Resistivity and thermal reproducibility of carbon black and metallic powder filled silicone rubber heaters

Flexible heaters were prepared by extruding platinum‐catalyzed silicone rubber composites with conductive carbon black (CB) and metallic fillers. The conductor resistivity of the extruded heaters decreased in order of conductive titanium dioxide (TiO₂) > aluminum powder ≈ zinc powder > copper powder. Thermoelectric switching phenomena were investigated for the silicone rubber/CB/metallic powder systems. The positive temperature coefficient effect was dependent mainly on the CB content rather than on the content of the metallic powders. Resistivity and thermal reproducibility of the extruded heaters were also investigated by periodically applying AC voltage of 110 V. The heaters containing copper and TiO₂ powders exhibited excellent electrical reproducibility. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1122–1128, 2005     

Time and shear dependent rheology of maleated polyethylene and its nanocomposites

Dipole-dipole and/or hydrogen-bonding interactions between the pendant functional groups within maleated high-density polyethylene (PE-g-MAn) establish a physical polymer network, whose formation kinetics and shear-sensitivity are revealed by dynamic oscillatory testing. The pronounced time and shear dependent viscoelastic properties of PE-g-MAn were not observed for a corresponding imide derivative, PE-g-imide, presumably due to weakened functional group associations in the latter material.The melt compounding of PE-g-MAn with onium-ion exchanged montmorillonite clay (NR₄⁺-MM) resulted in a partially exfoliated hybrid nanocomposite structure, whose viscoelastic behaviour differed significantly from that of the unfilled polymer. The presence of dispersed clay platelets altered the extent of functional group associations, thereby changing the dynamics of network formation.     

Performance of fluorine-added CoMoS/Al2O3 prepared by sonochemical and chemical vapor deposition methods in the hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

The performance of a new type of CoMoS/Al₂O₃ catalyst, with added fluorine and prepared by sonochemical and chemical vapor deposition (CVD) methods, was investigated in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT). The catalyst, which was designed to contain optimum amounts of fluorine and cobalt, exhibited a higher activity, ca. 4.6 times higher activity particularly in the HDS of 4,6-DMDBT, than a fluorine-free catalyst prepared by a conventional impregnation method. The enhanced activity of the new catalyst can be attributed to the cumulative effects of individual factors involved in the catalyst preparation. That is, the use of a sonochemical synthesis led to a high dispersion of small MoS₂ crystallites on the alumina, and the addition of the Co species to the catalyst by CVD caused a close interaction between the Co species and the MoS₂ crystallites to produce numerous CoMoS species, which are the catalytically active species for HDS. The addition of fluorine increased the amounts of acidic sites in the catalyst, which promoted hydrogenation (HYD) route to a greater extent than the direct desulfurization (DDS) route in DBT HDS and both HYD and DDS routes to similar extents in the case of 4,6-DMDBT HDS. Accordingly, the addition of fluorine led to a greater increase in catalytic activity for 4,6-DMDBT HDS than for DBT HDS.     

Spectral and complexity analysis of scalp EEG characteristics for mild cognitive impairment and early Alzheimer's disease

Amnestic mild cognitive impairment (aMCI) often is an early stage of Alzheimer's disease (AD). MCI is characterized by cognitive decline departing from normal cognitive aging but that does not significantly interfere with daily activities. This study explores the potential of scalp EEG for early detection of alterations from cognitively normal status of older adults signifying MCI and AD. Resting 32-channel EEG records from 48 age-matched participants (mean age 75.7 years)—15 normal controls (NC), 16 early MCI, and 17 early stage AD—are examined. Regional spectral and complexity features are computed and used in a support vector machine model to discriminate between groups. Analyses based on three-way classifications demonstrate overall discrimination accuracies of 83.3%, 85.4%, and 79.2% for resting eyes open, counting eyes closed, and resting eyes closed protocols, respectively. These results demonstrate the great promise for scalp EEG spectral and complexity features as noninvasive biomarkers for detection of MCI and early AD.     

