential for wounding and rapid incapacitation. This technique also determines the energy transfer in the first 15 cm and/or first 30 cm of tissue, which are important parameters in estimating the probability of rapid incapacitation in some of the ARL/BRL models. This method predicts that some 9mm bullets have a much higher probability of rapid incapacitation than others and the rank ordering of bullet effectiveness is in agreement with other studies.

physics.med-ph↗

arXiv2012

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.

physics.ed-ph↗

arXiv2012

Plump Cutthroat Trout and Thin Rainbow Trout in a Lentic Ecosystem

Background: Much has been written about introduced rainbow trout (Oncorhynchus mykiss) interbreeding and outcompeting cutthroat trout (Oncorhynchus clarkii). However, the specific mechanisms by which rainbow trout and their hybrids outcompete cutthroat trout have not been thoroughly explored, and the published data is limited to lotic ecosystems. Materials and Methods: Samples of rainbow trout and cutthroat trout were obtained from a lentic ecosystem by angling. The total length and weight of each fish was measured and the relative weight of each fish was computed (Anderson R.O., Neumann R.M. 1996. Length, Weight, and Associated Structural Indices, Pp. 447-481. In: Murphy B.E. and Willis D.W. (eds.) Fisheries Techniques, second edition. American Fisheries Society.), along with the mean and uncertainty in the mean for each species. Data from an independent source (K.D. Carlander, 1969. Handbook of Freshwater Fishery Biology, Volume One, Iowa University Press, Ames.) was also used to generate mean weight-length curves, as well as 25th and 75th percentile curves for each species to allow further comparison. Results: The mean relative weight of the rainbow trout was 72.5 (+/- 2.1); whereas, the mean relative weight of the cutthroat trout was 101.0 (+/- 4.9). The rainbow trout were thin; 80% weighed below the 25th percentile. The cutthroat trout were plump; 86% weighed above the 75th percentile, and 29% were above the heaviest recorded specimens at a given length in the Carlander (1969) data set. Conclusion: This data casts doubt on the hypothesis that rainbow trout are strong food competitors with cutthroat trout in lentic ecosystems. On the contrary, in the lake under study, the cutthroat trout seem to be outcompeting rainbow trout for the available food.

q-bio.PE↗

arXiv2012

Weight-Length Relationships in Gafftopsail Catfish (Bagre marinus) and Hardhead Catfish (Ariopsis felis) in Louisiana Waters

In spite of the abundance and commercial importance of these two species, there is little published weight-length data for the gafftopsail catfish (Bagre marinus) and hardhead catfish (Ariopsis felis). For this study 84 catfish were caught (hook and line) from the Calcasieu Estuary in Southwest Louisiana near the Gulf of Mexico and estuaries and near shore waters close to bayou Lafourche. Using least squares regression, best fit curves were determined for weight (W) vs. total length (L) relationships in gafftopsail catfish, W(L) = 1000(L/484.73)^3.2660, while the best-fit equation for the hardhead was W(L) = 1000(L/469.53)^3.0188, where W is the weight in grams and L is the total length in millimeters. Results showed that, when compared to gafftopsail and hardhead catfish caught in Florida, Louisiana gafftopsail catfish tend to weigh less at similar lengths; whereas, the Louisiana hardhead catfish tend to weigh about the same. Results also show that the total length (TL) can be related to the fork length (FL) as TL = 1.184 FL in gafftopsail catfish with R^2 = 0.9922 and TL = 1.140 FL with R^2 = 0.9667 in hardhead catfish.

