Conceptual configuration design of line-foldable deployable space truss structures employing graph theory

From the perspective of the truss as a whole, this research investigates the conceptual configuration design for deployable space truss structures that are line-foldable with the help of graph theory. First, the bijection between a truss and its graph model is established. Therefore, operations can be performed based on graph models. Second, by introducing Maxwell’s rule, maximum clique, and chordless cycle, the principle of conceptual configuration synthesis is analyzed. A corresponding procedure is formed and it is verified by a truss with seven nodes. Third, assisted by some theorems of graph theory, the simplified double-color topological graph of deployable space truss structures is acquired and it also displays the procedure with a case. Finally, based on the above analysis, it obtains the optimal conceptual configurations. This novel research lays the foundation for kinematic synthesis and geometric dimension designs.

Design and Experimental Investigations of Shape and Attitude Carding System for the Wires of Micro Coreless Motor Winding

The shape and attitude (S&A) of the electrode wire are important characteristics of micro coreless motor winding. The purpose of this paper is to present the design of a robotic micro-manipulation system for micro wire carding with arbitrary S&A, which can be used as the pretreatment system for wire micro-gripper systems. The system is based on the principle of flexible carding, and uses nylon, bristle, nanometer-silk and wool as materials for the brushing micro-manipulator. The trajectory of the brushing micro-manipulator is designed, and the S&A of the electrode wires are straightened through the combined motion mode of horizontal and vertical brushing micro-manipulators. The experimental results show that the material of the brushing micro-manipulator has a great impact on the carding quality. Nanometer-silk material is more suitable for horizontal brushing micro-manipulators, and wool material is more suitable for vertical brushing micro-manipulators. The geometric dimension of the brushing micro-manipulator also affects the carding quality. When the diameter is in the range of 1 mm, the carding effect of the horizontal brushing micro-manipulator with a length of 4.9–8 mm is better. The system can realize the automatic carding of flexible electrode wires with arbitrary S&A, and it will not damage the structure of wires in the process.

Conceptual Configuration Synthesis of Line-Foldable Deployable Space Truss Structures Utilizing Graph Theory and Entropy

From the perspective of the truss as a whole, this research presents an approach to synthesizing conceptual configurations for deployable space truss structures that are line-foldable with the help of graph theory and entropy. First, according to graph theory, the bijection between a truss and its graph model is established by defining a bijective mapping between set elements. Therefore, operations can be performed based on graph models. Second, the principle of configuration evolution is interpreted by employing Maxwell’s rule, it also discusses the necessary and sufficient condition of configuration evolution. Configurations of evolution belong to three phases: space configuration, transformation configuration, and linear configuration. And it finds that the reasonable transformation configuration plays a key role. Further, maximum clique detection depending on backtracking is used to screen out unreasonable transformation configurations. Third, it introduces entropy, and the phenomenon of entropy change in configuration evolution is revealed and induction weights of rigid links are defined. It calculates the weight value of a transformation configuration by adding up induction weights of rigid links removed, also, weight values are used to classify transformation configurations. Finally, based on the previous analysis, a procedure to synthesize transformation configurations is formed and it is verified by a truss model with 7 nodes. This research lays the foundation for geometric dimension design and engineering applications.

Numerical and Experimental Study on the Hot Cross Wedge Rolling of Ti-6Al-4V Vehicle Lower Arm Preform

Cross wedge rolling (CWR) has unique advantages in the production of shaft preforms with refined grains and improved mechanical properties. Considering the sensitivity of Ti-6Al-4V (TC4) alloy to heat treatment temperature, the effect of different initial deformation temperatures (IDTs) on the forming quality, mechanical properties and microstructure evolution of the TC4 alloy lower arm preforms in CWR forming were studied in this work. The flow stress curves of TC4 alloy in the two-phase region were obtained by isothermal compression experiments. The Arrhenius constitutive model was established and applied to DEFORM-3D finite element (FE) software to simulate the CWR forming process of TC4 alloy lower arm preforms. The forming quality of TC4 alloy parts was compared and analyzed by 3D FE simulation and experiment. And their mechanical properties at room temperature were tested by tensile test. The results showed that the rolled part has well forming quality (no steps and necking defects) and higher geometric dimension accuracy at the IDT 850°C. Moreover, with the increase of IDT, the radial force and torque in the rolling process decrease. In addition, there were no internal defects in the parts rolled by different IDTs, because the die gap reduces the number of alternating cycles of tensile-compressive stress in the rolled workpieces. Compared with the initial state, the microstructure was refined. When the IDT is 885 °C, the ultimate tensile strength (UTS), yield strength (YS) and elongation (EI) of the parts were 987 MPa, 924 MPa and 16.8 % respectively, which was able to ensure the mechanical performance requirements of the lower arm preform. The results provide theoretical guidance for the actual production of lower arm preform by CWR.

