A power spectrum analysis of effect of rolling texture on cutting forces in single-point diamond turning

In most of the existing metal cutting theories, the workpiece is assumed to be homogeneous and most continuum theories do not take into account the effect of crystallographic anisotropy that causes variations in the shear plane at the grain level and hence of the cutting force. As the depth of cut in single-point diamond turning (SPDT) is usually less than the average grain size of a polycrystalline aggregate, cutting is generally performed within a grain. At this scale, the difference in the individual grain properties cannot be integrated out and a continuum solution would be insufficient. As a result, this paper presents a power spectrum analysis of the periodic fluctuation of micro-cutting forces in SPDT of polycrystalline materials. The experimental results show that the features of the power spectra of the cutting forces can be well correlated with the change of rolling texture of the materials being cut. These findings help to explain quantitatively the fluctuation of micro-cutting forces and hence the effect of rolling texture in SPDT, which are not encountered in conventional machining.     

Electrically tunable dispersion compensator with fixed center wavelength using fiber Bragg grating

We present the design and development of a novel tunable dispersion compensator with fixed center wavelength that is based on the electrical adjustment of the chirp of a fiber Bragg grating (FBG). Both temperature gradient and strain gradient are employed to adjust the chirp of the FBG jointly. The electrical current flowing through the taper on-fiber thin-film heater will introduce a temperature gradient on the FBG. The shrinkage of a negative thermal expansion coefficient (NTEC) ceramic due to the temperature rise will compress the tapered FBG mounted inside it, and this will introduce a strain gradient on the FBG. The center wavelength of the FBG will be kept fixed because the effect of temperature rise on the FBG and the effect of compression of the FBG will offset each other. Applying an electrical power of less than 0.68 W, we demonstrate a linearly chirped FBG whose dispersion can be continuously adjusted from -178 ps/nm to -302 ps/nm with a central wavelength shift of as small as 0.16 nm.     

Lateral Load Capacity of Drilled Shafts in Jointed Rock

Large vertical (axial) and lateral loads often act on the heads of drilled shafts in jointed rock. In current design practice, the p-y curve method used in design of laterally loaded drilled shafts in soil is often also used for shafts in jointed rock. The p-y curve method treats the soil as a continuum, which is not appropriate in jointed rock, particularly when failure occurs due to sliding on joints. A new discontinuum model was developed to determine the lateral load capacity of drilled shafts or piers in a jointed rock mass with two and three joint sets. It consists two parts: a kinematic and a kinetic analysis. In the kinematic analysis, Goodman and Shi’s block theory is expanded to analyze the removability of a combination of blocks laterally loaded by a pier. Based on the expanded theory, a method was developed to select removable combinations of blocks using easily constructed two-dimensional diagrams. In the kinetic analysis, each kinematically selected removable combination of blocks is examined with the limit equilibrium approach to determine the ultimate lateral load capacity. Although the procedure is similar to slope stability analysis, it is more complicated with the addition of a lateral force and the vertical load exerted by the pier. Simple analytical relations were developed to solve for the ultimate lateral load capacity.     

Observation of Non-Radiative Recombination Enhanced Point Defect Reaction in Semiconductors

IntroductionWide-bandgapcompoundsemiconductorsforblue-greenlaserdiodesandlight-emittingdiodeshavebeenintensivelystudiedinrecentyears.Ithasbeenrecognizedthatpre-existingdefectsplayasignificantroleinthedevicedegradation.Reductionofthesedefectshasbeentheprimaryeffortinachievingalonglifetimeoflight-emittingdevices.Inthispaper,wepresentourmainexperimentalresultsonthenonradiativerecombinationenhancedpointdefectreactioninsemiconductorsbydirectlymonitoringtheprocessofradiativeelectron-holerecombinatio…     

An uncertainty vector adjustment for process modelling error compensation

A new uncertainty vector adjustment (UVA) was developed to compensate for the adverse effects of modelling errors and, thereby, to improve the robustness of two nonlinear control strategies: input output linearization; and Su-Hunt-Meyer transformation. The UVA provides an appropriate adjustment to the transformation relationships obtained from a nonlinear control strategy according to the overall effect of modelling errors. The effectiveness of the approach was verified by introducing parametric errors into the simulation of an evaporative stage of the liquor burning unit of the Bayer process for the production of alumina. Significant improvements in responses were observed based on the integral of the time-weighted absolute error performance index.     

