On Renting Edge Resources for Service Hosting

The rapid proliferation of shared edge computing platforms has enabled application service providers to deploy a wide variety of services with stringent latency and high bandwidth requirements. A key advantage of these platforms is that they provide pay-as-you-go flexibility by charging clients in proportion to their resource usage through short-term contracts. This affords the client significant cost-saving opportunities by dynamically deciding when to host its service on the platform, depending on the changing intensity of requests. A natural policy for our setting is the Time-To-Live (TTL) policy. We show that TTL performs poorly both in the adversarial arrival setting, i.e., in terms of the competitive ratio, and for i.i.d. stochastic arrivals with low arrival rates, irrespective of the value of the TTL timer. We propose an online policy called RetroRenting (RR) and characterize its performance in terms of the competitive ratio. Our results show that RR overcomes the limitations of TTL. In addition, we provide performance guarantees for RR for i.i.d. stochastic arrival processes coupled with negatively associated rent cost sequences and prove that it compares well with the optimal online policy. Further, we conduct simulations using both synthetic and real-world traces to compare the performance of RR with the optimal offline and online policies. The simulations show that the performance of RR is near optimal for all settings considered. Our results illustrate the universality of RR.

Accuracy of view factor calculations for digital terrain models of comets and asteroids

Context. Detailed shape and topographic models coupled with sophisticated thermal physics are critical elements to proper characterization of surfaces of small bodies in our solar system. Calculations of self-heating effects are especially important in the context of thermal evolution of non-convex surfaces, including craters, cracks, or openings between “rocks”. Aims. Our aim is to provide quantitative comparisons of multiple numerical methods for computing view factors for concave geometries and provide a more rigorous criteria for the validity of their application. Methods. We contrasted five methods of estimating the view factors. First, we studied specific geometries, including shared-edge facets for a reduced two-facet problem. Then, we applied these methods to the shape model of 67P/Churyumov-Gerasimenko. Nevertheless, the presented results are general and could be extended to shape models of other bodies as well. Results. The close loop transformation of the double area integration method for evaluating view factors of nearby or shared-edge facets is the most accurate, although computationally expensive. Two methods of facet subdivision we evaluate in this work provide reasonably accurate results for modest facet subdivision numbers, however, may result in a degraded performance for specific facet geometries. Increasing the number of subdivisions improves their accuracy, but also increases their computational burden. In practical applications, a trade-off between accuracy and computational speed has to be found, therefore, we propose a combined method based on a simple metric that incorporates a conditional application of various methods and an adaptive number of subdivisions. In our study case of a pit on 67P/CG, this method can reach average accuracy of 2–3% while being about an order of magnitude faster than the (most accurate) line integral method.

Di-μ3-chlorido-tetra-μ2-chlorido-dichloridotetrakis(N,N-diethylethane-1,2-diamine-κ2 N,N′)tetracadmium(II)

In the title compound, [Cd4Cl8(C6H16N2)4], the Cd2+ cations and Cl− anions form M 4Cl8 clusters with six of the Cl− ions bridging Cd2+ cations and two being pendant. Each Cd2+ cation has distorted octahedral coordination completed by four Cl− ions and two N atoms of the asymmetrical bidentate amino ligand. The cluster consists of pairs of face-sharing hexahedra linked by a shared edge.

The vanadate garnet Ca2NaCd2V3O12: a single-crystal X-ray diffraction study

Single crystals of the vanadate garnet Ca2NaCd2V3O12 (dicalcium sodium dicadmium trivanadate) were synthesized using the floating-zone method and the crystal structure was investigated using single-crystal X-ray diffraction. We considered the effectiveness of substitution of the Y-site cation with reference to previous structural studies of vanadate garnets. The structures of vanadate garnets are subject to geometric constraints similar to those of silicate garnets. These constraints force the tetrahedral–dodecahedral shared edge length in vanadate garnets to become shorter than the unshared dodecahedral edge length, as in ugrandite (uvarovite, grossular and andradite) garnets. However, the vanadate garnet Ca2NaCd2V3O12 exhibits the normal structural feature, similar to pyralspite (pyrope, almandine and spessartine) garnets, namely that the dodecahedral–dodecahedral shared edge length is shorter than the unshared dodecahedral edge length. With increasing ionic radius of the Y-site cation, the atomic coordinates x, y and z of oxygen adopt values which satisfy Pauling's third rule.

