Large area and wide dimensions X-ray lithography using energy variable synchrotron radiation

We developed a new X-ray lithography system for the lithographite, galvanoformung and abformung (LIGA) process using synchrotron radiation at the New SUBARU facility of the University of Hyogo. The X-ray lithography system can utilize two different energy regions: one is a high-energy region: from 2 to 12 keV, and the other is a low-energy region from 1 to 2 keV. Each energy region can be selected in accordance with the size and shape of the desired microstructures. Large-area patterning across an A4-size area was successfully performed with a highly uniform pattern thickness. Furthermore, high-aspect-ratio patterning using a high-X-ray-energy region was also achieved using this X-ray lithography system.     

Design of solenoidal electromagnetic microactuator utilizing 3D X-ray lithography and metalization

Investigations of microactuators are actively being pursued in various viewpoint, researchers are exploring output energy sources such as electrostatic, piezoelectric, electromagnetic and etc. We focus attention recently on the electromagnetic microactuator. In generally, electromagnetic actuator is not well suited to miniaturization because of decreased output force when miniaturized. However, we have already developed 3D-LIGA process to produce a spiral microcoil in 2003. Then, the production process of a smaller and higher output force microactuator was devised based on this technology.     

Composition and structure of apatite formed on organic polymer in simulated body fluid with a high content of carbonate ion

Apatite layer was formed on polyethyleneterephthalate (PET) substrate by the following biomimetic process. The PET substrate was placed on granular particles of a CaO, SiO₂-based glass in simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma to form apatite nuclei on their surfaces. The apatite nuclei was then grown into a continuous layer by subsequently soaking the substrate in SBF under air or CO₂ atmosphere in which CO₂ partial pressure in the ambient was adjusted to 14.8 kPa to increase the content of carbonate ion to a level nearly equal to that of blood plasma. The increase in the content of carbonate ions in SBF changed the Ca/P atomic ratio of the apatite from 1.51 to 1.63, content of CO₃ ^2- ions from 2.64 to 4.56 wt %, and lattice constants a from 94.32 to 94.23 nm and c from 68.70 to 68.83 nm, respectively. The Ca/P ratio and lattice constants of the apatite formed in SBF under CO₂ atmosphere were approximately identical to those of bone apatite, i.e. Ca/P atomic ratio 1.65, content of CO₃ ^2- ion 5.80 wt % and lattice constants a 94.20 and c 68.80 nm. This indicates that an apatite with composition and structure nearly identical to those of bone apatite can be produced in SBF by adjusting its ion concentrations including the content of carbonate ions to be equal to those of blood plasma.     

熔体超声波处理对Al-5%Si铸锭凝固组织的影响

为了研究超声波对金属熔体凝固过程中的影响,使用Al-5%Si合金进行了实验.在实验中采用几种不同的方法处理金属熔体:不添加除气剂、只添加除气剂、既添加除气剂又进行超声波处理.利用克劳修斯-克拉柏龙方程分析了超声波细化金属铸锭凝固组织的机理.结果表明,除气剂的添加与否对Al-5%Si合金铸锭组织的细化没有影响,铸锭由粗大的柱状晶组织构成;采用合适的超声波处理时间,Al-5%Si合金铸锭的等轴晶获得率大幅度提高,可使整个铸锭组织变为细化的等轴晶组织;超声波振动时间过长将导致铸锭内气孔的增加;根据克劳修斯-克拉柏龙方程,某一强度的超声波引起的压力冲击波作用,导致液相转变为固相,引起了超声波的细晶作用.     

超声波对分配系数K0＞1的铝合金铸锭组织的影响

研究了超声波对Al Ti合金、Al Zr合金、Al Cr合金等分配系数大于1的合金铸锭组织的影响,分析了超声波对铝合金铸锭细化的影响因素。结果表明,对于分配系数K0>1的合金,铸锭的细化效果随着C0|1 K0|的值增加而增大。     

