Synthesis and Performance of Advanced Ceramic Lasers

This paper reports recent progress in the production of polycrystalline Nd:YAG (Y₃Al₅O₁₂), Nd:YSAG (Y₃Sc_1.0Al_4.0O₁₂), Yb:YSAG ceramics, and a Nd-doped YAG single crystal with an almost perfect pore-free structure by advanced ceramic processing. The laser conversion efficiency of pore-free polycrystalline Nd- and Yb-doped ceramics is extremely high, and their optical qualities are comparable with that of commercial high-quality Nd:YAG single crystals. We have also succeeded in the fabrication of a Nd:YAG single crystal, which can be used for laser oscillation, by the solid-state reaction method. Laser oscillation efficiency was very low when the pores remained inside the single crystal; however, the laser oscillation efficiency of the pore-free Nd:YAG single crystal was slightly higher than that of polycrystalline Nd:YAG ceramics having high optical quality. From this fact, it was recognized that optical scattering occurs mainly in the residual pores inside the Nd:YAG ceramics and the scattering at the grain boundary is very less. In addition, we confirmed that a heavily doped Nd:YAG single crystal can be fabricated by the sintering method. Moreover, we have demonstrated the fabrication of a composite ceramic with complicated structures without the need for precise polishing and diffusion bonding. Advanced ceramic processing, which enables design flexibility of the laser element, presented in this work is important in the development of a high-performance laser (high efficiency, high beam quality, and high output energy, etc.)     

A system of automatic control of motion speed of a city transport system electric train

An adaptive system of automatic control of the electric train motion speed permitting one to take into account the specific requirements imposed by the control object is proposed. Such requirements include limitation of the level of the index of the movement smoothness during the transient movement modes characterizing the degree of comfort for the passengers, as well as the possibility of implementing accelerations (delays) differing from nominal ones. The methods of automatic control and simulation modeling theory are used while solving the problem. The required control quality is provided by the fact that the input drive signal for the speed control circuit is smoothed by means of an operator, which is based on integration with saturation. The speed control circuit parameters are determined as a result of solving the task of the parametrical synthesis. The result of the work is an operation algorithm of the automatic control system (ACS) of the electric train speed, application of which provides limitation of the level of the movement smoothness index within the transient movement modes. As a result of solving the task of the parametrical synthesis the analytical dependences are also obtained connecting the ACS control law parameters with the train weight, use of which provides independence of the control quality on the train weight.     

Effect of grain size and twins on corrosion behaviour of AZ31B magnesium alloy

Grain refining is a promising approach to improve mechanical properties of magnesium alloys, but how grain size and twins affect corrosion behaviour is not well understood. In this work, corrosion resistance of AZ31B alloy with different grain sizes is studied in 3.5% NaCl solution using immersion testing, evolved hydrogen gas measurement and potentiodynamic polarisation measurement. Intra-granular corrosion was predominant and the existence of twins further accelerated the corrosion. The effect of grain size was more pronounced in the corrosion of the untwinned microstructure. The corrosion rate significantly increased as the average grain size increased from 65 to 250 μm.     

Enhanced Thermoelectric Performance of PEDOT:PSS Films by Sequential Post‐Treatment with Formamide

This paper reports a series of sequential post‐treatments using a polar solvent formamide to enhance the thermoelectric performance of poly(3,4‐ethylenedioxythiophene) doped with poly(styrene sulfonate) anions (PEDOT:PSS). The electrical conductivity of PEDOT:PSS films significantly increases from 0.33 S cm^?1 for the pristine film to ≈2929 S cm^?1 for the treated film and meanwhile the Seebeck coefficient maintains as high as 17.4 µV K^?1, resulting in a power factor of 88.7 µW m^?1 K^?2. Formamide is a polar solvent with a high boiling point of 210 °C and high dielectric constant of 109, and PSS has a good solubility in it. Post‐treatment with formamide causes not only the phase segregation of PEDOT and PSS but also the removal of insulating PSS, therefore leading to the reorientation of PEDOT chains and enhancement in mobility without altering the doping level considerably. The cross‐plane thermal conductivity also reduces from 0.54 to 0.19 W m^?1 K^?1 after the post‐treatment, leading to a figure of merit (ZT) value of 0.04 at room temperature.     

Influence of rare earth additives and boron component on electrical conductivity of sodium rare earth borate glasses

Sodium rare earth borate glasses (Na₂O)_35.7(RE₂O₃)_7.2(B₂O₃)_57.1 (RE = Sm, Gd, Dy, Ho, Y, Er, and Yb), were prepared from a mixture of Na₂CO₃, RE₂O₃ and B₂O₃, and their properties as an Na⁺ ionic conductor were investigated. Density increased with increasing atomic weight of RE. Crystallization temperature and crystal melting temperature of the present borate system was lower than that of the previously reported silicate and germanate system. Results of the ¹¹B NMR measurement suggested that half of all boron atoms are coordinated by four oxide ions to give a [BO₄] tetrahedral unit and the others are coordinated by three oxide ions to give a [BO₃] planar triangular unit. The electrical conductivity slightly decreased with increasing the ionic radius of RE³⁺. (Na₂O)_35.7(Y₂O₃)_7.2(B₂O₃)_57.1 glass exhibited the electrical conductivity which is about one order of magnitude lower than those of the previously reported (Na₂O)_35.7(Y₂O₃)_7.2(SiO₂)_57.1 and (Na₂O)_35.7(Y₂O₃)_7.2(GeO₂)_57.1 glasses. It was assumed that this lower electrical conductivity is due to the lower content of Na⁺ ions as conduction species in the former glass, compared with the latter two glasses.     

Long-Term Transport Study of Bioartificial Tubule Devices in the Development of a Bioartificial Kidney

Introduction: A bioartificial kidney, which consists of a continuous hemofilter and a bioartificial tubule device using proximal tubular epithelial cells (LLC‐PK₁), is desired to develop for preventing long‐term complications in hemodialysis patients. A bioartificial tubule device should function for a long duration in terms of the simplicity and the economy. Continuous hemofiltration with 10 L/day of filtrate could maintain plasma urea, creatinine and β₂‐microglobulin in patients at low levels compared to those in standard hemodialysis patients. Methods: 6 bioartificial tubule devices, in which LLC‐PK₁ cells were grown on the inner surfaces of hollow fiber capillaries (membrane area: 0.4 m², 1600 fibers), were used to evaluate the transport ability of H₂O, glucose and Na⁺, and leak rates of urea and creatinine for 2 weeks when the medium containing 50 mg/dL of urea and 5.0 mg/dL of creatinine was perfused inside of the cell‐attached membranes and another medium containing 2.5 g/dL of albumin was perfused outside of the membranes. Scanning electron micrograph of cross‐sectional findings of the hollow fibers was taken at 6, 10, and 14 days after formation of confluence. Results: By conversion into 1 m² of membrane area, transport of H₂O, glucose, and Na⁺ was 6266 ± 995 mL/day, 22832 ± 7240 mg/day, and 941.3 ± 180 mEq/day, respectively at 6 days after confluence. Leak rates of urea and creatinine across the cell‐attached membranes were 22 ± 6.1% and 19.2 ± 4.9 with albumin addition, whereas 13.1 ± 1.9% and 12.2 ± 1.6 without albumin addition. Transport capacity of these components and the leak rates had continued for 10–13 days, and decreased thereafter because of the formation of the multilayers. Bioartificial tubule devices with membrane area 1.0 m² can reach the targeted amounts of H₂O, glucose, and Na⁺ transports when 6 L of 10 L/day of hemofiltrate has to be regenerated, substituting 4 L with meal and drinks.