An optimized design method of three-point support for precision horizontal machining center with T-shape bed

The support point layout of the machine tool has an important influence on the working performance of the machine tool, when the material, manufacturing process and internal structure of machine bed are determined. In order to ensure that the precision machine tool has good leveling performance, stability and anti-interference, this paper presents an optimized design method of three-point support for T-shape bed of precision horizontal machining center. This article first establishes the statics model of the T-shape bed and analyzes grillage beam model used to characterize the main static deformation trend of the bed based on the singular function method. After verifying the rationality of the model through simulation, the optimized three-point support position can be obtained. Then this paper measured the deformation of the upper surface of a simple bed due to gravity. The deviation between the experimental results and the simulation results is less than 20%, which verifies the reliability of the simulation and theoretical results. Based on the ISIGHT multi-disciplinary optimization platform, this paper completes the multi-objective optimization of the support point layout of the bed, and the optimization results prove the accuracy of the theoretical model. This paper takes the bed of M800H precision horizontal machining center as an example to illustrate the application process of the proposed method. Finally, this paper compares the optimization effect of the static characteristics of the bed and the whole machine. The maximum deformation of the bed has reduced by 27.1%. In the whole machine status, the deformation of the spindle end has reduced by 50.8%, and the maximum deformation of the workpiece end have reduced by 50.0%.

AN EXTENSION OF CITYJSON TO SUPPORT POINT CLOUDS

The combination between dense point clouds and 3D vector objects permits new cartographic representation of urban information. This paper proposes an extension for the CityJSON encoding to support point clouds. Following the 3.0 CityGML specifications, attributes and features are added to the core module of v1.0.1 CityJSON. Two solutions are proposed: inline complex geometries and external link to a remote file. The extended schema can be illustrated in four scenarios: detailed features visualization, fall-back solution in features reconstruction processes, simulating urban climate represented as vector fields, and true-to-life representation solution for complex elements such as solitary vegetation objects. It permits 3D city modelers to handle points clouds in a native way reducing files size and avoiding redundancy. All developments and documentation are available open-source.

On the maximal displacement of near-critical branching random walks

We consider a branching random walk on $$\mathbb {Z}$$ Z started by n particles at the origin, where each particle disperses according to a mean-zero random walk with bounded support and reproduces with mean number of offspring $$1+\theta /n$$ 1 + θ / n . For $$t\ge 0$$ t ≥ 0 , we study $$M_{nt}$$ M nt , the rightmost position reached by the branching random walk up to generation [nt]. Under certain moment assumptions on the branching law, we prove that $$M_{nt}/\sqrt{n}$$ M nt / n converges weakly to the rightmost support point of the local time of the limiting super-Brownian motion. The convergence result establishes a sharp exponential decay of the tail distribution of $$M_{nt}$$ M nt . We also confirm that when $$\theta >0$$ θ > 0 , the support of the branching random walk grows in a linear speed that is identical to that of the limiting super-Brownian motion which was studied by Pinsky (Ann Probab 23(4):1748–1754, 1995). The rightmost position over all generations, $$M:=\sup _t M_{nt}$$ M : = sup t M nt , is also shown to converge weakly to that of the limiting super-Brownian motion, whose tail is found to decay like a Gumbel distribution when $$\theta <0$$ θ < 0 .

CHEMICAL SCIENCE IN SVERDLOVSK, 1920s–1950s: EMERGENCE OF KEY RESEARCH THEMES AND SCHOOLS

The paper presents an overview analysis of development of chemical research in the city of Sverdlovsk in 1920s–1950s. The author, relying on the theory of frontier modernization, proposes the concepts of frontier and support-point development of Soviet science. The frontier development was associated with peripherality, concentration of efforts in extractive (mining) industries, and a lack of resources for growth. The result of such frontier development was the emergence of a research-educational complex which, by the mid-1930s, included deeply integrated branch research organizations, institutes of the Academy of Sciences, and universities. The leading role was played by physical chemistry of metallurgical processes (and particularly electrochemistry), chemistry of wood and coal, inorganic and analytical chemistry. By the end of 1930s this chemical complex started to lose its frontier characteristics, which is evident from the effort of coal chemists led by I. Ya. Postovsky to develop the pharmaceutical chemistry. Due to the evacuation of enterprises and institutes from the western parts of USSR during the Great Patriotic War, the chemical complex of Sverdlovsk acquired a support-point character associated with the appearance of duplicate centers on the periphery. The new branches of chemical science emerged, for instance, the chemistry of polymers and the chemical machine-building. The implementation of the Soviet atomic project in Urals in late 1940s — early 1950s completed the paradigm shift in development of chemical science in Sverdlovsk, laying the foundation for the transformation of the city into a leading center of materials science.

Wildland Fire Suppression with Water Assets from Nature

Wildland fires frequently happen and develop in hard-to-reach regions, fast covering large areas due to the presence of ignitable matters together with beneficial meteorological circumstances. Human actions and natural events are the main reasons for the appearance of wildland fires. Our study focusses on the idea of using natural resources, namely water assets on the fire-affected territory. Since fire suppression is primarily performed with water, the provision of sufficient water sources in the proximity of the burning area is critical. An investigation of the hydrological characteristics of the territory is needed, especially in the driest months, when most of the wildfire events are expected to occur. The construction of a support point for fire-fighting water supplies in the wildland territories is also a requirement for building a network of water assets in the wildland territories.