q-bio.PE↗

arXiv2012

Length, Weight, and Yield in Channel Catfish, Lake Diane, MI

Background: Channel catfish (Ictalurus punctatus) are important to both commercial aquaculture and recreational fisheries. Little published data is available on length-weight relationships of channel catfish in Michigan. Though there is no record of public or private stocking, channel catfish appeared in Lake Diane between 1984 and 1995 and it has developed into an excellent fishery. Results: NLLS regression yields parameter estimates of b = 3.2293 and a = 0.00522. The improved model yields the same estimate for the exponent, b, and a length estimate (parameter L1) of 45.23 cm. Estimates of uncertainty and covariance are smaller for the improved model, but the correlation coefficient is r = 0.995 in both cases. LLS regression produced different parameter values, a = 0.01356 and b = 2.9726, and a smaller correlation coefficient, r = 0.980. On average, catfish in the sample weighed 106.0% of the standard weight, (Brown et al.) and the linear regression (no slope) of fillet yield vs. total weight suggests a typical fillet yield of 28.1% with r = 0.989. Conclusion: Most of the fish in the sample were above the standard weight, heavier than the 75th percentile for their length. Channel catfish are doing well in Lake Diane and the population is well matched to the food supply. Management should attempt to maintain current population levels. In this case, the improved length-weight model, W(L) = (L/L1)^b, provided lower uncertainties in parameter estimates and smaller covariance than the traditional model.

q-bio.OT↗

arXiv2012

Relative Condition Factors of Fish as Bioindicators One Year after the Deepwater Horizon Oil Spill

Creel surveys were performed over a three week period in late spring, 2011, in the Lafourche and Calcasieu area estuaries of the Louisiana Gulf Coast. Weights and lengths were measured for black drum (Pogonias cromis), red drum (Sciaenops ocellatus), and spotted seatrout (Cynoscion nebulosus), and relative condition factors were calculated relative to expected weights from the long term (5 year) Louisiana data for each species. A normal relative condition factor is 1.00. The mean relative condition factors in the Lafourche area were black drum, 0.955 (0.020); red drum, 0.955 (0.011); spotted seatrout, 0.994 (0.009). In the Calcasieu area, the mean relative condition factors were black drum, 0.934 (0.017); red drum, 0.965 (0.014); spotted seatrout, 0.971 (0.010). Uncertainties are in parentheses. Results suggest that the abundance of primary food sources for black drum and red drum in Lafourche, including oysters and crab, were likely affected by the oil spill and continued to be reduced one year later. Increased harvest of oysters and blue crab in the Calcasieu area (in part to make up for the ban in most of Louisiana) resulted in less food for the black drum and red drum there, also. Spotted seatrout eat mainly shrimp and small fish and showed no significant reduction in relative condition factor in Lafourche and a slight reduction in Calcasieu one year after the oil spill.

q-bio.PE↗

arXiv2012

Science and Engineering Education: Who is the Customer?

As education systems move toward business models of operation, there is a strong tendency to misidentify the student as the customer. Misidentifying the student as the customer leads to interpretation of the course credit or degree as the product. The true product is the additional knowledge, skill, and ability that course credit and degree should represent. Consequences are potentially disastrous, because the notion that "the customer is always right" can lead to the perceived product (course credit or degree) meeting the desires of the misidentified "customer" (student) rather than the real product (value added to student) meeting the standards of the properly identified customers (future employers and taxpayers).

physics.ed-ph↗

arXiv2012

EI Videos

The Quantitative Reasoning Center (QRC) at USAFA has the institution's primary responsibility for offering after hours extra instruction (EI) in core technical disciplines (mathematics, chemistry, physics, and engineering mechanics). Demand has been tremendous, totaling over 3600 evening EI sessions in the Fall of 2010. Meeting this demand with only four (now five) full time faculty has been challenging. EI Videos have been produced to help serve cadets in need of well-modeled solutions to homework-type problems. These videos have been warmly received, being viewed over 14,000 times in Fall 2010 and probably contributing to a significant increase in the first attempt success rate on the Algebra Fundamental Skills Exam in Calculus 1. EI Video production is being extended to better support Calculus 2, Calculus 3, and Physics 1.

physics.ed-ph↗

arXiv2012

Oxy-acetylene driven laboratory scale shock tubes for studying blast wave effects

