Preparation and characterization of nanoporous thin films from fully aliphatic polyimides

Fully aliphatic polyimides (APIs) were prepared from rel-(1'R,3S5'S)-spiro[furan-3(2H),6'-[3]oxabicyclo[3.2.1]octane]-2,2',4',5(4H)-tetrone (DAn) as unsymmetrical spiro dianhydride, and either cis-trans-1,4-diaminocyclohexane (mix-DACH) or trans-1,4-diaminocyclohexane (trans-DACH) as diamine. Structure of all prepared monomers and polymers was confirmed via 1H-NMR and FT-IR. The solubility, optical transparency, and thermal properties of the full APIs were investigated. The solubility and decomposition temperature of the full APIs were found to be correlated with their intermolecular regularity confirmed via wide-angle X-ray diffraction (WAXD). Triblock copolyimides were synthesized through the incorporation of a thermally labile polymer, poly(propylene glycol) (PPG), into the full APIs, and their thermal properties were studied via thermogravimetric analysis (TGA). Nanoporous thin films of the full APIs were prepared via thermolysis of the labile block in the copolyimide films. Phase separation and nanopore formation in the copolymer films were confirmed via atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. Nanoporous pores were successfully prepared inside the films.     

Tip clearance effect on through-flow and performance of a centrifugal compressor

Numerical simulations have been performed to investigate tip clearance effect on through-flow and performance of a centrifugal compressor which has the same configuration of impeller with six different tip clearances. Secondary flow and loss distribution have been surveyed to understand the flow mechanism due to the tip clearance. Tip leakage flow strongly interacts with mainstream flow and considerably changes the secondary flow and the loss distribution inside the impeller passage. A method has been described to quantitatively estimate the tip clearance effect on the performance drop and the efficiency drop. The tip clearance has caused specific work reduction and additional entropy generation. The former, which is called inviscid loss, is independent of any internal loss and the latter, which is called viscous loss, is dependent on every loss in the flow passage. Two components equally affected the performance drop as the tip clearances were small, while the efficiency drop was influenced by the viscous component alone. The additional entropy generation was modeled with all the kinetic energy of the tip leakage flow. Therefore, the present paper can provide how to quantitatively estimate the tip clearance effect on the performance and efficiency.     

A study of the emotional evaluation models of color patterns based on the adaptive fuzzy system and the neural network

Proposed in this article are two kinds of emotional models based on the neural network and the adaptive fuzzy system that can transform the physical features of a color pattern into its emotional features. The purpose of this system of models is to evaluate the neural network and adaptive fuzzy system for its ability to model psychological experimental data in a way similar to what a human expert would do. Construction of the models was motivated by Soen's psychological experiments, in which he found that such physical features as average hue, saturation, and intensity and the dynamic components of color patterns affected the emotional features represented by a pair of adjectives having opposite meanings. One is based on the neural network in the proposed models, and the other consists of two adaptive fuzzy rule bases and a γ model, a fuzzy set operator, to fuse the evaluation values produced by them. The proposed models showed superior performances compared to Soen's model in the approximation of nonlinear transforms, whereas the latter showed an advantage in obtaining the linguistic interpretation from the trained results. The evaluated results of color patterns can be used to construct a emotion‐based color‐pattern retrieval system, which would be able to recommend the color patterns of a desired human feeling. We believe that in linguistic queries of human feelings, these color‐pattern retrieval systems would be able to select from a gallery the corresponding textile designs, wallpapers, or pictures. © 2002 Wiley Periodicals, Inc. Col Res Appl, 27, 208–216, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10052     

Anticancer drug-inorganic nanohybrid and its cellular interaction

An anticancer drug, methotrexate (MTX), has been successfully hybridized with layered double hydroxide (LDH) through co-precipitation route to produce MTX-LDH nanohybrids (MTX-LDH). According to the X-ray diffraction and FT-IR spectroscopy, it was confirmed that MTX molecules are stabilized in the interlayer space of LDHs by electrostatic interaction, maintaining their functional groups and structural integrity. According to the drug release study, the total amount of released MTX from the LDH lattice was determined to be larger under a simulated intracellular lysosomal condition (pH = 4.5) than simulated body fluid one (pH = 7.4). It is, therefore, expected that the MTX molecules in MTX-LDH can be effectively released in lysosomes, since the MTX release could be accelerated via ion-exchange reaction and dissolution of LDH in an acidic lysosomal condition. We also examined the anticancer efficacy of MTX-LDH in human breast adenocarcinoma MCF-7 cells. The cellular uptake of MTX was considerably higher in MTX-LDH-treated cells than in free MTX-treated cells, giving a lower IC50 value for the former than the latter. All the results demonstrated that the MTX-LDH nanohybrid allows the efficient drug delivery in cells, and thus enhances drug efficacy.     

