Adaptive control in a heating vessel: A comparative study

This paper presents experimental results obtained in temperature adaptive control of a heating vessel. A non-linear model of the process showed that the feed flow rate causes severe variations in time constant and process gain. An extended horizon self-tuning controller and two different model reference adaptive controllers were tested. The influence of design parameters on control performance for each algorithm was assessed. The control system was disturbed with load and setpoint changes.     

Series resonant ZCS‐PFM DC‐DC power converter with high‐frequency high‐voltage transformer link for high‐power magnetron drive

This paper presents a single lossless inductive snubber‐assisted ZCS‐PFM series resonant DC‐DC power converter with a high‐frequency high‐voltage transformer link for industrial‐use high‐power magnetron drive. The current flowing through the active power switches rises gradually at a turned‐on transient state with the aid of a single lossless snubber inductor, and ZCS turn‐on commutation based on overlapping current can be achieved via the wide range pulse frequency modulation control scheme. The high‐frequency high‐voltage transformer primary side resonant current always becomes continuous operation mode, by electromagnetic loose coupling design of the high‐frequency high‐voltage transformer and the magnetizing inductance of the high‐frequency high‐voltage transformer. As a result, this high‐voltage power converter circuit for the magnetron can achieve a complete zero current soft switching under the condition of broad width gate voltage signals. Furthermore, this high‐voltage DC‐DC power converter circuit can regulate the output power from zero to full over audible frequency range via the two resonant frequency circuit design. Its operating performances are evaluated and discussed on the basis of the power loss analysis simulation and the experimental results from a practical point of view. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 79–87, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20126     

Thermal characteristics of packed bed storage system

The thermal behaviour of a packed bed storage system charged with hot air is modelled using two partial differential equations representing the energy conservation in the air and solid phases constituting the bed. These two equations are coupled through the heat exchange process between the two phases. A fully implicit numerical scheme based on forward, upwind and central differencing for the time, first and second space derivatives, respectively, is used to solve the modelling equations. Marching technique is used for the air equation and a tri-diagonal matrix solver is employed to solve the solid equation. The solution yields the thermal structure of the bed, namely the air and solid temperature distribution inside the bed at any particular time, and the variation of total energy stored in the bed with time. The effect of bed length, solid diameter and void fraction on the thermal characteristics of the packed bed is studied. Further, the performance of the bed under variable inlet air temperature and mass flow rate is investigated.     

A simplified cascade current‐source inverter interconnected to a single‐phase three‐wire distribution system and its application to electric energy storage systems with batteries

A novel current source inverter system interconnected to the single‐phase grid is proposed. It has the same construction as the conventional three‐phase current source inverter that is interconnected to the single‐phase three‐wire distribution system. Though the proposed circuit has no output transformer, it can be equivalently performed as the single‐phase double cascade inverter by diverting the pole transformer in the utility system. By controlling the appropriate scheme, the output currents can be obtained as the five‐level waveforms and their distortions can be decreased sufficiently. It is applied to the interactive electric energy storage system with batteries and the basic discharging characteristics are discussed experimentally. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 50–61, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10380     

High cycle fatigue behaviour of Ti–6Al–4V alloy at elevated temperatures

High cycle fatigue behaviour of Ti–6Al–4V alloy was studied at 623 K and 723 K. Fatigue strength decreased at elevated temperatures compared with at ambient temperature. In the short life regime, fatigue strength was lower at 723 K than at 623 K, but in the long life regime it was nearly the same at both temperatures. At elevated temperatures, cracks were generated earlier at applied stresses below the fatigue limit at ambient temperature, indicating lowered crack initiation resistance. Small cracks grew faster at elevated temperatures than at ambient temperature, which became more noticeable with increasing temperature. After allowing for the elastic modulus, small cracks still grew faster at elevated temperatures.     

纺牵—步法中粗旦丙纶长丝沸水收缩率初探

在纺牵联合一步法纺丝机上研究了丙纶切片的熔融指数对纤维沸水收缩率的影响，发现熔融指数高的切片，其纤维的沸水收缩率变化大。沸水收缩率随热定型的温度升高而下降。沸水收缩率可根据用户提供中心值（Ｍ）通过实验确定，一般以Ｍ±１．５为宜。     

A203型低温氨合成催化剂使用小结

对Ａ２０３型低温氨合成催化剂的使用进行总结，介绍了该催化剂的装填，升温还原情况及使用效果。     

The adhesion of amorphous polystyrene surfaces below Tg

The bonding of polystyrene (PS) surfaces below T_g was investigated by two different fracture tests: the lap-shear joint method and the cantilever beam method. Adhesion energy values obtained by the two methods are in agreement and develop with (time)^1/2, at temperatures as low as T_g−16 °C. Even if the double cantilever method is the most common test found in the literature for adhesions above T_g, for low adhesion values, below T_g, the lap-shear joint geometry is more appropriate. Moreover, when the glass transition temperature is used as a reference temperature, polydisperse and monodisperse PS adhesion energy curves are superposable, suggesting that the auto-adhesion is not significantly favored by the presence of numerous chain ends at the surface (due to the low molecular weight chains provided by the polydisperse PS).