Magnetic penetration depth measurements with the microstrip resonator technique

The microstrip resonator technique is a convenient way to sensitively measure the temperature dependence of the magnetic penetration depth (T) in superconducting thin films. Because the method relies on measuring the resonant frequency of a high-Q transmission line resonator at microwave frequencies, one can very precisely measure small changes in (T). This technique is applied to studying the low-temperature dependence of (T), since that is in principle a measure of the low-lying pair-breaking excitations of the superconductor. We find that the penetration depth in niobium films is consistent with the predictions of weak coupled BCS theory. The low-temperature dependence of (T) inc-axis YBa₂Cu₃O_7– films can be interpreted as either a weak exponential or as a power law. In addition, the measured value of (0) is found to be strongly dependent on the form of the temperature dependence for (T) used in fitting the data. Best fits over the entire temperature range are obtained with a BCS temperature dependence having values for 2(0)/k _BT_c strictly less than 3.5, consistent with our measurements of the temperature dependence of (T) at low temperatures in YBa₂Cu₃O_7– .     

Fully-Coupled Numerical Analysis of High-Frequency Induction Heating for Thin-Wall Injection Molding

In recent years, rapid mold heating has served to enable the injection molding of thin-walled parts or micro/nano structures. Induction heating is an efficient way to heat metal parts by means of an electric current that flows through a conductive material by electromagnetic induction. The present study covers a numerical investigation of high-frequency induction heating of an injection mold in order to rapidly raise the mold temperature. To take into account the effects of thermal boundary conditions of induction heating, a fully coupled numerical analysis effectively connecting electromagnetic field calculation, heat transfer analysis, and injection molding simulation was carried out. The proposed integrated simulation was applied to the injection molding of a thin-wall part, and its results were compared with experimental findings in order to verify the validity of the proposed simulation.     

Effects of elongational flow on the isotropic-nematic phase transition in freely-jointed rod systems

Summary The effects of polymer chain flexibility and elongational flow field on the isotropic-nematic phase transition are studied by applying a freely-jointed rods model to the Onsager theory. The biphasic region becomes wider and the difference of order parameters between the coexisting phases becomes larger as the flexibility increases. Also, the onset concentration of highly ordered nematic phase becomes lower, the biphasic region narrower and a difference of the order parameters between the coexisting phases smaller as the stretching rate increases. It is shown that there exists a critical point at a sufficiently high stretching rate, which means the existence of a stable monophase above the critical point. We emphasize that there exists not only a unstable biphasic state but also a stable biphasic state in a weakly stretching rate. Thus the order parameter has double values in this stable biphasic region.     

Construction of methanol sensing <Emphasis Type="Italic">Escherichia coli</Emphasis> by the introduction of novel chimeric MxcQZ/OmpR two-component system from <Emphasis Type="Italic">Methylobacterium organophilum</Emphasis> XX

Methylobacterium organophilum XX is a type II facultative methylotroph that can grow on methanol. In M. organophilum XX, the MxcQ/MxcE two-component system (TCS) is involved in methanol metabolism. EnvZ/OmpR in E. coli TCS was exploited to develop a methanol biosensor by engaging the MxcQ/MxcE TCS system. The MxcQZ/OmpR methanol sensing chimeric TCS was constructed by integrating the sensing domain of M. organophilum MxcQ with the transmitter domain of E. coli EnvZ. The response regulator of the chimeric TCS system is OmpR, which regulates the expression of the ompC and gfp. The expression of ompC was monitored by real-time quantitative PCR analysis. The expression of gfp also confirmed the expression of the ompC. The maximum expression of ompC and gfp occurred with 0.05% of methanol, and the expression started to decline with further increases in methanol concentration. This system delivers rapid detection of methanol in the environment.     

The effect of dimethylsulfoxide on the dissociation process of physical complexes of polyacrylonitrile in N,N‐dimethylformamide

The physical properties and gelation behavior of polyacrylonitrile (PAN ) solutions were investigated in mixed solvents of N ,N ‐dimethylformamide (DMF ) and dimethylsulfoxide (DMSO ). For the individual solubility parameters, DMSO had the polar term closer to PAN than DMF . Small‐angle X‐ray scattering profiles and Fourier transform infrared spectra of 20 wt% PAN solutions confirmed that the internal structure and intermolecular complexes between nitrile groups were broken up by the DMSO molecules. The slope of Cole–Cole plot, a measure of the solution heterogeneity, increased with the mole fraction of DMSO (X _DMSO) via three distinct zones. The homogenization was particularly noticeable in Zone 1 (0.0 < X _DMSO < 0.4) and Zone 3 (0.7 < X _DMSO < 1.0). The Huggins constant and UV‐visible absorption at 268 nm of dilute solutions decreased sharply above X _DMSO of 0.7 in Zone 3. This indicated a marked increase of PAN solubility by dissociating the intramolecular complexes between nitrile groups. In Zone 1, the storage modulus of 20 wt% PAN solutions decreased but loss modulus remained almost constant with X _DMSO at lower frequency below 1 rad s^?1, indicating the weakening of the true entanglement points of the intermolecular complexes. The mechanism indicated that the intermolecular complexes between nitrile groups were dissociated by DMSO earlier than the intramolecular ones. © 2017 Society of Chemical Industry     