Synthesis and characterization of Eu3+ doped Gd2O3 nanotubes using multi wall carbon nanotubes as removable templates

Eu³⁺ doped Gd₂O₃ nanotubes have been synthesized using multi wall carbon nanotubes as removable templates by employing a liquid phase deposition method. The prepared Eu³⁺ doped Gd₂O₃ nanotubes were characterized by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy, fourier transform infrared sepctroscopy and thermogravimetry and differential thermal analysis. XRD patterns conrm the cubic phase of Eu³⁺ doped Gd₂O₃ nanotubes. From the measured SEM images, the average diameter of the Eu³⁺: Gd₂O₃ nanotubes were estimated to be in the range of 50–70 nm. The photoluminescence analysis revealed that the Eu³⁺: Gd₂O₃ nanotubes can display a strong red emission peak at around 616 nm, due to the ⁵D₀→⁷F₂ electric dipole transition of Eu³⁺ ions. Such luminescent powders are expected to find potential applications in fluorescent lamps and display device applications.     

Mathematical model and solution algorithms for selective disassembly sequencing with multiple target components and sequence-dependent setups

This study considers selective disassembly sequencing under the sequential disassembly environment in which one component is obtained at each disassembly operation. The problem is to determine the sequence of disassembly operations to obtain multiple target components of a used or end-of-life product for the purpose of repair, reuse, remanufacturing, disposal, etc. In particular, we consider sequence-dependent setups in which setup costs depend on the disassembly operation just completed and on the operation to be processed. The problem is represented as a disassembly precedence graph and then a new integer programming model is suggested for the objective of minimising the total disassembly cost. After it is proved that the problem is NP-hard, we suggest two types of heuristics: (1) branch and fathoming algorithm for small-to-medium-sized instances; and (2) priority-rule-based algorithm for large-sized instances. A series of computational experiments, i.e., effectiveness of the new integer programming model and performances of the two heuristic types, were done on various test instances, and the results are reported. In addition, to show the applicability of the mathematical model and the solution algorithms, a case study is reported on an end-of-life electronic calculator.     

Scheduling algorithms to minimise the total family flow time for job shops with job families

This paper considers the job scheduling problem in which jobs are grouped into job families, but they are processed individually. The decision variable is the sequence of the jobs assigned to each machine. This type of job shop scheduling can be found in various production systems, especially in remanufacturing systems with disassembly, reprocessing and reassembly shops. In other words, the reprocessing shop can be regarded as the job shop with job families since it performs the operations required to bring parts or sub-assemblies disassembled back to like-new condition before reassembling them. To minimise the deviations of the job completion times within each job family, we consider the objective of minimising the total family flow time. Here, the family flow time implies the maximum among the completion times of the jobs within a job family. To describe the problem clearly, a mixed integer programming model is suggested and then, due to the complexity of the problem, two types of heuristics are suggested. They are: (a) priority rule based heuristics; and (b) meta-heuristics. Computational experiments were performed on a number of test instances and the results show that some priority rule based heuristics are better than the existing ones. Also, the meta-heuristics improve the priority rule based heuristics significantly.     

A fluid-structure interaction analysis of design factor of subsurface irrigation PC dripper

A subsurface drip irrigation system delivers water and nutrients directly to the plant root zone; other conventional nozzles-type or sprinklers-type irrigation are not used, and water-saving can reach 42–78%. In order to achieve this impact effectively, the drip irrigation requires a constant water supply under variations in pressure, which is so-called pressure compensating (PC) performance. The pressure compensating feature can be obtained by physical interaction between water flow and deformable silicone rubber in the PC dripper. In addition, pressure condition to ensure uniform water flow as a tresholding point also should be well designed, but it is generally have relied on the empiricial optimization. Here, we applied computational fluid dynamics to investigate water flow features in terms of flow rate and pressure drop of a conventional PC dripper. To understand the quantitative effects of changes in design parameters, we explored the fluid-structure interaction scheme in the CFD analysis between water flow and silicone rubber deformation. In this study, it is found that the marginal space for the silicone rubber deformation determined the threshold pressure condition; the friction condition of the tortuous channel of the dripper controlled the flow rate. This parametric study gave the logical insight to design new drip emitter with well-controlled and improved performance.

     

Polymer Coated CaAl-Layered Double Hydroxide Nanomaterials for Potential Calcium Supplement

We have successfully prepared layered double hydroxide (LDH) nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH). The surface of CaAl-LDH was coated with enteric polymer, Eudragit^®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1%) of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit^®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 μg/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit^®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement.