Phase transition and piezoelectric properties of lead-free (Bi1/2Na1/2)TiO3–BaTiO3 ceramics

(1−x)(Bi_0.5Na_0.5)TiO₃–xBaTiO₃ ceramics (x=0.03, 0.06, 0.08, 0.12, 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, and 0.90) were fabricated by a conventional solid-state reaction and their phase transitions and piezoelectric properties were investigated using XRD analyses, Curie temperature, the frequency dependance of dielectric constant, and P–E curves. A complete solid solution with a perovskite structure was formed in the whole composition range of BNT–BT and more than two phase transitions arising from a compositional change were found. With increasing BaTiO₃ content, the sequence of phase transitions from a rhombohedral structure to unknown tetragonal structures and finally a tetragonal structure with the space group P4mm has been established. While the rhombohedral–tetragonal phase transition led to superior piezoelectric properties in BNT–BT ceramics, other phase transitions between tetragonal structures had a little effect on piezoelectric properties. The d₃₃, ε_r, k_p, k_t, and Q_m and values lied in ranges of 40–130 pC/N, 400–900, 10–30%, 15–30%, and 50–250, respectively.     

A hybrid approach for cam shape design and profile machining of general plate cam mechanisms

Plate cam mechanism can easily produce the positive and functional motions in contact of cam and follower. Generally cam mechanism is used in many fields of mechanical control, automation, and industrial machinery. To obtain the accurate motion of follower, the profile of cam must be designed and machined precisely. This paper proposes an instant velocity center method for the profile design and a biarc fitting method for the profile machining to 4 different types of plate cam mechanisms with reciprocating or oscillating motion and roller or flat-faced followers. The key of this paper is the introduction of a hybrid system combined the design procedures and the manufacturing procedures. The main idea is that the minimum machining data are built by the accurate biarc curves fitted directly from the design parameters. The radial direction angles toward biarc centers for the accurate biarc curve fitting can be defined directly by the contact angle of cam and follower given in the design procedures. An application of the proposed approach is verified the accurate profiles of a designed cam and a machining cam using the minimum NC data within a given machining tolerance.     

Preparation and characterization of thermally crosslinked chlorine resistant thin film composite polyamide membranes for reverse osmosis

Currently, polyamide reverse osmosis membranes are highly effective for desalination, industrial process water, and home drinking water. However, they have poor resistance to strong oxidants especially chlorine due to chain cleavage of aromatic polyamide. In general, aromatic polyamide RO membranes are essentially random copolymers consisting of the linear and crosslinked structures. The amide ring is sensitive to attack by chlorine because it is an electron-rich region. Therefore, the activated carbon or sulfite addition processes are essential to remove the chlorine in the separation processes. Many research groups have studied to improve the chlorine-resistance RO membrane having hydrophilic groups (− SO₃H and − COOH) or nitro groups (− NO₂) such as electron acceptors. In this study, thin film composite polyamide RO membranes were prepared by interfacial polymerization method including cross-linking agents having hydroxyl groups to improve the chlorine-resistance. The chlorine-resistance of polyamide RO membrane was influenced by the thermal cross-linking conditions (temperature and time) and cross-linking density of polyamide membranes.     

Effect of reaction time and temperature on the morphology and ion-exchange capacity of polystyrene beads sulfonated using different sulfonating agents

Monodisperse polystyrene (PS) beads 2.5 μm in size were synthesized by dispersion polymerization. The PS beads were chemically modified by three different sulfonating agents, namely, concentrated sulfuric acid, acetyl sulfate, and chlorosulfonic acid. When they were sulfonated using chlorosulfonic acid, the concentration of sulfonic acid (SO₃ ⁻) groups on the PS beads increased from 0.5 to 2.25 meq/g as the treatment time was increased from 10 to 360 min at 0 °C. As the reaction temperature was increased, the ion-exchange capacity (IEC) of the sulfonated PS beads increased. However, it can be seen that they lost their spherical shape. The PS surface was modified by the introduction of the SO₃ ⁻ groups to give an IEC of up to 2.28 meq/g, which provides 1.1 × 10¹⁰ SO₃ ⁻ groups per bead, without any deformation of their spherical shape.     

Continuous thermal degradation of pyrolytic oil in a bench scale CSTR reaction system

Continuous thermal degradation of two pyrolytic oils with low (LPO) and high boiling point distribution (HPO) was conducted in a constant stirrer tank reactor (CSTR) with bench scale. Raw pyrolytic oil as a reactant was obtained from the commercial rotary kiln pyrolysis plant for municipal plastic waste. The degradation experiment was conducted by temperature programming with 10 °C/min of heating rate up to 450 °C and then maintained with long lapse time at 450 °C. Liquid product was sampled at initial reaction time with different degradation temperatures up to 450 °C and then constant interval lapse time at 450 °C. The product characteristics over two pyrolytic oils were compared by using a continuous reaction system. As a reactant, heavy pyrolytic oil (HPO) showed higher boiling point distribution than that of diesel and also light pyrolytic oil (LPO) was mainly consisting of a mixture of gasoline and kerosene range components. In the continuous reaction, LPO showed higher yield of liquid product and lower residue than those of HPO. The characteristics of liquid products were influenced by the type of raw pyrolytic oil. Also, the result obtained under degradation temperature programming was described.     

