Shot Distance Research Articles

Muscular activity of different shooting distances, different release techniques, and different performance levels, with and without stabilizers, in target archery

The quadruple approach in the title refers to four different studies over a period of 3 years. The common factor in these studies is the methodology of the (Brussels) Electromyographic Signal Processing and Analysis System (ESPAS), a hardware and software EMG data acquisition system that has constantly been improved. Therefore, the ESPAS methodology is described extensively (i.e. the electrodes, amplifier, tape-recorder and processing hardware). Experiment 1 investigated muscular behaviour in target shooting, both indoors (18 and 25 m) and outdoors (50, 70 and 90 m). It was found (via iEMG) that a significant increase in activity only exists between 25 and 50 m, and that there is no linear increase of activity with increased distance. No differences in muscular pattern (IDANCO system: Clarys and Cabri, 1988) or activity between the indoor distances and between the outdoor distances were found. Experiment 2 investigated the muscular economy of four string grips: the three-finger grip, two-finger grip, thumb grip and reversed grip. The largest variations in activity were found for the two most unfamiliar grips, i.e. the thumb and reversed grips; however, low iEMG and the rapid precision improvement (over a limited number of shots) suggest that the thumb grip, if practised long enough, might be the most economical technique. Experiment 3 attempted to differentiate muscular activity and a number of performance variables in three different populations of archers--Olympic athletes, National competitors and beginners--in order to obtain feedback regarding improved performance. Apparently, overall muscle pattern, intensities and arrow speed were not discriminatory. The differences found between the groups (or levels of skill) were affected by the ability to reproduce identical patterns and arrow velocities in consecutive shots and by the constancy of neuromuscular control of the M. trapezius, M. biceps brachii and M. extensor digitorum. Finally, Experiment 4 investigated the muscular activity of elite archers shooting at distances of 70 and 90 m with and without stabilizers. Differences in iEMG were not supported by differences in precision. Over time, the low iEMG in shooting without stabilizers increases precision and delays fatigue.

Determination of gunshot residues (GSR) in biological samples by means of Zeeman atomic absorption spectrometry

In forensic science the determination of distance of shooting is generally performed by evidence of gunshot residues (GSR), especially lead, antimony, barium, and copper. Concerning the determination of shooting distance on the basis of skin, X-ray-fluorescence was exclusively used in the past. In order to increase the detection limits of GSR elements in connection with newly developed ammunitions, samples of test shootings on skin of pigs are analysed by direct Zeeman atomic absorption spectroscopy. The determination of GSR elements is made from skin samples without any preparations (only lead) and from freeze-dried and pulverised samples (lead and antimony).

Accuracy in determining long-range firing position of gunman

Treating the example of a 9 mm Parabellum bullet, the paper deals with the problem of shot distance determination at long ranges. It discusses the effects of inaccurately known angles of incidence as well as of weather and ammunition data and shows that the results of computations can only indicate a certain limited area as the possible position of the shooter.

The third Kurayosi explosion and the crustal structure in the western part of Japan.

The third Kurayosi explosion was fired by the Research Group for Explosion Seismology on November 21, 1970 in order to detect the seismic waves reflected from deep crustal boundaries. Very clear reflected waves from the Conrad discontinuity were recorded by the instrument for seismic prospecting (E.T.L. recorder). There was also weak indication of the reflection from the Mohorovicic discontinuity in the records obtained at closely spaced temporary observation points equipped with FM data recorders at the shot distance of about 100km. On the basis of these results, a revision was made for the previous model. The crustal thickness obtained is about 35km and the Pn velocity, about 7.8km/sec.

A study of apparent angles of emergence at Marathon Ontario from the Lake Superior data

Abstract A three component array of Willmore seismometers and a hydrophone were used to record the seismic events at Marathon, Ontario during the Lake Superior crustal experiment of 1963. The first part of each record was digitized and from an analysis of the particle motion diagrams, apparent angles of emergence of the seismic rays were determined. It was found that these angles can be used to distinguish between P2 and Pn waves. When the shot distance was less than 220 km., the first arrivals emerged with an apparent angle of 40-50°. As the shot distance was increased beyond 220 km., the rays emerged with an apparent angle of 51-70°. The apparent velocities of the (40-50) and the 51-70°) rays were 6.6 km/sec and 8.2 km/sec respectively. Further analysis of the results showed that the Moho below Marathon dipped downwards toward the south west with an angle of approximately 4°, indicating that the crust is considerably thicker on the south west side of Marathon than on the north east. A study of the ray azimuths gave some evidence of the presence of lateral inhomogeneities in the crust.

