An Effective Method of Simulation for the Leksell Gamma Knife Perfexion by Rotating Particles in the Phase Space File

Purpose: To develop an effective method of Monte Carlo simulation of the GammaKnife Perfexion system by rotating particles in the phase space file (PSF). This method does not require simulating of all 192 sources that are distributed in the conical form of the Perfexion collimator. The simulation was performed only for 5 out of 192 sources for each collimator size. Material and methods: Monte Carlo simulation of dose distribution for previous models of GammaKnife system requires phase space file for only one source, since this phase space is identical for all the 201 sources. The Perfexion model is more complex due to the non-coaxial positions of the sources and the complexity of the collimator system itself. In this work, we present an effective method to simulate the Perfexion model using a phase space file. Penelope Monte Carlo code was used to perform this simulation. In this method, the PSF was obtained for one source in each ring, resulting in five files for each collimator size. PSF for other sources were created by azimuthal redistribution of particles, in the obtained PSF, by rotation around the Z-axis. The phase space files of the same ring were then stored together in a single file. Results: The paper presented MC simulation using the azimuthal redistribution of particles in the phase space file by rotation around the Z-axis. The simulation has been validated comparing the dose profiles and output factors with the data of the algorithm TMR10 planning system Leksell Gamma Plan (LGP) in a homogeneous environment. The acceptance criterion between TMR10 and Monte Carlo calculations for the profiles was based on the gamma index (GI). Index values more than one were not detected in all cases, which indicates a good agreement of results. The differences between the output factors obtained in this work and the TMR10 data for collimators 8 mm and 4 mm are 0.74 and 0.73 %, respectively. Conclusion: In this work successfully implemented an effective method of simulating the Leksell Gamma knife Perfexion system. The presented method does not require modeling for all 192 sources distributed in the conical form of the Perfexion collimator. The simulation was performed for only five sources for each collimator and their files PSF were obtained. These files were used to create the PSF files for other sources by azimuthal redistribution of particles, in these files, by rotation around the Z-axis providing correct calculations of dose distributions in a homogeneous medium for 16, 8 and 4 mm collimators.

The role of shape-dependent flight stability in the origin of oriented meteorites

The atmospheric ablation of meteoroids is a striking example of the reshaping of a solid object due to its motion through a fluid. Motivated by meteorite samples collected on Earth that suggest fixed orientation during flight—most notably the conical shape of so-called oriented meteorites—we hypothesize that such forms result from an aerodynamic stabilization of posture that may be achieved only by specific shapes. Here, we investigate this issue of flight stability in the parallel context of fluid mechanical erosion of clay bodies in flowing water, which yields shapes resembling oriented meteorites. We conduct laboratory experiments on conical objects freely moving through water and fixed within imposed flows to determine the dependence of orientational stability on shape. During free motion, slender cones undergo postural instabilities, such as inversion and tumbling, and broad or dull forms exhibit oscillatory modes, such as rocking and fluttering. Only intermediate shapes, including the stereotypical form carved by erosion, achieve stable orientation and straight flight with apex leading. We corroborate these findings with systematic measurements of torque and stability potentials across cones of varying apex angle, which furnish a complete map of equilibrium postures and their stability. By showing that the particular conical form carved in unidirectional flows is also posturally stable as a free body in flight, these results suggest a self-consistent picture for the origin of oriented meteorites.

Investigation of the initiating ability of conically shaped charges

The influence of the shape of donor charges on their initiating ability is investigated. The composition of these charges, based on chopped ammonium nitrate(V) and nitromethane in the ratio of 95-80% to 5-20%, was investigated experimentally. The composition has a detonation velocity of 3000-3300 m/s and a critical diameter of 5-9 mm. It is established that the use of the truncated conical form of donor charges with a truncated taper angle of 15°, 30°and 45°, contributes to the concentration of the detonation wave along its axis. The use in these charges of a composition based on ammonium nitrate(V) and nitromethane with low energy characteristics will increase the quality of blasting operations. For reasons of safety, it is proposed that mixing is carried out on-site.

