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In this paper, the skin-core combined with the triple contour method is proposed to solve the density and roughness problems of selective laser melting. Based on the skin-core strategy, the surface roughness is optimized by laser parameter adjustment, and the high-quality side-surface formation is achieved by the triple contour method. The results showed that the relative density increases first and then decreases with increasing in-skin energy density, and surface roughness decreases with increasing up-skin energy density. The effects of the skin-core parameters have been analyzed. In addition, a triple contour scanning strategy was also conducted, and the variation of surface roughness caused by the different number of contours has been analyzed, along with the fabrication of the Ti6Al4V denture bracket. Results showed that the inclined surface roughness could be improved by the triple contour method to an average roughness (Ra) of 3.5 µm. An average surface roughness of less than 4.3 µm and a relative density of 99.8% have been achieved at the same time using the skin-core and triple contour strategy. The curved surface and overhanging structure quality of the denture bracket was also improved. This work provided a novel approach for the additive manufacturing of a medical titanium alloy. [ABSTRACT FROM AUTHOR]

Partially ordered Fe16N2 thin film with (001) texture is successfully grown on a Ag under layer using a facing target sputtering system. Fe16N2 phase is formed after post-annealing, which is detected by X-ray diffraction (XRD). High saturation magnetization (Ms) of Fe16N2 thin films is observed by vibrating sample magnetometry. It is found that Fe16N2 phase can be stable up to 225°C, which is demonstrated by the FeFe16N2 finger print peak (002) in XRD. After heating to 250°C, the Fe16N2 phase decomposes, which leads to low Ms and soft magnetic behavior. To further study Fe16N2 decomposition, X-ray photoelectron spectroscopy is performed to detect the binding energy of nitrogen atoms. Differences of binding energy corresponding to before and after heat treatment show the variation of nitrogen atom in electronic state with surrounding Fe atoms, indicating nitrogen atomic migration during heat treatment. [ABSTRACT FROM AUTHOR]

A strategy is developed to modulate the fluorescent color of carbon nanodots (CNDs) through regulating photon reabsorption and carbonization degree. On the one hand, the emission color is tuned through enhancing the photon reabsorption via the concentration increase. Essentially, the emitted photon of short wavelengths is supposed to be reabsorbed by a neighboring CND, subsequently resulting in a photon emission of long wavelengths. On the other hand, by reaction time control, a higher carbonization degree of CNDs is obtained, which renders larger sizes and less oxygen related groups of CNDs, giving rise to narrower bandgaps, e.g., emissions of longer wavelengths. Through cooperatively managing the carbonization degree and photon reabsorption, a single ultraviolet light can be converted into multi-color luminescence across the entire visible range by using our one-pot-pyrolysis CNDs. [ABSTRACT FROM AUTHOR]

The effects of a collector plasma in a relativistic backward wave oscillator are investigated using a numerical simulation. Analyzing mainly the diffusion process, the results show a fast plasma diffusion occurring as one of the most important reasons for pulse shortening. In this process, the fast plasma affects the modulation of the intense relativistic electron beams, leads to drifting of the microwave frequency, absorbs gigawatts of microwave power, and finally causes pulse shortening. Here, the mechanism underpinning fast diffusion is mainly attributed to the standing wave pattern of the microwave field in the interaction region and the space charge effect. This paper reveals the change in the system after pulse shortening caused by fast diffusion and suggests a measure to control this process by restraining the collector plasma. [ABSTRACT FROM AUTHOR]

(001) textured Fe16N2 thin film with Ag under layer is successfully grown on GaAs substrate using a facing target sputtering (FTS) system. After post annealing, chemically ordered Fe16N2 phase is formed and detected by X-ray diffraction (XRD). High saturation magnetization (Ms) is measured by a vibrating sample magnetometer (VSM). In comparison with Fe16N2 with Ag under layer on MgO substrate and Fe16N2 with Fe under layer on GaAs substrate, the current layer structure shows a higher Ms value, with a magnetically softer feature in contrast to the above cases. In addition, X-ray photoelectron spectroscopy (XPS) is performed to characterize the binding energy of N atoms. To verify the role of strain that the FeN layer experiences in the above three structures, Grazing Incidence X-ray Diffraction (GIXRD) is conducted to reveal a large in-plane lattice constant due to the in-plane biaxial tensile strain. [ABSTRACT FROM AUTHOR]

A dual-cavity TM02-TM01 mode converter is designed for a dual-mode operation over-moded relativistic backward-wave oscillator. With the converter, the fundamental mode output is achieved. Particle-in-cell simulation shows that the efficiency of beam-wave conversion was over 46% and a pureTM01 mode output was obtained. Effects of end reflection provided by the mode converter were studied. Adequate TM01 mode feedback provided by the converter enhances conversion efficiency. The distance between the mode converter and extraction cavity critically affect the generation of microwaves depending on the reflection phase of TM01 mode feedback. [ABSTRACT FROM AUTHOR]

A dual-mode operation mechanism in an overmoded relativistic backward wave oscillator is presented. The electron beam interacts with the - 1st space harmonic of TM01 mode synchronously in the slow wave structure. Then the backward propagating TM01 mode is converted to the forward propagating TM02 mode. As the phase velocity of the volume harmonic of TM02 mode is about twice that of the surface harmonic of TM01 mode, the TM02 mode also plays an important role in the high-power microwave generation. Particle-in-cell simulation shows that an efficiency of 48% and a significant improvement of the power capacity have been obtained. [ABSTRACT FROM AUTHOR]

Studies a new and reliable cooling method for diamond crystals in third generation light sources. Mounting method of diamond monochromator for high brilliance synchrotron radiation; Introduction of a diamond platement as an interface to reduce the strain from brazing between the diamond monochromator and its Cu block cooling device; Estimation of mounting strain.

Describes the design and installation of a double crystal monochromator accommodating water or liquid nitrogen cooling device for a first monochromator crystal in the x-ray undulator beamline NE3 of the TRISTAN accumulation ring. Silicon first crystal; Effect of the deformation of the rocking curve profile on the throughput of the monochromatic beam.

Describes a few kinds of x-ray optics together with x-ray sciences developed at the Photon Factory ring and the Tristan accumulation ring. Monolithic monochromator; Water-cooled quasi-doubly bent crystal monochromator; Asymmetric monochromator; Cryogenic cooling double-crystal monochromator; Function of the main ring; Fourth-generation light source.

Describes the design and installation of a scanning wire position monitor for insertion devices in an x-ray undulator beam line. Principle of the monitor and its limitations; Signal level of the monitor; Components.

Presents an abstract of a paper describing the construction of a test undulator beamline BL-BW-TL for use in a feasibility study for synchrotron radiation (SR) experiments using the Tristan Main Ring as a superbrilliant x-ray source in the autumn of 1995. Location of the SR experimental station; Cooling method for the first crystal of the monochromator.