一种面向HEVC的编码单元深度决策算法

新一代高性能视频编码(HEVC)标准采用灵活的四叉树自适应存储结构、可变尺寸的编码块、35种帧内预测模式等新技术,能够有效提升HEVC的编码效率,但也造成了更高的编码复杂度。为此,提出一种基于时空相关性的编码单元深度决策算法。融合关联帧编码单元的深度信息及当前帧相邻编码单元的深度信息,从而预测当前编码单元的深度范围。实验结果表明,与HEVC标准测试算法相比,该算法能在不明显影响编码质量的基础上平均减少30.2%的编码时间。     

High temperature properties of Cu–Cr–Zr alloys processed by conventional inverse extrusion of atomised powders and comparison with Conform consolidated powders

Abstract

Water atomised Cu–Cr–Zr alloy powders were consolidated by inverse warm extrusion and by the commercial continuous rotary extrusion method, Conform. Those alloys consolidated by inverse warm extrusion exhibited enhanced mechanical properties compared with their respective Conform extruded counterparts, when tested at both room and elevated temperatures. The processing parameters adopted in the inverse extrusion experiments resulted in products which retained enough amounts of solutes in solid solution, which in turn, led to improved mechanical properties after aging. Conversely, the excessive adiabatic heat generated in the Conform machine eliminated the saturation effect produced by rapid solidification, negating any possible further improvement on the mechanical properties by aging. The mechanical properties of an inverse extruded Cu–2.8Cr–0.39Zr (at.-%) alloy at temperatures above 450°C were higher than those strengths reported for Cu–Be alloys and comparable to that of Cu–Ta and Cu–Nb composites. Therefore, rapidly solidified Cu–Cr–Zr alloys can be possible candidates for replacing such alloy systems for high temperature applications.     

Turning and drilling of parts made from sinter hardenable steel powders

Abstract

The constant demand for improved mechanical properties and lower production costs of PM parts has lead to the development of sinter hardenable steel powders. These powders produce fully martensitic microstructures by appropriately controlling the cooling rate during the sintering operation. Thus, the heat treatment operation (oil quenching) that would generally be required to obtain hardened parts can be eliminated. However, machining of the relatively hard sinter hardened parts is difficult.It then becomes critical to optimise the tool selection and the machining conditions, such as surface speed and feed. This paper presents guidelines for the turning and drilling of parts made with sinter hardenable powders, as well as a discussion on the effect of manganese sulphide particles and chip formation during turning.     

Effects of processing parameters on direct laser sintering of multicomponent Cu based metal powder

Abstract

Direct laser sintering of a multicomponent Cu based metal powder was successfully processed through the mechanism of liquid phase sintering with partial melting of the powder. The effects of processing parameters such as laser power, scan speed, scan line spacing and layer thickness on the densification and microstructural evolution of the laser sintered powder were investigated. It was found that with increasing laser power or decreasing scan speed, the density of the sintered parts increased and the microstructures became denser. However, the combination of higher laser powers (>400 W) and higher scan speeds (≥0·06 ms^?1) gave rise to 'balling' effect. A successive transition from discontinuous scan tracks to coherently joined ones occurs with decreasing scan line spacing. Lowering the thickness of the powder layer promises an improvement in bonding coherence between sintered layers. A single factor termed 'energy density by volume' is defined to evaluate the combined effect of various processing parameters on the density of laser sintered powder. With increasing the energy density by volume up to ～0·16 kJ mm^?3, the densification rate is relatively high. However, with intensifying the energy density over ～0·23 kJ mm^?3, the mechanism of particle bonding may change into full melting/solidification, leading to a decrease in the sintered density.     

Synthesis and characterisation of Si3N4p/Cu nanocomposite powders by high energy ball milling

Abstract

The present work reported the preparation of Cu–25 wt-%Si₃N₄ nanocomposite powders via high energy ball milling (HEBM). The phases and morphologies of as-milled powders with various milling times were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results showed that with increasing the milling time, the irregularly shaped Cu powder became flattened, and, subsequently, refined and near spherical. After 12 h milling, the particle size of Cu–Si₃N₄ composite powders was in the range of 200–300 nm, while the grain size of Si₃N₄ particulates, 10–25 nm, was well within a nanometre scale. A uniform distribution of the nanosized Si₃N₄ reinforcing phase throughout the Cu matrix was successfully obtained. A reasonable mechanism for the formation of Cu–Si₃N₄ nanocomposite powders during HEBM was also proposed.     

5G无线网络CU/DU部署策略探讨

5G网络将满足三大类业务：eMBB、uRLLC、mMTC，不同业务对时延、可靠性、移动速度要求不相同。为了适应这些需求，3GPP标准化组织将BBU重构成CU和DU两个功能实体，在实际部署时的形态可以映射到不同物理设备上，也可以映射到同一物理实体。具体采用哪种方式要结合业务需求，应用场景，及网络要求综合分析，根据不同情况采用合适的部署策略。     

Early Coding Unit–Splitting Termination Algorithm for High Efficiency Video Coding (HEVC)

A new‐generation video coding standard, named High Efficiency Video Coding (HEVC), has recently been developed by JCT‐VC. This new standard provides a significant improvement in picture quality, especially for high‐resolution videos. However, one the most important challenges in HEVC is time complexity. A quadtree‐based structure is created for the encoding and decoding processes and the rate‐distortion (RD) cost is calculated for all possible dimensions of coding units in the quadtree. This provides a high encoding quality, but also causes computational complexity. We focus on a reduction scheme of the computational complexity and propose a new approach that can terminate the quadtree‐based structure early, based on the RD costs of the parent and current levels. Our proposed algorithm is compared with HEVC Test Model version 10.0 software and a previously proposed algorithm. Experimental results show that our algorithm provides a significant time reduction for encoding, with only a small loss in video quality.     

On solidification shrinkage of copper–lead and copper–tin–lead alloys

Abstract

Solidification shrinkage is an important concept in achieving sound castings. In the present work solidification shrinkage was studied in copper–lead and copper–lead–tin alloys. A series of solidification experiments was performed under different cooling rates using a dilatometer which was developed for melting and solidification purposes. The volume change was measured during primary solidification and the monotectic reaction. In order to explain the volume-changing results, the sample macrostructures were studied to evaluate gas and shrinkage cavities which were formed during the solidification. Furthermore, the volume fraction of the primary phase during solidification was evaluated in the samples that were quenched from different temperatures below the liquidus temperature. A shrinkage model was used to explain the volume changes during solidification.