Separation characteristics of acetic acid–water mixtures by using poly(vinyl alcohol‐g‐4‐vinyl pyridine) membranes by pervaporation and temperature difference evapomeation techniques

The separation of acetic acid–water mixtures was carried by using pervaporation (PV) and temperature difference evapomeation (TDEV) methods. For the separation process 4‐vinyl pyridine was grafted on poly(vinyl alcohol). Membranes were prepared from the graft‐copolymer by casting method and crosslinked by heat treatment. The effect of feed composition on the separation characteristics was studied and the performances of the separation methods were compared. Permeation rates obtained in PV were found to be high, whereas separation factors were high in TDEV method. Membranes gave permeation rates of 0.1–3.0 kg/(m² h) and separation factors of 2.0–61.0, depending on the composition of the feed mixture and the method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2030–2039, 2006     

Volatile glandular secretions of three species of new world army ants,Eciton burchelli,Labidus coecus,andLabidus praedator

The Dufour glands of workers ofEciton burchelli contain a mixture of small quantities of oxygenated compounds, some of which are derived from terpenes, and C₁₇-C₂₅ hydrocarbons. The secretion of the Dufour glands of soldiers was either similar to that of workers, with geranylacetone a significant component, or they contained geranyllinalool in large amounts. The glands of workers and soldiers ofLabidus praedator andLabidus coecus contained (E)--ocimene, a new substance for the Dufour glands of ants. 4-Methyl-3-heptanone was the dominant compound in the mandibular glands ofE. burchelli andL. coecus. Skatole and indole were found in the gasters ofL. praedator, and skatole was present in the venom glands of some soldiers ofE. burchelli.     

Preparation of free‐standing chitosan membranes for Chlorella vulgaris harvest and examination on suppression of algae‐fouling properties

Free‐standing chitosan membranes were prepared using genipin as crosslinker, using several molecular weights of polyethylene glycol (PEG) as a void‐forming agent. The membrane surface formation and chitosan polymer chain crosslinking were confirmed through SEM and FTIR, respectively. The water flux was remarkably increased with increasing molecular weight of PEG employed in preparation of composite chitosan membrane (J∝[PEG(MW)]0.85), it appeared over 6000 Da of PEG. During Chlorella vulgaris harvest using chitosan membranes, focus was made on algae‐fouling caused by the deposition of cells and extracellular organic matter, and it was found that membranes employing lower molecular weight of PEG (under 10000 Da) had been maintaining the high flux recovery after alternating filtration cycles, in addition to PEG20000 containing membrane. The chitosan membrane prepared with lower molecular weight of PEG exhibited better suppression of algae‐fouling properties. The Chlorella vulgaris harvesting results indicated that cell rejection rate reached above 98%.     

Analysis of interaction between mechanical force and chemical effect in cleaning phenomenon by probability density functional method

Probability density functional method was used to determine whether interaction between mechanical force and chemical action in cleaning was an additive effect, a synergistic effect, or an offsetting effect. As a soiled sample, iron (III) oxide soiled fabric, Sudan IV soiled fabric, commercially available artificial soiled fabric containing mixed stains, etc. were used and washed with a tergotometer. Mean value μ_rl and standard deviation σ_rl of the cleaning force distribution were calculated by using probability density functional method, and the interaction was judged using Δμ_rl which is the difference between μ_rl obtained under the two conditions. As results, additive effects between the mechanical force and the pH effect were confirmed in the cleaning of iron (III) oxide soiled fabric and commercially available artificially soiled fabric, and an additive effect between the mechanical force and the effect of the surfactant concentration was confirmed in the cleaning of Sudan IV soiled fabric. Therefore, it was presumed that an additive effect is often established between the mechanical action and the chemical action in cleaning, rather than a synergistic effect or an offsetting effect.     

Observer-based robust control giving consideration to transient behaviour for linear systems with

In this paper, we present an observer-based controller design method which achieves performance robustness together with robust stability for linear multivariable systems with structured uncertainties. The performance robustness means that the deterioration of control performance is suppressed when we compare the transient behaviour for the uncertain system with a desired one generated by using the nominal system directly and at the same time excessive control input is avoided. In this approach, we adopt a similar way to the model-following technique and assume that the control law consists of a state feedback law for the nominal system and a compensation input for the purpose of preventing the error between the transient behaviour for the uncertain system and the desired one. The compensation input is additional modification term given by feedback form of an estimated error signal and is determined so that an upper bound of a quadratic cost function for the error system between the real trajectory for the plant and the desired one is minimized. We show that a condition for the existence of the compensation input which minimizes an upper bound of the quadratic cost function for the error system is given in terms of linear matrix inequalities (LMIs). Finally, numerical examples are presented.     