This paper describes the development and characterization of modular, oxy-acetylene driven laboratory scale shock tubes. Such tools are needed to produce realistic blast waves in a laboratory setting. The pressure-time profiles measured at 1 MHz using high speed piezoelectric pressure sensors have relevant durations and show a true shock front and exponential decay characteristic of free-field blast waves. Descriptions are included for shock tube diameters of 27 - 79 mm. A range of peak pressures from 204 kPa to 1187 kPa (with 0.5 - 5.6% standard error of the mean) were produced by selection of the driver section diameter and distance from the shock tube opening. The peak pressures varied predictably with distance from the shock tube opening while maintaining both a true blast wave profile and relevant pulse duration for distances up to about one diameter from the shock tube opening. This shock tube design provides a more realistic blast profile than current compression-driven shock tubes, and it does not have a large jet effect. In addition, operation does not require specialized personnel or facilities like most blast-driven shock tubes, which reduces operating costs and effort and permits greater throughput and accessibility. It is expected to be useful in assessing the response of various sensors to shock wave loading; assessing the reflection, transmission, and absorption properties of candidate armor materials; assessing material properties at high rates of loading; assessing the response of biological materials to shock wave exposure; and providing a means to validate numerical models of the interaction of shock waves with structures. All of these activities have been difficult to pursue in a laboratory setting due in part to lack of appropriate means to produce a realistic blast loading profile.

physics.med-ph↗

arXiv2012

High-speed measurement of firearm primer blast waves

This article describes a method and results for direct high-speed measurements of firearm primer blast waves employing a high-speed pressure transducer located at the muzzle to record the blast pressure wave produced by primer ignition. Key findings are: 1) Most of the lead styphnate based primer models tested show 5.2-11.3% standard deviation in the magnitudes of their peak pressure. 2) In contrast, lead-free diazodinitrophenol (DDNP) based primers had standard deviations of the peak blast pressure of 8.2-25.0%. 3) Combined with smaller blast waves, these large variations in peak blast pressure of DDNP-based primers led to delayed ignition and failure to fire in brief field tests.

physics.pop-ph↗

arXiv2011

An Assessment of Weight-Length Relationships for Muskellunge,Northern Pike, and Chain Pickerel In Carlander's Handbook of Freshwater Fishery Biology

Carlander's Handbook of Freshwater Fishery Biology (1969) contains life history data from many species of freshwater fish found in North America. It has been cited over 1200 times and used to produce standard-weight curves for some species. Recent work (Cole-Fletcher et al. 2011) suggests Carlander (1969) contains numerous errors in listed weight-length equations. This paper assesses the weight-length relationships listed in Carlander for muskellunge, northern pike, and chain pickerel by comparing graphs of the weight vs. length equations with other data listed and with standard weight curves published by independent sources. A number of discrepancies are identified through this analysis and new weight-length relationships are produced from listed data.

q-bio.QM↗

arXiv2011

Demonstrating an Improved Length-weight Model in Largemouth Bass, Chain Pickerel, Yellow Perch, Black Crappie, and Brown Bullhead in Stilwell Reservoir, West Point, New York

The traditional power law model, W(L) = aL^b, is widely applied to describe weight (W) vs. length (L) in fish. The model, W(L) = (L/L1)^b, is proposed as an improvement. The Levenberg-Marquardt non-linear least squares technique is used to determine the best-fit parameters L1 and b. This model has the advantages that L1 has the same units (length) independent of the value of the exponent and has an easily interpreted physical meaning as the typical length of a fish with one unit of weight. This proposed model is compared with the traditional model on length-weight data sets for black crappie, largemouth bass, chain pickerel, yellow perch, and brown bullhead obtained from Stilwell Reservoir, West Point, New York. The resulting best-fit parameters, parameter standard errors, and covariances are compared between the two models. The average relative weight for these species is determined, along with typical meat yields for four species. For the five species, using the logarithmic approach and a linear least-squares, standard errors in the coefficient, a, range from 60.2% to 136.5% for the traditional model. Using a non-linear least squares technique to determine best fit parameters, the standard errors for the coefficient, a, range from 68.5% to 164.0% in the traditional model. In the improved model, standard errors in the parameter L1 range from 0.94% to 15.0%. The covariance between a and b in the traditional model has a magnitude between 0.999 and 1.000 in both linear and non-linear parameter estimation methods. In the improved model, the covariances between L1 and b are smaller. The improved model, W(L) = (L/L1)^b, is preferable for weight vs. length in fish, because the estimated parameter uncertainties and covariances are smaller in magnitude. Furthermore, the parameters both have consistent units and an easily interpreted physical meaning.