Burn injuries during paint thinner sniffing

Thinner sniffing is popular among school children in Asian countries because it is readily available at low cost. Besides its toxicity to major organs, thinner inhalation is associated with various burn accidents. Four teenagers were admitted to the Burns Unit of the Prince of Wales Hospital over the period of 1996-1997. They sustained 3-25% TBSA flame burn and two of them had inhalation injuries as a result of the ignition of a cigarette during thinner sniffing. None of them had evidence of thinner intoxication as shown by blood tests. In the management of their acute burn injuries, their hidden social and family problems were explored. With the cooperation of different disciplines, early psychosocial intervention was given and their behavioral and psychological disturbances were successfully managed.     

Structural Evolution of the Mn_(0.52)Sb_(0.48) Compound during High Energy Ball Milling

The structural transitions of the NiAs-type Mn0.52Sb0.48 magneto-ordered compound, ball milled to different periods, have been characterized by X-ray diffraction and DSC analysis. On the basis of lattice parameter results a structural evolution mode with three stages is proposed. In the first stage lattice parameters keep nearly unchanged with the refinement of grains and increase of lattice strain. In the second stage, microstrain shows a lowering tendency accompanying the successive decreases of grain size. The X-ray revealed internal strain is found to be strains inside the lattice, which can be relaxed with new grain formation. The change of Tc is shown to be affected by the dimension of c axis, however the overall magnetization is continuously decreased with milling, due to the disordering process occurred in milling. Correspondent disordering mechanisms have been tentatively postulated and discussed according to the changes of lattice para meters.     

Thermal property,morphology, and hydrolysis ability of poly(lactic acid)/chitosan nanocomposites using polyethylene oxide

Poly(lactic acid) (PLA) and chitosan (CS) are two natural resource polymers, which have been applied widely into different fields. Polymer composites based on PLA and CS have some advantages such as good adhesion, biodegradability, biocompatibility, and high stability. They can be prepared by different methods including the solution, emulsion, and electrospinning methods. In this work, the PLA/chitosan nanocomposites were prepared by solution method using poly(ethylene oxide) (PEO) as a compatibilizer in order to improve interaction and dispersion between PLA and CS phases. The characterization and morphology of the above nanocomposites were determined by Fourier Transform Infrared Spectroscopy (FTIR), thermograviety analysis, differential scanning calorimetry, and scanning electron microscopy. Hydrolysis ability of PLA/CS nanocomposites with and without PEO was also investigated in acid and phosphate buffer solutions. The obtained results showed the compatibility between PLA and CS phases in the PLA/CS nanocomposites using PEO was improved clearly and weight loss of PLA/CS/PEO nanocomposites in the above environments lower than that of PLA/CS nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41690.     

Effects of Curcumin on the Oxidative Stability of Oils Depending on Type of Matrix,Photosensitizers, and Temperature

The photosensitizing activity of curcumin was tested in corn oil and oil‐in‐water (O/W) emulsion systems under visible light irradiation. In addition, the antioxidative/prooxidative properties of curcumin were evaluated in corn oil at 100 °C and in O/W emulsion at room temperature under riboflavin photosensitization or at 60 °C in the dark. Curcumin acted as a photosensitizer in corn oil and O/W emulsions . The oxidative stability of corn oil samples containing curcumin (0–5.0 mmol/kg oil) were not significantly different (p > 0.05) at 100 °C, implying curcumin did not act as an antioxidant nor a prooxidant in corn oil. However, curcumin inhibited lipid oxidation in O/W emulsions under riboflavin photosensitization at room temperature and 60 °C in the dark. The photosensitization and antioxidant abilities of curcumin were greatly influenced by matrix types and presence of riboflavin. Therefore, antioxidative or prooxidative characteristics of curcumin should be evaluated considering matrix type including bulk oil or O/W emulsions and presence of visible light irradiation.     

In Vitro Selection of Single-Stranded DNA Molecular Recognition Elements against S. aureus Alpha Toxin and Sensitive Detection in Human Serum

Alpha toxin is one of the major virulence factors secreted by Staphylococcus aureus, a bacterium that is responsible for a wide variety of infections in both community and hospital settings. Due to the prevalence of S. aureus related infections and the emergence of methicillin-resistant S. aureus, rapid and accurate diagnosis of S. aureus infections is crucial in benefiting patient health outcomes. In this study, a rigorous Systematic Evolution of Ligands by Exponential Enrichment (SELEX) variant previously developed by our laboratory was utilized to select a single-stranded DNA molecular recognition element (MRE) targeting alpha toxin with high affinity and specificity. At the end of the 12-round selection, the selected MRE had an equilibrium dissociation constant (K_d) of 93.7 ± 7.0 nM. Additionally, a modified sandwich enzyme-linked immunosorbent assay (ELISA) was developed by using the selected ssDNA MRE as the toxin-capturing element and a sensitive detection of 200 nM alpha toxin in undiluted human serum samples was achieved.