Processing Parameters for Selective Laser Sintering or Melting of Oxide Ceramics

In this chapter, we present a detailed introduction to the factors which influence laser powder bed fusion (LPBF) on oxide ceramics. These factors can be in general divided in three main categories: laser-related factors (wavelength, power, scanning speed, hatch distance, scan pattern, beam diameter, etc.), powder- and material-related factors (flowability, size distribution, shape, powder deposition, thickness of deposited layers, etc.), and other factors (pre- or post-processing, inert gas atmosphere, etc.). The process parameters directly affect the amount of energy delivered to the surface of the thin layer and the energy density absorbed by the powders; therefore, decide the physical and mechanical properties of the built parts, such as relative density, porosity, surface roughness, dimensional accuracy, strength, etc. The parameter-property relation is hence reviewed for the most studied oxide ceramic materials, including families from alumina, silica, and some ceramic mixtures. Among those parameters, reducing temperature gradient which decreases the thermal stresses is one of the key factors to improve the ceramic quality. Although realizing crack-free ceramics combined with a smooth surface is still a major challenge, through optimizing the parameters, it is possible for LPBF processed ceramic parts to achieve properties close to those of conventionally produced ceramics

Artificial intelligence technology for myopia challenges: A review

Myopia is a significant global health concern and affects human visual function, resulting in blurred vision at a distance. There are still many unsolved challenges in this field that require the help of new technologies. Currently, artificial intelligence (AI) technology is dominating medical image and data analysis and has been introduced to address challenges in the clinical practice of many ocular diseases. AI research in myopia is still in its early stages. Understanding the strengths and limitations of each AI method in specific tasks of myopia could be of great value and might help us to choose appropriate approaches for different tasks. This article reviews and elaborates on the technical details of AI methods applied for myopia risk prediction, screening and diagnosis, pathogenesis, and treatment

Supply interruption supply chain network model with uncertain demand: an application of chance-constrained programming with fuzzy parameters

The downstream supply interruption of manufacturers is a disaster for the company when the demand is uncertain in the market; a fuzzy programming with fuzzy parameters model of supply interruption supply chain network is established by simulating market operation rules. The aim of the current study is to build a fuzzy chance-constrained programming method which is developed for supporting the uncertainty of demand. This method ensured that the fuzzy constraints can be satisfied at specified confidence levels, leading to cost-effective solutions under acceptable risk magnitudes. Finally, through the case of the electronic product manufacturing enterprise, the feasibility and effectiveness of the proposed model are verified by adopting a sensitivity analysis of capacity loss level and minimizing objective function. Numerical simulation shows that selecting two manufacturing centers can effectively reduce the supply chain cost and maintain business continuity

A New Estimate of B→(ρ,ω)+γB \to (\rho, \omega)+ \gamma In The Light-Cone QCD Sum Rule

We propose a new estimate of the process $B \to (\rho, \omega)+ \gamma$ by using the light-cone QCD sum rule. The aim is to choose the chiral quark current operators in order to eliminate the uncertainty arising from the chiral-even operators in the correlator. In the case of neglecting the corrections from $\rho$-meson mass, the sum rules for form factors are obtained, which are valid to the twist-three accuracy. The resulting branching ratios are consistent with the experimental data.Comment: Latex, 12 pages including 3 ps figure

Multi-Tooth Contact Analysis and Tooth Profile Modification Optimization for Cycloid Drives in Industrial Robots

Cycloid drives are widely used in industrial robots where high load carrying capacity, accurate positioning precision and smooth motion are required strictly. The meshing clearance obtained by tooth profile modifications of cycloid gears is thought to have significant effects on performances of cycloid drives. In this study, this issue is clarified by developing a quasi-static load distribution model with considering four types of tooth profile modifications. Firstly, the unloaded tooth contact analysis is introduced to determine the meshing information, and the nonlinear Hertzian contact mechanics is applied to develop force-displacement relationships, Then, the loads distributed on gears, contact stress, loaded transmission error and gear ratio are calculated by enforcing the deformation compatibility, and force and moment equilibrium conditions. The predicted contact stress and deformation are compared with those by the finite element method, which shows a good agreement. With this, a tooth profile modification optimization method is proposed to obtain the optimal tooth profile modification at given radial clearances by using the two-dimensional parameter map. This study provides a useful tool to predict the multi-tooth contact conditions and to determine the most suitable tooth profile modification during the design process