Anonymity and roles associated with aggressive posts in an online forum

Cyberbullying is a growing concern in online communications. Cyberbullying has negative impacts such as distress or suicide of a victim. One common type of cyberbullying attack utilizes aggressive forum posts to insult or threaten a victim. Automated tools to classify cyberbullying may aid in avoiding or reducing the negative impacts of cyberbullying. One approach to produce an automated tool is to identify features of forum posts which may be indicators of cyberbullying. One feature of a forum post is the role of the author of the forum post, such as a bully, victim, or defender. Another feature is whether the forum post insults or threatens an individual (e.g., contains insults directed at a victim). Attackers may use aggressive forum posts to attack someone and defenders may use aggressive forum posts to retaliate against attackers. Another feature is whether the communication is anonymous (e.g., sending forum posts with no identifier) since cyberbullies utilize anonymity to reduce the ability of the victim to defend themselves and to shield the cyberbully from social consequences. In this paper, forum posts were labeled in an online forum for these features. Text matching techniques had some success in identifying aggressiveness forum posts including both attacks and defends. Anonymity of forum posts (i.e., forum posts with no identifier) was identified as a criterion to distinguish attackers (more anonymous relative to non-aggressive communications) from defenders (less anonymous relative to non-aggressive communications).     

gBoost: a mathematical programming approach to graph classification and regression

Graph mining methods enumerate frequently appearing subgraph patterns, which can be used as features for subsequent classification or regression. However, frequent patterns are not necessarily informative for the given learning problem. We propose a mathematical programming boosting method (gBoost) that progressively collects informative patterns. Compared to AdaBoost, gBoost can build the prediction rule with fewer iterations. To apply the boosting method to graph data, a branch-and-bound pattern search algorithm is developed based on the DFS code tree. The constructed search space is reused in later iterations to minimize the computation time. Our method can learn more efficiently than the simpler method based on frequent substructure mining, because the output labels are used as an extra information source for pruning the search space. Furthermore, by engineering the mathematical program, a wide range of machine learning problems can be solved without modifying the pattern search algorithm.     

A refined EM algorithm for PH distributions

This paper proposes an improved computation method of maximum likelihood (ML) estimation for phase-type (PH) distributions with a number of phases. We focus on the EM (expectation-maximization) algorithm proposed by Asmussen et al. [27] and refine it in terms of time complexity. Two ideas behind our method are a uniformization-based procedure for computing a convolution integral of the matrix exponential and an improvement of the forward-backward algorithm using time intervals. Compared with the differential-equation-based EM algorithm discussed in Asmussen et al. [27], our approach succeeds in the reduction of computation time for the PH fitting with a moderate to large number of phases. In addition to the improvement of time complexity, this paper discusses how to estimate the canonical form by applying the EM algorithm. In numerical experiments, we examine computation times of the proposed and differential-equation-based EM algorithms. Furthermore, the proposed EM algorithm is also compared with the existing PH fitting methods in terms of computation time and fitting accuracy.     

High pressure synthesis and electrical properties of BaTiO3−xFx

The substitution of fluorine for oxygen in BaTiO₃ was investigated by the reaction of BaO₂, BaF₂, TiO₂ and Ti under the conditions of 3.0 GPa and 1300° C for 2 H. Batio_3–x F _x solid solutions were obtained as a single phase in the region of 0 x0.1. The X-ray diffraction data showed that the symmetrical change from tetragonal to cubic form occurred atx=0.08 at room temperature. Also, the solid solutions were characterized by TG-DTA analysis, ESCA spectroscopy and diffusion reflectance spectroscopy. As a result, the existence of Ti³⁺ was verified. The electrical resistivities of BaTiO_3–x F _x were in the range from 4cm for x=0.05 to 3Ocm forx=0.1 at 300 K and the relationship between In and 1000 T^–1 was linear. The thermoelectric powers at 300 K were –250V K^–1 forx=0.05 and –130VK^–1 forx=0.1. The electrical property of the solid solution was discussed on the basis of a conventional band model which involved localized donor levels associated with oxygen vacancies.     

Preparation of Tl2Ba2Ca3Cu4Oy by the capillary synthetic method

A new phase of Tl₂Ba₂Ca₃Cu₄O_y withT _c = 100 K was prepared by the capillary synthetic method using Tl₂O₃, BaCuO₂ and Ca₂CuO₃ as starting materials. The present capillary synthetic method was useful to obtain the single phase of Tl₂Ba₂CaCu₂O_y Tl₂Ba₂Ca₂Cu₃O_y and Tl₂Ba₂Ca₃Cu₄O_y by solid state reactions using Tl₂O₃ BaCuO₂, and Ca₂CuO₃ as starting materials.