Novel abrasive-free planarization of 4H-SiC (0001) using catalyst

A new abrasive-free planarization method for silicon carbide (SiC) wafers was proposed using the catalytic nature of platinum (Pt). We named it catalyst-referred etching (CARE). The setup equipped with a polishing pad made of Pt is almost the same as the lapping setup. However, CARE chemically removes SiC with an etching agent activated by a catalyst in contrast to mechanical removal by the lapping process. Hydrofluoric acid which is well known as an etchant of silicon dioxide (SiO₂) that cannot etch SiC, was used as the source of the etching agent to SiC. The processed surfaces were observed by Nomarski differential interference contrast (NDIC) microscopy, atomic force microscopy (AFM), and optical interferometry. Those observations presented a marked reduction in surface roughness. Moreover, low-energy electron diffraction (LEED) images showed that a crystallographically well-ordered surface was realized.     

Mechanochemical reaction between metals and liquid hydrocarbons Formation of V−, NB− and TA hydrides

Metal hydrides have been produced by the H₂ gas charging method in the past. This method is based on the adsorption and the dissociation of H₂ gas. But the high temperature, the high gas pressure or the complicated activation treatments are needed on the operations. The new production method to yield V-, Nb- and Ta hydrides, which is based on the use of the high reactivity of the fresh surface of metals and the dehydrogenation of liquid hydrocarbons, is introduced here. The fresh surfaces can be created by the continuous mechanical milling of metal powders. Metal hydrides were obtained at room temperature and at 1 atm.     

垂直堆垛InAs量子点材料的分子束外延生长

用MBF设备以Stranski-Krastanov生长方式外延生长了5个周期垂直堆垛的InAs量子点，在生长过程中使用对形状尺寸控制法来提高垂直堆垛InAs量子点质量和均匀性。样品外延的主要结构是500nm的GaAs外延层，15nm的Al0．5Ga0．5As势垒外延层，5个周期堆跺的InAs量子点，50nm的Al0．5Ga0．5Asnm势垒外延层等。在生长过程中用反射式高能电子衍射仪(RHEED)实时监控。生长后用原子力显微镜(AFM)进行表面形貌的表征，再利用光制发光(PL)对InAs量子点进行观测。     

Necking Effect on the Growth of Bi2Sr2CaCu2O8+δ Single Crystal by TSFZ Method

High-quality Bi ₂ Sr ₂ CaCu ₂ O ₈₊ single crystals have been grown by a travelling solvent floating zone method with a necking technique using a single crystal seed. The full-width at half maximum of the X-ray rocking curves was improved from 120 arcsec to 70 arcsec by the necking technique. The topographic results show that the crystals grown using the necking technique have better crystallinity. Especially, this technique is very effective on the growth of the atomically substituted single crystals. It results not only in the improvement of crystallinity but also in the enhancement of the single crystal size, especially for the crystals substituted by other elements.     

Measurement of twofold astigmatism of probe-forming lens using low-order zone-axis ronchigram

By using a low-order zone-axis ronchigram of a crystalline sample, a simple method for measuring twofold astigmatism of a probe-forming lens is proposed. This method allows precise measurement of the value of astigmatism from only one experimental ronchigram.     

Effects of rigid segments on structure and properties of unoriented and oriented poly(p-phenylene terephthalamide-co-ethylene terephthalates)

In poly(p-phenylene terephthalamide-co-ethylene terephthalate) the rigid segments of p-phenylene terephthalamide are aggregated as crystalline domains above the weight fraction of the rigid segments, 6 wt%. The rigid segments disturb the crystallization of the flexible segments of poly(ethylene terephthalate) (PET) and are preferentially contained in the amorphous phase of the PET segments. The crystallinity of the PET segments decreased with increasing the content of the rigid segments in the copolymers and the glass transition temperature is decreased by the decrease of the crystallinity below the weight fraction of the rigid segments, 6 wt%, in spite of the depression of micro-Brownian motion of the PET segments due to the rigid segments. The values of Young's modulus E, yield stress σ_y and breaking stress σ_b for the zone-drawn copolymer were conspicuously increased by the rigid segments contained in it, in comparison with those of the zone-drawn PET homopolymer. Such higher values of E, σ_y, and σ_b of the copolymer are originated by greater increases in the orientation of amorphous chains in the copolymer. The rigid segments in the amorphous phase effectively depressed the thermal shrinkage of the zone-drawn and the zone-annealed copolymers.     

Performance evaluation of portable time synchronization method using eBPF

The Precision Time Protocol (PTP) is a widely used protocol for high-precision time synchronization, but it requires hardware or driver support for network interface card. Therefore, we propose a portable time synchronization method that is independent of them. Our method uses eBPF to synchronize time by recording timestamps of PTP packets in the kernel. eBPF is provided by the kernel and is backward-compatible, making it independent of hardware or other software. To demonstrate the portability and high-precision time synchronization capabilities of our method, we compared the time synchronization precision in physical environment and virtual machine. We also modified server settings that could affect time synchronization precision, and clarified the effects of these changes. The experiments showed that our method can achieve the similar level of time synchronization precision as conventional methods while remaining portable and independent of other components.     

分布式光伏的共享价值及其对配电网影响的系统动力学仿真

随着以光伏为代表的分布式能源(DER)广泛开发利用,其对配电网的扰动、补贴缺口等问题使得局部区域内用户间分布式电能的共享模式得到普遍应用.文中从整体角度分析了共享模式下配电公司、共享协调管理员、分布式光伏拥有者和分享者等各相关参与主体的利益问题,搭建了包括分布式光伏电能共享模块、配电公司收益和输配电价等耦合模块的系统动力学模型,模拟仿真了不同分布式光伏安装率和上网电价下的共享价值变化,并就其对配电公司利益和输配电价的影响进行了前瞻性分析.算例分析结果表明,共享价值空间随区域内的分布式光伏安装率变化而存在一个峰值,因此合理规划区域内分布式光伏接入有利于各参与主体调整策略,促进多方收益协调.     

Effect of Powder Characteristics on Properties of Warm-Sprayed WC-Co Coatings

In high-velocity oxy-fuel (HVOF) spraying of WC-Co coatings, the decomposition and decarburization of WC during deposition are responsible for their much lower toughness compared with a sintered bulk WC-Co. In a previous study, Warm Spray (WS) process, which is capable to control the flame temperature used to propel powder particles, was successfully applied in an attempt to suppress such detrimental reactions by keeping particles’ temperature lower than their melting point. The coatings deposited by WS process showed no or little formation of W₂C and η phases and demonstrated moderately improved fracture properties. However, there is still a gap in fracture toughness between WS coatings and the corresponding sintered bulk. In order to optimize the properties of the WS coatings, the effect of original powder sizes were investigated. Microstructural characterization and phase analysis were carried out on deposited coatings by SEM and XRD. The results show that the feedstock powder size has substantial effects on the properties of the coatings, i.e., the smaller powder showed improved properties.