Reliability Case History of an Airborne Air Data Computer

The life of an airborne Air Data computer and some of its components have been observed in the field and in the laboratory. This paper treats 3 aspects of the reliability. Part 1 shows the relationship of predicted to actual MTBF and explains some seasonal fluctuations in actual MTBF. Monthly and yearly fluctuations are also explored. Part 2 shows some effects of workmanship-in-repair on reliability growth. The repair procedure was changed and the reliability gradually improved over a long period of time. Part 3 treats one of the components, a wirewound potentiometer, in some detail. A failure analysis and an improvement program are described.     

Generation of picosecond optical pulses with highly RF modulated AlGaAs DH laser

AlGaAs DH lasers with strong RF modulation superimposed on the relatively low dc bias below the oscillation threshold were demonstrated to be feasible for generation of a train of approximately 30 ps optical pulses at a repetitive frequency of sub-GHz range. The pulse envelope width was measured by three different methods: a fast response photodetector, the second-harmonic generation (SHG) correlation method, and an ultrafast streak camera. The results of the SHG correlation and the streak camera agreed fairly well. In order to explain the generation mechanism and the characteristics of these ultrashort optical pulses in a highly RF modulated semiconductor diode laser, the rate equation analysis was performed and the results were generally in good agreement with the experiment. Furthermore, from the computer simulation for the analysis of the SHG correlation traces, it was inferred that an individual ultrashort optical pulse has internal substructures made of fluctuating fields whose spike widths were of the order of subpicoseconds, due to the randomness of the phases among lasing modes.     

Self-Repairing Mechanical Systems

This paper reviews several types of self-repairing systems developed in the Mechanical Engineering Laboratory. We have developed a modular system capable of self-assembly and self-repair. The former means a set of units can form a given shape of the system without outside help; the latter means the system restores the original shape if an arbitrary part of the system is cut off. We show both two-dimensional and three-dimensional unit designs, and distributed algorithms for the units.     

A Petri Net-Based Controller for Flexible and Maintainable Sequence Control and its Applications in Factory Automation

A new type of software system for an industrial sequence controller is proposed. In this system, a control program is described with the Petri net-like language named Control-net (C-net). This language improves control software maintainability and flexibility. An efficient C-net interpretation schema for real-time control is presented and an overhead time evaluation model of the proposed schema is developed. Through the model analysis and measurement of the response time of an interpreter on a microcomputer, it is proved that the interpretation schema satisfies the required response time. Finally, a microcomputer based controller named Station Controller (SCR) in which the presented C-net interpreter was installed is described and several applications of this controller to real systems are illustrated.     

Fundamental studies on flat bunched optical fibers

To produce an ultra-high fiber count optical cable with ultra-high density for subscriber loop applications, a new multicore fiber format, called "flat bunch fiber" format has been developed and manufactured. Individual cores in a flat bunch fiber format were arranged in a line contacted with neighboring claddings. This new format gave some advantages over existing optical fibers, from high density and mass-spliceability viewpoints. In this paper, fundamental characteristics of a flat bunch fiber, such as optical loss, bending, microbending, and tensile strength were mainly studied experimentally, comparing with an existing fiber. As a result, good characteristics to use in practice were shown. Moreover, crosstalk, which was one item of great concern for this kind of optical fiber, was the order to -40 dB for 500-m long optical fiber.     

The influence of acupuncture stimulation on plasma levels of LH, FSH, progesterone and estradiol in normally ovulating women

Myelinated cultures of mouse spinal cord were exposed to sera obtained from rabbits affected by experimental allergic encephalomyelitis following challenge with whole white matter in complete Freund's adjuvant. In the presence of complement, the tissue response begins with an increased birefringence of its myelin sheaths. This is rapidly followed by a gamut of changes leading to demyelination. This study reports that, in the absence of complement, the response is arrested at the stage of increased birefringence. In this way, this early stage of the demyelinating process was available for detailed examination by light and electron microscopy. The brightened myelin sheaths appeared with a few hours of exposure and were seen around all axons and sometimes around cell bodies. This was often accompanied by abrupt breaks in the sheaths and angularly shaped myelin figures. Examination by electron microscope revealed a uniform increase in the myelin period from 11 nm. to 22 nm. The normally double intraperiod line was increased to four electron-dense leaflets, the additional two appearing to be derived from the close apposition of an additional electron-dense layer on the outer surface of the myelin sheath or oligodendrocytic membrane. Oligondendrocytes responsed with a prolific growth of processes whose membranes compacted to form swollen myelin. Neurons, astrocytes, and neuropil showed no changes. In its early stages, at least, the swelling was reversible. It would appear, therefore, that we have isolated the first stage of antiserum-induced demyelination in vitro, a stage which is now available for further study.     

