Systematic Control of Structural Changes in GeO2 Glass Induced by Femtosecond Laser Direct Writing

We report the structural changes inside germania glass induced by femtosecond laser pulses. Inspection by polarization microscopy and secondary electron microscopy indicate that the periodic nanostructures consist of oxygen defects such as ODCs (oxygen deficient centers) and NBOHCs (nonbridging oxygen hole centers) for laser pulse energy less than 0.2 μJ. However, the glass network was dissociated and O₂ molecules were generated for laser pulse energy greater than 0.4 μJ. Two different structural changes, form‐birefringence and dissociation, were induced in GeO₂ glass, depending on the laser pulse energy. The form‐birefringence exhibited by the nanogratings in GeO₂ glass is larger than that in SiO₂ glass for pulse energy less than 0.2 μJ, as the density of nanovoids enclosed by ODCs in GeO₂ glass is higher than that in SiO₂ glass. Arrhenius plots of the phase retardation caused by the nanogratings in GeO₂ and SiO₂ indicate that the oxygen defects are relaxed at a temperature 100°C above the glass‐transition temperature.     

Femtosecond laser direct writing in SiO2-Al2O3 binary glasses and thermal stability of Type II permanent modifications

We investigate the potential of fabricating thermally stable refractive index contrasts using femtosecond (fs) near-infrared (IR) radiation in aluminosilicate glasses. A set of pure SiO₂-Al₂O₃ glasses are manufactured, characterized (density and Raman), and investigated after being irradiated by fs laser within the Type II regime. The formation of nanogratings is identified and studied using quantitative birefringence measurements. Their thermal stability is then investigated through 30 minutes step isochronal annealing (up to 1250°C). For both SiO₂ and 50SiO₂-50Al₂O₃ compositions, the normalized birefringence does not decrease when tested up to 1100°C, while for the 4,6 mol% GeO₂-SiO₂ erased for 20% at 1000°C.     

Effect of the ethylene content of poly(ethylene-co-vinyl alcohol) on the formation of microporous membranes via thermally induced phase separation

Porous poly(ethylene-co-vinyl alcohol) (EVOH) membranes were prepared via thermally induced phase separation. The effect of the EVOH ethylene content on the membrane morphology and solute rejection property was investigated. For EVOHs with ethylene contents of 27–44 mol %, polymer crystallization (solid–liquid phase separation) occurred, and the membrane morphology was the particulate structure. However, the liquid–liquid phase separation occurred before crystallization for EVOH with a 60 mol % ethylene content. Cellular pores were formed in this membrane. For the particulate membranes, higher solute rejection and lower water permeance were obtained for EVOH with a lower ethylene content. The membrane formed by the liquid–liquid phase separation showed a sharper solute rejection change with a change in the solute radius than the particulate membranes did. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2583–2589, 2001     

Effects of addition of diacylglycerols on fat crystallization in oil‐in‐water emulsion

The effects of addition of diacylglycerols (DAGs) on the crystallization behavior of n‐hexadecane dispersed in oil‐in‐water emulsion (oil 20% and water 80%, v/v) were studied by differential scanning calorimetry (DSC) and ultrasonic velocity measurement. In an attempt to modify the crystallization rate of n‐hexadecane, five DAGs having the fatty acid moieties of behenic (DAB), stearic (DAS), palmitic (DAP), lauric (DAL) and oleic acid (DAO) were added to n‐hexadecane, which was mixed with water and Tween 20 for emulsification. The DSC study showed that the addition of DAB, DAS or DAP (1.0 wt‐% with respect to n‐hexadecane) increased the crystallization temperature (Tc) of a n‐hexadecane/water emulsion from 3 °C (without DAG) to 8 °C, whereas the addition of DAL and DAO showed no effect. The ultrasonic velocity measurement also revealed that the addition of DAGs resulted in increasing the Tc of n‐hexadecane in O/W emulsion. These effects were discussed by taking into account the formation of molecular aggregates at the interface due to the addition of DAGs, which act as a template for crystallization of n‐hexadecane. The template‐assisted crystallization depends on the structure of the fatty acid chains present in the DAG: the longer the fatty acid moiety of DAG , the more is the crystallization of n‐hexadecane in O/W emulsion accelerated.     