Synchronous curable deoxidizing capability of epoxy–anhydride adhesive: Deoxidation quantification via spectroscopic analysis

Thermoset resins have been extensively utilized as an adhesive for electronic devices. In particular, semiconductor packaging materials between chips/substrates require electrical interconnections by using deoxidizing agents along with thermoset adhesives. In this study, a facile combination of hydroxyl‐functionalized epoxy and cyclohexane‐structured cyclic anhydrides produced curable acidic moieties, thereby allowing synchronous deoxidizing and curing without the use of a deoxidizing agent. By contrast, unitary cyclic anhydrides rarely presented acidic moieties, probably due to their rapid networkable reactivity caused by structural flexibility once opened, which was detected and quantified by spectroscopic analyses. This binary system in the absence of additional deoxidizing agents achieved the complete wetting of common Sn‐based solders via chip bonding systems due to the generated acidic moieties. The binary mixture also showed an increased glass transition temperature of 110 °C and enhanced Young's modulus of 1.6 GPa, relative to the ternary mixture (85 °C and 0.8 GPa) comprising a deoxidizing agent. This discovery is beneficial in terms of the simplification of composition design and mechanical robustness of solderable adhesives. Quantification via spectroscopic studies can also help anticipate the deoxidizing capability of binary and ternary systems at different temperatures for various bondable and solderable applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46639.     

Applicability of sub- and supercritical water hydrolysis of woody biomass to produce monomeric sugars for cellulosic bioethanol fermentation

In this study two woody biomasses, poplar and pitch pine wood, were treated with sub- and supercritical water (SCW) at temperature of 325–425 °C, at pressure of 220 ± 10 atm and residence time of 60 s, respectively, to develop a time saving and efficient conversion process for the production of fermentable sugars from woody biomasses using supercritical water system. Cellulose/hemicellulose was easily hydrolyzed during SCW treatment into monomeric sugars with the total yield of 7.3% and 8.2% based on the oven dried weight of poplar and pitch pine, respectively. Total yield of the monomeric sugars was increased about threefolds to 23.0% and 25.1% in the presence of 0.05% of hydrochloric acid. Model experiment confirmed that glucose and xylose were readily converted into low molecular weight compounds during SCW hydrolysis. According to GC/MS analysis main compounds converted from glucose and xylose by SCW were identified to 5-hydroxymethyl furfural and 4-oxo-5-methoxy-2-penten-5-olide, respectively.     

Characterization of differently shaped carbon fiber composites prepared from naphtha cracking bottom oil

Different shaped carbon fibers (R-, I-, C-, Y-, and X-type) were prepared from melt-spinning of reformed naphtha cracking bottom oil precursors through various shaped spinnerets. These different shaped CFs (carbon fibers) and PVC (polyvinyl chloride) resin were compounded, and then CF/PVC composites were prepared. Precursor pitch, carbon fibers, and composites were characterized and their properties were compared. Mechanical properties of carbon fibers and composites were characterized relating to external surface area and ratio of perimeter to cross-sectional area of carbon fibers. The tensile strength of tetralobal fibers (X-type) showed five times higher than that of round-shaped fibers (R-type) due to extended external surface area. Their tensile strength of CF/PVC composite increased as ratio of perimeter to cross-sectional area of carbon fibers. The magnitude of the ratio was in order to X-, C-, I-, Y-, and R-type.     

Grafting of glycidyl methacrylate onto high‐density polyethylene with reaction time in the batch mixer

The melt grafting of glycidyl methacrylate (GMA) onto high‐density polyethylene (HDPE) in the presence of free radical initiators was investigated in the batch mixer. The graft content was determined with the titration and FTIR spectroscopy. The graft content increased with the increase of peroxide and initially introduced GMA concentration. Increase of the grafted GMA content resulted in decrease of the melt index. Interestingly, there was a sudden drop of GMA grafting content with the reaction time. It is assumed that depolymerization of GMA have taken place over the ceiling temperature. The crystallinity of the prepared glycidyl methacrylate grafted high density polyethylene (HDPE‐g‐GMA) was determined by the measurement of the heat of fusion. GMA grafted site acted as defect and crystallinity of the HDPE‐g‐GMA decreased with the increase of grafting reaction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical Properties of Silicon Nanowires

Nanowires have been taken much attention as a nanoscale building block, which can perform the excellent mechanical function as an electromechanical device. Here, we have performed atomic force microscope (AFM)-based nanoindentation experiments of silicon nanowires in order to investigate the mechanical properties of silicon nanowires. It is shown that stiffness of nanowires is well described by Hertz theory and that elastic modulus of silicon nanowires with various diameters from ~100 to ~600 nm is close to that of bulk silicon. This implies that the elastic modulus of silicon nanowires is independent of their diameters if the diameter is larger than 100 nm. This supports that finite size effect (due to surface effect) does not play a role on elastic behavior of silicon nanowires with diameter of >100 nm.