Norio Ohkubo

A 1.5-ns 32-b CMOS ALU in double pass-transistor logic

Describes circuit techniques for fabricating a high-speed adder using pass-transistor logic. Double pass-transistor logic (DPL) is shown to improve circuit performance at reduced supply voltage. Its symmetrical arrangement and double-transmission characteristics improve the gate speed without increasing the input capacitance. A carry propagation circuit technique called conditional carry selection (CCS) is shown to resolve the problem of series-connected pass transistors in the carry propagation path. By combining these techniques, the addition time of a 32-b ALU can be reduced by 30% from that of an ordinary CMOS ALU. A 32-b ALU test chip is fabricated in 0.25- mu m CMOS technology using these circuit techniques and is capable of an addition time of 1.5 ns at a supply voltage of 2.5 V. >

A 4.4 ns CMOS 54/spl times/54-b multiplier using pass-transistor multiplexer

A 54/spl times/54-b multiplier using pass-transistor multiplexers has been fabricated by 0.25 /spl mu/m CMOS technology. To enhance the speed performance, a new 4-2 compressor and a carry lookahead adder (CLA), both featuring pass-transistor multiplexers, have been developed. The new circuits have a speed advantage over conventional CMOS circuits because the number of critical-path gate stages is minimized due to the high logic functionality of pass-transistor multiplexers. The active size of the 54/spl times/54-b multiplier is 3.77/spl times/3.41 mm. The multiplication time is 4.4 ns at a 3.5-V power supply. >

Electric-energy generation using variable-capacitive resonator for power-free LSI: efficiency analysis and fundamental experiment

A power generator based on a vibration-to-electric energy converter using a variable-resonating capacitor is experimentally demonstrated. The generator consists of a complete system with a mechanical-variable capacitor, a charge-transporting LC tank circuit and an externally powered timing-capture controller. A practical design methodology to maximize the efficiency of the vibration-to-electric energy generation system is also described. The efficiency of the generator is estimated based on three factors: the mechanical-energy loss, the charge-transportation loss, and the timing-capture loss. Through the mechanical-energy analysis, the optimum condition for the resonance is found. The parasitic elements in the charge transporter and the timing management of the capture scheme dominate the generation efficiency. These analyses enable the optimum design of the energy-generation system. An experimentally fabricated and measured generator theoretically has a maximum power of 580 nW; the measured power is 120 nW, so conversion efficiency is 21%. This results from a 43% mechanical-energy loss and a 63% charge-transportation loss. The timing-capture scheme is manually determined and externally powered in the experiment, so its efficiency is not considered. With our result, a new system LSI application with an embedded power source can be explored for the ubiquitous computing era.

A 4.4-ns CMOS 54/spl times/54-b multiplier using pass-transistor multiplexer

A 54/spl times/54-b multiplier using pass-transistor multiplexer has been fabricated by 0.25-/spl mu/m CMOS technology. To enhance the speed performance, a new 4-2 compressor and a carry look-ahead adder (CLA) both featuring the use of pass-transistor multiplexers have been developed. The new circuits have a speed advantage over conventional CMOS circuits because the number of critical-path gate stages is minimized due to the high logic functionality of pass-transistor multiplexers. The active size of the 54/spl times/54-b multiplier is 3.77 mm/spl times/3.41 mm. The multiplication time is 4.4 ns at 2.5 V power supply.<<ETX>>

Studies on the succession of blue‐green algae, Microcystis, Anabaena, Oscillatoria and Phormidium in Lake Kasumigaura

Abstract This study was conducted to examine and determine the factors affecting dominance of the blue‐green algal species of genus Microcystis, Anabaena, Oscillatoria and Phormidium from 1988 to 1990 in eutrophic Lake Kasumigaura. The algal dominancy of the three Anabaena species, A. affinis,A. flos‐aquae and A. spiroides, took place in early summer, while the dominance of the Microcystis species, M. aeruginosa, M. viridis and M. wesenbergii, took place from summer to fall. Water samples were collected at Tsuchiura Harbour in Lake Kasumigaura. The correlations between cell numbers of blue‐green algal species and water qualities were investigated. The growth rates of algae in situ were determined. Af. aeruginosa showed the highest increasing growth rate, while Af. viridis was the lowest decay rate in the Microcystis species. M. aeruginosa exhibited high single correlations between water temperature, pH, total chemical oxygen demand (T‐COD) and dissolved chemical oxygen demand (D‐COD). The cell numbers of ...

