Effect of gel spinning accompanied with cross‐linking using boric acid on the structure and properties of high‐molecular‐weight poly(vinyl alcohol) fiber

To enhance the thermal stability of poly(vinyl alcohol) (PVA) fiber, the fiber was prepared from the gel spinning of high molecular weight (HMW) PVA by using dimethyl sulfoxide/water (8/2, v/v) as a solvent, accompanied with the cross‐link by boric acid (B‐PVA). In addition, the structure and properties of the B‐PVA fiber were compared with those of the HMW PVA fiber obtained by using the same spinning system without cross‐linking (NB‐PVA). Through a series of experiments, it turned out that cross‐linking actualized by an optimum amount of boric acid (0.3 wt % based on PVA) and zone drawing caused significant changes in the properties of HMW PVA gel fiber. That is, cross‐linking increased thermal degradation temperatures at each degradation step and amounts of final residues, resulting in improving thermal properties of the PVA fiber. On the contrary, it was found that in the case of the B‐PVA fiber, some broadening of the original PVA unit cell occurred, which was identified by the peak shift to lower angle in X‐ray diffractogram. The tensile strength and Young's modulus of B‐PVA fiber with draw ratio of 15 are 23.1 and 308.3 g/d, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Flexible nano-hybrid inverter based on inkjet-printed organic and 2D multilayer MoS2 thin film transistor

We report a novel platform on which we design a flexible high-performance complementary metal–oxide–semiconductor (CMOS) inverter based on an inkjet-printed polymer PMOS and a two-dimensional (2D) multilayer molybdenum disulfide (MoS₂) NMOS on a flexible substrate. The initial implementation of a hybrid complementary inverter, comprised of 2D MoS₂ NMOS and polymer PMOS on a flexible substrate, demonstrates a compelling new pathway to practical logic gates for digital circuits, achieving extremely low power consumption with low sub-1 nA leakage currents, high performance with a voltage gain of 35 at 12 V supply voltage, and high noise margin (larger than 3 V at 12 V supply voltage) with low processing costs. These results suggest that inkjet-printed organic thin film transistors and 2D multilayer semiconducting transistors may form the basis for potential future high performance and large area flexible integrated circuitry applications.     

Modeling of the non-catalytic semi-batch esterification of palm fatty acid distillate (PFAD)

Biodiesel fuel is one of the most attractive alternatives to the traditional diesel fuel derived from a petroleum refinery. Development of a reliable model for the biodiesel production process requires maximizing economics and enhancing safety in the commercial operation of biodiesel plants. We propose a model which represents effectively the non-catalytic biodiesel production reaction. In the modeling of the reaction, we employ a nonlinear programming scheme to estimate reaction kinetic parameters which minimize a specified objective function. The behavior of the methanol during the reaction is investigated both experimentally and numerically. Imperfect mixing in the liquid phase at the initial reaction stage causes a little discrepancy between the experimental data and results of simulations. Overall, the proposed model represents the biodiesel production reaction effectively.     

Electrochemical stability of bis(trifluoromethanesulfonyl)imide-based ionic liquids at elevated temperature as a solvent for a titanium oxide bronze electrode

Four different electrolytes are prepared by dissolving a Li salt in three different room-temperature ionic liquids (RTILs) and also in a conventional organic solvent. The cathodic (electrochemical reduction) stability of these electrolytes is compared at both ambient and elevated temperature by potential cycling on a TiO₂-B electrode. At room temperature, the stability of pyrrolidinium- and piperidinium-based RTILs is comparable with that of the carbonate-based organic solvent, which is in contrast to the severely decomposed imidazolium-based RTIL. At elevated temperature (120 °C), the imidazolium-based RTIL undergoes even more significant cathodic decomposition that results in the deposition of a resistive surface film and leads to eventual cell degradation. By contrast, the cathodic decomposition and concomitant film deposition are not serious with pyrrolidinium- and piperidinium-based RTILs even at this high-temperature, so that the TiO₂-B/Li cell operates with reasonably good cycle performance. The latter two RTILs appear to be promising solvents for lithium-ion batteries that are durable against occasional exposure to high-temperature.     