Two-layer tensioned-web-over-slot die coating: Effect of operating conditions on coating window

Tensioned-web-over-slot die (TWOSD) coating deploys elastohydrodynamic interaction to control the distance between the moving substrate and the coating die lip surface in order to be able to coat an ultra-thin liquid layer. Dual slot TWOSD coating is designed to deposit two thin uniform liquid layers onto a moving web simultaneously. Like in the fixed-gap dual slot coating, the interlayer separation point needs to be at the downstream corner of the mid lip in order to prevent coating defects. Different flow features, like weeping, bead breakup and feed slot vortices, limit the range of operating parameters that ensures uniform coating, and define the operating window of the process. In this study, we analyze dual slot TWOSD coating flow by solving the Navier–Stokes equation coupled with thin cylindrical shell equation using the finite element method. The boundaries in the parameter space that define the operating window or vortex-free window are automatically computed by a direct tracking method of flow features. The effect of operating conditions, such as liquid viscosity, web tension and web speed, on the critical layer thickness at which the coating becomes non-uniform is determined by this study.     

Effects of Orlistat on white adipose tissue (WAT) in the γ‐irradiated mouse model

In this study, we showed that γ‐irradiation could trigger biological response like the fat accumulation of gonadal white adipose tissue (gWAT) in mice. The irradiated animal can be used as a useful model for evaluation of anti‐obesity drugs. To induce the fat accumulation by γ‐irradiation, 2‐months‐old female C57BL/6 mice were irradiated at 5 Gy and further raised for 6 months. Subsequently, the mice were i.p. injected daily with Orlistat (25 mg/kg) or vehicle for 3 wk and analyzed for the adipose tissue weight and serum triglyceride and T‐cholesterol levels. The abdominal WAT of the γ‐irradiated mice weighed an average of 3.9/100 g body weight, 1.7‐fold higher than what was seen in normal mice (2.3/100 g body weight), indicating that γ‐irradiation induced the fat accumulation in the adipose tissue. However, the administration of Orlistat, a well‐known anti‐obesity agent, significantly reduced the adipose tissue weight to 1.7/100 g body weight in irradiated mice. In addition, in these Orlistat‐treated mice, a significant reduction of serum triglyceride and T‐cholesterol was observed up to 14% and 27%, respectively.     

Enantioselective Alcoholysis of meso‐Glutaric Anhydrides Catalyzed by Cinchona‐Based Sulfonamide Catalysts

The bifunctional Cinchona‐based sulfonamide catalysts showed the highest levels of enantioselectivity reported to date in the alcoholytic desymmetrization of meso‐glutaric anhydrides. Density functional theory (DFT) computational studies provide detailed insight into the observed sense of enantioselectivity. Moreover, detailed experimental studies and single crystal X‐ray analysis confirmed that these bifunctional organocatalysts 3 do not form H‐bonded self‐aggregates in both solution and solid state. The synthetic utility of this methodology was also demonstrated in the synthesis of pharmaceutically important γ‐amino acids, such as (S)‐pregabalin. Of the many asymmetric syntheses of enantiomerically pure (S)‐pregabalin reported to date, our synthesis requires the least number of and the simplest steps.     

Estimation of plasma position from tangentially viewed images on a toroidally symmetric device

Images of plasma from a fast-framing camera are the most intuitive and reliable data to understand the status of tokamak plasmas. Generation, movement, size variation, and disruptions of plasmas can be clearly observed from these images. However, it is not a simple task to obtain the exact positions and sizes of plasmas using these images because measured two-dimensional images inevitably lose the three-dimensional position information of their targets. In this paper, the exact positions and sizes of plasmas have been calculated from tangentially viewed images using the toroidal symmetry of the plasma in the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The positions and sizes of the plasmas have been manually determined with displayed cursors on images and automatically determined using a correlation factor with calculated virtual plasma images as well. These two results correspond well with each other. The estimated positions have also been compared with those obtained from magnetic diagnostics analysis.     

Characterization of a linear device developed for research on advanced plasma imaging and dynamics

Within the scope of long term research on imaging diagnostics for steady-state plasmas and understanding of edge plasma physics through diagnostics with conventional spectroscopic methods, we have constructed a linear electron cyclotron resonance (ECR) plasma device named Research on Advanced Plasma Imaging and Dynamics (RAPID). It has a variety of axial magnetic field profiles provided by eight water-cooled magnetic coils and two dc power supplies. The positions of the magnetic coils are freely adjustable along the axial direction and the power supplies can be operated with many combinations of electrical wiring to the coils. Here, a 6 kW 2.45 GHz magnetron is used to produce steady-state hydrogen, helium, and argon plasmas with central magnetic fields of 875 and/or 437.5 G (second harmonic). In order to achieve the highest possible plasma performance within the limited input parameters, wall conditioning experiments were carried out. Chamber bake-out was achieved with heating coils that were wound covering the vessel, and long-pulse electron cyclotron heating discharge cleaning was also followed after 4 days of bake-out. A uniform bake-out temperature (150?°C) was achieved by wrapping the vessel in high temperature thermal insulation textile and by controlling the heating coil current using a digital control system. The partial pressure changes were observed using a residual gas analyzer, and a total system pressure of 5×10(-8)?Torr was finally reached. Diagnostic systems including a millimeter-wave interferometer, a high resolution survey spectrometer, a Langmuir probe, and an ultrasoft x-ray detector were used to provide the evidence that the plasma performance was improved as we desired. In this work, we present characterization of the RAPID device for various system conditions and configurations.