Predicting flow state in daily work through continuous sensing of motion rhythm

We have constructed a new application of continuous sensing of human physiological data during daily a business setting. By capturing the subtle changes and differences in motion rhythm detected through an accelerator rather than trying to identify the context of human activities, we are envisioning the prediction of a persons psychological flow state, i.e., the engagement in ones task. A badge-shaped wearable sensor device called “Business Microscope” was developed and deployed in a real organization, an office supply firm, for one month to study how effectively flow states could be measured during daily work. We found that even though each subject behaved at different motion rhythms when they were in flow, the consistency of motion rhythm around 2 to 3 Hz was correlated with the richness of flow during work (r=0.47, p<0.01).

Electric power generation using piezoelectric resonator for power-free sensor node

This paper describes a power-free sensor node operated by ambient vibration energy. An electric power generator is based on a vibration-to-electric energy converter using a piezoelectric resonator. The power generator consists of a piezoelectric resonator, and a power control circuit for recharging. Key technologies are the analysis model that compensates for inertia moment of the piezoelectric resonator, and the power control circuit that stores scavenged current charge to supply instant power for radio communication. The condition optimization for the size of the resonator is match of resonance frequency, which achieves highly efficient resonator. The power control circuit that stores electric power of the 180 /spl mu/W and supplies electric power of 30 mW. As a result, the power generator achieves 5 minute intermittent operation of a power-free sensor node.

Effects of Humic and Fulvic Acids on the Growth of Microcystis Aeruginosa

The effects of chelate substances on the growth of Microcystis aeruginosa K-5 in Lake Kasumigaura water were investigated. A chelate compound, EDTA (Ethylenediaminetetraacetic acid disodium salt) and natural chelate substances, such as humic and fulvic acids isolated from Lake Kasumigaura sediment, stimulated the growth of the K-5 strain. We investigated the mechanism of this stimulation by chelate compounds. The toxicity of heavy metals such as copper, nickel, and zinc, and the alleviation of heavy metal toxicity by chelate compounds were determined. The 50% growth inhibition (EC50) values of copper and zinc for the K-5 strain were 8.4 and 11.4µg l−1, respectively, close to levels measured in Lake Kasumigaura. Humic and fulvic acids mitigated copper and zinc toxicity. Humic and fulvic acids may significantly affect the occurrence of water blooms of Microcystis in Lake Kasumigaura.

Beam-scan sensor node: Reliable sensing of human interactions in organization

We have developed a wearable sensor node with a low power and high detection rate by using sequential control of multiple infrared (IR) modules. Conventional sensor nodes are not practical in terms of size, sensing performance, and working hours. Therefore, we devised a name-tag-size (73 × 98 × 9 mm) sensor node, which captures face-to-face interactions within 2 meters and within an angle of 60°. The sensor node weighs 62 grams and works for more than twenty hours with a small 5-gram Li-ion battery. The sensor uses the beam-scan technique, in which four infrared modules, placed horizontally on the node, are controlled to be on and off sequentially, and this operation is done synchronously with other nodes. The beam-scan technique enables low-power operation with a consumption current of 7.2 mA and 21 hours of operation. We had tested the sensor node in a field trial that collected sensor data for six months from 20 people and had demonstrated that this technique is practical. Feedback from sensing data reminded us of the importance of meeting frequency and this improved our work habits.

An autonomous decentralized low-power system with adaptive-universal control for a chip multi-processor

A technique for adaptive-universal control of clock frequency, supply voltage, and body bias optimizes the performance-to-power ratio of chip multi-processors. The technique is based on a compound built-in self-test and self-instructed look-up table scheme for an autonomous and decentralized system. Applied to a 32b ALU, power is reduced by seventy times.