Characteristics and structural change of layered polysilane (Si6H6) anode for lithium ion batteries

Layered polysilane (Si₆H₆) has a graphite-like structure with higher capacity than crystalline silicon. The rate of increase of the thickness of a layered polysilane electrode after 10 charge-discharge cycles was smaller than that for a Si powder electrode, although the layered polysilane electrode has higher capacity. The structural changes of electrochemically lithiated and delithiated layered polysilane at room temperature were studied using scanning electron microscopy, X-ray diffraction and Raman spectroscopy. Layered polysilane became amorphous by insertion of lithium to 0 V, whereas insertion of lithium into crystalline silicon produces Li₁₅Si_4. Layered polysilane maintained an amorphous state during lithium insertion and deinsertion, whereas silicon changed between Li₁₅Si₄ and amorphous Li_xSi, which explains the smaller volume change of a layered polysilane electrode compared with a Si powder electrode.     

Effects of geometry and specimen size on out-of-plane tensile strength of aligned CFRP determined by direct tensile method

The out-of-plane tensile strength of CFRP laminate determined by the direct tensile method varies with specimen geometry and size. This effect was first experimentally observed using aligned CFRP. To explain the geometry and size effects from a mechanical point of view, an analytical model combining Weibull statistics, including the concept of effective volume, and a fracture criterion under multi-axial loading was constructed on the basis of stress distributions calculated using the finite element method. The predicted out-of-plane tensile strength of aligned CFRP was found to be consistent with experimental results. Thus, the present model is useful for reducing experimentally determined out-of-plane tensile strength under complex stress distributions to that under a uniaxial and uniform stress distribution.     

Highly strong and conductive carbon nanotube/cellulose composite paper

Carbon nanotube (CNT)/cellulose composite materials were fabricated in a paper making process optimized for a CNT network to form on the cellulose fibers. The measured electric conductivity was from 0.05 to 671 S/m for 0.5–16.7 wt.% CNT content, higher than that for other polymer composites. The real permittivities were the highest in the microwave region. The unique CNT network structure is thought to be the reason for these high conductivity and permittivity values. Compared to other carbon materials, our carbon CNT/cellulose composite material had improved parameters without decreased mechanical strength. The near-field electromagnetic shielding effectiveness (EMI SE) measured by a microstrip line method depended on the sheet conductivity and qualitatively matched the results of electromagnetic field simulations using a finite-difference time-domain simulator. A high near-field EMI SE of 50-dB was achieved in the 5–10 GHz frequency region with 4.8 wt.% composite paper. The far-field EMI SE was measured by a free space method. Fairly good agreement was obtained between the measured and calculated results. Approximately 10 wt.% CNT is required to achieve composite paper with 20-dB far-field EMI SE.     

Spatial ordering of self-organized InGaAs/AlGaAs quantum disks on GaAs (311)B substrates

We report the control of self-organization of In_xGa_1−xAs/AlGaAs quantum disks on GaAs (311)B surfaces using a novel technique based upon lithography-defined SiN dot arrays. A strained InGaAs island array selectively grown using the SiN dots provides periodic strain field. When the pitch of lateral ordering corresponds with the period of the strain field, self-organized quantum disks stacked on the InGaAs islands are precisely arranged just as the buried SiN dot array. The spacing of the array element is 250–300 nm (x = 0.3) and around 150 nm (x = 0.4). Vertical alignment by strain is achieved at a very thick (95 nm) separating layer. Characterization using atomic force microscopy reveals the size-fluctuation of disk is dramatically improved with spatial ordering.     

Surface coating and texturing on stainless-steel plates to decrease the contact resistance by using screen printing

Stainless steel is an attractive material for use in bipolar plates of polymer-electrolyte-membrane fuel cells, except for its high interfacial contact resistance (ICR). Inexpensive surface treatment is required to decrease the ICR. A carbonaceous conductive composite was coated on stainless-steel plate surfaces by using a screen-printing technique. A grid-like texture of the same material as the coating was also printed on the coated plate surface. The cross section showed that conductive carbon particles were well dispersed in the coating layer, which favors through-plane electrical conductivity. The coated and textured plates exhibited a much lower ICR than that of bare stainless steel. The ICR of textured plates was lower than that of coated plates under lower compaction pressures. A single cell with coated and textured bipolar plates exhibited higher power densities than that of bare stainless-steel bipolar plates.     

Torque characteristics and application of two‐phase induction motor driven by two power supplies with nearby frequencies

When two power supplies with nearby frequencies are connected to a two‐phase induction motor, the motor generates two kinds of oscillatory torque components, which have frequency components of the sum and the difference between the frequencies of the power supplies. These oscillatory torque components are sinusoidal, and the torque with the frequency component of the difference is considerably larger than the torque with the frequency component of the summation. Consequently, the motor behaves as a swing motor, which alternately changes the direction of rotation. Because of the regularity of the period of the human heartbeat, this swing motor is suitable for use as the driver of an artificial heart. We propose here to use this swing motor as the pump for artificial hearts. In this paper, we present the fundamental theory and the characteristics of the swing motor, and an outline of the motor action for artificial hearts. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 73–80, 2000     

Evaluation of the continuation bit in the cyclic pipeline computer

The Cyclic Pipeline Computer (CPC) is a shared resource computer which shares its pipeline among multiple instruction streams to create distinct virtual processors. This effectively removes data dependencies which reduce the performance of highly pipelined computers. However, when executing unbalanced parallel programs, the CPC suffers from performance degradation due to synchronization overhead. In this paper we introduce a hardware extension called the continuation bit. The continuation bit controls the instruction issue and determines whether an instruction is issued from the same stream or the next stream. Simulations of various programs indicate that the continuation bit is able to balance the execution of parallel programs by exploiting instruction level parallelism.     

A study of generator operating point regulation based on fuzzy control

As the load in a power system continually changes, it is important to regulate the generator operating point. In this paper, assuming a suitable operating range for the generator the regulations for typical generator operating points within this range are selected and then fuzzy controllers are designed accordingly. To investigate the adaptation of each controller, many simulations are carried out for the various operating point changes. By quantitative investigation of the control performance of the adaptive controllers, a design method for fuzzy controllers for generator operating point regulation is proposed. Furthermore, a comparative estimation of the fuzzy control formula and optimal control formula with an observer is made using a common quantitative criterion. In addition, a one-machine infinite-bus system (including limits on the AVR and governor) is used as the control object model.     

Coagulation and dispersion of red mud suspensions

Red mud is a waste stream the Bayer process for alumina production. This paper deals mainly with the influence of pH on the coagulation and dispersion of red mud suspensions.For the purpose of understanding the coagulation and dispersion phenomena of dilute red mud suspensions, the relationship between zeta potential of red mud and pH is measured, and the phenomena in the case of basic suspensions are analyzed by using the experimental data of zeta potential and the DLVO theory. It is shown that the theory agrees fairly well with the experimental results.Furthermore, measurements of the specific volume of sediment, the zeta potential, the mass fraction of less than 2 μm in red mud and the apparent viscosity of some kinds of slurries, show that in order to entirely disperse red mud suspensions, the addition of a dispersing agent to the suspensions is necessary.     

Disproportionation of triethylsilane over CaY zeolite

The disproportionation of triethylsilane over CaY zeolite was examined using a fixed-bed flow reactor. The reactions at 673–723 K gave diethylsilane and tetraethylsilane, the conversion of triethylsilane being 50%. Practically no hydrocarbons were included in the product. The effects of the degree of Ca²⁺ exchange and the reaction variables on the catalytic performance were examined. This revised version was published online in July 2006 with corrections to the Cover Date.