Scanning electron microscope for in situ study of crystallization of Ge2Sb2Te5 in phase-change memory

By introducing electrical connections into the chamber of a scanning electron microscope (SEM) via its holder assembly, it has become feasible to in situ observe and electrically characterize electronic devices. The in situ SEM was applied to investigate electric-pulse-induced behavior of Ge(2)Sb(2)Te(5) in a lateral phase-change memory cell. Randomly distributed nuclei with sizes from 20 to 80 nm were initiated at a low voltage pulse. Initially, grain growth depended strongly on pulse amplitude at around 60.3 nm/V and then a weak pulse amplitude dependence was observed at around 13.5 nm/V. Device resistance during crystallization dropped by two to three orders of magnitude with two falling steps, which probably resulted from amorphous to face-centered-cubic and subsequently to hexagonal transitions, respectively.     

Surface texture assessment of ultra-precision machined parts based on laser speckle pattern analysis

Surface texture plays an important role in overall product specification, because the surface quality of the product is dominated by the nano-scale surface texture. This paper presents a surface texture assessment method for evaluating roughness and periodicity of surface structure with a laser speckle pattern analysis. By investigating the relation between surface texture and laser speckle pattern, characteristic parameters for describing a laser speckle pattern are proposed. The proposed characteristic parameters can evaluate the surface texture in entire observed area and in limited area in any given direction. Furthermore, the surface texture can be qualitatively assessed with a radar chart of the proposed laser speckle characteristic parameters.     

The Development of the New Data Acquisition System Without Hardware Trigger for the Super-Kamiokande Experiment

An online system of the underground neutrino detector, Super-Kamiokande is scheduled to be upgraded in 2008 together with front-end electronics. This detector consists of 50 000 tons of pure water equipped with about 13 000 photo-multipliers (PMTs) to detect Cherenkov light. The new online system is required to accept the dataflow of up to 800 MB/s from the front-end electronics and process them for the offline analysis. We will utilize a Gigabit Ethernet network and parallel data processing to handle this large amount of flow. In the new data acquisition scheme, we will not use a hardware event-trigger but read out every hit data from the front-end electronics and process them by the online farm. Therefore, there is no threshold of the number of PMT hits and the detector will become more sensitive to important cosmic-ray events such as relic neutrino from supernova and low energy solar neutrino. In addition to that, a dead-timeless system is desirable for the continuous measurement 365 days a year. In this paper, the detailed design of the upgraded online system and testing activities using prototypes will be described.     

Direct Formation and Luminescence Properties of Yttrium Niobate YNbO4 Nanocrystals via Hydrothermal Method

Yttrium niobate YNbO₄ nanocrystals with ellipsoidal morphology were directly formed from the precursor solution mixtures of YCl₃ and NbCl₅ under weakly basic conditions in the presence of aqueous ammonia by hydrothermal method. The hydrothermal treatment at 180°C for 5 h was necessary to obtain nanocrystals (18 nm) with sufficient crystallinity. The optical band gap of the as‐prepared samples was 3.6 eV. The as‐prepared YNbO₄ nanocrystals showed UV‐blue and broadband emission centered at 405 nm under excitation at 235 nm, which was due to the blue recombination luminescence, associated with charge‐transfer transitions involving the tetrahedral NbO₄ group. The emission intensity increased with increased hydrothermal treatment temperature. The photoluminescence intensity of the YNbO₄ was extremely improved via heating above 1000°C in air, which was accompanied by the increase in the optical band gap from 3.6 to 4.0 eV. By heat treatment at 1300°C, the intensity of the UV‐blue and broadband emission (with maximum at 400 nm) for the YNbO₄ became more than 22.5 times as strong as that before heat treatment.     

On the pressure drop and the velocity distribution in the cylindrical vortex chamber with two inlet pipes for the control of vortex flow

Vortex flow is applied to a cyclone dust collector, a vortex combustion chamber, and a vortex diode for vortex control. In order to apply the vortex flow to the industries, it is necessary to keep the stable flow condition and to estimate the response time of the transient flow process and also the intensity of the vortex flow. For control vortex flow, two types of vortex chamber with two inlet pipes were designed. One of them is to promote the vortex flow named as Co-Rotating Flow System and another one is to hinder the vortex flow named as Counter-Rotating Flow System. The pressure drops and the velocity distributions were measured for these vortex chambers. The estimation of the tangential velocity by the application of the angular momentum flux is compared with the measured velocity by a cylindrical Pitot-tube. The characteristics of the total pressure drop could be explained by introducing the circulation.     

海苔发酵提取物对原发性高血压大鼠的降压效果研究

使用可以产生GABA的植物性乳酸菌对海苔进行发酵,得到富含10.5%GABA的海苔发酵提取物。本实验验证了海苔发酵提取物对原发性高血压模型大鼠(SHR)的降压效果。单次经口灌胃给药实验中,分别以2mg/kg·bw和0.2mg/kg·bw剂量的海苔发酵提取物一次性灌胃给药,给药后2、5、9、24h进行血压测定。结果表明,海苔发酵提取物2mg/kg·bw剂量组在给药后5h和24h均有显著降压效果(p<0.05,p<0.01)。长期摄食给药实验中,含有海苔发酵提取物0.001%和0.003%的饲料剂量组对成长期SHR和老龄期SHR分别摄食给药,给药后每2～3d进行一次血压和体重测量,结果显示含有海苔发酵提取物0.003%的饲料剂量组使成长期SHR和老龄期SHR血压均显著下降(p<0.01,p<0.05)。