Evaluation of chondroitin sulfate in shark cartilage powder as a dietary supplement: Raw materials and finished products

We evaluated the content and biochemical properties of chondroitin sulfate (CS) in shark cartilage powders being used as nutraceutical supplements. The quantities of CS in shark cartilage products (SCPs) and finished products containing shark cartilage powder were determined by analyzing unsaturated disaccharides after treatment with chondroitinase ABC, and the results were compared with the specifications on the product labels. This method was validated and good linearity (r ? 0.999) was obtained. The recovery ranged from 95.27% to 102.39% with precision from 2.27% to 3.95%. Furthermore, the average molecular weights (MW) and the origins of CS in SCPs and finished products were evaluated by agarose gel-electrophoresis and assessment of disaccharide compositional patterns, respectively. Quantitative and compositional analysis of disaccharides after enzymatic depolymerization showed that the amount of CS in the samples of SCPs ranged from 0% to 28.92 ± 0.03%. All of the SCP samples except for SCP D had ΔDi-2,6diS and had more ΔDi-6S than ΔDi-4S, indicating that they originated from shark cartilage. In the finished products, the amount of CS ranged from 0.58 ± 0.01% to 21.30 ± 0.08%. With the exception of SCP D and two finished products (F and D), which contained CS with lower MWs, the average MW of CS in the SCPs and finished products was approximately 40 kDa or higher than that of MW standard (40 kDa) of CS. These analyses contribute to the evaluation of the quantity and quality of CS in SCPs and finished products containing CS, which is necessary for the manufacture of high-grade nutraceuticals.     

Polymer Deformable Mirror for Optical Auto Focusing

A low‐stress organic polymer membrane is proposed as a deformable mirror that can be incorporated into a cellular phone camera to achieve auto focusing without motor‐type moving parts. It is demonstrated that our fabricated device has an optical power of 20 diopters and can switch focus in 14 ms. The surface roughness of the organic membrane is measured around 15 nm, less than λ/20 of the visible light. With curve fitting, we found that the actuated membrane is almost parabolic in shape, which leads to less aberration than spherical surfaces. It is suitable for reflective‐optics systems.     

Modeling and control of the melt index in HDPE process

We investigate the model for an industrial isothermal HDPE slurry reactor. The model, consisting of several nonlinear equations, can be linearized to give sets of linear time invariant state space model. The effectiveness of the linearized model is verified by the numerical simulations. A simple model predictive control scheme is constructed based on the linear state space model. The value of the melt index is obtained from the values of the manipulated and controlled variables generated from the control scheme. The control performance can be evaluated from the comparison between the computed melt index values and measured melt index values. The control scheme shows good tracking performance in the numerical simulations. We believe that the model developed in the present study can be effectively used to predict process variables as well as to control the melt index.     

Cyclic behavior of unit bucket for tripod foundation system supporting offshore wind turbine via model tests

Offshore wind energy has been growing up as a promising renewable energy source. Recently, tripod suction bucket foundation is rapidly expanding as a foundation system supporting the offshore wind turbine. In offshore environment, wind turbine foundation structures should be designed considering cyclic loading which can lead to permanent deformation of structure, tilting problem, and overall degradation of soil stiffness. However, it is technically difficult to predict the cyclic behavior of the tripod accurately because the cyclic behaviors of the tripod bucket can be inferred from vertical pullout and compression behaviors of each single bucket elements. In this paper, a series of model tests was performed by applying cyclic vertical compression and extension loadings to a single bucket element that is one element of the tripod foundation. Loading directions, level, and rate were controlled for investigating of cyclic behavior of tripod foundation. On the basis of testing results, the permanent deformation and cyclic stiffness response of tripod suction caisson were discussed. Based on the test results, it was confirmed that the cyclic behavior of the single bucket is affected by the load level and rate. In addition, the behavior showed quite different trends with the loading directions: compression, pullout, and two‐way.     

Impact of H‐Doping on n‐Type TMD Channels for Low‐Temperature Band‐Like Transport

Band‐like transport behavior of H‐doped transition metal dichalcogenide (TMD) channels in field effect transistors (FET) is studied by conducting low‐temperature electrical measurements, where MoTe₂, WSe₂, and MoS₂ are chosen for channels. Doped with H atoms through atomic layer deposition, those channels show strong n‐type conduction and their mobility increases without losing on‐state current as the measurement temperature decreases. In contrast, the mobility of unintentionally (naturally) doped TMD FETs always drops at low temperatures whether they are p‐ or n‐type. Density functional theory calculations show that H‐doped MoTe₂, WSe₂, and MoS₂ have Fermi levels above conduction band edge. It is thus concluded that the charge transport behavior in H‐doped TMD channels is metallic showing band‐like transport rather than thermal hopping. These results indicate that H‐doped TMD FETs are practically useful even at low‐temperature ranges.