Effects of titania content and plasma treatment on the interfacial adhesion mechanism of nano titania-hybridized polyimide and copper system

Nano-titania (TiO₂) incorporated into polyimide (PI) matrix can significantly enhance the adhesion strength for PI/TiO₂ hybrid film and copper system. Surface modifications by various plasma treatments (Ar, Ar/N₂ and Ar/O₂) were also applied in this study to improve the adhesion strength. The Ar/N₂ plasma treatment is regarded as the more effective way in promoting the adhesion strength. The maximum adhesion value of 9.53 N/cm was obtained for the PI/TiO₂-1 wt% hybrid film with Ar/N₂ plasma treatment. It is enhanced about 10 times as large as pristine PI. Furthermore, by Ar/O₂ plasma treatment, a weak boundary of copper oxide was formed at the interlayer between PI/TiO₂ hybrid film and copper which decreases the adhesion strength. The effects of plasma treatment and content of nanosized TiO₂ on the adhesion strength between PI/TiO₂ hybrid film and copper system were studied. Atomic force microscope and contact angle analyses were used to measure the changes in surface morphology and surface energy as a result of plasma treatment. Besides, the interfacial states of peeled-off polymer side and copper side were investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Based on the result of XPS spectra, the peeled-off failure mode between PI/TiO₂ hybrid film and copper was proposed in this study.     

Synthesis and dielectric properties of polystyrene‐clay nanocomposite materials

Polystyrene‐clay nanocomposite (PsCN) materials were synthesized and their properties of crystallinity, thermal behavior, and dielectric characteristics were investigated. A polymerizable cationic surfactant, [2‐(dimethylamino)ethyl]triphenylphonium bromide, was used for the intercalation of montmorillonite (MMT). The organophilic MMT was prepared by Na⁺‐exchanged MMT and ammonium cations of a cationic surfactant in an aqueous medium. Organophilic styrene monomers were intercalated into the interlayer regions of organophilic clay hosts followed by a free‐radical polymerization. Exfoliation to 2 wt % MMT in the polystyrene (PS) matrix was achieved as revealed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal properties by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also studied. The dielectric properties of PsCNs in the form of film with clay loading from 1.0 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 25–70°C. A decreased dielectric constant and low dielectric loss were observed for PsCN materials. The dielectric response at low frequency that originated from dipole orientation was suppressed due to the intercalation of clay materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1368–1373, 2004     

Fourier transform infrared (FTIR) authentication and batch-to-batch consistency for different types of paints using benchtop and handheld FTIR spectrophotometers for oil and gas industry

Standardization of Fourier transform infrared (FTIR) fingerprint region for paints and assessment on the reproducibility using different spectrophotometers were investigated. While selective fingerprint regions may be confusing for technicians/analysts who are non-chemists, we attempt to generalize these regions (e.g., 1300–1000 cm⁻¹ for Epoxy part A and 1400–1000 cm⁻¹ for Epoxy part B) by choosing a universal region (2000–900 cm⁻¹) that works for different paints. Comparison result using a paired student t-test shows that the degree of similarity (r) values from the studied regions are not statistically different. The paint fails the screening analysis occasionally on-site when analyzed using handheld FTIR due to the higher level of noise that gives low r values (r < 0.900 ± 0.002). The same samples were analyzed using a benchtop FTIR and the r values are above 0.900 ± 0.002. While the screening may lead to a false rejection of the sample on-site, there could be occurrence of false acceptance. The on-site screening of EPZ part A with different formulations, for instance, shows that the r values over the entire IR spectrum are above 0.900 ± 0.002 when analyzed using handheld FTIR. After the samples were analyzed using the benchtop, the r values fall below 0.900 ± 0.002.     

Effects of anodizing voltage on the anodized and hydrothermally treated titanium surface

Anodic oxidation is the process of creating a titanium oxide layer with various defects more dense and stable. In this study, a dense, stable and porous oxide layer was formed using anodic spark oxidation on pure titanium surface and hydroxyapatite crystals were formed on its surface via a hydrothermal treatment. A mixture of 0.02M−GP (Glycerolphosphate disodium salt) and 0.2M-CA (Calcium acetate) was used as an electrolyte. By increasing the anodizing voltage to 220, 260, 300, and 360 V, the effects of the anodizing voltage were examined by evaluating the film properties after anodization and a hydrothermal treatment. Breakdown occurred around 230 V. As the voltage increased after breakdown, the pore size increased. After the hydrothermal treatment, the amount of HA crystal precipitation was also increased as the voltage increased. The mean surface roughness (Ra) of the anodizing surface was also increased as the voltage increased. The Ra value was larger in the hydrothermally treated group compared with the group treated with anodization as a result of the HA crystals present on the surface after the hydrothermal treatment. Corrosion resistance of the surface modified by anodization was significantly increased in a saline solution compared to that for the non-treated group; this increased further after the hydrothermal treatment. These increases were most likely due to a thick stable oxide layer formed through anodization. Thus, it is believed that titanium with its surface modified through anodic spark oxidation would be a suitable biomaterial due to its corrosion resistance and biocompatibility.     

A computational study of strain inhomogeneity in wire drawing

Inhomogeneous plastic deformation that develops during wire-drawing, and its impact on the drawing force, are investigated with a computational method. The effects of critical parameters, including die angle, area reduction, friction coefficient, and material hardening are sorted out, and the accuracy of certain simple formulas presented in the literature is assessed. The results suggest that the redundant strains (strains beyond those necessary for area reduction) are dependent principally on the die angle and area reduction; the interfacial friction and the strain hardening tend to have little influence on the strains. In addition, the impact of spatial inhomogeneity in hardness induced by strain hardening from prior passes is investigated.     

