A 44-mm/sup 2/ four-bank eight-word page-read 64-Mb flash memory with flexible block redundancy and fast accurate word-line voltage controller

The highest bit-density 64-Mb NOR flash memory with dual-operation function of 44 mm/sup 2/ was developed by introducing negative-gate channel-erase NOR flash memory cell technology, 0.16-/spl mu/m CMOS flash memory process technology, and four-bank hierarchical word-line and bit-line architecture. The chip has flexible block redundancy for high yield, a fast accurate word-line voltage controller for a fast erasing time of 0.5 s, and an eight-word page-read access capability for high read performance of an effective access time of 30 ns at a wide supply voltage range of 2.3-3.6 V.     

Regeneration of periodontal Ruffini endings in adults and neonates

We reviewed the regeneration of periodontal Ruffini endings, primary mechanoreceptors in the periodontal ligament, following injury to the inferior alveolar nerve (IAN) in adult and neonatal rats. Morphologically, mature Ruffini endings are characterized by an extensive arborization of axonal terminals and association with specialized Schwann cells, called lamellar or terminal Schwann cells. Following injury to IAN in the adult, the periodontal Ruffini endings of the rat lower incisor ligament regenerate more rapidly than Ruffini endings in other tissues. During regeneration, terminal Schwann cells migrate into regions where they are never found under normal conditions. The development of periodontal Ruffini endings of the rat incisor is closely associated with the eruption of the teeth; the morphology and distribution of the terminal Schwann cells became almost identical to those in adults during postnatal days 15-18 (PN 15-18d) when the first molars appear in the oral cavity, while the axonal elements showed extensive ramification around PN 28d when the functional occlusion commences. When the IAN was injured in neonates, the regeneration of periodontal Ruffini endings was delayed compared with the adults. The migration of terminal Schwann cells is also observed following IAN injury, after which the distribution of terminal Schwann cells became almost identical to that of the adults, i.e., PN 14d. Since the interaction between axon and Schwann cell is important during regeneration and development, further studies are required to elucidate its molecular mechanism during the regeneration as well as the development of the periodontal Ruffini endings.     

Bridging conventional medicine and complementary and alternative medicine

Complementary and alternative medicine (CAM) therapies are classified into five major domains: alternative medical systems (which includes traditional Chinese medicine, ayurveda, homeopathy, and naturopathy); mind-body interventions (including meditation, hypnosis, dance music, and art therapy); biologically based treatments (such as vitamins, minerals, herbs, and vegetarianism); manipulative and body-based methods (including chiropractic and massage therapies); and energy therapies - with some overlap across categories. Biomedical engineering (BME) is essential for exploring the safety and efficacy of these CAM therapies in the context of rigorous science. Recently, integrative medicine (IM) has been considered the ideal medical system for integrating conventional medicine and CAM. For this purpose, the concept of how to integrate these methods first must be investigated, and independent verification of CAM methods will be necessary. Biomedical engineering will be expected to be the most important method for verifying CAM scientifically.     

A laminate composite with an infinite row of parallel cracks normal to the interfaces

Under the assumption of plane strain, the distribution of stresses in a laminate composite due to the presence of an infinite row parallel cracks situated normal to the bond lines is obtained. Using an integral transform technique, the problem is reduced to that of solving a Fredholm integral equation of the second kind. The singular stress field near the tip of a crack is then derived. The effects on the stress intensity factor due to the presence of many cracks in a laminate-composite are illustrated graphically.     

How do colors influence the haptic perception of textured surfaces?

Multimodality is considered a promising approach for universal access, and haptic interaction has the potential to constitute an added dimension to multimodal interfaces. This paper describes the influence of colors on the haptic perception of textured surfaces, based on 8 experiments. Our results show that (1) colors do have an influence on haptic perception, but they do not make the perception error rate higher than when no color is used; (2) up to 6 different types of colors can be used in haptic interfaces without worsening the haptic perception; (3) yellow has an error rate that is statistically significantly lower than that of 3 other color conditions, and can be used without worsening the haptic perception; (4) our finding of two special orders for haptic perception demonstrates that human haptic perception is very sensitive to continuously increasing or decreasing changes of roughness, but has difficulty discerning randomly changed roughness.     

Reliability of wire-bonding and solder joint for high temperature operation of power semiconductor device

Thick Al wires bonded on chips of power semiconductor devices were examined for thermal cycle tests, then the bonded joints were cut using microtome method, after that those were observed by scanning electron microscope and analyzed by electron back scattered diffraction. Some cracks were observed between Al wires and the chips, unexpectedly the crack lengths were almost constant for −40/150 °C, −40/200 °C and −40/250 °C tests. It is considered that re-crystallization has been progressed during the high temperature side of the thermal cycle tests.Furthermore, joint samples were prepared using high temperature solders such as Zn–Al and Bi with CuAlMn, Direct Bonded Copper insulated substrates and Mo heatsinks. The fabricated samples were evaluated by scanning acoustic microscope before and after thermal cycle tests. Consequently, almost neither serious damages nor delaminations were observed for −40/200 °C and −40/250 °C tests.     

Design of a sense circuit for low-voltage flash memories

A new sense circuit directly sensing the bitline voltage is proposed for low-voltage flash memories. A simple reference voltage generation method and a dataline switching method with matching of the stray capacitance between the dataline pairs are also proposed. A design method for the bitline clamp load transistors is described, taking bitline charging speed and process margins into account. The sense circuit was implemented in a 32-Mb flash memory fabricated with a 0.25-μm flash memory process and successfully operated at a low voltage of 1.5 V     

Disturbance suppression beyond Nyquist frequency in hard disk drives

In conventional hard disk drives, a control system compensates for vibration in which the frequency is higher than the Nyquist frequency by using a multi-rate filter that decreases the gain above the Nyquist frequency. However, such a control system can only avoid instability and cannot suppress disturbances above the Nyquist frequency. To overcome this problem, a control system design method that suppresses disturbances beyond the Nyquist frequency is proposed. This method uses frequency responses of a controlled object and a digital controller to calculate the gain of the sensitivity function in a sampled-data system without requiring complex calculations involving matrices, and realizes a stable resonant filter that decreases the gain of the sensitivity function above the Nyquist frequency. Significant suppression of the vibrations caused by the disturbances beyond the Nyquist frequency is demonstrated by implementing this method in the head-positioning system of a hard disk drive.     

Compensation for position‐dependent mechanical resonances in head‐positioning control of hard disk drives

We propose a compensation method for position‐dependent mechanical resonances in head‐positioning control system of hard disk drives (HDDs). To realize high‐accuracy head‐positioning control, it is important to compensate for the mechanical resonances in the head‐positioning control system. The some mechanical resonance characteristics depend on the magnetic head's location. In conventional design method, a notch filter must be designed to compensate for the mechanical resonances at any magnetic head location. The disadvantage is that phase lag caused by the notch filter worsens the stability of the head‐positioning control system. To overcome this disadvantage, we propose a magnetic head‐position‐dependent notch filter to compensate for the position‐dependent mechanical resonances in the head‐positioning control system. The simulation results in HDD benchmark model show that the proposed method can decrease the phase lag caused by the notch filter. That is, the proposed method can improve the stability compared to the conventional method. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.