Growth characteristics of two interacting cracks

This paper deals with the growth characteristics of two interacting cracks in a mixed mode condition. The problem considered is that of two cracks of different lengths, arbitrarily placed in a plane. A uniform load is applied in the plane at a large distance away from the cracks. The objectives of this study are threefold: (1) Solve the mixed boundary value problem described in the foregoing; (2) Predict the most vulnerable crack tip where the instability would first occur as the load is increased; (3) Determine the directions in which the cracks may grow. The numerical results given are only for the specific case of one crack lying along a radial line which emanates from the tip of the other crack at an arbitrary angle.     

A titania nanotube-array room-temperature sensor for selective detection of hydrogen at low concentrations

A tremendous variation in electrical resistance, from the semiconductor to metallic range, has been observed in titania nanotube arrays at room temperature, approximately 25 degrees C, in the presence of < or = 1000 ppm hydrogen gas. The nanotube arrays are fabricated by anodizing titanium foil in an aqueous electrolyte solution containing hydrofluoric acid and acetic acid. Subsequently, the arrays are coated with a 10 nm layer of palladium by evaporation. Electrical contacts are made by sputtering a 2 mm diameter platinum disk atop the Pd-coated nanotube array. These sensors exhibit a resistance variation of the order of 10(4) in the presence of 100 ppm hydrogen at 25 degrees C. The sensors demonstrate complete reversibility, repeatability, high selectivity, negligible drift and wide dynamic range. The nanoscale geometry of the nanotubes, in particular the points of tube-to-tube contact, is believed to be responsible for the outstanding hydrogen gas sensitivities.     

Sellmeier dispersion for phase-matched terahertz generation in ZnGeP2

A Sellmeier dispersion of zinc germanium diphosphide (ZnGeP2) crystal has been formulated to determine the phase-matching characteristics of the crystal for the generation of coherent tunable terahertz radiation by difference-frequency mixing techniques. The results computed with the formulated Sellmeier dispersion provide an excellent fit to the experimental data.     

Hardware vs software reliability—A comparative study

High levels of reliability can be predicted and achieved as far as the hardware portions of modern large and complex real-time computer-based control systems are concerned but software is a critical part and plays a vital role in influencing the overall system reliability. This paper presents a comparative study between hardware reliability and software reliability from three definitions: top level, intermediate level and low level based on user's point of view, system designer's point of view and quantitative measurement point of view, respectively. Also discussed is the hardware reliability theory vs software reliability theory on the basis of analysis of malfunctions and prevailing reliability trends.     

Linear and nonlinear optical properties of ZnGeP2 crystal for infrared laser device applications: revisited

Measurement of refractive indices in the spectral bands 9-11 microm and 1.32 microm from a cw CO2 laser and a Q-switched Nd:YAG laser, respectively, is reported in a ZnGeP2 crystal. A new set of Sellmeier dispersion relations has been derived from the measured refractive indices data in this crystal. Second-harmonic generation (SHG) of CO2 laser radiation in this crystal is also reported. It is also seen that the previously reported phase-matching data for others experiments in SHG and optical parametric devices is explained satisfactorily with this new set of Sellmeier dispersion relation.     

Application of Fuzzy Logic to Estimate Flow of Methane for Energy Generation at a Sanitary Landfill

This paper proposes the use of a multicriteria assessment technique to evaluate the methane flow during gas extraction from a sanitary landfill. A number of parameters determine the gas generation and the feasibility for its extraction from a landfill. These parameters form a complex set of information with unknown mathematical interrelationships making potential gas flow evaluations difficult and elusive. In addition, the data available for a particular landfill are very often imprecise, uncertain, or subjective, making it even more difficult to evaluate the potential for gas extraction without conducting pilot tests. The method proposed in this paper uses fuzzy composite programming that allows for the use of imprecise information. A landfill gas potential index has been defined, which can be determined by easily obtainable climatological, geological, and landfill parameters. The landfill gas (LFG) potential index is related to the landfill gas flow using an empirical equation. The LFG potential model was calibrated and verified using data obtained from 61 landfills where gas extraction is being conducted. A sensitivity analysis was done to study the impact of variations in the input data on model output.     

Electroactive Shape Memory Effect of Polyurethane Composites Filled with Carbon Nanotubes and Conducting Polymer

We report the electroactive shape memory composites obtained by shape memory polyurethane block copolymer (PU) and multi-walled carbon nanotubes (MWNTs), and polypyrrole (PPy). An addition of combined MWNTs and PPy contributed to an enhancement in conductivity of PU-MWNTs composites. PU containing 2.5% MWNTs showed better mechanical and thermal properties than other composites, but conductivity was not sufficient for showing the shape memory effect by applying electrical voltages. However, when the composite was lightly coated by PPy (2.5%), its conductivity was the highest than other composites. Such the conductivity of this composite was enough to show electroactive shape recovery by heating above transition temperature of 40-48°C due to melting of polycaprolactone soft segment domain. The good shape recovery of 90-96% could be obtained in the shape recovery test when an electric field of 25 V was applied.     

A Novel Electroless Process for Embedding a Thin Film Resistor on the Benzocyclobutene Dielectric

To realize embedded resistors on multilayer benzocyclobutene (BCB) either on-chip or on-board, a low-cost large format electroless process for deposition of NiP and NiWP thin-film resistors using both low-temperature (25°C) and high-temperature (90°C) baths has been developed. The electroless process exhibits uniform resistor thickness in the submicron range and offers low profile and excellent adhesion to the BCB dielectric layer. The resistor films also act as a seed layer for direct electroplating of copper traces. The NiP alloys can also be tailored to a variable temperature coefficient of resistance (TCR) with different alloy compositions. The electroless process can be adopted in the PCB manufacturing industries with no additional investment. This article is the first report on electroless plated thin film resistors on low loss BCB dielectric.     

Thermoluminescence characteristics of Sm<Superscript>3+</Superscript> doped NaYF<Subscript>4</Subscript> crystals

Thermoluminescence (TL) characteristics of NaYF₄ crystals doped with Sm³⁺ have been studied after γ-ray irradiation. Dependence of luminescence efficiency on Sm³⁺ concentration and radiation dose has been measured and possible applications of NaYF₄: Sm³⁺ as a novel phosphor for TL dosimetry have been investigated. The efficiency of 0·3 mole% Sm³⁺ doped NaYF₄ crystal has been found to be maximum and comparable with commercial thermoluminescence dosimetric (TLD) materials.     

State-of-the-art nanoplatform-integrated MALDI-MS impacting resolutions in urinary proteomics

Urine proteomics has become a subject of interest, since it has led to a number of breakthroughs in disease diagnostics. Urine contains information not only from the kidney and the urinary tract but also from other organs, thus urinary proteome analysis allows for identification of biomarkers for both urogenital and systemic diseases. The following review gives a brief overview of the analytical techniques that have been in practice for urinary proteomics. MALDI-MS technique and its current application status in this area of clinical research have been discussed. The review comments on the challenges facing the conventional MALDI-MS technique and the upgradation of this technique with the introduction of nanotechnology. This review projects nano-based techniques such as nano-MALDI-MS, surface-assisted laser desorption/ionization, and nanostructure-initiator MS as the platforms that have the potential in trafficking MALDI-MS from the lab to the bedside.