q-bio.QM↗

arXiv2011

Cerebrovascular injury caused by a high strain rate insult in the thorax

Primary blast-induced traumatic brain injury (TBI) has increased in documented incidence and public prominence in recent conflicts. Evidence for a thoracic mechanism of blast-induced TBI was recently reviewed and, while the totality is compelling, data from experiments isolating this mechanism is sparse. Notably, one recent study showed pericapillar haemorrhage in brain tissue from victims of single, fatal gunshot wounds to the chest. Here, qualitative results are reported for a small field study that isolated a thoracic mechanism for TBI caused by a high strain rate insult in white-tailed deer (Odocoileus virginianus, mass 49-80 kg) in a natural environment. In each of three cases, petechiae were present on the surface of the frontal, occipital and/or left parietal lobes, along with capillary damage in the choroid plexus. The location of the projectile impact to the thorax seemed to affect the degree of damage. This may be due to the proximity to the great vessels. The data reported here provides direct evidence of a thoracic mechanism resulting in gross injury to the cerebral vasculature.

physics.med-ph↗

arXiv2011

Errors in Length-weight Parameters at FishBase.org

To investigate possible errors, length-weight parameters from FishBase.org were used to graph length-weight curves for six different species: channel catfish, black crappie, largemouth bass, rainbow trout, flathead catfish, and lake trout along with the standard weight curves (Anderson and Neumann 1996, Bister et al. 2000). Parameters noted as doubtful by FishBase were excluded. For each species, variations in curves were noted, and the minimum and maximum predicted weights for a 30 cm long fish were compared with each other and with the standard weight for that length. For lake trout, additional comparisons were made between the parameters and study details reported in FishBase.org for 6 of 8 length-weight relationships and those reported in the reference (Carlander 1969) for those 6 relationships. In all species studied, minimum and maximum curves produced with the length-weight parameters at FishBase.org are notably different from each other, and in many cases predict weights that are clearly absurd. For example, one set of parameters predicts a 30 cm rainbow trout weighing 44 g. For 30 cm length, the range of weights (relative to the standard weight) for each species are: channel catfish (31.4% to 193.1%), black crappie (54.0% to 149.0%), largemouth bass (28.8% to 130.4%), rainbow trout (14.9% to 113.4%), flathead catfish (29.3% to 250.7%), and lake trout (44.0% to 152.7%). Length-weight tables at FishBase.org are not generally reliable and the on-line database contains dubious parameters. Assurance of quality probably will require a systematic review with more careful and comprehensive methods than those currently employed.

q-bio.QM↗

arXiv2011

Echo-based measurement of the speed of sound

The speed of sound in air can be measured by popping a balloon next to a microphone a measured distance away from a large flat wall, digitizing the sound waveform, and measuring the time between the sound of popping and return of the echo to the microphone. The round trip distance divided by the time is the speed of sound.

physics.pop-ph↗

arXiv2011

The Evening Tutoring Center at the United States Air Force Academy

The United States Air Force Academy (USAFA) has opened an Evening Tutoring Center to provide after-hours tutoring every evening before class days. The center focuses on first and second year courses in challenging quantitative disciplines: mathematics, physics, chemistry, and engineering mechanics. Staffed exclusively by faculty-level instructors, the center offers extra instruction to all first and second year cadets. Early demand has been remarkable, and early indications are that cadets who visit the center for extra instruction in mathematics perform better than peers with comparable backgrounds.

physics.ed-ph↗