An effective dissimilarity measure for clustering of high-dimensional categorical data

Clustering is to group similar data and find out hidden information about the characteristics of dataset for the further analysis. The concept of dissimilarity of objects is a decisive factor for good quality of results in clustering. When attributes of data are not just numerical but categorical and high dimensional, it is not simple to discriminate the dissimilarity of objects which have synonymous values or unimportant attributes. We suggest a method to quantify the level of difference between categorical values and to weigh the implicit influence of each attribute on constructing a particular cluster. Our method exploits distributional information of data correlated with each categorical value so that intrinsic relationship of values can be discovered. In addition, it measures significance of each attribute in constructing respective cluster dynamically. Experiments on real datasets show the propriety and effectiveness of the method, which improves the results considerably even with simple clustering algorithms. Our approach does not couple with a clustering algorithm tightly and can also be applied to various algorithms flexibly.     

Composition pattern oriented tag extraction from short documents using a structural learning method

With the rapid growth of web, automatic tagging that detects informative terms from a document becomes an important problem for information aggregation and sharing services. In particular, automatic tagging for short documents becomes more interesting as many users are increasingly publishing information through social media services which encourage users to create the documents of short length. In this paper, we propose a novel automatic tagging model for short text documents from social media services, following the framework of supervised learning. We redefine traditional frequency-based term features so that they can address the properties of the documents created under length limitation and consider sequential dependencies between successive terms in a document based on a structural support vector machine. In addition, our proposed approach incorporates composition patterns by which users put informative terms into their documents. Extensive experiments have been conducted to validate the presented approach, and it was found that the proposed term features were effective for extracting tags, and the tag extractor trained by considering the sequential dependencies and composition patterns achieved superior performance results over the existing alternative methods.     

Experimental and theoretical study on H2/CO2 separation by a five-step one-column psa process

An experimental and theoretical study is performed for bulk separation of H₂/CO₂ mixture (70/30 volume %) by PSA process with zeolite 5A, a process widely used commercially in conjunction with the catalytic steam reforming of natural gas or naphtha. For the optimized adsorption conditions of PSA, the characteristics of adsorption/desorption characteristics have been studied through breakthrough and desorption experiments under various conditions. The purge-to-feed ratio is important to the H₂ product purity only at a long adsorption step time. H₂ could be concentrated from 70% in the feed to 99.99% at H₂ recovery of 67.5%. The results of all five steps in PSA are successfully predicted by the LDF model considering an energy balance and nonlinear isotherm. For the model, the effective diffusivities (D,) are obtained separately from the uptake curves of H₂ and CO₂. The Langmuir-Freundlich isotherm is used to correlate the experimental equilibrium data and is very well fitted to the results.     

Tactile display with tangential and normal skin displacement for robot-assisted surgery

This paper proposes a tactile display providing both shear and normal feedback to the fingertip for generating three-axis tactile feedback during teleoperation of a surgical robot. The display is composed of five balloons actuated by controlling the pneumatic pressure. The implemented display is 18?mm?×?18?mm?×?15?mm. This size is suitable for mounting the display onto the master controls of a surgical robot. The maximum normal and shear displacements are 2 and 1.3?mm, respectively. The proposed tactile display may provide perceivable stimuli to a human finger pad in all five directions: normal, distal, proximal, radial, and ulnar. This paper also reports on the results of psychophysical measurement of the minimum perceivable movement of the developed tactile display for each of the five directions.     

Underactuated miniature bending joint composed of serial pulleyless rolling joints

This paper proposes a miniature bending joint composed of serial rolling joints; it refers to the classification of small joints of other products and studies on surgical applications according to the structures and transmissions. To achieve this, a pulleyless rolling joint is introduced as a unit component and the basic design principle is established for the joint. A simple mechanism guarantees a smooth rolling contact using elastic fixtures. Underactuation, which prevents S-shaped curvature similar to buckling, is applied to drive the bending joint with a limited number of wire cables. Using a 1-DOF real-sized prototype, experiments were performed to measure the motion accuracy and payload capacity from various angles to evaluate the efficacy of an improved design that enhances the payload on the distal end. This novel joint is applicable to a wider variety of surgical tools and catheters relative to other candidates owing to its small constant curvature, reasonable payload capacity, and miniature size.