Self-assembly of three dimensional micro mechanisms using thermal shrinkage of polyimide

This paper describes three-dimensional microstructures fabricated using a simple self-assembly process involving the thermal shrinkage of polyimide. The proposed method enables hinged structures to be automatically rotated out of the wafer plane and to remain bent without the need to use any interlocking mechanisms. The hinged structures were fabricated using surface micromachining techniques involving heating in a furnace. An increase in the bending angle due to the shrinkage of polyimide was observed with increasing heating temperature, heating time, and length of the polyimide hinge. Of these three parameters, the heating time was found to be the most suitable for precise control of the bending angle. Furthermore, microcubes were fabricated by this method and the self-assembly process was successfully visualized using a CCD camera.     

Preparation of porous sheet composite impregnated with TiO<Subscript>2</Subscript> photocatalyst by a papermaking technique

Titanium dioxide (TiO₂) powder-containing sheet composites, called TiO₂ sheet, were prepared by a papermaking technique, and their photocatalytic efficiency was investigated. The TiO₂ powders were homogeneously scattered over the fiber-mix networks tailored within the catalyst sheet. Under UV irradiation, the TiO₂ paper could decompose p-hydroxyacetophenone (p-HAP), although the degradation efficiency by the TiO₂ sheet was lower than that by the TiO₂ powder. Scanning electron microscopy revealed that coverage of the TiO₂ particles inside the sheet by alumina binder which was used to improve the sheet strength caused the deterioration of the photocatalytic performance. Internal addition of alumina binder made the TiO₂ sheet porous and such a TiO₂ sheet exhibited high photocatalytic performance equivalent to that of TiO₂ powder. The porous structure of TiO₂ sheet might contribute to effective transport of p-HAP to the surface of TiO₂ particles inside the sheet, resulting in high degradation performance. In addition, TiO₂ sheet prepared using TiO₂ sol showed higher photocatalytic efficiency than TiO₂ powder and it was indicated that the porous sheet structure might provide suitable conditions for TiO₂ catalysis for photodecomposition.     

Preparation of carbon microparticle assemblies from phenolic resin using an inverse opal templating method

Three-dimensionally (3D) well-ordered carbon microparticle assemblies with different particle morphologies were fabricated by infiltration of phenolic resin solution into SiO₂ inverse opal structures and subsequent carbonization. The effect of the phenolic resin solution concentration and the carbonization temperature on the morphology of the fabricated carbon microparticles was investigated. At a carbonization temperature of 1000 °C, carbon microparticles with interlocked bridges were obtained when the concentration of phenolic resin solution is 40 wt% and hollow carbon microparticles with opened window channels were obtained at a concentration of 30–35 wt%. When the carbonization temperature was decreased to 500 °C, carbon microparticles with interlocked bridges also were observed, even when the phenolic resin concentration was 30 wt%. The structures and properties of the carbon microparticles and their assemblies were characterized using SEM, XRD, and N₂ adsorption.     

Disintegration process of yttria-stabilized zirconia ceramics using hydrothermal conditions

Capability of the recycling of high strength and high fracture toughness yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) sintered body utilizing “low-temperature annealing degradation” phenomenon was investigated. Hydrothermal treatment was employed to induce the phase transformation from tetragonal to monoclinic zirconia and to disintegrate the Y-TZP sintered body. 3 mol% Y₂O₃–ZrO₂ specimens sintered at 1,550 °C and more were disintegrated without leaving the original appearances when the treatment temperature was between 200 °C and 400 °C. The size of the disintegrated fragments of Y-TZP sintered body was much affected by hydrothermal treatment conditions. Only with hydrothermal treatment and simple ball milling, the sintered body was pulverized into the primary particle level. This technique is expected to apply to a sustainable recycling system for the zirconia ceramics, which restrains an energy consumption compared to crushing zirconia using mechanical procedures.     

Spatial and Temporal Analysis of Hydrological Provision Ecosystem Services for Watershed Conservation Planning of Water Resources

Spatial planning for sustainable water resources development requires precise information on the local potential for providing water yield in a watershed. For water resource conservation, we analyzed spatial and temporal patterns of hydrological provision ecosystem services in the upper Teshio watershed of northernmost Japan. The Soil and Water Assessment Tool (SWAT) was applied to simulate hydrologic processes and determine parameters affecting the water cycle. The spatial increase of water yield at flat area near river channel in winter was explained by low field capacity of soil water, absence of water uptake by crops and gentle topography. The spatial patterns of snowmelt and rainfall were important drivers of the spatial pattern in water yield during other periods. The zonation model was applied to investigate dynamic changes in spatial conservation prioritization of hydrological provision ecosystem services, according to simulated water yields in February, April and October. The results showed that the conservation priority ranking dynamically changed spatially and temporally. Our economic assessment of hydrological provisioning services (irrigation, electricity production and household usage) indicated that the spatial pattern of the priority for water resources was different from that of economic value of the provisioning services. Our results indicated that a combination of hydrologic and cost zonation models would improve sustainable management planning of water resources and their hydrological ecosystem services have great spatiotemporal fluctuation.     

