Simulation of the Thermal Behavior and Analysis of Solidification Process During Selective Laser Melting of Alumina

Selective laser melting (SLM) has rapidly developed in the past decade. High precision-complex ceramics parts can be directly fabricated using this technology. To study the thermal behavior of molten pools in the selective laser melting of alumina （Al2O3）, we established a three-dimensional model based on ANSYS. Then, combined with simulation results, the physical phenomena during the rapid solidification process were discussed. The simulation results showed that the laser power and scanning speed exerts a marked influence on the maximum temperature, liquid lifetime, dimensions, and temperature gradient of the molten pool. Owing to the different temperature gradients in the molten pool, the thermal capillary force on the free surface varies. As a result, a slight difference exists between the stripy solidification structures. Different orientations of columnar crystals can be obtained. The underlying mechanism controls the direction of the temperature gradient with suitable processing routes, such as decreasing the scanning speed.Mechanical Engineerin

Pd(II)-Catalyzed Catellani-Type Domino Reaction Utilizing Arylboronic Acids as Substrates

The Catellani reaction provides a facile and efficient method for the synthesis of multifunctionalized arenes. However, the use of Pd(0) catalysts restricts the scope of accessible products. We have developed a Pd­(II)-catalyzed, Catellani-type reaction utilizing arylboronic acids as the substrates for the first time. The arylboronic acids can be mono- or dialkylated at the <i>ortho</i> positions with alkyl iodides and olefinated at the <i>ipso</i> positions with olefins, producing various multifunctionalized aromatic compounds. This work should open new avenues for developing novel Catellani reactions, in particular those using new electrophiles

Silver-Catalyzed C–H Trifluoromethylation of Arenes Using Trifluoroacetic Acid as the Trifluoromethylating Reagent

Direct trifluoromethylation of arenes using TFA as the trifluoromethylating reagent was achieved with Ag as the catalyst. This reaction not only provides a new protocol for aryl C–H trifluoromethylation, but the generation of CF₃· from TFA may prove useful in other contexts and could potentially be extended to other trifluoromethylation reactions

Enhancing Mechanical Properties of 3D Printing Metallic Lattice Structure Inspired by Bambusa Emeiensis

Metallic additive manufacturing process parameters, such as inclination angle and minimum radius, impose constraints on the printable lattice cell configurations in complex components. As a result, their mechanical properties are usually lower than their design values. Meanwhile, due to unavoidable process constraints (e.g., additional support structure), engineering structures filled with various lattice cells usually fail to be printed or cannot achieve the designed mechanical performances. Optimizing the cell configuration and printing process are effective ways to solve these problems, but this is becoming more and more difficult and costly with the increasing demand for properties. Therefore, it is very important to redesign the existing printable lattice structures to improve their mechanical properties. In this paper, inspired by the macro- and meso-structures of bamboo, a bionic lattice structure was partitioned, and the cell rod had a radius gradient, similar to the macro-scale bamboo joint and meso-scale bamboo tube, respectively. Experimental and simulated results showed that this design can significantly enhance the mechanical properties without adding mass and changing the printable cell configuration. Finally, the compression and shear properties of the Bambusa-lattice structure were analyzed. Compared with the original scheme, the bamboo lattice structure design can improve the strength by 1.51 times (β=1.5). This proposed strategy offers an effective pathway to manipulate the mechanical properties of lattice structures simultaneously, which is useful for practical applications

CEPC Conceptual Design Report: Volume 2 - Physics & Detector

The Circular Electron Positron Collider (CEPC) is a large international scientific facility proposed by the Chinese particle physics community to explore the Higgs boson and provide critical tests of the underlying fundamental physics principles of the Standard Model that might reveal new physics. The CEPC, to be hosted in China in a circular underground tunnel of approximately 100 km in circumference, is designed to operate as a Higgs factory producing electron-positron collisions with a center-of-mass energy of 240 GeV. The collider will also operate at around 91.2 GeV, as a Z factory, and at the WW production threshold (around 160 GeV). The CEPC will produce close to one trillion Z bosons, 100 million W bosons and over one million Higgs bosons. The vast amount of bottom quarks, charm quarks and tau-leptons produced in the decays of the Z bosons also makes the CEPC an effective B-factory and tau-charm factory. The CEPC will have two interaction points where two large detectors will be located. This document is the second volume of the CEPC Conceptual Design Report (CDR). It presents the physics case for the CEPC, describes conceptual designs of possible detectors and their technological options, highlights the expected detector and physics performance, and discusses future plans for detector R&D and physics investigations. The final CEPC detectors will be proposed and built by international collaborations but they are likely to be composed of the detector technologies included in the conceptual designs described in this document. A separate volume, Volume I, recently released, describes the design of the CEPC accelerator complex, its associated civil engineering, and strategic alternative scenarios

CEPC Conceptual Design Report: Volume 2 - Physics & Detector

The Circular Electron Positron Collider (CEPC) is a large international scientific facility proposed by the Chinese particle physics community to explore the Higgs boson and provide critical tests of the underlying fundamental physics principles of the Standard Model that might reveal new physics. The CEPC, to be hosted in China in a circular underground tunnel of approximately 100 km in circumference, is designed to operate as a Higgs factory producing electron-positron collisions with a center-of-mass energy of 240 GeV. The collider will also operate at around 91.2 GeV, as a Z factory, and at the WW production threshold (around 160 GeV). The CEPC will produce close to one trillion Z bosons, 100 million W bosons and over one million Higgs bosons. The vast amount of bottom quarks, charm quarks and tau-leptons produced in the decays of the Z bosons also makes the CEPC an effective B-factory and tau-charm factory. The CEPC will have two interaction points where two large detectors will be located. This document is the second volume of the CEPC Conceptual Design Report (CDR). It presents the physics case for the CEPC, describes conceptual designs of possible detectors and their technological options, highlights the expected detector and physics performance, and discusses future plans for detector R&D and physics investigations. The final CEPC detectors will be proposed and built by international collaborations but they are likely to be composed of the detector technologies included in the conceptual designs described in this document. A separate volume, Volume I, recently released, describes the design of the CEPC accelerator complex, its associated civil engineering, and strategic alternative scenarios