Structures and Binary Mixing Characteristics of Enantiomers of 1-Oleoyl-2,3-dipalmitoyl-sn-glycerol (S-OPP) and 1,2-Dipalmitoyl-3-oleoyl-sn-glycerol (R-PPO)

We performed differential scanning calorimetry (DSC) and synchrotron radiation X-ray diffraction (SR-XRD) experiments of polymorphic structures and binary mixing characteristics of the enantiomers of 1-oleoyl-2,3-dipalmitoyl-sn-glycerol (S-OPP) and 1,2-dipalmitoyl-3-oleoyl-sn-glycerol (R-PPO). In the two enantiomers, oleic and palmitic acid moieties are asymmetrically connected at the sn-1 and sn-3 positions of the glycerol groups, with palmitic acid moiety at the sn-2 position. Pure enantiomer samples (>99 %) were synthesized and employed throughout this study. The following results were obtained. (1) A basic feature of the mixture systems of S-OPP and R-PPO is of a eutectic nature due to different polymorphic structures of two enantiomers and the racemic compound of PPO (rac-PPO). (2) Polymorphic behavior of S-OPP and R-PPO was quite similar, both having α-2 and β′-3, whereas rac-PPO contained α _rac-3, β′_rac-2, and β′_rac-3. The DSC measurements showed that the melting points of β′-3 (S-OPP = 35.3 °C and R-PPO = 34.9 °C) were higher than that of β′_rac-3 (31.0 °C). β was not crystallized in the pure enantiomers, and rac-PPO. (3) α_rac-3 was crystallized at low cooling rates (~2 °C/min), whereas α-2 of the two enantiomers was crystallized only with very rapid cooling (~10 °C/min). (4) Triple-chain-length structures were formed in α_rac-3, β′_S-3 (=β′_R-3), and β′_rac-3; α-2 with a double-chain-length structure was formed in both enantiomers. These results indicate the importance of the relationship between subcell packing and glycerol conformation in the polymorphism and mixing characteristics of asymmetric unsaturated–saturated-saturated mixed-acid triacylglycerols.     

Crystal Phase and Orientation Control in Integrated Ferroelectric CaBi4Ti4O15 Using a Tailored Liquid of Alkoxides

We used a Ca–Bi–Ti complex alkoxide, in which metal–oxygen bonding was confirmed by spectroscopic analysis, to deposit CaBi₄Ti₄O₁₅ (CBTi144) thin films in various configurations. The phase transition of non-ferroelectric pyrochlore to ferroelectric perovskite in the complex-alkoxy-derived CBTi144 thin films was found to depend on the Pt bottom electrodes. Matching of the atomic arrangement to the Ca–Bi–Ti–O thin films was predominant rather than the strain and crystallinity of the bottom electrode. The thin films crystallized at 650°C on (111)-oriented Pt showed random orientation and ferroelectric P – V hysteresis loops. The endurance property was excellent against a number of switchings. For this reason, CBTi144 thin films would be expected to be excellent for application to ferroelectric random access memories (FeRAM). Polar-axis-oriented CBTi144 films were fabricated on Pt foils using the complex metal alkoxide solution. The 500-nm-thick film had a columnar structure comprising well-developed grains. The a / b -axis orientation of the ferroelectric films is considered to be associated with the preferred orientation of Pt foil. The film showed improved ferro- and piezoelectric properties. The P _r, E _c, and d ₃₃ values were enhanced to become twice those of CBTi144 thin films with random orientation. These polar-axis-oriented CBTi144 films are eminently useful in devices as Pb-free piezoelectric materials.     