Study on effects of solar radiation and rain on shrinkage, shrinkage cracking and creep of concrete

In this paper, the effects of actual environmental actions on shrinkage, creep and shrinkage cracking of concrete are studied comprehensively. Prismatic specimens of plain concrete were exposed to three sets of artificial outdoor conditions with or without solar radiation and rain to examine the shrinkage. For the purpose of studying shrinkage cracking behavior, prismatic concrete specimens with reinforcing steel were also subjected to the above conditions at the same time. The shrinkage behavior is described focusing on the effects of solar radiation and rain based on the moisture loss. The significant environment actions to induce shrinkage cracks are investigated from viewpoints of the amount of the shrinkage and the tensile strength. Finally, specific compressive creep behavior according to solar radiation and rainfall is discussed. It is found that rain can greatly inhibit the progresses of concrete shrinkage and creep while solar radiation is likely to promote shrinkage cracking and creep.     

DNA promotes the activation of oxygen molecules by binuclear cobalt(II) compounds

We have observed that binuclear cobalt(II) compounds with H(HPTP), Co₂(HPTP)(CH₃COO)(ClO₄)₂ and Co₂(HPTP)Cl(ClO₄)₂, react with oxygen molecules when DNA is present in the solution, cleaving the DNA (H(HPTP) denotes N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,3-diaminopropane-2- ol).     

Analysis of Dispatching Rules of AGV Systems with Multiple Vehicles

We study automated guided vehicle systems that contain multiple vehicles. Each vehicle transports an item from a certain point to its destination. The inter-arrival time of items to each node is assumed to be independently and geometrically distributed. Each node has an infinite buffer capacity, and thus no item is lost. The deadhead time of the empty vehicle and the transportation time of the loaded vehicle are assumed to be arbitrarily distributed. We propose two empty vehicle dispatching policies, and numerically calculate the waiting time distributions of the items for each policy using a state-space reduction technique for Markov chains. Several examples are given to demonstrate the advantages and disadvantages of each policy.     

Preparation of SrBi 2 Ta 2 O 9 Thin Films by Liquid-Delivery MOCVD Without Additional Solvents

SrBi 2 Ta 2 O 9 thin films were prepared by ECR plasma enhanced metalorganic chemical vapor deposition (ECR-MOCVD) with a liquid-delivery system using one cocktail source without an additional solvent. The strontium-tantalum double alkoxide, Sr{Ta[OC 2 H 4 H(CH 3 ) 2 ](OC 2 H 5 ) 5 } 2 , was dissolved in stabilized trimethyl bismuth, Bi(CH 3 ) 3 / dioxane. This source system has been used in a conventional bubbling system. Deposition rate and the composition of the films were strictly controlled by the concentration and the composition of the cocktail source. Therefore, high reproducibility was realized by using this system. The constituent phase of the stoichiometric SBT film as-deposited at 500 C on a (111)Pt/TiO 2 /SiO 2 /Si substrate was a fluorite phase and transformed to the single phase of SBT by the post annealing at 800 C. It showed almost the same ferroelectricity as the stoichiometric composition film.     

SOLUBILITY IN ORGANIC DILUENTS AND EXTRACTION BEHAVIOR OF CALIX[4]ARENE CARBOXYLATES WITH DIFFERENT ALKYL CHAINS

ABSTRACT

Two types of alkylcalix[4]arene carboxylates with different alkyl chains, together with three types with the same alkyl chains were synthesized to investigate their solubility in four different organic diluents. The solubility was found to be enhanced by using the calixarene compounds with longer alkyl chains and by using mixtures of compounds with different alkyl chains. The order of solubility in the different organic diluents was found to be:

chloroform > toluene ? EXXSOL D80 ≈ hexane.

The stoichiometry of the copper complex with the compounds having the same alkyl chains was also determined and the maximum loading capacity of copper with each extractant was estimated.