Modeling of tool wear in drilling by statistical analysis and artificial neural network

The useful life of a cutting tool and its operating conditions largely control the economics of the machining operations. Hence, it is imperative that the condition of the cutting tool, particularly some indication as to when it requires changing, to be monitored. The drilling operation is frequently used as a preliminary step for many operations like boring, reaming and tapping, however, the operation itself is complex and demanding.

Back propagation neural networks were used for detection of drill wear. The neural network consisted of three layers input, hidden and output. Drill size, feed, spindle speed, torque, machining time and thrust force are given as inputs to the ANN and the flank wear was estimated. Drilling experiments with 8 mm drill size were performed by changing the cutting speed and feed at two different levels. The number of neurons in the hidden layer were selected from 1, 2, 3, …, 20. The learning rate was selected as 0.01 and no smoothing factor was used. The estimated values of tool wear were obtained by statistical analysis and by various neural network structures. Comparative analysis has been done between statistical analysis, neural network structures and the actual values of tool wear obtained by experimentation.     

A Novel Data Centric Information Retrieval Protocol for Queries in Delay Tolerant Networks

Information Retrieval (IR) systems aim to retrieve data that satisfies certain requirements and constitute an important service in many types of networks, including Delay/Disruption Tolerant Networks (DTNs). In current DTN based IR systems, the data that satisfies a query is assumed to be stored on a single node. Therefore, once a node receives a query in which it has the corresponding data, the query can be resolved completely. However, in scenarios where a query requires data from multiple nodes, these IR systems may fail. Henceforth, in this paper, we propose Distributed Data-Centric Information Retrieval (DDC-IR), a data centric IR system that supports all query types; e.g., continuous and complex. More importantly, it is designed specifically to operate in DTNs. It also incorporates a new packet, aka Query Reply Packet, that includes both a query and one or more replies. We show how this packet facilitates efficient query resolution and enables data centric routing. In addition, it uses caching so that nodes store popular queries that has the effect of speeding up query resolution. We have conducted an extensive simulation study to compare DDC-IR to state of the art IR systems using the popular Random Waypoint model and a trace-file containing student movements on a campus. The results show that DDC-IR is able to resolve 50 % more queries and has an 80 % lower buffer occupancy level than existing IR systems. We also tested DDC-IR in networks with varying sizes. For networks with 100 nodes, DDC-IR is able to resolve queries while current IR systems fail to resolve any queries. In particular, when the number of nodes increases, current IR systems fail to resolve any queries, whilst DDC-IR is able to resolve complex and continuous queries. The influence of the number of sub-queries on query resolution time is also studied. Specifically, when the number of sub-queries in a complex query increases from five to nine, DDC-IR uses 50 % more time to resolve a query. In comparison, prior IR systems fail to resolve any queries.     

A Lyapunov functional approach to robust stability analysis of continuous-time uncertain linear systems in polytopic domains

In this paper, a sufficient linear matrix inequality (LMI) condition is presented for robust stability analysis of continuous-time linear time-invariant (LTI) systems in polytopic domains. The underlying idea behind the proposed approach is to introduce a family of complex functions which map the closed right-hand side of the complex plane into the inside of the closed unit circle centered at the origin. Then, the mapping properties are used to assure that all the eigenvalues of a system are located in the open left-hand side of the complex plane. Examples show the validity of the proposed condition.     

Out-of-sample extrapolation of learned manifolds

We investigate the problem of extrapolating the embedding of a manifold learned from finite samples to novel out-of-sample data. We concentrate on the manifold learning method called Maximum Variance Unfolding (MVU) for which the extrapolation problem is still largely unsolved. Taking the perspective of MVU learning being equivalent to Kernel PCA, our problem reduces to extending a kernel matrix generated from an unknown kernel function to novel points. Leveraging on previous developments, we propose a novel solution which involves approximating the kernel eigenfunction using Gaussian basis functions. We also show how the width of the Gaussian can be tuned to achieve extrapolation. Experimental results which demonstrate the effectiveness of the proposed approach are also included.     

The effect of flaming on computer-mediated negotiations

There is an increasing use of computer media for negotiations. However, the use of computer-mediated channels increases the hostile expressions of emotion, termed flaming. Although researchers agree that flaming has important effects on negotiation, predictions concerning these effects are inconsistent, suggesting a need for further investigation. We address this need by extending current flaming and negotiation research in two ways. First, we identify two different types of flaming: that which is motivated by perceptions concerning the negotiating opponent (e.g., he/she is unfair) and that which is motivated by perceptions concerning the negotiating context (e.g., the communication channel is too slow). Second, we differentiate between the effects of flaming on the concession behaviors of the flame sender and the flame recipient, and the effects of these behaviors on negotiated agreement. Via a laboratory study, we demonstrate that flames directed at the negotiation opponent slightly decrease the likelihood of reaching an agreement, and when an agreement is reached, it result in outcomes significantly favoring the flame recipient rather than the flame sender. In contrast, flames directed at the negotiation context significantly increase the likelihood of agreement, although outcomes still favor the flame recipient over the flame sender. These results suggest that flame senders are generally worse off than flame recipients, which provides an important basis for the strategic use of flaming in negotiations.