A 14-ns 14-Mb CMOS DRAM with 300-mW active power

A 4-Mb high-speed DRAM (HSDRAM) has been developed and fabricated by using 0.7-μm L_eff CMOS technology with PMOS arrays inside n-type wells and p-type substrate plate trench cells. The 13.18-mm×6.38-mm chip, organized as either 512 K word×8 b or 1 M word×4 b, achieves a nominal random-access time of 14 ns and a nominal column-access time of 7 ns, with a 3.6-V V_cc and provision of address multiplexing. The high level of performance is achieved by using a short-signal-path architecture with center bonding pads and a pulsed sensing scheme with a limited bit-line swing. A fast word-line boosting scheme and a two-stage word-line delay monitor provide fast word-line transition and detection. A new data output circuit, which interfaces a 3.6-V V_cc to a 5-V bus with an NMOS-only driver, also contributes to the fast access speed by means of a preconditioning scheme and boosting scheme. Limiting the bit-line voltage swing for bit-line sensing results in a low power dissipation of 300 mW for a 60-ns cycle time     

Continuous versus bilevel positive airway pressure in a patient with idiopathic central sleep apnea

A 57-yr-old man with idiopathic central apnea is reported. He presented at our hospital complaining of excessive daytime sleepiness. Polysomnography, including esophageal pressure monitoring, confirmed central sleep apnea with an apnea index of 27/h. He had mild non-insulin-dependent diabetes mellitus (NIDDM) but no signs of diabetic neuropathy or other background diseases. The ventilatory responses to hypoxia and hypercapnia tested while he was awake indicated increased respiratory chemosensitivity. We applied nasal continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BPAP) in an attempt to compare the possible difference in therapeutic efficacy. Although nasal CPAP completely reversed central apnea, nasal BPAP adversely affected both apnea length and frequency in an applied pressure-dependent manner. Arterial blood gas analyses while he was being treated indicted alveolar hypoventilation with CPAP and hyperventilation with BPAP. Additionally, administration of a mixed gas containing 5% CO2 through a face mask had a significant effect on the disappearance of central apnea in this patient. These findings support the theory that the arterial PCO2 level is critical in generating idiopathic central apnea and that nasal CPAP therapy may be effective in eliminating central apnea by raising the PaCO2.     

Preparation of ultrafine zirconium dioxide particles by thermal decomposition of zirconium alkoxide vapour

Ultrafine zirconia particles are produced by thermal decomposition of zirconium tetratertiary butoxide (ZrTB) vapour. The introduction of ZrTB vapour into the cylindrical electric furnace, is achieved by three different methods: (evaporator, pressurized nebulizer and ultrasonic nebulizer). The properties of the fine particles obtained by these methods are mainly analysed by X-ray diffraction and transmission electron microscopy. It is found that ultrafine zirconia particles produced at relatively low temperatures from 600 to 700° C are spherical in the diameter range 0.035 to 0.15 μm and of tetragonal phase. Furthermore, two-component fine particles of zirconia-ilver are generated by putting the silver solid inside the furnace containing alkoxide vapour, and are deposited by inertia on to a glass substrate under low pressure to form films having a thickness of 17 to 33 μm. The electrical characteristics of the films are evaluated, and the conductance of the film is found to increase with the content of the silver component.     

Properties of Bi-doped PbTe layers grown by liquid phase epitaxy under controlled Te vapor pressure

Effects of Bi doping in PbTe liquid-phase epitaxial layers grown by the temperature difference method under controlled vapor pressure (TDM-CVP) are investigated. For Bi concentrations in the solution, x_Bi, lower than 0.2 at.%, an excess deep-donor level (activation energy E_d≈0.03–0.04 eV) appears, and Hall mobility is low. In contrast, for x_Bi>0.2 at.%, Hall mobility becomes very high, while carrier concentration is in the range of 10¹⁷ cm⁻³. Inductive coupled plasma (ICP) emission analysis shows that, for x_Bi=1 at.%, Bi concentration in the epitaxial layer is as high as N_Bi=2.3–2.7 × 10¹⁹ cm⁻³. These results indicate that Bi behaves not only as a donor but also as an acceptor, and the nearest neighbor or very near donor-acceptor (D-A) pairs are formed, so that strong self-compensation of Bi takes place. Carrier concentration for highly Bi-doped layers shows a minimum at a Te vapor pressure of 2.2 × 10⁻⁵ torr for growth temperature 470°C, which is coincident with that of the undoped PbTe.     

Reactions between zirconium/permalloy bilayer thin films

The interdiffusion and reactions of zirconium/permalloy bilayer thin films annealed at 150 to 350 °C were investigated. Nickel atoms preferentially diffuse from the permalloy layer into the zirconium layer. This preferential diffusion results in the growth of an amorphous phase between the zirconium and permalloy thin films. Consequently, the magnetic properties of the permalloy thin layer in the bilayer thin films change. The starting temperature of interdiffusion between zirconium and permalloy films is higher than that of a titanium/permalloy system reported previously.     

Dielectric strength of transformer insulation at DC polarityreversal

Among special insulation tests for DC power converter transformers, polarity reversal tests can be substituted by applied AC voltage tests from a stress similarity in oil ducts. In order to investigate equivalent levels of other insulation tests to polarity reversal tests, the dielectric strength of a transformer at polarity reversals was examined by use of a model of typical oil/paper composite insulation. From the comparison of polarity reversal and other insulation tests, it was found that dielectric strength of transformer insulation at polarity reversals is phenomenally similar to that under switching impulse stresses. Equivalent AC test voltage to polarity reversal test was also estimated from the experimental results. The breakdown characteristics of polarity reversal tests showed that partial discharges at polarity reversals impose less harmful stress on insulation barriers than those at usual AC or impulse tests     

High-resolution electron microscopy of nanocrystalline Ni-Al alloys: instability of ordered structure and dynamic behaviour of grain boundaries

High-resolution transmission electron microscopy was performed on vacuum-deposited nanocrystalline nickel aluminide films. Several nickel aluminide ordered structures, i.e. L1₂(Ni₃Al)-, B2(NiAl)-, D5₁₃(Ni₂Al₃)- and D0₂₀(NiAl₃)-type structures, were observed in the deposited films. The L1₂ and B2 ordered structures became unstable with decreasing grain sizes. The critical grain size on transformation from the L1₂- and B2-type ordered structures into disordered structures was ca. 5 nm at ambient temperatures. High atomic diffusion, sufficient for grain growth, and an increase in the ordering occurred just above 400°C in the nanocrystalline Ni-Al films with L1₂- and B2-type structures. The diffusion bonding process, at ambient temperatures, between Ni-Al nanocrystallites with an L1₂-type structure was observed dynamically at atomic resolution under strong electron irradiation. It was found that the nanocrystallites rotated and slid without crack generation, and neck-growth proceeded even at ambient temperatures.     

Blocking Probability in Link-Frame Systems from the Viewpoint of Overflow Processes

From the development of the work concerning the overflow processes due to Palm and Taḱcs, we consider the blocking probability in four-stage type systems which are used for telephone services as speech-path connecting networks in central systems. First, the events causing failure in channel matching in the system and the stochastic properties in the system are considered. After that distribution of interval-times between the instants at which the link blocking occurs is considered from the viewpoint of overflow processes, taking into consideration the above obtained results, and finally this distribution and the blocking probability are determined.