GEOMETRIC PROBLEMS IN URBANISM

The article considers the phenomenon of urban geometry and the essence of geometric problems in urban planning. The proposed approach corresponds to the generally accepted understanding of cities through knowledge of the arts, humanities, social sciences and engineering. Geometry expands the understanding of cities and processes in them both in the historical context and in modern realities and conditions. The definiteness of the geometric dimension in the problems of spatial organization and development of urbanized systems is confirmed. Professional consideration and use of geometric indicators and properties is a condition for increasing the validity of architectural and urban planning decisions. The geometry of the functional city was based on ideas and solutions that focused on process control. The geometry of the space of today's city, according to the author, should stimulate its development by analogy with a living organism. Historical analysis expands the idea of the geometry of the city and its spatial implementation. The characteristics of the geometric measurement of different periods allowed us to conclude that the principles of geometry apply to cities of any time and any culture, are associated with the patterns of urban growth. Urban forms change depending on the scale: increasing the scale of the city to hypercomplex urban systems, the organic analogy grows, pure geometric planning is preserved on a local scale. The theoretical provisions of urban geometry, geometric problems and methods of their solution are substantiated. Identified dichotomies are important for understanding, researching and designing the development of urban systems. They are useful for generalizing different worldviews of space, time and urban geometry: the opposition of the concepts of simplicity and complexity; division and integrity; continuous and intermittent; homogeneity and heterogeneity of the system; certainty and uncertainty. New paradigms and thinking of the city as a hypercomplex system of organic complexity are covered. Geometry determines complexity, scale and shape. Views on space and geometry on the scale of human history have been studied. An attempt is made to understand the "reality" of development and spatial organization of cities. Geometry is used to display order and regularity, as well as in solving urban problems of today. The article highlights, structures and reveals the role of geometry and geometric problems in urban systems, their relationship with other dimensions and problems of spatial organization and urban development. In the model of multidimensional urban space "human - functions - conditions - geometry - time", which was substantiated by the author to solve problems of urban planning (spatial organization and development of urban systems) a special role is given to the geometric dimension, which is described in detail in the article. It includes many characteristics and indicators: size, configuration, shape, concentration of elements, as well as properties related to scale, intrasystem connections and location in the environment. The importance of urban geometry is illustrated using the author's model of multidimensional urban space on the example of geometric problems of Lviv, in particular placement, relocation and division. The solution of the communication and transport problem in the city is characterized and substantiated taking into account the requirements of the new geometry.

Composition of nanoclay supported silver nanoparticles in furtherance of mitigating cytotoxicity and genotoxicity

Silver nanoparticle (Ag-NP) is well known for its high antibacterial efficacy. However, its toxicity toward mammalian cells is still a concern in clinical applications. The aim of our study was to evaluate the composition effects of Ag-NP supported by silicate nanoplatelet (NSP) with respect to the cytotoxicity and genotoxicity, and was in reference to the poly (styrene-co-maleic anhydride)-supported Ag-NP (Ag-NP/SMA). The NSP at the geometric dimension of averaged 80 x 80 x 1 nm3 was prepared from the exfoliation of natural clays and used to support different weight ratio of Ag-NP. The supporting limitation of NSP on Ag-NP was below the weight ratio of 15/85 (Ag-NP to NSP), and the detached Ag-NP from the Ag-NP/NSP (30/70) and Ag-NP/SMA hybrids were observed by TEM. Ames test was performed to assess the mutagenic potential of different compositions of Ag-NP/NSP, only Ag-NP/NSP (30/70) and Ag-NP/SMA hybrids exhibited mutagenicity when the concentration was 1.09 ppm or higher. In viewing of cytotoxicity using MTT tests toward HaCaT cells, the IC30 of Ag-NP/NSP (1/99, 7/93 and 15/85) were 1416.7, 243.6, and 148.9 ppm respectively, while Ag-NP/SMA was 64.8 ppm. The IC30 of Ag-NP/NSP (1/99, 7/93 and 15/85) were at least 833, 78 and 7 folds higher than their corresponding minimum inhibitory concentrations (MIC) respectively, and whereas Ag-NP/SMA was 6.4 folds. The Ag-NP/NSP and Ag-NP/SMA hybrids had been further investigated for genotoxicity by chromosomal aberrations and in vivo micronucleus assay within the concentration at IC10 and IC30, only Ag-NP/SMA showed a higher frequency of chromosomal aberrations. Our findings indicated that the viability of utilizing the NSP to maintain Ag-NP for antimicrobial activity, and the high-surface area of NSP served as an excellent support for associating Ag-NP and consequently rendering the mitigation of the inherent toxicity of Ag-NP in clinical uses.