Sex pheromone of the scarab beetle Phyllophaga elenans and some intriguing minor components

Three amino acid-derived compounds were identified in extracts from the pheromone glands of the scarab beetle Phyllophaga elenans, i.e., L-isoleucine methyl ester (LIME), N-formyl L-isoleucine methyl ester (For-LIME), and N-acetyl L-isoleucine methyl ester (Ac-LIME). The compounds were characterized from their spectral data (MS and IR), confirmed by synthesis, and their absolute configurations were assigned by gas chromatography with a chiral phase column. The amount of LIME in calling females was ca. 2 g/gland, whereas only traces of For-LIME and Ac-LIME (0.005% of LIME) were detected in fresh extracts. Regardless of the storage temperature, the amounts of the minor constituents in the extracts increased over time. Field tests showed that traps baited with For-LIME captured more beetles than control traps. Ac-LIME per se was not attractive, and it did not increase trap catches when combined with For-LIME. Traps baited with LIME caught ca. 150 beetles/trap/day, but catches did not increase with the addition of For-LIME and/or Ac-LIME in binary or tertiary blends.     

Analysis of gas–liquid metal two-phase flows using a reactor safety analysis code SIMMER-III

SIMMER-III, a safety analysis code for liquid-metal fast reactors (LMFRs), includes a momentum exchange model based on conventional correlations for ordinary gas–liquid flows, such as an air–water system. From the viewpoint of safety evaluation of core disruptive accidents (CDAs) in LMFRs, we need to confirm that the code can predict the two-phase flow behaviors with high liquid-to-gas density ratios formed during a CDA. In the present study, the momentum exchange model of SIMMER-III was assessed and improved using experimental data of two-phase flows containing liquid metal, on which fundamental information, such as bubble shapes, void fractions and velocity fields, has been lacking.

It was found that the original SIMMER-III can suitably represent high liquid-to-gas density ratio flows including ellipsoidal bubbles as seen in lower gas fluxes. In addition, the employment of Kataoka–Ishii’s correlation has improved the accuracy of SIMMER-III for gas–liquid metal flows with cap-shape bubbles as identified in higher gas fluxes. Moreover, a new procedure, in which an appropriate drag coefficient can be automatically selected according to bubble shape, was developed.

Through this work, the reliability and the precision of SIMMER-III have been much raised with regard to bubbly flows for various liquid-to-gas density ratios.     

Deductive Synthesis of Numerical Simulation Programs from Networks of Algebraic and Ordinary Differential Equations

Scientists and engineers face recurring problems of constructing, testing and modifying numerical simulation programs. The process of coding and revising such simulators is extremely time-consuming, because they are almost always written in conventional programming languages. Scientists and engineers can therefore benefit from software that facilitates construction of programs for simulating physical systems. Our research adapts the methodology of deductive program synthesis to the problem of constructing numerical simulation codes. We have focused on simulators that can be represented as second order functional programs composed of numerical integration and root extraction routines. We have developed a system that uses first order Horn logic to synthesize numerical simulators built from these components. Our approach is based on two ideas: first, we axiomatize only the relationship between integration and differentiation. We neither attempt nor require a complete axiomatization of mathematical analysis. Second, our system uses a representation in which functions are reified as objects. Function objects are encoded as lambda expressions. Our knowledge base includes an axiomatization of term equality in the lambda calculus. It also includes axioms defining the semantics of numerical integration and root extraction routines. We use depth bounded SLD resolution to construct proofs and synthesize programs. Our system has successfully constructed numerical simulators for computational design of jet engine nozzles and sailing yachts, among others. Our results demonstrate that deductive synthesis techniques can be used to construct numerical simulation programs for realistic applications.     

Microstructural control of Ni-YSZ cermet anode for planer thin-film solid oxide fuel cells

Ni-Y₂O₃-stabilized ZrO₂ (Ni-YSZ) cermet anode was fabricated for solid oxide fuel cells (SOFCs) by conventional ceramic processing using NiO-YSZ composite particles. Microstructures of the anode were carefully characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Ni-YSZ cermet anode was consisting of fine YSZ connections, as the conducting pass of oxygen ions, on the surface of Ni network, as that of electrons, with continuous pore structure and as that of gaseous species. No amorphous phases were present at the interface between Ni and YSZ, and there was an orientation relationship between Ni and YSZ grains, (111)_Ni//(111)_YSZ. The cermet anode showed a high electrical performance at 800 °C. These results indicated that the electrochemical activity of the Ni-YSZ cermet anode was enhanced with the present microstructure.