Crystal structure of post-perovskite-type CaIrO3reinvestigated: new insights into atomic thermal vibration behaviors

Single crystals of the title compound, the post-perovskite-type CaIrO3[calcium iridium(IV) trioxide], have been grown from a CaCl2flux at atmospheric pressure. The crystal structure consists of an alternate stacking of IrO6octahedral layers and CaO8hendecahedral layers along [010]. Chains formed by edge-sharing of IrO6octahedra (point-group symmetry 2/m..) run along [100] and are interconnected along [001] by sharing apical O atoms to build up the IrO6octahedral layers. Chains formed by face-sharing of CaO8hendecahedra (point-group symmetrym2m) run along [100] and are interconnected along [001] by edge-sharing to build up the CaO8hendecahedral layers. The IrO6octahedral layers and CaO8hendecahedral layers are interconnected by sharing edges. The present structure refinement using a high-power X-ray source confirms the atomic positions determined by Hiraiet al.(2009) [Z. Kristallogr.224, 345–350], who had revised our previous report [Sugaharaet al.(2008).Am. Mineral.93, 1148–1152]. However, the displacement ellipsoids of the Ir and Ca atoms based on the present refinement can be approximated as uniaxial ellipsoids elongating along [100], unlike those reported by Hiraiet al.(2009). This suggests that the thermal vibrations of the Ir and Ca atoms are mutually suppressed towards the Ir...Ca direction across the shared edge because of the dominant repulsion between the two atoms.

Innovative designs of wood products plating in jointless gluing

The paper discusses the features of design and technology of finger joints in the manufacture of frame-paneled platings of doors and furniture fronts. At the design stage we solve two problems: a) the choice of shapes and sizes of studs and grooves according to GOST R 9330, b) calculation of probabilistic values of the maximum deviations of landings with interference by GOST 6449. It was proposed to abandon the finger joints, restrict ourselves to assembly in tongue and groove, so with conjugation in counterprofiles groove is milled on the ends the horizontal bars after pre-pruning to eliminate chipping and tongue - on inner shared edge of vertical bars.

Thermal expansion in C2/c pyroxenes: a review and new high-temperature structural data for a pyroxene of composition (Na0.53Ca0.47)(Al0.53Fe0.47)Si2O6 (Jd53Hd47)

Single-crystal X-ray data collection was performed in situ at T = 300 and 700°C on a sample synthesized along the jadeite–hedenbergite series. The structural data, together with those of a previous investigation of a crystal of the same composition, were compared to those of the endmembers. The evolution of the displacement parameters with temperature shows significant residuals for the O1, O2 and O3 oxygen at T = 0 K, most significantly in the O1, which were interpreted as an indication of positional disorder.Volume thermal expansion and axial deformation ellipsoids were calculated for the above sample together with those of a series of C2/c pyroxenes. Pyroxenes with a divalent M2 cation, Ca, Fe and Mg have a greater expansion than those with a monovalent M2, like Na and Li; the Na pyroxene endmembers with Al, Cr and Fe were observed to show greater expansion than corresponding Li ones.The greater axial expansion is found along the b axis, except in LiCrSi2O6; the changes along the b axis are related to the volume thermal expansion. The axial orientation and anisotropy of the two axes onto the (010) plane is different in Na, Li and Ca-Mg-Fe pyroxenes, but the overall expansion onto the (010) plane, given by the sum of the scalar expansion along the two axes on (010), is very similar in pyroxenes.The deformation along the b axis with temperature and composition is driven by the deformation along b of the octahedral M1 chain; most important is the contribution from the O1−O1 shared edge between M1 octahedra in the same octahedral chain.