Effects of gage length, loading rates, and damage on the strength of PPTA fibers

Axial tension and transverse compression experiments on single fibers were performed to investigate the mechanical behavior of three high-performance fibers (Kevlar^®, Kevlar^® 129, and Twaron^®) with diameters in the order of 9-12 μm. The single fibers were manufactured from 1998 through 2008. A miniaturized tensile Kolsky bar was used to determine the tensile response of PPTA single fibers at a high strain rate. Gage length and strain rate were found to have minimum effects on the tensile strength of PPTA single fibers. Manufacturing time over a decade was found to have negligible effects on the tensile strength of the fibers. Initial transverse compression on the fibers reduces their ultimate tensile strengths. A high resolution scanning electron microscope (SEM) was also used to examine the fracture modes of transversely deformed fibers. Different types of fracture morphology were observed.     

Developing crash modification functions to assess safety effects of adding bike lanes for urban arterials with different roadway and socio-economic characteristics

Although many researchers have estimated crash modification factors (CMFs) for specific treatments (or countermeasures), there is a lack of studies that explored the heterogeneous effects of roadway characteristics on crash frequency among treated sites. Generally, the CMF estimated by before–after studies represents overall safety effects of the treatment in a fixed value. However, as each treated site has different roadway characteristics, there is a need to assess the variation of CMFs among the treated sites with different roadway characteristics through crash modification functions (CMFunctions). The main objective of this research is to determine relationships between the safety effects of adding a bike lane and the roadway characteristics through (1) evaluation of CMFs for adding a bike lane using observational before–after with empirical Bayes (EB) and cross-sectional methods, and (2) development of simple and full CMFunctions which are describe the CMF in a function of roadway characteristics of the sites. Data was collected for urban arterials in Florida, and the Florida-specific full SPFs were developed. Moreover, socio-economic parameters were collected and included in CMFunctions and SPFs (1) to capture the effects of the variables that represent volume of bicyclists and (2) to identify general relationship between the CMFs and these characteristics. In order to achieve better performance of CMFunctions, data mining techniques were used.     

Geckoprinting: assembly of microelectronic devices on unconventional surfaces by transfer printing with isolated gecko setal arrays

Developing electronics in unconventional forms provides opportunities to expand the use of electronics in diverse applications including bio-integrated or implanted electronics. One of the key challenges lies in integrating semiconductor microdevices onto unconventional substrates without glue, high pressure or temperature that may cause damage to microdevices, substrates or interfaces. This paper describes a solution based on natural gecko setal arrays that switch adhesion mechanically on and off, enabling pick and place manipulation of thin microscale semiconductor materials onto diverse surfaces including plants and insects whose surfaces are usually rough and irregular. A demonstration of functional ‘geckoprinted’ microelectronic devices provides a proof of concept of our results in practical applications.     

A structured Co–B catalyst for hydrogen extraction from NaBH4 solution

A structured Co–B catalyst has been developed to produce hydrogen from an alkaline NaBH₄ solution. The catalyst was prepared by chemical reduction of Co precursors coated on a Ni foam support. The effects of catalyst preparation conditions on activity of the catalyst were investigated. The active catalyst was amorphous in structure and contains boron with a Co/B molar ratio of 1.5–2.8. With increasing the heat treatment temperature, the catalyst showed a maximum activity to hydrogen generation at approximately 250 °C. Adhesion of the catalyst to the support was also enhanced by heat treatment at 300–400 °C. The catalysts were successfully applied in both a batch reactor and a flow reactor for continuous generation of hydrogen.     

On the origin of electrodeposition mechanism of ZnO on ITO substrate

Zinc oxide (ZnO) was potentiostatically deposited on indium tin oxide (ITO) substrates. Comparing of the theoretical mass/charge ratio with experimental value measured byin-situ electrochemical quartz crystal microbalance, the origin of deposition mechanism of ZnO could be explained as follows: (i) surface pH enhancement due to the adsorption of hydroxide ion; (ii) the formation of intermediate species (i.e., zinc hydroxide (Zn(OH)⁺); (iii) ZnO deposition with production of water.Ex-situ morphological and structural analyses by scanning electron microscope and X-ray diffraction strongly supported the deposition mechanism of ZnO. This also showed that hexagonal shaped ZnO islands were first formed on ITO cathode and grew into compact ZnO films, and the formation behaviour of ZnO was clearly explainedvia analysis of the profile of measured current.     

Bioaffinity detection of pathogens on surfaces

The demand for improved technologies capable of rapidly detecting pathogens with high sensitivity and selectivity in complex environments continues to be a significant challenge that helps drive the development of new analytical techniques. Surface-based detection platforms are particularly attractive as multiple bioaffinity interactions between different targets and corresponding probe molecules can be monitored simultaneously in a single measurement. Furthermore, the possibilities for developing new signal transduction mechanisms alongside novel signal amplification strategies are much more varied. In this article, we describe some of the latest advances in the use of surface bioaffinity detection of pathogens. Three major sections will be discussed: (i) a brief overview on the choice of probe molecules such as antibodies, proteins and aptamers specific to pathogens and surface attachment chemistries to immobilize those probes onto various substrates, (ii) highlighting examples among the current generation of surface biosensors, and (iii) exploring emerging technologies that are highly promising and likely to form the basis of the next generation of pathogenic sensors.     

Influence of copper oxide modification of a platinum cathode on the activity of direct methanol fuel cell

To determine whether a copper oxide modified Pt cathode (PtCuO_m) improves a performance of direct methanol fuel cells (DMFC), we performed structural and morphological analysis of the cathode and measured current-potential profile and impedance spectroscopy. Comparing with an unmodified Pt cathode, we found that PtCuO_m prepared by rf sputtering techniques induced higher oxygen reduction reaction rate and suppressed electrocatalytic oxidation of methanol, which is the main reason of the mixed potential occurred at a cathode. Therefore, PtCuO_m increased the power performance of DMFC applying both oxygen and air and electrochemical impedance spectra clearly supported the difference of the performance between unmodified and modified Pt electrodes. These results may play a role in better long-term stability of DMFC systems.     

The effect of a hot-wire in the tandem GMAW process ascertained by developing a multiphysics simulation model

Journal of Mechanical Science and Technology - Physical phenomena such as arc interference, deflection in droplet transfer, and bulging in weld pool are observed in the tandem gas metal arc welding...     

Development of water content sensor composed of small copper electrodes for use during fire resistance tests of concrete and cement mortar elements

The purpose of this study is to develop a sensor for measuring the water content in concrete and cement mortar elements usable in fire tests. Annealed copper wires were used as electrodes of the water content sensor. Each electrode is 20 mm in length and 0.8 mm in diameter. The separation distance between the electrodes is 2 mm. By measuring the electric resistance, water content can be monitored continuously. Mortar bar specimens were used to calibrate the sensor by measuring electric resistance as a function of water content at a constant temperature of 26°C. The temperature dependence of the electrical resistance was approximated by a functional relationship developed by Ichinose for a similar type of sensor. As a result, a calibration formula was derived for electrical resistances in the range of 1.51 to 2330 kΩ, temperatures in the range of 10 to 175°C, and volumetric water content in the range of 0.084 to 0.201 m³/m³. To verify the applicability, the sensors were embedded in a wall specimen heated by ISO 834 fire for 30 minutes. As a result, it was possible to measure the water contents continuously.