Effect of Yb3+-Codoping on the Upconversion Emission Intensity in Er3+-Doped ZBLAN Fluoride Glasses under 800-nm Excitation

The effect of Yb³⁺-codoping on the upconversion emission intensity in Er³⁺-doped ZBLAN fluoride glasses is investigated. The codoping of Yb enhanced the emission intensity for the samples excited by an 800-nm laser diode beam. The enhancement in a constant YbF₃ content (2 mol%) increased with increasing ErF₃ content was about 70% of the initial value at 550 nm for the glasses containing 8 mol% of ErF₃. The emission intensity at 550 nm in a constant ErF₃ content (5 mol%) increased remarkably with the addition of YbF₃ and was maximized around 7 mol% of YbF₃ content, giving an increased ratio of about 200% of the initial value. The reason for the enhancement is discussed and it is derived mainly from two-step excitation of Er³⁺ assisted by Yb³⁺ excited through the energy transfer from Er³⁺.     

Synthesis and blend morphology of BA/BC-type binary graft copolymers composed of polyelectrolyte trunks

Poly(α-methylstyrene) (PMS) macromonomer having one vinylbenzyl group per polymer chain was prepared by the couplings of living PMS with p-chloromethylstyrene (CMS). Subsequently, well-defined poly[acrylic acid (AA)-g-α-methylstyrene (MS)] and poly[4-vinylpyridine (4VP)-g-MS] graft copolymers composed of polyelectrolyte trunks were prepared by radical copolymerization of PMS macromonomer with AA and 4VP monomers, respectively. Binary poly(AA-g-MS)/poly(4VP-g-MS) or poly[AA · triethyl amine (Et₃N) salt-g-MS)/poly(4VP-g-MS) graft copolymer blend films were cast from a benzene/methanol mixture. The morphological results of binary graft copolymer blends are discussed with respect to three-phase separated structures.     

Crystallization behavior of polypropylene filled with surface-modified calcium carbonate

Polypropylene (PP) and calcium carbonate (CaCO₃) were mixed in a two-roll mill. The mixed compounds were molded on the plate by using a compression press heater. To improve the affinity of the relation between CaCO₃ and the PP matrix, we modified the CaCO₃ surface through chemical reaction with alkyl dihydrogen phosphates. The CaCO₃ content and size modification affected the crystallization behavior of the filled PP composites. The crystallization temperature in the nonisothermal crystallization process increased with the increase of CaCO₃ content and the decrease of CaCO₃ size. The crystallization temperature revealed the function of log (1 + T_s) (T_s, total surface area of CaCO₃) irrespective of CaCO₃ content and size for modified and unmodified systems, respectively. The shoulder or double crystallization peak of PP composites is recognized for the unmodified system (particle sizes: 1.0 and 4.5 μm).     

Bonding properties of epoxy resins containing two mesogenic groups

Liquid‐crystalline epoxy resins, with introduced aliphatic chains between two mesogenic groups, were synthesized and their adhesive bonding properties were compared to those of the bisphenol‐A–type epoxy resin and the liquid‐crystalline epoxy resin, previously reported. The bonding strength of the former resin system was higher than that of the two later systems. We suggest that the high bonding strength of the twin mesogenic epoxy resins, cured with an aromatic amine, was attributable to the large plastic deformation of the adhesive layer in the fracturing process. We also investigated the effects of the aliphatic chain length in the twin mesogenic epoxy resin on their dynamic mechanical and bonding properties. The bonding strength of the cured twin mesogenic epoxy resins increased with an increase in the aliphatic chain length. We suggest that the high bonding strength of the system introduced by the long aliphatic chain was attributable to the large plastic deformation of the adhesive layer because of the higher network mobility. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3721–3729, 2004     

Oxidation and Degradation of Titanium Nitride Ultrafine Powders Exposed to Air

Titanium nitride ultrafine powders were synthesized by an active plasma-metal reaction method. Gas desorption measurements were conducted to estimate the surface chemistry of the powders after exposure to air and storage at room temperature. H₂O, H₂, CO₂, CO, and NH₃ gases were mainly evolved. These gases were considered to be formed by the surface reaction of adsorbed gases on surface oxide of the powders and decomposition of hydroxide-like or ammonialike compounds, which might be produced during a slow oxidation treatment and storage.     

