How the power spectrum of dust continuum images may hide the presence of a characteristic filament width

Context. Herschel observations of interstellar clouds support a paradigm for star formation in which molecular filaments play a central role. One of the foundations of this paradigm is the finding, based on detailed studies of the transverse column density profiles observed with Herschel, that nearby molecular filaments share a common inner width of ∼0.1 pc. The existence of a characteristic filament width has been recently questioned, however, on the grounds that it seems inconsistent with the scale-free nature of the power spectrum of interstellar cloud images. Aims. In an effort to clarify the origin of this apparent discrepancy, we examined the power spectra of the Herschel/SPIRE 250 μm images of the Polaris, Aquila, and Taurus–L1495 clouds in detail and performed a number of simple numerical experiments by injecting synthetic filaments in both the Herschel images and synthetic background images. Methods. We constructed several populations of synthetic filaments of 0.1 pc width with realistic area filling factors (Afil) and distributions of column density contrasts (δc). After adding synthetic filaments to the original Herschel images, we recomputed the image power spectra and compared the results with the original, essentially scale-free power spectra. We used the χ2variance of the residuals between the best power-law fit and the output power spectrum in each simulation as a diagnostic of the presence (or absence) of a significant departure from a scale-free power spectrum. Results. We find that χ2variance depends primarily on the combined parameter δ22 Afil. According to our numerical experiments, a significant departure from a scale-free behavior and thus the presence of a characteristic filament width become detectable in the power spectrum when δ22 Afil ⪆ 0.1 for synthetic filaments with Gaussian profiles and δ22 Afil ⪆ 0.4 for synthetic filaments with Plummer-like density profiles. Analysis of the real Herschel 250 μm data suggests that δ22 Afil is ∼0.01 in the case of the Polaris cloud and ∼0.016 in the Aquila cloud, significantly below the fiducial detection limit of δ22 Afil ∼ 0.1 in both cases. In both clouds, the observed filament contrasts and area filling factors are such that the filamentary structure contributes only ∼1/5 of the power in the image power spectrum at angular frequencies where an effect of the characteristic filament width is expected. Conclusions. We conclude that the essentially scale-free power spectra of Herschel images remain consistent with the existence of a characteristic filament width ∼0.1 pc and do not invalidate the conclusions drawn from studies of the filament profiles.

Analysis of load capacity usage for aircrafts in regular airlines

The rapid development of the air transport market in recent years, together with positive trends, brings also an amount of organizational problems related to, for example, strong congestion of airspace, lack of slots in large airports, etc. Such challenges point out the need to use every available kilo of aircraft load capacity. In such situation, an important component in the cargo transport gets to be the available load space of aircrafts, which operate on the regular airlines. In this article, the usage of such load space was analyzed. The research was done based on the data about baggage area filling of short- and medium-distance aircrafts, which operate from the selected Polish airport. This analysis shows the extent how aircrafts use their transport capacity. Also it specifies the possibilities to use these aerial vehicles in cargo transportations under the conditions of real payload depending on their types as well as under the conditions, which must be met by operating from the selected airport.

Energy Efficient Technologies to Support Mine Workings under Complicated Geomechanical Conditions

Objective of the studies is the substantiation of energy efficient technologies to support permanent mine workings under complicated conditions of mines in Western Donbass. The results of analysis of geomechanical processes within rock mass neighbouring extended mine working have been demonstrated. The possibility to fill up underpropped area at different stages of a mine working construction has been shown. Efficient technology to improve the stability of mine workings by means of underpropped area filling up with hardening mixtures pneumatically has been considered. The results of the new technology to fill up underpropped area while constructing the main crosscut in Samarskaia mine (“DTEK Pavlogradugol” Company) have been demonstrated.

Optimal space filling for additive manufacturing

Purpose In additive manufacturing (AM) process, the physical properties of the products made by fractal toolpaths are better as compared to those made by conventional toolpaths. Also, it is desirable to minimize the number of tool retractions. The purpose of this study is to describe three different methods to generate fractal-based computer numerical control (CNC) toolpath for area filling of a closed curve with minimum or zero tool retractions. Design/methodology/approach This work describes three different methods to generate fractal-based CNC toolpath for area filling of a closed curve with minimum or zero tool retractions. In the first method, a large fractal square is placed over the outer boundary and then rest of the unwanted curve is trimmed out. To reduce the number of retractions, ends of the trimmed toolpath are connected in such a way that overlapping within the existing toolpath is avoided. In the second method, the trimming of the fractal is similar to the first method but the ends of trimmed toolpath are connected such that the overlapping is found at the boundaries only. The toolpath in the third method is a combination of fractal and zigzag curves. This toolpath is capable of filling a given connected area in a single pass without any tool retraction and toolpath overlap within a tolerance value equal to stepover of the toolpath. Findings The generated toolpath has several applications in AM and constant Z-height surface finishing. Experiments have been performed to verify the toolpath by depositing material by hybrid layered manufacturing process. Research limitations/implications Third toolpath method is suitable for the hybrid layered manufacturing process only because the toolpath overlapping tolerance may not be enough for other AM processes. Originality/value Development of a CNC toolpath for AM specifically hybrid layered manufacturing which can completely fill any arbitrary connected area in single pass while maintaining a constant stepover.

A Direct Filling Algorithm of Isogram in Complex Boundary

On basis of summarizing the existing isogram filling algorithm, this paper puts forwards a direct filling algorithm of isogram in complex boundary. Compared with the point-by-point scanning method and algorithm of area filling, this new algorithm has no necessity not only in point-by-point calculation of interpolation, but also in tracing inclusion relation between equivalent areas and determination areas, which makes filling speed faster. It is proved with practice that the new method can fill isopleth map in milliseconds.