Ion implantation of Zn,Se and Cd in BP crystals

Ion implantation of 70 keV Zn, Se and Cd has been done in n-type BP as a function of dose and implantation temperature, and defects and lattice locations have been measured by means of channeling techniques. Crystals used were grown on Si substrates by vapor phase epitaxy. It was observed that epitaxial layers thicker than 6μm have no defects due to a lattice mismatch between Si and BP. High temperature implantation above 500°C gave high substitutional fraction of ～ 70% and low residual defects. Reordering of an amorphous layer formed by implantation below 400°C was not observed even after annealing at 900°C. The present results indicate that the effect of implantation temperature is the same with other III-V compounds such as GaAs and Gap.     

Neutron diffraction and IR spectroscopy on mechanically alloyed La-substituted PbWO4

Defect structures of the lanthanum-substituted PbWO₄ prepared by mechanical alloying (MA) were investigated by means of powder neutron diffraction and FT-IR, to compare with that of the oxide ion conductive sintered samples. Neutron diffraction revealed that Pb_1−xLa_xWO_4+x/2 prepared by MA possessed the lead site deficiency in the lattice. In addition, it was also found that occupation factors of the lead site were still smaller than the nominal value even for the mechanically alloyed Pb_1−xLa_2x/3WO₄. The vacancy formation at the lead site of the mechanically alloyed Pb_1−xLa_xWO_4+x/2 was also corroborated from the splitting of the absorption band around 800 cm⁻¹ ascribed to the W–O stretching vibration of WO₄ tetrahedron. At the end of this paper, the formation process of the lead site vacancy was discussed in the sintered Pb_1−xLa_xWO_4+x/2 during milling.     

Theoretical analysis of a wheel driven root crop harvester

A prototype of a wheel driven trailer was developed to simulate a wheel driven trailed root crop harvester. The mobility of the prototype tractor-trailer system was improved by driving the trailer wheels by a mounted engine. A mathematical model to predict the mobility and the stability of the system was developed. The model was validated by field experiments conducted in plowed, rotary tilled and untilled fields. The model was found to predict performance with a high accuracy. Parameter studies were conducted to investigate the effects of several design parameters, such as the peripheral velocity ratio (R_s), the weight of the trailer (m₁), the trailer's C.G. location (L_L) and the height of a hitch point (h), on the mobility and the stability of the system.     

Time-resolved Optical Emission Spectroscopy in Water Electrical Discharges

The characteristics of the plasma initiated in ultrapure water between pairs of tungsten and tantalum electrodes were investigated by time-resolved optical emission spectroscopy. The deexcitation processes of the reactive species formed in the water plasma depended on the electrode material, but had been independent on the polarity of the applied voltage pulses. All the reactive species presented the same evolution with time and have been identified with high concentration in the emission spectra between the pulses. The current–voltage characteristics showed the features of a spark discharge for the both types of electrodes used in the process. When tantalum electrodes were used to generate the discharge, a broad emission continuum (350–940 nm) dominated the spectrum due to a transition to arc discharge.