Dolomite overgrowths suggest a primary origin of cone-in-cone

A long-debated aspect of cone-in-cone structures is whether the mineral aggregates composing the structure precipitated with their conical form (primary cone-in-cone), or whether the cones formed after precipitation (secondary cone-in-cone). A calcite deposit from the Cretaceous of Jordan bears all the defining characteristics of the structure. Trace dolomite within the sample supports the primary cone-in-cone hypothesis. The host sediment is a biosiliceous mudstone containing abundant rhombohedral dolomite grains. Dolomite rhombohedra are also distributed throughout the calcite of the cone-in-cone. The rhombohedra within the calcite locally have dolomite overgrowths that are aligned with calcite fibres. Evidence that dolomite co-precipitated with calcite, and did not replace calcite, includes (i) preferential downward extension of dolomite overgrowths, in the presumed growth-direction of the cone-in-cone, from the dolomite grains on which they nucleate, and (ii) planar, vertical borders between dolomite crystals and calcite fibres. Because dolomite overgrows host-sediment rhombohedra and forms part of the cones, it follows that the host-sediment was incorporated into the growing cone-in-cone as the calcite precipitated, and not afterward. The host-sediment was not injected into the cone-in-cone along fractures, as the secondary-origin theory suggests. This finding implies that cone-in-cone in general does not form over multiple stages, and thus has greater potential to preserve the chemical signature of its original precipitation.

Modeling an Explosive Liquid Outflow from High Pressure Thin Tubes and Nozzles

To describe the explosive flow in thin tubes the model of vapor-liquid mixture with heat and mass transfer in two-dimensional axisymmetric formulation is employed. The phase transformation is significantly amplified with increasing of initial saturation temperature. The radial expansion of the jet outflow occurs due to the intensification of vaporization from cylindrical to conical form and parabolic form for supercritical initial state. Another problem applied to the outflow of a detonation wave in liquid filled with chemically active gas bubbles from the thin cylindrical tube. Modeling shows the important role of the opening angle of the outflow jet, which can either support the detonation or put it down.

Performance of Cooled Cone Grinding Machine in Cocoa Cake Processing

The process of cocoa paste pressing has a function to separate the fatty component of cocoa from its cake. Cocoa paste is further processed into cocoa powder using grinding machine for cocoa cake. The cooled cone type of cocoa grinding machine is used to solve the problem of plug in the maschine caused by melting of fat in cocoa cake due to hot effect as a result of friction in the grinding machine. Grinding machine of cocoa has conical form of cylinder for grinding and stator wall wrapped by source of cold and closed with jacket wool. Research was conducted at Kaliwining Experimental Garden of Indonesian Coffee and Cocoa Research Institute (ICCRI) using cocoa cake containing 26.75% originated from Forastero type of cocoa seed. The capacity and recovery of the machine was influenced by space between rotor cylinder and stator wall. Grinding machine operated at cooling temperature of 25.5oC and space between rotor – stator 0.9 cm and the capacity of 187.5 kg/hour with recovery of 200 mesh cocoa powder as much as 24%. The maximum power of machine required was 2.5 kW with efficiency of energy transfer of 97%. Results of proximate analysis showed that there was no change of protein content, but protein and carbohydrate content increased after processing, i.e. from 5.70% and 59.82% into 5.80% and 61.89% respectively.Key words : cocoa cake, cooling, grinding, cocoa powder

Design of an Ultra-Wideband Four Arms Sinuous Antenna

Due to the advantages of ultra-wideband, single caliber, symmetric pattern, full polarization, the sinuous antennas have gradually displaced the traditional spiral antennas in the Missile guider, reflector feed, wideband direction finding system. Based on the traditional planar sinuous antennas, this paper designed a novel 2-22 GHz 3D sinuous antenna in the conical form. Results show that the designed antenna showed high performance within 2-22 GHZ frequency band.

Conical functions of purely imaginary order and argument

Associated Legendre functions are studied for the case where the degree is in conical form −½ + iτ (τ real), and the order iμ and argument ix are purely imaginary (μ and x real). Conical functions in this form have applications to Fourier expansions of the eigenfunctions on a closed geodesic. Real-valued numerically satisfactory solutions are introduced which are continuous for all real x. Uniform asymptotic approximations and expansions are then derived for the cases where one or both of μ and τ are large; these results (which involve elementary, Airy, Bessel and parabolic cylinder functions) are uniformly valid for unbounded x.