Polypropylene nanocomposites prepared with natural and ODTABr‐modified montmorillonite

In this study, the main goal is to obtain montmorillonite nanocomposites of polypropylene (PP). To achieve this goal, a two‐phase study was performed. In the first part of the work, organomodified clay (OMMT) was synthesized and characterized. Octadecyltrimethylammonium bromide (ODTABr) cationic surfactant was added to the clay (Na‐activated montmorillonite, MMT) dispersions in different concentrations in the range of 5 × 10^?5–1 × 10^?2 mol/L. Rheologic, electrokinetic, and spectral analyses indicated that ODTABr has interacted with MMT at optimum conditions when the concentration was 1 × 10^?2 mol/L. In the second part, modified (OMMT) and unmodified (MMT) montmorillonite were used to obtain PP nanocomposites (OMMT/PP and MMT/PP, respectively). The nanocomposites were prepared by melt intercalation where the montmorillonite contents were 1 or 5% (w/w) for each case. The thermal analyses showed that the thermal properties of OMMT/PP nanocomposites were better than MMT/PP, and both of them were also better than pure polymer. Increase in the concentration of MMT (or OMMT) decreased the thermal resistance. Based on the IR absorption intensity changes of regularity and conformational bands, it is found that the content of the helical structure of macromolecular chains has increased with increasing concentrations of both MMT and OMMT in the nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

K-band 3-D MMIC low noise amplifier and mixer using TFMS lines with ground slit

Three-dimensional (3-D) microwave monolithic integrated circuit (MMIC) technology, that incorporates slits in the ground metal, was applied to K-band low noise amplifier (LNA) and I/Q mixer to provide a low cost solution for various K-band receivers such as for P-to-P radio, WLAN, and UWB sensors. The LNA incorporates a quasicoplanar stub in the input-matching network, improving the noise figure by 1 dB. This low-noise amplifier (LNA) exhibits a noise figure of 2.5 dB with an associated gain of 16 dB and an area of 0.75/spl times/0.65 mm/sup 2/. The I/Q resistive mixer incorporates a broadside 3-dB coupler with a 22-/spl mu/m-wide slit in the ground metal beneath the coupled thin-film micro-strip (TFMS) lines (patent pending). The insertion loss of the 3 dB coupler is 0.75 dB. The I/Q mixer exhibits a conversion loss of less than 14 dB at 0.1-2.0GHz IF frequencies for 2-dBm local input power. These LNA and mixer potentially make it easier to integrate receiver functions in a die.     

Axial compressive behaviour of reinforcing fibres and interphase in glass/epoxy composite materials

Axial compressive behaviour of reinforcing fibres and interphase in glass fibre/epoxy resin composites were examined. Axial compressive strengths of glass fibres were evaluated by the tensile recoil method. The effects of silane-based coupling surface treatment agent on the fibre compressive strengths were investigated. The glass fibres showed higher compressive strengths when coated by the surface treatment. Interphase behaviour was also investigated by means of the single-fibre embedded compressive test. The particular stress and strain distributions inside the specimen were examined by a three-dimensional finite element analysis. The parameter interfacial transmissibility instead of the conventional critical fibre length theory was introduced as an index of interfacial properties. This parameter was useful to estimate the interfacial properties at the elastic state apart from the complicated critical state. It was confirmed that the surface treatment improved the glass/epoxy interphase under axial compressive load.     

A Comparison Study of Moving Object Index Structures

The task of selecting the most appropriate method for indexing the data according to application requires a careful comparison study of indices of interests. In particular, we consider object movements by tracing their trajectories within a predefined road network. MV3DR-tree and 3DR-tree constitute our first group indexing the objects moving in free movement scenarios. Besides, Mapping and MON-tree are the second group indexing the locations of objects moving over a network of road. Those access methods mainly organize a group of R-tree in order to index the underlying road network and the object movements. Our goal in this study is to evaluate existing proposals under fair circumstances with respect to storage consumption and spatio-temporal query execution performance. In our comparisons, we discuss the structure’s sensibility to query’s spatial and/or temporal extent as well as the tradeoff arising between two groups in terms of reliability and disk access performance. We believe that revealing the vulnerabilities of the selected structures, especially Mapping and MON-tree motivates us to design more robust organizations.