Functionalizable coaxial PLLA/PDLA nanofibers with stereocomplexes at the internal interface

Multifunctionality of electrospun polylactic acid (PLA) nonwovens was generated by the morphological design of nanofibers. Coaxial fibers with a lower number average molar mass Mn PLLA core and a higher Mn PDLA shell form PDLA–PLLA stereocrystals at the interface, induced by annealing. In tensile tests under physiological conditions, the core–shell fibers with higher crystallinity (22% compared to 11–14%) had lower Young’s moduli E (9 ± 1 MPa) and lower elongation at break εb (26 ± 3%) than PDLA alone (E = 31 ± 9 MPa, εb = 80 ± 5%), which can be attributed to simultaneous crystallization and relaxation effects. Gelatin incorporated in the PDLA phase was presented on the outer surface providing a biointerface putatively favorable for cell adherence. Gelatin incorporation did not influence the crystallization behavior but slightly lowered Tg (60 → 54 °C). Employing exclusively polymers established in the clinic, multifunctionality was generated by design. Graphic abstract

Study on the Effect of Isotropic Initial Stress on the Anchoring Performance of Self-Expanding Bolts

In order to study the anchoring performance of a new type of self-expanding, high-strength, precompression anchoring technology with a large amount of expansion agent (ω ≥ 5) cement slurry as anchoring solids under confined surrounding rock conditions, a rock mass anchoring device and methods that simulate in situ stress are developed, and real-time monitoring of expansion stress and anchor pull-out tests are carried out. The results show that the internal interface stress has a loss effect over time, and the stress loss value shows a linear increase trend with the dosage, but the loss rate shows a linear decreasing relationship with the dosage. This paper defines the coordinated additional stress and obtains its temporal and spatial evolution law in the rock mass. It is pointed out that there is a lag time difference between the peak of internal interface stress and the peak of coordinated additional stress, explaining its mechanical mechanism from the perspective of stress transfer. The strong restraint of the sealing section of the anchor hole causes the anchor solid to form a “shuttle-shaped” microexpanded head with thin ends and a middle drum under the expansion stress. During the drawing process, the microexpanded head is “stuck” in the anchor hole and moves upward to form the unique “load platform effect” of the anchoring system. And the mechanical mechanism diagram of this effect is obtained. It is pointed out that this effect can greatly improve the ductility of the anchoring system and the ultimate energy consumption value of damage. A prediction model for the ultimate pull-out force of self-expanding bolts is established. It is pointed out that the initial confining stress value has an exponential effect on the ultimate pull-out force. It shows that the surrounding rock with strong confinement constraints can greatly increase the ultimate pull-out resistance of the bolt. The self-expanding strengthening coefficient λ and the surrounding rock stress influence coefficient k are introduced, the bolt interface mechanics formula and energy equation of the self-expanding anchor system are established, and the feasibility of the formula is verified by the calculation example. It is concluded that the ultimate pull-out resistance of the anchorage with ω = 30 is increased by 3.38 times compared with the ordinary anchorage under the initial confining stress condition of 0.7 MPa, the prepeak displacement of the bolt is increased by 2.08 times, and the prepeak energy consumption of the anchoring system is increased by 7.34 times. The cost only increased by 0.023% based on the literature example.

Design and implementation of adversarial virtual simulation training system

With a view to further enriching the college practical teaching conditions and also for the college teaching being closer to actual combat, a study is made on basis of system demand analysis in the early stage about the internal interface relationship and information/control process of the antagonistic virtual simulation training system with a key technology analysis made to lay a solid foundation for the implementation of the antagonistic virtual simulation training system.

Single-step synthesis and interface tuning of core–shell metal–organic framework nanoparticles

Core–shell metal–organic framework nanoparticles have been synthesised in which the internal interface and distribution of components is found to be highly tunable using simple variations in reaction conditions.

Oxidation and hot corrosion behavior of a directionally solidified W richen cobalt-based superalloy

In this study, isothermal and hot corrosion in molten 75 mass% Na2SO4+25 mass% NaCl at 900 °C was carried out on an W richen Co-based directionally solidified Co-27.53Cr-9.85W-10.29Ni-0.75Al superalloy. For comparison, K38G with composition of 16.34Cr-4Al-1.77Mo-3.81Ti-2.66W-8.38Co were also conducted under same condition. Isothermal oxidation indicates that Co-based superalloy forms a Co-oxide dispersion chromia scale. However, K38G forms a purer chromia scale due to higher weight percentage ratio of Cr to Al. Under molten Na2SO4-NaCl salts, the defects in Ni/Co oxide dispersion chromia layer make it feasible that the molten salt can penetrates along grain boundaries into the internal interface to form internal sulfides, which causes the spallation of scales and significantly decreases its hot corrosion resistance.

Conclusion

The book concludes with the suggestion that the key condition for the required paradigm change in organization design is a change in managerial discourse which depends to a large extent on the professional education of managers. According to traditional management education, managers have several roles and although organization design is included in many of them in a more or less implicit manner, designing remains relatively marginal. Organization designing, which is differentiated from managing and strategizing, is defined as comprising the following as a set of activities: creating, monitoring, shaping, reshaping, assessing, and improving artefacts at the three organizational interfaces: the identity and values interface, the market interface, and the internal interface. It is also suggested that for the new design role of managerial activity to flourish and take hold, it must be framed within a new type of culture, that is, a culture of human-centric, leaderful organization design(ing). The chapter ends with a summary of the key concepts used in the book, drawing attention to the issues that managers-as-designers need to be aware of.

Analysis of a misalignment-insensitive spur gear transmission using a Rzeppa joint

The design of a novel gear system based on a Rzeppa joint internal interface is presented and analysed. The joint allows the transmission of torque loads while allowing real-time re-alignment of the gear to eliminate non-torque loads arising from misalignment. This gear, when part of a misaligned pair, is shown by means of quasi-static FE simulations to remain essentially under the same stress conditions, even when under considerable misalignment, and to outperform crowned gears. The trade-off is increased contact stress at the ball elements of the joint interface. In addition, the mesh stiffness for the conventional and the novel design are estimated, showing that the proposed design produces a lower but nearly constant stiffness throughout the mesh cycle.

The Gibbs-Thomson Equation

The external surface of a material has an atomic or molecular structure that is different from the bulk material. So does any internal interface within a material. Because of this, the energy of a material or any grain or particle within it increases with the curvature of its bounding surface, as described by the Gibbs-Thomson equation. This chapter explains how surfaces control the nucleation of new phases during reactions such as solidification and precipitation, the coarsening and growth of particles during heat treatment, the equilibrium shape of crystals, and the surface adsorption and segregation of solutes and impurities. The Gibbs-Thomson was predated by a number of related equations; it is not clear whether it is named after J. J. Thomson or William Thomson (Lord Kelvin); and it was not put into its current usual form until after Gibbs’, Thomson’s and Kelvin’s time. J. J. Thomson was the third Cavendish Professor of Physics at Cambridge University. He discovered the electron, which had a profound impact on the world, notably via Thomas Edison’s invention of the light bulb, and subsequent building of the world’s first electricity distribution network. William Thomson was Professor of Natural Philosophy at Glasgow University. He made major scientific developments, notably in thermodynamics, and he helped build the first trans-Atlantic undersea telegraph. Because of his scientific pre-eminence, the absolute unit of temperature, the degree Kelvin, is named after him.