Spin‐on‐glass (SOG) for the trilayer imaging process

Maleic acid catalyzed hydrolysis and condensation of tetramethoxysilane was carried out in 1‐propoxy‐2‐propanol to prepare a spin‐on‐glass (SOG) material for the trilayer imaging process. The material was found to be stable enough for industry use. Minor amounts of methylsilsesquioxane and photoacid generators were introduced into the material. Thin resist (top layer) patterns were imaged on the SOG film (intermediate layer), which was coated on a hard‐baked i‐line resist (bottom layer). The SOG film showed sufficient adhesion to the resist patterns, and superior resist profiles were imaged on the film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 636–640, 2003     

Study of reactive diluent for air-dried alkyd paint

The conventional air-dried alkyd resin is generally used with 30% to 40% of some organic solvent which dissipates into atmosphere after painting and becomes a factor of air pollution. A reactive diluent was investigated to reduce the content of the organic solvent and to manufacture a high-solid or superhigh-solid paint. 1,1-Bis(1′-methyl-2′-vinyl-4′,6′-heptadienoxy)ethane was found to be suitable as the reactive diluent among the investigated compounds. A small addition of this compound to alkyd paint reduced the content of solvent to less than 15% with a conventional alkyd resin of high molecular weight (high-solid type); and, further, a superhigh solid paint (5% solvent) could be manufactured when this compound was added to a superlong oil-length alkyd resin of low molecular weight.     

Spectral indices for remote sensing of phytomass,deciduous shrubs,and productivity in Alaskan Arctic tundra

The relationships among in situ spectral indices, phytomass, plant functional types, and productivity were determined through field observations of moist acidic tundra (MAT), moist non-acidic tundra (MNT), heath tundra (HT), and sedge-shrub tundra (SST) in the Arctic coastal tundra, Alaska, USA. The two-band enhanced vegetation index (EVI2) was found more useful for estimating vascular plant green phytomass, leaf carbon and nitrogen, leaf carbon and nitrogen turnover, and vascular plant net primary productivity (NPP) without root production than the normalized difference vegetation index (NDVI). Deciduous shrub green phytomass was strongly correlated with deciduous shrub index (DSI), defined as EVI2 × (R_blue + R_green – R_red)/(R_blue + R_green + R_red) (with a coefficient of determination (R²) of 0.63). R_blue, R_green, and R_red denote the blue, green, and red bands, respectively. This is because R_blue and R_green values were higher than the R_red values for green leaves, deciduous shrub stems, lichens, and rocks compared with other ecosystem components, and EVI2 values of lichens and rocks were very low. The vascular plant NPP without root production was estimated with an R² of 0.67 using DSI and EVI2. Our results offer empirical evidence that a new spectral index predicts the distribution of deciduous shrub and plant production, which influences the interactions between tundra ecosystems and the atmosphere.     

Experimental evaluation of teleoperation system with force-free control and visual servo control by human operator perception

This research considers the teleoperation of an articulated robot arm by means of force-free control and visual servo control (VSC) over communication channels using the Internet technology. A semi-autonomous type teleoperation system contains a human supervisory control and VSC schemes and switches one scheme to another for accomplishing the required task accurately. The main investigation is carried out to find how it effectively improves the accuracy and the effectiveness of the teleoperation after provision of a visual feedback channel to the system. The system accuracy, effectiveness, repeatability and handleability based on the human operator’s skills and operator’s cognitive aspects are evaluated using experimental results and statistical data analysis. Effectiveness of the statistical analysis is assured by increasing the number of experiment data and assuming environmental factors, and implicit variables maintain to be unchanged. Correlation coefficients are calculated to find out how controlled input parameters are related to the successful output given by the system.     

Theoretical study of surface interaction stresses considering one-dimensional material distributions in the in-plane direction based on the Lennard–Jones potential

In this work, the interaction stresses (i.e., pressures and shear stresses) between a half-space comprising a uniform material and a half-space comprising one-dimensional material distributions in the in-plane direction were theoretically derived. The interaction stress was derived from the Lennard–Jones potential as a vector for the (0, 0, 1) surface using two different material distribution patterns. The first pattern was a periodic distribution of materials (Pattern 1) and the second was a distribution of two materials with a single interface (Pattern 2). The interaction stresses for Pattern 1 were derived based on a Fourier series, while those for Pattern 2 were derived as elementary functions. The pressures possessed non-fluctuation terms and fluctuation terms, while the shear stresses possessed fluctuation terms only. The basic characteristics of these interaction stresses for parallel planes were quantitatively clarified by presenting the distributions and vector diagrams of the interaction stresses.