CORRELATION A DISTANCE CONSTANTE EN SISMIQUE REFRACTION*

The usual computation methods in refraction seismic in the Sahara often involve considerable shot distances. Therefore, in addition to a high consumption of explosives, difficulties of operation and interpretation arise.In order to cut down the shot distances, it was necessary to study with great care the refracted waves having the shortest possible traveling path along the marker. Such paths correspond to the zone of great relative energy resulting, on one hand, from the sudden increase of reflected energy beyond the critical angle (total reflection) and, on the other hand, from the sudden appearance of refracted energy. The proposed method is founded on correlations of traces located in this “critical zone” on the different records shot on a profile; in order to get around certain difficulties due to insufficient knowledge of the marker velocity, the interpreter is led to select a constant correlation distance, at least for sections of the profile.The paper describes in detail the setting up and utilization of the proposed method, analyses a few examples and gives an estimate of the advantages and the restrictions of this method.

Remarks on refraction arrivals from a layer of finite thickness

I would like to discuss an unsolved problem which is particularly important from the practical point of view and to show on the basis of physical intuition in which direction the solution might lie. It deals with the character of the refraction arrival through a layer of finite thickness. One cannot arrive at conclusions regarding the character of the refraction arrival by studying only the disturbance which has traveled along the refraction path. To illustrate this point, consider a situation (Fig. 1) where the refracting layer is 5,000 feet deep and 100 feet across. In normal refraction work, the source-detector separation will be at least three times the depth to the refracting layer. our case, this corresponds to a shot distance of 15,000 feet. This means that the difference in the lengths of path traversed by the refracted ray and the ray which has been reflected once from the bottom of the layer is of the order of a foot. The wavelengths which are used in refraction work correspond to frequencies in the neighborhood of 10 cps. It follows that if the velocity in the refracting layer is 10,000 ft/sec, the ratio of wavelength to path difference is of the order of a thousand to one. In other words, a whole series of multiply reflected waves arrive within a time interval corresponding to one period. Therefore, in order to arrive at any conclusion regarding the character of the refraction arrival, one must consider the result obtained by superimposing all the waves which have been reflected at nearly grazing incidence.

NOMOGRAM FOR DIP COMPUTATIONS

A universal nomogram to be used in seismographing with three‐dimensional control is presented. This chart can be used for computing the dip components in and perpendicular to the wave‐travel plane. By a simple change of scales it can be adapted to all shot distances, geophone spreads, and all wave velocities which are functions of wave travel time only. Principles underlying the construction of the chart are given.

Melting point of diphenylamine

Shooting samples were produced on standard textile pats of six different ammunition types: four ammunitions with exclusively infrared luminescent propellant powder particles, one containing a mixture of luminescent and non-luminescent particles and one with only non-luminescent particles. Unburned propellant powder particles in the gunshot residue (GSR) on the textile of each sample were transferred onto TLC-plates with the aid of an organic solvent. The patterns of the partially and the all-luminescent propellant powder residue on the TLC-plates were visualized in the near infrared wavelength range by the aid of an IR-sensitive camera. The transfer TLC-plates of all six ammunition types were sprayed with a diphenylamine solution, which reacts with the nitrate groups of the nitrocellulose and nitroglycerine and produces deep blue dots thereof.A series of samples with different shooting distances produced with one of the ammunition types was used for the shooting distance determination study. Transfer on TLC-plates was performed and pictures of the plates were taken before and after the chemical reaction. An imaging software was used to measure the density of the particles on the transfer TLC-plate pictures within a defined area around the bullet hole. Curves were drawn with the particle density data vs. the shooting distance.It has been shown, that the transfer of the particles onto a TLC-plate and the chemical reaction eliminate the limitations of the IR-method presented in Part I. Therefore, this method allows shooting distance determination at any textile and for any ammunition type as soon as unburned propellant powder particles are left on the target tissue.