Evaluation of mechanical properties of adjacent flow weldline

Weldlines occur at the interface of two adjacent flows of material behind an obstructive pin in a cavity in injection molding (meldline or hot weldline). Tensile strength of such “adjacent flow weldline” in injection molded polystyrene plates was evaluated by a mechanical step‐by‐step milling technique. The strength when the milling depth was 1/5 of the thickness from each surface was about the same and independent of the distance from the pin. In contrast, the strength without milling decreased once and then increased along the flow direction. This demonstrates that the strength of a weldline is predominantly dependent on the properties of the surface layer of the weldline. The depth of the surface layer was defined as the depth of the weld, D_w. D_w reduced monotonously along the flow direction and faded away with the V‐notch, resulting in an increase of strength along the direction. On the other hand, it was considered that the farther from the pin, the flow‐induced molecular orientation in the surface layer is greater. It caused a decrease of the strength along the flow direction. The sequence of decrease and increase in tensile strength of adjacent flow weldline is due to the complex effect of these two contradictory factors. POLYM. ENG. SCI., 45:1180–1186, 2005. © 2005 Society of Plastics Engineers     

Identifying shocks in regionally integrated East Asian economies with structural VAR and block exogeneity

In this paper we use a structural VAR model with block exogeneity to investigate if external shocks originating from the USA played a dominant role in influencing the macroeconomic fluctuations in East Asia during the period 1978-2007. The empirical results show a dynamic effect of external shocks, implying that, even though regional integration appears to be deepening and accelerating, especially after the recent global financial crisis, the influence of US shocks on real output fluctuations in the East Asian region is still very strong. The effects of Chinese shocks show an increasing trend over time, but the impacts are still small and not comparable with those of US shocks. The world oil price shock has become increasingly important in influencing the stability of real output growth in the region. The results from variance decomposition and impulse response analysis confirm the findings. Even though Japanese firms have established production networks in East Asia through trade and investment, and China has also grown rapidly and become a key regional country, the results suggest that US influence in the region is still asymmetric and strong. Therefore, it is difficult to conclude that shocks to the East Asian economies have become more regionally oriented.     

Neural network based expectation learning in perception control: learning and control with unreliable sensory system

In this article, we investigate the viability of our proposed neural network-based extension of the perception control concept introduced by Randløv and Alstrøm. In their work, each of the expectation elements is linearly acquired such that the expectation gives only the dominant information of the recent past. This handicap could become a serious problem when the perception process is applied to real physical systems. Such an approach has no capability to sense the trend or the dynamics in the information. Here, we introduce an extension of the perception control process by using a radial basis function feedforward neural network to learn the trend and the dynamics in the information queue. Through our simulations, we show that our neural network-based method is better than the conventional method.This work was presented, in part, at the 8th International Symposium on Artificial Life and Robotics, Oita, Japan, January 24–26, 2003     

EXPLOITING SUBTREES IN AUTO‐PARSED DATA TO IMPROVE DEPENDENCY PARSING

Dependency parsing has attracted considerable interest from researchers and developers in natural language processing. However, to obtain a high‐accuracy dependency parser, supervised techniques require a large volume of hand‐annotated data, which are extremely expensive. This paper presents a simple and effective approach for improving dependency parsing with subtrees derived from unannotated data, which are easy to obtain. First, we use a baseline parser to parse large‐scale unannotated data. Then, we extract subtrees from dependency parse trees in the auto‐parsed data. Next, the extracted subtrees are classified into several sets according to their frequency. Finally, we design new features based on the subtree sets for parsing algorithms. To demonstrate the effectiveness of our proposed approach, we conduct experiments on the English Penn Treebank and Chinese Penn Treebank. The results show that our approach significantly outperforms baseline systems. It also achieves the best accuracy for the Chinese data and an accuracy competitive with the best known systems for the English data.